Journal
MOLECULAR AND CELLULAR BIOLOGY
Volume 22, Issue 6, Pages 1734-1741Publisher
AMER SOC MICROBIOLOGY
DOI: 10.1128/MCB.22.6.1734-1741.2002
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Funding
- NCI NIH HHS [CA 16087, P30 CA016087] Funding Source: Medline
- NIEHS NIH HHS [ES 05512, P42 ES010344, ES 10344, R01 ES005512, ES 00260, P30 ES000260] Funding Source: Medline
- NATIONAL CANCER INSTITUTE [P30CA016087] Funding Source: NIH RePORTER
- NATIONAL INSTITUTE OF ENVIRONMENTAL HEALTH SCIENCES [P42ES010344, R01ES005512, P30ES000260] Funding Source: NIH RePORTER
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Hypoxia causes the accumulation of the transcription factor hypoxia-inducible factor 1 (HIF-1), culminating in the expression of hypoxia-inducible genes such as those for vascular endothelial growth factor (VEGF) and NDRG-1/Cap43. Previously, we have demonstrated that intracellular calcium (Ca2+) is required for the expression of hypoxia-inducible genes. Here we found that, unlike with hypoxia or hypoxia-mimicking conditions, the elevation of intracellular Ca2+ neither induced the HIF-1alpha protein nor stimulated HIF-1-dependent transcription. Furthermore, the elevation of intracellular Ca2+ induced NDRG-1/Cap43 mRNA in HIF-1alpha-deficient cells. It also increased levels of c-Jun protein, causing its phosphorylation. The protein kinase inhibitor K252a abolished c-Jun induction and activator protein 1 (AP-1)-dependent reporter expression caused by Ca2+ ionophore or hypoxia. K252a also significantly decreased hypoxia-induced VEGF and NDRG-1/Cap43 gene expression in both human and mouse cells. Using a set of deletion VEGF-Luc promoter constructs, we found that both HIF-1 and two AP-1 sites contribute to hypoxia-mediated induction of transcription. In contrast, only AP-1 sites contributed to Ca2+-mediated VEGF-Luc induction. A dominant-negative AP-1 prevented Ca2+-dependent transcription and partially impaired hypoxia-mediated transcription. In addition, dominant-negative AP-1 diminished the expression of the NDRG-1/Cap43 gene following hypoxia. We conclude that during hypoxia, an increase in intracellular Ca2+ activates a HIF-1-independent signaling pathway that involves AP-1-dependent transcription. Cooperation between the HIF-1 and AP-1 pathways allows fine regulation of gene expression during hypoxia.
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