Regulated Shift from Helical to Polar Localization of Listeria monocytogenesCell Wall-Anchored Proteins

Abstract

Many virulence factors of Gram-positive bacterial pathogens are covalently anchored to the peptidoglycan (PG) by sortase enzymes. However, for rod-shaped bacteria little is known about the spatiotemporal organization of these surface proteins in the cell wall. Here we report the three-dimensional (3D) localization of the PG-bound virulence factors InlA, InlH, InlJ, and SvpA in the envelope of Listeria monocytogenes under different growth conditions. We found that all PG-anchored proteins are positioned along the lateral cell wall in nonoverlapping helices. However, these surface proteins can also become localized at the pole and asymmetrically distributed when specific regulatory pathways are activated. InlA and InlJ are enriched at poles when expressed at high levels in exponential-phase bacteria. InlA and InlH, which are B dependent, specifically relocalize to the septal cell wall and subsequently to the new pole in cells entering stationary phase. The accumulation of InlA and InlH in the septal region also occurs when oxidative stress impairs bacterial growth. In contrast, the iron-dependent protein SvpA is present at the old pole and is excluded from the septum and new pole of bacteria grown under low-iron conditions. We conclude that L. monocytogenes rapidly reorganizes the spatial localization of its PG proteins in response to changes in environmental conditions such as nutrient deprivation or other stresses. This dynamic control would distribute virulence factors at specific sites during the infectious process.

Host Actin Polymerization Tunes the Cell Division Cycle of an Intracellular Pathogen

“…Specifically, alkDala incorporation occurs at the fifth position of the muropeptide, is acutely sensitive to fosfomycin but not to penicillin, and yields signal that colocalizes with that of fluorescent vancomycin (Siegrist et al, 2013). Like E. coli and B. subtilis , Lm inserts new PG along the sidewall during dispersive elongation and at the septum during division (Bruck et al, 2011; Rafelski and Theriot, 2006). After a long alkDala incubation (~1 to 1.5 generations) followed by reaction with an azide-functionalized fluorophore (az-488), we observed clear septal labeling but dim sidewall signal in Lm replicating in broth or in macrophage-like J774 cells (Figure 1B); faint sidewall labeling likely reflects carboxypeptidase activity (Siegrist et al, 2013).…”

Cellular aspects of the distinct M protein and SfbI anchoring pathways in Streptococcus pyogenes

“…Studying the manner in which such a distribution pattern is achieved may provide clues for the regulation of SfbI translocation. Further insight into the manner by which non‐YSIRK‐G/S‐type proteins are anchored may come from studies dealing with rod‐shaped bacteria such as L. monocytogenes (Bierne et al ., 2004; Rafelski and Theriot, 2006; Bruck et al ., 2011). A direct comparison however, may be complicated by the different manner peptidoglycan synthesis is regulated in these organisms.…”

“…Although the YSIRK‐G/S motif is required for efficient signal sequence processing (Bae and Schneewind, 2003), mutations in this motif do not affect targeting to the septum (Carlsson et al ., 2006; DeDent et al ., 2008). Surface proteins possessing a YSIRK‐G/S motif are found in S. pyogenes (Carlsson et al ., 2006), Staphylococcus aureus (DeDent et al ., 2008) and Streptococcus pneumoniae (Tsui et al ., 2011), are rare in Enterococcus faecalis (Kline et al ., 2009) and are absent from Listeria monocytogenes (Bruck et al ., 2011).…”

Sec-secretion and sortase-mediated anchoring of proteins in Gram-positive bacteria

“…Thus, in S. aureus cell wall anchored proteins appear to be linked to lipid II and ultimately incorporated into the cell wall envelope via the transpeptidation and transglycosylation reactions of peptidoglycan synthesis [117–119] along with other secondary polymers such as carbohydrates and teichoic acids [113, 120]. It is interesting that in L. monocytogenes , some SrtA-substrates produced upon stress are anchored to the cell pole [121]. It has been proposed that either lipid II is present at the pole of low-dividing bacteria or that sortase A directly anchors such proteins to cross-linked peptidoglycan [122].…”