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Crystal structures of a GABAA-receptor chimera reveal new endogenous neurosteroid-binding sites

Nature Structural & Molecular Biology volume 24, pages 977–985 (2017)Cite this article

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Abstract

γ-Aminobutyric acid receptors (GABAARs) are vital for controlling excitability in the brain. This is emphasized by the numerous neuropsychiatric disorders that result from receptor dysfunction. A critical component of most native GABAARs is the α subunit. Its transmembrane domain is the target for many modulators, including endogenous brain neurosteroids that impact anxiety, stress and depression, and for therapeutic drugs, such as general anesthetics. Understanding the basis for the modulation of GABAAR function requires high-resolution structures. Here we present the first atomic structures of a GABAAR chimera at 2.8-Å resolution, including those bound with potentiating and inhibitory neurosteroids. These structures define new allosteric binding sites for these modulators that are associated with the α-subunit transmembrane domain. Our findings will enable the exploitation of neurosteroids for therapeutic drug design to regulate GABAARs in neurological disorders.

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Figure 1: Structure and function of the GLIC–GABAARα1 chimera.
Figure 2: Structure of the GABAAR chimera.
Figure 3: Coupling at the receptor-chimera ECD–TMD interface.
Figure 4: Structure of the GABAAR chimera channel in a desensitized state.
Figure 5: Interfacial subunit-binding site for the neurosteroid THDOC.
Figure 6: Inhibitory neurosteroid pregnenolone sulfate binds at a distinct site.
Figure 7: Intersubunit anesthetic-binding cavity and aqueous tunnel.

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Acknowledgements

This work was supported by the Medical Research Council (MR/K005537/1). D.L. was in receipt of an MRC PhD studentship. O.J.A. was supported by the Carlsberg Foundation. M.G.G. was funded by the Wellcome Trust and Royal Society (104194/Z/14/Z). We thank the beamline staff at Diamond Light Source and ESRF for assistance and advice, A. Cole for technical support (crystallization, data collection and processing), P.-J. Corringer for technical advice and C. Jones for additional mutagenesis and functional electrophysiology. We also thank the Advanced Research Computing (ARC) facility, the EPSRC UK National Service for Computational Chemistry Software (NSCCS) at Imperial College London (grant no. EP/J003921/1) and the ARCHER UK National Supercomputing Services for computer time granted via the UK High-End Computing Consortium for Biomolecular Simulation, HECBioSim (http://www.hecbiosim.ac.uk), supported by EPSRC (grant no. EP/L000253/1).

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  1. Marc Gielen

    Present address: CNRS UMR 3571, Channel-Receptors Unit, Institut Pasteur, Paris, France

Authors and Affiliations

  1. Department of Neuroscience, Physiology & Pharmacology, University College London, London, UK

    Duncan Laverty, Philip Thomas, Martin Field, Matthew G Gold, Marc Gielen & Trevor G Smart

  2. Department of Biochemistry, University of Oxford, Oxford, UK

    Ole J Andersen & Philip C Biggin

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Contributions

D.L. and T.G.S. jointly planned the project, performed data analyses and wrote the manuscript. D.L. generated the receptor constructs, optimized receptor expression, purification and crystallization, carried out structure solution and model building (assisted by M.G.G. with structural analysis). D.L. and P.T. performed electrophysiology experiments. M.F. carried out site-directed mutagenesis. T.G.S. performed the kinetic modeling. O.J.A. and P.C.B. performed the molecular dynamics simulations and docking. M.G. helped plan and design desensitization experiments. All authors contributed towards editing the manuscript.

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Correspondence to Trevor G Smart.

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Laverty, D., Thomas, P., Field, M. et al. Crystal structures of a GABAA-receptor chimera reveal new endogenous neurosteroid-binding sites. Nat Struct Mol Biol 24, 977–985 (2017). https://doi.org/10.1038/nsmb.3477

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