Use of non-cellular models to study the interaction of E. histolytica with mammalian cells

We have utilized liposomes constructed with individual mammalian cell membrane glycosphingolipids and latex beads conjugated with glycoproteins as models to investigate the molecular specificity and mechanism of interaction of E. histolytica with target cells. Synthetic liposomes constructed with a variety of glycosphingolipids bearing neutral, straight chain glycans with galactose or N-acetylgalactosamine termini stimulated rapid (90 sec), contact dependent polymerization of E. histolytica actin. Glycans with terminal N-acetylglucosamine residues were not, or only weakly, stimulatory. Attachment of N-acetylneuraminate to the terminal residue of stimulatory glycosphingolipids eliminated activity. Attachment of fucose to the penultimate sugar reduced glycan recognition. Latex beads conjugated with asialofetuin (galactose beta 1-4 glycan termini) adhered to amoebae more effectively than fetuin conjugated beads (N-acetylneuraminate termini) or agalactosyl asialofetuin conjugated beads (N-acetylglucosamine termini). However, none of the glycoprotein conjugated beads stimulated contact mediated polymerization of E. histolytica actin. The carbohydrate specificity of E. histolytica interaction with non-cellular particles resembles that observed with whole target cells our results demonstrate that carbohydrate recognition specificity extends to lipid as well as protein bound glycoconjugates. Further, these studies suggest that the biochemical consequences of binding to glycosphingolipids differ from those resulting from interaction with glycoprotein. This may be relevant to the mechanism of mammalian cell attack by this pathogen.