Abnormally expressed ER stress response chaperone Gp96 in CD favours adherent-invasive Escherichia coli invasion

Background and aims Crohn's disease (CD) ileal lesions are colonised by pathogenic adherent-invasive Escherichia coli (AIEC) producing outer membrane vesicles (OMVs) that contribute to the bacterial invasion process. In addition, increased expression of endoplasmic reticulum (ER)-localised stress response proteins, due to ER stress, is observed in patients with CD. The expression of the ER-localised stress response protein Gp96 in patients with CD and its biological role with regards to the ability of AIEC to invade intestinal epithelial cells were analysed.Methods and results Immunohistochemistry on tissue arrays showed that, together with CEACAM6 (carcinoembryonic antigen-related cell adhesion molecule 6) or the ER stress protein Grp78, Gp96 is also strongly expressed at the apical plasma membrane of the ileal epithelial cells of 50% of patients with CD. Invasion experiments in the presence of antibodies raised against Gp96, or after transfection of Intestine-407 cells with gp96 small interfering RNA (siRNA), indicated that Gp96 is essential to promote AIEC LF82 invasion, allowing, via the recognition of the outer membrane protein OmpA, OMVs to fuse with intestinal epithelial cells.Conclusions Gp96 is overexpressed on the apical surface of ileal epithelial cells in patients with CD and acts as a host cell receptor for OMVs, promoting AIEC invasion. From the results shown here, it is speculated that AIEC could take advantage of the abnormal expression of Gp96 in patients with CD to invade the ileal mucosa

The Salmonella SPI-2 effector SseJ exhibits eukaryotic activator-dependent phospholipase A and glycerophospholipid : cholesterol acyltransferase activity

Intracellular replication of Salmonella enterica serovar Typhimurium within membrane-bound compartments, called Salmonella-containing vacuoles, depends on the activities of several effector proteins translocated by the Salmonella pathogenicity island 2 (SPI-2)-encoded type III secretion system. The SPI-2 effector protein SseJ shows similarity at the amino acid level to several GDSL lipases with glycerophospholipid : cholesterol acyltransferase (GCAT) activity. In this study, we show that catalytic serine-dependent phospholipase A (PLA) and GCAT activity of recombinant SseJ is potentiated by factor(s) present in HeLa cells, RAW macrophages and Saccharomyces cerevisiae. SseJ activity was enhanced with increasing amounts of, or preincubation with, eukaryotic cell extracts. Analysis of the activating factor(s) shows that it is soluble and heat- and protease-sensitive. We conclude that PLA and GCAT activities of SseJ are potentiated by proteinaceous eukaryotic factor(s)

A milestone in screening for adherent‐invasive E. coli colonization in patients with Crohn’s disease?

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How the study of Listeria monocytogenes has led to new concepts in biology

The opportunistic intracellular bacterial pathogen Listeria monocytogenes has in 30 years emerged as an exceptional bacterial model system in infection biology. Research on this bacterium has provided considerable insight into how pathogenic bacteria adapt to mammalian hosts, invade eukaryotic cells, move intracellularly, interfere with host cell functions and disseminate within tissues. It also contributed to unveil features of normal host cell pathways and unsuspected functions of previously known cellular proteins. This review provides an updated overview of our knowledge on this pathogen. In many examples, findings on L. monocytogenes provided the basis for new concepts in bacterial regulation, cell biology and infection processes

Adherent-invasive Escherichia coli in inflammatory bowel disease

Auteur de correspondance : [email protected] audienceIncreased numbers of mucosa-associated Escherichia coli are observed in both major inflammatory bowel diseases, Crohn's disease (CD) and ulcerative colitis (UC). With the identification of mutations in the NOD2-encoding gene in patients with CD and given the intracellular location of NOD2, the presence of pathogenic invasive bacteria could be the link between innate immune response to invasive bacteria and the development of the inflammation. Adherent-invasive E. coli (AIEC) are isolated from ileal biopsies of 36.4% of patients with ileal involvement of CD. These pathogenic E. coli colonize the intestinal mucosa by adhering to intestinal epithelial cells and are also true invasive pathogens, able to invade intestinal epithelial cells and to replicate intracellularly. AIEC strains also survive and replicate extensively within macrophages without inducing host cell death, and their high replication rates induce the secretion of large amounts of tumor necrosis factor alpha (TNF-alpha). There is also evidence suggesting that AIEC is involved in the formation of granulomas. The presence of AIEC is restricted to CD patients. Mucosa-associated E. coli in patients with UC can adhere to intestinal epithelial cells and induce the secretion of IL-8, but there is no evidence that these E. coli strains are invasive

How the study of Listeria monocytogenes has led to new concepts in biology.

International audienceThe opportunistic intracellular bacterial pathogen Listeria monocytogenes has in 30 years emerged as an exceptional bacterial model system in infection biology. Research on this bacterium has provided considerable insight into how pathogenic bacteria adapt to mammalian hosts, invade eukaryotic cells, move intracellularly, interfere with host cell functions and disseminate within tissues. It also contributed to unveil features of normal host cell pathways and unsuspected functions of previously known cellular proteins. This review provides an updated overview of our knowledge on this pathogen. In many examples, findings on L. monocytogenes provided the basis for new concepts in bacterial regulation, cell biology and infection processes

When pathogenic bacteria meet the intestinal microbiota

International audienceThe intestinal microbiota is a large and diverse microbial community that inhabits the intestinal tract, containing about 100 trillion bacteria from 500-1000 distinct species that, collectively, provide multiple benefits to the host. The gut microbiota contributes to nutrient absorption and maturation of the immune system, and also plays a central role in protection of the host from enteric bacterial infection. On the other hand, many enteric pathogens have developed strategies in order to be able to outcompete the intestinal community, leading to infection and/or chronic diseases. This review will summarize findings describing the complex relationship occurring between the intestinal microbiota and enteric pathogens, as well as how future therapies can ultimately benefit from such discoveries. This article is part of the themed issue 'The new bacteriology'

Pouvoir d'adhésion et d'invasion des souches AIEC associées à la maladie de Crohn (facteurs de virulence et régulation de leur expression)

La maladie de Crohn (MC) est une affection inflammatoire chronique du tube digestif dont l'étiologie reste mal connue. Les lésions iléales de MC sont anormalement colonisées par des souches pathogènes de Escherichia coli appartenant au pathovar AIEC pour Adherent-Invasive E. coli. Ces souches sont capables d'adhérer et d'envahir les cellules épithéliales intestinales et ont la capacité de survivre et de se multiplier fortement en macrophages, en induisant une synthèse intense de TNF-a. L'objectif de ce travail s'inscrit dans la compréhension des mécanismes permettant aux bactéries AIEC d'adhérer et d'envahir les cellules épithéliales intestinales. Le criblage de la banque de mutants d'insertion du transposon Tn5phoA de la souche AIEC de référence LF82 a permis de mettre en évidence le rôle de la lipoprotéine YfgL dans le pouvoir invasif de la souche LF82. En effet, cette lipoprotéine participe à la formation de vésicules membranaires qui pourraient constituer un système de sécrétion et de transport de protéines bactériennes effectrices délivrées dans la cellule hôte et nécessaires à l'invasion des cellules par les bactéries. De plus, l'oxydoréductase DsbA est impliquée dans l'adhésion de la souche AIEC LF82 en régulant l'expression des flagelles et des pili de type 1, mais est également essentielle à la survie des bactéries AIEC LF82 en macrophages. Enfin, la protéine de membrane externe OmpC est essentielle chez la souche AIEC LF82 à l'adhésion et l'invasion des cellules épithéliales intestinales, mais son rôle dans la virulence est indirect. L'expression de la protéine OmpC est fortement induite à forte osmolarité, condition rencontrée par les bactéries AIEC au sein du tube digestif. Une surexpression de OmpC permet, chez la souche AIEC LF82, l'activation de la voie de régulation dépendante du facteur sigma alternatif RpoE (ou E) qui régule l'expression des pili de type 1, des flagelles et d'autres facteurs nécessaires au processus d'adhésion et d'invasion des cellules épithéliales intestinales. En conclusion, sur la base des facteurs de virulence identifiés chez la souche AIEC LF82 et de leur régulation, les souches aIEC semblent avoir évolué de façon à pouvoir coloniser et envahir la muqueuse intestinale.CLERMONT FD-BCIU-Santé (631132104) / SudocSudocFranceF

Tryptophan metabolites get the gut moving

International audienceHow gut microbes can regulate the enteric nervous system and gut-brain communications is a field of intense research. In this issue of Cell Host & Microbe, Ye et al. demonstrate that bacteria can control intestinal motility and vagal neuronal activation via tryptophan catabolites through the receptor TrpA1 of enteroendocrine cells

Tryptophan Metabolism as a Pharmacological Target

International audienceL-Tryptophan is an essential amino acid required for protein synthesis. It undergoes an extensive and complex metabolism along several pathways, resulting in many bioactive molecules acting in various organs through different action mechanisms. Enzymes involved in its metabolism, metabolites themselves, or their receptors, represent potential therapeutic targets, which are the subject of dynamic research. Disruptions in L-tryptophan metabolism are reported in several neurological, metabolic, psychiatric, and intestinal disorders, paving the way to develop drugs to target it. This review will briefly describe L-tryptophan metabolism and present and discuss the most recent pharmacological developments targeting it