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Query: UMLS:C0026850 (muscular dystrophy)
 5,870 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The dystrophin-glycoprotein complex (DGC) serves as a link between cytoplasmic actin, the membrane and the extracellular matrix of striated muscle. Genetic defects in genes encoding a subset of DGC proteins result in muscular dystrophy and a secondary decrease in other DGC proteins. Caveolae are dynamic structures that have been implicated in a number of functions including endocytosis, potocytosis and signal transduction. Caveolin (VIP-21) is thought to play a structural role in the formation of non-clathrin-coated vesicles in a number of different cell types. Caveolin-3, or M-caveolin, was identified as a muscle-specific form of the caveolin family. We show that caveolin-3 co-purifies with dystrophin, and that a fraction of caveolin-3 is a dystrophin-associated protein. We isolated the gene for human caveolin-3 and mapped it to chromosome 3p25. We determined the genomic organization of human caveolin-3 and devised a screening strategy to look for mutations in caveolin-3 in patients with muscular dystrophy. Of 82 patients screened, two nucleotide changes were found that resulted in amino acid substitutions (G55S and C71W); these changes were not seen in a control population. The amino acid changes map to a functionally important domain in caveolin-3, suggesting that these are not benign polymorphisms and instead are disease-causing mutations.
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PMID:Caveolin-3 in muscular dystrophy. 953 92

Caveolin-3, a muscle-specific caveolin-related protein, is the principal structural protein of caveolae membrane domains in striated muscle cell types (cardiac and skeletal). Autosomal dominant limb girdle muscular dystrophy (LGMD-1C) in humans is due to mutations within the caveolin-3 gene: (i) a 9-base pair microdeletion that removes three amino acids within the caveolin scaffolding domain (DeltaTFT) or (ii) a missense mutation within the membrane spanning domain (P --> L). The molecular mechanisms by which these two mutations cause muscular dystrophy remain unknown. Here, we investigate the phenotypic behavior of these caveolin-3 mutations using heterologous expression. Wild type caveolin-3 or caveolin-3 mutants were transiently expressed in NIH 3T3 cells. LGMD-1C mutants of caveolin-3 (DeltaTFT or P --> L) were primarily retained at the level of a perinuclear compartment that we identified as the Golgi complex in double-labeling experiments, while wild type caveolin-3 was efficiently targeted to the plasma membrane. In accordance with these observations, caveolin-3 mutants formed oligomers of a much larger size than wild type caveolin-3 and were excluded from caveolae-enriched membrane fractions as seen by sucrose density gradient centrifugation. In addition, these caveolin-3 mutants were expressed at significantly lower levels and had a dramatically shortened half-life of approximately 45-60 min. However, caveolin-3 mutants were palmitoylated to the same extent as wild type caveolin-3, indicating that targeting to the plasma membrane is not required for palmitoylation of caveolin-3. In conclusion, we show that LGMD-1C mutations lead to formation of unstable high molecular mass aggregates of caveolin-3 that are retained within the Golgi complex and are not targeted to the plasma membrane. Consistent with its autosomal dominant form of genetic transmission, we demonstrate that LGMD-1C mutants of caveolin-3 behave in a dominant-negative fashion, causing the retention of wild type caveolin-3 at the level of the Golgi. These data provide a molecular explanation for why caveolin-3 levels are down-regulated in patients with this form of limb girdle muscular dystrophy (LGMD-1C).
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PMID:Phenotypic behavior of caveolin-3 mutations that cause autosomal dominant limb girdle muscular dystrophy (LGMD-1C). Retention of LGMD-1C caveolin-3 mutants within the golgi complex. 1046 99

In adult animals and humans, signal transduction maintains homeostasis. When homeostatic mechanisms are interrupted, an illness or disease may ensue. Caveolae are plasma membrane specializations that contain the structural proteins caveolins, and appear to be important for normal signal transduction. The caveolin scaffolding domain interacts with several signaling molecules, sequestering them in the absence of activating signals, and thereby reducing the signal-to-noise ratio. Deletion and mutation of genes that encode caveolins is implicated in the pathogenesis of several human diseases. Down-regulation of caveolin-1 protein expression leads to deregulated signaling and consequently tumorigenesis, whereas naturally occurring dominant-negative caveolin-3 mutations cause muscular dystrophy.
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PMID:Caveolin proteins in signaling, oncogenic transformation and muscular dystrophy. 1082 83

Caveolin-3 protein is the only member of the caveolin family that shows a unique muscle-specific expression pattern, and loss of its functional activity causes muscular dystrophy. Caveolin-3 mRNA levels are dramatically increased during the formation of myotubes in the C2C12 cell line. In this study, we characterized the human caveolin-3 5'-flanking region. Promoter analyses demonstrate that the proximal E box element serves as a myogenin binding site and is both necessary and sufficient to control caveolin-3 gene transcription. Transient transfection assays indicated that overexpression of myogenin activates caveolin-3 reporter gene expression, whereas Id2 overexpression inhibited caveolin-3 promoter activation by myogenin. A mutant Id2 protein lacking the HLH domain was not capable of suppressing myogenin-mediated activation. Determination of caveolin-3 transcript distribution patterns in vivo revealed that mRNA was first detectable at day 10 of gestation in the developing somites and heart. Caveolin-3 protein in myoblasts and myotubes was expressed in both the plasma membrane and vesicular structures. During skeletal myogenesis the level of Id2, an inhibitor of differentiation, decreases, allowing the induced basic helix-loop-helix transcription factor myogenin to form transcriptionally active heterodimers that bind to the caveolin-3 promoter and thereby mediate its transcription.
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PMID:The basic helix-loop-helix transcription factors myogenin and Id2 mediate specific induction of caveolin-3 gene expression during embryonic development. 1083 21

Limb girdle muscular dystrophy is a group of clinically and genetically heterogeneous disorders inherited in an autosomal recessive or dominant mode. Caveolin-3, the muscle-specific member of the caveolin gene family, is implicated in the pathogenesis of autosomal dominant limb girdle muscular dystrophy 1C. Here we report on a 4-year-old girl presenting with myalgia and muscle cramps due to a caveolin-3 deficiency in her dystrophic skeletal muscle as a result of a heterozygous 136G-->A substitution in the caveolin-3 gene. The novel sporadic missense mutation in the caveolin signature sequence of the caveolin-3 gene changes an alanine to a threonine (A46T) and prevents the localization of caveolin-3 to the plasma membrane in a dominant negative fashion. Caveolin-3 has been suggested to interact with the dystrophin-glycoprotein complex, which in striated muscle fibers links the cytoskeleton to the extracellular matrix and with neuronal nitric oxide synthase. Similar to dystrophin-deficient Duchenne muscular dystrophy, a secondary decrease in neuronal nitric oxide synthase and alpha-dystroglycan expression was detected in the caveolin-3-deficient patient. These results implicate an important function of the caveolin signature sequence and common mechanisms in the pathogenesis of dystrophin-glycoprotein complex-associated muscular dystrophies with caveolin-3-deficient limb girdle muscular dystrophy.
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PMID:Dissociation of the dystroglycan complex in caveolin-3-deficient limb girdle muscular dystrophy. 1100 38

Limb-girdle muscular dystrophies (LGMD) are a heterogeneous group of genetic disorders usually with autosomal recessive (AR) inheritance and, less often, displaying autosomal dominant (AD) inheritance. Mutations in the caveolin-3 gene (CAV-3) associated with a reduction of protein expression cause AD-LGMD1C muscular dystrophy. Based on a previous study in the American and Brazilian population, it has been suggested that CAV-3 mutations might also cause AR-LGMD. Here we report the analysis of the CAV-3 gene in 61 additional Brazilian LGMD patients and 100 additional Brazilian normal controls. Two rare G55S and C71W missense changes previously detected only in LGMD patients (and not detected in 100 normal controls from the American population) were now found in normal Brazilian controls. In addition, we have identified a novel R125H missense change in one LGMD female patient that was also found in two of her unaffected siblings. These observations, together with the normal immunofluorescence caveolin pattern in the muscle biopsy from two patients with the G55W and R125H changes in the CAV-3 gene suggest that the G55S, C71W, and R125H polymorphisms, on their own, are not sufficient to produce the pathology.
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PMID:Mutations in the caveolin-3 gene: When are they pathogenic? 1125 97

Dysferlin is a surface membrane protein in skeletal muscle whose deficiency causes distal and proximal, recessively inherited, forms of muscular dystrophy designated Miyoshi myopathy (MM) and limb girdle muscular dystrophy type 2B (LGMD2B), respectively. The function of dysferlin is not defined. Caveolin-3 is another skeletal muscle membrane protein which is important in the formation of caveolae and whose mutations cause dominantly inherited limb girdle muscular dystrophy type 1C (LGMD1C). We report that dysferlin co-immunoprecipitates with caveolin-3 from biopsied normal human skeletal muscles. We also describe abnormal localization of dysferlin in muscles from patients with LGMD1C including novel missense mutation (T64P) in the human caveolin-3 gene (CAV3). The immunoprecipitation data are consistent with the parallel observation that dysferlin immunostaining is not normal in LGMD1C muscles. Amino acid sequence analysis of the dysferlin protein reveals seven sites that correspond to caveolin-3 scaffold-binding motifs, and one site that is a potential target to bind the WW domain of the caveolin-3 protein. This is the first description of a possible dysferlin interacting protein; it suggests the hypothesis that one function of dysferlin may be to interact with caveolin-3 to subserve signaling functions of caveolae.
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PMID:The sarcolemmal proteins dysferlin and caveolin-3 interact in skeletal muscle. 1153 85

A growing body of evidence suggests that muscle cell caveolae may function as specialized membrane micro-domains in which the dystrophin-glycoprotein complex and cellular signaling molecules reside. Caveolin-3 (Cav-3) is the only caveolin family member expressed in striated muscle cell types (cardiac and skeletal). Interestingly, skeletal muscle fibers from Cav-3 (-/-) knock-out mice show a number of myopathic changes, consistent with a mild-to-moderate muscular dystrophy phenotype. However, it remains unknown whether a loss of Cav-3 affects the phenotypic behavior cardiac myocytes in vivo. Here, we present a detailed characterization of the hearts of Cav-3 knock-out mice. We show that these mice develop a progressive cardiomyopathic phenotype. At four months of age, Cav-3 knock-out hearts display significant hypertrophy, dilation, and reduced fractional shortening, as revealed by gated cardiac MRI and transthoracic echocardiography. Histological analysis reveals marked cardiac myocyte hypertrophy, with accompanying cellular infiltrates and progressive interstitial/peri-vascular fibrosis. Interestingly, loss of Cav-3 expression in the heart does not change the expression or the membrane association of the dystrophin-glycoprotein (DG) complex. However, a marker of the DG complex, alpha-sarcoglycan, was specifically excluded from lipid raft domains in the absence of Cav-3. Because activation of the Ras-p42/44 MAPK pathway in cardiac myocytes can drive cardiac hypertrophy, we next assessed the activation state of this pathway using a phospho-specific antibody probe. We show that p42/44 MAPK (ERK1/2) is hyperactivated in hearts derived from Cav-3 knock-out mice. These results are consistent with previous in vitro data demonstrating that caveolins may function as negative regulators of the p42/44 MAPK cascade. Taken together, our data argue that loss of Cav-3 expression is sufficient to induce a molecular program leading to cardiac myocyte hypertrophy and cardiomyopathy.
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PMID:Caveolin-3 knock-out mice develop a progressive cardiomyopathy and show hyperactivation of the p42/44 MAPK cascade. 1213 67

We have recently shown that a deletion in the Large gene, encoding a putative glycosyltransferase, is the molecular defect underlying the myodystrophy (previously myd; now Large(myd)) mouse. Here we show that the muscular dystrophy phenotype is not confined to skeletal muscle, but is also present in the heart and tongue. Immunohistochemistry indicates disruption of the dystrophin-associated glycoprotein complex (DGC) in skeletal and cardiac muscle. Quantitative western blotting shows a general increase in the expression of DGC proteins and of dysferlin and caveolin-3 in mutant skeletal muscle. In contrast, the expression of DGC proteins is reduced in cardiac muscle. Overlay assays show loss of laminin binding by alpha-dystroglycan in Large(myd) skeletal and cardiac muscle and in brain. We also show that the phenotype of Large(myd) mice is not restricted to muscular dystrophy, but also includes ophthalmic and central nervous system (CNS) defects. Electroretinograms of homozygous mutant mice show gross abnormalities of b-wave characteristics, indicative of a complex defect in retinal transmission. The laminar architecture of the cortices of the cerebrum and the cerebellum is disturbed, indicating defective neuronal migration. Thus, the phenotype of the Large(myd) mouse shows similarities to the heterogeneous group of human muscle eye brain diseases characterized by severe congenital muscular dystrophy, eye abnormalities and CNS neuronal migration defects. These diseases include Fukuyama-type muscular dystrophy and muscle-eye-brain disease, both of which are also due to mutations in predicted glycosylation enzymes. Therefore, the Large(myd) mouse represents an important animal model for studying the function of glycosylation in muscle, brain and retina.
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PMID:Skeletal, cardiac and tongue muscle pathology, defective retinal transmission, and neuronal migration defects in the Large(myd) mouse defines a natural model for glycosylation-deficient muscle - eye - brain disorders. 1235 92

Dystroglycan is a key complex between basal lamina laminin, extracellularly and membrano-cytoskeleton, intracellularly. The damage of this linkage is turned out to cause muscular dystrophies. Dystroglycan knockout is lethal. Dystroglycan-associated intracellular proteins such as dystrophin, dystrobrevin, sarcoglycans, plectin and caveolin-3 are responsible for causing severe (Duchenne type) and moderate forms (Becker, LGMDs). Laminin, dystroglycan-binding extracellular protein, is deficient in the most severe form of congenital muscular dystrophy with normal intelligence and eye. Recently, a remarkable progress is made in most severe forms of congenital muscular dystrophy with anomalies of brain and eye such as Fukuyama type (Japan) and muscle-eye-brain disease (Finland). The gene product for Fukuyama type, fukutin, belongs to a family of glycosylation enzymes in bacteria and yeast. Since alpha-dystroglycan contains 14-15 o-glycans, ser/thr-mannose 2-1 GlcNAc 4-1 Gal 3-2 Sial in the middle third mucin-domain and the sial-o-glycan is essential for laminin-binding, and since alpha-dystroglycan is defective in Fukuyama type sarcolemma with anti both sugar moiety- and peptide-antidodies, defective fukutin causes incomplete o-glycosylation of alpha-dystroglycan. In '02, it is clarified that a glycosylation enzyme, POMGnT1 which modifies GlcNAc onto ser/thr-mannose, is defective in 6 MEB patients. The loss of the enzyme activity is turned out to lose alpha-dystroglycan from sarcolemma of MEB. These data strongly suggests that o-glycosylation defect of alpha-dystroglycan causes the most severe congenital muscular dystrophy such as Fukuyama type, MEB and Walker Warburg syndrome.
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PMID:[Dystroglycan linkage and muscular dystrophy]. 1278 74


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