title: Comparison of the interaction of uridine, cytidine, and other pyrimidine nucleoside analogues with recombinant human equilibrative nucleoside transporter 2 (hENT2) produced in Saccharomyces cerevisiae.
abstract: The human equilibrative nucleoside transporters I and 2 (hENT1, hENT2) share 50% amino acid identity and exhibit broad selectivities, accepting purine and pyrimidine nucleosides as permeants. The permeant selectivity of hENT2 is less well understood because of the low abundance of the native transporter in cells amenable to functional analysis. Recent studies of hENT2 produced in recombinant form in functional expression systems have shown that it differs from hENT1 in that it transports nucleobases. To further understand the structural requirements for permeant interaction with hENT2, we compared the relative abilities of uridine, cytidine, and their analogues to inhibit transport of [3H]uridine by recombinant hENT1 and hENT2 produced in yeast. hENT1 and hENT2 tolerated halogen modification at the 5 position of the base and the 2' and 5' positions of the ribose moieties of uridine whereas removal of the hydroxyl group at the 3' position of the ribose moiety of uridine eliminated interaction with both transporters. hENT2 displayed a lower ability, compared with hENT1, to interact with cytidine and cytidine analogues, suggesting a low tolerance for the presence of the amino group at the 4 position of the base.
authors.affiliation: Department of Oncology, University of Alberta, Cross Cancer Institute, Edmonton, Canada.
authors.forename: Mark F
authors.initials: MF
authors.lastname: Vickers
authors.forename: Rakesh
authors.initials: R
authors.lastname: Kumar
authors.forename: Frank
authors.initials: F
authors.lastname: Visser
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Jahangir
authors.initials: J
authors.lastname: Charania
authors.forename: R Taylor
authors.initials: RT
authors.lastname: Raborn
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Baldwin
authors.forename: James D
authors.initials: JD
authors.lastname: Young
authors.forename: Carol E
authors.initials: CE
authors.lastname: Cass
mesh_terms: D001692:Biological Transport; D003562:Cytidine / Q000031:analogs & derivatives / Q000378:metabolism*; D033721:Equilibrative Nucleoside Transporter 1 / Q000378:metabolism; D033722:Equilibrative-Nucleoside Transporter 2 / Q000378:metabolism*; D006801:Humans; D011741:Pyrimidine Nucleosides / Q000378:metabolism*; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D014529:Uridine / Q000031:analogs & derivatives / Q000378:metabolism*
chemical_list: D033721:Equilibrative Nucleoside Transporter 1; D033722:Equilibrative-Nucleoside Transporter 2; D011741:Pyrimidine Nucleosides; D011994:Recombinant Proteins; C438649:SLC29A1 protein, human; C438654:SLC29A2 protein, human; D003562:Cytidine; D014529:Uridine