Chemoenzymatic Synthesis of Glycosphingolipids having an HNK-1 Epitope for Erythrocyte Cell Surface Remodeling

Abstract

Several neuropathies, such as Guillain-Barre syndrome and myelin-associated glycoprotein neuropathy (MAG), are caused by antibodies targeting glycosphingolipids. Several studies have indicated that MAG arises from pathogenic IgM autoantibodies targeting sulfoglucuronyl (HNK-1) containing glycosphingolipids. The exact mechanism by which IgM-neuropathy occurs has not been fully elucidated. Furthermore, no appropriate diagnostic tools are available for MAG using sulfoglucuronyl containing glycosphingolipids. To address these limitations, we describe here a synthetic strategy that makes it possible to prepare sulfoglucuronyl paraglobosides using a neochemo-enzymatic approach. It is based on the enzymatic assembly of N-acetyl-lactosamine (LacNAc) backbones as thioglycosides that were subjected to protecting group manipulations to give glycosyl acceptors for the chemical installation of a sulfated glucuronic acid moiety. A late-stage conversion of the thioglycosides into anomeric fluorides made it possible to enzymatically introduce sphingosine. The resulting compounds were acetylated to provide 3-sulfo-glucuronyl- and glucuronyl-containing glycosphingolipids, respectively. The glycosphingolipids were employed to remodel the surface of erythrocytes to examine complement mediated toxicity by an anti-HNK-1 antibody. It was found that erythrocytes remodeled with exogenous administered HNK-1 containing glycosphingolipid undergo complement dependent lysis when incubated with an IgM anti-CD57 IgM antibody, whereas a compound lacking a sulfate was not able to induce this effect. The approach could be extended to the gangliosides GM1a and GD1a, which have been implicated in Guillain-Barre syndrome. The results highlight that cell surface remodeling will be attractive for diagnosis, disease monitoring and immunological research of diseases associated with pathogenic antibodies targeting glycosphingolipids. TOC graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=76 SRC="FIGDIR/small/642389v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@1c5a4e9org.highwire.dtl.DTLVardef@cddba7org.highwire.dtl.DTLVardef@10fc7eborg.highwire.dtl.DTLVardef@10e5678_HPS_FORMAT_FIGEXP M_FIG C_FIG