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Marçal Pastor-anglada - One of the best experts on this subject based on the ideXlab platform.
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Functional analysis of the human concentrative Nucleoside Transporter-1 variant hCNT1S546P provides insight into the sodium-binding pocket
American journal of physiology. Cell physiology, 2011Co-Authors: Pedro Cano-soldado, Ekaitz Errasti-murugarren, Edurne Gorraitz, F. Javier Casado, M. Pilar Lostao, Marçal Pastor-angladaAbstract:SLC28 genes, encoding concentrative Nucleoside Transporter proteins (CNT), show little genetic variability, although a few single nucleotide polymorphisms (SNPs) have been associated with marked fu...
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Expression and distribution of Nucleoside Transporter proteins in the human syncytiotrophoblast.
Molecular pharmacology, 2011Co-Authors: Ekaitz Errasti-murugarren, Paula Díaz, Valeria Godoy, Gloria Riquelme, Marçal Pastor-angladaAbstract:The plasma membrane distribution and related biological activity of Nucleoside Transporter proteins (NTs) were investigated in human syncytiotrophoblast from term placenta using a variety of approaches, including Nucleoside uptake measurements into vesicles from selected plasma membrane domains, NT immunohistochemistry, and subcellular localization (basal, heavy, and light apical membranes as well as raft-enriched membranes from the apical domain). In contrast with other epithelia, in this epithelium, we have identified the high-affinity pyrimidine-preferring human concentrative Nucleoside Transporter (hCNT) 1 as the only hCNT-type protein expressed at both the basal and apical membranes. hCNT1 localization in lipid rafts is also dependent on its subcellular localization in the apical plasma membrane, suggesting a complex cellular and regional expression. Overall, this result favors the view that the placenta is a pyrimidine-preferring Nucleoside sink from both maternal and fetal sides, and hCNT1 plays a major role in promoting pyrimidine salvage and placental growth. This finding may be of pharmacological relevance, because hCNT1 is known to interact with anticancer Nucleoside-derived drugs and other molecules, such as nicotine and caffeine, for which a great variety of harmful effects on placental and fetal development, including intrauterine growth retardation, have been reported.
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The human concentrative Nucleoside Transporter-3 C602R variant shows impaired sorting to lipid rafts and altered specificity for Nucleoside-derived drugs.
Molecular pharmacology, 2010Co-Authors: Ekaitz Errasti-murugarren, F. Javier Casado, Miriam Molina-arcas, Marçal Pastor-angladaAbstract:The human concentrative Nucleoside Transporter-3 C602R (hCNT3C602R), a recently identified human concentrative Nucleoside Transporter-3 (hCNT3) variant, has been shown to interact with natural Nucleosides with apparent Km values similar to those of the wild-type Transporter, although binding of one of the two sodium ions required for Nucleoside translocation is impaired, resulting in decreased Vmax values (Mol Pharmacol73:379–386, 2008). We have further analyzed the properties of this hCNT3 variant by determining its localization in plasma membrane lipid domains and its interaction with Nucleoside-derived drugs used in anticancer and antiviral therapies. When expressed heterologously in HeLa cells, wild-type hCNT3 localized to both lipid raft and nonlipid raft domains. Treatment of cells with the cholesterol-depleting agent methyl-β-cyclodextrin resulted in a marked decrease in hCNT3-related transport activity that was associated with the loss of wild-type hCNT3 from lipid rafts. It is noteworthy that although exogenously expressed hCNT3C602R was present in nonlipid raft domains at a level similar to that of the wild-type Transporter, the mutant Transporter was present at much lower amounts in lipid rafts. A substrate profile analysis showed that interactions with a variety of Nucleoside-derived drugs were altered in the hCNT3C602R variant and revealed that sugar hydroxyl residues are key structural determinants for substrate recognition by the hCNT3C602R variant.
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All-trans retinoic acid promotes trafficking of human concentrative Nucleoside Transporter-3 (hCNT3) to the plasma membrane by a TGF-β1-mediated mechanism
The Journal of biological chemistry, 2010Co-Authors: Paula Fernández-calotti, Marçal Pastor-angladaAbstract:Human concentrative Nucleoside Transporter-3 (hCNT3) is a sodium-coupled Nucleoside Transporter that exhibits high affinity and broad substrate selectivity, making it the most suitable candidate for mediating the uptake and cytotoxic action of most Nucleoside-derived drugs. The drug of this class most commonly used in the treatment of chronic lymphocytic leukemia (CLL) is the pro-apoptotic Nucleoside analog fludarabine (Flu), which enters CLL cells primarily through human equilibrative Nucleoside Transporters (hENTs). Although CLL cells lack hCNT3 activity, they do express this Transporter protein, which is located mostly in the cytosol. The aim of our study was to identify agents and mechanisms capable of promoting hCNT3 trafficking to the plasma membrane. Here, we report that all-trans-retinoic acid (ATRA), currently used in the treatment of acute promyelocytic leukemia (APL), increases hCNT3-related activity through a mechanism that involves trafficking of pre-existing hCNT3 proteins to the plasma membrane. This effect is mediated by the autocrine action of transforming growth factor (TGF)-beta1, which is transcriptionally activated by ATRA in a p38-dependent manner. TGF-beta1 acts through activation of ERK1/2 and the small GTPase RhoA to promote plasma membrane trafficking of the hCNT3 protein.
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SLC28 genes and concentrative Nucleoside Transporter (CNT) proteins.
Xenobiotica; the fate of foreign compounds in biological systems, 2008Co-Authors: Marçal Pastor-anglada, Pedro Cano-soldado, Ekaitz Errasti-murugarren, F J CasadoAbstract:The human concentrative Nucleoside Transporter (hCNT) protein family has three members, hCNT1, 2, and 3, encoded by SLC28A1, A2, and A3 genes, respectively. hCNT1 and hCNT2 translocate pyrimidine- and purine-Nucleosides, respectively, by a sodium-dependent mechanism, whereas hCNT3 shows broad substrate selectivity and the unique ability of translocating Nucleosides both in a sodium- and a proton-coupled manner. hCNT proteins are also responsible for the uptake of most Nucleoside-derived antiviral and anticancer drugs. Thus, hCNTs are key pharmacological targets. This review focuses on several crucial aspects of hCNT biology and pharmacology: protein structure-function, structural determinants for transportability, pharmacogenetics of hCNT-encoding genes, role of hCNT proteins in Nucleoside-based therapeutics, and finally hCNT physiology.
John K. Buolamwini - One of the best experts on this subject based on the ideXlab platform.
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A novel RNA variant of human concentrative Nucleoside Transporter 1 (hCNT1) that is a potential cancer biomarker.
Experimental hematology & oncology, 2019Co-Authors: Chunmei Wang, John K. BuolamwiniAbstract:The human concentrative Nucleoside Transporter 1 (hCNT1) a product of the SLC28A1 gene is one of the three concentrative Nucleoside Transporters, with a substrate specificity for physiological pyrimidine Nucleosides. It has recently been implicated in tumor suppression. We have unraveled a splice variant RNA transcript that is overexpressed in some tumor tissues and some cancer cells. This study established that observation. We examined several clones of hCNT1 generated from RT-PCR of total RNA from human kidney tissue purchased from Ambion. The resulting cDNA clones were then sequenced, and a variant that retained intron 4, and skipped some exons fully or partly, specifically exons 5 and 13 were completely missed and only part of exon 6 was spliced. Tissue expression analysis by PCR indicated a similar distribution of expression of RNA of the splice variant hCNT1-IR as that of the dominant variant hCNT1, particularly in the small intestine, kidney and liver. Further, analysis of various tumor samples with PCR primers designed from this novel hCNT1 splice variant (hCNT1-IR) revealed interestingly that it is overexpressed in some cancer tissues relative to normal tissues, particularly kidney, liver and pancreatic cancers. We have identified a novel intron retaining and exon skipping splice variant of the hCNT1 Nucleoside Transporter, and designated it hCNT1-IR, which has a similar tissue expression distribution as the normal hCNT1 variant, but unlike the normal transcript, hCNT1-IR is overexpressed in some cancers and may serve as a potential cancer biomarker.
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Synthesis and biological evaluation of phloridzin analogs as human concentrative Nucleoside Transporter 3 (hCNT3) inhibitors.
Bioorganic & medicinal chemistry letters, 2008Co-Authors: Amol Gupte, John K. BuolamwiniAbstract:Nucleoside Transporter inhibitors have potential therapeutic applications as anticancer, antiviral, cardioprotective and neuroprotective agents. Although quite a few potent inhibitors of the equilibrative Nucleoside Transporters are known, largely missing are the concentrative Nucleoside Transporter inhibitors. Phloridzin (3, K(i)=16.00 microM) is a known moderate inhibitor of the concentrative Nucleoside Transporters. We have synthesized and evaluated analogs of phloridzin at the hCNT3 Nucleoside Transporter. Within the series of synthesized analogs compound 16 (K(i)=2.88 microM), possessing a ribofuranose sugar unit instead of a glucopyranose as present in phloridzin, exhibited the highest binding affinity at the hCNT3 Transporter. Phloridzin and compound 16 have also been shown to be selective for the hCNT3 Transporter as compared with the hENT1 Transporter. Compound 16 can serve as a new lead which after further modifications could yield selective and potent hCNT3 inhibitors.
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CoMFA and CoMSIA 3D-QSAR studies on S6-(4-nitrobenzyl)mercaptopurine riboside (NBMPR) analogs as inhibitors of human equilibrative Nucleoside Transporter 1 (hENT1)
Bioorganic & medicinal chemistry letters, 2008Co-Authors: Amol Gupte, John K. BuolamwiniAbstract:Abstract 3D-QSAR (CoMFA and CoMSIA) studies were performed on human equlibrative Nucleoside Transporter (hENT1) inhibitors displaying Ki values ranging from 10,000 to 0.7 nM. Both CoMFA and CoMSIA analysis gave reliable models with q2 values >0.50 and r2 values >0.92. The models have been validated for their stability and robustness using group validation and bootstrapping techniques and for their predictive abilities using an external test set of nine compounds. The high predictive r2 values of the test set (0.72 for CoMFA model and 0.74 for CoMSIA model) reveals that the models can prove to be a useful tool for activity prediction of newly designed Nucleoside Transporter inhibitors. The CoMFA and CoMSIA contour maps identify features important for exhibiting good binding affinities at the Transporter, and can thus serve as a useful guide for the design of potential equilibrative Nucleoside Transporter inhibitors.
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Novel C2-Purine Position Analogs of Nitrobenzylmercaptopurine Riboside as Human Equilibrative Nucleoside Transporter 1 Inhibitors
Bioorganic & medicinal chemistry, 2007Co-Authors: Amol Gupte, John K. BuolamwiniAbstract:Abstract Nucleoside Transporter inhibitors have potential therapeutic applications as anticancer, antiviral, cardioprotective, and neuroprotective agents. S 6 -(4-nitrobenzyl)mercaptopurine riboside (NBMPR) is a prototype inhibitor of the human equilibrative Nucleoside Transporter (hENT1), and is a high affinity ligand with a K d of 0.1–1.0 nM. We have synthesized and flow cytometrically evaluated the binding affinity of a series of novel C 2 -purine position substituted analogs of NBMPR at the hENT1. The aim of this research was to understand the substituent requirements at the C 2 -purine position of NBMPR. Structure–activity relationships (SAR) indicate that increasing the steric bulk at the C 2 -purine position of NBMPR led to a decrease in binding affinity of these ligands at the hENT1. New high affinity inhibitors were identified, with the best compound, 2-fluoro-4-nitrobenzyl mercaptopurine riboside (7), exhibiting a K i of 2.1 nM. This information, when coupled with the information obtained from other structure–activity relationship studies should prove useful in efforts aimed at modeling the NMBPR and analogs pharmacophore of hENT1 inhibitors.
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Novel halogenated nitrobenzylthioinosine analogs as es Nucleoside Transporter inhibitors.
Bioorganic & medicinal chemistry letters, 2004Co-Authors: Amol Gupte, John K. BuolamwiniAbstract:Nucleoside Transporter inhibitors have potential therapeutic applications as anticancer, antiviral, cardioprotective, and neuroprotective agents. We have synthesized and flow cytometrically evaluated the binding affinity of a series of novel halogenated nitrobenzylthioinosine analogs at the human es Nucleoside Transporter. Structure-activity relationships indicate the importance of hydrophobicity and electron withdrawing capacity of substituents at the para-position of the 6-position benzyl substituent. All of the compounds showed high binding affinity as shown by their ability to displace the fluorescent es Transporter ligand, SAENTA-X8-fluorescein. Compound 16 (6-S-(para-iodobenzyl)-6-thioinosine) was the most tightly bound within the series with a K(i) of 3.88 nM (NBMPR exhibited a K(i) of 0.70 nM). This compound has higher affinity than the widely used nonNucleoside, Nucleoside transport inhibitor, dipyridamole (K(i) = 8.79 nM), and may serve as a new lead compound.
James D. Young - One of the best experts on this subject based on the ideXlab platform.
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The SLC28 (CNT) and SLC29 (ENT) Nucleoside Transporter families: a 30-year collaborative odyssey
Biochemical Society transactions, 2016Co-Authors: James D. YoungAbstract:Specialized Nucleoside Transporter (NT) proteins are required for passage of Nucleosides and hydrophilic Nucleoside analogues across biological membranes. Physiologic Nucleosides serve as central salvage metabolites in nucleotide biosynthesis, and Nucleoside analogues are used as chemotherapeutic agents in the treatment of cancer and antiviral diseases. The Nucleoside adenosine modulates numerous cellular events via purino-receptor cell signalling pathways. Human NTs are divided into two structurally unrelated protein families: the SLC28 concentrative Nucleoside Transporter (CNT) family and the SLC29 equilibrative Nucleoside Transporter (ENT) family. Human CNTs are inwardly directed Na + -dependent Nucleoside Transporters found predominantly in intestinal and renal epithelial and other specialized cell types. Human ENTs mediate bidirectional fluxes of purine and pyrimidine Nucleosides down their concentration gradients and are ubiquitously found in most, possibly all, cell types. Both protein families are evolutionarily old: CNTs are present in both eukaryotes and prokaryotes; ENTs are widely distributed in mammalian, lower vertebrate and other eukaryote species. This mini-review describes a 30-year collaboration with Professor Stephen Baldwin to identify and understand the structures and functions of these physiologically and clinically important transport proteins.
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Analysis of human equilibrative Nucleoside Transporter 1 (hENT1) protein in non-Hodgkin's lymphoma by immunohistochemistry
Modern pathology : an official journal of the United States and Canadian Academy of Pathology Inc, 2005Co-Authors: Laura Q M Chow, Carol E. Cass, James D. Young, Laith Dabbagh, Raymond Lai, Andrew Belch, John R MackeyAbstract:Analysis of human equilibrative Nucleoside Transporter 1 (hENT1) protein in non-Hodgkin's lymphoma by immunohistochemistry
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identification and functional characterization of variants in human concentrative Nucleoside Transporter 3 hcnt3 slc28a3 arising from single nucleotide polymorphisms in coding regions of the hcnt3 gene
Pharmacogenetics and Genomics, 2005Co-Authors: Sambasivarao Damaraju, Stephen A. Baldwin, Jing Zhang, Frank Visser, Tracey Tackaberry, Jennifer Dufour, Kyla M Smith, Melissa D Slugoski, Mabel W L Ritzel, James D. YoungAbstract:IntroductionHuman concentrative Nucleoside Transporter 3, hCNT3 (SLC28A3), which mediates transport of purine and pyrimidine Nucleosides and a variety of antiviral and anticancer Nucleoside drugs, was investigated to determine if there are single nucleotide polymorphisms in the coding regions of the
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the absence of human equilibrative Nucleoside Transporter 1 is associated with reduced survival in patients with gemcitabine treated pancreas adenocarcinoma
Clinical Cancer Research, 2004Co-Authors: Jennifer L Spratlin, Carol E. Cass, James D. Young, Randeep Sangha, Darryl D Glubrecht, Laith Dabbagh, Charles Dumontet, Raymond Lai, John R MackeyAbstract:Purpose: Gemcitabine monotherapy is the standard palliative chemotherapy for pancreatic adenocarcinoma. Gemcitabine requires plasma membrane Nucleoside Transporter proteins to efficiently enter cells and exert it cytotoxicity. In vitro studies have demonstrated that deficiency of human equilibrative Nucleoside Transporter 1 (hENT1), the most widely abundant and distributed Nucleoside Transporter in human cells, confers resistance to gemcitabine toxicity, but the distribution and abundance of Nucleoside Transporters in normal and malignant pancreatic tissue is unknown. Experimental Design: We studied tumor blocks from normal pancreas and 21 Alberta patients with gemcitabine-treated pancreatic cancer. Immunohistochemistry on the formalin-fixed, paraffin-embedded tissues was performed with specific hENT1 and human Concentrative Nucleoside Transporter 3 monoclonal antibodies and scored by a pathologist blinded to clinical outcomes. Results: hENT1 was detected in normal Langerhan cells and lymphocytes but not in normal glandular elements. Patients in whom all adenocarcinoma cells had detectable hENT1 had significantly longer median survivals from gemcitabine initiation than those for whom hENT1 was absent in a proportion (10 to 100%) of adenocarcinoma cells (median survival, 13 versus 4 months, P = 0.01). Immunohistochemistry for human Concentrative Nucleoside Transporter 3 revealed moderate to high-intensity staining in all adenocarcinoma tissue samples. Conclusions: Patients with pancreatic adenocarcinoma with uniformly detectable hENT1 immunostaining have a significantly longer survival after gemcitabine chemotherapy than tumors without detectable hENT1. Immunohistochemistry for hENT1 shows promise as a molecular predictive assay to appropriately select patients for palliative gemcitabine chemotherapy but requires formal validation in prospective, randomized trials.
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Immunocytochemical demonstration of the equilibrative Nucleoside Transporter rENT1 in rat sinoatrial node.
Journal of Histochemistry and Cytochemistry, 2002Co-Authors: Hanny Musa, Halina Dobrzynski, Z. Berry, Fatima Abidi, Carol E. Cass, James D. Young, Stephen A. BaldwinAbstract:Adenosine exerts multiple receptor-mediated effects in the heart, including a negative chronotropic effect on the sinoatrial node. The aim of this study was to investigate the distribution of the equilibrative Nucleoside Transporter rENT1 in rat sinoatrial node and atrial muscle. Immunocytochemistry and/or immunoblotting revealed abundant expression of this protein in plasma membranes of sinoatrial node and in atrial and ventricular cells. Because rENT1-mediated transport is likely to regulate the local concentrations of adenosine in the sinoatrial node and other parts of the heart, it represents a potential pharmacological target that might be exploited to ameliorate ischemic damage during heart surgery.
Myles H Akabas - One of the best experts on this subject based on the ideXlab platform.
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accessibility of substituted cysteines in tm2 and tm10 transmembrane segments in the plasmodium falciparum equilibrative Nucleoside Transporter pfent1
Journal of Biological Chemistry, 2019Co-Authors: Sita Nirupama Nishtala, Avish Arora, Jorge Reyes, Myles H AkabasAbstract:Infection with Plasmodium species parasites causes malaria. Plasmodium parasites are purine auxotrophic. They import purines via an equilibrative Nucleoside Transporter (ENT). In P. falciparum, the most virulent species, the equilibrative Nucleoside Transporter 1 (PfENT1) represents the primary purine uptake pathway. This Transporter is a potential target for the development of antimalarial drugs. In the absence of a high-resolution structure for either PfENT1 or a homologous ENT, we used the substituted cysteine accessibility method (SCAM) to investigate the membrane-spanning domain structure of PfENT1 to identify potential inhibitor-binding sites. We previously used SCAM to identify water-accessible residues that line the permeation pathway in transmembrane segment 11 (TM11). TM2 and TM10 lie adjacent to TM11 in an ab initio model of a homologous Leishmania donovani Nucleoside Transporter. To identify TM2 and TM10 residues in PfENT1 that are at least transiently on the water-accessible Transporter surface, we assayed the reactivity of single cysteine-substitution mutants with three methanethiosulfonate (MTS) derivatives. Cysteines substituted for 12 of 14 TM2 segment residues reacted with MTS-ethyl-ammonium-biotin (MTSEA-biotin). At eight positions, MTSEA-biotin inhibited transport, and at four positions substrate transport was potentiated. On an α helical wheel projection of TM2, the four positions where potentiation occurred were located in a cluster on one side of the helix. In contrast, although MTSEA-biotin inhibited 9 of 10 TM10 cysteine-substituted mutants, the reactive residues did not form a pattern consistent with either an α helix or β sheet. These results may help identify the binding site(s) of PfENT1 inhibitors.
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transmembrane segment 11 appears to line the purine permeation pathway of the plasmodium falciparum equilibrative Nucleoside Transporter 1 pfent1
Journal of Biological Chemistry, 2010Co-Authors: Paul M Riegelhaupt, I J Frame, Myles H AkabasAbstract: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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transmembrane segment 11 appears to line the purine permeation pathway of the plasmodium falciparum equilibrative Nucleoside Transporter 1 pfent1
Journal of Biological Chemistry, 2010Co-Authors: Paul M Riegelhaupt, I J Frame, Myles H AkabasAbstract: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 Km. 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 α-helical wheel, Leu-393, Ile-397, and Thr-400 lie on one face of the helix in a 60° arc suggesting that TM11 is largely α helical. We infer that they line a water-accessible surface, possibly the purine permeation pathway. These results advance our understanding of the ENT structure.
Amol Gupte - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and biological evaluation of phloridzin analogs as human concentrative Nucleoside Transporter 3 (hCNT3) inhibitors.
Bioorganic & medicinal chemistry letters, 2008Co-Authors: Amol Gupte, John K. BuolamwiniAbstract:Nucleoside Transporter inhibitors have potential therapeutic applications as anticancer, antiviral, cardioprotective and neuroprotective agents. Although quite a few potent inhibitors of the equilibrative Nucleoside Transporters are known, largely missing are the concentrative Nucleoside Transporter inhibitors. Phloridzin (3, K(i)=16.00 microM) is a known moderate inhibitor of the concentrative Nucleoside Transporters. We have synthesized and evaluated analogs of phloridzin at the hCNT3 Nucleoside Transporter. Within the series of synthesized analogs compound 16 (K(i)=2.88 microM), possessing a ribofuranose sugar unit instead of a glucopyranose as present in phloridzin, exhibited the highest binding affinity at the hCNT3 Transporter. Phloridzin and compound 16 have also been shown to be selective for the hCNT3 Transporter as compared with the hENT1 Transporter. Compound 16 can serve as a new lead which after further modifications could yield selective and potent hCNT3 inhibitors.
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CoMFA and CoMSIA 3D-QSAR studies on S6-(4-nitrobenzyl)mercaptopurine riboside (NBMPR) analogs as inhibitors of human equilibrative Nucleoside Transporter 1 (hENT1)
Bioorganic & medicinal chemistry letters, 2008Co-Authors: Amol Gupte, John K. BuolamwiniAbstract:Abstract 3D-QSAR (CoMFA and CoMSIA) studies were performed on human equlibrative Nucleoside Transporter (hENT1) inhibitors displaying Ki values ranging from 10,000 to 0.7 nM. Both CoMFA and CoMSIA analysis gave reliable models with q2 values >0.50 and r2 values >0.92. The models have been validated for their stability and robustness using group validation and bootstrapping techniques and for their predictive abilities using an external test set of nine compounds. The high predictive r2 values of the test set (0.72 for CoMFA model and 0.74 for CoMSIA model) reveals that the models can prove to be a useful tool for activity prediction of newly designed Nucleoside Transporter inhibitors. The CoMFA and CoMSIA contour maps identify features important for exhibiting good binding affinities at the Transporter, and can thus serve as a useful guide for the design of potential equilibrative Nucleoside Transporter inhibitors.
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Novel C2-Purine Position Analogs of Nitrobenzylmercaptopurine Riboside as Human Equilibrative Nucleoside Transporter 1 Inhibitors
Bioorganic & medicinal chemistry, 2007Co-Authors: Amol Gupte, John K. BuolamwiniAbstract:Abstract Nucleoside Transporter inhibitors have potential therapeutic applications as anticancer, antiviral, cardioprotective, and neuroprotective agents. S 6 -(4-nitrobenzyl)mercaptopurine riboside (NBMPR) is a prototype inhibitor of the human equilibrative Nucleoside Transporter (hENT1), and is a high affinity ligand with a K d of 0.1–1.0 nM. We have synthesized and flow cytometrically evaluated the binding affinity of a series of novel C 2 -purine position substituted analogs of NBMPR at the hENT1. The aim of this research was to understand the substituent requirements at the C 2 -purine position of NBMPR. Structure–activity relationships (SAR) indicate that increasing the steric bulk at the C 2 -purine position of NBMPR led to a decrease in binding affinity of these ligands at the hENT1. New high affinity inhibitors were identified, with the best compound, 2-fluoro-4-nitrobenzyl mercaptopurine riboside (7), exhibiting a K i of 2.1 nM. This information, when coupled with the information obtained from other structure–activity relationship studies should prove useful in efforts aimed at modeling the NMBPR and analogs pharmacophore of hENT1 inhibitors.
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Novel halogenated nitrobenzylthioinosine analogs as es Nucleoside Transporter inhibitors.
Bioorganic & medicinal chemistry letters, 2004Co-Authors: Amol Gupte, John K. BuolamwiniAbstract:Nucleoside Transporter inhibitors have potential therapeutic applications as anticancer, antiviral, cardioprotective, and neuroprotective agents. We have synthesized and flow cytometrically evaluated the binding affinity of a series of novel halogenated nitrobenzylthioinosine analogs at the human es Nucleoside Transporter. Structure-activity relationships indicate the importance of hydrophobicity and electron withdrawing capacity of substituents at the para-position of the 6-position benzyl substituent. All of the compounds showed high binding affinity as shown by their ability to displace the fluorescent es Transporter ligand, SAENTA-X8-fluorescein. Compound 16 (6-S-(para-iodobenzyl)-6-thioinosine) was the most tightly bound within the series with a K(i) of 3.88 nM (NBMPR exhibited a K(i) of 0.70 nM). This compound has higher affinity than the widely used nonNucleoside, Nucleoside transport inhibitor, dipyridamole (K(i) = 8.79 nM), and may serve as a new lead compound.
