R-Ras3, a brain-specific Ras-related protein, activates Akt and promotes cell survival in PC12 cells

Oncogene. 2000 Apr 13;19(16):2014-22. doi: 10.1038/sj.onc.1203530.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 3T3 Cells / metabolism
  • Androstadienes / pharmacology
  • Animals
  • Brain / cytology
  • Brain / enzymology*
  • COS Cells / metabolism
  • Cell Survival / drug effects
  • Chromones / pharmacology
  • Enzyme Activation
  • Enzyme Inhibitors / pharmacology
  • Genes, ras
  • Guanosine Triphosphate / metabolism
  • JNK Mitogen-Activated Protein Kinases
  • Mice
  • Mitogen-Activated Protein Kinase 1 / drug effects
  • Mitogen-Activated Protein Kinase 1 / genetics
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinases / metabolism
  • Morpholines / pharmacology
  • Nerve Growth Factor / pharmacology
  • Neurons / enzymology
  • Organ Specificity
  • PC12 Cells / cytology
  • PC12 Cells / drug effects
  • PC12 Cells / metabolism
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphoinositide-3 Kinase Inhibitors
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • Proto-Oncogene Proteins c-akt
  • Proto-Oncogene Proteins*
  • Rats
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Signal Transduction
  • Wortmannin
  • ras Proteins / genetics
  • ras Proteins / metabolism*

Substances

  • Androstadienes
  • Chromones
  • Enzyme Inhibitors
  • MRAS protein, human
  • Morpholines
  • Phosphoinositide-3 Kinase Inhibitors
  • Proto-Oncogene Proteins
  • Recombinant Proteins
  • 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
  • Guanosine Triphosphate
  • Nerve Growth Factor
  • Akt1 protein, rat
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • JNK Mitogen-Activated Protein Kinases
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinases
  • ras Proteins
  • Wortmannin