Expression of the high-affinity purine nucleobase transporter in mutant mouse S49 cells does not require a functional wild-type nucleoside-nucleobase transporter.

Ullman, Buddy; Patrick, J; McCartan, K

doi:10.1128/mcb.7.1.97

Cited by 19 publications

(10 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…34) However, one study reported the involvement of ENT1 in hypoxanthine transport in a murine T-lymphoma cell line, S49, which was mostly inhibited by 10 nM of NBMPR. 35) 4.2. ENT2/SLC29A2 Human ENT2 (hENT2) was identified as a NBMPR-insensitive nucleoside transporter by Crawford et al 36) and Griffiths et al 37) The amino acid sequence of hENT2 is 46% identical to that of hENT1.…”

Section: Facilitative Transport Systemsmentioning

confidence: 99%

Molecular Basis of Nucleobase Transport Systems in Mammals

Inoue

2017

Biological & Pharmaceutical Bulletin

View full text Add to dashboard Cite

Nucleobases are water-soluble compounds that need specific transporters to cross biological membranes. Cumulative evidence based on studies using animal tissues and cells indicates that the carrier-mediated transport systems for purine and pyrimidine nucleobases can be classified into the following two types: concentrative transport systems that mediate nucleobase transport depending on the sodium ion concentration gradient; and other systems that mediate facilitated diffusion depending on the concentration gradient of the substrate. Recently, several molecular transporters that are involved in both transport systems have been identified. The function and activity of these transporters could be of pharmacological significance considering the roles that they play not only in nucleotide synthesis and metabolism but also in the pharmacokinetics and delivery of a variety of nucleobase analogues used in anticancer and antiviral drug therapy. The present review provides an overview of the recent advances in our understanding of the molecular basis of nucleobase transport systems, focusing on the transporters that mediate purine nucleobases, and discusses the involvement of intracellular metabolism in purine nucleobase transport and chemotherapy using ganciclovir.Key words purine nucleobase; transporter; salvage enzyme; equilibrative nucleoside transporter 1 (ENT1)/ solute carrier (SLC)29A1; ENT2/SLC29A2; equilibrative nucleobase transporter 1 (ENBT1)/ SLC43A3

show abstract

Section: Facilitative Transport Systemsmentioning

confidence: 99%

Molecular Basis of Nucleobase Transport Systems in Mammals

Inoue

2017

Biological & Pharmaceutical Bulletin

View full text Add to dashboard Cite

show abstract

“…15) In addition to the shared mechanisms of transport of nucleobases and nucleosides, it has been suggested that there are independent transport processes specific for nucleosides or nucleobases. 16,17) Equilibrative nucleobase transport has been observed in human erythrocytes, human T-lymphoblastoid cells, LLC-PK1 cells, rabbit cornea cells and S49 mouse-derived lymphoma cells, [18][19][20][21] whereas concentrative nucleobase transport occurs in kidney, intestine, placenta, and choroid plexus. 19,[22][23][24][25][26] However, little is yet known about the molecular basis of nucleobase transport in mammalian cells.…”

mentioning

confidence: 99%

Characterization of Nucleobase Transport by Mouse Sertoli Cell Line TM4

Kato

Maeda

Akaike

et al. 2009

Biological & Pharmaceutical Bulletin

View full text Add to dashboard Cite

In the spermatogenesis, many nucleosides and nucleobases are needed for the salvage nucleotide biosynthesis. One of the roles of Sertoli cells is to provide such nutrients to spermatogenic cells located within the bloodtestis barrier (BTB). We have already shown that nucleoside transporters are expressed and are functional in primary-cultured rat Sertoli cells and TM4 cells derived from mouse testis. Here, we examined the uptakes of purine ([ 3 H]guanine) and pyrimidine ([ 3 H]uracil) nucleobases using TM4 cells. Uptakes of both nucleobases were time-and concentration-dependent, and kinetic analysis indicated the involvement of high-affinity transport systems. Uptake of uracil was significantly reduced in the absence of Na ؉ , although guanine uptake was mainly mediated by a sodium-independent transport system in TM4 cells. Guanine uptake was inhibited by other purine nucleobases, but not by pyrimidine nucleobases. Only pyrimidine nucleobases reduced uracil uptake. In addition, mycophenolic acid, an inosine monophosphate dehydrogenase inhibitor, up-regulated guanine uptake. These results suggested that there are distinct transport systems for purine and pyrimidine nucleobases in cells of mouse Sertoli cell line TM4.

show abstract

“…The almost 100-fold difference in K m for these transporters allows the study of the H2 transporter separately at a very low [ 3 H]hypoxanthine concentration. We have now determined the substrate recognition motif for H2 and compared it with that of the human facilitative diffusion nucleobase transporter (hFNT1), 1 which is the only nucleobase transporter in erythrocytes (11,12) but has also been described in various other tissues (13)(14)(15)(16)(17) and been shown to mediate the uptake of several chemotherapeutic purine analogues (17)(18)(19)(20). This approach to comparing transporters is all the more relevant because molecular approaches are unavailable: no protozoan or metazoan nucleobase transporters have yet been cloned.…”

mentioning

confidence: 99%

Different Substrate Recognition Motifs of Human and Trypanosome Nucleobase Transporters

Wallace

Candlish

Koning

2002

Journal of Biological Chemistry

142

View full text Add to dashboard Cite

The therapeutic index of antimetabolites such as purine analogues is in large part determined by the extent to which it is selectively accumulated by the target cell. In the current study we have compared the transport of purine nucleobase analogues by the H2 transporter of bloodstream form Trypanosoma brucei brucei and the equilibrative nucleobase transporter of human erythrocytes. The H2 transporter forms hydrogen bonds with hypoxanthine at positions N3, N7, N(1)H, and N(9)H of the purine ring, with apparent ⌬G 0 of 7.7-12.6 kJ/mol. The transporter also appears to H-bond with the amine group of adenine. The human transporter forms hydrogen bonds that form to (6)NH 2 and N1 of adenine. An H-bond is also formed with N3 and the 6-keto and amine groups of guanine but not with the protonated N1, thus explaining the low affinity for hypoxanthine. N7 and N9 do not directly interact with the human transporter in the form of H-bonds, and it is proposed that -stacking interactions contribute significantly to permeant binding. The potential for selective uptake of antimetabolites by the parasite transporter was demonstrated.Purine and pyrimidine antimetabolites are widely used to combat a variety of infectious diseases and other pathologies. However, many therapies suffer from a lack of selectivity, leading to severe side effects. The selectivity and efficacy of purine antimetabolites is achieved at two levels: the cell-surface transporters that mediate access to the cell, and the enzymes of the purine metabolic pathways that convert the prodrug to the cytotoxic metabolite, usually a nucleotide analogue. This report elucidates the mechanisms of selectivity at the transporter level.We have chosen Trypanosoma brucei, the etiological agent of sleeping sickness, as a model organism, because it lives freely in the host bloodstream rather than within a host cell. Therefore, the accumulation of most nucleobase and nucleoside drugs depends exclusively on the transporters expressed by the parasite itself. In addition, African trypanosomes are entirely dependent on purine salvage because they lack the capacity for de novo synthesis (1), and they consequently express several proton symporters that actively accumulate nucleosides (2, 3) and nucleobases (4 -6). For trypanosomes, nucleobases may make more efficient drugs than their corresponding nucleosides, because purine ribonucleosides are rapidly hydrolyzed in bloodstream form T. brucei, limiting their incorporation into the nucleotide pool (7). In contrast, nucleobases are efficiently assimilated by one-step reactions of phosphoribosyltransferases for adenine, hypoxanthineguanine, and xanthine (8). The current study therefore focuses on the main T. brucei brucei and human nucleobase transporters. This approach will allow the identification of groups that determine high affinity uptake by either the trypanosome or the cells of its mammalian host. The escalating epidemic of African trypanosomiasis (9) and the onset of drug resistance (10) necessitate the development of a new genera...

show abstract

Expression of the high-affinity purine nucleobase transporter in mutant mouse S49 cells does not require a functional wild-type nucleoside-nucleobase transporter.

Cited by 19 publications

References 38 publications

Molecular Basis of Nucleobase Transport Systems in Mammals

Molecular Basis of Nucleobase Transport Systems in Mammals

Characterization of Nucleobase Transport by Mouse Sertoli Cell Line TM4

Different Substrate Recognition Motifs of Human and Trypanosome Nucleobase Transporters

Contact Info

Product

Resources

About