pH Alterations "Reset" Ca2+ Sensitivity of Brain Na+ Channel 2, a Degenerin/Epithelial Na+ Ion Channel, in Planar Lipid Bilayers

Bakhrom K. Berdiev, Timothy B. Mapstone, James M. Markert, G. Yancey Gillespie, Jason Lockhart, Catherine M. Fuller, Dale J. Benos

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Abstract

Members of the degenerin/epithelial Na+ channel superfamily of ion channels subserve many functions, ranging from whole body sodium handling to mechanoelectrical transduction. We studied brain Na+ channel 2 (BNaC-2) in planar lipid bilayers to examine its single channel properties and regulation by Ca2+. Upon incorporation of vesicles made from membranes of oocytes expressing either wild-type (WT) BNaC-2 or BNaC-2 with a gain-of-function (GF) point mutation (G433F), functional channels with different properties were obtained. WT BNaC-2 resided in a closed state with short openings, whereas GF BNaC-2 was constitutively activated; a decrease in the pH in the trans compartment of the bilayer activated WT BNaC-2 and decreased its permeability for Na+ over K+. Moreover, these maneuvers made the WT channel more resistant to amiloride. In contrast, GF BNaC-2 did not respond to a decrease in pH, and its amiloride sensitivity and selectivity for Na+ over K+ were unaffected by this pH change. Buffering the bathing solutions with EGTA to reduce the free [Ca 2+] to <10 nM increased WT single channel open probability 10-fold, but not that of GF BNaC-2. Ca2+ blocked both WT and GF BNaC-2 in a dose- and voltage-dependent fashion; single channel conductances were unchanged. A drop in pH reduced the ability of Ca2+ to inhibit these channels. These results show that BNaC-2 is an amiloride-sensitive sodium channel and suggest that pH activation of these channels could be, in part, a consequence of H+ "interference" with channel regulation by Ca2+.

Original languageEnglish
Pages (from-to)38755-38761
Number of pages7
JournalJournal of Biological Chemistry
Volume276
Issue number42
DOIs
Publication statusPublished - Oct 19 2001

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ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

Berdiev, B. K., Mapstone, T. B., Markert, J. M., Gillespie, G. Y., Lockhart, J., Fuller, C. M., & Benos, D. J. (2001). pH Alterations "Reset" Ca2+ Sensitivity of Brain Na+ Channel 2, a Degenerin/Epithelial Na+ Ion Channel, in Planar Lipid Bilayers. Journal of Biological Chemistry, 276(42), 38755-38761. https://doi.org/10.1074/jbc.M107266200