The stable GTP analog, guanosine 5'-(3-O-thiotriphosphate), GTPγS, stimulated both inositol trisphosphate (InsP3) and choline generation by NIH 3T3 cell membranes. Choline generation was stimulated by GTPγS over the dose range for activation of GTP-binding proteins. Membranes from control and c-Ha-ras- or c-Ha-ras(61 leu)-transformed cells did not differ in the extent to which GTPγS stimulated InsP3 or choline formation despite 5-10 fold over expression of Ras in the transformed cells. Unlike GTPγS, GTP did not stimulate phospholipid hydrolysis, even in membranes from cells expressing Ras(61leu), a mutant protein having reduced GTPase activity. Thus there is G protein regulation of both phosphatidylcholine-specific phospholipase D and polyphosphoinositide-specific phospholipase C in NIH 3T3 cell membranes. However, the lack of difference in GTPγS-stimulated phospholipid metabolism between control and ras-transformed cell membranes suggests that Ras does not function as the G protein(s) that directly regulate either phospholipase.
|Original language||English (US)|
|Number of pages||9|
|Journal||Second Messengers and Phosphoproteins|
|State||Published - Dec 1 1990|
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