Related Experiment Video

Updated: Jul 20, 2025

A Kinetic Fluorescence-based Ca2+ Mobilization Assay to Identify G Protein-coupled Receptor Agonists, Antagonists, and Allosteric Modulators
07:41

A Kinetic Fluorescence-based Ca2+ Mobilization Assay to Identify G Protein-coupled Receptor Agonists, Antagonists, and Allosteric Modulators

Published on: February 20, 2018

8.9K

GPCR activation and GRK2 assembly by a biased intracellular agonist

Jia Duan1,2,3, Heng Liu4, Fenghui Zhao5

  • 1State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China. duanjia@simm.ac.cn.

Nature
|August 2, 2023
PubMed

Insights

This study reveals the structure of a G-protein-coupled receptor (GPCR) bound to a kinase and a biased ligand. This provides a molecular model for understanding GPCR-GRK interactions and biased signaling.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Pharmacology

Background:

  • G-protein-coupled receptors (GPCRs) are crucial cell surface receptors involved in numerous physiological processes.
  • Phosphorylation by GPCR kinases (GRKs) desensitizes GPCRs and mediates arrestin signaling, a process influenced by biased ligands.
  • The precise molecular mechanisms of GRK engagement with GPCRs and biased signaling remain poorly understood due to weak receptor-kinase interactions.

Purpose of the Study:

  • To elucidate the structural basis of GPCR-GRK interactions and GRK-mediated biased signaling.
  • To determine the complex structure of neurotensin receptor 1 (NTSR1) bound to GRK2, Gαq, and the arrestin-biased ligand SBI-553.

Main Methods:

  • Reported the complex structure of NTSR1, GRK2, Gαq, and SBI-553 using cryo-electron microscopy.
  • Analyzed the binding interfaces and molecular arrangements within the complex.

Main Results:

  • Revealed the intact GRK2 structure docked into an open pocket on NTSR1, formed by the outward movement of transmembrane helix 6.
  • Demonstrated that the arrestin-biased ligand SBI-553 enhances GRK2 binding by stabilizing the complex at the receptor-kinase interface.
  • Showed that SBI-553's binding mode favors arrestin engagement while sterically hindering Gαq binding, explaining its biased signaling.

Conclusions:

  • The determined structure provides a detailed molecular model for GPCR-GRK interactions.
  • Offers a mechanistic explanation for GRK2-mediated biased signaling driven by ligands like SBI-553.
  • Highlights the potential for structure-based drug design targeting GPCR signaling pathways.

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