title: Different effects of various phospholipids on Ki-Ras-, Ha-Ras-, and Rap1B-induced B-Raf activation.
abstract: We have recently purified a Ki-Ras- and Ha-Ras-dependent extracellular signal-regulated kinase kinase from bovine brain and identified it as B-Raf protein kinase complexed with 14-3-3 proteins (Yamamori, B., Kuroda, S., Shimizu, K., Fukui, K., Ohtsuka, T., and Takai, Y. (1995) J. Biol. Chem. 270, 11723-11726). Moreover, we found that Rap1B as well as Ki-Ras and Ha-Ras stimulate the B-Raf activity. Since B-Raf contains a cysteine-rich domain originally found in protein kinase C as a domain responsible for interaction with phosphatidylserine (PS) and diacylglycerol or 12-O-tetradecanoylphorbol-13-acetate, we have examined here the effect of these compounds on the Ki-Ras-, Ha-Ras-, and Rap1B-induced activation of bovine brain B-Raf. Bovine brain PS enhanced Ki-Ras-stimulated B-Raf activity. Phosphatidic acid was slightly active, but other phospholipids, such as phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol (PI), PI-4-monophosphate, PI-4,5-bisphosphate, and PI-3,4,5-trisphosphate, were inactive. However, none of the above phospholipids affected the Ha-Ras-stimulated B-Raf activity, whereas PI, PS, phosphatidylethanolamine, and phosphatidic acid inhibited the Rap1B-stimulated B-Raf activity. Phosphatidylcholine or PI-4-monophosphate did not show any effect on the Rap1B-stimulated B-Raf activity. Synthetic PS with two unsaturated fatty acids, such as 1,2-dioleoyl-PS or 1,2-dilinoleoyl-PS, showed the same effect toward the Ki-Ras- and Rap1B-stimulated B-Raf activities, but synthetic PS with two saturated fatty acids, such as 1, 2-distearoyl-PS, was inactive. 12-O-Tetradecanoylphorbol-13-acetate did not affect the stimulatory or inhibitory effect of PS on the Ki-Ras- and Rap1B-stimulated B-Raf activities, respectively. PS did not affect the Ki-Ras-, Ha-Ras-, or Rap1B-independent basal B-Raf activity or the mitogen-activated protein kinase kinase or extracellular signal-regulated kinase activity. These results indicate that various phospholipids differently affect Ki-Ras-, Ha-Ras, and Rap1B-induced B-Raf activation.
authors.affiliation: Department of Molecular Biology and Biochemistry, Osaka University Medical School, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Kuroda
authors.forename: T
authors.initials: T
authors.lastname: Ohtsuka
authors.forename: B
authors.initials: B
authors.lastname: Yamamori
authors.forename: K
authors.initials: K
authors.lastname: Fukui
authors.forename: K
authors.initials: K
authors.lastname: Shimizu
authors.forename: Y
authors.initials: Y
authors.lastname: Takai
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D002417:Cattle; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism / Q000494:pharmacology; D006153:Guanosine Diphosphate / Q000378:metabolism / Q000494:pharmacology; D007295:Inositol Phosphates / Q000494:pharmacology*; D007700:Kinetics; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism; D010743:Phospholipids / Q000494:pharmacology*; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D020668:rap GTP-Binding Proteins
chemical_list: D007295:Inositol Phosphates; D009419:Nerve Tissue Proteins; D010743:Phospholipids; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D019204:GTP-Binding Proteins; D016283:Proto-Oncogene Proteins p21(ras); D020668:rap GTP-Binding Proteins