Related Experiment Video
Updated: Jun 20, 2026

Quantifying Agonist Activity at G Protein-coupled Receptors
Published on: December 26, 2011
Single-channel kinetic analysis for activation and desensitization of homomeric 5-HT(3)A receptors
Jeremías Corradi1, Fernanda Gumilar, Cecilia Bouzat
1Instituto de Investigaciones Bioquímicas de Bahía Blanca, Universidad Nacional del Sur/Consejo Nacional de Investigaciones Científicas y Técnicas, Bahía Blanca, Argentina.
Abstract:
The 5-HT(3)A receptor is a member of the Cys-loop family of ligand-gated ion channels. To perform kinetic analysis, we mutated the 5-HT3A subunit to obtain a high-conductance form so that single-channel currents can be detected. At all 5-HT concentrations (> 0.1 microM), channel activity appears as openings in quick succession that form bursts, which coalesce into clusters. By combining single-channel and macroscopic data, we generated a kinetic model that perfectly describes activation, deactivation, and desensitization. The model shows that full activation arises from receptors with three molecules of agonist bound. It reveals an earlier conformational change of the fully liganded receptor that occurs while the channel is still closed. From this pre-open closed state, the receptor enters into an open-closed cycle involving three open states, which form the cluster whose duration parallels the time constant of desensitization. A similar model lacking the pre-open closed state can describe the data only if the opening rates are fixed to account for the slow activation rate. The application of the model to M4 mutant receptors shows that position 10' contributes to channel opening and closing rates. Thus, our kinetic model provides a foundation for understanding structural bases of activation and drug action.
More Related Videos
09:39Drug-induced Sensitization of Adenylyl Cyclase: Assay Streamlining and Miniaturization for Small Molecule and siRNA Screening Applications
Published on: January 27, 2014
07:41A Kinetic Fluorescence-based Ca2+ Mobilization Assay to Identify G Protein-coupled Receptor Agonists, Antagonists, and Allosteric Modulators
Published on: February 20, 2018
Related Concept Videos
GPCR Desensitization
Activation and Inactivation of G Proteins
Direct-Acting Cholinergic Agonists: Chemistry and Structure-Activity Relationship
The direct-acting...
The Two-State Receptor Model
The binding affinity of a drug determines its interaction with one...
Ligand-Gated Ion Channel Receptor: Gating Mechanism
G-Protein Gated Ion Channels
Sensory organs,...