Characterisation of the Major Extracellular Proteases of Stenotrophomonas maltophilia and Their Effects on Pulmonary Antiproteases.

Kevin Molloy,Stephen G. Smith,Gerard Cagney,Noel G. McElvaney,Eugene T. Dillon,Catherine M. Greene

doi:10.3390/pathogens8030092

Abstract

Stenotrophomonas maltophilia is an emerging global opportunistic pathogen that has been appearing with increasing prevalence in cystic fibrosis (CF). A secreted protease from S. maltophilia has been reported as its chief potential virulence factor. Here, using the reference clinical strain S. maltophilia K279a, the major secreted proteases were identified. Protein biochemistry and mass spectrometry were carried out on K279a culture supernatant. The effect of K279a culture supernatant on cleavage and anti-neutrophil elastase activity of the three majors pulmonary antiproteases was quantified. A deletion mutant of S. maltophilia lacking expression of a protease was constructed. The serine proteases StmPR1, StmPR2 and StmPR3, in addition to chitinase A and an outer membrane esterase were identified in culture supernatants. Protease activity was incompletely abrogated in a K279a-ΔStmPR1: Erm mutant. Wild type K279a culture supernatant degraded alpha-1 antitrypsin (AAT), secretory leucoprotease inhibitor (SLPI) and elafin, important components of the lung’s innate immune defences. Meanwhile SLPI and elafin, but not AAT, retained their ability to inhibit neutrophil elastase. StmPR3 together with StmPR1 and StmPR2, is likely to contribute to protease-mediated innate immune dysfunction in CF.

Highlights

Bacterial proteases have important pathological consequences in cystic fibrosis (CF) lung disease.The role of some, in particular proteases produced by P. aeruginosa, an opportunistic CF lung pathogen, have been investigated [1,2]
Detected in bands 4 and 6 (Figure 6B–E). These results indicate that StmPR1 is not the sole major serine protease secreted by S. maltophilia but that StmP3 may be a major extracellular protease of K279a
Given that K279a proteases were capable of degrading alpha-1 antitrypsin (AAT), secretory leucoprotease inhibitor (SLPI) and elafin, we investigated that K279a were capableneutrophil of degrading

Summary

Introduction

Bacterial proteases have important pathological consequences in cystic fibrosis (CF) lung disease. The role of some, in particular proteases produced by P. aeruginosa, an opportunistic CF lung pathogen, have been investigated [1,2]. Less is known regarding the role of proteases in the pathogenesis of Stenotrophomonas maltophilia lung disease in CF. S. maltophilia is commonly present in the CF respiratory tract [3,4]. The pathogenic role of this organism in CF is controversial with recent evidence indicating that colonisation is associated with an almost threefold increased risk of death or lung transplantation [5]. S. maltophilia produces both a major (StmPR1) and a minor (StmPR2) [6,7,8] extracellular protease

Methods

Results

Conclusion