Chemoenzymatically Synthesized O-Acetylated GD3 Gangliosides to Examine Viral Receptor Specificities in a Cellular Context
Gangliosides are a class of sialic acid-containing glycosphingolipids involved in a wide range of biological processes. The terminal sialic acid of gangliosides can be O-acetylated at C7 and/or C9 hydroxyl, contributing to ganglioside structural complexity and function. It has been difficult to obtain panels of structurally well-defined O-acetylated gangliosides for binding and functional studies. We describe here a chemoenzymatic strategy that can provide, for the first time, 7-O-, 9-O-, and 7,9-di-O-acetylated GD3 gangliosides. It is based on the chemical assembly of a common tetrasaccharide precursor as -glycosyl fluoride that is coupled to sphingosine by a glycosynthase, followed by O-acetyl editing by coronaviral hemagglutinin-esterases. The resulting synthetic glycosphingolipids have been employed for cell surface remodeling of erythrocytes. Analysis by liquid chromatography and ion mobility mass spectrometry (LC-IM-MS) demonstrated successful integration of the glycosphingolipids into the plasma membrane with preservation of acetyl ester patterns. Using human coronavirus HKU1 spike-functionalized virus-like particles, we demonstrate that the resulting glycan-remodeled erythrocytes can be utilized in hemagglutination studies as a label free method to investigate viral protein binding to individual glycoforms in a cellular environment. Entry for the Table of Contents O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=112 SRC="FIGDIR/small/670503v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@37de01org.highwire.dtl.DTLVardef@1d043faorg.highwire.dtl.DTLVardef@1ee57borg.highwire.dtl.DTLVardef@6bf474_HPS_FORMAT_FIGEXP M_FIG Table of Contents 7-O-, 9-O-, and 7,9-di-O-acetylated GD3 gangliosides can be prepared by chemical assembly of a tetrasaccharide as -glycosyl fluoride that is coupled to sphingosine using a glycosynthase, followed by O-acetyl editing by coronaviral hemagglutinin-esterases. Cell surface remodeling of erythrocytes using the GD3 derivatives provide a tool to examine viral receptor specificities. C_FIG