scholarly journals roles Hrp-dependent effector proteins and hrp gene regulation as determinants of virulence and host-specificity in Erwinia stewartii and E. herbicola pvs. gypsophilae and betae

2005 ◽  
Author(s):  
David L. Coplin ◽  
Shulamit Manulis ◽  
Isaac Barash
Keyword(s):  
Gene Expression ◽  
Host Specificity ◽  
Pathogenic Bacteria ◽  
Effector Proteins ◽  
Host Cells ◽  
Secretion Systems ◽  
Gram Negative ◽  
Regulatory Cascade ◽  
Effector Genes ◽  
Erwinia Stewartii

Gram-negative plant pathogenic bacteria employ specialized type-III secretion systems (TTSS) to deliver an arsenal of pathogenicity proteins directly into host cells. These secretion systems are encoded by hrp genes (for hypersensitive response and pathogenicity) and the effector proteins by so-called dsp or avr genes. The functions of effectors are to enable bacterial multiplication by damaging host cells and/or by blocking host defenses. We characterized essential hrp gene clusters in the Stewart's Wilt of maize pathogen, Pantoea stewartii subsp. stewartii (Pnss; formerly Erwinia stewartii) and the gall-forming bacterium, Pantoea agglomerans (formerly Erwinia herbicola) pvs. gypsophilae (Pag) and betae (Pab). We proposed that the virulence and host specificity of these pathogens is a function of a) the perception of specific host signals resulting in bacterial hrp gene expression and b) the action of specialized signal proteins (i.e. Hrp effectors) delivered into the plant cell. The specific objectives of the proposal were: 1) How is the expression of the hrp and effector genes regulated in response to host cell contact and the apoplastic environment? 2) What additional effector proteins are involved in pathogenicity? 3) Do the presently known Pantoea effector proteins enter host cells? 4) What host proteins interact with these effectors? We characterized the components of the hrp regulatory cascade (HrpXY ->7 HrpS ->7 HrpL ->7 hrp promoters), showed that they are conserved in both Pnss and Fag, and discovered that the regulation of the hrpS promoter (hrpSp) may be a key point in integrating apoplastic signals. We also analyzed the promoters recognized by HrpL and demonstrated the relationship between their composition and efficiency. Moreover, we showed that promoter strength can influence disease expression. In Pnss, we found that the HrpXY two-component signal system may sense the metabolic status of the bacterium and is required for full hrp gene expression in planta. In both species, acyl-homoserine lactone-mediated quorum sensing may also regulate epiphytic fitness and/or pathogenicity. A common Hrp effector protein, DspE/WtsE, is conserved and required for virulence of both species. When introduced into corn cells, Pnss WtsE protein caused water-soaked lesions. In other plants, it either caused cell death or acted as an Avr determinant. Using a yeast- two-hybrid system, WtsE was shown to interact with a number of maize signal transduction proteins that are likely to have roles in either programmed cell death or disease resistance. In Pag and Pab, we have characterized the effector proteins HsvG, HsvB and PthG. HsvG and HsvB are homologous proteins that determine host specificity of Pag and Pab on gypsophila and beet, respectively. Both possess a transcriptional activation domain that functions in yeast. PthG was found to act as an Avr determinant on multiple beet species, but was required for virulence on gypsophila. In addition, we demonstrated that PthG acts within the host cell. Additional effector genes have been characterized on the pathogenicity plasmid, pPATHₚₐg, in Pag. A screen for HrpL- regulated genes in Pnsspointed up 18 candidate effector proteins and four of these were required for full virulence. It is now well established that the virulence of Gram-negative plant pathogenic bacteria is governed by Hrp-dependent effector proteins. However; the mode of action of many effectors is still unresolved. This BARD supported research will significantly contribute to the understanding of how Hrp effectors operate in Pantoea spp. and how they control host specificity and affect symptom production. This may lead to novel approaches for genetically engineering plants resistant to a wide range of bacterial pathogens by inactivating the Hrp effectors with "plantabodies" or modifying their receptors, thereby blocking the induction of the susceptible response. Alternatively, innovative technologies could be used to interfere with the Hrp regulatory cascade by blocking a critical step or mimicking plant or quorum sensing signals.   

scholarly journals Modulating Pathogenesis with Mobile-CRISPRi

2019 ◽  
Vol 201 (22) ◽  
Author(s):  
Jiuxin Qu ◽  
Neha K. Prasad ◽  
Michelle A. Yu ◽  
Shuyan Chen ◽  
Amy Lyden ◽  
...  
Keyword(s):  
Gene Expression ◽  
Pathogenic Bacteria ◽  
Bacterial Species ◽  
Effector Proteins ◽  
Infection Model ◽  
Secretion Systems ◽  
Bacterial Genomes ◽  
Gene Encoding ◽  
Content Type ◽  
Animal Infection

ABSTRACT Conditionally essential (CE) genes are required by pathogenic bacteria to establish and maintain infections. CE genes encode virulence factors, such as secretion systems and effector proteins, as well as biosynthetic enzymes that produce metabolites not found in the host environment. Due to their outsized importance in pathogenesis, CE gene products are attractive targets for the next generation of antimicrobials. However, the precise manipulation of CE gene expression in the context of infection is technically challenging, limiting our ability to understand the roles of CE genes in pathogenesis and accordingly design effective inhibitors. We previously developed a suite of CRISPR interference-based gene knockdown tools that are transferred by conjugation and stably integrate into bacterial genomes that we call Mobile-CRISPRi. Here, we show the efficacy of Mobile-CRISPRi in controlling CE gene expression in an animal infection model. We optimize Mobile-CRISPRi in Pseudomonas aeruginosa for use in a murine model of pneumonia by tuning the expression of CRISPRi components to avoid nonspecific toxicity. As a proof of principle, we demonstrate that knock down of a CE gene encoding the type III secretion system (T3SS) activator ExsA blocks effector protein secretion in culture and attenuates virulence in mice. We anticipate that Mobile-CRISPRi will be a valuable tool to probe the function of CE genes across many bacterial species and pathogenesis models. IMPORTANCE Antibiotic resistance is a growing threat to global health. To optimize the use of our existing antibiotics and identify new targets for future inhibitors, understanding the fundamental drivers of bacterial growth in the context of the host immune response is paramount. Historically, these genetic drivers have been difficult to manipulate precisely, as they are requisite for pathogen survival. Here, we provide the first application of Mobile-CRISPRi to study conditionally essential virulence genes in mouse models of lung infection through partial gene perturbation. We envision the use of Mobile-CRISPRi in future pathogenesis models and antibiotic target discovery efforts.

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 Identification of Novel Host Interactors of Effectors Secreted by Salmonella and Citrobacter

mSystems ◽  
2016 ◽  
Vol 1 (4) ◽  
Author(s):  
Ryan L. Sontag ◽  
Ernesto S. Nakayasu ◽  
Roslyn N. Brown ◽  
George S. Niemann ◽  
Michael A. Sydor ◽  
...  
Keyword(s):  
Host Cell ◽  
Type Iii Secretion ◽  
Defense Mechanisms ◽  
Pathogenic Bacteria ◽  
Effector Proteins ◽  
Host Cells ◽  
Secretion Systems ◽  
Type Iii ◽  
Cell Cytosol ◽  
Host Cell Cytosol

ABSTRACT During infection, pathogenic bacteria face an adverse environment of factors driven by both cellular and humoral defense mechanisms. To help evade the immune response and ultimately proliferate inside the host, many bacteria evolved specialized secretion systems to deliver effector proteins directly into host cells. Translocated effector proteins function to subvert host defense mechanisms. Numerous pathogenic bacteria use a specialized secretion system called type III secretion to deliver effectors into the host cell cytosol. Here, we identified 75 new host targets of Salmonella and Citrobacter effectors, which will help elucidate their mechanisms of action. Many pathogenic bacteria of the family Enterobacteriaceae use type III secretion systems to inject virulence proteins, termed “effectors,” into the host cell cytosol. Although host-cellular activities of several effectors have been demonstrated, the function and host-targeted pathways of most of the effectors identified to date are largely undetermined. To gain insight into host proteins targeted by bacterial effectors, we performed coaffinity purification of host proteins from cell lysates using recombinant effectors from the Enterobacteriaceae intracellular pathogens Salmonella enterica serovar Typhimurium and Citrobacter rodentium. We identified 54 high-confidence host interactors for the Salmonella effectors GogA, GtgA, GtgE, SpvC, SrfH, SseL, SspH1, and SssB collectively and 21 interactors for the Citrobacter effectors EspT, NleA, NleG1, and NleK. We biochemically validated the interaction between the SrfH Salmonella protein and the extracellular signal-regulated kinase 2 (ERK2) host protein kinase, which revealed a role for this effector in regulating phosphorylation levels of this enzyme, which plays a central role in signal transduction. IMPORTANCE During infection, pathogenic bacteria face an adverse environment of factors driven by both cellular and humoral defense mechanisms. To help evade the immune response and ultimately proliferate inside the host, many bacteria evolved specialized secretion systems to deliver effector proteins directly into host cells. Translocated effector proteins function to subvert host defense mechanisms. Numerous pathogenic bacteria use a specialized secretion system called type III secretion to deliver effectors into the host cell cytosol. Here, we identified 75 new host targets of Salmonella and Citrobacter effectors, which will help elucidate their mechanisms of action.

scholarly journals The T3SS Effector Protease NleC Is Active within Citrobacter rodentium

Pathogens ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 589
Author(s):  
Md Kamrul Hasan ◽  
Samir El Qaidi ◽  
Philip R. Hardwidge
Keyword(s):  
Type Iii Secretion ◽  
Effector Proteins ◽  
Host Cells ◽  
Citrobacter Rodentium ◽  
Secretion Systems ◽  
Gram Negative ◽  
Virulence Proteins ◽  
T3ss Effector ◽  
Enhanced Resistance ◽  
Cleavage Motif

Whether type III secretion system (T3SS) effector proteins encoded by Gram-negative bacterial pathogens have intra-bacterial activities is an important and emerging area of investigation. Gram-negative bacteria interact with their mammalian hosts by using secretion systems to inject virulence proteins directly into infected host cells. Many of these injected protein effectors are enzymes that modify the structure and inhibit the function of mammalian proteins. The underlying dogma is that T3SS effectors are inactive until they are injected into host cells, where they then fold into their active conformations. We previously observed that the T3SS effectors NleB and SseK1 glycosylate Citrobacter rodentium and Salmonella enterica proteins, respectively, leading to enhanced resistance to environmental stress. Here, we sought to extend these studies to determine whether the T3SS effector protease NleC is also active within C. rodentium. To do this, we expressed the best-characterized mammalian substrate of NleC, the NF-κB p65 subunit in C. rodentium and monitored its proteolytic cleavage as a function of NleC activity. Intra-bacterial p65 cleavage was strictly dependent upon NleC. A p65 mutant lacking the known CE cleavage motif was resistant to NleC. Thus, we conclude that, in addition to NleB, NleC is also enzymatically active within C. rodentium.

scholarly journals The Modes of Action of MARTX Toxin Effector Domains

Toxins ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 507 ◽  
Author(s):  
Byoung Kim
Keyword(s):  
Host Cell ◽  
Structural Features ◽  
Effector Proteins ◽  
Host Cells ◽  
Cell Physiology ◽  
Cytotoxic Activities ◽  
Human Pathogens ◽  
Secretion Systems ◽  
Gram Negative ◽  
Effector Domains

Many Gram-negative bacterial pathogens directly deliver numerous effector proteins from the bacterium to the host cell, thereby altering the target cell physiology. The already well-characterized effector delivery systems are type III, type IV, and type VI secretion systems. Multifunctional autoprocessing repeats-in-toxin (MARTX) toxins are another effector delivery platform employed by some genera of Gram-negative bacteria. These single polypeptide exotoxins possess up to five effector domains in a modular fashion in their central regions. Upon binding to the host cell plasma membrane, MARTX toxins form a pore using amino- and carboxyl-terminal repeat-containing arms and translocate the effector domains into the cells. Consequently, MARTX toxins affect the integrity of the host cells and often induce cell death. Thus, they have been characterized as crucial virulence factors of certain human pathogens. This review covers how each of the MARTX toxin effector domains exhibits cytopathic and/or cytotoxic activities in cells, with their structural features revealed recently. In addition, future directions for the comprehensive understanding of MARTX toxin-mediated pathogenesis are discussed.

scholarly journals Small-Molecule Type III Secretion System Inhibitors Block Assembly of the Shigella Type III Secreton

2008 ◽  
Vol 191 (2) ◽  
pp. 563-570 ◽  
Author(s):  
Andreas K. J. Veenendaal ◽  
Charlotta Sundin ◽  
Ariel J. Blocker
Keyword(s):  
Type Iii Secretion ◽  
Bacterial Infections ◽  
Shigella Flexneri ◽  
Effector Proteins ◽  
Host Cells ◽  
Incomplete Penetrance ◽  
Secretion Systems ◽  
Bacterial Surface ◽  
Type Iii ◽  
Type Iii Secretion Systems

ABSTRACT Type III secretion systems (T3SSs) are essential virulence devices for many gram-negative bacteria that are pathogenic for plants, animals, and humans. They serve to translocate virulence effector proteins directly into eukaryotic host cells. T3SSs are composed of a large cytoplasmic bulb and a transmembrane region into which a needle is embedded, protruding above the bacterial surface. The emerging antibiotic resistance of bacterial pathogens urges the development of novel strategies to fight bacterial infections. Therapeutics that rather than kill bacteria only attenuate their virulence may reduce the frequency or progress of resistance emergence. Recently, a group of salicylidene acylhydrazides were identified as inhibitors of T3SSs in Yersinia, Chlamydia, and Salmonella species. Here we show that these are also effective on the T3SS of Shigella flexneri, where they block all related forms of protein secretion so far known, as well as the epithelial cell invasion and induction of macrophage apoptosis usually demonstrated by this bacterium. Furthermore, we show the first evidence for the detrimental effect of these compounds on T3SS needle assembly, as demonstrated by increased numbers of T3S apparatuses without needles or with shorter needles. Therefore, the compounds generate a phenocopy of T3SS export apparatus mutants but with incomplete penetrance. We discuss why this would be sufficient to almost completely block the later secretion of effector proteins and how this begins to narrow the search for the molecular target of these compounds.

scholarly journals A Salmonella type III effector, PipA, works in a different manner than the PipA family effectors GogA and GtgA

PLoS ONE ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. e0248975
Author(s):  
Momo Takemura ◽  
Takeshi Haneda ◽  
Hikari Idei ◽  
Tsuyoshi Miki ◽  
Nobuhiko Okada
Keyword(s):  
Hela Cells ◽  
Critical Role ◽  
Effector Proteins ◽  
Host Cells ◽  
Microbial Pathogens ◽  
Secretion Systems ◽  
Type Iii ◽  
Zinc Metalloprotease ◽  
Type Iii Secretion Systems ◽  
Serovar Typhimurium

Nuclear factor-kappa B (NF-κB) plays a critical role in the host defense against microbial pathogens. Many pathogens modulate NF-κB signaling to establish infection in their host. Salmonella enterica serovar Typhimurium (S. Typhimurium) possesses two type III secretion systems (T3SS-1 and T3SS-2) and directly injects many effector proteins into host cells. It has been reported that some effectors block NF-κB signaling, but the molecular mechanism of the inactivation of NF-κB signaling in S. Typhimurium is poorly understood. Here, we identified seven type III effectors—GogA, GtgA, PipA, SseK1, SseK2, SseK3, and SteE—that inhibited NF-κB activation in HeLa cells stimulated with TNF-α. We also determined that only GogA and GtgA are involved in regulation of the activation of NF-κB in HeLa cells infected with S. Typhimurium. GogA, GtgA, and PipA are highly homologous to one another and have the consensus zinc metalloprotease HEXXH motif. Our experiments demonstrated that GogA, GtgA, and PipA each directly cleaved NF-κB p65, whereas GogA and GtgA, but not PipA, inhibited the NF-κB activation in HeLa cells infected with S. Typhimurium. Further, expressions of the gogA or gtgA gene were induced under the SPI-1-and SPI-2-inducing conditions, but expression of the pipA gene was induced only under the SPI-2-inducing condition. We also showed that PipA was secreted into RAW264.7 cells through T3SS-2. Finally, we indicated that PipA elicits bacterial dissemination in the systemic stage of infection of S. Typhimurium via a T3SS-1-independent mechanism. Collectively, our results suggest that PipA, GogA and GtgA contribute to S. Typhimurium pathogenesis in different ways.

scholarly journals Cooperative Immune Suppression by Escherichia coli and Shigella Effector Proteins

2018 ◽  
Vol 86 (4) ◽  
Author(s):  
Maarten F. de Jong ◽  
Neal M. Alto
Keyword(s):  
Escherichia Coli ◽  
Defense Mechanisms ◽  
Immune Defense ◽  
Effector Proteins ◽  
Innate Immune ◽  
Host Cells ◽  
Secretion Systems ◽  
Content Type ◽  
E Coli ◽  
Type Iii Secretion Systems

ABSTRACT The enteric attaching and effacing (A/E) pathogens enterohemorrhagic Escherichia coli (EHEC) and enteropathogenic E. coli (EPEC) and the invasive pathogens enteroinvasive E. coli (EIEC) and Shigella encode type III secretion systems (T3SS) used to inject effector proteins into human host cells during infection. Among these are a group of effectors required for NF-κB-mediated host immune evasion. Recent studies have identified several effector proteins from A/E pathogens and EIEC/ Shigella that are involved in suppression of NF-κB and have uncovered their cellular and molecular functions. A novel mechanism among these effectors from both groups of pathogens is to coordinate effector function during infection. This cooperativity among effector proteins explains how bacterial pathogens are able to effectively suppress innate immune defense mechanisms in response to diverse classes of immune receptor signaling complexes (RSCs) stimulated during infection.

scholarly journals Export von Gefahrgut: Helicobacter pylori und sein CagA-Protein

BIOspektrum ◽  
2020 ◽  
Vol 26 (6) ◽  
pp. 597-599
Author(s):  
Clara Lettl ◽  
Wolfgang Fischer
Keyword(s):  
Helicobacter Pylori ◽  
Pathogenic Bacteria ◽  
Type Iv Secretion ◽  
Host Cells ◽  
Bacterial Protein ◽  
Secretion Systems ◽  
Unusual Structure ◽  
Type Iv ◽  
Single Protein ◽  
Protein Transporters

Abstract Pathogenic bacteria often utilize type IV secretion systems to interact with host cells and to modify their microenvironment in a favourable way. The human pathogen Helicobacter pylori produces such a system to inject only a single protein, CagA, into gastric cells, but this injection represents a major risk factor for gastric cancer development. Here, we discuss the unusual structure of the Cag secretion nanomachine and other features that make it unique among bacterial protein transporters.

Salmonella in Australia: understanding and controlling infection

2017 ◽  
Vol 38 (3) ◽  
pp. 112
Author(s):  
Joshua PM Newson
Keyword(s):  
Host Cell ◽  
Cell Biology ◽  
Protein Translocation ◽  
Cell Signalling ◽  
Effector Proteins ◽  
Host Cells ◽  
Secretion Systems ◽  
Significant Burden ◽  
Systemic Infections ◽  
Bacterial Effectors

The bacterium Salmonella causes a spectrum of foodborne diseases ranging from acute gastroenteritis to systemic infections, and represents a significant burden of disease globally. In Australia, Salmonella is frequently associated with outbreaks and is a leading cause of foodborne illness, which results in a significant medical and economic burden. Salmonella infection involves colonisation of the small intestine, where the bacteria invades host cells and establishes an intracellular infection. To survive within host cells, Salmonella employs type-three secretion systems to deliver bacterial effector proteins into the cytoplasm of host cells. These bacterial effectors seek out and modify specific host proteins, disrupting host processes such as cell signalling, intracellular trafficking, and programmed cell death. This strategy of impairing host cells allows Salmonella to establish a replicative niche within the cell, where they can replicate to high numbers before escaping to infect neighbouring cells, or be transmitted to new hosts. While the importance of effector protein translocation to infection is well established, our understanding of many effector proteins remains incomplete. Many Salmonella effectors have unknown function and unknown roles during infection. A greater understanding of how Salmonella manipulates host cells during infection will lead to improved strategies to prevent, control, and eliminate disease. Further, studying effector proteins can be a useful means for exploring host cell biology and elucidating the details of host cell signalling.

Sign in / Sign up

Export Citation Format

Share Document