The protein phosphatase-1 targeting subunit TIMAP regulates LAMR1 phosphorylation.
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.
Kim
Kwanghee
K
Department of Medicine, The Albert Einstein College of Medicine, Bronx, NY, USA.
Li
Laiji
L
Kozlowski
Kathy
K
Suh
Hyeon-Sook
HS
Cao
Wangsen
W
Ballermann
Barbara J
BJ
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*
D021122:Protein Subunits; D017474:Receptors, Laminin; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1