| 2013 |
GRA24 is a dense granule protein secreted by Toxoplasma gondii that traffics from the parasitophorous vacuole to the host cell nucleus, where it triggers prolonged autophosphorylation and nuclear translocation of host p38α MAP kinase (MAPK14), leading to upregulation of transcription factors Egr-1 and c-Fos and synthesis of proinflammatory cytokines IL-12 and MCP-1. This activation kinetics is non-canonical, distinct from the standard MAPK signaling cascade. |
Dense granule protein identification, subcellular fractionation/imaging showing nuclear trafficking, co-immunoprecipitation of GRA24-p38α complex, cytokine measurements in infected cells |
The Journal of experimental medicine |
High |
24043761
|
| 2016 |
GRA24 is an intrinsically disordered protein that binds two p38α kinase molecules independently via an adapted kinase interaction motif (KIM), forming a highly stable complex that bypasses canonical MAPK activation and competes with cytoplasmic regulatory partners. The purified recombinant GRA24-p38α complex is the only factor required to activate p38α in vitro. |
Structural analysis of recombinant GRA24-human p38α complex, in vitro reconstitution, biochemical assays, crystallography/biophysical characterization |
Structure (London, England : 1993) |
High |
27889209
|
| 2015 |
TgASP5, a Golgi-resident aspartyl protease, is required for export of GRA24 beyond the parasitophorous vacuole to the host cell nucleus. In the absence of ASP5, GRA24 is retained within the vacuolar space. Notably, GRA24 maturation/cleavage per se is TgASP5-independent, indicating ASP5 plays a role in GRA24 export through a mechanism other than direct proteolytic processing of GRA24. |
ASP5 knockout parasites, immunofluorescence assay tracking GRA24 localization, epitope-tagged constructs |
Cellular microbiology |
High |
26270241 26473595
|
| 2016 |
MYR1 is essential for transit of GRA24 to the host cell nucleus; deletion of MYR1 blocks GRA24 translocation across the parasitophorous vacuole membrane (PVM) into the host cell cytosol/nucleus. MYR1 localizes to the PVM and is cleaved by TgASP5, suggesting it is a component of the effector translocation machinery. |
MYR1 deletion mutants, immunofluorescence assay for GRA24 nuclear localization, whole-genome sequencing of mutants, subcellular fractionation |
mBio |
High |
26838724
|
| 2018 |
Novel proteins MYR2 and MYR3 are components of a complex with MYR1 at the PVM that is essential for translocation of GRA24 (and GRA16) into the host cell. MYR3 stably associates with MYR1 whose N- and C-terminal fragments are disulfide-linked. Fusion of GRA24 to a structured DHFR domain blocks its transport, consistent with a translocon-based unfolding mechanism. |
Genetic screen for c-Myc up-regulation defects, MYR2/MYR3 deletion, co-immunoprecipitation/co-localization of MYR1/2/3 at PVM, GFP-tracking of GRA24 nuclear localization, DHFR fusion experiments |
PLoS pathogens |
High |
29357375
|
| 2015 |
Yeast three-hybrid analysis identified GRA24 (also named TgBRADIN) as a parasite protein that interacts with the small-molecule Compound 2 (an imidazopyridine). Disruption of the GRA24 gene leads to enhanced bradyzoite differentiation, identifying GRA24 as a negative regulator of bradyzoite/stage conversion. |
Yeast three-hybrid screen, GRA24 gene disruption/knockout, differentiation assays measuring bradyzoite stage conversion |
PloS one |
Medium |
25789621
|
| 2018 |
GRA24 (and GRA16) are not secreted beyond the cyst wall membrane in bradyzoite tissue cysts. Using tetracycline-inducible expression of HA-tagged GRA16 and GRA24 after stage conversion, these proteins were retained within the cyst and did not traffic to the host cell nucleus, demonstrating that PVM effector export is stage-specific and absent in the bradyzoite/cyst stage. |
Tetracycline-inducible expression system, HA-tagged GRA16 and GRA24 in bradyzoite cysts, immunofluorescence assay |
Frontiers in cellular and infection microbiology |
Medium |
30406043
|
| 2019 |
GRA24 drives a sustained, non-canonical Egr-1 response in dendritic cells through p38 MAPK signaling. The extended-phase Egr-1 nuclear accumulation in infected DCs was dramatically reduced upon challenge with GRA24-deficient T. gondii parasites, and this response was MyD88-independent. GRA24-dependent Egr-1 upregulation suppressed DC maturation (reduced CD40, CD80 expression) and modulated IL-12 and IL-2 responses. |
GRA24 knockout parasites, Egr-1 siRNA silencing in primary DCs, pharmacological p38 inhibition, immunofluorescence for nuclear Egr-1, cytokine measurements, flow cytometry for surface markers |
Frontiers in cellular and infection microbiology |
High |
31681626
|
| 2020 |
GRA24 drives a late-phase p38 MAPK phosphorylation response in macrophages that is MyD88-independent and does not require active parasite proliferation, leading to IL-12 production. This GRA24-dependent p38 MAPK activation promotes a host-protective Th1 response independently of the TLR/MyD88 cascade. |
GRA24 knockout in uracil auxotrophic cps1-1 strain, bone marrow-derived macrophage infection assays, IL-12-YFP reporter mice, p38 phosphorylation assays, cytokine profiling in MyD88-/- mice |
PLoS pathogens |
High |
32413093
|
| 2020 |
GRA15 and GRA24 synergistically activate the innate immune response in TLR11-deficient mice and human macrophages. GRA15 and GRA24 are major drivers of IL-12, IL-18, and IL-1β secretion in human macrophages, which subsequently activates IFNγ secretion by PBMCs to control parasite proliferation. |
GRA15 and GRA24 single and double knockout parasites, infection of Tlr11-/- mice and human macrophages, cytokine ELISA (IL-12, IL-18, IL-1β, IFNγ), PBMC co-culture assays |
PLoS pathogens |
High |
32453782
|
| 2024 |
GRA24 promotes CCR7-mediated macrophage chemotaxis (hypermigration) via p38 MAPK signaling, enabling dissemination of T. gondii type II lineage. GRA24 and GRA15 act cooperatively: GRA15 activates NF-κB while GRA24 activates p38 MAPK, and GRA28 boosts chromatin accessibility at the Ccr7 gene locus to amplify CCR7 expression. In vivo, macrophages infected with wild-type T. gondii outcompeted GRA15/24 double-mutant-infected macrophages in migrating to secondary organs. |
GRA15/GRA24 single and double knockout parasites, CCR7 expression and chemotaxis assays, p38 MAPK and NF-κB signaling inhibitors, ATAC-seq for chromatin accessibility, adoptive transfer in vivo dissemination assay |
mBio |
High |
38370679 39207098
|
| 2024 |
GRA24 is one of four nuclear-targeted effectors (TgIST, GRA16, GRA24, GRA28) necessary for a complete block of IFNγ-driven host cell death and parasite premature egress in human (but not murine) cells. GRA24's protective action in this context depends on its interaction with p38 MAPK, and this function is MYR translocon-dependent. |
Genome-wide loss-of-function screens in IFNγ-stimulated human cells, combinatorial GRA knockout parasites, MYR translocon inhibition, cell death and egress assays, IFNγ-driven transcription assays |
mBio |
High |
39292011
|
| 2024 |
GRA24-dependent p38 MAPK signaling in host brain endothelial cells induces elevated transcription and secretion of TIMP1, which promotes non-disruptive T. gondii transmigration across polarized brain endothelial (bEnd.3) and intestinal epithelial (Caco-2) monolayers without disrupting barrier integrity. Pharmacological inhibition of p38 and use of GRA24 knockout parasites abolished TIMP1 induction. |
GRA24 knockout T. gondii, pharmacological p38 MAPK inhibition, transwell transmigration assays, TIMP1 ELISA and transcription analysis, barrier integrity measurements (TEER), recombinant TIMP1 supplementation |
mSphere |
Medium |
40265926
|
| 2026 |
GRA24 is one of eight MYR1-dependent dense granule effectors (IST, NSM, HCE1/TEEGR, GRA16, GRA18, GRA24, GRA28, GRA84) that function cooperatively to activate the non-canonical NF-κB pathway (RelB/p52) in host cells. This activation involves parasite-driven depletion of TRAF3, stabilization of NF-κB-inducing kinase (NIK), phosphorylation and processing of p100 to p52. No single effector alone accounts for this phenotype. |
Combinatorial GRA knockout parasites (panel-based), immunoblotting for RelB/p52/p100/NIK/TRAF3, nuclear fractionation, genome-wide loss-of-function screening |
bioRxiv : the preprint server for biologypreprint |
Medium |
41959509
|
| 2016 |
Deletion of GRA24 in uracil auxotrophic T. gondii strains severely abrogated antitumor immune responses, demonstrating that GRA24's trafficking to the host cell nucleus is functionally required for activating host immunity (CD8α+ dendritic cells, IL-12/IFNγ Th1 axis) that controls tumor growth. |
Targeted deletion of GRA24 in Δku80 vaccine strain, mouse tumor model, immune cell profiling by flow cytometry, cytokine measurements |
PLoS genetics |
Medium |
27447180
|
| 2024 |
GRA24-induced IL-12 production acts as a virulence factor in T cell-deficient (Tcrb-/-) and IL-10-deficient mouse hosts by driving fatal cytokine storm; resistance was restored in Tcrb-/- mice by monoclonal depletion of IL-12p40, demonstrating that GRA24-driven IL-12 underlies immunopathology in the absence of regulatory T cell responses. |
GRA24 knockout uracil auxotroph parasites, Tcrb-/- and IL-10-/- mice, antibody depletion of IL-12p40, survival assays, cytokine profiling |
mBio |
Medium |
39440975
|