GPCRs steer Gi and Gs selectivity via TM5-TM6 switches as revealed by structures of serotonin receptors

Sijie Huang; Peiyu Xu; Dan-Dan Shen; Icaro A Simon; Chunyou Mao; Yangxia Tan; Huibing Zhang; Kasper Harpsøe; Huadong Li; Yumu Zhang; Chongzhao You; Xuekui Yu; Yi Jiang; Yan Zhang; David E Gloriam; H Eric Xu

doi:10.1016/j.molcel.2022.05.031

GPCRs steer G_i and G_s selectivity via TM5-TM6 switches as revealed by structures of serotonin receptors

Mol Cell. 2022 Jul 21;82(14):2681-2695.e6. doi: 10.1016/j.molcel.2022.05.031. Epub 2022 Jun 16.

Authors

Sijie Huang¹, Peiyu Xu², Dan-Dan Shen³, Icaro A Simon⁴, Chunyou Mao³, Yangxia Tan¹, Huibing Zhang³, Kasper Harpsøe⁵, Huadong Li¹, Yumu Zhang¹, Chongzhao You², Xuekui Yu⁶, Yi Jiang², Yan Zhang⁷, David E Gloriam⁸, H Eric Xu⁹

Affiliations

¹ The CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; University of Chinese Academy of Sciences, Beijing 100049, China; School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China.
² The CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; University of Chinese Academy of Sciences, Beijing 100049, China.
³ Department of Biophysics and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China; Liangzhu Laboratory, Zhejiang University Medical Center, Hangzhou 311121, China; MOE Frontier Science Center for Brain Research and Brain-Machine Integration, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China.
⁴ Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark; SARomics Biostructures AB, Scheelevägen 2, 223 63 Lund, Sweden; Present address: Vrije Universiteit Amsterdam, Division of Medicinal Chemistry, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Faculty of Science, De Boelelaan 1108, 1081 HZ Amsterdam, Netherlands.
⁵ Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark.
⁶ The CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; Cryo-Electron Microscopy Research Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.
⁷ Department of Biophysics and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China; Liangzhu Laboratory, Zhejiang University Medical Center, Hangzhou 311121, China; MOE Frontier Science Center for Brain Research and Brain-Machine Integration, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China; Key Laboratory of Immunity and Inflammatory Diseases of Zhejiang Province, Hangzhou 310058, China. Electronic address: zhang_yan@zju.edu.cn.
⁸ Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark. Electronic address: david.gloriam@sund.ku.dk.
⁹ The CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; University of Chinese Academy of Sciences, Beijing 100049, China; School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China. Electronic address: eric.xu@simm.ac.cn.

PMID: 35714614
DOI: 10.1016/j.molcel.2022.05.031

Abstract

Serotonin (or 5-hydroxytryptamine, 5-HT) is an important neurotransmitter that activates 12 different G protein-coupled receptors (GPCRs) through selective coupling of G_s, G_i, or G_q proteins. The structural basis for G protein subtype selectivity by these GPCRs remains elusive. Here, we report the structures of the serotonin receptors 5-HT₄, 5-HT₆, and 5-HT₇ with G_s, and 5-HT₄ with G_i1. The structures reveal that transmembrane helices TM5 and TM6 alternate lengths as a macro-switch to determine receptor's selectivity for G_s and G_i, respectively. We find that the macro-switch by the TM5-TM6 length is shared by class A GPCR-G protein structures. Furthermore, we discover specific residues within TM5 and TM6 that function as micro-switches to form specific interactions with G_s or G_i. Together, these results present a common mechanism of G_s versus G_i protein coupling selectivity or promiscuity by class A GPCRs and extend the basis of ligand recognition at serotonin receptors.

Keywords: 5-HT; 5-HT(4) receptor; 5-HT(6) receptor; 5-HT(7) receptor; G protein selectivity; GPCR; cryo-EM structure; ligand selectivity; serotonin receptor; signaling complex.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

GTP-Binding Proteins / metabolism
Ligands
Receptors, G-Protein-Coupled* / metabolism
Receptors, Serotonin / genetics
Receptors, Serotonin / metabolism
Serotonin*

Substances

Ligands
Receptors, G-Protein-Coupled
Receptors, Serotonin
Serotonin
GTP-Binding Proteins