p38 kinase mediates nitric oxide-induced apoptosis of chondrocytes through the inhibition of protein kinase C ζ by blocking autophosphorylation

Abstract

This study investigated the molecular mechanisms underlying inhibition of protein kinase C (PKC) ζ by p38 kinase during nitric oxide (NO)-induced apoptosis of chondrocytes. Coimmunoprecipitation experiments showed that activation of p38 kinase following addition of an NO donor resulted in a physical association between PKCζ and p38 kinase. Direct interaction of p38 kinase with PKCζ was confirmed in vitro using p38 kinase and PKCζ recombinant proteins. p38 kinase interacts with the regulatory domain of PKCζ and its association blocked PKCζ autophosphorylation. Micro LC-MS/MS analysis using recombinant proteins indicated that the interaction of p38 kinase with PKCζ blocked autophosphorylation of PKCζ on Thr-560, which is required for PKCζ activation. Collectively, our results demonstrate a novel mechanism of PKCζ regulation: following activation by the production of NO, p38 kinase binds directly to the PKCζ regulatory domain, preventing PKCζ autophosphorylation on Thr-560, thereby inhibiting PKCζ activation. © 2005 Nature Publishing Group All rights reserved.