Identification of the Ca2+ Blocking Site of Acid-sensing Ion Channel (ASIC) 1: Implications for Channel Gating
Acid-sensing ion channels ASIC1a and ASIC1b are ligand-gated ion channels that are activated by H+ in the physiological range of pH. The apparent affinity for H+ of ASIC1a and 1b is modulated by extracellular Ca2+ through a competition between Ca2+ and H+. Here we show that, in addition to modulatin...
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The Rockefeller University Press
2004
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| Online Access: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2233906/ |
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pubmed-22339062008-03-21 Identification of the Ca2+ Blocking Site of Acid-sensing Ion Channel (ASIC) 1: Implications for Channel Gating Paukert, Martin Babini, Elena Pusch, Michael Gründer, Stefan Article Acid-sensing ion channels ASIC1a and ASIC1b are ligand-gated ion channels that are activated by H+ in the physiological range of pH. The apparent affinity for H+ of ASIC1a and 1b is modulated by extracellular Ca2+ through a competition between Ca2+ and H+. Here we show that, in addition to modulating the apparent H+ affinity, Ca2+ blocks ASIC1a in the open state (IC50 ∼ 3.9 mM at pH 5.5), whereas ASIC1b is blocked with reduced affinity (IC50 > 10 mM at pH 4.7). Moreover, we report the identification of the site that mediates this open channel block by Ca2+. ASICs have two transmembrane domains. The second transmembrane domain M2 has been shown to form the ion pore of the related epithelial Na+ channel. Conserved topology and high homology in M2 suggests that M2 forms the ion pore also of ASICs. Combined substitution of an aspartate and a glutamate residue at the beginning of M2 completely abolished block by Ca2+ of ASIC1a, showing that these two amino acids (E425 and D432) are crucial for Ca2+ block. It has previously been suggested that relief of Ca2+ block opens ASIC3 channels. However, substitutions of E425 or D432 individually or in combination did not open channels constitutively and did not abolish gating by H+ and modulation of H+ affinity by Ca2+. These results show that channel block by Ca2+ and H+ gating are not intrinsically linked. The Rockefeller University Press 2004-10 /pmc/articles/PMC2233906/ /pubmed/15452199 http://dx.doi.org/10.1085/jgp.200308973 Text en Copyright © 2004, The Rockefeller University Press 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 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/). |
| repository_type |
Open Access Journal |
| institution_category |
Foreign Institution |
| institution |
US National Center for Biotechnology Information |
| building |
NCBI PubMed |
| collection |
Online Access |
| language |
English |
| format |
Online |
| author |
Paukert, Martin Babini, Elena Pusch, Michael Gründer, Stefan |
| spellingShingle |
Paukert, Martin Babini, Elena Pusch, Michael Gründer, Stefan Identification of the Ca2+ Blocking Site of Acid-sensing Ion Channel (ASIC) 1: Implications for Channel Gating |
| author_facet |
Paukert, Martin Babini, Elena Pusch, Michael Gründer, Stefan |
| author_sort |
Paukert, Martin |
| title |
Identification of the Ca2+ Blocking Site of Acid-sensing Ion Channel (ASIC) 1: Implications for Channel Gating |
| title_short |
Identification of the Ca2+ Blocking Site of Acid-sensing Ion Channel (ASIC) 1: Implications for Channel Gating |
| title_full |
Identification of the Ca2+ Blocking Site of Acid-sensing Ion Channel (ASIC) 1: Implications for Channel Gating |
| title_fullStr |
Identification of the Ca2+ Blocking Site of Acid-sensing Ion Channel (ASIC) 1: Implications for Channel Gating |
| title_full_unstemmed |
Identification of the Ca2+ Blocking Site of Acid-sensing Ion Channel (ASIC) 1: Implications for Channel Gating |
| title_sort |
identification of the ca2+ blocking site of acid-sensing ion channel (asic) 1: implications for channel gating |
| description |
Acid-sensing ion channels ASIC1a and ASIC1b are ligand-gated ion channels that are activated by H+ in the physiological range of pH. The apparent affinity for H+ of ASIC1a and 1b is modulated by extracellular Ca2+ through a competition between Ca2+ and H+. Here we show that, in addition to modulating the apparent H+ affinity, Ca2+ blocks ASIC1a in the open state (IC50 ∼ 3.9 mM at pH 5.5), whereas ASIC1b is blocked with reduced affinity (IC50 > 10 mM at pH 4.7). Moreover, we report the identification of the site that mediates this open channel block by Ca2+. ASICs have two transmembrane domains. The second transmembrane domain M2 has been shown to form the ion pore of the related epithelial Na+ channel. Conserved topology and high homology in M2 suggests that M2 forms the ion pore also of ASICs. Combined substitution of an aspartate and a glutamate residue at the beginning of M2 completely abolished block by Ca2+ of ASIC1a, showing that these two amino acids (E425 and D432) are crucial for Ca2+ block. It has previously been suggested that relief of Ca2+ block opens ASIC3 channels. However, substitutions of E425 or D432 individually or in combination did not open channels constitutively and did not abolish gating by H+ and modulation of H+ affinity by Ca2+. These results show that channel block by Ca2+ and H+ gating are not intrinsically linked. |
| publisher |
The Rockefeller University Press |
| publishDate |
2004 |
| url |
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2233906/ |
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1611438380544950272 |