Project description:Toxoplasma gondii, the causative agent of toxoplasmosis, is an obligate intracellular protozoan parasite that resides inside a parasitophorous vacuole. During infection, Toxoplasma actively remodels the transcriptome of its hosting cells with profound and coupled impact on the host immune response. We report that Toxoplasma secretes GRA24, a novel dense granule protein which traffics from the vacuole to the host cell nucleus. Once released into the host cell, GRA24 has the unique ability to trigger prolonged autophosphorylation and nuclear translocation of the host cell p38M-NM-1 MAP kinase. This noncanonical kinetics of p38M-NM-1 activation correlates with the up-regulation of the transcription factors Egr-1 and c-Fos and the correlated synthesis of key proinflammatory cytokines, including interleukin-12 and the chemokine MCP-1, both known to control early parasite replication in vivo. Remarkably, the GRA24-p38M-NM-1 complex is defined by peculiar structural features and uncovers a new regulatory signaling path distinct from the MAPK signaling cascade and otherwise commonly activated by stress-related stimuli or various intracellular microbes. GRA24 = PSP7 Mouse bone marrow-derived macrophages (BMDM) were infected with the following Toxoplasma gondii strains: - RHku80 WT versus RHku80(deltaPSP7) mutant - Pruku80 WT versus Pruku80(deltaPSP7) mutant
Project description:To identify accessible chromatin regions in the human host cells during Toxoplasma parasite infection (uninfected, RH-infected and Pru-infected human foreskin fibroblasts) and in the obligate intracellular parasite Toxoplasma gondii (Type 1 RH strain and Type 2 Pru strain), ATAC-seq was performed.
Project description:Toxoplasma gondii is an obligate intracellular Apicomplexan parasite capable of invading and surviving within nucleated cells in most warm-blooded animals. This remarkable task is achieved through the delivery of effector proteins from the parasite into the parasitophorous vacuole and host cell cytosol that rewire host cellular pathways, facilitating parasite evasion of the immune system. Here, we have identified a novel export pathway in Toxoplasma that involves cleavage of effector proteins by the Golgi-resident aspartyl protease 5 (ASP5) prior to translocation into the host cell. We demonstrate that ASP5 cleaves a highly constrained amino acid motif that has some similarity to the PEXEL motif of Plasmodium parasites. We show that ASP5 can mature effectors at both the N- and C-terminal ends of proteins and is also required for the trafficking of proteins without this motif. Furthermore, we show that ASP5 controls establishment of the nanotubular network and is required for the efficient recruitment of host mitochondria to the parasitophorous vacuole membrane. Global assessment of host gene expression following infection reveals that ASP5-dependent pathways influence thousands of the transcriptional changes that Toxoplasma imparts on its host cell. This work characterizes the first identified machinery required for export of Toxoplasma effectors into the infected host cell. Three groups of human foreskin fibroblasts are compared. Each group has 3 replicates giving a total of 9 samples. The first group of samples are infected with wild type (GRA16HA) Toxoplasma gondii, the second group with Asp5 knock-out Toxoplasma gondii, and the final group remain uninfected. All fibroblasts are generated from one donor sample.
Project description:The closely related protozoan parasites Toxoplasma gondii and Neospora caninum display similar life cycles, subcellular ultrastructure, invasion mechanisms, metabolic pathways, and genome organization, but differ in their host range and disease pathogenesis. Type II (γ) interferon has long been known to be the major mediator of innate and adaptive immunity to Toxoplasma infection, but genome-wide expression profiling of infected host cells indicates that Neospora is a potent activator of the type I (α/β) interferon pathways typically associated with antiviral responses. Infection of macrophages from mice with targeted deletions in various innate sensing genes demonstrates that host responses to Neospora are dependent on the toll-like receptor Tlr3 and the adapter protein Trif. Consistent with this observation, RNA from Neospora elicits type I interferon responses when targeted to the host endo-lysosomal system. While live Toxoplasma fails to induce type I interferon, heat-killed parasites do trigger this response, and co-infection studies reveal that T. gondii actively suppresses the production of type I interferon. These findings reveal that eukaryotic pathogens can be potent inducers of type I interferon and that some parasite species, like Toxoplasma gondii, have evolved mechanisms to suppress this response. Human foreskin fibroblasts (HFF; line BJ-5ta) were cultured to confluency in T25 flasks, infected with one representative of each of the three architypial strains of Toxoplasma gondii: GT1 (type I), Prugniaud (type II) and VEG (type III), or the closely related parasite species, Neospora caninum (strain Nc-Liv). RNA was collected from biological replicates for expression profiling by microarray. Uninfected HFF cells were used as a reference.
Project description:Intracellular pathogens including the apicomplexan and opportunistic parasite Toxoplasma gondii profoundly modify their host cells in order to establish infection. We have shown previously that intracellular T. gondii inhibit up-regulation of regulatory and effector functions in murine macrophages (MΦ) stimulated with interferon (IFN)-γ, which is the cytokine crucial for controlling the parasites’ replication. Using genome-wide transcriptome analysis we show herein that infection with T. gondii leads to global unresponsiveness of murine macrophages to IFN-γ. More than 61% and 89% of the transcripts, which were induced or repressed by IFN-γ in non-infected MΦ, respectively, were not altered after stimulation of T. gondii-infected cells with IFN-γ. These genes are involved in a variety of biological processes, which are mostly but not exclusively related to immune responses. Analyses of the underlying mechanisms revealed that IFN-γ-triggered nuclear translocation of STAT1 still occurred in Toxoplasma-infected MΦ. However, STAT1 bound aberrantly to oligonucleotides containing the IFN-γ-responsive gamma-activated site (GAS) consensus sequence. Conversely, IFN-γ did not induce formation of active GAS-STAT1 complexes in nuclear extracts from infected MΦ. Mass spectrometry of protein complexes bound to GAS oligonucleotides showed that T. gondii-infected MΦ are unable to recruit non-muscle actin to IFN-γ-responsive DNA sequences, which appeared to be independent of stimulation with IFN-γ and of STAT1 binding. IFN-γ-induced recruitment of BRG-1 and acetylation of core histones at the IFN-γ-regulated CIITA promoter IV, but not β-actin was diminished by >90% in Toxoplasma-infected MΦ as compared to non-infected control cells. Remarkably, treatment with histone deacetylase inhibitors restored the ability of infected macrophages to express the IFN-γ regulated genes H2-A/E and CIITA. Taken together, these results indicate that Toxoplasma-infected MΦ are unable to respond to IFN-γ due to disturbed chromatin remodelling, but can be rescued using histone deacetylase inhibitors. Comparison of 4 different RNA pools with a 2-Color-Loop Design including 10 microarrays: [1] T. gondii infected and IFN-gamma treated, [2] T. gondii infected and untreated, [3] Non-infected and IFN-gamma treated, and [4] Non-infected and untreated.