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A Kinetic Fluorescence-based Ca2+ Mobilization Assay to Identify G Protein-coupled Receptor Agonists, Antagonists, and Allosteric Modulators
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G2A is a proton-sensing G-protein-coupled receptor antagonized by lysophosphatidylcholine

Naoka Murakami1, Takehiko Yokomizo, Toshiaki Okuno

  • 1Department of Biochemistry, Faculty of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan.

The Journal of Biological Chemistry
|July 29, 2004
PubMed

Insights

G2A, a G-protein-coupled receptor (GPCR), senses protons and regulates cell functions. Lysophosphatidylcholine (LPC) acts as an antagonist, inhibiting G2A

Area of Science:

  • Biochemistry
  • Cell Biology
  • Molecular Pharmacology

Background:

  • G2A is a G-protein-coupled receptor (GPCR) involved in cell cycle, proliferation, oncogenesis, and immunity.
  • G2A shares homology with OGR1, GPR4, and TDAG8, which are implicated in various cellular processes.
  • Lysophosphatidylcholine (LPC) and sphingosylphosphorylcholine (SPC) have been identified as potential ligands for these receptors.

Purpose of the Study:

  • To investigate the proton-sensing capabilities of the G2A receptor.
  • To determine the role of LPC in the function of G2A.

Main Methods:

  • Transient expression of G2A in cells.
  • Assays measuring zif 268 promoter activation and inositol phosphate (IP) accumulation.
  • Evaluation of G2A activity across a range of extracellular pH levels.
  • Dose-dependent inhibition assays using LPC.

Main Results:

  • G2A expression led to significant activation of the zif 268 promoter and IP accumulation at pH 7.6.
  • Lowering extracellular pH augmented G2A activation specifically in G2A-expressing cells.
  • LPC demonstrated a dose-dependent inhibitory effect on the pH-dependent activation of G2A.

Conclusions:

  • G2A functions as a proton-sensing GPCR.
  • LPC acts as an antagonist, not an agonist, for G2A.
  • LPC modulates the proton-dependent activation of G2A.

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