Title: The regulation of hypoxic genes by calcium involves c-Jun/AP-1, which cooperates with hypoxia-inducible factor 1 in response to hypoxia.
Authors: Salnikow, Konstantin; Kluz, Thomas; Costa, Max; Piquemal, David; Demidenko, Zoya N; Xie, Keping; Blagosklonny, Mikhail V
Published In Mol Cell Biol, (2002 Mar)
Abstract: 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 (Ca(2+)) is required for the expression of hypoxia-inducible genes. Here we found that, unlike with hypoxia or hypoxia-mimicking conditions, the elevation of intracellular Ca(2+) neither induced the HIF-1alpha protein nor stimulated HIF-1-dependent transcription. Furthermore, the elevation of intracellular Ca(2+) 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 Ca(2+) 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 Ca(2+)-mediated VEGF-Luc induction. A dominant-negative AP-1 prevented Ca(2+)-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 Ca(2+) 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.
PubMed ID: 11865053
MeSH Terms: Animals; Calcium/metabolism*; Calcium/pharmacology; Cell Cycle Proteins/metabolism; Cell Hypoxia/physiology*; Cell Line; Cell Nucleus/metabolism; DNA-Binding Proteins/metabolism*; Endothelial Growth Factors/genetics; Fibroblasts/cytology; Fibroblasts/metabolism; Gene Expression Regulation/drug effects; Gene Expression Regulation/physiology*; Genes, Dominant; Humans; Hypoxia-Inducible Factor 1; Hypoxia-Inducible Factor 1, alpha Subunit; Intracellular Fluid/metabolism; Intracellular Signaling Peptides and Proteins; Ionophores/pharmacology; Lymphokines/genetics; Mice; NFATC Transcription Factors; Nuclear Proteins/metabolism*; Promoter Regions, Genetic/physiology; Proto-Oncogene Proteins c-jun/metabolism*; Transcription Factor AP-1/genetics; Transcription Factor AP-1/metabolism*; Transcription Factors/metabolism; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors