title: Regulation of Ras-GAP and the neurofibromatosis-1 gene product by eicosanoids.
abstract: Ras-GAP (GTPase activating protein) is a regulatory protein that stimulates the intrinsic guanosine triphosphatase (GTPase) activity of the proto-oncogene product p21ras. A domain of the neurofibromatosis gene product (NF1) that has sequence similarity to the catalytic domain of Ras-GAP and to yeast IRA gene products also has a specific stimulatory activity toward p21ras GTPase. Arachidonic acid and phosphatidic acid inactivate GAP, but no agents have been identified that stimulate GAP and thereby switch p21ras off. With the use of recombinant Ha-c-Ras and Ras-GAP, NF1, and GAP catalytic domains, it was found that prostaglandins PGF2 alpha and PGA2 stimulated Ras-GAP and that prostacyclin PGI2 inhibited Ras-GAP. The stimulatory effect of PGF2 alpha was saturable and structure-specific and competed with the inhibitory effect of arachidonic acid. Arachidonic acid also inhibited the catalytic activity of NF1, but prostaglandins were not stimulatory. These results suggest a mechanism for the allosteric control of Ras function through the modulation of arachidonate metabolism.
authors.affiliation: Department of Biophysics, University of Rochester Medical Center, NY 14642.
authors.forename: J W
authors.initials: JW
authors.lastname: Han
authors.forename: F
authors.initials: F
authors.lastname: McCormick
authors.forename: I G
authors.initials: IG
authors.lastname: Macara
mesh_terms: D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000494:pharmacology; D015237:Dinoprost / Q000494:pharmacology; D020558:GTP Phosphohydrolases / Q000378:metabolism; D020690:GTPase-Activating Proteins; D005786:Gene Expression Regulation / Q000187:drug effects; D011905:Genes, ras / Q000187:drug effects*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D009456:Neurofibromatosis 1 / Q000235:genetics; D025542:Neurofibromin 1; D011453:Prostaglandins / Q000494:pharmacology*; D011506:Proteins / Q000235:genetics*; D000090063:Proto-Oncogene Mas; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D020703:ras GTPase-Activating Proteins
chemical_list: D001095:Arachidonic Acids; D020690:GTPase-Activating Proteins; C000715470:MAS1 protein, human; D025542:Neurofibromin 1; D011453:Prostaglandins; D011506:Proteins; D000090063:Proto-Oncogene Mas; D011994:Recombinant Proteins; D020703:ras GTPase-Activating Proteins; D016718:Arachidonic Acid; D006160:Guanosine Triphosphate; D015237:Dinoprost; D020558:GTP Phosphohydrolases; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)