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Updated: Jan 11, 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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Elucidating biased signaling in class A GPCRs
Ningyang Xu1, Edwin Legall1, Roger H Johnson2
1Cancer Center and Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Trends in Pharmacological Sciences
|November 8, 2025
Summary
Biased signaling in G protein-coupled receptors (GPCRs) allows drugs to target specific pathways, potentially reducing side effects. Understanding the structural basis of this bias is key for developing more effective therapeutics.
Area of Science:
- Pharmacology
- Structural Biology
- Biochemistry
Background:
- G protein-coupled receptors (GPCRs) are crucial drug targets, mediating numerous physiological processes.
- Biased signaling, where ligands selectively activate G proteins or β-arrestins, presents an opportunity for developing therapeutics with improved safety profiles.
- The structural mechanisms underlying biased signaling in Class A GPCRs remain largely undefined.
Purpose of the Study:
- To review the key mechanisms driving biased signaling in GPCRs.
- To integrate structural and functional data to understand ligand-induced conformational changes.
- To provide a mechanistic framework for developing pathway-selective GPCR therapeutics.
Main Methods:
- Utilizing cryo-electron microscopy (cryo-EM) to determine receptor structures.
- Employing real-time functional assays like bioluminescence resonance energy transfer (BRET) and NanoLuc Binary Technology (NanoBRET).
- Integrating structural and functional data to map signaling pathways.
Main Results:
- Distinct ligand binding modes induce specific receptor conformations.
- These conformations dictate the engagement of downstream signaling partners (G proteins or β-arrestins).
- Key mechanisms include microswitch transitions, intracellular interface remodeling, and allosteric modulation.
Conclusions:
- Understanding GPCR structural dynamics is crucial for biased ligand design.
- This knowledge facilitates the development of isoform- and tissue-specific therapeutics.
- Pathway-selective GPCR targeting offers improved efficacy and reduced off-target effects.
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