Dexamethasone stimulates transcription of the Na+-K +-ATPase β1 gene in adult rat lung epithelial cells

Hong Hao, Christine H. Wendt, Gurpreet Sandhu, David H. Ingbar

Research output: Contribution to journalArticle

14 Scopus citations

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 β 1-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 β1 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 β1 gene expression in adult rat lung epithelial cells through a GR-dependent mechanism that can act at multiple sites.

Original languageEnglish (US)
Pages (from-to)L593-L601
JournalAmerican Journal of Physiology - Lung Cellular and Molecular Physiology
Volume285
Issue number3 29-3
DOIs
StatePublished - Sep 1 2003

Keywords

  • Alveolar fluid
  • Glucocorticoid receptor
  • Glucocorticoid response element
  • Ion transport
  • Promoter
  • Sodium pump
  • Type II cells

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