288: Cryo-EM of rat cerebellar α1/α6 GABAA receptors reveals PZ‑II‑029 binding and β-α-β-α-γ assemblies

Sun C et al., Proc. Natl. Acad. Sci. U.S.A. 2026.123:e2524504123 - Using cryo-EM and mass spectrometry in rat cerebellum, α1- and α6-containing GABAA receptor assemblies (β‑α‑β‑α‑γ stoichiometry) and PZ-II-029 binding were defined. Key terms: GABAA receptor, cerebellum, α6 subunit, cryo-EM, pyrazoloquinolinone.

Study Highlights:
The study used rat cerebellum tissue and combined confocal immunofluorescence, affinity purification with mass spectrometry, and high-resolution cryo-EM to characterize native α1-containing GABAA receptors. Cryo-EM classification resolved eight distinct α1-containing receptor assemblies that conform to a conserved β-α-β-α-γ arrangement and include previously unreported α6-containing heteromers. Structural models of α6-containing receptors show near-symmetric ECD architecture with conserved GABA-binding geometry and distinct electrostatic differences that may affect ligand kinetics. Binding of the α6-selective pyrazoloquinolinone PZ-II-029 at α+/γ− pockets was visualized and found to induce coordinated outward expansion of the extracellular domain, providing a structural basis for subtype-selective modulation.

Conclusion:
Native α1-containing cerebellar GABAA receptors adopt a conserved β-α-β-α-γ pentameric scaffold that includes α6 subunits and binds PZ-II-029 at α+/γ− sites, producing extracellular domain expansion.

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Article title:
Molecular assemblies and pharmacology of cerebellar GABAA receptors

First author:
Sun C

Journal:
Proc. Natl. Acad. Sci. U.S.A. 2026.123:e2524504123

DOI:
10.1073/pnas.2524504123

Reference:
Sun C, Jahncke JN, Wright KM, Gouaux E. Molecular assemblies and pharmacology of cerebellar GABAA receptors. Proc. Natl. Acad. Sci. U.S.A. 2026;123:e2524504123. Published February 6, 2026. https://doi.org/10.1073/pnas.2524504123

License:
This episode is based on an open-access article published under the Creative Commons Attribution 4.0 International License (CC BY 4.0) - https://creativecommons.org/licenses/by/4.0/

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QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-02-12.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Audited sections cover GABAAR architecture, cerebellar α1/α6 coassembly, native purification and mass spectrometry, cryo-EM assembly identification, PZ-II-029 binding and allosteric effects, ligand-pocket differences, and study limitations.
- transcript topics: GABAAR architecture and subunit diversity; Cerebellar distribution of α1 and α6 subunits and mixed α1/α6 assemblies; Native cerebellar receptor purification, nanodisc reconstitution, and mass spectrometry findings; Cryo-EM identification of eight cerebellar GABAAR assemblies and β2-α1-β1-α6-γ2 configuration; PZ-II-029 binding at α+/γ− pockets (α1/γ2 and α6/γ2) and structural consequences; Ligand-induced extracellular-domain expansion and intersubunit distance changes

QC Summary:
- factual score: 10/10
- metadata score: 10/10
- supported core claims: 7
- claims flagged for review: 0
- metadata checks passed: 4
- metadata issues found: 0

Metadata Audited:
- article_doi
- article_title
- article_journal
- license

Factual Items Audited:
- Native cerebellar GABAARs include mixed α1 and α6 subunits forming β2-α1-β1-α6-γ2 assemblies
- Eight distinct cerebellar GABAAR assemblies were identified, all conforming to a β-α-β-α-γ scaffold
- PZ-II-029 binds at benzodiazepine pockets at α+/γ− interfaces, including α1/γ2 and α6/γ2 pockets, with site-specific interactions
- PZ-II-029 binding induces expansion of the extracellular domain and increases intersubunit distances across subunits
- Ki of PZ-II-029 is about 4.2 ± 0.4 nM in cerebellar receptor preparations
- Delta subunit is detected by mass spectrometry but is not resolved in cryo-EM reconstructions; delta-containing assemblies remain unresolved

QC result: Pass.