title: An endoplasmic reticulum transmembrane prolyl 4-hydroxylase is induced by hypoxia and acts on hypoxia-inducible factor alpha.
abstract: Prolyl 4-hydroxylases (P4Hs) act on collagens (C-P4Hs) and the oxygen-dependent degradation domains (ODDDs) of hypoxia-inducible factor alpha subunits (HIF-P4Hs) leading to degradation of the latter. We report data on a human P4H possessing a transmembrane domain (P4H-TM). Its gene is also found in zebrafish but not in flies and nematodes. Its sequence more closely resembles those of the C-P4Hs than the HIF-P4Hs, but it lacks the peptide substrate-binding domain of the C-P4Hs. P4H-TM levels in cultured cells are increased by hypoxia, and P4H-TM is N-glycosylated and is located in endoplasmic reticulum membranes with its catalytic site inside the lumen, a location differing from those of the HIF-P4Hs. Despite this, P4H-TM overexpression in cultured neuroblastoma cells reduced HIF-alpha ODDD reporter construct levels, and its small interfering RNA increased HIF-1alpha protein level, in the same way as those of HIF-P4Hs. Furthermore, recombinant P4H-TM hydroxylated the two critical prolines in HIF-1alpha ODDD in vitro, with a preference for the C-terminal proline, whereas it did not hydroxylate any prolines in recombinant type I procollagen chains.
authors.affiliation: Collagen Research Unit, University of Oulu, Finland.
authors.forename: Peppi
authors.initials: P
authors.lastname: Koivunen
authors.forename: Päivi
authors.initials: P
authors.lastname: Tiainen
authors.forename: Jaana
authors.initials: J
authors.lastname: Hyvärinen
authors.forename: Kim E
authors.initials: KE
authors.lastname: Williams
authors.forename: Raija
authors.initials: R
authors.lastname: Sormunen
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Klaus
authors.forename: Kari I
authors.initials: KI
authors.lastname: Kivirikko
authors.forename: Johanna
authors.initials: J
authors.lastname: Myllyharju
mesh_terms: D020134:Catalytic Domain / Q000502:physiology; D015687:Cell Hypoxia / Q000502:physiology; D045744:Cell Line, Tumor; D004721:Endoplasmic Reticulum / Q000201:enzymology* / Q000235:genetics; D006801:Humans; D006900:Hydroxylation; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D011393:Procollagen-Proline Dioxygenase / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000502:physiology*; D017434:Protein Structure, Tertiary / Q000502:physiology; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D011994:Recombinant Proteins; D011393:Procollagen-Proline Dioxygenase