EscI: a crucial component of the type III secretion system forms the inner rod structure in enteropathogenic Escherichia coli

The T3SS (type III secretion system) is a multi-protein complex that plays a central role in the virulence of many Gram-negative bacterial pathogens. This apparatus spans both bacterial membranes and transports virulence factors from the bacterial cytoplasm into eukaryotic host cells. The T3SS exports substrates in a hierarchical and temporal manner. The first secreted substrates are the rod/needle proteins which are incorporated into the T3SS apparatus and are required for the secretion of later substrates, the translocators and effectors. In the present study, we provide evidence that rOrf8/EscI, a poorly characterized locus of enterocyte effacement-encoded protein, functions as the inner rod protein of the T3SS of EPEC (enteropathogenic Escherichia coli). We demonstrate that EscI is essential for type III secretion and is also secreted as an early substrate of the T3SS. We found that EscI interacts with EscU, the integral membrane protein that is linked to substrate specificity switching, implicating EscI in the substrate-switching event. Furthermore, we showed that EscI self-associates and interacts with the outer membrane secretin EscC, further supporting its function as an inner rod protein. Overall, the results of the present study suggest that EscI is the YscI/PrgJ/MxiI homologue in the T3SS of attaching and effacing pathogens.

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EspZ of Enteropathogenic and Enterohemorrhagic Escherichia coli Regulates Type III Secretion System Protein Translocation

mBio ◽

10.1128/mbio.00317-12 ◽

2012 ◽

Vol 3 (5) ◽

Cited By ~ 29

Author(s):

Cedric N. Berger ◽

Valerie F. Crepin ◽

Kobi Baruch ◽

Aurelie Mousnier ◽

Ilan Rosenshine ◽

...

Keyword(s):

Escherichia Coli ◽

Type Iii Secretion ◽

Protein Translocation ◽

Type Iii Secretion System ◽

Secretion System ◽

Enterohemorrhagic Escherichia Coli ◽

Host Cells ◽

Dependent Manner ◽

Content Type ◽

Type Iii

ABSTRACTTranslocation of effector proteins via a type III secretion system (T3SS) is a widespread infection strategy among Gram-negative bacterial pathogens. Each pathogen translocates a particular set of effectors that subvert cell signaling in a way that suits its particular infection cycle. However, as effector unbalance might lead to cytotoxicity, the pathogens must employ mechanisms that regulate the intracellular effector concentration. We present evidence that the effector EspZ controls T3SS effector translocation from enteropathogenic (EPEC) and enterohemorrhagic (EHEC)Escherichia coli. Consistently, an EPECespZmutant is highly cytotoxic. Following ectopic expression, we found that EspZ inhibited the formation of actin pedestals as it blocked the translocation of Tir, as well as other effectors, including Map and EspF. Moreover, during infection EspZ inhibited effector translocation following superinfection. Importantly, while EspZ of EHEC O157:H7 had a universal “translocation stop” activity, EspZ of EPEC inhibited effector translocation from typical EPEC strains but not from EHEC O157:H7 or its progenitor, atypical EPEC O55:H7. We found that the N and C termini of EspZ, which contains two transmembrane domains, face the cytosolic leaflet of the plasma membrane at the site of bacterial attachment, while the extracellular loop of EspZ is responsible for its strain-specific activity. These results show that EPEC and EHEC acquired a sophisticated mechanism to regulate the effector translocation.IMPORTANCEEnteropathogenicEscherichia coli(EPEC) and enterohemorrhagicE. coli(EHEC) are important diarrheal pathogens responsible for significant morbidity and mortality in developing countries and the developed world, respectively. The virulence strategy of EPEC and EHEC revolves around a conserved type III secretion system (T3SS), which translocates bacterial proteins known as effectors directly into host cells. Previous studies have shown that when cells are infected in two waves with EPEC, the first wave inhibits effector translocation by the second wave in a T3SS-dependent manner, although the factor involved was not known. Importantly, we identified EspZ as the effector responsible for blocking protein translocation following a secondary EPEC infection. Interestingly, we found that while EspZ of EHEC can block protein translocation from both EPEC and EHEC strains, EPEC EspZ cannot block translocation from EHEC. These studies show that EPEC and EHEC employ a novel infection strategy to regulate T3SS translocation.

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Epithelial cells detect functional type III secretion system of enteropathogenic Escherichia coli through a novel NF-κB signaling pathway

PLoS Pathogens ◽

10.1371/journal.ppat.1006472 ◽

2017 ◽

Vol 13 (7) ◽

pp. e1006472 ◽

Cited By ~ 11

Author(s):

Yael Litvak ◽

Shir Sharon ◽

Meirav Hyams ◽

Li Zhang ◽

Simi Kobi ◽

...

Keyword(s):

Escherichia Coli ◽

Epithelial Cells ◽

Signaling Pathway ◽

Type Iii Secretion ◽

Type Iii Secretion System ◽

Secretion System ◽

Enteropathogenic Escherichia Coli ◽

Functional Type ◽

Type Iii

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Dynamics of Expression and Maturation of the Type III Secretion System of Enteropathogenic Escherichia coli

Journal of Bacteriology ◽

10.1128/jb.00069-14 ◽

2014 ◽

Vol 196 (15) ◽

pp. 2798-2806 ◽

Cited By ~ 12

Author(s):

G. Yerushalmi ◽

Y. Litvak ◽

L. Gur-Arie ◽

I. Rosenshine

Keyword(s):

Escherichia Coli ◽

Type Iii Secretion ◽

Type Iii Secretion System ◽

Secretion System ◽

Enteropathogenic Escherichia Coli ◽

Type Iii

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SepZ/EspZ Is Secreted and Translocated into HeLa Cells by the Enteropathogenic Escherichia coli Type III Secretion System

Infection and Immunity ◽

10.1128/iai.73.7.4327-4337.2005 ◽

2005 ◽

Vol 73 (7) ◽

pp. 4327-4337 ◽

Cited By ~ 50

Author(s):

Kristen J. Kanack ◽

J. Adam Crawford ◽

Ichiro Tatsuno ◽

Mohamed A. Karmali ◽

James B. Kaper

Keyword(s):

Escherichia Coli ◽

Hela Cells ◽

Type Iii Secretion ◽

Type Iii Secretion System ◽

Secretion System ◽

Bacterial Attachment ◽

Host Cells ◽

Dependent Manner ◽

Cell Infection ◽

Type Iii

ABSTRACT Enteropathogenic Escherichia coli (EPEC) is a major bacterial cause of infantile diarrhea in developing countries and is the prototype for a group of gastrointestinal pathogens causing characteristic attaching and effacing (A/E) histopathology on intestinal epithelia. A/E pathogens utilize a type III secretion system (TTSS), encoded by the locus of enterocyte effacement (LEE) pathogenicity island, to deliver effector proteins into host cells. Here, we investigate sequence divergence of the LEE-encoded SepZ protein and identify it as a TTSS-secreted and -translocated molecule. SepZ is hypervariable among A/E pathogens, with sequences sharing between 60 to 81% amino acid identity with SepZ of EPEC. A SepZ-CyaA fusion was secreted and translocated into HeLa cells in a TTSS-dependent manner. Additionally, we determined that the first 20 amino acids of SepZ were sufficient to direct its translocation. In contrast to previous studies suggesting a role in invasion and the structure and/or regulation of the TTSS, we found that SepZ does not mediate uptake of EPEC into host cells or affect translocation and tyrosine phosphorylation of the translocated intimin receptor. Immunohistochemistry reveals that, after an extended HeLa cell infection, accumulated SepZ can be detected beneath the site of bacterial attachment in a subset of pedestal regions. To indicate its newly identified status as a translocated effector protein, we propose to rename SepZ as EspZ.

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