Cadmium trapping in an epithelial sodium channel pore mutant.

Détails

ID Serval
serval:BIB_E323715B80F1
Type
Article: article d'un périodique ou d'un magazine.
Collection
Publications
Titre
Cadmium trapping in an epithelial sodium channel pore mutant.
Périodique
Journal of Biological Chemistry
Auteur(s)
Takeda A.N., Gautschi I., van Bemmelen M.X., Schild L.
ISSN
0021-9258
Statut éditorial
Publié
Date de publication
11/2007
Peer-reviewed
Oui
Volume
282
Numéro
44
Pages
31928-31936
Langue
anglais
Notes
Publication types: Journal Article
Résumé
The putative selectivity filter of the epithelial sodium channel (ENaC) comprises a three-residue sequence G/SXS, but it remains uncertain whether the backbone atoms of this sequence or whether their side chains are lining the pore. It has been reported that the S589C mutation in the selectivity filter of alphaENaC renders the channel sensitive to block by externally applied Cd2+; this was interpreted as evidence for Cd2+ coordination with the thiol group of the side chain of alpha589C, pointing toward the pore lumen. Because the alphaS589C mutation alters the monovalent to divalent cation selectivity ratio of ENaC and because internally applied Cd2+ blocks wild-type ENaC with high affinity, we hypothesized that the inhibition of alphaS589C ENaC by Cd2+ results rather from the coordination of this cation with native cysteine residues located in the internal pore of ENaC. We show here that Cd2+ inhibits not only ENaC alphaS589C and alphaS589D but also alphaS589N mutants and that Ca2+ weakly interacts with the S589D mutant. The block of alphaS589C, -D, and -N mutants is characterized by a slow on-rate, is nearly irreversible, is voltage-dependent, and can be prevented by amiloride. The C546S mutation in the second transmembrane helix of gamma subunit in the background of the ENaC alphaS589C, -D, or -N mutants reduces the sensitivity to block by Cd2+ and renders the block rapidly reversible. We conclude therefore that the block by Cd2+ of the alphaS589C, -D, and -N mutants results from the trapping of Cd2+ ions in the internal pore of the channel and involves Cys-546 in the second transmembrane helix of the gammaENaC subunit.
Mots-clé
Amino Acid Sequence, Amino Acid Substitution, Animals, Cadmium/pharmacology, Epithelial Sodium Channel/antagonists & inhibitors, Epithelial Sodium Channel/chemistry, Molecular Sequence Data, Mutagenesis, Site-Directed, Oocytes, Protein Structure, Secondary, Sequence Alignment, Xenopus Proteins/antagonists & inhibitors, Xenopus Proteins/chemistry, Xenopus laevis
Pubmed
Web of science
Open Access
Oui
Création de la notice
24/01/2008 13:55
Dernière modification de la notice
20/08/2019 17:06
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