Extranuclear estrogen receptor-[alpha] stimulates NeuroD1 binding to the insulin promoter and favors insulin synthesis

Estrogen receptors (ERs) protect pancreatic islet survival in mice through rapid extranuclear actions. ER[alpha] also enhances insulin synthesis in cultured islets. Whether ERa stimulates insulin synthesis in vivo and, if so, through which mechanism(s) remain largely unknown. To address these issues, we generated a pancreas-specific ERa knockout mouse (PER[alpha][KO.sup.-/-]) using the Cre-loxP strategy and used a combination of genetic and pharmacologic tools in cultured islets and [beta] cells. Whereas 17[beta]-estradiol (E2) treatment up-regulates pancreatic insulin gene and protein content in control ERcdox/lox mice, these E2 effects are abolished in PER[alpha][KO.sup.-/-] mice. We find that E2-activated ER[alpha] increases insulin synthesis by enhancing glucose stimulation of the insulin promoter activity. Using a knock-in mouse with a mutated ER[alpha] eliminating binding to the estrogen response elements (EREs), we show that E2 stimulation of insulin synthesis is independent of the ERE. We find that the extranuclear ER[alpha] interacts with the tyrosine kinase Src, which activates extracellular signal-regulated [kinases.sub.1/2], to increase nuclear localization and binding to the insulin promoter of the transcription factor NeuroD1. This study supports the importance of ERa in [beta] cells as a regulator of insulin synthesis in vivo. diabetes | islet doi/ 10.1073/pnas.0914501107