Insulin activates phospholipase C-gamma 1 via a PI-3 kinase dependent mechanism in 3T3-L1 adipocytes

Previously we have shown that the insulin receptor and phospholipase C-yl p hysically interact in the 3T3-L1 adipocyte cell line. In this study, we inv estigated the ability of insulin and PDGF to stimulate PLC-gamma1 enzyme ac tivity as measured by PI-(4,5)P-2 hydrolysis, Both insulin and PDGF caused a rapid (<1 min) increase in PLC activity associated with the respective re ceptor. PDGF treatment resulted in a higher and more sustained stimulation of PLC-<gamma>1 activity compared to insulin (0.95 pmol/min/mg vs 0.68 pmol /min/mg). Furthermore, insulin and PDGF promoted increases in total cellula r DAG, one of the products of PI-(4,5)P-2 hydrolysis. Insulin-stimulated PL C activity appears to be downstream of PI-3Kinase as the DAG; increase was partially blocked by Wortmannin and addition of PI-(3,4,5)P-3 activated PLC -gamma1 in vitro. Inhibition of PLC using U73122 or an inhibitory peptide c aused a decrease in insulin-stimulated 2-deoxyglucose transport and GLUT4 t ranslocation that was rescued by the addition of OAG, a cell-permeable synt hetic DAG. (C) 2001 Academic Press.