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 and Georgios Skiniotis ()
Additional contact information
Feng He: Stanford University School of Medicine
Cheng-Guo Wu: Stanford University School of Medicine
Yang Gao: Stanford University School of Medicine
Sabrina N. Rahman: University of Copenhagen
Magda Zaoralová: Stanford University School of Medicine
Makaía M. Papasergi-Scott: Stanford University School of Medicine
Ting-Jia Gu: University of Wisconsin-Madison
Michael J. Robertson: Stanford University School of Medicine
Alpay B. Seven: Stanford University School of Medicine
Lingjun Li: University of Wisconsin-Madison
Jesper M. Mathiesen: University of Copenhagen
Georgios Skiniotis: Stanford University School of Medicine

Nature, 2024, vol. 626, issue 8001, 1141-1148

Abstract: 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.

Date: 2024
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DOI: 10.1038/s41586-024-07055-2

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