1
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Bergh C, Heusser SA, Howard R, Lindahl E. Markov state models of proton- and pore-dependent activation in a pentameric ligand-gated ion channel. eLife 2021; 10:68369. [PMID: 34652272 PMCID: PMC8635979 DOI: 10.7554/elife.68369] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Accepted: 10/14/2021] [Indexed: 01/03/2023] Open
Abstract
Ligand-gated ion channels conduct currents in response to chemical stimuli, mediating electrochemical signaling in neurons and other excitable cells. For many channels, the details of gating remain unclear, partly due to limited structural data and simulation timescales. Here, we used enhanced sampling to simulate the pH-gated channel GLIC, and construct Markov state models (MSMs) of gating. Consistent with new functional recordings, we report in oocytes, our analysis revealed differential effects of protonation and mutation on free-energy wells. Clustering of closed- versus open-like states enabled estimation of open probabilities and transition rates, while higher-order clustering affirmed conformational trends in gating. Furthermore, our models uncovered state- and protonation-dependent symmetrization. This demonstrates the applicability of MSMs to map energetic and conformational transitions between ion-channel functional states, and how they reproduce shifts upon activation or mutation, with implications for modeling neuronal function and developing state-selective drugs.
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Affiliation(s)
- Cathrine Bergh
- Science for Life Laboratory and Swedish e-Science Research Center, Department of Applied Physics, KTH Royal Institute of Technology, Solna, Sweden
| | - Stephanie A Heusser
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Solna, Sweden
| | - Rebecca Howard
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Solna, Sweden
| | - Erik Lindahl
- Science for Life Laboratory and Swedish e-Science Research Center, Department of Applied Physics, KTH Royal Institute of Technology, Solna, Sweden.,Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Solna, Sweden
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2
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Lycksell M, Rovšnik U, Bergh C, Johansen NT, Martel A, Porcar L, Arleth L, Howard RJ, Lindahl E. Probing solution structure of the pentameric ligand-gated ion channel GLIC by small-angle neutron scattering. Proc Natl Acad Sci U S A 2021; 118:e2108006118. [PMID: 34504004 PMCID: PMC8449418 DOI: 10.1073/pnas.2108006118] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/26/2021] [Indexed: 02/03/2023] Open
Abstract
Pentameric ligand-gated ion channels undergo subtle conformational cycling to control electrochemical signal transduction in many kingdoms of life. Several crystal structures have now been reported in this family, but the functional relevance of such models remains unclear. Here, we used small-angle neutron scattering (SANS) to probe ambient solution-phase properties of the pH-gated bacterial ion channel GLIC under resting and activating conditions. Data collection was optimized by inline paused-flow size-exclusion chromatography, and exchanging into deuterated detergent to hide the micelle contribution. Resting-state GLIC was the best-fit crystal structure to SANS curves, with no evidence for divergent mechanisms. Moreover, enhanced-sampling molecular-dynamics simulations enabled differential modeling in resting versus activating conditions, with the latter corresponding to an intermediate ensemble of both the extracellular and transmembrane domains. This work demonstrates state-dependent changes in a pentameric ion channel by SANS, an increasingly accessible method for macromolecular characterization with the coming generation of neutron sources.
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Affiliation(s)
- Marie Lycksell
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, 10691 Stockholm, Sweden
| | - Urška Rovšnik
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, 10691 Stockholm, Sweden
| | - Cathrine Bergh
- Department of Applied Physics, Science for Life Laboratory, KTH Royal Institute of Technology, 10044 Stockholm, Sweden
| | - Nicolai T Johansen
- Structural Biophysics, X-ray and Neutron Science, The Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Anne Martel
- Institut Laue-Langevin, 38042 Grenoble, France
| | | | - Lise Arleth
- Structural Biophysics, X-ray and Neutron Science, The Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Rebecca J Howard
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, 10691 Stockholm, Sweden
| | - Erik Lindahl
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, 10691 Stockholm, Sweden;
- Department of Applied Physics, Science for Life Laboratory, KTH Royal Institute of Technology, 10044 Stockholm, Sweden
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3
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Földi MC, Pesti K, Zboray K, Toth AV, Hegedűs T, Málnási-Csizmadia A, Lukacs P, Mike A. The mechanism of non-blocking inhibition of sodium channels revealed by conformation-selective photolabeling. Br J Pharmacol 2021; 178:1200-1217. [PMID: 33450052 DOI: 10.1111/bph.15365] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 12/10/2020] [Accepted: 01/03/2021] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE Sodium channel inhibitors can be used to treat hyperexcitability-related diseases, including epilepsies, pain syndromes, neuromuscular disorders and cardiac arrhythmias. The applicability of these drugs is limited by their nonspecific effect on physiological function. They act mainly by sodium channel block and in addition by modulation of channel kinetics. While channel block inhibits healthy and pathological tissue equally, modulation can preferentially inhibit pathological activity. An ideal drug designed to target the sodium channels of pathological tissue would act predominantly by modulation. Thus far, no such drug has been described. EXPERIMENTAL APPROACH Patch-clamp experiments with ultra-fast solution exchange and photolabeling-coupled electrophysiology were applied to describe the unique mechanism of riluzole on Nav1.4 sodium channels. In silico docking experiments were used to study the molecular details of binding. KEY RESULTS We present evidence that riluzole acts predominantly by non-blocking modulation. We propose that, being a relatively small molecule, riluzole is able to stay bound to the binding site, but nonetheless stay off the conduction pathway, by residing in one of the fenestrations. We demonstrate how this mechanism can be recognized. CONCLUSIONS AND IMPLICATIONS Our results identify riluzole as the prototype of this new class of sodium channel inhibitors. Drugs of this class are expected to selectively prevent hyperexcitability, while having minimal effect on cells firing at a normal rate from a normal resting potential.
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Affiliation(s)
- Mátyás C Földi
- MTA-ELTE NAP B Opto-Neuropharmacology Group, Budapest, Hungary.,Plant Protection Institute, Centre for Agricultural Research, Martonvásár, Hungary
| | - Krisztina Pesti
- MTA-ELTE NAP B Opto-Neuropharmacology Group, Budapest, Hungary.,Department of Biochemistry, Eötvös Loránd University, Budapest, Hungary.,School of PhD Studies, Semmelweis University, Budapest, Hungary
| | - Katalin Zboray
- Plant Protection Institute, Centre for Agricultural Research, Martonvásár, Hungary
| | - Adam V Toth
- Plant Protection Institute, Centre for Agricultural Research, Martonvásár, Hungary
| | - Tamás Hegedűs
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
| | - András Málnási-Csizmadia
- Motor Pharmacology Research Group, Department of Biochemistry, Eötvös Loránd University, Budapest, Hungary
| | - Peter Lukacs
- MTA-ELTE NAP B Opto-Neuropharmacology Group, Budapest, Hungary.,Plant Protection Institute, Centre for Agricultural Research, Martonvásár, Hungary
| | - Arpad Mike
- MTA-ELTE NAP B Opto-Neuropharmacology Group, Budapest, Hungary.,Plant Protection Institute, Centre for Agricultural Research, Martonvásár, Hungary.,Department of Biochemistry, Eötvös Loránd University, Budapest, Hungary
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4
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Laszlovszky T, Schlingloff D, Hegedüs P, Freund TF, Gulyás A, Kepecs A, Hangya B. Distinct synchronization, cortical coupling and behavioral function of two basal forebrain cholinergic neuron types. Nat Neurosci 2020; 23:992-1003. [PMID: 32572235 PMCID: PMC7611978 DOI: 10.1038/s41593-020-0648-0] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2019] [Accepted: 04/27/2020] [Indexed: 01/05/2023]
Abstract
Basal forebrain cholinergic neurons (BFCNs) modulate synaptic plasticity, cortical processing, brain states and oscillations. However, whether distinct types of BFCNs support different functions remains unclear. Therefore, we recorded BFCNs in vivo, to examine their behavioral functions, and in vitro, to study their intrinsic properties. We identified two distinct types of BFCNs that differ in their firing modes, synchronization properties and behavioral correlates. Bursting cholinergic neurons (Burst-BFCNs) fired synchronously, phase-locked to cortical theta activity and fired precisely timed bursts after reward and punishment. Regular-firing cholinergic neurons (Reg-BFCNs) were found predominantly in the posterior basal forebrain, displayed strong theta rhythmicity and responded with precise single spikes after behavioral outcomes. In an auditory detection task, synchronization of Burst-BFCNs to the auditory cortex predicted the timing of behavioral responses, whereas tone-evoked cortical coupling of Reg-BFCNs predicted correct detections. We propose that differential recruitment of two basal forebrain cholinergic neuron types generates behavior-specific cortical activation.
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Affiliation(s)
- Tamás Laszlovszky
- Lendület Laboratory of Systems Neuroscience, Institute of Experimental Medicine, Budapest, Hungary
- János Szentágothai Doctoral School of Neurosciences, Semmelweis University, Budapest, Hungary
| | - Dániel Schlingloff
- János Szentágothai Doctoral School of Neurosciences, Semmelweis University, Budapest, Hungary
- Laboratory of Cerebral Cortex Research, Institute of Experimental Medicine, Budapest, Hungary
| | - Panna Hegedüs
- Lendület Laboratory of Systems Neuroscience, Institute of Experimental Medicine, Budapest, Hungary
- János Szentágothai Doctoral School of Neurosciences, Semmelweis University, Budapest, Hungary
| | - Tamás F Freund
- Laboratory of Cerebral Cortex Research, Institute of Experimental Medicine, Budapest, Hungary
| | - Attila Gulyás
- Laboratory of Cerebral Cortex Research, Institute of Experimental Medicine, Budapest, Hungary
| | - Adam Kepecs
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, USA
- Departments of Neuroscience and Psychiatry, Washington University in St Louis, St Louis, MO, USA
| | - Balázs Hangya
- Lendület Laboratory of Systems Neuroscience, Institute of Experimental Medicine, Budapest, Hungary.
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5
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Pismataro MC, Horenstein NA, Stokes C, Quadri M, De Amici M, Papke RL, Dallanoce C. Design, synthesis, and electrophysiological evaluation of NS6740 derivatives: Exploration of the structure-activity relationship for alpha7 nicotinic acetylcholine receptor silent activation. Eur J Med Chem 2020; 205:112669. [PMID: 32810771 DOI: 10.1016/j.ejmech.2020.112669] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2020] [Revised: 07/13/2020] [Accepted: 07/14/2020] [Indexed: 11/15/2022]
Abstract
The α7 nicotinic acetylcholine receptor (nAChR) silent agonists, able to induce receptor desensitization and promote the α7 metabotropic function, are emerging as new promising therapeutic anti-inflammatory agents. Herein, we report the structure-activity relationship investigation of the archetypal silent agonist NS6740 (1,4-diazabicyclo[3.2.2]nonan-4-yl(5-(3-(trifluoromethyl)-phenyl)-furan-2-yl)methanone) (1) to elucidate the ligand-receptor interactions responsible for the α7 silent activation. In this study, NS6740 fragments 11-16 and analogs 17-32 were designed, synthesized, and assayed on human α7 nAChRs expressed in Xenopus laevis oocytes with two-electrode voltage clamping experiments. All together the structural portions of NS6740 were critical to engender its peculiar activity profile. The diazabicyclic nucleus was essential but not sufficient for inducing α7 silent activation. The central hydrogen-bond acceptor core and the aromatic moiety were crucial for promoting prolonged α7 receptor binding and sustained desensitization. Compounds 13 and 17 were efficacious partial agonists. Compounds 12, 21, 23-26, and 30 strongly desensitized α7 nAChR and therefore may be of interest for additional investigation of inflammation responses. We gained key structural information useful for further silent agonist development.
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Affiliation(s)
- Maria Chiara Pismataro
- Department of Pharmaceutical Sciences, Medicinal Chemistry Section "Pietro Pratesi", University of Milan, Via L. Mangiagalli 25, 20133, Milan, Italy; Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL 32611-7200, USA; Department of Pharmacology and Therapeutics, University of Florida, P.O. Box 100267, Gainesville, FL 32610-0267, USA
| | - Nicole A Horenstein
- Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL 32611-7200, USA
| | - Clare Stokes
- Department of Pharmacology and Therapeutics, University of Florida, P.O. Box 100267, Gainesville, FL 32610-0267, USA
| | - Marta Quadri
- Department of Pharmaceutical Sciences, Medicinal Chemistry Section "Pietro Pratesi", University of Milan, Via L. Mangiagalli 25, 20133, Milan, Italy; Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL 32611-7200, USA; Department of Pharmacology and Therapeutics, University of Florida, P.O. Box 100267, Gainesville, FL 32610-0267, USA
| | - Marco De Amici
- Department of Pharmaceutical Sciences, Medicinal Chemistry Section "Pietro Pratesi", University of Milan, Via L. Mangiagalli 25, 20133, Milan, Italy
| | - Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, P.O. Box 100267, Gainesville, FL 32610-0267, USA
| | - Clelia Dallanoce
- Department of Pharmaceutical Sciences, Medicinal Chemistry Section "Pietro Pratesi", University of Milan, Via L. Mangiagalli 25, 20133, Milan, Italy.
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6
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Tarasenko O, Voytenko S, Koval L, Lykhmus O, Kalashnyk O, Skok M. Unusual properties of α7 nicotinic acetylcholine receptor ion channels in B lymphocyte-derived SP-2/0 cells. Int Immunopharmacol 2020; 82:106373. [PMID: 32163855 DOI: 10.1016/j.intimp.2020.106373] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 02/25/2020] [Accepted: 03/02/2020] [Indexed: 12/30/2022]
Abstract
This study demonstrates the presence of α7 nicotinic acetylcholine receptors (nAChR) in B lymphocyte-derived SP-2/0 cells by means of flow cytometry and immunocytochemistry. According to lectin and sandwich ELISA, the α7 subunits expressed in SP-2/0 cells are more glycosylated compared to those expressed in the brain or normal B lymphocytes and are combined with β2 subunits. At zero and negative pipette potentials, either acetylcholine or α7-specific agonist PNU282987 stimulated the ion channel activity in SP-2/0 cells revealed by single channel patch-clamp recordings. The conductivity was within the range of 19 to 39 pS and reversal potential was between -17 mV and +28 mV, the currents were potentiated by α7-specific positive allosteric modulator PNU120596 and were partially blocked by α7-specific antagonist methyllicaconitine (MLA). However, they were oriented downwards suggesting that the channels mediated the cation outflux rather than influx. As shown by Ca2+ imaging studies, PNU282987 did not stimulate immediate Ca2+ influx into SP-2/0 cells. Instead, Ca2+ influx through Ca-release-activated channels (CRACs) was observed within minutes after either PNU282987 or MLA application. It is concluded that SP-2/0 express α7β2 nAChRs, which mediate the cation outflux under negative pipette potentials applied, possibly, due to depolarized membrane or negative surface charge formed by carbohydrate residues. In addition, α7β2 nAChRs may influence CRACs in ion-independent way.
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Affiliation(s)
| | - Sergiy Voytenko
- Bogomoletz Institute of Physiology, 4, Bogomoletz Str, 01024 Kyiv, Ukraine
| | - Lyudmyla Koval
- Palladin Institute of Biochemistry, 9, Leontovycha Str., 01030 Kyiv, Ukraine.
| | - Olena Lykhmus
- Palladin Institute of Biochemistry, 9, Leontovycha Str., 01030 Kyiv, Ukraine
| | - Olena Kalashnyk
- Palladin Institute of Biochemistry, 9, Leontovycha Str., 01030 Kyiv, Ukraine
| | - Maryna Skok
- Palladin Institute of Biochemistry, 9, Leontovycha Str., 01030 Kyiv, Ukraine.
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7
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Pesti K, Lukacs P, Mike A. Type I-like behavior of the type II α7 nicotinic acetylcholine receptor positive allosteric modulator A-867744. PeerJ 2019; 7:e7542. [PMID: 31534841 PMCID: PMC6727837 DOI: 10.7717/peerj.7542] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Accepted: 07/24/2019] [Indexed: 11/24/2022] Open
Abstract
Cognitive impairment often involves the decreased expression or hypofunction of alpha 7-type nicotinic acetylcholine receptors (α7 nAChRs). Agonists or positive allosteric modulators (PAMs) of α7 nAChRs are known to be potential treatments for dementias, different neurodegenerative disorders, pain syndromes and conditions involving inflammation. In some of these conditions, it is desirable to maintain the temporal precision of fast cholinergic events, while in others, this temporal precision is unnecessary. For this reason, the optimal therapeutic effect for distinct indications may require PAMs with different mechanisms of action. The two major mechanisms are called “type I”, which are compounds that augment α7 nAChR-mediated currents but maintain their characteristic fast kinetics; and “type II”, which are compounds that produce augmented and prolonged currents. In this study, we performed a kinetic analysis of two type II PAMs of the α7 nAChR: PNU-120596 and A-867744, using a fast perfusion method that allowed high temporal resolution. We characterized the type of modulation produced by the two compounds, the state-dependence of the modulatory action, and the interaction between the two compounds. We found fundamental differences between the modulation mechanisms by PNU-120596 and A-867744. Most importantly, during brief agonist pulses, A-867744 caused a strikingly type I-like modulation, while PNU-120596 caused a type II-like prolonged activation. Our results demonstrate that specific compounds, even though all labeled as type II PAMs, can behave in completely different ways, including their onset and offset kinetics, state preference, and single channel open time. Our results emphasize that subtle details of the mechanism of action may be significant in assessing the therapeutic applicability of α7 nAChR PAM compounds.
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Affiliation(s)
- Krisztina Pesti
- MTA-ELTE NAP B Opto-Neuropharmacology Group, Eötvös Loránd University, Budapest, Hungary.,Department of Biochemistry, Eötvös Loránd University, Budapest, Hungary.,School of PhD Studies, Semmelweis University, Budapest, Hungary
| | - Peter Lukacs
- Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Martonvásár, Hungary
| | - Arpad Mike
- MTA-ELTE NAP B Opto-Neuropharmacology Group, Eötvös Loránd University, Budapest, Hungary.,Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Martonvásár, Hungary
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8
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Ihnatovych I, Nayak TK, Ouf A, Sule N, Birkaya B, Chaves L, Auerbach A, Szigeti K. iPSC model of CHRFAM7A effect on α7 nicotinic acetylcholine receptor function in the human context. Transl Psychiatry 2019; 9:59. [PMID: 30710073 PMCID: PMC6358606 DOI: 10.1038/s41398-019-0375-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 01/02/2019] [Indexed: 12/16/2022] Open
Abstract
The α7 nicotinic acetylcholine receptor (α7nAChR) has been a promising target for diseases affecting cognition and higher cortical functions; however, the effect observed in animal models failed to translate into human clinical trials identifying a translational gap. CHRFAM7A is a human-specific fusion gene with properties that enable incorporation into the α7nAChR and, being human specific, CHRFAM7A effect was not accounted for in preclinical studies. We hypothesized that CHRFAM7A may account for this translational gap and understanding its function may offer novel insights when exploring α7nAChR as a drug target. CHRFAM7A is present in different copy number variations (CNV) in the human genome with high frequency. To study the functional consequences of the presence of the CHRFAM7A, two induced pluripotent stem cell (iPSC) lines (0 copy and 1 copy direct) were developed. The 0 copy line was rescued with CHRFAM7A transfection to control for genetic heterogeneity. As readouts for genotype-phenotype correlation, α7nAChR synaptic transmission and amyloid beta 1-42 (Aβ1-42) uptake were tested. Synaptic transmission in the presence of CHRFAM7A demonstrated that PNU-modulated desensitization of α7nAChR currents increased as a function of CHRFAM7A dosage. CHRFAM7A mitigated the dose response of Aβ1-42 uptake suggesting a protective effect beyond physiological concentrations. Furthermore, in the presence of CHRFAM7A Aβ1-42 uptake activated neuronal interleukin 1β (IL-1β) and tumor necrosis factor α (TNF-α) without activating the canonical inflammasome pathway. Lead optimization may identify more potent molecules when the screen has a model harboring CHRFAM7A. Incorporating pharmacogenetics into clinical trials may enhance signals in efficacy measures.
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Affiliation(s)
- Ivanna Ihnatovych
- Department of Neurology, State University of New York at Buffalo, Buffalo, NY, USA
| | - Tapan K Nayak
- Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, NY, USA
- Kusuma School of Biological Sciences, IIT Delhi, Hauz Khas, New Delhi, 110016, India
| | - Aya Ouf
- Department of Neurology, State University of New York at Buffalo, Buffalo, NY, USA
| | - Norbert Sule
- Department of Pathology, Roswell Park Cancer Institute, Buffalo, NY, USA
| | - Barbara Birkaya
- Department of Neurology, State University of New York at Buffalo, Buffalo, NY, USA
| | - Lee Chaves
- Division of Nephrology, Department of Medicine, State University of New York at Buffalo, Buffalo, NY, USA
| | - Anthony Auerbach
- Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, NY, USA
| | - Kinga Szigeti
- Department of Neurology, State University of New York at Buffalo, Buffalo, NY, USA.
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9
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Bouzat C, Lasala M, Nielsen BE, Corradi J, Esandi MDC. Molecular function of α7 nicotinic receptors as drug targets. J Physiol 2017; 596:1847-1861. [PMID: 29131336 DOI: 10.1113/jp275101] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Accepted: 11/02/2017] [Indexed: 12/20/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) are pentameric ligand-gated ion channels involved in many physiological and pathological processes. In vertebrates, there are seventeen different nAChR subunits that combine to yield a variety of receptors with different pharmacology, function, and localization. The homomeric α7 receptor is one of the most abundant nAChRs in the nervous system and it is also present in non-neuronal cells. It plays important roles in cognition, memory, pain, neuroprotection, and inflammation. Its diverse physiological actions and associated disorders have made of α7 an attractive novel target for drug modulation. Potentiation of the α7 receptor has emerged as a novel therapeutic strategy for several neurological diseases, such as Alzheimer's and Parkinson's diseases, and inflammatory disorders. In contrast, increased α7 activity has been associated with cancer cell proliferation. The presence of different drug target sites offers a great potential for α7 modulation in different pathological contexts. In particular, compounds that target allosteric sites offer significant advantages over orthosteric agonists due to higher selectivity and a broader spectrum of degrees and mechanisms of modulation. Heterologous expression of α7, together with chaperone proteins, combined with patch clamp recordings have provided important advances in our knowledge of the molecular basis of α7 responses and their potential modulation for pathological processes. This review gives a synthetic view of α7 and its molecular function, focusing on how its unique activation and desensitization features can be modified by pharmacological agents. This fundamental information offers insights into therapeutic strategies.
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Affiliation(s)
- Cecilia Bouzat
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, CONICET/UNS, 8000, Bahía Blanca, Argentina
| | - Matías Lasala
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, CONICET/UNS, 8000, Bahía Blanca, Argentina
| | - Beatriz Elizabeth Nielsen
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, CONICET/UNS, 8000, Bahía Blanca, Argentina
| | - Jeremías Corradi
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, CONICET/UNS, 8000, Bahía Blanca, Argentina
| | - María Del Carmen Esandi
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, CONICET/UNS, 8000, Bahía Blanca, Argentina
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10
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Shelukhina I, Spirova E, Kudryavtsev D, Ojomoko L, Werner M, Methfessel C, Hollmann M, Tsetlin V. Calcium imaging with genetically encoded sensor Case12: Facile analysis of α7/α9 nAChR mutants. PLoS One 2017; 12:e0181936. [PMID: 28797116 PMCID: PMC5552293 DOI: 10.1371/journal.pone.0181936] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 07/10/2017] [Indexed: 11/17/2022] Open
Abstract
Elucidation of the structural basis of pharmacological differences for highly homologous α7 and α9 nicotinic acetylcholine receptors (nAChRs) may shed light on their involvement in different physiological functions and diseases. Combination of site-directed mutagenesis and electrophysiology is a powerful tool to pinpoint the key amino-acid residues in the receptor ligand-binding site, but for α7 and α9 nAChRs it is complicated by their poor expression and fast desensitization. Here, we probed the ligand-binding properties of α7/α9 nAChR mutants by a proposed simple and fast calcium imaging method. The method is based on transient co-expression of α7/α9 nAChR mutants in neuroblastoma cells together with Ric-3 or NACHO chaperones and Case12 fluorescent calcium ion sensor followed by analysis of their pharmacology using a fluorescence microscope or a fluorometric imaging plate reader (FLIPR) with a GFP filter set. The results obtained were confirmed by electrophysiology and by calcium imaging with the conventional calcium indicator Fluo-4. The affinities for acetylcholine and epibatidine were determined for human and rat α7 nAChRs, and for their mutants with homologous residues of α9 nAChR incorporated at positions 117-119, 184, 185, 187, and 189, which are anticipated to be involved in ligand binding. The strongest decrease in the affinity was observed for mutations at positions 187 and 119. The L119D mutation of α7 nAChR, showing a larger effect for epibatidine than for acetylcholine, may implicate this position in pharmacological differences between α7 and α9 nAChRs.
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Affiliation(s)
- Irina Shelukhina
- Department of Molecular Basis of Neurosignalling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Ekaterina Spirova
- Department of Molecular Basis of Neurosignalling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Denis Kudryavtsev
- Department of Molecular Basis of Neurosignalling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Lucy Ojomoko
- Department of Molecular Basis of Neurosignalling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Markus Werner
- Department of Biochemistry I, Ruhr University Bochum, Bochum, Germany
| | | | - Michael Hollmann
- Department of Biochemistry I, Ruhr University Bochum, Bochum, Germany
| | - Victor Tsetlin
- Department of Molecular Basis of Neurosignalling, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
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11
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The coupling interface and pore domain codetermine the single-channel activity of the α7 nicotinic receptor. Neuropharmacology 2015; 95:448-58. [PMID: 25908400 DOI: 10.1016/j.neuropharm.2015.04.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 03/26/2015] [Accepted: 04/09/2015] [Indexed: 11/22/2022]
Abstract
Ligand-gated ion channels play a role in mediating fast synaptic transmission for communication between neurons. However, the structural basis for the functional coupling of the binding and pore domains, resulting in channel opening, remains a topic of intense investigation. Here, a series of α7 nicotinic receptor mutants were constructed for expression in cultured mammalian cells, and their single-channel properties were examined using the patch-clamp technique combined with radio ligand binding and the fluorescence staining technique. We demonstrated that the replacement of the four pore-lining residues in the channel domain of the α7 nicotinic receptor with the hydrophilic residue serine prolongs the open-channel lifetime, although the conductance of these mutants decreases. At the coupling interface between the extracellular and transmembrane domains, when the VRW residues in the Cys-loop were substituted with the corresponding residues (i.e., IYN) in the 5-HT3A receptor, the single-channel activity elicited by acetylcholine is impaired. This effect occurred despite the expression of the mutant receptors on the cell surface and despite the fact that the apparent Kd values were much lower than those of the wild-type α7 receptor. When we further lowered the channel-gating barrier of this chimera to enhance the open-channel probability, the loss of function was rescued. Overall, we explored the microscopic mechanisms underlying the interplay between the channel domains and the coupling interface that affect the channel activity, and we generated an allosteric gating model for the α7 receptor. This model shows that the gating machinery and coupling assembly codetermine the single-channel gating kinetics. These results likely apply to all channels in the Cys-loop receptor family.
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12
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Mueller A, Starobova H, Inserra MC, Jin AH, Deuis JR, Dutertre S, Lewis RJ, Alewood PF, Daly NL, Vetter I. α-Conotoxin MrIC is a biased agonist at α7 nicotinic acetylcholine receptors. Biochem Pharmacol 2015; 94:155-63. [PMID: 25646788 DOI: 10.1016/j.bcp.2015.01.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Revised: 01/20/2015] [Accepted: 01/20/2015] [Indexed: 12/23/2022]
Abstract
MrIC is a recently described selective agonist of endogenously expressed α7 nAChR. In this study, we further characterize the pharmacological activity of MrIC using Ca(2+) imaging approaches in SH-SY5Y cells endogenously expressing α7 nAChR and demonstrate that MrIC exclusively activates α7 nAChR modulated by type II positive allosteric modulators, including PNU120596. MrIC was a full agonist at PNU120596-modulated α7 nAChR compared with choline, albeit with slower kinetics, but failed to elicit a Ca(2+) response in the absence of PNU120596. Interestingly, the NMR structure of MrIC showed a typical 4/7 α-conotoxin fold, indicating that its unusual pharmacological activity is likely sequence-dependent. Overall, our results suggest that MrIC acts as a biased agonist that can only activate α7 nAChR modified by type II positive allosteric modulators, and thus represents a valuable tool to probe the pharmacological properties of this important ion channel.
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Affiliation(s)
- Alexander Mueller
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - Hana Starobova
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - Marco C Inserra
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - Ai-Hua Jin
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - Jennifer R Deuis
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - Sébastien Dutertre
- Institut des Biomolécules Max Mousseron, UMR 5247, Université Montpellier 2-CNRS, Place Eugène Bataillon, Montpellier Cedex 5 34095, France
| | - Richard J Lewis
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - Paul F Alewood
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - Norelle L Daly
- Centre for Biodiscovery and Molecular Development of Therapeutics, AITHM, James Cook University, Queensland 4878, Australia
| | - Irina Vetter
- Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, The University of Queensland, St Lucia, Queensland 4072, Australia; School of Pharmacy, The University of Queensland, Woolloongabba, Queensland 4102, Australia.
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Abstract
We have characterized the effect of triazine derivatives on neuronal nicotinic receptors expressed in Xenopus oocytes. All triazines investigated inhibit the current of α7 and α3β4 neuronal nicotinic receptors elicited by acetylcholine. The effect is concentration dependent, reversible, and noncompetitive. In contrast, some derivatives have a dual effect on α4β2 receptors, by potentiating the currents at intermediate concentration and causing inhibition at higher concentrations. Triazine derivatives also affect the macroscopic kinetics of the heteromeric receptors α3β4 and α4β2 accelerating the rise and decay time course of the currents, but have no significant effect on the kinetics of homomeric α7 receptors. Two simple kinetic models are presented. The first reproduces the effects of different concentrations of triazines both on the peak currents and on the macroscopic kinetics of α7 with a simple inhibitory result. The second model describes the behavior of α4β2 receptors involving a more complex dual action.
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14
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Papke RL, Chojnacka K, Horenstein NA. The minimal pharmacophore for silent agonism of the α7 nicotinic acetylcholine receptor. J Pharmacol Exp Ther 2014; 350:665-80. [PMID: 24990939 DOI: 10.1124/jpet.114.215236] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The minimum pharmacophore for activation of the human α7 nicotinic acetylcholine receptor (nAChR) is the tetramethylammonium cation. Previous work demonstrated that larger quaternary ammonium compounds, such as diethyldimethylammonium or 1-methyl quinuclidine, were α7-selective partial agonists, but additional increase in the size of the ammonium cation or the quinuclidine N-alkyl group by a single carbon to an N-ethyl group led to a loss of efficacy for ion channel activation. We report that although such compounds are ineffective at inducing the normal channel open state, they nonetheless regulate the induction of specific conformational states normally considered downstream of channel activation. We synthesized several panels of quaternary ammonium nAChR ligands that systematically varied the size of the substituents bonded to the central positively charged nitrogen atom. In these molecular series, we found a correlation between the molecular volume of the ligand and/or charge density, and the receptor's preferred distribution among conformational states including the closed state, the active state, a nonconducting state that could be converted to an activated state by a positive allosteric modulator (PAM), and a PAM-insensitive nonconducting state. We hypothesize that the changes of molecular volume of an agonist's cationic core subtly impact interactions at the subunit interface constituting the orthosteric binding site in such a way as to regulate the probability of conversions among the conformational states. We define a new minimal pharmacophore for the class of compounds we have termed "silent agonists," which are able to induce allosteric modulator-dependent activation but not the normal activated state.
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Affiliation(s)
- Roger L Papke
- Departments of Pharmacology and Therapeutics (R.L.P.) and Chemistry (K.C., N.A.H.), University of Florida, Gainesville, Florida
| | - Kinga Chojnacka
- Departments of Pharmacology and Therapeutics (R.L.P.) and Chemistry (K.C., N.A.H.), University of Florida, Gainesville, Florida
| | - Nicole A Horenstein
- Departments of Pharmacology and Therapeutics (R.L.P.) and Chemistry (K.C., N.A.H.), University of Florida, Gainesville, Florida
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15
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Szabo AK, Pesti K, Mike A, Vizi ES. Mode of action of the positive modulator PNU-120596 on α7 nicotinic acetylcholine receptors. Neuropharmacology 2014; 81:42-54. [DOI: 10.1016/j.neuropharm.2014.01.033] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2013] [Revised: 01/13/2014] [Accepted: 01/21/2014] [Indexed: 01/13/2023]
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