Identification of an Adhesion Site within the Syndecan-4 Extracellular Protein Domain*
- From the Program in Cellular and Molecular Biology and Department of Pathology and Laboratory Medicine, University of Wisconsin-Madison, Madison, Wisconsin, 53706-1532
Abstract
The syndecan family of cell surface proteoglycans regulates cell adhesion and growth factor signaling by binding components of the extracellular matrix and growth factors. To date, all known ligand interactions are via the covalently attached glycosaminoglycan chains. To assay for potential extracellular interactions via the core proteins directly, the recombinant extracellular domain of syndecan-4 (S4ED), one of the four syndecan family members, was tested as a substratum for the attachment of mammalian cells. Human foreskin fibroblasts bind to mouse S4ED, and both mouse and chicken S4ED can block this binding, with 50% inhibition observed between 0.1 and 1 × 10−7 m. The extracellular domain of another syndecan family member, syndecan-1, fails to compete for cell binding to mouse S4ED. Amino acids 56–109 of the 120-amino acid mouse S4ED compete fully, suggesting that the cell binding domain is within this region. The ability of syndecan-4 to interact with molecules at the cell surface via its core protein as well as its glycosaminoglycan chains may uniquely regulate the formation of cell surface signaling complexes following engagement of this proteoglycan with its extracellular ligands.
Footnotes
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↵* This work was supported by Grant HD21881 from the National Institutes of Health.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 Pathology and Laboratory Medicine, University of Wisconsin-Madison, 1300 University Ave., Madison, WI 53706-1532. Tel.: 608-262-7577; Fax: 608-262-2327.
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↵1 The abbreviations used are: FGF, fibroblast growth factor; S4ED, syndecan-4 extracellular domain; mS4ED, mouse S4ED; cS4ED, chicken S4ED; mS1ED, mouse syndecan-1 extracellular domain; GST, glutathione-S-transferase; His, PET-30a vector-encoded His + S·Tag™ protein; DMEM, Dulbecco’s modified Eagle’s medium; HEPES/DMEM, HEPES-buffered DMEM (pH 7.4); BSA, bovine serum albumin; PCR, polymerase chain reaction.
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- Received February 20, 1997.
- Revision received March 18, 1997.
