The SLC30 family of zinc transporters - A review of current understanding of their biological and pathophysiological roles

Two families of zinc (Zn2 +) transporters are involved in zinc homeostasis in the body, SLC30 (ZnT, zinc transporter) and SLC39 (ZIP, Zinc(Zn2+)-Iron(Fe2+) Permease). The two zinc transporter family members function in opposite directions to maintain cellular zinc homeostasis. ZnT proteins contribute to the cytoplasmic zinc balance by exporting zinc out to the extracellular space or by sequestrating cytoplasmic zinc into intracellular compartments when cellular zinc levels are elevated. In contrast, ZIP proteins function to increase cytoplasmic zinc concentrations when cellular zinc is depleted. Since the cloning of the first zinc transporter (ZnT1) in 1995, there have been many advances in zinc transporter research including discovery of new members of zinc transporters, identification of gene expression patterns and regulations, recognition of protein distribution patterns in tissues and cells, and understanding of their physiological and pathological roles in humans and animal models. Ten members of the ZnT family have been identified so far. Here we give a review of these advances and discuss the pathological implications and future preventive or therapeutic applications of ZnTs.