Protein kinase C alpha is an effector of hexamethylene bisacetamide-induced differentiation of friend erythroleukemia cells

The program of biochemical and molecular events necessary for commitment to erythroid cell differentiation is particularly well characterized in murin e Friend erythroleukemia cell lines. Commitment to hemoglobin synthesis in response to a variety of chemical inducers, including hexamethylene bisacet amide and dimethyl sulfoxide is completed by 24 h and proceeds to terminal differentiation by 96 h. Phorbol 12-myristate 13-acetate, a classical tumor promoter phorbol ester that binds to protein kinase C, blocks differentiat ion in a reversible manner, suggesting an important role for protein kinase C signaling pathways. The classical protein kinase C isoforms alpha, beta I, and beta II, play distinct roles in the transduction of proliferative an d differentiative signals in human, as well as in murine, erythroleukemia c ells. Protein kinase C alpha has been implicated in differentiation of huma n erythroleukemia cells although its translocation to the nucleus has not b een observed. Taking advantage of the ability of phorbol 12-myristate 18-ac etate to block differentiation in Friend erythroleukemia cells, we determin ed the localization of the predominant protein kinase C isoforms alpha and beta I during differentiation and in response to their blockade. The abilit y of phorbol myristate acetate to preferentially diminish protein kinase C alpha-protein localization to the nucleus by 24 h and thereby block differe ntiation induced by hexamethylene bisacetamide was paralleled by the abilit y of protein kinase C alpha antisense transfection to block differentiation . In addition, beta-globin transcription, assessed by polymerase chain reac tion, was significantly decreased in protein kinase C alpha antisense-trans fected cells compared to that seen in vector transfected ones. Taken togeth er, these data suggest an important temporal role for nuclear protein kinas e C alpha localization in Friend erythroleukemia cell differentiation. (C) 1999 Academic Press.