The syndecans are transmembrane heparan sulfate (HS) proteoglycans expressed on all adherent cells (Bernfield et al. 1999; Rapraeger and Ott 1998). A family of four, they have diverse functions ranging from participation in cell–cell adhesion, regulation of the signaling of HS binding growth factors, and organization of cell–matrix adhesion and signaling. A paper published in this issue of The Journal of Cell Biology (Iba et al. 2000) provides novel information on the specificity of syndecans in carrying out the latter function.
The syndecan core proteins have several important domains, although much remains to be learned about their respective functions (Fig. 1; Bernfield et al. 1999; Rapraeger and Ott 1998). The syndecans may function with several types of receptors. They are expressed at cell–cell adhesion sites (Fig. 2 A), e.g.,...
