Protein phosphatase inhibitor that specifically inhibits protein phosphatase 2A (PP2A) during mitosis. When phosphorylated at Ser-62 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. May indirectly enhance GAP-43 expression. Interacts (when phosphorylated at Ser-62) with PPP2R2D (By similarity). Interacts with SNCA. Expression may be regulated by miR-451. Phosphorylation at Ser-62 by GWL during mitosis is essential for interaction with PPP2R2D (PR55-delta) and subsequent inactivation of PP2A (By similarity). Phosphorylated by PKA. Belongs to the endosulfine family.