title: Nitric oxide modulates oxygen sensing by hypoxia-inducible factor 1-dependent induction of prolyl hydroxylase 2.
abstract: The transcription factor complex hypoxia-inducible factor 1 (HIF-1) plays a crucial role in cellular adaptation to low oxygen availability. O(2)-dependent HIF prolyl hydroxylases (PHDs) modify HIF-1alpha, which is sent to proteasomal degradation under normoxia. Reduced activity of PHDs under hypoxia allows stabilization of HIF-1alpha and induction of HIF-1 target gene expression. Like hypoxia, nitric oxide (NO) was found to inhibit normoxic PHD activity leading to HIF-1alpha accumulation. In contrast under hypoxia, NO reduced HIF-1alpha levels due to enhanced PHD activity. Herein, we studied the role of NO in regulating PHD expression and the consequences thereof for HIF-1alpha degradation. We report a biphasic response of HIF-1alpha and PHDs to NO treatment both under normoxia and hypoxia. In the early phase, NO inhibits PHD activity that leads to HIF-1alpha accumulation, whereas in the late phase, increased PHD levels reduce HIF-1alpha. NO induces expression of PHD2 and -3 mRNA and protein under normoxia and hypoxia in a strictly HIF-1-dependent manner. NO-treated cells with elevated PHD levels displayed delayed HIF-1alpha accumulation and accelerated degradation of HIF-1alpha upon reoxygenation. Subsequent suppression of PHD2 and -3 expression using small interfering RNA revealed that PHD2 was exclusively responsible for regulating HIF-1alpha degradation under NO treatment. In conclusion, we identified the induction of PHD2 as an underlying mechanism of NO-induced degradation of HIF-1alpha.
authors.affiliation: Institut für Physiologie, Universität Duisburg-Essen, Hufelandstrasse 55, D-45122 Essen, Germany.
authors.forename: Utta
authors.initials: U
authors.lastname: Berchner-Pfannschmidt
authors.forename: Hatice
authors.initials: H
authors.lastname: Yamac
authors.forename: Buena
authors.initials: B
authors.lastname: Trinidad
authors.forename: Joachim
authors.initials: J
authors.lastname: Fandrey
mesh_terms: D045744:Cell Line, Tumor; D002470:Cell Survival; D006801:Humans; D000860:Hypoxia; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D008954:Models, Biological; D009569:Nitric Oxide / Q000737:chemistry / Q000378:metabolism*; D010100:Oxygen / Q000737:chemistry* / Q000378:metabolism; D011393:Procollagen-Proline Dioxygenase / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D013997:Time Factors
chemical_list: C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D009569:Nitric Oxide; D011393:Procollagen-Proline Dioxygenase; D046988:Proteasome Endopeptidase Complex; D010100:Oxygen