The effect of stretch on the cation permeability properties of ENaC in planar lipid bilayers

I. I. Ismailov, B. K. Berdiev, D. I. Benos

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A low conductance, amiloride-sensitive Na+ channel has been cloned from rat distal colon by Canessa al. (Nature (1994) 367:463-467). This channel, termed rENaC, consists of three homologous subunits, a, , and y, and forms single Naselective channels when incorporated into planar lipid bilayers. rENaC can be activated following imposition of a hydrostatic pressure gradient (AP) across the bilayer membrane. When AP = 0, the relative cation permeability sequence (determined from reversal potential measurements made under biionic conditions) of rENaC was: PL|(1.72) > PN>(1.00) > PK(0.11) > > PRb (0.01) - PC, (<0.01). Moreover, rENaC was inhibited by either Ca!(K/ = 74 ±12 M) or Mg2 (K,1 = 6.5 ±0.8 mM). When AP = 0.26 mm, single channel open probability increased from 0.15 ±0.03 to 0.65 ± 0.04, and rENaC lost its ability to discriminate between monovalent and divalent cations. Its relative permeability sequence under maximally stretched conditions was: PLi (1.12) > PN, (1.00) > PK (0.71) PMg (0.62) > Pc, (0.54) > PRb (0.32) > PC, (0.15) PS, (0.01) = PB, (<O.OI). Buffering the bilayer bathing solution with 10 mM EGTA (i.e., [Ca2]frtt < 1 nM) resulted in activation of a, , >-rENaC (P0 = 0.65 ±0.06) when AP = 0. Imposition of a hydrostatic pressure gradient under Ca2+-free conditions did not further activate these channels. These results suggest that activation rENaC produced by membrane stretch may be due to release of divalent cation block.

Original languageEnglish
Pages (from-to)A77
JournalFASEB Journal
Issue number3
Publication statusPublished - Dec 1 1996

ASJC Scopus subject areas

  • Biotechnology
  • Biochemistry
  • Molecular Biology
  • Genetics

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