Localization of diacylglycerol kinase ζ in rat pancreatic islet cells under normal and streptozotocin-induced stress conditions

Abstract

Summary. The pancreas comprises exocrine and endocrine portions, the latter of which is a glucose-responsive tissue that secretes hormones in response to serum glucose levels. One pathway implicated in the regulatory mechanism of this gland is the phosphoinositide (PI) cycle, which generates second messengers. Diacylglycerol (DG), the major second messenger in the PI signaling cascade, is catalyzed by the diacylglycerol kinase (DGK) family. We previously described characteristic expression and localization patterns of DGKs in various organs under pathophysiological conditions. Nevertheless, little is known about the characteristics and morphological aspects of this enzyme family in the pancreas. This study was conducted to investigate the pancreas, specifically the expression and localization of the DGK family. RT-PCR analysis reveals that DGKζ is the major isozyme in the pancreas. Additionally, we show that DGKζ is expressed in pancreatic islet cells, but not in the exocrine cells. It localizes predominantly to the nuclei of α-, β-, and δ-cells. We found further that DGKζ translocates from the nucleus to the cytoplasm in β-cells in response to a β-cell-selective toxin streptozotocin (STZ) and that it disappears over time. These findings will substantiate and extend our understanding of the functional roles of DGKζ in pancreatic islet cells.