Related Experiment Video
Updated: Jan 16, 2026
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A Kinetic Fluorescence-based Ca2+ Mobilization Assay to Identify G Protein-coupled Receptor Agonists, Antagonists, and Allosteric Modulators
Published on: February 20, 2018
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Ligand-specific activation trajectories dictate GPCR signalling in cells
Romy Thomas1,2,3, Pauline S Jacoby1, Chiara De Faveri4,5
1Rudolf Boehm Institute of Pharmacology and Toxicology, Medical Faculty, Leipzig University, Leipzig, Germany.
Nature
|January 14, 2026
Summary
Researchers developed biosensors to study G-protein-coupled receptors (GPCRs) in living cells. They found that different drug molecules can create at least four distinct active states of the M2 receptor, influencing cell communication and drug discovery.
Area of Science:
- Biochemistry
- Molecular Biology
- Pharmacology
Background:
- G-protein-coupled receptors (GPCRs) are crucial for cellular communication and are major drug targets.
- In vitro studies suggest GPCRs exist in equilibrium between inactive and active states, modulated by ligand efficacy.
- Uncertainty remains regarding how ligand efficacy is encoded and if multiple GPCR states exist within living cells.
Purpose of the Study:
- To investigate the conformational dynamics of GPCRs in living cells.
- To understand how ligand efficacy is encoded at the molecular level within intact cells.
- To explore the existence and function of distinct GPCR active states in real-time.
Main Methods:
- Utilized genetic code expansion and bioorthogonal labeling to create fluorescence-based biosensors.
- Developed biosensors for the M2 muscarinic acetylcholine receptor (M2R).
- Enabled real-time monitoring of agonist-induced conformational changes on the extracellular surface of M2R in intact cells.
Main Results:
- Demonstrated that different agonists induce equilibria of at least four distinct active states of the G-protein-bound M2R.
- Showed that these distinct states possess varying capacities for G-protein activation.
- Observed the formation of M2R-G-protein complexes over 0.2-5 seconds, involving common and ligand-specific conformational changes that dictate G-protein selectivity.
Conclusions:
- Revealed the molecular basis of ligand efficacy in living cells.
- Identified distinct active states of M2R and their differential G-protein activation capabilities.
- Suggests that exploiting GPCR activation trajectories and conformational equilibria could lead to novel drug discovery approaches.
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