Characterization of the expression, localization, and secretion of PANDER in α-cells

The novel islet-specific protein PANcreatic DERived Factor (PANDER; FAM3B) has been extensively characterized with respect to the β-cell, and these studies suggest a potential function for PANDER in the regulation of glucose homeostasis. Little is known regarding PANDER in pancreatic α-cells, which are critically involved in maintaining euglycemia. Here we present the first report elucidating the expression and regulation of PANDER within the α-cell. Pander mRNA and protein are detected in α-cells, with primary localization to a glucagon-negative granular cytosolic compartment. PANDER secretion from α-cells is nutritionally and hormonally regulated by l-arginine and insulin, demonstrating similarities and differences with glucagon. Signaling via the insulin receptor (IR) through the PI3K and Akt/PKB node is required for insulin-stimulated PANDER release. The separate localization of PANDER and glucagon is consistent with their differential regulation, and the effect of insulin suggests a paracrine/endocrine effect on PANDER release. This provides further insight into the potential glucose-regulatory role of PANDER.