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Rigalli JP, Theile D, Nilles J, Weiss J. Regulation of PXR Function by Coactivator and Corepressor Proteins: Ligand Binding Is Just the Beginning. Cells 2021; 10:cells10113137. [PMID: 34831358 PMCID: PMC8625645 DOI: 10.3390/cells10113137] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 11/09/2021] [Accepted: 11/10/2021] [Indexed: 12/13/2022] Open
Abstract
The pregnane X receptor (PXR, NR1I2) is a nuclear receptor which exerts its regulatory function by heterodimerization with the retinoid-X-receptor α (RXRα, NR2B1) and binding to the promoter and enhancer regions of diverse target genes. PXR is involved in the regulation of drug metabolism and excretion, metabolic and immunological functions and cancer pathogenesis. PXR activity is strongly regulated by the association with coactivator and corepressor proteins. Coactivator proteins exhibit histone acetyltransferase or histone methyltransferase activity or associate with proteins having one of these activities, thus promoting chromatin decondensation and activation of the gene expression. On the contrary, corepressor proteins promote histone deacetylation and therefore favor chromatin condensation and repression of the gene expression. Several studies pointed to clear cell- and ligand-specific differences in the activation of PXR. In this article, we will review the critical role of coactivator and corepressor proteins as molecular determinants of the specificity of PXR-mediated effects. As already known for other nuclear receptors, understanding the complex mechanism of PXR activation in each cell type and under particular physiological and pathophysiological conditions may lead to the development of selective modulators with therapeutic potential.
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Guillien M, le Maire A, Mouhand A, Bernadó P, Bourguet W, Banères JL, Sibille N. IDPs and their complexes in GPCR and nuclear receptor signaling. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2020; 174:105-155. [DOI: 10.1016/bs.pmbts.2020.05.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Márquez R, Ramírez‐Castañeda V, Amézquita A. Does batrachotoxin autoresistance coevolve with toxicity in
Phyllobates
poison‐dart frogs? Evolution 2019; 73:390-400. [DOI: 10.1111/evo.13672] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 11/29/2018] [Indexed: 12/01/2022]
Affiliation(s)
- Roberto Márquez
- Department of Ecology and Evolution University of Chicago 1101 East 57th St. Chicago Illinois 60637
- Department of Biological Sciences Universidad de los Andes A.A. 4976 Bogotá Colombia
| | | | - Adolfo Amézquita
- Department of Biological Sciences Universidad de los Andes A.A. 4976 Bogotá Colombia
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Harrus D, Déméné H, Vasquez E, Boulahtouf A, Germain P, Figueira AC, Privalsky ML, Bourguet W, le Maire A. Pathological Interactions Between Mutant Thyroid Hormone Receptors and Corepressors and Their Modulation by a Thyroid Hormone Analogue with Therapeutic Potential. Thyroid 2018; 28:1708-1722. [PMID: 30235988 DOI: 10.1089/thy.2017.0551] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
BACKGROUND Thyroid hormone receptors (TRs) are tightly regulated by the corepressors nuclear receptor corepressor (NCoR) and silencing mediator of retinoic acid and thyroid hormone receptors. Three conserved corepressor/NR signature box motifs (CoRNR1-3) forming the nuclear receptor interaction domain have been identified in these corepressors. Whereas TRs regulate multiple normal physiological and developmental pathways, mutations in TRs can result in endocrine diseases and be associated with cancers due to impairment of corepressor release. Three mutants that are located in helix H11 of TRs are of special interest: TRα-M388I, a mutant associated with the development of renal clear cell carcinomas (RCCCs), and TRβ-Δ430 and TRβ-Δ432, two deletion mutants causing resistance to thyroid hormone syndrome. METHODS Several cell-based and biophysical methods were used to measure the affinity between wild-type and mutant TRα and TRβ and all the CoRNR motifs from corepressors to quantify the effects of different thyroid hormone analogues on these interactions. This study was coupled with the measurement of interactions between wild-type and mutant TRs in the context of a heterodimer with RXR to a NCoR fragment in the presence of the same ligands. Structural insights into the binding mode of corepressors to TRs were assessed in parallel by nuclear magnetic resonance spectroscopy. RESULTS The study shows that TRs interact more avidly with the silencing mediator of retinoic acid and thyroid hormone receptors than with NCoR peptides, and that TRα binds most avidly to S-CoRNR3, whereas TRβ binds preferentially to S-CoRNR2. In the studied TR mutants, a transfer of the CoRNR-specificity toward CoRNR1 was observed, coupled with a significant increase in the binding strength. In contrast to 3,5,3'-triiodothyronine (T3), the agonist TRIAC and the antagonist NH-3 were very efficient at dissociating the abnormally strong interactions between mutant TRβs and corepressors. A strong impairment of T3-binding for TRβ mutants was shown compared to TRIAC and NH-3 and could explain the different efficiencies of the different ligands in releasing corepressors from the studied TRβ mutants. Consequently, TRIAC was found to be more effective than T3 in facilitating coactivator recruitment and decreasing the dominant activity of TRβ-Δ430. CONCLUSION This study helps to clarify the specific interaction surfaces involved in the pathologic phenotype of TR mutants and demonstrates that TRIAC is a potential therapeutic agent for patients suffering from resistance to thyroid hormone syndromes.
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Affiliation(s)
- Déborah Harrus
- 1 CBS, CNRS, INSERM; INSERM, ICM; University of Montpellier, Montpellier, France
| | - Hélène Déméné
- 1 CBS, CNRS, INSERM; INSERM, ICM; University of Montpellier, Montpellier, France
| | - Edwin Vasquez
- 2 Brazilian Biosciences National Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil
| | | | - Pierre Germain
- 1 CBS, CNRS, INSERM; INSERM, ICM; University of Montpellier, Montpellier, France
| | - Ana Carolina Figueira
- 2 Brazilian Biosciences National Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil
| | - Martin L Privalsky
- 4 Department of Microbiology and Molecular Genetics, College of Biological Sciences, University of California at Davis, Davis, California
| | - William Bourguet
- 1 CBS, CNRS, INSERM; INSERM, ICM; University of Montpellier, Montpellier, France
| | - Albane le Maire
- 1 CBS, CNRS, INSERM; INSERM, ICM; University of Montpellier, Montpellier, France
- 2 Brazilian Biosciences National Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, Brazil
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Using TR-FRET to Investigate Protein-Protein Interactions: A Case Study of PXR-Coregulator Interaction. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2017; 110:31-63. [PMID: 29412999 DOI: 10.1016/bs.apcsb.2017.06.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Time-resolved fluorescence resonance energy transfer (TR-FRET) protein-protein interaction assays, especially in the format of receptor coregulator (coactivator and corepressor) recruitment/repression assays, have been widely used in nuclear receptor research to characterize the modes of action, efficacies, and binding affinities of ligands (including their properties as agonists, antagonists, and inverse agonists). However, there has been only limited progress in using this assay format for pregnane X receptor (PXR). In this chapter, we discuss TR-FRET protein-protein interaction assays and focus on a novel PXR TR-FRET coactivator interaction assay that we have developed based on a PXR coactivator cocrystal study. This new PXR TR-FRET coactivator interaction assay can characterize the binding affinities of PXR ligands and also differentiate antagonists from agonists. This assay is very robust, with the signal remaining stable over a long incubation time (up to 300min has been tested). It can tolerate high concentrations of DMSO (up to 5%) and has a high signal-to-noise ratio (six under typical assay conditions). This newly developed PXR TR-FRET coactivator interaction assay has potential application in high-throughput screening to identify and characterize novel PXR agonists and antagonists.
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Yin C, Yang X, Wei M, Liu H. Predictive models for identifying the binding activity of structurally diverse chemicals to human pregnane X receptor. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2017; 24:20063-20071. [PMID: 28699014 DOI: 10.1007/s11356-017-9690-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2017] [Accepted: 06/30/2017] [Indexed: 06/07/2023]
Abstract
Toxic chemicals entered into human body would undergo a series of metabolism, transport and excretion, and the key roles played in there processes were metabolizing enzymes, which was regulated by the pregnane X receptor (PXR). However, some chemicals in environment could activate or antagonize human pregnane X receptor, thereby leading to a disturbance of normal physiological systems. In this study, based on a larger number of 2724 structurally diverse chemicals, we developed qualitative classification models by the k-nearest neighbor method. Moreover, the logarithm of 20 and 50% effective concentrations (log EC 20 and log EC 50) was used to establish quantitative structure-activity relationship (QSAR) models. With the classification model, two descriptors were enough to establish acceptable models, with the sensitivity, specificity, and accuracy being larger than 0.7, highlighting a high classification performance of the models. With two QSAR models, the statistics parameters with the correlation coefficient (R 2) of 0.702-0.749 and the cross-validation and external validation coefficient (Q 2) of 0.643-0.712, this indicated that the models complied with the criteria proposed in previous studies, i.e., R 2 > 0.6, Q 2 > 0.5. The small root mean square error (RMSE) of 0.254-0.414 and the good consistency between observed and predicted values proved satisfactory goodness of fit, robustness, and predictive ability of the developed QSAR models. Additionally, the applicability domains were characterized by the Euclidean distance-based approach and Williams plot, and results indicated that the current models had a wide applicability domain, which especially included a few classes of environmental contaminant, those that were not included in the previous models.
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Affiliation(s)
- Cen Yin
- Jiangsu Key Laboratory of Chemical Pollution Control and Resources Reuse, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu Province, 210094, China
| | - Xianhai Yang
- Ministry of Environmental Protection, Nanjing Institute of Environmental Sciences, Jiang-Wang-Miao Street, Nanjing, 210042, China.
| | - Mengbi Wei
- Jiangsu Key Laboratory of Chemical Pollution Control and Resources Reuse, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu Province, 210094, China
| | - Huihui Liu
- Jiangsu Key Laboratory of Chemical Pollution Control and Resources Reuse, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu Province, 210094, China.
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Oladimeji P, Cui H, Zhang C, Chen T. Regulation of PXR and CAR by protein-protein interaction and signaling crosstalk. Expert Opin Drug Metab Toxicol 2016; 12:997-1010. [PMID: 27295009 DOI: 10.1080/17425255.2016.1201069] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
INTRODUCTION Protein-protein interaction and signaling crosstalk contribute to the regulation of pregnane X receptor (PXR) and constitutive androstane receptor (CAR) and broaden their cellular function. AREA COVERED This review covers key historic discoveries and recent advances in our understanding of the broad function of PXR and CAR and their regulation by protein-protein interaction and signaling crosstalk. EXPERT OPINION PXR and CAR were first discovered as xenobiotic receptors; however, it is clear that PXR and CAR perform a much broader range of cellular functions through protein-protein interaction and signaling crosstalk, which typically mutually affect the function of all the partners involved. Future research on PXR and CAR should, therefore, look beyond their xenobiotic function.
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Affiliation(s)
- Peter Oladimeji
- a Department of Chemical Biology and Therapeutics , St. Jude Children's Research Hospital , Memphis , TN , USA
| | - Hongmei Cui
- a Department of Chemical Biology and Therapeutics , St. Jude Children's Research Hospital , Memphis , TN , USA
| | - Chen Zhang
- a Department of Chemical Biology and Therapeutics , St. Jude Children's Research Hospital , Memphis , TN , USA
| | - Taosheng Chen
- a Department of Chemical Biology and Therapeutics , St. Jude Children's Research Hospital , Memphis , TN , USA
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Lin YL, Tsay HJ, Lai TH, Tzeng TT, Shiao YJ. Lithospermic acid attenuates 1-methyl-4-phenylpyridine-induced neurotoxicity by blocking neuronal apoptotic and neuroinflammatory pathways. J Biomed Sci 2015; 22:37. [PMID: 26018660 PMCID: PMC4445499 DOI: 10.1186/s12929-015-0146-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 05/12/2015] [Indexed: 12/20/2022] Open
Abstract
Background Parkinson’s disease is the second most common neurodegenerative disorders after Alzheimer’s disease. The main cause of the disease is the massive degeneration of dopaminergic neurons in the substantia nigra. Neuronal apoptosis and neuroinflammation are thought to be the key contributors to the neuronal degeneration. Results Both CATH.a cells and ICR mice were treated with 1-methyl-4-phenylpyridin (MPP+) to induce neurotoxicity in vitro and in vivo. Western blotting and immunohistochemistry were also used to analyse neurotoxicity, neuroinflammation and aberrant neurogenesis in vivo. The experiment in CATH.a cells showed that the treatment of MPP+ impaired intake of cell membrane and activated caspase system, suggesting that the neurotoxic mechanisms of MPP+ might include both necrosis and apoptosis. Pretreatment of lithospermic acid might prevent these toxicities. Lithospermic acid possesses specific inhibitory effect on caspase 3. In mitochondria, MPP+ caused mitochondrial depolarization and induced endoplasmic reticulum stress via increasing expression of chaperone protein, GRP-78. All the effects mentioned above were reduced by lithospermic acid. In animal model, the immunohistochemistry of mice brain sections revealed that MPP+ decreased the amount of dopaminergic neurons, enhanced microglia activation, promoted astrogliosis in both substantia nigra and hippocampus, and MPP+ provoked the aberrant neurogenesis in hippocampus. Lithospermic acid significantly attenuates all of these effects induced by MPP+. Conclusions Lithospermic acid is a potential candidate drug for the novel therapeutic intervention on Parkinson’s disease.
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Affiliation(s)
- Yun-Lian Lin
- National Research Institute of Chinese Medicine, 11221, Taipei, Taiwan, Republic of China.
| | - Huey-Jen Tsay
- Institute of Neuroscience, Brain Research Center, National Yang-Ming University, 11221, Taipei, Taiwan, Republic of China.
| | - Tzu-Hsuan Lai
- Institute of Biopharmaceutical Science, National Yang-Ming University, 11221, Taipei, Taiwan, Republic of China.
| | - Tsai-Teng Tzeng
- Institute of Biopharmaceutical Science, National Yang-Ming University, 11221, Taipei, Taiwan, Republic of China.
| | - Young-Ji Shiao
- National Research Institute of Chinese Medicine, 11221, Taipei, Taiwan, Republic of China. .,Institute of Biopharmaceutical Science, National Yang-Ming University, 11221, Taipei, Taiwan, Republic of China. .,Ph.D Program for the Clinical Drug Discovery from Botanical Herbs, College of Pharmacy, Taipei Medical University, 110, Taipei, Taiwan, Republic of China.
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Frank JA, Moroni M, Moshourab R, Sumser M, Lewin GR, Trauner D. Photoswitchable fatty acids enable optical control of TRPV1. Nat Commun 2015; 6:7118. [PMID: 25997690 PMCID: PMC4455067 DOI: 10.1038/ncomms8118] [Citation(s) in RCA: 114] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 04/08/2015] [Indexed: 12/23/2022] Open
Abstract
Fatty acids (FAs) are not only essential components of cellular energy storage and structure, but play crucial roles in signalling. Here we present a toolkit of photoswitchable FA analogues (FAAzos) that incorporate an azobenzene photoswitch along the FA chain. By modifying the FAAzos to resemble capsaicin, we prepare a series of photolipids targeting the Vanilloid Receptor 1 (TRPV1), a non-selective cation channel known for its role in nociception. Several azo-capsaicin derivatives (AzCAs) emerge as photoswitchable agonists of TRPV1 that are relatively inactive in the dark and become active on irradiation with ultraviolet-A light. This effect can be rapidly reversed by irradiation with blue light and permits the robust optical control of dorsal root ganglion neurons and C-fibre nociceptors with precision timing and kinetics not available with any other technique. More generally, we expect that photolipids will find many applications in controlling biological pathways that rely on protein–lipid interactions. Fatty acids are ancient lipids with numerous functions, from metabolic processes as a source of energy to structural and signalling roles within cell membranes. Here, the authors present azobenzene-modified fatty acids and their application as photoswitchable agonists of the Vanilloid Receptor 1.
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Affiliation(s)
- James Allen Frank
- Department of Chemistry and Center for Integrated Protein Science, Ludwig Maximilians University Munich, Butenandtstrasse 5-13, Munich 81377, Germany
| | - Mirko Moroni
- Molecular Physiology of Somatic Sensation, Max Delbrück Center for Molecular Medicine, Berlin 13125, Germany
| | - Rabih Moshourab
- 1] Molecular Physiology of Somatic Sensation, Max Delbrück Center for Molecular Medicine, Berlin 13125, Germany [2] Department of Anesthesiology, Campus Charité Mitte und Virchow Klinikum, Charité Universitätsmedizin Berlin, Augustburgerplatz 1, Berlin 13353, Germany
| | - Martin Sumser
- Department of Chemistry and Center for Integrated Protein Science, Ludwig Maximilians University Munich, Butenandtstrasse 5-13, Munich 81377, Germany
| | - Gary R Lewin
- Molecular Physiology of Somatic Sensation, Max Delbrück Center for Molecular Medicine, Berlin 13125, Germany
| | - Dirk Trauner
- Department of Chemistry and Center for Integrated Protein Science, Ludwig Maximilians University Munich, Butenandtstrasse 5-13, Munich 81377, Germany
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Nardi A, Damann N, Hertrampf T, Kless A. Advances in targeting voltage-gated sodium channels with small molecules. ChemMedChem 2012; 7:1712-40. [PMID: 22945552 DOI: 10.1002/cmdc.201200298] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Revised: 07/30/2012] [Indexed: 12/19/2022]
Abstract
Blockade of voltage-gated sodium channels (VGSCs) has been used successfully in the clinic to enable control of pathological firing patterns that occur in conditions as diverse as chronic pain, epilepsy, and arrhythmias. Herein we review the state of the art in marketed sodium channel inhibitors, including a brief compendium of their binding sites and of the cellular and molecular biology of sodium channels. Despite the preferential action of this drug class toward over-excited cells, which significantly limits potential undesired side effects on other cells, the need to develop a second generation of sodium channel inhibitors to overcome their critical clinical shortcomings is apparent. Current approaches in drug discovery to deliver novel and truly innovative sodium channel inhibitors is next presented by surveying the most recent medicinal chemistry breakthroughs in the field of small molecules and developments in automated patch-clamp platforms. Various strategies aimed at identifying small molecules that target either particular isoforms of sodium channels involved in specific diseases or anomalous sodium channel currents, irrespective of the isoform by which they have been generated, are critically discussed and revised.
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Affiliation(s)
- Antonio Nardi
- Global Drug Discovery, Department of Medicinal Chemistry, Grünenthal, Zieglerstrasse 6, 52078 Aachen, Germany.
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Development of in silico filters to predict activation of the pregnane X receptor (PXR) by structurally diverse drug-like molecules. Bioorg Med Chem 2012; 20:5352-65. [PMID: 22560839 DOI: 10.1016/j.bmc.2012.04.020] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Revised: 03/28/2012] [Accepted: 04/07/2012] [Indexed: 01/22/2023]
Abstract
The pregnane X receptor (PXR), a member of the nuclear hormone superfamily, regulates the expression of several enzymes and transporters involved in metabolically relevant processes. The significant induction of CYP450 enzymes by PXR, in particular CYP3A4, might significantly alter the metabolism of prescribed drugs. In order to early identify molecules in drug discovery with a potential to activate PXR as antitarget, we developed fast and reliable in silico filters by ligand-based QSAR techniques. Two classification models were established on a diverse dataset of 434 drug-like molecules. A second augmented set allowed focusing on interesting regions in chemical space. These classifiers are based on decision trees combined with a genetic algorithm based variable selection to arrive at predictive models. The classifier for the first dataset on 29 descriptors showed good performance on a test set with a correct classification of both 100% for PXR activators and non-activators plus 87% for activators and 83% for non-activators in an external dataset. The second classifier then correctly predicts 97% activators and 91% non-activators in a test set and 94% for activators and 64% non-activators in an external set of 50 molecules, which still qualifies for application as a filter focusing on PXR activators. Finally a quantitative model for PXR activation for a subset of these molecules was derived using a regression-tree approach combined with GA variable selection. This final model shows a predictive r(2) of 0.774 for the test set and 0.452 for an external set of 33 molecules. Thus, the combination of these filters consistently provide guidelines for lowering PXR activation in novel candidate molecules.
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Heasley B. Chemical synthesis of the cardiotonic steroid glycosides and related natural products. Chemistry 2012; 18:3092-120. [PMID: 22354477 DOI: 10.1002/chem.201103733] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The active components from the extracts of Digitalis, cardiotonic steroid glycosides, have been ingested by humans for more than 200 years as a medicinal therapy for heart failure and abnormal heart rhythms. The positive inotropic activity of the cardiotonic steroids that mediates clinically useful physiological effects in patients has been attributed largely to a high affinity inhibitory interaction with the extracellular surface of the membrane-bound sodium pump (Na(+)/K(+)-ATPase). However, previously unrecognized intracellular signaling pathways continue to be uncovered. This Review examines both partial and de novo synthetic approaches to the medicinally important and structurally captivating cardenolide and bufadienolide steroid families, with an emphasis on the stereocontrolled construction of the pharmacophoric aglycone (genin) framework.
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Affiliation(s)
- Brian Heasley
- Scynexis, Inc. P. O. Box 12878, Research Triangle Park, NC 27709-2878, USA.
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Vijaykumar BVD, Mallesham P, Chandrasekhar S. Towards Allopumiliotoxins: A Concise Synthesis of the Indolizidine Core. European J Org Chem 2011. [DOI: 10.1002/ejoc.201101430] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Liu YH, Mo SL, Bi HC, Hu BF, Li CG, Wang YT, Huang L, Huang M, Duan W, Liu JP, Wei MQ, Zhou SF. Regulation of human pregnane X receptor and its target gene cytochrome P450 3A4 by Chinese herbal compounds and a molecular docking study. Xenobiotica 2010; 41:259-80. [PMID: 21117944 DOI: 10.3109/00498254.2010.537395] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The pregnane X receptor (PXR) plays a critical role in the regulation of human cytochrome P450 3A4 (CYP3A4) gene. In this study, we investigated the effect of an array of compounds isolated from Chinese herbal medicines on the activity of PXR using a luciferase reporter gene assay in transiently transfected HepG2 and Huh7 cells and on the expression of PXR and CYP3A4 in LS174T cells. Furthermore, molecular docking was performed to investigate the binding modes of herbal compounds with PXR. Praeruptorin A and C, salvianolic acid B, sodium danshensu, protocatechuic aldehyde, cryptotanshinone, emodin, morin, and tanshinone IIA significantly transactivated the CYP3A4 reporter gene construct in either HepG2 or Huh7 cells. The PXR mRNA expression in LS174T cells was significantly induced by physcion, protocatechuic aldehyde, salvianolic acid B, and sodium danshensu. However, epifriedelanol, morin, praeruptorin D, mulberroside A, tanshinone I, and tanshinone IIA significantly down-regulated the expression of PXR mRNA in LS174T cells. All the herbal compounds tested can be readily docked into the ligand-binding cavity of PXR mainly through hydrogen bond and aromatic interactions with Ser247, Gln285, His407, and Arg401. These findings suggest that herbal medicines can significantly regulate PXR and CYP3A4 and this has important implication in herb-drug interactions.
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Affiliation(s)
- Ya-He Liu
- School of Health Sciences & Health Innovations Research Institute, RMIT University, Bundoora, Victoria, Australia
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Yamaguchi H, Chen CT, Chou CK, Pal A, Bornmann W, Hortobagyi GN, Hung MC. Adenovirus 5 E1A enhances histone deacetylase inhibitors-induced apoptosis through Egr-1-mediated Bim upregulation. Oncogene 2010; 29:5619-29. [PMID: 20676141 DOI: 10.1038/onc.2010.295] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Histone deacetylase inhibitors (HDACi) are potent anti-cancer agents for variety of cancer types. Suberoylanilide hydroxamic acid (SAHA) has been approved as a drug to treat cutaneous T cell lymphoma, and the combination of HDACi and other agents have been actively tested in many clinical trials. Adenovirus 5 early region 1A (E1A) has been shown to exhibit high tumor suppressor activity, and gene therapy using E1A has been tested in clinical trials. Here, we showed that proapoptotic activity of HDACi was robustly enhanced by E1A in multiple cancer cells, but not in normal cells. Moreover, we showed that combination of E1A gene therapy and SAHA showed high therapeutic efficacy with low toxicity in vivo ovarian and breast xenograft models. SAHA downregulated Bcl-XL and upregulated proapoptotic BH3-only protein Bim, whose expression was further enhanced by E1A in cancer cells. These alterations of Bcl-2 family proteins were critical for apoptosis induced by the combination in cancer cells. SAHA enhanced acetylation of histone H3 in Bim promoter region, while E1A upregulated Egr-1, which was directly involved in Bim transactivation. Together, our results provide not only a novel insight into the mechanisms underlying anti-tumor activity of E1A, but also a rationale for the combined HDACi and E1A gene therapy in future clinical trials.
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Affiliation(s)
- H Yamaguchi
- Department of Molecular and Cellular Oncology, University of Texas MD Anderson Cancer Center, Houston, TX, USA
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Mukherjee S, Mani S. Orphan nuclear receptors as targets for drug development. Pharm Res 2010; 27:1439-68. [PMID: 20372994 PMCID: PMC3518931 DOI: 10.1007/s11095-010-0117-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Accepted: 03/04/2010] [Indexed: 12/31/2022]
Abstract
Orphan nuclear receptors regulate diverse biological processes. These important molecules are ligand-activated transcription factors that act as natural sensors for a wide range of steroid hormones and xenobiotic ligands. Because of their importance in regulating various novel signaling pathways, recent research has focused on identifying xenobiotics targeting these receptors for the treatment of multiple human diseases. In this review, we will highlight these receptors in several physiologic and pathophysiologic actions and demonstrate how their functions can be exploited for the successful development of newer drugs.
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Affiliation(s)
- Subhajit Mukherjee
- Departments of Medicine, Genetics and Cancer Center, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Chanin 302-D1, Bronx, New York 10461, USA
| | - Sridhar Mani
- Departments of Medicine, Genetics and Cancer Center, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Chanin 302-D1, Bronx, New York 10461, USA
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Bruhova I, Zhorov BS. A homology model of the pore domain of a voltage-gated calcium channel is consistent with available SCAM data. ACTA ACUST UNITED AC 2010; 135:261-74. [PMID: 20176854 PMCID: PMC2828909 DOI: 10.1085/jgp.200910288] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
In the absence of x-ray structures of calcium channels, their homology models are used to rationalize experimental data and design new experiments. The modeling relies on sequence alignments between calcium and potassium channels. Zhen et al. (2005. J. Gen. Physiol. doi:10.1085/jgp.200509292) used the substituted cysteine accessibility method (SCAM) to identify pore-lining residues in the Cav2.1 channel and concluded that their data are inconsistent with the symmetric architecture of the pore domain and published sequence alignments between calcium and potassium channels. Here, we have built Kv1.2-based models of the Cav2.1 channel with 2-(trimethylammonium)ethyl methanethiosulfonate (MTSET)-modified engineered cysteines and used Monte Carlo energy minimizations to predict their energetically optimal orientations. We found that depending on the position of an engineered cysteine in S6 and S5 helices, the ammonium group in the long flexible MTSET-modified side chain can orient into the inner pore, an interface between domains (repeats), or an interface between S5 and S6 helices. Different local environments of equivalent positions in the four repeats can lead to different SCAM results. The reported current inhibition by MTSET generally decreases with the predicted distances between the ammonium nitrogen and the pore axis. A possible explanation for outliers of this correlation is suggested. Our calculations rationalize the SCAM data, validate one of several published sequence alignments between calcium and potassium channels, and suggest similar spatial dispositions of S5 and S6 helices in voltage-gated potassium and calcium channels.
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Affiliation(s)
- Iva Bruhova
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8N 3Z5, Canada
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18
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Zhang J, Lee SM, Shannon S, Gao B, Chen W, Chen A, Divekar R, McBurney MW, Braley-Mullen H, Zaghouani H, Fang D. The type III histone deacetylase Sirt1 is essential for maintenance of T cell tolerance in mice. J Clin Invest 2010; 119:3048-58. [PMID: 19729833 DOI: 10.1172/jci38902] [Citation(s) in RCA: 229] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2009] [Accepted: 06/24/2009] [Indexed: 12/19/2022] Open
Abstract
Although many self-reactive T cells are eliminated by negative selection in the thymus, some of these cells escape into the periphery, where they must be controlled by additional mechanisms. However, the molecular mechanisms underlying peripheral T cell tolerance and its maintenance remain largely undefined. In this study, we report that sirtuin 1 (Sirt1), a type III histone deacetylase, negatively regulates T cell activation and plays a major role in clonal T cell anergy in mice. In vivo, we found that loss of Sirt1 function resulted in abnormally increased T cell activation and a breakdown of CD4+ T cell tolerance. Conversely, upregulation of Sirt1 expression led to T cell anergy, in which the activity of the transcription factor AP-1 was substantially diminished.Furthermore, Sirt1 interacted with and deacetylated c-Jun, yielding an inactive AP-1 factor. In addition, Sirt1-deficient mice were unable to maintain T cell tolerance and developed severe experimental allergic encephalomyelitis as well as spontaneous autoimmunity. These findings provide insight into the molecular mechanisms of T cell activation and anergy, and we suggest that activators of Sirt1 may be useful as therapeutic agents for the treatment and/or prevention of autoimmune diseases.
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Affiliation(s)
- Jinping Zhang
- Department of Otolaryngology-Head and Neck Surgery,University of Missouri, Columbia, MO 65212, USA
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19
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Abstract
Cooperation among transcription factors is central for their ability to execute specific transcriptional programmes. The AP1 complex exemplifies a network of transcription factors that function in unison under normal circumstances and during the course of tumour development and progression. This Perspective summarizes our current understanding of the changes in members of the AP1 complex and the role of ATF2 as part of this complex in tumorigenesis.
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Affiliation(s)
- Pablo Lopez-Bergami
- Instituto de Biologia y Medicina Experimental, Vuelta de Obligado 2490, Buenos Aires1428, Argentina,
| | - Eric Lau
- Signal Transduction Program, Burnham Institute for Medical Research, La Jolla, CA 92037, USA,
| | - Ze'ev Ronai
- Signal Transduction Program, Burnham Institute for Medical Research, La Jolla, CA 92037, USA
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20
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Ai N, Krasowski MD, Welsh WJ, Ekins S. Understanding nuclear receptors using computational methods. Drug Discov Today 2009; 14:486-94. [PMID: 19429508 DOI: 10.1016/j.drudis.2009.03.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2008] [Revised: 03/03/2009] [Accepted: 03/04/2009] [Indexed: 02/06/2023]
Abstract
Nuclear receptors (NRs) are important targets for therapeutic drugs. NRs regulate transcriptional activities through binding to ligands and interacting with several regulating proteins. Computational methods can provide insights into essential ligand-receptor and protein-protein interactions. These in turn have facilitated the discovery of novel agonists and antagonists with high affinity and specificity as well as have aided in the prediction of toxic side effects of drugs by identifying possible off-target interactions. Here, we review the application of computational methods toward several clinically important NRs (with special emphasis on PXR) and discuss their use for screening and predicting the toxic side effects of xenobiotics.
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Affiliation(s)
- Ni Ai
- Department of Pharmacology, Robert Wood Johnson Medical School, University of Medicine & Dentistry of New Jersey, Piscataway, NJ 08854, USA
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21
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Li CW, Dinh GK, Chen JD. Preferential physical and functional interaction of pregnane X receptor with the SMRTalpha isoform. Mol Pharmacol 2008; 75:363-73. [PMID: 18978041 DOI: 10.1124/mol.108.047845] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The silencing mediator for retinoid and thyroid hormone receptors (SMRT) serves as a platform for transcriptional repression elicited by several steroid/nuclear receptors and transcription factors. SMRT exists in two major splicing isoforms, alpha and tau, with SMRTalpha containing only an extra 46-amino acid sequence inserted immediately downstream from the C-terminal corepressor motif. Little is known about potential functional differences between these two isoforms. Here we show that the pregnane X receptor (PXR) interacts more strongly with SMRTalpha than with SMRTtau both in vitro and in vivo. It is interesting that the PXR-SMRTalpha interaction is also resistant to PXR ligand-induced dissociation, in contrast to the PXR-SMRTtau interaction. SMRTalpha consistently inhibits PXR activity more efficiently than does SMRTtau in transfection assays, although they possess comparable intrinsic repression activity and association with histone deacetylase. We further show that the mechanism for the enhanced PXR-SMRTalpha interaction involves both the 46-amino acid insert and the C-terminal corepressor motif. In particular, the first five amino acids of the SMRTalpha insert are essential and sufficient for the enhanced binding of SMRTalpha to PXR. Furthermore, we demonstrate that Tyr2354 and Asp2355 residues of the SMRTalpha insert are most critical for the enhanced interaction. In addition, expression data show that SMRTalpha is more abundantly expressed in most human tissues and cancer cell lines, and together these data suggest that SMRTalpha may play a more important role than SMRTtau in the negative regulation of PXR.
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Affiliation(s)
- Chia-Wei Li
- Department of Pharmacology,University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854-5635, USA
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22
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Ekins S, Kholodovych V, Ai N, Sinz M, Gal J, Gera L, Welsh WJ, Bachmann K, Mani S. Computational discovery of novel low micromolar human pregnane X receptor antagonists. Mol Pharmacol 2008; 74:662-72. [PMID: 18579710 DOI: 10.1124/mol.108.049437] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Very few antagonists have been identified for the human pregnane X receptor (PXR). These molecules may be of use for modulating the effects of therapeutic drugs, which are potent agonists for this receptor (e.g., some anticancer compounds and macrolide antibiotics), with subsequent effects on transcriptional regulation of xenobiotic metabolism and transporter genes. A recent novel pharmacophore for PXR antagonists was developed using three azoles and consisted of two hydrogen bond acceptor regions and two hydrophobic features. This pharmacophore also suggested an overall small binding site that was identified on the outer surface of the receptor at the AF-2 site and validated by docking studies. Using computational approaches to search libraries of known drugs or commercially available molecules is preferred over random screening. We have now described several new smaller antagonists of PXR discovered with the antagonist pharmacophore with in vitro activity in the low micromolar range [S-p-tolyl 3',5-dimethyl-3,5'-biisoxazole-4'-carbothioate (SPB03255) (IC(50), 6.3 microM) and 4-(3-chlorophenyl)-5-(2,4-dichlorobenzylthio)-4H-1,2,4-triazol-3-ol (SPB00574) (IC(50), 24.8 microM)]. We have also used our computational pharmacophore and docking tools to suggest that most of the known PXR antagonists, such as coumestrol and sulforaphane, could also interact on the outer surface of PXR at the AF-2 domain. The involvement of this domain was also suggested by further site-directed mutagenesis work. We have additionally described an FDA approved prodrug, leflunomide (IC(50), 6.8 microM), that seems to be a PXR antagonist in vitro. These observations are important for predicting whether further molecules may interact with PXR as antagonists in vivo with potential therapeutic applications.
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Affiliation(s)
- Sean Ekins
- Collaborations in Chemistry, Jenkintown, PA 19046, USA.
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23
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Khandelwal A, Krasowski MD, Reschly EJ, Sinz MW, Swaan PW, Ekins S. Machine learning methods and docking for predicting human pregnane X receptor activation. Chem Res Toxicol 2008; 21:1457-67. [PMID: 18547065 DOI: 10.1021/tx800102e] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The pregnane X receptor (PXR) regulates the expression of genes involved in xenobiotic metabolism and transport. In vitro methods to screen for PXR agonists are used widely. In the current study, computational models for human PXR activators and PXR nonactivators were developed using recursive partitioning (RP), random forest (RF), and support vector machine (SVM) algorithms with VolSurf descriptors. Following 10-fold randomization, the models correctly predicted 82.6-98.9% of activators and 62.0-88.6% of nonactivators. The models were validated using separate test sets. The overall ( n = 15) test set prediction accuracy for PXR activators with RP, RF, and SVM PXR models is 80-93.3%, representing an improvement over models previously reported. All models were tested with a second test set ( n = 145), and the prediction accuracy ranged from 63 to 67% overall. These test set molecules were found to cover the same area in a principal component analysis plot as the training set, suggesting that the predictions were within the applicability domain. The FlexX docking method combined with logistic regression performed poorly in classifying this PXR test set as compared with RP, RF, and SVM but may be useful for qualitative interpretion of interactions within the LBD. From this analysis, VolSurf descriptors and machine learning methods had good classification accuracy and made reliable predictions within the model applicability domain. These methods could be used for high throughput virtual screening to assess for PXR activation, prior to in vitro testing to predict potential drug-drug interactions.
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Affiliation(s)
- Akash Khandelwal
- Department of Pharmaceutical Sciences, University of Maryland, 20 Penn Street, Baltimore, Maryland 21201, USA
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24
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Concannon CG, Ward MW, Bonner HP, Kuroki K, Tuffy LP, Bonner CT, Woods I, Engel T, Henshall DC, Prehn JHM. NMDA receptor-mediated excitotoxic neuronal apoptosis in vitro and in vivo occurs in an ER stress and PUMA independent manner. J Neurochem 2008; 105:891-903. [PMID: 18088354 DOI: 10.1111/j.1471-4159.2007.05187.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Disruption of endoplasmic reticulum (ER) Ca2+ homeostasis and ER dysfunction have been suggested to contribute to excitotoxic and ischaemic neuronal injury. Previously, we have characterized the neural transcriptome following ER stress and identified the BH3-only protein, p53 up-regulated mediator of apoptosis (PUMA), as a central mediator of ER stress toxicity. In this study, we investigated the effects of excitotoxic injury on ER Ca2+ levels and induction of ER stress responses in models of glutamate- and NMDA-induced excitotoxic apoptosis. While exposure to the ER stressor tunicamycin induced an ER stress response in cerebellar granule neurons, transcriptional activation of targets of the ER stress response, including PUMA, were absent following glutamate-induced apoptosis. Confocal imaging revealed no long-term changes in the ER Ca2+ level in response to glutamate. Murine cortical neurons and organotypic hippocampal slice cultures from PUMA+/+ and PUMA-/- animals provided no evidence of ER stress and did not differ in their sensitivity to NMDA. Finally, NMDA-induced excitotoxic apoptosis in vivo was not associated with ER stress, nor did deficiency in PUMA alleviate the injury induced. Our data suggest that NMDA receptor-mediated excitotoxic apoptosis occurs in vitro and in vivo in an ER stress and PUMA independent manner.
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Affiliation(s)
- Caoimhín G Concannon
- Department of Physiology and Medical Physics and RCSI Neuroscience Research Centre, Royal College of Surgeons in Ireland, Dublin, Ireland
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25
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Nanba D, Inoue H, Shigemi Y, Shirakata Y, Hashimoto K, Higashiyama S. An intermediary role of proHB-EGF shedding in growth factor-induced c-Myc gene expression. J Cell Physiol 2007; 214:465-73. [PMID: 17674363 DOI: 10.1002/jcp.21233] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Activation of growth factor receptors by ligand binding leads to an increased expression of c-Myc, a transcriptional regulator for cell proliferation. The activation of transcriptional factors via the activated receptors is thought to be the main role of c-Myc gene expression. We demonstrate here that epidermal growth factor receptor (EGFR)- and fibroblast growth factor receptor (FGFR)-mediated c-Myc induction and cell cycle progression in primary cultured mouse embryonic fibroblasts (MEFs) are abrogated by knockout of the heparin-binding EGF-like growth factor (Hb-egf) gene, or by a metalloproteinase inhibitor, although molecules downstream of the receptors are activated. Induction of c-Myc expression by EGF or basic FGF is recovered in Hb-egf-depleted MEFs by overexpression of wild-type proHB-EGF, but no recovery was observed with an uncleavable mutant of proHB-EGF. The uncleavable mutant also inhibited EGF-induced acetylation of histone H3 at the mouse c-Myc first intron region, which could negatively affect transcriptional activation. We conclude that signal transduction initiated by generation of the carboxyl-terminal fragment of proHB-EGF (HB-EGF-CTF) in the shedding event plays an important intermediary role between growth factor receptor activation and c-Myc gene induction.
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MESH Headings
- Adenoviridae/genetics
- Alkaline Phosphatase/metabolism
- Animals
- Cell Culture Techniques
- Cell Cycle
- Cell Line, Tumor
- Cells, Cultured
- Chromatin Immunoprecipitation
- Dose-Response Relationship, Drug
- Embryo, Mammalian/cytology
- Embryo, Mammalian/metabolism
- Epidermal Growth Factor/genetics
- Epidermal Growth Factor/pharmacology
- Epigenesis, Genetic
- ErbB Receptors/physiology
- Fibroblast Growth Factor 2/genetics
- Fibroblast Growth Factor 2/pharmacology
- Fibroblasts
- Fibrosarcoma/pathology
- Gene Expression
- Genes, myc
- Heparin/deficiency
- Heparin/genetics
- Heparin/physiology
- Humans
- Keratinocytes/cytology
- Keratinocytes/metabolism
- Mice
- Mice, Transgenic
- Microscopy, Fluorescence
- Mutation
- Promoter Regions, Genetic
- Receptors, Fibroblast Growth Factor/physiology
- Recombinant Proteins/pharmacology
- Transfection
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Affiliation(s)
- Daisuke Nanba
- Department of Biochemistry and Molecular Genetics, Ehime University Graduate School of Medicine, Shitsukawa, Toon, Ehime, Japan
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26
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Ekins S, Chang C, Mani S, Krasowski MD, Reschly EJ, Iyer M, Kholodovych V, Ai N, Welsh WJ, Sinz M, Swaan PW, Patel R, Bachmann K. Human pregnane X receptor antagonists and agonists define molecular requirements for different binding sites. Mol Pharmacol 2007; 72:592-603. [PMID: 17576789 DOI: 10.1124/mol.107.038398] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The pregnane X receptor (PXR) is an important transcriptional regulator of the expression of xenobiotic metabolism and transporter genes. The receptor is promiscuous, binding many structural classes of molecules that act as agonists at the ligand-binding domain, triggering up-regulation of genes, increasing the metabolism and excretion of therapeutic agents, and causing drug-drug interactions. It has been suggested that human PXR antagonists represent a means to counteract such interactions. Several azoles have been hypothesized to bind the activation function-2 (AF-2) surface on the exterior of PXR when agonists are concurrently bound in the ligand-binding domain. In the present study, we have derived novel computational models for PXR agonists using different series of imidazoles, steroids, and a set of diverse molecules with experimental PXR agonist binding data. We have additionally defined a novel pharmacophore for the steroidal agonist site. All agonist pharmacophores showed that hydrophobic features are predominant. In contrast, a qualitative comparison with the corresponding PXR antagonist pharmacophore models using azoles and biphenyls showed that they are smaller and hydrophobic with increased emphasis on hydrogen bonding features. Azole antagonists were docked into a proposed hydrophobic binding pocket on the outer surface at the AF-2 site and fitted comfortably, making interactions with key amino acids involved in charge clamping. Combining computational and experimental data for different classes of molecules provided strong evidence for agonists and antagonists binding distinct regions on PXR. These observations bear significant implications for future discovery of molecules that are more selective and potent antagonists.
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MESH Headings
- Binding Sites
- Carcinoma, Hepatocellular/pathology
- Cell Line, Tumor
- Computer Simulation
- Genes, Reporter
- Humans
- Hydrogen Bonding
- Hydrophobic and Hydrophilic Interactions
- Inhibitory Concentration 50
- Liver Neoplasms/pathology
- Luciferases/metabolism
- Models, Chemical
- Models, Molecular
- Molecular Structure
- Plasmids
- Pregnane X Receptor
- Protein Binding
- Protein Structure, Tertiary
- Receptors, Steroid/agonists
- Receptors, Steroid/antagonists & inhibitors
- Receptors, Steroid/chemistry
- Receptors, Steroid/metabolism
- Transcriptional Activation
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Affiliation(s)
- Sean Ekins
- ACT LLC, 601 Runnymede Avenue, Jenkintown, PA 19046, USA.
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27
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Lim YP, Huang JD. Pregnane X receptor polymorphism affects CYP3A4 induction via a ligand-dependent interaction with steroid receptor coactivator-1. Pharmacogenet Genomics 2007; 17:369-82. [PMID: 17429319 DOI: 10.1097/fpc.0b013e32803e40d7] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND The human pregnane X receptor is a ligand-dependent transcription factor that plays critical roles in regulating detoxification genes such as CYP3A4 by recruiting transcriptional coactivators such as steroid receptor coactivator-1 in a ligand-dependent manner. In a previous study (Pharmacogenetics and Genomics 2005, 15: 337-341), we reported a novel pregnane X receptor single nucleotide polymorphism, Q158K, which impaired transactivation of CYP3A4. METHODS AND RESULTS By using DNA affinity precipitation assay and electrophoretic mobility shift assay, we have now shown that Q158K does not alter the binding affinity of pregnane X receptor for the CYP3A4 promoter. Instead, as shown using a mammalian two-hybrid assay, it decreased the interaction of pregnane X receptor with steroid receptor coactivator-1 in the presence of rifampin, clotrimazole, paclitaxel, or nifedipine but not in their absence. Rifampin treatment markedly increased pregnane X receptor protein in the wild-type pregnane X receptor-transfected cells as shown by coimmunoprecipitation but not in Q158K pregnane X receptor-transfected cells. The impaired transactivation of the CYP3A4 promoter was reversed by transfecting steroid receptor coactivator-1 expression plasmids. An additional nine pregnane X receptor variants were isolated and selected by random mutagenesis. Mutations Q158, W223, F257, I346, and L424 also reduced CYP3A4 transactivation and interaction in mammalian two-hybrid assays only in the presence of ligands. Although Q158K did not greatly affect the interaction of pregnane X receptor to silencing mediator of retinoid and thyroid hormone receptor, pregnane X receptor-silencing mediator of retinoid and thyroid hormone receptor interaction was impaired in the F257L and I346T variants with or without the presence of pregnane X receptor ligands. CONCLUSION Our data indicate that the impaired induction by the Q158K variant is probably due to defective steroid receptor coactivator-1 interaction in the presence of a pregnane X receptor ligand. As the whole ligand binding domain of pregnane X receptor is required for the interaction with steroid receptor coactivator-1, we propose that, not only the Q158K variant found in Chinese, but also in native pregnane X receptor variants in other ethnic groups (D163G, A370T, R381W, and I403V) affect CYP3A4 induction by altering steroid receptor coactivator-1 recruitment.
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Affiliation(s)
- Yun-Ping Lim
- Institute of Basic Medical Sciences, Department of Pharmacology, Medical College, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan
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