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Appiani R, Viscarra F, Biggin PC, Bermudez I, Giraudo A, Pallavicini M, Bolchi C. Selective Potentiation of the (α4) 3(β2) 2 Nicotinic Acetylcholine Receptor Response by NS9283 Analogues. ACS Chem Neurosci 2024; 15:1501-1514. [PMID: 38511291 DOI: 10.1021/acschemneuro.3c00797] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/22/2024] Open
Abstract
NS9283, 3-(3-pyridyl)-5-(3-cyanophenyl)-1,2,4-oxadiazole, is a selective positive allosteric modulator of (α4)3(β2)2 nicotinic acetylcholine receptors (nAChRs). It has good subtype selective therapeutic potential afforded by its specific binding to the unique α4-α4 subunit interface present in the (α4)3(β2)2 nAChR. However, there is currently a lack of structure activity relationship (SAR) studies aimed at developing a class of congeners endowed with the same profile of activity that can help consolidate the druggability of the α4-α4 subunit interface. In this study, new NS9283 analogues were designed, synthesized, and characterized for their ability to selectively potentiate the ACh activity at heterologous (α4)3(β2)2 nAChRs vs nAChR subtypes (α4)2(β2)3, α5α4β2, and α7. With few exceptions, all the NS9283 analogues exerted positive modulation of the (α4)3(β2)2 nAChR ACh-evoked responses. Above all, those modified at the 3-cyanophenyl moiety by replacement with 3-nitrophenyl (4), 4-cyanophenyl (10), and N-formyl-4-piperidinyl (20) showed the same efficacy as NS9283, although with lower potency. Molecular dynamics simulations of NS9283 and some selected analogues highlighted consistency between potentiation activity and pose of the ligand inside the α4-α4 site with the main interaction being with the complementary (-) side and induction of a significant conformational change of the Trp156 residue in the principal (+) side.
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Affiliation(s)
- Rebecca Appiani
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, via Mangiagalli 25, Milano I-20133, Italy
| | - Franco Viscarra
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford OX3 0BP, United Kingdom
- Structural Bioinformatics and Computational Biochemistry Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Philip C Biggin
- Structural Bioinformatics and Computational Biochemistry Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Isabel Bermudez
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford OX3 0BP, United Kingdom
| | - Alessandro Giraudo
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, via Mangiagalli 25, Milano I-20133, Italy
| | - Marco Pallavicini
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, via Mangiagalli 25, Milano I-20133, Italy
| | - Cristiano Bolchi
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, via Mangiagalli 25, Milano I-20133, Italy
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Son L, Kost V, Maiorov V, Sukhov D, Arkhangelskaya P, Ivanov I, Kudryavtsev D, Siniavin A, Utkin Y, Kasheverov I. Efficient Expression in Leishmania tarentolae (LEXSY) of the Receptor-Binding Domain of the SARS-CoV-2 S-Protein and the Acetylcholine-Binding Protein from Lymnaea stagnalis. Molecules 2024; 29:943. [PMID: 38474455 DOI: 10.3390/molecules29050943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Revised: 01/31/2024] [Accepted: 02/15/2024] [Indexed: 03/14/2024] Open
Abstract
Leishmania tarentolae (LEXSY) system is an inexpensive and effective expression approach for various research and medical purposes. The stated advantages of this system are the possibility of obtaining the soluble product in the cytoplasm, a high probability of correct protein folding with a full range of post-translational modifications (including uniform glycosylation), and the possibility of expressing multi-subunit proteins. In this paper, a LEXSY expression system has been employed for obtaining the receptor binding domain (RBD) of the spike-protein of the SARS-CoV-2 virus and the homopentameric acetylcholine-binding protein (AChBP) from Lymnaea stagnalis. RBD is actively used to obtain antibodies against the virus and in various scientific studies on the molecular mechanisms of the interaction of the virus with host cell targets. AChBP represents an excellent structural model of the ligand-binding extracellular domain of all subtypes of nicotinic acetylcholine receptors (nAChRs). Both products were obtained in a soluble glycosylated form, and their structural and functional characteristics were compared with those previously described.
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Affiliation(s)
- Lina Son
- Department of Molecular Bases of Neuroimmune Signaling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
| | - Vladimir Kost
- Department of Molecular Bases of Neuroimmune Signaling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
| | - Valery Maiorov
- Department of Molecular Bases of Neuroimmune Signaling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
| | - Dmitry Sukhov
- Department of Molecular Bases of Neuroimmune Signaling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
| | - Polina Arkhangelskaya
- Department of Molecular Bases of Neuroimmune Signaling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
| | - Igor Ivanov
- Department of Molecular Bases of Neuroimmune Signaling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
| | - Denis Kudryavtsev
- Department of Molecular Bases of Neuroimmune Signaling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
| | - Andrei Siniavin
- Department of Molecular Bases of Neuroimmune Signaling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
- Ivanovsky Institute of Virology, N.F. Gamaleya National Research Center for Epidemiology and Microbiology, Ministry of Health of the Russian Federation, 123098 Moscow, Russia
| | - Yuri Utkin
- Department of Molecular Bases of Neuroimmune Signaling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
| | - Igor Kasheverov
- Department of Molecular Bases of Neuroimmune Signaling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
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Zhou L, Dau V, Jensen AA. Discovery of a Novel Class of Benzimidazole-Based Nicotinic Acetylcholine Receptor Modulators: Positive and Negative Modulation Arising from Overlapping Allosteric Sites. J Med Chem 2023; 66:12586-12601. [PMID: 37650525 DOI: 10.1021/acs.jmedchem.3c01185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Abstract
Here, we present the discovery of a novel class of benzimidazole-based allosteric modulators of nicotinic acetylcholine receptors (nAChRs). The modulators were developed based on a compound (1) exhibiting positive modulatory activity at α4β2 nAChR in a compound library screening by functional characterization of 100 analogues of 1 at nAChRs. Two distinct series of positive and negative allosteric modulators (PAMs and NAMs, respectively) comprising benzimidazole as a shared structural moiety emerged from this SAR study. The PAMs mediated weak modulation of α4β2 and α6β2β3, whereas the NAMs exhibited essentially equipotent inhibition of α4β2, α6β2β3, α6β4β3, and α3β4 nAChRs, with analogue 9j [2-(2,4-dichlorophenoxy)-1,3-dimethyl-1-H-benzo[d]imidazole-3-ium] displaying high-nanomolar and low-micromolar IC50 values at the β2- and β4-containing receptor subtypes, respectively. We propose that the PAMs and NAMs act through overlapping sites in the nAChR, and these findings thus underline the heterogenous modes of modulation that can arise from a shared allosteric site in the receptor.
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Affiliation(s)
- Libin Zhou
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen Ø, Denmark
| | - Vidan Dau
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen Ø, Denmark
| | - Anders A Jensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen Ø, Denmark
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Xanomeline restores endogenous nicotinic acetylcholine receptor signaling in mouse prefrontal cortex. Neuropsychopharmacology 2023; 48:671-682. [PMID: 36635596 PMCID: PMC9938126 DOI: 10.1038/s41386-023-01531-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 12/20/2022] [Accepted: 12/31/2022] [Indexed: 01/13/2023]
Abstract
Cholinergic synapses in prefrontal cortex are vital for attention, but this modulatory system undergoes substantial pre- and post-synaptic alterations during adulthood. To examine the integrated impact of these changes, we optophysiologically probe cholinergic synapses ex vivo, revealing a clear decline in neurotransmission in middle adulthood. Pharmacological dissection of synaptic components reveals a selective reduction in postsynaptic nicotinic receptor currents. Other components of cholinergic synapses appear stable, by contrast, including acetylcholine autoinhibition, metabolism, and excitation of postsynaptic muscarinic receptors. Pursuing strategies to strengthen cholinergic neurotransmission, we find that positive allosteric modulation of nicotinic receptors with NS9283 is effective in young adults but wanes with age. To boost nicotinic receptor availability, we harness the second messenger pathways of the preserved excitatory muscarinic receptors with xanomeline. This muscarinic agonist and cognitive-enhancer restores nicotinic signaling in older mice significantly, in a muscarinic- and PKC-dependent manner. The rescued nicotinic component regains youthful sensitivity to allosteric enhancement: treatment with xanomeline and NS9283 restores cholinergic synapses in older mice to the strength, speed, and receptor mechanism of young adults. Our results reveal a new and efficient strategy to rescue age-related nicotinic signaling deficits, demonstrating a novel pathway for xanomeline to restore cognitively-essential endogenous cholinergic neurotransmission.
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Sanders VR, Sweeney A, Topf M, Millar NS. Stoichiometry-Selective Antagonism of α4β2 Nicotinic Acetylcholine Receptors by Fluoroquinolone Antibiotics. ACS Chem Neurosci 2022; 13:1805-1817. [PMID: 35657695 PMCID: PMC9204775 DOI: 10.1021/acschemneuro.2c00200] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
![]()
Quinolone antibiotics
disrupt bacterial DNA synthesis by interacting
with DNA gyrase and topoisomerase IV. However, in addition, they have
been shown to act as inhibitors of pentameric ligand-gated ion channels
such as GABAA receptors and the α7 nicotinic acetylcholine
receptor (nAChR). In the present study, we have examined the effects
of quinolone antibiotics on the human α4β2 nAChR, an important
subtype that is widely expressed in the central nervous system. A
key feature of α4β2 nAChRs is their ability to coassemble
into two distinct stoichiometries, (α4)2(β2)3 and (α4)3(β2)2, which results in differing affinities for acetylcholine.
The effects of nine quinolone antibiotics were examined on both stoichiometries
of the α4β2 receptor by two-electrode voltage-clamp recording.
All compounds exhibited significant inhibition of α4β2
nAChRs. However, all of the fluoroquinolone antibiotics examined (ciprofloxacin,
enoxacin, enrofloxacin, difloxacin, norfloxacin, pefloxacin, and sparfloxacin)
were significantly more potent inhibitors of (α4)2(β2)3 nAChRs than of (α4)3(β2)2 nAChRs. This stoichiometry-selective effect was most pronounced
with pefloxacin, which inhibited (α4)2(β2)3 nAChRs with an IC50 of 26.4 ± 3.4 μM
but displayed no significant inhibition of (α4)3(β2)2 nAChRs. In contrast, two nonfluorinated quinolone antibiotics
(cinoxacin and oxolinic acid) exhibited no selectivity in their inhibition
of the two stoichiometries of α4β2. Computational docking
studies suggest that pefloxacin interacts selectively with an allosteric
transmembrane site at the β2(+)/β2(−) subunit interface,
which is consistent with its selective inhibition of (α4)2(β2)3. These findings concerning the antagonist
effects of fluoroquinolones provide further evidence that differences
in the subunit stoichiometry of heteromeric nAChRs can result in substantial
differences in pharmacological properties.
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Affiliation(s)
- Victoria R. Sanders
- Division of Biosciences, University College London, London WC1E 6BT, United Kingdom
| | - Aaron Sweeney
- Institute of Structural and Molecular Biology, Birkbeck College, London WC1E 7HX, United Kingdom
| | - Maya Topf
- Institute of Structural and Molecular Biology, Birkbeck College, London WC1E 7HX, United Kingdom
| | - Neil S. Millar
- Division of Biosciences, University College London, London WC1E 6BT, United Kingdom
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Deba F, Munoz K, Peredia E, Akk G, Hamouda AK. Assessing potentiation of the (α4)3(β2)2 nicotinic acetylcholine receptor by the allosteric agonist CMPI. J Biol Chem 2021; 298:101455. [PMID: 34861241 PMCID: PMC8715118 DOI: 10.1016/j.jbc.2021.101455] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 11/20/2021] [Accepted: 11/29/2021] [Indexed: 12/11/2022] Open
Abstract
The extracellular domain of the nicotinic acetylcholine receptor isoforms formed by three α4 and two β2 subunits ((α4)3(β2)2 nAChR) harbors two high-affinity “canonical” acetylcholine (ACh)-binding sites located in the two α4:β2 intersubunit interfaces and a low-affinity “noncanonical” ACh-binding site located in the α4:α4 intersubunit interface. In this study, we used ACh, cytisine, and nicotine (which bind at both the α4:α4 and α4:β2 interfaces), TC-2559 (which binds at the α4:β2 but not at the α4:α4 interface), and 3-(2-chlorophenyl)-5-(5-methyl-1-(piperidin-4-yl)-1H-pyrrazol-4-yl)isoxazole (CMPI, which binds at the α4:α4 but not at the α4:β2 interface), to investigate the binding and gating properties of CMPI at the α4:α4 interface. We recorded whole-cell currents from Xenopus laevis oocytes expressing (α4)3(β2)2 nAChR in response to applications of these ligands, alone or in combination. The electrophysiological data were analyzed in the framework of a modified Monod–Wyman–Changeux allosteric activation model. We show that CMPI is a high-affinity, high-efficacy agonist at the α4:α4 binding site and that its weak direct activating effect is accounted for by its inability to productively interact with the α4:β2 sites. The data presented here enhance our understanding of the functional contributions of ligand binding at the α4:α4 subunit interface to (α4)3(β2)2 nAChR-channel gating. These findings support the potential use of α4:α4 specific ligands to increase the efficacy of the neurotransmitter ACh in conditions associated with decline in nAChRs activity in the brain.
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Affiliation(s)
- Farah Deba
- Department of Pharmaceutical Sciences, The University of Texas at Tyler, Tyler, Texas, USA
| | - Kemburli Munoz
- Department of Pharmaceutical Sciences, Texas A&M HSC, Kingsville, Texas, USA
| | - Eloisa Peredia
- Department of Pharmaceutical Sciences, The University of Texas at Tyler, Tyler, Texas, USA
| | - Gustav Akk
- Department of Anesthesiology, Washington University in St. Louis, St. Louis, Missouri, USA; The Taylor Family Institute for Innovative Psychiatric Research, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Ayman K Hamouda
- Department of Pharmaceutical Sciences, The University of Texas at Tyler, Tyler, Texas, USA.
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Prevost MS, Bouchenaki H, Barilone N, Gielen M, Corringer PJ. Concatemers to re-investigate the role of α5 in α4β2 nicotinic receptors. Cell Mol Life Sci 2021; 78:1051-1064. [PMID: 32472188 PMCID: PMC11071962 DOI: 10.1007/s00018-020-03558-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 05/15/2020] [Accepted: 05/22/2020] [Indexed: 01/08/2023]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are pentameric ion channels expressed in the central nervous systems. nAChRs containing the α4, β2 and α5 subunits are specifically involved in addictive processes, but their functional architecture is poorly understood due to the intricacy of assembly of these subunits. Here we constrained the subunit assembly by designing fully concatenated human α4β2 and α4β2α5 receptors and characterized their properties by two-electrodes voltage-clamp electrophysiology in Xenopus oocytes. We found that α5-containing nAChRs are irreversibly blocked by methanethiosulfonate (MTS) reagents through a covalent reaction with a cysteine present only in α5. MTS-block experiments establish that the concatemers are expressed in intact form at the oocyte surface, but that reconstitution of nAChRs from loose subunits show inefficient and highly variable assembly of α5 with α4 and β2. Mutational analysis shows that the concatemers assemble both in clockwise and anticlockwise orientations, and that α5 does not contribute to ACh binding from its principal (+) site. Reinvestigation of suspected α5-ligands such as galantamine show no specific effect on α5-containing concatemers. Analysis of the α5-D398N mutation that is linked to smoking and lung cancer shows no significant effect on the electrophysiological function, suggesting that its effect might arise from alteration of other cellular processes. The concatemeric strategy provides a well-characterized platform for mechanistic analysis and screening of human α5-specific ligands.
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Affiliation(s)
- Marie S Prevost
- Unité Récepteurs-Canaux, Institut Pasteur, UMR 3571, CNRS, 75015, Paris, France
| | - Hichem Bouchenaki
- Unité Récepteurs-Canaux, Institut Pasteur, UMR 3571, CNRS, 75015, Paris, France
| | - Nathalie Barilone
- Unité Récepteurs-Canaux, Institut Pasteur, UMR 3571, CNRS, 75015, Paris, France
| | - Marc Gielen
- Unité Récepteurs-Canaux, Institut Pasteur, UMR 3571, CNRS, 75015, Paris, France.
- Sorbonne Université, 21, rue de l'école de médecine, 75006, Paris, France.
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Chrna5 is Essential for a Rapid and Protected Response to Optogenetic Release of Endogenous Acetylcholine in Prefrontal Cortex. J Neurosci 2020; 40:7255-7268. [PMID: 32817066 DOI: 10.1523/jneurosci.1128-20.2020] [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: 05/11/2020] [Revised: 08/01/2020] [Accepted: 08/09/2020] [Indexed: 12/16/2022] Open
Abstract
Optimal attention performance requires cholinergic modulation of corticothalamic neurons in the prefrontal cortex. These pyramidal cells express specialized nicotinic acetylcholine receptors containing the α5 subunit encoded by Chrna5 Disruption of this gene impairs attention, but the advantage α5 confers on endogenous cholinergic signaling is unknown. To ascertain this underlying mechanism, we used optogenetics to stimulate cholinergic afferents in prefrontal cortex brain slices from compound-transgenic wild-type and Chrna5 knock-out mice of both sexes. These electrophysiological experiments identify that Chrna5 is critical for the rapid onset of the postsynaptic cholinergic response. Loss of α5 slows cholinergic excitation and delays its peak, and these effects are observed in two different optogenetic mouse lines. Disruption of Chrna5 does not otherwise perturb the magnitude of the response, which remains strongly mediated by nicotinic receptors and tightly controlled by autoinhibition via muscarinic M2 receptors. However, when conditions are altered to promote sustained cholinergic receptor stimulation, it becomes evident that α5 also works to protect nicotinic responses against desensitization. Rescuing Chrna5 disruption thus presents the double challenge of improving the onset of nicotinic signaling without triggering desensitization. Here, we identify that an agonist for the unorthodox α-α nicotinic binding site can allosterically enhance the cholinergic pathway considered vital for attention. Treatment with NS9283 restores the rapid onset of the postsynaptic cholinergic response without triggering desensitization. Together, this work demonstrates the advantages of speed and resilience that Chrna5 confers on endogenous cholinergic signaling, defining a critical window of interest for cue detection and attentional processing.SIGNIFICANCE STATEMENT The α5 nicotinic receptor subunit (Chrna5) is important for attention, but its advantage in detecting endogenous cholinergic signals is unknown. Here, we show that α5 subunits permit rapid cholinergic responses in prefrontal cortex and protect these responses from desensitization. Our findings clarify why Chrna5 is required for optimal attentional performance under demanding conditions. To treat the deficit arising from Chrna5 disruption without triggering desensitization, we enhanced nicotinic receptor affinity using NS9283 stimulation at the unorthodox α-α nicotinic binding site. This approach successfully restored the rapid-onset kinetics of endogenous cholinergic neurotransmission. In summary, we reveal a previously unknown role of Chrna5 as well as an effective approach to compensate for genetic disruption and permit fast cholinergic excitation of prefrontal attention circuits.
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Liao VWY, Kusay AS, Balle T, Ahring PK. Heterologous expression of concatenated nicotinic ACh receptors: Pros and cons of subunit concatenation and recommendations for construct designs. Br J Pharmacol 2020; 177:4275-4295. [PMID: 32627170 DOI: 10.1111/bph.15188] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Revised: 06/15/2020] [Accepted: 06/26/2020] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND AND PURPOSE Concatenation of Cys-loop receptor subunits is a commonly used technique to ensure experimental control of receptor assembly. However, we recently demonstrated that widely used constructs did not lead to the expression of uniform pools of ternary and more complex receptors. The aim was therefore to identify viable strategies for designing concatenated constructs that would allow strict control of resultant receptor pools. EXPERIMENTAL APPROACH Concatenated dimeric, tetrameric, and pentameric α4β2-containing nicotinic ACh (nACh) receptor constructs were designed with successively shorter linker lengths and expressed in Xenopus laevis oocytes. Resulting receptor stoichiometries were investigated by functional analysis in two-electrode voltage-clamp experiments. Molecular dynamics simulations were performed to investigate potential effects of linkers on the 3D structure of concatemers. KEY RESULTS Dimeric constructs were found to be unreliable and should be avoided for expression of ternary receptors. By introducing two short linkers, we obtained efficient expression of uniform receptor pools with tetrameric and pentameric constructs. However, linkers should not be excessively short as that introduces strain on the 3D structure of concatemers. CONCLUSION AND IMPLICATIONS The data demonstrate that design of concatenated Cys-loop receptors requires a compromise between the desire for control of assembly and avoiding introduction of strain on the resulting protein. The overall best strategy was found to be pentameric constructs with carefully optimised linker lengths. Our findings will advance studies of ternary or more complex Cys-loop receptors as well as enabling detailed analysis of how pharmacological agents interact with stoichiometry-specific binding sites.
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Affiliation(s)
- Vivian Wan Yu Liao
- Brain and Mind Centre, The University of Sydney, 94 Mallett Street, Camperdown, NSW, 2050, Australia.,Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, NSW, 2006, Australia
| | - Ali Saad Kusay
- Brain and Mind Centre, The University of Sydney, 94 Mallett Street, Camperdown, NSW, 2050, Australia.,Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, NSW, 2006, Australia
| | - Thomas Balle
- Brain and Mind Centre, The University of Sydney, 94 Mallett Street, Camperdown, NSW, 2050, Australia.,Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, NSW, 2006, Australia
| | - Philip Kiaer Ahring
- Brain and Mind Centre, The University of Sydney, 94 Mallett Street, Camperdown, NSW, 2050, Australia.,Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, NSW, 2006, Australia
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10
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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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11
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Deba F, Ramos K, Vannoy M, Munoz K, Akinola LS, Damaj MI, Hamouda AK. Examining the Effects of (α4)3(β2)2 Nicotinic Acetylcholine Receptor-Selective Positive Allosteric Modulator on Acute Thermal Nociception in Rats. Molecules 2020; 25:molecules25122923. [PMID: 32630476 PMCID: PMC7355939 DOI: 10.3390/molecules25122923] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 06/19/2020] [Accepted: 06/22/2020] [Indexed: 12/14/2022] Open
Abstract
Neuronal nicotinic acetylcholine receptor (nAChR)-based therapeutics are sought as a potential alternative strategy to opioids for pain management. In this study, we examine the antinociceptive effects of 3-(2-chlorophenyl)-5-(5-methyl-1-(piperidin-4-yl)-1H-pyrazol-4-yl)isoxazole (CMPI), a novel positive allosteric modulator (PAM), with preferential selectivity to the low agonist sensitivity (α4)3(β2)2 nAChR and desformylflustrabromine (dFBr), a PAM for α4-containing nAChRs. We used hot plate and tail flick tests to measure the effect of dFBr and CMPI on the latency to acute thermal nociceptive responses in rats. Intraperitoneal injection of dFBr, but not CMPI, dose-dependently increased latency in the hot plate test. In the tail flick test, the effect achieved at the highest dFBr or CMPI dose tested was only <20% of the maximum possible effects reported for nicotine and other nicotinic agonists. Moreover, the coadministration of dFBr did not enhance the antinociceptive effect of a low dose of nicotine. Our results show that the direct acute effect of dFBr is superior to that for CMPI, indicating that selectivity to (α4)3(β2)2 nAChR is not advantageous in alleviating responses to acute thermal nociceptive stimulus. However, further studies are necessary to test the suitability of (α4)3(β2)2 nAChR-selective PAMs in chronic pain models.
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Affiliation(s)
- Farah Deba
- Department of Pharmaceutical Sciences, College of Pharmacy, The University of Texas at Tyler, Tyler, TX 75799, USA;
- Department of Pharmaceutical Sciences, College of Pharmacy, Texas A&M Health Sciences Center MS 131, 1010 W. Ave. B, Kingsville, TX 78363, USA; (K.R.); (M.V.); (K.M.)
| | - Kara Ramos
- Department of Pharmaceutical Sciences, College of Pharmacy, Texas A&M Health Sciences Center MS 131, 1010 W. Ave. B, Kingsville, TX 78363, USA; (K.R.); (M.V.); (K.M.)
| | - Matthew Vannoy
- Department of Pharmaceutical Sciences, College of Pharmacy, Texas A&M Health Sciences Center MS 131, 1010 W. Ave. B, Kingsville, TX 78363, USA; (K.R.); (M.V.); (K.M.)
| | - Kemburli Munoz
- Department of Pharmaceutical Sciences, College of Pharmacy, Texas A&M Health Sciences Center MS 131, 1010 W. Ave. B, Kingsville, TX 78363, USA; (K.R.); (M.V.); (K.M.)
| | - Lois S. Akinola
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Kontos Medical Science Building, 1217 E. Marshall St., P.O. Box 980613, Richmond, VA 23298, USA; (L.S.A.); (M.I.D.)
| | - M. Imad Damaj
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Kontos Medical Science Building, 1217 E. Marshall St., P.O. Box 980613, Richmond, VA 23298, USA; (L.S.A.); (M.I.D.)
| | - Ayman K. Hamouda
- Department of Pharmaceutical Sciences, College of Pharmacy, The University of Texas at Tyler, Tyler, TX 75799, USA;
- Department of Pharmaceutical Sciences, College of Pharmacy, Texas A&M Health Sciences Center MS 131, 1010 W. Ave. B, Kingsville, TX 78363, USA; (K.R.); (M.V.); (K.M.)
- Correspondence: ; Tel.: +1-903-565-6578
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12
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Laikowski MM, Reisdorfer F, Moura S. NAChR α4β2 Subtype and their Relation with Nicotine Addiction, Cognition, Depression and Hyperactivity Disorder. Curr Med Chem 2019; 26:3792-3811. [PMID: 29637850 DOI: 10.2174/0929867325666180410105135] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 12/27/2017] [Accepted: 04/05/2018] [Indexed: 01/07/2023]
Abstract
BACKGROUND Neuronal α4β2 nAChRs are receptors involved in the role of neurotransmitters regulation and release, and this ionic channel participates in biological process of memory, learning and attention. This work aims to review the structure and functioning of the α4β2 nAChR emphasizing its role in the treatment of associated diseases like nicotine addiction and underlying pathologies such as cognition, depression and attention-deficit hyperactivity disorder. METHODS The authors realized extensive bibliographic research using the descriptors "Nicotine Receptor α4β2" and "cognition", "depression", "attention-deficit hyperactivity disorder", besides cross-references of the selected articles and after analysis of references in the specific literature. RESULTS As results, it was that found 179 relevant articles presenting the main molecules with affinity to nAChR α4β2 related to the cited diseases. The α4β2 nAChR subtype is a remarkable therapeutic target since this is the most abundant receptor in the central nervous system. CONCLUSION In summary, this review presents perspectives on the pharmacology and therapeutic targeting of α4β2 nAChRs for the treatment of cognition and diseases like nicotine dependence, depression and attention-deficit hyperactivity disorder.
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Affiliation(s)
- Manuela M Laikowski
- Laboratory of Natural and Synthetics Products, University of Caxias do Sul, Caxias do Sul, Brazil
| | - Fávero Reisdorfer
- Laboratory of Drug Development and Quality Control, University Federal of Pampa, Brazil
| | - Sidnei Moura
- Laboratory of Natural and Synthetics Products, University of Caxias do Sul, Caxias do Sul, Brazil
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13
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Mazzaferro S, Bermudez I, Sine SM. Potentiation of a neuronal nicotinic receptor via pseudo-agonist site. Cell Mol Life Sci 2019; 76:1151-1167. [PMID: 30600358 PMCID: PMC8022356 DOI: 10.1007/s00018-018-2993-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 11/28/2018] [Accepted: 12/10/2018] [Indexed: 11/26/2022]
Abstract
Neuronal nicotinic receptors containing α4 and β2 subunits assemble in two pentameric stoichiometries, (α4)3(β2)2 and (α4)2(β2)3, each with distinct pharmacological signatures; (α4)3(β2)2 receptors are strongly potentiated by the drug NS9283, whereas (α4)2(β2)3 receptors are unaffected. Despite this stoichiometry-selective pharmacology, the molecular identity of the target for NS9283 remains elusive. Here, studying (α4)3(β2)2 receptors, we show that mutations at either the principal face of the β2 subunit or the complementary face of the α4 subunit prevent NS9283 potentiation of ACh-elicited single-channel currents, suggesting the drug targets the β2-α4 pseudo-agonist sites, the α4-α4 agonist site, or both sites. To distinguish among these possibilities, we generated concatemeric receptors with mutations at specified subunit interfaces, and monitored the ability of NS9283 to potentiate ACh-elicited single-channel currents. We find that a mutation at the principal face of the β2 subunit at either β2-α4 pseudo-agonist site suppresses potentiation, whereas mutation at the complementary face of the α4 subunit at the α4-α4 agonist site allows a significant potentiation. Thus, monitoring potentiation of single concatemeric receptor channels reveals that the β2-α4 pseudo-agonist sites are required for stoichiometry-selective drug action. Together with the recently determined structure of the (α4)3(β2)2 receptor, the findings have implications for structure-guided drug design.
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Affiliation(s)
- Simone Mazzaferro
- Receptor Biology Laboratory, Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN, 55905, USA
| | - Isabel Bermudez
- School of Life Sciences, Oxford Brookes University, Oxford, OX3 OBP, UK
| | - Steven M Sine
- Receptor Biology Laboratory, Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN, 55905, USA.
- Department of Neurology, Mayo Clinic College of Medicine, Rochester, MN, 55905, USA.
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, MN, 55905, USA.
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14
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Kowal NM, Ahring PK, Liao VWY, Indurti DC, Harvey BS, O'Connor SM, Chebib M, Olafsdottir ES, Balle T. Galantamine is not a positive allosteric modulator of human α4β2 or α7 nicotinic acetylcholine receptors. Br J Pharmacol 2018; 175:2911-2925. [PMID: 29669164 DOI: 10.1111/bph.14329] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 03/13/2018] [Accepted: 03/15/2018] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND AND PURPOSE The alkaloid galantamine was originally isolated from the green snowdrop Galanthus woronowii and is currently marketed as a drug for treatment of mild to moderate dementia in patients with Alzheimer's disease. In addition to a well-documented proficiency to inhibit acetylcholinesterase, galantamine has been reported to increase neuronal nicotinic ACh (nACh) receptor function by acting as a positive allosteric modulator. Yet there remains controversy regarding these findings in the literature. To resolve this conundrum, we evaluated galantamine actions at α4β2 and α7, which represent the nACh receptors most commonly associated with mammalian cognitive domains. EXPERIMENTAL APPROACH α4β2 [in (α4)3 (β2)2 and (α4)2 (β2)3 stoichiometries] and α7 nACh receptors were expressed in Xenopus laevis oocytes and subjected to two-electrode voltage-clamp electrophysiological experiments. Galantamine (10 nM to 100 μM) was evaluated for direct agonist effects and for positive modulation by co-application with sub-maximally efficacious concentrations of ACh. In addition, similar experiments were performed with α7 nACh receptors stably expressed in HEK293 cells using patch-clamp electrophysiology. KEY RESULTS In concentrations ranging from 10 nM to 1 μM, galantamine did not display direct agonism nor positive modulatory effects at any receptor combination tested. At concentrations from 10 μM and above, galantamine inhibited the activity with a mechanism of action consistent with open-channel pore blockade at all receptor types. CONCLUSION AND IMPLICATIONS Based on our data, we conclude that galantamine is not a positive allosteric modulator of α7 or α4β2 receptors, which represent the majority of nACh receptors in mammalian brain.
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Affiliation(s)
- Natalia M Kowal
- Sydney School of Pharmacy, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, 2006, Australia.,Faculty of Pharmaceutical Sciences, School of Health Sciences, University of Iceland, Reykjavik, IS-107, Iceland
| | - Philip K Ahring
- Sydney School of Pharmacy, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Vivian W Y Liao
- Sydney School of Pharmacy, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Dinesh C Indurti
- Sydney School of Pharmacy, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, 2006, Australia
| | | | | | - Mary Chebib
- Sydney School of Pharmacy, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Elin S Olafsdottir
- Faculty of Pharmaceutical Sciences, School of Health Sciences, University of Iceland, Reykjavik, IS-107, Iceland
| | - Thomas Balle
- Sydney School of Pharmacy, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, 2006, Australia
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15
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Ahring PK, Liao VWY, Balle T. Concatenated nicotinic acetylcholine receptors: A gift or a curse? J Gen Physiol 2018; 150:453-473. [PMID: 29382698 PMCID: PMC5839718 DOI: 10.1085/jgp.201711846] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 11/15/2017] [Accepted: 12/22/2017] [Indexed: 11/20/2022] Open
Abstract
Nicotine acetylcholine receptors can form countless heteromeric stoichiometries from a common set of subunits. Ahring et al. present the limitations of subunit concatenation and establish a refinement that achieves substantiated expression of uniform receptor pools from complex stoichiometric origins. Nicotinic acetylcholine receptors (nAChRs) belong to the Cys-loop receptor family and are vital for normal mammalian brain function. Cys-loop receptors are pentameric ligand-gated ion channels formed from five identical or homologous subunits oriented around a central ion-conducting pore, which result in homomeric or heteromeric receptors, respectively. Within a given Cys-loop receptor family, many different heteromeric receptors can assemble from a common set of subunits, and understanding the properties of these heteromeric receptors is crucial for the continuing quest to generate novel treatments for human diseases. Yet this complexity also presents a hindrance for studying Cys-loop receptors in heterologous expression systems, where full control of the receptor stoichiometry and assembly is required. Therefore, subunit concatenation technology is commonly used to control receptor assembly. In theory, this methodology should facilitate full control of the stoichiometry. In reality, however, we find that commonly used constructs do not yield the expected receptor stoichiometries. With ternary or more complex receptors, concatenated subunits must assemble uniformly in only one orientation; otherwise, the resulting receptor pool will consist of receptors with mixed stoichiometries. We find that typically used constructs of α4β2 nAChR dimers, tetramers, and pentamers assemble readily in both the clockwise and the counterclockwise orientations. Consequently, we investigate the possibility of successfully directing the receptor assembly process using concatenation. We begin by investigating the three-dimensional structures of the α4β2 nAChR. Based on this, we hypothesize that the minimum linker length required to bridge the C terminus of one subunit to the N terminus of the next is shortest in the counterclockwise orientation. We then successfully express receptors with a uniform stoichiometry by systematically shortening linker lengths, proving the hypothesis correct. Our results will significantly aid future studies of heteromeric Cys-loop receptors and enable clarification of the current contradictions in the literature.
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Affiliation(s)
| | | | - Thomas Balle
- Faculty of Pharmacy, The University of Sydney, Sydney, Australia
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16
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Deba F, Ali HI, Tairu A, Ramos K, Ali J, Hamouda AK. LY2087101 and dFBr share transmembrane binding sites in the (α4)3(β2)2 Nicotinic Acetylcholine Receptor. Sci Rep 2018; 8:1249. [PMID: 29352227 PMCID: PMC5775429 DOI: 10.1038/s41598-018-19790-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 01/08/2018] [Indexed: 12/17/2022] Open
Abstract
Positive allosteric modulators (PAMs) of nicotinic acetylcholine receptors (nAChRs) have potential therapeutic application in neuropathologies associated with decrease in function or loss of nAChRs. In this study, we characterize the pharmacological interactions of the nAChRs PAM, LY2087101, with the α4β2 nAChR using mutational and computational analyses. LY2087101 potentiated ACh-induced currents of low-sensitivity (α4)3(β2)2 and high-sensitivity (α4)2(β2)3 nAChRs with similar potencies albeit to a different maximum potentiation (potentiation I max = ~840 and 450%, respectively). Amino acid substitutions within the α4 subunit transmembrane domain [e.g. α4Leu256 and α4Leu260 within the transmembrane helix 1 (TM1); α4Phe316 within the TM3; and α4Gly613 within TM4] significantly reduced LY2087101 potentiation of (α4)3(β2)2 nAChR. The locations of these amino acid residues and LY2087101 computational docking analyses identify two LY2087101 binding sites: an intrasubunit binding site within the transmembrane helix bundle of α4 subunit at the level of α4Leu260/α4Phe316 and intersubunit binding site at the α4:α4 subunit interface at the level of α4Leu256/α4Ile315 with both sites extending toward the extracellular end of the transmembrane domain. We also show that desformylflustrabromine (dFBr) binds to these two sites identified for LY2087101. These results provide structural information that are pertinent to structure-based design of nAChR allosteric modulators.
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Affiliation(s)
- Farah Deba
- Department of Pharmaceutical Sciences, Rangel College of Pharmacy, Texas A&M Health Sciences Center, Kingsville, TX, 78363, USA
| | - Hamed I Ali
- Department of Pharmaceutical Sciences, Rangel College of Pharmacy, Texas A&M Health Sciences Center, Kingsville, TX, 78363, USA
| | - Abisola Tairu
- Department of Pharmaceutical Sciences, Rangel College of Pharmacy, Texas A&M Health Sciences Center, Kingsville, TX, 78363, USA
| | - Kara Ramos
- Department of Pharmaceutical Sciences, Rangel College of Pharmacy, Texas A&M Health Sciences Center, Kingsville, TX, 78363, USA
| | - Jihad Ali
- Department of Pharmaceutical Sciences, Rangel College of Pharmacy, Texas A&M Health Sciences Center, Kingsville, TX, 78363, USA
| | - Ayman K Hamouda
- Department of Pharmaceutical Sciences, Rangel College of Pharmacy, Texas A&M Health Sciences Center, Kingsville, TX, 78363, USA.
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17
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Hone AJ, McIntosh JM. Nicotinic acetylcholine receptors in neuropathic and inflammatory pain. FEBS Lett 2017; 592:1045-1062. [PMID: 29030971 DOI: 10.1002/1873-3468.12884] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Revised: 09/22/2017] [Accepted: 10/05/2017] [Indexed: 01/11/2023]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are actively being investigated as therapeutic targets for the treatment of pain and inflammation, but despite more than 30 years of research, there are currently no FDA-approved analgesics that are specific for these receptors. Much of the initial research effort focused on the α4β2 nAChR subtype, but more recently, additional subtypes have been identified as promising new leads and include α6β4, α7, and α9-containing nAChRs. This Review will focus on the distribution of these nAChRs in the cell types involved in neuropathic pain and inflammation and the activity of currently available nicotinic ligands.
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Affiliation(s)
- Arik J Hone
- Department of Biology, University of Utah, Salt Lake City, UT, USA
| | - J Michael McIntosh
- Department of Biology, University of Utah, Salt Lake City, UT, USA.,Department of Psychiatry, University of Utah, Salt Lake City, UT, USA.,George E. Whalen Veterans Affairs Medical Center, Salt Lake City, UT, USA
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18
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Yu Z, Cohen JB. Enantiomeric barbiturates bind distinct inter- and intrasubunit binding sites in a nicotinic acetylcholine receptor (nAChR). J Biol Chem 2017; 292:17258-17271. [PMID: 28878016 DOI: 10.1074/jbc.m117.808592] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Revised: 09/05/2017] [Indexed: 11/06/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) and γ-aminobutyric acid type A receptors (GABAARs) are members of the pentameric ligand-gated ion channel superfamily. Drugs acting as positive allosteric modulators of muscle-type α2βγδ nAChRs, of use in treatment of neuromuscular disorders, have been hard to identify. However, identification of nAChR allosteric modulator binding sites has been facilitated by using drugs developed as photoreactive GABAAR modulators. Recently, R-1-methyl-5-allyl-5-(m-trifluoromethyl-diazirinylphenyl) barbituric acid (R-mTFD-MPAB), an anesthetic and GABAAR potentiator, has been shown to inhibit Torpedo α2βγδ nAChRs, binding in the ion channel and to a γ+-α- subunit interface site similar to its GABAAR intersubunit binding site. In contrast, S-1-methyl-5-propyl-5-(m-trifluoromethyl-diazirinylphenyl) barbituric acid (S-mTFD-MPPB) acts as a convulsant and GABAAR inhibitor. Photolabeling studies established that S-mTFD-MPPB binds to the same GABAAR intersubunit binding site as R-mTFD-MPAB, but with negative rather than positive energetic coupling to GABA binding. We now show that S-mTFD-MPPB binds with the same state (agonist) dependence as R-mTFD-MPAB within the nAChR ion channel, but it does not bind to the intersubunit binding site. Rather, S-mTFD-MPPB binds to intrasubunit sites within the α and δ subunits, photolabeling αVal-218 (αM1), δPhe-232 (δM1), δThr-274 (δM2), and δIle-288 (δM3). Propofol, a general anesthetic that binds to GABAAR intersubunit sites, inhibited [3H]S-mTFD-MPPB photolabeling of these nAChR intrasubunit binding sites. These results demonstrate that in an nAChR, the subtle difference in structure between S-mTFD-MPPB and R-mTFD-MPAB (chirality; 5-propyl versus 5-allyl) determines selectivity for intra- versus intersubunit sites, in contrast to GABAARs, where this difference affects state dependence of binding to a common site.
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Affiliation(s)
- Zhiyi Yu
- From the Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115
| | - Jonathan B Cohen
- From the Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115
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19
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Wang ZJ, Deba F, Mohamed TS, Chiara DC, Ramos K, Hamouda AK. Unraveling amino acid residues critical for allosteric potentiation of (α4)3(β2)2-type nicotinic acetylcholine receptor responses. J Biol Chem 2017; 292:9988-10001. [PMID: 28446611 DOI: 10.1074/jbc.m116.771246] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Revised: 04/20/2017] [Indexed: 01/29/2023] Open
Abstract
Neuronal nicotinic acetylcholine receptors (nAChRs) are promising drug targets to manage several neurological disorders and nicotine addiction. Growing evidence indicates that positive allosteric modulators of nAChRs improve pharmacological specificity by binding to unique sites present only in a subpopulation of nAChRs. Furthermore, nAChR positive allosteric modulators such as NS9283 and CMPI have been shown to potentiate responses of (α4)3(β2)2 but not (α4)2(β2)3 nAChR isoforms. This selective potentiation underlines that the α4:α4 interface, which is present only in the (α4)3(β2)2 nAChR, is an important and promising drug target. In this report we used site-directed mutagenesis to substitute specific amino acid residues and computational analyses to elucidate CMPI's binding mode at the α4:α4 subunit extracellular interface and identified a unique set of amino acid residues that determined its affinity. We found that amino acid residues α4Gly-41, α4Lys-64, and α4Thr-66 were critical for (α4)3(β2)2 nAChR potentiation by CMPI, but not by NS9283, whereas amino acid substitution at α4His-116, a known determinant of NS9283 and of agonist binding at the α4:α4 subunit interface, did not reduce CMPI potentiation. In contrast, substitutions at α4Gln-124 and α4Thr-126 reduced potentiation by CMPI and NS9283, indicating that their binding sites partially overlap. These results delineate the role of amino acid residues contributing to the α4:α4 subunit extracellular interface in nAChR potentiation. These findings also provide structural information that will facilitate the structure-based design of novel therapeutics that target selectively the (α4)3(β2)2 nAChR.
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Affiliation(s)
- Ze-Jun Wang
- From the Department of Pharmaceutical Sciences, Texas A&M Health Sciences Center, Kingsville, Texas 78363
| | - Farah Deba
- From the Department of Pharmaceutical Sciences, Texas A&M Health Sciences Center, Kingsville, Texas 78363
| | - Tasnim S Mohamed
- From the Department of Pharmaceutical Sciences, Texas A&M Health Sciences Center, Kingsville, Texas 78363
| | - David C Chiara
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115
| | - Kara Ramos
- From the Department of Pharmaceutical Sciences, Texas A&M Health Sciences Center, Kingsville, Texas 78363
| | - Ayman K Hamouda
- From the Department of Pharmaceutical Sciences, Texas A&M Health Sciences Center, Kingsville, Texas 78363, .,Department of Neuroscience and Experimental Therapeutics, Texas A&M Health Sciences Center, Bryan, Texas 77807, and
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20
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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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21
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Jayakar SS, Ang G, Chiara DC, Hamouda AK. Photoaffinity Labeling of Pentameric Ligand-Gated Ion Channels: A Proteomic Approach to Identify Allosteric Modulator Binding Sites. Methods Mol Biol 2017; 1598:157-197. [PMID: 28508361 DOI: 10.1007/978-1-4939-6952-4_7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Photoaffinity labeling techniques have been used for decades to identify drug binding sites and to study the structural biology of allosteric transitions in transmembrane proteins including pentameric ligand-gated ion channels (pLGIC). In a typical photoaffinity labeling experiment, to identify drug binding sites, UV light is used to introduce a covalent bond between a photoreactive ligand (which upon irradiation at the appropriate wavelength converts to a reactive intermediate) and amino acid residues that lie within its binding site. Then protein chemistry and peptide microsequencing techniques are used to identify these amino acids within the protein primary sequence. These amino acid residues are located within homology models of the receptor to identify the binding site of the photoreactive probe. Molecular modeling techniques are then used to model the binding of the photoreactive probe within the binding site using docking protocols. Photoaffinity labeling directly identifies amino acids that contribute to drug binding sites regardless of their location within the protein structure and distinguishes them from amino acids that are only involved in the transduction of the conformational changes mediated by the drug, but may not be part of its binding site (such as those identified by mutational studies). Major limitations of photoaffinity labeling include the availability of photoreactive ligands that faithfully mimic the properties of the parent molecule and protein preparations that supply large enough quantities suitable for photoaffinity labeling experiments. When the ligand of interest is not intrinsically photoreactive, chemical modifications to add a photoreactive group to the parent drug, and pharmacological evaluation of these chemical modifications become necessary. With few exceptions, expression and affinity-purification of proteins are required prior to photolabeling. Methods to isolate milligram quantities of highly enriched pLGIC suitable for photoaffinity labeling experiments have been developed. In this chapter, we discuss practical aspects of experimental strategies to identify allosteric modulator binding sites in pLGIC using photoaffinity labeling.
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Affiliation(s)
- Selwyn S Jayakar
- Department of Neurobiology, Harvard Medical School, Boston, MA, USA
| | - Gordon Ang
- Department of Pharmaceutical Sciences, College of Pharmacy, Texas A&M Health Sciences Center, Kingsville, TX, USA
| | - David C Chiara
- Department of Neurobiology, Harvard Medical School, Boston, MA, USA
| | - Ayman K Hamouda
- Department of Pharmaceutical Sciences, College of Pharmacy, Texas A&M Health Sciences Center, Kingsville, TX, USA. .,Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M Health Science Center, Bryan, TX, USA. .,Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M Health Science Center, Kingsville, TX, USA.
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22
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Indurthi DC, Lewis TM, Ahring PK, Balle T, Chebib M, Absalom NL. Ligand Binding at the 4-4 Agonist-Binding Site of the 42 nAChR Triggers Receptor Activation through a Pre-Activated Conformational State. PLoS One 2016; 11:e0161154. [PMID: 27552221 PMCID: PMC4995024 DOI: 10.1371/journal.pone.0161154] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 08/01/2016] [Indexed: 11/18/2022] Open
Abstract
The α4β2 nicotinic acetylcholine receptor (nAChR) is the most abundant subtype in the brain and exists in two functional stoichiometries: (α4)3(β2)2 and (α4)2(β2)3. A distinct feature of the (α4)3(β2)2 receptor is the biphasic activation response to the endogenous agonist acetylcholine, where it is activated with high potency and low efficacy when two α4-β2 binding sites are occupied and with low potency/high efficacy when a third α4-α4 binding site is occupied. Further, exogenous ligands can bind to the third α4-α4 binding site and potentiate the activation of the receptor by ACh that is bound at the two α4-β2 sites. We propose that perturbations of the recently described pre-activation step when a third binding site is occupied are a key driver of these distinct activation properties. To investigate this, we used a combination of simple linear kinetic models and voltage clamp electrophysiology to determine whether transitions into the pre-activated state were increased when three binding sites were occupied. We separated the binding at the two different sites with ligands selective for the α4-β2 site (Sazetidine-A and TC-2559) and the α4-α4 site (NS9283) and identified that when a third binding site was occupied, changes in the concentration-response curves were best explained by an increase in transitions into a pre-activated state. We propose that perturbations of transitions into a pre-activated state are essential to explain the activation properties of the (α4)3(β2)2 receptor by acetylcholine and other ligands. Considering the widespread clinical use of benzodiazepines, this discovery of a conserved mechanism that benzodiazepines and ACh potentiate receptor activation via a third binding site can be exploited to develop therapeutics with similar properties at other cys-loop receptors.
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Affiliation(s)
| | - Trevor M. Lewis
- School of Medical Sciences, University of NSW, Kensington, NSW, 2052, Australia
| | | | - Thomas Balle
- Faculty of Pharmacy, University of Sydney, NSW, 2006, Australia
| | - Mary Chebib
- Faculty of Pharmacy, University of Sydney, NSW, 2006, Australia
- * E-mail: (NLA); (MC)
| | - Nathan L. Absalom
- Faculty of Pharmacy, University of Sydney, NSW, 2006, Australia
- * E-mail: (NLA); (MC)
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23
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Hamouda AK, Deba F, Wang ZJ, Cohen JB. Photolabeling a Nicotinic Acetylcholine Receptor (nAChR) with an (α4)3(β2)2 nAChR-Selective Positive Allosteric Modulator. Mol Pharmacol 2016; 89:575-84. [PMID: 26976945 DOI: 10.1124/mol.116.103341] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Accepted: 03/09/2016] [Indexed: 01/25/2023] Open
Abstract
Positive allosteric modulators (PAMs) of nicotinic acetylcholine (ACh) receptors (nAChRs) have potential clinical applications in the treatment of nicotine dependence and many neuropsychiatric conditions associated with decreased brain cholinergic activity, and 3-(2-chlorophenyl)-5-(5-methyl-1-(piperidin-4-yl)-1H-pyrrazol-4-yl)isoxazole (CMPI) has been identified as a PAM selective for neuronal nAChRs containing theα4 subunit. In this report, we compare CMPI interactions with low-sensitivity (α4)3(β2)2 and high-sensitivity (α4)2(β2)3 nAChRs, and with muscle-type nAChRs. In addition, we use the intrinsic reactivity of [(3)H]CMPI upon photolysis at 312 nm to identify its binding sites inTorpedonAChRs. Recording fromXenopusoocytes, we found that CMPI potentiated maximally the responses of (α4)3(β2)2nAChR to 10μM ACh (EC10) by 400% and with anEC50of ∼1µM. CMPI produced a left shift of the ACh concentration-response curve without altering ACh efficacy. In contrast, CMPI inhibited (∼35% at 10µM) ACh responses of (α4)2(β2)3nAChRs and fully inhibited human muscle andTorpedonAChRs with IC50values of ∼0.5µM. Upon irradiation at 312 nm, [(3)H]CMPI photoincorporated into eachTorpedo[(α1)2β1γδ] nAChR subunit. Sequencing of peptide fragments isolated from [(3)H]CMPI-photolabeled nAChR subunits established photolabeling of amino acids contributing to the ACh binding sites (αTyr(190),αTyr(198),γTrp(55),γTyr(111),γTyr(117),δTrp(57)) that was fully inhibitable by agonist and lower-efficiency, state-dependent [(3)H]CMPI photolabeling within the ion channel. Our results establish that CMPI is a potent potentiator of nAChRs containing anα4:α4 subunit interface, and that its intrinsic photoreactivy makes it of potential use to identify its binding sites in the (α4)3(β2)2nAChR.
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Affiliation(s)
- Ayman K Hamouda
- Department of Pharmaceutical Sciences, Rangel College of Pharmacy, Texas A&M Health Sciences Center, Kingsville, Texas (A.K.H., F.D., Z.-J.W.); and Department of Neurobiology, Harvard Medical School, Boston, Massachusetts (A.K.H., J.B.C.)
| | - Farah Deba
- Department of Pharmaceutical Sciences, Rangel College of Pharmacy, Texas A&M Health Sciences Center, Kingsville, Texas (A.K.H., F.D., Z.-J.W.); and Department of Neurobiology, Harvard Medical School, Boston, Massachusetts (A.K.H., J.B.C.)
| | - Ze-Jun Wang
- Department of Pharmaceutical Sciences, Rangel College of Pharmacy, Texas A&M Health Sciences Center, Kingsville, Texas (A.K.H., F.D., Z.-J.W.); and Department of Neurobiology, Harvard Medical School, Boston, Massachusetts (A.K.H., J.B.C.)
| | - Jonathan B Cohen
- Department of Pharmaceutical Sciences, Rangel College of Pharmacy, Texas A&M Health Sciences Center, Kingsville, Texas (A.K.H., F.D., Z.-J.W.); and Department of Neurobiology, Harvard Medical School, Boston, Massachusetts (A.K.H., J.B.C.)
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24
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High and low GABA sensitivity α4β2δ GABAA receptors are expressed in Xenopus laevis oocytes with divergent stoichiometries. Biochem Pharmacol 2016; 103:98-108. [DOI: 10.1016/j.bcp.2015.12.021] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 12/29/2015] [Indexed: 12/11/2022]
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25
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Shahsavar A, Gajhede M, Kastrup JS, Balle T. Structural Studies of Nicotinic Acetylcholine Receptors: Using Acetylcholine-Binding Protein as a Structural Surrogate. Basic Clin Pharmacol Toxicol 2016; 118:399-407. [DOI: 10.1111/bcpt.12528] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 11/02/2015] [Indexed: 01/09/2023]
Affiliation(s)
- Azadeh Shahsavar
- Department of Molecular Biology and Genetics; Danish Research Institute of Translational Neuroscience - DANDRITE; Aarhus University; Aarhus Denmark
- Department of Drug Design and Pharmacology; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen Denmark
| | - Michael Gajhede
- Department of Drug Design and Pharmacology; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen Denmark
| | - Jette S. Kastrup
- Department of Drug Design and Pharmacology; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen Denmark
| | - Thomas Balle
- Faculty of Pharmacy; The University of Sydney; Sydney NSW Australia
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26
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Mohamed TS, Jayakar SS, Hamouda AK. Orthosteric and Allosteric Ligands of Nicotinic Acetylcholine Receptors for Smoking Cessation. Front Mol Neurosci 2015; 8:71. [PMID: 26635524 PMCID: PMC4658446 DOI: 10.3389/fnmol.2015.00071] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 11/06/2015] [Indexed: 12/23/2022] Open
Abstract
Nicotine addiction, the result of tobacco use, leads to over six million premature deaths world-wide per year, a number that is expected to increase by a third within the next two decades. While more than half of smokers want and attempt to quit, only a small percentage of smokers are able to quit without pharmacological interventions. Therefore, over the past decades, researchers in academia and the pharmaceutical industry have focused their attention on the development of more effective smoking cessation therapies, which is now a growing 1.9 billion dollar market. Because the role of neuronal nicotinic acetylcholine receptors (nAChR) in nicotine addiction is well established, nAChR based therapeutics remain the leading strategy for smoking cessation. However, the development of neuronal nAChR drugs that are selective for a nAChR subpopulation is challenging, and only few neuronal nAChR drugs are clinically available. Among the many neuronal nAChR subtypes that have been identified in the brain, the α4β2 subtype is the most abundant and plays a critical role in nicotine addiction. Here, we review the role of neuronal nAChRs, especially the α4β2 subtype, in the development and treatment of nicotine addiction. We also compare available smoking cessation medications and other nAChR orthosteric and allosteric ligands that have been developed with emphasis on the difficulties faced in the development of clinically useful compounds with high nAChR subtype selectivity.
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Affiliation(s)
- Tasnim S Mohamed
- Department of Pharmaceutical Sciences, College of Pharmacy, Texas A&M Health Sciences Center Kingsville, TX, USA
| | - Selwyn S Jayakar
- Department of Neurobiology, Harvard Medical School Boston, MA, USA
| | - Ayman K Hamouda
- Department of Pharmaceutical Sciences, College of Pharmacy, Texas A&M Health Sciences Center Kingsville, TX, USA ; Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M Health Sciences Center Bryan, TX, USA
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27
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Balle T, Olsen JA, Shahsavar A, Kastrup JS, Peter D, Gajhede M, Ahring PK. Modulation of α4β2 NACHRs via an extracellular binding site: Structural studies and novel engineered receptors to aid drug discovery. Biochem Pharmacol 2015. [DOI: 10.1016/j.bcp.2015.08.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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28
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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: 69] [Impact Index Per Article: 7.7] [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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29
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Shahsavar A, Ahring PK, Olsen JA, Krintel C, Kastrup JS, Balle T, Gajhede M. Acetylcholine-Binding Protein Engineered to Mimic the α4-α4 Binding Pocket in α4β2 Nicotinic Acetylcholine Receptors Reveals Interface Specific Interactions Important for Binding and Activity. Mol Pharmacol 2015; 88:697-707. [DOI: 10.1124/mol.115.098061] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 07/15/2015] [Indexed: 12/23/2022] Open
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30
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Hamouda AK, Wang ZJ, Stewart DS, Jain AD, Glennon RA, Cohen JB. Desformylflustrabromine (dFBr) and [3H]dFBr-Labeled Binding Sites in a Nicotinic Acetylcholine Receptor. Mol Pharmacol 2015; 88:1-11. [PMID: 25870334 PMCID: PMC4468644 DOI: 10.1124/mol.115.098913] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 04/13/2015] [Indexed: 12/11/2022] Open
Abstract
Desformylflustrabromine (dFBr) is a positive allosteric modulator (PAM) of α4β2 and α2β2 nAChRs that, at concentrations >1 µM, also inhibits these receptors and α7 nAChRs. However, its interactions with muscle-type nAChRs have not been characterized, and the locations of its binding site(s) in any nAChR are not known. We report here that dFBr inhibits human muscle (αβεδ) and Torpedo (αβγδ) nAChR expressed in Xenopus oocytes with IC50 values of ∼ 1 μM. dFBr also inhibited the equilibrium binding of ion channel blockers to Torpedo nAChRs with higher affinity in the nAChR desensitized state ([(3)H]phencyclidine; IC50 = 4 μM) than in the resting state ([(3)H]tetracaine; IC50 = 60 μM), whereas it bound with only very low affinity to the ACh binding sites ([(3)H]ACh, IC50 = 1 mM). Upon irradiation at 312 nm, [(3)H]dFBr photoincorporated into amino acids within the Torpedo nAChR ion channel with the efficiency of photoincorporation enhanced in the presence of agonist and the agonist-enhanced photolabeling inhibitable by phencyclidine. In the presence of agonist, [(3)H]dFBr also photolabeled amino acids in the nAChR extracellular domain within binding pockets identified previously for the nonselective nAChR PAMs galantamine and physostigmine at the canonical α-γ interface containing the transmitter binding sites and at the noncanonical δ-β subunit interface. These results establish that dFBr inhibits muscle-type nAChR by binding in the ion channel and that [(3)H]dFBr is a photoaffinity probe with broad amino acid side chain reactivity.
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Affiliation(s)
- Ayman K Hamouda
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts (A.K.H., D.S.S., J.B.C.); Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia (A.D.J., R.A.G.); and Department of Pharmaceutical Sciences, Rangel College of Pharmacy, Texas A&M Health Sciences Center, Kingsville,Texas (A.K.H., Z.-J.W.)
| | - Ze-Jun Wang
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts (A.K.H., D.S.S., J.B.C.); Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia (A.D.J., R.A.G.); and Department of Pharmaceutical Sciences, Rangel College of Pharmacy, Texas A&M Health Sciences Center, Kingsville,Texas (A.K.H., Z.-J.W.)
| | - Deirdre S Stewart
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts (A.K.H., D.S.S., J.B.C.); Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia (A.D.J., R.A.G.); and Department of Pharmaceutical Sciences, Rangel College of Pharmacy, Texas A&M Health Sciences Center, Kingsville,Texas (A.K.H., Z.-J.W.)
| | - Atul D Jain
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts (A.K.H., D.S.S., J.B.C.); Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia (A.D.J., R.A.G.); and Department of Pharmaceutical Sciences, Rangel College of Pharmacy, Texas A&M Health Sciences Center, Kingsville,Texas (A.K.H., Z.-J.W.)
| | - Richard A Glennon
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts (A.K.H., D.S.S., J.B.C.); Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia (A.D.J., R.A.G.); and Department of Pharmaceutical Sciences, Rangel College of Pharmacy, Texas A&M Health Sciences Center, Kingsville,Texas (A.K.H., Z.-J.W.)
| | - Jonathan B Cohen
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts (A.K.H., D.S.S., J.B.C.); Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia (A.D.J., R.A.G.); and Department of Pharmaceutical Sciences, Rangel College of Pharmacy, Texas A&M Health Sciences Center, Kingsville,Texas (A.K.H., Z.-J.W.)
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31
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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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32
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Ahring PK, Olsen JA, Nielsen EØ, Peters D, Pedersen MHF, Rohde LA, Kastrup JS, Shahsavar A, Indurthi DC, Chebib M, Gajhede M, Balle T. Engineered α4β2 nicotinic acetylcholine receptors as models for measuring agonist binding and effect at the orthosteric low-affinity α4-α4 interface. Neuropharmacology 2015; 92:135-45. [PMID: 25595102 DOI: 10.1016/j.neuropharm.2014.12.035] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Revised: 11/19/2014] [Accepted: 12/07/2014] [Indexed: 10/24/2022]
Abstract
The nicotinic acetylcholine receptor α4β2 is important for normal mammalian brain function and is known to express in two different stoichiometries, (α4)2(β2)3 and (α4)3(β2)2. While these are similar in many aspects, the (α4)3(β2)2 stoichiometry differs by harboring a third orthosteric acetylcholine binding site located at the α4-α4 interface. Interestingly, the third binding site has, so far, only been documented using electrophysiological assays, actual binding affinities of nicotinic receptor ligands to this site are not known. The present study was therefore aimed at determining binding affinities of nicotinic ligands to the α4-α4 interface. Given that epibatidine shows large functional potency differences at α4-β2 vs. α4-α4 interfaces, biphasic binding properties would be expected at (α4)3(β2)2 receptors. However, standard saturation binding experiments with [(3)H]epibatidine did not reveal biphasic binding under the conditions utilized. Therefore, an engineered β2 construct (β2(HQT)), which converts the β(-) face to resemble that of an α4(-) face, was utilized to create (α4)3(β2(HQT))2 receptors harboring three α4-α4 interfaces. With this receptor, low affinity binding of epibatidine with a Kd of ∼5 nM was observed in sharp contrast to a Kd value of ∼10 pM observed for wild-type receptors. A strong correlation between binding affinities at the (α4)3(β2(HQT))2 receptor and functional potencies at the wild-type receptor of a range of nicotinic ligands highlighted the validity of using the mutational approach. Finally, large differences in activities at α4-β2 vs. α4-α4 interfaces were observed for structurally related agonists underscoring the need for establishing all binding parameters of compounds at α4β2 receptors.
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Affiliation(s)
- Philip K Ahring
- Faculty of Pharmacy, The University of Sydney, NSW 2006, Australia; Saniona AB, 2750 Ballerup, Denmark
| | - Jeppe A Olsen
- Faculty of Pharmacy, The University of Sydney, NSW 2006, Australia; NeuroSearch A/S, 2750 Ballerup, Denmark; Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | | | | | - Martin H F Pedersen
- Hevesy Laboratory, Technical University of Denmark, DTU Nutech, 4000 Roskilde, Denmark
| | - Line A Rohde
- NeuroSearch A/S, 2750 Ballerup, Denmark; Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Jette S Kastrup
- Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Azadeh Shahsavar
- Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark
| | | | - Mary Chebib
- Faculty of Pharmacy, The University of Sydney, NSW 2006, Australia
| | - Michael Gajhede
- Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark.
| | - Thomas Balle
- Faculty of Pharmacy, The University of Sydney, NSW 2006, Australia.
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33
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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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