Defining the role of Pseudomonas aeruginosa PilY1 in signaling and virulence.

Pseudomonas aeruginosa (Pa) is an important opportunistic pathogen that has many virulence factors expressed in a coordinated manner to cause infection. The PilY1 protein is a component of the type IV pili (T4P) but has additional signaling functions outside of the pilus. A major function of PilY1 is to prevent the AlgZ/R two-component system from functioning. However, the complete effects of PilY1 signaling through the control of the AlgZ/R or other regulatory systems are not well understood. In this study, we determine new genes controlled by the AlgZ/R system that are impacted by PilY1. We discovered that PilY1 impacts cAMP by preventing the AlgZ/R system from activating the major adenylate cyclase, cyaB. PilY1 also prevents the AlgZ/R system from activating itself and a putative c-di-GMP phosphodiesterase, PA4781. Furthermore, PilY1 functions in different P. aeruginosa strains, including mucoid strains. Surprisingly, bacterial survival in the lung, liver, and blood did not require PilY1. Overall, these findings suggest that PilY1 is critical for preventing AlgZ/R activity to prevent improper second messenger production. This work identifies new AlgZ/R targets and implicates the AlgZ/R system in the control of cAMP in P. aeruginosa. This work identifies a possible way to use PilY1 to prevent the expression of the major adenylate cyclase using PilY1 which could be used to impact P. aeruginosa virulence.IMPORTANCEUnderstanding PilY1 signaling is important for elucidating how P. aeruginosa adapts to different environments. A major function for PilY1 is to interfere with the AlgZ/R two-component system. Here, we use transcriptomics to determine genes PilY1 affects through the AlgZ/R system. We identified new AlgZ/R targets and established a mechanism for impacting cAMP levels. Our findings further our understanding of PilY1 and the AlgZ/R system and suggest a possible way that PilY1 might be used to prevent cAMP from increasing in P. aeruginosa.