1
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Sohail I, Hassan MU, Schmid D, Chiba P. The noncanonical nucleotide binding site 1 of the bile salt export pump is optimized for proper function of the transporter. Cell Biol Int 2024; 48:638-646. [PMID: 38328902 DOI: 10.1002/cbin.12136] [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: 08/15/2023] [Revised: 12/19/2023] [Accepted: 01/28/2024] [Indexed: 02/09/2024]
Abstract
The bile salt export pump (ABCB11/BSEP) is a hepatocyte plasma membrane-resident protein translocating bile salts into bile canaliculi. The sequence alignment of the four full-length transporters of the ABCB subfamily (ABCB1, ABCB4, ABCB5 and ABCB11) indicates that the NBD-NBD contact interface of ABCB11 differs from that of other members in only four residues. Notably, these are all located in the noncanonical nucleotide binding site 1 (NBS1). Substitution of all four deviant residues with canonical ones (quadruple mutant) significantly decreased the transport activity of the protein. In this study, we mutated two deviant residues in the signature sequence to generate a double mutant (R1221G/E1223Q). Furthermore, a triple mutant (E502S/R1221G/E1223Q) was generated, in which the deviant residues of the signature sequence and Q-loop were mutated concurrently to canonical residues. The double and triple mutants showed 80% and 60%, respectively, of the activity of wild-type BSEP. As expected, an increasing number of mutations gradually impair transport as an intricate network of interactions within the ABC proteins ensures proper functioning.
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Affiliation(s)
- Imran Sohail
- Department of Zoology, Government College University Lahore, Lahore, Pakistan
- Institute of Medical Chemistry, Medical University of Vienna, Vienna, Austria
| | - Mahmood Ul Hassan
- Institute of Medical Chemistry, Medical University of Vienna, Vienna, Austria
- Institute of Industrial Biotechnology, Government College University Lahore, Lahore, Pakistan
| | - Diethart Schmid
- Institute of Physiology, Medical University of Vienna, Vienna, Austria
| | - Peter Chiba
- Institute of Medical Chemistry, Medical University of Vienna, Vienna, Austria
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2
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Gao Y, Wei C, Luo L, Tang Y, Yu Y, Li Y, Xing J, Pan X. Membrane-assisted tariquidar access and binding mechanisms of human ATP-binding cassette transporter P-glycoprotein. Front Mol Biosci 2024; 11:1364494. [PMID: 38560519 PMCID: PMC10979361 DOI: 10.3389/fmolb.2024.1364494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Accepted: 02/20/2024] [Indexed: 04/04/2024] Open
Abstract
The human multidrug transporter P-glycoprotein (P-gp) is physiologically essential and of key relevance to biomedicine. Recent structural studies have shed light on the mode of inhibition of the third-generation inhibitors for human P-gp, but the molecular mechanism by which these inhibitors enter the transmembrane sites remains poorly understood. In this study, we utilized all-atom molecular dynamics (MD) simulations to characterize human P-gp dynamics under a potent inhibitor, tariquidar, bound condition, as well as the atomic-level binding pathways in an explicit membrane/water environment. Extensive unbiased simulations show that human P-gp remains relatively stable in tariquidar-free and bound states, while exhibiting a high dynamic binding mode at either the drug-binding pocket or the regulatory site. Free energy estimations by partial nudged elastic band (PNEB) simulations and Molecular Mechanics Generalized Born Surface Area (MM/GBSA) method identify two energetically favorable binding pathways originating from the cytoplasmic gate with an extended tariquidar conformation. Interestingly, free tariquidar in the lipid membrane predominantly adopts extended conformations similar to those observed at the regulatory site. These results suggest that membrane lipids may preconfigure tariquidar into an active ligand conformation for efficient binding to the regulatory site. However, due to its conformational plasticity, tariquidar ultimately moves toward the drug-binding pocket in both pathways, explaining how it acts as a substrate at low concentrations. Our molecular findings propose a membrane-assisted mechanism for the access and binding of the third-generation inhibitors to the binding sites of human P-gp, and offer deeper insights into the molecule design of more potent inhibitors against P-gp-mediated drug resistance.
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Affiliation(s)
- Yingjie Gao
- Department of Medicinal Chemistry, School of Pharmacy, Southwest Medical University, Luzhou, Sichuan, China
| | - Caiyan Wei
- Department of Medicinal Chemistry, School of Pharmacy, Southwest Medical University, Luzhou, Sichuan, China
| | - Lanxin Luo
- Department of Pathophysiology, School of Basic Medical Science, Southwest Medical University, Luzhou, Sichuan, China
| | - Yang Tang
- Department of Medicinal Chemistry, School of Pharmacy, Southwest Medical University, Luzhou, Sichuan, China
| | - Yongzhen Yu
- Department of Medicinal Chemistry, School of Pharmacy, Southwest Medical University, Luzhou, Sichuan, China
| | - Yaling Li
- Department of Pharmacy, The Affiliated Hospital, Southwest Medical University, Luzhou, Sichuan, China
| | - Juan Xing
- Department of Pathophysiology, School of Basic Medical Science, Southwest Medical University, Luzhou, Sichuan, China
| | - Xianchao Pan
- Department of Medicinal Chemistry, School of Pharmacy, Southwest Medical University, Luzhou, Sichuan, China
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3
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Gewering T, Waghray D, Parey K, Jung H, Tran NNB, Zapata J, Zhao P, Chen H, Januliene D, Hummer G, Urbatsch I, Moeller A, Zhang Q. Tracing the substrate translocation mechanism in P-glycoprotein. eLife 2024; 12:RP90174. [PMID: 38259172 PMCID: PMC10945689 DOI: 10.7554/elife.90174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2024] Open
Abstract
P-glycoprotein (Pgp) is a prototypical ATP-binding cassette (ABC) transporter of great biological and clinical significance.Pgp confers cancer multidrug resistance and mediates the bioavailability and pharmacokinetics of many drugs (Juliano and Ling, 1976; Ueda et al., 1986; Sharom, 2011). Decades of structural and biochemical studies have provided insights into how Pgp binds diverse compounds (Loo and Clarke, 2000; Loo et al., 2009; Aller et al., 2009; Alam et al., 2019; Nosol et al., 2020; Chufan et al., 2015), but how they are translocated through the membrane has remained elusive. Here, we covalently attached a cyclic substrate to discrete sites of Pgp and determined multiple complex structures in inward- and outward-facing states by cryoEM. In conjunction with molecular dynamics simulations, our structures trace the substrate passage across the membrane and identify conformational changes in transmembrane helix 1 (TM1) as regulators of substrate transport. In mid-transport conformations, TM1 breaks at glycine 72. Mutation of this residue significantly impairs drug transport of Pgp in vivo, corroborating the importance of its regulatory role. Importantly, our data suggest that the cyclic substrate can exit Pgp without the requirement of a wide-open outward-facing conformation, diverting from the common efflux model for Pgp and other ABC exporters. The substrate transport mechanism of Pgp revealed here pinpoints critical targets for future drug discovery studies of this medically relevant system.
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Affiliation(s)
- Theresa Gewering
- Osnabrück University, Department of Biology/Chemistry, Structural Biology SectionOsnabrückGermany
- Department of Structural Biology, Max Planck Institute of BiophysicsFrankfurtGermany
| | - Deepali Waghray
- Department of Integrative Structural and Computational Biology, The Scripps Research InstituteLa JollaUnited States
| | - Kristian Parey
- Osnabrück University, Department of Biology/Chemistry, Structural Biology SectionOsnabrückGermany
- Department of Structural Biology, Max Planck Institute of BiophysicsFrankfurtGermany
- Osnabrück University, Center of Cellular Nanoanalytic Osnabrück (CellNanOs)OsnabrückGermany
| | - Hendrik Jung
- Department of Theoretical Biophysics, Max Planck Institute of BiophysicsFrankfurtGermany
| | - Nghi NB Tran
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences CenterLubbockUnited States
| | - Joel Zapata
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences CenterLubbockUnited States
| | - Pengyi Zhao
- Department of Chemistry & Environmental Science, New Jersey Institute of TechnologyNewarkUnited States
| | - Hao Chen
- Department of Chemistry & Environmental Science, New Jersey Institute of TechnologyNewarkUnited States
| | - Dovile Januliene
- Osnabrück University, Department of Biology/Chemistry, Structural Biology SectionOsnabrückGermany
- Department of Structural Biology, Max Planck Institute of BiophysicsFrankfurtGermany
- Osnabrück University, Center of Cellular Nanoanalytic Osnabrück (CellNanOs)OsnabrückGermany
| | - Gerhard Hummer
- Department of Theoretical Biophysics, Max Planck Institute of BiophysicsFrankfurtGermany
- Institute for Biophysics, Goethe University FrankfurtFrankfurtGermany
| | - Ina Urbatsch
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences CenterLubbockUnited States
| | - Arne Moeller
- Osnabrück University, Department of Biology/Chemistry, Structural Biology SectionOsnabrückGermany
- Department of Structural Biology, Max Planck Institute of BiophysicsFrankfurtGermany
- Osnabrück University, Center of Cellular Nanoanalytic Osnabrück (CellNanOs)OsnabrückGermany
| | - Qinghai Zhang
- Department of Integrative Structural and Computational Biology, The Scripps Research InstituteLa JollaUnited States
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4
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Veiga-Matos J, Morales AI, Prieto M, Remião F, Silva R. Study Models of Drug-Drug Interactions Involving P-Glycoprotein: The Potential Benefit of P-Glycoprotein Modulation at the Kidney and Intestinal Levels. Molecules 2023; 28:7532. [PMID: 38005253 PMCID: PMC10673607 DOI: 10.3390/molecules28227532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Revised: 11/03/2023] [Accepted: 11/03/2023] [Indexed: 11/26/2023] Open
Abstract
P-glycoprotein (P-gp) is a crucial membrane transporter situated on the cell's apical surface, being responsible for eliminating xenobiotics and endobiotics. P-gp modulators are compounds that can directly or indirectly affect this protein, leading to changes in its expression and function. These modulators can act as inhibitors, inducers, or activators, potentially causing drug-drug interactions (DDIs). This comprehensive review explores diverse models and techniques used to assess drug-induced P-gp modulation. We cover several approaches, including in silico, in vitro, ex vivo, and in vivo methods, with their respective strengths and limitations. Additionally, we explore the therapeutic implications of DDIs involving P-gp, with a special focus on the renal and intestinal elimination of P-gp substrates. This involves enhancing the removal of toxic substances from proximal tubular epithelial cells into the urine or increasing the transport of compounds from enterocytes into the intestinal lumen, thereby facilitating their excretion in the feces. A better understanding of these interactions, and of the distinct techniques applied for their study, will be of utmost importance for optimizing drug therapy, consequently minimizing drug-induced adverse and toxic effects.
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Affiliation(s)
- Jéssica Veiga-Matos
- UCIBIO-Applied Molecular Biosciences Unit, Laboratory of Toxicology, Department of Biological Sciences, Faculty of Pharmacy, University of Porto, 4050-313 Porto, Portugal;
- Associate Laboratory i4HB—Institute for Health and Bioeconomy, Faculty of Pharmacy, University of Porto, 4050-313 Porto, Portugal
- Toxicology Unit (Universidad de Salamanca), Group of Translational Research on Renal and Cardiovascular Diseases (TRECARD), Institute of Biomedical Research of Salamanca (IBSAL), 37007 Salamanca, Spain; (A.I.M.); (M.P.)
| | - Ana I. Morales
- Toxicology Unit (Universidad de Salamanca), Group of Translational Research on Renal and Cardiovascular Diseases (TRECARD), Institute of Biomedical Research of Salamanca (IBSAL), 37007 Salamanca, Spain; (A.I.M.); (M.P.)
| | - Marta Prieto
- Toxicology Unit (Universidad de Salamanca), Group of Translational Research on Renal and Cardiovascular Diseases (TRECARD), Institute of Biomedical Research of Salamanca (IBSAL), 37007 Salamanca, Spain; (A.I.M.); (M.P.)
| | - Fernando Remião
- UCIBIO-Applied Molecular Biosciences Unit, Laboratory of Toxicology, Department of Biological Sciences, Faculty of Pharmacy, University of Porto, 4050-313 Porto, Portugal;
- Associate Laboratory i4HB—Institute for Health and Bioeconomy, Faculty of Pharmacy, University of Porto, 4050-313 Porto, Portugal
| | - Renata Silva
- UCIBIO-Applied Molecular Biosciences Unit, Laboratory of Toxicology, Department of Biological Sciences, Faculty of Pharmacy, University of Porto, 4050-313 Porto, Portugal;
- Associate Laboratory i4HB—Institute for Health and Bioeconomy, Faculty of Pharmacy, University of Porto, 4050-313 Porto, Portugal
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5
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Naphthoquinone derivatives as P-glycoprotein inducers in inflammatory bowel disease: 2D monolayers, 3D spheroids, and in vivo models. Pharmacol Res 2022; 179:106233. [DOI: 10.1016/j.phrs.2022.106233] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 04/07/2022] [Accepted: 04/19/2022] [Indexed: 12/21/2022]
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6
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Stockner T, Gradisch R, Schmitt L. The role of the degenerate nucleotide binding site in type I ABC exporters. FEBS Lett 2020; 594:3815-3838. [PMID: 33179257 PMCID: PMC7756269 DOI: 10.1002/1873-3468.13997] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 09/26/2020] [Accepted: 10/15/2020] [Indexed: 12/18/2022]
Abstract
ATP‐binding cassette (ABC) transporters are fascinating molecular machines that are capable of transporting a large variety of chemically diverse compounds. The energy required for translocation is derived from binding and hydrolysis of ATP. All ABC transporters share a basic architecture and are composed of two transmembrane domains and two nucleotide binding domains (NBDs). The latter harbor all conserved sequence motifs that hallmark the ABC transporter superfamily. The NBDs form the nucleotide binding sites (NBSs) in their interface. Transporters with two active NBSs are called canonical transporters, while ABC exporters from eukaryotic organisms, including humans, frequently have a degenerate NBS1 containing noncanonical residues that strongly impair ATP hydrolysis. Here, we summarize current knowledge on degenerate ABC transporters. By integrating structural information with biophysical and biochemical evidence of asymmetric function, we develop a model for the transport cycle of degenerate ABC transporters. We will elaborate on the unclear functional advantages of a degenerate NBS.
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Affiliation(s)
- Thomas Stockner
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Ralph Gradisch
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Lutz Schmitt
- Institute of Biochemistry, Heinrich Heine University, Düsseldorf, Germany
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7
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Farman S, Javed A, Arshia, Khan KM, Nasir A, Khan AU, Lodhi MA, Gul H, Khan F, Asad M, Parveen Z. Benzophenone Sulfonamide Derivatives as Interacting Partners and Inhibitors of Human P-glycoprotein. Anticancer Agents Med Chem 2020; 20:1739-1751. [PMID: 32416700 DOI: 10.2174/1871520620666200516144403] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2019] [Revised: 02/24/2020] [Accepted: 03/08/2020] [Indexed: 11/22/2022]
Abstract
BACKGROUND Human P-glycoprotein (P-gp) is a transmembrane protein that belongs to the ATPBinding Cassette (ABC) transporters family. Physiologically, it exports toxins out of the cell, however, its overexpression leads to the phenomena of Multidrug-Resistance (MDR) by exporting a diverse range of compounds, which are structurally and chemically different from each other, thus creating a hurdle in the treatment of various diseases including cancer. The current study was designed to screen benzophenone sulfonamide derivatives as a class of inhibitors and potential anticancer agents for P-gp. METHODS A total number of 15 compounds were evaluated. These compounds were screened in daunorubicin efflux inhibition assays using CCRF-CEM Vcr1000 cell line that overexpressed human P-gp. Cytotoxicity assay was also performed for active compounds 11, 14, and 13. These scaffolds were then docked in the homology model of human P-gp using mouse P-gp as a template (PDB ID: 4MIM) and the recently published Cryo Electron Microscopy (CEM) structure of human mouse chimeric P-gp to find their interactions with specified residues in the binding pocket. Analysis was performed using Labview VI and Graph pad prism version 5.0. RESULTS Results revealed the potency of all these compounds in low nanomolar range whereas, compound 14 was found to be most active with IC50 value of 18.35nM±4.90 followed by 11 and 13 having IC50 values of 30.66nM±5.49 and 46.12nM±3.06, respectively. Moreover, IC50 values calculated for 14, 11 and 13 in cytotoxicity assay were found to be 22.97μM±0.026, 583.1μM±0.027 and 117.8μM±0.062, respectively. Docking results showed the interaction of these scaffolds in transmembrane helices (TM) where Tyr307, Tyr310, Tyr953, Met986 and Gln946 were found to be the major interaction partners, thus they might play a significant role in the transport of these scaffolds. CONCLUSION Benzophenone sulfonamide derivatives showed IC50 values in low nanomolar range comparable to the standard inhibitor Verapamil, therefore they can be good inhibitors of P-gp and can serve as anticancer agents. Also, they have shown interactions in the transmembrane region sharing the same binding region of verapamil and zosuquidar.
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Affiliation(s)
- Saira Farman
- Department of Biochemistry, Abdul Wali Khan University Mardan, Khyber Pakhtunkhwa, Pakistan
| | - Aneela Javed
- Atta-Ur-Rehman School of Applied Biosciences, National University of Science and Technology (NUST), Sector H-12, Islamabad, Pakistan
| | - Arshia
- H.E.J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi-75270, Pakistan
| | - Khalid M Khan
- H.E.J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi-75270, Pakistan.,Department of Clinical Pharmacy, Institute for Research and Medical Consultations (IRMC), Imam Abdulrahman Bin
Faisal University, P.O. Box 31441, Dammam, Saudi Arabia
| | - Abdul Nasir
- Synthetic Protein Engineering Lab (SPEL), Department of Molecular Science and Technology, Ajou University, Suwon 443-749, South Korea
| | - Asif Ullah Khan
- Department of Biochemistry, Abdul Wali Khan University Mardan, Khyber Pakhtunkhwa, Pakistan
| | - Muhammad A Lodhi
- Department of Biochemistry, Abdul Wali Khan University Mardan, Khyber Pakhtunkhwa, Pakistan
| | - Humaira Gul
- Department of Botany, Abdul Wali Khan University, Mardan, Khyber Pakhtunkhwa, Pakistan
| | - Faisal Khan
- Department of Biochemistry, Abdul Wali Khan University Mardan, Khyber Pakhtunkhwa, Pakistan
| | - Muhammad Asad
- Department of Biochemistry, Abdul Wali Khan University Mardan, Khyber Pakhtunkhwa, Pakistan
| | - Zahida Parveen
- Department of Biochemistry, Abdul Wali Khan University Mardan, Khyber Pakhtunkhwa, Pakistan
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8
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Nasim F, Schmid D, Szakács G, Sohail A, Sitte HH, Chiba P, Stockner T. Active transport of rhodamine 123 by the human multidrug transporter P-glycoprotein involves two independent outer gates. Pharmacol Res Perspect 2020; 8:e00572. [PMID: 32232949 PMCID: PMC7105846 DOI: 10.1002/prp2.572] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 02/07/2020] [Indexed: 12/20/2022] Open
Abstract
Human P-glycoprotein (P-gp) is a multispecific drug-efflux transporter, which plays an important role in drug resistance and drug disposition. Recent cryo-electron microscopy structures confirmed its rotationally symmetric architecture, which allows dual interaction with ATP and substrates. We here report the existence of two distinct, symmetry-related outer gates. Experiments were aided by availability of the X-ray structure of a homodimeric eukaryotic homolog of P-gp from red alga (CmABCB1), which defined the role of an apical tyrosine residue (Y358) in outer gate formation. We mutated analogous tyrosine residues in each half of the human full-length transporter (Y310, Y953) to alanine. These mutants were introduced in engineered transporters which bind rhodamine 123 in one of two symmetry-related binding modes only. Outer gate dysfunction was detected by a loss of active transport characteristics, while these mutants retained the ability for outward downhill transport. Our data demonstrate that symmetric tyrosine residues Y310 and Y953 are involved in formation of two distinct symmetry-related outer gates, which operate contingent on the rhodamine 123 binding mode. Hence, the rotationally symmetric architecture of P-gp, which determines duality in ATP binding and rhodamine 123 interaction, also forms the basis for the existence of two independently operating outer gates.
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Affiliation(s)
- Fauzia Nasim
- Institute of Medical ChemistryCenter for Pathobiochemistry and GeneticsMedical University of ViennaViennaAustria
| | - Diethart Schmid
- Institute of PhysiologyCenter for Physiology and PharmacologyMedical University of ViennaViennaAustria
| | - Gergely Szakács
- Institute of Cancer ResearchMedical University of ViennaViennaAustria
| | - Azmat Sohail
- Institute of PharmacologyCenter for Physiology and PharmacologyMedical University of ViennaViennaAustria
| | - Harald H. Sitte
- Institute of PharmacologyCenter for Physiology and PharmacologyMedical University of ViennaViennaAustria
| | - Peter Chiba
- Institute of Medical ChemistryCenter for Pathobiochemistry and GeneticsMedical University of ViennaViennaAustria
| | - Thomas Stockner
- Institute of PharmacologyCenter for Physiology and PharmacologyMedical University of ViennaViennaAustria
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9
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Zhang T, Liu Y, Yan JK, Cai W. Early downregulation of P-glycoprotein facilitates bacterial attachment to intestinal epithelial cells and thereby triggers barrier dysfunction in a rodent model of total parenteral nutrition. FASEB J 2020; 34:4670-4683. [PMID: 32027421 DOI: 10.1096/fj.201902513r] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 01/08/2020] [Accepted: 01/20/2020] [Indexed: 12/19/2022]
Abstract
Intestinal barrier dysfunction is a major complication of total parenteral nutrition (TPN). Our preliminary study revealed that intestinal P-glycoprotein (P-gp) was significantly downregulated under TPN treatment followed by disruption of barrier function, and thus the significance of early downregulation of P-gp needs to be addressed. Herein, we report a pivotal role of P-gp in the development of intestinal barrier dysfunction under TPN. Functional suppression of P-gp may facilitate bacterial attachment to intestinal epithelial cells (IECs) and thereby induce degradation of tight junctions to trigger barrier dysfunction. By using a rat model of TPN, we found early downregulation of P-gp function in ileum after 3-day TPN, followed by disruption of barrier function after 7-day TPN. By using Escherichia coli (E. coli) k88 and DH5α as type strains, we found significantly increased bacterial attachment to IECs in TPN group compared to sham. By using Caco-2 cells as an IEC model in vitro, we found that functional suppression of P-gp remarkably facilitated bacterial attachment to Caco-2 cells, leading to subsequent disruption of intestinal barrier function. Of note, Occludin was significantly downregulated by bacterial attachment when P-gp was functionally suppressed. Mechanistically, changes on Occludin were attributed to enhanced protein degradation instead of suppressed protein translation. Despite the half-life of Occludin protein being unchanged by DH5α treatment alone, it was decreased by about 40% when P-gp was simultaneously suppressed. Taken together, our findings revealed that early downregulation of intestinal P-gp under TPN may be a potential therapeutic target to prevent the development of barrier dysfunction.
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Affiliation(s)
- Tian Zhang
- School of Medicine, Xinhua Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Yang Liu
- School of Medicine, Xinhua Hospital, Shanghai Jiao Tong University, Shanghai, China
| | - Jun-Kai Yan
- School of Medicine, Xinhua Hospital, Shanghai Jiao Tong University, Shanghai, China.,Shanghai Key Laboratory of Pediatric Gastroenterology and Nutrition, Shanghai Institute for Pediatric Research, Shanghai, China
| | - Wei Cai
- School of Medicine, Xinhua Hospital, Shanghai Jiao Tong University, Shanghai, China.,Shanghai Key Laboratory of Pediatric Gastroenterology and Nutrition, Shanghai Institute for Pediatric Research, Shanghai, China
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10
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Xing J, Mei H, Huang S, Zhang D, Pan X. An Energetically Favorable Ligand Entrance Gate of a Multidrug Transporter Revealed by Partial Nudged Elastic Band Simulations. Comput Struct Biotechnol J 2019; 17:319-323. [PMID: 30899446 PMCID: PMC6406077 DOI: 10.1016/j.csbj.2019.02.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 02/14/2019] [Accepted: 02/15/2019] [Indexed: 11/08/2022] Open
Abstract
P-glycoprotein (P-gp) is a multidrug transporter, which harnesses the chemical energy of ATP to power the efflux of diverse chemotherapeutics out of cells and thus contributes to the development of multidrug resistance (MDR) in cancer. It has been proved that the ligand-binding pocket of P-gp is located at the transmembrane domains (TMDs). However, the access of ligands into the binding pocket remains to be elucidated, which definitely hinder the development of P-gp inhibitors. Herein, the access pathways of a well-known substrate rhodamine-123 and a cyclopeptide inhibitor QZ-Leu were characterized by time-independent partial nudged elastic band (PNEB) simulations. The decreasing free energies along the PNEB-optimized access pathway indicated that TM4/6 cleft may be an energetically favorable entrance gate for ligand entry into the binding pocket of P-gp. The results can be reconciled with a range of experimental studies, further corroborating the reliability of the gate revealed by computational simulations. Our atomic level description of the ligand access pathway provides valuable insights into the gating mechanism for drug uptake and transport by P-gp and other multidrug transporters. P-gp contributes to the development of multidrug resistance in cancer. The entrance of drugs into P-gp binding pocket has yet to be elucidated. An energetically favorable entrance gate was revealed by PNEB simulations. The computational results were reconciled with the experimental data. The atomic simulations provide insights into the gating mechanism of P-gp.
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Affiliation(s)
- Juan Xing
- Key Laboratory of Biorheological Science and Technology (Ministry of Education), College of Bioengineering, Chongqing University, Chongqing 400045, China.,Department of Pathophysiology, College of Basic Medical Science, Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Hu Mei
- Key Laboratory of Biorheological Science and Technology (Ministry of Education), College of Bioengineering, Chongqing University, Chongqing 400045, China
| | - ShuHeng Huang
- Key Laboratory of Biorheological Science and Technology (Ministry of Education), College of Bioengineering, Chongqing University, Chongqing 400045, China
| | - Duo Zhang
- Key Laboratory of Biorheological Science and Technology (Ministry of Education), College of Bioengineering, Chongqing University, Chongqing 400045, China
| | - XianChao Pan
- Key Laboratory of Biorheological Science and Technology (Ministry of Education), College of Bioengineering, Chongqing University, Chongqing 400045, China.,Department of Medicinal Chemistry, College of Pharmacy, Southwest Medical University, Luzhou, Sichuan 646000, China
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11
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Subramanian N, Schumann-Gillett A, Mark AE, O’Mara ML. Probing the Pharmacological Binding Sites of P-Glycoprotein Using Umbrella Sampling Simulations. J Chem Inf Model 2018; 59:2287-2298. [DOI: 10.1021/acs.jcim.8b00624] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Nandhitha Subramanian
- School of Chemistry and Molecular Biosciences (SCMB), University of Queensland, Brisbane, QLD 4072, Australia
- Research School of Chemistry (RSC), Australian National University, Canberra, ACT 2601, Australia
| | | | - Alan E. Mark
- School of Chemistry and Molecular Biosciences (SCMB), University of Queensland, Brisbane, QLD 4072, Australia
- The Institute for Molecular Biosciences (IMB), University of Queensland, Brisbane, QLD 4072, Australia
| | - Megan L. O’Mara
- School of Chemistry and Molecular Biosciences (SCMB), University of Queensland, Brisbane, QLD 4072, Australia
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12
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Szöllősi D, Rose-Sperling D, Hellmich UA, Stockner T. Comparison of mechanistic transport cycle models of ABC exporters. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:818-832. [PMID: 29097275 PMCID: PMC7610611 DOI: 10.1016/j.bbamem.2017.10.028] [Citation(s) in RCA: 78] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Revised: 10/23/2017] [Accepted: 10/25/2017] [Indexed: 12/25/2022]
Abstract
ABC (ATP binding cassette) transporters, ubiquitous in all kingdoms of life, carry out essential substrate transport reactions across cell membranes. Their transmembrane domains bind and translocate substrates and are connected to a pair of nucleotide binding domains, which bind and hydrolyze ATP to energize import or export of substrates. Over four decades of investigations into ABC transporters have revealed numerous details from atomic-level structural insights to their functional and physiological roles. Despite all these advances, a comprehensive understanding of the mechanistic principles of ABC transporter function remains elusive. The human multidrug resistance transporter ABCB1, also referred to as P-glycoprotein (P-gp), is one of the most intensively studied ABC exporters. Using ABCB1 as the reference point, we aim to compare the dominating mechanistic models of substrate transport and ATP hydrolysis for ABC exporters and to highlight the experimental and computational evidence in their support. In particular, we point out in silico studies that enhance and complement available biochemical data. “This article is part of a Special Issue entitled: Beyond the Structure Function Horizon of Membrane Proteins edited by Ute Hellmich, Rupak Doshi and Benjamin McIlwain.”
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Affiliation(s)
- Dániel Szöllősi
- Medical University of Vienna, Institute of Pharmacology, Waehringerstr. 13A, Vienna 1090, Austria
| | - Dania Rose-Sperling
- Johannes Gutenberg-University, Department of Pharmacy and Biochemistry, Johann-Joachim-Becher-Weg 30, Mainz 55128, Germany; Centre for Biomolecular Magnetic Resonance (BMRZ), Goethe-University Frankfurt, Max von Laue-Str. 9, 60438 Frankfurt am Main, Germany
| | - Ute A Hellmich
- Johannes Gutenberg-University, Department of Pharmacy and Biochemistry, Johann-Joachim-Becher-Weg 30, Mainz 55128, Germany; Centre for Biomolecular Magnetic Resonance (BMRZ), Goethe-University Frankfurt, Max von Laue-Str. 9, 60438 Frankfurt am Main, Germany
| | - Thomas Stockner
- Medical University of Vienna, Institute of Pharmacology, Waehringerstr. 13A, Vienna 1090, Austria.
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13
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A Critical View on In Vitro Analysis of P-glycoprotein (P-gp) Transport Kinetics. J Pharm Sci 2017; 106:2257-2264. [DOI: 10.1016/j.xphs.2017.04.022] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 04/12/2017] [Accepted: 04/12/2017] [Indexed: 01/11/2023]
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14
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Sohail MI, Schmid D, Wlcek K, Spork M, Szakács G, Trauner M, Stockner T, Chiba P. Molecular Mechanism of Taurocholate Transport by the Bile Salt Export Pump, an ABC Transporter Associated with Intrahepatic Cholestasis. Mol Pharmacol 2017; 92:401-413. [PMID: 28784620 DOI: 10.1124/mol.117.108688] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Accepted: 07/31/2017] [Indexed: 12/12/2022] Open
Abstract
The bile salt export pump (BSEP/ABCB11) transports bile salts from hepatocytes into bile canaliculi. Its malfunction is associated with severe liver disease. One reason for functional impairment of BSEP is systemic administration of drugs, which as a side effect inhibit the transporter. Therefore, drug candidates are routinely screened for potential interaction with this transporter. Hence, understanding the functional biology of BSEP is of key importance. In this study, we engineered the transporter to dissect interdomain communication paths. We introduced mutations in noncanonical and in conserved residues of either of the two nucleotide binding domains and determined the effect on BSEP basal and substrate-stimulated ATPase activity as well as on taurocholate transport. Replacement of the noncanonical methionine residue M584 (Walker B sequence of nucleotide binding site 1) by glutamate imparted hydrolysis competency to this site. Importantly, this mutation was able to sustain 15% of wild-type transport activity, when the catalytic glutamate of the canonical nucleotide binding site 2 was mutated to glutamine. Kinetic modeling of experimental results for the ensuing M584E/E1244Q mutant suggests that a transfer of hydrolytic capacity from the canonical to the noncanonical nucleotide binding site results in loss of active and adoption of facilitative characteristics. This facilitative transport is ATP-gated. To the best of our knowledge, this result is unprecedented in ATP-binding cassette proteins with one noncanonical nucleotide binding site. Our study promotes an understanding of the domain interplay in BSEP as a basis for exploration of drug interactions with this transporter.
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Affiliation(s)
- Muhammad Imran Sohail
- Institute of Medical Chemistry, Center for Pathobiochemistry and Genetics (M.I.S., M.S., P.C.), Institute of Physiology, Center for Physiology and Pharmacology (D.S.), Institute of Cancer Research (G.S.), Hans Popper Laboratory of Molecular Hepatology, Division of Gastroenterology and Hepatology, Department of Internal Medicine III (M.T.), and Institute of Pharmacology, Center for Physiology and Pharmacology (T.S.), Medical University of Vienna, Vienna, Austria; Department of Zoology, Government College University Lahore, Lahore, Pakistan (M.I.S.); and Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna, Vienna, Austria (K.W.)
| | - Diethart Schmid
- Institute of Medical Chemistry, Center for Pathobiochemistry and Genetics (M.I.S., M.S., P.C.), Institute of Physiology, Center for Physiology and Pharmacology (D.S.), Institute of Cancer Research (G.S.), Hans Popper Laboratory of Molecular Hepatology, Division of Gastroenterology and Hepatology, Department of Internal Medicine III (M.T.), and Institute of Pharmacology, Center for Physiology and Pharmacology (T.S.), Medical University of Vienna, Vienna, Austria; Department of Zoology, Government College University Lahore, Lahore, Pakistan (M.I.S.); and Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna, Vienna, Austria (K.W.)
| | - Katrin Wlcek
- Institute of Medical Chemistry, Center for Pathobiochemistry and Genetics (M.I.S., M.S., P.C.), Institute of Physiology, Center for Physiology and Pharmacology (D.S.), Institute of Cancer Research (G.S.), Hans Popper Laboratory of Molecular Hepatology, Division of Gastroenterology and Hepatology, Department of Internal Medicine III (M.T.), and Institute of Pharmacology, Center for Physiology and Pharmacology (T.S.), Medical University of Vienna, Vienna, Austria; Department of Zoology, Government College University Lahore, Lahore, Pakistan (M.I.S.); and Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna, Vienna, Austria (K.W.)
| | - Matthias Spork
- Institute of Medical Chemistry, Center for Pathobiochemistry and Genetics (M.I.S., M.S., P.C.), Institute of Physiology, Center for Physiology and Pharmacology (D.S.), Institute of Cancer Research (G.S.), Hans Popper Laboratory of Molecular Hepatology, Division of Gastroenterology and Hepatology, Department of Internal Medicine III (M.T.), and Institute of Pharmacology, Center for Physiology and Pharmacology (T.S.), Medical University of Vienna, Vienna, Austria; Department of Zoology, Government College University Lahore, Lahore, Pakistan (M.I.S.); and Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna, Vienna, Austria (K.W.)
| | - Gergely Szakács
- Institute of Medical Chemistry, Center for Pathobiochemistry and Genetics (M.I.S., M.S., P.C.), Institute of Physiology, Center for Physiology and Pharmacology (D.S.), Institute of Cancer Research (G.S.), Hans Popper Laboratory of Molecular Hepatology, Division of Gastroenterology and Hepatology, Department of Internal Medicine III (M.T.), and Institute of Pharmacology, Center for Physiology and Pharmacology (T.S.), Medical University of Vienna, Vienna, Austria; Department of Zoology, Government College University Lahore, Lahore, Pakistan (M.I.S.); and Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna, Vienna, Austria (K.W.)
| | - Michael Trauner
- Institute of Medical Chemistry, Center for Pathobiochemistry and Genetics (M.I.S., M.S., P.C.), Institute of Physiology, Center for Physiology and Pharmacology (D.S.), Institute of Cancer Research (G.S.), Hans Popper Laboratory of Molecular Hepatology, Division of Gastroenterology and Hepatology, Department of Internal Medicine III (M.T.), and Institute of Pharmacology, Center for Physiology and Pharmacology (T.S.), Medical University of Vienna, Vienna, Austria; Department of Zoology, Government College University Lahore, Lahore, Pakistan (M.I.S.); and Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna, Vienna, Austria (K.W.)
| | - Thomas Stockner
- Institute of Medical Chemistry, Center for Pathobiochemistry and Genetics (M.I.S., M.S., P.C.), Institute of Physiology, Center for Physiology and Pharmacology (D.S.), Institute of Cancer Research (G.S.), Hans Popper Laboratory of Molecular Hepatology, Division of Gastroenterology and Hepatology, Department of Internal Medicine III (M.T.), and Institute of Pharmacology, Center for Physiology and Pharmacology (T.S.), Medical University of Vienna, Vienna, Austria; Department of Zoology, Government College University Lahore, Lahore, Pakistan (M.I.S.); and Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna, Vienna, Austria (K.W.)
| | - Peter Chiba
- Institute of Medical Chemistry, Center for Pathobiochemistry and Genetics (M.I.S., M.S., P.C.), Institute of Physiology, Center for Physiology and Pharmacology (D.S.), Institute of Cancer Research (G.S.), Hans Popper Laboratory of Molecular Hepatology, Division of Gastroenterology and Hepatology, Department of Internal Medicine III (M.T.), and Institute of Pharmacology, Center for Physiology and Pharmacology (T.S.), Medical University of Vienna, Vienna, Austria; Department of Zoology, Government College University Lahore, Lahore, Pakistan (M.I.S.); and Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna, Vienna, Austria (K.W.)
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15
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Global alteration of the drug-binding pocket of human P-glycoprotein (ABCB1) by substitution of fifteen conserved residues reveals a negative correlation between substrate size and transport efficiency. Biochem Pharmacol 2017; 143:53-64. [PMID: 28728917 DOI: 10.1016/j.bcp.2017.07.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Accepted: 07/13/2017] [Indexed: 11/21/2022]
Abstract
P-glycoprotein (P-gp), an ATP-dependent efflux pump, is linked to the development of multidrug resistance in cancer cells. However, the drug-binding sites and translocation pathways of this transporter are not yet well-characterized. We recently demonstrated the important role of tyrosine residues in regulating P-gp ATP hydrolysis via hydrogen bond formations with high affinity modulators. Since tyrosine is both a hydrogen bond donor and acceptor, and non-covalent interactions are key in drug transport, in this study we investigated the global effect of enrichment of tyrosine residues in the drug-binding pocket on the drug binding and transport function of P-gp. By employing computational analysis, 15 conserved residues in the drug-binding pocket of human P-gp that interact with substrates were identified and then substituted with tyrosine, including 11 phenylalanine (F72, F303, F314, F336, F732, F759, F770, F938, F942, F983, F994), two leucine (L339, L975), one isoleucine (I306), and one methionine (M949). Characterization of the tyrosine-rich P-gp mutant in HeLa cells demonstrated that this major alteration in the drug-binding pocket by introducing fifteen additional tyrosine residues is well tolerated and has no measurable effect on total or cell surface expression of this mutant. Although the tyrosine-enriched mutant P-gp could transport small to moderate size (<1000 Daltons) fluorescent substrates, its ability to transport large (>1000 Daltons) substrates such as NBD-cyclosporine A, Bodipy-paclitaxel and Bodipy-vinblastine was significantly decreased. This was further supported by the physico-chemical characterization of seventeen tested substrates, which revealed a negative correlation between drug transport and molecular size for the tyrosine-enriched P-gp mutant.
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16
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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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17
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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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18
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Tarapcsák S, Szalóki G, Telbisz Á, Gyöngy Z, Matúz K, Csősz É, Nagy P, Holb IJ, Rühl R, Nagy L, Szabó G, Goda K. Interactions of retinoids with the ABC transporters P-glycoprotein and Breast Cancer Resistance Protein. Sci Rep 2017; 7:41376. [PMID: 28145501 PMCID: PMC5286421 DOI: 10.1038/srep41376] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 12/20/2016] [Indexed: 01/16/2023] Open
Abstract
Retinoids – derivatives of vitamin A – are important cell permeant signaling molecules that regulate gene expression through activation of nuclear receptors. P-glycoprotein (Pgp) and ABCG2 are plasma membrane efflux transporters affecting the tissue distribution of numerous structurally unrelated lipophilic compounds. In the present work we aimed to study the interaction of the above ABC transporters with retinoid derivatives. We have found that 13-cis-retinoic acid, retinol and retinyl-acetate inhibited the Pgp and ABCG2 mediated substrate transport as well as the substrate stimulated ATPase activity of these transporters. Interestingly, 9-cis-retinoic acid and ATRA (all-trans retinoic acid), both are stereoisomers of 13-cis-retinoic acid, did not have any effect on the transporters’ activity. Our fluorescence anisotropy measurements revealed that 13-cis-retinoic acid, retinol and retinyl-acetate selectively increase the viscosity and packing density of the membrane. Thus, the mixed-type inhibition of both transporters by retinol and ABCG2 by 13-cis-retinoic acid may be the collective result of direct interactions of these retinoids with the substrate binding site(s) and of indirect interactions mediated by their membrane rigidifying effects.
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Affiliation(s)
- Szabolcs Tarapcsák
- Department of Biophysics and Cell Biology, University of Debrecen, Debrecen, H-4002 Egyetem tér 1, P.O.B. 400, Hungary
| | - Gábor Szalóki
- Department of Biophysics and Cell Biology, University of Debrecen, Debrecen, H-4002 Egyetem tér 1, P.O.B. 400, Hungary
| | - Ágnes Telbisz
- Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, H-1117 Magyar tudósok körútja 2, P.O.B. 286, Hungary
| | - Zsuzsanna Gyöngy
- Department of Biophysics and Cell Biology, University of Debrecen, Debrecen, H-4002 Egyetem tér 1, P.O.B. 400, Hungary
| | - Krisztina Matúz
- Department of Biochemistry and Molecular Biology, University of Debrecen, Debrecen, H-4002 Egyetem tér 1, P.O.B. 400, Hungary
| | - Éva Csősz
- Department of Biochemistry and Molecular Biology, University of Debrecen, Debrecen, H-4002 Egyetem tér 1, P.O.B. 400, Hungary
| | - Péter Nagy
- Department of Biophysics and Cell Biology, University of Debrecen, Debrecen, H-4002 Egyetem tér 1, P.O.B. 400, Hungary
| | - Imre J Holb
- Institute of Horticulture, University of Debrecen, Debrecen, H-4015 Böszörményi út 138, P.O.B. 400, Hungary.,Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, H-1525 Hermann Ottó út 15, P.O.B. 525, Hungary
| | - Ralph Rühl
- MTA-DE, Public Health Research Group of the Hungarian Academy of Sciences, Faculty of Public Health, University of Debrecen, Debrecen, H-4028 Kassai út 26, P.O.B. 400, Hungary
| | - László Nagy
- Department of Biochemistry and Molecular Biology, University of Debrecen, Debrecen, H-4002 Egyetem tér 1, P.O.B. 400, Hungary
| | - Gábor Szabó
- Department of Biophysics and Cell Biology, University of Debrecen, Debrecen, H-4002 Egyetem tér 1, P.O.B. 400, Hungary
| | - Katalin Goda
- Department of Biophysics and Cell Biology, University of Debrecen, Debrecen, H-4002 Egyetem tér 1, P.O.B. 400, Hungary
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19
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ATP-dependent substrate transport by the ABC transporter MsbA is proton-coupled. Nat Commun 2016; 7:12387. [PMID: 27499013 PMCID: PMC4979069 DOI: 10.1038/ncomms12387] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 06/22/2016] [Indexed: 01/11/2023] Open
Abstract
ATP-binding cassette transporters mediate the transbilayer movement of a vast number of substrates in or out of cells in organisms ranging from bacteria to humans. Current alternating access models for ABC exporters including the multidrug and Lipid A transporter MsbA from Escherichia coli suggest a role for nucleotide as the fundamental source of free energy. These models involve cycling between conformations with inward- and outward-facing substrate-binding sites in response to engagement and hydrolysis of ATP at the nucleotide-binding domains. Here we report that MsbA also utilizes another major energy currency in the cell by coupling substrate transport to a transmembrane electrochemical proton gradient. The dependence of ATP-dependent transport on proton coupling, and the stimulation of MsbA-ATPase by the chemical proton gradient highlight the functional integration of both forms of metabolic energy. These findings introduce ion coupling as a new parameter in the mechanism of this homodimeric ABC transporter. ABC exporters mediate the translocation of cytotoxic compounds to the cell exterior via ATP hydrolysis. Here, the authors show that the bacterial transporter MsbA requires additional energy from the transmembrane electrochemical proton gradient to facilitate drug transport.
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20
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Subramanian N, Condic-Jurkic K, O'Mara ML. Structural and dynamic perspectives on the promiscuous transport activity of P-glycoprotein. Neurochem Int 2016; 98:146-52. [PMID: 27180050 DOI: 10.1016/j.neuint.2016.05.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Revised: 04/28/2016] [Accepted: 05/03/2016] [Indexed: 11/25/2022]
Abstract
The multidrug transporter P-glycoprotein (P-gp) is expressed in the blood-brain barrier endothelium where it effluxes a range of drug substrates, preventing their accumulation within the brain. P-gp has been studied extensively for 40 years because of its crucial role in the absorption, distribution, metabolism and elimination of a range of pharmaceutical compounds. Despite this, many aspects of the structure-function mechanism of P-gp are unresolved. Here we review the emerging role of molecular dynamics simulation techniques in our understanding of the membrane-embedded conformation of P-gp. We discuss its conformational plasticity in the presence and absence of ATP, and recent efforts to characterize the drug binding sites and uptake pathways.
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Affiliation(s)
- Nandhitha Subramanian
- Research School of Chemistry (RSC), The Australian National University, Canberra, ACT, 2601, Australia
| | - Karmen Condic-Jurkic
- School of Chemistry and Molecular Biosciences (SCMB), University of Queensland, Brisbane, QLD, 4072, Australia
| | - Megan L O'Mara
- Research School of Chemistry (RSC), The Australian National University, Canberra, ACT, 2601, Australia. megan.o'
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21
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Ferreira RJ, Ferreira MJU, Dos Santos DJVA. Do drugs have access to the P-glycoprotein drug-binding pocket through gates? J Chem Theory Comput 2015; 11:4525-9. [PMID: 26574244 DOI: 10.1021/acs.jctc.5b00652] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The P-glycoprotein efflux mechanism is being studied since its identification as a leading protagonist in multidrug resistance. Recently, it was suggested that drugs enter the drug-binding pocket (DBP) through gates located between the transmembrane domains. For both a substrate and a modulator, the potential of mean force curves along the reaction coordinate obtained with the WHAM approach were similar, with no activation energy required for crossing the gate. Moreover, drug transit from bulk water into the DBP was characterized as an overall free-energy downhill process.
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Affiliation(s)
- Ricardo J Ferreira
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa , Avenida Prof. Gama Pinto, 1649-003 Lisboa, Portugal
| | - Maria-José U Ferreira
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa , Avenida Prof. Gama Pinto, 1649-003 Lisboa, Portugal
| | - Daniel J V A Dos Santos
- REQUIMTE, Department of Chemistry & Biochemistry, Faculty of Sciences, University of Porto , Rua do Campo Alegre, 4169-007 Porto, Portugal
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22
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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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23
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Trencsényi G, Kertész I, Krasznai ZT, Máté G, Szalóki G, Szabó Judit P, Kárpáti L, Krasznai Z, Márián T, Goda K. 2'[(18)F]-fluoroethylrhodamine B is a promising radiotracer to measure P-glycoprotein function. Eur J Pharm Sci 2015; 74:27-35. [PMID: 25857708 DOI: 10.1016/j.ejps.2015.03.026] [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: 12/10/2014] [Revised: 03/12/2015] [Accepted: 03/31/2015] [Indexed: 12/21/2022]
Abstract
In vivo detection of the emergence of P-glycoprotein (Pgp) mediated multidrug resistance in tumors could be beneficial for patients treated with anticancer drugs. PET technique in combination with appropriate radiotracers could be the most convenient method for detection of Pgp function. Rhodamine derivatives are validated fluorescent probes for measurement of mitochondrial membrane potential and also Pgp function. The aim of this study was to investigate whether 2'[(18)F]-fluoroethylrhodamine B ((18)FRB) a halogenated rhodamine derivative previously synthesized for PET assessment of myocardial perfusion preserved its Pgp substrate character. ATPase assay as well as accumulation experiments carried out using Pgp(+) and Pgp(-) human gynecologic (A2780/A2780(AD) and KB-3-1/KB-V1) and a mouse fibroblast cell pairs (NIH 3T3 and NIH 3T3 MDR1) were applied to study the interaction of (18)FRB with Pgp. ATPase assay proved that (18)FRB is a high affinity substrate of Pgp. Pgp(-) cells accumulated the (18)FRB rapidly in accordance with its lipophilic character. Dissipation of the mitochondrial proton gradient by a proton ionophore CCCP decreased the accumulation of rhodamine 123 (R123) and (18)FRB into Pgp(-) cells. Pgp(+) cells exhibited very low R123 and (18)FRB accumulation (around 1-8% of the Pgp(-) cell lines) which was not sensitive to the mitochondrial proton gradient; rather it was increased by the Pgp inhibitor cyclosporine A (CsA). Based on the above data we conclude that (18)FRB is a high affinity Pgp substrate and consequently a potential PET tracer to detect multidrug resistant tumors as well as the function of physiological barriers expressing Pgp.
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Affiliation(s)
- György Trencsényi
- Department of Nuclear Medicine, University of Debrecen, Nagyerdei krt. 98, H-4032 Debrecen, Hungary
| | - István Kertész
- Department of Nuclear Medicine, University of Debrecen, Nagyerdei krt. 98, H-4032 Debrecen, Hungary
| | - Zoárd T Krasznai
- Department of Obstetrics and Gynecology, University of Debrecen, Nagyerdei krt. 98, H-4032 Debrecen, Hungary
| | - Gábor Máté
- Department of Nuclear Medicine, University of Debrecen, Nagyerdei krt. 98, H-4032 Debrecen, Hungary
| | - Gábor Szalóki
- Department of Biophysics and Cell Biology, University of Debrecen, Nagyerdei krt. 98, H-4032 Debrecen, Hungary
| | - P Szabó Judit
- Department of Nuclear Medicine, University of Debrecen, Nagyerdei krt. 98, H-4032 Debrecen, Hungary
| | - Levente Kárpáti
- Department of Nuclear Medicine, University of Debrecen, Nagyerdei krt. 98, H-4032 Debrecen, Hungary
| | - Zoltán Krasznai
- Department of Biophysics and Cell Biology, University of Debrecen, Nagyerdei krt. 98, H-4032 Debrecen, Hungary
| | - Teréz Márián
- Department of Nuclear Medicine, University of Debrecen, Nagyerdei krt. 98, H-4032 Debrecen, Hungary.
| | - Katalin Goda
- Department of Biophysics and Cell Biology, University of Debrecen, Nagyerdei krt. 98, H-4032 Debrecen, Hungary
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24
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Rudashevskaya EL, Stockner T, Trauner M, Freissmuth M, Chiba P. Pharmacological correction of misfolding of ABC proteins. DRUG DISCOVERY TODAY. TECHNOLOGIES 2015; 12:e87-94. [PMID: 25027379 PMCID: PMC4039138 DOI: 10.1016/j.ddtec.2014.03.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The endoplasmic reticulum (ER) quality control system distinguishes between correctly and incorrectly folded proteins to prevent processing of aberrantly folded conformations along the secretory pathway. Non-synonymous mutations can lead to misfolding of ABC proteins and associated disease phenotypes. Specific phenotypes may at least partially be corrected by small molecules, so-called pharmacological chaperones. Screening for folding correctors is expected to open an avenue for treatment of diseases such as cystic fibrosis and intrahepatic cholestasis.
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Affiliation(s)
- Elena L Rudashevskaya
- Institute of Medical Chemistry, Medical University of Vienna, Waehringerstrasse 10, Vienna, Austria
| | - Thomas Stockner
- Institute of Pharmacology, Medical University of Vienna, Waehringerstrasse 13, Vienna, Austria
| | - Michael Trauner
- Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Waehringer Guertel 18-20, Austria
| | - Michael Freissmuth
- Institute of Pharmacology, Medical University of Vienna, Waehringerstrasse 13, Vienna, Austria
| | - Peter Chiba
- Institute of Medical Chemistry, Medical University of Vienna, Waehringerstrasse 10, Vienna, Austria
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25
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Chufan EE, Sim HM, Ambudkar SV. Molecular basis of the polyspecificity of P-glycoprotein (ABCB1): recent biochemical and structural studies. Adv Cancer Res 2015; 125:71-96. [PMID: 25640267 DOI: 10.1016/bs.acr.2014.10.003] [Citation(s) in RCA: 101] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
ABCB1 (P-glycoprotein/P-gp) is an ATP-binding cassette transporter well known for its association with multidrug resistance in cancer cells. Powered by the hydrolysis of ATP, it effluxes structurally diverse compounds. In this chapter, we discuss current views on the molecular basis of the substrate polyspecificity of P-gp. One of the features that accounts for this property is the structural flexibility observed in P-gp. Several X-ray crystal structures of mouse P-gp have been published recently in the absence of nucleotide, with and without bound inhibitors. All the structures are in an inward-facing conformation exhibiting different degrees of domain separation, thus revealing a highly flexible protein. Biochemical and biophysical studies also demonstrate this flexibility in mouse as well as human P-gp. Site-directed mutagenesis has revealed the existence of multiple transport-active binding sites in P-gp for a single substrate. Thus, drugs can bind at either primary or secondary sites. Biochemical, molecular modeling, and structure-activity relationship studies suggest a large, common drug-binding pocket with overlapping sites for different substrates. We propose that in addition to the structural flexibility, the molecular or chemical flexibility also contributes to the binding of substrates to multiple sites forming the basis of polyspecificity.
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Affiliation(s)
- Eduardo E Chufan
- Center for Cancer Research, Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Hong-May Sim
- Center for Cancer Research, Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Suresh V Ambudkar
- Center for Cancer Research, Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA.
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26
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Ferreira RJ, Ferreira MJU, dos Santos DJVA. Reversing cancer multidrug resistance: insights into the efflux by ABC transports fromin silicostudies. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2014. [DOI: 10.1002/wcms.1196] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Ricardo J. Ferreira
- Instituto de Investigação do Medicamento (iMed.ULisboa), Faculdade de Farmácia; Universidade de Lisboa; Lisboa Portugal
| | - Maria-José U. Ferreira
- Instituto de Investigação do Medicamento (iMed.ULisboa), Faculdade de Farmácia; Universidade de Lisboa; Lisboa Portugal
| | - Daniel J. V. A. dos Santos
- Instituto de Investigação do Medicamento (iMed.ULisboa), Faculdade de Farmácia; Universidade de Lisboa; Lisboa Portugal
- REQUIMTE, Department of Chemistry & Biochemistry, Faculty of Sciences; University of Porto; Porto Portugal
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27
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Zolnerciks JK, Akkaya BG, Snippe M, Chiba P, Seelig A, Linton KJ. The Q loops of the human multidrug resistance transporter ABCB1 are necessary to couple drug binding to the ATP catalytic cycle. FASEB J 2014; 28:4335-46. [PMID: 25016028 DOI: 10.1096/fj.13-245639] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
For a primary active pump, such as the human ATP-binding-cassette (ABC) transporter ABCB1, coupling of drug-binding by the two transmembrane domains (TMDs) to the ATP catalytic cycle of the two nucleotide-binding domains (NBDs) is fundamental to the transport mechanism, but is poorly understood at the biochemical level. Structure data suggest that signals are transduced through intracellular loops of the TMDs that slot into grooves on the NBDs. At the base of these grooves is the Q loop. We therefore mutated the eponymous glutamine in one or both NBD Q loops and measured the effect on conformation and function by using a conformation-sensitive antibody (UIC2) and a fluorescent drug (Bodipy-verapamil), respectively. We showed that the double mutant is trapped in the inward-open state, which binds the drug, but cannot couple to the ATPase cycle. Our data also describe marked redundancy within the transport mechanism, because single-Q-loop mutants are functional for Bodipy-verapamil transport. This result allowed us to elucidate transduction pathways from twin drug-binding cavities to the Q loops using point mutations to favor one cavity over the other. Together, the data show that the Q loop is the central flexion point where the aspect of the drug-binding cavities is coupled to the ATP catalytic cycle.
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Affiliation(s)
- Joseph K Zolnerciks
- Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary, University of London, London UK
| | - Begum G Akkaya
- Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary, University of London, London UK
| | - Marjolein Snippe
- Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary, University of London, London UK
| | - Peter Chiba
- Institute of Medical Chemistry, Medical University of Vienna, Vienna, Austria; and
| | - Anna Seelig
- Biophysical Chemistry Biozentrum, University of Basel, Basel, Switzerland
| | - Kenneth J Linton
- Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary, University of London, London UK;
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28
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Silva R, Carmo H, Vilas-Boas V, Barbosa DJ, Palmeira A, Sousa E, Carvalho F, Bastos MDL, Remião F. Colchicine effect on P-glycoprotein expression and activity: In silico and in vitro studies. Chem Biol Interact 2014; 218:50-62. [PMID: 24759273 DOI: 10.1016/j.cbi.2014.04.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Revised: 03/31/2014] [Accepted: 04/14/2014] [Indexed: 01/22/2023]
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29
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Abstract
AbstractABC transporters comprise a large, diverse, and ubiquitous superfamily of membrane active transporters. Their core architecture is a dimer of dimers, comprising two transmembrane (TM) domains that bind substrate, and two ATP-binding cassettes, which use the cell's energy currency to couple substrate translocation to ATP hydrolysis. Despite the availability of over a dozen resolved structures and a wealth of biochemical and biophysical data, this field is bedeviled by controversy and long-standing mechanistic questions remain unresolved. The prevailing paradigm for the ABC transport mechanism is the Switch Model, in which the ATP-binding cassettes dimerize upon binding two ATP molecules, and thence dissociate upon sequential ATP hydrolysis. This cycle of nucleotide-binding domain (NBD) dimerization and dissociation is coupled to a switch between inward- or outward facing conformations of a single TM channel; this alternating access enables substrate binding on one face of the membrane and its release at the other. Notwithstanding widespread acceptance of the Switch Model, there is substantial evidence that the NBDs do not separate very much, if at all, and thus physical separation of the ATP cassettes observed in crystallographic structures may be an artefact. An alternative Constant Contact Model has been proposed, in which ATP hydrolysis occurs alternately at the two ATP-binding sites, with one of the sites remaining closed and containing occluded nucleotide at all times. In this model, the cassettes remain in contact and the active sites swing open in an alternately seesawing motion. Whilst the concept of NBD association/dissociation in the Switch Model is naturally compatible with a single alternating-access channel, the asymmetric functioning proposed by the Constant Contact model suggests an alternating or reciprocating function in the TMDs. Here, a new model for the function of ABC transporters is proposed in which the sequence of ATP binding, hydrolysis, and product release in each active site is directly coupled to the analogous sequence of substrate binding, translocation and release in one of two functionally separate substrate translocation pathways. Each translocation pathway functions 180° out of phase. A wide and diverse selection of data for both ABC importers and exporters is examined, and the ability of the Switch and Reciprocating Models to explain the data is compared and contrasted. This analysis shows that not only can the Reciprocating Model readily explain the data; it also suggests straightforward explanations for the function of a number of atypical ABC transporters. This study represents the most coherent and complete attempt at an all-encompassing scheme to explain how these important proteins work, one that is consistent with sound biochemical and biophysical evidence.
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30
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Li W, Sharma M, Kaur P. The DrrAB efflux system of Streptomyces peucetius is a multidrug transporter of broad substrate specificity. J Biol Chem 2014; 289:12633-46. [PMID: 24634217 DOI: 10.1074/jbc.m113.536136] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The soil bacterium Streptomyces peucetius produces two widely used anticancer antibiotics, doxorubicin and daunorubicin. Present within the biosynthesis gene cluster in S. peucetius is the drrAB operon, which codes for a dedicated ABC (ATP binding cassette)-type transporter for the export of these two closely related antibiotics. Because of its dedicated nature, the DrrAB system is believed to belong to the category of single-drug transporters. However, whether it also contains specificity for other known substrates of multidrug transporters has never been tested. In this study we demonstrate under both in vivo and in vitro conditions that the DrrAB system can transport not only doxorubicin but is also able to export two most commonly studied MDR substrates, Hoechst 33342 and ethidium bromide. Moreover, we demonstrate that many other substrates (including verapamil, vinblastine, and rifampicin) of the well studied multidrug transporters inhibit DrrAB-mediated Dox transport with high efficiency, indicating that they are also substrates of the DrrAB pump. Kinetic studies show that inhibition of doxorubicin transport by Hoechst 33342 and rifampicin occurs by a competitive mechanism, whereas verapamil inhibits transport by a non-competitive mechanism, thus suggesting the possibility of more than one drug binding site in the DrrAB system. This is the first in-depth study of a drug resistance system from a producer organism, and it shows that a dedicated efflux system like DrrAB contains specificity for multiple drugs. The significance of these findings in evolution of poly-specificity in drug resistance systems is discussed.
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Affiliation(s)
- Wen Li
- From the Department of Biology, Georgia State University, Atlanta, Georgia 30303
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31
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Sharom FJ. Complex Interplay between the P-Glycoprotein Multidrug Efflux Pump and the Membrane: Its Role in Modulating Protein Function. Front Oncol 2014; 4:41. [PMID: 24624364 PMCID: PMC3939933 DOI: 10.3389/fonc.2014.00041] [Citation(s) in RCA: 184] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Accepted: 02/17/2014] [Indexed: 11/16/2022] Open
Abstract
Multidrug resistance in cancer is linked to expression of the P-glycoprotein multidrug transporter (Pgp, ABCB1), which exports many structurally diverse compounds from cells. Substrates first partition into the bilayer and then interact with a large flexible binding pocket within the transporter's transmembrane regions. Pgp has been described as a hydrophobic vacuum cleaner or an outwardly directed drug/lipid flippase. Recent X-ray crystal structures have shed some light on the nature of the drug-binding pocket and suggested routes by which substrates can enter it from the membrane. Detergents have profound effects on Pgp function, and several appear to be substrates. Biochemical and biophysical studies in vitro, some using purified reconstituted protein, have explored the effects of the membrane environment. They have demonstrated that Pgp is involved in a complex relationship with its lipid environment, which modulates the behavior of its substrates, as well as various functions of the protein, including ATP hydrolysis, drug binding, and drug transport. Membrane lipid composition and fluidity, phospholipid headgroup and acyl chain length all influence Pgp function. Recent studies focusing on thermodynamics and kinetics have revealed some important principles governing Pgp-lipid and substrate-lipid interactions, and how these affect drug-binding and transport. In some cells, Pgp is associated with cholesterol-rich microdomains, which may modulate its functions. The relationship between Pgp and cholesterol remains an open question; however, it clearly affects several aspects of its function in addition to substrate-membrane partitioning. The action of Pgp modulators appears to depend on their membrane permeability, and membrane fluidizers and surfactants reverse drug resistance, likely via an indirect mechanism. A detailed understanding of how the membrane affects Pgp substrates and Pgp's catalytic cycle may lead to new strategies to combat clinical drug resistance.
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Affiliation(s)
- Frances Jane Sharom
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada
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32
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Scian M, Acchione M, Li M, Atkins WM. Reaction dynamics of ATP hydrolysis catalyzed by P-glycoprotein. Biochemistry 2014; 53:991-1000. [PMID: 24506763 PMCID: PMC3985762 DOI: 10.1021/bi401280v] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
![]()
P-glycoprotein
(P-gp) is a member of the ABC transporter family
that confers drug resistance to many tumors by catalyzing their efflux,
and it is a major component of drug–drug interactions. P-gp
couples drug efflux with ATP hydrolysis by coordinating conformational
changes in the drug binding sites with the hydrolysis of ATP and release
of ADP. To understand the relative rates of the chemical step for
hydrolysis and the conformational changes that follow it, we exploited
isotope exchange methods to determine the extent to which the ATP
hydrolysis step is reversible. With γ18O4-labeled ATP, no positional isotope exchange is detectable at the
bridging β-phosphorus–O−γ-phosphorus bond.
Furthermore, the phosphate derived from hydrolysis includes a constant
ratio of three 18O/two 18O/one 18O that reflects the isotopic composition of the starting ATP in multiple
experiments. Thus, H2O-exchange with HPO42– (Pi) was negligible, suggesting that a
[P-gp·ADP·Pi] is not long-lived. This further
demonstrates that the hydrolysis is essentially irreversible in the
active site. These mechanistic details of ATP hydrolysis are consistent
with a very fast conformational change immediately following, or concomitant
with, hydrolysis of the γ-phosphate linkage that ensures a high
commitment to catalysis in both drug-free and drug-bound states.
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Affiliation(s)
- Michele Scian
- Department of Medicinal Chemistry, University of Washington , Box 357610, Seattle, Washington 98195-7610, United States
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33
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Klepsch F, Vasanthanathan P, Ecker GF. Ligand and structure-based classification models for prediction of P-glycoprotein inhibitors. J Chem Inf Model 2014; 54:218-29. [PMID: 24050383 PMCID: PMC3904775 DOI: 10.1021/ci400289j] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The ABC transporter P-glycoprotein (P-gp) actively transports a wide range of drugs and toxins out of cells, and is therefore related to multidrug resistance and the ADME profile of therapeutics. Thus, development of predictive in silico models for the identification of P-gp inhibitors is of great interest in the field of drug discovery and development. So far in silico P-gp inhibitor prediction was dominated by ligand-based approaches because of the lack of high-quality structural information about P-gp. The present study aims at comparing the P-gp inhibitor/noninhibitor classification performance obtained by docking into a homology model of P-gp, to supervised machine learning methods, such as Kappa nearest neighbor, support vector machine (SVM), random fores,t and binary QSAR, by using a large, structurally diverse data set. In addition, the applicability domain of the models was assessed using an algorithm based on Euclidean distance. Results show that random forest and SVM performed best for classification of P-gp inhibitors and noninhibitors, correctly predicting 73/75% of the external test set compounds. Classification based on the docking experiments using the scoring function ChemScore resulted in the correct prediction of 61% of the external test set. This demonstrates that ligand-based models currently remain the methods of choice for accurately predicting P-gp inhibitors. However, structure-based classification offers information about possible drug/protein interactions, which helps in understanding the molecular basis of ligand-transporter interaction and could therefore also support lead optimization.
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Affiliation(s)
- Freya Klepsch
- University of Vienna , Department of Medicinal Chemistry, Althanstraße 14, 1090 Vienna, Austria
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Dönmez Cakil Y, Khunweeraphong N, Parveen Z, Schmid D, Artaker M, Ecker GF, Sitte HH, Pusch O, Stockner T, Chiba P. Pore-exposed tyrosine residues of P-glycoprotein are important hydrogen-bonding partners for drugs. Mol Pharmacol 2013; 85:420-8. [PMID: 24366667 DOI: 10.1124/mol.113.088526] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The multispecific efflux transporter, P-glycoprotein, plays an important role in drug disposition. Substrate translocation occurs along the interface of its transmembrane domains. The rotational C2 symmetry of ATP-binding cassette transporters implies the existence of two symmetry-related sets of substrate-interacting amino acids. These sets are identical in homodimeric transporters, and remain evolutionary related in full transporters, such as P-glycoprotein, in which substrates bind preferentially, but nonexclusively, to one of two binding sites. We explored the role of pore-exposed tyrosines for hydrogen-bonding interactions with propafenone type ligands in their preferred binding site 2. Tyrosine 953 is shown to form hydrogen bonds not only with propafenone analogs, but also with the preferred site 1 substrate rhodamine123. Furthermore, an accessory role of tyrosine 950 for binding of selected propafenone analogs is demonstrated. The present study demonstrates the importance of domain interface tyrosine residues for interaction of small molecules with P-glycoprotein.
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Affiliation(s)
- Yaprak Dönmez Cakil
- Institutes of Medical Chemistry (Y.D.C., N.K., Z.P., P.C.), Pharmacology (Y.D.C., H.H.S., T.S.), and Physiology (D.S.), Department of Medical Biochemistry, Max F. Perutz Laboratories (M.A.), and Department of Cell and Developmental Biology (O.P.), Medical University of Vienna, Vienna, Austria; Department of Biochemistry, Abdul Wali Khan University Mardan, Pakistan (Z.P.); and Emerging Field Pharmacoinformatics, Department of Medicinal Chemistry, University of Vienna, Vienna, Austria (G.F.E.)
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35
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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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36
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Jabeen I, Pleban K, Rinner U, Chiba P, Ecker GF. Structure-activity relationships, ligand efficiency, and lipophilic efficiency profiles of benzophenone-type inhibitors of the multidrug transporter P-glycoprotein. J Med Chem 2012; 55:3261-73. [PMID: 22452412 PMCID: PMC3326594 DOI: 10.1021/jm201705f] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
![]()
The drug efflux pump P-glycoprotein (P-gp) has been shown
to promote
multidrug resistance (MDR) in tumors as well as to influence ADME
properties of drug candidates. Here we synthesized and tested a series
of benzophenone derivatives structurally analogous to propafenone-type
inhibitors of P-gp. Some of the compounds showed ligand efficiency
and lipophilic efficiency (LipE) values in the range of compounds
which entered clinical trials as MDR modulators. Interestingly, although
lipophilicity plays a dominant role for P-gp inhibitors, all compounds
investigated showed LipE values below the threshold for promising
drug candidates. Docking studies of selected analogues into a homology
model of P-glycoprotein suggest that benzophenones show an interaction
pattern similar to that previously identified for propafenone-type
inhibitors.
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Affiliation(s)
- Ishrat Jabeen
- University of Vienna, Department of Medicinal Chemistry, Althanstrasse 14, 1090, Vienna, Austria
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37
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Mandal D, Moitra K, Ghosh D, Xia D, Dey S. Evidence for modulatory sites at the lipid-protein interface of the human multidrug transporter P-glycoprotein. Biochemistry 2012; 51:2852-66. [PMID: 22360349 DOI: 10.1021/bi201479k] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The human multidrug transporter P-glycoprotein (Pgp or ABCB1) sets up pharmacological barriers to many clinically important drugs, a therapeutic remedy for which has yet to be formulated. For the rational design of mechanism-based inhibitors (or modulators), it is necessary to map the potential sites for modulator interaction and understand their modes of communication with the other functional domains of Pgp. In this study, combining directed mutagenesis with homology modeling, we provide evidence of two modulator-specific sites at the lipid protein interface of Pgp. Targeting 21 variant positions in the COOH-terminal transmembrane (TM) regions, we find residues M948 (in TM11) and F983, M986, V988, and Q990 (all four in TM12) critically involved in substrate-site modulation by a thioxanthene-based allosteric modulator cis-(Z)-flupentixol. Interestingly, for ATP-site modulation by the same modulator, only two (M948 and Q990) of those four residues appear indispensable, together with two additional residues, T837 and I864 in TM9 and TM10, respectively, suggesting independent modes of communication linking the allosteric site with the substrate binding and ATPase domains. None of the seven residues identified prove to be critical for modulation of the substrate or ATP sites by Pgp modulators that are transported by the pump, such as cyclosporin A or verapamil, indicating their specificity for cis-(Z)-flupentixol. On the other hand, ATP-site modulation by verapamil proves to be highly sensitive to replacement at positions F716 (in TM7) and I765 (in TM8), and to a more moderate extent at I764 and L772 (both in TM8). Homology modeling based on the known crystal structures of the bacterial multidrug transporter SAV1866 and the mouse Pgp homologue maps the identified residues primarily at the lipid-protein interface of Pgp, in two spatially distinct modulator-specific clusters. The two modulatory sites demonstrate negative synergism in influencing ATP hydrolysis, consolidating their spatial distinctness. Because Pgp is known to recruit drug molecules directly from the lipid bilayer, identification of modulatory sites at the lipid-protein interface and at the same time outside the conventional central drug binding cavity is mechanistically revealing.
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Affiliation(s)
- Debjani Mandal
- Department of Biochemistry, Uniformed Services University School of Medicine, Bethesda, Maryland 20814, United States
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Sodani K, Tiwari AK, Singh S, Patel A, Xiao ZJ, Chen JJ, Sun YL, Talele TT, Chen ZS. GW583340 and GW2974, human EGFR and HER-2 inhibitors, reverse ABCG2- and ABCB1-mediated drug resistance. Biochem Pharmacol 2012; 83:1613-22. [PMID: 22414725 DOI: 10.1016/j.bcp.2012.02.028] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2012] [Revised: 02/27/2012] [Accepted: 02/28/2012] [Indexed: 01/31/2023]
Abstract
The overexpression of ATP binding cassette (ABC) transporters often leads to the development of multidrug resistance (MDR) and results in a suboptimal response to chemotherapy. Previously, we reported that lapatinib (GW572016), a human epidermal growth factor receptor (EGFR) and HER-2 tyrosine kinase inhibitor (TKI), significantly reverses MDR in cancer cells by blocking the efflux function of ABC subfamily B member 1 (ABCB1) and ABC subfamily G member 2 (ABCG2). In the present study, we conducted in vitro experiments to evaluate if GW583340 and GW2974, structural analogues of lapatinib, could reverse ABCB1- and ABCG2-mediated MDR. Our results showed that GW583340 and GW2974 significantly sensitized ABCB1 and ABCG2 overexpressing MDR cells to their anticancer substrates. GW583340 and GW2974 significantly increased the intracellular accumulation of [(3)H]-paclitaxel in ABCB1 overexpressing cells and [(3)H]-mitoxantrone in ABCG2 overexpressing cells respectively. In addition, GW583340 and GW2974 significantly inhibited ABCG2-mediated transport of methotrexate in ABCG2 overexpressing membrane vesicles. There was no significant change in the expression levels of ABCB1 and ABCG2 in the cell lines exposed to 5μM of either GW583340 or GW2974 for 3 days. In addition, a docking model predicted the binding conformation of GW583340 and GW2974 to be within the transmembrane region of homology modeled human ABCB1 and ABCG2. We conclude that GW583340 and GW2974, at clinically achievable plasma concentrations, reverse ABCB1- and ABCG2-mediated MDR by blocking the drug efflux function of these transporters. These findings may be useful in developing combination therapy for cancer treatment with EGFR TKIs.
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Affiliation(s)
- Kamlesh Sodani
- Department of Pharmaceutical Sciences, College of Pharmacy and Allied Health Professions, St. John's University, Queens, NY 11439, USA
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Determining P-glycoprotein-drug interactions: evaluation of reconstituted P-glycoprotein in a liposomal system and LLC-MDR1 polarized cell monolayers. J Pharmacol Toxicol Methods 2012; 65:64-74. [PMID: 22394995 DOI: 10.1016/j.vascn.2012.02.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Revised: 02/14/2012] [Accepted: 02/17/2012] [Indexed: 11/22/2022]
Abstract
INTRODUCTION P-Glycoprotein (ABCB1, MDR1) is a multidrug efflux pump that is a member of the ATP-binding cassette (ABC) superfamily. Many drugs in common clinical use are either substrates or inhibitors of this transporter. Quantitative details of P-glycoprotein inhibition by pharmaceutical agents are essential for assessment of their pharmacokinetic behavior and prevention of negative patient reactions. Cell-based systems have been widely used for determination of drug interactions with P-glycoprotein, but they suffer from several disadvantages, and results are often widely variable between laboratories. We aimed to demonstrate that a novel liposomal system employing contemporary biochemical methodologies could measure the ability of clinically used drugs to inhibit the P-glycoprotein pump. To accomplish this we compared results with those of cell-based approaches. METHODS Purified transport-competent hamster Abcb1a P-glycoprotein was reconstituted into a unilamellar liposomal system, Fluorosome-trans-pgp, whose aqueous interior contains fluorescent drug sensors. This provides a well-defined system for measuring P-glycoprotein transport inhibition by test drugs in real time using rapid fluorescence-based technology. RESULTS Inhibition of ATP-driven transport by Fluorosome-trans-pgp employed a panel of 46 representative drugs. Resulting IC50 values correlated well (r2=0.80) with Kd values for drug binding to purified P-glycoprotein. They also showed a similar trend to transport inhibition data obtained using LLC-MDR1 cell monolayers. Fluorosome-trans-pgp IC50 values were in agreement with published results of digoxin drug-drug interaction studies in humans. DISCUSSION This novel approach using a liposomal system and fluorescence-based technology is shown to be suitable to study whether marketed drugs and drug candidates are P-glycoprotein inhibitors. The assay is rapid, allowing a 7-point IC50 determination in <6 min, and requires minimal quantities of test drug. The method is amenable to robotics and offers a cost advantage relative to conventional cell-based assays. The well-defined nature of this assay also obviates many of the inherent complications and ambiguities of cell-based systems.
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Exhaustive sampling of docking poses reveals binding hypotheses for propafenone type inhibitors of P-glycoprotein. PLoS Comput Biol 2011. [PMID: 21589945 DOI: 10.1371/journal.pcbi.1002036]] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Overexpression of the xenotoxin transporter P-glycoprotein (P-gp) represents one major reason for the development of multidrug resistance (MDR), leading to the failure of antibiotic and cancer therapies. Inhibitors of P-gp have thus been advocated as promising candidates for overcoming the problem of MDR. However, due to lack of a high-resolution structure the concrete mode of interaction of both substrates and inhibitors is still not known. Therefore, structure-based design studies have to rely on protein homology models. In order to identify binding hypotheses for propafenone-type P-gp inhibitors, five different propafenone derivatives with known structure-activity relationship (SAR) pattern were docked into homology models of the apo and the nucleotide-bound conformation of the transporter. To circumvent the uncertainty of scoring functions, we exhaustively sampled the pose space and analyzed the poses by combining information retrieved from SAR studies with common scaffold clustering. The results suggest propafenone binding at the transmembrane helices 5, 6, 7 and 8 in both models, with the amino acid residue Y307 playing a crucial role. The identified binding site in the non-energized state is overlapping with, but not identical to, known binding areas of cyclic P-gp inhibitors and verapamil. These findings support the idea of several small binding sites forming one large binding cavity. Furthermore, the binding hypotheses for both catalytic states were analyzed and showed only small differences in their protein-ligand interaction fingerprints, which indicates only small movements of the ligand during the catalytic cycle.
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Klepsch F, Chiba P, Ecker GF. Exhaustive sampling of docking poses reveals binding hypotheses for propafenone type inhibitors of P-glycoprotein. PLoS Comput Biol 2011; 7:e1002036. [PMID: 21589945 PMCID: PMC3093348 DOI: 10.1371/journal.pcbi.1002036] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2010] [Accepted: 03/09/2011] [Indexed: 01/01/2023] Open
Abstract
Overexpression of the xenotoxin transporter P-glycoprotein (P-gp) represents one major reason for the development of multidrug resistance (MDR), leading to the failure of antibiotic and cancer therapies. Inhibitors of P-gp have thus been advocated as promising candidates for overcoming the problem of MDR. However, due to lack of a high-resolution structure the concrete mode of interaction of both substrates and inhibitors is still not known. Therefore, structure-based design studies have to rely on protein homology models. In order to identify binding hypotheses for propafenone-type P-gp inhibitors, five different propafenone derivatives with known structure-activity relationship (SAR) pattern were docked into homology models of the apo and the nucleotide-bound conformation of the transporter. To circumvent the uncertainty of scoring functions, we exhaustively sampled the pose space and analyzed the poses by combining information retrieved from SAR studies with common scaffold clustering. The results suggest propafenone binding at the transmembrane helices 5, 6, 7 and 8 in both models, with the amino acid residue Y307 playing a crucial role. The identified binding site in the non-energized state is overlapping with, but not identical to, known binding areas of cyclic P-gp inhibitors and verapamil. These findings support the idea of several small binding sites forming one large binding cavity. Furthermore, the binding hypotheses for both catalytic states were analyzed and showed only small differences in their protein-ligand interaction fingerprints, which indicates only small movements of the ligand during the catalytic cycle.
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Affiliation(s)
- Freya Klepsch
- Department of Medicinal Chemistry, University of Vienna, Vienna, Austria
| | - Peter Chiba
- Institute of Medical Chemistry, Medical University of Vienna, Vienna, Austria
| | - Gerhard F. Ecker
- Department of Medicinal Chemistry, University of Vienna, Vienna, Austria
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Gao M, Yamazaki M, Loe DW, Westlake CJ, Grant CE, Cole SP, Deeley RG. Multidrug resistance protein. Identification of regions required for active transport of leukotriene C4. J Biol Chem 1998; 273:10733-10740. [PMID: 9553138 DOI: 10.1002/9781118705308.ch9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023] Open
Abstract
Multidrug resistance protein (MRP) is a broad specificity, primary active transporter of organic anion conjugates that confers a multidrug resistance phenotype when transfected into drug-sensitive cells. The protein was the first example of a subgroup of the ATP-binding cassette superfamily whose members have three membrane-spanning domains (MSDs) and two nucleotide binding domains. The role(s) of the third MSD of MRP and its related transporters is not known. To begin to address this question, we examined the ability of various MRP fragments, expressed individually and in combination, to transport the MRP substrate, leukotriene C4 (LTC4). We found that elimination of the entire NH2-terminal MSD or just the first putative transmembrane helix, or substitution of the MSD with the comparable region of the functionally and structurally related transporter, the canalicular multispecific organic anion transporter (cMOAT/MRP2), had little effect on protein accumulation in the membrane. However, all three modifications decreased LTC4 transport activity by at least 90%. Transport activity could be reconstituted by co-expression of the NH2-terminal MSD with a fragment corresponding to the remainder of the MRP molecule, but this required both the region encoding the transmembrane helices of the NH2-terminal MSD and the cytoplasmic region linking it to the next MSD. In contrast, a major part of the cytoplasmic region linking the NH2-proximal nucleotide binding domain of the protein to the COOH-proximal MSD was not required for active transport of LTC4.
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Affiliation(s)
- M Gao
- Cancer Research Laboratories, Queen's University, Kingston, Ontario K7L 3N6, Canada
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