title: Binding and degradation of thrombospondin-1 mediated through heparan sulphate proteoglycans and low-density-lipoprotein receptor-related protein: localization of the functional activity to the trimeric N-terminal heparin-binding region of thrombospondin-1.
abstract: Thrombospondin-1 (TSP-1) is a multimodular trimeric protein involved in cell adhesion, motility and growth. TSP-1 binds to cells and is internalized and degraded in a process that requires the presence of heparan sulphate proteoglycan; the process is inhibited by heparin or receptor-associated protein (RAP), an antagonist of the low-density-lipoprotein receptor (LDLR) family. We characterized the attributes of TSP-1 that mediate the process. TSP277, which is truncated at Gln-277 of TSP-1 and contains the heparin-binding domain and the heptad repeat region that mediates trimerization, bound to and was degraded by a variety of cells with kinetics similar to those of the binding and degradation of intact TSP-1. Degradation of TSP277 was inhibited by heparin or RAP with dose responses similar to those for inhibition of degradation of TSP-1. Binding and degradation of TSP277 were decreased in Chinese hamster ovary cells lacking heparan sulphate. These results indicate that the N-terminal heparin-binding domain in a trivalent configuration is sufficient to mediate binding and degradation of TSP-1 via the proteoglycan-LDLR family pathway.
authors.affiliation: Department of Biomolecular Chemistry, University of Wisconsin-Madison 53706, USA.
authors.forename: H
authors.initials: H
authors.lastname: Chen
authors.forename: J
authors.initials: J
authors.lastname: Sottile
authors.forename: D K
authors.initials: DK
authors.lastname: Strickland
authors.forename: D F
authors.initials: DF
authors.lastname: Mosher
mesh_terms: D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D002478:Cells, Cultured; D006224:Cricetinae; D019812:Heparan Sulfate Proteoglycans; D006493:Heparin / Q000378:metabolism; D006497:Heparan Sulfate / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D011509:Proteoglycans / Q000378:metabolism*; D011971:Receptors, Immunologic / Q000378:metabolism*; D011973:Receptors, LDL / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019699:Thrombospondins
chemical_list: D019812:Heparan Sulfate Proteoglycans; D006493:Heparin; D006497:Heparan Sulfate; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D008562:Membrane Glycoproteins; D010446:Peptide Fragments; D011509:Proteoglycans; D011971:Receptors, Immunologic; D011973:Receptors, LDL; D011994:Recombinant Proteins; D019699:Thrombospondins