{"gene":"ISM1","run_date":"2026-04-28T18:06:54","timeline":{"discoveries":[{"year":2022,"finding":"ISM1 selectively triggers apoptosis of alveolar macrophages (AMs) that harbor high levels of its receptor cell-surface GRP78 (csGRP78), thereby regulating AM number and lung homeostasis; recombinant ISM1 depleted csGRP78-high AMs in vivo and blocked emphysema development.","method":"Ism1-/- mouse model, flow cytometry, intratracheal delivery of recombinant ISM1, loss-of-function with defined cellular phenotype","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — reciprocal in vivo rescue with recombinant protein, multiple orthogonal methods (flow cytometry, lung function, histology), replicated across Ism1-/- and CS-induced COPD models","pmids":["35046017"],"is_preprint":false},{"year":2022,"finding":"ISM1 suppresses LPS-induced NF-κB activation in alveolar macrophages, thereby dampening pro-inflammatory cytokine/chemokine production; ISM1 deficiency exacerbates neutrophil and monocyte-derived macrophage infiltration and post-ALI lung fibrosis with increased TGF-β and myofibroblasts.","method":"Ism1-/- mice with intratracheal LPS model, Western blot for NF-κB pathway, recombinant ISM1 rescue in cultured macrophages, flow cytometry, IHC","journal":"Molecular medicine (Cambridge, Mass.)","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (in vivo KO, in vitro macrophage assay, recombinant protein rescue) in a single study with defined molecular pathway","pmids":["35752760"],"is_preprint":false},{"year":2019,"finding":"ISM1 is an extracellular antagonist of NODAL signaling: it specifically inhibits NODAL-induced SMAD2 phosphorylation without affecting TGF-β1, ACTIVIN-A, or BMP4 signaling. Mechanistically, ISM1 binds the NODAL ligand and type I receptor ACVR1B through its AMOP domain, competing with NODAL-ACVR1B interaction. Ectopic ISM1 causes left-right asymmetry defects and abnormal heart positioning in chick embryos.","method":"Co-immunoprecipitation/interaction assay, SMAD2 phosphorylation assays, AMOP domain mutagenesis, ectopic expression in chick embryos","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1-2 — direct binding assays combined with signaling readouts and in vivo embryonic phenotype with domain-level mechanistic dissection","pmids":["31171630"],"is_preprint":false},{"year":2023,"finding":"ISM1 interacts with integrin α8β1 (identified by HRP-induced proximity labelling) in the developing kidney, promoting cell-cell adhesion through this receptor and thereby sustaining Gdnf/Ret signaling; Ism1-/- mice exhibit defective ureteric bud bifurcation, impaired metanephric mesenchyme condensation, and renal agenesis/hypoplasia.","method":"HRP-induced proximity labelling, single-cell RNA-seq, Ism1-/- mouse embryos, functional adhesion assay","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1-2 — receptor identification by proximity labelling combined with KO phenotype and downstream signaling measurement across multiple embryonic stages","pmids":["37185772"],"is_preprint":false},{"year":2023,"finding":"ISM1 co-localizes with its receptors GRP78 and integrin αvβ5 on podocytes; recombinant ISM1 treatment of human podocytes decreases cell viability via caspase-dependent apoptosis at low doses, and via caspase-independent mitochondrial membrane potential collapse and nuclear AIF translocation at higher doses.","method":"Confocal co-localization, recombinant ISM1 treatment of cultured human podocytes, caspase activation assay, mitochondrial membrane potential measurement, AIF nuclear translocation","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 — multiple in vitro mechanistic assays in single study; receptor co-localization supports mechanism but no genetic confirmation of receptor requirement","pmids":["36769045"],"is_preprint":false},{"year":2019,"finding":"ISM1 is a direct target of miR-1307-3p; dual luciferase reporter assay confirmed that miR-1307-3p binds ISM1 3′-UTR and inhibits its expression. ISM1 activity promotes Wnt3a/β-catenin signaling, reversing the anti-proliferative and pro-apoptotic effects of miR-1307-3p in colon cancer cells.","method":"Dual luciferase reporter assay, Western blot, flow cytometry, siRNA knockdown and overexpression experiments","journal":"Molecular and cellular probes","confidence":"Medium","confidence_rationale":"Tier 2 — dual luciferase validates direct miRNA-target interaction; pathway placement via rescue experiment, single lab","pmids":["31513891"],"is_preprint":false},{"year":2018,"finding":"Zebrafish ism1 (ortholog of human ISM1) is required for normal generation of hematopoietic stem and progenitor cells (HSPCs) and their downstream myeloid and erythroid progeny; ism1 morphant knockdown reduces neutrophils, macrophages, and erythrocytes.","method":"Morpholino knockdown in zebrafish, transgenic lineage-specific reporters, methylcellulose clonal assay for HSPCs","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 — loss-of-function with defined hematopoietic phenotype using multiple lineage markers; ortholog confirmed by synteny, single lab","pmids":["29758043"],"is_preprint":false},{"year":2021,"finding":"Zebrafish Ism1 promotes antiviral innate immunity by inducing type I interferon gene expression and the antiviral protein Mxa via the Tbk1-Irf3-Ifn signaling pathway; recombinant Ism1 reduces cytopathic effect and viral load in virus-infected cells.","method":"Recombinant Ism1 treatment of virus-infected cells, qRT-PCR for IFN, Mxa, tbk1, irf3, irf7; viral titer measurement","journal":"Developmental and comparative immunology","confidence":"Low","confidence_rationale":"Tier 3 — recombinant protein treatment with gene expression readouts; pathway inferred without genetic epistasis, single lab","pmids":["34302859"],"is_preprint":false},{"year":2025,"finding":"ISM1 impairs preadipocyte differentiation into adipocytes and promotes myofibroblast-like differentiation; it also amplifies pro-inflammatory responses in adipocyte progenitors and macrophages under palmitate stimulation. In vivo, WAT-specific ISM1 overexpression inhibits adipocyte progenitor differentiation and enhances macrophage accumulation.","method":"Stable overexpression in 3T3-F442A preadipocytes, differentiation assay, cytokine measurement, in vivo adeno-associated virus overexpression in WAT with HFD","journal":"Diabetes, obesity & metabolism","confidence":"Medium","confidence_rationale":"Tier 2 — in vitro and in vivo overexpression with defined cellular phenotypes; single lab, multiple orthogonal readouts","pmids":["40051329"],"is_preprint":false}],"current_model":"ISM1 is a secreted multifunctional protein that (1) triggers apoptosis of pro-inflammatory cells (alveolar macrophages, podocytes) via cell-surface GRP78 and integrin αvβ5 receptors using both caspase-dependent and AIF-mediated caspase-independent pathways, (2) suppresses NF-κB activation to limit inflammatory cytokine production in macrophages, (3) acts as an extracellular NODAL antagonist by binding the NODAL ligand and receptor ACVR1B through its AMOP domain to block SMAD2 phosphorylation, (4) promotes cell-cell adhesion via integrin α8β1 to sustain Gdnf/Ret signaling during kidney development, and (5) modulates adipocyte differentiation and inflammatory responses in adipose tissue."},"narrative":{"teleology":[{"year":2018,"claim":"Establishing that ISM1 has a conserved role in blood cell development: zebrafish ism1 morphant knockdown revealed a requirement for ISM1 in generating hematopoietic stem and progenitor cells and their myeloid/erythroid progeny, providing the first loss-of-function evidence for ISM1 in a developmental hematopoietic context.","evidence":"Morpholino knockdown in zebrafish with transgenic lineage-specific reporters and clonal HSPC assays","pmids":["29758043"],"confidence":"Medium","gaps":["Mammalian hematopoietic phenotype not examined","Receptor and downstream signaling pathway mediating HSPC effects unknown","No genetic mutant confirmation of morpholino specificity"]},{"year":2019,"claim":"Defining ISM1 as a specific extracellular NODAL antagonist resolved how ISM1 participates in embryonic patterning: ISM1 binds NODAL and ACVR1B through its AMOP domain, competitively blocking NODAL-induced SMAD2 phosphorylation without affecting TGF-β1, Activin-A, or BMP4 signaling, and ectopic ISM1 disrupts left-right asymmetry in chick embryos.","evidence":"Co-immunoprecipitation, SMAD2 phosphorylation assays, AMOP domain mutagenesis, and ectopic expression in chick embryos","pmids":["31171630"],"confidence":"High","gaps":["Endogenous loss-of-function for left-right asymmetry not shown in mammals","Structural basis of AMOP–NODAL interaction unresolved","Whether ISM1 antagonism of NODAL operates in adult tissues is unknown"]},{"year":2022,"claim":"Identifying csGRP78 as the receptor through which ISM1 selectively eliminates pro-inflammatory alveolar macrophages established the molecular basis for ISM1's lung-protective function: Ism1-knockout mice showed AM expansion and spontaneous emphysema, and recombinant ISM1 rescued this by depleting csGRP78-high AMs.","evidence":"Ism1−/− mouse model, intratracheal recombinant ISM1, flow cytometry, lung function and histology in both genetic and cigarette-smoke COPD models","pmids":["35046017"],"confidence":"High","gaps":["Precise signaling cascade downstream of csGRP78 leading to AM apoptosis not fully dissected","Whether csGRP78 acts alone or requires a co-receptor on AMs unknown"]},{"year":2022,"claim":"Demonstrating ISM1's anti-inflammatory mechanism via NF-κB suppression extended its role beyond apoptosis to cytokine regulation: ISM1 deficiency exacerbated LPS-induced neutrophil/macrophage infiltration, TGF-β upregulation, and post-injury lung fibrosis, all rescued by recombinant ISM1.","evidence":"Ism1−/− mice with intratracheal LPS, Western blot for NF-κB, recombinant ISM1 rescue in cultured macrophages, flow cytometry, IHC","pmids":["35752760"],"confidence":"High","gaps":["Direct molecular target through which ISM1 inhibits NF-κB not identified","Whether NF-κB suppression and AM apoptosis are mechanistically coupled or independent pathways is unresolved"]},{"year":2023,"claim":"Identifying integrin α8β1 as an ISM1 receptor in the developing kidney and linking it to GDNF/RET signaling explained the renal agenesis phenotype of Ism1-knockout mice, establishing ISM1 as a cell-adhesion factor critical for ureteric bud branching and mesenchyme condensation.","evidence":"HRP-induced proximity labelling, single-cell RNA-seq, Ism1−/− mouse embryos, functional adhesion assay","pmids":["37185772"],"confidence":"High","gaps":["Binding site on ISM1 for integrin α8β1 not mapped","Whether ISM1-integrin α8β1 interaction is relevant outside kidney development is unknown"]},{"year":2023,"claim":"Demonstrating dual apoptotic pathways (caspase-dependent and AIF-mediated caspase-independent) in podocytes exposed to ISM1 via GRP78 and integrin αvβ5 extended the cell-type repertoire of ISM1-induced death beyond alveolar macrophages.","evidence":"Confocal co-localization, recombinant ISM1 treatment of cultured human podocytes, caspase activation and mitochondrial membrane potential assays, AIF nuclear translocation","pmids":["36769045"],"confidence":"Medium","gaps":["Genetic confirmation of GRP78 or integrin αvβ5 requirement in podocyte apoptosis not performed","In vivo podocyte-specific relevance not demonstrated","Whether dose-dependent switch between caspase-dependent and AIF pathways occurs in vivo is unknown"]},{"year":2025,"claim":"Revealing ISM1's role in adipose tissue — impairing preadipocyte differentiation, promoting myofibroblast-like conversion, and amplifying macrophage inflammatory responses — broadened ISM1 function to metabolic tissue remodeling.","evidence":"Stable overexpression in 3T3-F442A preadipocytes, differentiation and cytokine assays, AAV-mediated WAT-specific overexpression in mice on HFD","pmids":["40051329"],"confidence":"Medium","gaps":["Receptor mediating ISM1 effects in adipocyte progenitors not identified","Loss-of-function adipose phenotype not reported","Whether adipose ISM1 acts in an autocrine or paracrine manner is unresolved"]},{"year":null,"claim":"A unified structural and signaling model explaining how ISM1 engages its multiple receptors (GRP78, integrin αvβ5, integrin α8β1, ACVR1B/NODAL) in different tissues and the molecular determinants that dictate apoptotic versus adhesive versus anti-inflammatory outcomes remains unestablished.","evidence":"","pmids":[],"confidence":"Low","gaps":["No crystal or cryo-EM structure of ISM1 or ISM1–receptor complexes","Relative contributions of distinct receptor engagements to each biological outcome not genetically resolved","Physiological concentrations and regulation of circulating versus local ISM1 poorly characterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,2]},{"term_id":"GO:0098631","term_label":"cell adhesion mediator activity","supporting_discovery_ids":[3]},{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[0,4]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[0,2,3,4]}],"pathway":[{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[0,4]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,2,5]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,1]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[2,3]}],"complexes":[],"partners":["GRP78","ACVR1B","ITGA8","ITGB1","ITGAV","ITGB5","NODAL"],"other_free_text":[]},"mechanistic_narrative":"ISM1 is a secreted immunomodulatory and developmental signaling protein that acts through multiple cell-surface receptors to control apoptosis, inflammation, and tissue morphogenesis. In the lung, ISM1 selectively induces apoptosis of alveolar macrophages expressing high levels of cell-surface GRP78 (csGRP78), thereby maintaining immune homeostasis and protecting against emphysema, while simultaneously suppressing NF-κB–driven pro-inflammatory cytokine production to limit acute lung injury and fibrosis [PMID:35046017, PMID:35752760]. During embryonic development, ISM1 functions as an extracellular NODAL antagonist by binding NODAL and its type I receptor ACVR1B through the AMOP domain to block SMAD2 phosphorylation and regulate left-right asymmetry, and separately engages integrin α8β1 to promote cell-cell adhesion and sustain GDNF/RET signaling required for kidney morphogenesis [PMID:31171630, PMID:37185772]. ISM1 also triggers apoptosis of podocytes via GRP78 and integrin αvβ5 through both caspase-dependent and AIF-mediated caspase-independent pathways, and modulates adipocyte progenitor differentiation and macrophage inflammatory responses in adipose tissue [PMID:36769045, PMID:40051329]."},"prefetch_data":{"uniprot":{"accession":"B1AKI9","full_name":"Isthmin-1","aliases":[],"length_aa":464,"mass_kda":52.1,"function":"Acts as an angiogenesis inhibitor","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/B1AKI9/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ISM1","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/ISM1","total_profiled":1310},"omim":[{"mim_id":"615793","title":"ISTHMIN 1; ISM1","url":"https://www.omim.org/entry/615793"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"blood vessel","ntpm":22.6},{"tissue":"thyroid gland","ntpm":34.9}],"url":"https://www.proteinatlas.org/search/ISM1"},"hgnc":{"alias_symbol":["bA149I18.1"],"prev_symbol":["C20orf82"]},"alphafold":{"accession":"B1AKI9","domains":[{"cath_id":"-","chopping":"224-259","consensus_level":"medium","plddt":81.2061,"start":224,"end":259},{"cath_id":"-","chopping":"301-464","consensus_level":"high","plddt":91.6275,"start":301,"end":464}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/B1AKI9","model_url":"https://alphafold.ebi.ac.uk/files/AF-B1AKI9-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-B1AKI9-F1-predicted_aligned_error_v6.png","plddt_mean":64.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ISM1","jax_strain_url":"https://www.jax.org/strain/search?query=ISM1"},"sequence":{"accession":"B1AKI9","fasta_url":"https://rest.uniprot.org/uniprotkb/B1AKI9.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/B1AKI9/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/B1AKI9"}},"corpus_meta":[{"pmid":"35752760","id":"PMC_35752760","title":"ISM1 suppresses LPS-induced acute lung injury and post-injury lung fibrosis in mice.","date":"2022","source":"Molecular medicine (Cambridge, Mass.)","url":"https://pubmed.ncbi.nlm.nih.gov/35752760","citation_count":52,"is_preprint":false},{"pmid":"35046017","id":"PMC_35046017","title":"ISM1 protects lung homeostasis via cell-surface GRP78-mediated alveolar macrophage apoptosis.","date":"2022","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/35046017","citation_count":46,"is_preprint":false},{"pmid":"24675886","id":"PMC_24675886","title":"Distinct spatiotemporal expression of ISM1 during mouse and chick development.","date":"2014","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/24675886","citation_count":41,"is_preprint":false},{"pmid":"29758043","id":"PMC_29758043","title":"Isthmin 1 (ism1) is required for normal hematopoiesis in developing zebrafish.","date":"2018","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/29758043","citation_count":28,"is_preprint":false},{"pmid":"31513891","id":"PMC_31513891","title":"miR-1307-3p overexpression inhibits cell proliferation and promotes cell apoptosis by targeting ISM1 in colon cancer.","date":"2019","source":"Molecular and cellular probes","url":"https://pubmed.ncbi.nlm.nih.gov/31513891","citation_count":26,"is_preprint":false},{"pmid":"31171630","id":"PMC_31171630","title":"ISM1 regulates NODAL signaling and asymmetric organ morphogenesis during development.","date":"2019","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/31171630","citation_count":24,"is_preprint":false},{"pmid":"34350177","id":"PMC_34350177","title":"Effect of ISM1 on the Immune Microenvironment and Epithelial-Mesenchymal Transition in Colorectal Cancer.","date":"2021","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/34350177","citation_count":24,"is_preprint":false},{"pmid":"34302859","id":"PMC_34302859","title":"Zebrafish Ism1 is a novel antiviral factor that positively regulates antiviral immune responses.","date":"2021","source":"Developmental and comparative immunology","url":"https://pubmed.ncbi.nlm.nih.gov/34302859","citation_count":8,"is_preprint":false},{"pmid":"37185772","id":"PMC_37185772","title":"Isthmin-1 (Ism1) modulates renal branching morphogenesis and mesenchyme condensation during early kidney development.","date":"2023","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/37185772","citation_count":7,"is_preprint":false},{"pmid":"38066623","id":"PMC_38066623","title":"Isthmin-1 (ISM1), a novel adipokine that reflects abdominal adipose tissue distribution in individuals with obesity.","date":"2023","source":"Cardiovascular diabetology","url":"https://pubmed.ncbi.nlm.nih.gov/38066623","citation_count":7,"is_preprint":false},{"pmid":"36769045","id":"PMC_36769045","title":"The Angiogenesis Inhibitor Isthmin-1 (ISM1) Is Overexpressed in Experimental Models of Glomerulopathy and Impairs the Viability of Podocytes.","date":"2023","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/36769045","citation_count":4,"is_preprint":false},{"pmid":"40051329","id":"PMC_40051329","title":"ISM1 regulates white adipose tissue remodelling by dampening adipocyte differentiation and enhancing inflammation.","date":"2025","source":"Diabetes, obesity & metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/40051329","citation_count":1,"is_preprint":false},{"pmid":"37980676","id":"PMC_37980676","title":"Ferroptotic Potency of ISM1 Expression in the Drug-Induced Alzheimer's Disease-Like Phenotype Under the Influence of Betulin.","date":"2023","source":"Journal of Alzheimer's disease : JAD","url":"https://pubmed.ncbi.nlm.nih.gov/37980676","citation_count":1,"is_preprint":false},{"pmid":"41630249","id":"PMC_41630249","title":"ISM-1 expression in cutaneous mastocytosis: Diagnostic potential and comparison with CD117.","date":"2026","source":"Medicine","url":"https://pubmed.ncbi.nlm.nih.gov/41630249","citation_count":0,"is_preprint":false},{"pmid":"41901559","id":"PMC_41901559","title":"Comparative Analysis of ISM-1 and B7-H3 Expression in Castration-Resistant Prostate Adenocarcinoma: Associations with Tumor Aggressiveness and Resistance Dynamics.","date":"2026","source":"Medicina (Kaunas, Lithuania)","url":"https://pubmed.ncbi.nlm.nih.gov/41901559","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9584,"output_tokens":2446,"usd":0.032721},"stage2":{"model":"claude-opus-4-6","input_tokens":5782,"output_tokens":2516,"usd":0.137715},"total_usd":0.170436,"stage1_batch_id":"msgbatch_01DzrsgVgYngY1hvM3DU1yF2","stage2_batch_id":"msgbatch_01KA9b7iRzKFdhoBUT7vCvSe","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2022,\n      \"finding\": \"ISM1 selectively triggers apoptosis of alveolar macrophages (AMs) that harbor high levels of its receptor cell-surface GRP78 (csGRP78), thereby regulating AM number and lung homeostasis; recombinant ISM1 depleted csGRP78-high AMs in vivo and blocked emphysema development.\",\n      \"method\": \"Ism1-/- mouse model, flow cytometry, intratracheal delivery of recombinant ISM1, loss-of-function with defined cellular phenotype\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal in vivo rescue with recombinant protein, multiple orthogonal methods (flow cytometry, lung function, histology), replicated across Ism1-/- and CS-induced COPD models\",\n      \"pmids\": [\"35046017\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ISM1 suppresses LPS-induced NF-κB activation in alveolar macrophages, thereby dampening pro-inflammatory cytokine/chemokine production; ISM1 deficiency exacerbates neutrophil and monocyte-derived macrophage infiltration and post-ALI lung fibrosis with increased TGF-β and myofibroblasts.\",\n      \"method\": \"Ism1-/- mice with intratracheal LPS model, Western blot for NF-κB pathway, recombinant ISM1 rescue in cultured macrophages, flow cytometry, IHC\",\n      \"journal\": \"Molecular medicine (Cambridge, Mass.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (in vivo KO, in vitro macrophage assay, recombinant protein rescue) in a single study with defined molecular pathway\",\n      \"pmids\": [\"35752760\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"ISM1 is an extracellular antagonist of NODAL signaling: it specifically inhibits NODAL-induced SMAD2 phosphorylation without affecting TGF-β1, ACTIVIN-A, or BMP4 signaling. Mechanistically, ISM1 binds the NODAL ligand and type I receptor ACVR1B through its AMOP domain, competing with NODAL-ACVR1B interaction. Ectopic ISM1 causes left-right asymmetry defects and abnormal heart positioning in chick embryos.\",\n      \"method\": \"Co-immunoprecipitation/interaction assay, SMAD2 phosphorylation assays, AMOP domain mutagenesis, ectopic expression in chick embryos\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct binding assays combined with signaling readouts and in vivo embryonic phenotype with domain-level mechanistic dissection\",\n      \"pmids\": [\"31171630\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"ISM1 interacts with integrin α8β1 (identified by HRP-induced proximity labelling) in the developing kidney, promoting cell-cell adhesion through this receptor and thereby sustaining Gdnf/Ret signaling; Ism1-/- mice exhibit defective ureteric bud bifurcation, impaired metanephric mesenchyme condensation, and renal agenesis/hypoplasia.\",\n      \"method\": \"HRP-induced proximity labelling, single-cell RNA-seq, Ism1-/- mouse embryos, functional adhesion assay\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — receptor identification by proximity labelling combined with KO phenotype and downstream signaling measurement across multiple embryonic stages\",\n      \"pmids\": [\"37185772\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"ISM1 co-localizes with its receptors GRP78 and integrin αvβ5 on podocytes; recombinant ISM1 treatment of human podocytes decreases cell viability via caspase-dependent apoptosis at low doses, and via caspase-independent mitochondrial membrane potential collapse and nuclear AIF translocation at higher doses.\",\n      \"method\": \"Confocal co-localization, recombinant ISM1 treatment of cultured human podocytes, caspase activation assay, mitochondrial membrane potential measurement, AIF nuclear translocation\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple in vitro mechanistic assays in single study; receptor co-localization supports mechanism but no genetic confirmation of receptor requirement\",\n      \"pmids\": [\"36769045\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"ISM1 is a direct target of miR-1307-3p; dual luciferase reporter assay confirmed that miR-1307-3p binds ISM1 3′-UTR and inhibits its expression. ISM1 activity promotes Wnt3a/β-catenin signaling, reversing the anti-proliferative and pro-apoptotic effects of miR-1307-3p in colon cancer cells.\",\n      \"method\": \"Dual luciferase reporter assay, Western blot, flow cytometry, siRNA knockdown and overexpression experiments\",\n      \"journal\": \"Molecular and cellular probes\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — dual luciferase validates direct miRNA-target interaction; pathway placement via rescue experiment, single lab\",\n      \"pmids\": [\"31513891\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Zebrafish ism1 (ortholog of human ISM1) is required for normal generation of hematopoietic stem and progenitor cells (HSPCs) and their downstream myeloid and erythroid progeny; ism1 morphant knockdown reduces neutrophils, macrophages, and erythrocytes.\",\n      \"method\": \"Morpholino knockdown in zebrafish, transgenic lineage-specific reporters, methylcellulose clonal assay for HSPCs\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function with defined hematopoietic phenotype using multiple lineage markers; ortholog confirmed by synteny, single lab\",\n      \"pmids\": [\"29758043\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Zebrafish Ism1 promotes antiviral innate immunity by inducing type I interferon gene expression and the antiviral protein Mxa via the Tbk1-Irf3-Ifn signaling pathway; recombinant Ism1 reduces cytopathic effect and viral load in virus-infected cells.\",\n      \"method\": \"Recombinant Ism1 treatment of virus-infected cells, qRT-PCR for IFN, Mxa, tbk1, irf3, irf7; viral titer measurement\",\n      \"journal\": \"Developmental and comparative immunology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — recombinant protein treatment with gene expression readouts; pathway inferred without genetic epistasis, single lab\",\n      \"pmids\": [\"34302859\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ISM1 impairs preadipocyte differentiation into adipocytes and promotes myofibroblast-like differentiation; it also amplifies pro-inflammatory responses in adipocyte progenitors and macrophages under palmitate stimulation. In vivo, WAT-specific ISM1 overexpression inhibits adipocyte progenitor differentiation and enhances macrophage accumulation.\",\n      \"method\": \"Stable overexpression in 3T3-F442A preadipocytes, differentiation assay, cytokine measurement, in vivo adeno-associated virus overexpression in WAT with HFD\",\n      \"journal\": \"Diabetes, obesity & metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vitro and in vivo overexpression with defined cellular phenotypes; single lab, multiple orthogonal readouts\",\n      \"pmids\": [\"40051329\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ISM1 is a secreted multifunctional protein that (1) triggers apoptosis of pro-inflammatory cells (alveolar macrophages, podocytes) via cell-surface GRP78 and integrin αvβ5 receptors using both caspase-dependent and AIF-mediated caspase-independent pathways, (2) suppresses NF-κB activation to limit inflammatory cytokine production in macrophages, (3) acts as an extracellular NODAL antagonist by binding the NODAL ligand and receptor ACVR1B through its AMOP domain to block SMAD2 phosphorylation, (4) promotes cell-cell adhesion via integrin α8β1 to sustain Gdnf/Ret signaling during kidney development, and (5) modulates adipocyte differentiation and inflammatory responses in adipose tissue.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"ISM1 is a secreted immunomodulatory and developmental signaling protein that acts through multiple cell-surface receptors to control apoptosis, inflammation, and tissue morphogenesis. In the lung, ISM1 selectively induces apoptosis of alveolar macrophages expressing high levels of cell-surface GRP78 (csGRP78), thereby maintaining immune homeostasis and protecting against emphysema, while simultaneously suppressing NF-κB–driven pro-inflammatory cytokine production to limit acute lung injury and fibrosis [PMID:35046017, PMID:35752760]. During embryonic development, ISM1 functions as an extracellular NODAL antagonist by binding NODAL and its type I receptor ACVR1B through the AMOP domain to block SMAD2 phosphorylation and regulate left-right asymmetry, and separately engages integrin α8β1 to promote cell-cell adhesion and sustain GDNF/RET signaling required for kidney morphogenesis [PMID:31171630, PMID:37185772]. ISM1 also triggers apoptosis of podocytes via GRP78 and integrin αvβ5 through both caspase-dependent and AIF-mediated caspase-independent pathways, and modulates adipocyte progenitor differentiation and macrophage inflammatory responses in adipose tissue [PMID:36769045, PMID:40051329].\",\n  \"teleology\": [\n    {\n      \"year\": 2018,\n      \"claim\": \"Establishing that ISM1 has a conserved role in blood cell development: zebrafish ism1 morphant knockdown revealed a requirement for ISM1 in generating hematopoietic stem and progenitor cells and their myeloid/erythroid progeny, providing the first loss-of-function evidence for ISM1 in a developmental hematopoietic context.\",\n      \"evidence\": \"Morpholino knockdown in zebrafish with transgenic lineage-specific reporters and clonal HSPC assays\",\n      \"pmids\": [\"29758043\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mammalian hematopoietic phenotype not examined\", \"Receptor and downstream signaling pathway mediating HSPC effects unknown\", \"No genetic mutant confirmation of morpholino specificity\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Defining ISM1 as a specific extracellular NODAL antagonist resolved how ISM1 participates in embryonic patterning: ISM1 binds NODAL and ACVR1B through its AMOP domain, competitively blocking NODAL-induced SMAD2 phosphorylation without affecting TGF-β1, Activin-A, or BMP4 signaling, and ectopic ISM1 disrupts left-right asymmetry in chick embryos.\",\n      \"evidence\": \"Co-immunoprecipitation, SMAD2 phosphorylation assays, AMOP domain mutagenesis, and ectopic expression in chick embryos\",\n      \"pmids\": [\"31171630\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Endogenous loss-of-function for left-right asymmetry not shown in mammals\", \"Structural basis of AMOP–NODAL interaction unresolved\", \"Whether ISM1 antagonism of NODAL operates in adult tissues is unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identifying csGRP78 as the receptor through which ISM1 selectively eliminates pro-inflammatory alveolar macrophages established the molecular basis for ISM1's lung-protective function: Ism1-knockout mice showed AM expansion and spontaneous emphysema, and recombinant ISM1 rescued this by depleting csGRP78-high AMs.\",\n      \"evidence\": \"Ism1−/− mouse model, intratracheal recombinant ISM1, flow cytometry, lung function and histology in both genetic and cigarette-smoke COPD models\",\n      \"pmids\": [\"35046017\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise signaling cascade downstream of csGRP78 leading to AM apoptosis not fully dissected\", \"Whether csGRP78 acts alone or requires a co-receptor on AMs unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Demonstrating ISM1's anti-inflammatory mechanism via NF-κB suppression extended its role beyond apoptosis to cytokine regulation: ISM1 deficiency exacerbated LPS-induced neutrophil/macrophage infiltration, TGF-β upregulation, and post-injury lung fibrosis, all rescued by recombinant ISM1.\",\n      \"evidence\": \"Ism1−/− mice with intratracheal LPS, Western blot for NF-κB, recombinant ISM1 rescue in cultured macrophages, flow cytometry, IHC\",\n      \"pmids\": [\"35752760\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct molecular target through which ISM1 inhibits NF-κB not identified\", \"Whether NF-κB suppression and AM apoptosis are mechanistically coupled or independent pathways is unresolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identifying integrin α8β1 as an ISM1 receptor in the developing kidney and linking it to GDNF/RET signaling explained the renal agenesis phenotype of Ism1-knockout mice, establishing ISM1 as a cell-adhesion factor critical for ureteric bud branching and mesenchyme condensation.\",\n      \"evidence\": \"HRP-induced proximity labelling, single-cell RNA-seq, Ism1−/− mouse embryos, functional adhesion assay\",\n      \"pmids\": [\"37185772\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Binding site on ISM1 for integrin α8β1 not mapped\", \"Whether ISM1-integrin α8β1 interaction is relevant outside kidney development is unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Demonstrating dual apoptotic pathways (caspase-dependent and AIF-mediated caspase-independent) in podocytes exposed to ISM1 via GRP78 and integrin αvβ5 extended the cell-type repertoire of ISM1-induced death beyond alveolar macrophages.\",\n      \"evidence\": \"Confocal co-localization, recombinant ISM1 treatment of cultured human podocytes, caspase activation and mitochondrial membrane potential assays, AIF nuclear translocation\",\n      \"pmids\": [\"36769045\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Genetic confirmation of GRP78 or integrin αvβ5 requirement in podocyte apoptosis not performed\", \"In vivo podocyte-specific relevance not demonstrated\", \"Whether dose-dependent switch between caspase-dependent and AIF pathways occurs in vivo is unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Revealing ISM1's role in adipose tissue — impairing preadipocyte differentiation, promoting myofibroblast-like conversion, and amplifying macrophage inflammatory responses — broadened ISM1 function to metabolic tissue remodeling.\",\n      \"evidence\": \"Stable overexpression in 3T3-F442A preadipocytes, differentiation and cytokine assays, AAV-mediated WAT-specific overexpression in mice on HFD\",\n      \"pmids\": [\"40051329\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor mediating ISM1 effects in adipocyte progenitors not identified\", \"Loss-of-function adipose phenotype not reported\", \"Whether adipose ISM1 acts in an autocrine or paracrine manner is unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A unified structural and signaling model explaining how ISM1 engages its multiple receptors (GRP78, integrin αvβ5, integrin α8β1, ACVR1B/NODAL) in different tissues and the molecular determinants that dictate apoptotic versus adhesive versus anti-inflammatory outcomes remains unestablished.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No crystal or cryo-EM structure of ISM1 or ISM1–receptor complexes\", \"Relative contributions of distinct receptor engagements to each biological outcome not genetically resolved\", \"Physiological concentrations and regulation of circulating versus local ISM1 poorly characterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"GO:0098631\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [0, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0, 2, 3, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0005357801\", \"supporting_discovery_ids\": [0, 4]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [0, 4]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 2, 5]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [2, 3]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"GRP78\", \"ACVR1B\", \"ITGA8\", \"ITGB1\", \"ITGAV\", \"ITGB5\", \"NODAL\"],\n    \"other_free_text\": []\n  }\n}\n```"}