title: Cloning of a human nucleoside transporter implicated in the cellular uptake of adenosine and chemotherapeutic drugs.
abstract: In most mammalian cells nucleoside uptake occurs primarily via broad-specificity, es (e, equilibrative; 5, sensitive to NBMPR inhibition) transporters that are potently inhibited by nitrobenzylthioinosine (NBMPR). These transporters are essential for nucleotide synthesis by salvage pathways in hemopoietic and other cells that lack de novo pathways and are the route of cellular uptake for many cytotoxic nucleosides used in cancer and viral chemotherapy. They play an important role in adenosine-mediated regulation of many physiological processes, including neurotransmission and platelet aggregation, and are a target for coronary vasodilator drugs. We have previously reported the purification of the prototypic es transporter from human erythrocytes and have shown that this glycoprotein of apparent M, 55,000 is immunologically related to nucleoside transporters from several other species and tissues, including human placenta. Here we report the isolation of a human placental cDNA encoding a 456-residue glycoprotein with functional characteristics typical of an es-type transporter. It is predicted to possess 11 membrane-spanning regions and is homologous to several proteins of unknown function in yeast, nematodes, plants and mammals. Because of its central role in the uptake both of adenosine and of chemotherapeutic nucleosides, study of this protein should not only provide insights into the physiological roles of nucleoside transport but also open the way to improved therapies.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Leeds, UK.
authors.forename: M
authors.initials: M
authors.lastname: Griffiths
authors.forename: N
authors.initials: N
authors.lastname: Beaumont
authors.forename: S Y
authors.initials: SY
authors.lastname: Yao
authors.forename: M
authors.initials: M
authors.lastname: Sundaram
authors.forename: C E
authors.initials: CE
authors.lastname: Boumah
authors.forename: A
authors.initials: A
authors.lastname: Davies
authors.forename: F Y
authors.initials: FY
authors.lastname: Kwong
authors.forename: I
authors.initials: I
authors.lastname: Coe
authors.forename: C E
authors.initials: CE
authors.lastname: Cass
authors.forename: J D
authors.initials: JD
authors.lastname: Young
authors.forename: S A
authors.initials: SA
authors.lastname: Baldwin
mesh_terms: D000241:Adenosine / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism*; D017338:Cladribine / Q000494:pharmacology; D003001:Cloning, Molecular; D003561:Cytarabine / Q000494:pharmacology; D018076:DNA, Complementary; D016208:Databases, Factual; D033721:Equilibrative Nucleoside Transporter 1; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D009705:Nucleosides / Q000378:metabolism; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D014529:Uridine / Q000378:metabolism / Q000493:pharmacokinetics; D014740:Vidarabine / Q000031:analogs & derivatives / Q000494:pharmacology; D014981:Xenopus
chemical_list: D000970:Antineoplastic Agents; D002352:Carrier Proteins; D018076:DNA, Complementary; D033721:Equilibrative Nucleoside Transporter 1; D008565:Membrane Proteins; D009705:Nucleosides; D011994:Recombinant Proteins; D003561:Cytarabine; D017338:Cladribine; D014740:Vidarabine; D000241:Adenosine; C024352:fludarabine; D014529:Uridine