title: Hypoxia-inducible factor-1alpha stabilization in nonhypoxic conditions: role of oxidation and intracellular ascorbate depletion.
abstract: Hypoxia-inducible factor-1 (HIF-1) is a decisive element for the transcriptional regulation of many genes induced under low oxygen conditions. Under normal oxygen conditions, HIF-1alpha, the active subunit of HIF-1, is hydroxylated on proline residues by specific HIF prolyl-hydroxylases, leading to ubiquitination and degradation by the proteasome. In hypoxia, hydroxylation and ubiquitination are blocked and HIF-1alpha accumulates in cells. Recent studies have shown that in normal oxygen conditions G-protein-coupled receptor agonists, including angiotensin (Ang) II and thrombin, potently induce and activate HIF-1 in vascular smooth muscle cells. The current study identifies HIF-1alpha protein stabilization as a key mechanism for HIF-1 induction by Ang II. We show that hydroxylation on proline 402 is altered by Ang II, decreasing pVHL binding to HIF-1alpha and allowing HIF-1alpha protein to escape subsequent ubiquitination and degradation mechanisms. We show that HIF-1alpha stability is mediated through the Ang II-mediated generation of hydrogen peroxide and a subsequent decrease in ascorbate levels, leading to decreased HIF prolyl-hydroxylase activity and HIF-1alpha stabilization. These findings identify novel and intricate signaling mechanisms involved in HIF-1 complex activation and will lead to the elucidation of the importance of HIF-1 in different Ang II-related cell responses.
authors.affiliation: Centre de recherche de L'Hôtel-Dieu de Québec, Department of Medicine, Université Laval, Québec, QC, G1R 2J6, Canada.
authors.forename: Elisabeth L
authors.initials: EL
authors.lastname: Pagé
authors.forename: Denise A
authors.initials: DA
authors.lastname: Chan
authors.forename: Amato J
authors.initials: AJ
authors.lastname: Giaccia
authors.forename: Mark
authors.initials: M
authors.lastname: Levine
authors.forename: Darren E
authors.initials: DE
authors.lastname: Richard
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001205:Ascorbic Acid / Q000378:metabolism*; D015687:Cell Hypoxia / Q000187:drug effects; D003067:Coenzymes / Q000378:metabolism; D006207:Half-Life; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D006900:Hydroxylation / Q000187:drug effects; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000737:chemistry / Q000378:metabolism*; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010084:Oxidation-Reduction / Q000187:drug effects; D011393:Procollagen-Proline Dioxygenase / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D017434:Protein Structure, Tertiary; D051381:Rats; D017208:Rats, Wistar; D013816:Thermodynamics; D054875:Ubiquitination / Q000187:drug effects; D051794:Von Hippel-Lindau Tumor Suppressor Protein / Q000378:metabolism
chemical_list: D003067:Coenzymes; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D000804:Angiotensin II; D006861:Hydrogen Peroxide; D011393:Procollagen-Proline Dioxygenase; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D001205:Ascorbic Acid