Bacteria hijack integrin-linked kinase to stabilize focal adhesions and block cell detachment

Abstract

The rapid turnover and exfoliation of mucosal epithelial cells provides an innate defence system against bacterial infection. Nevertheless, many pathogenic bacteria, including Shigella, are able to surmount exfoliation and colonize the epithelium efficiently. Here we show that the Shigella flexneri effector OspE (consisting of OspE1 and OspE2 proteins), which is highly conserved among enteropathogenic Escherichia coli, enterohaemorrhagic E. coli, Citrobacter rodentium and Salmonella strains, reinforces host cell adherence to the basement membrane by interacting with integrin-linked kinase (ILK). The number of focal adhesions was augmented along with membrane fraction ILK by ILK-OspE binding. The interaction between ILK and OspE increased cell surface levels of 1 integrin and suppressed phosphorylation of focal adhesion kinase and paxillin, which are required for rapid turnover of focal adhesion in cell motility. Nocodazole-washout-induced focal adhesion disassembly was blocked by expression of OspE. Polarized epithelial cells infected with a Shigella mutant lacking the ospE gene underwent more rapid cell detachment than cells infected with wild-type Shigella. Infection of guinea pig colons with Shigella corroborated the pivotal role of the OspE-ILK interaction in suppressing epithelial detachment, increasing bacterial cell-to-cell spreading, and promoting bacterial colonization. These results indicate that Shigella sustain their infectious foothold by using special tactics to prevent detachment of infected cells.

Vasodilator-stimulated phosphoprotein restricts cell-to-cell spread of Shigella flexneri at the cell periphery

“…We speculate that VASP-mediated modification of focal adhesions inhibits Shigella recruitment of critical focal adhesion components to protrusions. As the efficiency of Shigella spread is directly correlated with the stabilization of focal adhesions and reduction in focal adhesion turnover (Kim et al, 2009), a mechanism that theoretically could contribute to the observed phenotype is a relative increase in focal adhesion turnover, associated with increased phosphorylation of focal adhesion kinase and paxillin, although whether VASP modulates focal adhesion turnover or stability is currently unclear. Mena, but not VASP, promotes clathrin-mediated uptake of Shigella protrusions in recipient cells (Fukumatsu et al, 2012); our data indicating that the role of the VASP EVH1 domain in restriction of spread is largely in the recipient cell raise the possibility that VASP competitively inhibits Mena function in this process.…”

“…Focal adhesions are dynamic complexes containing w50 proteins that actively participate in cell migration by connecting contractile cytoskeletal elements to the plasma membrane and transmitting the force that is generated to the extracellular matrix (Lo, 2006;Plotnikov & Waterman, 2013). The number and stability of focal adhesions contribute to cell-to-cell spread of Shigella, and components of focal adhesions are recruited to bacterial protrusions and sites of entry (Kim et al, 2009;Mounier et al, 1999).…”

“…The ability of VASP (and likely EVL) to restrict spread depends both on subcellular localization to focal adhesions and/or the leading edge and on phosphorylation at Ser153. The number and stability of focal adhesions contribute to cell-to-cell spread of Shigella, and components of focal adhesions are recruited to bacterial protrusions (Kim et al, 2009;Mounier et al, 1999). Our data demonstrate that localization of VASP to focal adhesions is critical to the role of VASP in restricting Shigella spread.…”

The Inside Story of Shigella Invasion of Intestinal Epithelial Cells

“…1) (Kim et al 2009). Reinforcement of cell adhesion to the matrix may represent an important factor during infection, by preventing their clearing in the intestinal lumen (Kim et al 2009). …”

“…Another T3S effector, OspE, binds to ILK (integrin-like kinase) to stabilize integrin-dependent attachment of the cell to the basal matrix ( Fig. 1) (Kim et al 2009). Reinforcement of cell adhesion to the matrix may represent an important factor during infection, by preventing their clearing in the intestinal lumen (Kim et al 2009).…”