alpha-synuclein and Brain-Neoplasms

α-synuclein (aSyn) is a major player in Parkinson's disease and a group of other disorders collectively known as synucleinopathies, but the precise molecular mechanisms involved are still unclear. aSyn, as virtually all proteins, undergoes a series of posttranslational modifications during its lifetime, which can affect its biology and pathobiology. We recently showed that glycation of aSyn by methylglyoxal (MGO) potentiates its oligomerization and toxicity, induces dopaminergic neuronal cell loss in mice, and affects motor performance in flies. Small heat-shock proteins (sHsps) are molecular chaperones that facilitate the folding of proteins or target misfolded proteins for clearance. Importantly, sHsps were shown to prevent aSyn aggregation and cytotoxicity. Upon treating cells with increasing amounts of methylglyoxal, we found that the levels of Hsp27 decreased in a dose-dependent manner. Therefore, we hypothesized that restoring the levels of Hsp27 in glycating environments could alleviate the pathogenicity of aSyn. Consistently, we found that Hsp27 reduced MGO-induced aSyn aggregation in cells, leading to the formation of nontoxic aSyn species. Remarkably, increasing the levels of Hsp27 suppressed the deleterious effects induced by MGO. Our findings suggest that in glycating environments, the levels of Hsp27 are important for modulating the glycation-associated cellular pathologies in synucleinopathies.

Topics: alpha-Synuclein; Brain Neoplasms; Glioma; Glycosylation; Heat-Shock Proteins; Humans; Molecular Chaperones; Protein Aggregates; Pyruvaldehyde; Tumor Cells, Cultured

The purinergic P2X7 receptor (P2X7R) belongs to a family of trimeric ion channels that are gated by extracellular adenosine 5'-triphosphate (ATP). Several studies have pointed to a role of P2X7R-dependent signalling in Parkinson's disease (PD)-related neurodegeneration. The pathology of (PD) is characterized by the formation of insoluble alpha-synuclein (α-Syn) aggregates-Lewy bodies, but the mechanisms underlying α-Syn-induced dopaminergic cell death are still partially unclear. Our previous studies indicate that extracellular α-Syn directly interact with neuronal P2X7R and induces intracellular free calcium mobilization in neuronal cells. The main objective of this study was to examine the involvement of P2X7R receptor in α-Syn-induced mitochondrial dysfunction and cell death. We found that P2X7R stimulation is responsible for α-Syn-induced oxidative stress and activation of the molecular pathways of programmed cell death. Exogenous α-Syn treatment led to P2X7R-dependent decrease in mitochondrial membrane potential as well as elevation of mitochondrial ROS production resulting in breakdown of cellular energy production. Moreover, P2X7R-dependent deregulation of AMP-activated protein kinase as well as decrease in parkin protein level could be responsible for α-Syn-induced mitophagy impairment and accumulation of dysfunctional mitochondria. P2X7R might be putative pharmacological targets in molecular mechanism of extracellular α-Syn toxicity.

Topics: Adenosine Triphosphate; alpha-Synuclein; AMP-Activated Protein Kinases; Brain Neoplasms; Cell Line, Tumor; Cell Survival; Free Radicals; Gene Expression Regulation, Neoplastic; Humans; Membrane Potential, Mitochondrial; Mitochondria; Mitophagy; Neuroblastoma; Neurons; Oxidation-Reduction; Oxidative Stress; Receptors, Purinergic P2X7; Signal Transduction

Medulloblastoma (MB) is the most common malignant brain tumor in childhood. It contains at least four distinct molecular subgroups. The aim of this study is to explore novel diagnostic and potential therapeutic markers within each subgroup of MB, in particular within Group 4, the largest subgroup, to facilitate diagnosis together with gene therapy. One hundred and six MB samples were examined. Tumor subtype was evaluated with the NanoString assay. Several novel tumor related genes were shown to have high subgroup sensitivity and specificity, including PDGFRA, FGFR1, and ALK in the WNT group, CCND1 in the SHH group, and α-synuclein (SNCA) in Group 4. Knockdown and overexpression assays of SNCA revealed the ability of this gene to inhibit tumor invasion and induce apoptosis. Methylation-specific PCR and pyrosequencing analysis showed that epigenetic mechanisms, rather than DNA hypermethylation, might play the key role in the regulation of SNCA expression in MB tumors. In conclusion, we identify SNCA as a novel diagnostic biomarker for Group 4 MB. Some other subgroup signature genes have also been found as candidate therapeutic targets for this tumor.

Topics: Adolescent; Adult; alpha-Synuclein; Apoptosis; Biomarkers, Tumor; Brain Neoplasms; Cell Line, Tumor; Child; Child, Preschool; DNA Methylation; Epigenesis, Genetic; Female; Gene Expression; Gene Expression Profiling; Humans; Infant; Male; Medulloblastoma; Middle Aged; Neoplasm Invasiveness; Sensitivity and Specificity; Young Adult

α-Synuclein is the major component of Lewy bodies, Lewy neurites, and glial cytoplasmic inclusions. It plays an important role in neurodegenerative diseases such as Parkinson's disease, multiple system atrophy, and other synucleinopathies. However, the pathogenesis and neurodegenerative effects of α-synuclein remain unknown. In this study, we established an α-synuclein and an α-synuclein-EGFP overexpressing U251 cell line. α-Synuclein overexpression increases oxidative stress and alters the cell surface and mitochondrial morphologies. We provide fluorescent-protein tagging, immunofluorescence and ultrastructural evidence showing that α-synuclein accumulations are associated with clusters of cytoplasmic vesicles and the diameter of these vesicles increases by H

Topics: alpha-Synuclein; Brain Neoplasms; Cell Line, Tumor; Cytoplasmic Vesicles; Glioblastoma; Humans; Hydrogen Peroxide; Malondialdehyde; Oxidative Stress; Protein Binding

Melanoma is the major cause of skin cancer death worldwide. Parkinson's disease is a neurodegenerative disorder that is caused by mutation of alpha-synuclein or other genes. Importantly, epidemiological studies have reported co-occurrence of melanoma and Parkinson's disease, suggesting that these two diseases could share common genetic components.. Recently, we found that human melanoma cell lines highly express alpha-synuclein, whereas the protein is undetectable in the non-melanoma cancer cell lines tested. To investigate the expression of alpha-synuclein in human melanoma tissues, we immunostained sections of melanoma, nevus, non-melanocytic cutaneous carcinoma, and normal skin. alpha-Synuclein was positively detected in 86% of the primary and 85% of the metastatic melanoma sections, as well as in 89% of nevus sections. However, alpha-synuclein was undetectable in non-melanocytic cutaneous carcinoma and normal skin.. The Parkinson's disease-related protein, alpha-synuclein, is expressed in both malignant and benign melanocytic lesions, such as melanomas and nevi. Although alpha-synuclein cannot be used to distinguish between malignant and benign melanocytic skin lesions, it might be a useful biomarker for the diagnosis of metastatic melanoma.

Topics: Adult; Aged; alpha-Synuclein; Antigens, Neoplasm; Biomarkers, Tumor; Brain Neoplasms; Cell Line, Tumor; Female; Humans; Male; MART-1 Antigen; Melanins; Melanoma; Middle Aged; Neoplasm Proteins; Nevus; Parkinson Disease; Pigmentation; Retinoblastoma; Skin Neoplasms

Because a limited study previously showed that alpha-synuclein (alpha-syn), the major pathogenic protein for Parkinson disease, was expressed in differentiating brain tumors as well as various peripheral cancers, the main objective of the present study was to determine whether alpha-syn might be involved in the regulation of tumor differentiation. For this purpose, alpha-syn and its non-amyloidogenic homologue beta-syn were stably transfected to human osteosarcoma MG63 cell line. Compared with beta-syn-overexpressing and vector-transfected cells, alpha-syn-overexpressing cells exhibited distinct features of differentiated osteoblastic phenotype, as shown by up-regulation of alkaline phosphatase and osteocalcin as well as inductive matrix mineralization. Further studies revealed that proteasome activity was significantly decreased in alpha-syn-overexpressing cells compared with other cell types, consistent with the fact that proteasome inhibitors stimulate differentiation of various osteoblastic cells. In alpha-syn-overexpressing cells, protein kinase C (PKC) activity was significantly decreased, and reactivation of PKC by phorbol ester significantly restored the proteasome activity and abrogated cellular differentiation. Moreover, activity of lysosome was up-regulated in alpha-syn-overexpressing cells, and treatment of these cells with autophagy-lysosomal inhibitors resulted in a decrease of proteasome activity associated with up-regulation of alpha-syn expression, leading to enhance cellular differentiation. Taken together, these results suggest that the stimulatory effect of alpha-syn on tumor differentiation may be attributed to down-regulation of proteasome, which is further modulated by alterations of various factors, such as protein kinase C signaling pathway and a autophagy-lysosomal degradation system. Thus, the mechanism of alpha-syn regulation of tumor differentiation and neuropathological effects of alpha-syn may considerably overlap with each other.

Topics: alpha-Synuclein; Autophagy; beta-Synuclein; Brain Neoplasms; Cell Differentiation; Down-Regulation; Enzyme Activation; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Neoplastic; Humans; Neoplasm Proteins; Osteoblasts; Osteosarcoma; Phorbol Esters; Proteasome Endopeptidase Complex; Protein Kinase C

alpha-, beta- and gamma-synuclein are highly homologous proteins that are found predominantly in neurons. Abnormal accumulation of synucleins has been associated with diseases of the central nervous system particularly Parkinson's disease. Immunoreactivity of alpha-synuclein is demonstrated in brain tumors with neuronal differentiation and in schwannomas, whereas gamma-synuclein has been demonstrated in breast and ovarian carcinomas. The immunoreactivity of synucleins has not been described in glial tumors. Immunoreactivity of synucleins in glial cells in culture and in pathological conditions, however, suggests that synucleins may be expressed by glial tumors. We studied the expression of alpha-, beta-, and gamma-synuclein in 84 human brain tumors (24 ependymomas, 31 astrocytomas, 8 oligodendrogliomas, and 21 medulloblastomas) by immunohistochemistry. Our study demonstrates immunoreactivity for gamma-synuclein in high-grade glial tumors; immunoreactivity is found in all anaplastic ependymomas but in only 33% of ependymomas and 16% of myxopapillary ependymomas. Immunoreactivity for gamma-synuclein is noted in 63% of glioblastomas but not in other astrocytic tumors. Of medulloblastomas, 76% have immunoreactivity for either alpha- or beta-synuclein or both; no immunoreactivity for gamma-synuclein is seen in medulloblastomas.

Topics: alpha-Synuclein; Astrocytes; beta-Synuclein; Brain Neoplasms; Cerebellar Neoplasms; Child, Preschool; Ependymoma; gamma-Synuclein; Glioma; Humans; Immunohistochemistry; Medulloblastoma; Nerve Tissue Proteins; Neuroectodermal Tumors, Primitive; Oligodendroglia; Synucleins

Intracellular alpha-synuclein inclusion formation in glial cells is frequently seen in Parkinson's disease and multiple system atrophy. Microglial activation in these neurodegenerative disorders suggests that neuroinflammatory responses might interact with alpha-synuclein and contribute to the pathogenesis of these disorders. To study the role of tumor necrosis factor-alpha (TNF-alpha), an important proinflammatory cytokine produced by microglia, on cells overexpressing alpha-synuclein we have used the astrocytoma cell line U373 engineered to express C-terminally truncated alpha-synuclein as a fusion protein with red or green fluorescent proteins. We demonstrate that alpha-synuclein overexpression augmented TNF-alpha-induced apoptotic cell death in U373 cells by induction of caspase activation. Furthermore, TNF-alpha exposure was associated with significant cytoskeletal changes characterized by altered inclusion composition with loss of cytoskeletal proteins and elevation of high-molecular-weight alpha-synuclein species. We conclude that alpha-synuclein overexpression significantly increases the vulnerability of U373 cells to apoptosis through TNF-alpha-mediated pathways.

Topics: alpha-Synuclein; Antineoplastic Agents; Apoptosis; Brain Neoplasms; Cytoskeleton; Gene Expression; Glioblastoma; Humans; Nerve Tissue Proteins; Synucleins; Transfection; Tumor Cells, Cultured; Tumor Necrosis Factor-alpha

alpha-Synuclein is presynaptic nerve terminal protein and its immunoreactivity has been observed in such neurodegenerative structures as senile plaques of Alzheimer's disease or Lewy bodies of Parkinson's disease. The physiological role of alpha-synuclein is still unknown. It is speculated that alpha-synuclein may be expressed in brain tumors, especially in those showing neuronal differentiation. We examined the immunohistochemical localization of alpha-synuclein in 77 human brain tumors. alpha-Synuclein was widely distributed in the brain tumors showing neuronal differentiation. As a result, positive immunostaining for alpha-synuclein was observed in ganglioglioma, medulloblastoma, neuroblastoma, primitive neuroectodermal tumor, pineocytoma/pineoblastoma, and central neurocytoma. Compared with other neuronal markers, the positive ratio of alpha-synuclein was not as high as synaptophysin, microtubule-associated protein 2, neuron-specific enolase and tau, but it was higher than neurofilament and chromogranin A. The expression of synaptophysin was diffusely observed in the cytoplasm, cellular processes and nucleus in tumors showing neuronal differentiation; however, the expression of alpha-synuclein was predominantly observed in the cytoplasm of the tumors as well as in the cellular processes. On the other hand, non-neuronal brain tumors such as astrocytic tumors or meningiomas were totally negative for alpha-synuclein. In conclusion, the appearance of an alpha-synuclein-positive structure was not limited to neurodegenerative diseases, but could also be detected in neoplastic cells showing neuronal differentiation.

Topics: Adolescent; Adult; Aged; alpha-Synuclein; Astrocytoma; Brain Neoplasms; Cell Differentiation; Cerebellar Neoplasms; Child; Child, Preschool; Female; Ganglioglioma; Humans; Immunohistochemistry; Infant; Male; Medulloblastoma; Middle Aged; Nerve Tissue Proteins; Neuroblastoma; Neurocytoma; Neurons; Oligodendroglioma; Pinealoma; Pituitary Neoplasms; Synucleins