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Updated: Jun 18, 2026

A Kinetic Fluorescence-based Ca2+ Mobilization Assay to Identify G Protein-coupled Receptor Agonists, Antagonists, and Allosteric Modulators
Published on: February 20, 2018
G protein subunit dissociation and translocation regulate cellular response to receptor stimulation
Mariangela Chisari1, Deepak Kumar Saini, Joon-Ho Cho
1Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri, United States of America.
Cellular signaling intensity is modulated by G protein behavior. Receptor activation causes G betagamma translocation, which can attenuate cellular responses, while non-dissociating G betagamma enhances them.
Area of Science:
- Cellular biology
- Molecular signaling
- Biochemistry
Background:
- G proteins are key mediators of cellular responses to extracellular signals.
- Receptor activation triggers complex G protein signaling cascades.
- The precise role of G protein subunit dynamics in signal modulation requires further elucidation.
Purpose of the Study:
- To investigate how G protein behavior, specifically G betagamma translocation, influences cellular responses to receptor activation.
- To understand the differential impact of translocating versus non-translocating G betagamma subunits on effector activation.
- To explore the role of G protein heterotrimer stability in signal intensity.
Main Methods:
- Utilized biosensors to measure the generation of inositol triphosphate and diacylglycerol, downstream effectors of G proteins.
- Employed Förster Resonance Energy Transfer (FRET) based G protein sensors to monitor subunit interactions and translocation.
- Investigated M3 muscarinic receptor activation in cells with varying G protein subunit dynamics, including tethered alpha q subunits.
Main Results:
- G betagamma translocation from the plasma membrane to endomembranes upon receptor activation was found to attenuate the cellular response.
- Non-translocating G betagamma subunits, which remained associated with the alpha q subunit, led to a prolonged heterotrimer state and an accentuated cellular response.
- M3 receptors with tethered alpha q subunits demonstrated differential signaling outcomes depending on the presence of translocation-competent gamma subunits.
Conclusions:
- G protein heterotrimer dissociation and G betagamma translocation are critical, previously unrecognized modulators of cellular response intensity.
- The dynamic behavior of G protein subunits significantly impacts the fidelity and amplitude of signal transduction pathways.
- Understanding these mechanisms offers new insights into cellular communication and signal processing.
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