Syndecan: Regulator of Cell Morphology and Growth Factor Action at the Cell-matrix Interface.

Abstract

Syndecans are family of four cell surface proteoglycans with conserved plasma membrane and cytoplasmic domains. The ectodomains contain convalently linked glycosaminogly can chains which mainly consist of heparan sulfate (HS) but also of chondroitin sulfate (CS). The prototype of syndecan family, syndecan-I, has been shown to bind selectively several extracellular matrix molecules via its HS chains. It can simultaneously bind also heparin binding growth factors and predict the site of growth promotion by immoblizing the tyrosine kinase receptor complex to site of syndecan-matrix interaction. Besides growth promotion syndecan also participates in the regulation of cell morphology by supporting the organization of cytoskeletal elements of epithelial cells. This type of regulation could be important for normal maintenance of epithelial morphology because syndecan expression has been shown to decline or to be lost in several transformed epithelial cell. Binding of two types of extracellular effector molecules by HS chains has provided for syndecan an unique way to participate in the regulation of cell growth and morphology, and indicates the importance of carbohydrate studies in cell biology.