Neurobiology of Sulfated Glucuronyl Glycoconjugates
Sulfoglucuronyl carbohydrate (SGC) is expressed on an important group of cell surface glycoproteins which have been implicated in cell-cell interactions during development of the nervous system.. Our previous studies suggested that the many of the biological functions of the SGC may be mediated by a receptor or SGC-binding protein (i.e., acting as a lectin). We isolated and purified from brain a 30 kDa SGC-binding protein, SBP-1, which specifically bound to SGC of SGGLs and SGC-glycoproteins in vitro, suggesting that SBP-1 may act as a receptor for SGC in vivo. It was shown that N-Acetylglucosaminyl transferase regulated the expression of SGGLs in cerebral cortex and cerebellum. The down regulated synthesis of SGGLs in the mature granule neurons was restored, when a precursor glucuronyl neolactotetraosylceramide (GlcAnLcOse4, GGL-1), which is beyond the GlcNAc-Tr step, was exogenously provided to these cells. The biological effect of such restoration in the mature granule neurons led to cell aggregation and enhanced outgrowth of neurites, amounting to dedifferentiation. The expression of SGC and SBP-1 was shown to be present in apposing cell surfaces in cerebral cortex and cerebellum by immunocytochemistry, suggesting availability for interaction for the migrating cells.