ABILITY OF ABH BLOOD GROUP ?ACTIVE GLYCOCONJUGATES TO ACT AS E. COLI HEAT-LABILE TOXIN RECEPTORS.
Galván EM, Monferran CG.
The heat-labile type I enterotoxin produced by enterotoxigenic Escherichia coli strains (LT-I) share considerable structural and functional properties with cholera toxin (CT). However, LT-I but not CT is able to recognize glycoconjugates other than the GM1 ganglioside. Our results showed that LT-I was able to interact with glycosphingolipids and glycoproteins from pig and rabbit intestinal brush border membranes carrying ABH blood group polimorphism. LT-I induced fluid secretion using ABH-active glycocconjugates as receptors. This functional response was mediated by adenylate cyclase activation and it was inhibited by ABH ligands in a dose-dependent way. Binding of LT-I to additional receptors in HT29 cells triggered cyclic AMP accumulation and this effect was also blocked by blood group A-ligands. Several complex blood group A-active glycosphingolipids isolated from HT29 cells were recognized by LT-I. Treatment of cells with an inhibitor of glucosylceramide sintase (PPMP) diminished A-active glycosphingolipid expression and LT-I binding to non-GM1 receptors. These results suggest that ABH blood group-active glycoconjugates are capable to act as LT-I functional alternative receptors in intestinal epithelial cells.
