Document Detail

Mutation of lasA and lasB reduces Pseudomonas aeruginosa invasion of epithelial cells.
MedLine Citation:
PMID:  12904569     Owner:  NLM     Status:  MEDLINE    
Pseudomonas aeruginosa is an opportunistic bacterial pathogen implicated in a variety of devastating conditions. Its flexibility as a pathogen is attributed to a myriad of virulence factors and regulatory elements that respond to prevailing environmental conditions. ExoS and ExoT are type III secreted effector proteins, regulated by the transcriptional activator ExsA, that can inhibit invasion of epithelial cells by cytotoxic strains of P. aeruginosa. This study sought to understand why invasive strains, which can secrete both ExoS and ExoT, still invade epithelial cells. The results showed that LasA and elastase (LasB), which are regulated by the Las and Rhl quorum-sensing systems, modulated P. aeruginosa invasion. Mutation of lasA and/or lasB reduced P. aeruginosa invasion, which was not fully restored by extracellularly added LasB, P. aeruginosa conditioned medium containing LasA and LasB, or EGTA pretreatment of cells. This indicated that protease effects on invasion involved factors additional to tight junction disruption and subsequent alterations to cell polarity. Upon mutation of lasA and/or lasB, steady-state levels of ExoS and ExoT were increased in culture medium of P. aeruginosa grown under conditions stimulatory for these toxins. The increase in ExoS was significantly correlated with reduced invasion. In vitro experiments showed that purified LasB degraded recombinant ExoS. Taken together, these studies suggest a mechanism by which invasive strains can synthesize inhibitors of invasion, ExoS and ExoT, yet still invade epithelial cells. By this mechanism, LasA and LasB decrease the levels of the toxins directly or indirectly, and thus reduce inhibition of invasion.
Brigitte A Cowell; Sally S Twining; Jeffrey A Hobden; Mary S F Kwong; Suzanne M J Fleiszig
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Microbiology (Reading, England)     Volume:  149     ISSN:  1350-0872     ISO Abbreviation:  Microbiology (Reading, Engl.)     Publication Date:  2003 Aug 
Date Detail:
Created Date:  2003-08-07     Completed Date:  2003-10-23     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  9430468     Medline TA:  Microbiology     Country:  England    
Other Details:
Languages:  eng     Pagination:  2291-9     Citation Subset:  IM    
School of Optometry, University of California, Berkeley 94720-2020, CA, USA.
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MeSH Terms
ADP Ribose Transferases / genetics,  metabolism
Bacterial Proteins / genetics*,  metabolism
Bacterial Toxins / genetics,  metabolism
Caseins / metabolism
Cell Line
DNA-Binding Proteins / genetics,  metabolism
Elastin / metabolism
Endopeptidases / metabolism
Epithelial Cells / microbiology
GTPase-Activating Proteins
Metalloendopeptidases / genetics*,  metabolism
Pseudomonas aeruginosa / genetics*,  metabolism,  pathogenicity*
Recombinant Proteins / genetics,  metabolism
Trans-Activators / genetics,  metabolism
Virulence / genetics,  physiology
Grant Support
Reg. No./Substance:
0/Bacterial Proteins; 0/Bacterial Toxins; 0/Caseins; 0/DNA-Binding Proteins; 0/ExoT protein, Pseudomonas aeruginosa; 0/ExsA protein, bacteria; 0/GTPase-Activating Proteins; 0/Recombinant Proteins; 0/Trans-Activators; 9007-58-3/Elastin; EC 2.4.2.-/ADP Ribose Transferases; EC S; EC 3.4.-/Endopeptidases; EC 3.4.24.-/Metalloendopeptidases; EC, Pseudomonas aeruginosa; EC 3.4.99.-/alkaline protease; EC 3.4.99.-/staphylolytic protease

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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