scholarly journals A Toxoplasma dense granule protein, GRA24, modulates the early immune response to infection by promoting a direct and sustained host p38 MAPK activation

2013 ◽  
Vol 210 (10) ◽  
pp. 2071-2086 ◽  
Author(s):  
Laurence Braun ◽  
Marie-Pierre Brenier-Pinchart ◽  
Manickam Yogavel ◽  
Aurélie Curt-Varesano ◽  
Rose-Laurence Curt-Bertini ◽  
...  
Keyword(s):  
Immune Response ◽  
Host Cell ◽  
Nuclear Translocation ◽  
Parasitophorous Vacuole ◽  
Structural Features ◽  
Mapk Signaling ◽  
Dense Granule ◽  
Interleukin 12 ◽  
Granule Protein

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 p38α MAP kinase. This noncanonical kinetics of p38α 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–p38α 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.

scholarly journals Strain-specific activation of the NF-κB pathway by GRA15, a novel Toxoplasma gondii dense granule protein

2011 ◽  
Vol 208 (1) ◽  
pp. 195-212 ◽  
Author(s):  
Emily E. Rosowski ◽  
Diana Lu ◽  
Lindsay Julien ◽  
Lauren Rodda ◽  
Rogier A. Gaiser ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Host Cell ◽  
Nuclear Translocation ◽  
Strain Differences ◽  
Dense Granule ◽  
Forward Genetics ◽  
Type I ◽  
Type Ii ◽  
Granule Protein

NF-κB is an integral component of the immune response to Toxoplasma gondii. Although evidence exists that T. gondii can directly modulate the NF-κB pathway, the parasite-derived effectors involved are unknown. We determined that type II strains of T. gondii activate more NF-κB than type I or type III strains, and using forward genetics we found that this difference is a result of the polymorphic protein GRA15, a novel dense granule protein which T. gondii secretes into the host cell upon invasion. A GRA15-deficient type II strain has a severe defect in both NF-κB nuclear translocation and NF-κB–mediated transcription. Furthermore, human cells expressing type II GRA15 also activate NF-κB, demonstrating that GRA15 alone is sufficient for NF-κB activation. Along with the rhoptry protein ROP16, GRA15 is responsible for a large part of the strain differences in the induction of IL-12 secretion by infected mouse macrophages. In vivo bioluminescent imaging showed that a GRA15-deficient type II strain grows faster compared with wild-type, most likely through its reduced induction of IFN-γ. These results show for the first time that a dense granule protein can modulate host signaling pathways, and dense granule proteins can therefore join rhoptry proteins in T. gondii’s host cell–modifying arsenal.

In vivo expression and distribution of dense granule protein 7 (GRA7) in the exoenteric (tachyzoite, bradyzoite) and enteric (coccidian) forms of Toxoplasma gondii

Parasitology ◽  
1999 ◽  
Vol 119 (3) ◽  
pp. 259-265 ◽  
Author(s):  
D. J. P. FERGUSON ◽  
D. JACOBS ◽  
E. SAMAN ◽  
J-F. DUBREMETZ ◽  
S. E. WRIGHT
Keyword(s):  
Toxoplasma Gondii ◽  
Staining Pattern ◽  
Parasitophorous Vacuole ◽  
Dense Granule ◽  
Parasite Development ◽  
Double Labelling ◽  
Granule Protein ◽  
Specific Variation ◽  
Strong Staining

The in vivo expression and distribution of the dense granule protein GRA7 was examined in both the exoenteric (tachyzoite and bradyzoite) and enteric (coccidian) forms of Toxoplasma gondii by immunocytochemistry. There was strong staining of GRA7 in granules within all the infectious stages (tachyzoite, bradyzoite, merozoite and sporozoite). During tachyzoite development, GRA7 was secreted and was associated with the parasitophorous vacuole. In contrast, although there was staining of granules within the bradyzoites of more mature cysts, there appeared to be little staining of the tissue cyst wall or host cell. The apparent stage-specific variation in secretion of GRA7 between tachyzoites and bradyzoites was confirmed by double labelling using stage-specific markers (SAG1 and BAG1). In the enteric forms in the cat gut there was strong labelling of the PV containing early asexual and sexual stages and staining of a few granules in the apical cytoplasm of the merozoite. The positive enteric staining pattern differentiates GRA7 from the other GRA proteins (GRA1–6) which were absent in the merozoites and enteric stages. The staining pattern of GRA7 with strong staining during tachyzoite and enteric development and reduced staining in the tissue cysts is similar to that seen for NTPases. The function of GRA7 is unknown but it is unique among the dense granule proteins in being expressed in all the infectious forms of T. gondii which would point to a basic role in the vacuolar adaptations required for active parasite development.

scholarly journals First Characterization of theNeospora caninumDense Granule Protein GRA9

2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Margret Leineweber ◽  
Katrin Spekker-Bosker ◽  
Vanessa Ince ◽  
Gereon Schares ◽  
Andrew Hemphill ◽  
...  
Keyword(s):  
Host Cell ◽  
Cell Invasion ◽  
Neospora Caninum ◽  
Parasitophorous Vacuole ◽  
Dense Granule ◽  
Immunogold Electron Microscopy ◽  
Host Cell Invasion ◽  
Dense Granules ◽  
Granule Protein

The obligate intracellular apicomplexan parasiteNeospora caninum (N. caninum)is closely related toToxoplasma gondii (T. gondii). The dense granules, which are present in all apicomplexan parasites, are important secretory organelles. Dense granule (GRA) proteins are released into the parasitophorous vacuole (PV) following host cell invasion and are known to play important roles in the maintenance of the host-parasite relationship and in the acquisition of nutrients. Here, we provide a detailed characterization of theN. caninumdense granule protein NcGRA9. The in silico genomic organization and key protein characteristics are described. Immunofluorescence-based localization studies revealed that NcGRA9 is located in the dense granules and is released into the interior of the PV following host cell invasion. Immunogold-electron microscopy confirmed the dense granule localization and showed that NcGRA9 is associated with the intravacuolar network. In addition, NcGRA9 is found in the “excreted secreted antigen” (ESA) fraction ofN. caninum. Furthermore, by analysing the distribution of truncated versions of NcGRA9, we provide evidence that the C-terminal region of this protein is essential for the targeting of NcGRA9 into the dense granules ofN. caninum, and the truncated proteins show reduced secretion.

scholarly journals The Toxoplasma gondii Dense Granule Protein GRA7 Is Phosphorylated upon Invasion and Forms an Unexpected Association with the Rhoptry Proteins ROP2 and ROP4

2008 ◽  
Vol 76 (12) ◽  
pp. 5853-5861 ◽  
Author(s):  
Joe Dan Dunn ◽  
Sandeep Ravindran ◽  
Seon-Kyeong Kim ◽  
John C. Boothroyd
Keyword(s):  
Toxoplasma Gondii ◽  
Host Cell ◽  
Parasitophorous Vacuole ◽  
Opportunistic Pathogen ◽  
Dense Granule ◽  
Host Cells ◽  
Obligate Intracellular ◽  
Dense Granules ◽  
Obligate Intracellular Parasite ◽  
Granule Protein

ABSTRACT The obligate intracellular parasite Toxoplasma gondii infects warm-blooded animals throughout the world and is an opportunistic pathogen of humans. As it invades a host cell, Toxoplasma forms a novel organelle, the parasitophorous vacuole, in which it resides during its intracellular development. The parasite modifies the parasitophorous vacuole and its host cell with numerous proteins delivered from rhoptries and dense granules, which are secretory organelles unique to the phylum Apicomplexa. For the majority of these proteins, little is known other than their localization. Here we show that the dense granule protein GRA7 is phosphorylated but only in the presence of host cells. Within 10 min of invasion, GRA7 is present in strand-like structures in the host cytosol that contain rhoptry proteins. GRA7 strands also contain GRA1 and GRA3. Independently of its phosphorylation state, GRA7 associates with the rhoptry proteins ROP2 and ROP4 in infected host cells. This is the first report of interactions between proteins secreted from rhoptries and dense granules.

scholarly journals In Vivo Biotinylation of the Toxoplasma Parasitophorous Vacuole Reveals Novel Dense Granule Proteins Important for Parasite Growth and Pathogenesis

mBio ◽  
2016 ◽  
Vol 7 (4) ◽  
Author(s):  
Santhosh M. Nadipuram ◽  
Elliot W. Kim ◽  
Ajay A. Vashisht ◽  
Andrew H. Lin ◽  
Hannah N. Bell ◽  
...  
Keyword(s):  
Host Cell ◽  
Gene Knockout ◽  
Affinity Purification ◽  
Parasitophorous Vacuole ◽  
Dense Granule ◽  
Parasite Growth ◽  
Host Cells ◽  
Biotin Ligase ◽  
Granule Proteins

ABSTRACT Toxoplasma gondii is an obligate intracellular parasite that invades host cells and replicates within a unique parasitophorous vacuole. To maintain this intracellular niche, the parasite secretes an array of dense granule proteins (GRAs) into the nascent parasitophorous vacuole. These GRAs are believed to play key roles in vacuolar remodeling, nutrient uptake, and immune evasion while the parasite is replicating within the host cell. Despite the central role of GRAs in the Toxoplasma life cycle, only a subset of these proteins have been identified, and many of their roles have not been fully elucidated. In this report, we utilize the promiscuous biotin ligase BirA* to biotinylate GRA proteins secreted into the vacuole and then identify those proteins by affinity purification and mass spectrometry. Using GRA-BirA* fusion proteins as bait, we have identified a large number of known and candidate GRAs and verified localization of 13 novel GRA proteins by endogenous gene tagging. We proceeded to functionally characterize three related GRAs from this group (GRA38, GRA39, and GRA40) by gene knockout. While Δ gra38 and Δ gra40 parasites showed no altered phenotype, disruption of GRA39 results in slow-growing parasites that contain striking lipid deposits in the parasitophorous vacuole, suggesting a role in lipid regulation that is important for parasite growth. In addition, parasites lacking GRA39 showed dramatically reduced virulence and a lower tissue cyst burden in vivo . Together, the findings from this work reveal a partial vacuolar proteome of T. gondii and identify a novel GRA that plays a key role in parasite replication and pathogenesis. IMPORTANCE Most intracellular pathogens reside inside a membrane-bound vacuole within their host cell that is extensively modified by the pathogen to optimize intracellular growth and avoid host defenses. In Toxoplasma , this vacuole is modified by a host of secretory GRA proteins, many of which remain unidentified. Here we demonstrate that in vivo biotinylation of proximal and interacting proteins using the promiscuous biotin ligase BirA* is a powerful approach to rapidly identify vacuolar GRA proteins. We further demonstrate that one factor identified by this approach, GRA39, plays an important role in the ability of the parasite to replicate within its host cell and cause disease.

Oligomannose-coated liposome-entrapped dense granule protein 7 induces protective immune response to Neospora caninum in cattle

Vaccine ◽  
2013 ◽  
Vol 31 (35) ◽  
pp. 3528-3535 ◽  
Author(s):  
Maki Nishimura ◽  
Junko Kohara ◽  
Yasuhiro Kuroda ◽  
Jun Hiasa ◽  
Sachi Tanaka ◽  
...  
Keyword(s):  
Immune Response ◽  
Neospora Caninum ◽  
Dense Granule ◽  
Protective Immune Response ◽  
Granule Protein

scholarly journals Tim-3 Induces Th2-Biased Immunity and Alternative Macrophage Activation during Schistosoma japonicum Infection

2015 ◽  
Vol 83 (8) ◽  
pp. 3074-3082 ◽  
Author(s):  
Nan Hou ◽  
Xianyu Piao ◽  
Shuai Liu ◽  
Chuang Wu ◽  
Qijun Chen
Keyword(s):  
Immune Response ◽  
T Cells ◽  
Schistosoma Japonicum ◽  
Immune Cell ◽  
Nk Cell ◽  
Alternative Activation ◽  
Interleukin 12 ◽  
Content Type

T cell immunoglobulin- and mucin-domain-containing molecule 3 (Tim-3) has been regarded as an important regulatory factor in both adaptive and innate immunity. Recently, Tim-3 was reported to be involved in Th2-biased immune responses in mice infected withSchistosoma japonicum, but the exact mechanism behind the involvement of Tim-3 remains unknown. The present study aims to understand the role of Tim-3 in the immune response againstS. japonicuminfection. Tim-3 expression was determined by flow cytometry, and increased Tim-3 expression was observed on CD4+and CD8+T cells, NK1.1+cells, and CD11b+cells from the livers ofS. japonicum-infected mice. However, the increased level of Tim-3 was lower in the spleen than in the liver, and no increase in Tim-3 expression was observed on splenic CD8+T cells or CD11b+cells. The schistosome-induced upregulation of Tim-3 on natural killer (NK) cells was accompanied by reduced NK cell numbersin vitroandin vivo. Tim-3 antibody blockade led to upregulation of inducible nitric oxide synthase and interleukin-12 (IL-12) mRNA in CD11b+cells cocultured with soluble egg antigen and downregulation of Arg1 and IL-10, which are markers of M2 macrophages. In summary, we observed schistosome-induced expression of Tim-3 on critical immune cell populations, which may be involved in the Th2-biased immune response and alternative activation of macrophages during infection.

Sign in / Sign up

Export Citation Format

Share Document