InlG and Vip are functionally connected with the stress regulator SigB in Listeria monocytogenes

LAURA BOTELLO-MORTE; JAVIER FERNANDO MARISCOTTI; M. GRACIELA PUCCIARELLI; FRANCISCO GARCÍA-DEL PORTILLO

Zaragoza

Congreso; The V National Congress of the Institute for Biocomputation and Physics of Complex Systems (BIFI2011); 2011

Institute for Biocomputation and Physics of Complex Systems

Listeria monocytogenes is a Gram positive intracellular bacterium that causes serious systemic diseases in humans and animals. This pathogen-has the ability to cross natural host barriers such as intestinal epithelium, placenta or blood-brain barriers. Comparative genomic analyses between pathogenic and non-pathogenic Listeria species revealed the existence of surface proteins exclusively codified in pathogenic species. The genome of L. monocytogenes EGDe-strain encodes 41 surface proteins containing a conserved LPXTG motif which covalently anchors these proteins to the peptidoglycan. 13 of these LPXTG proteins are absent in the non-pathogenic strain L. innocua. Few LPXTG proteins have been characterized at biological and functional levels, such as InlA which has been proposed as a key virulence factor in Listeria. In a collaborative effort with other European groups, we have performed a global and detailed functional approach to characterize the 41 LPXTG proteins present in' EGDe-strain. To this aim, we have constructed a complete mutant collection lacking each LPXTG protein. Proteomic analyses using peptidoglycan samples from these mutants suggest the existence of co-regulatory mechanisms for some of these LPXTG proteins. Additionally, the 41 LPXTG proteins present in L. monocytogenes have been purified to generate specific antibodies used in Western blot assays to confirm our proteomic data. Specifically, mutants lacking the Lmo0262 (InIG) or Lmo0320 (Vip) proteins show a notable decrease in Lmo0263 (InIH), Lmo061O, Lmo0880 and Lm02085 protein levels. Interestingly, the expression of these four LPXTG-coding genes is positively¬regulated by SigB, the major stress response sigma factor in Listeria. Surprisingly, we have found additional mutations in components of the SigB-mediated stress response in mutants lacking InlG or Vip. We have experimentally demonstrated that these mutations in SigB machinery confer lower tolerance to different cell wall-damaging stresses. Therefore, our model suggests a novel functional connection betWeen LPXTG proteins and the stress response apparatus in L. monocytogenes.