Pseudomonas aeruginosa Toxin ExoU as a Therapeutic Target in the Treatment of Bacterial Infections

The opportunistic pathogen Pseudomonas aeruginosa employs the type III secretion system (T3SS) and four effector proteins, ExoS, ExoT, ExoU, and ExoY, to disrupt cellular physiology and subvert the host's innate immune response. Of the effector proteins delivered by the T3SS, ExoU is the most toxic. In P. aeruginosa infections, where the ExoU gene is expressed, disease severity is increased with poorer prognoses. This is considered to be due to the rapid and irreversible damage exerted by the phospholipase activity of ExoU, which cannot be halted before conventional antibiotics can successfully eliminate the pathogen. This review will discuss what is currently known about ExoU and explore its potential as a therapeutic target, highlighting some of the small molecule ExoU inhibitors that have been discovered from screening approaches.