{"gene":"PRAP1","run_date":"2026-06-10T06:43:35","timeline":{"discoveries":[{"year":2020,"finding":"PRAP1 directly binds triglyceride (TG) and forms a ternary complex with TG and MTTP in the endoplasmic reticulum; a single amino acid mutation (E85V) abolishes ternary complex formation and impairs MTTP-mediated apoB-containing lipoprotein assembly and secretion, demonstrating that ternary complex formation is required for PRAP1 to facilitate MTTP-mediated lipid transport.","method":"Co-localization (ER), in vitro lipid-binding assay, mutagenesis (E85V knock-in), lipoprotein secretion assay, Prap1-/- and E85V knock-in mouse models","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — direct lipid-binding assay, mutagenesis with functional validation, and genetic mouse models all converge on the same mechanism in one rigorous study","pmids":["33168624"],"is_preprint":false},{"year":2012,"finding":"PRAP1 is a direct transcriptional target of p53: functional p53-response elements in PRAP1 intron 1 physically interact with p53 (ChIP assay). Under DNA-damage conditions, p53-induced PRAP1 promotes cell-cycle arrest and protects cancer cells from apoptosis; PRAP1 knockdown increases apoptosis after 5-FU treatment.","method":"ChIP assay (p53–PRAP1 intron 1 interaction), siRNA knockdown, cell viability/apoptosis assays after chemotherapy and irradiation","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal ChIP plus functional knockdown in a single lab with two orthogonal methods","pmids":["23235459"],"is_preprint":false},{"year":2014,"finding":"PRAP1 physically interacts with MAD1 (and its isoform MAD1β), identified by yeast two-hybrid screening and confirmed by co-immunoprecipitation. Stable overexpression of PRAP1 in mitotic-checkpoint-competent HCC cells impairs the mitotic checkpoint, causes chromosome bridges and aberrant chromosome numbers, and leads to significant down-regulation of MAD1 protein levels.","method":"Yeast two-hybrid screening, co-immunoprecipitation, stable PRAP1 overexpression, mitotic checkpoint assay, chromosome analysis","journal":"The Journal of pathology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid plus reciprocal Co-IP plus functional mitotic checkpoint assay in a single lab","pmids":["24374861"],"is_preprint":false},{"year":2020,"finding":"PRAP1 is an intrinsically disordered 17 kDa protein highly expressed in small intestinal epithelium. Prap1-/- mice show increased apoptosis and p21 expression in the small intestinal epithelium after total-body irradiation, establishing a protective role for PRAP1 against oxidative/irradiation-induced apoptosis in the gastrointestinal barrier.","method":"Recombinant protein biochemical characterization, Prap1-/- mouse model, total body irradiation challenge, apoptosis assay, p21 immunostaining, intestinal enteroids","journal":"Cellular and molecular gastroenterology and hepatology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockout with defined phenotypic readout (apoptosis, p21) plus ex vivo enteroid validation in a single study","pmids":["32629119"],"is_preprint":false},{"year":2018,"finding":"PRAP1 knockdown increases γH2AX levels in microvascular endothelial cells exposed chronically to cisplatin, indicating that PRAP1 contributes to DNA damage repair. Pathway analysis suggests PRAP1 regulates YWHAB, MDM2, ISG15, LYN, and CUL1 during cisplatin-induced DNA damage.","method":"siRNA knockdown, γH2AX immunostaining, microarray/gene expression analysis","journal":"Gene","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single knockdown method with one functional readout; pathway partners inferred from expression data, not direct interaction experiments","pmids":["29886035"],"is_preprint":false},{"year":2019,"finding":"PRAP1 expression in the murine uterus is regulated by ARID1A and progesterone receptor (PGR): progesterone suppresses PRAP1 in luminal and glandular epithelium, and this suppression requires both ARID1A and PGR, as Pgr-knockout and PRKO mice fail to suppress PRAP1 upon progesterone treatment.","method":"Uterus-specific Arid1a knockout (Pgr-Cre) mice, PRKO mice, ovariectomy + progesterone treatment, RT-qPCR, immunohistochemistry","journal":"Development & reproduction","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two independent genetic knockout models with consistent suppression phenotype establish ARID1A/PGR as upstream regulators of PRAP1","pmids":["31660454"],"is_preprint":false},{"year":2025,"finding":"PRAP1 promotes colorectal cancer cell proliferation and inhibits ferroptosis by activating the Nrf2 signaling pathway; overexpression activates Nrf2 pathway proteins and reduces iron/Fe2+ accumulation, while PRAP1 silencing blocks Nrf2 signaling and inhibits tumor growth in xenograft models.","method":"PRAP1 overexpression/siRNA knockdown, CCK-8/EdU proliferation assays, TUNEL apoptosis assay, prussian blue staining, iron assay, Western blot for Nrf2 pathway proteins, nude mouse xenograft","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro and in vivo experiments in a single study with multiple orthogonal readouts linking PRAP1 to Nrf2-mediated ferroptosis suppression","pmids":["40373840"],"is_preprint":false}],"current_model":"PRAP1 is a multifunctional intrinsically disordered protein that (1) acts as a lipid-binding cofactor in the endoplasmic reticulum, forming a ternary complex with triglyceride and MTTP to facilitate lipid transport and lipoprotein secretion; (2) is a direct p53 transcriptional target that promotes cell survival and cell-cycle arrest after DNA damage; (3) physically interacts with the spindle-assembly checkpoint protein MAD1 to suppress mitotic checkpoint signaling; (4) protects the intestinal epithelium from irradiation-induced apoptosis; (5) is transcriptionally regulated by ARID1A and progesterone receptor in the uterus; and (6) promotes colorectal cancer cell proliferation while suppressing ferroptosis via activation of the Nrf2 pathway."},"narrative":{"mechanistic_narrative":"PRAP1 is an intrinsically disordered ~17 kDa protein that functions as a stress-protective and lipid-handling factor across epithelial and cancer contexts [PMID:32629119, PMID:33168624]. In the endoplasmic reticulum it acts as a lipid-binding cofactor, directly binding triglyceride and forming a ternary complex with MTTP that is required to facilitate MTTP-mediated lipid transport and apoB-containing lipoprotein assembly and secretion; the E85V mutation abolishes ternary complex formation and impairs this activity [PMID:33168624]. PRAP1 is a direct transcriptional target of p53, with functional p53-response elements in its first intron, and upon DNA damage it promotes cell-cycle arrest and protects cells from apoptosis [PMID:23235459]. Consistent with a cytoprotective role, PRAP1 is highly expressed in small intestinal epithelium, where its loss increases apoptosis and p21 expression after total-body irradiation [PMID:32629119]. In cancer cells it exerts dual roles: it physically interacts with the spindle-assembly checkpoint protein MAD1 and, when overexpressed, impairs the mitotic checkpoint and down-regulates MAD1 protein, producing chromosomal instability [PMID:24374861]; and in colorectal cancer it promotes proliferation and suppresses ferroptosis through activation of Nrf2 signaling [PMID:40373840]. PRAP1 expression is itself controlled upstream by ARID1A and progesterone receptor in the uterine epithelium [PMID:31660454].","teleology":[{"year":2012,"claim":"Established the transcriptional control and pro-survival function of PRAP1 by showing it is a direct p53 target that limits apoptosis after DNA damage, answering how PRAP1 is induced and what it does under genotoxic stress.","evidence":"ChIP of p53 at PRAP1 intron 1, siRNA knockdown with apoptosis/viability assays after 5-FU and irradiation","pmids":["23235459"],"confidence":"Medium","gaps":["Mechanism by which PRAP1 protein blocks apoptosis is not defined","Single-lab functional data","Downstream effectors of PRAP1-induced arrest unknown"]},{"year":2014,"claim":"Identified a physical PRAP1–MAD1 interaction and linked PRAP1 overexpression to mitotic checkpoint failure and chromosomal instability, connecting PRAP1 to genome stability control.","evidence":"Yeast two-hybrid screen, reciprocal co-immunoprecipitation, mitotic checkpoint and chromosome analysis in HCC cells with stable PRAP1 overexpression","pmids":["24374861"],"confidence":"Medium","gaps":["Whether interaction is direct in vitro not shown","Mechanism of MAD1 down-regulation (degradation vs transcription) undefined","Single cell-type context"]},{"year":2018,"claim":"Proposed a role for PRAP1 in DNA-damage repair by showing knockdown elevates γH2AX under chronic cisplatin exposure, extending its stress-protective role to endothelial cells.","evidence":"siRNA knockdown, γH2AX immunostaining and microarray expression profiling in microvascular endothelial cells","pmids":["29886035"],"confidence":"Low","gaps":["Pathway partners (YWHAB, MDM2, ISG15, LYN, CUL1) inferred from expression, not direct interaction","Single knockdown method with one functional readout","No mechanistic link to repair machinery"]},{"year":2019,"claim":"Defined upstream regulation of PRAP1, showing that progesterone suppresses uterine PRAP1 in an ARID1A- and PGR-dependent manner, placing PRAP1 within hormonal/chromatin-remodeling control.","evidence":"Uterus-specific Arid1a knockout and PGR knockout mice with ovariectomy/progesterone challenge, RT-qPCR and IHC","pmids":["31660454"],"confidence":"Medium","gaps":["Direct vs indirect regulation of the PRAP1 locus not resolved","Functional consequence of uterine PRAP1 regulation unknown"]},{"year":2020,"claim":"Resolved a molecular biochemical function for PRAP1 as an ER lipid-binding cofactor that forms a TG–MTTP ternary complex required for lipoprotein secretion, the most mechanistically defined PRAP1 activity.","evidence":"In vitro lipid binding, E85V mutagenesis with functional rescue/loss, lipoprotein secretion assays, Prap1-/- and E85V knock-in mouse models","pmids":["33168624"],"confidence":"High","gaps":["Structural basis of TG/MTTP binding not determined","Relationship between lipid-binding role and cytoprotective/cancer roles unexplored"]},{"year":2020,"claim":"Demonstrated an in vivo cytoprotective role in the gastrointestinal barrier, with PRAP1 loss increasing irradiation-induced apoptosis and p21 in intestinal epithelium.","evidence":"Recombinant protein characterization, Prap1-/- mice with total-body irradiation, apoptosis/p21 readouts, intestinal enteroids","pmids":["32629119"],"confidence":"Medium","gaps":["Molecular pathway connecting PRAP1 to apoptosis suppression in vivo undefined","Relation to its p53-target status not tested directly"]},{"year":2025,"claim":"Extended PRAP1's pro-survival function to cancer by showing it promotes colorectal cancer proliferation and suppresses ferroptosis via Nrf2 pathway activation.","evidence":"Overexpression/knockdown, proliferation/apoptosis assays, iron and Prussian blue staining, Nrf2 pathway Western blots, nude mouse xenografts","pmids":["40373840"],"confidence":"Medium","gaps":["Direct molecular link between PRAP1 and Nrf2 activation not established","Whether ferroptosis suppression depends on lipid-binding activity unknown"]},{"year":null,"claim":"How PRAP1's defined ER lipid-binding/MTTP cofactor activity mechanistically connects to its diverse cytoprotective, mitotic-checkpoint, and Nrf2/ferroptosis roles remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model unifying the disordered protein's multiple activities","No direct biochemical link from PRAP1 to Nrf2 or to apoptosis machinery","Tissue-specific function determinants unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[0]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,2]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[3,6]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[2]}],"complexes":[],"partners":["MTTP","MAD1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q96NZ9","full_name":"Proline-rich acidic protein 1","aliases":["Epididymis tissue protein Li 178","Uterine-specific proline-rich acidic protein"],"length_aa":151,"mass_kda":17.2,"function":"Lipid-binding protein which promotes lipid absorption by facilitating MTTP-mediated lipid transfer (mainly triglycerides and phospholipids) and MTTP-mediated apoB lipoprotein assembly and secretion (By similarity). Protects the gastrointestinal epithelium from irradiation-induced apoptosis (By similarity). May play an important role in maintaining normal growth homeostasis in epithelial cells (PubMed:14583459). Involved in p53/TP53-dependent cell survival after DNA damage (PubMed:23235459). May down-regulate the expression of MAD1L1 and exert a suppressive role in mitotic spindle assembly checkpoint in hepatocellular carcinomas (PubMed:24374861)","subcellular_location":"Secreted; Endoplasmic reticulum","url":"https://www.uniprot.org/uniprotkb/Q96NZ9/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PRAP1","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/PRAP1","total_profiled":1310},"omim":[{"mim_id":"609776","title":"PROLINE-RICH ACIDIC PROTEIN 1; PRAP1","url":"https://www.omim.org/entry/609776"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"intestine","ntpm":1069.3},{"tissue":"liver","ntpm":718.1}],"url":"https://www.proteinatlas.org/search/PRAP1"},"hgnc":{"alias_symbol":["UPA"],"prev_symbol":[]},"alphafold":{"accession":"Q96NZ9","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96NZ9","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q96NZ9-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q96NZ9-F1-predicted_aligned_error_v6.png","plddt_mean":61.47},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PRAP1","jax_strain_url":"https://www.jax.org/strain/search?query=PRAP1"},"sequence":{"accession":"Q96NZ9","fasta_url":"https://rest.uniprot.org/uniprotkb/Q96NZ9.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q96NZ9/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96NZ9"}},"corpus_meta":[{"pmid":"33168624","id":"PMC_33168624","title":"PRAP1 is a novel lipid-binding protein that promotes lipid absorption by facilitating MTTP-mediated lipid transport.","date":"2020","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/33168624","citation_count":35,"is_preprint":false},{"pmid":"23235459","id":"PMC_23235459","title":"PRAP1 is a novel executor of p53-dependent mechanisms in cell survival after DNA damage.","date":"2012","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/23235459","citation_count":28,"is_preprint":false},{"pmid":"20674898","id":"PMC_20674898","title":"Uterine luminal epithelium-specific proline-rich acidic protein 1 (PRAP1) as a marker for successful embryo implantation.","date":"2010","source":"Fertility and sterility","url":"https://pubmed.ncbi.nlm.nih.gov/20674898","citation_count":21,"is_preprint":false},{"pmid":"32629119","id":"PMC_32629119","title":"Proline-Rich Acidic Protein 1 (PRAP1) Protects the Gastrointestinal Epithelium From Irradiation-Induced Apoptosis.","date":"2020","source":"Cellular and molecular gastroenterology and hepatology","url":"https://pubmed.ncbi.nlm.nih.gov/32629119","citation_count":17,"is_preprint":false},{"pmid":"29886035","id":"PMC_29886035","title":"ATF3 and PRAP1 play important roles in cisplatin-induced damages in microvascular endothelial cells.","date":"2018","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/29886035","citation_count":15,"is_preprint":false},{"pmid":"24374861","id":"PMC_24374861","title":"Proline-rich acidic protein 1 (PRAP1) is a novel interacting partner of MAD1 and has a suppressive role in mitotic checkpoint signalling in hepatocellular carcinoma.","date":"2014","source":"The Journal of pathology","url":"https://pubmed.ncbi.nlm.nih.gov/24374861","citation_count":12,"is_preprint":false},{"pmid":"38192816","id":"PMC_38192816","title":"ANP32B promotes colorectal cancer cell progression and reduces cell sensitivity to PRAP1 inhibitor through up-regulating HPF1.","date":"2023","source":"Heliyon","url":"https://pubmed.ncbi.nlm.nih.gov/38192816","citation_count":3,"is_preprint":false},{"pmid":"31660454","id":"PMC_31660454","title":"Proline-Rich Acidic Protein 1 (PRAP1) is a Target of ARID1A and PGR in the Murine Uterus.","date":"2019","source":"Development & reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/31660454","citation_count":3,"is_preprint":false},{"pmid":"40373840","id":"PMC_40373840","title":"PRAP1 regulates colorectal cancer cell proliferation and ferroptosis through the Nrf2 signaling pathway.","date":"2025","source":"Cellular signalling","url":"https://pubmed.ncbi.nlm.nih.gov/40373840","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":6755,"output_tokens":1988,"usd":0.025042,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8965,"output_tokens":2916,"usd":0.058862,"stage2_stop_reason":"end_turn"},"total_usd":0.083904,"stage1_batch_id":"msgbatch_01CNoDbkChHEkgrJnL7BwtGJ","stage2_batch_id":"msgbatch_016Y4x9E9Wg5VQDANj9quSQD","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2020,\n      \"finding\": \"PRAP1 directly binds triglyceride (TG) and forms a ternary complex with TG and MTTP in the endoplasmic reticulum; a single amino acid mutation (E85V) abolishes ternary complex formation and impairs MTTP-mediated apoB-containing lipoprotein assembly and secretion, demonstrating that ternary complex formation is required for PRAP1 to facilitate MTTP-mediated lipid transport.\",\n      \"method\": \"Co-localization (ER), in vitro lipid-binding assay, mutagenesis (E85V knock-in), lipoprotein secretion assay, Prap1-/- and E85V knock-in mouse models\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — direct lipid-binding assay, mutagenesis with functional validation, and genetic mouse models all converge on the same mechanism in one rigorous study\",\n      \"pmids\": [\"33168624\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PRAP1 is a direct transcriptional target of p53: functional p53-response elements in PRAP1 intron 1 physically interact with p53 (ChIP assay). Under DNA-damage conditions, p53-induced PRAP1 promotes cell-cycle arrest and protects cancer cells from apoptosis; PRAP1 knockdown increases apoptosis after 5-FU treatment.\",\n      \"method\": \"ChIP assay (p53–PRAP1 intron 1 interaction), siRNA knockdown, cell viability/apoptosis assays after chemotherapy and irradiation\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal ChIP plus functional knockdown in a single lab with two orthogonal methods\",\n      \"pmids\": [\"23235459\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PRAP1 physically interacts with MAD1 (and its isoform MAD1β), identified by yeast two-hybrid screening and confirmed by co-immunoprecipitation. Stable overexpression of PRAP1 in mitotic-checkpoint-competent HCC cells impairs the mitotic checkpoint, causes chromosome bridges and aberrant chromosome numbers, and leads to significant down-regulation of MAD1 protein levels.\",\n      \"method\": \"Yeast two-hybrid screening, co-immunoprecipitation, stable PRAP1 overexpression, mitotic checkpoint assay, chromosome analysis\",\n      \"journal\": \"The Journal of pathology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid plus reciprocal Co-IP plus functional mitotic checkpoint assay in a single lab\",\n      \"pmids\": [\"24374861\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PRAP1 is an intrinsically disordered 17 kDa protein highly expressed in small intestinal epithelium. Prap1-/- mice show increased apoptosis and p21 expression in the small intestinal epithelium after total-body irradiation, establishing a protective role for PRAP1 against oxidative/irradiation-induced apoptosis in the gastrointestinal barrier.\",\n      \"method\": \"Recombinant protein biochemical characterization, Prap1-/- mouse model, total body irradiation challenge, apoptosis assay, p21 immunostaining, intestinal enteroids\",\n      \"journal\": \"Cellular and molecular gastroenterology and hepatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockout with defined phenotypic readout (apoptosis, p21) plus ex vivo enteroid validation in a single study\",\n      \"pmids\": [\"32629119\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PRAP1 knockdown increases γH2AX levels in microvascular endothelial cells exposed chronically to cisplatin, indicating that PRAP1 contributes to DNA damage repair. Pathway analysis suggests PRAP1 regulates YWHAB, MDM2, ISG15, LYN, and CUL1 during cisplatin-induced DNA damage.\",\n      \"method\": \"siRNA knockdown, γH2AX immunostaining, microarray/gene expression analysis\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single knockdown method with one functional readout; pathway partners inferred from expression data, not direct interaction experiments\",\n      \"pmids\": [\"29886035\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PRAP1 expression in the murine uterus is regulated by ARID1A and progesterone receptor (PGR): progesterone suppresses PRAP1 in luminal and glandular epithelium, and this suppression requires both ARID1A and PGR, as Pgr-knockout and PRKO mice fail to suppress PRAP1 upon progesterone treatment.\",\n      \"method\": \"Uterus-specific Arid1a knockout (Pgr-Cre) mice, PRKO mice, ovariectomy + progesterone treatment, RT-qPCR, immunohistochemistry\",\n      \"journal\": \"Development & reproduction\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two independent genetic knockout models with consistent suppression phenotype establish ARID1A/PGR as upstream regulators of PRAP1\",\n      \"pmids\": [\"31660454\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PRAP1 promotes colorectal cancer cell proliferation and inhibits ferroptosis by activating the Nrf2 signaling pathway; overexpression activates Nrf2 pathway proteins and reduces iron/Fe2+ accumulation, while PRAP1 silencing blocks Nrf2 signaling and inhibits tumor growth in xenograft models.\",\n      \"method\": \"PRAP1 overexpression/siRNA knockdown, CCK-8/EdU proliferation assays, TUNEL apoptosis assay, prussian blue staining, iron assay, Western blot for Nrf2 pathway proteins, nude mouse xenograft\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro and in vivo experiments in a single study with multiple orthogonal readouts linking PRAP1 to Nrf2-mediated ferroptosis suppression\",\n      \"pmids\": [\"40373840\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PRAP1 is a multifunctional intrinsically disordered protein that (1) acts as a lipid-binding cofactor in the endoplasmic reticulum, forming a ternary complex with triglyceride and MTTP to facilitate lipid transport and lipoprotein secretion; (2) is a direct p53 transcriptional target that promotes cell survival and cell-cycle arrest after DNA damage; (3) physically interacts with the spindle-assembly checkpoint protein MAD1 to suppress mitotic checkpoint signaling; (4) protects the intestinal epithelium from irradiation-induced apoptosis; (5) is transcriptionally regulated by ARID1A and progesterone receptor in the uterus; and (6) promotes colorectal cancer cell proliferation while suppressing ferroptosis via activation of the Nrf2 pathway.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PRAP1 is an intrinsically disordered ~17 kDa protein that functions as a stress-protective and lipid-handling factor across epithelial and cancer contexts [#3, #0]. In the endoplasmic reticulum it acts as a lipid-binding cofactor, directly binding triglyceride and forming a ternary complex with MTTP that is required to facilitate MTTP-mediated lipid transport and apoB-containing lipoprotein assembly and secretion; the E85V mutation abolishes ternary complex formation and impairs this activity [#0]. PRAP1 is a direct transcriptional target of p53, with functional p53-response elements in its first intron, and upon DNA damage it promotes cell-cycle arrest and protects cells from apoptosis [#1]. Consistent with a cytoprotective role, PRAP1 is highly expressed in small intestinal epithelium, where its loss increases apoptosis and p21 expression after total-body irradiation [#3]. In cancer cells it exerts dual roles: it physically interacts with the spindle-assembly checkpoint protein MAD1 and, when overexpressed, impairs the mitotic checkpoint and down-regulates MAD1 protein, producing chromosomal instability [#2]; and in colorectal cancer it promotes proliferation and suppresses ferroptosis through activation of Nrf2 signaling [#6]. PRAP1 expression is itself controlled upstream by ARID1A and progesterone receptor in the uterine epithelium [#5].\",\n  \"teleology\": [\n    {\n      \"year\": 2012,\n      \"claim\": \"Established the transcriptional control and pro-survival function of PRAP1 by showing it is a direct p53 target that limits apoptosis after DNA damage, answering how PRAP1 is induced and what it does under genotoxic stress.\",\n      \"evidence\": \"ChIP of p53 at PRAP1 intron 1, siRNA knockdown with apoptosis/viability assays after 5-FU and irradiation\",\n      \"pmids\": [\"23235459\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Mechanism by which PRAP1 protein blocks apoptosis is not defined\", \"Single-lab functional data\", \"Downstream effectors of PRAP1-induced arrest unknown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identified a physical PRAP1\\u2013MAD1 interaction and linked PRAP1 overexpression to mitotic checkpoint failure and chromosomal instability, connecting PRAP1 to genome stability control.\",\n      \"evidence\": \"Yeast two-hybrid screen, reciprocal co-immunoprecipitation, mitotic checkpoint and chromosome analysis in HCC cells with stable PRAP1 overexpression\",\n      \"pmids\": [\"24374861\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Whether interaction is direct in vitro not shown\", \"Mechanism of MAD1 down-regulation (degradation vs transcription) undefined\", \"Single cell-type context\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Proposed a role for PRAP1 in DNA-damage repair by showing knockdown elevates \\u03b3H2AX under chronic cisplatin exposure, extending its stress-protective role to endothelial cells.\",\n      \"evidence\": \"siRNA knockdown, \\u03b3H2AX immunostaining and microarray expression profiling in microvascular endothelial cells\",\n      \"pmids\": [\"29886035\"],\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Pathway partners (YWHAB, MDM2, ISG15, LYN, CUL1) inferred from expression, not direct interaction\", \"Single knockdown method with one functional readout\", \"No mechanistic link to repair machinery\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Defined upstream regulation of PRAP1, showing that progesterone suppresses uterine PRAP1 in an ARID1A- and PGR-dependent manner, placing PRAP1 within hormonal/chromatin-remodeling control.\",\n      \"evidence\": \"Uterus-specific Arid1a knockout and PGR knockout mice with ovariectomy/progesterone challenge, RT-qPCR and IHC\",\n      \"pmids\": [\"31660454\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Direct vs indirect regulation of the PRAP1 locus not resolved\", \"Functional consequence of uterine PRAP1 regulation unknown\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Resolved a molecular biochemical function for PRAP1 as an ER lipid-binding cofactor that forms a TG\\u2013MTTP ternary complex required for lipoprotein secretion, the most mechanistically defined PRAP1 activity.\",\n      \"evidence\": \"In vitro lipid binding, E85V mutagenesis with functional rescue/loss, lipoprotein secretion assays, Prap1-/- and E85V knock-in mouse models\",\n      \"pmids\": [\"33168624\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Structural basis of TG/MTTP binding not determined\", \"Relationship between lipid-binding role and cytoprotective/cancer roles unexplored\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Demonstrated an in vivo cytoprotective role in the gastrointestinal barrier, with PRAP1 loss increasing irradiation-induced apoptosis and p21 in intestinal epithelium.\",\n      \"evidence\": \"Recombinant protein characterization, Prap1-/- mice with total-body irradiation, apoptosis/p21 readouts, intestinal enteroids\",\n      \"pmids\": [\"32629119\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Molecular pathway connecting PRAP1 to apoptosis suppression in vivo undefined\", \"Relation to its p53-target status not tested directly\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Extended PRAP1's pro-survival function to cancer by showing it promotes colorectal cancer proliferation and suppresses ferroptosis via Nrf2 pathway activation.\",\n      \"evidence\": \"Overexpression/knockdown, proliferation/apoptosis assays, iron and Prussian blue staining, Nrf2 pathway Western blots, nude mouse xenografts\",\n      \"pmids\": [\"40373840\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Direct molecular link between PRAP1 and Nrf2 activation not established\", \"Whether ferroptosis suppression depends on lipid-binding activity unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How PRAP1's defined ER lipid-binding/MTTP cofactor activity mechanistically connects to its diverse cytoprotective, mitotic-checkpoint, and Nrf2/ferroptosis roles remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"No structural model unifying the disordered protein's multiple activities\", \"No direct biochemical link from PRAP1 to Nrf2 or to apoptosis machinery\", \"Tissue-specific function determinants unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [3, 6]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"MTTP\", \"MAD1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}