title: Roles of ZIP8, ZIP14, and DMT1 in transport of cadmium and manganese in mouse kidney proximal tubule cells.
abstract: Chronic exposure to cadmium causes preferential accumulation of cadmium in the kidney, leading to nephrotoxicity. In the process of renal cadmium accumulation, the cadmium bound to a low-molecular-weight metal-binding protein, metallothionein, has been considered to play an important role in reabsorption by epithelial cells of proximal tubules in the kidney. However, the role and mechanism of the transport of Cd(2+) ions in proximal tubule cells remain unclear. Zinc transporters such as Zrt, Irt-related protein 8 (ZIP8) and ZIP14, and divalent metal transporter 1 (DMT1) have been reported to have affinities for Cd(2+) and Mn(2+). To examine the roles of these metal transporters in the absorption of luminal Cd(2+) and Mn(2+) into proximal tubule cells, we utilized a cell culture system, in which apical and basolateral transport of metals can be separately examined. The uptake of Cd(2+) and Mn(2+) from the apical side of proximal tubule cells was inhibited by simultaneous addition of Mn(2+) and Cd(2+), respectively. The knockdown of ZIP8, ZIP14 or DMT1 by siRNA transfection significantly reduced the uptake of Cd(2+) and Mn(2+) from the apical membrane. The excretion of Cd(2+) and Mn(2+) was detected predominantly in the apical side of the proximal tubule cells. In situ hybridization of these transporters revealed that ZIP8 and ZIP14 are highly expressed in the proximal tubules of the outer stripe of the outer medulla. These results suggest that ZIP8 and ZIP14 expressed in the S3 segment of proximal tubules play significant roles in the absorption of Cd(2+) and Mn(2+) in the kidney.
authors.affiliation: Laboratory of Molecular Nutrition and Toxicology, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Tokushima 770-8514, Japan.
authors.forename: Hitomi
authors.initials: H
authors.lastname: Fujishiro
authors.forename: Yu
authors.initials: Y
authors.lastname: Yano
authors.forename: Yukina
authors.initials: Y
authors.lastname: Takada
authors.forename: Maya
authors.initials: M
authors.lastname: Tanihara
authors.forename: Seiichiro
authors.initials: S
authors.lastname: Himeno
mesh_terms: D000818:Animals; D001692:Biological Transport; D002104:Cadmium / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity; D005786:Gene Expression Regulation; D020868:Gene Silencing; D007687:Kidney Tubules, Proximal / Q000166:cytology* / Q000378:metabolism*; D008345:Manganese / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D021381:Protein Transport; D034741:RNA, Small Interfering / Q000378:metabolism; D015203:Reproducibility of Results; D000099236:Solute Carrier Family 11, Member 2
chemical_list: D002104:Cadmium; D027682:Cation Transport Proteins; D008345:Manganese; D034741:RNA, Small Interfering; D000099236:Solute Carrier Family 11, Member 2; C500556:SLC39A14 protein, mouse; C499256:Slc39a8 protein, mouse