Role of EscU auto-cleavage in promoting type III effector translocation into host cells by enteropathogenic Escherichia coli

Enteropathogenic Escherichia coli (EPEC) belongs to a family of related bacterial pathogens, including enterohemorrhagic Escherichia coli (EHEC) O157:H7 and other human and animal diarrheagenic pathogens that form attaching and effacing (A/E) lesions on host epithelial surfaces. Bacterial secreted Esp proteins and a type III secretion system are conserved among these pathogens and trigger host cell signal transduction pathways and cytoskeletal rearrangements, and mediate intimate bacterial adherence to epithelial cell surfaces in vitro. However, their role in pathogenesis is still unclear. To investigate the role of Esp proteins in disease, mutations in espA and espB were constructed in rabbit EPEC serotype O103 and infection characteristics were compared to that of the wild-type strain using histology, scanning and transmission electron microscopy, and confocal laser scanning microscopy in a weaned rabbit infection model. The virulence of EspA and EspB mutant strains was severely attenuated. Additionally, neither mutant strain formed A/E lesions, nor did either one cause cytoskeletal actin rearrangements beneath the attached bacteria in the rabbit intestine. Collectively, this study shows for the first time that the type III secreted proteins EspA and EspB are needed to form A/E lesions in vivo and are indeed virulence factors. It also confirms the role of A/E lesions in disease processes.

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Distribution of espI among clinical enterohaemorrhagic and enteropathogenic Escherichia coli isolates

Journal of Medical Microbiology ◽

10.1099/jmm.0.45684-0 ◽

2004 ◽

Vol 53 (11) ◽

pp. 1145-1149 ◽

Cited By ~ 29

Author(s):

Rosanna Mundy ◽

Claire Jenkins ◽

Jun Yu ◽

Henry Smith ◽

Gad Frankel

Keyword(s):

Escherichia Coli ◽

Type Iii Secretion ◽

Severe Disease ◽

Pathogenicity Island ◽

Effector Proteins ◽

Effector Protein ◽

Enteropathogenic Escherichia Coli ◽

Type Iii Effector ◽

Type Iii

Enterohaemorrhagic (EHEC) and enteropathogenic (EPEC) Escherichia coli are important diarrhoeagenic pathogens; infection is dependent on translocation of a number of type III effector proteins. Until recently all the known effectors were encoded on the LEE pathogenicity island, which also encodes the adhesin intimin and the type III secretion apparatus. Recently, a novel non-LEE effector protein, EspI/NleA, which is required for full virulence in vivo and is encoded on a prophage, was identified. The aim of this study was to determine the distribution of espI among clinical EHEC and EPEC isolates. espI was detected in 86 % and 53 % of LEE+ EHEC and EPEC strains, respectively. Moreover, the espI gene was more commonly found in patients suffering from a more severe disease.

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

Biochemical Journal ◽

10.1042/bj20111620 ◽

2012 ◽

Vol 442 (1) ◽

pp. 119-125 ◽

Cited By ~ 28

Author(s):

Neta Sal-Man ◽

Wanyin Deng ◽

B. Brett Finlay

Keyword(s):

Escherichia Coli ◽

Type Iii Secretion ◽

Type Iii Secretion System ◽

Integral Membrane Protein ◽

Secretion System ◽

Host Cells ◽

Enteropathogenic Escherichia Coli ◽

Bacterial Membranes ◽

Type Iii ◽

Protein Functions

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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