Heteromerization of G2A and OGR1 enhances proton sensitivity and proton-induced calcium signals

Abstract

Proton-sensing G-protein-coupled receptors (GPCRs; OGR1, GPR4, G2A, TDAG8), with full activation at pH 6.4 ∼ 6.8, are important to pH homeostasis, immune responses and acid-induced pain. Although G2A mediates the G13-Rho pathway in response to acid, whether G2A activates Gs, Gi or Gq proteins remains debated. In this study, we examined the response of this fluorescence protein-tagged OGR1 family to acid stimulation in HEK293T cells. G2A did not generate detectable intracellular calcium or cAMP signals or show apparent receptor redistribution with moderate acid (pH ≥ 6.0) stimulation but reduced cAMP accumulation under strong acid stimulation (pH ≤ 5.5). Surprisingly, coexpression of OGR1- and G2A-enhanced proton sensitivity and proton-induced calcium signals. This alteration is attributed to oligomerization of OGR1 and G2A. The oligomeric potential locates receptors at a specific site, which leads to enhanced proton-induced calcium signals through channels.

• Proton-sensing G protein-coupled receptor
• OGR1
• G2A
• heteromerization
• G-protein signaling

Acknowledgements

We thank the support of the Biophysics and Soft Mater at National Central University for calcium imaging. We also thank Dr. Chien-Chang Chen for providing NNC550396 and Nicardipine, and thank KAI Pharmaceuticals, Inc. (CA) for providing PKCɛV_1–2 peptide. This work was supported in part by the funds from the Ministry of Science and Technology, Taiwan (grant no. NSC102–2321-B-008–001; MOST 103–2321-B-008–001).

Declaration of interest

The authors declare no conflicts of interest. The authors alone are responsible for the content and writing of this article.