{"gene":"PF3D7_1019900","run_date":"2026-09-08T12:51:28","timeline":{"discoveries":[{"year":2013,"finding":"P. falciparum ATG8 (PfATG8) requires its C-terminal glycine for association with autophagosome membranes and for localization to the apicoplast membrane and apicoplast-targeted vesicles; mutation of this glycine abolishes both localizations. Amino acid starvation provoked increased colocalization of PfATG8-labeled vesicles with PfRAB7, and acidification of co-labeled structures consistent with RAB7-mediated autophagosome maturation. Immuno-electron microscopy detected PfATG8 on double-membrane-bound vesicles and near/within the food vacuole, consistent with autophagosome fusion with the endosomal system.","method":"C-terminal glycine mutagenesis, immunofluorescence colocalization with PfRAB7, acidification assay, immuno-electron microscopy","journal":"Autophagy","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (mutagenesis, IFA colocalization, immuno-EM) in a single study, all supporting the same conclusion","pmids":["24025672"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2012,"finding":"P. falciparum ATG8 (PfAtg8) is expressed during intra-erythrocytic development and associates with membranes as a lipid-conjugated form. Fluorescence microscopy and immunoelectron microscopy demonstrate that PfAtg8 localizes to the apicoplast (a four-membrane-bound non-photosynthetic plastid). Autophagosome-like structures are not observed in the erythrocytic stages, suggesting the Atg8 conjugation system is used for the apicoplast rather than classical autophagy.","method":"Fluorescence microscopy, immunoelectron microscopy, membrane association/lipidation assay","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Strong — two orthogonal localization methods (fluorescence microscopy and immuno-EM) plus biochemical lipidation assay, replicated independently from PMID:24025672","pmids":["22900071"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2012,"finding":"The co-crystal structure of P. falciparum ATG8 (PfAtg8) with an Atg3 peptide (residues 103–110) was solved to 2.2 Å resolution, identifying an Atg8 family interacting motif (AIM) in PfAtg3 that binds PfAtg8. In vitro interaction studies confirmed the binding. A unique apicomplexan loop in PfAtg8 (absent from human Atg8 homologs) was found to be important for Atg3 binding. The full-length PfAtg8–PfAtg3 protein-protein interaction was inhibited at low micromolar concentrations by 1,2,3-trihydroxybenzene.","method":"X-ray crystallography (2.2 Å co-crystal structure), in vitro binding assay, small-molecule inhibition","journal":"Journal of structural biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with functional validation by in vitro binding and inhibitor studies in one study","pmids":["22982544"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2013,"finding":"PfATG8 localizes to the apicoplast and cytosolic vesicles throughout asexual and sexual erythrocytic stages. In apicoplast-minus parasites, immunofluorescence of PfATG8 is consistent with a role in apicoplast biogenesis. Treatment with the autophagy inhibitors bafilomycin A1 and chloroquine caused dramatic morphological changes to the apicoplast and parasite death. Deep proteomic analysis of PfATG8-associated components suggested possible involvement in ribophagy and piecemeal microautophagy of the nucleus.","method":"Immunofluorescence assay (IFA), pharmacological inhibition (bafilomycin A1, chloroquine), mass spectrometry-based proteomics of ATG8-associated proteins","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple methods in single lab; proteomic data are associative; nuclear/ribophagy roles not directly confirmed","pmids":["24275162"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2013,"finding":"In P. berghei liver-stage parasites, PbAtg8 localizes to the apicoplast. Relocalization of PbAtg8 to autophagosome-like vesicles was not observed in dying parasites, indicating that PbAtg8 function during liver stage is restricted to apicoplast biology rather than classical autophagic cell death.","method":"Immunofluorescence/live imaging of PbAtg8 in liver-stage parasites, examination of dying parasites","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiment with functional inference; single lab; negative result (no relocalization) is informative","pmids":["23388496"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2013,"finding":"The ATG8-conjugation system (PfATG8, PfATG3, PfATG7) is active across the P. falciparum lifecycle. In P. berghei liver stages, PbATG8 associates with the limiting membranes of the apicoplast, and this association increases as the apicoplast expands during hepatocyte replication. P. berghei ATG8 cannot functionally complement an atg8Δ yeast mutant, and does not localize to autophagosomes in starved mammalian cells, indicating a novel mechanism of interaction compared to other orthologs.","method":"Transgenic mCherry-PfATG8 expression across lifecycle stages, EM and colocalization studies in P. berghei, yeast complementation assay, mammalian cell autophagy assay","journal":"Autophagy","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods across two species, including functional complementation showing inability to replace yeast Atg8","pmids":["24342964"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium berghei","strain":""}]},{"year":2014,"finding":"In P. falciparum, PfAtg8 is found exclusively in the pellet (membrane) fraction as an integral membrane protein throughout asexual and sexual stages, in contrast to yeast/mammalian Atg8 which distributes between cytosolic and membrane fractions. Starvation decreased PfAtg8 levels ~3-fold. ATG8-associated puncta and expression were not altered by E64, pepstatin, 3-methyladenine, or chloroquine. PfAtg8 showed partial colocalization with the apicoplast; doxycycline-induced apicoplast disruption did not affect ATG8 localization.","method":"Subcellular fractionation, western blotting, immunofluorescence, pharmacological inhibitor treatment, doxycycline-mediated apicoplast disruption","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal biochemical and cell biological methods; single lab","pmids":["25426852"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2014,"finding":"Inhibitors of the PfAtg8–PfAtg3 protein-protein interaction were identified from the Malaria Medicine Venture Malaria Box using surface plasmon resonance. These inhibitors prevent PfAtg8 lipidation with phosphatidylethanolamine and inhibit P. falciparum growth in blood and liver stages.","method":"Surface plasmon resonance-based inhibitor screening, PfAtg8 lipidation assay, P. falciparum growth inhibition assay (blood stage and liver stage)","journal":"Journal of medicinal chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct biochemical lipidation assay plus parasite growth assay; single lab","pmids":["24786226"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"finding":"In P. berghei liver forms, overexpression of ATG8 impairs development into late liver stages and produces small merosomes with immature merozoites unable to establish blood infection. Micronemes were found to colocalize with PbATG8-containing structures before expulsion. PbATG8 overexpression caused delayed clearance of micronemes via ATG8-containing autophagosomes and abnormally fast apicoplast proliferation followed by apicoplast collapse. PbATG8 was not incorporated into the progeny of mutant parasites.","method":"ATG8 overexpression (gain-of-function transgenic line), immunostaining (ACP for apicoplast, microneme markers), colocalization analysis, mouse infectivity assay","journal":"mBio","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple organelle phenotypes assessed with orthogonal markers; functional consequence (loss of infectivity) confirmed in vivo; single lab with rigorous controls","pmids":["27353755"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2017,"finding":"P. falciparum ATG18 (PfATG18) regulates membrane association and apicoplast localization of ATG8. Conditional knockdown of PfATG18 results in loss of the apicoplast, and its interaction with phosphatidylinositol 3-phosphate (PI3P) is critical for apicoplast inheritance and for proper ATG8 apicoplast localization.","method":"Conditional knockdown of PfATG18, immunofluorescence of ATG8 localization, PI3P interaction assay","journal":"mBio","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis experiment placing ATG18 upstream of ATG8 membrane association; single lab; ATG8 localization is a downstream readout","pmids":["29089429"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2017,"finding":"P. falciparum OTU-like cysteine protease (PfOTU) provides evidence of a biological function in membrane deconjugation (delipidation) of ATG8, which may be linked to apicoplast protein import. Knockdown of PfOTU resulted in abnormal apicoplast development.","method":"Degradation-tag-mediated knockdown of PfOTU, immunofluorescence of apicoplast markers, isoprenoid (IPP) rescue experiment","journal":"Cellular microbiology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — functional knockdown with apicoplast phenotype; ATG8 deconjugation role inferred from deconjugation assay; single lab","pmids":["28423214"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"finding":"Conditional depletion of P. falciparum ATG8 (PfATG8) is lethal to blood-stage parasites, and this growth inhibition is fully rescued by isopentenyl pyrophosphate (IPP), which rescues apicoplast metabolic defects. IPP-rescued, ATG8-depleted parasites lose their apicoplast. Loss of ATG8 does not affect apicoplast protein import or membrane expansion but prevents apicoplast inheritance by daughter parasites, establishing that PfATG8's essential function is specifically in apicoplast fission/segregation during replication, not in autophagy.","method":"Conditional expression regulation, IPP rescue assay, fluorescence in situ hybridization (FISH) for apicoplast genome, apicoplast protein import assay, membrane expansion assay, apicoplast inheritance assay","journal":"mBio","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional knockdown with IPP rescue epistasis, multiple orthogonal functional assays (FISH, import, membrane expansion, inheritance); single lab but multiple methods with rigorous controls","pmids":["29295911"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"finding":"Virtual library screening targeting the unique apicomplexan A-loop of PfAtg8, which mediates PfAtg3 binding and is absent from human Atg8 homologs, identified small molecules that inhibit the PfAtg8–PfAtg3 interaction, shift the lipidation state of PfAtg8, and inhibit P. falciparum growth in blood and liver stages.","method":"Virtual screening targeting PfAtg8 A-loop, PfAtg8 lipidation state assay, P. falciparum blood- and liver-stage growth inhibition assay","journal":"ChemMedChem","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — structure-guided design with direct lipidation assay and parasite growth readout; single lab","pmids":["26748931"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2023,"finding":"In P. berghei, Atg4 is the primary deconjugating (delipidating) enzyme for ATG8; Atg4 KO sporozoites showed elevated ATG8 levels and impaired ATG8 deconjugation. Atg4 KO sporozoites invade hepatocytes and develop into early liver stages normally but fail to complete nuclear and organelle differentiation, unable to mature into hepatic merozoites. OTU (Otu) can partially compensate for deconjugation but cleaves at the N-terminal side of glycine, thereby irreversibly inactivating ATG8 rather than recycling it. Simultaneous deletion of both Atg4 and Otu was lethal, confirming their combined essentiality for ATG8 deconjugation.","method":"Gene disruption (individual KO of Atg4 and Otu; simultaneous double-KO refractory), in vitro and in vivo ATG8 deconjugation assay, western blot for ATG8 levels, mouse sporozoite infection assay","journal":"Cellular and molecular life sciences : CMLS","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean individual and attempted double KO with biochemical deconjugation assay and in vivo phenotype; mechanistic distinction between Atg4 and Otu cleavage sites established","pmids":["37910326"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2023,"finding":"Functional complementation experiments in P. falciparum showed that the LC3-interacting region (LIR) docking site (LDS) of PfATG8 is required for apicoplast localization and function, likely via ATG8 lipidation. The N-terminal helix of PfATG8 is dispensable for apicoplast-specific function. The unique apicomplexan-specific loop, previously implicated in membrane conjugation machinery interaction in vitro, is not required for membrane conjugation or apicoplast-specific effector function in P. falciparum or Toxoplasma gondii.","method":"Functional complementation with ATG8 domain mutants, apicoplast localization assay, lipidation assay","journal":"mBio","confidence":"High","confidence_rationale":"Tier 1 / Strong — mutagenesis-based structure-function analysis with functional complementation and direct lipidation/localization readouts; tested in two apicomplexan species","pmids":["36625582"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Toxoplasma gondii","strain":""}]},{"year":2024,"finding":"In P. berghei, Atg7 (E1-like enzyme) is essential for ATG8 lipidation onto membranes. Depletion of Atg7 abolishes ATG8 membrane localization and lipidation, impairs microneme exocytosis, and blocks organelle biogenesis and merozoite formation during liver-stage development. Atg7 is also required for blood-stage parasite development.","method":"Conditional knockdown of Atg7 (degradation-tag system), western blot for ATG8 lipidation, immunofluorescence for ATG8 membrane localization and organelle markers, microneme exocytosis assay, blood and liver stage growth assay","journal":"mBio","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO with direct lipidation assay plus multiple downstream phenotypic readouts; Atg7 placed upstream of ATG8 membrane conjugation","pmids":["39714137"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2018,"finding":"PfAtg8 is expressed in intraerythrocytic stages and basal autophagy is constitutively active, mediating intraerythrocytic development and RBC re-invasion. PfAtg8 shows punctate localization throughout the parasite and responds to both autophagy inducers and inhibitors. PfAtg8 partially colocalizes with PfAtg5, which itself is present on double-membrane-bound vesicles and partially colocalizes with ER, mitochondria, and apicoplast.","method":"Immunofluorescence, western blot for autophagy protein expression, autophagy induction/inhibition assays, colocalization analysis","journal":"Cell death discovery","confidence":"Low","confidence_rationale":"Tier 3 / Weak — descriptive colocalization and expression assays; single lab; no direct mechanistic experiment specific to ATG8 beyond what prior papers established","pmids":["30302277"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2013,"finding":"Distribution of PfATG8 immunofluorescence signal differs between chloroquine-sensitive and chloroquine-resistant trophozoite-stage P. falciparum parasites at LD50 (cytocidal) but not IC50 (cytostatic) concentrations, suggesting an autophagy-like process is altered in chloroquine-resistant parasites.","method":"Indirect immunofluorescence of PfATG8 in synchronized CQS vs CQR trophozoites, quantitative trait loci analysis","journal":"PloS one","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single IFA comparison with no functional mechanistic follow-up; association rather than mechanism","pmids":["24278114"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2034,"finding":"In P. berghei liver stage, GRASP associates with PbATG8-containing autophagosomes that contain micronemes; however, GRASP-KO parasites can still expel micronemes, indicating GRASP is not strictly required for ATG8-autophagosome-mediated microneme clearance.","method":"GRASP gene knockout, colocalization of GRASP with PbATG8-positive autophagosomes, microneme expulsion assay in KO parasites","journal":"Molecular microbiology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — colocalization with ATG8 established but functional role of ATG8 itself not directly probed; finding is primarily about GRASP","pmids":["40143578"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]}],"current_model":"P. falciparum ATG8 (PF3D7_1019900) is a ubiquitin-like protein that is constitutively lipidated (conjugated to phosphatidylethanolamine) and membrane-associated in intraerythrocytic parasites; its C-terminal glycine and the LIR docking site (LDS) are required for membrane association and apicoplast localization, while its N-terminal helix and the unique apicomplexan-specific loop are dispensable for apicoplast function. ATG8 lipidation is catalyzed by the E1-like enzyme Atg7, which loads ATG8 onto the E2-like enzyme Atg3 via an AIM motif interaction whose co-crystal structure has been solved at 2.2 Å; membrane deconjugation is performed primarily by the cysteine protease Atg4, with OTU providing partial but irreversible (inactivating) compensation. In blood-stage parasites, the only essential function of ATG8 is in apicoplast inheritance (fission/segregation to daughter parasites), not in canonical autophagy or protein import; in liver-stage parasites, ATG8 additionally mediates microneme clearance via autophagosome-like structures and apicoplast biogenesis, with dysregulation of ATG8 levels being detrimental to merozoite maturation and infectivity."},"narrative":{"mechanistic_narrative":"ATG8 (PF3D7_1019900) is a ubiquitin-like protein of Plasmodium falciparum that, in contrast to its yeast and mammalian counterparts, functions predominantly in apicoplast biology rather than canonical autophagy during blood-stage development [PMID:22900071, PMID:29295911]. In intraerythrocytic parasites it exists almost exclusively as a membrane-associated, phosphatidylethanolamine-conjugated (lipidated) form and localizes to the apicoplast, a four-membrane plastid, with no accumulation of classical autophagosome-like structures [PMID:22900071, PMID:25426852]. Membrane association and apicoplast targeting depend on its C-terminal glycine and its LIR docking site (LDS), whereas the N-terminal helix and the apicomplexan-specific loop are dispensable for apicoplast-specific function [PMID:24025672, PMID:36625582]. Conditional depletion is lethal to blood-stage parasites and is fully rescued by isopentenyl pyrophosphate; ATG8-depleted parasites lose the apicoplast without defects in protein import or membrane expansion, establishing that its sole essential blood-stage role is in apicoplast inheritance—fission and segregation to daughter parasites [PMID:29295911]. Lipidation is executed by an ATG8 conjugation system in which the E1-like enzyme Atg7 (P. berghei) loads ATG8 onto the E2-like Atg3, engaged through an Atg8-family-interacting (AIM) motif whose PfATG8–PfAtg3 co-crystal structure was solved to 2.2 Å [PMID:22982544, PMID:39714137]; membrane deconjugation is performed principally by the cysteine protease Atg4, with OTU providing partial but irreversible compensation (P. berghei) [PMID:37910326]. Upstream, PfATG18 acting through its PI3P interaction controls ATG8 membrane association and apicoplast inheritance [PMID:29089429]. In liver-stage parasites, ATG8 additionally participates in microneme clearance via autophagosome-like structures and apicoplast biogenesis, and dysregulation of ATG8 levels impairs merozoite maturation and infectivity [PMID:27353755, PMID:39714137]. The PfATG8–PfAtg3 interface and the apicomplexan-specific loop have been exploited as antimalarial targets [PMID:24786226, PMID:26748931].","teleology":[{"year":2012,"claim":"Established that ATG8 in P. falciparum is a lipidated, membrane-associated protein directed to the apicoplast rather than to classical autophagosomes, redefining its expected function away from canonical autophagy.","evidence":"Fluorescence and immuno-EM localization plus membrane lipidation assay in intraerythrocytic parasites","pmids":["22900071"],"confidence":"High","gaps":["Did not define which enzymes catalyze lipidation","Did not establish the essential function of the apicoplast localization"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2012,"claim":"Resolved the structural basis of how ATG8 is engaged by the conjugation machinery, identifying an AIM in Atg3 and a unique apicomplexan loop as the binding interface.","evidence":"2.2 Å co-crystal structure of PfATG8 with an Atg3 peptide, in vitro binding, and small-molecule inhibition","pmids":["22982544"],"confidence":"High","gaps":["Whether the apicomplexan loop is required in vivo was not tested","Structure did not address lipidation on membranes"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2013,"claim":"Defined the C-terminal glycine as the determinant of ATG8 membrane and apicoplast association, and documented starvation-responsive autophagosome-like structures, framing dual apicoplast and autophagy-associated roles.","evidence":"C-terminal glycine mutagenesis, colocalization with RAB7, acidification assays, and immuno-EM in P. falciparum","pmids":["24025672","24275162"],"confidence":"High","gaps":["Whether starvation-induced vesicle behavior reflects an essential function was not resolved","Proteomic ribophagy/nucleophagy associations were not functionally confirmed"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2013,"claim":"Showed that the parasite ATG8 system is functionally divergent from other orthologs and restricted to apicoplast biology in liver stages, not autophagic cell death.","evidence":"Transgenic expression across the P. falciparum lifecycle, EM in P. berghei liver stages, yeast complementation, and mammalian autophagy assays","pmids":["24342964","23388496"],"confidence":"High","gaps":["Mechanism of the novel interaction with membranes not defined","Did not distinguish apicoplast biogenesis from inheritance"],"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium berghei","strain":""}]},{"year":2014,"claim":"Confirmed ATG8 as a constitutively membrane-integral protein distinct from the cytosol/membrane equilibrium of other orthologs and largely insensitive to autophagy inhibitors.","evidence":"Subcellular fractionation, western blot, IFA, and pharmacological/doxycycline perturbation in P. falciparum","pmids":["25426852"],"confidence":"Medium","gaps":["Partial apicoplast colocalization left additional membrane pools unexplained","Did not test essentiality directly"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2014,"claim":"Validated the ATG8–Atg3 interaction and ATG8 lipidation as druggable antimalarial nodes acting in both blood and liver stages.","evidence":"SPR-based inhibitor screening, lipidation assay, and blood/liver-stage growth inhibition (Malaria Box)","pmids":["24786226"],"confidence":"Medium","gaps":["Cellular target engagement not directly proven","Selectivity over host homologs not fully established"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"claim":"Demonstrated that ATG8 levels must be tightly balanced: overexpression drives aberrant microneme clearance and apicoplast collapse, blocking liver-stage maturation and infectivity.","evidence":"ATG8 gain-of-function transgenic P. berghei with organelle-marker imaging and mouse infectivity assays","pmids":["27353755"],"confidence":"High","gaps":["Whether microneme clearance is a physiological ATG8 function or an overexpression artifact","Molecular link between ATG8 dosage and apicoplast collapse unresolved"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2016,"claim":"Confirmed the apicomplexan A-loop as an exploitable, host-divergent target by structure-guided inhibitors that block ATG8–Atg3 binding and shift ATG8 lipidation.","evidence":"Virtual screening against the PfATG8 A-loop, lipidation-state assay, and blood/liver-stage growth inhibition","pmids":["26748931"],"confidence":"Medium","gaps":["In vivo efficacy not established","Later work questioned the A-loop's functional requirement in vivo"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2017,"claim":"Placed PfATG18 upstream of ATG8, showing that PI3P-dependent ATG18 controls ATG8 membrane/apicoplast localization and apicoplast inheritance.","evidence":"Conditional knockdown of PfATG18, ATG8 localization readout, and PI3P interaction assay","pmids":["29089429"],"confidence":"Medium","gaps":["Direct biochemical interaction between ATG18 and ATG8 not shown","ATG8 localization is an indirect downstream readout"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2017,"claim":"Identified OTU as an ATG8 deconjugating (delipidating) protease linked to apicoplast development, extending the enzymatic control of ATG8 turnover.","evidence":"Degradation-tag knockdown of PfOTU, apicoplast marker IFA, deconjugation assay, and IPP rescue","pmids":["28423214"],"confidence":"Medium","gaps":["Relationship between OTU and Atg4 not resolved here","Deconjugation role inferred rather than shown to be primary"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"claim":"Established the single essential blood-stage function of ATG8 as apicoplast inheritance (fission/segregation), decoupled from autophagy, protein import, and membrane expansion.","evidence":"Conditional depletion with IPP rescue, apicoplast FISH, import, membrane expansion, and inheritance assays in P. falciparum","pmids":["29295911"],"confidence":"High","gaps":["Molecular mechanism by which ATG8 drives fission/segregation unknown","Interactors executing segregation not identified"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2023,"claim":"Defined the enzymatic logic of ATG8 deconjugation, showing Atg4 as the primary delipidase required for liver-stage differentiation and OTU as an irreversible, non-recycling backup.","evidence":"Individual and attempted double KO of Atg4 and Otu in P. berghei, ATG8 deconjugation assays, western blot, and sporozoite infection","pmids":["37910326"],"confidence":"High","gaps":["Timing/spatial regulation of deconjugation during replication unclear","Whether irreversible OTU cleavage serves a distinct signaling role unknown"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2023,"claim":"Mapped the structural determinants of ATG8's apicoplast function, showing the LDS is required and the N-terminal helix and apicomplexan loop are dispensable in vivo, overturning the earlier in vitro emphasis on the loop.","evidence":"Functional complementation with ATG8 domain mutants, apicoplast localization, and lipidation assays in P. falciparum and T. gondii","pmids":["36625582"],"confidence":"High","gaps":["Identity of LDS-binding effectors mediating apicoplast function not defined","Reconciliation with A-loop inhibitor strategy not fully resolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Toxoplasma gondii","strain":""}]},{"year":2024,"claim":"Placed the E1-like Atg7 at the apex of ATG8 lipidation, showing it is required for ATG8 membrane conjugation and for downstream microneme exocytosis, organelle biogenesis, and merozoite formation.","evidence":"Conditional knockdown of Atg7 in P. berghei with lipidation western blots, ATG8/organelle IFA, and blood/liver-stage growth assays","pmids":["39714137"],"confidence":"High","gaps":["Whether Atg7 has ATG8-independent activities not resolved","Coupling between lipidation and specific effector recruitment unmapped"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":null,"claim":"The molecular mechanism by which lipidated, LDS-competent ATG8 drives apicoplast fission and segregation—and the effectors it recruits at the apicoplast membrane—remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No ATG8 effector proteins executing apicoplast fission identified","Mechanistic link between LDS engagement and organelle division unknown","Species-divergent liver-stage microneme role not mechanistically integrated with the blood-stage inheritance role"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["ATG8 conjugation system (ATG8–Atg7–Atg3)"],"partners":["ATG3 (E2-LIKE; AIM/A-LOOP INTERACTION, CO-CRYSTAL STRUCTURE) [#2, #14]","ATG7 (E1-LIKE ACTIVATING ENZYME; P. BERGHEI) [#15]","ATG4 (PRIMARY DECONJUGATING CYSTEINE PROTEASE; P. BERGHEI) [#13]","OTU (BACKUP DECONJUGATING PROTEASE, IRREVERSIBLE CLEAVAGE) [#10, #13]","PFATG18 (PI3P-DEPENDENT, UPSTREAM REGULATOR OF ATG8 MEMBRANE ASSOCIATION) [#9]","PFRAB7 (COLOCALIZATION ON MATURING VESICLES) [#0]","PFATG5 (PARTIAL COLOCALIZATION) [#16]","GRASP (COLOCALIZES WITH ATG8-POSITIVE AUTOPHAGOSOMES; P. BERGHEI) [#18]"],"other_free_text":["Constitutively lipidated (PE-conjugated) and membrane-integral in intraerythrocytic stages, unlike cytosol/membrane-partitioning yeast and mammalian orthologs [#1, #6].","Sole essential blood-stage function is apicoplast inheritance (fission/segregation); dispensable for apicoplast protein import and membrane expansion [#11].","Depletion lethality is rescued by isopentenyl pyrophosphate, marking an apicoplast metabolic dependency [#11].","C-terminal glycine and LDS required for apicoplast localization; N-terminal helix and apicomplexan-specific loop dispensable in vivo [#0, #14].","Liver-stage roles include microneme clearance via autophagosome-like structures and apicoplast biogenesis; ATG8 dosage must be balanced for merozoite maturation [#8, #15].","PfATG8–PfAtg3 interface and the apicomplexan A-loop are validated antimalarial drug targets [#7, #12].","Cannot complement yeast atg8Δ and does not localize to autophagosomes in starved mammalian cells, indicating a divergent mechanism [#5]."]}},"prefetch_data":{},"corpus_meta":[{"pmid":"24025672","id":"PMC_24025672","title":"Plasmodium falciparum ATG8 implicated in both autophagy and apicoplast formation.","date":"2013","source":"Autophagy","url":"https://pubmed.ncbi.nlm.nih.gov/24025672","citation_count":79,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ATG8","PfATG8"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"22900071","id":"PMC_22900071","title":"Autophagy-related Atg8 localizes to the apicoplast of the human malaria parasite Plasmodium falciparum.","date":"2012","source":"PloS 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glycine abolishes both localizations. Amino acid starvation provoked increased colocalization of PfATG8-labeled vesicles with PfRAB7, and acidification of co-labeled structures consistent with RAB7-mediated autophagosome maturation. Immuno-electron microscopy detected PfATG8 on double-membrane-bound vesicles and near/within the food vacuole, consistent with autophagosome fusion with the endosomal system.\",\n      \"method\": \"C-terminal glycine mutagenesis, immunofluorescence colocalization with PfRAB7, acidification assay, immuno-electron microscopy\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (mutagenesis, IFA colocalization, immuno-EM) in a single study, all supporting the same conclusion\",\n      \"pmids\": [\"24025672\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"P. falciparum ATG8 (PfAtg8) is expressed during intra-erythrocytic development and associates with membranes as a lipid-conjugated form. Fluorescence microscopy and immunoelectron microscopy demonstrate that PfAtg8 localizes to the apicoplast (a four-membrane-bound non-photosynthetic plastid). Autophagosome-like structures are not observed in the erythrocytic stages, suggesting the Atg8 conjugation system is used for the apicoplast rather than classical autophagy.\",\n      \"method\": \"Fluorescence microscopy, immunoelectron microscopy, membrane association/lipidation assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two orthogonal localization methods (fluorescence microscopy and immuno-EM) plus biochemical lipidation assay, replicated independently from PMID:24025672\",\n      \"pmids\": [\"22900071\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The co-crystal structure of P. falciparum ATG8 (PfAtg8) with an Atg3 peptide (residues 103–110) was solved to 2.2 Å resolution, identifying an Atg8 family interacting motif (AIM) in PfAtg3 that binds PfAtg8. In vitro interaction studies confirmed the binding. A unique apicomplexan loop in PfAtg8 (absent from human Atg8 homologs) was found to be important for Atg3 binding. The full-length PfAtg8–PfAtg3 protein-protein interaction was inhibited at low micromolar concentrations by 1,2,3-trihydroxybenzene.\",\n      \"method\": \"X-ray crystallography (2.2 Å co-crystal structure), in vitro binding assay, small-molecule inhibition\",\n      \"journal\": \"Journal of structural biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with functional validation by in vitro binding and inhibitor studies in one study\",\n      \"pmids\": [\"22982544\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PfATG8 localizes to the apicoplast and cytosolic vesicles throughout asexual and sexual erythrocytic stages. In apicoplast-minus parasites, immunofluorescence of PfATG8 is consistent with a role in apicoplast biogenesis. Treatment with the autophagy inhibitors bafilomycin A1 and chloroquine caused dramatic morphological changes to the apicoplast and parasite death. Deep proteomic analysis of PfATG8-associated components suggested possible involvement in ribophagy and piecemeal microautophagy of the nucleus.\",\n      \"method\": \"Immunofluorescence assay (IFA), pharmacological inhibition (bafilomycin A1, chloroquine), mass spectrometry-based proteomics of ATG8-associated proteins\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple methods in single lab; proteomic data are associative; nuclear/ribophagy roles not directly confirmed\",\n      \"pmids\": [\"24275162\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"In P. berghei liver-stage parasites, PbAtg8 localizes to the apicoplast. Relocalization of PbAtg8 to autophagosome-like vesicles was not observed in dying parasites, indicating that PbAtg8 function during liver stage is restricted to apicoplast biology rather than classical autophagic cell death.\",\n      \"method\": \"Immunofluorescence/live imaging of PbAtg8 in liver-stage parasites, examination of dying parasites\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiment with functional inference; single lab; negative result (no relocalization) is informative\",\n      \"pmids\": [\"23388496\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The ATG8-conjugation system (PfATG8, PfATG3, PfATG7) is active across the P. falciparum lifecycle. In P. berghei liver stages, PbATG8 associates with the limiting membranes of the apicoplast, and this association increases as the apicoplast expands during hepatocyte replication. P. berghei ATG8 cannot functionally complement an atg8Δ yeast mutant, and does not localize to autophagosomes in starved mammalian cells, indicating a novel mechanism of interaction compared to other orthologs.\",\n      \"method\": \"Transgenic mCherry-PfATG8 expression across lifecycle stages, EM and colocalization studies in P. berghei, yeast complementation assay, mammalian cell autophagy assay\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods across two species, including functional complementation showing inability to replace yeast Atg8\",\n      \"pmids\": [\"24342964\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"},\n        {\"species\": \"Plasmodium berghei\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"In P. falciparum, PfAtg8 is found exclusively in the pellet (membrane) fraction as an integral membrane protein throughout asexual and sexual stages, in contrast to yeast/mammalian Atg8 which distributes between cytosolic and membrane fractions. Starvation decreased PfAtg8 levels ~3-fold. ATG8-associated puncta and expression were not altered by E64, pepstatin, 3-methyladenine, or chloroquine. PfAtg8 showed partial colocalization with the apicoplast; doxycycline-induced apicoplast disruption did not affect ATG8 localization.\",\n      \"method\": \"Subcellular fractionation, western blotting, immunofluorescence, pharmacological inhibitor treatment, doxycycline-mediated apicoplast disruption\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal biochemical and cell biological methods; single lab\",\n      \"pmids\": [\"25426852\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Inhibitors of the PfAtg8–PfAtg3 protein-protein interaction were identified from the Malaria Medicine Venture Malaria Box using surface plasmon resonance. These inhibitors prevent PfAtg8 lipidation with phosphatidylethanolamine and inhibit P. falciparum growth in blood and liver stages.\",\n      \"method\": \"Surface plasmon resonance-based inhibitor screening, PfAtg8 lipidation assay, P. falciparum growth inhibition assay (blood stage and liver stage)\",\n      \"journal\": \"Journal of medicinal chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct biochemical lipidation assay plus parasite growth assay; single lab\",\n      \"pmids\": [\"24786226\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"In P. berghei liver forms, overexpression of ATG8 impairs development into late liver stages and produces small merosomes with immature merozoites unable to establish blood infection. Micronemes were found to colocalize with PbATG8-containing structures before expulsion. PbATG8 overexpression caused delayed clearance of micronemes via ATG8-containing autophagosomes and abnormally fast apicoplast proliferation followed by apicoplast collapse. PbATG8 was not incorporated into the progeny of mutant parasites.\",\n      \"method\": \"ATG8 overexpression (gain-of-function transgenic line), immunostaining (ACP for apicoplast, microneme markers), colocalization analysis, mouse infectivity assay\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple organelle phenotypes assessed with orthogonal markers; functional consequence (loss of infectivity) confirmed in vivo; single lab with rigorous controls\",\n      \"pmids\": [\"27353755\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"P. falciparum ATG18 (PfATG18) regulates membrane association and apicoplast localization of ATG8. Conditional knockdown of PfATG18 results in loss of the apicoplast, and its interaction with phosphatidylinositol 3-phosphate (PI3P) is critical for apicoplast inheritance and for proper ATG8 apicoplast localization.\",\n      \"method\": \"Conditional knockdown of PfATG18, immunofluorescence of ATG8 localization, PI3P interaction assay\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis experiment placing ATG18 upstream of ATG8 membrane association; single lab; ATG8 localization is a downstream readout\",\n      \"pmids\": [\"29089429\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"P. falciparum OTU-like cysteine protease (PfOTU) provides evidence of a biological function in membrane deconjugation (delipidation) of ATG8, which may be linked to apicoplast protein import. Knockdown of PfOTU resulted in abnormal apicoplast development.\",\n      \"method\": \"Degradation-tag-mediated knockdown of PfOTU, immunofluorescence of apicoplast markers, isoprenoid (IPP) rescue experiment\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — functional knockdown with apicoplast phenotype; ATG8 deconjugation role inferred from deconjugation assay; single lab\",\n      \"pmids\": [\"28423214\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Conditional depletion of P. falciparum ATG8 (PfATG8) is lethal to blood-stage parasites, and this growth inhibition is fully rescued by isopentenyl pyrophosphate (IPP), which rescues apicoplast metabolic defects. IPP-rescued, ATG8-depleted parasites lose their apicoplast. Loss of ATG8 does not affect apicoplast protein import or membrane expansion but prevents apicoplast inheritance by daughter parasites, establishing that PfATG8's essential function is specifically in apicoplast fission/segregation during replication, not in autophagy.\",\n      \"method\": \"Conditional expression regulation, IPP rescue assay, fluorescence in situ hybridization (FISH) for apicoplast genome, apicoplast protein import assay, membrane expansion assay, apicoplast inheritance assay\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional knockdown with IPP rescue epistasis, multiple orthogonal functional assays (FISH, import, membrane expansion, inheritance); single lab but multiple methods with rigorous controls\",\n      \"pmids\": [\"29295911\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Virtual library screening targeting the unique apicomplexan A-loop of PfAtg8, which mediates PfAtg3 binding and is absent from human Atg8 homologs, identified small molecules that inhibit the PfAtg8–PfAtg3 interaction, shift the lipidation state of PfAtg8, and inhibit P. falciparum growth in blood and liver stages.\",\n      \"method\": \"Virtual screening targeting PfAtg8 A-loop, PfAtg8 lipidation state assay, P. falciparum blood- and liver-stage growth inhibition assay\",\n      \"journal\": \"ChemMedChem\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — structure-guided design with direct lipidation assay and parasite growth readout; single lab\",\n      \"pmids\": [\"26748931\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"In P. berghei, Atg4 is the primary deconjugating (delipidating) enzyme for ATG8; Atg4 KO sporozoites showed elevated ATG8 levels and impaired ATG8 deconjugation. Atg4 KO sporozoites invade hepatocytes and develop into early liver stages normally but fail to complete nuclear and organelle differentiation, unable to mature into hepatic merozoites. OTU (Otu) can partially compensate for deconjugation but cleaves at the N-terminal side of glycine, thereby irreversibly inactivating ATG8 rather than recycling it. Simultaneous deletion of both Atg4 and Otu was lethal, confirming their combined essentiality for ATG8 deconjugation.\",\n      \"method\": \"Gene disruption (individual KO of Atg4 and Otu; simultaneous double-KO refractory), in vitro and in vivo ATG8 deconjugation assay, western blot for ATG8 levels, mouse sporozoite infection assay\",\n      \"journal\": \"Cellular and molecular life sciences : CMLS\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean individual and attempted double KO with biochemical deconjugation assay and in vivo phenotype; mechanistic distinction between Atg4 and Otu cleavage sites established\",\n      \"pmids\": [\"37910326\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Functional complementation experiments in P. falciparum showed that the LC3-interacting region (LIR) docking site (LDS) of PfATG8 is required for apicoplast localization and function, likely via ATG8 lipidation. The N-terminal helix of PfATG8 is dispensable for apicoplast-specific function. The unique apicomplexan-specific loop, previously implicated in membrane conjugation machinery interaction in vitro, is not required for membrane conjugation or apicoplast-specific effector function in P. falciparum or Toxoplasma gondii.\",\n      \"method\": \"Functional complementation with ATG8 domain mutants, apicoplast localization assay, lipidation assay\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mutagenesis-based structure-function analysis with functional complementation and direct lipidation/localization readouts; tested in two apicomplexan species\",\n      \"pmids\": [\"36625582\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"},\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"In P. berghei, Atg7 (E1-like enzyme) is essential for ATG8 lipidation onto membranes. Depletion of Atg7 abolishes ATG8 membrane localization and lipidation, impairs microneme exocytosis, and blocks organelle biogenesis and merozoite formation during liver-stage development. Atg7 is also required for blood-stage parasite development.\",\n      \"method\": \"Conditional knockdown of Atg7 (degradation-tag system), western blot for ATG8 lipidation, immunofluorescence for ATG8 membrane localization and organelle markers, microneme exocytosis assay, blood and liver stage growth assay\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO with direct lipidation assay plus multiple downstream phenotypic readouts; Atg7 placed upstream of ATG8 membrane conjugation\",\n      \"pmids\": [\"39714137\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PfAtg8 is expressed in intraerythrocytic stages and basal autophagy is constitutively active, mediating intraerythrocytic development and RBC re-invasion. PfAtg8 shows punctate localization throughout the parasite and responds to both autophagy inducers and inhibitors. PfAtg8 partially colocalizes with PfAtg5, which itself is present on double-membrane-bound vesicles and partially colocalizes with ER, mitochondria, and apicoplast.\",\n      \"method\": \"Immunofluorescence, western blot for autophagy protein expression, autophagy induction/inhibition assays, colocalization analysis\",\n      \"journal\": \"Cell death discovery\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — descriptive colocalization and expression assays; single lab; no direct mechanistic experiment specific to ATG8 beyond what prior papers established\",\n      \"pmids\": [\"30302277\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Distribution of PfATG8 immunofluorescence signal differs between chloroquine-sensitive and chloroquine-resistant trophozoite-stage P. falciparum parasites at LD50 (cytocidal) but not IC50 (cytostatic) concentrations, suggesting an autophagy-like process is altered in chloroquine-resistant parasites.\",\n      \"method\": \"Indirect immunofluorescence of PfATG8 in synchronized CQS vs CQR trophozoites, quantitative trait loci analysis\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single IFA comparison with no functional mechanistic follow-up; association rather than mechanism\",\n      \"pmids\": [\"24278114\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2034,\n      \"finding\": \"In P. berghei liver stage, GRASP associates with PbATG8-containing autophagosomes that contain micronemes; however, GRASP-KO parasites can still expel micronemes, indicating GRASP is not strictly required for ATG8-autophagosome-mediated microneme clearance.\",\n      \"method\": \"GRASP gene knockout, colocalization of GRASP with PbATG8-positive autophagosomes, microneme expulsion assay in KO parasites\",\n      \"journal\": \"Molecular microbiology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — colocalization with ATG8 established but functional role of ATG8 itself not directly probed; finding is primarily about GRASP\",\n      \"pmids\": [\"40143578\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"P. falciparum ATG8 (PF3D7_1019900) is a ubiquitin-like protein that is constitutively lipidated (conjugated to phosphatidylethanolamine) and membrane-associated in intraerythrocytic parasites; its C-terminal glycine and the LIR docking site (LDS) are required for membrane association and apicoplast localization, while its N-terminal helix and the unique apicomplexan-specific loop are dispensable for apicoplast function. ATG8 lipidation is catalyzed by the E1-like enzyme Atg7, which loads ATG8 onto the E2-like enzyme Atg3 via an AIM motif interaction whose co-crystal structure has been solved at 2.2 Å; membrane deconjugation is performed primarily by the cysteine protease Atg4, with OTU providing partial but irreversible (inactivating) compensation. In blood-stage parasites, the only essential function of ATG8 is in apicoplast inheritance (fission/segregation to daughter parasites), not in canonical autophagy or protein import; in liver-stage parasites, ATG8 additionally mediates microneme clearance via autophagosome-like structures and apicoplast biogenesis, with dysregulation of ATG8 levels being detrimental to merozoite maturation and infectivity.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ATG8 (PF3D7_1019900) is a ubiquitin-like protein of Plasmodium falciparum that, in contrast to its yeast and mammalian counterparts, functions predominantly in apicoplast biology rather than canonical autophagy during blood-stage development [#1, #11]. In intraerythrocytic parasites it exists almost exclusively as a membrane-associated, phosphatidylethanolamine-conjugated (lipidated) form and localizes to the apicoplast, a four-membrane plastid, with no accumulation of classical autophagosome-like structures [#1, #6]. Membrane association and apicoplast targeting depend on its C-terminal glycine and its LIR docking site (LDS), whereas the N-terminal helix and the apicomplexan-specific loop are dispensable for apicoplast-specific function [#0, #14]. Conditional depletion is lethal to blood-stage parasites and is fully rescued by isopentenyl pyrophosphate; ATG8-depleted parasites lose the apicoplast without defects in protein import or membrane expansion, establishing that its sole essential blood-stage role is in apicoplast inheritance—fission and segregation to daughter parasites [#11]. Lipidation is executed by an ATG8 conjugation system in which the E1-like enzyme Atg7 (P. berghei) loads ATG8 onto the E2-like Atg3, engaged through an Atg8-family-interacting (AIM) motif whose PfATG8–PfAtg3 co-crystal structure was solved to 2.2 Å [#2, #15]; membrane deconjugation is performed principally by the cysteine protease Atg4, with OTU providing partial but irreversible compensation (P. berghei) [#13]. Upstream, PfATG18 acting through its PI3P interaction controls ATG8 membrane association and apicoplast inheritance [#9]. In liver-stage parasites, ATG8 additionally participates in microneme clearance via autophagosome-like structures and apicoplast biogenesis, and dysregulation of ATG8 levels impairs merozoite maturation and infectivity [#8, #15]. The PfATG8–PfAtg3 interface and the apicomplexan-specific loop have been exploited as antimalarial targets [#7, #12].\",\n  \"teleology\": [\n    {\n      \"year\": 2012,\n      \"claim\": \"Established that ATG8 in P. falciparum is a lipidated, membrane-associated protein directed to the apicoplast rather than to classical autophagosomes, redefining its expected function away from canonical autophagy.\",\n      \"evidence\": \"Fluorescence and immuno-EM localization plus membrane lipidation assay in intraerythrocytic parasites\",\n      \"pmids\": [\"22900071\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define which enzymes catalyze lipidation\", \"Did not establish the essential function of the apicoplast localization\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Resolved the structural basis of how ATG8 is engaged by the conjugation machinery, identifying an AIM in Atg3 and a unique apicomplexan loop as the binding interface.\",\n      \"evidence\": \"2.2 Å co-crystal structure of PfATG8 with an Atg3 peptide, in vitro binding, and small-molecule inhibition\",\n      \"pmids\": [\"22982544\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the apicomplexan loop is required in vivo was not tested\", \"Structure did not address lipidation on membranes\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined the C-terminal glycine as the determinant of ATG8 membrane and apicoplast association, and documented starvation-responsive autophagosome-like structures, framing dual apicoplast and autophagy-associated roles.\",\n      \"evidence\": \"C-terminal glycine mutagenesis, colocalization with RAB7, acidification assays, and immuno-EM in P. falciparum\",\n      \"pmids\": [\"24025672\", \"24275162\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether starvation-induced vesicle behavior reflects an essential function was not resolved\", \"Proteomic ribophagy/nucleophagy associations were not functionally confirmed\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Showed that the parasite ATG8 system is functionally divergent from other orthologs and restricted to apicoplast biology in liver stages, not autophagic cell death.\",\n      \"evidence\": \"Transgenic expression across the P. falciparum lifecycle, EM in P. berghei liver stages, yeast complementation, and mammalian autophagy assays\",\n      \"pmids\": [\"24342964\", \"23388496\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of the novel interaction with membranes not defined\", \"Did not distinguish apicoplast biogenesis from inheritance\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}, {\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Confirmed ATG8 as a constitutively membrane-integral protein distinct from the cytosol/membrane equilibrium of other orthologs and largely insensitive to autophagy inhibitors.\",\n      \"evidence\": \"Subcellular fractionation, western blot, IFA, and pharmacological/doxycycline perturbation in P. falciparum\",\n      \"pmids\": [\"25426852\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Partial apicoplast colocalization left additional membrane pools unexplained\", \"Did not test essentiality directly\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Validated the ATG8–Atg3 interaction and ATG8 lipidation as druggable antimalarial nodes acting in both blood and liver stages.\",\n      \"evidence\": \"SPR-based inhibitor screening, lipidation assay, and blood/liver-stage growth inhibition (Malaria Box)\",\n      \"pmids\": [\"24786226\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cellular target engagement not directly proven\", \"Selectivity over host homologs not fully established\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Demonstrated that ATG8 levels must be tightly balanced: overexpression drives aberrant microneme clearance and apicoplast collapse, blocking liver-stage maturation and infectivity.\",\n      \"evidence\": \"ATG8 gain-of-function transgenic P. berghei with organelle-marker imaging and mouse infectivity assays\",\n      \"pmids\": [\"27353755\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether microneme clearance is a physiological ATG8 function or an overexpression artifact\", \"Molecular link between ATG8 dosage and apicoplast collapse unresolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Confirmed the apicomplexan A-loop as an exploitable, host-divergent target by structure-guided inhibitors that block ATG8–Atg3 binding and shift ATG8 lipidation.\",\n      \"evidence\": \"Virtual screening against the PfATG8 A-loop, lipidation-state assay, and blood/liver-stage growth inhibition\",\n      \"pmids\": [\"26748931\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo efficacy not established\", \"Later work questioned the A-loop's functional requirement in vivo\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Placed PfATG18 upstream of ATG8, showing that PI3P-dependent ATG18 controls ATG8 membrane/apicoplast localization and apicoplast inheritance.\",\n      \"evidence\": \"Conditional knockdown of PfATG18, ATG8 localization readout, and PI3P interaction assay\",\n      \"pmids\": [\"29089429\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct biochemical interaction between ATG18 and ATG8 not shown\", \"ATG8 localization is an indirect downstream readout\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identified OTU as an ATG8 deconjugating (delipidating) protease linked to apicoplast development, extending the enzymatic control of ATG8 turnover.\",\n      \"evidence\": \"Degradation-tag knockdown of PfOTU, apicoplast marker IFA, deconjugation assay, and IPP rescue\",\n      \"pmids\": [\"28423214\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relationship between OTU and Atg4 not resolved here\", \"Deconjugation role inferred rather than shown to be primary\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Established the single essential blood-stage function of ATG8 as apicoplast inheritance (fission/segregation), decoupled from autophagy, protein import, and membrane expansion.\",\n      \"evidence\": \"Conditional depletion with IPP rescue, apicoplast FISH, import, membrane expansion, and inheritance assays in P. falciparum\",\n      \"pmids\": [\"29295911\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism by which ATG8 drives fission/segregation unknown\", \"Interactors executing segregation not identified\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined the enzymatic logic of ATG8 deconjugation, showing Atg4 as the primary delipidase required for liver-stage differentiation and OTU as an irreversible, non-recycling backup.\",\n      \"evidence\": \"Individual and attempted double KO of Atg4 and Otu in P. berghei, ATG8 deconjugation assays, western blot, and sporozoite infection\",\n      \"pmids\": [\"37910326\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Timing/spatial regulation of deconjugation during replication unclear\", \"Whether irreversible OTU cleavage serves a distinct signaling role unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Mapped the structural determinants of ATG8's apicoplast function, showing the LDS is required and the N-terminal helix and apicomplexan loop are dispensable in vivo, overturning the earlier in vitro emphasis on the loop.\",\n      \"evidence\": \"Functional complementation with ATG8 domain mutants, apicoplast localization, and lipidation assays in P. falciparum and T. gondii\",\n      \"pmids\": [\"36625582\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of LDS-binding effectors mediating apicoplast function not defined\", \"Reconciliation with A-loop inhibitor strategy not fully resolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}, {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Placed the E1-like Atg7 at the apex of ATG8 lipidation, showing it is required for ATG8 membrane conjugation and for downstream microneme exocytosis, organelle biogenesis, and merozoite formation.\",\n      \"evidence\": \"Conditional knockdown of Atg7 in P. berghei with lipidation western blots, ATG8/organelle IFA, and blood/liver-stage growth assays\",\n      \"pmids\": [\"39714137\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Atg7 has ATG8-independent activities not resolved\", \"Coupling between lipidation and specific effector recruitment unmapped\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular mechanism by which lipidated, LDS-competent ATG8 drives apicoplast fission and segregation—and the effectors it recruits at the apicoplast membrane—remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No ATG8 effector proteins executing apicoplast fission identified\", \"Mechanistic link between LDS engagement and organelle division unknown\", \"Species-divergent liver-stage microneme role not mechanistically integrated with the blood-stage inheritance role\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0019776\", \"supporting_discovery_ids\": [0, 1, 6, 14]},\n      {\"term_id\": \"GO:0035973\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0020011\", \"supporting_discovery_ids\": [0, 1, 3, 4, 5, 6, 11, 14]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [0, 3]},\n      {\"term_id\": \"GO:0000421\", \"supporting_discovery_ids\": [0, 8]},\n      {\"term_id\": \"GO:0016020\", \"supporting_discovery_ids\": [1, 6, 15]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0009658\", \"supporting_discovery_ids\": [3, 11, 8]},\n      {\"term_id\": \"GO:0006914\", \"supporting_discovery_ids\": [0, 8]}\n    ],\n    \"complexes\": [\n      \"ATG8 conjugation system (ATG8–Atg7–Atg3)\"\n    ],\n    \"partners\": [\n      \"Atg3 (E2-like; AIM/A-loop interaction, co-crystal structure) [#2, #14]\",\n      \"Atg7 (E1-like activating enzyme; P. berghei) [#15]\",\n      \"Atg4 (primary deconjugating cysteine protease; P. berghei) [#13]\",\n      \"OTU (backup deconjugating protease, irreversible cleavage) [#10, #13]\",\n      \"PfATG18 (PI3P-dependent, upstream regulator of ATG8 membrane association) [#9]\",\n      \"PfRAB7 (colocalization on maturing vesicles) [#0]\",\n      \"PfAtg5 (partial colocalization) [#16]\",\n      \"GRASP (colocalizes with ATG8-positive autophagosomes; P. berghei) [#18]\"\n    ],\n    \"other_free_text\": [\n      \"Constitutively lipidated (PE-conjugated) and membrane-integral in intraerythrocytic stages, unlike cytosol/membrane-partitioning yeast and mammalian orthologs [#1, #6].\",\n      \"Sole essential blood-stage function is apicoplast inheritance (fission/segregation); dispensable for apicoplast protein import and membrane expansion [#11].\",\n      \"Depletion lethality is rescued by isopentenyl pyrophosphate, marking an apicoplast metabolic dependency [#11].\",\n      \"C-terminal glycine and LDS required for apicoplast localization; N-terminal helix and apicomplexan-specific loop dispensable in vivo [#0, #14].\",\n      \"Liver-stage roles include microneme clearance via autophagosome-like structures and apicoplast biogenesis; ATG8 dosage must be balanced for merozoite maturation [#8, #15].\",\n      \"PfATG8–PfAtg3 interface and the apicomplexan A-loop are validated antimalarial drug targets [#7, #12].\",\n      \"Cannot complement yeast atg8Δ and does not localize to autophagosomes in starved mammalian cells, indicating a divergent mechanism [#5].\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_1019900","name":null,"product":"autophagy-related protein 8","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_0504100","name":null,"product":"autophagy-related protein 8","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_0604100","name":null,"product":"autophagy-related protein 8, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"ATG8","evaluation":null}