Pseudomonas aeruginosa Type III secretion system (T3SS)

The Pseudomonas aeruginosa Type III secretion system (T3SS) is a sophisticated, needle-like protein apparatus, often called an injectisome, that allows the bacterium to deliver toxic effector proteins (ExoS, ExoT, ExoU, and ExoY) directly into the cytoplasm of host cells (Hauser, 2009, Nature Reviews Microbiology). This system is a critical virulence factor that facilitates immune evasion by killing phagocytes and disrupting epithelial barriers, which is essential for the pathogenesis of acute infections such as ventilator-associated pneumonia and septicemia (Galle et al., 2012, Current Opinion in Microbiology). The T3SS consists of a basal body spanning both bacterial membranes, a needle-like projection (PscF), and a translocon complex (PcrV, PopB, PopD) that forms a pore in the host cell membrane (Anantharajah et al., 2016, Frontiers in Microbiology). Because the T3SS is essential for virulence but not for bacterial growth, it is a prime target for anti-virulence therapies that aim to disarm the pathogen without exerting the strong selective pressure associated with traditional antibiotics, potentially reducing the development of resistance (Dickey et al., 2017, Nature Reviews Drug Discovery). Current drug development efforts include monoclonal antibodies like MEDI3902, which targets the PcrV tip protein to prevent translocon assembly, and various small molecules designed to inhibit the secretion machinery or effector translocation (Warrener et al., 2014, Antimicrobial Agents and Chemotherapy). This target is particularly relevant for treating multi-drug resistant P. aeruginosa infections in vulnerable populations, including cystic fibrosis patients and those in intensive care units.

Other names

InjectisomePsc secretion systemType 3 secretion systemT3SS apparatusHrp-like secretion system

Drugs targeting the T3SS primarily function by blocking the assembly or function of the translocon pore at the needle tip (e.g., anti-PcrV antibodies), inhibiting the ATPase (PscN) that powers protein secretion, or preventing the expression of T3SS genes through interference with regulatory pathways (Anantharajah et al., 2016, Frontiers in Microbiology; Warrener et al., 2014, Antimicrobial Agents and Chemotherapy).