Shigella invades the intestinal epithelium following injection of type III secretion effectors (T3S) and causes inflammatory, neutrophil-mediated tissue destruction. The host lab has shown that Shigella invasion induces oscillatory Ca2+-signalling and hemichannel-dependent release of ATP, which is a potent immunostimulatory signal. I propose 1) that ATP release from epithelial cells attracts neutrophils to sites of infection and promotes their activation and 2) that some Shigella T3S effectors counter these effects during early stages of infection, to escape neutrophil-mediated killing. I will focus on the effector IpgD. I will determine the ability of IpgD to dampen hemichannel opening during Shigella invasion of epithelial cells. By means of 4D live imaging, I will correlate neutrophil migration with wild-type and ipgD mutant Shigella invasion of epithelial cells and formation of ATP gradients. Also, I will test immune functions of neutrophils exposed to extracellular ATP during wild-type and ipgD mutant Shigella invasion. Further, using a transwell chemotaxis assay and 4D live imaging, I will investigate IpgD-mediated inhibition of cytoskeletal dynamics, i.e. migration, in neutrophils. My work will assess the physiological significance of ATP release during Shigella invasion and contribute to define T3S effectors functions other than invasion, i.e. immunomodulation. This may allow to design new therapeutic approaches. Live imaging, work with live pathogens and primary immune cell cultures are new techniques for me. Together with the expertise acquired previously, the training I will receive in the lab of Prof. Philippe Sansonetti will be integral to my carrier studying host-pathogen interaction.
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