Redox-sensitive protein phosphatase activity regulates the phosphorylation state of p38 protein kinase in primary astrocyte culture

✍ Scribed by Kent A. Robinson; Charles A. Stewart; Quentin N. Pye; Xuan Nguyen; Lauren Kenney; Scott Salzman; Robert A. Floyd; Kenneth Hensley

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 105 KB
• Volume: 55
• Category: Article
• ISSN: 0360-4012
• DOI: 10.1002/(sici)1097-4547(19990315)55:6<724::aid-jnr7>3.0.co;2-9

✦ Synopsis

Reactive oxygen species (ROS) have been implicated as second messengers that activate protein kinase cascades, although the means by which ROS regulate signal transduction remains unclear. In the present study, we show that interleukin 1␤ (IL1␤), H 2 O 2 , and sorbitol-induced hyperosmolarity mediate a 5-to10fold increase in phosphorylation (activation) of the p38 protein kinase in rat primary glial cells as measured by analyses of Western blots using an antibody directed against the dually phosphorylated (active) p38. Additionally, IL1␤ was found to elicit H 2 O 2 synthesis in these cells. Concurrent with p38 phosphorylation, all three stimulation paradigms caused an inhibition of protein phosphatase activity. Phenyl-tert-butyl nitrone (PBN), a nitrone-based free radical trap and N-acetyl-cysteine (NAC), a thiol reducing agent, were examined for their effects on the phosphorylation of p38 as well as phosphatase activity. Pretreatment of cells with either PBN or NAC at 1.0 mM suppressed IL1␤ H 2 O 2, and sorbitol-mediated activation of p38 and significantly increased phosphatase activity. These data suggest that ROS, particularly H 2 O 2 , are used as second messenger substances that activate p38 in part via the transient inactivation of regulatory protein phosphatases.