ERK and calcium in activation of HIF-1.
HIF-1 (hypoxia-inducible factor-1) is the main transcription factor responsible for increased gene expression in hypoxia. The oxygen-dependent regulation of HIF-1 activity occurs at multiple levels in vivo. The mechanisms regulating HIF-1alpha protein expression have been most extensively analyzed, but the ones modulating HIF-1 transcriptional activity remain unclear. Changes in the phosphorylation and/or redox status of HIF-1alpha certainly play a role. Here, we show that ionomycin could activate HIF-1 transcriptional activity in a way that is additive to the effect of hypoxia without affecting HIF-1alpha protein level and HIF-1 DNA binding capacity. In addition, a calmodulin dominant-negative mutant as well as BAPTA, an intracellular calcium chelator, inhibited the hypoxia-induced HIF-1 activation. These results indicate that elevated calcium in hypoxia could participate in HIF-1 activation. PD98059, an inhibitor of the ERK pathway, but not KN-93, an inhibitor of calmodulin kinases II and IV, also blocked HIF-1 activation by hypoxia and by ionomycin. Altogether, these results suggest that calcium and calmodulin would act upstream of ERK in the hypoxia signal transduction pathway leading to enhanced HIF-1 transcriptional activity.
Mottet
Denis
D
Laboratory of Biochemistry and Cellular Biology, University of Namur, 5000 Namur, Belgium.
Michel
Gaetan
G
Renard
Patricia
P
Ninane
Noelle
N
Raes
Martine
M
Michiels
Carine
C
D002118:Calcium / Q000502:physiology*; D020013:Calcium Signaling / Q000502:physiology*; D006528:Carcinoma, Hepatocellular; D015687:Cell Hypoxia; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D015759:Ionomycin / Q000494:pharmacology*; D008113:Liver Neoplasms; D020935:MAP Kinase Signaling System / Q000502:physiology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009687:Nuclear Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D010957:Plasmids; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; C497442:HIF1A protein, human; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins; D014157:Transcription Factors; D015759:Ionomycin; D020928:Mitogen-Activated Protein Kinases; D002118:Calcium