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Liang Y, Gong Y, Jiang Q, Yu Y, Zhang J. Environmental endocrine disruptors and pregnane X receptor action: A review. Food Chem Toxicol 2023; 179:113976. [PMID: 37532173 DOI: 10.1016/j.fct.2023.113976] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Revised: 07/11/2023] [Accepted: 07/28/2023] [Indexed: 08/04/2023]
Abstract
The pregnane X receptor (PXR) is a kind of orphan nuclear receptor activated by a series of ligands. Environmental endocrine disruptors (EEDs) are a wide class of molecules present in the environment that are suspected to have adverse effects on the endocrine system by interfering with the synthesis, transport, degradation, or action of endogenous hormones. Since EEDs may modulate human/rodent PXR, this review aims to summarize EEDs as PXR modulators, including agonists and antagonists. The modular structure of PXR is also described, interestingly, the pharmacology of PXR have been confirmed to vary among different species. Furthermore, PXR play a key role in the regulation of endocrine function. Endocrine disruption of EEDs via PXR and its related pathways are systematically summarized. In brief, this review may provide a way to understand the roles of EEDs in interaction with the nuclear receptors (such as PXR) and the related pathways.
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Affiliation(s)
- Yuan Liang
- College of Food Science and Engineering, Jilin University, Changchun, 130062, China
| | - Yiyao Gong
- College of Food Science and Engineering, Jilin University, Changchun, 130062, China
| | - Qiuyan Jiang
- College of Food Science and Engineering, Jilin University, Changchun, 130062, China
| | - Yifan Yu
- College of Food Science and Engineering, Jilin University, Changchun, 130062, China
| | - Jie Zhang
- College of Food Science and Engineering, Jilin University, Changchun, 130062, China.
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2
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Ramanjulu JM, Williams SP, Lakdawala AS, DeMartino MP, Lan Y, Marquis RW. Overcoming the Pregnane X Receptor Liability: Rational Design to Eliminate PXR-Mediated CYP Induction. ACS Med Chem Lett 2021; 12:1396-1404. [PMID: 34531948 DOI: 10.1021/acsmedchemlett.1c00187] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Accepted: 08/02/2021] [Indexed: 12/26/2022] Open
Abstract
The pregnane X receptor (PXR) regulates expression of proteins responsible for all three phases required for the detoxification mechanism, which include CYP450 enzymes, phase II enzymes, and multidrug efflux pumps. Therefore, PXR is a prominent receptor that is responsible for xenobiotic excretion and drug-drug interactions. Pyrimidinone 1 is an antagonist of the calcium sensing receptor (CaSR) and a strong activator of PXR. Repeat oral administration revealed diminished exposures over time, which prohibited further progression. A medicinal chemistry campaign was initiated to understand and abolish activation of PXR in order to increase systemic exposures. Rational structure-activity relationship investigations utilizing cocrystal structures and a de novo pharmacophore model resulted in compounds devoid of PXR activation. These studies culminated in the first orally active CaSR antagonist 8 suitable for progression. Cocrystallography, the pharmacophore model employed, and additional observations reported herein supported rational elimination of PXR activation and have applicability across diverse chemical classes to help erase PXR-driven drug-drug interactions.
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Affiliation(s)
- Joshi M. Ramanjulu
- GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426, United States
| | - Shawn P. Williams
- GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426, United States
| | - Ami S. Lakdawala
- GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426, United States
| | - Michael P. DeMartino
- GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426, United States
| | - Yunfeng Lan
- GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426, United States
| | - Robert W. Marquis
- GlaxoSmithKline, 1250 South Collegeville Road, Collegeville, Pennsylvania 19426, United States
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Hall A, Chanteux H, Ménochet K, Ledecq M, Schulze MSED. Designing Out PXR Activity on Drug Discovery Projects: A Review of Structure-Based Methods, Empirical and Computational Approaches. J Med Chem 2021; 64:6413-6522. [PMID: 34003642 DOI: 10.1021/acs.jmedchem.0c02245] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
This perspective discusses the role of pregnane xenobiotic receptor (PXR) in drug discovery and the impact of its activation on CYP3A4 induction. The use of structural biology to reduce PXR activity on drug discovery projects has become more common in recent years. Analysis of this work highlights several important molecular interactions, and the resultant structural modifications to reduce PXR activity are summarized. The computational approaches undertaken to support the design of new drugs devoid of PXR activation potential are also discussed. Finally, the SAR of empirical design strategies to reduce PXR activity is reviewed, and the key SAR transformations are discussed and summarized. In conclusion, this perspective demonstrates that PXR activity can be greatly diminished or negated on active drug discovery projects with the knowledge now available. This perspective should be useful to anyone who seeks to reduce PXR activity on a drug discovery project.
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Affiliation(s)
- Adrian Hall
- UCB, Avenue de l'Industrie, Braine-L'Alleud 1420, Belgium
| | | | | | - Marie Ledecq
- UCB, Avenue de l'Industrie, Braine-L'Alleud 1420, Belgium
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4
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Egorova A, Ekins S, Schmidtke M, Makarov V. Back to the future: Advances in development of broad-spectrum capsid-binding inhibitors of enteroviruses. Eur J Med Chem 2019; 178:606-622. [PMID: 31226653 PMCID: PMC8194503 DOI: 10.1016/j.ejmech.2019.06.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 06/03/2019] [Accepted: 06/03/2019] [Indexed: 01/16/2023]
Abstract
The hydrophobic pocket within viral capsid protein 1 is a target to combat the rhino- and enteroviruses (RV and EV) using small molecules. The highly conserved amino acids lining this pocket enable the development of antivirals with broad-spectrum of activity against numerous RVs and EVs. Inhibitor binding blocks: the attachment of the virion to the host cell membrane, viral uncoating, and/or production of infectious virus particles. Syntheses and biological studies of the most well-known antipicornaviral capsid binders have been reviewed and we propose next steps in this research.
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Affiliation(s)
- Anna Egorova
- Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Leninsky prospekt 33-2, Moscow, 119071, Russia
| | - Sean Ekins
- Collaborations Pharmaceuticals, Inc., 840 Main Campus Drive, Lab 3510, Raleigh, NC27606, USA
| | - Michaela Schmidtke
- Jena University Hospital, Department of Medical Microbiology, Section Experimental Virology, Hans-Knöll-Str. 2, 07745, Jena, Germany
| | - Vadim Makarov
- Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Leninsky prospekt 33-2, Moscow, 119071, Russia.
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Lin W, Wang YM, Chai SC, Lv L, Zheng J, Wu J, Zhang Q, Wang YD, Griffin PR, Chen T. SPA70 is a potent antagonist of human pregnane X receptor. Nat Commun 2017; 8:741. [PMID: 28963450 PMCID: PMC5622171 DOI: 10.1038/s41467-017-00780-5] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 07/27/2017] [Indexed: 02/06/2023] Open
Abstract
Many drugs bind to and activate human pregnane X receptor (hPXR) to upregulate drug-metabolizing enzymes, resulting in decreased drug efficacy and increased resistance. This suggests that hPXR antagonists have therapeutic value. Here we report that SPA70 is a potent and selective hPXR antagonist. SPA70 inhibits hPXR in human hepatocytes and humanized mouse models and enhances the chemosensitivity of cancer cells, consistent with the role of hPXR in drug resistance. Unexpectedly, SJB7, a close analog of SPA70, is an hPXR agonist. X-ray crystallography reveals that SJB7 resides in the ligand-binding domain (LBD) of hPXR, interacting with the AF-2 helix to stabilize the LBD for coactivator binding. Differential hydrogen/deuterium exchange analysis demonstrates that SPA70 and SJB7 interact with the hPXR LBD. Docking studies suggest that the lack of the para-methoxy group in SPA70 compromises its interaction with the AF-2, thus explaining its antagonism. SPA70 is an hPXR antagonist and promising therapeutic tool.The xenobiotic-activated human pregnane X receptor (hPXR) regulates drug metabolism. Here the authors develop hPXR modulators, which are of potential therapeutic interest and functionally and structurally characterize the antagonist SPA70 and the structurally related agonist SJB7.
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Affiliation(s)
- Wenwei Lin
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, TN, 38105-3678, USA
| | - Yue-Ming Wang
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, TN, 38105-3678, USA
| | - Sergio C Chai
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, TN, 38105-3678, USA
| | - Lili Lv
- Structure Biology, Shanghai Medicilon Inc., Shanghai, 201299, China
| | - Jie Zheng
- Department of Molecular Medicine, The Scripps Research Institute, Scripps Florida, Jupiter, FL, 33458, USA
| | - Jing Wu
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, TN, 38105-3678, USA
| | - Qijun Zhang
- Structure Biology, Shanghai Medicilon Inc., Shanghai, 201299, China
| | - Yong-Dong Wang
- Department of Computational Biology, St. Jude Children's Research Hospital, Memphis, TN, 38105-3678, USA
| | - Patrick R Griffin
- Department of Molecular Medicine, The Scripps Research Institute, Scripps Florida, Jupiter, FL, 33458, USA
| | - Taosheng Chen
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, TN, 38105-3678, USA.
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Lau AJ, Chang TKH. 3-Hydroxyflavone and structural analogues differentially activate pregnane X receptor: Implication for inflammatory bowel disease. Pharmacol Res 2015; 100:64-72. [PMID: 26238175 DOI: 10.1016/j.phrs.2015.07.031] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Revised: 07/29/2015] [Accepted: 07/29/2015] [Indexed: 02/06/2023]
Abstract
Pregnane X receptor (PXR; NR1I2) is a member of the superfamily of nuclear receptors that regulates the expression of genes involved in various biological processes, including drug transport and biotransformation. In the present study, we investigated the effect of 3-hydroxyflavone and its structurally-related analogues on PXR activity. 3-Hydroxyflavone, galangin, kaempferol, querceetin, isorhamnetin, and tamarixetin, but not but not datiscetin, morin, myricetin, or syringetin, activated mouse PXR, as assessed in a cell-based reporter gene assay. By comparison, 3-hydroxyflavone activated rat PXR, whereas 3-hydroxyflavone, galangin, quercetin, isorhamnetin, and tamarixetin activated human PXR (hPXR). A time-resolved fluorescence resonance energy transfer competitive ligand-binding assay showed binding to the ligand-binding domain of hPXR by 3-hydroxyflavone, galangin, quercetin, isorhamnetin, and tamarixetin. 3-Hydroxyflavone and galangin, but not quercetin, isorhamnetin, or tamarixetin, recruited steroid receptor coactivator (SRC)-1, SRC-2, and SRC-3 to hPXR. In LS180 human colon adenocarcinoma cells, 3-hydroxyflavone, quercetin, and tamarixetin increased CYP3A4, CYP3A5, and ABCB1 mRNA expression, whereas galangin and isorhamnetin increased CYP3A4 and ABCB1 but not CYP3A5 mRNA expression. Datiscetin, kaempferol, morin, myricetin, and syringetin did not attenuate the extent of hPXR activation by rifampicin, suggesting they are not hPXR antagonists. Overall, flavonols activate PXR in an analogue-specific and species-dependent manner. Substitution at the C2' or C5' position of 3-hydroxyflavone with a hydroxyl or methoxy group rendered it incapable of activating hPXR. Understanding the structure-activity relationship of flavonols in hPXR activation may facilitate nutraceutical development efforts in the treatment of PXR-associated intestinal diseases, such as inflammatory bowel disease.
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Affiliation(s)
- Aik Jiang Lau
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Thomas K H Chang
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, Canada.
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Banerjee M, Robbins D, Chen T. Targeting xenobiotic receptors PXR and CAR in human diseases. Drug Discov Today 2014; 20:618-28. [PMID: 25463033 DOI: 10.1016/j.drudis.2014.11.011] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Revised: 10/28/2014] [Accepted: 11/17/2014] [Indexed: 12/20/2022]
Abstract
Nuclear receptors such as the pregnane X receptor (PXR) and constitutive androstane receptor (CAR) are xenobiotic receptors regulating not only drug metabolism and disposition but also various human diseases such as cancer, diabetes, inflammatory disease, metabolic disease and liver diseases, suggesting that PXR and CAR are promising targets for drug discovery. Consequently, there is an urgent need to discover and develop small molecules that target these PXR- and/or CAR-mediated human-disease-related pathways for relevant therapeutic applications. This review proposes approaches to target PXR and CAR, either individually or simultaneously, in the context of various human diseases, taking into consideration the structural differences between PXR and CAR.
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Affiliation(s)
- Monimoy Banerjee
- Department of Chemical Biology and Therapeutics, St Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - Delira Robbins
- Department of Chemical Biology and Therapeutics, St Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - Taosheng Chen
- Department of Chemical Biology and Therapeutics, St Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA.
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8
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Ekins S. Progress in computational toxicology. J Pharmacol Toxicol Methods 2013; 69:115-40. [PMID: 24361690 DOI: 10.1016/j.vascn.2013.12.003] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Accepted: 12/08/2013] [Indexed: 01/02/2023]
Abstract
INTRODUCTION Computational methods have been widely applied to toxicology across pharmaceutical, consumer product and environmental fields over the past decade. Progress in computational toxicology is now reviewed. METHODS A literature review was performed on computational models for hepatotoxicity (e.g. for drug-induced liver injury (DILI)), cardiotoxicity, renal toxicity and genotoxicity. In addition various publications have been highlighted that use machine learning methods. Several computational toxicology model datasets from past publications were used to compare Bayesian and Support Vector Machine (SVM) learning methods. RESULTS The increasing amounts of data for defined toxicology endpoints have enabled machine learning models that have been increasingly used for predictions. It is shown that across many different models Bayesian and SVM perform similarly based on cross validation data. DISCUSSION Considerable progress has been made in computational toxicology in a decade in both model development and availability of larger scale or 'big data' models. The future efforts in toxicology data generation will likely provide us with hundreds of thousands of compounds that are readily accessible for machine learning models. These models will cover relevant chemistry space for pharmaceutical, consumer product and environmental applications.
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Affiliation(s)
- Sean Ekins
- Collaborations in Chemistry, 5616 Hilltop Needmore Road, Fuquay Varina, NC 27526, USA; Department of Pharmaceutical Sciences, University of Maryland, 20 Penn Street, Baltimore, MD 21201, USA; Department of Pharmacology, Rutgers University-Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854, USA; Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, NC 27599-7355, USA.
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Kandel BA, Ekins S, Leuner K, Thasler WE, Harteneck C, Zanger UM. No Activation of Human Pregnane X Receptor by Hyperforin-Related Phloroglucinols. J Pharmacol Exp Ther 2013; 348:393-400. [DOI: 10.1124/jpet.113.209916] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
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10
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Schumacher M, Mattern C, Ghoumari A, Oudinet JP, Liere P, Labombarda F, Sitruk-Ware R, De Nicola AF, Guennoun R. Revisiting the roles of progesterone and allopregnanolone in the nervous system: resurgence of the progesterone receptors. Prog Neurobiol 2013; 113:6-39. [PMID: 24172649 DOI: 10.1016/j.pneurobio.2013.09.004] [Citation(s) in RCA: 245] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 09/15/2013] [Accepted: 09/21/2013] [Indexed: 02/08/2023]
Abstract
Progesterone is commonly considered as a female reproductive hormone and is well-known for its role in pregnancy. It is less well appreciated that progesterone and its metabolite allopregnanolone are also male hormones, as they are produced in both sexes by the adrenal glands. In addition, they are synthesized within the nervous system. Progesterone and allopregnanolone are associated with adaptation to stress, and increased production of progesterone within the brain may be part of the response of neural cells to injury. Progesterone receptors (PR) are widely distributed throughout the brain, but their study has been mainly limited to the hypothalamus and reproductive functions, and the extra-hypothalamic receptors have been neglected. This lack of information about brain functions of PR is unexpected, as the protective and trophic effects of progesterone are much investigated, and as the therapeutic potential of progesterone as a neuroprotective and promyelinating agent is currently being assessed in clinical trials. The little attention devoted to the brain functions of PR may relate to the widely accepted assumption that non-reproductive actions of progesterone may be mainly mediated by allopregnanolone, which does not bind to PR, but acts as a potent positive modulator of γ-aminobutyric acid type A (GABA(A) receptors. The aim of this review is to critically discuss effects of progesterone on the nervous system via PR, and of allopregnanolone via its modulation of GABA(A) receptors, with main focus on the brain.
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Affiliation(s)
- M Schumacher
- UMR 788 Inserm and University Paris-Sud, Kremlin-Bicêtre, France.
| | - C Mattern
- M et P Pharma AG, Emmetten, Switzerland
| | - A Ghoumari
- UMR 788 Inserm and University Paris-Sud, Kremlin-Bicêtre, France
| | - J P Oudinet
- UMR 788 Inserm and University Paris-Sud, Kremlin-Bicêtre, France
| | - P Liere
- UMR 788 Inserm and University Paris-Sud, Kremlin-Bicêtre, France
| | - F Labombarda
- Instituto de Biologia y Medicina Experimental and University of Buenos Aires, Argentina
| | - R Sitruk-Ware
- Population Council and Rockefeller University, New York, USA
| | - A F De Nicola
- Instituto de Biologia y Medicina Experimental and University of Buenos Aires, Argentina
| | - R Guennoun
- UMR 788 Inserm and University Paris-Sud, Kremlin-Bicêtre, France
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YANG KYUNGHEE, KÖCK KATHLEEN, SEDYKH ALEXANDER, TROPSHA ALEXANDER, BROUWER KIML. An updated review on drug-induced cholestasis: mechanisms and investigation of physicochemical properties and pharmacokinetic parameters. J Pharm Sci 2013; 102:3037-57. [PMID: 23653385 PMCID: PMC4369767 DOI: 10.1002/jps.23584] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Revised: 04/13/2013] [Accepted: 04/16/2013] [Indexed: 12/15/2022]
Abstract
Drug-induced cholestasis is an important form of acquired liver disease and is associated with significant morbidity and mortality. Bile acids are key signaling molecules, but they can exert toxic responses when they accumulate in hepatocytes. This review focuses on the physiological mechanisms of drug-induced cholestasis associated with altered bile acid homeostasis due to direct (e.g., bile acid transporter inhibition) or indirect (e.g., activation of nuclear receptors, altered function/expression of bile acid transporters) processes. Mechanistic information about the effects of a drug on bile acid homeostasis is important when evaluating the cholestatic potential of a compound, but experimental data often are not available. The relationship between physicochemical properties, pharmacokinetic parameters, and inhibition of the bile salt export pump among 77 cholestatic drugs with different pathophysiological mechanisms of cholestasis (i.e., impaired formation of bile vs. physical obstruction of bile flow) was investigated. The utility of in silico models to obtain mechanistic information about the impact of compounds on bile acid homeostasis to aid in predicting the cholestatic potential of drugs is highlighted.
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Affiliation(s)
- KYUNGHEE YANG
- Division of Pharmacotherapy and Experimental Therapeutics, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - KATHLEEN KÖCK
- Division of Pharmacotherapy and Experimental Therapeutics, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - ALEXANDER SEDYKH
- Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - ALEXANDER TROPSHA
- Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - KIM L.R. BROUWER
- Division of Pharmacotherapy and Experimental Therapeutics, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
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Kortagere S, Fontana ACK, Rose DR, Mortensen OV. Identification of an allosteric modulator of the serotonin transporter with novel mechanism of action. Neuropharmacology 2013; 72:282-90. [PMID: 23632081 DOI: 10.1016/j.neuropharm.2013.04.026] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2012] [Revised: 03/22/2013] [Accepted: 04/15/2013] [Indexed: 10/26/2022]
Abstract
Serotonin transporters (SERTs) play an essential role in the termination and regulation of serotonin signaling in the brain. SERT is also the target of antidepressants and psychostimulants. Molecules with novel activities and modes of interaction with regard to SERT function are of great scientific and clinical interest. We explored structural regions outside the putative serotonin translocation pathway to identify potential binding sites for allosteric transporter modulators (ATMs). Mutational studies revealed a pocket of amino acids outside the orthosteric substrate binding sites located in the interface between extracellular loops 1 and 3 that when mutated affect transporter function. Using the structure of the bacterial transporter homolog leucine transporter as a template, we developed a structural model of SERT. We performed molecular dynamics simulations to further characterize the allosteric pocket that was identified by site-directed mutagenesis studies and employed this pocket in a virtual screen for small-molecule modulators of SERT function. In functional transport assays, we found that one of the identified molecules, ATM7, increased the reuptake of serotonin, possibly by facilitating the interaction of serotonin with transport-ready conformations of SERT when concentrations of serotonin were low and rate limiting. In addition, ATM7 potentiates 3,4-methylenedioxy-N-methylamphetamine (MDMA, "Ecstasy")-induced reversed transport by SERT. Taking advantage of a conformationally sensitive residue in transmembrane domain 6, we demonstrate that ATM7 mechanistically stabilizes an outward-facing conformation of SERT. Taken together these observations demonstrate that ATM7 acts through a novel mechanism that involves allosteric modulation of SERT function.
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Affiliation(s)
- Sandhya Kortagere
- Department of Microbiology and Immunology, Institute for Molecular Medicine, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, PA 19129, USA.
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