Abstract
Infection with Verotoxin producing Escherichia coli (VTEC) has been implicated in hemolytic uremic syndrome, the leading cause of pediatric renal failure. Verotoxin (VT) binds to globotriaosylceramide (Galฮฑ1โ4Galฮฒ1โ4GlcCer Gb~3~) in susceptible cells. Gb~3~ is required for cytotoxicity and toxinโresistant cells deficient in Gb~3~ can be sensitized to VT cytotoxicity by incorporation of exogenous Gb~3~ into the cells. However, the absolute Gb~3~ content of cell lines does not necessarily correspond directly with the degree of sensitivity to VT. The present study demonstrates that susceptibility to VT is a function of cell growth and that stationary phase cells are resistant to VT. Using chemically synchronized Vero cells, we have also found a tenfold difference in susceptibility to VT during the cell cycle. Our experiments define a maximal sensitivity โwindowโ of 1โ2 hours from the G1/S boundary. This corresponds to increased VT binding without change in overall Gb~3~ content. Cell surface labelling indicated that cyclic turnover and exposure of Gb~3~ may be the critical parameter in determining VT sensitivity. Such changes during the cell cycle may also be of relevance in vivo in determining toxin pathology during VTEC infections and the physiology of plasma membrane Gb~3~.