Calcium-sensing receptor residues with loss- and gain-of-function mutations are located in regions of conformational change and cause signalling bias



Gorvin, Caroline M, Frost, Morten, Malinauskas, Tomas, Cranston, Treena, Boon, Hannah, Siebold, Christian, Jones, E Yvonne, Hannan, Fadil M ORCID: 0000-0002-2975-5170 and Thakker, Rajesh V
(2018) Calcium-sensing receptor residues with loss- and gain-of-function mutations are located in regions of conformational change and cause signalling bias. HUMAN MOLECULAR GENETICS, 27 (21). pp. 3720-3733.

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Abstract

The calcium-sensing receptor (CaSR) is a homodimeric G-protein-coupled receptor that signals via intracellular calcium (Ca2+i) mobilisation and phosphorylation of extracellular signal-regulated kinase 1/2 (ERK) to regulate extracellular calcium (Ca2+e) homeostasis. The central importance of the CaSR in Ca2+e homeostasis has been demonstrated by the identification of loss- or gain-of-function CaSR mutations that lead to familial hypocalciuric hypercalcaemia (FHH) or autosomal dominant hypocalcaemia (ADH), respectively. However, the mechanisms determining whether the CaSR signals via Ca2+i or ERK have not been established, and we hypothesised that some CaSR residues, which are the site of both loss- and gain-of-function mutations, may act as molecular switches to direct signalling through these pathways. An analysis of CaSR mutations identified in >300 hypercalcaemic and hypocalcaemic probands revealed five 'disease-switch' residues (Gln27, Asn178, Ser657, Ser820 and Thr828) that are affected by FHH and ADH mutations. Functional expression studies using HEK293 cells showed disease-switch residue mutations to commonly display signalling bias. For example, two FHH-associated mutations (p.Asn178Asp and p.Ser820Ala) impaired Ca2+i signalling without altering ERK phosphorylation. In contrast, an ADH-associated p.Ser657Cys mutation uncoupled signalling by leading to increased Ca2+i mobilization while decreasing ERK phosphorylation. Structural analysis of these five CaSR disease-switch residues together with four reported disease-switch residues revealed these residues to be located at conformationally active regions of the CaSR such as the extracellular dimer interface and transmembrane domain. Thus, our findings indicate that disease-switch residues are located at sites critical for CaSR activation and play a role in mediating signalling bias.

Item Type: Article
Uncontrolled Keywords: Humans, Hypocalcemia, Hypoparathyroidism, Receptors, Calcium-Sensing, Sequence Alignment, DNA Mutational Analysis, Signal Transduction, Calcium Signaling, Amino Acid Sequence, Protein Conformation, Hypercalciuria, HEK293 Cells, Loss of Function Mutation, Gain of Function Mutation
Depositing User: Symplectic Admin
Date Deposited: 10 Sep 2018 06:57
Last Modified: 19 Jan 2023 01:24
DOI: 10.1093/hmg/ddy263
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3025950