Affinage · Toxoplasma gondii

GRA8

dense granule protein GRA8 · UniProt S8F761

Annotated
2026-09-08
30 papers in source corpus 7 papers cited in narrative 7 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

GRA8 is a proline-rich, transmembrane-domain-containing dense granule protein of Toxoplasma gondii that is secreted into the parasitophorous vacuole during or shortly after invasion and associates with the vacuole periphery (PMID:10613696). Its transcription is developmentally upregulated during the tachyzoite-to-bradyzoite transition (PMID:12455982), and in bradyzoites it participates in a BPK1-associated cyst wall complex together with MAG1, MCP4, and GRA9 (PMID:23291621); consistent with a role in chronic-stage biology, deletion in the type II Pru strain severely impairs in vivo cyst development without affecting growth or in vitro differentiation (PMID:31266861). Beyond the vacuole, GRA8 is a component of the parasite sub-pellicular cytoskeleton, associating with sub-pellicular microtubules and actin, and its loss in RH abolishes conoid extrusion and reduces host cell invasion and egress with accompanying microtubule meshwork defects (PMID:30949853). GRA8 also manipulates host cell metabolism: following PKCα-mediated phosphorylation at Thr220, it traffics into host mitochondria where its C-terminal domain binds the nucleotide-binding domain of ATP5A1 and engages SIRT3 to drive SIRT3-mediated deacetylation of ATP5A1 at K506/K531, increasing ATP production and conferring anti-septic activity in vivo (PMID:29869623).

Mechanistic history

Synthesis pass · year-by-year structured walk · 7 steps
  1. 2000 High

    Establishing GRA8's identity resolved the question of whether it is a secreted parasite factor and where it acts, defining it as a dense granule protein delivered to the parasitophorous vacuole.

    Evidence Monoclonal antibody generation, immunoelectron microscopy, and cDNA cloning/sequence analysis in T. gondii

    PMID:10613696

    Open questions at the time
    • The function of the proline-rich repeats and C-terminal transmembrane domain was not tested
    • No genetic disruption to assign a phenotype
  2. 2001 Medium

    Independent proteomic mapping confirmed GRA8 as an excretory dense granule protein, corroborating its secreted status.

    Evidence 2D PAGE and Western blotting of tachyzoite lysate in T. gondii

    PMID:11511000

    Open questions at the time
    • No functional readout
    • Descriptive proteomic placement only
  3. 2002 Medium

    Transcript profiling linked GRA8 expression to stage conversion, raising the hypothesis that it functions in bradyzoite/chronic-stage biology.

    Evidence cDNA microarray of transcript levels during stage differentiation in T. gondii

    PMID:12455982

    Open questions at the time
    • Transcript-level only; no protein-level or functional confirmation of a bradyzoite role
  4. 2013 Medium

    Co-immunoprecipitation placed GRA8 within a defined bradyzoite protein complex, physically connecting it to the cyst wall machinery.

    Evidence Immunoprecipitation of BPK1 with protein identification from in vitro bradyzoite cultures of T. gondii

    PMID:23291621

    Open questions at the time
    • Single Co-IP without reported reciprocal pull-down
    • Direct vs indirect association with BPK1 not resolved
  5. 2018 Medium

    Identification of Thr220 phosphorylation and mitochondrial trafficking revealed a mechanism by which GRA8 reprograms host mitochondrial metabolism.

    Evidence Co-IP, phosphorylation assay, Thr220 mutagenesis, mitochondrial fractionation, and an in vivo sepsis model in T. gondii

    PMID:29869623

    Open questions at the time
    • Single-lab study across orthogonal methods
    • How host PKCα accesses/phosphorylates GRA8 is not defined
    • Relationship between this host-mitochondrial role and the vacuolar/cytoskeletal roles is unclear
  6. 2019 High

    Genetic knockout in RH assigned GRA8 a cytoskeletal function, showing it is required for conoid extrusion, invasion, and egress via association with sub-pellicular microtubules and actin.

    Evidence ImmunoEM, proteomics, biochemical fractionation, RHΔku80Δgra8 knockout with conoid/invasion/egress assays, and docking analysis

    PMID:30949853

    Open questions at the time
    • Direct microtubule/actin binding inferred from docking, not biochemically demonstrated
    • How a secreted dense granule protein also localizes to the cytoskeleton is unexplained
  7. 2019 High

    Knockout in the type II Pru strain established GRA8's in vivo requirement for chronic cyst development, distinct from any growth or differentiation defect.

    Evidence Gene deletion in Pru strain, in vivo mouse infection, and in vitro cyst formation assays in T. gondii

    PMID:31266861

    Open questions at the time
    • Molecular basis of the chronic-stage defect not defined
    • Connection to the BPK1 cyst wall complex not directly tested in this system

Open questions

Synthesis pass · forward-looking unresolved questions
  • How GRA8's distinct localizations—vacuolar membrane, parasite sub-pellicular cytoskeleton, and host mitochondria—are coordinated from a single secreted protein remains unresolved.
  • Trafficking signals directing GRA8 to each compartment are unknown
  • Whether the same protein pool serves all roles is untested
  • No structural model of GRA8

Mechanism profile

Synthesis pass · controlled-vocabulary classification
Partners
ACTIN (DOCKING) [#5]ATP5A1 (HOST) [#4]BPK1 [#3]GRA9 [#3]MAG1 [#3]MCP4 [#3]PKCΑ (HOST, KINASE FOR THR220) [#4]SIRT3 (HOST) [#4]Β-TUBULIN (DOCKING) [#5]
Complex memberships
BPK1-associated cyst wall complex (with MAG1, MCP4, GRA9) [#3]

Evidence

Reading pass · 7 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2000 GRA8 is a novel 38 kDa dense granule protein of Toxoplasma gondii; it is released into the parasitophorous vacuole during or shortly after invasion and associates with the periphery of the vacuole. Its deduced amino acid sequence contains an N-terminal signal peptide, three degenerate proline-rich repeats, and a potential C-terminal transmembrane domain. Monoclonal antibody generation, immunoelectron microscopy, cDNA library screening, sequence analysis Molecular and biochemical parasitology High 10613696
2001 GRA8 was identified as an excretory dense granule protein and mapped on the two-dimensional proteome map of Toxoplasma gondii tachyzoite lysate by Western blotting of 2D-separated protein spots. 2D polyacrylamide gel electrophoresis, Western blotting Parasitology research Medium 11511000
2002 GRA8 transcript levels are developmentally regulated, being upregulated during tachyzoite-to-bradyzoite differentiation, classifying it among secretory organelle protein genes with stage-specific expression. cDNA microarray analysis of transcript levels during stage differentiation Eukaryotic cell Medium 12455982
2013 GRA8 was identified as one of at least four proteins (along with MAG1, MCP4, and GRA9) that co-immunoprecipitate with bradyzoite pseudokinase 1 (BPK1) from in vitro bradyzoite cultures, indicating GRA8 is a component of the BPK1-associated complex in the cyst wall. Immunoprecipitation of BPK1 followed by protein identification (mass spectrometry implied) Eukaryotic cell Medium 23291621
2018 PKCα-mediated phosphorylation of GRA8 at Thr220 is required for mitochondrial trafficking of GRA8 into host cell mitochondria. In mitochondria, GRA8 interacts with ATP5A1 (via its C-terminal domain binding the nucleotide-binding domain of ATP5A1) and with SIRT3, facilitating SIRT3-mediated deacetylation of ATP5A1 at K506 and K531, leading to increased ATP production and anti-septic activity in vivo. Co-immunoprecipitation, phosphorylation assay, mutagenesis (Thr220), mitochondrial fractionation/trafficking assay, in vivo sepsis model Experimental & molecular medicine Medium 29869623
2019 GRA8 (TgGRA8I) is a component of the sub-pellicular cytoskeleton of Toxoplasma gondii; it associates with sub-pellicular microtubules and actin as shown by immunoelectron microscopy, proteomics, and biochemical fractionation. Deletion of gra8 (RHΔku80Δgra8) causes loss of conoid extrusion, diminished host cell infection, and reduced egress, accompanied by structural alterations in sub-pellicular microtubules and the meshwork. In silico docking also suggested interaction with β-tubulin and actin. Immunoelectron microscopy, proteomic analysis, biochemical fractionation, gene knockout (RHΔku80Δgra8), conoid extrusion assay, invasion and egress assays, docking analysis Parasitology research High 30949853
2019 Deletion of GRA8 in the type II Prugniaud (Pru) strain (PruΔgra8) induced severe defects in development of chronic-stage cysts in vivo without affecting parasite growth rate or the ability to differentiate into cysts in vitro, placing GRA8 as a PVM-associated dense granule protein required for chronic infection. Gene deletion (knockout) in type II Pru strain, in vivo mouse infection model, in vitro cyst formation assay mBio High 31266861

Source papers

Stage 0 corpus · 30 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2002 Toxoplasma gondii asexual development: identification of developmentally regulated genes and distinct patterns of gene expression. Eukaryotic cell 131 12455982
2005 Seroreactivity to and avidity for recombinant antigens in toxoplasmosis. Clinical and diagnostic laboratory immunology 89 16085916
2019 Toxoplasma gondii Parasitophorous Vacuole Membrane-Associated Dense Granule Proteins Orchestrate Chronic Infection and GRA12 Underpins Resistance to Host Gamma Interferon. mBio 75 31266861
2000 Identification and molecular characterization of GRA8, a novel, proline-rich, dense granule protein of Toxoplasma gondii. Molecular and biochemical parasitology 70 10613696
2003 Molecular dissection of the human B-cell response against Toxoplasma gondii infection by lambda display of cDNA libraries. International journal for parasitology 54 12633654
2013 Bradyzoite pseudokinase 1 is crucial for efficient oral infectivity of the Toxoplasma gondii tissue cyst. Eukaryotic cell 41 23291621
2017 Detection of Toxoplasma gondii in chicken and soil of chicken farms in Nanjing region, China. Infectious diseases of poverty 26 28482918
2018 Toxoplasma gondii GRA8 induces ATP5A1-SIRT3-mediated mitochondrial metabolic resuscitation: a potential therapy for sepsis. Experimental & molecular medicine 24 29869623
2018 Discovery of new Toxoplasma gondii antigenic proteins using a high throughput protein microarray approach screening sera of murine model infected orally with oocysts and tissue cysts. Parasites & vectors 24 29973272
2011 Prevalence of specific IgG-antibodies against Toxoplasma gondii in domestic turkeys determined by kinetic ELISA based on recombinant GRA7 and GRA8. Veterinary parasitology 23 21524853
2020 Toxoplasma gondii GRA8-derived peptide immunotherapy improves tumor targeting of colorectal cancer. Oncotarget 20 32002124
2001 Towards the Toxoplasma gondii proteome: position of 13 parasite excretory antigens on a standardized map of two-dimensionally separated tachyzoite proteins. Parasitology research 20 11511000
2020 Serological diagnosis of Toxoplasma gondii: analysis of false-positive IgG results and implications. Parasite (Paris, France) 19 32031519
2011 Expression and Single-step Purification of GRA8 Antigen of Toxoplasma gondii in Escherichia coli. Avicenna journal of medical biotechnology 13 23407862
2021 Development and evaluation of recombinant GRA8 protein for the serodiagnosis of Toxoplasma gondii infection in goats. BMC veterinary research 12 33422085
2021 GRA8 DNA vaccine formulations protect against chronic toxoplasmosis. Microbial pathogenesis 12 34098019
2021 Development and validation of a time-resolved fluorescence immunoassay for the detection of anti-Toxoplasma gondii antibodies in goats. Veterinary parasitology 12 33915322
2018 Semiquantitative Dot Blot with the GRA8 antigen to differentiate the stages of toxoplasmosis infection. Journal of microbiological methods 12 29684398
2005 Genetic characteristics of the Korean isolate KI-1 of Toxoplasma gondii. The Korean journal of parasitology 12 15793356
2020 A novel luciferase-linked antibody capture assay (LACA) for the diagnosis of Toxoplasma gondii infection in chickens. Parasitology international 11 32311471
2019 The dense granule protein 8 (GRA8) is a component of the sub-pellicular cytoskeleton in Toxoplasma gondii. Parasitology research 11 30949853
2009 Bacterial production of dense granule antigen GRA8 of Toxoplasma gondii. Iranian biomedical journal 10 19688020
2018 Evaluation of LIPS (luciferase immunoprecipitation system) for serodiagnosis of Toxoplasmosis. Journal of immunological methods 8 30201391
2016 Immunochemical evaluation of two Toxoplasma gondii GRA8 sequences to detect acute toxoplasmosis infection. Microbial pathogenesis 8 27693576
2018 Evaluation of Protective Immune Response Induced by a DNA Vaccine Encoding GRA8 against Acute Toxoplasmosis in a Murine Model. The Korean journal of parasitology 6 30196664
2018 T-cell profiles elicited by Toxoplasma gondii in acutely/chronically infected humans. Parasite immunology 5 29633283
2022 Comparative performance of five recombinant and chimeric antigens in a time-resolved fluorescence immunoassay for detection of Toxoplasma gondii infection in cats. Veterinary parasitology 3 35367904
2022 Diagnostic value of recombinant nanoluciferase fused Toxoplasma gondii antigens in Luciferase-linked Antibody Capture Assay (LACA) for Toxoplasma infection in pigs. The Journal of veterinary medical science 3 35584943
2021 Exposure to Toxoplasma gondii in Asian Elephants (Elephas maximus indicus) in Thailand. Pathogens (Basel, Switzerland) 1 35055950
2005 [Expression of truncated Toxoplasma gondii GRA8 in the prokaryotic expression plasmids]. Zhongguo ji sheng chong xue yu ji sheng chong bing za zhi = Chinese journal of parasitology & parasitic diseases 0 16299997