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{{Short description|Mammalian protein found in humans}}
{{PBB|geneid=846}}
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The '''calcium-sensing receptor''' (CaSR) is a [[G-protein coupled receptor]] which senses extracellular levels of [[calcium]] ion. In the [[parathyroid gland]], the calcium-sensing receptor controls calcium [[homeostasis]] by regulating the release of [[parathyroid hormone]] (PTH).<ref name="pmid17117288">{{cite journal | author = D'Souza-Li L | title = The calcium-sensing receptor and related diseases | journal = Arquivos brasileiros de endocrinologia e metabologia | volume = 50 | issue = 4 | pages = 628–39 | year = 2006 | pmid = 17117288 | doi = 10.1590/S0004-27302006000400008 | issn = }}</ref>
The '''calcium-sensing receptor''' ('''CaSR''') is a [[Class C GPCR|Class C]] [[G-protein coupled receptor]] which senses extracellular levels of [[calcium]] ions. It is primarily expressed in the [[parathyroid gland]], the [[Nephron|renal tubules]] of the [[kidney]] and the [[brain]].<ref>{{cite journal | vauthors = Yano S, Brown EM, Chattopadhyay N | title = Calcium-sensing receptor in the brain | journal = Cell Calcium | volume = 35 | issue = 3 | pages = 257–264 | date = March 2004 | pmid = 15200149 | doi = 10.1016/j.ceca.2003.10.008 }}</ref><ref>{{cite journal | vauthors = Giudice ML, Mihalik B, Dinnyés A, Kobolák J | title = The Nervous System Relevance of the Calcium Sensing Receptor in Health and Disease | journal = Molecules | volume = 24 | issue = 14 | pages = 2546 | date = July 2019 | pmid = 31336912 | pmc = 6680999 | doi = 10.3390/molecules24142546 | doi-access = free }}</ref> In the parathyroid gland, it controls calcium [[homeostasis]] by regulating the release of [[parathyroid hormone]] (PTH).<ref name="pmid17117288">{{cite journal | vauthors = D'Souza-Li L | title = The calcium-sensing receptor and related diseases | journal = Arquivos Brasileiros de Endocrinologia e Metabologia | volume = 50 | issue = 4 | pages = 628–639 | date = August 2006 | pmid = 17117288 | doi = 10.1590/S0004-27302006000400008 | doi-access = free }}</ref> In the kidney it has an inhibitory effect on the reabsorption of calcium, [[potassium]], [[sodium]], and water depending on which segment of the tubule is being activated.<ref>{{cite journal | vauthors = Vezzoli G, Soldati L, Gambaro G | title = Roles of calcium-sensing receptor (CaSR) in renal mineral ion transport | journal = Current Pharmaceutical Biotechnology | volume = 10 | issue = 3 | pages = 302–310 | date = April 2009 | pmid = 19355940 | doi = 10.2174/138920109787847475 }}</ref>

Since the initial review of CaSR,<ref>{{cite journal | vauthors = Brown EM, Pollak M, Riccardi D, Hebert SC | title = Cloning and characterization of an extracellular Ca(2+)-sensing receptor from parathyroid and kidney: new insights into the physiology and pathophysiology of calcium metabolism | journal = Nephrology, Dialysis, Transplantation | volume = 9 | issue = 12 | pages = 1703–1706 | date = 1994 | pmid = 7708247 | url = https://pubmed.ncbi.nlm.nih.gov/7708247/ }}</ref> there has been in-depth analysis of its role related to parathyroid disease and other roles related to tissues and organs in the body. 1993, Brown et al.<ref>{{Cite journal|date=1994|title=Cloning and characterization of an extracellular Ca<sup>2+</sup> -sensing receptor from parathyroid and kidney: new insights into the physiology and pathophysiology of calcium metabolism|journal=Nephrology Dialysis Transplantation|doi=10.1093/ndt/9.12.1703|issn=1460-2385|doi-access=free}}</ref> isolated a clone named BoPCaR (bovine parathyroid calcium receptor) which replicated the effect when introduced to polyvalent cations. Because of this, the ability to clone full-length CaSRs from mammals were performed.<ref>{{cite journal | vauthors = Aida K, Koishi S, Tawata M, Onaya T | title = Molecular cloning of a putative Ca(2+)-sensing receptor cDNA from human kidney | journal = Biochemical and Biophysical Research Communications | volume = 214 | issue = 2 | pages = 524–529 | date = September 1995 | pmid = 7677761 | doi = 10.1006/bbrc.1995.2318 }}</ref>

== Structure ==
Each [[Protomer (structural biology)|protomer]] of the receptor has a large, N-terminal extracellular domain that linked to create VFT (Venus flytrap) domain. The receptor has a CR (cysteine-rich) domain that links the VFT to the 7 transmembrane domains of the receptor. The 7 transmembrane domain is followed by a long cytoplasmatic tail. The tail has no structure, but still, it has an important role in trafficking and phosphorylation.<ref>{{cite journal | vauthors = Leach K, Hannan FM, Josephs TM, Keller AN, Møller TC, Ward DT, Kallay E, Mason RS, Thakker RV, Riccardi D, Conigrave AD, Bräuner-Osborne H | title = International Union of Basic and Clinical Pharmacology. CVIII. Calcium-Sensing Receptor Nomenclature, Pharmacology, and Function | journal = Pharmacological Reviews | volume = 72 | issue = 3 | pages = 558–604 | date = July 2020 | pmid = 32467152 | pmc = 7116503 | doi = 10.1124/pr.119.018531 }}</ref>

The CaSR is a homodimer receptor. The signal transmission occurs only when the agonist binds to the homodimer of the CaSR. Binding of a single protomer will not lead to signal transmission. In vitro experiments showed that the receptor can form a heterodimer with mGlu1/5 or with [[GABAB receptor]]. The heterodimerization may facilitate the varied functional roles of the CaSR in different tissues, particularly in the brain.

The CryoEM structures of CasR homodimer was recently solved

=== Extracellular domain ===
The VFT extends outside the cell and is composed of two lobe subdomains. Each lobe forms part of the ligand binding cleft.

In contrast to the conservative structure of other class C GPCR receptors, the CaSR cleft is an allosteric or co-agonist binding site, with the cations (Ca<sup>2+</sup>) binding elsewhere.

The inactive state of the receptor has two extracellular domains, oriented in an open conformation with an empty intradomain part. When the receptor is activated, the two lobes interact with each other and creates a rotation of the interdomain cleft.<ref name="Geng_2016">{{cite journal | vauthors = Geng Y, Mosyak L, Kurinov I, Zuo H, Sturchler E, Cheng TC, Subramanyam P, Brown AP, Brennan SC, Mun HC, Bush M, Chen Y, Nguyen TX, Cao B, Chang DD, Quick M, Conigrave AD, Colecraft HM, McDonald P, Fan QR | title = Structural mechanism of ligand activation in human calcium-sensing receptor | journal = eLife | volume = 5 | pages = e13662 | date = July 2016 | pmid = 27434672 | pmc = 4977154 | doi = 10.7554/eLife.13662 | doi-access = free | veditors = Isacoff EY }}</ref>

==== Cation binding sites ====
The cation binding sites varied in their location and in the number of repetitive appearances.<ref name="Geng_2016" />

The receptor has four Calcium binding sites that have a role in the stabilization<ref name="Geng_2016" /> of the extracellular domain (ECD) and in the activation of the receptor. The stabilization maintains the receptor in its active conformation.

Calcium cations bind to the first Calcium binding site in the inactive conformation. In the second binding site, Calcium cations are bound to both the active and inactive structures. In the third binding Site, the binding of the calcium facilitates the closure of lobe 1 and 2. This closure permits the interaction between the two lobes. The fourth binding site is located on lobe 2 in a place close to the CR domain. The agonist binding to the fourth binding site leads formation of homodimer interface bridge. This bridge between lobe 2 domain of subunit 1 and the CR domain of subunit 2, stabilize the open conformation.

The order of Calcium binding affinity to four of the bindings sites is as follows: 1 = 2 > 3 > 4. The lower affinity of Calcium to site 4 indicates that the receptor is activated only when the calcium concentration is elevated above the required concentration. That behavior makes the binding of calcium at site 4 to hold a major role in stabilization.

The CaSR also has binding sites for Magnesium and [[Gadolinium]].

==== Anion binding sites ====
There are four anion binding sites in the ECD. Sites 1-3 are occupied in the inactive structure, whereas in the active structure only sites 2 and 4 are occupied.

=== 7-Transmembrane domain ===
Based on a similarity of CaSR to mGlu5, it is believed that in the inactivated form of the receptor, the VFT domain disrupts the interface between the 7TM domains, and the activation of the receptor force a reorientation of the 7TM domains.<ref>{{cite journal | vauthors = Koehl A, Hu H, Feng D, Sun B, Zhang Y, Robertson MJ, Chu M, Kobilka TS, Laeremans T, Steyaert J, Tarrasch J, Dutta S, Fonseca R, Weis WI, Mathiesen JM, Skiniotis G, Kobilka BK | title = Structural insights into the activation of metabotropic glutamate receptors | journal = Nature | volume = 566 | issue = 7742 | pages = 79–84 | date = February 2019 | pmid = 30675062 | pmc = 6709600 | doi = 10.1038/s41586-019-0881-4 | bibcode = 2019Natur.566...79K }}</ref>


==Signal transduction==
==Signal transduction==
The inactivated form of the receptor has an open conformation. upon binding of the fourth binding site, the structure of the receptor changes to a close conformation. The change in the structure conformation leads to inhibition of PTH release.
The release of PTH is inhibited in response to elevations in plasma calcium concentrations and activation of the calcium receptor. Decreased calcium binding on the extracellular side gives a conformation change in the receptor, which, on the intracellular side, initiates the [[phospholipase C pathway]],<ref>[http://www.ebi.ac.uk/interpro/IEntry?ac=IPR000068 InterPro: IPR000068 GPCR, family 3, extracellular calcium-sensing receptor-related] Retrieved on June 2, 2009</ref><ref name=coburn> {{cite journal |author=Coburn JW, Elangovan L, Goodman WG, Frazaõ JM |title=Calcium-sensing receptor and calcimimetic agents |journal=Kidney Int. Suppl. |volume=73 |issue= |pages=S52–8 |year=1999 |month=December |pmid=10633465 |doi= |url=}}</ref> presumably through a [[Gq alpha subunit|G<sub>qα</sub> type of G protein]], which ultimately increases intracellular concentration of calcium, which triggers [[vesicle fusion]] and exocytosis of parathyroid hormone. It also inhibits (not stimulates, as some<ref name=brs>{{cite book

| last = Costanzo
On the intracellular side, initiates the [[phospholipase C pathway]],<ref>[http://www.ebi.ac.uk/interpro/IEntry?ac=IPR000068 InterPro: IPR000068 GPCR, family 3, extracellular calcium-sensing receptor-related] Retrieved on June 2, 2009</ref><ref name="coburn">{{cite journal | vauthors = Coburn JW, Elangovan L, Goodman WG, Frazaõ JM | title = Calcium-sensing receptor and calcimimetic agents | journal = Kidney International. Supplement | volume = 73 | pages = S52–S58 | date = December 1999 | pmid = 10633465 | doi = 10.1046/j.1523-1755.1999.07303.x | doi-access = free }}</ref> presumably through a [[Gq alpha subunit|G<sub>qα</sub> type of G protein]], which ultimately increases intracellular concentration of calcium, which inhibits [[vesicle fusion]] and exocytosis of parathyroid hormone. It also inhibits (not stimulates, as some<ref name="brs">{{cite book | vauthors = Costanzo LS | title = BRS Physiology (Board Review Series) | year = 2007 | pages = [https://archive.org/details/physiology00cost_0/page/260 260] | publisher = Lippincott Williams & Wilkins | url = https://archive.org/details/physiology00cost_0/page/260 | isbn = 978-0-7817-7311-9 | url-access = registration }}</ref> sources state) the [[cAMP dependent pathway]].<ref name="coburn" />
| first = Linda S.

| authorlink =
=== Ligands ===
| coauthors =

| title = BRS Physiology
==== Agonists ====
| publisher = Lippincott, Williams, & Wilkins

| date = 2007
* Calcium
| location =
* [[Spermine]]<ref name="Gregory_2018">{{cite journal | vauthors = Gregory KJ, Kufareva I, Keller AN, Khajehali E, Mun HC, Goolam MA, Mason RS, Capuano B, Conigrave AD, Christopoulos A, Leach K | title = Dual Action Calcium-Sensing Receptor Modulator Unmasks Novel Mode-Switching Mechanism | journal = ACS Pharmacology & Translational Science | volume = 1 | issue = 2 | pages = 96–109 | date = November 2018 | pmid = 32219206 | pmc = 7089027 | doi = 10.1021/acsptsci.8b00021 }}</ref>
| pages = 260
* [[Neomycin]]<ref>{{cite journal | vauthors = McLarnon SJ, Riccardi D | title = Physiological and pharmacological agonists of the extracellular Ca2+-sensing receptor | journal = European Journal of Pharmacology | volume = 447 | issue = 2–3 | pages = 271–278 | date = July 2002 | pmid = 12151018 | doi = 10.1016/S0014-2999(02)01849-6 | series = Ca2+ and Neuronal Pathology }}</ref>
| url = http://www.amazon.com/Physiology-Board-Review-Linda-Costanzo/dp/0781773113/
* Vitamin D
| doi =

| id =
==== Positive allosteric modulators ====
| isbn = 978-0781773119}}</ref> sources state) the [[cAMP dependent pathway]].<ref name=coburn/>

* Gamma-Glutamyl peptides
* L- amino acids
* [[Cinacalcet]]
* [[Evocalcet]]
* NPS R-568
* NPS R-467
* [[Etelcalcetide]]
* Calhex 231

==== Antagonists ====

* Calcilytics
* Phosphate<ref>{{cite journal | vauthors = Centeno PP, Herberger A, Mun HC, Tu C, Nemeth EF, Chang W, Conigrave AD, Ward DT | title = Phosphate acts directly on the calcium-sensing receptor to stimulate parathyroid hormone secretion | journal = Nature Communications | volume = 10 | issue = 1 | pages = 4693 | date = October 2019 | pmid = 31619668 | pmc = 6795806 | doi = 10.1038/s41467-019-12399-9 | bibcode = 2019NatCo..10.4693C }}</ref>

==== Negative allosteric modulators ====

* NPS 2143
* Ronacaleret
* Calhex 231

It is unknown whether Ca<sup>2+</sup> alone can activate the receptor, but L-amino acids and g-Glutamyl peptides are shown to act as co-activator of the receptor. Those molecules intensify the intracellular responses evoked by Calcium cation.<ref>{{cite journal | vauthors = Zhang C, Zhuo Y, Moniz HA, Wang S, Moremen KW, Prestegard JH, Brown EM, Yang JJ | title = Direct determination of multiple ligand interactions with the extracellular domain of the calcium-sensing receptor | journal = The Journal of Biological Chemistry | volume = 289 | issue = 48 | pages = 33529–33542 | date = November 2014 | pmid = 25305020 | pmc = 4246106 | doi = 10.1074/jbc.m114.604652 | doi-access = free }}</ref>


==Pathology==
==Pathology==
Mutations that inactivate CASR cause '''familial hypocalciuric [[hypercalcemia]]''' (FHH) (also known as [[familial benign hypercalcemia]] because it is generally asymptomatic and does not require treatment),<ref name="pmid15879434">{{cite journal | author = Pidasheva S, Canaff L, Simonds WF, Marx SJ, Hendy GN | title = Impaired cotranslational processing of the calcium-sensing receptor due to signal peptide missense mutations in familial hypocalciuric hypercalcemia | journal = Hum. Mol. Genet. | volume = 14 | issue = 12 | pages = 1679–90 | year = 2005 | pmid = 15879434 | doi = 10.1093/hmg/ddi176 | issn = }}</ref> whereas mutations that activate CASR are the cause of autosomal dominant [[hypocalcemia]]<ref name="pmid9719629">{{cite journal | author = Mancilla EE, De Luca F, Baron J | title = Activating mutations of the Ca<sup>2+</sup>-sensing receptor | journal = Mol. Genet. Metab. | volume = 64 | issue = 3 | pages = 198–204 | year = 1998 | pmid = 9719629 | doi = 10.1006/mgme.1998.2716 | issn = }}</ref> or Type 5 [[Bartter syndrome]]. An [[alternative splicing|alternatively spliced]] transcript variant encoding 1088 aa has been found for this gene, but its full-length nature has not been defined.<ref>{{cite web | title = Entrez Gene: CASR calcium-sensing receptor (hypocalciuric hypercalcemia 1, severe neonatal hyperparathyroidism)| url = http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=846| accessdate = }}</ref>
Mutations that inactivate a CaSR gene cause [[familial hypocalciuric hypercalcemia]] (FHH) (also known as familial benign hypercalcemia because it is generally asymptomatic and does not require treatment),<ref name="pmid15879434">{{cite journal | vauthors = Pidasheva S, Canaff L, Simonds WF, Marx SJ, Hendy GN | title = Impaired cotranslational processing of the calcium-sensing receptor due to signal peptide missense mutations in familial hypocalciuric hypercalcemia | journal = Human Molecular Genetics | volume = 14 | issue = 12 | pages = 1679–1690 | date = June 2005 | pmid = 15879434 | doi = 10.1093/hmg/ddi176 | doi-access = free }}</ref> when present in [[Zygosity#Heterozygous|heterozygotes]]. Patients who are [[Zygosity#Homozygous|homozygous]] for CaSR inactivating mutations have more severe hypercalcemia.<ref>{{cite journal | vauthors = Egbuna OI, Brown EM | title = Hypercalcaemic and hypocalcaemic conditions due to calcium-sensing receptor mutations | journal = Best Practice & Research. Clinical Rheumatology | volume = 22 | issue = 1 | pages = 129–148 | date = March 2008 | pmid = 18328986 | pmc = 2364635 | doi = 10.1016/j.berh.2007.11.006 }}</ref> Other mutations that activate CaSR are the cause of autosomal dominant [[hypocalcemia]]<ref name="pmid9719629">{{cite journal | vauthors = Mancilla EE, De Luca F, Baron J | title = Activating mutations of the Ca2+-sensing receptor | journal = Molecular Genetics and Metabolism | volume = 64 | issue = 3 | pages = 198–204 | date = July 1998 | pmid = 9719629 | doi = 10.1006/mgme.1998.2716 }}</ref> or Type 5 [[Bartter syndrome]]. An [[alternative splicing|alternatively spliced]] transcript variant encoding 1088 aa has been found for this gene, but its full-length nature has not been defined.<ref>{{cite web | title = Entrez Gene: CaSR calcium-sensing receptor (hypocalciuric hypercalcemia 1, severe neonatal hyperparathyroidism)| url = https://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=846}}</ref>

=== Role in Chronic kidney disease ===
In [[Chronic kidney disease|CKD]], the dysregulation of CaSR leads to a secondary hyperparathyroidism linked with osteoporosis, which considered as one of the main complications.

Patients suffers from secondary hyperparathyroidism require to make changes in their diet in order to balance the disease.<ref>{{cite journal | vauthors = Ikizler TA, Burrowes JD, Byham-Gray LD, Campbell KL, Carrero JJ, Chan W, Fouque D, Friedman AN, Ghaddar S, Goldstein-Fuchs DJ, Kaysen GA, Kopple JD, Teta D, Yee-Moon Wang A, Cuppari L | title = KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update | journal = American Journal of Kidney Diseases | volume = 76 | issue = 3 Suppl 1 | pages = S1–S107 | date = September 2020 | pmid = 32829751 | doi = 10.1053/j.ajkd.2020.05.006 | doi-access = free }}</ref> The diet recommendation includes restriction of Calcium, phosphate, and protein intake. Those nutrients are abundance in our diet and because of that, avoiding foods that contains those nutrients may limit our dietary options and can lead to other nutrients deficiencies.


==Therapeutic application==
==Therapeutic application==
The drug [[cinacalcet]] is an [[allosteric]] modifier of the calcium-sensing receptor.<ref name="pmid16825031">{{cite journal | author = Torres PU | title = Cinacalcet HCl: a novel treatment for secondary hyperparathyroidism caused by chronic kidney disease | journal = Journal of renal nutrition : the official journal of the Council on Renal Nutrition of the National Kidney Foundation | volume = 16 | issue = 3 | pages = 253–8 | year = 2006 | pmid = 16825031 | doi = 10.1053/j.jrn.2006.04.010 | issn = }}</ref> It is classified as a calcimimetic, which binds to the calcium-sensing receptor and decreases parathyroid hormone release.
The drugs [[cinacalcet]] and [[etelcalcetide]] are [[allosteric]] modifiers of the calcium-sensing receptor.<ref name="pmid16825031">{{cite journal | vauthors = Torres PU | title = Cinacalcet HCl: a novel treatment for secondary hyperparathyroidism caused by chronic kidney disease | journal = Journal of Renal Nutrition | volume = 16 | issue = 3 | pages = 253–258 | date = July 2006 | pmid = 16825031 | doi = 10.1053/j.jrn.2006.04.010 }}</ref> They are classified as a [[calcimimetic]]s, binding to the calcium-sensing receptor and decreasing parathyroid hormone release.


[[Calcilytic]] drugs, which block CaSR, produce increased bone density in animal studies and have been researched for the treatment of [[osteoporosis]]. Unfortunately clinical trial results in humans have proved disappointing, with sustained changes in bone density not observed despite the drug being well tolerated.<ref>{{cite journal | vauthors = Nemeth EF, Shoback D | title = Calcimimetic and calcilytic drugs for treating bone and mineral-related disorders | journal = Best Practice & Research. Clinical Endocrinology & Metabolism | volume = 27 | issue = 3 | pages = 373–384 | date = June 2013 | pmid = 23856266 | doi = 10.1016/j.beem.2013.02.008 }}</ref><ref>{{cite journal | vauthors = John MR, Harfst E, Loeffler J, Belleli R, Mason J, Bruin GJ, Seuwen K, Klickstein LB, Mindeholm L, Widler L, Kneissel M | title = AXT914 a novel, orally-active parathyroid hormone-releasing drug in two early studies of healthy volunteers and postmenopausal women | journal = Bone | volume = 64 | pages = 204–210 | date = July 2014 | pmid = 24769332 | doi = 10.1016/j.bone.2014.04.015 }}</ref> More recent research has shown the CaSR receptor to be involved in numerous other conditions including [[Alzheimer's disease]], [[asthma]] and some forms of [[cancer]],<ref>{{cite journal | vauthors = Kim JY, Ho H, Kim N, Liu J, Tu CL, Yenari MA, Chang W | title = Calcium-sensing receptor (CaSR) as a novel target for ischemic neuroprotection | journal = Annals of Clinical and Translational Neurology | volume = 1 | issue = 11 | pages = 851–866 | date = November 2014 | pmid = 25540800 | pmc = 4265057 | doi = 10.1002/acn3.118 }}</ref><ref>{{cite journal | vauthors = Aggarwal A, Prinz-Wohlgenannt M, Tennakoon S, Höbaus J, Boudot C, Mentaverri R, Brown EM, Baumgartner-Parzer S, Kállay E | title = The calcium-sensing receptor: A promising target for prevention of colorectal cancer | journal = Biochimica et Biophysica Acta (BBA) - Molecular Cell Research | volume = 1853 | issue = 9 | pages = 2158–2167 | date = September 2015 | pmid = 25701758 | pmc = 4549785 | doi = 10.1016/j.bbamcr.2015.02.011 }}</ref><ref name="ReferenceA">{{cite journal | vauthors = Dal Prà I, Chiarini A, Armato U | title = Antagonizing amyloid-β/calcium-sensing receptor signaling in human astrocytes and neurons: a key to halt Alzheimer's disease progression? | journal = Neural Regeneration Research | volume = 10 | issue = 2 | pages = 213–218 | date = February 2015 | pmid = 25883618 | pmc = 4392667 | doi = 10.4103/1673-5374.152373 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Yarova PL, Stewart AL, Sathish V, Britt RD, Thompson MA, P Lowe AP, Freeman M, Aravamudan B, Kita H, Brennan SC, Schepelmann M, Davies T, Yung S, Cholisoh Z, Kidd EJ, Ford WR, Broadley KJ, Rietdorf K, Chang W, Bin Khayat ME, Ward DT, Corrigan CJ, T Ward JP, Kemp PJ, Pabelick CM, Prakash YS, Riccardi D | title = Calcium-sensing receptor antagonists abrogate airway hyperresponsiveness and inflammation in allergic asthma | journal = Science Translational Medicine | volume = 7 | issue = 284 | pages = 284ra60 | date = April 2015 | pmid = 25904744 | pmc = 4725057 | doi = 10.1126/scitranslmed.aaa0282 }}</ref> and calcilytic drugs are being researched as potential treatments for these. Recently it has been shown that biomimetic bone like [[apatite]] inhibits formation of bone through [[endochondral ossification]] pathway via hyperstimulation of extracellular calcium sensing receptor.<ref>{{cite journal | vauthors = Sarem M, Heizmann M, Barbero A, Martin I, Shastri VP | title = Hyperstimulation of CaSR in human MSCs by biomimetic apatite inhibits endochondral ossification via temporal down-regulation of PTH1R | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 115 | issue = 27 | pages = E6135–E6144 | date = July 2018 | pmid = 29915064 | pmc = 6142224 | doi = 10.1073/pnas.1805159115 | doi-access = free | bibcode = 2018PNAS..115E6135S }}</ref>
==Interactions==
Calcium-sensing receptor has been shown to [[Protein-protein_interaction|interact]] with [[Filamin]].<ref name=pmid11390380>{{cite journal |last=Hjälm |first=G |authorlink= |coauthors=MacLeod R J, Kifor O, Chattopadhyay N, Brown E M |year=[[2001]]|month=Sep. |title=Filamin-A binds to the carboxyl-terminal tail of the calcium-sensing receptor, an interaction that participates in CaR-mediated activation of mitogen-activated protein kinase |journal=J. Biol. Chem. |volume=276 |issue=37 |pages=34880–7 |publisher= |location = United States| issn = 0021-9258| pmid = 11390380 |doi = 10.1074/jbc.M100784200 | bibcode = | oclc =| id = | url = | language = | format = | accessdate = | laysummary = | laysource = | laydate = | quote = }}</ref><ref name=pmid11390379>{{cite journal |last=Awata |first=H |authorlink= |coauthors=Huang C, Handlogten M E, Miller R T |year=[[2001]]|month=Sep. |title=Interaction of the calcium-sensing receptor and filamin, a potential scaffolding protein |journal=J. Biol. Chem. |volume=276 |issue=37 |pages=34871–9 |publisher= |location = United States| issn = 0021-9258| pmid = 11390379 |doi = 10.1074/jbc.M100775200 | bibcode = | oclc =| id = | url = | language = | format = | accessdate = | laysummary = | laysource = | laydate = | quote = }}</ref>


Transactivation across the dimer can result in unique pharmacology for CaSR allosteric modulators. For example, Calhex 231, which shows a positive allosteric activity when bound to the allosteric site in just one protomer. In contrast, it shows a negative allosteric activity when occupying both the allosteric sites of the dimer.<ref name="Gregory_2018" />
==References==

== Interactions ==
Calcium-sensing receptor has been shown to [[Protein-protein interaction|interact]] with [[filamin]].<ref name=pmid11390380>{{cite journal | vauthors = Hjälm G, MacLeod RJ, Kifor O, Chattopadhyay N, Brown EM | title = Filamin-A binds to the carboxyl-terminal tail of the calcium-sensing receptor, an interaction that participates in CaR-mediated activation of mitogen-activated protein kinase | journal = The Journal of Biological Chemistry | volume = 276 | issue = 37 | pages = 34880–34887 | date = September 2001 | pmid = 11390380 | doi = 10.1074/jbc.M100784200 | doi-access = free }}</ref><ref name=pmid11390379>{{cite journal | vauthors = Awata H, Huang C, Handlogten ME, Miller RT | title = Interaction of the calcium-sensing receptor and filamin, a potential scaffolding protein | journal = The Journal of Biological Chemistry | volume = 276 | issue = 37 | pages = 34871–34879 | date = September 2001 | pmid = 11390379 | doi = 10.1074/jbc.M100775200 | doi-access = free }}</ref>

== Role in sensory evaluation of food ==
Kokumi was discovered in Japan, 1989. It is defined as a sensation that enhances existing flavors and creates feelings of roundness, complexity, and richness in the mouth. The kokumi is present in different foods such as fish sauce, soybean, garlic, beans, etc.<ref name="Amino_2016">{{cite journal | vauthors = Amino Y, Nakazawa M, Kaneko M, Miyaki T, Miyamura N, Maruyama Y, Eto Y | title = Structure-CaSR-Activity Relation of Kokumi γ-Glutamyl Peptides | journal = Chemical & Pharmaceutical Bulletin | volume = 64 | issue = 8 | pages = 1181–1189 | date = 2016 | pmid = 27477658 | doi = 10.1248/cpb.c16-00293 | doi-access = free }}</ref> The Kokumi substances are Gamma-glutamyl peptides.

CaSR is known to be expressed in the parathyroid gland and kidneys, but recent experiments showed that the receptor is also expressed in the alimentary canal (known as the digestive tract) and the near the taste buds on the back of the tongue.<ref name="Ohsu_2010">{{cite journal | vauthors = Ohsu T, Amino Y, Nagasaki H, Yamanaka T, Takeshita S, Hatanaka T, Maruyama Y, Miyamura N, Eto Y | title = Involvement of the calcium-sensing receptor in human taste perception | journal = The Journal of Biological Chemistry | volume = 285 | issue = 2 | pages = 1016–1022 | date = January 2010 | pmid = 19892707 | pmc = 2801228 | doi = 10.1074/jbc.m109.029165 | doi-access = free }}</ref>

Gamma-glutamyl peptides are allosteric modulators of the CaSR, and the binding of those peptides to the CaSR on the tongue is what mediates the Kokumi sensation in the mouth.

In the mouth, unlike in other tissues, the influx of the extracellular Calcium does not affect the receptor activity. Instead, the activation of the CaSR is by the binding of the Gamma glutamine peptides.

Taste signal involves a release of intracellular calcium as respond to the molecule binding to the taste receptor, leads to secretion of neurotransmitter and taste perception. The simultaneous binding of gamma glutamine peptides to the CaSR increases the level of the intracellular calcium, and that intensify the taste perception.<ref name="Ohsu_2010" /><ref>{{cite journal | vauthors = Maruyama Y, Yasuda R, Kuroda M, Eto Y | title = Kokumi substances, enhancers of basic tastes, induce responses in calcium-sensing receptor expressing taste cells | journal = PLOS ONE | volume = 7 | issue = 4 | pages = e34489 | date = 2012-04-12 | pmid = 22511946 | pmc = 3325276 | doi = 10.1371/journal.pone.0034489 | doi-access = free | bibcode = 2012PLoSO...734489M }}</ref><ref name="Amino_2016" />

== References ==
{{Reflist|2}}
{{Reflist|2}}


==Further reading==
== Further reading ==
{{refbegin | 2}}
{{refbegin | 2}}
* {{cite journal | vauthors = Hendy GN, D'Souza-Li L, Yang B, Canaff L, Cole DE | title = Mutations of the calcium-sensing receptor (CASR) in familial hypocalciuric hypercalcemia, neonatal severe hyperparathyroidism, and autosomal dominant hypocalcemia | journal = Human Mutation | volume = 16 | issue = 4 | pages = 281–296 | date = October 2000 | pmid = 11013439 | doi = 10.1002/1098-1004(200010)16:4<281::AID-HUMU1>3.0.CO;2-A | s2cid = 31157004 | doi-access = free }}
{{PBB_Further_reading
* {{cite journal | vauthors = Fukumoto S | title = [Calcium-sensing receptor in bone cells] | journal = Nihon Rinsho. Japanese Journal of Clinical Medicine | volume = 60 Suppl 3 | issue = Suppl 3 | pages = 57–63 | date = March 2002 | pmid = 11979955 }}
| citations =
*{{cite journal | author=Hendy GN, D'Souza-Li L, Yang B, ''et al.'' |title=Mutations of the calcium-sensing receptor (CASR) in familial hypocalciuric hypercalcemia, neonatal severe hyperparathyroidism, and autosomal dominant hypocalcemia. |journal=Hum. Mutat. |volume=16 |issue= 4 |pages= 281–96 |year= 2000 |pmid= 11013439 |doi= 10.1002/1098-1004(200010)16:4<281::AID-HUMU1>3.0.CO;2-A }}
* {{cite journal | vauthors = Tfelt-Hansen J, Schwarz P, Brown EM, Chattopadhyay N | title = The calcium-sensing receptor in human disease | journal = Frontiers in Bioscience | volume = 8 | issue = 6 | pages = s377–s390 | date = May 2003 | pmid = 12700051 | doi = 10.2741/1068 | doi-access = free }}
*{{cite journal | author=Fukumoto S |title=[Calcium-sensing receptor in bone cells] |journal=Nippon Rinsho |volume=60 Suppl 3 |issue= |pages= 57–63 |year= 2002 |pmid= 11979955 |doi= }}
* {{cite journal | vauthors = Hu J, Spiegel AM | title = Naturally occurring mutations of the extracellular Ca2+-sensing receptor: implications for its structure and function | journal = Trends in Endocrinology and Metabolism | volume = 14 | issue = 6 | pages = 282–288 | date = August 2003 | pmid = 12890593 | doi = 10.1016/S1043-2760(03)00104-8 | s2cid = 28822680 }}
*{{cite journal | author=Tfelt-Hansen J, Schwarz P, Brown EM, Chattopadhyay N |title=The calcium-sensing receptor in human disease. |journal=Front. Biosci. |volume=8 |issue= |pages= s377–90 |year= 2004 |pmid= 12700051 |doi=10.2741/1068 }}
* {{cite journal | vauthors = Aida K, Koishi S, Inoue M, Nakazato M, Tawata M, Onaya T | title = Familial hypocalciuric hypercalcemia associated with mutation in the human Ca(2+)-sensing receptor gene | journal = The Journal of Clinical Endocrinology and Metabolism | volume = 80 | issue = 9 | pages = 2594–2598 | date = September 1995 | pmid = 7673400 | doi = 10.1210/jcem.80.9.7673400 }}
*{{cite journal | author=Hu J, Spiegel AM |title=Naturally occurring mutations of the extracellular Ca2+-sensing receptor: implications for its structure and function. |journal=Trends Endocrinol. Metab. |volume=14 |issue= 6 |pages= 282–8 |year= 2004 |pmid= 12890593 |doi= }}
* {{cite journal | vauthors = Aida K, Koishi S, Tawata M, Onaya T | title = Molecular cloning of a putative Ca(2+)-sensing receptor cDNA from human kidney | journal = Biochemical and Biophysical Research Communications | volume = 214 | issue = 2 | pages = 524–529 | date = September 1995 | pmid = 7677761 | doi = 10.1006/bbrc.1995.2318 }}
*{{cite journal | author=Aida K, Koishi S, Inoue M, ''et al.'' |title=Familial hypocalciuric hypercalcemia associated with mutation in the human Ca(2+)-sensing receptor gene. |journal=J. Clin. Endocrinol. Metab. |volume=80 |issue= 9 |pages= 2594–8 |year= 1995 |pmid= 7673400 |doi=10.1210/jc.80.9.2594 }}
* {{cite journal | vauthors = Chou YH, Pollak MR, Brandi ML, Toss G, Arnqvist H, Atkinson AB, Papapoulos SE, Marx S, Brown EM, Seidman JG | title = Mutations in the human Ca(2+)-sensing-receptor gene that cause familial hypocalciuric hypercalcemia | journal = American Journal of Human Genetics | volume = 56 | issue = 5 | pages = 1075–1079 | date = May 1995 | pmid = 7726161 | pmc = 1801464 }}
*{{cite journal | author=Aida K, Koishi S, Tawata M, Onaya T |title=Molecular cloning of a putative Ca(2+)-sensing receptor cDNA from human kidney. |journal=Biochem. Biophys. Res. Commun. |volume=214 |issue= 2 |pages= 524–9 |year= 1995 |pmid= 7677761 |doi= 10.1006/bbrc.1995.2318 }}
* {{cite journal | vauthors = Garrett JE, Capuano IV, Hammerland LG, Hung BC, Brown EM, Hebert SC, Nemeth EF, Fuller F | title = Molecular cloning and functional expression of human parathyroid calcium receptor cDNAs | journal = The Journal of Biological Chemistry | volume = 270 | issue = 21 | pages = 12919–12925 | date = May 1995 | pmid = 7759551 | doi = 10.1074/jbc.270.21.12919 | doi-access = free }}
*{{cite journal | author=Chou YH, Pollak MR, Brandi ML, ''et al.'' |title=Mutations in the human Ca(2+)-sensing-receptor gene that cause familial hypocalciuric hypercalcemia. |journal=Am. J. Hum. Genet. |volume=56 |issue= 5 |pages= 1075–9 |year= 1995 |pmid= 7726161 |doi= | pmc=1801464 }}
* {{cite journal | vauthors = Pollak MR, Brown EM, Estep HL, McLaine PN, Kifor O, Park J, Hebert SC, Seidman CE, Seidman JG | title = Autosomal dominant hypocalcaemia caused by a Ca(2+)-sensing receptor gene mutation | journal = Nature Genetics | volume = 8 | issue = 3 | pages = 303–307 | date = November 1994 | pmid = 7874174 | doi = 10.1038/ng1194-303 | s2cid = 22941518 }}
*{{cite journal | author=Garrett JE, Capuano IV, Hammerland LG, ''et al.'' |title=Molecular cloning and functional expression of human parathyroid calcium receptor cDNAs. |journal=J. Biol. Chem. |volume=270 |issue= 21 |pages= 12919–25 |year= 1995 |pmid= 7759551 |doi=10.1074/jbc.270.21.12919 }}
* {{cite journal | vauthors = Pollak MR, Brown EM, Chou YH, Hebert SC, Marx SJ, Steinmann B, Levi T, Seidman CE, Seidman JG | title = Mutations in the human Ca(2+)-sensing receptor gene cause familial hypocalciuric hypercalcemia and neonatal severe hyperparathyroidism | journal = Cell | volume = 75 | issue = 7 | pages = 1297–1303 | date = December 1993 | pmid = 7916660 | doi = 10.1016/0092-8674(93)90617-Y | s2cid = 40886966 }}
*{{cite journal | author=Pollak MR, Brown EM, Estep HL, ''et al.'' |title=Autosomal dominant hypocalcaemia caused by a Ca(2+)-sensing receptor gene mutation. |journal=Nat. Genet. |volume=8 |issue= 3 |pages= 303–7 |year= 1995 |pmid= 7874174 |doi= 10.1038/ng1194-303 }}
* {{cite journal | vauthors = Janicic N, Soliman E, Pausova Z, Seldin MF, Rivière M, Szpirer J, Szpirer C, Hendy GN | title = Mapping of the calcium-sensing receptor gene (CASR) to human chromosome 3q13.3-21 by fluorescence in situ hybridization, and localization to rat chromosome 11 and mouse chromosome 16 | journal = Mammalian Genome | volume = 6 | issue = 11 | pages = 798–801 | date = November 1995 | pmid = 8597637 | doi = 10.1007/BF00539007 | s2cid = 19835161 }}
*{{cite journal | author=Pollak MR, Brown EM, Chou YH, ''et al.'' |title=Mutations in the human Ca(2+)-sensing receptor gene cause familial hypocalciuric hypercalcemia and neonatal severe hyperparathyroidism. |journal=Cell |volume=75 |issue= 7 |pages= 1297–303 |year= 1994 |pmid= 7916660 |doi=10.1016/0092-8674(93)90617-Y }}
* {{cite journal | vauthors = Bikle DD, Ratnam A, Mauro T, Harris J, Pillai S | title = Changes in calcium responsiveness and handling during keratinocyte differentiation. Potential role of the calcium receptor | journal = The Journal of Clinical Investigation | volume = 97 | issue = 4 | pages = 1085–1093 | date = February 1996 | pmid = 8613532 | pmc = 507156 | doi = 10.1172/JCI118501 }}
*{{cite journal | author=Janicic N, Soliman E, Pausova Z, ''et al.'' |title=Mapping of the calcium-sensing receptor gene (CASR) to human chromosome 3q13.3-21 by fluorescence in situ hybridization, and localization to rat chromosome 11 and mouse chromosome 16. |journal=Mamm. Genome |volume=6 |issue= 11 |pages= 798–801 |year= 1996 |pmid= 8597637 |doi=10.1007/BF00539007 }}
* {{cite journal | vauthors = Pearce SH, Trump D, Wooding C, Besser GM, Chew SL, Grant DB, Heath DA, Hughes IA, Paterson CR, Whyte MP | title = Calcium-sensing receptor mutations in familial benign hypercalcemia and neonatal hyperparathyroidism | journal = The Journal of Clinical Investigation | volume = 96 | issue = 6 | pages = 2683–2692 | date = December 1995 | pmid = 8675635 | pmc = 185975 | doi = 10.1172/JCI118335 }}
*{{cite journal | author=Bikle DD, Ratnam A, Mauro T, ''et al.'' |title=Changes in calcium responsiveness and handling during keratinocyte differentiation. Potential role of the calcium receptor. |journal=J. Clin. Invest. |volume=97 |issue= 4 |pages= 1085–93 |year= 1996 |pmid= 8613532 |doi=10.1172/JCI118501 | pmc=507156 }}
* {{cite journal | vauthors = Bai M, Quinn S, Trivedi S, Kifor O, Pearce SH, Pollak MR, Krapcho K, Hebert SC, Brown EM | title = Expression and characterization of inactivating and activating mutations in the human Ca2+o-sensing receptor | journal = The Journal of Biological Chemistry | volume = 271 | issue = 32 | pages = 19537–19545 | date = August 1996 | pmid = 8702647 | doi = 10.1074/jbc.271.32.19537 | doi-access = free }}
*{{cite journal | author=Pearce SH, Trump D, Wooding C, ''et al.'' |title=Calcium-sensing receptor mutations in familial benign hypercalcemia and neonatal hyperparathyroidism. |journal=J. Clin. Invest. |volume=96 |issue= 6 |pages= 2683–92 |year= 1996 |pmid= 8675635 |doi=10.1172/JCI118335 | pmc=185975 }}
* {{cite journal | vauthors = Baron J, Winer KK, Yanovski JA, Cunningham AW, Laue L, Zimmerman D, Cutler GB | title = Mutations in the Ca(2+)-sensing receptor gene cause autosomal dominant and sporadic hypoparathyroidism | journal = Human Molecular Genetics | volume = 5 | issue = 5 | pages = 601–606 | date = May 1996 | pmid = 8733126 | doi = 10.1093/hmg/5.5.601 | doi-access = }}
*{{cite journal | author=Bai M, Quinn S, Trivedi S, ''et al.'' |title=Expression and characterization of inactivating and activating mutations in the human Ca2+o-sensing receptor. |journal=J. Biol. Chem. |volume=271 |issue= 32 |pages= 19537–45 |year= 1996 |pmid= 8702647 |doi=10.1074/jbc.271.32.19537 }}
* {{cite journal | vauthors = Freichel M, Zink-Lorenz A, Holloschi A, Hafner M, Flockerzi V, Raue F | title = Expression of a calcium-sensing receptor in a human medullary thyroid carcinoma cell line and its contribution to calcitonin secretion | journal = Endocrinology | volume = 137 | issue = 9 | pages = 3842–3848 | date = September 1996 | pmid = 8756555 | doi = 10.1210/endo.137.9.8756555 | doi-access = free }}
*{{cite journal | author=Baron J, Winer KK, Yanovski JA, ''et al.'' |title=Mutations in the Ca(2+)-sensing receptor gene cause autosomal dominant and sporadic hypoparathyroidism. |journal=Hum. Mol. Genet. |volume=5 |issue= 5 |pages= 601–6 |year= 1997 |pmid= 8733126 |doi=10.1093/hmg/5.5.601 }}
* {{cite journal | vauthors = Chattopadhyay N, Ye C, Singh DP, Kifor O, Vassilev PM, Shinohara T, Chylack LT, Brown EM | title = Expression of extracellular calcium-sensing receptor by human lens epithelial cells | journal = Biochemical and Biophysical Research Communications | volume = 233 | issue = 3 | pages = 801–805 | date = April 1997 | pmid = 9168937 | doi = 10.1006/bbrc.1997.6553 }}
*{{cite journal | author=Freichel M, Zink-Lorenz A, Holloschi A, ''et al.'' |title=Expression of a calcium-sensing receptor in a human medullary thyroid carcinoma cell line and its contribution to calcitonin secretion. |journal=Endocrinology |volume=137 |issue= 9 |pages= 3842–8 |year= 1996 |pmid= 8756555 |doi=10.1210/en.137.9.3842 }}
* {{cite journal | vauthors = Cole DE, Janicic N, Salisbury SR, Hendy GN | title = Neonatal severe hyperparathyroidism, secondary hyperparathyroidism, and familial hypocalciuric hypercalcemia: multiple different phenotypes associated with an inactivating Alu insertion mutation of the calcium-sensing receptor gene | journal = American Journal of Medical Genetics | volume = 71 | issue = 2 | pages = 202–210 | date = August 1997 | pmid = 9217223 | doi = 10.1002/(SICI)1096-8628(19970808)71:2<202::AID-AJMG16>3.0.CO;2-I }}
*{{cite journal | author=Chattopadhyay N, Ye C, Singh DP, ''et al.'' |title=Expression of extracellular calcium-sensing receptor by human lens epithelial cells. |journal=Biochem. Biophys. Res. Commun. |volume=233 |issue= 3 |pages= 801–5 |year= 1997 |pmid= 9168937 |doi= 10.1006/bbrc.1997.6553 }}
* {{cite journal | vauthors = Ward BK, Stuckey BG, Gutteridge DH, Laing NG, Pullan PT, Ratajczak T | title = A novel mutation (L174R) in the Ca2+-sensing receptor gene associated with familial hypocalciuric hypercalcemia | journal = Human Mutation | volume = 10 | issue = 3 | pages = 233–235 | year = 1997 | pmid = 9298824 | doi = 10.1002/(SICI)1098-1004(1997)10:3<233::AID-HUMU9>3.0.CO;2-J | s2cid = 34382961 | doi-access = free }}
*{{cite journal | author=Cole DE, Janicic N, Salisbury SR, Hendy GN |title=Neonatal severe hyperparathyroidism, secondary hyperparathyroidism, and familial hypocalciuric hypercalcemia: multiple different phenotypes associated with an inactivating Alu insertion mutation of the calcium-sensing receptor gene. |journal=Am. J. Med. Genet. |volume=71 |issue= 2 |pages= 202–10 |year= 1997 |pmid= 9217223 |doi=10.1002/(SICI)1096-8628(19970808)71:2<202::AID-AJMG16>3.0.CO;2-I }}
* {{cite journal | vauthors = Quinn SJ, Kifor O, Trivedi S, Diaz R, Vassilev P, Brown E | title = Sodium and ionic strength sensing by the calcium receptor | journal = The Journal of Biological Chemistry | volume = 273 | issue = 31 | pages = 19579–19586 | date = July 1998 | pmid = 9677383 | doi = 10.1074/jbc.273.31.19579 | doi-access = free }}
*{{cite journal | author=Ward BK, Stuckey BG, Gutteridge DH, ''et al.'' |title=A novel mutation (L174R) in the Ca2+-sensing receptor gene associated with familial hypocalciuric hypercalcemia. |journal=Hum. Mutat. |volume=10 |issue= 3 |pages= 233–5 |year= 1997 |pmid= 9298824 |doi= 10.1002/(SICI)1098-1004(1997)10:3<233::AID-HUMU9>3.0.CO;2-J }}
* {{cite journal | vauthors = Magno AL, Ward BK, Ratajczak T | title = The calcium-sensing receptor: a molecular perspective | journal = Endocrine Reviews | volume = 32 | issue = 1 | pages = 3–30 | date = February 2011 | pmid = 20729338 | doi = 10.1210/er.2009-0043 | doi-access = free }}
*{{cite journal | author=Quinn SJ, Kifor O, Trivedi S, ''et al.'' |title=Sodium and ionic strength sensing by the calcium receptor. |journal=J. Biol. Chem. |volume=273 |issue= 31 |pages= 19579–86 |year= 1998 |pmid= 9677383 |doi=10.1074/jbc.273.31.19579 }}
}}
{{refend}}
{{refend}}


==External links==
== External links ==
* {{cite web | url = http://www.iuphar-db.org/GPCR/ChapterMenuForward?chapterID=1322 | title = Calcium-Sensing Receptors | accessdate = | author = | authorlink = | coauthors = | date = | format = | work = IUPHAR Database of Receptors and Ion Channels | publisher = International Union of Basic and Clinical Pharmacology | pages = | language = | archiveurl = | archivedate = | quote = }}
* {{cite web | url = http://www.iuphar-db.org/GPCR/ChapterMenuForward?chapterID=1322 | title = Calcium-Sensing Receptors | work = IUPHAR Database of Receptors and Ion Channels | publisher = International Union of Basic and Clinical Pharmacology | access-date = 2007-10-25 | archive-date = 2016-03-03 | archive-url = https://web.archive.org/web/20160303203259/http://www.iuphar-db.org/GPCR/ChapterMenuForward?chapterID=1322 | url-status = dead }}
* [http://www.casrdb.mcgill.ca/ CASRdb - Calcium Sensing Receptor Database], [[McGill University]]
* [http://www.casrdb.mcgill.ca/ CASRdb - Calcium Sensing Receptor Database], [[McGill University]]
*{{MeshName|Receptors,+Calcium-Sensing}}
*{{MeshName|Receptors,+Calcium-Sensing}}
*{{MeshName|CASR+protein}}
*{{MeshName|CASR+protein}}


{{G protein-coupled receptors|g3}}
{{transmembranereceptor-stub}}
{{G protein-coupled receptors}}
[[Category:G protein coupled receptors]]

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[[Category:G protein-coupled receptors]]
[[de:Calciumsensitiver Rezeptor]]
[[es:Receptor sensor de calcio]]
[[he:קולטן לסידן]]
[[ja:カルシウム感知受容体]]

Latest revision as of 20:22, 27 August 2024

CASR
Available structures
PDBOrtholog search: PDBe RCSB
Identifiers
AliasesCASR, CAR, EIG8, FHH, FIH, GPRC2A, HHC, HHC1, HYPOC1, NSHPT, PCAR1, calcium sensing receptor, hCasR, Calcium-sensing receptor+CaSR
External IDsOMIM: 601199; MGI: 1351351; HomoloGene: 332; GeneCards: CASR; OMA:CASR - orthologs
Orthologs
SpeciesHumanMouse
Entrez
Ensembl
UniProt
RefSeq (mRNA)

NM_000388
NM_001178065

NM_013803

RefSeq (protein)

NP_000379
NP_001171536

NP_038831

Location (UCSC)Chr 3: 122.18 – 122.29 MbChr 16: 36.31 – 36.38 Mb
PubMed search[3][4]
Wikidata
View/Edit HumanView/Edit Mouse

The calcium-sensing receptor (CaSR) is a Class C G-protein coupled receptor which senses extracellular levels of calcium ions. It is primarily expressed in the parathyroid gland, the renal tubules of the kidney and the brain.[5][6] In the parathyroid gland, it controls calcium homeostasis by regulating the release of parathyroid hormone (PTH).[7] In the kidney it has an inhibitory effect on the reabsorption of calcium, potassium, sodium, and water depending on which segment of the tubule is being activated.[8]

Since the initial review of CaSR,[9] there has been in-depth analysis of its role related to parathyroid disease and other roles related to tissues and organs in the body. 1993, Brown et al.[10] isolated a clone named BoPCaR (bovine parathyroid calcium receptor) which replicated the effect when introduced to polyvalent cations. Because of this, the ability to clone full-length CaSRs from mammals were performed.[11]

Structure

[edit]

Each protomer of the receptor has a large, N-terminal extracellular domain that linked to create VFT (Venus flytrap) domain. The receptor has a CR (cysteine-rich) domain that links the VFT to the 7 transmembrane domains of the receptor. The 7 transmembrane domain is followed by a long cytoplasmatic tail. The tail has no structure, but still, it has an important role in trafficking and phosphorylation.[12]

The CaSR is a homodimer receptor. The signal transmission occurs only when the agonist binds to the homodimer of the CaSR. Binding of a single protomer will not lead to signal transmission. In vitro experiments showed that the receptor can form a heterodimer with mGlu1/5 or with GABAB receptor. The heterodimerization may facilitate the varied functional roles of the CaSR in different tissues, particularly in the brain.

The CryoEM structures of CasR homodimer was recently solved

Extracellular domain

[edit]

The VFT extends outside the cell and is composed of two lobe subdomains. Each lobe forms part of the ligand binding cleft.

In contrast to the conservative structure of other class C GPCR receptors, the CaSR cleft is an allosteric or co-agonist binding site, with the cations (Ca2+) binding elsewhere.

The inactive state of the receptor has two extracellular domains, oriented in an open conformation with an empty intradomain part. When the receptor is activated, the two lobes interact with each other and creates a rotation of the interdomain cleft.[13]

Cation binding sites

[edit]

The cation binding sites varied in their location and in the number of repetitive appearances.[13]

The receptor has four Calcium binding sites that have a role in the stabilization[13] of the extracellular domain (ECD) and in the activation of the receptor. The stabilization maintains the receptor in its active conformation.

Calcium cations bind to the first Calcium binding site in the inactive conformation. In the second binding site, Calcium cations are bound to both the active and inactive structures. In the third binding Site, the binding of the calcium facilitates the closure of lobe 1 and 2. This closure permits the interaction between the two lobes. The fourth binding site is located on lobe 2 in a place close to the CR domain. The agonist binding to the fourth binding site leads formation of homodimer interface bridge. This bridge between lobe 2 domain of subunit 1 and the CR domain of subunit 2, stabilize the open conformation.

The order of Calcium binding affinity to four of the bindings sites is as follows: 1 = 2 > 3 > 4. The lower affinity of Calcium to site 4 indicates that the receptor is activated only when the calcium concentration is elevated above the required concentration. That behavior makes the binding of calcium at site 4 to hold a major role in stabilization.

The CaSR also has binding sites for Magnesium and Gadolinium.

Anion binding sites

[edit]

There are four anion binding sites in the ECD. Sites 1-3 are occupied in the inactive structure, whereas in the active structure only sites 2 and 4 are occupied.

7-Transmembrane domain

[edit]

Based on a similarity of CaSR to mGlu5, it is believed that in the inactivated form of the receptor, the VFT domain disrupts the interface between the 7TM domains, and the activation of the receptor force a reorientation of the 7TM domains.[14]

Signal transduction

[edit]

The inactivated form of the receptor has an open conformation. upon binding of the fourth binding site, the structure of the receptor changes to a close conformation. The change in the structure conformation leads to inhibition of PTH release.

On the intracellular side, initiates the phospholipase C pathway,[15][16] presumably through a G type of G protein, which ultimately increases intracellular concentration of calcium, which inhibits vesicle fusion and exocytosis of parathyroid hormone. It also inhibits (not stimulates, as some[17] sources state) the cAMP dependent pathway.[16]

Ligands

[edit]

Agonists

[edit]

Positive allosteric modulators

[edit]

Antagonists

[edit]
  • Calcilytics
  • Phosphate[20]

Negative allosteric modulators

[edit]
  • NPS 2143
  • Ronacaleret
  • Calhex 231

It is unknown whether Ca2+ alone can activate the receptor, but L-amino acids and g-Glutamyl peptides are shown to act as co-activator of the receptor. Those molecules intensify the intracellular responses evoked by Calcium cation.[21]

Pathology

[edit]

Mutations that inactivate a CaSR gene cause familial hypocalciuric hypercalcemia (FHH) (also known as familial benign hypercalcemia because it is generally asymptomatic and does not require treatment),[22] when present in heterozygotes. Patients who are homozygous for CaSR inactivating mutations have more severe hypercalcemia.[23] Other mutations that activate CaSR are the cause of autosomal dominant hypocalcemia[24] or Type 5 Bartter syndrome. An alternatively spliced transcript variant encoding 1088 aa has been found for this gene, but its full-length nature has not been defined.[25]

Role in Chronic kidney disease

[edit]

In CKD, the dysregulation of CaSR leads to a secondary hyperparathyroidism linked with osteoporosis, which considered as one of the main complications.

Patients suffers from secondary hyperparathyroidism require to make changes in their diet in order to balance the disease.[26] The diet recommendation includes restriction of Calcium, phosphate, and protein intake. Those nutrients are abundance in our diet and because of that, avoiding foods that contains those nutrients may limit our dietary options and can lead to other nutrients deficiencies.

Therapeutic application

[edit]

The drugs cinacalcet and etelcalcetide are allosteric modifiers of the calcium-sensing receptor.[27] They are classified as a calcimimetics, binding to the calcium-sensing receptor and decreasing parathyroid hormone release.

Calcilytic drugs, which block CaSR, produce increased bone density in animal studies and have been researched for the treatment of osteoporosis. Unfortunately clinical trial results in humans have proved disappointing, with sustained changes in bone density not observed despite the drug being well tolerated.[28][29] More recent research has shown the CaSR receptor to be involved in numerous other conditions including Alzheimer's disease, asthma and some forms of cancer,[30][31][32][33] and calcilytic drugs are being researched as potential treatments for these. Recently it has been shown that biomimetic bone like apatite inhibits formation of bone through endochondral ossification pathway via hyperstimulation of extracellular calcium sensing receptor.[34]

Transactivation across the dimer can result in unique pharmacology for CaSR allosteric modulators. For example, Calhex 231, which shows a positive allosteric activity when bound to the allosteric site in just one protomer. In contrast, it shows a negative allosteric activity when occupying both the allosteric sites of the dimer.[18]

Interactions

[edit]

Calcium-sensing receptor has been shown to interact with filamin.[35][36]

Role in sensory evaluation of food

[edit]

Kokumi was discovered in Japan, 1989. It is defined as a sensation that enhances existing flavors and creates feelings of roundness, complexity, and richness in the mouth. The kokumi is present in different foods such as fish sauce, soybean, garlic, beans, etc.[37] The Kokumi substances are Gamma-glutamyl peptides.

CaSR is known to be expressed in the parathyroid gland and kidneys, but recent experiments showed that the receptor is also expressed in the alimentary canal (known as the digestive tract) and the near the taste buds on the back of the tongue.[38]

Gamma-glutamyl peptides are allosteric modulators of the CaSR, and the binding of those peptides to the CaSR on the tongue is what mediates the Kokumi sensation in the mouth.

In the mouth, unlike in other tissues, the influx of the extracellular Calcium does not affect the receptor activity. Instead, the activation of the CaSR is by the binding of the Gamma glutamine peptides.

Taste signal involves a release of intracellular calcium as respond to the molecule binding to the taste receptor, leads to secretion of neurotransmitter and taste perception. The simultaneous binding of gamma glutamine peptides to the CaSR increases the level of the intracellular calcium, and that intensify the taste perception.[38][39][37]

References

[edit]
  1. ^ a b c GRCh38: Ensembl release 89: ENSG00000036828Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000051980Ensembl, May 2017
  3. ^ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  4. ^ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
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