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) whi ch are Ca2+ independent and phospholipid-dependent protein kinases, de creased in the cytosolic fraction and increased in the membrane fracti on during treatment with insulin or phorbol ester for 10 min. Immunobl ot analysis of novel PKCs, -epsilon, -delta and -zeta; showed that ins ulin stimulated the translocation of these PKC isoforms from cytosol t o membrane, similar to the translocation of conventional Ca2+/phosphol ipid-dependent PKCs (cPKCs), -alpha, -beta, and -gamma. Phorbol esters stimulated the translocation of PKC-alpha, -beta, -gamma, -epsilon an d -delta, but not PKC-zeta. These results suggest that (a) insulin and phorbol esters similarly stimulate the translocation of each PKC isof orm except for PKC-zeta, and (b) the translocation of both nPKCs and c PKCs occurs during insulin and TPA actions in rat adipocytes.