title: Multilineage hematopoietic growth factor interleukin 3 and direct activators of protein kinase C stimulate phosphorylation of common substrates.
abstract: In order to investigate early signal transduction events in myeloid cells, the phosphosubstrates of an interleukin 3 (IL 3)-dependent cell line, FDC-P1, have been analyzed. Using synthetic diacylglycerol as a direct activator of the unique calcium-phospholipid-dependent phosphotransferase protein kinase C (PK-C) and genetically engineered homogeneous IL 3, we have demonstrated a common element to signal transduction events associated with these stimulants. One novel substrate, p68 (68,000 kd), was rapidly phosphorylated in either IL 3- or diacylglycerol-stimulated cells. The phosphorylation of p68 was dose-dependent, with both the physiological ligand and diacylglycerol inducing the same maximal level of phosphorylation. Phosphorylation of p68 occurred in a time-dependent manner analogous to previously described kinetics of PK-C subcellular redistribution in the FDC-P1 cell line. The p68 substrate was also phosphorylated in a cell-free system under conditions designed to activate PK-C. Phosphoamino acid analysis demonstrated that the p68 molecule phosphorylated in intact cells as well as in a calcium-phospho-lipid-dependent cell-free system was phosphorylated on threonine residues, not tyrosine. These data support the hypothesis that the activation of PK-C that occurs after IL 3-receptor interaction which leads to the rapid phosphorylation of cellular proteins is an important element of the signal transduction mechanism in FDC-P1 cells. We propose that phosphorylation of the p68 molecule is a physiochemical marker for the activation of PK-C in myeloid cells, in response to the growth-promoting physiological ligand.
mesh_terms: D000818:Animals; D002117:Calcitriol / Q000494:pharmacology; D002451:Cell Compartmentation / Q000187:drug effects; D002453:Cell Cycle; D002460:Cell Line; D003115:Colony-Stimulating Factors / Q000494:pharmacology; D004075:Diglycerides / Q000494:pharmacology; D004789:Enzyme Activation; D007377:Interleukin-3 / Q000494:pharmacology*; D007700:Kinetics; D051379:Mice; D008970:Molecular Weight; D010750:Phosphoproteins / Q000502:physiology*; D010766:Phosphorylation; D010769:Phosphothreonine / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D003115:Colony-Stimulating Factors; D004075:Diglycerides; D007377:Interleukin-3; D010750:Phosphoproteins; D010769:Phosphothreonine; C038237:1-oleoyl-2-acetylglycerol; D011493:Protein Kinase C; D002117:Calcitriol; D013755:Tetradecanoylphorbol Acetate