Oncogenic K-Ras and basic fibroblast growth factor prevent Fas-mediated apoptosis in fibroblasts through activation of mitogen-activated protein kinase.
By an expression cloning method using Fas-transgenic Balb3T3 cells, we tried to obtain inhibitory genes against Fas-mediated apoptosis and identified proto-oncogene c-K-ras. Transient expression of K-Ras mutants revealed that oncogenic mutant K-Ras (RasV12) strongly inhibited, whereas dominant-inhibitory mutant K-Ras (RasN17) enhanced, Fas-mediated apoptosis by inhibiting Fas-triggered activation of caspases without affecting an expression level of Fas. Among the target molecules of Ras, including Raf (mitogen-activated protein kinase kinase kinase [MAPKKK]), phosphatidylinositol 3 (PI-3) kinase, and Ral guanine nucleotide exchange factor (RalGDS), only the constitutively active form of Raf (Raf-CAAX) could inhibit Fas-mediated apoptosis. In addition, the constitutively active form of MAPKK (SDSE-MAPKK) suppressed Fas-mediated apoptosis, and MKP-1, a phosphatase specific for classical MAPK, canceled the protective activity of oncogenic K-Ras (K-RasV12), Raf-CAAX, and SDSE-MAPKK. Furthermore, physiological activation of Ras by basic fibroblast growth factor (bFGF) protected Fas-transgenic Balb3T3 cells from Fas-mediated apoptosis. bFGF protection was also dependent on the activation of the MAPK pathway through Ras. All the results indicate that the activation of MAPK through Ras inhibits Fas-mediated apoptosis in Balb3T3 cells, which may play a role in oncogenesis.
Kazama
H
H
Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan.
Yonehara
S
S
D016475:3T3 Cells; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D004789:Enzyme Activation; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D020935:MAP Kinase Signaling System; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D000090063:Proto-Oncogene Mas; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics / Q000378:metabolism*; D019014:fas Receptor / Q000235:genetics / Q000378:metabolism*
C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D019014:fas Receptor; D016222:Fibroblast Growth Factor 2; D020928:Mitogen-Activated Protein Kinases; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)