Affinage · Toxoplasma gondii

ALV1

alveolin domain containing intermediate filament IMC1 · UniProt A0A125YFV7

Annotated
2026-09-10
12 papers in source corpus 8 papers cited in narrative 8 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

ALV1 (TgIMC1) is the founding alveolin and a central structural component of the subpellicular network, a filamentous membrane skeleton of interwoven 8–10 nm filaments associated with the cytoplasmic face of the Toxoplasma gondii pellicle (PMID:11420112). It is assembled onto daughter cytoskeletons during endodyogeny and multiple-daughter formation (PMID:11854415), being loaded onto forming daughter buds together with IMC4 but later than IMC3, IMC6, and IMC10; a subregion of its alveolin domain is sufficient for IMC targeting and required for its function, and it binds IMC4 directly, with IMC1 loss mislocalizing IMC4 in daughter buds (PMID:42113865, PMID:40501855). Network maturation depends on proteolytic processing of the ALV1 C-terminus—requiring a single C-terminal cysteine—that converts the detergent-labile immature network into a detergent-resistant mature form (PMID:12177058), a maturation step that requires the metacaspases MCA1 and MCA2 in RH (PMID:34384491). ALV1 also binds directly to IMT1, the protein bridging the IMC to subpellicular microtubules (PMID:40768331). ALV1 is expressed across tachyzoite, sporozoite, and other stages but absent from gametocytes (PMID:29062899), and its disruption causes loss of cytoskeletal integrity with defects in invasion, replication, and egress, abolishing chronic infection in a type II (ME49) strain in vivo (PMID:42113865, PMID:40501855). Beyond these findings, nothing further about ALV1 is established in the available corpus.

Mechanistic history

Synthesis pass · year-by-year structured walk · 7 steps
  1. 2001 High

    Establishing that ALV1/TgIMC1 is a genuine structural component of the parasite membrane skeleton answered whether the pellicle-associated filamentous network had defined protein constituents.

    Evidence Electron microscopy of detergent-extracted tachyzoites with protein identification and sequence analysis

    PMID:11420112

    Open questions at the time
    • Filament assembly mechanism not resolved
    • Partner proteins within the network not yet identified
  2. 2002 High

    Live imaging of an IMC1–YFP reporter answered when and how the network is built, showing it is assembled de novo during endodyogeny and multiple-daughter formation.

    Evidence Live-cell time-lapse fluorescence microscopy of an IMC1–YFP fusion in T. gondii

    PMID:11854415

    Open questions at the time
    • Targeting determinants for daughter bud loading not defined
    • Order relative to other IMC proteins unknown
  3. 2002 High

    Identifying C-terminal proteolytic processing coupled to a detergent-labile-to-resistant transition answered how the immature network matures into a stable skeleton.

    Evidence Detergent fractionation plus site-directed mutagenesis of a C-terminal cysteine and immunoblotting

    PMID:12177058

    Open questions at the time
    • Protease responsible not identified in this study
    • Molecular basis of detergent resistance unresolved
  4. 2017 Medium

    Mapping IMC1 expression across the life cycle answered whether its role is stage-specific, showing presence in tachyzoites and sporozoites but absence from gametocytes.

    Evidence Immunofluorescence across multiple life-cycle stages

    PMID:29062899

    Open questions at the time
    • Functional consequence of gametocyte absence not tested
    • Stage-specific regulation mechanism unknown
  5. 2021 Medium

    Genetic loss of MCA1/MCA2 identified the enzymes required for IMC1 maturation, linking metacaspase activity to conversion of the network to its detergent-resistant form.

    Evidence MCA1/MCA2 double knockout in RHΔku80 with detergent fractionation and IFA

    PMID:34384491

    Open questions at the time
    • Direct cleavage of IMC1 by metacaspases not demonstrated
    • Whether processing is direct or indirect not resolved
  6. 2025 Medium

    Direct binding of IMT1 to IMC1 answered how the alveolin network physically couples to subpellicular microtubules.

    Evidence Proximity labeling (BioID), co-immunoprecipitation/pulldown, and deletion analyses

    PMID:40768331

    Open questions at the time
    • Binding interface on IMC1 not mapped
    • Functional consequence of the IMC1–IMT1 interaction for microtubule anchoring not tested
  7. 2025 High

    Knockout combined with domain mapping and interaction analysis established ALV1 as essential for cytoskeletal integrity and defined its daughter-bud loading order and its direct role in positioning IMC4.

    Evidence Gene knockout with morphology, invasion, replication, egress and mouse infection assays; fluorescent tagging with time-resolved IFA, deletion/mutagenesis, and IMC1–IMC4 pulldown

    PMID:42113865 PMID:40501855

    Open questions at the time
    • Structure of the alveolin targeting subregion not determined
    • How IMC1 nucleates or organizes the broader network hierarchy not resolved

Mechanism profile

Synthesis pass · controlled-vocabulary classification
Partners
IMC4 (DIRECT BINDING)IMT1 (DIRECT BINDING, IMC-MICROTUBULE BRIDGE)MCA1/MCA2 METACASPASES (REQUIRED FOR MATURATION)
Complex memberships
Subpellicular network / inner membrane complex alveolin meshwork

Evidence

Reading pass · 8 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2001 TgIMC1 (ALV1) is a component of the subpellicular network, a filamentous membrane skeletal structure composed of interwoven 8–10 nm filaments associated with the cytoplasmic face of the pellicle of Toxoplasma gondii. TgIMC1 has predicted extended coiled-coil domains and is homologous to articulins, the major components of the membrane skeleton of algae and free-living protists. Electron microscopy of detergent-extracted tachyzoites; protein identification and sequence analysis Molecular and biochemical parasitology High 11420112
2002 An IMC1–YFP fusion protein was used to visualize daughter scaffold (inner membrane complex) formation in live T. gondii by time-lapse video microscopy, demonstrating that the IMC1-based subpellicular network is assembled during endodyogeny and can also form during production of multiple daughters. Live-cell time-lapse fluorescence microscopy using IMC1–YFP fusion protein Molecular biology of the cell High 11854415
2002 TgIMC1 (ALV1) undergoes proteolytic processing of its carboxyl terminus during daughter parasite maturation. In immature parasites the network is detergent-soluble; in mature parasites it becomes entirely detergent-resistant. Conversion from detergent-labile to detergent-resistant network is coupled to proteolytic cleavage of the TgIMC1 C-terminus. A single cysteine residue in the C-terminus is essential for this processing event. Detergent fractionation assays; site-directed mutagenesis of TgIMC1 cysteine residue; immunoblotting to detect processing The Journal of biological chemistry High 12177058
2017 IMC1 (ALV1) is present in both mother and daughter cytoskeletons during asexual tachyzoite division, is absent from developing macro- and microgametocytes, and is present in sporozoites. IMC1 is thus present across multiple life cycle stages but absent from gametocytes, indicating a stage-specific role distinct from other IMC alveolins. Immunofluorescence assay (IFA) across multiple life-cycle stages of T. gondii and Sarcocystis neurona mSphere Medium 29062899
2021 Double knockout of metacaspase-1 (MCA1) and metacaspase-2 (MCA2) in T. gondii results in detergent-soluble IMC1, indicating that MCA1 and MCA2 are required for IMC1 (ALV1) maturation (conversion to detergent-resistant form) and for normal endodyogeny. Double-knockout of MCA1/MCA2 in RHΔku80; detergent fractionation to assess IMC1 solubility; IFA to assess IMC1 expression and endodyogeny Parasites & vectors Medium 34384491
2025 IMT1, a protein that bridges the IMC and subpellicular microtubules, binds directly to the cytoskeletal IMC proteins IMC1 (ALV1), IMC18, and IMC24, as shown by deletion analyses and proximity labeling. Proximity labeling (BioID), co-immunoprecipitation/pulldown, deletion analyses Molecular biology of the cell Medium 40768331
2025 Disruption of IMC1 (ALV1) causes severe morphological defects, loss of cytoskeletal integrity, and defects in invasion, replication, and egress. In a type II strain, IMC1 loss causes dramatic reduction in infectivity and complete failure to establish chronic infection in vivo. Gene knockout; morphological analysis; invasion, replication, and egress assays; mouse infection studies PLoS pathogens High 40501855 42113865
2025 IMC1 (ALV1) is loaded onto forming daughter buds together with IMC4, but later than IMC3, IMC6, and IMC10. A key subregion of the alveolin domain is sufficient for IMC targeting and is also required for IMC1 function. IMC1 interacts directly with IMC4, and loss of IMC1 results in mislocalization of IMC4 specifically in forming daughter buds. Fluorescent protein tagging with time-resolved IFA; deletion analysis; mutagenesis; co-immunoprecipitation/pulldown to establish direct IMC1–IMC4 interaction; IFA of IMC4 localization in IMC1 knockout PLoS pathogens High 40501855 42113865

Source papers

Stage 0 corpus · 12 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2001 Characterization of the subpellicular network, a filamentous membrane skeletal component in the parasite Toxoplasma gondii. Molecular and biochemical parasitology 200 11420112
2002 Daughter cell assembly in the protozoan parasite Toxoplasma gondii. Molecular biology of the cell 151 11854415
2002 Proteolytic processing of TgIMC1 during maturation of the membrane skeleton of Toxoplasma gondii. The Journal of biological chemistry 70 12177058
2017 Differential Roles for Inner Membrane Complex Proteins across Toxoplasma gondii and Sarcocystis neurona Development. mSphere 50 29062899
2013 Identification of differentially expressed proteins in sulfadiazine resistant and sensitive strains of Toxoplasma gondii using difference-gel electrophoresis (DIGE). International journal for parasitology. Drugs and drug resistance 42 24533291
2008 Toxoplasma gondii Hsp20 is a stripe-arranged chaperone-like protein associated with the outer leaflet of the inner membrane complex. Biology of the cell 34 18315523
2008 A novel actin-related protein is associated with daughter cell formation in Toxoplasma gondii. Eukaryotic cell 19 18408052
2021 Requirement of Toxoplasma gondii metacaspases for IMC1 maturation, endodyogeny and virulence in mice. Parasites & vectors 5 34384491
2025 Research on inner membrane complex protein 1: a novel nanovaccines against Toxoplasma gondii. BMC veterinary research 3 40849645
2025 Function and interactions of a protein bridge between the inner membrane complex and subpellicular microtubules in Toxoplasma gondii. Molecular biology of the cell 2 40768331
2026 Toxoplasma IMC1 is a central component of the subpellicular network and plays critical roles in parasite morphology, replication, and infectivity. PLoS pathogens 0 42113865
2025 Toxoplasma IMC1 is a central component of the subpellicular network and plays critical roles in parasite morphology, replication, and infectivity. bioRxiv : the preprint server for biology 0 40501855