calpain and Muscular-Atrophy--Spinal

Camptocormia is defined by a pathological involuntary flexion of the thoracic and lumbar spine that is fully reducible in the supine position. Although originally described as a manifestation of conversion disorder, it is more commonly caused by a wide range of neurological diseases, in particular movement and neuromuscular disorders. We describe here a rare case of late onset camptocormia caused by autosomal dominant calpainopathy due to a heterozygous in-frame deletion in CAPN3 leading to loss of a single lysin amino acid in the catalytic domain of calpain-3. Creatine kinase levels, electromyography, and thigh muscle MRI were normal. Muscle biopsy did not show lobulated fibers and calpain-3 protein expression was not decreased, but in vitro functional assays showed impaired proteolytic function of. Lys254del CAPN3. Autosomal dominant calpainopathy should be considered in the differential diagnosis of late onset camptocormia and unexplained paravertebral myopathies even in presence of normal creatine kinase levels, and in absence of lobulated fibers, of decreased calpain-3 protein expression, and of muscle limb involvement.

Topics: Age of Onset; Aged; Calpain; Electromyography; Female; Heterozygote; Humans; Magnetic Resonance Imaging; Muscle Proteins; Muscle, Skeletal; Muscular Atrophy, Spinal; Muscular Dystrophies, Limb-Girdle; Sequence Deletion; Spinal Curvatures

Spinal muscular atrophy (SMA) is a severe neuromuscular disorder caused by loss of the survival motor neuron 1 (SMN1) gene. SMA is characterized by the degeneration of spinal cord motoneurons (MNs), progressive skeletal muscle atrophy, and weakness. The cellular and molecular mechanisms causing MN loss of function are only partially known. Recent advances in SMA research postulate the role of calpain protease regulating survival motor neuron (SMN) protein and the positive effect on SMA phenotype of treatment with calpain inhibitors. We analyzed the level of calpain pathway members in mice and human cellular SMA models. Results indicate an increase of calpain activity in SMN-reduced MNs. Spinal cord analysis of SMA mice treated with calpeptin, a calpain inhibitor, showed an increase of SMN, calpain, and its endogenous inhibitor calpastatin in MNs. Finally, in vitro calpeptin treatment prevented microtubule-associated protein 1A/1B-light chain 3 (LC3) increase in MNs neurites, indicating that calpain inhibition may reduce autophagosome accumulation in neuron prolongations, but not in soma. Thus, our results show that calpain activity is increased in SMA MNs and its inhibition may have a beneficial effect on SMA phenotype through the increase of SMN in spinal cord MNs.

Topics: Animals; Calcium-Binding Proteins; Calpain; Carrier Proteins; Cell Differentiation; Cell Line; Cell Survival; Cells, Cultured; Dipeptides; Disease Models, Animal; Fibroblasts; Humans; Induced Pluripotent Stem Cells; Mice; Mice, Mutant Strains; Microfilament Proteins; Microtubule-Associated Proteins; Motor Neurons; Muscular Atrophy, Spinal; Proteolysis; Spinal Cord; Survival of Motor Neuron 1 Protein

Spinal muscular atrophy (SMA), a leading genetic cause of infant death, is caused by the loss of survival motor neuron 1 (SMN1) gene. SMA is characterized by the degeneration and loss of spinal cord motoneurons (MNs), muscular atrophy, and weakness. SMN2 is the centromeric duplication of the SMN gene, whose numbers of copies determine the intracellular levels of SMN protein and define the disease onset and severity. It has been demonstrated that elevating SMN levels can be an important strategy in treating SMA and can be achieved by several mechanisms, including promotion of protein stability. SMN protein is a direct target of the calcium-dependent protease calpain and induces its proteolytic cleavage in muscle cells. In this study, we examined the involvement of calpain in SMN regulation on MNs. In vitro experiments showed that calpain activation induces SMN cleavage in CD1 and SMA mouse spinal cord MNs. Additionally, calpain 1 knockdown or inhibition increased SMN level and prevent neurite degeneration in these cells. We examined the effects of calpain inhibition on the phenotype of two severe SMA mouse models. Treatment with the calpain inhibitor, calpeptin, significantly improved the lifespan and motor function of these mice. Our observations show that calpain regulates SMN level in MNs and calpeptin administration improves SMA phenotype demonstrating the potential utility of calpain inhibitors in SMA therapy.

Topics: Animals; Calpain; Cells, Cultured; Dipeptides; Gene Knockdown Techniques; Glycoproteins; Membrane Potentials; Mice, Transgenic; Motor Activity; Motor Neurons; Muscular Atrophy, Spinal; Mutation; Nerve Degeneration; Neurites; Phenotype; Potassium; Spinal Cord; Survival of Motor Neuron 1 Protein

Topics: Aging; Animals; Calcium; Calcium Channels, L-Type; Calpain; Cations, Divalent; Cell Nucleus; Gene Expression Regulation; Humans; Mice; Muscle Strength; Muscle, Skeletal; Muscular Atrophy, Spinal; Ryanodine Receptor Calcium Release Channel; Sarcopenia; Sarcoplasmic Reticulum; Signal Transduction; Sulfonamides; Troponin T

Camptocormia is a debilitating gait disorder characterized by the hyperflexion of the thoracolumbar spine during the upright position. Its etiologies are heterogenous, including parkinsonism and various neuromuscular disorders. Here, we report a camptocormia patient due to a late-onset axial myopathy with numerous lobulated fibers. The patient's father reportedly had similar symptoms. Myriad lobulated fibers are common among patients with an autosomal recessive muscular dystrophy due to calpain-3 gene (CAPN3) mutations or calpainopathy. CAPN3 sequencing revealed a single c.759-761delGAA mutation. Calpainopathy carriers are generally asymptomatic. The presence of lobulated fibers in this patient suggests that camptocormia could be a manifestation of calpainopathy carrier, although the possibility of a coexisting undiagnosed myopathy cannot be excluded. The current patient should spur the evaluation of camptocormia among calpainopathy carriers.

Topics: Aged; Biopsy; Calpain; Humans; Magnetic Resonance Imaging; Male; Muscle Fibers, Skeletal; Muscle Proteins; Muscular Atrophy, Spinal; Muscular Diseases; Muscular Dystrophies, Limb-Girdle; Mutation; Spinal Curvatures

Spinal muscular atrophy (SMA) is a recessive neuromuscular disease caused by mutations in the human survival motor neuron 1 (SMN1) gene. The human SMN protein is part of a large macromolecular complex involved in the biogenesis of small ribonucleoproteins. Previously, we showed that SMN is a sarcomeric protein in flies and mice. In this report, we show that the entire mouse Smn complex localizes to the sarcomeric Z-disc. Smn colocalizes with alpha-actinin, a Z-disc marker protein, in both skeletal and cardiac myofibrils. Furthermore, this localization is both calcium- and calpain-dependent. Calpains are known to release proteins from various regions of the sarcomere as a part of the normal functioning of the muscle; however, this removal can be either direct or indirect. Using mammalian cell lysates, purified native SMN complexes, as well as recombinant SMN protein, we show that SMN is a direct target of calpain cleavage. Finally, myofibers from a mouse model of severe SMA, but not controls, display morphological defects that are consistent with a Z-disc deficiency. These results support the view that the SMN complex performs a muscle-specific function at the Z-discs.

Topics: Animals; Calcium; Calpain; Disease Models, Animal; Mice; Mice, Inbred C57BL; Muscle Proteins; Muscle, Striated; Muscular Atrophy, Spinal; Ribonucleoproteins, Small Nuclear; Sarcomeres; SMN Complex Proteins; Survival of Motor Neuron 1 Protein

Topics: Alleles; Calpain; Diagnosis, Differential; DNA Mutational Analysis; Female; Gene Frequency; Genetic Testing; Humans; Isoenzymes; Male; Muscle Proteins; Muscular Atrophy, Spinal; Muscular Dystrophies, Limb-Girdle; Muscular Dystrophy, Duchenne; Mutation; Mutation, Missense; Polymorphism, Genetic; Sequence Deletion

Five affected siblings were referred with a probable diagnosis of proximal adult-type spinal muscular atrophy (SMA) based on lower motor neuron signs (muscle weakness and atrophy, hypotony, hypoactive or absent reflexes, and fasciculations), normal or borderline serum creatine kinase levels, and a neurogenic pattern on electromyography, compatible with motor neuron disease, in one patient. No exon 7-8 deletion in the survival motor neuron (SMN) gene was found. Linkage analysis excluded the SMN and all known autosomal recessive limb girdle muscular dystrophy loci, with the exception of LGMD-2A. A homozygous R769Q mutation in the calpain-3 gene and absence of muscle calpain-3 protein confirmed a calpainopathy. This family suggests that the clinical spectrum of calpainopathy might be broader and that this diagnosis might be considered in patients with an atypical motor neuron disease.

Topics: Adult; Biopsy; Calpain; Chromosome Mapping; Cyclic AMP Response Element-Binding Protein; DNA Mutational Analysis; Electromyography; Female; Gene Deletion; Genetic Testing; Genetic Variation; Humans; Isoenzymes; Male; Middle Aged; Muscle Fibers, Skeletal; Muscle Proteins; Muscle, Skeletal; Muscular Atrophy, Spinal; Mutation; Nerve Tissue Proteins; Pedigree; Phenotype; RNA-Binding Proteins; SMN Complex Proteins