PROTEIN-KINASE-C ISOFORMS IN MURINE ERYTHROLEUKEMIA-CELLS AND THEIR INVOLVEMENT IN THE DIFFERENTIATION PROCESS

In addition to alpha, delta and epsilon-protein kinase C, murine erythroleukemia cells contain xi-PKC and also a c-PKC isoform, named alpha(1), which shows cross-reactivity with an anti-alpha-PKC antipeptide antibody. In a C44 MEL cell clone, characterized by a high rate of differentiation, both c-PKC forms are expressed al a level higher than that of the N23 MEL cell clone which differentiates at a low rate and contains higher levels of epsilon-PKC and particularly of the delta-PKC isozyme. In the course of MEL cell differentiation, delta-PKC in N23 cells and alpha(1)-PKC in C44 cells are rapidly down-regulated and the overall process is almost completed before cell commitment. Of the other three PKC isozymes present in both clones, only alpha-PKC is down-regulated to a significant extent. It is proposed that modulation of the signal delivered by each PKC isozyme is one of the biochemical mechanisms involved in MEL cell differentiation.