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Updated: Nov 23, 2025

Tracking Drug-induced Changes in Receptor Post-internalization Trafficking by Colocalizational Analysis
Published on: July 3, 2015
Spatiotemporal Characterization of GPCR Activity and Function during Endosomal Trafficking Pathway
Hyunbin Kim1,2, Hae Nim Lee1,3, Jaesik Choi4
1Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea.
Internalized G protein-coupled receptors (GPCRs), like beta-2 adrenergic receptor (B2AR), remain active for hours within endosomes, continuing to signal. This sustained activity impacts cellular functions and can be tracked using novel biosensors and kinetic models.
Area of Science:
- Cellular Biology
- Molecular Pharmacology
- Biophysics
Background:
- G protein-coupled receptors (GPCRs) mediate cellular responses to external signals.
- While typically desensitized after internalization, some GPCRs retain activity within endosomes.
- The spatiotemporal activity of internalized GPCRs, such as beta-2 adrenergic receptor (B2AR), remains poorly understood.
Purpose of the Study:
- To characterize the real-time activity and downstream signaling of internalized B2AR.
- To investigate the duration and localization of B2AR activity during endosomal trafficking.
- To develop a kinetic model for describing B2AR activity over time.
Main Methods:
- Utilized a fluorescence resonance energy transfer (FRET)-based B2AR biosensor.
- Employed cAMP reporters tethered to endosomes at various trafficking stages.
- Analyzed agonist-induced B2AR activity at the single-vesicle level.
Main Results:
- Internalized B2ARs demonstrated sustained activity for several hours within endosomes.
- Continued cAMP production was observed from internalized B2ARs.
- A modified Ricker model accurately described the temporal kinetics of B2AR activity.
Conclusions:
- Internalized B2ARs maintain functional activity and downstream signaling for extended periods.
- The developed GPCR monitoring system and kinetic model offer insights into spatiotemporal GPCR activity.
- This approach can advance the understanding of GPCR dynamics in endosomal trafficking.
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