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Salmonella subverts autophagy balancing bacterial fate and cellular inflammation

ABSTRACT: Salmonella Typhimurium (S. Typhimurium) is an enteric bacterium capable of invading a wide range of host cell types and adopting different intracellular lifestyles for survival. Host endocytic trafficking and autophagy have been implied to regulate the S. Typhimurium subcellular localization and survival. To reveal alternative host regulators on S. Typhimurium lifestyle, we combined a novel fluorescent reporter, Salmonella Intracellular Analyzer (SINA) with haploid forward genetic screening. This identified transcription factor c-MYC as a negative regulator of S. Typhimurium cytosolic lifestyle via stabilizing the Salmonella-containing vacuole (SCV). We further confirmed that c-MYC downstream regulated LC3 acts to maintain SCV stability and limits S. Typhimurium cytosolic lifestyle. We demonstrated that LC3 is recruited to the SCV prior to the endomembrane damage marker Galectin 3, and it regulates SCV stability independent of the autophagosome adaptor NDP52. The LC3 processing enzymes ATG3 and ATG4 reciprocally act on SCV stability, where the loss of LC3-PE conjugation in the absence of ATG3 limits SCV damages. We further identified the dosage-dependent function of the S. Typhimurium effector SopF in mediating SCV stability by actively avoiding LC3 recruitment to the proximity of the SCV to reduce its catastrophic rupture and host cell death. Altogether, we offer insights on the significance of cellular transcription profile in the determination of S. Typhimurium pathophysiology as well as the underlying host-evasion strategy of S. Typhimurium.

ORGANISM(S): Homo sapiens

PROVIDER: GSE161812 | GEO | 2022/09/25

REPOSITORIES: GEO

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Project description:Raghunathan2009 - Genome-scale metabolic network of Salmonella typhimurium (iRR1083) This model is described in the article: Constraint-based analysis of metabolic capacity of Salmonella typhimurium during host-pathogen interaction. Raghunathan A, Reed J, Shin S, Palsson B, Daefler S. BMC Syst Biol 2009; 3: 38 Abstract: BACKGROUND: Infections with Salmonella cause significant morbidity and mortality worldwide. Replication of Salmonella typhimurium inside its host cell is a model system for studying the pathogenesis of intracellular bacterial infections. Genome-scale modeling of bacterial metabolic networks provides a powerful tool to identify and analyze pathways required for successful intracellular replication during host-pathogen interaction. RESULTS: We have developed and validated a genome-scale metabolic network of Salmonella typhimurium LT2 (iRR1083). This model accounts for 1,083 genes that encode proteins catalyzing 1,087 unique metabolic and transport reactions in the bacterium. We employed flux balance analysis and in silico gene essentiality analysis to investigate growth under a wide range of conditions that mimic in vitro and host cell environments. Gene expression profiling of S. typhimurium isolated from macrophage cell lines was used to constrain the model to predict metabolic pathways that are likely to be operational during infection. CONCLUSION: Our analysis suggests that there is a robust minimal set of metabolic pathways that is required for successful replication of Salmonella inside the host cell. This model also serves as platform for the integration of high-throughput data. Its computational power allows identification of networked metabolic pathways and generation of hypotheses about metabolism during infection, which might be used for the rational design of novel antibiotics or vaccine strains. This model is hosted on BioModels Database and identified by: MODEL1507180058. To cite BioModels Database, please use: BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information.

Project description:Intracellular bacterial pathogens inject a cocktail of effector proteins into host cells to hijack diverse cellular processes and promote their survival and proliferation. Salmonella enterica serovar Typhimurium (STm) uses two Type 3 secretion system (T3SS) to deliver a suite of effector proteins into host cells, however, knowledge of their host-targets remains sparse. To systematically map STm effector-host protein-protein interactions (PPIs) during active infection, we generated a library of 32 STm strains expressing affinity-tagged effector proteins from their endogenous chromosomal loci. Tagged-effector strains were then used to infect macrophages or epithelial cells, and PPIs were detected by Affinity-Purification Quantitative Mass-Spectrometry (AP-QMS) under both native and cross-linking conditions. We recovered 25 previously described effector-host PPIs, along with 421 novel interactions across the two cell lines tested, as well as several effector-effector PPIs. While effectors converged on specific host cellular processes, which varied across cell types, most had multiple host targets. Using reciprocal co-immunoprecipitations, we could validated 13 out of 22 new PPIs, demonstrating an accuracy of at least 59% for the AP-QMS approach. To illustrate the utility of this resource for discovering novel infection biology, we first showed that SseJ and SseL cooperate to control cholesterol transport at the Salmonella Containing Vacuole (SCV) via the Niemann-Pick C1 protein (NPC1). Second, we uncovered that PipB directly binds and recruits the organelle contact site protein PDZD8 to the SCV. Third, we elucidated a novel mechanism whereby the effector kinase SteC promotes host actin bundling, by directly interacting and phosphorylating formin-like proteins. Overall, we provide a systems-wide host-bacterial pathogen physical interactome resource, to our knowledge the first in an infection context, with broad implications for effector function and cooperation.

Project description:We have observed that for a number of S. aureus strains as they switch to a SCV lifestyle there is the formation of an extracellular matrix. We focused our analysis on one strain, WCH-SK2. For bacterial survival in the host, the combination of low nutrients and the prolonged timeframe forms a stress that selects for a specific cell-type from the population. In this context, we used steady-state growth conditions with low nutrients and a controlled low growth rate, for a prolonged time and with methylglyoxal. These conditions induced S. aureus WCH-SK2 into a stable SCV cell-type, they did not revert after sub-culturing. Methods: Transcriptomic profiles of wild-type (WT) and SCV were generated in continuous culture in the presence of stress (high and low level of methylglyoxal). Results: Analysis revealed these cells possessed a metabolic and surface profile that was different from previously described SCVs or biofilm cells. The extracellular matrix was protein and extracellular DNA; but not polysaccharide. The SCV cells induced expression of certain surface proteins (such as Ebh) and lantibiotic synthesis while down-regulating factors that stimulates immune response (leucocidin, capsule, carotenoid). We also studied further their genetic characteristics. They possessed an increased viability in the presence of antibiotics compared to their non-SCV form. Their stability implied there had been genetic changes, we determined the whole genome sequence of WCH-SK2 and its stable SCV forms at a single base resolution, employing Single Molecular Real-Time (SMRT) sequencing that also enables the methylome to be determined. The genetic features of this isolate have been identified; the SCCmec type, the pathogenicity and genetic islands and virulence factors. The comparison has identified a set of genetic changes that occurred in the stable SCV form; most notably to the global regulator MgrA and the phosphoserine phosphatase RsbU (part of the regulatory pathway of the sigma factor SigB). There was a shift in the methylation across the genome. Conclusions: Our data reveal a cell heterogeneity within a S. aureus population and using conditions that resemble long-term survival in the host has identified a previously unnoticed S. aureus cell-type, with a distinctive metabolic and molecular profile. The results from this study represent a unique identification of a suite of epigenetic, genetic and transcriptional factors that are implicated in the switch in S. aureus to its persistent SCV form

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Salmonella subverts autophagy balancing bacterial fate and cellular inflammation

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