A missense mutation of Leu74Pro of OGR1 found in familial amelogenesis imperfecta actually causes the loss of the pH-sensing mechanism.

Abstract

Ovarian cancer G protein-coupled receptor 1 (OGR1), also known as GPR68, is a proton-sensing G protein-coupled receptor (GPCR) coupling to Gq/11/phospholipase C/Ca2+ signaling pathways. The specific histidine residues at the extracellular surface of OGR1 are suggested to be involved in the proton sensing. Later, some metal ions, including nickel ion (Ni2+), are also indicated to be OGR1 ligands. OGR1 polymorphic variants have recently been found in three families with amelogenesis imperfecta, which suggested that OGR1 is required for the process of dental enamel formation. One of these families possesses a missense mutation from leucine to proline at 74 (L74P) of OGR1. In the present study, we characterized HEK293 cells with L74P OGR1 (L74P-OGR1) and hemagglutinin (HA)-tag, as compared with cells with wild-type OGR1 (WT-OGR1) and HA-tag. We found that either acidic pH or NiCl2 induced intracellular Ca2+ mobilization and morphological change in WT-OGR1-transfected cells; however, the extracellular stimulus-induced actions were severely damaged in L74P-OGR1-transfected cells. We further confirmed that either WT-OGR1 or L74P-OGR1 is localized mainly in the surface of the cells, but only WT-OGR1 is internalized in response to acidification or NiCl2. Thus, the L74P-OGR1 protein may be distributed in the plasma membranes but severely damaged in the receptor functions. We speculate that L74P in the second transmembrane domain in OGR1 may result in conformational changes in the receptor, thereby disturbing the sensing extracellular signals, i.e., protons or metal ions, and/or transducing them to the intracellular signaling machinery through G proteins.

• Authors: Koichi Sato, Chihiro Mogi, Alan J Mighell, Fumikazu Okajima
• Journal: Biochemical and biophysical research communications (Biochem Biophys Res Commun) Vol. 526 Issue 4 Pg. 920-926 (06 11 2020) ISSN: 1090-2104 [Electronic] United States
• PMID: 32279993 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2020 Elsevier Inc. All rights reserved.

Chemical References

• GPR68 protein, human
• Lysophospholipids
• RNA, Messenger
• Receptors, G-Protein-Coupled
• nickel chloride
• Nickel
• lysophosphatidic acid

Topics

• Amelogenesis Imperfecta (genetics, metabolism)
• Calcium Signaling
• Cell Shape (drug effects)
• Endocytosis (drug effects)
• HEK293 Cells
• Humans
• Hydrogen-Ion Concentration
• Lysophospholipids (pharmacology)
• Mutation, Missense (genetics)
• Nickel (toxicity)
• Protein Structure, Secondary
• RNA, Messenger (genetics, metabolism)
• Receptors, G-Protein-Coupled (chemistry, genetics, metabolism)