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© The Rockefeller University Press,
0021-9525/2000//557 $5.00
The Journal of Cell Biology, Volume 148, Number 3,
, 2000 557-566
Original Article |
Oncogenic K-Ras and Basic Fibroblast Growth Factor Prevent FAS-Mediated Apoptosis in Fibroblasts through Activation of Mitogen-Activated Protein Kinase
syonehar{at}virus.kyoto-u.ac.jp
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.
Key Words: basic fibroblast growth factor • Fas • mitogen-activated protein kinase • oncogenesis • Ras
© 2000 The Rockefeller University Press
Abbreviations used in this paper: bFGF, basic FGF; EF1
, elongation factor 1; FADD, Fas-associated death domain; FLICE, FADD-like interleukin-1β–converting enzyme; FLIP, FLICE-inhibitory protein; GFP, green fluorescence protein; IGF, insulin-like growth factor; K-RasV12, oncogenic K-Ras; MAP , mitogen-activated protein; MAPK, MAP kinase; MAPKK, MAPK kinase; MAPKKK, MAPKK kinase; MKP-1, MAPK phosphatase 1; MST1, mammalian STE-20–like protein kinase; MST1-KD, kinase-defective MST1; PE, phycoerythrin; PI-3, phosphatidylinositol 3; PKB, protein kinase B; Raf-CAAX, constitutively active Raf; RalGDS, Ral guanine nucleotide exchange factor; RT, reverse trancription; SDSE-MAPKK, constitutively active MAPKK.
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