INSULIN ACTIVATES MYELIN BASIC-PROTEIN (P42 MAP) KINASE BY A PROTEIN KINASE-C-INDEPENDENT PATHWAY IN RAT ADIPOCYTES - DISSOCIATION FROM GLUCOSE-TRANSPORT

Myelin basic protein kinase (MBPK) activity of rat adipocytes was measured directly or in gels after purification of p42 microtubule-associated protein kinase (MAPK). Insulin and phorbol esters provoked 2- to 3-fold increases in MBPK/MAPK activity within 5-10 min. Whereas phorbol ester effects were blocked by protein kinase C (PKC) depletion or inhibition, insulin effects were fully intact, indicating that insulin activates MBPK/MAPK independently of PKC. In contrast, PKC depletion or inhibition markedly inhibited insulin effects on [H-3]2-deoxyglucose uptake, suggesting that this effect requires PKC, rather than a factor within the ras/MAPK cascade.