title: Structural mechanism of ligand activation in human calcium-sensing receptor.
abstract: Human calcium-sensing receptor (CaSR) is a G-protein-coupled receptor (GPCR) that maintains extracellular Ca(2+) homeostasis through the regulation of parathyroid hormone secretion. It functions as a disulfide-tethered homodimer composed of three main domains, the Venus Flytrap module, cysteine-rich domain, and seven-helix transmembrane region. Here, we present the crystal structures of the entire extracellular domain of CaSR in the resting and active conformations. We provide direct evidence that L-amino acids are agonists of the receptor. In the active structure, L-Trp occupies the orthosteric agonist-binding site at the interdomain cleft and is primarily responsible for inducing extracellular domain closure to initiate receptor activation. Our structures reveal multiple binding sites for Ca(2+) and PO4(3-) ions. Both ions are crucial for structural integrity of the receptor. While Ca(2+) ions stabilize the active state, PO4(3-) ions reinforce the inactive conformation. The activation mechanism of CaSR involves the formation of a novel dimer interface between subunits.
authors.affiliation: Department of Pharmacology, Columbia University, New York, United States.|Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Geng
authors.affiliation: Department of Pharmacology, Columbia University, New York, United States.
authors.forename: Lidia
authors.initials: L
authors.lastname: Mosyak
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University, Ithaca, United States.
authors.forename: Igor
authors.initials: I
authors.lastname: Kurinov
authors.affiliation: Department of Pharmacology, Columbia University, New York, United States.
authors.forename: Hao
authors.initials: H
authors.lastname: Zuo
authors.affiliation: Department of Molecular Therapeutics, The Scripps Translational Science Institute, Jupiter, United States.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Sturchler
authors.affiliation: Department of Pharmacology, Columbia University, New York, United States.
authors.forename: Tat Cheung
authors.initials: TC
authors.lastname: Cheng
authors.affiliation: Department of Physiology and Cellular Biophysics, Columbia University, New York, United States.
authors.forename: Prakash
authors.initials: P
authors.lastname: Subramanyam
authors.affiliation: School of Life and Environmental Sciences, University of Sydney, New South Wales, Australia.
authors.forename: Alice P
authors.initials: AP
authors.lastname: Brown
authors.affiliation: School of Life and Environmental Sciences, University of Sydney, New South Wales, Australia.
authors.forename: Sarah C
authors.initials: SC
authors.lastname: Brennan
authors.affiliation: School of Life and Environmental Sciences, University of Sydney, New South Wales, Australia.
authors.forename: Hee-Chang
authors.initials: HC
authors.lastname: Mun
authors.affiliation: Department of Pharmacology, Columbia University, New York, United States.
authors.forename: Martin
authors.initials: M
authors.lastname: Bush
authors.affiliation: Department of Pharmacology, Columbia University, New York, United States.
authors.forename: Yan
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Psychiatry, Columbia University, New York, United States.
authors.forename: Trang X
authors.initials: TX
authors.lastname: Nguyen
authors.affiliation: Department of Pharmacology, Columbia University, New York, United States.
authors.forename: Baohua
authors.initials: B
authors.lastname: Cao
authors.affiliation: Department of Physiology and Cellular Biophysics, Columbia University, New York, United States.
authors.forename: Donald D
authors.initials: DD
authors.lastname: Chang
authors.affiliation: Department of Psychiatry, Columbia University, New York, United States.
authors.forename: Matthias
authors.initials: M
authors.lastname: Quick
authors.affiliation: School of Life and Environmental Sciences, University of Sydney, New South Wales, Australia.
authors.forename: Arthur D
authors.initials: AD
authors.lastname: Conigrave
authors.affiliation: Department of Physiology and Cellular Biophysics, Columbia University, New York, United States.
authors.forename: Henry M
authors.initials: HM
authors.lastname: Colecraft
authors.affiliation: Department of Molecular Therapeutics, The Scripps Translational Science Institute, Jupiter, United States.
authors.forename: Patricia
authors.initials: P
authors.lastname: McDonald
authors.affiliation: Department of Pharmacology, Columbia University, New York, United States.|Department of Pathology and Cell Biology, Columbia University, New York, United States.
authors.forename: Qing R
authors.identifier: 0000-0002-9330-0963
authors.initials: QR
authors.lastname: Fan
mesh_terms: D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D018360:Crystallography, X-Ray; D006801:Humans; D008958:Models, Molecular; D010710:Phosphates / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D055503:Protein Multimerization; D044169:Receptors, Calcium-Sensing / Q000819:agonists* / Q000737:chemistry*; D014364:Tryptophan / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D010710:Phosphates; D044169:Receptors, Calcium-Sensing; D014364:Tryptophan; D002118:Calcium
keywords: amino acids; biochemistry; biophysics; calcium-sensing receptor; extracellular calcium homeostasis; extracellular domain structure; human; principal agonist; receptor activation mechanism; structural biology