Crystal structures of human glycine receptor α3 bound to a novel class of analgesic potentiators

Huang, Xin; Shaffer, Paul; Ayube, Shawn; Bregman, Howard; Chen, Hao; Lehto, Sonya G.; Luther, Jason A.; Matson, David J.; McDonough, Stefan I.; Michelsen, Klaus; Plant, Matthew; Schneider, Stephen E.; Simard, Jeffrey R.; Teffera, Yohannes; Yi, Shuyan; Zhang, Maosheng; DiMauro, Erin F.; Gingras, Jacinthe

doi:10.1038/nsmb.3329

Cited by 110 publications

(133 citation statements)

References 49 publications

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“…In the glycine complex, the agonist’s amino group forms hydrogen bonds with the backbone carbonyl oxygen of Phe175 (loop B) and a cation-π interaction with Phe223 (loop C), while the carboxyl group interacts with Thr220 (loop C), Arg81 (β2) and Ser145 (β6) (Fig. 3d), consistent with the GlyR-α3 crystal structure 22 . While the orientation of taurine and GABA is similar to that of glycine, the interactions between the amino groups of the agonists and receptor residues are different (Fig.…”

Section: Neurotransmitter Binding Sitesupporting

confidence: 75%

Mechanism of gating and partial agonist action in the glycine receptor

Zhu

Lape

et al. 2019

Preprint

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21 22 channel states, thus explaining their lesser efficacy, yet also populate agonist-bound open and 32 desensitized states. Measurements within the neurotransmitter binding pocket, as a function of 33 bound agonist, provide a metric to correlate the extent of agonist-induced conformational changes 34 to open channel probability across the Cys-loop receptor family. 35 36 to change the conformation to a short-lived pre-open intermediate (flipped/primed), rather than 62the reduced ability to open the receptor once the intermediate is reached 12,15,16 . 63Here we investigate the structural basis of partial agonist activation in GlyR, a paradigm 64Cys-loop receptor, exploiting extensive functional characterization showing that taurine and 65 GABA act as partial agonists [17][18][19] . Previous GlyR structures have shed light on the mechanism of 66 action of full agonists and antagonists 20-23 , but structures of the receptor bound to partial agonists 67 are still absent. Furthermore, the previously solved GlyR structures are in detergent micelles and 68 lack the M3/M4 cytoplasmic loop, factors that likely underlie the anomalously high Po of the 69 receptor constructs and the physiologically 'too large' open state of the ion channel pore 24,25 . 70Here we isolated the full length GlyR with native lipids and determined high resolution structures 71 of the receptor bound to glycine, taurine or GABA. The receptors were imaged by cryo-electron 72 microscopy (cryo-EM) in MSP nanodiscs or after solubilization by styrene maleic acid (SMA) 73 copolymers 26 , showing by MD simulations that the SMA complex adopts a physiologically relevant 74 open state. Importantly, cryo-EM structures of GlyR bound to taurine or GABA reveal, for the first 75 time, agonist-bound closed states as well as open and desensitized states. 76 Glycine-bound states 77The wild-type GlyR is robustly activated by glycine and single-channel analysis of clusters 78 of receptor activity, excluding the long-lived desensitized states, reveal a maximum open 79 probability (PO) of 97% at saturating concentrations of glycine (Fig. 1a). Macroscopic current 80 recordings of GlyR activity elicited by rapid application of 10 mM glycine to outside out patches 81show that the current decays to ~ 57% of peak after 1s application because of desensitization 82 (Extended Data Fig. 1a). Taken together, single channel and macroscopic results suggest that, 83 under steady state conditions, the glycine-bound GlyR substantially populates both open and 84 desensitized states. Hence, we reconstituted detergent-purified GlyR into nanodiscs or we directly 85 page 5 of 43 extracted the receptor using SMA copolymers, followed by preparation of cryo-EM grids in the 86 presence of 10 mM glycine. 87The glycine-bound receptor in nanodiscs (GlyR-nanodisc-gly) yielded a reconstruction 88 with a single 3D class at 3.2 Å resolution (Fig. 1c, Extended Data Fig. 7, Supplementary Fig. 1, 89 Supplementary Table 1). The receptor features are well resolved and there is clear density for 90 lipi...

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Section: Neurotransmitter Binding Sitesupporting

confidence: 75%

Mechanism of gating and partial agonist action in the glycine receptor

Zhu

Lape

et al. 2019

Preprint

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“…This structure shows a wide open activation gate in the M2 9 /13 region, but a hydrophobic constriction at the −2 proline, where the pore radius narrows down to 1.6Å, thereby precluding the flow of chloride ions whose Pauling radius is 1.8Å. More recently, several pLGICs have been solved in similar conformations: the human α3 GlyR in complex with both glycine and a positive allosteric modulator, AM-3607 (Huang et al 2017), as well as a GLIC-(GABA A α1) and a (GABA A β3)-(GABA A α5) chimera, the former carrying a α1 G258V mutation promoting desensitization (Laverty et al 2017;Miller et al 2017). All these structures show a conserved pore conformation and were assigned to a desensitized state, since they correspond to agonist-bound shut states.…”

Section: Structural Data Corroborate the Desensitization Gate Modelmentioning

confidence: 99%

“…More recently, several pLGICs have been solved in similar conformations: the human α3 GlyR in complex with both glycine and a positive allosteric modulator, AM‐3607 (Huang et al . ), as well as a GLIC–(GABA A α1) and a (GABA A β3)–(GABA A α5) chimera, the former carrying a α1 G258V mutation promoting desensitization (Laverty et al . ; Miller et al .…”

Section: Introductionmentioning

confidence: 99%

The dual‐gate model for pentameric ligand‐gated ion channels activation and desensitization

Gielen

Corringer

2018

The Journal of Physiology

122

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Pentameric ligand-gated ion channels (pLGICs) mediate fast neurotransmission in the nervous system. Their dysfunction is associated with psychiatric, neurological and neurodegenerative disorders such as schizophrenia, epilepsy and Alzheimer's disease. Understanding their biophysical and pharmacological properties, at both the functional and the structural level, thus holds many therapeutic promises. In addition to their agonist-elicited activation, most pLGICs display another key allosteric property, namely desensitization, in which they enter a shut state refractory to activation upon sustained agonist binding. While the activation mechanisms of several pLGICs have been revealed at near-atomic resolution, the structural foundation of desensitization has long remained elusive. Recent structural and functional data now suggest that the activation and desensitization gates are distinct, and are located at both sides of the ion channel. Such a 'dual gate mechanism' accounts for the marked allosteric effects of channel blockers, a feature illustrated herein by theoretical kinetics simulations. Comparison with other classes of ligand- and voltage-gated ion channels shows that this dual gate mechanism emerges as a common theme for the desensitization and inactivation properties of structurally unrelated ion channels.

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“…2016 yielded another high-resolution view of a pLGIC binding site, that of glycine bound to the homomeric α3 GlyR in an X-ray crystal structure at 2.61 Å (the protein is bound also to the positive allosteric modulator AM-3607 and to zinc ions [48**]). This GlyR is also likely to be desensitised, given that the narrowest point of the pore is at its intracellular end [37**], at the Pro residue in -2’ (this residue is not present in cationic channels).…”

Section: The Structure Of the Plgic Binding Site: One Heteromer And Mmentioning

confidence: 99%

A tale of ligands big and small: An update on how pentameric ligand-gated ion channels interact with agonists and proteins

Pless

Sivilotti

2018

Current Opinion in Physiology

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Pentameric ligand-gated ion channels (pLGICs, also known as Cys-loop receptors) are a large family of ion channels expressed in all Bilateria and in several groups of bacteria and archaea. They are activated by small-molecule neurotransmitters to mediate fast transmission at many central and peripheral nervous system synapses and are the target of several drugs and insecticides. Here we review recent advances in the field, focussing on new insights on the structure of the agonist-binding site and on newly discovered protein-protein interactions involving pLGICs.

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Crystal structures of human glycine receptor α3 bound to a novel class of analgesic potentiators

Cited by 110 publications

References 49 publications

Mechanism of gating and partial agonist action in the glycine receptor

Mechanism of gating and partial agonist action in the glycine receptor

The dual‐gate model for pentameric ligand‐gated ion channels activation and desensitization

A tale of ligands big and small: An update on how pentameric ligand-gated ion channels interact with agonists and proteins

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