Zinc transporter 2

Intracellular zinc homeostasis is regulated by zinc-binding proteins and zinc transporters (Rink et al. 2007). The zinc transporters are encoded by two SLC ("solute linked carrier") gene families.

Members of the SLC39 family (Zip, "Zrt- and Irt-like proteins") increase the cytoplasmic zinc level by zinc uptake.

Members of the SLC30 family (ZnT, zinc transporter/exporter; CDF family, "cation diffusion facilitator") lower the intracellular zinc concentration by transporting zinc out of the cell or into vesicular structures.

So far, 15 Zips and 9 ZnTs have been detected in various human cells.

Zinc transporter 2, ZnT-2, is localized in acidic endosomal or lysosomal vesicles, respectively, thus enabling vesicular zinc accumulation. This zinc exporter is found in the intestine, kidney, placenta, testicles and prostate (Iguchi et al 2002). ZnT-2 is also expressed in the breast epithelium where it regulates the zinc concentration in milk. Zinc transporter 2 (ZnT-2) is not expressed in liver, muscle, body fat, thymus and spleen (Cousins et al 2003). A missense mutation in the ZnT-2 gene is responsible for a reduced zinc concentration in milk (Chowanadisai et al., 2006). Animal experiments have shown that the regulation of this zinc transporter takes place through the zinc concentration in the intestine.

1. Chowanadisai W et al (2006) Identification of a mutation in SLC30A2 (ZnT-2) in women with low milk zinc concentration that results in transient neonatal zinc deficiency. J Biol Chem 281: 39699-39707.
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