SLC30A family expression in the pancreatic islets of humans and mice: cellular localization in the β-cells

Zinc is a vital co-factor for insulin metabolism in the pancreatic beta-cell, involved in synthesis, maturation, and crystallization. Two families of zinc transporters, namely SLC30A (ZNT) and SLC39A (ZIP) are involved in maintaining cellular zinc homeostasis in mammalian cells. Single nuclear polymorphisms or mutations in zinc transporters have been associated with insulin resistance and risk of type 2 diabetes (T2D) in both humans and mice. Thus, mice can be useful for studying the underlying mechanisms of zinc-associated risk of T2D development. To determine potential differences in zinc transporter expression and cellular localization in the pancreatic beta-cells between humans and mice, we examined all members (ZNT1-10) of the ZNT family in pancreatic islets and in beta-cell lines derived from both species using immunohistochemistry and immunofluorescence microscopic analysis. We found that there were no substantial differences in the expression of nine ZNT proteins in the human and mouse islets and beta-cells with exception of ZNT3, which was only detected in human beta-cells, but not in mouse beta-cells. Moreover, we found that ZNT2 was localized on the cell surface of both human and mouse beta-cells, suggesting a role of ZNT2 in direct export of zinc out of the beta-cell. Together, our study suggests functional conservations of the ZNT proteins between humans and mice. We believe that our results are of interest for future studies in the association of zinc metabolism with risk of T2D in humans using mouse models.