No abstract

Chondroitin sulfate proteoglycans (CSPGs) represent a major barrier to regenerating axons in the central nervous system (CNS), but the structural diversity of their polysaccharides has hampered efforts to dissect the structure-activity relationships underlying their physiological activity. By taking advantage of our ability to chemically synthesize specific oligosaccharides, we demonstrate that a sugar epitope on CSPGs, chondroitin sulfate-E (CS-E), potently inhibits axon growth. Removal of the CS-E motif significantly attenuates the inhibitory activity of CSPGs on axon growth. Furthermore, CS-E functions as a protein recognition element to engage receptors including the transmembrane protein tyrosine phosphatase PTPσ, thereby triggering downstream pathways that inhibit axon growth. Finally, masking the CS-E motif using a CS-Especific antibody reversed the inhibitory activity of CSPGs and stimulated axon regeneration in vivo. These results demonstrate that a specific sugar epitope within chondroitin sulfate polysaccharides can direct important physiological processes and provide new therapeutic strategies to regenerate axons after CNS injury.

General MethodsUnless stated otherwise, reactions were performed in flame-dried glassware under a nitrogen or an argon environment, using freshly distilled solvents. All other commercially obtained reagents were used as received. Thinlayer chromatography (TLC) was performed using E. Merck silica gel 60 F254 precoated plates (0.25 mm).Visualization of the developed chromatogram was performed by fluorescence quenching, cerium ammonium molybdate stain, or ninhydrin stain as necessary. ICN silica gel (particle size 0.032 -0.063 mm) was used for flash chromatography. Gel filtration chromatography (Sephadex G-10 and G-25 ultrafine) was used in order to achieve purification of the final products.