The Enhancer-Binding Protein MifR, an Essential Regulator of α-Ketoglutarate Transport, Is Required for Full Virulence of Pseudomonas aeruginosa PAO1 in a Mouse Model of Pneumonia

Abstract

The opportunistic human pathogen Pseudomonas aeruginosa PAO1 has an extensive metabolism, enabling it to utilize a wide range of structurally diverse compounds to meet its nutritional and energy needs. Interestingly, the utilization of some of the more unusual compounds often associated with a eukaryotic-host environment is regulated via enhancer-binding proteins (EBPs) in P. aeruginosa . Whether the utilization of such compounds and the EBPs involved contribute to the pathogenesis of P. aeruginosa remains to be fully understood. To narrow this gap, we investigated the roles of the EBPs EatR (regulator of ethanolamine catabolism), DdaR (regulator of methylarginine catabolism), and MifR (regulator of α-ketoglutarate or α-KG transport) in the virulence of P. aeruginosa PAO1 in a pneumonia-induced septic mouse model. Deletion of genes encoding EatR and DdaR had no significant effect on the mortality of P. aeruginosa PAO1-infected mice compared to wide-type (WT) PAO1-infected mice. In contrast, infected mice with Δ mifR mutant exhibited a significant reduction (~50%) in the mortality rate compared with WT PAO1 ( P < 0.05). Infected mice with Δ mifR PAO1 had lower lung injury scores, fewer inflammatory cells, decreased proinflammatory cytokines, and decreased apoptosis and cell death compared to mice infected with WT PAO1 ( P < 0.05). Furthermore, molecular analysis revealed decreased NLRP3 inflammasome activation in infected mice with Δ mifR PAO1 compared to WT PAO1 ( P < 0.05). These results suggested that the utilization of α-KG was a contributing factor in P. aeruginosa -mediated pneumonia and sepsis and that MifR-associated regulation may be a potential therapeutic target for P. aeruginosa infectious disease.

Transcriptional Regulators Controlling Virulence in Pseudomonas aeruginosa

“…MifR has also been shown to alter the production of at least 18 proteins when mutated or overexpressed, many of which are involved in growth under anaerobic conditions, suggesting a link between biofilm formation and oxygen restriction [42]. In a pneumonia mouse model, a mifR mutant showed significant defects in virulence and mortality, with fewer lung injuries, a lower inflammatory response, and reduced cell death [150].…”

Novel evidence on sepsis-inducing pathogens: from laboratory to bedside

“…Several genes related to P. aeruginosa metabolism have been associated with the level of virulence of the strain PAO1, extensively used in sepsis models. Deletion of the regulator of α-ketoglutarate transport mifR resulted in a significant improvement of survival following pneumonia-induced sepsis in a murine model as well as a reduction in pro-inflammatory cytokines and reduced NLRP3 inflammasome activation (Xiong et al, 2022). In addition, expression of enzymes able to degrade host extracellular matrix components such as heparinase contribute to the virulence of sepsis-inducing strain P. aeruginosa PA14.…”