{"gene":"IPO8","run_date":"2026-06-10T01:55:23","timeline":{"discoveries":[{"year":2001,"finding":"Importin 8 (IPO8/RanBP8) directly imports SRP19 (the 19 kDa subunit of the signal recognition particle) into the nucleus in vitro; this was the first cargo function assigned to importin 8. Import was shown to be mediated by members of the importin-β superfamily and is consistent with nuclear assembly of SRP.","method":"In vitro nuclear import assay using recombinant importin 8 and SRP19; localization of endogenous SRP19 to nucleus and nucleolus","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstituted nuclear import assay with direct functional readout; endogenous localization confirmed by independent method in same study","pmids":["11682607"],"is_preprint":false},{"year":2013,"finding":"IPO8 mediates nuclear translocation of NF-κB/p65 independently of the canonical NLS of p65; NLS-mutated p65 still entered the nucleus and co-immunoprecipitated with IPO8. Knockdown of IPO8 reduced nuclear p65 levels and NF-κB transcriptional activity after TNF-α stimulation.","method":"High-content siRNA screen of 17 importin-β family members; co-immunoprecipitation of NLS-mutated p65 with IPO8; nuclear fractionation; NF-κB reporter assay","journal":"Traffic (Copenhagen, Denmark)","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP with NLS-mutant p65, siRNA knockdown with quantitative nuclear fractionation, and functional NF-κB reporter assay; multiple orthogonal methods in one study","pmids":["23906023"],"is_preprint":false},{"year":2021,"finding":"Bi-allelic loss-of-function of IPO8 causes thoracic aortic aneurysm (TAA) associated with dysregulated TGF-β signaling; Ipo8 knockout mice develop TAA with elastic fiber disorganization, nuclear accumulation of pSmad2, decreased Smad6/7, and increased Mmp2/Ccn2 expression in the aortic wall, placing IPO8 as a regulator of TGF-β/SMAD nuclear import upstream of aortic wall homeostasis.","method":"Ipo8 knockout mouse model (C57BL/6N); immunohistochemistry for pSmad2; compliance assays; RT-qPCR of aortic wall gene expression; human genetic analysis (bi-allelic loss-of-function variants in patients)","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — knockout mouse model with multiple orthogonal readouts (histology, immunostaining for pSmad2, qPCR, biomechanical assay) corroborated by human genetics across six unrelated families","pmids":["34010605"],"is_preprint":false},{"year":2025,"finding":"IPO8 forms a trimeric complex with the lncRNA LINC1467 and NF-κB/p65; this complex facilitates phosphorylation and nuclear translocation of p65, thereby activating NF-κB-driven pro-inflammatory cytokine expression during enterovirus infection.","method":"Co-immunoprecipitation of LINC1467/IPO8/p65 complex; functional assays (viral replication, cytokine expression); mouse model of viral infection; loss-of-function of LINC1467","journal":"Pathogens (Basel, Switzerland)","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — Co-IP demonstrating ternary complex and functional NF-κB readout, but single lab, no structural validation or in vitro reconstitution; consistent with PMID:23906023 on IPO8/p65 axis","pmids":["41156681"],"is_preprint":false},{"year":2016,"finding":"The transcription factor RUNX2 directly binds the IPO8 promoter at positions −496 to −501 bp and activates IPO8 basal transcription; RUNX2 knockdown reduces IPO8 mRNA levels, and IPO8 and RUNX2 expression are co-regulated during osteoblast induction.","method":"ChIP-on-chip in human mesenchymal stem cells; luciferase reporter assays with truncated IPO8 promoter constructs; ChIP validation of RUNX2 binding; RUNX2 siRNA knockdown with RT-qPCR; osteoblast differentiation assay","journal":"Molecular medicine reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP confirmation plus luciferase reporter deletion analysis and knockdown experiment; multiple orthogonal methods but single lab","pmids":["27277970"],"is_preprint":false}],"current_model":"IPO8 (importin 8) is an importin-β family nuclear transport receptor that imports cargo molecules—including SRP19, NF-κB/p65 (via an NLS-independent route facilitated by the lncRNA LINC1467), and TGF-β/SMAD signaling components—into the nucleus in a RanGTP-dependent manner; loss of IPO8 disrupts SMAD nuclear accumulation and TGF-β pathway homeostasis, leading to thoracic aortic aneurysm, while its own transcription is directly activated by RUNX2 binding to a specific promoter element."},"narrative":{"mechanistic_narrative":"IPO8 is an importin-β superfamily nuclear transport receptor that delivers diverse cargoes into the nucleus, functioning as a hub coupling cytoplasmic signaling to nuclear gene-regulatory programs [PMID:11682607, PMID:23906023]. Its earliest defined cargo was the signal recognition particle subunit SRP19, which IPO8 imports in a reconstituted system consistent with nuclear assembly of the SRP [PMID:11682607]. IPO8 also mediates nuclear translocation of NF-κB/p65 through a route independent of the canonical p65 NLS, with knockdown reducing nuclear p65 and NF-κB transcriptional output after TNF-α stimulation [PMID:23906023]; during enterovirus infection IPO8 assembles into a trimeric complex with the lncRNA LINC1467 and p65 that promotes p65 phosphorylation, nuclear entry, and pro-inflammatory cytokine expression [PMID:41156681]. IPO8 is additionally required for proper TGF-β/SMAD signaling: bi-allelic loss-of-function causes thoracic aortic aneurysm, and Ipo8-knockout mice show aortic-wall pSmad2 accumulation, reduced Smad6/7, and elastic fiber disorganization [PMID:34010605]. IPO8 transcription is itself directly activated by RUNX2 binding to a defined promoter element, linking IPO8 expression to osteoblast differentiation programs [PMID:27277970].","teleology":[{"year":2001,"claim":"Established IPO8 as a functional nuclear import receptor by assigning it a first defined cargo, addressing whether this importin-β family member carries protein substrates into the nucleus.","evidence":"In vitro reconstituted nuclear import assay with recombinant importin 8 and SRP19, plus endogenous SRP19 localization","pmids":["11682607"],"confidence":"High","gaps":["RanGTP dependence not directly dissected in this entry","Does not address physiological cargo range beyond SRP19","No structural basis for cargo recognition"]},{"year":2013,"claim":"Showed IPO8 imports NF-κB/p65 by an NLS-independent route, answering how p65 reaches the nucleus when the canonical NLS pathway is bypassed.","evidence":"siRNA screen of importin-β family, Co-IP of NLS-mutant p65 with IPO8, nuclear fractionation, and NF-κB reporter assay","pmids":["23906023"],"confidence":"High","gaps":["Binding interface between IPO8 and NLS-mutant p65 not mapped","Does not establish whether import is RanGTP-dependent","Relationship to canonical importin-α/β p65 import unresolved"]},{"year":2016,"claim":"Identified an upstream transcriptional regulator of IPO8, addressing how IPO8 expression is controlled in a differentiation context.","evidence":"ChIP-on-chip, luciferase reporter promoter-deletion analysis, RUNX2 siRNA knockdown with RT-qPCR, and osteoblast differentiation assay in human mesenchymal stem cells","pmids":["27277970"],"confidence":"Medium","gaps":["Single lab without independent confirmation","Functional consequence of RUNX2-driven IPO8 induction on nuclear transport not tested","Cell-type specificity of the regulation unknown"]},{"year":2021,"claim":"Connected IPO8 loss to a Mendelian disease and a specific signaling defect, defining its physiological role in TGF-β/SMAD nuclear transport and aortic homeostasis.","evidence":"Ipo8 knockout mouse with histology, pSmad2 immunostaining, biomechanical compliance assays, aortic-wall RT-qPCR, and human bi-allelic loss-of-function variants across families","pmids":["34010605"],"confidence":"High","gaps":["Direct demonstration that IPO8 imports specific SMAD proteins not shown biochemically","Mechanism linking IPO8 loss to elevated pSmad2 (rather than reduced) not fully resolved","Tissue specificity of the aortic phenotype unexplained"]},{"year":2025,"claim":"Refined the IPO8/p65 axis by defining a lncRNA-containing ternary complex, addressing how IPO8-mediated p65 import is regulated during infection.","evidence":"Co-IP of LINC1467/IPO8/p65 ternary complex, viral replication and cytokine assays, and LINC1467 loss-of-function in a mouse viral infection model","pmids":["41156681"],"confidence":"Medium","gaps":["Single lab, no structural validation or in vitro reconstitution","Stoichiometry and direct binding contacts within the trimeric complex not resolved","Whether LINC1467 is required for p65 import in non-infection contexts unknown"]},{"year":null,"claim":"Whether IPO8 cargo recognition shares a unified structural basis and how RanGTP-dependent release operates across its diverse substrates (SRP19, p65, SMADs) remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of IPO8-cargo complexes in the corpus","Direct biochemical demonstration of SMAD import by IPO8 lacking","Full cargo repertoire and selectivity determinants uncharacterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140104","term_label":"molecular carrier activity","supporting_discovery_ids":[0,1,3]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[0]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,1]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,1]}],"pathway":[{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[0,1,2]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,2,3]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[1,3]}],"complexes":["IPO8–LINC1467–p65 ternary complex"],"partners":["SRP19","RELA","RUNX2","LINC1467"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O15397","full_name":"Importin-8","aliases":["Ran-binding protein 8","RanBP8"],"length_aa":1037,"mass_kda":119.9,"function":"Involved in nuclear protein import, either by acting as autonomous nuclear transport receptor or as an adapter-like protein in association with the importin-beta subunit KPNB1. Acting autonomously, may serve as receptor for nuclear localization signals (NLS) and promote translocation of import substrates through the nuclear pore complex (NPC) by an energy requiring, Ran-dependent mechanism. At the nucleoplasmic side of the NPC, Ran binds to importin, the importin/substrate complex dissociates and importin is re-exported from the nucleus to the cytoplasm where GTP hydrolysis releases Ran. The directionality of nuclear import is thought to be conferred by an asymmetric distribution of the GTP- and GDP-bound forms of Ran between the cytoplasm and nucleus (PubMed:9214382). In vitro mediates the nuclear import of the signal recognition particle protein SRP19 (PubMed:11682607). May also be involved in cytoplasm-to-nucleus shuttling of a broad spectrum of other cargos, including Argonaute-microRNAs complexes, the JUN protein, RELA/NF-kappa-B p65 subunit, the translation initiation factor EIF4E and a set of receptor-activated mothers against decapentaplegic homolog (SMAD) transcription factors that play a critical role downstream of the large family of transforming growth factor beta and bone morphogenetic protein (BMP) cytokines (Probable)","subcellular_location":"Cytoplasm; Nucleus","url":"https://www.uniprot.org/uniprotkb/O15397/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/IPO8","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000133704","cell_line_id":"CID001556","localizations":[{"compartment":"cytoplasmic","grade":3},{"compartment":"nucleoplasm","grade":3}],"interactors":[{"gene":"ZBTB10","stoichiometry":10.0},{"gene":"ZNF629","stoichiometry":4.0},{"gene":"CAPZB","stoichiometry":0.2},{"gene":"CDX2","stoichiometry":0.2},{"gene":"ZFP1","stoichiometry":0.2},{"gene":"TRIM28","stoichiometry":0.2},{"gene":"ZNF460","stoichiometry":0.2},{"gene":"RANBP1","stoichiometry":0.2},{"gene":"WEE1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID001556","total_profiled":1310},"omim":[{"mim_id":"619472","title":"VISS SYNDROME; VISS","url":"https://www.omim.org/entry/619472"},{"mim_id":"605600","title":"IMPORTIN 8; IPO8","url":"https://www.omim.org/entry/605600"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Vesicles","reliability":"Additional"},{"location":"End piece","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/IPO8"},"hgnc":{"alias_symbol":["IMP8"],"prev_symbol":["RANBP8"]},"alphafold":{"accession":"O15397","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O15397","model_url":"https://alphafold.ebi.ac.uk/files/AF-O15397-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O15397-F1-predicted_aligned_error_v6.png","plddt_mean":87.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=IPO8","jax_strain_url":"https://www.jax.org/strain/search?query=IPO8"},"sequence":{"accession":"O15397","fasta_url":"https://rest.uniprot.org/uniprotkb/O15397.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O15397/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O15397"}},"corpus_meta":[{"pmid":"23906023","id":"PMC_23906023","title":"KPNB1, XPO7 and IPO8 mediate the translocation ofNF-κB/p65 into the nucleus.","date":"2013","source":"Traffic (Copenhagen, Denmark)","url":"https://pubmed.ncbi.nlm.nih.gov/23906023","citation_count":90,"is_preprint":false},{"pmid":"11451699","id":"PMC_11451699","title":"Identification of a plasmid encoding SHV-12, TEM-1, and a variant of IMP-2 metallo-beta-lactamase, IMP-8, from a clinical isolate of Klebsiella pneumoniae.","date":"2001","source":"Antimicrobial agents and chemotherapy","url":"https://pubmed.ncbi.nlm.nih.gov/11451699","citation_count":81,"is_preprint":false},{"pmid":"11682607","id":"PMC_11682607","title":"Signal recognition particle protein 19 is imported into the nucleus by importin 8 (RanBP8) and transportin.","date":"2001","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/11682607","citation_count":55,"is_preprint":false},{"pmid":"19014639","id":"PMC_19014639","title":"Identification of importin 8 (IPO8) as the most accurate reference gene for the clinicopathological analysis of lung specimens.","date":"2008","source":"BMC molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/19014639","citation_count":45,"is_preprint":false},{"pmid":"22992193","id":"PMC_22992193","title":"Occurrence of IMP-8, IMP-10, and IMP-13 metallo-β-lactamases located on class 1 integrons and other extended-spectrum β-lactamases in bacterial isolates from Tunisian rivers.","date":"2012","source":"Scandinavian journal of infectious diseases","url":"https://pubmed.ncbi.nlm.nih.gov/22992193","citation_count":34,"is_preprint":false},{"pmid":"21422214","id":"PMC_21422214","title":"First report of Klebsiella oxytoca strain coproducing KPC-2 and IMP-8 carbapenemases.","date":"2011","source":"Antimicrobial agents and chemotherapy","url":"https://pubmed.ncbi.nlm.nih.gov/21422214","citation_count":34,"is_preprint":false},{"pmid":"26033721","id":"PMC_26033721","title":"Characterization of pKP-M1144, a Novel ColE1-Like Plasmid Encoding IMP-8, GES-5, and BEL-1 β-Lactamases, from a Klebsiella pneumoniae Sequence Type 252 Isolate.","date":"2015","source":"Antimicrobial agents and chemotherapy","url":"https://pubmed.ncbi.nlm.nih.gov/26033721","citation_count":31,"is_preprint":false},{"pmid":"34010605","id":"PMC_34010605","title":"A human importin-β-related disorder: Syndromic thoracic aortic aneurysm caused by bi-allelic loss-of-function variants in IPO8.","date":"2021","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/34010605","citation_count":14,"is_preprint":false},{"pmid":"31181270","id":"PMC_31181270","title":"Complete genome sequence of an IMP-8, CTX-M-14, CTX-M-3 and QnrS1 co-producing Enterobacter asburiae isolate from a patient with wound infection.","date":"2019","source":"Journal of global antimicrobial resistance","url":"https://pubmed.ncbi.nlm.nih.gov/31181270","citation_count":13,"is_preprint":false},{"pmid":"25356340","id":"PMC_25356340","title":"Emergence of Citrobacter freundii carrying IMP-8 metallo-β-lactamase in Germany.","date":"2014","source":"New microbes and new infections","url":"https://pubmed.ncbi.nlm.nih.gov/25356340","citation_count":9,"is_preprint":false},{"pmid":"20381610","id":"PMC_20381610","title":"First description of bla IMP-8 in a Pseudomonas mendocina isolated at the Hospital Infante D. Pedro, Aveiro, Portugal.","date":"2010","source":"Research in microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/20381610","citation_count":9,"is_preprint":false},{"pmid":"37478009","id":"PMC_37478009","title":"Analysis of NDM-1 and IMP-8 carbapenemase producing Raoultella planticola clinical isolates.","date":"2023","source":"Acta microbiologica et immunologica Hungarica","url":"https://pubmed.ncbi.nlm.nih.gov/37478009","citation_count":4,"is_preprint":false},{"pmid":"39727411","id":"PMC_39727411","title":"Phenotypic and genotypic characterization of clinical carbapenem-resistant Acinetobacter species harboring the metallo-beta-lactamases IMP-8 or NDM-1 in China.","date":"2024","source":"Microbiology spectrum","url":"https://pubmed.ncbi.nlm.nih.gov/39727411","citation_count":4,"is_preprint":false},{"pmid":"27277970","id":"PMC_27277970","title":"RUNX2 controls human IPO8 basal transcription in Saos-2 cells.","date":"2016","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/27277970","citation_count":3,"is_preprint":false},{"pmid":"25202959","id":"PMC_25202959","title":"[Cloning of IPO8 promoter and analysis of its transcription activity].","date":"2014","source":"Zhong nan da xue xue bao. Yi xue ban = Journal of Central South University. Medical sciences","url":"https://pubmed.ncbi.nlm.nih.gov/25202959","citation_count":0,"is_preprint":false},{"pmid":"36905820","id":"PMC_36905820","title":"Generation of one induced pluripotent cell (iPSC) line (BBANTWi011-A) from a patient carrying an IPO8 bi-allelic loss-of-function mutation.","date":"2023","source":"Stem cell research","url":"https://pubmed.ncbi.nlm.nih.gov/36905820","citation_count":0,"is_preprint":false},{"pmid":"41156681","id":"PMC_41156681","title":"LINC1467 Activates the IPO8-p65 Axis to Restrict Hand, Foot, and Mouth Disease Virus Replication.","date":"2025","source":"Pathogens (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/41156681","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9991,"output_tokens":1532,"usd":0.026477,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8302,"output_tokens":2384,"usd":0.050555,"stage2_stop_reason":"end_turn"},"total_usd":0.077032,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2001,\n      \"finding\": \"Importin 8 (IPO8/RanBP8) directly imports SRP19 (the 19 kDa subunit of the signal recognition particle) into the nucleus in vitro; this was the first cargo function assigned to importin 8. Import was shown to be mediated by members of the importin-β superfamily and is consistent with nuclear assembly of SRP.\",\n      \"method\": \"In vitro nuclear import assay using recombinant importin 8 and SRP19; localization of endogenous SRP19 to nucleus and nucleolus\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstituted nuclear import assay with direct functional readout; endogenous localization confirmed by independent method in same study\",\n      \"pmids\": [\"11682607\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"IPO8 mediates nuclear translocation of NF-κB/p65 independently of the canonical NLS of p65; NLS-mutated p65 still entered the nucleus and co-immunoprecipitated with IPO8. Knockdown of IPO8 reduced nuclear p65 levels and NF-κB transcriptional activity after TNF-α stimulation.\",\n      \"method\": \"High-content siRNA screen of 17 importin-β family members; co-immunoprecipitation of NLS-mutated p65 with IPO8; nuclear fractionation; NF-κB reporter assay\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP with NLS-mutant p65, siRNA knockdown with quantitative nuclear fractionation, and functional NF-κB reporter assay; multiple orthogonal methods in one study\",\n      \"pmids\": [\"23906023\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Bi-allelic loss-of-function of IPO8 causes thoracic aortic aneurysm (TAA) associated with dysregulated TGF-β signaling; Ipo8 knockout mice develop TAA with elastic fiber disorganization, nuclear accumulation of pSmad2, decreased Smad6/7, and increased Mmp2/Ccn2 expression in the aortic wall, placing IPO8 as a regulator of TGF-β/SMAD nuclear import upstream of aortic wall homeostasis.\",\n      \"method\": \"Ipo8 knockout mouse model (C57BL/6N); immunohistochemistry for pSmad2; compliance assays; RT-qPCR of aortic wall gene expression; human genetic analysis (bi-allelic loss-of-function variants in patients)\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — knockout mouse model with multiple orthogonal readouts (histology, immunostaining for pSmad2, qPCR, biomechanical assay) corroborated by human genetics across six unrelated families\",\n      \"pmids\": [\"34010605\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"IPO8 forms a trimeric complex with the lncRNA LINC1467 and NF-κB/p65; this complex facilitates phosphorylation and nuclear translocation of p65, thereby activating NF-κB-driven pro-inflammatory cytokine expression during enterovirus infection.\",\n      \"method\": \"Co-immunoprecipitation of LINC1467/IPO8/p65 complex; functional assays (viral replication, cytokine expression); mouse model of viral infection; loss-of-function of LINC1467\",\n      \"journal\": \"Pathogens (Basel, Switzerland)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — Co-IP demonstrating ternary complex and functional NF-κB readout, but single lab, no structural validation or in vitro reconstitution; consistent with PMID:23906023 on IPO8/p65 axis\",\n      \"pmids\": [\"41156681\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The transcription factor RUNX2 directly binds the IPO8 promoter at positions −496 to −501 bp and activates IPO8 basal transcription; RUNX2 knockdown reduces IPO8 mRNA levels, and IPO8 and RUNX2 expression are co-regulated during osteoblast induction.\",\n      \"method\": \"ChIP-on-chip in human mesenchymal stem cells; luciferase reporter assays with truncated IPO8 promoter constructs; ChIP validation of RUNX2 binding; RUNX2 siRNA knockdown with RT-qPCR; osteoblast differentiation assay\",\n      \"journal\": \"Molecular medicine reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP confirmation plus luciferase reporter deletion analysis and knockdown experiment; multiple orthogonal methods but single lab\",\n      \"pmids\": [\"27277970\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"IPO8 (importin 8) is an importin-β family nuclear transport receptor that imports cargo molecules—including SRP19, NF-κB/p65 (via an NLS-independent route facilitated by the lncRNA LINC1467), and TGF-β/SMAD signaling components—into the nucleus in a RanGTP-dependent manner; loss of IPO8 disrupts SMAD nuclear accumulation and TGF-β pathway homeostasis, leading to thoracic aortic aneurysm, while its own transcription is directly activated by RUNX2 binding to a specific promoter element.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"IPO8 is an importin-β superfamily nuclear transport receptor that delivers diverse cargoes into the nucleus, functioning as a hub coupling cytoplasmic signaling to nuclear gene-regulatory programs [#0, #1]. Its earliest defined cargo was the signal recognition particle subunit SRP19, which IPO8 imports in a reconstituted system consistent with nuclear assembly of the SRP [#0]. IPO8 also mediates nuclear translocation of NF-κB/p65 through a route independent of the canonical p65 NLS, with knockdown reducing nuclear p65 and NF-κB transcriptional output after TNF-α stimulation [#1]; during enterovirus infection IPO8 assembles into a trimeric complex with the lncRNA LINC1467 and p65 that promotes p65 phosphorylation, nuclear entry, and pro-inflammatory cytokine expression [#3]. IPO8 is additionally required for proper TGF-β/SMAD signaling: bi-allelic loss-of-function causes thoracic aortic aneurysm, and Ipo8-knockout mice show aortic-wall pSmad2 accumulation, reduced Smad6/7, and elastic fiber disorganization [#2]. IPO8 transcription is itself directly activated by RUNX2 binding to a defined promoter element, linking IPO8 expression to osteoblast differentiation programs [#4].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Established IPO8 as a functional nuclear import receptor by assigning it a first defined cargo, addressing whether this importin-β family member carries protein substrates into the nucleus.\",\n      \"evidence\": \"In vitro reconstituted nuclear import assay with recombinant importin 8 and SRP19, plus endogenous SRP19 localization\",\n      \"pmids\": [\"11682607\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"RanGTP dependence not directly dissected in this entry\", \"Does not address physiological cargo range beyond SRP19\", \"No structural basis for cargo recognition\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Showed IPO8 imports NF-κB/p65 by an NLS-independent route, answering how p65 reaches the nucleus when the canonical NLS pathway is bypassed.\",\n      \"evidence\": \"siRNA screen of importin-β family, Co-IP of NLS-mutant p65 with IPO8, nuclear fractionation, and NF-κB reporter assay\",\n      \"pmids\": [\"23906023\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Binding interface between IPO8 and NLS-mutant p65 not mapped\", \"Does not establish whether import is RanGTP-dependent\", \"Relationship to canonical importin-α/β p65 import unresolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identified an upstream transcriptional regulator of IPO8, addressing how IPO8 expression is controlled in a differentiation context.\",\n      \"evidence\": \"ChIP-on-chip, luciferase reporter promoter-deletion analysis, RUNX2 siRNA knockdown with RT-qPCR, and osteoblast differentiation assay in human mesenchymal stem cells\",\n      \"pmids\": [\"27277970\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab without independent confirmation\", \"Functional consequence of RUNX2-driven IPO8 induction on nuclear transport not tested\", \"Cell-type specificity of the regulation unknown\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Connected IPO8 loss to a Mendelian disease and a specific signaling defect, defining its physiological role in TGF-β/SMAD nuclear transport and aortic homeostasis.\",\n      \"evidence\": \"Ipo8 knockout mouse with histology, pSmad2 immunostaining, biomechanical compliance assays, aortic-wall RT-qPCR, and human bi-allelic loss-of-function variants across families\",\n      \"pmids\": [\"34010605\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct demonstration that IPO8 imports specific SMAD proteins not shown biochemically\", \"Mechanism linking IPO8 loss to elevated pSmad2 (rather than reduced) not fully resolved\", \"Tissue specificity of the aortic phenotype unexplained\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Refined the IPO8/p65 axis by defining a lncRNA-containing ternary complex, addressing how IPO8-mediated p65 import is regulated during infection.\",\n      \"evidence\": \"Co-IP of LINC1467/IPO8/p65 ternary complex, viral replication and cytokine assays, and LINC1467 loss-of-function in a mouse viral infection model\",\n      \"pmids\": [\"41156681\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab, no structural validation or in vitro reconstitution\", \"Stoichiometry and direct binding contacts within the trimeric complex not resolved\", \"Whether LINC1467 is required for p65 import in non-infection contexts unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Whether IPO8 cargo recognition shares a unified structural basis and how RanGTP-dependent release operates across its diverse substrates (SRP19, p65, SMADs) remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of IPO8-cargo complexes in the corpus\", \"Direct biochemical demonstration of SMAD import by IPO8 lacking\", \"Full cargo repertoire and selectivity determinants uncharacterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140104\", \"supporting_discovery_ids\": [0, 1, 3]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 2, 3]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [1, 3]}\n    ],\n    \"complexes\": [\"IPO8–LINC1467–p65 ternary complex\"],\n    \"partners\": [\"SRP19\", \"RELA\", \"RUNX2\", \"LINC1467\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}