title: Inhibitory effect of divalent metal cations on zinc uptake via mouse Zrt-/Irt-like protein 8 (ZIP8).
abstract: OBJECTIVE
  There is controversy regarding the substrate specificity of ZIP8, a ZIP isoform, involved in regulation of extra- and intracellular zinc levels. Here, we investigated the inhibitory effects of divalent metal cations on zinc uptake via mouse ZIP8 (mZIP8).
  
  
  METHODS
  mZIP8 cDNA was transfected into HEK293T cells by a lipofection method, and its functional expression was evaluated by immunocytochemistry, Western blotting and65Zn (65ZnCl2) uptake measurement.
  
  
  RESULTS
  Transfection of mZIP8 cDNA into HEK293T cells induced expression of mZIP8 in the cells, and increased zinc uptake. mZIP8-mediated zinc uptake depended on extracellular bicarbonate, and the Michaelis constant for the uptake was estimated to be 8.48±2.46μM. In the inhibition study, iron and cadmium competitively, and cobalt, nickel and copper non-competitively inhibited the mZIP8-mediated zinc uptake, the inhibition constants being calculated to be 3.37, 55.5, 80.6, 198 and 48.3μM, respectively. In contrast, magnesium and manganese at concentrations of up to 1500 and 200μM, respectively, had no inhibitory effect on the zinc uptake via mZIP8.
  
  
  CONCLUSIONS
  In this study, we reveal that the inhibition profiles of divalent metal cations as to zinc uptake via mZIP8 apparently differ from those for mZIP1, especially in the affinity and inhibition manner of nickel. These findings should contribute to identification of ZIP isoforms involved in total cellular zinc transport.
authors.affiliation: Department of Environmental Biochemistry, Kyoto Pharmaceutical University, 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Koike
authors.affiliation: Department of Environmental Biochemistry, Kyoto Pharmaceutical University, 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan.
authors.forename: Jyakusho
authors.initials: J
authors.lastname: Sou
authors.affiliation: Department of Environmental Biochemistry, Kyoto Pharmaceutical University, 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Ohishi
authors.affiliation: Department of Environmental Biochemistry, Kyoto Pharmaceutical University, 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Nishida
authors.affiliation: Department of Environmental Biochemistry, Kyoto Pharmaceutical University, 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan. Electronic address: nagasawa@mb.kyoto-phu.ac.jp.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Nagasawa
mesh_terms: D000818:Animals; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D002413:Cations, Divalent / Q000494:pharmacology; D002712:Chlorides / Q000493:pharmacokinetics / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D017136:Ion Transport / Q000187:drug effects / Q000502:physiology; D019216:Metals, Heavy / Q000494:pharmacology*; D051379:Mice; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D015032:Zinc / Q000378:metabolism*; D017967:Zinc Compounds / Q000493:pharmacokinetics / Q000494:pharmacology
chemical_list: D027682:Cation Transport Proteins; D002413:Cations, Divalent; D002712:Chlorides; D019216:Metals, Heavy; D020033:Protein Isoforms; C499256:Slc39a8 protein, mouse; D017967:Zinc Compounds; C016837:zinc chloride; D015032:Zinc
keywords: Inhibition manner; Substrate specificity; ZIP8; Zinc uptake