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Novel methyllycaconitine analogues selective for the α4β2 over α7 nicotinic acetylcholine receptors. Bioorg Med Chem 2021; 51:116516. [PMID: 34798380 DOI: 10.1016/j.bmc.2021.116516] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 10/20/2021] [Accepted: 10/22/2021] [Indexed: 10/19/2022]
Abstract
Analogues of methyllycaconitine (MLA) based on a (3-ethyl-9-methylidene-3-azabicyclo[3.3.1]nonan-1-yl)methanol template have been designed and synthesised that incorporate the modified ester sidechains distinct from that present in the natural product. Electrophysiology experiments using Xenopus oocytes expressing nicotinic acetylcholine receptors (nAChRs) revealed selected analogues served as non-competitive inhibitors that showed selectivity for the α4β2 over α7 nAChR subtypes, and selectivity for the (α4)3(β2)2 over (α4)2(β2)3 stoichiometry. This study more clearly defines the biological effects of MLA analogues and identifies strategies for the development of MLA analogues as selective ligands for the α4β2 nAChR subtype.
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Duarte Y, Rojas M, Canan J, Pérez EG, González-Nilo F, García-Colunga J. Different Classes of Antidepressants Inhibit the Rat α7 Nicotinic Acetylcholine Receptor by Interacting within the Ion Channel: A Functional and Structural Study. Molecules 2021; 26:molecules26040998. [PMID: 33668529 PMCID: PMC7918632 DOI: 10.3390/molecules26040998] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 02/05/2021] [Accepted: 02/11/2021] [Indexed: 12/21/2022] Open
Abstract
Several antidepressants inhibit nicotinic acetylcholine receptors (nAChRs) in a non-competitive and voltage-dependent fashion. Here, we asked whether antidepressants with a different structure and pharmacological profile modulate the rat α7 nAChR through a similar mechanism by interacting within the ion-channel. We applied electrophysiological (recording of the ion current elicited by choline, ICh, which activates α7 nAChRs from rat CA1 hippocampal interneurons) and in silico approaches (homology modeling of the rat α7 nAChR, molecular docking, molecular dynamics simulations, and binding free energy calculations). The antidepressants inhibited ICh with the order: norfluoxetine ~ mirtazapine ~ imipramine < bupropion ~ fluoxetine ~ venlafaxine ~ escitalopram. The constructed homology model of the rat α7 nAChR resulted in the extracellular vestibule and the channel pore is highly negatively charged, which facilitates the permeation of cations and the entrance of the protonated form of antidepressants. Molecular docking and molecular dynamics simulations were carried out within the ion−channel of the α7 nAChR, revealing that the antidepressants adopt poses along the receptor channel, with slightly different binding-free energy values. Furthermore, the inhibition of ICh and free energy values for each antidepressant-receptor complex were highly correlated. Thus, the α7 nAChR is negatively modulated by a variety of antidepressants interacting in the ion−channel.
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Affiliation(s)
- Yorley Duarte
- Center for Bioinformatics and Integrative Biology, Facultad de Ciencias de la Vida, Universidad Andrés Bello, Av. República 330, Santiago 8370146, Chile; (Y.D.); (M.R.); (J.C.); (F.G.-N.)
- Interdisciplinary Centre for Neuroscience of Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2381850, Chile
| | - Maximiliano Rojas
- Center for Bioinformatics and Integrative Biology, Facultad de Ciencias de la Vida, Universidad Andrés Bello, Av. República 330, Santiago 8370146, Chile; (Y.D.); (M.R.); (J.C.); (F.G.-N.)
| | - Jonathan Canan
- Center for Bioinformatics and Integrative Biology, Facultad de Ciencias de la Vida, Universidad Andrés Bello, Av. República 330, Santiago 8370146, Chile; (Y.D.); (M.R.); (J.C.); (F.G.-N.)
| | - Edwin G. Pérez
- Department of Organic Chemistry, Faculty of Chemistry and Pharmacy, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile;
| | - Fernando González-Nilo
- Center for Bioinformatics and Integrative Biology, Facultad de Ciencias de la Vida, Universidad Andrés Bello, Av. República 330, Santiago 8370146, Chile; (Y.D.); (M.R.); (J.C.); (F.G.-N.)
- Interdisciplinary Centre for Neuroscience of Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2381850, Chile
| | - Jesús García-Colunga
- Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus Juriquilla, Boulevard Juriquilla 3001, Juriquilla, Querétaro 76230, Mexico
- Correspondence: ; Tel.: +52-442-238-1063
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Ho TNT, Abraham N, Lewis RJ. Structure-Function of Neuronal Nicotinic Acetylcholine Receptor Inhibitors Derived From Natural Toxins. Front Neurosci 2020; 14:609005. [PMID: 33324158 PMCID: PMC7723979 DOI: 10.3389/fnins.2020.609005] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Accepted: 10/30/2020] [Indexed: 12/19/2022] Open
Abstract
Neuronal nicotinic acetylcholine receptors (nAChRs) are prototypical cation-selective, ligand-gated ion channels that mediate fast neurotransmission in the central and peripheral nervous systems. nAChRs are involved in a range of physiological and pathological functions and hence are important therapeutic targets. Their subunit homology and diverse pentameric assembly contribute to their challenging pharmacology and limit their drug development potential. Toxins produced by an extensive range of algae, plants and animals target nAChRs, with many proving pivotal in elucidating receptor pharmacology and biochemistry, as well as providing templates for structure-based drug design. The crystal structures of these toxins with diverse chemical profiles in complex with acetylcholine binding protein (AChBP), a soluble homolog of the extracellular ligand-binding domain of the nAChRs and more recently the extracellular domain of human α9 nAChRs, have been reported. These studies have shed light on the diverse molecular mechanisms of ligand-binding at neuronal nAChR subtypes and uncovered critical insights useful for rational drug design. This review provides a comprehensive overview and perspectives obtained from structure and function studies of diverse plant and animal toxins and their associated inhibitory mechanisms at neuronal nAChRs.
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Affiliation(s)
| | | | - Richard J. Lewis
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, Australia
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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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Eldridge C, Quek G, Sako M, Ryan JH, Saubern S, Chebib M, Macdonald JM. The preparation of novel histrionicotoxin analogues and their activity towards the α4β2 and α7 nicotinic acetylcholine receptors. Tetrahedron 2018. [DOI: 10.1016/j.tet.2017.11.047] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Bach TB, Jensen AA, Petersen JG, Sørensen TE, Della Volpe S, Liu J, Blaazer AR, van Muijlwijk-Koezen JE, Balle T, Frølund B. Exploration of the molecular architecture of the orthosteric binding site in the α4β2 nicotinic acetylcholine receptor with analogs of 3-(dimethylamino)butyl dimethylcarbamate (DMABC) and 1-(pyridin-3-yl)-1,4-diazepane. Eur J Med Chem 2015; 102:425-44. [DOI: 10.1016/j.ejmech.2015.07.024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Revised: 07/10/2015] [Accepted: 07/13/2015] [Indexed: 10/23/2022]
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Biomolecular recognition of antagonists by α7 nicotinic acetylcholine receptor: Antagonistic mechanism and structure-activity relationships studies. Eur J Pharm Sci 2015; 76:119-32. [PMID: 25963024 DOI: 10.1016/j.ejps.2015.05.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Revised: 04/24/2015] [Accepted: 05/06/2015] [Indexed: 12/20/2022]
Abstract
As the key constituent of ligand-gated ion channels in the central nervous system, nicotinic acetylcholine receptors (nAChRs) and neurodegenerative diseases are strongly coupled in the human species. In recently years the developments of selective agonists by using nAChRs as the drug target have made a large progress, but the studies of selective antagonists are severely lacked. Currently these antagonists rest mainly on the extraction of partly natural products from some animals and plants; however, the production of these crude substances is quite restricted, and artificial synthesis of nAChR antagonists is still one of the completely new research fields. In the context of this manuscript, our primary objective was to comprehensively analyze the recognition patterns and the critical interaction descriptors between target α7 nAChR and a series of the novel compounds with potentially antagonistic activity by means of virtual screening, molecular docking and molecular dynamics simulation, and meanwhile these recognition reactions were also compared with the biointeraction of α7 nAChR with a commercially natural antagonist - methyllycaconitine. The results suggested clearly that there are relatively obvious differences of molecular structures between synthetic antagonists and methyllycaconitine, while the two systems have similar recognition modes on the whole. The interaction energy and the crucially noncovalent forces of the α7 nAChR-antagonists are ascertained according to the method of Molecular Mechanics/Generalized Born Surface Area. Several amino acid residues, such as B/Tyr-93, B/Lys-143, B/Trp-147, B/Tyr-188, B/Tyr-195, A/Trp-55 and A/Leu-118 played a major role in the α7 nAChR-antagonist recognition processes, in particular, residues B/Tyr-93, B/Trp-147 and B/Tyr-188 are the most important. These outcomes tally satisfactorily with the discussions of amino acid mutations. Based on the explorations of three-dimensional quantitative structure-activity relationships, the structure-antagonistic activity relationships of antagonists and the characteristics of α7 nAChR-ligand recognitions were received a reasonable summary as well. These attempts emerged herein would not only provide helpful guidance for the design of α7 nAChR antagonists, but shed new light on the subsequent researches in antagonistic mechanism.
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Gallagher R, Chebib M, Balle T, McLeod MD. Thiol-Reactive Analogues of Galanthamine, Codeine, and Morphine as Potential Probes to Interrogate Allosteric Binding within Nicotinic Acetylcholine Receptors. Aust J Chem 2015. [DOI: 10.1071/ch15475] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Alkaloids including galanthamine (1) and codeine (2) are reported to be positive allosteric modulators of nicotinic acetylcholine receptors (nAChRs), but the binding sites responsible for this activity are not known with certainty. Analogues of galanthamine (1), codeine (2), and morphine (3) with reactivity towards cysteine thiols were synthesized including conjugated enone derivatives of the three alkaloids 4–6 and two chloro-alkane derivatives of codeine 7 and 8. The stability of the enones was deemed sufficient for use in buffered aqueous solutions, and their reactivity towards thiols was assessed by determining the kinetics of reaction with a cysteine derivative. All three enone derivatives were of sufficient reactivity and stability to be used in covalent trapping, an extension of the substituted cysteine accessibility method, to elucidate the allosteric binding sites of galanthamine and codeine at nAChRs.
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Absalom NL, Quek G, Lewis TM, Qudah T, von Arenstorff I, Ambrus JI, Harpsøe K, Karim N, Balle T, McLeod MD, Chebib M. Covalent trapping of methyllycaconitine at the α4-α4 interface of the α4β2 nicotinic acetylcholine receptor: antagonist binding site and mode of receptor inhibition revealed. J Biol Chem 2013; 288:26521-32. [PMID: 23893416 DOI: 10.1074/jbc.m113.475053] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The α4β2 nicotinic acetylcholine receptors (nAChRs) are widely expressed in the brain and are implicated in a variety of physiological processes. There are two stoichiometries of the α4β2 nAChR, (α4)2(β2)3 and (α4)3(β2)2, with different sensitivities to acetylcholine (ACh), but their pharmacological profiles are not fully understood. Methyllycaconitine (MLA) is known to be an antagonist of nAChRs. Using the two-electrode voltage clamp technique and α4β2 nAChRs in the Xenopus oocyte expression system, we demonstrate that inhibition by MLA occurs via two different mechanisms; that is, a direct competitive antagonism and an apparently insurmountable mechanism that only occurs after preincubation with MLA. We hypothesized an additional MLA binding site in the α4-α4 interface that is unique to this stoichiometry. To prove this, we covalently trapped a cysteine-reactive MLA analog at an α4β2 receptor containing an α4(D204C) mutation predicted by homology modeling to be within reach of the reactive probe. We demonstrate that covalent trapping results in irreversible reduction of ACh-elicited currents in the (α4)3(β2)2 stoichiometry, indicating that MLA binds to the α4-α4 interface of the (α4)3(β2)2 and providing direct evidence of ligand binding to the α4-α4 interface. Consistent with other studies, we propose that the α4-α4 interface is a structural target for potential therapeutics that modulate (α4)3(β2)2 nAChRs.
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Affiliation(s)
- Nathan L Absalom
- From the Faculty of Pharmacy, University of Sydney, Sydney, NSW 2006, Australia
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NMR structures of the transmembrane domains of the α4β2 nAChR. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:1261-8. [PMID: 22361591 DOI: 10.1016/j.bbamem.2012.02.008] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Revised: 01/30/2012] [Accepted: 02/07/2012] [Indexed: 11/21/2022]
Abstract
The α4β2 nicotinic acetylcholine receptor (nAChR) is the predominant heteromeric subtype of nAChRs in the brain, which has been implicated in numerous neurological conditions. The structural information specifically for the α4β2 and other neuronal nAChRs is presently limited. In this study, we determined structures of the transmembrane (TM) domains of the α4 and β2 subunits in lauryldimethylamine-oxide (LDAO) micelles using solution NMR spectroscopy. NMR experiments and size exclusion chromatography-multi-angle light scattering (SEC-MALS) analysis demonstrated that the TM domains of α4 and β2 interacted with each other and spontaneously formed pentameric assemblies in the LDAO micelles. The Na(+) flux assay revealed that α4β2 formed Na(+) permeable channels in lipid vesicles. Efflux of Na(+) through the α4β2 channels reduced intra-vesicle Sodium Green™ fluorescence in a time-dependent manner that was not observed in vesicles without incorporating α4β2. The study provides structural insight into the TM domains of the α4β2 nAChR. It offers a valuable structural framework for rationalizing extensive biochemical data collected previously on the α4β2 nAChR and for designing new therapeutic modulators.
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Ambrus JI, Halliday JI, Kanizaj N, Absalom N, Harpsøe K, Balle T, Chebib M, McLeod MD. Covalent attachment of antagonists to the α7 nicotinic acetylcholine receptor: synthesis and reactivity of substituted maleimides. Chem Commun (Camb) 2012; 48:6699-701. [DOI: 10.1039/c2cc32442c] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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