Listeria monocytogenes infection and the host cell cycle
Zusammenfassung der Projektergebnisse
Preliminary studies suggested that susceptibility for Listen'a monocytogenes infection might be influenced by the cell cycle stage of the host cell. We asked the question, whether the bacterium can actively manipulate the host cell cycle to create a more advantageous environment for growth and colonization. By using various approaches addressing the impact of cell cycle for Listeria monocytogenes infection, we did not find strong indication of active bacterial interference with host cell cycle. Therefore, although non-diving cells are a more favourable target for Listeria monocytogenes, the bacterium itself seems not to have evolved strategies to influence host cell environment in that manner. A more robust and striking phenotype was observed with another set of host cell factors. Inhibition of the RhoA/ROCK pathway in host cells by pharmacological inhibitors or RNA interference (RNAi) results in increased L. monocytogenes invasion of murine fibroblasts and hepatocytes. In addition, InlF, a member of the internalin multigene family with no known function, was identified as a L. monocytogenes-specific factor mediating increased host cell binding and entry in a RhoA/ROCK dependent mariner. Conversely, activation of RhoA/ROCK activity resulted in decreased L. monocytogenes adhesion and invasion. Furthermore, virulence of wild-type bacteria during infection of mice was significantly increased upon inhibition of ROCK activity, whereas colonization and virulence of an inlF deletion mutant was not affected, thus supporting a role for InlF as a functional virulence determinant in vivo under specific conditions. In conclusion, a new bacterial virulence factor for Listeria monocytogenes, InlF, was identified and functionally characterized. The underlying host cell signalling pathway, involved in mediating InlF dependent virulence, has been elucidated. In addition, this study provides another example for distinct host specificity, a common feature in bacterial pathogenesis. By identifying InlF as an important virulence factor for Listeria monocytogenes, this study opens up new directions in the field and for the laboratory. Its potential role in brain colonization will be investigated intensively, since the discovery of the underlying mechanism is extremely relevant in order to understand the development of meningitis, a serious public health problem, caused by Listeria monocytogenes as well as by other pathogenic microbes. New and sophisticated experimental approaches will be applied in collaboration with several excellent laboratories. Extremely valuable tools, such as new animal model systems, access to relevant types of primary cells and the use of real time monitoring technologies to follow the in vivo infection will allow to obtain significant information regarding infection mechanisms and strategies of Listeria monocytogenes.
Projektbezogene Publikationen (Auswahl)
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A Role for ROCK Kinase Activity in Listeria monocytogenes Infection. Boston Bacterial Meeting, Boston, USA, 2007
Kirchner, M., Higgins, D.E.
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(2008) Inhibition of ROCK activity allows InlF-mediated invasion and increased virulence of Listeria monocytogenes. Mol Microbiol. 68(3)
Kirchner, M., Higgins, D.E.
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Inhibition of ROCK activity allows InlF-mediated invasion and increased virulence of Listeria monocytogenes. Gordon Research Conference "Microbial Toxins and Pathogenesis, Andover, NH, USA, 2008
Kirchner, M., Higgins, D.E.
