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

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

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Abstract

Serotonin (or 5-hydroxytryptamine, 5-HT) is an important neurotransmitter that activates 12 different G protein-coupled receptors (GPCRs) through selective coupling of Gs, Gi, or Gq 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 Gs, and 5-HT4 with Gi1. The structures reveal that transmembrane helices TM5 and TM6 alternate lengths as a macro-switch to determine receptor's selectivity for Gs and Gi, 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 Gs or Gi. Together, these results present a common mechanism of Gs versus Gi protein coupling selectivity or promiscuity by class A GPCRs and extend the basis of ligand recognition at serotonin receptors.

Original languageEnglish
Pages (from-to)2681-2695.e6
Number of pages22
JournalMolecular cell
Volume82
Issue number14
Early online date16 Jun 2022
DOIs
Publication statusPublished - 21 Jul 2022

Bibliographical note

Funding Information:
The cryo-EM data were collected at the Center of Cryo-Electron Microscopy, Shanghai Institute of Materia Medica, and at the Center of Cryo-Electron Microscopy, Zhejiang University. Cryo-EM data collection for the 5-HT 4 -G s complex was carried out at Shuimu BioSciences Ltd. The authors thank all staff at Shuimu BioSciences Ltd. for their technical support. This work was partially supported by the National Key R&D Programs of China ( 2018YFA0507002 ), the Shanghai Municipal Science and Technology Major Project ( 2019SHZDZX02 ), the CAS Strategic Priority Research Program ( XDB37030103 ) to H.E.X.; the National Key Basic Research Program of China ( 2019YFA0508800 ), the National Natural Science Foundation of China ( 81922071 ), the Zhejiang Province Natural Science Fund for Excellent Young Scholars ( LR19H310001 ), Key R & D Projects of Zhejiang Province ( 2021C03039 ) to Y.Z.; the National Natural Science Foundation of China ( 31770796 ) and National Science and Technology Major Project ( 2018ZX09711002-002-002 ) to Y.J.; the EU Horizon 2020, Innovative Training Network SAFER ( 765657 ) to I.A.S.; the Lundbeck Foundation ( R163-2013-16327 ) and Novo Nordisk Foundation ( NNF18OC0031226 ) to D.E.G. and K.H. We thank Albert J. Kooistra and Gáspár Pándy-Szekeres for structure annotation, and Henrik Daver for scripts to calculate G protein insertion angles. Cartoons in graphical abstract, Figure 1 A, and Figure 6L were created with BioRender.com .

Publisher Copyright:
© 2022 Elsevier Inc.

Funding

The cryo-EM data were collected at the Center of Cryo-Electron Microscopy, Shanghai Institute of Materia Medica, and at the Center of Cryo-Electron Microscopy, Zhejiang University. Cryo-EM data collection for the 5-HT 4 -G s complex was carried out at Shuimu BioSciences Ltd. The authors thank all staff at Shuimu BioSciences Ltd. for their technical support. This work was partially supported by the National Key R&D Programs of China ( 2018YFA0507002 ), the Shanghai Municipal Science and Technology Major Project ( 2019SHZDZX02 ), the CAS Strategic Priority Research Program ( XDB37030103 ) to H.E.X.; the National Key Basic Research Program of China ( 2019YFA0508800 ), the National Natural Science Foundation of China ( 81922071 ), the Zhejiang Province Natural Science Fund for Excellent Young Scholars ( LR19H310001 ), Key R & D Projects of Zhejiang Province ( 2021C03039 ) to Y.Z.; the National Natural Science Foundation of China ( 31770796 ) and National Science and Technology Major Project ( 2018ZX09711002-002-002 ) to Y.J.; the EU Horizon 2020, Innovative Training Network SAFER ( 765657 ) to I.A.S.; the Lundbeck Foundation ( R163-2013-16327 ) and Novo Nordisk Foundation ( NNF18OC0031226 ) to D.E.G. and K.H. We thank Albert J. Kooistra and Gáspár Pándy-Szekeres for structure annotation, and Henrik Daver for scripts to calculate G protein insertion angles. Cartoons in graphical abstract, Figure 1 A, and Figure 6L were created with BioRender.com .

FundersFunder number
Key R & D Projects of Zhejiang Province2021C03039, 31770796
Zhejiang Province Natural Science Fund for Excellent Young ScholarsLR19H310001
National Natural Science Foundation of China81922071
National Natural Science Foundation of China
Chinese Academy of SciencesXDB37030103
Chinese Academy of Sciences
Science and Technology Commission of Shanghai Municipality2019SHZDZX02
Science and Technology Commission of Shanghai Municipality
LundbeckfondenR163-2013-16327
Lundbeckfonden
Horizon 2020765657
Horizon 2020
Novo Nordisk FondenNNF18OC0031226
Novo Nordisk Fonden
National Key Research and Development Program of China2018YFA0507002, 2019YFA0508800
National Key Research and Development Program of China
National Major Science and Technology Projects of China2018ZX09711002-002-002
National Major Science and Technology Projects of China

    Keywords

    • 5-HT
    • 5-HT receptor
    • cryo-EM structure
    • G protein selectivity
    • GPCR
    • ligand selectivity
    • serotonin receptor
    • signaling complex

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