Structural insights into the activation of human calcium-sensing receptor
Abstract
Human calcium-sensing receptor (CaSR) is a G-protein-coupled receptor that maintains Ca2+ homeostasis in serum. Here, we present the cryo-electron microscopy structures of the CaSR in the inactive and agonist+PAM bound states. Complemented with previously reported structures of CaSR, we show that in addition to the full inactive and active states, there are multiple intermediate states during the activation of CaSR. We used a negative allosteric nanobody to stabilize the CaSR in the fully inactive state and found a new binding site for Ca2+ ion that acts as a composite agonist with L-amino acid to stabilize the closure of active Venus flytraps. Our data show that agonist binding leads to compaction of the dimer, proximity of the cysteine-rich domains, large-scale transitions of 7-transmembrane domains, and inter- and intrasubunit conformational changes of 7-transmembrane domains to accommodate downstream transducers. Our results reveal the structural basis for activation mechanisms of CaSR and clarify the mode of action of Ca2+ ions and L-amino acid leading to the activation of the receptor.
Data availability
All data is available in the main text or the supplementary materials. Cryo-EM maps of active CaSR in complex with TNCA and inactive CaSR in complex with NB-2D11 have been deposited in the Electron Microscopy Data Bank under accession codes: EMD-30997 (NB-2D11 bound CaSR), EMD-30996 (TNCA bound CaSR). Atomic coordinates for the CaSR in complex with TNCA or NB-2D11 have been deposited in the Protein Data Bank under accession codes: 7E6U (NB-2D11 bound CaSR), 7E6T (TNCA bound CaSR).
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Cryo-EM structure of CaSR in complex with NB-2D11RCSB Protein Data Bank,7E6U.
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Cryo-EM structure of CaSR in complex with TNCARCSB Protein Data Bank,7E6T.
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Crystal structure of the inactive form of human calcium-sensing receptor extracellular domainPublicly available at the RCSB Protein Data Bank (accession no. 5K5T).
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Crystal structure of the active form of human calcium-sensing receptor extracellular domainPublicly available at the RCSB Protein Data Bank (accession no. 5K5S).
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Metabotropic Glutamate Receptor 5 bound to L-quisqualate and Nb43RCSB Protein Data Bank,6N51.
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Cryo-EM structure of the baclofen/BHFF-bound human GABA(B) receptor in active stateRCSB Protein Data Bank,7C7Q.
Article and author information
Author details
Funding
National Natural Science Foundation of China (No. 31670743)
- Yong Geng
Shanghai Institute of Materia Medica, Chinese Academy of Sciences (5112345601)
- Yong Geng
Shanghai Institute of Materia Medica, Chinese Academy of Sciences (2015123456005)
- Yong Geng
National Natural Science Foundation of China (118180359901)
- Yong Geng
Science and Technology Commission of Shanghai Municipality (No. 18JC1415400)
- Yong Geng
Joint Research Fund for Overseas Chinese Scholars and Scholars in Hong Kong and Macao (No. 81628013)
- Yong Geng
Natural Science Foundation of Shanghai (16ZR1442900)
- Yong Geng
Shanghai Institute of Materia Medica, Chinese Academy of Sciences (CASIMM0120164013)
- Yong Geng
Shanghai Institute of Materia Medica, Chinese Academy of Sciences (SIMM1606YZZ-06)
- Yong Geng
Shanghai Institute of Materia Medica, Chinese Academy of Sciences (SIMM1601KF-06)
- Yong Geng
Shanghai Institute of Materia Medica, Chinese Academy of Sciences (55201631121116101)
- Yong Geng
Shanghai Institute of Materia Medica, Chinese Academy of Sciences (55201631121108000)
- Yong Geng
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Animal experimentation: The animal work was approved and under the supervision of Shanghai Institute of Materia Medica, Chinese Academy of Sciences (Permit Number: SYXK 2015-0027)
Reviewing Editor
- Randy B Stockbridge, University of Michigan, United States
Publication history
- Received: March 19, 2021
- Preprint posted: March 31, 2021 (view preprint)
- Accepted: August 31, 2021
- Accepted Manuscript published: September 1, 2021 (version 1)
- Version of Record published: September 27, 2021 (version 2)
Copyright
© 2021, Chen et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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