Cellular uptake of the Clostridium perfringens binary iota-toxin

Area of Science:

• Microbiology
• Cell Biology
• Toxicology

Background:

• Clostridium perfringens type E produces iota-toxin, a binary toxin.
• Iota-toxin comprises a binding component (iota b) and an enzyme component (iota a).
• Iota b facilitates iota a translocation into host cells.

Purpose of the Study:

• Investigate the cellular uptake mechanism of iota-toxin.
• Determine the oligomeric state of the iota b component.
• Analyze the entry pathway and receptor localization of iota-toxin in polarized cells.

Main Methods:

• Cytotoxicity assays using Vero cells with inhibitors like Bafilomycin A1.
• pH-dependent uptake studies.
• Analytical ultracentrifugation to determine oligomer mass.
• Transepithelial electrical resistance measurements in CaCo-2 cells.

Main Results:

• Iota-toxin uptake involves translocation from an endosomal compartment.
• Acidification of the extracellular medium facilitates direct cytosolic entry of iota a.
• Chymotrypsin activation induces iota b heptamer formation (530 kDa).
• Iota-toxin enters polarized CaCo-2 cells primarily via the basolateral surface.

Conclusions:

• Iota-toxin utilizes an endosomal pathway for cellular entry.
• The binding component iota b forms functional heptamers.
• The iota-toxin receptor exhibits polarized distribution on epithelial cells.