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Pseudomonas aeruginosa internalization by corneal epithelial cells involves MEK and ERK signal transduction proteins
David J Evans1, Inna A Maltseva, Josephine Wu
1Morton D. Sarver Laboratory for Cornea and Contact Lens Research, School of Optometry, University of California, Berkeley, CA 94720, USA.
Abstract:
Invasion of epithelial cells represents a potential pathogenic mechanism for Pseudomonas aeruginosa. We explored the role of mitogen-activated protein kinase kinases (MEK 1/2) and the extracellular signal-regulated kinases (ERK 1/2) in P. aeruginosa invasion. Treatment of corneal epithelial cells with MEK inhibitors, PD98059 (20 microM) or UO126 (100 microM), reduced P. aeruginosa invasion by approximately 60% without affecting bacterial association with the cells (P=0.0001). UO124, a negative control for UO126, had no effect on bacterial internalization. Infection of cells with an internalization-defective flhA mutant of P. aeruginosa was associated with less ERK 1/2 tyrosine phosphorylation than infection with wild-type invasive P. aeruginosa. An ERK-2 inhibitor, 5-iodotubercidin (20 microM), reduced P. aeruginosa invasion by approximately 40% (P=0.035). Together, these data suggest that P. aeruginosa internalization by epithelial cells involves a pathway(s) that includes MEK and ERK signaling proteins.
Insights
Pseudomonas aeruginosa invasion of epithelial cells involves MEK and ERK signaling pathways. Inhibiting these pathways significantly reduced bacterial internalization, suggesting therapeutic targets for P. aeruginosa infections.
Area of Science:
- Microbiology
- Cell Biology
- Molecular Biology
Background:
- Pseudomonas aeruginosa is an opportunistic pathogen.
- Bacterial invasion of host epithelial cells is a key pathogenic mechanism.
- The role of specific intracellular signaling pathways in bacterial invasion is not fully understood.
Purpose of the Study:
- To investigate the involvement of mitogen-activated protein kinase kinases (MEK 1/2) and extracellular signal-regulated kinases (ERK 1/2) in Pseudomonas aeruginosa invasion of corneal epithelial cells.
Main Methods:
- Corneal epithelial cells were treated with MEK inhibitors (PD98059, UO126) and an ERK-2 inhibitor (5-iodotubercidin).
- Bacterial association and internalization of P. aeruginosa were quantified.
- ERK 1/2 tyrosine phosphorylation levels were assessed after infection with wild-type and mutant P. aeruginosa.
Main Results:
- MEK inhibitors (PD98059, UO126) reduced P. aeruginosa invasion by approximately 60% without affecting bacterial association.
- An ERK-2 inhibitor (5-iodotubercidin) reduced invasion by approximately 40%.
- Infection with an internalization-defective P. aeruginosa mutant showed reduced ERK 1/2 phosphorylation compared to wild-type.
Conclusions:
- The MEK and ERK signaling pathways are involved in P. aeruginosa internalization by epithelial cells.
- These signaling proteins represent potential targets for therapeutic intervention against P. aeruginosa infections.