A cloned renal epithelial Na+ channel protein displays stretch activation in planar lipid bilayers

M. S. Awayda, I. I. Ismailov, B. K. Berdiev, D. J. Benos

Research output: Contribution to journalArticlepeer-review

107 Citations (Scopus)

Abstract

We have previously cloned a bovine renal epithelial channel homologue (α- bENaC) belonging to the epithelial Na+ channel (ENaC) family. With the use of a rabbit nuclease-treated in vitro translation system, mRNA coding for α- bENaC was translated and the polypeptide products were reconstituted into liposomes. On incorporation into planar lipid bilayers, in vitro-translated α-bENaC protein 1) displayed voltage-independent Na+ channel activity with a single-channel conductance of 40 pS, 2) was mechanosensitive in that the single-channel open probability was maximally activated with a hydrostatic pressure gradient of 0.26 mmHg across the bilayer, 3) was blocked by low concentrations of amiloride [apparent inhibitory constant of amiloride (K(amil)) ≃ 150 nM], and 4) was cation selective with a Li+:Na+:K+ permselectivity of 2:1:0.14 under nonstretched conditions. These pharmacological and selectivity characteristics were altered to a lower amiloride affinity (K(amil) > 25 μM) and a lack of monovalent cation selectivity in the presence of a hydrostatic pressure gradient. This observation of stretch activation (SA) of α-bENaC was confirmed in dual electrode recordings of heterologously expressed α-bENaC whole cell currents in Xenopus oocytes swelled by the injection of 15 nl of a 100 mM KCl solution. We conclude that α-bENaC, and by analogy other ENaCs, represent a novel family of cloned SA channels.

Original languageEnglish
Pages (from-to)C1450-C1459
JournalAmerican Journal of Physiology - Cell Physiology
Volume268
Issue number6 37-6
DOIs
Publication statusPublished - 1995

Keywords

  • Xenopus
  • amiloride
  • bovine
  • kidney
  • mechanosensitivity
  • sodium ion

ASJC Scopus subject areas

  • Physiology
  • Cell Biology

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