{"gene":"TMEM219","run_date":"2026-06-10T10:51:55","timeline":{"discoveries":[{"year":2016,"finding":"TMEM219 is a direct binding partner of IL-13Rα2, forming a complex that mediates chitinase 3-like-1 (Chi3l1) signaling. TMEM219 physically interacts with IL-13Rα2-Chi3l1 complexes as demonstrated by yeast two-hybrid, co-immunoprecipitation, co-localization, bimolecular fluorescence complementation, and fluorescence anisotropy nanodisc assays. Null mutations or siRNA silencing of TMEM219 decreased Chi3l1-stimulated epithelial cell HB-EGF production and macrophage MAPK/Erk and PKB/Akt activation, phenocopying IL-13Rα2 loss. TMEM219 also contributed to the decoy function of IL-13Rα2.","method":"Yeast two-hybrid, co-immunoprecipitation, co-localization, bimolecular fluorescence complementation, fluorescence anisotropy nanodisc assays, null mutation and siRNA knockdown with signaling readouts","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods including direct biophysical interaction assay, genetic null mutations, and siRNA with defined signaling readouts in a single study","pmids":["27629921"],"is_preprint":false},{"year":2016,"finding":"Galectin-3 physically interacts with IL-13Rα2 and competes with TMEM219 for IL-13Rα2 binding, thereby diminishing the antiapoptotic signaling induced by Chi3l1 in epithelial cells via the IL-13Rα2/TMEM219 complex.","method":"Biophysical and signaling assays demonstrating competition between Galectin-3 and TMEM219 for IL-13Rα2","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biophysical competition assay with signaling readout, single lab","pmids":["29427412"],"is_preprint":false},{"year":2015,"finding":"TMEM219 functions as a receptor for IGFBP-3 on colonic stem cells (CoSCs) in an IGF-I-independent manner. IGFBP-3 binding to TMEM219 prevents in vitro growth of patient-derived intestinal organoids. Treatment with recombinant ecto-TMEM219 protein normalized CoSC homeostasis in a preclinical diabetic enteropathy model.","method":"Patient-derived organoid culture, in vivo preclinical model with ecto-TMEM219 recombinant protein treatment, proteomic profiling of patient serum","journal":"Cell stem cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — receptor-ligand interaction validated in organoid system and in vivo preclinical model, recombinant protein intervention with defined functional readout","pmids":["26431183"],"is_preprint":false},{"year":2022,"finding":"TMEM219 is expressed on pancreatic beta cells and functions as a death receptor whose activation by IGFBP-3 leads to beta cell loss and dysfunction. In vitro and in vivo short-term IGFBP-3/TMEM219 inhibition and TMEM219 genetic ablation preserved beta cells and prevented/delayed diabetes onset; long-term blockade allowed beta cell expansion.","method":"In vitro IGFBP3/TMEM219 inhibition assays, in vivo genetic ablation of TMEM219, preclinical diabetes models with pharmacological blockade","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic ablation combined with pharmacological inhibition in vivo, replicated across multiple model systems and patient cohorts","pmids":["35115561"],"is_preprint":false},{"year":2022,"finding":"TMEM219 (IGFBP-3 receptor) expressed in mammalian cells has an apparent molecular weight of approximately 22 kDa and is localized to the cell surface, as confirmed by flow cytometry showing ~84% surface expression in transfected HeLa cells.","method":"Stable overexpression in HeLa cells, western blotting, flow cytometry, SDS-PAGE of purified recombinant protein","journal":"Advanced biomedical research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct surface localization by flow cytometry and western blot, single lab","pmids":["35386539"],"is_preprint":false},{"year":2024,"finding":"TMEM219 is expressed on fetal pancreas, beta cell precursors, and in vitro embryonic-derived endocrine progenitors. TMEM219 signaling negatively regulates beta cells at early stages and induces Caspase 8-mediated cell death. miR-129-2 acts as an upstream regulator that downregulates TMEM219 expression in islets and in vitro endocrine progenitors.","method":"Pharmacological blockade of TMEM219, miR-129-2 mimic/inhibitor experiments in islets and insulinoma-derived cells, assessment of Caspase 8 activation and proliferation markers","journal":"Frontiers in endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological and miRNA-based functional studies with defined caspase-8 readout, single lab","pmids":["38318298"],"is_preprint":false},{"year":2025,"finding":"TMEM219 mediates intestinal stem cell (ISC) death in Crohn's disease via a proapoptotic molecular signature involving Caspase-8 activation. Pharmacological blockade of IGFBP3/TMEM219 binding with recombinant ecto-TMEM219 restored ISC self-renewal in patient-derived organoids and ameliorated colitis in vivo. Tissue-specific deletion of TMEM219 in ISCs (TMEM219fl/fl LGR5cre mice) revived mucosal regenerative abilities both in vitro and in vivo.","method":"Patient-derived organoids, DSS-induced and T cell-mediated colitis in vivo models, tissue-specific genetic deletion (TMEM219fl/fl LGR5cre mice), ecto-TMEM219 recombinant protein treatment, Caspase-8 activity assays","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — tissue-specific genetic deletion in vivo combined with organoid rescue and pharmacological blockade, multiple orthogonal methods with defined mechanistic readout","pmids":["40371646"],"is_preprint":false},{"year":2025,"finding":"Anti-TMEM219 monoclonal antibodies generated by phage display (particularly Ent001) block IGFBP3/TMEM219 binding, rescue ISC markers and function in IGFBP3-treated human mini-guts, downregulate Caspase-8, and improve colitis and prevent inflammatory-mediated carcinogenesis in vivo.","method":"Phage display antibody generation, in vitro organoid assays, DSS-induced chronic colitis and inflammatory carcinogenesis in vivo models, Caspase-8 expression assays","journal":"Pharmacological research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological blocking antibody with defined binding displacement and functional readouts in vitro and in vivo, single lab","pmids":["40783087"],"is_preprint":false},{"year":2025,"finding":"IGFBP3 overexpression in hepatocytes activates the TMEM219/Caspase-8 signaling pathway, driving hepatocyte apoptosis. Liver-specific IGFBP3 knockout mice showed attenuated alcoholic liver injury with reduced apoptosis. An IGF1-binding site mutant of IGFBP3 (IGFBP3GGG) showed significantly lower apoptosis than wild-type IGFBP3 overexpression, implicating IGF-independent TMEM219 signaling in IGFBP3-induced hepatocyte apoptosis.","method":"IGFBP3 overexpression and IGF1-binding mutant (IGFBP3GGG) in AML12 cells, liver-specific IGFBP3 knockout mice, caspase-8 activation assays, chronic ethanol exposure model","journal":"Frontiers in physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockout and mutagenesis with defined caspase-8 mechanistic readout, single lab","pmids":["42222293"],"is_preprint":false},{"year":2025,"finding":"IGFBP-3/TMEM219 pathway is upregulated during bile duct ligation-induced liver fibrosis progression in rats, with coordinated increases in IGFBP-3 and TMEM219 gene expression alongside activation of Caspase-3/7 and Caspase-8, indicating that TMEM219-mediated hepatocyte apoptosis contributes to liver fibrosis progression.","method":"Bile duct ligation rat model, RT-PCR for IGFBP-3 and TMEM219 gene expression, caspase 3/7 and caspase 8 activity assays, histopathology, immunofluorescence","journal":"Molecular biology reports","confidence":"Low","confidence_rationale":"Tier 3 / Weak — correlative gene expression and caspase activity in a single disease model without direct mechanistic intervention on TMEM219","pmids":["40853400"],"is_preprint":false},{"year":2013,"finding":"TMEM219 was identified as a receptor for IGFBP-3 with a demonstrated role in inducing caspase-8-dependent apoptosis.","method":"Biochemical assays establishing IGFBP-3/TMEM219 receptor interaction with caspase-8 apoptosis readout (as reviewed/cited)","journal":"Journal of cell communication and signaling","confidence":"Low","confidence_rationale":"Tier 3 / Weak — review paper citing prior findings; no new primary experimental data described in this abstract","pmids":["23700234"],"is_preprint":false}],"current_model":"TMEM219 is a transmembrane death receptor expressed on intestinal stem cells, colonic stem cells, pancreatic beta cells, and other epithelial cell types that mediates pro-apoptotic signaling upon binding its circulating ligand IGFBP-3 (in an IGF-I-independent manner), activating Caspase-8-dependent apoptosis; it also acts as a co-receptor within the IL-13Rα2/Chi3l1 signaling complex to activate MAPK/Erk and PKB/Akt pathways, and its expression is post-transcriptionally regulated by miR-129-2, with blockade of IGFBP-3/TMEM219 signaling preserving stem cell and beta cell homeostasis in preclinical models of diabetes, inflammatory bowel disease, and liver fibrosis."},"narrative":{"mechanistic_narrative":"TMEM219 is a cell-surface death receptor that couples binding of its circulating ligand IGFBP-3 to Caspase-8-dependent apoptosis in epithelial and endocrine cell populations, thereby acting as a negative regulator of tissue stem cell and beta cell homeostasis [PMID:26431183, PMID:35115561, PMID:40371646]. It is expressed on colonic and intestinal stem cells, pancreatic beta cells and their fetal precursors, and hepatocytes, where IGFBP-3 engagement drives cell loss in a manner independent of IGF-I sequestration [PMID:26431183, PMID:38318298, PMID:42222293]. Pro-apoptotic signaling proceeds through Caspase-8 activation, and genetic ablation or tissue-specific deletion of TMEM219, recombinant ecto-TMEM219 decoy protein, or anti-TMEM219 blocking antibodies (e.g. Ent001) restore stem cell self-renewal and beta cell mass and ameliorate diabetic enteropathy, colitis, inflammatory carcinogenesis, and diabetes in preclinical models [PMID:35115561, PMID:40371646, PMID:40783087]. Independently of its IGFBP-3 receptor role, TMEM219 is a direct binding partner of IL-13Rα2 within the Chi3l1 signaling complex, where it is required for Chi3l1-stimulated epithelial HB-EGF production and macrophage MAPK/Erk and PKB/Akt activation and contributes to IL-13Rα2 decoy function; Galectin-3 competes with TMEM219 for IL-13Rα2 binding [PMID:27629921, PMID:29427412]. TMEM219 expression is post-transcriptionally downregulated by miR-129-2 [PMID:38318298].","teleology":[{"year":2015,"claim":"Established that TMEM219 acts as a functional IGFBP-3 receptor on colonic stem cells controlling their homeostasis, defining a receptor for a previously orphan ligand activity independent of IGF-I.","evidence":"Patient-derived intestinal organoids and a preclinical diabetic enteropathy model with recombinant ecto-TMEM219 treatment","pmids":["26431183"],"confidence":"High","gaps":["Downstream signaling cascade not yet defined","Did not establish the apoptotic effector mechanism"]},{"year":2016,"claim":"Revealed a second, distinct role for TMEM219 as a direct binding partner of IL-13Rα2 required for Chi3l1-driven MAPK/Erk and Akt signaling, showing the protein participates in a receptor complex beyond IGFBP-3 binding.","evidence":"Yeast two-hybrid, co-IP, BiFC, fluorescence anisotropy nanodisc assays, plus null mutation and siRNA with signaling readouts","pmids":["27629921"],"confidence":"High","gaps":["Relationship between the IGFBP-3 receptor role and the IL-13Rα2 co-receptor role unresolved","Stoichiometry within the complex not defined"]},{"year":2018,"claim":"Showed that Galectin-3 competes with TMEM219 for IL-13Rα2 binding, identifying a regulatory input that modulates the antiapoptotic Chi3l1 signaling axis.","evidence":"Biophysical competition and signaling assays in epithelial cells","pmids":["29427412"],"confidence":"Medium","gaps":["Single-lab competition assay","Physiological context of competition not established in vivo"]},{"year":2022,"claim":"Demonstrated that TMEM219 functions as a death receptor on pancreatic beta cells, connecting IGFBP-3 engagement to beta cell loss and providing a therapeutic rationale for blockade.","evidence":"In vitro and in vivo IGFBP-3/TMEM219 inhibition, TMEM219 genetic ablation, and preclinical diabetes models","pmids":["35115561"],"confidence":"High","gaps":["Molecular link from receptor to caspase activation not detailed","Long-term consequences of chronic blockade incompletely characterized"]},{"year":2022,"claim":"Confirmed TMEM219 as a ~22 kDa cell-surface protein in mammalian cells, grounding the receptor model in direct localization data.","evidence":"Stable overexpression in HeLa cells with western blot and flow cytometry","pmids":["35386539"],"confidence":"Medium","gaps":["No structural information on ligand-binding interface","Single-lab overexpression system"]},{"year":2024,"claim":"Extended the death-receptor model to fetal beta cell precursors and identified miR-129-2 as an upstream post-transcriptional regulator of TMEM219, defining a Caspase-8-mediated effector pathway and its regulation.","evidence":"Pharmacological blockade and miR-129-2 mimic/inhibitor experiments in islets and insulinoma cells with Caspase-8 readouts","pmids":["38318298"],"confidence":"Medium","gaps":["Direct miR-129-2 targeting of TMEM219 transcript not shown mechanistically","Single-lab study"]},{"year":2025,"claim":"Demonstrated through tissue-specific deletion and organoid/antibody blockade that TMEM219-driven Caspase-8 activation mediates intestinal stem cell death in Crohn's disease and that blockade restores regeneration, establishing causality in inflammatory bowel disease.","evidence":"Patient-derived organoids, DSS and T cell colitis models, TMEM219fl/fl LGR5cre mice, ecto-TMEM219 and anti-TMEM219 antibody (Ent001) treatment","pmids":["40371646","40783087"],"confidence":"High","gaps":["Receptor proximal signaling adaptors upstream of Caspase-8 not identified","Antibody data from single lab"]},{"year":2025,"claim":"Implicated IGF-independent TMEM219/Caspase-8 signaling in hepatocyte apoptosis during liver injury and fibrosis, broadening the pathway to liver disease.","evidence":"IGFBP3 overexpression and IGF1-binding mutant in hepatocytes, liver-specific IGFBP3 knockout mice, bile duct ligation rat model, caspase activity assays","pmids":["42222293","40853400"],"confidence":"Medium","gaps":["Liver fibrosis evidence is correlative without direct TMEM219 intervention","Hepatocyte-specific TMEM219 deletion not tested"]},{"year":null,"claim":"The proximal molecular events linking TMEM219 ligand engagement to Caspase-8 activation, and how the IGFBP-3 death-receptor role integrates with the IL-13Rα2 co-receptor role, remain undefined.","evidence":"","pmids":[],"confidence":"Low","gaps":["No identified adaptor or signaling intermediate between receptor and Caspase-8","No structural model of the IGFBP-3/TMEM219 interface","Reconciliation of pro-apoptotic and Chi3l1 co-receptor functions unresolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[2,3]},{"term_id":"GO:0038024","term_label":"cargo receptor activity","supporting_discovery_ids":[2]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[4]}],"pathway":[{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[3,5,6]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0]}],"complexes":["IL-13Rα2–Chi3l1 signaling complex"],"partners":["IGFBP3","IL13RA2","LGALS3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q86XT9","full_name":"Insulin-like growth factor-binding protein 3 receptor","aliases":["Transmembrane protein 219"],"length_aa":240,"mass_kda":25.7,"function":"Cell death receptor specific for IGFBP3, may mediate caspase-8-dependent apoptosis upon ligand binding","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/Q86XT9/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TMEM219","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/TMEM219","total_profiled":1310},"omim":[{"mim_id":"620290","title":"TRANSMEMBRANE PROTEIN 219; TMEM219","url":"https://www.omim.org/entry/620290"},{"mim_id":"615851","title":"PONTOCEREBELLAR HYPOPLASIA, TYPE 2E; PCH2E","url":"https://www.omim.org/entry/615851"},{"mim_id":"615850","title":"VPS53 SUBUNIT OF GARP COMPLEX; VPS53","url":"https://www.omim.org/entry/615850"},{"mim_id":"300130","title":"INTERLEUKIN 13 RECEPTOR, ALPHA-2; IL13RA2","url":"https://www.omim.org/entry/300130"},{"mim_id":"146732","title":"INSULIN-LIKE GROWTH FACTOR-BINDING PROTEIN 3; IGFBP3","url":"https://www.omim.org/entry/146732"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/TMEM219"},"hgnc":{"alias_symbol":["IGFBP-3R"],"prev_symbol":[]},"alphafold":{"accession":"Q86XT9","domains":[{"cath_id":"-","chopping":"54-179","consensus_level":"high","plddt":66.6779,"start":54,"end":179},{"cath_id":"1.10.287","chopping":"19-45_194-226","consensus_level":"high","plddt":83.8982,"start":19,"end":226}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q86XT9","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q86XT9-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q86XT9-F1-predicted_aligned_error_v6.png","plddt_mean":67.88},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TMEM219","jax_strain_url":"https://www.jax.org/strain/search?query=TMEM219"},"sequence":{"accession":"Q86XT9","fasta_url":"https://rest.uniprot.org/uniprotkb/Q86XT9.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q86XT9/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q86XT9"}},"corpus_meta":[{"pmid":"27629921","id":"PMC_27629921","title":"IL-13Rα2 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TMEM219 physically interacts with IL-13Rα2-Chi3l1 complexes as demonstrated by yeast two-hybrid, co-immunoprecipitation, co-localization, bimolecular fluorescence complementation, and fluorescence anisotropy nanodisc assays. Null mutations or siRNA silencing of TMEM219 decreased Chi3l1-stimulated epithelial cell HB-EGF production and macrophage MAPK/Erk and PKB/Akt activation, phenocopying IL-13Rα2 loss. TMEM219 also contributed to the decoy function of IL-13Rα2.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, co-localization, bimolecular fluorescence complementation, fluorescence anisotropy nanodisc assays, null mutation and siRNA knockdown with signaling readouts\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal methods including direct biophysical interaction assay, genetic null mutations, and siRNA with defined signaling readouts in a single study\",\n      \"pmids\": [\"27629921\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Galectin-3 physically interacts with IL-13Rα2 and competes with TMEM219 for IL-13Rα2 binding, thereby diminishing the antiapoptotic signaling induced by Chi3l1 in epithelial cells via the IL-13Rα2/TMEM219 complex.\",\n      \"method\": \"Biophysical and signaling assays demonstrating competition between Galectin-3 and TMEM219 for IL-13Rα2\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biophysical competition assay with signaling readout, single lab\",\n      \"pmids\": [\"29427412\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"TMEM219 functions as a receptor for IGFBP-3 on colonic stem cells (CoSCs) in an IGF-I-independent manner. IGFBP-3 binding to TMEM219 prevents in vitro growth of patient-derived intestinal organoids. Treatment with recombinant ecto-TMEM219 protein normalized CoSC homeostasis in a preclinical diabetic enteropathy model.\",\n      \"method\": \"Patient-derived organoid culture, in vivo preclinical model with ecto-TMEM219 recombinant protein treatment, proteomic profiling of patient serum\",\n      \"journal\": \"Cell stem cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — receptor-ligand interaction validated in organoid system and in vivo preclinical model, recombinant protein intervention with defined functional readout\",\n      \"pmids\": [\"26431183\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"TMEM219 is expressed on pancreatic beta cells and functions as a death receptor whose activation by IGFBP-3 leads to beta cell loss and dysfunction. In vitro and in vivo short-term IGFBP-3/TMEM219 inhibition and TMEM219 genetic ablation preserved beta cells and prevented/delayed diabetes onset; long-term blockade allowed beta cell expansion.\",\n      \"method\": \"In vitro IGFBP3/TMEM219 inhibition assays, in vivo genetic ablation of TMEM219, preclinical diabetes models with pharmacological blockade\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic ablation combined with pharmacological inhibition in vivo, replicated across multiple model systems and patient cohorts\",\n      \"pmids\": [\"35115561\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"TMEM219 (IGFBP-3 receptor) expressed in mammalian cells has an apparent molecular weight of approximately 22 kDa and is localized to the cell surface, as confirmed by flow cytometry showing ~84% surface expression in transfected HeLa cells.\",\n      \"method\": \"Stable overexpression in HeLa cells, western blotting, flow cytometry, SDS-PAGE of purified recombinant protein\",\n      \"journal\": \"Advanced biomedical research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct surface localization by flow cytometry and western blot, single lab\",\n      \"pmids\": [\"35386539\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"TMEM219 is expressed on fetal pancreas, beta cell precursors, and in vitro embryonic-derived endocrine progenitors. TMEM219 signaling negatively regulates beta cells at early stages and induces Caspase 8-mediated cell death. miR-129-2 acts as an upstream regulator that downregulates TMEM219 expression in islets and in vitro endocrine progenitors.\",\n      \"method\": \"Pharmacological blockade of TMEM219, miR-129-2 mimic/inhibitor experiments in islets and insulinoma-derived cells, assessment of Caspase 8 activation and proliferation markers\",\n      \"journal\": \"Frontiers in endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological and miRNA-based functional studies with defined caspase-8 readout, single lab\",\n      \"pmids\": [\"38318298\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"TMEM219 mediates intestinal stem cell (ISC) death in Crohn's disease via a proapoptotic molecular signature involving Caspase-8 activation. Pharmacological blockade of IGFBP3/TMEM219 binding with recombinant ecto-TMEM219 restored ISC self-renewal in patient-derived organoids and ameliorated colitis in vivo. Tissue-specific deletion of TMEM219 in ISCs (TMEM219fl/fl LGR5cre mice) revived mucosal regenerative abilities both in vitro and in vivo.\",\n      \"method\": \"Patient-derived organoids, DSS-induced and T cell-mediated colitis in vivo models, tissue-specific genetic deletion (TMEM219fl/fl LGR5cre mice), ecto-TMEM219 recombinant protein treatment, Caspase-8 activity assays\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — tissue-specific genetic deletion in vivo combined with organoid rescue and pharmacological blockade, multiple orthogonal methods with defined mechanistic readout\",\n      \"pmids\": [\"40371646\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Anti-TMEM219 monoclonal antibodies generated by phage display (particularly Ent001) block IGFBP3/TMEM219 binding, rescue ISC markers and function in IGFBP3-treated human mini-guts, downregulate Caspase-8, and improve colitis and prevent inflammatory-mediated carcinogenesis in vivo.\",\n      \"method\": \"Phage display antibody generation, in vitro organoid assays, DSS-induced chronic colitis and inflammatory carcinogenesis in vivo models, Caspase-8 expression assays\",\n      \"journal\": \"Pharmacological research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological blocking antibody with defined binding displacement and functional readouts in vitro and in vivo, single lab\",\n      \"pmids\": [\"40783087\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"IGFBP3 overexpression in hepatocytes activates the TMEM219/Caspase-8 signaling pathway, driving hepatocyte apoptosis. Liver-specific IGFBP3 knockout mice showed attenuated alcoholic liver injury with reduced apoptosis. An IGF1-binding site mutant of IGFBP3 (IGFBP3GGG) showed significantly lower apoptosis than wild-type IGFBP3 overexpression, implicating IGF-independent TMEM219 signaling in IGFBP3-induced hepatocyte apoptosis.\",\n      \"method\": \"IGFBP3 overexpression and IGF1-binding mutant (IGFBP3GGG) in AML12 cells, liver-specific IGFBP3 knockout mice, caspase-8 activation assays, chronic ethanol exposure model\",\n      \"journal\": \"Frontiers in physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockout and mutagenesis with defined caspase-8 mechanistic readout, single lab\",\n      \"pmids\": [\"42222293\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"IGFBP-3/TMEM219 pathway is upregulated during bile duct ligation-induced liver fibrosis progression in rats, with coordinated increases in IGFBP-3 and TMEM219 gene expression alongside activation of Caspase-3/7 and Caspase-8, indicating that TMEM219-mediated hepatocyte apoptosis contributes to liver fibrosis progression.\",\n      \"method\": \"Bile duct ligation rat model, RT-PCR for IGFBP-3 and TMEM219 gene expression, caspase 3/7 and caspase 8 activity assays, histopathology, immunofluorescence\",\n      \"journal\": \"Molecular biology reports\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — correlative gene expression and caspase activity in a single disease model without direct mechanistic intervention on TMEM219\",\n      \"pmids\": [\"40853400\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"TMEM219 was identified as a receptor for IGFBP-3 with a demonstrated role in inducing caspase-8-dependent apoptosis.\",\n      \"method\": \"Biochemical assays establishing IGFBP-3/TMEM219 receptor interaction with caspase-8 apoptosis readout (as reviewed/cited)\",\n      \"journal\": \"Journal of cell communication and signaling\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — review paper citing prior findings; no new primary experimental data described in this abstract\",\n      \"pmids\": [\"23700234\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TMEM219 is a transmembrane death receptor expressed on intestinal stem cells, colonic stem cells, pancreatic beta cells, and other epithelial cell types that mediates pro-apoptotic signaling upon binding its circulating ligand IGFBP-3 (in an IGF-I-independent manner), activating Caspase-8-dependent apoptosis; it also acts as a co-receptor within the IL-13Rα2/Chi3l1 signaling complex to activate MAPK/Erk and PKB/Akt pathways, and its expression is post-transcriptionally regulated by miR-129-2, with blockade of IGFBP-3/TMEM219 signaling preserving stem cell and beta cell homeostasis in preclinical models of diabetes, inflammatory bowel disease, and liver fibrosis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TMEM219 is a cell-surface death receptor that couples binding of its circulating ligand IGFBP-3 to Caspase-8-dependent apoptosis in epithelial and endocrine cell populations, thereby acting as a negative regulator of tissue stem cell and beta cell homeostasis [#2, #3, #6]. It is expressed on colonic and intestinal stem cells, pancreatic beta cells and their fetal precursors, and hepatocytes, where IGFBP-3 engagement drives cell loss in a manner independent of IGF-I sequestration [#2, #5, #8]. Pro-apoptotic signaling proceeds through Caspase-8 activation, and genetic ablation or tissue-specific deletion of TMEM219, recombinant ecto-TMEM219 decoy protein, or anti-TMEM219 blocking antibodies (e.g. Ent001) restore stem cell self-renewal and beta cell mass and ameliorate diabetic enteropathy, colitis, inflammatory carcinogenesis, and diabetes in preclinical models [#3, #6, #7]. Independently of its IGFBP-3 receptor role, TMEM219 is a direct binding partner of IL-13Rα2 within the Chi3l1 signaling complex, where it is required for Chi3l1-stimulated epithelial HB-EGF production and macrophage MAPK/Erk and PKB/Akt activation and contributes to IL-13Rα2 decoy function; Galectin-3 competes with TMEM219 for IL-13Rα2 binding [#0, #1]. TMEM219 expression is post-transcriptionally downregulated by miR-129-2 [#5].\"\n,\n  \"teleology\": [\n    {\n      \"year\": 2015,\n      \"claim\": \"Established that TMEM219 acts as a functional IGFBP-3 receptor on colonic stem cells controlling their homeostasis, defining a receptor for a previously orphan ligand activity independent of IGF-I.\",\n      \"evidence\": \"Patient-derived intestinal organoids and a preclinical diabetic enteropathy model with recombinant ecto-TMEM219 treatment\",\n      \"pmids\": [\"26431183\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream signaling cascade not yet defined\", \"Did not establish the apoptotic effector mechanism\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Revealed a second, distinct role for TMEM219 as a direct binding partner of IL-13Rα2 required for Chi3l1-driven MAPK/Erk and Akt signaling, showing the protein participates in a receptor complex beyond IGFBP-3 binding.\",\n      \"evidence\": \"Yeast two-hybrid, co-IP, BiFC, fluorescence anisotropy nanodisc assays, plus null mutation and siRNA with signaling readouts\",\n      \"pmids\": [\"27629921\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relationship between the IGFBP-3 receptor role and the IL-13Rα2 co-receptor role unresolved\", \"Stoichiometry within the complex not defined\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Showed that Galectin-3 competes with TMEM219 for IL-13Rα2 binding, identifying a regulatory input that modulates the antiapoptotic Chi3l1 signaling axis.\",\n      \"evidence\": \"Biophysical competition and signaling assays in epithelial cells\",\n      \"pmids\": [\"29427412\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab competition assay\", \"Physiological context of competition not established in vivo\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Demonstrated that TMEM219 functions as a death receptor on pancreatic beta cells, connecting IGFBP-3 engagement to beta cell loss and providing a therapeutic rationale for blockade.\",\n      \"evidence\": \"In vitro and in vivo IGFBP-3/TMEM219 inhibition, TMEM219 genetic ablation, and preclinical diabetes models\",\n      \"pmids\": [\"35115561\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular link from receptor to caspase activation not detailed\", \"Long-term consequences of chronic blockade incompletely characterized\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Confirmed TMEM219 as a ~22 kDa cell-surface protein in mammalian cells, grounding the receptor model in direct localization data.\",\n      \"evidence\": \"Stable overexpression in HeLa cells with western blot and flow cytometry\",\n      \"pmids\": [\"35386539\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural information on ligand-binding interface\", \"Single-lab overexpression system\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Extended the death-receptor model to fetal beta cell precursors and identified miR-129-2 as an upstream post-transcriptional regulator of TMEM219, defining a Caspase-8-mediated effector pathway and its regulation.\",\n      \"evidence\": \"Pharmacological blockade and miR-129-2 mimic/inhibitor experiments in islets and insulinoma cells with Caspase-8 readouts\",\n      \"pmids\": [\"38318298\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct miR-129-2 targeting of TMEM219 transcript not shown mechanistically\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Demonstrated through tissue-specific deletion and organoid/antibody blockade that TMEM219-driven Caspase-8 activation mediates intestinal stem cell death in Crohn's disease and that blockade restores regeneration, establishing causality in inflammatory bowel disease.\",\n      \"evidence\": \"Patient-derived organoids, DSS and T cell colitis models, TMEM219fl/fl LGR5cre mice, ecto-TMEM219 and anti-TMEM219 antibody (Ent001) treatment\",\n      \"pmids\": [\"40371646\", \"40783087\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor proximal signaling adaptors upstream of Caspase-8 not identified\", \"Antibody data from single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Implicated IGF-independent TMEM219/Caspase-8 signaling in hepatocyte apoptosis during liver injury and fibrosis, broadening the pathway to liver disease.\",\n      \"evidence\": \"IGFBP3 overexpression and IGF1-binding mutant in hepatocytes, liver-specific IGFBP3 knockout mice, bile duct ligation rat model, caspase activity assays\",\n      \"pmids\": [\"42222293\", \"40853400\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Liver fibrosis evidence is correlative without direct TMEM219 intervention\", \"Hepatocyte-specific TMEM219 deletion not tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The proximal molecular events linking TMEM219 ligand engagement to Caspase-8 activation, and how the IGFBP-3 death-receptor role integrates with the IL-13Rα2 co-receptor role, remain undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No identified adaptor or signaling intermediate between receptor and Caspase-8\", \"No structural model of the IGFBP-3/TMEM219 interface\", \"Reconciliation of pro-apoptotic and Chi3l1 co-receptor functions unresolved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"GO:0038024\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [3, 5, 6]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"complexes\": [\"IL-13Rα2–Chi3l1 signaling complex\"],\n    \"partners\": [\"IGFBP3\", \"IL13RA2\", \"LGALS3\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}