Differential assembly diversifies GABAA receptor structures and signalling.
Andrija Sente1, Rooma Desai2, Katerina Naydenova3
1MRC Laboratory of Molecular Biology, Cambridge, UK. asente@mrc-lmb.cam.ac.uk.
Nature
|March 31, 2022
Summary
The study reveals how different arrangements of gamma-aminobutyric acid type A receptors (GABAARs) impact their function and drug responses. Differential assembly generates diverse receptor subtypes, affecting inhibitory signaling in the brain.
Area of Science:
- Neuroscience
- Molecular Biology
- Pharmacology
Background:
- Type A gamma-aminobutyric acid receptors (GABAARs) are crucial ligand-gated chloride channels for fast inhibitory neurotransmission.
- Human GABAAR diversity arises from 19 genes, theoretically yielding over 495,000 receptor types, but assembly principles are unclear.
- Understanding GABAAR assembly is key to explaining their diverse roles and modulation by drugs like anesthetics and benzodiazepines.
Purpose of the Study:
- To elucidate the structural principles governing GABAAR pentamer formation and the resulting diversity.
- To investigate how different subunit arrangements affect receptor function and pharmacology.
- To explore the potential of specific GABAAR subtypes to act as coincidence detectors for neurotransmitters.
Main Methods:
- Cryo-electron microscopy was used to determine the structures of extrasynaptic GABAARs with specific subunit compositions (α4, β3, δ, and γ2).
- Functional assays were performed to assess receptor responses to physiological and synthetic modulators.
- Assembly simulations and single-cell RNA sequencing data were utilized to estimate receptor diversity in vitro and in vivo.
Main Results:
- Two distinct GABAAR subtypes with novel stoichiometries and arrangements were identified for both δ- and γ2-containing receptors, differing from previously studied synaptic receptors.
- Receptor arrangement significantly impacts ligand-binding sites, altering responses to modulators.
- Evidence suggests certain GABAAR subtypes function as coincidence detectors, responding to both GABA and histamine.
Conclusions:
- Differential assembly is a fundamental mechanism controlling GABAAR physiology and pharmacology, leading to significant receptor diversity.
- The identified receptor subtypes and their unique arrangements offer new insights into inhibitory signaling.
- This structural and functional diversity allows GABAARs to act as sophisticated molecular coincidence detectors, integrating multiple signals.
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