A Novel Virulence Strategy for Pseudomonas aeruginosa Mediated by an Autotransporter with Arginine-Specific Aminopeptidase Activity

Abstract

The opportunistic human pathogen, Pseudomonas aeruginosa, is a major cause of infections in chronic wounds, burns and the lungs of cystic fibrosis patients. The P. aeruginosa genome encodes at least three proteins exhibiting the characteristic three domain structure of autotransporters, but much remains to be understood about the functions of these three proteins and their role in pathogenicity. Autotransporters are the largest family of secreted proteins in Gram-negative bacteria, and those characterised are virulence factors. Here, we demonstrate that the PA0328 autotransporter is a cell-surface tethered, arginine-specific aminopeptidase, and have defined its active site by site directed mutagenesis. Hence, we have assigned PA0328 with the name AaaA, for arginine-specific autotransporter of P. aeruginosa. We show that AaaA provides a fitness advantage in environments where the sole source of nitrogen is peptides with an aminoterminal arginine, and that this could be important for establishing an infection, as the lack of AaaA led to attenuation in a mouse chronic wound infection which correlated with lower levels of the cytokines TNFα, IL-1α, KC and COX-2. Consequently AaaA is an important virulence factor playing a significant role in the successful establishment of P. aeruginosa infections.

The Pseudomonas aeruginosa PA14 ABC Transporter NppA1A2BCD Is Required for Uptake of Peptidyl Nucleoside Antibiotics

“…The bacterial strains and plasmids used in this study are listed in Table 1. P. aeruginosa strains were cultured at 37°C in double yeast tryptone (dYT) medium or minimal medium P (MMP) (10). For growth assays, MMP was modified by omitting NH 4 Cl (MMP-N) so that various peptides could be used as sole nitrogen sources.…”

Extracellular Ser/Thr/Tyr phosphorylated proteins of Pseudomonas aeruginosa PA14 strain

“…Pseudomonas aeruginosa is a well‐known opportunistic pathogen that causes a variety of diseases in predisposed individuals . The virulence of P. aeruginosa is largely related to its ability to secrete into the environment an immense battery of virulence factors . In the present study, we investigated the Ser/Thr/Tyr phosphorylated extracellular proteins that remain unexplored up to now.…”

EprS, an autotransporter serine protease, plays an important role in various pathogenic phenotypes of Pseudomonas aeruginosa

“…Several P. aeruginosa proteases have been isolated and shown to be involved in pathogenesis. Of the proteases analysed, alkaline protease (AprA) (Kharazmi, 1991), elastase (LasA and LasB) (Preston et al, 1997;Suter, 1994), protease IV (PrpL) (Engel et al, 1998;O'Callaghan et al, 1996), small protease (PasP) (Marquart et al, 2005;Tang et al, 2009), immunomodulating metalloprotease (ImpA) (Bardoel et al, 2012), aminopeptidase (Luckett et al, 2012), large extracellular protease (LepA) (Kida et al, 2008(Kida et al, , 2011 and extracellular serine protease (EprS) (Kida et al, 2013) have been characterized extensively. We previously reported that EprS, an autotransporter protease of P. aeruginosa, induces host inflammatory responses through protease-activated receptors (PARs) (Kida et al, 2013).…”