SLC39A9 (ZIP9) regulates zinc homeostasis in the secretory pathway: characterization of the ZIP subfamily I protein in vertebrate cells.
The SLC39A family of zinc transporters can be divided into four subfamilies (I, II, LIV-1, and gufA) in vertebrates, but studies of their functions have been restricted exclusively to members of subfamilies II and LIV-1. In this study, we characterized SLC39A9 (ZIP9), the only member of subfamily I in vertebrates. Confocal microscopy demonstrated that transiently expressed, HA-tagged human ZIP9 (hZIP9-HA) was localized to the trans-Golgi network regardless of zinc status. Disruption of the ZIP9 gene in DT40 cells did not change the growth rate, sensitivity to high zinc and manganese concentrations during long-term culture, or cellular zinc status after short-term incubation with zinc. The alkaline phosphatase activity of ZIP9(-/-) cells did not change in cells cultured in medium containing normal zinc levels. In contrast, the activity of this enzyme decreased in wild-type cells cultured in zinc deficient medium but less so in ZIP9(-/-) cells under these conditions. Stable over-expression of hZIP9-HA moderately decreased alkaline phophatase activity. These results suggest that ZIP9 functions to regulate zinc homeostasis in the secretory pathway without significantly altering cytosolic zinc homeostasis.
Matsuura
Wataru
W
Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto, Japan.
Yamazaki
Tomohiro
T
Yamaguchi-Iwai
Yuko
Y
Masuda
Seiji
S
Nagao
Masaya
M
Andrews
Glen K
GK
Kambe
Taiho
T
D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D027682:Cation Transport Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006706:Homeostasis; D006801:Humans; D008969:Molecular Sequence Data; D055571:Secretory Pathway; D015032:Zinc / Q000378:metabolism*; D021601:trans-Golgi Network / Q000378:metabolism
D027682:Cation Transport Proteins; C543108:Slc39a9 protein, human; D000469:Alkaline Phosphatase; D015032:Zinc