or 12F3-15F3 [70–72], respectively. Syndecans act as co-receptors to modulate integrin-mediated cell–matrix adhesion [73], and distinct signal-transduction events appear to follow syndecan ligation by heparin-binding sites in matrix molecules [22]. CHO cells that lack glycosaminoglycan synthesis poorly assemble fibronectin [74]. Cells lacking syndecan-2 are deficient in a5b1- mediated attachment to fibronectin [75], and cells expressing syndecan-2 without the C-terminal 14 amino acids of the cytoplasmic domain do not assemble fibronectin into a fibrillar matrix [72]. The effect of uPAR on fibronectin cell adhesion also appears to involve a5b1, so that a5b1 recognizes a site in the 12F3-15F3 region under the influence of uPAR [70]. 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