The small non-coding RNA sRNA102 regulates Pseudomonas aeruginosa virulence and host immunity by targeting the T3SS component PcrG.

This study investigates the regulatory role of a functionally under-characterized small non-coding RNA (sRNA), sRNA102, in Pseudomonas aeruginosa, focusing on its mechanisms of influencing bacterial virulence and host immune modulation. Using an in vivo murine intraperitoneal infection model and transcriptomic sequencing, we found that the expression of sRNA102 is host immune-dependent: its expression was significantly upregulated by approximately 3-fold in immunocompetent mouse infection models, whereas no significant upregulation was observed in immunodeficient mouse models. This trend was further validated in in vitro PAO1-immune cell co-culture systems and a whole-blood infection model. Functional studies demonstrated that sRNA102 enhances hemolytic activity by 2.5-fold, reduces cytotoxicity toward A549 epithelial cells by approximately 43%, and increases adhesion and invasion capabilities by 2.1-fold. Mechanistically, we confirmed that sRNA102 directly targets and positively regulates pcrG, a key gene of the type III secretion system (T3SS), thereby upregulating the expression of the downstream effector protein ExoS. In infection models, the expression of sRNA102 suppressed the expression of the anti-inflammatory cytokine interleukin-10 (IL-10) (downregulated by approximately 50% in the sRNA102-overexpressing infection group), while promoting the expression of the pro-inflammatory cytokine tumor necrosis factor-alpha (TNF-α) and the immunomodulatory marker arginase 1 (Arg1), ultimately leading to increased bacterial colonization in the mouse peritoneal cavity. These findings reveal a novel regulatory pathway driven by sRNA102, which integrates the pcrG-exoS-T3SS axis to modulate bacterial virulence and host immune responses, deepening our understanding of the fine-tuned, sRNA-mediated regulatory mechanisms during P. aeruginosa infection.