scholarly journals Effector ExoU from the Type III Secretion System Is An Important Modulator of Gene Expression in Lung Epithelial Cells in Response to Pseudomonas aeruginosa Infection

2003 ◽  
Vol 71 (12) ◽  
pp. 7240-7240 ◽  
Author(s):  
B. McMorran ◽  
L. Town ◽  
E. Costelloe ◽  
J. Palmer ◽  
J. Engel ◽  
...  
Keyword(s):  
Gene Expression ◽  
Pseudomonas Aeruginosa ◽  
Epithelial Cells ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Lung Epithelial Cells ◽  
Type Iii ◽  
Lung Epithelial ◽  
Pseudomonas Aeruginosa Infection

scholarly journals Macrophages and Epithelial Cells Respond Differently to the Pseudomonas aeruginosa Type III Secretion System

1999 ◽  
Vol 67 (6) ◽  
pp. 3151-3154 ◽  
Author(s):  
Jenifer Coburn ◽  
Dara W. Frank
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Epithelial Cells ◽  
Target Cell ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Lung Epithelial Cells ◽  
Cell Type ◽  
Type Iii ◽  
Lung Epithelial

ABSTRACT The multiple effects of Pseudomonas aeruginosa type III secretion have largely been attributed to variations in cytotoxin expression between strains. Here we show that the target cell type is also important. While lung epithelial cells showed significant changes in morphology but not viability when infected with P. aeruginosa, macrophages were efficiently killed by P. aeruginosa. Both responses were dependent on the type III secretion system.

scholarly journals Effector ExoU from the Type III Secretion System Is an Important Modulator of Gene Expression in Lung Epithelial Cells in Response to Pseudomonas aeruginosa Infection

2003 ◽  
Vol 71 (10) ◽  
pp. 6035-6044 ◽  
Author(s):  
B. McMorran ◽  
L. Town ◽  
E. Costelloe ◽  
J. Palmer ◽  
J. Engel ◽  
...  
Keyword(s):  
Gene Expression ◽  
Pseudomonas Aeruginosa ◽  
Transcription Factor ◽  
Epithelial Cells ◽  
Type Iii Secretion ◽  
Lung Epithelial Cells ◽  
Type Iii ◽  
Lung Epithelial ◽  
Factor C ◽  
Host Genes

ABSTRACT Pseudomonas aeruginosa is an important pathogen in immunocompromised patients and secretes a diverse set of virulence factors that aid colonization and influence host cell defenses. An important early step in the establishment of infection is the production of type III-secreted effectors translocated into host cells by the bacteria. We used cDNA microarrays to compare the transcriptomic response of lung epithelial cells to P. aeruginosa mutants defective in type IV pili, the type III secretion apparatus, or in the production of specific type III-secreted effectors. Of the 18,000 cDNA clones analyzed, 55 were induced or repressed after 4 h of infection and could be classified into four different expression patterns. These include (i) host genes that are induced or repressed in a type III secretion-independent manner (32 clones), (ii) host genes induced specifically by ExoU (20 clones), and (iii) host genes induced in an ExoU-independent but type III secretion dependent manner (3 clones). In particular, ExoU was essential for the expression of immediate-early response genes, including the transcription factor c-Fos. ExoU-dependent gene expression was mediated in part by early and transient activation of the AP1 transcription factor complex. In conclusion, the present study provides a detailed insight into the response of epithelial cells to infection and indicates the significant role played by the type III virulence mechanism in the initial host response.

scholarly journals The RNA Helicase DeaD Stimulates ExsA Translation To Promote Expression of the Pseudomonas aeruginosa Type III Secretion System

2015 ◽  
Vol 197 (16) ◽  
pp. 2664-2674 ◽  
Author(s):  
Peter J. Intile ◽  
Grant J. Balzer ◽  
Matthew C. Wolfgang ◽  
Timothy L. Yahr
Keyword(s):  
Gene Expression ◽  
Pseudomonas Aeruginosa ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Rna Helicase ◽  
Secretion System ◽  
Extrinsic Factors ◽  
Content Type ◽  
Type Iii ◽  
Dead Box

ABSTRACTThePseudomonas aeruginosatype III secretion system (T3SS) is a primary virulence factor important for phagocytic avoidance, disruption of host cell signaling, and host cell cytotoxicity. ExsA is the master regulator of T3SS transcription. The expression, synthesis, and activity of ExsA is tightly regulated by both intrinsic and extrinsic factors. Intrinsic regulation consists of the well-characterized ExsECDA partner-switching cascade, while extrinsic factors include global regulators that alterexsAtranscription and/or translation. To identify novel extrinsic regulators of ExsA, we conducted a transposon mutagenesis screen in the absence of intrinsic control. Transposon disruptions within gene PA2840, which encodes a homolog of theEscherichia coliRNA-helicase DeaD, significantly reduced T3SS gene expression. Recent studies indicate thatE. coliDeaD can promote translation by relieving inhibitory secondary structures within target mRNAs. We report here that PA2840, renamed DeaD, stimulates ExsA synthesis at the posttranscriptional level. Genetic experiments demonstrate that the activity of anexsAtranslational fusion is reduced in adeaDmutant. In addition,exsAexpression intransfails to restore T3SS gene expression in adeaDmutant. We hypothesized that DeaD relaxes mRNA secondary structure to promoteexsAtranslation and found that altering the mRNA sequence ofexsAor the nativeexsAShine-Dalgarno sequence relieved the requirement for DeaDin vivo. Finally, we show that purified DeaD promotes ExsA synthesis usingin vitrotranslation assays. Together, these data reveal a novel regulatory mechanism forP. aeruginosaDeaD and add to the complexity of global regulation of T3SS.IMPORTANCEAlthough members of the DEAD box family of RNA helicases are appreciated for their roles in mRNA degradation and ribosome biogenesis, an additional role in gene regulation is now emerging in bacteria. By relaxing secondary structures in mRNAs, DEAD box helicases are now thought to promote translation by enhancing ribosomal recruitment. We identify here an RNA helicase that plays a critical role in promoting ExsA synthesis, the central regulator of thePseudomonas aeruginosatype III secretion system, and provide additional evidence that DEAD box helicases directly stimulate translation of target genes. The finding that DeaD stimulatesexsAtranslation adds to a growing list of transcriptional and posttranscriptional regulatory mechanisms that control type III gene expression.

scholarly journals PsrA Is a Positive Transcriptional Regulator of the Type III Secretion System in Pseudomonas aeruginosa

2006 ◽  
Vol 74 (2) ◽  
pp. 1121-1129 ◽  
Author(s):  
D. K. Shen ◽  
D. Filopon ◽  
L. Kuhn ◽  
B. Polack ◽  
B. Toussaint
Keyword(s):  
Gene Expression ◽  
Pseudomonas Aeruginosa ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Cell Contact ◽  
Transcriptional Level ◽  
Calcium Depletion ◽  
Type Iii ◽  
Full Activation

ABSTRACT The type III secretion system (TTSS) of Pseudomonas aeruginosa is induced in vivo upon contact with eukaryotic cells and in vitro by calcium depletion in culture medium. We have observed a previously identified protein, PsrA, necessary for full activation of TTSS gene expression in P. aeruginosa. Electrophoretic mobility shift assays showed that recombinant PsrA could bind to the exsCEBA promoter region. A mutant with a deletion in the psrA gene was constructed. Using transcriptional fusions, we demonstrated that PsrA is required for the full activation of transcription of the TTSS regulatory operon exsCEBA and effector exoS, although the deletion mutant still responded to calcium depletion, to serum, and to host cell contact. The psrA mutant showed a marked decrease in the secretion of the type III effectors and weak resistance to phagocyte-like PLB-985 cells. The defect in TTSS transcription and secretion in the psrA mutant could be complemented by expression in trans of psrA. PsrA was previously identified as a transcriptional activator of RpoS, a central regulator during stationary phase. We confirmed with our strain that RpoS has a negative effect on TTSS gene expression. Taken altogether, these results suggest that PsrA is a newly identified activator that is involved in the expression of the TTSS by enhancing the exsCEBA transcriptional level.

scholarly journals Killing from the inside: Intracellular role of T3SS in the fate ofPseudomonas aeruginosawithin macrophages revealed bymgtCandoprFmutants

2018 ◽  
Author(s):  
Preeti Garai ◽  
Laurence Berry ◽  
Malika Moussouni ◽  
Sophie Bleves ◽  
Anne-Béatrice Blanc-Potard
Keyword(s):  
Gene Expression ◽  
Pseudomonas Aeruginosa ◽  
Type Iii Secretion ◽  
Gene Expression Pattern ◽  
Type Iii Secretion System ◽  
Cell Types ◽  
Cell Lysis ◽  
Secretion System ◽  
Intracellular Bacteria ◽  
Type Iii

AbstractWhile considered solely an extracellular pathogen, increasing evidence indicates thatPseudomonas aeruginosaencounters intracellular environment in diverse mammalian cell types, including macrophages. In the present study, we have deciphered the intramacrophage fate of wild-typeP. aeruginosaPAO1 strain by live and electron microscopy.P. aeruginosafirst resided in phagosomal vacuoles and subsequently could be detected in the cytoplasm, indicating phagosomal escape of the pathogen, a finding also supported by vacuolar rupture assay. The intracellular bacteria could eventually induce cell lysis. Two bacterial factors, MgtC and OprF, recently identified to be important for survival ofP. aeruginosain macrophages, were found to be involved in bacterial escape from the phagosome as well as cell lysis caused by intracellular bacteria. Strikingly, type III secretion system (T3SS) genes ofP. aeruginosawere down-regulated within macrophages in bothmgtCandoprFmutants. Concordantly, cyclic di-GMP (c-di-GMP) level was increased in both mutants, providing a clue for negative regulation of T3SS inside macrophages. Consistent with the phenotypes and gene expression pattern ofmgtCandoprFmutants, a T3SS mutant(ΔpscN)exhibited defect in phagosomal escape and macrophage lysis driven by internalized bacteria. Importantly, these effects appeared to be largely dependent on the ExoS effector, in contrast with the known T3SS-dependent, but ExoS independent, cytotoxicity caused by extracellularP. aeruginosatowards macrophages. Hence, our work highlights T3SS and ExoS, whose expression is modulated by MgtC and OprF, as key players in the intramacrophage life ofP. aeruginosa, allowing internalized bacteria to evade macrophages.Author summaryThe ability of professional phagocytes to ingest and kill microorganisms is central to host defense andPseudomonas aeruginosahas developed mechanisms to avoid being killed by phagocytes. While considered an extracellular pathogen,P. aeruginosahas been reported to be engulfed by macrophages in animal models. Here, we visualized the fate ofP. aeruginosawithin cultured macrophages, revealing macrophage lysis driven by intracellularP. aeruginosa. Two bacterial factors, MgtC and OprF, recently discovered to be involved in the intramacrophage survival ofP. aeruginosa, appeared to play role in this cytotoxicity caused by intracellular bacteria. We provided evidence that type III secretion system (T3SS) gene expression is lowered intracellularly inmgtCandoprFmutants. We further showed that intramacrophageP. aeruginosauses its T3SS, specifically the ExoS effector, to promote phagosomal escape and cell lysis. We thus describe a transient intramacrophage stage ofP. aeruginosathat could contribute to bacterial dissemination.

scholarly journals Pseudomonas aeruginosa Magnesium Transporter MgtE Inhibits Type III Secretion System Gene Expression by Stimulating rsmYZ Transcription

2017 ◽  
Vol 199 (23) ◽  
Author(s):  
Shubham Chakravarty ◽  
Cameron N. Melton ◽  
Adam Bailin ◽  
Timothy L. Yahr ◽  
Gregory G. Anderson
Keyword(s):  
Gene Expression ◽  
Pseudomonas Aeruginosa ◽  
Gene Transcription ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Host Cells ◽  
Content Type ◽  
Type Iii ◽  
Magnesium Transporter

ABSTRACT Pseudomonas aeruginosa causes numerous acute and chronic opportunistic infections in humans. One of its most formidable weapons is a type III secretion system (T3SS), which injects powerful toxins directly into host cells. The toxins lead to cell dysfunction and, ultimately, cell death. Identification of regulatory pathways that control T3SS gene expression may lead to the discovery of novel therapeutics to treat P. aeruginosa infections. In a previous study, we found that expression of the magnesium transporter gene mgtE inhibits T3SS gene transcription. MgtE-dependent inhibition appeared to interfere with the synthesis or function of the master T3SS transcriptional activator ExsA, although the exact mechanism was unclear. We now demonstrate that mgtE expression acts through the GacAS two-component system to activate rsmY and rsmZ transcription. This event ultimately leads to inhibition of exsA translation. This inhibitory effect is specific to exsA as translation of other genes in the exsCEBA operon is not inhibited by mgtE. Moreover, our data reveal that MgtE acts solely through this pathway to regulate T3SS gene transcription. Our study reveals an important mechanism that may allow P. aeruginosa to fine-tune T3SS activity in response to certain environmental stimuli. IMPORTANCE The type III secretion system (T3SS) is a critical virulence factor utilized by numerous Gram-negative bacteria, including Pseudomonas aeruginosa, to intoxicate and kill host cells. Elucidating T3SS regulatory mechanisms may uncover targets for novel anti-P. aeruginosa therapeutics and provide deeper understanding of bacterial pathogenesis. We previously found that the magnesium transporter MgtE inhibits T3SS gene transcription in P. aeruginosa. In this study, we describe the mechanism of MgtE-dependent inhibition of the T3SS. Our report also illustrates how MgtE might respond to environmental cues, such as magnesium levels, to fine-tune T3SS gene expression.

Sign in / Sign up

Export Citation Format

Share Document