Recombinant Clb domain of PKCδ triggers meiotic maturation upon microinjection in Xenopus laevis oocytes

The C1 domains are 50 amino acid sequences present in protein kinase C (PKC) isozymes that are responsible for binding of phorbol esters and the lipid second messenger diacylglycerol (DAG), We found that bacterially expressed C1b domain of PKC delta induces germinal vesicle breakdown (GVBD) when microinjected into Xenopus laevis oocytes. Injection of the C1b domain of PKC delta significantly enhanced insulin- but not progesterone-induced maturation. Interestingly, the PKC delta C1b domain markedly synergized with normal Ras protein to induce oocyte maturation when both proteins were coinjected in oocytes. Our results demonstrate that the purified C1b domain of PKC delta is sufficient to promote meiotic maturation of X. laevis oocytes probably through activation of components of the insulin/Ras signaling pathway. (C) 2000 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.