title: Regulation of Na-K-ATPase gene expression by hyperoxia in MDCK cells.
abstract: Na-K-ATPase plays a central role in a variety of physiological processes, including ion transport and regulation of cell volume. Our previous data showed that hyperoxia increased the expression of Na-K-ATPase alpha 1 and beta 1 mRNA in lung type II cells. We similarly show that hyperoxia (> or = 95% O2 for 24-48 h) increased steady-state mRNA levels in both Na-K-ATPase subunits in Madin-Darby canine kidney (MDCK) cells. The mechanism of gene regulation by hyperoxia was assessed. Stability of the Na-K-ATPase mRNA levels of both subunits was unchanged in hyperoxia-exposed MDCK cells. To determine whether gene transcription was augmented by hyperoxia, MDCK cells were transfected with a beta 1-subunit promoter-reporter construct. Transfection with the wild-type promoter (beta 1-817) revealed a 1.9 +/- 0.2-fold increase in promoter activity. Transfection with 5' deletion constructs identified a 61-base pair (bp) region between -102 and -41 that was necessary for this increase in promoter activity by hyperoxia. Incorporation of this 61-bp region into a minimal promoter (mouse mammary tumor virus) similarly increased promoter activity 2.3-fold in the presence of hyperoxia. This increase in promoter activity was not seen when MDCK cells were incubated with various concentrations of hydrogen peroxide. In summary, hyperoxia increased Na-K-ATPase beta 1-subunit mRNA steady-state level due to increased transcription in MDCK cells. A region necessary for this hyperoxic effect on beta 1 transcription is located between base pairs -102 and -41 on the promoter.
authors.affiliation: University of Minnesota Medical School, Minneapolis 55455, USA.
authors.forename: C H
authors.initials: CH
authors.lastname: Wendt
authors.forename: H
authors.initials: H
authors.lastname: Towle
authors.forename: R
authors.initials: R
authors.lastname: Sharma
authors.forename: S
authors.initials: S
authors.lastname: Duvick
authors.forename: K
authors.initials: K
authors.lastname: Kawakami
authors.forename: G
authors.initials: G
authors.lastname: Gick
authors.forename: D H
authors.initials: DH
authors.lastname: Ingbar
mesh_terms: D000818:Animals; D002460:Cell Line; D004285:Dogs; D004790:Enzyme Induction; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007668:Kidney / Q000201:enzymology; D016877:Oxidants / Q000494:pharmacology; D010100:Oxygen / Q000502:physiology*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000096:biosynthesis / Q000235:genetics*; D014158:Transcription, Genetic / Q000187:drug effects; D015854:Up-Regulation
chemical_list: D016877:Oxidants; D012333:RNA, Messenger; D006861:Hydrogen Peroxide; D000254:Sodium-Potassium-Exchanging ATPase; D010100:Oxygen