Differential Effect of Phorbol Esters and Interleukin-3 on Protein Kinase

FD/PMA is a subclone of the interleukin-3 (IL-3)-dependent, FDC-P1 cell line, which proliferates in response to either 12-0-tetradecanoylphorbol-13 acetate (PMA) or IL-3. While several endogenous substrates were phosphorylated in response t o protein kinase C (PKC) activation in FDC-P1, phospholipid-dependent phosphorylation in the FD/ PMA grown in PMA was not observed. Basal, phosphatidylserineindependent, and diolein-independent phosphorylation of cytosolic substrates with molecular weights of 17,52,57, and 105 Kd were enhanced in FD/PMA cells grown in PMA as compared with FDC-P1 cells cultured in IL-3. Phosphorylation of a 105-Kd substrate was enhanced in the particulate fraction of FD/PMA cells maintained in PMA. The 17-Kd substrate in FD/PMA cells comigrated with a substrate phosphorylated in a PKC-dependent manner in FDC-P1 cells. Phosphorylation of the 52and 57-Kd substrates, but not of