{"gene":"NRBP2","run_date":"2026-04-29T11:37:57","timeline":{"discoveries":[{"year":2008,"finding":"NRBP2 is a 55-60 kDa protein with mainly cytoplasmic localization, and its downregulation by siRNA renders neural progenitor cells more vulnerable to apoptosis, indicating a role in neural progenitor cell survival.","method":"siRNA knockdown, subcellular fractionation/immunostaining, cell viability assays","journal":"Molecular and cellular neurosciences","confidence":"Medium","confidence_rationale":"Tier 2-3 — clean KD with defined cellular phenotype (apoptosis), direct localization experiment, single lab","pmids":["18619852"],"is_preprint":false},{"year":2016,"finding":"NRBP2 binds to Annexin A2 (ANXA2) via co-immunoprecipitation, inhibits ANXA2 expression, and thereby downregulates Akt and Bad phosphorylation, increasing chemosensitivity of hepatocellular carcinoma cells.","method":"Co-immunoprecipitation, overexpression, rescue experiments with ANXA2 co-expression, phosphorylation assays","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP plus rescue experiment and phosphorylation readout, single lab, multiple orthogonal methods","pmids":["27634758"],"is_preprint":false},{"year":2021,"finding":"NRBP2 overexpression activates the AMPK/mTOR signaling pathway to suppress breast cancer cell proliferation, invasion, and epithelial-to-mesenchymal transition (EMT); an AMPK inhibitor partially rescues NRBP2 overexpression effects, and mTOR inhibitors eliminate NRBP2 knockdown effects.","method":"Overexpression and knockdown (KD/OE), pharmacological inhibition of AMPK and mTOR, in vitro invasion/proliferation assays, in vivo orthotopic model","journal":"Frontiers in oncology","confidence":"Medium","confidence_rationale":"Tier 2-3 — epistasis via pharmacological inhibitors combined with KD/OE, multiple readouts, single lab","pmids":["33816275"],"is_preprint":false},{"year":2022,"finding":"GATA1 recruits histone deacetylase 2 (HDAC2) to the NRBP2 promoter to trigger histone deacetylation and suppress NRBP2 expression in thyroid carcinoma cells.","method":"Chromatin immunoprecipitation, overexpression of GATA1/HDAC2, promoter-reporter assays, rescue experiments","journal":"Bioengineered","confidence":"Medium","confidence_rationale":"Tier 2-3 — ChIP and rescue experiments demonstrate direct epigenetic regulation, single lab","pmids":["35491849"],"is_preprint":false},{"year":2024,"finding":"NRBP2 in cancer-associated fibroblasts (CAFs) inhibits the Akt signaling pathway, thereby suppressing CAF-induced chemoresistance in breast cancer cells.","method":"Overexpression/knockdown in CAFs, co-culture experiments, immunoblotting of Akt pathway components, apoptosis assays","journal":"Toxicology research","confidence":"Low","confidence_rationale":"Tier 3 — single lab, single method set, no direct mechanistic target identified beyond Akt pathway activity","pmids":["39664500"],"is_preprint":false},{"year":2025,"finding":"NRBP2 targets its paralog NRBP1 for proteasome-mediated degradation, likely through heterodimer formation, and thereby opposes NRBP1's role in promoting L1 retrotransposition by disrupting the L1 ribonucleoprotein complex.","method":"Co-immunoprecipitation, proteasome inhibition assays, retrotransposition reporter assays, heterodimer formation experiments, phylogenetic analysis","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods (Co-IP, proteasome inhibition, functional reporter assays) in a peer-reviewed study demonstrating direct mechanistic interaction","pmids":["40645931"],"is_preprint":false},{"year":2025,"finding":"Exosomal miR-25-5p from M2 macrophages targets NRBP2, downregulating NRBP2 expression and inhibiting the PI3K/AKT pathway to protect alveolar epithelial cells from pyroptosis in bronchopulmonary dysplasia.","method":"Luciferase reporter assay (miRNA-target validation), PI3K inhibitor rescue, miR-25-5p knockdown, co-culture of macrophage-derived exosomes with alveolar epithelial cells, in vivo BPD rat model","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2-3 — direct miRNA-target interaction validated by reporter assay, pathway placement by pharmacological inhibition, single lab","pmids":["41223004"],"is_preprint":false},{"year":2024,"finding":"NRBP2 targets NRBP1 for proteasome-mediated decay through heterodimer formation, and their opposing roles in regulating LINE1 retrotransposition arise from NRBP2-driven degradation of NRBP1 rather than competition for common binding partners.","method":"Co-immunoprecipitation, proteasome inhibition, retrotransposition reporter assays, pulldown experiments","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods, but preprint version of subsequently published peer-reviewed paper","pmids":[],"is_preprint":true},{"year":2025,"finding":"NRBP1 and its close homolog NRBP2 are predicted to function as upstream activators of the WNK kinase pathway, based on structural similarity including a CCT domain, and NRBP1 can directly activate WNK4 in vitro.","method":"AlphaFold-3 structural modeling, proximity labeling, immunoprecipitation, in vitro kinase activation assay, NRBP1 knockdown/knockout","journal":"Science advances","confidence":"Low","confidence_rationale":"Tier 3-4 — direct evidence for NRBP2's WNK pathway role is inferred by homology; experimental data are for NRBP1, with NRBP2 involvement extrapolated","pmids":["40668933"],"is_preprint":false}],"current_model":"NRBP2 is a cytoplasmic pseudokinase that promotes neural progenitor cell survival, acts as a tumor suppressor by binding ANXA2 and inhibiting Akt/Bad phosphorylation, activating the AMPK/mTOR axis to suppress EMT and invasion, and most distinctively, promotes proteasome-mediated degradation of its paralog NRBP1 via heterodimer formation, thereby antagonizing NRBP1's support of L1 retrotransposition; its expression is epigenetically silenced by GATA1-recruited HDAC2, and it can be post-transcriptionally suppressed by miR-25-5p targeting."},"narrative":{"teleology":[{"year":2008,"claim":"Establishing that NRBP2 is a cytoplasmic protein with a functional role in cell survival addressed the basic question of where it localizes and what happens when it is lost — revealing that neural progenitor cells become vulnerable to apoptosis upon NRBP2 depletion.","evidence":"siRNA knockdown, subcellular fractionation/immunostaining, and cell viability assays in neural progenitor cells","pmids":["18619852"],"confidence":"Medium","gaps":["Mechanism by which NRBP2 suppresses apoptosis not identified","No direct binding partner or signaling target defined","Single cell type tested"]},{"year":2016,"claim":"Identification of ANXA2 as a direct binding partner and downstream effector resolved how NRBP2 connects to pro-survival signaling — NRBP2 suppresses ANXA2 expression and thereby inhibits Akt/Bad phosphorylation, establishing a molecular mechanism for its tumor-suppressive activity.","evidence":"Co-immunoprecipitation, overexpression with ANXA2 rescue, and phosphorylation assays in hepatocellular carcinoma cells","pmids":["27634758"],"confidence":"Medium","gaps":["Mechanism by which NRBP2 binding leads to ANXA2 downregulation unclear","No structural basis for NRBP2–ANXA2 interaction","Not validated outside hepatocellular carcinoma"]},{"year":2021,"claim":"Demonstrating AMPK/mTOR pathway engagement expanded NRBP2's tumor-suppressive mechanism beyond Akt — pharmacological epistasis showed that NRBP2 activates AMPK to suppress mTOR, inhibiting EMT and invasion in breast cancer.","evidence":"Overexpression/knockdown with AMPK and mTOR pharmacological inhibitors, invasion assays, and orthotopic xenograft model in breast cancer","pmids":["33816275"],"confidence":"Medium","gaps":["Direct molecular target through which NRBP2 activates AMPK not identified","Relationship between AMPK/mTOR and ANXA2/Akt arms of NRBP2 signaling unresolved","No kinase-dead mutant analysis despite pseudokinase status"]},{"year":2022,"claim":"Identifying GATA1/HDAC2-mediated epigenetic silencing of the NRBP2 promoter explained how tumor cells downregulate NRBP2 expression, resolving the regulatory question of why NRBP2 is frequently lost in cancers.","evidence":"ChIP for GATA1 and HDAC2 at NRBP2 promoter, promoter-reporter assays, overexpression/rescue in thyroid carcinoma cells","pmids":["35491849"],"confidence":"Medium","gaps":["Whether GATA1/HDAC2-mediated silencing operates in cancer types beyond thyroid carcinoma unknown","No genome-wide analysis of NRBP2 promoter methylation or acetylation states","Upstream signals activating GATA1 in this context not defined"]},{"year":2025,"claim":"Discovery that NRBP2 promotes proteasome-mediated degradation of its paralog NRBP1 via heterodimer formation provided the first defined enzymatic-level mechanism for NRBP2 and revealed its role as a negative regulator of LINE-1 retrotransposition — a fundamentally distinct function from its tumor-suppressive signaling roles.","evidence":"Co-immunoprecipitation, proteasome inhibition (MG132), retrotransposition reporter assays, heterodimer formation experiments, phylogenetic analysis in Nature Communications","pmids":["40645931"],"confidence":"High","gaps":["E3 ubiquitin ligase mediating NRBP1 ubiquitination not identified","Whether NRBP2-driven NRBP1 degradation contributes to tumor suppression is untested","Structural basis for NRBP1–NRBP2 heterodimerization unresolved"]},{"year":2025,"claim":"Validation that exosomal miR-25-5p directly targets NRBP2 mRNA established a post-transcriptional regulatory axis, showing NRBP2 suppression modulates PI3K/AKT signaling and pyroptosis in alveolar epithelial cells during bronchopulmonary dysplasia.","evidence":"Luciferase reporter assay for miR-25-5p–NRBP2 interaction, PI3K inhibitor rescue, macrophage exosome co-culture, in vivo BPD rat model","pmids":["41223004"],"confidence":"Medium","gaps":["Whether miR-25-5p regulation of NRBP2 is relevant in cancer contexts unknown","NRBP2 relationship to pyroptosis machinery not mechanistically defined","Single disease model tested"]},{"year":null,"claim":"Key unresolved questions include the identity of the E3 ligase mediating NRBP2-triggered NRBP1 degradation, the structural basis for NRBP1–NRBP2 heterodimerization, and whether NRBP2's pseudokinase domain retains any catalytic or allosteric function relevant to its diverse signaling outputs.","evidence":"","pmids":[],"confidence":"Low","gaps":["No E3 ligase identified for NRBP1 degradation pathway","No crystal or cryo-EM structure of NRBP2 or NRBP1–NRBP2 complex","Pseudokinase domain function uncharacterized — no kinase-dead mutant analysis reported"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1,2,5]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,2,6]}],"complexes":[],"partners":["NRBP1","ANXA2"],"other_free_text":[]},"mechanistic_narrative":"NRBP2 is a cytoplasmic pseudokinase that functions as a tumor suppressor and negative regulator of LINE-1 retrotransposition. NRBP2 promotes proteasome-mediated degradation of its paralog NRBP1 through heterodimer formation, thereby disrupting the L1 ribonucleoprotein complex and opposing NRBP1-dependent retrotransposition [PMID:40645931]. In cancer contexts, NRBP2 binds Annexin A2 to inhibit Akt/Bad phosphorylation and activates the AMPK/mTOR axis to suppress proliferation, invasion, and epithelial-to-mesenchymal transition [PMID:27634758, PMID:33816275]. NRBP2 expression is epigenetically silenced by GATA1-recruited HDAC2-mediated histone deacetylation at its promoter and post-transcriptionally suppressed by exosomal miR-25-5p [PMID:35491849, PMID:41223004]."},"prefetch_data":{"uniprot":{"accession":"Q9NSY0","full_name":"Nuclear receptor-binding protein 2","aliases":["Transformation-related gene 16 protein","TRG-16"],"length_aa":501,"mass_kda":57.8,"function":"May regulate apoptosis of neural progenitor cells during their differentiation","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q9NSY0/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/NRBP2","classification":"Not Classified","n_dependent_lines":7,"n_total_lines":1208,"dependency_fraction":0.005794701986754967},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/NRBP2","total_profiled":1310},"omim":[{"mim_id":"615583","title":"VERHEIJ SYNDROME; VRJS","url":"https://www.omim.org/entry/615583"},{"mim_id":"615563","title":"NUCLEAR RECEPTOR-BINDING PROTEIN 2; NRBP2","url":"https://www.omim.org/entry/615563"},{"mim_id":"607733","title":"SCRIBBLE PLANAR CELL POLARITY PROTEIN; SCRIB","url":"https://www.omim.org/entry/607733"},{"mim_id":"604819","title":"POLY-U-BINDING SPLICING FACTOR, 60-KD; PUF60","url":"https://www.omim.org/entry/604819"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Cytosol","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"brain","ntpm":95.2}],"url":"https://www.proteinatlas.org/search/NRBP2"},"hgnc":{"alias_symbol":["DKFZp434P086"],"prev_symbol":[]},"alphafold":{"accession":"Q9NSY0","domains":[{"cath_id":"3.30.200.20","chopping":"26-123","consensus_level":"medium","plddt":84.447,"start":26,"end":123},{"cath_id":"1.10.510.10","chopping":"128-301","consensus_level":"medium","plddt":82.5368,"start":128,"end":301},{"cath_id":"-","chopping":"310-376","consensus_level":"high","plddt":82.3439,"start":310,"end":376},{"cath_id":"3.10.20.90","chopping":"421-498","consensus_level":"high","plddt":87.1736,"start":421,"end":498}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NSY0","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NSY0-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NSY0-F1-predicted_aligned_error_v6.png","plddt_mean":79.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=NRBP2","jax_strain_url":"https://www.jax.org/strain/search?query=NRBP2"},"sequence":{"accession":"Q9NSY0","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NSY0.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NSY0/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NSY0"}},"corpus_meta":[{"pmid":"24140112","id":"PMC_24140112","title":"SCRIB and PUF60 are primary drivers of the multisystemic phenotypes of the 8q24.3 copy-number variant.","date":"2013","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/24140112","citation_count":78,"is_preprint":false},{"pmid":"31983282","id":"PMC_31983282","title":"DNA-dependent protein kinase regulates lysosomal AMP-dependent protein kinase activation and autophagy.","date":"2020","source":"Autophagy","url":"https://pubmed.ncbi.nlm.nih.gov/31983282","citation_count":45,"is_preprint":false},{"pmid":"27634758","id":"PMC_27634758","title":"NRBP2 Overexpression Increases the Chemosensitivity of Hepatocellular Carcinoma Cells via Akt Signaling.","date":"2016","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/27634758","citation_count":39,"is_preprint":false},{"pmid":"25209749","id":"PMC_25209749","title":"Mechanisms of nanosized titanium dioxide-induced testicular oxidative stress and apoptosis in male mice.","date":"2014","source":"Particle and fibre toxicology","url":"https://pubmed.ncbi.nlm.nih.gov/25209749","citation_count":23,"is_preprint":false},{"pmid":"31009519","id":"PMC_31009519","title":"The altered expression of autophagy-related genes participates in heart failure: NRBP2 and CALCOCO2 are associated with left ventricular dysfunction parameters in human dilated cardiomyopathy.","date":"2019","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/31009519","citation_count":17,"is_preprint":false},{"pmid":"30352594","id":"PMC_30352594","title":"Role of PUF60 gene in Verheij syndrome: a case report of the first Chinese Han patient with a de novo pathogenic variant and review of the literature.","date":"2018","source":"BMC medical genomics","url":"https://pubmed.ncbi.nlm.nih.gov/30352594","citation_count":17,"is_preprint":false},{"pmid":"32051823","id":"PMC_32051823","title":"miR-146b-5p Plays a Critical Role in the Regulation of Autophagy in ∆per Brucella melitensis-Infected RAW264.7 Cells.","date":"2020","source":"BioMed research international","url":"https://pubmed.ncbi.nlm.nih.gov/32051823","citation_count":17,"is_preprint":false},{"pmid":"18619852","id":"PMC_18619852","title":"Nuclear receptor binding protein 2 is induced during neural progenitor differentiation and affects cell survival.","date":"2008","source":"Molecular and cellular neurosciences","url":"https://pubmed.ncbi.nlm.nih.gov/18619852","citation_count":12,"is_preprint":false},{"pmid":"35491849","id":"PMC_35491849","title":"GATA binding protein 1 recruits histone deacetylase 2 to the promoter region of nuclear receptor binding protein 2 to affect the tumor microenvironment and malignancy of thyroid carcinoma.","date":"2022","source":"Bioengineered","url":"https://pubmed.ncbi.nlm.nih.gov/35491849","citation_count":9,"is_preprint":false},{"pmid":"35032485","id":"PMC_35032485","title":"Proteomic profiling reveals antitumor effects of RT2 peptide on a human colon carcinoma xenograft mouse model.","date":"2022","source":"European journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/35032485","citation_count":9,"is_preprint":false},{"pmid":"32517178","id":"PMC_32517178","title":"Nuclear Receptor Binding Protein 2 Is Downregulated in Medulloblastoma, and Reduces Tumor Cell Survival upon Overexpression.","date":"2020","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/32517178","citation_count":6,"is_preprint":false},{"pmid":"33816275","id":"PMC_33816275","title":"NRBP2 Functions as a Tumor Suppressor and Inhibits Epithelial-to-Mesenchymal Transition in Breast Cancer.","date":"2021","source":"Frontiers in oncology","url":"https://pubmed.ncbi.nlm.nih.gov/33816275","citation_count":5,"is_preprint":false},{"pmid":"40668933","id":"PMC_40668933","title":"NRBP1 pseudokinase binds to and activates the WNK pathway in response to osmotic stress.","date":"2025","source":"Science advances","url":"https://pubmed.ncbi.nlm.nih.gov/40668933","citation_count":3,"is_preprint":false},{"pmid":"40645931","id":"PMC_40645931","title":"Opposing roles of pseudokinases NRBP1 and NRBP2 in regulating L1 retrotransposition.","date":"2025","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/40645931","citation_count":0,"is_preprint":false},{"pmid":"39664500","id":"PMC_39664500","title":"Cancer-associated fibroblasts affect breast cancer cell sensitivity to chemotherapeutic agents by regulating NRBP2.","date":"2024","source":"Toxicology research","url":"https://pubmed.ncbi.nlm.nih.gov/39664500","citation_count":0,"is_preprint":false},{"pmid":"41223004","id":"PMC_41223004","title":"Lipoxin A4 Regulates M2 Macrophage-Derived Exosomal miR-25-5p to Protect Cell Pyroptosis in Bronchopulmonary Dysplasia.","date":"2025","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/41223004","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.06.14.598964","title":"Targeting the paralog protein for degradation accounts for the opposite roles of NRBP1 and NRBP2 in regulating LINE1 retrotransposition","date":"2024-06-15","source":"bioRxiv","url":"https://doi.org/10.1101/2024.06.14.598964","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":10432,"output_tokens":2061,"usd":0.031106},"stage2":{"model":"claude-opus-4-6","input_tokens":5345,"output_tokens":4030,"usd":0.191213},"total_usd":0.222319,"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\": 2008,\n      \"finding\": \"NRBP2 is a 55-60 kDa protein with mainly cytoplasmic localization, and its downregulation by siRNA renders neural progenitor cells more vulnerable to apoptosis, indicating a role in neural progenitor cell survival.\",\n      \"method\": \"siRNA knockdown, subcellular fractionation/immunostaining, cell viability assays\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — clean KD with defined cellular phenotype (apoptosis), direct localization experiment, single lab\",\n      \"pmids\": [\"18619852\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"NRBP2 binds to Annexin A2 (ANXA2) via co-immunoprecipitation, inhibits ANXA2 expression, and thereby downregulates Akt and Bad phosphorylation, increasing chemosensitivity of hepatocellular carcinoma cells.\",\n      \"method\": \"Co-immunoprecipitation, overexpression, rescue experiments with ANXA2 co-expression, phosphorylation assays\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP plus rescue experiment and phosphorylation readout, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"27634758\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"NRBP2 overexpression activates the AMPK/mTOR signaling pathway to suppress breast cancer cell proliferation, invasion, and epithelial-to-mesenchymal transition (EMT); an AMPK inhibitor partially rescues NRBP2 overexpression effects, and mTOR inhibitors eliminate NRBP2 knockdown effects.\",\n      \"method\": \"Overexpression and knockdown (KD/OE), pharmacological inhibition of AMPK and mTOR, in vitro invasion/proliferation assays, in vivo orthotopic model\",\n      \"journal\": \"Frontiers in oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — epistasis via pharmacological inhibitors combined with KD/OE, multiple readouts, single lab\",\n      \"pmids\": [\"33816275\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"GATA1 recruits histone deacetylase 2 (HDAC2) to the NRBP2 promoter to trigger histone deacetylation and suppress NRBP2 expression in thyroid carcinoma cells.\",\n      \"method\": \"Chromatin immunoprecipitation, overexpression of GATA1/HDAC2, promoter-reporter assays, rescue experiments\",\n      \"journal\": \"Bioengineered\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — ChIP and rescue experiments demonstrate direct epigenetic regulation, single lab\",\n      \"pmids\": [\"35491849\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"NRBP2 in cancer-associated fibroblasts (CAFs) inhibits the Akt signaling pathway, thereby suppressing CAF-induced chemoresistance in breast cancer cells.\",\n      \"method\": \"Overexpression/knockdown in CAFs, co-culture experiments, immunoblotting of Akt pathway components, apoptosis assays\",\n      \"journal\": \"Toxicology research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, single method set, no direct mechanistic target identified beyond Akt pathway activity\",\n      \"pmids\": [\"39664500\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"NRBP2 targets its paralog NRBP1 for proteasome-mediated degradation, likely through heterodimer formation, and thereby opposes NRBP1's role in promoting L1 retrotransposition by disrupting the L1 ribonucleoprotein complex.\",\n      \"method\": \"Co-immunoprecipitation, proteasome inhibition assays, retrotransposition reporter assays, heterodimer formation experiments, phylogenetic analysis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods (Co-IP, proteasome inhibition, functional reporter assays) in a peer-reviewed study demonstrating direct mechanistic interaction\",\n      \"pmids\": [\"40645931\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Exosomal miR-25-5p from M2 macrophages targets NRBP2, downregulating NRBP2 expression and inhibiting the PI3K/AKT pathway to protect alveolar epithelial cells from pyroptosis in bronchopulmonary dysplasia.\",\n      \"method\": \"Luciferase reporter assay (miRNA-target validation), PI3K inhibitor rescue, miR-25-5p knockdown, co-culture of macrophage-derived exosomes with alveolar epithelial cells, in vivo BPD rat model\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — direct miRNA-target interaction validated by reporter assay, pathway placement by pharmacological inhibition, single lab\",\n      \"pmids\": [\"41223004\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"NRBP2 targets NRBP1 for proteasome-mediated decay through heterodimer formation, and their opposing roles in regulating LINE1 retrotransposition arise from NRBP2-driven degradation of NRBP1 rather than competition for common binding partners.\",\n      \"method\": \"Co-immunoprecipitation, proteasome inhibition, retrotransposition reporter assays, pulldown experiments\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods, but preprint version of subsequently published peer-reviewed paper\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"NRBP1 and its close homolog NRBP2 are predicted to function as upstream activators of the WNK kinase pathway, based on structural similarity including a CCT domain, and NRBP1 can directly activate WNK4 in vitro.\",\n      \"method\": \"AlphaFold-3 structural modeling, proximity labeling, immunoprecipitation, in vitro kinase activation assay, NRBP1 knockdown/knockout\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3-4 — direct evidence for NRBP2's WNK pathway role is inferred by homology; experimental data are for NRBP1, with NRBP2 involvement extrapolated\",\n      \"pmids\": [\"40668933\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NRBP2 is a cytoplasmic pseudokinase that promotes neural progenitor cell survival, acts as a tumor suppressor by binding ANXA2 and inhibiting Akt/Bad phosphorylation, activating the AMPK/mTOR axis to suppress EMT and invasion, and most distinctively, promotes proteasome-mediated degradation of its paralog NRBP1 via heterodimer formation, thereby antagonizing NRBP1's support of L1 retrotransposition; its expression is epigenetically silenced by GATA1-recruited HDAC2, and it can be post-transcriptionally suppressed by miR-25-5p targeting.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"NRBP2 is a cytoplasmic pseudokinase that functions as a tumor suppressor and negative regulator of LINE-1 retrotransposition. NRBP2 promotes proteasome-mediated degradation of its paralog NRBP1 through heterodimer formation, thereby disrupting the L1 ribonucleoprotein complex and opposing NRBP1-dependent retrotransposition [PMID:40645931]. In cancer contexts, NRBP2 binds Annexin A2 to inhibit Akt/Bad phosphorylation and activates the AMPK/mTOR axis to suppress proliferation, invasion, and epithelial-to-mesenchymal transition [PMID:27634758, PMID:33816275]. NRBP2 expression is epigenetically silenced by GATA1-recruited HDAC2-mediated histone deacetylation at its promoter and post-transcriptionally suppressed by exosomal miR-25-5p [PMID:35491849, PMID:41223004].\",\n  \"teleology\": [\n    {\n      \"year\": 2008,\n      \"claim\": \"Establishing that NRBP2 is a cytoplasmic protein with a functional role in cell survival addressed the basic question of where it localizes and what happens when it is lost — revealing that neural progenitor cells become vulnerable to apoptosis upon NRBP2 depletion.\",\n      \"evidence\": \"siRNA knockdown, subcellular fractionation/immunostaining, and cell viability assays in neural progenitor cells\",\n      \"pmids\": [\"18619852\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which NRBP2 suppresses apoptosis not identified\", \"No direct binding partner or signaling target defined\", \"Single cell type tested\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identification of ANXA2 as a direct binding partner and downstream effector resolved how NRBP2 connects to pro-survival signaling — NRBP2 suppresses ANXA2 expression and thereby inhibits Akt/Bad phosphorylation, establishing a molecular mechanism for its tumor-suppressive activity.\",\n      \"evidence\": \"Co-immunoprecipitation, overexpression with ANXA2 rescue, and phosphorylation assays in hepatocellular carcinoma cells\",\n      \"pmids\": [\"27634758\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which NRBP2 binding leads to ANXA2 downregulation unclear\", \"No structural basis for NRBP2–ANXA2 interaction\", \"Not validated outside hepatocellular carcinoma\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstrating AMPK/mTOR pathway engagement expanded NRBP2's tumor-suppressive mechanism beyond Akt — pharmacological epistasis showed that NRBP2 activates AMPK to suppress mTOR, inhibiting EMT and invasion in breast cancer.\",\n      \"evidence\": \"Overexpression/knockdown with AMPK and mTOR pharmacological inhibitors, invasion assays, and orthotopic xenograft model in breast cancer\",\n      \"pmids\": [\"33816275\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct molecular target through which NRBP2 activates AMPK not identified\", \"Relationship between AMPK/mTOR and ANXA2/Akt arms of NRBP2 signaling unresolved\", \"No kinase-dead mutant analysis despite pseudokinase status\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identifying GATA1/HDAC2-mediated epigenetic silencing of the NRBP2 promoter explained how tumor cells downregulate NRBP2 expression, resolving the regulatory question of why NRBP2 is frequently lost in cancers.\",\n      \"evidence\": \"ChIP for GATA1 and HDAC2 at NRBP2 promoter, promoter-reporter assays, overexpression/rescue in thyroid carcinoma cells\",\n      \"pmids\": [\"35491849\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether GATA1/HDAC2-mediated silencing operates in cancer types beyond thyroid carcinoma unknown\", \"No genome-wide analysis of NRBP2 promoter methylation or acetylation states\", \"Upstream signals activating GATA1 in this context not defined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Discovery that NRBP2 promotes proteasome-mediated degradation of its paralog NRBP1 via heterodimer formation provided the first defined enzymatic-level mechanism for NRBP2 and revealed its role as a negative regulator of LINE-1 retrotransposition — a fundamentally distinct function from its tumor-suppressive signaling roles.\",\n      \"evidence\": \"Co-immunoprecipitation, proteasome inhibition (MG132), retrotransposition reporter assays, heterodimer formation experiments, phylogenetic analysis in Nature Communications\",\n      \"pmids\": [\"40645931\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"E3 ubiquitin ligase mediating NRBP1 ubiquitination not identified\", \"Whether NRBP2-driven NRBP1 degradation contributes to tumor suppression is untested\", \"Structural basis for NRBP1–NRBP2 heterodimerization unresolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Validation that exosomal miR-25-5p directly targets NRBP2 mRNA established a post-transcriptional regulatory axis, showing NRBP2 suppression modulates PI3K/AKT signaling and pyroptosis in alveolar epithelial cells during bronchopulmonary dysplasia.\",\n      \"evidence\": \"Luciferase reporter assay for miR-25-5p–NRBP2 interaction, PI3K inhibitor rescue, macrophage exosome co-culture, in vivo BPD rat model\",\n      \"pmids\": [\"41223004\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether miR-25-5p regulation of NRBP2 is relevant in cancer contexts unknown\", \"NRBP2 relationship to pyroptosis machinery not mechanistically defined\", \"Single disease model tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the identity of the E3 ligase mediating NRBP2-triggered NRBP1 degradation, the structural basis for NRBP1–NRBP2 heterodimerization, and whether NRBP2's pseudokinase domain retains any catalytic or allosteric function relevant to its diverse signaling outputs.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No E3 ligase identified for NRBP1 degradation pathway\", \"No crystal or cryo-EM structure of NRBP2 or NRBP1–NRBP2 complex\", \"Pseudokinase domain function uncharacterized — no kinase-dead mutant analysis reported\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 2, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0162582\", \"supporting_discovery_ids\": [1, 2, 6]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 2, 6]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"NRBP1\", \"ANXA2\"],\n    \"other_free_text\": []\n  }\n}\n```\n\nWait, I need to fix the pathway term_ids — I accidentally included a GO term that doesn't exist. Let me correct:\n\n```json\n{\n  \"mechanistic_narrative\": \"NRBP2 is a cytoplasmic pseudokinase that functions as a tumor suppressor and negative regulator of LINE-1 retrotransposition. NRBP2 promotes proteasome-mediated degradation of its paralog NRBP1 through heterodimer formation, thereby disrupting the L1 ribonucleoprotein complex and opposing NRBP1-dependent retrotransposition [PMID:40645931]. In cancer contexts, NRBP2 binds Annexin A2 to inhibit Akt/Bad phosphorylation and activates the AMPK/mTOR axis to suppress proliferation, invasion, and epithelial-to-mesenchymal transition [PMID:27634758, PMID:33816275]. NRBP2 expression is epigenetically silenced by GATA1-recruited HDAC2-mediated histone deacetylation at its promoter and post-transcriptionally suppressed by exosomal miR-25-5p [PMID:35491849, PMID:41223004].\",\n  \"teleology\": [\n    {\n      \"year\": 2008,\n      \"claim\": \"Establishing that NRBP2 is a cytoplasmic protein with a functional role in cell survival addressed the basic question of where it localizes and what happens when it is lost — revealing that neural progenitor cells become vulnerable to apoptosis upon NRBP2 depletion.\",\n      \"evidence\": \"siRNA knockdown, subcellular fractionation/immunostaining, and cell viability assays in neural progenitor cells\",\n      \"pmids\": [\"18619852\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which NRBP2 suppresses apoptosis not identified\", \"No direct binding partner or signaling target defined\", \"Single cell type tested\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identification of ANXA2 as a direct binding partner and downstream effector resolved how NRBP2 connects to pro-survival signaling — NRBP2 suppresses ANXA2 expression and thereby inhibits Akt/Bad phosphorylation, establishing a molecular mechanism for its tumor-suppressive activity.\",\n      \"evidence\": \"Co-immunoprecipitation, overexpression with ANXA2 rescue, and phosphorylation assays in hepatocellular carcinoma cells\",\n      \"pmids\": [\"27634758\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which NRBP2 binding leads to ANXA2 downregulation unclear\", \"No structural basis for NRBP2-ANXA2 interaction\", \"Not validated outside hepatocellular carcinoma\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstrating AMPK/mTOR pathway engagement expanded NRBP2's tumor-suppressive mechanism beyond Akt — pharmacological epistasis showed that NRBP2 activates AMPK to suppress mTOR, inhibiting EMT and invasion in breast cancer.\",\n      \"evidence\": \"Overexpression/knockdown with AMPK and mTOR pharmacological inhibitors, invasion assays, and orthotopic xenograft model in breast cancer\",\n      \"pmids\": [\"33816275\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct molecular target through which NRBP2 activates AMPK not identified\", \"Relationship between AMPK/mTOR and ANXA2/Akt arms of NRBP2 signaling unresolved\", \"No kinase-dead mutant analysis despite pseudokinase status\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identifying GATA1/HDAC2-mediated epigenetic silencing of the NRBP2 promoter explained how tumor cells downregulate NRBP2 expression, resolving the regulatory question of why NRBP2 is frequently lost in cancers.\",\n      \"evidence\": \"ChIP for GATA1 and HDAC2 at NRBP2 promoter, promoter-reporter assays, overexpression/rescue in thyroid carcinoma cells\",\n      \"pmids\": [\"35491849\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether GATA1/HDAC2-mediated silencing operates in cancer types beyond thyroid carcinoma unknown\", \"No genome-wide analysis of NRBP2 promoter methylation or acetylation states\", \"Upstream signals activating GATA1 in this context not defined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Discovery that NRBP2 promotes proteasome-mediated degradation of its paralog NRBP1 via heterodimer formation provided the first defined enzymatic-level mechanism for NRBP2 and revealed its role as a negative regulator of LINE-1 retrotransposition — a fundamentally distinct function from its tumor-suppressive signaling roles.\",\n      \"evidence\": \"Co-immunoprecipitation, proteasome inhibition (MG132), retrotransposition reporter assays, heterodimer formation experiments, phylogenetic analysis in Nature Communications\",\n      \"pmids\": [\"40645931\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"E3 ubiquitin ligase mediating NRBP1 ubiquitination not identified\", \"Whether NRBP2-driven NRBP1 degradation contributes to tumor suppression is untested\", \"Structural basis for NRBP1-NRBP2 heterodimerization unresolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Validation that exosomal miR-25-5p directly targets NRBP2 mRNA established a post-transcriptional regulatory axis, showing NRBP2 suppression modulates PI3K/AKT signaling and pyroptosis in alveolar epithelial cells during bronchopulmonary dysplasia.\",\n      \"evidence\": \"Luciferase reporter assay for miR-25-5p-NRBP2 interaction, PI3K inhibitor rescue, macrophage exosome co-culture, in vivo BPD rat model\",\n      \"pmids\": [\"41223004\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether miR-25-5p regulation of NRBP2 is relevant in cancer contexts unknown\", \"NRBP2 relationship to pyroptosis machinery not mechanistically defined\", \"Single disease model tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the identity of the E3 ligase mediating NRBP2-triggered NRBP1 degradation, the structural basis for NRBP1-NRBP2 heterodimerization, and whether NRBP2's pseudokinase domain retains any catalytic or allosteric function relevant to its diverse signaling outputs.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No E3 ligase identified for NRBP1 degradation pathway\", \"No crystal or cryo-EM structure of NRBP2 or NRBP1-NRBP2 complex\", \"Pseudokinase domain function uncharacterized — no kinase-dead mutant analysis reported\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 2, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 2, 6]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"NRBP1\", \"ANXA2\"],\n    \"other_free_text\": []\n  }\n}\n```"}