Activation and inhibition of TMEM16A calcium-activated chloride channels.
Activation and inhibition of TMEM16A calcium-activated chloride channels.
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DOI：
10.1371/journal.pone.0086734
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发表时间：
2014
期刊：
影响因子：
3.7
通讯作者：
Chen TY
中科院分区：
文献类型：
--
作者：
Ni YL;Kuan AS;Chen TY
钙激活的氯离子通道（CaCC）是由功能未知的跨膜蛋白16（TMEM 16）家族成员编码的，近年来人们对其功能特性以及作为氯离子通道在各种组织中的生理作用进行了深入研究。研究这些通道的一个技术障碍是众所周知的通道中断，其经常损害通道的电生理测量的精度。使用采用快速溶液交换的实验方案，我们通过将Ca2+诱导的电流归一化为在通道下降可以忽略不计的时间段内获得的最大激活电流来规避通道下降的问题。我们表征了Ca2+、Sr2+和Ba2+对TMEM16A编码的CaCC（也称为ANO1）的激活，并发现Mg2+与Ca2+竞争结合到二价阳离子结合位点而不激活通道。我们还研究了各种阴离子的ANO1孔的渗透性，并发现，在孔中的阴离子占有率显示这些阴离子的渗透率比出现负相关的ANO1抑制尼氟酸（NFA）的表观亲和力。另一方面，NFA抑制既不受通道激活程度的影响，也不受用于通道激活的二价阳离子的类型的影响。这些结果表明，NFA对ANO1的抑制可能是通过改变孔功能而不是通过改变通道门控来介导的。我们的研究提供了一个精确的表征ANO1和文件的因素，可以影响二价阳离子激活和NFA抑制ANO1。
Calcium-activated chloride channels (CaCC) encoded by family members of transmembrane proteins of unknown function 16 (TMEM16) have recently been intensely studied for functional properties as well as their physiological roles as chloride channels in various tissues. One technical hurdle in studying these channels is the well-known channel rundown that frequently impairs the precision of electrophysiological measurements for the channels. Using experimental protocols that employ fast-solution exchange, we circumvented the problem of channel rundown by normalizing the Ca2+-induced current to the maximally-activated current obtained within a time period in which the channel rundown was negligible. We characterized the activation of the TMEM16A-encoded CaCC (also called ANO1) by Ca2+, Sr2+, and Ba2+, and discovered that Mg2+ competes with Ca2+ in binding to the divalent-cation binding site without activating the channel. We also studied the permeability of the ANO1 pore for various anions and found that the anion occupancy in the pore–as revealed by the permeability ratios of these anions–appeared to be inversely correlated with the apparent affinity of the ANO1 inhibition by niflumic acid (NFA). On the other hand, the NFA inhibition was neither affected by the degree of the channel activation nor influenced by the types of divalent cations used for the channel activation. These results suggest that the NFA inhibition of ANO1 is likely mediated by altering the pore function but not through changing the channel gating. Our study provides a precise characterization of ANO1 and documents factors that can affect divalent cation activation and NFA inhibition of ANO1.
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影响因子：
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