Regulation by Na+ and Ca2+ of renal epithelial Na+ channels reconstituted into planar lipid bilayers

Iskander I. Ismailov, Bakhram K. Berdiev, Dale J. Benos

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

Purified bovine renal epithelial Na+ channels when reconstituted into planar lipid bilayers displayed a specific orientation when the membrane was clamped to -40 mV (cis-side) during incorporation. The trons-facing portion of the channel was extracellular (i.e., amiloride-sensitive), whereas the cis-facing side was intracellular (i.e., protein kinase A-sensitive). Single channels had a main state unitary conductance of 40 pS and displayed two subconductive states each of 12-13 pS, or one of 12-13 pS and the second of 24-26 pS. Elevation of the [Na+] gradient from the trans-side increased single-channel open probability (Po) only when the cis-side was bathed with a solution containing low [Na+] (2+]. Under these conditions, Po saturated with increasing [Na+] trans. Buffering of the cis compartment [Ca2+] to nearly zero (o = 0.12 ± 0.02 vs 0.02 ± 0.01 in control), but markedly reduced the influence of both cis- and trans- [Na+] on Po. Elevating [Ca2+] cis at constant [Na+] resulted in inhibition of channel activity with an apparent [Ki Ca2+] of 10-100 μM. Protein kinase C-induced phosphorylation shifted the dependence of channel Po on [Ca2+]cis to 1-3 μM at stationary [Na+]. The direct modulation of single-channel Po by Na+ and Ca2+ demonstrates that the gating of amiloride-sensitive Na+ channels is indeed dependent upon the specific ionic environment surrounding the channels.

Original languageEnglish
Pages (from-to)445-466
Number of pages22
JournalJournal of General Physiology
Volume106
Issue number3
Publication statusPublished - Sep 1995
Externally publishedYes

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Epithelial Sodium Channels
Lipid Bilayers
Kidney
Amiloride
Cyclic AMP-Dependent Protein Kinases
Protein Kinase C
Phosphorylation
Membranes

ASJC Scopus subject areas

  • Physiology

Cite this

Regulation by Na+ and Ca2+ of renal epithelial Na+ channels reconstituted into planar lipid bilayers. / Ismailov, Iskander I.; Berdiev, Bakhram K.; Benos, Dale J.

In: Journal of General Physiology, Vol. 106, No. 3, 09.1995, p. 445-466.

Research output: Contribution to journalArticle

Ismailov, Iskander I. ; Berdiev, Bakhram K. ; Benos, Dale J. / Regulation by Na+ and Ca2+ of renal epithelial Na+ channels reconstituted into planar lipid bilayers. In: Journal of General Physiology. 1995 ; Vol. 106, No. 3. pp. 445-466.
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