Pili binding to asialo-GM1 on epithelial cells can mediate cytotoxicity orbacterial internalization by Pseudomonas aeruginosa

The interaction of Pseudomonas aeruginosa type TV pill and the glycosphingo lipid asialo-GM1 (aGM1) can mediate bacterial adherence to epithelial cells , but the steps subsequent to this adherence have not been elucidated. To i nvestigate the result of the interaction of pill and aGM1, we used polarize d epithelial monolayers of Madin-Darby canine kidney (MDCK) cells in cultur e, which contained little detectable aGM1 on their apical surface but were able to incorporate exogenous aGM1. Compared to an untreated monolayer, P. aeruginosa PA103 displayed an eightfold increase in association with and fi vefold more cytotoxicity toward MDCK cells pretreated with aGM1. Cytotoxici ty of either carrier-treated or aGM1-treated monolayers required the type I II secreted protein ExoU. Asialo-GM1 pretreatment of MDCK monolayers likewi se augmented bacterial internalization of an isogenic invasive strain appro ximately fourfold. These increases were not seen in monolayers treated with GM1, the sialyated form of the glycolipid, and were inhibited by treatment with an antibody to aGM1. Also, the aGM1-mediated adhesion, cytotoxicity, and internalization required intact type IV pill since nonpiliated PA103 mu tants were unaffected by aGM1 pretreatment of MDCK cells. These results dem onstrate that epithelial cell injury and bacterial internalization can proc eed from the same adhesin-receptor interaction, and they indicate that P. a eruginosa exoproducts solely determine the steps subsequent to adhesion.