title: Glycosaminoglycans in human retinoblastoma cells: heparan sulfate, a modulator of the pigment epithelium-derived factor-receptor interactions.
abstract: BACKGROUND
  Pigment epithelium-derived factor (PEDF) has binding affinity for cell-surface receptors in retinoblastoma cells and for glycosaminoglycans. We investigated the effects of glycosaminoglycans on PEDF-receptor interactions.
  
  
  RESULTS
  125I-PEDF formed complexes with protease-resistant components of medium conditioned by human retinoblastoma Y-79 cells. Using specific glycosaminoglycan degrading enzymes in spectrophotometric assays and PEDF-affinity chromatography, we detected heparin and heparan sulfate-like glycosaminoglycans in the Y-79 conditioned media, which had binding affinity for PEDF. The Y-79 conditioned media significantly enhanced the binding of 125I-PEDF to Y-79 cell-surface receptors. However, enzymatic and chemical depletion of sulfated glycosaminoglycans from the Y-79 cell cultures by heparitinase and chlorate treatments decreased the degree of 125I-PEDF binding to cell-surface receptors.
  
  
  CONCLUSIONS
  These data indicate that retinoblastoma cells secrete heparin/heparan sulfate with binding affinity for PEDF, which may be important in efficient cell-surface receptor binding.
authors.affiliation: Laboratory of Retinal cell and Molecular Biology, National Eye Institute, Bethesda, MD 20892, USA. onvalale@lg.ehu.es
authors.forename: Elena M
authors.initials: EM
authors.lastname: Alberdi
authors.forename: John E
authors.initials: JE
authors.lastname: Weldon
authors.forename: S Patricia
authors.initials: SP
authors.lastname: Becerra
mesh_terms: D002704:Chlorates / Q000494:pharmacology; D017077:Culture Media, Conditioned / Q000737:chemistry; D006025:Glycosaminoglycans / Q000378:metabolism / Q000494:pharmacology*; D006493:Heparin / Q000378:metabolism; D006497:Heparan Sulfate / Q000378:metabolism*; D006801:Humans; D007457:Iodine Radioisotopes / Q000378:metabolism / Q000494:pharmacology; D008190:Lyases / Q000494:pharmacology; D010857:Pigment Epithelium of Eye / Q000187:drug effects; D011956:Receptors, Cell Surface / Q000378:metabolism; D018013:Receptors, Neuropeptide / Q000378:metabolism*; D019572:Retinal Neoplasms / Q000737:chemistry* / Q000378:metabolism / Q000473:pathology*; D012175:Retinoblastoma / Q000737:chemistry* / Q000378:metabolism / Q000473:pathology*; D014407:Tumor Cells, Cultured
chemical_list: D002704:Chlorates; D017077:Culture Media, Conditioned; D006025:Glycosaminoglycans; D006493:Heparin; D006497:Heparan Sulfate; D007457:Iodine Radioisotopes; D008190:Lyases; D011956:Receptors, Cell Surface; D018013:Receptors, Neuropeptide; C400531:pigment epithelium-derived factor receptor