Prolactin Receptor Signaling in the Pancreatic β-cell: The Role of STAT5

Science Center A154

The lactogenic hormone, prolactin (PRL), has many critical functions during pregnancy including a role in the adaptive response of β-cell expansion and glucose homeostasis in murine models. Previous data indicates targets of PRL signaling in pancreatic β-cells include the genes Tph1, Hopx, and IVD. The prolactin signaling pathway through the prolactin receptor (PRLR) is mediated in part by transcription factor STAT5. The objective of this study is to determine if STAT5 is a direct mediator of gene transcription for these genes, further elucidating the signaling pathway of the PRLR and its gene targets. We used both a mouse insulinoma cell line (MIN6) and isolated mouse islets, treated with and without PRL. The localization of STAT5 binding was detected with the chromatin immunoprecipitation (ChIP) assay, a method that allows fxor the direct detection of protein-DNA interaction, using a rabbit α-STAT5a/b antibody to immunoprecipitate. With overnight PRL treatments, Tph1 expression increased 50+ fold in islets and 6+ fold in MIN6. When compared to control IgG antibody, PRL treatment resulted in a 3-fold enrichment of the STAT5 response element, upstream of the Tph1 gene in MIN6 cells. Enrichment at the STAT5 response element suggests that STAT5 is a mediator for Tph1 expression. Further method refinement is needed for successful islet ChIP. Validation of STAT5 binding for Hopx and IVD is ongoing.