Hypoxia regulates xanthine dehydrogenase activity at pre- and posttranslational levels.
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.
Terada
L S
LS
Webb-Waring Institute for Biomedical Research, University of Colorado Health Sciences Center, Denver 80262, USA. lance.terada@uchsc.edu
Piermattei
D
D
Shibao
G N
GN
McManaman
J L
JL
Wright
R M
RM
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
D012333:RNA, Messenger; D003513:Cycloheximide; D014968:Xanthine Dehydrogenase; D014969:Xanthine Oxidase