Interplay between T3SS effectors, ExoY activation, and cGMP signaling in Pseudomonas aeruginosa infection

ExoY is a nucleotidyl cyclase, secreted by the Pseudomonas aeruginosa type 3 secretion system (T3SS), which generates various cyclic nucleotides within host cells, predominantly cGMP. How ExoY-catalyzed cNMPs production contributes to the infection process remains unclear. Using recombinant P. aeruginosa strains expressing ExoY variants with different substrate specificities, we identified that ExoY-derived cGMP modulates the cytotoxicity of ExoT, a co-injected T3SS exotoxin. Our results demonstrated that dephosphorylation of the host CrkII adaptor protein, a downstream effect of the ADP-ribosyltransferase activity of ExoT, is limited by ExoY-derived cGMP, therefore antagonizing ExoT-induced cell retraction. We also revealed a reciprocal interaction between T3SS effectors, showing that ExoT and ExoS, can in turn, suppress ExoY activity and its production of cGMP in certain cell types, thereby limiting their regulation by ExoY-synthesized cGMP. These findings highlight the intricate interplay between T3SS effectors and uncover a novel host cell-dependent regulation within P. aeruginosa infections.