Laminin Receptor Involvement in the Anti-angiogenic Activity of Pigment Epithelium-derived Factor

Abstract

Pigment epithelium-derived factor (PEDF) is a multifunctional protein with neurotrophic, anti-oxidative, and anti-inflammatory properties. It is also one of the most potent endogenous inhibitors of angiogenesis, playing an important role in restricting tumor growth, invasion, and metastasis. Studies show that PEDF binds to cell surface proteins, but little is known about how it exerts its effects. Recently, research identified phospholipase A 2 /nutrin/patatin-like phospholipase domaincontaining 2 as one PEDF receptor. To identify other receptors, we performed yeast two-hybrid screening using PEDF as bait and discovered that the non-integrin 37/67-kDa laminin receptor (LR) is another PEDF receptor. Co-immunoprecipitation, His tag pulldown, and surface plasmon resonance assays confirmed the interaction between PEDF and LR. Using the yeast two-hybrid method, we further restricted the LR-interacting domain on PEDF to a 34-amino acid (aa) peptide (aa 44 -77) and the PEDF-interacting domain on LR to a 91-aa fragment (aa 120 -210). A 25-mer peptide named P46 (aa 46 -70), derived from 34-mer, interacts with LR in surface plasmon resonance assays and binds to endothelial cell (EC) membranes. This peptide induces EC apoptosis and inhibits EC migration, tube-like network formation in vitro, and retinal angiogenesis ex vivo, like PEDF. Our results suggest that LR is a real PEDF receptor that mediates PEDF angiogenesis inhibition.Pigmented epithelium-derived factor (PEDF), 2 also known as SERPIN F1 and EPC1, is a 50-kDa serpin-like peptide. Although first identified in cultured pigment epithelial cells from fetal human retinas (1), we now know that liver, kidney, heart, testis, and lung tissues also express PEDF (2). PEDF influences many biological processes. It is anti-angiogenic, anti-tumorigenic, anti-inflammatory, anti-oxidative, neurotrophic, and neuroprotective, and it exhibits anti-vasopermeability properties (3-9). These diverse actions affect many cell types, including retinal cells (10), neuronal cells (11), endothelial cells (12), and hematopoietic stem cells (13). X-ray diffraction studies show that PEDF has an asymmetrical charge distribution (14). A high density of basic residues on one side of the molecule (positive) interact with heparin and glycosaminoglycans, whereas acidic residues on the opposite side (negative) interact with type-1 collagen (15)(16)(17)(18)(19)). Yet the mechanisms explaining the diverse biological activities of PEDF remain unclear.A ligand/receptor interaction at the cell membrane seemed likely, in addition to interactions within extracellular matrices, because of the diverse effects and ubiquitous expression of PEDF and the fact that most PEDF deposits remain within extracellular matrices (20). We suspected that distinct PEDF receptors elicit divergent signals to cause different biological effects. Indeed, evidence shows that PEDF binds at least two receptors: a 60-kDa receptor in ECs and an 80-kDa receptor in neuronal cells (21)(22)(23)(24). Research has identified two functional epi...

Phosphomimetic Mutants of Pigment Epithelium-Derived Factor with Enhanced Antiangiogenic Activity as Potent Anticancer Agents

“…The main obstacle on the way to full delineation of the signaling pathways involved in the antitumor activity of PEDF is the question of existence of a putative PEDF receptor, which is still obscure. A few candidates have been identified thus far, including extracellular matrix components (36,37), a phospholipase-linked membrane protein (38), and a laminin receptor (39). Thus, the observed enhanced activity of the phosphomimetic PEDF toward endothelial cells can have several explanations.…”

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

“…We have identified the novel gene PNPLA2 in the retina that encodes a lipase-linked cell membrane protein with high affinity for PEDF and termed it PEDF-R (26). Later, other PEDF-binding proteins were reported in endothelial and tumor cells (37/67-kDa non-integrin laminin receptor (27) and cell surface F 1 F 0 -ATP synthase (28,29)) and * This work was supported, in whole or in part, by the National Institutes of on ARPE-19 cells (LRP6, a Wnt co-receptor (30)). However, it is not yet known if PEDF-R is a functional receptor for PEDF activity on the retina.…”

Emetine Di-HCl Attenuates Type 1 Diabetes Mellitus in Mice

“…PEDF modulates target cell responses by signaling via a family of unrelated high affinity receptors. The anti-angiogenic activity of PEDF is mediated by the laminin receptor (19)(20)(21); low-density lipoprotein receptor-related protein 6 (LPR6; Wnt co-receptor) (22); and cell surface F 1 F 0 -ATP synthase (23). The macrophage stimulating (16) and neurotrophic activities (24) of PEDF are mediated by adipose mice were more than >200 mg/dL by d 7, and remained at that level thereafter ( Figure 1A).…”