Role of the Salmonella Pathogenicity Island 1 Effector Proteins SipA, SopB, SopE, and SopE2 in Salmonella enterica Subspecies 1 Serovar Typhimurium Colitis in Streptomycin-Pretreated Mice

ABSTRACT Salmonella enterica subspecies 1 serovar Typhimurium (serovar Typhimurium) induces enterocolitis in humans and cattle. The mechanisms of enteric salmonellosis have been studied most extensively in calf infection models. The previous studies established that effector protein translocation into host cells via the Salmonella pathogenicity island 1 (SPI-1) type III secretion system (TTSS) is of central importance in serovar Typhimurium enterocolitis. We recently found that orally streptomycin-pretreated mice provide an alternative model for serovar Typhimurium colitis. In this model the SPI-1 TTSS also plays a key role in the elicitation of intestinal inflammation. However, whether intestinal inflammation in calves and intestinal inflammation in streptomycin-pretreated mice are induced by the same SPI-1 effector proteins is still unclear. Therefore, we analyzed the role of the SPI-1 effector proteins SopB/SigD, SopE, SopE2, and SipA/SspA in elicitation of intestinal inflammation in the murine model. We found that sipA, sopE, and, to a lesser degree, sopE2 contribute to murine colitis, but we could not assign an inflammation phenotype to sopB. These findings are in line with previous studies performed with orally infected calves. Extending these observations, we demonstrated that in addition to SipA, SopE and SopE2 can induce intestinal inflammation independent of each other and in the absence of SopB. In conclusion, our data corroborate the finding that streptomycin-pretreated mice provide a useful model for studying the molecular mechanisms of serovar Typhimurium colitis and are an important starting point for analysis of the molecular events triggered by SopE, SopE2, and SipA in vivo.

Download Full-text

Presence of Salmonella pathogenicity island 2 genes in seafood-associated Salmonella serovars and the role of the sseC gene in survival of Salmonella enterica serovar Weltevreden in epithelial cells

Microbiology ◽

10.1099/mic.0.043596-0 ◽

2011 ◽

Vol 157 (1) ◽

pp. 160-168 ◽

Cited By ~ 6

Author(s):

Patit P. Bhowmick ◽

Devananda Devegowda ◽

H. A. Darshanee Ruwandeepika ◽

Iddya Karunasagar ◽

Indrani Karunasagar

Keyword(s):

Clinical Isolate ◽

Type Iii Secretion ◽

Crucial Role ◽

Salmonella Enterica ◽

Pcr Amplification ◽

Pathogenicity Island ◽

Host Cells ◽

Serovar Typhimurium ◽

Systemic Infections

The type III secretion system encoded by the Salmonella pathogenicity island 2 (SPI-2) has a central role in the pathogenesis of systemic infections by Salmonella. Sixteen genes (ssaU, ssaB, ssaR, ssaQ, ssaO, ssaS, ssaP, ssaT, sscB, sseF, sseG, sseE, sseD, sseC, ssaD and sscA) of SPI-2 were targeted for PCR amplification in 57 seafood-associated serovars of Salmonella. The sseC gene of SPI-2 was found to be absent in two isolates of Salmonella enterica serovar Weltevreden, SW13 and SW39. Absence of sseC was confirmed by sequencing using flanking primers. SW13 had only 66 bp sequence of the sseC gene and SW39 had 58 bp sequence of this gene. A clinical isolate, S. Weltevreden – SW3, 10 : r : z6 – was used to construct a deletion mutant for the sseC gene. Significant reduction in the survival of SW3, 10 : r : z6 ΔsseC and natural mutants SW13 and SW39 in HeLa cells suggests that sseC has a crucial role in the intracellular survival of S. Weltevreden. Expression of sseC was upregulated during the intracellular phase of both S. enterica serovar Typhimurium and clinical isolate S. Weltevreden SW3, 10 : r : z6, suggesting a crucial role for this gene in the survival of S. Weltevreden inside host cells.

Download Full-text

Dormant Intracellular Salmonella enterica Serovar Typhimurium Discriminates among Salmonella Pathogenicity Island 2 Effectors To Persist inside Fibroblasts

Infection and Immunity ◽

10.1128/iai.01304-13 ◽

2013 ◽

Vol 82 (1) ◽

pp. 221-232 ◽

Cited By ~ 16

Author(s):

Cristina Núñez-Hernández ◽

Ana Alonso ◽

M. Graciela Pucciarelli ◽

Josep Casadesús ◽

Francisco García-del Portillo

Keyword(s):

Salmonella Enterica ◽

Pathogenicity Island ◽

Effector Proteins ◽

Intracellular Bacteria ◽

Secretion Systems ◽

Cultured Fibroblasts ◽

Content Type ◽

Type Iii Secretion Systems ◽

Serovar Typhimurium

ABSTRACTSalmonella entericauses effector proteins delivered by type III secretion systems (TTSS) to colonize eukaryotic cells. Recentin vivostudies have shown that intracellular bacteria activate the TTSS encoded bySalmonellapathogenicity island-2 (SPI-2) to restrain growth inside phagocytes. Growth attenuation is also observedin vivoin bacteria colonizing nonphagocytic stromal cells of the intestinal lamina propria and in cultured fibroblasts. SPI-2 is required for survival of nongrowing bacteria persisting inside fibroblasts, but its induction mode and the effectors involved remain unknown. Here, we show that nongrowing dormant intracellular bacteria use the two-component system OmpR-EnvZ to induce SPI-2 expression and the PhoP-PhoQ system to regulate the time at which induction takes place, 2 h postentry. Dormant bacteria were shown to discriminate the usage of SPI-2 effectors. Among the effectors tested, SseF, SseG, and SseJ were required for survival, while others, such as SifA and SifB, were not. SifA and SifB dispensability correlated with the inability of intracellular bacteria to secrete these effectors even when overexpressed. Conversely, SseJ overproduction resulted in augmented secretion and exacerbated bacterial growth. Dormant bacteria produced other effectors, such as PipB and PipB2, that, unlike what was reported for epithelial cells, did not to traffic outside the phagosomal compartment. Therefore, permissiveness for secreting only a subset of SPI-2 effectors may be instrumental for dormancy. We propose that theS. entericaserovar Typhimurium nonproliferative intracellular lifestyle is sustained by selection of SPI-2 effectors that are produced in tightly defined amounts and delivered to phagosome-confined locations.

Download Full-text

Differences in Host Cell Invasion and Salmonella Pathogenicity Island 1 Expression between Salmonella enterica Serovar Paratyphi A and NontyphoidalS. Typhimurium

Infection and Immunity ◽

10.1128/iai.01461-15 ◽

2016 ◽

Vol 84 (4) ◽

pp. 1150-1165 ◽

Cited By ~ 13

Author(s):

Dana Elhadad ◽

Prerak Desai ◽

Guntram A. Grassl ◽

Michael McClelland ◽

Galia Rahav ◽

...

Keyword(s):

Host Cell ◽

Cell Invasion ◽

Salmonella Enterica ◽

Intestinal Inflammation ◽

Pathogenicity Island ◽

Effector Proteins ◽

Host Cells ◽

Host Cell Invasion ◽

Content Type ◽

Microaerobic Conditions

Active invasion into nonphagocytic host cells is central toSalmonella entericapathogenicity and dependent on multiple genes withinSalmonellapathogenicity island 1 (SPI-1). Here, we explored the invasion phenotype and the expression of SPI-1 in the typhoidal serovarS. Paratyphi A compared to that of the nontyphoidal serovarS. Typhimurium. We demonstrate that whileS. Typhimurium is equally invasive under both aerobic and microaerobic conditions,S. Paratyphi A invades only following growth under microaerobic conditions. Transcriptome sequencing (RNA-Seq), reverse transcription-PCR (RT-PCR), Western blot, and secretome analyses established thatS. Paratyphi A expresses much lower levels of SPI-1 genes and secretes lesser amounts of SPI-1 effector proteins thanS. Typhimurium, especially under aerobic growth. Bypassing the native SPI-1 regulation by inducible expression of the SPI-1 activator, HilA, considerably elevated SPI-1 gene expression, host cell invasion, disruption of epithelial integrity, and induction of proinflammatory cytokine secretion byS. Paratyphi A but not byS. Typhimurium, suggesting that SPI-1 expression is naturally downregulated inS. Paratyphi A. Using streptomycin-treated mice, we were able to establish substantial intestinal colonization byS. Paratyphi A and showed moderately higher pathology and intestinal inflammation in mice infected withS. Paratyphi A overexpressinghilA. Collectively, our results reveal unexpected differences in SPI-1 expression betweenS. Paratyphi A andS. Typhimurium, indicate thatS. Paratyphi A host cell invasion is suppressed under aerobic conditions, and suggest that lower invasion in aerobic sites and suppressed expression of immunogenic SPI-1 components contributes to the restrained inflammatory infection elicited byS. Paratyphi A.

Download Full-text

Role of the Salmonella Pathogenicity Island 1 (SPI-1) Protein InvB in Type III Secretion of SopE and SopE2, Two Salmonella Effector Proteins Encoded Outside of SPI-1

Journal of Bacteriology ◽

10.1128/jb.185.23.6950-6967.2003 ◽

2003 ◽

Vol 185 (23) ◽

pp. 6950-6967 ◽

Cited By ~ 62

Author(s):

Kristin Ehrbar ◽

Andrea Friebel ◽

Samuel I. Miller ◽

Wolf-Dietrich Hardt

Keyword(s):

Type Iii Secretion ◽

Inflammatory Responses ◽

Pathogenicity Island ◽

Effector Proteins ◽

Host Cells ◽

Effector Protein ◽

Dependent Manner ◽

Type Iii ◽

Serovar Typhimurium

ABSTRACT Salmonella enterica subspecies 1 serovar Typhimurium encodes a type III secretion system (TTSS) within Salmonella pathogenicity island 1 (SPI-1). This TTSS injects effector proteins into host cells to trigger invasion and inflammatory responses. Effector proteins are recognized by the TTSS via signals encoded in their N termini. Specific chaperones can be involved in this process. The chaperones InvB, SicA, and SicP are encoded in SPI-1 and are required for transport of SPI-1-encoded effectors. Several key effector proteins, like SopE and SopE2, are located outside of SPI-1 but are secreted in an SPI-1-dependent manner. It has not been clear how these effector proteins are recognized by the SPI-1 TTSS. Using pull-down and coimmunoprecipitation assays, we found that SopE is copurified with InvB, the known chaperone for the SPI-1-encoded effector protein Sip/SspA. We also found that InvB is required for secretion and translocation of SopE and SopE2 and for stabilization of SopE2 in the bacterial cytosol. Our data demonstrate that effector proteins encoded within and outside of SPI-1 use the same chaperone for secretion via the SPI-1 TTSS.

Download Full-text

Novel Salmonella enterica Serovar Typhimurium Protein That Is Indispensable for Virulence and Intracellular Replication

Infection and Immunity ◽

10.1128/iai.69.12.7413-7418.2001 ◽

2001 ◽

Vol 69 (12) ◽

pp. 7413-7418 ◽

Cited By ~ 11

Author(s):

Tahar van der Straaten ◽

Angela van Diepen ◽

Kitty Kwappenberg ◽

Sjaak van Voorden ◽

Kees Franken ◽

...

Keyword(s):

Amino Acid ◽

Protein Function ◽

Salmonella Enterica ◽

Host Cells ◽

Wild Type ◽

Intracellular Replication ◽

Oxygen Intermediates ◽

Serovar Typhimurium

ABSTRACT Upon contact with host cells, the intracellular pathogenSalmonella enterica serovar Typhimurium promotes its uptake, targeting, and survival in intracellular niches. In this process, the bacterium evades the microbicidal effector mechanisms of the macrophage, including oxygen intermediates. This study reports the phenotypic and genotypic characterization of an S. enterica serovar Typhimurium mutant that is hypersusceptible to superoxide. The susceptible phenotype is due to a MudJ insertion-inactivation of a previously undescribedSalmonella gene designated sspJ that is located between 54.4 and 64 min of the Salmonellachromosome and encodes a 392-amino-acid protein. In vivo, upon intraperitoneal injection of 104 to 107bacteria in C3H/HeN and 101 to 104 bacteria in BALB/c mice, the mutant strain was less virulent than the wild type. Consistent with this finding, during the first hour after ingestion by macrophage-like J774 and RAW264.7 cells in vitro, the intracellular killing of the strain carrying sspJ::MudJ is enhanced fivefold over that of wild-type microorganisms. Wild-type salmonellae displayed significant intracellular replication during the first 24 h after uptake, but sspJ::MudJ mutants failed to do so. This phenotype could be restored to that of the wild type by sspJ complementation. The SspJ protein is found in the cytoplasmic membrane and periplasmic space. Amino acid sequence homology analysis did reveal a leader sequence and putative pyrroloquinoline quinone-binding domains, but no putative protein function. We excluded the possibility that SspJ is a scavenger of superoxide or has superoxide dismutase activity.

Download Full-text

The enzyme phosphoglucomutase (Pgm) is required by Salmonella enterica serovar Typhimurium for O-antigen production, resistance to antimicrobial peptides and in vivo fitness

Microbiology ◽

10.1099/mic.0.029553-0 ◽

2009 ◽

Vol 155 (10) ◽

pp. 3403-3410 ◽

Cited By ~ 22

Author(s):

G. K. Paterson ◽

D. B. Cone ◽

S. E. Peters ◽

D. J. Maskell

Keyword(s):

Antimicrobial Peptides ◽

Salmonella Enterica ◽

Salmonella Enterica Serovar Typhimurium ◽

Live Attenuated Vaccine ◽

Antigen Production ◽

O Antigen ◽

Serovar Typhimurium

The enzyme phosphoglucomutase (Pgm) catalyses the interconversion of glucose 1-phosphate and glucose 6-phosphate and contributes to glycolysis and the generation of sugar nucleotides for biosynthesis. To assess the role of this enzyme in the biology of the pathogen Salmonella enterica serovar Typhimurium we have characterized a pgm deletion mutant in strain SL1344. Compared to SL1344, SL1344 pgm had impaired growth in vitro, was deficient in the ability to utilize galactose as a carbon source and displayed reduced O-antigen polymer length. The mutant was also more susceptible to antimicrobial peptides and showed decreased fitness in the mouse typhoid model. The in vivo phenotype of SL1344 pgm indicated a role for pgm in the early stages of infection, most likely through deficient O-antigen production. Although pgm mutants in other pathogens have potential as live attenuated vaccine strains, SL1344 pgm was not sufficiently attenuated for such use.

Download Full-text

Butyrate Specifically Down-Regulates Salmonella Pathogenicity Island 1 Gene Expression

Applied and Environmental Microbiology ◽

10.1128/aem.72.1.946-949.2006 ◽

2006 ◽

Vol 72 (1) ◽

pp. 946-949 ◽

Cited By ~ 194

Author(s):

I. Gantois ◽

R. Ducatelle ◽

F. Pasmans ◽

F. Haesebrouck ◽

I. Hautefort ◽

...

Keyword(s):

Salmonella Enterica ◽

Molecular Mechanisms ◽

Intestinal Epithelial Cells ◽

Pathogenicity Island ◽

Effector Protein ◽

Intestinal Epithelial ◽

Penicillin Binding Protein ◽

Serovar Typhimurium ◽

Separate Site ◽

Comparative Transcriptomic Analysis

ABSTRACT Invasion of intestinal epithelial cells by Salmonella enterica is decreased after exposure to butyric acid. To understand the molecular mechanisms of this phenomenon, a comparative transcriptomic analysis of Salmonella enterica serovar Enteritidis and Salmonella enterica serovar Typhimurium grown in medium supplemented with butyrate was performed. We found that butyrate down-regulated the expression of 19 genes common to both serovars by a factor of twofold or more, and 17 of these genes localized to the Salmonella pathogenicity island 1 (SPI1). These included the SPI1 regulatory genes hilD and invF. Of the remaining two genes, ampH has 91% homology to an Escherichia coli penicillin-binding protein and sopE2 encodes a type III-secreted effector protein associated with invasion but located at a separate site on the chromosome from SPI1.

Download Full-text

Cytosporone B, an Inhibitor of the Type III Secretion System of Salmonella enterica Serovar Typhimurium

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02421-12 ◽

2013 ◽

Vol 57 (5) ◽

pp. 2191-2198 ◽

Cited By ~ 40

Author(s):

Jianfang Li ◽

Chao Lv ◽

Weiyang Sun ◽

Zhenyu Li ◽

Xiaowei Han ◽

...

Keyword(s):

Type Iii Secretion ◽

Salmonella Enterica ◽

Bacterial Resistance ◽

Type Iii Secretion System ◽

Secretion System ◽

Effector Proteins ◽

Host Cells ◽

Content Type ◽

Type Iii ◽

Serovar Typhimurium

ABSTRACTBacterial virulence factors have been increasingly regarded as attractive targets for development of novel antibacterial agents. Virulence inhibitors are less likely to generate bacterial resistance, which makes them superior to traditional antibiotics that target bacterial viability.Salmonella entericaserovar Typhimurium, an important food-borne human pathogen, has type III secretion system (T3SS) as its major virulence factor. T3SS secretes effector proteins to facilitate invasion into host cells. In this study, we identified several analogs of cytosporone B (Csn-B) that strongly block the secretion ofSalmonellapathogenicity island 1 (SPI-1)-associated effector proteins, without affecting the secretion of flagellar protein FliCin vitro. Csn-B and two other derivatives exhibited a strong inhibitory effect on SPI-1-mediated invasion to HeLa cells, while no significant toxicity to bacteria was observed. Nucleoid proteins Hha and H-NS bind to the promoters of SPI-1 regulator geneshilD,hilC, andrtsAto repress their expression and consequently regulate the expression of SPI-1 apparatus and effector genes. We found that Csn-B upregulated the transcription ofhhaandhns, implying that Csn-B probably affected the secretion of effectors through the Hha–H-NS regulatory pathway. In summary, this study presented an effective SPI-1 inhibitor, Csn-B, which may have potential in drug development against antibiotic-resistantSalmonella.

Download Full-text

Tumor Necrosis Factor Receptor-Associated Factor 6 (TRAF6) Mediates Ubiquitination-Dependent STAT3 Activation upon Salmonella enterica Serovar Typhimurium Infection

Infection and Immunity ◽

10.1128/iai.00081-17 ◽

2017 ◽

Vol 85 (8) ◽

Cited By ~ 7

Author(s):

Hai-Hua Ruan ◽

Zhen Zhang ◽

Su-Ying Wang ◽

Logan M. Nickels ◽

Li Tian ◽

...

Keyword(s):

Tumor Necrosis Factor ◽

Salmonella Enterica ◽

Tumor Necrosis ◽

Tumor Necrosis Factor Receptor ◽

Effector Proteins ◽

Host Cells ◽

Associated Factor ◽

Content Type ◽

Serovar Typhimurium ◽

Necrosis Factor

ABSTRACT Salmonella enterica serovar Typhimurium can inject effector proteins into host cells via type III secretion systems (T3SSs). These effector proteins modulate a variety of host transcriptional responses to facilitate bacterial growth and survival. Here we show that infection of host cells with S. Typhimurium specifically induces the ubiquitination of tumor necrosis factor receptor-associated factor 6 (TRAF6). This TRAF6 ubiquitination is triggered by the Salmonella pathogenicity island 1 (SPI-1) T3SS effectors SopB and SopE2. We also demonstrate that TRAF6 is involved in the SopB/SopE2-induced phosphorylation of signal transducer and activator of transcription 3 (STAT3), a signaling event conducive to the intracellular growth of S. Typhimurium. Specifically, TRAF6 mediates lysine-63 ubiquitination within the Src homology 2 (SH2) domain of STAT3, which is an essential step for STAT3 membrane recruitment and subsequent phosphorylation in response to S. Typhimurium infection. TRAF6 ubiquitination participates in STAT3 phosphorylation rather than serving as only a hallmark of E3 ubiquitin ligase activation. Our results reveal a novel strategy in which S. Typhimurium T3SS effectors broaden their functions through the activation of host proteins in a ubiquitination-dependent manner to manipulate host cells into becoming a Salmonella-friendly zone.

Download Full-text