Protein kinase C activities with different characteristics, including substrate specificity, from two human HL-60 leukemia cell variants

To evaluate the role of protein kinase C in the cellular maturation processes induced by phorbol diesters, we examined the biochemical activity of protein kinase C from HL-205, a cell variant from the human promyelocytic HL-60 leukemia that is susceptible to differentiation induced by phorbol 12-myristate 13-acetate, and from HL-525, an HL-60 variant that is resistant to such an induction. The activities of protein kinase C from the two cell types differed in their requirements for the cofactors Ca2+ and lipids. These enzyme activities also differed in their abilities to phosphorylate protamine and a series of four oligopeptides. We suggest that the differences in vitro in the activities of protein kinase C between HL-205 and HL-525 cells, especially in their substrate specificity, are closely related to the different phosphorylation patterns induced in vivo by phorbol 12-myristate 13-acetate in these cells. We also suggest that these differences may be responsible for the different susceptibilities of the two cell types to maturation induced by phorbol diesters.