A personal voyage through the proteoglycan field

The concept of “proteoglycans” as discrete molecules surfaced some 40years ago, out of previously muddled notions of the extracellular matrix. Core proteins were gradually recognized as molecular entities, distinct with regard to location, substitution with glycosaminoglycan (GAG) chains and biological function. This development is surveyed, with brief outline of methodological approaches, biosynthesis, and functional aspects. Special emphasis is given to the impact of genomics on the field. Some outstanding unresolved issues are emphasized, including regulation of GAG biosynthesis and the specificity of GAG-protein interactions. •Core proteins — determinants of glycosaminoglycan (GAG) type but not GAG structure•How is GAG structure controlled by the “GAGosome”?•How is GAG structure related to specific interactions with proteins?•Impact of genetics on the proteoglycan field