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Sajid A, Lusvarghi S, Chufan EE, Ambudkar SV. Evidence for the critical role of transmembrane helices 1 and 7 in substrate transport by human P-glycoprotein (ABCB1). PLoS One 2018; 13:e0204693. [PMID: 30265721 PMCID: PMC6161881 DOI: 10.1371/journal.pone.0204693] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 09/12/2018] [Indexed: 12/15/2022] Open
Abstract
P-glycoprotein (P-gp) is an ABC transporter that exports many amphipathic or hydrophobic compounds, including chemically and functionally dissimilar anticancer drugs, from cells. To understand the role of transmembrane helices (TMH) 1 and 7 in drug-binding and transport, we selected six residues from both TMH1 (V53, I59, I60, L65, M68 and F72) and TMH7 (V713, I719, I720, Q725, F728 and F732); and substituted them with alanine by gene synthesis to generate a variant termed "TMH1,7 mutant P-gp". The expression and function of TMH1,7 mutant P-gp with twelve mutations was characterized using the BacMam baculovirus-HeLa cell expression system. The expression and conformation of TMH1,7 mutant P-gp was not altered by the introduction of the twelve mutations, as confirmed by using the human P-gp-specific antibodies UIC2, MRK16 and 4E3. We tested 25 fluorescently-labeled substrates and found that only three substrates, NBD-cyclosporine A, Rhod-2-AM and X-Rhod-1-AM were transported by the TMH1,7 mutant. The basal ATPase activity of TMH1,7 mutant P-gp was lower (40-50%) compared to wild-type (WT) P-gp, despite similar level of expression. Although most of the substrates modulate ATPase activity of P-gp, the activity of TMH1,7 mutant transporter was not significantly modulated by any of the tested substrates. Docking of selected substrates in homology models showed comparable docking scores for the TMH1,7 mutant and WT P-gp, although the binding conformations were different. Both the ATPase assay and in silico docking analyses suggest that the interactions with residues in the drug-binding pocket are altered as a consequence of the mutations. We demonstrate that it is possible to generate a variant of P-gp with a loss of broad substrate specificity and propose that TMH1 and TMH7 play a critical role in the drug efflux function of this multidrug transporter.
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Affiliation(s)
- Andaleeb Sajid
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Sabrina Lusvarghi
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Eduardo E. Chufan
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Suresh V. Ambudkar
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
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Shukla S, Abel B, Chufan EE, Ambudkar SV. Effects of a detergent micelle environment on P-glycoprotein (ABCB1)-ligand interactions. J Biol Chem 2017; 292:7066-7076. [PMID: 28283574 DOI: 10.1074/jbc.m116.771634] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Revised: 03/06/2017] [Indexed: 11/06/2022] Open
Abstract
P-glycoprotein (P-gp) is a multidrug transporter that uses energy from ATP hydrolysis to export many structurally dissimilar hydrophobic and amphipathic compounds, including anticancer drugs from cells. Several structural studies on purified P-gp have been reported, but only limited and sometimes conflicting information is available on ligand interactions with the isolated transporter in a dodecyl-maltoside detergent environment. In this report we compared the biochemical properties of P-gp in native membranes, detergent micelles, and when reconstituted in artificial membranes. We found that the modulators zosuquidar, tariquidar, and elacridar stimulated the ATPase activity of purified human or mouse P-gp in a detergent micelle environment. In contrast, these drugs inhibited ATPase activity in native membranes or in proteoliposomes, with IC50 values in the 10-40 nm range. Similarly, a 30-150-fold decrease in the apparent affinity for verapamil and cyclic peptide inhibitor QZ59-SSS was observed in detergent micelles compared with native or artificial membranes. Together, these findings demonstrate that the high-affinity site is inaccessible because of either a conformational change or binding of detergent at the binding site in a detergent micelle environment. The ligands bind to a low-affinity site, resulting in altered modulation of P-gp ATPase activity. We, therefore, recommend studying structural and functional aspects of ligand interactions with purified P-gp and other ATP-binding cassette transporters that transport amphipathic or hydrophobic substrates in a detergent-free native or artificial membrane environment.
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Affiliation(s)
- Suneet Shukla
- From the Laboratory of Cell Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Biebele Abel
- From the Laboratory of Cell Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Eduardo E Chufan
- From the Laboratory of Cell Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Suresh V Ambudkar
- From the Laboratory of Cell Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
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Esser L, Zhou F, Pluchino KM, Shiloach J, Ma J, Tang WK, Gutierrez C, Zhang A, Shukla S, Madigan JP, Zhou T, Kwong PD, Ambudkar SV, Gottesman MM, Xia D. Structures of the Multidrug Transporter P-glycoprotein Reveal Asymmetric ATP Binding and the Mechanism of Polyspecificity. J Biol Chem 2016; 292:446-461. [PMID: 27864369 DOI: 10.1074/jbc.m116.755884] [Citation(s) in RCA: 132] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Revised: 11/15/2016] [Indexed: 12/25/2022] Open
Abstract
P-glycoprotein (P-gp) is a polyspecific ATP-dependent transporter linked to multidrug resistance in cancer; it plays important roles in determining the pharmacokinetics of many drugs. Understanding the structural basis of P-gp, substrate polyspecificity has been hampered by its intrinsic flexibility, which is facilitated by a 75-residue linker that connects the two halves of P-gp. Here we constructed a mutant murine P-gp with a shortened linker to facilitate structural determination. Despite dramatic reduction in rhodamine 123 and calcein-AM transport, the linker-shortened mutant P-gp possesses basal ATPase activity and binds ATP only in its N-terminal nucleotide-binding domain. Nine independently determined structures of wild type, the linker mutant, and a methylated P-gp at up to 3.3 Å resolution display significant movements of individual transmembrane domain helices, which correlated with the opening and closing motion of the two halves of P-gp. The open-and-close motion alters the surface topology of P-gp within the drug-binding pocket, providing a mechanistic explanation for the polyspecificity of P-gp in substrate interactions.
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Affiliation(s)
- Lothar Esser
- From the Laboratory of Cell Biology, Center for Cancer Research, NCI
| | - Fei Zhou
- From the Laboratory of Cell Biology, Center for Cancer Research, NCI
| | | | | | - Jichun Ma
- From the Laboratory of Cell Biology, Center for Cancer Research, NCI
| | - Wai-Kwan Tang
- From the Laboratory of Cell Biology, Center for Cancer Research, NCI
| | - Camilo Gutierrez
- From the Laboratory of Cell Biology, Center for Cancer Research, NCI
| | - Alex Zhang
- From the Laboratory of Cell Biology, Center for Cancer Research, NCI
| | - Suneet Shukla
- From the Laboratory of Cell Biology, Center for Cancer Research, NCI
| | - James P Madigan
- From the Laboratory of Cell Biology, Center for Cancer Research, NCI
| | - Tongqing Zhou
- the Vaccine Research Center, NIAID, National Institutes of Health, Bethesda, Maryland 20892
| | - Peter D Kwong
- the Vaccine Research Center, NIAID, National Institutes of Health, Bethesda, Maryland 20892
| | - Suresh V Ambudkar
- From the Laboratory of Cell Biology, Center for Cancer Research, NCI
| | | | - Di Xia
- From the Laboratory of Cell Biology, Center for Cancer Research, NCI,
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Pluchino KM, Hall MD, Moen JK, Chufan EE, Fetsch PA, Shukla S, Gill DR, Hyde SC, Xia D, Ambudkar SV, Gottesman MM. Human-Mouse Chimeras with Normal Expression and Function Reveal That Major Domain Swapping Is Tolerated by P-Glycoprotein (ABCB1). Biochemistry 2016; 55:1010-23. [PMID: 26820614 DOI: 10.1021/acs.biochem.5b01064] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The efflux transporter P-glycoprotein (P-gp) plays a vital role in the transport of molecules across cell membranes and has been shown to interact with a panoply of functionally and structurally unrelated compounds. How human P-gp interacts with this large number of drugs has not been well understood, although structural flexibility has been implicated. To gain insight into this transporter's broad substrate specificity and to assess its ability to accommodate a variety of molecular and structural changes, we generated human-mouse P-gp chimeras by the exchange of homologous transmembrane and nucleotide-binding domains. High-level expression of these chimeras by BacMam- and baculovirus-mediated transduction in mammalian (HeLa) and insect cells, respectively, was achieved. There were no detectable differences between wild-type and chimeric P-gp in terms of cell surface expression, ability to efflux the P-gp substrates rhodamine 123, calcein-AM, and JC-1, or to be inhibited by the substrate cyclosporine A and the inhibitors tariquidar and elacridar. Additionally, expression of chimeric P-gp was able to confer a paclitaxel-resistant phenotype to HeLa cells characteristic of P-gp-mediated drug resistance. P-gp ATPase assays and photo-cross-linking with [(125)I]iodoarylazidoprazosin confirmed that transport and biochemical properties of P-gp chimeras were similar to those of wild-type P-gp, although differences in drug binding were detected when human and mouse transmembrane domains were combined. Overall, chimeras with one or two mouse P-gp domains were deemed functionally equivalent to human wild-type P-gp, demonstrating the ability of human P-gp to tolerate major structural changes.
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Affiliation(s)
- Kristen M Pluchino
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health , Bethesda, Maryland 20892, United States.,Gene Medicine Research Group, Nuffield Department of Clinical Laboratory Sciences, Radcliffe Department of Medicine, University of Oxford , Oxford OX3 9DU, U.K
| | - Matthew D Hall
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health , Bethesda, Maryland 20892, United States
| | - Janna K Moen
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health , Bethesda, Maryland 20892, United States
| | - Eduardo E Chufan
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health , Bethesda, Maryland 20892, United States
| | - Patricia A Fetsch
- Laboratory of Pathology, National Cancer Institute, National Institutes of Health , Bethesda, Maryland 20892, United States
| | - Suneet Shukla
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health , Bethesda, Maryland 20892, United States
| | - Deborah R Gill
- Gene Medicine Research Group, Nuffield Department of Clinical Laboratory Sciences, Radcliffe Department of Medicine, University of Oxford , Oxford OX3 9DU, U.K
| | - Stephen C Hyde
- Gene Medicine Research Group, Nuffield Department of Clinical Laboratory Sciences, Radcliffe Department of Medicine, University of Oxford , Oxford OX3 9DU, U.K
| | - Di Xia
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health , Bethesda, Maryland 20892, United States
| | - Suresh V Ambudkar
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health , Bethesda, Maryland 20892, United States
| | - Michael M Gottesman
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health , Bethesda, Maryland 20892, United States
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Weidner LD, Fung KL, Kannan P, Moen JK, Kumar JS, Mulder J, Innis RB, Gottesman MM, Hall MD. Tariquidar Is an Inhibitor and Not a Substrate of Human and Mouse P-glycoprotein. ACTA ACUST UNITED AC 2015; 44:275-82. [PMID: 26658428 DOI: 10.1124/dmd.115.067785] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Accepted: 12/08/2015] [Indexed: 01/15/2023]
Abstract
Since its development, tariquidar (TQR; XR9576; N-[2-[[4-[2-(6,7-Dimethoxy-3,4-dihydro-1H-isoquinolin-2-yl)ethyl]phenyl]carbamoyl]-4,5-dimethoxyphenyl]quinoline-3-carboxamide) has been widely regarded as one of the more potent inhibitors of P-glycoprotein (P-gp), an efflux transporter of the ATP-binding cassette (ABC) transporter family. A third-generation inhibitor, TQR exhibits high affinity for P-gp, although it is also a substrate of another ABC transporter, breast cancer resistance protein (BCRP). Recently, several studies have questioned the mechanism by which TQR interfaces with P-gp, suggesting that TQR is a substrate for P-gp instead of a noncompetitive inhibitor. We investigated TQR and its interaction with human and mouse P-gp to determine if TQR is a substrate of P-gp in vitro. To address these questions, we used multiple in vitro transporter assays, including cytotoxicity, flow cytometry, accumulation, ATPase, and transwell assays. A newly generated BCRP cell line was used as a positive control that demonstrates TQR-mediated transport. Based on our results, we conclude that TQR is a potent inhibitor of both human and mouse P-gp and shows no signs of being a substrate at the concentrations tested. These in vitro data further support our position that the in vivo uptake of [(11)C]TQR into the brain can be explained by its high-affinity binding to P-gp and by it being a substrate of BCRP, followed by amplification of the brain signal by ionic trapping in acidic lysosomes.
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Affiliation(s)
- Lora D Weidner
- Molecular Imaging Branch, National Institute of Mental Health, Bethesda, Maryland (L.D.W., P.K., R.B.I.); Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland (K.L.F., J.K.M., J.S.K., M.M.G., M.D.H.); and Karolinska Institutet, Department of Neuroscience, Stockholm, Sweden (L.D.W., J.M.)
| | - King Leung Fung
- Molecular Imaging Branch, National Institute of Mental Health, Bethesda, Maryland (L.D.W., P.K., R.B.I.); Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland (K.L.F., J.K.M., J.S.K., M.M.G., M.D.H.); and Karolinska Institutet, Department of Neuroscience, Stockholm, Sweden (L.D.W., J.M.)
| | - Pavitra Kannan
- Molecular Imaging Branch, National Institute of Mental Health, Bethesda, Maryland (L.D.W., P.K., R.B.I.); Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland (K.L.F., J.K.M., J.S.K., M.M.G., M.D.H.); and Karolinska Institutet, Department of Neuroscience, Stockholm, Sweden (L.D.W., J.M.)
| | - Janna K Moen
- Molecular Imaging Branch, National Institute of Mental Health, Bethesda, Maryland (L.D.W., P.K., R.B.I.); Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland (K.L.F., J.K.M., J.S.K., M.M.G., M.D.H.); and Karolinska Institutet, Department of Neuroscience, Stockholm, Sweden (L.D.W., J.M.)
| | - Jeyan S Kumar
- Molecular Imaging Branch, National Institute of Mental Health, Bethesda, Maryland (L.D.W., P.K., R.B.I.); Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland (K.L.F., J.K.M., J.S.K., M.M.G., M.D.H.); and Karolinska Institutet, Department of Neuroscience, Stockholm, Sweden (L.D.W., J.M.)
| | - Jan Mulder
- Molecular Imaging Branch, National Institute of Mental Health, Bethesda, Maryland (L.D.W., P.K., R.B.I.); Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland (K.L.F., J.K.M., J.S.K., M.M.G., M.D.H.); and Karolinska Institutet, Department of Neuroscience, Stockholm, Sweden (L.D.W., J.M.)
| | - Robert B Innis
- Molecular Imaging Branch, National Institute of Mental Health, Bethesda, Maryland (L.D.W., P.K., R.B.I.); Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland (K.L.F., J.K.M., J.S.K., M.M.G., M.D.H.); and Karolinska Institutet, Department of Neuroscience, Stockholm, Sweden (L.D.W., J.M.)
| | - Michael M Gottesman
- Molecular Imaging Branch, National Institute of Mental Health, Bethesda, Maryland (L.D.W., P.K., R.B.I.); Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland (K.L.F., J.K.M., J.S.K., M.M.G., M.D.H.); and Karolinska Institutet, Department of Neuroscience, Stockholm, Sweden (L.D.W., J.M.)
| | - Matthew D Hall
- Molecular Imaging Branch, National Institute of Mental Health, Bethesda, Maryland (L.D.W., P.K., R.B.I.); Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland (K.L.F., J.K.M., J.S.K., M.M.G., M.D.H.); and Karolinska Institutet, Department of Neuroscience, Stockholm, Sweden (L.D.W., J.M.)
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