The isoforms generated by alternative translation initiation adopt similar conformation in the selectivity filter in TREK-2
The isoforms generated by alternative translation initiation adopt similar conformation in the selectivity filter in TREK-2
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DOI：
10.1007/s13105-015-0422-z
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发表时间：
2015-08
影响因子：
3.4
通讯作者：
Rengong Zhuo;Peng Peng-Peng;Xiao-Yan Liu;Shu-zhuo Zhang;Jiang-Ping Xu;Jian-quan Zheng;Xiao-Li Wei;Xiaoyan Ma
中科院分区：
文献类型：
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作者：
Rengong Zhuo;Peng Peng-Peng;Xiao-Yan Liu;Shu-zhuo Zhang;Jiang-Ping Xu;Jian-quan Zheng;Xiao-Li Wei;Xiaoyan Ma
TREK-2（TWIK-related K+channel-2）是双孔结构域钾通道家族的一员，通过传导漏电流或背景电流调节细胞的兴奋性。在TREK-2中，通过交替翻译起始（ATI）机制产生的异构体在单位电导方面表现出很大的差异，但对K+的选择性相似。到目前为止，这种离子选择性相似性的结构基础是未知的。在这里，我们报告说，外部施加的Ba 2+抑制TREK-2的电流在浓度和时间依赖性的方式。细胞外K+浓度的升高或S4 K+结合位点的突变可使这种阻断作用减弱，提示Ba 2+的抑制机制是由于其在选择性过滤器（SF）内的竞争性对接特性。接下来，我们证明了所有的ATI亚型表现出类似的行为后，应用的Ba 2+和细胞外pH值（pH值）的变化，这对SF的外部位置的行为。这些结果有力地支持了TREK-2的所有ATI异构体在S4位点和由pHo定义的位置具有相似的SF构象的观点，这暗示N-末端（Nt）的作用和单位电导与SF构象无关。本研究结果有助于深入了解TREK-2和K2 P通道的门控机制。
TREK-2 (TWIK-related K+channel-2), a member of two-pore domain potassium (K2P) channel family, tunes cellular excitability via conducting leak or background currents. In TREK-2, the isoforms generated by alternative translation initiation (ATI) mechanism exhibit large divergence in unitary conductance, but similar in selectivity to K+. Up to now, the structural basis for this similarity in ion selectivity is unknown. Here, we report that externally applied Ba2+inhibits the currents of TREK-2 in a concentration- and time-dependent manner. The blocking effect is blunted by elevated extracellular K+or mutation of S4 K+binding site, which suggests that the inhibitory mechanism of Ba2+is due to its competitive docking properties within the selectivity filter (SF). Next, we demonstrate that all the ATI isoforms exhibit analogous behaviors upon the application of Ba2+and alteration of extracellular pH (pHo), which acts on the outer position of the SF. These results strongly support the notion that all the ATI isoforms of TREK-2 possess resembled SF conformation in S4 site and the position defined by pHo, which implicates that neither the role of N-terminus (Nt) nor the unitary conductance is associated with SF conformation. Our findings might help to understand the detail gating mechanism of TREK-2 and K2P channels.