Activation of skeletal muscle calpain-3 by eccentric exercise in humans does not result in its translocation to the nucleus or cytosol

作者：Murphy Robyn M^*; Vissing Kristian; Latchman Heidy; Lamboley Cedric; McKenna Michael J; Overgaard Kristian; Lamb Graham D

来源：Journal of Applied Physiology, 2011, 111(5): 1448-1458.

DOI：10.1152/japplphysiol.00441.2011

• muscle injury
• calcium-dependent protease
• calpains
• nuclear
• cytosolic

Murphy RM, Vissing K, Latchman H, Lamboley C, McKenna MJ, Overgaard K, Lamb GD. Activation of skeletal muscle calpain-3 by eccentric exercise in humans does not result in its translocation to the nucleus or cytosol. J Appl Physiol 111: 1448-1458, 2011. First published August 11, 2011; doi: 10.1152/japplphysiol.00441.2011.-The skeletal muscle-specific calpain-3 protease is likely involved in muscle repair, although the mechanism is not known. Physiological activation of calpain-3 occurs 24 h following eccentric exercise in humans. Functional consequences of calpain-3 activation are not known; however, calpain-3 has been suggested to be involved in nuclear signaling via NF-kappa B. To test this and help identify how/where calpain-3 acts, we investigated whether calpain-3 autolysis (hence, activation) following eccentric exercise results in translocation from its normal myofibrillar location to the nucleus or the cytosol. In resting human skeletal muscle, the majority (87%) of calpain-3 was present in myofibrillar fractions, with only a small proportion (<10%) in an autolyzed state. Enriched nuclear fractions contained similar to 8% of the total calpain-3, which was present in a predominantly (>80%) autolyzed state. Using freshly dissected human muscle fibers to identify freely diffusible proteins, we showed that only similar to 5% of the total calpain-3 pool was cytosolic. At 3 and 24 h following eccentric step exercise, there was an similar to 70% increase in autolysis in whole muscle samples (n = 11, P < 0.05, by 1-way ANOVA with repeated measures and Newman-Keuls post hoc analysis). This exercise-induced autolysis was attributed to myofibrillar-bound calpain-3, since neither the amount of calpain-3 nor the proportion autolyzed was significantly changed in enriched nuclear or cytosolic fractions following the exercise intervention. We present a model for calpain-3 localization at rest and following activation in human skeletal muscle and suggest that the functional importance of calpain-3 remains predominantly tightly associated with its localization within the myofibrillar compartment.

• 出版日期2011-11