scholarly journals The Ruler Protein EscP of the Enteropathogenic Escherichia coli Type III Secretion System Is Involved in Calcium Sensing and Secretion Hierarchy Regulation by Interacting with the Gatekeeper Protein SepL

mBio ◽  
2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Lihi Shaulov ◽  
Jenia Gershberg ◽  
Wanyin Deng ◽  
B. Brett Finlay ◽  
Neta Sal-Man
Keyword(s):  
Host Cell ◽  
Type Iii Secretion ◽  
Bacterial Pathogens ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Bacterial Virulence ◽  
Effector Proteins ◽  
Host Cells ◽  
Gram Negative ◽  
Type Iii

ABSTRACT The type III secretion system (T3SS) is a multiprotein complex that plays a central role in the virulence of many Gram-negative bacterial pathogens. To ensure that effector proteins are efficiently translocated into the host cell, bacteria must be able to sense their contact with the host cell. In this study, we found that EscP, which was previously shown to function as the ruler protein of the enteropathogenic Escherichia coli T3SS, is also involved in the switch from the secretion of translocator proteins to the secretion of effector proteins. In addition, we demonstrated that EscP can interact with the gatekeeper protein SepL and that the EscP-SepL complex dissociates upon a calcium concentration drop. We suggest a model in which bacterial contact with the host cell is accompanied by a drop in the calcium concentration that causes SepL-EscP complex dissociation and triggers the secretion of effector proteins. IMPORTANCE The emergence of multidrug-resistant bacterial strains, especially those of pathogenic bacteria, has serious medical and clinical implications. At the same time, the development and approval of new antibiotics have been limited for years. Recently, antivirulence drugs have received considerable attention as a novel antibiotic strategy that specifically targets bacterial virulence rather than growth, an approach that applies milder evolutionary pressure on the bacteria to develop resistance. A highly attractive target for the development of antivirulence compounds is the type III secretion system, a specialized secretory system possessed by many Gram-negative bacterial pathogens for injecting virulence factors (effectors) into host cells. In this study, we shed light on the molecular mechanism that allows bacteria to sense their contact with the host cell and to respond with the timed secretion of effector proteins. Understanding this critical step for bacterial virulence may provide a new therapeutic strategy. IMPORTANCE The emergence of multidrug-resistant bacterial strains, especially those of pathogenic bacteria, has serious medical and clinical implications. At the same time, the development and approval of new antibiotics have been limited for years. Recently, antivirulence drugs have received considerable attention as a novel antibiotic strategy that specifically targets bacterial virulence rather than growth, an approach that applies milder evolutionary pressure on the bacteria to develop resistance. A highly attractive target for the development of antivirulence compounds is the type III secretion system, a specialized secretory system possessed by many Gram-negative bacterial pathogens for injecting virulence factors (effectors) into host cells. In this study, we shed light on the molecular mechanism that allows bacteria to sense their contact with the host cell and to respond with the timed secretion of effector proteins. Understanding this critical step for bacterial virulence may provide a new therapeutic strategy.

scholarly journals Antibodies Inhibiting the Type III Secretion System of Gram-Negative Pathogenic Bacteria

Antibodies ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 35
Author(s):  
Julia A. Hotinger ◽  
Aaron E. May
Keyword(s):  
Type Iii Secretion ◽  
Pathogenic Bacteria ◽  
Type Iii Secretion System ◽  
The United States ◽  
Secretion System ◽  
Effector Proteins ◽  
Host Cells ◽  
Gram Negative ◽  
Type Iii ◽  
Shigella Spp

Pathogenic bacteria are a global health threat, with over 2 million infections caused by Gram-negative bacteria every year in the United States. This problem is exacerbated by the increase in resistance to common antibiotics that are routinely used to treat these infections, creating an urgent need for innovative ways to treat and prevent virulence caused by these pathogens. Many Gram-negative pathogenic bacteria use a type III secretion system (T3SS) to inject toxins and other effector proteins directly into host cells. The T3SS has become a popular anti-virulence target because it is required for pathogenesis and knockouts have attenuated virulence. It is also not required for survival, which should result in less selective pressure for resistance formation against T3SS inhibitors. In this review, we will highlight selected examples of direct antibody immunizations and the use of antibodies in immunotherapy treatments that target the bacterial T3SS. These examples include antibodies targeting the T3SS of Pseudomonas aeruginosa, Yersinia pestis, Escherichia coli, Salmonella enterica, Shigella spp., and Chlamydia trachomatis.

scholarly journals The Type III System-Secreted Effector EspZ Localizes to Host Mitochondria and Interacts with the Translocase of Inner Mitochondrial Membrane 17b

2011 ◽  
Vol 79 (12) ◽  
pp. 4784-4790 ◽  
Author(s):  
Stephanie R. Shames ◽  
Matthew A. Croxen ◽  
Wanyin Deng ◽  
B. Brett Finlay
Keyword(s):  
Host Cell ◽  
Type Iii Secretion ◽  
Mitochondrial Membrane ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Host Cells ◽  
Infected Host ◽  
Inner Mitochondrial Membrane ◽  
Type Iii

ABSTRACTEnteropathogenic and enterohemorrhagicEscherichia coli(EPEC and EHEC, respectively) are attaching and effacing (A/E) bacterial pathogens that cause severe diarrheal disease worldwide. To cause disease, A/E pathogens require a type III secretion system, which facilitates transport of bacterial effector proteins directly into infected host cells. One of these effector proteins translocated by the type III secretion system, EspZ, is essential for A/E pathogen infection and functions to prevent rapid death of EPEC-infected cells. We further investigated the mechanism of EspZ-mediated protection of infected host cells and found that a severe decrease in host mitochondrial membrane potential (Δψm) occurs concurrently with host cell lysis during infection with EPEC lacking EspZ (ΔespZ). It was also demonstrated that EspZ localizes to host cell mitochondria and interacts with the translocase of inner mitochondrial membrane 17b (TIM17b). In addition, host cell cytotoxicity was exacerbated in the absence of TIM17b during wild-type (WT) EPEC infection. The findings of this study together provide the first evidence that EspZ localizes to host mitochondria and that TIM17b contributes to protection against rapid cell death during EPEC infection.

scholarly journals Identification of Two Translocon Proteins of Vibrio parahaemolyticus Type III Secretion System 2

2008 ◽  
Vol 76 (9) ◽  
pp. 4282-4289 ◽  
Author(s):  
Toshio Kodama ◽  
Hirotaka Hiyoshi ◽  
Kazuyoshi Gotoh ◽  
Yukihiro Akeda ◽  
Shigeaki Matsuda ◽  
...  
Keyword(s):  
Host Cell ◽  
Type Iii Secretion ◽  
Vibrio Parahaemolyticus ◽  
Critical Role ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Host Cells ◽  
Host Cell Membrane ◽  
Type Iii

ABSTRACT The type III secretion system (T3SS) translocon complex is composed of several associated proteins, which form a translocation channel through the host cell plasma membrane. These proteins are key molecules that are involved in the pathogenicity of many T3SS-positive bacteria, because they are necessary to deliver effector proteins into host cells. A T3SS designated T3SS2 of Vibrio parahaemolyticus is thought to be related to the enterotoxicity of this bacterium in humans, but the effector translocation mechanism of T3SS2 is unclear because there is only one gene (the VPA1362 gene) in the T3SS2 region that is homologous to other translocon protein genes. It is also not known whether the VPA1362 protein is functional in the translocon of T3SS2 or whether it is sufficient to form the translocation channel of T3SS2. In this study, we identified both VPA1362 (designated VopB2) and VPA1361 (designated VopD2) as T3SS2-dependent secretion proteins. Functional analysis of these proteins showed that they are essential for T3SS2-dependent cytotoxicity, for the translocation of one of the T3SS2 effector proteins (VopT), and for the contact-dependent activity of pore formation in infected cells in vitro. Their targeting to the host cell membrane depends on T3SS2, and furthermore, they are necessary for T3SS2-dependent enterotoxicity in vivo. These results indicate that VopB2 and VopD2 act as translocon proteins of V. parahaemolyticus T3SS2 and hence have a critical role in the T3SS2-dependent enterotoxicity of this bacterium.

scholarly journals Characterization of the Ruler Protein Interaction Interface on the Substrate Specificity Switch Protein in the Yersinia Type III Secretion System

2016 ◽  
Vol 292 (8) ◽  
pp. 3299-3311 ◽  
Author(s):  
Oanh Ho ◽  
Per Rogne ◽  
Tomas Edgren ◽  
Hans Wolf-Watz ◽  
Frédéric H. Login ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Host Cells ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Type Iii ◽  
Binding Interface ◽  
Interaction Interface

Many pathogenic Gram-negative bacteria use the type III secretion system (T3SS) to deliver effector proteins into eukaryotic host cells. In Yersinia, the switch to secretion of effector proteins is induced first after intimate contact between the bacterium and its eukaryotic target cell has been established, and the T3SS proteins YscP and YscU play a central role in this process. Here we identify the molecular details of the YscP binding site on YscU by means of nuclear magnetic resonance (NMR) spectroscopy. The binding interface is centered on the C-terminal domain of YscU. Disrupting the YscU-YscP interaction by introducing point mutations at the interaction interface significantly reduced the secretion of effector proteins and HeLa cell cytotoxicity. Interestingly, the binding of YscP to the slowly self-cleaving YscU variant P264A conferred significant protection against autoproteolysis. The YscP-mediated inhibition of YscU autoproteolysis suggests that the cleavage event may act as a timing switch in the regulation of early versus late T3SS substrates. We also show that YscUC binds to the inner rod protein YscI with a dissociation constant (Kd) of 3.8 μm and with 1:1 stoichiometry. The significant similarity among different members of the YscU, YscP, and YscI families suggests that the protein-protein interactions discussed in this study are also relevant for other T3SS-containing Gram-negative bacteria.

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 Control of Type III Secretion System Effector/Chaperone Ratio Fosters Pathogen Adaptation to Host-Adherent Lifestyle

mBio ◽  
2019 ◽  
Vol 10 (5) ◽  
Author(s):  
Netanel Elbaz ◽  
Yaakov Socol ◽  
Naama Katsowich ◽  
Ilan Rosenshine
Keyword(s):  
Gene Expression ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Host Cells ◽  
Host Colonization ◽  
Content Type ◽  
Type Iii ◽  
Attached State

ABSTRACT The transition from a planktonic lifestyle to a host-attached state is often critical for bacterial virulence. Upon attachment to host cells, enteropathogenic Escherichia coli (EPEC) employs a type III secretion system (T3SS) to inject into the host cells ∼20 effector proteins, including Tir. CesT, which is encoded from the same operon downstream of tir, is a Tir-bound chaperone that facilitates Tir translocation. Upon Tir translocation, the liberated CesT remains in the bacterial cytoplasm and antagonizes the posttranscriptional regulator CsrA, thus eliciting global regulation in the infecting pathogen. Importantly, tight control of the Tir/CesT ratio is vital, since an uncontrolled surge in free CesT levels may repress CsrA in an untimely manner, thus abrogating colonization. We investigated how fluctuations in Tir translation affect the regulation of this ratio. By creating mutations that cause the premature termination of Tir translation, we revealed that the untranslated tir mRNA becomes highly unstable, resulting in a rapid drop in cesT mRNA levels and, thus, CesT levels. This mechanism couples Tir and CesT levels to ensure a stable Tir/CesT ratio. Our results expose an additional level of regulation that enhances the efficacy of the initial interaction of EPEC with the host cell, providing a better understanding of the bacterial switch from the planktonic to the cell-adherent lifestyle. IMPORTANCE Host colonization by extracellular pathogens often entails the transition from a planktonic lifestyle to a host-attached state. Enteropathogenic E. coli (EPEC), a Gram-negative pathogen, attaches to the intestinal epithelium of the host and employs a type III secretion system (T3SS) to inject effector proteins into the cytoplasm of infected cells. The most abundant effector protein injected is Tir, whose translocation is dependent on the Tir-bound chaperon CesT. Upon Tir injection, the liberated CesT binds to and inhibits the posttranscriptional regulator CsrA, resulting in reprogramming of gene expression in the host-attached bacteria. Thus, adaptation to the host-attached state involves dynamic remodeling of EPEC gene expression, which is mediated by the relative levels of Tir and CesT. Fluctuating from the optimal Tir/CesT ratio results in a decrease in EPEC virulence. Here we elucidate a posttranscriptional circuit that prevents sharp variations from this ratio, thus improving host colonization.

scholarly journals The Plant Phenolic Compound p-Coumaric Acid Represses Gene Expression in the Dickeya dadantii Type III Secretion System

2008 ◽  
Vol 75 (5) ◽  
pp. 1223-1228 ◽  
Author(s):  
Yan Li ◽  
Quan Peng ◽  
Dija Selimi ◽  
Qi Wang ◽  
Amy O. Charkowski ◽  
...  
Keyword(s):  
Phenolic Compound ◽  
Type Iii Secretion ◽  
Bacterial Pathogens ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Host Cells ◽  
Hydroxyl Group ◽  
Coumaric Acid ◽  
Dickeya Dadantii ◽  
Type Iii

ABSTRACT The type III secretion system (T3SS) is a major virulence factor in many gram-negative bacterial pathogens. This secretion system translocates effectors directly into the cytosol of eukaryotic host cells, where the effector proteins facilitate bacterial pathogenesis by interfering with host cell signal transduction and other cellular processes. Plants defend themselves against bacterial pathogens by recognizing either the type 3 effectors or their actions and initiating a cascade of defense responses that often results in programmed cell death of the plant cell being attacked. Here we show that a plant phenolic compound, p-coumaric acid (PCA), represses the expression of T3SS genes of the plant pathogen Dickeya dadantii, suggesting that plants can also defend against bacterial pathogens by manipulating the expression of the T3SS. PCA repressed the expression of T3SS regulatory genes through the HrpX/Y two-component system, a core regulator of the T3SS, rather than through the global regulator GacS/A, which indirectly regulates the T3SS. A further analysis of several PCA analogs suggests that the para positioning of the hydroxyl group in the phenyl ring and the double bond of PCA may be important for its biological activity.

scholarly journals The Type III Secretion System and Cytotoxic Enterotoxin Alter the Virulence of Aeromonas hydrophila

2005 ◽  
Vol 73 (10) ◽  
pp. 6446-6457 ◽  
Author(s):  
Jian Sha ◽  
Lakshmi Pillai ◽  
Amin A. Fadl ◽  
Cristi L. Galindo ◽  
Tatiana E. Erova ◽  
...  
Keyword(s):  
Aeromonas Hydrophila ◽  
Type Iii Secretion ◽  
Cultured Cells ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Host Cells ◽  
Gene Encoding ◽  
Type Iii ◽  
Isogenic Mutants

ABSTRACT Many gram-negative bacteria use a type III secretion system (TTSS) to deliver effector proteins into host cells. Here we report the characterization of a TTSS chromosomal operon from the diarrheal isolate SSU of Aeromonas hydrophila. We deleted the gene encoding Aeromonas outer membrane protein B (AopB), which is predicted to be involved in the formation of the TTSS translocon, from wild-type (WT) A. hydrophila as well as from a previously characterized cytotoxic enterotoxin gene (act)-minus strain of A. hydrophila, thus generating aopB and act/aopB isogenic mutants. The act gene encodes a type II-secreted cytotoxic enterotoxin (Act) that has hemolytic, cytotoxic, and enterotoxic activities and induces lethality in a mouse model. These isogenic mutants (aopB, act, and act/aopB) were highly attenuated in their ability to induce cytotoxicity in RAW 264.7 murine macrophages and HT-29 human colonic epithelial cells. The act/aopB mutant demonstrated the greatest reduction in cytotoxicity to cultured cells after 4 h of infection, as measured by the release of lactate dehydrogenase enzyme, and was avirulent in mice, with a 90% survival rate compared to that of animals infected with Act and AopB mutants, which caused 50 to 60% of the animals to die at a dose of three 50% lethal doses. In contrast, WT A. hydrophila killed 100% of the mice within 48 h. The effects of these mutations on cytotoxicity could be complemented with the native genes. Our studies further revealed that the production of lactones, which are involved in quorum sensing (QS), was decreased in the act (32%) and aopB (64%) mutants and was minimal (only 8%) in the act/aopB mutant, compared to that of WT A. hydrophila SSU. The effects of act and aopB gene deletions on lactone production could also be complemented with the native genes, indicating specific effects of Act and the TTSS on lactone production. Although recent studies with other bacteria have indicated TTSS regulation by QS, this is the first report describing a correlation between the TTSS and Act of A. hydrophila and the production of lactones.

scholarly journals Cytosporone B, an Inhibitor of the Type III Secretion System of Salmonella enterica Serovar Typhimurium

2013 ◽  
Vol 57 (5) ◽  
pp. 2191-2198 ◽  
Author(s):  
Jianfang Li ◽  
Chao Lv ◽  
Weiyang Sun ◽  
Zhenyu Li ◽  
Xiaowei Han ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Salmonella Enterica ◽  
Bacterial Resistance ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Host Cells ◽  
Content Type ◽  
Type Iii ◽  
Serovar Typhimurium

ABSTRACTBacterial virulence factors have been increasingly regarded as attractive targets for development of novel antibacterial agents. Virulence inhibitors are less likely to generate bacterial resistance, which makes them superior to traditional antibiotics that target bacterial viability.Salmonella entericaserovar Typhimurium, an important food-borne human pathogen, has type III secretion system (T3SS) as its major virulence factor. T3SS secretes effector proteins to facilitate invasion into host cells. In this study, we identified several analogs of cytosporone B (Csn-B) that strongly block the secretion ofSalmonellapathogenicity island 1 (SPI-1)-associated effector proteins, without affecting the secretion of flagellar protein FliCin vitro. Csn-B and two other derivatives exhibited a strong inhibitory effect on SPI-1-mediated invasion to HeLa cells, while no significant toxicity to bacteria was observed. Nucleoid proteins Hha and H-NS bind to the promoters of SPI-1 regulator geneshilD,hilC, andrtsAto repress their expression and consequently regulate the expression of SPI-1 apparatus and effector genes. We found that Csn-B upregulated the transcription ofhhaandhns, implying that Csn-B probably affected the secretion of effectors through the Hha–H-NS regulatory pathway. In summary, this study presented an effective SPI-1 inhibitor, Csn-B, which may have potential in drug development against antibiotic-resistantSalmonella.

scholarly journals The Salmonella enterica Serotype Typhimurium Effector Proteins SipA, SopA, SopB, SopD, and SopE2 Act in Concert To Induce Diarrhea in Calves

2002 ◽  
Vol 70 (7) ◽  
pp. 3843-3855 ◽  
Author(s):  
Shuping Zhang ◽  
Renato L. Santos ◽  
Renee M. Tsolis ◽  
Silke Stender ◽  
Wolf-Dietrich Hardt ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Salmonella Enterica ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Host Cells ◽  
Loop Model ◽  
Fluid Accumulation ◽  
Ileal Loop ◽  
Type Iii

ABSTRACT Salmonella enterica serotype Typhimurium requires a functional type III secretion system encoded by Salmonella pathogenicity island 1 (SPI1) to cause diarrhea. We investigated the role of genes encoding secreted target proteins of the SPI1-associated type III secretion system for enteropathogenicity in calves. Salmonella serotype Typhimurium strains having mutations in sptP, avrA, sspH1, or slrP induced fluid secretion in the bovine ligated ileal loop model at levels similar to that of the wild type. In contrast, mutations in sipA, sopA, sopB, sopD, or sopE2 significantly reduced fluid accumulation in bovine ligated ileal loops at 8 h postinfection. A strain carrying mutations in sipA, sopA, sopB, sopD, and sopE2 (sipA sopABDE2 mutant) caused the same level of fluid accumulation in bovine ligated ileal loops as a strain carrying a mutation in sipB, a SPI1 gene required for the translocation of effector proteins into host cells. A positive correlation was observed between the severity of histopathological lesions detected in the ileal mucosa and the levels of fluid accumulation induced by the different mutants. After oral infection of calves, the Salmonella serotype Typhimurium sipAsopABDE2 mutant caused only mild diarrhea and was more strongly attenuated than strains having only single mutations. These data demonstrate that SipA, SopA, SopB, SopD, and SopE2 are major virulence factors responsible for diarrhea during Salmonella serotype Typhimurium infection of calves.

Sign in / Sign up

Export Citation Format

Share Document