UC San Diego

Heparan sulfate structural heterogeneity is driven, in part, by the placement of sulfate groups at various positions in the polysaccharide. While many ligands bind to heparan sulfate without strict requirements for the positions of sulfate groups, binding of a small number of known ligands is influenced by the presence of a sulfate at the C3 position of a glucosamine residue. In mammals, seven enzymes can catalyze the addition of 3-O-sulfate groups, suggesting the possibility of other, previously unidentified, ligands whose binding is influenced by 3-O- sulfated sequences. Chapter 1 contains a comprehensive review of the synthesis, biochemistry and physiology related to 3-O-sulfate. Chapter 2 describes the development and use of heparan sulfate affinity matrices to identify ligands that rely on 3-O-sulfate. Neuropilin-1, a modulator of vasculogenesis and axonal guidance, is one of the 3-O-sulfate dependent ligands identified. Chapter 3 demonstrates that 3-O-sulfate is required for high affinity binding of neuropilin-1 to heparan sulfate. Furthermore, 3-O-sulfation influences a neuropilin- 1 dependent process, namely neuronal growth cone collapse. Chapter 4 elaborates on the implications of these findings and the future work needed to fully characterize 3-O- sulfation. This work indicates the existence of many proteins that rely on 3-O-sulfate and outlines the methodology needed to identify and characterize their interaction with heparan sulfate