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Zhang H, Wang H, Gao X, Wang G, Sun L. Identification of Scutebarbatine B metabolites in rats using UHPLC-Q-Orbitrap-MS/MS and exploration of its mechanism of reversal multidrug resistance in breast cancer by network pharmacology and molecular docking studies. J Pharm Biomed Anal 2024; 246:116207. [PMID: 38744199 DOI: 10.1016/j.jpba.2024.116207] [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: 01/05/2024] [Revised: 04/30/2024] [Accepted: 05/05/2024] [Indexed: 05/16/2024]
Abstract
Scutebarbatine B (SBT-B) is a neo-clerodane diterpenic compound isolated from Scutellaria barbata D. Don (S. barbata), which has been reported to exhibit inhibitory P-glycoprotein (P-gp) property in MCF-7/ADR cells. However, its metabolism and molecular mechanism of reversal multidrug resistance (MDR) in breast cancer remains unclear. This study investigated the metabolite profile of SBT-B in rats by UHPLC-Q-Orbitrap-MS/MS, and explored its mechanism of reversal MDR through network pharmacology and molecular docking studies. A total of 16 Phase I metabolites and 2 Phase II metabolites were identified, and 18 metabolites were all newly discovered metabolites as novel compounds. The metabolic pathway of SBT-B mainly includes oxidization, reduction, hydrolysis, acetylation and glycination. Meanwhile, network pharmacology analyses showed that SBT-B mainly regulated p27 phosphorylation during cell cycle progression, p53 signaling pathway, influence of Ras and Rho proteins on G1 to S Transition. Molecular docking studies revealed that SBT-B exhibits the potential to inhibit P-gp expression by selectively binding to GLN721 and ALA981 residue sites at the interface of P-gp. In addition, SBT-B exhibits moderate binding affinity with CDK2 and E2F1. This study illustrated the major metabolic pathways of SBT-B in vivo, clarified detailed information on SBT-B metabolites in rats, and uncovered the potential mechanism of SBT-B reversal MDR in breast cancer, providing new insights for the development of P-gp inhibitors.
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Affiliation(s)
- Hao Zhang
- School of Pharmacy, Shenyang Pharmaceutical University, Shenyang, PR China
| | - Hongjin Wang
- School of Pharmacy, Shenyang Pharmaceutical University, Shenyang, PR China
| | - Xiang Gao
- School of Pharmacy, Shenyang Pharmaceutical University, Shenyang, PR China
| | - Guanghou Wang
- R&D Center, Beijing Sciecure Pharmaceutical Co., Ltd., Beijing, PR China.
| | - Lixin Sun
- School of Pharmacy, Shenyang Pharmaceutical University, Shenyang, PR China.
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2
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Teodori E, Braconi L, Manetti D, Romanelli MN, Dei S. The Tetrahydroisoquinoline Scaffold in ABC Transporter Inhibitors that Act as Multidrug Resistance (MDR) Reversers. Curr Top Med Chem 2022; 22:2535-2569. [PMID: 36284399 DOI: 10.2174/1568026623666221025111528] [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: 05/12/2022] [Revised: 08/08/2022] [Accepted: 09/27/2022] [Indexed: 01/20/2023]
Abstract
BACKGROUND The failure of anticancer chemotherapy is often due to the development of resistance to a variety of anticancer drugs. This phenomenon is called multidrug resistance (MDR) and is related to the overexpression of ABC transporters, such as P-glycoprotein, multidrug resistance- associated protein 1 and breast cancer resistance protein. Over the past few decades, several ABC protein modulators have been discovered and studied as a possible approach to evade MDR and increase the success of anticancer chemotherapy. Nevertheless, the co-administration of pump inhibitors with cytotoxic drugs, which are substrates of the transporters, does not appear to be associated with an improvement in the therapeutic efficacy of antitumor agents. However, more recently discovered MDR reversing agents, such as the two tetrahydroisoquinoline derivatives tariquidar and elacridar, are characterized by high affinity towards the ABC proteins and by reduced negative properties. Consequently, many analogs of these two derivatives have been synthesized, with the aim of optimizing their MDR reversal properties. OBJECTIVE This review aims to describe the MDR modulators carrying the tetraidroisoquinoline scaffold reported in the literature in the period 2009-2021, highlighting the structural characteristics that confer potency and/or selectivity towards the three ABC transport proteins. RESULTS AND CONCLUSION Many compounds have been synthesized in the last twelve years showing interesting properties, both in terms of potency and selectivity. Although clear structure-activity relationships can be drawn only by considering strictly related compounds, some of the compounds reviewed could be promising starting points for the design of new ABC protein inhibitors.
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Affiliation(s)
- Elisabetta Teodori
- Department of Neuroscience, Psychology, Drug Research and Child's Health, Section of Pharmaceutical and Nutraceutical Sciences, University of Florence, via Ugo Schiff 6, 50019, Sesto Fiorentino (FI), Italy
| | - Laura Braconi
- Department of Neuroscience, Psychology, Drug Research and Child's Health, Section of Pharmaceutical and Nutraceutical Sciences, University of Florence, via Ugo Schiff 6, 50019, Sesto Fiorentino (FI), Italy
| | - Dina Manetti
- Department of Neuroscience, Psychology, Drug Research and Child's Health, Section of Pharmaceutical and Nutraceutical Sciences, University of Florence, via Ugo Schiff 6, 50019, Sesto Fiorentino (FI), Italy
| | - Maria Novella Romanelli
- Department of Neuroscience, Psychology, Drug Research and Child's Health, Section of Pharmaceutical and Nutraceutical Sciences, University of Florence, via Ugo Schiff 6, 50019, Sesto Fiorentino (FI), Italy
| | - Silvia Dei
- Department of Neuroscience, Psychology, Drug Research and Child's Health, Section of Pharmaceutical and Nutraceutical Sciences, University of Florence, via Ugo Schiff 6, 50019, Sesto Fiorentino (FI), Italy
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3
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Yang T, Wang S, Zheng H, Wang L, Liu D, Chen X, Li R. Understanding dihydro-β-agarofuran sesquiterpenes from Tripterygium hypoglaucum as the modulators of multi-drug resistance in HepG2/Adr cells. Biochem Biophys Res Commun 2019; 508:742-748. [DOI: 10.1016/j.bbrc.2018.11.188] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Accepted: 11/29/2018] [Indexed: 12/24/2022]
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4
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Zhou G, Latchoumanin O, Hebbard L, Duan W, Liddle C, George J, Qiao L. Aptamers as targeting ligands and therapeutic molecules for overcoming drug resistance in cancers. Adv Drug Deliv Rev 2018. [DOI: '10.1016/j.addr.2018.04.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2023]
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5
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Zhou G, Latchoumanin O, Hebbard L, Duan W, Liddle C, George J, Qiao L. Aptamers as targeting ligands and therapeutic molecules for overcoming drug resistance in cancers. Adv Drug Deliv Rev 2018; 134:107-121. [PMID: 29627370 DOI: 10.1016/j.addr.2018.04.005] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 03/28/2018] [Accepted: 04/03/2018] [Indexed: 12/18/2022]
Abstract
Traditional anticancer therapies are often unable to completely eradicate the tumor bulk due to multi-drug resistance (MDR) of cancers. A number of mechanisms such as micro-environmental stress and overexpression of drug efflux pumps are involved in the MDR process. Hence, therapeutic strategies for overcoming MDR are urgently needed to improve cancer treatment efficacy. Aptamers are short single-stranded oligonucleotides or peptides exhibiting unique three-dimensional structures and possess several unique advantages over conventional antibodies such as low immunogenicity and stronger tissue-penetration capacity. Aptamers targeting cancer-associated receptors have been explored to selectively deliver a therapeutic cargo (anticancer drugs, siRNAs, miRNAs and drug-carriers) to the intratumoral compartment where they can exert better tumor-killing effects. In this review, we summarize current knowledge of the multiple regulatory mechanisms of MDR, with a particular emphasis on aptamer-mediated novel therapeutic agents and strategies that seek to reversing MDR. The challenges associated with aptamer-based agents and approaches are also discussed.
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6
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Spork M, Sohail MI, Schmid D, Ecker GF, Freissmuth M, Chiba P, Stockner T. Folding correction of ABC-transporter ABCB1 by pharmacological chaperones: a mechanistic concept. Pharmacol Res Perspect 2017; 5:e00325. [PMID: 28603639 PMCID: PMC5464349 DOI: 10.1002/prp2.325] [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] [Received: 09/23/2016] [Accepted: 03/21/2017] [Indexed: 12/20/2022] Open
Abstract
Point mutations of ATP‐binding cassette (ABC) proteins are a common cause of human diseases. Available crystal structures indicate a similarity in the architecture of several members of this protein family. Their molecular architecture makes these proteins vulnerable to mutation, when critical structural elements are affected. The latter preferentially involve the two transmembrane domain (TMD)/nucleotide‐binding domain (NBD) interfaces (transmission interfaces), formation of which requires engagement of coupling helices of intracellular loops with NBDs. Both, formation of the active sites and engagement of the coupling helices, are contingent on correct positioning of ICLs 2 and 4 and thus an important prerequisite for proper folding. Here, we show that active site compounds are capable of rescuing P‐glycoprotein (P‐gp) mutants ∆Y490 and ∆Y1133 in a concentration‐dependent manner. These trafficking deficient mutations are located at the transmission interface in pseudosymmetric position to each other. In addition, the ability of propafenone analogs to correct folding correlates with their ability to inhibit transport of model substrates. This finding indicates that folding correction and transport inhibition by propafenone analogs are brought about by binding to the active sites. Furthermore, this study demonstrates an asymmetry in folding correction with cis‐flupentixol, which reflects the asymmetric binding properties of this modulator to P‐gp. Our results suggest a mechanistic model for corrector action in a model ABC transporter based on insights into the molecular architecture of these transporters.
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Affiliation(s)
- Matthias Spork
- Institute of Medical Chemistry Center of Pathobiochemistry and Genetics Medical University of Vienna Waehringerstrasse 10 Vienna A-1090 Austria
| | - Muhammad Imran Sohail
- Institute of Medical Chemistry Center of Pathobiochemistry and Genetics Medical University of Vienna Waehringerstrasse 10 Vienna A-1090 Austria.,Department of Zoology Government College University Lahore Katchery Road Lahore 54000 Pakistan
| | - Diethart Schmid
- Institute of Physiology Center of Physiology und Pharmacology Medical University of Vienna Schwarzspanierstrasse 17 Vienna A -1090 Austria
| | - Gerhard F Ecker
- Department of Medicinal Chemistry University of Vienna Emerging Field Pharmacoinformatics Althanstrasse 14 Vienna A-1090 Austria (GFE)
| | - Michael Freissmuth
- Institute of Pharmacology Center of Physiology und Pharmacology Medical University of Vienna Waehringerstrasse 13a Vienna A-1090 Austria
| | - Peter Chiba
- Institute of Medical Chemistry Center of Pathobiochemistry and Genetics Medical University of Vienna Waehringerstrasse 10 Vienna A-1090 Austria
| | - Thomas Stockner
- Institute of Pharmacology Center of Physiology und Pharmacology Medical University of Vienna Waehringerstrasse 13a Vienna A-1090 Austria
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Ferreira RJ, Bonito CA, Ferreira MJU, dos Santos DJ. About P-glycoprotein: a new drugable domain is emerging from structural data. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2017. [DOI: 10.1002/wcms.1316] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Ricardo J. Ferreira
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy; Universidade de Lisboa; Lisboa Portugal
| | - Cátia A. Bonito
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy; Universidade de Lisboa; Lisboa Portugal
- LAQV@REQUIMTE/Department of Chemistry and Biochemistry, Faculty of Sciences; University of Porto; Porto Portugal
| | - Maria José U. Ferreira
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy; Universidade de Lisboa; Lisboa Portugal
| | - Daniel J.V.A. dos Santos
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy; Universidade de Lisboa; Lisboa Portugal
- LAQV@REQUIMTE/Department of Chemistry and Biochemistry, Faculty of Sciences; University of Porto; Porto Portugal
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8
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Thioxanthenes, chlorprothixene and flupentixol inhibit proton currents in BV2 microglial cells. Eur J Pharmacol 2016; 779:31-7. [PMID: 26945819 DOI: 10.1016/j.ejphar.2016.03.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 03/02/2016] [Accepted: 03/02/2016] [Indexed: 01/28/2023]
Abstract
The thioxanthene antipsychotic drugs chlorprothixene and flupentixol have anti-inflammatory and antioxidant properties. The reactive oxygen species produced by NADPH oxidase during microglia-mediated inflammatory responses cause neuronal damage, thereby contributing to various neurodegenerative diseases. Voltage-gated proton channels sustain the NADPH oxidase activity, and inhibition of the channels' activity reduces the production of reactive oxygen species. Herein, the effects of chlorprothixene and flupentixol on proton currents were investigated in BV2 microglial cells using the whole-cell patch-clamp method. Both drugs inhibited the proton currents in a concentration-dependent manner (IC50=1.7μM and 6.6μM, respectively). Chlorprothixene at 3μM slightly shifted the activation voltage toward depolarization. Both the activation and the deactivation kinetics of the proton currents were slowed by chlorprothixene 1.2- and 3.5-fold, respectively. Thus, the inhibition of proton currents may be partly responsible for the antioxidant effects of thioxanthene antipsychotic drugs.
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9
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Overcoming Multidrug Resistance in Cancer Stem Cells. BIOMED RESEARCH INTERNATIONAL 2015; 2015:635745. [PMID: 26649310 PMCID: PMC4663294 DOI: 10.1155/2015/635745] [Citation(s) in RCA: 112] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/09/2015] [Revised: 10/09/2015] [Accepted: 10/19/2015] [Indexed: 01/03/2023]
Abstract
The principle mechanism of protection of stem cells is through the expression of ATP-binding cassette (ABC) transporters. These transporters serve as the guardians of the stem cell population in the body. Unfortunately these very same ABC efflux pumps afford protection to cancer stem cells in tumors, shielding them from the adverse effects of chemotherapy. A number of strategies to circumvent the function of these transporters in cancer stem cells are currently under investigation. These strategies include the development of competitive and allosteric modulators, nanoparticle mediated delivery of inhibitors, targeted transcriptional regulation of ABC transporters, miRNA mediated inhibition, and targeting of signaling pathways that modulate ABC transporters. The role of ABC transporters in cancer stem cells will be explored in this paper and strategies aimed at overcoming drug resistance caused by these particular transporters will also be discussed.
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10
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Xu Y, Egido E, Li-Blatter X, Müller R, Merino G, Bernèche S, Seelig A. Allocrite Sensing and Binding by the Breast Cancer Resistance Protein (ABCG2) and P-Glycoprotein (ABCB1). Biochemistry 2015; 54:6195-206. [PMID: 26381710 DOI: 10.1021/acs.biochem.5b00649] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The ATP binding cassette (ABC) transporters ABCG2 and ABCB1 perform ATP hydrolysis-dependent efflux of structurally highly diverse compounds, collectively called allocrites. Whereas much is known about allocrite-ABCB1 interactions, the chemical nature and strength of ABCG2-allocrite interactions have not yet been assessed. We quantified and characterized interactions of allocrite with ABCG2 and ABCB1 using a set of 39 diverse compounds. We also investigated potential allocrite binding sites based on available transporter structures and structural models. We demonstrate that ABCG2 binds its allocrites from the lipid membrane, despite their hydrophilicity. Hence, binding of allocrite to both transporters is a two-step process, starting with a lipid-water partitioning step, driven mainly by hydrophobic interactions, followed by a transporter binding step in the lipid membrane. We show that binding of allocrite to both transporters increases with the number of hydrogen bond acceptors in allocrites. Scrutinizing the transporter translocation pathways revealed ample hydrogen bond donors for allocrite binding. Importantly, the hydrogen bond donor strength is, on average, higher in ABCG2 than in ABCB1, which explains the higher measured affinity of allocrite for ABCG2. π-π stacking and π-cation interactions play additional roles in binding of allocrite to ABCG2 and ABCB1. With this analysis, we demonstrate that these membrane-mediated weak electrostatic interactions between transporters and allocrites allow for transporter promiscuity toward allocrites. The different sensitivities of the transporters to allocrites' charge and amphiphilicity provide transporter specificity. In addition, we show that the different hydrogen bond donor strengths in the two transporters allow for affinity tuning.
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Affiliation(s)
- Yanyan Xu
- University of Basel, Biozentrum , Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland.,SIB Swiss Institute of Bioinformatics , Klingelbergstrasse 61, CH-4056 Basel, Switzerland
| | - Estefanía Egido
- University of Basel, Biozentrum , Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland.,INDEGSAL, Campus Vegazana s/n, University of Leon , 24071 Leon, Spain.,Department of Biomedical Sciences-Physiology, Veterinary Faculty, Campus Vegazana s/n, University of Leon , 24071 Leon, Spain
| | - Xiaochun Li-Blatter
- University of Basel, Biozentrum , Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland
| | - Rita Müller
- University of Basel, Biozentrum , Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland
| | - Gracia Merino
- INDEGSAL, Campus Vegazana s/n, University of Leon , 24071 Leon, Spain.,Department of Biomedical Sciences-Physiology, Veterinary Faculty, Campus Vegazana s/n, University of Leon , 24071 Leon, Spain
| | - Simon Bernèche
- University of Basel, Biozentrum , Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland.,SIB Swiss Institute of Bioinformatics , Klingelbergstrasse 61, CH-4056 Basel, Switzerland
| | - Anna Seelig
- University of Basel, Biozentrum , Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland
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11
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Subramanian N, Condic-Jurkic K, Mark AE, O'Mara ML. Identification of Possible Binding Sites for Morphine and Nicardipine on the Multidrug Transporter P-Glycoprotein Using Umbrella Sampling Techniques. J Chem Inf Model 2015; 55:1202-17. [PMID: 25938863 DOI: 10.1021/ci5007382] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The multidrug transporter P-glycoprotein (P-gp) is central to the development of multidrug resistance in cancer. While residues essential for transport and binding have been identified, the location, composition, and specificity of potential drug binding sites are uncertain. Here molecular dynamics simulations are used to calculate the free energy profile for the binding of morphine and nicardipine to P-gp. We show that morphine and nicardipine primarily interact with key residues implicated in binding and transport from mutational studies, binding at different but overlapping sites within the transmembrane pore. Their permeation pathways were distinct but involved overlapping sets of residues. The results indicate that the binding location and permeation pathways of morphine and nicardipine are not well separated and cannot be considered as unique. This has important implications for our understanding of substrate uptake and transport by P-gp. Our results are independent of the choice of starting structure and consistent with a range of experimental studies.
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Affiliation(s)
- Nandhitha Subramanian
- †School of Chemistry and Molecular Biosciences, §The Institute for Molecular Biosciences, and ‡School of Mathematics and Physics, University of Queensland, Brisbane, QLD 4072, Australia
| | - Karmen Condic-Jurkic
- †School of Chemistry and Molecular Biosciences, §The Institute for Molecular Biosciences, and ‡School of Mathematics and Physics, University of Queensland, Brisbane, QLD 4072, Australia
| | - Alan E Mark
- †School of Chemistry and Molecular Biosciences, §The Institute for Molecular Biosciences, and ‡School of Mathematics and Physics, University of Queensland, Brisbane, QLD 4072, Australia
| | - Megan L O'Mara
- †School of Chemistry and Molecular Biosciences, §The Institute for Molecular Biosciences, and ‡School of Mathematics and Physics, University of Queensland, Brisbane, QLD 4072, Australia
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12
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Ferreira RJ, Ferreira MJU, dos Santos DJVA. Molecular Docking Characterizes Substrate-Binding Sites and Efflux Modulation Mechanisms within P-Glycoprotein. J Chem Inf Model 2013; 53:1747-60. [DOI: 10.1021/ci400195v] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Ricardo J. Ferreira
- Research Institute for Medicines
and Pharmaceutical Sciences (iMed.UL), Faculty of Pharmacy, University of Lisbon, Av. Prof. Gama Pinto, 1649-003
Lisbon, Portugal
| | - Maria-José U. Ferreira
- Research Institute for Medicines
and Pharmaceutical Sciences (iMed.UL), Faculty of Pharmacy, University of Lisbon, Av. Prof. Gama Pinto, 1649-003
Lisbon, Portugal
| | - Daniel J. V. A. dos Santos
- Research Institute for Medicines
and Pharmaceutical Sciences (iMed.UL), Faculty of Pharmacy, University of Lisbon, Av. Prof. Gama Pinto, 1649-003
Lisbon, Portugal
- REQUIMTE, Department of Chemistry & Biochemistry, Faculty of Sciences, University of Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal
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13
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Screening compounds with a novel high-throughput ABCB1-mediated efflux assay identifies drugs with known therapeutic targets at risk for multidrug resistance interference. PLoS One 2013; 8:e60334. [PMID: 23593196 PMCID: PMC3622673 DOI: 10.1371/journal.pone.0060334] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Accepted: 02/25/2013] [Indexed: 11/19/2022] Open
Abstract
ABCB1, also known as P-glycoprotein (P-gp) or multidrug resistance protein 1 (MDR1), is a membrane-associated multidrug transporter of the ATP-binding cassette (ABC) transporter family. It is one of the most widely studied transporters that enable cancer cells to develop drug resistance. Reliable high-throughput assays that can identify compounds that interact with ABCB1 are crucial for developing new therapeutic drugs. A high-throughput assay for measuring ABCB1-mediated calcein AM efflux was developed using a fluorescent and phase-contrast live cell imaging system. This assay demonstrated the time- and dose-dependent accumulation of fluorescent calcein in ABCB1-overexpressing KB-V1 cells. Validation of the assay was performed with known ABCB1 inhibitors, XR9576, verapamil, and cyclosporin A, all of which displayed dose-dependent inhibition of ABCB1-mediated calcein AM efflux in this assay. Phase-contrast and fluorescent images taken by the imaging system provided additional opportunities for evaluating compounds that are cytotoxic or produce false positive signals. Compounds with known therapeutic targets and a kinase inhibitor library were screened. The assay identified multiple agents as inhibitors of ABCB1-mediated efflux and is highly reproducible. Among compounds identified as ABCB1 inhibitors, BEZ235, BI 2536, IKK 16, and ispinesib were further evaluated. The four compounds inhibited calcein AM efflux in a dose-dependent manner and were also active in the flow cytometry-based calcein AM efflux assay. BEZ235, BI 2536, and IKK 16 also successfully inhibited the labeling of ABCB1 with radiolabeled photoaffinity substrate [125I]iodoarylazidoprazosin. Inhibition of ABCB1 with XR9576 and cyclosporin A enhanced the cytotoxicity of BI 2536 to ABCB1-overexpressing cancer cells, HCT-15-Pgp, and decreased the IC50 value of BI 2536 by several orders of magnitude. This efficient, reliable, and simple high-throughput assay has identified ABCB1 substrates/inhibitors that may influence drug potency or drug-drug interactions and predict multidrug resistance in clinical treatment.
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14
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Loo TW, Bartlett MC, Detty MR, Clarke DM. The ATPase activity of the P-glycoprotein drug pump is highly activated when the N-terminal and central regions of the nucleotide-binding domains are linked closely together. J Biol Chem 2012; 287:26806-16. [PMID: 22700974 DOI: 10.1074/jbc.m112.376202] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The P-glycoprotein (P-gp, ABCB1) drug pump protects us from toxic compounds and confers multidrug resistance. Each of the homologous halves of P-gp is composed of a transmembrane domain (TMD) with 6 TM segments followed by a nucleotide-binding domain (NBD). The predicted drug- and ATP-binding sites reside at the interface between the TMDs and NBDs, respectively. Crystal structures and EM projection images suggest that the two halves of P-gp are separated by a central cavity that closes upon binding of nucleotide. Binding of drug substrates may induce further structural rearrangements because they stimulate ATPase activity. Here, we used disulfide cross-linking with short (8 Å) or long (22 Å) cross-linkers to identify domain-domain interactions that activate ATPase activity. It was found that cross-linking of cysteines that lie close to the LSGGQ (P517C) and Walker A (I1050C) sites of NBD1 and NBD2, respectively, as well as the cytoplasmic extensions of TM segments 3 (D177C or L175C) and 9 (N820C) with a short cross-linker activated ATPase activity over 10-fold. A pyrylium compound that inhibits ATPase activity blocked cross-linking at these sites. Cross-linking between the NBDs was not inhibited by tariquidar, a drug transport inhibitor that stimulates P-gp ATPase activity but is not transported. Cross-linking between extracellular cysteines (T333C/L975C) predicted to lock P-gp into a conformation that prevents close NBD association inhibited ATPase activity. The results suggest that trapping P-gp in a conformation in which the NBDs are closely associated likely mimics the structural rearrangements caused by binding of drug substrates that stimulate ATPase activity.
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Affiliation(s)
- Tip W Loo
- Department of Medicine and Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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