THE DSD-1 CARBOHYDRATE EPITOPE DEPENDS ON SULFATION, CORRELATES WITH CHONDROITIN SULFATE-D MOTIFS, AND IS SUFFICIENT TO PROMOTE NEURITE OUTGROWTH

The neural chondroitin sulfate (CS) proteoglycan (PG) DSD-1-PG was ori ginally identified with the monoclonal antibody (mAb) 473HD. It promot es neurite outgrowth of hippocampal neurons when coated as a substrate in the presence of polycations. This effect is inhibited by mAb 473HD that specifically recognizes the DSD-1 epitope. The DSD-1 epitope is also detectable in CS-C and CS-D preparations from shark cartilage but not in other chondroitin sulfates that are structurally related and d iffer in their sulfation patterns. Non-sulfated DSD-1-PG and chemicall y desulfated CS-D were not recognized by mAb 473HD, suggesting that th e DSD-1 epitope depends on sulfation. It was possible to enrich DSD-1 epitope-bearing carbohydrates and D disaccharide units from CS-C and C S-D preparations on a mAb 473HD affinity matrix. This indicates that t he DSD-1 epitope represents a distinct glycosaminoglycan structure con taining D units. The analysis of glycosaminoglycan digestion products by high pressure liquid chromatography revealed that DSD-1-PG preparat ions contain a unique D disaccharide unit as well as an A, a C, and a non-sulfated disaccharide unit. In neurite outgrowth assays with hippo campal neurons, substrate-bound CS-D promoted neurite outgrowth, where as CS-A, CS-B, or CS-C did not. This effect of CS-D was inhibited by m Ab 473HD. DSD-1 epitope enriched fractions obtained from CS-D and CS-C promoted neurite outgrowth, whereas CS-C had no such effect prior to enrichment on the mAb 473HD matrix. Based on these findings we conclud e that the DSD-1 epitope by itself is sufficient to promote neurite ou tgrowth and that this activity is possibly associated with D motifs.