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Kalinichenko L, Kornhuber J, Sinning S, Haase J, Müller CP. Serotonin Signaling through Lipid Membranes. ACS Chem Neurosci 2024; 15:1298-1320. [PMID: 38499042 PMCID: PMC10995955 DOI: 10.1021/acschemneuro.3c00823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 02/22/2024] [Accepted: 02/27/2024] [Indexed: 03/20/2024] Open
Abstract
Serotonin (5-HT) is a vital modulatory neurotransmitter responsible for regulating most behaviors in the brain. An inefficient 5-HT synaptic function is often linked to various mental disorders. Primarily, membrane proteins controlling the expression and activity of 5-HT synthesis, storage, release, receptor activation, and inactivation are critical to 5-HT signaling in synaptic and extra-synaptic sites. Moreover, these signals represent information transmission across membranes. Although the lipid membrane environment is often viewed as fairly stable, emerging research suggests significant functional lipid-protein interactions with many synaptic 5-HT proteins. These protein-lipid interactions extend to almost all the primary lipid classes that form the plasma membrane. Collectively, these lipid classes and lipid-protein interactions affect 5-HT synaptic efficacy at the synapse. The highly dynamic lipid composition of synaptic membranes suggests that these lipids and their interactions with proteins may contribute to the plasticity of the 5-HT synapse. Therefore, this broader protein-lipid model of the 5-HT synapse necessitates a reconsideration of 5-HT's role in various associated mental disorders.
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Affiliation(s)
- Liubov
S. Kalinichenko
- Department
of Psychiatry and Psychotherapy, University
Clinic, Friedrich-Alexander-University of Erlangen-Nürnberg, Schwabachanlage 6, 91054, Erlangen, Germany
| | - Johannes Kornhuber
- Department
of Psychiatry and Psychotherapy, University
Clinic, Friedrich-Alexander-University of Erlangen-Nürnberg, Schwabachanlage 6, 91054, Erlangen, Germany
| | - Steffen Sinning
- Department
of Forensic Medicine, Aarhus University, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark
| | - Jana Haase
- School
of Biomolecular and Biomedical Science, UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Christian P. Müller
- Department
of Psychiatry and Psychotherapy, University
Clinic, Friedrich-Alexander-University of Erlangen-Nürnberg, Schwabachanlage 6, 91054, Erlangen, Germany
- Institute
of Psychopharmacology, Central Institute of Mental Health, Medical
Faculty Mannheim, Heidelberg University, 69047, Mannheim, Germany
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2
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Bukowski L, Strøm ME, Andersen JL, Maesen JB, Tian L, Sinning S. 5-HT_FAsTR: a versatile, label-free, high-throughput, fluorescence-based microplate assay to quantify serotonin transport and release. Sci Rep 2024; 14:6541. [PMID: 38504103 PMCID: PMC10951269 DOI: 10.1038/s41598-024-56712-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Accepted: 03/09/2024] [Indexed: 03/21/2024] Open
Abstract
The neurotransmitter serotonin plays a pivotal role in mood and depression. It also acts as a vasoconstrictor within blood vessels and is the main neurotransmitter in the gastrointestinal system. In neurotransmission, released serotonin is taken up by serotonin transporters, which are principal targets of antidepressants and the psychostimulant, ecstasy. The investigation of serotonin transporters have relied almost exclusively on the use of radiolabeled serotonin in heterogenous end-point assays. Here we adapt the genetically encoded fluorescent biosensor, iSeroSnFR, to establish and validate the Serotonin (5-HT) Fluorescence Assay for Transport and Release (5-HT_FAsTR) for functional and pharmacological studies of serotonin transport and release. We demonstrate the applicability of the method for the study of a neuronal, high-affinity, low-capacity serotonin transporter (SERT) as well as an extraneuronal low-affinity, high-capacity organic cation transporter and mutants thereof. 5HT_FAsTR offers an accessible, versatile and reliable semi-homogenous assay format that only relies on a fluorescence plate reader for repeated, real-time measurements of serotonin influx and efflux. 5HT_FAsTR accelerates and democratizes functional characterization and pharmacological studies of serotonin transporters and genetic variants thereof in disease states such as depression, anxiety and ADHD.
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Affiliation(s)
- Lina Bukowski
- Department of Forensic Medicine, Aarhus University, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark
| | - Markus Emanuel Strøm
- Department of Forensic Medicine, Aarhus University, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark
| | - Jens Lindengren Andersen
- Department of Forensic Medicine, Aarhus University, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark
| | - Jannick Bang Maesen
- Department of Forensic Medicine, Aarhus University, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark
| | - Lin Tian
- Department of Biochemistry and Molecular Medicine, University of California, Davis, CA, 95616-8635, USA
- Max Planck Florida Institute for Neuroscience, Jupiter, FL, 33458, USA
| | - Steffen Sinning
- Department of Forensic Medicine, Aarhus University, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark.
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3
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Busk M, Sinning S, Alstrup AKO, Munk OL, Vendelbo MH. Nuclear Medicine Preclinical Research: The Role of Cell Cultures. Semin Nucl Med 2023; 53:558-569. [PMID: 37268499 DOI: 10.1053/j.semnuclmed.2023.04.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Accepted: 04/30/2023] [Indexed: 06/04/2023]
Abstract
Cell lines are essential in biomedical research due to their adaptability and precise simulation of physiological and pathophysiological conditions. Cell culture techniques have greatly advanced our understanding of biology in various fields and are widely regarded as a reliable and durable tool. Their diverse applications make them indispensable in scientific research. Radiation-emitting compounds are commonly used in cell culture research to investigate biological processes. Radiolabeled compounds are utilized to study cell function, metabolism, molecular markers, receptor density, drug binding and kinetics, as well as to analyze the direct interaction of radiotracers with target organ cells. This allows for the examination of normal physiology and disease states. The In Vitro system simplifies the study and filters out nonspecific signals from the In Vivo environment, leading to more specific results. Moreover, cell cultures offer ethical advantages when evaluating new tracers and drugs in preclinical studies. While cell experiments cannot entirely replace animal experiments, they reduce the need for live animals in experimentation.
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Affiliation(s)
- Morten Busk
- Department of experimental clinical oncology, Aarhus University Hospital, Aarhus, Denmark; Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark
| | - Steffen Sinning
- Department of Forensic Medicine, Aarhus University, Aarhus, Denmark
| | - Aage K O Alstrup
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark; Department of Nuclear Medicine and PET, Aarhus University Hospital, Aarhus, Denmark
| | - Ole L Munk
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark; Department of Nuclear Medicine and PET, Aarhus University Hospital, Aarhus, Denmark
| | - Mikkel H Vendelbo
- Department of Nuclear Medicine and PET, Aarhus University Hospital, Aarhus, Denmark; Department of Biomedicine, Aarhus University, Aarhus, Denmark.
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4
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Shahsavar A, Stohler P, Bourenkov G, Zimmermann I, Siegrist M, Guba W, Pinard E, Sinning S, Seeger M, Schneider T, Dawson R, Nissen P. Structural insights into mechanism of glycine reuptake inhibition. Acta Cryst Sect A 2022. [DOI: 10.1107/s2053273322096164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/19/2023]
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5
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Unger EK, Keller JP, Altermatt M, Liang R, Matsui A, Dong C, Hon OJ, Yao Z, Sun J, Banala S, Flanigan ME, Jaffe DA, Hartanto S, Carlen J, Mizuno GO, Borden PM, Shivange AV, Cameron LP, Sinning S, Underhill SM, Olson DE, Amara SG, Temple Lang D, Rudnick G, Marvin JS, Lavis LD, Lester HA, Alvarez VA, Fisher AJ, Prescher JA, Kash TL, Yarov-Yarovoy V, Gradinaru V, Looger LL, Tian L. Directed Evolution of a Selective and Sensitive Serotonin Sensor via Machine Learning. Cell 2020; 183:1986-2002.e26. [PMID: 33333022 PMCID: PMC8025677 DOI: 10.1016/j.cell.2020.11.040] [Citation(s) in RCA: 88] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2019] [Revised: 06/22/2020] [Accepted: 11/20/2020] [Indexed: 12/28/2022]
Abstract
Serotonin plays a central role in cognition and is the target of most pharmaceuticals for psychiatric disorders. Existing drugs have limited efficacy; creation of improved versions will require better understanding of serotonergic circuitry, which has been hampered by our inability to monitor serotonin release and transport with high spatial and temporal resolution. We developed and applied a binding-pocket redesign strategy, guided by machine learning, to create a high-performance, soluble, fluorescent serotonin sensor (iSeroSnFR), enabling optical detection of millisecond-scale serotonin transients. We demonstrate that iSeroSnFR can be used to detect serotonin release in freely behaving mice during fear conditioning, social interaction, and sleep/wake transitions. We also developed a robust assay of serotonin transporter function and modulation by drugs. We expect that both machine-learning-guided binding-pocket redesign and iSeroSnFR will have broad utility for the development of other sensors and in vitro and in vivo serotonin detection, respectively.
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Affiliation(s)
- Elizabeth K Unger
- Departments of Biochemistry and Molecular Medicine, Chemistry, Statistics, Molecular and Cellular Biology, and Physiology and Membrane Biology, the Center for Neuroscience, and Graduate Programs in Molecular, Cellular, and Integrative Physiology, Biochemistry, Molecular, Cellular and Developmental Biology and Neuroscience, University of California, Davis, Davis, CA 95616, USA
| | - Jacob P Keller
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20174, USA
| | - Michael Altermatt
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Ruqiang Liang
- Departments of Biochemistry and Molecular Medicine, Chemistry, Statistics, Molecular and Cellular Biology, and Physiology and Membrane Biology, the Center for Neuroscience, and Graduate Programs in Molecular, Cellular, and Integrative Physiology, Biochemistry, Molecular, Cellular and Developmental Biology and Neuroscience, University of California, Davis, Davis, CA 95616, USA
| | - Aya Matsui
- Laboratory on Neurobiology of Compulsive Behaviors, National Institute on Alcohol Abuse and Alcoholism, NIH, Bethesda, MD 20892, USA
| | - Chunyang Dong
- Departments of Biochemistry and Molecular Medicine, Chemistry, Statistics, Molecular and Cellular Biology, and Physiology and Membrane Biology, the Center for Neuroscience, and Graduate Programs in Molecular, Cellular, and Integrative Physiology, Biochemistry, Molecular, Cellular and Developmental Biology and Neuroscience, University of California, Davis, Davis, CA 95616, USA
| | - Olivia J Hon
- Bowles Center for Alcohol Studies, Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Zi Yao
- Department of Chemistry, University of California, Irvine, Irvine, CA 92697, USA
| | - Junqing Sun
- Departments of Biochemistry and Molecular Medicine, Chemistry, Statistics, Molecular and Cellular Biology, and Physiology and Membrane Biology, the Center for Neuroscience, and Graduate Programs in Molecular, Cellular, and Integrative Physiology, Biochemistry, Molecular, Cellular and Developmental Biology and Neuroscience, University of California, Davis, Davis, CA 95616, USA
| | - Samba Banala
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20174, USA
| | - Meghan E Flanigan
- Bowles Center for Alcohol Studies, Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - David A Jaffe
- Departments of Biochemistry and Molecular Medicine, Chemistry, Statistics, Molecular and Cellular Biology, and Physiology and Membrane Biology, the Center for Neuroscience, and Graduate Programs in Molecular, Cellular, and Integrative Physiology, Biochemistry, Molecular, Cellular and Developmental Biology and Neuroscience, University of California, Davis, Davis, CA 95616, USA
| | - Samantha Hartanto
- Departments of Biochemistry and Molecular Medicine, Chemistry, Statistics, Molecular and Cellular Biology, and Physiology and Membrane Biology, the Center for Neuroscience, and Graduate Programs in Molecular, Cellular, and Integrative Physiology, Biochemistry, Molecular, Cellular and Developmental Biology and Neuroscience, University of California, Davis, Davis, CA 95616, USA
| | - Jane Carlen
- Departments of Biochemistry and Molecular Medicine, Chemistry, Statistics, Molecular and Cellular Biology, and Physiology and Membrane Biology, the Center for Neuroscience, and Graduate Programs in Molecular, Cellular, and Integrative Physiology, Biochemistry, Molecular, Cellular and Developmental Biology and Neuroscience, University of California, Davis, Davis, CA 95616, USA
| | - Grace O Mizuno
- Departments of Biochemistry and Molecular Medicine, Chemistry, Statistics, Molecular and Cellular Biology, and Physiology and Membrane Biology, the Center for Neuroscience, and Graduate Programs in Molecular, Cellular, and Integrative Physiology, Biochemistry, Molecular, Cellular and Developmental Biology and Neuroscience, University of California, Davis, Davis, CA 95616, USA
| | - Phillip M Borden
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20174, USA
| | - Amol V Shivange
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Lindsay P Cameron
- Departments of Biochemistry and Molecular Medicine, Chemistry, Statistics, Molecular and Cellular Biology, and Physiology and Membrane Biology, the Center for Neuroscience, and Graduate Programs in Molecular, Cellular, and Integrative Physiology, Biochemistry, Molecular, Cellular and Developmental Biology and Neuroscience, University of California, Davis, Davis, CA 95616, USA
| | - Steffen Sinning
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Suzanne M Underhill
- Laboratory of Molecular and Cellular Neurobiology, National Institute on Mental Health, NIH, Bethesda, MD 20892, USA
| | - David E Olson
- Departments of Biochemistry and Molecular Medicine, Chemistry, Statistics, Molecular and Cellular Biology, and Physiology and Membrane Biology, the Center for Neuroscience, and Graduate Programs in Molecular, Cellular, and Integrative Physiology, Biochemistry, Molecular, Cellular and Developmental Biology and Neuroscience, University of California, Davis, Davis, CA 95616, USA
| | - Susan G Amara
- Laboratory of Molecular and Cellular Neurobiology, National Institute on Mental Health, NIH, Bethesda, MD 20892, USA
| | - Duncan Temple Lang
- Departments of Biochemistry and Molecular Medicine, Chemistry, Statistics, Molecular and Cellular Biology, and Physiology and Membrane Biology, the Center for Neuroscience, and Graduate Programs in Molecular, Cellular, and Integrative Physiology, Biochemistry, Molecular, Cellular and Developmental Biology and Neuroscience, University of California, Davis, Davis, CA 95616, USA
| | - Gary Rudnick
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Jonathan S Marvin
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20174, USA
| | - Luke D Lavis
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20174, USA
| | - Henry A Lester
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Veronica A Alvarez
- Laboratory on Neurobiology of Compulsive Behaviors, National Institute on Alcohol Abuse and Alcoholism, NIH, Bethesda, MD 20892, USA
| | - Andrew J Fisher
- Departments of Biochemistry and Molecular Medicine, Chemistry, Statistics, Molecular and Cellular Biology, and Physiology and Membrane Biology, the Center for Neuroscience, and Graduate Programs in Molecular, Cellular, and Integrative Physiology, Biochemistry, Molecular, Cellular and Developmental Biology and Neuroscience, University of California, Davis, Davis, CA 95616, USA
| | - Jennifer A Prescher
- Department of Chemistry, University of California, Irvine, Irvine, CA 92697, USA
| | - Thomas L Kash
- Bowles Center for Alcohol Studies, Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Vladimir Yarov-Yarovoy
- Departments of Biochemistry and Molecular Medicine, Chemistry, Statistics, Molecular and Cellular Biology, and Physiology and Membrane Biology, the Center for Neuroscience, and Graduate Programs in Molecular, Cellular, and Integrative Physiology, Biochemistry, Molecular, Cellular and Developmental Biology and Neuroscience, University of California, Davis, Davis, CA 95616, USA
| | - Viviana Gradinaru
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Loren L Looger
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20174, USA.
| | - Lin Tian
- Departments of Biochemistry and Molecular Medicine, Chemistry, Statistics, Molecular and Cellular Biology, and Physiology and Membrane Biology, the Center for Neuroscience, and Graduate Programs in Molecular, Cellular, and Integrative Physiology, Biochemistry, Molecular, Cellular and Developmental Biology and Neuroscience, University of California, Davis, Davis, CA 95616, USA.
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6
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Cheng B, Morstein J, Ladefoged LK, Maesen JB, Schiøtt B, Sinning S, Trauner D. A Photoswitchable Inhibitor of the Human Serotonin Transporter. ACS Chem Neurosci 2020; 11:1231-1237. [PMID: 32275382 DOI: 10.1021/acschemneuro.9b00521] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The human serotonin transporter (hSERT) terminates serotonergic signaling through reuptake of neurotransmitter into presynaptic neurons and is a target for many antidepressant drugs. We describe here the development of a photoswitchable hSERT inhibitor, termed azo-escitalopram, that can be reversibly switched between trans and cis configurations using light of different wavelengths. The dark-adapted trans isomer was found to be significantly less active than the cis isomer, formed upon irradiation.
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Affiliation(s)
- Bichu Cheng
- School of Science, Harbin Institute of Technology (Shenzhen), Shenzhen 518055, China
- Department of Chemistry, New York University, 100 Washington Square East, New York, New York 10003, United States
| | - Johannes Morstein
- Department of Chemistry, New York University, 100 Washington Square East, New York, New York 10003, United States
| | - Lucy Kate Ladefoged
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark
| | - Jannick Bang Maesen
- Department of Forensic Medicine, Aarhus University, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark
| | - Birgit Schiøtt
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark
| | - Steffen Sinning
- Department of Forensic Medicine, Aarhus University, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark
| | - Dirk Trauner
- Department of Chemistry, New York University, 100 Washington Square East, New York, New York 10003, United States
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7
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Laursen L, Severinsen K, Kristensen KB, Periole X, Overby M, Müller HK, Schiøtt B, Sinning S. Cholesterol binding to a conserved site modulates the conformation, pharmacology, and transport kinetics of the human serotonin transporter. J Biol Chem 2018; 293:3510-3523. [PMID: 29352106 DOI: 10.1074/jbc.m117.809046] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 01/14/2018] [Indexed: 12/31/2022] Open
Abstract
The serotonin transporter (SERT) is important for reuptake of the neurotransmitter serotonin from the synaptic cleft and is also the target of most antidepressants. It has previously been shown that cholesterol in the membrane bilayer affects the conformation of SERT. Although recent crystal structures have identified several potential cholesterol-binding sites, it is unclear whether any of these potential cholesterol sites are occupied by cholesterol and functionally relevant. In the present study, we focus on the conserved cholesterol site 1 (CHOL1) located in a hydrophobic groove between TM1a, TM5, and TM7. By molecular dynamics simulations, we demonstrate a strong binding of cholesterol to CHOL1 in a membrane bilayer environment. In biochemical experiments, we find that cholesterol depletion induces a more inward-facing conformation favoring substrate analog binding. Consistent with this, we find that mutations in CHOL1 with a negative impact on cholesterol binding induce a more inward-facing conformation, and, vice versa, mutations with a positive impact on cholesterol binding induce a more outward-facing conformation. This shift in transporter conformation dictated by the ability to bind cholesterol in CHOL1 affects the apparent substrate affinity, maximum transport velocity, and turnover rates. Taken together, we show that occupation of CHOL1 by cholesterol is of major importance in the transporter conformational equilibrium, which in turn dictates ligand potency and serotonin transport activity. Based on our findings, we propose a mechanistic model that incorporates the role of cholesterol binding to CHOL1 in the function of SERT.
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Affiliation(s)
- Louise Laursen
- From the Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus University Hospital, Skovagervej 2, DK-8240 Risskov, Denmark and
| | - Kasper Severinsen
- From the Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus University Hospital, Skovagervej 2, DK-8240 Risskov, Denmark and
| | - Kristina Birch Kristensen
- From the Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus University Hospital, Skovagervej 2, DK-8240 Risskov, Denmark and
| | - Xavier Periole
- the Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Malene Overby
- From the Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus University Hospital, Skovagervej 2, DK-8240 Risskov, Denmark and
| | - Heidi Kaastrup Müller
- From the Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus University Hospital, Skovagervej 2, DK-8240 Risskov, Denmark and
| | - Birgit Schiøtt
- the Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Steffen Sinning
- From the Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus University Hospital, Skovagervej 2, DK-8240 Risskov, Denmark and
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8
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Zeppelin T, Ladefoged LK, Sinning S, Periole X, Schiøtt B. A direct interaction of cholesterol with the dopamine transporter prevents its out-to-inward transition. PLoS Comput Biol 2018; 14:e1005907. [PMID: 29329285 PMCID: PMC5811071 DOI: 10.1371/journal.pcbi.1005907] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 02/13/2018] [Accepted: 11/29/2017] [Indexed: 01/30/2023] Open
Abstract
Monoamine transporters (MATs) carry out neurotransmitter reuptake from the synaptic cleft, a key step in neurotransmission, which is targeted in the treatment of neurological disorders. Cholesterol (CHOL), a major component of the synaptic plasma membrane, has been shown to exhibit a modulatory effect on MATs. Recent crystal structures of the dopamine transporter (DAT) revealed the presence of two conserved CHOL-like molecules, suggesting a functional protein-CHOL direct interaction. Here, we present extensive atomistic molecular dynamics (MD) simulations of DAT in an outward-facing conformation. In the absence of bound CHOL, DAT undergoes structural changes reflecting early events of dopamine transport: transition to an inward-facing conformation. In contrast, in the presence of bound CHOL, these conformational changes are inhibited, seemingly by an immobilization of the intracellular interface of transmembrane helix 1a and 5 by CHOL. We also provide evidence, from coarse grain MD simulations that the CHOL sites observed in the DAT crystal structures are preserved in all human monoamine transporters (dopamine, serotonin and norepinephrine), suggesting that our findings might extend to the entire family.
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Affiliation(s)
- Talia Zeppelin
- Department of Chemistry, Aarhus University, Aarhus C, Denmark
| | - Lucy Kate Ladefoged
- Department of Chemistry, Aarhus University, Aarhus C, Denmark
- Interdisciplinary Nanoscience Center, Aarhus University, Aarhus C, Denmark
| | - Steffen Sinning
- Department of Chemistry, Aarhus University, Aarhus C, Denmark
- Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus C, Denmark
| | - Xavier Periole
- Department of Chemistry, Aarhus University, Aarhus C, Denmark
| | - Birgit Schiøtt
- Department of Chemistry, Aarhus University, Aarhus C, Denmark
- Interdisciplinary Nanoscience Center, Aarhus University, Aarhus C, Denmark
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9
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Malinauskaite L, Said S, Sahin C, Grouleff J, Shahsavar A, Bjerregaard H, Noer P, Severinsen K, Boesen T, Schiøtt B, Sinning S, Nissen P. A conserved leucine occupies the empty substrate site of LeuT in the Na(+)-free return state. Nat Commun 2016; 7:11673. [PMID: 27221344 PMCID: PMC4894957 DOI: 10.1038/ncomms11673] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Accepted: 04/18/2016] [Indexed: 02/05/2023] Open
Abstract
Bacterial members of the neurotransmitter:sodium symporter (NSS) family perform Na(+)-dependent amino-acid uptake and extrude H(+) in return. Previous NSS structures represent intermediates of Na(+)/substrate binding or intracellular release, but not the inward-to-outward return transition. Here we report crystal structures of Aquifex aeolicus LeuT in an outward-oriented, Na(+)- and substrate-free state likely to be H(+)-occluded. We find a remarkable rotation of the conserved Leu25 into the empty substrate-binding pocket and rearrangements of the empty Na(+) sites. Mutational studies of the equivalent Leu99 in the human serotonin transporter show a critical role of this residue on the transport rate. Molecular dynamics simulations show that extracellular Na(+) is blocked unless Leu25 is rotated out of the substrate-binding pocket. We propose that Leu25 facilitates the inward-to-outward transition by compensating a Na(+)- and substrate-free state and acts as the gatekeeper for Na(+) binding that prevents leak in inward-outward return transitions.
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Affiliation(s)
- Lina Malinauskaite
- Danish Research Institute of Translational Neuroscience-DANDRITE, Nordic-EMBL Partnership for Molecular Medicine, Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, Aarhus C DK-8000, Denmark
| | - Saida Said
- Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Skovagervej 2, Risskov DK-8240, Denmark
| | - Caglanur Sahin
- Danish Research Institute of Translational Neuroscience-DANDRITE, Nordic-EMBL Partnership for Molecular Medicine, Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, Aarhus C DK-8000, Denmark
| | - Julie Grouleff
- inSPIN and iNANO centers, Department of Chemistry, Aarhus University, Langelandsgade 140, Aarhus C DK-8000, Denmark
| | - Azadeh Shahsavar
- Danish Research Institute of Translational Neuroscience-DANDRITE, Nordic-EMBL Partnership for Molecular Medicine, Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, Aarhus C DK-8000, Denmark
| | - Henriette Bjerregaard
- Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Skovagervej 2, Risskov DK-8240, Denmark
| | - Pernille Noer
- Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Skovagervej 2, Risskov DK-8240, Denmark
| | - Kasper Severinsen
- Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Skovagervej 2, Risskov DK-8240, Denmark
| | - Thomas Boesen
- Danish Research Institute of Translational Neuroscience-DANDRITE, Nordic-EMBL Partnership for Molecular Medicine, Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, Aarhus C DK-8000, Denmark
| | - Birgit Schiøtt
- inSPIN and iNANO centers, Department of Chemistry, Aarhus University, Langelandsgade 140, Aarhus C DK-8000, Denmark
| | - Steffen Sinning
- Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Skovagervej 2, Risskov DK-8240, Denmark
| | - Poul Nissen
- Danish Research Institute of Translational Neuroscience-DANDRITE, Nordic-EMBL Partnership for Molecular Medicine, Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, Aarhus C DK-8000, Denmark
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10
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Rannversson H, Wilson P, Kristensen KB, Sinning S, Kristensen AS, Strømgaard K, Andersen J. Importance of the Extracellular Loop 4 in the Human Serotonin Transporter for Inhibitor Binding and Substrate Translocation. J Biol Chem 2015; 290:14582-94. [PMID: 25903124 DOI: 10.1074/jbc.m114.629071] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Indexed: 12/20/2022] Open
Abstract
The serotonin transporter (SERT) terminates serotonergic neurotransmission by performing reuptake of released serotonin, and SERT is the primary target for antidepressants. SERT mediates the reuptake of serotonin through an alternating access mechanism, implying that a central substrate site is connected to both sides of the membrane by permeation pathways, of which only one is accessible at a time. The coordinated conformational changes in SERT associated with substrate translocation are not fully understood. Here, we have identified a Leu to Glu mutation at position 406 (L406E) in the extracellular loop 4 (EL4) of human SERT, which induced a remarkable gain-of-potency (up to >40-fold) for a range of SERT inhibitors. The effects were highly specific for L406E relative to six other mutations in the same position, including the closely related L406D mutation, showing that the effects induced by L406E are not simply charge-related effects. Leu(406) is located >10 Å from the central inhibitor binding site indicating that the mutation affects inhibitor binding in an indirect manner. We found that L406E decreased accessibility to a residue in the cytoplasmic pathway. The shift in equilibrium to favor a more outward-facing conformation of SERT can explain the reduced turnover rate and increased association rate of inhibitor binding we found for L406E. Together, our findings show that EL4 allosterically can modulate inhibitor binding within the central binding site, and substantiates that EL4 has an important role in controlling the conformational equilibrium of human SERT.
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Affiliation(s)
- Hafsteinn Rannversson
- From the Department of Drug Design and Pharmacology, University of Copenhagen, DK-2100 Copenhagen and
| | - Pamela Wilson
- From the Department of Drug Design and Pharmacology, University of Copenhagen, DK-2100 Copenhagen and
| | - Kristina Birch Kristensen
- the Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, DK-8240 Risskov, Denmark
| | - Steffen Sinning
- the Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, DK-8240 Risskov, Denmark
| | - Anders Skov Kristensen
- From the Department of Drug Design and Pharmacology, University of Copenhagen, DK-2100 Copenhagen and
| | - Kristian Strømgaard
- From the Department of Drug Design and Pharmacology, University of Copenhagen, DK-2100 Copenhagen and
| | - Jacob Andersen
- From the Department of Drug Design and Pharmacology, University of Copenhagen, DK-2100 Copenhagen and
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11
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Bjerregaard H, Severinsen K, Said S, Wiborg O, Sinning S. A dualistic conformational response to substrate binding in the human serotonin transporter reveals a high affinity state for serotonin. J Biol Chem 2015; 290:7747-55. [PMID: 25614630 DOI: 10.1074/jbc.m114.573477] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Serotonergic neurotransmission is modulated by the membrane-embedded serotonin transporter (SERT). SERT mediates the reuptake of serotonin into the presynaptic neurons. Conformational changes in SERT occur upon binding of ions and substrate and are crucial for translocation of serotonin across the membrane. Our understanding of these conformational changes is mainly based on crystal structures of a bacterial homolog in various conformations, derived homology models of eukaryotic neurotransmitter transporters, and substituted cysteine accessibility method of SERT. However, the dynamic changes that occur in the human SERT upon binding of ions, the translocation of substrate, and the role of cholesterol in this interplay are not fully elucidated. Here we show that serotonin induces a dualistic conformational response in SERT. We exploited the substituted cysteine scanning method under conditions that were sensitized to detect a more outward-facing conformation of SERT. We found a novel high affinity outward-facing conformational state of the human SERT induced by serotonin. The ionic requirements for this new conformational response to serotonin mirror the ionic requirements for translocation. Furthermore, we found that membrane cholesterol plays a role in the dualistic conformational response in SERT induced by serotonin. Our results indicate the existence of a subpopulation of SERT responding differently to serotonin binding than hitherto believed and that membrane cholesterol plays a role in this subpopulation of SERT.
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Affiliation(s)
- Henriette Bjerregaard
- From the Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus University Hospital, Skovagervej 2, DK-8240 Risskov, Denmark
| | - Kasper Severinsen
- From the Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus University Hospital, Skovagervej 2, DK-8240 Risskov, Denmark
| | - Saida Said
- From the Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus University Hospital, Skovagervej 2, DK-8240 Risskov, Denmark
| | - Ove Wiborg
- From the Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus University Hospital, Skovagervej 2, DK-8240 Risskov, Denmark
| | - Steffen Sinning
- From the Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus University Hospital, Skovagervej 2, DK-8240 Risskov, Denmark
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12
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Severinsen K, Koldsø H, Thorup KAV, Schjøth-Eskesen C, Møller PT, Wiborg O, Jensen HH, Sinning S, Schiøtt B. Binding of Mazindol and Analogs to the Human Serotonin and Dopamine Transporters. Mol Pharmacol 2013; 85:208-17. [DOI: 10.1124/mol.113.088922] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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13
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Bright SA, Brinkø A, Larsen MT, Sinning S, Williams DC, Jensen HH. Basic N-interlinked imipramines show apoptotic activity against malignant cells including Burkitt’s lymphoma. Bioorg Med Chem Lett 2013; 23:1220-4. [DOI: 10.1016/j.bmcl.2013.01.020] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Revised: 01/01/2013] [Accepted: 01/04/2013] [Indexed: 11/15/2022]
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14
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Koldsø H, Christiansen AB, Sinning S, Schiøtt B. Comparative modeling of the human monoamine transporters: similarities in substrate binding. ACS Chem Neurosci 2013; 4:295-309. [PMID: 23421681 PMCID: PMC3582297 DOI: 10.1021/cn300148r] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Accepted: 10/24/2012] [Indexed: 11/30/2022] Open
Abstract
The amino acid compositions of the substrate binding pockets of the three human monoamine transporters are compared as is the orientation of the endogenous substrates, serotonin, dopamine, and norepinephrine, bound in these. Through a combination of homology modeling, induced fit dockings, molecular dynamics simulations, and uptake experiments in mutant transporters, we propose a common binding mode for the three substrates. The longitudinal axis of the substrates is similarly oriented with these, forming an ionic interaction between the ammonium group and a highly conserved aspartate, Asp98 (serotonin transporter, hSERT), Asp79 (dopamine transporter, hDAT), and Asp75 (norepinephrine transporter, hNET). The 6-position of serotonin and the para-hydroxyl groups of dopamine and norepinephrine were found to face Ala173 in hSERT, Gly153 in hDAT, and Gly149 in hNET. Three rotations of the substrates around the longitudinal axis were identified. In each mode, an aromatic hydroxyl group of the substrates occupied equivalent volumes of the three binding pockets, where small changes in amino acid composition explains the differences in selectivity. Uptake experiments support that the 5-hydroxyl group of serotonin and the meta-hydroxyl group norepinephrine and dopamine are placed in the hydrophilic pocket around Ala173, Ser438, and Thr439 in hSERT corresponding to Gly149, Ser419, Ser420 in hNET and Gly153 Ser422 and Ala423 in hDAT. Furthermore, hDAT was found to possess an additional hydrophilic pocket around Ser149 to accommodate the para-hydroxyl group. Understanding these subtle differences between the binding site compositions of the three transporters is imperative for understanding the substrate selectivity, which could eventually aid in developing future selective medicines.
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Affiliation(s)
- Heidi Koldsø
- Center for Insoluble Protein
Structures (inSPIN) and Interdisciplinary Nanoscience
Center (iNANO), Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus
C, Denmark
| | - Anja B. Christiansen
- Laboratory of
Molecular Neurobiology,
Centre for Psychiatric Research, Aarhus University Hospital, Skovagervej 2, 8240 Risskov, Denmark
| | - Steffen Sinning
- Laboratory of
Molecular Neurobiology,
Centre for Psychiatric Research, Aarhus University Hospital, Skovagervej 2, 8240 Risskov, Denmark
| | - Birgit Schiøtt
- Center for Insoluble Protein
Structures (inSPIN) and Interdisciplinary Nanoscience
Center (iNANO), Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus
C, Denmark
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15
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Severinsen K, Kraft JF, Koldsø H, Vinberg KA, Rothman RB, Partilla JS, Wiborg O, Blough B, Schiøtt B, Sinning S. Binding of the amphetamine-like 1-phenyl-piperazine to monoamine transporters. ACS Chem Neurosci 2012; 3:693-705. [PMID: 23019496 DOI: 10.1021/cn300040f] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Accepted: 06/10/2012] [Indexed: 11/29/2022] Open
Abstract
The human serotonin transporter (hSERT), the human dopamine transporter (hDAT), and the human norepinephrine transporter (hNET) facilitate the active uptake of the neurotransmitters serotonin, dopamine, and norepinephrine from the synaptic cleft. Drugs of abuse such as MDMA (streetname "ecstasy") and certain 1-phenyl-piperazine (PP) analogs such as 1-(3-chlorophenyl)-piperazine (mCPP) elicit their stimulatory effect by elevating the synaptic concentration of serotonin by blocking or reversing the normal transport activity of hSERT. Recent data suggest that certain analogs of PP may be able to counteract the addictive effect of cocaine. Little is still known about the precise mechanism by which MDMA and PP analogs function at hSERT, hDAT, and hNET and even less is known about the specific protein-ligand interactions. In this study, we provide a comprehensive biochemical examination of a repertoire of PP analogs in hSERT, hDAT, and hNET. Combined with induced fit docking models and molecular dynamics simulations of PP and 1-(3-hydroxyphenyl)-piperazine (3-OH-PP) bound to hSERT and hDAT, we present detailed molecular insight into the promiscuous binding of PP analogs in the monoamine transporters. We find that PP analogs inhibit uptake as well as induce release in all three monoamine transporters. We also find that the selectivity of the PP analogs can be adjusted by carefully selecting substituents on the PP skeleton.
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Affiliation(s)
- Kasper Severinsen
- Laboratory of Molecular Neurobiology,
Centre for Psychiatric Research, Aarhus University Hospital, Risskov, Denmark
| | - Johan F. Kraft
- Center
for Insoluble Protein
Structures (inSPIN), Interdisciplinary Nanoscience
Center (iNANO), Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus
C, Denmark
| | - Heidi Koldsø
- Center
for Insoluble Protein
Structures (inSPIN), Interdisciplinary Nanoscience
Center (iNANO), Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus
C, Denmark
| | - Katrine A. Vinberg
- Laboratory of Molecular Neurobiology,
Centre for Psychiatric Research, Aarhus University Hospital, Risskov, Denmark
| | - Richard B. Rothman
- Translational Pharmacology Section,
Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland
21224, United States
| | - John S. Partilla
- Translational Pharmacology Section,
Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland
21224, United States
| | - Ove Wiborg
- Laboratory of Molecular Neurobiology,
Centre for Psychiatric Research, Aarhus University Hospital, Risskov, Denmark
| | - Bruce Blough
- Center for Organic
and Medicinal
Chemistry, Research Triangle Institute,
Research Triangle Park, North Carolina, United States
| | - Birgit Schiøtt
- Center
for Insoluble Protein
Structures (inSPIN), Interdisciplinary Nanoscience
Center (iNANO), Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus
C, Denmark
| | - Steffen Sinning
- Laboratory of Molecular Neurobiology,
Centre for Psychiatric Research, Aarhus University Hospital, Risskov, Denmark
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16
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Koldsø H, Noer P, Grouleff J, Autzen HE, Sinning S, Schiøtt B. Unbiased simulations reveal the inward-facing conformation of the human serotonin transporter and Na(+) ion release. PLoS Comput Biol 2011; 7:e1002246. [PMID: 22046120 PMCID: PMC3203053 DOI: 10.1371/journal.pcbi.1002246] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Accepted: 09/12/2011] [Indexed: 11/19/2022] Open
Abstract
Monoamine transporters are responsible for termination of synaptic signaling and are involved in depression, control of appetite, and anxiety amongst other neurological processes. Despite extensive efforts, the structures of the monoamine transporters and the transport mechanism of ions and substrates are still largely unknown. Structural knowledge of the human serotonin transporter (hSERT) is much awaited for understanding the mechanistic details of substrate translocation and binding of antidepressants and drugs of abuse. The publication of the crystal structure of the homologous leucine transporter has resulted in homology models of the monoamine transporters. Here we present extended molecular dynamics simulations of an experimentally supported homology model of hSERT with and without the natural substrate yielding a total of more than 1.5 µs of simulation of the protein dimer. The simulations reveal a transition of hSERT from an outward-facing occluded conformation to an inward-facing conformation in a one-substrate-bound state. Simulations with a second substrate in the proposed symport effector site did not lead to conformational changes associated with translocation. The central substrate binding site becomes fully exposed to the cytoplasm leaving both the Na+-ion in the Na2-site and the substrate in direct contact with the cytoplasm through water interactions. The simulations reveal how sodium is released and show indications of early events of substrate transport. The notion that ion dissociation from the Na2-site drives translocation is supported by experimental studies of a Na2-site mutant. Transmembrane helices (TMs) 1 and 6 are identified as the helices involved in the largest movements during transport. The human serotonin transporter belongs to the family of neurotransmitter transporters, which are located in the presynaptic nerve end, from where it is responsible for termination of synaptic serotonin signaling. Imbalance in serotonin concentration is related to various neuronal conditions such as depression, regulation of appetite etc. Very limited structural information of hSERT is available, but it is believed that the protein functions through an alternating access mechanism, where the central binding site is either exposed to the outside or the inside of the cell. We have previously published an experimentally validated outward-occluded homology model of hSERT, and here we reveal the inward-facing conformation of hSERT from molecular dynamics simulations, from which we can identify the main movements occurring during the translocation. From the inward-facing conformation we observe ion release, revealing important information on the sequence of events during transport. Following transport of the sodium ion, the substrate also shows early events of transport. The ion follows a cytoplasmic pathway as hinted at from experiments, and the ligand binding site becomes fully solvated by water through this same pathway. Experiments using an Asp437Asn mutant of hSERT confirm the prediction that Asp437 is a central residue in controlling ion transport.
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Affiliation(s)
- Heidi Koldsø
- Center for Insoluble Protein Structures (inSPIN) and Interdisciplinary Nanoscience Center (iNANO), Department of Chemistry, Aarhus University, Aarhus, Denmark
| | - Pernille Noer
- Laboratory of Molecular Neurobiology, Centre for Psychiatric Research, Aarhus University Hospital, Risskov, Denmark
| | - Julie Grouleff
- Center for Insoluble Protein Structures (inSPIN) and Interdisciplinary Nanoscience Center (iNANO), Department of Chemistry, Aarhus University, Aarhus, Denmark
| | - Henriette Elisabeth Autzen
- Center for Insoluble Protein Structures (inSPIN) and Interdisciplinary Nanoscience Center (iNANO), Department of Chemistry, Aarhus University, Aarhus, Denmark
| | - Steffen Sinning
- Laboratory of Molecular Neurobiology, Centre for Psychiatric Research, Aarhus University Hospital, Risskov, Denmark
| | - Birgit Schiøtt
- Center for Insoluble Protein Structures (inSPIN) and Interdisciplinary Nanoscience Center (iNANO), Department of Chemistry, Aarhus University, Aarhus, Denmark
- * E-mail:
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17
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Christensen H, Schjøth‐Eskesen C, Jensen M, Sinning S, Jensen HH. Synthesis of 3,7‐Disubstituted Imipramines by Palladium‐Catalysed Amination/Cyclisation and Evaluation of Their Inhibition of Monoamine Transporters. Chemistry 2011; 17:10618-27. [DOI: 10.1002/chem.201100885] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Indexed: 11/10/2022]
Affiliation(s)
- Helle Christensen
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C (Denmark), Fax: (+45)8619‐6199
| | - Christina Schjøth‐Eskesen
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C (Denmark), Fax: (+45)8619‐6199
| | - Marie Jensen
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C (Denmark), Fax: (+45)8619‐6199
| | - Steffen Sinning
- Laboratory of Molecular Neurobiology, Centre for Psychiatric Research, Aarhus University Hospital, Skovagervej 2, 8240 Risskov (Denmark)
| | - Henrik H. Jensen
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C (Denmark), Fax: (+45)8619‐6199
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18
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Fjorback AW, Sundbye S, Dächsel JC, Sinning S, Wiborg O, Jensen PH. P25α / TPPP expression increases plasma membrane presentation of the dopamine transporter and enhances cellular sensitivity to dopamine toxicity. FEBS J 2010; 278:493-505. [PMID: 21182589 DOI: 10.1111/j.1742-4658.2010.07970.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Parkinson's disease is characterized by preferential degeneration of the dopamine-producing neurons of the brain stem substantia nigra. Imbalances between mechanisms governing dopamine transport across the plasma membrane and cellular storage vesicles increase the level of toxic pro-oxidative cytosolic dopamine. The microtubule-stabilizing protein p25α accumulates in dopaminergic neurons in Parkinson's disease. We hypothesized that p25α modulates the subcellular localization of the dopamine transporter via effects on sorting vesicles, and thereby indirectly affects its cellular activity. Here we show that co-expression of the dopamine transporter with p25α in HEK-293-MSR cells increases dopamine uptake via increased plasma membrane presentation of the transporter. No direct interaction between p25α and the dopamine transporter was demonstrated, but they co-fractionated during subcellular fractionation of brain tissue from striatum, and direct binding of p25α peptides to brain vesicles was demonstrated. Truncations of the p25α peptide revealed that the requirement for stimulating dopamine uptake is located in the central core and were similar to those required for vesicle binding. Co-expression of p25α and the dopamine transporter in HEK-293-MSR cells sensitized them to the toxicity of extracellular dopamine. Neuronal expression of p25α thus holds the potential to sensitize the cells toward dopamine and toxins carried by the dopamine transporter.
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Affiliation(s)
- Anja W Fjorback
- Centre for Psychiatric Research, Aarhus University Hospital, Denmark
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19
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Koldsø H, Severinsen K, Tran TT, Celik L, Jensen HH, Wiborg O, Schiøtt B, Sinning S. The two enantiomers of citalopram bind to the human serotonin transporter in reversed orientations. J Am Chem Soc 2010; 132:1311-22. [PMID: 20055463 DOI: 10.1021/ja906923j] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The two enantiomers of the antidepressant citalopram inhibit the human serotonin transporter substantially differently. Previous studies revealed Tyr95 and Ile172 as important for citalopram binding, however, the overall orientation of the ligands in the binding site and the protein-ligand interaction points remain unknown. The binding of S- and R-citalopram to a human serotonin transporter homology model are herein examined via docking simulations including induced fit effects. For a better description of the formal charges of the ligand when bound inside the protein, polarization effects of the protein were included by additional quantum-polarized ligand docking calculations, where ligand charges are evaluated using QM/MM calculations. By this approach a much clearer picture emerged of the positions of the functional groups of citalopram. The two enantiomers are predicted to bind in the substrate binding pocket with opposite orientations of their aromatic groups. The predicted binding modes are experimentally validated using human wild type and 15 serotonin transporter mutants and 13 optically pure citalopram analogues. Important protein-ligand interaction points were identified validating one binding model for each enantiomer. In the validated model of the high affinity enantiomer, S-citalopram, the fluorine atom is located near Ala173 and Thr439 and the cyano group is in close proximity of Phe341; these contacts are found to be reversed for the R-enantiomer.
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Affiliation(s)
- Heidi Koldsø
- Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
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20
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Koldsø H, Severinsen K, Tran TT, Celik L, Helligsø Jensen H, Wiborg O, Sinning S, Schiøtt B. The Two Enantiomers of Citalopram Bind to the Human Serotonin Transporter in Reversed Orientations. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.2321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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21
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Sinning S, Musgaard M, Jensen M, Severinsen K, Celik L, Koldsø H, Meyer T, Bols M, Jensen HH, Schiøtt B, Wiborg O. Binding and orientation of tricyclic antidepressants within the central substrate site of the human serotonin transporter. J Biol Chem 2009; 285:8363-74. [PMID: 19948720 DOI: 10.1074/jbc.m109.045401] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tricyclic antidepressants (TCAs) have been used for decades, but their orientation within and molecular interactions with their primary target is yet unsettled. The recent finding of a TCA binding site in the extracellular vestibule of the bacterial leucine transporter 11 A above the central site has prompted debate about whether this vestibular site in the bacterial transporter is applicable to binding of antidepressants to their relevant physiological target, the human serotonin transporter (hSERT). We present an experimentally validated structural model of imipramine and analogous TCAs in the central substrate binding site of hSERT. Two possible binding modes were observed from induced fit docking calculations. We experimentally validated a single binding mode by combining mutagenesis of hSERT with uptake inhibition studies of different TCA analogs according to the paired mutation ligand analog complementation paradigm. Using this experimental method, we identify a salt bridge between the tertiary aliphatic amine and Asp(98). Furthermore, the 7-position of the imipramine ring is found vicinal to Phe(335), and the pocket lined by Ala(173) and Thr(439) is utilized by 3-substituents. These protein-ligand contact points unambiguously orient the TCA within the central binding site and reveal differences between substrate binding and inhibitor binding, giving important clues to the inhibition mechanism. Consonant with the well established competitive inhibition of uptake by TCAs, the resulting binding site for TCAs in hSERT is fully overlapping with the serotonin binding site in hSERT and dissimilar to the low affinity noncompetitive TCA site reported in the leucine transporter (LeuT).
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Affiliation(s)
- Steffen Sinning
- Laboratory of Molecular Neurobiology, Centre for Psychiatric Research, Aarhus University Hospital, Skovagervej 2, 8240 Risskov, Denmark
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22
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Nielsen S, Pedersen CM, Hansen SG, Petersen MD, Sinning S, Wiborg O, Jensen HH, Bols M. An extended study of dimeric phenyl tropanes. Bioorg Med Chem 2009; 17:4900-9. [DOI: 10.1016/j.bmc.2009.06.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2009] [Revised: 05/29/2009] [Accepted: 06/05/2009] [Indexed: 10/20/2022]
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23
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Celik L, Sinning S, Severinsen K, Hansen CG, Møller MS, Bols M, Wiborg O, Schiøtt B. Binding of serotonin to the human serotonin transporter. Molecular modeling and experimental validation. J Am Chem Soc 2008; 130:3853-65. [PMID: 18314975 DOI: 10.1021/ja076403h] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Molecular modeling and structure-activity relationship studies were performed to propose a model for binding of the neurotransmitter serotonin (5-HT) to the human serotonin transporter (hSERT). Homology models were constructed using the crystal structure of a bacterial homologue, the leucine transporter from Aquifex aeolicus, as the template and three slightly different sequence alignments. Induced fit docking of 5-HT into hSERT homology models resulted in two different binding modes. Both show a salt bridge between Asp98 and the charged primary amine of 5-HT, and both have the 5-HT C6 position of the indole ring pointing toward Ala173. The difference between the two orientations of 5-HT is an enantiofacial discrimination of the indole ring, resulting in the 5-hydroxyl group of 5-HT being vicinal to either Ser438/Thr439 or Ala169/Ile172/Ala173. To assess the binding experimentally, binding affinities for 5-HT and 17 analogues toward wild type and 13 single point mutants of hSERT were measured using an approach termed paired mutant-ligand analogue complementation (PaMLAC). The proposed ligand-protein interaction was systematically examined by disrupting it through site-directed mutagenesis and re-establishing another interaction via a ligand analogue matching the mutated residue, thereby minimizing the risk of identifying indirect effects. The interactions between Asp98 and the primary amine of 5-HT and the interaction between the C6-position of 5-HT and hSERT position 173 was confirmed using PaMLAC. The measured binding affinities of various mutants and 5-HT analogues allowed for a distinction between the two proposed binding modes of 5-HT and biochemically support the model for 5-HT binding in hSERT where the 5-hydroxyl group is in close proximity to Thr439.
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Affiliation(s)
- Leyla Celik
- The iNANO and inSPIN Centers, the Department of Chemistry, University of Aarhus, Aarhus, Denmark
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Severinsen K, Sinning S, Müller HK, Wiborg O. Characterisation of the zebrafish serotonin transporter functionally links TM10 to the ligand binding site. J Neurochem 2008; 105:1794-805. [PMID: 18266934 DOI: 10.1111/j.1471-4159.2008.05285.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The selective serotonin reuptake inhibitors and tricyclic antidepressants act by inhibiting pre-synaptic reuptake of serotonin (5-HT) leading to elevated synaptic 5-HT concentrations. However, despite extensive efforts little is known about the protein-ligand interactions of serotonin transporter (SERT) and inhibitors. To identify domains and individual amino acids important for ligand binding, we cloned the serotonin transporter from zebrafish, Danio rerio, (drSERT) and compared its pharmacological profile to that of the human serotonin transporter (hSERT) with respect to inhibition of [3H]5-HT uptake and [3H]-escitalopram binding in transiently transfected human embryonic kidney cells; HEK293-MSR. Residues responsible for altered affinities inhibitors were pinpointed by generating cross-species chimeras and subsequent point mutations by site directed mutagenesis. drSERT has a higher affinity towards compounds of the imipramine class, desipramine in particular, exhibiting a 35-fold increased affinity compared to hSERT. drSERT has a 15-30-fold lower affinity towards cocaine and cocaine analogues. The differences in ligand recognition are shown to be primarily caused by interspecies differences in TM10 and were tracked down to three residues (Ala(505), Leu(506) and Ile(507)).
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Affiliation(s)
- Kasper Severinsen
- Centre for Psychiatric Research, Aarhus University Hospital, Risskov, Denmark
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Boye SV, Ortega-Caballero F, Sinning S, Wiborg O, Jensen HH, Bols M. High dopamine transporter selectivity can be displayed by remarkably simple non-nitrogen containing inhibitors. Bioorg Med Chem Lett 2007; 17:6019-25. [PMID: 17869101 DOI: 10.1016/j.bmcl.2007.07.076] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2007] [Revised: 07/12/2007] [Accepted: 07/15/2007] [Indexed: 11/27/2022]
Abstract
A series of 2-(3,4-dichlorophenyl)-cyclopent-1-enyl carboxylic acid esters and amides were prepared and tested for binding to the DAT, SERT, and NET. The achiral compounds were easily attained and found to inhibit DAT binding with K(i)-values ranging from 0.095 to 0.00003 mM. Among the compounds tested 2-(3,4-dichlorophenyl)-cyclopent-1-enyl carboxylic acid 2-methylphenyl ester was found to be highly selective with SERT/DAT>7000; NET/DAT>1700, K(i)=60 nM.
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Affiliation(s)
- Søren V Boye
- Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000 Aarhus C, Denmark
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Petersen MD, Boye SV, Nielsen EH, Willumsen J, Sinning S, Wiborg O, Bols M. Synthesis, inhibition and binding of simple non-nitrogen inhibitors of monoamine transporters. Bioorg Med Chem 2007; 15:4159-74. [PMID: 17446076 DOI: 10.1016/j.bmc.2007.03.069] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2006] [Revised: 03/20/2007] [Accepted: 03/23/2007] [Indexed: 11/22/2022]
Abstract
A series of simple truncated analogues of phenyl tropanes, 2-arylcycloalk-1-enyl carboxylic acid methylesters, were prepared and investigated for their activity towards the dopamine, serotonin and norepinephrine transporters. The compounds were prepared from cyclic ketoesters, which were converted to enolic triflates and reacted with arylboronates using the Suzuki coupling. For comparison the corresponding piperidines were also made and investigated. The new compounds inhibit monoamine-transporters with Ki values ranging from 0.1 to 1000 microM.
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Affiliation(s)
- Mikkel Due Petersen
- Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000 Aarhus C, Denmark
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Christensen HS, Boye SV, Thinggaard J, Sinning S, Wiborg O, Schiøtt B, Bols M. QSAR studies and pharmacophore identification for arylsubstituted cycloalkenecarboxylic acid methyl esters with affinity for the human dopamine transporter. Bioorg Med Chem 2007; 15:5262-74. [PMID: 17517511 DOI: 10.1016/j.bmc.2007.05.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2006] [Revised: 02/25/2007] [Accepted: 05/04/2007] [Indexed: 11/15/2022]
Abstract
Data from a series of 29 monoamine transport inhibitors were used to generate 2D and 3D QSAR models for their binding affinity to the human dopamine transporter (hDAT). Among the inhibitors were many non-nitrogen containing compounds. The 2D QSAR analysis resulted in the equation -logK(i)=4.00-3.93E(LUMO)-0.67E(HOMO)-3.24sigma(p), which predicted the importance of electron withdrawing groups in the aromatic moiety. However, the model failed to predict the observed poor binding of nitro-substituted compounds. In contrast, a derived 3D QSAR model was capable of predicting these more correctly.
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Affiliation(s)
- Helena S Christensen
- Department of Chemistry, University of Aarhus, Langelandsgade 140, Aarhus C, Denmark
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28
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Pedersen H, Sinning S, Bulow A, Wiborg O, Falborg L, Bols M. Combinatorial synthesis of benztropine libraries and their evaluation as monoamine transporter inhibitors. Org Biomol Chem 2004; 2:2861-9. [PMID: 15455161 DOI: 10.1039/b405768f] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A combinatorial synthesis of benztropine analogues is presented. Radical azidonation of 3-benzyloxy-8-azabicyclo[3.2.1]octane-8-carboxylic acid tert-butyl ester 3 to 3-(1-azidobenzyloxy)-8-azabicyclo[3.2.1]octane-8-carboxylic acid tert-butyl ester 4 was used as a key step in the synthesis. This step was optimized by adding 10% DMF to the reaction. Reaction of 4 with phenyl magnesium bromide followed by Boc removal and N-methylation gave benztropine 1. Reaction of five-component Grignard reagents with 4 was used to create a two-dimensional library of 25 N-normethylbenztropine analogues. Further reaction of this library with five alkyl bromides was carried out to create a three-dimensional library containing 125 compounds. Screening of the libraries towards binding and inhibition of uptake of the human dopamine (hDAT), serotonin (hSERT) and norepinephrine transporters (hNET) was carried out. None of the synthesized compounds were found to be stronger than benztropine, and none were selective for inhibition of binding over monoamine uptake.
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Affiliation(s)
- Hanne Pedersen
- Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000, Aarhus C
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Abstract
The conjugate addition of five component Grignard reagents to methyl ecgonidine was used to create libraries of 3-substituted tropanes. By variation in the reagent combination in 10 such 5-membered sublibraries, a library of 25 compounds was made in a two-dimensional format. Screening of this library led to identification of two new potent monoamine transporter ligands that were subsequently synthesized. The most potent compound in this library was (1R,2S,3S,5S)-3-(3,4-dimethylphenyl)-8-methyl-8-azabicyclo[3.2.1]octane-2-carboxylic acid methyl ester, which inhibited dopamine transporter (hDAT) binding and reuptake with a K(i) of 26 and 20 nM, respectively. The conjugate addition to a 5-membered library of methyl ecgonidine analogues with variation of nitrogen substituent was also carried out and used to create 15 sublibraries of 25 compounds, which displayed 125 compounds in a three-dimensional format. From this 3D library, several potent dopamine transport inhibitors were likewise identified and synthesized. The most potent hDAT inhibitor discovered was (1R,2S,3S,5S)-3-(3,4-dimethylphenyl)-8-pentyl-8-azabicyclo[3.2.1]octane-2-carboxylic acid methyl ester. The study also showed that 3-alkyltropanes were poor inhibitors of monoamine transporters.
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Affiliation(s)
- Anne Bülow
- Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000 Aarhus C, Denmark
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