Деякі проблеми використання тимчасово зайнятих земель

<div><p>Glucocorticoid induced-leucine zipper (GILZ) has been shown to be induced in cells by different stimuli such as glucocorticoids, IL-10 or deprivation of IL-2. GILZ has anti-inflammatory properties and may be involved in signalling modulating apoptosis. Herein we demonstrate that wildtype <em>Yersinia enterocolitica</em> which carry the pYV plasmid upregulated GILZ mRNA levels and protein expression in epithelial cells. Infection of HeLa cells with different <em>Yersinia</em> mutant strains revealed that the protease activity of YopT, which cleaves the membrane-bound form of Rho GTPases was sufficient to induce GILZ expression. Similarly, <em>Clostridium difficile</em> toxin B, another bacterial inhibitor of Rho GTPases induced GILZ expression. YopT and toxin B both increased transcriptional activity of the GILZ promoter in HeLa cells. GILZ expression could not be linked to the inactivation of an individual Rho GTPase by these toxins. However, forced expression of RhoA and RhoB decreased basal <em>GILZ</em> promoter activity. Furthermore, MAPK activation proved necessary for profound GILZ induction by toxin B. Promoter studies and gel shift analyses defined binding of upstream stimulatory factor (USF) 1 and 2 to a canonical c-Myc binding site (E-box) in the <em>GILZ</em> promoter as a crucial step of its trans-activation. In addition we could show that USF-1 and USF-2 are essential for basal as well as toxin B induced GILZ expression. These findings define a novel way of <em>GILZ</em> promoter trans-activation mediated by bacterial toxins and differentiate it from those mediated by dexamethasone or deprivation of IL-2.</p> </div

Caractérisation fonctionnelle d une cyclomoduline pro-apoptotique nommée Cif (Cycle Inhibiting Factor) chez les bactéries entomopathogènes du genre Photorhabdus

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

The emerging human pathogen Photorhabdus asymbiotica is a facultative intracellular bacterium and induces apoptosis of macrophage-like cells

Correspondance auteur: R. Zumbihl E-mail: [email protected] audiencePhotorhabdus species are gram-negative entomopathogenic bacteria of the family Enterobacteriaceae. Among the different members of the genus, one species, Photorhabdus asymbiotica, is a pathogen of both insects and humans. The pathogenicity mechanisms of this bacterium are unknown. Here we show that P. asymbiotica is a facultative intracellular pathogen that is able to replicate inside human macrophage-like cells. Furthermore, P. asymbiotica was shown for the first time in an intracellular location after insect infection. We also demonstrated that among Australian and American clinical isolates, only the Australian strains were able to invade nonphagocytic human cells. In cell culture infection experiments, Australian clinical isolates as well as cell-free bacterial culture supernatant induced strong apoptosis of a macrophage cell line at 6 h postinfection. American isolates also induced cellular death, but much later than that induced by Australian ones. Mammalian cultured cells analyzed for key features of apoptosis displayed apoptotic nuclear morphology, activation of the initiator caspases 8 and 9 and the executioner caspases 3 and 7, and poly(ADP-ribose) polymerase proteolysis, suggesting activation of both the intrinsic and extrinsic apoptotic pathway

Etude de l'interaction des bactéries du genre Photorhabdus avec les cellules du système immunitaire

Les entérobactéries du genre Photorhabdus sont pathogènes pour les insectes et récemment ont été décrites des souches cliniques de l'espèce P. asymbiotica, isolées aux États-Unis et en Australie. Nous nous sommes consacrés à l'étude de certains mécanismes de virulence utilisés par Photorhabdus. Le génome de P. luminescens subsp laumondii, souche TT01, présente un locus qui code pour un système de sécrétion de type trois et un effecteur, LopT. Nous avons étudié un nouvel effecteur de P. luminescens, homologue de LopT et appelé LopT2, mais codée sur un prophage défectif. Comme LopT, LopT2 présente une activité de cysteine protéase dont les cibles sont les protéines de la famille des Rho GTPases. LopT2 est produit in vivo spécifiquement dans des organes de défense, ce qui suggère qu'il joue un rôle essentiel dans l'inhibition des réactions de défense immunitaire de l'insecte. Pour ce qui concerne P. asymbiotica, notre travail montre, pour la première fois, qu'il s'agit d'une bactérie à croissance intracellulaire facultative. Les souches américaines sont faiblement internalisées par les macrophages THP-1 tandis que les souches australiennes pénètrent facilement dans les THP-1 aussi bien que dans des cellules non phagocytaires (HeLa). En plus, seules les souches australiennes induisent une forte et rapide apoptose des cellules du systeme immunitaire d'insectes et de mammifères. Nous montrons que la plus grande virulence des souches australiennes vis-à-vis de cellules in vitro, peut être corrélée à la plus grande gravité des cas cliniques enrégistrés en Australie par rapport aux Etats-UnisMONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Wortmannin blocks Yersinia invasin-triggered internalization, but not interleukin-8 production by epithelial cells

In response to bacterial infection epithelial cells up-regulate expression and secretion of proinflammatory cytokines. Previous work from our laboratory showed that basolateral infection of polarized T84 cells with Yersinia enterocolitica induces interleukin-8 (IL-8) secretion in the absence of significant invasion. Here we studied Y. enterocolitica-induced IL-8 secretion by epithelial HeLa cells as a function of Yersinia invasion or adhesion. For this purpose we tried to separated induction of IL-8 secretion from invasion by treating HeLa cells with signal transduction inhibitors prior to infection. While staurosporin and genistein inhibited both Yersinia invasion and Yersinia-triggered IL-8 secretion, wortmannin, an inhibitor of the phosphatidylinositol-3-phosphate kinase (PI3-K), blocked invasion of Y. enterocolitica into HeLa cells but did not show any effect on IL-8 secretion. These results suggest that Yersinia adhesion might be sufficient to induce IL-8 secretion by epithelial cells. Further analysis demonstrated the requirement of the Yersinia invasion locus inv for adhesion-mediated induction of IL-8 secretion. Thus, HeLa cells infected with an E. coli strain expressing the Y. enterocolitica inv locus induced IL-8 secretion in the presence and absence of wortmannin. Reverse transcription-polymerase chain reaction analysis revealed that adhesion of inv-expressing Y. enterocolitica or E. coli results in the transcriptional activation of the IL-8 gene. These results suggest that Y. enterocolitica adhesion to host cells via Inv activates de novo synthesis and secretion of IL-8.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Variation in the Effectors of the Type III Secretion System among Photorhabdus Species as Revealed by Genomic Analysis

Entomopathogenic bacteria of the genus Photorhabdus harbor a type III secretion system. This system was probably acquired prior to the separation of the species within this genus. Furthermore, the core components of the secretion machinery are highly conserved but the predicted effectors differ between Photorhabdus luminescens and P. asymbiotica, two highly related species with different hosts

The xaxAB genes encoding a new apoptotic toxin from the insect pathogen Xenorhabdus nematophila are present in plant and human pathogens

International audienceXenorhabdus nematophila, a member of the Enterobacteriaceae, kills many species of insects by strongly depressing the immune system and colonizing the entire body. A peptide cytotoxin has been purified from X. nematophila broth growth, and the cytolytic effect on insect immunocytes and hemolytic effect on mammalian red blood cells of this toxin have been described (Ribeiro, C., Vignes, M., and Brehelin, M. (2003) J. Mal. Chem. 278, 3030-3039). We show here that this toxin, Xenorhabdus alpha-xenorhabdolysin (Xax), triggers apoptosis in both insect and mammalian cells. We also report the cloning and sequencing of two genes, xaxAB, encoding this toxin in X. nematophila. The expression of both genes in recombinant Escherichia coli led to the production of active cytotoxin/hemolysin. However, hemolytic activity was observed only if the two peptides were added in the appropriate order. Furthermore, we report here that inactivation of xaxAB genes in X. nematophila abolished the major cytotoxic activity present in broth growth, called C I. We also show that these genes are present in various entomopathogenic bacteria of the genera Xenorhabdus and Photorhabdus, in Pseudomonas entomophila, in the human pathogens Yersinia enterocolitica and Proteus mirabilis, and in the plant pathogen Pseudomonas syringae. This toxin cannot be classified in any known family of cytotoxins on the basis of amino acid sequences, locus organization, and activity features. It is, therefore, probably the prototype of a new family of binary toxins