Microarray analysis of Shigella flexneri-infected epithelial cells identifies host factors important for apoptosis inhibition

Christina S Faherty,D Scott Merrell,Aishwarya V Ramaswamy,Anthony T Maurelli,Cristina Semino-Mora,Andre Dubois

doi:10.1186/1471-2164-11-272

Christina S Faherty, D Scott Merrell + Show 4 more

Open Access

https://doi.org/10.1186/1471-2164-11-272

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Abstract

BackgroundShigella flexneri inhibits apoptosis in infected epithelial cells. In order to understand the pro-survival effects induced by the bacteria, we utilized apoptosis-specific microarrays to analyze the changes in eukaryotic gene expression in both infected and uninfected cells in the presence and absence of staurosporine, a chemical inducer of the intrinsic pathway of apoptosis. The goal of this research was to identify host factors that contribute to apoptosis inhibition in infected cells.ResultsThe microarray analysis revealed distinct expression profiles in uninfected and infected cells, and these changes were altered in the presence of staurosporine. These profiles allowed us to make comparisons between the treatment groups. Compared to uninfected cells, Shigella-infected epithelial cells, both in the presence and absence of staurosporine, showed significant induced expression of JUN, several members of the inhibitor of apoptosis gene family, nuclear factor κB and related genes, genes involving tumor protein 53 and the retinoblastoma protein, and surprisingly, genes important for the inhibition of the extrinsic pathway of apoptosis. We confirmed the microarray results for a selection of genes using in situ hybridization analysis.ConclusionInfection of epithelial cells with S. flexneri induces a pro-survival state in the cell that results in apoptosis inhibition in the presence and absence of staurosporine. The bacteria may target these host factors directly while some induced genes may represent downstream effects due to the presence of the bacteria. Our results indicate that the bacteria block apoptosis at multiple checkpoints along both pathways so that even if a cell fails to prevent apoptosis at an early step, Shigella will block apoptosis at the level of caspase-3. Apoptosis inhibition is most likely vital to the survival of the bacteria in vivo. Future characterization of these host factors is required to fully understand how S. flexneri inhibits apoptosis in epithelial cells.

Highlights

Shigella flexneri inhibits apoptosis in infected epithelial cells
We found numerous alterations in host factors, including the jun oncogene, inhibitor of apoptosis gene family members, nuclear factor κB (NF-κB), and genes involving tumor protein 53 and the retinoblastoma protein, all of which are important for the pro-survival state of the infected cell
To highlight our previous report that S. flexneri inhibits STS-induced apoptosis, we performed the apoptosis assay with a strain of bacteria expressing a green fluorescence protein (GFP) on a low copy plasmid

Summary

Introduction

Shigella flexneri inhibits apoptosis in infected epithelial cells. The goal of this research was to identify host factors that contribute to apoptosis inhibition in infected cells. Shigella flexneri is a Gram-negative, facultative intracellular organism, and the causative agent of bacillary dysentery. Infection with Shigella causes an intense acute inflammatory reaction that leads to the destruction of the colonic epithelium [1]. Clinical symptoms include watery diarrhea, severe abdominal pain, and bloody, mucoid stools. These symptoms of dysentery are due to the penetration of Shigella into colonic epithelial cells, which pro-. We previously demonstrated that S. flexneri inhibits apoptosis in epithelial cells [2].

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