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Determination of exponential rate constants for calpain-mediated degradation of myofibrillar complexed proteins

University of British Columbia

The purpose of this study was to test the hypothesis that an orderly sequence or time course of calpain action on purified myofibrillar/cytoskeletal complexes from cardiac and fast muscle tissue exists. To test the response of individual substrate proteins to degradation (i.e. susceptibility), exogenous calpain (1.5U/ml) was incubated with 40 ug of highly purified rat myofibrillar complexes from cardiac and gastrocnemius muscles (0 to 60 min), in vitro. Apparent molecular weights (SDS-PAGE) were used to compare and identify individual myofibril proteins. Myofibrillar yields for cardiac (n=9) and fast skeletal (n=9) muscles were 62.93 ± 6.58 and 98.42 ± 9.36 mg/g (p<0.05). Following 30 minutes of calpain treatment, the amount of cardiac desmin, C-protein, a-actinin and troponin-T remaining in complex were 0%, 19%, 23% and 68%, compared to controls (p<0.05). For fast skeletal muscle, the remaining desmin, C-protein, a-actinin and tropomyosin after 30 minutes of calpain digestion was 0%, 38%, 51% and 17%, respectively, compared to control (p<0.05). The estimated exponential rate constants (k) for degradation/loss for each protein (in both tissues) had the following order: desmin>C-protein>a -actinin (p<0.05). The results of this study support the hypothesis that there are selective degradation rates and an ordered sequence of degradation for myofibrillar complexed proteins. Factors contributing to the heterogeneity of k values for myofibril proteins, and therefore their susceptibility to calpain degradation, may be their spatial arrangement (peripheral -> central) within the myofibril and/or their primary amino acid residue composition.

Thesis/Dissertation

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2009-03-07

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http://hdl.handle.net/2429/5726

Human Kinetics

University of British Columbia

UBCV

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