Open-State Dynamics and Allosteric Modulation of the α1β3γ2 GABA_A Receptor Stabilized by L9'T/S Substitutions

Area of Science:

• Neuroscience
• Structural Biology
• Computational Chemistry

Background:

• Pentameric GABA type A receptors (GABA_ARs) are crucial for inhibitory neurotransmission.
• They are key targets for neuroactive drugs, but their open states are poorly understood.
• Defining the structure and mechanism of open GABA_ARs is essential for drug development.

Purpose of the Study:

• To characterize atomistically the open state of heteropentameric α1β3γ2 GABA_ARs.
• To link pore hydration, ion permeation, and conformational changes in open-like receptor ensembles.
• To elucidate how allosteric modulators affect GABA_AR gating.

Main Methods:

• In-silico mutagenesis to create hydrophilic substitutions at the 9' gate.
• Gaussian-accelerated molecular dynamics to stabilize open-like receptor ensembles.
• Computational electrophysiology to calculate ion conductance.
• Two-electrode voltage-clamp recordings to validate findings.

Main Results:

• Mutants exhibited expanded pores, increased hydration, and significantly reduced Cl- permeation barriers.
• Stabilized open-like ensembles showed reduced global twist and M2 helix tilts.
• Positive allosteric modulators tuned the -2' constriction, while bicuculline induced a sequential closing.
• Experimental recordings confirmed spontaneous activity in mutant receptors.

Conclusions:

• Provided a coherent, atomistic framework for GABA_AR gating and allosteric modulation.
• Established a tractable platform for state-selective, structure-based drug design.
• Advanced understanding of neuroreceptor mechanisms and drug targeting.