Modes and models of GABA(A) receptor gating
Gareth M C Lema1, Anthony Auerbach
1Center for Single Molecule Biophysics, Department of Physiology and Biophysics, State University of New York at Buffalo, 3435 Main Street, Buffalo, NY 14214, USA.
The Journal of Physiology
|February 4, 2006
Summary
Researchers identified distinct gating modes for GABA-A receptors, revealing a complex kinetic model with multiple open and closed states. This advances understanding of neuronal inhibition and receptor function.
Area of Science:
- Neuroscience
- Molecular Biology
- Biophysics
Background:
- The type A gamma-aminobutyric acid receptor (GABA-A receptor) is crucial for fast neuronal inhibition.
- A consensus kinetic model for GABA-A receptor gating remains elusive.
- Understanding receptor kinetics is vital for drug development and neurological research.
Purpose of the Study:
- To elucidate the kinetic gating mechanism of human alpha(1)beta(1)gamma(2S) GABA-A receptors.
- To identify distinct functional states and their associated kinetic parameters.
- To develop a robust kinetic model for GABA-A receptor activation.
Main Methods:
- Single-channel current recordings in HEK 293 cells using cell-attached configuration.
- Application of varying GABA concentrations (50-5000 microm).
- Analysis using critical time, maximum likelihood fitting, autocorrelation, and macroscopic current simulation.
Main Results:
- Identified three distinct gating modes (High, Mid, Low) with differing open probabilities (0.73, 0.50, 0.21).
- Discovered bursts containing three closed and three open components across all modes.
- Developed kinetic models, with the best fitting models including two to three closed states and two to three open states.
- Estimated GABA binding rate constants: k(+)= 3 microm(-1) s(-1), k(-)= 272 s(-1), yielding a K(D)= 91 microm.
Conclusions:
- GABA-A receptor gating exhibits multiple modes, suggesting complex conformational dynamics.
- A kinetic model incorporating multiple closed and open states accurately describes receptor function.
- The derived binding constants provide quantitative insights into GABA interaction with the receptor.
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