Key Laboratory of Magnetic Resonance in Biological Systems of the Chinese Academy of Sciences, State Key Laboratory of Magnetic Resonance and Atomic Molecular Physics, National Center for Magnetic Resonance at Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy of Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, Hubei 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Key Laboratory of Magnetic Resonance in Biological Systems of the Chinese Academy of Sciences, State Key Laboratory of Magnetic Resonance and Atomic Molecular Physics, National Center for Magnetic Resonance at Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy of Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, Hubei 430071, China.
J Mol Biol. 2020 Jul 24;432(16):4596-4611. doi: 10.1016/j.jmb.2020.06.009. Epub 2020 Jun 15.
Class-A G protein-coupled receptors (GPCRs) are known to homo-dimerize in the membrane. Yet, methods to characterize the structure of GPCR dimer in the native environment are lacking. Accordingly, the molecular basis and functional relevance of the class-A GPCR dimerization remain unclear. Here, we present the dimeric structural model of GPR17 in the cell membrane. The dimer mainly involves transmembrane helix 5 (TM5) at the interface, with F229 in TM5, a critical residue. An F229A mutation makes GPR17 monomeric regardless of the expression level of the receptor. Monomeric mutants of GPR17 display impaired ERK1/2 activation and cannot be properly internalized upon agonist treatment. Conversely, the F229C mutant is cross-linked as a dimer and behaves like wild-type. Importantly, the GPR17 dimer structure has been modeled using sparse inter-protomer FRET distance restraints obtained from fluorescence lifetime imaging microscopy. The same approach can be applied to characterizing the interactions of other important membrane proteins in the cell.
A 类 G 蛋白偶联受体（GPCRs）已知在膜中发生同源二聚化。然而，用于描述天然环境中 GPCR 二聚体结构的方法仍很缺乏。因此，A 类 GPCR 二聚化的分子基础和功能相关性仍不清楚。在这里，我们提出了 GPR17 在细胞膜中的二聚体结构模型。该二聚体主要涉及跨膜螺旋 5（TM5）作为界面，其中 TM5 中的 F229 是一个关键残基。F229A 突变使 GPR17 即使在受体表达水平很高的情况下也成为单体。GPR17 的单体突变体显示 ERK1/2 激活受损，并且在激动剂处理时不能被正确内化。相反，F229C 突变体交联为二聚体并表现出类似于野生型的行为。重要的是，使用荧光寿命成像显微镜获得的稀疏的蛋白间 FRET 距离约束，已经对 GPR17 二聚体结构进行了建模。同样的方法可以应用于描述细胞中其他重要膜蛋白的相互作用。
