Translocated EspF protein from enteropathogenic Escherichia coli disrupts host intestinal barrier function

Area of Science:

• Microbiology
• Cell Biology
• Pathogenesis

Background:

• Enteropathogenic Escherichia coli (EPEC) causes infant diarrhea, but its mechanisms are unclear.
• EPEC utilizes a type III secretion system for attaching and effacing (A/E) lesions, altering host cell cytoskeleton and surface.
• EPEC infection reduces transepithelial electrical resistance (TER) in intestinal cells, a process dependent on the type III secretion system.

Purpose of the Study:

• To investigate the role of the EPEC secreted protein EspF in host cellpathogenesis.
• To determine if EspF is involved in A/E lesion formation or intestinal barrier disruption.
• To elucidate the mechanism by which EspF affects intestinal epithelial cells.

Main Methods:

• Utilized EPEC strains with and without EspF to infect polarized intestinal epithelial cell monolayers.
• Assessed A/E lesion formation, transepithelial electrical resistance (TER), and monolayer permeability.
• Investigated the localization of EspF within host cells using EspF-adenylate cyclase fusion proteins and immunofluorescence microscopy.

Main Results:

• EspF is not essential for typical A/E lesion formation by EPEC.
• EspF is required in a dose-dependent manner to decrease TER and increase monolayer permeability.
• EspF mediates the redistribution of the tight junction protein occludin.
• EspF is translocated into the host cell cytoplasm via the type III secretion system.

Conclusions:

• EspF acts as an effector protein of EPEC that disrupts intestinal barrier function.
• EspF contributes to EPEC-induced diarrhea by compromising intestinal epithelial integrity.
• The mechanism of barrier disruption by EspF is distinct from A/E lesion formation.