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Molecular and Cellular Biology, October 2006, p. 7145-7154, Vol. 26, No. 19
0270-7306/06/$08.00+0 doi:10.1128/MCB.00476-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
and
Andrew M.-L. Chan*
Department of Oncological Sciences, The Mount Sinai School of Medicine, New York, New York 10029
Received 17 March 2006/ Returned for modification 28 April 2006/ Accepted 7 July 2006
R-Ras3/M-Ras is a member of the RAS superfamily of small-molecular-weight GTP-binding proteins. Previous studies have demonstrated high levels of expression in several regions of the central nervous system, and a constitutively active form of M-Ras promotes cytoskeletal reorganization, cellular transformation, survival, and differentiation. However, the physiological functions of M-Ras during embryogenesis and postnatal development have not been elucidated. By using a specific M-Ras antibody, we demonstrated a high level of M-Ras expression in astrocytes, in addition to neurons. Endogenous M-Ras was activated by several trophic factors in astrocytes, including epidermal growth factor (EGF), basic fibroblast growth factor, and hepatocyte growth factor. Interestingly, M-Ras activation by EGF was more sustained compared to prototypic Ras. A mouse strain deficient in M-Ras was generated to investigate its role in development. M-Ras null mice appeared phenotypically normal, and there was a lack of detectable morphological and neurological defects. In addition, primary astrocytes derived from Mras/ mice did not appear to display substantial alterations in the activation of both the mitogen-activated protein kinase and phosphatidylinositol 3-kinase pathways in response to trophic factors.
Supplemental material for this article may be found at http://mcb.asm.org/.
Present address: Harvard Radiation Oncology Program, Harvard Medical School, Boston, MA 02115.
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