scholarly journals Transcriptional Induction of the Pseudomonas aeruginosa Type III Secretion System by Low Ca2+ and Host Cell Contact Proceeds through Two Distinct Signaling Pathways

2006 ◽  
Vol 74 (6) ◽  
pp. 3334-3341 ◽  
Author(s):  
Nandini Dasgupta ◽  
Alix Ashare ◽  
Gary W. Hunninghake ◽  
Timothy L. Yahr
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Host Cell ◽  
Type Iii Secretion ◽  
Mammalian Cells ◽  
Type Iii Secretion System ◽  
Growth Conditions ◽  
Secretion System ◽  
Host Cells ◽  
Dependent Manner ◽  
Type Iii

ABSTRACT The opportunistic pathogen Pseudomonas aeruginosa utilizes a type III secretion system (T3SS) to intoxicate eukaryotic host cells. Transcription of the T3SS is induced under calcium-limited growth conditions or following intimate contact of P. aeruginosa with host cells. In the present study, we demonstrate that expression of the T3SS is controlled by two distinct regulatory mechanisms and that these mechanisms are differentially activated in a host cell-dependent manner. The first mechanism is dependent upon ExsC, a regulatory protein that couples transcription of the T3SS to the activity of the type III secretion machinery. ExsC is essential for induction of the T3SS under low-calcium-growth conditions and for T3SS-dependent cytotoxicity towards social amoebae, insect cells, and erythrocytes. The second regulatory mechanism functions independently of ExsC and is sufficient to elicit T3SS-dependent cytotoxicity towards certain types of mammalian cells. Although this second pathway (ExsC independent) is sufficient, an exsC mutant demonstrates a lag in the induction of cytotoxicity towards Chinese hamster ovary cells and is attenuated for virulence in a mouse pneumonia model. We propose that the ExsC-dependent pathway is required for full cytotoxicity towards all host cell types tested whereas the ExsC-independent pathway may represent an adaptation that allows P. aeruginosa to increase expression of the T3SS in response to specific types of mammalian cells.

scholarly journals Pseudomonas aeruginosa injects NDK into host cells through a type III secretion system

Microbiology ◽  
2014 ◽  
Vol 160 (7) ◽  
pp. 1417-1426 ◽  
Author(s):  
Dennis Neeld ◽  
Yongxin Jin ◽  
Candace Bichsel ◽  
Jinghua Jia ◽  
Jianhui Guo ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Host Cells ◽  
Eukaryotic Cells ◽  
Mammalian Host ◽  
Type I ◽  
Dependent Manner ◽  
Type Iii

Pseudomonas aeruginosa is a Gram-negative opportunistic human pathogen possessing a type III secretion system (T3SS) which injects toxic effector proteins into mammalian host cells. In previous studies, P. aeruginosa strains lacking all of the known type III effectors were shown to cause cytotoxicity upon prolonged infection time. In this study, we report the identification of a new cytotoxin, nucleoside diphosphate kinase (NDK), which is injected into eukaryotic cells in a T3SS-dependent manner. Injection of NDK is inhibited by the presence of previously known effectors of the T3SS, with an effectorless strain injecting the highest amount, suggesting active competition with the known T3SS effectors. NDK is shown to cause a cytotoxic response when expressed in eukaryotic cells, and P. aeruginosa strains harbouring NDK also show a greater toxicity than strains lacking it. Interestingly, the cytotoxic effect of intracellular NDK is independent of its kinase activity. In previous studies, NDK was shown to be secreted into culture supernatants via a type I secretion system and cause cytotoxicity in a kinase-dependent manner. Therefore, the current study highlights an alternative route of NDK secretion as well as two different cytotoxic mechanisms of NDK, depending on the extra- or intra-cellular location of the protein.

scholarly journals Pseudomonas aeruginosa Pore-Forming Exolysin and Type IV Pili Cooperate To Induce Host Cell Lysis

mBio ◽  
2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Pauline Basso ◽  
Michel Ragno ◽  
Sylvie Elsen ◽  
Emeline Reboud ◽  
Guillaume Golovkine ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Host Cell ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Type Iv Pili ◽  
Clinical Strain ◽  
Type Iii ◽  
Type Iv ◽  
Cell Membrane Disruption

ABSTRACT   Clinical strains of Pseudomonas aeruginosa lacking the type III secretion system genes employ a toxin, exolysin (ExlA), for host cell membrane disruption. Here, we demonstrated that ExlA export requires a predicted outer membrane protein, ExlB, showing that ExlA and ExlB define a new active two-partner secretion (TPS) system of P. aeruginosa . In addition to the TPS signals, ExlA harbors several distinct domains, which include one hemagglutinin domain, five arginine-glycine-aspartic acid (RGD) motifs, and a C-terminal region lacking any identifiable sequence motifs. However, this C-terminal region is important for the toxic activity, since its deletion abolishes host cell lysis. Using lipid vesicles and eukaryotic cells, including red blood cells, we demonstrated that ExlA has a pore-forming activity which precedes cell membrane disruption of nucleated cells. Finally, we developed a high-throughput cell-based live-dead assay and used it to screen a transposon mutant library of an ExlA-producing P. aeruginosa clinical strain for bacterial factors required for ExlA-mediated toxicity. The screen resulted in the identification of proteins involved in the formation of type IV pili as being required for ExlA to exert its cytotoxic activity by promoting close contact between bacteria and the host cell. These findings represent the first example of cooperation between a pore-forming toxin of the TPS family and surface appendages in host cell intoxication. IMPORTANCE The course and outcome of acute, toxigenic infections by Pseudomonas aeruginosa clinical isolates rely on the deployment of one of two virulence strategies: delivery of effectors by the well-known type III secretion system or the cytolytic activity of the recently identified two-partner secreted toxin, exolysin. Here, we characterize several features of the mammalian cell intoxication process mediated by exolysin. We found that exolysin requires the outer membrane protein ExlB for export into extracellular medium. Using in vitro recombinant protein and ex vivo assays, we demonstrated a pore-forming activity of exolysin. A cellular cytotoxicity screen of a transposon mutant library, made in an exolysin-producing clinical strain, identified type IV pili as bacterial appendages required for exolysin toxic function. This work deciphers molecular mechanisms underlying the activity of novel virulence factors used by P. aeruginosa clinical strains lacking the type III secretion system, including a requirement for the toxin-producing bacteria to be attached to the targeted cell to induce cytolysis, and defines new targets for developing antivirulence strategies.

scholarly journals RNase E Promotes Expression of Type III Secretion System Genes in Pseudomonas aeruginosa

2019 ◽  
Vol 201 (22) ◽  
Author(s):  
Josh S. Sharp ◽  
Arne Rietsch ◽  
Simon L. Dove
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Host Cells ◽  
Rnase E ◽  
Content Type ◽  
Type Iii ◽  
Small Regulatory Rnas

ABSTRACT Pseudomonas aeruginosa is an important opportunistic pathogen that employs a type III secretion system (T3SS) to inject effector proteins into host cells. Using a protein depletion system, we show that the endoribonuclease RNase E positively regulates expression of the T3SS genes. We also present evidence that RNase E antagonizes the expression of genes of the type VI secretion system and limits biofilm production in P. aeruginosa. Thus, RNase E, which is thought to be the principal endoribonuclease involved in the initiation of RNA degradation in P. aeruginosa, plays a key role in controlling the production of factors involved in both acute and chronic stages of infection. Although the posttranscriptional regulator RsmA is also known to positively regulate expression of the T3SS genes, we find that RNase E does not appreciably influence the abundance of RsmA in P. aeruginosa. Moreover, we show that RNase E still exerts its effects on T3SS gene expression in cells lacking all four of the key small regulatory RNAs that function by sequestering RsmA. IMPORTANCE The type III secretion system (T3SS) is a protein complex produced by many Gram-negative pathogens. It is capable of injecting effector proteins into host cells that can manipulate cell metabolism and have toxic effects. Understanding how the T3SS is regulated is important in understanding the pathogenesis of bacteria with such systems. Here, we show that RNase E, which is typically thought of as a global regulator of RNA stability, plays a role in regulating the T3SS in Pseudomonas aeruginosa. Depleting RNase E results in the loss of T3SS gene expression as well as a concomitant increase in biofilm formation. These observations are reminiscent of the phenotypes associated with the loss of activity of the posttranscriptional regulator RsmA. However, RNase E-mediated regulation of these systems does not involve changes in the abundance of RsmA and is independent of the known small regulatory RNAs that modulate RsmA activity.

scholarly journals EspZ of Enteropathogenic and Enterohemorrhagic Escherichia coli Regulates Type III Secretion System Protein Translocation

mBio ◽  
2012 ◽  
Vol 3 (5) ◽  
Author(s):  
Cedric N. Berger ◽  
Valerie F. Crepin ◽  
Kobi Baruch ◽  
Aurelie Mousnier ◽  
Ilan Rosenshine ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Type Iii Secretion ◽  
Protein Translocation ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Enterohemorrhagic Escherichia Coli ◽  
Host Cells ◽  
Dependent Manner ◽  
Content Type ◽  
Type Iii

ABSTRACTTranslocation of effector proteins via a type III secretion system (T3SS) is a widespread infection strategy among Gram-negative bacterial pathogens. Each pathogen translocates a particular set of effectors that subvert cell signaling in a way that suits its particular infection cycle. However, as effector unbalance might lead to cytotoxicity, the pathogens must employ mechanisms that regulate the intracellular effector concentration. We present evidence that the effector EspZ controls T3SS effector translocation from enteropathogenic (EPEC) and enterohemorrhagic (EHEC)Escherichia coli. Consistently, an EPECespZmutant is highly cytotoxic. Following ectopic expression, we found that EspZ inhibited the formation of actin pedestals as it blocked the translocation of Tir, as well as other effectors, including Map and EspF. Moreover, during infection EspZ inhibited effector translocation following superinfection. Importantly, while EspZ of EHEC O157:H7 had a universal “translocation stop” activity, EspZ of EPEC inhibited effector translocation from typical EPEC strains but not from EHEC O157:H7 or its progenitor, atypical EPEC O55:H7. We found that the N and C termini of EspZ, which contains two transmembrane domains, face the cytosolic leaflet of the plasma membrane at the site of bacterial attachment, while the extracellular loop of EspZ is responsible for its strain-specific activity. These results show that EPEC and EHEC acquired a sophisticated mechanism to regulate the effector translocation.IMPORTANCEEnteropathogenicEscherichia coli(EPEC) and enterohemorrhagicE. coli(EHEC) are important diarrheal pathogens responsible for significant morbidity and mortality in developing countries and the developed world, respectively. The virulence strategy of EPEC and EHEC revolves around a conserved type III secretion system (T3SS), which translocates bacterial proteins known as effectors directly into host cells. Previous studies have shown that when cells are infected in two waves with EPEC, the first wave inhibits effector translocation by the second wave in a T3SS-dependent manner, although the factor involved was not known. Importantly, we identified EspZ as the effector responsible for blocking protein translocation following a secondary EPEC infection. Interestingly, we found that while EspZ of EHEC can block protein translocation from both EPEC and EHEC strains, EPEC EspZ cannot block translocation from EHEC. These studies show that EPEC and EHEC employ a novel infection strategy to regulate T3SS translocation.

scholarly journals Novel Type III Effectors in Pseudomonas aeruginosa

mBio ◽  
2015 ◽  
Vol 6 (2) ◽  
Author(s):  
David Burstein ◽  
Shirley Satanower ◽  
Michal Simovitch ◽  
Yana Belnik ◽  
Meital Zehavi ◽  
...  
Keyword(s):  
Machine Learning ◽  
Pseudomonas Aeruginosa ◽  
Host Cell ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Content Type ◽  
Machine Learning Classification ◽  
Type Iii ◽  
Wide Range

ABSTRACT Pseudomonas aeruginosa is a Gram-negative, opportunistic pathogen that causes chronic and acute infections in immunocompromised patients. Most P. aeruginosa strains encode an active type III secretion system (T3SS), utilized by the bacteria to deliver effector proteins from the bacterial cell directly into the cytoplasm of the host cell. Four T3SS effectors have been discovered and extensively studied in P. aeruginosa: ExoT, ExoS, ExoU, and ExoY. This is especially intriguing in light of P. aeruginosa's ability to infect a wide range of hosts. We therefore hypothesized that additional T3SS effectors that have not yet been discovered are encoded in the genome of P. aeruginosa. Here, we applied a machine learning classification algorithm to identify novel P. aeruginosa effectors. In this approach, various types of data are integrated to differentiate effectors from the rest of the open reading frames of the bacterial genome. Due to the lack of a sufficient learning set of positive effectors, our machine learning algorithm integrated genomic information from another Pseudomonas species and utilized dozens of features accounting for various aspects of the effector coding genes and their products. Twelve top-ranking predictions were experimentally tested for T3SS-specific translocation, leading to the discovery of two novel T3SS effectors. We demonstrate that these effectors are not part of the injection structural complex and report initial efforts toward their characterization. IMPORTANCE Pseudomonas aeruginosa uses a type III secretion system (T3SS) to secrete toxic proteins, termed effectors, directly into the cytoplasm of the host cell. The activation of this secretion system is correlated with disease severity and patient death. Compared with many other T3SS-utilizing pathogenic bacteria, P. aeruginosa has a fairly limited arsenal of effectors that have been identified. This is in sharp contrast with the wide range of hosts that this bacterium can infect. The discovery of two novel effectors described here is an important step toward better understanding of the virulence and host evasion mechanisms adopted by this versatile pathogen and may provide novel approaches to treat P. aeruginosa infections.

scholarly journals SseL Is a Salmonella-Specific Translocated Effector Integrated into the SsrB-Controlled Salmonella Pathogenicity Island 2 Type III Secretion System

2006 ◽  
Vol 75 (2) ◽  
pp. 574-580 ◽  
Author(s):  
Brian K. Coombes ◽  
Michael J. Lowden ◽  
Jennifer L. Bishop ◽  
Mark E. Wickham ◽  
Nat F. Brown ◽  
...  
Keyword(s):  
Virulence Factors ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Regulatory System ◽  
Pathogenicity Island ◽  
Secretion System ◽  
Host Cells ◽  
Dependent Manner ◽  
Host Colonization ◽  
Type Iii

ABSTRACT Bacterial pathogens use horizontal gene transfer to acquire virulence factors that influence host colonization, alter virulence traits, and ultimately shape the outcome of disease following infection. One hallmark of the host-pathogen interaction is the prokaryotic type III secretion system that translocates virulence factors into host cells during infection. Salmonella enterica possesses two type III secretion systems that are utilized during host colonization and intracellular replication. Salmonella pathogenicity island 2 (SPI2) is a genomic island containing approximately 30 contiguous genes required to assemble a functional secretion system including the two-component regulatory system called SsrA-SsrB that positively regulates transcription of the secretion apparatus. We used transcriptional profiling with DNA microarrays to search for genes that coregulate with the SPI2 type III secretion machinery in an SsrB-dependent manner. Here we report the identification of a Salmonella-specific translocated effector called SseL that is required for full virulence during murine typhoid-like disease. Analysis of infected macrophages using fluorescence-activated cell sorting revealed that sseL is induced inside cells and requires SsrB for expression. SseL is retained predominantly in the cytoplasm of infected cells following translocation by the type III system encoded in SPI2. Animal infection experiments with sseL mutant bacteria indicate that integration of SseL into the SsrB response regulatory system contributes to systemic virulence of this pathogen.

scholarly journals SepZ/EspZ Is Secreted and Translocated into HeLa Cells by the Enteropathogenic Escherichia coli Type III Secretion System

2005 ◽  
Vol 73 (7) ◽  
pp. 4327-4337 ◽  
Author(s):  
Kristen J. Kanack ◽  
J. Adam Crawford ◽  
Ichiro Tatsuno ◽  
Mohamed A. Karmali ◽  
James B. Kaper
Keyword(s):  
Escherichia Coli ◽  
Hela Cells ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Bacterial Attachment ◽  
Host Cells ◽  
Dependent Manner ◽  
Cell Infection ◽  
Type Iii

ABSTRACT Enteropathogenic Escherichia coli (EPEC) is a major bacterial cause of infantile diarrhea in developing countries and is the prototype for a group of gastrointestinal pathogens causing characteristic attaching and effacing (A/E) histopathology on intestinal epithelia. A/E pathogens utilize a type III secretion system (TTSS), encoded by the locus of enterocyte effacement (LEE) pathogenicity island, to deliver effector proteins into host cells. Here, we investigate sequence divergence of the LEE-encoded SepZ protein and identify it as a TTSS-secreted and -translocated molecule. SepZ is hypervariable among A/E pathogens, with sequences sharing between 60 to 81% amino acid identity with SepZ of EPEC. A SepZ-CyaA fusion was secreted and translocated into HeLa cells in a TTSS-dependent manner. Additionally, we determined that the first 20 amino acids of SepZ were sufficient to direct its translocation. In contrast to previous studies suggesting a role in invasion and the structure and/or regulation of the TTSS, we found that SepZ does not mediate uptake of EPEC into host cells or affect translocation and tyrosine phosphorylation of the translocated intimin receptor. Immunohistochemistry reveals that, after an extended HeLa cell infection, accumulated SepZ can be detected beneath the site of bacterial attachment in a subset of pedestal regions. To indicate its newly identified status as a translocated effector protein, we propose to rename SepZ as EspZ.

scholarly journals Pseudomonas aeruginosa-Induced Apoptosis Involves Mitochondria and Stress-Activated Protein Kinases

2001 ◽  
Vol 69 (4) ◽  
pp. 2675-2683 ◽  
Author(s):  
Verena Jendrossek ◽  
Heike Grassmé ◽  
Ilka Mueller ◽  
Florian Lang ◽  
Erich Gulbins
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Type Iii Secretion ◽  
Mammalian Cells ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Oxygen Intermediates ◽  
Type Iii ◽  
Rapid Induction ◽  
Severe Infections ◽  
Induced Apoptosis

ABSTRACT Pseudomonas aeruginosa, a gram-negative facultative pathogen, causes severe infections in immunocompromised and cystic fibrosis patients. However, the molecular details of the interaction between P. aeruginosa and mammalian cells are still largely unknown. Here we demonstrate that infection of human conjunctiva epithelial Chang cells with the well-characterized P. aeruginosa strain PAO-I results in rapid induction of apoptosis. Apoptosis was mediated by mitochondrial alterations, in particular mitochondrial depolarization, synthesis of reactive oxygen intermediates, and release of cytochrome c, as well as an activation of Jun N-terminal kinases (JNK). Stimulation of these events was dependent on upregulation of CD95 on infected cells, and a deficiency of CD95 or the CD95 ligand prevented mitochondrial changes, JNK activation, and apoptosis upon infection. Further, efficient apoptosis of Chang epithelial cells required infection with liveP. aeruginosa, adhesion but not invasion of the bacteria, and expression of the type III secretion system in PAO-I. The data indicate a type III secretion system-dependent, sequential activation of several signaling pathways by P. aeruginosa PAO-I, resulting in apoptosis of the infected cell.

scholarly journals Bcr4 is a Chaperone for the Inner Rod Protein in the Bordetella Type III Secretion System

2021 ◽  
Author(s):  
Masataka Goto ◽  
Akio Abe ◽  
Tomoko Hanawa ◽  
Asaomi Kuwae
Keyword(s):  
Type Iii Secretion ◽  
Mammalian Cells ◽  
Sequence Similarity ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Host Cells ◽  
Virulence Proteins ◽  
Type Iii ◽  
Bacterial Proteins ◽  
Small Proteins

Bordetella bronchiseptica injects virulence proteins called effectors into host cells via a type III secretion system (T3SS) conserved among many Gram-negative bacteria. Small proteins called chaperones are required for stabilizing some T3SS components or localizing them to the T3SS machinery. In a previous study, we identified a chaperone-like protein named Bcr4 that regulates T3SS activity in B. bronchiseptica. Bcr4 does not show strong sequence similarity to well-studied T3SS proteins of other bacteria, and its function remains to be elucidated. Here, we investigated the mechanism by which Bcr4 controls T3SS activity. A pull-down assay revealed that Bcr4 interacts with BscI, based on its homology to other bacterial proteins, to be an inner rod protein of the T3SS machinery. A pull-down assay using truncated Bcr4 derivatives and secretion profiles of B. bronchiseptica producing truncated Bcr4 derivatives showed that the Bcr4 C-terminal region is necessary to interact with BscI and to activate the T3SS. Moreover, the deletion of BscI abolished the secretion of type III secreted proteins from B. bronchiseptica and the translocation of a cytotoxic effector into cultured mammalian cells. Finally, we showed that BscI is unstable in the absence of Bcr4. These results suggest that Bcr4 supports the construction of the T3SS machinery by stabilizing BscI. This is the first demonstration of a chaperone for the T3SS inner rod protein among the virulence bacteria possessing the T3SS.

scholarly journals Type III Secretion System Translocon Component EseB Forms Filaments on and Mediates Autoaggregation of and Biofilm Formation by Edwardsiella tarda

2015 ◽  
Vol 81 (17) ◽  
pp. 6078-6087 ◽  
Author(s):  
Zhi Peng Gao ◽  
Pin Nie ◽  
Jin Fang Lu ◽  
Lu Yi Liu ◽  
Tiao Yi Xiao ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Biofilm Formation ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Host Cells ◽  
Edwardsiella Tarda ◽  
Dependent Manner ◽  
Content Type ◽  
Type Iii

ABSTRACTThe type III secretion system (T3SS) ofEdwardsiella tardaplays an important role in infection by translocating effector proteins into host cells. EseB, a component required for effector translocation, is reported to mediate autoaggregation ofE. tarda. In this study, we demonstrate that EseB forms filamentous appendages on the surface ofE. tardaand is required for biofilm formation byE. tardain Dulbecco's modified Eagle's medium (DMEM). Biofilm formation byE. tardain DMEM does not require FlhB, an essential component for assembling flagella. Dynamic analysis of EseB filament formation, autoaggregation, and biofilm formation shows that the formation of EseB filaments occurs prior to autoaggregation and biofilm formation. The addition of an EseB antibody toE. tardacultures before bacterial autoaggregation prevents autoaggregation and biofilm formation in a dose-dependent manner, whereas the addition of the EseB antibody toE. tardacultures in which biofilm is already formed does not destroy the biofilm. Therefore, EseB filament-mediated bacterial cell-cell interaction is a prerequisite for autoaggregation and biofilm formation.

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