基于分子动力学模拟的TRPM8通道门控特性分析

TRPM8通道的温度感知等生理功能依赖于正常的门控, 但现有晶体结构中S6跨膜螺旋C末端形成的门控结构存在氨基酸缺失, 所以其门控特性未能揭晓. 本文基于已有的晶体结构和AlphaFold算法构建了 11个完整不同构象的TRPM8通道, 发现其S6跨膜螺旋C末端构成的门控存在回环和螺旋2种构象. 在回环构象中, 多个氨基酸参与形成阻碍离子通透的孔道区; 而在螺旋构象中, 仅有关键氨基酸V956发挥门控作用. 由于回环构象的柔性大于螺旋构象, 导致回环构象参与阻碍离子通透的关键氨基酸构象和数量变化多样. 二级结构预测与模建结果表明, S6跨膜螺旋C末端存在回环构象向螺旋构象的转变, 此过程中柔性的回环构象结构域向胞外侧上移, 关键氨基酸向孔道衬外扭转, 增强了与相邻跨膜螺旋S5的相互作用以及S5与TRP螺旋之间的相互作用, 进而形成刚性、 稳定且有序的螺旋构象. 这增加了TRPM8通道各结构域间的协同性, 使能量信息更高效地传递到门控结构域, 为TRPM8通道开启蓄势.

Analysis of Gating Characteristics of TRPM8 Channel Based on Molecular Dynamics

Physiological functions of TRPM8 channel， such as temperature sensing， depend on normal gating. Due to the lack and insufficient number of existing crystal structures， the gating characteristics of TRPM8 channels need to be further explored. Therefore， 11 TRPM8 channels with different conformations were constructed， basing on the existing crystal structure and AlphaFold algorithm. It was found that there were two different architectural in the S6 transmembrane helical bundle crossing domain（gating）： loop state and helix state. At the loop state， multiple amino acids participated in the formation of pore regions that hinder ion permeability， while in the helical architecture. Only the key amino acid V956 played a gating role. Because the flexibility of the gated loop architecture was greater than that of the helical， and the number of key amino acids involved in gating was different. The secondary structure prediction showed that the loop architecture could change to the helical. In this process， the flexible loop domain moved upward to the outside of the cell， and the gated amino acids twisted to the outside of the pore lining. At the same time， the interaction with the adjacent transmembrane S5 helix was enhanced， and a rigid， stable and orderly helical architecture was formed. This promoted the coordination between the various domains of TRPM8 channel， enabled energy and information to be transmitted to the bundle crossing more efficiently， which was conducive to channel opening.