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. Bi ochem. Biochem. 367, 233-239, 1999). In an attempt to explore the Fas downs tream factor contributing to the activation of phospholipase D, we have inv estigated the possible involvement of a small GTP hiding protein Res in sig naling events that were triggered by Fas cross-linking, Upon adenoviral exp ression of dominant negative mutant of Res (N17Ras), an increase in phospho lipase 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 i n diacylglycerol level, and the translocation of protein kinase C to membra ne fraction were all reduced by N17Ras expression. When parallel experiment s were performed with manumycin-A, a Ras farnensyltransferase inhibitor, al most identical inhibitory effects on Fas downstream signaling were exhibite d. These data suggest that Ras GTPase is essential in transmitting phosphol ipase D activation signal induced by Fas cross-linking and is located at ph osphatidylcholine-specific phospholipase C upstream in Fas signaling cascad es. (C) 2000 Academic Press.