Identification of the Ca2+ blocking site of acid-sensing ion channel (ASIC) 1: implications for channel gating.
Identification of the Ca2+ blocking site of acid-sensing ion channel (ASIC) 1: implications for channel gating.
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DOI：
10.1085/jgp.200308973
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发表时间：
2004-10
期刊：
影响因子：
--
通讯作者：
Gründer S
中科院分区：
文献类型：
--
作者：
Paukert M;Babini E;Pusch M;Gründer S
酸敏感离子通道ASIC1a和ASIC1b是配体门控离子通道，在生理ph范围内被H+激活。ASIC1a和1b对H+的表观亲和力是由细胞外Ca2+通过Ca2+和H+之间的竞争来调节的。在这里，我们表明，除了调节表观H+亲和力外，Ca2+在开放状态下阻断ASIC1a（在pH 5.5下IC50 ~ 3.9 mM），而ASIC1b以降低的亲和力被阻断（在pH 4.7下IC50 ~ 10 mM）。此外，我们报告了Ca2+介导这种开放通道阻滞的位点的鉴定。asic有两个跨膜结构域。第二跨膜结构域M2已被证明形成相关上皮Na+通道的离子孔。M2的保守拓扑结构和高度同源性表明，M2也形成了asic的离子孔。M2开头的一个天冬氨酸和一个谷氨酸残基的联合取代完全消除了Ca2+对ASIC1a的阻断，表明这两个氨基酸（E425和D432）对Ca2+阻断至关重要。先前有研究表明，Ca2+阻滞的缓解打开了ASIC3通道。然而，E425或D432单独或组合的取代都不会构成性地打开通道，也不会消除H+的门控和Ca2+对H+亲和力的调节。这些结果表明，Ca2+和H+门控的通道阻塞并不是内在联系的。
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.
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DOI：
10.1085/jgp.114.1.13
发表时间：
1999-07
期刊：
The Journal of general physiology
影响因子：
--
作者：
Kellenberger S;Hoffmann-Pochon N;Gautschi I;Schneeberger E;Schild L
通讯作者：
Schild L
DOI：
10.1085/jgp.112.4.423
发表时间：
1998-10
期刊：
The Journal of general physiology
影响因子：
--
作者：
Fyfe GK;Canessa CM
通讯作者：
Canessa CM
影响因子：
4.8
作者：
Babini, E;Paukert, M;Gründer, S
通讯作者：
Gründer, S
DOI：
10.1073/pnas.79.10.3188
发表时间：
1982-01-01
期刊：
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA-BIOLOGICAL SCIENCES
影响因子：
--
作者：
BAUD, C;KADO, RT;MARCHER, K
通讯作者：
MARCHER, K
影响因子：
2.9
作者：
de Weille, J;Bassilana, F
通讯作者：
Bassilana, F