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A disease-associated mutation in the adhesion GPCR BAI2 (ADGRB2) increases receptor signaling activity.

ABSTRACT: Mutations in G protein-coupled receptors (GPCRs) that increase constitutive signaling activity can cause human disease. A de novo C-terminal mutation (R1465W) in the adhesion GPCR BAI2 (also known as ADGRB2) was identified in a patient suffering from progressive spastic paraparesis and other neurological symptoms. In vitro studies revealed that this mutation strongly increases the constitutive signaling activity of an N-terminally cleaved form of BAI2, which represents the activated form of the receptor. Further studies dissecting the mechanism(s) underling this effect revealed that wild-type BAI2 primarily couples to G?z , with the R1465W mutation conferring increased coupling to G?i . The R1465W mutation also increases the total and surface expression of BAI2. The mutation has no effect on receptor binding to ?-arrestins, but does perturb binding to the endocytic protein endophilin A1, identified here as a novel interacting partner for BAI2. These studies provide new insights into the signaling capabilities of the adhesion GPCR BAI2/ADGRB2 and shed light on how an apparent gain-of-function mutation to the receptor's C-terminus may lead to human disease.

SUBMITTER: Purcell RH

PROVIDER: S-EPMC5679302 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature

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A disease-associated mutation in the adhesion GPCR BAI2 (ADGRB2) increases receptor signaling activity.

Purcell Ryan H RH Toro Camilo C Gahl William A WA Hall Randy A RA

Human mutation 20170920 12

Mutations in G protein-coupled receptors (GPCRs) that increase constitutive signaling activity can cause human disease. A de novo C-terminal mutation (R1465W) in the adhesion GPCR BAI2 (also known as ADGRB2) was identified in a patient suffering from progressive spastic paraparesis and other neurological symptoms. In vitro studies revealed that this mutation strongly increases the constitutive signaling activity of an N-terminally cleaved form of BAI2, which represents the activated form of the ...[more]

PMID: 28891236

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Project description:Abnormal feedback of serum calcium to parathyroid hormone (PTH) secretion is the hallmark of primary hyperparathyroidism (PHPT). Although the molecular pathogenesis of parathyroid neoplasia in PHPT has been linked to abnormal expression of genes involved in cell growth (e.g., cyclin D1, retinoblastoma, and β-catenin), the molecular basis of abnormal calcium sensing by calcium-sensing receptor (CaSR) and PTH hypersecretion in PHPT are incompletely understood. Through gene expression profiling, we discovered that an orphan adhesion G protein-coupled receptor (GPCR), GPR64/ADGRG2, is expressed in human normal parathyroid glands and is overexpressed in parathyroid tumors from patients with PHPT. Using immunohistochemistry, Western blotting, and coimmunoprecipitation, we found that GPR64 is expressed on the cell surface of parathyroid cells, is overexpressed in parathyroid tumors, and physically interacts with the CaSR. By using reporter gene assay and GPCR second messenger readouts we identified Gαs, 3',5'-cyclic adenosine monophosphate (cAMP), protein kinase A, and cAMP response element binding protein (CREB) as the signaling cascade downstream of GPR64. Furthermore, we found that an N-terminally truncated human GPR64 is constitutively active and a 15-amino acid-long peptide C-terminal to the GPCR proteolysis site (GPS) of GPR64 activates this receptor. Functional characterization of GPR64 demonstrated its ability to increase PTH release from human parathyroid cells at a range of calcium concentrations. We discovered that the truncated constitutively active, but not the full-length GPR64 physically interacts with CaSR and attenuates the CaSR-mediated intracellular Ca2+ signaling and cAMP suppression in HEK293 cells. Our results indicate that GPR64 may be a physiologic regulator of PTH release that is dysregulated in parathyroid tumors, and suggest a role for GPR64 in pathologic calcium sensing in PHPT. © 2016 American Society for Bone and Mineral Research.

Dataset Information

A disease-associated mutation in the adhesion GPCR BAI2 (ADGRB2) increases receptor signaling activity.

Publications

A disease-associated mutation in the adhesion GPCR BAI2 (ADGRB2) increases receptor signaling activity.

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