Binding of fibronectin to syndecan involves the interaction of fibronectin’s carboxyl- terminal heparin-binding domain with heparan sulfate glycosaminoglycan chains on syndecan

The interaction of cells with the extracellular matrix is important in regulating cell growth, differentiation, migration and survival (Hynes, 1990). Integrins are a major class of transmembrane receptors that mediate cell adhesion to fibronectin (Hynes, 1992; Pytela et al., 1985) as well as to other extracellular matrix proteins (Hynes, 1992; Ruoslahti, 1988; Yamada, 1989). Binding of extracellular matrix proteins to integrins leads to the generation of intracellular signals, many of which are similar to intracellular signals generated by growth factor stimulation (Assoian, 1997; Juliano, 1996; Schwartz, 1997). Integrin-extracellular matrix interactions are also important for cell survival, as disruption of integrinmediated attachment to the extracellular matrix induces apoptosis in epithelial and endothelial cells (Frisch and Francis, 1994; Meredith et al., 1993; Ruoslahti and Reed, 1994). Integrins and integrin-dependent signalling events also regulate the deposition of fibronectin into the extracellular matrix (Giancotti and Ruoslahti, 1990; Wu et al., 1993; Wu et al., 1998). Fibronectin also binds to cell surface proteoglycans, including syndecans (Carey, 1997; Saunders and Bernfield, 1988) and CD44 (Naor et al., 1997). Binding of fibronectin to syndecan involves the interaction of fibronectin’s carboxylterminal heparin-binding domain with heparan sulfate glycosaminoglycan chains on syndecan (Saunders and Bernfield, 1988). Much data have suggested that the heparinbinding domain of fibronectin contributes to cell spreading and stress fiber formation in a variety of cell types (Bloom et al., 1999; Izzard et al., 1986; Woods et al., 1986). The addition of heparin-binding fragments of fibronectin in solution or 4287 Journal of Cell Science 113, 4287-4299 (2000) Printed in Great Britain © The Company of Biologists Limited 2000 JCS1610