title: Raf/MAPK and rapamycin-sensitive pathways mediate the anti-apoptotic function of p21Ras in IL-3-dependent hematopoietic cells.
abstract: The Ras signal transduction pathway is activated by a number of hematopoietic cytokines and is implicated in the prevention of apoptotic death in hematopoietic cells. Recent studies have provided evidence that the downstream of Ras is highly divergent and several independent pathways appear to mediate distinct biological functions of Ras. In the present study, we investigated the downstream pathway(s) of Ras responsible for the maintenance of hematopoietic cell survival by using various mutants of signaling molecules. Activation of the Raf/MAPK pathway in interleukin (IL) 3-dependent cells by expression of an oncogenic Raf or a Ras mutant (G12V/T35S) prevented apoptosis following IL-3 deprivation. In contrast, another Ras mutant (G12V/V45E), which is apparently incapable of activating MAPK, efficiently blocked apoptosis as well. It is therefore likely that the activation of the Raf/MAPK pathway is not an absolute requirement for the prevention of apoptosis, and there appears to be a Raf/MAPK-independent pathway that contributes to hematopoietic cell survival. Since Ras(G12V/V45E) was able to cause the phosphorylation of p70/S6 kinase, we inhibited the S6 kinase pathway by rapamycin and by wortmannin, and found that the anti-apoptotic function of Ras(G12V/V45E), but not of Ras(G12V), was critically influenced by both inhibitors. These results indicate that the Raf/MAPK and a rapamycin/wortmannin-sensitive pathways mediate Ras function to prevent apoptotic death in hematopoietic cells.
authors.affiliation: Department of Cellular Biosynthesis, Institute of Molecular and Cellular Bioscience, The University of Tokyo, Bunkyo-ku, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kinoshita
authors.forename: M
authors.initials: M
authors.lastname: Shirouzu
authors.forename: A
authors.initials: A
authors.lastname: Kamiya
authors.forename: K
authors.initials: K
authors.lastname: Hashimoto
authors.forename: S
authors.initials: S
authors.lastname: Yokoyama
authors.forename: A
authors.initials: A
authors.lastname: Miyajima
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D002470:Cell Survival; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases; D005347:Fibroblasts; D006412:Hematopoietic Stem Cells / Q000378:metabolism* / Q000502:physiology*; D007377:Interleukin-3 / Q000378:metabolism; D020930:MAP Kinase Kinase Kinases; D051379:Mice; D011090:Polyenes / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D011995:Recombination, Genetic; D019893:Ribosomal Protein S6 Kinases; D015398:Signal Transduction; D020123:Sirolimus; D014162:Transfection; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D000903:Antibiotics, Antineoplastic; D004791:Enzyme Inhibitors; D007377:Interleukin-3; D011090:Polyenes; D017346:Protein Serine-Threonine Kinases; D019893:Ribosomal Protein S6 Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D020930:MAP Kinase Kinase Kinases; C089319:Ras-dependent mitogen-activated protein kinase kinase kinase; D016283:Proto-Oncogene Proteins p21(ras); D020123:Sirolimus; D000077191:Wortmannin