State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine at Shanghai, Medicinal Chemistry and Bioinformatics Center, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China.
Key Laboratory of Protection, Development and Utilization of Medicinal Resources in Liupanshan Area, Ministry of Education, Peptide & Protein Drug Research Center, School of Pharmacy, Ningxia Medical University, Yinchuan, 750004, China.
Nat Commun. 2024 Aug 30;15(1):7519. doi: 10.1038/s41467-024-51999-y.
Two-thirds of signaling hormones and one-third of approved drugs exert their effects by binding and modulating the G protein-coupled receptors (GPCRs) activation. While the activation mechanism for monomeric GPCRs has been well-established, little is known about GPCRs in dimeric form. Here, by combining transition pathway generation, extensive atomistic simulation-based Markov state models, and experimental signaling assays, we reveal an asymmetric, stepwise millisecond allosteric activation mechanism for the metabotropic glutamate receptor subtype 5 receptor (mGlu5), an obligate dimeric class C GPCR. The dynamic picture is presented that agonist binding induces dimeric ectodomains compaction, amplified by the precise association of the cysteine-rich domains, ultimately loosely bringing the intracellular 7-transmembrane (7TM) domains into proximity and establishing an asymmetric TM6-TM6 interface. The active inter-domain interface enhances their intra-domain flexibility, triggering the activation of micro-switches crucial for downstream signal transduction. Furthermore, we show that the positive allosteric modulator stabilizes both the active inter-domain 7TM interface and an open, extended intra-domain ICL2 conformation. This stabilization leads to the formation of a pseudo-cavity composed of the ICL2, ICL3, TM3, and C-terminus, which facilitates G protein coordination. Our strategy may be generalizable for characterizing millisecond events in other allosteric systems.
三分之二的信号激素和三分之一的批准药物通过结合和调节 G 蛋白偶联受体（GPCR）的激活来发挥作用。虽然单体 GPCR 的激活机制已经得到很好的建立，但对于二聚体形式的 GPCR 知之甚少。在这里，我们通过结合过渡途径生成、广泛的基于原子模拟的马尔可夫状态模型和实验信号检测，揭示了代谢型谷氨酸受体亚型 5 受体（mGlu5）的一种不对称的、逐步的毫秒级变构激活机制，mGlu5 是一种必需的二聚体 C 类 GPCR。呈现出一个动态画面，即激动剂结合诱导二聚体胞外结构域紧缩，通过富含半胱氨酸结构域的精确结合得到放大，最终使细胞内的 7 跨膜（7TM）结构域松散地接近，并建立一个不对称的 TM6-TM6 界面。活性的跨域界面增强了它们的域内灵活性，触发了下游信号转导中关键的微开关的激活。此外，我们还表明，正变构调节剂稳定了活性的跨域 7TM 界面和开放的、延伸的域内 ICL2 构象。这种稳定导致了由 ICL2、ICL3、TM3 和 C 末端组成的伪腔的形成，这有利于 G 蛋白的协调。我们的策略可能适用于表征其他变构系统中的毫秒级事件。
