1
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Söllner J, Derler I. Genetic code expansion, an emerging tool in the Ca 2+ ion channel field. J Physiol 2024; 602:3297-3313. [PMID: 38695316 DOI: 10.1113/jp285840] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Accepted: 04/15/2024] [Indexed: 07/17/2024] Open
Abstract
Various methods for characterizing binding forces as well as for monitoring and remote control of ion channels are still emerging. A recent innovation is the direct incorporation of unnatural amino acids (UAAs) with corresponding biophysical or biochemical properties, which are integrated using genetic code expansion technology. Minimal changes to natural amino acids, which are achieved by chemical synthesis of corresponding UAAs, are valuable tools to provide insight into the contributions of physicochemical properties of side chains in binding events. To gain unique control over the conformational changes or function of ion channels, a series of light-sensitive, chemically reactive and posttranslationally modified UAAs have been developed and utilized. Here, we present the existing UAA tools, their mode of action, their potential and limitations as well as their previous applications to Ca2+-permeable ion channels.
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Affiliation(s)
- Julia Söllner
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz, Austria
| | - Isabella Derler
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, Linz, Austria
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2
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Middya P, Karmakar M, Frontera A, Chattopadhyay S. Insight into the role of pseudo-halides as multiple hydrogen bond acceptors in the formation of supramolecular 1D assembly of di and trinuclear zinc complexes. Inorganica Chim Acta 2023. [DOI: 10.1016/j.ica.2023.121516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2023]
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3
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Knox HJ, Rego Campello H, Lester HA, Gallagher T, Dougherty DA. Characterization of Binding Site Interactions and Selectivity Principles in the α3β4 Nicotinic Acetylcholine Receptor. J Am Chem Soc 2022; 144:16101-16117. [PMID: 36006801 DOI: 10.1021/jacs.2c06495] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) play an important role in neurotransmission and are also involved in addiction and several disease states. There is significant interest in therapeutic targeting of nAChRs; however, achieving selectivity for one subtype over others has been a longstanding challenge, given the close structural similarities across the family. Here, we characterize binding interactions in the α3β4 nAChR subtype via structure-function studies involving noncanonical amino acid mutagenesis and two-electrode voltage clamp electrophysiology. We establish comprehensive binding models for both the endogenous neurotransmitter ACh and the smoking cessation drug cytisine. We also use a panel of C(10)-substituted cytisine derivatives to probe the effects of subtle changes in the ligand structure on binding. By comparing our results to those obtained for the well-studied α4β2 subtype, we identify several features of both the receptor and agonist structure that can be utilized to enhance selectivity for either α3β4 or α4β2. Finally, we characterize binding interactions of the α3β4-selective partial agonist AT-1001 to determine factors that contribute to its selectivity. These results shed new light on the design of selective nAChR-targeted ligands and can be used to inform the design of improved therapies with minimized off-target effects.
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Affiliation(s)
- Hailey J Knox
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | | | - Henry A Lester
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | | | - Dennis A Dougherty
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
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4
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Shao J, Kuiper BP, Thunnissen AMWH, Cool RH, Zhou L, Huang C, Dijkstra BW, Broos J. The Role of Tryptophan in π Interactions in Proteins: An Experimental Approach. J Am Chem Soc 2022; 144:13815-13822. [PMID: 35868012 PMCID: PMC9354243 DOI: 10.1021/jacs.2c04986] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
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In proteins, the amino acids Phe, Tyr, and especially
Trp are frequently
involved in π interactions such as π–π, cation−π,
and CH−π bonds. These interactions are often crucial
for protein structure and protein–ligand binding. A powerful
means to study these interactions is progressive fluorination of these
aromatic residues to modulate the electrostatic component of the interaction.
However, to date no protein expression platform is available to produce
milligram amounts of proteins labeled with such fluorinated amino
acids. Here, we present a Lactococcus lactis Trp
auxotroph-based expression system for efficient incorporation (≥95%)
of mono-, di-, tri-, and tetrafluorinated, as well as a methylated
Trp analog. As a model protein we have chosen LmrR, a dimeric multidrug
transcriptional repressor protein from L. lactis. LmrR binds aromatic drugs, like daunomycin and riboflavin, between
Trp96 and Trp96′ in the dimer interface. Progressive fluorination
of Trp96 decreased the affinity for the drugs 6- to 70-fold, clearly
establishing the importance of electrostatic π–π
interactions for drug binding. Presteady state kinetic data of the
LmrR–drug interaction support the enthalpic nature of the interaction,
while high resolution crystal structures of the labeled protein–drug
complexes provide for the first time a structural view of the progressive
fluorination approach. The L. lactis expression system
was also used to study the role of Trp68 in the binding of riboflavin
by the membrane-bound riboflavin transport protein RibU from L. lactis. Progressive fluorination of Trp68 revealed a
strong electrostatic component that contributed 15–20% to the
total riboflavin-RibU binding energy.
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Affiliation(s)
- Jinfeng Shao
- Groningen Biomolecular Science and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Bastiaan P Kuiper
- Groningen Biomolecular Science and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Andy-Mark W H Thunnissen
- Groningen Biomolecular Science and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Robbert H Cool
- Department of Chemical and Pharmaceutical Biology, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | - Liang Zhou
- Groningen Biomolecular Science and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Chenxi Huang
- Groningen Biomolecular Science and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Bauke W Dijkstra
- Groningen Biomolecular Science and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Jaap Broos
- Groningen Biomolecular Science and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
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5
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Banerjee A, Chowdhury D, Gomila RM, Chattopadhyay S. Recent advances on the tetrel bonding interaction in the solid state structure of lead complexes with hydrazine based bis-pyridine Schiff base ligands. Polyhedron 2022. [DOI: 10.1016/j.poly.2022.115670] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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6
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Verma S, Pathak RK. Discovery and optimization of lead molecules in drug designing. Bioinformatics 2022. [DOI: 10.1016/b978-0-323-89775-4.00004-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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7
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Zhao C, Hong L, Galpin JD, Riahi S, Lim VT, Webster PD, Tobias DJ, Ahern CA, Tombola F. HIFs: New arginine mimic inhibitors of the Hv1 channel with improved VSD-ligand interactions. J Gen Physiol 2021; 153:212451. [PMID: 34228044 PMCID: PMC8263924 DOI: 10.1085/jgp.202012832] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 06/14/2021] [Indexed: 12/14/2022] Open
Abstract
The human voltage-gated proton channel Hv1 is a drug target for cancer, ischemic stroke, and neuroinflammation. It resides on the plasma membrane and endocytic compartments of a variety of cell types, where it mediates outward proton movement and regulates the activity of NOX enzymes. Its voltage-sensing domain (VSD) contains a gated and proton-selective conduction pathway, which can be blocked by aromatic guanidine derivatives such as 2-guanidinobenzimidazole (2GBI). Mutation of Hv1 residue F150 to alanine (F150A) was previously found to increase 2GBI apparent binding affinity more than two orders of magnitude. Here, we explore the contribution of aromatic interactions between the inhibitor and the channel in the presence and absence of the F150A mutation, using a combination of electrophysiological recordings, classic mutagenesis, and site-specific incorporation of fluorinated phenylalanines via nonsense suppression methodology. Our data suggest that the increase in apparent binding affinity is due to a rearrangement of the binding site allowed by the smaller residue at position 150. We used this information to design new arginine mimics with improved affinity for the nonrearranged binding site of the wild-type channel. The new compounds, named “Hv1 Inhibitor Flexibles” (HIFs), consist of two “prongs,” an aminoimidazole ring, and an aromatic group connected by extended flexible linkers. Some HIF compounds display inhibitory properties that are superior to those of 2GBI, thus providing a promising scaffold for further development of high-affinity Hv1 inhibitors.
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Affiliation(s)
- Chang Zhao
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA.,Chao Family Comprehensive Cancer Center, University of California, Irvine, Irvine, CA
| | - Liang Hong
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA
| | - Jason D Galpin
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA
| | - Saleh Riahi
- Department of Chemistry, University of California, Irvine, Irvine, CA
| | - Victoria T Lim
- Department of Chemistry, University of California, Irvine, Irvine, CA
| | - Parker D Webster
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA
| | - Douglas J Tobias
- Chao Family Comprehensive Cancer Center, University of California, Irvine, Irvine, CA.,Department of Chemistry, University of California, Irvine, Irvine, CA
| | - Christopher A Ahern
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA
| | - Francesco Tombola
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA.,Chao Family Comprehensive Cancer Center, University of California, Irvine, Irvine, CA
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8
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Dämgen MA, Biggin PC. State-dependent protein-lipid interactions of a pentameric ligand-gated ion channel in a neuronal membrane. PLoS Comput Biol 2021; 17:e1007856. [PMID: 33571182 PMCID: PMC7904231 DOI: 10.1371/journal.pcbi.1007856] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 02/24/2021] [Accepted: 01/07/2021] [Indexed: 02/06/2023] Open
Abstract
Pentameric ligand-gated ion channels (pLGICs) are receptor proteins that are sensitive to their membrane environment, but the mechanism for how lipids modulate function under physiological conditions in a state dependent manner is not known. The glycine receptor is a pLGIC whose structure has been resolved in different functional states. Using a realistic model of a neuronal membrane coupled with coarse-grained molecular dynamics simulations, we demonstrate that some key lipid-protein interactions are dependent on the receptor state, suggesting that lipids may regulate the receptor's conformational dynamics. Comparison with existing structural data confirms known lipid binding sites, but we also predict further protein-lipid interactions including a site at the communication interface between the extracellular and transmembrane domain. Moreover, in the active state, cholesterol can bind to the binding site of the positive allosteric modulator ivermectin. These protein-lipid interaction sites could in future be exploited for the rational design of lipid-like allosteric drugs.
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Affiliation(s)
- Marc A. Dämgen
- Structural Bioinformatics and Computational Biochemistry, Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Philip C. Biggin
- Structural Bioinformatics and Computational Biochemistry, Department of Biochemistry, University of Oxford, Oxford, United Kingdom
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9
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Kumar P, Banerjee S, Radha A, Firdoos T, Sahoo SC, Pandey SK. Role of non-covalent interactions in the supramolecular architectures of mercury(ii) diphenyldithiophosphates: An experimental and theoretical investigation. NEW J CHEM 2021. [DOI: 10.1039/d0nj05709f] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The H-bond, spodium bond and CH⋯π interactions playing an important role in the supramolecular organization of two mercury(ii) diphenyldithiophosphate complexes have been discussed.
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Affiliation(s)
- Pretam Kumar
- Post Graduate Department of Chemistry
- University of Jammu
- Jammu Tawi-180006
- India
| | - Snehasis Banerjee
- Govt. College of Engineering and Leather Technology
- Kolkata-700106
- India
| | - Anu Radha
- Post Graduate Department of Chemistry
- University of Jammu
- Jammu Tawi-180006
- India
| | - Tahira Firdoos
- Post Graduate Department of Chemistry
- University of Jammu
- Jammu Tawi-180006
- India
| | - Subash Chandra Sahoo
- Department of Chemistry & Centre of Advanced Studies in Chemistry
- Panjab University
- Chandigarh-160014
- India
| | - Sushil K. Pandey
- Post Graduate Department of Chemistry
- University of Jammu
- Jammu Tawi-180006
- India
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10
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Kumar P, Frontera A, Pandey SK. Coordination versus spodium bonds in dinuclear Zn( ii) and Cd( ii) complexes with a dithiophosphate ligand. NEW J CHEM 2021. [DOI: 10.1039/d1nj03165a] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Two new d10-metal dithiophosphate complexes have been synthesized in purely aqueous media and characterized by elemental and spectral analyses. DFT calculations, QTAIM and NCI Plot index methods are preformed to differentiate the coordination and spodium bonds in the complexes.
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Affiliation(s)
- Pretam Kumar
- Post Graduate Department of Chemistry, University of Jammu, Baba Saheb Ambedkar Road, Jammu Tawi-180006, J&K, India
| | - Antonio Frontera
- Departament de Química, Universitat de les Illes Balears, Crta de Valldemossa km 7.5, 07122 Palma de Mallorca (Baleares), Spain
| | - Sushil K. Pandey
- Post Graduate Department of Chemistry, University of Jammu, Baba Saheb Ambedkar Road, Jammu Tawi-180006, J&K, India
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11
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Potapova NV, Kasaikina OT, Berezin MP, Plashchina IG. Catalytic Generation of Radicals in Supramolecular Systems with Acetylcholine. KINETICS AND CATALYSIS 2020. [DOI: 10.1134/s0023158420050079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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12
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Arunrungvichian K, Chongruchiroj S, Sarasamkan J, Schüürmann G, Brust P, Vajragupta O. In Silico Finding of Key Interaction Mediated α3β4 and α7 Nicotinic Acetylcholine Receptor Ligand Selectivity of Quinuclidine-Triazole Chemotype. Int J Mol Sci 2020; 21:E6189. [PMID: 32867140 PMCID: PMC7504379 DOI: 10.3390/ijms21176189] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 08/20/2020] [Accepted: 08/25/2020] [Indexed: 12/12/2022] Open
Abstract
The selective binding of six (S)-quinuclidine-triazoles and their (R)-enantiomers to nicotinic acetylcholine receptor (nAChR) subtypes α3β4 and α7, respectively, were analyzed by in silico docking to provide the insight into the molecular basis for the observed stereospecific subtype discrimination. Homology modeling followed by molecular docking and molecular dynamics (MD) simulations revealed that unique amino acid residues in the complementary subunits of the nAChR subtypes are involved in subtype-specific selectivity profiles. In the complementary β4-subunit of the α3β4 nAChR binding pocket, non-conserved AspB173 through a salt bridge was found to be the key determinant for the α3β4 selectivity of the quinuclidine-triazole chemotype, explaining the 47-327-fold affinity of the (S)-enantiomers as compared to their (R)-enantiomer counterparts. Regarding the α7 nAChR subtype, the amino acids promoting a however significantly lower preference for the (R)-enantiomers were the conserved TyrA93, TrpA149 and TrpB55 residues. The non-conserved amino acid residue in the complementary subunit of nAChR subtypes appeared to play a significant role for the nAChR subtype-selective binding, particularly at the heteropentameric subtype, whereas the conserved amino acid residues in both principal and complementary subunits are essential for ligand potency and efficacy.
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Affiliation(s)
- Kuntarat Arunrungvichian
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Mahidol University, 447 Sri-Ayutthaya Road, Bangkok 10400, Thailand;
| | - Sumet Chongruchiroj
- Department of Microbiology, Faculty of Pharmacy, Mahidol University, 447 Sri-Ayutthaya Road, Bangkok 10400, Thailand;
| | - Jiradanai Sarasamkan
- Division of Nuclear Medicine, Department of Radiology, Faculty of Medicine, Khon Kaen University, 123 Mittraparp Highway, Khon Kaen 4002, Thailand;
| | - Gerrit Schüürmann
- UFZ Department of Ecological Chemistry, Helmholtz Centre for Environmental Research, Permoserstrasse 15, 04318 Leipzig, Germany;
- Institute of Organic Chemistry, Technical University Bergakademie Freiberg, Leipziger Strasse 29, 09596 Freiberg, Germany
| | - Peter Brust
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Permoserstrasse 15, 04318 Leipzig, Germany;
| | - Opa Vajragupta
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Mahidol University, 447 Sri-Ayutthaya Road, Bangkok 10400, Thailand;
- Office of Research Affairs, Faculty of Pharmaceutical Sciences, Chulalongkorn University, 254 Phayathai Road, Bangkok 10330, Thailand
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13
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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: 28] [Impact Index Per Article: 7.0] [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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14
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Karmakar M, Frontera A, Chattopadhyay S. Methylene spacer regulated variation in supramolecular assembly of zinc( ii) dicyanamide complexes with reduced Schiff base ligands: synthesis, structure and DFT study. CrystEngComm 2020. [DOI: 10.1039/d0ce01105c] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Three tetranuclear zinc dicyanamide complexes with three potential hexadentate reduced Schiff base ligands have been synthesized and characterized. The DFT study is devoted to the analysis of the competition between C–H⋯π and π⋯π interactions.
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Affiliation(s)
- Mainak Karmakar
- Department of Chemistry
- Inorganic Section
- Jadavpur University
- Kolkata – 700032
- India
| | - Antonio Frontera
- Departamento de Química
- Universitat de les Illes Balears
- 07122 Palma
- Spain
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15
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Oliveira ASF, Edsall CJ, Woods CJ, Bates P, Nunez GV, Wonnacott S, Bermudez I, Ciccotti G, Gallagher T, Sessions RB, Mulholland AJ. A General Mechanism for Signal Propagation in the Nicotinic Acetylcholine Receptor Family. J Am Chem Soc 2019; 141:19953-19958. [PMID: 31805762 DOI: 10.1021/jacs.9b09055] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) modulate synaptic activity in the central nervous system. The α7 subtype, in particular, has attracted considerable interest in drug discovery as a target for several conditions, including Alzheimer's disease and schizophrenia. Identifying agonist-induced structural changes underlying nAChR activation is fundamentally important for understanding biological function and rational drug design. Here, extensive equilibrium and nonequilibrium molecular dynamics simulations, enabled by cloud-based high-performance computing, reveal the molecular mechanism by which structural changes induced by agonist unbinding are transmitted within the human α7 nAChR. The simulations reveal the sequence of coupled structural changes involved in driving conformational change responsible for biological function. Comparison with simulations of the α4β2 nAChR subtype identifies features of the dynamical architecture common to both receptors, suggesting a general structural mechanism for signal propagation in this important family of receptors.
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Affiliation(s)
- Ana Sofia F Oliveira
- School of Biochemistry , University of Bristol , Bristol BS8 1DT , United Kingdom
- Centre for Computational Chemistry, School of Chemistry , University of Bristol , Bristol BS8 1TS , United Kingdom
| | - Christopher J Edsall
- Research Software Engineering, Advanced Computing Research Centre , University of Bristol , Bristol BS1 5QD , United Kingdom
| | - Christopher J Woods
- Centre for Computational Chemistry, School of Chemistry , University of Bristol , Bristol BS8 1TS , United Kingdom
- Research Software Engineering, Advanced Computing Research Centre , University of Bristol , Bristol BS1 5QD , United Kingdom
| | - Phil Bates
- Department of Computer Science, Faculty of Engineering , University of Bristol , Bristol BS8 1TR , United Kingdom
- Oracle Corporation, Oracle Cloud Development Centre , Bristol BS2 2JJ , United Kingdom
| | - Gerardo Viedma Nunez
- Oracle Corporation, Oracle Cloud Development Centre , Bristol BS2 2JJ , United Kingdom
| | - Susan Wonnacott
- Department of Biology and Biochemistry , University of Bath , Bath BA2 7AY , United Kingdom
| | - Isabel Bermudez
- Department of Biological and Medical Sciences , Oxford Brookes University , Oxford OX30BP , United Kingdom
| | - Giovanni Ciccotti
- Institute for Applied Computing "Mauro Picone" (IAC), CNR , Via dei Taurini 19 , 00185 Rome , Italy
- School of Physics , University College of Dublin UCD-Belfield , Dublin 4, Ireland
- Università di Roma La Sapienza , Ple. A. Moro 5 , 00185 Roma , Italy
| | - Timothy Gallagher
- Centre for Computational Chemistry, School of Chemistry , University of Bristol , Bristol BS8 1TS , United Kingdom
| | - Richard B Sessions
- School of Biochemistry , University of Bristol , Bristol BS8 1DT , United Kingdom
| | - Adrian J Mulholland
- Centre for Computational Chemistry, School of Chemistry , University of Bristol , Bristol BS8 1TS , United Kingdom
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16
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Gupta K, Toombes GE, Swartz KJ. Exploring structural dynamics of a membrane protein by combining bioorthogonal chemistry and cysteine mutagenesis. eLife 2019; 8:50776. [PMID: 31714877 PMCID: PMC6850778 DOI: 10.7554/elife.50776] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 10/11/2019] [Indexed: 12/12/2022] Open
Abstract
The functional mechanisms of membrane proteins are extensively investigated with cysteine mutagenesis. To complement cysteine-based approaches, we engineered a membrane protein with thiol-independent crosslinkable groups using azidohomoalanine (AHA), a non-canonical methionine analogue containing an azide group that can selectively react with cycloalkynes through a strain-promoted azide-alkyne cycloaddition (SPAAC) reaction. We demonstrate that AHA can be readily incorporated into the Shaker Kv channel in place of methionine residues and modified with azide-reactive alkyne probes in Xenopus oocytes. Using voltage-clamp fluorometry, we show that AHA incorporation permits site-specific fluorescent labeling to track voltage-dependent conformational changes similar to cysteine-based methods. By combining AHA incorporation and cysteine mutagenesis in an orthogonal manner, we were able to site-specifically label the Shaker Kv channel with two different fluorophores simultaneously. Our results identify a facile and straightforward approach for chemical modification of membrane proteins with bioorthogonal chemistry to explore their structure-function relationships in live cells. Living cells can sense cues from their environment via molecules located at the interface between the inside and the outside of the cell. These molecules are mostly proteins and are made up of building blocks known as amino acids. To understand how these proteins work, fluorescent probes can be attached to amino acids within them – which can then tell when different parts of proteins move in response to a signal. Scientists often target fluorescent probes at the amino acid cysteine, because it has a chemically reactive side group and is rare enough so that unique positions can be labeled in the protein of interest. However, being able to target other amino acids would allow scientists to ask, and potentially solve, more precise questions about these proteins. Methionine is another amino acid that has a low abundance in most proteins. Previous research has shown that the cell’s normal protein-building machinery can incorporate synthetic versions of methionine into proteins. This suggested that the introduction of chemically reactive alternatives to methionine could offer a way to label membrane proteins with fluorescent probes and free up the cysteines to be targeted with other approaches. Gupta et al. set out to develop a straightforward method to achieve this and started with a well-studied membrane protein, called Shaker, and cells from female African clawed frogs, which are widely used to study membrane proteins. Gupta et al. found that the cells could readily take up a chemically reactive methionine alternative called azidohomoalanine (AHA) from their surrounding solution and incorporate it within the Shaker protein. The AHA took the place of the methionines that are normally found in Shaker, and just like in cysteine-based methods, fluorescent probes could be easily attached to the AHAs in this membrane protein. Shaker is a protein that allows potassium ions to flow across the cell membrane by changing shape in response to the membrane voltage. The fluorescence from those probes also changed with the membrane voltage in a way that was comparable to cysteine-mediated approaches. This indicated that the AHA modification could also be used to track structural changes in the Shaker protein. Finally, Gupta et al. showed that AHA- and cysteine-mediated labeling approaches could be combined to attach two different fluorescent probes onto the Shaker protein. This method will expand the toolbox for researchers studying the relationship between the structure and function of membrane proteins in live cells. In future, it could be applied more widely once the properties of the fluorescent probes for AHA-mediated labeling can be optimized.
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Affiliation(s)
- Kanchan Gupta
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, United States
| | - Gilman Es Toombes
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, United States
| | - Kenton J Swartz
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, United States
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17
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Blom AE, Campello HR, Lester HA, Gallagher T, Dougherty DA. Probing Binding Interactions of Cytisine Derivatives to the α4β2 Nicotinic Acetylcholine Receptor. J Am Chem Soc 2019; 141:15840-15849. [DOI: 10.1021/jacs.9b06580] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
| | - Hugo Rego Campello
- School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
| | | | - Timothy Gallagher
- School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
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18
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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: 13] [Impact Index Per Article: 2.6] [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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19
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Blunt CEW, Dougherty DA. Binding Interactions of NS6740, a Silent Agonist of the α7 Nicotinic Acetylcholine Receptor. Mol Pharmacol 2019; 96:212-218. [PMID: 31175182 DOI: 10.1124/mol.119.116244] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Accepted: 05/28/2019] [Indexed: 11/22/2022] Open
Abstract
The α7 nicotinic acetylcholine receptor (nAChR) is a potential drug target for the treatment of a number of neurologic and inflammatory disorders. Silent agonists are an emerging class of drugs that bind to the receptor but do not open the channel. Instead they shift the receptor to a desensitized state. Silent agonists may be able to target a subset of α7 nAChR-mediated signaling processes. Here we use noncanonical amino acid mutagenesis to characterize the binding to α7 by the silent agonist 1,4-diazabicyclo[3.2.2]nonan-4-yl(5-(3-(trifluoromethyl)phenyl)furan-2-yl)methanone (NS6740). We find that, like α7 agonists, NS6740 forms a cation-π interaction with Y115 (TyrA). We also showed that NS6740 makes a novel hydrogen bond to TyrA. This interaction is necessary for the silent agonist activity of NS6740; when the hydrogen bond is blocked, silent agonist NS6740 converts to a conventional partial agonist and appreciably opens the channel in the absence of a positive allosteric modulator (EC50 150 nM). SIGNIFICANCE STATEMENT: Noncanonical amino acids were used to show that a hydrogen bond to tyrosine (Y115) is required for silent agonist activity of NS6740 at the α7 nicotinic acetylcholine receptor.
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Affiliation(s)
- Catriona E W Blunt
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California
| | - Dennis A Dougherty
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California
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20
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Shivange AV, Borden PM, Muthusamy AK, Nichols AL, Bera K, Bao H, Bishara I, Jeon J, Mulcahy MJ, Cohen B, O'Riordan SL, Kim C, Dougherty DA, Chapman ER, Marvin JS, Looger LL, Lester HA. Determining the pharmacokinetics of nicotinic drugs in the endoplasmic reticulum using biosensors. J Gen Physiol 2019; 151:738-757. [PMID: 30718376 PMCID: PMC6571994 DOI: 10.1085/jgp.201812201] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 11/05/2018] [Accepted: 01/09/2019] [Indexed: 12/27/2022] Open
Abstract
Nicotine dependence is thought to arise in part because nicotine permeates into the endoplasmic reticulum (ER), where it binds to nicotinic receptors (nAChRs) and begins an "inside-out" pathway that leads to up-regulation of nAChRs on the plasma membrane. However, the dynamics of nicotine entry into the ER are unquantified. Here, we develop a family of genetically encoded fluorescent biosensors for nicotine, termed iNicSnFRs. The iNicSnFRs are fusions between two proteins: a circularly permutated GFP and a periplasmic choline-/betaine-binding protein engineered to bind nicotine. The biosensors iNicSnFR3a and iNicSnFR3b respond to nicotine by increasing fluorescence at [nicotine] <1 µM, the concentration in the plasma and cerebrospinal fluid of a smoker. We target iNicSnFR3 biosensors either to the plasma membrane or to the ER and measure nicotine kinetics in HeLa, SH-SY5Y, N2a, and HEK293 cell lines, as well as mouse hippocampal neurons and human stem cell-derived dopaminergic neurons. In all cell types, we find that nicotine equilibrates in the ER within 10 s (possibly within 1 s) of extracellular application and leaves as rapidly after removal from the extracellular solution. The [nicotine] in the ER is within twofold of the extracellular value. We use these data to run combined pharmacokinetic and pharmacodynamic simulations of human smoking. In the ER, the inside-out pathway begins when nicotine becomes a stabilizing pharmacological chaperone for some nAChR subtypes, even at concentrations as low as ∼10 nM. Such concentrations would persist during the 12 h of a typical smoker's day, continually activating the inside-out pathway by >75%. Reducing nicotine intake by 10-fold decreases activation to ∼20%. iNicSnFR3a and iNicSnFR3b also sense the smoking cessation drug varenicline, revealing that varenicline also permeates into the ER within seconds. Our iNicSnFRs enable optical subcellular pharmacokinetics for nicotine and varenicline during an early event in the inside-out pathway.
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Affiliation(s)
- Amol V Shivange
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA
| | - Philip M Borden
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA
| | - Anand K Muthusamy
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA
| | - Aaron L Nichols
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA
| | - Kallol Bera
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA
| | - Huan Bao
- Howard Hughes Medical Institute and Department of Neuroscience, University of Wisconsin, Madison, WI
| | - Ishak Bishara
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA
| | - Janice Jeon
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA
| | - Matthew J Mulcahy
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA
| | - Bruce Cohen
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA
| | - Saidhbhe L O'Riordan
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA
| | - Charlene Kim
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA
| | - Dennis A Dougherty
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA
| | - Edwin R Chapman
- Howard Hughes Medical Institute and Department of Neuroscience, University of Wisconsin, Madison, WI
| | - Jonathan S Marvin
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA
| | - Loren L Looger
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA
| | - Henry A Lester
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA
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21
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Joyce RL, Beyer NP, Vasilopoulos G, Woll KA, Hall AC, Eckenhoff RG, Barman DN, Warren JD, Tibbs GR, Goldstein PA. Alkylphenol inverse agonists of HCN1 gating: H-bond propensity, ring saturation and adduct geometry differentially determine efficacy and potency. Biochem Pharmacol 2019; 163:493-508. [PMID: 30768926 DOI: 10.1016/j.bcp.2019.02.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Accepted: 02/11/2019] [Indexed: 10/27/2022]
Abstract
BACKGROUND AND PURPOSE In models of neuropathic pain, inhibition of HCN1 is anti-hyperalgesic. 2,6-di-iso-propyl phenol (propofol) and its non-anesthetic congener, 2,6-di-tert-butyl phenol, inhibit HCN1 channels by stabilizing closed state(s). EXPERIMENTAL APPROACH Using in vitro electrophysiology and kinetic modeling, we systematically explore the contribution of ligand architecture to alkylphenol-channel coupling. KEY RESULTS When corrected for changes in hydrophobicity (and propensity for intra-membrane partitioning), the decrease in potency upon 1-position substitution (NCO∼OH >> SH >>> F) mirrors the ligands' H-bond acceptor (NCO > OH > SH >>> F) but not donor profile (OH > SH >>> NCO∼F). H-bond elimination (OH to F) corresponds to a ΔΔG of ∼4.5 kCal mol-1 loss of potency with little or no disruption of efficacy. Substitution of compact alkyl groups (iso-propyl, tert-butyl) with shorter (ethyl, methyl) or more extended (sec-butyl) adducts disrupts both potency and efficacy. Ring saturation (with the obligate loss of both planarity and π electrons) primarily disrupts efficacy. CONCLUSIONS AND IMPLICATIONS A hydrophobicity-independent decrement in potency at higher volumes suggests the alkylbenzene site has a volume of ≥800 Å3. Within this, a relatively static (with respect to ligand) H-bond donor contributes to initial binding with little involvement in generation of coupling energy. The influence of π electrons/ring planarity and alkyl adducts on efficacy reveals these aspects of the ligand present towards a face of the channel that undergoes structural changes during opening. The site's characteristics suggest it is "druggable"; introduction of other adducts on the ring may generate higher potency inverse agonists.
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Affiliation(s)
| | | | | | - Kellie A Woll
- University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, United States
| | - Adam C Hall
- Smith College, Northampton, MA, United States
| | - Roderic G Eckenhoff
- University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, United States
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22
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Sereikaitė V, Jensen TMT, Bartling CRO, Jemth P, Pless SA, Strømgaard K. Probing Backbone Hydrogen Bonds in Proteins by Amide-to-Ester Mutations. Chembiochem 2018; 19:2136-2145. [PMID: 30073762 DOI: 10.1002/cbic.201800350] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Indexed: 01/09/2023]
Abstract
All proteins contain characteristic backbones formed of consecutive amide bonds, which can engage in hydrogen bonds. However, the importance of these is not easily addressed by conventional technologies that only allow for side-chain substitutions. By contrast, technologies such as nonsense suppression mutagenesis and protein ligation allow for manipulation of the protein backbone. In particular, replacing the backbone amide groups with ester groups, that is, amide-to-ester mutations, is a powerful tool to examine backbone-mediated hydrogen bonds. In this minireview, we showcase examples of how amide-to-ester mutations can be used to uncover pivotal roles of backbone-mediated hydrogen bonds in protein recognition, folding, function, and structure.
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Affiliation(s)
- Vita Sereikaitė
- Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, 2200, Copenhagen, Denmark
| | - Thomas M T Jensen
- Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, 2200, Copenhagen, Denmark
| | - Christian R O Bartling
- Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, 2200, Copenhagen, Denmark
| | - Per Jemth
- Department of Medical Biochemistry and Microbiology, Uppsala University, BMC, Box 582, 75123, Uppsala, Sweden
| | - Stephan A Pless
- Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, 2200, Copenhagen, Denmark
| | - Kristian Strømgaard
- Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, 2200, Copenhagen, Denmark
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23
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24
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Pless SA, Sivilotti LG. A tale of ligands big and small: an update on how pentameric ligand-gated ion channels interact with agonists and proteins. CURRENT OPINION IN PHYSIOLOGY 2018; 2:19-26. [PMID: 31231710 DOI: 10.1016/j.cophys.2017.12.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Pentameric ligand-gated ion channels (pLGICs, also known as Cys-loop receptors) are a large family of ion channels expressed in all Bilateria and in several groups of bacteria and archaea. They are activated by small-molecule neurotransmitters to mediate fast transmission at many central and peripheral nervous system synapses and are the target of several drugs and insecticides. Here we review recent advances in the field, focussing on new insights on the structure of the agonist-binding site and on newly discovered protein-protein interactions involving pLGICs.
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Affiliation(s)
- Stephan A Pless
- Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Lucia G Sivilotti
- Department of Neuroscience, Physiology and Pharmacology, Division of Biosciences, University College London, Gower St, London WC1E 6BT, United Kingdom
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25
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Kudryavtsev DS, Spirova EN, Shelukhina IV, Son LV, Makarova YV, Utkina NK, Kasheverov IE, Tsetlin VI. Makaluvamine G from the Marine Sponge Zyzzia fuliginosa Inhibits Muscle nAChR by Binding at the Orthosteric and Allosteric Sites. Mar Drugs 2018; 16:md16040109. [PMID: 29597332 PMCID: PMC5923396 DOI: 10.3390/md16040109] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2018] [Revised: 03/16/2018] [Accepted: 03/23/2018] [Indexed: 12/19/2022] Open
Abstract
Diverse ligands of the muscle nicotinic acetylcholine receptor (nAChR) are used as muscle relaxants during surgery. Although a plethora of such molecules exists in the market, there is still a need for new drugs with rapid on/off-set, increased selectivity, and so forth. We found that pyrroloiminoquinone alkaloid Makaluvamine G (MG) inhibits several subtypes of nicotinic receptors and ionotropic γ-aminobutiric acid receptors, showing a higher affinity and moderate selectivity toward muscle nAChR. The action of MG on the latter was studied by a combination of electrophysiology, radioligand assay, fluorescent microscopy, and computer modeling. MG reveals a combination of competitive and un-competitive inhibition and caused an increase in the apparent desensitization rate of the murine muscle nAChR. Modeling ion channel kinetics provided evidence for MG binding in both orthosteric and allosteric sites. We also demonstrated that theα1 (G153S) mutant of the receptor, associated with the myasthenic syndrome, is more prone to inhibition by MG. Thus, MG appears to be a perspective hit molecule for the design of allosteric drugs targeting muscle nAChR, especially for treating slow-channel congenital myasthenic syndromes.
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Affiliation(s)
- Denis S Kudryavtsev
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russia.
| | - Ekaterina N Spirova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russia.
| | - Irina V Shelukhina
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russia.
| | - Lina V Son
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russia.
- Moscow Institute of Physics and Technology, Institutsky Per. 9, Dolgoprudny, 141700 Moscow Region, Russia.
| | - Yana V Makarova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russia.
| | - Natalia K Utkina
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry (PIBOC), Russian Academy of Sciences, Prospect 100 let Vladivostoku, 159, 690022 Vladivostok, Russia.
| | - Igor E Kasheverov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russia.
| | - Victor I Tsetlin
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russia.
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26
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Callau-Vázquez D, Pless SA, Lynagh T. Investigation of Agonist Recognition and Channel Properties in a Flatworm Glutamate-Gated Chloride Channel. Biochemistry 2018; 57:1360-1368. [PMID: 29411605 DOI: 10.1021/acs.biochem.7b01245] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Glutamate-gated chloride channels (GluCls) are neurotransmitter receptors that mediate crucial inhibitory signaling in invertebrate neuromuscular systems. Their role in invertebrate physiology and their absence from vertebrates make GluCls a prime target for antiparasitic drugs. GluCls from flatworm parasites are substantially different from and are much less understood than those from roundworm and insect parasites, hindering the development of potential therapeutics targeting GluCls in flatworm-related diseases such as schistosomiasis. Here, we sought to dissect the molecular and chemical basis for ligand recognition in the extracellular glutamate binding site of SmGluCl-2 from Schistosoma mansoni, using site-directed mutagenesis, noncanonical amino acid incorporation, and electrophysiological recordings. Our results indicate that aromatic residues in ligand binding loops A, B, and C are important for SmGluCl-2 function. Loop C, which differs in length compared to other pentameric ligand-gated ion channels (pLGICs), contributes to ligand recognition through both an aromatic residue and two vicinal threonine residues. We also show that, in contrast to other pLGICs, the hydrophobic channel gate in SmGluCl-2 extends from the 9' position to the 6' position in the channel-forming M2 helix. The 6' and 9' positions also seem to control sensitivity to the pore blocker picrotoxin.
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Affiliation(s)
- Daniel Callau-Vázquez
- Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen , Jagtvej 160, 2100 Copenhagen, Denmark
| | - Stephan A Pless
- Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen , Jagtvej 160, 2100 Copenhagen, Denmark
| | - Timothy Lynagh
- Center for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen , Jagtvej 160, 2100 Copenhagen, Denmark
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27
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Designing selective modulators for the nicotinic receptor subtypes: challenges and opportunities. Future Med Chem 2018; 10:433-459. [PMID: 29451400 DOI: 10.4155/fmc-2017-0169] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Nicotinic receptors are membrane proteins involved in several physiological processes. They are considered suitable drug targets for various CNS disorders or conditions, as shown by the large number of compounds which have entered clinical trials. In recent years, nonconventional agonists have been discovered: positive allosteric modulators, allosteric agonists, site-specific agonists and silent desensitizers are compounds able to modulate the receptor interacting at sites different from the orthodox one, or to desensitize the receptor without prior opening. While these new findings can further complicate the pharmacology of these proteins and the design and optimization of ligands, they undoubtedly offer new opportunities to find drugs for the many therapeutic indications involving nicotinic receptors.
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28
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Juszczak LJ, Eisenberg AS. The Color of Cation-π Interactions: Subtleties of Amine-Tryptophan Interaction Energetics Allow for Radical-like Visible Absorbance and Fluorescence. J Am Chem Soc 2017; 139:8302-8311. [PMID: 28537725 DOI: 10.1021/jacs.7b03442] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Several peptides and a protein with an inter- or intramolecular cation-π interaction between tryptophan (Trp) and an amine cation are shown to absorb and fluoresce in the visible region of the spectrum. Titration of indole with sodium hydroxide or ammonium hydroxide yields an increasing visible fluorescence as well. Visible absorption and multipeaked fluorescence excitation spectra correlate with experimental absorption spectra and the vibrational modes of calculated absorption spectra for the neutral Trp radical. The radical character of the cation-indole interaction is predicted to stem from the electrostatic dislocation of indole highest occupied molecular orbital (HOMO) charge density toward the cation with a subsequent electronic transition from the HOMO-2 to the HOMO. Because this is a vertical transition, fluorescence is possible. Hydrogen bonding at the indole amine most likely stabilizes the radical-like state. These results provide new spectroscopic tools for the investigation of cation-π interactions in numerous biological systems, among them, proteins and their myriad ligands, and show that one, or at most, two, point mutations with natural amino acids are all that is required to impart visible fluorescence to proteins.
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Affiliation(s)
- Laura J Juszczak
- Chemistry Department, Brooklyn College, The City University of New York , New York, New York 11210, United States.,PhD programs in Chemistry and Biochemistry, The Graduate Center, The City University of New York , New York, New York 10016, United States
| | - Azaria S Eisenberg
- Chemistry Department, Brooklyn College, The City University of New York , New York, New York 11210, United States
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29
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Secondary Ammonium Agonists Make Dual Cation-π Interactions in α4β2 Nicotinic Receptors. eNeuro 2017; 4:eN-NWR-0032-17. [PMID: 28589175 PMCID: PMC5458768 DOI: 10.1523/eneuro.0032-17.2017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Revised: 02/28/2017] [Accepted: 03/02/2017] [Indexed: 11/21/2022] Open
Abstract
A cation-π interaction between the ammonium group of an agonist and a conserved tryptophan termed TrpB is a near universal feature of agonist binding to nicotinic acetylcholine receptors (nAChRs). TrpB is one of five residues that form the aromatic box of the agonist binding site, and for the prototype agonists ACh and nicotine, only TrpB makes a functional cation-π interaction. We report that, in addition to TrpB, a significant cation-π interaction is made to a second aromatic, TyrC2, by the agonists metanicotine, TC299423, varenicline, and nornicotine. A common structural feature of these agonists, and a distinction from ACh and nicotine, is a protonated secondary amine that provides the cation for the cation-π interaction. These results indicate a distinction in binding modes between agonists with subtly different structures that may provide guidance for the development of subtype-selective agonists of nAChRs.
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30
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Post MR, Lester HA, Dougherty DA. Probing for and Quantifying Agonist Hydrogen Bonds in α6β2 Nicotinic Acetylcholine Receptors. Biochemistry 2017; 56:1836-1840. [PMID: 28287260 DOI: 10.1021/acs.biochem.7b00213] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Designing subtype-selective agonists for neuronal nicotinic acetylcholine receptors is a challenging and significant goal aided by intricate knowledge of each subtype's binding patterns. We previously reported that in α6β2 receptors, acetylcholine makes a functional cation-π interaction with Trp149, but nicotine and TC299423 do not, suggesting a distinctive binding site. This work explores hydrogen binding at the backbone carbonyl associated with α6β2 Trp149. Substituting residue i + 1, Thr150, with its α-hydroxy analogue (Tah) attenuates the carbonyl's hydrogen bond accepting ability. At α6(T150Tah)β2, nicotine shows a 24-fold loss of function, TC299423 shows a modest loss, and acetylcholine shows no effect. Nicotine was further analyzed via a double-mutant cycle analysis utilizing N'-methylnicotinium, which indicated a hydrogen bond in α6β2 with a ΔΔG of 2.6 kcal/mol. Thus, even though nicotine does not make the conserved cation-π interaction with Trp149, it still makes a functional hydrogen bond to its associated backbone carbonyl.
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Affiliation(s)
- Michael R Post
- Division of Chemistry and Chemical Engineering and ‡Division of Biology and Biological Engineering, California Institute of Technology , Pasadena, California 91125, United States
| | - Henry A Lester
- Division of Chemistry and Chemical Engineering and ‡Division of Biology and Biological Engineering, California Institute of Technology , Pasadena, California 91125, United States
| | - Dennis A Dougherty
- Division of Chemistry and Chemical Engineering and ‡Division of Biology and Biological Engineering, California Institute of Technology , Pasadena, California 91125, United States
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Zheng F, Du X, Chou TH, Robertson AP, Yu EW, VanVeller B, Martin RJ. (S)-5-ethynyl-anabasine, a novel compound, is a more potent agonist than other nicotine alkaloids on the nematode Asu-ACR-16 receptor. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2016; 7:12-22. [PMID: 28033523 PMCID: PMC5196235 DOI: 10.1016/j.ijpddr.2016.12.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 11/23/2016] [Accepted: 12/02/2016] [Indexed: 12/13/2022]
Abstract
Nematode parasites infect ∼2 billion people world-wide. Infections are treated and prevented by anthelmintic drugs, some of which act on nicotinic acetylcholine receptors (nAChRs). There is an unmet need for novel therapeutic agents because of concerns about the development of resistance. We have selected Asu-ACR-16 from a significant nematode parasite genus, Ascaris suum, as a pharmaceutical target and nicotine as our basic moiety (EC50 6.21 ± 0.56 μM, Imax 82.39 ± 2.52%) to facilitate the development of more effective anthelmintics. We expressed Asu-ACR-16 in Xenopus oocytes and used two-electrode voltage clamp electrophysiology to determine agonist concentration-current-response relationships and determine the potencies (EC50s) of the agonists. Here, we describe the synthesis of a novel agonist, (S)-5-ethynyl-anabasine, and show that it is more potent (EC50 0.14 ± 0.01 μM) than other nicotine alkaloids on Asu-ACR-16. Agonists acting on ACR-16 receptors have the potential to circumvent drug resistance to anthelmintics, like levamisole, that do not act on the ACR-16 receptors. ACR-16 receptor agonists may overcome resistance to anthelmintics like levamisole. We modeled the Asu-ACR-16 of Ascaris as a target for novel anthelmintic development. We synthesized novel nicotinic agonists including (S)-5-ethynyl-anabasine. We expressed Asu-ACR-16 in Xenopus oocytes to determine agonists potencies. (S)-5-ethynyl-anabasine is more potent (EC50 0.1 μM) than other nicotinic alkaloids.
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Affiliation(s)
- Fudan Zheng
- Department of Chemistry, College of Liberal Arts and Sciences, Iowa State University, Ames, IA, USA
| | - Xiangwei Du
- Department of Chemistry, College of Liberal Arts and Sciences, Iowa State University, Ames, IA, USA
| | - Tsung-Han Chou
- Department of Physics and Astronomy, College of Liberal Arts and Sciences, Iowa State University, Ames, IA, USA
| | - Alan P Robertson
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA, USA
| | - Edward W Yu
- Department of Physics and Astronomy, College of Liberal Arts and Sciences, Iowa State University, Ames, IA, USA
| | - Brett VanVeller
- Department of Chemistry, College of Liberal Arts and Sciences, Iowa State University, Ames, IA, USA
| | - Richard J Martin
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA, USA.
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Davis MR, Dougherty DA. Cation-π interactions: computational analyses of the aromatic box motif and the fluorination strategy for experimental evaluation. Phys Chem Chem Phys 2016; 17:29262-70. [PMID: 26467787 DOI: 10.1039/c5cp04668h] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Cation-π interactions are common in biological systems, and many structural studies have revealed the aromatic box as a common motif. With the aim of understanding the nature of the aromatic box, several computational methods were evaluated for their ability to reproduce experimental cation-π binding energies. We find the DFT method M06 with the 6-31G(d,p) basis set performs best of several methods tested. The binding of benzene to a number of different cations (sodium, potassium, ammonium, tetramethylammonium, and guanidinium) was studied. In addition, the binding of the organic cations NH4(+) and NMe4(+) to ab initio generated aromatic boxes as well as examples of aromatic boxes from protein crystal structures were investigated. These data, along with a study of the distance dependence of the cation-π interaction, indicate that multiple aromatic residues can meaningfully contribute to cation binding, even with displacements of more than an angstrom from the optimal cation-π interaction. Progressive fluorination of benzene and indole was studied as well, and binding energies obtained were used to reaffirm the validity of the "fluorination strategy" to study cation-π interactions in vivo.
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Affiliation(s)
- Matthew R Davis
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E California Blvd, Pasadena CA 91125, USA.
| | - Dennis A Dougherty
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E California Blvd, Pasadena CA 91125, USA.
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Abstract
On the basis of many literature measurements, a critical overview is given on essential noncovalent interactions in synthetic supramolecular complexes, accompanied by analyses with selected proteins. The methods, which can be applied to derive binding increments for single noncovalent interactions, start with the evaluation of consistency and additivity with a sufficiently large number of different host-guest complexes by applying linear free energy relations. Other strategies involve the use of double mutant cycles, of molecular balances, of dynamic combinatorial libraries, and of crystal structures. Promises and limitations of these strategies are discussed. Most of the analyses stem from solution studies, but a few also from gas phase. The empirically derived interactions are then presented on the basis of selected complexes with respect to ion pairing, hydrogen bonding, electrostatic contributions, halogen bonding, π-π-stacking, dispersive forces, cation-π and anion-π interactions, and contributions from the hydrophobic effect. Cooperativity in host-guest complexes as well as in self-assembly, and entropy factors are briefly highlighted. Tables with typical values for single noncovalent free energies and polarity parameters are in the Supporting Information.
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Affiliation(s)
- Frank Biedermann
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT) , Hermann-von-Helmholtz Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Hans-Jörg Schneider
- FR Organische Chemie der Universität des Saarlandes , D-66041 Saarbrücken, Germany
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Braun N, Lynagh T, Yu R, Biggin PC, Pless SA. Role of an Absolutely Conserved Tryptophan Pair in the Extracellular Domain of Cys-Loop Receptors. ACS Chem Neurosci 2016; 7:339-48. [PMID: 26764897 DOI: 10.1021/acschemneuro.5b00298] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Cys-loop receptors mediate fast synaptic transmission in the nervous system, and their dysfunction is associated with a number of diseases. While some sequence variability is essential to ensure specific recognition of a chemically diverse set of ligands, other parts of the underlying amino acid sequences show a high degree of conservation, possibly to preserve the overall structural fold across the protein family. In this study, we focus on the only two absolutely conserved residues across the Cys-loop receptor family, two Trp side chains in the WXD motif of Loop D and in the WXPD motif of Loop A. Using a combination of conventional mutagenesis, unnatural amino acid incorporation, immunohistochemistry and MD simulations, we demonstrate the crucial contributions of these two Trp residues to receptor expression and function in two prototypical Cys-loop receptors, the anion-selective GlyR α1 and the cation-selective nAChR α7. Specifically, our results rule out possible electrostatic contributions of these Trp side chains and instead suggest that the overall size and shape of this aromatic pair is required in stabilizing the Cys-loop receptor extracellular domain.
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Affiliation(s)
- Nina Braun
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen 2100, Denmark
| | - Timothy Lynagh
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen 2100, Denmark
| | - Rilei Yu
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Philip C. Biggin
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Stephan A. Pless
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen 2100, Denmark
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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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Post MR, Limapichat W, Lester HA, Dougherty DA. Heterologous expression and nonsense suppression provide insights into agonist behavior at α6β2 nicotinic acetylcholine receptors. Neuropharmacology 2015; 97:376-82. [PMID: 25908401 DOI: 10.1016/j.neuropharm.2015.04.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Revised: 03/27/2015] [Accepted: 04/10/2015] [Indexed: 10/23/2022]
Abstract
The α6-containing subtypes of the nicotinic acetylcholine receptor (nAChR) are localized to presynaptic terminals of the dopaminergic pathways of the central nervous system. Selective ligands for these nAChRs are potentially useful in both Parkinson's disease and addiction. For these and other goals, it is important to distinguish the binding behavior of agonists at the α6-β2 binding site versus other subtypes. To study this problem, we apply nonsense suppression-based non-canonical amino acid mutagenesis. We report a combination of four mutations in α6β2 that yield high-level heterologous expression in Xenopus oocytes. By varying mRNA injection ratios, two populations were observed with unique characteristics, likely due to differing stoichiometries. Responses to nine known nAChR agonists were analyzed at the receptor, and their corresponding EC50 values and efficacies are reported. The system is compatible with nonsense suppression, allowing structure-function studies between Trp149 - a conserved residue on loop B found to make a cation-π interaction at several nAChR subtypes - and several agonists. These studies reveal that acetylcholine forms a strong cation-π interaction with the conserved tryptophan, while nicotine and TC299423 do not, suggesting a unique pharmacology for the α6β2 nAChR.
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Affiliation(s)
- Michael R Post
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E California Blvd., Pasadena, CA 91125, USA
| | - Walrati Limapichat
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E California Blvd., Pasadena, CA 91125, USA
| | - Henry A Lester
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Dennis A Dougherty
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E California Blvd., Pasadena, CA 91125, USA.
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Selvam B, Graton J, Laurent AD, Alamiddine Z, Mathé-Allainmat M, Lebreton J, Coqueret O, Olivier C, Thany SH, Le Questel JY. Imidacloprid and thiacloprid neonicotinoids bind more favourably to cockroach than to honeybee α6 nicotinic acetylcholine receptor: Insights from computational studies. J Mol Graph Model 2015; 55:1-12. [DOI: 10.1016/j.jmgm.2014.10.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 10/30/2014] [Accepted: 10/31/2014] [Indexed: 11/26/2022]
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Miles TF, Lester HA, Dougherty DA. Allosteric activation of the 5-HT3AB receptor by mCPBG. Neuropharmacology 2014; 91:103-8. [PMID: 25541413 DOI: 10.1016/j.neuropharm.2014.12.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Revised: 10/16/2014] [Accepted: 12/10/2014] [Indexed: 10/25/2022]
Abstract
The 5-HT3AB receptor contains three A and two B subunits in an A-A-B-A-B order. However, serotonin function at the 5-HT3AB receptor has been shown to depend solely on the A-A interface present in the homomeric receptor. Using mutations at sites on both the primary (E122) and complementary (Y146) faces of the B subunit, we demonstrate that meta-chlorophenyl biguanide (mCPBG), a 5-HT3 selective agonist, is capable of binding to and activating the 5-HT3AB receptor at all five subunit interfaces of the heteromer. Further, mCPBG is capable of allosterically modulating the activity of serotonin from these sites. While these five binding sites are similar enough that they conform to a monophasic dose - response relationship, we uncover subtle differences in the heteromeric binding sites. We also find that the A-A interface appears to contribute disproportionately to the efficacy of 5-HT3AB receptor activation.
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Affiliation(s)
- Timothy F Miles
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125, USA
| | - Henry A Lester
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125, USA
| | - Dennis A Dougherty
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125, USA.
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Daeffler KNM, Lester HA, Dougherty DA. Functional evaluation of key interactions evident in the structure of the eukaryotic Cys-loop receptor GluCl. ACS Chem Biol 2014; 9:2283-90. [PMID: 25051140 PMCID: PMC4201344 DOI: 10.1021/cb500323d] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
![]()
The
publication of the first high-resolution crystal structure
of a eukaryotic Cys-loop receptor, GluClα, has provided valuable
structural information on this important class of ligand-gated ion
channels (LGIC). However, limited functional data exist for the GluCl
receptors. Before applying the structural insights from GluCl to mammalian
Cys-loop receptors such as nicotinic acetylcholine and GABA receptors,
it is important to ensure that established functional features of mammalian Cys-loop receptors are present in the more
distantly related GluCl receptors. Here, we seek to identify ligand-binding
interactions that are generally associated with Cys-loop receptors,
including the frequently observed cation−π interaction.
Our studies were performed on the highly homologous GluClβ receptor,
because GluClα is not activated by glutamate in Xenopus
laevis oocytes. Mutagenesis of the signal peptide and pore
lining helix was performed to enhance functional expression and sensitivity
to applied ligand, respectively. Conventional and unnatural amino
acid mutagenesis indicate a strong cation−π interaction
between Y206 and the protonated amine of glutamate, as well as other
important ionic and hydrogen bond interactions between the ligand
and the binding site, consistent with the crystal structure.
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Affiliation(s)
- Kristina N.-M. Daeffler
- Division of Chemistry & Chemical Engineering and ‡Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Henry A. Lester
- Division of Chemistry & Chemical Engineering and ‡Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Dennis A. Dougherty
- Division of Chemistry & Chemical Engineering and ‡Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125, United States
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