Fig. 1.

Top panels: Schematic showing general arrangement GAGs on proteoglycans, including cartlidge PG, syndecan and hepatocyte HSPG. GAGs in proteoglycans can consist of long chains of keratan sulfates (KS), dermatan sulfate (DS), chondroitin sulfates (CS), or heparan sulfates (HS). PI, phosphatidyl inositol linkage to cell membrane in hepatocyte PG. Bottom panels: The core disaccharide unit of HS (sulfonated uronic acid and glucosamines) is shown on the left. On the right is depicted a canonical proteoglycan HS modification showing the disaccharide chains linked with a xylosyl group to a core protein. Sulfonation of HS chains is not uniform, and the blue boxes represent highly sulfated regions of HS chains that may interact strongly with protein ligands. Figure generated using BioRender (www.biorender.com).