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  • 11
    Electronic Resource
    Electronic Resource
    Molecular genetic bases of Salmonella entry into host cells (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 20 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Salmonella spp. can enter into non-phagocytic cells, a property that is essential for their pathogenicity. Recently, considerable progress has been made in the understanding of the molecular genetic bases of this process. It is now evident that Salmonella entry functions are largely encoded on a 35–40 kb region of the Salmonella chromosome located at centisome 63. The majority of the loci in this region encode components of a type III or contact-dependent secretion system homologous to those described in a variety of animal and plant-pathogenic bacteria as well as a number of proteins that require this system for their export to the extracellular environment. A somewhat unexpected finding has been the remarkable homology between the Salmonella and Shigella proteins that mediate the entry of these organisms into cultured epithelial cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1996.tb02615.x
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  • 12
    Electronic Resource
    Electronic Resource
    The Salmonella typhimurium invasion genes invF and invG encode homologues of the AraC and PulD family of proteins (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 13 (1994), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We have identified two novel Salmonella typhimurium genes, invF and invG, which are required for the efficient entry of these organisms into cultured epithelial cells. invF and invG are located immediately upstream of invE, a previously identified gene also required for Salmonella entry. Non-polar mutations in these genes rendered S. typhimurium severely deficient for entry into cultured epithelial cells. The nucleotide sequences of invF and invG indicated that these genes encode polypeptides with predicted molecular weights of 24373 and 62275, respectively. Proteins of similar sizes were observed when invF and invG were expressed in a bacteriophage T7 RNA polymerase-based expression system. Comparison of the predicted sequence of InvF with translated sequences in the existing databases indicated that this protein is homologous to members of the AraC family of prokaryotic transcription regulators. However, mutations in invF did not significantly affect the expression of other members of the inv locus. InvG was found to be homologous to members of the PuID family of specialized translocases. This homology suggests that InvG may be necessary for the export of invasion-related determinants or involved in the assembly of a supramolecular structure that promotes entry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1994.tb00450.x
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  • 13
    Electronic Resource
    Electronic Resource
    Characterization of SprA, an AraC-like transcriptional regulator encoded within the Salmonella typhimurium pathogenicity island 1 (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 33 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Pathogenicity island 1 (SPI-1) located at centisome 63 of the Salmonella chromosome encodes a type III protein secretion system that is essential for its pathogenicity. The translocation of effector proteins through this system results in the stimulation of signalling events, leading to actin cytoskeletal rearrangements and nuclear responses. These cellular responses ultimately lead to bacterial uptake, production of proinflammatory cytokines in non-phagocytic cells and the initiation of programmed cell death in macrophages. The regulation of expression of components and substrates of this type III secretion system is complex and involves the activity of several specific transcriptional regulatory proteins encoded within SPI-1. Here, we describe two additional regulatory proteins, SprA and SprB, which are encoded within SPI-1. SprA and SprB exhibit significant sequence similarity to the AraC/XylS and the LuxR/UhaP family of transcriptional regulatory proteins respectively. Insertion mutations in sprA and sprB did not significantly affect the transcription of invasion-associated genes and, consequently, did not affect the ability of Salmonella typhimurium to gain access into host cells. However, expression of sprA from an inducible heterologous promoter resulted in increased expression of genes associated with the centisome 63 type III secretion system and increased the ability of S. typhimurium to enter into host cells. Further analysis demonstrated that SprA acts either upstream or at the same level as HilA in the SPI-1 transcriptional regulatory cascade.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01458.x
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  • 14
    Electronic Resource
    Electronic Resource
    Salmonella spp. are cytotoxic for cultured macrophages (1996)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 21 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We have shown by a variety of microscopical and biochemical techniques that Salmonella spp. are cytotoxic for cultured J774A.1 and bone marrow-derived murine macrophages. The cytotoxicity is initially manifested by inhibition of membrane ruffling and macropinocytosis in infected macrophages, and is followed by cell death. Macrophages killed by Salmonella spp. exhibited features of apoptosis such as condensation and fragmentation of chromatin, membrane blebbing, and the presence of cytoplasmic nucleosomes and apoptotic bodies. Cytotoxicity does not require bacterial internalization as cytochalasin D, a drug that prevents bacterial uptake, did not prevent Salmonella-induced macrophage cell death. However, the cytotoxic effects are strictly dependent upon the expression of the invasion-associated Type III protein-secretion system encoded at centisome 63 of the Salmonella chromosome. Wild-type Salmonella typhimurium grown under conditions that do not allow optimal expression of this system or strains of Salmonella carrying mutations in genes that encode components of this protein-secretion system were devoid of macrophage cytotoxicity. In addition, mutations in invJ, spaO, sipB, sipC and sipD, which encode proteins that are secreted via this secretion apparatus and are required for bacterial entry into non-phagocytic cells, also abolished the toxicity. In contrast, mutations in sipA and sptP, which encode secreted proteins that are not required for bacterial invasion, had no effect on macrophage cytotoxicity. These results indicate a close correlation between the mechanisms of bacterial internalization into non-phagocytic cells and those that lead to macrophage cytotoxicity. Host-adapted serotypes of Salmonella such as S. typhi, S. gallinarum and S. dublin were also toxic for murine macrophages, indicating that this virulence property is probably present in most Salmonella spp. and is not associated with the mechanisms responsible for host range.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1996.471410.x
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  • 15
    Electronic Resource
    Electronic Resource
    The related effector proteins SopD and SopD2 from Salmonella enterica serovar Typhimurium contribute to virulence during systemic infection of mice (2004)
    Oxford, UK : Blackwell Publishing Ltd.
    Molecular microbiology 54 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Salmonella resides within host cells in a vacuole that it modifies through the action of virulence proteins called effectors. Here we examined the role of two related effectors, SopD and SopD2, in Salmonella pathogenesis. Salmonella enterica serovar Typhimurium (S. Typhimurium) mutants lacking either sopD or sopD2 were attenuated for replication in the spleens of infected mice when competed against wild-type bacteria in mixed infection experiments. A double mutant lacking both effector genes did not display an additive attenuation of virulence in these experiments. The double mutant also competed equally with both of the single mutants. Deletion of either effector impaired bacterial replication in mouse macrophages but not human epithelial cells. Deletion of sopD2 impaired Salmonella’s ability to form tubular membrane filaments [Salmonella-induced filaments (Sifs)] in infected cells; the number of Sifs decreased, whereas the number of pseudo-Sifs (thought to be a precursor of Sifs) was increased. Transfection of HeLa cells with the effector SifA induced the formation of Sif-like tubules and these were observed in greater size and number after co-transfection of SifA with SopD2. In infected cells, SifA and SopD2 were localized both to Sifs and to pseudo-Sifs. In contrast, deletion of sopD had no effect on Sif formation. Our results indicate that both SopD and SopD2 contribute to virulence in mice and suggest a functional relationship between these two proteins during systemic infection of the host.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04344.x
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  • 16
    Electronic Resource
    Electronic Resource
    Salmonella type III secretion-associated chaperones confer secretion-pathway specificity (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 51 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Type III protein secretion systems (TTSSs) are ancestrally related to the flagellar export system and are essential for the virulence of many bacteria pathogenic for humans, animals and plants. Most proteins destined to travel the TTSS pathway possess at least two domains that specifically target them to the secretion apparatus. One of the domains is located within the amino terminal first ∼20 amino acids and the second domain, located within the first ∼140 amino acids, serves as a binding site for specific chaperones. It has been previously proposed that these two secretion signals are capable of operating independently of one another to facilitate secretion into the extracellular environment. We have found that in the absence of their chaperone-binding domains, the Salmonella typhimurium TTSS-secreted proteins SptP and SopE are no longer targeted for secretion through their cognate TTSS and, instead, are secreted through the flagellar export pathway. These results indicate the existence of an ‘ancestral’ flagellar secretion signal within TTSS-exported proteins that is revealed in the absence of the chaperone-binding domain. Furthermore, we found that secretion into culture supernatants as well as translocation into host cells by the cognate TTSS require both, the amino terminal and chaperone-binding domains. We conclude from these studies that a critical function for the TTSS-associated chaperones is to confer secretion-pathway specificity to their cognate secreted proteins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03840.x
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  • 17
    Electronic Resource
    Electronic Resource
    Molecular and functional analysis of the type III secretion signal of the Salmonella enterica InvJ protein (2002)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 46 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Central to the pathogenicity of Salmonella enterica is the function of a type III secretion system (TTSS) encoded within a pathogenicity island at centisome 63 (SPI-1). An essential component of this system is a supramolecular structure termed the needle complex. Proteins to be delivered into host cells possess specific signals that route them to the type III secretion pathway. In addition, some bacterial proteins have signals that deliver them to the secretion complex to either become their structural components or exert their function at that location. One of these proteins is InvJ, which controls the length of the needle substructure of the needle complex. In this study, we have analysed the signal that targets InvJ to the TTSS. We found that amino acid residues 4 to 7 of InvJ are necessary and sufficient to mediate secretion of InvJ or a reporter protein in a TTSS-dependent manner. InvJ secretion was found to be essential for its function in needle length determination, effector protein secretion and bacterial invasion of epithelial cells. Frameshift mutagenesis analysis indicated that the InvJ type III secretion signal sequence tolerates significant alterations in its amino acid sequence without affecting InvJ secretion. Introduction of silent mutations in the secretion signal coding sequence that result in drastically different predicted mRNA folds had no effect on InvJ secretion or expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.03196.x
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  • 18
    Electronic Resource
    Electronic Resource
    Chaperone release and unfolding of substrates in type III secretion (2005)
    [s.l.] : Nature Publishing Group
    Nature 437 (2005), S. 911-915 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Type III protein secretion systems are essential virulence factors of many bacteria pathogenic to humans, animals and plants. These systems mediate the transfer of bacterial virulence proteins directly into the host cell cytoplasm. Proteins are thought to travel this pathway in a largely ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature03992
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  • 19
    Electronic Resource
    Electronic Resource
    RICK/Rip2/CARDIAK mediates signalling for receptors of the innate and adaptive immune systems (2002)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 416 (2002), S. 194-199 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The immune system consists of two evolutionarily different but closely related responses, innate immunity and adaptive immunity. Each of these responses has characteristic receptors—Toll-like receptors (TLRs) for innate immunity and antigen-specific receptors for adaptive immunity. Here ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/416194a
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  • 20
    Electronic Resource
    Electronic Resource
    Maintenance of an unfolded polypeptide by a cognate chaperone in bacterial type III secretion (2001)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 414 (2001), S. 77-81 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Many bacterial pathogens use a type III protein secretion system to deliver virulence effector proteins directly into the host cell cytosol, where they modulate cellular processes. A requirement for the effective translocation of several such effector proteins is the binding of specific ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35102073
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