Tyrosine phosphorylation of specific protein kinase C isoenzymes participates in insulin stimulation of glucose transport in primary cultures of rat skeletal muscle

Several reports indicate that protein kinase C (PKC) plays a role in insuli n-induced glucose transport in certain cells. The precise effects of insuli n on specific PKC isoforms are as yet unknown. Utilizing primary cultures o f rat skeletal muscle, we investigated the possibility that insulin may inf luence the activation state of PRC isoenzymes by inducing their translocati on and tyrosine phosphorylation. This, in turn, may mediate insulin effects on glucose transport. We identified and determined the glucose transporter s and PKC isoforms affected by insulin and 12-O-tetradecanoylphorbol-13-ace tate (TPA). Insulin and TPA each caused an increase in glucose uptake. Insu lin translocated GLUT3 and GLUT4 without affecting GLUT1. In contrast, TP;I translocated GLUT1 and GLUT3 without affecting GLUT4. Insulin translocated and tyrosine phosphorylated and activated PKC-beta 2 and -zeta; these effe cts were blocked by phosphatidylinositol 3-kinase (P13K) inhibitors. TPA tr anslocated and activated PKC-alpha, -beta 2, and -delta; these effects were not noticeably affected by P13K inhibitors. Furthermore, wortmannin signif icantly inhibited both insulin and TPA effects on GLUT translocation and gl ucose uptake. Finally, insulin-induced glucose transport was blocked by the specific PKC-beta 2 inhibitor LY379196. These results indicate that specif ic PRC isoenzymes, when tyrosine-phosphorylated, are implicated in insulin- induced glucose transport in primary cultures of skeletal muscle.