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Dutta P, Hakimi S, Layton AT. How the kidney regulates magnesium: a modelling study. ROYAL SOCIETY OPEN SCIENCE 2024; 11:231484. [PMID: 38511086 PMCID: PMC10951724 DOI: 10.1098/rsos.231484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 01/23/2024] [Accepted: 02/15/2024] [Indexed: 03/22/2024]
Abstract
The kidneys are crucial for maintaining Mg2+ homeostasis. Along the proximal tubule and thick ascending limb, Mg2+ is reabsorbed paracellularly, while along the distal convoluted tubule (DCT), Mg2+ is reabsorbed transcellularly via transient receptor potential melastatin 6 (TRPM6). TRPM6 and other renal transporter expressions are regulated by sex hormones. To investigate renal Mg2 handling, we have developed sex-specific computational models of electrolyte transport along rat superficial nephron. Model simulations indicated that along the proximal tubule and thick ascending limb, Mg2+ and Na+ transport occur parallelly, but they are dissociated along the DCT. In addition, our models predicted higher paracellular Mg2+ permeability in females to attain similar cortical thick ascending limb fractional Mg2+ reabsorption in both sexes. Furthermore, DCT fractional Mg2+ reabsorption is higher in females than in males, allowing females to better fine-tune Mg2+ excretion. We validated our models by simulating the administration of three classes of diuretics. The model predicted significantly increased, marginally increased and significantly decreased Mg2+ excretions for loop, thiazide and K-sparing diuretics, respectively, aligning with experimental findings. The models can be used to conduct in silico studies on kidney adaptations to Mg2+ homeostasis alterations during conditions such as pregnancy, diabetes and chronic kidney disease.
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Affiliation(s)
- Pritha Dutta
- Department of Applied Mathematics, University of Waterloo, Waterloo, OntarioN2L 3G1, Canada
| | - Shervin Hakimi
- Department of Applied Mathematics, University of Waterloo, Waterloo, OntarioN2L 3G1, Canada
| | - Anita T. Layton
- Department of Applied Mathematics, University of Waterloo, Waterloo, OntarioN2L 3G1, Canada
- Department of Biology, University of Waterloo, Waterloo, OntarioN2L 3G1, Canada
- Cheriton School of Computer Science, University of Waterloo, Waterloo, OntarioN2L 3G1, Canada
- School of Pharmacology, University of Waterloo, Waterloo, OntarioN2L 3G1, Canada
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de Souza Goncalves L, Chu T, Master R, Chhetri PD, Gao Q, Cil O. Mg2+ supplementation treats secretory diarrhea in mice by activating calcium-sensing receptor in intestinal epithelial cells. J Clin Invest 2024; 134:e171249. [PMID: 37962961 PMCID: PMC10786700 DOI: 10.1172/jci171249] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Accepted: 11/09/2023] [Indexed: 11/16/2023] Open
Abstract
Cholera is a global health problem with no targeted therapies. The Ca2+-sensing receptor (CaSR) is a regulator of intestinal ion transport and a therapeutic target for diarrhea, and Ca2+ is considered its main agonist. We found that increasing extracellular Ca2+ had a minimal effect on forskolin-induced Cl- secretion in human intestinal epithelial T84 cells. However, extracellular Mg2+, an often-neglected CaSR agonist, suppressed forskolin-induced Cl- secretion in T84 cells by 65% at physiological levels seen in stool (10 mM). The effect of Mg2+ occurred via the CaSR/Gq signaling that led to cAMP hydrolysis. Mg2+ (10 mM) also suppressed Cl- secretion induced by cholera toxin, heat-stable E. coli enterotoxin, and vasoactive intestinal peptide by 50%. In mouse intestinal closed loops, luminal Mg2+ treatment (20 mM) inhibited cholera toxin-induced fluid accumulation by 40%. In a mouse intestinal perfusion model of cholera, addition of 10 mM Mg2+ to the perfusate reversed net fluid transport from secretion to absorption. These results suggest that Mg2+ is the key CaSR activator in mouse and human intestinal epithelia at physiological levels in stool. Since stool Mg2+ concentrations in patients with cholera are essentially zero, oral Mg2+ supplementation, alone or in an oral rehydration solution, could be a potential therapy for cholera and other cyclic nucleotide-mediated secretory diarrheas.
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Moon JE, Yang HY, Wee G, ParK SH, Ko CW. A cell function study on calcium regulation of a novel calcium-sensing receptor mutation (p.Tyr825Phe). Ann Pediatr Endocrinol Metab 2021; 26:24-30. [PMID: 32871647 PMCID: PMC8026336 DOI: 10.6065/apem.2040022.011] [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: 02/06/2020] [Accepted: 03/30/2020] [Indexed: 11/21/2022] Open
Abstract
PURPOSE Autosomal dominant hypocalcemia with hypercalciuria is a genetic disease characterized by hypoparathyroidism with hypercalciuria. We discovered a novel variant (p.Tyr825Phe[Y825F]) of the CASR gene in a neonate with congenital hypoparathyroidism and hypercalciuria and conducted a cell function study to determine whether the CASR-Y825F variant was pathogenic. METHODS To perform a functional study on CaSR-Y825F, we constructed expression vectors expressing wild-type (WT) CASR and CASR-Y825F. After transfection of each expression vector into HEK293 cells, we examined alterations in intracellular signaling. Mitogen-activated protein kinase (MAPK) signaling activity of HEK293 cells expressing CASR-WT or CASR-Y825F was determined. Changes in intracellular calcium ions ([Ca2+]i) by extracellular calcium ion ([Ca2+]e) stimulation were quantitatively compared and analyzed. RESULTS Cells expressing CASR-Y825F showed elevated of MAPK signaling (phospho-ERK [pERK], phospho-JNK [pJNK], phospho-p38 [pp38]) and increased [Ca2+]i levels at low [Ca2+]e stimulation compared with cells expressing CASR-WT. Additionally, [Ca2+]i levels in HEK293 cells expression CASR-WT and CASR-Y825F were determined at 340 nm/380 nm wavelength ratios using Fura-2 AM. At [Ca2+]e concentrations of 2.5 mM and 3 mM, the ratios of CASR-Y825F cells were higher (2.6 and 3.5, respectively) than those of CASR-WT cells (1.04 and 1.40, respectively). CONCLUSION This cell function study proved that the CASR-Y825F expressed in HEK293 cells elevated MAPK signaling (pERK, pJNK, pp38) and increased [Ca2+]i to induce hypocalcemia.
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Affiliation(s)
- Jung Eun Moon
- Department of Pediatrics, Kyungpook National University Hospital, School of Medicine, Kyungpook National University, Daegu, Korea
| | - Hee-Young Yang
- Laboratory Animal Center, Daegu-Gyeongbuk Medical Innovation Foundation (DGMIF), Daegu, Korea
| | - Gabbine Wee
- Laboratory Animal Center, Daegu-Gyeongbuk Medical Innovation Foundation (DGMIF), Daegu, Korea
| | - Suk-Hyun ParK
- Department of Pediatrics, Kyungpook National University Hospital, School of Medicine, Kyungpook National University, Daegu, Korea
| | - Cheol Woo Ko
- Department of Pediatrics, Kyungpook National University Hospital, School of Medicine, Kyungpook National University, Daegu, Korea,Address for correspondence: Cheol Woo Ko Department of Pediatric Endocrinology, Kyungpook National University Children's Hospital, 807, Hoguk-ro, Buk-gu, Daegu 41404, Korea
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A Novel Variant in the Calcium-Sensing Receptor Associated with Familial Hypocalciuric Hypercalcemia and Low-to-Normal PTH. Case Rep Endocrinol 2020; 2020:8752610. [PMID: 33062349 PMCID: PMC7555459 DOI: 10.1155/2020/8752610] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 09/03/2020] [Accepted: 09/16/2020] [Indexed: 12/18/2022] Open
Abstract
Familial hypocalciuric hypercalcemia (FHH) is considered a relatively benign condition characterized by mild elevations in serum calcium and relatively low urinary calcium excretion. It results from an elevated set point in serum calcium arising from variants in the calcium-sensing receptor (CaSR) gene but also AP2S1 and GNA11 genes, which encode for adaptor-related protein complex 2 and G11 proteins, respectively. The manifestations of FHH can vary and sometimes overlap with primary hyperparathyroidism making the diagnosis challenging. Case Presentations. We report a mother and daughter with a novel heterozygous variant in the CaSR gene resulting in a serine to leucine substitution at position 147 (S147L) of the CaSR. Both patients had mild hypercalcemia, relatively low urinary calcium excretion, elevated calcitriol, and low-to-normal intact PTH. The proband (daughter) presented with symptoms associated with hypercalcemia and was incidentally found to have a bony lesion suspicious for osteitis fibrosa cystica, and she was also diagnosed with sarcoidosis. Subtotal parathyroidectomy revealed normal-weight parathyroid glands comprised of 50–80% parathyroid epithelial cells, which has been documented as within the spectrum of normal. Her mother had no symptoms, and no intervention was pursued. Conclusion. We report a novel variant in the CaSR associated with FHH in two patients with similar biochemical features yet differing clinical manifestations. While the relationship of the bony findings and parathyroid histology with this variant remains unclear, these cases enrich our knowledge of CaSR physiology and provide further examples of how varied the manifestations of FHH can be.
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Leach K, Hannan FM, Josephs TM, Keller AN, Møller TC, Ward DT, Kallay E, Mason RS, Thakker RV, Riccardi D, Conigrave AD, Bräuner-Osborne H. International Union of Basic and Clinical Pharmacology. CVIII. Calcium-Sensing Receptor Nomenclature, Pharmacology, and Function. Pharmacol Rev 2020; 72:558-604. [PMID: 32467152 PMCID: PMC7116503 DOI: 10.1124/pr.119.018531] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The calcium-sensing receptor (CaSR) is a class C G protein-coupled receptor that responds to multiple endogenous agonists and allosteric modulators, including divalent and trivalent cations, L-amino acids, γ-glutamyl peptides, polyamines, polycationic peptides, and protons. The CaSR plays a critical role in extracellular calcium (Ca2+ o) homeostasis, as demonstrated by the many naturally occurring mutations in the CaSR or its signaling partners that cause Ca2+ o homeostasis disorders. However, CaSR tissue expression in mammals is broad and includes tissues unrelated to Ca2+ o homeostasis, in which it, for example, regulates the secretion of digestive hormones, airway constriction, cardiovascular effects, cellular differentiation, and proliferation. Thus, although the CaSR is targeted clinically by the positive allosteric modulators (PAMs) cinacalcet, evocalcet, and etelcalcetide in hyperparathyroidism, it is also a putative therapeutic target in diabetes, asthma, cardiovascular disease, and cancer. The CaSR is somewhat unique in possessing multiple ligand binding sites, including at least five putative sites for the "orthosteric" agonist Ca2+ o, an allosteric site for endogenous L-amino acids, two further allosteric sites for small molecules and the peptide PAM, etelcalcetide, and additional sites for other cations and anions. The CaSR is promiscuous in its G protein-coupling preferences, and signals via Gq/11, Gi/o, potentially G12/13, and even Gs in some cell types. Not surprisingly, the CaSR is subject to biased agonism, in which distinct ligands preferentially stimulate a subset of the CaSR's possible signaling responses, to the exclusion of others. The CaSR thus serves as a model receptor to study natural bias and allostery. SIGNIFICANCE STATEMENT: The calcium-sensing receptor (CaSR) is a complex G protein-coupled receptor that possesses multiple orthosteric and allosteric binding sites, is subject to biased signaling via several different G proteins, and has numerous (patho)physiological roles. Understanding the complexities of CaSR structure, function, and biology will aid future drug discovery efforts seeking to target this receptor for a diversity of diseases. This review summarizes what is known to date regarding key structural, pharmacological, and physiological features of the CaSR.
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Affiliation(s)
- Katie Leach
- Drug Discovery Biology, Monash Institute of Pharmaceutical Science, Monash University, Parkville, Australia (K.L., T.M.J., A.N.K.); Nuffield Department of Women's & Reproductive Health (F.M.H.) and Academic Endocrine Unit, Radcliffe Department of Clinical Medicine (F.M.H., R.V.T.), University of Oxford, Oxford, United Kingdom; Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (T.C.M., H.B.-O.); Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom (D.T.W.); Department of Pathophysiology and Allergy Research, Medical University of Vienna, Vienna, Austria (E.K.); Physiology, School of Medical Sciences and Bosch Institute (R.S.M.) and School of Life & Environmental Sciences, Charles Perkins Centre (A.D.C.), University of Sydney, Sydney, Australia; and School of Biosciences, Cardiff University, Cardiff, United Kingdom (D.R.)
| | - Fadil M Hannan
- Drug Discovery Biology, Monash Institute of Pharmaceutical Science, Monash University, Parkville, Australia (K.L., T.M.J., A.N.K.); Nuffield Department of Women's & Reproductive Health (F.M.H.) and Academic Endocrine Unit, Radcliffe Department of Clinical Medicine (F.M.H., R.V.T.), University of Oxford, Oxford, United Kingdom; Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (T.C.M., H.B.-O.); Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom (D.T.W.); Department of Pathophysiology and Allergy Research, Medical University of Vienna, Vienna, Austria (E.K.); Physiology, School of Medical Sciences and Bosch Institute (R.S.M.) and School of Life & Environmental Sciences, Charles Perkins Centre (A.D.C.), University of Sydney, Sydney, Australia; and School of Biosciences, Cardiff University, Cardiff, United Kingdom (D.R.)
| | - Tracy M Josephs
- Drug Discovery Biology, Monash Institute of Pharmaceutical Science, Monash University, Parkville, Australia (K.L., T.M.J., A.N.K.); Nuffield Department of Women's & Reproductive Health (F.M.H.) and Academic Endocrine Unit, Radcliffe Department of Clinical Medicine (F.M.H., R.V.T.), University of Oxford, Oxford, United Kingdom; Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (T.C.M., H.B.-O.); Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom (D.T.W.); Department of Pathophysiology and Allergy Research, Medical University of Vienna, Vienna, Austria (E.K.); Physiology, School of Medical Sciences and Bosch Institute (R.S.M.) and School of Life & Environmental Sciences, Charles Perkins Centre (A.D.C.), University of Sydney, Sydney, Australia; and School of Biosciences, Cardiff University, Cardiff, United Kingdom (D.R.)
| | - Andrew N Keller
- Drug Discovery Biology, Monash Institute of Pharmaceutical Science, Monash University, Parkville, Australia (K.L., T.M.J., A.N.K.); Nuffield Department of Women's & Reproductive Health (F.M.H.) and Academic Endocrine Unit, Radcliffe Department of Clinical Medicine (F.M.H., R.V.T.), University of Oxford, Oxford, United Kingdom; Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (T.C.M., H.B.-O.); Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom (D.T.W.); Department of Pathophysiology and Allergy Research, Medical University of Vienna, Vienna, Austria (E.K.); Physiology, School of Medical Sciences and Bosch Institute (R.S.M.) and School of Life & Environmental Sciences, Charles Perkins Centre (A.D.C.), University of Sydney, Sydney, Australia; and School of Biosciences, Cardiff University, Cardiff, United Kingdom (D.R.)
| | - Thor C Møller
- Drug Discovery Biology, Monash Institute of Pharmaceutical Science, Monash University, Parkville, Australia (K.L., T.M.J., A.N.K.); Nuffield Department of Women's & Reproductive Health (F.M.H.) and Academic Endocrine Unit, Radcliffe Department of Clinical Medicine (F.M.H., R.V.T.), University of Oxford, Oxford, United Kingdom; Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (T.C.M., H.B.-O.); Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom (D.T.W.); Department of Pathophysiology and Allergy Research, Medical University of Vienna, Vienna, Austria (E.K.); Physiology, School of Medical Sciences and Bosch Institute (R.S.M.) and School of Life & Environmental Sciences, Charles Perkins Centre (A.D.C.), University of Sydney, Sydney, Australia; and School of Biosciences, Cardiff University, Cardiff, United Kingdom (D.R.)
| | - Donald T Ward
- Drug Discovery Biology, Monash Institute of Pharmaceutical Science, Monash University, Parkville, Australia (K.L., T.M.J., A.N.K.); Nuffield Department of Women's & Reproductive Health (F.M.H.) and Academic Endocrine Unit, Radcliffe Department of Clinical Medicine (F.M.H., R.V.T.), University of Oxford, Oxford, United Kingdom; Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (T.C.M., H.B.-O.); Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom (D.T.W.); Department of Pathophysiology and Allergy Research, Medical University of Vienna, Vienna, Austria (E.K.); Physiology, School of Medical Sciences and Bosch Institute (R.S.M.) and School of Life & Environmental Sciences, Charles Perkins Centre (A.D.C.), University of Sydney, Sydney, Australia; and School of Biosciences, Cardiff University, Cardiff, United Kingdom (D.R.)
| | - Enikö Kallay
- Drug Discovery Biology, Monash Institute of Pharmaceutical Science, Monash University, Parkville, Australia (K.L., T.M.J., A.N.K.); Nuffield Department of Women's & Reproductive Health (F.M.H.) and Academic Endocrine Unit, Radcliffe Department of Clinical Medicine (F.M.H., R.V.T.), University of Oxford, Oxford, United Kingdom; Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (T.C.M., H.B.-O.); Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom (D.T.W.); Department of Pathophysiology and Allergy Research, Medical University of Vienna, Vienna, Austria (E.K.); Physiology, School of Medical Sciences and Bosch Institute (R.S.M.) and School of Life & Environmental Sciences, Charles Perkins Centre (A.D.C.), University of Sydney, Sydney, Australia; and School of Biosciences, Cardiff University, Cardiff, United Kingdom (D.R.)
| | - Rebecca S Mason
- Drug Discovery Biology, Monash Institute of Pharmaceutical Science, Monash University, Parkville, Australia (K.L., T.M.J., A.N.K.); Nuffield Department of Women's & Reproductive Health (F.M.H.) and Academic Endocrine Unit, Radcliffe Department of Clinical Medicine (F.M.H., R.V.T.), University of Oxford, Oxford, United Kingdom; Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (T.C.M., H.B.-O.); Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom (D.T.W.); Department of Pathophysiology and Allergy Research, Medical University of Vienna, Vienna, Austria (E.K.); Physiology, School of Medical Sciences and Bosch Institute (R.S.M.) and School of Life & Environmental Sciences, Charles Perkins Centre (A.D.C.), University of Sydney, Sydney, Australia; and School of Biosciences, Cardiff University, Cardiff, United Kingdom (D.R.)
| | - Rajesh V Thakker
- Drug Discovery Biology, Monash Institute of Pharmaceutical Science, Monash University, Parkville, Australia (K.L., T.M.J., A.N.K.); Nuffield Department of Women's & Reproductive Health (F.M.H.) and Academic Endocrine Unit, Radcliffe Department of Clinical Medicine (F.M.H., R.V.T.), University of Oxford, Oxford, United Kingdom; Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (T.C.M., H.B.-O.); Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom (D.T.W.); Department of Pathophysiology and Allergy Research, Medical University of Vienna, Vienna, Austria (E.K.); Physiology, School of Medical Sciences and Bosch Institute (R.S.M.) and School of Life & Environmental Sciences, Charles Perkins Centre (A.D.C.), University of Sydney, Sydney, Australia; and School of Biosciences, Cardiff University, Cardiff, United Kingdom (D.R.)
| | - Daniela Riccardi
- Drug Discovery Biology, Monash Institute of Pharmaceutical Science, Monash University, Parkville, Australia (K.L., T.M.J., A.N.K.); Nuffield Department of Women's & Reproductive Health (F.M.H.) and Academic Endocrine Unit, Radcliffe Department of Clinical Medicine (F.M.H., R.V.T.), University of Oxford, Oxford, United Kingdom; Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (T.C.M., H.B.-O.); Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom (D.T.W.); Department of Pathophysiology and Allergy Research, Medical University of Vienna, Vienna, Austria (E.K.); Physiology, School of Medical Sciences and Bosch Institute (R.S.M.) and School of Life & Environmental Sciences, Charles Perkins Centre (A.D.C.), University of Sydney, Sydney, Australia; and School of Biosciences, Cardiff University, Cardiff, United Kingdom (D.R.)
| | - Arthur D Conigrave
- Drug Discovery Biology, Monash Institute of Pharmaceutical Science, Monash University, Parkville, Australia (K.L., T.M.J., A.N.K.); Nuffield Department of Women's & Reproductive Health (F.M.H.) and Academic Endocrine Unit, Radcliffe Department of Clinical Medicine (F.M.H., R.V.T.), University of Oxford, Oxford, United Kingdom; Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (T.C.M., H.B.-O.); Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom (D.T.W.); Department of Pathophysiology and Allergy Research, Medical University of Vienna, Vienna, Austria (E.K.); Physiology, School of Medical Sciences and Bosch Institute (R.S.M.) and School of Life & Environmental Sciences, Charles Perkins Centre (A.D.C.), University of Sydney, Sydney, Australia; and School of Biosciences, Cardiff University, Cardiff, United Kingdom (D.R.)
| | - Hans Bräuner-Osborne
- Drug Discovery Biology, Monash Institute of Pharmaceutical Science, Monash University, Parkville, Australia (K.L., T.M.J., A.N.K.); Nuffield Department of Women's & Reproductive Health (F.M.H.) and Academic Endocrine Unit, Radcliffe Department of Clinical Medicine (F.M.H., R.V.T.), University of Oxford, Oxford, United Kingdom; Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (T.C.M., H.B.-O.); Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom (D.T.W.); Department of Pathophysiology and Allergy Research, Medical University of Vienna, Vienna, Austria (E.K.); Physiology, School of Medical Sciences and Bosch Institute (R.S.M.) and School of Life & Environmental Sciences, Charles Perkins Centre (A.D.C.), University of Sydney, Sydney, Australia; and School of Biosciences, Cardiff University, Cardiff, United Kingdom (D.R.)
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Mos I, Jacobsen SE, Foster SR, Bräuner-Osborne H. Calcium-Sensing Receptor Internalization Isβ-Arrestin–Dependent and Modulated by Allosteric Ligands. Mol Pharmacol 2019; 96:463-474. [DOI: 10.1124/mol.119.116772] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2019] [Accepted: 07/30/2019] [Indexed: 12/18/2022] Open
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Binmahfouz LS, Centeno PP, Conigrave AD, Ward DT. Identification of Serine-875 as an Inhibitory Phosphorylation Site in the Calcium-Sensing Receptor. Mol Pharmacol 2019; 96:204-211. [DOI: 10.1124/mol.119.116178] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Accepted: 05/20/2019] [Indexed: 11/22/2022] Open
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Ibeh CL, Yiu AJ, Kanaras YL, Paal E, Birnbaumer L, Jose PA, Bandyopadhyay BC. Evidence for a regulated Ca 2+ entry in proximal tubular cells and its implication in calcium stone formation. J Cell Sci 2019; 132:jcs.225268. [PMID: 30910829 DOI: 10.1242/jcs.225268] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Accepted: 03/14/2019] [Indexed: 12/14/2022] Open
Abstract
Calcium phosphate (CaP) crystals, which begin to form in the early segments of the loop of Henle (LOH), are known to act as precursors for calcium stone formation. The proximal tubule (PT), which is just upstream of the LOH and is a major site for Ca2+ reabsorption, could be a regulator of such CaP crystal formation. However, PT Ca2+ reabsorption is mostly described as being paracellular. Here, we show the existence of a regulated transcellular Ca2+ entry pathway in luminal membrane PT cells induced by Ca2+-sensing receptor (CSR, also known as CASR)-mediated activation of transient receptor potential canonical 3 (TRPC3) channels. In support of this idea, we found that both CSR and TRPC3 are physically and functionally coupled at the luminal membrane of PT cells. More importantly, TRPC3-deficient mice presented with a deficiency in PT Ca2+ entry/transport, elevated urinary [Ca2+], microcalcifications in LOH and urine microcrystals formations. Taken together, these data suggest that a signaling complex comprising CSR and TRPC3 exists in the PT and can mediate transcellular Ca2+ transport, which could be critical in maintaining the PT luminal [Ca2+] to mitigate formation of the CaP crystals in LOH and subsequent formation of calcium stones.
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Affiliation(s)
- Cliff-Lawrence Ibeh
- Calcium Signaling Laboratory, Research Service, Veterans Affairs Medical Center, 50 Irving Street, NW, Washington DC, DC 20422, USA
| | - Allen J Yiu
- Calcium Signaling Laboratory, Research Service, Veterans Affairs Medical Center, 50 Irving Street, NW, Washington DC, DC 20422, USA.,Department of Medicine, Division of Renal Diseases & Hypertension, The George Washington University, Washington DC, DC 20037, USA
| | - Yianni L Kanaras
- Calcium Signaling Laboratory, Research Service, Veterans Affairs Medical Center, 50 Irving Street, NW, Washington DC, DC 20422, USA
| | - Edina Paal
- Pathology and Laboratory Service, Veterans Affairs Medical Center, 50 Irving Street, NW, Washington DC, DC 20422, USA
| | - Lutz Birnbaumer
- Division of Intramural Research, NIEHS, Research Triangle Park, Durham, NC 27709, USA.,Institute for Biomedical Research (BIOMED), Catholic University of Argentina, C1107AFF Buenos Aires, Argentina
| | - Pedro A Jose
- Department of Medicine, Division of Renal Diseases & Hypertension, The George Washington University, Washington DC, DC 20037, USA.,Department of Pharmacology and Physiology, The George Washington University, Washington DC, DC 20037, USA
| | - Bidhan C Bandyopadhyay
- Calcium Signaling Laboratory, Research Service, Veterans Affairs Medical Center, 50 Irving Street, NW, Washington DC, DC 20422, USA .,Department of Medicine, Division of Renal Diseases & Hypertension, The George Washington University, Washington DC, DC 20037, USA.,Department of Pharmacology and Physiology, The George Washington University, Washington DC, DC 20037, USA
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Nemeth EF, Van Wagenen BC, Balandrin MF. Discovery and Development of Calcimimetic and Calcilytic Compounds. PROGRESS IN MEDICINAL CHEMISTRY 2018; 57:1-86. [PMID: 29680147 DOI: 10.1016/bs.pmch.2017.12.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The extracellular calcium receptor (CaR) is a G protein-coupled receptor (GPCR) and the pivotal molecule regulating systemic Ca2+ homeostasis. The CaR was a challenging target for drug discovery because its physiological ligand is an inorganic ion (Ca2+) rather than a molecule so there was no structural template to guide medicinal chemistry. Nonetheless, small molecules targeting this receptor were discovered. Calcimimetics are agonists or positive allosteric modulators of the CaR, while calcilytics are antagonists and all to date are negative allosteric modulators. The calcimimetic cinacalcet was the first allosteric modulator of a GPCR to achieve regulatory approval and is a first-in-class treatment for secondary hyperparathyroidism in patients on dialysis, and for hypercalcemia in some forms of primary hyperparathyroidism. It is also useful in treating some rare genetic diseases that cause hypercalcemia. Two other calcimimetics are now on the market (etelcalcetide) or under regulatory review (evocalcet). Calcilytics stimulate the secretion of parathyroid hormone and were initially developed as treatments for osteoporosis. Three different calcilytics of two different chemotypes failed in clinical trials due to lack of efficacy. Calcilytics are now being repurposed and might be useful in treating hypoparathyroidism and several rare genetic diseases causing hypocalcemia. The challenges ahead for medicinal chemists are to design compounds that select conformations of the CaR that preferentially target a particular signalling pathway and/or that affect the CaR in a tissue-selective manner.
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Investigating the molecular mechanism of positive and negative allosteric modulators in the calcium-sensing receptor dimer. Sci Rep 2017; 7:46355. [PMID: 28417952 PMCID: PMC5394417 DOI: 10.1038/srep46355] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 03/20/2017] [Indexed: 11/09/2022] Open
Abstract
Allosteric modulators that are targeting the calcium-sensing receptor (CaSR) hold great therapeutic potential, and elucidating the molecular basis for modulation would thus benefit the development of novel therapeutics. In the present study, we aimed at investigating the mechanism of allosteric modulation in CaSR by testing dimers carrying mutations in the allosteric site of one or both of the subunits. To ensure measurements on a well-defined dimer composition, we applied a trans-activation system in which only the specific heterodimer of two loss-of-function mutants responded to agonist. Although one of these mutants was potentiated by a positive allosteric modulator, we showed that receptor activity was further potentiated in a trans-activation heterodimer containing a single allosteric site, however only when the allosteric site was located in the subunit responsible for G protein coupling. On the contrary, preventing activation in both subunits was necessary for obtaining full inhibition by a negative allosteric modulator. These findings correlate with the proposed activation mechanism of the metabotropic glutamate receptors (mGluRs), in which only a single transmembrane domain is activated at a time. CaSR and mGluRs belong to the class C G protein-coupled receptors, and our findings thus suggest that the activation mechanism is common to this subfamily.
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11
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Yiu AJ, Ibeh CL, Roy SK, Bandyopadhyay BC. Melamine induces Ca 2+-sensing receptor activation and elicits apoptosis in proximal tubular cells. Am J Physiol Cell Physiol 2017; 313:C27-C41. [PMID: 28381520 DOI: 10.1152/ajpcell.00225.2016] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Revised: 03/29/2017] [Accepted: 03/30/2017] [Indexed: 01/06/2023]
Abstract
Melamine causes renal tubular cell injury through inflammation, fibrosis, and apoptosis. Although melamine affects the rise in intracellular Ca2+ concentration ([Ca2+]i), reactive oxygen species (ROS) production, and proapoptotic pathway activation, the mechanism of upstream Ca2+ signaling is unknown. Because melamine has some structural similarities with l-amino acids, which endogenously activate Ca2+-sensing receptors (CSR), we examined the effect of melamine on CSR-induced Ca2+ signaling and apoptotic cell death. We show here that melamine activates CSR, causing a sustained Ca2+ entry in the renal epithelial cell line, LLC-PK1. Moreover, such CSR stimulation resulted in a rise in [Ca2+]i, leading to enhanced ROS production. Furthermore, melamine-induced elevated [Ca2+]i and ROS production caused a dose-dependent increase in apoptotic (by DAPI staining, DNA laddering, and annexin V assay) and necrotic (propidium iodide staining) cell death. Upon examining the downstream mechanism, we found that transforming growth factor β1 (TGF-β1), which increases extracellular matrix genes and proapoptotic signaling, was also upregulated at lower doses of melamine, which could be due to an early event inducing apoptosis. Additionally, cells exposed to melamine displayed a rise in pERK activation and lactate dehydrogenase release resulting in cytotoxicity. These results offer a novel insight into the molecular mechanisms by which melamine exerts its effect on CSR, causing a sustained elevation of [Ca2+]i, leading to ROS generation, fibronectin production, proapoptotic pathway activation, and renal cell damage. Together, these results thus suggest that melamine-induced apoptosis and/or necrosis may subsequently result in acute kidney injury and promote kidney stone formation.
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Affiliation(s)
- Allen J Yiu
- Calcium Signaling Laboratory, Research Service, Veterans Affairs Medical Center, Washington, District of Columbia.,Department of Pharmacology and Physiology, School of Medicine, George Washington University, Washington, District of Columbia; and
| | - Cliff-Lawrence Ibeh
- Calcium Signaling Laboratory, Research Service, Veterans Affairs Medical Center, Washington, District of Columbia
| | - Sanjit K Roy
- Calcium Signaling Laboratory, Research Service, Veterans Affairs Medical Center, Washington, District of Columbia
| | - Bidhan C Bandyopadhyay
- Calcium Signaling Laboratory, Research Service, Veterans Affairs Medical Center, Washington, District of Columbia; .,Department of Pharmacology and Physiology, School of Medicine, George Washington University, Washington, District of Columbia; and.,Department of Pharmacology and Physiology, Georgetown University, Washington, District of Columbia
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12
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Geng Y, Mosyak L, Kurinov I, Zuo H, Sturchler E, Cheng TC, Subramanyam P, Brown AP, Brennan SC, Mun HC, Bush M, Chen Y, Nguyen TX, Cao B, Chang DD, Quick M, Conigrave AD, Colecraft HM, McDonald P, Fan QR. Structural mechanism of ligand activation in human calcium-sensing receptor. eLife 2016; 5. [PMID: 27434672 PMCID: PMC4977154 DOI: 10.7554/elife.13662] [Citation(s) in RCA: 155] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 07/18/2016] [Indexed: 12/21/2022] Open
Abstract
Human calcium-sensing receptor (CaSR) is a G-protein-coupled receptor (GPCR) that maintains extracellular Ca2+ homeostasis through the regulation of parathyroid hormone secretion. It functions as a disulfide-tethered homodimer composed of three main domains, the Venus Flytrap module, cysteine-rich domain, and seven-helix transmembrane region. Here, we present the crystal structures of the entire extracellular domain of CaSR in the resting and active conformations. We provide direct evidence that L-amino acids are agonists of the receptor. In the active structure, L-Trp occupies the orthosteric agonist-binding site at the interdomain cleft and is primarily responsible for inducing extracellular domain closure to initiate receptor activation. Our structures reveal multiple binding sites for Ca2+ and PO43- ions. Both ions are crucial for structural integrity of the receptor. While Ca2+ ions stabilize the active state, PO43- ions reinforce the inactive conformation. The activation mechanism of CaSR involves the formation of a novel dimer interface between subunits. DOI:http://dx.doi.org/10.7554/eLife.13662.001 Calcium ions regulate many processes in the human body. The calcium-sensing receptor, called CaSR, is responsible for maintaining a stable level of calcium ions in the blood. This receptor can detect small changes in the concentration of calcium ions, and activates signalling events within the cell to restore the level of calcium ions back to normal. Abnormal activity of this receptor is associated with severe diseases in humans CaSR is found in the surface membrane of cells and belongs to a family of proteins called G-protein coupled receptors. Much of the protein extends out of the cell and interacts with calcium ions, phosphate ions and certain other molecules such as amino acids. However, it was not well understood how these small molecules bind to CaSR and how this activates the receptor. Geng et al. have now used a technique called X-ray crystallography to view the three-dimensional structure of the exterior domain of CaSR in its resting state and active state. These structures revealed that, contrary to expectations, calcium ions are not the main activator of the receptor. Instead, Geng et al. found that CaSR adopts an inactive state in the absence or presence of calcium ions, while the active state only forms when an amino acid is bound. Furthermore investigation showed that calcium ions are needed to stabilise the active form, while phosphate ions keep the inactive form stable. Geng et al. also identified the shape changes that must occur as CaSR transitions from its inactive to its active state. In particular, an amino acid binding to the exterior domain causes it to close like a venus flytrap, which is a crucial step in activating the receptor. Taken together, the findings show that the amino acids and calcium ions act jointly to fully activate CaSR. The next steps are to determine the structure of the entire receptor with and without its small molecule partners and to use these structures to design drugs that can alter CaSR’s activity in order to treat human diseases. DOI:http://dx.doi.org/10.7554/eLife.13662.002
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Affiliation(s)
- Yong Geng
- Department of Pharmacology, Columbia University, New York, United States.,Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Lidia Mosyak
- Department of Pharmacology, Columbia University, New York, United States
| | - Igor Kurinov
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, United States
| | - Hao Zuo
- Department of Pharmacology, Columbia University, New York, United States
| | - Emmanuel Sturchler
- Department of Molecular Therapeutics, The Scripps Translational Science Institute, Jupiter, United States
| | - Tat Cheung Cheng
- Department of Pharmacology, Columbia University, New York, United States
| | - Prakash Subramanyam
- Department of Physiology and Cellular Biophysics, Columbia University, New York, United States
| | - Alice P Brown
- School of Life and Environmental Sciences, University of Sydney, New South Wales, Australia
| | - Sarah C Brennan
- School of Life and Environmental Sciences, University of Sydney, New South Wales, Australia
| | - Hee-Chang Mun
- School of Life and Environmental Sciences, University of Sydney, New South Wales, Australia
| | - Martin Bush
- Department of Pharmacology, Columbia University, New York, United States
| | - Yan Chen
- Department of Pharmacology, Columbia University, New York, United States
| | - Trang X Nguyen
- Department of Psychiatry, Columbia University, New York, United States
| | - Baohua Cao
- Department of Pharmacology, Columbia University, New York, United States
| | - Donald D Chang
- Department of Physiology and Cellular Biophysics, Columbia University, New York, United States
| | - Matthias Quick
- Department of Psychiatry, Columbia University, New York, United States
| | - Arthur D Conigrave
- School of Life and Environmental Sciences, University of Sydney, New South Wales, Australia
| | - Henry M Colecraft
- Department of Physiology and Cellular Biophysics, Columbia University, New York, United States
| | - Patricia McDonald
- Department of Molecular Therapeutics, The Scripps Translational Science Institute, Jupiter, United States
| | - Qing R Fan
- Department of Pharmacology, Columbia University, New York, United States.,Department of Pathology and Cell Biology, Columbia University, New York, United States
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Changcharoen B, Motosue M, Wong L, Arakaki R. A Woman and Her Father with Calcium-Sensing Receptor Mutation and Autosomal Dominant Hypocalcemia. AACE Clin Case Rep 2016. [DOI: 10.4158/ep15716.cr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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14
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Mace OJ, Tehan B, Marshall F. Pharmacology and physiology of gastrointestinal enteroendocrine cells. Pharmacol Res Perspect 2015. [PMID: 26213627 PMCID: PMC4506687 DOI: 10.1002/prp2.155] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Gastrointestinal (GI) polypeptides are secreted from enteroendocrine cells (EECs). Recent technical advances and the identification of endogenous and synthetic ligands have enabled exploration of the pharmacology and physiology of EECs. Enteroendocrine signaling pathways stimulating hormone secretion involve multiple nutrient transporters and G protein-coupled receptors (GPCRs), which are activated simultaneously under prevailing nutrient conditions in the intestine following a meal. The majority of studies investigate hormone secretion from EECs in response to single ligands and although the mechanisms behind how individual signaling pathways generate a hormonal output have been well characterized, our understanding of how these signaling pathways converge to generate a single hormone secretory response is still in its infancy. However, a picture is beginning to emerge of how nutrients and full, partial, or allosteric GPCR ligands differentially regulate the enteroendocrine system and its interaction with the enteric and central nervous system. So far, activation of multiple pathways underlies drug discovery efforts to harness the therapeutic potential of the enteroendocrine system to mimic the phenotypic changes observed in patients who have undergone Roux-en-Y gastric surgery. Typically obese patients exhibit ∼30% weight loss and greater than 80% of obese diabetics show remission of diabetes. Targeting combinations of enteroendocrine signaling pathways that work synergistically may manifest with significant, differentiated EEC secretory efficacy. Furthermore, allosteric modulators with their increased selectivity, self-limiting activity, and structural novelty may translate into more promising enteroendocrine drugs. Together with the potential to bias enteroendocrine GPCR signaling and/or to activate multiple divergent signaling pathways highlights the considerable range of therapeutic possibilities available. Here, we review the pharmacology and physiology of the EEC system.
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Affiliation(s)
- O J Mace
- Heptares Therapeutics Ltd BioPark, Broadwater Road, Welwyn Garden City, AL7 3AX, United Kingdom
| | - B Tehan
- Heptares Therapeutics Ltd BioPark, Broadwater Road, Welwyn Garden City, AL7 3AX, United Kingdom
| | - F Marshall
- Heptares Therapeutics Ltd BioPark, Broadwater Road, Welwyn Garden City, AL7 3AX, United Kingdom
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Baran N, ter Braak M, Saffrich R, Woelfle J, Schmitz U. Novel activating mutation of human calcium-sensing receptor in a family with autosomal dominant hypocalcaemia. Mol Cell Endocrinol 2015; 407:18-25. [PMID: 25766501 DOI: 10.1016/j.mce.2015.02.021] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 01/13/2015] [Accepted: 02/19/2015] [Indexed: 12/24/2022]
Abstract
INTRODUCTION Autosomal dominant hypocalcaemia (ADH) is caused by activating mutations in the calcium sensing receptor gene (CaR) and characterised by mostly asymptomatic mild to moderate hypocalcaemia with low, inappropriately serum concentration of PTH. OBJECTIVE The purpose of the present study was to biochemically and functionally characterise a novel mutation of CaR. PATIENTS A female proband presenting with hypocalcaemia was diagnosed to have "idiopathic hypoparathyroidism" at the age of 10 with a history of muscle pain and cramps. Further examinations demonstrated hypocalcaemia in nine additional family members, affecting three generations. MAIN OUTCOME MEASURE P136L CaR mutation was predicted to cause gain of function of CaR. RESULTS Affected family members showed relevant hypocalcaemia (mean ± SD; 1.9 ± 0.1 mmol/l). Patient history included mild seizures and recurrent nephrolithiasis. Genetic analysis confirmed that hypocalcaemia cosegregated with a heterozygous mutation at codon 136 (CCC → CTC/Pro → Leu) in exon 3 of CaR confirming the diagnosis of ADH. For in vitro studies P136L mutant CaR was generated by site-directed mutagenesis and examined in transiently transfected HEK293 cells. Extracellular calcium stimulation of transiently transfected HEK293 cells showed significantly increased intracellular Ca(2+) mobilisation and MAPK activity for mutant P136L CaR compared to wild type CaR. CONCLUSIONS The present study gives insight about a novel activating mutation of CaR and confirms that the novel P136L-CaR mutation is responsible for ADH in this family.
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Affiliation(s)
- Natalia Baran
- Department of Endocrinology and Diabetology, University of Bonn, Sigmund-Freud-Str. 25, 53127 Bonn, Germany; Department of Medicine V, University of Heidelberg, INF 410, 69120 Heidelberg, Germany.
| | - Michael ter Braak
- Institut of Pharmacology, University of Essen, Hufelandstr. 55, 45122 Essen, Germany
| | - Rainer Saffrich
- Department of Medicine V, University of Heidelberg, INF 410, 69120 Heidelberg, Germany
| | - Joachim Woelfle
- Pediatric Endocrinology Division, University of Bonn, Adenauerallee 119, 53113 Bonn, Germany
| | - Udo Schmitz
- Department of Endocrinology and Diabetology, University of Bonn, Sigmund-Freud-Str. 25, 53127 Bonn, Germany
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16
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Zhou H, Rigoutsos I. The emerging roles of GPRC5A in diseases. Oncoscience 2014; 1:765-76. [PMID: 25621293 PMCID: PMC4303886 DOI: 10.18632/oncoscience.104] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 11/24/2014] [Indexed: 12/14/2022] Open
Abstract
The ‘Retinoic Acid-Inducible G-protein-coupled receptors’ or RAIG are a group comprising the four orphan receptors GPRC5A, GPRC5B, GPRC5C and GPRC5D. As the name implies, their expression is induced by retinoic acid but beyond that very little is known about their function. In recent years, one member, GPRC5A, has been receiving increasing attention as it was shown to play important roles in human cancers. As a matter of fact, dysregulation of GPRC5A has been associated with several cancers including lung cancer, breast cancer, colorectal cancer, and pancreatic cancer. Here we review the current state of knowledge about the heterogeneity and evolution of GPRC5A, its regulation, its molecular functions, and its involvement in human disease.
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Affiliation(s)
- Honglei Zhou
- Computational Medicine Center, Jefferson Alumni Hall, Thomas Jefferson University, Philadelphia, PA
| | - Isidore Rigoutsos
- Computational Medicine Center, Jefferson Alumni Hall, Thomas Jefferson University, Philadelphia, PA
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Role of Ca2+ and L-Phe in regulating functional cooperativity of disease-associated "toggle" calcium-sensing receptor mutations. PLoS One 2014; 9:e113622. [PMID: 25420019 PMCID: PMC4242666 DOI: 10.1371/journal.pone.0113622] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 10/27/2014] [Indexed: 01/15/2023] Open
Abstract
The Ca2+-sensing receptor (CaSR) regulates Ca2+ homeostasis in the body by monitoring extracellular levels of Ca2+ ([Ca2+]o) and amino acids. Mutations at the hinge region of the N-terminal Venus flytrap domain (VFTD) produce either receptor inactivation (L173P, P221Q) or activation (L173F, P221L) related to hypercalcemic or hypocalcemic disorders. In this paper, we report that both L173P and P221Q markedly impair the functional positive cooperativity of the CaSR as reflected by [Ca2+]o–induced [Ca2+]i oscillations, inositol-1-phosphate (IP1) accumulation and extracellular signal-regulated kinases (ERK1/2) activity. In contrast, L173F and P221L show enhanced responsiveness of these three functional readouts to [Ca2+]o. Further analysis of the dynamics of the VFTD mutants using computational simulation studies supports disruption in the correlated motions in the loss-of-function CaSR mutants, while these motions are enhanced in the gain-of-function mutants. Wild type (WT) CaSR was modulated by L-Phe in a heterotropic positive cooperative way, achieving an EC50 similar to those of the two activating mutations. The response of the inactivating P221Q mutant to [Ca2+]o was partially rescued by L-Phe, illustrating the capacity of the L-Phe binding site to enhance the positive homotropic cooperativity of CaSR. L-Phe had no effect on the other inactivating mutant. Moreover, our results carried out both in silico and in intact cells indicate that residue Leu173, which is close to residues that are part of the L-Phe-binding pocket, exhibited impaired heterotropic cooperativity in the presence of L-Phe. Thus, Pro221 and Leu173 are important for the positive homo- and heterotropic cooperative regulation elicited by agonist binding.
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18
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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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19
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Conigrave AD, Ward DT. Calcium-sensing receptor (CaSR): pharmacological properties and signaling pathways. Best Pract Res Clin Endocrinol Metab 2013; 27:315-31. [PMID: 23856262 DOI: 10.1016/j.beem.2013.05.010] [Citation(s) in RCA: 151] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
In this article we consider the mechanisms by which the calcium-sensing receptor (CaSR) induces its cellular responses via the control (activation or inhibition) of signaling pathways. We consider key features of CaSR-mediated signaling including its control of the heterotrimeric G-proteins Gq/11, Gi/o and G12/13 and the downstream consequences recognizing that very few CaSR-mediated cell phenomena have been fully described. We also consider the manner in which the CaSR contributes to the formation of specific signaling scaffolds via peptide recognition sequences in its intracellular C-terminal along with the origins of its high level of cooperativity, particularly for Ca(2+)o, and its remarkable resistance to desensitization. We also consider the nature of the mechanisms by which the CaSR controls oscillatory and sustained Ca(2+)i mobilizing responses and inhibits or elevates cyclic adenosine monophosphate (cAMP) levels dependent on the cellular and signaling context. Finally, we consider the diversity of the receptor's ligands, ligand binding sites and broader compartment-dependent physiological roles leading to the identification of pronounced ligand-biased signaling for agonists including Sr(2+) and modulators including l-amino acids and the clinically effective calcimimetic cinacalcet. We note the implications of these findings for the development of new designer drugs that might target the CaSR in pathophysiological contexts beyond those established for the treatment of disorders of calcium metabolism.
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Affiliation(s)
- Arthur D Conigrave
- School of Molecular Bioscience, University of Sydney, NSW 2006, Australia.
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20
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Hannan FM, Thakker RV. Calcium-sensing receptor (CaSR) mutations and disorders of calcium, electrolyte and water metabolism. Best Pract Res Clin Endocrinol Metab 2013; 27:359-71. [PMID: 23856265 DOI: 10.1016/j.beem.2013.04.007] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The extracellular calcium-sensing receptor (CaSR) is a family C G-protein-coupled receptor (GPCR) that is expressed at multiple sites, including the parathyroids and kidneys. The human CASR gene, located on chromosome 3q21.1, encodes a 1078 amino acid protein. More than 230 different disease-causing mutations of the CaSR have been reported. Loss-of-function mutations lead to three hypercalcemic disorders, which are familial hypocalciuric hypercalcemia (FHH), neonatal severe hyperparathyroidism and primary hyperparathyroidism. Gain-of-function mutations, on the other hand, result in the hypocalcemic disorders of autosomal dominant hypocalcemia and Bartter syndrome type V. Moreover, autoantibodies directed against the extracellular domain of the CaSR have been found to be associated with FHH in some patients, and also in some patients with hypoparathyroidism that may be part of autoimmune polyglandular syndrome type 1. Studies of disease-causing CASR mutations have provided insights into structure-function relationships and highlighted intra-molecular domains that are critical for ligand binding, intracellular signaling, and receptor trafficking.
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Affiliation(s)
- Fadil M Hannan
- Academic Endocrine Unit, Oxford Centre for Diabetes, Endocrinology and Metabolism, Nuffield Department of Clinical Medicine, University of Oxford, Churchill Hospital, Oxford OX3 7LJ, UK.
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Maîtrepierre E, Sigoillot M, Le Pessot L, Briand L. An efficient Escherichia coli expression system for the production of a functional N-terminal domain of the T1R3 taste receptor. Bioengineered 2012; 4:25-9. [PMID: 22909933 PMCID: PMC3566016 DOI: 10.4161/bioe.21877] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Sweet taste is mediated by a dimeric receptor composed of two distinct subunits, T1R2 and T1R3, whereas the T1R1/T1R3 receptor is involved in umami taste perception. The T1R1, T1R2, and T1R3 subunits are members of the small family of class C G protein-coupled receptors (GPCRs). The members of this family are characterized by a large N-terminal domain (NTD), which is structurally similar to bacterial periplasmic-binding proteins and contains the primary ligand-binding site. In a recent study, we described a strategy to produce a functional dimeric human T1R3-NTD. Although the protein was expressed as inclusion bodies (IBs) using the Escherichia coli system, the conditions for the refolding of functional hT1R3-NTD were determined using a fractional factorial screen coupled to a binding assay. Here, we report that this refolding strategy can be used to produce T1R1- and T1R2-NTDs in large quantities. We also discuss that our findings could be more generally applicable to other class C GPCR-NTDs, including the γ-aminobutyric acid type B receptor (GABABR), the extracellular calcium-sensing receptor (CaSR) and the large family of pheromone (V2R) orphan receptors.
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Affiliation(s)
- Elodie Maîtrepierre
- Centre des Sciences du Goût et de l'Alimentation, UMR-1324 INRA, UMR-6265 CNRS, Université de Bourgogne, 21000 Dijon, France
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Bandyopadhyay BC, Swaim WD, Sarkar A, Liu X, Ambudkar IS. Extracellular Ca(2+) sensing in salivary ductal cells. J Biol Chem 2012; 287:30305-16. [PMID: 22778254 DOI: 10.1074/jbc.m112.394122] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ca(2+) is secreted from the salivary acinar cells as an ionic constituent of primary saliva. Ions such as Na(+) and Cl(-) get reabsorbed whereas primary saliva flows through the salivary ductal system. Although earlier studies have shown that salivary [Ca(2+)] decreases as it flows down the ductal tree into the oral cavity, ductal reabsorption of Ca(2+) remains enigmatic. Here we report a potential role for the G protein-coupled receptor, calcium-sensing receptor (CSR), in the regulation of Ca(2+) reabsorption by salivary gland ducts. Our data show that CSR is present in the apical region of ductal cells where it is co-localized with transient receptor potential canonical 3 (TRPC3). CSR is activated in isolated salivary gland ducts as well as a ductal cell line (SMIE) by altering extracellular [Ca(2+)] or by aromatic amino acid, L-phenylalanine (L-Phe, endogenous component of saliva), as well as neomycin. CSR activation leads to Ca(2+) influx that, in polarized cells grown on a filter support, is initiated in the luminal region. We show that TRPC3 contributes to Ca(2+) entry triggered by CSR activation. Further, stimulation of CSR in SMIE cells enhances the CSR-TRPC3 association as well as surface expression of TRPC3. Together our findings suggest that CSR could serve as a Ca(2+) sensor in the luminal membrane of salivary gland ducts and regulate reabsorption of [Ca(2+)] from the saliva via TRPC3, thus contributing to maintenance of salivary [Ca(2+)]. CSR could therefore be a potentially important protective mechanism against formation of salivary gland stones (sialolithiasis) and infection (sialoadenitis).
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Affiliation(s)
- Bidhan C Bandyopadhyay
- Calcium Signaling Laboratory, Research Service, Veterans Affairs Medical Center, Washington, DC 20422, USA.
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23
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Breitwieser GE. Minireview: the intimate link between calcium sensing receptor trafficking and signaling: implications for disorders of calcium homeostasis. Mol Endocrinol 2012; 26:1482-95. [PMID: 22745192 DOI: 10.1210/me.2011-1370] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The calcium-sensing receptor (CaSR) regulates organismal Ca(2+) homeostasis. Dysregulation of CaSR expression or mutations in the CASR gene cause disorders of Ca(2+) homeostasis and contribute to the progression or severity of cancers and cardiovascular disease. This brief review highlights recent findings that define the CaSR life cycle, which controls the cellular abundance of CaSR and CaSR signaling. A novel mechanism, termed agonist-driven insertional signaling (ADIS), contributes to the unique hallmarks of CaSR signaling, including the high degree of cooperativity and the lack of functional desensitization. Agonist-mediated activation of plasma membrane-localized CaSR increases the rate of insertion of CaSR at the plasma membrane without altering the constitutive endocytosis rate, thereby acutely increasing the maximum signaling response. Prolonged CaSR signaling requires a large intracellular ADIS-mobilizable pool of CaSR, which is maintained by signaling-mediated increases in biosynthesis. This model provides a rational framework for characterizing the defects caused by CaSR mutations and the altered functional expression of wild-type CaSR in disease states. Mechanistic dissection of ADIS of CaSR should lead to optimized pharmacological approaches to normalize CaSR signaling in disorders of Ca(2+) homeostasis.
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Affiliation(s)
- Gerda E Breitwieser
- Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania 17822-2604, USA.
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Masuda K, Koizumi A, Nakajima KI, Tanaka T, Abe K, Misaka T, Ishiguro M. Characterization of the modes of binding between human sweet taste receptor and low-molecular-weight sweet compounds. PLoS One 2012; 7:e35380. [PMID: 22536376 PMCID: PMC3335050 DOI: 10.1371/journal.pone.0035380] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Accepted: 03/16/2012] [Indexed: 12/04/2022] Open
Abstract
One of the most distinctive features of human sweet taste perception is its broad tuning to chemically diverse compounds ranging from low-molecular-weight sweeteners to sweet-tasting proteins. Many reports suggest that the human sweet taste receptor (hT1R2–hT1R3), a heteromeric complex composed of T1R2 and T1R3 subunits belonging to the class C G protein–coupled receptor family, has multiple binding sites for these sweeteners. However, it remains unclear how the same receptor recognizes such diverse structures. Here we aim to characterize the modes of binding between hT1R2–hT1R3 and low-molecular-weight sweet compounds by functional analysis of a series of site-directed mutants and by molecular modeling–based docking simulation at the binding pocket formed on the large extracellular amino-terminal domain (ATD) of hT1R2. We successfully determined the amino acid residues responsible for binding to sweeteners in the cleft of hT1R2 ATD. Our results suggest that individual ligands have sets of specific residues for binding in correspondence with the chemical structures and other residues responsible for interacting with multiple ligands.
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Affiliation(s)
- Katsuyoshi Masuda
- Suntory Institute for Bioorganic Research, Mishima-gun, Osaka, Japan
| | - Ayako Koizumi
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Ken-ichiro Nakajima
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Takaharu Tanaka
- Suntory Institute for Bioorganic Research, Mishima-gun, Osaka, Japan
| | - Keiko Abe
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
- Food Safety and Reliability Project, Kanagawa Academy of Science and Technology, Kawasaki, Kanagawa, Japan
| | - Takumi Misaka
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
- * E-mail: (MI); (TM)
| | - Masaji Ishiguro
- Suntory Institute for Bioorganic Research, Mishima-gun, Osaka, Japan
- Niigata University of Pharmacy and Applied Life Sciences, Akiha-ku, Niigata, Japan
- * E-mail: (MI); (TM)
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25
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Smajilovic S, Yano S, Jabbari R, Tfelt-Hansen J. The calcium-sensing receptor and calcimimetics in blood pressure modulation. Br J Pharmacol 2012; 164:884-93. [PMID: 21410453 DOI: 10.1111/j.1476-5381.2011.01317.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Calcium is a crucial second messenger in the cardiovascular system. However, calcium may also be an extracellular first messenger through a G-protein-coupled receptor that senses extracellular concentration (Ca(2+)(o)), the calcium-sensing receptor (CaR). The most prominent physiological function of the CaR is to maintain the extracellular Ca(2+) level in a very tight range by regulating the circulating levels of parathyroid hormone (PTH). This control over PTH and Ca(2+) levels is partially lost in patients suffering from primary and secondary hyperparathyroidism. Allosteric modulators of the CaR (calcimimetics) are the first drugs in their class to become available for clinical use and have been shown to successfully treat certain forms of primary and secondary hyperparathyroidism. In addition, several studies suggest beneficial effects of calcimimetics on cardiovascular risk factors associated with hyperparathyroidism. Although a plethora of studies demonstrated the CaR in heart and blood vessels, exact roles of the receptor in the cardiovascular system still remain to be elucidated. However, several studies point toward a possibility that the CaR might be involved in the regulation of vascular tone. This review will summarize the current knowledge on the possible functions of the CaR and calcimimetics on blood pressure regulation.
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Affiliation(s)
- Sanela Smajilovic
- Laboratory of Molecular Cardiology, Department of Cardiology, Copenhagen University Hospital, Denmark
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26
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Hannan FM, Nesbit MA, Zhang C, Cranston T, Curley AJ, Harding B, Fratter C, Rust N, Christie PT, Turner JJO, Lemos MC, Bowl MR, Bouillon R, Brain C, Bridges N, Burren C, Connell JM, Jung H, Marks E, McCredie D, Mughal Z, Rodda C, Tollefsen S, Brown EM, Yang JJ, Thakker RV. Identification of 70 calcium-sensing receptor mutations in hyper- and hypo-calcaemic patients: evidence for clustering of extracellular domain mutations at calcium-binding sites. Hum Mol Genet 2012; 21:2768-78. [DOI: 10.1093/hmg/dds105] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Abstract
The G-protein-coupled receptors (GPCRs) are one of the largest super families of cell-surface receptors and play crucial roles in virtually every organ system. One particular family of GPCRs, the class C GPCRs, is distinguished by a characteristically large extracellular domain and constitutive dimerization. The structure and activation mechanism of this family result in potentially unique ligand recognition sites, thereby offering a variety of possibilities by which receptor activity might be modulated using novel compounds. In the present article, we aim to provide an overview of the exact sites and structural features involved in ligand recognition of the class C GPCRs. Furthermore, we demonstrate the precise steps that occur during the receptor activation process, which underlie the possibilities by which receptor function may be altered by different approaches. Finally, we use four typical family members to illustrate orthosteric and allosteric sites with representative ligands and their corresponding therapeutic potential.
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Thomsen ARB, Hvidtfeldt M, Bräuner-Osborne H. Biased agonism of the calcium-sensing receptor. Cell Calcium 2012; 51:107-16. [PMID: 22192592 DOI: 10.1016/j.ceca.2011.11.009] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Revised: 11/05/2011] [Accepted: 11/24/2011] [Indexed: 02/01/2023]
Abstract
After the discovery of molecules modulating G protein-coupled receptors (GPCRs) that are able to selectively affect one signaling pathway over others for a specific GPCR, thereby "biasing" the signaling, it has become obvious that the original model of GPCRs existing in either an "on" or "off" conformation is too simple. The current explanation for this biased agonism is that GPCRs can adopt multiple active conformations stabilized by different molecules, and that each conformation affects intracellular signaling in a different way. In the present study we sought to investigate biased agonism of the calcium-sensing receptor (CaSR), by looking at 12 well-known orthosteric CaSR agonists in 3 different CaSR signaling pathways: G(q/11) protein, G(i/o) protein, and extracellular signal-regulated kinases 1 and 2 (ERK1/2). Here we show that apart from G(q/11) and G(i/o) signaling, ERK1/2 is activated through recruitment of β-arrestins. Next, by measuring activity of all three signaling pathways we found that barium, spermine, neomycin, and tobramycin act as biased agonist in terms of efficacy and/or potency. Finally, polyamines and aminoglycosides in general were biased in their potencies toward ERK1/2 signaling. In conclusion, the results of this study indicate that several active conformations of CaSR, stabilized by different molecules, exist, which affect intracellular signaling distinctly.
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Affiliation(s)
- Alex Rojas Bie Thomsen
- Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Fruebjergvej 3, Copenhagen, Denmark
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Bouschet T, Martin S, Henley JM. Regulation of calcium sensing receptor trafficking by RAMPs. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 744:39-48. [PMID: 22434106 DOI: 10.1007/978-1-4614-2364-5_4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
As mentioned earlier in this book, RAMPs were identified as proteins escorting the Calcitonin Receptor-Like Receptor (CRLR) to the plasma membrane (PM) to generate either CGRP (when associated with RAMP1), or adrenomedullin receptors (when associated with RAMP2 or RAMP3). Some years after this initial discovery, it was established that RAMPs can accompany four additional class B G Protein-Coupled Receptors-GPCRs- (PTH1, PTH2, glucagon receptor and VPAC1) to the PM.(1) By demonstrating that the sorting traffic of the Calcium Sensing Receptor (CaSR), a class C GPCR, is positively modulated by RAMP1 and RAMP3,(2) our data extended the concept of RAMPs as escorting molecules to another class of GPCRs.
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Affiliation(s)
- Tristan Bouschet
- Institut de Génomique Fonctionnelle, INSERM U661-CNRS UMR5203, Montpellier, France
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Urwyler S. Allosteric modulation of family C G-protein-coupled receptors: from molecular insights to therapeutic perspectives. Pharmacol Rev 2011; 63:59-126. [PMID: 21228259 DOI: 10.1124/pr.109.002501] [Citation(s) in RCA: 164] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Allosteric receptor modulation is an attractive concept in drug targeting because it offers important potential advantages over conventional orthosteric agonism or antagonism. Allosteric ligands modulate receptor function by binding to a site distinct from the recognition site for the endogenous agonist. They often have no effect on their own and therefore act only in conjunction with physiological receptor activation. This article reviews the current status of allosteric modulation at family C G-protein coupled receptors in the light of their specific structural features on the one hand and current concepts in receptor theory on the other hand. Family C G-protein-coupled receptors are characterized by a large extracellular domain containing the orthosteric agonist binding site known as the "venus flytrap module" because of its bilobal structure and the dynamics of its activation mechanism. Mutational analysis and chimeric constructs have revealed that allosteric modulators of the calcium-sensing, metabotropic glutamate and GABA(B) receptors bind to the seven transmembrane domain, through which they modify signal transduction after receptor activation. This is in contrast to taste-enhancing molecules, which bind to different parts of sweet and umami receptors. The complexity of interactions between orthosteric and allosteric ligands is revealed by a number of adequate biochemical and electrophysiological assay systems. Many allosteric family C GPCR modulators show in vivo efficacy in behavioral models for a variety of clinical indications. The positive allosteric calcium sensing receptor modulator cinacalcet is the first drug of this type to enter the market and therefore provides proof of principle in humans.
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Affiliation(s)
- Stephan Urwyler
- Department of Chemistry and Biochemistry, University of Berne, P/A Weissensteinweg 3, CH-3303 Jegenstorf, Berne, Switzerland.
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31
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Faure H, Gorojankina T, Rice N, Dauban P, Dodd RH, Bräuner-Osborne H, Rognan D, Ruat M. Molecular determinants of non-competitive antagonist binding to the mouse GPRC6A receptor. Cell Calcium 2010; 46:323-32. [PMID: 19836834 DOI: 10.1016/j.ceca.2009.09.004] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2009] [Accepted: 09/16/2009] [Indexed: 10/20/2022]
Abstract
GPRC6A displays high sequence homology to the Ca2+-sensing receptor (CaSR). Here we report that the calcimimetic Calindol and the calcilytic NPS2143 antagonize increases in inositol phosphate elicited by L-ornithine-induced activation of mouse GPRC6A after transient coexpression with Galpha(qG66D) in HEK293 cells. The calcilytic Calhex 231 did not modulate this response. A three-dimensional model of the GPRC6A seven transmembrane domains (TMs) was constructed. It was used to identify seven residues strictly conserved within the CaSR and GPRC6A allosteric binding pockets, and previously demonstrated to interact with calcilytics or calcimimetics. The mutations F666A(3.32), F670A(3.36), W797A(6.48) caused a loss of L-ornithine ability to activate GPRC6A mutants. The F800A(6.51) mutant was not implicated in either Calindol or NPS 2143 recognition. The E816Q(7.39) mutation led to a loss of Calindol antagonist activity but was without effect on NPS2143 inhibitory response. In summary, these data suggest that Calindol is primarily anchored through an H-bond to E816(7.39) in TM7 and highlight important local differences at the level of the CaSR and GPRC6A allosteric binding pockets. We have identified the first antagonists of GPRC6A that could represent new tools to analyze GPRC6A functions and serve as chemical leads for the development of more specific modulators.
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Affiliation(s)
- Helene Faure
- CNRS, UPR9040, Institut de Neurobiologie Alfred Fessard-IFR 2118, Signal Transduction and Developmental Neuropharmacology Team, 1 Avenue de la Terrasse, F-91198 Gif-sur-Yvette, France
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32
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Jensen AA, Bräuner-Osborne H. Allosteric modulation of the calcium-sensing receptor. Curr Neuropharmacol 2010; 5:180-6. [PMID: 19305800 PMCID: PMC2656812 DOI: 10.2174/157015907781695982] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2007] [Accepted: 04/05/2007] [Indexed: 12/20/2022] Open
Abstract
The calcium (Ca2+)-sensing receptor (CaR) belongs to family C of the G-protein coupled receptors (GPCRs). The receptor is activated by physiological levels of Ca2+ (and Mg2+) and positively modulated by a range of proteinogenic L-α-amino acids. Recently, several synthetic allosteric modulators of the receptor have been developed, which either act as positive modulators (termed calcimimetics) or negative modulators (termed calcilytics). These ligands do not activate the wild-type receptor directly, but rather shift the concentration-response curves of Ca2+ to the left or right, respectively. Like other family C GPCRs, the CaR contains a large amino-terminal domain and a 7-transmembrane domain. Whereas the endogenous ligands for the receptor, Ca2+, Mg2+ and the L-α-amino acids, bind to the amino-terminal domain, most if not all of the synthetic modulators published so far bind to the 7-transmembrane domain. The most prominent physiological function of the CaR is to maintain the extracellular Ca2+ level in a very tight range via control of secretion of parathyroid hormone (PTH). Influence on e.g. secretion of calcitonin from thyroid C-cells and direct action on the tubule of the kidney also contribute to the control of the extracellular Ca2+ level. This control over PTH and Ca2+ levels is partially lost in patients suffering from primary and secondary hyperparathyroidism. The perspectives in CaR as a therapeutic target have been underlined by the recent approval of the calcimimetic cinacalcet for the treatment of certain forms of primary and secondary hyperparathyroidism. Cinacalcet is the first clinically administered allosteric modulator acting on a GPCR, and thus the compound constitutes an important proof-of-concept for future development of allosteric modulators on other GPCR drug targets.
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Affiliation(s)
- Anders A Jensen
- Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark
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33
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McCann LM, Beto J. Roles of Calcium-Sensing Receptor and Vitamin D Receptor in the Pathophysiology of Secondary Hyperparathyroidism. J Ren Nutr 2010; 20:141-50. [DOI: 10.1053/j.jrn.2010.01.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2009] [Indexed: 01/01/2023] Open
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34
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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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35
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Cortijo J, Milara J, Mata M, Donet E, Gavara N, Peel SE, Hall IP, Morcillo EJ. Nickel induces intracellular calcium mobilization and pathophysiological responses in human cultured airway epithelial cells. Chem Biol Interact 2010; 183:25-33. [PMID: 19781536 DOI: 10.1016/j.cbi.2009.09.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2009] [Revised: 09/02/2009] [Accepted: 09/17/2009] [Indexed: 10/20/2022]
Abstract
Environmental exposure to nickel is associated to respiratory disorders and potential toxicity in the lung but molecular mechanisms remain incompletely explored. The extracellular Ca(2+)-sensing receptor (CaSR) is widely distributed and may be activated by divalent cations. In this study, we investigated the presence of CaSR in human cultured airway epithelial cells and its activation by nickel. Nickel transiently increased intracellular calcium (-logEC(50)=4.67+/-0.06) in A549 and human bronchial epithelial cells as measured by epifluorescence microscopy. Nickel (20muM)-induced calcium responses were reduced after thapsigargin or ryanodine exposure but not by Ca(2+)-free medium. Inhibition of phospholipase-C or inositol trisphosphate release reduced intracellular calcium responses to nickel indicating activation of G(q)-signaling. CaSR mRNA and protein expression in epithelial cells was demonstrated by RT-PCR, western blot and immunofluorescence. Transfection of specific siRNA inhibited CaSR expression and suppressed nickel-induced intracellular calcium responses in A549 cells thus confirming nickel-CaSR activation. NPS2390, a CaSR antagonist, abolished the calcium response to nickel. Nickel-induced contraction, proliferation, alpha(1)(I)collagen production and inflammatory cytokines mRNA expression by epithelial cells as measured by traction microscopy, BrdU assay and RT-PCR, respectively. These responses were blocked by NPS2390. In conclusion, micromolar nickel concentrations, relevant to nickel found in the lung tissue of humans exposed to high environmental nickel, trigger intracellular Ca(2+) mobilization in human airway epithelial cells through the activation of CaSR which translates into pathophysiological outputs potentially related to pulmonary disease.
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Affiliation(s)
- Julio Cortijo
- Department of Pharmacology, Faculty of Medicine, University of Valencia, Valencia, Spain
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36
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Wellendorph P, Johansen LD, Bräuner-Osborne H. The Emerging Role of Promiscuous 7TM Receptors as Chemosensors for Food Intake. INCRETINS AND INSULIN SECRETION 2010; 84:151-84. [DOI: 10.1016/b978-0-12-381517-0.00005-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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37
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Novel Ca receptor signaling pathways for control of renal ion transport. Curr Opin Nephrol Hypertens 2010; 19:106-12. [DOI: 10.1097/mnh.0b013e328332e7b2] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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38
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Parathyroid Hormone and Parathyroid Hormone–Related Peptide in the Regulation of Calcium Homeostasis and Bone Development. Endocrinology 2010. [DOI: 10.1016/b978-1-4160-5583-9.00056-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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39
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Wellendorph P, Bräuner-Osborne H. Molecular basis for amino acid sensing by family C G-protein-coupled receptors. Br J Pharmacol 2009; 156:869-84. [PMID: 19298394 DOI: 10.1111/j.1476-5381.2008.00078.x] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Family C of human G-protein-coupled receptors (GPCRs) is constituted by eight metabotropic glutamate receptors, two gamma-aminobutyric acid type B (GABA(B1-2)) subunits forming the heterodimeric GABA(B) receptor, the calcium-sensing receptor, three taste1 receptors (T1R1-3), a promiscuous L-alpha;-amino acid receptor G-protein-coupled receptor family C, group 6, subtype A (GPRC6A) and seven orphan receptors. Aside from the orphan receptors, the family C GPCRs are dimeric receptors characterized by a large extracellular Venus flytrap domain which bind the endogenous agonists. Except from the GABA(B1-2) and T1R2-3 receptor, all receptors are either activated or positively modulated by amino acids. In this review, we outline mutational, biophysical and structural studies which have elucidated the interaction of the amino acids with the Venus flytrap domains, molecular mechanisms of receptor selectivity and the initial steps in receptor activation.
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Affiliation(s)
- P Wellendorph
- Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark
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40
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Günzel D, Amasheh S, Pfaffenbach S, Richter JF, Kausalya PJ, Hunziker W, Fromm M. Claudin-16 affects transcellular Cl- secretion in MDCK cells. J Physiol 2009; 587:3777-93. [PMID: 19528248 DOI: 10.1113/jphysiol.2009.173401] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Claudin-16 (paracellin-1) is a tight junction protein localized mainly in the thick ascending limb of Henle's loop and also in the distal nephron. Its defect causes familial hypomagnesaemia with hypercalciuria and nephrocalcinosis. This had been taken as an indication that claudin-16 conveys paracellular Mg(2+) and Ca(2+) transport; however, evidence is still conflicting. We studied paracellular ion permeabilities as well as effects of claudin-16 on the driving forces for passive ion movement. MDCK-C7 cells were stably transfected with wild-type (wt) and mutant (R146T, T233R) claudin-16. Results indicated that paracellular permeability to Mg(2+) but not to Ca(2+) is increased in cells transfected with wt compared to mutant claudin-16 and control cells. Increased basolateral Mg(2+) concentration activated a transcellular Cl(-) current which was greatly enhanced in cells transfected with wt and T233R claudin-16, as compared to R146T claudin-16-transfected or control cells. This current was triggered by the basolateral calcium-sensing receptor causing Ca(2+) release from internal stores, thus activating apical Ca(2+)-sensitive Cl(-) channels and basolateral Ca(2+)-sensitive K(+) channels. Immunohistochemical data suggest that the Cl(-) channel involved is bestrophin. We conclude that claudin-16 itself possesses only moderate paracellular Mg(2+) permeability but governs transcellular Cl(-) currents by interaction with apical Ca(2+)-activated Cl(-) channels, presumably bestrophin. As the transepithelial voltage generated by such a current alters the driving force for all ions, this may be the major mechanism to regulate Mg(2+) and Ca(2+) absorption in the kidney.
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Affiliation(s)
- Dorothee Günzel
- Institut für Klinische Physiologie, Charité Berlin, Campus Benjamin Franklin, Hindenburgdamm 30, 12203 Berlin, Germany.
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41
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Wellendorph P, Johansen LD, Bräuner-Osborne H. Molecular pharmacology of promiscuous seven transmembrane receptors sensing organic nutrients. Mol Pharmacol 2009; 76:453-65. [PMID: 19487246 DOI: 10.1124/mol.109.055244] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
A number of highly promiscuous seven transmembrane (7TM) receptors have been cloned and characterized within the last few years. It is noteworthy that many of these receptors are activated broadly by amino acids, proteolytic degradation products, carbohydrates, or free fatty acids and are expressed in taste tissue, the gastrointestinal tract, endocrine glands, adipose tissue, and/or kidney. These receptors thus hold the potential to act as sensors of food intake, regulating, for example, release of incretin hormones from the gut, insulin/glucagon from the pancreas, and leptin from adipose tissue. The promiscuous tendency in ligand recognition of these receptors is in contrast to the typical specific interaction with one physiological agonist seen for most receptors, which challenges the classic "lock-and-key" concept. We here review the molecular mechanisms of nutrient sensing of the calcium-sensing receptor, the G protein-coupled receptor family C, group 6, subtype A (GPRC6A), and the taste1 receptor T1R1/T1R3, which are sensing L-alpha-amino acids, the carbohydrate-sensing T1R2/T1R3 receptor, the proteolytic degradation product sensor GPR93 (also termed GPR92), and the free fatty acid (FFA) sensing receptors FFA1, FFA2, FFA3, GPR84, and GPR120. The involvement of the individual receptors in sensing of food intake has been validated to different degrees because of limited availability of specific pharmacological tools and/or receptor knockout mice. However, as a group, the receptors represent potential drug targets, to treat, for example, type II diabetes by mimicking food intake by potent agonists or positive allosteric modulators. The ligand-receptor interactions of the promiscuous receptors of organic nutrients thus remain an interesting subject of emerging functional importance.
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Affiliation(s)
- Petrine Wellendorph
- UNIK centre for life-style diseases, Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark
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42
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Ahier A, Rondard P, Gouignard N, Khayath N, Huang S, Trolet J, Donoghue DJ, Gauthier M, Pin JP, Dissous C. A new family of receptor tyrosine kinases with a venus flytrap binding domain in insects and other invertebrates activated by aminoacids. PLoS One 2009; 4:e5651. [PMID: 19461966 PMCID: PMC2680970 DOI: 10.1371/journal.pone.0005651] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2009] [Accepted: 04/20/2009] [Indexed: 11/30/2022] Open
Abstract
Background Tyrosine kinase receptors (RTKs) comprise a large family of membrane receptors that regulate various cellular processes in cell biology of diverse organisms. We previously described an atypical RTK in the platyhelminth parasite Schistosoma mansoni, composed of an extracellular Venus flytrap module (VFT) linked through a single transmembrane domain to an intracellular tyrosine kinase domain similar to that of the insulin receptor. Methods and Findings Here we show that this receptor is a member of a new family of RTKs found in invertebrates, and particularly in insects. Sixteen new members of this family, named Venus Kinase Receptor (VKR), were identified in many insects. Structural and phylogenetic studies performed on VFT and TK domains showed that VKR sequences formed monophyletic groups, the VFT group being close to that of GABAB receptors and the TK one being close to that of insulin receptors. We show that a recombinant VKR is able to autophosphorylate on tyrosine residues, and report that it can be activated by L-arginine. This is in agreement with the high degree of conservation of the alpha amino acid binding residues found in many amino acid binding VFTs. The presence of high levels of vkr transcripts in larval forms and in female gonads indicates a putative function of VKR in reproduction and/or development. Conclusion The identification of RTKs specific for parasites and insect vectors raises new perspectives for the control of human parasitic and infectious diseases.
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Affiliation(s)
- Arnaud Ahier
- Inserm U547, Université de Lille 2, Institut Pasteur de Lille, Lille, France
| | - Philippe Rondard
- CNRS UMR5203, Institut de Génomique Fonctionnelle, Inserm U661, and Université Montpellier 1,2, Montpellier, France
| | - Nadège Gouignard
- Inserm U547, Université de Lille 2, Institut Pasteur de Lille, Lille, France
| | - Naji Khayath
- Inserm U547, Université de Lille 2, Institut Pasteur de Lille, Lille, France
| | - Siluo Huang
- CNRS UMR5203, Institut de Génomique Fonctionnelle, Inserm U661, and Université Montpellier 1,2, Montpellier, France
| | - Jacques Trolet
- Inserm U547, Université de Lille 2, Institut Pasteur de Lille, Lille, France
| | - Daniel J. Donoghue
- Department of Chemistry and Biochemistry and Moores UCSD Cancer Center, University of California San Diego, La Jolla, California, United States of America
| | - Monique Gauthier
- Centre de Recherches sur la Cognition Animale, CNRS UMR 5169, Université Paul Sabatier, Toulouse, France
| | - Jean-Philippe Pin
- CNRS UMR5203, Institut de Génomique Fonctionnelle, Inserm U661, and Université Montpellier 1,2, Montpellier, France
| | - Colette Dissous
- Inserm U547, Université de Lille 2, Institut Pasteur de Lille, Lille, France
- * E-mail:
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43
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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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Bouschet T, Martin S, Henley JM. Regulation of calcium-sensing-receptor trafficking and cell-surface expression by GPCRs and RAMPs. Trends Pharmacol Sci 2008; 29:633-9. [PMID: 18930324 DOI: 10.1016/j.tips.2008.09.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2008] [Revised: 09/15/2008] [Accepted: 09/16/2008] [Indexed: 12/14/2022]
Abstract
The calcium-sensing (CaS) receptor is a G-protein-coupled receptor (GPCR) that is of fundamental importance for extracellular calcium signalling and calcium homeostasis. The CaS receptor detects changes in free, ionized extracellular calcium concentration and initiates pathways that constantly re-adjust levels of circulating calcium. In addition, the CaS receptor is involved in processes such as stem-cell homing and regulation of neuronal-process outgrowth. To perform these functions, the CaS receptor must be appropriately targeted to the plasma membrane so that its large N-terminal calcium-sensing domain is positioned in the extracellular environment to detect dynamic changes in ionic calcium concentration. Here, we provide an overview of the molecular determinants controlling CaS receptor forward traffic and highlight the roles of CaS receptor interactors such as receptor-activity-modifying proteins and subunits of other class C GPCRs in this process.
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Affiliation(s)
- Tristan Bouschet
- Department of Anatomy, Medical Research Council Centre for Synaptic Plasticity, School of Medical Sciences, University of Bristol, University Walk, Bristol, UK
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45
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van den Hurk MJJ, Cruijsen PMJM, Schoeber JPH, Scheenen WJJM, Roubos EW, Jenks BG. Intracellular signal transduction by the extracellular calcium-sensing receptor of Xenopus melanotrope cells. Gen Comp Endocrinol 2008; 157:156-64. [PMID: 18508053 DOI: 10.1016/j.ygcen.2008.04.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2008] [Revised: 03/28/2008] [Accepted: 04/14/2008] [Indexed: 11/17/2022]
Abstract
The extracellular calcium-sensing receptor (CaR) is expressed in various types of endocrine pituitary cell, but the intracellular mechanism this G protein-coupled receptor uses in these cells is not known. In the present study we investigated possible intracellular signal transduction pathway(s) utilized by the CaR of the endocrine melanotrope cells in the intermediate pituitary lobe of the South African-clawed toad Xenopus laevis. For this purpose, the effects of various pharmacological agents on CaR-evoked secretion of radiolabeled secretory peptides from cultured melanotrope cells were assessed. CaR-evoked secretion, induced by the potent CaR agonist L-phenylalanine (L-Phe), could not be inhibited by cholera toxin, nor by NPC-15437 and PMA, indicating that neither G(s)/PKA nor G(q)/PKC pathways are involved. However, pertussis toxin (G(i/o) protein inhibitor), genistein (inhibitor of PTKs), wortmannin/LY-294002 (PI3-K inhibitor) and U-0126 (inhibitor of extracellular signal-regulated kinase, ERK) all substantially inhibited CaR-evoked secretion, indicating that the Xenopus melanotrope cell possesses a PI3-K/MAPK system that plays some role in CaR-signaling. Since no direct effect of L-Phe on ERK phosphorylation could be shown it is concluded that CaR must act primarily through another, still unknown, signaling pathway in Xenopus melanotropes. Our results indicate that the PI3-K/MAPK system has a facilitating effect on CaR-induced secretion, possibly by sensitizing the CaR.
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Affiliation(s)
- Maarten J J van den Hurk
- Department of Cellular Animal Physiology, Donders Centre for Neuroscience, EURON European Graduate School for Neuroscience, Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands
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46
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Lagerström MC, Schiöth HB. Structural diversity of G protein-coupled receptors and significance for drug discovery. Nat Rev Drug Discov 2008; 7:339-57. [PMID: 18382464 DOI: 10.1038/nrd2518] [Citation(s) in RCA: 1063] [Impact Index Per Article: 66.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
G protein-coupled receptors (GPCRs) are the largest family of membrane-bound receptors and also the targets of many drugs. Understanding of the functional significance of the wide structural diversity of GPCRs has been aided considerably in recent years by the sequencing of the human genome and by structural studies, and has important implications for the future therapeutic potential of targeting this receptor family. This article aims to provide a comprehensive overview of the five main human GPCR families--Rhodopsin, Secretin, Adhesion, Glutamate and Frizzled/Taste2--with a focus on gene repertoire, general ligand preference, common and unique structural features, and the potential for future drug discovery.
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Affiliation(s)
- Malin C Lagerström
- Department of Neuroscience, Functional Pharmacology, Uppsala University, BMC, BOX 593, 751 24, Uppsala, Sweden
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47
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Bu L, Michino M, Wolf RM, Brooks CL. Improved model building and assessment of the Calcium-sensing receptor transmembrane domain. Proteins 2008; 71:215-26. [DOI: 10.1002/prot.21685] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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48
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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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49
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Hu J, Spiegel AM. Structure and function of the human calcium-sensing receptor: insights from natural and engineered mutations and allosteric modulators. J Cell Mol Med 2008; 11:908-22. [PMID: 17979873 PMCID: PMC4401263 DOI: 10.1111/j.1582-4934.2007.00096.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The human extracellular Ca(2+)-sensing receptor (CaR), a member of the G protein-coupled receptor family 3, plays a key role in the regulation of extracellular calcium homeostasis. It is one of just a few G protein-coupled receptors with a large number of naturally occurring mutations identified in patients. In contrast to the small sizes of its agonists, this large dimeric receptor consists of domains with topologically distinctive orthosteric and allosteric sites. Information derived from studies of naturally occurring mutations, engineered mutations, allosteric modulators and crystal structures of the agonist-binding domain of homologous type 1 metabotropic glutamate receptor and G protein-coupled rhodopsin offers new insights into the structure and function of the CaR.
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Affiliation(s)
- Jianxin Hu
- Molecular Signalling Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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50
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Riccardi D, Martin D. The role of the calcium-sensing receptor in the pathophysiology of secondary hyperparathyroidism. NDT Plus 2008; 1:i7-i11. [PMID: 25983956 PMCID: PMC4421157 DOI: 10.1093/ndtplus/sfm038] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2007] [Accepted: 09/10/2007] [Indexed: 11/21/2022] Open
Abstract
The calcium-sensing receptor (CaR), a seven-transmembrane domain receptor belonging to the G protein-coupled receptor family, is responsible for calcium-mediated signalling initiated at the surface of parathyroid cells that controls the synthesis and secretion of parathyroid hormone (PTH). Expression of the CaR is downregulated in animal models of uraemia and in patients with secondary hyperparathyroidism (SHPT). Cinacalcet is a type II calcimimetic agent that acts as an allosteric modulator of CaR signalling. It has been shown in clinical studies to improve control of serum PTH levels and in preclinical studies to attenuate SHPT disease progression and parathyroid hyperplasia. Cinacalcet represents the first of this novel class of agents and a major advance in the treatment of SHPT.
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