Novel Inactivating Mutations of the Calcium-Sensing Receptor: The Calcimimetic NPS R-568 Improves Signal Transduction of Mutant Receptors

Rus, Ramona; Haag, Christine; Bumke-Vogt, Christiane; Bähr, V.; Mayr, B; Möhlig, Matthias; Schulze, Egbert; Frank‐Raue, Karin; Raue, Friedhelm; Schöfl, Christof

doi:10.1210/jc.2008-1076

Cited by 66 publications

(42 citation statements)

References 22 publications

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“…Hypercalcemia with hypercalciuria has already been observed in a Swedish family presenting p.F881L mutation in CASR (28). Thereafter, several other mutations (p.T100I, p.L650P, p.V689M (27), p.Q926R, and p.D1005N (30)) have been associated with atypical 'FHH' presentations including hypercalciuria. One hypothesis could be that various biochemical phenotypes in FHH patients could be correlated with specific genotypes (17) and that mutations may not have the same impact on the distinct signaling pathways regulated by CASR (MAPK pathways activation vs PI-PLC for instance) and in different tissues (parathyroid glands vs cortical thick ascending limb).…”

Section: Discussionmentioning

confidence: 90%

Two novel mutations of the calcium-sensing receptor gene affecting the same amino acid position lead to opposite phenotypes and reveal the importance of p.N802 on receptor activity

Lia-Baldini

Magdelaine

Nizou

et al. 2013

European Journal of Endocrinology

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Objective: Gain-of-function mutations of the calcium-sensing receptor (CASR) gene have been identified in patients with sporadic or familial autosomal dominant hypocalcemia (ADH). Inactivating mutations of the CASR gene cause familial hypocalciuric hypercalcemia (FHH). Here, we report two novel CASR mutations affecting the same amino acid (p.N802); one causes ADH and the other atypical FHH. Patients and methods: The first patient, an 11-year-old girl suffering from hypocalcemia, developed nephrocalcinosis when she was only 5 years old. The second patient is a 30-year-old woman who presented with mild hypercalcemia. PCR amplification of CASR coding exons and direct sequencing of PCR products were used to identify mutations. Site-directed mutagenesis was used to generate mutated CASR cDNAs in an expression plasmid. Using the MAPK assay system and transient transfection of Cos-7 cells with wild-type (WT) and mutated CASR, we studied the responses of these mutated receptors to extracellular Ca 2C and to the negative allosteric CASR modulator, NPS2143. Results: Two heterozygous missense mutations (p.N802I and p.N802S) affecting a residue in the sixth transmembrane domain of CASR were identified. In functional tests, the response of the p.N802S mutant to calcium was typical of an inactivating mutation. However, the p.N802I mutant had 70% of the maximally stimulated WT receptor activity even in the absence of extracellular calcium. This constitutive activity was only partially inhibited by the inhibitor, NPS2143. Conclusions: The asparagine at amino acid position 802 appears to be essential for the activity of the CASR protein and is implicated in the mechanism of CASR signaling.

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Section: Discussionmentioning

confidence: 90%

Two novel mutations of the calcium-sensing receptor gene affecting the same amino acid position lead to opposite phenotypes and reveal the importance of p.N802 on receptor activity

Lia-Baldini

Magdelaine

Nizou

et al. 2013

European Journal of Endocrinology

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“…Loss-of-function mutations in one or both of the CASR alleles result in hypercalcemic disorders, whereas gain-of-function mutations cause autosomal dominant hypocalcemia with hypercalciuria (ADHH) (Gunn and Gaffney, 2004;Thakker, 2004;Rus et al, 2008;Brown, 2006, Letz et al, 2010). The gain-of-function mutation at nucleotide C662 (CCG to CTG) results in the substitution of a leucine residue for a proline residue in the extracellular bilobed Venus-fly-trap domain (VFTD) of the CaSR, which is predicted to contain five Ca 2+ -binding sites (CaBSs) (Huang et al, 2007).…”

Section: Discussionmentioning

confidence: 99%

“…Mutations in the CASR gene have been associated with inherited disorders of divalent mineral homeostasis Hannan et al, 2012). Loss-of-function mutations in one or both of the CASR alleles result in hypercalcemic disorders as a result of upward resetting of the receptor EC 50 value (effective concentration necessary to induce a 50% effect) for ionized Ca 2+ in both the parathyroid glands and the kidney (Gunn and Gaffney, 2004;Thakker, 2004;Rus et al, 2008). Conversely, gain-of-function mutations of the CASR gene result in hypocalcemia because of downward resetting of the receptor EC 50 (Chattopadhyay and Brown, 2006;Letz et al, 2010).…”

Section: +mentioning

confidence: 99%

Activation of the calcium-sensing receptor induces deposition of tight junction components to the epithelial cell plasma membrane

Jouret

Hull

et al. 2013

Journal of Cell Science

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SummaryThe Ca 2+ -sensing receptor (CaSR) belongs to the G-protein-coupled receptor superfamily and plays essential roles in divalent ion homeostasis and cell differentiation. Because extracellular Ca 2+ is essential for the development of stable epithelial tight junctions (TJs), we hypothesized that the CaSR participates in regulating TJ assembly. We first assessed the expression of the CaSR in Madin-Darby canine kidney (MDCK) cells at steady state and following manipulations that modulate TJ assembly. Next, we examined the effects of CaSR agonists and antagonists on TJ assembly. Immunofluorescence studies indicate that endogenous CaSR is located at the basolateral pole of MDCK cells. Stable transfection of human CaSR in MDCK cells further reveals that this protein co-distributes with b-catenin on the basolateral membrane. Switching MDCK cells from low-Ca 2+ medium to medium containing a normal Ca 2+ concentration significantly increases CaSR expression at both the mRNA and protein levels. Exposure of MDCK cells maintained in low-Ca 2+ conditions to the CaSR agonists neomycin, Gd 3+ or R-568 causes the transient relocation of the tight junction components ZO-1 and occludin to sites of cell-cell contact, while inducing no significant changes in the expression of mRNAs encoding junction-associated proteins. Stimulation of CaSR also increases the interaction between ZO-1 and the F-actin-binding protein I-afadin. This effect does not involve activation of the AMP-activated protein kinase. By contrast, CaSR inhibition by NPS-2143 significantly decreases interaction of ZO-1 with I-afadin and reduces deposition of ZO-1 at the cell surface following a Ca 2+ switch from 5 mM to 200 mM [Ca 2+ ] e . Pre-exposure of MDCK cells to the cell-permeant Ca 2+ chelator BAPTA-AM, similarly prevents TJ assembly caused by CaSR activation. Finally, stable transfection of MDCK cells with a cDNA encoding a human disease-associated gain-of-function mutant form of the CaSR increases the transepithelial electrical resistance of these cells in comparison to expression of the wild-type human CaSR. These observations suggest that the CaSR participates in regulating TJ assembly.

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“…The first described mutation F881L, associated with atypical FHH-like phenotype (50), is located in the region encoding the C-terminal tail. Thereafter, Rus et al (51) described two novel mutations with atypical phenotype affecting amino acids in the C-terminal tail: Q926R and D1005N. Several other mutations (V268del-11X273, E250K, T100I, L650P, V689M, and 1008delAAG) have been associated with atypical presentations, including severe hypercalcemia, hypercalciuria with or without nephrolithiasis and/or nephrocalcinosis, kindreds with affected members displaying either hypercalciuria or hypocalciuria, and normal calcium levels after surgery and pancreatitis (10,49).…”

Section: Discussionmentioning

confidence: 99%

Mutations of calcium-sensing receptor gene: two novel mutations and overview of impact on calcium homeostasis

Livadariu¹,

Auriemma²,

Rydlewski³

et al. 2011

European Journal of Endocrinology

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Objective: Genetic disorders of calcium metabolism arise in a familial or sporadic setting. The calciumsensing receptor (CASR) plays a key role in maintaining calcium homeostasis and study of the CASR gene can be clinically useful in determining etiology and appropriate therapeutic approaches. We report two cases of novel CASR gene mutations that illustrate the varying clinical presentations and discuss these in terms of the current understanding of CASR function. Patients and methods: A 16-year-old patient had mild hypercalcemia associated with low-normal urinary calcium excretion and normal-to-high parathyroid hormone (PTH) levels. Because of negative family history, familial hypocalciuric hypercalcemia was originally excluded. The second patient was a 54-year-old man with symptomatic hypocalcemia, hyperphosphatemia, low PTH, and mild hypercalciuria. Familial investigation revealed the same phenotype in the patient's sister. The coding region of the CASR gene was sequenced in both probands and their available first-degree relatives. Results: The first patient had a novel heterozygous inactivating CASR mutation in exon 4, which predicted a p.A423K change; genetic analysis was negative in the parents. The second patient had a novel heterozygous activating CASR mutation in exon 6, which predicted a p.E556K change; the affected sister of the proband was also positive. Conclusions: We reported two novel heterozygous mutations of the CASR gene, an inactivating mutation in exon 4 and the first activating mutation reported to date in exon 6. These cases illustrate the importance of genetic testing of CASR gene to aid correct diagnosis and to assist in clinical management.

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Novel Inactivating Mutations of the Calcium-Sensing Receptor: The Calcimimetic NPS R-568 Improves Signal Transduction of Mutant Receptors

Abstract: Therefore, calcimimetics might offer medical treatment for symptomatic FHH patients, and more important, for patients with neonatal severe hyperparathyroidism that harbor calcimimetic-sensitive CaSR mutants.

Cited by 66 publications

References 22 publications

Two novel mutations of the calcium-sensing receptor gene affecting the same amino acid position lead to opposite phenotypes and reveal the importance of p.N802 on receptor activity

Two novel mutations of the calcium-sensing receptor gene affecting the same amino acid position lead to opposite phenotypes and reveal the importance of p.N802 on receptor activity

Activation of the calcium-sensing receptor induces deposition of tight junction components to the epithelial cell plasma membrane

Mutations of calcium-sensing receptor gene: two novel mutations and overview of impact on calcium homeostasis

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