Fibulin-1 is a ligand for the C-type lectin domains of aggrecan and versican.
The aggregating proteoglycans (aggrecan, versican, neurocan, and brevican) are important components of many extracellular matrices. Their N-terminal globular domain binds to hyaluronan, but the function of their C-terminal region containing a C-type lectin domain is less clear. We now report that a 90-kDa protein copurifies with recombinant lectin domains from aggrecan and versican, but not from the brain-specific neurocan and brevican. Amino acid sequencing of tryptic peptides from this protein identified it as fibulin-1. This extracellular matrix glycoprotein is strongly expressed in tissues where versican is expressed (blood vessels, skin, and developing heart), and also expressed in developing cartilage and bone. It is thus likely to interact with these proteoglycans in vivo. Surface plasmon resonance measurements confirmed that aggrecan and versican lectin domains bind fibulin-1, whereas brevican and neurocan do not. As expected for a C-type lectin, the interactions with fibulin-1 are Ca2+-dependent, with KD values in the low nanomolar range. Using various deletion mutants, the binding site for aggrecan and versican lectin domains was mapped to the epidermal growth factor-like repeats in domain II of fibulin-1. No difference in affinity was found for deglycosylated fibulin-1, indicating that the proteoglycan C-type lectin domains bind to the protein part of fibulin-1.
Department of Cell and Molecular Biology, Section for Connective Tissue Biology, Lund University, P. O. Box 94, SE-221 00 Lund, Sweden. anders.aspberg@medlem.lu.se
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Aspberg
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Adam
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Kostka
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Timpl
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Heinegård
D053674:Aggrecans; D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D011508:Chondroitin Sulfate Proteoglycans / Q000737:chemistry / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000737:chemistry / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D007150:Immunohistochemistry; D037102:Lectins / Q000378:metabolism*; D037181:Lectins, C-Type; D008024:Ligands; D011485:Protein Binding; D011509:Proteoglycans / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D053675:Versicans
D053674:Aggrecans; D002135:Calcium-Binding Proteins; D011508:Chondroitin Sulfate Proteoglycans; D016326:Extracellular Matrix Proteins; D037102:Lectins; D037181:Lectins, C-Type; D008024:Ligands; D011509:Proteoglycans; D011994:Recombinant Proteins; C508322:VCAN protein, human; C060820:fibulin; D053675:Versicans; D004815:Epidermal Growth Factor; D002118:Calcium