A potential role for protein kinase C-epsilon in regulating megakaryocyticlineage commitment

Multiple studies have shown that intracellular signal transduction by the p rotein kinase C (PKC) family participates in the initiation of megakaryocyt e differentiation. In this study, multiple approaches addressed the functio nal contributions by specific PKC isozymes to megakaryocytic lineage commit ment of two independent cell lines, K562 and human erythroleukemia (HEL). P harmacologic profiles of induction and inhibition of megakaryocytic differe ntiation in both cell lines suggested a role for the calcium-independent no vel PKCs, in particular PKC-epsilon. In transfection studies, the isolated variable domain of PKC-epsilon selectively blocked exogenous activation of the megakaryocyte-specific alpha IIb promoter. Constitutively active mutant s of PKC-epsilon, but not of other PKC isozymes, cooperated with the transc ription factor GATA-1 in the activation of the alpha IIb promoter. The func tional cooperation between GATA-1 and PKC-epsilon displayed dependence on c ellular milieu, as well as on the promoter context of GATA binding sites. I n aggregate, the data suggest that PKC-epsilon specifically participates in megakaryocytic lineage commitment through functional cooperation with GATA -1 in the activation of megakaryocytic promoters.