INSULIN REGULATES PKC ISOFORM MESSENGER-RNA IN RAT ADIPOCYTES

Insulin and 12-O-tetradecanoyl phorbol-13-acetate (TPA) induce both gl ucose uptake and translocation of protein kinase C (PKC) from cytosol to membrane in insulin-sensitive tissues as previously reported by sev eral investigators. We examined insulin-mediated PKC beta I, beta II, and epsilon translocation from cytosol to cytoskeleton, and expression of PKC alpha, beta I, beta II, gamma, and epsilon isoforms using the reverse transcription polymerase chain reaction (RT-PCR) method during treatment with insulin for 240 min in rat adipocytes. Insulin-induced increases in PKC beta I, beta II, and epsilon were greater in the cyt oskeleton fraction than those in the membrane fraction. Insulin induce d time-dependent increases in PKC alpha, gamma, epsilon and zeta mRNA levels for up to 240 min (555%, 117%, 236% and 138% increase, respecti vely). TPA also induced time-dependent increases in PKC alpha and gamm a (34% and 500%, increase, respectively) but not in PKC zeta. However, PKC beta I mRNA was decreased for up to 60 min and then maintained at tinder the basal level during stimulation with insulin and TPA. On th e other hand, PKC beta II mRNA was markedly increased for up to 240 mi n. These results suggest that insulin-regulated PKC alpha, gamma and e psilon mRNA levels and PKC beta mRNA alternative splicing may occur in rat adipocytes.