Recombinant C1b domain of PKCδ triggers meiotic maturation upon microinjection inXenopus laevisoocytes

Abstract
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 PKCδ induces germinal vesicle breakdown (GVBD) when microinjected into Xenopus laevis oocytes. Injection of the C1b domain of PKCδ significantly enhanced insulin‐ but not progesterone‐induced maturation. Interestingly, the PKCδ C1b domain markedly synergized with normal Ras protein to induce oocyte maturation when both proteins were co‐injected in oocytes. Our results demonstrate that the purified C1b domain of PKCδ is sufficient to promote meiotic maturation of X. laevis oocytes probably through activation of components of the insulin/Ras signaling pathway.