Effects of ethanol on protein kinase C activity induced by filamentous actin

摘要

Protein kinase C (PKC) can be activated by interaction with filamentous actin (F-actin) in the absence of membrane lipids (S. J. Slater, S. K. Milano, B. A. Stagliano, K. J. Gergich, J. P. Curry, F. J. Taddeo and C. D. Stubbs, Biochemistry 39 (2000) 271-280). Here, the effects of ethanol on the F-actin-induced activities of a panel of PKC isoforms consisting of 'conventional' (cPKC) α, βI, γ, 'novel' (nPKC) δ, ε and 'atypical' (aPKC) ζ were investigated using purified PKC and F-actin. Ethanol was found to inhibit the Ca~(2+)- and phorbol ester-dependent activities of cPKCα and βI, and the Ca~(2+)- and phorbol ester-independent activity of cPKCγ, whereas the activities of nPKCδ, ε and aPKCζ were unaffected. Although the activities of cPKCα and βI induced by saturating levels of phorbol ester were inhibited by ethanol, the binding of these isozymes to F-actin was unaffected within the same phorbol ester concentration range. Conversely, within submaximal levels of phorbol ester, cPKCα and βI activities were unaffected by ethanol whereas binding to F-actin was inhibited. The potency of the inhibition of F-actin-induced cPKCβI activity increased with n-alkanol chain length up to n-hexanol, after which it declined. The results indicate that PKC activities associated with F-actin, and therefore cellular processes involving the actin cytoskeleton, are potential targets for ethanol action. The effects of ethanol on these processes may differ according to the particular regulating PKC isoform, its intracellular localization and the presence of activators and cofactors.