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Mollick T, Darekar S, Dalarun B, Plastino F, Zhang J, Fernández AP, Alkasalias T, André H, Laín S. Retinoblastoma vulnerability to combined de novo and salvage pyrimidine ribonucleotide synthesis pharmacologic blockage. Heliyon 2024; 10:e23831. [PMID: 38332874 PMCID: PMC10851301 DOI: 10.1016/j.heliyon.2023.e23831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 12/05/2023] [Accepted: 12/13/2023] [Indexed: 02/10/2024] Open
Abstract
Retinoblastoma is an eye cancer that commonly affects young children. Despite significant advances, current treatments cause side effects even when administered locally, and patients may still have to undergo enucleation. This is particularly disheartening in cases of bilateral retinoblastoma. Hence, there is an urgent need for novel therapeutic strategies. Inhibitors of the enzyme dihydroorotate dehydrogenase (DHODH), which is involved in the de novo pyrimidine ribonucleotide synthesis pathway, have proven to be effective in preclinical trials against several cancers including pediatric cancers. Here we tested whether blocking pyrimidine ribonucleotide synthesis promotes retinoblastoma cell death. Cultured retinoblastoma cell lines were treated with small molecule inhibitors of DHODH alone or in combination with inhibitors of nucleoside uptake to also block the salvage pathway for pyrimidine ribonucleotide formation. On their own, DHODH inhibitors had a moderate killing effect. However, the combination with nucleoside uptake inhibitors greatly enhanced the effect of DHODH inhibition. In addition, we observed that pyrimidine ribonucleotide synthesis blockage can cause cell death in a p53 mutant retinoblastoma cell line derived from a patient with metastasis. Explaining these results, the analysis of a published patient cohort revealed that loss of chr16q22.2 (containing the DHODH gene) is amongst the most frequent alterations in retinoblastoma and that these tumors often show gains in chromosome regions expressing pyrimidine ribonucleotide salvage factors. Furthermore, these genome alterations associate with malignancy. These results indicate that targeting pyrimidine ribonucleotide synthesis may be an effective therapeutic strategy to consider as a treatment for retinoblastoma.
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Affiliation(s)
- Tanzina Mollick
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, 17165, Solna, Stockholm, Sweden
| | - Suhas Darekar
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, 17165, Solna, Stockholm, Sweden
| | - Basile Dalarun
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, 17165, Solna, Stockholm, Sweden
| | - Flavia Plastino
- Department of Clinical Neuroscience, Division of Eye and Vision, St. Erik Eye Hospital, Karolinska Institutet, 17177, Stockholm, Sweden
| | - Juan Zhang
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, 17165, Solna, Stockholm, Sweden
| | - Andres Pastor Fernández
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, 17165, Solna, Stockholm, Sweden
| | - Twana Alkasalias
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, 17165, Solna, Stockholm, Sweden
- General Directorate of Scientific Research Center, Salahaddin University-Erbil, Erbil, Kurdistan Region, Iraq
| | - Helder André
- Department of Clinical Neuroscience, Division of Eye and Vision, St. Erik Eye Hospital, Karolinska Institutet, 17177, Stockholm, Sweden
| | - Sonia Laín
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, 17165, Solna, Stockholm, Sweden
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Hau RK, Wright SH, Cherrington NJ. Addressing the Clinical Importance of Equilibrative Nucleoside Transporters in Drug Discovery and Development. Clin Pharmacol Ther 2023; 114:780-794. [PMID: 37404197 DOI: 10.1002/cpt.2984] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Accepted: 05/30/2023] [Indexed: 07/06/2023]
Abstract
The US Food and Drug Administration (FDA), European Medicines Agency (EMA), and Pharmaceuticals and Medical Devices Agency (PMDA) guidances on small-molecule drug-drug interactions (DDIs), with input from the International Transporter Consortium (ITC), recommend the evaluation of nine drug transporters. Although other clinically relevant drug uptake and efflux transporters have been discussed in ITC white papers, they have been excluded from further recommendation by the ITC and are not included in current regulatory guidances. These include the ubiquitously expressed equilibrative nucleoside transporters (ENT) 1 and ENT2, which have been recognized by the ITC for their potential role in clinically relevant nucleoside analog drug interactions for patients with cancer. Although there is comparatively limited clinical evidence supporting their role in DDI risk or other adverse drug reactions (ADRs) compared with the nine highlighted transporters, several in vitro and in vivo studies have identified ENT interactions with non-nucleoside/non-nucleotide drugs, in addition to nucleoside/nucleotide analogs. Some noteworthy examples of compounds that interact with ENTs include cannabidiol and selected protein kinase inhibitors, as well as the nucleoside analogs remdesivir, EIDD-1931, gemcitabine, and fialuridine. Consequently, DDIs involving the ENTs may be responsible for therapeutic inefficacy or off-target toxicity. Evidence suggests that ENT1 and ENT2 should be considered as transporters potentially involved in clinically relevant DDIs and ADRs, thereby warranting further investigation and regulatory consideration.
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Affiliation(s)
- Raymond K Hau
- Department of Pharmacology & Toxicology, College of Pharmacy, The University of Arizona, Tucson, Arizona, USA
| | - Stephen H Wright
- Department of Physiology, College of Medicine, The University of Arizona, Tucson, Arizona, USA
| | - Nathan J Cherrington
- Department of Pharmacology & Toxicology, College of Pharmacy, The University of Arizona, Tucson, Arizona, USA
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Gao J, Zhou C, Zhong Y, Shi L, Luo X, Su H, Li M, Xu Y, Zhang N, Zhou H. Dipyridamole interacts with the N-terminal domain of HSP90 and antagonizes the function of the chaperone in multiple cancer cell lines. Biochem Pharmacol 2023; 207:115376. [PMID: 36513142 DOI: 10.1016/j.bcp.2022.115376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 12/06/2022] [Accepted: 12/06/2022] [Indexed: 12/14/2022]
Abstract
Molecular chaperone HSP90 has been considered as a promising target for anti-cancer drug development for years. However, due to the heat shock response induced by the ATP competitive inhibitors against HSP90, the therapeutic efficacies of the compounds are compromised, which consequently restricts the clinical use of HSP90-targeted inhibitors. Therefore, there is a need to discover novel HSP90-targeted modulators which exhibit acceptable inhibition activity against the chaperone and do not induce significant heat shock response in the meantime. Here in this study, we firstly developed a tip-based affinity selection-mass spectrometry platform with optimized experimental conditions/parameters for HSP90-targeted active compound screening, and then applied it to fish out inhibitors against HSP90 from a collection of 2,395 compounds composed of FDA-approved drugs and drug candidates. Dipyridamole, which acts as an anti-thrombotic agent by modulating multiple targets and has a long history of safe use, was identified to interact with HSP90's N-terminal domain. The following conducted biophysical and biochemical experiments demonstrated that Dipyridamole could bind to HSP90's ATP binding pocket and function as an ATP competitive inhibitor of the chaperone. Finally, cellular-based assays including CESTA, cell viability assessment and proteomic analysis etc. were performed to evaluate whether the interaction between HSP90 and Dipyridamole contributes to the anti-tumor effects of the compound. We then found that Dipyridamole inhibits the growth and proliferation of human cancer cells by downregulating cell cycle regulators and upregulating apoptotic cell signaling, which are potentially mediated by the binding of Dipyridamole to HSP90 and to PDEs (phosphodiesterases), respectively.
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Affiliation(s)
- Jing Gao
- Analytical Research Center for Organic and Biological Molecules, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Shanghai 201203, China; State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Shanghai 201203, China
| | - Chen Zhou
- Analytical Research Center for Organic and Biological Molecules, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Shanghai 201203, China
| | - Yan Zhong
- Analytical Research Center for Organic and Biological Molecules, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Shanghai 201203, China; University of the Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, China
| | - Li Shi
- Analytical Research Center for Organic and Biological Molecules, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Shanghai 201203, China
| | - Xuanyang Luo
- Analytical Research Center for Organic and Biological Molecules, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Shanghai 201203, China; State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Shanghai 201203, China; University of the Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, China
| | - Haixia Su
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Shanghai 201203, China; University of the Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, China
| | - Minjun Li
- Shanghai Synchrotron Radiation Facility, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, China
| | - Yechun Xu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Shanghai 201203, China; University of the Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, China
| | - Naixia Zhang
- Analytical Research Center for Organic and Biological Molecules, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Shanghai 201203, China; University of the Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, China.
| | - Hu Zhou
- Analytical Research Center for Organic and Biological Molecules, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Shanghai 201203, China; State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Shanghai 201203, China; University of the Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, China.
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Abstract
Nucleosides play central roles in all facets of life, from metabolism to cellular signaling. Because of their physiochemical properties, nucleosides are lipid bilayer impermeable and thus rely on dedicated transport systems to cross biological membranes. In humans, two unrelated protein families mediate nucleoside membrane transport: the concentrative and equilibrative nucleoside transporter families. The objective of this review is to provide a broad outlook on the current status of nucleoside transport research. We will discuss the role played by nucleoside transporters in human health and disease, with emphasis placed on recent structural advancements that have revealed detailed molecular principles of these important cellular transport systems and exploitable pharmacological features.
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Affiliation(s)
- Nicholas J. Wright
- Department of Biochemistry, Duke University Medical Center, 303 Research Drive, Durham, North Carolina, 27710, USA
| | - Seok-Yong Lee
- Department of Biochemistry, Duke University Medical Center, 303 Research Drive, Durham, North Carolina, 27710, USA
- Correspondence and requests for materials should be addressed to: S.-Y. Lee., , tel: 919-684-1005, fax: 919-684-8885
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IMPROvER: the Integral Membrane Protein Stability Selector. Sci Rep 2020; 10:15165. [PMID: 32938971 PMCID: PMC7495477 DOI: 10.1038/s41598-020-71744-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2019] [Accepted: 08/04/2020] [Indexed: 01/20/2023] Open
Abstract
Identifying stabilising variants of membrane protein targets is often required for structure determination. Our new computational pipeline, the Integral Membrane Protein Stability Selector (IMPROvER) provides a rational approach to variant selection by employing three independent approaches: deep-sequence, model-based and data-driven. In silico tests using known stability data, and in vitro tests using three membrane protein targets with 7, 11 and 16 transmembrane helices provided measures of success. In vitro, individual approaches alone all identified stabilising variants at a rate better than expected by random selection. Low numbers of overlapping predictions between approaches meant a greater success rate was achieved (fourfold better than random) when approaches were combined and selections restricted to the highest ranked sites. The mix of information IMPROvER uses can be extracted for any helical membrane protein. We have developed the first general-purpose tool for selecting stabilising variants of \documentclass[12pt]{minimal}
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\begin{document}$$\upalpha$$\end{document}α-helical membrane proteins, increasing efficiency and reducing workload. IMPROvER can be accessed at http://improver.ddns.net/IMPROvER/.
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Rehan S, Shahid S, Salminen TA, Jaakola VP, Paavilainen VO. Current Progress on Equilibrative Nucleoside Transporter Function and Inhibitor Design. SLAS DISCOVERY 2019; 24:953-968. [PMID: 31503511 DOI: 10.1177/2472555219870123] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Physiological nucleosides are used for the synthesis of DNA, RNA, and ATP in the cell and serve as universal mammalian signaling molecules that regulate physiological processes such as vasodilation and platelet aggregation by engaging with cell surface receptors. The same pathways that allow uptake of physiological nucleosides mediate the cellular import of synthetic nucleoside analogs used against cancer, HIV, and other viral diseases. Physiological nucleosides and nucleoside drugs are imported by two families of nucleoside transporters: the SLC28 concentrative nucleoside transporters (CNTs) and SLC29 equilibrative nucleoside transporters (ENTs). The four human ENT paralogs are expressed in distinct tissues, localize to different subcellular sites, and transport a variety of different molecules. Here we provide an overview of the known structure-function relationships of the ENT family with a focus on ligand binding and transport in the context of a new hENT1 homology model. We provide a generic residue numbering system for the different ENTs to facilitate the interpretation of mutational data produced using different ENT homologs. The discovery of paralog-selective small-molecule modulators is highly relevant for the design of new therapies and for uncovering the functions of poorly characterized ENT family members. Here, we discuss recent developments in the discovery of new paralog-selective small-molecule ENT inhibitors, including new natural product-inspired compounds. Recent progress in the ability to heterologously produce functional ENTs will allow us to gain insight into the structure and functions of different ENT family members as well as the rational discovery of highly selective inhibitors.
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Affiliation(s)
- Shahid Rehan
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland.,HiLIFE, University of Helsinki, Helsinki, Finland
| | - Saman Shahid
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - Tiina A Salminen
- Structural Bioinformatics Laboratory, Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - Veli-Pekka Jaakola
- Chemical Biology & Therapeutics, Novartis Institutes for BioMedical Research, Novartis Pharma AG, Basel, Switzerland
| | - Ville O Paavilainen
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland.,HiLIFE, University of Helsinki, Helsinki, Finland
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Structures of human ENT1 in complex with adenosine reuptake inhibitors. Nat Struct Mol Biol 2019; 26:599-606. [PMID: 31235912 PMCID: PMC6705415 DOI: 10.1038/s41594-019-0245-7] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Accepted: 05/08/2019] [Indexed: 02/06/2023]
Abstract
The human Equilibrative Nucleoside Transporter 1 (hENT1), a member of the SLC29 family, plays crucial roles in adenosine signaling, cellular uptake of nucleoside for DNA and RNA synthesis, and nucleoside-derived anticancer and antiviral drug transport in human. Because of its central role in adenosine signaling, it is the target of adenosine reuptake inhibitors (AdoRI), several of which are clinically used. Despite its importance in human physiology and pharmacology, the molecular basis of hENT1-mediated adenosine transport and its inhibition by AdoRIs are limited due to the absence of structural information on hENT1. Here we present crystal structures of hENT1 in complex with two chemically distinct AdoRIs: dilazep and S-(4-Nitrobenzyl)-6-thioinosine (NBMPR). Combined with mutagenesis study, our structural analyses elucidate two distinct inhibitory mechanisms exhibited on hENT1, while giving insight into adenosine recognition and transport. Our studies provide the platform for improved pharmacological intervention of adenosine and nucleoside analog drug transport by hENT1.
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Role of cysteine 416 in N-ethylmaleimide sensitivity of human equilibrative nucleoside transporter 1 (hENT1). Biochem J 2018; 475:3293-3309. [PMID: 30254099 DOI: 10.1042/bcj20180543] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 09/19/2018] [Accepted: 09/25/2018] [Indexed: 12/23/2022]
Abstract
Human equilibrative nucleoside transporter 1 (hENT1), the first identified member of the ENT family of integral membrane proteins, is the primary mechanism for cellular uptake of physiologic nucleosides and many antineoplastic and antiviral nucleoside drugs. hENT1, which is potently inhibited by nitrobenzylthioinosine (NBMPR), possesses 11 transmembrane helical domains with an intracellular N-terminus and an extracellular C-terminus. As a protein with 10 endogenous cysteine residues, it is sensitive to inhibition by the membrane permeable sulfhydryl-reactive reagent N-ethylmaleimide (NEM) but is unaffected by the membrane impermeable sulfhydryl-reactive reagent p-chloromercuriphenyl sulfonate. To identify the residue(s) involved in NEM inhibition, we created a cysteine-less version of hENT1 (hENT1C-), with all 10 endogenous cysteine residues mutated to serine, and showed that it displays wild-type uridine transport and NBMPR-binding characteristics when produced in the Xenopus oocyte heterologous expression system, indicating that endogenous cysteine residues are not essential for hENT1 function. We then tested NEM sensitivity of recombinant wild-type hENT1, hENT1 mutants C1S to C10S (single cysteine residues replaced by serine), hENT1C- (all cysteine residues replaced by serine), and hENT1C- mutants S1C to S10C (single serine residues converted back to cysteine). Mutants C9S (C416S/hENT1) and S9C (S416C/hENT1C-) were insensitive and sensitive, respectively, to inhibition by NEM, identifying Cys416 as the endofacial cysteine residue in hENT1 responsible for NEM inhibition. Kinetic experiments suggested that NEM modification of Cys416, which is located at the inner extremity of TM10, results in the inhibition of hENT1 uridine transport and NBMPR binding by constraining the protein in its inward-facing conformation.
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Boswell-Casteel RC, Hays FA. Equilibrative nucleoside transporters-A review. NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2016; 36:7-30. [PMID: 27759477 DOI: 10.1080/15257770.2016.1210805] [Citation(s) in RCA: 125] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Equilibrative nucleoside transporters (ENTs) are polytopic integral membrane proteins that mediate the transport of nucleosides, nucleobases, and therapeutic analogs. The best-characterized ENTs are the human transporters hENT1 and hENT2. However, non-mammalian eukaryotic ENTs have also been studied (e.g., yeast, parasitic protozoa). ENTs are major pharmaceutical targets responsible for modulating the efficacy of more than 30 approved drugs. However, the molecular mechanisms and chemical determinants of ENT-mediated substrate recognition, binding, inhibition, and transport are poorly understood. This review highlights findings on the characterization of ENTs by surveying studies on genetics, permeant and inhibitor interactions, mutagenesis, and structural models of ENT function.
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Affiliation(s)
- Rebba C Boswell-Casteel
- a Department of Biochemistry and Molecular Biology , University of Oklahoma Health Sciences Center , Oklahoma City , OK , USA
| | - Franklin A Hays
- a Department of Biochemistry and Molecular Biology , University of Oklahoma Health Sciences Center , Oklahoma City , OK , USA.,b Stephenson Cancer Center , University of Oklahoma Health Sciences Center , Oklahoma City , OK , USA.,c Harold Hamm Diabetes Center , University of Oklahoma Health Sciences Center , Oklahoma City , OK , USA
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10
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Damaraju VL, Weber D, Kuzma M, Cass CE, Sawyer MB. Selective Inhibition of Human Equilibrative and Concentrative Nucleoside Transporters by BCR-ABL Kinase Inhibitors: IDENTIFICATION OF KEY hENT1 AMINO ACID RESIDUES FOR INTERACTION WITH BCR-ABL KINASE INHIBITORS. J Biol Chem 2016; 291:18809-17. [PMID: 27432881 DOI: 10.1074/jbc.m116.741074] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Indexed: 01/10/2023] Open
Abstract
Human nucleoside transporters (hNTs) mediate cellular influx of anticancer nucleoside drugs, including cytarabine, cladribine, and fludarabine. BCR-ABL tyrosine kinase inhibitors (TKIs) imatinib and dasatinib inhibit fludarabine and cytarabine uptake. We assessed interactions of bosutinib, dasatinib, imatinib, nilotinib, and ponatinib with recombinant hNTs (hENT1, 2; hCNT1, -2, and -3) produced individually in yeast Saccharomyces cerevisiae Nilotinib inhibited hENT1-mediated uridine transport most potently (IC50 value, 0.7 μm) followed by ponatinib > bosutinib > dasatinib > imatinib. Imatinib inhibited hCNT2 with an IC50 value of 2.3 μm Ponatinib inhibited all five hNTs with the greatest effect seen for hENT1 (IC50 value, 9 μm). TKIs inhibited [(3)H]uridine uptake in a competitive manner. Studies in yeast with mutants at two amino acid residues of hENT1 (L442I, L442T, M33A, M33A/L442I) previously shown to be involved in uridine and dipyridamole binding, suggested that BCR-ABL TKIs interacted with Met(33) (TM1) and Leu(442) (TM11) residues of hENT1. In cultured human CEM lymphoblastoid cells, which possess a single hNT type (hENT1), accumulation of [(3)H]cytarabine, [(3)H]cladribine, or [(3)H]fludarabine was reduced by each of the five TKIs, and also caused a reduction in cell surface expression of hENT1 protein. In conclusion, BCR-ABL TKIs variously inhibit five different hNTs, cause a decrease in cell surface hENT1 expression, and decrease uridine accumulation when presented together with uridine or when given before uridine. In experiments with mutant hENT1, we showed for the first time interaction of Met(33) (involved in dipyridamole binding) with BCR-ABL inhibitors and reduced interaction with M33A mutant hENT1.
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Affiliation(s)
- Vijaya L Damaraju
- From the Department of Oncology, University of Alberta and Cross Cancer Institute, Edmonton, Alberta T6G 1Z2, Canada
| | - Dwayne Weber
- From the Department of Oncology, University of Alberta and Cross Cancer Institute, Edmonton, Alberta T6G 1Z2, Canada
| | - Michelle Kuzma
- From the Department of Oncology, University of Alberta and Cross Cancer Institute, Edmonton, Alberta T6G 1Z2, Canada
| | - Carol E Cass
- From the Department of Oncology, University of Alberta and Cross Cancer Institute, Edmonton, Alberta T6G 1Z2, Canada
| | - Michael B Sawyer
- From the Department of Oncology, University of Alberta and Cross Cancer Institute, Edmonton, Alberta T6G 1Z2, Canada
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Cappato S, Tonachini L, Giacopelli F, Tirone M, Galietta LJV, Sormani M, Giovenzana A, Spinelli AE, Canciani B, Brunelli S, Ravazzolo R, Bocciardi R. High-throughput screening for modulators of ACVR1 transcription: discovery of potential therapeutics for fibrodysplasia ossificans progressiva. Dis Model Mech 2016; 9:685-96. [PMID: 27125279 PMCID: PMC4920148 DOI: 10.1242/dmm.023929] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 04/22/2016] [Indexed: 01/10/2023] Open
Abstract
The ACVR1 gene encodes a type I receptor of bone morphogenetic proteins (BMPs). Activating mutations in ACVR1 are responsible for fibrodysplasia ossificans progressiva (FOP), a rare disease characterized by congenital toe malformation and progressive heterotopic endochondral ossification leading to severe and cumulative disability. Until now, no therapy has been available to prevent soft-tissue swelling (flare-ups) that trigger the ossification process. With the aim of finding a new therapeutic strategy for FOP, we developed a high-throughput screening (HTS) assay to identify inhibitors of ACVR1 gene expression among drugs already approved for the therapy of other diseases. The screening, based on an ACVR1 promoter assay, was followed by an in vitro and in vivo test to validate and characterize candidate molecules. Among compounds that modulate the ACVR1 promoter activity, we selected the one showing the highest inhibitory effect, dipyridamole, a drug that is currently used as a platelet anti-aggregant. The inhibitory effect was detectable on ACVR1 gene expression, on the whole Smad-dependent BMP signaling pathway, and on chondrogenic and osteogenic differentiation processes by in vitro cellular assays. Moreover, dipyridamole reduced the process of heterotopic bone formation in vivo. Our drug repositioning strategy has led to the identification of dipyridamole as a possible therapeutic tool for the treatment of FOP. Furthermore, our study has also defined a pipeline of assays that will be useful for the evaluation of other pharmacological inhibitors of heterotopic ossification. Summary: We describe the identification of dipyridamole as a potential therapeutic tool for FOP, through a series of in vitro and in vivo assays to screen and validate FDA-approved compounds.
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Affiliation(s)
- Serena Cappato
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health and CEBR, Università degli Studi di Genova, Genova 16132, Italy
| | - Laura Tonachini
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health and CEBR, Università degli Studi di Genova, Genova 16132, Italy
| | - Francesca Giacopelli
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health and CEBR, Università degli Studi di Genova, Genova 16132, Italy
| | - Mario Tirone
- Division of Immunology, Transplantation and Infectious Diseases, San Raffaele Scientific Institute, Milano 20132, Italy School of Medicine and Surgery, University of Milano-Bicocca, Monza 20900, Italy
| | - Luis J V Galietta
- Medical Genetics Unit, IRCCS Istituto Giannina Gaslini, Genova 16147, Italy
| | - Martina Sormani
- School of Medicine and Surgery, University of Milano-Bicocca, Monza 20900, Italy
| | - Anna Giovenzana
- School of Medicine and Surgery, University of Milano-Bicocca, Monza 20900, Italy
| | - Antonello E Spinelli
- Medical Physics Department and Centre for Experimental Imaging, San Raffaele Scientific Institute, Milano 20132, Italy
| | - Barbara Canciani
- Dipartimento di Medicina Sperimentale, Università di Genova & IRCCS AOU San Martino-IST, Istituto Nazionale per la Ricerca sul Cancro, 16132 Genova, Italy
| | - Silvia Brunelli
- School of Medicine and Surgery, University of Milano-Bicocca, Monza 20900, Italy
| | - Roberto Ravazzolo
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health and CEBR, Università degli Studi di Genova, Genova 16132, Italy Medical Genetics Unit, IRCCS Istituto Giannina Gaslini, Genova 16147, Italy
| | - Renata Bocciardi
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health and CEBR, Università degli Studi di Genova, Genova 16132, Italy Medical Genetics Unit, IRCCS Istituto Giannina Gaslini, Genova 16147, Italy
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12
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Valdés R, Shinde U, Landfear SM. Cysteine cross-linking defines the extracellular gate for the Leishmania donovani nucleoside transporter 1.1 (LdNT1.1). J Biol Chem 2012; 287:44036-45. [PMID: 23150661 DOI: 10.1074/jbc.m112.414433] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Equilibrative nucleoside transporters are a unique family of proteins that enable uptake of nucleosides/nucleobases into a wide range of eukaryotes and internalize a myriad of drugs used in the treatment of cancer, heart disease, AIDs, and parasitic infections. In previous work we generated a structural model for such a transporter, the LdNT1.1 nucleoside permease from the parasitic protozoan Leishmania donovani, using ab initio computation. The model suggested that aromatic residues present in transmembrane helices 1, 2, and 7 interact to form an extracellular gate that closes the permeation pathway in the inward-open conformation. Mutation of residues Phe-48(TM1) and Trp-75(TM2) abrogated transport activity, consistent with such prediction. In this study cysteine mutagenesis and oxidative cross-linking were combined to analyze proximity relationships of helices 1, 2, and 7 in LdNT1.1. Disulfide bond formation between introduced paired cysteines at the interface of such helices (A61C(TM1)/F74C(TM2), A61C(TM1)/G350C(TM7), and F74C(TM2)/G350C(TM7)) was analyzed by transport measurement and gel mobility shifts upon oxidation with Cu (II)-(1,10-phenanthroline)(3). In all cases cross-linking inhibited transport. However, if LdNT1.1 ligands were included during cross-linking, inhibition of transport was reduced, suggesting that ligands moved the three gating helices apart. Moreover, all paired cysteine mutants exhibited a mobility shift upon oxidation, corroborating the formation of a disulfide bond. These data support the notion that helices 1, 2, and 7 constitute the extracellular gate of LdNT1.1, thus further validating the computational model and the previously demonstrated importance of F48(TM1) and Trp-75(TM2) in tethering together helices that are part of the gate.
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Affiliation(s)
- Raquel Valdés
- Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, Oregon 97239, USA
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13
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Park JS, Hammond JR. Cysteine Residues in the Transmembrane (TM) 9 to TM11 Region of the Human Equilibrative Nucleoside Transporter Subtype 1 Play an Important Role in Inhibitor Binding and Translocation Function. Mol Pharmacol 2012; 82:784-94. [DOI: 10.1124/mol.112.079616] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
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14
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Abstract
BACKGROUND Nucleoside/nucleobase transporters have been investigated since the 1960s. In particular, equilibrative nucleoside transporters were thought to be valuable drug targets, since they are involved in various kinds of viral and parasitic diseases as well as cancers. DISCUSSION In the postgenomic era multiple transporters, including different subtypes, have been cloned and characterized on the molecular level. In this article we summarize recent advances regarding structure, function and localization of nucleoside/nucleobase transporters as well as the pharmacological profile of selected drugs. CONCLUSION Knowledge of the different kinetic properties and structural features of nucleoside transporters can either be used for the rational design of therapeutics directly targeting the transporter itself or for the delivery of drugs using the transporter as a port of entry into the target cell. Equilibrative nucleoside transporters are of considerable pharmacological interest as drug targets for the development of drugs tailored to each patient's need for the treatment of cardiac disease, cancer and viral infections.
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15
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Cano-Soldado P, Pastor-Anglada M. Transporters that translocate nucleosides and structural similar drugs: structural requirements for substrate recognition. Med Res Rev 2011; 32:428-57. [DOI: 10.1002/med.20221] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Pedro Cano-Soldado
- Departament de Bioquímica i Biologia Molecular; Institut de Biomedicina de la Universitat de Barcelona (IBUB); Universitat de Barcelona and CIBER EHD; Barcelona Spain
| | - Marçal Pastor-Anglada
- Departament de Bioquímica i Biologia Molecular; Institut de Biomedicina de la Universitat de Barcelona (IBUB); Universitat de Barcelona and CIBER EHD; Barcelona Spain
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16
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Riegelhaupt PM, Frame IJ, Akabas MH. Transmembrane segment 11 appears to line the purine permeation pathway of the Plasmodium falciparum equilibrative nucleoside transporter 1 (PfENT1). J Biol Chem 2010; 285:17001-10. [PMID: 20335165 DOI: 10.1074/jbc.m110.115758] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Purine transport is essential for malaria parasites to grow because they lack the enzymes necessary for de novo purine biosynthesis. The Plasmodium falciparum Equilibrative Nucleoside Transporter 1 (PfENT1) is a member of the equilibrative nucleoside transporter (ENT) gene family. PfENT1 is a primary purine transport pathway across the P. falciparum plasma membrane because PfENT1 knock-out parasites are not viable at physiologic extracellular purine concentrations. Topology predictions and experimental data indicate that ENT family members have eleven transmembrane (TM) segments although their tertiary structure is unknown. In the current work, we showed that a naturally occurring polymorphism, F394L, in TM11 affects transport substrate K(m). We investigated the structure and function of the TM11 segment using the substituted cysteine accessibility method. We showed that mutation to Cys of two highly conserved glycine residues in a GXXXG motif significantly reduces PfENT1 protein expression levels. We speculate that the conserved TM11 GXXXG glycines may be critical for folding and/or assembly. Small, cysteine-specific methanethiosulfonate (MTS) reagents reacted with four TM11 Cys substitution mutants, L393C, I397C, T400C, and Y403C. Larger MTS reagents do not react with the more cytoplasmic positions. Hypoxanthine, a transported substrate, protected L393C, I397C, and T400C from covalent modification by the MTS reagents. Plotted on an alpha-helical wheel, Leu-393, Ile-397, and Thr-400 lie on one face of the helix in a 60 degrees arc suggesting that TM11 is largely alpha helical. We infer that they line a water-accessible surface, possibly the purine permeation pathway. These results advance our understanding of the ENT structure.
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Affiliation(s)
- Paul M Riegelhaupt
- Department of Physiology and Biophysics, Albert Einstein College of Medicine of Yeshiva University, Bronx, New York 10461, USA
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17
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Arendt CS, Ullman B. Role of transmembrane domain 4 in ligand permeation by Crithidia fasciculata equilibrative nucleoside transporter 2 (CfNT2). J Biol Chem 2009; 285:6024-35. [PMID: 20037157 DOI: 10.1074/jbc.m109.074351] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Equilibrative nucleoside transporters play essential roles in nutrient uptake, cardiovascular and renal function, and purine analog drug chemotherapies. Limited structural information is available for this family of transporters; however, residues in transmembrane domains 1, 2, 4, and 5 appear to be important for ligand and inhibitor binding. In order to identify regions of the transporter that are important for ligand specificity, a genetic selection for mutants of the inosine-guanosine-specific Crithidia fasciculata nucleoside transporter 2 (CfNT2) that had gained the ability to transport adenosine was carried out in the yeast Saccharomyces cerevisiae. Nearly all positive clones from the genetic selection carried mutations at lysine 155 in transmembrane domain 4, highlighting lysine 155 as a pivotal residue governing the ligand specificity of CfNT2. Mutation of lysine 155 to asparagine conferred affinity for adenosine on the mutant transporter at the expense of inosine and guanosine affinity due to weakened contacts to the purine ring of the ligand. Following systematic cysteine-scanning mutagenesis, thiol-specific modification of several positions within transmembrane domain 4 was found to interfere with inosine transport capability, indicating that this helix lines the water-filled ligand translocation channel. Additionally, the pattern of modification of transmembrane domain 4 suggested that it may deviate from helicity in the vicinity of residue 155. Position 155 was also protected from modification in the presence of ligand, suggesting that lysine 155 is in or near the ligand binding site. Transmembrane domain 4 and particularly lysine 155 appear to play key roles in ligand discrimination and translocation by CfNT2.
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Affiliation(s)
- Cassandra S Arendt
- School of Pharmacy, Pacific University Oregon, Hillsboro, Oregon 97123, USA.
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18
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Valdés R, Arastu-Kapur S, Landfear SM, Shinde U. An ab Initio structural model of a nucleoside permease predicts functionally important residues. J Biol Chem 2009; 284:19067-76. [PMID: 19429678 PMCID: PMC2707223 DOI: 10.1074/jbc.m109.017947] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2009] [Revised: 05/06/2009] [Indexed: 11/06/2022] Open
Abstract
Permeases belonging to the equilibrative nucleoside transporter family promote uptake of nucleosides and/or nucleobases into a wide range of eukaryotes and mediate the uptake of a variety of drugs used in the treatment of cancer, heart disease, AIDS, and parasitic infections. No experimental three-dimensional structure exists for any of these permeases, and they are not present in prokaryotes, the source of many membrane proteins used in crystal structure determination. To generate a structural model for such a transporter, the LdNT1.1 nucleoside permease from the parasitic protozoan Leishmania donovani was modeled using ab initio computation. Site-directed mutations that strongly impair transport or that alter substrate specificity map to the central pore of the ab initio model, whereas mutations that have less pronounced phenotypes map to peripheral positions. The model suggests that aromatic residues present in transmembrane helices 1, 2, and 7 may interact to form an extracellular gate that closes the permeation pathway in the inward oriented conformation. Mutation of two of these three residues abrogated transport activity, consistent with the prediction of the model. The ab initio model is similar to one derived previously using threading analysis, a distinct computational approach, supporting the overall accuracy of both models. However, significant differences in helix orientation and residue position between the two models are apparent, and the mutagenesis data suggest that the ab initio model represents an improvement regarding structural details over the threading model. The putative gating interaction may also help explain differences in substrate specificity between members of this family.
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Affiliation(s)
- Raquel Valdés
- From the Departments of Molecular Microbiology and Immunology and
| | - Shirin Arastu-Kapur
- Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, Oregon 97239
| | | | - Ujwal Shinde
- Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, Oregon 97239
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19
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Zimmerman EI, Huang M, Leisewitz AV, Wang Y, Yang J, Graves LM. Identification of a novel point mutation in ENT1 that confers resistance to Ara-C in human T cell leukemia CCRF-CEM cells. FEBS Lett 2008; 583:425-9. [PMID: 19116148 DOI: 10.1016/j.febslet.2008.12.041] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2008] [Revised: 12/16/2008] [Accepted: 12/17/2008] [Indexed: 11/18/2022]
Abstract
The genetic basis for the Ara-C resistance of CCRF-CEM Ara-C/8C leukemia cells was investigated. DNA sequencing revealed that these cells expressed an equilibrative nucleoside transporter 1 (ENT1) with a single missense mutation resulting in glycine to arginine replacement (G24R). To test the importance of this residue, additional G24 mutants were created and examined for [3H]-uridine and [3H]-Ara-C uptake. Both a G24E and G24A mutant showed reduced ENT1-dependent activity. An EGFP-tagged G24R ENT1 displayed plasma membrane localization even though it was unable to bind [3H]-NBMPR, an ENT1-specific inhibitor. These results define G24 as critical amino acid for ENT1 nucleoside uptake and suggest that mutations in TM1 may provide a mechanism for Ara-C resistance in CCRF-CEM Ara-C/8C cells.
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Affiliation(s)
- Eric I Zimmerman
- Department of Pharmacology, 4009 Genetic Medicine Bldg., 120 Mason Farm Rd. CB# 7365, University of North Carolina @ Chapel Hill, Chapel Hill, NC 27599-7365, United States
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20
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Young JD, Yao SYM, Sun L, Cass CE, Baldwin SA. Human equilibrative nucleoside transporter (ENT) family of nucleoside and nucleobase transporter proteins. Xenobiotica 2008; 38:995-1021. [PMID: 18668437 DOI: 10.1080/00498250801927427] [Citation(s) in RCA: 156] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
1. The human (h) SLC29 family of integral membrane proteins is represented by four members, designated equilibrative nucleoside transporters (ENTs) because of the properties of the first-characterized family member, hENT1. They belong to the widely distributed eukaryotic ENT family of equilibrative and concentrative nucleoside/nucleobase transporter proteins. 2. A predicted topology of eleven transmembrane helices has been experimentally confirmed for hENT1. The best-characterized members of the family, hENT1 and hENT2, possess similar broad permeant selectivities for purine and pyrimidine nucleosides, but hENT2 also efficiently transports nucleobases. hENT3 has a similar broad permeant selectivity for nucleosides and nucleobases and appears to function in intracellular membranes, including lysosomes. 3. hENT4 is uniquely selective for adenosine, and also transports a variety of organic cations. hENT3 and hENT4 are pH sensitive, and optimally active under acidic conditions. ENTs, including those in parasitic protozoa, function in nucleoside and nucleobase uptake for salvage pathways of nucleotide synthesis and, in humans, are also responsible for the cellular uptake of nucleoside analogues used in the treatment of cancers and viral diseases. 4. By regulating the concentration of adenosine available to cell surface receptors, mammalian ENTs additionally influence physiological processes ranging from cardiovascular activity to neurotransmission.
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Affiliation(s)
- J D Young
- Membrane Protein Research Group, Department of Physiology and Department of Oncology, University of Alberta, Edmonton, Alberta, Canada.
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21
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Mutation of Trp29 of human equilibrative nucleoside transporter 1 alters affinity for coronary vasodilator drugs and nucleoside selectivity. Biochem J 2008; 414:291-300. [PMID: 18462193 DOI: 10.1042/bj20080074] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
hENT1 (human equilibrative nucleoside transporter 1) is inhibited by nanomolar concentrations of various structurally distinct coronary vasodilator drugs, including dipyridamole, dilazep, draflazine, soluflazine and NBMPR (nitrobenzylmercaptopurine ribonucleoside). When a library of randomly mutated hENT1 cDNAs was screened using a yeast-based functional complementation assay for resistance to dilazep, a clone containing the W29G mutation was identified. Multiple sequence alignments revealed that this residue was highly conserved. Mutations at Trp29 were generated and tested for adenosine transport activity and inhibitor sensitivity. Trp29 mutations significantly reduced the apparent V(max) and/or increased the apparent K(m) values for adenosine transport. Trp29 mutations increased the IC50 values for hENT1 inhibition by dipyridamole, dilazep, NBMPR, soluflazine and draflazine. NBMPR and soluflazine displayed remarkably similar trends, with large aromatic substitutions at residue 29 resulting in the lowest IC50 values, suggesting that both drugs could interact via ring-stacking interactions with Trp29. The W29T mutant displayed a selective loss of pyrimidine nucleoside transport activity, which contrasts with the previously identified L442I mutant that displayed a selective loss of purine nucleoside transport. W29T, L442I and the double mutant W29T/L442I were characterized kinetically for nucleoside transport activity. A helical wheel projection of TM (transmembrane segment) 1 suggests that Trp29 is positioned close to Met33, implicated previously in nucleoside and inhibitor recognition, and that both residues line the permeant translocation pathway. The data also suggest that Trp29 forms part of, or lies close to, the binding sites for dipyridamole, dilazep, NBMPR, soluflazine and draflazine.
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22
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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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23
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Zhang J, Visser F, King KM, Baldwin SA, Young JD, Cass CE. The role of nucleoside transporters in cancer chemotherapy with nucleoside drugs. Cancer Metastasis Rev 2007; 26:85-110. [PMID: 17345146 DOI: 10.1007/s10555-007-9044-4] [Citation(s) in RCA: 178] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Nucleoside analogs are important components of treatment regimens for various malignancies. Nucleoside-specific membrane transporters mediate plasma membrane permeation of physiologic nucleosides and most nucleoside analogs, for which the initial event is cellular conversion of nucleosides to active agents. Understanding of the roles of nucleoside transporters in nucleoside drug toxicity and resistance will provide opportunities for potentiating anticancer efficacy and avoiding resistance. Because transportability is a possible determinant of toxicity and resistance of many nucleoside analogs, nucleoside transporter abundance might be a prognostic marker to assess drug resistance. Elucidation of the structural determinants of nucleoside analogs for interaction with transporter proteins as well as the structural features of transporter proteins required for permeant interaction and translocation will lead to "transportability guidelines" for the rational design and therapeutic application of nucleoside analogs as anticancer drugs. It should eventually be possible to develop clinical assays that predict sensitivity and/or resistance to nucleoside anti-cancer drugs and thus to identify those patient populations that will most likely benefit from optimal nucleoside analog treatments. This review discusses recent results from structure/function studies of human nucleoside transporters, the role of nucleoside transport processes in the cytotoxicity and resistance of several anticancer nucleoside analogs and strategies to improve the nucleoside transporter-related anticancer effects of nucleoside analogs.
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Affiliation(s)
- Jing Zhang
- Membrane Protein Research Group, University of Alberta, Edmonton, AB, Canada
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24
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Visser F, Sun L, Damaraju V, Tackaberry T, Peng Y, Robins MJ, Baldwin SA, Young JD, Cass CE. Residues 334 and 338 in transmembrane segment 8 of human equilibrative nucleoside transporter 1 are important determinants of inhibitor sensitivity, protein folding, and catalytic turnover. J Biol Chem 2007; 282:14148-57. [PMID: 17379602 DOI: 10.1074/jbc.m701735200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Equilibrative nucleoside transporters (ENTs) are important for the metabolic salvage of nucleosides and the cellular uptake of antineoplastic and antiviral nucleoside analogs. Human equilibrative nucleoside transporter 1 (hENT1) is inhibited by nanomolar concentrations of structurally diverse compounds, including dipyridamole, dilazep, nitrobenzylmercaptopurine ribonucleoside (NBMPR), draflazine, and soluflazine. Random mutagenesis and screening by functional complementation for inhibitor-resistant mutants in yeast revealed mutations at Phe-334 and Asn-338. Both residues are predicted to lie in transmembrane segment 8 (TM 8), which contains residues that are highly conserved in the ENT family. F334Y displayed increased V(max) values that were attributed to increased rates of catalytic turnover, and N338Q and N338C displayed altered membrane distributions that appeared to be because of protein folding defects. Mutations of Phe-334 or Asn-338 impaired interactions with dilazep and dipyridamole, whereas mutations of Asn-338 impaired interactions with draflazine and soluflazine. A helical wheel projection of TM 8 predicted that Phe-334 and Asn-338 lie in close proximity to other highly conserved and/or hydrophilic residues, suggesting that they form part of a structurally important region that influences interactions with inhibitors, protein folding, and rates of conformational change during the transport cycle.
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Affiliation(s)
- Frank Visser
- Membrane Protein Research Group, Departments of Oncology and Physiology, University of Alberta, Alberta, Canada
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25
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Zhang J, Smith KM, Tackaberry T, Sun X, Carpenter P, Slugoski MD, Robins MJ, Nielsen LPC, Nowak I, Baldwin SA, Young JD, Cass CE. Characterization of the transport mechanism and permeant binding profile of the uridine permease Fui1p of Saccharomyces cerevisiae. J Biol Chem 2006; 281:28210-21. [PMID: 16854981 DOI: 10.1074/jbc.m605129200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The uptake of Urd into the yeast Saccharomyces cerevisiae is mediated by Fui1p, a Urd-specific nucleoside transporter encoded by the FUI1 gene and a member of the yeast Fur permease family, which also includes the uracil, allantoin, and thiamine permeases. When Fui1p was produced in a double-permease knock-out strain (fur4Deltafui1Delta) of yeast, Urd uptake was stimulated at acidic pH and sensitive to the protonophore carbonyl cyanide m-chlorophenylhydrazone. Electrophysiological analysis of recombinant Fui1p produced in Xenopus oocytes demonstrated that Fui1p-mediated Urd uptake was dependent on proton cotransport with a 1:1 stoichiometry. Mutagenesis analysis of three charged amino acids (Glu(259), Lys(288), and Asp(474) in putative transmembrane segments 3, 4, and 7, respectively) revealed that only Lys(288) was required for maintaining high Urd transport efficiency. Analysis of binding energies between Fui1p and different Urd analogs indicated that Fuip1 interacted with C(3')-OH, C(2')-OH, C(5)-H, and N(3)-H of Urd. Fui1p-mediated transport of Urd was inhibited by analogs with modifications at C-5', but was not inhibited significantly by analogs with modifications at C-3', C-5, and N-3 or inversions of configuration at C-2' and C-3'. This characterization of Fui1p contributes to the emerging knowledge of the structure and function of the Fur family of permeases, including the Fui1p orthologs of pathogenic fungi.
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Affiliation(s)
- Jing Zhang
- Membrane Protein Research Group and the Department of Oncology, University of Alberta, Alberta T6H 1Z2, Canada
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26
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Zhang J, Sun X, Smith KM, Visser F, Carpenter P, Barron G, Peng Y, Robins MJ, Baldwin SA, Young JD, Cass CE. Studies of Nucleoside Transporters Using Novel Autofluorescent Nucleoside Probes. Biochemistry 2006; 45:1087-98. [PMID: 16430205 DOI: 10.1021/bi0520535] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
To better understand nucleoside transport processes and intracellular fates of nucleosides, we have developed a pair of fluorescent nucleoside analogues, FuPmR and dFuPmR, that differ only in the sugar moiety (ribofuranosyl versus 2'-deoxy, respectively), for real-time analysis of nucleoside transport into living cells by confocal microscopy. The binding and transportability of the two compounds were assessed for five recombinant human nucleoside transporters (hENT1/2, hCNT1/2/3) produced in Saccharomyces cerevisiae and/or oocytes of Xenopus laevis. The ribosyl derivative (FuPmR) was used to demonstrate proof of principle in live cell imaging studies in 11 cultured human cancer cell lines with different hENT1 activities. The autofluorescence emitted from FuPmR enabled direct visualization of its movement from the extracellular medium into the intracellular compartment of live cells, and this process was blocked by inhibitors of hENT1 (nitrobenzylmercaptopurine ribonucleoside, dipyridamole, and dilazep). Quantitative analysis of fluorescence signals revealed two stages of FuPmR uptake: a fast first stage that represented the initial uptake rate (i.e., transport rate) followed by a slow long-lasting second stage. The accumulation of FuPmR and/or its metabolites in nuclei and mitochondria was also visualized by live cell imaging. Measurements of fluorescence intensity increases in nuclei and mitochondria revealed rate-limited processes of permeant translocation across intracellular membranes, demonstrating for the first time the intracellular distribution of nucleosides and/or nucleoside metabolites in living cells. The use of autofluorescent nucleosides in time-lapse confocal microscopy is a novel strategy to quantitatively study membrane transport of nucleosides and their metabolites that will provide new knowledge of nucleoside biology.
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Affiliation(s)
- Jing Zhang
- Membrane Protein Research Group, Department of Oncology, University of Alberta, and Cross Cancer Institute, Edmonton, Alberta T6G 1Z2, Canada
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Kim SR, Saito Y, Maekawa K, Sugiyama E, Kaniwa N, Ueno H, Okusaka T, Morizane C, Yamamoto N, Ikeda M, Yoshida T, Minami H, Furuse J, Ishii H, Saijo N, Kamatani N, Ozawa S, Sawada JI. Thirty Novel Genetic Variations in the SLC29A1 Gene Encoding Human Equilibrative Nucleoside Transporter 1 (hENT1). Drug Metab Pharmacokinet 2006; 21:248-56. [PMID: 16858130 DOI: 10.2133/dmpk.21.248] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Thirty-nine genetic variations, including thirty novel ones, were found in the human SLC29A1 gene, which encodes equilibrative nucleoside transporter 1, from 256 Japanese cancer patients administered gemcitabine. The found novel variations included -8,166G>A, -81,10A>G, -7,947G>A, -7,789T>C, -5,595G>A, -3,803_-3,783delTCGGGGAGGTGGCAGTGGGCG, -3,548G>C, -3,414G>A, -1355T>C, -34C>G, IVS1+141G>A, IVS1+260C>T, IVS1-82C>T, 177C>G, IVS3-6C>T, 564C>T, IVS8+44T>C, IVS8+90T>C, IVS8+97T>C, IVS8+131C>T, IVS8+169G>A, 933T>C, 954C>T, IVS11-52G>C, IVS11-46G>A, 1,288G>A, 1,641C>G, 1,703_1,704delGT, 1812C>T, and 1861C>T. The frequencies were 0.051 for IVS8+169G>A, 0.012 for -7,947G>A, 0.006 for IVS1+141G>A and 1,703_1,704delGT, 0.004 for -8,166G>A, -8,110A>G, -3,548G>C, -1,355T>C, -34C>G, IVS8+44T>C, and 1,812C>T, and 0.002 for the other 19 variations. Among them, 177C>G and 1,288G>A resulted in amino acid substitutions Asp59Glu and Ala430Thr, respectively. Using the detected polymorphisms, linkage disequilibrium analysis was performed, and 28 haplotypes were identified or inferred. Our findings would provide fundamental and useful information for genotyping SLC29A1 in the Japanese and probably other Asian populations.
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Affiliation(s)
- Su-Ryang Kim
- Project Team for Pharmacogenetics, National Institute of Health Sciences, Tokyo 158-8501, Japan.
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28
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Hirose N, Makita N, Yamaya T, Sakakibara H. Functional characterization and expression analysis of a gene, OsENT2, encoding an equilibrative nucleoside transporter in rice suggest a function in cytokinin transport. PLANT PHYSIOLOGY 2005; 138:196-206. [PMID: 15849298 PMCID: PMC1104175 DOI: 10.1104/pp.105.060137] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2005] [Revised: 02/28/2005] [Accepted: 03/04/2005] [Indexed: 05/18/2023]
Abstract
We identified four genes for potential equilibrative nucleoside transporters (ENTs) from rice (Oryza sativa; designated OsENT1 through OsENT4). Growth analysis of budding yeast (Saccharomyces cerevisiae) cells expressing OsENTs showed that OsENT2 transported adenosine and uridine with high affinity (adenosine, K(m) = 3.0 microm; uridine, K(m) = 0.7 microm). Purine or pyrimidine nucleosides and 2'-deoxynucleosides strongly inhibited adenosine transport via OsENT2, suggesting that OsENT2 possesses broad substrate specificity. OsENT2-mediated adenosine transport was resistant to the typical inhibitors of mammalian ENTs, nitrobenzylmercaptopurine ribonucleoside, dilazep, and dipyridamole. The transport activity was maximal at pH 5.0 and decreased slightly at lower as well as higher pH. In competition experiments with various cytokinins, adenosine transport by OsENT2 was inhibited by isopentenyladenine riboside (iPR). Direct measurements with radiolabeled cytokinins demonstrated that OsENT2 mediated uptake of iPR (K(m) = 32 microm) and trans-zeatin riboside (K(m) = 660 microm), suggesting that OsENT2 participates in iPR transport in planta. In mature plants, OsENT2 was predominantly expressed in roots. The OsENT2 promoter drove the expression of the beta-glucuronidase reporter gene in the scutellum during germination and in vascular tissues in germinated plants, suggesting a participation of OsENT2 in the retrieval of endosperm-derived nucleosides by the germinating embryo and in the long-distance transport of nucleosides in growing plants, respectively.
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Affiliation(s)
- Naoya Hirose
- RIKEN (The Institute of Physical and Chemical Research) Plant Science Center, Tsurumi-ku, Yokohama 230-0045, Japan
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