An Inhibitory Peptide Derived from the α-subunit of the Epithelial Sodium Channel (ENaC) Shows a Helical Conformation

Language
en
Document Type
Article
Issue Date
2014-04-17
Issue Year
2012
Authors
Haerteis, Silke
Schaal, Daniel
Brauer, Felix
Brüschke, Stefan
Schweimer, Kristian
Rauh, Robert
Sticht, Heinrich
Rösch, Paul
Schwarzinger, Stephan
Korbmacher, Christoph
Editor
Abstract

Proteolytic activation of the heteromeric epithelial sodium channel (ENaC) is thought to involve the release of inhibitory peptides from the extracellular domains of its α- and γ-subunit. Recently, we demonstrated that an α-13-mer peptide, corresponding to a putative inhibitory region within the extracellular domain of human αENaC, inhibits human αβγENaC. The aim of the present study was to investigate the structural basis of the inhibitory effect of this α-13-mer peptide. Analysis of the peptide by replica exchange molecular dynamics method, circular dichroism spectroscopy, nuclear magnetic resonance spectroscopy, and molecular dynamics simulations suggested that a helical turn at the carboxy-terminus is the preferred conformational state of the α-13-mer peptide. From this we predicted that a specific mutation (leucine 188 to alanine) should have a strong effect on the conformational preferences of the peptide. To functionally test this, we compared the effect of the wild-type α-13-mer with that of a mutant α-L188A- 13-mer on ENaC currents in Xenopus laevis oocytes heterologously expressing human αβγENaC. We demonstrated that replacing the leucine 188 by alanine abolished the inhibitory effect of the α-13-mer peptide on ENaC. These findings suggest that a helical conformation in its carboxyterminal part is functionally important to mediate ENaC inhibition by the α-13-mer peptide. However, high resolution structural information on the complex of the inhibitory αENaC peptide and the channel are needed to confirm this conclusion.

Journal Title
Cellular Physiology and Biochemistry
Volume
29
Citation
Cellular Physiology and Biochemistry 2012; 29: 761-774. <http://www.karger.com/Article/Pdf/312590> Copyright © 2012 S. Karger AG, Basel
DOI
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