title: Heparan sulfate proteoglycans mediate the angiogenic activity of the vascular endothelial growth factor receptor-2 agonist gremlin.
abstract: OBJECTIVE
  Heparan sulfate proteoglycans (HSPGs) modulate the interaction of proangiogenic heparin-binding vascular endothelial growth factors (VEGFs) with signaling VEGF receptor-2 (VEGFR2) and neuropilin coreceptors in endothelial cells (ECs). The bone morphogenic protein antagonist gremlin is a proangiogenic ligand of VEGFR2, distinct from canonical VEGFs. Here we investigated the role of HSPGs in VEGFR2 interaction, signaling, and proangiogenic capacity of gremlin in ECs.
  
  
  RESULTS
  Surface plasmon resonance demonstrated that gremlin binds heparin and heparan sulfate, but not other glycosaminoglycans, via N-, 2-O, and 6-O-sulfated groups of the polysaccharide. Accordingly, gremlin binds HSPGs of the EC surface and extracellular matrix. Gremlin/HSPG interaction is prevented by free heparin and heparan sulfate digestion or undersulfation following EC treatment with heparinase II or sodium chlorate. However, at variance with canonical heparin-binding VEGFs, gremlin does not interact with neuropilin-1 coreceptor. On the other hand, HSPGs mediate VEGFR2 engagement and autophosphorylation, extracellular signaling-regulated kinase(1/2) and p38 mitogen-activated protein kinase activation, and consequent proangiogenic responses of ECs to gremlin. On this basis, we evaluated the gremlin-antagonist activity of a panel of chemically sulfated derivatives of the Escherichia coli K5 polysaccharide. The results demonstrate that the highly N,O-sulfated derivative K5-N,OS(H) binds gremlin with high potency, thus inhibiting VEGFR2 interaction and angiogenic activity in vitro and in vivo.
  
  
  CONCLUSIONS
  HSPGs act as functional gremlin coreceptors in ECs, affecting its productive interaction with VEGFR2 and angiogenic activity. This has allowed the identification of the biotechnological K5-N,OS(H) as a novel angiostatic gremlin antagonist.
authors.affiliation: Unit of General Pathology and Immunology, Department of Biomedical Sciences and Biotechnology, School of Medicine, University of Brescia, Brescia, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Chiodelli
authors.forename: Stefania
authors.initials: S
authors.lastname: Mitola
authors.forename: Cosetta
authors.initials: C
authors.lastname: Ravelli
authors.forename: Pasqua
authors.initials: P
authors.lastname: Oreste
authors.forename: Marco
authors.initials: M
authors.lastname: Rusnati
authors.forename: Marco
authors.initials: M
authors.lastname: Presta
mesh_terms: D000818:Animals; D016667:Bacterial Capsules / Q000494:pharmacology; D002417:Cattle; D002460:Cell Line; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D019812:Heparan Sulfate Proteoglycans / Q000378:metabolism*; D006493:Heparin / Q000378:metabolism; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism* / Q000494:pharmacology; D008024:Ligands; D023421:Models, Animal; D018919:Neovascularization, Physiologic / Q000187:drug effects / Q000502:physiology*; D039942:Neuropilin-1 / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000819:agonists*
chemical_list: C486399:GREM1 protein, human; D019812:Heparan Sulfate Proteoglycans; D036341:Intercellular Signaling Peptides and Proteins; D008024:Ligands; D039942:Neuropilin-1; C050673:capsular polysaccharide K5; D006493:Heparin; D040301:Vascular Endothelial Growth Factor Receptor-2