Cargando…
Ca(2+) block and flickering both contribute to the negative slope of the IV curve in BK channels
Single-channel current–voltage (IV) curves of human large-conductance, voltage- and Ca(2+)-activated K(+) (BK) channels are quite linear in 150 mM KCl. In the presence of Ca(2+) and/or Mg(2+), they show a negative slope conductance at high positive potentials. This is generally explained by a Ca(2+)...
Autores principales: | , , |
---|---|
Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
The Rockefeller University Press
2013
|
Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3607826/ https://www.ncbi.nlm.nih.gov/pubmed/23530139 http://dx.doi.org/10.1085/jgp.201210956 |
_version_ | 1782264148087799808 |
---|---|
author | Schroeder, Indra Thiel, Gerhard Hansen, Ulf-Peter |
author_facet | Schroeder, Indra Thiel, Gerhard Hansen, Ulf-Peter |
author_sort | Schroeder, Indra |
collection | PubMed |
description | Single-channel current–voltage (IV) curves of human large-conductance, voltage- and Ca(2+)-activated K(+) (BK) channels are quite linear in 150 mM KCl. In the presence of Ca(2+) and/or Mg(2+), they show a negative slope conductance at high positive potentials. This is generally explained by a Ca(2+)/Mg(2+) block as by Geng et al. (2013. J. Gen. Physiol. http://dx.doi.org/10.1085/jgp.201210955) in this issue. Here, we basically support this finding but add a refinement: the analysis of the open-channel noise by means of β distributions reveals what would be found if measurements were done with an amplifier of sufficient temporal resolution (10 MHz), namely that the block by 2.5 mM Ca(2+) and 2.5 mM Mg(2+) per se would only cause a saturating curve up to +160 mV. Further bending down requires the involvement of a second process related to flickering in the microsecond range. This flickering is hardly affected by the presence or absence of Ca(2+)/Mg(2+). In contrast to the experiments reported here, previous experiments in BK channels (Schroeder and Hansen. 2007. J. Gen. Physiol. http://dx.doi.org/10.1085/jgp.200709802) showed saturating IV curves already in the absence of Ca(2+)/Mg(2+). The reason for this discrepancy could not be identified so far. However, the flickering component was very similar in the old and new experiments, regardless of the occurrence of noncanonical IV curves. |
format | Online Article Text |
id | pubmed-3607826 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2013 |
publisher | The Rockefeller University Press |
record_format | MEDLINE/PubMed |
spelling | pubmed-36078262013-10-01 Ca(2+) block and flickering both contribute to the negative slope of the IV curve in BK channels Schroeder, Indra Thiel, Gerhard Hansen, Ulf-Peter J Gen Physiol Communication Single-channel current–voltage (IV) curves of human large-conductance, voltage- and Ca(2+)-activated K(+) (BK) channels are quite linear in 150 mM KCl. In the presence of Ca(2+) and/or Mg(2+), they show a negative slope conductance at high positive potentials. This is generally explained by a Ca(2+)/Mg(2+) block as by Geng et al. (2013. J. Gen. Physiol. http://dx.doi.org/10.1085/jgp.201210955) in this issue. Here, we basically support this finding but add a refinement: the analysis of the open-channel noise by means of β distributions reveals what would be found if measurements were done with an amplifier of sufficient temporal resolution (10 MHz), namely that the block by 2.5 mM Ca(2+) and 2.5 mM Mg(2+) per se would only cause a saturating curve up to +160 mV. Further bending down requires the involvement of a second process related to flickering in the microsecond range. This flickering is hardly affected by the presence or absence of Ca(2+)/Mg(2+). In contrast to the experiments reported here, previous experiments in BK channels (Schroeder and Hansen. 2007. J. Gen. Physiol. http://dx.doi.org/10.1085/jgp.200709802) showed saturating IV curves already in the absence of Ca(2+)/Mg(2+). The reason for this discrepancy could not be identified so far. However, the flickering component was very similar in the old and new experiments, regardless of the occurrence of noncanonical IV curves. The Rockefeller University Press 2013-04 /pmc/articles/PMC3607826/ /pubmed/23530139 http://dx.doi.org/10.1085/jgp.201210956 Text en © 2013 Schroeder et al. This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 3.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/3.0/). |
spellingShingle | Communication Schroeder, Indra Thiel, Gerhard Hansen, Ulf-Peter Ca(2+) block and flickering both contribute to the negative slope of the IV curve in BK channels |
title | Ca(2+) block and flickering both contribute to the negative slope of the IV curve in BK channels |
title_full | Ca(2+) block and flickering both contribute to the negative slope of the IV curve in BK channels |
title_fullStr | Ca(2+) block and flickering both contribute to the negative slope of the IV curve in BK channels |
title_full_unstemmed | Ca(2+) block and flickering both contribute to the negative slope of the IV curve in BK channels |
title_short | Ca(2+) block and flickering both contribute to the negative slope of the IV curve in BK channels |
title_sort | ca(2+) block and flickering both contribute to the negative slope of the iv curve in bk channels |
topic | Communication |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3607826/ https://www.ncbi.nlm.nih.gov/pubmed/23530139 http://dx.doi.org/10.1085/jgp.201210956 |
work_keys_str_mv | AT schroederindra ca2blockandflickeringbothcontributetothenegativeslopeoftheivcurveinbkchannels AT thielgerhard ca2blockandflickeringbothcontributetothenegativeslopeoftheivcurveinbkchannels AT hansenulfpeter ca2blockandflickeringbothcontributetothenegativeslopeoftheivcurveinbkchannels |