Modulation of bacterial entry into epithelial cells by association between vinculin and the Shigella IpaA invasin.
ABSTRACT Shigella flexneri is the causative agent of bacillary dysentery in humans. Shigella invasion of epithelial cells is characterized by cytoskeletal rearrangements and formation of cellular projections engulfing the bacterium in a macropinocytic process. We show here that vinculin, a protein involved in linking actin filaments to the plasma membrane, is a direct target of Shigella during cell invasion. IpaA, a Shigella protein secreted upon cell contact, rapidly associates with vinculin during bacterial invasion. Although defective for cell entry, an ipaA mutant is still able to induce foci of actin polymerization, but differs from wild-type Shigella in its ability to recruit vinculin and alpha-actinin. Presumably, IpaA-vinculin interaction initiates the formation of focal adhesion-like structures required for efficient invasion.
Full-textDOI: · Available from: Avri Ben-Ze'ev, Jun 22, 2015
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ABSTRACT: Photocontrol of functional peptides is a powerful tool for spatial and temporal control of cell signaling events. We show that the genetically encoded light-sensitive LOV2 domain of Avena Sativa phototropin 1 (AsLOV2) can be used to reversibly photomodulate the affinity of peptides for their binding partners. Sequence analysis and molecular modeling were used to embed two peptides into the Jα helix of the AsLOV2 domain while maintaining AsLOV2 structure in the dark but allowing for binding to effector proteins when the Jα helix unfolds in the light. Caged versions of the ipaA and SsrA peptides, LOV-ipaA and LOV-SsrA, bind their targets with 49- and 8-fold enhanced affinity in the light, respectively. These switches can be used as general tools for light-dependent colocalization, which we demonstrate with photo-activable gene transcription in yeast.Chemistry & biology 04/2012; 19(4):507-17. DOI:10.1016/j.chembiol.2012.02.006 · 6.59 Impact Factor
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ABSTRACT: Shigella, the Gram-negative enteroinvasive bacterium that causes shigellosis, relies on its type III secretion system (TTSS) and injected effectors to modulate host cell functions. However, consequences of the interaction between Shigella and lymphocytes have not been investigated. We show that Shigella invades activated human CD4(+) T lymphocytes. Invasion requires a functional TTSS and results in inhibition of chemokine-induced T cell migration, an effect mediated by the TTSS effector IpgD, a phosphoinositide 4-phosphatase. Remarkably, IpgD injection into bystander T cells can occur in the absence of cell invasion. Upon IpgD-mediated hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP(2)), the pool of PIP(2) at the plasma membrane is reduced, leading to dephosphorylation of the ERM proteins and their inability to relocalize at one T cell pole upon chemokine stimulus, likely affecting the formation of the polarized edge required for cell migration. These results reveal a bacterial TTSS effector-mediated strategy to impair T cell function.Cell host & microbe 04/2011; 9(4):263-72. DOI:10.1016/j.chom.2011.03.010 · 12.19 Impact Factor
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ABSTRACT: Salmonella typhimurium colonizes the intestinal epithelium by injecting an array of effector proteins into host cells that induces phagocytic uptake of attached bacteria. However, the host molecules targeted by these effectors remain poorly defined. Here, we demonstrate that S. typhimurium induces formation of focal adhesion-like complexes at sites of bacterial attachment and that both focal adhesion kinase (FAK) and the scaffolding protein p130Cas are required for Salmonella uptake. Entry of Salmonella into FAK(-/-) cells is dramatically impaired and can be restored to control levels by expression of wild-type FAK. Surprisingly, reconstitution of bacterial internalization requires neither the kinase domain of FAK nor activation of c-Src, but does require a C-terminal PXXP motif through which FAK interacts with Cas. Infection of Cas(-/-) cells is also impaired, and reconstitution of invasiveness requires the central Cas YXXP repeat domain. The invasion defect in Cas(-/-) cells can be suppressed by overexpression of FAK, suggesting a functional link between FAK and Cas in the regulation of Salmonella invasion. Together, these findings reveal a novel role for focal adhesion proteins in the invasion of host cells by Salmonella.Molecular Biology of the Cell 12/2006; 17(11):4698-708. DOI:10.1091/mbc.E06-06-0492 · 4.55 Impact Factor