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• infectious disease and the immune system

• Medicine
• Paediatrics

• Gastroenterology
• Infectious diseases

My laboratory interest is in the pathogenesis of infectious and inflammatory disease of the gastrointestinal tract. We are particularly interested in studying the interface between microbial pathogens and the host mucosal surface. Recent projects conducted in close collaboration with UCD colleagues involved in cell biology (Ulla Knaus) include understanding how intestinal reactive oxygen species (ROS) function to protect the host from bacterial challenge despite low concentrations at the mucosal surface (Corcionivoschi et al. Cell Host and Microbe 2012, Alvarez et al. Proceedings of the National Academy of Sciences 2016). In addition, together colleagues interested in microbial pathogenesis (Marguerite Clyne, Tadhg O'Croinin) we have been studying how the zoonotic pathogen Campylobacter jejuni interacts with mucus and mucins with particular reference to how this organism behaves in chickens as a commensal and humans as a pathogen (Shortt et al. MBio 2016, Naughton et al. Infection & Immunity 2013).

Characterisation of the tyrosine phosphoproteome of Campylobacter jejuni and its role in virulence and survival:
Protein tyrosine phosphorylation, long known for its importance in cell signaling in human cells and other eukaryotes, increasingly is recognized as a highly conserved, widespread and possibly essential signaling cascade in bacteria. Of major importance in infection biology is the recognition of its key role in control of capsular polysaccharide production and other aspects of bacterial virulence and survival. By converting phosphotyrosines to protein bound-DOPA, we have shown that mucosal reactive oxygen species (ROS) subvert phosphotyrosine signaling thereby attenuating pathogenicity (Alvarez et al PNAS 2016). Our understanding of the mechanism of this early innate defense system mediated by epithelial NADPH oxidases underlines both the contribution of bacterial tyrosine phosphorylation to infection and its potential as a target for novel anti-virulence strategies.

Bacterial tyrosine kinases (BYKs) are structurally different to their eukaryotic counterparts (and therefore could represent potential drug targets). However, emerging evidence suggests major redundancy in tyrosine phosphorylation pathways in bacteria (Mijakovic et al. Front Microbiol 2015). Therefore, we need a deeper understanding of the prokaryotic tyrosine phosphorylation landscape before considering drug development in this area.

This proposal will:

1. Use a state-of-the-art phosphoproteomics approach to identify the tyrosine phosphorylated proteins of C. jejuni and compare differences in tyrosine phosphorylation patterns among C. jejuni Type strains, those isolated from humans and from fresh poultry meat to identify alterations in tyrosine phosphorylation potentially related to pathogenicity and survival.

2. Create inducible deletion mutant strains with disruptions in genes encoding phosphorylated proteins predicted to be involved in pathogenicity and survival.

3. Examine and compare the fitness and virulence of strains with these specific mutations.

4. Identify and determine the biological effect of phosphorylation of amino acids other than tyrosine and the effects of H2O2 exposure on the single known bacterial tyrosne kinase in C. jejuni Omp50/Cjtk.