Small Leucine-rich Proteoglycans: Prelude to a Function

A family of proteoglycans (PGs) originally known as “small proteoglycans” has recently been defined. The members of the family are decorin, biglycan, fibromodulin and lumican. All are indeed small for proteoglycans with core proteins of approximately 40kDa; they are made up of consecutive leucinerich repeats and carry only a few glycosaminoglycan chains. The best charcterized members of this group are decorin and biglycan. In vivo experiments indicate a role for small proteoglycans in adhesion, multiplication, differentiation and migration of cells and they have been shown to bind growth factors, various collagens and fibronectin. In this article, decorin will be used as the model for the small proteoglycans. Biosynthesis, function and regulation of gene expression will be examined.