Pigment Epithelium-derived Factor Receptor (PEDF-R): A Plasma Membrane-linked Phospholipase with PEDF Binding Affinity (original) (raw)
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Identification of a lipase-linked cell membrane receptor for pigment epithelium-derived factor
Journal of Biological …, 2006
Pigment epithelium-derived factor (PEDF) is an extracellular multifunctional protein belonging to the serpin superfamily with demonstrable neurotrophic, gliastatic, neuronotrophic, antiangiogenic, and antitumorigenic properties. We have previously provided biochemical evidence for high affinity PEDFbinding sites and proteins in plasma membranes of retina, retinoblastoma, and CNS cells. This study was designed to reveal a receptor involved in the biological activities of PEDF. Using a yeast two-hybrid screening, we identified a novel gene from pigment epithelium of the human retina that codes for a PEDFbinding partner, which we term PEDF-R. The derived polypeptide has putative transmembrane, intracellular and extracellular regions, and a phospholipase domain. Recently, PEDF-R (TTS-2.2/independent phospholipase A 2 (PLA 2 ) and mouse desnutrin/ATGL) has been described in adipose cells as a member of the new calcium-independent PLA 2 /nutrin/patatin-like phospholipase domain-containing 2 (PNPLA2) family that possesses triglyceride lipase and acylglycerol transacylase activities. Here we describe the PEDF-R gene expression in the retina and its heterologous expression by bacterial and eukaryotic systems, and we demonstrate that its protein product has specific and high binding affinity for PEDF, has a potent phospholipase A 2 activity that liberates fatty acids, and is associated with eukaryotic cell membranes. Most importantly, PEDF binding stimulates the enzymatic phospholipase A 2 activity of PEDF-R. In conclusion, we have identified a novel PEDF-R gene in the retina for a phospholipase-linked membrane protein with high affinity for PEDF, suggesting a molecular pathway by which ligand/receptor interaction on the cell surface could generate a cellular signal.
Journal of Biological Chemistry, 2013
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. The extracellular pigment epithelium-derived factor (PEDF) displays retina survival activity by interacting with receptor proteins on cell surfaces. We have previously reported that PEDF binds and stimulates PEDF receptor (PEDF-R), a transmembrane phospholipase. However, the PEDF binding site of PEDF-R and its involvement in survival activity have not been identified. The purpose of this work is to identify a biologically relevant ligand
PurposeTo examine the contribution of PEDF-R to the phagocytosis process. Previously, we identified PEDF-R, the protein encoded by thePNPLA2gene, as a phospholipase A2 in the retinal pigment epithelium (RPE). During phagocytosis, RPE cells ingest abundant phospholipids and protein in the form of photoreceptor outer segment (POS) tips, which are then hydrolyzed. The role of PEDF-R in RPE phagocytosis is not known.MethodsMice in whichPNPLA2was conditionally knocked out in the RPE were generated (cKO). Mouse RPE/choroid explants were cultured. Human ARPE-19 cells were transfected with siPNPLA2silencing duplexes. POS were isolated from bovine retinas. The phospholipase A2 inhibitor bromoenol lactone was used. Transmission electron microscopy, immunofluorescence, lipid labeling, pulse-chase experiments, western blots, and free fatty acid and β-hydroxybutyrate assays were performed.ResultsThe RPE of the cKO mice accumulated lipids as well as more abundant and larger rhodopsin particles co...
2016
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. The extracellular pigment epithelium-derived factor (PEDF) displays retina survival activity by interacting with receptor proteins on cell surfaces. We have previously reported that PEDF binds and stimulates PEDF receptor (PEDF-R), a transmembrane phospholipase. However, the PEDF binding site of PEDF-R and its involvement in survival activity have not been identified. The purpose of this work is to identify a biologically relevant ligand
Pigment Epithelium-Derived Factor (PEDF) in the Retina
Retinal Degenerative Diseases and Experimental Therapy, 1999
The pedf gene is closely linked to an autosomal-dominant locus for retinitis pigmentosa, suggesting that PEDF could be a survival factor for photoreceptors. We have investigated this possibility by injecting PEDF into the eyes of homozygous retinal degeneration (rd) and retinal degeneration slow (rds) mice, two mutants displaying apoptotic photoreceptor loss. This procedure resulted in a transient delay of photoreceptor loss in the rd mouse and a reduction in apoptotic photoreceptor profiles in the rds mouse. We conclude that PEDF can act as a survival-promoting factor for photoreceptors in vivo and could potentially be useful for the treatment of photoreceptor diseases.
Experimental Eye Research, 2009
Keywords: calcium-independent phospholipase A 2 retinal pigment epithelium cell proliferation proliferative vitreoretinopathy a b s t r a c t Calcium-independent phospholipase A 2 , group VIA (iPLA 2 -VIA) is involved in cell proliferation. This study aimed to evaluate the role of iPLA 2 -VIA in retinal pigment epithelium (RPE) cell proliferation and in retinal diseases involving RPE proliferation. A human RPE cell line (ARPE-19) was used to explore this role in vitro. Proliferating ARPE-19 cells had increased expression and activity of iPLA 2 -VIA. iPLA 2 -VIA was found in the nuclei of proliferating ARPE-19 cells, whereas in confluent ARPE-19 cells, with limited proliferation, iPLA 2 -VIA was primarily found in the cytosol. Inhibition of iPLA 2 -VIA decreased the rate of proliferation, whereas over expression of iPLA 2 -VIA increased the rate of proliferation. Using an experimental porcine model of RPE proliferation we demonstrated significant nuclear upregulation of iPLA 2 -VIA in proliferating RPE cells in vivo. We furthermore evaluated the expression of iPLA 2 -VIA in proliferative vitreoretinopathy (PVR). PVR membranes revealed nuclear expression of iPLA 2 -VIA in the RPE cells which had migrated and participated in the formation of the membranes. Overall, the present results point to an important role of iPLA 2 -VIA in the regulation of RPE proliferation suggesting that iPLA 2 -VIA may be considered as a possible pharmaceutical target in retinal diseases involving RPE proliferation and migration.
Journal of Biological Chemistry, 1999
Pigment epithelium-derived factor (PEDF) has neuronal differentiation and survival activity on retinoblastoma and cerebellar granule (CG) cells. Here, we investigated the presence of PEDF receptors on retinoblastoma Y-79 and CG cells. PEDF radiolabeled with l25 I remained biologically active and was used for radioligand binding analysis. The binding was saturable and specific to a single class of receptors on both cells and with similar affinities (K d ؍ 1.7-3.6 nM, B max ؍ 0.5-2.7 ؋ 10 5 sites/Y-79 cell; and K d ؍ 3.2 nM, B max ؍ 1.1 ؋ 10 3 sites/CG cell). A polyclonal antiserum to PEDF, previously shown to block the PEDF neurotrophic activity, prevented the 125 I-PEDF binding. We designed two peptides from a region previously shown to confer the neurotrophic property to human PEDF, synthetic peptides 34-mer (positions 44-77) and 44-mer (positions 78-121). Only peptide 44-mer competed for the binding to Y-79 cell receptors (EC 50 ؍ 5 nM) and exhibited neuronal differentiating activity. PEDF affinity column chromatography of membrane proteins from both cell types revealed a PEDF-binding protein of ϳ80 kDa. These results are the first demonstration of a PEDF-binding protein with characteristics of a PEDF receptor and suggest that the region comprising amino acid positions 78-121 of PEDF might be involved in ligand-receptor interactions.
PEDF and Derived Peptides Prevent Apoptosis and Promote Differentiation of Retinal Photoreceptors
Pigment epithelium-derived factor (PEDF) is a cytoprotective protein for the retina. We hypothesize that this protein acts on neuronal survival and differentiation of photoreceptor cells in culture. The purpose of the present study was to evaluate the neurotrophic effects of PEDF and its fragments in an in vitro model of cultured primary retinal neurons that die spontaneously in the absence of trophic factors. Results show that PEDF protected photoreceptor precursors from apoptosis, preserved mitochondrial function and promoted polarization of opsin enhancing their developmental process, as well as induced neurite outgrowth in amacrine neurons. These effects were abolished by an inhibitor of the PEDF receptor or receptor-derived peptides that block ligand/receptor interactions. While all the activities were specifically conferred by short peptide fragments (17 amino acid residues) derived from the PEDF neurotrophic domain, no effects were triggered by peptides from the PEDF antiangi...
1999
Pigment epithelium-derived factor (PEDF) is a member of the serine protease inhibitor superfamily produced by retinal pigment epithelial cells in the developing and adult retina. In vitro, it induces neuronal differentiation of retinoblastoma cells and promotes survival of cerebellar granule neurons. The pedf gene is closely linked to an autosomal-dominant locus for retinitis pigmentosa, suggesting that PEDF could be a survival factor for photoreceptors. We have investigated this possibility by injecting PEDF into the eyes of homozygous retinal degeneration (rd) and retinal degeneration slow (rds) mice, two mutants displaying apoptotic photoreceptor loss. This procedure resulted in a transient delay of photoreceptor loss in the rd mouse and a reduction in apoptotic photoreceptor profiles in the rds mouse. We conclude that PEDF can act as a survival-promoting factor for photoreceptors in vivo and could potentially be useful for the treatment of photoreceptor diseases. 1999 Academic Press
The Ochsner journal, 2008
Neuroprotectin D1 is a stereospecific cytoprotective messenger synthesized from docosahexaenoic acid in retinal pigment epithelial cells challenged by oxidative stress. A key step in neuroprotectin D1 synthesis is to define how growth factors may modulate its formation and its bioavailability. Here we have explored the action of pigment epithelium derived factor, a neurotrophin made in retinal pigment epithelial cells, on neuroprotectin D1. ARPE-19 cells were serum starved and exposed to TNFα/H(2)O(2) in the presence and absence of pigment epithelium derived factor (10 mg/mL). Cells and incubation media were collected. LC-PDA-MS-MS-based lipidomic analysis was used to identify and quantitate neuroprotectin D1. Immunostaining for BCLxL was performed. Oxidative stress promotes increases in neuroprotectin D1 levels in ARPE-19 cells, showing a rapid increase up to 6 hrs of incubation of 12 folds measured on cell pellets. Cell media, on the other hand, show time dependent accumulation of...