Similar Datasets
Project description:Toxoplasma gondii translocates effector proteins into its host cell to subvert various host pathways. T. gondii effector TgIST blocks the transcription of interferon-stimulated genes to reduce immune defense. Interferons upregulate numerous genes, including protein kinase R (PKR), which induce necrosome formation to activate mixed-lineage-kinase-domain-like (MLKL) pseudokinase and induce necroptosis. Whether these interferon functions are targeted by Toxoplasma is unknown. Here, we examine secreted effectors that localize to the host cell nucleus and find that the chronic bradyzoite stage secretes effector TgNSM that targets the NCoR/SMRT complex, a repressor for various transcription factors, to inhibit interferon-regulated genes involved in cell death. TgNSM acts with TgIST to block IFN-driven expression of PKR and MLKL, thus preventing host cell necroptotic death and protecting the parasite's intracellular niche. The mechanism of action of TgNSM uncovers a role of NCoR/SMRT in necroptosis, assuring survival of intracellular cysts and chronic infection.
| S-EPMC8711274 | biostudies-literature
Project description:During infection, Toxoplasma gondii translocate effector proteins directly into the infected host cells to subvert various immune signaling pathways. We identified a novel secreted effector-TgNSM that localizes to the host cell nucleus. Mechanistically, TgNSM drives increased NCoR/SMRT repressor complex levels and enhances transcriptional repression of interferon regulated genes (ISGs). Type I and type II interferons can induce necroptosis by upregulating protein kinase PKR that induces the formation of a necrosome complex consisting of the RIPK1 and RIPK3. The necrosome then activates the pro-necroptotic protein MLKL to execute necrotic cell death. TgNSM acts together with another secreted effector TgIST, previously shown to down-modulate IFN-γ signaling. TgNSM and TgIST block IFN driven expression of PKR and MLKL, thus preventing host cell necroptotic death and assuring survival of intracellular cysts. The mechanism of action of TgNSM highlights a previously unappreciated role of NCoR/SMRT in regulation of necroptosis.
2021-05-27 | GSE166936 | GEO
Project description:During infection, Toxoplasma gondii translocate effector proteins directly into the infected host cells to subvert various immune signaling pathways. We identified a novel secreted effector-TgNSM that localizes to the host cell nucleus. Mechanistically, TgNSM drives increased NCoR/SMRT repressor complex levels and enhances transcriptional repression of interferon regulated genes (ISGs). Type I and type II interferons can induce necroptosis by upregulating protein kinase PKR that induces the formation of a necrosome complex consisting of the RIPK1 and RIPK3. The necrosome then activates the pro-necroptotic protein MLKL to execute necrotic cell death. TgNSM acts together with another secreted effector TgIST, previously shown to down-modulate IFN-γ signaling. TgNSM and TgIST block IFN driven expression of PKR and MLKL, thus preventing host cell necroptotic death and assuring survival of intracellular cysts. The mechanism of action of TgNSM highlights a previously unappreciated role of NCoR/SMRT in regulation of necroptosis.
2021-05-27 | GSE157018 | GEO
Project description:Toxoplasma gondii secreted effectors co-opt host repressor complexes to inhibit necroptosis
| PRJNA702441 | ENA
Project description:Toxoplasma gondii secreted effectors co-opt host repressor complexes to inhibit necroptosis [II]
| PRJNA702443 | ENA
Project description:Toxoplasma gondii secreted effectors co-opt host repressor complexes to inhibit necroptosis [I]
| PRJNA659791 | ENA
Project description:Toxoplasma gondii is a common parasite of animals and humans and can cause serious opportunistic infections. However, the majority of infections are asymptomatic, possibly because the organism has co-evolved with its many vertebrate hosts and has developed multiple strategies to persist asymptomatically for the lifetime of the host. Over the past two decades, infection studies in the mouse, combined with forward-genetics approaches aimed at unravelling the molecular basis of infection, have revealed that T. gondii virulence is mediated, in part, by secretion of effector proteins into the host cell during invasion. Here, we review recent advances that illustrate how these virulence factors disarm innate immunity and promote survival of the parasite.
| S-EPMC3689224 | biostudies-literature
Project description:BackgroundToxoplasma gondii is an opportunistic protozoan apicomplexan and obligate intracellular parasite that infects a wide range of animals and humans. Rhoptry proteins 5 (ROP5), ROP16, ROP18 and dense granules 15 (GRA15) are the important effectors secreted by T. gondii which link to the strain virulence for mice and modulate the host's response to the parasite. Little has been known about these molecules as well as GRA3 in type Chinese 1 strains that show polymorphism among strains of archetypical genotypes. This study examined the genetic diversity of these effectors and its correlated virulence in mice among T. gondii isolates from China.ResultsTwenty-one isolates from stray cats were detected, of which 15 belong to Chinese 1, and 6 to ToxoDB #205. Wh6 isolate, a Chinese 1 strain, has an avirulent phenotype. PCR-RFLP results of ROP5 and ROP18 presented few variations among the strains. Genotyping of GRA15 and ROP16 revealed that all the strains belong to type II allele except Xz7 which carries type I allele. ROP16 amino acid alignment at 503 locus demonstrated that 17 isolates are featured as type I or type III (ROP16I/III), and the other 4 as type II (ROP16II). The strains investigated may be divided into four groups based on GRA3 amino acid alignment, and all isolates of type Chinese 1 belong to the μ-1 allele except Wh6 which is identical to type II strain.ConclusionsPCR-RFLP and sequence alignment analyses of ROP5, ROP16, ROP18, GRA3, and GRA15 in T. gondii revealed that strains with the same genotype may have variations in some of their key genes. GRA3 variation exhibited by Wh6 strain may be associated with the difference in phenotype and pathogenesis.
| S-EPMC5697216 | biostudies-literature
Project description:Congenital and acquired toxoplasmosis caused by the food- and water-born parasite Toxoplasma gondii (T. gondii) is one of the most prevalent zoonotic infection of global importance. T. gondii is an obligate intracellular parasite with limited capacity for extracellular survival, thus a successful, efficient and robust host cell invasion process is crucial for its survival, proliferation and transmission. In this study, we screened a series of novel 1,3,4-thiadiazole-2-halophenylamines functionalized at the C5 position with the imidazole ring (1b-12b) for their effects on T. gondii host cell invasion and proliferation. To achieve this goal, these compounds were initially subjected to in vitro assays to assess their cytotoxicity on human fibroblasts and then antiparasitic efficacy. Results showed that all of them compare favorably to control drugs sulfadiazine and trimethoprim in terms of T. gondii growth inhibition (IC50) and selectivity toward the parasite, expressed as selectivity index (SI). Subsequently, the most potent of them with meta-fluoro 2b, meta-chloro 5b, meta-bromo 8b, meta-iodo 11b and para-iodo 12b substitution were tested for their efficacy in inhibition of tachyzoites invasion and subsequent proliferation by direct action on established intracellular infection. All the compounds significantly inhibited the parasite invasion and intracellular proliferation via direct action on both tachyzoites and parasitophorous vacuoles formation. The most effective was para-iodo derivative 12b that caused reduction in the percentage of infected host cells by 44% and number of tachyzoites per vacuole by 93% compared to non-treated host cells. Collectively, these studies indicate that 1,3,4-thiadiazoles 1b-12b, especially 12b with IC50 of 4.70 µg/mL and SI of 20.89, could be considered as early hit compounds for future design and synthesis of anti-Toxoplasma agents that effectively and selectively block the invasion and subsequent proliferation of T. gondii into host cells.
| S-EPMC8145641 | biostudies-literature
Project description:Toxoplasma gondii secretes rhoptry (ROP) and dense granule (GRA) effector proteins to evade host immune clearance mediated by interferon gamma (IFN-γ), immunity-related GTPase (IRG) effectors, and CD8+ T cells. Here, we investigated the role of parasite-secreted effectors in regulating host access to parasitophorous vacuole (PV) localized parasite antigens and their presentation to CD8+ T cells by the major histocompatibility class I (MHC-I) pathway. Antigen presentation of PV localized parasite antigens by MHC-I was significantly increased in macrophages and/or dendritic cells infected with mutant parasites that lacked expression of secreted GRA (GRA2, GRA3, GRA4, GRA5, GRA7, GRA12) or ROP (ROP5, ROP18) effectors. The ability of various secreted GRA or ROP effectors to suppress antigen presentation by MHC-I was dependent on cell type, expression of IFN-γ, or host IRG effectors. The suppression of antigen presentation by ROP5, ROP18, and GRA7 correlated with a role for these molecules in preventing PV disruption by IFN-γ-activated host IRG effectors. However, GRA2 mediated suppression of antigen presentation was not correlated with PV disruption. In addition, the GRA2 antigen presentation phenotypes were strictly co-dependent on the expression of the GRA6 protein. These results show that MHC-I antigen presentation of PV localized parasite antigens was controlled by mechanisms that were dependent or independent of IRG effector mediated PV disruption. Our findings suggest that the GRA6 protein underpins an important mechanism that enhances CD8+ T cell recognition of parasite-infected cells with damaged or ruptured PV membranes. However, in intact PVs, parasite secreted effector proteins that associate with the PV membrane or the intravacuolar network membranes play important roles to actively suppress antigen presentation by MHC-I to reduce CD8+ T cell recognition and clearance of Toxoplasma gondii infected host cells.
| S-EPMC6742963 | biostudies-literature