Downregulation of TGF-β Receptor-2 Expression and Signaling through Inhibition of Na/K-ATPase

PLoS One. 2016 Dec 22;11(12):e0168363. doi: 10.1371/journal.pone.0168363. eCollection 2016.

Abstract

Transforming growth factor-beta (TGF-β) is a multi-functional cytokine implicated in the control of cell growth and differentiation. TGF-β signals through a complex of TGF-β receptors 1 and 2 (TGFβR1 and TGFβR2) that phosphorylate and activate Smad2/3 transcription factors driving transcription of the Smad-target genes. The Na+/K+-ATPase is an integral plasma membrane protein critical for maintaining the electro-chemical gradient of Na+ and K+ in the cell. We found that inhibition of the Na+/K+ ATPase by ouabain results in a dramatic decrease in the expression of TGFβR2 in human lung fibrobalsts (HLF) at the mRNA and protein levels. This was accompanied by inhibition of TGF-β-induced Smad phosphorylation and the expression of TGF-β target genes, such as fibronectin and smooth muscle alpha-actin. Inhibition of Na+/K+ ATPase by an alternative approach (removal of extracellular potassium) had a similar effect in HLF. Finally, treatment of lung alveolar epithelial cells (A549) with ouabain also resulted in the downregulation of TGFβR2, the inhibition of TGF-β-induced Smad phosphorylation and of the expression of mesenchymal markers, vimentin and fibronectin. Together, these data demonstrate a critical role of Na+/K+-ATPase in the control of TGFβR2 expression, TGF-β signaling and cell responses to TGF-β.

MeSH terms

  • Cells, Cultured
  • Down-Regulation
  • Fibroblasts / cytology
  • Fibroblasts / metabolism*
  • Humans
  • Lung / cytology
  • Lung / metabolism*
  • Phosphorylation
  • Protein Serine-Threonine Kinases / antagonists & inhibitors*
  • Protein Serine-Threonine Kinases / metabolism
  • Receptor, Transforming Growth Factor-beta Type II
  • Receptors, Transforming Growth Factor beta / antagonists & inhibitors*
  • Receptors, Transforming Growth Factor beta / metabolism
  • Signal Transduction
  • Sodium-Potassium-Exchanging ATPase / antagonists & inhibitors*
  • Sodium-Potassium-Exchanging ATPase / metabolism
  • Transforming Growth Factor beta / metabolism*

Substances

  • Receptors, Transforming Growth Factor beta
  • Transforming Growth Factor beta
  • Protein Serine-Threonine Kinases
  • Receptor, Transforming Growth Factor-beta Type II
  • Sodium-Potassium-Exchanging ATPase