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Recent Advances in the Discovery of Nicotinic Acetylcholine Receptor Allosteric Modulators. Molecules 2023; 28:molecules28031270. [PMID: 36770942 PMCID: PMC9920195 DOI: 10.3390/molecules28031270] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 01/18/2023] [Accepted: 01/26/2023] [Indexed: 01/31/2023] Open
Abstract
Positive allosteric modulators (PAMs), negative allosteric modulators (NAMs), silent agonists, allosteric activating PAMs and neutral or silent allosteric modulators are compounds capable of modulating the nicotinic receptor by interacting at allosteric modulatory sites distinct from the orthosteric sites. This survey is focused on the compounds that have been shown or have been designed to interact with nicotinic receptors as allosteric modulators of different subtypes, mainly α7 and α4β2. Minimal chemical changes can cause a different pharmacological profile, which can then lead to the design of selective modulators. Experimental evidence supports the use of allosteric modulators as therapeutic tools for neurological and non-neurological conditions.
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Moerke MJ, McMahon LR, Wilkerson JL. More than Smoke and Patches: The Quest for Pharmacotherapies to Treat Tobacco Use Disorder. Pharmacol Rev 2020; 72:527-557. [PMID: 32205338 DOI: 10.1124/pr.119.018028] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Tobacco use is a persistent public health issue. It kills up to half its users and is the cause of nearly 90% of all lung cancers. The main psychoactive component of tobacco is nicotine, primarily responsible for its abuse-related effects. Accordingly, most pharmacotherapies for smoking cessation target nicotinic acetylcholine receptors (nAChRs), nicotine's major site of action in the brain. The goal of the current review is twofold: first, to provide a brief overview of the most commonly used behavioral procedures for evaluating smoking cessation pharmacotherapies and an introduction to pharmacokinetic and pharmacodynamic properties of nicotine important for consideration in the development of new pharmacotherapies; and second, to discuss current and potential future pharmacological interventions aimed at decreasing tobacco use. Attention will focus on the potential for allosteric modulators of nAChRs to offer an improvement over currently approved pharmacotherapies. Additionally, given increasing public concern for the potential health consequences of using electronic nicotine delivery systems, which allow users to inhale aerosolized solutions as an alternative to smoking tobacco, an effort will be made throughout this review to address the implications of this relatively new form of nicotine delivery, specifically as it relates to smoking cessation. SIGNIFICANCE STATEMENT: Despite decades of research that have vastly improved our understanding of nicotine and its effects on the body, only a handful of pharmacotherapies have been successfully developed for use in smoking cessation. Thus, investigation of alternative pharmacological strategies for treating tobacco use disorder remains active; allosteric modulators of nicotinic acetylcholine receptors represent one class of compounds currently under development for this purpose.
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Affiliation(s)
- M J Moerke
- Division of Preclinical Pharmacology, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland (M.J.M.) and Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, Florida (L.R.M., J.L.W.)
| | - L R McMahon
- Division of Preclinical Pharmacology, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland (M.J.M.) and Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, Florida (L.R.M., J.L.W.)
| | - J L Wilkerson
- Division of Preclinical Pharmacology, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland (M.J.M.) and Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, Florida (L.R.M., J.L.W.)
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Allosterism of Nicotinic Acetylcholine Receptors: Therapeutic Potential for Neuroinflammation Underlying Brain Trauma and Degenerative Disorders. Int J Mol Sci 2020; 21:ijms21144918. [PMID: 32664647 PMCID: PMC7404387 DOI: 10.3390/ijms21144918] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 07/06/2020] [Accepted: 07/10/2020] [Indexed: 12/21/2022] Open
Abstract
Inflammation is a key physiological phenomenon that can be pervasive when dysregulated. Persistent chronic inflammation precedes several pathophysiological conditions forming one of the critical cellular homeostatic checkpoints. With a steady global surge in inflammatory diseases, it is imperative to delineate underlying mechanisms and design suitable drug molecules targeting the cellular partners that mediate and regulate inflammation. Nicotinic acetylcholine receptors have a confirmed role in influencing inflammatory pathways and have been a subject of scientific scrutiny underlying drug development in recent years. Drugs designed to target allosteric sites on the nicotinic acetylcholine receptors present a unique opportunity to unravel the role of the cholinergic system in regulating and restoring inflammatory homeostasis. Such a therapeutic approach holds promise in treating several inflammatory conditions and diseases with inflammation as an underlying pathology. Here, we briefly describe the potential of cholinergic allosterism and some allosteric modulators as a promising therapeutic option for the treatment of neuroinflammation.
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Dukat M, Jain A, German N, Ferrara-Pontoriero R, Huang Y, Ma Y, Schulte MK, Glennon RA. des-Formylflustrabromine (dFBr): A Structure-Activity Study on Its Ability To Potentiate the Action of Acetylcholine at α4β2 Nicotinic Acetylcholine Receptors. ACS Chem Neurosci 2018; 9:2984-2996. [PMID: 30028943 DOI: 10.1021/acschemneuro.8b00156] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The naturally occurring indole alkaloid des-formylflustrabromine (dFBr; 1) is one of the first agents shown to act as a selective positive allosteric modulator (PAM) at α4β2 nicotinic acetylcholine receptors (nAChRs). We previously deconstructed this agent to determine which of its structural features contribute to its actions and have identified an agent that might serve as the basis for a " working pharmacophore". Here, we elaborate the dFBr (1; EC50 = 0.2 μM) structure to identify how various structural modifications impact its actions. Electrophysiological studies with Xenopus laevis oocytes identified several compounds with dFBr-like potency and one, the 5-bromo analogue of 1 (i.e., 5-bromo dFBr; 25; EC50 = 0.4 μM), with more than twice the efficacy of 1 as a PAM at α4β2 nAChRs.
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Affiliation(s)
- Małgorzata Dukat
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia 23298-0540, United States
| | - Atul Jain
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia 23298-0540, United States
| | - Nadezhda German
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia 23298-0540, United States
| | - Rossana Ferrara-Pontoriero
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia 23298-0540, United States
| | - Yanzhou Huang
- Department of Pharmaceutical Sciences, Philadelphia College of Pharmacy, University of the Sciences, 600 S 43rd Street, Philadelphia, Pennsylvania 19104-4495, United States
| | - Yilong Ma
- Institute of Arctic Biology, Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, Alaska 99775-7000, United States
| | - Marvin K. Schulte
- Department of Pharmaceutical Sciences, Philadelphia College of Pharmacy, University of the Sciences, 600 S 43rd Street, Philadelphia, Pennsylvania 19104-4495, United States
| | - Richard A. Glennon
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia 23298-0540, United States
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Depping R, Seeger K. 1H-NMR spectroscopy shows cellular uptake of HEPES buffer by human cell lines-an effect to be considered in cell culture experiments. Anal Bioanal Chem 2018; 411:797-802. [PMID: 30506504 DOI: 10.1007/s00216-018-1518-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Revised: 11/06/2018] [Accepted: 11/26/2018] [Indexed: 11/27/2022]
Abstract
HEPES is commonly used in cell culture media as a buffering substance. Compared to the bicarbonate/CO2 buffer system, it does not require a CO2 atmosphere, thereby ensuring stable pH values during handling of cell culture media outside of an incubator. Due to its intrinsic charge, HEPES is considered not to be taken up by cells, which was a prerequisite during buffer development for cell culture by Good and colleagues. However, during the last years, evidence has emerged that HEPES seems to be taken up into cells and that it has major effects on cellular functions. Investigating three different cell lines (MCF-7, U2OS, HeLa) showed that all of them accommodated HEPES-containing medium, i.e., they survive and proliferate in the presence of HEPES. Determination of intracellular metabolites revealed the presence of HEPES for all cell lines. Further analysis of MCF-7 cells showed that even 48 h after medium exchange from HEPES-containing medium to HEPES-free medium, intracellular HEPES could still be detected. Thus, contrary to the common view, HEPES is taken up by cells which should be taken into consideration for studies of specific cellular functions. Graphical abstract ᅟ.
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Affiliation(s)
- Reinhard Depping
- Institute of Physiology, University of Lübeck, Ratzeburger Allee 160, 23562, Lübeck, Germany
| | - Karsten Seeger
- Institute of Chemistry and Metabolomics, University of Lübeck, Ratzeburger Allee 160, 23562, Lübeck, Germany.
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Wang J, Lindstrom J. Orthosteric and allosteric potentiation of heteromeric neuronal nicotinic acetylcholine receptors. Br J Pharmacol 2017; 175:1805-1821. [PMID: 28199738 DOI: 10.1111/bph.13745] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 01/30/2017] [Accepted: 02/06/2017] [Indexed: 12/16/2022] Open
Abstract
Heteromeric nicotinic ACh receptors (nAChRs) were thought to have two orthodox agonist-binding sites at two α/β subunit interfaces. Highly selective ligands are hard to develop by targeting orthodox agonist sites because of high sequence similarity of this binding pocket among different subunits. Recently, unorthodox ACh-binding sites have been discovered at some α/α and β/α subunit interfaces, such as α4/α4, α5/α4 and β3/α4. Targeting unorthodox sites may yield subtype-selective ligands, such as those for (α4β2)2 α5, (α4β2)2 β3 and (α6β2)2 β3 nAChRs. The unorthodox sites have unique pharmacology. Agonist binding at one unorthodox site is not sufficient to activate nAChRs, but it increases activation from the orthodox sites. NS9283, a selective agonist for the unorthodox α4/α4 site, was initially thought to be a positive allosteric modulator (PAM). NS9283 activates nAChRs with three engineered α4/α4 sites. PAMs, on the other hand, act at allosteric sites where ACh cannot bind. Known PAM sites include the ACh-homologous non-canonical site (e.g. morantel at β/α), the C-terminus (e.g. Br-PBTC and 17β-estradiol), a transmembrane domain (e.g. LY2087101) or extracellular and transmembrane domain interfaces (e.g. NS206). Some of these PAMs, such as Br-PBTC and 17β-estradiol, require only one subunit to potentiate activation of nAChRs. In this review, we will discuss differences between activation from orthosteric and allosteric sites, their selective ligands and clinical implications. These studies have advanced understanding of the structure, assembly and pharmacology of heteromeric neuronal nAChRs. 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)
- Jingyi Wang
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, Austin, TX, USA
| | - Jon Lindstrom
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
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Alcaino C, Musgaard M, Minguez T, Mazzaferro S, Faundez M, Iturriaga-Vasquez P, Biggin PC, Bermudez I. Role of the Cys Loop and Transmembrane Domain in the Allosteric Modulation of α4β2 Nicotinic Acetylcholine Receptors. J Biol Chem 2016; 292:551-562. [PMID: 27864368 DOI: 10.1074/jbc.m116.751206] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2016] [Revised: 11/04/2016] [Indexed: 11/06/2022] Open
Abstract
Allosteric modulators of pentameric ligand-gated ion channels are thought to act on elements of the pathways that couple agonist binding to channel gating. Using α4β2 nicotinic acetylcholine receptors and the α4β2-selective positive modulators 17β-estradiol (βEST) and desformylflustrabromine (dFBr), we have identified pathways that link the binding sites for these modulators to the Cys loop, a region that is critical for channel gating in all pentameric ligand-gated ion channels. Previous studies have shown that the binding site for potentiating βEST is in the C-terminal (post-M4) region of the α4 subunit. Here, using homology modeling in combination with mutagenesis and electrophysiology, we identified the binding site for potentiating dFBr on the top half of a cavity between the third (M3) and fourth transmembrane (M4) α-helices of the α4 subunit. We found that the binding sites for βEST and dFBr communicate with the Cys loop, through interactions between the last residue of post-M4 and Phe170 of the conserved FPF sequence of the Cys loop, and that these interactions affect potentiating efficacy. In addition, interactions between a residue in M3 (Tyr309) and Phe167, a residue adjacent to the Cys loop FPF motif, also affect dFBr potentiating efficacy. Thus, the Cys loop acts as a key control element in the allosteric transduction pathway for potentiating βEST and dFBr. Overall, we propose that positive allosteric modulators that bind the M3-M4 cavity or post-M4 region increase the efficacy of channel gating through interactions with the Cys loop.
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Affiliation(s)
- Constanza Alcaino
- From the Department of Biological and Medical Sciences, Oxford Brookes University, Oxford OX3 0BP, United Kingdom
| | - Maria Musgaard
- the Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Teresa Minguez
- From the Department of Biological and Medical Sciences, Oxford Brookes University, Oxford OX3 0BP, United Kingdom
| | - Simone Mazzaferro
- From the Department of Biological and Medical Sciences, Oxford Brookes University, Oxford OX3 0BP, United Kingdom
| | - Manuel Faundez
- the Faculty of Sciences, University of Chile, Santiago 7800003, Chile, and
| | - Patricio Iturriaga-Vasquez
- the Departamento de Ciencias Quimicas y Recursos Naturales, Facultad de Ingenieria y Ciencias, Universidad de la Frontera, Temuco 4811230, Chile
| | - Philip C Biggin
- the Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Isabel Bermudez
- From the Department of Biological and Medical Sciences, Oxford Brookes University, Oxford OX3 0BP, United Kingdom,
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8
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Allosteric modulation of nicotinic acetylcholine receptors. Biochem Pharmacol 2015; 97:408-417. [PMID: 26231943 DOI: 10.1016/j.bcp.2015.07.028] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 07/24/2015] [Indexed: 12/12/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are receptors for the neurotransmitter acetylcholine and are members of the 'Cys-loop' family of pentameric ligand-gated ion channels (LGICs). Acetylcholine binds in the receptor extracellular domain at the interface between two subunits and research has identified a large number of nAChR-selective ligands, including agonists and competitive antagonists, that bind at the same site as acetylcholine (commonly referred to as the orthosteric binding site). In addition, more recent research has identified ligands that are able to modulate nAChR function by binding to sites that are distinct from the binding site for acetylcholine, including sites located in the transmembrane domain. These include positive allosteric modulators (PAMs), negative allosteric modulators (NAMs), silent allosteric modulators (SAMs) and compounds that are able to activate nAChRs via an allosteric binding site (allosteric agonists). Our aim in this article is to review important aspects of the pharmacological diversity of nAChR allosteric modulators and to describe recent evidence aimed at identifying binding sites for allosteric modulators on nAChRs.
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Weltzin MM, Schulte MK. Desformylflustrabromine Modulates α4β2 Neuronal Nicotinic Acetylcholine Receptor High- and Low-Sensitivity Isoforms at Allosteric Clefts Containing the β2 Subunit. J Pharmacol Exp Ther 2015; 354:184-94. [PMID: 26025967 DOI: 10.1124/jpet.115.223933] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Accepted: 05/22/2015] [Indexed: 12/13/2022] Open
Abstract
Alterations in expression patterns of α4β2 nicotinic acetylcholine receptors have been demonstrated to alter cholinergic neurotransmission and are implicated in neurologic disorders, including autism, nicotine addiction, Alzheimer's disease, and Parkinson's disease. Positive allosteric modulators (PAMs) represent promising new leads in the development of therapeutic agents for the treatment of these disorders. This study investigates the involvement of the β2-containing subunit interfaces of α4β2 receptors in the modulation of acetylcholine (ACh)-induced responses by the PAM desformylflustrabromine (dFBr). Eight amino acids on the principal face of the β2 subunit were mutated to alanine to explore the involvement of this region in the potentiation of ACh-induced currents by dFBr. ACh-induced responses obtained from wild-type and mutant α4β2 receptors expressed in Xenopus laevis oocytes were recorded in the presence and absence of dFBr using two-electrode voltage clamp electrophysiology. Wild-type and mutant receptors were expressed in both high and low ACh sensitivity isoforms by using biased injection ratios of 1:5 or 5:1 α4 to β2 complementary RNA. Mutations were made in the B, C, and A loops of the principal face of the β2 subunit, which are regions not involved in the binding of ACh. Mutant β2(Y120A) significantly eliminated dFBr potency in both isoform preparations. Several other mutations altered dFBr potentiation levels in both preparations. Our findings support the involvement of the principal face of the β2 subunit in dFBr modulation of ACh-induced responses. Findings from this study will aid in the improved design of dFBr-like PAMs for potential therapeutic use.
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Affiliation(s)
- Maegan M Weltzin
- Division of Neurobiology, Barrow Neurologic Institute, Phoenix, Arizona (M.M.W.); and Department of Pharmaceutical Science, Philadelphia College of Pharmacy, University of the Sciences, Philadelphia, Pennsylvania (M.K.S.)
| | - Marvin K Schulte
- Division of Neurobiology, Barrow Neurologic Institute, Phoenix, Arizona (M.M.W.); and Department of Pharmaceutical Science, Philadelphia College of Pharmacy, University of the Sciences, Philadelphia, Pennsylvania (M.K.S.)
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Grupe M, Grunnet M, Bastlund JF, Jensen AA. Targeting α4β2 Nicotinic Acetylcholine Receptors in Central Nervous System Disorders: Perspectives on Positive Allosteric Modulation as a Therapeutic Approach. Basic Clin Pharmacol Toxicol 2014; 116:187-200. [DOI: 10.1111/bcpt.12361] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Accepted: 11/24/2014] [Indexed: 12/11/2022]
Affiliation(s)
- Morten Grupe
- Synaptic Transmission; H. Lundbeck A/S; Valby Denmark
| | - Morten Grunnet
- Synaptic Transmission; H. Lundbeck A/S; Valby Denmark
- Department of Drug Design and Pharmacology; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen Denmark
| | | | - Anders A. Jensen
- Department of Drug Design and Pharmacology; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen Denmark
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