Analysis of the expression, regulation and export of NleA–E in Escherichia coli O157 : H7

Roe, Andrew J.; Tysall, Luke; Dransfield, Tracy; Wang, Dai; Fraser-Pitt, D.; Mahajan, Aditya; Constandinou, Chrystala; Inglis, Neil F.; Downing, Alison; Talbot, Richard; Smith, David George Emslie; Gally, David L.

doi:10.1099/mic.0.2006/003707-0

Cited by 46 publications

(57 citation statements)

References 43 publications

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“…As non-LEEencoded effectors are secreted by the LEE-encoded T3SS, it has been tempting to speculate that their expression is coregulated with the LEE. In this regard, it has been recently reported that nleA, nleB, nleD, and nleE are transcribed in EHEC under secretion-permissive conditions and that the expression of nleA::gfp, nleA::bla, and nleD::bla translational reporter fusions showed a reduction in the absence of Ler (53). This result, however, did not distinguish whether Ler-mediated regulation occurs at the transcriptional or posttranslational level.…”

Section: Discussionmentioning

confidence: 83%

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Regulation of Expression and Secretion of NleH, a New Non-Locus of Enterocyte Effacement-Encoded Effector in Citrobacter rodentium

et al. 2008

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Together with enterohemorrhagic Escherichia coli and enteropathogenic Escherichia coli, Citrobacter rodentium is a member of the attaching-and-effacing (A/E) family of bacterial pathogens. A/E pathogens use a type III secretion system (T3SS) to translocate an assortment of effector proteins, encoded both within and outside the locus of enterocyte effacement (LEE), into the colonized host cell, leading to the formation of A/E lesions and disease. Here we report the identification and characterization of a new non-LEE encoded effector, NleH, in C. rodentium. NleH is conserved among A/E pathogens and shares identity with OspG, a type III secreted effector protein in Shigella flexneri. Downstream of nleH, genes encoding homologues of the non-LEE-encoded effectors EspJ and NleG/NleI are found. NleH secretion and translocation into Caco-2 cells requires a functional T3SS and signals located at its amino-terminal domain. Transcription of nleH is not significantly reduced in mutants lacking the LEE-encoded regulators Ler and GrlA; however, NleH protein levels are highly reduced in these strains, as well as in escN and cesT mutants. Inactivation of Lon, but not of ClpP, protease restores NleH levels even in the absence of CesT. Our results indicate that the efficient engagement of NleH in active secretion is needed for its stability, thus establishing a posttranslational regulatory mechanism that coregulates NleH levels with the expression of LEE-encoded proteins. A C. rodentium nleH mutant shows a moderate defect during the colonization of C57BL/6 mice at early stages of infection.

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Section: Discussionmentioning

confidence: 83%

“…Ler and GrlA have been shown to play an essential role in vivo (15,68). Furthermore, the regulatory mechanisms associated with the expression of effector genes located outside the LEE have just started to be elucidated (47,51,53).…”

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confidence: 99%

Regulation of Expression and Secretion of NleH, a New Non-Locus of Enterocyte Effacement-Encoded Effector in Citrobacter rodentium

et al. 2008

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“…NleA is conserved in many A/E pathogens (113,114), and evidence indicates that it affects protein trafficking and secretion through the rough endoplasmic reticulum by binding to the COPII coat protein (112,113). NleA is secreted into the EHEC extracellular milieu (115) and is coordinately regulated with the LEE. As for the LEE, the regulatory proteins H-NS, Ler, and GrlA control expression of the phage-encoded nleA gene (115)(116)(117).…”

Section: Injection Of Effectorsmentioning

confidence: 99%

“…NleA is secreted into the EHEC extracellular milieu (115) and is coordinately regulated with the LEE. As for the LEE, the regulatory proteins H-NS, Ler, and GrlA control expression of the phage-encoded nleA gene (115)(116)(117). Ler acts directly, binding to the regulatory region upstream of the nleA promoter.…”

Section: Injection Of Effectorsmentioning

confidence: 99%

Enterohemorrhagic Escherichia coli Virulence Gene Regulation

Mellies

Lorenzen

2014

Microbiol Spectr

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Coordinated expression of enterohemorrhagic Escherichia coli virulence genes enables the bacterium to cause hemorrhagic colitis and the complication known as hemolytic-uremic syndrome. Horizontally acquired genes and those common to E. coli contribute to the disease process, and increased virulence gene expression is correlated with more severe disease in humans. Researchers have gained considerable knowledge about how the type III secretion system, secreted effectors, adhesin molecules, and the Shiga toxins are regulated by environmental signals and multiple genetic pathways. Also emergent from the data is an understanding of how enterohemorrhagic E. coli regulates response to acid stress, the role of flagellar motility, and how passage through the human host and bovine intestinal tract causes disease and supports carriage in the cattle reservoir, respectively. Particularly exciting areas of discovery include data suggesting how expression of the myriad effectors is coordinately regulated with their cognate type III secretion system and how virulence is correlated with bacterial metabolism and gut physiology.As a species, Escherichia coli is highly successful, adapting to inhabit the lower intestine of warm-blooded animals. Commensal E. coli, part of the normal biota, resides harmlessly in the gut, producing vitamin K. However, E. coli also causes three types of disease in humans: urinary tract infections, sepsis in newborns, and diarrheal disease. Enterohemorrhagic E. coli (EHEC) plays a prominent role in the third type of illness. It has been estimated that, for the pan genome of E. coli, the nonpathogenic and pathogenic strains only contain a core set of genes comprising approximately 20% of any one genome (1, 2). Much of the horizontally acquired genetic information is clustered within genomic islands in pathogens. As for EHEC, this has allowed the organism to not only attach and colonize the large intestine of humans and other animals, to outcompete commensal E. coli and other bacteria at the site of infection, but also to cause serious disease.Horizontally acquired genetic information in EHEC results in evolution into a specific pathotype-genotype dictates phenotype. How this genetic information is controlled is of equal importance for the success and virulence of the organism. Indeed, investigated differences in virulence gene regulation in two distinct EHEC isolate lineages, clade 8 and clade 2. A clade is a group of EHEC isolates with one ancestor and all its descendants. Eight clades of E. coli O157 isolates were defined by single nucleotide polymorphism (SNP) analyses, where clade 8 was a group of hypervirulent bacteria compared to the other seven clades (4). By examining multiple strains per lineage, the investigators found increased expression of horizontally acquired virulence genes in clade 8 versus clade 2. Genes expressed to higher levels in clade 8, which is associated with a greater number of cases of E. coli hemorrhagic

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“…One hypothesis is through its regulatory effects on LEE expression. Both LEE-encoded activators Ler and GrlA regulate nleA expression (71)(72)(73). Moreover, LEE-encoded GrlR has been shown to repress nleB and nleH (71).…”

Section: Discussionmentioning

confidence: 99%

Global Regulator of Virulence A (GrvA) Coordinates Expression of Discrete Pathogenic Mechanisms in Enterohemorrhagic Escherichia coli through Interactions with GadW-GadE

et al. 2016

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Global regulator of virulence A (GrvA) is a ToxR-family transcriptional regulator that activates locus of enterocyte effacement (LEE)-dependent adherence in enterohemorrhagic Escherichia coli (EHEC). LEE activation by GrvA requires the Rcs phosphorelay response regulator RcsB and is sensitive to physiologically relevant concentrations of bicarbonate, a known stimulant of virulence systems in intestinal pathogens. This study determines the genomic scale of GrvA-dependent regulation and uncovers details of the molecular mechanism underlying GrvA-dependent regulation of pathogenic mechanisms in EHEC. In a grvA-null background of EHEC strain TW14359, RNA sequencing analysis revealed the altered expression of over 700 genes, including the downregulation of LEE-and non-LEE-encoded effectors and the upregulation of genes for glutamate-dependent acid resistance (GDAR). Upregulation of GDAR genes corresponded with a marked increase in acid resistance. GrvA-dependent regulation of GDAR and the LEE required gadE, the central activator of GDAR genes and a direct repressor of the LEE. Control of gadE by GrvA was further determined to occur through downregulation of the gadE activator GadW. This interaction of GrvA with GadW-GadE represses the acid resistance phenotype, while it concomitantly activates the LEE-dependent adherence and secretion of immune subversion effectors. The results of this study significantly broaden the scope of GrvA-dependent regulation and its role in EHEC pathogenesis. IMPORTANCEEnterohemorrhagic Escherichia coli (EHEC) is an intestinal human pathogen causing acute hemorrhagic colitis and life-threatening hemolytic-uremic syndrome. For successful transmission and gut colonization, EHEC relies on the glutamate-dependent acid resistance (GDAR) system and a type III secretion apparatus, encoded on the LEE pathogenicity island. This study investigates the mechanism whereby the DNA-binding regulator GrvA coordinates activation of the LEE with repression of GDAR. Investigating how these systems are regulated leads to an understanding of pathogenic behavior and novel strategies aimed at disease prevention and control.

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Analysis of the expression, regulation and export of NleA–E in Escherichia coli O157 : H7

Cited by 46 publications

References 43 publications

Regulation of Expression and Secretion of NleH, a New Non-Locus of Enterocyte Effacement-Encoded Effector in Citrobacter rodentium

Regulation of Expression and Secretion of NleH, a New Non-Locus of Enterocyte Effacement-Encoded Effector in Citrobacter rodentium

Enterohemorrhagic Escherichia coli Virulence Gene Regulation

Global Regulator of Virulence A (GrvA) Coordinates Expression of Discrete Pathogenic Mechanisms in Enterohemorrhagic Escherichia coli through Interactions with GadW-GadE

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