New inhibitors of the Pseudomonas aeruginosa enzyme, PqsE, and methods assessing their potential to induce a conformational change via active site binding
Samantha B. Orr, Hannah A. Jones, Margaret G. O’Hara, Kaitlyn R. Smith, Isabelle R. Taylor · mSphere · 2026
ABSTRACT Pseudomonas aeruginosa is an opportunistic pathogen known for its ability to produce virulence factors and biofilms. These, among many other traits, enable P. aeruginosa to cause infections and resist treatment with antimicrobial agents. Both the ability to form biofilms and produce virulence factors are regulated via the bacterial cell-cell communication process called quorum sensing. A key molecular event that enables quorum sensing in P. aeruginosa is the physical interaction between an enzyme, PqsE, and a quorum-sensing receptor/transcription factor RhlR, which regulates the expression of a wide variety of virulence-associated genes. Previous work identified active site mutations in PqsE that induce a conformational change, weakening the interaction with RhlR. These mutations weakened the PqsE-RhlR interaction to the extent that the mutant strains of P. aeruginosa failed to colonize the lungs of a mouse. We designed a series of molecules to probe binding in the active site of PqsE as a strategy for inhibiting the PqsE-RhlR interaction. HJ1 and HJ5 are new molecules that both bind in the active site of PqsE. While HJ5 appears to bind in an alternate mode compared to HJ1, neither induces a conformational change to weaken the PqsE-RhlR interaction. Here, we introduce multiple experimental approaches to assess the way in which these new molecules engage in the PqsE active site. HJ5 can serve as a promising starting point for the development of molecules that target the PqsE active site and allosterically inhibit the interaction with RhlR, thus decreasing virulence in P. aeruginosa . IMPORTANCE Pseudomonas aeruginosa is an opportunistic human pathogen that causes infections in the most vulnerable, immunocompromised patient population. Additionally, P. aeruginosa infections are notoriously hard to treat with even the strongest antibiotics available in the clinic. P. aeruginosa relies heavily on its communication mechanism, quorum sensing, in order to stage infections. The quorum sensing system presents an ideal opportunity for the discovery of new antibiotics that are effective in treating P. aeruginosa infections. The work here presents new tools for the development of antibiotics targeting a key protein-protein interaction of the P. aeruginosa quorum-sensing system. The molecules, methods, and insights described here will be of great value in the discovery of anti-quorum-sensing therapies against a pathogen that presents a formidable threat to human health.