{"gene":"ERN2","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":2008,"finding":"IRE1β (ERN2) selectively degrades MTP (microsomal triglyceride transfer protein) mRNA through increased posttranscriptional degradation in enterocytes, thereby inhibiting chylomicron production. This activity is specific to IRE1β and not shared by its ubiquitous homolog IRE1α. Knockdown of IRE1β enhanced MTP expression, and Ire1b−/− mice fed high-fat/cholesterol diets secreted more chylomicrons and expressed more intestinal MTP.","method":"Ire1b−/− mouse model, primary enterocyte isolation, cell culture knockdown, mRNA stability assays, lipid secretion measurements","journal":"Cell metabolism","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal genetic (KO mice) and cell culture knockdown with multiple orthogonal readouts (mRNA levels, chylomicron secretion, MTP expression), replicated across in vivo and in vitro systems","pmids":["18460335"],"is_preprint":false},{"year":2012,"finding":"Loss of Ire1β in Apoe−/− mice results in increased intestinal MTP expression, enhanced lipid absorption, hyperlipidemia, and greater atherosclerotic plaque burden compared to Apoe−/− controls, confirming that ERN2/IRE1β regulates intestinal lipid absorption in vivo.","method":"Ire1b−/−/Apoe−/− double-knockout mouse model, lipid absorption assays, atherosclerotic plaque quantification, intestinal MTP protein measurement","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO model with multiple physiological readouts, independent replication of the MTP regulatory role established in PMID 18460335","pmids":["22556338"],"is_preprint":false},{"year":2019,"finding":"ERN2/IRE1β acts downstream of IL-1β and the transcription factor SPDEF in airway epithelial cells to upregulate mucin gene expression (MUC5B and MUC5AC), contributing to mucus hyperconcentration in cystic fibrosis airways.","method":"Human bronchial epithelial (HBE) cell cultures, CF lung tissue mRNA analysis, cytokine stimulation experiments, gene expression analysis","journal":"The Journal of clinical investigation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pathway placement via defined cellular phenotype in primary human cells and patient tissue, single lab with multiple readouts but no reconstitution or mutagenesis","pmids":["31524632"],"is_preprint":false},{"year":2019,"finding":"ERN2/IRE1β acts as an ER stress sensor that, through its downstream effector spliced XBP1 (XBP1S), regulates MUC5B and MUC5AC expression in airway epithelia. XBP1S binds the proximal MUC5B promoter and differentially upregulates MUC5B in the context of the rs35705950 risk variant. KIRA6 (IRE1 kinase inhibitor) and XBP1 CRISPR-Cas9 knockout blocked cytokine-induced MUC5B expression.","method":"Primary human airway epithelial cells, transgenic mouse models, XBP1S overexpression, MUC5B promoter reporter assays, KIRA6 inhibitor, CRISPR-Cas9 XBP1 knockout, ChIP/binding assays","journal":"American journal of respiratory and critical care medicine","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal methods including promoter binding assays, transgenic mouse models, pharmacological inhibition, and CRISPR KO, all in one study","pmids":["30973754"],"is_preprint":false},{"year":2022,"finding":"ERN2/IRE1β is required for microbiota-induced goblet cell maturation and mucus barrier assembly in the colon. ERN2 acts by splicing Xbp1 mRNA to expand ER function and prevent ER stress in goblet cells. Although ERN1 can also splice Xbp1, it did not act redundantly with ERN2 in this context. Loss of ERN2 resulted in dysbiotic microbiota and increased susceptibility to colitis.","method":"Ern2−/− mice (conventionally raised and germ-free), germ-free colonization experiments, Xbp1 mRNA splicing assays, histological analysis of goblet cells, colitis susceptibility transfer experiments","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO model with germ-free/colonization experiments, multiple orthogonal readouts (goblet cell morphology, Xbp1 splicing, mucus assembly, microbiota transfer), single lab but highly rigorous multi-method design","pmids":["35727638"],"is_preprint":false},{"year":2024,"finding":"The transcription factor SPDEF promotes classical pancreatic ductal adenocarcinoma differentiation through target genes AGR2 and ERN2/IRE1β that regulate mucus production. Inactivation of the SPDEF programme impairs tumor growth and facilitates subtype interconversion from classical towards basal-like differentiation.","method":"Mouse PDA models, organoids, cell lines, orthotopically grafted tumor models, immunolabeling, single-cell expression profiling","journal":"Gut","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple model systems (mouse, organoid, orthotopic graft) identifying ERN2 as a SPDEF target in PDA, but ERN2-specific mechanistic experiments not detailed at the molecular level in the abstract","pmids":["38262672"],"is_preprint":false},{"year":2025,"finding":"IRE1α and IRE1β protect intestinal epithelium and suppress colorectal tumorigenesis through distinct mechanisms. IRE1α-mediated splicing of Xbp1 mRNA was maintained following Ire1β deletion but was abolished in double Ire1α−/−Ire1β−/− mice. Single deletion of either Ire1α or Ire1β produced a growth advantage increasing tumor burden in AOM-DSS and APCmin models, whereas double deletion caused progressive intestinal injury and tumorigenesis with loss of defense-associated mRNAs and gain of inflammatory mRNAs.","method":"Intestine-specific Ire1α deletion, germline Ire1β deletion, double-KO mice, RNA-Seq, AOM-DSS and APCmin tumorigenesis models, Xbp1 splicing assays","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple genetic models and orthogonal readouts in a preprint, not yet peer-reviewed","pmids":["40654814"],"is_preprint":true},{"year":2024,"finding":"TNF signaling in Paneth cells transcriptionally downregulates Ern1 and Ern2 (IRE1 key UPR mediators), abolishing steady-state UPR, causing reduced antimicrobial peptide production and bacterial translocation leading to sepsis. This effect required TNF receptor P55 and IFNAR1.","method":"PC-specific P55 deletion mice, IFNAR1-deficient mice, gene expression analysis, antimicrobial peptide measurement, bacterial translocation assays","journal":"Cell host & microbe","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic models with defined phenotypic readouts, but ERN2 is one of two IRE1 genes downregulated and specific ERN2-only contribution is not isolated","pmids":["39243761"],"is_preprint":false},{"year":2026,"finding":"ERN2/IRE1β promotes mucus hypersecretion in neutrophilic asthma via the ERN2/XBP1-AGR2 axis, increasing MUC5AC secretion. Inhibiting ERN2 in vivo (with 4μ8C) and in vitro (lentiviral knockdown) reduced mucus secretion, ER stress markers, and inflammatory cytokines. The physical interaction between ERN2 and AGR2 was confirmed by Co-IP and molecular dynamics simulation.","method":"NA mouse model, HBE135-E6E7 cell ER stress model, lentivirus-mediated ERN2 knockdown, 4μ8C inhibitor, Co-immunoprecipitation, molecular dynamics simulation, BALF analysis","journal":"International immunopharmacology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP binding interaction confirmed plus in vivo and in vitro functional inhibition, single lab","pmids":["41483622"],"is_preprint":false}],"current_model":"ERN2/IRE1β is an ER-resident kinase/endoribonuclease expressed predominantly in intestinal and airway mucosal epithelial cells that functions as an ER stress sensor: it selectively degrades MTP mRNA in enterocytes to suppress chylomicron production, splices XBP1 mRNA to expand ER capacity and support goblet cell mucus production in response to gut microbiota, and drives mucin gene (MUC5B, MUC5AC) expression downstream of SPDEF and IL-1β signaling through XBP1S in airway epithelia, with its RNase activity also mediating physical interaction with AGR2 to promote mucus hypersecretion."},"narrative":{"mechanistic_narrative":"ERN2 (IRE1β) is a mucosal epithelial-restricted ER stress sensor with dual kinase/endoribonuclease activity that governs lipid handling and mucus production in the intestine and airway [PMID:18460335, PMID:35727638]. In enterocytes it selectively accelerates degradation of MTP mRNA to restrain microsomal triglyceride transfer protein levels and thereby limit chylomicron assembly, an activity not shared by the ubiquitous homolog IRE1α; loss of ERN2 raises intestinal MTP, lipid absorption, and atherosclerotic burden in vivo [PMID:18460335, PMID:22556338]. In its other principal role, ERN2 splices XBP1 mRNA to generate XBP1S, expanding ER capacity to support goblet cell maturation and mucus barrier assembly in response to gut microbiota, with ERN2 loss producing dysbiosis and colitis susceptibility [PMID:35727638]. In airway epithelia ERN2 acts downstream of IL-1β and the transcription factor SPDEF, and via XBP1S, which binds the proximal MUC5B promoter, drives MUC5B and MUC5AC mucin expression contributing to mucus hyperconcentration in cystic fibrosis [PMID:31524632, PMID:30973754]. Its RNase activity additionally mediates a physical interaction with AGR2 that promotes MUC5AC hypersecretion in neutrophilic asthma [PMID:41483622]. ERN2 is a SPDEF target gene also implicated in mucus production in pancreatic ductal adenocarcinoma differentiation [PMID:38262672], and together with IRE1α it suppresses colorectal tumorigenesis [PMID:40654814].","teleology":[{"year":2008,"claim":"Established a tissue-specific catabolic function for ERN2 distinct from IRE1α: it post-transcriptionally degrades MTP mRNA in enterocytes to limit chylomicron production.","evidence":"Ire1b−/− mice, primary enterocyte knockdown, mRNA stability and lipid secretion assays","pmids":["18460335"],"confidence":"High","gaps":["Whether MTP mRNA is a direct RNase cleavage substrate was not biochemically resolved","Mechanism of substrate selectivity over IRE1α not defined"]},{"year":2012,"claim":"Confirmed the physiological consequence of ERN2-mediated MTP regulation by linking its loss to enhanced lipid absorption and atherosclerosis in vivo.","evidence":"Ire1b−/−/Apoe−/− double-knockout mice, lipid absorption and plaque quantification","pmids":["22556338"],"confidence":"High","gaps":["Does not establish the molecular trigger for ERN2 activation in enterocytes","Tissue-autonomy of the effect not dissected"]},{"year":2019,"claim":"Placed ERN2 in an airway mucin-induction pathway downstream of IL-1β and SPDEF and identified XBP1S as the effector binding the MUC5B promoter, defining how ER stress signaling drives mucin gene expression.","evidence":"Primary HBE cells, CF tissue, transgenic mice, MUC5B promoter reporters/ChIP, KIRA6 inhibition, XBP1 CRISPR KO","pmids":["31524632","30973754"],"confidence":"High","gaps":["How IL-1β/SPDEF signaling activates ERN2 RNase activity not resolved","MUC5AC regulation mechanism less defined than MUC5B"]},{"year":2022,"claim":"Demonstrated that microbiota induce ERN2-dependent XBP1 splicing to expand ER function for goblet cell maturation and mucus barrier assembly, and that IRE1α cannot substitute in this context.","evidence":"Ern2−/− conventional and germ-free mice, colonization experiments, Xbp1 splicing assays, goblet cell histology, colitis transfer","pmids":["35727638"],"confidence":"High","gaps":["Microbial signal and receptor activating ERN2 not identified","Basis for non-redundancy with ERN1 unexplained"]},{"year":2024,"claim":"Extended the SPDEF-ERN2-mucus axis to disease by identifying ERN2 as a SPDEF target supporting classical PDA differentiation and tumor growth.","evidence":"Mouse PDA models, organoids, orthotopic grafts, single-cell profiling","pmids":["38262672"],"confidence":"Medium","gaps":["ERN2-specific molecular mechanism in PDA not isolated from AGR2","Causal contribution of ERN2 vs other SPDEF targets not separated"]},{"year":2024,"claim":"Showed that inflammatory TNF signaling in Paneth cells transcriptionally suppresses Ern1/Ern2 to abolish steady-state UPR, linking ERN2 downregulation to antimicrobial defense failure and sepsis.","evidence":"Paneth-cell P55-deletion and IFNAR1-deficient mice, antimicrobial peptide and bacterial translocation assays","pmids":["39243761"],"confidence":"Medium","gaps":["ERN2-only contribution not isolated from co-downregulated Ern1","Direct RNase targets in Paneth cells not identified"]},{"year":2026,"claim":"Identified a physical ERN2-AGR2 interaction as the effector arm of an ERN2/XBP1-AGR2 axis driving MUC5AC hypersecretion in neutrophilic asthma.","evidence":"NA mouse model, HBE135-E6E7 ER stress model, lentiviral ERN2 knockdown, 4μ8C inhibitor, Co-IP, molecular dynamics simulation","pmids":["41483622"],"confidence":"Medium","gaps":["Co-IP not reciprocally validated and interaction interface inferred from simulation","Whether the interaction depends on ERN2 catalytic activity not directly tested"]},{"year":null,"claim":"The upstream activating signals and the direct RNase substrate repertoire that distinguish ERN2 from IRE1α across mucosal tissues remain undefined.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of ERN2 substrate recognition in the corpus","Determinants of MTP mRNA versus XBP1 mRNA selectivity unresolved","Mechanism of ERN2-specific activation by microbiota and cytokines unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[0,3,4]},{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[3]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[0,4]},{"term_id":"GO:0140299","term_label":"molecular sensor activity","supporting_discovery_ids":[3,4]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[3,4]}],"pathway":[{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[3,4]},{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[0,4]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,1]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[1,2,6]}],"complexes":[],"partners":["AGR2","XBP1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q76MJ5","full_name":"Serine/threonine-protein kinase/endoribonuclease IRE2","aliases":["Endoplasmic reticulum-to-nucleus signaling 2","Inositol-requiring protein 2","hIRE2p","Ire1-beta","IRE1b"],"length_aa":926,"mass_kda":102.5,"function":"Induces translational repression through 28S ribosomal RNA cleavage in response to ER stress. Pro-apoptotic. Appears to play no role in the unfolded-protein response, unlike closely related proteins","subcellular_location":"Endoplasmic reticulum membrane","url":"https://www.uniprot.org/uniprotkb/Q76MJ5/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ERN2","classification":"Not Classified","n_dependent_lines":16,"n_total_lines":1208,"dependency_fraction":0.013245033112582781},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/ERN2","total_profiled":1310},"omim":[{"mim_id":"604034","title":"ENDOPLASMIC RETICULUM-TO-NUCLEUS SIGNALING 2; ERN2","url":"https://www.omim.org/entry/604034"},{"mim_id":"604033","title":"ENDOPLASMIC RETICULUM-TO-NUCLEUS SIGNALING 1; ERN1","url":"https://www.omim.org/entry/604033"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Endoplasmic reticulum","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"}],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"cervix","ntpm":18.3},{"tissue":"gallbladder","ntpm":15.9},{"tissue":"intestine","ntpm":27.7},{"tissue":"salivary gland","ntpm":22.5},{"tissue":"stomach 1","ntpm":49.0}],"url":"https://www.proteinatlas.org/search/ERN2"},"hgnc":{"alias_symbol":["IRE1b"],"prev_symbol":[]},"alphafold":{"accession":"Q76MJ5","domains":[{"cath_id":"-","chopping":"38-319_354-364","consensus_level":"medium","plddt":74.5124,"start":38,"end":364},{"cath_id":"3.30.200.20","chopping":"514-593","consensus_level":"medium","plddt":86.4612,"start":514,"end":593},{"cath_id":"1.10.510.10","chopping":"622-782","consensus_level":"medium","plddt":88.7513,"start":622,"end":782},{"cath_id":"1.20.1440.180","chopping":"786-910","consensus_level":"high","plddt":92.8434,"start":786,"end":910}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q76MJ5","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q76MJ5-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q76MJ5-F1-predicted_aligned_error_v6.png","plddt_mean":70.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ERN2","jax_strain_url":"https://www.jax.org/strain/search?query=ERN2"},"sequence":{"accession":"Q76MJ5","fasta_url":"https://rest.uniprot.org/uniprotkb/Q76MJ5.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q76MJ5/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q76MJ5"}},"corpus_meta":[{"pmid":"22359644","id":"PMC_22359644","title":"IRE1/bZIP60-mediated 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response and the cytoplasmic heat stress response during heat stress in maize","date":"2024-11-08","source":"bioRxiv","url":"https://doi.org/10.1101/2024.11.06.622333","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":20301,"output_tokens":2649,"usd":0.050319,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10065,"output_tokens":2923,"usd":0.0617,"stage2_stop_reason":"end_turn"},"total_usd":0.112019,"stage1_batch_id":"msgbatch_01AsR7g8dGTEiEw9U83bJeWn","stage2_batch_id":"msgbatch_01YV5ZyxtFNUZEjxRcpd9jzb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2008,\n      \"finding\": \"IRE1β (ERN2) selectively degrades MTP (microsomal triglyceride transfer protein) mRNA through increased posttranscriptional degradation in enterocytes, thereby inhibiting chylomicron production. This activity is specific to IRE1β and not shared by its ubiquitous homolog IRE1α. Knockdown of IRE1β enhanced MTP expression, and Ire1b−/− mice fed high-fat/cholesterol diets secreted more chylomicrons and expressed more intestinal MTP.\",\n      \"method\": \"Ire1b−/− mouse model, primary enterocyte isolation, cell culture knockdown, mRNA stability assays, lipid secretion measurements\",\n      \"journal\": \"Cell metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal genetic (KO mice) and cell culture knockdown with multiple orthogonal readouts (mRNA levels, chylomicron secretion, MTP expression), replicated across in vivo and in vitro systems\",\n      \"pmids\": [\"18460335\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Loss of Ire1β in Apoe−/− mice results in increased intestinal MTP expression, enhanced lipid absorption, hyperlipidemia, and greater atherosclerotic plaque burden compared to Apoe−/− controls, confirming that ERN2/IRE1β regulates intestinal lipid absorption in vivo.\",\n      \"method\": \"Ire1b−/−/Apoe−/− double-knockout mouse model, lipid absorption assays, atherosclerotic plaque quantification, intestinal MTP protein measurement\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO model with multiple physiological readouts, independent replication of the MTP regulatory role established in PMID 18460335\",\n      \"pmids\": [\"22556338\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"ERN2/IRE1β acts downstream of IL-1β and the transcription factor SPDEF in airway epithelial cells to upregulate mucin gene expression (MUC5B and MUC5AC), contributing to mucus hyperconcentration in cystic fibrosis airways.\",\n      \"method\": \"Human bronchial epithelial (HBE) cell cultures, CF lung tissue mRNA analysis, cytokine stimulation experiments, gene expression analysis\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pathway placement via defined cellular phenotype in primary human cells and patient tissue, single lab with multiple readouts but no reconstitution or mutagenesis\",\n      \"pmids\": [\"31524632\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"ERN2/IRE1β acts as an ER stress sensor that, through its downstream effector spliced XBP1 (XBP1S), regulates MUC5B and MUC5AC expression in airway epithelia. XBP1S binds the proximal MUC5B promoter and differentially upregulates MUC5B in the context of the rs35705950 risk variant. KIRA6 (IRE1 kinase inhibitor) and XBP1 CRISPR-Cas9 knockout blocked cytokine-induced MUC5B expression.\",\n      \"method\": \"Primary human airway epithelial cells, transgenic mouse models, XBP1S overexpression, MUC5B promoter reporter assays, KIRA6 inhibitor, CRISPR-Cas9 XBP1 knockout, ChIP/binding assays\",\n      \"journal\": \"American journal of respiratory and critical care medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal methods including promoter binding assays, transgenic mouse models, pharmacological inhibition, and CRISPR KO, all in one study\",\n      \"pmids\": [\"30973754\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ERN2/IRE1β is required for microbiota-induced goblet cell maturation and mucus barrier assembly in the colon. ERN2 acts by splicing Xbp1 mRNA to expand ER function and prevent ER stress in goblet cells. Although ERN1 can also splice Xbp1, it did not act redundantly with ERN2 in this context. Loss of ERN2 resulted in dysbiotic microbiota and increased susceptibility to colitis.\",\n      \"method\": \"Ern2−/− mice (conventionally raised and germ-free), germ-free colonization experiments, Xbp1 mRNA splicing assays, histological analysis of goblet cells, colitis susceptibility transfer experiments\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO model with germ-free/colonization experiments, multiple orthogonal readouts (goblet cell morphology, Xbp1 splicing, mucus assembly, microbiota transfer), single lab but highly rigorous multi-method design\",\n      \"pmids\": [\"35727638\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The transcription factor SPDEF promotes classical pancreatic ductal adenocarcinoma differentiation through target genes AGR2 and ERN2/IRE1β that regulate mucus production. Inactivation of the SPDEF programme impairs tumor growth and facilitates subtype interconversion from classical towards basal-like differentiation.\",\n      \"method\": \"Mouse PDA models, organoids, cell lines, orthotopically grafted tumor models, immunolabeling, single-cell expression profiling\",\n      \"journal\": \"Gut\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple model systems (mouse, organoid, orthotopic graft) identifying ERN2 as a SPDEF target in PDA, but ERN2-specific mechanistic experiments not detailed at the molecular level in the abstract\",\n      \"pmids\": [\"38262672\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"IRE1α and IRE1β protect intestinal epithelium and suppress colorectal tumorigenesis through distinct mechanisms. IRE1α-mediated splicing of Xbp1 mRNA was maintained following Ire1β deletion but was abolished in double Ire1α−/−Ire1β−/− mice. Single deletion of either Ire1α or Ire1β produced a growth advantage increasing tumor burden in AOM-DSS and APCmin models, whereas double deletion caused progressive intestinal injury and tumorigenesis with loss of defense-associated mRNAs and gain of inflammatory mRNAs.\",\n      \"method\": \"Intestine-specific Ire1α deletion, germline Ire1β deletion, double-KO mice, RNA-Seq, AOM-DSS and APCmin tumorigenesis models, Xbp1 splicing assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple genetic models and orthogonal readouts in a preprint, not yet peer-reviewed\",\n      \"pmids\": [\"40654814\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"TNF signaling in Paneth cells transcriptionally downregulates Ern1 and Ern2 (IRE1 key UPR mediators), abolishing steady-state UPR, causing reduced antimicrobial peptide production and bacterial translocation leading to sepsis. This effect required TNF receptor P55 and IFNAR1.\",\n      \"method\": \"PC-specific P55 deletion mice, IFNAR1-deficient mice, gene expression analysis, antimicrobial peptide measurement, bacterial translocation assays\",\n      \"journal\": \"Cell host & microbe\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic models with defined phenotypic readouts, but ERN2 is one of two IRE1 genes downregulated and specific ERN2-only contribution is not isolated\",\n      \"pmids\": [\"39243761\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"ERN2/IRE1β promotes mucus hypersecretion in neutrophilic asthma via the ERN2/XBP1-AGR2 axis, increasing MUC5AC secretion. Inhibiting ERN2 in vivo (with 4μ8C) and in vitro (lentiviral knockdown) reduced mucus secretion, ER stress markers, and inflammatory cytokines. The physical interaction between ERN2 and AGR2 was confirmed by Co-IP and molecular dynamics simulation.\",\n      \"method\": \"NA mouse model, HBE135-E6E7 cell ER stress model, lentivirus-mediated ERN2 knockdown, 4μ8C inhibitor, Co-immunoprecipitation, molecular dynamics simulation, BALF analysis\",\n      \"journal\": \"International immunopharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP binding interaction confirmed plus in vivo and in vitro functional inhibition, single lab\",\n      \"pmids\": [\"41483622\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ERN2/IRE1β is an ER-resident kinase/endoribonuclease expressed predominantly in intestinal and airway mucosal epithelial cells that functions as an ER stress sensor: it selectively degrades MTP mRNA in enterocytes to suppress chylomicron production, splices XBP1 mRNA to expand ER capacity and support goblet cell mucus production in response to gut microbiota, and drives mucin gene (MUC5B, MUC5AC) expression downstream of SPDEF and IL-1β signaling through XBP1S in airway epithelia, with its RNase activity also mediating physical interaction with AGR2 to promote mucus hypersecretion.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ERN2 (IRE1\\u03b2) is a mucosal epithelial-restricted ER stress sensor with dual kinase/endoribonuclease activity that governs lipid handling and mucus production in the intestine and airway [#0, #4]. In enterocytes it selectively accelerates degradation of MTP mRNA to restrain microsomal triglyceride transfer protein levels and thereby limit chylomicron assembly, an activity not shared by the ubiquitous homolog IRE1\\u03b1; loss of ERN2 raises intestinal MTP, lipid absorption, and atherosclerotic burden in vivo [#0, #1]. In its other principal role, ERN2 splices XBP1 mRNA to generate XBP1S, expanding ER capacity to support goblet cell maturation and mucus barrier assembly in response to gut microbiota, with ERN2 loss producing dysbiosis and colitis susceptibility [#4]. In airway epithelia ERN2 acts downstream of IL-1\\u03b2 and the transcription factor SPDEF, and via XBP1S, which binds the proximal MUC5B promoter, drives MUC5B and MUC5AC mucin expression contributing to mucus hyperconcentration in cystic fibrosis [#2, #3]. Its RNase activity additionally mediates a physical interaction with AGR2 that promotes MUC5AC hypersecretion in neutrophilic asthma [#8]. ERN2 is a SPDEF target gene also implicated in mucus production in pancreatic ductal adenocarcinoma differentiation [#5], and together with IRE1\\u03b1 it suppresses colorectal tumorigenesis [#6].\",\n  \"teleology\": [\n    {\n      \"year\": 2008,\n      \"claim\": \"Established a tissue-specific catabolic function for ERN2 distinct from IRE1\\u03b1: it post-transcriptionally degrades MTP mRNA in enterocytes to limit chylomicron production.\",\n      \"evidence\": \"Ire1b\\u2212/\\u2212 mice, primary enterocyte knockdown, mRNA stability and lipid secretion assays\",\n      \"pmids\": [\"18460335\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether MTP mRNA is a direct RNase cleavage substrate was not biochemically resolved\", \"Mechanism of substrate selectivity over IRE1\\u03b1 not defined\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Confirmed the physiological consequence of ERN2-mediated MTP regulation by linking its loss to enhanced lipid absorption and atherosclerosis in vivo.\",\n      \"evidence\": \"Ire1b\\u2212/\\u2212/Apoe\\u2212/\\u2212 double-knockout mice, lipid absorption and plaque quantification\",\n      \"pmids\": [\"22556338\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not establish the molecular trigger for ERN2 activation in enterocytes\", \"Tissue-autonomy of the effect not dissected\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Placed ERN2 in an airway mucin-induction pathway downstream of IL-1\\u03b2 and SPDEF and identified XBP1S as the effector binding the MUC5B promoter, defining how ER stress signaling drives mucin gene expression.\",\n      \"evidence\": \"Primary HBE cells, CF tissue, transgenic mice, MUC5B promoter reporters/ChIP, KIRA6 inhibition, XBP1 CRISPR KO\",\n      \"pmids\": [\"31524632\", \"30973754\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How IL-1\\u03b2/SPDEF signaling activates ERN2 RNase activity not resolved\", \"MUC5AC regulation mechanism less defined than MUC5B\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Demonstrated that microbiota induce ERN2-dependent XBP1 splicing to expand ER function for goblet cell maturation and mucus barrier assembly, and that IRE1\\u03b1 cannot substitute in this context.\",\n      \"evidence\": \"Ern2\\u2212/\\u2212 conventional and germ-free mice, colonization experiments, Xbp1 splicing assays, goblet cell histology, colitis transfer\",\n      \"pmids\": [\"35727638\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Microbial signal and receptor activating ERN2 not identified\", \"Basis for non-redundancy with ERN1 unexplained\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Extended the SPDEF-ERN2-mucus axis to disease by identifying ERN2 as a SPDEF target supporting classical PDA differentiation and tumor growth.\",\n      \"evidence\": \"Mouse PDA models, organoids, orthotopic grafts, single-cell profiling\",\n      \"pmids\": [\"38262672\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"ERN2-specific molecular mechanism in PDA not isolated from AGR2\", \"Causal contribution of ERN2 vs other SPDEF targets not separated\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Showed that inflammatory TNF signaling in Paneth cells transcriptionally suppresses Ern1/Ern2 to abolish steady-state UPR, linking ERN2 downregulation to antimicrobial defense failure and sepsis.\",\n      \"evidence\": \"Paneth-cell P55-deletion and IFNAR1-deficient mice, antimicrobial peptide and bacterial translocation assays\",\n      \"pmids\": [\"39243761\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"ERN2-only contribution not isolated from co-downregulated Ern1\", \"Direct RNase targets in Paneth cells not identified\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Identified a physical ERN2-AGR2 interaction as the effector arm of an ERN2/XBP1-AGR2 axis driving MUC5AC hypersecretion in neutrophilic asthma.\",\n      \"evidence\": \"NA mouse model, HBE135-E6E7 ER stress model, lentiviral ERN2 knockdown, 4\\u03bc8C inhibitor, Co-IP, molecular dynamics simulation\",\n      \"pmids\": [\"41483622\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Co-IP not reciprocally validated and interaction interface inferred from simulation\", \"Whether the interaction depends on ERN2 catalytic activity not directly tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The upstream activating signals and the direct RNase substrate repertoire that distinguish ERN2 from IRE1\\u03b1 across mucosal tissues remain undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of ERN2 substrate recognition in the corpus\", \"Determinants of MTP mRNA versus XBP1 mRNA selectivity unresolved\", \"Mechanism of ERN2-specific activation by microbiota and cytokines unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [0, 3, 4]},\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [0, 4]},\n      {\"term_id\": \"GO:0140299\", \"supporting_discovery_ids\": [3, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [3, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [3, 4]},\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [0, 4]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [1, 2, 6]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"AGR2\", \"XBP1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}