Regulation of the epithelial Na+ channel and airway surface liquid volume by serine proteases

  • Erol A. Gaillard
  • Pradeep Kota
  • Martina Gentzsch
  • Nikolay V. Dokholyan
  • M. Jackson Stutts
  • Robert Tarran
Invited Review

DOI: 10.1007/s00424-010-0827-z

Cite this article as:
Gaillard, E.A., Kota, P., Gentzsch, M. et al. Pflugers Arch - Eur J Physiol (2010) 460: 1. doi:10.1007/s00424-010-0827-z

Abstract

Mammalian airways are protected from infection by a thin film of airway surface liquid (ASL) which covers airway epithelial surfaces and acts as a lubricant to keep mucus from adhering to the epithelial surface. Precise regulation of ASL volume is essential for efficient mucus clearance and too great a reduction in ASL volume causes mucus dehydration and mucus stasis which contributes to chronic airway infection. The epithelial Na+ channel (ENaC) is the rate-limiting step that governs Na+ absorption in the airways. Recent in vitro and in vivo data have demonstrated that ENaC is a critical determinant of ASL volume and hence mucus clearance. ENaC must be cleaved by either intracellular furin-type proteases or extracellular serine proteases to be active and conduct Na+, and this process can be inhibited by protease inhibitors. ENaC can be regulated by multiple pathways, and once proteolytically cleaved ENaC may then be inhibited by intracellular second messengers such as cAMP and PIP2. In the airways, however, regulation of ENaC by proteases seems to be the predominant mode of regulation since knockdown of either endogenous serine proteases such as prostasin, or inhibitors of ENaC proteolysis such as SPLUNC1, has large effects on ENaC activity in airway epithelia. In this review, we shall discuss how ENaC is proteolytically cleaved, how this process can regulate ASL volume, and how its failure to operate correctly may contribute to chronic airway disease.

Keywords

Na+ channel Cystic fibrosis Epithelial transport Fluid absorption Lung liquid 

Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Erol A. Gaillard
    • 2
  • Pradeep Kota
    • 3
  • Martina Gentzsch
    • 1
  • Nikolay V. Dokholyan
    • 3
  • M. Jackson Stutts
    • 1
  • Robert Tarran
    • 1
  1. 1.Cystic Fibrosis/Pulmonary Research and Treatment CenterThe University of North CarolinaChapel HillUSA
  2. 2.Department of Infection, Immunity and InflammationUniversity of LeicesterLeicesterUK
  3. 3.Department of Biochemistry and BiophysicsUniversity of North CarolinaChapel HillUSA