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ABSTRACT: Inactivation of the host GTPase RhoA by staphylococcal epidermal cell differentiation inhibitor (EDIN) exotoxins triggers the formation of large transcellular tunnels, named macroapertures, in endothelial cells. We used bioluminescent strains of Staphylococcus aureus to monitor the formation of infection foci during the first 24 h of hematogenous bacterial dissemination. Clinically derived EDIN-expressing S. aureus strains S25 and Xen36 produced many disseminated foci. EDIN had no detectable impact on infection foci in terms of histopathology or the intensity of emitted light. Moreover, EDIN did not modify the course of bacterial clearance from the bloodstream. In contrast, we show that EDIN expression promotes a 5-fold increase in the number of infection foci produced by Xen36. This virulence activity of EDIN requires RhoA ADP-ribosyltranferase activity. These results suggest that EDIN is a risk factor for S. aureus dissemination through the vasculature by virtue of its ability to promote the formation of infection foci in deep-seated tissues.
Infection and immunity 08/2010; 78(8):3404-11. · 4.21 Impact Factor
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ABSTRACT: Studies on the interactions of bacterial pathogens with their host have provided an invaluable source of information on the major functions of eukaryotic and prokaryotic cell biology. In addition, this expanding field of research, known as cellular microbiology, has revealed fascinating examples of trans-kingdom functional interplay. Bacterial factors actually exploit eukaryotic cell machineries using refined molecular strategies to promote invasion and proliferation within their host. Here, we review a family of bacterial toxins that modulate their activity in eukaryotic cells by activating Rho GTPases and exploiting the ubiquitin/proteasome machineries. This family, found in human and animal pathogenic Gram-negative bacteria, encompasses the cytotoxic necrotizing factors (CNFs) from Escherichia coli and Yersinia species as well as dermonecrotic toxins from Bordetella species. We survey the genetics, biochemistry, molecular and cellular biology of these bacterial factors from the standpoint of the CNF1 toxin, the paradigm of Rho GTPase-activating toxins produced by urinary tract infections causing pathogenic Escherichia coli. Because it reveals important connections between bacterial invasion and the host inflammatory response, the mode of action of CNF1 and its related Rho GTPase-targetting toxins addresses major issues of basic and medical research and constitutes a privileged experimental model for host-pathogen interaction.
FEMS Microbiology Reviews 10/2007; 31(5):515-34. · 10.96 Impact Factor
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Medecine sciences: M/S 06/2007; 23(5):459-60. · 0.64 Impact Factor
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ABSTRACT: Escherichia coli are the most common etiological agents of urinary tract infections (UTIs). Uropathogenic E. coli (UPECs) produce specific toxins including the cytotoxic necrotizing factor-1 (CNF1) and the alpha-hemolysin (alpha-Hly). CNF1 triggers, through Rho protein activation, a specific gene response of host cells, which results in the production for instance of interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1) and the macrophage inflammatory protein-3alpha (MIP-3alpha). The alpha hemolysin alpha-Hly also triggers the production of inflammatory mediators. Cnf1 is always associated with alpha-hly in a pathogenicity island conserved among UPECs. Using two complementary approaches we have investigated whether alpha-hly and cnf1 bearing UPECs are associated with a specific type of UTI both in term of pathology and host response. Here we report that UPECs bearing alpha-hly/cnf1 have a prevalence of 50% in UPECs isolated from hemorrhagic UTIs, as compared to 30% in the overall UPEC population. In addition, we observed that MCP-1, and IL-8 to a lower extent, is produced in urine at higher concentrations in UTIs caused by UPECs carrying alpha-hly/cnf1.
Cytokine 02/2007; 37(1):22-5. · 3.02 Impact Factor
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Trends in Microbiology 08/2006; 14(7):292-4. · 7.91 Impact Factor
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Laurent Boyer,
Anne Doye,
Monica Rolando,
Gilles Flatau,
Patrick Munro,
Pierre Gounon,
René Clément,
Céline Pulcini,
Michel R Popoff,
Amel Mettouchi, Luce Landraud,
Olivier Dussurget,
Emmanuel Lemichez
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ABSTRACT: The GTPase RhoA is a major regulator of the assembly of actin stress fibers and the contractility of the actomyosin cytoskeleton. The epidermal cell differentiation inhibitor (EDIN) and EDIN-like ADP-ribosyltransferases of Staphylococcus aureus catalyze the inactivation of RhoA, producing actin cable disruption. We report that purified recombinant EDIN and EDIN-producing S. aureus provoke large transcellular tunnels in endothelial cells that we have named macroapertures (MAs). These structures open transiently, followed by the appearance of actin-containing membrane waves extending over the aperture. Disruption of actin cables, either directly or indirectly, through rhoA RNAi knockdown also triggers the formation of MAs. Intoxication of endothelial monolayers by EDIN produces a loss of barrier function and provides direct access of the endothelium basement membrane to S. aureus.
The Journal of Cell Biology 07/2006; 173(5):809-19. · 10.26 Impact Factor
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ABSTRACT: Interleukin-8 elevation in urine during urinary tract infections (UTIs) has been documented for different uropathogenic germs in 85 patients. We showed that for 17 different isolates, IL-8 was increased in 92% of UTIs with an average value of 627 pg/ml for infected, as compared to 45 pg/ml for uninfected patients. We suggest that the high negative predictive value of the IL-8 urine assay could be useful to eliminate UTIs in routine screenings.
Cytokine 10/2005; 31(6):415-8. · 3.02 Impact Factor
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ABSTRACT: The CNF1 toxin is produced by uropathogenic and meningitis-causing Escherichia coli. CNF1 penetrates autonomously into cells and confers phagocytic properties to epithelial and endothelial cells. CNF1 acts at the molecular level by constitutively activating Rho GTPases attenuated by their cellular ubiquitin-mediated proteasomal degradation. Here we report the relationship between the ubiquitin-mediated proteasomal degradation of activated Rho and the endothelial cell response to the toxin. The type of cellular response to CNF1 intoxication, first screened by DNA microarray analysis, revealed the launching of a program oriented toward an inflammatory response. Parallel to Rho protein activation by CNF1, we also established the kinetics of production of monocyte chemotactic protein-1 (MCP-1), interleukin-8 (IL-8), IL-6, monocyte inflammatory protein-3alpha (MIP-3alpha) and E-selectin. Both the mutation of the catalytic domain of the toxin (CNF1-C866S) and the inhibition of Rho proteins abrogate the CNF1-induced production of the immunomodulators MIP-3alpha, MCP-1, and IL-8. These immunomodulators are also produced upon activation of Cdc42 and Rac preferentially. Our results indicate that, in addition to pathogen molecular pattern recognition by host-receptors, a direct activation of Rho proteins by the CNF1 virulence factor efficiently triggers a cellular reaction of host alert. Consistently, we assume that the CNF1-induced ubiquitin-mediated proteasomal degradation of activated Rho proteins may limit the amplitude of the host cell immune responses.
Journal of Biological Chemistry 09/2004; 279(34):35849-57. · 4.77 Impact Factor
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ABSTRACT: The cytotoxic necrotizing factor-1 (CNF1), a bacterial toxin of uropathogenic bacteria (UPEC), hijacks cellular Rho proteins of the Ras GTPase super-family. Recently, we have made three important findings. First, we have established that, following Rho protein activation by deamidation, these cellular proteins are ubiquitylated and degraded by the proteasome. Second, the low level of activated Rho proteins which results from the dual molecular mechanism of action of CNF1 (Rho protein activation followed by their degradation), confers high invasive properties to UPECs. Finally, we have reported that ubiquitylation and degradation of Rac is lost in HEp-2 carcinoma cells, thereby suggesting a possible link between Rho protein ubiquitylation and tumor progression.
International Journal of Medical Microbiology 05/2004; 293(7-8):513-8. · 4.17 Impact Factor
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ABSTRACT: Mycobacterium tuberculosis infection remains a major health problem throughout the world. In France, tuberculosis is endemic, particularly in the Paris area (Ile-de-France) and in the south (Provence Alpes côte d'Azur) where immigration is greater than in other countries in northern Europe. Culture is the gold standard for diagnosis of tuberculosis and is the only method enabling a study of strain sensitivity to treatment. Histology contributes to diagnosis in most cases by revealing typical necrotizing granulomatous lesions. The diagnosis is then confirmed by the detection of acid-fast bacilli with Ziehl-Neelsen staining. However, the Ziehl-Neelsen stain is not sensitive and does not allow identification of different species. The polymerase chain reaction (PCR) DNA amplification method has been used to detect M. tuberculosis in formalin-fixed paraffin-embedded tissues. The aim of the present study was to investigate the value of this method for the diagnosis of M. tuberculosis infection. The results obtained with PCR assay were compared to those obtained with histological and microbiological methods (direct examination and culture). Sixty-three specimens (mainly lymph node and lung specimens) exhibiting a positive culture for M. tuberculosis were analyzed. Tuberculosis granulomas were noted in 32/63 cases, tuberculoid granulomas in 18/63, pyoepitheloid granuloms in 10/63, and non-specific inflammation in 3/63. Ziehl-Neelsen staining was positive in 11/63 cases. PCR assay on tissue sections was positive for M. tuberculosis in 58/63 cases. Controls of the PCR method (granulomas due to other mycobacterial species, foreign body granulomas, sarcoidosis granulomas) were all negative. This study shows that PCR from deparaffinized sections, 1) greatly increases the sensitivity of diagnosis of tuberculosis, 2) enables the diagnosis of M. tuberculosis infection. However, although this method reduces the time to diagnosis, culture remains the gold standard for identification of the mycobacterium and for determining the sensitivity of the isolated strain to treatment.
Annales de Pathologie 07/2003; 23(3):206-15. · 0.25 Impact Factor
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Medecine sciences: M/S 05/2003; 19(4):403-5. · 0.64 Impact Factor
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ABSTRACT: Examination of 55 clinical isolates of uropathogenic Escherichia coli producing the CNF1 toxin demonstrated that the cnf1 gene is systematically associated with a hly operon via a highly conserved hlyD-cnf1 intergenic region (igs, 943 bp) as shown in the J96 UPEC strain. We examined if this association could reflect a co-regulation of the production of these toxins. Translation of cnf1 from an immediately upstream promoter has been shown to be controlled by means of an anti-Shine-Dalgarno sequence present in the cnf1 coding sequence [fold-back inhibition (cnf1 fbi)]. The cnf1 fbi was not regulated by elements present in the igs. An RNA covering the full hlyD sequence, the igs and extending on the cnf1 gene, was then detected in the J96 strain. This RNA could be part of a HlyCABD mRNA. Transcription of the haemolysin operon requires RfaH antitermination activity. Inactivation of rfaH in J96 resulted in a 100-fold reduction of the CNF1 content of bacteria. The production of CNF1 from a plasmidic igscnf1 DNA was not sensitive to RfaH, indicating that this factor acted on cnf1 transcription via the hly promoter. This way the cnf1 fbi mechanism might be overcome by transcription of cnf1 from the haemolysin promoter and antitermination by RfaH. This constitutes a novel system of bacterial virulence factors co-regulation.
Molecular Microbiology 04/2003; 47(6):1653-67. · 5.01 Impact Factor
