Genetic and Mechanistic Analyses of the Periplasmic Domain of the Enterohemorrhagic Escherichia coli QseC Histidine Sensor Kinase

ABSTRACT The histidine sensor kinase (HK) QseC senses autoinducer 3 (AI-3) and the adrenergic hormones epinephrine and norepinephrine. Upon sensing these signals, QseC acts through three response regulators (RRs) to regulate the expression of virulence genes in enterohemorrhagic Escherichia coli (EHEC). The QseB, QseF, and KdpE RRs that are phosphorylated by QseC constitute a tripartite signaling cascade having different and overlapping targets, including flagella and motility, the type three secretion system encoded by the locus of enterocyte effacement (LEE), and Shiga toxin. We modeled the tertiary structure of QseC's periplasmic sensing domain and aligned the sequences from 12 different species to identify the most conserved amino acids. We selected eight amino acids conserved in all of these QseC homologues. The corresponding QseC site-directed mutants were expressed and still able to autophosphorylate; however, four mutants demonstrated an increased basal level of phosphorylation. These mutants have differential flagellar, motility, LEE, and Shiga toxin expression phenotypes. We selected four mutants for more in-depth analyses and found that they differed in their ability to phosphorylate QseB, KdpE, and QseF. This suggests that these mutations in the periplasmic sensing domain affected the region downstream of the QseC signaling cascade and therefore can influence which pathway QseC regulates. IMPORTANCE In the foodborne pathogen EHEC, QseC senses AI-3, epinephrine, and norepinephrine, increases its autophosphorylation, and then transfers its phosphate to three RRs: QseB, QseF, and KdpE. QseB controls expression of flagella and motility, KdpE controls expression of the LEE region, and QseF controls the expression of Shiga toxin. This tripartite signaling pathway must be tightly controlled, given that flagella and the type three secretion system (T3SS) are energetically expensive appendages and Shiga toxin expression leads to bacterial cell lysis. Our data suggest that mutations in the periplasmic sensing loop of QseC differentially affect the expression of the three arms of this signaling cascade. This suggests that these point mutations may change QseC's phosphotransfer preferences for its RRs.

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Immune Response in Calves Vaccinated with Type Three Secretion System Antigens and Shiga Toxin 2B Subunit of Escherichia coli O157:H7

PLoS ONE ◽

10.1371/journal.pone.0169422 ◽

2017 ◽

Vol 12 (1) ◽

pp. e0169422 ◽

Cited By ~ 8

Author(s):

Luisina Martorelli ◽

Sergio Garbaccio ◽

Daniel A. Vilte ◽

Adriana A. Albanese ◽

María P. Mejías ◽

...

Keyword(s):

Escherichia Coli ◽

Immune Response ◽

Shiga Toxin ◽

Secretion System ◽

Escherichia Coli O157 ◽

Type Three Secretion System ◽

Type Three Secretion

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The Type Three Secretion System 2-Encoded Regulator EtrB Modulates Enterohemorrhagic Escherichia coli Virulence Gene Expression

Infection and Immunity ◽

10.1128/iai.00407-16 ◽

2016 ◽

Vol 84 (9) ◽

pp. 2555-2565 ◽

Cited By ~ 6

Author(s):

Deborah H. Luzader ◽

Graham G. Willsey ◽

Matthew J. Wargo ◽

Melissa M. Kendall

Keyword(s):

Escherichia Coli ◽

Regulatory Region ◽

Secretion System ◽

Enterohemorrhagic Escherichia Coli ◽

Lesion Formation ◽

Content Type ◽

Regulatory Circuit ◽

Type Three Secretion System ◽

System 2 ◽

Type Three Secretion

EnterohemorrhagicEscherichia coliO157:H7 (EHEC) is a foodborne pathogen that causes bloody diarrhea and hemolytic uremic syndrome throughout the world. A defining feature of EHEC pathogenesis is the formation of attaching and effacing (AE) lesions on colonic epithelial cells. Most of the genes that code for AE lesion formation, including a type three secretion system (T3SS) and effectors, are carried within a chromosomal pathogenicity island called the locus of enterocyte effacement (LEE). In this study, we report that a putative regulator, which is encoded in the crypticE. colitype three secretion system 2 (ETT2) locus and herein renamed EtrB, plays an important role in EHEC pathogenesis. TheetrBgene is expressed as a monocistronic transcript, and EtrB autoregulates expression. We provide evidence that EtrB directly interacts with thelerregulatory region to activate LEE expression and promote AE lesion formation. Additionally, we mapped the EtrB regulatory circuit in EHEC to determine a global role for EtrB. EtrB is regulated by the transcription factor QseA, suggesting that these proteins comprise a regulatory circuit important for EHEC colonization of the gastrointestinal tract.

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Type Three Secretion System-Dependent Microvascular Thrombosis and Ischemic Enteritis in Human Gut Xenografts Infected with Enteropathogenic Escherichia coli

Infection and Immunity ◽

10.1128/iai.00558-17 ◽

2017 ◽

Vol 85 (11) ◽

Cited By ~ 4

Author(s):

Einat Nissim-Eliraz ◽

Eilam Nir ◽

Irit Shoval ◽

Noga Marsiano ◽

Israel Nissan ◽

...

Keyword(s):

Escherichia Coli ◽

Blood Vessels ◽

Secretion System ◽

Infection Model ◽

Apical Surface ◽

Muscularis Mucosa ◽

Human Gut ◽

Type Three Secretion System ◽

Type Three Secretion ◽

Ischemic Enteritis

ABSTRACT Enteropathogenic Escherichia coli (EPEC) is a leading cause of severe intestinal disease and infant mortality in developing countries. Virulence is mediated by a type three secretion system (T3SS), causing the hallmark attaching and effacing (AE) lesions and actin-rich pedestal formation beneath the infecting bacteria on the apical surface of enterocytes. EPEC is a human-specific pathogen whose pathogenesis cannot be studied in animal models. We therefore established an EPEC infection model in human gut xenografts in SCID mice and used it to study the role of T3SS in the pathogenesis of the disease. Following EPEC O127:H6 strain E2348/69 infection, T3SS-dependent AE lesions and pedestals were demonstrated in all infected xenografts. We report here the development of T3SS-dependent intestinal thrombotic microangiopathy (iTMA) and ischemic enteritis in ∼50% of infected human gut xenografts. Using species-specific CD31 immunostaining, we showed that iTMA was limited to the larger human-mouse chimeric blood vessels, which are located between the muscularis mucosa and circular muscular layer of the human gut. These blood vessels were massively invaded by bacteria, which adhered to and formed pedestals on endothelial cells and aggregated with mouse neutrophils in the lumen. We conclude that endothelial infection, iTMA, and ischemic enteritis might be central mechanisms underlying severe EPEC-mediated disease.

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Bovine Colostrum Contains Immunoglobulin G Antibodies against Intimin, EspA, and EspB and Inhibits Hemolytic Activity Mediated by the Type Three Secretion System of Attaching and Effacing Escherichia coli

Clinical and Vaccine Immunology ◽

10.1128/cvi.00027-08 ◽

2008 ◽

Vol 15 (8) ◽

pp. 1208-1213 ◽

Cited By ~ 16

Author(s):

Daniel A. Vilte ◽

Mariano Larzábal ◽

Ángel A. Cataldi ◽

Elsa C. Mercado

Keyword(s):

Escherichia Coli ◽

Immunoglobulin G ◽

Hemolytic Activity ◽

Secretion System ◽

Bovine Colostrum ◽

Serological Response ◽

Prophylactic Measure ◽

E Coli ◽

Type Three Secretion System ◽

Type Three Secretion

ABSTRACT Enterohemorrhagic Escherichia coli (EHEC) is the main cause of hemolytic-uremic syndrome, an endemic disease in Argentina which had an incidence in 2005 of 13.9 cases per 100,000 children younger than 5 years old. Cattle appear to be a major reservoir of EHEC, and a serological response to EHEC antigens has been demonstrated in natural and experimental infections. In the current study, antibodies against proteins implicated in EHEC's ability to form attaching and effacing lesions, some of which are exported to the host cell via a type three secretion system (TTSS), were identified in bovine colostrum by Western blot analysis. Twenty-seven (77.0%) of the 35 samples examined contained immunoglobulin G (IgG) antibodies against the three proteins assayed in this study: EspA, EspB, and the carboxy-terminal 280 amino acids of γ-intimin, an intimin subtype associated mainly with O157:H7 and O145:H- serotypes. Every colostrum sample was able to inhibit, in a range between 45.9 and 96.7%, the TTSS-mediated hemolytic activity of attaching and effacing E. coli. The inhibitory effect was partially mediated by IgG and lactoferrin. In conclusion, we found that early colostrum from cows contains antibodies, lactoferrin, and other unidentified substances that impair TTSS function in attaching and effacing E. coli strains. Bovine colostrum might act by reducing EHEC colonization in newborn calves and could be used as a prophylactic measure to protect non-breast-fed children against EHEC infection in an area of endemicity.

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