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J. Biol. Chem., Vol. 283, Issue 21, 14430-14444, May 23, 2008

This Article Full Text Full Text (PDF) All Versions of this Article: 283/21/14430    most recent M801519200v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Gopalakrishna, R. Articles by McNeill, T. H. PubMed PubMed Citation Articles by Gopalakrishna, R. Articles by McNeill, T. H. Social Bookmarking                      What's this?

A Direct Redox Regulation of Protein Kinase C Isoenzymes Mediates Oxidant-induced Neuritogenesis in PC12 Cells^*

Rayudu Gopalakrishna¹, Usha Gundimeda, Jason Eric Schiffman, and Thomas H. McNeill^¶

From the Department of Cell and Neurobiology, the Department of Neurology, Keck School of Medicine, the ^¶Neuroscience Graduate Program, University of Southern California, Los Angeles, California 90089

In this study, we have used the PC12 cell model to elucidate the mechanisms by which sublethal doses of oxidants induce neuritogenesis. The xanthine/xanthine oxidase (X/XO) system was used for the steady state generation of superoxide, and CoCl₂ was used as a representative transition metal redox catalyst. Upon treatment of purified protein kinase C (PKC) with these oxidants, there was an increase in its cofactor-independent activation. Redox-active cobalt competed with the redoxinert zinc present in the zinc-thiolates of the PKC regulatory domain and induced the oxidation of these cysteine-rich regions. Both CoCl₂ and X/XO induced neurite outgrowth in PC12 cells, as determined by an overexpression of neuronal marker genes. Furthermore, these oxidants induced a translocation of PKC from cytosol to membrane and subsequent conversion of PKC to a cofactor-independent form. Isoenzyme-specific PKC inhibitors demonstrated that PKC plays a crucial role in neuritogenesis. Moreover, oxidant-induced neurite outgrowth was increased with a conditional overexpression of PKC and decreased with its knock-out by small interfering RNA. Parallel with PKC activation, an increase in phosphorylation of the growth-associated neuronal protein GAP-43 at Ser⁴¹ was observed. Additionally, there was a sustained activation of extracellular signal-regulated kinases 1 and 2, which was correlated with activating phosphorylation (Ser¹³³) of cAMP-responsive element-binding protein. All of these signaling events that are causally linked to neuritogenesis were blocked by antioxidant N-acetylcysteine (both L and D-forms) and by a variety of PKC-specific inhibitors. Taken together, these results strongly suggest that sublethal doses of oxidants induce neuritogenesis via a direct redox activation of PKC.

Received for publication, February 25, 2008 , and in revised form, March 28, 2008.

^* This work was supported, in whole or in part, by National Institutes of Health Grant NS 046538 (to T. H. M.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed: Dept. of Cell and Neurobiology, Keck School of Medicine, BMT 403, 1333 San Pablo St., Los Angeles, CA 90089-9112. Tel.: 323-442-1770; Fax: 323-442-1771; E-mail: rgopalak{at}usc.edu.

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