The Experts below are selected from a list of 22506 Experts worldwide ranked by ideXlab platform
Sarah C R Lummis - One of the best experts on this subject based on the ideXlab platform.
-
modulation of the erwinia ligand gated ion channel elic and the 5 ht3 receptor via a common vestibule site
eLife, 2020Co-Authors: Marijke Brams, Kerry L Price, Radovan Spurny, Cedric Govaerts, Kumiko Kambara, Anant Gharpure, Els Pardon, Genevieve L Evans, D Bertrand, Sarah C R LummisAbstract:Pentameric ligand-gated ion channels (pLGICs) or Cys-Loop Receptors are involved in fast synaptic signaling in the nervous system. Allosteric modulators bind to sites that are remote from the neurotransmitter binding site, but modify coupling of ligand binding to channel opening. In this study, we developed nanobodies (single domain antibodies), which are functionally active as allosteric modulators, and solved co-crystal structures of the prokaryote (Erwinia) channel ELIC bound either to a positive or a negative allosteric modulator. The allosteric nanobody binding sites partially overlap with those of small molecule modulators, including a vestibule binding site that is not accessible in some pLGICs. Using mutagenesis, we extrapolate the functional importance of the vestibule binding site to the human 5-HT3 receptor, suggesting a common mechanism of modulation in this protein and ELIC. Thus we identify key elements of allosteric binding sites, and extend drug design possibilities in pLGICs with an accessible vestibule site.
-
Modulation of the Erwinia ligand-gated ion channel (ELIC) and the 5-HT 3 receptor via a common vestibule site
'Organisation for Economic Co-Operation and Development (OECD)', 2020Co-Authors: Brams Marijke, Spurny Radovan, Bertrand Daniel, Price, Kerry L, Govaerts Cedric, Pardon Els, Kambara Kumiko, Gharpure Anant, Evans, Genevieve G.l., Sarah C R LummisAbstract:Funder: Instruct-ERICPentameric ligand-gated ion channels (pLGICs) or Cys-Loop Receptors are involved in fast synaptic signaling in the nervous system. Allosteric modulators bind to sites that are remote from the neurotransmitter binding site, but modify coupling of ligand binding to channel opening. In this study, we developed nanobodies (single domain antibodies), which are functionally active as allosteric modulators, and solved co-crystal structures of the prokaryote (Erwinia) channel ELIC bound either to a positive or a negative allosteric modulator. The allosteric nanobody binding sites partially overlap with those of small molecule modulators, including a vestibule binding site that is not accessible in some pLGICs. Using mutagenesis, we extrapolate the functional importance of the vestibule binding site to the human 5-HT3 receptor, suggesting a common mechanism of modulation in this protein and ELIC. Thus we identify key elements of allosteric binding sites, and extend drug design possibilities in pLGICs with an accessible vestibule site
-
proline residues in the transmembrane extracellular domain interface loops have different behaviors in 5 ht3 and nach Receptors
ACS Chemical Neuroscience, 2019Co-Authors: Richard Mosesso, Dennis A Dougherty, Sarah C R LummisAbstract:Cys-Loop Receptors are important drug targets that are involved in signaling in the nervous system. The binding of neurotransmitters in the extracellular region of these Receptors triggers an allosteric activation mechanism, the full details of which remain elusive, although structurally flexible loops in the interface between the extracellular region of Cys-Loop Receptors and the pore-forming transmembrane domain are known to play an important role. Here we explore the roles of three largely conserved Pro residues in two of these loops, the Cys-Loop and M2-M3 loop, in 5-HT3A and α7 nACh Receptors. The data from natural and noncanonical amino acid mutagenesis suggest that in both proteins a Pro is essential in the Cys-Loop, probably because of its enhanced ability to form a cis peptide bond, although other factors are also involved. The important characteristics of Pros in the M2-M3 loop, however, differ in these two Receptors: in the 5-HT3 receptor, the Pros can be replaced by some charged amino acids resulting in EC50s similar to those of wild-type Receptors, while such substitutions in the nACh receptor ablate function. Ala substitution at one of these Pros also has different effects in the two Receptors. Thus, our data show that even highly conserved residues can have distinct behaviors in related Cys-Loop Receptors.
-
curare alkaloids from matis dart poison comparison with d tubocurarine in interactions with nicotinic 5 ht3 serotonin and gabaa Receptors
PLOS ONE, 2019Co-Authors: Ekaterina N. Spirova, Sarah C R Lummis, Denis S Kudryavtsev, Igor E. Kasheverov, Irina V. Shelukhina, Alexandra I. Garifulina, Lina V. Son, Igor Ivanov, Gonzalo R Malcagarcia, Rainer W. BussmannAbstract:Several novel bisbenzylisoquinoline alkaloids (BBIQAs) have recently been isolated from a Matis tribe arrow poison and shown by two-electrode voltage-clamp to inhibit mouse muscle nicotinic acetylcholine Receptors (nAChR). Here, using radioligand assay with Aplysia californica AChBP and radioiodinated α-bungarotoxin ([125I]-αBgt), we show that BBIQA1, BBIQA2, and d-tubocurarine (d-TC) have similar affinities to nAChR orthosteric site. However, a competition with [125I]-αBgt for binding to the Torpedo californica muscle-type nAChR revealed that BBIQAs1, 2, and 3 are less potent (IC50s = 26.3, 8.75, and 17.0 μM) than d-TC (IC50 = 0.39 μM), while with α7 nAChR in GH4C1 cells, BBIQA1 was less potent that d-TC (IC50s = 162 μM and 7.77 μM, respectively), but BBIQA2 was similar (IC50 = 5.52 μM). In inhibiting the Ca2+ responses induced by acetylcholine in Neuro2a cells expressing the mouse adult α1β1eδ nAChR or human α7 nAChR, BBIQAs1 and 2 had similar potencies to d-TC (IC50s in the range 0.75–3.08 μM). Our data suggest that BBIQA1 and BBIQA2 can inhibit adult muscle α1β1eδ nAChR by both competitive and noncompetitive mechanisms. Further experiments on neuronal α3β2, α4β2, and α9α10 nAChRs, expressed in Xenopus laevis oocytes, showed that similar potencies for BBIQAs1, 2, and d-TC. With α3β2γ2 GABAAR currents were almost completely inhibited by d-TC at a high (100 μM) concentration, but BBIQAs1 and 2 were less potent (only 40–50% inhibition), whereas in competition with Alexa Fluor 546-α-cobratoxin for binding to α1β3γ2 GABAAR in Neuro2a cells, d-TC and these analogs had comparable affinities. Especially interesting effects of BBIQAs1 and 2 in comparison with d-TC were observed for 5-HT3AR: BBIQA1 and BBIQA2 were 5- and 87-fold less potent than d-TC (IC50 = 22.63 nM). Thus, our results reveal that these BBIQAs differ from d-TC in their potencies towards certain Cys-Loop Receptors, and we suggest that understanding the reasons behind this might be useful for future drug design.
-
Curare alkaloids from Matis Dart Poison: Comparison with d-tubocurarine in interactions with nicotinic, 5-HT3 serotonin and GABAA Receptors
2019Co-Authors: Ekaterina N. Spirova, Sarah C R Lummis, Denis S Kudryavtsev, Igor A. Ivanov, Igor E. Kasheverov, Irina V. Shelukhina, Alexandra I. Garifulina, Lina V. Son, Gonzalo R. Malca-garcia, Rainer W. BussmannAbstract:Several novel bisbenzylisoquinoline alkaloids (BBIQAs) have recently been isolated from a Matis tribe arrow poison and shown by two-electrode voltage-clamp to inhibit mouse muscle nicotinic acetylcholine Receptors (nAChR). Here, using radioligand assay with Aplysia californica AChBP and radioiodinated α-bungarotoxin ([125I]-αBgt), we show that BBIQA1, BBIQA2, and d-tubocurarine (d-TC) have similar affinities to nAChR orthosteric site. However, a competition with [125I]-αBgt for binding to the Torpedo californica muscle-type nAChR revealed that BBIQAs1, 2, and 3 are less potent (IC50s = 26.3, 8.75, and 17.0 μM) than d-TC (IC50 = 0.39 μM), while with α7 nAChR in GH4C1 cells, BBIQA1 was less potent that d-TC (IC50s = 162 μM and 7.77 μM, respectively), but BBIQA2 was similar (IC50 = 5.52 μM). In inhibiting the Ca2+ responses induced by acetylcholine in Neuro2a cells expressing the mouse adult α1β1εδ nAChR or human α7 nAChR, BBIQAs1 and 2 had similar potencies to d-TC (IC50s in the range 0.75–3.08 μM). Our data suggest that BBIQA1 and BBIQA2 can inhibit adult muscle α1β1εδ nAChR by both competitive and noncompetitive mechanisms. Further experiments on neuronal α3β2, α4β2, and α9α10 nAChRs, expressed in Xenopus laevis oocytes, showed that similar potencies for BBIQAs1, 2, and d-TC. With α3β2γ2 GABAAR currents were almost completely inhibited by d-TC at a high (100 μM) concentration, but BBIQAs1 and 2 were less potent (only 40–50% inhibition), whereas in competition with Alexa Fluor 546-α-cobratoxin for binding to α1β3γ2 GABAAR in Neuro2a cells, d-TC and these analogs had comparable affinities. Especially interesting effects of BBIQAs1 and 2 in comparison with d-TC were observed for 5-HT3AR: BBIQA1 and BBIQA2 were 5- and 87-fold less potent than d-TC (IC50 = 22.63 nM). Thus, our results reveal that these BBIQAs differ from d-TC in their potencies towards certain Cys-Loop Receptors, and we suggest that understanding the reasons behind this might be useful for future drug design.
Eric Gouaux - One of the best experts on this subject based on the ideXlab platform.
-
mechanism of gating and partial agonist action in the glycine receptor
Cell, 2021Co-Authors: Hongtao Zhu, Remigijus Lape, Timo Greiner, Lucia G. Sivilotti, Eric GouauxAbstract:Ligand-gated ion channels mediate signal transduction at chemical synapses and transition between resting, open, and desensitized states in response to neurotransmitter binding. Neurotransmitters that produce maximum open channel probabilities (Po) are full agonists, whereas those that yield lower than maximum Po are partial agonists. Cys-Loop Receptors are an important class of neurotransmitter Receptors, yet a structure-based understanding of the mechanism of partial agonist action has proven elusive. Here, we study the glycine receptor with the full agonist glycine and the partial agonists taurine and γ-amino butyric acid (GABA). We use electrophysiology to show how partial agonists populate agonist-bound, closed channel states and cryo-EM reconstructions to illuminate the structures of intermediate, pre-open states, providing insights into previously unseen conformational states along the receptor reaction pathway. We further correlate agonist-induced conformational changes to Po across members of the receptor family, providing a hypothetical mechanism for partial and full agonist action at Cys-Loop Receptors.
-
cryo em structure of the benzodiazepine sensitive α1β1γ2s tri heteromeric gabaa receptor in complex with gaba
eLife, 2018Co-Authors: Swastik Phulera, Hongtao Zhu, Derek P Claxton, Nate Yoder, Craig Yoshioka, Eric GouauxAbstract:Fast inhibitory neurotransmission in the mammalian nervous system is largely mediated by GABAA Receptors, chloride-selective members of the superfamily of pentameric Cys-Loop Receptors. Native GABAA Receptors are heteromeric assemblies sensitive to many important drugs, from sedatives to anesthetics and anticonvulsant agents, with mutant forms of GABAA Receptors implicated in multiple neurological diseases. Despite the profound importance of heteromeric GABAA Receptors in neuroscience and medicine, they have proven recalcitrant to structure determination. Here we present the structure of a tri-heteromeric α1β1γ2SEM GABAA receptor in complex with GABA, determined by single particle cryo-EM at 3.1-3.8 A resolution, elucidating molecular principles of receptor assembly and agonist binding. Remarkable N-linked glycosylation on the α1 subunit occludes the extracellular vestibule of the ion channel and is poised to modulate receptor assembly and perhaps ion channel gating. Our work provides a pathway to structural studies of heteromeric GABAA Receptors and a framework for rational design of novel therapeutic agents.
-
cryo em structure of the benzodiazepine sensitive α1β1γ2 heterotrimeric gabaa receptor in complex with gaba illuminates mechanism of receptor assembly and agonist binding
bioRxiv, 2018Co-Authors: Swastik Phulera, Derek P Claxton, Nate Yoder, Craig Yoshioka, Jie Yu, Eric GouauxAbstract:Fast inhibitory neurotransmission in the mammalian nervous system is largely mediated by GABAA Receptors, chloride-selective members of the superfamily of pentameric Cys-Loop Receptors. Native GABAA Receptors are heteromeric assemblies sensitive to many important drugs, from sedatives to anesthetics and anticonvulsive agents, with mutant forms of GABAA Receptors implicated in multiple neurological diseases, including epilepsy. Despite the profound importance of heteromeric GABAA Receptors in neuroscience and medicine, they have proven recalcitrant to structure determination. Here we present the structure of the triheteromeric α1β1γ2EM GABAA receptor in complex with GABA, determined by single particle cryo-EM at 3.1-3.8 A resolution, elucidating the molecular principles of receptor assembly and agonist binding. Remarkable N-linked glycosylation on the α1 subunit occludes the extracellular vestibule of the ion channel and is poised to modulate receptor assembly and perhaps ion channel gating. Our work provides a pathway to structural studies of heteromeric GABAA Receptors and a framework for the rational design of novel therapeutic agents.
-
cryo em structure of the benzodiazepine sensitive alpha 1 beta 1 gamma 2 heterotrimeric gabaa receptor in complex with gaba illuminates mechanism of receptor assembly and agonist binding
bioRxiv, 2018Co-Authors: Swastik Phulera, Hongtao Zhu, Derek P Claxton, Nate Yoder, Craig Yoshioka, Eric GouauxAbstract:Inhibitory neurotransmission in the mammalian nervous system is largely mediated by GABAA Receptors, chloride-selective members of the superfamily of pentameric Cys-Loop Receptors. Native GABAA Receptors are heteromeric assemblies sensitive to a tremendous array of important drugs, from sedatives to anesthetics and anticonvulsive agents, and mutant forms of GABAA Receptors are implicated in multiple neurological diseases, including epilepsy. Despite the profound importance of heteromeric GABAA Receptors in neuroscience and medicine, they have proven recalcitrant to structure determination. Here we present the structure of the triheteromeric 1{beta}1{gamma}2 GABAA receptor in complex with GABA, determined by single particle cryo-EM at 3.1-3.5 [A] resolution. The structure elucidates the molecular principles of receptor assembly and agonist binding as well as showing how remarkable N-linked glycosylation on the 1 subunit occludes the extracellular vestibule of the ion channel and is poised to modulate receptor gating and assembly. Our work provides a pathway to structural studies of heteromeric GABAA Receptors and thus a framework for the rational design of novel therapeutic agents.
-
principles of activation and permeation in an anion selective cys loop receptor
Nature, 2011Co-Authors: Ryan E. Hibbs, Eric GouauxAbstract:Fast inhibitory neurotransmission is essential for nervous system function and is mediated by binding of inhibitory neurotransmitters to Receptors of the Cys-Loop family embedded in the membranes of neurons. Neurotransmitter binding triggers a conformational change in the receptor, opening an intrinsic chloride channel and thereby dampening neuronal excitability. Here we present the first three-dimensional structure, to our knowledge, of an inhibitory anion-selective Cys-Loop receptor, the homopentameric Caenorhabditis elegans glutamate-gated chloride channel α (GluCl), at 3.3 A resolution. The X-ray structure of the GluCl-Fab complex was determined with the allosteric agonist ivermectin and in additional structures with the endogenous neurotransmitter L-glutamate and the open-channel blocker picrotoxin. Ivermectin, used to treat river blindness, binds in the transmembrane domain of the receptor and stabilizes an open-pore conformation. Glutamate binds in the classical agonist site at subunit interfaces, and picrotoxin directly occludes the pore near its cytosolic base. GluCl provides a framework for understanding mechanisms of fast inhibitory neurotransmission and allosteric modulation of Cys-Loop Receptors.
Carmen Villmann - One of the best experts on this subject based on the ideXlab platform.
-
the glyr extracellular β8 β9 loop a functional determinant of agonist potency
Frontiers in Molecular Neuroscience, 2017Co-Authors: Dieter Janzen, Natascha Schaefer, Carolyn F Delto, Hermann Schindelin, Carmen VillmannAbstract:Ligand-binding of Cys-Loop Receptors results in rearrangements of extracellular loop structures which are further translated into the tilting of membrane spanning helices, and finally opening of the ion channels. The cryo-EM structure of the homopentameric 1 glycine receptor (GlyR) demonstrated an involvement of the extracellular β8-β9 loop in the transition from ligand-bound Receptors to the open channel state. Recently, we identified a functional role of the β8-β9 loop in a novel startle disease mouse model shaky. The mutation of residue GlyRα1Q177 to lysine present in shaky mice resulted in reduced glycine potency, reduced synaptic expression, and a disrupted hydrogen network at the structural level around position GlyRα1Q177. Here, we investigated the role of amino acid volume, side chain length, and charge at position Q177 to get deeper insights into the functional role of the β8-β9 loop. We used a combined approach of in vitro expression analysis, functional electrophysiological recordings, and GlyR modeling to describe the role of Q177 for GlyR ion channel function. GlyRα1Q177 variants do not disturb ion channel transport to the cellular surface of transfected cells, neither in homomeric nor in heteromeric glycine receptor configurations. The EC50 values were increased for all GlyRα1Q177 variants in comparison to the wild type. The largest decrease in glycine potency was observed for the variant GlyRα1Q177R. Potencies of the partial agonists -alanine and taurine were also reduced. Our data are further supported by homology modeling. The GlyRα1Q177R variant does not form hydrogen bonds with the surrounding network of residue Q177 similar to the substitution with a basic lysine present in the mouse mutant shaky. Among all investigated Q177 mutants, the neutral exchange of glutamine to asparagine as well as the introduction of the closely related amino acid glutamic acid preserve the hydrogen bond network. Introduction of amino acids with small side chains or larger volume resulted in a loss of their hydrogen bonds to neighboring residues. The β8-β9 loop is thus an important structural and functional determinant of the inhibitory glycine receptor.
-
The GlyR Extracellular β8–β9 Loop – A Functional Determinant of Agonist Potency
Frontiers Media S.A., 2017Co-Authors: Dieter Janzen, Natascha Schaefer, Carolyn F Delto, Hermann Schindelin, Carmen VillmannAbstract:Ligand-binding of Cys-Loop Receptors results in rearrangements of extracellular loop structures which are further translated into the tilting of membrane spanning helices, and finally opening of the ion channels. The cryo-EM structure of the homopentameric α1 glycine receptor (GlyR) demonstrated an involvement of the extracellular β8–β9 loop in the transition from ligand-bound Receptors to the open channel state. Recently, we identified a functional role of the β8–β9 loop in a novel startle disease mouse model shaky. The mutation of residue GlyRα1Q177 to lysine present in shaky mice resulted in reduced glycine potency, reduced synaptic expression, and a disrupted hydrogen network at the structural level around position GlyRα1Q177. Here, we investigated the role of amino acid volume, side chain length, and charge at position Q177 to get deeper insights into the functional role of the β8–β9 loop. We used a combined approach of in vitro expression analysis, functional electrophysiological recordings, and GlyR modeling to describe the role of Q177 for GlyR ion channel function. GlyRα1Q177 variants do not disturb ion channel transport to the cellular surface of transfected cells, neither in homomeric nor in heteromeric GlyR configurations. The EC50 values were increased for all GlyRα1Q177 variants in comparison to the wild type. The largest decrease in glycine potency was observed for the variant GlyRα1Q177R. Potencies of the partial agonists β-alanine and taurine were also reduced. Our data are further supported by homology modeling. The GlyRα1Q177R variant does not form hydrogen bonds with the surrounding network of residue Q177 similar to the substitution with a basic lysine present in the mouse mutant shaky. Among all investigated Q177 mutants, the neutral exchange of glutamine to asparagine as well as the introduction of the closely related amino acid glutamic acid preserve the hydrogen bond network. Introduction of amino acids with small side chains or larger volume resulted in a loss of their hydrogen bonds to neighboring residues. The β8–β9 loop is thus an important structural and functional determinant of the inhibitory GlyR
-
disturbances of ligand potency and enhanced degradation of the human glycine receptor at affected positions g160 and t162 originally identified in patients suffering from hyperekplexia
Frontiers in Molecular Neuroscience, 2015Co-Authors: Sinem Atak, Natascha Schaefer, Carolyn F Delto, Hermann Schindelin, Georg Langlhofer, Denise Kessler, Heike Meiselbach, Carmen VillmannAbstract:Ligand-binding of Cys-Loop Receptors is determined by N-terminal extracellular loop structures from the plus as well as from the minus side of two adjacent subunits in the pentameric receptor complex. An aromatic residue in loop B of the glycine receptor (GlyR) undergoes direct interaction with the incoming ligand via cation-π interactions. Recently we showed that mutated residues in loop B identified from human patients suffering from hyperekplexia disturb ligand-binding. Here, we exchanged the affected human residues by amino acids found in related members of the Cys-Loop receptor family to determine the effects of side chain volume for ion channel properties. GlyR variants were characterized in vitro following transfection into cell lines in order to analyze protein expression, trafficking, degradation and ion channel function. GlyR α1 G160 mutations significantly decrease glycine potency arguing for a positional effect on neighboring aromatic residues and consequently glycine-binding within the ligand-binding pocket. Disturbed glycinergic inhibition due to T162 α1 mutations is an additive effect of affected biogenesis and structural changes within the ligand-binding site. Protein trafficking from the ER towards ER-Golgi intermediate compartment, the secretory Golgi pathways and finally the cell surface is largely diminished, but still sufficient to deliver ion channels that are functional at least at high glycine concentrations. The majority of T162 mutant protein accumulates in the ER and is conducted to ER-associated proteasomal degradation. Hence, G160 is an important determinant during glycine binding. In contrast, T162 assigns primarily receptor biogenesis whereas exchanges in functionality are secondary effects thereof.
Erik D. Herzog - One of the best experts on this subject based on the ideXlab platform.
-
picrotoxin dramatically speeds the mammalian circadian clock independent of cys loop Receptors
Journal of Neurophysiology, 2013Co-Authors: Mark G Freeman, Hiroki R Ueda, Masato Nakajima, Erik D. HerzogAbstract:Picrotoxin is extensively and specifically used to inhibit GABAA Receptors and other members of the Cys-Loop receptor superfamily. We find that picrotoxin acts independently of known Cys-Loop Receptors to shorten the period of the circadian clock markedly by specifically advancing the accumulation of PERIOD2 protein. We show that this mechanism is surprisingly tetrodotoxin-insensitive, and the effect is larger than any known chemical or genetic manipulation. Notably, our results indicate that the circadian target of picrotoxin is common to a variety of human and rodent cell types but not Drosophila, thereby ruling out all conserved Cys-Loop Receptors and known regulators of mammalian PERIOD protein stability. Given that the circadian clock modulates significant aspects of cell physiology including synaptic plasticity, these results have immediate and broad experimental implications. Furthermore, our data point to the existence of an important and novel target within the mammalian circadian timing system.
-
picrotoxin dramatically speeds the mammalian circadian clock independent of cys loop Receptors
Journal of Neurophysiology, 2013Co-Authors: Mark G Freeman, Hiroki R Ueda, Masato Nakajima, Erik D. HerzogAbstract:Picrotoxin is extensively and specifically used to inhibit GABAA Receptors and other members of the Cys-Loop receptor superfamily. We find that picrotoxin acts independently of known Cys-Loop Receptors to shorten the period of the circadian clock markedly by specifically advancing the accumulation of PERIOD2 protein. We show that this mechanism is surprisingly tetrodotoxin-insensitive, and the effect is larger than any known chemical or genetic manipulation. Notably, our results indicate that the circadian target of picrotoxin is common to a variety of human and rodent cell types but not Drosophila, thereby ruling out all conserved Cys-Loop Receptors and known regulators of mammalian PERIOD protein stability. Given that the circadian clock modulates significant aspects of cell physiology including synaptic plasticity, these results have immediate and broad experimental implications. Furthermore, our data point to the existence of an important and novel target within the mammalian circadian timing system.
Ryan E. Hibbs - One of the best experts on this subject based on the ideXlab platform.
-
X-ray structure of the human α4β2 nicotinic receptor
Nature, 2016Co-Authors: Claudio L. Morales-perez, Colleen M. Noviello, Ryan E. HibbsAbstract:Nicotinic acetylcholine Receptors are ligand-gated ion channels that mediate fast chemical neurotransmission at the neuromuscular junction and have diverse signalling roles in the central nervous system. The nicotinic receptor has been a model system for cell-surface Receptors, and specifically for ligand-gated ion channels, for well over a century. In addition to the Receptors' prominent roles in the development of the fields of pharmacology and neurobiology, nicotinic Receptors are important therapeutic targets for neuromuscular disease, addiction, epilepsy and for neuromuscular blocking agents used during surgery. The overall architecture of the receptor was described in landmark studies of the nicotinic receptor isolated from the electric organ of Torpedo marmorata. Structures of a soluble ligand-binding domain have provided atomic-scale insights into receptor-ligand interactions, while high-resolution structures of other members of the pentameric receptor superfamily provide touchstones for an emerging allosteric gating mechanism. All available high-resolution structures are of homopentameric Receptors. However, the vast majority of pentameric Receptors (called Cys-Loop Receptors in eukaryotes) present physiologically are heteromeric. Here we present the X-ray crystallographic structure of the human α4β2 nicotinic receptor, the most abundant nicotinic subtype in the brain. This structure provides insights into the architectural principles governing ligand recognition, heteromer assembly, ion permeation and desensitization in this prototypical receptor class.
-
principles of activation and permeation in an anion selective cys loop receptor
Nature, 2011Co-Authors: Ryan E. Hibbs, Eric GouauxAbstract:Fast inhibitory neurotransmission is essential for nervous system function and is mediated by binding of inhibitory neurotransmitters to Receptors of the Cys-Loop family embedded in the membranes of neurons. Neurotransmitter binding triggers a conformational change in the receptor, opening an intrinsic chloride channel and thereby dampening neuronal excitability. Here we present the first three-dimensional structure, to our knowledge, of an inhibitory anion-selective Cys-Loop receptor, the homopentameric Caenorhabditis elegans glutamate-gated chloride channel α (GluCl), at 3.3 A resolution. The X-ray structure of the GluCl-Fab complex was determined with the allosteric agonist ivermectin and in additional structures with the endogenous neurotransmitter L-glutamate and the open-channel blocker picrotoxin. Ivermectin, used to treat river blindness, binds in the transmembrane domain of the receptor and stabilizes an open-pore conformation. Glutamate binds in the classical agonist site at subunit interfaces, and picrotoxin directly occludes the pore near its cytosolic base. GluCl provides a framework for understanding mechanisms of fast inhibitory neurotransmission and allosteric modulation of Cys-Loop Receptors.
-
principles of activation and permeation in an anion selective cys loop receptor
Nature, 2011Co-Authors: Ryan E. Hibbs, Eric GouauxAbstract:Fast inhibitory neurotransmission is essential for nervous system function and is mediated by binding of inhibitory neurotransmitters to Receptors of the Cys-Loop family embedded in the membranes of neurons. Neurotransmitter binding triggers a conformational change in the receptor, opening an intrinsic chloride channel and thereby dampening neuronal excitability. Here we present the first three-dimensional structure, to our knowledge, of an inhibitory anion-selective Cys-Loop receptor, the homopentameric Caenorhabditis elegans glutamate-gated chloride channel α (GluCl), at 3.3 A resolution. The X-ray structure of the GluCl–Fab complex was determined with the allosteric agonist ivermectin and in additional structures with the endogenous neurotransmitter l-glutamate and the open-channel blocker picrotoxin. Ivermectin, used to treat river blindness, binds in the transmembrane domain of the receptor and stabilizes an open-pore conformation. Glutamate binds in the classical agonist site at subunit interfaces, and picrotoxin directly occludes the pore near its cytosolic base. GluCl provides a framework for understanding mechanisms of fast inhibitory neurotransmission and allosteric modulation of Cys-Loop Receptors. The atomic resolution structure of the glutamate-gated chloride channel (GluCl) from Caenorhabditis elegans has been determined, in the presence of the allosteric agonist ivermectin, the endogenous neurotransmitter L-glutamate and the open-channel blocker picrotoxin. These structures provide a framework for understanding mechanisms of the fast inhibitory neurotransmission that is essential for nervous system function.
