Pigment Epithelium-derived Factor (PEDF) Prevents Retinal Cell Death via PEDF Receptor (PEDF-R)

Abstract

Background: PEDF has neurotrophic activity and interacts with PEDF-R, a membrane-linked lipase. Results: A PEDF-binding region of PEDF-R is required for PEDF-R enzymatic stimulation, and peptides derived from this region block PEDF⅐PEDF-R-mediated retinal survival activities. Conclusion: A ligand binding domain is identified in PEDF-R, a critical receptor for the survival activity of PEDF. Significance: The findings provide mechanistic insight into the survival activity of PEDF.

Small Retinoprotective Peptides Reveal a Receptor-binding Region on Pigment Epithelium-derived Factor

“…R28 cells (Gift from Gail Seigel, University of Buffalo) were cultured in DMEM with 10% FBS and 1% penicillin/streptomycin at 37°C and 5% CO 2 (23). Cell passages 50 -58 were used in experiments in this study.…”

“…Ligand Blot Binding Assay-Binding of fluorescently tagged PEDF or peptides to immobilized P1 peptide was assayed by ligand blot, as reported previously (23). P1 peptide (1 g) was immobilized on nitrocellulose by vacuum filtration using the convertible filtration manifold system (Invitrogen, Life Technologies).…”

“…Full-length His 6 / Xpress-tagged PEDF-R was synthesized in an in vitro translation system (yield of ϳ933 ng per 50 l of reaction) as described before (23). The 34-mer and 44-mer peptides chemically synthesized containing FITC at their N terminus end were used.…”

“…This novel protein encoded by PNPLA2 (patatin-like phospholipase domain containing family) is a membrane-linked lipase enzyme, which PEDF binding can stimulate (22). Plasma membranes of retina cells contain PEDF-R, which has affinity for PEDF and is essential for cytoprotective activity of PEDF (23). We have also mapped the ligand-binding domain (LBD) to an extracellular loop of the human PEDF-R (positions 203-232) and shown that peptides derived from this ectodomain act as soluble receptor fragments that block both PEDF/PEDF-R interactions and PEDF-mediating survival action (23).…”

“…Plasma membranes of retina cells contain PEDF-R, which has affinity for PEDF and is essential for cytoprotective activity of PEDF (23). We have also mapped the ligand-binding domain (LBD) to an extracellular loop of the human PEDF-R (positions 203-232) and shown that peptides derived from this ectodomain act as soluble receptor fragments that block both PEDF/PEDF-R interactions and PEDF-mediating survival action (23). However, the region of PEDF that binds PEDF-R remains to be identified.…”