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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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).
The authors declare no competing financial interests.
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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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