Fibulin-1 Is a Ligand for the C-type Lectin Domains of Aggrecan and Versican*
- From the ‡Department of Cell and Molecular Biology, Section for Connective Tissue Biology, Lund University, P. O. Box 94, SE-221 00 Lund, Sweden and the ¶Max-Planck-Institut für Biochemie, D-82152 Martinsried, Germany
Abstract
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, withK D 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.
Footnotes
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↵* This work was supported by the Swedish Medical Research Council, Crafoord’s stiftelse, Greta och Johan Kocks stiftelser, Konung Gustaf V:s 80-Årsfond, Åke Wibergs stiftelse, AlfredÖsterlunds stiftelse, and the Deutsche Forschungsgemeinschaft (SFB 266).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵§ To whom correspondence should be addressed: Dept. of Cell and Molecular Biology, Section for Connective Tissue Biology, Lund University, P. O. Box 94, SE-221 00 Lund, Sweden. Tel.: 46-46-222-9587; Fax: 46-46-211-3417; E-mail: anders.aspberg@medkem.lu.se.
- Abbreviations:
- EGF
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epidermal growth factor
- rCLD
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recombinant C-type lectin domain
- PAGE
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polyacrylamide gel electrophoresis
- MALDI-TOF
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matrix-assisted laser desorption ionization-time of flight
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- Received March 24, 1998.
- Revision received April 21, 1999.
- The American Society for Biochemistry and Molecular Biology, Inc.
