Oxidative stress induces lipid-raft-mediated activation of Src homology 2 domain-containing protein-tyrosine phosphatase 2 in astrocytes

Abstract

Several protein phosphatases are involved in neuroprotection in response to ischemic brain injury. Here, we report that reactive oxygen species (ROS)-mediated oxidative stress promotes phosphorylation of endogenous SHP-2 through lipid rafts in rat primary astrocytes. SHP-2 was transiently phosphorylated during hypoxia/reoxygenation, an effect abrogated by a ROS scavenger and an NADPH oxidase inhibitor. Additionally, exogenous treatment with hydrogen peroxide (H 2O 2) triggered SHP-2 phosphorylation in a time- and dose-dependent manner and led to its translocation into lipid rafts. H 2O 2-mediated SHP-2 phosphorylation and translocation were inhibited by filipin III and methyl-β-cyclodextrin (MCD), lipid-raft-disrupting agents. In the presence of H 2O 2, SHP-2 formed a complex with STAT-3 and reduced the steady-state STAT-3 phosphorylation level. Interestingly, the effect of H 2O 2 on SHP-2 phosphorylation was cell-type specific. Remarkably, SHP-2 phosphorylation was induced strongly by H 2O 2 in astrocytes, but barely detectable in microglia. Our results collectively indicate that SHP-2 is activated by ROS-mediated oxidative stress in astrocytes and functions as a component of the raft-mediated signaling pathway that acts through dephosphorylation and inactivation of other phosphotyrosine proteins, such as STAT-3.