Alpha-endosulfine (ENSA),a member of the endosulfine family, is also known as ARPP-19e,which is widely expressed with high levels in skeletal muscle and brain and lower levels in the pancreas. ENSA is a protein phosphatase inhibitor that specifically inhibits protein phosphatase 2A (PP2A) during mitosis. When phosphorylated at Ser-67 during mitosis, ENSA is able to specifically interact with PPP2R2D (PR55-delta) and inhibit its activity, leading to inactivation of PP2A, an essential condition to keep cyclin-B1-CDK1 activity high during M phase (By similarity). ENSA 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.
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