An activated mutant of R-Ras inhibits cell death caused by cytokine deprivation in BaF3 cells in the presence of IGF-I.
R-Ras belongs to a family of low molecular weight GTP-binding proteins and exhibits 55% amino acid identity to H-Ras. It has been demonstrated that H-Ras inhibits cell death caused by interleukin-3 (IL-3) withdrawal in BaF3 cells (Kinoshita et al. (1995b); Terada et al. (1995)). In the present study, we examined whether R-Ras also rescues BaF3 cells from the factor-deprived cell death. To do this, several BaF3 transfectants were established, in which expression of wild-type as well as mutant R-Ras was regulated by an inducible promoter. Using these transfectants, we found that expression of an activated R-Ras mutant, R-Ras (Q87L), suppressed the death of IL-3-deprived BaF3 cells. On the other hand, expression of the wild-type and the dominant-negative mutant of R-Ras showed no inhibitory effect on cell death, indicating that R-Ras x GTP abrogated cell death caused by deprivation of IL-3. Furthermore, it was found that IGF-I in serum was required for the anti-apoptotic activity of R-Ras. Suppression of cell death by R-Ras(Q87L) was inhibited by wortmannin, LY294002 (phosphatidylinositol 3-kinase (PI3K) inhibitors), or PD98059 (inhibitor for MEK, a specific activator of mitogen-activated protein kinase (MAPK)). In addition, we have shown that, in HEK293 cells, R-Ras and IGF-I could activate MAPK synergistically. Also, PI3K activity was co-immunoprecipitated with an activated mutant of R-Ras. These results suggest that R-Ras in collaboration with IGF-I suppressed apoptotic cell death of BaF3 caused by IL-3 deprivation, presumably by modulating the activitites of MAPK and PI3K.
Suzuki
J
J
Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Japan.
Kaziro
Y
Y
Koide
H
H
D000730:Androstadienes / Q000494:pharmacology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000502:physiology; D016923:Cell Death; D016207:Cytokines / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000502:physiology*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; D009154:Mutation; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D015398:Signal Transduction; D000077191:Wortmannin; D018631:ras Proteins / Q000235:genetics / Q000502:physiology*
D000730:Androstadienes; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D016207:Cytokines; D004791:Enzyme Inhibitors; D005419:Flavonoids; D020558:GTP Phosphohydrolases; D007334:Insulin-Like Growth Factor I; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases; D000077191:Wortmannin; D018631:ras Proteins; C482125:MAP2K1 protein, human; C085929:RRAS protein, human; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one