title: Dexamethasone stimulates transcription of the Na+-K+-ATPase beta1 gene in adult rat lung epithelial cells.
abstract: Na+-K+-ATPase plays an essential role in active alveolar epithelial fluid resorption. In fetal and adult alveolar epithelial cells, glucocorticoids (GC) increase Na+-K+-ATPase activity and mRNA levels. We sought to define the mechanism of Na+-K+-ATPase gene upregulation by GC. In a rat alveolar epithelial cell line (RLE), dexamethasone (Dex) increased beta1-subunit Na+-K+-ATPase mRNA expression two- to threefold within 3 h after exposure to the GC. The increased gene expression was due to increased transcription as demonstrated by nuclear run-on assays, whereas mRNA stability remained unchanged. Transient transfection of 5' deletion mutants of a beta1 promoter-reporter construct demonstrated a 1.5- to 2.2-fold increase in promoter activity by Dex. All of the 5' deletion constructs contained partial or palindromic GC regulatory elements (GRE) and responded to GC. The increased expression of promoter reporter was inhibited by RU-486, a GC receptor (GR) antagonist, suggesting the involvement of GR. The palindromic GRE at -631 demonstrated Dex induction in a heterologous promoter construct. Gel mobility shift assays using RLE nuclear extracts demonstrated specific binding to this site and the presence of GR. We conclude that GC directly stimulate transcription of Na+-K+-ATPase beta1 gene expression in adult rat lung epithelial cells through a GR-dependent mechanism that can act at multiple sites.
authors.affiliation: Pulmonary and Critical Care Div., Dept. of Medicine, MMC 276, Univ. of Minnesota, Minneapolis, MN 55455, USA.
authors.forename: Hong
authors.initials: H
authors.lastname: Hao
authors.forename: Christine H
authors.initials: CH
authors.lastname: Wendt
authors.forename: Gurpreet
authors.initials: G
authors.lastname: Sandhu
authors.forename: David H
authors.initials: DH
authors.lastname: Ingbar
mesh_terms: D000367:Age Factors; D000818:Animals; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology*; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology; D017353:Gene Deletion; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D005938:Glucocorticoids / Q000494:pharmacology*; D006727:Hormone Antagonists / Q000494:pharmacology; D015735:Mifepristone / Q000494:pharmacology; D016296:Mutagenesis; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D020545:Respiratory Mucosa / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D005938:Glucocorticoids; D006727:Hormone Antagonists; D012333:RNA, Messenger; D015735:Mifepristone; D003907:Dexamethasone; D000254:Sodium-Potassium-Exchanging ATPase