ABSTRACT
Molecular components of the extracellular matrix (ECM) are critical for matrix stabilization, cellular differentiation, and tissue morphogenesis. Once thought to function only as the extracellular glue that primarily binds cells together, proteoglycans in the ECM carry out a diverse array of activities and can be grouped into fi ve functionally based families: (i) hyalectins (lecticans), which contain lectin-like carbohydrate-recognition domains (CRDs) and bind hyaluronan (HA); (ii) heparan sulfate (HS) proteoglycans that sequester growth factors via their HS chains; (iii) small leucine-rich proteoglycans (SLRPs) containing leucine-rich domains that interact with collagens and other ECM proteins; (iv) phosphacans that function primarily as receptor-like protein-tyrosine phosphatases; and (v) part-time proteoglycans that reside both on the cell surface and in the ECM. More than 40 cDNAs encoding proteoglycan core proteins have been discovered thus far [1]. For the sake of brevity, this chapter will focus only on the four lecticans that bind HA (Figure 15.1): Aggrecan, neurocan, brevican, and versican.
