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Otvos RA, Krishnamoorthy Iyer J, van Elk R, Ulens C, Niessen WMA, Somsen GW, Kini RM, Smit AB, Kool J. Development of Plate Reader and On-Line Microfluidic Screening to Identify Ligands of the 5-Hydroxytryptamine Binding Protein in Venoms. Toxins (Basel) 2015; 7:2336-53. [PMID: 26114334 PMCID: PMC4516916 DOI: 10.3390/toxins7072336] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 05/06/2015] [Accepted: 06/16/2015] [Indexed: 11/16/2022] Open
Abstract
The 5-HT3 receptor is a ligand-gated ion channel, which is expressed in the nervous system. Its antagonists are used clinically for treatment of postoperative- and radiotherapy-induced emesis and irritable bowel syndrome. In order to better understand the structure and function of the 5-HT3 receptor, and to allow for compound screening at this receptor, recently a serotonin binding protein (5HTBP) was engineered with the Acetylcholine Binding Protein as template. In this study, a fluorescence enhancement assay for 5HTBP ligands was developed in plate-reader format and subsequently used in an on-line microfluidic format. Both assay types were validated using an existing radioligand binding assay. The on-line microfluidic assay was coupled to HPLC via a post-column split which allowed parallel coupling to a mass spectrometer to collect MS data. This high-resolution screening (HRS) system is well suitable for compound mixture analysis. As a proof of principle, the venoms of Dendroapsis polylepis, Pseudonaja affinis and Pseudonaja inframacula snakes were screened and the accurate masses of the found bioactives were established. To demonstrate the subsequent workflow towards structural identification of bioactive proteins and peptides, the partial amino acid sequence of one of the bioactives from the Pseudonaja affinis venom was determined using a bottom-up proteomics approach.
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Affiliation(s)
- Reka A. Otvos
- AIMMS Division of BioAnalytical Chemistry, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands; E-Mails: (R.A.O.); (W.M.A.N.); (G.W.S.)
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands; E-Mails: (R.E.); (A.B.S.)
| | - Janaki Krishnamoorthy Iyer
- Department of Biological Sciences, Faculty of Science, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore; E-Mails: (J.K.I.); (R.M.K.)
| | - René van Elk
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands; E-Mails: (R.E.); (A.B.S.)
| | - Chris Ulens
- Laboratory of Structural Neurobiology, Department of Cellular and Molecular Medicine, Katholieke Universiteit Leuven, Herestraat 49, PB 601, B-3000 Leuven, Belgium; E-Mail:
| | - Wilfried M. A. Niessen
- AIMMS Division of BioAnalytical Chemistry, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands; E-Mails: (R.A.O.); (W.M.A.N.); (G.W.S.)
- Hyphen MassSpec, de Wetstraat 8, 2332 XT Leiden, The Netherlands
| | - Govert W. Somsen
- AIMMS Division of BioAnalytical Chemistry, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands; E-Mails: (R.A.O.); (W.M.A.N.); (G.W.S.)
| | - R. Manjunatha Kini
- Department of Biological Sciences, Faculty of Science, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore; E-Mails: (J.K.I.); (R.M.K.)
| | - August B. Smit
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands; E-Mails: (R.E.); (A.B.S.)
| | - Jeroen Kool
- AIMMS Division of BioAnalytical Chemistry, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands; E-Mails: (R.A.O.); (W.M.A.N.); (G.W.S.)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +31-20-5987542; Fax: +31-20-5987543
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Stornaiuolo M, De Kloe GE, Rucktooa P, Fish A, van Elk R, Edink ES, Bertrand D, Smit AB, de Esch IJP, Sixma TK. Assembly of a π-π stack of ligands in the binding site of an acetylcholine-binding protein. Nat Commun 2013; 4:1875. [PMID: 23695669 PMCID: PMC3674282 DOI: 10.1038/ncomms2900] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Accepted: 04/17/2013] [Indexed: 12/11/2022] Open
Abstract
Acetylcholine-binding protein is a water-soluble homologue of the extracellular ligand-binding domain of cys-loop receptors. It is used as a structurally accessible prototype for studying ligand binding to these pharmaceutically important pentameric ion channels, in particular to nicotinic acetylcholine receptors, due to conserved binding site residues present at the interface between two subunits. Here we report that an aromatic conjugated small molecule binds acetylcholine-binding protein in an ordered π-π stack of three identical molecules per binding site, two parallel and one antiparallel. Acetylcholine-binding protein stabilizes the assembly of the stack by aromatic contacts. Thanks to the plasticity of its ligand-binding site, acetylcholine-binding protein can accommodate the formation of aromatic stacks of different size by simple loop repositioning and minimal adjustment of the interactions. This type of supramolecular binding provides a novel paradigm in drug design.
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Affiliation(s)
- Mariano Stornaiuolo
- Division of Biochemistry and Center for Biomedical Genetics, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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3
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Zhang HK, Eaton JB, Yu LF, Nys M, Mazzolari A, van Elk R, Smit AB, Alexandrov V, Hanania T, Sabath E, Fedolak A, Brunner D, Lukas RJ, Vistoli G, Ulens C, Kozikowski AP. Insights into the structural determinants required for high-affinity binding of chiral cyclopropane-containing ligands to α4β2-nicotinic acetylcholine receptors: an integrated approach to behaviorally active nicotinic ligands. J Med Chem 2012; 55:8028-37. [PMID: 22928944 DOI: 10.1021/jm3008739] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Structure-based drug design can potentially accelerate the development of new therapeutics. In this study, a cocrystal structure of the acetylcholine binding protein (AChBP) from Capitella teleta (Ct) in complex with a cyclopropane-containing selective α4β2-nicotinic acetylcholine receptor (nAChR) partial agonist (compound 5) was acquired. The structural determinants required for ligand binding obtained from this AChBP X-ray structure were used to refine a previous model of the human α4β2-nAChR, thus possibly providing a better understanding of the structure of the human receptor. To validate the potential application of the structure of the Ct-AChBP in the engineering of new α4β2-nAChR ligands, homology modeling methods, combined with in silico ADME calculations, were used to design analogues of compound 5. The most promising compound, 12, exhibited an improved metabolic stability in comparison to the parent compound 5 while retaining favorable pharmacological parameters together with appropriate behavioral end points in the rodent studies.
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Affiliation(s)
- Han-Kun Zhang
- Drug Discovery Program, Department of Medicinal Chemistry and Pharmacognosy, University of Illinois at Chicago, 833 South Wood Street, Chicago, Illinois 60612, USA
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4
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Rucktooa P, Haseler CA, van Elk R, Smit AB, Gallagher T, Sixma TK. Structural characterization of binding mode of smoking cessation drugs to nicotinic acetylcholine receptors through study of ligand complexes with acetylcholine-binding protein. J Biol Chem 2012; 287:23283-93. [PMID: 22553201 PMCID: PMC3390607 DOI: 10.1074/jbc.m112.360347] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Smoking cessation is an important aim in public health worldwide as tobacco smoking causes many preventable deaths. Addiction to tobacco smoking results from the binding of nicotine to nicotinic acetylcholine receptors (nAChRs) in the brain, in particular the α4β2 receptor. One way to aid smoking cessation is by the use of nicotine replacement therapies or partial nAChR agonists like cytisine or varenicline. Here we present the co-crystal structures of cytisine and varenicline in complex with Aplysia californica acetylcholine-binding protein and use these as models to investigate binding of these ligands binding to nAChRs. This analysis of the binding properties of these two partial agonists provides insight into differences with nicotine binding to nAChRs. A mutational analysis reveals that the residues conveying subtype selectivity in nAChRs reside on the binding site complementary face and include features extending beyond the first shell of contacting residues.
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Affiliation(s)
- Prakash Rucktooa
- Division of Biochemistry and Center for Biomedical Genetics, Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands
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5
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Edink E, Akdemir A, Jansen C, van Elk R, Zuiderveld O, de Kanter FJJ, van Muijlwijk-Koezen JE, Smit AB, Leurs R, de Esch IJP. Structure-based design, synthesis and structure-activity relationships of dibenzosuberyl- and benzoate-substituted tropines as ligands for acetylcholine-binding protein. Bioorg Med Chem Lett 2011; 22:1448-54. [PMID: 22243960 DOI: 10.1016/j.bmcl.2011.12.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Revised: 11/30/2011] [Accepted: 12/01/2011] [Indexed: 12/26/2022]
Abstract
Using structure-based optimization procedures on in silico hits, dibenzosuberyl- and benzoate substituted tropines were designed as ligands for acetylcholine-binding protein (AChBP). This protein is a homolog to the ligand binding domain of the nicotinic acetylcholine receptor (nAChR). Distinct SAR is observed between two AChBP species variants and between the α7 and α4β2 nAChR subtype. The AChBP species differences are indicative of a difference in accessibility of a ligand-inducible subpocket. Hereby, we have identified a region that can be scrutinized to achieve selectivity for nicotinic receptor subtypes.
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Affiliation(s)
- Ewald Edink
- Leiden/Amsterdam Center of Drug Research, Division of Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines and Systems, VU University Amsterdam, The Netherlands
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6
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Brams M, Pandya A, Kuzmin D, van Elk R, Krijnen L, Yakel JL, Tsetlin V, Smit AB, Ulens C. A structural and mutagenic blueprint for molecular recognition of strychnine and d-tubocurarine by different cys-loop receptors. PLoS Biol 2011; 9:e1001034. [PMID: 21468359 PMCID: PMC3066128 DOI: 10.1371/journal.pbio.1001034] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Accepted: 02/09/2011] [Indexed: 11/18/2022] Open
Abstract
Cys-loop receptors (CLR) are pentameric ligand-gated ion channels that mediate fast excitatory or inhibitory transmission in the nervous system. Strychnine and d-tubocurarine (d-TC) are neurotoxins that have been highly instrumental in decades of research on glycine receptors (GlyR) and nicotinic acetylcholine receptors (nAChR), respectively. In this study we addressed the question how the molecular recognition of strychnine and d-TC occurs with high affinity and yet low specificity towards diverse CLR family members. X-ray crystal structures of the complexes with AChBP, a well-described structural homolog of the extracellular domain of the nAChRs, revealed that strychnine and d-TC adopt multiple occupancies and different ligand orientations, stabilizing the homopentameric protein in an asymmetric state. This introduces a new level of structural diversity in CLRs. Unlike protein and peptide neurotoxins, strychnine and d-TC form a limited number of contacts in the binding pocket of AChBP, offering an explanation for their low selectivity. Based on the ligand interactions observed in strychnine- and d-TC-AChBP complexes we performed alanine-scanning mutagenesis in the binding pocket of the human α1 GlyR and α7 nAChR and showed the functional relevance of these residues in conferring high potency of strychnine and d-TC, respectively. Our results demonstrate that a limited number of ligand interactions in the binding pocket together with an energetic stabilization of the extracellular domain are key to the poor selective recognition of strychnine and d-TC by CLRs as diverse as the GlyR, nAChR, and 5-HT3R. Ligand-gated ion channels play an important role in fast electrochemical signaling in the brain. Cys-loop receptors are a class of pentameric ligand-gated ion channels that are activated by specific neurotransmitters, including acetylcholine (ACh), serotonin (5-HT), glycine (Gly), and γ-aminobutyric acid (GABA). Each type of cys-loop receptor contains an extracellular domain that specifically recognizes only one of these four neurotransmitters and opens an ion-conducting channel pore upon ligand binding. In this study, we investigated the poor specificity with which two potent neurotoxic inhibitors, namely strychnine and d-tubocurarine, are recognized by different cys-loop receptors. Using X-ray crystallography we solved 3-dimensional structures of strychnine or d-tubocurarine in complex with ACh binding protein (AChBP), a well-recognized structural homolog of the nicotinic ACh receptor. Based on ligand-receptor interactions observed in AChBP structures we designed mutant GlyR and α7 nAChR to identify hot spots in the binding pocket of these receptors that define potent inhibition by strychnine and d-tubocurarine, respectively. Combined, our results offer detailed understanding of the molecular recognition of antagonists that have high affinity but poor specificity for different cys-loop receptors.
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Affiliation(s)
- Marijke Brams
- Laboratory of Structural Neurobiology, KULeuven, Leuven, Belgium
| | - Anshul Pandya
- Laboratory of Neurobiology, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina, United States of America
| | - Dmitry Kuzmin
- Department of Molecular Basis of Neurosignaling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - René van Elk
- Department of Molecular & Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands
| | - Liz Krijnen
- Laboratory of Structural Neurobiology, KULeuven, Leuven, Belgium
| | - Jerrel L. Yakel
- Laboratory of Neurobiology, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina, United States of America
| | - Victor Tsetlin
- Department of Molecular Basis of Neurosignaling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - August B. Smit
- Department of Molecular & Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands
| | - Chris Ulens
- Laboratory of Structural Neurobiology, KULeuven, Leuven, Belgium
- * E-mail:
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7
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Edink E, Rucktooa P, Retra K, Akdemir A, Nahar T, Zuiderveld O, van Elk R, Janssen E, van Nierop P, van Muijlwijk-Koezen J, Smit AB, Sixma TK, Leurs R, de Esch IJP. Fragment Growing Induces Conformational Changes in Acetylcholine-Binding Protein: A Structural and Thermodynamic Analysis. J Am Chem Soc 2011; 133:5363-71. [DOI: 10.1021/ja110571r] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ewald Edink
- Leiden/Amsterdam Center of Drug
Research (LACDR), Division of Medicinal Chemistry, Faculty of Sciences,
VU University Amsterdam, The Netherlands
| | - Prakash Rucktooa
- Divison of Biochemistry, Netherlands
Cancer Institute, The Netherlands
| | - Kim Retra
- Leiden/Amsterdam Center of Drug
Research (LACDR), Division of Medicinal Chemistry, Faculty of Sciences,
VU University Amsterdam, The Netherlands
| | - Atilla Akdemir
- Leiden/Amsterdam Center of Drug
Research (LACDR), Division of Medicinal Chemistry, Faculty of Sciences,
VU University Amsterdam, The Netherlands
| | - Tariq Nahar
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics & Cognitive Research, VU University Amsterdam, The Netherlands
| | - Obbe Zuiderveld
- Leiden/Amsterdam Center of Drug
Research (LACDR), Division of Medicinal Chemistry, Faculty of Sciences,
VU University Amsterdam, The Netherlands
| | - René van Elk
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics & Cognitive Research, VU University Amsterdam, The Netherlands
| | - Elwin Janssen
- Department of Chemistry and
Pharmaceutical Sciences, VU University Amsterdam, The Netherlands
| | - Pim van Nierop
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics & Cognitive Research, VU University Amsterdam, The Netherlands
| | - Jacqueline van Muijlwijk-Koezen
- Leiden/Amsterdam Center of Drug
Research (LACDR), Division of Medicinal Chemistry, Faculty of Sciences,
VU University Amsterdam, The Netherlands
| | - August B. Smit
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics & Cognitive Research, VU University Amsterdam, The Netherlands
| | - Titia K. Sixma
- Divison of Biochemistry, Netherlands
Cancer Institute, The Netherlands
| | - Rob Leurs
- Leiden/Amsterdam Center of Drug
Research (LACDR), Division of Medicinal Chemistry, Faculty of Sciences,
VU University Amsterdam, The Netherlands
| | - Iwan J. P. de Esch
- Leiden/Amsterdam Center of Drug
Research (LACDR), Division of Medicinal Chemistry, Faculty of Sciences,
VU University Amsterdam, The Netherlands
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8
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Brams M, Gay EA, Sáez JC, Guskov A, van Elk R, van der Schors RC, Peigneur S, Tytgat J, Strelkov SV, Smit AB, Yakel JL, Ulens C. Crystal structures of a cysteine-modified mutant in loop D of acetylcholine-binding protein. J Biol Chem 2010; 286:4420-8. [PMID: 21115477 DOI: 10.1074/jbc.m110.188730] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Covalent modification of α7 W55C nicotinic acetylcholine receptors (nAChR) with the cysteine-modifying reagent [2-(trimethylammonium)ethyl] methanethiosulfonate (MTSET(+)) produces receptors that are unresponsive to acetylcholine, whereas methyl methanethiolsulfonate (MMTS) produces enhanced acetylcholine-gated currents. Here, we investigate structural changes that underlie the opposite effects of MTSET(+) and MMTS using acetylcholine-binding protein (AChBP), a homolog of the extracellular domain of the nAChR. Crystal structures of Y53C AChBP show that MTSET(+)-modification stabilizes loop C in an extended conformation that resembles the antagonist-bound state, which parallels our observation that MTSET(+) produces unresponsive W55C nAChRs. The MMTS-modified mutant in complex with acetylcholine is characterized by a contracted C-loop, similar to other agonist-bound complexes. Surprisingly, we find two acetylcholine molecules bound in the ligand-binding site, which might explain the potentiating effect of MMTS modification in W55C nAChRs. Unexpectedly, we observed in the MMTS-Y53C structure that ten phosphate ions arranged in two rings at adjacent sites are bound in the vestibule of AChBP. We mutated homologous residues in the vestibule of α1 GlyR and observed a reduction in the single channel conductance, suggesting a role of this site in ion permeation. Taken together, our results demonstrate that targeted modification of a conserved aromatic residue in loop D is sufficient for a conformational switch of AChBP and that a defined region in the vestibule of the extracellular domain contributes to ion conduction in anion-selective Cys-loop receptors.
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Affiliation(s)
- Marijke Brams
- Laboratory of Structural Neurobiology, KULeuven, 3000 Leuven, Belgium
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de Kloe GE, Retra K, Geitmann M, Källblad P, Nahar T, van Elk R, Smit AB, van Muijlwijk-Koezen JE, Leurs R, Irth H, Danielson UH, de Esch IJP. Surface Plasmon Resonance Biosensor Based Fragment Screening Using Acetylcholine Binding Protein Identifies Ligand Efficiency Hot Spots (LE Hot Spots) by Deconstruction of Nicotinic Acetylcholine Receptor α7 Ligands. J Med Chem 2010; 53:7192-201. [DOI: 10.1021/jm100834y] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Gerdien E. de Kloe
- Leiden/Amsterdam Center for Drug Research (LACDR), Division of Medicinal Chemistry, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | - Kim Retra
- Leiden/Amsterdam Center for Drug Research (LACDR), Division of BioMolecular Analysis, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | | | | | - Tariq Nahar
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University Amsterdam, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands
| | - René van Elk
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University Amsterdam, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands
| | - August B. Smit
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University Amsterdam, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands
| | - Jacqueline E. van Muijlwijk-Koezen
- Leiden/Amsterdam Center for Drug Research (LACDR), Division of Medicinal Chemistry, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | - Rob Leurs
- Leiden/Amsterdam Center for Drug Research (LACDR), Division of Medicinal Chemistry, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | - Hubertus Irth
- Leiden/Amsterdam Center for Drug Research (LACDR), Division of BioMolecular Analysis, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | - U. Helena Danielson
- Beactica AB, Box 567, SE-751 22 Uppsala, Sweden
- Department of Biochemistry and Organic Chemistry, Uppsala University, BMC, Box 576, SE-751 23, Uppsala, Sweden
| | - Iwan J. P. de Esch
- Leiden/Amsterdam Center for Drug Research (LACDR), Division of Medicinal Chemistry, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
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10
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Dutertre S, Ulens C, Büttner R, Fish A, van Elk R, Kendel Y, Hopping G, Alewood PF, Schroeder C, Nicke A, Smit AB, Sixma TK, Lewis RJ. AChBP-targeted alpha-conotoxin correlates distinct binding orientations with nAChR subtype selectivity. EMBO J 2007; 26:3858-67. [PMID: 17660751 PMCID: PMC1952216 DOI: 10.1038/sj.emboj.7601785] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2007] [Accepted: 06/12/2007] [Indexed: 11/09/2022] Open
Abstract
Neuronal nAChRs are a diverse family of pentameric ion channels with wide distribution throughout cells of the nervous and immune systems. However, the role of specific subtypes in normal and pathological states remains poorly understood due to the lack of selective probes. Here, we used a binding assay based on acetylcholine-binding protein (AChBP), a homolog of the nicotinic acetylcholine ligand-binding domain, to discover a novel alpha-conotoxin (alpha-TxIA) in the venom of Conus textile. Alpha-TxIA bound with high affinity to AChBPs from different species and selectively targeted the alpha(3)beta(2) nAChR subtype. A co-crystal structure of Ac-AChBP with the enhanced potency analog TxIA(A10L), revealed a 20 degrees backbone tilt compared to other AChBP-conotoxin complexes. This reorientation was coordinated by a key salt bridge formed between Arg5 (TxIA) and Asp195 (Ac-AChBP). Mutagenesis studies, biochemical assays and electrophysiological recordings directly correlated the interactions observed in the co-crystal structure to binding affinity at AChBP and different nAChR subtypes. Together, these results establish a new pharmacophore for the design of novel subtype-selective ligands with therapeutic potential in nAChR-related diseases.
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Affiliation(s)
- Sébastien Dutertre
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
| | - Chris Ulens
- Division of Molecular Carcinogenesis and Center for Biomedical Genetics, Netherlands Cancer Institute, Plesmanlaan, CX Amsterdam, The Netherlands
| | - Regina Büttner
- Department of Neurochemistry, Max Planck Institute for Brain Research, Deutschordenstrasse 46, Frankfurt am Main, Germany
| | - Alexander Fish
- Division of Molecular Carcinogenesis and Center for Biomedical Genetics, Netherlands Cancer Institute, Plesmanlaan, CX Amsterdam, The Netherlands
| | - René van Elk
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, Vrije Universiteit, Amsterdam, The Netherlands
| | - Yvonne Kendel
- Zentrum der Rechtsmedizin, University of Frankfurt, Frankfurt am Main, Germany
| | - Gene Hopping
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
| | - Paul F Alewood
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
| | - Christina Schroeder
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
| | - Annette Nicke
- Department of Neurochemistry, Max Planck Institute for Brain Research, Deutschordenstrasse 46, Frankfurt am Main, Germany
| | - August B Smit
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, Vrije Universiteit, Amsterdam, The Netherlands
| | - Titia K Sixma
- Division of Molecular Carcinogenesis and Center for Biomedical Genetics, Netherlands Cancer Institute, Plesmanlaan, CX Amsterdam, The Netherlands
- Division of Molecular Carcinogenesis and Center for Biomedical Genetics, Netherlands Cancer Institute, Plesmanlaan, 1066 CX Amsterdam, The Netherlands. E-mail:
| | - Richard J Lewis
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
- Institute for Molecular Bioscience, The University of Queensland, Carmodty Rd, Brisbane, Queensland 4072, Australia. Tel.: +617 3346 2984; Fax: +617 3346 2101; E-mail:
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11
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Kasheverov IE, Zhmak MN, Vulfius CA, Gorbacheva EV, Mordvintsev DY, Utkin YN, van Elk R, Smit AB, Tsetlin VI. ?-Conotoxin analogs with additional positive charge show increased selectivity towards Torpedo�californica and some neuronal subtypes of nicotinic acetylcholine receptors. FEBS J 2006; 273:4470-81. [PMID: 16956365 DOI: 10.1111/j.1742-4658.2006.05453.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Alpha-conotoxins from Conus snails are indispensable tools for distinguishing various subtypes of nicotinic acetylcholine receptors (nAChRs), and synthesis of alpha-conotoxin analogs may yield novel antagonists of higher potency and selectivity. We incorporated additional positive charges into alpha-conotoxins and analyzed their binding to nAChRs. Introduction of Arg or Lys residues instead of Ser12 in alpha-conotoxins GI and SI, or D12K substitution in alpha-conotoxin SIA increased the affinity for both the high- and low-affinity sites in membrane-bound Torpedo californica nAChR. The effect was most pronounced for [D12K]SIA with 30- and 200-fold enhancement for the respective sites, resulting in the most potent alpha-conotoxin blocker of the Torpedo nAChR among those tested. Similarly, D14K substitution in alpha-conotoxin [A10L]PnIA, a blocker of neuronal alpha7 nAChR, was previously shown to increase the affinity for this receptor and endowed [A10L,D14K]PnIA with the capacity to distinguish between acetylcholine-binding proteins from the mollusks Lymnaea stagnalis and Aplysia californica. We found that [A10L,D14K]PnIA also distinguishes two alpha7-like anion-selective nAChR subtypes present on identified neurons of L. stagnalis: [D14K] mutation affected only slightly the potency of [A10L]PnIA to block nAChRs on neurons with low sensitivity to alpha-conotoxin ImI, but gave a 50-fold enhancement of blocking activity in cells with high sensitivity to ImI. Therefore, the introduction of an additional positive charge in the C-terminus of alpha-conotoxins targeting some muscle or neuronal nAChRs made them more discriminative towards the respective nAChR subtypes. In the case of muscle-type alpha-conotoxin [D12K]SIA, the contribution of the Lys12 positive charge to enhanced affinity towards Torpedo nAChR was rationalized with the aid of computer modeling.
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Affiliation(s)
- Igor E Kasheverov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
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Celie PHN, Klaassen RV, van Rossum-Fikkert SE, van Elk R, van Nierop P, Smit AB, Sixma TK. Crystal Structure of Acetylcholine-binding Protein from Bulinus truncatus Reveals the Conserved Structural Scaffold and Sites of Variation in Nicotinic Acetylcholine Receptors. J Biol Chem 2005; 280:26457-66. [PMID: 15899893 DOI: 10.1074/jbc.m414476200] [Citation(s) in RCA: 161] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The crystal structure of acetylcholine-binding protein (AChBP) from the mollusk Lymnaea stagnalis is the established model for the ligand binding domains of the ligand-gated ion channel family, which includes nicotinic acetylcholine, 5-hydroxytryptamine (5-HT3), gamma-aminobutyric acid (GABA), types A and C, and glycine receptors. Here we present the crystal structure of a remote homolog, AChBP from Bulinus truncatus, which reveals both the conserved structural scaffold and the sites of variation in this receptor family. These include rigid body movements of loops that are close to the transmembrane interface in the receptors and changes in the intermonomer contacts, which alter the pentamer stability drastically. Structural, pharmacological and mutational analysis of both AChBPs shows how 3 amino acid changes in the binding site contribute to a 5-10-fold difference in affinity for nicotinic ligands. Comparison of these structures will be valuable for improving structure-function studies of ligand-gated ion channel receptors, including signal transduction, homology modeling, and drug design.
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Affiliation(s)
- Patrick H N Celie
- Division of Molecular Carcinogenesis, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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Celie PHN, Kasheverov IE, Mordvintsev DY, Hogg RC, van Nierop P, van Elk R, van Rossum-Fikkert SE, Zhmak MN, Bertrand D, Tsetlin V, Sixma TK, Smit AB. Crystal structure of nicotinic acetylcholine receptor homolog AChBP in complex with an α-conotoxin PnIA variant. Nat Struct Mol Biol 2005; 12:582-8. [PMID: 15951818 DOI: 10.1038/nsmb951] [Citation(s) in RCA: 267] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2005] [Accepted: 05/16/2005] [Indexed: 11/08/2022]
Abstract
Conotoxins (Ctx) form a large family of peptide toxins from cone snail venoms that act on a broad spectrum of ion channels and receptors. The subgroup alpha-Ctx specifically and selectively binds to subtypes of nicotinic acetylcholine receptors (nAChRs), which are targets for treatment of several neurological disorders. Here we present the structure at a resolution of 2.4 A of alpha-Ctx PnIA (A10L D14K), a potent blocker of the alpha(7)-nAChR, bound with high affinity to acetylcholine binding protein (AChBP), the prototype for the ligand-binding domains of the nAChR superfamily. Alpha-Ctx is buried deep within the ligand-binding site and interacts with residues on both faces of adjacent subunits. The toxin itself does not change conformation, but displaces the C loop of AChBP and induces a rigid-body subunit movement. Knowledge of these contacts could facilitate the rational design of drug leads using the Ctx framework and may lead to compounds with increased receptor subtype selectivity.
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Affiliation(s)
- Patrick H N Celie
- Division of Molecular Carcinogenesis, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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