AGRIN - AN EXTRACELLULAR-MATRIX HEPARAN-SULFATE PROTEOGLYCAN INVOLVEDIN CELL-INTERACTIONS AND SYNAPTOGENESIS

Recent studies have documented important roles for heparan sulfate pro teoglycans in the control of nervous system development. Agrin is an e xtracellular matrix protein identified and named based on its involvem ent in the aggregation of acetylcholine receptors (AChRs) during synap togenesis at the neuromuscular junction. Recent studies have demonstra ted that agrin is a large extracellular heparan sulfate proteoglycan, with a molecular mass in excess of 500 kDa and a protein core of 220 k Da. Emerging evidence indicates that agrin's function is not limited t o its role in AChR aggregation during synaptogenesis, as the majority of agrin expression occurs in the developing central nervous system, e specially in developing axonal tracts. This review examines recent stu dies suggesting a role for agrin in the regulation of cell-cell intera ctions, most notably by its ability to interact with the neural cell a dhesion molecule. In addition, other potential roles for the heparan s ulfate chains of agrin during nervous system development are explored.