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Pechlivanidou M, Vakrakou AG, Karagiorgou K, Tüzün E, Karachaliou E, Chroni E, Afrantou T, Grigoriadis N, Argyropoulou C, Paschalidis N, Şanlı E, Tsantila A, Dandoulaki M, Ninou EI, Zisimopoulou P, Mantegazza R, Andreetta F, Dudeck L, Steiner J, Lindstrom JM, Tzanetakos D, Voumvourakis K, Giannopoulos S, Tsivgoulis G, Tzartos SJ, Tzartos J. Neuronal nicotinic acetylcholine receptor antibodies in autoimmune central nervous system disorders. Front Immunol 2024; 15:1388998. [PMID: 38863705 PMCID: PMC11165060 DOI: 10.3389/fimmu.2024.1388998] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Accepted: 05/13/2024] [Indexed: 06/13/2024] Open
Abstract
Background Neuronal nicotinic acetylcholine receptors (nAChRs) are abundant in the central nervous system (CNS), playing critical roles in brain function. Antigenicity of nAChRs has been well demonstrated with antibodies to ganglionic AChR subtypes (i.e., subunit α3 of α3β4-nAChR) and muscle AChR autoantibodies, thus making nAChRs candidate autoantigens in autoimmune CNS disorders. Antibodies to several membrane receptors, like NMDAR, have been identified in autoimmune encephalitis syndromes (AES), but many AES patients have yet to be unidentified for autoantibodies. This study aimed to develop of a cell-based assay (CBA) that selectively detects potentially pathogenic antibodies to subunits of the major nAChR subtypes (α4β2- and α7-nAChRs) and its use for the identification of such antibodies in "orphan" AES cases. Methods The study involved screening of sera derived from 1752 patients from Greece, Turkey and Italy, who requested testing for AES-associated antibodies, and from 1203 "control" patients with other neuropsychiatric diseases, from the same countries or from Germany. A sensitive live-CBA with α4β2-or α7-nAChR-transfected cells was developed to detect antibodies against extracellular domains of nAChR major subunits. Flow cytometry (FACS) was performed to confirm the CBA findings and indirect immunohistochemistry (IHC) to investigate serum autoantibodies' binding to rat brain tissue. Results Three patients were found to be positive for serum antibodies against nAChR α4 subunit by CBA and the presence of the specific antibodies was quantitatively confirmed by FACS. We detected specific binding of patient-derived serum anti-nAChR α4 subunit antibodies to rat cerebellum and hippocampus tissue. No serum antibodies bound to the α7-nAChR-transfected or control-transfected cells, and no control serum antibodies bound to the transfected cells. All patients positive for serum anti-nAChRs α4 subunit antibodies were negative for other AES-associated antibodies. All three of the anti-nAChR α4 subunit serum antibody-positive patients fall into the AES spectrum, with one having Rasmussen encephalitis, another autoimmune meningoencephalomyelitis and another being diagnosed with possible autoimmune encephalitis. Conclusion This study lends credence to the hypothesis that the major nAChR subunits are autoimmune targets in some cases of AES and establishes a sensitive live-CBA for the identification of such patients.
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Affiliation(s)
| | - Aigli G. Vakrakou
- First Department of Neurology, School of Medicine, Aeginition Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Katerina Karagiorgou
- Tzartos NeuroDiagnostics, Athens, Greece
- Department of Biochemistry and Biotechnology, University of Thessaly, Larissa, Greece
| | - Erdem Tüzün
- Department of Neuroscience, Aziz Sancar Institute for Experimental Medical Research, Istanbul University, Istanbul, Türkiye
| | - Eleni Karachaliou
- Tzartos NeuroDiagnostics, Athens, Greece
- Second Department of Neurology, School of Medicine, “Attikon” University Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Elisabeth Chroni
- Department of Neurology, School of Medicine, University of Patras, Patras, Greece
| | - Theodora Afrantou
- Second Department of Neurology, “AHEPA“ University Hospital, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Nikolaos Grigoriadis
- Second Department of Neurology, “AHEPA“ University Hospital, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | | | - Nikolaos Paschalidis
- Mass Cytometry-CyTOF Laboratory, Center for Clinical Research, Experimental Surgery and Translational Research, Biomedical Research Foundation of the Academy of Athens (BRFAA), Athens, Greece
| | - Elif Şanlı
- Department of Neuroscience, Aziz Sancar Institute for Experimental Medical Research, Istanbul University, Istanbul, Türkiye
| | | | | | | | | | - Renato Mantegazza
- Neuroimmunology and Neuromuscular Diseases Unit, Fondazione I.R.C.C.S. Istituto Neurologico Carlo Besta, Milan, Italy
| | - Francesca Andreetta
- Neuroimmunology and Neuromuscular Diseases Unit, Fondazione I.R.C.C.S. Istituto Neurologico Carlo Besta, Milan, Italy
| | - Leon Dudeck
- Department of Psychiatry and Psychotherapy, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany
| | - Johann Steiner
- Department of Psychiatry and Psychotherapy, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany
| | - Jon Martin Lindstrom
- Department of Neuroscience, Medical School, University of Pennsylvania, Philadelphia, PA, United States
| | - Dimitrios Tzanetakos
- Second Department of Neurology, School of Medicine, “Attikon” University Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Konstantinos Voumvourakis
- Second Department of Neurology, School of Medicine, “Attikon” University Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Sotirios Giannopoulos
- Second Department of Neurology, School of Medicine, “Attikon” University Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Georgios Tsivgoulis
- Second Department of Neurology, School of Medicine, “Attikon” University Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Socrates J. Tzartos
- Tzartos NeuroDiagnostics, Athens, Greece
- Department of Neurobiology, Hellenic Pasteur Institute, Athens, Greece
- Department of Pharmacy, University of Patras, Patras, Greece
| | - John Tzartos
- Second Department of Neurology, School of Medicine, “Attikon” University Hospital, National and Kapodistrian University of Athens, Athens, Greece
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York JM, Borghese CM, George AA, Cannatella DC, Zakon HH. A potential cost of evolving epibatidine resistance in poison frogs. BMC Biol 2023; 21:144. [PMID: 37370119 DOI: 10.1186/s12915-023-01637-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Accepted: 05/30/2023] [Indexed: 06/29/2023] Open
Abstract
BACKGROUND Some dendrobatid poison frogs sequester the toxin epibatidine as a defense against predators. We previously identified an amino acid substitution (S108C) at a highly conserved site in a nicotinic acetylcholine receptor β2 subunit of dendrobatid frogs that decreases sensitivity to epibatidine in the brain-expressing α4β2 receptor. Introduction of S108C to the orthologous high-sensitivity human receptor similarly decreased sensitivity to epibatidine but also decreased sensitivity to acetylcholine, a potential cost if this were to occur in dendrobatids. This decrease in the acetylcholine sensitivity manifested as a biphasic acetylcholine concentration-response curve consistent with the addition of low-sensitivity receptors. Surprisingly, the addition of the β2 S108C into the α4β2 receptor of the dendrobatid Epipedobates anthonyi did not change acetylcholine sensitivity, appearing cost-free. We proposed that toxin-bearing dendrobatids may have additional amino acid substitutions protecting their receptors from alterations in acetylcholine sensitivity. To test this, in the current study, we compared the dendrobatid receptor to its homologs from two non-dendrobatid frogs. RESULTS The introduction of S108C into the α4β2 receptors of two non-dendrobatid frogs also does not affect acetylcholine sensitivity suggesting no additional dendrobatid-specific substitutions. However, S108C decreased the magnitude of neurotransmitter-induced currents in Epipedobates and the non-dendrobatid frogs. We confirmed that decreased current resulted from fewer receptors in the plasma membrane in Epipedobates using radiolabeled antibodies against the receptors. To test whether S108C alteration of acetylcholine sensitivity in the human receptor was due to (1) adding low-sensitivity binding sites by changing stoichiometry or (2) converting existing high- to low-sensitivity binding sites with no stoichiometric alteration, we made concatenated α4β2 receptors in stoichiometry with only high-sensitivity sites. S108C substitutions decreased maximal current and number of immunolabeled receptors but no longer altered acetylcholine sensitivity. CONCLUSIONS The most parsimonious explanation of our current and previous work is that the S108C substitution renders the β2 subunit less efficient in assembling/trafficking, thereby decreasing the number of receptors in the plasma membrane. Thus, while β2 S108C protects dendrobatids against sequestered epibatidine, it incurs a potential physiological cost of disrupted α4β2 receptor function.
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Affiliation(s)
- Julia M York
- Department of Neuroscience, The University of Texas, Austin, TX, USA
- Department of Integrative Biology, and Biodiversity Center, The University of Texas, Austin, TX, USA
| | | | - Andrew A George
- Department of Neurobiology, The Barrow Neurological Institute, Phoenix, AZ, USA
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, USA
| | - David C Cannatella
- Department of Integrative Biology, and Biodiversity Center, The University of Texas, Austin, TX, USA
| | - Harold H Zakon
- Department of Neuroscience, The University of Texas, Austin, TX, USA.
- Department of Integrative Biology, and Biodiversity Center, The University of Texas, Austin, TX, USA.
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O'Brien BCV, Weber L, Hueffer K, Weltzin MM. SARS-CoV-2 spike ectodomain targets α7 nicotinic acetylcholine receptors. J Biol Chem 2023; 299:104707. [PMID: 37061001 PMCID: PMC10101490 DOI: 10.1016/j.jbc.2023.104707] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 03/13/2023] [Accepted: 04/10/2023] [Indexed: 04/17/2023] Open
Abstract
Virus entry into animal cells is initiated by attachment to target macromolecules located on host cells. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) trimeric spike glycoprotein targets host angiotensin converting enzyme 2 to gain cellular access. The SARS-CoV-2 glycoprotein contains a neurotoxin-like region that has sequence similarities to the rabies virus and the HIV glycoproteins, as well as to snake neurotoxins, which interact with nicotinic acetylcholine receptor (nAChR) subtypes via this region. Using a peptide of the neurotoxin-like region of SARS-CoV-2 (SARS-CoV-2 glycoprotein peptide [SCoV2P]), we identified that this area moderately inhibits α3β2, α3β4, and α4β2 subtypes, while potentiating and inhibiting α7 nAChRs. These nAChR subtypes are found in target tissues including the nose, lung, central nervous system, and immune cells. Importantly, SCoV2P potentiates and inhibits ACh-induced α7 nAChR responses by an allosteric mechanism, with nicotine enhancing these effects. Live-cell confocal microscopy was used to confirm that SCoV2P interacts with α7 nAChRs in transfected neuronal-like N2a and human embryonic kidney 293 cells. The SARS-CoV-2 ectodomain functionally potentiates and inhibits the α7 subtype with nanomolar potency. Our functional findings identify that the α7 nAChR is a target for the SARS-CoV-2 glycoprotein, providing a new aspect to our understanding of SARS-CoV-2 and host cell interactions, in addition to disease pathogenesis.
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Affiliation(s)
- Brittany C V O'Brien
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, Alaska, USA
| | - Lahra Weber
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, Alaska, USA
| | - Karsten Hueffer
- Department of Veterinary Medicine, University of Alaska Fairbanks, Fairbanks, Alaska, USA
| | - Maegan M Weltzin
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, Alaska, USA.
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4
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York JM, Borghese CM, George AA, Cannatella DC, Zakon HH. A potential cost of evolving epibatidine resistance in poison frogs. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.04.522789. [PMID: 36711899 PMCID: PMC9882002 DOI: 10.1101/2023.01.04.522789] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Background Some poison arrow frogs sequester the toxin epibatidine as a defense against predators. We previously identified a single amino acid substitution (S108C) at a highly conserved site in a neuronal nicotinic acetylcholine receptor (nAChR) ß2 subunit that prevents epibatidine from binding to this receptor. When placed in a homologous mammalian nAChR this substitution minimized epibatidine binding but also perturbed acetylcholine binding, a clear cost. However, in the nAChRs of poison arrow frogs, this substitution appeared to have no detrimental effect on acetylcholine binding and, thus, appeared cost-free. Results The introduction of S108C into the α4β2 nAChRs of non-dendrobatid frogs also does not affect ACh sensitivity, when these receptors are expressed in Xenopus laevis oocytes. However, α4β2 nAChRs with C108 had a decreased magnitude of neurotransmitter-induced currents in all species tested ( Epipedobates anthonyi , non-dendrobatid frogs, as well as human), compared with α4β2 nAChRs with the conserved S108. Immunolabeling of frog or human α4β2 nAChRs in the plasma membrane using radiolabeled antibody against the β2 nAChR subunit shows that C108 significantly decreased the number of cell-surface α4β2 nAChRs, compared with S108. Conclusions While S108C protects these species against sequestered epibatidine, it incurs a potential physiological cost of disrupted α4β2 nAChR function. These results may explain the high conservation of a serine at this site in vertebrates, as well as provide an example of a tradeoff between beneficial and deleterious effects of an evolutionary change. They also provide important clues for future work on assembly and trafficking of this important neurotransmitter receptor.
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Akinola LS, Bagdas D, Alkhlaif Y, Jackson A, Gurdap CO, Rahimpour E, Carroll FI, Papke RL, Damaj MI. Pharmacological characterization of 5-iodo-A-85380, a β2-selective nicotinic receptor agonist, in mice. J Psychopharmacol 2022; 36:1280-1293. [PMID: 36321267 PMCID: PMC9817006 DOI: 10.1177/02698811221132214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND Because of their implications in several pathological conditions, α4β2* nicotinic acetylcholine receptors (nAChRs) are potential targets for the treatment of nicotine dependence, pain, and many psychiatric and neurodegenerative diseases. However, they exist in various subtypes, and finding selective tools to investigate them has proved challenging. The nicotinic receptor agonist, 5-iodo-A-85380 (5IA), has helped in delineating the function of β2-containing subtypes in vitro; however, much is still unknown about its behavioral effects. Furthermore, its effectiveness on α6-containing subtypes is limited. AIMS To investigate the effects of 5IA on nociception (formalin, hot-plate, and tail-flick tests), locomotion, hypothermia, and conditioned reward after acute and repeated administration, and to examine the potential role of β2 and α6 nAChR subunits in these effects. Lastly, its selectivity for expressed low sensitivity (LS) and high sensitivity (HS) α4β2 receptors is investigated. RESULTS 5IA dose-dependently induced hypothermia, locomotion suppression, conditioned place preference, and antinociception (only in the formalin test but not in the hot-plate or tail-flick tests). Furthermore, these effects were mediated by β2 but not α6 nicotinic subunits. Finally, we show that 5-iodo-A-85380 potently activates both stoichiometries of α4β2 nAChRs with differential efficacies, being a full agonist on HS α4(2)β2(3) nAChRs, and a partial agonist on LS α4(3)β2(2) nAChRs and α6-containing subtypes as well.
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Affiliation(s)
- Lois S Akinola
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, USA
| | - Deniz Bagdas
- Department of Psychiatry, School of Medicine, Yale University, USA
- Yale Tobacco Center of Regulatory Science, Yale University, USA
| | - Yasmin Alkhlaif
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, USA
| | - Asti Jackson
- Department of Psychiatry, School of Medicine, Yale University, USA
- Yale Tobacco Center of Regulatory Science, Yale University, USA
| | - Cenk O Gurdap
- Science for Life Laboratory, Department of Women’s and Children’s Health, Karolinska Institutet, Sweden
| | - Elnaz Rahimpour
- Yale Tobacco Center of Regulatory Science, Yale University, USA
| | - F Ivy Carroll
- Center for Organic and Medicinal Chemistry, Research Triangle Institute, Research Triangle Park, USA
| | - Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, USA
| | - M Imad Damaj
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, USA
- Translational Research Initiative for Pain and Neuropathy, Medical College of Virginia Campus, Virginia Commonwealth University, USA
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6
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Papke RL, Karaffa M, Horenstein NA, Stokes C. Coffee and cigarettes: Modulation of high and low sensitivity α4β2 nicotinic acetylcholine receptors by n-MP, a biomarker of coffee consumption. Neuropharmacology 2022; 216:109173. [PMID: 35772522 PMCID: PMC9524580 DOI: 10.1016/j.neuropharm.2022.109173] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 05/27/2022] [Accepted: 06/23/2022] [Indexed: 10/17/2022]
Abstract
Smokers report particular appreciation for coffee with their first cigarettes of the day. We investigated with voltage-clamp experiments, effects of aqueous extracts (coffees) of unroasted and roasted coffee beans on the activity of human brain nicotinic acetylcholine receptor (nAChR) subtypes expressed in Xenopus oocytes, looking at complex brews, low molecular weight (LMW) fractions, and specific compounds present in coffee. When co-applied with PNU-120596, a positive allosteric modulator (PAM), the coffees stimulated currents from cells expressing α7 nAChR that were larger than ACh controls. The PAM-dependent responses to green bean coffee were three-fold greater than those to dark roasted coffee, consistent with α7 receptor activation by choline, a component of coffee that is partially degraded in the roasting process. Coffees were tested on both high sensitivity (HS) and low sensitivity (LS) forms of α4β2 nAChR, which are associated with nicotine addiction. To varying degrees, these receptors were both activated and inhibited by the coffees and LMW extracts. We also examined the activity of nine small molecules present in coffee. Only two compounds, 1-methylpyridinium and 1-1-dimethylpiperidium, produced during the process of roasting coffee beans, showed significant effects on nAChR. The compounds were competitive antagonists of the HS α4β2 receptors, but were PAMs for LS α4β2 receptors. HS receptors in smokers are likely to progressively desensitize through a day of smoking but may be hypersensitive in the mornings when brain nicotine levels are low. A smoker's first cup of coffee may therefore balance the effects of the day's first cigarette in the brain.
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Affiliation(s)
- Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267, Gainesville, FL, 32610-0267, (RLP, MK, CS), USA.
| | - Madison Karaffa
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267, Gainesville, FL, 32610-0267, (RLP, MK, CS), USA
| | - Nicole A Horenstein
- Department of Chemistry, University of Florida, Gainesville, FL, 32611-7200, (NAH), USA
| | - Clare Stokes
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267, Gainesville, FL, 32610-0267, (RLP, MK, CS), USA
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Prevost MS, Bouchenaki H, Barilone N, Gielen M, Corringer PJ. Concatemers to re-investigate the role of α5 in α4β2 nicotinic receptors. Cell Mol Life Sci 2021; 78:1051-1064. [PMID: 32472188 PMCID: PMC11071962 DOI: 10.1007/s00018-020-03558-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 05/15/2020] [Accepted: 05/22/2020] [Indexed: 01/08/2023]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are pentameric ion channels expressed in the central nervous systems. nAChRs containing the α4, β2 and α5 subunits are specifically involved in addictive processes, but their functional architecture is poorly understood due to the intricacy of assembly of these subunits. Here we constrained the subunit assembly by designing fully concatenated human α4β2 and α4β2α5 receptors and characterized their properties by two-electrodes voltage-clamp electrophysiology in Xenopus oocytes. We found that α5-containing nAChRs are irreversibly blocked by methanethiosulfonate (MTS) reagents through a covalent reaction with a cysteine present only in α5. MTS-block experiments establish that the concatemers are expressed in intact form at the oocyte surface, but that reconstitution of nAChRs from loose subunits show inefficient and highly variable assembly of α5 with α4 and β2. Mutational analysis shows that the concatemers assemble both in clockwise and anticlockwise orientations, and that α5 does not contribute to ACh binding from its principal (+) site. Reinvestigation of suspected α5-ligands such as galantamine show no specific effect on α5-containing concatemers. Analysis of the α5-D398N mutation that is linked to smoking and lung cancer shows no significant effect on the electrophysiological function, suggesting that its effect might arise from alteration of other cellular processes. The concatemeric strategy provides a well-characterized platform for mechanistic analysis and screening of human α5-specific ligands.
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Affiliation(s)
- Marie S Prevost
- Unité Récepteurs-Canaux, Institut Pasteur, UMR 3571, CNRS, 75015, Paris, France
| | - Hichem Bouchenaki
- Unité Récepteurs-Canaux, Institut Pasteur, UMR 3571, CNRS, 75015, Paris, France
| | - Nathalie Barilone
- Unité Récepteurs-Canaux, Institut Pasteur, UMR 3571, CNRS, 75015, Paris, France
| | - Marc Gielen
- Unité Récepteurs-Canaux, Institut Pasteur, UMR 3571, CNRS, 75015, Paris, France.
- Sorbonne Université, 21, rue de l'école de médecine, 75006, Paris, France.
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8
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Liao VWY, Kusay AS, Balle T, Ahring PK. Heterologous expression of concatenated nicotinic ACh receptors: Pros and cons of subunit concatenation and recommendations for construct designs. Br J Pharmacol 2020; 177:4275-4295. [PMID: 32627170 DOI: 10.1111/bph.15188] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Revised: 06/15/2020] [Accepted: 06/26/2020] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND AND PURPOSE Concatenation of Cys-loop receptor subunits is a commonly used technique to ensure experimental control of receptor assembly. However, we recently demonstrated that widely used constructs did not lead to the expression of uniform pools of ternary and more complex receptors. The aim was therefore to identify viable strategies for designing concatenated constructs that would allow strict control of resultant receptor pools. EXPERIMENTAL APPROACH Concatenated dimeric, tetrameric, and pentameric α4β2-containing nicotinic ACh (nACh) receptor constructs were designed with successively shorter linker lengths and expressed in Xenopus laevis oocytes. Resulting receptor stoichiometries were investigated by functional analysis in two-electrode voltage-clamp experiments. Molecular dynamics simulations were performed to investigate potential effects of linkers on the 3D structure of concatemers. KEY RESULTS Dimeric constructs were found to be unreliable and should be avoided for expression of ternary receptors. By introducing two short linkers, we obtained efficient expression of uniform receptor pools with tetrameric and pentameric constructs. However, linkers should not be excessively short as that introduces strain on the 3D structure of concatemers. CONCLUSION AND IMPLICATIONS The data demonstrate that design of concatenated Cys-loop receptors requires a compromise between the desire for control of assembly and avoiding introduction of strain on the resulting protein. The overall best strategy was found to be pentameric constructs with carefully optimised linker lengths. Our findings will advance studies of ternary or more complex Cys-loop receptors as well as enabling detailed analysis of how pharmacological agents interact with stoichiometry-specific binding sites.
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Affiliation(s)
- Vivian Wan Yu Liao
- Brain and Mind Centre, The University of Sydney, 94 Mallett Street, Camperdown, NSW, 2050, Australia.,Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, NSW, 2006, Australia
| | - Ali Saad Kusay
- Brain and Mind Centre, The University of Sydney, 94 Mallett Street, Camperdown, NSW, 2050, Australia.,Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, NSW, 2006, Australia
| | - Thomas Balle
- Brain and Mind Centre, The University of Sydney, 94 Mallett Street, Camperdown, NSW, 2050, Australia.,Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, NSW, 2006, Australia
| | - Philip Kiaer Ahring
- Brain and Mind Centre, The University of Sydney, 94 Mallett Street, Camperdown, NSW, 2050, Australia.,Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, NSW, 2006, Australia
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9
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Corrie LW, Stokes C, Wilkerson JL, Carroll FI, McMahon LR, Papke RL. Nicotinic Acetylcholine Receptor Accessory Subunits Determine the Activity Profile of Epibatidine Derivatives. Mol Pharmacol 2020; 98:328-342. [PMID: 32690626 DOI: 10.1124/molpharm.120.000037] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Accepted: 07/02/2020] [Indexed: 12/25/2022] Open
Abstract
Epibatidine is a potent analgetic agent with very high affinity for brain nicotinic acetylcholine receptors (nAChR). We determined the activity profiles of three epibatidine derivatives, RTI-36, RTI-76, and RTI-102, which have affinity for brain nAChR equivalent to that of epibatidine but reduced analgetic activity. RNAs coding for nAChR monomeric subunits and/or concatamers were injected into Xenopus oocytes to obtain receptors of defined subunit composition and stoichiometry. The epibatidine analogs produced protracted activation of high sensitivity (HS) α4- and α2-containing receptors with the stoichiometry of 2alpha:3beta subunits but not low sensitivity (LS) receptors with the reverse ratio of alpha and beta subunits. Although not strongly activated by the epibatidine analogs, LS α4- and α2-containing receptors were potently desensitized by the epibatidine analogs. In general, the responses of α4(2)β2(2)α5 and β3α4β2α6β2 receptors were similar to those of the HS α4β2 receptors. RTI-36, the analog closest in structure to epibatidine, was the most efficacious of the three compounds, also effectively activating α7 and α3β4 receptors, albeit with lower potency and less desensitizing effect. Although not the most efficacious agonist, RTI-76 was the most potent desensitizer of α4- and α2-containing receptors. RTI-102, a strong partial agonist for HS α4β2 receptors, was effectively an antagonist for LS α4β2 receptors. Our results highlight the importance of subunit stoichiometry and the presence or absence of specific accessory subunits for determining the activity of these drugs on brain nAChR, affecting the interpretation of in vivo studies since in most cases these structural details are not known. SIGNIFICANCE STATEMENT: Epibatidine and related compounds are potent ligands for the high-affinity nicotine receptors of the brain, which are therapeutic targets and mediators of nicotine addiction. Far from being a homogeneous population, these receptors are diverse in subunit composition and vary in subunit stoichiometry. We show the importance of these structural details for drug activity profiles, which present a challenge for the interpretation of in vivo experiments since conventional methods, such as in situ hybridization and immunohistochemistry, cannot illuminate these details.
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Affiliation(s)
- Lu Wenchi Corrie
- Department of Pharmacology and Therapeutics, College of Medicine (L.W.C., C.S., R.L.P.) and Department of Pharmacodynamics, College of Pharmacy, (J.L.W., L.R.M.), University of Florida, Gainesville, Florida; and Center for Drug Discovery, Research Triangle Institute, Durham, North Carolina (F.I.C.)
| | - Clare Stokes
- Department of Pharmacology and Therapeutics, College of Medicine (L.W.C., C.S., R.L.P.) and Department of Pharmacodynamics, College of Pharmacy, (J.L.W., L.R.M.), University of Florida, Gainesville, Florida; and Center for Drug Discovery, Research Triangle Institute, Durham, North Carolina (F.I.C.)
| | - Jenny L Wilkerson
- Department of Pharmacology and Therapeutics, College of Medicine (L.W.C., C.S., R.L.P.) and Department of Pharmacodynamics, College of Pharmacy, (J.L.W., L.R.M.), University of Florida, Gainesville, Florida; and Center for Drug Discovery, Research Triangle Institute, Durham, North Carolina (F.I.C.)
| | - F Ivy Carroll
- Department of Pharmacology and Therapeutics, College of Medicine (L.W.C., C.S., R.L.P.) and Department of Pharmacodynamics, College of Pharmacy, (J.L.W., L.R.M.), University of Florida, Gainesville, Florida; and Center for Drug Discovery, Research Triangle Institute, Durham, North Carolina (F.I.C.)
| | - Lance R McMahon
- Department of Pharmacology and Therapeutics, College of Medicine (L.W.C., C.S., R.L.P.) and Department of Pharmacodynamics, College of Pharmacy, (J.L.W., L.R.M.), University of Florida, Gainesville, Florida; and Center for Drug Discovery, Research Triangle Institute, Durham, North Carolina (F.I.C.)
| | - Roger L Papke
- Department of Pharmacology and Therapeutics, College of Medicine (L.W.C., C.S., R.L.P.) and Department of Pharmacodynamics, College of Pharmacy, (J.L.W., L.R.M.), University of Florida, Gainesville, Florida; and Center for Drug Discovery, Research Triangle Institute, Durham, North Carolina (F.I.C.)
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10
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Shen XM, Di L, Shen S, Zhao Y, Neumeyer AM, Selcen D, Sine SM, Engel AG. A novel fast-channel myasthenia caused by mutation in β subunit of AChR reveals subunit-specific contribution of the intracellular M1-M2 linker to channel gating. Exp Neurol 2020; 331:113375. [PMID: 32504635 DOI: 10.1016/j.expneurol.2020.113375] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 05/27/2020] [Accepted: 06/01/2020] [Indexed: 10/24/2022]
Abstract
Genetic variants causing the fast-channel congenital myasthenic syndrome (CMS) have been identified in the α, δ, and ε but not the β subunit of acetylcholine receptor (AChR). A 16-year-old girl with severe myasthenia had low-amplitude and fast-decaying miniature endplate potentials. Mutation analysis revealed two heteroallelic variants in CHRNB1 encoding the AChR β subunit: a novel c.812C>T (p.P248L) variant in M1-M2 linker (p.P271L in HGVS nomenclature), and a ~430 bp deletion causing loss of exon 8 leading to frame-shift and a premature stop codon (p.G251Dfs*21). P248 is conserved in all β subunits of different species, but not in other AChR subunits. Measurements of radio-labeled α-bungarotoxin binding show that βP248L reduces AChR expression to 60% of wild-type. Patch clamp recordings of ACh-elicited single channel currents demonstrate that βP248L shortens channel opening bursts from 3.3 ms to 1.2 ms, and kinetic analyses predict that the decay of the synaptic response is accelerated 2.4-fold due to reduced probability of channel reopening. Substituting βP248 with threonine, alanine or glycine reduces the burst duration to 2.3, 1.7, and 1.5 ms, respectively. In non-β subunits, substituting leucine for residues corresponding to βP248 prolongs the burst duration to 4.5 ms in the α subunit, shortens it to 2.2 ms in the δ subunit, and has no effect in the ε subunit. Conversely, substituting proline for residues corresponding to βP248 prolongs the burst duration to 8.7 ms in the α subunit, to 4.6 ms in the δ subunit, but has no effect in the ε subunit. Thus, this fast channel CMS is caused by the dual defects of βP248L in reducing expression of the mutant receptor and accelerating the decay of the synaptic response. The results also reveal subunit-specific contributions of the M1-M2 linker to the durations of channel opening bursts.
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Affiliation(s)
- Xin-Ming Shen
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, MN, USA.
| | - Li Di
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, MN, USA
| | - Shelley Shen
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, MN, USA
| | - Yuying Zhao
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, MN, USA
| | - Ann M Neumeyer
- Department of Child Neurology, Massachusetts General Hospital for Children, Lexington, MA, USA
| | - Duygu Selcen
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, MN, USA
| | - Steven M Sine
- Department of Physiology and Biomedical Engineering and Receptor Biology Laboratory, Mayo Clinic, Rochester, MN, USA; Department of Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN, USA; Department of Neurology, Mayo Clinic, Rochester, MN, USA
| | - Andrew G Engel
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, MN, USA.
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11
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Papke RL, Lindstrom JM. Nicotinic acetylcholine receptors: Conventional and unconventional ligands and signaling. Neuropharmacology 2020; 168:108021. [PMID: 32146229 PMCID: PMC7610230 DOI: 10.1016/j.neuropharm.2020.108021] [Citation(s) in RCA: 65] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 02/05/2020] [Accepted: 02/25/2020] [Indexed: 12/28/2022]
Abstract
Postsynaptic nAChRs in the peripheral nervous system are critical for neuromuscular and autonomic neurotransmission. Pre- and peri-synaptic nAChRs in the brain modulate neurotransmission and are responsible for the addictive effects of nicotine. Subtypes of nAChRs in lymphocytes and non-synaptic locations may modulate inflammation and other cellular functions. All AChRs that function as ligand-gated ion channels are formed from five homologous subunits organized to form a central cation channel whose opening is regulated by ACh bound at extracellular subunit interfaces. nAChR subtype subunit composition can range from α7 homomers to α4β2α6β2β3 heteromers. Subtypes differ in affinities for ACh and other agonists like nicotine and in efficiencies with which their channels are opened and desensitized. Subtypes also differ in affinities for antagonists and for positive and negative allosteric modulators. Some agonists are "silent" with respect to channel opening, and AChRs may be able to signal metabotropic pathways by releasing G-proteins independent of channel opening. Electrophysiological studies that can resolve single-channel openings and molecular genetic approaches have allowed characterization of the structures of ligand binding sites, the cation channel, and the linkages between them, as well as the organization of AChR subunits and their contributions to function. Crystallography and cryo-electron-microscopy are providing increasing insights into the structures and functions of AChRs. However, much remains to be learned about both AChR structure and function, the in vivo functional roles of some AChR subtypes, and the development of better pharmacological tools directed at AChRs to treat addiction, pain, inflammation, and other medically important issues. This article is part of the special issue on 'Contemporary Advances in Nicotine Neuropharmacology'.
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Affiliation(s)
- Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, P.O. Box 100267, Gainesville, FL, 32610-0267, USA.
| | - Jon M Lindstrom
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
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12
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Abstract
Human behavior can be controlled by physical or psychological dependencies associated with addiction. One of the most insidious addictions in our society is the use of tobacco products which contain nicotine. This addiction can be associated with specific receptors in the brain that respond to the natural neurotransmitter acetylcholine. These nicotinic acetylcholine receptors (nAChR) are ligand-gated ion channels formed by the assembly of one or multiple types of nAChR receptor subunits. In this paper, we review the structure and diversity of nAChR subunits and our understanding for how different nAChR subtypes play specific roles in the phenomenon of nicotine addiction. We focus on receptors containing β2 and/or α6 subunits and the special significance of α5-containing receptors. These subtypes all have roles in regulating dopamine-mediated neurotransmission in the mesolimbic reward pathways of the brain. We also discuss the unique roles of homomeric α7 nAChR in behavioral responses to nicotine and how our knowledge of nAChR functional diversity may help guide pharmacotherapeutic approaches for treating nicotine addiction. While nicotine addiction is a truly global problem, the use of areca nut (betel) products is also a serious addiction associated with public health issues across most of South Asia, impacting as many as 600 million people. We discuss how cholinergic receptors of the brain are also involved with areca addiction and the unique challenges for dealing with addiction to this substance.
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13
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Kamio Y, Miyamoto T, Kimura T, Mitsui K, Furukawa H, Zhang D, Yokosuka K, Korai M, Kudo D, Lukas RJ, Lawton MT, Hashimoto T. Roles of Nicotine in the Development of Intracranial Aneurysm Rupture. Stroke 2019; 49:2445-2452. [PMID: 30355112 DOI: 10.1161/strokeaha.118.021706] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Background and Purpose- Tobacco cigarette smoking is considered to be a strong risk factor for intracranial aneurysmal rupture. Nicotine is a major biologically active constituent of tobacco products. Nicotine's interactions with vascular cell nicotinic acetylcholine receptors containing α7 subunits (α7*-nAChR) are thought to promote local inflammation and sustained angiogenesis. In this study, using a mouse intracranial aneurysm model, we assessed potential contributions of nicotine exposure and activation of α7*-nAChR to the development of aneurysmal rupture. Methods- Intracranial aneurysms were induced by a combination of deoxycorticosterone-salt induced hypertension and a single-dose elastase injection into cerebrospinal fluid in mice. Results- Exposure to nicotine or an α7*-nAChR-selective agonist significantly increased aneurysm rupture rate. Coexposure to an α7*-nAChR antagonist abolished nicotine's deleterious effect. In addition, nicotine's promotion of aneurysm rupture was absent in smooth muscle cell-specific α7*-nAChR subunit knockout mice but not in mice lacking α7*-nAChR on endothelial cells or macrophages. Nicotine treatment increased the mRNA levels of vascular endothelial growth factor, platelet-derived growth factor-B, and inflammatory cytokines. α7*-nAChR antagonist reversed nicotine-induced upregulation of these growth factors and cytokines. Conclusions- Our findings indicate that nicotine exposure promotes aneurysmal rupture through actions on vascular smooth muscle cell α7*-nAChR.
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Affiliation(s)
- Yoshinobu Kamio
- From the Departments of Neurosurgery (Y.K., T.M., T.K., D.K., M.T.L., T.H.), Barrow Neurological Institute, Phoenix, AZ.,Barrow Aneurysm and AVM Research Center (Y.K., T.M., T.K., D.K., M.T.L., T.H.), Barrow Neurological Institute, Phoenix, AZ
| | - Takeshi Miyamoto
- From the Departments of Neurosurgery (Y.K., T.M., T.K., D.K., M.T.L., T.H.), Barrow Neurological Institute, Phoenix, AZ.,Neurobiology (T.M., T.K., D.K., R.J.L., T.H.), Barrow Neurological Institute, Phoenix, AZ.,Barrow Aneurysm and AVM Research Center (Y.K., T.M., T.K., D.K., M.T.L., T.H.), Barrow Neurological Institute, Phoenix, AZ
| | - Tetsuro Kimura
- From the Departments of Neurosurgery (Y.K., T.M., T.K., D.K., M.T.L., T.H.), Barrow Neurological Institute, Phoenix, AZ.,Neurobiology (T.M., T.K., D.K., R.J.L., T.H.), Barrow Neurological Institute, Phoenix, AZ.,Barrow Aneurysm and AVM Research Center (Y.K., T.M., T.K., D.K., M.T.L., T.H.), Barrow Neurological Institute, Phoenix, AZ
| | - Kazuha Mitsui
- Department of Anesthesia and Perioperative Care, University of California, San Francisco (K.M., H.F., D.Z., K.Y., M.K.)
| | - Hajime Furukawa
- Department of Anesthesia and Perioperative Care, University of California, San Francisco (K.M., H.F., D.Z., K.Y., M.K.)
| | - Dingding Zhang
- Department of Anesthesia and Perioperative Care, University of California, San Francisco (K.M., H.F., D.Z., K.Y., M.K.)
| | - Kimihiko Yokosuka
- Department of Anesthesia and Perioperative Care, University of California, San Francisco (K.M., H.F., D.Z., K.Y., M.K.)
| | - Masaaki Korai
- Department of Anesthesia and Perioperative Care, University of California, San Francisco (K.M., H.F., D.Z., K.Y., M.K.)
| | - Daisuke Kudo
- From the Departments of Neurosurgery (Y.K., T.M., T.K., D.K., M.T.L., T.H.), Barrow Neurological Institute, Phoenix, AZ.,Neurobiology (T.M., T.K., D.K., R.J.L., T.H.), Barrow Neurological Institute, Phoenix, AZ.,Barrow Aneurysm and AVM Research Center (Y.K., T.M., T.K., D.K., M.T.L., T.H.), Barrow Neurological Institute, Phoenix, AZ
| | - Ronald J Lukas
- Neurobiology (T.M., T.K., D.K., R.J.L., T.H.), Barrow Neurological Institute, Phoenix, AZ
| | - Michael T Lawton
- From the Departments of Neurosurgery (Y.K., T.M., T.K., D.K., M.T.L., T.H.), Barrow Neurological Institute, Phoenix, AZ.,Barrow Aneurysm and AVM Research Center (Y.K., T.M., T.K., D.K., M.T.L., T.H.), Barrow Neurological Institute, Phoenix, AZ
| | - Tomoki Hashimoto
- From the Departments of Neurosurgery (Y.K., T.M., T.K., D.K., M.T.L., T.H.), Barrow Neurological Institute, Phoenix, AZ.,Neurobiology (T.M., T.K., D.K., R.J.L., T.H.), Barrow Neurological Institute, Phoenix, AZ.,Barrow Aneurysm and AVM Research Center (Y.K., T.M., T.K., D.K., M.T.L., T.H.), Barrow Neurological Institute, Phoenix, AZ
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14
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Stokes C, Garai S, Kulkarni AR, Cantwell LN, Noviello CM, Hibbs RE, Horenstein NA, Abboud KA, Thakur GA, Papke RL. Heteromeric Neuronal Nicotinic Acetylcholine Receptors with Mutant β Subunits Acquire Sensitivity to α7-Selective Positive Allosteric Modulators. J Pharmacol Exp Ther 2019; 370:252-268. [PMID: 31175218 DOI: 10.1124/jpet.119.259499] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Accepted: 06/04/2019] [Indexed: 01/29/2023] Open
Abstract
Homomeric α7 nicotinic acetylcholine receptors (nAChR) have an intrinsically low probability of opening that can be overcome by α7-selective positive allosteric modulators (PAMs), which bind at a site involving the second transmembrane domain (TM2). Mutation of a methionine that is unique to α7 at the 15' position of TM2 to leucine, the residue in most other nAChR subunits, largely eliminates the activity of such PAMs. We tested the effect of the reverse mutation (L15'M) in heteromeric nAChR receptors containing α4 and β2, which are the nAChR subunits that are most abundant in the brain. Receptors containing these mutations were found to be strongly potentiated by the α7 PAM 3a,4,5,9b-tetrahydro-4-(1-naphthalenyl)-3H-cyclopentan[c]quinoline-8-sulfonamide (TQS) but insensitive to the alternative PAM 1-(5-chloro-2,4-dimethoxyphenyl)-3-(5-methylisoxazol-3-yl)-urea. The presence of the mutation in the β2 subunit was necessary and sufficient for TQS sensitivity. The primary effect of the mutation in the α4 subunit was to reduce responses to acetylcholine applied alone. Sensitivity to TQS required only a single mutant β subunit, regardless of the position of the mutant β subunit within the pentameric complex. Similar results were obtained when β2L15'M was coexpressed with α2 or α3 and when the L15'M mutation was placed in β4 and coexpressed with α2, α3, or α4. Functional receptors were not observed when β1L15'M subunits were coexpressed with other muscle nAChR subunits. The unique structure-activity relationship of PAMs and the α4β2L15'M receptor compared with α7 and the availability of high-resolution α4β2 structures may provide new insights into the fundamental mechanisms of nAChR allosteric potentiation. SIGNIFICANCE STATEMENT: Heteromeric neuronal nAChRs have a relatively high initial probability of channel activation compared to receptors that are homomers of α7 subunits but are insensitive to PAMs, which greatly increase the open probability of α7 receptors. These features of heteromeric nAChR can be reversed by mutation of a single residue present in all neuronal heteromeric nAChR subunits to the sequence found in α7. Specifically, the mutation of the TM2 15' leucine to methionine in α subunits reduces heteromeric receptor channel activation, while the same mutation in neuronal β subunits allows heteromeric receptors to respond to select α7 PAMs. The results indicate a key role for this residue in the functional differences in the two main classes of neuronal nAChRs.
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Affiliation(s)
- Clare Stokes
- Departments of Pharmacology and Therapeutics (C.S., R.L.P.) and Chemistry (N.A.H., K.A.A.), University of Florida, Gainesville, Florida; Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., A.R.K., L.N.C., G.A.T.); and Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas (C.M.N., R.E.H.)
| | - Sumanta Garai
- Departments of Pharmacology and Therapeutics (C.S., R.L.P.) and Chemistry (N.A.H., K.A.A.), University of Florida, Gainesville, Florida; Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., A.R.K., L.N.C., G.A.T.); and Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas (C.M.N., R.E.H.)
| | - Abhijit R Kulkarni
- Departments of Pharmacology and Therapeutics (C.S., R.L.P.) and Chemistry (N.A.H., K.A.A.), University of Florida, Gainesville, Florida; Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., A.R.K., L.N.C., G.A.T.); and Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas (C.M.N., R.E.H.)
| | - Lucas N Cantwell
- Departments of Pharmacology and Therapeutics (C.S., R.L.P.) and Chemistry (N.A.H., K.A.A.), University of Florida, Gainesville, Florida; Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., A.R.K., L.N.C., G.A.T.); and Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas (C.M.N., R.E.H.)
| | - Colleen M Noviello
- Departments of Pharmacology and Therapeutics (C.S., R.L.P.) and Chemistry (N.A.H., K.A.A.), University of Florida, Gainesville, Florida; Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., A.R.K., L.N.C., G.A.T.); and Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas (C.M.N., R.E.H.)
| | - Ryan E Hibbs
- Departments of Pharmacology and Therapeutics (C.S., R.L.P.) and Chemistry (N.A.H., K.A.A.), University of Florida, Gainesville, Florida; Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., A.R.K., L.N.C., G.A.T.); and Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas (C.M.N., R.E.H.)
| | - Nicole A Horenstein
- Departments of Pharmacology and Therapeutics (C.S., R.L.P.) and Chemistry (N.A.H., K.A.A.), University of Florida, Gainesville, Florida; Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., A.R.K., L.N.C., G.A.T.); and Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas (C.M.N., R.E.H.)
| | - Khalil A Abboud
- Departments of Pharmacology and Therapeutics (C.S., R.L.P.) and Chemistry (N.A.H., K.A.A.), University of Florida, Gainesville, Florida; Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., A.R.K., L.N.C., G.A.T.); and Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas (C.M.N., R.E.H.)
| | - Ganesh A Thakur
- Departments of Pharmacology and Therapeutics (C.S., R.L.P.) and Chemistry (N.A.H., K.A.A.), University of Florida, Gainesville, Florida; Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., A.R.K., L.N.C., G.A.T.); and Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas (C.M.N., R.E.H.)
| | - Roger L Papke
- Departments of Pharmacology and Therapeutics (C.S., R.L.P.) and Chemistry (N.A.H., K.A.A.), University of Florida, Gainesville, Florida; Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., A.R.K., L.N.C., G.A.T.); and Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas (C.M.N., R.E.H.)
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15
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Weltzin MM, George AA, Lukas RJ, Whiteaker P. Distinctive single-channel properties of α4β2-nicotinic acetylcholine receptor isoforms. PLoS One 2019; 14:e0213143. [PMID: 30845161 PMCID: PMC6405073 DOI: 10.1371/journal.pone.0213143] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Accepted: 02/17/2019] [Indexed: 11/19/2022] Open
Abstract
Central nervous system nicotinic acetylcholine receptors (nAChR) are predominantly of the α4β2 subtype. Two isoforms exist, with high or low agonist sensitivity (HS-(α4β2)2β2- and LS-(α4β2)2α4-nAChR). Both isoforms exhibit similar macroscopic potency and efficacy values at low acetylcholine (ACh) concentrations, mediated by a common pair of high-affinity α4(+)/(-)β2 subunit binding interfaces. However LS-(α4β2)2α4-nAChR also respond to higher concentrations of ACh, acting at a third α4(+)/(-)α4 subunit interface. To probe isoform functional differences further, HS- and LS-α4β2-nAChR were expressed in Xenopus laevis oocytes and single-channel responses were assessed using cell-attached patch-clamp. In the presence of a low ACh concentration, both isoforms produce low-bursting function. HS-(α4β2)2β2-nAChR exhibit a single conductance state, whereas LS-(α4β2)2α4-nAChR display two distinctive conductance states. A higher ACh concentration did not preferentially recruit either conductance state, but did result in increased LS-(α4β2)2α4-nAChR bursting and reduced closed times. Introduction of an α4(+)/(-)α4-interface loss-of-function α4W182A mutation abolished these changes, confirming this site's role in mediating LS-(α4β2)2α4-nAChR responses. Small or large amplitude openings are highly-correlated within individual LS-(α4β2)2α4-nAChR bursts, suggesting that they arise from distinct intermediate states, each of which is stabilized by α4(+)/(-)α4 site ACh binding. These findings are consistent with α4(+)/(-)α4 subunit interface occupation resulting in allosteric potentiation of agonist actions at α4(+)/(-)β2 subunit interfaces, rather than independent induction of high conductance channel openings.
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Affiliation(s)
- Maegan M. Weltzin
- Division of Neurobiology, Barrow Neurological Institute, Phoenix, Arizona, United States of America
- * E-mail:
| | - Andrew A. George
- Division of Neurobiology, Barrow Neurological Institute, Phoenix, Arizona, United States of America
| | - Ronald J. Lukas
- Division of Neurobiology, Barrow Neurological Institute, Phoenix, Arizona, United States of America
| | - Paul Whiteaker
- Division of Neurobiology, Barrow Neurological Institute, Phoenix, Arizona, United States of America
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16
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Mazzaferro S, Bermudez I, Sine SM. Potentiation of a neuronal nicotinic receptor via pseudo-agonist site. Cell Mol Life Sci 2019; 76:1151-1167. [PMID: 30600358 PMCID: PMC8022356 DOI: 10.1007/s00018-018-2993-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 11/28/2018] [Accepted: 12/10/2018] [Indexed: 11/26/2022]
Abstract
Neuronal nicotinic receptors containing α4 and β2 subunits assemble in two pentameric stoichiometries, (α4)3(β2)2 and (α4)2(β2)3, each with distinct pharmacological signatures; (α4)3(β2)2 receptors are strongly potentiated by the drug NS9283, whereas (α4)2(β2)3 receptors are unaffected. Despite this stoichiometry-selective pharmacology, the molecular identity of the target for NS9283 remains elusive. Here, studying (α4)3(β2)2 receptors, we show that mutations at either the principal face of the β2 subunit or the complementary face of the α4 subunit prevent NS9283 potentiation of ACh-elicited single-channel currents, suggesting the drug targets the β2-α4 pseudo-agonist sites, the α4-α4 agonist site, or both sites. To distinguish among these possibilities, we generated concatemeric receptors with mutations at specified subunit interfaces, and monitored the ability of NS9283 to potentiate ACh-elicited single-channel currents. We find that a mutation at the principal face of the β2 subunit at either β2-α4 pseudo-agonist site suppresses potentiation, whereas mutation at the complementary face of the α4 subunit at the α4-α4 agonist site allows a significant potentiation. Thus, monitoring potentiation of single concatemeric receptor channels reveals that the β2-α4 pseudo-agonist sites are required for stoichiometry-selective drug action. Together with the recently determined structure of the (α4)3(β2)2 receptor, the findings have implications for structure-guided drug design.
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Affiliation(s)
- Simone Mazzaferro
- Receptor Biology Laboratory, Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN, 55905, USA
| | - Isabel Bermudez
- School of Life Sciences, Oxford Brookes University, Oxford, OX3 OBP, UK
| | - Steven M Sine
- Receptor Biology Laboratory, Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN, 55905, USA.
- Department of Neurology, Mayo Clinic College of Medicine, Rochester, MN, 55905, USA.
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, MN, 55905, USA.
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17
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New K, Del Villar SG, Mazzaferro S, Alcaino C, Bermudez I. The fifth subunit of the (α4β2) 2 β2 nicotinic ACh receptor modulates maximal ACh responses. Br J Pharmacol 2018; 175:1822-1837. [PMID: 28600847 PMCID: PMC5978951 DOI: 10.1111/bph.13905] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 05/16/2017] [Accepted: 06/05/2017] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE The fifth subunit in the (α4β2)2 α4 nicotinic ACh receptor (nAChR) plays a determining role in the pharmacology of this nAChR type. Here, we have examined the role of the fifth subunit in the ACh responses of the (α4β2)2 β2 nAChR type. EXPERIMENTAL APPROACH The role of the fifth subunit in receptor function was explored using two-electrode voltage clamp electrophysiology, along with subunit-targeted mutagenesis and the substituted cysteine scanning method applied to fully linked (α4β2)2 β2 receptors. KEY RESULTS Covalent modification of the cysteine-substituted fifth subunit with a thiol-reactive agent (MTS) caused irreversible inhibition of receptor function. ACh reduced the rate of the reaction to MTS, but the competitive inhibitor dihydro-β-erythroidine had no effect. Alanine substitution of conserved residues that line the core of the agonist sites on α4(+)/β2(-) interfaces did not impair receptor function. However, impairment of agonist binding to α4(+)/β2(-) agonist sites by mutagenesis modified the effect of ACh on the rate of the reaction to MTS. The extent of this effect was dependent on the position of the agonist site relative to the fifth subunit. CONCLUSIONS AND IMPLICATIONS The fifth subunit in the (α4β2)2 β2 receptor isoform modulates maximal ACh responses. This effect appears to be driven by a modulatory, and asymmetric, association with the α4(+)/β2(-) agonist sites. LINKED ARTICLES This article is part of a themed section on Nicotinic Acetylcholine Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.11/issuetoc.
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Affiliation(s)
- Karina New
- Department of Biological and Medical Sciences, Faculty of Health and Life SciencesOxford Brookes UniversityOxfordUK
| | - Silvia Garcia Del Villar
- Department of Biological and Medical Sciences, Faculty of Health and Life SciencesOxford Brookes UniversityOxfordUK
| | - Simone Mazzaferro
- Department of Biological and Medical Sciences, Faculty of Health and Life SciencesOxford Brookes UniversityOxfordUK
| | - Constanza Alcaino
- Department of Biological and Medical Sciences, Faculty of Health and Life SciencesOxford Brookes UniversityOxfordUK
| | - Isabel Bermudez
- Department of Biological and Medical Sciences, Faculty of Health and Life SciencesOxford Brookes UniversityOxfordUK
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18
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Calarco CA, Li Z, Taylor SR, Lee S, Zhou W, Friedman JM, Mineur YS, Gotti C, Picciotto MR. Molecular and cellular characterization of nicotinic acetylcholine receptor subtypes in the arcuate nucleus of the mouse hypothalamus. Eur J Neurosci 2018; 48:10.1111/ejn.13966. [PMID: 29791746 PMCID: PMC6251769 DOI: 10.1111/ejn.13966] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Revised: 04/26/2018] [Accepted: 05/09/2018] [Indexed: 12/22/2022]
Abstract
Nicotine, acting through nicotinic acetylcholine receptors (nAChRs), increases the firing rate of both orexigenic agouti-related peptide (AgRP) and anorexigenic pro-opiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus (ARC), yet nicotine and other nAChR agonists decrease food intake in mice. Viral-mediated knockdown of the β4 nAChR subunit in all neuronal cell types in the ARC prevents the nicotinic agonist cytisine from decreasing food intake, but it is not known whether the β4 subunit is selectively expressed in anorexigenic neurons or how other nAChR subtypes are distributed in this nucleus. Using translating ribosome affinity purification (TRAP) on ARC tissue from mice with ribosomes tagged in either AgRP or POMC cells, we examined nAChR subunit mRNA levels using real-time PCR. Both AgRP and POMC cells express a comparable panel of nAChR subunits with differences in α7 mRNA levels and a trend for difference in α4 levels, but no differences in β4 expression. Immunoprecipitation of assembled nAChRs revealed that the β4 subunit forms assembled channels with α3, β2 and α4, but not other subunits found in the ARC. Finally, using cell type-selective, virally delivered small hairpin RNAs targeting either the β4 or α7 subunit, we examined the contribution of each subunit in either AgRP or POMC cells to the behavioural response to nicotine, refining the understanding of nicotinic regulation of this feeding circuit. These experiments identify a more complex set of nAChRs expressed in ARC than in other hypothalamic regions. Thus, the ARC appears to be a particular target of nicotinic modulation.
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Affiliation(s)
- Cali A. Calarco
- Department of Psychiatry and Interdepartmental Neuroscience Program, Yale University School of Medicine, New Haven, CT 06508, USA
| | | | - Seth R. Taylor
- Department of Psychiatry and Interdepartmental Neuroscience Program, Yale University School of Medicine, New Haven, CT 06508, USA
| | - Somin Lee
- Department of Psychiatry and Interdepartmental Neuroscience Program, Yale University School of Medicine, New Haven, CT 06508, USA
| | - Wenliang Zhou
- Department of Psychiatry and Interdepartmental Neuroscience Program, Yale University School of Medicine, New Haven, CT 06508, USA
| | | | - Yann S. Mineur
- Department of Psychiatry and Interdepartmental Neuroscience Program, Yale University School of Medicine, New Haven, CT 06508, USA
| | | | - Marina R. Picciotto
- Department of Psychiatry and Interdepartmental Neuroscience Program, Yale University School of Medicine, New Haven, CT 06508, USA
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19
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Tarvin RD, Borghese CM, Sachs W, Santos JC, Lu Y, O'Connell LA, Cannatella DC, Harris RA, Zakon HH. Interacting amino acid replacements allow poison frogs to evolve epibatidine resistance. Science 2018; 357:1261-1266. [PMID: 28935799 DOI: 10.1126/science.aan5061] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Accepted: 08/24/2017] [Indexed: 12/18/2022]
Abstract
Animals that wield toxins face self-intoxication. Poison frogs have a diverse arsenal of defensive alkaloids that target the nervous system. Among them is epibatidine, a nicotinic acetylcholine receptor (nAChR) agonist that is lethal at microgram doses. Epibatidine shares a highly conserved binding site with acetylcholine, making it difficult to evolve resistance yet maintain nAChR function. Electrophysiological assays of human and frog nAChR revealed that one amino acid replacement, which evolved three times in poison frogs, decreased epibatidine sensitivity but at a cost of acetylcholine sensitivity. However, receptor functionality was rescued by additional amino acid replacements that differed among poison frog lineages. Our results demonstrate how resistance to agonist toxins can evolve and that such genetic changes propel organisms toward an adaptive peak of chemical defense.
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Affiliation(s)
- Rebecca D Tarvin
- Department of Integrative Biology, University of Texas at Austin, Austin, TX 78712, USA.
| | - Cecilia M Borghese
- Waggoner Center for Alcohol and Addiction Research, University of Texas at Austin, Austin, TX 78712, USA
| | - Wiebke Sachs
- Waggoner Center for Alcohol and Addiction Research, University of Texas at Austin, Austin, TX 78712, USA.,Department of Biology, University of Konstanz, Konstanz, Germany 78457
| | - Juan C Santos
- Department of Biological Sciences, St. John's University, Queens, NY 11439, USA
| | - Ying Lu
- Department of Integrative Biology, University of Texas at Austin, Austin, TX 78712, USA
| | - Lauren A O'Connell
- Faculty of Arts and Sciences Center for Systems Biology, Harvard University, Cambridge, MA 02138, USA
| | - David C Cannatella
- Department of Integrative Biology, University of Texas at Austin, Austin, TX 78712, USA.,Biodiversity Center, University of Texas at Austin, Austin, TX 78712, USA
| | - R Adron Harris
- Waggoner Center for Alcohol and Addiction Research, University of Texas at Austin, Austin, TX 78712, USA
| | - Harold H Zakon
- Department of Integrative Biology, University of Texas at Austin, Austin, TX 78712, USA
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20
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Ahring PK, Liao VWY, Balle T. Concatenated nicotinic acetylcholine receptors: A gift or a curse? J Gen Physiol 2018; 150:453-473. [PMID: 29382698 PMCID: PMC5839718 DOI: 10.1085/jgp.201711846] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 11/15/2017] [Accepted: 12/22/2017] [Indexed: 11/20/2022] Open
Abstract
Nicotine acetylcholine receptors can form countless heteromeric stoichiometries from a common set of subunits. Ahring et al. present the limitations of subunit concatenation and establish a refinement that achieves substantiated expression of uniform receptor pools from complex stoichiometric origins. Nicotinic acetylcholine receptors (nAChRs) belong to the Cys-loop receptor family and are vital for normal mammalian brain function. Cys-loop receptors are pentameric ligand-gated ion channels formed from five identical or homologous subunits oriented around a central ion-conducting pore, which result in homomeric or heteromeric receptors, respectively. Within a given Cys-loop receptor family, many different heteromeric receptors can assemble from a common set of subunits, and understanding the properties of these heteromeric receptors is crucial for the continuing quest to generate novel treatments for human diseases. Yet this complexity also presents a hindrance for studying Cys-loop receptors in heterologous expression systems, where full control of the receptor stoichiometry and assembly is required. Therefore, subunit concatenation technology is commonly used to control receptor assembly. In theory, this methodology should facilitate full control of the stoichiometry. In reality, however, we find that commonly used constructs do not yield the expected receptor stoichiometries. With ternary or more complex receptors, concatenated subunits must assemble uniformly in only one orientation; otherwise, the resulting receptor pool will consist of receptors with mixed stoichiometries. We find that typically used constructs of α4β2 nAChR dimers, tetramers, and pentamers assemble readily in both the clockwise and the counterclockwise orientations. Consequently, we investigate the possibility of successfully directing the receptor assembly process using concatenation. We begin by investigating the three-dimensional structures of the α4β2 nAChR. Based on this, we hypothesize that the minimum linker length required to bridge the C terminus of one subunit to the N terminus of the next is shortest in the counterclockwise orientation. We then successfully express receptors with a uniform stoichiometry by systematically shortening linker lengths, proving the hypothesis correct. Our results will significantly aid future studies of heteromeric Cys-loop receptors and enable clarification of the current contradictions in the literature.
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Affiliation(s)
| | | | - Thomas Balle
- Faculty of Pharmacy, The University of Sydney, Sydney, Australia
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21
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Jin X, Germann AL, Shin DJ, Akk G, Steinbach JH. Determination of the Residues in the Extracellular Domain of the Nicotinic α Subunit Required for the Actions of Physostigmine on Neuronal Nicotinic Receptors. Mol Pharmacol 2017; 92:318-326. [PMID: 28630263 PMCID: PMC5548365 DOI: 10.1124/mol.117.108894] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Accepted: 06/14/2017] [Indexed: 11/22/2022] Open
Abstract
Physostigmine can potentiate and inhibit neuronal nicotinic receptors, in addition to inhibiting the activity of acetylcholinesterase. We found that receptors containing three copies of the α2 subunit are inhibited by low concentrations of physostigmine in contrast to receptors containing three copies of the α4 subunit that are potentiated. We exploited this observation to determine the regions required for the actions of physostigmine. Chimeric constructs of the α2 and α4 subunits located two regions in the extracellular amino-terminal domain of the subunit: the E loop (a loop of the transmitter-binding domain) and a region closer to the amino-terminus that collectively could completely determine the different effects of physostigmine. Point mutations then identified a single residue, α2(I92) versus α4(R92), that, when combined with transfer of the E loop, could convert the inhibition seen with α2 subunits to potentiation and the potentiation seen with α4 subunits to inhibition. In addition, other point mutations could affect the extent of potentiation or inhibition, indicating that a more extensive set of interactions in the amino-terminal domain plays some role in the actions of physostigmine.
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Affiliation(s)
- Xiaochun Jin
- Department of Anesthesiology, Washington University School of Medicine in St. Louis, St. Louis, Missouri (X.J., A.L.G., D.J.S., G.A., J.H.S.); and Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine in St. Louis, St. Louis, Missouri (G.A., J.H.S.)
| | - Allison L Germann
- Department of Anesthesiology, Washington University School of Medicine in St. Louis, St. Louis, Missouri (X.J., A.L.G., D.J.S., G.A., J.H.S.); and Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine in St. Louis, St. Louis, Missouri (G.A., J.H.S.)
| | - Daniel J Shin
- Department of Anesthesiology, Washington University School of Medicine in St. Louis, St. Louis, Missouri (X.J., A.L.G., D.J.S., G.A., J.H.S.); and Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine in St. Louis, St. Louis, Missouri (G.A., J.H.S.)
| | - Gustav Akk
- Department of Anesthesiology, Washington University School of Medicine in St. Louis, St. Louis, Missouri (X.J., A.L.G., D.J.S., G.A., J.H.S.); and Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine in St. Louis, St. Louis, Missouri (G.A., J.H.S.)
| | - Joe Henry Steinbach
- Department of Anesthesiology, Washington University School of Medicine in St. Louis, St. Louis, Missouri (X.J., A.L.G., D.J.S., G.A., J.H.S.); and Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine in St. Louis, St. Louis, Missouri (G.A., J.H.S.)
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22
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Jin X, McCollum MM, Germann AL, Akk G, Steinbach JH. The E Loop of the Transmitter Binding Site Is a Key Determinant of the Modulatory Effects of Physostigmine on Neuronal Nicotinic α4β2 Receptors. Mol Pharmacol 2017; 91:100-109. [PMID: 27895161 PMCID: PMC5267520 DOI: 10.1124/mol.116.106484] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Accepted: 11/23/2016] [Indexed: 11/22/2022] Open
Abstract
Physostigmine is a well known inhibitor of acetylcholinesterase, which can also activate, potentiate, and inhibit acetylcholine receptors, including neuronal nicotinic receptors comprising α4 and β2 subunits. We have found that the two stoichiometric forms of this receptor differ in the effects of physostigmine. The form containing three copies of α4 and two of β2 was potentiated at low concentrations of acetylcholine chloride (ACh) and physostigmine, whereas the form containing two copies of α4 and three of β2 was inhibited. Chimeric constructs of subunits indicated that the presence of inhibition or potentiation depended on the source of the extracellular ligand binding domain of the subunit. Further sets of chimeric constructs demonstrated that a portion of the ACh binding domain, the E loop, is a key determinant. Transferring the E loop from the β2 subunit to the α4 subunit resulted in strong inhibition, whereas the reciprocal transfer reduced inhibition. To control the number and position of the incorporated chimeric subunits, we expressed chimeric constructs with subunit dimers. Surprisingly, incorporation of a subunit with an altered E loop had similar effects whether it contributed either to an intersubunit interface containing a canonical ACh binding site or to an alternative interface. The observation that the α4 E loop is involved suggests that physostigmine interacts with regions of subunits that contribute to the ACh binding site, whereas the lack of interface specificity indicates that interaction with a particular ACh binding site is not the critical factor.
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Affiliation(s)
- Xiaochun Jin
- Department of Anesthesiology (X.J., M.M.C., A.L.G., G.A., J.H.S.) and Taylor Family Institute for Innovative Psychiatric Research (G.A., J.H.S.), Washington University School of Medicine, St. Louis, Missouri
| | - Megan M McCollum
- Department of Anesthesiology (X.J., M.M.C., A.L.G., G.A., J.H.S.) and Taylor Family Institute for Innovative Psychiatric Research (G.A., J.H.S.), Washington University School of Medicine, St. Louis, Missouri
| | - Allison L Germann
- Department of Anesthesiology (X.J., M.M.C., A.L.G., G.A., J.H.S.) and Taylor Family Institute for Innovative Psychiatric Research (G.A., J.H.S.), Washington University School of Medicine, St. Louis, Missouri
| | - Gustav Akk
- Department of Anesthesiology (X.J., M.M.C., A.L.G., G.A., J.H.S.) and Taylor Family Institute for Innovative Psychiatric Research (G.A., J.H.S.), Washington University School of Medicine, St. Louis, Missouri
| | - Joe Henry Steinbach
- Department of Anesthesiology (X.J., M.M.C., A.L.G., G.A., J.H.S.) and Taylor Family Institute for Innovative Psychiatric Research (G.A., J.H.S.), Washington University School of Medicine, St. Louis, Missouri
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23
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George AA, Bloy A, Miwa JM, Lindstrom JM, Lukas RJ, Whiteaker P. Isoform-specific mechanisms of α3β4*-nicotinic acetylcholine receptor modulation by the prototoxin lynx1. FASEB J 2017; 31:1398-1420. [PMID: 28100642 DOI: 10.1096/fj.201600733r] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 12/12/2016] [Indexed: 11/11/2022]
Abstract
This study investigates-for the first time to our knowledge-the existence and mechanisms of functional interactions between the endogenous mammalian prototoxin, lynx1, and α3- and β4-subunit-containing human nicotinic acetylcholine receptors (α3β4*-nAChRs). Concatenated gene constructs were used to express precisely defined α3β4*-nAChR isoforms (α3β4)2β4-, (α3β4)2α3-, (α3β4)2α5(398D)-, and (α3β4)2α5(398N)-nAChR in Xenopus oocytes. In the presence or absence of lynx1, α3β4*-nAChR agonist responses were recorded by using 2-electrode voltage clamp and single-channel electrophysiology, whereas radioimmunolabeling measured cell-surface expression. Lynx1 reduced (α3β4)2β4-nAChR function principally by lowering cell-surface expression, whereas single-channel effects were primarily responsible for reducing (α3β4)2α3-nAChR function [decreased unitary conductance (≥50%), altered burst proportions (3-fold reduction in the proportion of long bursts), and enhanced closed dwell times (3- to 6-fold increase)]. Alterations in both cell-surface expression and single-channel properties accounted for the reduction in (α3β4)2α5-nAChR function that was mediated by lynx1. No effects were observed when α3β4*-nAChRs were coexpressed with mutated lynx1 (control). Lynx1 is expressed in the habenulopeduncular tract, where α3β4*-α5*-nAChR subtypes are critical contributors to the balance between nicotine aversion and reward. This gives our findings a high likelihood of physiologic significance. The exquisite isoform selectivity of lynx1 interactions provides new insights into the mechanisms and allosteric sites [α(-)-interface containing] by which prototoxins can modulate nAChR function.-George, A. A., Bloy, A., Miwa, J. M., Lindstrom, J. M., Lukas, R. J., Whiteaker, P. Isoform-specific mechanisms of α3β4*-nicotinic acetylcholine receptor modulation by the prototoxin lynx1.
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Affiliation(s)
- Andrew A George
- Division of Neurobiology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA;
| | - Abigail Bloy
- Division of Neurobiology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA.,Leeds Institute of Cancer and Pathology, St. James' University Hospital, Leeds, United Kingdom
| | - Julie M Miwa
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania, USA
| | - Jon M Lindstrom
- Department of Neuroscience, University of Pennsylvania Medical School, Philadelphia, Pennsylvania, USA
| | - Ronald J Lukas
- Division of Neurobiology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Paul Whiteaker
- Division of Neurobiology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
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24
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Mazzaferro S, Bermudez I, Sine SM. α4β2 Nicotinic Acetylcholine Receptors: RELATIONSHIPS BETWEEN SUBUNIT STOICHIOMETRY AND FUNCTION AT THE SINGLE CHANNEL LEVEL. J Biol Chem 2016; 292:2729-2740. [PMID: 28031459 DOI: 10.1074/jbc.m116.764183] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Revised: 12/09/2016] [Indexed: 11/06/2022] Open
Abstract
Acetylcholine receptors comprising α4 and β2 subunits are the most abundant class of nicotinic acetylcholine receptor in the brain. They contribute to cognition, reward, mood, and nociception and are implicated in a range of neurological disorders. Previous measurements of whole-cell macroscopic currents showed that α4 and β2 subunits assemble in two predominant pentameric stoichiometries, which differ in their sensitivity to agonists, antagonists, and allosteric modulators. Here we compare agonist-elicited single channel currents from receptors assembled with an excess of either the α4 or β2 subunit, forming receptor populations biased toward one or the other stoichiometry, with currents from receptors composed of five concatemeric subunits in which the subunit stoichiometry is predetermined. Our results associate each subunit stoichiometry with a unique single channel conductance, mean open channel lifetime, and sensitivity to the allosteric potentiator 3-[3-(3-pyridinyl)-1,2,4-oxadiazol-5-yl]benzonitrile (NS-9283). Receptors with the composition (α4β2)2α4 exhibit high single channel conductance, brief mean open lifetime, and strong potentiation by NS-9283, whereas receptors with the composition (α4β2)2β2 exhibit low single channel conductance and long mean open lifetime and are not potentiated by NS-9283. Thus single channel current measurements reveal bases for the distinct functional and pharmacological properties endowed by different stoichiometries of α4 and β2 subunits and establish pentameric concatemers as a means to delineate interactions between subunits that confer these properties.
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Affiliation(s)
- Simone Mazzaferro
- From the Receptor Biology Laboratory, Department of Physiology and Biomedical Engineering and
| | - Isabel Bermudez
- the School of Life Sciences, Oxford Brookes University, Oxford OX3 OBP, United Kingdom
| | - Steven M Sine
- From the Receptor Biology Laboratory, Department of Physiology and Biomedical Engineering and .,Departments of Neurology and.,Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, Minnesota 55905 and
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25
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Jain A, Kuryatov A, Wang J, Kamenecka TM, Lindstrom J. Unorthodox Acetylcholine Binding Sites Formed by α5 and β3 Accessory Subunits in α4β2* Nicotinic Acetylcholine Receptors. J Biol Chem 2016; 291:23452-23463. [PMID: 27645992 DOI: 10.1074/jbc.m116.749150] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Indexed: 11/06/2022] Open
Abstract
All nicotinic acetylcholine receptors (nAChRs) evolved from homomeric nAChRs in which all five subunits are involved in forming acetylcholine (ACh) binding sites at their interfaces. Heteromeric α4β2* nAChRs typically have two ACh binding sites at α4/β2 interfaces and a fifth accessory subunit surrounding the central cation channel. β2 accessory subunits do not form ACh binding sites, but α4 accessory subunits do at the α4/α4 interface in (α4β2)2α4 nAChRs. α5 and β3 are closely related subunits that had been thought to act only as accessory subunits and not take part in forming ACh binding sites. The effect of agonists at various subunit interfaces was determined by blocking homologous sites at these interfaces using the thioreactive agent 2-((trimethylammonium)ethyl) methanethiosulfonate (MTSET). We found that α5/α4 and β3/α4 interfaces formed ACh binding sites in (α4β2)2α5 and (α4β2)2β3 nAChRs. The α4/α5 interface in (β2α4)2α5 nAChRs also formed an ACh binding site. Blocking of these sites with MTSET reduced the maximal ACh evoked responses of these nAChRs by 30-50%. However, site-selective agonists NS9283 (for the α4/α4 site) and sazetidine-A (for the α4/β2 site) did not act on the ACh sites formed by the α5/α4 or β3/α4 interfaces. This suggests that unorthodox sites formed by α5 and β3 subunits have unique ligand selectivity. Agonists or antagonists for these unorthodox sites might be selective and effective drugs for modulating nAChR function to treat nicotine addiction and other disorders.
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Affiliation(s)
- Akansha Jain
- From the Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Alexander Kuryatov
- From the Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Jingyi Wang
- the Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, Austin, Texas 78712, and
| | - Theodore M Kamenecka
- the Department of Molecular Therapeutics, Scripps Research Institute, Jupiter, Florida 33458
| | - Jon Lindstrom
- From the Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania 19104,
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26
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Onajole OK, Vallerini GP, Eaton JB, Lukas RJ, Brunner D, Caldarone BJ, Kozikowski AP. Synthesis and Behavioral Studies of Chiral Cyclopropanes as Selective α4β2-Nicotinic Acetylcholine Receptor Partial Agonists Exhibiting an Antidepressant Profile. Part III. ACS Chem Neurosci 2016; 7:811-22. [PMID: 27035276 DOI: 10.1021/acschemneuro.6b00050] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
We report the synthesis and biological characterization of novel derivatives of 3-[(1-methyl-2(S)-pyrrolidinyl)methoxy]-5-cyclopropylpyridine (4a-f and 5) as potent and highly selective α4β2-nicotinic acetylcholine receptor (nAChR) full or partial agonists. A systematic structure-activity study was carried out on the previously described compound 3b, particularly concerning its (2-methoxyethyl)cyclopropyl side-chain, in an effort to improve its metabolic stability while maintaining receptor selectivity. Compound 4d exhibited very similar subnanomolar binding affinity for α4β2- and α4β2*-nAChRs compared to 3b, and it showed excellent potency in activating high-sensitivity (HS) α4β2-nAChRs with an EC50 value of 8.2 nM. Testing of 4d in the SmartCube assay revealed that the compound has a combined antidepressant plus antipsychotic signature. In the forced swim test at a dose of 30 mg/kg given intraperitoneally, 4d was found to be as efficacious as sertraline, thus providing evidence of the potential use of the compound as an antidepressant. Additional promise for use of 4d in humans comes from pharmacokinetic studies in mice indicating brain penetration, and additional assays show compound stability in the presence of human microsomes and hepatocytes. Thus, 4d has a very favorable preclinical drug profile.
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Affiliation(s)
- Oluseye K. Onajole
- Drug
Discovery Program, Department of Medicinal Chemistry and Pharmacognosy,
College of Pharmacy, University of Illinois at Chicago, 833 South
Wood Street, Chicago, Illinois 60612, United States
- Department
of Biological, Chemical and Physical Sciences, Roosevelt University, 425 S. Wabash Avenue, Chicago, Illinois 60605, United States
| | - Gian Paolo Vallerini
- Drug
Discovery Program, Department of Medicinal Chemistry and Pharmacognosy,
College of Pharmacy, University of Illinois at Chicago, 833 South
Wood Street, Chicago, Illinois 60612, United States
| | - J. Brek Eaton
- Division
of Neurobiology, Barrow Neurological Institute, 350 West Thomas Road, Phoenix, Arizona 85013, United States
| | - Ronald J. Lukas
- Division
of Neurobiology, Barrow Neurological Institute, 350 West Thomas Road, Phoenix, Arizona 85013, United States
| | - Dani Brunner
- PsychoGenics, Inc., 765 Old Saw Mill
River Road, Tarrytown, New
York 10591, United States
| | - Barbara J. Caldarone
- Harvard
NeuroDiscovery Center and Department of Neurology, Brigham and Women’s Hospital, 77 Avenue Louis Pasteur, Boston, Massachusetts 02115, United States
| | - Alan P. Kozikowski
- Drug
Discovery Program, Department of Medicinal Chemistry and Pharmacognosy,
College of Pharmacy, University of Illinois at Chicago, 833 South
Wood Street, Chicago, Illinois 60612, United States
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