Inhibition of Hypoxia-inducible Factor 1 Activation by Carbon Monoxide and Nitric Oxide
IMPLICATIONS FOR OXYGEN SENSING AND SIGNALING*
- From the Division of Hematology, Brigham & Women’s Hospital, Harvard Medical School, Boston, Massachusetts 02115
Abstract
It has been proposed that cells sense hypoxia by a heme protein, which transmits a signal that activates the heterodimeric transcription factor hypoxia-inducible factor 1 (HIF-1), thereby inducing a number of physiologically relevant genes such as erythropoietin (Epo). We have investigated the mechanism by which two heme-binding ligands, carbon monoxide and nitric oxide, affect oxygen sensing and signaling. Two concentrations of CO (10 and 80%) suppressed the activation of HIF-1 and induction of Epo mRNA by hypoxia in a dose-dependent manner. In contrast, CO had no effect on the induction of HIF-1 activity and Epo expression by either cobalt chloride or the iron chelator desferrioxamine. The affinity of CO for the putative sensor was much lower than that of oxygen (Haldane coefficient, ∼0.5). Parallel experiments were done with 100 μm sodium nitroprusside, a nitric oxide donor. Both NO and CO inhibited HIF-1 DNA binding by abrogating hypoxia-induced accumulation of HIF-1α protein. Moreover, both NO and CO specifically targeted the internal oxygen-dependent degradation domain of HIF-1α, and also repressed the C-terminal transactivation domain of HIF-1α. Thus, NO and CO act proximally, presumably as heme ligands binding to the oxygen sensor, whereas desferrioxamine and perhaps cobalt appear to act at a site downstream.
Footnotes
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↵* This work was supported in part by National Institutes of Health Grants RO1-DK41234 (to H. F. B.) and RO1-DK45098 (to M. A. G.) and by National Institutes of Health Individual National Research Service Award F32-DK09365 (to L. E. H.).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.
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↵‡ Contributed equally to this work.
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↵§ To whom correspondence should be addressed: Hematology-Oncology Division, LMRC-2, Brigham & Women’s Hospital, Harvard Medical School, 221 Longwood Ave., Boston, MA 02115. Tel.: 617-732-5841; Fax: 617-739-0748; E-mail: bunn{at}calvin.bwh.harvard.edu.
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↵2 H. Zhu, J. Olsen, and A. Riggs, personal communicacation.
- Abbreviations:
- HIF-1
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hypoxia-inducible factor 1
- ODD
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oxygen-dependent degradation
- SNP
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sodium nitroprusside
- Epo
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erythropoietin
- CMV
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cytomegalovirus
- HA
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hemagglutinin
- EMSA
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electrophoretic mobility shift assay
- luc
-
luciferase
- ROS
-
reactive oxygen species
- ARNT
-
aryl hydrocarbon nuclear translocater
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- Received October 7, 1998.
- Revision received December 29, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
