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Cong Z, Zhao F, Li Y, Luo G, Mai Y, Chen X, Chen Y, Lin S, Cai X, Zhou Q, Yang D, Wang MW. Molecular features of the ligand-free GLP-1R, GCGR and GIPR in complex with G s proteins. Cell Discov 2024; 10:18. [PMID: 38346960 PMCID: PMC10861504 DOI: 10.1038/s41421-024-00649-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Accepted: 01/15/2024] [Indexed: 02/15/2024] Open
Abstract
Class B1 G protein-coupled receptors (GPCRs) are important regulators of many physiological functions such as glucose homeostasis, which is mainly mediated by three peptide hormones, i.e., glucagon-like peptide-1 (GLP-1), glucagon (GCG), and glucose-dependent insulinotropic polypeptide (GIP). They trigger a cascade of signaling events leading to the formation of an active agonist-receptor-G protein complex. However, intracellular signal transducers can also activate the receptor independent of extracellular stimuli, suggesting an intrinsic role of G proteins in this process. Here, we report cryo-electron microscopy structures of the human GLP-1 receptor (GLP-1R), GCG receptor (GCGR), and GIP receptor (GIPR) in complex with Gs proteins without the presence of cognate ligands. These ligand-free complexes share a similar intracellular architecture to those bound by endogenous peptides, in which, the Gs protein alone directly opens the intracellular binding cavity and rewires the extracellular orthosteric pocket to stabilize the receptor in a state unseen before. While the peptide-binding site is partially occupied by the inward folded transmembrane helix 6 (TM6)-extracellular loop 3 (ECL3) juncture of GIPR or a segment of GCGR ECL2, the extracellular portion of GLP-1R adopts a conformation close to the active state. Our findings offer valuable insights into the distinct activation mechanisms of these three important receptors. It is possible that in the absence of a ligand, the intracellular half of transmembrane domain is mobilized with the help of Gs protein, which in turn rearranges the extracellular half to form a transitional conformation, facilitating the entry of the peptide N-terminus.
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Affiliation(s)
- Zhaotong Cong
- Department of Pharmacology, School of Basic Medical Sciences, Fudan University, Shanghai, China
| | - Fenghui Zhao
- State Key Laboratory of Chemical Biology, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
- The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Yang Li
- Shanghai Institute of Infectious Disease and Biosecurity, Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences, Fudan University, Shanghai, China
| | - Gan Luo
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), School of Basic Medical Sciences, Fudan University, Shanghai, China
| | - Yiting Mai
- Research Center for Deepsea Bioresources, Sanya, Hainan, China
| | - Xianyue Chen
- Research Center for Deepsea Bioresources, Sanya, Hainan, China
| | - Yanyan Chen
- Research Center for Deepsea Bioresources, Sanya, Hainan, China
| | - Shi Lin
- Research Center for Deepsea Bioresources, Sanya, Hainan, China
| | - Xiaoqing Cai
- State Key Laboratory of Chemical Biology, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
- The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Qingtong Zhou
- Department of Pharmacology, School of Basic Medical Sciences, Fudan University, Shanghai, China.
- Research Center for Deepsea Bioresources, Sanya, Hainan, China.
| | - Dehua Yang
- State Key Laboratory of Chemical Biology, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.
- The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.
- Research Center for Deepsea Bioresources, Sanya, Hainan, China.
| | - Ming-Wei Wang
- Research Center for Deepsea Bioresources, Sanya, Hainan, China.
- Department of Chemistry, School of Science, The University of Tokyo, Tokyo, Japan.
- School of Pharmacy, Hainan Medical University, Haikou, Hainan, China.
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