siRNA-mediated knock-down of ZnT3 and ZnT8 affects production and secretion of insulin and apoptosis in INS-1E cells

Zinc is essential for the crystallization of insulin in pancreatic beta-cells and is thought to induce apoptosis in a dose-dependent manner, thereby regulating beta-cell mass. Therefore, a tight intracellular regulation of Zn2+ is required. The zinc-transporter family SLC30A is an important factor in the regulation of zinc homeostasis. The aim of this study was to examine the effect of the zinc transporters ZnT3 and ZnT8 on insulin metabolism and apoptosis. Both these proteins are present in pancreatic beta-cells and have been linked to diabetes. The objective of our study was to perform a considerable siRNA-mediated knock-down of ZnT3 and ZnT8 in INS-1E cells, a pancreatic beta-cell model, and afterwards examine the impact on cell viability and insulin metabolism. Increased levels of apoptosis were observed after knock-down of both ZnT3 and ZnT8. Insulin secretion was significantly reduced by ZnT3 knock-down, whereas knock-down of ZnT8 resulted in increased intracellular content of insulin accompanied by a relatively lowered secretion. Both zinc transporters in this way seem to play a role in beta-cell survival and the ability of these cells to react appropriately to surrounding glucose concentrations.