PHORBOL ESTER AND INSULIN STIMULATE PROTEIN-KINASE-C ISOFORMS IN RAT ADIPOCYTES

We examined effect of insulin or 12-O-tetradecanoyl phorbol 13-acetate (TPA) on the subcellular redistribution of protein kinase C isoforms in rat adipocytes. Total Mono Q column-elutable novel PKCs (nPKCs) which are Ca2+ independent and phospholipid-dependent protein kinases, decreased in the cytosolic fraction and increased in the membrane fraction during treatment with insulin or phorbol ester for 10 min. Immunoblot analysis of novel PKCs, -epsilon, -delta and -zeta; showed that insulin stimulated the translocation of these PKC isoforms from cytosol to membrane, similar to the translocation of conventional Ca2+/phospholipid-dependent PKCs (cPKCs), -alpha, -beta, and -gamma. Phorbol esters stimulated the translocation of PKC-alpha, -beta, -gamma, -epsilon and -delta, but not PKC-zeta. These results suggest that (a) insulin and phorbol esters similarly stimulate the translocation of each PKC isoform except for PKC-zeta, and (b) the translocation of both nPKCs and cPKCs occurs during insulin and TPA actions in rat adipocytes.