Biochemical status of renal epithelial Na+ channels determines apparent channel conductance, ion selectivity, and amiloride sensitivity

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

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Abstract

Purified bovine renal papillary Na+ channels, when reconstituted into planar lipid bilayers, reside in three conductance states: a 40-pS main state, and two subconductive states (12-13 pS and 24-26 pS). The activity of these channels is regulated by phosphorylation and by G-proteins. Protein kinase A (PKA)-induced phosphorylation increased channel activity by increasing the open state time constants from 160 ± 30 (main conductance), and 15 ± 5 ms (both lower conductances), respectively, to 365 ± 30 ms for all of them, PKA phosphorylation also altered the closed time of the channel from 250 ± 30 ms to 200 ± 35 ms, thus shifting the channel into a lower- conductance, long open time mode. PKA phosphorylation increased the P(Na):P(K) of the channel from 7:1 to 20:1, and shifted the amiloride inhibition curve to the right (apparent K(i)/(amil) from 0.7 to 20 μM). Pertussis toxin-induced ADP-ribosylation of either phosphorylated or nonphosphorylated channels decreased the P(Na):P(K) to 2:1 and 4:1, respectively, and altered K(i)/(amil) to 8 and 2 μM for phosphorylated and nonphosphorylated channels, respectively. GTP-γ-S treatment of either phosphorylated or nonphosphorylated channels resulted in an increase of P(Na):P(K) to 30:1 and 10:1, respectively, and produced a leftward shift in the amiloride dose-response curve, altering K(i)/(amil) to 0.5 and 0.1 μM, respectively. These results suggest that amiloride-sensitive renal Na+ channel biophysical characteristics are not static, but depend upon the biochemical state of the channel protein and/or its associated G-protein.

Original languageEnglish
Pages (from-to)1789-1800
Number of pages12
JournalBiophysical Journal
Volume69
Issue number5
Publication statusPublished - 1995
Externally publishedYes

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Epithelial Sodium Channels
Amiloride
Ion Channels
Cyclic AMP-Dependent Protein Kinases
Phosphorylation
Kidney
GTP-Binding Proteins
Pertussis Toxin
Lipid Bilayers
Guanosine Triphosphate
Adenosine Diphosphate
Proteins

ASJC Scopus subject areas

  • Biophysics

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Biochemical status of renal epithelial Na+ channels determines apparent channel conductance, ion selectivity, and amiloride sensitivity. / Ismailov, I. I.; Berdiev, B. K.; Benos, D. J.

In: Biophysical Journal, Vol. 69, No. 5, 1995, p. 1789-1800.

Research output: Contribution to journalArticle

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