Molecular interactions of syndecans during development

The syndecans, cell surface heparan sulfate proteoglycans (HSPGs), bind num erous ligands via their HS glycosaminoglycan chains. The response to this b inding is flavored by the identity of the core protein that bears the HS ch ains. Each of the syndecan core proteins has a short cytoplasmic domain tha t binds cytosolic regulatory factors. The syndecans also contain highly con served transmembrane domain and extra-cellular domains for which important activities are slowly emerging. These protein domains, which will be the fo cus of this review, localize the syndecan to sites at the cell surface duri ng development where they collaborate with other receptors to regulate sign aling and cytoskeletal organization.