GTP-binding protein-stimulated phospholipase C and phospholipase D activities in ras-transformed NIH 3T3 fibroblasts.
The stable GTP analog, guanosine 5'-(3-O-thiotriphosphate), GTP gamma S, stimulated both inositol trisphosphate (InsP3) and choline generation by NIH 3T3 cell membranes. Choline generation was stimulated by GTP gamma S 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 GTP gamma S stimulated InsP3 or choline formation despite 5-10 fold over expression of Ras in the transformed cells. Unlike GTP gamma S, GTP did not stimulate phospholipid hydrolysis, even in membranes from cells expressing Ras61leu, 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 GTP gamma S-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.
Quilliam
L A
LA
Department of Pharmacology, University of California, San Diego, La Jolla 92093.
Der
C J
CJ
Brown
J H
JH
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D002461:Cell Line, Transformed; D002462:Cell Membrane / Q000378:metabolism; D002471:Cell Transformation, Neoplastic; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000494:pharmacology*; D011905:Genes, ras; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D007295:Inositol Phosphates / Q000378:metabolism; D051379:Mice; D010713:Phosphatidylcholines / Q000378:metabolism; D010739:Phospholipase D / Q000378:metabolism*; D014162:Transfection; D010738:Type C Phospholipases / Q000378:metabolism*
D007295:Inositol Phosphates; D010713:Phosphatidylcholines; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D010738:Type C Phospholipases; D010739:Phospholipase D; D000251:Adenosine Triphosphatases; D019204:GTP-Binding Proteins