Binds actin and PPP1CA; thus inhibiting the protein phosphatase 1 (PP1) activity. Localized to the nuclear matrix-intermediate filament scaffold. Isoform 2 is also found in some cytoplasmic extensions. Abundantly expressed in brain. Also found in several tumors such as lung carcinomas, nervous tumors and HL-60 leukemia cells. Isoform 3 is the major form in U-937, GOTO and HL-60 leukemia cells. Down-regulated in HL-60 leukemia cells by RA, PMA and dimethyl sulfoxide. Belongs to the phosphatase and actin regulator family.