The LasB Elastase of Pseudomonas aeruginosa Acts in Concert with Alkaline Protease AprA To Prevent Flagellin-Mediated Immune Recognition

Abstract

eThe opportunistic pathogen Pseudomonas aeruginosa is capable of establishing severe and persistent infections in various eukaryotic hosts. It encodes a wide array of virulence factors and employs several strategies to evade immune detection. In the present study, we screened the Harvard Medical School transposon mutant library of P. aeruginosa PA14 for bacterial factors that modulate interleukin-8 responses in A549 human airway epithelial cells. We found that in addition to the previously identified alkaline protease AprA, the elastase LasB is capable of degrading exogenous flagellin under calcium-replete conditions and prevents flagellin-mediated immune recognition. Our results indicate that the production of two proteases with anti-flagellin activity provides a failsafe mechanism for P. aeruginosa to ensure the maintenance of protease-dependent immune-modulating functions.

Characterization of Ocular Clinical Isolates of Pseudomonas aeruginosa from Non-Contact Lens Related Keratitis Patients from South India

“…However, 78% of patients that underwent penetrating keratoplasty were infected with isolates harboring exoS. Along with the exotoxins, P. aeruginosa also produces several extracellular proteases of which alkaline proteases (aprA), elastase B (lasB) and protease IV (prpL) are often implicated in infections and helps the pathogen in immune evasion [46]. All the isolates investigated in this study were found to be positive for the genes lasB, aprA and prpL.…”

Quantitative mapping of mRNA 3’ ends inPseudomonas aeruginosareveals a pervasive role for premature 3’ end formation in response to azithromycin

“…Importantly, we found AZM also induced premature transcripts in key transcriptional regulators of biofilm formation and virulence ( Supplementary Table S6). Such increases in premature transcript formation accompanied the downregulation of rpoS, rpoH, vqsR and anr [83][84][85]87,88,92]. Anr regulates QS and virulence gene expression in low-oxygen environments such as biofilms [87,88].…”

“…In AZM treated biofilms ( Figure 3D), we observed reduced transcript levels of several global gene expression modulators associated with stress responses (rpoS [83,84], rpoH [85], and relA [86]), anaerobic metabolism (anr [87,88] Figure 3D). The expression of stress, virulence, biofilm, motility, and metabolism-related genes, many of which are controlled by these regulators, were also downregulated.…”

“…Figure 4C and 4D). These include well-known P. aeruginosa regulators rpoS, anr, and relA, as well as genes involved in biofilm formation, stress response, and virulence factor genes such as hemN ( Figure 4C), lasB ( Figure 4D), rahU, phzB1-G1 and pelABCDEFG [83,84,86,87,98,110]. The targets that exhibit no evidence of early transcription termination in their transcript leaders, yet are still significantly downregulated upon AZM treatment, may reflect expression changes in upstream regulators by AZM.…”

Importance of flagella in acute and chronic Pseudomonas aeruginosa infections

“…LasR governs the production of the two proteases AprA and LasB. Both have previously been demonstrated to degrade flagellin (Bardoel et al, 2011;Casilag et al, 2015). Thus, it is conceivable that in tumours infected by the lasR mutant even more flagellin is present than in PA14 colonized tumours.…”