Cellular uptake of the Clostridium perfringens binary iota-toxin.
The binary iota-toxin is produced by Clostridium perfringens type E strains and consists of two separate proteins, the binding component iota b (98 kDa) and an actin-ADP-ribosylating enzyme component iota a (47 kDa). Iota b binds to the cell surface receptor and mediates the translocation of iota a into the cytosol. Here we studied the cellular uptake of iota-toxin into Vero cells. Bafilomycin A1, but not brefeldin A or nocodazole, inhibited the cytotoxic effects of iota-toxin, indicating that toxin is translocated from an endosomal compartment into the cytoplasm. Acidification (pH < or = 5.0) of the extracellular medium enabled iota a to directly enter the cytosol in the presence of iota b. Activation by chymotrypsin induced oligomerization of iota b in solution. An average mass of 530 +/- 28 kDa for oligomers was determined by analytical ultracentrifugation, indicating heptamer formation. The entry of iota-toxin into polarized CaCo-2 cells was studied by measuring the decrease in transepithelial resistance after toxin treatment. Iota-toxin led to a significant decrease in resistance when it was applied to the basolateral surface of the cells but not following application to the apical surface, indicating a polarized localization of the iota-toxin receptor.
Blöcker
D
D
Institut für Experimentelle und Klinische Pharmakologie und Toxikologie der Albert-Ludwigs-Universität Freiburg, D-79104 Freiburg, Germany.
Behlke
J
J
Aktories
K
K
Barth
H
H
D036002:ADP Ribose Transferases; D000818:Animals; D001427:Bacterial Toxins / Q000737:chemistry / Q000378:metabolism*; D020126:Brefeldin A / Q000494:pharmacology; D016764:Cell Polarity; D002478:Cells, Cultured; D002918:Chymotrypsin / Q000494:pharmacology; D003016:Clostridium perfringens / Q000472:pathogenicity*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008870:Microtubules / Q000502:physiology
D001427:Bacterial Toxins; C050737:iota toxin, Clostridium perfringens; D020126:Brefeldin A; D036002:ADP Ribose Transferases; D002918:Chymotrypsin