{"gene":"PF3D7_0628300","run_date":"2026-09-08T19:44:17","timeline":{"discoveries":[{"year":2010,"finding":"CEPT (PF3D7_0628300 ortholog in P. berghei) is refractory to gene knockout, indicating it is essential for asexual blood-stage development. GFP-tagging of the P. berghei CEPT showed it localizes primarily to the endoplasmic reticulum, in contrast to the cytosolic localization of CCT, ECT, and CK. Sequence analysis confirmed the presence of all catalytic domains and essential residues/motifs necessary for enzymatic activity.","method":"Gene knockout attempts (consistently refractory), GFP-fusion live imaging, sequence analysis of catalytic domains","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct GFP localization experiment with functional consequence (essentiality inferred from refractory knockouts), single lab but two orthogonal methods (KO attempts + GFP tagging)","pmids":["20478340"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2012,"finding":"CEPT enzymatic activity (CDP-choline/ethanolamine phosphotransferase) was measured in P. falciparum parasite extracts via radiolabelled substrate incorporation assay, yielding a Km for CDP-choline of 13.2 ± 0.7 µM under Michaelis-Menten kinetics. Albitiazolium inhibited CEPT activity with an IC50 of 4.2 mM in vitro, demonstrating that albitiazolium affects the final enzymatic step of de novo PC biosynthesis.","method":"Radiolabelled substrate enzyme activity assay, Michaelis-Menten kinetics, inhibitor dose-response (IC50 determination)","journal":"British journal of pharmacology","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro enzymatic assay with kinetic characterization, single lab, single method","pmids":["22471905"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2014,"finding":"CEPT (PF3D7_0628300) was identified as the primary protein target of albitiazolium in living P. falciparum parasites using a bifunctional photoactivatable and clickable albitiazolium-derived probe (UA1936). Competitive displacement with free albitiazolium caused the greatest reduction in CEPT peptide spectral matches (3-fold), confirming the albitiazolium pharmacophore directly interacts with CEPT. The probe co-localized with the endoplasmic reticulum and trans-Golgi network.","method":"Chemical proteomics: photocrosslinking in live parasites, click-chemistry affinity purification, mass spectrometry, competitive displacement assay","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in-cell photo-crosslinking with competitive displacement controls and MS identification, two orthogonal methods (AfBPP + competition), single lab","pmids":["25470252"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2008,"finding":"CEPT (PfCEPT) protein levels were significantly decreased in P. falciparum parasites treated with the bisthiazolium compound T4, as detected by proteomics, while no corresponding transcriptional change was observed, suggesting post-transcriptional or post-translational regulation of CEPT. Metabolic studies confirmed that T4 treatment caused a major reduction in PC synthesis from choline and ethanolamine, consistent with CEPT inhibition.","method":"Quantitative proteomics (peptide spectral counts), transcriptome profiling, metabolic radiolabelling assay","journal":"BMC genomics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two orthogonal methods (proteomics + metabolic labelling), single lab, no direct mechanistic follow-up of the post-translational regulation","pmids":["18973684"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2022,"finding":"CEPT (PF3D7_0628300) was found to interact with phosphatidylserine synthase (PfPSS) in P. falciparum, as demonstrated by co-immunoprecipitation in transgenic parasites expressing PfPSS-GFP. Both proteins localize to the ER, supporting a model in which the ER is the major site for phospholipid biosynthesis and that ER-mitochondria contact sites (ERMC) mediate phospholipid synthesis/transport.","method":"Co-immunoprecipitation using GFP-tagged PfPSS in transgenic parasites, high-resolution microscopy","journal":"Mitochondrion","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP without reciprocal confirmation, single lab, interaction inferred from GFP-tagged partner pulldown","pmids":["35623558"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2021,"finding":"The CEPT gene (PF3D7_0628300) is enriched with repressive H3K36me2 and H3K36me3 histone modifications in stage II gametocytes of P. falciparum, correlating with its transcriptional repression at this developmental stage. This implicates H3K36me2/3 as a regulatory mechanism controlling CEPT expression during early sexual development.","method":"Chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq) for H3K36me2 and H3K36me3","journal":"Epigenetics & chromatin","confidence":"Low","confidence_rationale":"Tier 3 / Weak — ChIP-seq identifies chromatin association but no direct functional consequence for CEPT specifically was established, single lab","pmids":["33794978"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"current_model":"CEPT (PF3D7_0628300) is an essential endoplasmic reticulum-localized choline/ethanolamine phosphotransferase in Plasmodium that catalyzes the final step of both PC and PE biosynthesis via the Kennedy pathway (Km for CDP-choline ~13 µM), is the primary molecular target of the antimalarial albitiazolium (displaced by competitive photocrosslinking in live parasites), physically interacts with phosphatidylserine synthase (PfPSS) at the ER, and is subject to post-transcriptional/post-translational downregulation upon disruption of its substrate supply; in blood-stage parasites the gene is refractory to knockout and its locus is marked by repressive H3K36me2/3 in stage II gametocytes."},"narrative":{"mechanistic_narrative":"CEPT (PF3D7_0628300) is an endoplasmic reticulum-localized choline/ethanolaminephosphotransferase that catalyzes the terminal step of de novo phosphatidylcholine biosynthesis in Plasmodium and is essential for asexual blood-stage development [PMID:20478340, PMID:22471905]. In P. berghei the gene is refractory to knockout, and GFP-tagging localizes the protein to the ER, distinguishing it from the cytosolic upstream Kennedy-pathway enzymes; sequence analysis confirms the catalytic domains and residues required for phosphotransferase activity [PMID:20478340]. In P. falciparum, CEPT displays CDP-choline phosphotransferase activity with a Km of ~13 µM and is the primary molecular target of the antimalarial albitiazolium, which inhibits the enzyme in vitro and directly engages CEPT in living parasites as shown by competitive photocrosslinking with a clickable albitiazolium probe that co-localizes to the ER and trans-Golgi [PMID:22471905, PMID:25470252]. CEPT protein levels fall upon pharmacological disruption of phospholipid synthesis without a matching transcriptional change, indicating post-transcriptional/post-translational regulation [PMID:18973684]. Co-immunoprecipitation places CEPT in physical association with phosphatidylserine synthase at the ER [PMID:35623558], and its locus is marked by repressive H3K36me2/3 in stage II gametocytes, correlating with stage-specific transcriptional silencing [PMID:33794978]. Beyond these findings, no further mechanistic detail on CEPT has been characterized in the available corpus.","teleology":[{"year":2008,"claim":"Established that CEPT protein abundance, but not transcript level, responds to bisthiazolium (T4) treatment that blocks PC synthesis, revealing a post-transcriptional/post-translational control layer coupled to phospholipid pathway status.","evidence":"Quantitative proteomics with parallel transcriptome profiling and metabolic radiolabelling in T4-treated P. falciparum","pmids":["18973684"],"confidence":"Medium","gaps":["Mechanism of the post-translational downregulation not identified","Does not establish whether CEPT is a direct T4 target versus a downstream responder"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2010,"claim":"Determined that CEPT is essential for asexual blood-stage growth and localizes to the ER, unlike the cytosolic upstream Kennedy-pathway enzymes, placing the terminal biosynthetic step at the ER.","evidence":"Refractory gene-knockout attempts plus GFP-fusion live imaging and catalytic-domain sequence analysis in P. berghei","pmids":["20478340"],"confidence":"Medium","gaps":["Essentiality inferred from refractory KO rather than conditional depletion","Enzymatic activity not directly demonstrated in this study"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2012,"claim":"Provided direct enzymatic characterization of CEPT as a CDP-choline phosphotransferase and linked the antimalarial albitiazolium to inhibition of this terminal PC-biosynthesis step.","evidence":"Radiolabelled-substrate activity assay with Michaelis-Menten kinetics (Km CDP-choline ~13 µM) and albitiazolium IC50 determination in P. falciparum extracts","pmids":["22471905"],"confidence":"Medium","gaps":["Activity measured in crude extracts rather than purified recombinant enzyme","In vitro IC50 (~4.2 mM) leaves cellular relevance of inhibition unresolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2014,"claim":"Confirmed in living parasites that the albitiazolium pharmacophore directly engages CEPT, identifying it as the primary drug target and reinforcing ER/trans-Golgi localization.","evidence":"In-cell photocrosslinking with a bifunctional albitiazolium probe, click-chemistry affinity purification, mass spectrometry, and competitive displacement in P. falciparum","pmids":["25470252"],"confidence":"High","gaps":["Binding site on CEPT not mapped","Whether target engagement fully accounts for antimalarial killing not established"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2021,"claim":"Linked stage-specific transcriptional repression of the CEPT locus to repressive H3K36me2/3 chromatin marks during early gametocytogenesis.","evidence":"ChIP-seq for H3K36me2 and H3K36me3 in stage II gametocytes of P. falciparum","pmids":["33794978"],"confidence":"Low","gaps":["Chromatin association shown but no direct functional consequence for CEPT demonstrated","Causal role of the marks in silencing untested"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2022,"claim":"Placed CEPT in physical proximity to phosphatidylserine synthase at the ER, suggesting spatial coordination of phospholipid biosynthesis.","evidence":"Co-immunoprecipitation via GFP-tagged PfPSS in transgenic P. falciparum with high-resolution microscopy","pmids":["35623558"],"confidence":"Low","gaps":["Single Co-IP without reciprocal validation","Direct versus indirect interaction not distinguished","Functional significance of the association untested"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":null,"claim":"How CEPT activity is regulated at the protein level in response to phospholipid supply, and the structural basis of albitiazolium binding, remain unresolved.","evidence":"No discovery in the corpus addresses the regulatory or structural mechanism directly","pmids":[],"confidence":"Low","gaps":["No structural model of CEPT or its drug-binding site","Mechanism of post-translational downregulation unknown","No purified recombinant enzyme characterization"],"attribution":[]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":["PHOSPHATIDYLSERINE SYNTHASE (PFPSS)"],"other_free_text":["Primary molecular target of the antimalarial albitiazolium, directly engaged in live parasites [#2].","Refractory to knockout in P. berghei, indicating essentiality for asexual blood-stage development [#0].","Km for CDP-choline ~13 µM measured in P. falciparum extracts [#1].","Protein level downregulated post-transcriptionally upon disruption of PC synthesis [#3].","Locus marked by repressive H3K36me2/3 in stage II gametocytes, correlating with transcriptional repression [#5]."]}},"prefetch_data":{},"corpus_meta":[{"pmid":"20478340","id":"PMC_20478340","title":"The Kennedy phospholipid biosynthesis pathways are refractory to genetic disruption in Plasmodium berghei and therefore appear essential in blood stages.","date":"2010","source":"Molecular and biochemical parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/20478340","citation_count":46,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CEPT"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"35623558","id":"PMC_35623558","title":"Defining ER-mitochondria contact dynamics in Plasmodium falciparum by targeting component of phospholipid synthesis pathway, phosphatidylserine synthase (PfPSS).","date":"2022","source":"Mitochondrion","url":"https://pubmed.ncbi.nlm.nih.gov/35623558","citation_count":7,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CEPT"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"36576255","id":"","title":"A choline-releasing glycerophosphodiesterase essential for phosphatidylcholine biosynthesis and blood stage development in the malaria parasite.","date":"2022","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/36576255","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CEPT"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"34834257","id":"","title":"New Compounds with Bioisosteric Replacement of Classic Choline Kinase Inhibitors Show Potent Antiplasmodial Activity.","date":"2021","source":"Pharmaceutics","url":"https://pubmed.ncbi.nlm.nih.gov/34834257","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CEPT"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"37232495","id":"","title":"Chemo-proteomics in antimalarial target identification and engagement.","date":"2023","source":"Medicinal research reviews","url":"https://pubmed.ncbi.nlm.nih.gov/37232495","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CEPT"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"32589689","id":"","title":"System-wide biochemical analysis reveals ozonide antimalarials initially act by disrupting Plasmodium falciparum haemoglobin digestion.","date":"2020","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/32589689","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CEPT"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"33794978","id":"","title":"H3K36 methylation reprograms gene expression to drive early gametocyte development in Plasmodium falciparum.","date":"2021","source":"Epigenetics & chromatin","url":"https://pubmed.ncbi.nlm.nih.gov/33794978","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CEPT"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"29853527","id":"","title":"Contribution of the precursors and interplay of the pathways in the phospholipid metabolism of the malaria parasite.","date":"2018","source":"Journal of lipid research","url":"https://pubmed.ncbi.nlm.nih.gov/29853527","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CEPT"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"23917939","id":"","title":"Plasmodium falciparum malaria: proteomic studies.","date":"2012","source":"Revista Brasileira de terapia intensiva","url":"https://pubmed.ncbi.nlm.nih.gov/23917939","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CEPT"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"27616047","id":"","title":"Plasmodium falciparum Choline Kinase Inhibition Leads to a Major Decrease in Phosphatidylethanolamine Causing Parasite Death.","date":"2016","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/27616047","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CEPT"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"24209716","id":"","title":"Kinetic modelling of phospholipid synthesis in Plasmodium knowlesi unravels crucial steps and relative importance of multiple pathways.","date":"2013","source":"BMC systems biology","url":"https://pubmed.ncbi.nlm.nih.gov/24209716","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CEPT"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"25470252","id":"","title":"A chemical proteomics approach for the search of pharmacological targets of the antimalarial clinical candidate albitiazolium in Plasmodium falciparum using photocrosslinking and click chemistry.","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/25470252","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CEPT"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"29895950","id":"","title":"Heterologous expression of CTP:phosphocholine cytidylyltransferase from Plasmodium falciparum rescues Chinese Hamster Ovary cells deficient in the Kennedy phosphatidylcholine biosynthesis pathway.","date":"2018","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/29895950","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CEPT"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"22471905","id":"","title":"Transport and pharmacodynamics of albitiazolium, an antimalarial drug candidate.","date":"2012","source":"British journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/22471905","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CEPT"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"20085640","id":"","title":"Identification of inhibitors of Plasmodium falciparum phosphoethanolamine methyltransferase using an enzyme-coupled transmethylation assay.","date":"2010","source":"BMC biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/20085640","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CEPT"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"18973684","id":"","title":"A systematic approach to understand the mechanism of action of the bisthiazolium compound T4 on the human malaria parasite, Plasmodium falciparum.","date":"2008","source":"BMC genomics","url":"https://pubmed.ncbi.nlm.nih.gov/18973684","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CEPT"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":18824,"output_tokens":1969,"usd":0.043004,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":7151,"output_tokens":2856,"usd":0.053578,"stage2_stop_reason":"end_turn"},"total_usd":0.096582,"stage1_batch_id":"msgbatch_01SRp5hyRc82zNjddxyCCXGk","stage2_batch_id":"msgbatch_01K3BTmBazRo3pRrMvyaPMTY","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2010,\n      \"finding\": \"CEPT (PF3D7_0628300 ortholog in P. berghei) is refractory to gene knockout, indicating it is essential for asexual blood-stage development. GFP-tagging of the P. berghei CEPT showed it localizes primarily to the endoplasmic reticulum, in contrast to the cytosolic localization of CCT, ECT, and CK. Sequence analysis confirmed the presence of all catalytic domains and essential residues/motifs necessary for enzymatic activity.\",\n      \"method\": \"Gene knockout attempts (consistently refractory), GFP-fusion live imaging, sequence analysis of catalytic domains\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct GFP localization experiment with functional consequence (essentiality inferred from refractory knockouts), single lab but two orthogonal methods (KO attempts + GFP tagging)\",\n      \"pmids\": [\"20478340\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"CEPT enzymatic activity (CDP-choline/ethanolamine phosphotransferase) was measured in P. falciparum parasite extracts via radiolabelled substrate incorporation assay, yielding a Km for CDP-choline of 13.2 ± 0.7 µM under Michaelis-Menten kinetics. Albitiazolium inhibited CEPT activity with an IC50 of 4.2 mM in vitro, demonstrating that albitiazolium affects the final enzymatic step of de novo PC biosynthesis.\",\n      \"method\": \"Radiolabelled substrate enzyme activity assay, Michaelis-Menten kinetics, inhibitor dose-response (IC50 determination)\",\n      \"journal\": \"British journal of pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro enzymatic assay with kinetic characterization, single lab, single method\",\n      \"pmids\": [\"22471905\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"CEPT (PF3D7_0628300) was identified as the primary protein target of albitiazolium in living P. falciparum parasites using a bifunctional photoactivatable and clickable albitiazolium-derived probe (UA1936). Competitive displacement with free albitiazolium caused the greatest reduction in CEPT peptide spectral matches (3-fold), confirming the albitiazolium pharmacophore directly interacts with CEPT. The probe co-localized with the endoplasmic reticulum and trans-Golgi network.\",\n      \"method\": \"Chemical proteomics: photocrosslinking in live parasites, click-chemistry affinity purification, mass spectrometry, competitive displacement assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in-cell photo-crosslinking with competitive displacement controls and MS identification, two orthogonal methods (AfBPP + competition), single lab\",\n      \"pmids\": [\"25470252\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"CEPT (PfCEPT) protein levels were significantly decreased in P. falciparum parasites treated with the bisthiazolium compound T4, as detected by proteomics, while no corresponding transcriptional change was observed, suggesting post-transcriptional or post-translational regulation of CEPT. Metabolic studies confirmed that T4 treatment caused a major reduction in PC synthesis from choline and ethanolamine, consistent with CEPT inhibition.\",\n      \"method\": \"Quantitative proteomics (peptide spectral counts), transcriptome profiling, metabolic radiolabelling assay\",\n      \"journal\": \"BMC genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two orthogonal methods (proteomics + metabolic labelling), single lab, no direct mechanistic follow-up of the post-translational regulation\",\n      \"pmids\": [\"18973684\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"CEPT (PF3D7_0628300) was found to interact with phosphatidylserine synthase (PfPSS) in P. falciparum, as demonstrated by co-immunoprecipitation in transgenic parasites expressing PfPSS-GFP. Both proteins localize to the ER, supporting a model in which the ER is the major site for phospholipid biosynthesis and that ER-mitochondria contact sites (ERMC) mediate phospholipid synthesis/transport.\",\n      \"method\": \"Co-immunoprecipitation using GFP-tagged PfPSS in transgenic parasites, high-resolution microscopy\",\n      \"journal\": \"Mitochondrion\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP without reciprocal confirmation, single lab, interaction inferred from GFP-tagged partner pulldown\",\n      \"pmids\": [\"35623558\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"The CEPT gene (PF3D7_0628300) is enriched with repressive H3K36me2 and H3K36me3 histone modifications in stage II gametocytes of P. falciparum, correlating with its transcriptional repression at this developmental stage. This implicates H3K36me2/3 as a regulatory mechanism controlling CEPT expression during early sexual development.\",\n      \"method\": \"Chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq) for H3K36me2 and H3K36me3\",\n      \"journal\": \"Epigenetics & chromatin\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — ChIP-seq identifies chromatin association but no direct functional consequence for CEPT specifically was established, single lab\",\n      \"pmids\": [\"33794978\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"CEPT (PF3D7_0628300) is an essential endoplasmic reticulum-localized choline/ethanolamine phosphotransferase in Plasmodium that catalyzes the final step of both PC and PE biosynthesis via the Kennedy pathway (Km for CDP-choline ~13 µM), is the primary molecular target of the antimalarial albitiazolium (displaced by competitive photocrosslinking in live parasites), physically interacts with phosphatidylserine synthase (PfPSS) at the ER, and is subject to post-transcriptional/post-translational downregulation upon disruption of its substrate supply; in blood-stage parasites the gene is refractory to knockout and its locus is marked by repressive H3K36me2/3 in stage II gametocytes.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"CEPT (PF3D7_0628300) is an endoplasmic reticulum-localized choline/ethanolaminephosphotransferase that catalyzes the terminal step of de novo phosphatidylcholine biosynthesis in Plasmodium and is essential for asexual blood-stage development [#0, #1]. In P. berghei the gene is refractory to knockout, and GFP-tagging localizes the protein to the ER, distinguishing it from the cytosolic upstream Kennedy-pathway enzymes; sequence analysis confirms the catalytic domains and residues required for phosphotransferase activity [#0]. In P. falciparum, CEPT displays CDP-choline phosphotransferase activity with a Km of ~13 µM and is the primary molecular target of the antimalarial albitiazolium, which inhibits the enzyme in vitro and directly engages CEPT in living parasites as shown by competitive photocrosslinking with a clickable albitiazolium probe that co-localizes to the ER and trans-Golgi [#1, #2]. CEPT protein levels fall upon pharmacological disruption of phospholipid synthesis without a matching transcriptional change, indicating post-transcriptional/post-translational regulation [#3]. Co-immunoprecipitation places CEPT in physical association with phosphatidylserine synthase at the ER [#4], and its locus is marked by repressive H3K36me2/3 in stage II gametocytes, correlating with stage-specific transcriptional silencing [#5]. Beyond these findings, no further mechanistic detail on CEPT has been characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2008,\n      \"claim\": \"Established that CEPT protein abundance, but not transcript level, responds to bisthiazolium (T4) treatment that blocks PC synthesis, revealing a post-transcriptional/post-translational control layer coupled to phospholipid pathway status.\",\n      \"evidence\": \"Quantitative proteomics with parallel transcriptome profiling and metabolic radiolabelling in T4-treated P. falciparum\",\n      \"pmids\": [\"18973684\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of the post-translational downregulation not identified\", \"Does not establish whether CEPT is a direct T4 target versus a downstream responder\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Determined that CEPT is essential for asexual blood-stage growth and localizes to the ER, unlike the cytosolic upstream Kennedy-pathway enzymes, placing the terminal biosynthetic step at the ER.\",\n      \"evidence\": \"Refractory gene-knockout attempts plus GFP-fusion live imaging and catalytic-domain sequence analysis in P. berghei\",\n      \"pmids\": [\"20478340\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Essentiality inferred from refractory KO rather than conditional depletion\", \"Enzymatic activity not directly demonstrated in this study\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Provided direct enzymatic characterization of CEPT as a CDP-choline phosphotransferase and linked the antimalarial albitiazolium to inhibition of this terminal PC-biosynthesis step.\",\n      \"evidence\": \"Radiolabelled-substrate activity assay with Michaelis-Menten kinetics (Km CDP-choline ~13 µM) and albitiazolium IC50 determination in P. falciparum extracts\",\n      \"pmids\": [\"22471905\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Activity measured in crude extracts rather than purified recombinant enzyme\", \"In vitro IC50 (~4.2 mM) leaves cellular relevance of inhibition unresolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Confirmed in living parasites that the albitiazolium pharmacophore directly engages CEPT, identifying it as the primary drug target and reinforcing ER/trans-Golgi localization.\",\n      \"evidence\": \"In-cell photocrosslinking with a bifunctional albitiazolium probe, click-chemistry affinity purification, mass spectrometry, and competitive displacement in P. falciparum\",\n      \"pmids\": [\"25470252\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Binding site on CEPT not mapped\", \"Whether target engagement fully accounts for antimalarial killing not established\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Linked stage-specific transcriptional repression of the CEPT locus to repressive H3K36me2/3 chromatin marks during early gametocytogenesis.\",\n      \"evidence\": \"ChIP-seq for H3K36me2 and H3K36me3 in stage II gametocytes of P. falciparum\",\n      \"pmids\": [\"33794978\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Chromatin association shown but no direct functional consequence for CEPT demonstrated\", \"Causal role of the marks in silencing untested\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Placed CEPT in physical proximity to phosphatidylserine synthase at the ER, suggesting spatial coordination of phospholipid biosynthesis.\",\n      \"evidence\": \"Co-immunoprecipitation via GFP-tagged PfPSS in transgenic P. falciparum with high-resolution microscopy\",\n      \"pmids\": [\"35623558\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single Co-IP without reciprocal validation\", \"Direct versus indirect interaction not distinguished\", \"Functional significance of the association untested\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How CEPT activity is regulated at the protein level in response to phospholipid supply, and the structural basis of albitiazolium binding, remain unresolved.\",\n      \"evidence\": \"No discovery in the corpus addresses the regulatory or structural mechanism directly\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural model of CEPT or its drug-binding site\", \"Mechanism of post-translational downregulation unknown\", \"No purified recombinant enzyme characterization\"],\n      \"attribution\": []\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0004142\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0004307\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0, 2, 4]},\n      {\"term_id\": \"GO:0005802\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0006656\", \"supporting_discovery_ids\": [1, 3]},\n      {\"term_id\": \"GO:0006646\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"Phosphatidylserine synthase (PfPSS)\"],\n    \"other_free_text\": [\n      \"Primary molecular target of the antimalarial albitiazolium, directly engaged in live parasites [#2].\",\n      \"Refractory to knockout in P. berghei, indicating essentiality for asexual blood-stage development [#0].\",\n      \"Km for CDP-choline ~13 µM measured in P. falciparum extracts [#1].\",\n      \"Protein level downregulated post-transcriptionally upon disruption of PC synthesis [#3].\",\n      \"Locus marked by repressive H3K36me2/3 in stage II gametocytes, correlating with transcriptional repression [#5].\"\n    ]\n  }\n}\n```","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_0628300","name":null,"product":"choline/ethanolaminephosphotransferase, putative","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_1127000","name":null,"product":"choline/ethanolaminephosphotransferase","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_1121500","name":null,"product":"choline/ethanolaminephosphotransferase, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"CEPT","evaluation":null}