Identification of the O-linked sialyloligosaccharides of glycophorin A as the erythrocyte receptors for S-fimbriated Escherichia coli

Abstract

The erythrocyte receptors for S-fimbriated Escherichia coli, which causes sepsis and meningitis in newborn infants, were investigated. Neuraminidase and trypsin treatments of erythrocytes abolished the hemagglutination ability of the bacteria. To identify the receptor glycoproteins, we separated erythrocyte membrane proteins by gel electrophoresis, blotted them to nitrocellulose, and incubated them with 125I-labeled bacteria. The only bacterium-binding bands identified corresponded to glycophorin A dimer and monomer, and the binding was abolished by neuraminidase treatment of the blot. Radiolabled bacteria also bound to purified glycophorin A adsorbed to polyvinyl chloride microwells, and the binding was inhibited by other sialoglycoproteins and isolated sialyloligosaccharides containing the NeuAcα2-3Gal sequence. Oligosaccharides which contain the NeuAcα2-3Galβ1-3GalNAc and NeuAcα2-3Galβ1-3(NeuAcα2-6)GalNAc sequence and which are identical to the O-linked saccharides of glycophorin A were twofold more effective inhibitors of binding than were other oligosaccharides containing the NeuAcα2-3Gal sequence. The replacement of sialic acid in asialoerythrocytes with a purified Galβ1-3GalNAc α2-3 sialytransferase, which forms the O-linked NeuAcα2-3Galβ1-3GalNAc sequence in asialoglycophorins, restored bacterial hemagglutination. These results indicated that the major erythrocyte receptor for S-fimbriated E. coli is the NeuAcα2-3Galβ1-3GalNAc sequence of the O-linked oligosaccharide chains of glycophorin A.