UDP-GLUCOSE DEFICIENCY IN A MUTANT-CELL LINE PROTECTS AGAINST GLUCOSYLTRANSFERASE TOXINS FROM CLOSTRIDIUM-DIFFICILE AND CLOSTRIDIUM-SORDELLII

We have previously isolated a fibroblast mutant cell with high resista nce to the two Rho-modifying glucosyltransferase toxins A and B of Clo stridium difficile. We demonstrate here a low level of UDP-glucose in the mutant, which explains its toxin resistance since: (i) to obtain a detectable toxin B-mediated Rho modification in lysates of mutant cel ls, addition of UDP-glucose was required, and it promoted the Rho modi fication dose-dependently; (ii) high pressure liquid chromatography an alysis of nucleotide extracts of cells indicated that the level of UDP -glucose in the mutant (0.8 nmol/10(6) cells) was lower than in the wi ld type (3.7 nmol/10(6) cells); and (iii) sensitivity to toxin B was p estered upon microinjection of UDP-glucose, Using the mutant as indica tor cell we also found that the related Clostridium sordellii lethal t oxin is a glucosyltransferase which requires UDP-glucose as a cofactor . Like toxin B it glucosylated 21-23-kDa proteins in cell lysates, but Rho was not a substrate for lethal toxin.