Selective Activation of p38α and p38γ by Hypoxia

doi:10.1074/jbc.274.33.23570

Selective Activation of p38α and p38γ by Hypoxia

ROLE IN REGULATION OF CYCLIN D1 BY HYPOXIA IN PC12 CELLS*

From the Department of Molecular and Cellular Physiology, College of Medicine, University of Cincinnati, Cincinnati, Ohio 45267-0576 and the ^‡Department of Immunology, The Scripps Research Institute, La Jolla, California 92037

Abstract

Hypoxic/ischemic trauma is a primary factor in the pathology of a multitude of disease states. The effects of hypoxia on the stress- and mitogen-activated protein kinase signaling pathways were studied in PC12 cells. Exposure to moderate hypoxia (5% O₂) progressively stimulated phosphorylation and activation of p38γ in particular, and also p38α, two stress-activated protein kinases. In contrast, hypoxia had no effect on enzyme activity of p38β, p38β₂, p38δ, or on c-Jun N-terminal kinase, another stress-activated protein kinase. Prolonged hypoxia also induced phosphorylation and activation of p42/p44 mitogen-activated protein kinase, although this activation was modest compared with nerve growth factor- and ultraviolet light-induced activation. Hypoxia also dramatically down-regulated immunoreactivity of cyclin D1, a gene that is known to be regulated negatively by p38 at the level of gene expression (Lavoie, J. N., L’Allemain, G., Brunet, A., Muller, R., and Pouyssegur, J. (1996) J. Biol. Chem. 271, 20608–20616). This effect was partially blocked by SB203580, an inhibitor of p38α but not p38γ. Overexpression of a kinase-inactive form of p38γ was also able to reverse in part the effect of hypoxia on cyclin D1 levels, suggesting that p38α and p38γ converge to regulate cyclin D1 during hypoxia. These studies demonstrate that an extremely typical physiological stress (hypoxia) causes selective activation of specific p38 signaling elements; and they also identify a downstream target of these pathways.

Footnotes

↵* This work was supported by Grant 9806242 from the American Heart Association, Ohio Valley Affiliate, and a grant from the Parker B. Francis Foundation (both to D. B.-J.), National Institutes of Health Grants R37HL33831 and RO1HL59945 (to D. E. M.), U.S. Army Grant DAMD 17-99-1-9544 (to D. E. M.), and National Institutes of Health Training Grant HL07571 (to P. W. C.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵§ To whom correspondence should be addressed: Dept. of Molecular and Cellular Physiology, College of Medicine, University of Cincinnati, P.O. Box 67-0576, Cincinnati, OH 45267-0576. Tel.: 513-558-6009; Fax: 513-558-5738; E-mail: dana.johnson@uc.edu.
↵2 P. W. Conrad, unpublished data.
Abbreviations:

SAPK

stress activated protein kinase

MAPK

mitogen activated protein kinase

JNK

c-Jun N-terminal kinase

ERK

extracellular signal-regulated kinase

NGF

nerve growth factor

PBS

phosphate-buffered saline

MOPS

4-morpholinepropanesulfonic acid

PDZ

PSD-95,Discs-Large, ZO-1

RK

reactivating kinase

MAPKAP

mitogen-activated protein kinase activated protein
- Received January 26, 1999.
- Revision received May 15, 1999.
The American Society for Biochemistry and Molecular Biology, Inc.