title: The antiangiogenic effect of thrombospondin-2 is mediated by CD36 and modulated by histidine-rich glycoprotein.
abstract: Thrombospondins-1 and -2 (TSP-1, TSP-2) are matricellular glycoproteins with potent antiangiogenic activity. We have previously shown that the antiangiogenic activity of TSP-1 is mediated by the interaction of the type I repeats (TSR) with the receptor CD36, although other domains of TSP-1 have also been implicated. We now show that the antiangiogenic activity of TSP-2, which contains three TSRs but, unlike TSP-1, lacks the capacity to activate TGF-beta, is similarly dependent on CD36. Using the corneal pocket assay we found that TSP-2 did not inhibit bFGF-induced angiogenesis in CD36 null mice. We then demonstrated that (125)[I]-TSP-2 bound to murine macrophages and that binding was diminished by 70% by anti-CD36 antibody or by using cells from CD36 null animals. Solid-phase binding studies revealed that (125)[I]-TSP-2 bound to CD36/glutathione-S-transferase (GST) fusion proteins encoding the region spanning amino acids 93-120, but not amino acids 298-439. This 93-120 amino acid region, previously identified as the TSP-1 binding site, is homologous to domains on other TSP binding proteins, such as LIMP-2 and histidine-rich glycoprotein (HRGP). Finally, we showed with an immunoabsorbent binding assay that TSP-2 bound HRGP with high affinity and that HRGP blocked the antiangiogenic activity of TSP-2, acting like a "decoy" receptor. These data suggest that modulation of the TSR/CD36 system may play an important role in the regulation of the angiogenic "switch," and may provide a target for therapeutic interventions.
authors.affiliation: Division of Hematology, Department of Medicine, Weill Medical College of Cornell University, New York, NY, USA.
authors.forename: R
authors.initials: R
authors.lastname: Simantov
authors.forename: M
authors.initials: M
authors.lastname: Febbraio
authors.forename: R L
authors.initials: RL
authors.lastname: Silverstein
mesh_terms: D020533:Angiogenesis Inhibitors / Q000494:pharmacology; D000818:Animals; D018955:CD36 Antigens / Q000737:chemistry / Q000494:pharmacology*; D015815:Cell Adhesion Molecules / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D046911:Macromolecular Substances / Q000737:chemistry; D008264:Macrophages / Q000378:metabolism; D017737:Macrophages, Peritoneal / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009389:Neovascularization, Pathologic; D010455:Peptides / Q000737:chemistry; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry*; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D013696:Temperature; D019699:Thrombospondins / Q000737:chemistry / Q000494:pharmacology*; D013997:Time Factors; D000099053:Histidine-Rich Glycoprotein; D000099262:Thrombospondin 2
chemical_list: D020533:Angiogenesis Inhibitors; D018955:CD36 Antigens; D015815:Cell Adhesion Molecules; D016222:Fibroblast Growth Factor 2; D005982:Glutathione Transferase; D046911:Macromolecular Substances; D010455:Peptides; D010980:Platelet Membrane Glycoproteins; D011506:Proteins; D011993:Recombinant Fusion Proteins; D019699:Thrombospondins; D000099053:Histidine-Rich Glycoprotein; D000099262:Thrombospondin 2