Nardilysin regulates Slc2a2 expression through ISLET1 recruitment to an evolutionarily conserved enhancer in pancreatic β-cells

Abstract

GLUT2 (Slc2a2) is a key glucose transporter in pancreatic {beta}-cells, and its reduced expression is closely linked to defective glucose-stimulated insulin secretion (GSIS) and diabetes. We previously reported that pancreatic {beta}-cell-specific nardilysin (NRDC)-deficient mice (BetaKO) exhibit severe diabetic phenotype with defective GSIS and reduced Slc2a2 expression in islets. However, because BetaKO mice also showed reduced MafA, a key upstream regulator of Slc2a2, along with an increased -cell/{beta}-cell ratio and other secondary changes that could influence GLUT2 levels, the mechanism by which NRDC regulates Slc2a2 transcription remained unclear. Here, we demonstrate that NRDC controls Slc2a2 expression in a {beta}-cell autonomous and MafA-independent manner. By integrating publicly available ATAC-seq and ChIP-seq datasets, we identified four active enhancer regions around the murine Slc2a2 locus, two of which are evolutionarily conserved in human islets. Luciferase assays revealed that NRDC selectively controls the activity of a conserved enhancer located 39k bp downstream of the Slc2a2 transcriptional start site. Chromatin immunoprecipitation (ChIP) and re-ChIP assays further revealed that NRDC binds to this enhancer and is required for efficient recruitment of ISLET1, a transcription factor upstream of Slc2a2. These findings indicate that NRDC directly regulates Slc2a2 in addition to MafA, highlighting multifaceted roles of NRDC in pancreatic {beta}-cell gene regulation.