The Structure and Function of Type III Secretion Systems

Notti, Ryan Q.; Stebbins, C. Erec

doi:10.1128/microbiolspec.vmbf-0004-2015

Cited by 104 publications

(68 citation statements)

References 173 publications

(259 reference statements)

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“…Recent advances in assembly, structure, and mechanistic studies have considerably increased our current understanding of the function of this macromolecular complex (62)(63)(64)(65). Despite this, there are still several gaps in our knowledge on the molecular mechanisms underlying effector protein translocation into host cells.…”

Section: Discussionmentioning

confidence: 99%

Functional Characterization of EscK (Orf4), a Sorting Platform Component of the Enteropathogenic Escherichia coli Injectisome

et al. 2017

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The type III secretion system (T3SS) is a supramolecular machine used by many bacterial pathogens to translocate effector proteins directly into the eukaryotic host cell cytoplasm. Enteropathogenic Escherichia coli (EPEC) is an important cause of infantile diarrheal disease in underdeveloped countries. EPEC virulence relies on a T3SS encoded within a chromosomal pathogenicity island known as the locus of enterocyte effacement (LEE). In this work, we pursued the functional characterization of the LEE-encoded protein EscK (previously known as Orf4). We provide evidence indicating that EscK is crucial for efficient T3S and belongs to the SctK (OrgA/YscK/MxiK) protein family, whose members have been implicated in the formation of a sorting platform for secretion of T3S substrates. Bacterial fractionation studies showed that EscK localizes to the inner membrane independently of the presence of any other T3SS component. Combining yeast two-hybrid screening and pulldown assays, we identified an interaction between EscK and the C-ring/sorting platform component EscQ. Site-directed mutagenesis of conserved residues revealed amino acids that are critical for EscK function and for its interaction with EscQ. In addition, we found that T3S substrate overproduction is capable of compensating for the absence of EscK. Overall, our data suggest that EscK is a structural component of the EPEC T3SS sorting platform, playing a central role in the recruitment of T3S substrates for boosting the efficiency of the protein translocation process.IMPORTANCE The type III secretion system (T3SS) is an essential virulence determinant for enteropathogenic Escherichia coli (EPEC) colonization of intestinal epithelial cells. Multiple EPEC effector proteins are injected via the T3SS into enterocyte cells, leading to diarrheal disease. The T3SS is encoded within a genomic pathogenicity island termed the locus of enterocyte effacement (LEE). Here we unravel the function of EscK, a previously uncharacterized LEE-encoded protein. We show that EscK is central for T3SS biogenesis and function. EscK forms a protein complex with EscQ, the main component of the cytoplasmic sorting platform, serving as a docking site for T3S substrates. Our results provide a comprehensive functional analysis of an understudied component of T3SSs.

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Section: Discussionmentioning

confidence: 99%

Functional Characterization of EscK (Orf4), a Sorting Platform Component of the Enteropathogenic Escherichia coli Injectisome

et al. 2017

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“…Studies have revealed many mechanisms that are important for disease and environmental adaptation, including extracellular enzymes (protease, mannanase, etc. ), extracellular polysaccharides (EPS), diffusible signal factor (DSF)‐dependent cell–cell signalling, and proteins secreted by the type II secretion system (T2SS), type III secretion system (T3SS), type IV secretion system (T4SS) and more recently type VI secretion system (T6SS) (He and Zhang, ; Büttner and Bonas, ; Ryan et al , , ; Notti and Stebbins, ; Zhou et al , ). In Xcc , one of the best‐studied mechanisms that contributes to virulence is the T3SS apparatus.…”

Section: Introductionmentioning

confidence: 99%

Flp, a Fis‐like protein, contributes to the regulation of type III secretion and virulence processes in the phytopathogen Xanthomonas campestris pv. campestris

Leng

Qin

et al. 2019

Molecular Plant Pathology

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Summary The ability of the plant pathogen Xanthomonas campestris pv. campestris ( Xcc ) to cause disease is dependent on its ability to adapt quickly to the host environment during infection. Like most bacterial pathogens, Xcc has evolved complex regulatory networks that ensure expression and regulation of their virulence genes. Here, we describe the identification and characterization of a Fis‐like protein (named Flp), which plays an important role in virulence and type III secretion system (T3SS) gene expression in Xcc . Deletion of flp caused reduced virulence and hypersensitive response (HR) induction of Xcc and alterations in stress tolerance. Global transcriptome analyses revealed the Flp had a broad regulatory role and that most T3SS HR and pathogenicity ( hrp ) genes were down‐regulated in the flp mutant. β ‐glucuronidase activity assays implied that Flp regulates the expression of hrp genes via controlling the expression of hrpX . More assays confirmed that Flp binds to the promoter of hrpX and affected the transcription of hrpX directly. Interestingly, the constitutive expression of hrpX in the flp mutant restored the HR phenotype but not full virulence. Taken together, the findings describe the unrecognized regulatory role of Flp protein that controls hrp gene expression and pathogenesis in Xcc .

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“…Seven T3SS injectisome families have been identified (9) and share a number of homologous membrane-associated components with the flagellar basal body (10). While many aspects of T3SS structure are similar among different T3SS families, the repertoire of encoded T3SS effector proteins is unique for each genus or even species (11,12). For example, pathogenic Yersinia species, which include the plague agent Yersinia pestis and the enteropathogens Yersinia enterocolitica and Yersinia pseudotuberculosis, and the opportunistic pathogen Pseudomonas aeruginosa encode a Ysc family T3SS that contributes to virulence.…”

mentioning

confidence: 99%

Synthetic Cyclic Peptomers as Type III Secretion System Inhibitors

Lam

Schwochert

Lao

et al. 2017

Antimicrob Agents Chemother

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Antibiotic-resistant bacteria are an emerging threat to global public health. New classes of antibiotics and tools for antimicrobial discovery are urgently needed. Type III secretion systems (T3SS), which are required by dozens of Gramnegative bacteria for virulence but largely absent from nonpathogenic bacteria, are promising virulence blocker targets. The ability of mammalian cells to recognize the presence of a functional T3SS and trigger NF-B activation provides a rapid and sensitive method for identifying chemical inhibitors of T3SS activity. In this study, we generated a HEK293 stable cell line expressing green fluorescent protein (GFP) driven by a promoter containing NF-B enhancer elements to serve as a readout of T3SS function. We identified a family of synthetic cyclic peptide-peptoid hybrid molecules (peptomers) that exhibited dose-dependent inhibition of T3SS effector secretion in Yersinia pseudotuberculosis and Pseudomonas aeruginosa without affecting bacterial growth or motility. Among these inhibitors, EpD-3=N, EpD-1,2N, EpD-1,3=N, EpD-1,2,3=N, and EpD-1,2,4=N exhibited strong inhibitory effects on translocation of the Yersinia YopM effector protein into mammalian cells (Ͼ40% translocation inhibition at 7.5 M) and showed no toxicity to mammalian cells at 240 M. In addition, EpD-3=N and EpD-1,2,4=N reduced the rounding of HeLa cells caused by the activity of Yersinia effector proteins that target the actin cytoskeleton. In summary, we have discovered a family of novel cyclic peptomers that inhibit the injectisome T3SS but not the flagellar T3SS.

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The Structure and Function of Type III Secretion Systems

Cited by 104 publications

References 173 publications

Functional Characterization of EscK (Orf4), a Sorting Platform Component of the Enteropathogenic Escherichia coli Injectisome

Functional Characterization of EscK (Orf4), a Sorting Platform Component of the Enteropathogenic Escherichia coli Injectisome

Flp, a Fis‐like protein, contributes to the regulation of type III secretion and virulence processes in the phytopathogen Xanthomonas campestris pv. campestris

Synthetic Cyclic Peptomers as Type III Secretion System Inhibitors

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