Molecular mechanisms required for injection of Yersinia outer proteins (Yops) into host cells, and consequences for the host immune response
Zusammenfassung der Projektergebnisse
Adhesins and the type III secretion system (TTSS) play a central role for the virulence of human pathogenic Gram-negative bacteria. According to the current paradigm Yersinia enterocolitica adhesins Inv bind directly and YadA indirectly via extracellular matrix protein to b1 integrins. These adhesion events lead to subsequent delivery of Yops via the TTSS into host cells. The Yops contribute critically to immune evasion and ensure successful infection. In this study we demonstrated that during mouse infection YadA is the major adhesin responsible for subsequent Yop injection while Inv plays a transient and minor role. Challenge of the paradigm revealed that Invasin mediated adhesion/Yop injection is strictly β1 integrin dependent at/into fibroblast or epithelial cells but not in leukocytes; invasin also binds to yet unknown leukocyte receptors. We found that YadA mediates adhesion to fibroblasts not only via β1 integrins but also exploits αV integrins. αV integrins also mediates Yop injection into epithelial cells. Together these findings indicate that despite similar integrin receptor repertoires in fibroblasts and epithelial cells, additional factors operating only in epithelial cells and leukocytes may contribute to Yop injection. EM analysis showed an association between the distance of bacteria to host cells and subsequent Yop injection despite similar adhesion, indicating that the “quality” of adhesion determines whether Yop injection occurs or not. Comparison of different YadA subtypes further lead to the hypothesis that domains in the YadA head region may also determine the receptor repertoire needed for adhesion followed by Yop injection. In further studies we want to identify the unknown receptors and YadA domains contributing to adhesion followed by Yop injection, using transgenic mouse (integrin null mice), generation of host cell lines lacking or overexpressing the hypothesized candidate factors, and YadA mutants. By using force microscopy, flow chamber experiments and determination of the location of the TTSS at the contact side of the cell we want to define in further studies the properties of the Ye/host cell interaction which permit Yop injection.
Projektbezogene Publikationen (Auswahl)
- 2014, Doktorarbeit. Untersuchungen zur Rolle von bakteriellen und Wirtszellfaktoren für die Injektion von Yersinia outer proteins in Wirtszellen durch Yersinia enterocolitica
Birgit Keller
