Regulation of T3SS synthesis, assembly and secretion in Pseudomonas aeruginosa

Abstract

T3SS is an important virulence factor of Pseudomonas aeruginosa and has a central role in the infection process. However, the functional regulation of the T3SS by environmental signals is poorly understood. In our lab, we use fluorescence microscopy to study protein kinetics in real-time in live cells. In P. aeruginosa, results have shown that T3SS appears as bright foci at the cell membrane with no specific arrangement. In addition, T3SS is tightly controlled as it appears under a limited time period with the highest intensity at 3 h then disappears. Surprisingly, only 2.5% of the all assembled T3SS in the population have detectable ExoS synthesis. While T3SS assembly and ExoS synthesis increased under high salt concentration, they unexpectedly were not affected by different cyclic di-GMP levels. On the other hand, T3SS itself has an effect on the cyclic di-GMP levels inside the cell. Data have shown that despite T3SS in P. aeruginosa and Yersinia enterocolitica belong to the same the group, the two systems differentiate greatly in activity and regulation. We can conclude that every T3SS is unique and thus further studies are needed to elucidate the functional regulation of each system to better help effective inhibitor design.

Pseudomonas aeruginosa two-component system CprRS regulates HigBA expression and bacterial cytotoxicity in response to LL-37 stress

“…Since T3SS plays a crucial role in the interaction between P . aeruginosa and the host immune system, particularly in immune evasion and cytotoxicity towards host cells [ 41 , 42 ], we subsequently assessed and compared the expression of key regulators and effectors of T3SS in WT and mutant strains under LL-37 stimulation ( Fig 6E ). We demonstrated that LL-37 treatment significantly upregulated the expression of exsA and effectors exoS , exoT , and exoU by 2.74- to 6.68-fold in the WT strain compared to untreated group.…”

“…In the case of P . aeruginosa infections, the bacteria heavily rely on the T3SS to deliver effectors into host cells, thereby interfering with the expression of pro-inflammatory factors and subverting host immunity [ 28 , 41 ]. To explore the impact of CprRS on host inflammatory responses, we assessed the levels of critical inflammatory cytokines [tumor necrosis factor–α (TNF-α), interleukin-1β (IL-1β), IL-8, and IL-12] in RAW264.7 macrophages following infections [ 45 ].…”

“…T3SS is a complex "molecular syringe" that injects various effectors (e.g., ExoS, ExoU, ExoY, and ExoT) that target essential cell signaling pathways [ 28 , 41 ], disrupt cytoskeleton synthesis, and inhibit inflammasome activation. T3SS also activates caspase-1 proteolysis and inflammasome-mediated responses, resulting in pyroptosis and the release of inflammatory cytokines.…”

Transcriptome Dynamics of Pseudomonas aeruginosa during Transition from Overlapping To Non-Overlapping Cell Cycles

“…A high activity was seen for oxidative phosphorylation and also for biosynthesis of the vitamins folate (B9) and cobalamin (B12), in accordance with their respective roles in DNA and methionine synthesis. Expression of the type III secretion system gene clusters psc and pcr and the exoT effector ( 17 ) peaked at 2 h of cultivation followed by a steep decline.…”

Transcriptome dynamics ofPseudomonas aeruginosaduring transition from replication-uncoupled to -coupled growth

“…Expression of the type III secretion system gene clusters psc and pcr and the exoT effector 17 peaked at 2 h of cultivation followed by a steep decline. Cluster 4 to 6 contained genes that were transiently activated at the end of exponential growth.…”