title: Hypoxia regulates xanthine dehydrogenase activity at pre- and posttranslational levels.
abstract: Hypoxia increases the activity of xanthine oxidase (XO) and its precursor, xanthine dehydrogenase (XDH), but the mechanism of regulation is unclear. In hypoxic Swiss 3T3 cells, an early (0-24 h) cycloheximide-insensitive increase in XO-XDH activity, coupled with a lack of increase in de novo XO-XDH synthesis (immunoprecipitation) or mRNA levels (quantitative RT-PCR), demonstrated a posttranslational effect of hypoxia. Similarly, hyperoxia decreased XO-XDH activity faster than could be accounted for by cessation of XO-XDH protein synthesis. In further support of a posttranslational effect, cells transfected with a constitutively driven XDH construct displayed an exaggerated increase in activity in hypoxia but no increase in activity in hyperoxia. However, more prolonged exposure to hypoxia (24-48 h) induced an increase in XO-XDH mRNA levels and de novo XO-XDH protein synthesis, suggesting an additional pretranslational effect. Finally, hypoxic induction of XO-XDH activity was found to be cell-type-restricted. We conclude that control of XO-XDH levels by oxygen tension is a complex process which involves several points of regulation.
authors.affiliation: Webb-Waring Institute for Biomedical Research, University of Colorado Health Sciences Center, Denver 80262, USA. lance.terada@uchsc.edu
authors.forename: L S
authors.initials: LS
authors.lastname: Terada
authors.forename: D
authors.initials: D
authors.lastname: Piermattei
authors.forename: G N
authors.initials: GN
authors.lastname: Shibao
authors.forename: J L
authors.initials: JL
authors.lastname: McManaman
authors.forename: R M
authors.initials: RM
authors.lastname: Wright
mesh_terms: D016475:3T3 Cells; D000818:Animals; D015687:Cell Hypoxia / Q000502:physiology*; D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D007700:Kinetics; D051379:Mice; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D013997:Time Factors; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D014968:Xanthine Dehydrogenase / Q000096:biosynthesis* / Q000378:metabolism; D014969:Xanthine Oxidase / Q000096:biosynthesis* / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D003513:Cycloheximide; D014968:Xanthine Dehydrogenase; D014969:Xanthine Oxidase