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UBC Theses and Dissertations

Host target and function of the type III secreted effectors NleB and EspL of attaching and effacing bacterial pathogens Law, Robyn Jamie


Enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli (EHEC) cause enteric diseases resulting in significant morbidity and mortality worldwide. EPEC is a leading cause of potentially fatal watery diarrhea associated with vomiting, fever and dehydration in young children in developing countries, while EHEC causes severe gastroenteritis in both developing and industrialized nations. The success of these pathogens relies on their ability to inject secreted effectors directly into host cells that manipulate a variety of host cell signaling pathways while the pathogen remains extracellular. Much work has been done to identify EPEC/EHEC secreted effectors but the molecular mechanisms of action of many effectors and their contribution to virulence remain poorly understood. To identify novel host targets for EPEC/EHEC-secreted effectors we performed a global mass spectrometry screen using the SILAC (stable isotope labeling with amino acids in cell culture)-labeling method. Using this technology, we were able to identify host binding partners for a number of EPEC/EHEC effectors. Among them, two conserved effectors, NleB and EspL, were found to interact with the same host factor, ensconsin. Ensconsin is a microtubule associated protein that has been identified as an essential cofactor of kinesin-1. This thesis describes the identification and characterization of the interaction between NleB/EspL and ensconsin and identifies a role for these effectors during infection. We use fluorescent time-lapse imaging to demonstrate the significant effect EPEC have on the kinetics of host receptor trafficking during on-going infections and use the Citrobacter rodentium-mouse model of infection to further characterize how these effectors impact virulence during infection. We hypothesize that NleB and EspL play critical roles during A/E pathogen infections and contribute to pathogenesis through alteration of ensconsin function. Information gathered from this study provides insight into our current understanding of the virulence mechanisms of these pathogens as well as the role of secreted effectors during host cell interactions. A more detailed understanding of how pathogenic bacteria alter host cellular functions as part of the disease process could ultimately lead to development of new therapeutics to help control these significant enteric pathogens.

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Attribution-NonCommercial-NoDerivs 2.5 Canada