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The epithelial Na+ Channel (ENaC) mediates Na+ reabsorption in a variety of epithelial tissues. ENaC is composed of three homologous subunits, termed alpha, beta, and gamma. All three subunits participate in channel formation as the absence of any one subunit results in a significant reduction or complete abrogation of Na+ current expression in Xenopus(More)
Epithelial sodium channels (ENaC) have a crucial role in the regulation of extracellular fluid volume and blood pressure. To study the structure of the pore region of ENaC, the susceptibility of introduced cysteine residues to sulfhydryl-reactive methanethiosulfonate derivatives ((2-aminoethyl)methanethiosulfonate hydrobromide (MTSEA) and(More)
The epithelial sodium channel (ENaC) is composed of three homologous subunits termed alpha, beta, and gamma. Previous studies suggest that selected residues within a hydrophobic region immediately preceding the second membrane-spanning domain of each subunit contribute to the conducting pore of ENaC. We probed the pore of mouse ENaC by systematically(More)
Epithelial sodium channels (ENaC) are regulated by various intracellular and extracellular factors including divalent cations. We studied the inhibitory effect and mechanism of external Ni(2+) on cloned mouse alpha-beta-gamma ENaC expressed in Xenopus oocytes. Ni(2+) reduced amiloride-sensitive Na(+) currents of the wild type mouse ENaC in a dose-dependent(More)
The degenerin/epithelial Na+ channel (ENaC) superfamily is a group of structurally related ion channels that are involved in diverse biological processes, including responses to mechanical stimuli. In renal cortical collecting ducts, changes in rates of perfusion affect Na+ reabsorption through an amiloride-sensitive pathway, suggesting that ENaC may be a(More)
Epithelial Na(+) channels (ENaCs) selectively conduct Na(+) and Li(+) but exclude K(+). A three-residue tract ((G/S)XS) present within all three subunits has been identified as a key structure forming a putative selectivity filter. We investigated the side chain orientation of residues within this tract by analyzing accessibility of the introduced(More)
Epithelial Na+ channels (ENaC) are inhibited by extracellular Na+, a process referred to as Na+ self-inhibition. We previously demonstrated that mutation of key residues within two furin cleavage consensus sites in alpha, or one site in gamma, blocked subunit proteolysis and inhibited channel activity when mutant channels were expressed in Xenopus laevis(More)
Amiloride is a prototypic inhibitor of epithelial sodium channels. Rapid progress has been made in our understanding of the structure of the sodium channel and related cation-selective channels. This work, coupled with experiments examining how selected sodium channel mutations affect amiloride binding, provides critical clues towards defining sites within(More)
Epithelial sodium channels (ENaC) are composed of three structurally related subunits (alpha, beta, and gamma). Each subunit has two transmembrane domains termed M1 and M2, and residues conferring cation selectivity have been shown to reside in a pore region immediately preceding the M2 domains of the three subunits. Negatively charged residues are(More)
The epithelial Na ؉ channel (ENaC) is typically formed by three homologous subunits (␣, ␤, and ␥) that possess a characteristic large extracellular loop (ECL) containing 16 conserved cysteine (Cys) residues. We investigated the functional role of these Cys residues in Na ؉ self-inhibition, an allosteric inhibition of ENaC activity by extracellular Na ؉. All(More)