Allosteric modulation and G-protein selectivity of the Ca2+-sensing receptor

Feng He, Cheng Guo Wu, Yang Gao, Sabrina N. Rahman, Magda Zaoralová, Makaía M. Papasergi-Scott, Ting Jia Gu, Michael J. Robertson, Alpay B. Seven, Lingjun Li, Jesper M. Mathiesen, Georgios Skiniotis*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

10 Citations (Scopus)

Abstract

The calcium-sensing receptor (CaSR) is a family C G-protein-coupled receptor1 (GPCR) that has a central role in regulating systemic calcium homeostasis2,3. Here we use cryo-electron microscopy and functional assays to investigate the activation of human CaSR embedded in lipid nanodiscs and its coupling to functional Gi versus Gq proteins in the presence and absence of the calcimimetic drug cinacalcet. High-resolution structures show that both Gi and Gq drive additional conformational changes in the activated CaSR dimer to stabilize a more extensive asymmetric interface of the seven-transmembrane domain (7TM) that involves key protein–lipid interactions. Selective Gi and Gq coupling by the receptor is achieved through substantial rearrangements of intracellular loop 2 and the C terminus, which contribute differentially towards the binding of the two G-protein subtypes, resulting in distinct CaSR–G-protein interfaces. The structures also reveal that natural polyamines target multiple sites on CaSR to enhance receptor activation by zipping negatively charged regions between two protomers. Furthermore, we find that the amino acid l-tryptophan, a well-known ligand of CaSR extracellular domains, occupies the 7TM bundle of the G-protein-coupled protomer at the same location as cinacalcet and other allosteric modulators. Together, these results provide a framework for G-protein activation and selectivity by CaSR, as well as its allosteric modulation by endogenous and exogenous ligands.

Original languageEnglish
JournalNature
Volume626
Pages (from-to)1141–1148
ISSN0028-0836
DOIs
Publication statusPublished - 2024

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© The Author(s), under exclusive licence to Springer Nature Limited 2024.

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