Effect of exercise on protein kinase C activity and localization in human skeletal muscle.

To investigate the effect of exercise on protein kinase C (PKC) activity and localization in human skeletal muscle, eight healthy men performed cycle ergometer exercise for 40 min at 76 +/- 1% the peak pulmonary O(2) uptake , with muscle samples obtained at rest and after 5 and 40 min of exercise. PKC expression, phosphorylation and activities were examined by immunoblotting and in vitro kinase assays of fractionated and whole tissue preparations. In response to exercise, total PKC activity was slightly higher at 40 min in an enriched membrane fraction, and using a pSer-PKC-substrate motif antibody it was revealed that exercise increased the serine phosphorylation of an approximately 50 kDa protein. There were no changes in conventional PKC (cPKC) or PKC activities; however, atypical PKC (aPKC) activity was approximately 70% higher at 5 and 40 min, and aPKC expression and Thr(410/403) phosphorylation were unaltered by exercise. There were no effects of exercise on the abundance of PKCalpha, PKCdelta, PKC and aPKC within cytosolic or enriched membrane fractions of skeletal muscle. These data indicate that aPKC, but not cPKC or PKC, are activated by exercise in contracting muscle suggesting a potential role for aPKC in the regulation of skeletal muscle function and metabolism during exercise in humans.