Enteropathogenic E. coli-induced barrier function alteration is not a consequence of host cell apoptosis

Area of Science:

• Microbiology
• Cell Biology
• Pathogen-Host Interactions

Background:

• Enteropathogenic Escherichia coli (EPEC) is a significant diarrheal pathogen.
• EPEC utilizes a type III secretion system to deliver effector proteins into host intestinal epithelial cells.
• The effector protein EspF is implicated in disrupting epithelial barrier function and inducing host cell death.

Purpose of the Study:

• To investigate the relationship between EspF-mediated host cell death and epithelial barrier disruption.
• To determine if EspF's mitochondrial localization is essential for its effects on barrier function.

Main Methods:

• Site-directed mutagenesis of the EspF leucine 16 residue (L16E) to abolish mitochondrial localization and cell death.
• Assessment of EPEC's ability to secrete wild-type and mutant EspF.
• Evaluation of tight junction protein redistribution and epithelial barrier function.
• Utilizing a pan-caspase inhibitor (Q-VD-OPH) to assess the role of apoptosis in barrier disruption.

Main Results:

• Mutating EspF at L16 impaired mitochondrial localization and host cell death but not tight junction alteration or barrier disruption.
• EspF(L16E) was efficiently secreted by EPEC.
• Inhibition of caspases reduced EPEC-induced cell death but did not affect infection-mediated barrier function alteration.

Conclusions:

• EPEC alters intestinal epithelial barrier function independently of its ability to induce host cell death.
• EspF's role in epithelial barrier disruption is separable from its role in triggering mitochondrial-mediated cell death.