{"gene":"NRG2","run_date":"2026-04-29T11:37:57","timeline":{"discoveries":[{"year":1997,"finding":"NRG2 (Don-1) was identified as a ligand for the ErbB family of receptors, capable of inducing tyrosine phosphorylation of ErbB3, ErbB4, and ErbB2, with high expression restricted to cerebellum and dentate gyrus in adult brain.","method":"Cloning, functional assay (tyrosine phosphorylation of ErbB receptors)","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 — direct receptor phosphorylation assay, foundational cloning paper with >100 citations","pmids":["9199335"],"is_preprint":false},{"year":1998,"finding":"NRG2 (NTAK) recombinant soluble protein binds directly to ErbB3 and ErbB4 but not ErbB1 or ErbB2; it transactivates ErbB heterodimers (B1/B3, B1/B4, B2/B3, B2/B4, B3/B4) and competitively inhibits [125I]NRG-1 binding to MDA-MB-453 cells.","method":"Direct binding assay, receptor transactivation assay, competitive binding with radiolabeled NRG-1","journal":"Nihon shinkei seishin yakurigaku zasshi","confidence":"High","confidence_rationale":"Tier 1 — in vitro binding reconstitution with radiolabel competition and mutagenesis-equivalent isoform analysis","pmids":["9866830"],"is_preprint":false},{"year":2004,"finding":"NRG2 (NTAK) N-terminal region containing the Ig-like domain (but not the EGF-like domain) inhibits vascular endothelial cell proliferation, causes G1 arrest by preventing hyperphosphorylation of Rb, and displays anti-angiogenic activity in the chick CAM assay.","method":"Cell proliferation assay, DNA synthesis assay, cell cycle analysis, in vivo CAM assay, domain deletion analysis with multiple isoforms","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — domain-level functional dissection with multiple isoforms and in vivo validation","pmids":["14722120"],"is_preprint":false},{"year":2019,"finding":"NRG2 activates ErbB4 receptor signaling, leading to phosphorylation of ErbB4 (pErbB4) and downstream Akt1 (pAkt1), and promotes cell migration in HT22 neurons in a dose-dependent manner.","method":"Western blot for pErbB4 and pAkt1, scratch wound healing assay","journal":"Iranian journal of basic medical sciences","confidence":"Medium","confidence_rationale":"Tier 2 — clean loss-of-function and dose-response in cell line, but single lab single method set","pmids":["40584443"],"is_preprint":false},{"year":2021,"finding":"NRG2 promotes migration of human glioma cells (SHG44, U251, U-87 MG) in vitro, as demonstrated by wound healing and transwell transmigration assays.","method":"Wound healing assay, cell transmigration assay","journal":"Folia neuropathologica","confidence":"Low","confidence_rationale":"Tier 3 — single lab, phenotypic assays without pathway placement","pmids":["34284546"],"is_preprint":false},{"year":2022,"finding":"NRG2 fusions, like NRG1 fusions, are proposed to constitutively activate HER3 signaling by concentrating NRG2 near HER3 via transmembrane fusion partners, acting as a ligand-fusion oncogenic mechanism; disruption of NRG1 binding to HER3 and HER3/HER2 heterodimerization by monoclonal antibody leads to tumor shrinkage.","method":"Clinical tumor response to monoclonal antibody disrupting ligand-receptor interaction, structural/mechanistic inference from fusion architecture","journal":"Trends in cancer","confidence":"Low","confidence_rationale":"Tier 3 — mechanistic model inferred from clinical observation and structural analogy, not direct experiment on NRG2","pmids":["34996744"],"is_preprint":false},{"year":2025,"finding":"NRG2 is ubiquitinated at lysine 223 (K223) by the E3 ubiquitin ligase HECW1, leading to its degradation; NDRG1 promotes this interaction between HECW1 and NRG2, and stabilization of NDRG1 by the compound Magnolin reduces NRG2 levels and reverses EGFR TKI resistance in NSCLC cells.","method":"RNA-seq, exome sequencing, western blot, site-specific ubiquitination analysis (K223), protein-protein interaction assays, in vivo xenograft","journal":"Acta pharmacologica Sinica","confidence":"Medium","confidence_rationale":"Tier 2 — site-specific ubiquitination identified with in vivo validation, single lab","pmids":["41193668"],"is_preprint":false},{"year":2025,"finding":"NRG2 secreted by CD163+/Dab2+ macrophages signals through the ErbB4 receptor on cardiomyocytes to alleviate hypertrophy, preserve mitochondrial structure, and restore bioenergetics (oxidative phosphorylation); Nrg2 knockdown abolishes the protective effect of these macrophages in vitro.","method":"Genetic knockdown, recombinant NRG2 treatment, single-nucleus RNA-seq, proteomics, metabolomics, mouse pressure overload model, immunofluorescence","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 — genetic and pharmacological modulation with multi-omics validation, but preprint","pmids":["bio_10.1101_2025.05.22.655661"],"is_preprint":true},{"year":2025,"finding":"UBP1 transcription factor activates the NRG2/Akt signaling axis in breast cancer cells to promote EMT, stemness, and macrophage polarization toward an immunosuppressive phenotype.","method":"Knockdown/overexpression assays, western blot for PI3K-Akt pathway, functional EMT and stemness assays","journal":"International journal of biological macromolecules","confidence":"Low","confidence_rationale":"Tier 3 — single lab, NRG2 is downstream effector without direct mechanistic dissection of NRG2 itself","pmids":["40064277"],"is_preprint":false}],"current_model":"NRG2 is a secreted EGF-family ligand that directly binds ErbB3 and ErbB4 (but not ErbB1/ErbB2) and transactivates ErbB heterodimers, thereby activating downstream PI3K-Akt signaling; its N-terminal Ig-like domain (distinct from the EGF-like domain) mediates anti-angiogenic and anti-proliferative effects, while its protein stability is regulated by HECW1-mediated ubiquitination at K223 promoted by NDRG1, and in cardiac tissue NRG2 from macrophages signals via ErbB4 to support mitochondrial function and oppose hypertrophy."},"narrative":{"teleology":[{"year":1997,"claim":"Identification of NRG2 as a novel ErbB ligand resolved whether additional neuregulin family members existed and established its capacity to activate ErbB2, ErbB3, and ErbB4 phosphorylation, with a distinctive brain-restricted expression pattern.","evidence":"Cloning and receptor tyrosine phosphorylation assays in transfected cells","pmids":["9199335"],"confidence":"High","gaps":["Receptor binding specificity not yet resolved (direct vs. indirect phosphorylation)","Downstream signaling pathways not characterized","In vivo function unknown"]},{"year":1998,"claim":"Direct binding studies clarified that NRG2 engages ErbB3 and ErbB4 but not ErbB1 or ErbB2, and transactivates heterodimer pairs, establishing its receptor selectivity as distinct from NRG1.","evidence":"Radiolabeled competitive binding assay and receptor transactivation assay using recombinant soluble NRG2","pmids":["9866830"],"confidence":"High","gaps":["No crystal structure of the NRG2–receptor complex","Mechanism by which NRG2 transactivates heterodimers containing ErbB1/ErbB2 without direct binding unclear","Physiological relevance in vivo not tested"]},{"year":2004,"claim":"Domain dissection revealed that the Ig-like domain, not the EGF-like domain, mediates anti-proliferative and anti-angiogenic effects, uncoupling receptor-activating and non-canonical functions of NRG2.","evidence":"Domain deletion constructs tested in endothelial cell proliferation, cell cycle (Rb phosphorylation), and chick chorioallantoic membrane angiogenesis assays","pmids":["14722120"],"confidence":"High","gaps":["Receptor or binding partner for the Ig-like domain not identified","Mechanism linking Ig-like domain to Rb hypophosphorylation unknown","Relevance to tumor vasculature not tested in mammalian models"]},{"year":2019,"claim":"Demonstration that NRG2 activates ErbB4–Akt signaling and promotes neuronal migration connected this ligand to a defined intracellular cascade in a neural context.","evidence":"Western blot for pErbB4 and pAkt1 with dose-response, scratch wound healing assay in HT22 neurons","pmids":["40584443"],"confidence":"Medium","gaps":["Single cell line, awaits replication in primary neurons","No genetic loss-of-function in this study","Contribution of ErbB3 vs. ErbB4 heterodimers not resolved"]},{"year":2025,"claim":"Identification of HECW1 as the E3 ligase ubiquitinating NRG2 at K223, promoted by NDRG1, established the first post-translational regulatory mechanism controlling NRG2 protein turnover and linked it to EGFR TKI resistance.","evidence":"Site-specific ubiquitination assays, protein interaction studies, and in vivo xenograft experiments in NSCLC models","pmids":["41193668"],"confidence":"Medium","gaps":["Single lab; HECW1-NRG2 interaction awaits independent confirmation","Whether ubiquitination occurs on membrane-tethered or shed NRG2 is unresolved","Structural basis for NDRG1-mediated promotion of HECW1 activity unknown"]},{"year":2025,"claim":"Macrophage-derived NRG2 was shown to signal through cardiomyocyte ErbB4 to protect against hypertrophy and restore mitochondrial bioenergetics, establishing a paracrine cardioprotective role. (preprint)","evidence":"Nrg2 knockdown in macrophages, recombinant NRG2 treatment, multi-omics, and mouse pressure-overload model","pmids":["bio_10.1101_2025.05.22.655661"],"confidence":"Medium","gaps":["Preprint; awaits peer review","Whether NRG2 is required in vivo (conditional knockout) not shown","Relative contribution of NRG2 vs. NRG1 in cardiac protection not delineated"]},{"year":null,"claim":"The receptor or binding partner mediating the anti-angiogenic activity of the NRG2 Ig-like domain remains unidentified, and in vivo genetic studies of NRG2 function in brain, heart, and vasculature using conditional knockouts are lacking.","evidence":"","pmids":[],"confidence":"High","gaps":["No conditional knockout phenotype reported in any tissue","No structural model of NRG2 in complex with any receptor","Physiological relevance of Ig-like domain anti-angiogenic function untested in mammals"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[0,1,3,7]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[1,7]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,3]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[2,7]}],"complexes":[],"partners":["ERBB3","ERBB4","HECW1","NDRG1"],"other_free_text":[]},"mechanistic_narrative":"NRG2 is an EGF-family ligand that signals through ErbB3 and ErbB4 receptors to regulate cell proliferation, migration, and survival in neural, vascular, and cardiac tissues. NRG2 binds directly to ErbB3 and ErbB4 but not ErbB1 or ErbB2, transactivating ErbB heterodimers and stimulating downstream PI3K-Akt signaling [PMID:9866830, PMID:40584443]. Independent of its EGF-like domain, the N-terminal Ig-like domain of NRG2 inhibits endothelial cell proliferation by preventing Rb hyperphosphorylation and exerts anti-angiogenic activity in vivo [PMID:14722120]. NRG2 protein levels are controlled by HECW1-mediated ubiquitination at K223, a process promoted by NDRG1, and degradation of NRG2 through this axis reverses EGFR TKI resistance in NSCLC cells [PMID:41193668]."},"prefetch_data":{"uniprot":{"accession":"O14511","full_name":"Pro-neuregulin-2, membrane-bound isoform","aliases":[],"length_aa":850,"mass_kda":91.7,"function":"Direct ligand for ERBB3 and ERBB4 tyrosine kinase receptors. Concomitantly recruits ERBB1 and ERBB2 coreceptors, resulting in ligand-stimulated tyrosine phosphorylation and activation of the ERBB receptors. May also promote the heterodimerization with the EGF receptor","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/O14511/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/NRG2","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/NRG2","total_profiled":1310},"omim":[{"mim_id":"610894","title":"NEUREGULIN 4; NRG4","url":"https://www.omim.org/entry/610894"},{"mim_id":"610535","title":"GLAUCOMA 1, OPEN ANGLE, M; GLC1M","url":"https://www.omim.org/entry/610535"},{"mim_id":"605533","title":"NEUREGULIN 3; NRG3","url":"https://www.omim.org/entry/605533"},{"mim_id":"603818","title":"NEUREGULIN 2; NRG2","url":"https://www.omim.org/entry/603818"},{"mim_id":"600543","title":"ERB-B2 RECEPTOR TYROSINE KINASE 4; ERBB4","url":"https://www.omim.org/entry/600543"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Nucleoli","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":11.6}],"url":"https://www.proteinatlas.org/search/NRG2"},"hgnc":{"alias_symbol":["Don-1","NTAK","HRG2"],"prev_symbol":[]},"alphafold":{"accession":"O14511","domains":[{"cath_id":"2.40.50.120","chopping":"118-140_156-230","consensus_level":"high","plddt":79.5157,"start":118,"end":230},{"cath_id":"2.60.40.10","chopping":"239-330","consensus_level":"high","plddt":86.8322,"start":239,"end":330},{"cath_id":"2.10.25.10","chopping":"343-391","consensus_level":"high","plddt":77.9902,"start":343,"end":391}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O14511","model_url":"https://alphafold.ebi.ac.uk/files/AF-O14511-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O14511-F1-predicted_aligned_error_v6.png","plddt_mean":54.91},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=NRG2","jax_strain_url":"https://www.jax.org/strain/search?query=NRG2"},"sequence":{"accession":"O14511","fasta_url":"https://rest.uniprot.org/uniprotkb/O14511.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O14511/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O14511"}},"corpus_meta":[{"pmid":"12024013","id":"PMC_12024013","title":"Snf1 protein kinase and the repressors Nrg1 and Nrg2 regulate FLO11, haploid invasive growth, and diploid pseudohyphal differentiation.","date":"2002","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/12024013","citation_count":174,"is_preprint":false},{"pmid":"26744214","id":"PMC_26744214","title":"The Arabidopsis NRG2 Protein Mediates Nitrate Signaling and Interacts with and Regulates Key Nitrate Regulators.","date":"2016","source":"The Plant cell","url":"https://pubmed.ncbi.nlm.nih.gov/26744214","citation_count":134,"is_preprint":false},{"pmid":"9199335","id":"PMC_9199335","title":"Characterization of a neuregulin-related gene, Don-1, that is highly expressed in restricted regions of the cerebellum and hippocampus.","date":"1997","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/9199335","citation_count":106,"is_preprint":false},{"pmid":"16278455","id":"PMC_16278455","title":"Repressors Nrg1 and Nrg2 regulate a set of stress-responsive genes in Saccharomyces cerevisiae.","date":"2005","source":"Eukaryotic cell","url":"https://pubmed.ncbi.nlm.nih.gov/16278455","citation_count":60,"is_preprint":false},{"pmid":"23912956","id":"PMC_23912956","title":"Associations with growth factor genes (FGF1, FGF2, PDGFB, FGFR2, NRG2, EGF, ERBB2) with breast cancer risk and survival: the Breast Cancer Health Disparities Study.","date":"2013","source":"Breast cancer research and treatment","url":"https://pubmed.ncbi.nlm.nih.gov/23912956","citation_count":56,"is_preprint":false},{"pmid":"11404322","id":"PMC_11404322","title":"Interaction of the repressors Nrg1 and Nrg2 with the Snf1 protein kinase in Saccharomyces cerevisiae.","date":"2001","source":"Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/11404322","citation_count":54,"is_preprint":false},{"pmid":"34996744","id":"PMC_34996744","title":"NRG1 and NRG2 fusion positive solid tumor malignancies: a paradigm of ligand-fusion oncogenesis.","date":"2022","source":"Trends in cancer","url":"https://pubmed.ncbi.nlm.nih.gov/34996744","citation_count":39,"is_preprint":false},{"pmid":"15075261","id":"PMC_15075261","title":"Nrg1 and nrg2 transcriptional repressors are differently regulated in response to carbon source.","date":"2004","source":"Eukaryotic cell","url":"https://pubmed.ncbi.nlm.nih.gov/15075261","citation_count":32,"is_preprint":false},{"pmid":"10369162","id":"PMC_10369162","title":"The human neuregulin-2 (NRG2) gene: cloning, mapping and evaluation as a candidate for the autosomal recessive form of Charcot-Marie-Tooth disease linked to 5q.","date":"1999","source":"Human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/10369162","citation_count":23,"is_preprint":false},{"pmid":"14722120","id":"PMC_14722120","title":"The N-terminal region of NTAK/neuregulin-2 isoforms has an inhibitory activity on angiogenesis.","date":"2004","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/14722120","citation_count":18,"is_preprint":false},{"pmid":"10974560","id":"PMC_10974560","title":"Characterization of the human NTAK gene structure and distribution of the isoforms for rat NTAK mRNA.","date":"2000","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/10974560","citation_count":15,"is_preprint":false},{"pmid":"34706602","id":"PMC_34706602","title":"NRG1 and NRG2 fusions in non-small cell lung cancer (NSCLC): seven years between lights and shadows.","date":"2021","source":"Expert opinion on therapeutic targets","url":"https://pubmed.ncbi.nlm.nih.gov/34706602","citation_count":11,"is_preprint":false},{"pmid":"26244169","id":"PMC_26244169","title":"Detection and quantification of new psychoactive substances (NPSs) within the evolved \"legal high\" product, NRG-2, using high performance liquid chromatography-amperometric detection (HPLC-AD).","date":"2015","source":"The Analyst","url":"https://pubmed.ncbi.nlm.nih.gov/26244169","citation_count":10,"is_preprint":false},{"pmid":"34284546","id":"PMC_34284546","title":"Neuregulin 2 (NRG2) is expressed in gliomas and promotes migration of human glioma cells.","date":"2021","source":"Folia neuropathologica","url":"https://pubmed.ncbi.nlm.nih.gov/34284546","citation_count":8,"is_preprint":false},{"pmid":"9866830","id":"PMC_9866830","title":"[Structure and function of a novel ErbB ligand, NTAK].","date":"1998","source":"Nihon shinkei seishin yakurigaku zasshi = Japanese journal of psychopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/9866830","citation_count":4,"is_preprint":false},{"pmid":"38472740","id":"PMC_38472740","title":"NRG2 family members of Arabidopsis and maize regulate nitrate signalling and promote nitrogen use efficiency.","date":"2024","source":"Physiologia plantarum","url":"https://pubmed.ncbi.nlm.nih.gov/38472740","citation_count":4,"is_preprint":false},{"pmid":"40064277","id":"PMC_40064277","title":"Upstream-binding protein-1 promotes breast tumorigenesis by inducing NRG2-mediated metastasis, plasticity, and macrophage polarization.","date":"2025","source":"International journal of biological macromolecules","url":"https://pubmed.ncbi.nlm.nih.gov/40064277","citation_count":2,"is_preprint":false},{"pmid":"41193668","id":"PMC_41193668","title":"Magnolin overcomes EGFR TKI resistance in NSCLC by modulation of NDRG1-NRG2-HECW1 pathway.","date":"2025","source":"Acta pharmacologica Sinica","url":"https://pubmed.ncbi.nlm.nih.gov/41193668","citation_count":0,"is_preprint":false},{"pmid":"40584443","id":"PMC_40584443","title":"Down-regulation of neuregulin2 (NRG2) following spinal cord injury in C57BL/6 mice: Its implications in therapeutic potential.","date":"2025","source":"Iranian journal of basic medical sciences","url":"https://pubmed.ncbi.nlm.nih.gov/40584443","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.05.22.655661","title":"CD163⁺/Dab2⁺ Macrophages Alleviate Cardiac Hypertrophy via Nrg2/ErbB4-Mediated Mitochondrial Reprogramming","date":"2025-05-26","source":"bioRxiv","url":"https://doi.org/10.1101/2025.05.22.655661","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":10964,"output_tokens":2117,"usd":0.032323},"stage2":{"model":"claude-opus-4-6","input_tokens":5406,"output_tokens":1828,"usd":0.109095},"total_usd":0.141418,"stage1_batch_id":"msgbatch_012ZiiCUBfB62NCTQd4Bk1Jo","stage2_batch_id":"msgbatch_01Xuqq9aUHoQouS7UVGZNStZ","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1997,\n      \"finding\": \"NRG2 (Don-1) was identified as a ligand for the ErbB family of receptors, capable of inducing tyrosine phosphorylation of ErbB3, ErbB4, and ErbB2, with high expression restricted to cerebellum and dentate gyrus in adult brain.\",\n      \"method\": \"Cloning, functional assay (tyrosine phosphorylation of ErbB receptors)\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct receptor phosphorylation assay, foundational cloning paper with >100 citations\",\n      \"pmids\": [\"9199335\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"NRG2 (NTAK) recombinant soluble protein binds directly to ErbB3 and ErbB4 but not ErbB1 or ErbB2; it transactivates ErbB heterodimers (B1/B3, B1/B4, B2/B3, B2/B4, B3/B4) and competitively inhibits [125I]NRG-1 binding to MDA-MB-453 cells.\",\n      \"method\": \"Direct binding assay, receptor transactivation assay, competitive binding with radiolabeled NRG-1\",\n      \"journal\": \"Nihon shinkei seishin yakurigaku zasshi\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro binding reconstitution with radiolabel competition and mutagenesis-equivalent isoform analysis\",\n      \"pmids\": [\"9866830\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"NRG2 (NTAK) N-terminal region containing the Ig-like domain (but not the EGF-like domain) inhibits vascular endothelial cell proliferation, causes G1 arrest by preventing hyperphosphorylation of Rb, and displays anti-angiogenic activity in the chick CAM assay.\",\n      \"method\": \"Cell proliferation assay, DNA synthesis assay, cell cycle analysis, in vivo CAM assay, domain deletion analysis with multiple isoforms\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — domain-level functional dissection with multiple isoforms and in vivo validation\",\n      \"pmids\": [\"14722120\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"NRG2 activates ErbB4 receptor signaling, leading to phosphorylation of ErbB4 (pErbB4) and downstream Akt1 (pAkt1), and promotes cell migration in HT22 neurons in a dose-dependent manner.\",\n      \"method\": \"Western blot for pErbB4 and pAkt1, scratch wound healing assay\",\n      \"journal\": \"Iranian journal of basic medical sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean loss-of-function and dose-response in cell line, but single lab single method set\",\n      \"pmids\": [\"40584443\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"NRG2 promotes migration of human glioma cells (SHG44, U251, U-87 MG) in vitro, as demonstrated by wound healing and transwell transmigration assays.\",\n      \"method\": \"Wound healing assay, cell transmigration assay\",\n      \"journal\": \"Folia neuropathologica\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, phenotypic assays without pathway placement\",\n      \"pmids\": [\"34284546\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"NRG2 fusions, like NRG1 fusions, are proposed to constitutively activate HER3 signaling by concentrating NRG2 near HER3 via transmembrane fusion partners, acting as a ligand-fusion oncogenic mechanism; disruption of NRG1 binding to HER3 and HER3/HER2 heterodimerization by monoclonal antibody leads to tumor shrinkage.\",\n      \"method\": \"Clinical tumor response to monoclonal antibody disrupting ligand-receptor interaction, structural/mechanistic inference from fusion architecture\",\n      \"journal\": \"Trends in cancer\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — mechanistic model inferred from clinical observation and structural analogy, not direct experiment on NRG2\",\n      \"pmids\": [\"34996744\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"NRG2 is ubiquitinated at lysine 223 (K223) by the E3 ubiquitin ligase HECW1, leading to its degradation; NDRG1 promotes this interaction between HECW1 and NRG2, and stabilization of NDRG1 by the compound Magnolin reduces NRG2 levels and reverses EGFR TKI resistance in NSCLC cells.\",\n      \"method\": \"RNA-seq, exome sequencing, western blot, site-specific ubiquitination analysis (K223), protein-protein interaction assays, in vivo xenograft\",\n      \"journal\": \"Acta pharmacologica Sinica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — site-specific ubiquitination identified with in vivo validation, single lab\",\n      \"pmids\": [\"41193668\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"NRG2 secreted by CD163+/Dab2+ macrophages signals through the ErbB4 receptor on cardiomyocytes to alleviate hypertrophy, preserve mitochondrial structure, and restore bioenergetics (oxidative phosphorylation); Nrg2 knockdown abolishes the protective effect of these macrophages in vitro.\",\n      \"method\": \"Genetic knockdown, recombinant NRG2 treatment, single-nucleus RNA-seq, proteomics, metabolomics, mouse pressure overload model, immunofluorescence\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic and pharmacological modulation with multi-omics validation, but preprint\",\n      \"pmids\": [\"bio_10.1101_2025.05.22.655661\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"UBP1 transcription factor activates the NRG2/Akt signaling axis in breast cancer cells to promote EMT, stemness, and macrophage polarization toward an immunosuppressive phenotype.\",\n      \"method\": \"Knockdown/overexpression assays, western blot for PI3K-Akt pathway, functional EMT and stemness assays\",\n      \"journal\": \"International journal of biological macromolecules\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, NRG2 is downstream effector without direct mechanistic dissection of NRG2 itself\",\n      \"pmids\": [\"40064277\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NRG2 is a secreted EGF-family ligand that directly binds ErbB3 and ErbB4 (but not ErbB1/ErbB2) and transactivates ErbB heterodimers, thereby activating downstream PI3K-Akt signaling; its N-terminal Ig-like domain (distinct from the EGF-like domain) mediates anti-angiogenic and anti-proliferative effects, while its protein stability is regulated by HECW1-mediated ubiquitination at K223 promoted by NDRG1, and in cardiac tissue NRG2 from macrophages signals via ErbB4 to support mitochondrial function and oppose hypertrophy.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"NRG2 is an EGF-family ligand that signals through ErbB3 and ErbB4 receptors to regulate cell proliferation, migration, and survival in neural, vascular, and cardiac tissues. NRG2 binds directly to ErbB3 and ErbB4 but not ErbB1 or ErbB2, transactivating ErbB heterodimers and stimulating downstream PI3K-Akt signaling [PMID:9866830, PMID:40584443]. Independent of its EGF-like domain, the N-terminal Ig-like domain of NRG2 inhibits endothelial cell proliferation by preventing Rb hyperphosphorylation and exerts anti-angiogenic activity in vivo [PMID:14722120]. NRG2 protein levels are controlled by HECW1-mediated ubiquitination at K223, a process promoted by NDRG1, and degradation of NRG2 through this axis reverses EGFR TKI resistance in NSCLC cells [PMID:41193668].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Identification of NRG2 as a novel ErbB ligand resolved whether additional neuregulin family members existed and established its capacity to activate ErbB2, ErbB3, and ErbB4 phosphorylation, with a distinctive brain-restricted expression pattern.\",\n      \"evidence\": \"Cloning and receptor tyrosine phosphorylation assays in transfected cells\",\n      \"pmids\": [\"9199335\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor binding specificity not yet resolved (direct vs. indirect phosphorylation)\", \"Downstream signaling pathways not characterized\", \"In vivo function unknown\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Direct binding studies clarified that NRG2 engages ErbB3 and ErbB4 but not ErbB1 or ErbB2, and transactivates heterodimer pairs, establishing its receptor selectivity as distinct from NRG1.\",\n      \"evidence\": \"Radiolabeled competitive binding assay and receptor transactivation assay using recombinant soluble NRG2\",\n      \"pmids\": [\"9866830\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No crystal structure of the NRG2–receptor complex\", \"Mechanism by which NRG2 transactivates heterodimers containing ErbB1/ErbB2 without direct binding unclear\", \"Physiological relevance in vivo not tested\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Domain dissection revealed that the Ig-like domain, not the EGF-like domain, mediates anti-proliferative and anti-angiogenic effects, uncoupling receptor-activating and non-canonical functions of NRG2.\",\n      \"evidence\": \"Domain deletion constructs tested in endothelial cell proliferation, cell cycle (Rb phosphorylation), and chick chorioallantoic membrane angiogenesis assays\",\n      \"pmids\": [\"14722120\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor or binding partner for the Ig-like domain not identified\", \"Mechanism linking Ig-like domain to Rb hypophosphorylation unknown\", \"Relevance to tumor vasculature not tested in mammalian models\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Demonstration that NRG2 activates ErbB4–Akt signaling and promotes neuronal migration connected this ligand to a defined intracellular cascade in a neural context.\",\n      \"evidence\": \"Western blot for pErbB4 and pAkt1 with dose-response, scratch wound healing assay in HT22 neurons\",\n      \"pmids\": [\"40584443\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single cell line, awaits replication in primary neurons\", \"No genetic loss-of-function in this study\", \"Contribution of ErbB3 vs. ErbB4 heterodimers not resolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identification of HECW1 as the E3 ligase ubiquitinating NRG2 at K223, promoted by NDRG1, established the first post-translational regulatory mechanism controlling NRG2 protein turnover and linked it to EGFR TKI resistance.\",\n      \"evidence\": \"Site-specific ubiquitination assays, protein interaction studies, and in vivo xenograft experiments in NSCLC models\",\n      \"pmids\": [\"41193668\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; HECW1-NRG2 interaction awaits independent confirmation\", \"Whether ubiquitination occurs on membrane-tethered or shed NRG2 is unresolved\", \"Structural basis for NDRG1-mediated promotion of HECW1 activity unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Macrophage-derived NRG2 was shown to signal through cardiomyocyte ErbB4 to protect against hypertrophy and restore mitochondrial bioenergetics, establishing a paracrine cardioprotective role. (preprint)\",\n      \"evidence\": \"Nrg2 knockdown in macrophages, recombinant NRG2 treatment, multi-omics, and mouse pressure-overload model\",\n      \"pmids\": [\"bio_10.1101_2025.05.22.655661\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint; awaits peer review\", \"Whether NRG2 is required in vivo (conditional knockout) not shown\", \"Relative contribution of NRG2 vs. NRG1 in cardiac protection not delineated\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The receptor or binding partner mediating the anti-angiogenic activity of the NRG2 Ig-like domain remains unidentified, and in vivo genetic studies of NRG2 function in brain, heart, and vasculature using conditional knockouts are lacking.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No conditional knockout phenotype reported in any tissue\", \"No structural model of NRG2 in complex with any receptor\", \"Physiological relevance of Ig-like domain anti-angiogenic function untested in mammals\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [0, 1, 3, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [1, 7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 3]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [2, 7]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"ERBB3\", \"ERBB4\", \"HECW1\", \"NDRG1\"],\n    \"other_free_text\": []\n  }\n}\n```"}