Nucleoside Transporter Proteins of Saccharomyces cerevisiae

Vickers, Mark F.; Yao, Sylvia Y. M.; Baldwin, Stephen A.; Young, James D.; Cass, Carol E.

doi:10.1074/jbc.m000239200

Cited by 69 publications

(46 citation statements)

References 44 publications

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“…In contrast to hENT4, the functional properties of hENT3 have not yet been described. In light of the presence of a long (51 residues), hydrophilic N-terminal region preceding TM1, which possesses a putative dileucine-based targeting motif, we previously suggested that hENT3 might function intracellularly, as is the case for the yeast homologue FUN26 (9,17). In the present study we have confirmed this hypothesis by examining the effect of mutating the targeting motif on the subcellular location of hENT3 and have shown that the transporter is indeed intracellular and partially co-localizes with lysosomal markers.…”

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confidence: 99%

Functional Characterization of Novel Human and Mouse Equilibrative Nucleoside Transporters (hENT3 and mENT3) Located in Intracellular Membranes

Baldwin

Yao²,

Hyde

et al. 2005

Journal of Biological Chemistry

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The first mammalian examples of the equilibrative nucleoside transporter family to be characterized, hENT1 and hENT2, were passive transporters located predominantly in the plasma membranes of human cells. We now report the functional characterization of members of a third subgroup of the family, from human and mouse, which differ profoundly in their properties from previously characterized mammalian nucleoside transporters. The 475-residue human and mouse proteins, designated hENT3 and mENT3, respectively, are 73% identical in amino acid sequence and possess long N-terminal hydrophilic domains that bear typical (DE)XXXL(LI) endosomal/lysosomal targeting motifs. ENT3 transcripts and proteins are widely distributed in human and rodent tissues, with a particular abundance in placenta. However, in contrast to ENT1 and ENT2, the endogenous and green fluorescent proteintagged forms of the full-length hENT3 protein were found to be predominantly intracellular proteins that co-localized, in part, with lysosomal markers in cultured human cells. Truncation of the hydrophilic N-terminal region or mutation of its dileucine motif to alanine caused the protein to be relocated to the cell surface both in human cells and in Xenopus oocytes, allowing characterization of its transport activity in the latter. The protein proved to be a broad selectivity, low affinity nucleoside transporter that could also transport adenine. Transport activity was relatively insensitive to the classical nucleoside transport inhibitors nitrobenzylthioinosine, dipyridamole, and dilazep and was sodium ion-independent. However, it was strongly dependent upon pH, and the optimum pH value of 5.5 probably reflected the location of the transporter in acidic, intracellular compartments.

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confidence: 99%

Functional Characterization of Novel Human and Mouse Equilibrative Nucleoside Transporters (hENT3 and mENT3) Located in Intracellular Membranes

Baldwin

Yao²,

Hyde

et al. 2005

Journal of Biological Chemistry

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289

296

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“…Together, these results suggest that FUI1, which is a high-affinity uridine permease in S. cerevisiae (30), also is responsible for uridine transport in L. kluyveri. However, in L. kluyveri, there are additional permeases whose functions overlap this function.…”

Section: Discussionmentioning

confidence: 65%

Global Expression Analysis of the Yeast Lachancea (Saccharomyces) kluyveri Reveals New URC Genes Involved in Pyrimidine Catabolism

et al. 2014

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bPyrimidines are important nucleic acid precursors which are constantly synthesized, degraded, and rebuilt in the cell. Four degradation pathways, two of which are found in eukaryotes, have been described. One of them, the URC pathway, has been initially discovered in our laboratory in the yeast Lachancea kluyveri. Here, we present the global changes in gene expression in L. kluyveri in response to different nitrogen sources, including uracil, uridine, dihydrouracil, and ammonia. The expression pattern of the known URC genes, URC1-6, helped to identify nine putative novel URC genes with a similar expression pattern. The microarray analysis provided evidence that both the URC and PYD genes are under nitrogen catabolite repression in L. kluyveri and are induced by uracil or dihydrouracil, respectively. We determined the function of URC8, which was found to catalyze the reduction of malonate semialdehyde to 3-hydroxypropionate, the final degradation product of the pathway. The other eight genes studied were all putative permeases. Our analysis of double deletion strains showed that the L. kluyveri Fui1p protein transported uridine, just like its homolog in Saccharomyces cerevisiae, but we demonstrated that is was not the only uridine transporter in L. kluyveri. We also showed that the L. kluyveri homologs of DUR3 and FUR4 do not have the same function that they have in S. cerevisiae, where they transport urea and uracil, respectively. In L. kluyveri, both of these deletion strains grew normally on uracil and urea.

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“…Yeast FUN26 and mammalian ENT3 proteins are found on lysosomal membranes where they are thought to be responsible for the release of nucleosides from intracellular compartments following nucleic acid breakdown (30,24). The human ENT4 protein localizes to intracellular vesicles as well as the plasma membrane, and this localization appears to be dynamic (31).…”

Section: Discussionmentioning

confidence: 99%

“…The yeast strain fui1⌬ lacks the high affinity plasma membrane uridine permease Fui1; it is, as a result, deficient in uridine transport and, consequently, resistant to 5-FUrd (30). We used the PfNT2 fcy2 fusion protein to determine whether expression of PfNT2 at the surface of the yeast cell can, by complementation, reverse the 5-FUrd insensitivity seen in fui1⌬ yeast cells.…”

Section: Functional Characterization Of Pfnt2 In Yeast-despite Previomentioning

confidence: 99%

PfNT2, a Permease of the Equilibrative Nucleoside Transporter Family in the Endoplasmic Reticulum of Plasmodium falciparum

Downie

Bissati

Bobenchik

et al. 2010

Journal of Biological Chemistry

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The survival and proliferation of the obligate intracellular malaria parasite Plasmodium falciparum require salvage of essential purines from the host. Genetic studies have previously shown that the parasite plasma membrane purine permease, PfNT1, plays an essential function in the transport of all naturally occurring purine nucleosides and nucleobases across the parasite plasma membrane. Here, we describe an intracellular permease, PfNT2. PfNT2 is, like PfNT1, a member of the equilibrative nucleoside transporter family. Confocal and immunoelectron microscopic analyses of transgenic parasites harboring green fluorescent protein-or hemagglutinin-tagged PfNT2 demonstrated endoplasmic reticulum localization. This localization was confirmed by colocalization with the endoplasmic reticulum marker PfBiP. Using yeast as a surrogate system, we show that targeting PfNT2 to the plasma membrane of fui1⌬ cells lacking the plasma membrane nucleoside transporter Fui1 confers sensitivity to the toxic nucleoside analog 5-fluorouridine. This study provides the first evidence of an intracellular purine permease in apicomplexan parasites and suggests a novel biological function for the parasite endoplasmic reticulum during malaria infection.

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Nucleoside Transporter Proteins of Saccharomyces cerevisiae

Abstract: These results indicated that FUI1 has high selectivity for uracil-containing ribonucleosides and imports uridine across cell-surface membranes, whereas FUN26 has broad nucleoside selectivity and most likely functions to transport nucleosides across intracellular membranes.

Cited by 69 publications

References 44 publications

Functional Characterization of Novel Human and Mouse Equilibrative Nucleoside Transporters (hENT3 and mENT3) Located in Intracellular Membranes

Functional Characterization of Novel Human and Mouse Equilibrative Nucleoside Transporters (hENT3 and mENT3) Located in Intracellular Membranes

Global Expression Analysis of the Yeast Lachancea (Saccharomyces) kluyveri Reveals New URC Genes Involved in Pyrimidine Catabolism

PfNT2, a Permease of the Equilibrative Nucleoside Transporter Family in the Endoplasmic Reticulum of Plasmodium falciparum

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