Protein Phosphatase 1, Regulatory Subunit 18 (PPP1R18)

Protein phosphatase-1 (PP1) interacts with regulatory subunits that target the enzyme to different cellular locations and change its activity toward specific substrates. Phostensin is a regulatory subunit that targets PP1 to F-actin cytoskeleton. RT-PCR ELISA detected highest expression in spleen, followed by lung, liver, and ovary. Moderate expression was detected in all other adult and fetal tissues and specific brain regions examined. Phostensin interacted with PP1-alpha in transfected 293T and COS-7 cells. Pull-down assays showed that mutations in the PP1-binding motif of phostensin disrupted its interaction with PP1-alpha. Immunofluorescence analysis of transfected MDCK cells showed colocalization of PP1-alpha with phostensin at adherens junctions, a region rich in F-actin cytoskeleton.