PROTEIN-KINASE-C ISOZYMES THAT MEDIATE ENHANCEMENT OF NEURITE OUTGROWTH BY ETHANOL AND PHORBOL ESTERS IN PC12 CELLS

Using PC12 cells to study ethanol's effects on growth of neural proces ses, we found that ethanol enhances NGF- and basic FGF-induced neurite outgrowth. Chronic ethanol exposure selectively up-regulates delta an d epsilon protein kinase C (PKC) and increases PKC-mediated phosphoryl ation in PC12 cells. Since PKC regulates differentiation, we investiga ted the role of PKC in enhancement of neurite outgrowth by ethanol. Li ke ethanol, 0.3-10 nM phorbol 12-myristate, 13-acetate (PMA) increased NGF-induced neurite outgrowth. However, higher concentrations did not , and immunoblot analysis demonstrated that 100 nM PMA markedly deplet ed cells of beta, delta and epsilon PKC. PMA (100 nM) also down-regula ted beta, delta and epsilonPKC in ethanol-treated cells and completely prevented enhancement of neurite outgrowth by ethanol. In contrast, t he cAMP analogue 8-bromoadenosine cAMP did not completely mimic the ef fects of ethanol on neurite outgrowth, and ethanol was able to enhance neurite formation in mutant PC12 cells deficient in protein kinase A (PKA). These findings implicate beta, delta or epsilonPKC, but not PKA , in the neurite-promoting effects of ethanol and PMA. Since chronic e thanol exposure up-regulates delta and epsilon, but not betaPKC, these findings suggest that delta or epsilonPKC regulate neurite outgrowth.