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.
Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto, Japan.
Wataru
W
Matsuura
Tomohiro
T
Yamazaki
Yuko
Y
Yamaguchi-Iwai
Seiji
S
Masuda
Masaya
M
Nagao
Glen K
GK
Andrews
Taiho
T
Kambe
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