Wen Xin, Shang Pan, Chen Haidi, Guo Lulu, Rong Naikang, Jiang Xiaoyu, Li Xuan, Liu Junyan, Yang Gongming, Zhang Jiacheng, Zhu Kongkai, Meng Qingbiao, He Xuefei, Wang Zhihai, Liu Zili, Cheng Haoran, Zheng Yilin, Zhang Bifei, Pang Jiaojiao, Liu Zhaoqian, Xiao Peng, Chen Yuguo, Liu Lunxu, Luo Fengming, Yu Xiao, Yi Fan, Zhang Pengju, Yang Fan, Deng Cheng, Sun Jin-Peng
Key Laboratory Experimental Teratology of the Ministry of Education, New Cornerstone Science Laboratory, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Shandong University, Jinan, Shandong 250012, China; NHC Key Laboratory of Otorhinolaryngology, Qilu Hospital of Shandong University, Advanced Medical Research Institute, Shandong University, Jinan, China.
Key Laboratory Experimental Teratology of the Ministry of Education, New Cornerstone Science Laboratory, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Shandong University, Jinan, Shandong 250012, China.
Cell. 2025 Feb 6;188(3):653-670.e24. doi: 10.1016/j.cell.2024.12.001. Epub 2025 Jan 2.
Animals have evolved pH-sensing membrane receptors, such as G-protein-coupled receptor 4 (GPR4), to monitor pH changes related to their physiology and generate adaptive reactions. However, the evolutionary trajectory and structural mechanism of proton sensing by GPR4 remain unresolved. Here, we observed a positive correlation between the optimal pH of GPR4 activity and the blood pH range across different species. By solving 7-cryoelectron microscopy (cryo-EM) structures of Xenopus tropicalis GPR4 (xtGPR4) and Mus musculus GPR4 (mmGPR4) under varying pH conditions, we identified that protonation of H and H enabled polar network establishment and tighter association between the extracellular loop 2 (ECL2) and 7 transmembrane (7TM) domain, as well as a conserved propagating path, which are common mechanisms underlying protonation-induced GPR4 activation across different species. Moreover, protonation of distinct extracellular H contributed to the more acidic optimal pH range of xtGPR4. Overall, our study revealed common and distinct mechanisms of proton sensing by GPR4, from a structural, functional, and evolutionary perspective.
动物已经进化出pH感应膜受体，如G蛋白偶联受体4（GPR4），以监测与其生理相关的pH变化并产生适应性反应。然而，GPR4对质子感应的进化轨迹和结构机制仍未得到解决。在这里，我们观察到不同物种中GPR4活性的最佳pH值与血液pH范围之间存在正相关。通过解析热带爪蟾GPR4（xtGPR4）和小家鼠GPR4（mmGPR4）在不同pH条件下的7-冷冻电子显微镜（cryo-EM）结构，我们发现H和H的质子化能够建立极性网络，并使细胞外环2（ECL2）与7跨膜（7TM）结构域之间的结合更紧密，以及一条保守的传播路径，这些是不同物种中质子化诱导GPR4激活的共同机制。此外，不同细胞外H的质子化导致xtGPR4的最佳pH范围更偏酸性。总体而言，我们的研究从结构、功能和进化的角度揭示了GPR4对质子感应的共同和独特机制。
