The oncogenic protein p60v-src has competence activity but does not activate phosphatidylinositol turnover or protein kinase C in Balb/c 3T3 cells.
A Balb/c 3T3 cell-line infected with the temperature-sensitive Rous sarcoma virus LA90 has been used to investigate the mitogenic activity of p60v-src and the possible role of phosphatidylinositol turnover and protein kinase C activation in this process. Activation of the p60v-src tyrosine kinase alone was only weakly mitogenic to serum-deprived cells. However, transient activation of the kinase dramatically increased the mitogenic response to epidermal growth factor. Mitogenicity was not additive with phorbol esters. Down-regulation of protein kinase C by chronic administration of phorbol ester did not block the mitogenic effect of p60v-src. Following short-term activation of p60v-src, analysis of protein phosphorylations by giant two-dimensional electrophoresis revealed only very minor changes in any of the 1000 or so detectable phosphoproteins, whereas the activation of protein kinase C by a sub-optimal dose of phorbol ester significantly increased the phosphorylation of at least 10 proteins. Short-term activation of p60v-src did not cause any detectable increase in phosphatidylinositol turnover, or in diacylglycerol level. These results indicate that p60v-src can act, like platelet-derived growth factor, to induce competence in Balb/c 3T3 fibroblasts. They also suggest that even though p60v-src may activate phosphatidylinositol turnover in some other cell-lines, this effect is probably indirect and is not essential for induction of the transformed phenotype or for p60v-src-dependent mitogenesis.
Han
J W
JW
Department of Biophysics, University of Rochester Medical Center, NY 14642.
Gaut
J
J
Burstein
E
E
Sadowski
H
H
Young
D
D
Macara
I G
IG
D000818:Animals; D001358:Avian Sarcoma Viruses / Q000235:genetics*; D002455:Cell Division; D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured; D004789:Enzyme Activation; D007294:Inositol / Q000378:metabolism; D007295:Inositol Phosphates / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D008807:Mice, Inbred BALB C; D009154:Mutation; D015688:Oncogene Protein pp60(v-src) / Q000235:genetics / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D015398:Signal Transduction; D013696:Temperature; D040281:Vascular Endothelial Growth Factor Receptor-1
D007295:Inositol Phosphates; D010716:Phosphatidylinositols; D011518:Proto-Oncogene Proteins; D007294:Inositol; D040281:Vascular Endothelial Growth Factor Receptor-1; D015688:Oncogene Protein pp60(v-src); D011493:Protein Kinase C