Scrape-loaded p21ras down-regulates agonist-stimulated inositol phosphate production by a mechanism involving protein kinase C.
The effect of scrape-loaded [Val-12]p21ras on agonist-stimulated phosphatidylinositol 4,5-bisphosphate (PIP2) turnover in Swiss-3T3 cells was studied. Previously [Morris, Price, Lloyd, Marshall & Hall (1989) Oncogene 4, 27-31] we demonstrated that [Val-12]p21ras activates protein kinase C within 10 min of scrape loading. Here, we show that [Val-12]p21ras inhibits bombesin and platelet-derived growth factor-stimulated PIP2 breakdown 1.5-4 h after scrape loading. This effect persisted for at least 18 h and could be mimicked in control cells by activation of protein kinase C with 12-O-tetradecanoyl 13-acetate (TPA) 15 min prior to ligand stimulation. When protein kinase C was down-regulated by chronic TPA treatment, [Val-12]p21ras was no longer able to inhibit agonist-stimulated inositol phosphate production. These results indicate that changes in inositol phosphate levels caused by ras protein are probably due to activation of protein kinase C and not to an interaction of ras with phospholipase C.
Price
B D
BD
Institute of Cancer Research, Chester Beatty Laboratories, London, U.K.
Morris
J D
JD
Marshall
C J
CJ
Hall
A
A
D000818:Animals; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D015689:Oncogene Protein p21(ras); D009856:Oncogene Proteins, Viral / Q000494:pharmacology*; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols / Q000096:biosynthesis*; D010982:Platelet-Derived Growth Factor; D011493:Protein Kinase C / Q000378:metabolism*; D014764:Viral Proteins / Q000494:pharmacology
D009856:Oncogene Proteins, Viral; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D010982:Platelet-Derived Growth Factor; D014764:Viral Proteins; D011493:Protein Kinase C; D015689:Oncogene Protein p21(ras)