Characterization of the High Affinity Cell-binding Domain in the Cell Surface Proteoglycan Syndecan-4*
- 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 via their glycosaminoglycan chains and discrete domains of their core proteins. Core protein domains that are variable between syndecan family members may regulate syndecan-specific associations, thereby endowing individual syndecans with unique functions. A syndecan-4-specific domain has been identified in the extracellular syndecan-4 protein. This region mediates cell adhesion when provided as an artificial substratum and is localized within amino acids 56–109 of the recombinant extracellular protein domain of mouse syndecan-4 (mS4ED) (McFall, A. J., and Rapraeger, A. C. (1997) J. Biol. Chem. 272, 12901–12904). To characterize its interaction with the cell surface, radiolabeled ligand binding studies were performed. A single high affinity interaction, with a dissociation constant of 2 × 10−9 m, was observed between mS4ED and both human and mouse cells. Both chicken S4ED and mS4ED compete for this interaction, although they are only 34% identical within the cell-binding domain sequence. The extracellular protein domains of syndecan-1, -2, and -3, however, fail to compete. The interaction is also observed with native syndecan-4 shed from cell surfaces. Interestingly, the extracellular protein domain of syndecan-1 also mediates cell adhesion, suggesting a similar but discrete interaction for this family member.
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: 608-265-3301; E-mail: acraprae{at}facstaff.wisc.edu.
- Abbreviations:
- PKC
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protein kinase C
- mS1ED-mS4ED
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mouse syndecan-1 through -4 extracellular protein domains
- cS4ED
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chicken syndecan-4 extracellular domain
- GST
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glutathione S-transferase
- HEPES/DMEM
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HEPES-buffered Dulbecco’s modified Eagle’s medium
- BSA
-
bovine serum albumin
- PAGE
-
polyacrylamide gel electrophoresis.
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- Received May 7, 1998.
- Revision received July 22, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
