R-Ras3, a brain-specific Ras-related protein, activates Akt and promotes cell survival in PC12 cells.
The GTP-binding protein, R-Ras3/M-Ras, is a novel member of the Ras subfamily of GTPases which shows highest sequence similarity to the TC21 gene. R-Ras3 is highly expressed in both human and mouse brain and ectopic expression of a constitutively active mutant of R-Ras3 induces cellular transformation in NIH3T3 cells. To gain further insight into the normal cellular function of R-Ras3, we examined the ability of R-Ras3 in activating several known intracellular signaling cascades. We observed that R-Ras3 is a relatively weak activator of the mitogen-activated protein kinase/extracellular-signal-regulated kinases (MAPK/ERKs) when compared to the H-Ras oncogene. On the contrary, both R-Ras3 and H-Ras activated the Jun N-terminal kinase (JNK) to a similar extent. Under similar experimental conditions, R-Ras3 significantly stimulated one of the phosphatidylinositol 3-kinase (PI3-K) downstream substrates, Akt/PKB/RAC (Akt), which has been extensively implicated in mediating cell survival signaling. The activation of Akt by R-Ras3 was most likely to be PI3-K-dependent since this biochemical event was blocked by the pharmacological inhibitors, Wortmannin and LY294002, as well as by a dominant negative mutant of PI3-K. More importantly, R-Ras3 affinity-precipitated PI3-K from cell extracts in a GTP-dependent manner, and associated lipid kinase activity was readily detectable in R-Ras3 immune complexes. The biological significance of R-Ras3 in inducing Akt kinase activity is evidenced by the ability of an activated R-Ras3 to confer cell survival in the rat pheochromocytoma cell line, PC12. As expected, this biological activity of R-Ras3 was also abrogated by the addition of LY294002. Thus, R-Ras3 represents a novel G-protein which may play a role in cell survival of neural-derived cells.
Kimmelman
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AC
The Derald H Ruttenberg Cancer Center, The Mount Sinai School of Medicine, New York, NY 10029, USA.
Osada
M
M
Chan
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AM
D016475:3T3 Cells / Q000378:metabolism; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000166:cytology / Q000201:enzymology*; D019556:COS Cells / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002867:Chromones / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D011905:Genes, ras; D006160:Guanosine Triphosphate / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D020932:Nerve Growth Factor / Q000494:pharmacology; D009474:Neurons / Q000201:enzymology; D009928:Organ Specificity; D016716:PC12 Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D000077191:Wortmannin; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
D000730:Androstadienes; D002867:Chromones; D004791:Enzyme Inhibitors; D006160:Guanosine Triphosphate; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D020928:Mitogen-Activated Protein Kinases; D009025:Morpholines; D020932:Nerve Growth Factor; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011994:Recombinant Proteins; D000077191:Wortmannin; D018631:ras Proteins; C109523:MRAS protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C494920:Akt1 protein, rat