Allosteric pathways of pH-sensitivity in a proton activated chloride channel
Allosteric pathways of pH-sensitivity in a proton activated chloride channel
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质子激活氯通道中 pH 敏感性的变构途径
DOI：
10.1016/j.bpj.2021.11.505
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发表时间：
2022
影响因子：
3.4
通讯作者：
Weinstein, Harel
中科院分区：
文献类型：
--
作者：
Kots, Ekaterina D.;Osei-Owusu, James;Qiu, Zhaozhu;Weinstein, Harel
质子激活的氯离子通道（TMEM 206）在低pH值的哺乳动物细胞中对质子激活的氯离子电流是必不可少的。它在酸诱导的细胞死亡和内体酸化中起重要作用。从Cryo-EM结构数据发现，从中性pH下的非活性PAC通道到酸性pH下的氯离子传导状态的构象转变影响PAC三聚体的几个区域。最显著的构象重排涉及TM 1，其在pH 4.5下从平行构象转变为交叉构象。为了探索pH依赖的激活机制，我们进行了扩展的全原子分子动力学（MD）模拟的PAC通道在酸性和中性构象，并确定了pH敏感的变构途径之间的功能重要区域的PAC从N体信息理论（NbIT）分析的轨迹。这些揭示了在WT PAC的pH 4状态下，“指”结构域中的可滴定残基与TM 1之间的变构信号的传播。这种长距离信号从“指”结构域通过“指”-“β球”结构域接头，并通过α-A和α-B螺旋区进行，以通过“掌”结构域连接到H98和酸性口袋。值得注意的是，这种变构途径在pH 8的WT PAC中不形成。位于变构途径上的残基响应于pH增加而改变其构象和相互作用伴侣，被鉴定为变构信号传导的开关。WT和具有“指”结构域的突变残基的PAC构建体的NbIT结果的比较揭示，在后者中，变构途径比WT PAC更能适应pH的变化，这与在较高pH下测量的通道活性完全一致。
The proton-activated chloride (PAC) channel (TMEM206) was shown to be essential for proton-activated chloride currents in mammalian cells at low pHs. It plays an important role in acid-induced cell death and endosomal acidification. The conformational transition from the inactive PAC channel at neutral pH to a chloride conducting state at acidic pH was found from Cryo-EM structural data to affect several regions of the PAC trimer. The most significant conformational rearrangement involves TM1 which transitions from a parallel to a crossed conformation at pH 4.5. To explore the pH-dependent mechanism of activation we carried out extended all-atom molecular dynamics (MD) simulations of the PAC channels in both acidic and neutral conformations, and identified the pH-sensitive allosteric pathways between functionally important regions of PAC from N-body Information Theory (NbIT) analysis of the trajectories. These revealed the propagation of the allosteric signal between the titratable residues in the “finger” domains and TM1 in the pH 4 state of WT PAC. This long-distance signal passes from the “finger” domain through the “finger”-“beta-ball” domain linkers, and proceeds through the alpha-A and alpha-B helical regions to connect through the “palm” domain to H98 and the acidic pocket. Remarkably, this allosteric pathway is not formed in WT PAC at pH 8. Residues located on the allosteric pathway that change their conformation and interaction partners in response to the pH increase were identified as switches of allosteric signaling. Comparisons of NbIT results for the WT and the PAC constructs with mutated residues of the “finger” domain revealed that in the latter, the allosteric pathway is more resilient to change with pH than the WT PAC, fully consistent with the measured channel activity at higher pH.