title: Mouse equilibrative nucleoside transporter 2 (mENT2) transports nucleosides and purine nucleobases differing from human and rat ENT2.
abstract: Several mammalian nucleoside transporters have been identified at the molecular level. Human and rat equilibrative nucleoside transporter 2 (hENT2 and rENT2, respectively) was previously reported to have the dual ability of transporting both nucleosides and nucleobases. In the present study, we characterized the transport of a variety of nucleosides and nucleobases via recombinant mouse ENT2 (mENT2). Cloned mENT2 mediated the uptake of nucleosides and purine nucleobases, but not pyrimidine nucleobases. The mENT2-mediated uptake of adenosine was significantly inhibited by nucleosides and nucleobases, irrespective of purine and pyrimidine. The K(m) values for the uptake of nucleosides and purine nucleobases mediated by mENT2 varied between 1.24 and 16.3 microM, and the transport clearances of adenosine and hypoxanthine via the transporter were greater than those of other substrates. Therefore, we concluded that mENT2 is nucleoside and purine nucleobase transporter, and pyrimidine nucleobases are blockers for the transporter, differing from hENT2 and rENT2 that were reported to also transport pyrimidine nucleobases.
authors.affiliation: Department of Environmental Biochemistry, Kyoto Pharmaceutical University, Kyoto, Japan. nagai@mb.kyoto-phu.ac.jp
authors.forename: Katsuhito
authors.initials: K
authors.lastname: Nagai
authors.forename: Kazuki
authors.initials: K
authors.lastname: Nagasawa
authors.forename: Yoji
authors.initials: Y
authors.lastname: Kyotani
authors.forename: Natsuko
authors.initials: N
authors.lastname: Hifumi
authors.forename: Sadaki
authors.initials: S
authors.lastname: Fujimoto
mesh_terms: D000818:Animals; D001692:Biological Transport; D019556:COS Cells; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D004305:Dose-Response Relationship, Drug; D033721:Equilibrative Nucleoside Transporter 1 / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D051379:Mice; D033703:Nucleoside Transport Proteins / Q000502:physiology*; D009705:Nucleosides / Q000378:metabolism*; D011687:Purines / Q000378:metabolism*; D051381:Rats; D013045:Species Specificity; D013997:Time Factors; D014162:Transfection
chemical_list: D033721:Equilibrative Nucleoside Transporter 1; D033703:Nucleoside Transport Proteins; D009705:Nucleosides; D011687:Purines; C438649:SLC29A1 protein, human; C498476:SLC29A1 protein, mouse; C438652:Slc29a1 protein, rat