Inhibits phosphatase activities of protein phosphatase 1 (PP1) and protein phosphatase 2A (PP2A) complexes. Highly expressed in cerebellum. Substrate for cGMP-dependent protein kinase. Phosphorylated by PRKG1 isoform alpha. Phosphorylation of Thr-68 and Thr-119 is required for its phosphatase activity (By similarity). Substrate for cGMP-dependent protein kinase.