alpha-synuclein and Gaucher-Disease

Topics: alpha-Synuclein; Autophagy; Gaucher Disease; Glucosylceramidase; Humans; Hydrolases; Lysosomes; Parkinson Disease

Gaucher disease (GD), one of the most common lysosomal storage diseases, is caused by mutations in the gene, GBA1, that leads to defective glucocerebrosidase activity resulting in the accumulation and storage of glycosphingolipids. However, the pathophysiology of GD is more complicated leading to various associated conditions such as skeletal manifestations and Parkinson's disease (PD). These may result from oxidative stress and inflammatory responses due to complex interconnection of downstream factors such as substrate accumulation, endoplasmic reticulum (ER) stress, unfolded protein response (UPR), calcium dysregulation, mitochondrial dysfunction, defective autophagy, accumulation of α-synuclein aggregates, altered secretion and function of extracellular vesicles (EVs), and immunologic hyperactivity. Here we provide an overview of lysosomal storage diseases followed by a comprehensive review of the factors contributing to oxidative stress and inflammation in GD pathophysiology, mechanisms underlying the possible associated complications, current established treatments for GD, their limitations, and potential primary and adjunctive treatment options targeting these factors.

Topics: alpha-Synuclein; Gaucher Disease; Glucosylceramidase; Humans; Lipids; Lysosomes; Parkinson Disease

Lysosomes have a critical role in maintaining normal cellular homeostasis mediated by their involvement in secretion, plasma membrane repair, cell signaling and energy metabolism. Lysosomal storage disorders (LSDs) are a group of approximately 50 rare disorders caused by lysosomal dysfunction that occur due to mutations in a gene of a lysosomal protein. Gaucher disease (GD), an autosomal recessive disorder and one of the most common LSDs, is caused by the deficiency of the lysosomal enzyme acid-β-glucocerebrosidase (GCase), due to biallelic mutations in the GBA1 gene. Reduced GCase activity leads to the accumulation of glucosylceramide (GlcCer), which is deacylated by lysosomal acid ceramidase to a toxic metabolite, glucosylshpingosine (GlcSph). Most GBA1 variants are recognized as misfolded in the ER, where the retention for refolding attempts initiates stress and activates the stress response known as the Unfolded Protein Response (UPR). The distinct clinical subtypes of GD are based on whether there is primary involvement of the central nervous system. Type 1 GD (GD1) is the nonneuropathic type, however, the recent recognition of the association of GD with the development of parkinsonism defies this classification. Patients with GD1 and carriers of GBA1 mutations are at risk for the development of parkinsonian manifestations. Parkinson disease (PD), the second most prevalent neurodegenerative disease, culminates in a movement disorder with the premature death of the patients. In PD and related disorders, collectively called synucleinopathies, the hallmark pathology is α-synuclein positive aggregates referred to as Lewy bodies or Lewy neurites and the death of dopaminergic neurons. While PD is mostly sporadic, in ∼5-10% of cases, the disease results from pathogenic variants in a growing number of genes. The most common genetic cause of PD is mutations in GBA1. Two mechanisms have been proposed for this link: (A) a "gain of function" mechanism, in which mutant GCase (protein) contributes to aggregate formation and to the development of PD, and the (B) "haploinsufficiency" ("loss of function") model, suggesting that one normal GBA1 allele is insufficient to carry adequate GCase activity and functional deficiency of GCase impedes α-synuclein metabolism. Lysosomal dysfunction, compromised autophagy and mitophagy further enhance the accumulation of α-synuclein, which results in the development of PD pathology. The present review will elaborate on the biology

Topics: alpha-Synuclein; Gaucher Disease; Glucosylceramidase; Humans; Lysosomes; Mutation; Neurodegenerative Diseases; Parkinson Disease

Parkinson's disease (PD) and related neurodegenerative disorders, termed the synucleinopathies, are characterized pathologically by the accumulation of protein aggregates containing α-synuclein (aSyn), resulting in progressive neuronal loss. There is considerable need for the development of neuroprotective strategies to halt or slow disease progression in these disorders. To this end, evaluation of genetic mutations associated with the synucleinopathies has helped to elucidate crucial mechanisms of disease pathogenesis, revealing key roles for lysosomal and mitochondrial dysfunction. The GBA1 gene, which encodes the lysosomal hydrolase β-glucocerebrosidase (GCase) is the most common genetic risk factor for PD and is also linked to other neurodegenerative disorders including dementia with Lewy bodies (DLB). Additionally, homozygous mutations in GBA1 are associated with the rare lysosomal storage disorder, Gaucher's disease (GD). In this review, we discuss the current knowledge in the field regarding the diverse roles of GCase in neurons and the multifactorial effects of loss of GCase enzymatic activity. Importantly, GCase has been shown to have a bidirectional relationship with aSyn, resulting in a pathogenic feedback loop that can lead to progressive aSyn accumulation. Alterations in GCase activity have furthermore been linked to multiple distinct pathways involved in neurodegeneration, and therefore GCase has emerged as a promising target for therapeutic drug development for PD and related neurodegenerative disorders, particularly DLB.

Topics: alpha-Synuclein; Gaucher Disease; Glucosylceramidase; Humans; Lysosomes; Neurodegenerative Diseases; Parkinson Disease

Neuronal loss in Parkinson's disease and related brain diseases has been firmly linked to the abundant neuronal protein α-synuclein (αS). However, we have gained surprisingly little insight into how exactly αS exerts toxicity in these diseases. Hypotheses of proteotoxicity, disturbed vesicle trafficking, mitochondrial dysfunction and other toxicity mechanisms have been proposed, and it seems possible that a combination of different mechanisms may drive pathology. A toxicity mechanism that has caught increased attention in the recent years is αS-related lipotoxicity. Lipotoxicity typically occurs in a cell when fatty acids exceed the metabolic needs, triggering a flux into harmful pathways of non-oxidative metabolism. Genetic and experimental approaches have revealed a significant overlap between lipid storage disorders, most notably Gaucher's disease, and synucleinopathies. There is accumulating evidence for lipid aberrations causing synuclein misfolding as well as for αS excess and misfolding causing lipid aberration. Does that mean the key problem in synucleinopathies is lipotoxicity, the accumulation of harmful lipid species or alteration in lipid equilibrium? Here, we review the existing literature in an attempt to get closer to an answer.

Topics: alpha-Synuclein; Gaucher Disease; Humans; Neurons; Parkinson Disease; Synucleinopathies

Current therapies for Parkinson's disease (PD) are palliative, of which the levodopa/carbidopa therapy remains the primary choice but is unable to modulate the progression of neurodegeneration. Due to the complication of such a multifactorial disorder and significant limitations of the therapy, numerous genetic approaches have been proved effective in finding out genes and mechanisms implicated in this disease. Following the observation of a higher frequency of PD in Gaucher's disease (GD), a lysosomal storage condition, mutations of glycosylceramidase beta (GBA) encoding glucocerebrosidase (GCase) have been shown to be involved and have been explored in the context of PD. GBA mutations are the most common genetic risk factor of PD. Various studies have revealed the relationships between PD and GBA gene mutations, facilitating a better understanding of this disorder. Various hypotheses delineate that the pathological mutations of GBA minimize the enzymatic activity of GCase, which affects the proliferation and clearance of α-synuclein; this affects the lysosomal homeostasis, exacerbating the endoplasmic reticulum stress or encouraging the mitochondrial dysfunction. Identification of the pathological mechanisms underlying the GBA-associated parkinsonism (GBA + PD) advances our understanding of PD. This review based on current literature aims to elucidate various genetic and clinical characteristics correlated with GBA mutations and to identify the numerous pathological processes underlying GBA + PD. We also delineate the therapeutic strategies to interfere with the mutant GCase function for further improvement of the related α-synuclein-GCase crosstalks. Moreover, the various therapeutic approaches such as gene therapy, chaperone proteins, and histone deacetylase inhibitors for the treatment of GBA + PD are discussed.

Topics: alpha-Synuclein; Gaucher Disease; Genetic Therapy; Glucosylceramidase; Humans; Mutation; Parkinson Disease

The discovery that patients with Gaucher Disease (GD), a rare lysosomal storage disorder, were developing symptoms similar to Parkinson's disease (PD) led to investigation of the relationship between the two seemingly unrelated pathologies. GD, an autosomal recessive disorder, is the result of a biallelic mutation in the gene GBA1, which encodes for the enzyme glucocerebrosidase (GCase). Since the observation of its relation to PD, GBA1 mutations have become recognized as the most common genetic risk factor for development of synucleinopathies such as PD and dementia with Lewy bodies. Although the exact mechanism by which GBA1 mutations promote PD is unknown, current understanding suggests that impaired GCase inhibits lysosomal activity and decreases the overall ability of the cell to degrade proteins, specifically the neuronal protein α-synuclein. Decreased elimination of α-synuclein can lead to its abnormal accumulation and aggregation, an important component of PD development. Further understanding of how decreased GCase activity increases risk for α-synuclein pathology can assist with the development of clinical biomarkers for early detection of synucleinopathies, as well as promote novel treatments tailored for people with a GBA1 mutation. Historically, α-synuclein has not been a reliable biomarker for PD. However, recent research on α-synuclein content within exosomes, which are small vesicles released by cells that carry specific cellular cargo, has yielded encouraging results. Moreover, decreased GCase activity has been shown to influence exosomal contents. Exosomes have emerged as a promising new avenue for the identification of novel biomarkers and therapeutic targets aimed at improving neuronal GCase function and limiting the development of synucleinopathies.

Topics: alpha-Synuclein; Animals; Biomarkers; Clinical Trials as Topic; Gaucher Disease; Glucosylceramidase; Humans; Lysosomes; Mice; Mutation; Parkinson Disease; Synucleinopathies

Topics: alpha-Synuclein; Animals; Brain; Gaucher Disease; Genetic Therapy; Glucosylceramidase; Humans; Molecular Targeted Therapy; Mutation; Parkinson Disease

Glucocerebrosidase is a lysosomal enzyme. The characterization of a direct link between mutations in the gene coding for glucocerebrosidase (GBA1) with the development of Parkinson's disease and dementia with Lewy bodies has heightened interest in this enzyme. Although the mechanisms through which glucocerebrosidase regulates the homeostasis of α-synuclein remains poorly understood, the identification of reduced glucocerebrosidase activity in the brains of patients with PD and dementia with Lewy bodies has paved the way for the development of novel therapeutic strategies directed at enhancing glucocerebrosidase activity and reducing α-synuclein burden, thereby slowing down or even preventing neuronal death. Here we reviewed the current literature relating to the mechanisms underlying the cross talk between glucocerebrosidase and α-synuclein, the GBA1 mutation-associated clinical phenotypes, and ongoing therapeutic approaches targeting glucocerebrosidase. © 2018 International Parkinson and Movement Disorder Society.

Topics: alpha-Synuclein; Gaucher Disease; Glucosylceramidase; Humans; Lysosomes; Precision Medicine; Synucleinopathies

GBA1 mutations, which result in the lysosomal disorder Gaucher disease, are the most common known genetic risk factor for Parkinson disease and Dementia with Lewy Bodies (DLB). The pathogenesis of this association is not fully understood, but further elucidation of this link could lead to new therapeutic options.. The characteristic clinical phenotype of GBA1-PD resembles sporadic Parkinson disease, but with an earlier onset and more severe course. Many different GBA1 mutations increase the risk of Parkinson disease, some primarily detected in specific populations. Glucocerebrosidase deficiency appears to be associated with increased α-synuclein aggregation and accumulation, mitochondrial dysfunction because of impaired autophagy, and increased endoplasmic reticulum stress.. As our understanding of GBA1-associated Parkinson disease increases, new treatment opportunities emerge. MicroRNA profiles are providing examples of both up-regulated and down-regulated proteins related to GBA1 and may provide new therapeutic targets. Chaperone therapy, directed at either misfolded glucocerebrosidase or α-synuclein aggregation, is currently under development and there are several early clinical trials ongoing. Substrate reduction therapy, aimed at lowering the accumulation of metabolic by-products, especially glucosylsphingosine, is also being explored. Basic science insights from the rare disorder Gaucher disease are serving to catapult drug discovery for parkinsonism.

Topics: alpha-Synuclein; Gaucher Disease; Glucosylceramidase; Humans; Lewy Body Disease; Mutation; Parkinsonian Disorders; Protein Aggregates

Homozygous and heterozygous mutations in GBA1, the gene implicated in Gaucher disease, increase the risk and severity of Parkinson disease (PD). We evaluated the design, phenotype, strengths, and limitations of current GBA1-associated PD mouse models. Although faithful modeling of a genetic risk factor poses many challenges, the different approaches taken were successful in revealing predisposing abnormalities in heterozygotes for GBA1 mutations and demonstrating the deleterious effects of GBA1 impairment on the PD course in PD models. GBA1-PD models differ in key parameters, with no single model recapitulating all aspects of the GBA1-PD puzzle, emphasizing the importance of selecting the proper in vivo model depending on the specific molecular mechanism or potential therapy being studied.

Topics: alpha-Synuclein; Animals; Disease Models, Animal; Gaucher Disease; Glucosylceramidase; Humans; Mutation; Parkinson Disease

Parkinson's disease (PD) is a common neurodegenerative disease characterized by the degeneration of dopaminergic neurons in the substantia nigra and the intraneuronal Lewy bodies in this area. Genetic mutations in PD pathogenesis have been explored and better understood in recent years. GBA variants are now considered to be the single largest risk factor for PD. Gaucher disease (GD) is a lysosomal storage disorder disease and an inherited deficiency of lysosomal glucocerebrosidase (GCase) arising from mutations in the gene GBA. A group of patients with GD exhibit parkinsonian symptoms, meanwhile, GBA mutations are more frequently observed in patients with PD. These lines of evidence suggest a close relationship between GBA mutations and PD. GBA mutations are associated with an earlier onset age and a distinct cognitive decline in PD. GCase loss-of-function caused by GBA mutations interferes with the degradation of α-synuclein, and α-synuclein pathology in turn inhibits normal GCase function in PD, which forms a vicious cycle. However, the exact mechanisms for this bidirectional pathogenic loop have not to be fully elucidated. In this review, we summarize the current understandings on the potential link between GBA mutations and PD pathogenesis, which may show novel insights into PD etiology and therapeutics.

Topics: alpha-Synuclein; Cognitive Dysfunction; Dopaminergic Neurons; Gaucher Disease; Glucosylceramidase; Humans; Mutation; Parkinson Disease; Parkinsonian Disorders; Risk Factors; Substantia Nigra

Gaucher disease, the most common lysosomal storage disorder, is caused by mutations in the gene encoding the acid-β-glucosidase lysosomal hydrolase enzyme that cleaves glucocerebroside into glucose and ceramide. Reduced enzyme activity and impaired structural stability arise due to >300 known disease-causing mutations. Several of these mutations have also been associated with an increased risk of Parkinson disease (PD). Since the discovery of the acid-β-glucosidase X-ray structure, there have been major advances in our understanding of the structural properties of the protein. Analysis of specific residues has provided insight into their functional and structural importance and provided insight into the pathogenesis of Gaucher disease and the contribution to PD. Disease-causing mutations are positioned throughout the acid-β-glucosidase structure, with many located far from the active site and thus retaining some enzymatic activity however, thus far no clear relationship between mutation location and disease severity has been established. Here, we review the crystal structure of acid-β-glucosidase, while highlighting important structural aspects of the protein in detail. This review discusses the structural stability of acid-β-glucosidase, which can be altered by pH and glycosylation, and explores the relationship between known Gaucher disease and PD mutations, structural stability and disease severity.

Topics: alpha-Synuclein; Animals; Gaucher Disease; Glycosylation; Humans; Lysosomes; Mutation; Parkinson Disease

Gaucher disease is an autosomal recessive lysosomal storage disorder, caused by mutations in the GBA gene. The frequency of Gaucher disease patients and heterozygote carriers that developed Parkinson disease has been found to be above that of the control population. This fact suggests that mutations in the GBA gene can be involved in Parkison's etiology. Analysis of large cohorts of patients with Parkinson disease has shown that there are significantly more cases bearing GBA mutations than those found among healthy individuals. Functional studies have proven an interaction between α-synuclein and GBA, the levels of which presented an inverse correlation. Mutant GBA proteins cause increases in α-synuclein levels, while an inhibition of GBA by α-synuclein has been also demonstrated. Saposin C, a coactivator of GBA, has been shown to protect GBA from this inhibition. Among the GBA variants associated with Parkinson disease, E326K seems to be one of the most prevalent. Interestingly, it is involved in Gaucher disease only when it forms part of a double-mutant allele, usually with the L444P mutation. Structural analyses have revealed that both residues (E326 and L444) interact with Saposin C and, probably, also with α-synuclein. This could explain the antagonistic role of these two proteins in relation to GBA.

Topics: Alleles; alpha-Synuclein; Gaucher Disease; Gene Expression; Gene Frequency; Glucosylceramidase; Humans; Lysosomes; Mutation; Parkinson Disease; Saposins

Lysosomal dysfunction has been implicated in multiple diseases, including lysosomal storage disorders such as Gaucher's disease, in which loss-of-function mutations in the GBA1 gene encoding the lysosomal hydrolase β-glucocerebrosidase result in lipid substrate accumulation. In Parkinson's disease, α-synuclein accumulates in Lewy bodies and neurites contributing to neuronal death. Previous clinical and genetic evidence has demonstrated an important link between Parkinson's and Gaucher's disease, as GBA1 mutations and variants increase the risk of Parkinson's and Parkinson's patients exhibit decreased β-glucocerebrosidase activity. Using human midbrain neuron cultures, we have found that loss of β-glucocerebrosidase activity promotes α-synuclein accumulation and toxicity, whereas α-synuclein accumulation further contributes to decreased lysosomal β-glucocerebrosidase activity by disrupting β-glucocerebrosidase trafficking to lysosomes. Moreover, α-synuclein accumulation disrupts trafficking of additional lysosomal hydrolases, further contributing to lysosomal dysfunction and neuronal dyshomeostasis. Importantly, promoting β-glucocerebrosidase activity reduces α-synuclein accumulation and rescues lysosomal and neuronal dysfunction, suggesting that β-glucocerebrosidase may be an important therapeutic target for advancing drug discovery in synucleinopathies including Parkinson's disease. © 2016 International Parkinson and Movement Disorder Society.

Topics: alpha-Synuclein; Gaucher Disease; Glucosylceramidase; Humans; Lysosomes; Parkinson Disease

Gaucher disease, the most common lysosomal storage disease, is caused by a recessively inherited deficiency in glucocerebrosidase and subsequent accumulation of toxic lipid substrates. Heterozygous mutations in the lysosomal glucocerebrosidase gene (GBA1) have recently been recognized as the highest genetic risk factor for the development of α-synuclein aggregation disorders ("synucleinopathies"), including Parkinson's disease (PD) and dementia with Lewy bodies (DLB). Despite the wealth of experimental, clinical and genetic evidence that supports the association between mutant genotypes and synucleinopathy risk, the precise mechanisms by which GBA1 mutations lead to PD and DLB remain unclear. Decreased glucocerebrosidase activity has been demonstrated to promote α-synuclein misprocessing. Furthermore, aberrant α-synuclein species have been reported to downregulate glucocerebrosidase activity, which further contributes to disease progression. In this review, we summarize the recent findings that highlight the complexity of this pathogenetic link and how several pathways that connect glucocerebrosidase insufficiency with α-synuclein misprocessing have emerged as potential therapeutic targets. From a translational perspective, we discuss how various therapeutic approaches to lysosomal dysfunction have been explored for the treatment of GBA1-related synucleinopathies, and potentially, for non-GBA1-associated neurodegenerative diseases. In summary, the link between GBA1 and synucleinopathies has become the paradigm of how the study of a rare lysosomal disease can transform the understanding of the etiopathology, and hopefully the treatment, of a more prevalent and multifactorial disorder.

Topics: alpha-Synuclein; Gaucher Disease; Glucosylceramidase; Humans; Mutation; Neurodegenerative Diseases

Gaucher disease is associated with Parkinson's disease (PD) by mutations in glucocerebrosidase (GCase). The gene encoding GCase, glucosidase beta acid (GBA), is an important risk factor for PD. Findings from large studies have shown that patients with PD have an increased frequency of mutations in GBA and that GBA mutation carriers exhibit diverse parkinsonian phenotypes and Lewy body pathology. Although the mechanism for this association remains elusive, some hypotheses have been proposed to explain it, including gain of function caused by GBA mutations, which increases α-synuclein (α-syn) aggregation, loss of function due to lysosomal enzyme deficiency, which affects α-syn clearance, and even a bidirectional feedback loop, but each of these hypotheses has its limitations. It is also worth noting that many findings have implicated the interaction between α-syn and GCase, indicating the essential role of the interaction in the pathogenesis of GBA-associated parkinsonism. Therefore, the current review focuses on α-syn and GCase, and it provides some new thoughts that may be helpful for understanding the α-syn-GCase interaction and unraveling the exact mechanism underlying GBA-associated parkinsonism.

Topics: alpha-Synuclein; Animals; Epistasis, Genetic; Gaucher Disease; Glucosylceramidase; Heterozygote; Humans; Mutation; Parkinsonian Disorders

The lysosomal enzyme glucocerebrosidase, encoded by the glucocerebrosidase gene, is involved in the breakdown of glucocerebroside into glucose and ceramide. Lysosomal build-up of the substrate glucocerebroside occurs in cells of the reticulo-endothelial system in patients with Gaucher disease, a rare lysosomal storage disorder caused by the recessively inherited deficiency of glucocerebrosidase. Gaucher disease has a broad clinical phenotypic spectrum, divided into non-neuronopathic and neuronopathic forms. Like many monogenic diseases, the correlation between clinical manifestations and molecular genotype is not straightforward. There is now a well-established clinical association between mutations in the glucocerebrosidase gene and the development of more prevalent multifactorial disorders including Parkinson's disease and other synucleinopathies. In this review we discuss recent studies advancing our understanding of the cellular relationship between glucocerebrosidase and α-synuclein, the potential impact of established and emerging therapeutics for Gaucher disease for the treatment of the synucleinopathies, and the role of lysosomal pathways in the pathogenesis of these neurodegenerative disorders.

Topics: alpha-Synuclein; Gaucher Disease; Genetic Association Studies; Genotype; Glucosylceramidase; Humans; Mutation; Parkinson Disease; Phenotype

Therapeutic efforts in neurodegenerative diseases have been very challenging, particularly due to a lack of validated and mechanism-based therapeutic targets and biomarkers. The basic idea underlying the novel therapeutic approaches reviewed here is that by exploring the molecular basis of neurodegeneration in a rare lysosomal disease such as Gaucher's disease (GD), new molecular targets will be identified for therapeutic development in common synucleinopathies. Accumulation of α-synuclein plays a key role in the pathogenesis of Parkinson's disease (PD) and other synucleinopathies, suggesting that improved clearance of α-synuclein may be of therapeutic benefit. To achieve this goal, it is important to identify specific mechanisms and targets involved in the clearance of α-synuclein. Recent discovery of clinical, genetic, and pathological linkage between GD and PD offers a unique opportunity to examine lysosomal glucocerebrosidase, an enzyme mutated in GD, for development of targeted therapies in synucleinopathies. While modulation of glucocerebrosidase and glycolipid metabolism offers a viable approach to treating disorders associated with synuclein accumulation, the compounds described to date either lack the ability to penetrate the CNS or have off-target effects that may counteract or limit their capabilities to mediate the desired pharmacological action. However, recent emergence of selective inhibitors of glycosphingolipid biosynthesis and noninhibitory pharmacological chaperones of glycosphingolipid processing enzymes that gain access to the CNS provide a novel approach that may overcome some of the limitations of compounds reported to date. These new strategies may allow for development of targeted treatments for synucleinopathies that affect both children and adults.

Topics: Adolescent; Adult; alpha-Synuclein; Child; Child, Preschool; Gaucher Disease; Glucosylceramidase; Glycolipids; Humans; Lipid Metabolism; Mutation; Parkinson Disease

Mutations in the gene encoding glucocerebrosidase (GBA1) cause Gaucher disease (GD), a lysosomal storage disease with recessive inheritance. Glucocerebrosidase (GCase) is a lysosomal lipid hydrolase that digests glycolipid substrates, such as glucosylceramide and glucosylsphingosine. GBA1 mutations have been implicated in Lewy body diseases (LBDs), such as Parkinson's disease and dementia with Lewy bodies. Parkinsonism occurs more frequently in certain types of GD, and GBA1 mutation carriers are more likely to have LBDs than non-carriers. Furthermore, GCase is often found in Lewy bodies, which are composed of α-synuclein fibrils as well as a variety of proteins and vesicles. In this review, we discuss potential mechanisms of action of GBA1 mutations in LBDs with particular emphasis on α-synuclein aggregation by reviewing the current literature on the role of GCase in lysosomal functions and glycolipid metabolism.

Topics: alpha-Synuclein; Gaucher Disease; Glucosylceramidase; Glycolipids; Humans; Lewy Body Disease; Lysosomes; Mutation

Mutations in the ß-glucocerebrosidase gene (GBA), which encodes the lysosomal enzyme ß-glucocerebrosidase, have traditionally been implicated in Gaucher disease, an autosomal recessive lysosomal storage disorder. Yet the past two decades have yielded an explosion of epidemiological and basic-science evidence linking mutations in GBA with the development of Parkinson disease (PD) as well. Although the specific contribution of mutant GBA to the pathogenesis of parkinsonism remains unknown, evidence suggests that both loss of function and toxic gain of function by abnormal ß-glucocerebrosidase may be important, and implicates a close relationship between ß-glucocerebrosidase and α-synuclein. Furthermore, multiple lines of evidence suggest that although GBA-associated PD closely mimics idiopathic PD (IPD), it may present at a younger age, and is more frequently complicated by cognitive dysfunction. Understanding the clinical association between GBA and PD, and the relationship between ß-glucocerebrosidase and α-synuclein, may enhance understanding of the pathogenesis of IPD, improve prognostication and treatment of GBA carriers with parkinsonism, and furthermore inform therapies for IPD not due to GBA mutations.

Topics: alpha-Synuclein; Endophenotypes; Gaucher Disease; Genetic Counseling; Genetic Predisposition to Disease; Glucosylceramidase; Humans; Molecular Targeted Therapy; Mutation; Neuroimaging; Parkinsonian Disorders

Gaucher disease (GD) is a lysosomal disorder caused by inherited deficiency of glucocerebrosidase (GCase), resulting in the accumulation of glucocerebroside in macrophages, termed "Gaucher cells," leading to multiorgan involvement, with hepatosplenomegaly, cytopenias, pulmonary hypertension, and skeletal complications. Various mutations, encoding the GCase gene, cause acute or chronic neuronopathic forms of the disease. The hallmark of GD is the macrophages infiltrating organs, bone marrow, and nervous system compromising their function by inflammation, infarcts, fibrosis, and neuronal damage. Coagulation abnormalities are frequent among GD patients due to reduced production and chronic consumption of coagulation factors. Splenic and bone infarcts often occur in GD patients, but hypercoagulability is not frequent. Detection of thrombophilic risk factors in GD patients may predict a more severe course of the disease. Clinical and genetic studies revealed an association between reduced GCase activity in carriers of GD mutations and GD patients and occurrence of Parkinson disease (PD) and showed that GCase gene mutations are risk factors for PD development. The mechanisms underlying the association of PD and GD are not yet elucidated and should be further explored, particularly the potential involvement of inflammation and coagulation in the neurovascular unit.

Topics: alpha-Synuclein; Blood Coagulation Factors; Gaucher Disease; Glucosylceramidase; Humans; Mutation; Parkinson Disease; Risk Factors; Thrombophilia

Gaucher disease (OMIM 230800, 230900, 231000), the most common lysosomal storage disorder, is due to a deficiency in the enzyme glucocerebrosidase. Gaucher patients display a wide spectrum of clinical presentation, with hepatosplenomegaly, haematological changes, and orthopaedic complications being the predominant symptoms. Gaucher disease is classified into three broad phenotypes based upon the presence or absence of neurological involvement: Type 1 (non-neuronopathic), Type 2 (acute neuronopathic), and Type 3 (subacute neuronopathic). Nearly 300 mutations have been identified in Gaucher patients, with the majority being missense mutations. Though studies of genotype-to-phenotype correlations have revealed significant heterogeneity, some consistent patterns have emerged to inform prognostic and therapeutic decisions. Recent research has highlighted a potential role for Gaucher disease in other comorbidities such as cancer and Parkinson's Disease. In this review, we will examine the potential relationship between Gaucher disease and the synucleinopathies, a group of neurodegenerative disorders characterized by the development of intracellular aggregates of α-synuclein. Possible mechanisms of interaction will be discussed.

Topics: alpha-Synuclein; Gaucher Disease; Heredodegenerative Disorders, Nervous System; Humans; Mutation, Missense

Heterozygous mutations in the glucocerebrosidase gene (GBA1) are associated with increased risk for α-synuclein aggregation disorders ('synucleinopathies'), which include Parkinson's disease (PD) and dementia with Lewy bodies (DLB). Homozygous GBA1 mutations lead to reduced GBA1 lysosomal activity underlying three variants of Gaucher disease (GD). Despite the wealth of clinical and genetic evidence supporting the association between mutant genotypes and synucleinopathy risk, the precise mechanisms by which GBA1 mutations lead to PD and DLB remain unclear. Here, we summarize recent findings that highlight the complexity of this pathogenetic link. In neural cells, both gain and loss of function mechanisms, as conferred by mutant GBA1 expression and activity loss, respectively, seem to promote aberrant α-synuclein processing. In addition, we draw attention to recent insights gleaned from GD animal models regarding axonal pathology, brain inflammation and memory dysfunction. From a translational perspective, we discuss the concepts of neural enzyme replacement therapy and pharmacological agents as potential treatment strategies for GBA1-associated synucleinopathies. Finally, we touch on the issue whether aberrant α-synuclein species may coregulate GBA1 activity in the vertebrate brain, thereby providing a reverse link, i.e., between an important synucleinopathy risk factor and the enzyme's lysosomal function. In summary, several leads connecting GBA1 mutations with α-synuclein misprocessing have emerged as potential targets for the treatment of GBA1-related synucleinopathies, and possibly, for non-GBA1-associated neurodegenerative diseases.

Topics: alpha-Synuclein; Animals; Brain; Disease Models, Animal; Gaucher Disease; Gene Expression Regulation; Glucosylceramidase; Humans; Mice; Mutation

Clinical, genetic and pathological studies demonstrate that mutations in glucocerebrosidase (GBA), which encodes the lysosomal enzyme deficient in Gaucher disease (GD), are risk factors for Parkinson disease (PD) and related disorders. Some patients with GD and Gaucher carriers develop parkinsonism. Furthermore, subjects with PD have an increased frequency of GBA mutations. GBA-mutation carriers exhibit diverse parkinsonian phenotypes and have glucocerebrosidase-positive Lewy bodies. Although the mechanism for this association is unknown, we present several theories, including protein aggregation, prion transmission, lipid accumulation and impaired autophagy, mitophagy or trafficking. Each model has inherent limitations, and a second-hit mutation might be essential. Elucidation of the basis for this link will have important consequences for studying these diseases and should provide insights into lysosomal pathways and potential treatment strategies.

Topics: alpha-Synuclein; Autophagy; Endoplasmic Reticulum-Associated Degradation; Gaucher Disease; Glucosylceramidase; Humans; Lewy Bodies; Lipid Metabolism; Lysosomes; Mutation; Parkinsonian Disorders; Prions

Topics: alpha-Synuclein; Animals; Gaucher Disease; Glucosylceramidase; Humans; Lysosomes; Models, Biological; Parkinson Disease

A body of work has emerged over the past decade demonstrating a relationship between mutations in glucocerebrosidase gene (GBA), the gene implicated in Gaucher disease (GD), and the development of parkinsonism. Several different lines of research support this relationship. First, patients with GD who are homozygous for mutations in GBA have a higher than expected propensity to develop Parkinson's disease (PD). Furthermore, carriers of GBA mutations, particularly family members of patients with GD, have displayed an increased rate of parkinsonism. Subsequently, investigators from centers around the world screened cohorts of patients with parkinsonism for GBA mutations and found that overall, subjects with PD, as well as other Lewy body disorders, have at least a fivefold increase in the number of carriers of GBA mutations as compared to age-matched controls. In addition, neuropathologic studies of subjects with parkinsonism carrying GBA mutations demonstrate Lewy bodies, depletion of neurons of the substantia nigra, and involvement of hippocampal layers CA2-4. Although the basis for this association has yet to be elucidated, evidence continues to support the role of GBA as a PD risk factor across different centers, synucleinopathies, and ethnicities. Further studies of the association between GD and parkinsonism will stimulate new insights into the pathophysiology of the two disorders and will prove crucial for both genetic counseling of patients and family members and the design of relevant therapeutic strategies for specific patients with parkinsonism.

Topics: Adult; Aged; alpha-Synuclein; Child; DNA Mutational Analysis; Enzyme Replacement Therapy; Ethnicity; Female; Gaucher Disease; Genetic Counseling; Genetic Predisposition to Disease; Glucosylceramidase; Hippocampus; Humans; Lewy Body Disease; Lysosomes; Male; Middle Aged; Mutation; Parkinsonian Disorders; Risk Factors; Substantia Nigra

Topics: alpha-Synuclein; Dementia; Gaucher Disease; Glucosylceramidase; Humans; Mutation; Parkinson Disease

It is well established that patients with Gaucher disease, as well as carriers of the disease have an increased risk for developing Parkinson's disease. A plethora of evidence suggests that disturbed α-Synuclein homeostasis is the link between Gaucher disease and Parkinson's disease. The pathogenic mechanism linking these entities is still a topic of debate and both gain- and loss-of-function theories have been put forward, which however are not mutually exclusive. In the present study we expanded our previous studies to include not only Gaucher disease patients but also Gaucher disease carriers and Gaucher disease patients following Enzyme Replacement Therapy. In these groups we investigated α-Synuclein in red blood cell membranes in association with lipid abnormalities described in Gaucher disease. These included glucosylceramide and its species, glucosylsphingosine, glucosylcholesterol and plasmalogens. Increased oligomerization of α-Synuclein in red blood cell membranes was observed not only in Gaucher disease patients but also in carriers of the disease. There were no qualitative differences in the lipids identified in the groups studied. However, significant quantitative differences compared to controls were observed in Gaucher disease patients but not in Gaucher disease carriers. Enzyme Replacement Therapy reversed the biochemical defects and normalized α-Synuclein homeostasis, providing for the first time evidence in human subjects that such homeostatic dysregulation is reversible. Further studies investigating α-Synuclein status during the differentiation of erythroid progenitors could provide new data on the pathogenic mechanism of α-Synuclein oligomerization in this system.

Topics: alpha-Synuclein; Enzyme Replacement Therapy; Erythrocytes; Gaucher Disease; Glucosylceramidase; Humans; Parkinson Disease

Bi-allelic mutations in GBA1, the gene that encodes β-glucocerebrosidase (GCase), cause Gaucher disease (GD), whereas mono-allelic mutations do not cause overt pathology. Yet mono- or bi-allelic GBA1 mutations are the highest known risk factor for Parkinson's disease (PD). GCase deficiency results in the accumulation of glucosylceramide (GluCer) and its deacylated metabolite glucosylsphingosine (GluSph). Brains from patients with neuronopathic GD have high levels of GluSph, and elevation of this lipid in GBA1-associated PD has been reported. To uncover the mechanisms involved in GBA1-associated PD, we used human induced pluripotent stem cell-derived dopaminergic (DA) neurons from patients harboring heterozygote mutations in GBA1 (GBA1/PD-DA neurons). We found that compared with gene-edited isogenic controls, GBA1/PD-DA neurons exhibit mammalian target of rapamycin complex 1 (mTORC1) hyperactivity, a block in autophagy, an increase in the levels of phosphorylated α-synuclein (129) and α-synuclein aggregation. These alterations were prevented by incubation with mTOR inhibitors. Inhibition of acid ceramidase, the lysosomal enzyme that deacylates GluCer to GluSph, prevented mTOR hyperactivity, restored autophagic flux and lowered α-synuclein levels, suggesting that GluSph was responsible for these alterations. Incubation of gene-edited wild type (WT) controls with exogenous GluSph recapitulated the mTOR/α-synuclein abnormalities of GBA1/PD neurons, and these phenotypic alterations were prevented when GluSph treatment was in the presence of mTOR inhibitors. We conclude that GluSph causes an aberrant activation of mTORC1, suppressing normal lysosomal functions, including the clearance of pathogenic α-synuclein species. Our results implicate acid ceramidase in the pathogenesis of GBA1-associated PD, suggesting that this enzyme is a potential therapeutic target for treating synucleinopathies caused by GCase deficiency.

Topics: Acid Ceramidase; alpha-Synuclein; Dopaminergic Neurons; Gaucher Disease; Glucosylceramidase; Humans; Induced Pluripotent Stem Cells; Lysosomes; Mechanistic Target of Rapamycin Complex 1; MTOR Inhibitors; Mutation; Parkinson Disease; TOR Serine-Threonine Kinases

Mutations in glucocerebrosidase cause the lysosomal storage disorder Gaucher's disease and are the most common risk factor for Parkinson's disease. Therapies to restore the enzyme's function in the brain hold great promise for treating the neurological implications. Thus, we developed blood-brain barrier penetrant therapeutic molecules by fusing transferrin receptor-binding moieties to β-glucocerebrosidase (referred to as GCase-BS). We demonstrate that these fusion proteins show significantly increased uptake and lysosomal efficiency compared to the enzyme alone. In a cellular disease model, GCase-BS rapidly rescues the lysosomal proteome and lipid accumulations beyond known substrates. In a mouse disease model, intravenous injection of GCase-BS leads to a sustained reduction of glucosylsphingosine and can lower neurofilament-light chain plasma levels. Collectively, these findings demonstrate the potential of GCase-BS for treating GBA1-associated lysosomal dysfunction, provide insight into candidate biomarkers, and may ultimately open a promising treatment paradigm for lysosomal storage diseases extending beyond the central nervous system.

Topics: alpha-Synuclein; Animals; Brain; Gaucher Disease; Glucosylceramidase; Lysosomes; Mice; Mutation; Neurons; Parkinson Disease

Gaucher disease (GD) is the most frequent sphingolipidosis, caused by biallelic pathogenic variants in the

Topics: alpha-Synuclein; Enzyme Replacement Therapy; Gaucher Disease; Heterozygote; Humans; Mutation; Parkinson Disease

Topics: alpha-Synuclein; Gaucher Disease; Glucosylceramidase; Humans; Parkinson Disease

Topics: alpha-Synuclein; Biomarkers; Gaucher Disease; Glucosylceramidase; Humans; Mutation; Parkinson Disease

Loss of activity of the lysosomal glycosidase β-glucocerebrosidase (GCase) causes the lysosomal storage disease Gaucher disease (GD) and has emerged as the greatest genetic risk factor for the development of both Parkinson disease (PD) and dementia with Lewy bodies. There is significant interest into how GCase dysfunction contributes to these diseases, however, progress toward a full understanding is complicated by presence of endogenous cellular factors that influence lysosomal GCase activity. Indeed, such factors are thought to contribute to the high degree of variable penetrance of

Topics: alpha-Synuclein; Gaucher Disease; Glucosylceramidase; Humans; Lewy Bodies; Lewy Body Disease; Lysosomes; Mutation; Parkinson Disease; Substrate Specificity

Topics: alpha-Synuclein; Biomarkers; Gaucher Disease; Glucosylceramidase; Humans; Mutation; Parkinson Disease

Topics: alpha-Synuclein; Gaucher Disease; Glucosylceramidase; Humans; Mutation; Parkinson Disease

Topics: alpha-Synuclein; Amyloid; Autophagy; beta-Synuclein; Brain; Gaucher Disease; Glucosylceramidase; Humans; Intracellular Signaling Peptides and Proteins; Lysosomes; Models, Biological; Mutation; Niemann-Pick C1 Protein; Parkinson Disease; Reactive Oxygen Species; Risk; Risk Factors; Treatment Outcome

Homozygous mutations in the lysosomal glucocerebrosidase gene, GBA1, cause Gaucher's disease (GD), while heterozygous mutations in GBA1 are a strong risk factor for Parkinson's disease (PD), whose pathological hallmark is intraneuronal α-synuclein (asyn) aggregates. We previously reported that gba1 knockout (KO) medaka exhibited glucosylceramide accumulation and neuronopathic GD phenotypes, including short lifespan, the dopaminergic and noradrenergic neuronal cell loss, microglial activation, and swimming abnormality, with asyn accumulation in the brains. A recent study reported that deletion of GBA2, non-lysosomal glucocerebrosidase, in a non-neuronopathic GD mouse model rescued its phenotypes. In the present study, we generated gba2 KO medaka and examined the effect of Gba2 deletion on the phenotypes of gba1 KO medaka. The Gba2 deletion in gba1 KO medaka resulted in the exacerbation of glucosylceramide accumulation and no improvement in neuronopathic GD pathological changes, asyn accumulation, or swimming abnormalities. Meanwhile, though gba2 KO medaka did not show any apparent phenotypes, biochemical analysis revealed asyn accumulation in the brains. gba2 KO medaka showed a trend towards an increase in sphingolipids in the brains, which is one of the possible causes of asyn accumulation. In conclusion, this study demonstrated that the deletion of Gba2 does not rescue the pathological changes or behavioral abnormalities of gba1 KO medaka, and GBA2 represents a novel factor affecting asyn accumulation in the brains.

Topics: Alkaline Phosphatase; alpha-Synuclein; Animals; Autophagy; Brain; Gaucher Disease; Gene Deletion; Gene Knockout Techniques; Glucosylceramidase; Models, Biological; Mutation; Neurons; Oryzias; Phenotype; Sphingolipids

A major risk factor for Gaucher's disease is loss of function mutations in the

Topics: alpha-Synuclein; Amyloid; Gaucher Disease; Glucosylceramides; Humans; Parkinson Disease

While astrocytes, the most abundant cells found in the brain, have many diverse functions, their role in the lysosomal storage disorder Gaucher disease (GD) has not been explored. GD, resulting from the inherited deficiency of the enzyme glucocerebrosidase and subsequent accumulation of glucosylceramide and its acylated derivative glucosylsphingosine, has both non-neuronopathic (GD1) and neuronopathic forms (GD2 and 3). Furthermore, mutations in GBA1, the gene mutated in GD, are an important risk factor for Parkinson's disease (PD). To elucidate the role of astrocytes in the disease pathogenesis, we generated iAstrocytes from induced pluripotent stem cells made from fibroblasts taken from controls and patients with GD1, with and without PD. We also made iAstrocytes from an infant with GD2, the most severe and progressive form, manifesting in infancy. Gaucher iAstrocytes appropriately showed deficient glucocerebrosidase activity and levels and substrate accumulation. These cells exhibited varying degrees of astrogliosis, Glial Fibrillary Acidic Protein (GFAP) up-regulation and cellular proliferation, depending on the level of residual glucocerebrosidase activity. Glutamte uptake assays demonstrated that the cells were functionally active, although the glutamine transporter EEAT2 was upregulated and EEAT1 downregulated in the GD2 samples. GD2 iAstrocytes were morphologically different, with severe cytoskeletal hypertrophy, overlapping of astrocyte processes, pronounced up-regulation of GFAP and S100β, and significant astrocyte proliferation, recapitulating the neuropathology observed in patients with GD2. Although astrocytes do not express α-synuclein, when the iAstrocytes were co-cultured with dopaminergic neurons generated from the same iPSC lines, excessive α-synuclein released from neurons was endocytosed by astrocytes, translocating into lysosomes. Levels of aggregated α-synuclein increased significantly when cells were treated with monomeric or fibrillar α-synuclein. GD1-PD and GD2 iAstrocytes also exhibited impaired Cathepsin D activity, leading to further α-synuclein accumulation. Cytokine and chemokine profiling of the iAstrocytes demonstrated an inflammatory response. Thus, in patients with GBA1-associated parkinsonism, astrocytes appear to play a role in α-synuclein accumulation and processing, contributing to neuroinflammation.

Topics: alpha-Synuclein; Astrocytes; Gaucher Disease; Humans; Induced Pluripotent Stem Cells; Parkinson Disease

Mutations in the GBA gene, which encodes the lysosomal enzyme glucocerebrosidase (GCase), are the most important genetic risk factor for Parkinson disease (PD). GCase activity is also decreased in sporadic PD brains and with normal ageing. Loss of GCase activity impairs the autophagy lysosomal pathway resulting in increased α-synuclein (α-syn) levels. Furthermore, elevated α-syn results in decreased GCase activity. Although the role of α-syn in PD remains unclear, evidence indicates that aggregated α-syn fibrils are a pathogenic species in PD, passing between neurons and inducing endogenous native α-syn to aggregate; spreading pathology through the brain. We have investigated if preformed α-syn fibrils (PFFs) impair GCase activity in mouse cortical neurons and differentiated dopaminergic cells, and whether GCase deficiency in these models increased the transfer of α-syn pathology to naïve cells. Neurons treated with PFFs induced endogenous α-syn to become insoluble and phosphorylated at Ser129 to a greater extent than monomeric α-syn-treatment. PFFs, but not monomeric α-syn, inhibited lysosomal GCase activity in these cells and induced the unfolded protein response. Neurons in which GCase was inhibited by conduritol β-epoxide did not increase the amount of insoluble monomeric α-syn or its phosphorylation status. Instead the release of α-syn fibrils from GCase deficient cells was significantly increased. Co-culture studies showed that the transfer of α-syn pathology to naïve cells was greater from GCase deficient cells. This study suggests that GCase deficiency increases the spread of α-syn pathology and likely contributes to the earlier age of onset and increased cognitive decline associated with GBA-PD.

Topics: Aging; alpha-Synuclein; Animals; Autophagy; Brain; Disease Models, Animal; Gaucher Disease; Glucosylceramidase; Humans; Lysosomes; Mice; Mutation; Neurons; Parkinson Disease; Phosphorylation; Synucleinopathies

Gaucher disease (GD) patients and carriers of GD mutations have a higher propensity to develop Parkinson's disease (PD) in comparison to the non-GD population. This implies that mutant GBA1 allele is a predisposing factor for the development of PD. One of the major characteristics of PD is the presence of oligomeric α-synuclein-positive inclusions known as Lewy bodies in the dopaminergic neurons localized to the substantia nigra pars compacta. In the present study we tested whether presence of human mutant GCase leads to accumulation and aggregation of α-synuclein in two models: in SHSY5Y neuroblastoma cells endogenously expressing α-synuclein and stably transfected with human GCase variants, and in Drosophila melanogaster co-expressing normal human α-synuclein and mutant human GCase. Our results showed that heterologous expression of mutant, but not WT, human GCase in SHSY5Y cells, led to a significant stabilization of α-synuclein and to its aggregation. In parallel, there was also a significant stabilization of mutant, but not WT, GCase. Co-expression of human α-synuclein and human mutant GCase in the dopaminergic cells of flies initiated α-synuclein aggregation, earlier death of these cells and significantly shorter life span, compared with flies expressing α-synuclein or mutant GCase alone. Taken together, our results strongly indicate that human mutant GCase contributes to accumulation and aggregation of α-synuclein. In the fly, this aggregation leads to development of more severe parkinsonian signs in comparison to flies expressing either mutant GCase or α-synuclein alone.

Topics: alpha-Synuclein; Animals; Animals, Genetically Modified; Disease Models, Animal; Dopaminergic Neurons; Drosophila melanogaster; Gaucher Disease; Gene Expression Regulation; Glucosylceramidase; Heterozygote; Humans; Lewy Bodies; Lysosomes; Mutation; Parkinson Disease; Pars Compacta; Protein Aggregation, Pathological

Heterozygous mutations in glucocerebrosidase 1 (GBA1) are a major genetic risk factor for Parkinson's disease and Dementia with Lewy bodies. Mutations in GBA1 leads to GBA1 enzyme deficiency, and GBA1-associated parkinsonism has an earlier age of onset and more progressive parkinsonism. To investigate a potential influence of GBA1 deficiency caused by mutations in GBA1 on the disease progression of PD, GBA1 mice carrying D409H knock-in mutation were crossbred with the human A53T (hA53T) α-synuclein transgenic mice. Here, we show that GBA1 enzyme activity plays a significant role in the hA53T α-synuclein induced α-synucleinopathy. The expression of D409H GBA1 markedly shortens the lifespan of hA53T α-synuclein transgenic mice. Moreover, D409H GBA1 expression exacerbates the formation of insoluble aggregates of α-synuclein, glial activation, neuronal degeneration, and motor abnormalities in the hA53T α-synuclein transgenic mice. Interestingly, the expression of D409H GBA1 results in the loss of dopaminergic neurons in the substantia nigra pars compacta of hA53T transgenic mice. Taken together, these results indicate that GBA1 deficiency due to D409H mutation affects the disease onset and course in hA53T α-synuclein transgenic mice. Therefore, strategies aimed to maintain GBA1 enzyme activity could be employed to develop an effective novel therapy for GBA1 linked-PD and related α-synucleinopathies.

Topics: alpha-Synuclein; Animals; Aspartic Acid; Brain Stem; Disease Progression; Endoplasmic Reticulum Stress; Gaucher Disease; Gene Expression Regulation; Glial Fibrillary Acidic Protein; Glucosylceramidase; Histidine; Humans; Longevity; Mice; Mice, Inbred C57BL; Mice, Transgenic; Motor Activity; Mutation; Tyrosine 3-Monooxygenase

Common forms of Parkinson's disease have long been described as idiopathic, with no single penetrant genetic factor capable of influencing disease aetiology. Recent genetic studies indicate a clear association of variants within several lysosomal genes as risk factors for idiopathic Parkinson's disease. The emergence of novel variants suggest that the aetiology of idiopathic Parkinson's disease may be explained by the interaction of several partially penetrant mutations that, while seemingly complex, all appear to converge on cellular clearance pathways. These newly evolving data are consistent with mechanistic studies linking α-synuclein toxicity to lysosomal abnormalities, and indicate that idiopathic Parkinson's disease resembles features of Mendelian lysosomal storage disorders at a genetic and biochemical level. These findings offer novel pathways to exploit for the development of disease-altering therapies for idiopathic Parkinson's disease that target specific components of the lysosomal system.

Topics: alpha-Synuclein; Gaucher Disease; Humans; Lysosomal Storage Diseases; Lysosomes; Mitochondria; Parkinson Disease; Risk Factors

Mutations in the GBA1 gene encoding the lysosomal enzyme glucocerebrosidase (GBA1) are important risk factors for Parkinson's disease (PD). In vitro, altered GBA1 activity promotes alpha-synuclein accumulation whereas elevated levels of alpha-synuclein compromise GBA1 function, thus supporting a pathogenic mechanism in PD. However, the mechanisms by which GBA1 deficiency is linked to increased risk of PD remain elusive, partially because of lack of aged models of GBA1 deficiency. As knocking-out GBA1 in the entire brain induces massive neurodegeneration and early death, we generated a mouse model of GBA1 deficiency amenable to investigate the long-term consequences of compromised GBA1 function in dopaminergic neurons. DAT-Cre and GBA1-floxed mice were bred to obtain selective homozygous disruption of GBA1 in midbrain dopamine neurons (DAT-GBA1-KO). Mice were followed for motor function, neuronal survival, alpha-synuclein phosphorylation and glial activation. Susceptibility to nigral viral vector-mediated overexpression of mutated (A53T) alpha-synuclein was assessed. Despite loss of GBA1 and substrate accumulation, DAT-GBA1-KO mice displayed normal motor performances and preserved dopaminergic neurons despite robust microglial activation in the substantia nigra, without accumulation of endogenous alpha-synuclein with respect to wild-type mice. Lysosomal function was only marginally affected. Screening of micro-RNAs linked to the regulation of GBA1, alpha-synuclein or neuroinflammation did not reveal significant alterations. Viral-mediated overexpression of A53T-alpha-synuclein yielded similar neurodegeneration in DAT-GBA1-KO mice and wild-type mice. These results indicate that loss of GBA1 function in mouse dopaminergic neurons is not critical for alpha-synuclein accumulation or neurodegeneration and suggest the involvement of GBA1 deficiency in other cell types as a potential mechanism.

Topics: alpha-Synuclein; Animals; Brain; Dopaminergic Neurons; Gaucher Disease; Genetic Vectors; Glucosylceramidase; Mesencephalon; Mice; Mice, Knockout; Microglia; Models, Animal; Parkinson Disease; Substantia Nigra

Several observations suggest that disturbed homeostasis of α-Synuclein (α-Syn) may provide a link between Gaucher disease (GD) and Parkinson's disease (PD). We recently reported increased dimerization of α-Syn in the red blood cell (RBC) membrane of patients with GD. Several studies indicate a crucial relationship between lipids, oxidative stress and α-Syn status. Here we investigated the relationship between the observed increased dimerization of α-Syn in the cell membranes of RBCs, cells devoid of lysosomes and lacking lysosomal enzyme synthesis, and the lipid abnormalities and oxidative stress already described in GD. Correlation studies showed that in GD the α-Syn dimer/monomer ratio is positively correlated with the levels of glucosylceramide (GlcCer) and the glucosylceramide/ceramide (GlcCer/Cer) ratio and negatively with the levels of malonyldialdehyde (MDA) and plasmalogens. In conclusion, we have shown that the increased tendency of α-Syn to form dimers in the RBC membrane of patients with GD, is correlated with both the level of lipids, including GlcCer, the primary lipid abnormality in GD, and the increased oxidative stress observed in this disorder. The study of other tissues, and in particular brain, will be important in order to elucidate the significance of these findings regarding the link between GD and PD.

Topics: Adolescent; Adult; Aged; alpha-Synuclein; Case-Control Studies; Ceramides; Child, Preschool; Dimerization; Erythrocytes; Gaucher Disease; Humans; Lipids; Malondialdehyde; Middle Aged; Oxidative Stress; Plasmalogens; Young Adult

Mutations in the glucosidase, beta, acid (GBA1) gene cause Gaucher's disease, and are the most common genetic risk factor for Parkinson's disease (PD) and dementia with Lewy bodies (DLB) excluding variants of low penetrance. Because α-synuclein-containing neuronal aggregates are a defining feature of PD and DLB, it is widely believed that mutations in GBA1 act by enhancing α-synuclein toxicity. To explore this hypothesis, we deleted the Drosophila GBA1 homolog, dGBA1b, and compared the phenotypes of dGBA1b mutants in the presence and absence of α-synuclein expression. Homozygous dGBA1b mutants exhibit shortened lifespan, locomotor and memory deficits, neurodegeneration, and dramatically increased accumulation of ubiquitinated protein aggregates that are normally degraded through an autophagic mechanism. Ectopic expression of human α-synuclein in dGBA1b mutants resulted in a mild enhancement of dopaminergic neuron loss and increased α-synuclein aggregation relative to controls. However, α-synuclein expression did not substantially enhance other dGBA1b mutant phenotypes. Our findings indicate that dGBA1b plays an important role in the metabolism of protein aggregates, but that the deleterious consequences of mutations in dGBA1b are largely independent of α-synuclein. Future work with dGBA1b mutants should reveal the mechanism by which mutations in dGBA1b lead to accumulation of protein aggregates, and the potential influence of this protein aggregation on neuronal integrity.

Topics: alpha-Synuclein; Animals; Dopaminergic Neurons; Drosophila melanogaster; Gaucher Disease; Glucosylceramidase; Humans; Lysosomes; Nerve Degeneration; Parkinson Disease; Phenotype; Protein Aggregation, Pathological

Mutations in GBA1, the gene encoding glucocerebrosidase, are associated with an enhanced risk of developing synucleinopathies such as Parkinson's disease (PD) and dementia with Lewy bodies. A higher prevalence and increased severity of motor and non-motor symptoms is observed in PD patients harboring mutant GBA1 alleles, suggesting a link between the gene or gene product and disease development. Interestingly, PD patients without mutations in GBA1 also exhibit lower levels of glucocerebrosidase activity in the central nervous system (CNS), implicating this lysosomal enzyme in disease pathogenesis. Here, we investigated whether modulation of glucocerebrosidase activity in murine models of synucleinopathy (expressing wild type Gba1) affected α-synuclein accumulation and behavioral phenotypes. Partial inhibition of glucocerebrosidase activity in PrP-A53T-SNCA mice using the covalent inhibitor conduritol-B-epoxide induced a profound increase in soluble α-synuclein in the CNS and exacerbated cognitive and motor deficits. Conversely, augmenting glucocerebrosidase activity in the Thy1-SNCA mouse model of PD delayed the progression of synucleinopathy. Adeno-associated virus-mediated expression of glucocerebrosidase in the Thy1-SNCA mouse striatum led to decrease in the levels of the proteinase K-resistant fraction of α-synuclein, amelioration of behavioral aberrations and protection from loss of striatal dopaminergic markers. These data indicate that increasing glucocerebrosidase activity can influence α-synuclein homeostasis, thereby reducing the progression of synucleinopathies. This study provides robust in vivo evidence that augmentation of CNS glucocerebrosidase activity is a potential therapeutic strategy for PD, regardless of the mutation status of GBA1.

Topics: alpha-Synuclein; Animals; Cognition; Disease Models, Animal; Dopamine; Gaucher Disease; Gene Expression; Glucosylceramidase; Humans; Mice; Motor Activity; Mutation; Parkinson Disease

Glucocerebrosidase (GBA1) gene mutations increase the risk of Parkinson disease (PD). While the cellular mechanisms associating GBA1 mutations and PD are unknown, loss of the glucocerebrosidase enzyme (GCase) activity, inhibition of autophagy and increased α-synuclein levels have been implicated. Here we show that autophagy lysosomal reformation (ALR) is compromised in cells lacking functional GCase. ALR is a cellular process controlled by mTOR which regenerates functional lysosomes from autolysosomes formed during macroautophagy. A decrease in phopho-S6K levels, a marker of mTOR activity, was observed in models of GCase deficiency, including primary mouse neurons and the PD patient derived fibroblasts with GBA1 mutations, suggesting that ALR is compromised. Importantly Rab7, a GTPase crucial for endosome-lysosome trafficking and ALR, accumulated in GCase deficient cells, supporting the notion that lysosomal recycling is impaired. Recombinant GCase treatment reversed ALR inhibition and lysosomal dysfunction. Moreover, ALR dysfunction was accompanied by impairment of macroautophagy and chaperone-mediated autophagy, increased levels of total and phosphorylated (S129) monomeric α-synuclein, evidence of amyloid oligomers and increased α-synuclein release. Concurrently, we found increased cholesterol and altered glucosylceramide homeostasis which could compromise ALR. We propose that GCase deficiency in PD inhibits lysosomal recycling. Consequently neurons are unable to maintain the pool of mature and functional lysosomes required for the autophagic clearance of α-synuclein, leading to the accumulation and spread of pathogenic α-synuclein species in the brain. Since GCase deficiency and lysosomal dysfunction occur with ageing and sporadic PD pathology, the decrease in lysosomal reformation may be a common feature in PD.

Topics: alpha-Synuclein; Animals; Autophagy; Brain; Fibroblasts; Gaucher Disease; Glucosylceramidase; Humans; Lysosomes; Mice; Mutation; Neurons; Parkinson Disease; rab GTP-Binding Proteins; rab7 GTP-Binding Proteins

Among the known genetic risk factors for Parkinson disease, mutations in GBA1, the gene responsible for the lysosomal disorder Gaucher disease, are the most common. This genetic link has directed attention to the role of the lysosome in the pathogenesis of parkinsonism. To study how glucocerebrosidase impacts parkinsonism and to evaluate new therapeutics, we generated induced human pluripotent stem cells from four patients with Type 1 (non-neuronopathic) Gaucher disease, two with and two without parkinsonism, and one patient with Type 2 (acute neuronopathic) Gaucher disease, and differentiated them into macrophages and dopaminergic neurons. These cells exhibited decreased glucocerebrosidase activity and stored the glycolipid substrates glucosylceramide and glucosylsphingosine, demonstrating their similarity to patients with Gaucher disease. Dopaminergic neurons from patients with Type 2 and Type 1 Gaucher disease with parkinsonism had reduced dopamine storage and dopamine transporter reuptake. Levels of α-synuclein, a protein present as aggregates in Parkinson disease and related synucleinopathies, were selectively elevated in neurons from the patients with parkinsonism or Type 2 Gaucher disease. The cells were then treated with NCGC607, a small-molecule noninhibitory chaperone of glucocerebrosidase identified by high-throughput screening and medicinal chemistry structure optimization. This compound successfully chaperoned the mutant enzyme, restored glucocerebrosidase activity and protein levels, and reduced glycolipid storage in both iPSC-derived macrophages and dopaminergic neurons, indicating its potential for treating neuronopathic Gaucher disease. In addition, NCGC607 reduced α-synuclein levels in dopaminergic neurons from the patients with parkinsonism, suggesting that noninhibitory small-molecule chaperones of glucocerebrosidase may prove useful for the treatment of Parkinson disease.. Because GBA1 mutations are the most common genetic risk factor for Parkinson disease, dopaminergic neurons were generated from iPSC lines derived from patients with Gaucher disease with and without parkinsonism. These cells exhibit deficient enzymatic activity, reduced lysosomal glucocerebrosidase levels, and storage of glucosylceramide and glucosylsphingosine. Lines generated from the patients with parkinsonism demonstrated elevated levels of α-synuclein. To reverse the observed phenotype, the neurons were treated with a novel noninhibitory glucocerebrosidase chaperone, which successfully restored glucocerebrosidase activity and protein levels and reduced glycolipid storage. In addition, the small-molecule chaperone reduced α-synuclein levels in dopaminergic neurons, indicating that chaperoning glucocerebrosidase to the lysosome may provide a novel therapeutic strategy for both Parkinson disease and neuronopathic forms of Gaucher disease.

Topics: Acetanilides; alpha-Synuclein; Benzamides; beta-Glucosidase; Catecholamines; Cell Differentiation; Dopaminergic Neurons; Female; Gaucher Disease; Glucosylceramidase; Glucosylceramides; Glycolipids; Humans; Induced Pluripotent Stem Cells; Inhibitory Postsynaptic Potentials; Lysosomal-Associated Membrane Protein 2; Macrophages; Male; Membrane Potentials; Mutation; Parkinsonian Disorders; Patch-Clamp Techniques

To study the neuronal deficits in neuronopathic Gaucher Disease (nGD), the chronological behavioral profiles and the age of onset of brain abnormalities were characterized in a chronic nGD mouse model (9V/null). Progressive accumulation of glucosylceramide (GC) and glucosylsphingosine (GS) in the brain of 9V/null mice were observed at as early as 6 and 3 months of age for GC and GS, respectively. Abnormal accumulation of α-synuclein was present in the 9V/null brain as detected by immunofluorescence and Western blot analysis. In a repeated open-field test, the 9V/null mice (9 months and older) displayed significantly less environmental habituation and spent more time exploring the open-field than age-matched WT group, indicating the onset of short-term spatial memory deficits. In the marble burying test, the 9V/null group had a shorter latency to initiate burying activity at 3 months of age, whereas the latency increased significantly at ≥12 months of age; 9V/null females buried significantly more marbles to completion than the WT group, suggesting an abnormal response to the instinctive behavior and an abnormal activity in non-associative anxiety-like behavior. In the conditional fear test, only the 9V/null males exhibited a significant decrease in response to contextual fear, but both genders showed less response to auditory-cued fear compared to age- and gender-matched WT at 12 months of age. These results indicate hippocampus-related emotional memory defects. Abnormal gait emerged in 9V/null mice with wider front-paw and hind-paw widths, as well as longer stride in a gender-dependent manner with different ages of onset. Significantly higher liver- and spleen-to-body weight ratios were detected in 9V/null mice with different ages of onsets. These data provide temporal evaluation of neurobehavioral dysfunctions and brain pathology in 9V/null mice that can be used for experimental designs to evaluate novel therapies for nGD.

Topics: Acoustic Stimulation; Aging; alpha-Synuclein; Animals; Behavior, Animal; Conditioning, Psychological; Disease Models, Animal; Disease Progression; Exploratory Behavior; Fear; Female; Gait; Gaucher Disease; Glucosylceramidase; Glucosylceramides; Hippocampus; Male; Memory Disorders; Mice; Psychosine; Sex Factors; Spatial Memory

Topics: Alleles; alpha-Synuclein; Animals; Gaucher Disease; Glucosylceramidase; Glucosylceramides; Humans; Lysosomes; Mice; Models, Biological; Mutation; Parkinson Disease; Uncertainty

Topics: alpha-Synuclein; Cognition; Gaucher Disease; Glucosylceramidase; Humans; Mutation; Parkinson Disease

Gaucher disease is caused by mutations in the glucocerebrosidase 1 gene that result in deficiency of the lysosomal enzyme glucocerebrosidase. Both homozygous and heterozygous glucocerebrosidase 1 mutations confer an increased risk for developing Parkinson disease. Current estimates indicate that 10 to 25% of Parkinson patients carry glucocerebrosidase 1 mutations. Ambroxol is a small molecule chaperone that has been shown to increase glucocerebrosidase activity in vitro. This study investigated the effect of ambroxol treatment on glucocerebrosidase activity and on α-synuclein and phosphorylated α-synuclein protein levels in mice.. Mice were treated with ambroxol for 12 days. After the treatment, glucocerebrosidase activity was measured in the mouse brain lysates. The brain lysates were also analyzed for α-synuclein and phosphorylated α-synuclein protein levels.. Ambroxol treatment resulted in increased brain glucocerebrosidase activity in (1) wild-type mice, (2) transgenic mice expressing the heterozygous L444P mutation in the murine glucocerebrosidase 1 gene, and (3) transgenic mice overexpressing human α-synuclein. Furthermore, in the mice overexpressing human α-synuclein, ambroxol treatment decreased both α-synuclein and phosphorylated α-synuclein protein levels.. Our work supports the proposition that ambroxol should be further investigated as a potential novel disease-modifying therapy for treatment of Parkinson disease and neuronopathic Gaucher disease to increase glucocerebrosidase activity and decrease α-synuclein and phosphorylated α-synuclein protein levels. Ann Neurol 2016;80:766-775.

Topics: alpha-Synuclein; Ambroxol; Animals; Brain; Disease Models, Animal; Expectorants; Gaucher Disease; Glucosylceramidase; Humans; Mice; Mice, Transgenic; Parkinson Disease

Mutations in glucocerebrosidase (GCase), the enzyme deficient in Gaucher disease, are a common genetic risk factor for the development of Parkinson disease and related disorders, implicating the role of this lysosomal hydrolase in the disease etiology. A specific physical interaction exists between the Parkinson disease-related protein α-synuclein (α-syn) and GCase both in solution and on the lipid membrane, resulting in efficient enzyme inhibition. Here, neutron reflectometry was employed as a first direct structural characterization of GCase and α-syn·GCase complex on a sparsely-tethered lipid bilayer, revealing the orientation of the membrane-bound GCase. GCase binds to and partially inserts into the bilayer with its active site most likely lying just above the membrane-water interface. The interaction was further characterized by intrinsic Trp fluorescence, circular dichroism, and surface plasmon resonance spectroscopy. Both Trp fluorescence and neutron reflectometry results suggest a rearrangement of loops surrounding the catalytic site, where they extend into the hydrocarbon chain region of the outer leaflet. Taking advantage of contrasting neutron scattering length densities, the use of deuterated α-syn versus protiated GCase showed a large change in the membrane-bound structure of α-syn in the complex. We propose a model of α-syn·GCase on the membrane, providing structural insights into inhibition of GCase by α-syn. The interaction displaces GCase away from the membrane, possibly impeding substrate access and perturbing the active site. GCase greatly alters membrane-bound α-syn, moving helical residues away from the bilayer, which could impact the degradation of α-syn in the lysosome where these two proteins interact.

Topics: alpha-Synuclein; Gaucher Disease; Glucosylceramidase; Humans; Lipid Bilayers; Mutation; Neutron Diffraction; Parkinson Disease; Protein Binding; Spectrometry, Fluorescence; Surface Plasmon Resonance; Tryptophan

Mutations in the gene for the lysosomal enzyme glucocerebrosidase (GCase) cause Gaucher disease and are the most common risk factor for Parkinson disease (PD). Analytical ultracentrifugation of 8 μM GCase shows equilibrium between monomer and dimer forms. However, in the presence of its co-factor saposin C (Sap C), only monomer GCase is seen. Isothermal calorimetry confirms that Sap C associates with GCase in solution in a 1:1 complex (Kd = 2.1 ± 1.1 μM). Saturation cross-transfer NMR determined that the region of Sap C contacting GCase includes residues 63-66 and 74-76, which is distinct from the region known to enhance GCase activity. Because α-synuclein (α-syn), a protein closely associated with PD etiology, competes with Sap C for GCase binding, its interaction with GCase was also measured by ultracentrifugation and saturation cross-transfer. Unlike Sap C, binding of α-syn to GCase does not affect multimerization. However, adding α-syn reduces saturation cross-transfer from Sap C to GCase, confirming displacement. To explore where Sap C might disrupt multimeric GCase, GCase x-ray structures were analyzed using the program PISA, which predicted stable dimer and tetramer forms. For the most frequently predicted multimer interface, the GCase active sites are partially buried, suggesting that Sap C might disrupt the multimer by binding near the active site.

Topics: alpha-Synuclein; Catalytic Domain; Gaucher Disease; Glucosylceramidase; Humans; Models, Molecular; Nuclear Magnetic Resonance, Biomolecular; Parkinson Disease; Protein Multimerization; Protein Stability; Saposins

Gaucher disease (GD) is caused by insufficient activity of acid β-glucosidase (GCase) resulting from mutations in GBA1. To understand the pathogenesis of the neuronopathic GD, induced pluripotent stem cells (iPSCs) were generated from fibroblasts isolated from three GD type 2 (GD2) and 2 unaffected (normal and GD carrier) individuals. The iPSCs were converted to neural precursor cells (NPCs) which were further differentiated into neurons. Parental GD2 fibroblasts as well as iPSCs, NPCs, and neurons had similar degrees of GCase deficiency. Lipid analyses showed increases of glucosylsphingosine and glucosylceramide in the GD2 cells. In addition, GD2 neurons showed increased α-synuclein protein compared to control neurons. Whole cell patch-clamping of the GD2 and control iPSCs-derived neurons demonstrated excitation characteristics of neurons, but intriguingly, those from GD2 exhibited consistently less negative resting membrane potentials with various degree of reduction in action potential amplitudes, sodium and potassium currents. Culture of control neurons in the presence of the GCase inhibitor (conduritol B epoxide) recapitulated these findings, providing a functional link between decreased GCase activity in GD and abnormal neuronal electrophysiological properties. To our knowledge, this study is first to report abnormal electrophysiological properties in GD2 iPSC-derived neurons that may underlie the neuropathic phenotype in Gaucher disease.

Topics: alpha-Synuclein; Cells, Cultured; Fibroblasts; Gaucher Disease; Glucosylceramidase; Glucosylceramides; Humans; Induced Pluripotent Stem Cells; Membrane Potentials; Neural Stem Cells; Neurogenesis; Neurons; Psychosine

Homozygous mutations in the glucocerebrosidase (GBA) gene result in Gaucher disease (GD), the most common lysosomal storage disease. Recent genetic studies have revealed that GBA mutations confer a strong risk for sporadic Parkinson's disease (PD). To investigate how GBA mutations cause PD, we generated GBA nonsense mutant (GBA-/-) medaka that are completely deficient in glucocerebrosidase (GCase) activity. In contrast to the perinatal death in humans and mice lacking GCase activity, GBA-/- medaka survived for months, enabling analysis of the pathological progression. GBA-/- medaka displayed the pathological phenotypes resembling human neuronopathic GD including infiltration of Gaucher cell-like cells into the brains, progressive neuronal loss, and microgliosis. Detailed pathological findings represented lysosomal abnormalities in neurons and alpha-synuclein (α-syn) accumulation in axonal swellings containing autophagosomes. Unexpectedly, disruption of α-syn did not improve the life span, formation of axonal swellings, neuronal loss, or neuroinflammation in GBA-/- medaka. Taken together, the present study revealed GBA-/- medaka as a novel neuronopathic GD model, the pahological mechanisms of α-syn accumulation caused by GCase deficiency, and the minimal contribution of α-syn to the pathogenesis of neuronopathic GD.

Topics: alpha-Synuclein; Animals; Axons; Disease Models, Animal; Gaucher Disease; Glucosylceramidase; Oryzias; Phagosomes

The link between Parkinson's disease (PD) and Gaucher disease (GD), the most common lysosomal storage disease associated with loss of glucocerebrosidase (GBA) activity, can be explained by abnormal accumulation of oligomeric alpha-synuclein (α-Syn) species resulting from mutations in the GBA gene. However, in GD, the relationship between GBA activity and α-Syn accumulation in biological fluids has not been investigated.. We analyzed plasma oligomeric α-Syn levels, leucocyte GBA activity, and plasma chitotriosidase activity in 21 patients with GD.. Negative correlation between plasma oligomeric α-Syn levels, and leucocyte GBA activity was observed in patients with GD (R(2)  = 0.487; P < 0.001).. The decrease in GBA activity may influence α-Syn oligomerization, explaining the high risk of PD development in GD patients. © 2015 International Parkinson and Movement Disorder Society.

Topics: Aged; alpha-Synuclein; Child; Child, Preschool; Female; Gaucher Disease; Glucosylceramidase; Humans; Infant; Male

Autosomal recessively inherited glucocerebrosidase 1 (GBA1) mutations cause the lysosomal storage disorder Gaucher's disease (GD). Heterozygous GBA1 mutations (GBA1(+/-)) are the most common risk factor for Parkinson's disease (PD). Previous studies typically focused on the interaction between the reduction of glucocerebrosidase (enzymatic) activity in GBA1(+/-) carriers and alpha-synuclein-mediated neurotoxicity. However, it is unclear whether other mechanisms also contribute to the increased risk of PD in GBA1(+/-) carriers. The zebrafish genome does not contain alpha-synuclein (SNCA), thus providing a unique opportunity to study pathogenic mechanisms unrelated to alpha-synuclein toxicity. Here we describe a mutant zebrafish line created by TALEN genome editing carrying a 23 bp deletion in gba1 (gba1(c.1276_1298del)), the zebrafish orthologue of human GBA1. Marked sphingolipid accumulation was already detected at 5 days post-fertilization with accompanying microglial activation and early, sustained up-regulation of miR-155, a master regulator of inflammation. gba1(c.1276_1298del) mutant zebrafish developed a rapidly worsening phenotype from 8 weeks onwards with striking reduction in motor activity by 12 weeks. Histopathologically, we observed marked Gaucher cell invasion of the brain and other organs. Dopaminergic neuronal cell count was normal through development but reduced by >30% at 12 weeks in the presence of ubiquitin-positive, intra-neuronal inclusions. This gba1(c.1276_1298del) zebrafish line is the first viable vertebrate model sharing key pathological features of GD in both neuronal and non-neuronal tissue. Our study also provides evidence for early microglial activation prior to alpha-synuclein-independent neuronal cell death in GBA1 deficiency and suggests upregulation of miR-155 as a common denominator across different neurodegenerative disorders.

Topics: alpha-Synuclein; Animals; Cell Death; Disease Models, Animal; Gaucher Disease; Glucosylceramidase; Microglia; MicroRNAs; Neurons; Sequence Deletion; Up-Regulation; Zebrafish; Zebrafish Proteins

Loss-of-function mutations in the gene encoding GBA (glucocerebrosidase, β, acid), the enzyme deficient in the lysosomal storage disorder Gaucher disease, elevate the risk of Parkinson disease (PD), which is characterized by the misprocessing of SNCA/α-synuclein. However, the mechanistic link between GBA deficiency and SNCA accumulation remains poorly understood. In this study, we found that loss of GBA function resulted in increased levels of SNCA via inhibition of the autophagic pathway in SK-N-SH neuroblastoma cells, primary rat cortical neurons, or the rat striatum. Furthermore, expression of the autophagy pathway component BECN1 was downregulated as a result of the GBA knockdown-induced decrease in glucocerebrosidase activity. Most importantly, inhibition of autophagy by loss of GBA function was associated with PPP2A (protein phosphatase 2A) inactivation via Tyr307 phosphorylation. C2-ceramide (C2), a PPP2A agonist, activated autophagy in GBA-silenced cells, while GBA knockdown-induced SNCA accumulation was reversed by C2 or rapamycin (an autophagy inducer), suggesting that PPP2A plays an important role in the GBA knockdown-mediated inhibition of autophagy. These findings demonstrate that loss of GBA function may contribute to SNCA accumulation through inhibition of autophagy via PPP2A inactivation, thereby providing a mechanistic basis for the increased PD risk associated with GBA deficiency.

Topics: alpha-Synuclein; Animals; Autophagy; Gaucher Disease; Gene Expression; Glucosylceramidase; Humans; Lysosomes; Mice, Transgenic; Mutation; Neurons; Parkinson Disease; Protein Phosphatase 2; Rats

Lysosomal dysfunction has been implicated both pathologically and genetically in neurodegenerative disorders, such as Alzheimer's disease and Parkinson's disease (PD). Lysosomal gene deficiencies cause lysosomal storage disorders, many of which involve neurodegeneration. Heterozygous mutations of some of these genes, such as GBA1, are associated with PD. CTSD is the gene encoding Cathepsin D (CTSD), a lysosomal protein hydrolase, and homozygous CTSD deficiency results in neuronal ceroid-lipofuscinosis, which is characterized by the early onset, progressive neurodegeneration. CTSD deficiency was also associated with deposition of α-synuclein aggregates, the hallmark of PD. However, whether partial deficiency of CTSD has a role in the late onset progressive neurodegenerative disorders, including PD, remains unknown. Here, we generated cell lines harboring heterozygous nonsense mutations in CTSD with genomic editing using the zinc finger nucleases. Heterozygous mutation in CTSD resulted in partial loss of CTSD activity, leading to reduced lysosomal activity. The CTSD mutation also resulted in increased accumulation of intracellular α-synuclein aggregates and the secretion of the aggregates. When α-synuclein was introduced in the media, internalized α-synuclein aggregates accumulated at higher levels in CTSD+/- cells than in the wild-type cells. Consistent with these results, transcellular transmission of α-synuclein aggregates was increased in CTSD+/- cells. The increased transmission of α-synuclein aggregates sustained during the successive passages of CTSD+/- cells. These results suggest that partial loss of CTSD activity is sufficient to cause a reduction in lysosomal function, which in turn leads to α-synuclein aggregation and propagation of the aggregates.

Topics: alpha-Synuclein; Base Sequence; Cathepsin D; Cell Line, Tumor; Codon, Nonsense; Gaucher Disease; Haploinsufficiency; Humans; Lysosomes; Protein Aggregates; Protein Transport

Clinical, epidemiological and experimental studies confirm a connection between the common degenerative movement disorder Parkinson's disease (PD) that affects over 1 million individuals, and Gaucher disease, the most prevalent lysosomal storage disorder. Recently, human imaging studies have implicated impaired striatal dopaminergic neurotransmission in early PD pathogenesis in the context of Gaucher disease mutations, but the underlying mechanisms have yet to be characterized. In this report we describe and characterize two novel long-lived transgenic mouse models of Gba deficiency, along with a subchronic conduritol-ß-epoxide (CBE) exposure paradigm. All three murine models revealed striking glial activation within nigrostriatal pathways, accompanied by abnormal α-synuclein accumulation. Importantly, the CBE-induced, pharmacological Gaucher mouse model replicated this change in dopamine neurotransmission, revealing a markedly reduced evoked striatal dopamine release (approximately 2-fold) that indicates synaptic dysfunction. Other changes in synaptic plasticity markers, including microRNA profile and a 24.9% reduction in post-synaptic density size, were concomitant with diminished evoked dopamine release following CBE exposure. These studies afford new insights into the mechanisms underlying the Parkinson's-Gaucher disease connection, and into the physiological impact of related abnormal α-synuclein accumulation and neuroinflammation on nigrostriatal dopaminergic neurotransmission.

Topics: alpha-Synuclein; Animals; Corpus Striatum; Disease Models, Animal; Dopamine; Evoked Potentials, Motor; Female; Gaucher Disease; Glucosylceramidase; Humans; Inflammation; Inositol; Male; Mice; MicroRNAs; Mutation; Neuronal Plasticity; Parkinson Disease; Synapses; Synaptic Transmission

Gaucher disease, a prevalent lysosomal storage disease (LSD), is caused by insufficient activity of acid β-glucosidase (GCase) and the resultant glucosylceramide (GC)/glucosylsphingosine (GS) accumulation in visceral organs (Type 1) and the central nervous system (Types 2 and 3). Recent clinical and genetic studies implicate a pathogenic link between Gaucher and neurodegenerative diseases. The aggregation and inclusion bodies of α-synuclein with ubiquitin are present in the brains of Gaucher disease patients and mouse models. Indirect evidence of β-amyloid pathology promoting α-synuclein fibrillation supports these pathogenic proteins as a common feature in neurodegenerative diseases. Here, multiple proteins are implicated in the pathogenesis of chronic neuronopathic Gaucher disease (nGD). Immunohistochemical and biochemical analyses showed significant amounts of β-amyloid and amyloid precursor protein (APP) aggregates in the cortex, hippocampus, stratum and substantia nigra of the nGD mice. APP aggregates were in neuronal cells and colocalized with α-synuclein signals. A majority of APP co-localized with the mitochondrial markers TOM40 and Cox IV; a small portion co-localized with the autophagy proteins, P62/LC3, and the lysosomal marker, LAMP1. In cultured wild-type brain cortical neural cells, the GCase-irreversible inhibitor, conduritol B epoxide (CBE), reproduced the APP/α-synuclein aggregation and the accumulation of GC/GS. Ultrastructural studies showed numerous larger-sized and electron-dense mitochondria in nGD cerebral cortical neural cells. Significant reductions of mitochondrial adenosine triphosphate production and oxygen consumption (28-40%) were detected in nGD brains and in CBE-treated neural cells. These studies implicate defective GCase function and GC/GS accumulation as risk factors for mitochondrial dysfunction and the multi-proteinopathies (α-synuclein-, APP- and Aβ-aggregates) in nGD.

Topics: alpha-Synuclein; Amyloid beta-Protein Precursor; Animals; beta-Glucosidase; Cells, Cultured; Cerebral Cortex; Corpus Striatum; Disease Models, Animal; Enzyme Inhibitors; Gaucher Disease; Gene Expression Regulation; Hippocampus; Humans; Inositol; Lysosomal Membrane Proteins; Membrane Transport Proteins; Mice; Microtubule-Associated Proteins; Mitochondria; Mitochondrial Proteins; Neurons; Prostaglandin-Endoperoxide Synthases; Protein Aggregation, Pathological; Substantia Nigra

Topics: alpha-Synuclein; Ambroxol; Female; Fibroblasts; Gaucher Disease; Glucosylceramidase; Humans; Male; Mutation; Parkinson Disease

Mutations in β-glucocerebrosidase, the genetic defect in Gaucher disease (GD), are an important susceptibility factor for Parkinson disease (PD). A PD effector is α-synuclein (SNCA) hypothesized to selectively interact with β-glucocerebrosidase under lysosomal conditions. SNCA polymorphism rs356219 may be associated with early-age-onset PD, common among patients with GD+PD. The objective of this study was to ascertain rs356219 genotypes of GD+PD patients. All GD+PD patients at our Gaucher referral clinic were asked to participate. A GD-only sex-, age-, GD genotype-, and enzyme therapy (ERT)-matched control was found for each GD+PD participant. Student's t-test was used (p-value <0.05 as significant). There were 14 GD+PD patients: all Ashkenazi Jewish; 11 males (78.6%); mean (range) age diagnosed GD 34.2 (5-62) years; 50% N370S homozygous; mild to moderate GD; 3 asplenic and only these have osteonecrosis; 5 received ERT; mean age (range) diagnosed PD was 57.8 (43-70) years; first PD sign was tremor in 9 (64.3%); cognitive dysfunction in all. In GD+PD, frequency for AG+GG (9) was greater than AA (5); in GD only, there was equality (7). Odds Ratio risk for PD increases with number minor alleles: but not significantly greater among GD+PD than GD only; in aggregate, there was no difference between cohorts for frequency of minor alleles. The limitation of this study is few GD+PD, albeit virtually all the GD+PD cohort >500 adult GD patients in our clinic. Nonetheless, as a foray into potential genetic GD susceptibility for a synucleinopathy, this study suggests the need for collaboration to achieve larger sample size.

Topics: Aged; Aged, 80 and over; alpha-Synuclein; Case-Control Studies; Female; Gaucher Disease; Genetic Association Studies; Genetic Predisposition to Disease; Humans; Jews; Male; Middle Aged; Parkinson Disease; Polymorphism, Single Nucleotide

The involvement of the protein α-synuclein (SNCA) in the pathogenesis of Parkinson's disease is strongly supported by the facts that (i) missense and copy number mutations in the SNCA gene can cause inherited Parkinson's disease; and (ii) Lewy bodies in sporadic Parkinson's disease are largely composed of aggregated SNCA. Unaffected heterozygous carriers of Gaucher disease mutations have an increased risk for Parkinson's disease. As mutations in the GBA gene encoding glucocerebrosidase (GBA) are known to interfere with lysosomal protein degradation, GBA heterozygotes may demonstrate reduced lysosomal SNCA degradation, leading to increased steady-state SNCA levels and promoting its aggregation. We have created mouse models to investigate the interaction between GBA mutations and synucleinopathies. We investigated the rate of SNCA degradation in cultured primary cortical neurons from mice expressing wild-type mouse SNCA, wild-type human SNCA, or mutant A53T SNCA, in a background of either wild-type Gba or heterozygosity for the L444P GBA mutation associated with Gaucher disease. We also tested the effect of this Gaucher mutation on motor and enteric nervous system function in these transgenic animals. We found that human SNCA is stable, with a half-life of 61 h, and that the A53T mutation did not significantly affect its half-life. Heterozygosity for a naturally occurring Gaucher mutation, L444P, reduced GBA activity by 40%, reduced SNCA degradation and triggered accumulation of the protein in culture. This mutation also resulted in the exacerbation of motor and gastrointestinal deficits found in the A53T mouse model of Parkinson's disease. This study demonstrates that heterozygosity for a Gaucher disease-associated mutation in Gba interferes with SNCA degradation and contributes to its accumulation, and exacerbates the phenotype in a mouse model of Parkinson's disease.

Topics: alpha-Synuclein; Animals; Disease Models, Animal; Gaucher Disease; Gene Expression; Genotype; Glucosylceramidase; Heterozygote; Mice, 129 Strain; Mice, Transgenic; Mutation; Parkinson Disease; Phenotype

Topics: alpha-Synuclein; Animals; Brain; Gaucher Disease; Glucosylceramidase; Humans; Parkinsonian Disorders

To date, a plethora of studies have provided evidence favoring an association between Gaucher disease (GD) and Parkinson's disease (PD). GD, the most common lysosomal storage disorder, results from the diminished activity of the lysosomal enzyme β-glucocerebrosidase (GCase), caused by mutations in the β-glucocerebrosidase gene (GBA). Alpha-synuclein (ASYN), a presynaptic protein, has been strongly implicated in PD pathogenesis. ASYN may in part be degraded by the lysosomes and may itself aberrantly impact lysosomal function. Therefore, a putative link between deficient GCase and ASYN, involving lysosomal dysfunction, has been proposed to be responsible for the risk for PD conferred by GBA mutations. In this current work, we aimed to investigate the effects of pharmacological inhibition of GCase on ASYN accumulation/aggregation, as well as on lysosomal function, in differentiated SH-SY5Y cells and in primary neuronal cultures. Following profound inhibition of the enzyme activity, we did not find significant alterations in ASYN levels, or any changes in the clearance or formation of its oligomeric species. We further observed no significant impairment of the lysosomal degradation machinery. These findings suggest that additional interaction pathways together with aberrant GCase and ASYN must govern this complex relation between GD and PD.

Topics: alpha-Synuclein; Animals; Autophagy; Cell Differentiation; Cell Line; Gaucher Disease; Glucosylceramidase; Humans; Inositol; Lysosomes; Neurons; Parkinson Disease; Protein Multimerization; Rats

Topics: alpha-Synuclein; Alzheimer Disease; Animals; Brain; Female; Gaucher Disease; Glucosylceramidase; Humans; Lewy Body Disease; Male; Mutation; Parkinson Disease; Parkinsonian Disorders; Residence Characteristics

Mutations in the glucocerebrosidase (gba) gene cause Gaucher disease (GD), the most common lysosomal storage disorder, and increase susceptibility to Parkinson's disease (PD). While the clinical and pathological features of idiopathic PD and PD related to gba (PD-GBA) mutations are very similar, cellular mechanisms underlying neurodegeneration in each are unclear. Using a mouse model of neuronopathic GD, we show that autophagic machinery and proteasomal machinery are defective in neurons and astrocytes lacking gba. Markers of neurodegeneration--p62/SQSTM1, ubiquitinated proteins, and insoluble α-synuclein--accumulate. Mitochondria were dysfunctional and fragmented, with impaired respiration, reduced respiratory chain complex activities, and a decreased potential maintained by reversal of the ATP synthase. Thus a primary lysosomal defect causes accumulation of dysfunctional mitochondria as a result of impaired autophagy and dysfunctional proteasomal pathways. These data provide conclusive evidence for mitochondrial dysfunction in GD and provide insight into the pathogenesis of PD and PD-GBA.

Topics: Adaptor Proteins, Signal Transducing; alpha-Synuclein; Animals; Astrocytes; Autophagy; Cells, Cultured; Disease Models, Animal; Electron Transport; Gaucher Disease; Glucosylceramidase; Heat-Shock Proteins; Humans; Lysosomes; Mice; Mice, Knockout; Mitochondria; Mitochondrial Diseases; Neurons; Parkinson Disease; Sequestosome-1 Protein

Mutations of GBA1, the gene encoding glucocerebrosidase, represent a common genetic risk factor for developing the synucleinopathies Parkinson disease (PD) and dementia with Lewy bodies. PD patients with or without GBA1 mutations also exhibit lower enzymatic levels of glucocerebrosidase in the central nervous system (CNS), suggesting a possible link between the enzyme and the development of the disease. Previously, we have shown that early treatment with glucocerebrosidase can modulate α-synuclein aggregation in a presymptomatic mouse model of Gaucher-related synucleinopathy (Gba1(D409V/D409V)) and ameliorate the associated cognitive deficit. To probe this link further, we have now evaluated the efficacy of augmenting glucocerebrosidase activity in the CNS of symptomatic Gba1(D409V/D409V) mice and in a transgenic mouse model overexpressing A53T α-synuclein. Adeno-associated virus-mediated expression of glucocerebrosidase in the CNS of symptomatic Gba1(D409V/D409V) mice completely corrected the aberrant accumulation of the toxic lipid glucosylsphingosine and reduced the levels of ubiquitin, tau, and proteinase K-resistant α-synuclein aggregates. Importantly, hippocampal expression of glucocerebrosidase in Gba1(D409V/D409V) mice (starting at 4 or 12 mo of age) also reversed their cognitive impairment when examined using a novel object recognition test. Correspondingly, overexpression of glucocerebrosidase in the CNS of A53T α-synuclein mice reduced the levels of soluble α-synuclein, suggesting that increasing the glycosidase activity can modulate α-synuclein processing and may modulate the progression of α-synucleinopathies. Hence, increasing glucocerebrosidase activity in the CNS represents a potential therapeutic strategy for GBA1-related and non-GBA1-associated synucleinopathies, including PD.

Topics: alpha-Synuclein; Animals; Brain; Dependovirus; Disease Models, Animal; Gaucher Disease; Glucosylceramidase; Hippocampus; Humans; Memory; Mice; Mice, Transgenic; Parkinsonian Disorders; Protein Structure, Quaternary; Psychosine; tau Proteins

Gaucher disease (GD) patients and carriers of glucocerebrosidase mutations are at an increased risk for Parkinson's disease (PD). The presynaptic protein alpha-synuclein (AS) is linked to PD. In the current work we examined biochemical properties of AS in GD patients. We generated membrane-enriched lysates from erythrocytes of 27 patients with GD and 32 age- and sex-matched controls and performed Western immunoblotting with antibodies against AS. Levels of monomeric AS did not differ between GD patients and controls and did not change as a function of age. However, the ratio of dimeric to monomeric AS was significantly increased in GD patients, and showed a significant positive correlation with age. Therefore, two major risk factors for PD, aging and GD status, are associated with an increased AS dimer to monomer ratio in erythrocytes. This ratio needs to be validated in further studies as a potential biomarker for PD risk.

Topics: Adolescent; Adult; Aged; Aging; alpha-Synuclein; Case-Control Studies; Child; Child, Preschool; Erythrocytes; Female; Gaucher Disease; Humans; Infant; Infant, Newborn; Male; Middle Aged; Protein Multimerization; Young Adult

Mutations in the glucocerebrosidase gene (GBA) represent a significant risk factor for developing Parkinson disease (PD). We investigated the enzymatic activity of glucocerebrosidase (GCase) in PD brains carrying heterozygote GBA mutations (PD+GBA) and sporadic PD brains.. GCase activity was measured using a fluorescent assay in cerebellum, frontal cortex, putamen, amygdala, and substantia nigra of PD+GBA (n = 9-14) and sporadic PD brains (n = 12-14). Protein expression of GCase and other lysosomal proteins was determined by western blotting. The relation between GCase, α-synuclein, and mitochondria function was also investigated in vitro.. A significant decrease in GCase activity was observed in all PD+GBA brain areas except the frontal cortex. The greatest deficiency was in the substantia nigra (58% decrease; p < 0.01). GCase activity was also significantly decreased in the substantia nigra (33% decrease; p < 0.05) and cerebellum (24% decrease; p < 0.05) of sporadic PD brains. GCase protein expression was lower in PD+GBA and PD brains, whereas increased C/EBP homologous protein and binding immunoglobulin protein levels indicated that the unfolded protein response was activated. Elevated α-synuclein levels or PTEN-induced putative kinase 1 deficiency in cultured cells had a significant effect on GCase protein levels.. GCase deficiency in PD brains with GBA mutations is a combination of decreased catalytic activity and reduced protein levels. This is most pronounced in the substantia nigra. Biochemical changes involved in PD pathogenesis affect wild-type GCase protein expression in vitro, and these could be contributing factors to the GCase deficiency observed in sporadic PD brains.

Topics: Aged; Aged, 80 and over; alpha-Synuclein; Cell Line, Tumor; Female; Gaucher Disease; Gene Expression Regulation, Enzymologic; Glucosylceramidase; Heterozygote; Humans; Immunoprecipitation; Male; Middle Aged; Mitochondria; Mutation; Neuroblastoma; Parkinson Disease; Protein Kinases; RNA, Small Interfering; Substantia Nigra

Gaucher disease, a prevalent lysosomal storage disease, is caused by insufficient activity of acid β-glucosidase (GCase) and resultant glucosylceramide accumulation. Recently in Parkinson disease (PD) patients, heterozygous mutations in GCase have been associated with earlier onset and more progressive PD. To understand the pathogenic relationships between GCase variants and Parkinsonism, α-synuclein and ubiquitin distributions and levels in the brains of several mouse models containing GCase variants were evaluated by immunohistochemistry. Progressive α-synuclein and ubiquitin aggregate accumulations were observed in the cortex, hippocampus, basal ganglia, brainstem, and some cerebellar regions between 4 and 24 weeks in mice that were homozygous for GCase [D409H (9H) or V394L (4L)] variants and also had a prosaposin hypomorphic (PS-NA) transgene. In 4L/PS-NA and 9H/PS-NA mice, this was coincident with progressive neurological manifestations and brain glucosylceramide accumulation. Ultrastructural studies showed electron dense inclusion bodies in neurons and axons of 9H/PS-NA brains. α-synuclein aggregates were also observed in ventricular, brainstem, and cerebellar regions of older mice (>42-weeks) with the GCase variant (D409H/D409H) without overt neurological disease. In a chemically induced GCase deficiency, α-synuclein aggregates and glucosylceramide accumulation also occurred. These studies demonstrate a relationship between glucosylceramide accumulation and α-synuclein aggregates, and implicate glucosylceramide accumulation as risk factor for the α-synucleinopathies.

Topics: Age Factors; alpha-Synuclein; Animals; beta-Glucosidase; Brain; Disease Models, Animal; Gaucher Disease; Glucosylceramides; Inclusion Bodies; Inositol; Mice; Mutation, Missense; Phenotype; Psychosine; Ubiquitin

Heterozygous mutations in the GBA1 gene elevate the risk of Parkinson disease and dementia with Lewy bodies; both disorders are characterized by misprocessing of α-synuclein (SNCA). A loss in lysosomal acid-β-glucosidase enzyme (GCase) activity due to biallelic GBA1 mutations underlies Gaucher disease. We explored mechanisms for the gene's association with increased synucleinopathy risk.. We analyzed the effects of wild-type (WT) and several GBA mutants on SNCA in cellular and in vivo models using biochemical and immunohistochemical protocols.. We observed that overexpression of all GBA mutants examined (N370S, L444P, D409H, D409V, E235A, and E340A) significantly raised human SNCA levels to 121 to 248% of vector control (p < 0.029) in neural MES23.5 and PC12 cells, but without altering GCase activity. Overexpression of WT GBA in neural and HEK293-SNCA cells increased GCase activity, as expected (ie, to 167% in MES-SNCA, 128% in PC12-SNCA, and 233% in HEK293-SNCA; p < 0.002), but had mixed effects on SNCA. Nevertheless, in HEK293-SNCA cells high GCase activity was associated with SNCA reduction by ≤32% (p = 0.009). Inhibition of cellular GCase activity (to 8-20% of WT; p < 0.0017) did not detectably alter SNCA levels. Mutant GBA-induced SNCA accumulation could be pharmacologically reversed in D409V-expressing PC12-SNCA cells by rapamycin, an autophagy-inducer (≤40%; 10μM; p < 0.02). Isofagomine, a GBA chaperone, showed a related trend. In mice expressing two D409Vgba knockin alleles without signs of Gaucher disease (residual GCase activity, ≥20%), we recorded an age-dependent rise of endogenous Snca in hippocampal membranes (125% vs WT at 52 weeks; p = 0.019). In young Gaucher disease mice (V394Lgba+/+//prosaposin[ps]-null//ps-transgene), which demonstrate neurological dysfunction after age 10 weeks (GCase activity, ≤10%), we recorded no significant change in endogenous Snca levels at 12 weeks of age. However, enhanced neuronal ubiquitin signals and axonal spheroid formation were already present. The latter changes were similar to those seen in three week-old cathepsin D-deficient mice.. Our results demonstrate that GBA mutants promote SNCA accumulation in a dose- and time-dependent manner, thereby identifying a biochemical link between GBA1 mutation carrier status and increased synucleinopathy risk. In cell culture models, this gain of toxic function effect can be mitigated by rapamycin. Loss in GCase activity did not immediately raise SNCA concentrations, but first led to neuronal ubiquitinopathy and axonal spheroids, a phenotype shared with other lysosomal storage disorders.

Topics: alpha-Synuclein; Animals; Cathepsin D; Cell Line; Disease Models, Animal; Dose-Response Relationship, Drug; Enzyme-Linked Immunosorbent Assay; Gaucher Disease; Gene Expression Regulation; Glucosylceramidase; Green Fluorescent Proteins; Humans; Immunosuppressive Agents; Lewy Body Disease; Mice; Mice, Knockout; Mutagenesis, Site-Directed; Mutation; Parkinson Disease; Rats; Sirolimus; Transfection

The presynaptic protein α-synuclein (α-syn), particularly in its amyloid form, is widely recognized for its involvement in Parkinson disease (PD). Recent genetic studies reveal that mutations in the gene GBA are the most widespread genetic risk factor for parkinsonism identified to date. GBA encodes for glucocerebrosidase (GCase), the enzyme deficient in the lysosomal storage disorder, Gaucher disease (GD). In this work, we investigated the possibility of a physical linkage between α-syn and GCase, examining both wild type and the GD-related N370S mutant enzyme. Using fluorescence and nuclear magnetic resonance spectroscopy, we determined that α-syn and GCase interact selectively under lysosomal solution conditions (pH 5.5) and mapped the interaction site to the α-syn C-terminal residues, 118-137. This α-syn-GCase complex does not form at pH 7.4 and is stabilized by electrostatics, with dissociation constants ranging from 1.2 to 22 μm in the presence of 25 to 100 mm NaCl. Intriguingly, the N370S mutant form of GCase has a reduced affinity for α-syn, as does the inhibitor conduritol-β-epoxide-bound enzyme. Immunoprecipitation and immunofluorescence studies verified this interaction in human tissue and neuronal cell culture, respectively. Although our data do not preclude protein-protein interactions in other cellular milieux, we suggest that the α-syn-GCase association is favored in the lysosome, and that this noncovalent interaction provides the groundwork to explore molecular mechanisms linking PD with mutant GBA alleles.

Topics: alpha-Synuclein; Amino Acid Substitution; Cell Line, Tumor; Enzyme Inhibitors; Gaucher Disease; Glucosylceramidase; Humans; Hydrogen-Ion Concentration; Inositol; Lysosomes; Multiprotein Complexes; Mutation, Missense; Parkinson Disease

Parkinson's disease (PD), an adult neurodegenerative disorder, has been clinically linked to the lysosomal storage disorder Gaucher disease (GD), but the mechanistic connection is not known. Here, we show that functional loss of GD-linked glucocerebrosidase (GCase) in primary cultures or human iPS neurons compromises lysosomal protein degradation, causes accumulation of α-synuclein (α-syn), and results in neurotoxicity through aggregation-dependent mechanisms. Glucosylceramide (GlcCer), the GCase substrate, directly influenced amyloid formation of purified α-syn by stabilizing soluble oligomeric intermediates. We further demonstrate that α-syn inhibits the lysosomal activity of normal GCase in neurons and idiopathic PD brain, suggesting that GCase depletion contributes to the pathogenesis of sporadic synucleinopathies. These findings suggest that the bidirectional effect of α-syn and GCase forms a positive feedback loop that may lead to a self-propagating disease. Therefore, improved targeting of GCase to lysosomes may represent a specific therapeutic approach for PD and other synucleinopathies.

Topics: alpha-Synuclein; Animals; Brain; Cells, Cultured; Disease Models, Animal; Feedback, Physiological; Gaucher Disease; Glucosylceramidase; Glucosylceramides; Humans; Lysosomes; Mice; Neurons

Emerging genetic and clinical evidence suggests a link between Gaucher disease and the synucleinopathies Parkinson disease and dementia with Lewy bodies. Here, we provide evidence that a mouse model of Gaucher disease (Gba1(D409V/D409V)) exhibits characteristics of synucleinopathies, including progressive accumulation of proteinase K-resistant α-synuclein/ubiquitin aggregates in hippocampal neurons and a coincident memory deficit. Analysis of homozygous (Gba1(D409V/D409V)) and heterozygous (Gba1(D409V/+) and Gba1(+/-)) Gaucher mice indicated that these pathologies are a result of the combination of a loss of glucocerebrosidase activity and a toxic gain-of-function resulting from expression of the mutant enzyme. Importantly, adeno-associated virus-mediated expression of exogenous glucocerebrosidase injected into the hippocampus of Gba1(D409V/D409V) mice ameliorated both the histopathological and memory aberrations. The data support the contention that mutations in GBA1 can cause Parkinson disease-like α-synuclein pathology, and that rescuing brain glucocerebrosidase activity might represent a therapeutic strategy for GBA1-associated synucleinopathies.

Topics: alpha-Synuclein; Analysis of Variance; Animals; Blotting, Western; Dependovirus; Endopeptidase K; Gaucher Disease; Gene Transfer Techniques; Genetic Vectors; Glucosylceramidase; Hippocampus; Immunohistochemistry; Mice

Parkinson's disease (PD) is a progressive neurodegenerative disorder that affects movement. Although many of the causes of PD remain unclear, a consistent finding is the abnormal accumulation of the protein α-synuclein. In a recent issue of Cell, Mazzuli et al. provide a molecular explanation for the unexpected link between PD and Gaucher's disease, a glycolipid lysosomal storage disorder caused by loss of the enzyme glucocerebrosidase (GBA). They report a reciprocal connection between loss of GBA activity and the accumulation of α-synuclein in lysosomes that establishes a bidirectional positive feedback loop with pathogenic consequences. Understanding how lysosomes are implicated in PD may reveal new therapeutic targets for treating this disease.

Topics: alpha-Synuclein; Animals; Brain; Gaucher Disease; Glucosylceramidase; Humans; Lysosomes; Mice; Models, Biological; Parkinson Disease

Mutations in the gene encoding the lysosomal enzyme glucocerebrosidase, known to cause Gaucher disease (GD), are a risk factor for the development of Parkinson disease (PD) and related disorders. This association is based on the concurrence of parkinsonism and GD, the identification of glucocerebrosidase mutations in cohorts with PD from centers around the world, and neuropathologic findings. The contribution of glucocerebrosidase to the development of parkinsonian pathology was explored by studying seven brain samples from subjects carrying glucocerebrosidase mutations with pathologic diagnoses of PD and/or Lewy body dementia. Three individuals had GD and four were heterozygous for glucocerebrosidase mutations. All cases had no known family history of PD and the mean age of disease onset was 59 years (range 42-77). Immunofluorescence studies on brain tissue samples from patients with parkinsonism associated with glucocerebrosidase mutations showed that glucocerebrosidase was present in 32-90% of Lewy bodies (mean 75%), some ubiquitinated and others non-ubiquitinated. In samples from seven subjects without mutations, <10% of Lewy bodies were glucocerebrosidase positive (mean 4%). This data demonstrates that glucocerebrosidase can be an important component of α-synuclein-positive pathological inclusions. Unraveling the role of mutant glucocerebrosidase in the development of this pathology will further our understanding of the lysosomal pathways that likely contribute to the formation and/or clearance of these protein aggregates.

Topics: Adult; Aged; Aged, 80 and over; alpha-Synuclein; Blotting, Southern; Brain; Female; Fluorescent Antibody Technique; Gaucher Disease; Glucosylceramidase; Humans; Immunohistochemistry; Lewy Bodies; Lewy Body Disease; Male; Microscopy, Confocal; Middle Aged; Mutation; Neurites; Parkinson Disease; Ubiquitination

A growing body of experimental and clinical literature indicates an association between Gaucher disease and parkinsonism, raising the possibility that convergent mechanisms may contribute to neurodegeneration in these disorders. The aim of this study was to determine whether there is a relationship between alpha-synuclein (alpha-syn), a key protein in Parkinson's disease pathogenesis, and abnormalities in glucocerebroside (GC) catabolism that lead to the development of Gaucher disease. We inhibited glucocerebrosidase (GCase) with conduritol B epoxide (CBE) in neuroblastoma cells and mice to test whether a biological link exists between GCase activity and alpha-syn. After CBE exposure, enhanced alpha-syn protein was detected in differentiated cells challenged with CBE as compared to vehicle, with no change in alpha-syn mRNA. In the mouse model, after one injection of CBE, elevated nigral alpha-syn levels were also detected. Analyses by Western blot and confocal microscopy revealed that normal alpha-syn distribution was perturbed after CBE exposure with its accumulation apparent within nigral cell bodies as well as astroglia. These findings raise the possibility that alpha-syn may contribute to the cascade of events that promote neuronal dysfunction in Gaucher disease and are the first to implicate this protein as a plausible biological intersection between Gaucher disease and parkinsonism using a pharmacological model.

Topics: alpha-Synuclein; Analysis of Variance; Animals; Cell Differentiation; Disease Models, Animal; Dose-Response Relationship, Drug; Gaucher Disease; Gene Expression Regulation; Glial Fibrillary Acidic Protein; Humans; Inositol; Mice; Mice, Inbred C57BL; Neuroblastoma; RNA, Messenger; Substantia Nigra

Type 1 Gaucher disease is considered the non-neuronopathic form of this autosomal recessively inherited lysosomal storage disease. We report the simultaneous occurrence of Gaucher disease with parkinsonian in four adult patients. The patients had a relatively early onset of parkinsonian manifestations, and their disease was rapidly progressive and refractory to therapy. Each had a different Gaucher genotype, although four alleles carried the common N370S mutation. No mutations were identified in the genes for parkin or alpha-synuclein. The concurrence of these two phenotypes, both in this series of patients and in others in the literature, suggests a shared pathway, modifier, or other genetic etiology.

Topics: Alleles; alpha-Synuclein; Female; Gaucher Disease; Genotype; Humans; Jews; Ligases; Male; Middle Aged; Mutation; Nerve Tissue Proteins; Parkinsonian Disorders; Phenotype; Synucleins; Ubiquitin-Protein Ligases