Basal protein phosphorylation is decreased and phosphatase activity increased by an antioxidant and a free radical trap in primary rat glia. |
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Authors: | K A Robinson C A Stewart Q Pye R A Floyd K Hensley |
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Institution: | Free Radical Biology and Aging Research Program, Oklahoma Medical Research Foundation, 825 Northeast 13th Street, Oklahoma City, Oklahoma, 73104, USA. |
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Abstract: | Reversible protein phosphorylation regulates a wide array of cellular functions. Cells respond to cytokines and various stressors via phosphorylation and thus activation of one or more of the mitogen-activated protein kinase (MAPK) pathways. Involvement of these signal transduction pathways has been implicated in numerous pathologies, including inflammation. Using a primary glia cell culture, we show here that the antioxidant N-acetylcysteine (NAC) and the nitrone-based free radical trap, alpha-phenyl-N-tert-butyl nitrone (PBN), reduce total basal protein phosphorylation in a concentration-dependent manner as assessed by phosphotyrosine analysis and by gamma-32P]ATP transfer radioassay. In addition we show that NAC inhibits H2O2-induced phosphatase inactivation in glia cell lysate. The PBN- and NAC-induced reduction in protein phosphorylation is accompanied by an increase in phosphatase activity, suggesting that PBN and NAC reduce protein phosphorylation by globally augmenting oxidant-sensitive phosphatase activities. These results partly explain why certain antioxidants also possess anti-inflammatory actions. |
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