TRPV6 channel modulates proliferation of insulin secreting INS-1E beta cell line

• TRPV6 is expressed in INS-1E cells and rat pancreatic beta cells.
• TRPV6 controls calcineurin/NFAT pathway in INS-1E cells.
• TRPV6 modulates INS-1E cell proliferation.
• TRPV6 regulates insulin mRNA expression in INS-1E cells.

Transient receptor potential channel vanilloid type 6 (TRPV6) is a non-selective cation channel with high permeability for Ca2 + ions. So far, the role of TRPV6 in pancreatic beta cells is unknown. In the present study, we characterized the role of TRPV6 in controlling calcium signaling, cell proliferation as well as insulin expression, and secretion in experimental INS-1E beta cell model. TRPV6 protein production was downregulated using siRNA by approx. 70%, as detected by Western blot. Intracellular free Ca2 + ([Ca2 +]i) was measured by fluorescence Ca2 + imaging using fura-2. Calcineurin/NFAT signaling was analyzed using a NFAT reporter assay as well as a calcineurin activity assay. TRPV6 downregulation resulted in impaired cellular calcium influx. Its downregulation also reduced cell proliferation and decreased insulin mRNA expression. These changes were companied by the inhibition of the calcineurin/NFAT signaling. In contrast, insulin exocytosis was not affected by TRPV6 downregulation. In conclusion, this study demonstrates for the first time the expression of TRPV6 in INS-1E cells and rat pancreatic beta cells and describes its role in modulating calcium signaling, beta cell proliferation and insulin mRNA expression. In contrast, TRPV6 fails to influence insulin secretion.