RGD Reference Report - Determination of epithelial Na+ channel subunit stoichiometry from single-channel conductances. - Rat Genome Database

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Determination of epithelial Na+ channel subunit stoichiometry from single-channel conductances.

Authors: Anantharam, Arun  Palmer, Lawrence G 
Citation: Anantharam A and Palmer LG, J Gen Physiol. 2007 Jul;130(1):55-70. doi: 10.1085/jgp.200609716. Epub 2007 Jun 11.
RGD ID: 150521638
Pubmed: PMID:17562820   (View Abstract at PubMed)
PMCID: PMC2154365   (View Article at PubMed Central)
DOI: DOI:10.1085/jgp.200609716   (Journal Full-text)

The epithelial Na(+) channel (ENaC) is a multimeric membrane protein consisting of three subunits, alpha, beta, and gamma. The total number of subunits per functional channel complex has been described variously to follow either a tetrameric arrangement of 2alpha:1beta:1gamma or a higher-ordered stoichiometry of 3alpha:3beta:3gamma. Therefore, while it is clear that all three ENaC subunits are required for full channel activity, the number of the subunits required remains controversial. We used a new approach, based on single-channel measurements in Xenopus oocytes to address this issue. Individual mutations that alter single-channel conductance were made in pore-lining residues of ENaC alpha, beta, or gamma subunits. Recordings from patches in oocytes expressing a single species, wild type or mutant, of alpha, beta, and gamma showed a well-defined current transition amplitude with a single Gaussian distribution. When cRNAs for all three wild-type subunits were mixed with an equimolar amount of a mutant alpha-subunit (either S589D or S592T), amplitudes corresponding to pure wild-type or mutant conductances could be observed in the same patch, along with a third intermediate amplitude most likely arising from channels with at least one wild-type and at least 1 mutant alpha-subunit. However, intermediate or hybrid conductances were not observed with coexpression of wild-type and mutant betaG529A or gammaG534E subunits. Our results support a tetrameric arrangement of ENaC subunits where 2alpha, 1beta, and 1gamma come together around central pore.



Gene Ontology Annotations    Click to see Annotation Detail View

Biological Process

  
Object SymbolSpeciesTermQualifierEvidenceWithNotesSourceOriginal Reference(s)
Scnn1aRatintracellular sodium ion homeostasis involved_inIDA PMID:17562820ComplexPortal 
Scnn1bRatintracellular sodium ion homeostasis involved_inIDA PMID:17562820ComplexPortal 
Scnn1gRatintracellular sodium ion homeostasis involved_inIDA PMID:17562820ComplexPortal 
Scnn1aRatsodium ion import across plasma membrane involved_inIDA PMID:17562820ComplexPortal 
Scnn1bRatsodium ion import across plasma membrane involved_inIDA PMID:17562820ComplexPortal 
Scnn1gRatsodium ion import across plasma membrane involved_inIDA PMID:17562820ComplexPortal 

Objects Annotated

Genes (Rattus norvegicus)
Scnn1a  (sodium channel epithelial 1 subunit alpha)
Scnn1b  (sodium channel epithelial 1 subunit beta)
Scnn1g  (sodium channel epithelial 1 subunit gamma)


Additional Information