Differing kinase activity of the c-yes and c-src gene proteins in TPA-induced megakaryocytic differentiation of T-33 and K562 cell lines.

We examined the protein kinase (PK) activity of the c-yes and c-src gene proteins (c-YES, c-SRC) at an early phase of 12-O-tetradecanoyl phorbol-13-acetate (TPA)-induced megakaryocytic differentiation of T-33 and K562 cells with use of immunoprecipitation and in vitro kinase assay. We found that c-SRC PK activity of TPA-treated T-33 and K562 cell lines had been enhanced compared with the untreated ones, but in contrast, no enhancement of c-YES PK activity by the TPA treatment was observed in these cell lines. We also examined PK activity in TPA-induced monocytic differentiation of U937 monoblastic cells that exhibited no megakaryocytic markers and found that both the c-YES and c-SRC PK activity was enhanced by the TPA treatment. Our data suggest that c-YES and c-SRC play different and unique roles in TPA-induced megakaryocytic differentiation in T-33 and K562 cells.