The phosphorylation of endogenous Nedd4-2 in Na+ - Absorbing human airway epithelial cells

Noor Akmal Shareela Ismail, Deborah L. Baines, Stuart M. Wilson

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Neural precursor cell expressed, developmentally down-regulated protein 4-2 (Nedd4-2) mediates the internalisation / degradation of epithelial Na + channel subunits (α-, β- and γ-ENaC). Serum / glucocorticoid inducible kinase 1 (SGK1) and protein kinase A (PKA) both appear to inhibit this process by phosphorylating Nedd4-2-Ser221, -Ser 327 and -Thr246. This Nedd4-2 inactivation process is thought to be central to the hormonal control of Na+ absorption. The present study of H441 human airway epithelial cells therefore explores the effects of SGK1 and / or PKA upon the phosphorylation / abundance of endogenous Nedd4-2; the surface expression of ENaC subunits, and electrogenic Na + transport. Effects on Nedd4-2 phosphorylation/abundance and the surface expression of ENaC were monitored by western analysis, whilst Na + absorption was quantified electrometrically. Acutely (20 min) activating PKA in glucocorticoid-deprived (24 h) cells increased the abundance of Ser221-phosphorylated, Ser327-phosphorylated and total Nedd4-2 without altering the abundance of Thr246-phosphorylated Nedd4-2. Activating PKA under these conditions did not cause a co-ordinated increase in the surface abundance of α-, β- and γ-ENaC and had only a very small effect upon electrogenic Na+ absorption. Activating PKA (20 min) in glucocorticoid-treated (0.2 μM dexamethasone, 24 h) cells, on the other hand, increased the abundance of Ser221-, Ser 327- and Thr246-phosphorylated and total Nedd4-2; increased the surface abundance of α-, β- and γ-ENaC and evoked a clear stimulation of Na+ transport. Chronic glucocorticoid stimulation therefore appears to allow cAMP-dependent control of Na+ absorption by facilitating the effects of PKA upon the Nedd4-2 and ENaC subunits.

Original languageEnglish
Pages (from-to)32-42
Number of pages11
JournalEuropean Journal of Pharmacology
Volume732
Issue number1
DOIs
Publication statusPublished - 5 Jun 2014

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Epithelial Cells
Phosphorylation
Cyclic AMP-Dependent Protein Kinases
Glucocorticoids
Proteins
Epithelial Sodium Channels
Dexamethasone

Keywords

  • Cellular signalling
  • Protein kinase A
  • Serum and glucocorticoid regulated kinase 1

ASJC Scopus subject areas

  • Pharmacology
  • Medicine(all)

Cite this

The phosphorylation of endogenous Nedd4-2 in Na+ - Absorbing human airway epithelial cells. / Ismail, Noor Akmal Shareela; Baines, Deborah L.; Wilson, Stuart M.

In: European Journal of Pharmacology, Vol. 732, No. 1, 05.06.2014, p. 32-42.

Research output: Contribution to journalArticle

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