title: Type 1 sodium-dependent phosphate transporter (SLC17A1 Protein) is a Cl(-)-dependent urate exporter.
abstract: SLC17A1 protein (NPT1) is the first identified member of the SLC17 phosphate transporter family and mediates the transmembrane cotransport of Na(+)/P(i) in oocytes. Although this protein is believed to be a renal polyspecific anion exporter, its transport properties are not well characterized. Here, we show that proteoliposomes containing purified SLC17A1 transport various organic anions such as p-aminohippuric acid and acetylsalicylic acid (aspirin) in an inside positive membrane potential (Deltapsi)-dependent manner. We found that NPT1 also transported urate. The uptake characteristics were similar to that of SLC17 members in its Cl(-) dependence and inhibitor sensitivity. When arginine 138, an essential amino acid residue for members of the SLC17 family such as the vesicular glutamate transporter, was specifically mutated to alanine, the resulting mutant protein was inactive in Deltapsi-dependent anion transport. Heterologously expressed and purified human NPT1 carrying the single nucleotide polymorphism mutation that is associated with increased risk of gout in humans exhibited 32% lower urate transport activity compared with the wild type protein. These results strongly suggested that NPT1 is a Cl(-)-dependent polyspecific anion exporter involved in urate excretion under physiological conditions.
authors.affiliation: Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Tokyo, Japan.
authors.forename: Masafumi
authors.initials: M
authors.lastname: Iharada
authors.forename: Takaaki
authors.initials: T
authors.lastname: Miyaji
authors.forename: Takahiro
authors.initials: T
authors.lastname: Fujimoto
authors.forename: Miki
authors.initials: M
authors.lastname: Hiasa
authors.forename: Naohiko
authors.initials: N
authors.lastname: Anzai
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Omote
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Moriyama
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D001692:Biological Transport; D002712:Chlorides; D004594:Electrophysiology; D006073:Gout / Q000235:genetics; D006801:Humans; D008081:Liposomes; D008564:Membrane Potentials; D051379:Mice; D008954:Models, Biological; D027361:Organic Anion Transporters / Q000378:metabolism*; D050609:Sodium-Phosphate Cotransporter Proteins, Type I / Q000378:metabolism / Q000502:physiology*; D014527:Uric Acid / Q000378:metabolism*
chemical_list: D002712:Chlorides; D008081:Liposomes; D027361:Organic Anion Transporters; C493546:SLC17A1 protein, human; C493547:Slc17a1 protein, mouse; D050609:Sodium-Phosphate Cotransporter Proteins, Type I; D014527:Uric Acid