Electrophysiological and Biochemical Evidence That DEG/ENaC Cation Channels Are Composed of Nine Subunits*
- From the Howard Hughes Medical Institute, Departments of Internal Medicine and Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, Iowa 52242
Abstract
Members of the DEG/ENaC protein family form ion channels with diverse functions. DEG/ENaC subunits associate as hetero- and homomultimers to generate channels; however the stoichiometry of these complexes is unknown. To determine the subunit stoichiometry of the human epithelial Na+ channel (hENaC), we expressed the three wild-type hENaC subunits (α, β, and γ) with subunits containing mutations that alter channel inhibition by methanethiosulfonates. The data indicate that hENaC contains three α, three β, and three γ subunits. Sucrose gradient sedimentation of αhENaC translated in vitro, as well as α-, β-, and γhENaC coexpressed in cells, was consistent with complexes containing nine subunits. FaNaCh and BNC1, two related DEG/ENaC channels, produced complexes of similar mass. Our results suggest a novel nine-subunit stoichiometry for the DEG/ENaC family of ion channels.
Footnotes
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↵* The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵‡ Supported by a Fellowship from the Roy J. Carver Charitable Trust and by the NHLBI and NIDDK, National Institutes of Health. To whom correspondence should be addressed: Dept. of Internal Medicine, University of Iowa College of Medicine, 200K EMRB, Iowa City, IA 52242. Tel.: 319-356-7481.
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↵§ Supported by a National Research Service Award from the NHLBI, National Institutes of Health.
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↵¶ Supported by the Howard Hughes Medical Institute.
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↵1 The abbreviations used are: MTS, methanethiosulfonate; MTSEA, (2-aminoethyl)methanethiosulfonate hydrobromide; MTSET, [2-(trimethylammonium)ethyl]methanethiosulfonate bromide; ER, endoplasmic reticulum; PAGE, polyacrylamide gel electrophoresis.
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↵2 L. S. Prince and M. J. Welsh, unpublished observations.
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↵3 P. M. Snyder and M. J. Welsh, unpublished observations.
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- Received September 19, 1997.
- Revision received October 22, 1997.
- The American Society for Biochemistry and Molecular Biology, Inc.
