Biological roles of dermatan sulphate proteoglycans

Dermatan sulphate-containing proteoglycans (DS-PGs) are widely distributed in the extracellular matrix of skin, sclera, tendon, cartilage and a variety of other connective tissues. Two species of dermatan sulphate proteoglycans, called DS-PGI and DS-PGII, have recently been isolated from mature bovine articular cartilages. In their monomeric forms, both DS-PGI and DS-PGII are polydisperse, have relative molecular masses (Mr) ranging from 80K to 140K, and possess protein cores with apparent Mr values of approximately 45K. DS-PGI readily self-associates whereas DS-PGII does not. Polyclonal and monoclonal antibodies against DS-PGII do not react with DS-PGI. DS-PGI and DS-PGII appear to possess different core proteins and represent two different species of dermatan sulphate proteoglycans. DS-PGs have dramatic effects on the biological functions of cells. For example, they inhibit the capacity of fibroblasts to adhere to a fibronectin substratum. BALB/c 3T3 cells were labelled with [3H]thymidine and plated onto dishes coated with plasma fibronectin, plasma fibronectin plus chondroitin sulphate proteoglycan (CS-PG, cartilage-specific proteoglycan monomer), or plasma fibronectin plus DS-PGs. In the absence of proteoglycan, approximately 55% of the cells were attached at 1 h. In the presence of CS-PG, cell attachment was slightly decreased. In the presence of DS-PGs, the adhesion of the fibroblasts to fibronectin was essentially abolished. Similar results were obtained if a plasma fibronectin substratum was preadsorbed with the DS-PGs and the DS-PGs were left in the attachment medium.