title: HIF-1 mediates adaptation to hypoxia by actively downregulating mitochondrial oxygen consumption.
abstract: The HIF-1 transcription factor drives hypoxic gene expression changes that are thought to be adaptive for cells exposed to a reduced-oxygen environment. For example, HIF-1 induces the expression of glycolytic genes. It is presumed that increased glycolysis is necessary to produce energy when low oxygen will not support oxidative phosphorylation at the mitochondria. However, we find that while HIF-1 stimulates glycolysis, it also actively represses mitochondrial function and oxygen consumption by inducing pyruvate dehydrogenase kinase 1 (PDK1). PDK1 phosphorylates and inhibits pyruvate dehydrogenase from using pyruvate to fuel the mitochondrial TCA cycle. This causes a drop in mitochondrial oxygen consumption and results in a relative increase in intracellular oxygen tension. We show by genetic means that HIF-1-dependent block to oxygen utilization results in increased oxygen availability, decreased cell death when total oxygen is limiting, and reduced cell death in response to the hypoxic cytotoxin tirapazamine.
authors.affiliation: Division of Radiation and Cancer Biology, Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California 94305, USA.
authors.forename: Ioanna
authors.initials: I
authors.lastname: Papandreou
authors.forename: Rob A
authors.initials: RA
authors.lastname: Cairns
authors.forename: Lucrezia
authors.initials: L
authors.lastname: Fontana
authors.forename: Ai Lin
authors.initials: AL
authors.lastname: Lim
authors.forename: Nicholas C
authors.initials: NC
authors.lastname: Denko
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D017209:Apoptosis; D015687:Cell Hypoxia / Q000502:physiology*; D002478:Cells, Cultured; D019295:Computational Biology; D015536:Down-Regulation / Q000235:genetics*; D023281:Genomics; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000172:deficiency / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism; D010101:Oxygen Consumption / Q000502:physiology*; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D015854:Up-Regulation / Q000235:genetics
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D024101:Mitochondrial Proteins; C000631429:PDK1 protein, human; C000631433:Pdk1 protein, mouse; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases