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Sun X, Shu Y, Yan P, Huang H, Gao R, Xu M, Lu L, Tian J, Huang D, Zhang J. Transcriptome profiling analysis reveals that ATP6V0E2 is involved in the lysosomal activation by anlotinib. Cell Death Dis 2020; 11:702. [PMID: 32839434 PMCID: PMC7445181 DOI: 10.1038/s41419-020-02904-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2019] [Revised: 08/06/2020] [Accepted: 08/07/2020] [Indexed: 12/18/2022]
Abstract
Anlotinib is a receptor tyrosine kinase inhibitor with potential anti-neoplastic and anti-angiogenic activities. It has been approved for the treatment of non-small-cell lung cancer. Lysosomes are acidic organelles and have been implicated in various mechanisms of cancer therapeutics. However, the effect of anlotinib on lysosomal function has not been investigated. In the present study, anlotinib induces apoptosis in human colon cancer cells. Through transcriptome sequencing, we found for the first time that anlotinib treatment upregulates ATP6V0E2 (ATPase H+ Transporting V0 Subunit E2) and other lysosome-related genes expression in human colon cancer. In human colon cancer, we validated that anlotinib activates lysosomal function and enhances the fusion of autophagosomes and lysosomes. Moreover, anlotinib treatment is shown to inhibit mTOR (mammalian target of rapamycin) signaling and the activation of lysosomal function by anlotinib is mTOR dependent. Furthermore, anlotinib treatment activates TFEB, a key nuclear transcription factor that controls lysosome biogenesis and function. We found that anlotinib treatment promotes TFEB nuclear translocation and enhances its transcriptional activity. When TFEB or ATP6V0E2 are knocked down, the enhanced lysosomal function and autophagy by anlotinib are attenuated. Finally, inhibition of lysosomal function enhances anlotinib-induced cell death and tumor suppression, which may be attributed to high levels of ROS (reactive oxygen species). These findings suggest that the activation of lysosomal function protects against anlotinib-mediated cell apoptosis via regulating the cellular redox status. Taken together, our results provide novel insights into the regulatory mechanisms of anlotinib on lysosomes, and this information could facilitate the development of potential novel cancer therapeutic agents that inhibit lysosomal function.
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Affiliation(s)
- Xin Sun
- Department of Oncology, Zhejiang Provincial People's Hospital, People's Hospital of Hangzhou Medical College, Hangzhou, China
| | - Yuhan Shu
- College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, China
| | - Peiyi Yan
- Department of Clinical Laboratory, Shanghai Putuo District People's Hospital, Shanghai, China
| | - Hongliang Huang
- School of Biosciences & Biopharmaceutics and Center for Bioresources & Drug Discovery, Guangdong Pharmaceutical University, Guangzhou, China
| | - Ruilan Gao
- Institution of Hematology Research, The First Affiliated Hospital of Zhejiang Chinese Medical University, Hangzhou, China
| | - Mengting Xu
- College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, China
| | - Liqin Lu
- Department of Oncology, Zhejiang Provincial People's Hospital, People's Hospital of Hangzhou Medical College, Hangzhou, China
| | - Jingkui Tian
- College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, China.
| | - Dongsheng Huang
- Key Laboratory of Tumor Molecular Diagnosis and Individualized Medicine of Zhejiang Province, Clinical Research Institute, People's Hospital of Hangzhou Medical College, Hangzhou, China.
| | - Jianbin Zhang
- Department of Oncology, Zhejiang Provincial People's Hospital, People's Hospital of Hangzhou Medical College, Hangzhou, China. .,Key Laboratory of Tumor Molecular Diagnosis and Individualized Medicine of Zhejiang Province, Clinical Research Institute, People's Hospital of Hangzhou Medical College, Hangzhou, China.
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Parker WAE, Eriksson N, Becker RC, Voora D, Åkerblom A, Himmelmann A, James SK, Wallentin L, Storey RF. Equilibrative nucleoside transporter 1 gene polymorphisms and clinical outcomes following acute coronary syndromes: findings from the PLATelet inhibition and patient Outcomes (PLATO) study. Platelets 2018; 30:579-588. [DOI: 10.1080/09537104.2018.1478404] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- William A. E. Parker
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom
| | - Niclas Eriksson
- Uppsala Clinical Research Center, Uppsala University, Uppsala, Sweden
| | - Richard C. Becker
- Division of Cardiovascular Health and Disease, Heart, Lung and Vascular Institute, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Deepak Voora
- Duke Clinical Research Institute, Duke University Medical Center, Durham, NC, USA
| | - Axel Åkerblom
- Department of Medical Sciences, Cardiology and Uppsala Clinical Research Center, Uppsala University, Uppsala, Sweden
| | | | - Stefan K. James
- Department of Medical Sciences, Cardiology and Uppsala Clinical Research Center, Uppsala University, Uppsala, Sweden
| | - Lars Wallentin
- Department of Medical Sciences, Cardiology and Uppsala Clinical Research Center, Uppsala University, Uppsala, Sweden
| | - Robert F. Storey
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom
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Colgan SP, Eltzschig HK. Adenosine and hypoxia-inducible factor signaling in intestinal injury and recovery. Annu Rev Physiol 2011; 74:153-75. [PMID: 21942704 DOI: 10.1146/annurev-physiol-020911-153230] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The gastrointestinal mucosa has proven to be an interesting tissue in which to investigate disease-related metabolism. In this review, we outline some of the evidence that implicates hypoxia-mediated adenosine signaling as an important signature within both healthy and diseased mucosa. Studies derived from cultured cell systems, animal models, and human patients have revealed that hypoxia is a significant component of the inflammatory microenvironment. These studies have revealed a prominent role for hypoxia-induced factor (HIF) and hypoxia signaling at several steps along the adenine nucleotide metabolism and adenosine receptor signaling pathways. Likewise, studies to date in animal models of intestinal inflammation have demonstrated an almost uniformly beneficial influence of HIF stabilization on disease outcomes. Ongoing studies to define potential similarities with and differences between innate and adaptive immune responses will continue to teach us important lessons about the complexity of the gastrointestinal tract. Such information has provided new insights into disease pathogenesis and, importantly, will provide insights into new therapeutic targets.
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Affiliation(s)
- Sean P Colgan
- Departments of Medicine and Anesthesiology and the Mucosal Inflammation Program, University of Colorado School of Medicine, Aurora, Colorado 80045, USA.
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4
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Wu J, Lee MR, Choi S, Kim T, Choi DS. ENT1 regulates ethanol-sensitive EAAT2 expression and function in astrocytes. Alcohol Clin Exp Res 2010; 34:1110-7. [PMID: 20374202 DOI: 10.1111/j.1530-0277.2010.01187.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Equilibrative nucleoside transporter 1 (ENT1) and excitatory amino acid transporter 2 (EAAT2) are predominantly expressed in astrocytes where they are thought to regulate synaptic adenosine and glutamate levels. Because mice lacking ENT1 display increased glutamate levels in the ventral striatum, we investigated whether ENT1 regulates the expression and function of EAAT2 in astrocytes, which could contribute to altered glutamate levels in the striatum. METHODS We examined the effect of ENT1 inhibition and overexpression on the expression of EAAT2 using quantitative real-time PCR and measured glutamate uptake activity in cultured astrocytes. We also examined the effect of 0 to 200 mM ethanol doses for 0 to 24 hours of ethanol exposure on EAAT2 expression and glutamate uptake activity. We further examined the effect of ENT1 knockdown by a specific siRNA on ethanol-induced EAAT2 expression. RESULTS An ENT1-specific antagonist and siRNA treatments significantly reduced both EAAT2 expression and glutamate uptake activity while ENT1 overexpression up-regulated EAAT2 mRNA expression. Interestingly, 100 or 200 mM ethanol exposure increased EAAT2 mRNA expression as well as glutamate uptake activity. Moreover, we found that ENT1 knockdown inhibited the ethanol-induced EAAT2 up-regulation. CONCLUSIONS Our results suggest that ENT1 regulates glutamate uptake activity by altering EAAT2 expression and function, which might be implicated in ethanol intoxication and preference.
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Affiliation(s)
- Jinhua Wu
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA
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5
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Robillard KR, Bone DB, Park JS, Hammond JR. Characterization of mENT1Δ11, a Novel Alternative Splice Variant of the Mouse Equilibrative Nucleoside Transporter 1. Mol Pharmacol 2008; 74:264-73. [DOI: 10.1124/mol.107.041871] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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6
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Abdulla P, Coe IR. Characterization and functional analysis of the promoter for the human equilibrative nucleoside transporter gene, hENT1. NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2007; 26:99-110. [PMID: 17162590 DOI: 10.1080/15257770601052331] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Equilibrative nucleoside transporters (ENTs) are membrane proteins that transport nucleosides, nucleobases and analogs across membranes. ENT genes and the regulation of their expression are poorly understood. Therefore, we isolated and functionally characterized the promoter of the prototypic human ENT, hENT1. A single transcriptional initiation site 58 bp downstream of the TATA box and 272 bp upstream of the translation initiation site is present. Limited sequence similarity exists between the hENT1 and mouse ENT1 (mENT1) promoters suggesting conservation of ENT1 transcriptional regulators in mammals. Putative consensus sites for transcription factors exist within the hENT1 promoter. Reporter assays revealed similar but not identical transcriptional activity profiles in human cells.
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Affiliation(s)
- Parween Abdulla
- Department of Biology, York University, Toronto, Ontario, Canada
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Löffler M, Morote-Garcia JC, Eltzschig SA, Coe IR, Eltzschig HK. Physiological roles of vascular nucleoside transporters. Arterioscler Thromb Vasc Biol 2007; 27:1004-13. [PMID: 17332491 DOI: 10.1161/atvbaha.106.126714] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Nucleoside transporters (NTs) comprise 2 widely expressed families, the equilibrative nucleoside transporters (diffusion-limited channels) and concentrative nucleoside transporters (sodium-dependent transporters). Because of their anatomic position at the blood-tissue interface, vascular NTs are in an ideal position to influence vascular nucleoside levels, particularly adenosine, which among others plays an important role in tissue protection during acute injury. For example, endothelial NTs contribute to preserving the vascular integrity during conditions of limited oxygen availability (hypoxia). Indeed, hypoxia-inducible factor-1-dependent repression of NTs results in enhanced extracellular adenosine signaling and thus attenuates hypoxia-associated increases in vascular leakage. In addition, vascular NTs also contribute to cardiac ischemic preconditioning, coronary vasodilation, and inhibition of platelet aggregation. Moreover, vascular nucleoside uptake via NTs is important for nucleoside recovery, particularly in cells lacking de novo nucleotide synthesis pathways (erythrocytes, leukocytes). Taken together, vascular NTs are critical in modulating adenosine-mediated responses during conditions such as inflammation or hypoxia.
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Affiliation(s)
- Michaela Löffler
- Department of Anesthesiology and Intensive Care Medicine, Tübingen University Hospital, Waldhörnle Str. 22, 72072, Tübingen, Germany
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8
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Myers SN, Goyal RK, Roy JD, Fairfull LD, Wilson JW, Ferrell RE. Functional single nucleotide polymorphism haplotypes in the human equilibrative nucleoside transporter 1. Pharmacogenet Genomics 2006; 16:315-20. [PMID: 16609362 DOI: 10.1097/01.fpc.0000189804.41962.15] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The human equilibrative nucleoside transporter 1 gene (hENT1) is the primary nucleoside transporter for cytosine arabinoside (AraC), a deoxycytidine analog used for treatment of acute leukemias and lymphomas. We screened approximately 1.6 kb upstream of the transcription initiation site of hENT1 for single nucleotide polymorphisms (SNPs) that affect gene expression. We identified one SNP at position -706G>C with a frequency of 21% in whites and 5% in African-Americans. In African-Americans, we observed two SNPs at positions -1345C>G and -1050G>A with allele frequencies of 8% and 19%, respectively. TRANSFAC analysis suggested that -1345C>G and -706G>C may alter transcription factor binding sites. Four naturally occurring haplotypes (CGG, CAG, CGC and GAG) were cloned into a luciferase expression plasmid, transfected into Cos-1 cells, and reporter activity measured at 24 and 48 h. Three haplotypes, CAG, CGC and GAG, respectively, showed average expression that was approximately two-fold (P<0.05), 1.4-fold (P<0.05) and 1.1-fold (P>0.05) higher than lowest expression haplotype CGG at 48 h. When reanalysed as single SNPs, the differences in expression were significant for -1345C>G and -1050G>A genotypes, and not for -706G>C. However, the magnitude of difference was reduced, suggesting that no single SNP completely accounts for the expression differences observed at the haplotype level. By real-time quantitative reverse transcriptase-polymerase chain reaction assay, individuals with CGG/CGC haplotypes showed 1.37-fold higher median expression of hENT1 transcript than those with common CGG/CGG haplotypes. Although not statistically significant (P=0.12), this difference is in the direction predicted by the in vitro data. hENT1 promoter region haplotypes may influence gene expression and alter AraC chemosensitivity.
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Affiliation(s)
- Scott N Myers
- Department of Pediatrics, School of Medicine, Children's Hospital of Pittsburgh, Pittsburgh, PA 15261, USA
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Vickers MF, Young JD, Baldwin SA, Mackey JR, Cass CE. Nucleoside transporter proteins: emerging targets for drug discovery. ACTA ACUST UNITED AC 2005. [DOI: 10.1517/14728222.4.4.515] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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10
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Damaraju VL, Damaraju S, Young JD, Baldwin SA, Mackey J, Sawyer MB, Cass CE. Nucleoside anticancer drugs: the role of nucleoside transporters in resistance to cancer chemotherapy. Oncogene 2003; 22:7524-36. [PMID: 14576856 DOI: 10.1038/sj.onc.1206952] [Citation(s) in RCA: 238] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The clinical efficacy of anticancer nucleoside drugs depends on a complex interplay of transporters mediating entry of nucleoside drugs into cells, efflux mechanisms that remove drugs from intracellular compartments and cellular metabolism to active metabolites. Nucleoside transporters (NTs) are important determinants for salvage of preformed nucleosides and mediated uptake of antimetabolite nucleoside drugs into target cells. The focus of this review is the two families of human nucleoside transporters (hENTs, hCNTs) and their role in transport of cytotoxic chemotherapeutic nucleoside drugs. Resistance to anticancer nucleoside drugs is a major clinical problem in which NTs have been implicated. Single nucleotide polymorphisms (SNPs) in drug transporters may contribute to interindividual variation in response to nucleoside drugs. In this review, we give an overview of the functional and molecular characteristics of human NTs and their potential role in resistance to nucleoside drugs and discuss the potential use of genetic polymorphism analyses for NTs to address drug resistance.
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Affiliation(s)
- Vijaya L Damaraju
- Membrane Protein Research Group, University of Alberta, 11560 University Avenue, Edmonton, Alberta, Canada T6G 1Z2
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11
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Clarke ML, Mackey JR, Baldwin SA, Young JD, Cass CE. The role of membrane transporters in cellular resistance to anticancer nucleoside drugs. Cancer Treat Res 2003; 112:27-47. [PMID: 12481710 DOI: 10.1007/978-1-4615-1173-1_2] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Affiliation(s)
- Marilyn L Clarke
- Department of Experimental Oncology, Cross Cancer Institute, Edmonton, Alberta, Canada
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12
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Cabrita MA, Baldwin SA, Young JD, Cass CE. Molecular biology and regulation of nucleoside and nucleobase transporter proteins in eukaryotes and prokaryotes. Biochem Cell Biol 2003; 80:623-38. [PMID: 12440702 DOI: 10.1139/o02-153] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The molecular cloning of cDNAs encoding nucleoside transporter proteins has greatly advanced understanding of how nucleoside permeants are translocated across cell membranes. The nucleoside transporter proteins identified thus far have been categorized into five distinct superfamilies. Two of these superfamilies, the equilibrative and concentrative nucleoside transporters, have human members and these will be examined in depth in this review. The human equilibrative nucleoside transporters translocate nucleosides and nucleobases bidirectionally down their concentration gradients and are important in the uptake of anticancer and antiviral nucleoside drugs. The human concentrative nucleoside transporters cotranslocate nucleosides and sodium unidirectionally against the nucleoside concentration gradients and play a vital role in certain tissues. The regulation of nucleoside and nucleobase transporters is being studied more intensely now that more tools are available. This review provides an overview of recent advances in the molecular biology and regulation of the nucleoside and nucleobase transporters.
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Affiliation(s)
- Miguel A Cabrita
- Department of Biochemistry, Cross Cancer Institute, University of Alberta, Edmonton, Canada
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13
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Sankar N, Machado J, Abdulla P, Hilliker AJ, Coe IR. Comparative genomic analysis of equilibrative nucleoside transporters suggests conserved protein structure despite limited sequence identity. Nucleic Acids Res 2002; 30:4339-50. [PMID: 12384580 PMCID: PMC137128 DOI: 10.1093/nar/gkf564] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2002] [Revised: 08/19/2002] [Accepted: 08/19/2002] [Indexed: 11/13/2022] Open
Abstract
Equilibrative nucleoside transporters (ENTs) are a recently characterized and poorly understood group of membrane proteins that are important in the uptake of endogenous nucleosides required for nucleic acid and nucleoside triphosphate synthesis. Despite their central importance in cellular metabolism and nucleoside analog chemotherapy, no human ENT gene has been described and nothing is known about gene structure and function. To gain insight into the ENT gene family, we used experimental and in silico comparative genomic approaches to identify ENT genes in three evolutionarily diverse organisms with completely (or almost completely) sequenced genomes, Homo sapiens, Caenorhabditis elegans and Drosophila melanogaster. We describe the chromosomal location, the predicted ENT gene structure and putative structural topologies of predicted ENT proteins derived from the open reading frames. Despite variations in genomic layout and limited ortholog protein sequence identity (< or =27.45%), predicted topologies of ENT proteins are strikingly similar, suggesting an evolutionary conservation of a prototypic structure. In addition, a similar distribution of protein domains on exons is apparent in all three taxa. These data demonstrate that comparative sequence analyses should be combined with other approaches (such as genomic and proteomic analyses) to fully understand structure, function and evolution of protein families.
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Affiliation(s)
- Narendra Sankar
- Department of Biology, York University, 4700 Keele Street, Toronto M3J 1P3, Canada
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Pennycooke M, Chaudary N, Shuralyova I, Zhang Y, Coe IR. Differential expression of human nucleoside transporters in normal and tumor tissue. Biochem Biophys Res Commun 2001; 280:951-9. [PMID: 11162617 DOI: 10.1006/bbrc.2000.4205] [Citation(s) in RCA: 140] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Responses to nucleoside analog drugs used in the treatment of cancers and viral infections can vary considerably between individuals. Genetic variability between individuals in their ability to transport drugs may be a contributory factor. Nucleoside transporters (NTs) move nucleosides and analog drugs across cell membranes. Four human NTs have been cloned: hENT1, hENT2, hCNT1, and hCNT2. Human NT expression profiles are not well defined; therefore, we undertook a comprehensive quantitative analysis of the differential expression of NTs within normal and tumor tissue. Results show tissue specific expression of the different NTs in normal tissue while matched normal/tumor tissue cDNA array data show considerable variability in all NT expression profiles from different individuals, in particular decreased expression in tumor tissue. Decreased NT expression in tumor tissue may contribute to reduced drug uptake and the development of resistance. These data suggest that nucleoside analog drug therapies may be optimized by determining individual NT expression profiles.
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Affiliation(s)
- M Pennycooke
- Department of Biology, York University, 4700 Keele Street, Toronto, Ontario, Canada M3J 1P3
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15
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Handa M, Choi DS, Caldeiro RM, Messing RO, Gordon AS, Diamond I. Cloning of a novel isoform of the mouse NBMPR-sensitive equilibrative nucleoside transporter (ENT1) lacking a putative phosphorylation site. Gene 2001; 262:301-7. [PMID: 11179696 DOI: 10.1016/s0378-1119(00)00555-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
We have isolated a mouse cDNA clone corresponding to a novel isoform of the NBMPR-sensitive equilibrative nucleoside transporter (ENT1). The cDNA contains a 6 bp deletion in the open reading frame that changes the amino acid composition in a consensus casein kinase II (CKII) phosphorylation site at Ser-254. The clone containing Ser-254 is termed mENT1.1 and the clone lacking the serine termed mENT1.2. The deduced amino acid sequence of mENT1.1 corresponds to the previously cloned human and rat ENT1 proteins at Ser-254. Tissue distribution studies show that mRNA for both ENT1 isoforms are ubiquitously co-expressed in mouse. Analysis of genomic DNA corresponding to mouse ENT1 indicates the isoforms can be produced by alternative splicing at the end of exon 7. CEM/C19 cells stably expressing mENT1.1 and mENT1.2 show similar dose response curves for NBMPR and dipyridamole inhibition of [(3)H]adenosine uptake as well as exhibiting comparable selectivity for both purine and pyrimidine nucleosides but not the corresponding nucleobases.
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Affiliation(s)
- M Handa
- Ernest Gallo Clinic and Research Center, Department of Neurology, University of California, San Francisco, CA 94608, USA
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16
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Choi DS, Handa M, Young H, Gordon AS, Diamond I, Messing RO. Genomic organization and expression of the mouse equilibrative, nitrobenzylthioinosine-sensitive nucleoside transporter 1 (ENT1) gene. Biochem Biophys Res Commun 2000; 277:200-8. [PMID: 11027664 DOI: 10.1006/bbrc.2000.3665] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have cloned and characterized the genomic structure of the mouse gene for the NBMPR-sensitive equilibrative nucleoside transporter (mENT1), which is located on chromosome 17C. About 12-kb of genomic DNA was sequenced including the promoter region, 12 exons, 11 introns, and the 3'-untranslated region. All exon-intron junction sequences conform to the GT/AG rule. Primer extension analysis demonstrated a transcription initiation site located 252 bp upstream of the translation start site. Analysis of the 2.5-kb 5'-flanking sequence shows putative binding sites for several transcription factors, including GATA-1, IRF-2, Pit-1, myogenin, CREB, Sp-1, Ap-2, MAZ, and GR. We demonstrated that mouse ENT1 mRNA was highly expressed in heart, spleen, lung, liver, and testis. Lower levels of expression were detected in brain and kidney. Functional analysis of the 5'-flanking region showed that the nucleotide sequence from -652 to -111 contains cis-regulatory elements that promote gene expression. We found two Sp-1 binding sites (-296/-303, -307/-313) and two MAZ binding sites (-353/-359, -522/-528) in this region. Luciferase assay results suggest that MAZ and Sp-1 transcription factors are important positive regulators of transcription for the ENT1 gene in NG108-15 cells.
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Affiliation(s)
- D S Choi
- Ernest Gallo Clinic and Research Center, Department of Neurology, Graduate Program in Neuroscience, University of California, San Francisco, 5858 Horton Street, Suite 200, Emeryville, California, USA.
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Chapter 9 Molecular mechanisms of nucleoside and nucleoside drug transport. CURRENT TOPICS IN MEMBRANES 2000. [DOI: 10.1016/s1063-5823(00)50011-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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Cass CE, Young JD, Baldwin SA, Cabrita MA, Graham KA, Griffiths M, Jennings LL, Mackey JR, Ng AM, Ritzel MW, Vickers MF, Yao SY. Nucleoside transporters of mammalian cells. PHARMACEUTICAL BIOTECHNOLOGY 1999; 12:313-52. [PMID: 10742981 DOI: 10.1007/0-306-46812-3_12] [Citation(s) in RCA: 97] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/14/2023]
Abstract
In this review, we have summarized recent advances in our understanding of the biology of nucleoside transport arising from new insights provided by the isolation and functional expression of cDNAs encoding the major nucleoside transporters of mammalian cells. Nucleoside transporters are required for permeation of nucleosides across biological membranes and are present in the plasma membranes of most cell types. There is growing evidence that functional nucleoside transporters are required for translocation of nucleosides between intracellular compartments and thus are also present in organellar membranes. Functional studies during the 1980s established that nucleoside transport in mammalian cells occurs by two mechanistically distinct processes, facilitated diffusion and Na(+)-nucleoside cotransport. The determination of the primary amino acid sequences of the equilibrative and concentrative transporters of human and rat cells has provided a structural basis for the functional differences among the different transporter subtypes. Although nucleoside transporter proteins were first purified from human erythrocytes a decade ago, the low abundance of nucleoside transporter proteins in membranes of mammalian cells has hindered analysis of relationships between transporter structure and function. The molecular cloning of cDNAs encoding nucleoside transporters and the development of heterologous expression systems for production of recombinant nucleoside transporters, when combined with recombinant DNA technologies, provide powerful tools for characterization of functional domains within transporter proteins that are involved in nucleoside recognition and translocation. As relationships between molecular structure and function are determined, it should be possible to develop new approaches for optimizing the transportability of nucleoside drugs into diseased tissues, for development of new transport inhibitors, including reagents that are targeted to the concentrative transporters, and, eventually, for manipulation of transporter function through an understanding of the regulation of transport activity.
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Affiliation(s)
- C E Cass
- Molecular Biology of Membranes Group, University of Alberta, Edmonton, Canada
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Jennings LL, Cass CE, Ritzel MW, Yao SY, Young JD, Griffiths M, Baldwin SA. Adenosine transport: Recent advances in the molecular biology of nucleoside transporter proteins. Drug Dev Res 1998. [DOI: 10.1002/(sici)1098-2299(199811/12)45:3/4<277::aid-ddr26>3.0.co;2-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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