Abstract 933 Infectious Diseases Platform, Tuesday, 5/4

Glycolipids serve as receptors for a number of microbial pathogens and toxins and are expressed in a tissue- and species-specific manner. Shiga-toxins produced by enterohemorrhagic E. coli bind to GbO3, a globoseries glycolipid, on human endothelial cells, resulting in hemolytic uremic syndrome (HUS). Forssman glycolipid is a closely related globoseries glycolipid that differs from GbO3 by two enzymatic steps and does not bind toxin. In contrast to humans, animal species that express Forssman glycolipid are relatively resistant to shiga-toxin associated injury. In order to examine the effects of altered glycolipid expression on toxin susceptibility, highly susceptible primate kidney cells were transfected with the cDNA encoding Forssman synthetase. Transfection resulted in depletion of the shiga-toxin receptor GbO3 and marked resistance to toxin. Despite diminished GbO3, a significant amount of toxin remained capable of binding to the transfected cells in an inhibitable fashion. With as little as a 5-fold difference in toxin binding, the difference in shiga-toxin susceptibility between wild type and Forssman synthetase expressing cells was greater than 10,000-fold. These results suggest two different pathways for toxin trafficking: 1)In wild type cells, toxin is transported to the endoplasmic reticulum resulting in cell death, as previously described; 2) In transfected cells, alterations in cell surface density or lipid content of toxin receptors may prevent this pathway thus allowing cell survival. Our findings demonstrate that perturbation of the biosynthetic pathway for globoseries glycolipids has a major effect on the interaction between shiga-toxins and host cells, potentially interrupting the pathogenesis of HUS.