Dynamics of the Type III Secretion System Activity of Enteropathogenic Escherichia coli

e Attaching and effacing (A/E) pathogens adhere intimately to intestinal enterocytes and efface brush border microvilli. A key virulence strategy of A/E pathogens is the type III secretion system (T3SS)-mediated delivery of effector proteins into host cells. The secreted protein EspZ is postulated to promote enterocyte survival by regulating the T3SS and/or by modulating epithelial signaling pathways. To explore the role of EspZ in A/E pathogen virulence, we generated an isogenic espZ deletion strain (⌬espZ) and corresponding cis-complemented derivatives of rabbit enteropathogenic Escherichia coli and compared their abilities to regulate the T3SS and influence host cell survival in vitro. For virulence studies, rabbits infected with these strains were monitored for bacterial colonization, clinical signs, and intestinal tissue alterations. Consistent with data from previous reports, espZtransfected epithelial cells were refractory to infection-dependent effector translocation. Also, the ⌬espZ strain induced greater host cell death than did the parent and complemented strains. In rabbit infections, fecal ⌬espZ strain levels were 10-fold lower than those of the parent strain at 1 day postinfection, while the complemented strain was recovered at intermediate levels. In contrast to the parent and complemented mutants, ⌬espZ mutant fecal carriage progressively decreased on subsequent days. ⌬espZ mutant-infected animals gained weight steadily over the infection period, failed to show characteristic disease symptoms, and displayed minimal infection-induced histological alterations. Terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) staining of intestinal sections revealed increased epithelial cell apoptosis on day 1 after infection with the ⌬espZ strain compared to animals infected with the parent or complemented strains. Thus, EspZ-dependent host cell cytoprotection likely prevents epithelial cell death and sloughing and thereby promotes bacterial colonization.

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“…Translocation assays were performed as previously described (21,27), with some modifications. For the experiments described in the legend of Fig.…”

Section: Methodsmentioning

confidence: 99%

The Secreted Effector Protein EspZ Is Essential for Virulence of Rabbit Enteropathogenic Escherichia coli

et al. 2015

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“…15 Regarding the effect of Tir on the host immune response, TNF-α-induced NF-κB activation can be inhibited when TRAF2 is targeted for degradation independent of the proteasome upon interacting with Tir. 16 The recruitment of Src-homology 2 (SH2) domaincontaining phosphatases to immunoreceptor tyrosine-based inhibition motifs (ITIMs) is essential for the restriction of eukaryotic signaling pathways.…”

Section: Inhibiting Traf Ubiquitination and Activationmentioning

confidence: 99%

Modulation of host signaling in the inflammatory response by enteropathogenic Escherichia coli virulence proteins

Zhuang

Chen

et al. 2016

Cell Mol Immunol

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To successfully infect host cells and evade the host immune response, a type III secretion system (T3SS) is commonly used by enteric bacterial pathogens such as enteropathogenic Escherichia coli (EPEC). Recent findings have revealed that various effectors are injected into host cells through the T3SS and exert an inhibitory effect on inflammatory signaling pathways, subverting the immune responses to these pathogens. Here we review recent studies aimed at addressing the modulation of several important inflammatory signaling pathways modulated by EPEC effector proteins, such as the nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) pathways, which provides insight into the unfinished work in this unexplored field and helps to identify novel positions in inflammatory signaling networks for EPEC effectors.

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“…6 The chaperone CesT binds and enhances the translocation of Tir, Map and other LEE-effectors (EspH, EspJ, EspZ) and non-LEE (Nle) effectors (A, B1, B2, C, G, H1 and H2). 7,42 With the aim of analyzing the levels of Map, another CesT-dependent effector, we infected Nck-deficient cells with EPEC which carried a plasmid expressing Map fused in frame, to enable WB detection, with haemagglutinin (HA) and T7 epitope tags (WTCT7-map-HA).…”

Section: Phosphorylation Status Of Tir and Levels Of Tir Phosphorylatmentioning

confidence: 99%

“…5 Microcolony formation enhances EPEC attachment to host cells and facilitates the injection of effectors via T3SS. 6,7 The attached EPEC delivers the translocated Intimin receptor (Tir), which drives the major pathway responsible for regulating actin polymerization. Other translocated effectors include Mitochondrial associated protein (Map) and EPEC-secreted proteins (Esp) H, F, G, and Z that are encoded within a pathogenicity island termed the locus of enterocyte effacement (LEE).…”

Section: Introductionmentioning

confidence: 99%

Nck adaptors, besides promoting N-WASP mediated actin-nucleation activity at pedestals, influence the cellular levels of enteropathogenicEscherichia coliTir effector

Nieto-Pelegrín

Kenny

Martı́nez-Quiles

2014

Cell Adhesion & Migration

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Enteropathogenic Escherichia coli (EPEC) binding to human intestinal cells triggers the formation of diseaseassociated actin rich structures called pedestals. The latter process requires the delivery, via a Type 3 secretion system, of the translocated Intimin receptor (Tir) protein into the host plasma membrane where binding of a host kinasemodified form to the bacterial surface protein Intimin triggers pedestal formation. Tir-Intimin interaction recruits the Nck adaptor to a Tir tyrosine phosphorylated residue where it activates neural Wiskott-Aldrich syndrome protein (N-WASP); initiating the major pathway to actin polymerization mediated by the actin-related protein (Arp) 2/3 complex. Previous studies with Nck-deficient mouse embryonic fibroblasts (MEFs) identified a key role for Nck in pedestal formation, presumed to reflect a lack of N-WASP activation. Here, we show the defect relates to reduced amounts of Tir within Nck-deficient cells. Indeed, Tir delivery and, thus, pedestal formation defects were much greater for MEFs than HeLa (human epithelial) cells. Crucially, the levels of two other effectors (EspB/EspF) within Nck-deficient MEFs were not reduced unlike that of Map (Mitochondrial associated protein) which, like Tir, requires CesT chaperone function for efficient delivery. Interestingly, drugs blocking various host protein degradation pathways failed to increase Tir cellular levels unlike an inhibitor of deacetylase activity (Trichostatin A; TSA). Treatments with TSA resulted in significant recovery of Tir levels, potentiation of actin polymerization and improvement in bacterial attachment to cells. Our findings have important implications for the current model of Tir-mediated actin polymerization and opens new lines of research in this area.

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Dynamics of the Type III Secretion System Activity of Enteropathogenic Escherichia coli

Cited by 54 publications

References 34 publications

The Secreted Effector Protein EspZ Is Essential for Virulence of Rabbit Enteropathogenic Escherichia coli

The Secreted Effector Protein EspZ Is Essential for Virulence of Rabbit Enteropathogenic Escherichia coli

Modulation of host signaling in the inflammatory response by enteropathogenic Escherichia coli virulence proteins

Nck adaptors, besides promoting N-WASP mediated actin-nucleation activity at pedestals, influence the cellular levels of enteropathogenicEscherichia coliTir effector

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