Abstract
Subtractive suppression hybridization was used to generate a cDNA library enriched in cDNA sequences corresponding to mRNA species that are specifically up-regulated by hypoxia (6 h, 1% O(2)) in the oxygen-responsive pheochromocytoma cell line. The dual specificity protein-tyrosine phosphatase MAPK phosphatase-1 (MKP-1) was highly represented in this library. Clones were arrayed on glass slides to create a hypoxia-specific cDNA microarray chip. Microarray, northern blot, and western blot analyses confirmed that MKP-1 mRNA and protein levels were up-regulated by hypoxia by approximately 8-fold. The magnitude of the effect of hypoxia on MKP-1 was approximately equal to that induced by KCl depolarization and much larger than the effects of either epidermal growth factor or nerve growth factor on MKP-1 mRNA levels. In contrast to the calcium-dependent induction of MKP-1 by KCl depolarization, the effect of hypoxia on MKP-1 persisted under calcium-free conditions. Cobalt and deferoxamine also increased MKP-1 mRNA levels, suggesting that hypoxia-inducible factor proteins may play a role in the regulation of MKP-1 by hypoxia. Pretreatment of cells with SB203580, which inhibits p38 kinase activity, significantly reduced the hypoxia-induced increase in MKP-1 RNA levels. Thus, hypoxia robustly increases MKP-1 levels, at least in part through a p38 kinase-mediated mechanism.
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