Proteoglycans in the developing brain: New conceptual insights for old proteins

Proteoglycans are a heterogeneous class of proteins bearing sulfated glycos aminoglycans. Some of the proteoglycans have distinct core protein structur es, and others display similarities and thus may be grouped into families s uch as the syndecans, the glypicans, or the hyalectans (or lecticans). Prot eoglycans can be found in almost all tissues being present in the extracell ular matrix, on cellular surfaces, or in intracellular granules. In recent years, brain proteoglycans have attracted growing interest due to their hig hly regulated spatiotemporal expression during nervous system development a nd maturation. There is increasing evidence that different proteoglycans ac t as regulators of cell migration, axonal pathfinding, synaptogenesis, and structural plasticity. This review summarizes the most recent data on struc tures and functions of brain proteoglycans and focuses on new physiological concepts for their potential roles in the developing central nervous syste m.