Poster Sessions

MOLBIO/BIOCHEM/BIOPHYS-5

Preeti Subramanian

P. Subramanian, M. Rapp, S. Locatelli-Hoops, S.P. Becerra

Mechanistic Insight into the Interaction of Pigment Epithelium-derived Factor and Its Receptor PEDF-R

Pigment epithelium-derived factor (PEDF) is a protein secreted by the retinal pigment epithelium (RPE) into the interphotoreceptor matrix where it acts on retinal cell survival. Recently, PEDF-R a novel membrane-linked lipase protein has been identified as a potential cell-surface receptor for PEDF. This newly identified protein is present in the surface of cells and has transmembrane topology. It specifically binds with high affinity to PEDF. It exhibits phospholipase A2 (PLA2) activity, which is stimulated by PEDF binding. In this study, we show that PEDF exhibited a concentration-dependent survival effect on R28 retinal cells upon induction of cell death by serum starvation. We demonstrate the presence of PEDF-R protein in the plasma membrane of R28 cells by western blotting. Furthermore, we found that R28 plasma membrane fractions exhibited in vitro PLA2 activity, which was stimulated by PEDF. Peptides from the extracellular loop region of PEDF-R were designed and two peptides, E4b and P1, specifically bound to PEDF by ligand blot. Most importantly, pre-incubation of PEDF with these peptides attenuated the survival effects of PEDF on R28 cells. In conclusion, these results demonstrate for the first time the role of PEDF-R in mediating the survival effects of PEDF on R28 cells.