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Batrachotoxin acts as a stent to hold open homotetrameric prokaryotic voltage-gated sodium channels
Batrachotoxin (BTX), an alkaloid from skin secretions of dendrobatid frogs, causes paralysis and death by facilitating activation and inhibiting deactivation of eukaryotic voltage-gated sodium (Nav) channels, which underlie action potentials in nerve, muscle, and heart. A full understanding of the m...
Autores principales: | , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Rockefeller University Press
2019
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6363421/ https://www.ncbi.nlm.nih.gov/pubmed/30587506 http://dx.doi.org/10.1085/jgp.201812278 |
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author | Finol-Urdaneta, Rocio K. McArthur, Jeffrey R. Goldschen-Ohm, Marcel P. Gaudet, Rachelle Tikhonov, Denis B. Zhorov, Boris S. French, Robert J. |
author_facet | Finol-Urdaneta, Rocio K. McArthur, Jeffrey R. Goldschen-Ohm, Marcel P. Gaudet, Rachelle Tikhonov, Denis B. Zhorov, Boris S. French, Robert J. |
author_sort | Finol-Urdaneta, Rocio K. |
collection | PubMed |
description | Batrachotoxin (BTX), an alkaloid from skin secretions of dendrobatid frogs, causes paralysis and death by facilitating activation and inhibiting deactivation of eukaryotic voltage-gated sodium (Nav) channels, which underlie action potentials in nerve, muscle, and heart. A full understanding of the mechanism by which BTX modifies eukaryotic Nav gating awaits determination of high-resolution structures of functional toxin–channel complexes. Here, we investigate the action of BTX on the homotetrameric prokaryotic Nav channels NaChBac and NavSp1. By combining mutational analysis and whole-cell patch clamp with molecular and kinetic modeling, we show that BTX hinders deactivation and facilitates activation in a use-dependent fashion. Our molecular model shows the horseshoe-shaped BTX molecule bound within the open pore, forming hydrophobic H-bonds and cation-π contacts with the pore-lining helices, leaving space for partially dehydrated sodium ions to permeate through the hydrophilic inner surface of the horseshoe. We infer that bulky BTX, bound at the level of the gating-hinge residues, prevents the S6 rearrangements that are necessary for closure of the activation gate. Our results reveal general similarities to, and differences from, BTX actions on eukaryotic Nav channels, whose major subunit is a single polypeptide formed by four concatenated, homologous, nonidentical domains that form a pseudosymmetric pore. Our determination of the mechanism by which BTX activates homotetrameric voltage-gated channels reveals further similarities between eukaryotic and prokaryotic Nav channels and emphasizes the tractability of bacterial Nav channels as models of voltage-dependent ion channel gating. The results contribute toward a deeper, atomic-level understanding of use-dependent natural and synthetic Nav channel agonists and antagonists, despite their overlapping binding motifs on the channel proteins. |
format | Online Article Text |
id | pubmed-6363421 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2019 |
publisher | Rockefeller University Press |
record_format | MEDLINE/PubMed |
spelling | pubmed-63634212019-02-06 Batrachotoxin acts as a stent to hold open homotetrameric prokaryotic voltage-gated sodium channels Finol-Urdaneta, Rocio K. McArthur, Jeffrey R. Goldschen-Ohm, Marcel P. Gaudet, Rachelle Tikhonov, Denis B. Zhorov, Boris S. French, Robert J. J Gen Physiol Research Articles Batrachotoxin (BTX), an alkaloid from skin secretions of dendrobatid frogs, causes paralysis and death by facilitating activation and inhibiting deactivation of eukaryotic voltage-gated sodium (Nav) channels, which underlie action potentials in nerve, muscle, and heart. A full understanding of the mechanism by which BTX modifies eukaryotic Nav gating awaits determination of high-resolution structures of functional toxin–channel complexes. Here, we investigate the action of BTX on the homotetrameric prokaryotic Nav channels NaChBac and NavSp1. By combining mutational analysis and whole-cell patch clamp with molecular and kinetic modeling, we show that BTX hinders deactivation and facilitates activation in a use-dependent fashion. Our molecular model shows the horseshoe-shaped BTX molecule bound within the open pore, forming hydrophobic H-bonds and cation-π contacts with the pore-lining helices, leaving space for partially dehydrated sodium ions to permeate through the hydrophilic inner surface of the horseshoe. We infer that bulky BTX, bound at the level of the gating-hinge residues, prevents the S6 rearrangements that are necessary for closure of the activation gate. Our results reveal general similarities to, and differences from, BTX actions on eukaryotic Nav channels, whose major subunit is a single polypeptide formed by four concatenated, homologous, nonidentical domains that form a pseudosymmetric pore. Our determination of the mechanism by which BTX activates homotetrameric voltage-gated channels reveals further similarities between eukaryotic and prokaryotic Nav channels and emphasizes the tractability of bacterial Nav channels as models of voltage-dependent ion channel gating. The results contribute toward a deeper, atomic-level understanding of use-dependent natural and synthetic Nav channel agonists and antagonists, despite their overlapping binding motifs on the channel proteins. Rockefeller University Press 2019-02-04 /pmc/articles/PMC6363421/ /pubmed/30587506 http://dx.doi.org/10.1085/jgp.201812278 Text en © 2019 Finol-Urdaneta et al. https://creativecommons.org/licenses/by/4.0/This article is available under a Creative Commons License (Attribution 4.0 International, as described at https://creativecommons.org/licenses/by/4.0/). |
spellingShingle | Research Articles Finol-Urdaneta, Rocio K. McArthur, Jeffrey R. Goldschen-Ohm, Marcel P. Gaudet, Rachelle Tikhonov, Denis B. Zhorov, Boris S. French, Robert J. Batrachotoxin acts as a stent to hold open homotetrameric prokaryotic voltage-gated sodium channels |
title | Batrachotoxin acts as a stent to hold open homotetrameric prokaryotic voltage-gated sodium channels |
title_full | Batrachotoxin acts as a stent to hold open homotetrameric prokaryotic voltage-gated sodium channels |
title_fullStr | Batrachotoxin acts as a stent to hold open homotetrameric prokaryotic voltage-gated sodium channels |
title_full_unstemmed | Batrachotoxin acts as a stent to hold open homotetrameric prokaryotic voltage-gated sodium channels |
title_short | Batrachotoxin acts as a stent to hold open homotetrameric prokaryotic voltage-gated sodium channels |
title_sort | batrachotoxin acts as a stent to hold open homotetrameric prokaryotic voltage-gated sodium channels |
topic | Research Articles |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6363421/ https://www.ncbi.nlm.nih.gov/pubmed/30587506 http://dx.doi.org/10.1085/jgp.201812278 |
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