Regulates myosin phosphatase activity. PP1 comprises a catalytic subunit, PPP1CA, PPP1CB or PPP1CC, and one or several targeting or regulatory subunits. PPP1R12C mediates binding to myosin. Interacts via its N-terminus with PPP1CB. Interacts with IL16. Interacts with the coiled-coil domain of MPRIP. Interacts with NOD2 (PubMed:27812135). Ubiquitously expressed. Highly expressed in heart. Phosphorylation at Thr-560 is essential for its interaction with PPP1CB. Although assigned as two separate genes (PPP1R12C and LENG3), it is probable that LENG3 does not exist by itself and is a part of the PPP1R12C gene. Unspliced mRNA.