1
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Ni W, Fan H, Zheng X, Xu F, Wu Y, Li X, Wang A, Huang S, Chen W, Wang S, Lu Y. Cryptotanshinone Inhibits ERα-Dependent and -Independent BCRP Oligomer Formation to Reverse Multidrug Resistance in Breast Cancer. Front Oncol 2021; 11:624811. [PMID: 33968724 PMCID: PMC8100513 DOI: 10.3389/fonc.2021.624811] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Accepted: 02/19/2021] [Indexed: 11/13/2022] Open
Abstract
Both long-term anti-estrogen therapy and estrogen receptor-negative breast cancer contribute to drug resistance, causing poor prognosis in breast cancer patients. Breast cancer resistance protein (BCRP) plays an important role in multidrug resistance. Here, we show that cryptotanshinone (CPT), an anti-estrogen compound, inhibited the oligomer formation of BCRP on the cell membrane, thus blocking its efflux function. The inhibitory effect of CPT on BCRP was dependent on the expression level of estrogen receptor α (ERα) in ERα-positive breast cancer cells. Furthermore, ERα-negative breast cancer cells with high expression of BCRP were also sensitive to CPT because CPT was able to bind to BCRP and inhibit its oligomer formation on the cell membrane, suggesting that the high level of BCRP expression is crucial for CPT to reverse drug resistance. The combination of CPT and chemotherapeutic agents displayed enhanced anticancer effects. The results suggest that CPT is a novel BCRP inhibitor via blocking the oligomer formation of BCRP on the cell membrane. CPT is able to inhibit the activity of BCRP in an ERα-dependent and -independent manner, sensitizing breast cancer cells to chemotherapy.
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Affiliation(s)
- Wenting Ni
- Jiangsu Key Laboratory for Pharmacology and Safety Evaluation of Chinese Materia Medica, School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, China
| | - Hui Fan
- Jiangsu Key Laboratory for Pharmacology and Safety Evaluation of Chinese Materia Medica, School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, China
| | - Xiuqin Zheng
- Jiangsu Key Laboratory for Pharmacology and Safety Evaluation of Chinese Materia Medica, School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, China
| | - Fangming Xu
- Jiangsu Key Laboratory for Pharmacology and Safety Evaluation of Chinese Materia Medica, School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, China
| | - Yuanyuan Wu
- Jiangsu Key Laboratory for Pharmacology and Safety Evaluation of Chinese Materia Medica, School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, China
| | - Xiaoman Li
- Jiangsu Key Laboratory for Pharmacology and Safety Evaluation of Chinese Materia Medica, School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, China
| | - Aiyun Wang
- Jiangsu Key Laboratory for Pharmacology and Safety Evaluation of Chinese Materia Medica, School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, China.,Jiangsu Collaborative Innovation Center of Traditional Chinese Medicine (TCM) Prevention and Treatment of Tumor, Nanjing, China
| | - Shile Huang
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, LA, United States
| | - Wenxing Chen
- Jiangsu Key Laboratory for Pharmacology and Safety Evaluation of Chinese Materia Medica, School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, China.,Jiangsu Collaborative Innovation Center of Traditional Chinese Medicine (TCM) Prevention and Treatment of Tumor, Nanjing, China
| | - Shijun Wang
- Shandong Co-Innovation Center of Traditional Chinese Medicine (TCM) Formula, College of Traditional Chinese Medicine, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Yin Lu
- Jiangsu Key Laboratory for Pharmacology and Safety Evaluation of Chinese Materia Medica, School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, China.,Jiangsu Collaborative Innovation Center of Traditional Chinese Medicine (TCM) Prevention and Treatment of Tumor, Nanjing, China
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2
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Zhang W, Yang Y, Dong Z, Shi Z, Zhang JT. Single-nucleotide polymorphisms in a short basic motif in the ABC transporter ABCG2 disable its trafficking out of endoplasmic reticulum and reduce cell resistance to anticancer drugs. J Biol Chem 2019; 294:20222-20232. [PMID: 31719146 DOI: 10.1074/jbc.ra119.008347] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Revised: 08/14/2019] [Indexed: 12/14/2022] Open
Abstract
ATP-binding cassette (ABC) subfamily G member 2 (ABCG2) belongs to the ABC transporter superfamily and has been implicated in multidrug resistance of cancers. Although the structure and function of ABCG2 have been extensively studied, little is known about its biogenesis and the regulation thereof. In this study, using mutagenesis and several biochemical analyses, we show that the positive charges in the vicinity of the RKR motif downstream of the ABC signature drive trafficking of nascent ABCG2 out of the endoplasmic reticulum (ER) onto plasma membranes. Substitutions of and naturally occurring single-nucleotide polymorphisms within these positively charged residues disabled the trafficking of ABCG2 out of the ER. A representative ABCG2 variant in which the RKR motif had been altered underwent increased ER stress-associated degradation. We also found that unlike WT ABCG2, genetic ABCG2 RKR variants have disrupted normal maturation and do not reduce accumulation of the anticancer drug mitoxantrone and no longer confer resistance to the drug. We conclude that the positive charges downstream of the ABC signature motif critically regulate ABCG2 trafficking and maturation. We propose that single-nucleotide polymorphisms of these residues reduce ABCG2 expression via ER stress-associated degradation pathway and may contribute to reduced cancer drug resistance, improving the success of cancer chemotherapy.
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Affiliation(s)
- Wenji Zhang
- Department of Pharmacology and Toxicology and Indiana University Simon Cancer Center, Indiana University School of Medicine, Indianapolis, Indiana 46202.,Department of Cell Biology & Institute of Biomedicine, National Engineering Research Center of Genetic Medicine, Guangdong Provincial Key Laboratory of Bioengineering Medicine, College of Life Science and Technology, Jinan University, Guangzhou, Guangdong 510632, China
| | - Yang Yang
- Department of Cell Biology & Institute of Biomedicine, National Engineering Research Center of Genetic Medicine, Guangdong Provincial Key Laboratory of Bioengineering Medicine, College of Life Science and Technology, Jinan University, Guangzhou, Guangdong 510632, China
| | - Zizheng Dong
- Department of Pharmacology and Toxicology and Indiana University Simon Cancer Center, Indiana University School of Medicine, Indianapolis, Indiana 46202.,Department of Cancer Biology, University of Toledo College of Medicine and Life Sciences, Toledo, Ohio 43614
| | - Zhi Shi
- Department of Cell Biology & Institute of Biomedicine, National Engineering Research Center of Genetic Medicine, Guangdong Provincial Key Laboratory of Bioengineering Medicine, College of Life Science and Technology, Jinan University, Guangzhou, Guangdong 510632, China
| | - Jian-Ting Zhang
- Department of Pharmacology and Toxicology and Indiana University Simon Cancer Center, Indiana University School of Medicine, Indianapolis, Indiana 46202 .,Department of Cancer Biology, University of Toledo College of Medicine and Life Sciences, Toledo, Ohio 43614
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3
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Grañé-Boladeras N, Spring CM, Hanna WJB, Pastor-Anglada M, Coe IR. Novel nuclear hENT2 isoforms regulate cell cycle progression via controlling nucleoside transport and nuclear reservoir. Cell Mol Life Sci 2016; 73:4559-4575. [PMID: 27271752 PMCID: PMC11108336 DOI: 10.1007/s00018-016-2288-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Revised: 05/26/2016] [Accepted: 05/31/2016] [Indexed: 10/25/2022]
Abstract
Nucleosides participate in many cellular processes and are the fundamental building blocks of nucleic acids. Nucleoside transporters translocate nucleosides across plasma membranes although the mechanism by which nucleos(t)ides are translocated into the nucleus during DNA replication is unknown. Here, we identify two novel functional splice variants of equilibrative nucleoside transporter 2 (ENT2), which are present at the nuclear envelope. Under proliferative conditions, these splice variants are up-regulated and recruit wild-type ENT2 to the nuclear envelope to translocate nucleosides into the nucleus for incorporation into DNA during replication. Reduced presence of hENT2 splice variants resulted in a dramatic decrease in cell proliferation and dysregulation of cell cycle due to a lower incorporation of nucleotides into DNA. Our findings support a novel model of nucleoside compartmentalisation at the nuclear envelope and translocation into the nucleus through hENT2 and its variants, which are essential for effective DNA synthesis and cell proliferation.
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Affiliation(s)
- Natalia Grañé-Boladeras
- Department of Biochemistry and Molecular Biology, Institute of Biomedicine (IBUB), University of Barcelona, 08028, Barcelona, Spain.
- Oncology Program, CIBER EHD, Instituto de Salud Carlos III, 28029, Madrid, Spain.
- Department of Chemistry and Biology, Ryerson University, Toronto, ON, M5B 2K3, Canada.
| | - Christopher M Spring
- Research Core Facilities, Keenan Research Centre, Li Ka Shing Knowledge Institute, Saint Michael's Hospital, Toronto, ON, M5B 1T8, Canada
| | - W J Brad Hanna
- Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - Marçal Pastor-Anglada
- Department of Biochemistry and Molecular Biology, Institute of Biomedicine (IBUB), University of Barcelona, 08028, Barcelona, Spain
- Oncology Program, CIBER EHD, Instituto de Salud Carlos III, 28029, Madrid, Spain
| | - Imogen R Coe
- Department of Chemistry and Biology, Ryerson University, Toronto, ON, M5B 2K3, Canada
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4
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Frixel S, Lotz-Havla AS, Kern S, Kaltenborn E, Wittmann T, Gersting SW, Muntau AC, Zarbock R, Griese M. Homooligomerization of ABCA3 and its functional significance. Int J Mol Med 2016; 38:558-66. [PMID: 27352740 DOI: 10.3892/ijmm.2016.2650] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 05/11/2016] [Indexed: 11/06/2022] Open
Abstract
ABCA3 is a surfactant lipid transporter in the limiting membrane of lamellar bodies in alveolar type II cells. Mutations in the ATP-binding cassette, sub-family A (ABC1), member 3 (ABCA3) gene cause respiratory distress syndrome in newborns, and chronic interstitial lung disease in children and adults. ABCA3 belongs to the class of full ABC transporters, which are supposed to be functional in their monomeric forms. Although other family members e.g., ABCA1 and ABCC7 have been shown to function as oligomers, the oligomerization state of ABCA3 is unknown. In the present study, the oligomerization of ABCA3 was investigated in cell lysates and crude membrane preparations from transiently and stably transfected 293 cells using blue native PAGE (BN-PAGE), gel filtration and co-immunoprecipitation. Additionally, homooligomerization was examined in vivo in cells using bioluminescence resonance energy transfer (BRET). Using BN-PAGE and gel filtration, we demonstrate that non-denatured ABCA3 exists in different oligomeric forms, with monomers (45%) and tetramers (30%) being the most abundant forms. Furthermore, we also show the existence of 20% dimers and 5% trimers. BRET analyses verified intermolecular interactions in vivo. Our results also demonstrated that the arrest of ABCA3 in the endoplasmic reticulum (ER), either through drug treatment or induced by mutations in ABCA3, inhibited the propensity of the protein to form dimers. Based on our results, we suggest that transporter oligomerization is crucial for ABCA3 function and that a disruption of oligomerization due to mutations represents a novel pathomechanism in ABCA3-associated lung disease.
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Affiliation(s)
- Sabrina Frixel
- German Centre for Lung Research, Dr von Hauner Children's Hospital, Ludwig-Maximilians University, D-80337 Munich, Germany
| | - Amelie S Lotz-Havla
- Department of Molecular Pediatrics, Dr von Hauner Children's Hospital, Ludwig-Maximilians University, D-80337 Munich, Germany
| | - Sunčana Kern
- German Centre for Lung Research, Dr von Hauner Children's Hospital, Ludwig-Maximilians University, D-80337 Munich, Germany
| | - Eva Kaltenborn
- German Centre for Lung Research, Dr von Hauner Children's Hospital, Ludwig-Maximilians University, D-80337 Munich, Germany
| | - Thomas Wittmann
- German Centre for Lung Research, Dr von Hauner Children's Hospital, Ludwig-Maximilians University, D-80337 Munich, Germany
| | - Søren W Gersting
- Department of Molecular Pediatrics, Dr von Hauner Children's Hospital, Ludwig-Maximilians University, D-80337 Munich, Germany
| | - Ania C Muntau
- University Children's Hospital, University Medical Center Hamburg-Eppendorf, D-20246 Hamburg, Germany
| | - Ralf Zarbock
- German Centre for Lung Research, Dr von Hauner Children's Hospital, Ludwig-Maximilians University, D-80337 Munich, Germany
| | - Matthias Griese
- German Centre for Lung Research, Dr von Hauner Children's Hospital, Ludwig-Maximilians University, D-80337 Munich, Germany
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5
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Liu H, Wu X, Huang J, Peng J, Guo L. miR-7 modulates chemoresistance of small cell lung cancer by repressing MRP1/ABCC1. Int J Exp Pathol 2015; 96:240-7. [PMID: 26108539 DOI: 10.1111/iep.12131] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Accepted: 03/16/2015] [Indexed: 11/30/2022] Open
Abstract
MicroRNAs (miRNAs) represent a class of small non-coding RNAs and have been shown to play important roles in various biological processes including cell growth, differentiation and apoptosis by regulating the target genes. miR-7 has been described not only as a tumour suppressor gene but also as an oncogene in human cancers. The aim of this study was to investigate the functional roles of miR-7 in chemoresistance of SCLC and its underlying mechanism. By using a bioinformatic assay, we found that MRP1/ABCC1 was a potential target gene of miR-7. Expression of miR-7 and MRP1/ABCC1 was examined in 44 SCLC samples by quantitative reverse transcription-polymerase chain reaction and immunohistochemistry methods. Low-level expression of miR-7 was associated significantly with drug responsiveness and overall survival rate of patients with SCLC, but not with gender, age and stage. There was an inverse relationship between miR-7 and MRP1/ABCC1 expression. Downregulation of MRP1/ABCC1 level was revealed after transfection with a miR-7 mimic in H69 AR cells. Transfection of a miR-7 inhibitor into H69 cells restored MRP1/ABCC1 expression. A dual-luciferase reporter assay confirmed that miR-7 targeted predicted sites in the 3'-untranslated region (3'-UTR) of the MRP1/ABCC1 gene. Our data suggested that miR-7 mediated SCLC chemoresistance by repressing MRP1/ABCC1 and may be a prognostic predictor and potential therapeutic target in human SCLC.
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Affiliation(s)
- Huanxin Liu
- Department of Pathology, Zhujiang Hospital, Southern Medical University, Guangzhou, China.,Department of Pathology, Guangdong Provincial Corps Hospital of Chinese People's Armed Police Forces, Guangzhou medical college, Guangzhou, China
| | - Xiaoxia Wu
- Department of Pathology, Guangdong Provincial Corps Hospital of Chinese People's Armed Police Forces, Guangzhou medical college, Guangzhou, China
| | - Jie Huang
- Department of Pathology, Zhujiang Hospital, Southern Medical University, Guangzhou, China
| | - Juan Peng
- Department of Pathology, Zhujiang Hospital, Southern Medical University, Guangzhou, China
| | - Linlang Guo
- Department of Pathology, Zhujiang Hospital, Southern Medical University, Guangzhou, China
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6
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Wei W, Smith N, Wu X, Kim H, Seravalli J, Khalimonchuk O, Lee J. YCF1-mediated cadmium resistance in yeast is dependent on copper metabolism and antioxidant enzymes. Antioxid Redox Signal 2014; 21:1475-89. [PMID: 24444374 PMCID: PMC4158973 DOI: 10.1089/ars.2013.5436] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
AIMS Acquisition and detoxification of metal ions are vital biological processes. Given the requirement of metallochaperones in cellular copper distribution and metallation of cuproproteins, this study investigates whether the metallochaperones also deliver metal ions for transporters functioning in metal detoxification. RESULTS Resistance to excess cadmium and copper of the yeast Saccharomyces cerevisiae, which is conferred by PCA1 and CaCRP1 metal efflux P-type ATPases, respectively, does not rely on known metallochaperones, Atx1p, Ccs1p, and Cox17p. Copper deficiency induced by the expression of CaCRP1 encoding a copper exporter occurs in the absence of Atx1p. Intriguingly, CCS1 encoding the copper chaperone for superoxide dismutase 1 (Sod1p) is necessary for cadmium resistance that is mediated by Ycf1p, a vacuolar cadmium sequestration transporter. This is attributed to Ccs1p's role in the maturation of Sod1p rather than its direct interaction with Ycf1p for cadmium transfer. Functional defect in Ycf1p associated with the absence of Sod1p as well as another antioxidant enzyme Glr1p is rescued by anaerobic growth or substitutions of specific cysteine residues of Ycf1p to alanine or serine. This further supports oxidative inactivation of Ycf1p in the absence of Ccs1p, Sod1p, or Glr1p. INNOVATION These results provide new insights into the mechanisms of metal metabolism, interaction among metal ions, and the roles for antioxidant systems in metal detoxification. CONCLUSION Copper metabolism and antioxidant enzymes maintain the function of Ycf1p for cadmium defense.
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Affiliation(s)
- Wenzhong Wei
- Department of Biochemistry, Redox Biology Center, University of Nebraska-Lincoln , Lincoln, Nebraska
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7
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Abstract
PURPOSE OF REVIEW To offer a comprehensive review on the role of ABCG1 in cellular sterol homeostasis. RECENT FINDINGS Early studies with Abcg1 mice indicated that ABCG1 was crucial for tissue lipid homeostasis, especially in the lung. More recent studies have demonstrated that loss of ABCG1 has wide-ranging consequences and impacts lymphocyte and stem cell proliferation, endothelial cell function, macrophage foam cell formation, as well as insulin secretion from pancreatic β cells. Recent studies have also demonstrated that ABCG1 functions as an intracellular lipid transporter, localizes to intracellular vesicles/endosomes, and that the transmembrane domains are sufficient for localization and transport function. SUMMARY ABCG1 plays a crucial role in maintaining intracellular sterol and lipid homeostasis. Loss of this transporter has significant, cell-type-specific consequences ranging from effects on cellular proliferation, to surfactant production and/or insulin secretion. Elucidation of the mechanisms by which ABCG1 affects intracellular sterol flux/movement should provide important information that may link ABCG1 to diseases of dysregulated tissue lipid homeostasis.
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Affiliation(s)
- Elizabeth J Tarling
- Departments of Biological Chemistry and Medicine, David Geffen School of Medicine at UCLA, University of California, Los Angeles, CA 90095-1737, USA.
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8
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Yin J, Zhang J. Multidrug resistance-associated protein 1 (MRP1/ABCC1) polymorphism: from discovery to clinical application. ZHONG NAN DA XUE XUE BAO. YI XUE BAN = JOURNAL OF CENTRAL SOUTH UNIVERSITY. MEDICAL SCIENCES 2013; 36:927-38. [PMID: 22086004 DOI: 10.3969/j.issn.1672-7347.2011.10.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Multidrug resistance-associated protein 1(MRP1/ABCC1) is the first identified member of ABCC subfamily which belongs to ATP-binding cassette (ABC) transporter superfamily. It is ubiquitously expressed in almost all human tissues and transports a wide spectrum of substrates including drugs, heavy metal anions, toxicants, and conjugates of glutathione, glucuronide and sulfate. With the advance of sequence technology, many MRP1/ABCC1 polymorphisms have been identified. Accumulating evidences show that some polymorphisms are significantly associated with drug resistance and disease susceptibility. In vitro reconstitution studies have also unveiled the mechanism for some polymorphisms. In this review, we present recent advances in understanding the role and mechanism of MRP1/ABCC1 polymorphisms in drug resistance, toxicity, disease susceptibility and severity, prognosis prediction, and Methods to select and predict functional polymorphisms.
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Affiliation(s)
- Jiye Yin
- Department of Pharmacology/Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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9
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Shuker N, Bouamar R, Weimar W, van Schaik RHN, van Gelder T, Hesselink DA. ATP-binding cassette transporters as pharmacogenetic biomarkers for kidney transplantation. Clin Chim Acta 2011; 413:1326-37. [PMID: 21996082 DOI: 10.1016/j.cca.2011.09.040] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 09/21/2011] [Accepted: 09/27/2011] [Indexed: 01/11/2023]
Abstract
Immunosuppressive drugs used in organ transplantation are highly effective in preventing acute rejection. However, the clinical use of these drugs is complicated by the fact that they display highly variable pharmacokinetics and pharmacodynamics between individual patients. The influence of genetic variation on the interindividual variability in immunosuppressive drug disposition, efficacy, and toxicity has been explored in recent years. The polymorphically-expressed ATP-binding cassette (ABC) transporter proteins, in particular ABCB1 and ABCC2, have been investigated extensively because they play an important role in the absorption, distribution and elimination of many immunosuppressive drugs in use today. From these studies it can be concluded that polymorphisms in ABCB1 and ABCC2 have no consistent effect on immunosuppressant pharmacokinetics and toxicity although polymorphisms in ABCB1 appear to be related to the risk of developing calcineurin inhibitor-related nephrotoxicity. However, the latter needs to be replicated before an individual's ABCB1 genotype can become a useful marker that is applied in clinical practice. Future studies evaluating the influence of ABC transporter gene polymorphisms should explore the relationship with intracellular rather than systemic drug concentrations further in well-designed clinical studies. Until then, single-nucleotide polymorphisms in ABC transporter genes are not suitable to act as biomarkers for solid organ transplantation.
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Affiliation(s)
- Nauras Shuker
- Department of Hospital Pharmacy, Clinical Pharmacology Unit, The Netherlands
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10
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Joce C, Wiener AA, Yin H. Multi-Tox: application of the ToxR-transcriptional reporter assay to the study of multi-pass protein transmembrane domain oligomerization. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2948-53. [PMID: 21791200 DOI: 10.1016/j.bbamem.2011.07.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2011] [Revised: 07/03/2011] [Accepted: 07/08/2011] [Indexed: 10/18/2022]
Abstract
ToxR-based transcriptional reporter assays allow the strength of transmembrane helix interactions in biological membranes to be measured. Previously, these assays have only been used to study single-pass transmembrane systems. To facilitate investigation of polytopic transmembrane domain (TMD) oligomerization, we applied the ToxR methodology to the study of multi-pass TMD oligomerization to give 'Multi-Tox'. Association propensities of the viral oncoprotein, latent membrane protein-1 (LMP-1), and the E. coli membrane-integral diacylglycerol kinase (DAGK) were studied by Multi-Tox, highlighting residues of particular mechanistic importance. Both homo- and hetero-oligomerizations were studied.
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Affiliation(s)
- Catherine Joce
- Department of Chemistry and Biochemistry, University of Colorado at Boulder, Boulder, CO 80309-0215, USA
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11
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Joce C, Wiener A, Yin H. Transmembrane domain oligomerization propensity determined by ToxR assay. J Vis Exp 2011:2721. [PMID: 21654625 DOI: 10.3791/2721] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The oversimplified view of protein transmembrane domains as merely anchors in phospholipid bilayers has long since been disproven. In many cases membrane-spanning proteins have evolved highly sophisticated mechanisms of action. One way in which membrane proteins can modulate their structures and functions is by direct and specific contact of hydrophobic helices, forming structured transmembrane oligomers. Much recent work has focused on the distribution of amino acids preferentially found in the membrane environment in comparison to aqueous solution and the different intermolecular forces that drive protein association. Nevertheless, studies of molecular recognition at the transmembrane domain of proteins still lags behind those of water-soluble regions. A major hurdle remains: despite the remarkable specificity and affinity that transmembrane oligomerization can achieve, direct measurement of their association is challenging. Traditional methodologies applied to the study of integral membrane protein function can be hampered by the inherent insolubility of the sequences under examination. Biophysical insights gained from studying synthetic peptides representing transmembrane domains can provide useful structural insight. However, the biological relevance of the detergent micellar or liposome systems used in these studies to mimic cellular membranes is often questioned; do peptides adopt a native-like structure under these conditions and does their functional behaviour truly reflect the mode of action within a native membrane? In order to study the interactions of transmembrane sequences in natural phospholipid bilayers, the Langosch lab developed ToxR transcriptional reporter assays. The transmembrane domain of interest is expressed as a chimeric protein with maltose binding protein for location to the periplasm and ToxR to provide a report of the level of oligomerization (Figure 1). In the last decade, several other groups (e.g. Engelman, DeGrado, Shai) further optimized and applied this ToxR reporter assay. The various ToxR assays have become a gold standard to test protein-protein interactions in cell membranes. We herein demonstrate a typical experimental operation conducted in our laboratory that primarily follows protocols developed by Langosch. This generally applicable method is useful for the analysis of transmembrane domain self-association in E. coli, where β-galactosidase production is used to assess the TMD oligomerization propensity. Upon TMD-induced dimerization, ToxR binds to the ctx promoter causing up-regulation of the LacZ gene for β-galactosidase. A colorimetric readout is obtained by addition of ONPG to lyzed cells. Hydrolytic cleavage of ONPG by β-galactosidase results in the production of the light absorbing species o-nitrophenolate (ONP) (Figure 2).
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Affiliation(s)
- Catherine Joce
- Department of Chemistry and Biochemistry, University of Colorado at Boulder, USA
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12
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Optimized purification of a heterodimeric ABC transporter in a highly stable form amenable to 2-D crystallization. PLoS One 2011; 6:e19677. [PMID: 21602923 PMCID: PMC3094339 DOI: 10.1371/journal.pone.0019677] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Accepted: 04/06/2011] [Indexed: 12/24/2022] Open
Abstract
Optimized protocols for achieving high-yield expression, purification and reconstitution of membrane proteins are required to study their structure and function. We previously reported high-level expression in Escherichia coli of active BmrC and BmrD proteins from Bacillus subtilis, previously named YheI and YheH. These proteins are half-transporters which belong to the ABC (ATP-Binding Cassette) superfamily and associate in vivo to form a functional transporter able to efflux drugs. In this report, high-yield purification and functional reconstitution were achieved for the heterodimer BmrC/BmrD. In contrast to other detergents more efficient for solubilizing the transporter, dodecyl-ß-D-maltoside (DDM) maintained it in a drug-sensitive and vanadate-sensitive ATPase-competent state after purification by affinity chromatography. High amounts of pure proteins were obtained which were shown either by analytical ultracentrifugation or gel filtration to form a monodisperse heterodimer in solution, which was notably stable for more than one month at 4°C. Functional reconstitution using different lipid compositions induced an 8-fold increase of the ATPase activity (kcat∼5 s−1). We further validated that the quality of the purified BmrC/BmrD heterodimer is suitable for structural analyses, as its reconstitution at high protein densities led to the formation of 2-D crystals. Electron microscopy of negatively stained crystals allowed the calculation of a projection map at 20 Å resolution revealing that BmrC/BmrD might assemble into oligomers in a lipidic environment.
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13
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Mendoza-Cózatl DG, Zhai Z, Jobe TO, Akmakjian GZ, Song WY, Limbo O, Russell MR, Kozlovskyy VI, Martinoia E, Vatamaniuk OK, Russell P, Schroeder JI. Tonoplast-localized Abc2 transporter mediates phytochelatin accumulation in vacuoles and confers cadmium tolerance. J Biol Chem 2010; 285:40416-26. [PMID: 20937798 PMCID: PMC3003340 DOI: 10.1074/jbc.m110.155408] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2010] [Revised: 09/20/2010] [Indexed: 11/06/2022] Open
Abstract
Phytochelatins mediate tolerance to heavy metals in plants and some fungi by sequestering phytochelatin-metal complexes into vacuoles. To date, only Schizosaccharomyces pombe Hmt1 has been described as a phytochelatin transporter and attempts to identify orthologous phytochelatin transporters in plants and other organisms have failed. Furthermore, recent data indicate that the hmt1 mutant accumulates significant phytochelatin levels in vacuoles, suggesting that unidentified phytochelatin transporters exist in fungi. Here, we show that deletion of all vacuolar ABC transporters abolishes phytochelatin accumulation in S. pombe vacuoles and abrogates (35)S-PC(2) uptake into S. pombe microsomal vesicles. Systematic analysis of the entire S. pombe ABC transporter family identified Abc2 as a full-size ABC transporter (ABCC-type) that mediates phytochelatin transport into vacuoles. The S. pombe abc1 abc2 abc3 abc4 hmt1 quintuple and abc2 hmt1 double mutant show no detectable phytochelatins in vacuoles. Abc2 expression restores phytochelatin accumulation into vacuoles and suppresses the cadmium sensitivity of the abc quintuple mutant. A novel, unexpected, function of Hmt1 in GS-conjugate transport is also shown. In contrast to Hmt1, Abc2 orthologs are widely distributed among kingdoms and are proposed as the long-sought vacuolar phytochelatin transporters in plants and other organisms.
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Affiliation(s)
- David G. Mendoza-Cózatl
- From the Division of Biological Sciences, Cell and Developmental Biology Section, University of California, San Diego, La Jolla, California 92093
| | - Zhiyang Zhai
- the Department of Crop and Soil Sciences, Cornell University, Ithaca, New York 14853
| | - Timothy O. Jobe
- From the Division of Biological Sciences, Cell and Developmental Biology Section, University of California, San Diego, La Jolla, California 92093
| | - Garo Z. Akmakjian
- From the Division of Biological Sciences, Cell and Developmental Biology Section, University of California, San Diego, La Jolla, California 92093
| | - Won-Yong Song
- the Institute of Plant Biology, University of Zurich, Zollikerstrasse 107, 8008 Zurich, Switzerland, and
| | - Oliver Limbo
- the Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037
| | - Matthew R. Russell
- the Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037
| | | | - Enrico Martinoia
- the Institute of Plant Biology, University of Zurich, Zollikerstrasse 107, 8008 Zurich, Switzerland, and
| | - Olena K. Vatamaniuk
- the Department of Crop and Soil Sciences, Cornell University, Ithaca, New York 14853
| | - Paul Russell
- the Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037
| | - Julian I. Schroeder
- From the Division of Biological Sciences, Cell and Developmental Biology Section, University of California, San Diego, La Jolla, California 92093
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14
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Peng H, Qi J, Dong Z, Zhang JT. Dynamic vs static ABCG2 inhibitors to sensitize drug resistant cancer cells. PLoS One 2010; 5:e15276. [PMID: 21151870 PMCID: PMC2998423 DOI: 10.1371/journal.pone.0015276] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Accepted: 11/03/2010] [Indexed: 12/14/2022] Open
Abstract
Human ABCG2, a member of the ATP-binding cassette transporter superfamily, plays a key role in multidrug resistance and protecting cancer stem cells. ABCG2-knockout had no apparent adverse effect on the development, biochemistry, and life of mice. Thus, ABCG2 is an interesting and promising target for development of chemo-sensitizing agents for better treatment of drug resistant cancers and for eliminating cancer stem cells. Previously, we reported a novel two mode-acting ABCG2 inhibitor, PZ-39, that induces ABCG2 degradation in addition to inhibiting its activity. In this manuscript, we report our recent progresses in identifying two different groups of ABCG2 inhibitors with one inhibiting only ABCG2 function (static) and the other induces ABCG2 degradation in lysosome in addition to inhibiting its function (dynamic). Thus, the inhibitor-induced ABCG2 degradation may be more common than we previously anticipated and further investigation of the dynamic inhibitors that induce ABCG2 degradation may provide a more effective way of sensitizing ABCG2-mediated MDR in cancer chemotherapy.
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Affiliation(s)
- Hui Peng
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Jing Qi
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Zizheng Dong
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Jian-Ting Zhang
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
- IU Simon Cancer Center, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
- * E-mail:
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15
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Ni Z, Bikadi Z, Rosenberg MF, Mao Q. Structure and function of the human breast cancer resistance protein (BCRP/ABCG2). Curr Drug Metab 2010; 11:603-17. [PMID: 20812902 DOI: 10.2174/138920010792927325] [Citation(s) in RCA: 189] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Accepted: 08/13/2010] [Indexed: 12/22/2022]
Abstract
The human breast cancer resistance protein (BCRP/ABCG2) is the second member of the G subfamily of the large ATP-binding cassette (ABC) transporter superfamily. BCRP was initially discovered in multidrug resistant breast cancer cell lines where it confers resistance to chemotherapeutic agents such as mitoxantrone, topotecan and methotrexate by extruding these compounds out of the cell. BCRP is capable of transporting non-chemotherapy drugs and xenobiotiocs as well, including nitrofurantoin, prazosin, glyburide, and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine. BCRP is frequently detected at high levels in stem cells, likely providing xenobiotic protection. BCRP is also highly expressed in normal human tissues including the small intestine, liver, brain endothelium, and placenta. Therefore, BCRP has been increasingly recognized for its important role in the absorption, elimination, and tissue distribution of drugs and xenobiotics. At present, little is known about the transport mechanism of BCRP, particularly how it recognizes and transports a large number of structurally and chemically unrelated drugs and xenobiotics. Here, we review current knowledge of structure and function of this medically important ABC efflux drug transporter.
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Affiliation(s)
- Zhanglin Ni
- Department of Pharmaceutics, School of Pharmacy, University of Washington, Health Science Building H272, 1959 NE Pacific Street, Seattle, Washington 98195-7610, USA
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16
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Dezi M, Fribourg PF, Di Cicco A, Arnaud O, Marco S, Falson P, Di Pietro A, Lévy D. The multidrug resistance half-transporter ABCG2 is purified as a tetramer upon selective extraction from membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:2094-101. [PMID: 20691149 DOI: 10.1016/j.bbamem.2010.07.034] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Revised: 07/27/2010] [Accepted: 07/27/2010] [Indexed: 01/07/2023]
Abstract
ABCG2 is a human membrane ATP-binding cassette half-transporter that hydrolyzes ATP to efflux a large number of chemotherapeutic agents. Several oligomeric states of ABCG2 from homodimers to dodecamers have been reported depending on the overexpression systems and/or the protocols used for purification. Here, we compared the oligomeric state of His(6)-ABCG2 expressed in Sf9 insect cells and in human Flp-In-293/ABCG2 cells after solubilization in mild detergents. His(6)-ABCG2 was purified through a new approach involving its specific recognition onto a functionalized lipid layer containing a Ni-NTA lipid. This approach allowed the purification of His-ABCG2 in presence of all solubilized membrane components that might be involved in the stabilisation of native oligomers and without requiring any additional washing or concentration passages. ABCG2 purified onto the NiNTA lipid surfaces were directly analyzed by electron microscopy and by biochemical assays. Altogether, our data are consistent with a tetrameric organization of ABCG2 when expressed in either heterologous Sf9 insect cells or in human homologous cells.
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Affiliation(s)
- Manuela Dezi
- Institut Curie, Centre de Recherche, Paris, F-75231, France
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