Host–pathogen interactions: Host resistance factor Nramp1 up-regulates the expression of
            <i>Salmonella</i>
            pathogenicity island-2 virulence genes

Zaharik, Michelle L.; Vallance, Bruce A.; Puente, José L.; Gros, Philippe; Finlay, B. Brett

doi:10.1073/pnas.252415599

Cited by 88 publications

(90 citation statements)

References 42 publications

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“…The expression of SPI-2 TTSS structural components and the associated secreted effectors is induced specifically inside host cells (Cirillo et al, 1998;Shea et al, 1996;Valdivia & Falkow, 1997), as well as under in vitro conditions that mimic the intracellular environment of the SCV, which include low osmolarity (Garmendia et al, 2003;Lee et al, 2000), calcium limitation (Garmendia et al, 2003), phosphate limitation (Deiwick et al, 1999) and iron limitation (Zaharik et al, 2002). The induction of SPI-2 genes in response to these stimuli is dependent on SsrA (also referred to as SpiR)/SsrB, a two-component regulatory system encoded within the SPI-2 region.…”

Section: Introductionmentioning

confidence: 99%

“…In Salmonella-infected epithelial cells, the SCV forms long filamentous structures referred to as Salmonellainduced filaments (Sifs), which are elongated tubules that appear to extend from the SCV membrane along the host cell microtubules (Guignot et al, 2004). (Zaharik et al, 2002). The induction of SPI-2 genes in response to these stimuli is dependent on SsrA (also referred to as SpiR)/SsrB, a two-component regulatory system encoded within the SPI-2 region.…”

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confidence: 99%

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Identification of amino acid residues of Salmonella SlyA that are critical for transcriptional regulation

Okada

Takeda‐Shitaka

et al. 2007

Microbiology

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The type III secretion system encoded by Salmonella pathogenicity island 2 (SPI-2) is essential for the intracellular survival and replication of Salmonella enterica. The expression of SPI-2 genes is dependent on a two-component regulatory system, SsrA (SpiR)/SsrB, encoded in the SPI-2 region. This paper shows that SlyA regulates transcription of the sensor kinase SsrA by binding to the ssrA promoter, indicating that SlyA is directly involved in the regulation of SPI-2 gene expression. A structure model of the SlyA dimer in complex with DNA was constructed. The model of SlyA indicated that its structure is very similar to that of other MarR family proteins. Based on this model, site-directed mutagenesis of residues located in the winged-helix region required for DNA binding and in the a-helices of the N-terminal and C-terminal regions required for dimerization of the SlyA protein was performed to identify the residues that are critical for SlyA function. Nine mutants of SlyA with single substitutions were unable to activate ssrA transcription in vivo. These mutant SlyA proteins revealed that the residues Leu-63, Val-64, Arg-65, Leu-67, Leu-70, Arg-86 and Lys-88 within the winged-helix region are required for DNA binding, and residues Leu-12 and Leu-126 within the a-helices of the N-terminal and C-terminal regions are required for efficient dimer formation. A Salmonella slyA mutant strain carrying a plasmid expressing SlyA derivatives containing mutations at these amino acid positions did not exhibit restored SlyA function in infected HeLa cells, thereby confirming the structural and functional relationships of the SlyA protein. INTRODUCTIONSalmonella enterica, a facultative intracellular pathogen, can replicate within macrophages. The intracellular survival of S. enterica serovar Typhimurium requires a number of virulence-associated proteins encoded in Salmonella pathogenicity island 2 (SPI-2) on the bacterial chromosome (Cirillo et al., 1998;Hensel, 2000;Ochman et al., 1996;Shea et al., 1996). SPI-2 encodes a two-component regulatory system, structural components of a type III secretion system (TTSS), effector proteins and chaperones, which mediate the secretion of the effectors (Cirillo et al., 1998;Hensel et al., 1998;Ochman et al., 1996;Shea et al., 1996). In infected macrophages, Salmonella replicates within a membranebound compartment (Salmonella-containing vacuole, SCV) inside the host cells (Steele-Mortimer et al., 2002). Intracellular activation of SPI-2 function is essential for SCV maturation along the phagolysosomal fusion pathway, which is responsible for the inhibition of bacterial degradation in phagolysosomes. The SPI-2 TTSS functions to export effector proteins across the SCV membrane and into the cytosol of host cells, resulting in the prevention of the recruitment of NADPH oxidase to the SCV (Gallois et al., 2001;Vazquez-Torres et al., 2000), as well as leading to the rearrangement of cellular microfilaments (Meresse et al., 2001;Miao et al., 2002) and microtubule networks (Brumell et al., 20...

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Section: Introductionmentioning

confidence: 99%

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confidence: 99%

Identification of amino acid residues of Salmonella SlyA that are critical for transcriptional regulation

Okada

Takeda‐Shitaka

et al. 2007

Microbiology

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“…Found in many Gram-negative pathogenic bacteria, T3S is a needle-like structure that physically connects the cytoplasms of bacterial and host cells, permitting direct translocation of bacterial effector proteins into the cytosol of host cells to alter the function of host cells in favor of disease progression (6 -9). Nramp1 activity competes with the ability of STM to control the biogenesis of SCV, probably via up-regulation of some SPI-2-related genes, and increases the traffic of lysosomal hydrolases to the SCV to facilitate the killing of STM (10,11).…”

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confidence: 99%

Proteomic Analysis of Salmonella enterica Serovar Typhimurium Isolated from RAW 264.7 Macrophages

Shi

Adkins

Coleman

et al. 2006

Journal of Biological Chemistry

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137

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To evade host resistance mechanisms, Salmonella enterica serovar Typhimurium (STM), a facultative intracellular pathogen, must alter its proteome following macrophage infection. To identify new colonization and virulence factors that mediate STM pathogenesis, we have isolated STM cells from RAW 264.7 macrophages at various time points following infection and used a liquid chromatography-mass spectrometry-based proteomic approach to detect the changes in STM protein abundance. Because host resistance to STM infection is strongly modulated by the expression of a functional host-resistant regulator, i.e. natural resistanceassociated macrophage protein 1 (Nramp1, also called Slc11a1), we have also examined the effects of Nramp1 activity on the changes of STM protein abundances. A total of 315 STM proteins have been identified from isolated STM cells, which are largely housekeeping proteins whose abundances remain relatively constant during the time course of infection. However, 39 STM proteins are strongly induced after infection, suggesting their involvement in modulating colonization and infection. Of the 39 induced proteins, 6 proteins are specifically modulated by Nramp1 activity, including STM3117, as well as STM3118 -3119 whose time-dependent abundance changes were confirmed using Western blot analysis. Deletion of the gene encoding STM3117 resulted in a dramatic reduction in the ability of STM to colonize wild-type RAW 264.7 macrophages, demonstrating a critical involvement of STM3117 in promoting the replication of STM inside macrophages. The predicted function common for STM3117-3119 is biosynthesis and modification of the peptidoglycan layer of the STM cell wall.

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“…This proposition is supported by recent experiments with Salmonella carrying a number of transcriptional LacZ fusions that were used to infect Nramp1-positive and -negative mice in vivo, and corresponding macrophages ex vivo. These studies showed that intracellular Salmonella respond to the presence of Nramp1 by induction of a number of ''virulence'' genes that map within Salmonella pathogenicity island 2 (SPI2), including ssrA and sseJ (45). The Nramp1 effect on SPI2 gene induction in vivo can also be reproduced in vitro in cell-free conditions after addition of iron chelators (such as dipyridyl) to Salmonella culture medium (45).…”

Section: Discussionmentioning

confidence: 99%

“…These studies showed that intracellular Salmonella respond to the presence of Nramp1 by induction of a number of ''virulence'' genes that map within Salmonella pathogenicity island 2 (SPI2), including ssrA and sseJ (45). The Nramp1 effect on SPI2 gene induction in vivo can also be reproduced in vitro in cell-free conditions after addition of iron chelators (such as dipyridyl) to Salmonella culture medium (45). Similarly, we have noted an effect of Nramp1 on the level of transcriptional induction of the mycobacterial gene MbtB (J. R. Forbes and P.G., unpublished data) that participates in the synthesis of iron siderophores (mycobactins) and that is absolutely required for intracellular survival of Mycobacterium tuberculosis (46).…”

Section: Discussionmentioning

confidence: 99%

Iron chelators modulate the fusogenic properties of Salmonella -containing phagosomes

Jabado

Cuéllar-Mata

Grinstein

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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In macrophages, the divalent cations transporter Nramp1 is recruited from the lysosomal compartment to the membrane of phagosomes formed in these cells. Nramp1 mutations cause susceptibility to infection with intracellular pathogens such as Salmonella and Mycobacterium. Intracellular survival of Salmonella involves segregation in an endomembrane compartment (Salmonella-containing vacuole, SCV) that remains negative for the mannose-6-phosphate receptor (M6PR) and that is inaccessible to the endocytic pathway. Expression of Nramp1 at the membrane of SCVs stimulates both acquisition of M6PR and accessibility to newly formed endosomes. The possible role of Nramp1-mediated iron transport on SCV maturation was investigated with membrane-permeant iron chelators. Pretreatment of primary macrophages from Nramp1 mutant mice or of RAW264.7 macrophages (from BALB͞c mice bearing an Nramp1 D169 -deficient allele) with either desferrioxamine or salicylaldehyde isocotinoyl hydrazone restored recruitment of M6PR and delivery of the fluid phase marker rhodamine dextran to SCVs to levels similar to those seen in macrophages expressing WT Nramp1. The effect was specific and dose-dependent and could be abrogated by preincubation with excess iron. These data suggest that Nramp1-mediated deprivation of iron and possibly of other divalent metals in macrophages antagonizes the ability of Salmonella to alter phagosome maturation.

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Host–pathogen interactions: Host resistance factor Nramp1 up-regulates the expression of Salmonella pathogenicity island-2 virulence genes

Cited by 88 publications

References 42 publications

Identification of amino acid residues of Salmonella SlyA that are critical for transcriptional regulation

Identification of amino acid residues of Salmonella SlyA that are critical for transcriptional regulation

Proteomic Analysis of Salmonella enterica Serovar Typhimurium Isolated from RAW 264.7 Macrophages

Iron chelators modulate the fusogenic properties of Salmonella -containing phagosomes

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