A NanoLuc luciferase-based assay enabling the real-time analysis of protein secretion and injection by bacterial type III secretion systems

Mapping Intimacies ◽

10.1101/745471 ◽

2019 ◽

Cited By ~ 1

Author(s):

Sibel Westerhausen ◽

Melanie Nowak ◽

Claudia Torres-Vargas ◽

Ursula Bilitewski ◽

Erwin Bohn ◽

...

Keyword(s):

Protein Secretion ◽

High Throughput ◽

Type Iii Secretion ◽

Molecular Mechanisms ◽

Host Cells ◽

Target Cells ◽

Secretion Systems ◽

Type Iii ◽

Nanoluc Luciferase ◽

Type Iii Secretion Systems

AbstractThe elucidation of the molecular mechanisms of secretion through bacterial protein secretion systems is impeded by a lack of assays to quantitatively assess secretion kinetics. Also the analysis of the biological role of these secretion systems as well as the identification of inhibitors targeting these systems would greatly benefit from the availability of a simple, quick and quantitative assay to monitor principle secretion and injection into host cells. Here we present a versatile solution to this need, utilizing the small and very bright NanoLuc luciferase to assess secretion and injection through the type III secretion system encoded by Salmonella pathogenicity island 1. The NanoLuc-based secretion assay features a very high signal-to-noise ratio and sensitivity down to the nanoliter scale. The assay enables monitoring of secretion kinetics and is adaptable to a high throughput screening format in 384-well microplates. We further developed NanoLuc and split-NanoLuc-based assays that enable the monitoring of type III secretion-dependent injection of effector proteins into host cells.ImportanceThe ability to secrete proteins to the bacterial cell surface, to the extracellular environment, or even into target cells is one of the foundations of interbacterial as well as pathogen-host interaction. While great progress has been made in elucidating assembly and structure of secretion systems, our understanding of their secretion mechanism often lags behind, not last because of the challenge to quantitatively assess secretion function. Here, we developed a luciferase-based assay to enable the simple, quick, quantitative, and high throughput-compatible assessment of secretion and injection through virulence-associated type III secretion systems. The assay allows detection of minute amounts of secreted substrate proteins either in the supernatant of the bacterial culture or within eukaryotic host cells. It thus provides an enabling technology to elucidate the mechanisms of secretion and injection of type III secretion systems and is likely adaptable to assay secretion through other bacterial secretion systems.

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Type III Protein Secretion Systems in Bacterial Pathogens of Animals and Plants

Microbiology and Molecular Biology Reviews ◽

10.1128/mmbr.62.2.379-433.1998 ◽

1998 ◽

Vol 62 (2) ◽

pp. 379-433 ◽

Cited By ~ 1674

Author(s):

Christoph J. Hueck

Keyword(s):

Host Cell ◽

Protein Secretion ◽

Type Iii Secretion ◽

Plant Pathogens ◽

Host Cells ◽

Secretion Systems ◽

Type Iii ◽

Type Iii Secretion Systems ◽

Animal Pathogens ◽

Type Iii Protein Secretion

SUMMARY Various gram-negative animal and plant pathogens use a novel, sec-independent protein secretion system as a basic virulence mechanism. It is becoming increasingly clear that these so-called type III secretion systems inject (translocate) proteins into the cytosol of eukaryotic cells, where the translocated proteins facilitate bacterial pathogenesis by specifically interfering with host cell signal transduction and other cellular processes. Accordingly, some type III secretion systems are activated by bacterial contact with host cell surfaces. Individual type III secretion systems direct the secretion and translocation of a variety of unrelated proteins, which account for species-specific pathogenesis phenotypes. In contrast to the secreted virulence factors, most of the 15 to 20 membrane-associated proteins which constitute the type III secretion apparatus are conserved among different pathogens. Most of the inner membrane components of the type III secretion apparatus show additional homologies to flagellar biosynthetic proteins, while a conserved outer membrane factor is similar to secretins from type II and other secretion pathways. Structurally conserved chaperones which specifically bind to individual secreted proteins play an important role in type III protein secretion, apparently by preventing premature interactions of the secreted factors with other proteins. The genes encoding type III secretion systems are clustered, and various pieces of evidence suggest that these systems have been acquired by horizontal genetic transfer during evolution. Expression of type III secretion systems is coordinately regulated in response to host environmental stimuli by networks of transcription factors. This review comprises a comparison of the structure, function, regulation, and impact on host cells of the type III secretion systems in the animal pathogens Yersinia spp., Pseudomonas aeruginosa, Shigella flexneri, Salmonella typhimurium, enteropathogenic Escherichia coli, and Chlamydia spp. and the plant pathogens Pseudomonas syringae, Erwinia spp., Ralstonia solanacearum, Xanthomonas campestris, and Rhizobium spp.

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High-Throughput Screening of Type III Secretion Determinants Reveals a Major Chaperone-Independent Pathway

mBio ◽

10.1128/mbio.01050-18 ◽

2018 ◽

Vol 9 (3) ◽

Cited By ~ 5

Author(s):

Nadja Heinz Ernst ◽

Analise Z. Reeves ◽

Julia E. Ramseyer ◽

Cammie F. Lesser

Keyword(s):

High Throughput ◽

Type Iii Secretion ◽

Bacterial Pathogens ◽

Host Cells ◽

Review Of The Literature ◽

Secretion Systems ◽

Type Iii Effectors ◽

Type Iii ◽

Type Iii Secretion Systems ◽

Effector Secretion

ABSTRACTNumerous Gram-negative bacterial pathogens utilize type III secretion systems (T3SSs) to inject tens of effector proteins directly into the cytosol of host cells. Through interactions with cognate chaperones, type III effectors are defined and recruited to the sorting platform, a cytoplasmic component of these membrane-embedded nanomachines. However, notably, a comprehensive review of the literature reveals that the secretion of most type III effectors has not yet been linked to a chaperone, raising questions regarding the existence of unknown chaperones as well as the universality of chaperones in effector secretion. Here, we describe the development of the first high-throughput type III secretion (T3S) assay, a semiautomated solid-plate-based assay, which enables the side-by-side comparison of secretion of over 20Shigellaeffectors under a multitude of conditions. Strikingly, we found that the majority ofShigellaeffectors are secreted at equivalent levels by wild-type and variants ofShigellathat no longer encode one or all knownShigellaT3S effector chaperones. In addition, we found thatShigellaeffectors are efficiently secreted from a laboratory strain ofEscherichia coliexpressing the coreShigellatype III secretion apparatus (T3SA) but no otherShigella-specific proteins. Furthermore, we observed that the sequences necessary and sufficient to define chaperone-dependent and -independent effectors are fundamentally different. Together, these findings support the existence of a major, previously unrecognized, noncanonical chaperone-independent secretion pathway that is likely common to many T3SSs.IMPORTANCEMany bacterial pathogens use specialized nanomachines, including type III secretion systems, to directly inject virulence proteins (effectors) into host cells. Here, we present the first extensive analysis of chaperone dependence in the process of type III effector secretion, providing strong evidence for the existence of a previously unrecognized chaperone-independent pathway. This noncanonical pathway is likely common to many bacteria, as an extensive review of the literature reveals that the secretion of multiple type III effectors has not yet been knowingly linked to a chaperone. While additional studies will be required to discern the molecular details of this pathway, its prevalence suggests that it can likely serve as a new target for the development of antimicrobial agents.

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

Journal of Bacteriology ◽

10.1128/jb.01004-08 ◽

2008 ◽

Vol 191 (2) ◽

pp. 563-570 ◽

Cited By ~ 71

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.

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An Amino-Terminal Secretion Signal Is Required for YplA Export by the Ysa, Ysc, and Flagellar Type III Secretion Systems of Yersinia enterocolitica Biovar 1B

Journal of Bacteriology ◽

10.1128/jb.187.17.6075-6083.2005 ◽

2005 ◽

Vol 187 (17) ◽

pp. 6075-6083 ◽

Cited By ~ 15

Author(s):

Sasha M. Warren ◽

Glenn M. Young

Keyword(s):

Yersinia Enterocolitica ◽

Type Iii Secretion ◽

Distinct Type ◽

Host Cells ◽

Amino Acid Residues ◽

Secretion Systems ◽

Type Iii ◽

Secretion Signal ◽

Amino Terminal ◽

Type Iii Secretion Systems

ABSTRACT Yersinia enterocolitica biovar 1B maintains three distinct type III secretion (TTS) systems, which independently operate to target proteins to extracellular sites. The Ysa and Ysc systems are prototypical contact-dependent TTS systems that translocate toxic effectors to the cytosols of targeted eukaryotic host cells during infection. The flagellar TTS system is utilized during the assembly of the flagellum and is required for secretion of the virulence-associated phospholipase YplA to the bacterial milieu. When ectopically produced, YplA is also a secretion substrate for the Ysa and Ysc TTS systems. In this study, we define elements that allow YplA recognition and export by the Ysa, Ysc, and flagellar TTS systems. Fusion of various amino-terminal regions of YplA to Escherichia coli alkaline phosphatase (PhoA) lacking its native secretion signal demonstrated that the first 20 amino acids or corresponding mRNA codons of YplA were sufficient for export of YplA-PhoA chimeras by each TTS system. Export of native YplA by each of the three TTS systems was also found to depend on the integrity of its amino terminus. Introduction of a frameshift mutation or deletion of yplA sequences encoding the amino-terminal 20 residues negatively impacted YplA secretion. Deletion of other yplA regions was tolerated, including that resulting in the removal of amino acid residues 30 through 40 of the polypeptide and removal of the 5′ untranslated region of the mRNA. This work supports a model in which independent and distantly related TTS systems of Y. enterocolitica recognize protein substrates by a similar mechanism.

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Type III Secretion Effectors with Arginine N-Glycosyltransferase Activity

Microorganisms ◽

10.3390/microorganisms8030357 ◽

2020 ◽

Vol 8 (3) ◽

pp. 357 ◽

Cited By ~ 4

Author(s):

Juan Luis Araujo-Garrido ◽

Joaquín Bernal-Bayard ◽

Francisco Ramos-Morales

Keyword(s):

Type Iii Secretion ◽

Enterohemorrhagic Escherichia Coli ◽

Host Cells ◽

Secretion Systems ◽

Type Iii ◽

Cellular Processes ◽

Host Cell Death ◽

Pathway Activation ◽

Type Iii Secretion Systems ◽

Arginine Residues

Type III secretion systems are used by many Gram-negative bacterial pathogens to inject proteins, known as effectors, into the cytosol of host cells. These virulence factors interfere with a diverse array of host signal transduction pathways and cellular processes. Many effectors have catalytic activities to promote post-translational modifications of host proteins. This review focuses on a family of effectors with glycosyltransferase activity that catalyze addition of N-acetyl-d-glucosamine to specific arginine residues in target proteins, leading to reduced NF-κB pathway activation and impaired host cell death. This family includes NleB from Citrobacter rodentium, NleB1 and NleB2 from enteropathogenic and enterohemorrhagic Escherichia coli, and SseK1, SseK2, and SseK3 from Salmonella enterica. First, we place these effectors in the general framework of the glycosyltransferase superfamily and in the particular context of the role of glycosylation in bacterial pathogenesis. Then, we provide detailed information about currently known members of this family, their role in virulence, and their targets.

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Bacterial Type III Secretion Systems: Specialized Nanomachines for Protein Delivery into Target Cells

Annual Review of Microbiology ◽

10.1146/annurev-micro-092412-155725 ◽

2014 ◽

Vol 68 (1) ◽

pp. 415-438 ◽

Cited By ~ 307

Author(s):

Jorge E. Galán ◽

Maria Lara-Tejero ◽

Thomas C. Marlovits ◽

Samuel Wagner

Keyword(s):

Type Iii Secretion ◽

Protein Delivery ◽

Target Cells ◽

Secretion Systems ◽

Type Iii ◽

Type Iii Secretion Systems ◽

Bacterial Type

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Impact of Salmonella enterica Type III Secretion System Effectors on the Eukaryotic Host Cell

ISRN Cell Biology ◽

10.5402/2012/787934 ◽

2012 ◽

Vol 2012 ◽

pp. 1-36 ◽

Cited By ~ 52

Author(s):

Francisco Ramos-Morales

Keyword(s):

Type Iii Secretion ◽

Salmonella Enterica ◽

Current Knowledge ◽

Cellular Level ◽

Host Cells ◽

Secretion Systems ◽

Type Iii ◽

Cellular Processes ◽

Type Iii Secretion Systems ◽

Near Future

Type III secretion systems are molecular machines used by many Gram-negative bacterial pathogens to inject proteins, known as effectors, directly into eukaryotic host cells. These proteins manipulate host signal transduction pathways and cellular processes to the pathogen’s advantage. Salmonella enterica possesses two virulence-related type III secretion systems that deliver more than forty effectors. This paper reviews our current knowledge about the functions, biochemical activities, host targets, and impact on host cells of these effectors. First, the concerted action of effectors at the cellular level in relevant aspects of the interaction between Salmonella and its hosts is analyzed. Then, particular issues that will drive research in the field in the near future are discussed. Finally, detailed information about each individual effector is provided.

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Effect of the O-Antigen Length of Lipopolysaccharide on the Functions of Type III Secretion Systems in Salmonella enterica

Infection and Immunity ◽

10.1128/iai.00871-09 ◽

2009 ◽

Vol 77 (12) ◽

pp. 5458-5470 ◽

Cited By ~ 50

Author(s):

Stefanie U. Hölzer ◽

Markus C. Schlumberger ◽

Daniela Jäckel ◽

Michael Hensel

Keyword(s):

Type Iii Secretion ◽

Salmonella Enterica ◽

Defense Mechanisms ◽

Host Cells ◽

Effector Protein ◽

Secretion Systems ◽

Type Iii ◽

O Antigen ◽

T3ss Effector ◽

Type Iii Secretion Systems

ABSTRACT The virulence of Salmonella enterica critically depends on the functions of two type III secretion systems (T3SS), with the Salmonella pathogenicity island 1 (SPI1)-encoded T3SS required for host cell invasion and the SPI2-T3SS enabling Salmonella to proliferate within host cells. A further T3SS is required for the assembly of the flagella. Most serovars of Salmonella also possess a lipopolysaccharide with a complex O-antigen (OAg) structure. The number of OAg units attached to the core polysaccharide varies between 16 and more than 100 repeats, with a trimodal distribution. This work investigated the correlation of the OAg length with the functions of the SPI1-T3SS and the SPI2-T3SS. We observed that the number of repeats of OAg units had no effect on bacterial motility. The interaction of Salmonella with epithelial cells was altered if the OAg structure was changed by mutations in regulators of OAg. Strains defective in synthesis of very long or long and very long OAg species showed increased translocation of a SPI1-T3SS effector protein and increased invasion. Invasion of a strain entirely lacking OAg was increased, but this mutant strain also showed increased adhesion. In contrast, translocation of a SPI2-T3SS effector protein and intracellular replication were not affected by modification of the OAg length. Mutant strains lacking the entire OAg or long and very long OAg were highly susceptible to complement killing. These observations indicate that the architecture of the outer membrane of Salmonella is balanced to permit sufficient T3SS function but also to confer optimal protection against antimicrobial defense mechanisms.

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Visualization of the type III secretion mediated Salmonella–host cell interface using cryo-electron tomography

eLife ◽

10.7554/elife.39514 ◽

2018 ◽

Vol 7 ◽

Cited By ~ 34

Author(s):

Donghyun Park ◽

Maria Lara-Tejero ◽

M Neal Waxham ◽

Wenwei Li ◽

Bo Hu ◽

...

Keyword(s):

Cell Membrane ◽

Host Cell ◽

Protein Secretion ◽

Electron Tomography ◽

Host Cells ◽

Target Cells ◽

Secretion Systems ◽

Type Iii ◽

Cryo Electron Tomography ◽

Cell Interface

Many important gram-negative bacterial pathogens use highly sophisticated type III protein secretion systems (T3SSs) to establish complex host-pathogen interactions. Bacterial-host cell contact triggers the activation of the T3SS and the subsequent insertion of a translocon pore into the target cell membrane, which serves as a conduit for the passage of effector proteins. Therefore the initial interaction between T3SS-bearing bacteria and host cells is the critical step in the deployment of the protein secretion machine, yet this process remains poorly understood. Here, we use high-throughput cryo-electron tomography (cryo-ET) to visualize the T3SS-mediated Salmonella-host cell interface. Our analysis reveals the intact translocon at an unprecedented level of resolution, its deployment in the host cell membrane, and the establishment of an intimate association between the bacteria and the target cells, which is essential for effector translocation. Our studies provide critical data supporting the long postulated direct injection model for effector translocation.

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