Single-molecule diffusion-based estimation of ligand effects on G protein-coupled receptors

Sci Signal. 2018 Sep 18;11(548):eaao1917. doi: 10.1126/scisignal.aao1917.

Abstract

G protein-coupled receptors (GPCRs) are major drug targets. Developing a method to measure the activities of GPCRs is essential for pharmacology and drug screening. However, it is difficult to measure the effects of a drug by monitoring the receptor on the cell surface; thus, changes in the concentrations of downstream signaling molecules, which depend on the signaling pathway selectivity of the receptor, are often used as an index of receptor activity. We show that single-molecule imaging analysis provides an alternative method for assessing the effects of ligands on GPCRs. Using total internal reflection fluorescence microscopy (TIRFM), we monitored the dynamics of the diffusion of metabotropic glutamate receptor 3 (mGluR3), a class C GPCR, under various ligand conditions. Our single-molecule tracking analysis demonstrated that increases and decreases in the average diffusion coefficient of mGluR3 quantitatively reflected the ligand-dependent inactivation and activation of receptors, respectively. Through experiments with inhibitors and dual-color single-molecule imaging analysis, we found that the diffusion of receptor molecules was altered by common physiological events associated with GPCRs, including G protein binding, and receptor accumulation in clathrin-coated pits. We also confirmed that agonist also decreased the average diffusion coefficient for class A and B GPCRs, demonstrating that this parameter is a good index for estimating ligand effects on many GPCRs regardless of their phylogenetic groups, the chemical properties of the ligands, or G protein-coupling selectivity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acids / metabolism
  • GTP-Binding Proteins / metabolism*
  • HEK293 Cells
  • Humans
  • Ligands
  • Microscopy, Fluorescence / methods*
  • Pertussis Toxin / metabolism
  • Pertussis Toxin / pharmacology
  • Protein Binding / drug effects
  • Radioligand Assay / methods
  • Receptors, G-Protein-Coupled / analysis
  • Receptors, G-Protein-Coupled / genetics
  • Receptors, G-Protein-Coupled / metabolism*
  • Receptors, Metabotropic Glutamate / analysis
  • Receptors, Metabotropic Glutamate / genetics
  • Receptors, Metabotropic Glutamate / metabolism
  • Signal Transduction*
  • Xanthenes / metabolism

Substances

  • Amino Acids
  • LY 341495
  • Ligands
  • Receptors, G-Protein-Coupled
  • Receptors, Metabotropic Glutamate
  • Xanthenes
  • metabotropic glutamate receptor 3
  • Pertussis Toxin
  • GTP-Binding Proteins