title: The protein phosphatase-1 targeting subunit TIMAP regulates LAMR1 phosphorylation.
abstract: TIMAP is a prenylated endothelial cell protein with a domain structure that predicts it to be a protein phosphatase-1 (PP-1) regulatory subunit. We found that TIMAP interacts with the 37/67 kDa laminin receptor (LAMR1) in yeast two-hybrid assays. In endothelial cells, endogenous TIMAP and LAMR1 co-immunoprecipitated and co-localized at the plasma membrane. TIMAP amino acids 261-290, representing the fourth ankyrin repeat of TIMAP, are necessary and sufficient for the interaction. In MDCK cells, lacking endogenous TIMAP, overexpression of full-length TIMAP, but not TIMAP deleted in the fourth ankyrin domain, allowed co-immunoprecipitation with LAMR1. PP-1 co-precipitated with overexpressed and endogenous TIMAP in MDCK and endothelial cells, respectively. In MDCK cells, PP-1 associated with LAMR1 in the presence, but not in the absence, of TIMAP. LAMR1 was a substrate for PP-1 in vitro, and in MDCK cells its phosphorylation was abrogated by expression of full-length TIMAP but not by TIMAP deficient in the fourth ankyrin domain. Hence, TIMAP targets PP-1 to LAMR1, and LAMR1 is a TIMAP-dependent PP-1 substrate.
authors.affiliation: Department of Medicine, The Albert Einstein College of Medicine, Bronx, NY, USA.
authors.forename: Kwanghee
authors.initials: K
authors.lastname: Kim
authors.forename: Laiji
authors.initials: L
authors.lastname: Li
authors.forename: Kathy
authors.initials: K
authors.lastname: Kozlowski
authors.forename: Hyeon-Sook
authors.initials: HS
authors.lastname: Suh
authors.forename: Wangsen
authors.initials: W
authors.lastname: Cao
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Ballermann
mesh_terms: D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D004285:Dogs; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D014176:Protein Biosynthesis; D054645:Protein Phosphatase 1; D021122:Protein Subunits / Q000378:metabolism*; D021381:Protein Transport; D017474:Receptors, Laminin / Q000235:genetics / Q000378:metabolism*
chemical_list: D021122:Protein Subunits; D017474:Receptors, Laminin; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1