Identification of Epithelial Na+ Channel (ENaC) Intersubunit Cl− Inhibitory Residues Suggests a Trimeric αγβ Channel Architecture

Daniel M Collier; Peter M Snyder

doi:10.1074/jbc.M110.198127

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Identification of Epithelial Na+ Channel (ENaC) Intersubunit Cl− Inhibitory Residues Suggests a Trimeric αγβ Channel Architecture

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Identification of Epithelial Na+ Channel (ENaC) Intersubunit Cl− Inhibitory Residues Suggests a Trimeric αγβ Channel Architecture

Daniel M Collier and Peter M Snyder

The Journal of biological chemistry, Vol.286(8), pp.6027-6032

02/25/2011

DOI: 10.1074/jbc.M110.198127

PMCID: PMC3057804

PMID: 21149458

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Abstract

The extracellular domain of the epithelial Na + channel (ENaC) is exposed to a wide range of anion concentrations in the kidney. We have previously demonstrated that extracellular Cl − inhibits ENaC activity. To identify sites involved in Cl − inhibition, we mutated residues in the extracellular domain of α-, β-, and γENaC that are homologous to the Cl − binding site in acid-sensing ion channel 1a and tested the effect of Cl − on the activity of ENaC expressed in Xenopus oocytes. We identified two Cl − inhibitory sites in ENaC. One is formed by residues in the thumb domain of αENaC and the palm domain of βENaC. Mutation of residues at this interface decreased Cl − inhibition and decreased Na + self-inhibition. The second site is formed by residues at the interface of the thumb domain of βENaC and the palm domain of γENaC. Mutation of these residues also decreased Cl − inhibition yet had no effect on Na + self-inhibition. In contrast, mutations in the thumb domain of γENaC and palm of αENaC had little or no effect on Cl − inhibition or Na + self-inhibition. The data demonstrate that Cl − inhibits ENaC activity by two distinct Na + -dependent and Na + -independent mechanisms that correspond to the two functional Cl − inhibitory sites. Furthermore, based on the effects of mutagenesis on Cl − inhibition, the additive nature of mutations, and on differences in the mechanisms of Cl − inhibition, the data support a model in which ENaC subunits assemble in an αγβ orientation (listed clockwise when viewed from the top).

Amiloride

Chloride

Ion Channels

Membrane Biology

Sodium Channels

Epithelial Cell

ENaC

Acid-sensing Ion Channel (ASIC)

Kidney

Details

Title: Subtitle: Identification of Epithelial Na+ Channel (ENaC) Intersubunit Cl− Inhibitory Residues Suggests a Trimeric αγβ Channel Architecture
Creators: Daniel M Collier - From the Departments of Internal Medicine and Molecular Physiology and Biophysics, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242
Peter M Snyder - From the Departments of Internal Medicine and Molecular Physiology and Biophysics, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242
Resource Type: Journal article
Publication Details: The Journal of biological chemistry, Vol.286(8), pp.6027-6032
DOI: 10.1074/jbc.M110.198127
PMID: 21149458
PMCID: PMC3057804
NLM abbreviation: J Biol Chem
ISSN: 0021-9258
eISSN: 1083-351X
Publisher: American Society for Biochemistry and Molecular Biology; 9650 Rockville Pike, Bethesda, MD 20814, U.S.A
Grant note: HL072256 / National Institutes of Health
Alternative title: αγβ ENaC Architecture
Language: English
Date published: 02/25/2011
Academic Unit: Molecular Physiology and Biophysics; Cardiovascular Medicine; Medicine Administration; Internal Medicine
Record Identifier: 9984025570602771

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