Global analysis of the Listeria monocytogenes surface proteins of the LPXTG family

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

Porto

Simposio; ISOPOL XVII (International Symposium On Problems Of Listeriosis); 2010

Universidade Católica Portuguesa

Listeria monocytogenes is a Gram-positive intracellular bacterial pathogen that causes serious systemic diseases in humans and animals. Comparative genomics revealed the presence in the Listeria genus of a large number of genes encoding surface proteins containing an LPXTG sorting motif. This signature makes these proteins recognized by sortases, the enzymatic machinery that anchors proteins covalently to the peptidoglycan. In the case of the L. monocytogenes EGD-e strain, a total of 41 genes encoding LPXTG proteins were discovered. Despite the relevance of surface proteins for communication with the environment and the host, the biological role of most members of this family remains unknown in L. monocytogenes. In a collaborative effort with other European groups that contributed to generate mutants defective in specific LPXTG proteins, we accomplished a comprehensive proteomic analysis in peptidoglycan material purified from each of these mutants. A total of 30 LPXTG mutants have been analysed to date. Proteomic analysis was also performed in peptidoglycan purified from intracellular wild-type bacteria upon infection of epithelial cells. A major finding of this global approach was the cross-regulation existing among certain LPXTG proteins. This phenomenon involved in most cases the down-regulation of concrete LPXTG proteins in response to the lack of a specific LPXTG protein. Interestingly, the inverse phenomenon, the up-regulation of a LPXTG protein in response to a deficiency in another LPXTG protein, was also observed. These proteomic data were confirmed with specific antibodies. Proteins subjected to these regulatory processes, currently investigated in detail by our group, include Lmo0320 (Vip), Lmo0514, Lmo0610, Lmo0880, InlE, InlG, InlH, and Lmo2085.