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Gao X, Guan Y, Wang C, Jia M, Ahmad S, Nouman MF, Ai H. Specific interaction from different Aβ 42 peptide fragments to α7nAChR-A study of molecular dynamics simulation. J Mol Model 2024; 30:233. [PMID: 38937296 DOI: 10.1007/s00894-024-06032-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2024] [Accepted: 06/18/2024] [Indexed: 06/29/2024]
Abstract
CONTEXT Existing researches confirmed that β amyloid (Aβ) has a high affinity for the α7 nicotinic acetylcholine receptor (α7nAChR), associating closely to Alzheimer's disease. The majority of related studies focused on the experimental reports on the neuroprotective role of Aβ fragment (Aβx), however, with a lack of investigation into the most suitable binding region and mechanism of action between Aβ fragment and α7nAChR. In the study, we employed four Aβ1-42 fragments Aβx, Aβ1-16, Aβ10-16, Aβ12-28, and Aβ30-42, of which the first three were confirmed to play neuroprotective roles upon directly binding, to interact with α7nAChR. METHODS The protein-ligand docking server of CABS-DOCK was employed to obtain the α7nAChR-Aβx complexes. Only the top α7nAChR-Aβx complexes were used to perform all-atom GROMACS dynamics simulation in combination with Charmm36 force field, by which α7nAChR-Aβx interactions' dynamic behavior and specific locations of these different Aβx fragments were identified. MM-PBSA calculations were also done to estimate the binding free energies and the different contributions from the residues in the Aβx. Two distinct results for the first three and fourth Aβx fragments in binding site, strength, key residue, and orientation, account for why the fourth fails to play a neuroprotective role at the molecular level.
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Affiliation(s)
- Xvzhi Gao
- School of Chemistry and Chemical Engineering, University of Jinan, Jinan, 250022, People's Republic of China
| | - Yvning Guan
- School of Chemistry and Chemical Engineering, University of Jinan, Jinan, 250022, People's Republic of China
| | - Chuanbo Wang
- School of Chemistry and Chemical Engineering, University of Jinan, Jinan, 250022, People's Republic of China
| | - Mengke Jia
- School of Chemistry and Chemical Engineering, University of Jinan, Jinan, 250022, People's Republic of China
| | - Sajjad Ahmad
- School of Chemistry and Chemical Engineering, University of Jinan, Jinan, 250022, People's Republic of China
| | - Muhammad Fahad Nouman
- School of Chemistry and Chemical Engineering, University of Jinan, Jinan, 250022, People's Republic of China
| | - Hongqi Ai
- School of Chemistry and Chemical Engineering, University of Jinan, Jinan, 250022, People's Republic of China.
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Shan H, Wang N, Gao X, Wang Z, Yu J, Zhangsun D, Zhu X, Luo S. Fluorescent α-Conotoxin [Q1G, ΔR14]LvIB Identifies the Distribution of α7 Nicotinic Acetylcholine Receptor in the Rat Brain. Mar Drugs 2024; 22:200. [PMID: 38786593 PMCID: PMC11122421 DOI: 10.3390/md22050200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2024] [Revised: 04/22/2024] [Accepted: 04/23/2024] [Indexed: 05/25/2024] Open
Abstract
α7 nicotinic acetylcholine receptors (nAChRs) are mainly distributed in the central nervous system (CNS), including the hippocampus, striatum, and cortex of the brain. The α7 nAChR has high Ca2+ permeability and can be quickly activated and desensitized, and is closely related to Alzheimer's disease (AD), epilepsy, schizophrenia, lung cancer, Parkinson's disease (PD), inflammation, and other diseases. α-conotoxins from marine cone snail venom are typically short, disulfide-rich neuropeptides targeting nAChRs and can distinguish various subtypes, providing vital pharmacological tools for the functional research of nAChRs. [Q1G, ΔR14]LvΙB is a rat α7 nAChRs selective antagonist, modified from α-conotoxin LvΙB. In this study, we utilized three types of fluorescein after N-Hydroxy succinimide (NHS) activation treatment: 6-TAMRA-SE, Cy3 NHS, and BODIPY-FL NHS, labeling the N-Terminal of [Q1G, ΔR14]LvΙB under weak alkaline conditions, obtaining three fluorescent analogs: LvIB-R, LvIB-C, and LvIB-B, respectively. The potency of [Q1G, ΔR14]LvΙB fluorescent analogs was evaluated at rat α7 nAChRs expressed in Xenopus laevis oocytes. Using a two-electrode voltage clamp (TEVC), the half-maximal inhibitory concentration (IC50) values of LvIB-R, LvIB-C, and LvIB-B were 643.3 nM, 298.0 nM, and 186.9 nM, respectively. The stability of cerebrospinal fluid analysis showed that after incubation for 12 h, the retention rates of the three fluorescent analogs were 52.2%, 22.1%, and 0%, respectively. [Q1G, ΔR14]LvΙB fluorescent analogs were applied to explore the distribution of α7 nAChRs in the hippocampus and striatum of rat brain tissue and it was found that Cy3- and BODIPY FL-labeled [Q1G, ΔR14]LvΙB exhibited better imaging characteristics than 6-TAMARA-. It was also found that α7 nAChRs are widely distributed in the cerebral cortex and cerebellar lobules. Taking into account potency, imaging, and stability, [Q1G, ΔR14]LvΙB -BODIPY FL is an ideal pharmacological tool to investigate the tissue distribution and function of α7 nAChRs. Our findings not only provide a foundation for the development of conotoxins as visual pharmacological probes, but also demonstrate the distribution of α7 nAChRs in the rat brain.
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Affiliation(s)
- Hongyu Shan
- Guangxi Key Laboratory of Special Biomedicine, School of Medicine, Guangxi University, Nanning 530004, China; (H.S.); (N.W.); (X.G.); (Z.W.); (J.Y.); (D.Z.)
| | - Nan Wang
- Guangxi Key Laboratory of Special Biomedicine, School of Medicine, Guangxi University, Nanning 530004, China; (H.S.); (N.W.); (X.G.); (Z.W.); (J.Y.); (D.Z.)
| | - Xinyu Gao
- Guangxi Key Laboratory of Special Biomedicine, School of Medicine, Guangxi University, Nanning 530004, China; (H.S.); (N.W.); (X.G.); (Z.W.); (J.Y.); (D.Z.)
| | - Zihan Wang
- Guangxi Key Laboratory of Special Biomedicine, School of Medicine, Guangxi University, Nanning 530004, China; (H.S.); (N.W.); (X.G.); (Z.W.); (J.Y.); (D.Z.)
| | - Jinpeng Yu
- Guangxi Key Laboratory of Special Biomedicine, School of Medicine, Guangxi University, Nanning 530004, China; (H.S.); (N.W.); (X.G.); (Z.W.); (J.Y.); (D.Z.)
| | - Dongting Zhangsun
- Guangxi Key Laboratory of Special Biomedicine, School of Medicine, Guangxi University, Nanning 530004, China; (H.S.); (N.W.); (X.G.); (Z.W.); (J.Y.); (D.Z.)
- Key Laboratory of Tropical Biological Resources of Ministry of Education, Hainan University, Haikou 570228, China
| | - Xiaopeng Zhu
- Guangxi Key Laboratory of Special Biomedicine, School of Medicine, Guangxi University, Nanning 530004, China; (H.S.); (N.W.); (X.G.); (Z.W.); (J.Y.); (D.Z.)
| | - Sulan Luo
- Guangxi Key Laboratory of Special Biomedicine, School of Medicine, Guangxi University, Nanning 530004, China; (H.S.); (N.W.); (X.G.); (Z.W.); (J.Y.); (D.Z.)
- Key Laboratory of Tropical Biological Resources of Ministry of Education, Hainan University, Haikou 570228, China
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Sanderson NSR. Complement and myasthenia gravis. Mol Immunol 2022; 151:11-18. [PMID: 36063582 DOI: 10.1016/j.molimm.2022.08.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 08/26/2022] [Accepted: 08/28/2022] [Indexed: 11/17/2022]
Abstract
Myasthenia gravis is a neuromuscular disease associated with antibodies against components of the neuromuscular junction, most often against the acetylcholine receptor (AChR). Although several mechanisms have been postulated to explain how these autoantibodies can lead to the pathology of the disease, convincing evidence suggests that destruction of the receptor-bearing postsynaptic membrane by complement membrane attack complex is of central importance. In this review, evidence for the importance of complement, and possible relationships between autoantigen, autoantibodies, complement activation, and the destruction of the membrane are discussed. More recent insights from the results of the complement-inhibiting therapeutic antibody eculizumab are also described, and the mechanisms connecting antibody binding to complement activation are considered from a structural viewpoint.
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Khatoon N, Adusumilli S, Dey P, Sharma R, Kampani P, Shandilya J, Nayak TK. Protein engineering and design in ion channels and receptors. Methods Cell Biol 2022; 169:143-168. [DOI: 10.1016/bs.mcb.2021.12.031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Elephants in the Dark: Insights and Incongruities in Pentameric Ligand-gated Ion Channel Models. J Mol Biol 2021; 433:167128. [PMID: 34224751 DOI: 10.1016/j.jmb.2021.167128] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Revised: 06/25/2021] [Accepted: 06/25/2021] [Indexed: 02/06/2023]
Abstract
The superfamily of pentameric ligand-gated ion channels (pLGICs) comprises key players in electrochemical signal transduction across evolution, including historic model systems for receptor allostery and targets for drug development. Accordingly, structural studies of these channels have steadily increased, and now approach 250 depositions in the protein data bank. This review contextualizes currently available structures in the pLGIC family, focusing on morphology, ligand binding, and gating in three model subfamilies: the prokaryotic channel GLIC, the cation-selective nicotinic acetylcholine receptor, and the anion-selective glycine receptor. Common themes include the challenging process of capturing and annotating channels in distinct functional states; partially conserved gating mechanisms, including remodeling at the extracellular/transmembrane-domain interface; and diversity beyond the protein level, arising from posttranslational modifications, ligands, lipids, and signaling partners. Interpreting pLGIC structures can be compared to describing an elephant in the dark, relying on touch alone to comprehend the many parts of a monumental beast: each structure represents a snapshot in time under specific experimental conditions, which must be integrated with further structure, function, and simulations data to build a comprehensive model, and understand how one channel may fundamentally differ from another.
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Amend N, Niessen KV, Seeger T, Wille T, Worek F, Thiermann H. Diagnostics and treatment of nerve agent poisoning—current status and future developments. Ann N Y Acad Sci 2020; 1479:13-28. [DOI: 10.1111/nyas.14336] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 02/25/2020] [Accepted: 03/05/2020] [Indexed: 12/20/2022]
Affiliation(s)
- Niko Amend
- Bundeswehr Institute of Pharmacology and Toxicology Munich Germany
| | - Karin V. Niessen
- Bundeswehr Institute of Pharmacology and Toxicology Munich Germany
| | - Thomas Seeger
- Bundeswehr Institute of Pharmacology and Toxicology Munich Germany
| | - Timo Wille
- Bundeswehr Institute of Pharmacology and Toxicology Munich Germany
| | - Franz Worek
- Bundeswehr Institute of Pharmacology and Toxicology Munich Germany
| | - Horst Thiermann
- Bundeswehr Institute of Pharmacology and Toxicology Munich Germany
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Al Rawashdah S, Hamrouni A, Sadek B, Amer R, Metwaly M, Atatreh N, Ghattas MA. Molecular modelling studies on ɑ7 nicotinic receptor allosteric modulators yields novel filter-based virtual screening protocol. J Mol Graph Model 2019; 92:44-54. [DOI: 10.1016/j.jmgm.2019.07.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 06/30/2019] [Accepted: 07/01/2019] [Indexed: 11/26/2022]
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van Goethem NP, Paes D, Puzzo D, Fedele E, Rebosio C, Gulisano W, Palmeri A, Wennogle LP, Peng Y, Bertrand D, Prickaerts J. Antagonizing α7 nicotinic receptors with methyllycaconitine (MLA) potentiates receptor activity and memory acquisition. Cell Signal 2019; 62:109338. [PMID: 31176021 DOI: 10.1016/j.cellsig.2019.06.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 06/03/2019] [Accepted: 06/03/2019] [Indexed: 12/11/2022]
Abstract
α7 nicotinic acetylcholine receptors (α7nAChRs) have been targeted to improve cognition in different neurological and psychiatric disorders. Nevertheless, no α7nAChR activating ligand has been clinically approved. Here, we investigated the effects of antagonizing α7nAChRs using the selective antagonist methyllycaconitine (MLA) on receptor activity in vitro and cognitive functioning in vivo. Picomolar concentrations of MLA significantly potentiated receptor responses in electrophysiological experiments mimicking the in vivo situation. Furthermore, microdialysis studies showed that MLA administration substantially increased hippocampal glutamate efflux which is related to memory processes. Accordingly, pre-tetanus administration of low MLA concentrations produced longer lasting potentiation (long-term potentiation, LTP) in studies examining hippocampal plasticity. Moreover, low doses of MLA improved acquisition, but not consolidation memory processes in rats. While the focus to enhance cognition by modulating α7nAChRs lies on agonists and positive modulators, antagonists at low doses should provide a novel approach to improve cognition in neurological and psychiatric disorders.
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Affiliation(s)
- Nick P van Goethem
- Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, Maastricht University, 6200, MD, Maastricht, The Netherlands
| | - Dean Paes
- Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, Maastricht University, 6200, MD, Maastricht, The Netherlands
| | - Daniela Puzzo
- Department of Biomedical and Biotechnological Sciences, Section of Physiology, University of Catania, 95124 Catania, Italy
| | - Ernesto Fedele
- Department of Pharmacy, Section of Pharmacology and Toxicology, School of Medical and Pharmaceutical Sciences, Centre of Excellence for Biomedical Research, University of Genoa, 16148 Genoa, Italy; IRCCS Polyclinic Hospital San Martino, 16132 Genoa, Italy
| | - Claudia Rebosio
- Department of Pharmacy, Section of Pharmacology and Toxicology, School of Medical and Pharmaceutical Sciences, Centre of Excellence for Biomedical Research, University of Genoa, 16148 Genoa, Italy
| | - Walter Gulisano
- Department of Biomedical and Biotechnological Sciences, Section of Physiology, University of Catania, 95124 Catania, Italy
| | - Agostino Palmeri
- Department of Biomedical and Biotechnological Sciences, Section of Physiology, University of Catania, 95124 Catania, Italy
| | | | - Youyi Peng
- Intra-Cellular Therapies, Inc., New York 10016, United States
| | - Daniel Bertrand
- HiQScreen Sàrl, 6, rte de Compois, 1222, Vésenaz, Geneva, Switzerland
| | - Jos Prickaerts
- Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, Maastricht University, 6200, MD, Maastricht, The Netherlands.
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Nichols AL, Noridomi K, Hughes CR, Jalali-Yazdi F, Eaton JB, Lai LH, Advani G, Lukas RJ, Lester HA, Chen L, Roberts RW. α1-FANGs: Protein Ligands Selective for the α-Bungarotoxin Site of the α1-Nicotinic Acetylcholine Receptor. ACS Chem Biol 2018; 13:2568-2576. [PMID: 30059207 DOI: 10.1021/acschembio.8b00513] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are pentameric ligand-gated ion channels that play a central role in neuronal and neuromuscular signal transduction. Here, we have developed FANG ligands, fibronectin antibody-mimetic nicotinic acetylcholine receptor-generated ligands, using mRNA display. We generated a 1 trillion-member primary e10FnIII library to target a stabilized α1 nicotinic subunit (α211). This library yielded 270000 independent potential protein binding ligands. The lead sequence, α1-FANG1, represented 25% of all library sequences, showed the highest-affinity binding, and competed with α-bungarotoxin (α-Btx). To improve this clone, a new library based on α1-FANG1 was subjected to heat, protease, binding, off-rate selective pressures, and point mutations. This resulted in α1-FANG2 and α1-FANG3. These proteins bind α211 with KD values of 3.5 nM and 670 pM, respectively, compete with α-Btx, and show improved subunit specificity. α1-FANG3 is thermostable ( Tm = 62 °C) with a 6 kcal/mol improvement in folding free energy compared with that of the parent α1-FANG1. α1-FANG3 competes directly with the α-Btx binding site of intact neuromuscular heteropentamers [(α1)2β1γδ] in mammalian culture-derived cellular membranes and in Xenopus laevis oocytes expressing these nAChRs. This work demonstrates that mRNA display against a monomeric ecto-domain of a pentamer has the capability to select ligands that bind that subunit in both a monomeric and a pentameric context. Overall, our work provides a route to creating a new family of stable, well-behaved proteins that specifically target this important receptor family.
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Affiliation(s)
- Aaron L. Nichols
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-1062, United States
| | - Kaori Noridomi
- Molecular and Computational Biology, Department of Biology, University of Southern California, Los Angeles, California 90089-0371, United States
| | - Christopher R. Hughes
- Mork Family Department of Chemical Engineering and Material Sciences, University of Southern California, Los Angeles, California 90089-1211, United States
| | - Farzad Jalali-Yazdi
- Mork Family Department of Chemical Engineering and Material Sciences, University of Southern California, Los Angeles, California 90089-1211, United States
| | - J. Brek Eaton
- Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, University of Arizona, Phoenix, Arizona 85013-4409, United States
| | - Lan Huong Lai
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-1062, United States
| | - Gaurav Advani
- Mork Family Department of Chemical Engineering and Material Sciences, University of Southern California, Los Angeles, California 90089-1211, United States
| | - Ronald J. Lukas
- Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, University of Arizona, Phoenix, Arizona 85013-4409, United States
| | - Henry A. Lester
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125-0001, United States
| | - Lin Chen
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-1062, United States
- Molecular and Computational Biology, Department of Biology, University of Southern California, Los Angeles, California 90089-0371, United States
- Norris Cancer Center, University of Southern California, Los Angeles, California 90033, United States
| | - Richard W. Roberts
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-1062, United States
- Molecular and Computational Biology, Department of Biology, University of Southern California, Los Angeles, California 90089-0371, United States
- Mork Family Department of Chemical Engineering and Material Sciences, University of Southern California, Los Angeles, California 90089-1211, United States
- Norris Cancer Center, University of Southern California, Los Angeles, California 90033, United States
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California 90089-1111, United States
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Liu W, Li MD. Insights Into Nicotinic Receptor Signaling in Nicotine Addiction: Implications for Prevention and Treatment. Curr Neuropharmacol 2018; 16:350-370. [PMID: 28762314 PMCID: PMC6018190 DOI: 10.2174/1570159x15666170801103009] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 06/18/2017] [Accepted: 07/28/2017] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Nicotinic acetylcholine receptors (nAChRs) belong to the Cys-loop ligandgated ion-channel (LGIC) superfamily, which also includes the GABA, glycine, and serotonin receptors. Many nAChR subunits have been identified and shown to be involved in signal transduction on binding to them of either the neurotransmitter acetylcholine or exogenous ligands such as nicotine. The nAChRs are pentameric assemblies of homologous subunits surrounding a central pore that gates cation flux, and they are expressed at neuromuscular junctions throughout the nervous system. METHODS AND RESULTS Because different nAChR subunits assemble into a variety of pharmacologically distinct receptor subtypes, and different nAChRs are implicated in various physiological functions and pathophysiological conditions, nAChRs represent potential molecular targets for drug addiction and medical therapeutic research. This review intends to provide insights into recent advances in nAChR signaling, considering the subtypes and subunits of nAChRs and their roles in nicotinic cholinergic systems, including structure, diversity, functional allosteric modulation, targeted knockout mutations, and rare variations of specific subunits, and the potency and functional effects of mutations by focusing on their effects on nicotine addiction (NA) and smoking cessation (SC). Furthermore, we review the possible mechanisms of action of nAChRs in NA and SC based on our current knowledge. CONCLUSION Understanding these cellular and molecular mechanisms will lead to better translational and therapeutic operations and outcomes for the prevention and treatment of NA and other drug addictions, as well as chronic diseases, such as Alzheimer's and Parkinson's. Finally, we put forward some suggestions and recommendations for therapy and treatment of NA and other chronic diseases.
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Affiliation(s)
- Wuyi Liu
- State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Zhejiang University School of Medicine, Hangzhou, China.,School of Biological Sciences and Food Engineering, Fuyang Normal University, Fuyang, Anuhi 236041, China
| | - Ming D Li
- State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Zhejiang University School of Medicine, Hangzhou, China.,Research Center for Air Pollution and Health, Zhejiang University, Hangzhou, China.,Institute of NeuroImmune Pharmacology, Seton Hall University, South Orange, NJ, United States
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Laule CF, Wing CR, Odean EJ, Wilcox JA, Gilbert JS, Regal JF. Effect of nicotine on placental ischemia-induced complement activation and hypertension in the rat. J Immunotoxicol 2018; 14:235-240. [PMID: 29185370 DOI: 10.1080/1547691x.2017.1394934] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Preeclampsia is a pregnancy-specific condition manifested by new-onset maternal hypertension with systemic inflammation, including increased innate immune system complement activation. While exact pathophysiology is unknown, evidence suggests that inadequate spiral artery invasion and resulting utero-placental insufficiency is the initiating event. Cigarette smoking during pregnancy decreases the risk of preeclampsia. Nicotine, a major component of cigarettes, stimulates the efferent cholinergic anti-inflammatory pathway through peripherally expressed nicotinic acetylcholine receptors (nAChR) and is known to attenuate ischemia-reperfusion injury in kidney and liver. Prior studies indicated that complement activation was critical for placental ischemia-induced hypertension in a rat model. Thus, it was hypothesized here that nicotine was responsible for the protective effect of cigarette smoking in preeclampsia and would attenuate placental ischemia-induced systemic complement activation and hypertension. The Reduced Utero-placental Perfusion Pressure (RUPP) model in the pregnant rat was employed to induce placental ischemia, resulting in complement activation, fetal resorptions, and hypertension. On gestation day (GD)14, nicotine (1 mg/kg) or saline was administered via subcutaneous injection prior to RUPP surgery and daily through GD18. On GD19, placental ischemia significantly increased mean arterial pressure (MAP) in saline injected animals. However, the placental ischemia-induced increase in blood pressure was not evident in nicotine-treated animals and nicotine treatment significantly increased MAP variability. Circulating C3a was measured as an indicator of complement activation and increased C3a in RUPP compared to Sham persisted with nicotine treatment, as did fetal resorptions. These data suggested to us that nicotine may contribute to the decreased risk of preeclampsia with cigarette smoking, but this protective effect was confounded by additional effects of nicotine on the cardiovascular system.
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Affiliation(s)
- Connor F Laule
- a Department of Biomedical Sciences , University of Minnesota, Medical School , Duluth , MN , USA
| | - Cameron R Wing
- a Department of Biomedical Sciences , University of Minnesota, Medical School , Duluth , MN , USA
| | - Evan J Odean
- a Department of Biomedical Sciences , University of Minnesota, Medical School , Duluth , MN , USA
| | - Jacob A Wilcox
- a Department of Biomedical Sciences , University of Minnesota, Medical School , Duluth , MN , USA
| | - Jeffrey S Gilbert
- a Department of Biomedical Sciences , University of Minnesota, Medical School , Duluth , MN , USA
| | - Jean F Regal
- a Department of Biomedical Sciences , University of Minnesota, Medical School , Duluth , MN , USA
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Targowska-Duda KM, Kaczor AA, Jozwiak K, Arias HR. Molecular interactions of type I and type II positive allosteric modulators with the human α7 nicotinic acetylcholine receptor: an in silico study. J Biomol Struct Dyn 2018; 37:411-439. [PMID: 29363414 DOI: 10.1080/07391102.2018.1427634] [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: 10/18/2022]
Abstract
The binding site locations and structural components for type I and type II positive allosteric modulators (PAMs) of the α7 nicotinic acetylcholine receptor (nAChR) have not been fully characterized yet. In this regard, homology models of the human α7 nAChR and hα7/m5-HT3A chimera, built using the crystal structure of the serotonin type 3A receptor (5-ΗΤ3ΑR), were used for molecular docking and molecular dynamics simulations to study the molecular interactions of selected type I (5-hydroxyindol, NS-1738, and LY-2087101) and type II (PNU-120596, PAM-2, and TBS-516) PAMs. The docking results indicate: (1) a site located in the extracellular domain (ECD) for type I PAMs such as NS-1738 and LY-2087101, but not for 5-HI; (2) an overlapping site in the ECD-transmembrane domain (TMD) junction for all studied PAMs. Additional docking results on the hα7/m5-HT3A chimera supported experimental results indicating that the ECD site might be relevant for type I PAM activity; and (3) two TMD sites, an intrasubunit site that recognizes type II PAMs, and an intersubunit pocket with high specificity for 5-HI (type I PAM). The in silico α7TSLMF mutant results support the view that M1-Ser223 and M3-Ile281 are key residues for the interaction of PAM-2 and PNU-120596 with the intrasubunit cavity. Our in silico results are in agreement with experimental data showing that the intrasubunit cavity is relevant for the activity of type II PAMs, and suggest that the ECD-TMD junction and intersubunit sites could be significant for the activity of type I PAMs.
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Affiliation(s)
| | - Agnieszka A Kaczor
- b Department of Synthesis and Chemical Technology of Pharmaceutical Substances with Computer Modeling Lab , Medical University of Lublin , Lublin , Poland.,c School of Pharmacy , University of Eastern Finland , Kuopio , Finland
| | - Krzysztof Jozwiak
- a Department of Biopharmacy , Medical University of Lublin , Lublin , Poland
| | - Hugo R Arias
- d Department of Basic Sciences , California Northstate University College of Medicine , Elk Grove , CA , USA
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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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14
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Bürgi JJ, Bertrand S, Marger F, Bertrand D, Reymond J. Fluorescent Agonists of the
α
7 Nicotinic Acetylcholine Receptor Derived from 3‐Amino‐Quinuclidine. Helv Chim Acta 2016. [DOI: 10.1002/hlca.201600120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Justus J. Bürgi
- Department of Chemistry and Biochemistry University of Berne Freiestrasse 3 CH‐3012 Berne
| | - Sonia Bertrand
- HiQScreen Sàrl 6 route de Compois CH‐1222 Vésenaz Geneva
| | - Fabrice Marger
- HiQScreen Sàrl 6 route de Compois CH‐1222 Vésenaz Geneva
| | | | - Jean‐Louis Reymond
- Department of Chemistry and Biochemistry University of Berne Freiestrasse 3 CH‐3012 Berne
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15
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Zhang M, Qiao X, Li Y, Fang B, Zuo Y, Chen M. Cloning of eight Rhopalosiphum padi (Hemiptera: Aphididae) nAChR subunit genes and mutation detection of the β1 subunit in field samples from China. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2016; 132:89-95. [PMID: 27521918 DOI: 10.1016/j.pestbp.2016.02.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 02/21/2016] [Accepted: 02/23/2016] [Indexed: 06/06/2023]
Abstract
The bird cherry-oat aphid, Rhopalosiphum padi (L.), is one of the most important wheat pests. This aphid damages through direct feeding and by transmitting the Barley yellow dwarf virus (BYDV). Both types of damage significantly reduce the quality and yield of wheat crops globally. Insecticides are the primary method of controlling the bird cherry-oat aphid in China, yet this aphid species has developed resistance to different types of insecticides, especially organophosphates and carbamates. In the last decade, control of R. padi depends primarily on the spray of neonicotinoid insecticides, however, research on the resistance of R. padi to neonicotinoids has been limited. In this study, the full lengths of seven α-subunit (Rpα1, Rpα2, Rpα3, Rpα4, Rpα5, Rpα7-1, and Rpα7-2) and one β-subunit (Rpβ1) genes from R. padi were obtained with RT-PCR and RACE techniques. Sequence analysis showed that these genes had all the characteristics of the nAChR gene family and were highly homologous with the reported nAChR genes from other insects, and alternative splicing was detected in Rpα3 and Rpα5 subunits. Analysis of the cDNA sequence of the extracellular region of the nicotinic acetylcholine receptor β1 subunit gene from 120 R. padi field samples collected in 11 Provinces revealed 17 single nucleotides polymorphism (SNP) sites, of which seven were amino acid polymorphism sites (V53I, V53G, N54T, A60T, F61L, W79C, and V83I) and two were in the loop D region (W79C and V83I). The current study will facilitate further studies on the molecular mechanisms of targeted resistance of the aphid to neonicotinoid insecticides.
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Affiliation(s)
- Meng Zhang
- College of Plant Protection, Key Laboratory of Crop Pest Integrated Pest Management on the Loess Plateau of Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Xianfeng Qiao
- College of Plant Protection, Key Laboratory of Crop Pest Integrated Pest Management on the Loess Plateau of Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Yuting Li
- College of Plant Protection, Key Laboratory of Crop Pest Integrated Pest Management on the Loess Plateau of Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Bing Fang
- College of Plant Protection, Key Laboratory of Crop Pest Integrated Pest Management on the Loess Plateau of Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Yayun Zuo
- College of Plant Protection, Key Laboratory of Crop Pest Integrated Pest Management on the Loess Plateau of Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Maohua Chen
- College of Plant Protection, Key Laboratory of Crop Pest Integrated Pest Management on the Loess Plateau of Ministry of Agriculture, Northwest A&F University, Yangling, Shaanxi 712100, China.
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16
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Chalon S, Vercouillie J, Guilloteau D, Suzenet F, Routier S. PET tracers for imaging brain α7 nicotinic receptors: an update. Chem Commun (Camb) 2016; 51:14826-31. [PMID: 26359819 DOI: 10.1039/c5cc04536c] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Positron emission tomography (PET) molecular imaging of brain targets is a powerful tool to diagnose, follow up, and develop treatments and personalized medicine for a number of acute and chronic brain disorders. The availability of β+ emitter tracers labelled with [(11)C] or [(18)F] having optimal characteristics of affinity and selectivity for alpha-7 nicotinic receptors (α7R) has received considerable attention, due to the major implication of these receptors in brain functions. The aim of this review is to identify the interest and need for the in vivo exploration of α7R by PET molecular imaging, which tools are currently available for this and how to progress.
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Affiliation(s)
- S Chalon
- UMR Inserm U930, Université François-Rabelais de Tours, F-37000 Tours, France.
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17
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Javed H, Menon SA, Al-Mansoori KM, Al-Wandi A, Majbour NK, Ardah MT, Varghese S, Vaikath NN, Haque ME, Azzouz M, El-Agnaf OM. Development of Nonviral Vectors Targeting the Brain as a Therapeutic Approach For Parkinson's Disease and Other Brain Disorders. Mol Ther 2016; 24:746-758. [PMID: 26700614 PMCID: PMC4886934 DOI: 10.1038/mt.2015.232] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Accepted: 12/16/2015] [Indexed: 01/08/2023] Open
Abstract
Parkinson's disease (PD) is a debilitating neurodegenerative disease characterized by tremor, rigidity, bradykinesia, and postural instability, for which there is no effective treatment available till date. Here, we report the development of nonviral vectors specific for neuronal cells that can deliver short interfering RNA (siRNA) against the α-synuclein gene (SNCA), and prevent PD-like symptoms both in vitro and in vivo. These vectors not only help siRNA duplexes cross the blood-brain barrier in mice, but also stabilize these siRNAs leading to a sustainable 60-90% knockdown of α-synuclein protein. Mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine rapidly develop PD-like symptoms which were significantly alleviated when SNCA was knocked down using our vectors. Together, our data not only confirm the central role of α-synuclein in the onset of PD, but also provide a proof of principle that these nonviral vectors can be used as novel tools to design effective strategies to combat central nervous system diseases.
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Affiliation(s)
- Hayate Javed
- Department of Biochemistry, College of Medicine and Health Science, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Sindhu A Menon
- Department of Biochemistry, College of Medicine and Health Science, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Karima M Al-Mansoori
- Department of Biochemistry, College of Medicine and Health Science, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Abdelmojib Al-Wandi
- Department of Biochemistry, College of Medicine and Health Science, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Nour K Majbour
- Department of Biochemistry, College of Medicine and Health Science, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Mustafa T Ardah
- Department of Biochemistry, College of Medicine and Health Science, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Shiji Varghese
- Department of Biochemistry, College of Medicine and Health Science, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Nishant N Vaikath
- Department of Biochemistry, College of Medicine and Health Science, United Arab Emirates University, Al Ain, United Arab Emirates
| | - M Emdadul Haque
- Department of Biochemistry, College of Medicine and Health Science, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Mimoun Azzouz
- Department of Neuroscience, Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, Sheffield, UK
| | - Omar Ma El-Agnaf
- Neurological Disorders Center, Qatar Biomedical Research Institute, and College of Science and Engineering, Hamad Bin Khalifa University (HBKU), Education City, Qatar Foundation, P.O. Box 5825 Doha, Qatar.
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18
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Zheng F, Robertson AP, Abongwa M, Yu EW, Martin RJ. The Ascaris suum nicotinic receptor, ACR-16, as a drug target: Four novel negative allosteric modulators from virtual screening. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2016; 6:60-73. [PMID: 27054065 PMCID: PMC4805779 DOI: 10.1016/j.ijpddr.2016.02.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Revised: 01/28/2016] [Accepted: 02/05/2016] [Indexed: 12/22/2022]
Abstract
Soil-transmitted helminth infections in humans and livestock cause significant debility, reduced productivity and economic losses globally. There are a limited number of effective anthelmintic drugs available for treating helminths infections, and their frequent use has led to the development of resistance in many parasite species. There is an urgent need for novel therapeutic drugs for treating these parasites. We have chosen the ACR-16 nicotinic acetylcholine receptor of Ascaris suum (Asu-ACR-16), as a drug target and have developed three-dimensional models of this transmembrane protein receptor to facilitate the search for new bioactive compounds. Using the human α7 nAChR chimeras and Torpedo marmorata nAChR for homology modeling, we defined orthosteric and allosteric binding sites on the Asu-ACR-16 receptor for virtual screening. We identified four ligands that bind to sites on Asu-ACR-16 and tested their activity using electrophysiological recording from Asu-ACR-16 receptors expressed in Xenopus oocytes. The four ligands were acetylcholine inhibitors (SB-277011-A, IC50, 3.12 ± 1.29 μM; (+)-butaclamol Cl, IC50, 9.85 ± 2.37 μM; fmoc-1, IC50, 10.00 ± 1.38 μM; fmoc-2, IC50, 16.67 ± 1.95 μM) that behaved like negative allosteric modulators. Our work illustrates a structure-based in silico screening method for seeking anthelmintic hits, which can then be tested electrophysiologically for further characterization. Three-dimensional structural models of the Ascaris nicotinic (Asu-ACR-16) receptor made by homology modeling. High affinity ligands selected by in silico screening. Four ligands validated by electrophysiological studies as negative allosteric modulators.
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Affiliation(s)
- Fudan Zheng
- Department of Chemistry, College of Liberal Arts and Sciences, Iowa State University, Ames, IA 50011, USA
| | - Alan P Robertson
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA
| | - Melanie Abongwa
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA
| | - Edward W Yu
- Department of Chemistry, College of Liberal Arts and Sciences, Iowa State University, Ames, IA 50011, USA; Department of Physics and Astronomy, College of Liberal Arts and Sciences, Iowa State University, Ames, IA 50011, USA
| | - Richard J Martin
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA.
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19
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Kim GR, Yoon TH, Park WG, Park JY, Kang JH, Kim HW. Five nicotinic acetylcholine receptor subunits from the Morotoge shrimp,Pandalopsis japonica: cloning, tissue distribution, and functional expression inXenopusoocytes. Anim Cells Syst (Seoul) 2015. [DOI: 10.1080/19768354.2015.1109547] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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20
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Allosteric modulation of nicotinic acetylcholine receptors. Biochem Pharmacol 2015; 97:408-417. [PMID: 26231943 DOI: 10.1016/j.bcp.2015.07.028] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 07/24/2015] [Indexed: 12/12/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are receptors for the neurotransmitter acetylcholine and are members of the 'Cys-loop' family of pentameric ligand-gated ion channels (LGICs). Acetylcholine binds in the receptor extracellular domain at the interface between two subunits and research has identified a large number of nAChR-selective ligands, including agonists and competitive antagonists, that bind at the same site as acetylcholine (commonly referred to as the orthosteric binding site). In addition, more recent research has identified ligands that are able to modulate nAChR function by binding to sites that are distinct from the binding site for acetylcholine, including sites located in the transmembrane domain. These include positive allosteric modulators (PAMs), negative allosteric modulators (NAMs), silent allosteric modulators (SAMs) and compounds that are able to activate nAChRs via an allosteric binding site (allosteric agonists). Our aim in this article is to review important aspects of the pharmacological diversity of nAChR allosteric modulators and to describe recent evidence aimed at identifying binding sites for allosteric modulators on nAChRs.
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21
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Kumar RB, Suresh MX, Priya BS. Pharmacophore modeling, in silico screening, molecular docking and molecular dynamics approaches for potential alpha-delta bungarotoxin-4 inhibitors discovery. Pharmacogn Mag 2015; 11:S19-28. [PMID: 26109766 PMCID: PMC4461960 DOI: 10.4103/0973-1296.157670] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Revised: 10/14/2014] [Accepted: 05/27/2015] [Indexed: 11/25/2022] Open
Abstract
Background: The alpha-delta bungartoxin-4 (α-δ-Bgt-4) is a potent neurotoxin produced by highly venomous snake species, Bungarus caeruleus, mainly targeting neuronal acetylcholine receptors (nAchRs) and producing adverse biological malfunctions leading to respiratory paralysis and mortality. Objective: In this study, we predicted the three-dimensional structure of α-δ-Bgt-4 using homology modeling and investigated the conformational changes and the key residues responsible for nAchRs inhibiting activity. Materials and Methods: From the selected plants, which are traditionally used for snake bites, the active compounds are taken and performed molecular interaction studies and also used for modern techniques like pharmacophore modeling and mapping and absorption, distribution, metabolism, elimination and toxicity analysis which may increase the possibility of success. Results: Moreover, 100's of drug-like compounds were retrieved and analyzed through computational virtual screening and allowed for pharmacokinetic profiling, molecular docking and dynamics simulation. Conclusion: Finally the top five drug-like compounds having competing level of inhibition toward α-δ-Bgt-4 toxin were suggested based on their interaction with α-δ-Bgt-4 toxin.
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Affiliation(s)
- R Barani Kumar
- Department of Bioinformatics, Sathyabama University, Chennai, Tamil Nadu, India
| | - M Xavier Suresh
- Department of Bioinformatics, Sathyabama University, Chennai, Tamil Nadu, India
| | - B Shanmuga Priya
- Department of Bioinformatics, Sathyabama University, Chennai, Tamil Nadu, India
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22
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Chatzidaki A, D'Oyley JM, Gill-Thind JK, Sheppard TD, Millar NS. The influence of allosteric modulators and transmembrane mutations on desensitisation and activation of α7 nicotinic acetylcholine receptors. Neuropharmacology 2015; 97:75-85. [PMID: 25998276 PMCID: PMC4548482 DOI: 10.1016/j.neuropharm.2015.05.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 04/23/2015] [Accepted: 05/04/2015] [Indexed: 11/29/2022]
Abstract
Acetylcholine activates nicotinic acetylcholine receptors (nAChRs) by binding at an extracellular orthosteric site. Previous studies have described several positive allosteric modulators (PAMs) that are selective for homomeric α7 nAChRs. These include type I PAMs, which exert little or no effect on the rate of receptor desensitisation, and type II PAMs, which cause a dramatic loss of agonist-induced desensitisation. Here we report evidence that transmembrane mutations in α7 nAChRs have diverse effects on receptor activation and desensitisation by allosteric ligands. It has been reported previously that the L247T mutation, located toward the middle of the second transmembrane domain (at the 9′ position), confers reduced levels of desensitisation. In contrast, the M260L mutation, located higher up in the TM2 domain (at the 22′ position), does not show any difference in desensitisation compared to wild-type receptors. We have found that in receptors containing the L247T mutation, both type I PAMs and type II PAMs are converted into non-desensitising agonists. In contrast, in receptors containing the M260L mutation, this effect is seen only with type II PAMs. These findings, indicating that the M260L mutation has a selective effect on type II PAMs, have been confirmed both with previously described PAMs and also with a series of novel α7-selective PAMs. The novel PAMs examined in this study have close chemical similarity but diverse pharmacological properties. For example, they include compounds displaying effects on receptor desensitisation that are typical of classical type I and type II PAMs but, in addition, they include compounds with intermediate properties. A series of novel positive allosteric modulators (PAMs) is described. The series of PAMs display differing effects on α7 nAChR desensitisation. Transmembrane mutations influencing PAM activity are examined. Transmembrane mutations can convert PAMs into agonists. Identification of a mutation with differing effects on type I and type II PAMs.
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Affiliation(s)
- Anna Chatzidaki
- Department of Neuroscience, Physiology & Pharmacology, University College London, London, United Kingdom
| | - Jarryl M D'Oyley
- Department of Chemistry, University College London, London, United Kingdom
| | - JasKiran K Gill-Thind
- Department of Neuroscience, Physiology & Pharmacology, University College London, London, United Kingdom
| | - Tom D Sheppard
- Department of Chemistry, University College London, London, United Kingdom
| | - Neil S Millar
- Department of Neuroscience, Physiology & Pharmacology, University College London, London, United Kingdom.
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23
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Magnussen JH, Ettrup A, Donat CK, Peters D, Pedersen MHF, Knudsen GM, Mikkelsen JD. Radiosynthesis and in vitro validation of (3)H-NS14492 as a novel high affinity alpha7 nicotinic receptor radioligand. Eur J Pharmacol 2015; 762:35-41. [PMID: 25941084 DOI: 10.1016/j.ejphar.2015.04.036] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Revised: 04/22/2015] [Accepted: 04/23/2015] [Indexed: 11/30/2022]
Abstract
The neuronal α7 nicotinic acetylcholine receptor is a homo-pentameric ligand-gated ion channel that is a promising drug target for cognitive deficits in Alzheimer׳s disease and schizophrenia. We have previously described (11)C-NS14492 as a suitable agonist radioligand for in vivo positron emission tomography (PET) occupancy studies of the α7 nicotinic receptor in the pig brain. In order to investigate the utility of the same compound for in vitro studies, (3)H-NS14492 was synthesized and its binding properties were characterized using in vitro autoradiography and homogenate binding assays in pig frontal cortex. (3)H-NS14492 showed specific binding to α7 nicotinic receptors in autoradiography, revealing a dissociation constant (Kd) of 2.1±0.7nM and a maximum number of binding sites (Bmax) of 15.7±2.0fmol/mg tissue equivalent. Binding distribution was similar to that of another selective ligand (125)I-α-bungarotoxin ((125)I-BTX) in autoradiography, and unlabeled NS14492 displaced (125)I-BTX with an inhibition constant (Ki) of 23nM. (3)H-NS14492 bound to α7 nicotinic receptors in homogenized pig frontal cortex with a Kd of 0.8±0.3nM and a Bmax of 30.2±11.6fmol/mg protein. This binding assay further revealed the Ki rank order for a number of α7 nicotinic receptor agonists, and positive allosteric modulators (PAMs). Further, we saw increased binding of (3)H-NS14492 to pig frontal cortex membranes when co-incubated with PNU-120596, a type II PAM. Taken together, these findings show that (3)H-NS14492 is a useful new in vitro radioligand for the pig α7 nicotinic receptor.
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Affiliation(s)
- Janus H Magnussen
- Neurobiology Research Unit, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | - Anders Ettrup
- Neurobiology Research Unit, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | - Cornelius K Donat
- Neurobiology Research Unit, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | | | - Martin H F Pedersen
- The Hevesy Laboratory, DTU Nutech, The Technical University of Denmark, Denmark
| | - Gitte M Knudsen
- Neurobiology Research Unit, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | - Jens D Mikkelsen
- Neurobiology Research Unit, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
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24
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Fan H, Gu R, Wei D. The α7 nAChR selective agonists as drug candidates for Alzheimer's disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 827:353-65. [PMID: 25387975 DOI: 10.1007/978-94-017-9245-5_21] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The nicotinic acetylcholine receptors (nAChRs) are ion channels distribute in the central or peripheral nervous system. They are receptors of the neurotransmitter acetylcholine and activation of them by agonists mediates synaptic transmission in the neuron and muscle contraction in the neuromuscular junction. Current studies reveal relationship between the nAChRs and the learning and memory as well as cognation deficit in various neurological disorders such as Alzheimer's disease, Parkinson's disease, schizophrenia and drug addiction. There are various subtypes in the nAChR family and the α7 nAChR is one of the most abundant subtypes in the brain. The α7 nAChR is significantly reduced in the patients of Alzheimer's disease and is believed to interact with the Aβ amyloid. Aβ amyloid is co-localized with α7 nAChR in the senile plaque and interaction between them induces neuron apoptosis and reduction of the α7 nAChR expression. Treatment with α7 agonist in vivo shows its neuron protective and procognation properties and significantly improves the learning and memory ability of the animal models. Therefore, the α7 nAChR agonists are excellent drug candidates for Alzheimer's disease and we summarized here the current agonists that have selectivity of the α7 nAChR over the other nAChR, introduced recent molecular modeling works trying to explain the molecular mechanism of their selectivity and described the design of novel allosteric modulators in our lab.
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Affiliation(s)
- Huaimeng Fan
- State Key Laboratory of Microbial Metabolism, College of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
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25
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Gill-Thind JK, Dhankher P, D'Oyley JM, Sheppard TD, Millar NS. Structurally similar allosteric modulators of α7 nicotinic acetylcholine receptors exhibit five distinct pharmacological effects. J Biol Chem 2014; 290:3552-62. [PMID: 25516597 PMCID: PMC4319022 DOI: 10.1074/jbc.m114.619221] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activation of nicotinic acetylcholine receptors (nAChRs) is associated with the binding of agonists such as acetylcholine to an extracellular site that is located at the interface between two adjacent receptor subunits. More recently, there has been considerable interest in compounds, such as positive and negative allosteric modulators (PAMs and NAMs), that are able to modulate nAChR function by binding to distinct allosteric sites. Here we examined a series of compounds differing only in methyl substitution of a single aromatic ring. This series of compounds includes a previously described α7-selective allosteric agonist, cis-cis-4-p-tolyl-3a,4,5,9b-tetrahydro-3H-cyclopenta[c]quinoline-8-sulfonamide (4MP-TQS), together with all other possible combinations of methyl substitution at a phenyl ring (18 additional compounds). Studies conducted with this series of compounds have revealed five distinct pharmacological effects on α7 nAChRs. These five effects can be summarized as: 1) nondesensitizing activation (allosteric agonists), 2) potentiation associated with minimal effects on receptor desensitization (type I PAMs), 3) potentiation associated with reduced desensitization (type II PAMs), 4) noncompetitive antagonism (NAMs), and 5) compounds that have no effect on orthosteric agonist responses but block allosteric modulation (silent allosteric modulators (SAMs)). Several lines of experimental evidence are consistent with all of these compounds acting at a common, transmembrane allosteric site. Notably, all of these chemically similar compounds that have been classified as nondesensitizing allosteric agonists or as nondesensitizing (type II) PAMs are cis-cis-diastereoisomers, whereas all of the NAMs, SAMs, and type I PAMs are cis-trans-diastereoisomers. Our data illustrate the remarkable pharmacological diversity of allosteric modulators acting on nAChRs.
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Affiliation(s)
- JasKiran K Gill-Thind
- From the Department of Neuroscience, Physiology & Pharmacology, University College London, London, WC1E 6BT, United Kingdom and
| | - Persis Dhankher
- the Department of Chemistry, University College London, London, WC1H 0AJ, United Kingdom
| | - Jarryl M D'Oyley
- the Department of Chemistry, University College London, London, WC1H 0AJ, United Kingdom
| | - Tom D Sheppard
- the Department of Chemistry, University College London, London, WC1H 0AJ, United Kingdom
| | - Neil S Millar
- From the Department of Neuroscience, Physiology & Pharmacology, University College London, London, WC1E 6BT, United Kingdom and
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Lansdell SJ, Sathyaprakash C, Doward A, Millar NS. Activation of human 5-hydroxytryptamine type 3 receptors via an allosteric transmembrane site. Mol Pharmacol 2014; 87:87-95. [PMID: 25338672 DOI: 10.1124/mol.114.094540] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In common with other members of the Cys-loop family of pentameric ligand-gated ion channels, 5-hydroxytryptamine type 3 receptors (5-HT3Rs) are activated by the binding of a neurotransmitter to an extracellular orthosteric site, located at the interface of two adjacent receptor subunits. In addition, a variety of compounds have been identified that modulate agonist-evoked responses of 5-HT3Rs, and other Cys-loop receptors, by binding to distinct allosteric sites. In this study, we examined the pharmacological effects of a group of monoterpene compounds on recombinant 5-HT3Rs expressed in Xenopus oocytes. Two phenolic monoterpenes (carvacrol and thymol) display allosteric agonist activity on human homomeric 5-HT3ARs (64 ± 7% and 80 ± 4% of the maximum response evoked by the endogenous orthosteric agonist 5-HT, respectively). In addition, at lower concentrations, where agonist effects are less apparent, carvacrol and thymol act as potentiators of responses evoked by submaximal concentrations of 5-HT. By contrast, carvacrol and thymol have no agonist or potentiating activity on the closely related mouse 5-HT3ARs. Using subunit chimeras containing regions of the human and mouse 5-HT3A subunits, and by use of site-directed mutagenesis, we have identified transmembrane amino acids that either abolish the agonist activity of carvacrol and thymol on human 5-HT3ARs or are able to confer this property on mouse 5-HT3ARs. By contrast, these mutations have no significant effect on orthosteric activation of 5-HT3ARs by 5-HT. We conclude that 5-HT3ARs can be activated by the binding of ligands to an allosteric transmembrane site, a conclusion that is supported by computer docking studies.
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Affiliation(s)
- Stuart J Lansdell
- Department of Neuroscience, Physiology, and Pharmacology, University College London, London, United Kingdom
| | - Chaitra Sathyaprakash
- Department of Neuroscience, Physiology, and Pharmacology, University College London, London, United Kingdom
| | - Anne Doward
- Department of Neuroscience, Physiology, and Pharmacology, University College London, London, United Kingdom
| | - Neil S Millar
- Department of Neuroscience, Physiology, and Pharmacology, University College London, London, United Kingdom
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Sepsova V, Krusek J, Zdarova Karasova J, Zemek F, Musilek K, Kuca K, Soukup O. The interaction of quaternary reversible acetylcholinesterase inhibitors with the nicotinic receptor. Physiol Res 2014; 63:771-7. [PMID: 25157661 DOI: 10.33549/physiolres.932768] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Acetylcholinesterase inhibitors (AChEIs) are used in the treatment of myasthenia gravis (MG). We investigated the effects of AChEIs on peripheral nicotinic receptors (nAChR), which play a crucial role in the treatment of MG symptoms. The positive modulation of those receptors by AChE inhibitors could have an added value to the anti-AChE activity and might be useful in the therapy of MG. Furthermore, to estimate the potential drawbacks of the compounds, cytotoxicity has been assessed on various cell lines. The whole-cell mode of the patch-clamp method was employed. The experiments were performed on medulloblastoma/rhabdomyosarcoma cell line TE671 expressing human embryonic muscle-like receptor with subunits alpha2betagammadelta. The effect of the compounds on cell viability was measured by standard MTT assay (Sigma Aldrich) on ACHN (renal cell adenocarcinoma), HeLa (immortal cell line derived from a cervical carcinoma), HEPG2 (hepatocellular carcinoma) and BJ (skin fibroblasts) cell lines. No positive modulation by the tested AChE inhibitors was observed. Moreover, the compounds exhibited antagonistic activity on the peripheral nAChR. Standard drugs used in MG treatment were shown to be less potent inhibitors of muscle-type nAChR than the newly synthesized compounds. The new compounds showed very little effect on cell viability, and toxicities were comparable to standards. Newly synthesized AChEIs inhibited peripheral nAChR. Furthermore, the inhibition was higher than that of standards used for the treatment of MG. They could be used for the study of nAChR function, thanks to their high antagonizing potency and fast recovery of receptor activity after their removal. However, since no positive modulation was observed, the new compounds do not seem to be promising candidates for MG treatment, even though their cytotoxic effect was relatively low.
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Affiliation(s)
- V Sepsova
- Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Hradec Kralove, Czech Republic, Biomedical Research Center, Hradec Kralove, Czech Republic.
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Green BT, Lee ST, Welch KD, Panter KE. Plant alkaloids that cause developmental defects through the disruption of cholinergic neurotransmission. ACTA ACUST UNITED AC 2014; 99:235-46. [PMID: 24339035 DOI: 10.1002/bdrc.21049] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 10/24/2013] [Accepted: 10/24/2013] [Indexed: 12/26/2022]
Abstract
The exposure of a developing embryo or fetus to alkaloids from plants, plant products, or plant extracts has the potential to cause developmental defects in humans and animals. These defects may have multiple causes, but those induced by piperidine and quinolizidine alkaloids arise from the inhibition of fetal movement and are generally referred to as multiple congenital contracture-type deformities. These skeletal deformities include arthrogyrposis, kyposis, lordosis, scoliosis, and torticollis, associated secondary defects, and cleft palate. Structure-function studies have shown that plant alkaloids with a piperidine ring and a minimum of a three-carbon side-chain α to the piperidine nitrogen are teratogenic. Further studies determined that an unsaturation in the piperidine ring, as occurs in gamma coniceine, or anabaseine, enhances the toxic and teratogenic activity, whereas the N-methyl derivatives are less potent. Enantiomers of the piperidine teratogens, coniine, ammodendrine, and anabasine, also exhibit differences in biological activity, as shown in cell culture studies, suggesting variability in the activity due to the optical rotation at the chiral center of these stereoisomers. In this article, we review the molecular mechanism at the nicotinic pharmacophore and biological activities, as it is currently understood, of a group of piperidine and quinolizidine alkaloid teratogens that impart a series of flexure-type skeletal defects and cleft palate in animals.
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Affiliation(s)
- Benedict T Green
- United States Department of Agriculture, Poisonous Plant Research Laboratory, Agricultural Research Service, 1150 E 1400 N, Logan, Utah, 84321
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White SH, Carter CJ, Magoski NS. A potentially novel nicotinic receptor in Aplysia neuroendocrine cells. J Neurophysiol 2014; 112:446-62. [DOI: 10.1152/jn.00796.2013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nicotinic receptors form a diverse group of ligand-gated ionotropic receptors with roles in both synaptic transmission and the control of excitability. In the bag cell neurons of Aplysia, acetylcholine activates an ionotropic receptor, which passes inward current to produce a long-lasting afterdischarge and hormone release, leading to reproduction. While testing the agonist profile of the cholinergic response, we observed a second current that appeared to be gated only by nicotine and not acetylcholine. The peak nicotine-evoked current was markedly smaller in magnitude than the acetylcholine-induced current, cooperative (Hill value of 2.7), had an EC50 near 500 μM, readily recovered from desensitization, showed Ca2+ permeability, and was blocked by mecamylamine, dihydro-β-erythroidine, or strychnine, but not by α-conotoxin ImI, methyllycaconitine, or hexamethonium. Aplysia transcriptome analysis followed by PCR yielded 20 full-length potential nicotinic receptor subunits. Sixteen of these were predicted to be cation selective, and real-time PCR suggested that 15 of the 16 subunits were expressed to varying degrees in the bag cell neurons. The acetylcholine-induced current, but not the nicotine current, was reduced by double-strand RNA treatment targeted to both subunits ApAChR-C and -E. Conversely, the nicotine-evoked current, but not the acetylcholine current, was lessened by targeting both subunits ApAChR-H and -P. To the best of our knowledge, this is the first report suggesting that a nicotinic receptor is not gated by acetylcholine. Separate receptors may serve as a means to differentially trigger plasticity or safeguard propagation by assuring that only acetylcholine, the endogenous agonist, initiates large enough responses to trigger reproduction.
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Affiliation(s)
- Sean H. White
- Department of Biomedical and Molecular Sciences, Physiology Graduate Program, Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada
| | - Christopher J. Carter
- Department of Biomedical and Molecular Sciences, Physiology Graduate Program, Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada
| | - Neil S. Magoski
- Department of Biomedical and Molecular Sciences, Physiology Graduate Program, Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada
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Ellis-Hutchings RG, Rasoulpour RJ, Terry C, Carney EW, Billington R. Human relevance framework evaluation of a novel rat developmental toxicity mode of action induced by sulfoxaflor. Crit Rev Toxicol 2014; 44 Suppl 2:45-62. [DOI: 10.3109/10408444.2014.910752] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Brunzell DH, McIntosh JM, Papke RL. Diverse strategies targeting α7 homomeric and α6β2* heteromeric nicotinic acetylcholine receptors for smoking cessation. Ann N Y Acad Sci 2014; 1327:27-45. [PMID: 24730978 DOI: 10.1111/nyas.12421] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Preclinical studies suggest that a diversity of nicotinic acetylcholine receptors (nAChRs) with different sensitivities to nicotine may contribute to tobacco addiction. Using rodent intravenous nicotine self-administration as a preclinical model with good predictive validity for therapeutic efficacy for tobacco cessation, investigators have identified heteromeric α6β2* and homomeric α7 nAChRs as promising novel therapeutic targets to promote smoking abstinence (*denotes possible assembly with other subunits). The data suggest that diverse strategies that target these subclasses of nAChRs, namely inhibition of α6β2* nAChRs and stimulation of α7 nAChRs, will support tobacco cessation. α6β2* nAChRs, members of the high-affinity family of β2* nAChRs, function similarly to α4β2* nAChRs, the primary target of the FDA-approved drug varenicline, but have a much more selective neuroanatomical pattern of expression in catecholaminergic nuclei. Although activation of β2* nAChRs facilitates nicotine self-administration, stimulation of α7 nAChRs appears to negatively modulate both nicotine reinforcement and β2* nAChR function in the mesolimbic dopamine system. Although challenges and caveats must be considered in the development of therapeutics that target these nAChR subpopulations, an accumulation of data suggests that α7 nAChR agonists, partial agonists, or positive allosteric modulators and α6β2* nAChR antagonists, partial agonists, or negative allosteric modulators may prove to be effective therapeutics for tobacco cessation.
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Affiliation(s)
- Darlene H Brunzell
- Department of Pharmacology and Toxicology, Interdisciplinary Neuroscience Program and Institute for Drug and Alcohol Studies, Virginia Commonwealth University School of Medicine, Richmond, Virginia
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Sambasivarao SV, Roberts J, Bharadwaj VS, Slingsby JG, Rohleder C, Mallory C, Groome JR, McDougal OM, Maupin CM. Acetylcholine promotes binding of α-conotoxin MII at α3 β2 nicotinic acetylcholine receptors. Chembiochem 2014; 15:413-24. [PMID: 24420650 DOI: 10.1002/cbic.201300577] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Indexed: 11/09/2022]
Abstract
α-Conotoxin MII (α-CTxMII) is a 16-residue peptide with the sequence GCCSNPVCHLEHSNLC, containing Cys2-Cys8 and Cys3-Cys16 disulfide bonds. This peptide, isolated from the venom of the marine cone snail Conus magus, is a potent and selective antagonist of neuronal nicotinic acetylcholine receptors (nAChRs). To evaluate the impact of channel-ligand interactions on ligand-binding affinity, homology models of the heteropentameric α3β2-nAChR were constructed. The models were created in MODELLER with the aid of experimentally characterized structures of the Torpedo marmorata-nAChR (Tm-nAChR, PDB ID: 2BG9) and the Aplysia californica-acetylcholine binding protein (Ac-AChBP, PDB ID: 2BR8) as templates for the α3- and β2-subunit isoforms derived from rat neuronal nAChR primary amino acid sequences. Molecular docking calculations were performed with AutoDock to evaluate interactions of the heteropentameric nAChR homology models with the ligands acetylcholine (ACh) and α-CTxMII. The nAChR homology models described here bind ACh with binding energies commensurate with those of previously reported systems, and identify critical interactions that facilitate both ACh and α-CTxMII ligand binding. The docking calculations revealed an increased binding affinity of the α3β2-nAChR for α-CTxMII with ACh bound to the receptor, and this was confirmed through two-electrode voltage clamp experiments on oocytes from Xenopus laevis. These findings provide insights into the inhibition and mechanism of electrostatically driven antagonist properties of the α-CTxMIIs on nAChRs.
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Affiliation(s)
- Somisetti V Sambasivarao
- Chemical and Biological Engineering Department, Colorado School of Mines, 1500 Illinois Street, Golden, CO 80401 (USA)
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Fedosov AÉ, Moshkovskiĭ SA, Kuznetsova KG, Olivera BM. [Conotoxins: from the biodiversity of gastropods to new drugs]. BIOMEDIT︠S︡INSKAI︠A︡ KHIMII︠A︡ 2013; 59:267-94. [PMID: 23987066 DOI: 10.18097/pbmc20135903267] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A review describes general trends in research of conotoxins that are peptide toxins isolated from sea gastropods of the Conus genus, since the toxins were discovered in 1970th. There are disclosed a conotoxin classification, their structure diversity and different ways of action to their molecular targets, mainly, ion channels. In the applied aspect of conotoxin research, drug discovery and development is discussed, the drugs being based on conotoxin structure. A first exemplary drug is a ziconotide, which is an analgesic of new generation.
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Nery AA, Magdesian MH, Trujillo CA, Sathler LB, Juliano MA, Juliano L, Ulrich H, Ferreira ST. Rescue of amyloid-Beta-induced inhibition of nicotinic acetylcholine receptors by a peptide homologous to the nicotine binding domain of the alpha 7 subtype. PLoS One 2013; 8:e67194. [PMID: 23894286 PMCID: PMC3718777 DOI: 10.1371/journal.pone.0067194] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Accepted: 05/15/2013] [Indexed: 11/19/2022] Open
Abstract
Alzheimer's disease (AD) is characterized by brain accumulation of the neurotoxic amyloid-β peptide (Aβ) and by loss of cholinergic neurons and nicotinic acetylcholine receptors (nAChRs). Recent evidence indicates that memory loss and cognitive decline in AD correlate better with the amount of soluble Aβ than with the extent of amyloid plaque deposits in affected brains. Inhibition of nAChRs by soluble Aβ40 is suggested to contribute to early cholinergic dysfunction in AD. Using phage display screening, we have previously identified a heptapeptide, termed IQ, homologous to most nAChR subtypes, binding with nanomolar affinity to soluble Aβ40 and blocking Aβ-induced inhibition of carbamylcholine-induced currents in PC12 cells expressing α7 nAChRs. Using alanine scanning mutagenesis and whole-cell current recording, we have now defined the amino acids in IQ essential for reversal of Aβ40 inhibition of carbamylcholine-induced responses in PC12 cells, mediated by α7 subtypes and other endogenously expressed nAChRs. We further investigated the effects of soluble Aβ, IQ and analogues of IQ on α3β4 nAChRs recombinantly expressed in HEK293 cells. Results show that nanomolar concentrations of soluble Aβ40 potently inhibit the function of α3β4 nAChRs, and that subsequent addition of IQ or its analogues does not reverse this effect. However, co-application of IQ makes the inhibition of α3β4 nAChRs by Aβ40 reversible. These findings indicate that Aβ40 inhibits different subtypes of nAChRs by interacting with specific receptor domains homologous to the IQ peptide, suggesting that IQ may be a lead for novel drugs to block the inhibition of cholinergic function in AD.
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Affiliation(s)
- Arthur A. Nery
- Department of Biochemistry, Chemistry Institute, São Paulo University, São Paulo, SP, Brazil
| | - Margaret H. Magdesian
- Institute of Medical Biochemistry, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Cleber A. Trujillo
- Department of Biochemistry, Chemistry Institute, São Paulo University, São Paulo, SP, Brazil
| | - Luciana B. Sathler
- Institute of Medical Biochemistry, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Maria A. Juliano
- Department of Biophysics, Federal University of São Paulo, São Paulo, SP, Brazil
| | - Luiz Juliano
- Department of Biophysics, Federal University of São Paulo, São Paulo, SP, Brazil
| | - Henning Ulrich
- Department of Biochemistry, Chemistry Institute, São Paulo University, São Paulo, SP, Brazil
- * E-mail: (HU); (STF)
| | - Sergio T. Ferreira
- Institute of Medical Biochemistry, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil
- * E-mail: (HU); (STF)
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Ritzenthaler JD, Roser-Page S, Guidot DM, Roman J. Nicotinic acetylcholine receptors are sensors for ethanol in lung fibroblasts. Alcohol Clin Exp Res 2013; 37:914-23. [PMID: 23421903 DOI: 10.1111/acer.12044] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Accepted: 10/09/2012] [Indexed: 11/27/2022]
Abstract
BACKGROUND Chronic ethanol (EtOH) abuse in humans is known to independently increase the incidence of and mortality due to acute lung injury in at-risk individuals. However, the mechanisms by which EtOH affects lung cells remain incompletely elucidated. In earlier work, we reported that EtOH increased the expression in lung fibroblasts of fibronectin, a matrix glycoprotein implicated in lung injury and repair. This effect was blocked by α-bungarotoxin, a neurotoxin that binds certain nicotinic acetylcholine receptors (nAChRs) thereby implicating nAChRs in this process. Here, we examine the identity of these receptors. METHODS Mouse lung fibroblasts were stimulated with EtOH (60 mM) or acetylcholine (100 to 500 μM) and evaluated for the expression of fibronectin and nAChRs. Inhibitors to nAChRs or the antioxidant N-acetyl cysteine (NAC) were used to assess changes in fibronectin expression. Animals exposed to EtOH for up to 6 weeks were used to evaluate the expression of nAChRs in vivo. RESULTS First, in EtOH-treated fibroblasts, we observed increased expression of α4 and α9 nAChR subunits. Second, we found that acetylcholine, a natural ligand for nAChRs, mimicked the effects of EtOH. Dihydro-β-erythroidin hydrobromide, a competitive inhibitor of α4 nAChR, blocked the increase in fibronectin expression and cell proliferation. Furthermore, EtOH-induced fibronectin expression was inhibited in cells silenced for α4 nAChR. However, EtOH-treated cells showed increased α-bungarotoxin binding suggesting that α4 nAChR mediates the effects of EtOH via a ligand-independent pathway. Knowing there are several important cysteine residues near the ligand-binding site of α4 nAChRs, we tested the antioxidant NAC and found that it too blocked the induction of fibronectin expression by EtOH. Also, fibroblasts exposed to oxidant stress showed increased fibronectin expression that was blocked with α-bungarotoxin. Finally, we showed increased expression of α4 nAChRs in the lung tissue of mice and rats exposed to EtOH suggesting a role for these receptors in vivo. CONCLUSIONS Altogether, our observations suggest that α4 nAChRs serve as sensors for EtOH-induced oxidant stress in lung fibroblasts, thereby revealing a new mechanism by which EtOH may affect lung cells and tissue remodeling and pointing to nAChRs as potential targets for intervention.
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Affiliation(s)
- Jeffrey D Ritzenthaler
- Division of Pulmonary, Critical Care, and Sleep Disorders, Department of Medicine, University of Louisville School of Medicine, Louisville, KY 40202, USA
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Gill JK, Chatzidaki A, Ursu D, Sher E, Millar NS. Contrasting properties of α7-selective orthosteric and allosteric agonists examined on native nicotinic acetylcholine receptors. PLoS One 2013; 8:e55047. [PMID: 23383051 PMCID: PMC3558472 DOI: 10.1371/journal.pone.0055047] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Accepted: 12/18/2012] [Indexed: 12/04/2022] Open
Abstract
Subtype-selective ligands are important tools for the pharmacological characterisation of neurotransmitter receptors. This is particularly the case for nicotinic acetylcholine receptors (nAChRs), given the heterogeneity of their subunit composition. In addition to agonists and antagonists that interact with the extracellular orthosteric nAChR binding site, a series of nAChR allosteric modulators have been identified that interact with a distinct transmembrane site. Here we report studies conducted with three pharmacologically distinct nicotinic ligands, an orthosteric agonist (compound B), a positive allosteric modulator (TQS) and an allosteric agonist (4BP-TQS). The primary focus of the work described in this study is to examine the suitability of these compounds for the characterisation of native neuronal receptors (both rat and human). However, initial experiments were conducted on recombinant nAChRs demonstrating the selectivity of these three compounds for α7 nAChRs. In patch-clamp recordings on rat primary hippocampal neurons we found that all these compounds displayed pharmacological properties that mimicked closely those observed on recombinant α7 nAChRs. However, it was not possible to detect functional responses with compound B, an orthosteric agonist, using a fluorescent intracellular calcium assay on either rat hippocampal neurons or with human induced pluripotent stem cell-derived neurons (iCell neurons). This is, presumably, due to the rapid desensitisation of α7 nAChR that is induced by orthosteric agonists. In contrast, clear agonist-evoked responses were observed in fluorescence-based assays with the non-desensitising allosteric agonist 4BP-TQS and also when compound B was co-applied with the non-desensitising positive allosteric modulator TQS. In summary, we have demonstrated the suitability of subtype-selective orthosteric and allosteric ligands for the pharmacological identification and characterisation of native nAChRs and the usefulness of ligands that minimise receptor desensitisation for the characterisation of α7 nAChRs in fluorescence-based assays.
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Affiliation(s)
- JasKiran K. Gill
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
| | - Anna Chatzidaki
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
| | - Daniel Ursu
- Lilly Research Centre, Eli Lilly & Co. Ltd., Windlesham, Surrey, United Kingdom
| | - Emanuele Sher
- Lilly Research Centre, Eli Lilly & Co. Ltd., Windlesham, Surrey, United Kingdom
| | - Neil S. Millar
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
- * E-mail:
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Pérez EG, Ocampo C, Feuerbach D, López JJ, Morelo GL, Tapia RA, Arias HR. Novel 1-(1-benzyl-1H-indol-3-yl)-N,N,N-trimethylmethanaminium iodides are competitive antagonists for the human α4β2 and α7 nicotinic acetylcholine receptors. MEDCHEMCOMM 2013. [DOI: 10.1039/c3md00042g] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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Bagal SK, Brown AD, Cox PJ, Omoto K, Owen RM, Pryde DC, Sidders B, Skerratt SE, Stevens EB, Storer RI, Swain NA. Ion Channels as Therapeutic Targets: A Drug Discovery Perspective. J Med Chem 2012; 56:593-624. [DOI: 10.1021/jm3011433] [Citation(s) in RCA: 198] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sharan K. Bagal
- Worldwide Medicinal Chemistry, Pfizer Neusentis, The Portway Building, Granta Park,
Great Abington, Cambridge, CB21 6GS, U.K
| | - Alan D. Brown
- Worldwide Medicinal Chemistry, Pfizer Neusentis, The Portway Building, Granta Park,
Great Abington, Cambridge, CB21 6GS, U.K
| | - Peter J. Cox
- Pfizer Neusentis, The
Portway Building, Granta Park, Great Abington, Cambridge, CB21
6GS, U.K
| | - Kiyoyuki Omoto
- Worldwide Medicinal Chemistry, Pfizer Neusentis, The Portway Building, Granta Park,
Great Abington, Cambridge, CB21 6GS, U.K
| | - Robert M. Owen
- Worldwide Medicinal Chemistry, Pfizer Neusentis, The Portway Building, Granta Park,
Great Abington, Cambridge, CB21 6GS, U.K
| | - David C. Pryde
- Worldwide Medicinal Chemistry, Pfizer Neusentis, The Portway Building, Granta Park,
Great Abington, Cambridge, CB21 6GS, U.K
| | - Benjamin Sidders
- Pfizer Neusentis, The
Portway Building, Granta Park, Great Abington, Cambridge, CB21
6GS, U.K
| | - Sarah E. Skerratt
- Worldwide Medicinal Chemistry, Pfizer Neusentis, The Portway Building, Granta Park,
Great Abington, Cambridge, CB21 6GS, U.K
| | - Edward B. Stevens
- Pfizer Neusentis, The
Portway Building, Granta Park, Great Abington, Cambridge, CB21
6GS, U.K
| | - R. Ian Storer
- Worldwide Medicinal Chemistry, Pfizer Neusentis, The Portway Building, Granta Park,
Great Abington, Cambridge, CB21 6GS, U.K
| | - Nigel A. Swain
- Worldwide Medicinal Chemistry, Pfizer Neusentis, The Portway Building, Granta Park,
Great Abington, Cambridge, CB21 6GS, U.K
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Lee C, Lee SH, Kim DH, Han KH. Molecular docking study on the α3β2 neuronal nicotinic acetylcholine receptor complexed with α-conotoxin GIC. BMB Rep 2012; 45:275-80. [PMID: 22617450 DOI: 10.5483/bmbrep.2012.45.5.275] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) are a diverse family of homo- or heteropentameric ligand-gated ion channels. Understanding the physiological role of each nAChR subtype and the key residues responsible for normal and pathological states is important. α-Conotoxin neuropeptides are highly selective probes capable of discriminating different subtypes of nAChRs. In this study, we performed homology modeling to generate the neuronal α3, β2 and β4 subunits using the x-ray structure of the α1 subunit as a template. The structures of the extracellular domains containing ligand binding sites in the α3β2 and α3β4 nAChR subtypes were constructed using MD simulations and ligand docking processes in their free and ligand-bound states using α-conotoxin GIC, which exhibited the highest α3β2 vs. α3β4 discrimination ratio. The results provide a reasonable structural basis for such a discriminatory ability, supporting the idea that the present strategy can be used for future investigations on nAChR-ligand complexes.
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Affiliation(s)
- Chewook Lee
- Biomedical Translational Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 305-806, Korea
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The Drosophila nicotinic acetylcholine receptor subunits Dα5 and Dα7 form functional homomeric and heteromeric ion channels. BMC Neurosci 2012; 13:73. [PMID: 22727315 PMCID: PMC3444433 DOI: 10.1186/1471-2202-13-73] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Accepted: 05/17/2012] [Indexed: 11/29/2022] Open
Abstract
Background Nicotinic acetylcholine receptors (nAChRs) play an important role as excitatory neurotransmitters in vertebrate and invertebrate species. In insects, nAChRs are the site of action of commercially important insecticides and, as a consequence, there is considerable interest in examining their functional properties. However, problems have been encountered in the successful functional expression of insect nAChRs, although a number of strategies have been developed in an attempt to overcome such difficulties. Ten nAChR subunits have been identified in the model insect Drosophila melanogaster (Dα1-Dα7 and Dβ1-Dβ3) and a similar number have been identified in other insect species. The focus of the present study is the Dα5, Dα6 and Dα7 subunits, which are distinguished by their sequence similarity to one another and also by their close similarity to the vertebrate α7 nAChR subunit. Results A full-length cDNA clone encoding the Drosophila nAChR Dα5 subunit has been isolated and the properties of Dα5-, Dα6- and Dα7-containing nAChRs examined in a variety of cell expression systems. We have demonstrated the functional expression, as homomeric nAChRs, of the Dα5 and Dα7 subunits in Xenopus oocytes by their co-expression with the molecular chaperone RIC-3. Also, using a similar approach, we have demonstrated the functional expression of a heteromeric ‘triplet’ nAChR (Dα5 + Dα6 + Dα7) with substantially higher apparent affinity for acetylcholine than is seen with other subunit combinations. In addition, specific cell-surface binding of [125I]-α-bungarotoxin was detected in both Drosophila and mammalian cell lines when Dα5 was co-expressed with Dα6 and RIC-3. In contrast, co-expression of additional subunits (including Dα7) with Dα5 and Dα6 prevented specific binding of [125I]-α-bungarotoxin in cell lines, suggesting that co-assembly with other nAChR subunits can block maturation of correctly folded nAChRs in some cellular environments. Conclusion Data are presented demonstrating the ability of the Drosophila Dα5 and Dα7 subunits to generate functional homomeric and also heteromeric nAChRs.
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Green BT, Lee ST, Panter KE, Brown DR. Piperidine alkaloids: human and food animal teratogens. Food Chem Toxicol 2012; 50:2049-55. [PMID: 22449544 DOI: 10.1016/j.fct.2012.03.049] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Revised: 03/08/2012] [Accepted: 03/10/2012] [Indexed: 11/17/2022]
Abstract
Piperidine alkaloids are acutely toxic to adult livestock species and produce musculoskeletal deformities in neonatal animals. These teratogenic effects include multiple congenital contracture (MCC) deformities and cleft palate in cattle, pigs, sheep, and goats. Poisonous plants containing teratogenic piperidine alkaloids include poison hemlock (Conium maculatum), lupine (Lupinus spp.), and tobacco (Nicotiana tabacum) [including wild tree tobacco (Nicotiana glauca)]. There is abundant epidemiological evidence in humans that link maternal tobacco use with a high incidence of oral clefting in newborns; this association may be partly attributable to the presence of piperidine alkaloids in tobacco products. In this review, we summarize the evidence for piperidine alkaloids that act as teratogens in livestock, piperidine alkaloid structure-activity relationships and their potential implications for human health.
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Affiliation(s)
- Benedict T Green
- Poisonous Plant Research Laboratory, Agricultural Research Service, United States Department of Agriculture, Logan, UT 84341, USA.
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Yu R, Kaas Q, Craik DJ. Delineation of the unbinding pathway of α-conotoxin ImI from the α7 nicotinic acetylcholine receptor. J Phys Chem B 2012; 116:6097-105. [PMID: 22571488 DOI: 10.1021/jp301352d] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
α-Conotoxins potently and specifically inhibit isoforms of nicotinic acetylcholine receptors (nAChRs) and are used as molecular probes and as drugs or drug leads. Interactions occurring during binding and unbinding events are linked to binding kinetics, and knowledge of these interactions could help in the development of α-conotoxins as drugs. Here, the unbinding process for the prototypical α-conotoxin ImI/α7-nAChR system was investigated theoretically, and three exit routes were identified using random accelerated molecular dynamics simulations. The route involving the smallest conformation perturbation was further divided into three subpathways, which were studied using steered molecular dynamics simulations. Of the three subpathways, two had better experimental support and lower potential of mean force, indicating that they might be sampled more frequently. Additionally, these subpathways were supported by previous experimental studies. Several pairwise interactions, including a cation-π interaction and charge and hydrogen bond interactions, were identified as potentially playing important roles in the unbinding event.
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Affiliation(s)
- Rilei Yu
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Australia
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Brunzell DH. Preclinical evidence that activation of mesolimbic alpha 6 subunit containing nicotinic acetylcholine receptors supports nicotine addiction phenotype. Nicotine Tob Res 2012; 14:1258-69. [PMID: 22492084 DOI: 10.1093/ntr/nts089] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
INTRODUCTION Nicotine is a major psychoactive ingredient in tobacco yet very few individuals quit smoking with the aid of nicotine replacement therapy. Targeted therapies with more selective action at nicotinic acetylcholine receptors (nAChRs) that contain a β2 subunit (β2*nAChRs; *denotes assembly with other subunits) have enjoyed significantly greater success, but exhibit potential for unwanted cardiac, gastrointestinal, and emotive side effects. DISCUSSION This literature review focuses on the preclinical evidence that suggests that subclasses of β2*nAChRs that assemble with the α6 subunit may provide an effective target for tobacco cessation. α6β2*nAChRs have a highly selective pattern of neuroanatomical expression in catecholaminergic nuclei including the ventral tegmental area and its projection regions. α6β2*nAChRs promote dopamine (DA) neuron activity and DA release in the mesolimbic dopamine system, a brain circuitry that is well-studied for its contributions to addiction behavior. A combination of genetic and pharmacological studies indicates that activation of α6β2*nAChRs is necessary and sufficient for nicotine psychostimulant effects and nicotine self-administration. α6β2*nAChRs support maintenance of nicotine use, support the conditioned reinforcing effects of drug-associated cues, and regulate nicotine withdrawal. CONCLUSIONS These data suggest that α6β2*nAChRs represent a critical pool of high affinity β2*nAChRs that regulates nicotine dependence phenotype and suggest that inhibition of these receptors may provide an effective strategy for tobacco cessation therapy.
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Affiliation(s)
- Darlene H Brunzell
- Department of Pharmacology and Toxicology, Virginia Commonwealth University School of Medicine, Richmond, VA, USA.
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Rasoulpour RJ, Ellis-Hutchings RG, Terry C, Millar NS, Zablotny CL, Gibb A, Marshall V, Collins T, Carney EW, Billington R. A Novel Mode-of-Action Mediated by the Fetal Muscle Nicotinic Acetylcholine Receptor Resulting in Developmental Toxicity in Rats. Toxicol Sci 2012; 127:522-34. [DOI: 10.1093/toxsci/kfs118] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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A novel halogen bond and a better-known hydrogen bond cooperation of neonicotinoid and insect nicotinic acetylcholine receptor recognition. J Mol Model 2012; 18:3867-75. [DOI: 10.1007/s00894-012-1393-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2012] [Accepted: 02/22/2012] [Indexed: 02/06/2023]
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Pohanka M. Alpha7 nicotinic acetylcholine receptor is a target in pharmacology and toxicology. Int J Mol Sci 2012; 13:2219-2238. [PMID: 22408449 PMCID: PMC3292018 DOI: 10.3390/ijms13022219] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Revised: 01/26/2012] [Accepted: 02/14/2012] [Indexed: 01/18/2023] Open
Abstract
Alpha7 nicotinic acetylcholine receptor (α7 nAChR) is an important part of the cholinergic nerve system in the brain. Moreover, it is associated with a cholinergic anti-inflammatory pathway in the termination of the parasympathetic nervous system. Antagonists of α7 nAChR are a wide group represented by conotoxin and bungarotoxin. Even Alzheimer's disease drug memantine acting as an antagonist in its side pathway belongs in this group. Agonists of α7 nAChR are suitable for treatment of multiple cognitive dysfunctions such as Alzheimer's disease or schizophrenia. Inflammation or even sepsis can be ameliorated by the agonistic acting compounds. Preparations RG3487, SEN34625/WYE-103914, SEN12333, ABT-107, Clozapine, GTS-21, CNI-1493, and AR-R17779 are representative examples of the novel compounds with affinity toward the α7 nAChR. Pharmacological, toxicological, and medicinal significance of α7 nAChR are discussed throughout this paper.
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Affiliation(s)
- Miroslav Pohanka
- Faculty of Military Health Sciences, University of Defence, Trebesska 1575, 50001 Hradec Kralove, Czech Republic; E-Mail: ; Tel.: +420-973253091; Fax: +420-973253091
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Gill JK, Dhankher P, Sheppard TD, Sher E, Millar NS. A series of α7 nicotinic acetylcholine receptor allosteric modulators with close chemical similarity but diverse pharmacological properties. Mol Pharmacol 2012; 81:710-8. [PMID: 22328718 DOI: 10.1124/mol.111.076026] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Acetylcholine activates nicotinic acetylcholine receptors (nAChRs) by binding to an extracellular site located at the interface of two adjacent subunits. In contrast, recent studies have provided evidence that positive allosteric modulators (PAMs) such as TQS (4-(naphthalen-2-yl)-3a,4,5,9b-tetrahydro-3H-cyclopenta[c]quinoline-8-sulfonamide) and allosteric agonists such as 4BP-TQS (4-(4-bromophenyl)-3a,4,5,9b-tetrahydro-3H-cyclopenta[c]quinoline-8-sulfonamide) interact at an intrasubunit transmembrane site. Here, we describe the synthesis and pharmacological characterization of a series of chemically related allosteric modulators of the α7 nAChR. Minimal changes in the chemical structure of these compounds have been found to exert profound effects on their pharmacological properties. For example, compounds containing a bromine atom at either the ortho or meta position on the phenyl ring, such as 2BP-TQS (4-(2-bromophenyl)-3a,4,5,9b-tetrahydro-3H-cyclopenta[c]quinoline-8-sulfonamide) and 3BP-TQS (4-(3-bromophenyl)-3a,4,5,9b-tetrahydro-3H-cyclopenta[c]quinoline-8-sulfonamide), rather than at the para position (4BP-TQS), display no allosteric agonist activity but retain PAM activity on α7 nAChRs, demonstrating the importance of the location of the halogen atom on pharmacological properties. Replacement of the bromine atom in 4BP-TQS with either a chlorine [4CP-TQS (4-(4-chloroophenyl)-3a,4,5,9b-tetrahydro-3H-cyclopenta[c]quinoline-8-sulfonamide)] or an iodine atom [4IP-TQS (4-(4-iodoophenyl)-3a,4,5,9b-tetrahydro-3H-cyclopenta[c]quinoline-8-sulfonamide)] results in compounds that have pharmacological properties characteristic of allosteric agonists but display differences in activation rates, in inactivation rates, and in levels of desensitization. In contrast, replacement of the bromine atom in 4BP-TQS with a fluorine atom [4FP-TQS (4-(4-fluorophenyl)-3a,4,5,9b-tetrahydro-3H-cyclopenta[c]quinoline-8-sulfonamide)] generated a compound that lacks allosteric agonist activity but acts a potentiator of responses to acetylcholine. In addition, 4FP-TQS was found to act as an antagonist of responses evoked by allosteric agonists such as 4BP-TQS. These findings provide evidence of the pharmacological diversity of compounds interacting with the allosteric transmembrane site on α7 nAChRs.
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Affiliation(s)
- JasKiran K Gill
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
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The Molecular Anatomy of Human Hsp60 and its Similarity with that of Bacterial Orthologs and Acetylcholine Receptor Reveal a Potential Pathogenetic Role of Anti-Chaperonin Immunity in Myasthenia Gravis. Cell Mol Neurobiol 2012; 32:943-7. [DOI: 10.1007/s10571-011-9789-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Accepted: 12/20/2011] [Indexed: 11/27/2022]
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Cesa LC, Higgins CA, Sando SR, Kuo DW, Levandoski MM. Specificity determinants of allosteric modulation in the neuronal nicotinic acetylcholine receptor: a fine line between inhibition and potentiation. Mol Pharmacol 2011; 81:239-49. [PMID: 22064677 DOI: 10.1124/mol.111.076059] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
We are interested in the allosteric modulation of neuronal nicotinic acetylcholine receptors (nAChRs). We have postulated that the anthelmintic morantel (Mor) positively modulates (potentiates) rat α3β2 receptors through a site located at the β(+)/α(-) interface that is homologous to the canonical agonist site (J Neurosci 29:8734-8742, 2009). On this basis, we aimed to determine the site specificity by studying differences in modulation between α3β2 and α4β2 receptors. We also compared modulation by Mor with that of the related compound oxantel (Oxa). Whereas Mor and Oxa each potentiated α3β2 receptors 2-fold at saturating acetylcholine (ACh) concentrations, Mor had no effect on α4β2 receptors, and Oxa inhibited ACh-evoked responses. The inhibition was noncompetitive, but not due to open channel block. Furthermore, the nature and extent of modulation did not depend on subunit stoichiometry. We studied six positions at the α(-) interface that differ between α3 and α4. Two positions (α3Ile57 and α3Thr115) help mediate the effects of the modulators but do not seem to contribute to specificity. Mutations in two others (α3Leu107 and α3Ile117) yielded receptors with appreciable α4-character; that is, Mor potentiation was reduced compared with wild-type α3β2 control and Oxa inhibition was evident. A fifth position (α3Glu113) was unique in that it discriminated between the two compounds, showing no change in Mor potentiation from control but substantial Oxa inhibition. Our work has implications for rational drug design for nicotinic receptors and sheds light on mechanisms of allosteric modulation in nAChRs, especially the subtle differences between potentiation and inhibition.
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Affiliation(s)
- Laura C Cesa
- Department of Chemistry, Grinnell College, Grinnell, Iowa, USA
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50
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Dey R, Chen L. In search of allosteric modulators of a7-nAChR by solvent density guided virtual screening. J Biomol Struct Dyn 2011; 28:695-715. [PMID: 21294583 DOI: 10.1080/07391102.2011.10508600] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Nicotinic acetylcholine receptors (nAChR) are pentameric ligand gated ion channels whose activity can be modulated by endogenous neurotransmitters as well as by synthetic ligands that bind the same or distinct sites from the natural ligand. The subtype of α7 nAChR has been considered as a potenial therapeutic target for Alzheimer's disease, schizophrenia and other neurological and psychiatric disorders. Here we have developed a homology model of α7 nAChR based on two high resolution crystal structures with Brookhaven Protein Data Bank (PDB) codes 2QC1 and 2WN9 for threading on one monomer and then for building a pentamer, respectively. A number of small molecule binding sites are identified using Pocket Finder (J. An, M. Tortov, and R. Abagyan, Molecular & Cellular Proteomics, 4.6, 752-761 (2005)) of Internal Coordinate Mechanics (ICM). Remarkably, these computer-identified sites match perfectly with ordered solvent densities found in the high-resolution crystal structure of α1 nAChR, suggesting that the surface cavities in the α7 nAChR model are likely binding sites of small molecules. A high throughput virtual screening by flexible ligand docking of 5008 small molecule compounds was performed at three potential allosteric modulator (AM) binding sites of α7 nAChR using Molsoft ICM software (R. Abagyan, M. Tortov and D. Kuznetsov, J Comput Chem 15, 488-506, (1994)). Some experimentally verified allosteric modulators of α7 like CCMI comp-6, LY 7082101, 5-HI, TQS, PNU-120596, genistein, and NS-1738 ranked among top 100 compounds, while the rest of the compounds in the list could guide further search for new allosteric modulators.
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Affiliation(s)
- Raja Dey
- Molecular and Computational Biology, Department of Biological Sciences,University of Southern California, Los Angeles, CA 90089, USA.
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