Unfarnesylated transforming Ras mutant inhibits the Ras-signaling pathway by forming a stable Ras.Raf complex in the cytosol.
Farnesyltransferase inhibitors cause the growth arrest of ras-transformed cells, but not that of normal cells. To elucidate the mechanism of this differential effect, we examined the effect of accumulation of unfarnesylated Ras in the cytosol by using RasG12V,C186S and RasC186S, which mimic unfarnesylated form of the oncogenic and the normal Ras, respectively. We found that RasG12,C186S inhibited activation and membrane translocation of Raf by forming a stable complex with Raf in the cytosol. In contrast, RasC186S showed inhibitory effect on neither Raf activation nor Raf translocation. These results indicate that unfarnesylated oncogenic Ras interacts with Raf in the cytosol and inhibits its membrane translocation, a crucial step for the Raf activation, while unfarnesylated normal Ras does not.
Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Japan.
M
M
Miyake
S
S
Mizutani
H
H
Koide
Y
Y
Kaziro
D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004622:Embryo, Mammalian; D020558:GTP Phosphohydrolases / Q000378:metabolism; D011905:Genes, ras; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D007163:Immunosorbent Techniques; D007668:Kidney; D009154:Mutation; D017368:Protein Prenylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D018631:ras Proteins / Q000737:chemistry / Q000378:metabolism*
D011518:Proto-Oncogene Proteins; D006160:Guanosine Triphosphate; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D020558:GTP Phosphohydrolases; D018631:ras Proteins