Endosulfine alpha, also known as ENSA, belongs to the endosulfine family. It is a highly conserved cAMP-regulated phosphoprotein (ARPP) family. Endosulfine alpha is widely expressed with high levels in skeletal muscle and brain and lower levels in the pancreas. As a protein phosphatase inhibitor, ENSA specifically inhibits protein phosphatase 2A (PP2A) during mitosis. When phosphorylated at Ser-67 during mitosis, specifically interacts with PPP2R2D (PR55-delta) and inhibits its activity, leading to inactivation of PP2A, an essential condition to keep cyclin-B1-CDK1 activity high during M phase By similarity. Endosulfine alpha also acts as a stimulator of insulin secretion by interacting with sulfonylurea receptor (ABCC8), thereby preventing sulfonylurea from binding to its receptor and reducing K(ATP) channel currents.
