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Christie LA, Brice NL, Rowland A, Dickson L, Anand R, Teall M, Doyle KJ, Narayana L, Mitchell C, Harvey JRM, Mulligan V, Dawson LA, Cragg SJ, Carlton M, Bürli RW. Discovery of CVN417, a Novel Brain-Penetrant α6-Containing Nicotinic Receptor Antagonist for the Modulation of Motor Dysfunction. J Med Chem 2023; 66:11718-11731. [PMID: 37651656 DOI: 10.1021/acs.jmedchem.3c00630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
Abstract
Nicotinic acetylcholine receptor (nAChR) α6 subunit RNA expression is relatively restricted to midbrain regions and is located presynaptically on dopaminergic neurons projecting to the striatum. This subunit modulates dopamine neurotransmission and may have therapeutic potential in movement disorders. We aimed to develop potent and selective α6-containing nAChR antagonists to explore modulation of dopamine release and regulation of motor function in vivo. High-throughput screening (HTS) identified novel α6-containing nAChR antagonists and led to the development of CVN417. This molecule blocks α6-containing nAChR activity in recombinant cells and reduces firing frequency of noradrenergic neurons in the rodent locus coeruleus. CVN417 modulated phasic dopaminergic neurotransmission in an impulse-dependent manner. In a rodent model of resting tremor, CVN417 attenuated this behavioral phenotype. These data suggest that selective antagonism of α6-containing nAChR, with molecules such as CVN417, may have therapeutic utility in treating the movement dysfunctions observed in conditions such as Parkinson's disease.
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Affiliation(s)
- Louisa A Christie
- Cerevance Limited, 418 Cambridge Science Park, Cambridge CB4 0PZ, United Kingdom
- Takeda Cambridge Limited, 418 Cambridge Science Park, Cambridge CB4 0PZ, United Kingdom
| | - Nicola L Brice
- Cerevance Limited, 418 Cambridge Science Park, Cambridge CB4 0PZ, United Kingdom
- Takeda Cambridge Limited, 418 Cambridge Science Park, Cambridge CB4 0PZ, United Kingdom
| | - Anna Rowland
- Cerevance Limited, 418 Cambridge Science Park, Cambridge CB4 0PZ, United Kingdom
- Takeda Cambridge Limited, 418 Cambridge Science Park, Cambridge CB4 0PZ, United Kingdom
| | - Louise Dickson
- Cerevance Limited, 418 Cambridge Science Park, Cambridge CB4 0PZ, United Kingdom
- Takeda Cambridge Limited, 418 Cambridge Science Park, Cambridge CB4 0PZ, United Kingdom
| | - Rishi Anand
- Centre for Cellular and Molecular Neurobiology, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, United Kingdom
| | - Martin Teall
- Cerevance Limited, 418 Cambridge Science Park, Cambridge CB4 0PZ, United Kingdom
- Takeda Cambridge Limited, 418 Cambridge Science Park, Cambridge CB4 0PZ, United Kingdom
| | - Kevin J Doyle
- Cerevance Limited, 418 Cambridge Science Park, Cambridge CB4 0PZ, United Kingdom
| | - Lakshminarayana Narayana
- Aragen Lifesciences Limited, Plot #284A (part), Bommasandra-Jigani Link Road Industrial Area, Bengaluru 562106, India
| | - Christine Mitchell
- Takeda Cambridge Limited, 418 Cambridge Science Park, Cambridge CB4 0PZ, United Kingdom
| | - Jenna R M Harvey
- Cerevance Limited, 418 Cambridge Science Park, Cambridge CB4 0PZ, United Kingdom
- Takeda Cambridge Limited, 418 Cambridge Science Park, Cambridge CB4 0PZ, United Kingdom
| | - Victoria Mulligan
- Cerevance Limited, 418 Cambridge Science Park, Cambridge CB4 0PZ, United Kingdom
- Takeda Cambridge Limited, 418 Cambridge Science Park, Cambridge CB4 0PZ, United Kingdom
| | - Lee A Dawson
- Cerevance Limited, 418 Cambridge Science Park, Cambridge CB4 0PZ, United Kingdom
| | - Stephanie J Cragg
- Centre for Cellular and Molecular Neurobiology, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, United Kingdom
| | - Mark Carlton
- Cerevance Limited, 418 Cambridge Science Park, Cambridge CB4 0PZ, United Kingdom
- Takeda Cambridge Limited, 418 Cambridge Science Park, Cambridge CB4 0PZ, United Kingdom
| | - Roland W Bürli
- Cerevance Limited, 418 Cambridge Science Park, Cambridge CB4 0PZ, United Kingdom
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2
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Richter K, Grau V. Signaling of nicotinic acetylcholine receptors in mononuclear phagocytes. Pharmacol Res 2023; 191:106727. [PMID: 36966897 DOI: 10.1016/j.phrs.2023.106727] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Revised: 03/07/2023] [Accepted: 03/10/2023] [Indexed: 03/28/2023]
Abstract
Nicotinic acetylcholine receptors are not only expressed by the nervous system and at the neuro-muscular junction but also by mononuclear phagocytes, which belong to the innate immune system. Mononuclear phagocyte is an umbrella term for monocytes, macrophages, and dendritic cells. These cells play pivotal roles in host defense against infection but also in numerous often debilitating diseases that are characterized by exuberant inflammation. Nicotinic acetylcholine receptors of the neuronal type dominate in these cells, and their stimulation is mainly associated with anti-inflammatory effects. Although the cholinergic modulation of mononuclear phagocytes is of eminent clinical relevance for the prevention and treatment of inflammatory diseases and neuropathic pain, we are only beginning to understand the underlying mechanisms on the molecular level. The purpose of this review is to report and critically discuss the current knowledge on signal transduction mechanisms elicited by nicotinic acetylcholine receptors in mononuclear phagocytes.
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Affiliation(s)
- Katrin Richter
- Laboratory of Experimental Surgery, Department of General and Thoracic Surgery, Justus-Liebig-University Giessen, Germany
| | - Veronika Grau
- Laboratory of Experimental Surgery, Department of General and Thoracic Surgery, Justus-Liebig-University Giessen, Germany; German Centre for Lung Research (DZL), Giessen, Germany; Cardiopulmonary Institute (CPI), Giessen, Germany.
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Pursuing High-Resolution Structures of Nicotinic Acetylcholine Receptors: Lessons Learned from Five Decades. Molecules 2021; 26:molecules26195753. [PMID: 34641297 PMCID: PMC8510392 DOI: 10.3390/molecules26195753] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Revised: 09/19/2021] [Accepted: 09/20/2021] [Indexed: 01/04/2023] Open
Abstract
Since their discovery, nicotinic acetylcholine receptors (nAChRs) have been extensively studied to understand their function, as well as the consequence of alterations leading to disease states. Importantly, these receptors represent pharmacological targets to treat a number of neurological and neurodegenerative disorders. Nevertheless, their therapeutic value has been limited by the absence of high-resolution structures that allow for the design of more specific and effective drugs. This article offers a comprehensive review of five decades of research pursuing high-resolution structures of nAChRs. We provide a historical perspective, from initial structural studies to the most recent X-ray and cryogenic electron microscopy (Cryo-EM) nAChR structures. We also discuss the most relevant structural features that emerged from these studies, as well as perspectives in the field.
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Cartereau A, Taillebois E, Le Questel JY, Thany SH. Mode of Action of Neonicotinoid Insecticides Imidacloprid and Thiacloprid to the Cockroach Pameα7 Nicotinic Acetylcholine Receptor. Int J Mol Sci 2021; 22:9880. [PMID: 34576043 PMCID: PMC8471617 DOI: 10.3390/ijms22189880] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 09/01/2021] [Accepted: 09/08/2021] [Indexed: 12/28/2022] Open
Abstract
The functional expression of the cockroach Pameα7 nicotinic acetylcholine receptor subunit has been previously studied, and was found to be able to form a homomeric receptor when expressed in Xenopus laevis oocytes. In this study, we found that the neonicotinoid insecticide imidacloprid is unable to activate the cockroach Pameα7 receptor, although thiacloprid induces low inward currents, suggesting that it is a partial agonist. In addition, the co-application or 5 min pretreatment with 10 µM imidacloprid increased nicotine current amplitudes, while the co-application or 5 min pretreatment with 10 µM thiacloprid decreased nicotine-evoked current amplitudes by 54% and 28%, respectively. This suggesting that these two representatives of neonicotinoid insecticides bind differently to the cockroach Pameα7 receptor. Interestingly, the docking models demonstrate that the orientation and interactions of the two insecticides in the cockroach Pameα7 nAChR binding pocket are very similar. Electrophysiological results have provided evidence to suggest that imidacloprid and thiacloprid could act as modulators of the cockroach Pameα7 receptors.
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Affiliation(s)
- Alison Cartereau
- Université d’Orléans, LBLGC USC INRAE 1328, 45067 Orléans, France; (A.C.); (E.T.)
| | - Emiliane Taillebois
- Université d’Orléans, LBLGC USC INRAE 1328, 45067 Orléans, France; (A.C.); (E.T.)
| | | | - Steeve H. Thany
- Université d’Orléans, LBLGC USC INRAE 1328, 45067 Orléans, France; (A.C.); (E.T.)
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Cooper SY, Henderson BJ. The Impact of Electronic Nicotine Delivery System (ENDS) Flavors on Nicotinic Acetylcholine Receptors and Nicotine Addiction-Related Behaviors. Molecules 2020; 25:E4223. [PMID: 32942576 PMCID: PMC7571084 DOI: 10.3390/molecules25184223] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 09/11/2020] [Accepted: 09/13/2020] [Indexed: 12/18/2022] Open
Abstract
Over the past two decades, combustible cigarette smoking has slowly declined by nearly 11% in America; however, the use of electronic cigarettes has increased tremendously, including among adolescents. While nicotine is the main addictive component of tobacco products and a primary concern in electronic cigarettes, this is not the only constituent of concern. There is a growing market of flavored products and a growing use of zero-nicotine e-liquids among electronic cigarette users. Accordingly, there are few studies that examine the impact of flavors on health and behavior. Menthol has been studied most extensively due to its lone exception in combustible cigarettes. Thus, there is a broad understanding of the neurobiological effects that menthol plus nicotine has on the brain including enhancing nicotine reward, altering nicotinic acetylcholine receptor number and function, and altering midbrain neuron excitability. Although flavors other than menthol were banned from combustible cigarettes, over 15,000 flavorants are available for use in electronic cigarettes. This review seeks to summarize the current knowledge on nicotine addiction and the various brain regions and nicotinic acetylcholine receptor subtypes involved, as well as describe the most recent findings regarding menthol and green apple flavorants, and their roles in nicotine addiction and vaping-related behaviors.
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Affiliation(s)
| | - Brandon J. Henderson
- Department of Biomedical Sciences, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25703, USA;
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Velic D, Charlier C, Popova M, Jaunet-Lahary T, Bouchouireb Z, Henry S, Weigel P, Masson JY, Laurent A, Nabiev I, Fleury F. Interactions of the Rad51 inhibitor DIDS with human and bovine serum albumins: Optical spectroscopy and isothermal calorimetry approaches. Biochimie 2019; 167:187-197. [PMID: 31562898 DOI: 10.1016/j.biochi.2019.09.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 09/23/2019] [Indexed: 12/11/2022]
Abstract
Rad51 is a key protein in DNA repair by homologous recombination and an important target for development of drugs in cancer therapy. 4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) has been used in clinic during the past 30 years as an inhibitor of anion transporters and channels. Recently DIDS has been demonstrated to affect Rad51-mediated homologous pairing and strand exchange, key processes in homologous recombination. Consequently, DIDS has been considered as a potential revertant of radio- and chemo-resistance of cancer cells, the major causes of therapy failure. Here, we have investigated the behavior of DIDS towards serum albumins. The effects of environmental factors, primarily, solvent polarity, on DIDS stability were evaluated, and the mechanisms of interaction of DIDS with human or bovine serum albumin were analyzed using isothermal calorimetry, circular dichroism and fluorescence spectroscopies. DIDS interaction with both serum albumins have been demonstrated, and the interaction characteristics have been determined. By comparing these characteristics for several DIDS derivatives, we have identified the DIDS moiety essential for the interaction. Furthermore, site competition data indicate that human albumin has two DIDS-binding sites: a high-affinity site in the IIIA subdomain and a low-affinity one in the IB subdomain. Molecular docking has revealed the key molecular moieties of DIDS responsible for its interactions in each site and shown that the IB site can bind two ligands. These findings show that binding of DIDS to serum albumin may change the balance between the free and bound DIDS forms, thereby affecting its bioavailability and efficacy against Rad51.
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Affiliation(s)
- Denis Velic
- Group of Mechanism and Regulation of DNA Repair and IMPACT Platform, UFIP UMR CNRS 6286, University of Nantes, 44322, Nantes, France; Centre de Recherche en Cancérologie de l'Université Laval, Laboratoire de Stabilité du Génome, 9, rue McMahon, G1R 3S3, Québec, Canada
| | - Cathy Charlier
- Group of Mechanism and Regulation of DNA Repair and IMPACT Platform, UFIP UMR CNRS 6286, University of Nantes, 44322, Nantes, France
| | - Milena Popova
- Group of Mechanism and Regulation of DNA Repair and IMPACT Platform, UFIP UMR CNRS 6286, University of Nantes, 44322, Nantes, France
| | - Titouan Jaunet-Lahary
- Laboratoire CEISAM - UMR CNR 6230, Université de Nantes, 2 Rue de la Houssinière, BP 92208, 44322, Nantes Cedex 3, France
| | - Zakaria Bouchouireb
- Laboratoire CEISAM - UMR CNR 6230, Université de Nantes, 2 Rue de la Houssinière, BP 92208, 44322, Nantes Cedex 3, France
| | - Sébastien Henry
- Group of Mechanism and Regulation of DNA Repair and IMPACT Platform, UFIP UMR CNRS 6286, University of Nantes, 44322, Nantes, France
| | - Pierre Weigel
- Group of Mechanism and Regulation of DNA Repair and IMPACT Platform, UFIP UMR CNRS 6286, University of Nantes, 44322, Nantes, France
| | - Jean-Yves Masson
- Centre de Recherche en Cancérologie de l'Université Laval, Laboratoire de Stabilité du Génome, 9, rue McMahon, G1R 3S3, Québec, Canada
| | - Adèle Laurent
- Laboratoire CEISAM - UMR CNR 6230, Université de Nantes, 2 Rue de la Houssinière, BP 92208, 44322, Nantes Cedex 3, France
| | - Igor Nabiev
- Laboratoire de Recherche en Nanosciences EA4682-LRB, Université de Reims Champagne-Ardenne, 51100, Reims, France; National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 31 Kashirskoe Shosse, 115522, Moscow, Russian Federation; Department of Clinical Immunology and Allergology, Sechenov First Moscow State Medical University, 119992, Moscow, Russian Federation
| | - Fabrice Fleury
- Group of Mechanism and Regulation of DNA Repair and IMPACT Platform, UFIP UMR CNRS 6286, University of Nantes, 44322, Nantes, France.
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Abraham N, Paul B, Ragnarsson L, Lewis RJ. Escherichia coli Protein Expression System for Acetylcholine Binding Proteins (AChBPs). PLoS One 2016; 11:e0157363. [PMID: 27304486 PMCID: PMC4909209 DOI: 10.1371/journal.pone.0157363] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Accepted: 05/27/2016] [Indexed: 01/22/2023] Open
Abstract
Nicotinic acetylcholine receptors (nAChR) are ligand gated ion channels, identified as therapeutic targets for a range of human diseases. Drug design for nAChR related disorders is increasingly using structure-based approaches. Many of these structural insights for therapeutic lead development have been obtained from co-crystal structures of nAChR agonists and antagonists with the acetylcholine binding protein (AChBP). AChBP is a water soluble, structural and functional homolog of the extracellular, ligand-binding domain of nAChRs. Currently, AChBPs are recombinantly expressed in eukaryotic expression systems for structural and biophysical studies. Here, we report the establishment of an Escherichia coli (E. coli) expression system that significantly reduces the cost and time of production compared to the existing expression systems. E. coli can efficiently express unglycosylated AChBP for crystallography and makes the expression of isotopically labelled forms feasible for NMR. We used a pHUE vector containing an N-terminal His-tagged ubiquitin fusion protein to facilitate AChBP expression in the soluble fractions, and thus avoid the need to recover protein from inclusion bodies. The purified protein yield obtained from the E. coli expression system is comparable to that obtained from existing AChBP expression systems. E. coli expressed AChBP bound nAChR agonists and antagonists with affinities matching those previously reported. Thus, the E. coli expression system significantly simplifies the expression and purification of functional AChBP for structural and biophysical studies.
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Affiliation(s)
- Nikita Abraham
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Brisbane, Australia
| | - Blessy Paul
- Division of Molecular Cell Biology, Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Brisbane, Australia
| | - Lotten Ragnarsson
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Brisbane, Australia
| | - Richard J. Lewis
- Centre for Pain Research, Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Brisbane, Australia
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Malczewska-Jaskóła K, Jasiewicz B, Mrówczyńska L. Nicotine alkaloids as antioxidant and potential protective agents against in vitro oxidative haemolysis. Chem Biol Interact 2015; 243:62-71. [PMID: 26658032 DOI: 10.1016/j.cbi.2015.11.030] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 10/28/2015] [Accepted: 11/26/2015] [Indexed: 01/01/2023]
Abstract
The capacity of eleven nicotine alkaloids to reduce oxidative stress was investigated. In order to provide a structure-activity relationships analysis, new nicotine derivatives with a substituent introduced into the pyrrolidine ring were synthesized and investigated together with nicotine and its known analogs. All newly synthesized compounds were characterized by (1)H, (13)C NMR and EI-MS technique. The antioxidant properties of nicotine, its known analogs and newly produced derivatives, were evaluated by various antioxidant assays such 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH(•)) scavenging, ferrous ions (Fe(2+)) chelating activity and total reducing ability determination by Fe(3+) → Fe(2+) transformation assay. The protective effects of all compounds tested against 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AAPH) and tert-butyl hydroperoxide (t-BuOOH)-induced oxidative haemolysis and morphological injury of human erythrocytes, were estimated in vitro. The results showed that nicotine alkaloids exhibited various antiradical efficacy and antioxidant activity in a structure- and a dose-dependent manner. In addition, the capacity of nicotine alkaloids to protect erythrocytes from AAPH- and t-BuOOH-induced oxidative haemolysis, was dependent on its incubation time with cells. Our findings showed that chemical and biological investigations conducted simultaneously can provide comprehensive knowledge concerning the antioxidant potential of nicotine alkaloids. This knowledge can be helpful in better understanding the properties of nicotine alkaloids under oxidative stress conditions.
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Affiliation(s)
| | - Beata Jasiewicz
- Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61-614 Poznań, Poland.
| | - Lucyna Mrówczyńska
- Department Cell Biology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland.
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Selvam B, Graton J, Laurent AD, Alamiddine Z, Mathé-Allainmat M, Lebreton J, Coqueret O, Olivier C, Thany SH, Le Questel JY. Imidacloprid and thiacloprid neonicotinoids bind more favourably to cockroach than to honeybee α6 nicotinic acetylcholine receptor: Insights from computational studies. J Mol Graph Model 2015; 55:1-12. [DOI: 10.1016/j.jmgm.2014.10.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 10/30/2014] [Accepted: 10/31/2014] [Indexed: 11/26/2022]
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Bregier-Jarzębowska R, Malczewska-Jaskóła K, Jankowski W, Jasiewicz B, Hoffmann M, Gąsowska A, Jastrząb R. Experimental and quantum-chemical studies of anabasine complexes with copper(II) and zinc(II) ions. Polyhedron 2015. [DOI: 10.1016/j.poly.2014.10.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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A randomized, double-blind, placebo-controlled crossover study of α4β 2* nicotinic acetylcholine receptor agonist AZD1446 (TC-6683) in adults with attention-deficit/hyperactivity disorder. Psychopharmacology (Berl) 2014; 231:1251-65. [PMID: 23640072 PMCID: PMC3838503 DOI: 10.1007/s00213-013-3116-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Accepted: 04/04/2013] [Indexed: 10/26/2022]
Abstract
RATIONALE Stimulation of nicotinic cholinergic systems has been shown to alleviate ADHD symptoms and to improve cognitive performance. AZD1446 is a selective α4β2* nicotinic acetylcholine receptor agonist with potential effect on the symptoms of ADHD. OBJECTIVES The purpose of this study is to evaluate the efficacy, safety, and pharmacokinetics of AZD1446 in adults with ADHD treated for 2 weeks. METHOD This was a randomized, double-blind, placebo-controlled crossover trial. Participants were 79 adults with ADHD, grouped according to their use of nicotine-containing products. Nicotine non-users received placebo and two of three AZD1446 treatment regimens (80 mg tid, 80 mg qd, 10 mg tid). Nicotine users received placebo, AZD1446 80 mg tid and 80 mg qd. Efficacy measures included the Conners' Adult ADHD Rating Scale and cognitive measures of immediate and delayed verbal episodic memory, learning, attention, working memory, executive functioning, and spatial problem solving (CogState computerized test battery). RESULTS There was no significant effect of AZD1446 on any of the clinical scores irrespective of dose, schedule, or concomitant use of nicotine products. A statistically significant improvement was seen on the Groton Maze Learning Task, a measure of executive functioning, in nicotine non-users after treatment with AZD1446 80 mg qd. CONCLUSIONS AZD1446 was well tolerated, but did not significantly improve ADHD symptoms after 2 weeks of treatment compared to placebo. While the present study does not support the therapeutic utility of AZD1446 in ADHD, its potential pro-cognitive effects remain to be explored in other neuropsychiatric disorders.
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12
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New Insights on the Molecular Recognition of Imidacloprid with Aplysia californica AChBP: A Computational Study. J Phys Chem B 2013; 117:3944-53. [DOI: 10.1021/jp310242n] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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13
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DuBois DW, Damborsky JC, Fincher AS, Frye GD, Winzer-Serhan UH. Varenicline and nicotine enhance GABAergic synaptic transmission in rat CA1 hippocampal and medial septum/diagonal band neurons. Life Sci 2013; 92:337-44. [PMID: 23352971 DOI: 10.1016/j.lfs.2012.12.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Revised: 12/18/2012] [Accepted: 12/26/2012] [Indexed: 11/16/2022]
Abstract
AIMS The FDA approved smoking cessation aid varenicline can effectively attenuate nicotine-stimulated dopamine release. Varenicline may also exert important actions on other transmitter systems that also influence nicotine reinforcement or contribute to the drug's cognitive and affective side effects. In this study, we determined if varenicline, like nicotine, can stimulate presynaptic GABA release. MAIN METHODS Using whole-cell patch-clamp techniques, we measured GABA(A)R-mediated asynchronous, spontaneous miniature inhibitory postsynaptic currents (mIPSCs) in acute brain slices from two brain regions important for learning and memory, the hippocampus and basal forebrain. KEY FINDINGS Both varenicline (10 μM) and nicotine (10 μM) applications alone resulted in small but significant increases in amplitude, as well as robustly enhanced frequency of mIPSCs in hippocampal CA1 pyramidal neurons and medial septum/diagonal band (MS/DB) neurons. A unique subpopulation of MS/DB neurons showed decreases in frequency. In the presence of nicotine, varenicline effectively attenuated the expected enhancement of hippocampal mIPSC frequency like a competitive antagonist. However, in the MS/DB, varenicline only partially attenuated nicotine's effects. Reversing the order of drug application by adding nicotine to varenicline-exposed slices had little effect. SIGNIFICANCE Varenicline, like nicotine, stimulates presynaptic GABA release, and also exerts a partial agonist action by attenuating nicotine-stimulated release in both the hippocampus and basal forebrain. These effects could potentially affect cognitive functions.
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Affiliation(s)
- Dustin W DuBois
- Department of Neuroscience & Experimental Therapeutics, College of Medicine, Texas A&M System Health Science Center, Bryan, TX 77807, USA
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Molecular actions of smoking cessation drugs at α4β2 nicotinic receptors defined in crystal structures of a homologous binding protein. Proc Natl Acad Sci U S A 2012; 109:9173-8. [PMID: 22619328 DOI: 10.1073/pnas.1116397109] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Partial agonists of the α4β2 nicotinic acetylcholine receptor (nAChR), such as varenicline, are therapeutically used in smoking cessation treatment. These drugs derive their therapeutic effect from fundamental molecular actions, which are to desensitize α4β2 nAChRs and induce channel opening with higher affinity, but lower efficacy than a full agonist at equal receptor occupancy. Here, we report X-ray crystal structures of a unique acetylcholine binding protein (AChBP) from the annelid Capitella teleta, Ct-AChBP, in complex with varenicline or lobeline, which are both partial agonists. These structures highlight the architecture for molecular recognition of these ligands, indicating the contact residues that potentially mediate their molecular actions in α4β2 nAChRs. We then used structure-guided mutagenesis and electrophysiological recordings to pinpoint crucial interactions of varenicline with residues on the complementary face of the binding site in α4β2 nAChRs. We observe that residues in loops D and E are molecular determinants of desensitization and channel opening with limited efficacy by the partial agonist varenicline. Together, this study analyzes molecular recognition of smoking cessation drugs by nAChRs in a structural context.
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Linden AH, Lange S, Franks WT, Akbey U, Specker E, van Rossum BJ, Oschkinat H. Neurotoxin II bound to acetylcholine receptors in native membranes studied by dynamic nuclear polarization NMR. J Am Chem Soc 2011; 133:19266-9. [PMID: 22039931 DOI: 10.1021/ja206999c] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Methods enabling structural studies of membrane-integrated receptor systems without the necessity of purification provide an attractive perspective in membrane protein structural and molecular biology. This has become feasible in principle since the advent of dynamic nuclear polarization (DNP) magic-angle-spinning NMR spectroscopy, which delivers the required sensitivity. In this pilot study, we observed well-resolved solid-state NMR spectra of extensively (13)C-labeled neurotoxin II bound to the nicotinic acetylcholine receptor (nAChR) in native membranes. We show that TOTAPOL, a biradical required for DNP, is localized at membrane and protein surfaces. The concentration of active, membrane-attached biradical decreases with time, probably because of reactive components of the membrane preparation. An optimal distribution of active biradical has strong effects on the NMR data. The presence of inactive TOTAPOL in membrane-proximal situations but active biradical in the surrounding water/glycerol "glass" leads to well-resolved spectra, yet a considerable enhancement (ε = 12) is observed. The resulting spectra of a protein ligand bound to its receptor are paving the way for further DNP investigations of proteins embedded in native membrane patches.
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Affiliation(s)
- Arne H Linden
- Leibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125 Berlin, Germany
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New insights on the molecular features and electrophysiological properties of dinotefuran, imidacloprid and acetamiprid neonicotinoid insecticides. Bioorg Med Chem 2011; 19:7623-34. [PMID: 22056840 DOI: 10.1016/j.bmc.2011.10.019] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Revised: 10/06/2011] [Accepted: 10/07/2011] [Indexed: 11/23/2022]
Abstract
Structural features and hydrogen-bond interactions of dinotefuran (DIN), imidacoloprid (IMI) and acetamiprid (ACE) have been investigated experimentally through analyses of new crystal structures and observations in structural databases, as well as by Density Functional Theory quantum chemical calculations. Several conformations are observed experimentally in the solid state, highlighting the large flexibility of these compounds. This feature is confirmed by the theoretical calculations in the gas phase, the numerous and different energetic minima of the three neonicotinoids being located within a 10kJ/mol range. Comparisons of the observed and simulated data sheds light on the hydrogen-bond (HB) strength of the functional group at the tip of the electronegative fragment of each pharmacophore (NO(2) for DIN and IMI and CN for ACE). This effect originates in the 'push-pull' nature of these fragments and the related extensive electron delocalization. Molecular electrostatic potential calculations provide a ranking of the two fragments of the three neonicotinoid in terms of HB strength. Thus, the NO(2) group of DIN is the strongest HB acceptor of the electronegative fragment, closely followed by the cyano group of ACE. These two groups are significantly more potent than the NO(2) group of IMI. With respect to the other fragments of the three neonicotinoids, the nitrogen atom of the pyridine of IMI and ACE are stronger HB acceptors than the oxygen atom of the furanyl moiety of DIN. Finally, compared to electrophysiological studies obtained from cockroach synaptic and extrasynaptic receptors, DIN appears more effective than IMI and ACE because it strongly increases dose-dependently the ganglionic depolarisation and the currents amplitudes. These data suggest that DIN, IMI and ACE belong to two subgroups which act differently as agonists of insect nicotinic receptors.
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17
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Martínez-Delgado G, Estrada-Mondragón A, Miledi R, Martínez-Torres A. An Update on GABAρ Receptors. Curr Neuropharmacol 2011; 8:422-33. [PMID: 21629448 PMCID: PMC3080597 DOI: 10.2174/157015910793358141] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Revised: 04/08/2010] [Accepted: 06/21/2010] [Indexed: 01/29/2023] Open
Abstract
The present review discusses the functional and molecular diversity of GABAρ receptors. These receptors were originally described in the mammalian retina, and their functional role in the visual pathway has been recently elucidated; however new studies on their distribution in the brain and spinal cord have revealed that they are more spread than originally thought, and thus it will be important to determine their physiological contribution to the GABAergic transmission in other areas of the central nervous system. In addition, molecular modeling has revealed peculiar traits of these receptors that have impacted on the interpretations of the latest pharmacolgical and biophysical findings. Finally, sequencing of several vertebrate genomes has permitted a comparative analysis of the organization of the GABAρ genes.
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Affiliation(s)
- Gustavo Martínez-Delgado
- Instituto de Neurbiología, Departamento de Neurobiología Celular y Molecular, Laboratorio D15, Campus UNAM Juriquilla. Querétaro 76230, México
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18
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Hamouda AK, Stewart DS, Husain SS, Cohen JB. Multiple transmembrane binding sites for p-trifluoromethyldiazirinyl-etomidate, a photoreactive Torpedo nicotinic acetylcholine receptor allosteric inhibitor. J Biol Chem 2011; 286:20466-77. [PMID: 21498509 DOI: 10.1074/jbc.m111.219071] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Photoreactive derivatives of the general anesthetic etomidate have been developed to identify their binding sites in γ-aminobutyric acid, type A and nicotinic acetylcholine receptors. One such drug, [(3)H]TDBzl-etomidate (4-[3-(trifluoromethyl)-3H-diazirin-3-yl]benzyl-[(3)H]1-(1-phenylethyl)-1H-imidazole-5-carboxylate), acts as a positive allosteric potentiator of Torpedo nACh receptor (nAChR) and binds to a novel site in the transmembrane domain at the γ-α subunit interface. To extend our understanding of the locations of allosteric modulator binding sites in the nAChR, we now characterize the interactions of a second aryl diazirine etomidate derivative, TFD-etomidate (ethyl-1-(1-(4-(3-trifluoromethyl)-3H-diazirin-3-yl)phenylethyl)-1H-imidazole-5-carboxylate). TFD-etomidate inhibited acetylcholine-induced currents with an IC(50) = 4 μM, whereas it inhibited the binding of [(3)H]phencyclidine to the Torpedo nAChR ion channel in the resting and desensitized states with IC(50) values of 2.5 and 0.7 mm, respectively. Similar to [(3)H]TDBzl-etomidate, [(3)H]TFD-etomidate bound to a site at the γ-α subunit interface, photolabeling αM2-10 (αSer-252) and γMet-295 and γMet-299 within γM3, and to a site in the ion channel, photolabeling amino acids within each subunit M2 helix that line the lumen of the ion channel. In addition, [(3)H]TFD-etomidate photolabeled in an agonist-dependent manner amino acids within the δ subunit M2-M3 loop (δIle-288) and the δ subunit transmembrane helix bundle (δPhe-232 and δCys-236 within δM1). The fact that TFD-etomidate does not compete with ion channel blockers at concentrations that inhibit acetylcholine responses indicates that binding to sites at the γ-α subunit interface and/or within δ subunit helix bundle mediates the TFD-etomidate inhibitory effect. These results also suggest that the γ-α subunit interface is a binding site for Torpedo nAChR negative allosteric modulators (TFD-etomidate) and for positive modulators (TDBzl-etomidate).
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Affiliation(s)
- Ayman K Hamouda
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, USA
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19
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The Conformational Landscape of Nicotinoids: Solving the Conformational Disparity of Anabasine. Chemistry 2010; 16:10214-9. [DOI: 10.1002/chem.201000849] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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20
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Yamodo IH, Chiara DC, Cohen JB, Miller KW. Conformational changes in the nicotinic acetylcholine receptor during gating and desensitization. Biochemistry 2010; 49:156-65. [PMID: 19961216 DOI: 10.1021/bi901550p] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The nicotinic acetylcholine receptor (nAChR) is a member of the important Cys loop ligand-gated ion channel superfamily that modulates neuronal excitability. After they respond to their agonists, their actions are terminated either by removal of ligand or by fast and slow desensitization, processes that play an important role in modulating the duration of conducting states and hence of integrated neuronal behavior. We monitored structural changes occurring during fast and slow desensitization in the transmembrane domain of the Torpedo nAChR using time-resolved photolabeling with the hydrophobic probe 3-(trifluoromethyl)-3-(m-iodophenyl)diazirine (TID). After channel opening, TID photolabels a residue on the delta-subunit's M2-M3 loop and a cluster of four residues on deltaM1 and deltaM2, defining an open state pocket [Arevalo, E., et al. (2005) J. Biol. Chem. 280, 13631-13640]. We now find that photolabeling of this pocket persists during the transition to the fast desensitized state, the extent of photoincorporation decreasing only with the transition to the slow desensitized state. In contrast, the extent of photoincorporation in the channel lumen at the conserved 9'-leucines on the second transmembrane helix (M2-9') decreased successively during the resting to open and open to fast desensitized state transitions, implying that the local conformation is different in each state, a conclusion consistent with the hypothesis that there are separate gates for channel opening and desensitization. Thus, although during fast desensitization there is a conformation change in the channel lumen at the level of M2-9', there is none in the regions of the delta-subunit's M2-M3 loop and the interior of its M1-M4 helix bundle until slow desensitization occurs.
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Affiliation(s)
- Innocent H Yamodo
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
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21
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Chen L. In pursuit of the high-resolution structure of nicotinic acetylcholine receptors. J Physiol 2009; 588:557-64. [PMID: 19995851 DOI: 10.1113/jphysiol.2009.184085] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The nicotinic acetylcholine receptor (nAChR) has been studied extensively for well over four decades because of its important physiological roles and medical relevance. A large body of data from biochemical and biophysical studies are now available. The structural information, which is needed to integrate existing data to address the mechanism and function of nAChRs, started to emerge in recent years. Structural studies of acetylcholine binding proteins (AChBPs) have greatly facilitated the study of nAChRs. The recently determined crystal structures of the prokaryotic homologues of nAChRs will probably have similar impact over time. However, a direct structural model of nAChRs at high resolution will be important for mechanistic studies and drug development. Here we will review some of the recent efforts in this area and use the high-resolution structure of the extracellular domains of nAChR alpha1 to illustrate the potential insights one may gain at higher resolution.
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Affiliation(s)
- Lin Chen
- Molecular and Computational Biology, Departments of Biological Sciences and Chemistry, Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089, USA.
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Hu ZJ, Bai L, Tizabi Y, Southerland W. Computational modeling study of human nicotinic acetylcholine receptor for developing new drugs in the treatment of alcoholism. Interdiscip Sci 2009; 1:254-62. [PMID: 20640803 DOI: 10.1007/s12539-009-0052-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2009] [Revised: 06/10/2009] [Accepted: 07/08/2009] [Indexed: 11/26/2022]
Abstract
Alcohol abuse and alcoholism are serious and costly problem in USA. Thus, the development of anti-alcoholism agents could be very significant. The understanding of the neurochemical basis underlying the addictive properties of drugs of abuse is imperative for the development of new pharmacological means to reverse the addictive state, prevent relapse or to reduce the intake of addictive compounds. The nicotinic acetylcholine receptors (nAChRs) are important therapeutic targets for various diseases. Recent studies have revealed that the alpha3beta2, alpha3beta3, and alpha6 subunits of nAChR protein family might be pharmacological targets for developing new drugs in the treatment of alcoholism. We have performed computational homology modeling of the alpha3beta2, alpha3beta3, and alpha6 subunits of human nACHRs based upon the recently determined crystal structure of the extracellular domain (ECD) of the mouse nAChR alpha1 subunit complexed with alpha-bungarotoxin at 1.94 A resolution. For comparison, we also built the ECD models of alpha4beta2, and alpha7 subunits of human nACHRs which are neurochemical targets for cessation of smoking. The three-dimensional (3D) models of the ECD of the monomer, and pentamer of these human nAChR were constructed. The docking of the agonist in the ligand-binding pocket of the human nAChR dimers was also performed. Since the nAChR ligand-binding site is a useful target for mutagenesis studies and the rational design of drugs against various diseases, these models provide useful information for future investigation.
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Affiliation(s)
- Zeng-Jian Hu
- Department of Biochemistry and Molecular Biology, Howard University College of Medicine, Washington, DC 20059, USA.
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23
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Dome P, Lazary J, Kalapos MP, Rihmer Z. Smoking, nicotine and neuropsychiatric disorders. Neurosci Biobehav Rev 2009; 34:295-342. [PMID: 19665479 DOI: 10.1016/j.neubiorev.2009.07.013] [Citation(s) in RCA: 149] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2009] [Revised: 07/23/2009] [Accepted: 07/30/2009] [Indexed: 12/20/2022]
Abstract
Tobacco smoking is an extremely addictive and harmful form of nicotine (NIC) consumption, but unfortunately also the most prevalent. Although disproportionately high frequencies of smoking and its health consequences among psychiatric patients are widely known, the neurobiological background of this epidemiological association is still obscure. The diverse neuroactive effects of NIC and some other major tobacco smoke constituents in the central nervous system may underlie this association. This present paper summarizes the pharmacology of NIC and its receptors (nAChR) based on a systematic review of the literature. The role of the brain's reward system(s) in NIC addiction and the results of functional and structural neuroimaging studies on smoking-related states and behaviors (i.e. dependence, craving, withdrawal) are also discussed. In addition, the epidemiological, neurobiological, and genetic aspects of smoking in several specific neuropsychiatric disorders are reviewed and the clinical relevance of smoking in these disease states addressed.
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Affiliation(s)
- Peter Dome
- Department of Clinical and Theoretical Mental Health, Kutvolgyi Clinical Center, Semmelweis University, Faculty of Medicine, Kutvolgyi ut 4, 1125 Budapest, Hungary.
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Srivastava S, Hamouda AK, Pandhare A, Duddempudi PK, Sanghvi M, Cohen JB, Blanton MP. [(3)H]Epibatidine photolabels non-equivalent amino acids in the agonist binding site of Torpedo and alpha4beta2 nicotinic acetylcholine receptors. J Biol Chem 2009; 284:24939-47. [PMID: 19620239 DOI: 10.1074/jbc.m109.019083] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nicotinic acetylcholine receptor (nAChR) agonists, such as epibatidine and its molecular derivatives, are potential therapeutic agents for a variety of neurological disorders. In order to identify determinants for subtype-selective agonist binding, it is important to determine whether an agonist binds in a common orientation in different nAChR subtypes. To compare the mode of binding of epibatidine in a muscle and a neuronal nAChR, we photolabeled Torpedo alpha(2)betagammadelta and expressed human alpha4beta2 nAChRs with [(3)H]epibatidine and identified by Edman degradation the photolabeled amino acids. Irradiation at 254 nm resulted in photolabeling of alphaTyr(198) in agonist binding site Segment C of the principal (+) face in both alpha subunits and of gammaLeu(109) and gammaTyr(117) in Segment E of the complementary (-) face, with no labeling detected in the delta subunit. For affinity-purified alpha4beta2 nAChRs, [(3)H]epibatidine photolabeled alpha4Tyr(195) (equivalent to Torpedo alphaTyr(190)) in Segment C as well as beta2Val(111) and beta2Ser(113) in Segment E (equivalent to Torpedo gammaLeu(109) and gammaTyr(111), respectively). Consideration of the location of the photolabeled amino acids in homology models of the nAChRs based upon the acetylcholine-binding protein structure and the results of ligand docking simulations suggests that epibatidine binds in a single preferred orientation within the alpha-gamma transmitter binding site, whereas it binds in two distinct orientations in the alpha4beta2 nAChR.
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Affiliation(s)
- Shouryadeep Srivastava
- Department of Pharmacology and Neuroscience and the Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA
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Krabben L, van Rossum BJ, Jehle S, Bocharov E, Lyukmanova EN, Schulga AA, Arseniev A, Hucho F, Oschkinat H. Loop 3 of Short Neurotoxin II is an Additional Interaction Site with Membrane-bound Nicotinic Acetylcholine Receptor as Detected by Solid-state NMR Spectroscopy. J Mol Biol 2009; 390:662-71. [DOI: 10.1016/j.jmb.2009.05.016] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2008] [Revised: 04/23/2009] [Accepted: 05/12/2009] [Indexed: 11/30/2022]
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Son JH, Winzer-Serhan UH. Chronic neonatal nicotine exposure increases mRNA expression of neurotrophic factors in the postnatal rat hippocampus. Brain Res 2009; 1278:1-14. [DOI: 10.1016/j.brainres.2009.04.046] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Revised: 04/21/2009] [Accepted: 04/27/2009] [Indexed: 01/19/2023]
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28
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Bernal JA, Mulet J, Castillo M, Criado M, Sala S, Sala F. Binding-gating coupling in a nondesensitizing alpha7 nicotinic receptor A single channel pharmacological study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1788:410-6. [PMID: 19063861 DOI: 10.1016/j.bbamem.2008.11.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2008] [Revised: 10/31/2008] [Accepted: 11/04/2008] [Indexed: 11/29/2022]
Abstract
The highly conserved alphaLys145 has been suggested to play an important role in the early steps of activation of the nicotinic acetylcholine receptor (nAChR) by acetylcholine. Both macroscopic and single channel currents were recorded in the slowly desensitizing mutants L248T- and K145A-L248T-alpha7 receptors expressed in Xenopus oocytes. On ACh-evoked currents, substitution of Lys145 by alanine showed the same effects that in wild type receptors: moderately decreased gating function and a more-than-expected loss of ACh potency, thus validating the experimental model. Single channel analysis quantitatively agreed with macroscopic data and revealed that impaired gating function in the double mutant alpha7K145A/L248T is the consequence of a slower opening rate, beta. Several nicotinic agonists were also studied, showing important features. Particularly, dimethylphenylpiperazinium (DMPP), acting as an antagonist in alpha7K145A, became a full agonist in alpha7K145A/L248T. Single channel analysis of DMPP-evoked currents showed effects of Lys145 removal similar to those observed with ACh. Data suggest that alpha7Lys145 facilitates the early steps of channel activation. Moreover, the slowly desensitizing mutant alpha7L248T could be an interesting tool for the study of channel activation in alpha7 receptors. Nevertheless, its extensively altered pharmacology precludes the simple extrapolation of pharmacological data obtained in singly mutated alpha7 receptors.
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Affiliation(s)
- José Antonio Bernal
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, Sant Joan d'Alacant, 03550-Alicante, Spain
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