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Yang R, Ji CL, Zhang M, Zhang J, Yuan HJ, Luo MJ, Jiao GZ, Tan JH. Role of calcium-sensing receptor in regulating activation susceptibility of postovulatory aging mouse oocytes. J Reprod Dev 2023; 69:185-191. [PMID: 37245986 PMCID: PMC10435528 DOI: 10.1262/jrd.2023-026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Accepted: 05/02/2023] [Indexed: 05/30/2023] Open
Abstract
The mechanisms underlying postovulatory oocyte aging (POA) remain largely unknown. The expression of the calcium-sensing receptor (CaSR) in mouse oocytes and its role in POA need to be explored. Our objective was to observe CaSR expression and its role in the susceptibility to activating stimuli (STAS) in POA mouse oocytes. The results showed that, although none of the newly ovulated oocytes were activated, 40% and 94% of the oocytes recovered 19 and 25 h after human chorionic gonadotropin (hCG) injection were activated, respectively, after ethanol treatment. The level of the CaSR functional dimer protein in oocytes increased significantly from 13 to 25 h post hCG. Thus, the CaSR functional dimer level was positively correlated with the STAS of POA oocytes. Aging in vitro with a CaSR antagonist suppressed the elevation of STAS, and cytoplasmic calcium in oocytes recovered 19 h post hCG, whereas aging with a CaSR agonist increased STAS, and cytoplasmic calcium of oocytes recovered 13 h post hCG. Furthermore, the CaSR was more important than the Na-Ca2+ exchanger in regulating oocyte STAS, and T- and L-type calcium channels were inactive in aging oocytes. We conclude that the CaSR is involved in regulating STAS in POA mouse oocytes, and that it is more important than the other calcium channels tested in this connection.
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Affiliation(s)
- Rui Yang
- College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai'an City 271018, Shandong, P. R. China
- Laboratory Animal Center, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan 250021, Shandong, P. R. China
| | - Chang-Li Ji
- College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai'an City 271018, Shandong, P. R. China
| | - Min Zhang
- College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai'an City 271018, Shandong, P. R. China
| | - Jie Zhang
- College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai'an City 271018, Shandong, P. R. China
| | - Hong-Jie Yuan
- College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai'an City 271018, Shandong, P. R. China
| | - Ming-Jiu Luo
- College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai'an City 271018, Shandong, P. R. China
| | - Guang-Zhong Jiao
- College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai'an City 271018, Shandong, P. R. China
- Department of Reproductive Medicine, the Affiliated Yantai Yuhuangding Hospital of Qingdao University, Yantai City 264000, Shandong Province, P. R. China
| | - Jing-He Tan
- College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai'an City 271018, Shandong, P. R. China
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2
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Goolam MA, Brown AP, Edwards KT, Gregory KJ, Leach K, Conigrave AD. Cell Surface Calcium-Sensing Receptor Heterodimers: Mutant Gene Dosage Affects Ca 2+ Sensing but Not G Protein Interaction. J Bone Miner Res 2022; 37:1787-1807. [PMID: 35848051 PMCID: PMC9545990 DOI: 10.1002/jbmr.4651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 06/20/2022] [Accepted: 07/14/2022] [Indexed: 11/20/2022]
Abstract
The calcium-sensing receptor is a homodimeric class C G protein-coupled receptor (GPCR) that senses extracellular Ca2+ (Ca2+ o ) via a dimeric extracellular Venus flytrap (VFT) unit that activates G protein-dependent signaling via twin Cysteine-rich domains linked to transmembrane heptahelical (HH) bundles. It plays a key role in the regulation of human calcium and thus mineral metabolism. However, the nature of interactions between VFT units and HH bundles, and the impacts of heterozygous or homozygous inactivating mutations, which have implications for disorders of calcium metabolism are not yet clearly defined. Herein we generated CaSR-GABAB1 and CaSR-GABAB2 chimeras subject to GABAB -dependent endoplasmic reticulum sorting to traffic mutant heterodimers to the cell surface. Transfected HEK-293 cells were assessed for Ca2+ o -stimulated Ca2+ i mobilization using mutations in either the VFT domains and/or HH bundle intraloop-2 or intraloop-3. When the same mutation was present in both VFT domains of receptor dimers, analogous to homozygous neonatal severe hyperparathyroidism (NSHPT), receptor function was markedly impaired. Mutant heterodimers containing one wild-type (WT) and one mutant VFT domain, however, corresponding to heterozygous familial hypocalciuric hypercalcemia type-1 (FHH-1), supported maximal signaling with reduced Ca2+ o potency. Thus two WT VFT domains were required for normal Ca2+ o potency and there was a pronounced gene-dosage effect. In contrast, a single WT HH bundle was insufficient for maximal signaling and there was no functional difference between heterodimers in which the mutation was present in one or both intraloops; ie, no gene-dosage effect. Finally, we observed that the Ca2+ o -stimulated CaSR operated exclusively via signaling in-trans and not via combined in-trans and in-cis signaling. We consider how receptor asymmetry may support the underlying mechanisms. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Mahvash A Goolam
- School of Life and Environmental Sciences, Charles Perkins Centre (D17), University of Sydney, NSW, Australia
| | - Alice P Brown
- School of Life and Environmental Sciences, Charles Perkins Centre (D17), University of Sydney, NSW, Australia
| | - Kimberly T Edwards
- School of Life and Environmental Sciences, Charles Perkins Centre (D17), University of Sydney, NSW, Australia
| | - Karen J Gregory
- Monash Institute of Pharmaceutical Sciences and Department of Pharmacology, Monash University, Parkville, Victoria, Australia
| | - Katie Leach
- Monash Institute of Pharmaceutical Sciences and Department of Pharmacology, Monash University, Parkville, Victoria, Australia
| | - Arthur D Conigrave
- School of Life and Environmental Sciences, Charles Perkins Centre (D17), University of Sydney, NSW, Australia
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3
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Xu R, Cheng P, Meng K, Li L, Jiao M, Zhao X, Jia P, Zheng X, Xiao C. Extracellular domain of human calcium sensing receptor immobilized to silica beads as biomaterial: a rapid chromatographic method for recognizing ligands from complex matrix ‘Shuangdan’. J Chromatogr B Analyt Technol Biomed Life Sci 2022; 1208:123409. [DOI: 10.1016/j.jchromb.2022.123409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 08/03/2022] [Accepted: 08/04/2022] [Indexed: 10/15/2022]
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4
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de Alarcón R, Alburquerque-González B, Fernández-Valera Á, Molina-Nuñez M, Álvarez Fernandez G, Consuegra-Sánchez L, Luengo-Gil G, Conesa-Zamora P. Pharmacogenetic role of vitamin D-binding protein and vitamin D receptor polymorphisms in the treatment response of dialysis patients with secondary hyperparathyroidism. Nephrol Dial Transplant 2021; 37:792-795. [PMID: 34888693 DOI: 10.1093/ndt/gfab353] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Indexed: 11/14/2022] Open
Affiliation(s)
- Rosa de Alarcón
- Nephrology Department, Santa Lucia University Hospital, Cartagena, Spain
| | | | | | | | | | | | - Ginés Luengo-Gil
- Pathology Department. Santa Lucía General University Hospital (HGUSL), Cartagena, Spain.,Group of Molecular Pathology and Pharmacogenetics, Instituto Murciano de Investigación Biosanitaria (IMIB), Hospital Universitario Santa Lucía, Cartagena, Spain.,Clinical Analysis Department, Santa Lucia University Hospital, Cartagena, Spain
| | - Pablo Conesa-Zamora
- Facultad de Ciencias de la Salud, Universidad Católica de Murcia (UCAM), Guadalupe, Spain.,Group of Molecular Pathology and Pharmacogenetics, Instituto Murciano de Investigación Biosanitaria (IMIB), Hospital Universitario Santa Lucía, Cartagena, Spain.,Clinical Analysis Department, Santa Lucia University Hospital, Cartagena, Spain
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5
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Liu H, Zhou D, Liu C, Zhuan Q, Luo Y, Mo X, Fu X, Hou Y. The Calcium-Sensing Receptor Is Involved in Follicle-Stimulating Hormone-Induced Cumulus Expansion in in vitro Cultured Porcine Cumulus-Oocyte Complexes. Front Cell Dev Biol 2021; 9:625036. [PMID: 34095106 PMCID: PMC8173154 DOI: 10.3389/fcell.2021.625036] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 04/07/2021] [Indexed: 12/02/2022] Open
Abstract
The Calcium-Sensing Receptor (CASR) is a G protein-coupled receptor of the C family that reportedly promotes maturation of porcine oocytes. However, its role in cumulus expansion of cumulus-oocyte complexes (COCs) is not well known. This study was conducted to determine the role of CASR and potential mechanisms involved during in vitro maturation (IVM) of porcine COCs. After culture of COCs in follicle-stimulating hormone (FSH)-supplement maturation medium for 24 h, the time of breakdown of the germinal vesicle (GVBD), indicative of initiation of meiotic maturation, resulted in an increased (p < 0.05) CASR mRNA expression level in cumulus cells. Moreover, IVM of COCs in 10 μM of the CASR agonist NPS R-568 promoted (p < 0.05) cumulus expansion but only in FSH-containing medium. Conversely, 20 μM of the CASR inhibitor NPS2390 precluded cumulus expansion. We next tested the effect of the CASR agonist/inhibitor on the expression of cumulus expansion-related genes. The CASR agonist significantly upregulated the expression of hyaluronan acid synthase 2 (HAS2), whereas the CASR inhibitor downregulated the expression of all HAS2, prostaglandin-endoperoxide synthase 2 (PTGS2), and tumor necrosis factor a-induced protein 6 (TNFAIP6). Altogether, these results suggest that CASR activity is involved in FSH-stimulated porcine cumulus expansion.
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Affiliation(s)
- Huage Liu
- Institute of Reproductive Medicine, Nantong University, Nantong, China.,State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Dan Zhou
- Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture and National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, China
| | - Cong Liu
- School of Basic Medical Sciences, Wuhan University, Wuhan, China
| | - Qingrui Zhuan
- Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture and National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, China
| | - Yan Luo
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Xianhong Mo
- College of Life Sciences, Chifeng University, Chifeng, China
| | - Xiangwei Fu
- Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture and National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, China
| | - Yunpeng Hou
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
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6
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Ramezani A, Rasaee MJ, Jalaeefar A, Salmanian AH. Efficient detection of eukaryotic calcium-sensing receptor (CaSR) by polyclonal antibody against prokaryotic expressed truncated CaSR. Mol Biol Rep 2020; 47:7723-7734. [PMID: 33001312 DOI: 10.1007/s11033-020-05847-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 09/15/2020] [Indexed: 11/26/2022]
Abstract
Calcium-sensing receptor (CaSR), which is better known for its action as regulating calcium homeostasis, can bind various ligands. To facilitate research on CaSR and understand the receptor's function further, an in silico designed truncated protein was developed. The resulting protein folding indicated that 99% of predicted three dimensional (3D) structure residues are located in favored and allowed Ramachandran plots. However, it was found that such protein does not fold properly when expressed in prokaryotic host cells. Thioredoxin (Trx) tag was conjugated to increase the final protein's solubility, which could help obtain the soluble antigen with better immunogenic properties. The truncated recombinant proteins were expressed and purified in two forms (Trx-CaSR: RR19 and CaSR: RRJ19). The polyclonal antibody was induced by the rabbit immunization with the form of RR19. Western blot on mouse kidney lysates evidenced the proper immune recognition of the receptor by the produced antibody. The specificity and sensitivity of antibodies were also assayed by immunohistofluorescence. These experiments affirmed antibody's ability to indicate the receptor on the cell surface in native form and the possibility of applying such antibodies in further cellular and tissue assays.
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Affiliation(s)
- Aghdas Ramezani
- Department of Medical Biotechnology, Faculty of Medical Sciences, Tarbiat Modares University, Jalal Ale Ahmad Highway, PO Box 14115-331, Tehran, Iran
| | - Mohammad Javad Rasaee
- Department of Medical Biotechnology, Faculty of Medical Sciences, Tarbiat Modares University, Jalal Ale Ahmad Highway, PO Box 14115-331, Tehran, Iran.
| | - Amirmohsen Jalaeefar
- Department of Surgical Oncology, Cancer Institute, Tehran University of Medical Sciences, Tehran, Iran
| | - Ali Hatef Salmanian
- Departments of Plant Biotechnology, National Institute of Genetic Engineering and Biotechnology (NIGEB), Tehran, Iran
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7
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Structural Mechanism of Cooperative Regulation of Calcium-Sensing Receptor-Mediated Cellular Signaling. CURRENT OPINION IN PHYSIOLOGY 2020; 17:269-277. [PMID: 33709045 DOI: 10.1016/j.cophys.2020.08.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Calcaium sensing receptors (CaSRs) play a central role in regulating extracellular calcium (Ca2+) homeostasis and many (patho)physiological processes. This regulation is primarily orchestrated in response to extracellular stimuli via the extracellular domain (ECD). This paper first reviews the modeled structure of the CaSR ECD and the prediction and investigation of the Ca2+ and amino acid binding sites. Several recently solved X-ray structures are then compared to support a proposed CaSR activation model involving functional cooperativity. The review also discusses recent implications for drug development. These studies provide new insights into the molecular basis of diseases and the design of therapeutic agents that target CaSR and other family C G protein-coupled receptors (cGPCRs).
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Sensing Extracellular Calcium - An Insight into the Structure and Function of the Calcium-Sensing Receptor (CaSR). ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1131:1031-1063. [PMID: 31646544 DOI: 10.1007/978-3-030-12457-1_41] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The calcium-sensing receptor (CaSR) is a G protein-coupled receptor that plays a key role in calcium homeostasis, by sensing free calcium levels in blood and regulating parathyroid hormone secretion in response. The CaSR is highly expressed in parathyroid gland and kidney where its role is well characterised, but also in other tissues where its function remains to be determined. The CaSR can be activated by a variety of endogenous ligands, as well as by synthetic modulators such as Cinacalcet, used in the clinic to treat secondary hyperparathyroidism in patients with chronic kidney disease. The CaSR couples to multiple G proteins, in a tissue-specific manner, activating several signalling pathways and thus regulating diverse intracellular events. The multifaceted nature of this receptor makes it a valuable therapeutic target for calciotropic and non-calciotropic diseases. It is therefore essential to understand the complexity behind the pharmacology, trafficking, and signalling characteristics of this receptor. This review provides an overview of the latest knowledge about the CaSR and discusses future hot topics in this field.
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9
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Yang R, Sun HH, Ji CL, Zhang J, Yuan HJ, Luo MJ, Liu XY, Tan JH. Role of calcium-sensing receptor in regulating spontaneous activation of postovulatory aging rat oocytes. Biol Reprod 2019; 98:218-226. [PMID: 29267849 DOI: 10.1093/biolre/iox178] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Accepted: 12/17/2017] [Indexed: 11/14/2022] Open
Abstract
Mechanisms for postovulatory aging (POA) of oocytes and for spontaneous activation (SA) of rat oocytes are largely unknown. Expression of calcium-sensing receptor (CaSR) in rat oocytes and its role in POA remain unexplored. In this study, expression of CaSR in rat oocytes aging for different times was detected by immunofluorescence microscopy, and western blotting and the role of CaSR in POA was determined by observing the effects of regulating its activity on SA susceptibility and cytoplasmic calcium levels. The results showed that CaSR was expressed in rat oocytes. Oocytes recovered 19 h post human chorionic gonadotropin (hCG) injection were more susceptible to SA and expressed more functional CaSR than oocytes recovered 13 h after hCG injection, although both expressed the same level of total CaSR protein. Treatment with CaSR antagonist significantly suppressed cytoplasmic calcium elevation and SA of oocytes. Activation of Na-Ca2+ exchanger with NaCl inhibited SA to a greater extent than suppression of CaSR with NPS-2143, suggesting that calcium sources other than CaSR-controlled channels contributed to the elevation of cytoplasmic calcium. Treatment with T- or L-type calcium channel blockers significantly reduced SA. Suppression of all calcium channels tested reduced SA to minimum. It is concluded that the level of CaSR functional dimer protein, but not that of the total CaSR protein, was positively correlated with the SA susceptibility during POA of rat oocytes confirming that CaSR is involved in POA regulation. Blocking multiple calcium channels might be a better choice for efficient control of SA in rat oocytes.
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Affiliation(s)
- Rui Yang
- College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai'an City, P. R. China
| | - Huan-Huan Sun
- College of Life Science, Northeast Agricultural University, Harbin, P. R. China
| | - Chang-Li Ji
- College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai'an City, P. R. China
| | - Jie Zhang
- College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai'an City, P. R. China
| | - Hong-Jie Yuan
- College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai'an City, P. R. China
| | - Ming-Jiu Luo
- College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai'an City, P. R. China
| | - Xin-Yong Liu
- Center for Reproductive Medicine, Tai'an City Central Hospital, Tai'an City, P. R. China
| | - Jing-He Tan
- College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai'an City, P. R. China
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Molecular Basis for Modulation of Metabotropic Glutamate Receptors and Their Drug Actions by Extracellular Ca 2. Int J Mol Sci 2017; 18:ijms18030672. [PMID: 28335551 PMCID: PMC5372683 DOI: 10.3390/ijms18030672] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Revised: 03/13/2017] [Accepted: 03/17/2017] [Indexed: 12/24/2022] Open
Abstract
Metabotropic glutamate receptors (mGluRs) associated with the slow phase of the glutamatergic signaling pathway in neurons of the central nervous system have gained importance as drug targets for chronic neurodegenerative diseases. While extracellular Ca2+ was reported to exhibit direct activation and modulation via an allosteric site, the identification of those binding sites was challenged by weak binding. Herein, we review the discovery of extracellular Ca2+ in regulation of mGluRs, summarize the recent developments in probing Ca2+ binding and its co-regulation of the receptor based on structural and biochemical analysis, and discuss the molecular basis for Ca2+ to regulate various classes of drug action as well as its importance as an allosteric modulator in mGluRs.
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11
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Zhang C, Miller CL, Gorkhali R, Zou J, Huang K, Brown EM, Yang JJ. Molecular Basis of the Extracellular Ligands Mediated Signaling by the Calcium Sensing Receptor. Front Physiol 2016; 7:441. [PMID: 27746744 PMCID: PMC5043022 DOI: 10.3389/fphys.2016.00441] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 09/16/2016] [Indexed: 12/20/2022] Open
Abstract
Ca2+-sensing receptors (CaSRs) play a central role in regulating extracellular calcium concentration ([Ca2+]o) homeostasis and many (patho)physiological processes in multiple organs. This regulation is orchestrated by a cooperative response to extracellular stimuli such as small changes in Ca2+, Mg2+, amino acids, and other ligands. In addition, CaSR is a pleiotropic receptor regulating several intracellular signaling pathways, including calcium mobilization and intracellular calcium oscillation. Nearly 200 mutations and polymorphisms have been found in CaSR in relation to a variety of human disorders associated with abnormal Ca2+ homeostasis. In this review, we summarize efforts directed at identifying binding sites for calcium and amino acids. Both homotropic cooperativity among multiple calcium binding sites and heterotropic cooperativity between calcium and amino acid were revealed using computational modeling, predictions, and site-directed mutagenesis coupled with functional assays. The hinge region of the bilobed Venus flytrap (VFT) domain of CaSR plays a pivotal role in coordinating multiple extracellular stimuli, leading to cooperative responses from the receptor. We further highlight the extensive number of disease-associated mutations that have also been shown to affect CaSR's cooperative action via several types of mechanisms. These results provide insights into the molecular bases of the structure and functional cooperativity of this receptor and other members of family C of the G protein-coupled receptors (cGPCRs) in health and disease states, and may assist in the prospective development of novel receptor-based therapeutics.
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Affiliation(s)
- Chen Zhang
- Department of Chemistry, Georgia State University Atlanta, GA, USA
| | | | - Rakshya Gorkhali
- Department of Chemistry, Georgia State University Atlanta, GA, USA
| | - Juan Zou
- Department of Chemistry, Georgia State University Atlanta, GA, USA
| | - Kenneth Huang
- Department of Chemistry, Georgia State University Atlanta, GA, USA
| | - Edward M Brown
- Center for Diagnostics and Therapeutics, Georgia State UniversityAtlanta, GA, USA; Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, Brigham and Women's HospitalBoston, MA, USA
| | - Jenny J Yang
- Department of Chemistry, Georgia State University Atlanta, GA, USA
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Díaz-Soto G, Rocher A, García-Rodríguez C, Núñez L, Villalobos C. The Calcium-Sensing Receptor in Health and Disease. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2016; 327:321-369. [PMID: 27692178 DOI: 10.1016/bs.ircmb.2016.05.004] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The extracellular calcium-sensing receptor (CaSR) is a unique G protein-coupled receptor (GPCR) activated by extracellular Ca2+ and by other physiological cations including Mg2+, amino acids, and polyamines. CaSR is the most important master controller of the extracellular Ca2+ homeostatic system being expressed at high levels in the parathyroid gland, kidney, gut and bone, where it regulates parathyroid hormone (PTH) secretion, vitamin D synthesis, and Ca2+ absorption and resorption, respectively. Gain and loss of function mutations in the CaSR are responsible for severe disturbances in extracellular Ca2+ metabolism. CaSR agonists (calcimimetics) and antagonists (calcilytics) are in use or under intense research for treatment of hyperparathyroidism secondary to kidney failure and hypocalcemia with hypercalciuria, respectively. Expression of the CaSR extends to other tissues and systems beyond the extracellular Ca2+ homeostatic system including the cardiovascular system, the airways, and the nervous system where it may play physiological functions yet to be fully understood. As a consequence, CaSR has been recently involved in different pathologies including uncontrolled blood pressure, vascular calcification, asthma, and Alzheimer's disease. Finally, the CaSR has been shown to play a critical role in cancer either contributing to bone metastasis and/or acting as a tumor suppressor in some forms of cancer (parathyroid cancer, colon cancer, and neuroblastoma) and as oncogene in others (breast and prostate cancers). Here we review the role of CaSR in health and disease in calciotropic tissues and others beyond the extracellular calcium homeostatic system.
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Affiliation(s)
- G Díaz-Soto
- Endocrinology and Nutrition, Valladolid University Hospital, Valladolid, Spain
| | - A Rocher
- Department of Biochemistry and Molecular Biology and Physiology, University of Valladolid, Valladolid, Spain; Institute of Molecular Biology and Genetics (IBGM), University of Valladolid and National Research Council (CSIC), Valladolid, Spain
| | - C García-Rodríguez
- Institute of Molecular Biology and Genetics (IBGM), University of Valladolid and National Research Council (CSIC), Valladolid, Spain
| | - L Núñez
- Department of Biochemistry and Molecular Biology and Physiology, University of Valladolid, Valladolid, Spain; Institute of Molecular Biology and Genetics (IBGM), University of Valladolid and National Research Council (CSIC), Valladolid, Spain
| | - C Villalobos
- Institute of Molecular Biology and Genetics (IBGM), University of Valladolid and National Research Council (CSIC), Valladolid, Spain.
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Bioinspired design of a polymer gel sensor for the realization of extracellular Ca(2+) imaging. Sci Rep 2016; 6:24275. [PMID: 27067646 PMCID: PMC4828671 DOI: 10.1038/srep24275] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 03/21/2016] [Indexed: 12/20/2022] Open
Abstract
Although the role of extracellular Ca2+ draws increasing attention as a messenger in intercellular communications, there is currently no tool available for imaging Ca2+ dynamics in extracellular regions. Here we report the first solid-state fluorescent Ca2+ sensor that fulfills the essential requirements for realizing extracellular Ca2+ imaging. Inspired by natural extracellular Ca2+-sensing receptors, we designed a particular type of chemically-crosslinked polyacrylic acid gel, which can undergo single-chain aggregation in the presence of Ca2+. By attaching aggregation-induced emission luminogen to the polyacrylic acid as a pendant, the conformational state of the main chain at a given Ca2+ concentration is successfully translated into fluorescence property. The Ca2+ sensor has a millimolar-order apparent dissociation constant compatible with extracellular Ca2+ concentrations, and exhibits sufficient dynamic range and excellent selectivity in the presence of physiological concentrations of biologically relevant ions, thus enabling monitoring of submillimolar fluctuations of Ca2+ in flowing analytes containing millimolar Ca2+ concentrations.
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14
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Liu C, Wu GQ, Fu XW, Mo XH, Zhao LH, Hu HM, Zhu SE, Hou YP. The Extracellular Calcium-Sensing Receptor (CASR) Regulates Gonadotropins-Induced Meiotic Maturation of Porcine Oocytes. Biol Reprod 2015; 93:131. [PMID: 26490840 DOI: 10.1095/biolreprod.115.128579] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 10/14/2015] [Indexed: 12/16/2022] Open
Abstract
Gonadotropins and epidermal growth factor (EGF) play crucial roles in promoting oocyte maturation. The regulatory network downstream of these key factors is not well understood. The present study was designed to investigate the role of the calcium-sensing receptor (CASR) in porcine oocyte in vitro maturation. CASR expression was up-regulated in oocytes matured in gonadotropin-containing medium. Cortical distribution of CASR was enhanced with gonadotropins but not EGF. Supplementation of a CASR agonist (NPS R-568) in the gonadotropin (FSH and/or LH)-containing maturation medium significantly enhanced oocyte nuclear maturation. Addition of NPS2390, a CASR antagonist, compromised oocyte nuclear maturation. Furthermore, increased cortical distribution and decreased expression of CASR was observed after the NPS R-568 treatment. Oocytes treated with NPS R-568 had higher concentration of CYCLIN B1, decreased reactive oxygen species, and increased glutathione levels, indicative of advanced cytoplasmic maturation. In contrast, NPS2390 treatment compromised oocyte cytoplasmic maturation. A higher blastocyst formation rate after parthenogenetic activation was observed when oocytes were matured in the presence of the CASR agonist, NPS R-568. MAPK3/1 phosphorylation was increased during in vitro maturation and after NPS R-568 treatment, and decreased following CASR antagonist supplementation. Taken together, our data showed that the CASR is a gonadotropin-regulated factor that promotes porcine oocyte maturation in a MAPK-dependent manner.
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Affiliation(s)
- Cong Liu
- State Key Laboratory for Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Guo-Quan Wu
- Yunnan Animal Science and Veterinary Institute, Kunming, Yunnan, China
| | - Xiang-Wei Fu
- Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture and National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, China
| | - Xian-Hong Mo
- State Key Laboratory for Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Li-Hong Zhao
- State Key Laboratory for Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Hong-Mei Hu
- State Key Laboratory for Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Shi-En Zhu
- Key Laboratory of Animal Genetics, Breeding and Reproduction, Ministry of Agriculture and National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing, China
| | - Yun-Peng Hou
- State Key Laboratory for Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
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15
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Computational analysis of the extracellular domain of the Ca²⁺-sensing receptor: an alternate model for the Ca²⁺ sensing region. Biochem Biophys Res Commun 2015; 459:36-41. [PMID: 25701780 DOI: 10.1016/j.bbrc.2015.02.049] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Accepted: 02/10/2015] [Indexed: 11/21/2022]
Abstract
The extracellular Ca(2+) sensing receptor (CaSR) belongs to Class C G-protein-coupled receptors (GPCRs) which include receptors for amino acids, γ-aminobutyric acid and glutamate neurotransmitters. CaSR has been described as having an extended sequence containing a Ca(2+) binding pocket within an extracellular amino (N)-terminal domain, called a Venus Fly Trap (VFT) module. CaSR is thought to consist of three domains: 1) a Ca(2+-)sensory domain, 2) a region containing 7 transmembrane (TM) helices, and 3) a carboxy (C)-terminal tail. We find that SPOCTOPUS (a combination of hidden Markov models and artificial neural networks) predicts that Homo sapiens CaSR contains two additional TM helices ((190)D - G(210); (262)S-E(282)), with the second TM helix containing a pore-lining region ((265)K - I(280)). This predicts that the putative Ca(2+) sensory domain is within an extracellular loop, N-terminal to the highly conserved heptahelical bundle. This loop contains both the cysteine-rich domain ((537)V - C(598)) and a 14 residue "linker" sequence ((599)I - F(612)) thought to support signal transmission to the heptahelical bundle. Thus domain 1 may contain a 189 residue N-terminal extracellular region followed successively by TM-1, a short intracellular loop, TM-2 and a 329 residue extracellular loop; rather than the proposed 620 residue VFT module based on crystallography of the N-terminal region of mGluR1. Since the topologies of the two proteins differ, the published CaSR VFT model is questionable. CaSR also contains multiple caveolin-binding motifs and cholesterol-binding (CRAC/CARC) domains, facilitating localization to plasma membrane lipid rafts. Ion sensing may involve combination of pore-lining regions from CaSR dimers and CaSR-bound caveolins to form ion channels capable of monitoring ionized Ca(2+) levels.
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16
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Zhang C, Zhuo Y, Moniz HA, Wang S, Moremen KW, Prestegard JH, Brown EM, Yang JJ. Direct determination of multiple ligand interactions with the extracellular domain of the calcium-sensing receptor. J Biol Chem 2014; 289:33529-42. [PMID: 25305020 DOI: 10.1074/jbc.m114.604652] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Numerous in vivo functional studies have indicated that the dimeric extracellular domain (ECD) of the CaSR plays a crucial role in regulating Ca(2+) homeostasis by sensing Ca(2+) and l-Phe. However, direct interaction of Ca(2+) and Phe with the ECD of the receptor and the resultant impact on its structure and associated conformational changes have been hampered by the large size of the ECD, its high degree of glycosylation, and the lack of biophysical methods to monitor weak interactions in solution. In the present study, we purified the glycosylated extracellular domain of calcium-sensing receptor (CaSR) (ECD) (residues 20-612), containing either complex or high mannose N-glycan structures depending on the host cell line employed for recombinant expression. Both glycosylated forms of the CaSR ECD were purified as dimers and exhibit similar secondary structures with ∼ 50% α-helix, ∼ 20% β-sheet content, and a well buried Trp environment. Using various spectroscopic methods, we have shown that both protein variants bind Ca(2+) with a Kd of 3.0-5.0 mm. The local conformational changes of the proteins induced by their interactions with Ca(2+) were visualized by NMR with specific (15)N Phe-labeled forms of the ECD. Saturation transfer difference NMR approaches demonstrated for the first time a direct interaction between the CaSR ECD and l-Phe. We further demonstrated that l-Phe increases the binding affinity of the CaSR ECD for Ca(2+). Our findings provide new insights into the mechanisms by which Ca(2+) and amino acids regulate the CaSR and may pave the way for exploration of the structural properties of CaSR and other members of family C of the GPCR superfamily.
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Affiliation(s)
- Chen Zhang
- From the Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30303
| | - You Zhuo
- From the Department of Chemistry
| | - Heather A Moniz
- the Department of Biochemistry and Molecular Biology and the Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602, and
| | - Shuo Wang
- the Department of Biochemistry and Molecular Biology and the Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602, and
| | - Kelley W Moremen
- the Department of Biochemistry and Molecular Biology and the Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602, and
| | - James H Prestegard
- the Department of Biochemistry and Molecular Biology and the Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602, and
| | - Edward M Brown
- the Department of Medicine, Division of Endocrinology, Brigham and Women's Hospital, Boston, Massachusetts 02115
| | - Jenny J Yang
- From the Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30303,
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17
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Zhang C, Huang Y, Jiang Y, Mulpuri N, Wei L, Hamelberg D, Brown EM, Yang JJ. Identification of an L-phenylalanine binding site enhancing the cooperative responses of the calcium-sensing receptor to calcium. J Biol Chem 2014; 289:5296-309. [PMID: 24394414 DOI: 10.1074/jbc.m113.537357] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Functional positive cooperative activation of the extracellular calcium ([Ca(2+)]o)-sensing receptor (CaSR), a member of the family C G protein-coupled receptors, by [Ca(2+)]o or amino acids elicits intracellular Ca(2+) ([Ca(2+)]i) oscillations. Here, we report the central role of predicted Ca(2+)-binding site 1 within the hinge region of the extracellular domain (ECD) of CaSR and its interaction with other Ca(2+)-binding sites within the ECD in tuning functional positive homotropic cooperativity caused by changes in [Ca(2+)]o. Next, we identify an adjacent L-Phe-binding pocket that is responsible for positive heterotropic cooperativity between [Ca(2+)]o and L-Phe in eliciting CaSR-mediated [Ca(2+)]i oscillations. The heterocommunication between Ca(2+) and an amino acid globally enhances functional positive homotropic cooperative activation of CaSR in response to [Ca(2+)]o signaling by positively impacting multiple [Ca(2+)]o-binding sites within the ECD. Elucidation of the underlying mechanism provides important insights into the longstanding question of how the receptor transduces signals initiated by [Ca(2+)]o and amino acids into intracellular signaling events.
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Affiliation(s)
- Chen Zhang
- From the Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30303 and
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18
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He YH, Kong WL, Wang G, Zhao Y, Bi MX, Na LX, Wang MQ, Perry B, Li Y. The calcium-sensing receptor R990G polymorphism is associated with increased risk of hypertriglyceridemia in obese Chinese. Gene 2014; 533:67-71. [PMID: 24120622 DOI: 10.1016/j.gene.2013.09.122] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Revised: 09/11/2013] [Accepted: 09/30/2013] [Indexed: 11/18/2022]
Abstract
BACKGROUND We have demonstrated that the calcium-sensing receptor (CaSR) is involved in lipid metabolism; however, whether CaSR polymorphisms affect lipid metabolism in obesity is still unclear. The present study aimed to determine the effects of CaSR polymorphisms on HTG risk in obese Chinese. METHODS A total of 972 subjects with HTG and 1197 with normal triglyceride (NTG) were stratified by body mass index (BMI) into normal weight, overweight or obesity subgroups. After 12-h fasting, CaSR polymorphisms in exon 7 were determined in the blood. Serum lipids and glucose, as well as height, body weight and waist circumference were measured. The anthropometric and metabolic characteristics of the NTG subjects were re-evaluated 3 years later. RESULTS There were no genotypic or allelic distribution differences for the A986S or Q1011E polymorphisms between the NTG and HTG groups. However, the G/G genotypic and G allelic distributions of the CaSR R990G polymorphism in the HTG group were higher than the NTG group (p<0.001). After stratification, in obese subjects, the homozygous (G/G) distribution of the CaSR R990G polymorphism in the HTG group was significantly higher than in the NTG group (p=0.001), and showed an increased risk of HTG at baseline [OR=2.55, 95% CI=1.65-3.92, p<0.006]. Interaction of the CaSR R990G polymorphism with BMI was associated with increased risk of HTG (β=0.927, p<0.001). Re-evaluation of the NTG subjects revealed significantly increased serum triglyceride levels in obese homozygous versus wildtype carriers (p<0.05). CONCLUSIONS These results suggest that the CaSR R990G polymorphism is associated with increased risk of HTG, especially in obese Chinese, and may be a potential genetic predictor of diseases related to HTG.
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Affiliation(s)
- Yong-Han He
- National Key Discipline of Nutrition and Food Hygiene, Public Health College, Harbin Medical University, China; State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China
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19
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Ward DT, Mughal MZ, Ranieri M, Dvorak-Ewell MM, Valenti G, Riccardi D. Molecular and clinical analysis of a neonatal severe hyperparathyroidism case caused by a stop mutation in the calcium-sensing receptor extracellular domain representing in effect a human 'knockout'. Eur J Endocrinol 2013; 169:K1-7. [PMID: 23612447 DOI: 10.1530/eje-13-0094] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
OBJECTIVE Loss-of-function calcium-sensing receptor (CAR) mutations cause elevated parathyroid hormone (PTH) secretion and hypercalcaemia. Although full Car deletion is possible in mice, most human CAR mutations result from a single amino acid substitution that maintains partial function. However, here, we report a case of neonatal severe hyperparathyroidism (NSHPT) in which the truncated CaR lacks any transmembrane domain (CaR(R392X)), in effect a full CAR 'knockout'. CASE REPORT The infant (daughter of distant cousins) presented with hypercalcaemia (5.5-6 mmol/l corrected calcium (2.15-2.65)) and elevated PTH concentrations (650-950 pmol/l (12-81)) together with skeletal demineralisation. NSHPT was confirmed by CAR gene sequencing (homozygous c.1174C-to-T mutation) requiring total parathyroidectomy during which only two glands were located and removed, resulting in normalisation of her serum PTH/calcium levels. DESIGN AND METHODS The R392X stop codon was inserted into human CAR and the resulting mutant (CaR(R392X)) expressed transiently in HEK-293 cells. RESULTS CaR(R392X) expressed as a 54 kDa dimeric glycoprotein that was undetectable in conditioned medium or in the patient's urine. The membrane localisation observed for wild-type CaR in parathyroid gland and transfected HEK-293 cells was absent from the proband's parathyroid gland and from CaR(R392X)-transfected cells. Expression of the mutant was localised to endoplasmic reticulum consistent with its lack of functional activity. CONCLUSIONS Intriguingly, the patient remained normocalcaemic throughout childhood (2.5 mM corrected calcium, 11 pg/ml PTH (10-71), age 8 years) but exhibited mild asymptomatic hypocalcaemia at age 10 years, now treated with 1-hydroxycholecalciferol and Ca2+ supplementation. Despite representing a virtual CAR knockout, the patient displays no obvious pathologies beyond her calcium homeostatic dysfunction.
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Affiliation(s)
- D T Ward
- Faculty of Life Sciences, The University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK.
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20
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Hendy GN, Canaff L, Cole DEC. The CASR gene: alternative splicing and transcriptional control, and calcium-sensing receptor (CaSR) protein: structure and ligand binding sites. Best Pract Res Clin Endocrinol Metab 2013; 27:285-301. [PMID: 23856260 DOI: 10.1016/j.beem.2013.02.009] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The calcium-sensing receptor (CaSR) is a G protein-coupled receptor encoded by a single copy gene. The human CASR gene spans ~103-kb and has eight exons. Promoters P1 and P2 drive transcription of exons 1A and 1B, respectively, encoding alternative 5'-UTRs that splice to exon 2 encoding the common part of the 5'-UTR. Exons 2-7 encode the CaSR protein of 1078 amino acids. Functional elements responsive to 1,25-dihydroxyvitamin D, proinflammatory cytokines, and glial cells missing-2 are present in the CASR promoters. Evolutionarily, the exon structure, first seen in aquatic vertebrates, is well-conserved with a single linkage disequilibrium haplotype block for protein coding exons 2-7. Structural features of the human CaSR protein are: an N-terminal signal peptide (19 amino acids (aa)); an extracellular domain (~600 aa) having a bi-lobed Venus Flytrap (VFT) domain with several Ca(2+)-binding sites; and a nine-cysteines domain that transduces the activation signal to the 7-transmembrane domain (250 aa) and the C-terminal tail (216 aa).
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Affiliation(s)
- Geoffrey N Hendy
- Calcium Research Laboratory, and Hormones and Cancer Research Unit, Royal Victoria Hospital and McGill University Health Centre, Montreal, QC H3A 1A1, Canada.
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21
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22
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Abstract
The calcium-sensing receptor (CaR) is the key controller of extracellular calcium (Ca(2+)(o)) homeostasis via its regulation of parathyroid hormone (PTH) secretion and renal Ca(2+) reabsorption. The CaR-selective calcimimetic drug Cinacalcet stimulates the CaR to suppress PTH secretion in chronic kidney disease and represents the world's first clinically available receptor positive allosteric modulator (PAM). Negative CaR allosteric modulators (NAMs), known as calcilytics, can increase PTH secretion and are being investigated as possible bone anabolic treatments against age-related osteoporosis. Here we address the current state of development and clinical use of a series of positive and negative CaR modulators. In addition, clinical CaR mutations and transgenic mice carrying tissue-specific CaR deletions have provided a novel understanding of the relative functional importance of CaR in both calciotropic tissues and those elsewhere in the body. The development of CaR-selective modulators and signalling reagents have provided us with a more detailed appreciation of how the CaR signals in vivo. Thus, both of these areas of CaR research will be reviewed.
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Affiliation(s)
- Donald T Ward
- Faculty of Life Sciences, The University of ManchesterManchester, UK
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23
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Al-Salameh A, Cetani F, Pardi E, Vulpoi C, Pierre P, de Calan L, Guyetant S, Jeunemaitre X, Lecomte P. A novel mutation in the calcium-sensing receptor in a French family with familial hypocalciuric hypercalcaemia. Eur J Endocrinol 2011; 165:359-63. [PMID: 21566075 DOI: 10.1530/eje-11-0141] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
OBJECTIVE The calcium-sensing receptor (CASR) has an important role in calcium homoeostasis by controlling PTH secretion and renal calcium handling. Inactivating mutations in the CASR gene (HGNC ID: 1514) cause familial hypocalciuric hypercalcaemia (FHH). We present a case of FHH patient to describe a novel mutation in the CASR. SUBJECTS AND METHODS A 34-year-old patient was referred because of recurrent hypercalcaemia after resection of two hyperplastic parathyroids. Extensive evaluation found elevated PTH and low calcium/creatinine clearance ratio. One of her three children had high serum calcium concentrations. Genetic studies were performed by PCR amplification of CASR coding exons and direct sequencing of PCR products. Transient transfection of the wild-type (WT) CASR and the mutant CASR into COS-7 was performed to assess functional impact of the mutation and the capacity of either protein to mediate increases in cellular levels of inositol phosphates (IPs). RESULTS CASR sequencing found a previously undescribed heterozygous base substitution, determining a change of threonine to isoleucine at codon 550 (p.T550I) in the sixth exon. In contrast to those transfected with WT CASR, which showed a five- to eightfold increase in total IPs at high levels of calcium, COS-7 cells transfected with the (p.T550I) mutant showed no increase confirming to the inactivating nature of the mutation. COS-7 cells co-transfected with the WT and the (p.T550I) mutant showed an intermediate response suggesting a possible dominant negative effect. CONCLUSION This case report presents a not-yet-described mutation in the cysteine-rich region of the CASR extracellular domain, a mutation with a possible dominant negative effect.
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Affiliation(s)
- Abdallah Al-Salameh
- Department of Endocrinology, CHRU Bretonneau, University Hospital of Tours, 2 Bis Boulevard Tonnellé, 37044 Tours Cedex 9, France
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24
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Rogers AC, Hanly AM, Collins D, Baird AW, Winter DC. Review article: loss of the calcium-sensing receptor in colonic epithelium is a key event in the pathogenesis of colon cancer. Clin Colorectal Cancer 2011; 11:24-30. [PMID: 21723793 DOI: 10.1016/j.clcc.2011.04.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2011] [Revised: 03/29/2011] [Accepted: 04/15/2011] [Indexed: 01/29/2023]
Abstract
The calcium-sensing receptor (CaSR) is expressed abundantly in normal colonic epithelium and lost in colon cancer, but its exact role on a molecular level and within the carcinogenesis pathway is yet to be described. Epidemiologic studies show that inadequate dietary calcium predisposes to colon cancer; this may be due to the ability of calcium to bind and upregulate the CaSR. Loss of CaSR expression does not seem to be an early event in carcinogenesis; indeed it is associated with late stage, poorly differentiated, chemo-resistant tumors. Induction of CaSR expression in neoplastic colonocytes arrests tumor progression and deems tumors more sensitive to chemotherapy; hence CaSR may be an important target in colon cancer treatment. The CaSR has a complex role in colon cancer; however, more investigation is required on a molecular level to clarify its exact function in carcinogenesis. This review describes the mechanisms by which the CaSR is currently implicated in colon cancer and identifies areas where further study is needed.
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Affiliation(s)
- Ailín C Rogers
- Institute for Clinical Outcomes, Research and Education (iCORE), St. Vincents University Hospital, Dublin, Ireland.
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25
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Khan MA, Conigrave AD. Mechanisms of multimodal sensing by extracellular Ca(2+)-sensing receptors: a domain-based survey of requirements for binding and signalling. Br J Pharmacol 2010; 159:1039-50. [PMID: 20136834 DOI: 10.1111/j.1476-5381.2009.00603.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
In this article we consider the molecular basis of sensing and signalling by the extracellular calcium-sensing receptor. We consider the nature of its ligands and sensing modalities, the identities of its major protein domains and their roles in sensing, signalling and trafficking as well as the significance of receptor homo- and hetero-dimerization. Finally, we consider the current, incomplete, state of knowledge regarding the requirements for ligand-specific signalling.
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26
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Nemoto W, Fukui K, Toh H. GRIP: a server for predicting interfaces for GPCR oligomerization. J Recept Signal Transduct Res 2010; 29:312-7. [PMID: 19888901 DOI: 10.3109/10799890903295143] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
G-Protein Coupled Receptors (GPCRs) are one of the most important pharmaceutical targets. Recent studies have revealed that many GPCRs form homo- and/or hetero-oligomers. The molecular mechanisms of oligomerization are not fully understood yet, due to the lack of structural data for GPCR complexes. Therefore, accurate interface prediction would accelerate investigations of the molecular mechanisms of oligomerization and signaling via GPCRs. However, interface prediction for GPCR oligomerization is difficult, because the various GPCR subtypes often use different structural regions as their interfaces, even when the subtypes belong to the same subfamily. Previously, we developed a method to predict the interfaces for GPCR oligomerization, which overcomes the difficulty described above. We have now launched a web service, named G-protein coupled Receptors Interaction Partners (GRIP) ( http://grip.cbrc.jp/GRIP/index.html ), to predict the interfaces for GPCR oligomerization. As far as we know, it is the only service to predict the interfaces for GPCR oligomerization.
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Affiliation(s)
- Wataru Nemoto
- Computational Biology Research Center (CBRC), Advanced Industrial Science and Technology (AIST), Koto-ku, Tokyo, Japan.
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27
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Nanjo K, Nagai S, Shimizu C, Tajima T, Kondo T, Miyoshi H, Yoshioka N, Koike T. Identification and functional analysis of novel calcium-sensing receptor gene mutation in familial hypocalciuric hypercalcemia. Endocr J 2010; 57:787-92. [PMID: 20697181 DOI: 10.1507/endocrj.k10e-178] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Familial hypocalciuric hypercalcemia (FHH) is a benign disorder with heterozygous inactivating mutations in the calcium-sensing receptor (CASR) gene. The present study describes the identification and functional analysis of a novel CASR gene mutation leading to FHH. The proband is a 33-yr-old woman (Ca 11.0 mg/dL, intact-PTH 68 pg/mL, FECa 0.17 %). Leukocyte DNA was isolated in four family members and a novel heterozygous mutation (D190G, GAT>GGT) in exon 4 of CASR gene was identified by direct sequence analysis. The mutant CASR expression vector was constructed by mutagenesis procedure and its response to Ca(2+) was characterized by transient transfection into human embryonic kidney (HEK) 293 cells and treatment with increasing extracellular Ca(2+) concentrations. HEK cells didn't activate intracellular signaling (MAPK activation) in response to increases of extracellular Ca(2+) concentrations when the mutant receptor was expressed normally at the cell surface. The novel heterozygous mutation (D190G) identified in the present study showed that the reduction of activity of CASR to extracellular Ca(2+) caused FHH in patients and our study demonstrated the importance of Asp-190 participated in response to Ca(2+) in CASR.
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Affiliation(s)
- Kazuhiro Nanjo
- Department of Medicine II, Hokkaido University Graduate School of Medicine, Sapporo, Japan
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28
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Abstract
The versatility of Ca(2+) as an intracellular messenger derives largely from the spatial organization of cytosolic Ca(2+) signals, most of which are generated by regulated openings of Ca(2+)-permeable channels. Most Ca(2+) channels are expressed in the plasma membrane (PM). Others, including the almost ubiquitous inositol 1,4,5-trisphosphate receptors (IP(3)R) and their relatives, the ryanodine receptors (RyR), are predominantly expressed in membranes of the sarcoplasmic or endoplasmic reticulum (ER). Targeting of these channels to appropriate destinations underpins their ability to generate spatially organized Ca(2+) signals. All Ca(2+) channels begin life in the cytosol, and the vast majority are then functionally assembled in the ER, where they may either remain or be dispatched to other membranes. Here, by means of selective examples, we review two issues related to this trafficking of Ca(2+) channels via the ER. How do cells avoid wayward activity of Ca(2+) channels in transit as they pass from the ER via other membranes to their final destination? How and why do some cells express small numbers of the archetypal intracellular Ca(2+) channels, IP(3)R and RyR, in the PM?
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Affiliation(s)
- Colin W Taylor
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, UK.
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29
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De Santis T, Casavola V, Reshkin SJ, Guerra L, Ambruosi B, Fiandanese N, Dalbies-Tran R, Goudet G, Dell'Aquila ME. The extracellular calcium-sensing receptor is expressed in the cumulus-oocyte complex in mammals and modulates oocyte meiotic maturation. Reproduction 2009; 138:439-52. [PMID: 19494043 DOI: 10.1530/rep-09-0078] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The extracellular calcium-sensing receptor (CASR) plays an important role in cells involved in calcium (Ca2+) homeostasis by directly sensing changes in the extracellular Ca2+ ion concentration. We previously reported the localization and quantitative expression of CASR protein in human oocytes. In this study, we examined the expression and the functional role of CASR during oocyte meiotic maturation in a large mammal animal model, the horse. As in humans, CASR protein was found to be expressed in equine oocytes and cumulus cells. Western-blot analysis revealed a single 130 kDa band in denuded oocytes and a doublet of 130-120 kDa in cumulus cells. CASR labeling was observed by confocal microscopy in cumulus cells and in oocytes on the plasma membrane and within the cytoplasm at all examined stages of meiosis. Functionally, the CASR allosteric effector NPS R-467, in the presence of 2.92 mM external Ca2+, increased oocyte maturation rate in a dose-dependent manner and its stimulatory effect was attenuated by pre-treatment with the CASR antagonist NPS 2390. NPS R-467 had no effect in suboptimal external Ca2+ (0.5 mM), indicating that it requires higher external Ca2+ to promote oocyte maturation. In oocytes treated with NPS R-467, CASR staining increased at the plasmalemma and was reduced in the cytosol. Moreover, NPS R-467 increased the activity of MAPK, also called ERK, in cumulus cells and oocytes. These results provide evidence of a novel signal transduction pathway modulating oocyte meiotic maturation in mammals in addition to the well-known systemic hormones.
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Affiliation(s)
- Teresa De Santis
- Department of Animal Production, University of Bari, 70010 Valenzano, Bari, Italy
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30
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Loretz CA, Pollina C, Hyodo S, Takei Y. Extracellular calcium-sensing receptor distribution in osmoregulatory and endocrine tissues of the tilapia. Gen Comp Endocrinol 2009; 161:216-28. [PMID: 19523399 DOI: 10.1016/j.ygcen.2008.12.020] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2008] [Revised: 12/24/2008] [Accepted: 12/29/2008] [Indexed: 01/02/2023]
Abstract
The extracellular calcium-sensing receptor (CaSR) serves an important detector function in vertebrate Ca(2+) homeostasis. In this study, we surveyed using immunohistochemistry the tissue and cellular distribution of the CaSR protein in the Mozambique tilapia (Oreochromis mossambicus) and the Japanese eel (Anguilla japonica). Specifically, we examined receptor expression in ion-transporting barrier tissues that may be directly responsive to extracellular Ca(2+) levels, and in tissues that are implicated in endocrine signaling to homeostatic effectors such as Ca(2+)-transporting epithelia. In tilapia osmoregulatory tissues, CaSR protein is strongly expressed in proximal segments of renal tubule, but not in distal segments (where Na(+),K(+)-ATPase is prominently expressed) or in glomeruli. The receptor was also localized in the ion-transporting mitochondria-rich cells of gill and in ion- and nutrient-transporting epithelia of middle and posterior intestine. Consistent with our earlier RT-PCR assessment of mRNA expression in tilapia, CaSR protein expression was salinity dependent in some osmoregulatory tissues. In tilapia pituitary gland, CaSR expression was observed in the rostral pars distalis (containing prolactin-secreting cells, and in the pars intermedia (containing somatolactin-secreting and melanocyte-stimulating hormone-secreting cells), with notably greater expression in the latter. In the eel, weak immunostaining was seen in the stanniocalcin-secreting cells of the corpuscles of Stannius. Olfactory lobe CaSR expression suggests an environment-sensing role for the receptor. Altogether, these findings support the involvement of CaSR in piscine Ca(2+) homeostasis at the levels of environmental sensing, of integrative endocrine signaling through both hypercalcemic (prolactin, and perhaps somatolactin) and hypocalcemic (stanniocalcin) hormones, and of direct local regulation of Ca(2+)-transporting tissues.
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Affiliation(s)
- Christopher A Loretz
- Department of Biological Sciences, University at Buffalo, Buffalo, NY 14260-1300, USA.
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Messa P, Alfieri C, Brezzi B. Cinacalcet: pharmacological and clinical aspects. Expert Opin Drug Metab Toxicol 2009; 4:1551-60. [PMID: 19040330 DOI: 10.1517/17425250802587017] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The calcium sensing receptor (CaSR) is expressed in cells secreting calcium-regulating hormones, in cells involved in calcium transport and in many other tissues, with an as yet not completely defined role. In parathyroid cells, the CaSR stimulation inhibits parathyroid hormone (PTH) secretion, synthesis and parathyroid cell proliferation. Cinacalcet belongs to calcimimetic type II compounds that can interact with CaSR, increasing its affinity for calcium. Clinical studies have proved cinacalcet to be effective in reducing calcium and PTH levels in primary hyperparathyroidism and in reducing PTH, calcium and phosphate in patients with secondary hyperparathyroidism owing to chronic renal failure, with a relatively safe profile, the only reported adverse events being hypocalcaemia and gastrointestinal symptoms. However, though calcimimetics do represent a real advancement in the field of the treatment of PTH secretion disturbances, there is a need for clinical trials, which should aim to demonstrate that a better control of biochemical parameters is also matched with better clinical outcomes.
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Affiliation(s)
- Piergiorgio Messa
- Nefrologia, Dialisi e Trapianto, Padiglione Croff, Ospedale Maggiore-Policlinico, v. Commenda 15, 20122 Milano, Italy.
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Huang Y, Zhou Y, Castiblanco A, Yang W, Brown EM, Yang JJ. Multiple Ca(2+)-binding sites in the extracellular domain of the Ca(2+)-sensing receptor corresponding to cooperative Ca(2+) response. Biochemistry 2009; 48:388-98. [PMID: 19102677 DOI: 10.1021/bi8014604] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
A small change in the extracellular Ca(2+) concentration ([Ca(2+)](o)) integrates cell signaling responses in multiple cellular and tissue networks and functions via activation of Ca(2+)-sensing receptors (CaSR). Mainly through binding of Ca(2+) to the large extracellular domain (ECD) of the dimeric CaSR, intracellular Ca(2+) responses are highly cooperative with an apparent Hill coefficient ranging from 2 to 4. We have previously reported the identification of two continuous putative Ca(2+)-binding sites by grafting CaSR-derived, Ca(2+)-binding peptides to a scaffold protein, CD2, that does not bind Ca(2+). In this paper, we predict more potential noncontinuous Ca(2+)-binding sites in the ECD. We dissect the intact CaSR into three globular subdomains, each of which contains two to three predicted Ca(2+)-binding sites. This approach enables us to further understand the mechanisms underlying the binding of multiple metal ions to extended polypeptides derived from a location within the ECD of the CaSR, which would be anticipated to more closely mimic the structure of the native CaSR ECD. Tb(3+) luminescence energy transfer, ANS fluorescence, and NMR studies show biphasic metal-binding components and Ca(2+)-dependent conformational changes in these subdomains. Removing the predicted Ca(2+)-binding ligands in site 1 and site 3 abolishes the first binding step and second binding step, respectively. Studies on these subdomains suggest the existence of multiple metal-binding sites and metal-induced conformational changes that might be responsible for the switching on and off the CaSR by the transition between its open inactive form and closed active form.
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Affiliation(s)
- Yun Huang
- Department of Chemistry, Center of Drug Design and Advanced Biotechnology, Georgia State University, Atlanta, Georgia 30303, USA
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Hurtel-Lemaire AS, Mentaverri R, Caudrillier A, Cournarie F, Wattel A, Kamel S, Terwilliger EF, Brown EM, Brazier M. The Calcium-sensing Receptor Is Involved in Strontium Ranelate-induced Osteoclast Apoptosis. J Biol Chem 2009; 284:575-584. [DOI: 10.1074/jbc.m801668200] [Citation(s) in RCA: 185] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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Hendy GN, Guarnieri V, Canaff L. Chapter 3 Calcium-Sensing Receptor and Associated Diseases. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 89:31-95. [DOI: 10.1016/s1877-1173(09)89003-0] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Aquaporin 2 and Apical Calcium-Sensing Receptor: New Players in Polyuric Disorders Associated With Hypercalciuria. Semin Nephrol 2008; 28:297-305. [DOI: 10.1016/j.semnephrol.2008.03.007] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Extracellular calcium-sensing receptors in fishes. Comp Biochem Physiol A Mol Integr Physiol 2008; 149:225-45. [DOI: 10.1016/j.cbpa.2008.01.037] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2007] [Revised: 01/23/2008] [Accepted: 01/23/2008] [Indexed: 11/19/2022]
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Chang W, Tu C, Cheng Z, Rodriguez L, Chen TH, Gassmann M, Bettler B, Margeta M, Jan LY, Shoback D. Complex Formation with the Type B γ-Aminobutyric Acid Receptor Affects the Expression and Signal Transduction of the Extracellular Calcium-sensing Receptor. J Biol Chem 2007; 282:25030-40. [PMID: 17591780 DOI: 10.1074/jbc.m700924200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We co-immunoprecipitated the Ca(2+)-sensing receptor (CaR) and type B gamma-aminobutyric acid receptor (GABA-B-R) from human embryonic kidney (HEK)-293 cells expressing these receptors and from brain lysates where both receptors are present. CaRs extensively co-localized with the two subunits of the GABA-B-R (R1 and R2) in HEK-293 cell membranes and intracellular organelles. Coexpressing CaRs and GABA-B-R1s in HEK-293 cells suppressed the total cellular and cell surface expression of CaRs and inhibited phospholipase C activation in response to high extracellular [Ca(2+)] ([Ca(2+)](e)). In contrast, coexpressing CaRs and GABA-B-R2s enhanced CaR expression and signaling responses to raising [Ca(2+)](e). The latter effects of the GABA-B-R2 on the CaR were blunted by coexpressing the GABA-B-R1. Coexpressing the CaR with GABA-B-R1 or R2 enhanced the total cellular and cell surface expression of the GABA-B-R1 or R2, respectively. Studies with truncated CaRs indicated that the N-terminal extracellular domain of the CaR participated in the interaction of the CaR with the GABA-B-R1 and R2. In cultured mouse hippocampal neurons, CaRs co-localized with the GABA-B-R1 and R2. CaRs and GABA-B-R1s also co-immunoprecipitated from brain lysates. The expression of the CaR was increased in lysates from GABA-B-R1 knock-out mouse brains and in cultured hippocampal neurons with their GABA-B-R1 genes deleted in vitro. Thus, CaRs and GABA-B-R subunits can form heteromeric complexes in cells, and their interactions affect cell surface expression and signaling of CaR, which may contribute to extracellular Ca(2+)-dependent receptor activation in target tissues.
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Affiliation(s)
- Wenhan Chang
- Endocrine Research Unit, Department of Veterans Affairs Medical Center, Department of Medicine, University of California, San Francisco, California 94121, USA.
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Zajickova K, Vrbikova J, Canaff L, Pawelek PD, Goltzman D, Hendy GN. Identification and functional characterization of a novel mutation in the calcium-sensing receptor gene in familial hypocalciuric hypercalcemia: modulation of clinical severity by vitamin D status. J Clin Endocrinol Metab 2007; 92:2616-23. [PMID: 17473068 DOI: 10.1210/jc.2007-0123] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
CONTEXT Familial hypocalciuric hypercalcemia (FHH) is a benign condition associated with heterogeneous inactivating mutations in the calcium-sensing receptor (CASR) gene. OBJECTIVE The objective of the study was to identify and characterize a CASR mutation in a moderately hypercalcemic, hyperparathyroid individual and his family and assess the influence of vitamin D status on the clinical expression of the defect. SUBJECTS We studied a kindred with FHH, in which the proband (a 34-yr-old male) was initially diagnosed with primary hyperparathyroidism due to frankly elevated serum PTH levels. METHODS CASR gene mutation analysis was performed on genomic DNA of the proband and family members. The mutant CASR was functionally characterized by transient transfection studies in kidney cells in vitro. RESULTS A novel heterozygous mutation (F180C, TTC>TGC) in exon 4 of the CASR gene was identified. Although the mutant receptor was expressed normally at the cell surface, it was unresponsive with respect to intracellular signaling (MAPK activation) to increases in extracellular calcium concentrations. The baby daughter of the proband presented with neonatal hyperparathyroidism with markedly elevated PTH. Vitamin D supplementation of both the proband and the baby resulted in reduction of serum PTH levels to the normal range. The serum calcium level remained at a constant and moderately elevated level. CONCLUSION The identification of a novel CASR gene mutation established the basis of the hypercalcemia in the kindred. Concomitant vitamin D deficiency modulates the severity of the presentation of FHH.
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Huang Y, Zhou Y, Yang W, Butters R, Lee HW, Li S, Castiblanco A, Brown EM, Yang JJ. Identification and dissection of Ca(2+)-binding sites in the extracellular domain of Ca(2+)-sensing receptor. J Biol Chem 2007; 282:19000-10. [PMID: 17478419 PMCID: PMC2867057 DOI: 10.1074/jbc.m701096200] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Ca(2+)-sensing receptors (CaSRs) represent a class of receptors that respond to changes in the extracellular Ca(2+) concentration ([Ca(2+)](o)) and activate multiple signaling pathways. A major barrier to advancing our understanding of the role of Ca(2+) in regulating CaSRs is the lack of adequate information about their Ca(2+)-binding locations, which is largely hindered by the lack of a solved three-dimensional structure and rapid off rates due to low Ca(2+)-binding affinities. In this paper, we have reported the identification of three potential Ca(2+)-binding sites in a modeled CaSR structure using computational algorithms based on the geometric description and surface electrostatic potentials. Mutation of the predicted ligand residues in the full-length CaSR caused abnormal responses to [Ca(2+)](o), similar to those observed with naturally occurring activating or inactivating mutations of the CaR, supporting the essential role of these predicted Ca(2+)-binding sites in the sensing capability of the CaSR. In addition, to probe the intrinsic Ca(2+)-binding properties of the predicted sequences, we engineered two predicted continuous Ca(2+)-binding sequences individually into a scaffold protein provided by a non-Ca(2+)-binding protein, CD2. We report herein the estimation of the metal-binding affinities of these predicted sites in the CaSR by monitoring aromatic-sensitized Tb(3+) fluorescence energy transfer. Removing the predicted Ca(2+)-binding ligands resulted in the loss of or significantly weakened cation binding. The potential Ca(2+)-binding residues were shown to be involved in Ca(2+)/Ln(3+) binding by high resolution NMR and site-directed mutagenesis, further validating our prediction of Ca(2+)-binding sites within the extracellular domain of the CaSR.
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MESH Headings
- Algorithms
- Animals
- Binding Sites/physiology
- Calcium/metabolism
- Cell Line
- Extracellular Space/metabolism
- Humans
- Kidney/cytology
- Mice
- Models, Chemical
- Mutagenesis, Site-Directed
- Nuclear Magnetic Resonance, Biomolecular
- Protein Engineering
- Protein Structure, Quaternary
- Protein Structure, Tertiary
- Receptors, Calcium-Sensing/chemistry
- Receptors, Calcium-Sensing/genetics
- Receptors, Calcium-Sensing/metabolism
- Receptors, Metabotropic Glutamate/chemistry
- Receptors, Metabotropic Glutamate/metabolism
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Affiliation(s)
- Yun Huang
- Department of Chemistry, Center for Biotechnology and Drug Design Georgia State University, Atlanta, Georgia 30303
| | - Yubin Zhou
- Department of Chemistry, Center for Biotechnology and Drug Design Georgia State University, Atlanta, Georgia 30303
| | - Wei Yang
- Department of Chemistry, Center for Biotechnology and Drug Design Georgia State University, Atlanta, Georgia 30303
| | - Robert Butters
- Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115
| | - Hsiau-Wei Lee
- Department of Chemistry, Center for Biotechnology and Drug Design Georgia State University, Atlanta, Georgia 30303
| | - Shunyi Li
- Department of Chemistry, Center for Biotechnology and Drug Design Georgia State University, Atlanta, Georgia 30303
| | - Adriana Castiblanco
- Department of Chemistry, Center for Biotechnology and Drug Design Georgia State University, Atlanta, Georgia 30303
| | - Edward M. Brown
- Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115
| | - Jenny J. Yang
- Department of Chemistry, Center for Biotechnology and Drug Design Georgia State University, Atlanta, Georgia 30303
- To whom correspondence should be addressed: Dept. of Chemistry, Georgia State University, University Plaza, Atlanta, GA 30303. Tel.: 404-651-4620; Fax: 404-651-2751;
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Abstract
Calcium sensing receptors (CaR) are unique among G-protein-coupled receptors (GPCRs) since both the first (extracellular) and second (intracellular) messengers are Ca(2+). CaR serves to translate small fluctuations in extracellular Ca(2+) into intracellular Ca(2+) oscillations. In many cells and tissues, CaR also acts as a coincidence detector, sensing both changes in extracellular Ca(2+) plus the presence of various allosteric activators including amino acids, polyamines, and/or peptides. CaR oscillations are uniquely shaped by the activating agonist, that is, Ca(2+) triggers sinusoidal oscillations while Ca(2+) plus phenylalanine trigger transient oscillations of lower frequency. The distinct oscillation patterns generated by Ca(2+)versus Ca(2+) plus phenylalanine are the results of activation of distinct signal transduction pathways. CaR is a member of Family C GPCRs, having a large extracellular agonist binding domain, and functioning as a disulfide-linked dimer. The CaR dimer likely can be driven to distinct active conformations by various Ca(2+) plus modulator combinations, which can drive preferential coupling to divergent signaling pathways. Such plasticity with respect to both agonist and signaling outcomes allows CaR to uniquely contribute to the physiology of organs and tissues where it is expressed. This chapter will examine the structural features of CaR, which contribute to its unique properties, the nature of CaR-induced intracellular Ca(2+) signals and the potential role(s) for CaR in development and differentiation.
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Affiliation(s)
- Gerda E Breitwieser
- Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania 17822, USA
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Mittelman SD, Hendy GN, Fefferman RA, Canaff L, Mosesova I, Cole DEC, Burkett L, Geffner ME. A hypocalcemic child with a novel activating mutation of the calcium-sensing receptor gene: successful treatment with recombinant human parathyroid hormone. J Clin Endocrinol Metab 2006; 91:2474-9. [PMID: 16608894 DOI: 10.1210/jc.2005-2605] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
CONTEXT Persistent hypercalciuria, with the attendant risk of nephrocalcinosis and eventual renal failure, is common in hypoparathyroid patients, especially those with activating mutations of the calcium-sensing receptor (CASR) gene, being treated with oral calcium and calcitriol. Treatment with replacement PTH may be warranted, although this has yet to be evaluated in children. OBJECTIVES The objectives of this study were to identify the cause of the disorder in a young hypocalcemic patient and to assess the efficacy of treatment of the patient with recombinant human PTH(1-34). SUBJECT An infant presenting with hypocalcemia at 3 wk of age was studied. METHODS CASR gene mutation analysis was performed on genomic DNA of the proband and family members. The patient was treated with twice-daily administration of recombinant human PTH(1-34) over a 17-month period. RESULTS The proband was heterozygous for a de novo novel missense mutation (L727Q), on the border between transmembrane helix 4 and intracellular loop 2 of the CASR. When transiently expressed in a human embryonic kidney 293 cell line, the mutant receptor demonstrated a significant leftward shift in the extracellular calcium/intracellular signaling dose-response curve vs. that for the wild-type receptor [EC(50); mutant, 2.59 +/- 0.11 mm (mean +/- se) vs. wild-type, 3.78 +/- 0.12 mm, P < 0.001]. During treatment with PTH(1-34), the patient had no further serious hypocalcemic episodes, and his urinary calcium excretion declined remarkably. CONCLUSION PTH should be evaluated further as a treatment of autosomal dominant hypocalcemia in young patients.
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Affiliation(s)
- Steven D Mittelman
- Division of Endocrinology, Diabetes, and Metabolism, Childrens Hospital Los Angeles, 4650 Sunset Boulevard, Mail Stop Number 61, Los Angeles, California 90027, USA.
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Abstract
A constant extracellular Ca2+ concentration is required for numerous physiological functions at tissue and cellular levels. This suggests that minor changes in Ca2+ will be corrected by appropriate homeostatic systems. The system regulating Ca2+ homeostasis involves several organs and hormones. The former are mainly the kidneys, skeleton, intestine and the parathyroid glands. The latter comprise, amongst others, the parathyroid hormone, vitamin D and calcitonin. Progress has recently been made in the identification and characterisation of Ca2+ transport proteins CaT1 and ECaC and this has provided new insights into the molecular mechanisms of Ca2+ transport in cells. The G-protein coupled calcium-sensing receptor, responsible for the exquisite ability of the parathyroid gland to respond to small changes in serum Ca2+ concentration was discovered about a decade ago. Research has focussed on the molecular mechanisms determining the serum levels of 1,25(OH)2D3, and on the transcriptional activity of the vitamin D receptor. The aim of recent work has been to elucidate the mechanisms and the intracellular signalling pathways by which parathyroid hormone, vitamin D and calcitonin affect Ca2+ homeostasis. This article summarises recent advances in the understanding and the molecular basis of physiological Ca2+ homeostasis.
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Affiliation(s)
- Indra Ramasamy
- Department of Chemical Pathology, Newham University Hospital, London, UK.
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Dell'Aquila ME, De Santis T, Cho YS, Reshkin SJ, Caroli AM, Maritato F, Minoia P, Casavola V. Localization and quantitative expression of the calcium-sensing receptor protein in human oocytes. Fertil Steril 2006; 85 Suppl 1:1240-7. [PMID: 16616098 DOI: 10.1016/j.fertnstert.2005.11.033] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2005] [Revised: 11/03/2005] [Accepted: 11/03/2005] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To investigate the expression of the calcium-sensing receptor (CaSR) protein in human oocytes at the germinal vesicle (GV) and metaphase I (MI) and II (MII) stages. DESIGN Prospective study. SETTING Academic basic research laboratory and hospital-based fertility center. PATIENT(S) Immature and supernumerary mature oocytes (n = 118) excluded from intracytoplasmic sperm injection treatment. INTERVENTION(S) Immunofluorescence and Western blot with a primary antibody against human CaSR. Confocal laser scanning microscopy (CLSM) together with quantitative image analysis used to measure the fluorescence intensity variations in oocytes at GV, MI, and MII stages. MAIN OUTCOME MEASURE(S) The CaSR expression pattern as evaluated by immunostaining in denuded oocytes and cumulus cells, CLSM, and three-dimensional image reconstructions; quantitative analysis at the equatorial plane of the oocyte. RESULT(S) We identified CaSR in human oocytes and cumulus cells. The fluorescence intensity within the oocyte varied with the developmental stage, with the greatest increase at the MI stage. CONCLUSION(S) The present study demonstrates for the first time the expression and localization of CaSR protein in human oocytes. Increased CaSR protein expression in the MI stage suggests that it may be involved in the regulation of human oocyte development and maturation.
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Abstract
Ca2+ is a universal second messenger that is a key component of myriad processes in all cell types. Perturbations in normal intracellular Ca2+ concentrations underlie many common pathological conditions, ranging from cardiac hypertrophy to ischemic death of neurons. A recent meeting addressed the contributions of Ca2+ and Ca2+ binding proteins to health and disease. Insights gleaned from mechanistic studies offered the potential for new therapeutic approaches to combat a variety of diseases resulting from alterations in Ca2+ homeostasis.
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Affiliation(s)
- Craig Montell
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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Petersen OH, Michalak M, Verkhratsky A. Calcium signalling: Past, present and future. Cell Calcium 2005; 38:161-9. [PMID: 16076488 DOI: 10.1016/j.ceca.2005.06.023] [Citation(s) in RCA: 151] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Accepted: 06/28/2005] [Indexed: 01/25/2023]
Abstract
Ca2+ is a universal second messenger controlling a wide variety of cellular reactions and adaptive responses. The initial appreciation of Ca2+ as a universal signalling molecule was based on the work of Sydney Ringer and Lewis Heilbrunn. More recent developments in this field were critically influenced by the invention of the patch clamp technique and the generation of fluorescent Ca2+ indicators. Currently the molecular Ca2+ signalling mechanisms are being worked out and we are beginning to assemble a reasonably complete picture of overall Ca2+ homeostasis. Furthermore, investigations of organellar Ca2+ homeostasis have added complexity to our understanding of Ca2+ signalling. The future of the Ca2+ signalling field lies with detailed investigations of the integrative function in vivo and clarification of the pathology associated with malfunctions of Ca2+ signalling cascades.
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Affiliation(s)
- Ole H Petersen
- Physiological Laboratory, University of Liverpool, Crown Street, Liverpool L69 3BX, UK
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46
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Abstract
The presence of the extracellular calcium-sensing receptor (CaSR) has been demonstrated in numerous cells that are key in the control of serum calcium concentrations, underscoring its relevance in systemic calcium homeostasis. The more recent evidence of its presence in tissues not involved in this function has broadened the spectrum of interest in this protein, now known to regulate diverse cell functions such as proliferation, differentiation, and apoptosis. This study shows the expression of CaSR in human omental adipose tissue, isolated adipocytes, and adipocyte progenitor cells as assessed by RT-PCR and immunoblotting. This is the first report of CaSR being expressed in human adipocytes and adipocyte progenitor cells, opening the possibility to investigate the physiological implications and thus contributing a novel component for adipose tissue biology research.
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Affiliation(s)
- Mariana Cifuentes
- Institute of Nutrition and Food Technology, University of Chile, Macul, Casilla, Santiago, Chile.
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47
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Zhang M, Breitwieser GE. High Affinity Interaction with Filamin A Protects against Calcium-sensing Receptor Degradation. J Biol Chem 2005; 280:11140-6. [PMID: 15657061 DOI: 10.1074/jbc.m412242200] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Calcium-sensing receptors (CaR) regulate cell proliferation, differentiation, and apoptosis through the MAPK pathway. MAPK pathway activation requires the cytoskeletal scaffold protein filamin A. Here we examine the interactions of CaR with filamin A in HEK-293 and M2 or A7 melanoma cells to determine how interactions with filamin A facilitate signaling. Filamin A interacts with CaR through two predicted beta-strands from residues 962 to 981; interactions between filamin A and CaR are greatly enhanced by exposure to 5 mM Ca2+. Truncations or deletions (from 972 to 997 or 962 to 981) of the CaR carboxyl terminus eliminate high affinity interactions with filamin A, but CaR-mediated MAPK pathway activation still occurs. CaR-mediated ERK phosphorylation can be localized to a predicted alpha-helix proximal to the membrane, which has been shown to be important for G protein-mediated signaling (residues 868-879). In M2 cells (-filamin A), CaR expression levels are very low; cotransfection of CaR with filamin A increases total cellular CaR and increases plasma membrane localization of CaR, facilitating CaR signaling to the MAPK pathway; similar results were obtained in HEK-293 cells. Interaction with filamin A increases cellular CaR by preventing CaR degradation, thereby facilitating CaR signaling. In addition, filamin A facilitates signaling to the MAPK pathway even by CaR truncations or deletion mutants that cannot engage in high affinity interactions with filamin A, suggesting the targeting of critical signaling proteins to CaR.
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Affiliation(s)
- Mingliang Zhang
- Department of Biology, Syracuse University, Syracuse, New York 13244, USA
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48
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Loretz CA, Pollina C, Hyodo S, Takei Y, Chang W, Shoback D. cDNA Cloning and Functional Expression of a Ca2+-sensing Receptor with Truncated C-terminal Tail from the Mozambique Tilapia (Oreochromis mossambicus). J Biol Chem 2004; 279:53288-97. [PMID: 15456780 DOI: 10.1074/jbc.m410098200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The complete cDNA sequence of the tilapia extracellular Ca(2+)-sensing receptor (CaR) was determined. The transcript length of tilapia CaR (tCaR) is 3.4 kbp and encodes a 940-amino acid, 7-transmembrane domain protein that is consistent in its structural features with known mammalian and piscine CaRs. The tCaR extracellular domain includes a characteristic hydrophobic segment, conserved cysteine residues that are implicated in receptor dimerization (Cys(129) and Cys(131)) and in coupling to the transmembrane domain (nine conserved cysteine residues), and conserved serine residues (Ser(147) and Ser(169-171)) that are linked to receptor binding of Ca(2+) and L-amino acid-mediated potentiation of function. mRNA expression of tCaR was strong in kidney, brain, and gill. Weaker expression was observed in pituitary, stomach, intestine, urinary bladder, and heart. This distribution is consistent with possible physiological roles in endocrine cells, excitable tissues, and ion-transporting barrier epithelia. Expression of tCaR mRNA in kidney and intestine was salinity-dependent, suggesting a role for the receptor in iono-/osmoregulation in this euryhaline teleost species. Human embryonic kidney-293 cells transiently transfected with tCaR cDNA demonstrated dose-dependent phospholipase C activation in response to elevations in the extracellular Ca(2+) concentration ([Ca(2+)](o)). Functional activation of the mitogen-activated protein kinase cascade by high [Ca(2+)](o) was also confirmed in these cells despite the naturally occurring truncation of the receptor's intracellular tail, which removes segments variably linked in mammalian CaRs to filamin-coupled activation of mitogen-activated protein kinase cascades. Sensitivity of phospholipase C activation to [Ca(2+)](o) was dependent on the ionic strength of the bathing medium, supporting a role in salinity sensing.
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MESH Headings
- Amino Acid Sequence
- Animals
- Blotting, Northern
- Calcium/chemistry
- Cell Line
- Cloning, Molecular
- Contractile Proteins/chemistry
- Cystine/chemistry
- DNA, Complementary/metabolism
- Dimerization
- Dose-Response Relationship, Drug
- Electrophoresis, Agar Gel
- Enzyme Activation
- Filamins
- Humans
- Ions
- MAP Kinase Signaling System
- Microfilament Proteins/chemistry
- Molecular Sequence Data
- Protein Structure, Tertiary
- RNA/metabolism
- RNA, Messenger/metabolism
- Receptors, Calcium-Sensing/chemistry
- Receptors, Calcium-Sensing/genetics
- Receptors, Calcium-Sensing/physiology
- Sequence Homology, Amino Acid
- Serine/chemistry
- Signal Transduction
- Tilapia/genetics
- Time Factors
- Tissue Distribution
- Transfection
- Type C Phospholipases/metabolism
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Affiliation(s)
- Christopher A Loretz
- National Science Foundation Tokyo Regional Office, American Embassy, 1-10-5, Akasaka, Minato-ku, Tokyo 107-8420, Japan.
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