孤儿受体GPR12自激活机制的结构基础  

Structural insight into the constitutive activity of human orphan receptor GPR12

作　　者：李昊 张进一 喻亚男 罗峰 武丽杰 刘俊林 陈娜 刘志杰 华甜 Hao Li;Jinyi Zhang;Yanan Yu;Feng Luo;Lijie Wu;Junlin Liu;Na Chen;Zhijie Liu;Tian Hua(iHuman Institute,ShanghaiTech University,Shanghai 201210,China;School of Life Science and Technology,ShanghaiTech University,Shanghai 201210,China)

机构地区：[1]iHuman Institute,ShanghaiTech University,Shanghai 201210,China [2]School of Life Science and Technology,ShanghaiTech University,Shanghai 201210,China

出　　处：《Science Bulletin》2023年第1期95-104,共10页科学通报（英文版）

基　　金：supported by the National Natural Science Foundation of China(91953202,31930060,and 31870744);the CAS Strategic Priority Research Program(XDB37030104);the National Science Fund for Distinguished Young Scholars(32022038);the National Key Research and Development Program of China(2018YFA0507000);the Shanghai Rising-Star Program(20QA1406500);the Shanghai Science and Technology Plan(21DZ2260400);the Shanghai Municipal Government and ShanghaiTech University for financial support;supported by Shanghai Frontiers Science Center for Biomacromolecules and Precision Medicine at ShanghaiTech University。

摘　　要：G蛋白偶联受体12(G protein-coupled receptor 12,GPR12)是G蛋白偶联受体(G protein-coupled receptor,GPCR)class A家族的孤儿受体成员.GPR12在丘脑中高表达,在丘脑皮层的短期记忆调控中发挥重要作用.GPR12具有高度的自激活能力,即在没有激动剂激活的情况下可以结合下游的G蛋白Gs,使细胞内的第二信使cAMP水平上升.然而,目前关于GPR12自激活机制的分子基础以及内源性配体等都还不清楚.本研究报道了GPR12-G_(s)复合物的高分辨率单颗粒冷冻电镜结构,结合细胞水平突变实验,揭示了GPR12具有高水平自激活能力的分子机制.结构分析显示受体的胞外第二个环(extracellular loop 2,ECL2)指向正构配体结合口袋,跨膜螺旋TM1和TM7的胞外部分紧密互作,以及TM6和TM7上具有与GPR12激活相关的关键氨基酸.这些结构特征使得GPR12能够在没有激动剂作用下,受体处于激活构象状态,招募下游G蛋白进行信号传递.本研究将为靶向GPR12的内源性配体发现及相关药物分子设计提供重要的结构基础.G protein-coupled receptor 12(GPR12)is an orphan G protein-coupled receptor that is highly expressed in the thalamus of the brain and plays a vital role in driving thalamocortical functions in short-term memory.GPR12 performs high constitutive activity and couples with Gs,increasing the intracellular cyclic adenosine monophosphate(cAMP)level when it is expressed.However,exploitation for drug development is limited since it is unclear how GPR12 initiates self-activation and signal transduction,and whether it can be modulated by endogenous or synthetic ligands.Here,we report the cryo-electron microscopy structure of the GPR12-G_(s)complex in the absence of agonists.Our structure reveals the key determinants for the intrinsically high basal activity of GPR12,including extracellular loop 2 partially occupying the orthosteric binding pocket,a tight-packed TM1 and TM7,and unique activation-related residues in TM6 and TM7.Together with mutagenesis data,this study will improve our understanding of the function and self-activation of the orphan receptor GPR12,enable the identification of endogenous ligands,and guide drug discovery efforts that target GPR12.

关 键 词：内源性配体 G蛋白偶联受体 短期记忆 激活机制 药物分子设计 孤儿受体 信号传递 激动剂 

分 类 号：R3[医药卫生—基础医学]