101
|
Munić V, Kelnerić Z, Mikac L, Eraković Haber V. Differences in assessment of macrolide interaction with human MDR1 (ABCB1, P-gp) using rhodamine-123 efflux, ATPase activity and cellular accumulation assays. Eur J Pharm Sci 2010; 41:86-95. [PMID: 20621639 DOI: 10.1016/j.ejps.2010.05.016] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2010] [Revised: 05/19/2010] [Accepted: 05/30/2010] [Indexed: 11/16/2022]
Abstract
In this study five macrolide antibiotics (azithromycin, erythromycin, clarithromycin, roxithromycin and telithromycin) were compared based on their ability to interact with human MDR1 (ABCB1, P-glycoprotein), studied from two main aspects: by determining the influence of macrolide antibiotics on MDR1 function, as well as the influence of MDR1 on macrolide accumulation in MES-SA/Dx5 cells overexpressing human MDR1. At higher micromolar concentrations five tested macrolides were shown to inhibit MDR1 function in terms of rhodamine-123 efflux and verapamil-activated ATPase function, whereas at lower concentrations they activated MDR1 ATPase. They were confirmed to be substrates of MDR1 and to compete with each other, as well as with verapamil for transport via this transporter. Expression of MDR1 on cells decreased macrolide accumulation in cells from 2- to 80-fold with the most pronounced change observed for azithromycin and erythromycin. Moreover, presence of active MDR1 highly affected the relative ranking of tested macrolides according to their accumulation in cells. In conclusion, out of seven applied methods and assessed parameters, four of them gave similar rough evaluation on the strength of interaction of five macrolides with MDR1, with clarithromycin, roxithromycin and telithromycin showing stronger interaction than azithromycin and erythromycin.
Collapse
Affiliation(s)
- Vesna Munić
- GlaxoSmithKline Research Centre Zagreb Ltd, Prilaz baruna Filipovića 29, HR-10000 Zagreb, Croatia.
| | | | | | | |
Collapse
|
102
|
Kumar A, Shukla S, Mandal A, Shukla S, Ambudkar SV, Prasad R. Divergent signature motifs of nucleotide binding domains of ABC multidrug transporter, CaCdr1p of pathogenic Candida albicans, are functionally asymmetric and noninterchangeable. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:1757-66. [PMID: 20546701 DOI: 10.1016/j.bbamem.2010.05.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2010] [Revised: 05/03/2010] [Accepted: 05/17/2010] [Indexed: 02/04/2023]
Abstract
Nucleotide binding domains (NBDs) of the multidrug transporter of Candida albicans, CaCdr1p, possess unique divergent amino acids in their conserved motifs. For example, NBD1 (N-terminal-NBD) possesses conserved signature motifs, while the same motif is divergent in NBD2 (C-terminal-NBD). In this study, we have evaluated the contribution of these conserved and divergent signature motifs of CaCdr1p in ATP catalysis and drug transport. By employing site-directed mutagenesis, we made three categories of mutant variants. These included mutants where all the signature motif residues were replaced with either alanines or mutants with exchanged equipositional residues to mimic the conservancy and degeneracy in opposite domain. In addition, a set of mutants where signature motifs were swapped to have variants with either both the conserved or degenerated entire signature motif. We observed that conserved and equipositional residues of NBD1 and NBD2 and swapped signature motif mutants showed high susceptibility to all the tested drugs with simultaneous abrogation in ATPase and R6G efflux activities. However, some of the mutants displayed a selective increase in susceptibility to the drugs. Notably, none of the mutant variants and WT-CaCdr1p showed any difference in drug and nucleotide binding. Our mutational analyses show not only that certain conserved residues of NBD1 signature sequence (S304, G306, and E307) are important in ATP hydrolysis and R6G efflux but also that a few divergent residues (N1002 and E1004) of NBD2 signature motif have evolved to be functionally relevant and are not interchangeable. Taken together, our data suggest that the signature motifs of CaCdr1p, whether it is divergent or conserved, are nonexchangeable and are functionally critical for ATP hydrolysis.
Collapse
Affiliation(s)
- Antresh Kumar
- Membrane Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi 110067, India
| | | | | | | | | | | |
Collapse
|
103
|
Gravel M, Iliescu A, Horth C, Apuzzo S, Gros P. Molecular and cellular mechanisms underlying neural tube defects in the loop-tail mutant mouse. Biochemistry 2010; 49:3445-55. [PMID: 20329788 DOI: 10.1021/bi902180m] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Loop-tail (Lp) mice show a very severe neural tube defect (craniorachischisis) caused by mutations in the Vangl2 gene (D255E, S464N). Mammalian Vangl1 and Vangl2 are membrane proteins that play critical roles in development such as establishment of planar cell polarity (PCP) in epithelial layers and convergent extension movements during neurogenesis and cardiogenesis. Vangl proteins are thought to assemble with other PCP proteins (Dvl, Pk) to form membrane-bound PCP signaling complexes that provide polarity information to the cell. In the present study, we show that Vangl1 is expressed exclusively at the plasma membrane of transfected MDCK cells, where it is targeted to the basolateral membrane. Experiments with an inserted exofacial HA epitope indicate that the segment delimited by the predicted transmembrane domains 1 and 2 is exposed to the extracellular milieu. Comparative studies of the Lp-associated pathogenic mutation D255E indicate that the targeting of the mutant variant at the plasma membrane is greatly reduced; the mutant variant is predominantly retained intracellularly in endoplasmic reticulum (ER) vesicles colocalizing with the ER marker calreticulin. In addition, the D255E variant shows drastically reduced stability with a half-life of approximately 2 h, compared to >9 h for its wild type counterpart and is rapidly degraded in a proteasome-dependent and MG132 sensitive pathway. These findings highlight a critical role for D255 for normal folding and processing of Vangl proteins, with highly conservative substitutions not tolerated at that site. Our study provide an experimental framework for the analysis of human VANGL mutations recently identified in familial and sporadic cases of spina bifida.
Collapse
Affiliation(s)
- Michel Gravel
- Department of Biochemistry and Complex Traits Program, McGill University, Montreal, Quebec, Canada H3G 0B1
| | | | | | | | | |
Collapse
|
104
|
Heikkinen AT, Mönkkönen J, Korjamo T. Determination of permeation resistance distribution in in vitro cell monolayer permeation experiments. Eur J Pharm Sci 2010; 40:132-42. [DOI: 10.1016/j.ejps.2010.03.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Revised: 03/09/2010] [Accepted: 03/13/2010] [Indexed: 10/19/2022]
|
105
|
Ishikawa T, Sakurai A, Hirano H, Lezhava A, Sakurai M, Hayashizaki Y. Emerging New Technologies in Pharamcogenomics: Rapid SNP detection, molecular dynamic simulation, and QSAR analysis methods to validate clinically important genetic variants of human ABC Transporter ABCB1 (P-gp/MDR1). Pharmacol Ther 2010; 126:69-81. [DOI: 10.1016/j.pharmthera.2010.01.005] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2010] [Accepted: 01/19/2010] [Indexed: 01/18/2023]
|
106
|
Abstract
The development of multidrug resistance (MDR) to chemotherapy remains a major challenge in the treatment of cancer. Resistance exists against every effective anticancer drug and can develop by numerous mechanisms including decreased drug uptake, increased drug efflux, activation of detoxifying systems, activation of DNA repair mechanisms, evasion of drug-induced apoptosis, etc. In the first part of this chapter, we briefly summarize the current knowledge on individual cellular mechanisms responsible for MDR, with a special emphasis on ATP-binding cassette transporters, perhaps the main theme of this textbook. Although extensive work has been done to characterize MDR mechanisms in vitro, the translation of this knowledge to the clinic has not been crowned with success. Therefore, identifying genes and mechanisms critical to the development of MDR in vivo and establishing a reliable method for analyzing clinical samples could help to predict the development of resistance and lead to treatments designed to circumvent it. Our thoughts about translational research needed to achieve significant progress in the understanding of this complex phenomenon are therefore discussed in a third section. The pleotropic response of cancer cells to chemotherapy is summarized in a concluding diagram.
Collapse
|
107
|
Panagiotopoulou V, Richardson G, Jensen OE, Rauch C. On a biophysical and mathematical model of Pgp-mediated multidrug resistance: understanding the “space–time” dimension of MDR. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 39:201-11. [DOI: 10.1007/s00249-009-0555-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Revised: 10/05/2009] [Accepted: 10/09/2009] [Indexed: 11/28/2022]
|
108
|
Krämer S, Lombardi D, Primorac A, Thomae A, Wunderli-Allenspach H. Lipid-Bilayer Permeation of Drug-Like Compounds. Chem Biodivers 2009; 6:1900-16. [DOI: 10.1002/cbdv.200900122] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
109
|
Synthesis of 4-substituted 3-[3-(dialkylaminomethyl)indol-1-yl]maleimides and study of their ability to inhibit protein kinase C-α, prevent development of multiple drug resistance of tumor cells and cytotoxicity. Russ Chem Bull 2009. [DOI: 10.1007/s11172-008-0271-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
110
|
Kopriva F, Dzubak P, Potesil J, Hajduch M. The anti-inflammatory effects of inhaled corticosteroids versus anti-leukotrienes on the lymphocyte P-glycoprotein (PGP) expression in asthmatic children. J Asthma 2009; 46:366-70. [PMID: 19484671 DOI: 10.1080/02770900902777767] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
BACKGROUND Inhaled corticosteroids (ICS) are used in asthma therapy for their anti-inflammatory effects. P-glycoprotein (PGP) is a transmembrane efflux pump for many drugs, including corticosteroids. Expression of PGP is associated with therapy resistant disease. OBJECTIVE The purpose of this study was to compare expression levels of PGP in blood lymphocytes of pediatric asthma patients either on ICS or on the leukotriene inhibitor montelukast medication. PATIENTS AND METHODS The evaluation of lymphocyte PGP expression was performed on a sample of 99 children (66 boys and 33 girls) aged 2-18 (median 12) years with intermittent or persisting mild asthma, (as defined by GINY 2002). The asthmatic children were divided into 3 groups: (1) treated by ICS budesonide 200-400 microg per day (n = 27) more than 1 year; (2) treated by oral montelukast 4 or 5 mg at an age-based dose (n = 16); and (3) treated by inhaled corticosteroids and montelukast (n = 45). Reference PGP values were obtained from a group of 64 healthy children (23 boys and 29 girls) aged 2-15 years (median, 10 years). The expression of lymphocyte PGP was determined on fixed and permeabilized blood mononuclear cells using indirect immunofluorescence staining technique by flow cytometry modified according to Boer et al., 1997. RESULTS Based on the weighted medians for PGP expression in peripheral blood lymphocytes, we found a significant difference (p < 10(-3)) between the group of asthma patients (n = 99), (619 +/- 5.3) and healthy controls (n = 64) (446.9 +/- 4.4). Second, there was a lower level of PGP expression in the group treated by ICS (548.6 +/- 9) than the group treated by montelukast and montelukast with budesonide (643.2 +/- 6.3) (p < 10(-6)). CONCLUSIONS The anti-inflammatory activity of ICS is more effective in decreasing the production of pro-inflammatory mediators and results in reduced multidrug resistence (MDR-1) gene activity and expression of lymphocyte PGP in asthmatic children.
Collapse
|
111
|
Belli S, Elsener PM, Wunderli-Allenspach H, Krämer SD. Cholesterol-mediated activation of P-glycoprotein: distinct effects on basal and drug-induced ATPase activities. J Pharm Sci 2009; 98:1905-18. [PMID: 18937360 DOI: 10.1002/jps.21558] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Cholesterol promotes basal and verapamil-induced ATPase activity of P-glycoprotein (P-gp). We investigated whether these effects are related to each other and to the impact of the sterol on bilayer fluidity and verapamil membrane affinity. P-gp was reconstituted in egg-phosphatidylcholine (PhC) liposomes with or without cholesterol, 1,2-dipalmitoyl-phosphatidylcholine (DPPC), alpha-tocopherol (alpha-Toc) or 2,2,5,7,8-pentamethyl-6-chromanol (PMC). Basal and verapamil-induced ATPase activities were studied with an enzymatic assay. Membrane fluidity was characterized with diphenyl-hexatriene anisotropy measurements and membrane affinity by equilibrium dialysis. DPPC (70% mol/mol) decreased the fluidity of PhC bilayers to the same level as 20% cholesterol. PMC (20%) and alpha-Toc (20%) decreased the fluidity to lesser extents. alpha-Toc and PMC, but not DPPC increased the verapamil membrane affinity. While 20% cholesterol strikingly enhanced the basal ATPase activity, none of the other constituents had a similar effect. In contrast, verapamil stimulation of P-gp ATPase activity was not only enabled by cholesterol but also by alpha-Toc and DPPC. PMC had no effect. In conclusion, cholesterol exerts distinct effects on basal and verapamil-induced ATPase activity. The influence on basal ATPase activity is sterol-specific while its effect on verapamil-induced ATPase activity is unspecific and not related to its influence on membrane fluidity and on verapamil membrane affinity.
Collapse
Affiliation(s)
- Sara Belli
- Department of Chemistry and Applied Biosciences, Institute of Pharmaceutical Sciences, ETH Zürich, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, Switzerland
| | | | | | | |
Collapse
|
112
|
Shen F, Bailey BJ, Chu S, Bence AK, Xue X, Erickson P, Safa AR, Beck WT, Erickson LC. Dynamic assessment of mitoxantrone resistance and modulation of multidrug resistance by valspodar (PSC833) in multidrug resistance human cancer cells. J Pharmacol Exp Ther 2009; 330:423-9. [PMID: 19423841 DOI: 10.1124/jpet.109.153551] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
P-glycoprotein (Pgp), a member of the ATP-binding cassette transporter family, is one of the major causes for multidrug resistance (MDR). We report using confocal microscopy to study the roles of Pgp in mediating the efflux of the anticancer agent mitoxantrone and the reversal of MDR by the specific Pgp inhibitor valspodar (PSC833). The net uptake and efflux of mitoxantrone and the effect of PSC833 were quantified and compared in Pgp-expressing human cancer MDA-MB-435 (MDR) cells and in parental wild-type cells. The MDR cells, transduced with the human Pgp-encoding gene MDR1 construct, were approximately 8-fold more resistant to mitoxantrone than the wild-type cells. Mitoxantrone accumulation in the MDR cells was 3-fold lower than that in the wild-type cells. The net uptake of mitoxantrone in the nuclei and cytoplasm of MDR cells was only 58 and 67% of that in the same intracellular compartment of the wild-type cells. Pretreatment with PSC833 increased the accumulation of mitoxantrone in the MDR cells to 85% of that in the wild-type cells. In living animals, the accumulation of mitoxantrone in MDA-MB-435mdr xenograft tumors was 61% of that in the wild-type tumors. Administration of PSC833 to animals before mitoxantrone treatment increased the accumulation of mitoxantrone in the MDR tumors to 94% of that in the wild-type tumors. These studies have added direct in vitro and in vivo visual information on how Pgp processes anticancer compounds and how Pgp inhibitors modulate MDR in resistant cancer cells.
Collapse
Affiliation(s)
- Fei Shen
- Department of Pharmacology and Toxicology, Indiana University Simon Cancer Center, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
113
|
Identification of novel specific and general inhibitors of the three major human ATP-binding cassette transporters P-gp, BCRP and MRP2 among registered drugs. Pharm Res 2009; 26:1816-31. [PMID: 19421845 DOI: 10.1007/s11095-009-9896-0] [Citation(s) in RCA: 237] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2009] [Accepted: 04/11/2009] [Indexed: 01/16/2023]
Abstract
PURPOSE To study the inhibition patterns of the three major human ABC transporters P-gp (ABCB1), BCRP (ABCG2) and MRP2 (ABCC2), using a dataset of 122 structurally diverse drugs. METHODS Inhibition was investigated in cellular and vesicular systems over-expressing single transporters. Computational models discriminating either single or general inhibitors from non-inhibitors were developed using multivariate statistics. RESULTS Specific (n = 23) and overlapping (n = 19) inhibitors of the three ABC transporters were identified. GF120918 and Ko143 were verified to specifically inhibit P-gp/BCRP and BCRP in defined concentration intervals, whereas the MRP inhibitor MK571 was revealed to inhibit all three transporters within one log unit of concentration. Virtual docking experiments showed that MK571 binds to the ATP catalytic site, which could contribute to its multi-specific inhibition profile. A computational model predicting general ABC inhibition correctly classified 80% of both ABC transporter inhibitors and non-inhibitors in an external test set. CONCLUSIONS The inhibitor specificities of P-gp, BCRP and MRP2 were shown to be highly overlapping. General ABC inhibitors were more lipophilic and aromatic than specific inhibitors and non-inhibitors. The identified specific inhibitors can be used to delineate transport processes in complex experimental systems, whereas the multi-specific inhibitors are useful in primary ABC transporter screening in drug discovery settings.
Collapse
|
114
|
Fung KL, Gottesman MM. A synonymous polymorphism in a common MDR1 (ABCB1) haplotype shapes protein function. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2009; 1794:860-71. [PMID: 19285158 DOI: 10.1016/j.bbapap.2009.02.014] [Citation(s) in RCA: 248] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2008] [Revised: 02/23/2009] [Accepted: 02/26/2009] [Indexed: 12/30/2022]
Abstract
The MDR1 (ABCB1) gene encodes a membrane-bound transporter that actively effluxes a wide range of compounds from cells. The overexpression of MDR1 by multidrug-resistant cancer cells is a serious impediment to chemotherapy. MDR1 is expressed in various tissues to protect them from the adverse effect of toxins. The pharmacokinetics of drugs that are also MDR1 substrates also influence disease outcome and treatment efficacy. Although MDR1 is a well-conserved gene, there is increasing evidence that its polymorphisms affect substrate specificity. Three single nucleotide polymorphisms (SNPs) occur frequently and have strong linkage, creating a common haplotype at positions 1236C>T (G412G), 2677G>T (A893S) and 3435C>T (I1145I). The frequency of the synonymous 3435C>T polymorphism has been shown to vary significantly according to ethnicity. Existing literature suggests that the haplotype plays a role in response to drugs and disease susceptibility. This review summarizes recent findings on the 3435C>T polymorphism of MDR1 and the haplotype to which it belongs. A possible molecular mechanism of action by ribosome stalling that can change protein structure and function by altering protein folding is discussed.
Collapse
Affiliation(s)
- King Leung Fung
- Laboratory of Cell Biology, Center of Cancer Research, National Cancer Institute, National Institutes of Health, 37 Convent Drive, Room 2108, Bethesda, MD 20892-4254, USA
| | | |
Collapse
|
115
|
In vitro–in vivo correlation in p-glycoprotein mediated transport in intestinal absorption. Eur J Pharm Sci 2009; 36:200-11. [DOI: 10.1016/j.ejps.2008.11.005] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2008] [Revised: 11/07/2008] [Accepted: 11/10/2008] [Indexed: 01/11/2023]
|
116
|
Stanley LA, Horsburgh BC, Ross J, Scheer N, Wolf CR. Drug transporters: Gatekeepers controlling access of xenobiotics to the cellular interior. Drug Metab Rev 2009; 41:27-65. [DOI: 10.1080/03602530802605040] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
|
117
|
Vigl C, Leithner K, Albrecht K, Bernkop-Schnurch A. The efflux pump inhibitory properties of (thiolated) polyallylamines. J Drug Deliv Sci Technol 2009. [DOI: 10.1016/s1773-2247(09)50084-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
|
118
|
Titapiwatanakun B, Murphy AS. Post-transcriptional regulation of auxin transport proteins: cellular trafficking, protein phosphorylation, protein maturation, ubiquitination, and membrane composition. JOURNAL OF EXPERIMENTAL BOTANY 2009; 60:1093-107. [PMID: 18824505 DOI: 10.1093/jxb/ern240] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Auxin concentration gradients, established by polar transport of auxin, are essential for the establishment and maintenance of polar growth and morphological patterning. Three families of cellular transport proteins, PIN-formed (PIN), P-glycoprotein (ABCB/PGP), and AUXIN RESISTANT 1/LIKE AUX1 (AUX1/LAX), can independently and co-ordinately transport auxin in plants. Regulation of these proteins involves intricate and co-ordinated cellular processes, including protein-protein interactions, vesicular trafficking, protein phosphorylation, ubiquitination, and stabilization of the transporter complexes on the plasma membrane.
Collapse
|
119
|
Giri N, Agarwal S, Shaik N, Pan G, Chen Y, Elmquist WF. Substrate-dependent breast cancer resistance protein (Bcrp1/Abcg2)-mediated interactions: consideration of multiple binding sites in in vitro assay design. Drug Metab Dispos 2008; 37:560-70. [PMID: 19056916 DOI: 10.1124/dmd.108.022046] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
In vitro assays are frequently used for the screening of substrates and inhibitors of transporter-mediated efflux. Examining directional flux across Madin-Darby canine kidney (MDCK) II cell monolayers that overexpress a transporter protein is particularly useful in identifying whether or not a candidate compound is an inhibitor or substrate for that transport system. Studies that use a single substrate or inhibitor in competition assays can be challenging to interpret because of the possible multiple mechanisms involved in substrate/inhibitor-protein interactions. During our previous studies of substrate-inhibitor-transporter interactions, we observed differences in breast cancer resistance protein (BCRP) inhibition, depending on the substrate and the inhibitor. Therefore, we investigated BCRP-mediated interactions with a 4 x 4 matrix of substrates and inhibitors using monolayers formed from MDCKII cells transfected with murine BCRP (Bcrp1/Abcg2). The selective BCRP inhibitor 3-(6-isobutyl-9-methoxy-1,4-dioxo-1,2,3,4,6,7,12,12a-octahydropyrazino [1',2':1,6] pyrido [3,4-b]indol-3-yl)-propionic acid tert-butyl ester (Ko143) effectively inhibited the Bcrp1-mediated transport of all substrates examined. However, N-(4-[2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl)ethyl]-phenyl)-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamide (GF120918), nelfinavir, and Pluronic P85 exhibited differences in inhibition depending on the substrate examined. Our findings support recent reports suggesting that the interactions of substrate molecules with BCRP involve multiple binding regions in the protein. The nucleoside substrates zidovudine and abacavir seem to bind to a region on BCRP that may have little or no overlap with the binding regions of either prazosin or imatinib. In conclusion, the choice of substrate or inhibitor molecules for an in vitro assay system can be crucial for the optimal design of experiments to evaluate transporter-mediated drug-drug interactions.
Collapse
Affiliation(s)
- Nagdeep Giri
- Department of Pharmaceutics, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | | | | | | | | | | |
Collapse
|
120
|
Dietrich D, Schmuths H, De Marcos Lousa C, Baldwin JM, Baldwin SA, Baker A, Theodoulou FL, Holdsworth MJ. Mutations in the Arabidopsis peroxisomal ABC transporter COMATOSE allow differentiation between multiple functions in planta: insights from an allelic series. Mol Biol Cell 2008; 20:530-43. [PMID: 19019987 DOI: 10.1091/mbc.e08-07-0745] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
COMATOSE (CTS), the Arabidopsis homologue of human Adrenoleukodystrophy protein (ALDP), is required for import of substrates for peroxisomal beta-oxidation. A new allelic series and a homology model based on the bacterial ABC transporter, Sav1866, provide novel insights into structure-function relations of ABC subfamily D proteins. In contrast to ALDP, where the majority of mutations result in protein absence from the peroxisomal membrane, all CTS mutants produced stable protein. Mutation of conserved residues in the Walker A and B motifs in CTS nucleotide-binding domain (NBD) 1 resulted in a null phenotype but had little effect in NBD2, indicating that the NBDs are functionally distinct in vivo. Two alleles containing mutations in NBD1 outside the Walker motifs (E617K and C631Y) exhibited resistance to auxin precursors 2,4-dichlorophenoxybutyric acid (2,4-DB) and indole butyric acid (IBA) but were wild type in all other tests. The homology model predicted that the transmission interfaces are domain-swapped in CTS, and the differential effects of mutations in the conserved "EAA motif" of coupling helix 2 supported this prediction, consistent with distinct roles for each NBD. Our findings demonstrate that CTS functions can be separated by mutagenesis and the structural model provides a framework for interpretation of phenotypic data.
Collapse
Affiliation(s)
- Daniela Dietrich
- Department of Plant and Crop Sciences, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, United Kingdom
| | | | | | | | | | | | | | | |
Collapse
|
121
|
Abstract
This article provides an overview of principles and barriers relevant to intracellular drug and gene transport, accumulation and retention (collectively called as drug delivery) by means of nanovehicles (NV). The aim is to deliver a cargo to a particular intracellular site, if possible, to exert a local action. Some of the principles discussed in this article apply to noncolloidal drugs that are not permeable to the plasma membrane or to the blood-brain barrier. NV are defined as a wide range of nanosized particles leading to colloidal objects which are capable of entering cells and tissues and delivering a cargo intracelullarly. Different localization and targeting means are discussed. Limited discussion on pharmacokinetics and pharmacodynamics is also presented. NVs are contrasted to micro-delivery and current nanotechnologies which are already in commercial use. Newer developments in NV technologies are outlined and future applications are stressed. We also briefly review the existing modeling tools and approaches to quantitatively describe the behavior of targeted NV within the vascular and tumor compartments, an area of particular importance. While we list "elementary" phenomena related to different level of complexity of delivery to cancer, we also stress importance of multi-scale modeling and bottom-up systems biology approach.
Collapse
Affiliation(s)
- Ales Prokop
- Department of Chemical Engineering, 24th Avenue & Garland Avenues, 107 Olin Hall, Vanderbilt University, Nashville, Tennessee 37235, USA.
| | | |
Collapse
|
122
|
von Richter O, Glavinas H, Krajcsi P, Liehner S, Siewert B, Zech K. A novel screening strategy to identify ABCB1 substrates and inhibitors. Naunyn Schmiedebergs Arch Pharmacol 2008; 379:11-26. [PMID: 18758752 DOI: 10.1007/s00210-008-0345-0] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2008] [Accepted: 08/04/2008] [Indexed: 12/19/2022]
Abstract
We tested the hypothesis whether data on ABCB1 ATPase activity and passive permeability can be used in combination to identify ABCB1 substrates and inhibitors. We determined passive permeability using an artificial membrane permeability assay (HDM-PAMPA) and ABCB1 function, i.e., vanadate-sensitive ATPase activity for a training set (40 INN drugs) and a validation set (26 development compounds). In parallel experiments, we determined ABCB1 function, i.e., vectorial transport in a Caco-2 cell monolayer, and ABCB1 inhibition, i.e., calcein AM extrusion out of K562-MDR cells, to cross-validate the results with cellular assays. We found that compounds that did not modulate ABCB1-ATPase did also not affect calcein AM extrusion and were not actively transported by ABCB1 in Caco-2 cell monolayers. The results corroborated the effect of passive permeability as an important covariate of active transport: active transport in Caco-2 monolayer was only apparent for compounds showing low passive permeability (<5.0 cmx10(-6)/s) in the HDM-PAMPA assay whereas compounds with high passive permeability (>50 cmx10(-6)/s) were shown to inhibit calcein AM efflux with IC50 values close to their respective Km value obtained for ABCB1-ATPase. The use of HDM-PAMPA in combination with ABCB1-ATPase offers a simple, inexpensive experimental approach capable of identifying ABCB1 inhibitors as well as transported substrates.
Collapse
Affiliation(s)
- Oliver von Richter
- Division of Drug Metabolism and Pharmacokinetics, Altana Pharma AG, Konstanz, Germany.
| | | | | | | | | | | |
Collapse
|
123
|
MARTINEZ M, MODRIC S, SHARKEY M, TROUTMAN L, WALKER L, MEALEY K. The pharmacogenomics of P-glycoprotein and its role in veterinary medicine. J Vet Pharmacol Ther 2008; 31:285-300. [DOI: 10.1111/j.1365-2885.2008.00964.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
|
124
|
Sauna ZE, Kim IW, Ambudkar SV. Genomics and the mechanism of P-glycoprotein (ABCB1). J Bioenerg Biomembr 2008; 39:481-7. [PMID: 18058211 DOI: 10.1007/s10863-007-9115-9] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
The development of effective clinical interventions against multidrug resistance (MDR) in cancer remains a significant challenge. Single nucleotide polymorphisms (SNPs) contribute to wide variations in how individuals respond to medications and there are several SNPs in human P-glycoprotein (P-gp) that may influence the interactions of drug-substrates with the transporter. Interestingly, even some of the synonymous SNPs have functional consequences for P-gp. It is also becoming increasingly evident that an understanding of the transport pathway of P-gp may be necessary to design effective modulators. In this review we discuss: (1) The potential importance of SNPs (both synonymous and non-synonymous) in MDR and (2) How new concepts that have emerged from structural studies with isolated nucleotide binding domains of bacterial ABC transporters have prompted biochemical studies on P-gp, leading to a better understanding of the mechanism of P-gp mediated transport. Our results suggest that the power-stroke is provided only after formation of the pre-hydrolysis transition-like (E.S) state during ATP hydrolysis.
Collapse
Affiliation(s)
- Zuben E Sauna
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, DHHS, Building 37, 37 Convent Drive, Bethesda, MD 20892-4256, USA
| | | | | |
Collapse
|
125
|
Luckenbach T, Epel D. ABCB- and ABCC-type transporters confer multixenobiotic resistance and form an environment-tissue barrier in bivalve gills. Am J Physiol Regul Integr Comp Physiol 2008; 294:R1919-29. [PMID: 18401003 DOI: 10.1152/ajpregu.00563.2007] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Aquatic organisms and, in particular, filter feeders, such as mussels, are continuously exposed to toxicants dissolved in the water and, presumably, require adaptations to avoid the detrimental effects from such chemicals. Previous work indicates that activity of ATP-binding cassette (ABC) transporters protects mussels against toxicants, but the nature of these transporters and the structural basis of protection are not known. Here we meld studies on transporter function, gene expression, and localization of transporter protein in mussel gill tissue and show activity and expression of two xenobiotic transporter types in the gills, where they provide an effective structural barrier against chemicals. Activity of ABCB/MDR/P-glycoprotein and ABCC/MRP-type transporters was indicated by sensitivity of efflux of the test substrate calcein-AM to the ABCB inhibitor PSC-833 and the ABCC inhibitor MK-571. This activity profile is supported by our cloning of the complete sequence of two ABC transporter types from RNA in mussel tissue with a high degree of identity to transporters from the ABCB and ABCC subfamilies. Overall identity of the amino acid sequences with corresponding homologs from other organisms was 38-50% (ABCB) and 27-44% (ABCC). C219 antibody staining specific for ABCB revealed that this transporter was restricted to cells in the gill filaments with direct exposure to water flow. Taken together, our data demonstrate that ABC transporters form an active, physiological barrier at the tissue-environment interface in mussel gills, providing protection against environmental xenotoxicants.
Collapse
Affiliation(s)
- Till Luckenbach
- Department of Cell Toxicology, UFZ, Helmholtz Centre for Environmental Research, Permoserstrasse 15, Leipzig, Germany.
| | | |
Collapse
|
126
|
Sharom FJ. ABC multidrug transporters: structure, function and role in chemoresistance. Pharmacogenomics 2008; 9:105-27. [PMID: 18154452 DOI: 10.2217/14622416.9.1.105] [Citation(s) in RCA: 695] [Impact Index Per Article: 43.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Three ATP-binding cassette (ABC)-superfamily multidrug efflux pumps are known to be responsible for chemoresistance; P-glycoprotein (ABCB1), MRP1 (ABCC1) and ABCG2 (BCRP). These transporters play an important role in normal physiology by protecting tissues from toxic xenobiotics and endogenous metabolites. Hydrophobic amphipathic compounds, including many clinically used drugs, interact with the substrate-binding pocket of these proteins via flexible hydrophobic and H-bonding interactions. These efflux pumps are expressed in many human tumors, where they likely contribute to resistance to chemotherapy treatment. However, the use of efflux-pump modulators in clinical cancer treatment has proved disappointing. Single nucleotide polymorphisms in ABC drug-efflux pumps may play a role in responses to drug therapy and disease susceptibility. The effect of various genotypes and haplotypes on the expression and function of these proteins is not yet clear, and their true impact remains controversial.
Collapse
Affiliation(s)
- Frances J Sharom
- University of Guelph, Department of Molecular & Cellular Biology, Guelph Ontario, N1G 2W1, Canada.
| |
Collapse
|
127
|
Heredi-Szabo K, Kis E, Molnar E, Gyorfi A, Krajcsi P. Characterization of 5(6)-carboxy-2,'7'-dichlorofluorescein transport by MRP2 and utilization of this substrate as a fluorescent surrogate for LTC4. ACTA ACUST UNITED AC 2008; 13:295-301. [PMID: 18349419 DOI: 10.1177/1087057108316702] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
MRP2 (ABCC2) is an efflux transporter expressed on the apical membrane of polarized cells. This protein has a major role in the biliary elimination of toxic compounds from the liver. As MRP2 transports many endogenous compounds, including LTC4 as well as xenobiotics and toxic phase II metabolites, blockade of this transporter may cause the accumulation of these compounds in the hepatocyte, resulting in hepatotoxicity. The vesicular transport assay is a great tool to study drug-drug and drug-endogenous compound interactions of ABC transporters. In this assay, inside-out membrane vesicles are used, so the test compound can readily access the transporter. As MRP2 transports many ionic compounds that are difficult to investigate in a whole-cell system because of permeability reasons, the vesicular transport assay is a good choice for screening MRP2-mediated interactions. LTC4 is not an optimal substrate for high-throughput screening for MRP2 interactors, even though it is an important MRP2 substrate. Therefore, the transport of a drug surrogate, 5(6)-carboxy-2,'7'-dichlorofluorescein (CDCF), by MRP2 was characterized using the vesicular transport assay. The data indicate that CDCF proves to be an ideal substrate for MRP2 vesicular transport assay with its optimal detection and transport properties.
Collapse
|
128
|
Tombline G, Holt JJ, Gannon MK, Donnelly DJ, Wetzel B, Sawada GA, Raub TJ, Detty MR. ATP occlusion by P-glycoprotein as a surrogate measure for drug coupling. Biochemistry 2008; 47:3294-307. [PMID: 18275155 DOI: 10.1021/bi7021393] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The multidrug efflux pump P-glycoprotein (Pgp) couples drug transport to ATP hydrolysis. Previously, using a synthetic library of tetramethylrosamine ( TMR) analogues, we observed significant variation in ATPase stimulation ( V m (D)). Concentrations required for half-maximal ATPase stimulation ( K m (D)) correlated with ATP hydrolysis transition-state stabilization and ATP occlusion (EC 50 (D)) at a single site. Herein, we characterize several TMR analogues that elicit modest turnover ( k cat <or= 1-2 s (-1)) compared to verapamil (VER) ( k cat approximately 10 s (-1)). Apparent ATPase activities manifest as nearly equivalent to basal values. In some cases, K m (D) parameters for drug stimulation of ATPase could not be accurately determined, yet these same TMR analogues promoted ATP occlusion at relatively low concentrations ( approximately 0.4-40 microM). Moreover, the TMR analogues competitively inhibited VER-dependent ATPase activity at concentrations similar to those required for ATP occlusion. Finally, the TMR analogues facilitated uptake of calcein-AM into CR1R12 and MDCK-MDR1 cells and are actively transported by Pgp in monolayers of MDCK-MDR1 cells at similarly low concentrations ( approximately 1-20 microM). ADP.V i release kinetics were identical in the presence of the TMR derivatives, VER, or in the absence of drug, suggesting that slow turnover is not likely due to slow release of the ATP hydrolysis products ADP and P i. These data support the partition model in which drug site occupancy converts residual basal ATPase activity to a drug-dependent mechanism even in cases where stimulation appears to be exactly compensatory to basal values. It is noteworthy that when compared to previously reported TMR analogues, subtle modification of the TMR scaffold can confer large differences in ATP turnover.
Collapse
Affiliation(s)
- Gregory Tombline
- Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, New York 14260-3000, USA.
| | | | | | | | | | | | | | | |
Collapse
|
129
|
Orelle C, Gubellini F, Durand A, Marco S, Lévy D, Gros P, Di Pietro A, Jault JM. Conformational change induced by ATP binding in the multidrug ATP-binding cassette transporter BmrA. Biochemistry 2008; 47:2404-12. [PMID: 18215075 DOI: 10.1021/bi702303s] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
ATP-binding cassette (ABC) transporters are involved in the transport of a wide variety of substrates, and ATP-driven dimerization of their nucleotide binding domains (NBDs) has been suggested to be one of the most energetic steps of their catalytic cycle. Taking advantage of the propensity of BmrA, a bacterial multidrug resistance ABC transporter, to form stable, highly ordered ring-shaped structures [Chami et al. (2002) J. Mol. Biol. 315, 1075-1085], we show here that addition of ATP in the presence of Mg2+ prevented ring formation or destroyed the previously formed rings. To pinpoint the catalytic step responsible for such an effect, two classes of hydrolysis-deficient mutants were further studied. In contrast to hydrolytically inactive glutamate mutants that behaved essentially as the wild-type, lysine Walker A mutants formed ring-shaped structures even in the presence of ATP-Mg. Although the latter mutants still bound ATP-Mg, and even slowly hydrolyzed it for the K380R mutant, they were most likely unable to undergo a proper NBD dimerization upon ATP-Mg addition. The ATP-driven dimerization step, which was still permitted in glutamate mutants and led to a stable conformation suitable to monitor the growth of 2D crystals, appeared therefore responsible for destabilization of the BmrA ring structures. Our results provide direct visual evidence that the ATP-induced NBD dimerization triggers a conformational change large enough in BmrA to destabilize the rings, which is consistent with the assumption that this step might constitute the "power stroke" for ABC transporters.
Collapse
Affiliation(s)
- Cédric Orelle
- Institut de Biologie et Chimie des Protéines, UMR 5086 CNRS-Université de Lyon 1 and IFR 128 BioSciences Gerland-Lyon Sud, 7 passage du Vercors, 69367 Lyon, France
| | | | | | | | | | | | | | | |
Collapse
|
130
|
Callaghan R, Crowley E, Potter S, Kerr ID. P-glycoprotein: so many ways to turn it on. J Clin Pharmacol 2007; 48:365-78. [PMID: 18156365 DOI: 10.1177/0091270007311568] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Expression of the ABC transporter P-glycoprotein (P-gp or ABCB1) is associated with resistance to chemotherapy in cancer. However, early investigations into the regulation of ABCB1 expression revealed that the process is not a classical induction as observed for certain metabolizing enzymes. The process involves the cellular stress response pathway initiated by either inflicted (e.g., chemotherapy damage) or endogenous (e.g., hypoxia) factors. However, ABCB1 is also expressed in a number of noncancerous tissues. In particular, the protein is found at tissues providing a barrier or secretory function. The localization of ABCB1 in normal tissues will impact significantly on drug pharmacokinetics, in particular the absorption and elimination processes. This review also describes the mechanism underlying ABCB1 expression in noncancerous tissue, a process that does not involve the stress response.
Collapse
Affiliation(s)
- Richard Callaghan
- Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford, UK.
| | | | | | | |
Collapse
|
131
|
Lima SAC, Tavares J, Gameiro P, de Castro B, Cordeiro-da-Silva A. Flurazepam inhibits the P-glycoprotein transport function: an insight to revert multidrug-resistance phenotype. Eur J Pharmacol 2007; 581:30-6. [PMID: 18190907 DOI: 10.1016/j.ejphar.2007.11.045] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2007] [Revised: 11/12/2007] [Accepted: 11/21/2007] [Indexed: 11/25/2022]
Abstract
P-glycoprotein mediated drug transport may lead to a multidrug resistance phenotype often associated with a poor response to the successful treatment of a variety of human disorders. Several agents have been found to modulate P-glycoprotein drug resistance, most probably by blocking its transport function. The aim of this study was to examine the effects of some benzodiazepines (bromazepam, chlordiazepoxide, diazepam and flurazepam) able to bind to P-glycoprotein in proteoliposomes on its transport function and ATPase activity in the human cancer cell line, KB-V1. The toxicity of the benzodiazepines drugs towards KB-V1 cells was first evaluated and the non toxic drugs concentrations were used to assess the drug efflux and the ATPase activity. Using the flow cytometry approach, the accumulation and efflux of daunorubicin were followed by measuring the daunorubicin associated geometric mean fluorescence intensity. Vanadate was employed as a comparative inhibitory compound. Flurazepam was able to inhibit the daunorubicin efflux in 80%. ATPase activity determined by a colorimetric assay revealed that flurazepam inhibits the P-glycoprotein enzymatic activity, indicating coupling between drug transport and ATP hydrolysis. Bromazepam, chlordiazepoxide and diazepam behaved as activators of the P-glycoprotein ATPase activity, suggesting a role as transported substrates and did not interfere in the daunorubicin transport.
Collapse
Affiliation(s)
- Sofia A C Lima
- REQUIMTE - Departamento de Química da Faculdade Ciências, Universidade do Porto, Porto, Portugal
| | | | | | | | | |
Collapse
|
132
|
Sauna ZE, Kim IW, Nandigama K, Kopp S, Chiba P, Ambudkar SV. Catalytic cycle of ATP hydrolysis by P-glycoprotein: evidence for formation of the E.S reaction intermediate with ATP-gamma-S, a nonhydrolyzable analogue of ATP. Biochemistry 2007; 46:13787-99. [PMID: 17988154 DOI: 10.1021/bi701385t] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Structural and biochemical studies of ATP-binding cassette (ABC) transporters suggest that an ATP-driven dimerization of the nucleotide-binding domains (NBDs) is an important reaction intermediate of the transport cycle. Moreover, an asymmetric occlusion of ATP at one of the two ATP sites of P-glycoprotein (Pgp) may follow the formation of the symmetric dimer. It has also been postulated that ADP drives the dissociation of the dimer. In this study, we show that the E.S conformation of Pgp (previously demonstrated in the E556Q/E1201Q mutant Pgp) can be obtained with the wild-type protein by use of the nonhydrolyzable ATP analogue ATP-gamma-S. ATP-gamma-S is occluded into the Pgp NBDs at 34 degrees C but not at 4 degrees C, whereas ATP is not occluded at either temperature. Using purified Pgp incorporated into proteoliposomes and ATP-gamma-35S, we demonstrate that the occlusion of ATP-gamma-35S has an Eact of 60 kJ/mol and the stoichiometry of ATP-gamma-35S:Pgp is 1:1 (mol/mol). Additionally, in the conserved Walker B mutant (E556Q/E1201Q) of Pgp, we find occlusion of the nucleoside triphosphate but not the nucleoside diphosphate. Furthermore, Pgp in the occluded nucleotide conformation has reduced affinity for transport substrates. These data provide evidence for the ATP-driven dimerization and ADP-driven dissociation of the NBDs, and although two ATP molecules may initiate dimerization, only one is driven to an occluded pre-hydrolysis intermediate state. Thus, in a full-length ABC transporter like Pgp, it is unlikely that there is complete association and disassociation of NBDs and the occluded nucleotide conformation at one of the NBDs provides the power-stroke at the transport-substrate site.
Collapse
Affiliation(s)
- Zuben E Sauna
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892-4256, USA
| | | | | | | | | | | |
Collapse
|
133
|
Golin J, Kon ZN, Wu CP, Martello J, Hanson L, Supernavage S, Ambudkar SV, Sauna ZE. Complete inhibition of the Pdr5p multidrug efflux pump ATPase activity by its transport substrate clotrimazole suggests that GTP as well as ATP may be used as an energy source. Biochemistry 2007; 46:13109-19. [PMID: 17956128 DOI: 10.1021/bi701414f] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The yeast Pdr5p transporter is a 160 kDa protein that effluxes a large variety of xenobiotic compounds. In this study, we characterize its ATPase activity and demonstrate that it has biochemical features reminiscent of those of other ATP-binding cassette multidrug transporters: a relatively high Km for ATP (1.9 mM), inhibition by orthovanadate, and the ability to specifically bind an azidoATP analogue at the nucleotide-binding domains. Pdr5p-specific ATPase activity shows complete, concentration-dependent inhibition by clotrimazole, which is also known to be a potent transport substrate. Our results indicate, however, that this inhibition is noncompetitive and caused by the interaction of clotrimazole with the transporter at a site that is distinct from the ATP-binding domains. Curiously, Pdr5p-mediated transport of clotrimazole continues at intracellular concentrations of substrate that should eliminate all ATPase activity. Significantly, however, we observed that the Pdr5p has GTPase and UTPase activities that are relatively resistant to clotrimazole. Furthermore, the Km(GTPase) roughly matches the intracellular concentrations of the nucleotide reported for yeast. Using purified plasma membrane vesicles, we demonstrate that Pdr5p can use GTP to fuel substrate transport. We propose that Pdr5p increases its multidrug transport substrate specificity by using more than one nucleotide as an energy source.
Collapse
Affiliation(s)
- John Golin
- Department of Biology, The Catholic University of America, Washington, DC 20064, USA
| | | | | | | | | | | | | | | |
Collapse
|
134
|
Kuhnke D, Jedlitschky G, Grube M, Krohn M, Jucker M, Mosyagin I, Cascorbi I, Walker LC, Kroemer HK, Warzok RW, Vogelgesang S. MDR1-P-Glycoprotein (ABCB1) Mediates Transport of Alzheimer's amyloid-beta peptides--implications for the mechanisms of Abeta clearance at the blood-brain barrier. Brain Pathol 2007; 17:347-53. [PMID: 17610523 PMCID: PMC8095502 DOI: 10.1111/j.1750-3639.2007.00075.x] [Citation(s) in RCA: 177] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Amyloid-beta (Abeta) is the major component of the insoluble amyloid plaques that accumulate intracerebrally in patients with Alzheimer's disease (AD). It has been suggested that MDR1-P-glycoprotein (ABCB1, P-gp) plays a substantial role in the elimination of Abeta from the brain. In the present study, MDR1-transfected LLC cells growing in a polarized cell layer were used to characterize the interaction of Abeta1-40/1-42 with P-gp. In this system, P-gp-mediated transport can be followed by the efflux of the fluorescent dye rhodamine-123, or of Abeta itself from the cells into the apical extracellular space. Abeta significantly decreased the apical efflux of rhodamine-123, and the transcellular transport of Abeta1-40 and Abeta1-42 into the apical chamber could be demonstrated using both ELISA and fluorescence (FITC)-labeled peptides. This transport was inhibited by a P-gp modulator. Furthermore, ATP-dependent, P-gp-mediated transport of the fluorescence-labeled peptides could be demonstrated in isolated, inside-out membrane vesicles. Our data support the concept that P-gp is important for the clearance of Abeta from brain, and thus may represent a target protein for the prevention and/or treatment of neurodegenerative disorders such as AD.
Collapse
Affiliation(s)
- Diana Kuhnke
- Department of Pharmacology, Research Center of Pharmacology and Experimental Therapeutics, and
| | - Gabriele Jedlitschky
- Department of Pharmacology, Research Center of Pharmacology and Experimental Therapeutics, and
| | - Markus Grube
- Department of Pharmacology, Research Center of Pharmacology and Experimental Therapeutics, and
| | - Markus Krohn
- Department of Neuropathology, Ernst‐Moritz‐Arndt‐University, Greifswald, Germany
| | - Mathias Jucker
- Department of Cellular Neurology, Hertie‐Institute for Clinical Brain Research, University of Tübingen, Germany
| | - Igor Mosyagin
- Institute of Pharmacology, University Hospital Schleswig Holstein, Kiel, Germany
| | - Ingolf Cascorbi
- Institute of Pharmacology, University Hospital Schleswig Holstein, Kiel, Germany
| | - Lary C. Walker
- Yerkes National Primate Research Center and Department of Neurology, Emory University, Atlanta, Ga
| | - Heyo K. Kroemer
- Department of Pharmacology, Research Center of Pharmacology and Experimental Therapeutics, and
| | - Rolf W. Warzok
- Department of Neuropathology, Ernst‐Moritz‐Arndt‐University, Greifswald, Germany
| | - Silke Vogelgesang
- Department of Neuropathology, Ernst‐Moritz‐Arndt‐University, Greifswald, Germany
| |
Collapse
|
135
|
Shi Z, Jain S, Kim IW, Peng XX, Abraham I, Youssef DTA, Fu LW, El Sayed K, Ambudkar SV, Chen ZS. Sipholenol A, a marine-derived sipholane triterpene, potently reverses P-glycoprotein (ABCB1)-mediated multidrug resistance in cancer cells. Cancer Sci 2007; 98:1373-80. [PMID: 17640301 PMCID: PMC11159823 DOI: 10.1111/j.1349-7006.2007.00554.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2007] [Revised: 05/11/2007] [Accepted: 05/15/2007] [Indexed: 01/02/2023] Open
Abstract
Through extensive screening of marine sponge compounds, the authors have found that sipholenol A, a sipholane triterpene isolated from the Red Sea sponge, Callyspongia siphonella, potently reversed multidrug resistance (MDR) in cancer cells that overexpressed P-glycoprotein (P-gp). In experiments, sipholenol A potentiated the cytotoxicity of several P-gp substrate anticancer drugs, including colchicine, vinblastine, and paclitaxel, but not the non-P-gp substrate cisplatin, and significantly reversed the MDR of cancer cells KB-C2 and KB-V1 in a concentration-dependent manner. Furthermore, sipholenol A had no effect on the response to cytotoxic agents in cells lacking P-gp expression or expressing MDR protein 1 or breast cancer resistance protein. Sipholenol A (IC(50) > 50 microM) is not toxic to all the cell lines that were used, regardless of their membrane transporter status. Accumulation and efflux studies with the P-gp substrate [(3)H]-paclitaxel demonstrated that sipholenol A time-dependently increased the intracellular accumulation of [(3)H]-paclitaxel by directly inhibiting P-gp-mediated drug efflux. In addition, sipholenol A did not alter the expression of P-gp after treating KB-C2 and KB-V1 cells for 36 h and 72 h. However, it efficaciously stimulated the activity of ATPase of P-gp and inhibited the photolabeling of this transporter with its transport substrate [(125)I]-iodoarylazidoprazosin. Overall, the present results indicate that sipholenol A efficiently inhibits the function of P-gp through direct interactions, and sipholane triterpenes are a new class of potential reversing agents for treatment of MDR in P-gp-overexpressing tumors.
Collapse
MESH Headings
- ATP Binding Cassette Transporter, Subfamily B
- ATP Binding Cassette Transporter, Subfamily B, Member 1/antagonists & inhibitors
- ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism
- ATP Binding Cassette Transporter, Subfamily B, Member 1/physiology
- ATP Binding Cassette Transporter, Subfamily G, Member 2
- ATP-Binding Cassette Transporters/biosynthesis
- Animals
- Antineoplastic Agents, Phytogenic/pharmacology
- Azides/metabolism
- Callyspongia
- Cell Line, Tumor
- Drug Resistance, Multiple
- Drug Resistance, Neoplasm/drug effects
- Humans
- Iodine Radioisotopes/metabolism
- KB Cells
- Multidrug Resistance-Associated Proteins/biosynthesis
- Neoplasm Proteins/biosynthesis
- Photoaffinity Labels/metabolism
- Prazosin/analogs & derivatives
- Prazosin/metabolism
- Triterpenes/isolation & purification
- Triterpenes/pharmacology
Collapse
Affiliation(s)
- Zhi Shi
- Department of Pharmaceutical Sciences, College of Pharmacy and Allied Health Professions, St John's University, Jamaica, NY 11439, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
136
|
Greer D, Ivey S. Distinct N-glycan glycosylation of P-glycoprotein isolated from the human uterine sarcoma cell line MES-SA/Dx5. Biochim Biophys Acta Gen Subj 2007; 1770:1275-82. [PMID: 17692467 PMCID: PMC2034348 DOI: 10.1016/j.bbagen.2007.07.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2007] [Revised: 07/10/2007] [Accepted: 07/10/2007] [Indexed: 02/03/2023]
Abstract
The uterine sarcoma human cell line MES-SA/Dx5 overexpresses the MDR1 gene product, P-glycoprotein (Pgp). Pgp is a heavily glycosylated, ATP-dependent drug efflux pump expressed in many human cancers. There are more than 150 known isoforms of Pgp, which complicates the characterization of Pgp glycans because each isoform could present a different glycome. The contribution of these oligosaccharides to the structure and function of Pgp remains unclear. We identified distinct Pgp glycans recognized by the lectins in the digoxigenin (DIG) glycan differentiation kit from Roche Allied Science, all of which were N-glycans. Pgp was isolated using both slab and preparative gel elution. The monoclonal antibody C219 was used to identify the presence of Pgp and Pgp treated with PNGase F on our blots. Pgp isolated from MES-SA/Dx5 cells contains at least two different complex N-glycans--one high mannose tree, detected by GNA, and one branched hybrid oligosaccharide-capped with terminal sialic acids, detected by SNA and MAA. DSA, specific for biantennary oligosaccharides possessing beta(1-4)-N-acetyl-D-glucosamine residues, also recognized the blotted Pgp and is probably detecting the core Galbeta(1-4)-GlcNAc(x) component found in other Pgps.
Collapse
Affiliation(s)
- D.A. Greer
- Roger Williams Medical Center, Providence, RI 02908 USA
| | - S. Ivey
- Department of Biological Sciences, Delaware State University, Dover, DE 19901 USA
- *Corresponding author: Tel. +302 857-6524; Fax +302 857-7378; E-mail
| |
Collapse
|
137
|
Matsson P, Englund G, Ahlin G, Bergström CAS, Norinder U, Artursson P. A global drug inhibition pattern for the human ATP-binding cassette transporter breast cancer resistance protein (ABCG2). J Pharmacol Exp Ther 2007; 323:19-30. [PMID: 17616561 DOI: 10.1124/jpet.107.124768] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
In this article, we explore the entire structural space of registered drugs to obtain a global model for the inhibition of the drug efflux transporter breast cancer resistance protein (BCRP; ABCG2). For this purpose, the inhibitory effect of 123 structurally diverse drugs and drug-like compounds on mitoxantrone efflux was studied in Saos-2 cells transfected with human wild-type (Arg482) BCRP. The search for BCRP inhibitors throughout the drug-like chemical space resulted in the identification of 29 previously unknown inhibitors. The frequency of BCRP inhibition was 3 times higher for compounds reported to interact with other ATP-binding cassette (ABC) transporters than for compounds without reported ABC transporter affinity. An easily interpreted computational model capable of discriminating inhibitors from noninhibitors using only two molecular descriptors, octanol-water partition coefficient at pH 7.4 and molecular polarizability, was constructed. The discriminating power of this two-descriptor model was 93% for the training set and 79% for the test set, respectively. The results were supported by a global pharmacophore model and are in agreement with a two-step mechanism for the inhibition of BCRP, where both the drug's capacity to insert into the cell membrane and to interact with the inhibitory binding site of the transporter are important.
Collapse
Affiliation(s)
- Pär Matsson
- Pharmaceutical Screening and Informatics, Department of Pharmacy, Uppsala University, P.O. Box 580, SE-751 23 Uppsala, Sweden.
| | | | | | | | | | | |
Collapse
|
138
|
Sakurai A, Onishi Y, Hirano H, Seigneuret M, Obanayama K, Kim G, Liew EL, Sakaeda T, Yoshiura KI, Niikawa N, Sakurai M, Ishikawa T. Quantitative Structure−Activity Relationship Analysis and Molecular Dynamics Simulation To Functionally Validate Nonsynonymous Polymorphisms of Human ABC Transporter ABCB1 (P-Glycoprotein/MDR1). Biochemistry 2007; 46:7678-93. [PMID: 17559192 DOI: 10.1021/bi700330b] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Several preclinical and clinical studies suggest the importance of naturally occurring polymorphisms of drug transporters in the individual difference of drug response. To functionally validate the nonsynonymous polymorphisms of ABCB1 (P-glycoprotein/MDR1) in vitro, we generated SNP variant forms (i.e., S400N, R492C, R669C, I849M, A893P, A893S, A893T, M986V, A999T, P1051A, and G1063A) and expressed them in Sf9 cells. The kinetic properties (Km and Vmax) of those variants were analyzed by measuring the ATPase activity to obtain the ATPase profile for each variant toward structurally unrelated substrates. On the basis of the experimental data, we determined the substrate specificity of ABCB1 WT and its variants by the quantitative structure-activity relationship (QSAR) analysis method. While several SNP variants appeared to influence the substrate specificity of ABCB1, the nonsynonymous polymorphisms of 2677G > T, A, or C at amino acid position 893 (Ala > Ser, Thr, or Pro) have great impacts on both the activity and the substrate specificity of ABCB1. The A893P variant (2677G > C), a rare mutation, exhibited markedly high activity of ATPase toward different test compounds. Molecular dynamics (MD) simulation based on a three-dimensional structural model of human ABCB1 revealed that multiple kinks are formed in the intracellular loop between transmembrane domains 10 and 11 of the A893P variant (2677G > C) protein. The polymorphisms of 2677G, 2677T, and 2677A exhibit wide ethnic differences in the allele frequency, and these nonsynonymous polymorphisms are suggested to be clinically important because of their altered ATPase activity and substrate specificity toward different drugs.
Collapse
Affiliation(s)
- Aki Sakurai
- Department of Biomolecular Engineering, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Japan
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
139
|
Bucher K, Belli S, Wunderli-Allenspach H, Krämer SD. P-glycoprotein in proteoliposomes with low residual detergent: the effects of cholesterol. Pharm Res 2007; 24:1993-2004. [PMID: 17497080 DOI: 10.1007/s11095-007-9326-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2007] [Accepted: 04/25/2007] [Indexed: 11/29/2022]
Abstract
PURPOSE There is evidence that cholesterol affects the ATPase and transport functions of P-glycoprotein (P-gp). To study the influence of cholesterol on P-gp in a well defined lipid environment, we reconstituted P-gp in egg phosphatidylcholine (PhC) and PhC/cholesterol proteoliposomes with negligible residual amounts of detergents. MATERIALS AND METHODS P-gp proteoliposomes were prepared by continuous dialysis from micelles consisting of P-gp, lipids, sodium dodecyl sulfate and cholate. Basal and modulator-induced ATPase activities were studied in an established enzyme assay. Modulator affinities to P-gp and to the lipid bilayers were determined by equilibrium dialysis. RESULTS In the absence of cholesterol the basal ATPase activity was six fold lower than in the presence of 20 or 40% cholesterol, and no P-gp binding and ATPase induction was detected for the tested modulators verapamil and progesterone. In proteoliposomes containing 20 and 40% cholesterol, respectively, the modulators showed significant P-gp binding and ATPase activation. The concentration of the modulators for half maximal activation of the ATPase was higher with 40% than with 20% cholesterol. CONCLUSIONS Cholesterol influences P-gp in three ways: (a) it enhances its basal ATPase activity, (b) it renders P-gp sensitive towards the modulators verapamil and progesterone and (c) it affects the modulator concentration at half maximal ATPase activation.
Collapse
Affiliation(s)
- Karsten Bucher
- Department of Chemistry and Applied Biosciences, Institute of Pharmaceutical Sciences, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093, Zurich, Switzerland
| | | | | | | |
Collapse
|
140
|
Paterson JK, Gottesman MM. P-Glycoprotein is not present in mitochondrial membranes. Exp Cell Res 2007; 313:3100-5. [PMID: 17512524 PMCID: PMC2075362 DOI: 10.1016/j.yexcr.2007.04.019] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2007] [Revised: 04/16/2007] [Accepted: 04/18/2007] [Indexed: 11/15/2022]
Abstract
Recent reports have indicated the presence of P-glycoprotein in crude mitochondrial membrane fractions, leading to the assumption that P-glycoprotein is present in mitochondrial membranes, and may be involved in transport across these membranes. To determine the validity of this claim, two cell lines overexpressing endogenous P-glycoprotein were investigated. Using various centrifugation steps, mitochondria were purified from these cells and analyzed by Western blot reaction with the anti-P-glycoprotein antibody C219 and organelle-specific antibodies. While P-glycoprotein is present in crude mitochondrial fractions, these fractions are contaminated with plasma membranes. Further purification of the mitochondria to remove plasma membranes revealed that P-glycoprotein is not expressed in mitochondria of the KB-V1 (vinblastine-resistant KB-3-1 cells) or MCF-7(ADR) (adriamycin-resistant MCF-7 cells) cell lines. To further substantiate these findings, we used confocal microscopy and the anti-P-glycoprotein antibody 17F9. This demonstrated that in intact cells, P-glycoprotein is not present in mitochondria and is primarily localized to the plasma membrane. These findings are consistent with the role of P-glycoprotein in conferring multidrug resistance by decreasing cellular drug accumulation. Therefore, contrary to previous speculation, P-glycoprotein does not confer cellular protection by residing in mitochondrial membranes.
Collapse
Affiliation(s)
| | - Michael M. Gottesman
- *To whom correspondence should be addressed: Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, DHHS, Bethesda, MD, 20892-4256. , telephone: 301-496-1530, fax: 301-402-0450
| |
Collapse
|
141
|
Soranzo N, Kelly L, Martinian L, Burley MW, Thom M, Sali A, Kroetz DL, Goldstein DB, Sisodiya SM. Lack of Support for a Role for RLIP76 (RALBP1) in Response to Treatment or Predisposition to Epilepsy. Epilepsia 2007; 48:674-83. [PMID: 17437410 DOI: 10.1111/j.1528-1167.2007.00926.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
BACKGROUND Multidrug transporters are postulated to contribute to antiepileptic drug (AED) resistance. The transporter best studied is P-glycoprotein, an ATP-Binding Cassette (ABC) transporter superfamily member. RLIP76 is suggested to be an energy-dependent non-ABC transporter, reducing AED blood-brain barrier penetration, with a more important role than P-glycoprotein. Knowledge of which transporters may be critical in drug resistance is important for design of potential therapies. We tested the hypothesis that RLIP76 mediates AED resistance using methods complementary to those in the original report. METHODS Double-labeling fluorescent immunohistochemistry localized RLIP76 expression. Population genetics was used to explore association of variation in the RLIP76-encoding gene with drug-response and epilepsy phenotypes. Comparative protein structure modeling and bioinformatic annotation were used to predict RLIP76 structure and features. RESULTS In normal and epileptogenic brain tissue, immunoreactivity for RLIP76 was cytoplasmic, with colocalization with a neuronal, but not an endothelial, marker. Genotyping of six tagging SNPs, representing common genetic variation in RLIP76, in patients with epilepsy responsive (n = 262) or resistant (n = 107) to AEDs showed no association with phenotype at any level. RLIP76 genotypic and haplotypic frequencies in 783 patients with epilepsy and 359 healthy controls showed no association with epilepsy susceptibility. RLIP76 is not predicted to have transmembrane localization or ATPase activity. CONCLUSIONS No support for RLIP76 itself in directly mediating resistance to AEDs nor in increasing susceptibility to epilepsy was found. More evidence is required before either a role for RLIP76 in drug resistance can be accepted or focus directed away from other transporters, such as P-glycoprotein.
Collapse
Affiliation(s)
- Nicole Soranzo
- Department of Clinical and Experimental Epilepsy, Institute of Neurology, UCL, London, UK
| | | | | | | | | | | | | | | | | |
Collapse
|
142
|
Golin J, Ambudkar SV, May L. The yeast Pdr5p multidrug transporter: How does it recognize so many substrates? Biochem Biophys Res Commun 2007; 356:1-5. [PMID: 17316560 DOI: 10.1016/j.bbrc.2007.02.011] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2007] [Accepted: 02/02/2007] [Indexed: 11/19/2022]
Abstract
Multidrug transporters are of considerable importance because they present problems in the treatment of infectious disease and cancer. A central issue is the ability of efflux pumps to recognize an astounding array of structurally diverse compounds. The yeast Pdr5p efflux pump, which is a member of the ATP-binding cassette superfamily, has at least 3 substrate-binding sites, each of which appears to use different chemical properties to transport compounds. All Pdr5p substrates, however, have a size requirement that is independent of hydrophobicity.
Collapse
Affiliation(s)
- John Golin
- Department of Biology, The Catholic University of America, Washington, DC 20064, USA.
| | | | | |
Collapse
|
143
|
Sharom FJ. Shedding light on drug transport: structure and function of the P-glycoprotein multidrug transporter (ABCB1). Biochem Cell Biol 2007; 84:979-92. [PMID: 17215884 DOI: 10.1139/o06-199] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
P-glycoprotein (Pgp; ABCB1), a member of the ATP-binding cassette (ABC) superfamily, exports structurally diverse hydrophobic compounds from the cell, driven by ATP hydrolysis. Pgp expression has been linked to the efflux of chemotherapeutic drugs in human cancers, leading to multidrug resistance (MDR). The protein also plays an important physiological role in limiting drug uptake in the gut and entry into the brain. Substrates partition into the lipid bilayer before interacting with Pgp, which has been proposed to function as a hydrophobic vacuum cleaner. Low- and medium-resolution structural models of Pgp suggest that the 2 nucleotide-binding domains are closely associated to form a nucleotide sandwich dimer. Pgp is an outwardly directed flippase for fluorescent phospholipid and glycosphingolipid derivatives, which suggests that it may also translocate drug molecules from the inner to the outer membrane leaflet. The ATPase catalytic cycle of the protein is thought to proceed via an alternating site mechanism, although the details are not understood. The lipid bilayer plays an important role in Pgp function, and may regulate both the binding and transport of drugs. This review focuses on the structure and function of Pgp, and highlights the importance of fluorescence spectroscopic techniques in exploring the molecular details of this enigmatic transporter.
Collapse
MESH Headings
- ATP Binding Cassette Transporter, Subfamily B
- 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 Transporter, Subfamily B, Member 1/physiology
- ATP-Binding Cassette Transporters/metabolism
- Adenosine Triphosphate/metabolism
- Animals
- Awards and Prizes
- Biological Transport/drug effects
- Drug Resistance, Multiple
- Humans
- Models, Biological
- Models, Molecular
- Organic Anion Transporters/metabolism
- Spectrometry, Fluorescence
- Structure-Activity Relationship
- Substrate Specificity
Collapse
Affiliation(s)
- Frances J Sharom
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada.
| |
Collapse
|
144
|
Sauna ZE, Ambudkar SV. About a switch: how P-glycoprotein (ABCB1) harnesses the energy of ATP binding and hydrolysis to do mechanical work. Mol Cancer Ther 2007; 6:13-23. [PMID: 17237262 DOI: 10.1158/1535-7163.mct-06-0155] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The efflux of drugs by the multidrug transporter P-glycoprotein (Pgp; ABCB1) is one of the principal means by which cancer cells evade chemotherapy and exhibit multidrug resistance. Mechanistic studies of Pgp-mediated transport, however, transcend the importance of this protein per se as they help us understand the transport pathway of the ATP-binding cassette proteins in general. The ATP-binding cassette proteins comprise one of the largest protein families, are central to cellular physiology, and constitute important drug targets. The functional unit of Pgp consists of two nucleotide-binding domains (NBD) and two transmembrane domains that are involved in the transport of drug substrates. Early studies postulated that conformational changes as a result of ATP hydrolysis were transmitted to the transmembrane domains bringing about drug transport. More recent structural and biochemical studies on the other hand suggested that ATP binds at the interface of the two NBDs and induces the formation of a closed dimer, and it has been hypothesized that this dimerization and subsequent ATP hydrolysis powers transport. Based on the mutational and biochemical work on Pgp and structural studies with isolated NBDs, we review proposed schemes for the catalytic cycle of ATP hydrolysis and the transport pathway.
Collapse
Affiliation(s)
- Zuben E Sauna
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Building 37, Room 2120, 37 Convent Drive, Bethesda, MD 20892-4256, USA
| | | |
Collapse
|
145
|
McDevitt CA, Callaghan R. How can we best use structural information on P-glycoprotein to design inhibitors? Pharmacol Ther 2007; 113:429-41. [PMID: 17208306 DOI: 10.1016/j.pharmthera.2006.10.003] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2006] [Accepted: 10/13/2006] [Indexed: 10/23/2022]
Abstract
This year marks the 30th anniversary of the discovery of the multidrug resistance (MDR) ATP-binding cassette (ABC) transporter P-glycoprotein (P-gp). Since then a considerable research effort has attempted to provide a greater understanding of the biological enigma of "multidrug" efflux. Moreover, the growing correlation between P-gp expression and a negative prognosis or poor outcome for chemotherapy has sparked significant interest in the generation of inhibitors. How close are we to overcoming the unwanted actions of P-gp in resistant cancer following 30 years of research? The initial inhibitors were pre-existing clinically used compounds and exploited the broad specificity of P-gp. Unfortunately, the concentrations required to inhibit P-gp meant that these compounds generated considerable toxicity. Pharmacological investigations progressed to rational design using the 1st generation compounds as a template structure. Inherent toxicity of the drugs was reduced; however, pharmacokinetic interactions with the anticancer drugs were unsustainable. Generation of the most recent of inhibitors employed combinatorial chemistry to produce a handful of potent and selective P-gp inhibitors. Some of these drugs have progressed to clinical trials with poor results or in some cases, undisclosed progress. There remains a clear need for the generation of P-gp inhibitors and this review describes the potential for a structure-based design to facilitate this undertaking. In particular, the plethora of functional data can provide important regions on the protein that could conceivably be exploited as inhibitor targets.
Collapse
Affiliation(s)
- Christopher A McDevitt
- Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, UK
| | | |
Collapse
|
146
|
Yadav S, Zajac E, Singhal SS, Awasthi S. Linking stress-signaling, glutathione metabolism, signaling pathways and xenobiotic transporters. Cancer Metastasis Rev 2007; 26:59-69. [PMID: 17260165 DOI: 10.1007/s10555-007-9043-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Multi-specific drug-transport mechanisms are intricately involved in mediating a pleiotropic drug-resistance in cancer cells by mediating drug-accumulation defects in cells in which they are over-expressed. The existence and over-expression in drug-resistant neoplasms of transporter proteins belonging to ATP-binding cassette (ABC) family indicate that these myriad transporters contribute to the multidrug-resistance phenomena by removing or sequestering of toxins and metabolites. Another prominent mechanism of multispecific drug-resistance involves glutathione and glutathione linked enzymes, particularly those of the mercapturic acid pathway, which are involved in metabolism and excretion of both endogenous and exogenous electrophilic toxins. A key step in the mercapturic acid pathway, efflux of the glutathione-electrophile conjugate has recently been shown to be catalyzed largely by the stress-responsive protein RLIP76, a splice variant peptide endowed by the human gene RALBP1. The known involvement of RLIP76 in membrane signaling pathways and endocytosis has resulted in a new paradigm for transport and metabolism related drug-resistance in which RLIP76 plays a central role. Our recent studies demonstrating a key anti-apoptotic and stress-responsive role of RLIP76, and the demonstration of dramatic response in malignancies to RLIP76 depletion indicate that targeting this mercapturic acid pathway transporter may be a highly effective and multifaceted antineoplastic strategy.
Collapse
Affiliation(s)
- Sushma Yadav
- Department of Chemistry and Biochemistry, University of Texas at Arlington, TX 76019-0065, USA
| | | | | | | |
Collapse
|
147
|
Elkins CA, Mullis LB. Substrate competition studies using whole-cell accumulation assays with the major tripartite multidrug efflux pumps of Escherichia coli. Antimicrob Agents Chemother 2007; 51:923-9. [PMID: 17210767 PMCID: PMC1803133 DOI: 10.1128/aac.01048-06] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AcrAB-TolC is the major, constitutively expressed tripartite multidrug efflux system in Escherichia coli that recognizes various structurally unrelated molecules, including many antibiotics, dyes, and steroids. The AcrB inner membrane pump portion of the efflux system has been shown in recent structural studies to bind substrates at multiple sites, suggesting that particular substrate "sets" may compete for efflux by interfering with a certain binding site(s). However, our data indicate that the general structural class does not appear to dictate a particular substrate binding site that can be competitively inhibited in whole cells. In our study, substrate competition failed to increase cell-associated levels of steroids or dyes to levels characteristic of AcrB- or AcrB/EmrAB-deficient genomic mutants or achieved with the pump inhibitor carbonyl cyanide m-chlorophenylhydrazone. In addition, this general observation was sustained even with (i) a cocktail containing seven-pump substrates supplied slightly below their respective wild-type MIC levels, (ii) competing drug substrates of the same structural class (steroids or macrolides), and (iii) hyper-MIC levels of the exogenously supplied agents. Thus, this pump system (and possibly EmrAB-TolC) may have an extraordinary capacity to simultaneously handle multiple-drug substrates that is not necessarily reflected in MIC analyses. In addition, our study has extended the range of substrates recognized by the AcrAB- and EmrAB-TolC systems.
Collapse
Affiliation(s)
- Christopher A Elkins
- Division of Microbiology, National Center for Toxicological Research, 3900 NCTR Drive, Jefferson, AR 72079-9502, USA.
| | | |
Collapse
|
148
|
Kalen JD, Hirsch JI, Kurdziel KA, Eckelman WC, Kiesewetter DO. Automated synthesis of 18F analogue of paclitaxel (PAC): [18F]Paclitaxel (FPAC). Appl Radiat Isot 2006; 65:696-700. [PMID: 17161952 PMCID: PMC1904428 DOI: 10.1016/j.apradiso.2006.10.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2006] [Revised: 10/20/2006] [Accepted: 10/31/2006] [Indexed: 12/21/2022]
Abstract
A positron-emitting paclitaxel (PAC) derivative could allow in vivo measurement of multidrug resistance in tumors and, therefore, predict a potential chemotherapeutic benefit to patients. [18F]Paclitaxel was produced using a 2-reaction vessel automated synthesizer followed by HPLC purification. Optimized reaction conditions resulted in radiochemical yields of 21.2+/-9.6% at end of bombardment, radiochemical purity >99%, and specific activity of 159+/-43 G Bq/micromol. [18F]Paclitaxel activities of 1.33+/-0.729 G Bq (n=7) were obtained in sterile, pyrogen-free solution for IV administration.
Collapse
Affiliation(s)
- Joseph D Kalen
- Molecular Imaging Center, Department of Radiology, Virginia Commonwealth University, Richmond, VA, USA.
| | | | | | | | | |
Collapse
|
149
|
Seeger MA, Schiefner A, Eicher T, Verrey F, Diederichs K, Pos KM. Structural Asymmetry of AcrB Trimer Suggests a Peristaltic Pump Mechanism. Science 2006; 313:1295-8. [PMID: 16946072 DOI: 10.1126/science.1131542] [Citation(s) in RCA: 417] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The AcrA/AcrB/TolC complex spans the inner and outer membranes of Escherichia coli and serves as its major drug-resistance pump. Driven by the proton motive force, it mediates the efflux of bile salts, detergents, organic solvents, and many structurally unrelated antibiotics. Here, we report a crystallographic structure of trimeric AcrB determined at 2.9 and 3.0 angstrom resolution in space groups that allow asymmetry of the monomers. This structure reveals three different monomer conformations representing consecutive states in a transport cycle. The structural data imply an alternating access mechanism and a novel peristaltic mode of drug transport by this type of transporter.
Collapse
Affiliation(s)
- Markus A Seeger
- Institute of Physiology and Zurich Centre for Integrative Human Physiology (ZIHP), University of Zurich, Winterthurerstrasse 190, Zürich, Switzerland
| | | | | | | | | | | |
Collapse
|
150
|
Varma MVS, Perumal OP, Panchagnula R. Functional role of P-glycoprotein in limiting peroral drug absorption: optimizing drug delivery. Curr Opin Chem Biol 2006; 10:367-73. [PMID: 16814593 DOI: 10.1016/j.cbpa.2006.06.015] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2006] [Accepted: 06/16/2006] [Indexed: 01/16/2023]
Abstract
P-glycoprotein (P-gp) associated multi-drug resistance is one of the major challenges in the chemotherapy of various cancers. On the other hand, it is now widely recognized that P-gp influences drug transport across various biological membranes. To this end, there is an increasing trend to optimize pharmacokinetics and drug delivery right from the initial stages of drug discovery by exploring all the possible mechanisms involved in 'deliverability'. Recent advances in molecular biology techniques and biochemical characterization methodologies have helped in identification of various transporters involved in absorption or secretion of drugs. P-gp, an efflux pump expressed along the gastrointestinal tract, limits the permeability of many drugs and thus affects their peroral absorption and bioavailability. A fundamental insight and thorough understanding of P-gp and its functional role in limiting drug absorption is critical to improve predictability of dynamic absorption models and aid in selection of new candidates for development, and also widen the scope of peroral delivery for 'challenging' molecules.
Collapse
Affiliation(s)
- Manthena V S Varma
- Department of Pharmaceutics, College of Pharmacy, University of Minnesota, 308 Harvard Street SE, Minneapolis, MN 55455, USA
| | | | | |
Collapse
|