Project description:Listeria monocytogenes causes severe foodborne illness in pregnant women and immunocompromised individuals. After the intestinal phase of infection, the liver plays a central role in the clearance of this pathogen through its important functions in immunity. However, recent evidence suggests that subpopulations of L. monocytogenes may escape eradication after prolonged infection of hepatocytes, by entering a persistence phase in vacuoles. Here, we examine whether this long-term infection alters hepatocyte defense pathways, which may be instrumental for bacterial persistence. We first established models of Listeria infection in human hepatocyte cell lines HepG2 and Huh7 and in primary mouse hepatocytes (PMH). In these cells, Listeria efficiently enters the persistence stage after a 3-day infection, while inducing a type I (PMH) or type I/III (HepG2) or no (Huh7) interferon response. RNA-seq analysis identified a common signature of long-term Listeria infection on the hepatocyte transcriptome, characterized by overexpression of a set of genes involved in antiviral immunity and under-expression of many acute phase protein (APP) genes, particularly involved in the complement and coagulation systems. The decrease in APP transcript amounts correlated with lower protein abundance in the secretome of infected cells, as shown by proteomics, and also occurred in the presence of APP inducers (IL-6 or IL-1b). The results also suggest that long-term Listeria infection affects lipid metabolism pathways. Collectively, these results reveal that long-term infection with L. monocytogenes profoundly deregulates the innate immune functions of hepatocytes, which could generate an environment favorable to the establishment of persistent infection.
Project description:Phosphopeptides were identified in Listeria monocytogesn strain constitutivally expressing PrfA. Also, the phosphoproteins and proteins were identified that are overexpressed/underextressed in response to PrfA.
Project description:ISG15 is primarily documented as an interferon-stimulated, ubiquitin-like protein (ubl), which has anti-viral activity. Although ISG15 was the founding member of the ubl protein family, very little is known about its function. We have found that ISG15 expression in non-phagocytic cells is dramatically induced upon Listeria infection and that surprisingly this induction can be Type I Interferon independent. Listeria-mediated ISG15 induction depends on the cytosolic surveillance pathway, which senses bacterial DNA and signals through STING, TBK1, IRF3 and IRF7. Most importantly, we observed that ISG15 expression restricts Listeria infection both in vitro and in vivo. We then made use of Stable Isotope Labeling in tissue culture (SILAC) to identify the ISGylated proteins that could be responsible for the ISG15-mediated protective effect. Our SILAC analysis revealed that overexpression of ISG15 leads to a striking ISGylation of integral membrane proteins of the endoplasmic reticulum and Golgi apparatus, which correlates with increased canonical secretion of cytokines. Taken together, our data reveal a previously uncharacterized signaling pathway that restricts Listeria infection and acts via ISGylation, reinforcing the view that ISG15 is a key component of the innate immune arsenal of the mammalian host.
Project description:Adaptation of Listeria weihenstephanensis to anaerobiosis. Trascriptional profiling at two different temperatures of L. weihenstephanensis
Project description:The foodborne pathogen Listeria monocytogenes uses a number of transcriptional regulators, including the negative regulator HrcA, to control gene expression under different environmental conditions and in response to stress. Gene expression patterns of DhrcA stationary phase cells were compared to wt to identify hrcA-dependent genes. We identified 61 HrcA-dependent genes that showed significant expression ratios (adj. P < 0.05), with ≥ 1.5-fold differential expression between ΔhrcA and wt. Combined with microarray analysis, Hidden Markov Model searches show HrcA directly repress at least 8 genes. Keywords: Listeria monocytogenes, HrcA regulon, stationary phase
Project description:The foodborne pathogen Listeria monocytogenes uses a number of transcriptional regulators, including the negative regulator CtsR, to control gene expression under different environmental conditions and in response to stress. Gene expression patterns of DctsR log phase cells were compared to both wt and ictsR-mcsA log phase cells grown with 0.5mM IPTG to identify CtsR-dependent genes.We identified 62 CtsR-dependent genes that showed significant expression ratios (adj. P < 0.05), with ≥ 1.5-fold differential expression either between ΔctsR and wt or between ΔctsR and ictsR-mcsA. Keywords: Listeria monocytogenes, CtsR regulon, log phase
Project description:Listeria monocytogenes strain 10403S has been studied extensively for stress response activity toward multiple stressors (acid, osmotic, cold, high temperature, etc.) as well as multiple stress regulons (SigB, CtsR, HrcA, etc.). Here we aimed to determine the transcriptional response of Listeria monocytogenes in early log phase towards the strong oxidative stress imposed by ClO2. The elucidation of such a response allows for further a more completel understanding of the mechanism of inactivation by sanitizers, specifically ClO2.
Project description:This dataset contains spectral information of protein N-terminal peptides isolated from Listeria monocytogenes EGD-e, a bacterial model organism and human pathogen. When mapped onto the Listeria genome these peptides indicate the exact location of translation initiation sites (TIS). The large majority of the identified TIS corresponded to start sites of predicted open reading frames (ORFs), however, a significant fraction of the identified TIS indicated deviations from the current genome annotation. The latter include primarily TIS inside the sequence of predicted ORFs or TIS that delineate the start position of novel ORFs.