Identification of Extracellular Domain Residues Required for Epithelial Na+ Channel Activation by Acidic pH

Daniel M Collier; Zerubbabel J Peterson; Ilya O Blokhin; Christopher J Benson; Peter M Snyder

doi:10.1074/jbc.M112.417519

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Identification of Extracellular Domain Residues Required for Epithelial Na+ Channel Activation by Acidic pH

Journal article

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Identification of Extracellular Domain Residues Required for Epithelial Na+ Channel Activation by Acidic pH

Daniel M Collier, Zerubbabel J Peterson, Ilya O Blokhin, Christopher J Benson and Peter M Snyder

The Journal of biological chemistry, Vol.287(49), pp.40907-40914

11/30/2012

DOI: 10.1074/jbc.M112.417519

PMCID: PMC3510795

PMID: 23060445

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Abstract

Background: The epithelial Na + channel (ENaC) functions as a pathway for Na + absorption across epithelia. Results: Seven acidic residues in the extracellular domain of γENaC and one in βENaC are required for regulation by acidic pH. Conclusion: The ENaC extracellular domains function as sensors to detect changes in extracellular pH. Significance: These findings provide new insights into mechanisms that regulate Na + homeostasis and blood pressure. A growing body of evidence suggests that the extracellular domain of the epithelial Na + channel (ENaC) functions as a sensor that fine tunes channel activity in response to changes in the extracellular environment. We previously found that acidic pH increases the activity of human ENaC, which results from a decrease in Na + self-inhibition. In the current work, we identified extracellular domain residues responsible for this regulation. We found that rat ENaC is less sensitive to pH than human ENaC, an effect mediated in part by the γ subunit. We identified a group of seven residues in the extracellular domain of γENaC (Asp-164, Gln-165, Asp-166, Glu-292, Asp-335, His-439, and Glu-455) that, when individually mutated to Ala, decreased proton activation of ENaC. γ E455 is conserved in βENaC (Glu-446); mutation of this residue to neutral amino acids (Ala, Cys) reduced ENaC stimulation by acidic pH, whereas reintroduction of a negative charge (by MTSES modification of Cys) restored pH regulation. Combination of the seven γENaC mutations with β E446A generated a channel that was not activated by acidic pH, but inhibition by alkaline pH was intact. Moreover, these mutations reduced the effect of pH on Na + self-inhibition. Together, the data identify eight extracellular domain residues in human β- and γENaC that are required for regulation by acidic pH.

Hypertension

Site-directed Mutagenesis

Ion Channels

Membrane Biology

Electrophysiology

Biophysics

ENaC

Kidney

Details

Title: Subtitle: Identification of Extracellular Domain Residues Required for Epithelial Na+ Channel Activation by Acidic pH
Creators: Daniel M Collier - From the Departments of
Zerubbabel J Peterson - From the Departments of
Ilya O Blokhin - From the Departments of
Christopher J Benson - From the Departments of
Peter M Snyder - From the Departments of
Resource Type: Journal article
Publication Details: The Journal of biological chemistry, Vol.287(49), pp.40907-40914
DOI: 10.1074/jbc.M112.417519
PMID: 23060445
PMCID: PMC3510795
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; 2T32HL007121-36; DK25295 / National Institutes of Health
Alternative title: pH Regulation of ENaC
Language: English
Date published: 11/30/2012
Academic Unit: Molecular Physiology and Biophysics; Cardiovascular Medicine; Fraternal Order of Eagles Diabetes Research Center; Neuroscience and Pharmacology; Medicine Administration; Internal Medicine
Record Identifier: 9984025681902771

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