Proteolytic activity of proteasome on myofibrillar structures

Taylor, Richard G.; Tassy, Caroline; Briand, M.; Robert, Nathalie; Briand, Yves; Ouali, Ahmed

doi:10.1007/bf00990974

Cited by 69 publications

(42 citation statements)

References 16 publications

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“…This process is exactly reversed to the time-course of myofibril assembly, where the first organized complexes consist of α-actinin, actin and Z-disk epitopes of titin at a time when all the thick filament components are still completely diffuse throughout the sarcomere . Conversely, myofibril disassembly as it occurs during myopathies or muscle wasting is also characterized by degradation of Z-disk and I-band material before the rest of the sarcomere is affected (Taylor et al, 1995). During this process, degradation of myofibrils seems to be mainly regulated by the activity of muscle-specific calpain, which can associate with the I-band region of titin (Kinbara et al, 1998) and thereafter by the ubiquitin-proteasome pathway (Hasselgren and Fischer, 2001).…”

Section: Discussionmentioning

confidence: 99%

Sequential myofibrillar breakdown accompanies mitotic division of mammalian cardiomyocytes

Ahuja¹,

Perriard²,

Perriard³

et al. 2004

Journal of Cell Science

144

123

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The contractile tissue of the heart is composed of individual cardiomyocytes. During mammalian embryonic development, heart growth is achieved by cell division while at the same time the heart is already exerting its essential pumping activity. There is still some debate whether the proliferative activity is carried out by a less differentiated, stem cell-like type of cardiomyocytes or whether embryonic cardiomyocytes are able to perform both of these completely different dynamic tasks, contraction and cell division. Our analysis of triple-stained specimen of cultured embryonic cardiomyocytes and of whole mount preparations of embryonic mouse hearts by confocal microscopy revealed that differentiated cardiomyocytes are indeed able to proliferate. However, to go through cell division, a disassembly of the contractile elements, the myofibrils, has to take place. This disassembly occurs in two steps with Z-disk and thin (actin)-filament-associated proteins getting disassembled before disassembly of the M-bands and the thick (myosin) filaments happens. After cytokinesis reassembly of the myofibrillar proteins to their mature cross-striated pattern can be seen. Another interesting observation was that the cell-cell contacts remain seemingly intact during division, probably reflecting the requirement of intact integration sites of the individual cells in the contractile tissue. Our results suggest that embryonic cardiomyocytes have developed an interesting strategy to deal with their major cytoskeletal elements, the myofibrils, during mitosis. The complex disassembly-reassembly process might also provide a mechanistic explanation, why cardiomyocytes cede to divide postnatally.

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Section: Discussionmentioning

confidence: 99%

Sequential myofibrillar breakdown accompanies mitotic division of mammalian cardiomyocytes

Ahuja¹,

Perriard²,

Perriard³

et al. 2004

Journal of Cell Science

144

123

View full text Add to dashboard Cite

show abstract

“…These lysosomal and Ca 2ϩ -dependent proteinases may be qualitatively important for the degradation of specific but quantitatively minor muscle proteins. For example, calpains are involved in rapid removal of Z-disks (53,54) and N2 lines (54), and degrade nebulin, titin, troponin, tropomyosin, but not myosin and actin (53), which are quantitatively important.…”

Section: Discussionmentioning

confidence: 99%

Muscle wasting in a rat model of long-lasting sepsis results from the activation of lysosomal, Ca2+ -activated, and ubiquitin-proteasome proteolytic pathways.

Voisin¹,

Breuillé²,

Combaret³

et al. 1996

J. Clin. Invest.

209

160

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We studied the alterations in skeletal muscle protein breakdown in long lasting sepsis using a rat model that reproduces a sustained and reversible catabolic state, as observed in humans. Rats were injected intravenously with live Escherichia coli ; control rats were pair-fed to the intake of infected rats. Rats were studied in an acute septic phase (day 2 postinfection), in a chronic septic phase (day 6), and in a late septic phase (day 10). The importance of the lysosomal, Ca 2 ϩ -dependent, and ubiquitin-proteasome proteolytic processes was investigated using proteolytic inhibitors in incubated epitrochlearis muscles and by measuring mRNA levels for critical components of these pathways. Protein breakdown was elevated during the acute and chronic septic phases (when significant muscle wasting occurred) and returned to control values in the late septic phase (when wasting was stopped). A nonlysosomal and Ca 2 ϩ -independent process accounted for the enhanced proteolysis, and only mRNA levels for ubiquitin and subunits of the 20 S proteasome, the proteolytic core of the 26 S proteasome that degrades ubiquitin conjugates, paralleled the increased and decreased rates of proteolysis throughout. However, increased mRNA levels for the 14-kD ubiquitin conjugating enzyme E2, involved in substrate ubiquitylation, and for cathepsin B and m-calpain were observed in chronic sepsis. These data clearly support a major role for the ubiquitinproteasome dependent proteolytic process during sepsis but also suggest that the activation of lysosomal and Ca 2 ϩ -dependent proteolysis may be important in the chronic phase. (

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“…Proteasomes , representing multicatalytic protease complexes , are believed to play a central role in the nonlysosomal ATPubiquitin-dependent proteolytic pathway for intracellular protein degradation (8)(9)(10)(11)(12)(13)(14). At least two forms of proteasomes are known: a 26S complex responsible for ubiquitin-conjugate degradation and requiring ATP; and a 20S proteasome (700 kD) which represents the proteolytic core of the 26S proteasome (8).…”

Section: Discussionmentioning

confidence: 99%

“…Recent evidence has indicated that the nonlysosomal ATPubiquitin-dependent proteolytic protease, as a multicatalytic protease complex (proteasome), participates in muscle wasting during various catabolic states (8)(9)(10)(11)(12)(13)(14). Degradation ofa protein via this pathway involves two distinct steps: signaling by the covalent attachment of multiple ubiquitin molecules, followed by degradation of the targeted protein by an ATP-dependent protease, the 26S (1 ,500 kD) proteasome (14), with the release of free, reutilizable ubiquitin.…”

Section: Introductionmentioning

confidence: 99%

Proteasomes in Distal Myopathy with Rimmed Vacuoles.

et al. 1998

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In a previous report we suggested that muscle fibers in distal myopathywith rimmedvacuoles (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 rimmedvacuoles, and in the cytoplasm of atrophic fibers. Ubiquitin accumulation was marked within rimmedvacuoles 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. Wesuggest 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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Proteolytic activity of proteasome on myofibrillar structures

Cited by 69 publications

References 16 publications

Sequential myofibrillar breakdown accompanies mitotic division of mammalian cardiomyocytes

Sequential myofibrillar breakdown accompanies mitotic division of mammalian cardiomyocytes

Muscle wasting in a rat model of long-lasting sepsis results from the activation of lysosomal, Ca2+ -activated, and ubiquitin-proteasome proteolytic pathways.

Proteasomes in Distal Myopathy with Rimmed Vacuoles.

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