Vibrio cholerae (VC)is an intestinal non-invasive pathogen that produces cholera,an acute watery diarrhea disease in humans. Besides cholera toxin,VC secretes a haemolytic toxin termed El Tor Hemolysin (ETH). This exotoxin causes extensive vacuolization in epithelial cells. However, the contribution of this phenomenon in VC pathogenesis has not still been elucidated. In this study, we explored the relationship between the vacuolization caused by ETH and the autophagic pathway. Treatment of cells with purified ETH increases the association of LC3 to membranes, a feature indicative of autophagosome formation. Thus, ETH-induced vacuoles colocalize with LC3 indicating the interaction of these vacuoles with autophagic vesicles. Moreover, culture supernatants from both wt and ETH-defective VC strains,confirmed that ETH is the only VC-exotoxin triggering authophagy. Electron microscopy analysis indicates that the vacuoles present hallmarks of autophagosomes. Furthermore, autophagy inhibition resulted in decreased survival of CHO and CaCo-2 cells upon ETH treatment. These results demonstrate for the first time that autophagy acts as a cellular defense pathway against secreted toxins such as ETH.
Both, first and second author contributed equally to this work.
