Aggrecan, versican, and neurocan are members of the family of hyaluronic acid-binding proteoglycans and therefore each contains hyaluronic acid binding regions, Ig-like domains, EGF like domains, lectin-like domains, and complement regulatory-like domains. Phosphacan is distinct; it contains a region of similarity to carbonic anhydrase, a fibronectin type III domain, and is a splice variant of the transmembrane protein receptor tyrosine phosphatase equivalent to its extracellular portion.
Although aggrecan was traditionally thought of as a cartilage proteoglycan and neurocan and phosphacan were thought of as neural proteoglycans, recent studies indicate that all four of these proteoglycans have broad yet distinctive distribution patterns inearly embryos. The presence of these proteoglycans has not been carefully examined in adult tissue beyond the expected sites. These proteoglycans are anti-adhesion molecules and are capable of inhibiting both cell-ECM and cell-cell adhesion.