title: Protective role of autophagy against Vibrio cholerae cytolysin, a pore-forming toxin from V. cholerae.
abstract: Autophagy is the unique, regulated mechanism for the degradation of organelles. This intracellular process acts as a prosurvival pathway during cell starvation or stress and is also involved in cellular response against specific bacterial infections. Vibrio cholerae is a noninvasive intestinal pathogen that has been studied extensively as the causative agent of the human disease cholera. V. cholerae illness is produced primarily through the expression of a potent toxin (cholera toxin) within the human intestine. Besides cholera toxin, this bacterium secretes a hemolytic exotoxin termed V. cholerae cytolysin (VCC) that causes extensive vacuolation in epithelial cells. In this work, we explored the relationship between the vacuolation caused by VCC and the autophagic pathway. Treatment of cells with VCC increased the punctate distribution of LC3, a feature indicative of autophagosome formation. Moreover, VCC-induced vacuoles colocalized with LC3 in several cell lines, including human intestinal Caco-2 cells, indicating the interaction of the large vacuoles with autophagic vesicles. Electron microscopy analysis confirmed that the vacuoles caused by VCC presented hallmarks of autophagosomes. Additionally, biochemical evidence demonstrated the degradative nature of the VCC-generated vacuoles. Interestingly, autophagy inhibition resulted in decreased survival of Caco-2 cells upon VCC intoxication. Also, VCC failed to induce vacuolization in Atg5-/- cells, and the survival response of these cells against the toxin was dramatically impaired. These results demonstrate that autophagy acts as a cellular defense pathway against secreted bacterial toxins.
authors.affiliation: Laboratorio de Biología Celular y Molecular, Instituto de Histología y Embriología-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Mendoza, Argentina.
authors.forename: Maximiliano Gabriel
authors.initials: MG
authors.lastname: Gutierrez
authors.forename: Hector Alex
authors.initials: HA
authors.lastname: Saka
authors.forename: Isabel
authors.initials: I
authors.lastname: Chinen
authors.forename: Felipe C M
authors.initials: FC
authors.lastname: Zoppino
authors.forename: Tamotsu
authors.initials: T
authors.lastname: Yoshimori
authors.forename: Jose Luis
authors.initials: JL
authors.lastname: Bocco
authors.forename: María Isabel
authors.initials: MI
authors.lastname: Colombo
mesh_terms: D000818:Animals; D001343:Autophagy / Q000502:physiology*; D016466:CHO Cells; D018938:Caco-2 Cells; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins / Q000378:metabolism*; D014734:Vibrio cholerae / Q000472:pathogenicity / Q000502:physiology* / Q000648:ultrastructure
chemical_list: D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D054353:Perforin