Ras GTPase is essential for fas-mediated activation of phospholipase D in A20 cells.
We have previously reported that Fas cross-linking resulted in an increase in phospholipase D activity in A20 murine cells (J.-S. Han et al., Arch. Biochem. Biophys. 367, 233-239, 1999). In an attempt to explore the Fas downstream factor contributing to the activation of phospholipase D, we have investigated the possible involvement of a small GTP biding protein Ras in signaling events that were triggered by Fas cross-linking. Upon adenoviral expression of dominant negative mutant of Ras (N17Ras), an increase in phospholipase D activity by anti-Fas monoclonal antibody was diminished. Also, the Fas downstream signaling events triggered by Fas cross-linking such as the activation of phosphatidylcholine-specific phospholipase C, the increase in diacylglycerol level, and the translocation of protein kinase C to membrane fraction were all reduced by N17Ras expression. When parallel experiments were performed with manumycin-A, a Ras farnensyltransferase inhibitor, almost identical inhibitory effects on Fas downstream signaling were exhibited. These data suggest that Ras GTPase is essential in transmitting phospholipase D activation signal induced by Fas cross-linking and is located at phosphatidylcholine-specific phospholipase C upstream in Fas signaling cascades.
Shin
I
I
Institute of Biomedical Science, Hanyang University, Seoul, 133-791, Korea.
Han
J S
JS
D000256:Adenoviridae / Q000378:metabolism; D000818:Animals; D004075:Diglycerides / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005799:Genes, Dominant; D011905:Genes, ras / Q000235:genetics; D006868:Hydrolysis; D051379:Mice; D020559:Monomeric GTP-Binding Proteins / Q000502:physiology*; D009154:Mutation; D010713:Phosphatidylcholines / Q000378:metabolism; D010739:Phospholipase D / Q000378:metabolism*; D011090:Polyenes / Q000494:pharmacology; D053284:Polyunsaturated Alkamides; D017368:Protein Prenylation; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000378:metabolism; D019014:fas Receptor / Q000378:metabolism*; D018631:ras Proteins / Q000502:physiology*
D004075:Diglycerides; D004791:Enzyme Inhibitors; D010713:Phosphatidylcholines; D011090:Polyenes; D053284:Polyunsaturated Alkamides; D019014:fas Receptor; D010738:Type C Phospholipases; D010739:Phospholipase D; D020559:Monomeric GTP-Binding Proteins; D018631:ras Proteins; C054474:manumycin