Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0026850 (muscular dystrophy)
 5,870 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Increased expression of critical components of the ubiquitin-dependent proteolytic pathway occurs in any muscle wasting condition so far studied in rodents where proteolysis rises. We have recently reported similar adaptations in head trauma patients [Mansoor et al. (1996) Proc. Natl. Acad. Sci. USA 93, 2714-2718]. We demonstrate here that the increased muscle protein breakdown seen in mdx mice only correlated with enhanced expression of m-calpain, a Ca(2+)-activated proteinase. By contrast, no change in mRNA levels for components of the ubiquitin-proteasome proteolytic process was seen in muscles from both mdx mice and Duchenne muscular dystrophy patients. Thus, gene expression of components of this pathway is not regulated in the chronic wasting that characterizes muscular dystrophy.
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PMID:No alteration in gene expression of components of the ubiquitin-proteasome proteolytic pathway in dystrophin-deficient muscles. 881 7

In a previous report we suggested that muscle fibers in distal myopathy with rimmed vacuoles (DMRV) were degraded by both lysosomal proteolysis (cathepsins) and Ca2+-dependent, nonlysosomal proteolysis (calpain). Given recent evidence of abnormal ubiquitin accumulation in rimmed vacuoles, we examined the role of the ATP-ubiquitin-dependent proteolytic pathway (proteasomes) in myofiber degradation in this myopathy. Immunohistochemically, proteasomes (26S) were located in the cytoplasm in normal human muscle, but the staining intensity was weak. Quantitative analysis showed more reactivity for proteasomes in DMRV muscles and, to a lesser extent, in muscles from muscular dystrophy, polymyositis, and amyotrophic lateral sclerosis patients. In DMRV, proteasomes often were located within or on the rim of rimmed vacuoles, and in the cytoplasm of atrophic fibers. Ubiquitin accumulation was marked within rimmed vacuoles and was seen less extensively in the cytoplasm of atrophic fibers. The latter proteins colocalized well. In other diseased muscles, proteasomes and ubiquitin showed a positive reaction in the atrophic or necrotic fibers. The results indicate increased proteasome and ubiquitin in these muscle fibers as well as in other diseased muscle fibers. We suggest that the ATP-ubiquitin-proteasome proteolytic pathway as well as the nonlysosomal calpain and the lysosomal proteolytic pathway may participate in the muscle fiber degradation in DMRV.
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PMID:Proteasomes in distal myopathy with rimmed vacuoles. 980 76

The limb-girdle muscular dystrophies (LGMDs) are a group of muscular dystrophies that share a similar clinical phenotype. Despite this clinical homogeneity, at least 15 different genetic forms of LGMD are now known. Some of these share pathogenetic mechanisms with other forms of muscular dystrophy, such as the sarcoglycanopathies (LGMD 2C-F) and the dystrophinopathies (Duchenne and Becker muscular dystrophy). Some are allelic with other forms of muscular dystrophy; LGMD 1B is allelic with autosomal dominant Emery-Dreifuss muscular dystrophy. Still others introduce totally unique pathogenetic mechanisms to the study of muscular dystrophy. For example, LGMD 2H appears to be due to mutations affecting the ubiquitin-proteasome pathway. A diagnostic approach is outlined based on clinical features, genetics, and commercially available testing.
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PMID:Limb-girdle muscular dystrophy. 1250 16

Calpain-3 deficiency leads to muscular dystrophy in humans and mice and to perturbation of the NFkappaB/IkappaB pathway. As this phenotype is mainly atrophic, this study was performed to determine whether protein turnover and/or proteolytic gene expression was altered in muscles following calpain-3 deficiency. In vitro rates of protein turnover and of substrate ubiquitination, cathepsin B and B+L activities, and mRNA levels for several proteolytic genes were measured in skeletal muscles from 4-5 month-old control and calpain-3 knockout mice. Rates of protein synthesis and breakdown, cathepsin activities, and rates of substrate ubiquitination remained stable in muscles from calpain-3 deficient mice. However, and surprisingly, mRNA levels for cathepsin L, the 14-kDa ubiquitin-conjugating enzyme E2, and the C2 subunit of the 20S proteasome decreased by approximately 47% (P<0.005) in the gastrocnemius muscle from calpain-3 deficient mice. In contrast, muscle mRNA levels for ubiquitin and subunit S5a of the 26S proteasome were unaffected by calpain-3 deficiency. Taken together these data demonstrate that the expression of some genes that are involved in distinct proteolytic pathways is selectively and coordinately down-regulated without any effect on proteolysis. This suggests new pathophysiological hypotheses, e.g. a lack of maturation of NFkappaB precursor and/or a defect in specific substrate targeting.
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PMID:Down-regulation of genes in the lysosomal and ubiquitin-proteasome proteolytic pathways in calpain-3-deficient muscle. 1267 59

Oculopharyngeal muscular dystrophy (OPMD) is a late-onset autosomal dominant muscular dystrophy that results from small expansions of a polyalanine tract in the PABPN1 gene. Intranuclear inclusions are the pathological hallmark of OPMD. The mechanism by which protein aggregation in OPMD might relate to a toxic gain-of-function has so far remained elusive. Whether protein aggregates themselves are pathogenic or are the consequence of an unidentified underlying molecular mechanism is still unclear. Here, we report that protein aggregation in a cell model of OPMD directly impaires the function of the ubiquitin-proteasome pathway (UPP) as well as molecular chaperone functions. The proteasome inhibitor lactacystin causes significant increase of protein aggregation and toxicity. Moreover, overexpression of molecular chaperones (HSP40 and HSP70) suppressed protein aggregation and toxicity. We also provide evidence that mPABPN1-ala17 protein aggregation proportionally correlates with toxicity. Furthermore, we show that co-expression of chaperones in our OPMD cell model increases the solubility of mPABPN1-ala17 and transfected cell survival rate. Our studies suggest that molecular regulators of polyalanine protein solubility and degradation may provide insights into new mechanisms in OPMD pathogenesis. Further analysis of the cellular and molecular mechanisms by which UPP and molecular chaperones influence the degradation of misfolded proteins could provide novel concepts and targets for the treatment and understanding of the pathogenesis of OPMD and neurodegenerative diseases.
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PMID:Involvement of the ubiquitin-proteasome pathway and molecular chaperones in oculopharyngeal muscular dystrophy. 1294 20

Mutations in the gene encoding fukutin-related protein (FKRP) cause a spectrum of diseases including congenital muscular dystrophy type 1C (MDC1C), limb girdle muscular dystrophy 2I (LGMD2I) and congenital muscular dystrophies (CMDs) with brain malformations and mental retardation. Although these diseases are associated with abnormal dystroglycan processing, the cellular consequences of the idiosyncratic FKRP mutations have not been determined. Here we show, in cultured cells, that FKRP mutants associated with the more severe disease phenotypes (S221R, A455D, P448L) are retained in the endoplasmic reticulum (ER), whereas the wild-type protein and the mutant L276I that causes LGMD2I are found predominantly in the Golgi apparatus. The ER-retained proteins have a shorter half-life than the wild-type FKRP and are preferentially degraded by the proteasome. Furthermore, calnexin binds preferentially to the ER-retained mutants suggesting that it may participate in the quality control pathway for FKRP. These data provide the first evidence that the ER-retention of mutant FKRP may play a role in the pathogenesis of CMD and potentially explain why the allelic disorder LGMD2I is milder, because the mutated protein is able to reach the Golgi apparatus.
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PMID:Fukutin-related protein mutations that cause congenital muscular dystrophy result in ER-retention of the mutant protein in cultured cells. 1557 64

Ubiquitin-proteasome system (UPS) mediated proteolysis is responsible for the degradation of majority of cellular proteins, thereby playing essential roles in maintaining cellular homeostasis and regulating a number of cellular functions. UPS dysfunction was implicated in the pathogenesis of numerous disorders, including neurodegenerative disease, muscular dystrophy, and a subset of cardiomyopathies. However, monitoring in vivo functional changes of the UPS remains a challenge, which hinders the elucidation of UPS pathophysiology. We have recently created a novel transgenic mouse model that ubiquitously expresses a surrogate protein substrate for the UPS. The present study validates its suitability to monitor in vivo changes of UPS proteolytic function in virtually all major organs. Primary culture of cells derived from the adult transgenic mice was also developed and tested for their applications in probing UPS involvement in pathogenesis. Applying these newly established in vivo and in vitro approaches, we have proven in the present study that doxorubicin enhances UPS function in the heart and in cultured cardiomyocytes, suggesting that UPS hyper-function may play an important role in the acute cardiotoxicity of doxorubicin therapy.
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PMID:A novel transgenic mouse model reveals deregulation of the ubiquitin-proteasome system in the heart by doxorubicin. 1667 52

We investigated the response to deletion of the titin M-line region in striated muscle, using a titin knockout model and a range of techniques that include histology, in situ hybridization, electron microscopy, and 2D gel analysis. We found that the loss of titin's kinase domain and binding sites for myomesin and MURF-1 causes structural changes in the sarcomere that proceed from the M-line to the Z-disc and ultimately result in disassembly of the sarcomere. Disassembly goes along with central localization of nuclei (a hallmark for muscular dystrophy), up-regulation of heat-shock proteins, and induction of proteasome activity. While fiber type composition does not change in soleus and extensor digitorum longus muscle, fiber size is reduced. Animals die from complications of muscle atrophy at five weeks of age. In addition to the structural importance of the titin M-line region in any striated muscle, our data show how differences in M-line composition between heart and skeletal muscle affect sarcomere stability and function.
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PMID:Muscle atrophy in titin M-line deficient mice. 1647 Mar 36

Limb girdle muscular dystrophy type 2A results from mutations in the gene encoding the calpain 3 protease. Mutations in this disease are inherited in an autosomal recessive fashion and result in progressive proximal skeletal muscle wasting but no cardiac abnormalities. Calpain 3 has been shown to proteolytically cleave a wide variety of cytoskeletal and myofibrillar proteins and to act upstream of the ubiquitin-proteasome pathway. In this review, we summarize the known biochemical and physiological features of calpain 3 and hypothesize why mutations result in disease.
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PMID:Molecular and cellular basis of calpainopathy (limb girdle muscular dystrophy type 2A). 1693 40

Duchenne Muscular Dystrophy (DMD) is an incurable inherited disease of childhood, characterized by progressive muscle degeneration and weakness. Our previous findings supported the idea that dystrophin and associated proteins, absent or greatly reduced in DMD, are degraded in dystrophin-deficient muscle by the proteasomal-dependent pathway. Indeed, treatment with the proteasome inhibitor MG-132 of skeletal muscles from mdx mice--a spontaneous mouse model of DMD--as well as from DMD patients, effectively rescued the expression and correct cellular localization of dystrophin and associated proteins. These promising results led us to further explore the use of proteasome inhibitors as a therapy for DMD. Therefore, we directed our attention towards two new dipeptide boronic acid inhibitors blocking the proteasomal-dependent degradation pathway: Velcade (bortezomib or PS-341) and MLN273 (PS-273). The exciting aspect of this development is that these drugs have already progressed to preclinical and clinical trials, in different fields than muscular dystrophy. Indeed, Velcade has been already FDA-approved for treatment of multiple myeloma and its side effects had been already explored and managed. Promisingly, MLN273 is currently in the preclinical trial phase. Here, we test the effectiveness of Velcade and MLN273 by local injection into the gastrocnemius muscle of mdx mice. We show the rescue of expression and membrane localization of alpha-dystroglycan, beta-dystroglycan, alpha-sarcoglycan, and dystrophin after Velcade and MLN273 localized treatment, versus untreated (PBS only) mdx mice. Intriguingly, we also show that localized treatment with Velcade and MLN273 reduces the activation of Nuclear Factor-kappaB (NFkB). Because the NFkB pathway has been shown to be involved in inflammation responses in myopathies and DMD, our current results may have important clinical implications. Clearly, more investigations are needed, but our results emphasize the effectiveness of the pharmacological approach as a potential treatment for Duchenne muscular dystrophy.
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PMID:Localized treatment with a novel FDA-approved proteasome inhibitor blocks the degradation of dystrophin and dystrophin-associated proteins in mdx mice. 1749 27


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