Pathogenesis of Shigella diarrhoea: XVII- A mammalian cell membrane glycolipid, Gb<SUB>3</SUB>, is required but sufficient to confirm sensitivity to shiga toxin

Shiga toxin recognizesa galactose-α1 → 4-galactose terminal glycolipid,globotriaosylceramide (Gb<SUB>3</SUB>), in sensitive mammalian cells and is translocated by endocytosis to the cytoplasm, where it blocks protein synthesis. To determine if Gb<SUB>3</SUB> is both required and sufficient for toxicity, Gb<SUB>3</SUB> content in cells was altered by blocking key biosynthetic or degradative path enzymes with specific inhibitors. The resulting decrease or increase in cellular Gb<SUB>3</SUB> was associated with a decrease or increase in binding of and response to Shiga toxin. Toxin-resistant Gb<SUB>3</SUB>-deficient variants of sensitive cells fused with liposomes containing Gb<SUB>3</SUB> but not globotetraosylceramide (Gb<SUB>4</SUB>) became susceptible, whereas fusion of Gb<SUB>3</SUB> liposomes to naturally resistant Gb<SUB>3</SUB>-deficient CHD cells increased toxin binding but not cytotoxicity. These data demonstrate that Gb<SUB>3</SUB> is required, but not sufficient, for the action of Shiga toxin and suggest the existence of a toxin translocation mechanism linked to surface glycolipids that is not expressed in CHD cells