Stimulation of angiotensin‐converting enzyme 2 promoter activity by hepatocyte nuclear factor 1β (HNF1β) in insulinoma cells

Abstract

We previously showed that Angiotensin-converting enzyme 2 (ACE2) gene therapy increases insulin secretion (Bindom et al, 2010). Moreover, others reported that exogenous expression of hepatocyte nuclear factor 1β (HNF1β) activates the ACE2 promoter in HEK293 cells that have no endogenous HNF1β. However, physical interaction with the ACE2 promoter was not shown and the relevance to diabetes is unclear. Our objective was to determine whether HNF1β directly binds to the ACE2 gene promoter and whether HNF1β overexpression stimulates promoter activity in insulinoma cells. Chromatin immunoprecipitation assays showed binding of HNF1β to the ACE2 gene promoter region in HEK293T cells transfected with an HNF1β expression plasmid. Human and mouse ACE2 promoter regions containing 2 putative HNF1 binding sites were cloned into the luciferase vector pGL3-Basic. The ACE2 promoter sequences were active in driving the expression of luciferase in insulinoma cell lines βTC-3 and 832/13. Furthermore, overexpression of HNF1β markedly induced expression of luciferase (> 20-fold in βTC-3 cells and > 100-fold in 832/13 cells) and ACE2 mRNA (> 10-fold in 832/13 cells). Our data show that HNF1β binds and stimulates ACE2 promoter activity in insulinoma cells. These findings bring new evidence for a role of ACE2 in type 2 diabetes by providing a possible new mechanism leading to insulin secretion. Support: NIH/NIDDK (DK084466).