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Brems BM, Sullivan EE, Connolly JG, Zhang J, Chang A, Ortiz R, Cantwell L, Kulkarni P, Thakur GA, Ferris CF. Dose-dependent effects of GAT107, a novel allosteric agonist-positive allosteric modulator (ago-PAM) for the α7 nicotinic cholinergic receptor: a BOLD phMRI and connectivity study on awake rats. Front Neurosci 2023; 17:1196786. [PMID: 37424993 PMCID: PMC10326388 DOI: 10.3389/fnins.2023.1196786] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Accepted: 06/06/2023] [Indexed: 07/11/2023] Open
Abstract
Background Alpha 7 nicotinic acetylcholine receptor (α7nAChR) agonists have been developed to treat schizophrenia but failed in clinical trials due to rapid desensitization. GAT107, a type 2 allosteric agonist-positive allosteric modulator (ago-PAM) to the α7 nAChR was designed to activate the α7 nAChR while reducing desensitization. We hypothesized GAT107 would alter the activity of thalamocortical neural circuitry associated with cognition, emotion, and sensory perception. Methods The present study used pharmacological magnetic resonance imaging (phMRI) to evaluate the dose-dependent effect of GAT107 on brain activity in awake male rats. Rats were given a vehicle or one of three different doses of GAT107 (1, 3, and 10 mg/kg) during a 35 min scanning session. Changes in BOLD signal and resting state functional connectivity were evaluated and analyzed using a rat 3D MRI atlas with 173 brain areas. Results GAT107 presented with an inverted-U dose response curve with the 3 mg/kg dose having the greatest effect on the positive BOLD volume of activation. The primary somatosensory cortex, prefrontal cortex, thalamus, and basal ganglia, particularly areas with efferent connections from the midbrain dopaminergic system were activated as compared to vehicle. The hippocampus, hypothalamus, amygdala, brainstem, and cerebellum showed little activation. Forty-five min post treatment with GAT107, data for resting state functional connectivity were acquired and showed a global decrease in connectivity as compared to vehicle. Discussion GAT107 activated specific brain regions involved in cognitive control, motivation, and sensory perception using a BOLD provocation imaging protocol. However, when analyzed for resting state functional connectivity there was an inexplicable, general decrease in connectivity across all brain areas.
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Affiliation(s)
- Brittany M. Brems
- Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, United States
| | - Erin E. Sullivan
- Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, United States
| | - Jenna G. Connolly
- Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, United States
| | - Jingchun Zhang
- Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, United States
| | - Arnold Chang
- Center for Translational Neuroimaging, Northeastern University, Boston, MA, United States
| | - Richard Ortiz
- Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, NM, United States
| | - Lucas Cantwell
- Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, United States
| | - Praveen Kulkarni
- Center for Translational Neuroimaging, Northeastern University, Boston, MA, United States
| | - Ganesh A. Thakur
- Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, United States
| | - Craig F. Ferris
- Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, United States
- Center for Translational Neuroimaging, Northeastern University, Boston, MA, United States
- Department of Psychology, Northeastern University, Boston, MA, United States
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2
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Sanders VR, Millar NS. Potentiation and allosteric agonist activation of α7 nicotinic acetylcholine receptors: binding sites and hypotheses. Pharmacol Res 2023; 191:106759. [PMID: 37023990 DOI: 10.1016/j.phrs.2023.106759] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 03/27/2023] [Accepted: 03/30/2023] [Indexed: 04/07/2023]
Abstract
Considerable progress has been made in recent years towards the identification and characterisation of novel subtype-selective modulators of nicotinic acetylcholine receptors (nAChRs). In particular, this has focussed on modulators of α7 nAChRs, a nAChR subtype that has been identified as a target for drug discovery in connection with a range of potential therapeutic applications. This review focusses upon α7-selective modulators that bind to receptor sites other than the extracellular 'orthosteric' agonist binding site for the endogenous agonist acetylcholine (ACh). Such compounds include those that are able to potentiate responses evoked by orthosteric agonists such as ACh (positive allosteric modulators; PAMs) and those that are able to activate α7 nAChRs by direct allosteric activation in the absence of an orthosteric agonist (allosteric agonists or 'ago-PAMs'). There has been considerable debate about the mechanism of action of α7-selective PAMs and allosteric agonists, much of which has centred around identifying the location of their binding sites on α7 nAChRs. Based on a variety of experimental evidence, including recent structural data, there is now clear evidence indicating that at least some α7-selective PAMs bind to an inter-subunit site located in the transmembrane domain. In contrast, there are differing hypotheses about the site or sites at which allosteric agonists bind to α7 nAChRs. It will be argued that the available evidence supports the conclusion that direct allosteric activation by allosteric agonists/ago-PAMs occurs via the same inter-subunit transmembrane site that has been identified for several α7-selective PAMs.
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Affiliation(s)
- Victoria R Sanders
- Division of Biosciences, University College London, London WC1E 6BT, United Kingdom
| | - Neil S Millar
- Division of Biosciences, University College London, London WC1E 6BT, United Kingdom.
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3
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Papke RL, Quadri M, Gulsevin A. Silent agonists for α7 nicotinic acetylcholine receptors. Pharmacol Res 2023; 190:106736. [PMID: 36940890 DOI: 10.1016/j.phrs.2023.106736] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2022] [Revised: 03/07/2023] [Accepted: 03/14/2023] [Indexed: 03/23/2023]
Abstract
We discuss models for the activation and desensitization of α7 nicotinic acetylcholine receptors (nAChRs) and the effects of efficacious type II positive allosteric modulators (PAMs) that destabilize α7 desensitized states. Type II PAMs such as PNU-120596 can be used to distinguish inactive compounds from silent agonists, compounds that produce little or no channel activation but stabilize the non-conducting conformations associated with desensitization. We discuss the effects of α7 nAChRs in cells of the immune system and their roles in modulating inflammation and pain through what has come to be known as the cholinergic anti-inflammatory system (CAS). Cells controlling CAS do not generate ion channel currents but rather respond to α7 drugs by modulating intracellular signaling pathways analogous to the effects of metabotropic receptors. Metabotropic signaling by α7 receptors appears to be mediated by receptors in nonconducting conformations and can be accomplished by silent agonists. We discuss electrophysiological structure-activity relationships for α7 silent agonists and their use in cell-based and in vivo assays for CAS regulation. We discuss the strongly desensitizing partial agonist GTS-21 and its effectiveness in modulation of CAS. We also review the properties of the silent agonist NS6740, which is remarkably effective at maintaining α7 receptors in PAM-sensitive desensitized states. Most silent agonists bind to sites overlapping those for orthosteric agonists, but some appear to bind to allosteric sites. Finally, we discuss α9⁎ nAChRs and their potential role in CAS, and ligands that will be useful in defining and distinguishing the specific roles of α7 and α9 in CAS.
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Affiliation(s)
- Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267 Gainesville, FL 32610 USA (RLP); Olon S.p.A., Strada Rivoltana, Km 6/7 - 20053 Rodano (MI) - ITALY (MQ); Department of Chemistry, Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, USA, 37212 (AG).
| | - Marta Quadri
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267 Gainesville, FL 32610 USA (RLP); Olon S.p.A., Strada Rivoltana, Km 6/7 - 20053 Rodano (MI) - ITALY (MQ); Department of Chemistry, Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, USA, 37212 (AG)
| | - Alican Gulsevin
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267 Gainesville, FL 32610 USA (RLP); Olon S.p.A., Strada Rivoltana, Km 6/7 - 20053 Rodano (MI) - ITALY (MQ); Department of Chemistry, Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, USA, 37212 (AG)
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4
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Recent Advances in the Discovery of Nicotinic Acetylcholine Receptor Allosteric Modulators. Molecules 2023; 28:molecules28031270. [PMID: 36770942 PMCID: PMC9920195 DOI: 10.3390/molecules28031270] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 01/18/2023] [Accepted: 01/26/2023] [Indexed: 01/31/2023] Open
Abstract
Positive allosteric modulators (PAMs), negative allosteric modulators (NAMs), silent agonists, allosteric activating PAMs and neutral or silent allosteric modulators are compounds capable of modulating the nicotinic receptor by interacting at allosteric modulatory sites distinct from the orthosteric sites. This survey is focused on the compounds that have been shown or have been designed to interact with nicotinic receptors as allosteric modulators of different subtypes, mainly α7 and α4β2. Minimal chemical changes can cause a different pharmacological profile, which can then lead to the design of selective modulators. Experimental evidence supports the use of allosteric modulators as therapeutic tools for neurological and non-neurological conditions.
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5
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Stokes C, Camacho-Hernandez GA, Thakur GA, Wu X, Taylor P, Papke RL. Differential Activation and Desensitization States Promoted by Noncanonical α7 Nicotinic Acetylcholine Receptor Agonists. J Pharmacol Exp Ther 2022; 383:157-171. [PMID: 36279397 PMCID: PMC9553115 DOI: 10.1124/jpet.122.001354] [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] [Received: 06/14/2022] [Accepted: 08/11/2022] [Indexed: 01/07/2023] Open
Abstract
A series of dipicolyl amine pyrimidines (DPPs) were previously identified as potential α7 agonists by means of a calcium influx assay in the presence of the positive allosteric modulator (PAM) 1-(5-chloro-2,4-dimethoxy-phenyl)-3-(5-methyl-isoxazol-3-yl)-urea (PNU-120596). The compounds lack the quaternary or strongly basic nitrogens of typical nicotinic agonists. Although differing in structure from typical nicotinic agonists, based on crystallographic data with the acetylcholine binding protein, they appeared to engage the site shared by such typical orthosteric agonists. Using oocytes expressing human α7 receptors, we found that the DPPs were efficacious activators of the receptor, with currents showing rapid desensitization characteristic of α7 receptors. However, we note that the rate of recovery from this desensitization depends strongly on structural features within the DPP family. Although the activation of receptors by DPP was blocked by the competitive antagonist methyllycaconitine (MLA), MLA had no effect on the DPP-induced desensitization, suggesting multiple modes of DPP binding. As expected, the desensitized conformational states could be reactivated by PAMs. Mutants made insensitive to acetylcholine by the C190A mutation in the agonist binding site were weakly activated by DPPs. The observation that activation of C190A mutants by the DPP compounds was resistant to the allosteric antagonist (-)cis-trans-4-(2,3,5,6-tetramethylphenyl)-3a,4,5,9b-tetrahydro-3H-cyclopenta[c]quinoline-8-sulfonamide supports the hypothesis that the activity of these noncanonical agonists in the orthosteric binding sites was not entirely dependent on the classic epitopes controlling activation by typical agonists and that perhaps they may access alternative modes for promoting the conformational changes associated with activation and desensitization. SIGNIFICANCE STATEMENT: This study reports a family of nicotinic acetylcholine receptor agonists that break the rules about what the structure of a nicotinic acetylcholine receptor agonist should be. It shows that the activity of these noncanonical agonists in the orthosteric binding sites is not dependent on the classical epitopes controlling activation by typical agonists and that through different binding poses, they promote unique conformational changes associated with receptor activation and desensitization.
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Affiliation(s)
- Clare Stokes
- Department of Pharmacology, Skaggs School of Pharmacy & Pharmaceutical Sciences, University of California-San Diego, La Jolla, California (G.A.C.-H., X.W., P.T.); Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida (C.S., R.L.P.); and Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (G.A.T.)
| | - Gisela Andrea Camacho-Hernandez
- Department of Pharmacology, Skaggs School of Pharmacy & Pharmaceutical Sciences, University of California-San Diego, La Jolla, California (G.A.C.-H., X.W., P.T.); Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida (C.S., R.L.P.); and Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (G.A.T.)
| | - Ganesh A Thakur
- Department of Pharmacology, Skaggs School of Pharmacy & Pharmaceutical Sciences, University of California-San Diego, La Jolla, California (G.A.C.-H., X.W., P.T.); Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida (C.S., R.L.P.); and Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (G.A.T.)
| | - Xiaoxuan Wu
- Department of Pharmacology, Skaggs School of Pharmacy & Pharmaceutical Sciences, University of California-San Diego, La Jolla, California (G.A.C.-H., X.W., P.T.); Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida (C.S., R.L.P.); and Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (G.A.T.)
| | - Palmer Taylor
- Department of Pharmacology, Skaggs School of Pharmacy & Pharmaceutical Sciences, University of California-San Diego, La Jolla, California (G.A.C.-H., X.W., P.T.); Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida (C.S., R.L.P.); and Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (G.A.T.)
| | - Roger L Papke
- Department of Pharmacology, Skaggs School of Pharmacy & Pharmaceutical Sciences, University of California-San Diego, La Jolla, California (G.A.C.-H., X.W., P.T.); Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida (C.S., R.L.P.); and Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (G.A.T.)
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6
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Zhuang Y, Noviello CM, Hibbs RE, Howard RJ, Lindahl E. Differential interactions of resting, activated, and desensitized states of the α7 nicotinic acetylcholine receptor with lipidic modulators. Proc Natl Acad Sci U S A 2022; 119:e2208081119. [PMID: 36251999 PMCID: PMC9618078 DOI: 10.1073/pnas.2208081119] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Accepted: 09/08/2022] [Indexed: 11/18/2022] Open
Abstract
The α7 nicotinic acetylcholine receptor is a pentameric ligand-gated ion channel that modulates neuronal excitability, largely by allowing Ca2+ permeation. Agonist binding promotes transition from a resting state to an activated state, and then rapidly to a desensitized state. Recently, cryogenic electron microscopy (cryo-EM) structures of the human α7 receptor in nanodiscs were reported in multiple conformations. These were selectively stabilized by inhibitory, activating, or potentiating compounds. However, the functional annotation of these structures and their differential interactions with unresolved lipids and ligands remain incomplete. Here, we characterized their ion permeation, membrane interactions, and ligand binding using computational electrophysiology, free-energy calculations, and coarse-grained molecular dynamics. In contrast to nonconductive structures in apparent resting and desensitized states, the structure determined in the presence of the potentiator PNU-120596 was consistent with an activated state permeable to Ca2+. Transition to this state was associated with compression and rearrangement of the membrane, particularly in the vicinity of the peripheral MX helix. An intersubunit transmembrane site was implicated in selective binding of either PNU-120596 in the activated state or cholesterol in the desensitized state. This substantiates functional assignment of all three lipid-embedded α7-receptor structures with ion-permeation simulations. It also proposes testable models of their state-dependent interactions with lipophilic ligands, including a mechanism for allosteric modulation at the transmembrane subunit interface.
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Affiliation(s)
- Yuxuan Zhuang
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, PO Box 1031, Solna, 171 21 Sweden
| | - Colleen M. Noviello
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Ryan E. Hibbs
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Rebecca J. Howard
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, PO Box 1031, Solna, 171 21 Sweden
| | - Erik Lindahl
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, PO Box 1031, Solna, 171 21 Sweden
- Department of Applied Physics, Swedish e-Science Research Center, KTH Royal Institute of Technology, PO Box 1031, Solna, 171 21 Sweden
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7
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Horenstein NA, Stokes C, Papke RL. Sulfonium Ligands of the α7 nAChR. Molecules 2021; 26:5643. [PMID: 34577114 PMCID: PMC8464850 DOI: 10.3390/molecules26185643] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 09/13/2021] [Accepted: 09/13/2021] [Indexed: 11/16/2022] Open
Abstract
The α7 nicotinic acetylcholine receptor (nAChR) is an important target given its role in cognitive function as well as in the cholinergic anti-inflammatory pathway, where ligands that are effective at stabilizing desensitized states of the receptor are of particular interest. The typical structural element associated with a good desensitizer is the ammonium pharmacophore, but recent work has identified that a trivalent sulfur, in the positively charged sulfonium form, can substitute for the nitrogen in the ammonium pharmacophore. However, the breadth and scope of employing the sulfonium group is largely unexplored. In this work, we have surveyed a disparate group of sulfonium compounds for their functional activity with α7 as well as other nAChR subtypes. Amongst them, we found that there is a wide range of ability to induce α7 desensitization, with 4-hydroxyphenyldimethylsulfonium and suplatast sulfonium salts being the most desensitizing. The smallest sulfonium compound, trimethylsulfonium, was a partial agonist for α7 and other neuronal nAChR. Molecular docking into the α7 receptor extracellular domain revealed preferred poses in the orthosteric binding site for all but one compound, with typical cation-pi interactions as seen with traditional ammonium compounds. A number of the compounds tested may serve as useful platforms for further development of α7 desensitizing ability and for receptor subtype selectivity.
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Affiliation(s)
| | - Clare Stokes
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL 32610-0267, USA; (C.S.); (R.L.P.)
| | - Roger L. Papke
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL 32610-0267, USA; (C.S.); (R.L.P.)
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8
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Gulsevin A, Papke RL, Stokes C, Tran HNT, Jin AH, Vetter I, Meiler J. The Allosteric Activation of α7 nAChR by α-Conotoxin MrIC Is Modified by Mutations at the Vestibular Site. Toxins (Basel) 2021; 13:toxins13080555. [PMID: 34437426 PMCID: PMC8402416 DOI: 10.3390/toxins13080555] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 08/02/2021] [Accepted: 08/09/2021] [Indexed: 12/18/2022] Open
Abstract
α-conotoxins are 13–19 amino acid toxin peptides that bind various nicotinic acetylcholine receptor (nAChR) subtypes. α-conotoxin Mr1.7c (MrIC) is a 17 amino acid peptide that targets α7 nAChR. Although MrIC has no activating effect on α7 nAChR when applied by itself, it evokes a large response when co-applied with the type II positive allosteric modulator PNU-120596, which potentiates the α7 nAChR response by recovering it from a desensitized state. A lack of standalone activity, despite activation upon co-application with a positive allosteric modulator, was previously observed for molecules that bind to an extracellular domain allosteric activation (AA) site at the vestibule of the receptor. We hypothesized that MrIC may activate α7 nAChR allosterically through this site. We ran voltage-clamp electrophysiology experiments and in silico peptide docking calculations in order to gather evidence in support of α7 nAChR activation by MrIC through the AA site. The experiments with the wild-type α7 nAChR supported an allosteric mode of action, which was confirmed by the significantly increased MrIC + PNU-120596 responses of three α7 nAChR AA site mutants that were designed in silico to improve MrIC binding. Overall, our results shed light on the allosteric activation of α7 nAChR by MrIC and suggest the involvement of the AA site.
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Affiliation(s)
- Alican Gulsevin
- Center for Structural Biology, Department of Chemistry, Vanderbilt University, Nashville, TN 37212, USA;
- Correspondence:
| | - Roger L. Papke
- Department of Pharmacology and Therapeutics, College of Medicine, University of Florida, Gainesville, FL 32610, USA; (R.L.P.); (C.S.)
| | - Clare Stokes
- Department of Pharmacology and Therapeutics, College of Medicine, University of Florida, Gainesville, FL 32610, USA; (R.L.P.); (C.S.)
| | - Hue N. T. Tran
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD 4072, Australia; (H.N.T.T.); (A.H.J.); (I.V.)
| | - Aihua H. Jin
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD 4072, Australia; (H.N.T.T.); (A.H.J.); (I.V.)
| | - Irina Vetter
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD 4072, Australia; (H.N.T.T.); (A.H.J.); (I.V.)
- School of Pharmacy, The University of Queensland, Woolloongabba, QLD 4102, Australia
| | - Jens Meiler
- Center for Structural Biology, Department of Chemistry, Vanderbilt University, Nashville, TN 37212, USA;
- Institute for Drug Discovery, Leipzig University Medical School, 04103 Leipzig, Germany
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Abstract
The α7-type nicotinic acetylcholine receptor is one of the most unique and interesting of all the members of the cys-loop superfamily of ligand-gated ion channels. Since it was first identified initially as a binding site for α-bungarotoxin in mammalian brain and later as a functional homomeric receptor with relatively high calcium permeability, it has been pursued as a potential therapeutic target for numerous indications, from Alzheimer disease to asthma. In this review, we discuss the history and state of the art for targeting α7 receptors, beginning with subtype-selective agonists and the basic pharmacophore for the selective activation of α7 receptors. A key feature of α7 receptors is their rapid desensitization by standard "orthosteric" agonist, and we discuss insights into the conformational landscape of α7 receptors that has been gained by the development of ligands binding to allosteric sites. Some of these sites are targeted by positive allosteric modulators that have a wide range of effects on the activation profile of the receptors. Other sites are targeted by direct allosteric agonist or antagonists. We include a perspective on the potential importance of α7 receptors for metabotropic as well as ionotropic signaling. We outline the challenges that exist for future development of drugs to target this important receptor and approaches that may be considered to address those challenges. SIGNIFICANCE STATEMENT: The α7-type nicotinic acetylcholine receptor (nAChR) is acknowledged as a potentially important therapeutic target with functional properties associated with both ionotropic and metabotropic signaling. The functional properties of α7 nAChR can be regulated in diverse ways with the variety of orthosteric and allosteric ligands described in this review.
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Affiliation(s)
- Roger L Papke
- Departments of Pharmacology and Therapeutics (R.L.P) and Chemistry (N.A.H.), University of Florida, Gainesville, FL
| | - Nicole A Horenstein
- Departments of Pharmacology and Therapeutics (R.L.P) and Chemistry (N.A.H.), University of Florida, Gainesville, FL
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Pismataro MC, Horenstein NA, Stokes C, Dallanoce C, Thakur GA, Papke RL. Stable desensitization of α 7 nicotinic acetylcholine receptors by NS6740 requires interaction with S36 in the orthosteric agonist binding site. Eur J Pharmacol 2021; 905:174179. [PMID: 34004208 DOI: 10.1016/j.ejphar.2021.174179] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 05/05/2021] [Accepted: 05/12/2021] [Indexed: 01/09/2023]
Abstract
NS6740 is an α7 nicotinic acetylcholine receptor-selective partial agonist with low efficacy for channel activation, capable of promoting the stable conversion of the receptors to nonconducting (desensitized) states that can be reactivated with the application of positive allosteric modulators (PAMs). In spite of its low efficacy for channel activation, NS6740 is an effective activator of the cholinergic anti-inflammatory pathway. We observed that the concentration-response relationships for channel activation, both when applied alone and when co-applied with the PAM PNU-120596 are inverted-U shaped with inhibitory/desensitizing activities dominant at high concentrations. We evaluated the potential importance of recently identified binding sites for allosteric activators and tested the hypotheses that the stable desensitization produced by NS6740 may be due to binding to these sites. Our experiments were guided by molecular modeling of NS6740 binding to both the allosteric and orthosteric activation sites on the receptor. Our results indicate that with α7C190A mutants, which have compromised orthosteric activation sites, NS6740 may work at the allosteric activation sites to promote transient PAM-dependent currents but not the stable desensitization seen with wild-type α7 receptors. Modeling NS6740 in the orthosteric binding sites identified S36 as an important residue for NS6740 binding and predicted that an S36V mutation would limit NS6740 activity. The efficacy of NS6740 for α7S36V receptors was reduced to zero, and applications of the compound to α7S36V receptors failed to induce the desensitization observed with wild-type receptors. The results indicate that the unique properties of NS6740 are due primarily to binding at the sites for orthosteric agonists.
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Affiliation(s)
- Maria Chiara Pismataro
- Department of Pharmaceutical Sciences, Medicinal Chemistry Section "Pietro Pratesi", University of Milan, Via L. Mangiagalli 25, 20133, Milan, Italy; Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL, 32611-7200, USA
| | - Nicole A Horenstein
- Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL, 32611-7200, USA
| | - Clare Stokes
- Department of Pharmacology and Therapeutics, University of Florida, P.O. Box 100267, Gainesville, FL, 32610-0267, USA
| | - Clelia Dallanoce
- Department of Pharmaceutical Sciences, Medicinal Chemistry Section "Pietro Pratesi", University of Milan, Via L. Mangiagalli 25, 20133, Milan, Italy.
| | - Ganesh A Thakur
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, MA, 02115, USA
| | - Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, P.O. Box 100267, Gainesville, FL, 32610-0267, USA
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Camacho-Hernandez GA, Taylor P. Lessons from nature: Structural studies and drug design driven by a homologous surrogate from invertebrates, AChBP. Neuropharmacology 2020; 179:108108. [DOI: 10.1016/j.neuropharm.2020.108108] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 04/08/2020] [Accepted: 04/12/2020] [Indexed: 02/07/2023]
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Gulsevin A, Meiler J, Horenstein NA. A Computational Analysis of the Factors Governing the Dynamics of α7 nAChR and Its Homologs. Biophys J 2020; 119:1656-1669. [PMID: 33010233 PMCID: PMC7642335 DOI: 10.1016/j.bpj.2020.09.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 09/10/2020] [Accepted: 09/10/2020] [Indexed: 12/18/2022] Open
Abstract
The α7 nicotinic acetylcholine receptor is a homopentameric ion channel from the Cys-loop receptor superfamily targeted for psychiatric indications and inflammatory pain. Molecular dynamics studies of the receptor have focused on residue mobility and global conformational changes to address receptor function. However, a comparative analysis of α7 with its homologs that cannot trigger channel opening has not been made so far. To identify the residues involved in α7 activation, we ran triplicate 500-ns molecular dynamics simulations with an α7 extracellular domain homology model and two acetylcholine-binding protein homologs. We tested the effect of ligand binding and amino acid sequence on the structure and dynamics of the three proteins. We found that mobile regions identified based on root mean-square deviation and root mean-square fluctuation values are not always consistent among the individual α7 extracellular domain simulations. Comparison of the replica-average properties of the three proteins based on dynamic cross-correlation maps showed that ligand binding affects the coupling between the C-loop and the Cys-loop, vestibular loop, and β1-β2 loops. In addition, the main-immunogenic-region-like domain of α7 went through correlated motions with multiple domains of the receptor. These correlated motions were absent or diminished in α7 homologs, suggesting a unique role in α7 activation.
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Affiliation(s)
- Alican Gulsevin
- Department of Chemistry, Biochemistry Division, University of Florida, Gainesville, Florida; Department of Chemistry, Vanderbilt University, Nashville, Tennessee.
| | - Jens Meiler
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee; Leipzig University Medical School, Institute for Drug Discovery, Leipzig, Germany
| | - Nicole A Horenstein
- Department of Chemistry, Biochemistry Division, University of Florida, Gainesville, Florida
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Moreira LK, de Brito AF, Fontana C, de Carvalho FS, Sanz G, Vaz BG, Lião LM, da Rocha FF, Verli H, Menegatti R, Costa EA. Neuropharmacological assessment in mice and molecular docking of piperazine derivative LQFM212. Behav Brain Res 2020; 394:112827. [PMID: 32730857 DOI: 10.1016/j.bbr.2020.112827] [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: 12/16/2019] [Revised: 06/25/2020] [Accepted: 07/20/2020] [Indexed: 10/23/2022]
Abstract
Piperazine derivatives are an attractive class of chemical compounds for the treatment of various mental illness. Herein, we demonstrated the synthesis of LQFM212, a piperazine derivative, behavioral evaluation in mice and computational studies. In neuropharmacological assessment, LQFM212 treatment at doses of 18, 54 or 162 μmol/kg increased the sleep duration in sodium pentobarbital-induced sleep test. LQFM212 at dose of 162 μmol/kg increased climbing time in the chimney test and decreased the number of squares crossed in the open field test, suggesting that LQFM212 in high doses reduces spontaneous movement. However, LQFM212 treatment at the doses of 18 or 54 μmol/kg increased the preference for the center of field which could be indicative of anxiolytic-like effects. In elevated plus maze and light-dark box tests, LQFM212 treatment altered all parameters observed that demonstrate anxiolytic-like activity. These effects were reversed by flumazenil, mecamylamine, WAY-100635 and PCPA, but not with ketanserin, showing that anxiolytic-like activity involve benzodiazepine site of GABAA receptor, nicotinic and serotonergic pathways. Molecular docking of LQFM212 showed that the ligand has more interactions with GABAA receptor than with 5-HT1A receptor. Despite the involvement of benzodiazepine site on anxiolytic-like effect of LQFM212, treatment with this compound did not alter cognitive function in the step-down avoidance test. In this sense, this piperazine derivative is a good prototype for treating anxiety disorders with putative mechanism of action.
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Affiliation(s)
- Lorrane Kelle Moreira
- Laboratory of Pharmacology of Natural and Synthetic Products, Institute of Biological Sciences, Federal University of Goiás, Campus Samambaia, Goiânia, GO, Brazil
| | - Adriane Ferreira de Brito
- Laboratory of Pharmacology of Natural and Synthetic Products, Institute of Biological Sciences, Federal University of Goiás, Campus Samambaia, Goiânia, GO, Brazil
| | - Crisciele Fontana
- Center of Biotechnology, Federal University of Rio Grande do Sul, RS, Brazil
| | - Flávio Souza de Carvalho
- Laboratory of Medicinal Pharmaceutical Chemistry, Faculty of Pharmacy, Federal University of Goiás, Goiânia, GO, Brazil
| | - Germán Sanz
- Chemistry Institute, Federal University of Goiás, Campus Samambaia, Goiânia, GO, Brazil
| | - Boniek Gontijo Vaz
- Chemistry Institute, Federal University of Goiás, Campus Samambaia, Goiânia, GO, Brazil
| | - Luciano Morais Lião
- Chemistry Institute, Federal University of Goiás, Campus Samambaia, Goiânia, GO, Brazil
| | - Fábio Fagundes da Rocha
- Department of Physiological Sciences, Institute of Biology, Federal Rural University of Rio de Janeiro, Seropédica, RJ, Brazil
| | - Hugo Verli
- Center of Biotechnology, Federal University of Rio Grande do Sul, RS, Brazil
| | - Ricardo Menegatti
- Laboratory of Medicinal Pharmaceutical Chemistry, Faculty of Pharmacy, Federal University of Goiás, Goiânia, GO, Brazil
| | - Elson Alves Costa
- Laboratory of Pharmacology of Natural and Synthetic Products, Institute of Biological Sciences, Federal University of Goiás, Campus Samambaia, Goiânia, GO, Brazil.
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14
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Gulsevin A. Nicotinic receptor pharmacology in silico: Insights and challenges. Neuropharmacology 2020; 177:108257. [PMID: 32738311 DOI: 10.1016/j.neuropharm.2020.108257] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Revised: 07/16/2020] [Accepted: 07/26/2020] [Indexed: 02/07/2023]
Abstract
Nicotinic acetylcholine receptors (nAChR) are homo- or hetero-pentameric ligand-gated ion channels of the Cys-loop superfamily and play important roles in the nervous system and muscles. Studies on nAChR benefit from in silico modeling due to the lack of high-resolution structures for most receptor subtypes and challenges in experiments addressing the complex mechanism of activation involving allosteric sites. Although there is myriad of computational modeling studies on nAChR, the multitude of the methods and parameters used in these studies makes modeling nAChR a daunting task, particularly for the non-experts in the field. To address this problem, the modeling literature on Torpedo nAChR and α7 nAChR were focused on as examples of heteromeric and homomeric nAChR, and the key in silico modeling studies between the years 1995-2019 were concisely reviewed. This was followed by a critical analysis of these studies by comparing the findings with each other and with the emerging experimental and computational data on nAChR. Based on these critical analyses, suggestions were made to guide the future researchers in the field of in silico modeling of nAChR. This article is part of the special issue on 'Contemporary Advances in Nicotine Neuropharmacology'.
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Affiliation(s)
- Alican Gulsevin
- Department of Chemistry, Vanderbilt University, Nashville, TN, USA, 37221.
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15
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Pismataro MC, Horenstein NA, Stokes C, Quadri M, De Amici M, Papke RL, Dallanoce C. Design, synthesis, and electrophysiological evaluation of NS6740 derivatives: Exploration of the structure-activity relationship for alpha7 nicotinic acetylcholine receptor silent activation. Eur J Med Chem 2020; 205:112669. [PMID: 32810771 DOI: 10.1016/j.ejmech.2020.112669] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2020] [Revised: 07/13/2020] [Accepted: 07/14/2020] [Indexed: 11/15/2022]
Abstract
The α7 nicotinic acetylcholine receptor (nAChR) silent agonists, able to induce receptor desensitization and promote the α7 metabotropic function, are emerging as new promising therapeutic anti-inflammatory agents. Herein, we report the structure-activity relationship investigation of the archetypal silent agonist NS6740 (1,4-diazabicyclo[3.2.2]nonan-4-yl(5-(3-(trifluoromethyl)-phenyl)-furan-2-yl)methanone) (1) to elucidate the ligand-receptor interactions responsible for the α7 silent activation. In this study, NS6740 fragments 11-16 and analogs 17-32 were designed, synthesized, and assayed on human α7 nAChRs expressed in Xenopus laevis oocytes with two-electrode voltage clamping experiments. All together the structural portions of NS6740 were critical to engender its peculiar activity profile. The diazabicyclic nucleus was essential but not sufficient for inducing α7 silent activation. The central hydrogen-bond acceptor core and the aromatic moiety were crucial for promoting prolonged α7 receptor binding and sustained desensitization. Compounds 13 and 17 were efficacious partial agonists. Compounds 12, 21, 23-26, and 30 strongly desensitized α7 nAChR and therefore may be of interest for additional investigation of inflammation responses. We gained key structural information useful for further silent agonist development.
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Affiliation(s)
- Maria Chiara Pismataro
- Department of Pharmaceutical Sciences, Medicinal Chemistry Section "Pietro Pratesi", University of Milan, Via L. Mangiagalli 25, 20133, Milan, Italy; Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL 32611-7200, USA; Department of Pharmacology and Therapeutics, University of Florida, P.O. Box 100267, Gainesville, FL 32610-0267, USA
| | - Nicole A Horenstein
- Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL 32611-7200, USA
| | - Clare Stokes
- Department of Pharmacology and Therapeutics, University of Florida, P.O. Box 100267, Gainesville, FL 32610-0267, USA
| | - Marta Quadri
- Department of Pharmaceutical Sciences, Medicinal Chemistry Section "Pietro Pratesi", University of Milan, Via L. Mangiagalli 25, 20133, Milan, Italy; Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL 32611-7200, USA; Department of Pharmacology and Therapeutics, University of Florida, P.O. Box 100267, Gainesville, FL 32610-0267, USA
| | - Marco De Amici
- Department of Pharmaceutical Sciences, Medicinal Chemistry Section "Pietro Pratesi", University of Milan, Via L. Mangiagalli 25, 20133, Milan, Italy
| | - Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, P.O. Box 100267, Gainesville, FL 32610-0267, USA
| | - Clelia Dallanoce
- Department of Pharmaceutical Sciences, Medicinal Chemistry Section "Pietro Pratesi", University of Milan, Via L. Mangiagalli 25, 20133, Milan, Italy.
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16
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Papke RL, Garai S, Stokes C, Horenstein NA, Zimmerman AD, Abboud KA, Thakur GA. Differing Activity Profiles of the Stereoisomers of 2,3,5,6TMP-TQS, a Putative Silent Allosteric Modulator of α7 nAChR. Mol Pharmacol 2020; 98:292-302. [PMID: 32690627 DOI: 10.1124/mol.120.119958] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 07/13/2020] [Indexed: 12/20/2022] Open
Abstract
Many synthetic compounds to which we attribute specific activities are produced as racemic mixtures of stereoisomers, and it may be that all the desired activity comes from a single enantiomer. We have previously shown this to be the case with the α7 nicotinic acetylcholine receptor positive allosteric modulator (PAM) 3a,4,5,9b-Tetrahydro-4-(1-naphthalenyl)-3H-cyclopentan[c]quinoline-8-sulfonamide (TQS) and the α7 ago-PAM 4BP-TQS. Cis-trans-4-(2,3,5,6-tetramethylphenyl)-3a,4,5,9b-te-trahydro-3H-cyclopenta[c]quinoline-8-sulfonamide (2,3,5,6TMP-TQS), previously published as a "silent allosteric modulator" and an antagonist of α7 allosteric activation, shares the same scaffold with three chiral centers as the aforementioned compounds. We isolated the enantiomers of 2,3,5,6TMP-TQS and determined that the (-) isomer was a significantly better antagonist than the (+) isomer of the allosteric activation of both wild-type α7 and the nonorthosterically activatible C190A α7 mutant by the ago-PAM GAT107 (the active isomer of 4BP-TQS). In contrast, (+)2,3,5,6TMP-TQS proved to be an α7 PAM. (-)2,3,5,6TMP-TQS was shown to antagonize the allosteric activation of α7 by the structurally unrelated ago-PAM B-973B as well as the allosteric activation of the TQS-sensitive α4β2L15'M mutant. In silico docking of 2,3,5,6TMP-TQS in the putative allosteric activation binding site suggested a specific interaction of the (-) enantiomer with α7T106, and allosteric activation of α7T106 mutants was not inhibited by (-)2,3,5,6TMP-TQS, confirming the importance of this interaction and supporting the model of the allosteric binding site. Comparisons and contrasts between 2,3,5,6TMP-TQS isomers and active and inactive enantiomers of other TQS-related compounds identify the orientation of the cyclopentenyl ring to the plane of the core quinoline to be a crucial determinate of PAM activity. SIGNIFICANCE STATEMENT: Many synthetic ligands are in use as racemic preparations. We show that one enantiomer of the TQS analog Cis-trans-4-(2,3,5,6-tetramethylphenyl)-3a,4,5,9b-te-trahydro-3H-cyclopenta[c]quinoline-8-sulfonamide, originally reported to lack activity when used as a racemic preparation, is an α7 nicotinic acetylcholine receptor positive allosteric modulator (PAM). The other enantiomer is not a PAM, but it is an effective allosteric antagonist. In silico studies and structural comparisons identify essential elements of both the allosteric ligands and receptor binding sites important for these allosteric activities.
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Affiliation(s)
- Roger L Papke
- Departments of Pharmacology and Therapeutics (R.L.P., C.S., A.D.Z.) and Chemistry (N.A.H., K.A.A.), University of Florida, Gainesville, Florida; and Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., G.A.T.)
| | - Sumanta Garai
- Departments of Pharmacology and Therapeutics (R.L.P., C.S., A.D.Z.) and Chemistry (N.A.H., K.A.A.), University of Florida, Gainesville, Florida; and Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., G.A.T.)
| | - Clare Stokes
- Departments of Pharmacology and Therapeutics (R.L.P., C.S., A.D.Z.) and Chemistry (N.A.H., K.A.A.), University of Florida, Gainesville, Florida; and Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., G.A.T.)
| | - Nicole A Horenstein
- Departments of Pharmacology and Therapeutics (R.L.P., C.S., A.D.Z.) and Chemistry (N.A.H., K.A.A.), University of Florida, Gainesville, Florida; and Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., G.A.T.)
| | - Arthur D Zimmerman
- Departments of Pharmacology and Therapeutics (R.L.P., C.S., A.D.Z.) and Chemistry (N.A.H., K.A.A.), University of Florida, Gainesville, Florida; and Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., G.A.T.)
| | - Khalil A Abboud
- Departments of Pharmacology and Therapeutics (R.L.P., C.S., A.D.Z.) and Chemistry (N.A.H., K.A.A.), University of Florida, Gainesville, Florida; and Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., G.A.T.)
| | - Ganesh A Thakur
- Departments of Pharmacology and Therapeutics (R.L.P., C.S., A.D.Z.) and Chemistry (N.A.H., K.A.A.), University of Florida, Gainesville, Florida; and Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., G.A.T.)
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17
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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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18
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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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19
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Gulsevin A, Papke RL, Horenstein N. In Silico Modeling of the α7 Nicotinic Acetylcholine Receptor: New Pharmacological Challenges Associated with Multiple Modes of Signaling. Mini Rev Med Chem 2020; 20:841-864. [PMID: 32000651 PMCID: PMC8719523 DOI: 10.2174/1389557520666200130105256] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2019] [Revised: 11/06/2019] [Accepted: 11/07/2019] [Indexed: 12/13/2022]
Abstract
The α7 nicotinic acetylcholine receptor is a homopentameric ion-channel of the Cys-loop superfamily characterized by its low probability of opening, high calcium permeability, and rapid desensitization. The α7 receptor has been targeted for the treatment of the cognitive symptoms of schizophrenia, depression, and Alzheimer's disease, but it is also involved in inflammatory modulation as a part of the cholinergic anti-inflammatory pathway. Despite its functional importance, in silico studies of the α7 receptor cannot produce a general model explaining the structural features of receptor activation, nor predict the mode of action for various ligand classes. Two particular problems in modeling the α7 nAChR are the absence of a high-resolution structure and the presence of five potentially nonequivalent orthosteric ligand binding sites. There is wide variability regarding the templates used for homology modeling, types of ligands investigated, simulation methods, and simulation times. However, a systematic survey focusing on the methodological similarities and differences in modeling α7 has not been done. In this work, we make a critical analysis of the modeling literature of α7 nAChR by comparing the findings of computational studies with each other and with experimental studies under the main topics of structural studies, ligand binding studies, and comparisons with other nAChR. In light of our findings, we also summarize current problems in the field and make suggestions for future studies concerning modeling of the α7 receptor.
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Affiliation(s)
- Alican Gulsevin
- Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL, 32611-7200, United States
| | - Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, P.O. Box 100267, Gainesville, FL 32610, United States
| | - Nicole Horenstein
- Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL, 32611-7200, United States
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20
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Camacho-Hernandez GA, Stokes C, Duggan BM, Kaczanowska K, Brandao-Araiza S, Doan L, Papke RL, Taylor P. Synthesis, Pharmacological Characterization, and Structure-Activity Relationships of Noncanonical Selective Agonists for α7 nAChRs. J Med Chem 2019; 62:10376-10390. [PMID: 31675224 DOI: 10.1021/acs.jmedchem.9b01467] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A lack of selectivity of classical agonists for the nicotinic acetylcholine receptors (nAChR) has prompted us to identify and develop a distinct scaffold of α7 nAChR-selective ligands. Noncanonical 2,4,6-substituted pyrimidine analogues were framed around compound 40 for a structure-activity relationship study. The new lead compounds activate selectively the α7 nAChRs with EC50's between 30 and 140 nM in a PNU-120596-dependent, cell-based calcium influx assay. After characterizing the expanded lead landscape, we ranked the compounds for rapid activation using Xenopus oocytes expressing human α7 nAChR with a two-electrode voltage clamp. This approach enabled us to define the molecular determinants governing rapid activation, agonist potency, and desensitization of α7 nAChRs after exposure to pyrimidine analogues, thereby distinguishing this subclass of noncanonical agonists from previously defined types of agonists (agonists, partial agonists, silent agonists, and ago-PAMs). By NMR, we analyzed pKa values for ionization of lead candidates, demonstrating distinctive modes of interaction for this landscape of ligands.
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Affiliation(s)
- Gisela Andrea Camacho-Hernandez
- Department of Pharmacology, Skaggs School of Pharmacy & Pharmaceutical Sciences , University of California-San Diego , La Jolla , California 92093-0751 , United States
| | - Clare Stokes
- Department of Pharmacology & Therapeutics , University of Florida , P.O. Box 100267, Gainesville , Florida 32610-0267 , United States
| | - Brendan M Duggan
- Department of Pharmacology, Skaggs School of Pharmacy & Pharmaceutical Sciences , University of California-San Diego , La Jolla , California 92093-0751 , United States
| | - Katarzyna Kaczanowska
- Department of Pharmacology, Skaggs School of Pharmacy & Pharmaceutical Sciences , University of California-San Diego , La Jolla , California 92093-0751 , United States
| | - Stefania Brandao-Araiza
- Department of Pharmacology, Skaggs School of Pharmacy & Pharmaceutical Sciences , University of California-San Diego , La Jolla , California 92093-0751 , United States
| | - Lisa Doan
- Department of Pharmacology, Skaggs School of Pharmacy & Pharmaceutical Sciences , University of California-San Diego , La Jolla , California 92093-0751 , United States
| | - Roger L Papke
- Department of Pharmacology & Therapeutics , University of Florida , P.O. Box 100267, Gainesville , Florida 32610-0267 , United States
| | - Palmer Taylor
- Department of Pharmacology & Therapeutics , University of Florida , P.O. Box 100267, Gainesville , Florida 32610-0267 , United States
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21
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Ma F, Luo X, Ma J, Yang Z, Yao Z, Luo X. The effect of the α7nAChR agonist on Wnt/β-catenin signaling in osteoporosis. INTERNATIONAL JOURNAL OF CLINICAL AND EXPERIMENTAL PATHOLOGY 2019; 12:2867-2874. [PMID: 31934123 PMCID: PMC6949712] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 04/28/2019] [Accepted: 05/27/2019] [Indexed: 06/10/2023]
Abstract
The cholinergic pathway neurotransmitter acetylcholine (ACh) regulates the inflammatory cascade through a specific α7 nicotinic acetylcholine receptor (α7nAChR). However, the role and related mechanisms of α7nAChR in osteoporosis (OP) remain unclear. Therefore, this study aims to analyze the effects of α7nAChR on osteoblasts and related mechanisms. Mouse osteoblast MC3T3-E1 was cultured in vitro and divided into a control group and an α7nAChR agonist group (2.4 and 4.8 mg/kg.d). An MTT assay was used to detect the osteoblast activity, an ARS staining assay was used to analyze the formation of calcified nodules of osteoblasts, and an alkaline phosphatase (ALP) activity colorimetric assay was used to determine the ALP activity. Real-time PCR was performed to analyze the expression of RUNX2 and OPN mRNA. The inflammatory factor tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) secretions were analyzed by ELISA. The α7nAChR agonists dose-dependently promoted osteoblast proliferation, increased calcified nodules, ALP activity, RUNX2 and OPN mRNA expression, decreased inflammatory factors TNF-α and IL-6 secretion, and increased Wnt1, β-catenin mRNA and protein expression. Compared with the control group, the differences were statistically significant (P<0.05). α7nAChR agonists can inhibit the proliferation and differentiation of osteoblasts by regulating the Wnt/β-catenin signaling pathway, and then participate in the regulation of osteoporosis.
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Affiliation(s)
- Feng Ma
- Department of Orthopaedics, People's Hospital of Ningxia Hui Autonomous Region Yinchuan, Ningxia, China
| | - Xiaohai Luo
- Department of Orthopaedics, People's Hospital of Ningxia Hui Autonomous Region Yinchuan, Ningxia, China
| | - Jingzu Ma
- Department of Orthopaedics, People's Hospital of Ningxia Hui Autonomous Region Yinchuan, Ningxia, China
| | - Ziyang Yang
- Department of Orthopaedics, People's Hospital of Ningxia Hui Autonomous Region Yinchuan, Ningxia, China
| | - Zhanchuan Yao
- Department of Orthopaedics, People's Hospital of Ningxia Hui Autonomous Region Yinchuan, Ningxia, China
| | - Xiaojun Luo
- Department of Orthopaedics, People's Hospital of Ningxia Hui Autonomous Region Yinchuan, Ningxia, China
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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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