{"gene":"ULBP1","run_date":"2026-04-28T21:43:01","timeline":{"discoveries":[{"year":2001,"finding":"ULBP1, ULBP2, and ULBP3 are novel MHC class I-related molecules that bind human cytomegalovirus glycoprotein UL16 and activate NK cells, inducing cytokine/chemokine production, proliferation, cytotoxic activity, and upregulation of activation-associated surface molecules. Soluble recombinant UL16 protein inhibited ULBP-mediated biological activities, establishing a viral immune evasion mechanism.","method":"Binding assays, NK cell functional assays (cytokine production, cytotoxicity, proliferation), competition experiments with soluble UL16","journal":"European journal of immunology","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal functional assays, direct binding demonstrated, replicated across human and mouse NK cells","pmids":["11465099"],"is_preprint":false},{"year":2003,"finding":"HCMV glycoprotein UL16 retains ULBP1 and ULBP2 in the endoplasmic reticulum of infected cells, preventing their surface expression and thereby limiting NKG2D-dependent NK cell recognition. Infection with a UL16 deletion mutant virus resulted in surface expression of all three ULBPs and a pronounced, entirely NKG2D-dependent increase in NK sensitivity.","method":"Viral infection with wild-type vs. UL16-deletion mutant HCMV, flow cytometry for surface expression, NK cell cytotoxicity assays, immunofluorescence/subcellular localization","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 — genetic deletion of UL16 with direct surface localization and functional NK readout, multiple orthogonal methods","pmids":["12847260"],"is_preprint":false},{"year":2006,"finding":"ULBP1 transcription is driven by binding of Sp1 and Sp3 to a CRE(1) site in the ULBP1 minimal promoter, with Sp3 being the essential activator (>500-fold upregulation upon Sp3 overexpression in SL2 cells). AP-2alpha represses ULBP1 expression by interfering with Sp1/Sp3 binding to the ULBP1 promoter.","method":"Promoter reporter assays, site-directed mutagenesis of the CRE(1) site, Sp1/Sp3/AP-2alpha overexpression, EMSA, transcription factor binding studies in SL2 (Drosophila) cells and HeLa cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — mutagenesis of promoter element combined with overexpression and reporter assays, multiple cell systems","pmids":["16901903"],"is_preprint":false},{"year":2006,"finding":"ULBP1 is expressed on mature dendritic cells both in situ in lymph node T cell areas and in vitro after artificial maturation, suggesting a role for NKG2D-ULBP1 in initiation or reactivation of T cell responses.","method":"Flow cytometry, in situ detection in sentinel lymph nodes, in vitro DC maturation assays","journal":"European journal of immunology","confidence":"Medium","confidence_rationale":"Tier 3 — direct localization by flow cytometry and in situ staining, but functional link is inferential","pmids":["16342232"],"is_preprint":false},{"year":2009,"finding":"Proteasome inhibition (by bortezomib and other proteasome inhibitors) dramatically and specifically upregulates ULBP1 mRNA and cell surface protein by acting at a site within the 522-bp ULBP1 promoter, through a mechanism independent of ATM/ATR DNA damage signaling.","method":"Proteasome inhibitor treatment, ULBP1 mRNA/surface protein measurement by RT-PCR and flow cytometry, promoter reporter assays, ATM/ATR inhibitor experiments, pharmacological and radiation treatments","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods including promoter reporter assays and pathway inhibition; multiple cell lines and inhibitors tested","pmids":["19414815"],"is_preprint":false},{"year":2009,"finding":"HCV protease NS3/4A inhibits ULBP1 transcription, as demonstrated by reduced luciferase activity from a ULBP1 promoter reporter construct co-transfected with NS3/4A expression plasmid.","method":"Luciferase reporter assay with ULBP1 promoter construct, NS3/4A expression vector co-transfection","journal":"Xi bao yu fen zi mian yi xue za zhi","confidence":"Low","confidence_rationale":"Tier 3 — single reporter assay, single lab, no corroborating in vivo or protein-level data","pmids":["19500498"],"is_preprint":false},{"year":2010,"finding":"ULBP1 expression levels are a nonredundant determinant of lymphoma susceptibility to gammadelta T cell-mediated cytolysis; NKG2D blockade significantly inhibits lymphoma killing, and specific ULBP1 loss-of-function reduces gammadelta T cell cytotoxicity against lymphoma cells.","method":"NKG2D blocking antibodies, ULBP1-specific siRNA knockdown, cytotoxicity assays with primary gammadelta T cells, flow cytometry","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 — specific loss-of-function (siRNA) plus receptor blockade with defined cytotoxicity readout, nonredundancy established","pmids":["20101024"],"is_preprint":false},{"year":2011,"finding":"Wild-type p53, but not mutant p53, strongly upregulates ULBP1 and ULBP2 mRNA and cell surface expression via intronic p53-responsive elements in these genes, enhancing NKG2D-dependent NK cell degranulation and IFN-γ production.","method":"p53 induction in human tumor cells, RT-PCR and flow cytometry for ULBP1/2 expression, identification of intronic p53-responsive elements, NK cell degranulation and IFN-γ assays, NKG2D blocking, p53-reactivating compound RITA treatment","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 — identification of p53 response elements in ULBP1 locus, multiple orthogonal methods, functional NK readout; highly cited","pmids":["21764762"],"is_preprint":false},{"year":2011,"finding":"The 3' UTR of ULBP1 mRNA mediates post-transcriptional repression; AU-rich elements (ARE) within the 3' UTR have an mRNA-stabilizing effect when mutated, and specific microRNAs (miR-140-5p, miR-409-3p, miR-433-3p, miR-650) expressed in HeLa and Jurkat cells may contribute to ULBP1 regulation.","method":"Luciferase reporter assays with full-length and truncated ULBP1 3' UTR constructs, ARE mutagenesis, microRNA overexpression, Drosha partial silencing","journal":"Human immunology","confidence":"Medium","confidence_rationale":"Tier 3 — reporter assays and mutagenesis, but microRNA role not definitively established; single lab","pmids":["21406206"],"is_preprint":false},{"year":2014,"finding":"c-Myc directly binds the ULBP1 and ULBP3 gene loci and regulates their expression; cytarabine-resistant AML cells exhibit c-Myc induction driving ULBP1/2/3 upregulation and increased susceptibility to NK-mediated lysis, reversed by c-Myc inhibition.","method":"Chromatin immunoprecipitation (ChIP) assay for c-Myc binding to ULBP1/3 loci, c-Myc inhibition, flow cytometry for NKG2D ligand expression, NK cell lysis assays with primary AML blasts","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 — ChIP demonstrating direct c-Myc binding to ULBP1 locus, combined with functional inhibition and NK cytotoxicity assays","pmids":["24677544"],"is_preprint":false},{"year":2015,"finding":"A forward genetic screen identified ATF4 as a transcription factor that drives ULBP1 gene expression in cancer cell lines, and RNA-binding protein RBM4 supports ULBP1 expression by suppressing a novel alternatively spliced isoform of ULBP1 mRNA, revealing that independent pathways work at multiple stages of ULBP1 biogenesis.","method":"Forward genetic screen in tumor-derived human cell line, identification and validation of ATF4 and RBM4 as regulators, alternative splicing analysis","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 — forward genetic screen with experimental validation at transcriptional and post-transcriptional levels; multiple mechanistic layers","pmids":["26565589"],"is_preprint":false},{"year":2016,"finding":"ULBP1 has a shorter half-life at the cell surface than other ULBP molecules due to rapid proteasomal degradation following internalization, not due to shedding or increased internalization rate; proteasome inhibition blocks this post-internalization degradation.","method":"Surface stability assays, proteasome inhibitors, shedding assays, internalization assays, pulse-chase experiments","journal":"Immunology and cell biology","confidence":"Medium","confidence_rationale":"Tier 2 — multiple mechanistic assays distinguishing internalization from degradation, but single lab","pmids":["26732147"],"is_preprint":false},{"year":2016,"finding":"SV40 infection downregulates ULBP1 surface expression, allowing viral evasion from NK cell cytotoxicity mediated through NKG2D.","method":"SV40 infection of target cells, flow cytometry for ULBP1 surface expression, NK cell cytotoxicity assays","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 3 — direct surface expression measurement combined with NK cytotoxicity assay, but mechanism of downregulation not fully characterized","pmids":["26992229"],"is_preprint":false},{"year":2018,"finding":"Hepatitis C virus infection induces cell surface expression of ULBP1 in human hepatocytes, and NK cells (NK-92 line) recognize HCV-infected cells via NKG2D-ULBP1 interaction, triggering cytotoxicity and IFN-γ expression that reduces HCV RNA replication.","method":"HCV infection of PH5CH8 and RSc cells, flow cytometry for ULBP1, NK-92 co-culture cytotoxicity and IFN-γ assays, HCV RNA quantification","journal":"FEBS open bio","confidence":"Medium","confidence_rationale":"Tier 2 — direct infection model with ULBP1 induction, functional NK cytotoxicity and antiviral outcome measured","pmids":["29511613"],"is_preprint":false},{"year":2018,"finding":"Celecoxib induces ULBP-1 expression in colon cancer cells via COX-2-independent and ER stress-independent pathways, increasing susceptibility to NK cell-mediated cytotoxicity in both COX-2 negative and positive cell lines.","method":"Celecoxib treatment with/without COX-2 inhibition or ER stress induction (thapsigargin), flow cytometry for ULBP-1, DELFIA NK cytotoxicity assay, soft agar colony forming assay","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods to rule out COX-2 and ER stress pathways; functional NK assay","pmids":["25218028"],"is_preprint":false},{"year":2020,"finding":"Celecoxib upregulates ULBP-1 expression in lung cancer cells via JNK and PI3K signaling pathways (both inhibited by respective pathway inhibitors), and this ULBP-1 induction increases susceptibility to NK cell-mediated cytotoxicity.","method":"Celecoxib treatment with JNK/PI3K inhibitors, PCR and immunoblotting for ULBP-1, flow cytometry, NK cell cytotoxicity assay, fluorescence microscopy","journal":"Oncology letters","confidence":"Medium","confidence_rationale":"Tier 2 — pathway inhibitors combined with receptor blocking and functional NK assay; single lab","pmids":["33014157"],"is_preprint":false},{"year":2021,"finding":"Tanshinone IIA increases ULBP1 expression in NSCLC cells via ATF4 (downstream of p-PERK), as ATF4 knockdown completely reverses ULBP1 upregulation; this ULBP1 induction mediates enhanced NK cell cytotoxicity.","method":"TIIA treatment, ATF4/CHOP siRNA knockdown, immunoblotting for p-PERK/ATF4/CHOP, flow cytometry for ULBP1, NK cell cytotoxicity assay, in vivo syngeneic and xenograft mouse models with NK cell depletion","journal":"Journal of leukocyte biology","confidence":"Medium","confidence_rationale":"Tier 2 — specific siRNA knockdown of ATF4 with ULBP1 readout, in vivo validation, multiple cell lines","pmids":["33909909"],"is_preprint":false},{"year":2024,"finding":"HHV-6B glycoprotein U20 binds directly to ULBP1 with sub-micromolar affinity, masking it from NKG2D recognition at the cell surface without reducing ULBP1 protein levels, thereby blocking NK cell activation.","method":"Recombinant protein binding assays, U20 transduction into target cells, NKG2D binding competition assay, NK cell activation assays, small-angle X-ray scattering (SAXS) for structural modeling of U20-ULBP1 complex","journal":"Frontiers in immunology","confidence":"High","confidence_rationale":"Tier 1-2 — direct binding measured with quantitative affinity, structural modeling, functional NK assay, multiple approaches in single study","pmids":["38953028"],"is_preprint":false},{"year":2025,"finding":"Cyclosporin A (CsA) induces ubiquitination-dependent proteasomal degradation of endothelial ULBP1, reducing NKG2D ligand availability and thereby weakening NK cell PI3K/AKT signaling and effector function in renal microvascular inflammation.","method":"CsA treatment of endothelial cells, co-culture with NK cells, ubiquitination assays, proteasome inhibition, PI3K/AKT signaling measurement, NK cell activation/cytotoxicity assays","journal":"International immunopharmacology","confidence":"Medium","confidence_rationale":"Tier 2 — ubiquitination assay combined with NK signaling and functional readout; single lab, relatively recent","pmids":["41297348"],"is_preprint":false},{"year":2024,"finding":"SIRT4 activates AMPKα to promote p53 phosphorylation and nuclear translocation, which induces transcription of ULBP1 (and ULBP2), thereby enhancing NK cell cytotoxicity against activated hepatic stellate cells.","method":"SIRT4 overexpression/knockdown, AMPKα activation assays, p53 phosphorylation and nuclear translocation assays, ULBP1/2 transcription measurement, NK cell cytotoxicity assays, AAV-mediated SIRT4 delivery in mouse LF models","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 — mechanistic pathway established with multiple assays, but preprint not yet peer-reviewed","pmids":[],"is_preprint":true},{"year":2011,"finding":"Recombinant ULBP1 extracellular domain was successfully expressed in E. coli, refolded, and crystallized, yielding initial X-ray diffraction data to 4.6 Å, establishing conditions for structural characterization of the protein.","method":"Recombinant protein expression in E. coli, refolding from inclusion bodies, site-directed mutagenesis of unpaired cysteines, size exclusion and ion exchange chromatography, X-ray crystallography","journal":"Protein expression and purification","confidence":"Low","confidence_rationale":"Tier 1 method (crystallography) but only preliminary diffraction reported, no resolved structure with functional validation","pmids":["21575723"],"is_preprint":false}],"current_model":"ULBP1 is a GPI-anchored MHC class I-related stress ligand whose surface expression is controlled at multiple levels: transcriptionally by Sp3 (via a CRE1 promoter element), p53 (via intronic response elements), c-Myc, ATF4, and proteasome activity, and repressed by AP-2alpha; post-transcriptionally by its 3' UTR (ARE elements and microRNAs) and the RNA-binding protein RBM4; and post-translationally by rapid ubiquitin-proteasomal degradation after internalization and by cyclosporin A-induced ubiquitination. At the cell surface, ULBP1 engages the activating NK/T cell receptor NKG2D to trigger cytotoxicity and cytokine production, while pathogens evade this response through direct ULBP1 sequestration by viral proteins (HCMV UL16 retains ULBP1 in the ER; HHV-6B U20 binds ULBP1 at the surface to block NKG2D engagement) or transcriptional suppression (HCV NS3/4A, SV40 infection)."},"narrative":{"teleology":[{"year":2001,"claim":"Establishing ULBP1 as an NKG2D ligand that activates NK cells resolved how UL16-binding proteins translate stress signals into innate immune recognition.","evidence":"Binding assays, NK cytotoxicity/cytokine/proliferation assays, soluble UL16 competition experiments","pmids":["11465099"],"confidence":"High","gaps":["NKG2D-independent roles of ULBP1 not addressed","structural basis of ULBP1–NKG2D interaction not determined","transcriptional regulation unknown"]},{"year":2003,"claim":"Demonstrating that HCMV UL16 retains ULBP1 in the ER established the first defined mechanism by which a pathogen evades NKG2D-mediated immunity by preventing ligand surface display.","evidence":"WT vs. UL16-deletion mutant HCMV infection, flow cytometry, immunofluorescence, NK cytotoxicity assays","pmids":["12847260"],"confidence":"High","gaps":["Whether UL16 directly binds ULBP1 in cis in the ER membrane not resolved at atomic level","mechanism of ER retention (coat-protein signals, chaperone involvement) undefined"]},{"year":2006,"claim":"Identification of the CRE1 promoter element bound by Sp3 (activator) and AP-2α (repressor) defined the basal transcriptional logic governing ULBP1 expression.","evidence":"Promoter reporter assays, CRE1 mutagenesis, EMSA, Sp1/Sp3/AP-2α overexpression in Drosophila SL2 and HeLa cells","pmids":["16901903"],"confidence":"High","gaps":["Chromatin context and epigenetic regulation not explored","how stress signals converge on Sp3/AP-2α balance unknown"]},{"year":2009,"claim":"Proteasome inhibition was shown to specifically upregulate ULBP1 transcription through its proximal promoter independently of DNA-damage signaling, separating proteasome-dependent control from ATM/ATR pathways.","evidence":"Bortezomib treatment, RT-PCR/flow cytometry, promoter reporter, ATM/ATR inhibitors across multiple cell lines","pmids":["19414815"],"confidence":"High","gaps":["Identity of the proteasome-sensitive transcription factor acting at the ULBP1 promoter not determined","in vivo relevance of proteasome-dependent transcriptional regulation not tested"]},{"year":2011,"claim":"Discovery that wild-type p53 drives ULBP1 transcription via intronic response elements linked the tumor suppressor pathway to NKG2D-dependent immunosurveillance, while 3′ UTR AU-rich elements and microRNAs added a post-transcriptional regulatory layer.","evidence":"p53 induction, intronic response element mapping, NK degranulation/IFN-γ assays, NKG2D blocking (p53 arm); 3′ UTR reporter constructs, ARE mutagenesis, microRNA overexpression (post-transcriptional arm)","pmids":["21764762","21406206"],"confidence":"High","gaps":["Relative contributions of p53-dependent transcription vs. microRNA repression in physiological settings not quantified","microRNA effects not validated by individual antagomir rescue at endogenous ULBP1 protein level"]},{"year":2014,"claim":"ChIP evidence that c-Myc directly binds the ULBP1 locus and drives its expression in AML cells revealed an oncogene-dependent route to NKG2D ligand upregulation that can sensitize drug-resistant leukemia to NK killing.","evidence":"ChIP for c-Myc at ULBP1/3 loci, c-Myc inhibition, flow cytometry, NK lysis of primary AML blasts","pmids":["24677544"],"confidence":"High","gaps":["Whether c-Myc acts through the same CRE1 or distinct promoter/enhancer elements not resolved","cooperation or antagonism between c-Myc and p53 at the ULBP1 locus not addressed"]},{"year":2015,"claim":"A forward genetic screen identified ATF4 as a transcriptional activator and RBM4 as a post-transcriptional regulator of ULBP1 (suppressing an aberrant splice isoform), revealing that independent pathways converge at multiple biogenesis stages.","evidence":"Forward genetic screen in tumor cells, ATF4 and RBM4 validation, alternative splicing analysis","pmids":["26565589"],"confidence":"High","gaps":["Structure and function of the alternatively spliced ULBP1 isoform not characterized","whether ATF4-driven ULBP1 induction requires integrated stress response activation in vivo unknown"]},{"year":2016,"claim":"ULBP1 was shown to have an unusually short surface half-life due to rapid ubiquitin-proteasomal degradation after internalization, distinguishing it from other ULBPs and explaining why proteasome inhibitors preferentially boost ULBP1 surface levels.","evidence":"Surface stability assays, proteasome inhibition, shedding/internalization rate measurements, pulse-chase","pmids":["26732147"],"confidence":"Medium","gaps":["E3 ligase responsible for ULBP1 ubiquitination not identified","sorting signals directing ULBP1 to proteasomal rather than lysosomal degradation unknown","single-lab finding"]},{"year":2018,"claim":"Celecoxib-induced ULBP1 upregulation via JNK/PI3K pathways (COX-2- and ER-stress-independent) and HCV-induced ULBP1 surface expression on hepatocytes broadened the range of stimuli and cell types activating NKG2D-mediated immunity through ULBP1.","evidence":"Celecoxib ± pathway inhibitors, flow cytometry, NK cytotoxicity (colon/lung cancer); HCV infection, ULBP1 surface detection, NK-92 co-culture, HCV RNA quantification (hepatocytes)","pmids":["25218028","29511613"],"confidence":"Medium","gaps":["Direct transcription factor(s) mediating JNK/PI3K-dependent ULBP1 induction not identified","contradiction between NS3/4A-mediated ULBP1 suppression and HCV-induced ULBP1 upregulation not reconciled"]},{"year":2024,"claim":"HHV-6B glycoprotein U20 was shown to directly bind ULBP1 at the cell surface with sub-micromolar affinity, blocking NKG2D engagement without reducing ULBP1 levels — a viral masking strategy distinct from HCMV's ER retention mechanism.","evidence":"Recombinant protein binding, U20 transduction, NKG2D competition, NK activation assays, SAXS structural modeling","pmids":["38953028"],"confidence":"High","gaps":["High-resolution crystal/cryo-EM structure of U20–ULBP1 complex not yet available","whether U20 also masks other NKG2D ligands not fully resolved"]},{"year":2025,"claim":"Cyclosporin A was found to induce ubiquitination-dependent proteasomal degradation of endothelial ULBP1, reducing NKG2D-mediated NK cell PI3K/AKT signaling — linking immunosuppressive drug action to ULBP1 post-translational turnover.","evidence":"CsA treatment of endothelial cells, ubiquitination assays, proteasome inhibition rescue, NK co-culture signaling and cytotoxicity assays","pmids":["41297348"],"confidence":"Medium","gaps":["E3 ligase mediating CsA-induced ULBP1 ubiquitination not identified","whether calcineurin inhibition is the upstream trigger unknown","single-lab finding"]},{"year":null,"claim":"The E3 ubiquitin ligase(s) targeting ULBP1 for post-internalization degradation remain unidentified, and no high-resolution structure of ULBP1 alone or in complex with NKG2D/viral evasins has been determined, limiting structure-guided therapeutic design.","evidence":"","pmids":[],"confidence":"High","gaps":["E3 ligase identity unknown","high-resolution ULBP1 structure lacking despite preliminary crystallization","relative in vivo contributions of transcriptional vs. post-translational regulation not quantified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[0,6,7,17]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,1,3,6,7,11,17]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[1]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,6,7,13,17]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[1,12,17]}],"complexes":[],"partners":["KLRK1","UL16","U20","SP3","TP53","MYC","ATF4","RBM4"],"other_free_text":[]},"mechanistic_narrative":"ULBP1 is a GPI-anchored MHC class I-related cell-surface glycoprotein that serves as a stress-induced ligand for the activating receptor NKG2D on NK cells and γδ T cells, triggering cytotoxicity, degranulation, and IFN-γ production [PMID:11465099, PMID:20101024, PMID:21764762]. Its surface expression is controlled at multiple levels: transcriptionally by Sp3 (via a CRE1 promoter element), p53 (via intronic response elements), c-Myc (direct binding to the ULBP1 locus), and ATF4; post-transcriptionally by AU-rich elements and microRNAs in its 3′ UTR and by the RNA-binding protein RBM4, which suppresses an alternatively spliced isoform [PMID:16901903, PMID:21764762, PMID:24677544, PMID:26565589, PMID:21406206]. ULBP1 is distinguished from other NKG2D ligands by its rapid post-internalization proteasomal degradation, which limits its surface half-life and can be pharmacologically reversed by proteasome inhibitors [PMID:26732147, PMID:19414815]. Viruses exploit ULBP1 regulation to evade immune surveillance: HCMV UL16 retains ULBP1 in the ER, and HHV-6B U20 masks surface ULBP1 from NKG2D engagement [PMID:12847260, PMID:38953028]."},"prefetch_data":{"uniprot":{"accession":"Q9BZM6","full_name":"UL16-binding protein 1","aliases":["ALCAN-beta","NKG2D ligand 1","N2DL-1","NKG2DL1","Retinoic acid early transcript 1I"],"length_aa":244,"mass_kda":28.0,"function":"Binds and activates the KLRK1/NKG2D receptor, mediating natural killer cell cytotoxicity","subcellular_location":"Cell membrane; Endoplasmic reticulum","url":"https://www.uniprot.org/uniprotkb/Q9BZM6/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ULBP1","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/ULBP1","total_profiled":1310},"omim":[{"mim_id":"611817","title":"KILLER CELL LECTIN-LIKE RECEPTOR, SUBFAMILY K, MEMBER 1; KLRK1","url":"https://www.omim.org/entry/611817"},{"mim_id":"609244","title":"RETINOIC ACID EARLY TRANSCRIPT 1G; RAET1G","url":"https://www.omim.org/entry/609244"},{"mim_id":"609243","title":"RETINOIC ACID EARLY TRANSCRIPT 1E; RAET1E","url":"https://www.omim.org/entry/609243"},{"mim_id":"605699","title":"UL16-BINDING PROTEIN 3; ULBP3","url":"https://www.omim.org/entry/605699"},{"mim_id":"605698","title":"UL16-BINDING PROTEIN 2; ULBP2","url":"https://www.omim.org/entry/605698"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Plasma membrane","reliability":"Supported"},{"location":"Cytosol","reliability":"Supported"}],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"brain","ntpm":3.6},{"tissue":"lung","ntpm":1.5},{"tissue":"testis","ntpm":3.2}],"url":"https://www.proteinatlas.org/search/ULBP1"},"hgnc":{"alias_symbol":["RAET1I"],"prev_symbol":[]},"alphafold":{"accession":"Q9BZM6","domains":[{"cath_id":"3.30.500.10","chopping":"32-206","consensus_level":"high","plddt":89.2414,"start":32,"end":206}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9BZM6","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9BZM6-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9BZM6-F1-predicted_aligned_error_v6.png","plddt_mean":80.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ULBP1","jax_strain_url":"https://www.jax.org/strain/search?query=ULBP1"},"sequence":{"accession":"Q9BZM6","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9BZM6.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9BZM6/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9BZM6"}},"corpus_meta":[{"pmid":"21764762","id":"PMC_21764762","title":"Human NK cells are alerted to induction of p53 in cancer cells by upregulation of the NKG2D ligands ULBP1 and ULBP2.","date":"2011","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/21764762","citation_count":181,"is_preprint":false},{"pmid":"12847260","id":"PMC_12847260","title":"Effects of human cytomegalovirus infection on ligands for the activating NKG2D receptor of NK cells: up-regulation of UL16-binding protein (ULBP)1 and ULBP2 is counteracted by the viral UL16 protein.","date":"2003","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/12847260","citation_count":131,"is_preprint":false},{"pmid":"11465099","id":"PMC_11465099","title":"ULBP1, 2, 3: novel MHC class I-related molecules that bind to human cytomegalovirus glycoprotein UL16, activate NK cells.","date":"2001","source":"European journal of immunology","url":"https://pubmed.ncbi.nlm.nih.gov/11465099","citation_count":123,"is_preprint":false},{"pmid":"20101024","id":"PMC_20101024","title":"The MHC class Ib protein ULBP1 is a nonredundant determinant of leukemia/lymphoma susceptibility to gammadelta T-cell cytotoxicity.","date":"2010","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/20101024","citation_count":109,"is_preprint":false},{"pmid":"19414815","id":"PMC_19414815","title":"Proteasome regulation of ULBP1 transcription.","date":"2009","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/19414815","citation_count":62,"is_preprint":false},{"pmid":"16901903","id":"PMC_16901903","title":"Transcriptional regulation of ULBP1, a human ligand of the NKG2D receptor.","date":"2006","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/16901903","citation_count":58,"is_preprint":false},{"pmid":"24677544","id":"PMC_24677544","title":"c-Myc regulates expression of NKG2D ligands ULBP1/2/3 in AML and modulates their susceptibility to NK-mediated lysis.","date":"2014","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/24677544","citation_count":45,"is_preprint":false},{"pmid":"26565589","id":"PMC_26565589","title":"A forward genetic screen reveals novel independent regulators of ULBP1, an activating ligand for natural killer cells.","date":"2015","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/26565589","citation_count":40,"is_preprint":false},{"pmid":"32077634","id":"PMC_32077634","title":"Epithelial-mesenchymal transition may be involved in the immune evasion of circulating gastric tumor cells via downregulation of ULBP1.","date":"2020","source":"Cancer medicine","url":"https://pubmed.ncbi.nlm.nih.gov/32077634","citation_count":34,"is_preprint":false},{"pmid":"26992229","id":"PMC_26992229","title":"Downregulation of the stress-induced ligand ULBP1 following SV40 infection confers viral evasion from NK cell cytotoxicity.","date":"2016","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/26992229","citation_count":24,"is_preprint":false},{"pmid":"34568062","id":"PMC_34568062","title":"Tumor Mutation Burden-Associated LINC00638/miR-4732-3p/ULBP1 Axis Promotes Immune Escape via PD-L1 in Hepatocellular Carcinoma.","date":"2021","source":"Frontiers in oncology","url":"https://pubmed.ncbi.nlm.nih.gov/34568062","citation_count":23,"is_preprint":false},{"pmid":"21406206","id":"PMC_21406206","title":"Post-transcriptional regulation of ULBP1 ligand for the activating immunoreceptor NKG2D involves 3' untranslated region.","date":"2011","source":"Human immunology","url":"https://pubmed.ncbi.nlm.nih.gov/21406206","citation_count":21,"is_preprint":false},{"pmid":"16342232","id":"PMC_16342232","title":"Expression of the NKG2D ligand UL16 binding protein-1 (ULBP-1) on dendritic cells.","date":"2006","source":"European journal of immunology","url":"https://pubmed.ncbi.nlm.nih.gov/16342232","citation_count":21,"is_preprint":false},{"pmid":"26732147","id":"PMC_26732147","title":"A short half-life of ULBP1 at the cell surface due to internalization and proteosomal degradation.","date":"2016","source":"Immunology and cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/26732147","citation_count":18,"is_preprint":false},{"pmid":"32656081","id":"PMC_32656081","title":"ULBP1 Is Elevated in Human Hepatocellular Carcinoma and Predicts Outcome.","date":"2020","source":"Frontiers in oncology","url":"https://pubmed.ncbi.nlm.nih.gov/32656081","citation_count":15,"is_preprint":false},{"pmid":"25218028","id":"PMC_25218028","title":"COX-2- and endoplasmic reticulum stress-independent induction of ULBP-1 and enhancement of sensitivity to NK cell-mediated cytotoxicity by celecoxib in colon cancer cells.","date":"2014","source":"Experimental cell research","url":"https://pubmed.ncbi.nlm.nih.gov/25218028","citation_count":15,"is_preprint":false},{"pmid":"33909909","id":"PMC_33909909","title":"Tanshinone IIA enhances susceptibility of non-small cell lung cancer cells to NK cell-mediated lysis by up-regulating ULBP1 and DR5.","date":"2021","source":"Journal of leukocyte biology","url":"https://pubmed.ncbi.nlm.nih.gov/33909909","citation_count":15,"is_preprint":false},{"pmid":"33014157","id":"PMC_33014157","title":"Celecoxib upregulates ULBP-1 expression in lung cancer cells via the JNK/PI3K signaling pathway and increases susceptibility to natural killer cell cytotoxicity.","date":"2020","source":"Oncology letters","url":"https://pubmed.ncbi.nlm.nih.gov/33014157","citation_count":11,"is_preprint":false},{"pmid":"29511613","id":"PMC_29511613","title":"ULBP1 is induced by hepatitis C virus infection and is the target of the NK cell-mediated innate immune response in human hepatocytes.","date":"2018","source":"FEBS open 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immunology","url":"https://pubmed.ncbi.nlm.nih.gov/38953028","citation_count":3,"is_preprint":false},{"pmid":"33122138","id":"PMC_33122138","title":"Production of a novel bispecific protein ULBP1×CD19-scFv targeting the NKG2D receptor and CD19 to promote the activation of NK cells.","date":"2020","source":"Protein expression and purification","url":"https://pubmed.ncbi.nlm.nih.gov/33122138","citation_count":1,"is_preprint":false},{"pmid":"37773572","id":"PMC_37773572","title":"Dynamics of Soluble Forms of the Immune Checkpoint Components PD-1/PD-L1/B7-H3, CD314/ULBP1, and HLA-G in Peripheral Blood of Melanoma Patients Receiving Blockers of Programmed Cell Death Protein PD-1.","date":"2023","source":"Bulletin of experimental biology and medicine","url":"https://pubmed.ncbi.nlm.nih.gov/37773572","citation_count":0,"is_preprint":false},{"pmid":"19500498","id":"PMC_19500498","title":"[The construction of reporter plasmid of ULBP1 and preliminary studying on the influence of NS3/4A on transcription of ULBP1].","date":"2009","source":"Xi bao yu fen zi mian yi xue za zhi = Chinese journal of cellular and molecular immunology","url":"https://pubmed.ncbi.nlm.nih.gov/19500498","citation_count":0,"is_preprint":false},{"pmid":"21575723","id":"PMC_21575723","title":"Expression, purification and crystallization of the human UL16-binding protein ULBP1.","date":"2011","source":"Protein expression and purification","url":"https://pubmed.ncbi.nlm.nih.gov/21575723","citation_count":0,"is_preprint":false},{"pmid":"41297348","id":"PMC_41297348","title":"Cyclosporin A indirectly suppresses NK cells activity in renal microvascular inflammation by inducing ubiquitination-dependent degradation of ULBP1.","date":"2025","source":"International immunopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/41297348","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.09.30.615768","title":"SIRT4 enhances the cytotoxicity of NK cells toward hepatic stellate cells and reverses liver fibrosis via AMPKα/P-p53/NKG2DL pathway","date":"2024-10-02","source":"bioRxiv","url":"https://doi.org/10.1101/2024.09.30.615768","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.08.07.606975","title":"Research on the Mechanism of Lphn1 Knockout in Inhibiting Colorectal Cancer","date":"2024-08-09","source":"bioRxiv","url":"https://doi.org/10.1101/2024.08.07.606975","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":15828,"output_tokens":5158,"usd":0.062427},"stage2":{"model":"claude-opus-4-6","input_tokens":8683,"output_tokens":3134,"usd":0.182647},"total_usd":0.245074,"stage1_batch_id":"msgbatch_01RPbVc9PDH9zQmYK5Hs6srm","stage2_batch_id":"msgbatch_01JVbVLzeKN2yVrsGp3zC8aM","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2001,\n      \"finding\": \"ULBP1, ULBP2, and ULBP3 are novel MHC class I-related molecules that bind human cytomegalovirus glycoprotein UL16 and activate NK cells, inducing cytokine/chemokine production, proliferation, cytotoxic activity, and upregulation of activation-associated surface molecules. Soluble recombinant UL16 protein inhibited ULBP-mediated biological activities, establishing a viral immune evasion mechanism.\",\n      \"method\": \"Binding assays, NK cell functional assays (cytokine production, cytotoxicity, proliferation), competition experiments with soluble UL16\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal functional assays, direct binding demonstrated, replicated across human and mouse NK cells\",\n      \"pmids\": [\"11465099\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"HCMV glycoprotein UL16 retains ULBP1 and ULBP2 in the endoplasmic reticulum of infected cells, preventing their surface expression and thereby limiting NKG2D-dependent NK cell recognition. Infection with a UL16 deletion mutant virus resulted in surface expression of all three ULBPs and a pronounced, entirely NKG2D-dependent increase in NK sensitivity.\",\n      \"method\": \"Viral infection with wild-type vs. UL16-deletion mutant HCMV, flow cytometry for surface expression, NK cell cytotoxicity assays, immunofluorescence/subcellular localization\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic deletion of UL16 with direct surface localization and functional NK readout, multiple orthogonal methods\",\n      \"pmids\": [\"12847260\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"ULBP1 transcription is driven by binding of Sp1 and Sp3 to a CRE(1) site in the ULBP1 minimal promoter, with Sp3 being the essential activator (>500-fold upregulation upon Sp3 overexpression in SL2 cells). AP-2alpha represses ULBP1 expression by interfering with Sp1/Sp3 binding to the ULBP1 promoter.\",\n      \"method\": \"Promoter reporter assays, site-directed mutagenesis of the CRE(1) site, Sp1/Sp3/AP-2alpha overexpression, EMSA, transcription factor binding studies in SL2 (Drosophila) cells and HeLa cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mutagenesis of promoter element combined with overexpression and reporter assays, multiple cell systems\",\n      \"pmids\": [\"16901903\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"ULBP1 is expressed on mature dendritic cells both in situ in lymph node T cell areas and in vitro after artificial maturation, suggesting a role for NKG2D-ULBP1 in initiation or reactivation of T cell responses.\",\n      \"method\": \"Flow cytometry, in situ detection in sentinel lymph nodes, in vitro DC maturation assays\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — direct localization by flow cytometry and in situ staining, but functional link is inferential\",\n      \"pmids\": [\"16342232\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Proteasome inhibition (by bortezomib and other proteasome inhibitors) dramatically and specifically upregulates ULBP1 mRNA and cell surface protein by acting at a site within the 522-bp ULBP1 promoter, through a mechanism independent of ATM/ATR DNA damage signaling.\",\n      \"method\": \"Proteasome inhibitor treatment, ULBP1 mRNA/surface protein measurement by RT-PCR and flow cytometry, promoter reporter assays, ATM/ATR inhibitor experiments, pharmacological and radiation treatments\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods including promoter reporter assays and pathway inhibition; multiple cell lines and inhibitors tested\",\n      \"pmids\": [\"19414815\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"HCV protease NS3/4A inhibits ULBP1 transcription, as demonstrated by reduced luciferase activity from a ULBP1 promoter reporter construct co-transfected with NS3/4A expression plasmid.\",\n      \"method\": \"Luciferase reporter assay with ULBP1 promoter construct, NS3/4A expression vector co-transfection\",\n      \"journal\": \"Xi bao yu fen zi mian yi xue za zhi\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single reporter assay, single lab, no corroborating in vivo or protein-level data\",\n      \"pmids\": [\"19500498\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"ULBP1 expression levels are a nonredundant determinant of lymphoma susceptibility to gammadelta T cell-mediated cytolysis; NKG2D blockade significantly inhibits lymphoma killing, and specific ULBP1 loss-of-function reduces gammadelta T cell cytotoxicity against lymphoma cells.\",\n      \"method\": \"NKG2D blocking antibodies, ULBP1-specific siRNA knockdown, cytotoxicity assays with primary gammadelta T cells, flow cytometry\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — specific loss-of-function (siRNA) plus receptor blockade with defined cytotoxicity readout, nonredundancy established\",\n      \"pmids\": [\"20101024\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Wild-type p53, but not mutant p53, strongly upregulates ULBP1 and ULBP2 mRNA and cell surface expression via intronic p53-responsive elements in these genes, enhancing NKG2D-dependent NK cell degranulation and IFN-γ production.\",\n      \"method\": \"p53 induction in human tumor cells, RT-PCR and flow cytometry for ULBP1/2 expression, identification of intronic p53-responsive elements, NK cell degranulation and IFN-γ assays, NKG2D blocking, p53-reactivating compound RITA treatment\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — identification of p53 response elements in ULBP1 locus, multiple orthogonal methods, functional NK readout; highly cited\",\n      \"pmids\": [\"21764762\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The 3' UTR of ULBP1 mRNA mediates post-transcriptional repression; AU-rich elements (ARE) within the 3' UTR have an mRNA-stabilizing effect when mutated, and specific microRNAs (miR-140-5p, miR-409-3p, miR-433-3p, miR-650) expressed in HeLa and Jurkat cells may contribute to ULBP1 regulation.\",\n      \"method\": \"Luciferase reporter assays with full-length and truncated ULBP1 3' UTR constructs, ARE mutagenesis, microRNA overexpression, Drosha partial silencing\",\n      \"journal\": \"Human immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — reporter assays and mutagenesis, but microRNA role not definitively established; single lab\",\n      \"pmids\": [\"21406206\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"c-Myc directly binds the ULBP1 and ULBP3 gene loci and regulates their expression; cytarabine-resistant AML cells exhibit c-Myc induction driving ULBP1/2/3 upregulation and increased susceptibility to NK-mediated lysis, reversed by c-Myc inhibition.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP) assay for c-Myc binding to ULBP1/3 loci, c-Myc inhibition, flow cytometry for NKG2D ligand expression, NK cell lysis assays with primary AML blasts\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — ChIP demonstrating direct c-Myc binding to ULBP1 locus, combined with functional inhibition and NK cytotoxicity assays\",\n      \"pmids\": [\"24677544\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"A forward genetic screen identified ATF4 as a transcription factor that drives ULBP1 gene expression in cancer cell lines, and RNA-binding protein RBM4 supports ULBP1 expression by suppressing a novel alternatively spliced isoform of ULBP1 mRNA, revealing that independent pathways work at multiple stages of ULBP1 biogenesis.\",\n      \"method\": \"Forward genetic screen in tumor-derived human cell line, identification and validation of ATF4 and RBM4 as regulators, alternative splicing analysis\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — forward genetic screen with experimental validation at transcriptional and post-transcriptional levels; multiple mechanistic layers\",\n      \"pmids\": [\"26565589\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"ULBP1 has a shorter half-life at the cell surface than other ULBP molecules due to rapid proteasomal degradation following internalization, not due to shedding or increased internalization rate; proteasome inhibition blocks this post-internalization degradation.\",\n      \"method\": \"Surface stability assays, proteasome inhibitors, shedding assays, internalization assays, pulse-chase experiments\",\n      \"journal\": \"Immunology and cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple mechanistic assays distinguishing internalization from degradation, but single lab\",\n      \"pmids\": [\"26732147\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"SV40 infection downregulates ULBP1 surface expression, allowing viral evasion from NK cell cytotoxicity mediated through NKG2D.\",\n      \"method\": \"SV40 infection of target cells, flow cytometry for ULBP1 surface expression, NK cell cytotoxicity assays\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — direct surface expression measurement combined with NK cytotoxicity assay, but mechanism of downregulation not fully characterized\",\n      \"pmids\": [\"26992229\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Hepatitis C virus infection induces cell surface expression of ULBP1 in human hepatocytes, and NK cells (NK-92 line) recognize HCV-infected cells via NKG2D-ULBP1 interaction, triggering cytotoxicity and IFN-γ expression that reduces HCV RNA replication.\",\n      \"method\": \"HCV infection of PH5CH8 and RSc cells, flow cytometry for ULBP1, NK-92 co-culture cytotoxicity and IFN-γ assays, HCV RNA quantification\",\n      \"journal\": \"FEBS open bio\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct infection model with ULBP1 induction, functional NK cytotoxicity and antiviral outcome measured\",\n      \"pmids\": [\"29511613\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Celecoxib induces ULBP-1 expression in colon cancer cells via COX-2-independent and ER stress-independent pathways, increasing susceptibility to NK cell-mediated cytotoxicity in both COX-2 negative and positive cell lines.\",\n      \"method\": \"Celecoxib treatment with/without COX-2 inhibition or ER stress induction (thapsigargin), flow cytometry for ULBP-1, DELFIA NK cytotoxicity assay, soft agar colony forming assay\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods to rule out COX-2 and ER stress pathways; functional NK assay\",\n      \"pmids\": [\"25218028\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Celecoxib upregulates ULBP-1 expression in lung cancer cells via JNK and PI3K signaling pathways (both inhibited by respective pathway inhibitors), and this ULBP-1 induction increases susceptibility to NK cell-mediated cytotoxicity.\",\n      \"method\": \"Celecoxib treatment with JNK/PI3K inhibitors, PCR and immunoblotting for ULBP-1, flow cytometry, NK cell cytotoxicity assay, fluorescence microscopy\",\n      \"journal\": \"Oncology letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pathway inhibitors combined with receptor blocking and functional NK assay; single lab\",\n      \"pmids\": [\"33014157\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Tanshinone IIA increases ULBP1 expression in NSCLC cells via ATF4 (downstream of p-PERK), as ATF4 knockdown completely reverses ULBP1 upregulation; this ULBP1 induction mediates enhanced NK cell cytotoxicity.\",\n      \"method\": \"TIIA treatment, ATF4/CHOP siRNA knockdown, immunoblotting for p-PERK/ATF4/CHOP, flow cytometry for ULBP1, NK cell cytotoxicity assay, in vivo syngeneic and xenograft mouse models with NK cell depletion\",\n      \"journal\": \"Journal of leukocyte biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — specific siRNA knockdown of ATF4 with ULBP1 readout, in vivo validation, multiple cell lines\",\n      \"pmids\": [\"33909909\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"HHV-6B glycoprotein U20 binds directly to ULBP1 with sub-micromolar affinity, masking it from NKG2D recognition at the cell surface without reducing ULBP1 protein levels, thereby blocking NK cell activation.\",\n      \"method\": \"Recombinant protein binding assays, U20 transduction into target cells, NKG2D binding competition assay, NK cell activation assays, small-angle X-ray scattering (SAXS) for structural modeling of U20-ULBP1 complex\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct binding measured with quantitative affinity, structural modeling, functional NK assay, multiple approaches in single study\",\n      \"pmids\": [\"38953028\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Cyclosporin A (CsA) induces ubiquitination-dependent proteasomal degradation of endothelial ULBP1, reducing NKG2D ligand availability and thereby weakening NK cell PI3K/AKT signaling and effector function in renal microvascular inflammation.\",\n      \"method\": \"CsA treatment of endothelial cells, co-culture with NK cells, ubiquitination assays, proteasome inhibition, PI3K/AKT signaling measurement, NK cell activation/cytotoxicity assays\",\n      \"journal\": \"International immunopharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ubiquitination assay combined with NK signaling and functional readout; single lab, relatively recent\",\n      \"pmids\": [\"41297348\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"SIRT4 activates AMPKα to promote p53 phosphorylation and nuclear translocation, which induces transcription of ULBP1 (and ULBP2), thereby enhancing NK cell cytotoxicity against activated hepatic stellate cells.\",\n      \"method\": \"SIRT4 overexpression/knockdown, AMPKα activation assays, p53 phosphorylation and nuclear translocation assays, ULBP1/2 transcription measurement, NK cell cytotoxicity assays, AAV-mediated SIRT4 delivery in mouse LF models\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mechanistic pathway established with multiple assays, but preprint not yet peer-reviewed\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Recombinant ULBP1 extracellular domain was successfully expressed in E. coli, refolded, and crystallized, yielding initial X-ray diffraction data to 4.6 Å, establishing conditions for structural characterization of the protein.\",\n      \"method\": \"Recombinant protein expression in E. coli, refolding from inclusion bodies, site-directed mutagenesis of unpaired cysteines, size exclusion and ion exchange chromatography, X-ray crystallography\",\n      \"journal\": \"Protein expression and purification\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 1 method (crystallography) but only preliminary diffraction reported, no resolved structure with functional validation\",\n      \"pmids\": [\"21575723\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ULBP1 is a GPI-anchored MHC class I-related stress ligand whose surface expression is controlled at multiple levels: transcriptionally by Sp3 (via a CRE1 promoter element), p53 (via intronic response elements), c-Myc, ATF4, and proteasome activity, and repressed by AP-2alpha; post-transcriptionally by its 3' UTR (ARE elements and microRNAs) and the RNA-binding protein RBM4; and post-translationally by rapid ubiquitin-proteasomal degradation after internalization and by cyclosporin A-induced ubiquitination. At the cell surface, ULBP1 engages the activating NK/T cell receptor NKG2D to trigger cytotoxicity and cytokine production, while pathogens evade this response through direct ULBP1 sequestration by viral proteins (HCMV UL16 retains ULBP1 in the ER; HHV-6B U20 binds ULBP1 at the surface to block NKG2D engagement) or transcriptional suppression (HCV NS3/4A, SV40 infection).\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"ULBP1 is a GPI-anchored MHC class I-related cell-surface glycoprotein that serves as a stress-induced ligand for the activating receptor NKG2D on NK cells and γδ T cells, triggering cytotoxicity, degranulation, and IFN-γ production [PMID:11465099, PMID:20101024, PMID:21764762]. Its surface expression is controlled at multiple levels: transcriptionally by Sp3 (via a CRE1 promoter element), p53 (via intronic response elements), c-Myc (direct binding to the ULBP1 locus), and ATF4; post-transcriptionally by AU-rich elements and microRNAs in its 3′ UTR and by the RNA-binding protein RBM4, which suppresses an alternatively spliced isoform [PMID:16901903, PMID:21764762, PMID:24677544, PMID:26565589, PMID:21406206]. ULBP1 is distinguished from other NKG2D ligands by its rapid post-internalization proteasomal degradation, which limits its surface half-life and can be pharmacologically reversed by proteasome inhibitors [PMID:26732147, PMID:19414815]. Viruses exploit ULBP1 regulation to evade immune surveillance: HCMV UL16 retains ULBP1 in the ER, and HHV-6B U20 masks surface ULBP1 from NKG2D engagement [PMID:12847260, PMID:38953028].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Establishing ULBP1 as an NKG2D ligand that activates NK cells resolved how UL16-binding proteins translate stress signals into innate immune recognition.\",\n      \"evidence\": \"Binding assays, NK cytotoxicity/cytokine/proliferation assays, soluble UL16 competition experiments\",\n      \"pmids\": [\"11465099\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"NKG2D-independent roles of ULBP1 not addressed\", \"structural basis of ULBP1–NKG2D interaction not determined\", \"transcriptional regulation unknown\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Demonstrating that HCMV UL16 retains ULBP1 in the ER established the first defined mechanism by which a pathogen evades NKG2D-mediated immunity by preventing ligand surface display.\",\n      \"evidence\": \"WT vs. UL16-deletion mutant HCMV infection, flow cytometry, immunofluorescence, NK cytotoxicity assays\",\n      \"pmids\": [\"12847260\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether UL16 directly binds ULBP1 in cis in the ER membrane not resolved at atomic level\", \"mechanism of ER retention (coat-protein signals, chaperone involvement) undefined\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Identification of the CRE1 promoter element bound by Sp3 (activator) and AP-2α (repressor) defined the basal transcriptional logic governing ULBP1 expression.\",\n      \"evidence\": \"Promoter reporter assays, CRE1 mutagenesis, EMSA, Sp1/Sp3/AP-2α overexpression in Drosophila SL2 and HeLa cells\",\n      \"pmids\": [\"16901903\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Chromatin context and epigenetic regulation not explored\", \"how stress signals converge on Sp3/AP-2α balance unknown\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Proteasome inhibition was shown to specifically upregulate ULBP1 transcription through its proximal promoter independently of DNA-damage signaling, separating proteasome-dependent control from ATM/ATR pathways.\",\n      \"evidence\": \"Bortezomib treatment, RT-PCR/flow cytometry, promoter reporter, ATM/ATR inhibitors across multiple cell lines\",\n      \"pmids\": [\"19414815\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the proteasome-sensitive transcription factor acting at the ULBP1 promoter not determined\", \"in vivo relevance of proteasome-dependent transcriptional regulation not tested\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Discovery that wild-type p53 drives ULBP1 transcription via intronic response elements linked the tumor suppressor pathway to NKG2D-dependent immunosurveillance, while 3′ UTR AU-rich elements and microRNAs added a post-transcriptional regulatory layer.\",\n      \"evidence\": \"p53 induction, intronic response element mapping, NK degranulation/IFN-γ assays, NKG2D blocking (p53 arm); 3′ UTR reporter constructs, ARE mutagenesis, microRNA overexpression (post-transcriptional arm)\",\n      \"pmids\": [\"21764762\", \"21406206\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contributions of p53-dependent transcription vs. microRNA repression in physiological settings not quantified\", \"microRNA effects not validated by individual antagomir rescue at endogenous ULBP1 protein level\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"ChIP evidence that c-Myc directly binds the ULBP1 locus and drives its expression in AML cells revealed an oncogene-dependent route to NKG2D ligand upregulation that can sensitize drug-resistant leukemia to NK killing.\",\n      \"evidence\": \"ChIP for c-Myc at ULBP1/3 loci, c-Myc inhibition, flow cytometry, NK lysis of primary AML blasts\",\n      \"pmids\": [\"24677544\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether c-Myc acts through the same CRE1 or distinct promoter/enhancer elements not resolved\", \"cooperation or antagonism between c-Myc and p53 at the ULBP1 locus not addressed\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"A forward genetic screen identified ATF4 as a transcriptional activator and RBM4 as a post-transcriptional regulator of ULBP1 (suppressing an aberrant splice isoform), revealing that independent pathways converge at multiple biogenesis stages.\",\n      \"evidence\": \"Forward genetic screen in tumor cells, ATF4 and RBM4 validation, alternative splicing analysis\",\n      \"pmids\": [\"26565589\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure and function of the alternatively spliced ULBP1 isoform not characterized\", \"whether ATF4-driven ULBP1 induction requires integrated stress response activation in vivo unknown\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"ULBP1 was shown to have an unusually short surface half-life due to rapid ubiquitin-proteasomal degradation after internalization, distinguishing it from other ULBPs and explaining why proteasome inhibitors preferentially boost ULBP1 surface levels.\",\n      \"evidence\": \"Surface stability assays, proteasome inhibition, shedding/internalization rate measurements, pulse-chase\",\n      \"pmids\": [\"26732147\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"E3 ligase responsible for ULBP1 ubiquitination not identified\", \"sorting signals directing ULBP1 to proteasomal rather than lysosomal degradation unknown\", \"single-lab finding\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Celecoxib-induced ULBP1 upregulation via JNK/PI3K pathways (COX-2- and ER-stress-independent) and HCV-induced ULBP1 surface expression on hepatocytes broadened the range of stimuli and cell types activating NKG2D-mediated immunity through ULBP1.\",\n      \"evidence\": \"Celecoxib ± pathway inhibitors, flow cytometry, NK cytotoxicity (colon/lung cancer); HCV infection, ULBP1 surface detection, NK-92 co-culture, HCV RNA quantification (hepatocytes)\",\n      \"pmids\": [\"25218028\", \"29511613\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct transcription factor(s) mediating JNK/PI3K-dependent ULBP1 induction not identified\", \"contradiction between NS3/4A-mediated ULBP1 suppression and HCV-induced ULBP1 upregulation not reconciled\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"HHV-6B glycoprotein U20 was shown to directly bind ULBP1 at the cell surface with sub-micromolar affinity, blocking NKG2D engagement without reducing ULBP1 levels — a viral masking strategy distinct from HCMV's ER retention mechanism.\",\n      \"evidence\": \"Recombinant protein binding, U20 transduction, NKG2D competition, NK activation assays, SAXS structural modeling\",\n      \"pmids\": [\"38953028\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"High-resolution crystal/cryo-EM structure of U20–ULBP1 complex not yet available\", \"whether U20 also masks other NKG2D ligands not fully resolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Cyclosporin A was found to induce ubiquitination-dependent proteasomal degradation of endothelial ULBP1, reducing NKG2D-mediated NK cell PI3K/AKT signaling — linking immunosuppressive drug action to ULBP1 post-translational turnover.\",\n      \"evidence\": \"CsA treatment of endothelial cells, ubiquitination assays, proteasome inhibition rescue, NK co-culture signaling and cytotoxicity assays\",\n      \"pmids\": [\"41297348\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"E3 ligase mediating CsA-induced ULBP1 ubiquitination not identified\", \"whether calcineurin inhibition is the upstream trigger unknown\", \"single-lab finding\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The E3 ubiquitin ligase(s) targeting ULBP1 for post-internalization degradation remain unidentified, and no high-resolution structure of ULBP1 alone or in complex with NKG2D/viral evasins has been determined, limiting structure-guided therapeutic design.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"E3 ligase identity unknown\", \"high-resolution ULBP1 structure lacking despite preliminary crystallization\", \"relative in vivo contributions of transcriptional vs. post-translational regulation not quantified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [0, 6, 7, 17]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1, 3, 6, 7, 11, 17]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 6, 7, 13, 17]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [1, 12, 17]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"KLRK1\",\n      \"UL16\",\n      \"U20\",\n      \"SP3\",\n      \"TP53\",\n      \"MYC\",\n      \"ATF4\",\n      \"RBM4\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}