title: Mechanism of iodide/chloride exchange by pendrin.
abstract: We performed an electrophysiological study to investigate ion transport of pendrin and thereby understand the pathogenesis of Pendred syndrome. Using pendrin-transfected COS-7 cells, we could show that pendrin transports both iodide and chloride measured as voltage-dependent inward and outward membrane currents. Chloride in the culture medium, [Cl-]o, was efficiently exchanged with cytoplasmic iodide, [I-]i, under physiological concentrations, indicating that pendrin is important for chloride uptake and iodide efflux. Although exchange of iodide in the medium, [I-]o, with cytoplasmic chloride, [Cl-]i, was observed, a significantly high concentration of iodide (10 mm) was required. In addition, either iodide or chloride was required on both sides of the cell membrane for the anion exchange activity of pendrin, indicating that iodide and chloride activate the exchange activity of pendrin while they are transported. The present study further supports that pendrin is responsible for the iodide efflux in thyroid cells where intracellular iodide concentration is high and that the general function of pendrin in other tissues is to transport chloride through exchange with other anions.
authors.affiliation: Division of Regenerative Medicine and Therapeutics, Tottori University Faculty of Medicine, 36-1 Nishimachi, Yonago, Tottori 683-8504, Japan. ayoshida@bronze.ocn.ne.jp.
authors.forename: Akio
authors.initials: A
authors.lastname: Yoshida
authors.forename: Ichiro
authors.initials: I
authors.lastname: Hisatome
authors.forename: Shinichi
authors.initials: S
authors.lastname: Taniguchi
authors.forename: Norihiro
authors.initials: N
authors.lastname: Sasaki
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Junichiro
authors.initials: J
authors.lastname: Miake
authors.forename: Hiroko
authors.initials: H
authors.lastname: Fukui
authors.forename: Hideki
authors.initials: H
authors.lastname: Shimizu
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Okamura
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Okura
authors.forename: Osamu
authors.initials: O
authors.lastname: Igawa
authors.forename: Chiaki
authors.initials: C
authors.lastname: Shigemasa
authors.forename: Eric D
authors.initials: ED
authors.lastname: Green
authors.forename: Leonard D
authors.initials: LD
authors.lastname: Kohn
authors.forename: Koichi
authors.initials: K
authors.lastname: Suzuki
mesh_terms: D000818:Animals; D000838:Anions / Q000378:metabolism; D019556:COS Cells; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism*; D002712:Chlorides / Q000493:pharmacokinetics*; D003593:Cytoplasm / Q000378:metabolism; D006801:Humans; D007454:Iodides / Q000493:pharmacokinetics*; D008564:Membrane Potentials / Q000502:physiology; D026901:Membrane Transport Proteins; D018408:Patch-Clamp Techniques; D000076988:Sulfate Transporters; D014162:Transfection
chemical_list: D000838:Anions; D002352:Carrier Proteins; D002712:Chlorides; D007454:Iodides; D026901:Membrane Transport Proteins; C085609:SLC26A4 protein, human; D000076988:Sulfate Transporters