Role of the Francisella tularensis Antioxidant Transcriptional Regulator OxyR in Oxidative Stress Resistance
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Issue Date
2016
Authors
Russo, Vincenzo '16
Degree
MS in Pharmaceutical Sciences
Advisor
Malik, Meenakshi
Committee Members
Dearborn, Richard E.
LaRocca, Timothy
Yager, Eric
LaRocca, Timothy
Yager, Eric
Journal Title
Journal ISSN
Volume Title
Abstract
Francisella tularensis is a highly virulent human pathogen. The ability of F. tularensis to cause a fulminate infection is due in part to its ability to survive and replicate in phagocytic cells involved in host\342\200\231s innate immune defense. In order to establish an intracellular niche, F. tularensis has to overcome oxidative stress posed by reactive oxygen species. The genome sequence analysis reveals the presence of oxyR, while both soxR/soxS regulons are absent in F. tularensis. The presence of OxyR as the only oxidant stress regulator indicates that regulation of oxidative stress response genes in Francisella are unique. However, nothing is known about the wider regulatory role of OxyR during Francisella infection. This study investigated the role of OxyR of F. tularensis in tularemia pathogenesis and regulation of genes involved in oxidative stress response. We generated a deletion mutant (\316\224oxyR) and a transcomplemented strain of oxyR gene of F. tularensis LVS. The oxyR mutant was characterized for its sensitivity towards oxidants and antibiotics. To investigate the regulatory role of OxyR, we performed iTRAQ analysis, chromatin immunoprecipitation (ChIP) and electrophoretic mobility shift assays (EMSA). To assess the role of OxyR in pathogenesis, we tested the capacity of the \357\201\204oxyR mutant to survive in macrophages, its virulence in mice and its impact on host cell defenses. We demonstrate that OxyR of F. tularensis is required for resistance to oxidants, survival in macrophages and virulence in mice, yet not for inflammasome activation. Proteomic analysis revealed differential expression of multiple proteins associated with oxidative stress resistance and cellular functions in the \316\224oxyR mutant as compared to the wild-type F. tularensis LVS, indicating that OxyR serves as a global regulator of oxidant stress response. Most importantly, OxyR regulates transcription of primary antioxidant enzyme genes ahpC, katG and sodB by binding directly to their upstream promoter regions. These results highlight that OxyR is an important regulator of oxidative stress response and renders F. tularensis a pathoadaptive advantage to establish an intracellular niche. An understanding of these unique pathogenic mechanisms is essential for the development of effective therapeutics and prophylactics against this important biothreat agent.
Citation
Russo V. Role of the Francisella Tularensis antioxidant transcriptional regulator OxyR in oxidative stress resistance [thesis]. Ann Arbor (MI): Proquest LLC; 2016. 96 p.
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