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Cartereau A, Bouchouireb Z, Kaaki S, Héricourt F, Taillebois E, Le Questel JY, Thany SH. Pharmacology and molecular modeling studies of sulfoxaflor, flupyradifurone and neonicotinoids on the human neuronal α7 nicotinic acetylcholine receptor. Toxicol Appl Pharmacol 2024:117123. [PMID: 39393466 DOI: 10.1016/j.taap.2024.117123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2024] [Revised: 10/06/2024] [Accepted: 10/06/2024] [Indexed: 10/13/2024]
Abstract
We conducted electrophysiological and molecular docking studies using a heterologous expression system (Xenopus oocytes) to compare the effects of four neonicotinoids (acetamiprid, imidacloprid, clothianidin and thiamethoxam), one sulfoximine, (sulfoxaflor), and one butenolide (flupyradifurone), on human α7 neuronal nicotinic acetylcholine receptors (nAChRs). All neonicotinoids (except thiamethoxam), as well as the recently introduced nAChR competitive modulators, flupyradifurone and sulfoxaflor, appear to be weaker agonists than acetylcholine. Two mutations in loop C (E211N and E211P) and one mutation in loop D (Q79K), known to be involved in the binding properties of neonicotinoids were introduced to the α7 wild type. Interestingly, the acetylcholine and nicotine-evoked activation was not modified in human α7 mutated receptors, but the net charge was enhanced for clothianidin and imidacloprid, respectively. Flupyradifurone responses strongly increased under the Q79K mutation. The molecular docking investigations demonstrated that the orientations and interactions of the ligands considered were in accordance with those observed experimentally. Specifically, the charged fragments of acetylcholine and nicotine, used as reference ligands, and their neonicotinoid homologs were found to be surrounded by aromatic residues, with key interactions with Trp171 and Y210. Furthermore, the molecular docking investigations predicted the water-mediated interaction between the carbonyl oxygen of acetylcholine and the Nsp2 nitrogen of the pyridine ring for nicotine (as well as for the majority of the corresponding neonicotinoid fragments) and main chain NH of L141. The docking scores, extending over a significant range of 6 kcal/mol, showed that most neonicotinoids were poorly stabilized in the α7 nAChR compared to acetylcholine, except sulfoxaflor.
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Affiliation(s)
- Alison Cartereau
- Université d'Orléans, USC INRAE 1328, Laboratoire Physiologie, Ecologie et Environnement (P2E), 1 rue de Chartres, 45067 Orléans, France
| | | | - Sara Kaaki
- Université d'Orléans, USC INRAE 1328, Laboratoire Physiologie, Ecologie et Environnement (P2E), 1 rue de Chartres, 45067 Orléans, France
| | - François Héricourt
- Université d'Orléans, USC INRAE 1328, Laboratoire Physiologie, Ecologie et Environnement (P2E), 1 rue de Chartres, 45067 Orléans, France
| | - Emiliane Taillebois
- Université d'Orléans, USC INRAE 1328, Laboratoire Physiologie, Ecologie et Environnement (P2E), 1 rue de Chartres, 45067 Orléans, France
| | | | - Steeve H Thany
- Université d'Orléans, USC INRAE 1328, Laboratoire Physiologie, Ecologie et Environnement (P2E), 1 rue de Chartres, 45067 Orléans, France; Institut Universitaire de France (IUF), 1 rue Descartes, 75005 Paris, France.
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2
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Papke RL. Functions and pharmacology of α2β2 nicotinic acetylcholine receptors; in and out of the shadow of α4β2 nicotinic acetylcholine receptors. Biochem Pharmacol 2024; 225:116263. [PMID: 38735444 PMCID: PMC11335000 DOI: 10.1016/j.bcp.2024.116263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2024] [Revised: 04/30/2024] [Accepted: 05/02/2024] [Indexed: 05/14/2024]
Abstract
Although α2 was the first neuronal nicotinic acetylcholine receptor (nAChR) receptor subunit to be cloned, due to its low level of expression in rodent brain, its study has largely been neglected. This study provides a comparison of the α2 and α4 structures and their functional similarities, especially in regard to the existence of low and high sensitivity forms based on subunit stoichiometry. We show that the pharmacological profiles of the low and high sensitivity forms of α2β2 and α4β2 receptors are very similar in their responses to nicotine, with high sensitivity receptors showing protracted responses. Sazetidine A, an agonist that is selective for the high sensitivity α4 receptors also selectively activates high sensitivity α2 receptors. Likewise, α2 receptors have similar responses as α4 receptors to the positive allosteric modulators (PAMs) desformylflustrabromine (dFBr) and NS9283. We show that the partial agonists for α4β2 receptors, cytisine and varenicline are also partial agonists for α2β2 receptors. Studies have shown that levels of α2 expression may be much higher in the brains of primates than those of rodents, suggesting a potential importance for human therapeutics. High-affinity nAChR have been studied in humans with PET ligands such as flubatine. We show that flubatine has similar activity with α2β2 and α4β2 receptors so that α2 receptors will also be detected in PET studies that have previously presumed to selectively detect α4β2 receptors. Therefore, α2 receptors need more consideration in the development of therapeutics to manage nicotine addiction and declining cholinergic function in age and disease.
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Affiliation(s)
- Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL 32610 USA.
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3
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Andleeb H, Papke RL, Stokes C, Richter K, Herz SM, Chiang K, Kanumuri SRR, Sharma A, Damaj MI, Grau V, Horenstein NA, Thakur GA. Explorations of Agonist Selectivity for the α9* nAChR with Novel Substituted Carbamoyl/Amido/Heteroaryl Dialkylpiperazinium Salts and Their Therapeutic Implications in Pain and Inflammation. J Med Chem 2024; 67:8642-8666. [PMID: 38748608 PMCID: PMC11181317 DOI: 10.1021/acs.jmedchem.3c02429] [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: 12/23/2023] [Revised: 04/01/2024] [Accepted: 04/29/2024] [Indexed: 06/14/2024]
Abstract
There is an urgent need for nonopioid treatments for chronic and neuropathic pain to provide effective alternatives amid the escalating opioid crisis. This study introduces novel compounds targeting the α9 nicotinic acetylcholine receptor (nAChR) subunit, which is crucial for pain regulation, inflammation, and inner ear functions. Specifically, it identifies novel substituted carbamoyl/amido/heteroaryl dialkylpiperazinium iodides as potent agonists selective for human α9 and α9α10 over α7 nAChRs, particularly compounds 3f, 3h, and 3j. Compound 3h (GAT2711) demonstrated a 230 nM potency as a full agonist at α9 nAChRs, being 340-fold selective over α7. Compound 3c was 10-fold selective for α9α10 over α9 nAChR. Compounds 2, 3f, and 3h inhibited ATP-induced interleukin-1β release in THP-1 cells. The analgesic activity of 3h was fully retained in α7 knockout mice, suggesting that analgesic effects were potentially mediated through α9* nAChRs. Our findings provide a blueprint for developing α9*-specific therapeutics for pain.
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Affiliation(s)
- Hina Andleeb
- Department
of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611-7200, United States
- Department
of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical
Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts 02115, United States
| | - Roger L. Papke
- Department
of Pharmacology and Therapeutics, University
of Florida, P.O. Box 100267, Gainesville, Florida 32610, United States
| | - Clare Stokes
- Department
of Pharmacology and Therapeutics, University
of Florida, P.O. Box 100267, Gainesville, Florida 32610, United States
| | - Katrin Richter
- Department
of General and Thoracic Surgery, Laboratory of Experimental Surgery,
Justus-Liebig-University, German Center for Lung Research [DZL], Cardio-Pulmonary Institute [CPI], Giessen 35385, Germany
| | - Sara M. Herz
- Department
of Pharmacology and Toxicology, Virginia
Commonwealth University, Richmond, Virginia 23298, United States
| | - Ka Chiang
- Department
of Pharmacology and Toxicology, Virginia
Commonwealth University, Richmond, Virginia 23298, United States
| | - Siva R. Raju Kanumuri
- Department
of Pharmaceutics, University of Florida, Gainesville, Florida 32610, United States
| | - Abhisheak Sharma
- Department
of Pharmaceutics, University of Florida, Gainesville, Florida 32610, United States
| | - M. Imad Damaj
- Department
of Pharmacology and Toxicology, Virginia
Commonwealth University, Richmond, Virginia 23298, United States
| | - Veronika Grau
- Department
of General and Thoracic Surgery, Laboratory of Experimental Surgery,
Justus-Liebig-University, German Center for Lung Research [DZL], Cardio-Pulmonary Institute [CPI], Giessen 35385, Germany
| | - Nicole A. Horenstein
- Department
of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611-7200, United States
| | - Ganesh A. Thakur
- Department
of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical
Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts 02115, United States
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Akinola LS, Gonzales J, Buzzi B, Mathews HL, Papke RL, Stitzel JA, Damaj MI. Investigating the role of nicotinic acetylcholine receptors in menthol's effects in mice. Drug Alcohol Depend 2024; 257:111262. [PMID: 38492255 PMCID: PMC11031278 DOI: 10.1016/j.drugalcdep.2024.111262] [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] [Received: 09/08/2023] [Revised: 02/13/2024] [Accepted: 03/01/2024] [Indexed: 03/18/2024]
Abstract
The use of menthol in tobacco products has been linked to an increased likelihood of developing nicotine dependence. The widespread use of menthol can be attributed to its unique sensory characteristics; however, emerging evidence suggests that menthol also alters sensitivity to nicotine through modulation of nicotinic acetylcholine receptors (nAChRs). Nicotinic subunits, such as β2 and α5, are of interest due to their implications in nicotine reward, reinforcement, intake regulation, and aversion. This study, therefore, examined the in vivo relevance of β2 and α5 nicotinic subunits on the pharmacological and behavioral effects of menthol. Data suggests that the α5 nicotinic subunit modulates menthol intake in mice. Overall, deletion or a reduction in function of the α5 subunit lessened aversion to menthol. α5 KO mice and mice possessing the humanized α5 SNP, a variant that confers a nicotine dependence phenotype in humans, demonstrated increased menthol intake compared to their WT counterparts and in a sex-related fashion for α5 SNP mice. We further reported that the modulatory effects of the α5 subunit do not extend to other aversive tastants like quinine, suggesting that deficits in α5* nAChR signaling may not abolish general sensitivity to the aversive effects of other noxious chemicals. Further probing into the role of α5 in other pharmacological properties of menthol revealed that the α5 subunit does not modulate the antinociceptive properties of menthol in mice and suggests that the in vivo differences observed are likely not due to the direct effects of menthol on α5-containing nAChRs in vitro.
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Affiliation(s)
- Lois S Akinola
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA, USA.
| | - Jada Gonzales
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA, USA
| | - Belle Buzzi
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA, USA
| | - Hunter L Mathews
- Department of Psychology and Neuroscience, The University of Colorado Boulder, Institute for Behavioral Genetics, Boulder, CO, USA
| | - Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA
| | - Jerry A Stitzel
- Department of Psychology and Neuroscience, The University of Colorado Boulder, Institute for Behavioral Genetics, Boulder, CO, USA; Department of Integrative Physiology, The University of Colorado Boulder, Institute for Behavioral Genetics, Boulder, CO, USA
| | - M Imad Damaj
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA, USA
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Dallanoce C, Richter K, Stokes C, Papotto C, Andleeb H, Thakur GA, Kerr A, Grau V, Papke RL. New Alpha9 nAChR Ligands Based on a 5-(Quinuclidin-3-ylmethyl)-1,2,4-oxadiazole Scaffold. ACS Chem Neurosci 2024; 15:827-843. [PMID: 38335726 PMCID: PMC11274740 DOI: 10.1021/acschemneuro.3c00720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2024] Open
Abstract
Several lines of evidence have indicated that nicotinic acetylcholine receptors (nAChR) that contain α9 subunits, probably in combination with α10 subunits, may be valuable targets for the management of pain associated with inflammatory diseases through a cholinergic anti-inflammatory system (CAS), which has also been associated with α7 nAChR. Both α7- and α9-containing neuronal nAChR can be pharmacologically distinguished from the high-affinity nicotinic receptors of the brain by their sensitivity to α-bungarotoxin, but in other ways, they have quite distinct pharmacological profiles. The early association of α7 with CAS led to the development of numerous new ligands, variously characterized as α7 agonists, partial agonists, or silent agonists that desensitized α7 receptors without activation. Subsequent reinvestigation of one such family of α7 ligands based on an N,N-diethyl-N'-phenylpiperazine scaffold led to the identification of potent agonists and antagonists for α9. In this paper, we characterize the α9/α10 activity of a series of compounds based on a 5-(quinuclidin-3-ylmethyl)-1,2,4-oxadiazole (QMO) scaffold and identify two new potent ligands of α9, QMO-28, an agonist, and QMO-17, an antagonist. We separated the stereoisomers of these compounds to identify the most potent agonist and discovered that only the 3R isomer of QMO-17 was an α9 antagonist, permitting an in silico model of α9 antagonism to be developed. The α9 activity of these compounds was confirmed to be potentially useful for CAS management of inflammatory pain in cell-based assays of cytokine release.
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Affiliation(s)
- Clelia Dallanoce
- Department of Pharmaceutical Sciences, Medicinal Chemistry Section "Pietro Pratesi″, University of Milan, Via L. Mangiagalli 25, 20133 Milan, Italy
| | - Katrin Richter
- Department of General and Thoracic Surgery, Laboratory of Experimental Surgery, Justus-Liebig-University, German Center for Lung Research [DZL], Cardio-Pulmonary Institute [CPI], Giessen 35390, Germany
| | - Clare Stokes
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267, Gainesville, Florida 32610 United States
| | - Claudio Papotto
- Department of Pharmaceutical Sciences, Medicinal Chemistry Section "Pietro Pratesi″, University of Milan, Via L. Mangiagalli 25, 20133 Milan, Italy
| | - Hina Andleeb
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts 02115, United States
| | - Ganesh A Thakur
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts 02115, United States
| | - Andrew Kerr
- United States Naval Research Laboratory, 6920 Washington, District of Columbia, United States
| | - Veronika Grau
- Department of General and Thoracic Surgery, Laboratory of Experimental Surgery, Justus-Liebig-University, German Center for Lung Research [DZL], Cardio-Pulmonary Institute [CPI], Giessen 35390, Germany
| | - Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267, Gainesville, Florida 32610 United States
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6
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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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7
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Papke RL, Stokes C. Insights Into the Differential Desensitization of α4 β2 Nicotinic Acetylcholine Receptor Isoforms Obtained With Positive Allosteric Modulation of Mutant Receptors. Mol Pharmacol 2023; 103:63-76. [PMID: 36414373 PMCID: PMC9881010 DOI: 10.1124/molpharm.122.000591] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Revised: 10/25/2022] [Accepted: 11/03/2022] [Indexed: 11/23/2022] Open
Abstract
The development of highly efficacious positive allosteric modulators (PAMs) of α7 nicotinic acetylcholine receptors (nAChR) has proven useful in defining the ligand dependence of the conformational dynamics of α7 receptors. No such effective modulators are known to exist for the α4β2 nAChR of the brain, limiting our ability to understand the importance of desensitization for the activity profile of specific ligands. In this study, we used mutant β2 subunits that allowed the use of the α7 PAM 3a,4,5,9b-tetrahydro-4-(1-naphthalenyl)-3H-cyclopentan[c]quinoline-8-sulfonamide (TQS) to probe the desensitizing effects of nicotinic ligands on the two forms of α4β2 receptors; high sensitivity (HS) (two α4 and three β2 subunits) and low sensitivity (LS) (three α4 and two β2 subunits). A total of 28 different ligands of 8 different categories, based on activity and selectivity, were tested for their ability to induce TQS-sensitive desensitization of HS and LS α4β2 receptors. Results confirm that HS α4β2 receptor responses are strongly limited by desensitization, by at least an order of magnitude more so than the responses of LS receptors. The activation of α4β2 receptors by the smoking-cessation drugs cytisine and varenicline is strongly limited by desensitization, as is the activation of LS receptors by the HS-selective agonists 6-[5-[(2S)-2-Azetidinylmethoxy]-3-pyridinyl]-5-hexyn-1-ol dihydrochloride and 4-(5-ethoxy-3-pyridinyl)-N-methyl-(3E)-3-buten-1-amine difumarate. The evaluation of drugs previously identified as α7-selective agonists revealed varying patterns of α4β2 cross-desensitization that were predictive of the effects of these drugs on the activation of wild-type α4β2 receptors by acetylcholine, supporting the utility of TQS-sensitive receptors for the development of focused therapeutics. SIGNIFICANCE STATEMENT: To varying degrees, ligands regulate the balance of active and desensitized states of the two forms of the primary nAChR subtypes in brain. Using mutant beta subunits, an allosteric modulator can reverse ligand-induced desensitization, revealing the differential desensitization of the receptors by specific ligands. This study shows that drugs believed to be selective for therapeutic targets may cross-desensitize other targets and that, within a class of drugs, improved specificity can be achieved by using agents that reduce such cross-desensitization.
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Affiliation(s)
- Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida
| | - Clare Stokes
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida
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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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9
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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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10
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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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11
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Stokes C, Pino JA, Hagan DW, Torres GE, Phelps EA, Horenstein NA, Papke RL. Betel quid: New insights into an ancient addiction. Addict Biol 2022; 27:e13223. [PMID: 36001424 PMCID: PMC9552247 DOI: 10.1111/adb.13223] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Accepted: 07/22/2022] [Indexed: 11/27/2022]
Abstract
The use of areca nuts (areca) in the form of betel quids constitutes the fourth most common addiction in the world, associated with high risk for oral disease and cancer. Areca is a complex natural product, making it difficult to identify specific components associated with the addictive and carcinogenic properties. It is commonly believed that the muscarinic agonist arecoline is at the core of the addiction. However, muscarinic receptor activation is not generally believed to support drug-taking behaviour. Subjective accounts of areca use include descriptions of both sedative and stimulatory effects, consistent with the presence of multiple psychoactive agents. We have previously reported partial agonism of α4-containing nicotinic acetylcholine receptors by arecoline and subsequent inhibition of those receptors by whole areca broth. In the present study, we report the inhibition of nicotinic acetylcholine receptors and other types of neurotransmitter receptors with compounds of high molecular weight in areca and the ability of low molecular weight areca extract to activate GABA and glutamate receptors. We confirm the presence of a high concentration of GABA and glutamate in areca. Additionally, data also indicate the presence of a dopamine and serotonin transporter blocking activity in areca that could account for the reported stimulant and antidepressant activity. Our data suggest that toxic elements of high molecular weight may contribute to the oral health liability of betel quid use, while two distinct low molecular weight components may provide elements of reward, and the nicotinic activity of arecoline contributes to the physical dependence of addiction.
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Affiliation(s)
- Clare Stokes
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267 Gainesville, FL 32610
| | - Jose A. Pino
- Department of Medicine, School of Medicine, University of Atacama, Copiapó, Chile
| | - D. Walker Hagan
- Department of Biomedical Engineering University of Florida, PO Box 100267 Gainesville, FL 32611
| | - Gonzalo E. Torres
- Department of Molecular, Cellular, and Biomedical Sciences, City University of New York School of Medicine at City College, New York, NY 10031
| | - Edward A. Phelps
- Department of Biomedical Engineering University of Florida, PO Box 100267 Gainesville, FL 32611
| | - Nicole A. Horenstein
- Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL 32611-7200
| | - Roger L. Papke
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267 Gainesville, FL 32610
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12
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Richter K, Papke RL, Stokes C, Roy DC, Espinosa ES, Wolf PMK, Hecker A, Liese J, Singh VK, Padberg W, Schlüter KD, Rohde M, McIntosh JM, Morley BJ, Horenstein NA, Grau V, Simard AR. Comparison of the Anti-inflammatory Properties of Two Nicotinic Acetylcholine Receptor Ligands, Phosphocholine and pCF3-diEPP. Front Cell Neurosci 2022; 16:779081. [PMID: 35431807 PMCID: PMC9008208 DOI: 10.3389/fncel.2022.779081] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Accepted: 03/10/2022] [Indexed: 12/14/2022] Open
Abstract
Activation of nicotinic acetylcholine receptors (nAChRs) expressed by innate immune cells can attenuate pro-inflammatory responses. Silent nAChR agonists, which down-modulate inflammation but have little or no ionotropic activity, are of outstanding clinical interest for the prevention and therapy of numerous inflammatory diseases. Here, we compare two silent nAChR agonists, phosphocholine, which is known to interact with nAChR subunits α7, α9, and α10, and pCF3-N,N-diethyl-N′-phenyl-piperazine (pCF3-diEPP), a previously identified α7 nAChR silent agonist, regarding their anti-inflammatory properties and their effects on ionotropic nAChR functions. The lipopolysaccharide (LPS)-induced release of interleukin (IL)-6 by primary murine macrophages was inhibited by pCF3-diEPP, while phosphocholine was ineffective presumably because of instability. In human whole blood cultures pCF3-diEPP inhibited the LPS-induced secretion of IL-6, TNF-α and IL-1β. The ATP-mediated release of IL-1β by LPS-primed human peripheral blood mononuclear leukocytes, monocytic THP-1 cells and THP-1-derived M1-like macrophages was reduced by both phosphocholine and femtomolar concentrations of pCF3-diEPP. These effects were sensitive to mecamylamine and to conopeptides RgIA4 and [V11L; V16D]ArIB, suggesting the involvement of nAChR subunits α7, α9 and/or α10. In two-electrode voltage-clamp measurements pCF3-diEPP functioned as a partial agonist and a strong desensitizer of classical human α9 and α9α10 nAChRs. Interestingly, pCF3-diEPP was more effective as an ionotropic agonist at these nAChRs than at α7 nAChR. In conclusion, phosphocholine and pCF3-diEPP are potent agonists at unconventional nAChRs expressed by monocytic and macrophage-like cells. pCF3-diEPP inhibits the LPS-induced release of pro-inflammatory cytokines, while phosphocholine is ineffective. However, both agonists signal via nAChR subunits α7, α9 and/or α10 to efficiently down-modulate the ATP-induced release of IL-1β. Compared to phosphocholine, pCF3-diEPP is expected to have better pharmacological properties. Thus, low concentrations of pCF3-diEPP may be a therapeutic option for the treatment of inflammatory diseases including trauma-induced sterile inflammation.
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Affiliation(s)
- Katrin Richter
- Department of General and Thoracic Surgery, Laboratory of Experimental Surgery, Justus-Liebig-University, German Center for Lung Research, Giessen, Germany
- *Correspondence: Katrin Richter,
| | - Roger L. Papke
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, United States
| | - Clare Stokes
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, United States
| | - Danika C. Roy
- Department of Chemistry and Biochemistry, Laurentian University, Sudbury, ON, Canada
| | | | - Philipp M. K. Wolf
- Department of General and Thoracic Surgery, Laboratory of Experimental Surgery, Justus-Liebig-University, German Center for Lung Research, Giessen, Germany
| | - Andreas Hecker
- Department of General and Thoracic Surgery, Laboratory of Experimental Surgery, Justus-Liebig-University, German Center for Lung Research, Giessen, Germany
| | - Juliane Liese
- Department of General and Thoracic Surgery, Laboratory of Experimental Surgery, Justus-Liebig-University, German Center for Lung Research, Giessen, Germany
| | - Vijay K. Singh
- Department of Pediatric Hematology and Oncology, Justus-Liebig-University, Giessen, Germany
| | - Winfried Padberg
- Department of General and Thoracic Surgery, Laboratory of Experimental Surgery, Justus-Liebig-University, German Center for Lung Research, Giessen, Germany
| | | | - Marius Rohde
- Department of Pediatric Hematology and Oncology, Justus-Liebig-University, Giessen, Germany
| | - J. Michael McIntosh
- Department of Biology, University of Utah, Salt Lake City, UT, United States
- George E. Wahlen Veterans Affairs Medical Center, Salt Lake City, UT, United States
- Department of Psychiatry, University of Utah, Salt Lake City, UT, United States
| | - Barbara J. Morley
- Center for Sensory Neuroscience, Boys Town National Research Hospital, Omaha, NE, United States
| | | | - Veronika Grau
- Department of General and Thoracic Surgery, Laboratory of Experimental Surgery, Justus-Liebig-University, German Center for Lung Research, Giessen, Germany
| | - Alain R. Simard
- Department of Chemistry and Biochemistry, Laurentian University, Sudbury, ON, Canada
- Department of Biology, Laurentian University, Sudbury, ON, Canada
- Northern Ontario School of Medicine, Sudbury, ON, Canada
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13
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Papke RL, Andleeb H, Stokes C, Quadri M, Horenstein NA. Selective Agonists and Antagonists of α9 Versus α7 Nicotinic Acetylcholine Receptors. ACS Chem Neurosci 2022; 13:624-637. [PMID: 35167270 PMCID: PMC9547379 DOI: 10.1021/acschemneuro.1c00747] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Nicotinic acetylcholine receptors containing α9 subunits are essential for the auditory function and have been implicated, along with α7-containing nicotinic receptors, as potential targets for the treatment of inflammatory and neuropathic pain. The study of α9-containing receptors has been hampered by the lack of selective agonists. The only α9-selective antagonists previously identified are peptide conotoxins. Curiously, the activity of α7 and α9 receptors as modulators of inflammatory pain appears to not rely strictly on ion channel activation, which led to the identification of α7 "silent agonists" and phosphocholine as an "unconventional agonist" for α9 containing receptors. The parallel testing of the α7 silent agonist p-CF3-diEPP and phosphocholine led to the discovery that p-CF3-diEPP was an α9 agonist. In this report, we compared the activity of α7 and α9 with a family of structurally related compounds, most of which were previously shown to be α7 partial or silent agonists. We identify several potent α9-selective agonists as well as numerous potent and selective α9 antagonists and describe the structural basis for these activities. Several of these compounds have previously been shown to be effective in animal models of inflammatory pain, an activity that was assumed to be due to α7 silent agonism but may, in fact, be due to α9 activity. The α9-selective conotoxin antagonists have also been shown to reduce pain in similar models. Our identification of these new α9 agonists and antagonists may prove to be invaluable for defining an optimal approach for treating pain, allowing for reduced use of opioid drugs.
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Affiliation(s)
- Roger L. Papke
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267 Gainesville, FL 32610 USA (CS, RLP),To whom correspondence should be addressed: Roger L. Papke, Ph.D., , Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267, Gainesville FL, 32610-0267
| | - Hina Andleeb
- Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL 32611-7200 USA (HA, MQ, NAH)
| | - Clare Stokes
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267 Gainesville, FL 32610 USA (CS, RLP)
| | - Marta Quadri
- Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL 32611-7200 USA (HA, MQ, NAH)
| | - Nicole A. Horenstein
- Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL 32611-7200 USA (HA, MQ, NAH)
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14
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Ågren R, Sahlholm K. Evidence for Two Modes of Binding of the Negative Allosteric Modulator SB269,652 to the Dopamine D2 Receptor. Biomedicines 2021; 10:biomedicines10010022. [PMID: 35052702 PMCID: PMC8772941 DOI: 10.3390/biomedicines10010022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Revised: 12/21/2021] [Accepted: 12/21/2021] [Indexed: 11/16/2022] Open
Abstract
SB269,652 has been described as the first negative allosteric modulator (NAM) of the dopamine D2 receptor (D2R), however, the binding mode and allosteric mechanism of action of this ligand remain incompletely understood. SB269,652 comprises an orthosteric, primary pharmacophore and a secondary (or allosteric) pharmacophore joined by a hydrophilic cyclohexyl linker and is known to form corresponding interactions with the orthosteric binding site (OBS) and the secondary binding pocket (SBP) in the D2R. Here, we observed a surprisingly low potency of SB269,652 to negatively modulate the D2R-mediated activation of G protein-coupled inward-rectifier potassium channels (GIRK) and decided to perform a more detailed investigation of the interaction between dopamine and SB269,652. The results indicated that the SB269,652 inhibitory potency is increased 6.6-fold upon ligand pre-incubation, compared to the simultaneous co-application with dopamine. Mutagenesis experiments implicated both S193 in the OBS and E95 in the SBP in the effect of pre-application. The present findings extend previous knowledge about how SB269,652 competes with dopamine at the D2R and may be useful for the development of novel D2R ligands, such as antipsychotic drug candidates.
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Affiliation(s)
- Richard Ågren
- Department of Neuroscience, Karolinska Institutet, 17177 Stockholm, Sweden
- Correspondence: (R.Å.); (K.S.)
| | - Kristoffer Sahlholm
- Department of Neuroscience, Karolinska Institutet, 17177 Stockholm, Sweden
- Wallenberg Centre for Molecular Medicine, Department of Integrative Medical Biology, Umeå University, 90187 Umea, Sweden
- Correspondence: (R.Å.); (K.S.)
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15
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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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16
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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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18
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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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Dopamine D 2 Receptor Agonist Binding Kinetics-Role of a Conserved Serine Residue. Int J Mol Sci 2021; 22:ijms22084078. [PMID: 33920848 PMCID: PMC8071183 DOI: 10.3390/ijms22084078] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 04/06/2021] [Accepted: 04/13/2021] [Indexed: 01/03/2023] Open
Abstract
The forward (kon) and reverse (koff) rate constants of drug–target interactions have important implications for therapeutic efficacy. Hence, time-resolved assays capable of measuring these binding rate constants may be informative to drug discovery efforts. Here, we used an ion channel activation assay to estimate the kons and koffs of four dopamine D2 receptor (D2R) agonists; dopamine (DA), p-tyramine, (R)- and (S)-5-OH-dipropylaminotetralin (DPAT). We further probed the role of the conserved serine S1935.42 by mutagenesis, taking advantage of the preferential interaction of (S)-, but not (R)-5-OH-DPAT with this residue. Results suggested similar koffs for the two 5-OH-DPAT enantiomers at wild-type (WT) D2R, both being slower than the koffs of DA and p-tyramine. Conversely, the kon of (S)-5-OH-DPAT was estimated to be higher than that of (R)-5-OH-DPAT, in agreement with the higher potency of the (S)-enantiomer. Furthermore, S1935.42A mutation lowered the kon of (S)-5-OH-DPAT and reduced the potency difference between the two 5-OH-DPAT enantiomers. Kinetic Kds derived from the koff and kon estimates correlated well with EC50 values for all four compounds across four orders of magnitude, strengthening the notion that our assay captured meaningful information about binding kinetics. The approach presented here may thus prove valuable for characterizing D2R agonist candidate drugs.
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20
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Cinquetti R, Imperiali FG, Bozzaro S, Zanella D, Vacca F, Roseti C, Peracino B, Castagna M, Bossi E. Characterization of Transport Activity of SLC11 Transporters in Xenopus laevis Oocytes by Fluorophore Quenching. SLAS DISCOVERY 2021; 26:798-810. [PMID: 33825579 DOI: 10.1177/24725552211004123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Membrane proteins are involved in different physiological functions and are the target of pharmaceutical and abuse drugs. Xenopus laevis oocytes provide a powerful heterologous expression system for functional studies of these proteins. Typical experiments investigate transport using electrophysiology and radiolabeled uptake. A two-electrode voltage clamp is suitable only for electrogenic proteins, and uptake measurements require the existence of radiolabeled substrates and adequate laboratory facilities.Recently, Dictyostelium discoideum Nramp1 and NrampB were characterized using multidisciplinary approaches. NrampB showed no measurable electrogenic activity, and it was investigated in Xenopus oocytes by acquiring confocal images of the quenching of injected fluorophore calcein.This method is adequate to measure the variation in emitted fluorescence, and thus transporter activity indirectly, but requires long experimental procedures to collect statistically consistent data. Considering that optimal expression of heterologous proteins lasts for 48-72 h, a slow acquiring process requires the use of more than one batch of oocytes to complete the experiments. Here, a novel approach to measure substrate uptake is reported. Upon injection of a fluorophore, oocytes were incubated with the substrate and the transport activity measured, evaluating fluorescence quenching in a microplate reader. The technique permits the testing of tens of oocytes in different experimental conditions simultaneously, and thus the collection of significant statistical data for each batch, saving time and animals.The method was tested with different metal transporters (SLC11), DMT1, DdNramp1, and DdNrampB, and verified with the peptide transporter PepT1 (SLC15). Comparison with traditional methods (uptake, two-electrode voltage clamp) and with quenching images acquired by fluorescence microscopy confirmed its efficacy.
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Affiliation(s)
| | | | | | - Daniele Zanella
- University of Insubria, Varese, Lombardia, Italy.,The University of Alabama, Birmingham, AL, USA
| | - Francesca Vacca
- University of Insubria, Varese, Lombardia, Italy.,Italian Institute of Technology (IIT), Genova, Italy
| | | | | | | | - Elena Bossi
- University of Insubria, Varese, Lombardia, Italy
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21
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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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22
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Paucar M, Ågren R, Li T, Lissmats S, Bergendal Å, Weinberg J, Nilsson D, Savichetva I, Sahlholm K, Nilsson J, Svenningsson P. V374A KCND3 Pathogenic Variant Associated With Paroxysmal Ataxia Exacerbations. NEUROLOGY-GENETICS 2021; 7:e546. [PMID: 33575485 PMCID: PMC7862093 DOI: 10.1212/nxg.0000000000000546] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Accepted: 10/27/2020] [Indexed: 12/27/2022]
Abstract
Objective Ataxia channelopathies share common features such as slow motor progression and variable degrees of cognitive dysfunction. Mutations in potassium voltage-gated channel subfamily D member 3 (KCND3), encoding the K+ channel, Kv4.3, are associated with spinocerebellar ataxia (SCA) 19, allelic with SCA22. Mutations in potassium voltage-gated channel subfamily C member 3 (KCNC3), encoding another K+ channel, Kv3.3, cause SCA13. First, a comprehensive phenotype assessment was carried out in a family with autosomal dominant ataxia harboring 2 genetic variants in KCNC3 and KCND3. To evaluate the physiological impact of these variants on channel currents, in vitro studies were performed. Methods Clinical and psychometric evaluations, neuroimaging, and genotyping of a family (mother and son) affected by ataxia were carried out. Heterozygous and homozygous Kv3.3 A671V and Kv4.3 V374A variants were evaluated in Xenopus laevis oocytes using 2-electrode voltage-clamp. The influence of Kv4 conductance on neuronal activity was investigated computationally using a Purkinje neuron model. Results The main clinical findings were consistent with adult-onset ataxia with cognitive dysfunction and acetazolamide-responsive paroxysmal motor exacerbations in the index case. Despite cognitive deficits, fluorodeoxyglucose (FDG)-PET displayed hypometabolism mainly in the severely atrophic cerebellum. Genetic analyses revealed the new variant c.1121T>C (V374A) in KCND3 and c.2012T>C (A671V) in KCNC3. In vitro electrophysiology experiments on Xenopus oocytes demonstrated that the V374A mutant was nonfunctional when expressed on its own. Upon equal co-expression of wild-type (WT) and V374A channel subunits, Kv4.3 currents were significantly reduced in a dominant negative manner, without alterations of the gating properties of the channel. By contrast, Kv3.3 A671V, when expressed alone, exhibited moderately reduced currents compared with WT, with no effects on channel activation or inactivation. Immunohistochemistry demonstrated adequate cell membrane translocation of the Kv4.3 V374A variant, thus suggesting an impairment of channel function, rather than of expression. Computational modeling predicted an increased Purkinje neuron firing frequency upon reduced Kv4.3 conductance. Conclusions Our findings suggest that Kv4.3 V374A is likely pathogenic and associated with paroxysmal ataxia exacerbations, a new trait for SCA19/22. The present FDG PET findings contrast with a previous study demonstrating widespread brain hypometabolism in SCA19/22.
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Affiliation(s)
- Martin Paucar
- Department of Clinical Neuroscience (M.P., R.Å., T.L., Å.B., J.N., P.S.), Department of Molecular Medicine and Surgery (D.N.), Center for Molecular Medicine (D.N.), and Science for Life Laboratory (D.N.), Karolinska Institutet (S.L., I.S.), Stockholm; Department of Neurology (M.P., J.W., P.S.), Department of Clinical Genetics (D.N.), Department of Nuclear Medicine (I.S.), and Department of Neurophysiology (J.N.), Karolinska University Hospital (R.Å.), Stockholm; Department of Integrative Medical Biology (K.S.), Umeå University; and Department of Medical Sciences (J.N.), Örebro University, Sweden
| | - Richard Ågren
- Department of Clinical Neuroscience (M.P., R.Å., T.L., Å.B., J.N., P.S.), Department of Molecular Medicine and Surgery (D.N.), Center for Molecular Medicine (D.N.), and Science for Life Laboratory (D.N.), Karolinska Institutet (S.L., I.S.), Stockholm; Department of Neurology (M.P., J.W., P.S.), Department of Clinical Genetics (D.N.), Department of Nuclear Medicine (I.S.), and Department of Neurophysiology (J.N.), Karolinska University Hospital (R.Å.), Stockholm; Department of Integrative Medical Biology (K.S.), Umeå University; and Department of Medical Sciences (J.N.), Örebro University, Sweden
| | - Tianyi Li
- Department of Clinical Neuroscience (M.P., R.Å., T.L., Å.B., J.N., P.S.), Department of Molecular Medicine and Surgery (D.N.), Center for Molecular Medicine (D.N.), and Science for Life Laboratory (D.N.), Karolinska Institutet (S.L., I.S.), Stockholm; Department of Neurology (M.P., J.W., P.S.), Department of Clinical Genetics (D.N.), Department of Nuclear Medicine (I.S.), and Department of Neurophysiology (J.N.), Karolinska University Hospital (R.Å.), Stockholm; Department of Integrative Medical Biology (K.S.), Umeå University; and Department of Medical Sciences (J.N.), Örebro University, Sweden
| | - Simon Lissmats
- Department of Clinical Neuroscience (M.P., R.Å., T.L., Å.B., J.N., P.S.), Department of Molecular Medicine and Surgery (D.N.), Center for Molecular Medicine (D.N.), and Science for Life Laboratory (D.N.), Karolinska Institutet (S.L., I.S.), Stockholm; Department of Neurology (M.P., J.W., P.S.), Department of Clinical Genetics (D.N.), Department of Nuclear Medicine (I.S.), and Department of Neurophysiology (J.N.), Karolinska University Hospital (R.Å.), Stockholm; Department of Integrative Medical Biology (K.S.), Umeå University; and Department of Medical Sciences (J.N.), Örebro University, Sweden
| | - Åsa Bergendal
- Department of Clinical Neuroscience (M.P., R.Å., T.L., Å.B., J.N., P.S.), Department of Molecular Medicine and Surgery (D.N.), Center for Molecular Medicine (D.N.), and Science for Life Laboratory (D.N.), Karolinska Institutet (S.L., I.S.), Stockholm; Department of Neurology (M.P., J.W., P.S.), Department of Clinical Genetics (D.N.), Department of Nuclear Medicine (I.S.), and Department of Neurophysiology (J.N.), Karolinska University Hospital (R.Å.), Stockholm; Department of Integrative Medical Biology (K.S.), Umeå University; and Department of Medical Sciences (J.N.), Örebro University, Sweden
| | - Jan Weinberg
- Department of Clinical Neuroscience (M.P., R.Å., T.L., Å.B., J.N., P.S.), Department of Molecular Medicine and Surgery (D.N.), Center for Molecular Medicine (D.N.), and Science for Life Laboratory (D.N.), Karolinska Institutet (S.L., I.S.), Stockholm; Department of Neurology (M.P., J.W., P.S.), Department of Clinical Genetics (D.N.), Department of Nuclear Medicine (I.S.), and Department of Neurophysiology (J.N.), Karolinska University Hospital (R.Å.), Stockholm; Department of Integrative Medical Biology (K.S.), Umeå University; and Department of Medical Sciences (J.N.), Örebro University, Sweden
| | - Daniel Nilsson
- Department of Clinical Neuroscience (M.P., R.Å., T.L., Å.B., J.N., P.S.), Department of Molecular Medicine and Surgery (D.N.), Center for Molecular Medicine (D.N.), and Science for Life Laboratory (D.N.), Karolinska Institutet (S.L., I.S.), Stockholm; Department of Neurology (M.P., J.W., P.S.), Department of Clinical Genetics (D.N.), Department of Nuclear Medicine (I.S.), and Department of Neurophysiology (J.N.), Karolinska University Hospital (R.Å.), Stockholm; Department of Integrative Medical Biology (K.S.), Umeå University; and Department of Medical Sciences (J.N.), Örebro University, Sweden
| | - Irina Savichetva
- Department of Clinical Neuroscience (M.P., R.Å., T.L., Å.B., J.N., P.S.), Department of Molecular Medicine and Surgery (D.N.), Center for Molecular Medicine (D.N.), and Science for Life Laboratory (D.N.), Karolinska Institutet (S.L., I.S.), Stockholm; Department of Neurology (M.P., J.W., P.S.), Department of Clinical Genetics (D.N.), Department of Nuclear Medicine (I.S.), and Department of Neurophysiology (J.N.), Karolinska University Hospital (R.Å.), Stockholm; Department of Integrative Medical Biology (K.S.), Umeå University; and Department of Medical Sciences (J.N.), Örebro University, Sweden
| | - Kristoffer Sahlholm
- Department of Clinical Neuroscience (M.P., R.Å., T.L., Å.B., J.N., P.S.), Department of Molecular Medicine and Surgery (D.N.), Center for Molecular Medicine (D.N.), and Science for Life Laboratory (D.N.), Karolinska Institutet (S.L., I.S.), Stockholm; Department of Neurology (M.P., J.W., P.S.), Department of Clinical Genetics (D.N.), Department of Nuclear Medicine (I.S.), and Department of Neurophysiology (J.N.), Karolinska University Hospital (R.Å.), Stockholm; Department of Integrative Medical Biology (K.S.), Umeå University; and Department of Medical Sciences (J.N.), Örebro University, Sweden
| | - Johanna Nilsson
- Department of Clinical Neuroscience (M.P., R.Å., T.L., Å.B., J.N., P.S.), Department of Molecular Medicine and Surgery (D.N.), Center for Molecular Medicine (D.N.), and Science for Life Laboratory (D.N.), Karolinska Institutet (S.L., I.S.), Stockholm; Department of Neurology (M.P., J.W., P.S.), Department of Clinical Genetics (D.N.), Department of Nuclear Medicine (I.S.), and Department of Neurophysiology (J.N.), Karolinska University Hospital (R.Å.), Stockholm; Department of Integrative Medical Biology (K.S.), Umeå University; and Department of Medical Sciences (J.N.), Örebro University, Sweden
| | - Per Svenningsson
- Department of Clinical Neuroscience (M.P., R.Å., T.L., Å.B., J.N., P.S.), Department of Molecular Medicine and Surgery (D.N.), Center for Molecular Medicine (D.N.), and Science for Life Laboratory (D.N.), Karolinska Institutet (S.L., I.S.), Stockholm; Department of Neurology (M.P., J.W., P.S.), Department of Clinical Genetics (D.N.), Department of Nuclear Medicine (I.S.), and Department of Neurophysiology (J.N.), Karolinska University Hospital (R.Å.), Stockholm; Department of Integrative Medical Biology (K.S.), Umeå University; and Department of Medical Sciences (J.N.), Örebro University, Sweden
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23
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Ågren R, Zeberg H. Low-Resistance silver bromide electrodes for recording fast ion channel kinetics under voltage clamp conditions. J Neurosci Methods 2020; 348:108984. [PMID: 33164817 DOI: 10.1016/j.jneumeth.2020.108984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2020] [Revised: 10/14/2020] [Accepted: 10/20/2020] [Indexed: 10/23/2022]
Abstract
BACKGROUND Two-electrode voltage clamp is a widely used technique for studying ionic currents. However, fast activation kinetics of ion channels are disguised by the capacitive transient during voltage clamp of Xenopus oocytes. The limiting factors of clamp performance include, but are not limited to, amplifier gain, membrane capacitance, and micropipette resistance. Previous work has focused on increasing amplifier gain (e.g.; high performing two-electrode amplifiers) or reducing the membrane capacitance (e.g.; the cut-open technique). NEW METHOD The use of an Ag-AgBr electrode with saturated KBr solution to reduce micropipette resistance. RESULTS The conductivity of 4 M KBr was 37 % higher compared to 3 M KCl and the micropipette resistance was reduced by 19 % when 4 M KBr was used, compared to the standard 3 M KCl solution. Micropipette resistances correlated positively with capacitive transient durations. Neither the current-voltage relationship of the voltage-gated sodium channel, Nav1.7, nor Xenopus oocyte stability were affected by bromide ions. COMPARISON WITH EXISTING METHODS The de facto standard for two-electrode voltage clamp is 3 M KCl and Ag-AgCl electrodes, which are associated an unnecessarily high micropipette resistance. Elsewise, cut-open voltage clamp techniques are technically demanding and require manipulation of the intracellular environment. CONCLUSIONS The use of an Ag-AgBr electrode with saturated KBr as micropipette solution reduces the capacitive transient in two-electrode voltage clamp recordings. Moreover, the exchange of chloride against bromide ions does not seem to affect oocyte physiology and ion channel kinetics.
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Affiliation(s)
- Richard Ågren
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
| | - Hugo Zeberg
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
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24
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Miller DR, Khoshbouei H, Garai S, Cantwell LN, Stokes C, Thakur G, Papke RL. Allosterically Potentiated α7 Nicotinic Acetylcholine Receptors: Reduced Calcium Permeability and Current-Independent Control of Intracellular Calcium. Mol Pharmacol 2020; 98:695-709. [PMID: 33020143 DOI: 10.1124/molpharm.120.000012] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 09/10/2020] [Indexed: 11/22/2022] Open
Abstract
The currents of α7 nicotinic acetylcholine receptors activated by acetylcholine (ACh) are brief. The channel has high permeability to calcium relative to monovalent cations and shows inward rectification. It has been previously noted that in the presence of positive allosteric modulators (PAMs), currents through the channels of α7 receptors differ from normal α7 currents both in sensitivity to specific channel blockers and their current-voltage (I-V) relationships, no longer showing inward rectification. Linear I-V functions are often associated with channels lacking calcium permeability, so we measured the I-V functions of α7 receptors activated by ACh when PAMs were bound to the allosteric binding site in the transmembrane domain. Currents were recorded in chloride-free Ringer's solution with low or high concentrations of extracellular calcium to determine the magnitude of the reversal potential shift in the two conditions as well as the I-V relationships. ACh-evoked currents potentiated by the allosteric agonist-PAMs (ago-PAMs) (3aR,4S,9bS)-4-(4-bromophenyl)-3a,4,5,9b-tetrahydro-3H-cyclopenta[c]quinoline-8-sulfonamide (GAT107) and 3-(3,4-difluorophenyl)-N-(1-(6-(4-(pyridin-2-yl)piperazin-1-yl)pyrazin-2-yl)ethyl)propenamide (B-973B) showed reduced inward rectification and calcium-dependent reversal potential shifts decreased by 80%, and 50%, respectively, compared with currents activated by ACh alone, indicative of reduced calcium permeability. Currents potentiated by 3a,4,5,9b-tetrahydro-4-(1-naphthalenyl)-3H-cyclopentan[c]quinoline-8-sulfonamide were also linear and showed no calcium-dependent reversal potential shifts. The ago-PAMs GAT-107 and B-973B stimulated increases in intracellular calcium in stably transfected HEK293 cells. However, these calcium signals were delayed relative to channel activation produced by these agents and were insensitive to the channel blocker mecamylamine. Our results indicate that, although allosterically activated α7 nicotinic ACh receptor may affect intracellular calcium levels, such effects are not likely due to large channel-dependent calcium influx. SIGNIFICANCE STATEMENT: Positive allosteric modulators (PAMs) of α7 nicotinic acetylcholine receptor can increase channel activation by two or more orders of magnitude, raising the concern that, due to the relatively high calcium permeability of α7 receptors activated by acetylcholine alone, such efficacious PAMs may have cytotoxic side effects. We show that PAMs alter the ion conduction pathway and, in general, reduce the calcium permeability of the channels. This supports the hypothesis that α7 effects on intracellular calcium may be independent of channel-mediated calcium influx.
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Affiliation(s)
- Douglas R Miller
- Departments of Neuroscience (D.R.M., H.K.) and Pharmacology and Therapeutics (C.S., R.L.P.), University of Florida, Gainesville, Florida; and Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., L.N.C., G.T.)
| | - Habibeh Khoshbouei
- Departments of Neuroscience (D.R.M., H.K.) and Pharmacology and Therapeutics (C.S., R.L.P.), University of Florida, Gainesville, Florida; and Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., L.N.C., G.T.)
| | - Sumanta Garai
- Departments of Neuroscience (D.R.M., H.K.) and Pharmacology and Therapeutics (C.S., R.L.P.), University of Florida, Gainesville, Florida; and Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., L.N.C., G.T.)
| | - Lucas N Cantwell
- Departments of Neuroscience (D.R.M., H.K.) and Pharmacology and Therapeutics (C.S., R.L.P.), University of Florida, Gainesville, Florida; and Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., L.N.C., G.T.)
| | - Clare Stokes
- Departments of Neuroscience (D.R.M., H.K.) and Pharmacology and Therapeutics (C.S., R.L.P.), University of Florida, Gainesville, Florida; and Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., L.N.C., G.T.)
| | - Ganesh Thakur
- Departments of Neuroscience (D.R.M., H.K.) and Pharmacology and Therapeutics (C.S., R.L.P.), University of Florida, Gainesville, Florida; and Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., L.N.C., G.T.)
| | - Roger L Papke
- Departments of Neuroscience (D.R.M., H.K.) and Pharmacology and Therapeutics (C.S., R.L.P.), University of Florida, Gainesville, Florida; and Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts (S.G., L.N.C., G.T.)
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25
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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 PMCID: PMC7472127 DOI: 10.1124/mol.120.119958] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [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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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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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: 10] [Impact Index Per Article: 2.5] [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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Godin JR, Roy P, Quadri M, Bagdas D, Toma W, Narendrula-Kotha R, Kishta OA, Damaj MI, Horenstein NA, Papke RL, Simard AR. A silent agonist of α7 nicotinic acetylcholine receptors modulates inflammation ex vivo and attenuates EAE. Brain Behav Immun 2020; 87:286-300. [PMID: 31874200 PMCID: PMC7604877 DOI: 10.1016/j.bbi.2019.12.014] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Revised: 12/20/2019] [Accepted: 12/20/2019] [Indexed: 12/20/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) are best known to function as ligand-gated ion channels in the nervous system. However, recent evidence suggests that nicotine modulates inflammation by desensitizing non-neuronal nAChRs, rather than by inducing channel opening. Silent agonists are molecules that selectively induce the desensitized state of nAChRs while producing little or no channel opening. A silent agonist of α7 nAChRs has recently been shown to reduce inflammation in an animal model of inflammatory pain. The objective of this study was to determine whether a silent agonist of α7 nAChRs can also effectively modulate inflammation and disease manifestation in an animal model of multiple sclerosis. We first evaluated the effects of various nAChR ligands and of an α7 nAChR-selective silent agonist, 1-ethyl-4-(3-(bromo)phenyl)piperazine (m-bromo PEP), on the modulation of mouse bone marrow-derived monocyte/macrophage (BMDM) numbers, phenotype and cytokine production. The non-competitive antagonist mecamylamine and the silent agonist m-bromo PEP reduced pro-inflammatory BMDM numbers by affecting their viability and proliferation. Both molecules also significantly reduced cytokine production by mouse BMDMs and significantly ameliorated disease in experimental autoimmune encephalomyelitis. Finally, m-bromo PEP also reduced chronic inflammatory pain in mice. Taken together, our results further support the hypothesis that nAChRs may modulate inflammation via receptor desensitization rather than channel opening. α7 nAChR-selective silent agonists may thus be a novel source of anti-inflammatory compounds that could be used for the treatment of inflammatory disorders.
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Affiliation(s)
- Jean-Rémi Godin
- Département de Chimie et Biochimie, Université de Moncton, Moncton, NB, Canada
| | - Patrick Roy
- Département de Chimie et Biochimie, Université de Moncton, Moncton, NB, Canada
| | - Marta Quadri
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267, Gainesville, FL, USA,Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL, USA
| | - Deniz Bagdas
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA, USA
| | - Wisam Toma
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA, USA
| | | | | | - M. Imad Damaj
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA, USA
| | - Nicole A. Horenstein
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267, Gainesville, FL, USA
| | - Roger L. Papke
- Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL, USA
| | - Alain R. Simard
- Département de Chimie et Biochimie, Université de Moncton, Moncton, NB, Canada,Northern Ontario School of Medicine, Sudbury, ON, Canada,Department of Chemistry and Biochemistry, Laurentian University, Sudbury, ON, Canada,Department of Biology, Laurentian University, Sudbury, ON, Canada,Corresponding author at: Northern Ontario School of Medicine, 935 Ramsey Lake Rd., Sudbury, ON P3E 2C6, Canada. (A.R. Simard)
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Horenstein NA, Quadri M, Stokes C, Shoaib M, Papke RL. Cracking the Betel Nut: Cholinergic Activity of Areca Alkaloids and Related Compounds. Nicotine Tob Res 2020; 21:805-812. [PMID: 29059390 DOI: 10.1093/ntr/ntx187] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2017] [Accepted: 09/14/2017] [Indexed: 12/12/2022]
Abstract
INTRODUCTION The use of betel quid is the most understudied major addiction in the world. The neuropsychological activity of betel quid has been attributed to alkaloids of Areca catechu. With the goal of developing novel addiction treatments, we evaluate the muscarinic and nicotinic activity of the four major Areca alkaloids: arecoline, arecaidine, guvacoline, and guvacine and four structurally related compounds. METHODS Acetylcholine receptors were expressed in Xenopus oocytes and studied with two-electrode voltage clamp. RESULTS Both arecoline- and guvacoline-activated muscarinic acetylcholine receptors (mAChR), while only arecoline produced significant activation of nicotinic AChR (nAChR). We characterized four additional arecoline-related compounds, seeking an analog that would retain selective activity for a α4* nAChR, with diminished effects on mAChR and not be a desensitizer of α7 nAChR. We show that this profile is largely met by isoarecolone. Three additional arecoline analogs were characterized. While the quaternary dimethyl analog had a broad range of activities, including activation of mAChR and muscle-type nAChR, the methyl analog only activated a range of α4* nAChR, albeit with low potency. The ethyl analog had no detectable cholinergic activity. CONCLUSIONS Evidence indicates that α4* nAChR are at the root of nicotine addiction, and this may also be the case for betel addiction. Our characterization of isoarecolone and 1-(4-methylpiperazin-1-yl) ethanone as truly selective α4*nAChR selective partial agonists with low muscarinic activity may point toward a promising new direction for the development of drugs to treat both nicotine and betel addiction. IMPLICATIONS Nearly 600 million people use Areca nut, often with tobacco. Two of the Areca alkaloids are muscarinic acetylcholine receptor agonists, and one, arecoline, is a partial agonist for the α4* nicotinic acetylcholine receptors (nAChR) associated with tobacco addiction. The profile of arecoline activity suggested its potential to be used as a scaffold for developing new tobacco cessation drugs if analogs can be identified that retain the same nicotinic receptor selectivity without muscarinic activity. We report that isoarecolone is a selective partial agonist for α4* nAChR with minimal muscarinic activity and 1-(4-methylpiperazin-1-yl) ethanone has similar nAChR selectivity and no detectable muscarinic action.
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Affiliation(s)
| | - Marta Quadri
- Department of Chemistry, University of Florida, Gainesville, FL.,Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL
| | - Clare Stokes
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL
| | - Mohammed Shoaib
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, UK
| | - Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL
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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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31
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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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Zeng SL, Sudlow LC, Berezin MY. Using Xenopus oocytes in neurological disease drug discovery. Expert Opin Drug Discov 2019; 15:39-52. [PMID: 31674217 DOI: 10.1080/17460441.2020.1682993] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Introduction: Neurological diseases present a difficult challenge in drug discovery. Many of the current treatments have limited efficiency or result in a variety of debilitating side effects. The search of new therapies is of a paramount importance, since the number of patients that require a better treatment is growing rapidly. As an in vitro model, Xenopus oocytes provide the drug developer with many distinct advantages, including size, durability, and efficiency in exogenous protein expression. However, there is an increasing need to refine the recent breakthroughs.Areas covered: This review covers the usage and recent advancements of Xenopus oocytes for drug discovery in neurological diseases from expression and functional measurement techniques to current applications in Alzheimer's disease, painful neuropathies, and amyotrophic lateral sclerosis (ALS). The existing limitations of Xenopus oocytes in drug discovery are also discussed.Expert opinion: With the rise of aging population and neurological disorders, Xenopus oocytes, will continue to play an important role in understanding the mechanism of the disease, identification and validation of novel molecular targets, and drug screening, providing high-quality data despite the technical limitations. With further advances in oocytes-related techniques toward an accurate modeling of the disease, the diagnostics and treatment of neuropathologies will be becoming increasing personalized.
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Affiliation(s)
- Steven L Zeng
- Department of Radiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Leland C Sudlow
- Department of Radiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Mikhail Y Berezin
- Department of Radiology, Washington University School of Medicine, St. Louis, MO, USA
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33
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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: 10] [Impact Index Per Article: 2.0] [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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Gulsevin A, Papke RL, Stokes C, Garai S, Thakur GA, Quadri M, Horenstein NA. Allosteric Agonism of α7 Nicotinic Acetylcholine Receptors: Receptor Modulation Outside the Orthosteric Site. Mol Pharmacol 2019; 95:606-614. [PMID: 30944209 DOI: 10.1124/mol.119.115758] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 03/24/2019] [Indexed: 12/15/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) are members of the Cys-loop superfamily of ligand-gated ion channels. Typically, channel activation follows the binding of agonists to the orthosteric binding sites of the receptor. α7 nAChRs have a very low probability of channel activation, which can be reversed by the binding of α7 selective positive allosteric modulators (PAMs) to putative sites within the transmembrane domains. Although typical PAMs, like PNU-120596, require coapplication of an orthosteric agonist to produce large channel activations, some, like GAT107 and B-973B [(S)-3-(3,4-difluorophenyl)-N-(1-(6-(4-(pyridin-2-yl)piperazin-1-yl)pyrazin-2-yl)ethyl)propanamide], are characterized as allosteric activating PAMs, which also bind to an allosteric activation (AA) site in the extracellular domain and activate the α7 ion channel by themselves. We had previously characterized N,N-diethyl-N'-phenylpiperazine analogs with various functions. In this work, we docked members of this family to a homology model of the α7 receptor extracellular domain. The compound 1,1-diethyl-4(naphthalene-2-yl)piperazin-1-ium (2NDEP) a weak partial agonist, showed particularly favorable docking and binding energies at the putative AA site of the receptor. We hypothesized that 2NDEP could couple with PAMs through the AA site. This hypothesis was tested with the α7 mutant C190A, which is not activated by orthosteric agonists but is effectively activated by GAT107. The results showed that 2NDEP acts as an allosteric agonist of α7C190A when coapplied with the PAM PNU-120596. Also, the allosteric activity was nearly abolished upon coapplication with the AA site-selective antagonist 2,3,5,6MP-TQS (cis-trans-4-(2,3,5,6-tetramethylphenyl)-3a,4,5,9b-tetrahydro-3H-cyclopenta[c]quinoline-8-sulfonamide), consistent with AA site involvement. Overall, our findings show a novel mode of agonism through an allosteric site in the extracellular domain of α7 nAChR.
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Affiliation(s)
- Alican Gulsevin
- Departments of Chemistry (A.G., M.Q., N.A.H.) and Pharmacology and Therapeutics (R.L.P, C.S., M.Q.), 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.)
| | - Roger L Papke
- Departments of Chemistry (A.G., M.Q., N.A.H.) and Pharmacology and Therapeutics (R.L.P, C.S., M.Q.), 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 Chemistry (A.G., M.Q., N.A.H.) and Pharmacology and Therapeutics (R.L.P, C.S., M.Q.), 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 Chemistry (A.G., M.Q., N.A.H.) and Pharmacology and Therapeutics (R.L.P, C.S., M.Q.), 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 Chemistry (A.G., M.Q., N.A.H.) and Pharmacology and Therapeutics (R.L.P, C.S., M.Q.), 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.)
| | - Marta Quadri
- Departments of Chemistry (A.G., M.Q., N.A.H.) and Pharmacology and Therapeutics (R.L.P, C.S., M.Q.), 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 Chemistry (A.G., M.Q., N.A.H.) and Pharmacology and Therapeutics (R.L.P, C.S., M.Q.), 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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Quadri M, Garai S, Thakur GA, Stokes C, Gulsevin A, Horenstein NA, Papke RL. Macroscopic and Microscopic Activation of α7 Nicotinic Acetylcholine Receptors by the Structurally Unrelated Allosteric Agonist-Positive Allosteric Modulators (ago-PAMs) B-973B and GAT107. Mol Pharmacol 2019; 95:43-61. [PMID: 30348894 PMCID: PMC6277926 DOI: 10.1124/mol.118.113340] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Accepted: 10/18/2018] [Indexed: 01/25/2023] Open
Abstract
B-973 is an efficacious type II positive allosteric modulator (PAM) of α7 nicotinic acetylcholine receptors that, like 4BP-TQS and its active isomer GAT107, can produce direct allosteric activation in addition to potentiation of orthosteric agonist activity, which identifies it as an allosteric activating (ago)-PAM. We compared the properties of B-973B, the active enantiomer of B-973, with those of GAT107 regarding the separation of allosteric potentiation and activation. Both ago-PAMs can strongly activate mutants of α7 that are insensitive to standard orthosteric agonists like acetylcholine. Likewise, the activity of both ago-PAMs is largely eliminated by the M254L mutation in the putative transmembrane PAM-binding site. Allosteric activation by B-973B appeared more protracted than that produced by GAT107, and B-973B responses were relatively insensitive to the noncompetitive antagonist mecamylamine compared with GAT107 responses. Similar differences are also seen in the single-channel currents. The two agents generate unique profiles of full-conductance and subconductance states, with B-973B producing protracted bursts, even in the presence of mecamylamine. Modeling and docking studies suggest that the molecular basis for these effects depends on specific interactions in both the extracellular and transmembrane domains of the receptor.
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Affiliation(s)
- Marta Quadri
- Departments of Pharmacology and Therapeutics (M.Q., C.S., R.L.P.) and Chemistry (M.Q., A.G., N.A.H.), University of Florida, Gainesville, Florida; and Department of Pharmaceutical Sciences, Northeastern University, Boston, Massachusetts (S.G., G.A.T.)
| | - Sumanta Garai
- Departments of Pharmacology and Therapeutics (M.Q., C.S., R.L.P.) and Chemistry (M.Q., A.G., N.A.H.), University of Florida, Gainesville, Florida; and Department of Pharmaceutical Sciences, Northeastern University, Boston, Massachusetts (S.G., G.A.T.)
| | - Ganesh A Thakur
- Departments of Pharmacology and Therapeutics (M.Q., C.S., R.L.P.) and Chemistry (M.Q., A.G., N.A.H.), University of Florida, Gainesville, Florida; and Department of Pharmaceutical Sciences, Northeastern University, Boston, Massachusetts (S.G., G.A.T.)
| | - Clare Stokes
- Departments of Pharmacology and Therapeutics (M.Q., C.S., R.L.P.) and Chemistry (M.Q., A.G., N.A.H.), University of Florida, Gainesville, Florida; and Department of Pharmaceutical Sciences, Northeastern University, Boston, Massachusetts (S.G., G.A.T.)
| | - Alican Gulsevin
- Departments of Pharmacology and Therapeutics (M.Q., C.S., R.L.P.) and Chemistry (M.Q., A.G., N.A.H.), University of Florida, Gainesville, Florida; and Department of Pharmaceutical Sciences, Northeastern University, Boston, Massachusetts (S.G., G.A.T.)
| | - Nicole A Horenstein
- Departments of Pharmacology and Therapeutics (M.Q., C.S., R.L.P.) and Chemistry (M.Q., A.G., N.A.H.), University of Florida, Gainesville, Florida; and Department of Pharmaceutical Sciences, Northeastern University, Boston, Massachusetts (S.G., G.A.T.)
| | - Roger L Papke
- Departments of Pharmacology and Therapeutics (M.Q., C.S., R.L.P.) and Chemistry (M.Q., A.G., N.A.H.), University of Florida, Gainesville, Florida; and Department of Pharmaceutical Sciences, Northeastern University, Boston, Massachusetts (S.G., G.A.T.)
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Novel 5-(quinuclidin-3-ylmethyl)-1,2,4-oxadiazoles to investigate the activation of the α7 nicotinic acetylcholine receptor subtype: Synthesis and electrophysiological evaluation. Eur J Med Chem 2018; 160:207-228. [PMID: 30342362 DOI: 10.1016/j.ejmech.2018.10.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 09/28/2018] [Accepted: 10/08/2018] [Indexed: 01/17/2023]
Abstract
α7 nicotinic acetylcholine receptors (nAChRs) are relevant therapeutic targets for a variety of disorders including neurodegeneration, cognitive impairment, and inflammation. Although traditionally identified as an ionotropic receptor, the α7 subtype showed metabotropic-like functions, mainly linked to the modulation of immune responses. In the present work, we investigated the structure-activity relationships in a set of novel α7 ligands incorporating the 5-(quinuclidin-3-ylmethyl)-1,2,4-oxadiazole scaffold, i.e. derivatives 21a-34a and 21b-34b, aiming to identify the structural requirements able to preferentially trigger one of the two activation modes of this receptor subtype. The new compounds were characterized as partial and silent α7 nAChR agonists in electrophysiological assays, which allowed to assess the contribution of the different groups towards the final pharmacological profile. Overall, modifications of the selected structural backbone mainly afforded partial agonists, among them tertiary bases 27a-33a, whereas additional hydrogen-bond acceptor groups in permanently charged ligands, such as 29b and 31b, favored a silent desensitizing profile at the α7 nAChR.
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Quadri M, Bagdas D, Toma W, Stokes C, Horenstein NA, Damaj MI, Papke RL. The Antinociceptive and Anti-Inflammatory Properties of the α7 nAChR Weak Partial Agonist p-CF 3 N, N-diethyl- N'-phenylpiperazine. J Pharmacol Exp Ther 2018; 367:203-214. [PMID: 30111636 DOI: 10.1124/jpet.118.249904] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Accepted: 08/13/2018] [Indexed: 12/13/2022] Open
Abstract
Chronic pain and inflammatory diseases can be regulated by complex mechanisms involving α7 nicotinic acetylcholine receptors (nAChRs), making this subtype a promising drug target for anti-inflammatory therapies. Recent evidence suggests that suchtreatment of inflammatory pain may rely on metabotropic-like rather than ionotropic activation of the α7 receptor subtype in non-neuronal cells. We previously identified para-trifluoromethyl (p-CF3) N,N-diethyl-N'-phenylpiperazinium (diEPP) iodide to be among the compounds classified as silent agonists, which are very weak α7 partial agonists that are able to induce positive allosteric modulator (PAM)-sensitive desensitization. Such drugs have been shown to selectively promote α7 ionotropic-independent functions. Therefore, we here further investigated the electrophysiological profile of p-CF3 diEPP and its in vivo antinociceptive activity using Xenopus oocytes expressing α7, α4β2, or α3β4 nAChRs. The evoked currents confirmed p-CF3 diEPP to be α7-selective with a maximal agonism 5% that of acetylcholine (ACh). Coapplication of p-CF3 diEPP with the type II PAM 4-naphthalene-1-yl-3a,4,5,9b-tetrahydro-3-H-cyclopenta[c]quinoline-8-sulfonic acid amide (TQS) produced desensitization that could be converted to PAM-potentiated currents, which at a negative holding potential were up to 13-fold greater than ACh controls. Voltage-dependence experiments indicated that channel block may limit both control ACh and TQS-potentiated responses. Although no p-CF3 diEPP agonist activity was detected for the heteromeric nAChRs, it was a noncompetitive antagonist of these receptors. The compound displayed remarkable antihyperalgesic and antiedema effects in in vivo assays. The antinociceptive activity was dose and time dependent. The anti-inflammatory components were sensitive to the α7-selective antagonist methyllycaconitine, which supports the idea that these effects are mediated by the α7 nAChR.
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Affiliation(s)
- Marta Quadri
- Departments of Pharmacology and Therapeutics (M.Q., C.S., R.L.P.) and Chemistry (M.Q., N.A.H.), University of Florida, Gainesville, Florida; and Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia (D.B., W.T., M.I.D.)
| | - Deniz Bagdas
- Departments of Pharmacology and Therapeutics (M.Q., C.S., R.L.P.) and Chemistry (M.Q., N.A.H.), University of Florida, Gainesville, Florida; and Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia (D.B., W.T., M.I.D.)
| | - Wisam Toma
- Departments of Pharmacology and Therapeutics (M.Q., C.S., R.L.P.) and Chemistry (M.Q., N.A.H.), University of Florida, Gainesville, Florida; and Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia (D.B., W.T., M.I.D.)
| | - Clare Stokes
- Departments of Pharmacology and Therapeutics (M.Q., C.S., R.L.P.) and Chemistry (M.Q., N.A.H.), University of Florida, Gainesville, Florida; and Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia (D.B., W.T., M.I.D.)
| | - Nicole A Horenstein
- Departments of Pharmacology and Therapeutics (M.Q., C.S., R.L.P.) and Chemistry (M.Q., N.A.H.), University of Florida, Gainesville, Florida; and Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia (D.B., W.T., M.I.D.)
| | - M Imad Damaj
- Departments of Pharmacology and Therapeutics (M.Q., C.S., R.L.P.) and Chemistry (M.Q., N.A.H.), University of Florida, Gainesville, Florida; and Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia (D.B., W.T., M.I.D.)
| | - Roger L Papke
- Departments of Pharmacology and Therapeutics (M.Q., C.S., R.L.P.) and Chemistry (M.Q., N.A.H.), University of Florida, Gainesville, Florida; and Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia (D.B., W.T., M.I.D.)
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Papke RL, Peng C, Kumar A, Stokes C. NS6740, an α7 nicotinic acetylcholine receptor silent agonist, disrupts hippocampal synaptic plasticity. Neurosci Lett 2018; 677:6-13. [PMID: 29679680 DOI: 10.1016/j.neulet.2018.04.025] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 03/29/2018] [Accepted: 04/16/2018] [Indexed: 01/06/2023]
Abstract
Long-term potentiation (LTP) in the dentate gyrus was previously shown to be enhanced by nicotine, an effect dependent on both homomeric α7 and heteromeric α2β2 nicotinic acetylcholine receptors (nAChR). In our experiments, bath-applied nicotine produced no significant enhancement of LTP. The α7 nAChR silent agonist NS6740, a weak activator of α7 nAChR ion channels but an effective modulator of the cholinergic anti-inflammatory pathway, decreased LTP and, additionally, produced a substantial reduction in the baseline synaptic function prior to the high frequency stimulation used to induce LTP. The effects of NS6740 on the various ligand-gated ion channels associated with the generation and modulation of dentate LTP were evaluated with receptors expressed in Xenopus oocytes. A 60 s pre-application of 5 μM NS6740 to α7 receptors blocked the response to subsequent applications of acetylcholine (ACh). In contrast, the responses of α2β2 nAChR to control applications of ACh were not significantly affected by NS6740. Likewise, responses of cells expressing GluR1 + GluR2 AMPA-type glutamate receptor subunits or GABAA α1, β2, and γ2L subunits to control agonist applications (100 μM kainic acid or 10 μM GABA, respectively), were unaffected by NS6740. The effects of NS6740 on α7 were inconsistent with simple antagonism since, while unresponsive to ACh, the receptors exposed to NS6740 were effectively activated by the positive allosteric modulator PNU-120596. The results support the hypothesis that NS6740 switches the mode of α7 signaling in a channel-independent manner that can reduce synaptic function.
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Affiliation(s)
- Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267, Gainesville, FL 32610, United States.
| | - Can Peng
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267, Gainesville, FL 32610, United States
| | - Ashok Kumar
- Department of Neuroscience, University of Florida, PO Box 100244, Gainesville, FL 32610, United States
| | - Clare Stokes
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267, Gainesville, FL 32610, United States
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Abstract
The Xenopus oocyte is a specialized single cell of colossal size (>1 mm diameter) that is highly amenable for microinjection and a stalwart model for heterologous expression. Oocytes are easily obtainable, robust in vitro, and faithfully express injected constructs. Their large size translational capacity provides a huge canvas for observing and recording integrated cellular responses-from studies of single molecules within single cells to medium-throughput drug-screening applications. Most eukaryotic promoters suffice for Xenopus expression, and the oocyte can functionally express proteins from many diverse organisms. This protocol provides a basic introduction for scientists keen to perform nuclear microinjections of cDNA constructs. These are easy methods to master, do not require elaborate equipment, and make accessible a wonderful model cell system for studying signaling, transport, cell architecture, and protein function.
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Fleischer J, Pregitzer P, Breer H, Krieger J. Access to the odor world: olfactory receptors and their role for signal transduction in insects. Cell Mol Life Sci 2018; 75:485-508. [PMID: 28828501 PMCID: PMC11105692 DOI: 10.1007/s00018-017-2627-5] [Citation(s) in RCA: 163] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Revised: 08/09/2017] [Accepted: 08/14/2017] [Indexed: 12/26/2022]
Abstract
The sense of smell enables insects to recognize and discriminate a broad range of volatile chemicals in their environment originating from prey, host plants and conspecifics. These olfactory cues are received by olfactory sensory neurons (OSNs) that relay information about food sources, oviposition sites and mates to the brain and thus elicit distinct odor-evoked behaviors. Research over the last decades has greatly advanced our knowledge concerning the molecular basis underlying the reception of odorous compounds and the mechanisms of signal transduction in OSNs. The emerging picture clearly indicates that OSNs of insects recognize odorants and pheromones by means of ligand-binding membrane proteins encoded by large and diverse families of receptor genes. In contrast, the mechanisms of the chemo-electrical transduction process are not fully understood; the present status suggests a contribution of ionotropic as well as metabotropic mechanisms. In this review, we will summarize current knowledge on the peripheral mechanisms of odor sensing in insects focusing on olfactory receptors and their specific role in the recognition and transduction of odorant and pheromone signals by OSNs.
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Affiliation(s)
- Joerg Fleischer
- Department of Animal Physiology, Institute of Biology/Zoology, Martin Luther University Halle-Wittenberg, 06120, Halle (Saale), Germany
| | - Pablo Pregitzer
- Institute of Physiology, University of Hohenheim, Stuttgart, Germany
| | - Heinz Breer
- Institute of Physiology, University of Hohenheim, Stuttgart, Germany
| | - Jürgen Krieger
- Department of Animal Physiology, Institute of Biology/Zoology, Martin Luther University Halle-Wittenberg, 06120, Halle (Saale), Germany.
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Hueffer K, Khatri S, Rideout S, Harris MB, Papke RL, Stokes C, Schulte MK. Rabies virus modifies host behaviour through a snake-toxin like region of its glycoprotein that inhibits neurotransmitter receptors in the CNS. Sci Rep 2017; 7:12818. [PMID: 28993633 PMCID: PMC5634495 DOI: 10.1038/s41598-017-12726-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Accepted: 09/13/2017] [Indexed: 01/04/2023] Open
Abstract
Rabies virus induces drastic behaviour modifications in infected hosts. The mechanisms used to achieve these changes in the host are not known. The main finding of this study is that a region in the rabies virus glycoprotein, with homologies to snake toxins, has the ability to alter behaviour in animals through inhibition of nicotinic acetylcholine receptors present in the central nervous system. This finding provides a novel aspect to virus receptor interaction and host manipulation by pathogens in general. The neurotoxin-like region of the rabies virus glycoprotein inhibited acetylcholine responses of α4β2 nicotinic receptors in vitro, as did full length ectodomain of the rabies virus glycoprotein. The same peptides significantly altered a nicotinic receptor induced behaviour in C. elegans and increased locomotor activity levels when injected into the central nervous system of mice. These results provide a mechanistic explanation for the behavioural changes in hosts infected by rabies virus.
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Affiliation(s)
- Karsten Hueffer
- Department of Veterinary Medicine, University of Alaska Fairbanks, Fairbanks, Alaska, United States of America.
| | - Shailesh Khatri
- Department of Pharmaceutical Sciences, University of the Sciences, Philadelphia, Pennsylvania, United States of America
| | - Shane Rideout
- Department of Biology and Wildlife & Institute of arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, United States of America
| | - Michael B Harris
- Department of Biology and Wildlife & Institute of arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, United States of America.,Department of Biology, California State University Long Beach, Long Beach, California, United States of America
| | - Roger L Papke
- Department of Pharmacology & Therapeutics University of Florida, Gainesville, Florida, United States of America
| | - Clare Stokes
- Department of Pharmacology & Therapeutics University of Florida, Gainesville, Florida, United States of America
| | - Marvin K Schulte
- Department of Pharmaceutical Sciences, University of the Sciences, Philadelphia, Pennsylvania, United States of America
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Papke RL, Stokes C, Damaj MI, Thakur GA, Manther K, Treinin M, Bagdas D, Kulkarni AR, Horenstein NA. Persistent activation of α7 nicotinic ACh receptors associated with stable induction of different desensitized states. Br J Pharmacol 2017; 175:1838-1854. [PMID: 28477386 DOI: 10.1111/bph.13851] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 04/25/2017] [Accepted: 05/03/2017] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND AND PURPOSE GAT107 ((3aR,4S,9bS)-4-(4-bromo-phenyl)-3a,4,5,9b-tetrahydro-3H-cyclopenta-[c]quinoline-8-sulfonamide) is a positive allosteric modulator (PAM) and agonist of α7 nicotinic acetylcholine receptors (nAChRs)that can cause a prolonged period of primed potentiation of acetylcholine responses after drug washout. NS6740 is a silent agonist of α7 nAChRs that has little or no efficacy for activating the ion channel but induces stable desensitization states, some of which can be converted into channel-active states by PAMs. Although GAT107 and NS6740 appear to stably induce different non-conducting states, both agents are effective treatment for inflammation and inflammatory pain models. We sought to better understand how both of these drugs that have opposite effects on channel activation could regulate signal transduction. EXPERIMENTAL APPROACH Voltage-clamp experiments were conducted with α7 nAChRs expressed in Xenopus oocytes. KEY RESULTS Long-lived sensitivity to a PAM or to an agonist was produced by NS6740 or GAT107 respectively. With sequential applications, these two drugs induced varying levels of persistent activation, which is a unique condition for a receptor that is known for rapid desensitization. The non-conducting states induced by NS6740 or GAT107 differ in their sensitivity to an α7 nAChR-selective antagonist and in how effectively they promote current. CONCLUSIONS & IMPLICATIONS Our data suggest that the persistent currents represent a dynamic interconversion between different stable desensitized states and the PAM-inducible conducting states. However, the similarity of NS6740 and GAT107 effects on inflammation and pain suggests that the different stable non-conducting states have common activity on signal transduction. 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)
- Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA
| | - Clare Stokes
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA
| | - M Imad Damaj
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA, USA
| | - Ganesh A Thakur
- Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, USA
| | - Khan Manther
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA
| | - Millet Treinin
- Department of Medical Neurobiology, Hadassah Medical School, Hebrew University, Jerusalem, Israel
| | - Deniz Bagdas
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA, USA.,Experimental Animals Breeding and Research Center, Faculty of Medicine, Uludag University, Bursa, Turkey
| | - Abhijit R Kulkarni
- Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, USA
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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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Horenstein NA, Papke RL, Kulkarni AR, Chaturbhuj GU, Stokes C, Manther K, Thakur GA. Critical Molecular Determinants of α7 Nicotinic Acetylcholine Receptor Allosteric Activation: SEPARATION OF DIRECT ALLOSTERIC ACTIVATION AND POSITIVE ALLOSTERIC MODULATION. J Biol Chem 2016; 291:5049-67. [PMID: 26742843 DOI: 10.1074/jbc.m115.692392] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Indexed: 01/08/2023] Open
Abstract
The α7 nicotinic acetylcholine receptors (nAChRs) are uniquely sensitive to selective positive allosteric modulators (PAMs), which increase the efficiency of channel activation to a level greater than that of other nAChRs. Although PAMs must work in concert with "orthosteric" agonists, compounds such as GAT107 ((3aR,4S,9bS)-4-(4-bromophenyl)-3a,4,5,9b-tetrahydro-3H-cyclopenta[c]quinoline-8-sulfonamide) have the combined properties of agonists and PAMs (ago-PAM) and produce very effective channel activation (direct allosteric activation (DAA)) by operating at two distinct sites in the absence of added agonist. One site is likely to be the same transmembrane site where PAMs like PNU-120596 function. We show that the other site, required for direct activation, is likely to be solvent-accessible at the extracellular domain vestibule. We identify key attributes of molecules in this family that are able to act at the DAA site through variation at the aryl ring substituent of the tetrahydroquinoline ring system and with two different classes of competitive antagonists of DAA. Analyses of molecular features of effective allosteric agonists allow us to propose a binding model for the DAA site, featuring a largely non-polar pocket accessed from the extracellular vestibule with an important role for Asp-101. This hypothesis is supported with data from site-directed mutants. Future refinement of the model and the characterization of specific GAT107 analogs will allow us to define critical structural elements that can be mapped onto the receptor surface for an improved understanding of this novel way to target α7 nAChR therapeutically.
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Affiliation(s)
- Nicole A Horenstein
- From the Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200
| | - Roger L Papke
- the Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida 32610-0267, and
| | - Abhijit R Kulkarni
- the Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts 02115
| | - Ganesh U Chaturbhuj
- the Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts 02115
| | - Clare Stokes
- the Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida 32610-0267, and
| | - Khan Manther
- the Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida 32610-0267, and
| | - Ganesh A Thakur
- the Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts 02115
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Picones A, Loza-Huerta A, Segura-Chama P, Lara-Figueroa CO. Contribution of Automated Technologies to Ion Channel Drug Discovery. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2016; 104:357-378. [DOI: 10.1016/bs.apcsb.2016.01.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Papke RL, Horenstein NA, Stokes C. Nicotinic Activity of Arecoline, the Psychoactive Element of "Betel Nuts", Suggests a Basis for Habitual Use and Anti-Inflammatory Activity. PLoS One 2015; 10:e0140907. [PMID: 26488401 PMCID: PMC4619380 DOI: 10.1371/journal.pone.0140907] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Accepted: 10/01/2015] [Indexed: 01/07/2023] Open
Abstract
Habitual chewing of "betel nut" preparations constitutes the fourth most common human self-administration of a psychoactive substance after alcohol, caffeine, and nicotine. The primary active ingredient in these preparations is arecoline, which comes from the areca nut, the key component of all such preparations. Arecoline is known to be a relatively non-selective muscarinic partial agonist, accounting for many of the overt peripheral and central nervous system effects, but not likely to account for the addictive properties of the drug. We report that arecoline has activity on select nicotinic acetylcholine receptor (nAChR) subtypes, including the two classes of nAChR most related to the addictive properties of nicotine: receptors containing α4 and β2 subunits and those which also contain α6 and β3 subunits. Arecoline is a partial agonist with about 6-10% efficacy for the α4* and α6* receptors expressed in Xenopus oocytes. Additionally, arecoline is a silent agonist of α7 nAChR; while it does not activate α7 receptors when applied alone, it produces substantial activation when co-applied with the positive allosteric modulator PNU-120696. Some α7 silent agonists are effective inhibitors of inflammation, which might account for anti-inflammatory effects of arecoline. Arecoline's activity on nAChR associated with addiction may account for the habitual use of areca nut preparations in spite of the well-documented risk to personal health associated with oral diseases and cancer. The common link between betel and tobacco suggests that partial agonist therapies with cytisine or the related compound varenicline may also be used to aid betel cessation attempts.
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Affiliation(s)
- Roger L. Papke
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267 Gainesville, Florida, 32610–0267, United States of America
| | - Nicole A. Horenstein
- Department of Chemistry, University of Florida, PO Box 117200, Gainesville, Florida, 32611–7200, United States of America
| | - Clare Stokes
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267 Gainesville, Florida, 32610–0267, United States of America
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Wang J, Kuryatov A, Sriram A, Jin Z, Kamenecka TM, Kenny PJ, Lindstrom J. An Accessory Agonist Binding Site Promotes Activation of α4β2* Nicotinic Acetylcholine Receptors. J Biol Chem 2015; 290:13907-18. [PMID: 25869137 DOI: 10.1074/jbc.m115.646786] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Indexed: 11/06/2022] Open
Abstract
Neuronal nicotinic acetylcholine receptors containing α4, β2, and sometimes other subunits (α4β2* nAChRs) regulate addictive and other behavioral effects of nicotine. These nAChRs exist in several stoichiometries, typically with two high affinity acetylcholine (ACh) binding sites at the interface of α4 and β2 subunits and a fifth accessory subunit. A third low affinity ACh binding site is formed when this accessory subunit is α4 but not if it is β2. Agonists selective for the accessory ACh site, such as 3-[3-(3-pyridyl)-1,2,4-oxadiazol-5-yl]benzonitrile (NS9283), cannot alone activate a nAChR but can facilitate more efficient activation in combination with agonists at the canonical α4β2 sites. We therefore suggest categorizing agonists according to their site selectivity. NS9283 binds to the accessory ACh binding site; thus it is termed an accessory site-selective agonist. We expressed (α4β2)2 concatamers in Xenopus oocytes with free accessory subunits to obtain defined nAChR stoichiometries and α4/accessory subunit interfaces. We show that α2, α3, α4, and α6 accessory subunits can form binding sites for ACh and NS9283 at interfaces with α4 subunits, but β2 and β4 accessory subunits cannot. To permit selective blockage of the accessory site, α4 threonine 126 located on the minus side of α4 that contributes to the accessory site, but not the α4β2 sites, was mutated to cysteine. Alkylation of this cysteine with a thioreactive reagent blocked activity of ACh and NS9283 at the accessory site. Accessory agonist binding sites are promising drug targets.
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Affiliation(s)
- Jingyi Wang
- 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
| | - Aarati Sriram
- From the Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Zhuang Jin
- Department of Molecular Therapeutics at the Scripps Research Institute, Scripps, Florida 33458, and
| | - Theodore M Kamenecka
- Department of Molecular Therapeutics at the Scripps Research Institute, Scripps, Florida 33458, and
| | - Paul J Kenny
- Department of Pharmacology and Systems Therapeutics, Icahn School of Medicine at Mount Sinai, New York, New York 10029
| | - Jon Lindstrom
- From the Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania 19104,
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Montagné N, de Fouchier A, Newcomb RD, Jacquin-Joly E. Advances in the identification and characterization of olfactory receptors in insects. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 130:55-80. [PMID: 25623337 DOI: 10.1016/bs.pmbts.2014.11.003] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
Olfactory receptors (ORs) are the key elements of the molecular machinery responsible for the detection of odors in insects. Since their initial discovery in Drosophila melanogaster at the beginning of the twenty-first century, insect ORs have been the focus of intense research, both for fundamental knowledge of sensory systems and for their potential as novel targets for the development of products that could impact harmful behaviors of crop pests and disease vectors. In recent years, studies on insect ORs have entered the genomic era, with an ever-increasing number of OR genes being characterized every year through the sequencing of genomes and transcriptomes. With the upcoming release of genomic sequences from hundreds of insect species, the insect OR family could very well become the largest multigene family known. This extremely rapid identification of ORs in many insects is driving the necessity for the development of high-throughput technologies that will allow the identification of ligands for this unprecedented number of receptors. Moreover, such technologies will also be important for the development of agonists or antagonists that could be used in the fight against pest insects.
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Affiliation(s)
- Nicolas Montagné
- Institute of Ecology & Environmental Sciences of Paris, UPMC-Sorbonne Universités, Paris, France
| | - Arthur de Fouchier
- Institute of Ecology & Environmental Sciences of Paris, INRA, Versailles, France
| | - Richard D Newcomb
- School of Biological Sciences, University of Auckland, Auckland, New Zealand; The New Zealand Institute for Plant & Food Research Limited, Auckland, New Zealand
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Papke RL, Bagdas D, Kulkarni AR, Gould T, AlSharari SD, Thakur GA, Damaj MI. The analgesic-like properties of the alpha7 nAChR silent agonist NS6740 is associated with non-conducting conformations of the receptor. Neuropharmacology 2014; 91:34-42. [PMID: 25497451 DOI: 10.1016/j.neuropharm.2014.12.002] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Revised: 11/09/2014] [Accepted: 12/02/2014] [Indexed: 01/28/2023]
Abstract
The α7 nicotinic acetylcholine receptor (nAChR) is a promising drug target for a number of neurological disorders including chronic pain and inflammatory diseases. Since α7 can function as a ligand-gated ion channel, drug development initially focused on ligands that were selective activators of the α7 ion channel. However, the best α7 drugs for chronic pain and inflammation indications may not be ion channel activators but rather "silent agonists", which bind to the receptor but preferentially induce non-conducting states that modulate signal transduction in non-neuronal cells. One such compound is NS6740. We show that NS6740 selectively induces prolonged desensitization of α7 nAChRs. There are two forms of α7 desensitization that can be distinguished by their sensitivity to the positive allosteric modulators (PAMs). At high concentrations, NS6740 preferentially induces PAM-insensitive desensitization, which over the course of several minutes reverts to the sensitive form. NS6740 was tested in several pain models after in vivo administration in the mouse. Although it had no effects in acute thermal pain, NS6740 induced significant dose- and time-dependent antinociceptive activity in formalin- and acetic acid-induced nociceptive behaviors as well as in the chronic constrictive nerve injury (CCI) model for neuropathic pain. The antinociceptive activity of NS6740 in these models was α7-dependent. In addition, NS6740 administration reversed pain-induced aversion, an important affective component of pain. The time and concentration dependence of the effects were consistent with NS6740 induction of PAM-insensitive non-conducting states, suggesting that signal transduction required for analgesia is accomplished by α7 receptors in that conformation.
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Affiliation(s)
- Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267, Gainesville, FL 32610-0267, USA
| | - Deniz Bagdas
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA 23298-0613, USA; Experimental Animals Breeding and Research Center, Faculty of Medicine, Uludag University, Bursa, 16059, Turkey.
| | - Abhijit R Kulkarni
- Department of Pharmaceutical Sciences & Center for Drug Discovery, Northeastern University, Boston, MA 02115, USA
| | - Timothy Gould
- Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL 32611-7200, USA
| | - Shakir D AlSharari
- Department of Pharmacology and Toxicology, College of Pharmacy, King Saud University, Kingdom of Saudi Arabia
| | - Ganesh A Thakur
- Department of Pharmaceutical Sciences & Center for Drug Discovery, Northeastern University, Boston, MA 02115, USA
| | - M Imad Damaj
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA 23298-0613, USA
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Ponzoni L, Braida D, Pucci L, Andrea D, Fasoli F, Manfredi I, Papke RL, Stokes C, Cannazza G, Clementi F, Gotti C, Sala M. The cytisine derivatives, CC4 and CC26, reduce nicotine-induced conditioned place preference in zebrafish by acting on heteromeric neuronal nicotinic acetylcholine receptors. Psychopharmacology (Berl) 2014; 231:4681-93. [PMID: 24862365 DOI: 10.1007/s00213-014-3619-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Accepted: 05/12/2014] [Indexed: 12/22/2022]
Abstract
RATIONALE Cigarette smoking is one of the most serious health problems worldwide and people trying to stop smoking have high rates of relapse. Zebrafish (Danio rerio), by combining pharmacological and behavioral assays, is a promising animal model for rapidly screening new compounds to induce smoking cessation. OBJECTIVES This study aims to identify possible acetylcholine nicotinic receptors (nAChRs) involved in mediating nicotine (NIC)-induced conditioned place preference (CPP) in zebrafish and investigate the effect of the CC4 and CC26 cytisine derivatives in reducing NIC-induced CPP. METHODS CPP was evaluated using a two-compartment chamber, and the zebrafish were given CC4 (0.001-5 mg/kg), CC26 (0.001-1 mg/kg), cytisine (0.1-2.5 mg/kg), and varenicline (1-10 mg/kg) alone or with NIC (0.001 mg/kg). Swimming activity was evaluated using a square observational chamber. The affinity of the nicotinic ligands for native zebrafish brain nAChRs was evaluated by binding studies using [(3)H]-Epibatidine (Epi) and [(125)I]-αBungarotoxin (αBgtx) radioligands, and their subtype specificity was determined by means of electrophysiological assay of oocyte-expressed α4β2 and α7 subtypes. RESULTS CC4 and CC26 induced CPP with an inverted U-shaped dose-response curve similar to that of NIC. However, when co-administered with NIC, they blocked its reinforcing or slightly aversive effect. Binding and electrophysiological studies showed that this effect was due to binding to high-affinity heteromeric but not α7-containing receptors. CONCLUSIONS We have further characterized CC4 and identified a new compound (CC26) that may be active in inducing smoking cessation. Zebrafish is a very useful model for screening new compounds that can affect the rewarding properties of NIC.
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Affiliation(s)
- Luisa Ponzoni
- Dipartimento di Biotecnologie Mediche e Medicina Traslazionale, Università degli Studi di Milano, Milan, Italy
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