title: The C-terminal peptide of chondroadherin modulates cellular activity by selectively binding to heparan sulfate chains.
abstract: Chondroadherin, a leucine-rich repeat family member, contains a very C-terminal sequence CKFPTKRSKKAGRH(359), now shown to bind to heparin with a K(D) of 13 μm. This observation led us to investigate whether chondroadherin interacts via this C-terminal heparin-binding domain with glycosaminoglycan chains of proteoglycans at the cell surface. Cells were shown to bind this heparin-binding peptide in FACS analysis, and the interaction was shown to be with glycosaminoglycans because it was abolished when sulfation was inhibited by chlorate treatment of the cells. In separate experiments, heparin and heparan sulfate inhibited the peptide interaction in a dose-dependent manner. Using a human chondrosarcoma and a murine osteoblast cell line, heparan sulfate proteoglycans were identified as the cell surface receptors involved in the binding. Different binding syndecans were identified in the two different cell lines, indicating that the same protein core of a proteoglycan may have structural and functional differences in the attached heparan sulfate chains. Upon binding to coated peptide, cells spread, demonstrating engagement of the cytoskeleton, but no focal adhesion complex was formed. The number of cells adhering via their β(1) integrin receptor to collagen type II or chondroadherin was profoundly and rapidly enhanced by the addition of the heparin-binding peptide. The peptide added to the cells caused ERK phosphorylation, showing that it triggered intracellular signaling. The results show that heparan sulfate chains differ between various members of the proteoglycan families on a given cell, but also differ between the same proteoglycan on different cells with a potential for differential regulation of cellular activities.
authors.affiliation: Department of Clinical Sciences, Lund, Section of Rheumatology, Molecular Skeletal Biology, Biomedical Center C12, Lund University, SE-22184 Lund, Sweden.
authors.forename: Lisbet
authors.initials: L
authors.lastname: Haglund
authors.forename: Viveka
authors.initials: V
authors.lastname: Tillgren
authors.forename: Patrik
authors.initials: P
authors.lastname: Önnerfjord
authors.forename: Dick
authors.initials: D
authors.lastname: Heinegård
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002151:Calorimetry; D002460:Cell Line; D002846:Chromatography, Affinity; D017931:DNA Primers; D005109:Extracellular Matrix / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000737:chemistry / Q000378:metabolism*; D006497:Heparan Sulfate / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: D017931:DNA Primers; D016326:Extracellular Matrix Proteins; D006497:Heparan Sulfate; D011994:Recombinant Proteins; C088980:chondroadherin