title: Orphan Adhesion GPCR GPR64/ADGRG2 Is Overexpressed in Parathyroid Tumors and Attenuates Calcium-Sensing Receptor-Mediated Signaling.
abstract: 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.
authors.affiliation: Division of General & Oncologic Surgery, Department of Surgery, University of Maryland School of Medicine, Baltimore, MD, USA.
authors.forename: Nariman
authors.initials: N
authors.lastname: Balenga
authors.affiliation: Division of General & Oncologic Surgery, Department of Surgery, University of Maryland School of Medicine, Baltimore, MD, USA.
authors.forename: Pedram
authors.initials: P
authors.lastname: Azimzadeh
authors.affiliation: Department of Surgery, Duke University Medical Center, Durham, NC, USA.
authors.forename: Joyce A
authors.initials: JA
authors.lastname: Hogue
authors.affiliation: Department of Pathology, University of Maryland School of Medicine, Baltimore, MD, USA.
authors.forename: Paul N
authors.initials: PN
authors.lastname: Staats
authors.affiliation: Division of General & Oncologic Surgery, Department of Surgery, University of Maryland School of Medicine, Baltimore, MD, USA.
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Shi
authors.affiliation: Department of Surgery, Duke University Medical Center, Durham, NC, USA.
authors.forename: James
authors.initials: J
authors.lastname: Koh
authors.affiliation: Department of Molecular Genetics and Microbiology, Duke University, Durham, NC, USA.
authors.forename: Holly
authors.initials: H
authors.lastname: Dressman
authors.affiliation: Division of General & Oncologic Surgery, Department of Surgery, University of Maryland School of Medicine, Baltimore, MD, USA.
authors.forename: John A
authors.initials: JA
authors.lastname: Olson
mesh_terms: D000236:Adenoma / Q000378:metabolism / Q000473:pathology; D002469:Cell Separation; D000242:Cyclic AMP / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D000089703:Fibroblast Growth Factor-23; D057809:HEK293 Cells; D006801:Humans; D049950:Hyperparathyroidism, Primary / Q000473:pathology; D010282:Parathyroid Neoplasms / Q000378:metabolism* / Q000473:pathology; D011485:Protein Binding; D059748:Proteolysis; D044169:Receptors, Calcium-Sensing / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D015398:Signal Transduction; D015854:Up-Regulation
chemical_list: C105986:ADGRG2 protein, human; D017362:Cyclic AMP Response Element-Binding Protein; C000717427:FGF23 protein, human; D044169:Receptors, Calcium-Sensing; D043562:Receptors, G-Protein-Coupled; D000089703:Fibroblast Growth Factor-23; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases
keywords: CELL/TISSUE SIGNALING; DISORDERS OF CALCIUM/PHOSPHATE METABOLISM; HORMONE REPLACEMENT/RECEPTOR MODULATORS; PTH/VIT D/FGF23; TRANSCRIPTION FACTORS