1
|
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: 26] [Impact Index Per Article: 2.4] [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.
Collapse
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.)
| | | | | | | | | | | | | | | | | | | |
Collapse
|
2
|
Germann UA, Chambers TC. Molecular analysis of the multidrug transporter, P-glycoprotein. Cytotechnology 2012; 27:31-60. [PMID: 19002782 DOI: 10.1023/a:1008023629269] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Inherent or acquired resistance of tumor cells to cytotoxic drugs represents a major limitation to the successful chemotherapeutic treatment of cancer. During the past three decades dramatic progress has been made in the understanding of the molecular basis of this phenomenon. Analyses of drug-selected tumor cells which exhibit simultaneous resistance to structurally unrelated anti-cancer drugs have led to the discovery of the human MDR1 gene product, P-glycoprotein, as one of the mechanisms responsible for multidrug resistance. Overexpression of this 170 kDa N-glycosylated plasma membrane protein in mammalian cells has been associated with ATP-dependent reduced drug accumulation, suggesting that P-glycoprotein may act as an energy-dependent drug efflux pump. P-glycoprotein consists of two highly homologous halves each of which contains a transmembrane domain and an ATP binding fold. This overall architecture is characteristic for members of the ATP-binding cassette or ABC superfamily of transporters. Cell biological, molecular genetic and biochemical approaches have been used for structure-function studies of P-glycoprotein and analysis of its mechanism of action. This review summarizes the current status of knowledge on the domain organization, topology and higher order structure of P-glycoprotein, the location of drug- and ATP binding sites within P-glycoprotein, its ATPase and drug transport activities, its possible functions as an ion channel, ATP channel and lipid transporter, its potential role in cholesterol biosynthesis, and the effects of phosphorylation on P-glycoprotein activity.
Collapse
Affiliation(s)
- U A Germann
- Vertex Pharmaceuticals Incorporated, 130 Waverly Street, Cambridge, MA, 02139-4242, U.S.A.,
| | | |
Collapse
|
3
|
Determinants, discriminants, conserved residues--a heuristic approach to detection of functional divergence in protein families. PLoS One 2011; 6:e24382. [PMID: 21931701 PMCID: PMC3171465 DOI: 10.1371/journal.pone.0024382] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Accepted: 08/08/2011] [Indexed: 11/19/2022] Open
Abstract
In this work, belonging to the field of comparative analysis of protein sequences, we focus on detection of functional specialization on the residue level. As the input, we take a set of sequences divided into groups of orthologues, each group known to be responsible for a different function. This provides two independent pieces of information: within group conservation and overlap in amino acid type across groups. We build our discussion around the set of scoring functions that keep the two separated and the source of the signal easy to trace back to its source.We propose a heuristic description of functional divergence that includes residue type exchangeability, both in the conservation and in the overlap measure, and does not make any assumptions on the rate of evolution in the groups other than the one under consideration. Residue types acceptable at a certain position within an orthologous group are described as a distribution which evolves in time, starting from a single ancestral type, and is subject to constraints that can be inferred only indirectly. To estimate the strength of the constraints, we compare the observed degrees of conservation and overlap with those expected in the hypothetical case of a freely evolving distribution.Our description matches the experiment well, but we also conclude that any attempt to capture the evolutionary behavior of specificity determining residues in terms of a scalar function will be tentative, because no single model can cover the variety of evolutionary behavior such residues exhibit. Especially, models expecting the same type of evolutionary behavior across functionally divergent groups tend to miss a portion of information otherwise retrievable by the conservation and overlap measures they use.
Collapse
|
4
|
Cole DJ, Rajendra E, Roberts-Thomson M, Hardwick B, McKenzie GJ, Payne MC, Venkitaraman AR, Skylaris CK. Interrogation of the protein-protein interactions between human BRCA2 BRC repeats and RAD51 reveals atomistic determinants of affinity. PLoS Comput Biol 2011; 7:e1002096. [PMID: 21789034 PMCID: PMC3136434 DOI: 10.1371/journal.pcbi.1002096] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2010] [Accepted: 05/04/2011] [Indexed: 11/23/2022] Open
Abstract
The breast cancer suppressor BRCA2 controls the recombinase RAD51 in the reactions that mediate homologous DNA recombination, an essential cellular process required for the error-free repair of DNA double-stranded breaks. The primary mode of interaction between BRCA2 and RAD51 is through the BRC repeats, which are ∼35 residue peptide motifs that interact directly with RAD51 in vitro. Human BRCA2, like its mammalian orthologues, contains 8 BRC repeats whose sequence and spacing are evolutionarily conserved. Despite their sequence conservation, there is evidence that the different human BRC repeats have distinct capacities to bind RAD51. A previously published crystal structure reports the structural basis of the interaction between human BRC4 and the catalytic core domain of RAD51. However, no structural information is available regarding the binding of the remaining seven BRC repeats to RAD51, nor is it known why the BRC repeats show marked variation in binding affinity to RAD51 despite only subtle sequence variation. To address these issues, we have performed fluorescence polarisation assays to indirectly measure relative binding affinity, and applied computational simulations to interrogate the behaviour of the eight human BRC-RAD51 complexes, as well as a suite of BRC cancer-associated mutations. Our computational approaches encompass a range of techniques designed to link sequence variation with binding free energy. They include MM-PBSA and thermodynamic integration, which are based on classical force fields, and a recently developed approach to computing binding free energies from large-scale quantum mechanical first principles calculations with the linear-scaling density functional code onetep. Our findings not only reveal how sequence variation in the BRC repeats directly affects affinity with RAD51 and provide significant new insights into the control of RAD51 by human BRCA2, but also exemplify a palette of computational and experimental tools for the analysis of protein-protein interactions for chemical biology and molecular therapeutics. The atomic scale interactions that occur at the interfaces between proteins are fundamental to all biological processes. One such critical interface is formed between the proteins, human BRCA2 and RAD51. BRCA2 binds to and delivers RAD51 to sites of DNA damage, where RAD51 mediates the error-free repair of double-stranded DNA breaks. Mutations in BRCA2 have been linked to breast cancer predisposition. Therefore, an accurate picture of the interactions between these two proteins is of great importance. BRCA2 interacts with RAD51 via eight “BRC repeats” that are similar, but not identical, in sequence. Due to lack of experimental structural information regarding the binding of seven of the eight BRC repeats to RAD51, it is unknown how subtle sequence variations in the repeats translate to measurable variations in their binding affinity. We have used a range of computational methods, firstly based on classical force fields, and secondly based on first principles quantum mechanical techniques whose computational cost scales linearly with the number of atoms, allowing us to perform calculations on the entire protein complex. This is the first study comparing all eight BRC repeats at the atomic scale and our results provide critical insights into the control of RAD51 by human BRCA2.
Collapse
Affiliation(s)
- Daniel J. Cole
- Theory of Condensed Matter Group, Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Eeson Rajendra
- MRC Cancer Cell Unit Hutchison/MRC Research Centre, Cambridge, United Kingdom
| | - Meredith Roberts-Thomson
- Cambridge Molecular Therapeutics Programme, Hutchison/MRC Research Centre, Cambridge, United Kingdom
| | - Bryn Hardwick
- MRC Cancer Cell Unit Hutchison/MRC Research Centre, Cambridge, United Kingdom
- Cambridge Molecular Therapeutics Programme, Hutchison/MRC Research Centre, Cambridge, United Kingdom
| | - Grahame J. McKenzie
- MRC Cancer Cell Unit Hutchison/MRC Research Centre, Cambridge, United Kingdom
- Cambridge Molecular Therapeutics Programme, Hutchison/MRC Research Centre, Cambridge, United Kingdom
| | - Mike C. Payne
- Theory of Condensed Matter Group, Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Ashok R. Venkitaraman
- MRC Cancer Cell Unit Hutchison/MRC Research Centre, Cambridge, United Kingdom
- Cambridge Molecular Therapeutics Programme, Hutchison/MRC Research Centre, Cambridge, United Kingdom
- * E-mail: (ARV); (CKS)
| | - Chris-Kriton Skylaris
- School of Chemistry, University of Southampton, Highfield, Southampton, United Kingdom
- * E-mail: (ARV); (CKS)
| |
Collapse
|
5
|
Ford RC, Kamis AB, Kerr ID, Callaghan R. The ABC Transporters: Structural Insights into Drug Transport. ACTA ACUST UNITED AC 2010. [DOI: 10.1002/9783527627424.ch1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
6
|
Globisch C, Pajeva IK, Wiese M. Identification of putative binding sites of P-glycoprotein based on its homology model. ChemMedChem 2008; 3:280-95. [PMID: 18175303 DOI: 10.1002/cmdc.200700249] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A homology model of P-glycoprotein based on the crystal structure of the multidrug transporter Sav1866 is developed, incorporated into a membrane environment, and optimized. The resulting model is analyzed in relation to the functional state and potential binding sites. The comparison of modeled distances to distances reported in experimental studies between particular residues suggests that the model corresponds most closely to the first ATP hydrolysis step of the protein transport cycle. Comparison to the protein 3D structure confirms this suggestion. Using SiteID and Site Finder programs three membrane related binding regions are identified: a region at the interface between the membrane and cytosol and two regions located in the transmembrane domains. The regions contain binding pockets of different size, orientation, and amino acids. A binding pocket located inside the membrane cavity is also identified. The pockets are analyzed in relation to amino acids shown experimentally to influence the protein function. The results suggest that the protein has multiple binding sites and may bind and/or release substrates in multiple pathways.
Collapse
|
7
|
Rosmorduc O, Poupon R. Low phospholipid associated cholelithiasis: association with mutation in the MDR3/ABCB4 gene. Orphanet J Rare Dis 2007; 2:29. [PMID: 17562004 PMCID: PMC1910597 DOI: 10.1186/1750-1172-2-29] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2007] [Accepted: 06/11/2007] [Indexed: 12/14/2022] Open
Abstract
Low phospholipid-associated cholelithiasis (LPAC) is characterized by the association of ABCB4 mutations and low biliary phospholipid concentration with symptomatic and recurring cholelithiasis. This syndrome is infrequent and corresponds to a peculiar small subgroup of patients with symptomatic gallstone disease. The patients with the LPAC syndrome present typically with the following main features: age less than 40 years at onset of symptoms, recurrence of biliary symptoms after cholecystectomy, intrahepatic hyperechoic foci or sludge or microlithiasis along the biliary tree. Defect in ABCB4 function causes the production of bile with low phospholipid content, increased lithogenicity and high detergent properties leading to bile duct luminal membrane injuries and resulting in cholestasis with increased serum gamma-glutamyltransferase (GGT) activity. Intrahepatic gallstones may be evidenced by ultrasonography (US), computing tomography (CT) abdominal scan or magnetic resonance cholangiopancreatography, intrahepatic hyperechogenic foci along the biliary tree may be evidenced by US, and hepatic bile composition (phospholipids) may be determined by duodenoscopy. In all cases where the ABCB4 genotyping confirms the diagnosis of LPAC syndrome in young adults, long-term curative or prophylactic therapy with ursodeoxycholic acid (UDCA) should be initiated early to prevent the occurrence or recurrence of the syndrome and its complications. Cholecystectomy is indicated in the case of symptomatic gallstones. Biliary drainage or partial hepatectomy may be indicated in the case of symptomatic intrahepatic bile duct dilatations filled with gallstones. Patients with end-stage liver disease may be candidates for liver transplantation.
Collapse
Affiliation(s)
- Olivier Rosmorduc
- Service d'Hépatologie, INSERM U 680, Centre de Référence de Maladies Rares et des Maladies Inflammatoires des Voies Biliaires; Hôpital Saint-Antoine, Assistance Publique-Hôpitaux de Paris; Faculté de Médecine Pierre et Marie Curie et Université Paris 6; Paris, France
| | - Raoul Poupon
- Service d'Hépatologie, INSERM U 680, Centre de Référence de Maladies Rares et des Maladies Inflammatoires des Voies Biliaires; Hôpital Saint-Antoine, Assistance Publique-Hôpitaux de Paris; Faculté de Médecine Pierre et Marie Curie et Université Paris 6; Paris, France
| |
Collapse
|
8
|
Shilling RA, Venter H, Velamakanni S, Bapna A, Woebking B, Shahi S, van Veen HW. New light on multidrug binding by an ATP-binding-cassette transporter. Trends Pharmacol Sci 2006; 27:195-203. [PMID: 16545467 DOI: 10.1016/j.tips.2006.02.008] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2005] [Revised: 11/23/2005] [Accepted: 02/22/2006] [Indexed: 11/26/2022]
Abstract
ATP-binding-cassette (ABC) multidrug transporters confer multidrug resistance to pathogenic microorganisms and human tumour cells by mediating the extrusion of structurally unrelated chemotherapeutic drugs from the cell. The molecular basis by which ABC multidrug transporters bind and transport drugs is far from clear. Genetic analyses during the past 14 years reveal that the replacement of many individual amino acids in mammalian multidrug resistance P-glycoproteins can affect cellular resistance to drugs, but these studies have failed to identify specific regions in the primary amino acid sequence that are part of a defined drug-binding pocket. The recent publication of an X-ray crystallographic structure of the bacterial P-glycoprotein homologue MsbA and an MsbA-based homology model of human P-glycoprotein creates an opportunity to compare the original mutagenesis data with the three-dimensional structures of transporters. Our comparisons reveal that mutations that alter specificity are present in three-dimensional 'hotspot' regions in the membrane domains of P-glycoprotein.
Collapse
MESH Headings
- ATP Binding Cassette Transporter, Subfamily B, Member 1/chemistry
- ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics
- ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism
- ATP-Binding Cassette Transporters/chemistry
- ATP-Binding Cassette Transporters/genetics
- ATP-Binding Cassette Transporters/metabolism
- Amino Acid Sequence
- Animals
- Antineoplastic Agents/metabolism
- Binding Sites/genetics
- Biological Transport
- Drug Resistance, Multiple
- Drug Resistance, Neoplasm
- Humans
- Models, Molecular
- Molecular Sequence Data
- Mutation
- Protein Structure, Tertiary
Collapse
Affiliation(s)
- Richard A Shilling
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, UK, CB2 1PD
| | | | | | | | | | | | | |
Collapse
|
9
|
Sidhu ABS, Valderramos SG, Fidock DA. pfmdr1 mutations contribute to quinine resistance and enhance mefloquine and artemisinin sensitivity in Plasmodium falciparum. Mol Microbiol 2005; 57:913-26. [PMID: 16091034 DOI: 10.1111/j.1365-2958.2005.04729.x] [Citation(s) in RCA: 278] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The emergence and spread of multidrug resistant Plasmodium falciparum has severely limited the therapeutic options for the treatment of malaria. With ever-increasing failure rates associated with chloroquine or sulphadoxine-pyrimethamine treatment, attention has turned to the few alternatives, which include quinine and mefloquine. Here, we have investigated the role of pfmdr1 3' coding region point mutations in antimalarial drug susceptibility by allelic exchange in the GC03 and 3BA6 parasite lines. Results with pfmdr1-recombinant clones indicate a significant role for the N1042D mutation in contributing to resistance to quinine and its diastereomer quinidine. The triple mutations S1034C/N1042D/D1246Y, highly prevalent in South America, were also found to enhance parasite susceptibility to mefloquine, halofantrine and artemisinin. pfmdr1 3' mutations showed minimal effect on P. falciparum resistance to chloroquine or its metabolite mono-desethylchloroquine in these parasite lines, in contrast to previously published results obtained with 7G8 parasites. This study supports the hypothesis that pfmdr1 3' point mutations can significantly affect parasite susceptibility to a wide range of antimalarials in a strain-specific manner that depends on the parasite genetic background.
Collapse
Affiliation(s)
- Amar Bir Singh Sidhu
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | | | | |
Collapse
|
10
|
Saini P, Prasad T, Gaur NA, Shukla S, Jha S, Komath SS, Khan LA, Haq QMR, Prasad R. Alanine scanning of transmembrane helix 11 of Cdr1p ABC antifungal efflux pump of Candida albicans: identification of amino acid residues critical for drug efflux. J Antimicrob Chemother 2005; 56:77-86. [PMID: 15937063 DOI: 10.1093/jac/dki183] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVES To investigate the role of transmembrane segment 11 (TMS11) of Candida albicans drug resistance protein (Cdr1p) in drug extrusion. METHODS We replaced each of the 21 putative residues of TMS11 with alanine by site-directed mutagenesis. The Saccharomyces cerevisiae AD1-8u(-) strain was used to overexpress the green fluorescent protein tagged wild-type and mutant variants of TMS11 of Cdr1p. The cells expressing mutant variants were functionally characterized. RESULTS Out of 21 residues of TMS11, substitution of seven residues, i.e. A1346G, A1347G, T1351A, T1355A, L1358A, F1360A and G1362A, affected differentially the substrate specificity of Cdr1p, while 14 mutants had no significant effect on Cdr1p function. TMS11 projection in an alpha-helical configuration revealed with few exceptions (A1346 and F1360), a distinct segregation of mutation-sensitive residues (A1347, T1351, T1355, L1358 and G1362) towards the more hydrophilic face. Interestingly, mutation-insensitive residues seem to cluster towards the hydrophobic side of the helix. Competition of rhodamine 6G efflux, in the presence of excess of various substrates in the cells expressing native Cdr1p, revealed for the first time the overlapping binding site between azoles (such as ketoconazole, miconazole and itraconazole) and rhodamine 6G. The ability of these azoles to compete with rhodamine 6G was completely lost in mutants F1360A and G1362A, while it was selectively lost in other variants of Cdr1p. We further confirmed that fungicidal synergism of calcineurin inhibitor FK520 with azoles is mediated by Cdr1p; wherein in addition to conserved T1351, substitution of T1355, L1358 and G1362 of TMS11 also resulted in abrogation of synergism. CONCLUSIONS Our study for the first time provides an insight into the possible role of TMS11 of Cdr1p in drug efflux.
Collapse
Affiliation(s)
- Preeti Saini
- Membrane Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Rothnie A, Storm J, Campbell J, Linton KJ, Kerr ID, Callaghan R. The topography of transmembrane segment six is altered during the catalytic cycle of P-glycoprotein. J Biol Chem 2004; 279:34913-21. [PMID: 15192095 DOI: 10.1074/jbc.m405336200] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Structural evidence has demonstrated that P-glycoprotein (P-gp) undergoes considerable conformational changes during catalysis, and these alterations are important in drug interaction. Knowledge of which regions in P-gp undergo conformational alterations will provide vital information to elucidate the locations of drug binding sites and the mechanism of coupling. A number of investigations have implicated transmembrane segment six (TM6) in drug-P-gp interactions, and a cysteine-scanning mutagenesis approach was directed to this segment. Introduction of cysteine residues into TM6 did not disturb basal or drug-stimulated ATPase activity per se. Under basal conditions the hydrophobic probe coumarin maleimide readily labeled all introduced cysteine residues, whereas the hydrophilic fluorescein maleimide only labeled residue Cys-343. The amphiphilic BODIPY-maleimide displayed a more complex labeling profile. The extent of labeling with coumarin maleimide did not vary during the catalytic cycle, whereas fluorescein maleimide labeling of F343C was lost after nucleotide binding or hydrolysis. BODIPY-maleimide labeling was markedly altered during the catalytic cycle and indicated that the adenosine 5'-(beta,gamma-imino)triphosphate-bound and ADP/vanadate-trapped intermediates were conformationally distinct. Our data are reconciled with a recent atomic scale model of P-gp and are consistent with a tilting of TM6 in response to nucleotide binding and ATP hydrolysis.
Collapse
Affiliation(s)
- Alice Rothnie
- Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, UK
| | | | | | | | | | | |
Collapse
|
12
|
Seigneuret M, Garnier-Suillerot A. A structural model for the open conformation of the mdr1 P-glycoprotein based on the MsbA crystal structure. J Biol Chem 2003; 278:30115-24. [PMID: 12777401 DOI: 10.1074/jbc.m302443200] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The validity of the structure of the Escherichia coli MsbA lipid transporter as a model from the mdr1 P-glycoprotein has been evaluated. Comparative sequence analyses, motif search and secondary structure prediction indicated that each of the two P-glycoprotein halves is structurally similar to the MsbA monomer and also suggested that the open dimer structure is valid for P-glycoprotein. Homology modeling was used to predict the structure of P-glycoprotein using MsbA as a template. The resulting modeled structure allowed a detailed study of the interactions between the intracellular domain and the nucleotide binding domain and suggested that these contacts are involved in mediating the coupling between nucleotide binding domain conformational changes and transmembrane helices reorientation during transport. In P-glycoprotein, the internal chamber open to the inner leaflet and the inner medium is significantly different in size and charge than in MsbA. These differences can be related to those of the transported substrates. Moreover an ensemble of 20 conserved aromatic residues appears to border the periphery of each side of the chamber in P-glycoprotein. These may be important for size selection and proper positioning of drugs for transport. The relevance of the modeled conformation to P-gp function is discussed.
Collapse
Affiliation(s)
- Michel Seigneuret
- Laboratoire de Physochimie Biomoléculaire et Cellulaire, UMR-CNRS 7033, Universitĕ Paris 6, France.
| | | |
Collapse
|
13
|
Rosmorduc O, Hermelin B, Boelle PY, Parc R, Taboury J, Poupon R. ABCB4 gene mutation-associated cholelithiasis in adults. Gastroenterology 2003; 125:452-9. [PMID: 12891548 DOI: 10.1016/s0016-5085(03)00898-9] [Citation(s) in RCA: 174] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
BACKGROUND & AIMS We recently put forward arguments in favor of ABCB4 gene (adenosine triphosphate-binding cassette, subfamily B, member 4) defects as a risk factor for symptomatic cholelithiasis in adults. In this study, we characterized ABCB4 gene mutations in a series of patients with symptomatic cholelithiasis to determine the genetic basis and the clinical phenotype of ABCB4 gene mutation-associated cholelithiasis. METHODS We analyzed the entire ABCB4 gene coding sequences in a first group of 32 patients who had a clinical history compatible with the syndrome previously described, in a second group of 28 patients who presented with a classic gallstone disease that justified a cholecystectomy, and in a third group of 33 patients without a history of cholelithiasis. RESULTS We identified both heterozygous and homozygous ABCB4 gene point mutations in 18 of 32 (56%) patients who presented with clinical criteria of the syndrome, whereas no mutation was detected in the 2 other groups of patients (P < 0.001). Three independent clinical features were strongly associated with point mutations: recurrence of symptoms after cholecystectomy (odds ratio, 8.5); intrahepatic hyperechoic foci, intrahepatic sludge, or microlithiasis (odds ratio, 6.1); and age <40 years at the onset of symptoms (odds ratio, 3.0). ABCB4 gene point mutations were detected exclusively in the patients who showed 2 or 3 of these clinical features. CONCLUSIONS Our results show that ABCB4 gene mutations represent a major genetic risk factor in a symptomatic and recurring form of cholelithiasis in young adults.
Collapse
|
14
|
Cai J, Gros P. Overexpression, purification, and functional characterization of ATP-binding cassette transporters in the yeast, Pichia pastoris. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1610:63-76. [PMID: 12586381 DOI: 10.1016/s0005-2736(02)00718-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The ATP-binding cassette (ABC) transporter superfamily is a large gene family that has been highly conserved throughout evolution. The physiological importance of these membrane transporters is highlighted by the large variety of substrates they transport, and by the observation that mutations in many of them cause heritable diseases in human. Likewise, overexpression of certain ABC transporters, such as P-glycoprotein and members of the multidrug resistance associated protein (MRP) family, is associated with multidrug resistance in various cells and organisms. Understanding the structure and molecular mechanisms of transport of the ABC transporters in normal tissues and their possibly altered function in human diseases requires large amounts of purified and active proteins. For this, efficient expression systems are needed. The methylotrophic yeast Pichia pastoris has proven to be an efficient and inexpensive experimental model for high-level expression of many proteins, including ABC transporters. In the present review, we will summarize recent advances on the use of this system for the expression, purification, and functional characterization of P-glycoprotein and two members of the MRP subfamily.
Collapse
Affiliation(s)
- Jie Cai
- Department of Biochemistry and McGill Cancer Center, McGill University, Montreal, Quebec, Canada
| | | |
Collapse
|
15
|
Abstract
In view of the increasing threat posed by fungal infections in immunocompromised patients and due to the non-availability of effective treatments, it has become imperative to find novel antifungals and vigorously search for new drug targets. Fungal pathogens acquire resistance to drugs (antifungals), a well-established phenomenon termed multidrug resistance (MDR), which hampers effective treatment strategies. The MDR phenomenon is spread throughout the evolutionary scale. Accordingly, a host of responsible genes have been identified in the genetically tractable budding yeast Saccharomyces cerevisiae, as well as in a pathogenic yeast Candida albicans. Studies so far suggest that, while antifungal resistance is the culmination of multiple factors, there may be a unifying mechanism of drug resistance in these pathogens. ABC (ATP binding cassette) and MFS (major facilitator superfamily) drug transporters belonging to two different superfamilies, are the most prominent contributors to MDR in yeasts. Considering the abundance of the drug transporters and their wider specificity, it is believed that these drug transporters may not exclusively export drugs in fungi. It has become apparent that the drug transporters of the ABC superfamily of S. cerevisiae and C. albicans are multifunctional proteins, which mediate important physiological functions. This review summarizes current research on the molecular mechanisms underlying drug resistance, the emerging regulatory circuits of MDR genes, and the physiological relevance of drug transporters.
Collapse
Affiliation(s)
- Rajendra Prasad
- Membrane Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi-110067, India
| | | |
Collapse
|
16
|
Song J, Melera PW. Transmembrane domain (TM) 9 represents a novel site in P-glycoprotein that affects drug resistance and cooperates with TM6 to mediate [125I]iodoarylazidoprazosin labeling. Mol Pharmacol 2001; 60:254-61. [PMID: 11455011 DOI: 10.1124/mol.60.2.254] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The multidrug resistant cell line DC-3F/ADII was obtained by stepwise selection for growth in actinomycin D (ActD). Compared with parental cells, it displays high resistance to ActD and vincristine and low resistance to colchicine and daunorubicin. These cells overexpress a form of P-glycoprotein (Pgp1) containing a double mutation, I837L and N839I, in transmembrane domain (TM) 9; when transfected into DC-3F, this mutation confers the DC-3F/ADII phenotype. We have shown previously that another cell line, DC-3F/ADX, also displays this phenotype and overexpresses a mutant form of Pgp1 containing a double mutation in TM6 (G338A, A339P). Hence, mutations in TM9 and TM6 are independently capable of conferring the same cross-resistance phenotype. The TM6 mutations inhibit the ability of cyclosporin A to reverse cross-resistance and to block labeling of the protein by [125I]iodoarylazidoprazosin (IAAP), whereas the TM9 mutations do not show similar effects. A chimeric protein containing both pairs of mutations confers twice the level of resistance to ActD than expected from the sum of the individual mutations, but it cannot be labeled to detectable levels with [125I]IAAP. Thus, TM9 represents a novel site that cooperates with TM6 to mediate drug resistance and [125I]IAAP labeling.
Collapse
MESH Headings
- ATP Binding Cassette Transporter, Subfamily B, Member 1/chemistry
- ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics
- ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism
- Adenosine Triphosphatases/metabolism
- Animals
- Azides/metabolism
- Binding, Competitive
- Cells, Cultured
- Cricetinae
- Cyclosporine/pharmacology
- Drug Interactions
- Drug Resistance/physiology
- Drug Resistance, Multiple/physiology
- Iodine Radioisotopes
- Membrane Proteins/chemistry
- Membrane Proteins/genetics
- Membrane Proteins/metabolism
- Mutagenesis, Site-Directed
- Prazosin/analogs & derivatives
- Prazosin/metabolism
- Protein Structure, Tertiary
- Transfection
- Verapamil/pharmacology
Collapse
Affiliation(s)
- J Song
- Department of Biochemistry, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | | |
Collapse
|
17
|
Gruol DJ, Bernd J, Phippard AE, Ojima I, Bernacki RJ. The use of a novel taxane-based P-glycoprotein inhibitor to identify mutations that alter the interaction of the protein with paclitaxel. Mol Pharmacol 2001; 60:104-13. [PMID: 11408605 DOI: 10.1124/mol.60.1.104] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Murine thymoma cell lines expressing mutated forms of the mdr1b P-glycoprotein were isolated using a novel taxane-based P-glycoprotein inhibitor tRA-96023 (SB-RA-31012). The selection strategy required resistance to a combination of tRA-96023 and colchicine. Five mutations were identified (N350I, I862F, L865F, L868W, and A933T) that reduce the capacity of tRA-96023 to inhibit P-glycoprotein-dependent drug resistance. These mutations also result in a loss of paclitaxel resistance ranging from 47 to 100%. Four mutations are located in the second half of the protein, within or near the proposed transmembrane segment (TMS) 10--11 regions. The fifth mutation (N350I) is within the first half of the protein, proximal (cytoplasmic) to TMS 6. The variant cell line expressing the L868W mutation was subjected to a second round of selection involving tRA-96023 and the toxic drug puromycin. This resulted in the isolation of a cell line expressing a P-glycoprotein with a double mutation. The additional mutation (N988D) is located within TMS 12 and conveys further decreases in resistance to paclitaxel and the capacity of tRA-96023 to inhibit drug resistance. Taken together, the results indicate a significant contribution by the TMS 10--12 portion of the protein to the recognition and transport of taxanes and give evidence that the cytoplasmic region proximal to TMS 6 also plays a role in taxane interactions with P-glycoproteins. Interestingly, mutations within TMS 6 and 12 were found to cause a partial loss of PSC-833 inhibitor activity, suggesting that these regions participate in the interactions with cyclosporin and its derivatives.
Collapse
Affiliation(s)
- D J Gruol
- The Sidney Kimmel Cancer Center, San Diego, California 92121, USA.
| | | | | | | | | |
Collapse
|
18
|
Hrycyna CA. Molecular genetic analysis and biochemical characterization of mammalian P-glycoproteins involved in multidrug resistance. Semin Cell Dev Biol 2001; 12:247-56. [PMID: 11428917 DOI: 10.1006/scdb.2000.0250] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
A variety of human cancers become resistant or are intrinsically resistant to treatment with conventional drug therapies. This phenomenon is due in large part to the overexpression of a 170 kDa plasma membrane ATP-dependent pump known as the multidrug resistance transporter or P-glycoprotein. P-glycoprotein is a member of the large ATP binding cassette (ABC) superfamily of membrane transporters. This review focuses on the use of structure-function analyses to elucidate further the mechanism of action of mammalian P-glycoproteins. Ultimately, a complete understanding of the mechanism is important for the development of novel strategies for the treatment of many human cancers.
Collapse
Affiliation(s)
- C A Hrycyna
- Department of Chemistry, Purdue University, 1393 Brown Building, West Lafayette, IN 47907-1393, USA.
| |
Collapse
|
19
|
Rosmorduc O, Hermelin B, Poupon R. MDR3 gene defect in adults with symptomatic intrahepatic and gallbladder cholesterol cholelithiasis. Gastroenterology 2001; 120:1459-67. [PMID: 11313316 DOI: 10.1053/gast.2001.23947] [Citation(s) in RCA: 191] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND & AIMS Many studies indicate that gallstone susceptibility has genetic components. MDR3 is the phosphatidylcholine translocator across the hepatocyte canalicular membrane. Because phospholipids are a carrier and a solvent of cholesterol in hepatic bile, we hypothesized that a defect in the MDR3 gene could be the genetic basis for peculiar forms of cholesterol gallstone disease, in particular those associated with symptoms and cholestasis without evident common bile duct stone. METHODS We studied 6 adult patients with a peculiar form of cholelithiasis. MDR3 gene sequence was determined by reverse-transcription polymerase chain reaction amplification of mononuclear cell RNAs followed by direct sequencing. Hepatic bile was analyzed in 2 patients. RESULTS All patients shared the following features: at least 1 episode of biliary colic, pancreatitis, or cholangitis; biochemical evidence of chronic cholestasis; recurrence of symptoms after cholecystectomy; presence of echogenic material in the intrahepatic bile ducts; and prevention of recurrence by ursodeoxycholic acid therapy. Hepatic bile composition showed a high cholesterol/phospholipid ratio and cholesterol crystals. In all patients, we found MDR3 gene mutations involving a conserved amino acid region. CONCLUSIONS These preliminary observations suggest that MDR3 gene mutations represent a genetic factor involved in this peculiar form of cholesterol gallstone disease in adults. They require further studies to assess the prevalence of MDR3 gene defects in symptomatic and silent cholesterol gallstone disease.
Collapse
Affiliation(s)
- O Rosmorduc
- Service d'Hépato-gastroentérologie, Hôpital Saint-Antoine, Assistance publique-Hôpitaux de Paris, France
| | | | | |
Collapse
|
20
|
Loo TW, Clarke DM. Identification of residues within the drug-binding domain of the human multidrug resistance P-glycoprotein by cysteine-scanning mutagenesis and reaction with dibromobimane. J Biol Chem 2000; 275:39272-8. [PMID: 11013259 DOI: 10.1074/jbc.m007741200] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
P-glycoprotein (P-gp) can transport a wide variety of cytotoxic compounds that have diverse structures. Therefore, the drug-binding domain of the human multidrug resistance P-gp likely consists of residues from multiple transmembrane (TM) segments. In this study, we completed cysteine-scanning mutagenesis of all the predicted TM segments of P-gp (TMs 1-5 and 7-10) and tested for inhibition by a thiol-reactive substrate (dibromobimane) to identify residues within the drug-binding domain. The activities of 189 mutants were analyzed. Verapamil-stimulated ATPase activities of seven mutants (Y118C and V125C (TM2), S222C (TM4), I306C (TM5), S766C (TM9), and I868C and G872C (TM10)) were inhibited by more than 50% by dibromobimane. The activities of mutants S222C (TM4), I306C (TM5), I868C (TM10), and G872C (TM10), but not that of mutants Y118C (TM2), V125C (TM2), and S776C (TM9), were protected from inhibition by dibromobimane by pretreatment with verapamil, vinblastine, or colchicine. These results and those from previous studies (Loo, T. W. and Clarke, D. M. (1997) J. Biol. Chem. 272, 31945-31948; Loo, T. W. and Clarke, D. M. (1999) J. Biol. Chem. 274, 35388-35392) indicate that the drug-binding domain of P-gp consists of residues in TMs 4, 5, 6, 10, 11, and 12.
Collapse
Affiliation(s)
- T W Loo
- Canadian Institute for Health Research Group in Membrane Biology, Departments of Medicine and Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | | |
Collapse
|
21
|
Putman M, van Veen HW, Konings WN. Molecular properties of bacterial multidrug transporters. Microbiol Mol Biol Rev 2000; 64:672-93. [PMID: 11104814 PMCID: PMC99009 DOI: 10.1128/mmbr.64.4.672-693.2000] [Citation(s) in RCA: 583] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
One of the mechanisms that bacteria utilize to evade the toxic effects of antibiotics is the active extrusion of structurally unrelated drugs from the cell. Both intrinsic and acquired multidrug transporters play an important role in antibiotic resistance of several pathogens, including Neisseria gonorrhoeae, Mycobacterium tuberculosis, Staphylococcus aureus, Streptococcus pneumoniae, Pseudomonas aeruginosa, and Vibrio cholerae. Detailed knowledge of the molecular basis of drug recognition and transport by multidrug transport systems is required for the development of new antibiotics that are not extruded or of inhibitors which block the multidrug transporter and allow traditional antibiotics to be effective. This review gives an extensive overview of the currently known multidrug transporters in bacteria. Based on energetics and structural characteristics, the bacterial multidrug transporters can be classified into five distinct families. Functional reconstitution in liposomes of purified multidrug transport proteins from four families revealed that these proteins are capable of mediating the export of structurally unrelated drugs independent of accessory proteins or cytoplasmic components. On the basis of (i) mutations that affect the activity or the substrate specificity of multidrug transporters and (ii) the three-dimensional structure of the drug-binding domain of the regulatory protein BmrR, the substrate-binding site for cationic drugs is predicted to consist of a hydrophobic pocket with a buried negatively charged residue that interacts electrostatically with the positively charged substrate. The aromatic and hydrophobic amino acid residues which form the drug-binding pocket impose restrictions on the shape and size of the substrates. Kinetic analysis of drug transport by multidrug transporters provided evidence that these proteins may contain multiple substrate-binding sites.
Collapse
Affiliation(s)
- M Putman
- Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, NL-9751 NN Haren, The Netherlands
| | | | | |
Collapse
|
22
|
Duraisingh MT, Roper C, Walliker D, Warhurst DC. Increased sensitivity to the antimalarials mefloquine and artemisinin is conferred by mutations in the pfmdr1 gene of Plasmodium falciparum. Mol Microbiol 2000; 36:955-61. [PMID: 10844681 DOI: 10.1046/j.1365-2958.2000.01914.x] [Citation(s) in RCA: 135] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The declining efficacy of chloroquine and pyrimethamine/sulphadoxine in the treatment of human malaria has led to the use of newer antimalarials such as mefloquine and artemisinin. Sequence polymorphisms in the pfmdr1 gene, the gene encoding the plasmodial homologue of mammalian multidrug resistance transporters, have previously been linked to resistance to chloroquine in some, but not all, studies. In this study, we have used a genetic cross between the strains HB3 and 3D7 to study inheritance of sensitivity to the structurally unrelated drugs mefloquine and artemisinin, and to several other antimalarials. We find a complete allelic association between the HB3-like pfmdr1 allele and increased sensitivity to these drugs in the progeny. Different pfmdr1 sequence polymorphisms in other unrelated lines were also associated with increased sensitivity to these drugs. Our results indicate that the pfmdr1 gene is an important determinant of susceptibility to antimalarials, which has major implications for the future development of resistance.
Collapse
Affiliation(s)
- M T Duraisingh
- London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | | | | | | |
Collapse
|
23
|
Egner R, Bauer BE, Kuchler K. The transmembrane domain 10 of the yeast Pdr5p ABC antifungal efflux pump determines both substrate specificity and inhibitor susceptibility. Mol Microbiol 2000; 35:1255-63. [PMID: 10712705 DOI: 10.1046/j.1365-2958.2000.01798.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have previously shown that a S1360F mutation in transmembrane domain 10 (TMD10) of the Pdr5p ABC transporter modulates substrate specificity and simultaneously leads to a loss of FK506 inhibition. In this study, we have constructed and characterized the S1360F/A/T and T1364F/A/S mutations located in the hydrophilic face of the amphipatic Pdr5p TMD10. A T1364F mutation leads to a reduction in Pdr5p-mediated azole and rhodamine 6G resistance. Like S1360F, the T1364F and T1364A mutants were nearly non-responsive to FK506 inhibition. Most remarkably, however, the S1360A mutation increases FK506 inhibitor susceptibility, because Pdr5p-S1360A is hypersensitive to FK506 inhibition when compared with either wild-type Pdr5p or the non-responsive S1360F variant. Hence, the Pdr5p TMD10 determines both azole substrate specificity and susceptibility to reversal agents. This is the first demonstration of a eukaryotic ABC transporter where a single residue change causes either a loss or a gain in inhibitor susceptibility, depending on the nature of the mutational change. These results have important implications for the design of efficient reversal agents that could be used to overcome multidrug resistance mediated by ABC transporter overexpression.
Collapse
Affiliation(s)
- R Egner
- Department of Medical Biochemistry, University and Bio Center of Vienna, A-1030 Vienna, Austria
| | | | | |
Collapse
|
24
|
Loo TW, Clarke DM. The packing of the transmembrane segments of human multidrug resistance P-glycoprotein is revealed by disulfide cross-linking analysis. J Biol Chem 2000; 275:5253-6. [PMID: 10681495 DOI: 10.1074/jbc.275.8.5253] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Residues from several transmembrane (TM) segments of P-glycoprotein (P-gp) likely form the drug-binding site(s). To determine the organization of the TM segments, pairs of cysteine residues were introduced into the predicted TM segments of a Cys-less P-gp, and the mutant protein was subjected to oxidative cross-linking. In SDS gels, the cross-linked product migrated with a slower mobility than the native protein. The cross-linked products were not detected in the presence of dithiothreitol. Cross-linking was observed in 12 of 125 mutants. The pattern of cross-linking suggested that TM6 is close to TMs 10, 11, and 12, while TM12 is close to TMs 4, 5, and 6. In some mutants the presence of drug substrate colchicine, verapamil, cyclosporin A, or vinblastine either enhanced or inhibited cross-linking. Cross-linking was inhibited in the presence of ATP plus vanadate. These results suggest that the TM segments critical for drug binding must be close to each other and exhibit different conformational changes in response to binding of drug substrate or vanadate trapping of nucleotide. Based on these results, we propose a model for the arrangement of the TM segments.
Collapse
Affiliation(s)
- T W Loo
- Medical Research Council Group in Membrane Biology, Department of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | | |
Collapse
|
25
|
Zheleznova EE, Markham P, Edgar R, Bibi E, Neyfakh AA, Brennan RG. A structure-based mechanism for drug binding by multidrug transporters. Trends Biochem Sci 2000; 25:39-43. [PMID: 10664577 DOI: 10.1016/s0968-0004(99)01514-5] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Multidrug transporters bind chemically dissimilar, potentially cytotoxic compounds and remove them from the cell. How these transporters carry out either of these functions is unknown. On the basis of crystal structures of the multidrug-binding domain of the transcription activator BmrR and mutagenesis studies on the bacterial multidrug transporter MdfA, we propose a possible mechanism for the binding of cationic lipophilic drugs by multidrug transporters. The key element of this mechanism includes a conformational change in the transporter that exposes a buried charged residue in the substrate-binding pocket and allows access to this site by only those drugs that are its steric and electrostatic complements.
Collapse
Affiliation(s)
- E E Zheleznova
- Dept of Biochemistry and Molecular Biology, Oregon Health Sciences University, Portland, OR, USA
| | | | | | | | | | | |
Collapse
|
26
|
Ferté J. Analysis of the tangled relationships between P-glycoprotein-mediated multidrug resistance and the lipid phase of the cell membrane. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:277-94. [PMID: 10632698 DOI: 10.1046/j.1432-1327.2000.01046.x] [Citation(s) in RCA: 151] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
P-glycoprotein (Pgp), the so-called multidrug transporter, is a plasma membrane glycoprotein often involved in the resistance of cancer cells towards multiple anticancer agents in the multidrug-resistant (MDR) phenotype. It has long been recognized that the lipid phase of the plasma membrane plays an important role with respect to multidrug resistance and Pgp because: the compounds involved in the MDR phenotype are hydrophobic and diffuse passively through the membrane; Pgp domains involved in drug binding are located within the putative transmembrane segments; Pgp activity is highly sensitive to its lipid environment; and Pgp may be involved in lipid trafficking and metabolism. Unraveling the different roles played by the membrane lipid phase in MDR is relevant, not only to the evaluation of the precise role of Pgp, but also to the understanding of the mechanism of action and function of Pgp. With this aim, I review the data from different fields (cancer research, medicinal chemistry, membrane biophysics, pharmaceutical research) concerning drug-membrane, as well as Pgp-membrane, interactions. It is emphasized that the lipid phase of the membrane cannot be overlooked while investigating the MDR phenotype. Taking into account these aspects should be useful in the search of ways to obviate MDR and could also be relevant to the study of other multidrug transporters.
Collapse
Affiliation(s)
- J Ferté
- Service de Biophysique des Protéines et des Membranes, DSV-DBCM-SBPM, CEA, Centre de Saclay, Gif-sur-Yvette, France.
| |
Collapse
|
27
|
Loo TW, Clarke DM. Identification of residues in the drug-binding domain of human P-glycoprotein. Analysis of transmembrane segment 11 by cysteine-scanning mutagenesis and inhibition by dibromobimane. J Biol Chem 1999; 274:35388-92. [PMID: 10585407 DOI: 10.1074/jbc.274.50.35388] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The drug-binding domain of the human multidrug resistance P-glycoprotein (P-gp) probably consists of residues from multiple transmembrane (TM) segments. In this study, we tested whether the amino acids in TM11 participate in binding drug substrates. Each residue in TM11 was initially altered by site-directed mutagenesis and assayed for drug-stimulated ATPase activity in the presence of verapamil, vinblastine, or colchicine. Mutants G939V, F942A, T945A, Q946A, A947L, Y953A, A954L, and G955V had altered drug-stimulated ATPase activities. Direct evidence for binding of drug substrate was then determined by cysteine-scanning mutagenesis of the residues in TM11 and inhibition of drug-stimulated ATPase activity by dibromobimane, a thiol-reactive substrate. Dibromobimane inhibited the drug-stimulated ATPase activities of two mutants, F942C and T945C, by more than 75%. These results suggest that residues Phe(942) and Thr(945) in TM11, together with residues previously identified in TM6 (Leu(339) and Ala(342)) and TM12 (Leu(975), Val(982), and Ala(985)) (Loo, T. W., and Clarke, D. M. (1997) J. Biol. Chem. 272, 31945-31948) form part of the drug-binding domain of P-gp.
Collapse
Affiliation(s)
- T W Loo
- Medical Research Council Group in Membrane Biology, Department of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | | |
Collapse
|
28
|
van Veen HW, Konings WN. Structure and function of multidrug transporters. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1999; 456:145-58. [PMID: 10549367 DOI: 10.1007/978-1-4615-4897-3_8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- H W van Veen
- Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Haren, The Netherlands.
| | | |
Collapse
|
29
|
Demmer A, Andreae S, Thole H, Tümmler B. Iodomycin and iodipine, a structural analogue of azidopine, bind to a common domain in hamster P-glycoprotein. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 264:800-5. [PMID: 10491126 DOI: 10.1046/j.1432-1327.1999.00702.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Both the overexpression of P-glycoprotein and the broad range of substrates of this ATP-binding cassette (ABC) transporter induce the phenomenon of multidrug resistance, one major cause of the failure of cancer chemotherapy in humans. This study reports that [125I]iodipine, a structural analogue of the 1,4-dihydropyridine azidopine, shares a common binding site with iodomycin, a Bolton-Hunter derivative of the anthracycline daunomycin. This binding site is different from that described for iodoarylazidoprazosin, which is presumed to share a common binding site with azidopine. Edman sequencing revealed that [125I]iodipine had photolabelled the same peptide as iodomycin and spans the primary sequence of hamster isoform pgp1 from amino acid 230 to amino acid 312.
Collapse
Affiliation(s)
- A Demmer
- Klinische Forschergruppe, Zentrum Biochemie, Medizinische Hochschule, Hannover, Germany.
| | | | | | | |
Collapse
|
30
|
Vo QD, Gruol DJ. Identification of P-glycoprotein mutations causing a loss of steroid recognition and transport. J Biol Chem 1999; 274:20318-27. [PMID: 10400654 DOI: 10.1074/jbc.274.29.20318] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
P-glycoproteins transport a wide variety of hydrophobic compounds out of cells. While the diversity of transported molecules suggests a mechanism involving broad specificity, there is evidence of significant discrimination within given classes of molecules. One example of this behavior is transport of corticosteroids by the murine mdr1 P-glycoprotein. The presence of hydroxyl groups, associated with specific steroid carbon atoms, regulates the ability of corticosteroids to be transported. This specificity is demonstrated here by experiments measuring the ability of steroids to inhibit drug transport. The results indicate that a keto oxygen associated with the 3- and 20-carbon atoms, as well as a 17-carbon hydroxyl group, each acts to enhance steroidal P-glycoprotein inhibitory activity. Moreover, inhibitory steroids can be used for directed selection of variant cells, expressing mutated P-glycoproteins with a severely impaired ability to transport dexamethasone. The five mutations, reported here, are located within transmembrane domains 4-6, proximal to the cytoplasmic interface. The altered P-glycoproteins exhibit reduced capacity to be inhibited by specific steroids, suggesting decreased capacity to bind these molecules avidly. Studies comparing the relative inhibitory activity of a series of steroids indicate that these mutations alter recognition of the 17alpha-hydroxyl group and the 20-keto oxygen atom.
Collapse
Affiliation(s)
- Q D Vo
- Sidney Kimmel Cancer Center, San Diego, California 92121, USA
| | | |
Collapse
|
31
|
Mackenzie SM, Brooker MR, Gill TR, Cox GB, Howells AJ, Ewart GD. Mutations in the white gene of Drosophila melanogaster affecting ABC transporters that determine eye colouration. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1419:173-85. [PMID: 10407069 DOI: 10.1016/s0005-2736(99)00064-4] [Citation(s) in RCA: 125] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The white, brown and scarlet genes of Drosophila melanogaster encode proteins which transport guanine or tryptophan (precursors of the red and brown eye colour pigments) and belong to the ABC transporter superfamily. Current models envisage that the white and brown gene products interact to form a guanine specific transporter, while white and scarlet gene products interact to form a tryptophan transporter. In this study, we report the nucleotide sequence of the coding regions of five white alleles isolated from flies with partially pigmented eyes. In all cases, single amino acid changes were identified, highlighting residues with roles in structure and/or function of the transporters. Mutations in w(cf) (G589E) and w(sat) (F590G) occur at the extracellular end of predicted transmembrane helix 5 and correlate with a major decrease in red pigments in the eyes, while brown pigments are near wild-type levels. Therefore, those residues have a more significant role in the guanine transporter than the tryptophan transporter. Mutations identified in w(crr) (H298N) and w(101) (G243S) affect amino acids which are highly conserved among the ABC transporter superfamily within the nucleotide binding domain. Both cause substantial and similar decreases of red and brown pigments indicating that both tryptophan and guanine transport are impaired. The mutation identified in w(Et87) alters an amino acid within an intracellular loop between transmembrane helices 2 and 3 of the predicted structure. Red and brown pigments are reduced to very low levels by this mutation indicating this loop region is important for the function of both guanine and tryptophan transporters.
Collapse
Affiliation(s)
- S M Mackenzie
- Division of Biochemistry and Molecular Biology, John Curtin School of Medical Research, The Australian National University, P.O. Box 4, Canberra City 0200, Australia
| | | | | | | | | | | |
Collapse
|
32
|
Ambudkar SV, Dey S, Hrycyna CA, Ramachandra M, Pastan I, Gottesman MM. Biochemical, cellular, and pharmacological aspects of the multidrug transporter. Annu Rev Pharmacol Toxicol 1999; 39:361-98. [PMID: 10331089 DOI: 10.1146/annurev.pharmtox.39.1.361] [Citation(s) in RCA: 1500] [Impact Index Per Article: 60.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Considerable evidence has accumulated indicating that the multidrug transporter or P-glycoprotein plays a role in the development of simultaneous resistance to multiple cytotoxic drugs in cancer cells. In recent years, various approaches such as mutational analyses and biochemical and pharmacological characterization have yielded significant information about the relationship of structure and function of P-glycoprotein. However, there is still considerable controversy about the mechanism of action of this efflux pump and its function in normal cells. This review summarizes current research on the structure-function analysis of P-glycoprotein, its mechanism of action, and facts and speculations about its normal physiological role.
Collapse
MESH Headings
- ATP Binding Cassette Transporter, Subfamily B, Member 1/chemistry
- ATP Binding Cassette Transporter, Subfamily B, Member 1/drug effects
- ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics
- ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism
- Animals
- Cell Membrane/metabolism
- Drug Resistance, Multiple/genetics
- Drug Resistance, Neoplasm/genetics
- Humans
- Neoplasms/genetics
- Neoplasms/metabolism
- Protein Conformation
- Structure-Activity Relationship
Collapse
Affiliation(s)
- S V Ambudkar
- Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
| | | | | | | | | | | |
Collapse
|
33
|
Eckhardt M, Gotza B, Gerardy-Schahn R. Membrane topology of the mammalian CMP-sialic acid transporter. J Biol Chem 1999; 274:8779-87. [PMID: 10085119 DOI: 10.1074/jbc.274.13.8779] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nucleotide sugar transporters form a family of distantly related membrane proteins of the Golgi apparatus and the endoplasmic reticulum. The first transporter sequences have been identified within the last 2 years. However, information about the secondary and tertiary structure for these molecules has been limited to theoretical considerations. In the present study, an epitope-insertion approach was used to investigate the membrane topology of the CMP-sialic acid transporter. Immunofluorescence studies were carried out to analyze the orientation of the introduced epitopes in semipermeabilized cells. Both an amino-terminally introduced FLAG sequence and a carboxyl-terminal hemagglutinin tag were found to be oriented toward the cytosol. Results obtained with CMP-sialic acid transporter variants that contained the hemagglutinin epitope in potential intermembrane loop structures were in good correlation with the presence of 10 transmembrane regions. This building concept seems to be preserved also in other mammalian and nonmammalian nucleotide sugar transporters. Moreover, the functional analysis of the generated mutants demonstrated that insertions in or very close to membrane-spanning regions inactivate the transport process, whereas those in hydrophilic loop structures have no detectable effect on the activity. This study points the way toward understanding structure-function relationships of nucleotide sugar transporters.
Collapse
Affiliation(s)
- M Eckhardt
- Institut für Medizinische Mikrobiologie, Medizinische Hochschule, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | | | | |
Collapse
|
34
|
Ambudkar SV. Drug-stimulatable ATPase activity in crude membranes of human MDR1-transfected mammalian cells. Methods Enzymol 1998; 292:504-14. [PMID: 9711578 DOI: 10.1016/s0076-6879(98)92039-0] [Citation(s) in RCA: 169] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
MESH Headings
- 3T3 Cells
- ATP Binding Cassette Transporter, Subfamily B, Member 1/biosynthesis
- ATP Binding Cassette Transporter, Subfamily B, Member 1/isolation & purification
- ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism
- Adenosine Triphosphatases/biosynthesis
- Adenosine Triphosphatases/isolation & purification
- Adenosine Triphosphatases/metabolism
- Animals
- Blotting, Western
- Cell Membrane/metabolism
- Chromatography, High Pressure Liquid/methods
- Drug Resistance, Multiple
- Electrophoresis, Polyacrylamide Gel/methods
- Humans
- Indicators and Reagents
- Kinetics
- Mammals
- Mice
- Recombinant Proteins/biosynthesis
- Recombinant Proteins/isolation & purification
- Recombinant Proteins/metabolism
- Transfection/methods
- Verapamil/pharmacology
- Vincristine/pharmacology
Collapse
Affiliation(s)
- S V Ambudkar
- Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| |
Collapse
|
35
|
Egner R, Rosenthal FE, Kralli A, Sanglard D, Kuchler K. Genetic separation of FK506 susceptibility and drug transport in the yeast Pdr5 ATP-binding cassette multidrug resistance transporter. Mol Biol Cell 1998; 9:523-43. [PMID: 9450972 PMCID: PMC25282 DOI: 10.1091/mbc.9.2.523] [Citation(s) in RCA: 118] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Overexpression of the yeast Pdr5 ATP-binding cassette transporter leads to pleiotropic drug resistance to a variety of structurally unrelated cytotoxic compounds. To identify Pdr5 residues involved in substrate recognition and/or drug transport, we used a combination of random in vitro mutagenesis and phenotypic screening to isolate novel mutant Pdr5 transporters with altered substrate specificity. A plasmid library containing randomly mutagenized PDR5 genes was transformed into appropriate drug-sensitive yeast cells followed by phenotypic selection of Pdr5 mutants. Selected mutant Pdr5 transporters were analyzed with respect to their expression levels, subcellular localization, drug resistance profiles to cycloheximide, rhodamines, antifungal azoles, steroids, and sensitivity to the inhibitor FK506. DNA sequencing of six PDR5 mutant genes identified amino acids important for substrate recognition, drug transport, and specific inhibition of the Pdr5 transporter. Mutations were found in each nucleotide-binding domain, the transmembrane domain 10, and, most surprisingly, even in predicted extracellular hydrophilic loops. At least some point mutations identified appear to influence folding of Pdr5, suggesting that the folded structure is a major substrate specificity determinant. Surprisingly, a S1360F exchange in transmembrane domain 10 not only caused limited substrate specificity, but also abolished Pdr5 susceptibility to inhibition by the immunosuppressant FK506. This is the first report of a mutation in a yeast ATP-binding cassette transporter that allows for the functional separation of substrate transport and inhibitor susceptibility.
Collapse
Affiliation(s)
- R Egner
- Department of Molecular Genetics, University and Biocenter of Vienna, A-1030 Vienna, Austria
| | | | | | | | | |
Collapse
|
36
|
Merino G, Shuman HA. Truncation of MalF results in lactose transport via the maltose transport system of Escherichia coli. J Biol Chem 1998; 273:2435-44. [PMID: 9442094 DOI: 10.1074/jbc.273.4.2435] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The active accumulation of maltose and maltodextrins by Escherichia coli is dependent on the maltose transport system. Several lines of evidence suggest that the substrate specificity of the system is not only determined by the periplasmic maltose-binding protein but that a further level of substrate specificity is contributed by the inner membrane integral membrane components of the system, MalF and MalG. We have isolated and characterized an altered substrate specificity mutant that transports lactose. The mutation responsible for the altered substrate specificity results in an amber stop codon at position 99 of MalF. The mutant requires functional MalK-ATPase activity and hydrolyzes ATP constitutively. It also requires MalG. The data suggest that in this mutant the MalG protein is capable of forming a low affinity transport path for substrate.
Collapse
Affiliation(s)
- G Merino
- Department of Microbiology, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA
| | | |
Collapse
|
37
|
Merino G, Shuman HA. Unliganded maltose-binding protein triggers lactose transport in an Escherichia coli mutant with an alteration in the maltose transport system. J Bacteriol 1997; 179:7687-94. [PMID: 9401026 PMCID: PMC179730 DOI: 10.1128/jb.179.24.7687-7694.1997] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Escherichia coli accumulates malto-oligosaccharides by the maltose transport system, which is a member of the ATP-binding-cassette (ABC) superfamily of transport systems. The proteins of this system are LamB in the outer membrane, maltose-binding protein (MBP) in the periplasm, and the proteins of the inner membrane complex (MalFGK2), composed of one MalF, one MalG, and two MalK subunits. Substrate specificity is determined primarily by the periplasmic component, MBP. However, several studies of the maltose transport system as well as other members of the ABC transporter superfamily have suggested that the integral inner membrane components MalF and MalG may play an important role in determining the specificity of the system. We show here that residue L334 in the fifth transmembrane helix of MalF plays an important role in determining the substrate specificity of the system. A leucine-to-tryptophan alteration at this position (L334W) results in the ability to transport lactose in a saturable manner. This mutant requires functional MalK-ATPase activity and the presence of MBP, even though MBP is incapable of binding lactose. The requirement for MBP confirms that unliganded MBP interacts with the inner membrane MalFGK2 complex and that MBP plays a crucial role in triggering the transport process.
Collapse
Affiliation(s)
- G Merino
- Department of Microbiology, College of Physicians & Surgeons, Columbia University, New York, New York 10032, USA
| | | |
Collapse
|
38
|
Shapiro AB, Corder AB, Ling V. P-glycoprotein-mediated Hoechst 33342 transport out of the lipid bilayer. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 250:115-21. [PMID: 9431998 DOI: 10.1111/j.1432-1033.1997.00115.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
High-level expression of P-glycoprotein, a 170-kDa mammalian plasma membrane ATPase, is the cause of an important and widespread form of cancer multidrug resistance. P-glycoprotein reduces cellular accumulation of an enormous variety of lipophilic compounds. The basis for this broad substrate specificity is not well understood. We explored this issue by measuring the kinetics of transport of the lipophilic P-glycoprotein substrate Hoechst 33342 by P-glycoprotein-rich plasma membrane vesicles from CH(R)B30 cells. Hoechst 33342 is fluorescent when bound to the membrane, but not when in the aqueous medium, allowing movement of the dye out of the membrane to be quantitated by fluorescence intensity. The initial specific rate of transport was directly proportional to the amount of Hoechst 33342 in the lipid phase and inversely proportional to the concentration in the aqueous phase. This demonstrates that P-glycoprotein removes Hoechst 33342 from the lipid membrane, where it concentrates due to its hydrophobicity. Because the membrane concentration of hydrophobic P-glycoprotein substrates is high, it may be that P-glycoprotein need not recognize them with high affinity. Transport of hydrophobic substrates out of the lipid bilayer instead of the cytoplasm thus helps to explain the broad substrate specificity of P-glycoprotein.
Collapse
Affiliation(s)
- A B Shapiro
- The British Columbia Cancer Research Centre, Vancouver, Canada
| | | | | |
Collapse
|
39
|
Taguchi Y, Morishima M, Komano T, Ueda K. Amino acid substitutions in the first transmembrane domain (TM1) of P-glycoprotein that alter substrate specificity. FEBS Lett 1997; 413:142-6. [PMID: 9287132 DOI: 10.1016/s0014-5793(97)00899-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Recently, we showed that the amino acid at position 61 in TM1 of human P-glycoprotein is important in deciding the substrate specificity of this protein. In this work, we investigated whether the amino acids other than His61 in TM1 of P-glycoprotein are also essential in the function of this protein. Nine amino acids residues, from Ala57 to Leu65 in TM1, were independently substituted to Arg, and analyzed the drug resistance of cells stably expressing each of these mutant P-glycoproteins. The mutant P-glycoproteins Ile60 --> Arg, His61 --> Arg, Ala63 --> Arg, Gly64 --> Arg, and Leu65 --> Arg were normally processed and expressed in the plasma membrane. Substrate specificities of mutant P-glycoproteins Gly64 --> Arg and Leu65 --> Arg were quite different from that of the wild type, and similar to that of the His61 --> Arg mutant, while the Ile60 --> Arg and Ala63 --> Arg mutant P-glycoproteins showed similar substrate specificities to that of the wild-type P-glycoprotein, suggesting that not only the amino acid residue at position 61 but also those at position 64 and 65 are also important in deciding the substrate specificity of P-glycoprotein. These three amino acids His61, Gly64, and Leu65 would form a compact region on an alpha-helix arrangement of TM1. These results suggest that a region consisting of His61, Gly64, and Leu65 in TM1 would participate in the formation of the recognition site for substrates of P-glycoprotein.
Collapse
Affiliation(s)
- Y Taguchi
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Japan
| | | | | | | |
Collapse
|
40
|
Ruetz S, Delling U, Brault M, Schurr E, Gros P. The pfmdr1 gene of Plasmodium falciparum confers cellular resistance to antimalarial drugs in yeast cells. Proc Natl Acad Sci U S A 1996; 93:9942-7. [PMID: 8790436 PMCID: PMC38534 DOI: 10.1073/pnas.93.18.9942] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The exact role of the pfmdr1 gene in the emergence of drug resistance in the malarial parasite Plasmodium falciparum remains controversial. pfmdr1 is a member of the ATP binding cassette (ABC) superfamily of transporters that includes the mammalian P-glycoprotein family. We have introduced wild-type and mutant variants of the pfmdr1 gene in the yeast Saccharomyces cerevisiae and have analyzed the effect of pfmdr1 expression on cellular resistance to quinoline-containing antimalarial drugs. Yeast transformants expressing either wild-type or a mutant variant of mouse P-glycoprotein were also analyzed. Dose-response studies showed that expression of wild-type pfmdr1 causes cellular resistance to quinine, quinacrine, mefloquine, and halofantrine in yeast cells. Using quinacrine as substrate, we observed that increased resistance to this drug in pfmdr1 transformants was associated with decreased cellular accumulation and a concomitant increase in drug release from preloaded cells. The introduction of amino acid polymorphisms in TM11 of Pgh-1 (pfmdr1 product) associated with drug resistance in certain field isolates of P. falciparum abolished the capacity of this protein to confer drug resistance. Thus, these findings suggest that Pgh-1 may act as a drug transporter in a manner similar to mammalian P-glycoprotein and that sequence variants associated with drug-resistance pfmdr1 alleles behave as loss of function mutations.
Collapse
Affiliation(s)
- S Ruetz
- Department of Biochemistry, McGill University, Montreal, QC Canada
| | | | | | | | | |
Collapse
|
41
|
Chapter 7 The P-glycoprotein family and multidrug resistance: An overview. ACTA ACUST UNITED AC 1996. [DOI: 10.1016/s1383-8121(96)80048-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/16/2023]
|