Secretome-Mediated Interactions with Intestinal Epithelial Cells: A Role for Secretome Components from Lactobacillus rhamnosus R0011 in the Attenuation of Salmonella enterica Serovar Typhimurium Secretome and TNF-α–Induced Proinflammatory Responses

ABSTRACT As enteric pathogens, the salmonellae have developed systems by which they can sense and adapt appropriately to deleterious intestinal components that include bile. Previously, growth in the presence of bile was shown to repress the transcription of prgH, a locus encoding components of the Salmonella pathogenicity island I (SPI-1) type III secretion system (TTSS) necessary for eukaryotic cell invasion. This result suggested an existing interaction between salmonellae, bile, and eukaryotic cell invasion. Transcription assays demonstrated that invasion gene regulators (e.g.,sirC and invF) are repressed by bile. However, bile does not interact with any of the invasion regulators directly but exerts its effect at or upstream of the two-component system at the apex of the invasion cascade, SirA-BarA. As suggested by the repression of invasion gene transcription in the presence of bile, Western blot analysis demonstrated that proteins secreted by the SPI-1 TTSS were markedly reduced in the presence of bile. Furthermore, Salmonella enterica serovar Typhimurium grown in the presence of bile was able to invade epithelial cells at only 4% of the level of serovar Typhimurium grown without bile. From these data, we propose a model whereby serovar Typhimurium uses bile as an environmental signal to repress its invasive capacity in the lumen of the intestine, but upon mucous layer penetration and association with intestinal epithelial cells, where the apparent bile concentration would be reduced, the system would become derepressed and invasion would be initiated.

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Transcriptional Organization and Function of Invasion Genes within Salmonella enterica Serovar Typhimurium Pathogenicity Island 1, Including the prgH,prgI, prgJ, prgK, orgA,orgB, and orgC Genes

Infection and Immunity ◽

10.1128/iai.68.6.3368-3376.2000 ◽

2000 ◽

Vol 68 (6) ◽

pp. 3368-3376 ◽

Cited By ~ 58

Author(s):

Joanna R. Klein ◽

Thomas F. Fahlen ◽

Bradley D. Jones

Keyword(s):

Epithelial Cells ◽

Salmonella Enterica ◽

Salmonella Enterica Serovar Typhimurium ◽

Pathogenicity Island ◽

Pcr Analysis ◽

Intestinal Epithelial ◽

Reading Frame ◽

Bacterial Proteins ◽

Serovar Typhimurium ◽

And Function

ABSTRACT Salmonella enterica serovar Typhimurium initiates infection of a host by inducing its own uptake into specialized M cells which reside within the epithelium overlaying Peyer's patches. Entry of Salmonella into intestinal epithelial cells is dependent upon invasion genes that are clustered together inSalmonella pathogenicity island 1 (SPI-1). Upon contact between serovar Typhimurium and epithelial cells targeted for bacterial internalization, bacterial proteins are injected into the host cell through a type III secretion system that leads to internalization of the bacteria. Previous work has established that the prgH, -I, -J, and -K and orgAgenes reside in SPI-1, and the products of these genes are predicted to be components of the invasion secretion apparatus. We report that an error in the published orgA DNA sequence has been identified so that this region encodes two small genes rather than a single large open reading frame. These genes have been designatedorgA and orgB. Additionally, an opening reading frame downstream of orgB, which we have designatedorgC, has been identified and partially characterized. Previously published work has indicated that the prgH, -I, -J, and -K genes are transcribed from a promoter distinct from that used by the gene immediately downstream, orgA. Here, we present experiments indicating that orgA expression is driven by theprgH promoter. In addition, using reverse transcriptase PCR analysis, we have found that this polycistronic message extends downstream of prgH to include a total of 10 genes. To more fully characterize this invasion operon, we demonstrate that theprgH, prgI, prgJ, prgK,orgA, and orgB genes are each required for invasion and secretion, while orgC is not essential for the invasive phenotype.

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Salmonella enterica serovar Typhimurium chitinases modulate the intestinal glycome and promote small intestinal invasion

10.1101/2021.12.06.471358 ◽

2021 ◽

Author(s):

Jason R Devlin ◽

William Santus ◽

Jorge Mendez ◽

Wenjing Peng ◽

Aiying Yu ◽

...

Keyword(s):

Epithelial Cells ◽

Virulence Factors ◽

Salmonella Enterica ◽

Intestinal Epithelial Cells ◽

Bacterial Species ◽

Intestinal Epithelial ◽

Food Borne ◽

Serovar Typhimurium ◽

Small Intestinal ◽

Adhesion And Invasion

AbstractSalmonella enterica serovar Typhimurium (Salmonella) is one of the leading causes of food-borne illnesses worldwide. To colonize the gastrointestinal tract, Salmonella produces multiple virulence factors that facilitate cellular invasion. Chitinases have been recently emerging as virulence factors for various pathogenic bacterial species and the Salmonella genome contains two annotated chitinases: STM0018 (chiA) and STM0233. However, the role of these chitinases during Salmonella pathogenesis is unknown. The putative chitinase STM0233 has not been studied previously and only limited data exists on ChiA. Chitinases typically hydrolyze chitin polymers, which are absent in vertebrates. However, chiA expression was detected in infection models and purified ChiA cleaved carbohydrate subunits present on mammalian surface glycoproteins, indicating a role during pathogenesis. Here, we demonstrate that expression of chiA and STM0233 is upregulated in the mouse gut and that both chitinases facilitate epithelial cell adhesion and invasion. Salmonella lacking both chitinases showed a 70% reduction in invasion of small intestinal epithelial cells in vitro. In a gastroenteritis mouse model, chitinase-deficient Salmonella strains were also significantly attenuated in the invasion of small intestinal tissue. This reduced invasion resulted in significantly delayed Salmonella dissemination to the spleen and the liver, but chitinases were not required for systemic survival. The invasion defect of the chitinase-deficient strain was rescued by the presence of wild-type Salmonella, suggesting that chitinases are secreted. By analyzing N-linked glycans of small intestinal cells, we identified specific N-acetylglucosamine-containing glycans as potential extracellular targets of Salmonella chitinases. This analysis also revealed differential abundance of Lewis X-containing glycans that is likely a result of host cell modulation due to the detection of Salmonella chitinases. Similar glycomic changes elicited by chitinase deficient strains indicate functional redundancy of the chitinases. Overall, our results demonstrate that Salmonella chitinases contribute to intestinal adhesion and invasion through modulation of the host glycome.Author SummarySalmonella Typhimurium infection is one of the leading causes of food-borne illnesses worldwide. In order for Salmonella to effectively cause disease, it has to invade the epithelial cells lining the intestinal tract. This invasion step allows Salmonella to replicate efficiently, causing further tissue damage and inflammation. In susceptible patients, Salmonella can spread past the intestines and infect peripheral organs. It is essential to fully understand the invasion mechanism used by Salmonella to design better treatments for infection. Here, we demonstrate that the two chitinases produced by Salmonella are involved in this invasion process. We show that Salmonella chitinases interact with surface glycans of intestinal epithelial cells and promote adhesion and invasion. Using a mouse infection model, we show that Salmonella chitinases are required for the invasion of the small intestine and enhance the dissemination of Salmonella to other organs. This study reveals an additional mechanism by which Salmonella invades and causes infection.

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Probiotics exert reciprocal effects on autophagy and interleukin-1β expression in Salmonella-infected intestinal epithelial cells via autophagy-related 16L1 protein

Beneficial Microbes ◽

10.3920/bm2019.0046 ◽

2019 ◽

Vol 10 (8) ◽

pp. 913-922 ◽

Cited By ~ 2

Author(s):

W.-T. Lai ◽

F.-C. Huang

Keyword(s):

Epithelial Cells ◽

Protein Expression ◽

Western Blot ◽

Inflammatory Responses ◽

Intestinal Epithelial Cells ◽

Bifidobacterium Longum ◽

Lactobacillus Rhamnosus ◽

Interleukin 1Β ◽

Intestinal Epithelial ◽

Serovar Typhimurium

This study aimed to examine how probiotics affect autophagy and interleukin-1β (IL-1β) expression in Salmonella-infected intestinal epithelial cells (IECs). The original Caco-2 cells and ATG16L1 siRNA-transfected Caco-2 cells were pretreated or left untreated with probiotics, including Lactobacillus rhamnosus GG (LGG; ATCC 53103) and Bifidobacterium longum (BL; ATCC15697), and these cells were infected with wild-type Salmonella enterica serovar Typhimurium (S. Typhimurium strain, SL1344). Western blot analysis was used to detect the conversion of microtubule-associated proteins 1A/1B light chain 3B (LC3)-I to LC3-II. Immunofluorescence was used to analyse LC3+ autophagosomes. Membrane proteins were analysed by western blot for protein (ATG16L1, NOD2), and total RNA by RT-PCR for mRNA expression [ATG16L1, vitamin D receptor (VDR)]. We demonstrated that probiotics enhanced both VDR mRNA, and nucleotide-binding oligomerisation domain-containing protein 2 (NOD2) and autophagy-related protein 16-like 1 (ATG16L1) protein expression. The enhanced expression resulted in autophagic LC3-II protein expression and formation of LC3 punctae in Salmonella-infected Caco-2 cells. It was observed that ATG16L1 siRNA could attenuate this mechanism, and ATG16L1-mediated IL-1β expression was suppressed by probiotics. These results suggest that probiotics enhance autophagy and also suppress inflammatory IL-1β expression in Salmonella-infected IECs via membrane ATG16L1 protein expression. Probiotics may enhance autophagic clearance of Salmonella infection and modulate inflammatory responses to protect the hosts. Hence, we can assume that probiotics could treat infectious and autoimmune diseases through mechanisms involving ATG16L1.

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