Abstract
Pseudomonas aeruginosa is an important opportunistic pathogen which is capable of causing both acute and chronic infections in immunocompromised patients. Successful adaptation of the bacterium to its host environment relies on the ability of the organism to tightly regulate gene expression. RsmA, a small RNA-binding protein, controls the expression of a large number of virulence-related genes in P. aeruginosa, including those encoding the type III secretion system and associated effector proteins, with important consequences for epithelial cell morphology and cytotoxicity. In order to examine the influence of RsmA-regulated functions in the pathogen on gene expression in the host, we compared global expression profiles of airway epithelial cells in response to infection with P. aeruginosa PAO1 and an rsmA mutant. The RsmA-dependent response of host cells was characterized by significant changes in the global transcriptional pattern, including the increased expression of two Kruppel-like factors, KLF2 and KLF6. This increased expression was mediated by specific type III effector proteins. ExoS was required for the enhanced expression of KLF2, whereas both ExoS and ExoY were required for the enhanced expression of KLF6. Neither ExoT nor ExoU influenced the expression of the transcription factors. Additionally, the increased gene expression of KLF2 and KLF6 was associated with ExoS-mediated cytotoxicity. Therefore, this study identifies for the first time the human transcription factors KLF2 and KLF6 as targets of the P. aeruginosa type III exoenzymes S and Y, with potential importance in host cell death.