Structural basis for activation and potentiation in a human α5β3 GABAA receptor

Structural basis for activation and potentiation in a human α5β3 GABAA receptor | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Structural basis for activation and potentiation in a human α5β3 GABA A receptor Erik Lindahl, John Cowgill, Chen Fan, Jan Steyaert, Rebecca Howard This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5975786/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract Neuromodulatory drugs, including anesthetics and anticonvulsants, have been shown to mediate inhibitory and excitatory effects through different populations of type-A ɣ-aminobutyric acid receptors (GABAARs) in the central nervous system. GABAARs in the hippocampus containing α5 subunits have been particularly implicated in learning and memory. The α5 subunit is thought to primarily coassemble with β3 and, in some cases, γ2 subunits, generating a variety of receptor subtypes with differential functional and pharmacological properties. However, the stoichiometry, structure and gating of these subpopulations are not well understood. Here we report cryogenic electron microscopy structures of human α5β3 GABAARs in context of various membrane mimetics, stoichiometries and ligands. Combined with electrophysiology in Xenopus oocytes, our data support a predominant assembly of 2:3 α:β subunits, though a minority population of 1:4 α:β indicates multiple assemblies are possible. Differential glycosylation of α5 and β3 enabled reconstruction of the heteromeric complex even in the absence of protein fiducials. In a resting-like state, ion conduction is blocked at a central conserved activation gate, and by Zn2+ coordinated at histidine residues on the β3 subunits. In activated receptors, GABA binding to an extracellular orthosteric site is associated with global rearrangements that propagate to release Zn2+ and open the activation gate. In contrast to the lower-efficacy α1β3 subtype, saturating GABA appears to drive activation of nearly all receptors. The GABA-bound structure is virtually unaffected by binding of the anesthetic etomidate or anticonvulsant topiramate, supporting both high GABA efficacy and a conformational selection mechanism of positive allosteric modulation. This work thus reveals the assembly, activation and modulation of a GABAAR subtype critical to cognition, including prospective templates for structure-based drug discovery. Biological sciences/Structural biology/Electron microscopy/Cryoelectron microscopy Biological sciences/Biochemistry/Ion channels/Ligand-gated ion channels GABAA receptors α5 GABAA receptor etomidate topiramate ligand-gated ion channel cryo-EM Cys-loop receptor Full Text Additional Declarations There is NO Competing Interest. Cite Share Download PDF Status: Under Review Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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