Effects of ionic strength on gating and permeation of TREK-2 K2P channels.
Effects of ionic strength on gating and permeation of TREK-2 K2P channels.
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DOI：
10.1371/journal.pone.0258275
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发表时间：
2021
期刊：
影响因子：
3.7
通讯作者：
Tucker SJ
中科院分区：
文献类型：
--
作者：
Conrad LJ;Proks P;Tucker SJ
除了由离子通道的电压敏感域（VSD）介导的经典电压依赖性行为之外，越来越多的电压依赖性门控行为被描述在缺乏典型VSD的通道中。它们的作用机制中的一个共同点是渗透离子对这种电压感测过程的贡献。多模态K2 P K+通道TREK 2通过由K+与其选择性过滤器的相互作用介导的门控过程响应膜电压。最近，我们发现这种作用可以通过小分子激动剂（例如BL 1249）来调节，所述小分子激动剂似乎对内腔内的K+结合具有静电影响，并产生TREK-2通道的单通道电导的增加。在这里，我们直接探测这种K+依赖性门控过程中记录宏观和单通道电流的TREK-2在高浓度的内部K+的存在下。令人惊讶的是，我们发现TREK-2被高内部K+浓度抑制，这是由伴随的离子强度增加介导的。然而，我们仍然能够确定，在高离子强度下，BL 1249存在下单通道电导的增加被钝化，而其激活作用（对通道开放概率）持续存在。这些效应与带负电荷的活化剂如BL 1249对渗透的静电作用机制一致，但也表明它们对通道门控的影响是复杂的。
In addition to the classical voltage-dependent behavior mediated by the voltage-sensing-domains (VSD) of ion channels, a growing number of voltage-dependent gating behaviors are being described in channels that lack canonical VSDs. A common thread in their mechanism of action is the contribution of the permeating ion to this voltage sensing process. The polymodal K2P K+ channel, TREK2 responds to membrane voltage through a gating process mediated by the interaction of K+ with its selectivity filter. Recently, we found that this action can be modulated by small molecule agonists (e.g. BL1249) which appear to have an electrostatic influence on K+ binding within the inner cavity and produce an increase in the single-channel conductance of TREK-2 channels. Here, we directly probed this K+-dependent gating process by recording both macroscopic and single-channel currents of TREK-2 in the presence of high concentrations of internal K+. Surprisingly we found TREK-2 is inhibited by high internal K+ concentrations and that this is mediated by the concomitant increase in ionic-strength. However, we were still able to determine that the increase in single channel conductance in the presence of BL1249 was blunted in high ionic-strength, whilst its activatory effect (on channel open probability) persisted. These effects are consistent with an electrostatic mechanism of action of negatively charged activators such as BL1249 on permeation, but also suggest that their influence on channel gating is complex.