膜磷脂PIP2调控内向整流型钾离子通道蛋白KIR2.1功能的微观动力学模拟

The anionic lipid PIP2 (phosphatidylinositol 4,5-bisphosphate) is essential and sufficient for activating the K+ transport of KIR2.1, one member of inwardly rectifying potassium family of KIR2. And the K+ permeation dynamic feature of KIR2.1 dependes on the synergetic gating dynamics of its three gates upon PIP2 binding, which including selectivity filter and TM2 locating in transmembrane domain, and G-loop locating in cytoplasmic domain. PIP2 binding could induce the opening of these three gates from their close conformations, while the microstructural evolution dynamics remains poorly understood. The scientific issue of this project focuses on investigating the micro-structural mechanism of PIP2 induced KIR2.1 gating. Using molecular dynamic simulations, the scientific aims include: 1) The conformational stability of KIR2.1 tetramer with or without PIP2 binding. 2) The conformational evolution dynamics of KIR2.1 between close and open states. The goal of this project is to offer insight into understanding the structure-function relationship of KIR2.1.

膜磷脂4,5二磷酸磷脂酰肌醇（PIP2）可以独自调控内向整流型钾离子通道蛋白KIR2.1在负向膜电位条件下将K+从胞外向胞内输运，而其K+通透动力学受KIR2.1四聚体跨膜区域的Selectivity filter、TM2门控，以及胞内区域的G-loop门控共同调控。PIP2与KIR2.1的相互作用诱导了KIR2.1的三个门控从关闭构象变构至开启构象，继而导致钾离子从细胞外向内输运。然而，目前关于PIP2如何诱导KIR2.1门控变构的微观结构动力学研究尚少。基于此，本项目针对PIP2调控KIR2.1微观结构演化这一科学问题，运用分子动力学模拟手段，系统考察1）PIP2分子诱导前后KIR2.1构象的稳定性，2）PIP2分子存在与否对KIR2.1构象动力学的影响。重点理解PIP2调控KIR2.1门控构象开启过程的微观结构机制，为深入认识KIR2.1生物学功能，阐明其结构-功能关系提供预测信息。

本项目一方面采用分子动力学模拟手段，以鸡源KIR2.2晶体结构为基础，预测了PIP2对KIR构象的调控作用，关键局域构象变化对KIR门控开启的影响，以及胞内CD-loop上保守氨基酸位点Ile/Leu调控KIR门控动力学的微观结构基础。另一方面采用电生理实验，以鼠源KIR2.1和人源KIR2.2为对象，系统测量了Ile/Leu位点突变对PIP2-KIR相互作用，KIR门控开启动力学以及关闭动力学的影响，模拟与实验相结合，为深入阐明KIR的结构-功能关系提供基础。