Pigment epithelium-derived factor (PEDF) prevents retinal cell death via PEDF Receptor (PEDF-R): identification of a functional ligand binding site.
J Biol Chem
; 288(33): 23928-42, 2013 Aug 16.
Article
em En
| MEDLINE
| ID: mdl-23818523
ABSTRACT
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-binding site on PEDF-R. PEDF bound the PEDF-R ectodomain L4 (Leu(159)-Met(325)) with affinity similar to the full-length PEDF-R (Met(1)-Leu(504)). Binding assays using synthetic peptides spanning L4 showed that PEDF selectively bound E5b (Ile(193)-Leu(232)) and P1 (Thr(210)-Leu(249)) peptides. Recombinant C-terminal truncated PEDF-R4 (Met(1)-Leu(232)) and internally truncated PEDF-R and PEDF-R4 (ΔHis(203)-Leu(232)) retained phospholipase activity of the full-length PEDF-R. However, PEDF-R polypeptides without the His(203)-Leu(232) region lost the PEDF affinity that stimulated their enzymatic activity. Cell surface labeling showed that PEDF-R is present in the plasma membranes of retina cells. Using siRNA to selectively knock down PEDF-R in retina cells, we demonstrated that PEDF-R is essential for PEDF-mediated cell survival and antiapoptotic activities. Furthermore, preincubation of PEDF with P1 and E5b peptides blocked the PEDF·PEDF-R-mediated retina cell survival activity, implying that peptide binding to PEDF excluded ligand-receptor interactions on the cell surface. Our findings establish that PEDF-R is required for the survival and antiapoptotic effects of PEDF on retina cells and has determinants for PEDF binding within its L4 ectodomain that are critical for enzymatic stimulation.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Retina
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Serpinas
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Receptores de Neuropeptídeos
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Proteínas do Olho
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Fatores de Crescimento Neural
Tipo de estudo:
Diagnostic_studies
/
Prognostic_studies
Limite:
Animals
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Humans
Idioma:
En
Ano de publicação:
2013
Tipo de documento:
Article