Novel roles of SUMO in pancreatic β-cells: thinking outside the nucleus

The endocrine pancreas is critically important in the regulation of energy metabolism, with defective insulin secretion from pancreatic islet beta-cells a major contributing factor to the development of type 2 diabetes. Small ubiquitin-like modifier (SUMO) proteins have been demonstrated to covalently modify a wide range of target proteins, mediating a broad range of cellular processes. While the effects of SUMOylation on beta-cell gene transcription have been previously reviewed, recent reports indicate roles for SUMO outside of the nucleus. In this review we shall focus on the reported non-nuclear roles of SUMOylation in the regulation of beta-cells, including SUMOylation as a novel signaling pathway in the acute regulation of insulin secretion.