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Islam MS, Gaston JP, Baker MAB. Fluorescence Approaches for Characterizing Ion Channels in Synthetic Bilayers. MEMBRANES 2021; 11:857. [PMID: 34832086 PMCID: PMC8619978 DOI: 10.3390/membranes11110857] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Revised: 10/25/2021] [Accepted: 10/28/2021] [Indexed: 12/12/2022]
Abstract
Ion channels are membrane proteins that play important roles in a wide range of fundamental cellular processes. Studying membrane proteins at a molecular level becomes challenging in complex cellular environments. Instead, many studies focus on the isolation and reconstitution of the membrane proteins into model lipid membranes. Such simpler, in vitro, systems offer the advantage of control over the membrane and protein composition and the lipid environment. Rhodopsin and rhodopsin-like ion channels are widely studied due to their light-interacting properties and are a natural candidate for investigation with fluorescence methods. Here we review techniques for synthesizing liposomes and for reconstituting membrane proteins into lipid bilayers. We then summarize fluorescence assays which can be used to verify the functionality of reconstituted membrane proteins in synthetic liposomes.
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Affiliation(s)
- Md. Sirajul Islam
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Kensington, NSW 2052, Australia; (M.S.I.); (J.P.G.)
| | - James P. Gaston
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Kensington, NSW 2052, Australia; (M.S.I.); (J.P.G.)
| | - Matthew A. B. Baker
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Kensington, NSW 2052, Australia; (M.S.I.); (J.P.G.)
- CSIRO Synthetic Biology Future Science Platform, GPO Box 2583, Brisbane, QLD 4001, Australia
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2
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Goodsell DS, Zardecki C, Di Costanzo L, Duarte JM, Hudson BP, Persikova I, Segura J, Shao C, Voigt M, Westbrook JD, Young JY, Burley SK. RCSB Protein Data Bank: Enabling biomedical research and drug discovery. Protein Sci 2020; 29:52-65. [PMID: 31531901 PMCID: PMC6933845 DOI: 10.1002/pro.3730] [Citation(s) in RCA: 186] [Impact Index Per Article: 46.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 09/09/2019] [Accepted: 09/10/2019] [Indexed: 12/11/2022]
Abstract
Analyses of publicly available structural data reveal interesting insights into the impact of the three-dimensional (3D) structures of protein targets important for discovery of new drugs (e.g., G-protein-coupled receptors, voltage-gated ion channels, ligand-gated ion channels, transporters, and E3 ubiquitin ligases). The Protein Data Bank (PDB) archive currently holds > 155,000 atomic-level 3D structures of biomolecules experimentally determined using crystallography, nuclear magnetic resonance spectroscopy, and electron microscopy. The PDB was established in 1971 as the first open-access, digital-data resource in biology, and is now managed by the Worldwide PDB partnership (wwPDB; wwPDB.org). US PDB operations are the responsibility of the Research Collaboratory for Structural Bioinformatics PDB (RCSB PDB). The RCSB PDB serves millions of RCSB.org users worldwide by delivering PDB data integrated with ∼40 external biodata resources, providing rich structural views of fundamental biology, biomedicine, and energy sciences. Recently published work showed that the PDB archival holdings facilitated discovery of ∼90% of the 210 new drugs approved by the US Food and Drug Administration 2010-2016. We review user-driven development of RCSB PDB services, examine growth of the PDB archive in terms of size and complexity, and present examples and opportunities for structure-guided drug discovery for challenging targets (e.g., integral membrane proteins).
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Affiliation(s)
- David S. Goodsell
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, RutgersThe State University of New JerseyPiscatawayNew Jersey
- Institute for Quantitative Biomedicine, RutgersThe State University of New JerseyPiscatawayNew Jersey
- The Scripps Research InstituteLa JollaCalifornia
| | - Christine Zardecki
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, RutgersThe State University of New JerseyPiscatawayNew Jersey
- Institute for Quantitative Biomedicine, RutgersThe State University of New JerseyPiscatawayNew Jersey
| | - Luigi Di Costanzo
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, RutgersThe State University of New JerseyPiscatawayNew Jersey
- Institute for Quantitative Biomedicine, RutgersThe State University of New JerseyPiscatawayNew Jersey
| | - Jose M. Duarte
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, San Diego Supercomputer CenterUniversity of CaliforniaSan DiegoCalifornia
| | - Brian P. Hudson
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, RutgersThe State University of New JerseyPiscatawayNew Jersey
- Institute for Quantitative Biomedicine, RutgersThe State University of New JerseyPiscatawayNew Jersey
| | - Irina Persikova
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, RutgersThe State University of New JerseyPiscatawayNew Jersey
- Institute for Quantitative Biomedicine, RutgersThe State University of New JerseyPiscatawayNew Jersey
| | - Joan Segura
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, San Diego Supercomputer CenterUniversity of CaliforniaSan DiegoCalifornia
| | - Chenghua Shao
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, RutgersThe State University of New JerseyPiscatawayNew Jersey
- Institute for Quantitative Biomedicine, RutgersThe State University of New JerseyPiscatawayNew Jersey
| | - Maria Voigt
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, RutgersThe State University of New JerseyPiscatawayNew Jersey
- Institute for Quantitative Biomedicine, RutgersThe State University of New JerseyPiscatawayNew Jersey
| | - John D. Westbrook
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, RutgersThe State University of New JerseyPiscatawayNew Jersey
- Institute for Quantitative Biomedicine, RutgersThe State University of New JerseyPiscatawayNew Jersey
| | - Jasmine Y. Young
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, RutgersThe State University of New JerseyPiscatawayNew Jersey
- Institute for Quantitative Biomedicine, RutgersThe State University of New JerseyPiscatawayNew Jersey
| | - Stephen K. Burley
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, RutgersThe State University of New JerseyPiscatawayNew Jersey
- Institute for Quantitative Biomedicine, RutgersThe State University of New JerseyPiscatawayNew Jersey
- Research Collaboratory for Structural Bioinformatics Protein Data Bank, San Diego Supercomputer CenterUniversity of CaliforniaSan DiegoCalifornia
- Rutgers Cancer Institute of New Jersey, RutgersThe State University of New JerseyNew BrunswickNew Jersey
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Kapoor R, Peyear TA, Koeppe RE, Andersen OS. Antidepressants are modifiers of lipid bilayer properties. J Gen Physiol 2019; 151:342-356. [PMID: 30796095 PMCID: PMC6400527 DOI: 10.1085/jgp.201812263] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Accepted: 01/17/2019] [Indexed: 12/28/2022] Open
Abstract
The two major classes of antidepressants, tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs), inhibit neurotransmitter reuptake at synapses. They also have off-target effects on proteins other than neurotransmitter transporters, which may contribute to both desired changes in brain function and the development of side effects. Many proteins modulated by antidepressants are bilayer spanning and coupled to the bilayer through hydrophobic interactions such that the conformational changes underlying their function will perturb the surrounding lipid bilayer, with an energetic cost (ΔG def) that varies with changes in bilayer properties. Here, we test whether changes in ΔG def caused by amphiphilic antidepressants partitioning into the bilayer are sufficient to alter membrane protein function. Using gramicidin A (gA) channels to probe whether TCAs and SSRIs alter the bilayer contribution to the free energy difference for the gramicidin monomer⇔dimer equilibrium (representing a well-defined conformational transition), we find that antidepressants alter gA channel activity with varying potency and no stereospecificity but with different effects on bilayer elasticity and intrinsic curvature. Measuring the antidepressant partition coefficients using isothermal titration calorimetry (ITC) or cLogP shows that the bilayer-modifying potency is predicted quite well by the ITC-determined partition coefficients, and channel activity is doubled at an antidepressant/lipid mole ratio of 0.02-0.07. These results suggest a mechanism by which antidepressants could alter the function of diverse membrane proteins by partitioning into cell membranes and thereby altering the bilayer contribution to the energetics of membrane protein conformational changes.
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Affiliation(s)
- Ruchi Kapoor
- Weill Cornell/Rockefeller/Sloan Kettering Tri-Institutional MD-PhD Program, New York, NY.,Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY
| | - Thasin A Peyear
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY
| | - Roger E Koeppe
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR
| | - Olaf S Andersen
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY
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Pandhare A, Pappu AS, Wilms H, Blanton MP, Jansen M. The antidepressant bupropion is a negative allosteric modulator of serotonin type 3A receptors. Neuropharmacology 2016; 113:89-99. [PMID: 27671323 DOI: 10.1016/j.neuropharm.2016.09.021] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Revised: 09/12/2016] [Accepted: 09/21/2016] [Indexed: 11/27/2022]
Abstract
The FDA-approved antidepressant and smoking cessation drug bupropion is known to inhibit dopamine and norepinephrine reuptake transporters, as well as nicotinic acetylcholine receptors (nAChRs) which are cation-conducting members of the Cys-loop superfamily of ion channels, and more broadly pentameric ligand-gated ion channels (pLGICs). In the present study, we examined the ability of bupropion and its primary metabolite hydroxybupropion to block the function of cation-selective serotonin type 3A receptors (5-HT3ARs), and further characterized bupropion's pharmacological effects at these receptors. Mouse 5-HT3ARs were heterologously expressed in HEK-293 cells or Xenopus laevis oocytes for equilibrium binding studies. In addition, the latter expression system was utilized for functional studies by employing two-electrode voltage-clamp recordings. Both bupropion and hydroxybupropion inhibited serotonin-gated currents from 5-HT3ARs reversibly and dose-dependently with inhibitory potencies of 87 μM and 112 μM, respectively. Notably, the measured IC50 value for hydroxybupropion is within its therapeutically-relevant concentrations. The blockade by bupropion was largely non-competitive and non-use-dependent. Unlike its modulation at cation-selective pLGICs, bupropion displayed no significant inhibition of the function of anion-selective pLGICs. In summary, our results demonstrate allosteric blockade by bupropion of the 5-HT3AR. Importantly, given the possibility that bupropion's major active metabolite may achieve clinically relevant concentrations in the brain, our novel findings delineate a not yet identified pharmacological principle underlying its antidepressant effect.
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Affiliation(s)
- Akash Pandhare
- Department of Cell Physiology and Molecular Biophysics, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USA; Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA.
| | - Aneesh Satya Pappu
- Department of Cell Physiology and Molecular Biophysics, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USA; The Clark Scholar Program, Texas Tech University, Lubbock, TX 79409, USA.
| | - Henrik Wilms
- Department of Neurology, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USA.
| | - Michael Paul Blanton
- Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA; Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USA.
| | - Michaela Jansen
- Department of Cell Physiology and Molecular Biophysics, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USA; Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA.
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5
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Lee HM, Kim Y. Drug Repurposing Is a New Opportunity for Developing Drugs against Neuropsychiatric Disorders. SCHIZOPHRENIA RESEARCH AND TREATMENT 2016; 2016:6378137. [PMID: 27073698 PMCID: PMC4814692 DOI: 10.1155/2016/6378137] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Accepted: 02/24/2016] [Indexed: 01/03/2023]
Abstract
Better the drugs you know than the drugs you do not know. Drug repurposing is a promising, fast, and cost effective method that can overcome traditional de novo drug discovery and development challenges of targeting neuropsychiatric and other disorders. Drug discovery and development targeting neuropsychiatric disorders are complicated because of the limitations in understanding pathophysiological phenomena. In addition, traditional de novo drug discovery and development are risky, expensive, and time-consuming processes. One alternative approach, drug repurposing, has emerged taking advantage of off-target effects of the existing drugs. In order to identify new opportunities for the existing drugs, it is essential for us to understand the mechanisms of action of drugs, both biologically and pharmacologically. By doing this, drug repurposing would be a more effective method to develop drugs against neuropsychiatric and other disorders. Here, we review the difficulties in drug discovery and development in neuropsychiatric disorders and the extent and perspectives of drug repurposing.
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Affiliation(s)
- Hyeong-Min Lee
- Department of Cell Biology & Physiology, School of Medicine, University of North Carolina, 115 Mason Farm Road, Chapel Hill, NC 27599, USA
| | - Yuna Kim
- Department of Pediatrics, School of Medicine, Duke University, 905 S. LaSalle Street, Durham, NC 27710, USA
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Leuchter AF, Hunter AM, Krantz DE, Cook IA. Rhythms and blues: modulation of oscillatory synchrony and the mechanism of action of antidepressant treatments. Ann N Y Acad Sci 2015; 1344:78-91. [PMID: 25809789 DOI: 10.1111/nyas.12742] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Treatments for major depressive disorder (MDD) act at different hierarchical levels of biological complexity, ranging from the individual synapse to the brain as a whole. Theories of antidepressant medication action traditionally have focused on the level of cell-to-cell interaction and synaptic neurotransmission. However, recent evidence suggests that modulation of synchronized electrical activity in neuronal networks is a common effect of antidepressant treatments, including not only medications, but also neuromodulatory treatments such as repetitive transcranial magnetic stimulation. Synchronization of oscillatory network activity in particular frequency bands has been proposed to underlie neurodevelopmental and learning processes, and also may be important in the mechanism of action of antidepressant treatments. Here, we review current research on the relationship between neuroplasticity and oscillatory synchrony, which suggests that oscillatory synchrony may help mediate neuroplastic changes related to neurodevelopment, learning, and memory, as well as medication and neuromodulatory treatment for MDD. We hypothesize that medication and neuromodulation treatments may have related effects on the rate and pattern of neuronal firing, and that these effects underlie antidepressant efficacy. Elucidating the mechanisms through which oscillatory synchrony may be related to neuroplasticity could lead to enhanced treatment strategies for MDD.
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Affiliation(s)
- Andrew F Leuchter
- Laboratory of Brain, Behavior, and Pharmacology, and the Depression Research and Clinic Program, Semel Institute for Neuroscience and Human Behavior at UCLA, Los Angeles, California; Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, University of California, Los Angeles, California
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7
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Proctor A, Bianchi MT. Clinical pharmacology in sleep medicine. ISRN PHARMACOLOGY 2012; 2012:914168. [PMID: 23213564 PMCID: PMC3504423 DOI: 10.5402/2012/914168] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Accepted: 06/07/2012] [Indexed: 11/23/2022]
Abstract
The basic treatment goals of pharmacological therapies in sleep medicine are to improve waking function by either improving sleep or by increasing energy during wakefulness. Stimulants to improve waking function include amphetamine derivatives, modafinil, and caffeine. Sleep aids encompass several classes, from benzodiazepine hypnotics to over-the-counter antihistamines. Other medications used in sleep medicine include those initially used in other disorders, such as epilepsy, Parkinson's disease, and psychiatric disorders. As these medications are prescribed or encountered by providers in diverse fields of medicine, it is important to recognize the distribution of adverse effects, drug interaction profiles, metabolism, and cytochrome substrate activity. In this paper, we review the pharmacological armamentarium in the field of sleep medicine to provide a framework for risk-benefit considerations in clinical practice.
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Affiliation(s)
- Ashley Proctor
- Sleep Division, Neurology Department, Massachusetts General Hospital, Wang 720, Boston, MA 02114, USA
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Kelly JM, Bianchi MT. Mammalian sleep genetics. Neurogenetics 2012; 13:287-326. [DOI: 10.1007/s10048-012-0341-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Accepted: 08/10/2012] [Indexed: 10/27/2022]
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9
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Sadek B, Ashoor A, Mansouri AA, Lorke DE, Nurulain SM, Petroianu G, Wainwright M, Oz M. N3,N7-diaminophenothiazinium derivatives as antagonists of α7-nicotinic acetylcholine receptors expressed in Xenopus oocytes. Pharmacol Res 2012; 66:213-8. [DOI: 10.1016/j.phrs.2012.05.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Revised: 05/28/2012] [Accepted: 05/28/2012] [Indexed: 10/28/2022]
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10
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Ababneh D, Ritchie H, Webster WS. Antidepressants Cause Bradycardia and Heart Block in GD 13 Rat Embryos In Vitro. ACTA ACUST UNITED AC 2012; 95:184-93. [DOI: 10.1002/bdrb.21003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Deena Ababneh
- Department of Anatomy and Histology; Sydney Medical School; University of Sydney; Sydney; Australia
| | - Helen Ritchie
- Discipline of Biomedical Sciences,; Sydney Medical School; University of Sydney; Sydney; Australia
| | - William S. Webster
- Department of Anatomy and Histology; Sydney Medical School; University of Sydney; Sydney; Australia
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Nothdurfter C, Giegling I, Konte B, Hartmann AM, Konnerth H, Friedl M, Rammes G, Rupprecht R, Rujescu D. Lack of association of the 5-HT(3A) receptor with schizophrenia. Am J Med Genet B Neuropsychiatr Genet 2012; 159B:310-5. [PMID: 22328445 DOI: 10.1002/ajmg.b.32028] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Accepted: 01/18/2012] [Indexed: 11/08/2022]
Abstract
The serotonin type 3 (5-HT(3) ) receptor (R) belongs to the family of ligand-gated ion channels. It is supposed to play an important role in the pathogenesis of schizophrenia and might also represent an interesting target for the pharmacological treatment of this disorder. In this study, we searched for variations within the 5-HT(3A) receptor gene which might be specifically associated to schizophrenia. Twenty-nine single nucleotide polymorphisms (SNPs) of 943 schizophrenic patients compared to 2,343 healthy individuals were analyzed. SNPs were selected taking into account previous results on a 5-HT(3A) receptor domain involved in neuroleptic binding. Dominant logistic and linear regression models were calculated for the phenotypes number of hospitalizations, duration of hospitalization, age at onset and case-control. The data did not show significant associations of any SNP under investigation specific for schizophrenic patients. In conclusion, our study does not support the hypothesis that the 5-HT(3A) receptor plays a major role in the pathogenesis of schizophrenia.
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Affiliation(s)
- Caroline Nothdurfter
- Department of Psychiatry, Psychotherapy, University of Regensburg, Regensburg, Germany.
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Effects of phenothiazine-class antipsychotics on the function of α7-nicotinic acetylcholine receptors. Eur J Pharmacol 2011; 673:25-32. [PMID: 22044918 DOI: 10.1016/j.ejphar.2011.10.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Revised: 10/03/2011] [Accepted: 10/11/2011] [Indexed: 11/22/2022]
Abstract
The effects of phenothiazine-class antipsychotics (chlorpromazine, fluphenazine, phenothiazine, promazine, thioridazine, and triflupromazine) upon the function of the cloned α₇ subunit of the human nicotinic acetylcholine receptor expressed in Xenopus oocytes were tested using the two-electrode voltage-clamp technique. Fluphenazine, thioridazine, triflupromazine, chlorpromazine, and promazine reversibly inhibited acetylcholine (100 μM)-induced currents with IC₅₀ values of 3.8; 5.8; 6.1; 10.6 and 18.3 μM, respectively. Unsubstituted phenothiazine did not have a significant effect up to a concentration of 30 μM. Inhibition was further characterized using fluphenazine, the strongest inhibitor. The effect of fluphenazine was not dependent on the membrane potential. Fluphenazine (10 μM) did not affect the activity of endogenous Ca²⁺-dependent Cl⁻ channels, since the extent of inhibition by fluphenazine was unaltered by intracellular injection of the Ca²⁺ chelator BAPTA and perfusion with Ca²⁺-free bathing solution containing 2 mM Ba²⁺. Inhibition by fluphenazine, but not by chlorpromazine was reversed by increasing acetylcholine concentrations. Furthermore, specific binding of [¹²⁵I] α-bungarotoxin, a radioligand selective for α₇-nicotinic acetylcholine receptor, was inhibited by fluphenazine (10 μM), but not by chlorpromazine in oocyte membranes. In hippocampal slices, epibatidine-evoked [³H] norepinephrine release was also inhibited by fluphenazine (10 μM) and chlorpromazine (10 μM). Our results indicate that phenothiazine-class typical antipsychotics inhibit, with varying potencies, the function of α₇-nicotinic acetylcholine receptor.
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Rantamäki T, Vesa L, Antila H, Di Lieto A, Tammela P, Schmitt A, Lesch KP, Rios M, Castrén E. Antidepressant drugs transactivate TrkB neurotrophin receptors in the adult rodent brain independently of BDNF and monoamine transporter blockade. PLoS One 2011; 6:e20567. [PMID: 21666748 PMCID: PMC3110188 DOI: 10.1371/journal.pone.0020567] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2011] [Accepted: 05/04/2011] [Indexed: 01/12/2023] Open
Abstract
Background Antidepressant drugs (ADs) have been shown to activate BDNF (brain-derived neurotrophic factor) receptor TrkB in the rodent brain but the mechanism underlying this phenomenon remains unclear. ADs act as monoamine reuptake inhibitors and after prolonged treatments regulate brain bdnf mRNA levels indicating that monoamine-BDNF signaling regulate AD-induced TrkB activation in vivo. However, recent findings demonstrate that Trk receptors can be transactivated independently of their neurotrophin ligands. Methodology In this study we examined the role of BDNF, TrkB kinase activity and monoamine reuptake in the AD-induced TrkB activation in vivo and in vitro by employing several transgenic mouse models, cultured neurons and TrkB-expressing cell lines. Principal Findings Using a chemical-genetic TrkBF616A mutant and TrkB overexpressing mice, we demonstrate that ADs specifically activate both the maturely and immaturely glycosylated forms of TrkB receptors in the brain in a TrkB kinase dependent manner. However, the tricyclic AD imipramine readily induced the phosphorylation of TrkB receptors in conditional bdnf−/− knock-out mice (132.4±8.5% of control; P = 0.01), indicating that BDNF is not required for the TrkB activation. Moreover, using serotonin transporter (SERT) deficient mice and chemical lesions of monoaminergic neurons we show that neither a functional SERT nor monoamines are required for the TrkB phosphorylation response induced by the serotonin selective reuptake inhibitors fluoxetine or citalopram, or norepinephrine selective reuptake inhibitor reboxetine. However, neither ADs nor monoamine transmitters activated TrkB in cultured neurons or cell lines expressing TrkB receptors, arguing that ADs do not directly bind to TrkB. Conclusions The present findings suggest that ADs transactivate brain TrkB receptors independently of BDNF and monoamine reuptake blockade and emphasize the need of an intact tissue context for the ability of ADs to induce TrkB activity in brain.
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Affiliation(s)
- Tomi Rantamäki
- Sigrid Jusélius Laboratory, Neuroscience Center, University of Helsinki, Helsinki, Finland.
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14
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Bianchi MT, Clark AG, Fisher JL. The wake-promoting transmitter histamine preferentially enhances α-4 subunit-containing GABAA receptors. Neuropharmacology 2011; 61:747-52. [PMID: 21640733 DOI: 10.1016/j.neuropharm.2011.05.020] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2011] [Revised: 05/13/2011] [Accepted: 05/17/2011] [Indexed: 12/17/2022]
Abstract
Histamine is an important wake-promoting neurotransmitter that activates seven-transmembrane G-protein coupled histamine receptors. However, histamine demonstrates target promiscuity, including direct interaction with the structurally unrelated glutamate (NMDA) and GABA(A) receptor channels. Previous work showed that histamine enhances the activity of recombinant GABA(A) receptor isoforms typically found in synaptic locations, although co-release of histamine and GABA is not known to occur in vivo. Here we used patch clamp recordings of various recombinant GABA(A) receptor isoforms (α1-6, β1-3, γ1-3, δ) to test the hypothesis that histamine might show subunit preference under low GABA concentration (extrasynaptic) conditions. We found that histamine potentiated the whole-cell responses to GABA for all tested subunit combinations. However, the magnitude of enhancement was largest (∼400% of EC(10) GABA-evoked currents) with α4β3 and α4β3X isoforms, where X could be γ or δ. In contrast, histamine (1 mM) had small effects on prolonging deactivation of α4β3γ2 receptors following brief (5 ms) pulses of 1 mM GABA. These findings suggest GABA-histamine cross-talk may occur preferentially at low GABA concentrations, which could theoretically be inhibitory (via enhancing tonic inhibition), directly excitatory (via enhancing presynaptic GABAergic signaling), or indirectly excitatory (via inhibiting GABAergic interneurons).
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Affiliation(s)
- Matt T Bianchi
- Sleep Division, Neurology Department, Massachusetts General Hospital, Boston, MA 02114, USA
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15
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Walstab J, Rappold G, Niesler B. 5-HT(3) receptors: role in disease and target of drugs. Pharmacol Ther 2010; 128:146-69. [PMID: 20621123 DOI: 10.1016/j.pharmthera.2010.07.001] [Citation(s) in RCA: 151] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2010] [Accepted: 06/21/2010] [Indexed: 12/19/2022]
Abstract
Serotonin type 3 (5-HT(3)) receptors are pentameric ion channels belonging to the superfamily of Cys-loop receptors. Receptor activation either leads to fast excitatory responses or modulation of neurotransmitter release depending on their neuronal localisation. 5-HT(3) receptors are known to be expressed in the central nervous system in regions involved in the vomiting reflex, processing of pain, the reward system, cognition and anxiety control. In the periphery they are present on a variety of neurons and immune cells. 5-HT(3) receptors are known to be involved in emesis, pain disorders, drug addiction, psychiatric and GI disorders. Progress in molecular genetics gives direction to personalised medical strategies for treating complex diseases such as psychiatric and functional GI disorders and unravelling individual drug responses in pharmacogenetic approaches. Here we discuss the molecular basis of 5-HT(3) receptor diversity at the DNA and protein level, of which our knowledge has greatly extended in the last decade. We also evaluate their role in health and disease and describe specific case-control studies addressing the involvement of polymorphisms of 5-HT3 subunit genes in complex disorders and responses to drugs. Furthermore, we focus on the actual state of the pharmacological knowledge concerning not only classical 5-HT(3) antagonists--the setrons--but also compounds of various substance classes targeting 5-HT(3) receptors such as anaesthetics, opioids, cannabinoids, steroids, antidepressants and antipsychotics as well as natural compounds derived from plants. This shall point to alternative treatment options modulating the 5-HT(3) receptor system and open new possibilities for drug development in the future.
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Affiliation(s)
- Jutta Walstab
- Department of Human Molecular Genetics, University of Heidelberg, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany
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Mayer SC, Butera JA, Diller DJ, Dunlop J, Ellingboe J, Fan KY, Kaftan E, Mekonnen B, Mobilio D, Paslay J, Tawa G, Vasilyev D, Bowlby MR. Ion channel screening plates: design, construction, and maintenance. Assay Drug Dev Technol 2010; 8:504-11. [PMID: 20470241 DOI: 10.1089/adt.2009.0239] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Abstract
Ion channels have provided a diverse set of therapeutic targets across all areas of the pharmaceutical industry. Many companies are pursuing this unique class of targets for areas of unmet medical need such as neuropathic and inflammatory pains. In the past, focused library screening sets had been designed for CNS and kinase targets. Our investigations were aimed at creating a similar dynamic screening set enriched for compounds targeting ion channels to aid screening efforts of this important class of targets. The key advantages of this approach for ion channel targets would be: (1) to identify tool compounds for novel targets and assist in assay validation, (2) to serve as a focused screen for non-384-well adaptable targets, and (3) to jump start a particular program, that is, catch-up to competition for validated, well-known targets.
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Affiliation(s)
- Scott C Mayer
- Chemical Sciences, Pfizer Global Research and Development, Princeton, New Jersey 08543, USA.
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Bianchi MT, Botzolakis EJ. Targeting ligand-gated ion channels in neurology and psychiatry: is pharmacological promiscuity an obstacle or an opportunity? BMC Pharmacol 2010; 10:3. [PMID: 20196850 PMCID: PMC2838756 DOI: 10.1186/1471-2210-10-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2009] [Accepted: 03/02/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The traditional emphasis on developing high specificity pharmaceuticals ("magic bullets") for the treatment of Neurological and Psychiatric disorders is being challenged by emerging pathophysiology concepts that view disease states as abnormal interactions within complex networks of molecular and cellular components. So-called network pharmacology focuses on modifying the behavior of entire systems rather than individual components, a therapeutic strategy that would ideally employ single pharmacological agents capable of interacting with multiple targets ("magic shotguns"). For this approach to be successful, however, a framework for understanding pharmacological "promiscuity"--the ability of individual agents to modulate multiple molecular targets--is needed. PRESENTATION OF THE HYPOTHESIS Pharmacological promiscuity is more often the rule than the exception for drugs that target the central nervous system (CNS). We hypothesize that promiscuity is an important contributor to clinical efficacy. Modulation patterns of existing therapeutic agents may provide critical templates for future drug discovery in Neurology and Psychiatry. TESTING THE HYPOTHESIS To demonstrate the extent of pharmacological promiscuity and develop a framework for guiding drug screening, we reviewed the ability of 170 therapeutic agents and endogenous molecules to directly modulate neurotransmitter receptors, a class of historically attractive therapeutic targets in Neurology and Psychiatry. The results are summarized in the form of 1) receptor-centric maps that illustrate the degree of promiscuity for GABA-, glycine-, serotonin-, and acetylcholine-gated ion channels, and 2) drug-centric maps that illustrated how characterization of promiscuity can guide drug development. IMPLICATIONS OF THE HYPOTHESIS Developing promiscuity maps of approved neuro-pharmaceuticals will provide therapeutic class-based templates against which candidate compounds can be screened. Importantly, compounds previously rejected in traditional screens due to poor specificity could be reconsidered in this framework. Further testing will require high throughput assays to systematically characterize interactions between available CNS-active drugs and surface receptors, both ionotropic and metabotropic.
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Affiliation(s)
- Matt T Bianchi
- Neurology Department, Sleep Division, Massachusetts General Hospital, Boston, MA, USA.
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Bianchi MT. Promiscuous modulation of ion channels by anti-psychotic and anti-dementia medications. Med Hypotheses 2010; 74:297-300. [DOI: 10.1016/j.mehy.2009.09.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2009] [Accepted: 09/06/2009] [Indexed: 10/20/2022]
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Rammes G, Hosp C, Eisensamer B, Tanasic S, Nothdurfter C, Zieglgänsberger W, Rupprecht R. Identification of a domain which affects kinetics and antagonistic potency of clozapine at 5-HT3 receptors. PLoS One 2009; 4:e6715. [PMID: 19696922 PMCID: PMC2725292 DOI: 10.1371/journal.pone.0006715] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Accepted: 07/17/2009] [Indexed: 11/18/2022] Open
Abstract
The widely used atypical antipsychotic clozapine is a potent competitive antagonist at 5-HT3 receptors which may contribute to its unique psychopharmacological profile. Clozapine binds to 5-HT3 receptors of various species. However, the structural requirements of the respective binding site for clozapine remain to be determined. Differences in the primary sequences within the 5-HT3A receptor gene in schizophrenic patients may result in an alteration of the antipsychotic potency and/or the side effect profile of clozapine. To determine these structural requirements we constructed chimeras with different 5-HT3A receptor sequences of murine and human origin and expressed these mutants in human embryonic kidney (HEK) 293 cells. Clozapine antagonises recombinant mouse 5-HT3A receptors with higher potency compared to recombinant human 5-HT3A receptors. 5-HT activation curves and clozapine inhibition curves yielded the parameters EC50 and IC50 for all receptors tested in the range of 0.6–2.7 µM and 1.5–83.3 nM, respectively. The use of the Cheng-Prusoff equation to calculate the dissociation constant Kb values for clozapine revealed that an extracellular sequence (length 86 aa) close to the transmembrane domain M1 strongly determines the binding affinity of clozapine. Kb values of clozapine were significantly lower (0.3–1.1 nM) for receptors containing the murine sequence and higher when compared with receptors containing the respective human sequence (5.8–13.4 nM). Thus, individual differences in the primary sequence of 5-HT3 receptors may be crucial for the antipsychotic potency and/or the side effect profile of clozapine.
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Freysoldt A, Fleckenstein J, Lang PM, Irnich D, Grafe P, Carr RW. Low concentrations of amitriptyline inhibit nicotinic receptors in unmyelinated axons of human peripheral nerve. Br J Pharmacol 2009; 158:797-805. [PMID: 19694730 DOI: 10.1111/j.1476-5381.2009.00347.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND AND PURPOSE Amitriptyline is often prescribed as a first-line treatment for neuropathic pain but its precise mode of analgesic action remains uncertain. Amitriptyline is known to inhibit voltage-dependent ion channels and also to act as an antagonist at ligand-gated ion channels, such as nicotinic acetylcholine receptors (nAChRs). In the present study, we tested the effect of amitriptyline on nicotinic responses of unmyelinated axons in isolated segments of human peripheral nerve. In particular, a comparison was made between the concentrations of amitriptyline necessary for inhibition of nAChRs and those required for inhibition of the compound C-fibre action potential. EXPERIMENTAL APPROACH Isolated axon fascicles were prepared from short segments of human sural nerve, and multiple measures of axonal excitability were recorded using computer-controlled threshold tracking software. KEY RESULTS Amitriptyline (EC(50) 2.6 microM) reduced the nicotine-induced increase in C-fibre excitability but only slightly altered the amplitude and latency to onset of the compound action potential. In contrast, tetrodotoxin produced a clear reduction in the amplitude and a prolongation of action potential onset latency but was without effect on the nicotine-induced increase in axonal excitability. CONCLUSIONS AND IMPLICATIONS These data demonstrate that low concentrations of amitriptyline suppress the response of human peripheral C-type axons to nicotine by directly inhibiting nAChRs. Blockade of tetrodotoxin-sensitive, voltage-dependent sodium channels does not contribute to this effect. An inhibitory action of amitriptyline on nAChRs in unmyelinated nociceptive axons may be an important component of amitriptyline's therapeutic effect in the treatment of neuropathic pain.
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Affiliation(s)
- A Freysoldt
- Institute of Physiology, University of Munich, Munich, Germany
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From ion channels to complex networks: Magic bullet versus magic shotgun approaches to anticonvulsant pharmacotherapy. Med Hypotheses 2009; 72:297-305. [PMID: 19046822 DOI: 10.1016/j.mehy.2008.09.049] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2008] [Revised: 08/05/2008] [Accepted: 09/18/2008] [Indexed: 01/15/2023]
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