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Tea M, Pan YK, Lister JGR, Perry SF, Gilmour KM. Effects of serta and sertb knockout on aggression in zebrafish (Danio rerio). J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2024:10.1007/s00359-024-01693-7. [PMID: 38416162 DOI: 10.1007/s00359-024-01693-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2023] [Revised: 01/12/2024] [Accepted: 02/01/2024] [Indexed: 02/29/2024]
Abstract
Zebrafish (Danio rerio) are unusual in having two paralogues of the serotonin re-uptake transporter (Sert), slc6a4a (serta) and slc6a4b (sertb), the transporter that serves in serotonin re-uptake from a synapse into the pre-synaptic cell or in serotonin uptake from the extracellular milieu into cells in the peripheral tissues. To address a knowledge gap concerning the specific roles of these paralogues, we used CRISPR/Cas9 technology to generate zebrafish knockout lines predicted to lack functional expression of Serta or Sertb. The consequences of loss-of-function of Serta or Sertb were assessed at the gene expression level, focusing on the serotonergic signalling pathway, and at the behaviour level, focusing on aggression. Whereas serta mRNA was expressed in all tissues examined, with high expression in the heart, gill and brain, only the brain displayed substantial sertb mRNA expression. In both serta-/- and sertb-/- fish, changes in transcript abundances of multiple components of the serotonin signalling pathway were detected, including proteins involved in serotonin synthesis (tph1a, tph1b, tph2, ddc), packaging (vmat2) and degradation (mao), and serotonin receptors (htr1aa, htr1ab). Using a mirror aggression test, serta-/- male but not female fish exhibited greater aggression than wildtype fish. However, both male and female sertb-/- fish displayed less aggression than their wildtype counterparts. These differences in behaviour between serta-/- and sertb-/- individuals hold promise for increasing our understanding of the neurophysiological basis of aggression in zebrafish.
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Affiliation(s)
- Michael Tea
- Department of Biology, University of Ottawa, 30 Marie Curie Pvt, Ottawa, ON, K1N 6N5, Canada
| | - Yihang Kevin Pan
- Department of Biology, University of Ottawa, 30 Marie Curie Pvt, Ottawa, ON, K1N 6N5, Canada
| | - Joshua G R Lister
- Department of Biology, University of Ottawa, 30 Marie Curie Pvt, Ottawa, ON, K1N 6N5, Canada
| | - Steve F Perry
- Department of Biology, University of Ottawa, 30 Marie Curie Pvt, Ottawa, ON, K1N 6N5, Canada
| | - Kathleen M Gilmour
- Department of Biology, University of Ottawa, 30 Marie Curie Pvt, Ottawa, ON, K1N 6N5, Canada.
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Li M, Zhang X, Chen S, Liu H, Zhang YW. Unique Substrate Recognition and Sodium-Substrate Binding Stoichiometry in a Bacterial Serotonin Transporter, TuriSERT. Int J Mol Sci 2023; 24:17112. [PMID: 38069433 PMCID: PMC10707687 DOI: 10.3390/ijms242317112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 11/27/2023] [Accepted: 12/02/2023] [Indexed: 12/18/2023] Open
Abstract
All resolved high-resolution structures of the transporters in the neurotransmitter sodium symporter (NSS) family revealed that the NSS members share common structural and mechanistic features for substrate and ion binding and transport. However, a recently reported bacterial orthologue of the human serotonin transporter (hSERT), TuriSERT, possesses a structural characteristic specific for amino acid substrate binding but does transport a biogenic amine. The unique structural feature of TuriSERT requires a novel configuration for coordinating its substrate and ions. In the present study, we characterized TuriSERT expressed in Escherichia coli cells with a fluorescent substrate by biochemical, structural, and pharmacological approaches. Substrate transport by TuriSERT requires Na+ but not Cl-. Replacement of Asp262 by asparagine renders TuriSERT Cl--dependent. Substitutions of the corresponding Na1 residues did not alter Na+ dependence on substrate transport, whereas the mutation of a Na2 site residue led to a loss of transport activity, suggesting that Na+ binds only to the Na2 site in TuriSERT. In addition, substitutions of several residues essential for recognizing 5-hydroxytryptamine (5-HT) in hSERT had little effect on 5-HT displacement potency in transport assay for TuriSERT. In contrast, mutations of the residues that are proposed to coordinate with 5-HT in our docking model dramatically reduced 5-HT displacement. Furthermore, our results indicated that all tested antidepressants showed a weak inhibitory effect on TuriSERT. The present study demonstrated the existence of a unique substrate binding site and 1:1 stoichiometry of sodium-substrate binding in TuriSERT, a novel structural finding for the NSS transporters.
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Affiliation(s)
| | | | | | | | - Yuan-Wei Zhang
- School of Life Sciences, Guangzhou University, Guangzhou 510006, China; (M.L.); (X.Z.); (S.C.); (H.L.)
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Fonseca ECM, Ferreira LR, Figueiredo PLB, Maia CDSF, Setzer WN, Da Silva JKR. Antidepressant Effects of Essential Oils: A Review of the Past Decade (2012-2022) and Molecular Docking Study of Their Major Chemical Components. Int J Mol Sci 2023; 24:ijms24119244. [PMID: 37298210 DOI: 10.3390/ijms24119244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 04/19/2023] [Accepted: 04/24/2023] [Indexed: 06/12/2023] Open
Abstract
Depression is a mental disorder that affects more than 300 million people worldwide. The medications available for treatment take a long time to exhibit therapeutic results and present several side effects. Furthermore, there is a decrease in the quality of life of people suffering from this affliction. Essential oils are traditionally used to relieve the symptoms of depression due to the properties of the constituents of these oils to cross the blood-brain barrier acting on depression-related biological receptors associated with reduced toxicity and side effects. In addition, compared to traditional drugs, they have several administration forms. This review provides a comprehensive assessment of studies on plants whose essential oil has exhibit antidepressant activity in the past decade and the mechanism of action of the major components and models tested. An additional in silico study was conducted with the frequent compounds in the composition of these essential oils, providing a molecular approach to the mechanism of action that has been reported in the past decade. This review is valuable for the development of potential antidepressant medications in addition to providing a molecular approach to the antidepressant mechanism of action of the major volatile compounds that have been reported in the past decade.
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Affiliation(s)
- Emily Christie M Fonseca
- Programa de Pós-Graduação em Farmacologia e Bioquímica, Universidade Federal do Pará, Belém 66075-110, Brazil
| | - Lanalice R Ferreira
- Programa de Pós-Graduação em Química, Universidade Federal do Pará, Belém 66075-110, Brazil
| | - Pablo Luis B Figueiredo
- Laboratório de Química dos Produtos Naturais, Centro de Ciências Biológicas e da Saúde, Universidade do Estado do Pará, Belém 66087-662, Brazil
| | - Cristiane do Socorro F Maia
- Programa de Pós-Graduação em Farmacologia e Bioquímica, Universidade Federal do Pará, Belém 66075-110, Brazil
| | | | - Joyce Kelly R Da Silva
- Programa de Pós-Graduação em Farmacologia e Bioquímica, Universidade Federal do Pará, Belém 66075-110, Brazil
- Programa de Pós-Graduação em Química, Universidade Federal do Pará, Belém 66075-110, Brazil
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Liu H, Wu Y, Li C, Tang Q, Zhang YW. Molecular docking and biochemical validation of (-)-syringaresinol-4-O-β-D-apiofuranosyl-(1→2)-β-D-glucopyranoside binding to an allosteric site in monoamine transporters. Front Pharmacol 2022; 13:1018473. [PMID: 36386236 PMCID: PMC9649612 DOI: 10.3389/fphar.2022.1018473] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Accepted: 10/17/2022] [Indexed: 06/11/2024] Open
Abstract
Albizia julibrissin Durazz is one of the most common herbs used for depression and anxiety treatment, but its mechanism of action as an antidepressant or anxiolytic drug have not been fully understood. We previously isolated and identified one lignan glycoside compound from Albizia Julibrissin Durazz, (-)-syringaresinol-4-O-β-D-apiofuranosyl-(1→2)-β-D-glucopyranoside (SAG), that inhibited all three monoamine transporters with a mechanism of action different from that of the conventional antidepressants. In this study, we generated homology models for human dopamine transporter and human norepinephrine transporter, based on the X-ray structure of Drosophila dopamine transporter, and conducted the molecular docking of SAG to all three human monoamine transporters. Our computational results indicated that SAG binds to an allosteric site (S2) that has been demonstrated to be formed by an aromatic pocket positioned in the scaffold domain in the extracellular vestibule connected to the central site (S1) in these monoamine transporters. In addition, we demonstrated that SAG stabilizes a conformation of serotonin transporter with both the extracellular and cytoplasmic pathways closed. Furthermore, we performed mutagenesis of the residues in both the allosteric and orthosteric sites to biochemically validate SAG binding in all three monoamine transporters. Our results are consistent with the molecular docking calculation and support the association of SAG with the allosteric site. We expect that this herbal molecule could become a lead compound for the development of new therapeutic agents with a novel mechanism of action.
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Affiliation(s)
- Hanhe Liu
- School of Life Sciences, Guangzhou University, Guangzhou, China
| | - Yingyao Wu
- School of Life Sciences, Guangzhou University, Guangzhou, China
| | - Chan Li
- School of Life Sciences, Guangzhou University, Guangzhou, China
| | - Qingfa Tang
- School of Traditional Chinese Medicine, Southern Medical University, Guangzhou, China
- Guangdong Provincial Key Laboratory of Chinese Medicine Pharmaceutics, Guangzhou, China
| | - Yuan-Wei Zhang
- School of Life Sciences, Guangzhou University, Guangzhou, China
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Rayff da Silva P, Diniz Nunes Pazos N, Karla Silva do Nascimento Gonzaga T, Cabral de Andrade J, Brito Monteiro Á, Caroline Ribeiro Portela A, Fernandes Oliveira Pires H, Dos Santos Maia M, Vilar da Fonsêca D, T Scotti M, Maria Barbosa Filho J, Pergentino de Sousa D, Francisco Bezerra Felipe C, Nóbrega de Almeida R, Scotti L. Anxiolytic and antidepressant-like effects of monoterpene tetrahydrolinalool and in silico approach of new potential targets. Curr Top Med Chem 2022; 22:1530-1552. [PMID: 35524664 DOI: 10.2174/1568026622666220505104726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 02/03/2022] [Accepted: 02/16/2022] [Indexed: 11/22/2022]
Abstract
INTRODUCTION- The drugs currently available for treatment of anxiety and depression act through modulation of the neurotransmission systems involved in the neurobiology of the disorder, yet they of-ten present side effects, which can impair patient adherence to treatment. METHOD- This, has driven the search for new molecules with anxiolytic and antidepressant potential. Aromatic plants are rich in essential oils, and their chemical constituents, such as monoterpenes, are be-ing studied for these disorders. This study aims to evaluate the anxiolytic and antidepressant-like poten-tial of the monoterpene tetrahydrolinalool in in vivo animal models, and review pharmacological targets with validation through molecular docking. Male Swiss mice (Mus musculus) were treated with THL (37.5-600 mg kg-1 p.o.) and submitted to the elevated plus maze, open field, rota rod, and forced swim tests. In the elevated plus-maze, THL at doses of 37.5 and 75 mg kg-1 induced a significant increase in the percentage of entries (72.7 and 64.3% respectively), and lengths of stay (80.3 and 76.8% respective-ly) in the open arms tests. RESULT- These doses did not compromise locomotor activity or motor coordination in the animals. In the open field, rota rod tests, and the forced swimming model, treatment with THL significantly reduced immobility times at doses of 150, 300, and 600 mg kg-1, and by respective percentages of 69.3, 60.9 and 68.7%. CONCLUSION- In molecular docking assay, which investigated potential targets, THL presented sat-isfactory energy values for: nNOs, SGC, IL-6, 5-HT1A, NMDAr, and D1. These demonstrate the po-tential of THL (a derivative of natural origin) in in vivo and in silico models, making it a drug candidate.
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Affiliation(s)
- Pablo Rayff da Silva
- Psychopharmacology Laboratory, Institute of Drugs and Medicines Research, Federal University of Paraíba, 58051-085, Via Ipê Amarelo, S/N, João Pessoa, Paraíba, Brazil
| | - Natalia Diniz Nunes Pazos
- Psychopharmacology Laboratory, Institute of Drugs and Medicines Research, Federal University of Paraíba, 58051-085, Via Ipê Amarelo, S/N, João Pessoa, Paraíba, Brazil
| | | | - Jéssica Cabral de Andrade
- Psychopharmacology Laboratory, Institute of Drugs and Medicines Research, Federal University of Paraíba, 58051-085, Via Ipê Amarelo, S/N, João Pessoa, Paraíba, Brazil
| | - Álefe Brito Monteiro
- Psychopharmacology Laboratory, Institute of Drugs and Medicines Research, Federal University of Paraíba, 58051-085, Via Ipê Amarelo, S/N, João Pessoa, Paraíba, Brazil
| | - Anne Caroline Ribeiro Portela
- Psychopharmacology Laboratory, Institute of Drugs and Medicines Research, Federal University of Paraíba, 58051-085, Via Ipê Amarelo, S/N, João Pessoa, Paraíba, Brazil
| | - Hugo Fernandes Oliveira Pires
- Psychopharmacology Laboratory, Institute of Drugs and Medicines Research, Federal University of Paraíba, 58051-085, Via Ipê Amarelo, S/N, João Pessoa, Paraíba, Brazil
| | - Mayara Dos Santos Maia
- Cheminformatics Laboratory, Institute of Drugs and Medicines Research, Federal University of Paraíba, 58051-900, Via Ipê Amarelo, S/N, João Pessoa, Paraíba, Brazil
| | - Diogo Vilar da Fonsêca
- Collegiate of Medicine, Federal University of São Francisco Valley, 48607-190, Rua Aurora, S/N, Bahia, Brazil
| | - Marcus T Scotti
- Cheminformatics Laboratory, Institute of Drugs and Medicines Research, Federal University of Paraíba, 58051-900, Via Ipê Amarelo, S/N, João Pessoa, Paraíba, Brazil
| | - José Maria Barbosa Filho
- Pharmaceutical Chemistry Laboratory, Department of Pharmaceutical Sciences, Federal University of Paraíba, 58051-900, Via Ipê Amarelo, S/N, João Pessoa, Brazil
| | - Damião Pergentino de Sousa
- Pharmaceutical Chemistry Laboratory, Department of Pharmaceutical Sciences, Federal University of Paraíba, 58051-900, Via Ipê Amarelo, S/N, João Pessoa, Brazil
| | - Cícero Francisco Bezerra Felipe
- Psychopharmacology Laboratory, Institute of Drugs and Medicines Research, Federal University of Paraíba, 58051-085, Via Ipê Amarelo, S/N, João Pessoa, Paraíba, Brazil
| | - Reinaldo Nóbrega de Almeida
- Psychopharmacology Laboratory, Institute of Drugs and Medicines Research, Federal University of Paraíba, 58051-085, Via Ipê Amarelo, S/N, João Pessoa, Paraíba, Brazil
| | - Luciana Scotti
- Cheminformatics Laboratory, Institute of Drugs and Medicines Research, Federal University of Paraíba, 58051-900, Via Ipê Amarelo, S/N, João Pessoa, Paraíba, Brazil
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Herz M, Brehm K. Serotonin stimulates Echinococcus multilocularis larval development. Parasit Vectors 2021; 14:14. [PMID: 33407815 PMCID: PMC7789706 DOI: 10.1186/s13071-020-04533-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 12/10/2020] [Indexed: 12/28/2022] Open
Abstract
Background Serotonin is a phylogenetically ancient molecule that is widely distributed in most metazoans, including flatworms. In addition to its role as a neurotransmitter, serotonin acts as a morphogen and regulates developmental processes. Although several studies have focused on the serotonergic nervous system in parasitic flatworms, little is known on the role of serotonin in flatworm development. Methods To study the effects of serotonin on proliferation and development of the cestode Echinococcus multilocularis, we cloned the genes encoding the E. multilocularis serotonin transporter (SERT) and tryptophan hydroxylase (TPH), analyzed gene expression by transcriptome analysis and whole mount in situ hybridization (WMISH) and performed cell culture experiments. Results We first characterized orthologues encoding the SERT and TPH, the rate-limiting enzyme in serotonin biosynthesis. WMISH and transcriptomic analyses indicated that the genes for both SERT and TPH are expressed in the parasite nervous system. Long-term treatment of parasite stem cell cultures with serotonin stimulated development towards the parasite metacestode stage. Mature metacestode vesicles treated with serotonin showed increased rates of incorporation of the thymidine analogue 5-ethynyl-2′-deoxyuridine (EdU), indicating stimulated cell proliferation. In contrast, treatment with the selective serotonin reuptake inhibitor paroxetine strongly affected the viability of parasite cells. Paroxetine also caused structural damage in metacestode vesicles, suggesting that serotonin transport is crucial for the integrity of parasite vesicles. Conclusions Our results indicate that serotonin plays an important role in E. multilocularis development and proliferation, providing evidence that the E. multilocularis SERT and TPH are expressed in the nervous system of the protoscolex. Our results further suggest that the E. multilocularis SERT has a secondary role outside the nervous system that is essential for parasite integrity and survival. Since serotonin stimulated E. multilocularis metacestode development and proliferation, serotonin might also contribute to the formation and growth of the parasite in the liver.![]()
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Affiliation(s)
- Michaela Herz
- Institut für Hygiene und Mikrobiologie, Universität Würzburg, Josef-Schneider-Straße 2/E1, 97080, Würzburg, Germany.
| | - Klaus Brehm
- Institut für Hygiene und Mikrobiologie, Universität Würzburg, Josef-Schneider-Straße 2/E1, 97080, Würzburg, Germany.
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Rasti AR, Coombe VE, Muzik JR, Kliethermes CL. Pharmacological characterization of the forced swim test in Drosophila melanogaster. INVERTEBRATE NEUROSCIENCE 2020; 20:22. [PMID: 33170389 DOI: 10.1007/s10158-020-00255-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 10/30/2020] [Indexed: 11/30/2022]
Abstract
The forced swim test is commonly used as a preclinical screen of antidepressant medication efficacy in rats and mice. Neckameyer and Nieto-Romero (Stress 18:254-66, 2015) adopted the forced swim test for use with the fruit fly Drosophila melanogaster and showed that behavior in this test is sensitive to several physiologically relevant stressors. However, whether this test might be sensitive to the effects of antidepressant medications or other compounds is unknown. In the current studies, we fed drugs to male and female flies that we expected to either decrease or increase the duration of immobility in the forced swim test, including fluoxetine, desipramine, picrotoxin, reserpine, 3-iodo-tyrosine, and ethanol. Fluoxetine was the only drug tested that affected behavior in this test, and surprisingly, the direction of the effect depended on the duration of feeding. Short-term (30 min) feeding of the drug prior to test resulted in the expected increase in latency to immobility, while a longer feeding duration (20-24 h) decreased this measure. These results suggest that the pharmacological profile of the fly FST is more restricted than that of the rat or mouse FST, and that the duration of drug exposure is an important consideration in pharmacological research using flies.
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Affiliation(s)
- Aryana R Rasti
- Department of Psychology and Neuroscience, Drake University, 318 Olin Hall, 1344 27th Street, Des Moines, IA, 50311, USA
| | - Victoria E Coombe
- Department of Psychology and Neuroscience, Drake University, 318 Olin Hall, 1344 27th Street, Des Moines, IA, 50311, USA
| | - Jerica R Muzik
- Department of Psychology and Neuroscience, Drake University, 318 Olin Hall, 1344 27th Street, Des Moines, IA, 50311, USA
| | - Christopher L Kliethermes
- Department of Psychology and Neuroscience, Drake University, 318 Olin Hall, 1344 27th Street, Des Moines, IA, 50311, USA.
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Xue W, Fu T, Zheng G, Tu G, Zhang Y, Yang F, Tao L, Yao L, Zhu F. Recent Advances and Challenges of the Drugs Acting on Monoamine Transporters. Curr Med Chem 2020; 27:3830-3876. [DOI: 10.2174/0929867325666181009123218] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Revised: 09/30/2018] [Accepted: 10/03/2018] [Indexed: 01/06/2023]
Abstract
Background:
The human Monoamine Transporters (hMATs), primarily including hSERT,
hNET and hDAT, are important targets for the treatment of depression and other behavioral disorders
with more than the availability of 30 approved drugs.
Objective:
This paper is to review the recent progress in the binding mode and inhibitory mechanism of
hMATs inhibitors with the central or allosteric binding sites, for the benefit of future hMATs inhibitor
design and discovery. The Structure-Activity Relationship (SAR) and the selectivity for hit/lead compounds
to hMATs that are evaluated by in vitro and in vivo experiments will be highlighted.
Methods:
PubMed and Web of Science databases were searched for protein-ligand interaction, novel
inhibitors design and synthesis studies related to hMATs.
Results:
Literature data indicate that since the first crystal structure determinations of the homologous
bacterial Leucine Transporter (LeuT) complexed with clomipramine, a sizable database of over 100 experimental
structures or computational models has been accumulated that now defines a substantial degree
of structural variability hMATs-ligands recognition. In the meanwhile, a number of novel hMATs
inhibitors have been discovered by medicinal chemistry with significant help from computational models.
Conclusion:
The reported new compounds act on hMATs as well as the structures of the transporters
complexed with diverse ligands by either experiment or computational modeling have shed light on the
poly-pharmacology, multimodal and allosteric regulation of the drugs to transporters. All of the studies
will greatly promote the Structure-Based Drug Design (SBDD) of structurally novel scaffolds with high
activity and selectivity for hMATs.
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Affiliation(s)
- Weiwei Xue
- Innovative Drug Research and Bioinformatics Group, School of Pharmaceutical Sciences and Chongqing Key Laboratory of Natural Drug Research, Chongqing University, Chongqing 401331, China
| | - Tingting Fu
- Innovative Drug Research and Bioinformatics Group, School of Pharmaceutical Sciences and Chongqing Key Laboratory of Natural Drug Research, Chongqing University, Chongqing 401331, China
| | - Guoxun Zheng
- Innovative Drug Research and Bioinformatics Group, School of Pharmaceutical Sciences and Chongqing Key Laboratory of Natural Drug Research, Chongqing University, Chongqing 401331, China
| | - Gao Tu
- Innovative Drug Research and Bioinformatics Group, School of Pharmaceutical Sciences and Chongqing Key Laboratory of Natural Drug Research, Chongqing University, Chongqing 401331, China
| | - Yang Zhang
- Innovative Drug Research and Bioinformatics Group, School of Pharmaceutical Sciences and Chongqing Key Laboratory of Natural Drug Research, Chongqing University, Chongqing 401331, China
| | - Fengyuan Yang
- Innovative Drug Research and Bioinformatics Group, School of Pharmaceutical Sciences and Chongqing Key Laboratory of Natural Drug Research, Chongqing University, Chongqing 401331, China
| | - Lin Tao
- Key Laboratory of Elemene Class Anti-cancer Chinese Medicine of Zhejiang Province, School of Medicine, Hangzhou Normal University, Hangzhou 310036, China
| | - Lixia Yao
- Department of Health Sciences Research, Mayo Clinic, Rochester, MN 55905, United States
| | - Feng Zhu
- Innovative Drug Research and Bioinformatics Group, School of Pharmaceutical Sciences and Chongqing Key Laboratory of Natural Drug Research, Chongqing University, Chongqing 401331, China
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McGovern AS, Hamlin AS, Winter G. A review of the antimicrobial side of antidepressants and its putative implications on the gut microbiome. Aust N Z J Psychiatry 2019; 53:1151-1166. [PMID: 31558039 DOI: 10.1177/0004867419877954] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
OBJECTIVE Serotonin reuptake inhibitors are the predominant treatment for major depressive disorder. In recent years, the diversity of the gut microbiota has emerged to play a significant role in the occurrence of major depressive disorder and other mood and anxiety disorders. Importantly, the role of the gut microbiota in the treatment of such disorders remains to be elucidated. Here, we provide a review of the literature regarding the effects of physiologically relevant concentrations of serotonin reuptake inhibitors on the gut microbiota and the implications this might have on their efficacy in the treatment of mood disorders. METHODS First, an estimation of gut serotonin reuptake inhibitor concentrations was computed based on pharmacokinetic and gastrointestinal transit properties of serotonin reuptake inhibitors. Literature regarding the in vivo and in vitro antimicrobial properties of serotonin reuptake inhibitors was gathered, and the estimated gut concentrations were examined in the context of these data. Computer-based investigation revealed putative mechanisms for the antimicrobial effects of serotonin reuptake inhibitors. RESULTS In vivo evidence using animal models shows an antimicrobial effect of serotonin reuptake inhibitors on the gut microbiota. Examination of the estimated physiological concentrations of serotonin reuptake inhibitors in the gastrointestinal tract collected from in vitro studies suggests that the microbial community of both the small intestine and the colon are exposed to serotonin reuptake inhibitors for at least 4 hours per day at concentrations that are likely to exert an antimicrobial effect. The potential mechanisms of the effect of serotonin reuptake inhibitors on the gut microbiota were postulated to include inhibition of efflux pumps and/or amino acid transporters. CONCLUSION This review raises important issues regarding the role that gut microbiota play in the treatment of mood-related behaviours, which holds substantial potential clinical outcomes for patients suffering from major depressive disorder and other mood-related disorders.
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Affiliation(s)
- Abigail S McGovern
- School of Science and Technology, University of New England, Armidale, NSW, Australia
| | - Adam S Hamlin
- School of Science and Technology, University of New England, Armidale, NSW, Australia
| | - Gal Winter
- School of Science and Technology, University of New England, Armidale, NSW, Australia
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Hellsberg E, Ecker GF, Stary-Weinzinger A, Forrest LR. A structural model of the human serotonin transporter in an outward-occluded state. PLoS One 2019; 14:e0217377. [PMID: 31251747 PMCID: PMC6599148 DOI: 10.1371/journal.pone.0217377] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 06/17/2019] [Indexed: 12/12/2022] Open
Abstract
The human serotonin transporter hSERT facilitates the reuptake of its endogenous substrate serotonin from the synaptic cleft into presynaptic neurons after signaling. Reuptake regulates the availability of this neurotransmitter and therefore hSERT plays an important role in balancing human mood conditions. In 2016, the first 3D structures of this membrane transporter were reported in an inhibitor-bound, outward-open conformation. These structures revealed valuable information about interactions of hSERT with antidepressant drugs. Nevertheless, the question remains how serotonin facilitates the specific conformational changes that open and close pathways from the synapse and to the cytoplasm as required for transport. Here, we present a serotonin-bound homology model of hSERT in an outward-occluded state, a key intermediate in the physiological cycle, in which the interactions with the substrate are likely to be optimal. Our approach uses two template structures and includes careful refinement and comprehensive computational validation. According to microsecond-long molecular dynamics simulations, this model exhibits interactions between the gating residues in the extracellular pathway, and these interactions differ from those in an outward-open conformation of hSERT bound to serotonin. Moreover, we predict several features of this state by monitoring the intracellular gating residues, the extent of hydration, and, most importantly, protein-ligand interactions in the central binding site. The results illustrate common and distinct characteristics of these two transporter states and provide a starting point for future investigations of the transport mechanism in hSERT.
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Affiliation(s)
- Eva Hellsberg
- Department of Pharmaceutical Chemistry, University of Vienna, Vienna, Austria
| | - Gerhard F. Ecker
- Department of Pharmaceutical Chemistry, University of Vienna, Vienna, Austria
| | | | - Lucy R. Forrest
- Computational Structural Biology Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, MD, United States of America
- * E-mail:
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Blackburn TP. Depressive disorders: Treatment failures and poor prognosis over the last 50 years. Pharmacol Res Perspect 2019; 7:e00472. [PMID: 31065377 PMCID: PMC6498411 DOI: 10.1002/prp2.472] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 02/11/2019] [Accepted: 03/18/2019] [Indexed: 12/12/2022] Open
Abstract
Depression like many diseases is pleiotropic but unlike cancer and Alzheimer's disease for example, is still largely stigmatized and falls into the dark shadows of human illness. The failure of depression to be in the spotlight for successful treatment options is inherent in the complexity of the disease(s), flawed clinical diagnosis, overgeneralization of the illness, inadequate and biased clinical trial design, restrictive and biased inclusion/exclusion criteria, lack of approved/robust biomarkers, expensive imaging technology along with few advances in neurobiological hypotheses in decades. Clinical trial studies summitted to the regulatory agencies (FDA/EMA) for approval, have continually failed to show significant differences between active and placebo. For decades, we have acknowledged this failure, despite vigorous debated by all stakeholders to provide adequate answers to this escalating problem, with only a few new antidepressants approved in the last 20 years with equivocal efficacy, little improvement in side effects or onset of efficacy. It is also clear that funding and initiatives for mental illness lags far behind other life-treating diseases. Thus, it is no surprise we have not achieved much success in the last 50 years in treating depression, but we are accountable for the many failures and suboptimal treatment. This review will therefore critically address where we have failed and how future advances in medical science offers a glimmer of light for the patient and aid our future understanding of the neurobiology and pathophysiology of the disease, enabling transformative therapies for the treatment of depressive disorders.
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12
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Silva DR, Barigye SJ, Santos-Garcia L, Fontes Ferreira da Cunha E. Molecular Modelling of Potential Candidates for the Treatment of Depression. Mol Inform 2019; 38:e1900024. [PMID: 31131991 DOI: 10.1002/minf.201900024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Accepted: 05/07/2019] [Indexed: 12/22/2022]
Abstract
A lot of research initiatives in the last decades have been focused on the search of new strategies to treat depression. However, despite the availability of various antidepressants, current treatment is still far from ideal. Unwanted side effects, modest response rates and the slow onset of action are the main shortcomings. As a strategy to improve symptomatic relief and response rates, the dual modulation of the serotonin transporter and the histamine H3 receptor by a single chemical entity has been proposed in the literature. Accordingly, this work aims to elucidate key structural features responsible for the dual inhibitory activity of the hexahydro-pyrrolo-isoquinoline derivatives. For this purpose, two approaches were employed, four-dimensional quantitative structure-activity relationship (4D-QSAR) and molecular docking. The 4D-QSAR models for both receptors allowed the identification of the pharmacophore groups critical for the modelled biological activity, whereas the binding mode of this class of compounds to the human serotonin transporter was assessed by molecular docking. The findings can be applicable to design new antidepressants.
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Affiliation(s)
- Daniela Rodrigues Silva
- Department of Chemistry, Universidade Federal de Lavras, P.O. Box 3037, 37200-000, Lavras, MG, Brazil
| | - Stephen J Barigye
- Department of Chemistry, McGill University, 801 Sherbrooke Street W., Montréal, QC, Canada, H3 A 0B8
| | - Letícia Santos-Garcia
- Department of Chemistry, Universidade Federal de Lavras, P.O. Box 3037, 37200-000, Lavras, MG, Brazil
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13
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Ladefoged LK, Zeppelin T, Schiøtt B. Molecular modeling of neurological membrane proteins − from binding sites to synapses. Neurosci Lett 2019; 700:38-49. [DOI: 10.1016/j.neulet.2018.05.034] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 05/18/2018] [Accepted: 05/22/2018] [Indexed: 01/07/2023]
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14
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Möller IR, Slivacka M, Nielsen AK, Rasmussen SGF, Gether U, Loland CJ, Rand KD. Conformational dynamics of the human serotonin transporter during substrate and drug binding. Nat Commun 2019; 10:1687. [PMID: 30976000 PMCID: PMC6459873 DOI: 10.1038/s41467-019-09675-z] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 03/22/2019] [Indexed: 12/24/2022] Open
Abstract
The serotonin transporter (SERT), a member of the neurotransmitter:sodium symporter family, is responsible for termination of serotonergic signaling by re-uptake of serotonin (5-HT) into the presynaptic neuron. Its key role in synaptic transmission makes it a major drug target, e.g. for the treatment of depression, anxiety and post-traumatic stress. Here, we apply hydrogen-deuterium exchange mass spectrometry to probe the conformational dynamics of human SERT in the absence and presence of known substrates and targeted drugs. Our results reveal significant changes in dynamics in regions TM1, EL3, EL4, and TM12 upon binding co-transported ions (Na+/K+) and ligand-mediated changes in TM1, EL3 and EL4 upon binding 5-HT, the drugs S-citalopram, cocaine and ibogaine. Our results provide a comprehensive direct view of the conformational response of SERT upon binding both biologically relevant substrate/ions and ligands of pharmaceutical interest, thus advancing our understanding of the structure-function relationship in SERT.
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Affiliation(s)
- Ingvar R Möller
- Protein Analysis Group, Department of Pharmacy, University of Copenhagen, Copenhagen, 2100, Denmark
- Laboratory for Membrane Protein Dynamics, Department of Neuroscience, University of Copenhagen, Copenhagen, 2200, Denmark
| | - Marika Slivacka
- Protein Analysis Group, Department of Pharmacy, University of Copenhagen, Copenhagen, 2100, Denmark
- Laboratory for Membrane Protein Dynamics, Department of Neuroscience, University of Copenhagen, Copenhagen, 2200, Denmark
| | - Anne Kathrine Nielsen
- Laboratory for Membrane Protein Dynamics, Department of Neuroscience, University of Copenhagen, Copenhagen, 2200, Denmark
| | - Søren G F Rasmussen
- Department of Neuroscience, University of Copenhagen, Copenhagen, 2200, Denmark
| | - Ulrik Gether
- Department of Neuroscience, University of Copenhagen, Copenhagen, 2200, Denmark
| | - Claus J Loland
- Laboratory for Membrane Protein Dynamics, Department of Neuroscience, University of Copenhagen, Copenhagen, 2200, Denmark.
| | - Kasper D Rand
- Protein Analysis Group, Department of Pharmacy, University of Copenhagen, Copenhagen, 2100, Denmark.
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15
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Substrate and inhibitor binding to the serotonin transporter: Insights from computational, crystallographic, and functional studies. Neuropharmacology 2019; 161:107548. [PMID: 30807752 DOI: 10.1016/j.neuropharm.2019.02.030] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 02/19/2019] [Accepted: 02/22/2019] [Indexed: 02/02/2023]
Abstract
The serotonin transporter (SERT) belongs to the monoamine transporter family, which also includes the dopamine and norepinephrine transporters. SERT is essential for regulating serotonergic signaling by the reuptake of serotonin from the synaptic cleft back into the presynaptic neuron. Dysregulation of SERT has been implicated in several major psychiatric disorders such as major depressive disorder (MDD). MDD was among the top five leading causes of years lived with disease in 2016 and is characterized as a major global burden. Several drugs have been developed to target SERT for use in the treatment of MDD, and their respective binding modes and locations within SERT have been studied. The elucidation of the first structure of a bacterial SERT homologue in 2005 has accelerated crystallographic, computational, and functional studies to further elucidate drug binding and method of action in SERT. Herein, we aim to highlight and compare these studies with an emphasis on what the different experimental methods conclude on substrate and inhibitor binding modes, and the potential caveats of using the different types of studies are discussed. We focus this review on the binding of cognate substrate and drugs belonging to the different families of antidepressants, including tricyclic antidepressants, selective serotonin reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors, and multimodal drugs, as well as illicit drugs such as cocaine, amphetamines, and ibogaine. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.
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16
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Xue W, Wang P, Tu G, Yang F, Zheng G, Li X, Li X, Chen Y, Yao X, Zhu F. Computational identification of the binding mechanism of a triple reuptake inhibitor amitifadine for the treatment of major depressive disorder. Phys Chem Chem Phys 2018; 20:6606-6616. [DOI: 10.1039/c7cp07869b] [Citation(s) in RCA: 93] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
A shared binding mode involving eleven key residues at the S1 site of MATs for the binding of amitifadine is identified.
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17
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Rannversson H, Andersen J, Bang-Andersen B, Strømgaard K. Mapping the Binding Site for Escitalopram and Paroxetine in the Human Serotonin Transporter Using Genetically Encoded Photo-Cross-Linkers. ACS Chem Biol 2017; 12:2558-2562. [PMID: 28910072 DOI: 10.1021/acschembio.7b00338] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In spite of the important role of the human serotonin transporter (hSERT) in depression treatment, the molecular details of how antidepressant drugs bind are still not completely understood, in particular those related to potential high- and low-affinity binding sites in hSERT. Here, we utilize amber codon suppression in hSERT to encode the photo-cross-linking unnatural amino acid p-azido-l-phenylalanine into the suggested high- and low-affinity binding sites. We then employ UV-induced cross-linking with azF to map the binding site of escitalopram and paroxetine, two prototypical selective serotonin reuptake inhibitors (SSRIs). We find that the two antidepressant drugs exclusively cross-link to azF incorporated at the high-affinity binding site of hSERT, while cross-linking is not observed at the low-affinity binding site. Combined with previous homology models and recent structural data on hSERT, our results provide important information to understand the molecular details of these clinical relevant binding sites.
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Affiliation(s)
- Hafsteinn Rannversson
- Center
for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen, Jagtvej 162, 2100 Copenhagen Ø, Denmark
| | - Jacob Andersen
- Center
for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen, Jagtvej 162, 2100 Copenhagen Ø, Denmark
| | | | - Kristian Strømgaard
- Center
for Biopharmaceuticals, Department of Drug Design and Pharmacology, University of Copenhagen, Jagtvej 162, 2100 Copenhagen Ø, Denmark
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18
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Spies M, James GM, Berroterán-Infante N, Ibeschitz H, Kranz GS, Unterholzner J, Godbersen M, Gryglewski G, Hienert M, Jungwirth J, Pichler V, Reiter B, Silberbauer L, Winkler D, Mitterhauser M, Stimpfl T, Hacker M, Kasper S, Lanzenberger R. Assessment of Ketamine Binding of the Serotonin Transporter in Humans with Positron Emission Tomography. Int J Neuropsychopharmacol 2017; 21:145-153. [PMID: 29045739 PMCID: PMC5793827 DOI: 10.1093/ijnp/pyx085] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 10/15/2017] [Indexed: 01/25/2023] Open
Abstract
BACKGROUND Comprehensive description of ketamine's molecular binding profile becomes increasingly pressing as use in real-life patient cohorts widens. Animal studies attribute a significant role in the substance's antidepressant effects to the serotonergic system. The serotonin transporter is a highly relevant target in this context, because it is central to depressive pathophysiology and treatment. This is, to our knowledge, the first study investigating ketamine's serotonin transporter binding in vivo in humans. METHODS Twelve healthy subjects were assessed twice using [11C]DASB positron emission tomography. A total of 0.50 mg/kg bodyweight ketamine was administered once i.v. prior to the second positron emission tomography scan. Ketamine plasma levels were determined during positron emission tomography. Serotonin transporter nondisplaceable binding potential was computed using a reference region model, and occupancy was calculated for 4 serotonin transporter-rich regions (caudate, putamen, thalamus, midbrain) and a whole-brain region of interest. RESULTS After administration of the routine antidepressant dose, ketamine showed <10% occupancy of the serotonin transporter, which is within the test-retest variability of [11C]DASB. A positive correlation between ketamine plasma levels and occupancy was shown. CONCLUSIONS Measurable occupancy of the serotonin transporter was not detectable after administration of an antidepressant dose of ketamine. This might suggest that ketamine binding of the serotonin transporter is unlikely to be a primary antidepressant mechanism at routine antidepressant doses, as substances that facilitate antidepressant effects via serotonin transporter binding (e.g., selective serotonin reuptake inhibitors) show 70% to 80% occupancy. Administration of high-dose ketamine is widening. Based on the positive relationship we find between ketamine plasma levels and occupancy, there is a need for investigation of ketamine's serotonin transporter binding at higher doses.
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Affiliation(s)
- Marie Spies
- Department of Psychiatry and Psychotherapy, Vienna, Austria
| | | | - Neydher Berroterán-Infante
- Department of Biomedical Imaging and Image-guided Therapy, Division of Nuclear Medicine, Vienna, Austria
| | - Harald Ibeschitz
- Department of Biomedical Imaging and Image-guided Therapy, Division of Nuclear Medicine, Vienna, Austria
| | - Georg S Kranz
- Department of Psychiatry and Psychotherapy, Vienna, Austria
| | | | | | | | - Marius Hienert
- Department of Psychiatry and Psychotherapy, Vienna, Austria
| | | | - Verena Pichler
- Department of Biomedical Imaging and Image-guided Therapy, Division of Nuclear Medicine, Vienna, Austria
| | | | | | | | - Markus Mitterhauser
- Department of Biomedical Imaging and Image-guided Therapy, Division of Nuclear Medicine, Vienna, Austria,Medical University of Vienna, Vienna, Austria,Ludwig Boltzmann Institute for Applied Diagnostics, Vienna, Austria
| | | | - Marcus Hacker
- Department of Biomedical Imaging and Image-guided Therapy, Division of Nuclear Medicine, Vienna, Austria
| | | | - Rupert Lanzenberger
- Department of Psychiatry and Psychotherapy, Vienna, Austria,Correspondence: Rupert Lanzenberger, MD, PD, Department of Psychiatry and Psychotherapy, Medical University of Vienna, Waehringer Guertel 18-20, A-1090 Wien ()
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19
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Krout D, Rodriquez M, Brose SA, Golovko MY, Henry LK, Thompson BJ. Inhibition of the Serotonin Transporter Is Altered by Metabolites of Selective Serotonin and Norepinephrine Reuptake Inhibitors and Represents a Caution to Acute or Chronic Treatment Paradigms. ACS Chem Neurosci 2017; 8:1011-1018. [PMID: 27959497 PMCID: PMC5437659 DOI: 10.1021/acschemneuro.6b00343] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Previous studies of transgenic mice carrying a single isoleucine to methionine substitution (I172M) in the serotonin transporter (SERT) demonstrated a loss of sensitivity to multiple antidepressants (ADs) at SERT. However, the ability of AD metabolites to antagonize SERT was not assessed. Here, we evaluated the selectivity and potency of these metabolites for inhibition of SERT in mouse brain-derived synaptosomes and blood platelets from wild-type (I172 mSERT) and the antidepressant-insensitive mouse M172 mSERT. The metabolites norfluoxetine and desmethylsertraline lost the selectivity demonstrated by the parent compounds for inhibition of wild-type mSERT over M172 mSERT, whereas desvenlafaxine and desmethylcitalopram retained selectivity. Furthermore, we show that the metabolite desmethylcitalopram accumulates in the brain and that the metabolites desmethylcitalopram, norfluoxetine, and desvenlafaxine inhibit serotonin uptake in wild-type mSERT at potencies similar to those of their parent compounds, suggesting that metabolites may play a role in effects observed following AD administration in wild-type and M172 mice.
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Affiliation(s)
- Danielle Krout
- Department
of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, North Dakota 58202, United States
| | - Meghan Rodriquez
- Department
of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, North Dakota 58202, United States
| | - Stephen A. Brose
- Department
of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, North Dakota 58202, United States
| | - Mikhail Y. Golovko
- Department
of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, North Dakota 58202, United States
| | - L. Keith Henry
- Department
of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, 1301 North Columbia Road, Grand Forks, North Dakota 58202, United States
| | - Brent J. Thompson
- Department
of Biomedical Sciences, Oakland University William Beaumont School of Medicine, Rochester, Michigan 48309, United States
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20
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Yang F, Fu T, Zhang X, Hu J, Xue W, Zheng G, Li B, Li Y, Yao X, Zhu F. Comparison of computational model and X-ray crystal structure of human serotonin transporter: potential application for the pharmacology of human monoamine transporters. MOLECULAR SIMULATION 2017. [DOI: 10.1080/08927022.2017.1309653] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Fengyuan Yang
- Innovative Drug Research and Bioinformatics Group, School of Pharmaceutical Sciences and School of Public Affairs, Chongqing University, Chongqing, P.R. China
| | - Tingting Fu
- Innovative Drug Research and Bioinformatics Group, School of Pharmaceutical Sciences and School of Public Affairs, Chongqing University, Chongqing, P.R. China
| | - Xiaoyu Zhang
- Innovative Drug Research and Bioinformatics Group, School of Pharmaceutical Sciences and School of Public Affairs, Chongqing University, Chongqing, P.R. China
| | - Jie Hu
- Innovative Drug Research and Bioinformatics Group, School of Pharmaceutical Sciences and School of Public Affairs, Chongqing University, Chongqing, P.R. China
| | - Weiwei Xue
- Innovative Drug Research and Bioinformatics Group, School of Pharmaceutical Sciences and School of Public Affairs, Chongqing University, Chongqing, P.R. China
| | - Guoxun Zheng
- Innovative Drug Research and Bioinformatics Group, School of Pharmaceutical Sciences and School of Public Affairs, Chongqing University, Chongqing, P.R. China
| | - Bo Li
- Innovative Drug Research and Bioinformatics Group, School of Pharmaceutical Sciences and School of Public Affairs, Chongqing University, Chongqing, P.R. China
| | - Yinghong Li
- Innovative Drug Research and Bioinformatics Group, School of Pharmaceutical Sciences and School of Public Affairs, Chongqing University, Chongqing, P.R. China
| | - Xiaojun Yao
- State Key Laboratory of Applied Organic Chemistry and Department of Chemistry, Lanzhou University, Lanzhou, P.R. China
| | - Feng Zhu
- Innovative Drug Research and Bioinformatics Group, School of Pharmaceutical Sciences and School of Public Affairs, Chongqing University, Chongqing, P.R. China
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21
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Andersen J, Ladefoged LK, Kristensen TNB, Munro L, Grouleff J, Stuhr-Hansen N, Kristensen AS, Schiøtt B, Strømgaard K. Interrogating the Molecular Basis for Substrate Recognition in Serotonin and Dopamine Transporters with High-Affinity Substrate-Based Bivalent Ligands. ACS Chem Neurosci 2016; 7:1406-1417. [PMID: 27425420 DOI: 10.1021/acschemneuro.6b00164] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The transporters for the neurotransmitters serotonin and dopamine (SERT and DAT, respectively) are targets for drugs used in the treatment of mental disorders and widely used drugs of abuse. Studies of prokaryotic homologues have advanced our structural understanding of SERT and DAT, but it still remains enigmatic whether the human transporters contain one or two high-affinity substrate binding sites. We have designed and employed 24 bivalent ligands possessing a highly systematic combination of substrate moieties (serotonin and/or dopamine) and aliphatic or poly(ethylene glycol) spacers to reveal insight into substrate recognition in SERT and DAT. An optimized bivalent ligand comprising two serotonin moieties binds SERT with 3,800-fold increased affinity compared to that of serotonin, suggesting that the human transporters have two distinct substrate binding sites. We show that the bivalent ligands are inhibitors of SERT and an experimentally validated docking model suggests that the bivalent compounds bind with one substrate moiety in the central binding site (the S1 site), whereas the other substrate moiety binds in a distinct binding site (the S2 site). A systematic study of nonconserved SERT/DAT residues surrounding the proposed binding region showed that nonconserved binding site residues do not contribute to selective recognition of substrates in SERT or DAT. This study provides novel insight into the molecular basis for substrate recognition in human transporters and provides an improved foundation for the development of new drugs targeting SERT and DAT.
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Affiliation(s)
- Jacob Andersen
- Department
of Drug Design and Pharmacology, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Lucy Kate Ladefoged
- Interdisciplinary
Nanoscience Center (iNANO), Department of Chemistry, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Trine N. Bjerre Kristensen
- Interdisciplinary
Nanoscience Center (iNANO), Department of Chemistry, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Lachlan Munro
- Department
of Drug Design and Pharmacology, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Julie Grouleff
- Interdisciplinary
Nanoscience Center (iNANO), Department of Chemistry, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Nicolai Stuhr-Hansen
- Department
of Drug Design and Pharmacology, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Anders S. Kristensen
- Department
of Drug Design and Pharmacology, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Birgit Schiøtt
- Interdisciplinary
Nanoscience Center (iNANO), Department of Chemistry, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Kristian Strømgaard
- Department
of Drug Design and Pharmacology, University of Copenhagen, DK-2100 Copenhagen, Denmark
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22
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Synthesis and inhibitory evaluation of 3-linked imipramines for the exploration of the S2 site of the human serotonin transporter. Bioorg Med Chem 2016; 24:2725-38. [PMID: 27160055 DOI: 10.1016/j.bmc.2016.04.039] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Revised: 04/16/2016] [Accepted: 04/20/2016] [Indexed: 01/10/2023]
Abstract
The human serotonin transporter is the primary target of several antidepressant drugs, and the importance of a primary, high affinity binding site (S1) for antidepressant binding is well documented. The existence of a lower affinity, secondary binding site (S2) has, however, been debated. Herein we report the synthesis of 3-position coupled imipramine ligands from clomipramine using a copper free Sonogashira reaction. Ligand design was inspired by results from docking and steered molecular dynamics simulations, and the ligands were utilized in a structure-activity relationship study of the positional relationship between the S1 and S2 sites. The computer simulations suggested that the S2 site does indeed exist although with lower affinity for imipramine than observed within the S1 site. Additionally, it was possible to dock the 3-linked imipramine analogs into positions which occupy the S1 and the S2 site simultaneously. The structure activity relationship study showed that the shortest ligands were the most potent, and mutations enlarging the proposed S2 site were found to affect the larger ligands positively, while the smaller ligands were mostly unaffected.
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23
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Genetically encoded photocrosslinkers locate the high-affinity binding site of antidepressant drugs in the human serotonin transporter. Nat Commun 2016; 7:11261. [PMID: 27089947 PMCID: PMC4838859 DOI: 10.1038/ncomms11261] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Accepted: 03/07/2016] [Indexed: 02/02/2023] Open
Abstract
Despite the well-established role of the human serotonin transporter (hSERT) in the treatment of depression, the molecular details of antidepressant drug binding are still not fully understood. Here we utilize amber codon suppression in a membrane-bound transporter protein to encode photocrosslinking unnatural amino acids (UAAs) into 75 different positions in hSERT. UAAs are incorporated with high specificity, and functionally active transporters have similar transport properties and pharmacological profiles compared with wild-type transporters. We employ ultraviolet-induced crosslinking with p-azido-L-phenylalanine (azF) at selected positions in hSERT to map the binding site of imipramine, a prototypical tricyclic antidepressant, and vortioxetine, a novel multimodal antidepressant. We find that the two antidepressants crosslink with azF incorporated at different positions within the central substrate-binding site of hSERT, while no crosslinking is observed at the vestibular-binding site. Taken together, our data provide direct evidence for defining the high-affinity antidepressant binding site in hSERT. Molecular details of how antidepressant drugs bind to the human serotonin transporter are not currently clear. Here, the authors introduce photo-cross-linkers into the protein and map the binding site of several antidepressants.
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24
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Davis BA, Nagarajan A, Forrest LR, Singh SK. Mechanism of Paroxetine (Paxil) Inhibition of the Serotonin Transporter. Sci Rep 2016; 6:23789. [PMID: 27032980 PMCID: PMC4817154 DOI: 10.1038/srep23789] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 03/15/2016] [Indexed: 11/11/2022] Open
Abstract
The serotonin transporter (SERT) is an integral membrane protein that exploits preexisting sodium-, chloride-, and potassium ion gradients to catalyze the thermodynamically unfavorable movement of synaptic serotonin into the presynaptic neuron. SERT has garnered significant clinical attention partly because it is the target of multiple psychoactive agents, including the antidepressant paroxetine (Paxil), the most potent selective serotonin reuptake inhibitor known. However, the binding site and orientation of paroxetine in SERT remain controversial. To provide molecular insight, we constructed SERT homology models based on the Drosophila melanogaster dopamine transporter and docked paroxetine to these models. We tested the predicted binding configurations with a combination of radioligand binding and flux assays on wild-type and mutant SERTs. Our data suggest that the orientation of paroxetine, specifically its fluorophenyl ring, in SERT’s substrate binding site directly depends on this pocket’s charge distribution, and thereby provide an avenue toward understanding and enhancing high-affinity antidepressant activity.
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Affiliation(s)
- Bruce A Davis
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520 USA
| | - Anu Nagarajan
- Computational Structural Biology Section, National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Bethesda, MD 20892 USA
| | - Lucy R Forrest
- Computational Structural Biology Section, National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Bethesda, MD 20892 USA
| | - Satinder K Singh
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520 USA
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25
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Larsen MAB, Plenge P, Andersen J, Eildal JNN, Kristensen AS, Bøgesø KP, Gether U, Strømgaard K, Bang-Andersen B, Loland CJ. Structure-activity relationship studies of citalopram derivatives: examining substituents conferring selectivity for the allosteric site in the 5-HT transporter. Br J Pharmacol 2016; 173:925-36. [PMID: 26699847 DOI: 10.1111/bph.13411] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 12/10/2015] [Accepted: 12/14/2015] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND AND PURPOSE The 5-HT transporter (SERT) is a target for antidepressant drugs. SERT possesses two binding sites: the orthosteric (S1) binding site, which is the presumed target for current SERT inhibitors, and an allosteric (S2) site for which potential therapeutic effects are unknown. The antidepressant drug citalopram displays high-affinity S1 binding and low-affinity S2 binding. To elucidate a possible therapeutic role of allosteric inhibition of SERT, a drug that specifically targets the allosteric site is required. The purpose of this study was to find a compound having higher selectivity towards the S2 site. EXPERIMENTAL APPROACH We performed a systematic structure-activity relationship study based on the scaffold of citalopram and the structurally closely related congener, talopram, which shows low-affinity S1 binding in SERT. The role of the four chemical substituents, which distinguish citalopram from talopram in conferring selectivity towards the S1 and S2 site, respectively, was assessed by determining the binding of 14 citalopram/talopram analogous to the S1 and S2 binding sites in SERT using membranes of COS7 cells transiently expressing SERT. KEY RESULTS The structure-activity relationship study revealed that dimethyl citalopram possesses the highest affinity for the allosteric site relative to the S1 site in SERT and has approximately twofold selectivity for the allosteric site relative to the S1 site in SERT. CONCLUSIONS AND IMPLICATIONS The compound could be a useful lead for future synthesis of drugs with high affinity and high selectivity towards the allosteric binding site.
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Affiliation(s)
- M Andreas B Larsen
- Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Per Plenge
- Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jacob Andersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jonas N N Eildal
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Anders S Kristensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Klaus P Bøgesø
- Neuroscience Drug Discovery, H. Lundbeck A/S, Valby, Denmark
| | - Ulrik Gether
- Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Kristian Strømgaard
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Benny Bang-Andersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Neuroscience Drug Discovery, H. Lundbeck A/S, Valby, Denmark
| | - Claus J Loland
- Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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26
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Xue W, Wang P, Li B, Li Y, Xu X, Yang F, Yao X, Chen YZ, Xu F, Zhu F. Identification of the inhibitory mechanism of FDA approved selective serotonin reuptake inhibitors: an insight from molecular dynamics simulation study. Phys Chem Chem Phys 2016; 18:3260-71. [DOI: 10.1039/c5cp05771j] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The binding mode shared by 4 FDA approved SSRIs treating major depression was identified by integrating multiple computational methods.
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27
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Andersen J, Ladefoged LK, Wang D, Kristensen TNB, Bang-Andersen B, Kristensen AS, Schiøtt B, Strømgaard K. Binding of the multimodal antidepressant drug vortioxetine to the human serotonin transporter. ACS Chem Neurosci 2015; 6:1892-900. [PMID: 26389667 DOI: 10.1021/acschemneuro.5b00225] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Selective inhibitors of the human serotonin transporter (hSERT) have been first-line treatment against depression for several decades. Recently, vortioxetine was approved as a new therapeutic option for the treatment of depression. Vortioxetine represents a new class of antidepressant drugs with a multimodal pharmacological profile that in addition to potent inhibition of hSERT include agonistic or antagonistic effects at different serotonin receptors. We used a combination of computational, chemical, and biological methods to decipher the molecular basis for high affinity binding of vortioxetine in hSERT. X-ray crystal structures of the bacterial amino acid transporter LeuT and the Drosophila melanogaster dopamine transporter were used to build homology models of hSERT. Comparative modeling and ligand docking suggest that vortioxetine can adopt several distinct binding modes within the central binding site of hSERT. To distinguish between the identified binding modes, we determined the effect of 57 functional hSERT point mutants on vortioxetine potency and characterized seven structurally related analogs of vortioxetine in a subset of the point mutants. This allowed us to determine the orientation of vortioxetine within the central binding site and showed that only one of the proposed binding modes is functionally relevant. The findings provide important new insight about the molecular basis for high affinity recognition of vortioxetine in hSERT, which is essential for future structure-based drug discovery of novel multimodal drugs with fine-tuned selectivity across different transporter and receptor proteins in the human brain.
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Affiliation(s)
- Jacob Andersen
- Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark
| | - Lucy Kate Ladefoged
- Center for Insoluble Protein Structures (inSPIN) and Interdisciplinary
Nanoscience Center (iNANO), Department of Chemistry, Aarhus University, Langelandsgade
140, DK-8000 Aarhus
C, Denmark
| | - Danyang Wang
- Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark
| | - Trine N. Bjerre Kristensen
- Center for Insoluble Protein Structures (inSPIN) and Interdisciplinary
Nanoscience Center (iNANO), Department of Chemistry, Aarhus University, Langelandsgade
140, DK-8000 Aarhus
C, Denmark
| | - Benny Bang-Andersen
- Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark
- Lundbeck Research Denmark, H. Lundbeck A/S, Ottiliavej 9, DK-2500 Valby, Denmark
| | - Anders S. Kristensen
- Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark
| | - Birgit Schiøtt
- Center for Insoluble Protein Structures (inSPIN) and Interdisciplinary
Nanoscience Center (iNANO), Department of Chemistry, Aarhus University, Langelandsgade
140, DK-8000 Aarhus
C, Denmark
| | - Kristian Strømgaard
- Department of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark
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28
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Andersen J, Ringsted KB, Bang-Andersen B, Strømgaard K, Kristensen AS. Binding site residues control inhibitor selectivity in the human norepinephrine transporter but not in the human dopamine transporter. Sci Rep 2015; 5:15650. [PMID: 26503701 PMCID: PMC4621520 DOI: 10.1038/srep15650] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Accepted: 10/01/2015] [Indexed: 02/08/2023] Open
Abstract
The transporters for norepinephrine and dopamine (NET and DAT, respectively) constitute the molecular targets for recreational drugs and therapeutics used in the treatment of psychiatric disorders. Despite a strikingly similar amino acid sequence and predicted topology between these transporters, some inhibitors display a high degree of selectivity between NET and DAT. Here, a systematic mutational analysis of non-conserved residues within the extracellular entry pathway and the high affinity binding site in NET and DAT was performed to examine their role for selective inhibitor recognition. Changing the six diverging residues in the central binding site of NET to the complementary residues in DAT transferred a DAT-like pharmacology to NET, showing that non-conserved binding site residues in NET are critical determinants for inhibitor selectivity. In contrast, changing the equivalent residues in the central site of DAT to the corresponding residues in NET had modest effects on the same inhibitors, suggesting that non-conserved binding site residues in DAT play a minor role for selective inhibitor recognition. Our data points towards distinct structural determinants governing inhibitor selectivity in NET and DAT, and provide important new insight into the molecular basis for NET/DAT selectivity of therapeutic and recreational drugs.
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Affiliation(s)
- Jacob Andersen
- Department of Drug Design and Pharmacology, University of Copenhagen, Jagtvej 162, DK-2100 Copenhagen, Denmark
| | - Kristoffer B Ringsted
- Department of Drug Design and Pharmacology, University of Copenhagen, Jagtvej 162, DK-2100 Copenhagen, Denmark
| | - Benny Bang-Andersen
- Department of Drug Design and Pharmacology, University of Copenhagen, Jagtvej 162, DK-2100 Copenhagen, Denmark.,Lundbeck Research Denmark, H. Lundbeck A/S, Ottiliavej 9, DK-2500 Valby, Denmark
| | - Kristian Strømgaard
- Department of Drug Design and Pharmacology, University of Copenhagen, Jagtvej 162, DK-2100 Copenhagen, Denmark
| | - Anders S Kristensen
- Department of Drug Design and Pharmacology, University of Copenhagen, Jagtvej 162, DK-2100 Copenhagen, Denmark
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29
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Grouleff J, Ladefoged LK, Koldsø H, Schiøtt B. Monoamine transporters: insights from molecular dynamics simulations. Front Pharmacol 2015; 6:235. [PMID: 26528185 PMCID: PMC4607855 DOI: 10.3389/fphar.2015.00235] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 10/01/2015] [Indexed: 01/31/2023] Open
Abstract
The human monoamine transporters (MATs) facilitate the reuptake of the neurotransmitters serotonin, dopamine, and norepinephrine from the synaptic cleft. Imbalance in monoaminergic neurotransmission is linked to various diseases including major depression, attention deficit hyperactivity disorder, schizophrenia, and Parkinson's disease. Inhibition of the MATs is thus an important strategy for treatment of such diseases. The MATs are sodium-coupled transport proteins belonging to the neurotransmitter/Na(+) symporter (NSS) family, and the publication of the first high-resolution structure of a NSS family member, the bacterial leucine transporter LeuT, in 2005, proved to be a major stepping stone for understanding this family of transporters. Structural data allows for the use of computational methods to study the MATs, which in turn has led to a number of important discoveries. The process of substrate translocation across the membrane is an intrinsically dynamic process. Molecular dynamics simulations, which can provide atomistic details of molecular motion on ns to ms timescales, are therefore well-suited for studying transport processes. In this review, we outline how molecular dynamics simulations have provided insight into the large scale motions associated with transport of the neurotransmitters, as well as the presence of external and internal gates, the coupling between ion and substrate transport, and differences in the conformational changes induced by substrates and inhibitors.
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Affiliation(s)
- Julie Grouleff
- Center for Insoluble Protein Structures and Interdisciplinary Nanoscience Center, Department of Chemistry, Aarhus University Aarhus, Denmark
| | - Lucy Kate Ladefoged
- Center for Insoluble Protein Structures and Interdisciplinary Nanoscience Center, Department of Chemistry, Aarhus University Aarhus, Denmark
| | - Heidi Koldsø
- Department of Biochemistry, University of Oxford Oxford, UK
| | - Birgit Schiøtt
- Center for Insoluble Protein Structures and Interdisciplinary Nanoscience Center, Department of Chemistry, Aarhus University Aarhus, Denmark
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30
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Mortensen OV, Kortagere S. Designing modulators of monoamine transporters using virtual screening techniques. Front Pharmacol 2015; 6:223. [PMID: 26483692 PMCID: PMC4586420 DOI: 10.3389/fphar.2015.00223] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 09/17/2015] [Indexed: 12/15/2022] Open
Abstract
The plasma-membrane monoamine transporters (MATs), including the serotonin (SERT), norepinephrine (NET) and dopamine (DAT) transporters, serve a pivotal role in limiting monoamine-mediated neurotransmission through the reuptake of their respective monoamine neurotransmitters. The transporters are the main target of clinically used psychostimulants and antidepressants. Despite the availability of several potent and selective MAT substrates and inhibitors the continuing need for therapeutic drugs to treat brain disorders involving aberrant monoamine signaling provides a compelling reason to identify novel ways of targeting and modulating the MATs. Designing novel modulators of MAT function have been limited by the lack of three dimensional structure information of the individual MATs. However, crystal structures of LeuT, a bacterial homolog of MATs, in a substrate-bound occluded, substrate-free outward-open, and an apo inward-open state and also with competitive and non-competitive inhibitors have been determined. In addition, several structures of the Drosophila DAT have also been resolved. Together with computational modeling and experimental data gathered over the past decade, these structures have dramatically advanced our understanding of several aspects of SERT, NET, and DAT transporter function, including some of the molecular determinants of ligand interaction at orthosteric substrate and inhibitor binding pockets. In addition progress has been made in the understanding of how allosteric modulation of MAT function can be achieved. Here we will review all the efforts up to date that has been made through computational approaches employing structural models of MATs to design small molecule modulators to the orthosteric and allosteric sites using virtual screening techniques.
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Affiliation(s)
- Ole V Mortensen
- Department of Pharmacology and Physiology, Drexel University College of Medicine , Philadelphia, PA, USA
| | - Sandhya Kortagere
- Department of Microbiology and Immunology, Drexel University College of Medicine , Philadelphia, PA, USA
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31
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Koldsø H, Grouleff J, Schiøtt B. Insights to ligand binding to the monoamine transporters-from homology modeling to LeuBAT and dDAT. Front Pharmacol 2015; 6:208. [PMID: 26441663 PMCID: PMC4585151 DOI: 10.3389/fphar.2015.00208] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 09/07/2015] [Indexed: 11/20/2022] Open
Abstract
Understanding of drug binding to the human biogenic amine transporters (BATs) is essential to explain the mechanism of action of these pharmaceuticals but more importantly to be able to develop new and improved compounds to be used in the treatment of depression or drug addiction. Until recently no high resolution structure was available of the BATs and homology modeling was a necessity. Various studies have revealed experimentally validated binding modes of numerous ligands to the BATs using homology modeling. Here we examine and discuss the similarities between the binding models of substrates, antidepressants, psychostimulants, and mazindol in homology models of the human BATs and the recently published crystal structures of the Drosophila dopamine transporter and the engineered protein, LeuBAT. The comparison reveals that careful computational modeling combined with experimental data can be utilized to predict binding of molecules to proteins that agree very well with crystal structures.
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Affiliation(s)
- Heidi Koldsø
- Department of Biochemistry, University of Oxford , Oxford, UK ; inSPIN and iNANO Centers, Department of Chemistry, Aarhus University , Aarhus C, Denmark
| | - Julie Grouleff
- inSPIN and iNANO Centers, Department of Chemistry, Aarhus University , Aarhus C, Denmark
| | - Birgit Schiøtt
- inSPIN and iNANO Centers, Department of Chemistry, Aarhus University , Aarhus C, Denmark
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32
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Söderhielm PC, Andersen J, Munro L, Nielsen AT, Kristensen AS. Substrate and Inhibitor-Specific Conformational Changes in the Human Serotonin Transporter Revealed by Voltage-Clamp Fluorometry. Mol Pharmacol 2015; 88:676-88. [PMID: 26174773 DOI: 10.1124/mol.115.099911] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 07/13/2015] [Indexed: 01/05/2023] Open
Abstract
The serotonin transporter (SERT) regulates neurotransmission by the biogenic monoamine neurotransmitter serotonin (5-HT, 5-hydroxytryptamine) in the central nervous system, and drugs inhibiting SERT are widely used for the treatment of a variety of central nervous system diseases. The conformational dynamics of SERT transport function and inhibition is currently poorly understood. We used voltage-clamp fluorometry to study conformational changes in human SERT (hSERT) during 5-HT transport and inhibitor binding. Cys residues were introduced at 12 positions in hSERT to enable covalent attachment of a rhodamine-based fluorophore. Transport-associated changes in fluorescence from fluorophore-labeled hSERT expressed in Xenopus oocytes could be robustly detected at four positions in hSERT: endogenous Cys109 in the top of transmembrane domain (TM) 1b, Cys substituted for Thr323 in the top of TM6, Ala419 in the interface between TM8 and extracellular loop (EL) 4, and Leu481 in EL5. The reporter positions were used for time-resolved measurement of conformational changes during 5-HT transport and binding of cocaine and the selective serotonin reuptake inhibitors fluoxetine and escitalopram. At all reporter positions, fluorescence changes observed upon substrate application were distinctly different from those observed upon inhibitor application, with respect to relative amplitude or direction. Furthermore, escitalopram, fluoxetine, and cocaine induced a very similar pattern of fluorescent changes overall, which included movements within or around TM1b, EL4, and EL5. Taken together, our data lead us to suggest that competitive inhibitors stabilize hSERT in a state that is different from the apo outward-open conformation as well as inward-facing conformations.
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Affiliation(s)
- Pella C Söderhielm
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Jacob Andersen
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Lachlan Munro
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Anne T Nielsen
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Anders S Kristensen
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
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33
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Kumar V, Yarravarapu N, Lapinsky DJ, Perley D, Felts B, Tomlinson MJ, Vaughan RA, Henry LK, Lever JR, Newman AH. Novel Azido-Iodo Photoaffinity Ligands for the Human Serotonin Transporter Based on the Selective Serotonin Reuptake Inhibitor (S)-Citalopram. J Med Chem 2015; 58:5609-19. [PMID: 26153715 PMCID: PMC4515784 DOI: 10.1021/acs.jmedchem.5b00682] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
Three photoaffinity ligands (PALs)
for the human serotonin transporter
(hSERT) were synthesized based on the selective serotonin reuptake
inhibitor (SSRI), (S)-citalopram (1).
The classic 4-azido-3-iodo-phenyl group was appended to either the
C-1 or C-5 position of the parent molecule, with variable-length linkers,
to generate ligands 15, 22, and 26. These ligands retained high to moderate affinity binding (Ki = 24–227 nM) for hSERT, as assessed
by [3H]5-HT transport inhibition. When tested against Ser438Thr
hSERT, all three PALs showed dramatic rightward shifts in inhibitory
potency, with Ki values ranging from 3.8
to 9.9 μM, consistent with the role of Ser438 as a key residue
for high-affinity binding of many SSRIs, including (S)-citalopram. Photoactivation studies demonstrated irreversible adduction
to hSERT by all ligands, but the reduced (S)-citalopram
inhibition of labeling by [125I]15 compared
to that by [125I]22 and [125I]26 suggests differences in binding mode(s). These radioligands
will be useful for characterizing the drug–protein binding
interactions for (S)-citalopram at hSERT.
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Affiliation(s)
- Vivek Kumar
- †Medicinal Chemistry Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, 333 Cassell Drive, Baltimore, Maryland 21224, United States
| | - Nageswari Yarravarapu
- ‡Division of Pharmaceutical Sciences, Duquesne University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, United States
| | - David J Lapinsky
- ‡Division of Pharmaceutical Sciences, Duquesne University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, United States
| | - Danielle Perley
- §Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58202, United States
| | - Bruce Felts
- §Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58202, United States
| | - Michael J Tomlinson
- §Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58202, United States
| | - Roxanne A Vaughan
- §Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58202, United States
| | - L Keith Henry
- §Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58202, United States
| | - John R Lever
- ∥Department of Radiology, University of Missouri, One Hospital Drive, Columbia, Missouri 65212, United States.,⊥Harry S. Truman Memorial Veterans' Hospital, 800 Hospital Drive, Columbia, Missouri 65201, United States
| | - Amy Hauck Newman
- †Medicinal Chemistry Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, 333 Cassell Drive, Baltimore, Maryland 21224, United States
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34
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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] [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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35
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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] [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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36
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Dahal RA, Pramod AB, Sharma B, Krout D, Foster JD, Cha JH, Cao J, Newman AH, Lever JR, Vaughan RA, Henry LK. Computational and biochemical docking of the irreversible cocaine analog RTI 82 directly demonstrates ligand positioning in the dopamine transporter central substrate-binding site. J Biol Chem 2014; 289:29712-27. [PMID: 25179220 PMCID: PMC4207985 DOI: 10.1074/jbc.m114.571521] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Revised: 08/09/2014] [Indexed: 12/20/2022] Open
Abstract
The dopamine transporter (DAT) functions as a key regulator of dopaminergic neurotransmission via re-uptake of synaptic dopamine (DA). Cocaine binding to DAT blocks this activity and elevates extracellular DA, leading to psychomotor stimulation and addiction, but the mechanisms by which cocaine interacts with DAT and inhibits transport remain incompletely understood. Here, we addressed these questions using computational and biochemical methodologies to localize the binding and adduction sites of the photoactivatable irreversible cocaine analog 3β-(p-chlorophenyl)tropane-2β-carboxylic acid, 4'-azido-3'-iodophenylethyl ester ([(125)I]RTI 82). Comparative modeling and small molecule docking indicated that the tropane pharmacophore of RTI 82 was positioned in the central DA active site with an orientation that juxtaposed the aryliodoazide group for cross-linking to rat DAT Phe-319. This prediction was verified by focused methionine substitution of residues flanking this site followed by cyanogen bromide mapping of the [(125)I]RTI 82-labeled mutants and by the substituted cysteine accessibility method protection analyses. These findings provide positive functional evidence linking tropane pharmacophore interaction with the core substrate-binding site and support a competitive mechanism for transport inhibition. This synergistic application of computational and biochemical methodologies overcomes many uncertainties inherent in other approaches and furnishes a schematic framework for elucidating the ligand-protein interactions of other classes of DA transport inhibitors.
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Affiliation(s)
- Rejwi Acharya Dahal
- From the Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58203
| | - Akula Bala Pramod
- From the Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58203
| | - Babita Sharma
- From the Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58203
| | - Danielle Krout
- From the Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58203
| | - James D Foster
- From the Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58203
| | - Joo Hwan Cha
- the Medicinal Chemistry Section, National Institute on Drug Abuse-Intramural Research Program, Baltimore, Maryland 21224
| | - Jianjing Cao
- the Medicinal Chemistry Section, National Institute on Drug Abuse-Intramural Research Program, Baltimore, Maryland 21224
| | - Amy Hauck Newman
- the Medicinal Chemistry Section, National Institute on Drug Abuse-Intramural Research Program, Baltimore, Maryland 21224
| | - John R Lever
- the Research Service, Harry S. Truman Memorial Veterans Hospital, Columbia, Missouri 65201, and the Department of Radiology, Radiopharmaceutical Sciences Institute, and Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri 65211
| | - Roxanne A Vaughan
- From the Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58203,
| | - L Keith Henry
- From the Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58203,
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37
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Nolan TL, Geffert LM, Kolber BJ, Madura JD, Surratt CK. Discovery of novel-scaffold monoamine transporter ligands via in silico screening with the S1 pocket of the serotonin transporter. ACS Chem Neurosci 2014; 5:784-92. [PMID: 25003748 PMCID: PMC4176318 DOI: 10.1021/cn500133b] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
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Discovery of new inhibitors of the
plasmalemmal monoamine transporters
(MATs) continues to provide pharmacotherapeutic options for depression,
addiction, attention deficit disorders, psychosis, narcolepsy, and
Parkinson’s disease. The windfall of high-resolution MAT structural
information afforded by X-ray crystallography has enabled the construction
of credible computational models. Elucidation of lead compounds, creation
of compound structure–activity series, and pharmacologic testing
are staggering expenses that could be reduced by using a MAT computational
model for virtual screening (VS) of structural libraries containing
millions of compounds. Here, VS of the PubChem small molecule structural
database using the S1 (primary substrate) ligand pocket of a serotonin
transporter homology model yielded 19 prominent “hit”
compounds. In vitro pharmacology of these VS hits revealed four structurally
unique MAT substrate uptake inhibitors with high nanomolar affinity
at one or more of the three MATs. In vivo characterization of three
of these hits revealed significant activity in a mouse model of acute
depression at doses that did not elicit untoward locomotor effects.
This constitutes the first report of MAT inhibitor discovery using
exclusively the primary substrate pocket as a VS tool. Novel-scaffold
MAT inhibitors offer hope of new medications that lack the many classic
adverse effects of existing antidepressant drugs.
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Affiliation(s)
- Tammy L. Nolan
- Division of Pharmaceutical Sciences,
Mylan School of Pharmacy, ‡Departments of Chemistry
and Biochemistry, Center for Computational Sciences,
and §Department of Biological
Sciences, Duquesne University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, United States
| | - Laura M. Geffert
- Division of Pharmaceutical Sciences,
Mylan School of Pharmacy, ‡Departments of Chemistry
and Biochemistry, Center for Computational Sciences,
and §Department of Biological
Sciences, Duquesne University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, United States
| | - Benedict J. Kolber
- Division of Pharmaceutical Sciences,
Mylan School of Pharmacy, ‡Departments of Chemistry
and Biochemistry, Center for Computational Sciences,
and §Department of Biological
Sciences, Duquesne University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, United States
| | - Jeffry D. Madura
- Division of Pharmaceutical Sciences,
Mylan School of Pharmacy, ‡Departments of Chemistry
and Biochemistry, Center for Computational Sciences,
and §Department of Biological
Sciences, Duquesne University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, United States
| | - Christopher K. Surratt
- Division of Pharmaceutical Sciences,
Mylan School of Pharmacy, ‡Departments of Chemistry
and Biochemistry, Center for Computational Sciences,
and §Department of Biological
Sciences, Duquesne University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, United States
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38
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LeVine MV, Weinstein H. NbIT--a new information theory-based analysis of allosteric mechanisms reveals residues that underlie function in the leucine transporter LeuT. PLoS Comput Biol 2014; 10:e1003603. [PMID: 24785005 PMCID: PMC4006702 DOI: 10.1371/journal.pcbi.1003603] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Accepted: 03/24/2014] [Indexed: 11/23/2022] Open
Abstract
Complex networks of interacting residues and microdomains in the structures of biomolecular systems underlie the reliable propagation of information from an input signal, such as the concentration of a ligand, to sites that generate the appropriate output signal, such as enzymatic activity. This information transduction often carries the signal across relatively large distances at the molecular scale in a form of allostery that is essential for the physiological functions performed by biomolecules. While allosteric behaviors have been documented from experiments and computation, the mechanism of this form of allostery proved difficult to identify at the molecular level. Here, we introduce a novel analysis framework, called N-body Information Theory (NbIT) analysis, which is based on information theory and uses measures of configurational entropy in a biomolecular system to identify microdomains and individual residues that act as (i)-channels for long-distance information sharing between functional sites, and (ii)-coordinators that organize dynamics within functional sites. Application of the new method to molecular dynamics (MD) trajectories of the occluded state of the bacterial leucine transporter LeuT identifies a channel of allosteric coupling between the functionally important intracellular gate and the substrate binding sites known to modulate it. NbIT analysis is shown also to differentiate residues involved primarily in stabilizing the functional sites, from those that contribute to allosteric couplings between sites. NbIT analysis of MD data thus reveals rigorous mechanistic elements of allostery underlying the dynamics of biomolecular systems. We developed the new information theory-based analysis framework presented here, NbIT analysis, for the study of allosteric mechanisms in biomolecular systems from Molecular Dynamics trajectories. The illustrative application of NbIT to the analysis of the occluded state in the bacterial transporter LeuT, produced a quantitative representation of the allosteric behavior, and identified intramolecular channels that enable the long-distance information transmission. Our findings, identifying the roles of specific residues in the communication of the allosteric information, were validated by the recognition of residues that have been previously shown to play functional roles in this very well studied system. In addition, we show that application of NbIT analysis leads to the discrimination of functional roles by differentiating between residues that are essential to the dynamics within functional sites (e.g., the substrate binding sites), and residues whose role is to communicate between such functional sites. These results demonstrate that the information theoretical analysis presented here is a powerful tool for quantifying complex allosteric behavior in biomolecular systems and for identifying the crucial components underlying those behaviors.
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Affiliation(s)
- Michael V. LeVine
- Department of Physiology and Biophysics, Weill Cornell Medical College of Cornell University (WCMC), New York, New York, United States of America
| | - Harel Weinstein
- Department of Physiology and Biophysics, Weill Cornell Medical College of Cornell University (WCMC), New York, New York, United States of America
- HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute of Computational Biomedicine, Weill Cornell Medical College of Cornell University, New York, New York, United States of America
- * E-mail:
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39
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Loland CJ. The use of LeuT as a model in elucidating binding sites for substrates and inhibitors in neurotransmitter transporters. Biochim Biophys Acta Gen Subj 2014; 1850:500-10. [PMID: 24769398 DOI: 10.1016/j.bbagen.2014.04.011] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2014] [Revised: 04/09/2014] [Accepted: 04/11/2014] [Indexed: 01/24/2023]
Abstract
BACKGROUND The mammalian neurotransmitter transporters are complex proteins playing a central role in synaptic transmission between neurons by rapid reuptake of neurotransmitters. The proteins which transport dopamine, noradrenaline and serotonin belong to the Neurotransmitter:Sodium Symporters (NSS). Due to their important role, dysfunctions are associated with several psychiatric and neurological diseases and they also serve as targets for a wide range of therapeutic and illicit drugs. Despite the central physiological and pharmacological importance, direct evidence on structure-function relationships on mammalian NSS proteins has so far been unsuccessful. The crystal structure of the bacterial NSS protein, LeuT, has been a turning point in structural investigations. SCOPE OF REVIEW To provide an update on what is known about the binding sites for substrates and inhibitors in the LeuT. The different binding modes and binding sites will be discussed with special emphasis on the possible existence of a second substrate binding site. It is the goal to give an insight into how investigations on ligand binding in LeuT have provided basic knowledge about transporter conformations and translocation mechanism which can pave the road for a deeper understanding of drug binding and function of the mammalian transporters. MAJOR CONCLUSIONS The LeuT is a suitable model for the structural investigation of NSS proteins including the possible location of drug binding sites. It is still debated whether the LeuT is a suitable model for the molecular mechanisms behind substrate translocation. GENERAL SIGNIFICANCE Structure and functional aspects of NSS proteins are central for understanding synaptic transmission. With the purification and crystallization of LeuT as well as the dopamine transporter from Drosophila melanogaster, the application of biophysical methods such as fluorescence spectroscopy, neutron- or x-ray scattering and NMR for understanding its function becomes increasingly available. This article is part of a Special Issue entitled Structural biochemistry and biophysics of membrane proteins.
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Affiliation(s)
- Claus J Loland
- Molecular Neuropharmacology Laboratory, Department of Neuroscience and Pharmacology, The Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen N, Denmark.
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40
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Guevara-Salazar JA, Quintana-Zavala D, Jiménez-Vázquez HA, Trujillo-Ferrara J. Use of the harmonic mean to the determination of dissociation constants of stereoisomeric mixtures of biologically active compounds. J Enzyme Inhib Med Chem 2014; 29:884-94. [PMID: 24517366 DOI: 10.3109/14756366.2013.866656] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Herein we introduce the derivation of a mathematical expression to evaluate the dissociation constant of a mixture of stereoisomers in equal amounts (KdMIX), when the corresponding dissociation constants (Kd) or medium response (MR50) of the pure stereoisomers are known; the final equation takes the form of the harmonic mean. In order to validate the equation, we carried out a bibliographic search of experimental data of enantiomeric molecules with biological activity, considering the Kd's or MR50's of the isolated enantiomers as well as that of the racemate. The comparisons between the experimental dissociation constants of the mixtures (KdEXP or MR50EXP) and the calculated values (KdMIX or MR50MIX) were consistent; the similarity between these values is supported through statistical analyses of group comparison and simple linear correlation. The equation we obtained, which corresponds to the harmonic mean, was used to predict the values of KdMIX (or MR50MIX) or Kd (or MR50) in systems when only two of the experimental values are known: either the dissociation constants of both enantiomers or the Kd (or MR50) of one of the enantiomers and dissociation constant of the racemate.
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41
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Andersen J, Stuhr-Hansen N, Zachariassen LG, Koldsø H, Schiøtt B, Strømgaard K, Kristensen AS. Molecular basis for selective serotonin reuptake inhibition by the antidepressant agent fluoxetine (Prozac). Mol Pharmacol 2014; 85:703-14. [PMID: 24516100 DOI: 10.1124/mol.113.091249] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Inhibitors of the serotonin transporter (SERT) are widely used antidepressant agents, but the structural mechanism for inhibitory activity and selectivity over the closely related norepinephrine transporter (NET) is not well understood. Here we use a combination of chemical, biological, and computational methods to decipher the molecular basis for high-affinity recognition in SERT and selectivity over NET for the prototypical antidepressant drug fluoxetine (Prozac; Eli Lilly, Indianapolis, IN). We show that fluoxetine binds within the central substrate site of human SERT, in agreement with recent X-ray crystal structures of LeuBAT, an engineered monoamine-like version of the bacterial amino acid transporter LeuT. However, the binding orientation of fluoxetine is reversed in our experimentally supported model compared with the LeuBAT structures, emphasizing the need for careful experimental verification when extrapolating findings from crystal structures of bacterial transporters to human relatives. We find that the selectivity of fluoxetine and nisoxetine, a NET selective structural congener of fluoxetine, is controlled by residues in different regions of the transporters, indicating a complex mechanism for selective recognition of structurally similar compounds in SERT and NET. Our findings add important new information on the molecular basis for SERT/NET selectivity of antidepressants, and provide the first assessment of the potential of LeuBAT as a model system for antidepressant binding in human transporters, which is essential for future structure-based drug development of antidepressant drugs with fine-tuned transporter selectivity.
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Affiliation(s)
- Jacob Andersen
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark (J.A., N.S.-H., L.G.Z., K.S., A.S.K.); and Center for Insoluble Structures (inSPIN) and Interdisciplinary Nanoscience Center (iNANO), Department of Chemistry, Aarhus University, Aarhus, Denmark (H.K., B.S.)
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42
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Banala AK, Zhang P, Plenge P, Cyriac G, Kopajtic T, Katz JL, Loland CJ, Newman AH. Design and synthesis of 1-(3-(dimethylamino)propyl)-1-(4-fluorophenyl)-1,3-dihydroisobenzofuran-5-carbonitrile (citalopram) analogues as novel probes for the serotonin transporter S1 and S2 binding sites. J Med Chem 2013; 56:9709-24. [PMID: 24237160 DOI: 10.1021/jm4014136] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The serotonin transporter (SERT) is the primary target for antidepressant drugs. The existence of a high affinity primary orthosteric binding site (S1) and a low affinity secondary site (S2) has been described, and their relation to antidepressant pharmacology has been debated. Herein, structural modifications to the N, 4, 5, and 4' positions of (±)citalopram (1) are reported. All of the analogues were SERT-selective and demonstrated that steric bulk was tolerated at the SERT S1 site, including two dimeric ligands (15 and 51). In addition, eight analogues were identified with similar potencies to S-1 for decreasing the dissociation of [(3)H]S-1 from the S1 site via allosteric modulation at S2. Both dimeric compounds had similar affinities for the SERT S1 site (Ki = 19.7 and 30.2 nM, respectively), whereas only the N-substituted analogue, 51, was as effective as S-1 in allosterically modulating the binding of [(3)H]S-1 via S2.
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Affiliation(s)
- Ashwini K Banala
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse-Intramural Research Program, National Institutes of Health , 333 Cassell Drive, Baltimore, Maryland 21224, United States
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43
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Gaffaney JD, Shetty M, Felts B, Pramod AB, Foster JD, Henry LK, Vaughan RA. Antagonist-induced conformational changes in dopamine transporter extracellular loop two involve residues in a potential salt bridge. Neurochem Int 2013; 73:16-26. [PMID: 24269640 DOI: 10.1016/j.neuint.2013.11.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Revised: 11/04/2013] [Accepted: 11/06/2013] [Indexed: 10/26/2022]
Abstract
Ligand-induced changes in the conformation of extracellular loop (EL) 2 in the rat (r) dopamine transporter (DAT) were examined using limited proteolysis with endoproteinase Asp-N and detection of cleavage products by epitope-specific immunoblotting. The principle N-terminal fragment produced by Asp-N was a 19kDa peptide likely derived by proteolysis of EL2 residue D174, which is present just past the extracellular end of TM3. Production of this fragment was significantly decreased by binding of cocaine and other uptake blockers, but was not affected by substrates or Zn(2+), indicating the presence of a conformational change at D174 that may be related to the mechanism of transport inhibition. DA transport activity and cocaine analog binding were decreased by Asp-N treatment, suggesting a requirement for EL2 integrity in these DAT functions. In a previous study we demonstrated that ligand-induced protease resistance also occurred at R218 on the C-terminal side of rDAT EL2. Here using substituted cysteine accessibility analysis of human (h) DAT we confirm cocaine-induced alterations in reactivity of the homologous R219 and identify conformational sensitivity of V221. Focused molecular modeling of D174 and R218 based on currently available Aquifex aeolicus leucine transporter crystal structures places these residues within 2.9Å of one another, suggesting their proximity as a structural basis for their similar conformational sensitivities and indicating their potential to form a salt bridge. These findings extend our understanding of DAT EL2 and its role in transport and binding functions.
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Affiliation(s)
- Jon D Gaffaney
- Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58202, United States
| | - Madhur Shetty
- Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58202, United States
| | - Bruce Felts
- Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58202, United States
| | - Akula-Bala Pramod
- Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58202, United States
| | - James D Foster
- Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58202, United States
| | - L Keith Henry
- Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58202, United States.
| | - Roxanne A Vaughan
- Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58202, United States.
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44
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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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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45
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Wang H, Goehring A, Wang KH, Penmatsa A, Ressler R, Gouaux E. Structural basis for action by diverse antidepressants on biogenic amine transporters. Nature 2013; 503:141-5. [PMID: 24121440 PMCID: PMC3904662 DOI: 10.1038/nature12648] [Citation(s) in RCA: 118] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2013] [Accepted: 09/11/2013] [Indexed: 12/18/2022]
Abstract
The biogenic amine transporters (BATs) regulate endogenous neurotransmitter concentrations and are targets for a broad range of therapeutic agents including selective serotonin reuptake inhibitors (SSRIs), serotonin-noradrenaline reuptake inhibitors (SNRIs) and tricyclic antidepressants (TCAs). Because eukaryotic BATs are recalcitrant to crystallographic analysis, our understanding of the mechanism of these inhibitors and antidepressants is limited. LeuT is a bacterial homologue of BATs and has proven to be a valuable paradigm for understanding relationships between their structure and function. However, because only approximately 25% of the amino acid sequence of LeuT is in common with that of BATs, and as LeuT is a promiscuous amino acid transporter, it does not recapitulate the pharmacological properties of BATs. Indeed, SSRIs and TCAs bind in the extracellular vestibule of LeuT and act as non-competitive inhibitors of transport. By contrast, multiple studies demonstrate that both TCAs and SSRIs are competitive inhibitors for eukaryotic BATs and bind to the primary binding pocket. Here we engineered LeuT to harbour human BAT-like pharmacology by mutating key residues around the primary binding pocket. The final LeuBAT mutant binds the SSRI sertraline with a binding constant of 18 nM and displays high-affinity binding to a range of SSRIs, SNRIs and a TCA. We determined 12 crystal structures of LeuBAT in complex with four classes of antidepressants. The chemically diverse inhibitors have a remarkably similar mode of binding in which they straddle transmembrane helix (TM) 3, wedge between TM3/TM8 and TM1/TM6, and lock the transporter in a sodium- and chloride-bound outward-facing open conformation. Together, these studies define common and simple principles for the action of SSRIs, SNRIs and TCAs on BATs.
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Affiliation(s)
- Hui Wang
- Vollum Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239
| | - April Goehring
- Vollum Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239
| | - Kevin H Wang
- Vollum Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239
| | - Aravind Penmatsa
- Vollum Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239
| | - Ryan Ressler
- Vollum Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239
| | - Eric Gouaux
- Vollum Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239
- Howard Hughes Medical Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239
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46
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Beckman ML, Pramod AB, Perley D, Henry LK. Stereoselective inhibition of serotonin transporters by antimalarial compounds. Neurochem Int 2013; 73:98-106. [PMID: 24161619 DOI: 10.1016/j.neuint.2013.10.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Revised: 10/11/2013] [Accepted: 10/15/2013] [Indexed: 10/26/2022]
Abstract
The serotonin (5-HT) transporter (SERT) is an integral membrane protein that functions to reuptake 5-HT released into the synapse following neurotransmission. This role serves an important regulatory mechanism in neuronal homeostasis. Previous studies have demonstrated that several clinically important antimalarial compounds inhibit serotonin (5-hydroxytryptamine, 5-HT) reuptake. In this study, we examined the details of antimalarial inhibition of 5-HT transport in both Drosophila (dSERT) and human SERT (hSERT) using electrophysiologic, biochemical and computational approaches. We found that the cinchona alkaloids quinidine and cinchonine, which have identical stereochemistry about carbons 8 and 9, exhibited the greatest inhibition of dSERT and hSERT transporter function whereas quinine and cinchonidine, enantiomers of quinidine and cinchonine, respectively, were weaker inhibitors of dSERT and hSERT. Furthermore, SERT mutations known to decrease the binding affinity of many antidepressants affected the cinchona alkaloids in a stereo-specific manner where the similar inhibitory profiles for quinine and cinchonidine (8S,9R) were distinct from quinidine and cinchonine (8R,9S). Small molecule docking studies with hSERT homology models predict that quinine and cinchonidine bind to the central 5-HT binding site (S1) whereas quinidine and cinchonine bind to the S2 site. Taken together, the data presented here support binding of cinchona alkaloids to two different sites on SERT defined by their stereochemistry which implies separate modes of transporter inhibition. Notably, the most potent antimalarial inhibitors of SERT appear to preferentially bind to the S2 site. Our findings provide important insight related to how this class of drugs can modulate the serotonergic system as well as identify compounds that may discriminate between the S1 and S2 binding sites and serve as lead compounds for novel SERT inhibitors.
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Affiliation(s)
- Matthew L Beckman
- Department of Biology, Augsburg College, 2211 Riverside Ave S, Minneapolis, MN 55454, United States.
| | - Akula Bala Pramod
- Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, 501 North Columbia Road, Room 1700, Grand Forks, ND 58203, United States
| | - Danielle Perley
- Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, 501 North Columbia Road, Room 1700, Grand Forks, ND 58203, United States
| | - L Keith Henry
- Department of Basic Sciences, University of North Dakota School of Medicine and Health Sciences, 501 North Columbia Road, Room 1700, Grand Forks, ND 58203, United States.
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47
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Extracellular loop 3 of the noradrenaline transporter contributes to substrate and inhibitor selectivity. Naunyn Schmiedebergs Arch Pharmacol 2013; 387:95-107. [PMID: 24081522 DOI: 10.1007/s00210-013-0923-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Accepted: 09/17/2013] [Indexed: 10/26/2022]
Abstract
The human noradrenaline transporter (NET) and 5-hydroxytryptamine (5-HT) transporter (SERT) are inhibited by antidepressants and psychoactive drugs such as cocaine. Both substrates and inhibitors bind in the transmembrane core of the protein, but molecular divergence at the binding site is not sufficient to account for the NET-selective and SERT-selective inhibition of the antidepressants, desipramine and citalopram, respectively. We considered that the poorly conserved third extracellular loop may contribute to these differences. We substituted single amino acid residues of the third extracellular loop in NET for equivalents from SERT, transiently transfected COS-7 cells with WT NET, 13 mutant NETs and WT SERT, and measured [(3)H]noradrenaline uptake, [(3)H]nisoxetine binding and [(3)H]5-HT uptake. Mutants F299W, Y300Q, R301K and K303L, at the C-terminal end of EL3, all showed significantly decreased [(3)H]nisoxetine binding, indicative of a reduced cell surface expression. Most mutants differed little, if at all, from WT NET regarding [(3)H]noradrenaline uptake; however, the I297P mutant showed no significant uptake activity despite intact cell surface expression, and the A293F mutant showed a significantly slower transporter turnover than WT NET in addition to [(3)H]5-HT uptake that was significantly greater than that of WT NET. The A293F mutation also decreased desipramine potency and increased the inhibition of [(3)H]noradrenaline uptake by citalopram compared to WT NET. These results suggest that the third extracellular loop allosterically regulates the ability of the transmembrane domains to transport substrates and bind inhibitors and thus contributes to the selectivity of substrates and antidepressants for NET and SERT.
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48
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Penmatsa A, Wang KH, Gouaux E. X-ray structure of dopamine transporter elucidates antidepressant mechanism. Nature 2013; 503:85-90. [PMID: 24037379 DOI: 10.1038/nature12533] [Citation(s) in RCA: 459] [Impact Index Per Article: 41.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2013] [Accepted: 08/07/2013] [Indexed: 12/11/2022]
Abstract
Antidepressants targeting Na(+)/Cl(-)-coupled neurotransmitter uptake define a key therapeutic strategy to treat clinical depression and neuropathic pain. However, identifying the molecular interactions that underlie the pharmacological activity of these transport inhibitors, and thus the mechanism by which the inhibitors lead to increased synaptic neurotransmitter levels, has proven elusive. Here we present the crystal structure of the Drosophila melanogaster dopamine transporter at 3.0 Å resolution bound to the tricyclic antidepressant nortriptyline. The transporter is locked in an outward-open conformation with nortriptyline wedged between transmembrane helices 1, 3, 6 and 8, blocking the transporter from binding substrate and from isomerizing to an inward-facing conformation. Although the overall structure of the dopamine transporter is similar to that of its prokaryotic relative LeuT, there are multiple distinctions, including a kink in transmembrane helix 12 halfway across the membrane bilayer, a latch-like carboxy-terminal helix that caps the cytoplasmic gate, and a cholesterol molecule wedged within a groove formed by transmembrane helices 1a, 5 and 7. Taken together, the dopamine transporter structure reveals the molecular basis for antidepressant action on sodium-coupled neurotransmitter symporters and elucidates critical elements of eukaryotic transporter structure and modulation by lipids, thus expanding our understanding of the mechanism and regulation of neurotransmitter uptake at chemical synapses.
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Affiliation(s)
- Aravind Penmatsa
- 1] Vollum Institute, Oregon Health & Science University, 3181 South West Sam Jackson Park Road, Portland, Oregon 97239, USA [2]
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49
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Pramod AB, Foster J, Carvelli L, Henry LK. SLC6 transporters: structure, function, regulation, disease association and therapeutics. Mol Aspects Med 2013; 34:197-219. [PMID: 23506866 DOI: 10.1016/j.mam.2012.07.002] [Citation(s) in RCA: 194] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Accepted: 07/03/2012] [Indexed: 02/08/2023]
Abstract
The SLC6 family of secondary active transporters are integral membrane solute carrier proteins characterized by the Na(+)-dependent translocation of small amino acid or amino acid-like substrates. SLC6 transporters, which include the serotonin, dopamine, norepinephrine, GABA, taurine, creatine, as well as amino acid transporters, are associated with a number of human diseases and disorders making this family a critical target for therapeutic development. In addition, several members of this family are directly involved in the action of drugs of abuse such as cocaine, amphetamines, and ecstasy. Recent advances providing structural insight into this family have vastly accelerated our ability to study these proteins and their involvement in complex biological processes.
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Affiliation(s)
- Akula Bala Pramod
- Department of Pharmacology, Physiology and Therapeutics, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58203, United States
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Immadisetty K, Geffert LM, Surratt CK, Madura JD. New design strategies for antidepressant drugs. Expert Opin Drug Discov 2013; 8:1399-414. [PMID: 23991860 DOI: 10.1517/17460441.2013.830102] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
INTRODUCTION In spite of research efforts spanning six decades, the most prominent antidepressant drugs to date still carry several adverse effects, often serious enough to warrant discontinuation of the drug. Molecular mechanisms of depression are now better understood such that some of the specific receptors responsible can be targeted for activation or inhibition. This advance, coupled with the recent availability of crystal structures of relevant drug targets or their homologs, has opened the door for new antidepressant therapeutic compounds. AREAS COVERED The authors review the evolution of monoamine-based antidepressant drugs, up to the selective serotonin reuptake inhibitors (SSRIs). The authors discuss classic and contemporary antidepressant drug design strategies, with a focus on virtual screening and fragment-based drug design methods. Furthermore, they discuss the recent advancements in the understanding of the serotonin transporter (SERT) structure/function relationship in the context of recognition of SSRIs and outline a strategy for the use of computational approaches in producing new SSRI lead compounds. EXPERT OPINION The authors suggest that given the long-awaited availability of credible three-dimensional structures for the SERT and related monoamine transporter proteins, cutting-edge computational methods should be the linchpin of future drug discovery efforts regarding monoamine-based antidepressant lead compounds. Because these transporter inhibitors cause a ubiquitous increase in extraneuronal neurotransmitter levels leading to side and adverse therapeutic effects, the drug discovery should extend to appropriate manipulation of the 'downstream' receptors affected by the neurotransmitter boost. Efficient use of new computational strategies will accelerate the drug discovery process and reduce its economic burden.
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Affiliation(s)
- Kalyan Immadisetty
- Duquesne University, Center for Computational Sciences, Department of Chemistry and Biochemistry , 600 Forbes Ave, 308 Mellon Hall, Pittsburgh, PA 15282 , USA +1 412 396 4129 ; +1 412 396 5683 ;
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