Differential responses to acute endurance exercise-induced signaling protein phosphorylation and abundance alterations in whole murine gastrocnemius muscle and isolated myofibers.

Skeletal muscle is composed of diverse cell types, including myofibers. In this study, we investigated how acute endurance exercise could induce signaling protein phosphorylation and abundance alterations using protein lysate extracted from whole-muscle tissue or isolated myofibers. We subjected 8-week-old male Institute Cancer Research mice to a single bout of treadmill running-based endurance exercise, and evaluated the signaling protein expression responses in the whole gastrocnemius muscle and isolated myofibers, obtained by incubation in 0.2 % collagenase/medium, immediately after exercise. Our results revealed that exercise activated mitochondrial biogenesis- and protein anabolism-related signaling, including 5'-adenosine monophosphate-activated kinase and Akt/p70 S6 kinases, respectively, as well as increased glucose metabolism-related proteins in whole-muscle samples immediately after exercise. However, these signaling responses were not present in the muscle fiber lysate and mitochondrial oxidative phosphorylation-related protein abundance significantly decreased postexercise. Our data suggest that signaling protein activation and quantitative alterations in myofibers digested in collagenase-dissolved medium post acute exercise do not necessarily reflect the expression responses in whole skeletal muscle tissue.