A potential role for protien kinase C-ε in regulating megakaryocytic lineage commitment

Abstract

Multiple studies have shown that intracellular signal transduction by the protein kinase C (PKC) family participates in the initiation of megakaryocyte differentiation. In this study, multiple approaches addressed the functional contributions by specific PKC isozymes to megakaryocytic lineage commitment of two independent cell lines, K562 and human erythroleukemia (HEL). Pharmacologic profiles of induction and inhibition of megakaryocytic differentiation in both cell lines suggested a role for the calcium-independent novel PKCs, in particular PKC-ε. In transfection studies, the isolated variable domain of PKC-ε selectively blocked exogenous activation of the megakaryocyte-specific αIIb promoter. Constitutively active mutants of PKC-ε, but not of other PKC isozymes, cooperated with the transcription factor GATA-1 in the activation of the αIIb promoter. The functional cooperation between GATA-1 and PKC-ε displayed dependence on cellular milieu, as well as on the promoter context of GATA binding sites. In aggregate, the data suggest that PKC-ε specifically participates in megakaryocytic lineage commitment through functional cooperation with GATA-1 in the activation of megakaryocytic promoters.