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Oxidative Medicine and Cellular Longevity
Volume 2012, Article ID 792705, 8 pages
http://dx.doi.org/10.1155/2012/792705
Research Article

Oxidative Stress Posttranslationally Regulates the Expression of Ha-Ras and Ki-Ras in Cultured Astrocytes

1Department of Human Sciences, Society, and Health, University of Cassino and Southern Lazio, 03043 Cassino, Italy
2Istituto Neurologico Mediterraneo, IRCCS Neuromed, 860177 Pozzilli, Italy
3Department of Structural and Functional Biology, University of Naples, Federico II, 80126 Naples, Italy

Received 11 July 2012; Revised 20 September 2012; Accepted 20 September 2012

Academic Editor: Felipe Dal-Pizzol

Copyright © 2012 Samantha Messina et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Addition of hydrogen peroxide to cultured astrocytes induced a rapid and transient increase in the expression of Ha-Ras and Ki-Ras. Pull-down experiments with the GTP-Ras-binding domain of Raf-1 showed that oxidative stress substantially increased the activation of Ha-Ras, whereas a putative farnesylated activated form of Ki-Ras was only slightly increased. The increase in both Ha-Ras and Ki-Ras was insensitive to the protein synthesis inhibitor, cycloheximide, and was occluded by the proteasomal inhibitor, MG-132. In addition, exposure to hydrogen peroxide reduced the levels of ubiquitinated Ras protein, indicating that oxidative stress leads to a reduced degradation of both isoforms through the ubiquitin/proteasome pathway. Indeed, the late reduction in Ha-Ras and Ki-Ras was due to a recovery of proteasomal degradation because it was sensitive to MG-132. The late reduction of Ha-Ras levels was abrogated by compound PD98059, which inhibits the MAP kinase pathway, whereas the late reduction of Ki-Ras was unaffected by PD98059. We conclude that oxidative stress differentially regulates the expression of Ha-Ras and Ki-Ras in cultured astrocytes, and that activation of the MAP kinase pathway by oxidative stress itself or by additional factors may act as a fail-safe mechanism limiting a sustained expression of the potentially detrimental Ha-Ras.