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The phosphorylation of endogenous Nedd4-2 In Na(+)-absorbing human airway epithelial cells.

Authors
  • Ismail, Noor A S1
  • Baines, Deborah L2
  • Wilson, Stuart M3
  • 1 Division of Cardiovascular and Diabetes Medicine, Medical Research Institute, College of Medicine, Dentistry & Nursing, University of Dundee, Dundee DD1 9SY, UK; Biochemistry Department, Faculty of Medicine, University Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300 Kuala Lumpur, Malaysia. , (Malaysia)
  • 2 Biomedical Sciences Research Centre, St Georges University of London, Cranmer Terrace, London, UK.
  • 3 Division of Cardiovascular and Diabetes Medicine, Medical Research Institute, College of Medicine, Dentistry & Nursing, University of Dundee, Dundee DD1 9SY, UK; Wolfson Research Institute, School of Medicine, Pharmacy and Health, Durham University Queen׳s Campus, Stockton on Tees, TS17 6BH, UK. Electronic address: [email protected]
Type
Published Article
Journal
European journal of pharmacology
Publication Date
Jun 05, 2014
Volume
732
Pages
32–42
Identifiers
DOI: 10.1016/j.ejphar.2014.03.005
PMID: 24657276
Source
Medline
Keywords
License
Unknown

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-Ser(221), -Ser(327) and -Thr(246). 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 (20min) activating PKA in glucocorticoid-deprived (24h) cells increased the abundance of Ser(221)-phosphorylated, Ser(327)-phosphorylated and total Nedd4-2 without altering the abundance of Thr(246)-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 (20min) in glucocorticoid-treated (0.2µM dexamethasone, 24h) cells, on the other hand, increased the abundance of Ser(221)-, Ser(327)- and Thr(246)-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.

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