Functional analysis of the LipA phosphatase, a new virulence factor of Listeria monocytogene

• Applicant: Didier Soulat, Ph.D.
• Subject Area: Parasitology and Biology of Tropical Infectious Disease Pathogens
• Term: from 2012 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 210777376

Listeria monocytogenes is a facultative intracellular Gram-positive bacterium responsible for listeriosis. This bacterium, like other intracellular pathogens, manipulates host cell functions by producing diverse virulence factors. L. monocytogenes expresses a secreted phosphatase, named LipA, specifically during infection. We previously showed that LipA dephosphorylated phosphotyrosines as well as phosphatidylinositol phosphates (PIP) in cell-free in vitro systems and that the virulence of bacteria deficient for LipA (ΔlipA) was strongly impaired in vivo, whereas the life cycle of ΔlipA L. monocytogenes mutants in macrophages or epithelial cells remained intact. This application aims to (1) define the cell types affected by LipA during infection and (2) to identify the substrates of LipA in infected host cells. To this end, we will test (1a) the hypothesis that LipA impairs the oxidative burst of neutrophils by inhibiting the PIP-dependent assembly of NADPH oxidase; (1b) the impact of LipA on the function of other innate immune cells; (2a) the identity and localization of PIPs targeted by LipA in infected host cells; (2b) the effect of LipA on the level of host cell protein phosphorylation. The project will not only improve our understanding of the mechanisms developed by L. monocytogenes to escape the immune response, but also has the potential to define a novel class of listerial virulence factors which could be suitable as drug targets.

• DFG Programme: Research Grants