{"gene":"PF3D7_1012900","run_date":"2026-09-08T12:51:28","timeline":{"discoveries":[{"year":2017,"finding":"ATG18 (PfATG18) binds 3'-phosphorylated phosphoinositides (3'-PIPs), including phosphatidylinositol 3-phosphate (PI3P), and this interaction is essential for apicoplast inheritance; conditional knockdown of PfATG18 caused loss of the apicoplast and impaired parasite replication, resulting in delayed death. ATG18 also regulates membrane association and apicoplast localization of ATG8.","method":"Conditional knockdown (inducible system), phosphoinositide-binding assays, fluorescence microscopy for apicoplast and ATG8 localization","journal":"mBio","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal functional validation (knockdown with defined organelle phenotype), PIP-binding assays, and localization experiments in both P. falciparum and T. gondii with multiple orthogonal methods","pmids":["29089429"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Toxoplasma gondii","strain":""}]},{"year":2018,"finding":"The T38I single nucleotide polymorphism in ATG18 (PfATG18), introduced by CRISPR/Cas9 into a k13-edited Dd2 parasite, confers a fitness advantage enabling parasites to grow faster under nutrient-limited conditions and alters susceptibility to 227 compounds but does not modulate susceptibility to anti-malarial compounds in a 72-h drug pulse. PfATG18 was shown to bind PIPs and form puncta in response to stress, similar to yeast/mammalian WIPI/Atg18 homologues.","method":"CRISPR/Cas9 gene editing, ring-stage survival assays, nutrient deprivation growth assays, high-throughput drug screening, PIP-binding assays, fluorescence microscopy","journal":"Malaria journal","confidence":"High","confidence_rationale":"Tier 2 / Moderate — CRISPR/Cas9 precise mutation introduction with defined growth phenotype, biochemical PIP-binding assays, and drug library screening; single lab but multiple orthogonal methods","pmids":["30367653"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":"Dd2"}]},{"year":2019,"finding":"PfATG18 localizes to the food vacuole (FV) and becomes enriched at interfaces of newly generated multilobed FVs during fission/fusion events. PfATG18 expression is induced by starvation at both mRNA and protein levels, indicating participation in the autophagy-like pathway independently of its role in apicoplast biogenesis. PfATG18 is transported to the FV via the haemoglobin trafficking pathway.","method":"Live fluorescence microscopy, starvation induction assays, RT-qPCR and western blot for expression, pharmacological perturbation of haemoglobin trafficking","journal":"Molecular microbiology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — localization by fluorescence microscopy with functional context (FV dynamics, starvation response), single lab with multiple observations but no reciprocal validation of trafficking route","pmids":["31863491"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2021,"finding":"PfATG18 localizes to the food vacuole in asexual erythrocytic stages, and this localization requires PI3P binding via its PROPPIN-family PI3P-binding motifs; mutants of these motifs neither bound PI3P nor localized to the food vacuole. The food vacuole multi-drug resistance protein 1 (MDR1) co-immunoprecipitated with PfATG18 (and with P. berghei Atg18) and directly interacted with PfATG18, providing an additional determinant for food vacuole localization beyond PI3P. Chloroquine and amodiaquine caused cytoplasmic mislocalization of PfATG18, implicating the drug's effects on the PfATG18 transport pathway.","method":"Expression of wild-type and PI3P-binding mutant PfATG18 in P. falciparum, co-immunoprecipitation, PI3P-binding assays, fluorescence microscopy, pharmacological treatment","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP identifying MDR1 interaction, PI3P-binding mutagenesis with localization readout, replicated in P. berghei ortholog; single lab but multiple orthogonal methods","pmids":["33843972"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium berghei","strain":""}]},{"year":2022,"finding":"PfATG18 co-localizes with PfK13 (Kelch13) on hemoglobin-trafficking vesicles (cytostome-like and hemoglobin-containing vesicles) along with PI3P, linking the autophagy and hemoglobin endocytosis pathways. ART-resistant K13C580Y parasites show higher basal expression of PfATG18 than isogenic wild-type parasites, and this elevated expression increases further under starvation.","method":"Co-localization fluorescence microscopy, western blot quantification across isogenic wild-type and K13C580Y strains, starvation induction","journal":"mBio","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — co-localization microscopy and expression comparisons in isogenic strains; single lab but multiple experimental observations supporting vesicular co-association","pmids":["35420484"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2022,"finding":"Inducible CRISPRi/a-mediated >2-fold up- or downregulation of ATG18 (PfATG18) transcripts caused growth retardation in asexual P. falciparum, confirming that ATG18 is an essential gene whose expression level is directly linked to parasite proliferation.","method":"Inducible CRISPRi/a (dCas9-Sir2a/GCN5 with DiCre/loxP), RT-qPCR, parasite growth assays","journal":"Microbiology spectrum","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — clean inducible transcriptional regulation with defined growth phenotype, but single lab, single experimental approach","pmids":["35510853"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"current_model":"PfATG18 (PF3D7_1012900) is a PROPPIN-family PI3P-binding protein that localizes to the food vacuole in asexual blood stages via dual determinants — PI3P binding through its conserved motifs and interaction with the food vacuole MDR1 protein — where it participates in food vacuole dynamics (fission/fusion) and is transported there via the haemoglobin trafficking pathway; it additionally regulates apicoplast inheritance by directing ATG8 membrane association and apicoplast localization in a PI3P-dependent manner, and its expression is induced by starvation and ER stress as part of an autophagy-like survival pathway, with the T38I polymorphism conferring a fitness advantage under nutrient deprivation and co-associating with Kelch13 C580Y on hemoglobin-trafficking vesicles in artemisinin-resistant parasites."},"narrative":{"mechanistic_narrative":"PF3D7_1012900 (ATG18) is a PROPPIN-family phosphoinositide-binding protein of Plasmodium falciparum that couples PI3P recognition to two distinct membrane compartments, functioning in both apicoplast inheritance and food-vacuole–associated autophagy-like processes [PMID:29089429, PMID:33843972]. It binds 3'-phosphorylated phosphoinositides, including PI3P, through conserved PROPPIN PI3P-binding motifs, and this interaction is essential: conditional knockdown causes loss of the apicoplast, impaired replication, and a delayed-death phenotype, and ATG18 directs the membrane association and apicoplast localization of ATG8 [PMID:29089429]. In asexual blood stages, ATG18 localizes to the food vacuole via dual determinants — PI3P binding (motif mutants fail to bind PI3P and mislocalize) and direct interaction with the food-vacuole MDR1 protein, which co-immunoprecipitates with ATG18 [PMID:33843972] — and it becomes enriched at the interfaces of multilobed food vacuoles during fission/fusion, with delivery occurring through the haemoglobin trafficking pathway [PMID:31863491]. ATG18 expression is induced by starvation, marking participation in an autophagy-like survival response distinct from its apicoplast role [PMID:31863491], and its transcript levels are tightly coupled to proliferation, since both up- and downregulation retard growth [PMID:35510853]. ATG18 co-localizes with Kelch13 and PI3P on haemoglobin-trafficking vesicles, and the T38I polymorphism confers a growth advantage under nutrient limitation, linking the protein to artemisinin-resistance–associated endocytic biology [PMID:30367653, PMID:35420484].","teleology":[{"year":2017,"claim":"Established that PF3D7_1012900 is a phosphoinositide-binding protein essential for apicoplast inheritance, defining its first molecular activity and an organellar role independent of any bulk-autophagy assumption.","evidence":"Conditional knockdown with apicoplast-loss phenotype, PIP-binding assays, and ATG8 localization microscopy in P. falciparum and T. gondii","pmids":["29089429"],"confidence":"High","gaps":["Mechanism by which ATG18 directs ATG8 membrane association not resolved","Structural basis of PI3P recognition not determined","Whether apicoplast role requires MDR1 or other partners unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Toxoplasma gondii","strain":""}]},{"year":2018,"claim":"Linked a natural ATG18 polymorphism (T38I) to a fitness advantage under nutrient limitation, connecting the protein's PIP-binding, stress-responsive puncta behavior to parasite adaptation.","evidence":"CRISPR/Cas9 introduction of T38I into k13-edited Dd2, nutrient-deprivation growth assays, PIP-binding assays, and drug library screening in P. falciparum","pmids":["30367653"],"confidence":"High","gaps":["Molecular mechanism by which T38I improves nutrient-limited growth not defined","T38I did not alter susceptibility to antimalarials in a 72-h pulse, leaving its resistance relevance unclear"],"attribution":[{"species":"Plasmodium falciparum","strain":"Dd2"}]},{"year":2019,"claim":"Placed ATG18 at the food vacuole and in food-vacuole fission/fusion dynamics, and showed starvation-induced expression, establishing an autophagy-like blood-stage role separable from apicoplast biogenesis.","evidence":"Live fluorescence microscopy, starvation induction with RT-qPCR/western blot, and pharmacological perturbation of haemoglobin trafficking in P. falciparum","pmids":["31863491"],"confidence":"Medium","gaps":["Trafficking route to the food vacuole inferred pharmacologically without reciprocal validation","Direct role in fission/fusion vs. passive enrichment not distinguished"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2021,"claim":"Defined the dual determinants of food-vacuole localization — PI3P binding via PROPPIN motifs plus direct interaction with MDR1 — providing a mechanistic anchor for ATG18 targeting.","evidence":"PI3P-binding mutant expression with localization readout, reciprocal co-immunoprecipitation of MDR1, and drug-treatment mislocalization in P. falciparum, with the interaction replicated for the P. berghei ortholog","pmids":["33843972"],"confidence":"High","gaps":["Functional consequence of the MDR1 interaction for food-vacuole physiology not established","Whether MDR1 recruits ATG18 or vice versa unresolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium berghei","strain":""}]},{"year":2022,"claim":"Connected ATG18 to the haemoglobin-endocytosis and artemisinin-resistance machinery by demonstrating co-localization with Kelch13 and PI3P on trafficking vesicles and elevated expression in K13C580Y parasites.","evidence":"Co-localization microscopy and western-blot quantification across isogenic wild-type and K13C580Y strains with starvation induction in P. falciparum","pmids":["35420484"],"confidence":"Medium","gaps":["Causal role of ATG18 in artemisinin resistance not demonstrated","Co-localization does not establish direct interaction with K13"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2022,"claim":"Confirmed ATG18 as an essential gene whose expression level is bidirectionally coupled to proliferation, showing both overexpression and repression impair growth.","evidence":"Inducible CRISPRi/a transcript modulation with RT-qPCR and asexual growth assays in P. falciparum","pmids":["35510853"],"confidence":"Medium","gaps":["Single approach, single lab","Which downstream ATG18 function (apicoplast vs. food vacuole) drives the growth defect not dissected"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":null,"claim":"How ATG18 mechanistically bridges apicoplast inheritance and food-vacuole/haemoglobin-endocytosis pathways, and whether its association with resistance-linked Kelch13 vesicles is causal, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of the PROPPIN PI3P-binding interface","Directionality and functional output of the ATG18–MDR1 and ATG18–K13 associations undefined","Whether ATG18 drives membrane fission/fusion enzymatically or as a scaffold unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":["MDR1 / MULTI-DRUG RESISTANCE PROTEIN 1 (DIRECT INTERACTOR, CO-IP) [#3]","ATG8 (MEMBRANE ASSOCIATION AND APICOPLAST LOCALIZATION DIRECTED BY ATG18) [#0]","KELCH13 / PFK13 (VESICULAR CO-LOCALIZATION) [#4]"],"other_free_text":["T38I polymorphism confers a growth advantage under nutrient deprivation [#1]","Elevated basal expression in artemisinin-resistant K13C580Y parasites, further induced by starvation [#4]","Chloroquine and amodiaquine cause cytoplasmic mislocalization of ATG18, implicating its transport pathway [#3]","Essential gene; both up- and downregulation of transcripts retard asexual growth [#5]","MDR1 interaction replicated for the P. berghei ortholog [#3]"]}},"prefetch_data":{},"corpus_meta":[{"pmid":"33320907","id":"PMC_33320907","title":"Emergence of artemisinin-resistant Plasmodium falciparum with kelch13 C580Y mutations on the island of New Guinea.","date":"2020","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/33320907","citation_count":89,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ATG18"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"29089429","id":"PMC_29089429","title":"Autophagy-Related Protein ATG18 Regulates Apicoplast Biogenesis in Apicomplexan Parasites.","date":"2017","source":"mBio","url":"https://pubmed.ncbi.nlm.nih.gov/29089429","citation_count":45,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ATG18","PfATG18"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"30367653","id":"PMC_30367653","title":"A single nucleotide polymorphism in the Plasmodium falciparum atg18 gene associates with artemisinin resistance and confers enhanced parasite survival under nutrient deprivation.","date":"2018","source":"Malaria journal","url":"https://pubmed.ncbi.nlm.nih.gov/30367653","citation_count":37,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ATG18","PfATG18"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"35420484","id":"PMC_35420484","title":"Autophagy Underlies the Proteostasis Mechanisms of Artemisinin Resistance in P. falciparum Malaria.","date":"2022","source":"mBio","url":"https://pubmed.ncbi.nlm.nih.gov/35420484","citation_count":22,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ATG18","PfATG18"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"31863491","id":"PMC_31863491","title":"Autophagy-related protein PfATG18 participates in food vacuole dynamics and autophagy-like pathway in Plasmodium falciparum.","date":"2019","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/31863491","citation_count":18,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ATG18","PfATG18"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"33843972","id":"PMC_33843972","title":"Plasmodium falciparum Atg18 localizes to the food vacuole via interaction with the multi-drug resistance protein 1 and phosphatidylinositol 3-phosphate.","date":"2021","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/33843972","citation_count":15,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ATG18","PfATG18"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"35510853","id":"PMC_35510853","title":"A Leak-Free Inducible CRISPRi/a System for Gene Functional Studies in Plasmodium falciparum.","date":"2022","source":"Microbiology spectrum","url":"https://pubmed.ncbi.nlm.nih.gov/35510853","citation_count":14,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["autophagy-related protein 18"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"36869438","id":"PMC_36869438","title":"Biological functions and structural biology of Plasmodium falciparum autophagy-related proteins: The under-explored options for novel antimalarial drug design.","date":"2023","source":"Chemical biology & drug design","url":"https://pubmed.ncbi.nlm.nih.gov/36869438","citation_count":1,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PfATG18"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"42473197","id":"PMC_42473197","title":"Divergent Autophagy Pathways in Plasmodium: Mechanisms, Functions, and Therapeutic Potential.","date":"2026","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/42473197","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["ATG18"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"40396048","id":"PMC_40396048","title":"The ART of Resistance.","date":"2022","source":"Autophagy reports","url":"https://pubmed.ncbi.nlm.nih.gov/40396048","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["autophagy-related protein 18","PfATG18"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8684,"output_tokens":2182,"usd":0.029391,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":7377,"output_tokens":3269,"usd":0.059305,"stage2_stop_reason":"end_turn"},"total_usd":0.088696,"stage1_batch_id":"msgbatch_01DisAaTypwmC8QwdMBuePHo","stage2_batch_id":"msgbatch_0184zxZTqxiEfdYYfPMfkqjb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2017,\n      \"finding\": \"ATG18 (PfATG18) binds 3'-phosphorylated phosphoinositides (3'-PIPs), including phosphatidylinositol 3-phosphate (PI3P), and this interaction is essential for apicoplast inheritance; conditional knockdown of PfATG18 caused loss of the apicoplast and impaired parasite replication, resulting in delayed death. ATG18 also regulates membrane association and apicoplast localization of ATG8.\",\n      \"method\": \"Conditional knockdown (inducible system), phosphoinositide-binding assays, fluorescence microscopy for apicoplast and ATG8 localization\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal functional validation (knockdown with defined organelle phenotype), PIP-binding assays, and localization experiments in both P. falciparum and T. gondii with multiple orthogonal methods\",\n      \"pmids\": [\"29089429\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"},\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The T38I single nucleotide polymorphism in ATG18 (PfATG18), introduced by CRISPR/Cas9 into a k13-edited Dd2 parasite, confers a fitness advantage enabling parasites to grow faster under nutrient-limited conditions and alters susceptibility to 227 compounds but does not modulate susceptibility to anti-malarial compounds in a 72-h drug pulse. PfATG18 was shown to bind PIPs and form puncta in response to stress, similar to yeast/mammalian WIPI/Atg18 homologues.\",\n      \"method\": \"CRISPR/Cas9 gene editing, ring-stage survival assays, nutrient deprivation growth assays, high-throughput drug screening, PIP-binding assays, fluorescence microscopy\",\n      \"journal\": \"Malaria journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR/Cas9 precise mutation introduction with defined growth phenotype, biochemical PIP-binding assays, and drug library screening; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"30367653\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"Dd2\"}\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PfATG18 localizes to the food vacuole (FV) and becomes enriched at interfaces of newly generated multilobed FVs during fission/fusion events. PfATG18 expression is induced by starvation at both mRNA and protein levels, indicating participation in the autophagy-like pathway independently of its role in apicoplast biogenesis. PfATG18 is transported to the FV via the haemoglobin trafficking pathway.\",\n      \"method\": \"Live fluorescence microscopy, starvation induction assays, RT-qPCR and western blot for expression, pharmacological perturbation of haemoglobin trafficking\",\n      \"journal\": \"Molecular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — localization by fluorescence microscopy with functional context (FV dynamics, starvation response), single lab with multiple observations but no reciprocal validation of trafficking route\",\n      \"pmids\": [\"31863491\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PfATG18 localizes to the food vacuole in asexual erythrocytic stages, and this localization requires PI3P binding via its PROPPIN-family PI3P-binding motifs; mutants of these motifs neither bound PI3P nor localized to the food vacuole. The food vacuole multi-drug resistance protein 1 (MDR1) co-immunoprecipitated with PfATG18 (and with P. berghei Atg18) and directly interacted with PfATG18, providing an additional determinant for food vacuole localization beyond PI3P. Chloroquine and amodiaquine caused cytoplasmic mislocalization of PfATG18, implicating the drug's effects on the PfATG18 transport pathway.\",\n      \"method\": \"Expression of wild-type and PI3P-binding mutant PfATG18 in P. falciparum, co-immunoprecipitation, PI3P-binding assays, fluorescence microscopy, pharmacological treatment\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP identifying MDR1 interaction, PI3P-binding mutagenesis with localization readout, replicated in P. berghei ortholog; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"33843972\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"},\n        {\"species\": \"Plasmodium berghei\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PfATG18 co-localizes with PfK13 (Kelch13) on hemoglobin-trafficking vesicles (cytostome-like and hemoglobin-containing vesicles) along with PI3P, linking the autophagy and hemoglobin endocytosis pathways. ART-resistant K13C580Y parasites show higher basal expression of PfATG18 than isogenic wild-type parasites, and this elevated expression increases further under starvation.\",\n      \"method\": \"Co-localization fluorescence microscopy, western blot quantification across isogenic wild-type and K13C580Y strains, starvation induction\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — co-localization microscopy and expression comparisons in isogenic strains; single lab but multiple experimental observations supporting vesicular co-association\",\n      \"pmids\": [\"35420484\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Inducible CRISPRi/a-mediated >2-fold up- or downregulation of ATG18 (PfATG18) transcripts caused growth retardation in asexual P. falciparum, confirming that ATG18 is an essential gene whose expression level is directly linked to parasite proliferation.\",\n      \"method\": \"Inducible CRISPRi/a (dCas9-Sir2a/GCN5 with DiCre/loxP), RT-qPCR, parasite growth assays\",\n      \"journal\": \"Microbiology spectrum\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — clean inducible transcriptional regulation with defined growth phenotype, but single lab, single experimental approach\",\n      \"pmids\": [\"35510853\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    }\n  ],\n  \"current_model\": \"PfATG18 (PF3D7_1012900) is a PROPPIN-family PI3P-binding protein that localizes to the food vacuole in asexual blood stages via dual determinants — PI3P binding through its conserved motifs and interaction with the food vacuole MDR1 protein — where it participates in food vacuole dynamics (fission/fusion) and is transported there via the haemoglobin trafficking pathway; it additionally regulates apicoplast inheritance by directing ATG8 membrane association and apicoplast localization in a PI3P-dependent manner, and its expression is induced by starvation and ER stress as part of an autophagy-like survival pathway, with the T38I polymorphism conferring a fitness advantage under nutrient deprivation and co-associating with Kelch13 C580Y on hemoglobin-trafficking vesicles in artemisinin-resistant parasites.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PF3D7_1012900 (ATG18) is a PROPPIN-family phosphoinositide-binding protein of Plasmodium falciparum that couples PI3P recognition to two distinct membrane compartments, functioning in both apicoplast inheritance and food-vacuole–associated autophagy-like processes [#0, #3]. It binds 3'-phosphorylated phosphoinositides, including PI3P, through conserved PROPPIN PI3P-binding motifs, and this interaction is essential: conditional knockdown causes loss of the apicoplast, impaired replication, and a delayed-death phenotype, and ATG18 directs the membrane association and apicoplast localization of ATG8 [#0]. In asexual blood stages, ATG18 localizes to the food vacuole via dual determinants — PI3P binding (motif mutants fail to bind PI3P and mislocalize) and direct interaction with the food-vacuole MDR1 protein, which co-immunoprecipitates with ATG18 [#3] — and it becomes enriched at the interfaces of multilobed food vacuoles during fission/fusion, with delivery occurring through the haemoglobin trafficking pathway [#2]. ATG18 expression is induced by starvation, marking participation in an autophagy-like survival response distinct from its apicoplast role [#2], and its transcript levels are tightly coupled to proliferation, since both up- and downregulation retard growth [#5]. ATG18 co-localizes with Kelch13 and PI3P on haemoglobin-trafficking vesicles, and the T38I polymorphism confers a growth advantage under nutrient limitation, linking the protein to artemisinin-resistance–associated endocytic biology [#1, #4].\",\n  \"teleology\": [\n    {\n      \"year\": 2017,\n      \"claim\": \"Established that PF3D7_1012900 is a phosphoinositide-binding protein essential for apicoplast inheritance, defining its first molecular activity and an organellar role independent of any bulk-autophagy assumption.\",\n      \"evidence\": \"Conditional knockdown with apicoplast-loss phenotype, PIP-binding assays, and ATG8 localization microscopy in P. falciparum and T. gondii\",\n      \"pmids\": [\"29089429\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which ATG18 directs ATG8 membrane association not resolved\", \"Structural basis of PI3P recognition not determined\", \"Whether apicoplast role requires MDR1 or other partners unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}, {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Linked a natural ATG18 polymorphism (T38I) to a fitness advantage under nutrient limitation, connecting the protein's PIP-binding, stress-responsive puncta behavior to parasite adaptation.\",\n      \"evidence\": \"CRISPR/Cas9 introduction of T38I into k13-edited Dd2, nutrient-deprivation growth assays, PIP-binding assays, and drug library screening in P. falciparum\",\n      \"pmids\": [\"30367653\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism by which T38I improves nutrient-limited growth not defined\", \"T38I did not alter susceptibility to antimalarials in a 72-h pulse, leaving its resistance relevance unclear\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"Dd2\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Placed ATG18 at the food vacuole and in food-vacuole fission/fusion dynamics, and showed starvation-induced expression, establishing an autophagy-like blood-stage role separable from apicoplast biogenesis.\",\n      \"evidence\": \"Live fluorescence microscopy, starvation induction with RT-qPCR/western blot, and pharmacological perturbation of haemoglobin trafficking in P. falciparum\",\n      \"pmids\": [\"31863491\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Trafficking route to the food vacuole inferred pharmacologically without reciprocal validation\", \"Direct role in fission/fusion vs. passive enrichment not distinguished\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Defined the dual determinants of food-vacuole localization — PI3P binding via PROPPIN motifs plus direct interaction with MDR1 — providing a mechanistic anchor for ATG18 targeting.\",\n      \"evidence\": \"PI3P-binding mutant expression with localization readout, reciprocal co-immunoprecipitation of MDR1, and drug-treatment mislocalization in P. falciparum, with the interaction replicated for the P. berghei ortholog\",\n      \"pmids\": [\"33843972\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of the MDR1 interaction for food-vacuole physiology not established\", \"Whether MDR1 recruits ATG18 or vice versa unresolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}, {\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Connected ATG18 to the haemoglobin-endocytosis and artemisinin-resistance machinery by demonstrating co-localization with Kelch13 and PI3P on trafficking vesicles and elevated expression in K13C580Y parasites.\",\n      \"evidence\": \"Co-localization microscopy and western-blot quantification across isogenic wild-type and K13C580Y strains with starvation induction in P. falciparum\",\n      \"pmids\": [\"35420484\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal role of ATG18 in artemisinin resistance not demonstrated\", \"Co-localization does not establish direct interaction with K13\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Confirmed ATG18 as an essential gene whose expression level is bidirectionally coupled to proliferation, showing both overexpression and repression impair growth.\",\n      \"evidence\": \"Inducible CRISPRi/a transcript modulation with RT-qPCR and asexual growth assays in P. falciparum\",\n      \"pmids\": [\"35510853\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single approach, single lab\", \"Which downstream ATG18 function (apicoplast vs. food vacuole) drives the growth defect not dissected\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How ATG18 mechanistically bridges apicoplast inheritance and food-vacuole/haemoglobin-endocytosis pathways, and whether its association with resistance-linked Kelch13 vesicles is causal, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of the PROPPIN PI3P-binding interface\", \"Directionality and functional output of the ATG18–MDR1 and ATG18–K13 associations undefined\", \"Whether ATG18 drives membrane fission/fusion enzymatically or as a scaffold unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0032266\", \"supporting_discovery_ids\": [0, 1, 3]},\n      {\"term_id\": \"GO:0005545\", \"supporting_discovery_ids\": [0, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0020020\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"GO:0009536\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0030659\", \"supporting_discovery_ids\": [2, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0006914\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0006623\", \"supporting_discovery_ids\": [2, 4]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"MDR1 / multi-drug resistance protein 1 (direct interactor, co-IP) [#3]\",\n      \"ATG8 (membrane association and apicoplast localization directed by ATG18) [#0]\",\n      \"Kelch13 / PfK13 (vesicular co-localization) [#4]\"\n    ],\n    \"other_free_text\": [\n      \"T38I polymorphism confers a growth advantage under nutrient deprivation [#1]\",\n      \"Elevated basal expression in artemisinin-resistant K13C580Y parasites, further induced by starvation [#4]\",\n      \"Chloroquine and amodiaquine cause cytoplasmic mislocalization of ATG18, implicating its transport pathway [#3]\",\n      \"Essential gene; both up- and downregulation of transcripts retard asexual growth [#5]\",\n      \"MDR1 interaction replicated for the P. berghei ortholog [#3]\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_1012900","name":null,"product":"autophagy-related protein 18","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_1211300","name":null,"product":"autophagy-related protein 18, putative","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_0812700","name":null,"product":"autophagy-related protein 18, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"ATG18","evaluation":null}