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Thompson MJ, Baenziger JE. Structural basis for the modulation of pentameric ligand-gated ion channel function by lipids. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183304. [DOI: 10.1016/j.bbamem.2020.183304] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 03/20/2020] [Accepted: 04/05/2020] [Indexed: 10/24/2022]
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102
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Identification of the hypertension drug niflumic acid as a glycine receptor inhibitor. Sci Rep 2020; 10:13999. [PMID: 32814817 PMCID: PMC7438329 DOI: 10.1038/s41598-020-70983-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 05/29/2020] [Indexed: 11/08/2022] Open
Abstract
Glycine is one of the major neurotransmitters in the brainstem and the spinal cord. Glycine binds to and activates glycine receptors (GlyRs), increasing Cl- conductance at postsynaptic sites. This glycinergic synaptic transmission contributes to the generation of respiratory rhythm and motor patterns. Strychnine inhibits GlyR by binding to glycine-binding site, while picrotoxin blocks GlyR by binding to the channel pore. We have previously reported that bath application of strychnine to zebrafish embryos causes bilateral muscle contractions in response to tactile stimulation. To explore the drug-mediated inhibition of GlyRs, we screened a chemical library of ~ 1,000 approved drugs and pharmacologically active molecules by observing touch-evoked response of zebrafish embryos in the presence of drugs. We found that exposure of zebrafish embryos to nifedipine (an inhibitor of voltage-gated calcium channel) or niflumic acid (an inhibitor of cyclooxygenase 2) caused bilateral muscle contractions just like strychnine-treated embryos showed. We then assayed strychnine, picrotoxin, nifedipine, and niflumic acid for concentration-dependent inhibition of glycine-mediated currents of GlyRs in oocytes and calculated IC50s. The results indicate that all of them concentration-dependently inhibit GlyR in the order of strychnine > picrotoxin > nifedipine > niflumic acid.
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103
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Mechanisms of activation and desensitization of full-length glycine receptor in lipid nanodiscs. Nat Commun 2020; 11:3752. [PMID: 32719334 PMCID: PMC7385131 DOI: 10.1038/s41467-020-17364-5] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Accepted: 06/25/2020] [Indexed: 12/31/2022] Open
Abstract
Glycinergic synapses play a central role in motor control and pain processing in the central nervous system. Glycine receptors (GlyRs) are key players in mediating fast inhibitory neurotransmission at these synapses. While previous high-resolution structures have provided insights into the molecular architecture of GlyR, several mechanistic questions pertaining to channel function are still unanswered. Here, we present Cryo-EM structures of the full-length GlyR protein complex reconstituted into lipid nanodiscs that are captured in the unliganded (closed), glycine-bound (open and desensitized), and allosteric modulator-bound conformations. A comparison of these states reveals global conformational changes underlying GlyR channel gating and modulation. The functional state assignments were validated by molecular dynamics simulations, and the observed permeation events are in agreement with the anion selectivity and conductance of GlyR. These studies provide the structural basis for gating, ion selectivity, and single-channel conductance properties of GlyR in a lipid environment. Glycinergic synapses play a central role in motor control and pain processing in the central nervous system. Here, authors present cryo-EM structures of the full-length glycine receptors (GlyRs) reconstituted into lipid nanodiscs in the unliganded, glycine-bound and allosteric modulator-bound conformations and reveal global conformational changes underlying GlyR channel gating and modulation.
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104
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Rauschenberger V, von Wardenburg N, Schaefer N, Ogino K, Hirata H, Lillesaar C, Kluck CJ, Meinck H, Borrmann M, Weishaupt A, Doppler K, Wickel J, Geis C, Sommer C, Villmann C. Glycine Receptor
Autoantibodies Impair Receptor Function and Induce Motor Dysfunction. Ann Neurol 2020; 88:544-561. [DOI: 10.1002/ana.25832] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2019] [Revised: 06/23/2020] [Accepted: 06/23/2020] [Indexed: 12/22/2022]
Affiliation(s)
- Vera Rauschenberger
- Institute for Clinical NeurobiologyUniversity Hospital, Julius Maximilian University of Würzburg Würzburg Germany
| | - Niels von Wardenburg
- Institute for Clinical NeurobiologyUniversity Hospital, Julius Maximilian University of Würzburg Würzburg Germany
| | - Natascha Schaefer
- Institute for Clinical NeurobiologyUniversity Hospital, Julius Maximilian University of Würzburg Würzburg Germany
| | - Kazutoyo Ogino
- Department of Chemistry and Biological ScienceCollege of Science and Engineering, Aoyama Gakuin University Tokyo Japan
| | - Hiromi Hirata
- Department of Chemistry and Biological ScienceCollege of Science and Engineering, Aoyama Gakuin University Tokyo Japan
| | - Christina Lillesaar
- Department of Child and Adolescent PsychiatryCenter of Mental Health, University Hospital of Würzburg Würzburg Germany
| | - Christoph J. Kluck
- Institute of Biochemistry, Emil Fischer Center, Friedrich Alexander University Erlangen–Nürnberg Erlangen Germany
| | | | - Marc Borrmann
- WittenHelios University Hospital Wuppertal, Department of Nephrology and Rheumatology, Witten/Herdecke University Germany
| | - Andreas Weishaupt
- Department of NeurologyUniversity Hospital Würzburg Würzburg Germany
| | - Kathrin Doppler
- Department of NeurologyUniversity Hospital Würzburg Würzburg Germany
| | - Jonathan Wickel
- Section of Translational Neuroimmunology, Department of NeurologyJena University Hospital Jena Germany
| | - Christian Geis
- Section of Translational Neuroimmunology, Department of NeurologyJena University Hospital Jena Germany
| | - Claudia Sommer
- Department of NeurologyUniversity Hospital Würzburg Würzburg Germany
| | - Carmen Villmann
- Institute for Clinical NeurobiologyUniversity Hospital, Julius Maximilian University of Würzburg Würzburg Germany
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105
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Saleh HA, Raafat KM, Temraz TA, Noureldin N, Breitinger HG, Breitinger U. Sarcophine and (7S, 8R)-dihydroxydeepoxysarcophine from the Red Sea soft coral Sarcophyton glaucum as in vitro and in vivo modulators of glycine receptors. Neurotoxicology 2020; 80:105-111. [PMID: 32702364 DOI: 10.1016/j.neuro.2020.07.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 07/13/2020] [Accepted: 07/14/2020] [Indexed: 01/16/2023]
Abstract
The inhibitory glycine receptor (GlyR) is a key mediator of synaptic signalling in spinal cord, brain stem, and higher centres of the central nervous system. We examined the glycinergic activity of sarcophine (SN), a marine terpenoid known for its various biological activities, and its trans-diol derivative (7S, 8R)-dihydroxy-deepoxysarcophine (DSN). SN was isolated from the Red Sea soft coral Sacrophyton glaucum, DSN was semisynthesized by hydrolysis of the epoxide ring. In cytotoxicity tests against HEK293 cells, SN and DSN had LD50 values of 29.3 ± 3.0 mM and 123.5 ± 13.0 mM, respectively. Both compounds were tested against recombinant human α1 glycine receptors in HEK293 cells using whole-cell recording techniques. Both, SN and DSN were shown for the first time to be inhibitors of recombinant glycine receptors, with KIvalues of 2.1 ± 0.3 μM for SN, and 109 ± 9 μM for DSN. Receptor inhibition was also studied in vivo in a mouse model of strychnine toxicity. Surprisingly, in mouse experiments strychnine inhibition was not augmented by either terpenoid. While DSN had no significant effect on strychnine toxicity, SN even delayed strychnine effects. This could be accounted for by assuming that strychnine and sarcophine derivatives compete for the same binding site on the receptor, so the less toxic sarcophine can prevent strychnine from binding. The combination of modulatory activity and low level of toxicity makes sarcophines attractive structures for novel glycinergic drugs.
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Affiliation(s)
- Hesham A Saleh
- Department of Pharmaceutical Chemistry, German University in Cairo, New Cairo, Egypt
| | - Karim M Raafat
- Department of Biochemistry, German University in Cairo, New Cairo, Egypt
| | - Tarek A Temraz
- Department of Marine Sciences, Suez Canal University, Ismailia, Egypt
| | - Nazih Noureldin
- Department of Pharmaceutical Chemistry, German University in Cairo, New Cairo, Egypt.
| | | | - Ulrike Breitinger
- Department of Biochemistry, German University in Cairo, New Cairo, Egypt
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106
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Identification of N-acyl amino acids that are positive allosteric modulators of glycine receptors. Biochem Pharmacol 2020; 180:114117. [PMID: 32579961 DOI: 10.1016/j.bcp.2020.114117] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 06/16/2020] [Accepted: 06/18/2020] [Indexed: 01/31/2023]
Abstract
Glycine receptors (GlyRs) mediate inhibitory neurotransmission within the spinal cord and play a crucial role in nociceptive signalling. This makes them primary targets for the development of novel chronic pain therapies. Endogenous lipids have previously been shown to modulate glycine receptors and produce analgesia in pain models, however little is known about what chemical features mediate these effects. In this study, we characterised lipid modulation of GlyRs by screening a library of N-acyl amino acids across all receptor subtypes and determined chemical features crucial for their activity. Acyl-glycine's with a C18 carbon tail were found to produce the greatest potentiation, and require a cis double bond within the central region of the carbon tail (ω6 - ω9) to be active. At 1 µM, C18 ω6,9 glycine potentiated glycine induced currents in α3 and α3β receptors by over 50%, and α1, α2, α1β and α2β receptors by over 100%. C18 ω9 glycine (N-oleoyl glycine) significantly enhance glycine induced peak currents and cause a dose-dependent shift in the glycine concentration response. In the presence of 3 µM C18 ω9 glycine, the EC5o of glycine at the α1 receptor was reduced from 17 µM to 10 µM. This study has identified several acyl-amino acids which are positive allosteric modulators of GlyRs and make promising lead compounds for the development of novel chronic pain therapies.
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107
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Abstract
The inhibitory glycine receptor is a member of the Cys-loop superfamily of ligand-gated ion channels. It is the principal mediator of rapid synaptic inhibition in the spinal cord and brainstem and plays an important role in the modulation of higher brain functions including vision, hearing, and pain signaling. Glycine receptor function is controlled by only a few agonists, while the number of antagonists and positive or biphasic modulators is steadily increasing. These modulators are important for the study of receptor activation and regulation and have found clinical interest as potential analgesics and anticonvulsants. High-resolution structures of the receptor have become available recently, adding to our understanding of structure-function relationships and revealing agonistic, inhibitory, and modulatory sites on the receptor protein. This Review presents an overview of compounds that activate, inhibit, or modulate glycine receptor function in vitro and in vivo.
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Affiliation(s)
- Ulrike Breitinger
- Department of Biochemistry, German University in Cairo, New Cairo 11835, Egypt
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108
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Dämgen MA, Zaki AM, Biggin PC. Comment on "On the Functional Annotation of Open-Channel Structures in the Glycine Receptor". Structure 2020; 28:601-603. [PMID: 32492412 DOI: 10.1016/j.str.2020.04.021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 03/30/2020] [Accepted: 04/28/2020] [Indexed: 12/26/2022]
Abstract
Recently, we reported the simulation of a stable open state of the glycine receptor. Central to the stability of the simulations was the behavior of the highly conserved leucine residues at the 9' gate, which were found to rotate into adjacent pockets, thus providing a structural rationale for decades of biochemical observations. In contrast, a previously reported model from Cerdan et al. (2018) resembled a more collapsed state. However, in support of their model, they draw attention to the agreement between calculated and experimental conductance measurements and argue that our model tends to overestimate ion flow. Here, we argue that there are many pitfalls with this approach and that the apparent agreement most likely reflects a fortuitous cancellation of errors. The computed values are highly sensitive to very small changes in model parameters. It is also likely that polarization effects will be very significant, and these have not yet been considered.
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Affiliation(s)
- Marc A Dämgen
- Structural Bioinformatics and Computational Biochemistry, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Afroditi Maria Zaki
- Structural Bioinformatics and Computational Biochemistry, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Philip C Biggin
- Structural Bioinformatics and Computational Biochemistry, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom.
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109
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Structural basis for allosteric transitions of a multidomain pentameric ligand-gated ion channel. Proc Natl Acad Sci U S A 2020; 117:13437-13446. [PMID: 32482881 DOI: 10.1073/pnas.1922701117] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Pentameric ligand-gated ion channels (pLGICs) are allosteric receptors that mediate rapid electrochemical signal transduction in the animal nervous system through the opening of an ion pore upon binding of neurotransmitters. Orthologs have been found and characterized in prokaryotes and they display highly similar structure-function relationships to eukaryotic pLGICs; however, they often encode greater architectural diversity involving additional amino-terminal domains (NTDs). Here we report structural, functional, and normal-mode analysis of two conformational states of a multidomain pLGIC, called DeCLIC, from a Desulfofustis deltaproteobacterium, including a periplasmic NTD fused to the conventional ligand-binding domain (LBD). X-ray structure determination revealed an NTD consisting of two jelly-roll domains interacting across each subunit interface. Binding of Ca2+ at the LBD subunit interface was associated with a closed transmembrane pore, with resolved monovalent cations intracellular to the hydrophobic gate. Accordingly, DeCLIC-injected oocytes conducted currents only upon depletion of extracellular Ca2+; these were insensitive to quaternary ammonium block. Furthermore, DeCLIC crystallized in the absence of Ca2+ with a wide-open pore and remodeled periplasmic domains, including increased contacts between the NTD and classic LBD agonist-binding sites. Functional, structural, and dynamical properties of DeCLIC paralleled those of sTeLIC, a pLGIC from another symbiotic prokaryote. Based on these DeCLIC structures, we would reclassify the previous structure of bacterial ELIC (the first high-resolution structure of a pLGIC) as a "locally closed" conformation. Taken together, structures of DeCLIC in multiple conformations illustrate dramatic conformational state transitions and diverse regulatory mechanisms available to ion channels in pLGICs, particularly involving Ca2+ modulation and periplasmic NTDs.
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110
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Cerdan AH, Sisquellas M, Pereira G, Barreto Gomes DE, Changeux JP, Cecchini M. The Glycine Receptor Allosteric Ligands Library (GRALL). Bioinformatics 2020; 36:3379-3384. [PMID: 32163115 PMCID: PMC7267813 DOI: 10.1093/bioinformatics/btaa170] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 02/19/2020] [Accepted: 03/09/2020] [Indexed: 01/01/2023] Open
Abstract
MOTIVATION Glycine receptors (GlyRs) mediate fast inhibitory neurotransmission in the brain and have been recognized as key pharmacological targets for pain. A large number of chemically diverse compounds that are able to modulate GlyR function both positively and negatively have been reported, which provides useful information for the development of pharmacological strategies and models for the allosteric modulation of these ion channels. RESULTS Based on existing literature, we have collected 218 unique chemical entities with documented modulatory activities at homomeric GlyR-α1 and -α3 and built a database named GRALL. This collection includes agonists, antagonists, positive and negative allosteric modulators and a number of experimentally inactive compounds. Most importantly, for a large fraction of them a structural annotation based on their putative binding site on the receptor is provided. This type of annotation, which is currently missing in other drug banks, along with the availability of cooperativity factors from radioligand displacement experiments are expected to improve the predictivity of in silico methodologies for allosteric drug discovery and boost the development of conformation-based pharmacological approaches. AVAILABILITY AND IMPLEMENTATION The GRALL library is distributed as a web-accessible database at the following link: https://ifm.chimie.unistra.fr/grall. For each molecular entry, it provides information on the chemical structure, the ligand-binding site, the direction of modulation, the potency, the 3D molecular structure and quantum-mechanical charges as determined by our in-house pipeline. CONTACT mcecchini@unistra.fr. SUPPLEMENTARY INFORMATION Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Adrien H Cerdan
- Institut de Chimie de Strasbourg, UMR7177, CNRS, Université de Strasbourg, F-67083 Strasbourg Cedex, France
- Channel-Receptors Unit, Institut Pasteur, 75015 Paris, France
| | - Marion Sisquellas
- Institut de Chimie de Strasbourg, UMR7177, CNRS, Université de Strasbourg, F-67083 Strasbourg Cedex, France
| | - Gilberto Pereira
- Institut de Chimie de Strasbourg, UMR7177, CNRS, Université de Strasbourg, F-67083 Strasbourg Cedex, France
| | - Diego E Barreto Gomes
- Diretoria de Metrologia Aplicada às Ciências da Vida-Instituto Nacional de Metrologia, Qualidade e Tecnologia, Duque de Caxias 25.250-020, Brazil
| | - Jean-Pierre Changeux
- CNRS, URA 2182, F-75015, Collège de France, F-75005 Paris, France
- Kavli Institute for Brain & Mind, University of California San Diego, La Jolla, CA 92093, USA
| | - Marco Cecchini
- Institut de Chimie de Strasbourg, UMR7177, CNRS, Université de Strasbourg, F-67083 Strasbourg Cedex, France
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111
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Joseph AP, Lagerstedt I, Jakobi A, Burnley T, Patwardhan A, Topf M, Winn M. Comparing Cryo-EM Reconstructions and Validating Atomic Model Fit Using Difference Maps. J Chem Inf Model 2020; 60:2552-2560. [PMID: 32043355 PMCID: PMC7254831 DOI: 10.1021/acs.jcim.9b01103] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cryogenic electron microscopy (cryo-EM) is a powerful technique for determining structures of multiple conformational or compositional states of macromolecular assemblies involved in cellular processes. Recent technological developments have led to a leap in the resolution of many cryo-EM data sets, making atomic model building more common for data interpretation. We present a method for calculating differences between two cryo-EM maps or a map and a fitted atomic model. The proposed approach works by scaling the maps using amplitude matching in resolution shells. To account for variability in local resolution of cryo-EM data, we include a procedure for local amplitude scaling that enables appropriate scaling of local map contrast. The approach is implemented as a user-friendly tool in the CCP-EM software package. To obtain clean and interpretable differences, we propose a protocol involving steps to process the input maps and output differences. We demonstrate the utility of the method for identifying conformational and compositional differences including ligands. We also highlight the use of difference maps for evaluating atomic model fit in cryo-EM maps.
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Affiliation(s)
- Agnel Praveen Joseph
- Scientific Computing Department, Science and Technology Facilities Council, Research Complex at Harwell, Didcot OX11 0FA, United Kingdom
| | - Ingvar Lagerstedt
- European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, Cambridge CB10 1SD, United Kingdom
| | - Arjen Jakobi
- Kavli Institute of Nanoscience Delft (KIND), Department of Bionanoscienes, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Tom Burnley
- Scientific Computing Department, Science and Technology Facilities Council, Research Complex at Harwell, Didcot OX11 0FA, United Kingdom
| | - Ardan Patwardhan
- European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, Cambridge CB10 1SD, United Kingdom
| | - Maya Topf
- Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck College, University of London, Malet Street, London WC1E 7HX, United Kingdom
| | - Martyn Winn
- Scientific Computing Department, Science and Technology Facilities Council, Research Complex at Harwell, Didcot OX11 0FA, United Kingdom
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112
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Wu Z, Lape R, Jopp-Saile L, O'Callaghan BJ, Greiner T, Sivilotti LG. The startle disease mutation α1S270T predicts shortening of glycinergic synaptic currents. J Physiol 2020; 598:3417-3438. [PMID: 32445491 PMCID: PMC7649747 DOI: 10.1113/jp279803] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 05/19/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Loss-of-function mutations in proteins found at glycinergic synapses, most commonly in the α1 subunit of the glycine receptor (GlyR), cause the startle disease/hyperekplexia channelopathy in man. It was recently proposed that the receptors responsible are presynaptic homomeric GlyRs, rather than postsynaptic heteromeric GlyRs (which mediate glycinergic synaptic transmission), because heteromeric GlyRs are less affected by many startle mutations than homomers. We examined the α1 startle mutation S270T, at the extracellular end of the M2 transmembrane helix. Recombinant heteromeric GlyRs were less impaired than homomers by this mutation when we measured their response to equilibrium applications of glycine. However, currents elicited by synaptic-like millisecond applications of glycine to outside-out patches were much shorter (7- to 10-fold) in all mutant receptors, both homomeric and heteromeric. Thus, the synaptic function of heteromeric receptors is likely to be impaired by the mutation. ABSTRACT Human startle disease is caused by mutations in glycine receptor (GlyR) subunits or in other proteins associated with glycinergic synapses. Many startle mutations are known, but it is hard to correlate the degree of impairment at molecular level with the severity of symptoms in patients. It was recently proposed that the disease is caused by disruption in the function of presynaptic homomeric GlyRs (rather than postsynaptic heteromeric GlyRs), because homomeric GlyRs are more sensitive to loss-of-function mutations than heteromers. Our patch-clamp recordings from heterologously expressed GlyRs characterised in detail the functional consequences of the α1S270T startle mutation, which is located at the extracellular end of the pore lining M2 transmembrane segment (18'). This mutation profoundly decreased the maximum single-channel open probability of homomeric GlyRs (to 0.16; cf. 0.99 for wild type) but reduced only marginally that of heteromeric GlyRs (0.96; cf. 0.99 for wild type). However, both heteromeric and homomeric mutant GlyRs became less sensitive to the neurotransmitter glycine. Responses evoked by brief, quasi-synaptic pulses of glycine onto outside-out patches were impaired in mutant receptors, as deactivation was approximately 10- and 7-fold faster for homomeric and heteromeric GlyRs, respectively. Our data suggest that the α1S270T mutation is likely to affect the opening step in GlyR activation. The faster decay of synaptic currents mediated by mutant heteromeric GlyRs is expected to reduce charge transfer at the synapse, despite the high equilibrium open probability of these mutant channels.
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Affiliation(s)
- Zhiyi Wu
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Remigijus Lape
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Lea Jopp-Saile
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Benjamin J O'Callaghan
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Timo Greiner
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Lucia G Sivilotti
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
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113
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A Novel Glycine Receptor Variant with Startle Disease Affects Syndapin I and Glycinergic Inhibition. J Neurosci 2020; 40:4954-4969. [PMID: 32354853 DOI: 10.1523/jneurosci.2490-19.2020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2019] [Revised: 03/24/2020] [Accepted: 04/24/2020] [Indexed: 11/21/2022] Open
Abstract
Glycine receptors (GlyRs) are the major mediators of fast synaptic inhibition in the adult human spinal cord and brainstem. Hereditary mutations to GlyRs can lead to the rare, but potentially fatal, neuromotor disorder hyperekplexia. Most mutations located in the large intracellular domain (TM3-4 loop) of the GlyRα1 impair surface expression levels of the receptors. The novel GLRA1 mutation P366L, located in the TM3-4 loop, showed normal surface expression but reduced chloride currents, and accelerated whole-cell desensitization observed in whole-cell recordings. At the single-channel level, we observed reduced unitary conductance accompanied by spontaneous opening events in the absence of extracellular glycine. Using peptide microarrays and tandem MS-based analysis methods, we show that the proline-rich stretch surrounding P366 mediates binding to syndapin I, an F-BAR domain protein involved in membrane remodeling. The disruption of the noncanonical Src homology 3 recognition motif by P366L reduces syndapin I binding. These data suggest that the GlyRα1 subunit interacts with intracellular binding partners and may therefore play a role in receptor trafficking or synaptic anchoring, a function thus far only ascribed to the GlyRβ subunit. Hence, the P366L GlyRα1 variant exhibits a unique set of properties that cumulatively affect GlyR functionality and thus might explain the neuropathological mechanism underlying hyperekplexia in the mutant carriers. P366L is the first dominant GLRA1 mutation identified within the GlyRα1 TM3-4 loop that affects GlyR physiology without altering protein expression at the whole-cell and surface levels.SIGNIFICANCE STATEMENT We show that the intracellular domain of the inhibitory glycine receptor α1 subunit contributes to trafficking and synaptic anchoring. A proline-rich stretch in this receptor domain forms a noncanonical recognition motif important for the interaction with syndapin I (PACSIN1). The disruption of this motif, as present in a human patient with hyperekplexia led to impaired syndapin I binding. Functional analysis revealed that the altered proline-rich stretch determines several functional physiological parameters of the ion channel (e.g., faster whole-cell desensitization) reduced unitary conductance and spontaneous opening events. Thus, the proline-rich stretch from the glycine receptor α1 subunit represents a multifunctional intracellular protein motif.
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114
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Rahman MM, Teng J, Worrell BT, Noviello CM, Lee M, Karlin A, Stowell MHB, Hibbs RE. Structure of the Native Muscle-type Nicotinic Receptor and Inhibition by Snake Venom Toxins. Neuron 2020; 106:952-962.e5. [PMID: 32275860 DOI: 10.1016/j.neuron.2020.03.012] [Citation(s) in RCA: 131] [Impact Index Per Article: 32.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 01/13/2020] [Accepted: 03/15/2020] [Indexed: 12/28/2022]
Abstract
The nicotinic acetylcholine receptor, a pentameric ligand-gated ion channel, converts the free energy of binding of the neurotransmitter acetylcholine into opening of its central pore. Here we present the first high-resolution structure of the receptor type found in muscle-endplate membrane and in the muscle-derived electric tissues of fish. The native receptor was purified from Torpedo electric tissue and functionally reconstituted in lipids optimal for cryo-electron microscopy. The receptor was stabilized in a closed state by the binding of α-bungarotoxin. The structure reveals the binding of a toxin molecule at each of two subunit interfaces in a manner that would block the binding of acetylcholine. It also reveals a closed gate in the ion-conducting pore, formed by hydrophobic amino acid side chains, located ∼60 Å from the toxin binding sites. The structure provides a framework for understanding gating in ligand-gated channels and how mutations in the acetylcholine receptor cause congenital myasthenic syndromes.
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Affiliation(s)
- Md Mahfuzur Rahman
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jinfeng Teng
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Brady T Worrell
- Department of Molecular, Cellular & Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - Colleen M Noviello
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Myeongseon Lee
- Department of Molecular, Cellular & Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - Arthur Karlin
- Center for Molecular Recognition & Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Michael H B Stowell
- Department of Molecular, Cellular & Developmental Biology, University of Colorado, Boulder, CO 80309, USA.
| | - Ryan E Hibbs
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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115
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Progress in nicotinic receptor structural biology. Neuropharmacology 2020; 171:108086. [PMID: 32272141 DOI: 10.1016/j.neuropharm.2020.108086] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Accepted: 03/31/2020] [Indexed: 02/07/2023]
Abstract
Here we begin by briefly reviewing landmark structural studies on the nicotinic acetylcholine receptor. We highlight challenges that had to be overcome to push through resolution barriers, then focus on what has been gleaned in the past few years from crystallographic and single particle cryo-EM studies of different nicotinic receptor subunit assemblies and ligand complexes. We discuss insights into ligand recognition, ion permeation, and allosteric gating. We then highlight some foundational aspects of nicotinic receptor structural biology that remain unresolved and are areas ripe for future exploration. This article is part of the special issue on 'Contemporary Advances in Nicotine Neuropharmacology'.
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116
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Brodzki M, Michałowski MA, Gos M, Mozrzymas JW. Mutations of α 1F45 residue of GABA A receptor loop G reveal its involvement in agonist binding and channel opening/closing transitions. Biochem Pharmacol 2020; 177:113917. [PMID: 32194055 DOI: 10.1016/j.bcp.2020.113917] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 03/12/2020] [Indexed: 10/24/2022]
Abstract
GABAA receptors (GABAARs) mediate inhibitory neurotransmission in the mammalian brain. Recently, numerous GABAAR static structures have been published, but the molecular mechanisms of receptor activation remain elusive. Loop G is a rigid β-strand belonging to an extensive β-sheet that spans the regions involved in GABA binding and the interdomain interface which is important in receptor gating. It has been reported that loop G participates in ligand binding and gating of GABAARs, however, it remains unclear which specific gating transitions are controlled by this loop. Analysis of macroscopic responses revealed that mutation at the α1F45 residue (loop G midpoint) resulted in slower macroscopic desensitization and accelerated deactivation. Single-channel analysis revealed that these mutations also affected open and closed times distributions and reduced open probability. Kinetic modeling demonstrated that mutations affected primarily channel opening/closing and ligand binding with a minor effect on preactivation. Thus, α1F45 residue, in spite of its localization close to binding site, affects late gating transitions. In silico structural analysis suggested an important role of α1F45 residue in loop G stability and rigidity as well as in general structure of the binding site. We propose that the rigid β-sheet comprising loop G is well suited for long range communication within GABAAR but this mechanism becomes impaired when α1F45 is mutated. In conclusion, we demonstrate that loop G is crucial in controlling both binding and gating of GABAARs. These data shed new light on GABAAR activation mechanism and may also be helpful in designing clinically relevant modulators.
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Affiliation(s)
- Marek Brodzki
- University of Wrocław, Department of Molecular Physiology and Neurobiology, ul. Sienkiewicza 21, 50-335 Wrocław, Poland; Wrocław Medical University, Department of Biophysics, Laboratory of Neuroscience, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland.
| | - Michał A Michałowski
- University of Wrocław, Department of Molecular Physiology and Neurobiology, ul. Sienkiewicza 21, 50-335 Wrocław, Poland; Wrocław Medical University, Department of Biophysics, Laboratory of Neuroscience, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland.
| | - Michalina Gos
- University of Wrocław, Department of Molecular Physiology and Neurobiology, ul. Sienkiewicza 21, 50-335 Wrocław, Poland; Wrocław Medical University, Department of Biophysics, Laboratory of Neuroscience, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland
| | - Jerzy W Mozrzymas
- Wrocław Medical University, Department of Biophysics, Laboratory of Neuroscience, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland.
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117
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Lev B, Allen TW. Simulating ion channel activation mechanisms using swarms of trajectories. J Comput Chem 2020; 41:387-401. [PMID: 31743478 DOI: 10.1002/jcc.26102] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 10/16/2019] [Accepted: 10/17/2019] [Indexed: 12/14/2022]
Abstract
Atomic-level studies of protein activity represent a significant challenge as a result of the complexity of conformational changes occurring on wide-ranging timescales, often greatly exceeding that of even the longest simulations. A prime example is the elucidation of protein allosteric mechanisms, where localized perturbations transmit throughout a large macromolecule to generate a response signal. For example, the conversion of chemical to electrical signals during synaptic neurotransmission in the brain is achieved by specialized membrane proteins called pentameric ligand-gated ion channels. Here, the binding of a neurotransmitter results in a global conformational change to open an ion-conducting pore across the nerve cell membrane. X-ray crystallography has produced static structures of the open and closed states of the proton-gated GLIC pentameric ligand-gated ion channel protein, allowing for atomistic simulations that can uncover changes related to activation. We discuss a range of enhanced sampling approaches that could be used to explore activation mechanisms. In particular, we describe recent application of an atomistic string method, based on Roux's "swarms of trajectories" approach, to elucidate the sequence and interdependence of conformational changes during activation. We illustrate how this can be combined with transition analysis and Brownian dynamics to extract thermodynamic and kinetic information, leading to understanding of what controls ion channel function. © 2019 Wiley Periodicals, Inc.
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Affiliation(s)
- Bogdan Lev
- School of Science, RMIT University, Melbourne, Victoria, 3000, Australia
| | - Toby W Allen
- School of Science, RMIT University, Melbourne, Victoria, 3000, Australia
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118
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Qudah T, Quek GX, Indurthi D, Karim N, Halliday JI, Absalom N, McLeod MD, Chebib M. AE Succinimide, an Analogue of Methyllycaconitine, When Bound Generates a Nonconducting Conformation of the α4β2 Nicotinic Acetylcholine Receptor. ACS Chem Neurosci 2020; 11:344-355. [PMID: 31898891 DOI: 10.1021/acschemneuro.9b00525] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Nicotinic acetylcholine (nACh) receptors are pentameric ligand-gated ion channels that mediate fast synaptic transmission. The α4β2 nACh receptor is highly expressed in the brain and exists in two functional stoichiometries: the (α4)2(β2)3 and (α4)3(β2)2 that differ by an ACh-binding site at the α4-α4 interface of (α4)3(β2)2 receptors. Methyllycaconitine (MLA) is an nACh receptor antagonist, and while potent at both α7 and α4β2 nACh receptors, it has a higher selectivity for the α7 nACh receptor. The anthranilate-succinimide ester side-chain is important for its activity and selectivity. Here we identify a simplified MLA analogue that contains only the A and E ring skeleton of MLA, AE succinimide, that binds close to the channel lumen to display insurmountable inhibition at α4β2 nACh receptors. Although inhibition by AE succinimide was found to be voltage-dependent indicating a possible pore channel blocker, substituted-cysteine accessibility experiments indicated it did not bind between 2'-16' region of the channel pore. Instead, we found that upon binding and in the presence of ACh, there is a conformational change to the channel membrane that was identified when the compound was assessed against (α4 V13'C)β2 nACh receptors. It was found that in the 3:2 stoichiometry the two adjacent α4 subunits containing 13' cysteine mutations formed a disulfide bond and occluded ion conductance. This was reversed by treatment with the reducing agent, dithiothreitol. Thus, AE succinimide has a different mechanism of inhibition to both MLA and other AE analogues, such as AE bicyclic alcohol, in that upon binding to an as yet unidentified site, AE succinimide in the presence of ACh induces a conformational change to the channel that generates a ligand-bound closed state.
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Affiliation(s)
- Taima Qudah
- Brain and Mind Centre, School of Pharmacy, Faculty of Medicine and Health, Sydney, NSW 2050, The University of Sydney
| | - Gracia X. Quek
- Brain and Mind Centre, School of Pharmacy, Faculty of Medicine and Health, Sydney, NSW 2050, The University of Sydney
| | - Dinesh Indurthi
- Brain and Mind Centre, School of Pharmacy, Faculty of Medicine and Health, Sydney, NSW 2050, The University of Sydney
| | - Nasiara Karim
- Brain and Mind Centre, School of Pharmacy, Faculty of Medicine and Health, Sydney, NSW 2050, The University of Sydney
| | - Jill I. Halliday
- Research School of Chemistry, College of Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Nathan Absalom
- Brain and Mind Centre, School of Pharmacy, Faculty of Medicine and Health, Sydney, NSW 2050, The University of Sydney
| | - Malcolm D. McLeod
- Research School of Chemistry, College of Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Mary Chebib
- Brain and Mind Centre, School of Pharmacy, Faculty of Medicine and Health, Sydney, NSW 2050, The University of Sydney
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119
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Shibayama N. Allosteric transitions in hemoglobin revisited. Biochim Biophys Acta Gen Subj 2020; 1864:129335. [DOI: 10.1016/j.bbagen.2019.03.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2018] [Revised: 03/27/2019] [Accepted: 03/30/2019] [Indexed: 12/19/2022]
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120
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Brams M, Govaerts C, Kambara K, Price KL, Spurny R, Gharpure A, Pardon E, Evans GL, Bertrand D, Lummis SCR, Hibbs RE, Steyaert J, Ulens C. Modulation of the Erwinia ligand-gated ion channel (ELIC) and the 5-HT 3 receptor via a common vestibule site. eLife 2020; 9:e51511. [PMID: 31990273 PMCID: PMC7015668 DOI: 10.7554/elife.51511] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 01/27/2020] [Indexed: 01/13/2023] Open
Abstract
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.
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Affiliation(s)
- Marijke Brams
- Laboratory of Structural Neurobiology, Department of Cellular and Molecular Medicine, Faculty of Medicine, KU LeuvenLeuvenBelgium
| | - Cedric Govaerts
- Laboratory for the Structure and Function of Biological Membranes, Center for Structural Biology and Bioinformatics, Université libre de BruxellesBrusselsBelgium
| | | | - Kerry L Price
- Department of Biochemistry, University of CambridgeCambridgeUnited Kingdom
| | - Radovan Spurny
- Laboratory of Structural Neurobiology, Department of Cellular and Molecular Medicine, Faculty of Medicine, KU LeuvenLeuvenBelgium
| | - Anant Gharpure
- Department of Neuroscience, University of Texas Southwestern Medical CenterDallasUnited States
- Department of Biophysics, University of Texas Southwestern Medical CenterDallasUnited States
| | - Els Pardon
- Structural Biology Brussels, Vrije Universiteit BrusselBrusselsBelgium
- VIB-VUB Center for Structural Biology, VIBBrusselsBelgium
| | - Genevieve L Evans
- Laboratory of Structural Neurobiology, Department of Cellular and Molecular Medicine, Faculty of Medicine, KU LeuvenLeuvenBelgium
| | | | - Sarah CR Lummis
- Department of Biochemistry, University of CambridgeCambridgeUnited Kingdom
| | - Ryan E Hibbs
- Department of Neuroscience, University of Texas Southwestern Medical CenterDallasUnited States
- Department of Biophysics, University of Texas Southwestern Medical CenterDallasUnited States
| | - Jan Steyaert
- Structural Biology Brussels, Vrije Universiteit BrusselBrusselsBelgium
- VIB-VUB Center for Structural Biology, VIBBrusselsBelgium
| | - Chris Ulens
- Laboratory of Structural Neurobiology, Department of Cellular and Molecular Medicine, Faculty of Medicine, KU LeuvenLeuvenBelgium
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121
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Dämgen MA, Biggin PC. A Refined Open State of the Glycine Receptor Obtained via Molecular Dynamics Simulations. Structure 2020; 28:130-139.e2. [PMID: 31753620 PMCID: PMC6945115 DOI: 10.1016/j.str.2019.10.019] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 10/11/2019] [Accepted: 10/30/2019] [Indexed: 01/22/2023]
Abstract
Pentameric ligand-gated ion channels are key players in mediating fast neurotransmission. Glycine receptors are chloride-selective members of this receptor family that mediate inhibitory synaptic transmission and are implicated in neurological disorders including autism and hyperekplexia. They have been structurally characterized by both X-ray crystallography and cryoelectron microscopy (cryo-EM) studies, with the latter giving rise to what was proposed as a possible open state. However, recent work has questioned the physiological relevance of this open state structure, since it rapidly collapses in molecular dynamics simulations. Here, we show that the collapse can be avoided by a careful equilibration protocol that reconciles the more problematic regions of the original density map and gives a stable open state that shows frequent selective chloride permeation. The protocol developed in this work provides a means to refine open-like structures of the whole pentameric ligand-gated ion channel superfamily and reconciles the previous issues with the cryo-EM structure.
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Affiliation(s)
- Marc A Dämgen
- Structural Bioinformatics and Computational Biochemistry, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Philip C Biggin
- Structural Bioinformatics and Computational Biochemistry, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
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122
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Zeng L, Ding W, Hao Q. Using cryo-electron microscopy maps for X-ray structure determination of homologues. ACTA CRYSTALLOGRAPHICA SECTION D-STRUCTURAL BIOLOGY 2020; 76:63-72. [PMID: 31909744 DOI: 10.1107/s2059798319015924] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Accepted: 11/25/2019] [Indexed: 11/10/2022]
Abstract
The combination of cryo-electron microscopy (cryo-EM) and X-ray crystallography reflects an important trend in structural biology. In a previously published study, a hybrid method for the determination of X-ray structures using initial phases provided by the corresponding parts of cryo-EM maps was presented. However, if the target structure of X-ray crystallography is not identical but homologous to the corresponding molecular model of the cryo-EM map, then the decrease in the accuracy of the starting phases makes the whole process more difficult. Here, a modified hybrid method is presented to handle such cases. The whole process includes three steps: cryo-EM map replacement, phase extension by NCS averaging and dual-space iterative model building. When the resolution gap between the cryo-EM and X-ray crystallographic data is large and the sequence identity is low, an intermediate stage of model building is necessary. Six test cases have been studied with sequence identity between the corresponding molecules in the cryo-EM and X-ray structures ranging from 34 to 52% and with sequence similarity ranging from 86 to 91%. This hybrid method consistently produced models with reasonable Rwork and Rfree values which agree well with the previously determined X-ray structures for all test cases, thus indicating the general applicability of the method for X-ray structure determination of homologues using cryo-EM maps as a starting point.
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Affiliation(s)
- Lingxiao Zeng
- School of Biomedical Sciences, University of Hong Kong, 21 Sassoon Road, Hong Kong
| | - Wei Ding
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Quan Hao
- School of Biomedical Sciences, University of Hong Kong, 21 Sassoon Road, Hong Kong
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123
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Rossokhin AV, Sharonova IN, Dvorzhak A, Bukanova JV, Skrebitsky VG. The mechanisms of potentiation and inhibition of GABA A receptors by non-steroidal anti-inflammatory drugs, mefenamic and niflumic acids. Neuropharmacology 2019; 160:107795. [PMID: 31560908 DOI: 10.1016/j.neuropharm.2019.107795] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 09/02/2019] [Accepted: 09/23/2019] [Indexed: 11/27/2022]
Abstract
Fenamates mefanamic and niflumic acids (MFA and NFA) induced dual potentiating and inhibitory effects on GABA currents recorded in isolated cerebellar Purkinje cells using the whole-cell patch-clamp and fast-application techniques. Regardless of the concentration, both drugs induced a pronounced prolongation of the current response. We demonstrated that the same concentration of drugs can produce both potentiating and inhibitory effects, depending on the GABA concentration, which indicates that both processes take place simultaneously and the net effect depends on the concentrations of both the agonist and fenamate. We found that the NFA-induced block is strongly voltage-dependent. The Woodhull analysis of the block suggests that NFA has two binding sites in the pore - shallow and deep. We built a homology model of the open GABAAR based on the cryo-EM structure of the open α1 GlyR and applied Monte-Carlo energy minimization to optimize the ligand-receptor complexes. A systematic search for MFA/NFA binding sites in the GABAAR pore revealed the existence of two sites, the location of which coincides well with predictions of the Woodhull model. In silico docking suggests that two fenamate molecules are necessary to occlude the pore. We showed that MFA, acting as a PAM, competes with an intravenous anesthetic etomidate for a common binding site. We built structural models of MFA and NFA binding at the transmembrane β(+)/α(-) intersubunit interface. We suggested a hypothesis on the molecular mechanism underlying the prolongation of the receptor lifetime in open state after MFA/NFA binding and β subunit specificity of the fenamate potentiation.
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Affiliation(s)
| | | | - Anton Dvorzhak
- Charité-Universitätsmedizin, Neuroscience Research Center, Berlin, Germany
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124
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Kirson D, Oleata CS, Roberto M. Taurine Suppression of Central Amygdala GABAergic Inhibitory Signaling via Glycine Receptors Is Disrupted in Alcohol Dependence. Alcohol Clin Exp Res 2019; 44:445-454. [PMID: 31782155 DOI: 10.1111/acer.14252] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Accepted: 11/18/2019] [Indexed: 11/28/2022]
Abstract
BACKGROUND Alcohol use disorder (AUD) increases brain stress systems while suppressing reward system functioning. One expression of stress system recruitment is elevated GABAergic activity in the central amygdala (CeA), which is involved in the excessive drinking seen with AUD. The sulfonic amino acid taurine, a glycine receptor partial agonist, modulates GABAergic activity in the rewarding effects of alcohol. Despite taurine abundance in the amygdala, its role in the dysregulation of GABAergic activity associated with AUD has not been studied. Thus, here, we evaluated the effects of taurine on locally stimulated GABAergic neurotransmission in the CeA of naïve- and alcohol-dependent rats. METHODS We recorded intracellularly from CeA neurons of naïve- and alcohol-dependent rats, quantifying locally evoked GABAA receptor-mediated inhibitory postsynaptic potentials (eIPSP). We examined the effects of taurine and alcohol on CeA eIPSP to characterize potential alcohol dependence-induced changes in the effects of taurine. RESULTS We found that taurine decreased amplitudes of eIPSP in CeA neurons of naïve rats, without affecting the acute alcohol-induced facilitation of GABAergic responses. In CeA neurons from dependent rats, taurine no longer had an effect on eIPSP, but now blocked the ethanol (EtOH)-induced increase in eIPSP amplitude normally seen. Additionally, preapplication of the glycine receptor-specific antagonist strychnine blocked the EtOH-induced increase in eIPSP amplitude in neurons from naïve rats. CONCLUSIONS These data suggest taurine may act to oppose the effects of acute alcohol via the glycine receptor in the CeA of naïve rats, and this modulatory system is altered in the CeA of dependent rats.
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Affiliation(s)
- Dean Kirson
- Department of Molecular Medicine, and Alcohol Research Center, The Scripps Research Institute, La Jolla, California
| | - Christopher S Oleata
- Department of Molecular Medicine, and Alcohol Research Center, The Scripps Research Institute, La Jolla, California
| | - Marisa Roberto
- Department of Molecular Medicine, and Alcohol Research Center, The Scripps Research Institute, La Jolla, California
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125
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Hussein RA, Ahmed M, Breitinger HG, Breitinger U. Modulation of Glycine Receptor-Mediated Pain Signaling in vitro and in vivo by Glucose. Front Mol Neurosci 2019; 12:280. [PMID: 31824259 PMCID: PMC6883931 DOI: 10.3389/fnmol.2019.00280] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 11/01/2019] [Indexed: 11/27/2022] Open
Abstract
The inhibitory glycine receptor (GlyR) plays an important role in rapid synaptic inhibition in mammalian spinal cord, brainstem, higher brain centers, and is involved in transmission of nociceptive signals. Glucose and related mono- and disaccharides potentiate currents mediated by recombinant α1, α1-β, and α3 GlyRs. Here, we confirmed the specific potentiation of α3 GlyR signaling by glucose through: (i) patch-clamp electrophysiology on recombinant receptors; and (ii) by verifying in vitro data in a mouse model in vivo. Mice were intraperitoneally (IP) injected with glucose (2 g/kg) or vehicle, and then challenged with sublethal doses of strychnine (0.2 mg/kg and 0.5 mg/kg). Pain-related behavior was assessed using two established models: (i) touch sensitivity tests using von Frey filaments; and (ii) hotplate assay. We observed a reduction of pain sensitivity in glucose-treated mice relative to vehicle-treated control mice. Injection of strychnine resulted in an increased sensitivity to tactile and heat stimuli, which was reversed in the presence of glucose. Analgesic effects of glucose were more pronounced in von Frey experiments, consistent with the established use of this model for neuropathic pain. Overall, glucose showed mild analgesic effects and was able to compensate for strychnine-induced allodynia in mice. Since the action of strychnine is specific for GlyR, these experiments show for the first time an in vivo potentiation of GlyR activity by glucose and suggest a molecular mechanism for glucose-mediated analgesia.
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Affiliation(s)
| | - Marwa Ahmed
- Department of Biochemistry, German University in Cairo, New Cairo, Egypt
| | | | - Ulrike Breitinger
- Department of Biochemistry, German University in Cairo, New Cairo, Egypt
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126
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Orellana L. Large-Scale Conformational Changes and Protein Function: Breaking the in silico Barrier. Front Mol Biosci 2019; 6:117. [PMID: 31750315 PMCID: PMC6848229 DOI: 10.3389/fmolb.2019.00117] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2019] [Accepted: 10/14/2019] [Indexed: 12/16/2022] Open
Abstract
Large-scale conformational changes are essential to link protein structures with their function at the cell and organism scale, but have been elusive both experimentally and computationally. Over the past few years developments in cryo-electron microscopy and crystallography techniques have started to reveal multiple snapshots of increasingly large and flexible systems, deemed impossible only short time ago. As structural information accumulates, theoretical methods become central to understand how different conformers interconvert to mediate biological function. Here we briefly survey current in silico methods to tackle large conformational changes, reviewing recent examples of cross-validation of experiments and computational predictions, which show how the integration of different scale simulations with biological information is already starting to break the barriers between the in silico, in vitro, and in vivo worlds, shedding new light onto complex biological problems inaccessible so far.
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Affiliation(s)
- Laura Orellana
- Institutionen för Biokemi och Biofysik, Stockholms Universitet, Stockholm, Sweden.,Science for Life Laboratory, Solna, Sweden
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127
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Dawson A, Trumper P, de Souza JO, Parker H, Jones MJ, Hales TG, Hunter WN. Engineering a surrogate human heteromeric α/β glycine receptor orthosteric site exploiting the structural homology and stability of acetylcholine-binding protein. IUCRJ 2019; 6:1014-1023. [PMID: 31709057 PMCID: PMC6830221 DOI: 10.1107/s205225251901114x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Accepted: 08/09/2019] [Indexed: 06/10/2023]
Abstract
Protein-engineering methods have been exploited to produce a surrogate system for the extracellular neurotransmitter-binding site of a heteromeric human ligand-gated ion channel, the glycine receptor. This approach circumvents two major issues: the inherent experimental difficulties in working with a membrane-bound ion channel and the complication that a heteromeric assembly is necessary to create a key, physiologically relevant binding site. Residues that form the orthosteric site in a highly stable ortholog, acetylcholine-binding protein, were selected for substitution. Recombinant proteins were prepared and characterized in stepwise fashion exploiting a range of biophysical techniques, including X-ray crystallography, married to the use of selected chemical probes. The decision making and development of the surrogate, which is termed a glycine-binding protein, are described, and comparisons are provided with wild-type and homomeric systems that establish features of molecular recognition in the binding site and the confidence that the system is suited for use in early-stage drug discovery targeting a heteromeric α/β glycine receptor.
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Affiliation(s)
- Alice Dawson
- Division of Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland
| | - Paul Trumper
- Division of Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland
| | - Juliana Oliveira de Souza
- Division of Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland
| | - Holly Parker
- Division of Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland
| | - Mathew J. Jones
- Division of Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland
| | - Tim G. Hales
- Division of Systems Medicine, School of Medicine, Ninewells Hospital, University of Dundee, Dundee DD1 9SY, Scotland
| | - William N. Hunter
- Division of Biological Chemistry and Drug Discovery, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland
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128
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Tikhonova TA, Rassokhina IV, Kondrakhin EA, Fedosov MA, Bukanova JV, Rossokhin AV, Sharonova IN, Kovalev GI, Zavarzin IV, Volkova YA. Development of 1,3-thiazole analogues of imidazopyridines as potent positive allosteric modulators of GABA A receptors. Bioorg Chem 2019; 94:103334. [PMID: 31711764 DOI: 10.1016/j.bioorg.2019.103334] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 09/17/2019] [Accepted: 09/30/2019] [Indexed: 12/14/2022]
Abstract
Structure-activity relationship studies were conducted in the search for 1,3-thiazole isosteric analogs of imidazopyridine drugs (Zolpidem, Alpidem). Three series of novel γ-aminobutyric acid receptor (GABAAR) ligands belonging to imidazo[2,1-b]thiazoles, imidazo[2,1-b][1,3,4]thiadiazoles, and benzo[d]imidazo[2,1-b]thiazoles were synthesized and characterized as active agents against GABAAR benzodiazepine-binding site. In each of these series, potent compounds were discovered using a radioligand competition binding assay. The functional properties of highest-affinity compounds 28 and 37 as GABAAR positive allosteric modulators (PAMs) were determined by electrophysiological measurements. In vivo studies on zebrafish demonstrated their potential for the further development of anxiolytics. Using the OECD "Fish, Acute Toxicity Test" active compounds were found safe and non-toxic. Structural bases for activity of benzo[d]imidazo[2,1-b]thiazoles were proposed using molecular docking studies. The isosteric replacement of the pyridine nuclei by 1,3-thiazole, 1,3,4-thiadiazole, or 1,3-benzothiazole in the ring-fused imidazole class of GABAAR PAMs was shown to be promising for the development of novel hypnotics, anxiolytics, anticonvulsants, and sedatives drug-candidates.
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Affiliation(s)
- Tatyana A Tikhonova
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 119991 Moscow, Russia
| | - Irina V Rassokhina
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 119991 Moscow, Russia
| | - Eugeny A Kondrakhin
- V. V. Zakusov Institute of Pharmacology, Russian Academy of Sciences, 8 Baltiyskaya Str., 125315 Moscow, Russia
| | - Mikhail A Fedosov
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 119991 Moscow, Russia
| | - Julia V Bukanova
- Research Center of Neurology, 5 By-str. Obukha, 105064 Moscow, Russia
| | | | - Irina N Sharonova
- Research Center of Neurology, 5 By-str. Obukha, 105064 Moscow, Russia
| | - Georgy I Kovalev
- V. V. Zakusov Institute of Pharmacology, Russian Academy of Sciences, 8 Baltiyskaya Str., 125315 Moscow, Russia
| | - Igor V Zavarzin
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 119991 Moscow, Russia
| | - Yulia A Volkova
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 119991 Moscow, Russia.
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129
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Hénault CM, Govaerts C, Spurny R, Brams M, Estrada-Mondragon A, Lynch J, Bertrand D, Pardon E, Evans GL, Woods K, Elberson BW, Cuello LG, Brannigan G, Nury H, Steyaert J, Baenziger JE, Ulens C. A lipid site shapes the agonist response of a pentameric ligand-gated ion channel. Nat Chem Biol 2019; 15:1156-1164. [PMID: 31591563 DOI: 10.1038/s41589-019-0369-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Accepted: 08/21/2019] [Indexed: 12/11/2022]
Abstract
Phospholipids are key components of cellular membranes and are emerging as important functional regulators of different membrane proteins, including pentameric ligand-gated ion channels (pLGICs). Here, we take advantage of the prokaryote channel ELIC (Erwinia ligand-gated ion channel) as a model to understand the determinants of phospholipid interactions in this family of receptors. A high-resolution structure of ELIC in a lipid-bound state reveals a phospholipid site at the lower half of pore-forming transmembrane helices M1 and M4 and at a nearby site for neurosteroids, cholesterol or general anesthetics. This site is shaped by an M4-helix kink and a Trp-Arg-Pro triad that is highly conserved in eukaryote GABAA/C and glycine receptors. A combined approach reveals that M4 is intrinsically flexible and that M4 deletions or disruptions of the lipid-binding site accelerate desensitization in ELIC, suggesting that lipid interactions shape the agonist response. Our data offer a structural context for understanding lipid modulation in pLGICs.
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Affiliation(s)
- Camille M Hénault
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario, Canada
| | - Cedric Govaerts
- Laboratory for the Structure and Function of Biological Membranes, Center for Structural Biology and Bioinformatics, Université libre de Bruxelles, Brussels, Belgium
| | - Radovan Spurny
- Laboratory of Structural Neurobiology, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
| | - Marijke Brams
- Laboratory of Structural Neurobiology, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
| | | | - Joseph Lynch
- Queensland Brain Institute, University of Queensland, Brisbane, Queensland, Australia
| | | | - Els Pardon
- Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium.,VIB-VUB Center for Structural Biology, VIB, Brussels, Belgium
| | - Genevieve L Evans
- Laboratory of Structural Neurobiology, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium
| | - Kristen Woods
- Center for Computational and Integrative Biology, Rutgers University-Camden, Camden, NJ, USA.,Department of Physics, Rutgers University-Camden, Camden, NJ, USA
| | - Benjamin W Elberson
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, TTUHSC, Lubbock, TX, USA
| | - Luis G Cuello
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, TTUHSC, Lubbock, TX, USA
| | - Grace Brannigan
- Center for Computational and Integrative Biology, Rutgers University-Camden, Camden, NJ, USA.,Department of Physics, Rutgers University-Camden, Camden, NJ, USA
| | - Hugues Nury
- University Grenoble Alpes, CNRS, IBS, Grenoble, France
| | - Jan Steyaert
- Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium.,VIB-VUB Center for Structural Biology, VIB, Brussels, Belgium
| | - John E Baenziger
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, Ontario, Canada.
| | - Chris Ulens
- Laboratory of Structural Neurobiology, Department of Cellular and Molecular Medicine, KU Leuven, Leuven, Belgium.
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130
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Munro L, Ladefoged LK, Padmanathan V, Andersen S, Schiøtt B, Kristensen AS. Conformational Changes in the 5-HT 3A Receptor Extracellular Domain Measured by Voltage-Clamp Fluorometry. Mol Pharmacol 2019; 96:720-734. [PMID: 31582575 DOI: 10.1124/mol.119.116657] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2019] [Accepted: 09/28/2019] [Indexed: 01/13/2023] Open
Abstract
The 5-hydroxytryptamine (5-HT) type 3 receptor is a member of the cysteine (Cys)-loop receptor super family of ligand-gated ion channels in the nervous system and is a clinical target in a range of diseases. The 5-HT3 receptor mediates fast serotonergic neurotransmission by undergoing a series of conformational changes initiated by ligand binding that lead to the rapid opening of an intrinsic cation-selective channel. However, despite the availability of high-resolution structures of a mouse 5-HT3 receptor, many important aspects of the mechanistic basis of 5-HT3 receptor function and modulation by drugs remain poorly understood. In particular, there is little direct evidence for the specific conformational changes predicted to occur during ligand-gated channel activation and desensitization. In the present study, we used voltage-clamp fluorometry (VCF) to measure conformational changes in regions surrounding the orthosteric binding site of the human 5-HT3A (h5-HT3A) receptor during binding of 5-HT and different classes of 5-HT3 receptor ligands. VCF utilizes parallel measurements of receptor currents with photon emission from fluorescent reporter groups covalently attached to specific positions in the receptor structure. Reporter groups that are highly sensitive to the local molecular environment can, in real time, report conformational changes as changes in fluorescence that can be correlated with changes in receptor currents reporting the functional states of the channel. Within the loop C, D, and E regions that surround the orthosteric binding site in the h5-HT3A receptor, we identify positions that are amenable to tagging with an environmentally sensitive reporter group that reports robust fluorescence changes upon 5-HT binding and receptor activation. We use these reporter positions to characterize the effect of ligand binding on the local structure of the orthosteric binding site by agonists, competitive antagonists, and allosterically acting channel activators. We observed that loop C appears to show distinct fluorescence changes for ligands of the same class, while loop D reports similar fluorescence changes for all ligands binding at the orthosteric site. In contrast, the loop E reporter position shows distinct changes for agonists, antagonists, and allosteric compounds, suggesting the conformational changes in this region are specific to ligand function. Interpretation of these results within the framework of current models of 5-HT3 and Cys-loop mechanisms are used to expand the understanding of how ligand binding in Cys-loop receptors relates to channel gating. SIGNIFICANCE STATEMENT: The 5-HT3 receptor is an important ligand-gated ion channel and drug target in the central and peripheral nervous system. Determining how ligand binding induced conformational changes in the receptor is central for understanding the structural mechanisms underlying 5-HT3 receptor function. Here, we employ voltage-gated fluorometry to characterize conformational changes in the extracellular domain of the human 5-HT3 receptor to identify intrareceptor motions during binding of a range of 5-HT3 receptor agonists and antagonists.
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Affiliation(s)
- Lachlan Munro
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark (L.M., V.P., S.A., A.S.K.); and Department of Chemistry (L.K.L., B.S.) and Interdisciplinary Nanoscience Center (B.S.), Aarhus University, Aarhus, Denmark
| | - Lucy Kate Ladefoged
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark (L.M., V.P., S.A., A.S.K.); and Department of Chemistry (L.K.L., B.S.) and Interdisciplinary Nanoscience Center (B.S.), Aarhus University, Aarhus, Denmark
| | - Vithushan Padmanathan
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark (L.M., V.P., S.A., A.S.K.); and Department of Chemistry (L.K.L., B.S.) and Interdisciplinary Nanoscience Center (B.S.), Aarhus University, Aarhus, Denmark
| | - Signe Andersen
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark (L.M., V.P., S.A., A.S.K.); and Department of Chemistry (L.K.L., B.S.) and Interdisciplinary Nanoscience Center (B.S.), Aarhus University, Aarhus, Denmark
| | - Birgit Schiøtt
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark (L.M., V.P., S.A., A.S.K.); and Department of Chemistry (L.K.L., B.S.) and Interdisciplinary Nanoscience Center (B.S.), Aarhus University, Aarhus, Denmark
| | - Anders S Kristensen
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark (L.M., V.P., S.A., A.S.K.); and Department of Chemistry (L.K.L., B.S.) and Interdisciplinary Nanoscience Center (B.S.), Aarhus University, Aarhus, Denmark
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131
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Fourati Z, Howard RJ, Heusser SA, Hu H, Ruza RR, Sauguet L, Lindahl E, Delarue M. Structural Basis for a Bimodal Allosteric Mechanism of General Anesthetic Modulation in Pentameric Ligand-Gated Ion Channels. Cell Rep 2019; 23:993-1004. [PMID: 29694907 DOI: 10.1016/j.celrep.2018.03.108] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Revised: 02/02/2018] [Accepted: 03/23/2018] [Indexed: 10/17/2022] Open
Abstract
Ion channel modulation by general anesthetics is a vital pharmacological process with implications for receptor biophysics and drug development. Functional studies have implicated conserved sites of both potentiation and inhibition in pentameric ligand-gated ion channels, but a detailed structural mechanism for these bimodal effects is lacking. The prokaryotic model protein GLIC recapitulates anesthetic modulation of human ion channels, and it is accessible to structure determination in both apparent open and closed states. Here, we report ten X-ray structures and electrophysiological characterization of GLIC variants in the presence and absence of general anesthetics, including the surgical agent propofol. We show that general anesthetics can allosterically favor closed channels by binding in the pore or favor open channels via various subsites in the transmembrane domain. Our results support an integrated, multi-site mechanism for allosteric modulation, and they provide atomic details of both potentiation and inhibition by one of the most common general anesthetics.
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Affiliation(s)
- Zaineb Fourati
- Unit of Structural Dynamics of Macromolecules, Institut Pasteur and UMR 3528 du CNRS, 75015 Paris, France
| | - Rebecca J Howard
- Department of Biochemistry and Biophysics and Science for Life Laboratory, Stockholm University, 17165 Solna, Sweden
| | - Stephanie A Heusser
- Department of Biochemistry and Biophysics and Science for Life Laboratory, Stockholm University, 17165 Solna, Sweden
| | - Haidai Hu
- Unit of Structural Dynamics of Macromolecules, Institut Pasteur and UMR 3528 du CNRS, 75015 Paris, France; Sorbonne Universités, UPMC University Paris 6, 75005 Paris, France
| | - Reinis R Ruza
- Unit of Structural Dynamics of Macromolecules, Institut Pasteur and UMR 3528 du CNRS, 75015 Paris, France
| | - Ludovic Sauguet
- Unit of Structural Dynamics of Macromolecules, Institut Pasteur and UMR 3528 du CNRS, 75015 Paris, France
| | - Erik Lindahl
- Department of Biochemistry and Biophysics and Science for Life Laboratory, Stockholm University, 17165 Solna, Sweden; Swedish e-Science Research Center, KTH Royal Institute of Technology, 11428 Stockholm, Sweden
| | - Marc Delarue
- Unit of Structural Dynamics of Macromolecules, Institut Pasteur and UMR 3528 du CNRS, 75015 Paris, France.
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132
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Alvarez LD, Pecci A. Mapping the neurosteroid binding sites on glycine receptors. J Steroid Biochem Mol Biol 2019; 192:105388. [PMID: 31176751 DOI: 10.1016/j.jsbmb.2019.105388] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 04/27/2019] [Accepted: 05/30/2019] [Indexed: 11/18/2022]
Abstract
Glycine is a major inhibitory neurotransmitter in the CNS, where it modulates both sensory and motor transduction throughout its binding to glycine receptors (GlyRs), pentameric chloride channels that share structural and functional properties with type A γ-aminobutyric acid receptors (GABAAR). A large number of structurally diverse organic compounds have been identified as GlyR and GABAAR allosteric modulators, making these receptors attractive pharmacological targets. Taking into account the recent resolved crystal structures of GABAAR/neurosteroid complexes, and due to the high sequence identity between the GABAAR and GlyR transmembrane domains, in this work we applied molecular modeling methods to explore the neurosteroid binding to GlyR. Our results indicated that neurosteroid binding sites of GABAARs are also conserved in the GlyRs. Furthermore, docking and molecular dynamics simulations predicted that neurosteroids are stably recognized at these sites, providing precise information on the molecular basis of the neurosteroid binding mode to GlyR. The comparison of how allopregnanolone and pregnanolone 3-OH moieties are recognized by the GlyR binding pocket revealed significant differences that may be associated to opposite effects of these isomers on the GlyR response.
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Affiliation(s)
- Lautaro D Alvarez
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Química Biológica, Ciudad Universitaria, Buenos Aires, C1428EGA, Argentina; CONICET - Universidad de Buenos Aires, UMYMFOR, Ciudad Universitaria, Buenos Aires, C1428EGA, Argentina.
| | - Adali Pecci
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Química Biológica, Ciudad Universitaria, Buenos Aires, C1428EGA, Argentina; CONICET - Universidad de Buenos Aires, IFIBYNE, Ciudad Universitaria, Buenos Aires, C1428EGA, Argentina
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133
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Zlotos DP, Mohsen AMY, Mandour YM, Marzouk MA, Breitinger U, Villmann C, Breitinger HG, Sotriffer C, Jensen AA, Holzgrabe U. 11-Aminostrychnine and N-(Strychnine-11-yl)propionamide: Synthesis, Configuration, and Pharmacological Evaluation at Glycine Receptors. JOURNAL OF NATURAL PRODUCTS 2019; 82:2332-2336. [PMID: 31385511 DOI: 10.1021/acs.jnatprod.9b00180] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
(11S)-11-Aminostrychnine (1) and N-[(11S)-strychnine-11-yl]propionamide (2) were synthesized and characterized as antagonists of homomeric α1 and heteromeric α1β glycine receptors in a functional fluorescence-based assay and a patch-clamp assay and in radioligand binding studies. The absolute configuration at C-11 of 1 was determined based on vicinal coupling constants and NOESY data. Docking experiments to the orthosteric binding site of the α3 glycine receptor showed a binding mode of compound 2 analogous to that of strychnine, explaining its high antagonistic potency. The findings identify the C-11 amide function of strychnine as a suitable linker group for the future development of dimeric strychnine analogues targeting glycine receptors. The findings extend the SAR of strychnine at glycine receptors.
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Affiliation(s)
- Darius P Zlotos
- Faculty of Pharmacy and Biotechnology , The German University in Cairo , New Cairo City, 11835 Cairo , Egypt
| | - Amal M Y Mohsen
- Faculty of Pharmacy and Biotechnology , The German University in Cairo , New Cairo City, 11835 Cairo , Egypt
| | - Yasmine M Mandour
- Faculty of Pharmacy and Biotechnology , The German University in Cairo , New Cairo City, 11835 Cairo , Egypt
| | - Mohamed A Marzouk
- Faculty of Pharmacy and Biotechnology , The German University in Cairo , New Cairo City, 11835 Cairo , Egypt
| | - Ulrike Breitinger
- Faculty of Pharmacy and Biotechnology , The German University in Cairo , New Cairo City, 11835 Cairo , Egypt
| | - Carmen Villmann
- Institute of Clinical Neurobiology , University of Würzburg , 97078 Würzburg , Germany
| | - Hans-Georg Breitinger
- Faculty of Pharmacy and Biotechnology , The German University in Cairo , New Cairo City, 11835 Cairo , Egypt
| | - Christoph Sotriffer
- Institute of Pharmacy and Food Chemistry , University of Würzburg , 97074 Würzburg , Germany
| | - Anders A Jensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences , University of Copenhagen , DK-2100 Copenhagen , Denmark
| | - Ulrike Holzgrabe
- Institute of Pharmacy and Food Chemistry , University of Würzburg , 97074 Würzburg , Germany
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134
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Pandhare A, Pirayesh E, Stuebler AG, Jansen M. Triple arginines as molecular determinants for pentameric assembly of the intracellular domain of 5-HT 3A receptors. J Gen Physiol 2019; 151:1135-1145. [PMID: 31409663 PMCID: PMC6719409 DOI: 10.1085/jgp.201912421] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Accepted: 07/15/2019] [Indexed: 11/20/2022] Open
Abstract
Serotonin type 3A receptors are homopentameric ligand-gated ion channels that are thought to assemble via interactions involving the subunits’ extracellular and transmembrane domains. Pandhare et al. reveal that channel assembly is also determined by three arginine residues in the receptor’s intracellular domain. Serotonin type 3 receptors (5-HT3Rs) are cation-conducting pentameric ligand-gated ion channels and members of the Cys-loop superfamily in eukaryotes. 5-HT3Rs are found in the peripheral and central nervous system, and they are targets for drugs used to treat anxiety, drug dependence, and schizophrenia, as well as chemotherapy-induced and postoperative nausea and emesis. Decades of research of Cys-loop receptors have identified motifs in both the extracellular and transmembrane domains that mediate pentameric assembly. Those efforts have largely ignored the most diverse domain of these channels, the intracellular domain (ICD). Here we identify molecular determinants within the ICD of serotonin type 3A (5-HT3A) subunits for pentameric assembly by first identifying the segments contributing to pentamerization using deletion constructs of, and finally by making defined amino acid substitutions within, an isolated soluble ICD. Our work provides direct experimental evidence for the contribution of three intracellular arginines, previously implicated in governing the low conductance of 5-HT3ARs, in structural features such as pentameric assembly.
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Affiliation(s)
- Akash Pandhare
- Department of Cell Physiology and Molecular Biophysics and Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX
| | - Elham Pirayesh
- Department of Cell Physiology and Molecular Biophysics and Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX
| | - Antonia G Stuebler
- Department of Cell Physiology and Molecular Biophysics and Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX
| | - Michaela Jansen
- Department of Cell Physiology and Molecular Biophysics and Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX
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135
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Basak S, Gicheru Y, Kapoor A, Mayer ML, Filizola M, Chakrapani S. Molecular mechanism of setron-mediated inhibition of full-length 5-HT 3A receptor. Nat Commun 2019; 10:3225. [PMID: 31324772 PMCID: PMC6642186 DOI: 10.1038/s41467-019-11142-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Accepted: 06/23/2019] [Indexed: 12/27/2022] Open
Abstract
Serotonin receptor (5-HT3AR) is the most common therapeutic target to manage the nausea and vomiting during cancer therapies and in the treatment of irritable bowel syndrome. Setrons, a class of competitive antagonists, cause functional inhibition of 5-HT3AR in the gastrointestinal tract and brainstem, acting as effective anti-emetic agents. Despite their prevalent use, the molecular mechanisms underlying setron binding and inhibition of 5-HT3AR are not fully understood. Here, we present the structure of granisetron-bound full-length 5-HT3AR solved by single-particle cryo-electron microscopy to 2.92 Å resolution. The reconstruction reveals the orientation of granisetron in the orthosteric site with unambiguous density for interacting sidechains. Molecular dynamics simulations and electrophysiology confirm the granisetron binding orientation and the residues central for ligand recognition. Comparison of granisetron-bound 5-HT3AR with the apo and serotonin-bound structures, reveals key insights into the mechanism underlying 5-HT3AR inhibition.
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Affiliation(s)
- Sandip Basak
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, 44106-4970, USA
| | - Yvonne Gicheru
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, 44106-4970, USA
| | - Abhijeet Kapoor
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Megan L Mayer
- Division of CryoEM and Bioimaging, SSRL, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA, 94025, USA
| | - Marta Filizola
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Sudha Chakrapani
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, 44106-4970, USA.
- Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106-4970, USA.
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136
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Oliveira ASF, Shoemark DK, Campello HR, Wonnacott S, Gallagher T, Sessions RB, Mulholland AJ. Identification of the Initial Steps in Signal Transduction in the α4β2 Nicotinic Receptor: Insights from Equilibrium and Nonequilibrium Simulations. Structure 2019; 27:1171-1183.e3. [PMID: 31130483 DOI: 10.1016/j.str.2019.04.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Revised: 01/28/2019] [Accepted: 04/10/2019] [Indexed: 02/02/2023]
Abstract
Nicotinic acetylcholine receptors (nAChRs) modulate synaptic transmission in the nervous system. These receptors have emerged as therapeutic targets in drug discovery for treating several conditions, including Alzheimer's disease, pain, and nicotine addiction. In this in silico study, we use a combination of equilibrium and nonequilibrium molecular dynamics simulations to map dynamic and structural changes induced by nicotine in the human α4β2 nAChR. They reveal a striking pattern of communication between the extracellular binding pockets and the transmembrane domains (TMDs) and show the sequence of conformational changes associated with the initial steps in this process. We propose a general mechanism for signal transduction for Cys-loop receptors: the mechanistic steps for communication proceed firstly through loop C in the principal subunit, and are subsequently transmitted, gradually and cumulatively, to loop F of the complementary subunit, and then to the TMDs through the M2-M3 linker.
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Affiliation(s)
- A Sofia F Oliveira
- School of Biochemistry, University of Bristol, Bristol BS8 1DT, UK; Centre for Computational Chemistry, School of Chemistry, University of Bristol, Bristol BS8 1TS, UK
| | | | - Hugo Rego Campello
- Centre for Computational Chemistry, School of Chemistry, University of Bristol, Bristol BS8 1TS, UK
| | - Susan Wonnacott
- Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK
| | - Timothy Gallagher
- Centre for Computational Chemistry, School of Chemistry, University of Bristol, Bristol BS8 1TS, UK
| | | | - Adrian J Mulholland
- Centre for Computational Chemistry, School of Chemistry, University of Bristol, Bristol BS8 1TS, UK.
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138
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Hernandez CC, XiangWei W, Hu N, Shen D, Shen W, Lagrange AH, Zhang Y, Dai L, Ding C, Sun Z, Hu J, Zhu H, Jiang Y, Macdonald RL. Altered inhibitory synapses in de novo GABRA5 and GABRA1 mutations associated with early onset epileptic encephalopathies. Brain 2019; 142:1938-1954. [PMID: 31056671 PMCID: PMC6598634 DOI: 10.1093/brain/awz123] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 02/20/2019] [Accepted: 03/07/2019] [Indexed: 12/22/2022] Open
Abstract
We performed next generation sequencing on 1696 patients with epilepsy and intellectual disability using a gene panel with 480 epilepsy-related genes including all GABAA receptor subunit genes (GABRs), and we identified six de novo GABR mutations, two novel GABRA5 mutations (c.880G>T, p.V294F and c.1238C>T, p.S413F), two novel GABRA1 mutations (c.778C>T, p.P260S and c.887T>C, p.L296S/c.944G>T, p.W315L) and two known GABRA1 mutations (c.335G>A, p.R112Q and c.343A>G, p.N115D) in six patients with intractable early onset epileptic encephalopathy. The α5(V294F and S413F) and α1(P260S and L296S/W315L) subunit residue substitutions were all in transmembrane domains, while the α1(R112Q and N115R) subunit residue substitutions were in the N-terminal GABA binding domain. Using multidisciplinary approaches, we compared effects of mutant GABAA receptor α5 and α1 subunits on the properties of recombinant α5β3γ2 and α1β3γ2 GABAA receptors in both neuronal and non-neuronal cells and characterized their effects on receptor clustering, biogenesis and channel function. GABAA receptors containing mutant α5 and α1 subunits all had reduced cell surface and total cell expression with altered endoplasmic reticulum processing, impaired synaptic clustering, reduced GABAA receptor function and decreased GABA binding potency. Our study identified GABRA5 as a causative gene for early onset epileptic encephalopathy and expands the mutant GABRA1 phenotypic spectrum, supporting growing evidence that defects in GABAergic neurotransmission contribute to early onset epileptic encephalopathy phenotypes.
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Affiliation(s)
- Ciria C Hernandez
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | - Wenshu XiangWei
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, China
- Center of Epilepsy, Beijing Institute for Brain Disorders, Beijing, China
| | - Ningning Hu
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Dingding Shen
- The Graduate Program of Neuroscience, Vanderbilt University, Nashville, TN, USA
- Department of Neurology, Rui Jin Hospital, Shanghai Jiao Tong University, School of Medicine. Shanghai, China
| | - Wangzhen Shen
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Andre H Lagrange
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Pharmacology and Molecular Physiology and Biophysics, Vanderbilt University, and the Veterans Affairs Tennessee Valley Healthcare System, Nashville, TN, USA
| | - Yujia Zhang
- Department of Neurology, Beijing Children’s Hospital, Capital Medical University, National Center for Children’s Health, Beijing, China
| | - Lifang Dai
- Department of Neurology, Beijing Children’s Hospital, Capital Medical University, National Center for Children’s Health, Beijing, China
| | - Changhong Ding
- Department of Neurology, Beijing Children’s Hospital, Capital Medical University, National Center for Children’s Health, Beijing, China
| | - Zhaohui Sun
- Epilepsy center of Yuquan Hospital, Tsinghua University, Beijing, China
| | - Jiasheng Hu
- Department of Neurology, Wuhan Children’s Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hongmin Zhu
- Department of Neurology, Wuhan Children’s Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yuwu Jiang
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, China
- Center of Epilepsy, Beijing Institute for Brain Disorders, Beijing, China
| | - Robert L Macdonald
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
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139
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A loss-of-function mutation of an inhibitory zinc- and proton-binding site reduces channel blocker potency in the glycine receptor. Neuropharmacology 2019; 153:121-133. [PMID: 31063738 DOI: 10.1016/j.neuropharm.2019.05.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Revised: 04/16/2019] [Accepted: 05/02/2019] [Indexed: 02/05/2023]
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140
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Flood E, Boiteux C, Lev B, Vorobyov I, Allen TW. Atomistic Simulations of Membrane Ion Channel Conduction, Gating, and Modulation. Chem Rev 2019; 119:7737-7832. [DOI: 10.1021/acs.chemrev.8b00630] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Emelie Flood
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia
| | - Céline Boiteux
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia
| | - Bogdan Lev
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia
| | - Igor Vorobyov
- Department of Physiology & Membrane Biology/Department of Pharmacology, University of California, Davis, 95616, United States
| | - Toby W. Allen
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia
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141
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Maleeva G, Wutz D, Rustler K, Nin-Hill A, Rovira C, Petukhova E, Bautista-Barrufet A, Gomila-Juaneda A, Scholze P, Peiretti F, Alfonso-Prieto M, König B, Gorostiza P, Bregestovski P. A photoswitchable GABA receptor channel blocker. Br J Pharmacol 2019; 176:2661-2677. [PMID: 30981211 PMCID: PMC6609548 DOI: 10.1111/bph.14689] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2018] [Revised: 03/03/2019] [Accepted: 04/03/2019] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND AND PURPOSE Anion-selective Cys-loop receptors (GABA and glycine receptors) provide the main inhibitory drive in the CNS. Both types of receptor operate via chloride-selective ion channels, though with different kinetics, pharmacological profiles, and localization. Disequilibrium in their function leads to a variety of disorders, which are often treated with allosteric modulators. The few available GABA and glycine receptor channel blockers effectively suppress inhibitory currents in neurons, but their systemic administration is highly toxic. With the aim of developing an efficient light-controllable modulator of GABA receptors, we constructed azobenzene-nitrazepam (Azo-NZ1), which is composed of a nitrazepam moiety merged to an azobenzene photoisomerizable group. EXPERIMENTAL APPROACH The experiments were carried out on cultured cells expressing Cys-loop receptors of known subunit composition and in brain slices using patch-clamp. Site-directed mutagenesis and molecular modelling approaches were applied to evaluate the mechanism of action of Azo-NZ1. KEY RESULTS At visible light, being in trans-configuration, Azo-NZ1 blocked heteromeric α1/β2/γ2 GABAA receptors, ρ2 GABAA (GABAC ), and α2 glycine receptors, whereas switching the compound into cis-state by UV illumination restored the activity. Azo-NZ1 successfully photomodulated GABAergic currents recorded from dentate gyrus neurons. We demonstrated that in trans-configuration, Azo-NZ1 blocks the Cl-selective ion pore of GABA receptors interacting mainly with the 2' level of the TM2 region. CONCLUSIONS AND IMPLICATIONS Azo-NZ1 is a soluble light-driven Cl-channel blocker, which allows photo-modulation of the activity induced by anion-selective Cys-loop receptors. Azo-NZ1 is able to control GABAergic postsynaptic currents and provides new opportunities to study inhibitory neurotransmission using patterned illumination.
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Affiliation(s)
- Galyna Maleeva
- INSERM, INS, Institut de Neurosciences des Systèmes, Aix-Marseille University, Marseille, France
| | - Daniel Wutz
- Institute of Organic Chemistry, University of Regensburg, Regensburg, Germany
| | - Karin Rustler
- Institute of Organic Chemistry, University of Regensburg, Regensburg, Germany
| | - Alba Nin-Hill
- Departament de Química Inorgànica i Orgànica (Secció de Química Orgànica) and Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, Barcelona, Spain
| | - Carme Rovira
- Departament de Química Inorgànica i Orgànica (Secció de Química Orgànica) and Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, Barcelona, Spain.,Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain
| | - Elena Petukhova
- Department of Normal Physiology, Kazan State Medical University, Kazan, Russia
| | - Antoni Bautista-Barrufet
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
| | - Alexandre Gomila-Juaneda
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
| | - Petra Scholze
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University Vienna, Vienna, Austria
| | - Franck Peiretti
- INSERM 1263, INRA 1260, C2VN, Aix-Marseille Université, Marseille, France
| | - Mercedes Alfonso-Prieto
- Department of Computational Biomedicine, Institute for Advanced Simulations IAS-5 and Institute of Neuroscience and Medicine INM-9, Forschungszentrum Jülich GmbH, Jülich, Germany.,Cécile and Oskar Vogt Institute for Brain Research, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Burkhard König
- Institute of Organic Chemistry, University of Regensburg, Regensburg, Germany
| | - Pau Gorostiza
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain.,Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain.,Network Biomedical Research Center in Biomaterials, Bioengineering and Nanomedicine (CIBER-BBN), Spain
| | - Piotr Bregestovski
- INSERM, INS, Institut de Neurosciences des Systèmes, Aix-Marseille University, Marseille, France.,Department of Normal Physiology, Kazan State Medical University, Kazan, Russia.,Institute of Neurosciences, Kazan State Medical University, Kazan, Russia
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142
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Norleans J, Wang J, Kuryatov A, Leffler A, Doebelin C, Kamenecka TM, Lindstrom J. Discovery of an intrasubunit nicotinic acetylcholine receptor-binding site for the positive allosteric modulator Br-PBTC. J Biol Chem 2019; 294:12132-12145. [PMID: 31221718 DOI: 10.1074/jbc.ra118.006253] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2018] [Revised: 06/19/2019] [Indexed: 11/06/2022] Open
Abstract
Nicotinic acetylcholine receptor (nAChR) ligands that lack agonist activity but enhance activation in the presence of an agonist are called positive allosteric modulators (PAMs). nAChR PAMs have therapeutic potential for the treatment of nicotine addiction and several neuropsychiatric disorders. PAMs need to be selectively targeted toward certain nAChR subtypes to tap this potential. We previously discovered a novel PAM, (R)-7-bromo-N-(piperidin-3-yl)benzo[b]thiophene-2-carboxamide (Br-PBTC), which selectively potentiates the opening of α4β2*, α2β2*, α2β4*, and (α4β4)2α4 nAChRs and reactivates some of these subtypes when desensitized (* indicates the presence of other subunits). We located the Br-PBTC-binding site through mutagenesis and docking in α4. The amino acids Glu-282 and Phe-286 near the extracellular domain on the third transmembrane helix were found to be crucial for Br-PBTC's PAM effect. E282Q abolishes Br-PBTC potentiation. Using (α4E282Qβ2)2α5 nAChRs, we discovered that the trifluoromethylated derivatives of Br-PBTC can potentiate channel opening of α5-containing nAChRs. Mutating Tyr-430 in the α5 M4 domain changed α5-selectivity among Br-PBTC derivatives. There are two kinds of α4 subunits in α4β2 nAChRs. Primary α4 forms an agonist-binding site with another β2 subunit. Accessory α4 forms an agonist-binding site with another α4 subunit. The pharmacological effect of Br-PBTC depends both on its own and agonists' occupancy of primary and accessory α4 subunits. Br-PBTC reactivates desensitized (α4β2)2α4 nAChRs. Its full efficacy requires intact Br-PBTC sites in at least one accessory and one primary α4 subunit. PAM potency increases with higher occupancy of the agonist sites. Br-PBTC and its derivatives should prove useful as α subunit-selective nAChR PAMs.
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Affiliation(s)
- Jack Norleans
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Jingyi Wang
- Department of Neuroscience, University of Texas at Austin, Austin, Texas 78712
| | - Alexander Kuryatov
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Abba Leffler
- Neuroscience Graduate Program, Sackler Institute of Graduate Biomedical Sciences, New York University School of Medicine, New York, New York 10010
| | - Christelle Doebelin
- Department of Molecular Medicine, The Scripps Research Institute, Scripps, Florida, Jupiter, Florida 33458
| | - Theodore M Kamenecka
- Department of Molecular Medicine, The Scripps Research Institute, Scripps, Florida, Jupiter, Florida 33458
| | - Jon Lindstrom
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania 19104.
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143
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Yu R, Tae HS, Xu Q, Craik DJ, Adams DJ, Jiang T, Kaas Q. Molecular dynamics simulations of dihydro-β-erythroidine bound to the human α4β2 nicotinic acetylcholine receptor. Br J Pharmacol 2019; 176:2750-2763. [PMID: 31062355 DOI: 10.1111/bph.14698] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2018] [Revised: 03/20/2019] [Accepted: 04/10/2019] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND AND PURPOSE The heteromeric α4β2 nicotinic acetylcholine receptor (nAChR) is abundant in the human brain and is associated with a range of CNS disorders. This nAChR subtype has been recently crystallised in a conformation that was proposed to represent a desensitised state. Here, we investigated the conformational transition mechanism of this nAChR from a desensitised to a closed/resting state. EXPERIMENTAL APPROACH The competitive antagonist dihydro-β-erythroidine (DHβE) was modelled by replacement of the agonist nicotine in the α4β2 nAChR experimental structure. DHβE is used both in vitro and in vivo for its ability to block α4β2 nAChRs. This system was studied by three molecular dynamics simulations with a combined simulation time of 2.6 μs. Electrophysiological studies of mutated receptors were performed to validate the simulation results. KEY RESULTS The relative positions of the extracellular and transmembrane domains in the models are distinct from those of the desensitised state structure and are compatible with experimental structures of Cys-loop receptors captured in a closed/resting state. CONCLUSIONS AND IMPLICATIONS Our model suggests that the side chains of α4 L257 (9') and α4 L264 (16') are the main constrictions in the transmembrane pore. The involvement of position 9' in channel gating is well established, but position 16' was only previously identified as a gate for the bacterial channels, ELIC and GLIC. L257 but not L264 was found to influence the slow component of desensitisation. The structure of the antagonist-bound state proposed here should be valuable for the development of therapeutic or insecticide compounds.
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Affiliation(s)
- Rilei Yu
- Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, Qingdao, China.,Laboratory for Marine Drugs and Bioproducts, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
| | - Han-Shen Tae
- Illawarra Health and Medical Research Institute (IHMRI), University of Wollongong, Wollongong, NSW, Australia
| | - Qingliang Xu
- Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, Qingdao, China.,Laboratory for Marine Drugs and Bioproducts, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
| | - David J Craik
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - David J Adams
- Illawarra Health and Medical Research Institute (IHMRI), University of Wollongong, Wollongong, NSW, Australia
| | - Tao Jiang
- Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, Qingdao, China.,Laboratory for Marine Drugs and Bioproducts, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
| | - Quentin Kaas
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
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144
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Crnjar A, Comitani F, Melis C, Molteni C. Mutagenesis computer experiments in pentameric ligand-gated ion channels: the role of simulation tools with different resolution. Interface Focus 2019; 9:20180067. [PMID: 31065340 PMCID: PMC6501341 DOI: 10.1098/rsfs.2018.0067] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/26/2019] [Indexed: 12/21/2022] Open
Abstract
Pentameric ligand-gated ion channels (pLGICs) are an important class of widely expressed membrane neuroreceptors, which play a crucial role in fast synaptic communications and are involved in several neurological conditions. They are activated by the binding of neurotransmitters, which trigger the transmission of an electrical signal via facilitated ion flux. They can also be activated, inhibited or modulated by a number of drugs. Mutagenesis electrophysiology experiments, with natural or unnatural amino acids, have provided a large body of functional data that, together with emerging structural information from X-ray spectroscopy and cryo-electron microscopy, are helping unravel the complex working mechanisms of these neuroreceptors. Computer simulations are complementing these mutagenesis experiments, with insights at various levels of accuracy and resolution. Here, we review how a selection of computational tools, including first principles methods, classical molecular dynamics and enhanced sampling techniques, are contributing to construct a picture of how pLGICs function and can be pharmacologically targeted to treat the disorders they are responsible for.
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Affiliation(s)
- Alessandro Crnjar
- King’s College London, Department of Physics, Strand, London WC2R 2LS, UK
| | - Federico Comitani
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Claudio Melis
- Universitá degli Studi di Cagliari, Complesso Universitario di Monserrato, Dipartimento di Fisica, S.P. Monserrato-Sestu Km 0,700, Monserrato (CA) 09042, Italy
| | - Carla Molteni
- King’s College London, Department of Physics, Strand, London WC2R 2LS, UK
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145
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Scott S, Aricescu AR. A structural perspective on GABA A receptor pharmacology. Curr Opin Struct Biol 2019; 54:189-197. [PMID: 31129381 DOI: 10.1016/j.sbi.2019.03.023] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Revised: 03/14/2019] [Accepted: 03/19/2019] [Indexed: 10/26/2022]
Abstract
GABAA receptors are pentameric ligand-gated chloride channels of crucial importance for the vertebrate nervous system physiology. They typically modulate the fast inhibitory neurotransmission, and represent the target receptors for major classes of drugs used in the clinic, such as benzodiazepines and general anesthetics. Recent technological progress in structural biology, in particular single-particle cryo-electron microscopy, has led to fundamental advances in understanding the detailed organization and signalling mechanisms of major GABAA receptor subtypes. This effort culminated with the high-resolution structural analysis of an intact, full-length human heteropentameric receptor, α1β3γ2, in a lipid bilayer and in complex with small molecule ligands including the commonly used benzodiazepines diazepam (Valium) and alprazolam (Xanax). These structures reveal multiple aspects of receptor activation and provide a path for rational design of subunit-specific GABAA receptor modulators.
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Affiliation(s)
- Suzanne Scott
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK; Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, OX1 3PT, UK.
| | - Alexandru Radu Aricescu
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK; Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK.
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146
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Lieb A, Weston M, Kullmann DM. Designer receptor technology for the treatment of epilepsy. EBioMedicine 2019; 43:641-649. [PMID: 31078519 PMCID: PMC6558262 DOI: 10.1016/j.ebiom.2019.04.059] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 04/26/2019] [Accepted: 04/29/2019] [Indexed: 12/20/2022] Open
Abstract
Epilepsy remains refractory to medical treatment in ~30% of patients despite decades of new drug development. Neurosurgery to remove or disconnect the seizure focus is often curative but frequently contraindicated by risks of irreversible impairment to brain function. Novel therapies are therefore required that better balance seizure suppression against the risks of side effects. Among experimental gene therapies, chemogenetics has the major advantage that the action on the epileptogenic zone can be modulated on demand. Two broad approaches are to use a designer G-protein-coupled receptor or a modified ligand gated ion channel, targeted to specific neurons in the epileptogenic zone using viral vectors and cell-type selective promoters. The receptor can be activated on demand by either an exogenous compound or by pathological levels of extracellular glutamate that occur in epileptogenic tissue. We review the principal designer receptor technologies and their modes of action. We compare the drawbacks and benefits of each designer receptor with particular focus on the drug activators and the potential for clinical translation in epilepsy. Inhibitory designer receptors (DRs) allow on-demand suppression of seizures upon activation by exogenous drugs or endogenous neurotransmitters. DRs include modified G-protein coupled receptors, chimaeric ligand-gated ion channels, and mutated non-mammalian channels. Identification of drug activators of DRs that are already approved for use in humans significantly accelerates clinical translation.
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Affiliation(s)
- Andreas Lieb
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, University College London, UK
| | - Mikail Weston
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, University College London, UK
| | - Dimitri M Kullmann
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, University College London, UK.
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147
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Harpole TJ, Grosman C. A Crucial Role for Side-Chain Conformation in the Versatile Charge Selectivity of Cys-Loop Receptors. Biophys J 2019; 116:1667-1681. [PMID: 31005237 PMCID: PMC6506641 DOI: 10.1016/j.bpj.2019.03.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 03/18/2019] [Accepted: 03/25/2019] [Indexed: 10/27/2022] Open
Abstract
Whether synaptic transmission is excitatory or inhibitory depends, to a large extent, on whether the ion channels that open upon binding the released neurotransmitter conduct cations or anions. The mechanistic basis of the opposite charge selectivities of Cys-loop receptors has only recently begun to emerge. It is now clear that ionized side chains-whether pore-facing or buried-in the first α-helical turn of the second transmembrane segments underlie this phenomenon and that the electrostatics of backbone atoms are not critically involved. Moreover, on the basis of electrophysiological observations, it has recently been suggested that not only the sign of charged side chains but also their conformation are crucial determinants of cation-anion selectivity. To challenge these ideas with the chemical and structural rigor that electrophysiological observations naturally lack, we performed molecular dynamics, Brownian dynamics, and electrostatics calculations of ion permeation. To this end, we used structural models of the open-channel conformation of the α1 glutamate-gated Cl- channel and the α1 glycine receptor. Our results provided full support to the notion that the conformation of charged sides chains matters for charge selectivity. Indeed, whereas some rotamers of the buried arginines at position 0' conferred high selectivity for anions, others supported the permeation of cations and anions at similar rates or even allowed the faster permeation of cations. Furthermore, we found that modeling glutamates at position -1' of the anion-selective α1 glycine receptor open-state structure-instead of the five native alanines-switches charge selectivity also in a conformation-dependent manner, with some glutamate rotamers being much more effective at conferring selectivity for cations than others. Regarding pore size, we found that the mere expansion of the pore has only a minimal impact on cation-anion selectivity. Overall, these results bring to light the previously unappreciated impact of side-chain conformation on charge selectivity in Cys-loop receptors.
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Affiliation(s)
- Tyler J Harpole
- Center for Biophysics and Quantitative Biology, Urbana, Illinois
| | - Claudio Grosman
- Center for Biophysics and Quantitative Biology, Urbana, Illinois; Department of Molecular and Integrative Physiology, Urbana, Illinois; Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, Illinois.
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148
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Mazzone GL, Nistri A. Modulation of extrasynaptic GABAergic receptor activity influences glutamate release and neuronal survival following excitotoxic damage to mouse spinal cord neurons. Neurochem Int 2019; 128:175-185. [PMID: 31051211 DOI: 10.1016/j.neuint.2019.04.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 04/08/2019] [Accepted: 04/30/2019] [Indexed: 12/14/2022]
Abstract
Excitotoxic levels of released glutamate trigger a cascade of deleterious cellular events leading to delayed neuronal death. This phenomenon implies extensive dysregulation in the balance between network excitation and inhibition. Our hypothesis was that enhancing network inhibition should prevent excitotoxicity and provide neuroprotection. To test this notion, we used mouse organotypic spinal slice cultures and explored if excitotoxicity caused by the potent glutamate analogue kainate was blocked by pharmacological increase in GABAA receptor activity. To this end we monitored (with a biosensor) real-time glutamate release following 1 h kainate application and quantified neuronal survival 24 h later. Glutamate release evoked by kainate was strongly decreased by the allosteric GABAA modulator midazolam (10 nM) or the GABA agonist THIP (10 μM), leading to neuroprotection. On the contrary, much higher glutamate release was induced by the GABA antagonist bicuculline (20 μM) that inhibits synaptic and extrasynaptic GABAA receptors. Gabazine (20 μM), an antagonist of synaptic GABAA receptors, had no effect on glutamate release or neuroprotection. No effect was observed with the glycine antagonist strychnine or the glycine agonist L-alanine. These findings indicate that enhancement of GABA receptor activity was an effective tool to counteract excitotoxic death in spinal networks. In view of the potent activity by THIP, preferentially acting on extrasynaptic GABAA receptors, the present data imply a significant role for extrasynaptic GABAA receptors in sparing spinal cord neurons from injury.
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Affiliation(s)
- Graciela L Mazzone
- Instituto de Investigaciones en Medicina Traslacional (IIMT), CONICET-Universidad Austral, Derqui-Pilar, Buenos Aires, Argentina.
| | - Andrea Nistri
- Neuroscience Dept., International School for Advanced Studies (SISSA), Trieste, Italy
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149
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Changeux JP. The nicotinic acetylcholine receptor: a typical 'allosteric machine'. Philos Trans R Soc Lond B Biol Sci 2019; 373:rstb.2017.0174. [PMID: 29735728 DOI: 10.1098/rstb.2017.0174] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/06/2017] [Indexed: 12/26/2022] Open
Abstract
The concept of allosteric interaction was initially proposed to account for the inhibitory feedback mechanism mediated by bacterial regulatory enzymes. In contrast with the classical mechanism of competitive, steric, interaction between ligands for a common site, allosteric interactions take place between topographically distinct sites and are mediated by a discrete and reversible conformational change of the protein. The concept was soon extended to membrane receptors for neurotransmitters and shown to apply to the signal transduction process which, in the case of the acetylcholine nicotinic receptor (nAChR), links the ACh binding site to the ion channel. Pharmacological effectors, referred to as allosteric modulators, such as Ca2+ ions and ivermectin, were discovered that enhance the transduction process when they bind to sites distinct from the orthosteric ACh site and the ion channel. The recent X-ray and electron microscopy structures, at atomic resolution, of the resting and active conformations of several homologues of the nAChR, in combination with atomistic molecular dynamics simulations reveal a stepwise quaternary transition in the transduction process with tertiary changes modifying the boundaries between subunits. These interfaces host orthosteric and allosteric modulatory sites which structural organization changes in the course of the transition. The nAChR appears as a typical allosteric machine. The model emerging from these studies has led to the conception and development of several new pharmacological agents.This article is part of a discussion meeting issue 'Allostery and molecular machines'.
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Affiliation(s)
- Jean-Pierre Changeux
- CNRS UMR 3571, Institut Pasteur, Paris 75724, France .,Communications Cellulaires, Collège de France, Paris 75005, France
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150
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San Martín VP, Burgos CF, Marileo AM, Lara CO, Sazo A, Fuentealba J, Guzmán L, Castro PA, Aguayo LG, Moraga-Cid G, Yévenes GE. Inhibitory Actions of Tropeines on the α3 Glycine Receptor Function. Front Pharmacol 2019; 10:331. [PMID: 31024303 PMCID: PMC6465966 DOI: 10.3389/fphar.2019.00331] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Accepted: 03/19/2019] [Indexed: 01/15/2023] Open
Abstract
Glycine receptors (GlyRs) are chloride-permeable pentameric ligand-gated ion channels. The inhibitory activity of GlyRs is essential for many physiological processes, such as motor control and respiration. In addition, several pathological states, such as hyperekplexia, epilepsy, and chronic pain, are associated with abnormal glycinergic inhibition. Recent studies have pointed out that positive allosteric modulators targeting the GlyR α3 subunit (α3GlyR) displayed beneficial effects in chronic pain models. Interestingly, previous electrophysiological studies have shown that tropeines, which are a family of synthetic antagonists of the serotonin type 3 receptors (5-HT3Rs), potentiate the activity of GlyRs conformed by α1 subunits. However, despite its importance as a pharmacological target in chronic pain, it is currently unknown whether the α3GlyR function is modulated by tropeines. Using electrophysiological techniques and molecular docking simulations, here we show that tropeines are inhibitors of the α3GlyR function. Tropisetron, a prototypical tropeine, exerted concentration-dependent inhibitory effects on α3GlyRs at the low micromolar range. In addition, three other tropeines showed similar effects. Single-channel recordings show that tropisetron inhibition is associated with a decrease in the open probability of the ion channel. Molecular docking assays suggest that tropeines preferentially bind to an agonist-free, closed state of the ion channel. The tropeine binding occurs in a discrete pocket around the vicinity of the orthosteric site within the extracellular domain of α3GlyR. Thus, our results describe the pharmacological modulation of tropeines on α3GlyRs. These findings may contribute to the development of GlyR-selective tropeine derivatives for basic and/or clinical applications.
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Affiliation(s)
- Victoria P San Martín
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile
| | - Carlos F Burgos
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile
| | - Ana M Marileo
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile
| | - Cesar O Lara
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile
| | - Anggelo Sazo
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile
| | - Jorge Fuentealba
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile
| | - Leonardo Guzmán
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile
| | - Patricio A Castro
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile
| | - Luis G Aguayo
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile
| | - Gustavo Moraga-Cid
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile
| | - Gonzalo E Yévenes
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile
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