LasB activation in Pseudomonas aeruginosa: Quorum sensing-mediated release of an auto-activation inhibitor

• Published in: The journal of microbiology Vol. 63; no. 2; pp. e2411005 - 22
• Main Authors: Lee, Cheol Seung, Li, Xi-Hui, Jeon, Chae-Ran, Lee, Joon-Hee
• Format: Journal Article
• Language: English
• Published: Korea (South) 한국미생물학회 01.02.2025
• Subjects: Bacterial Proteins - antagonists & inhibitors; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Escherichia coli - genetics; Escherichia coli - metabolism; Metalloendopeptidases - antagonists & inhibitors; Metalloendopeptidases - genetics; Metalloendopeptidases - metabolism; Pseudomonas aeruginosa - enzymology; Pseudomonas aeruginosa - genetics; Pseudomonas aeruginosa - metabolism; Pseudomonas aeruginosa - physiology; Quorum Sensing; 생물학; LasB; elastase; protease; protease inhibition; Pseudomonas aeruginosa; quorum sensing
• ISSN: 1225-8873; 1976-3794; 1976-3794
• DOI: 10.71150/jm.2411005

Pseudomonas aeruginosa secretes three major proteases: elastase B (LasB), protease IV (PIV), and elastase A (LasA), which play crucial roles in infection and pathogenesis. These proteases are activated sequentially from LasB in a proteolytic cascade, and LasB was previously thought to undergo auto-activation. However, our previous study suggested that LasB cannot auto-activate independently but requires additional quorum sensing (QS)-dependent factors for activation, as LasB remained inactive in QS-deficient P. aeruginosa (QS-) even under artificial overexpression. In this study, we provide evidence for the existence of a LasB inhibitor in QS- mutants: inactive LasB overexpressed in QS- strains was in its processed form and could be reactivated upon purification; when full-length LasB was overexpressed in Escherichia coli, a heterologous bacterium lacking both LasB activators and inhibitors, the protein underwent normal processing and activation; and purified active LasB was significantly inhibited by culture supernatant (CS) from QS- strains but not by CS from QS+ strains. These findings demonstrate that a LasB inhibitor exists in QS- strains, and in its absence, LasB can undergo auto-activation without requiring an activator. Based on these results, we propose an updated hypothesis: the QS-dependent LasB activator functions by removing the LasB inhibitor rather than acting directly on LasB itself, thus preventing premature LasB activation until QS response is initiated.