σ B contributes to Listeria monocytogenes invasion by controlling expression of inlA and inlB

Abstract

The ability of Listeria monocytogenes to invade non-phagocytic cells is important for development of a systemic listeriosis infection. The authors previously reported that a L. monocytogenes DsigB strain is defective in invasion into human intestinal epithelial cells, in part, due to decreased expression of a major invasion gene, inlA. To characterize additional invasion mechanisms under the control of s B , mutants were generated carrying combinations of in-frame deletions in inlA, inlB and sigB. Quantitative assessment of bacterial invasion into the human enterocyte Caco-2 and hepatocyte HepG-2 cell lines demonstrated that s B contributes to both InlA and InlB-mediated invasion of L. monocytogenes. Previous identification of the s B -dependent P2 prfA promoter upstream of the major virulence gene regulator, positive regulatory factor A (PrfA), suggested that the contributions of s B to expression of various virulence genes, including inlA, could be at least partially mediated through PrfA. To test this hypothesis, relative invasion capabilities of DsigB and DprfA strains were compared. Exponential-phase cells of the DsigB and DprfA strains were similarly defective at invasion; however, stationary-phase DsigB cells were significantly less invasive than stationary-phase DprfA cells, suggesting that the contributions of s B to invasion extend beyond those mediated through PrfA in stationary-phase L. monocytogenes. TaqMan quantitative reverse-transcriptase PCRs further demonstrated that expression of inlA and inlB was greatly increased in a s B -dependent manner in stationary-phase L. monocytogenes. Together, results from this study provide strong biological evidence of a critical role for s B in L. monocytogenes invasion into non-phagocytic cells, primarily mediated through control of inlA and inlB expression.

Contributions of Listeria monocytogenes σ B and PrfA to expression of virulence and stress response genes during extra- and intracellular growth

“…Although loss of expression from the P2prfA region affects in vitro virulence phenotypes, e.g. haemolysin production (Freitag & Portnoy, 1994;Nadon et al, 2002), it does not affect L. monocytogenes invasion capabilities in human intestinal epithelial cell lines (Kim et al, 2004(Kim et al, , 2005. In L. monocytogenes, s B also contributes to survival under a variety of lethal environmental stresses (Ferreira et al, 2001), including acidic conditions mimicking mammalian gastric fluid (Chaturongakul & Boor, 2004;Cotter et al, 2001;Wiedmann et al, 1998).…”

“…inlA, bsh) are regulated by both PrfA and s B (Kazmierczak et al, 2003;Kim et al, 2004;Nadon et al, 2002;Sue et al, 2003), a stress-responsive, stationary-phase sigma factor present in a number of Gram-positive bacteria. A DsigB strain exhibits reduced invasion of Caco-2 cells in parallel with reduced s B -dependent inlA expression (Kim et al, 2004(Kim et al, , 2005 and is virulence-attenuated in orally infected guinea pigs (Garner et al, 2006). Recent evidence suggests that s B activates transcription of prfA from a promoter located in the P2prfA region (Nadon et al, 2002;Rauch et al, 2005;Schwab et al, 2005).…”

Refinement of the Listeria monocytogenes σB regulon through quantitative proteomic analysis

“…microarray meta-analysis or proteomics) and (iii) 7/13 genes had a significant P c value and FC above 1.0 in all three microarray studies, but missed the FC cutoff of ¢1.5 in one or more microarray study. Two of the genes in Group C (inlA and inlB) are located in the same operon and are co-regulated by PrfA and s B (Kim et al, 2005;Oliver et al, 2009;Ollinger et al, 2009;Raengpradub et al, 2008) and were thus not identified as positively regulated by s B in the one microarray study that used a prfA* genetic background, which expresses a constitutively active PrfA (Ollinger et al, 2009). …”

Invasiveness of Listeria monocytogenes strains isolated from animals in Poland

“…Internalin InlA and InlB are the key surface proteins containing N-terminal leucine-rich repeats (LRRs) domain that interact with their respective host-cell receptors, leading to bacterial internalization (Bierne et al 2007). It has been shown that loss of inlA and inlB genes seriously hamper L. monocytogenes ability to invade epithelial cells (Kim et al 2005). A number of mutations in inlA gene, leading to premature stop codons (PMSCs), have been observed in L. monocytogenes.…”