{"gene":"HECTD2","run_date":"2026-06-10T01:55:22","timeline":{"discoveries":[{"year":2015,"finding":"HECTD2 functions as an E3 ubiquitin ligase that ubiquitinates PIAS1, targeting it for proteasomal degradation, thereby increasing inflammation. GSK3β phosphorylation of PIAS1 creates a phosphodegron required for HECTD2 targeting. A naturally occurring HECTD2(A19P) polymorphism mislocalizes HECTD2, preventing its nuclear interaction with PIAS1 and thus preventing PIAS1 degradation and reducing inflammation.","method":"Biochemical ubiquitination assay, co-immunoprecipitation, genetic polymorphism functional analysis, small-molecule inhibitor (BC-1382) targeting HECTD2 in LPS- and P. aeruginosa-induced lung inflammation models","journal":"Science translational medicine","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal methods (ubiquitination assay, co-IP, mutagenesis via A19P variant, in vivo pharmacological inhibition) in a single rigorous study establishing a defined E3 ligase–substrate relationship with mechanistic follow-up","pmids":["26157031"],"is_preprint":false},{"year":2022,"finding":"HECTD2 promotes proteasomal degradation of EHMT2 (euchromatic histone-lysine N-methyltransferase 2) in colorectal cancer cells. Propionate upregulates HECTD2, which then targets EHMT2 for degradation, reducing H3K9me2 levels on the TNFAIP1 promoter and activating TNFAIP1-induced apoptosis.","method":"Western blot for protein degradation, HECTD2 overexpression/knockdown experiments, co-immunoprecipitation, chromatin immunoprecipitation (ChIP) for H3K9me2, 3D spheroid culture models","journal":"The ISME journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP and ChIP supporting substrate identification, single lab with multiple orthogonal methods","pmids":["34972816"],"is_preprint":false},{"year":2024,"finding":"HECTD2 promotes proteasomal degradation of EHMT2 in renal cell carcinoma cells (confirmed by immunoprecipitation and western blot), leading to upregulation of TNFAIP1, which activates the p38/JNK signaling pathway to promote an inflammatory response.","method":"Immunoprecipitation, western blot, ChIP (validating TNFAIP1 as direct EHMT2 target), qRT-PCR, ELISA for cytokines, p38/JNK inhibitor rescue experiments","journal":"In vivo (Athens, Greece)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, ChIP, and pharmacological rescue with pathway inhibitors; single lab, multiple orthogonal methods","pmids":["38688591"],"is_preprint":false},{"year":2025,"finding":"HECTD2 functions as an E3 ubiquitin ligase for KEAP1, promoting KEAP1 proteasomal degradation, which in turn activates the NRF2 antioxidative response pathway and confers lenvatinib resistance in hepatocellular carcinoma. Histone H3K18 lactylation drives transcriptional upregulation of HECTD2.","method":"Unbiased proteomic screening, in vitro and in vivo overexpression/knockdown experiments, patient-derived organoids and xenograft models, western blot for KEAP1 degradation","journal":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — substrate identification (KEAP1) supported by protein degradation assays and in vivo models; single lab with multiple complementary approaches","pmids":["39976163"],"is_preprint":false},{"year":2013,"finding":"HECTD2 is a direct target of miR-221 in prostate cancer cells. Downregulation of HECTD2 by miR-221 significantly affects androgen-induced and androgen receptor (AR)-mediated transcription, contributing to castration-resistant prostate cancer (CRPC) phenotype development.","method":"Systematic biochemical and bioinformatics analyses identifying miR-221 targets; stable miR-221 overexpression in LNCaP; HECTD2 knockdown with measurement of AR-mediated transcription","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — target identification via bioinformatics confirmed by functional knockdown with defined transcriptional readout; single lab, two complementary approaches","pmids":["23770851"],"is_preprint":false},{"year":2009,"finding":"HECTD2 (Hectd2 in mice) is identified as an E3 ubiquitin ligase acting as a quantitative trait gene for prion disease incubation time. A genotype-associated differential expression of Hectd2 mRNA was observed in mouse brains, and transcript was significantly upregulated in mice at the terminal stage of prion disease, implicating proteasome-directed protein degradation in neurodegeneration.","method":"Heterogeneous stock mouse quantitative trait locus (QTL) mapping, mRNA expression analysis in mouse brain and human lymphocytes, human haplotype association study (vCJD and kuru)","journal":"PLoS genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis via QTL mapping combined with expression analysis; replicated in human disease association; substrate unknown, limiting mechanistic precision","pmids":["19214206"],"is_preprint":false},{"year":2022,"finding":"HECTD2 co-immunoprecipitates with ubiquitinated LPCAT1 in colorectal cancer cells, and HECTD2 overexpression promotes LPCAT1 ubiquitination and degradation, thereby repressing CRC cell proliferation.","method":"Co-immunoprecipitation detecting HECTD2–LPCAT1 interaction with ubiquitinated LPCAT1, HECTD2 overexpression with LPCAT1 rescue experiment measuring cell proliferation","journal":"Molekuliarnaia biologiia","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single co-IP and overexpression rescue; single lab, single method per claim","pmids":["35964314"],"is_preprint":false},{"year":2021,"finding":"HECTD2 cell-autonomously drives melanoma cell proliferation by accelerating the cell cycle, and regulates cancer cell production of immune mediators including through the COX2 pathway, initiating immune suppressive pathways.","method":"Loss-of-function and gain-of-function experiments in human and murine melanoma cell lines; murine melanoma model with model tumour antigen; cell cycle analysis","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined cellular phenotypes (cell cycle acceleration, COX2 pathway activation) via KO/KD with multiple readouts; single lab","pmids":["34145398"],"is_preprint":false},{"year":2025,"finding":"Rare loss-of-function variants in HECTD2 confer risk of bipolar disorder. HECTD2 protein interacts with GSK3β, a lithium target, placing HECTD2 in the GSK3β signaling axis relevant to mood stabilization.","method":"Whole-genome sequencing variant burden analysis (gene-based LOF aggregation) in Icelandic and UK Biobank cohorts; confirmed with Bipolar Exome dataset; protein–protein interaction noted for HECTD2 and GSK3β","journal":"Nature genetics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — GSK3β interaction is stated but not directly demonstrated with biochemical experiments in this paper; genetic association provides pathway placement but no direct mechanistic experiment on HECTD2 protein function","pmids":["40133559"],"is_preprint":false}],"current_model":"HECTD2 is a HECT-domain E3 ubiquitin ligase that promotes proteasomal degradation of multiple substrates—including PIAS1 (requiring prior GSK3β phosphorylation), EHMT2, KEAP1, and LPCAT1—thereby modulating inflammatory signaling (JAK-STAT/NF-κB via PIAS1, p38/JNK via TNFAIP1), antioxidative stress responses (NRF2 via KEAP1), and cell proliferation; a naturally occurring A19P polymorphism mislocalizes HECTD2 and prevents PIAS1 degradation, and HECTD2 itself is regulated transcriptionally by miR-221 and by histone lactylation."},"narrative":{"mechanistic_narrative":"HECTD2 is a HECT-domain E3 ubiquitin ligase that drives proteasomal degradation of multiple substrates to control inflammatory signaling, antioxidant responses, and cell proliferation [PMID:26157031, PMID:39976163]. Its founding substrate is PIAS1: HECTD2 ubiquitinates PIAS1 to target it for degradation and thereby promote inflammation, an event that requires prior GSK3β phosphorylation of PIAS1 to generate a phosphodegron, with a naturally occurring HECTD2(A19P) polymorphism mislocalizing the ligase, preventing its nuclear interaction with PIAS1, and dampening inflammation [PMID:26157031]. Beyond PIAS1, HECTD2 degrades the histone methyltransferase EHMT2, reducing repressive H3K9me2 at the TNFAIP1 promoter to derepress TNFAIP1 and engage p38/JNK signaling and apoptotic programs [PMID:34972816, PMID:38688591], and degrades KEAP1 to activate the NRF2 antioxidative stress pathway [PMID:39976163]. HECTD2 expression is itself tightly regulated—repressed as a direct target of miR-221 [PMID:23770851] and induced by histone H3K18 lactylation [PMID:39976163]—and it influences proliferative and cell-cycle phenotypes in cancer cells [PMID:34145398]. Genetic studies link HECTD2 to prion disease incubation time as a quantitative trait gene [PMID:19214206] and identify rare loss-of-function variants as risk factors for bipolar disorder, placing it in the GSK3β signaling axis [PMID:40133559].","teleology":[{"year":2009,"claim":"Established HECTD2 as a disease-relevant E3 ubiquitin ligase by linking its expression to a neurodegenerative phenotype, raising the question of which substrates it acts on.","evidence":"Heterogeneous stock mouse QTL mapping with brain mRNA expression analysis and human haplotype association in prion disease","pmids":["19214206"],"confidence":"Medium","gaps":["No substrate identified","Mechanism linking degradation activity to prion incubation time unresolved"]},{"year":2013,"claim":"Identified an upstream regulator of HECTD2, showing it is transcriptionally repressed by miR-221 with consequences for androgen receptor signaling.","evidence":"miR-221 target identification by bioinformatics plus stable overexpression in LNCaP and HECTD2 knockdown with AR-mediated transcription readout","pmids":["23770851"],"confidence":"Medium","gaps":["Direct ubiquitination substrate in this context not defined","Mechanism linking HECTD2 to AR transcription unresolved"]},{"year":2015,"claim":"Defined the first molecular substrate of HECTD2, establishing it as a PIAS1-degrading ligase that requires a GSK3β-generated phosphodegron and is disabled by a localization-altering polymorphism.","evidence":"Biochemical ubiquitination assay, co-IP, A19P variant functional analysis, and small-molecule inhibition in LPS- and P. aeruginosa-induced lung inflammation models","pmids":["26157031"],"confidence":"High","gaps":["Direct demonstration of HECTD2 HECT catalytic residues not detailed","Generality of phosphodegron requirement across substrates unknown"]},{"year":2021,"claim":"Connected HECTD2 to cell-autonomous proliferation and immune modulation, broadening its role beyond a single substrate axis.","evidence":"Loss- and gain-of-function in human and murine melanoma cell lines with cell cycle analysis and a murine melanoma model","pmids":["34145398"],"confidence":"Medium","gaps":["Substrate mediating cell-cycle acceleration not identified","Direct mechanism of COX2 pathway regulation unresolved"]},{"year":2022,"claim":"Identified EHMT2 as a HECTD2 substrate and linked its degradation to epigenetic derepression of TNFAIP1, providing a chromatin-to-apoptosis mechanism.","evidence":"Western blot degradation assays, reciprocal co-IP, and ChIP for H3K9me2 in colorectal cancer spheroid models with propionate stimulation","pmids":["34972816"],"confidence":"Medium","gaps":["Direct ubiquitination of EHMT2 by purified HECTD2 not reconstituted","Generalizability beyond CRC at the time uncertain"]},{"year":2022,"claim":"Added LPCAT1 as a candidate substrate whose degradation represses proliferation, extending the substrate repertoire.","evidence":"Co-IP detecting ubiquitinated LPCAT1 and HECTD2 overexpression with LPCAT1 rescue measuring proliferation in CRC cells","pmids":["35964314"],"confidence":"Low","gaps":["Single co-IP and overexpression rescue without reciprocal or in vitro validation","Direct ubiquitination not demonstrated biochemically"]},{"year":2024,"claim":"Confirmed the HECTD2–EHMT2–TNFAIP1 axis in a second cancer context and connected it to p38/JNK inflammatory signaling.","evidence":"Immunoprecipitation, western blot, ChIP, qRT-PCR, ELISA, and p38/JNK inhibitor rescue in renal cell carcinoma","pmids":["38688591"],"confidence":"Medium","gaps":["Direct enzymatic ubiquitination of EHMT2 still not reconstituted","Relative contribution of inflammation versus apoptosis outcomes unclear"]},{"year":2025,"claim":"Identified KEAP1 as a HECTD2 substrate linking the ligase to NRF2-driven antioxidant defense and drug resistance, and defined H3K18 lactylation as an inducer of HECTD2 expression.","evidence":"Unbiased proteomic screening, in vitro/in vivo knockdown-overexpression, patient-derived organoids and xenografts in hepatocellular carcinoma","pmids":["39976163"],"confidence":"Medium","gaps":["Direct ubiquitination of KEAP1 by purified HECTD2 not reconstituted","Interplay with other HECTD2 substrates in the same cell not addressed"]},{"year":2025,"claim":"Genetically implicated HECTD2 loss-of-function in bipolar disorder and placed it within the GSK3β signaling axis relevant to lithium response.","evidence":"Whole-genome sequencing LOF burden analysis in Icelandic and UK Biobank cohorts with a noted HECTD2–GSK3β interaction","pmids":["40133559"],"confidence":"Low","gaps":["GSK3β interaction stated but not biochemically demonstrated in this study","No direct mechanistic experiment on HECTD2 protein function in neurons"]},{"year":null,"claim":"Whether HECTD2 selects its diverse substrates (PIAS1, EHMT2, KEAP1, LPCAT1) through a shared phosphodegron logic and how its subcellular localization governs substrate access remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No unified substrate-recognition mechanism defined","Structural basis of HECT catalysis for these substrates not determined","Determinants of nuclear versus cytoplasmic targeting beyond A19P unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[0,3]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,3]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,3]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,2]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[3]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[1,2]}],"complexes":[],"partners":["PIAS1","EHMT2","KEAP1","LPCAT1","GSK3B"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q5U5R9","full_name":"Probable E3 ubiquitin-protein ligase HECTD2","aliases":["HECT domain-containing protein 2","HECT-type E3 ubiquitin transferase HECTD2"],"length_aa":776,"mass_kda":88.1,"function":"E3 ubiquitin-protein ligase which accepts ubiquitin from an E2 ubiquitin-conjugating enzyme in the form of a thioester and then directly transfers the ubiquitin to targeted substrates (Microbial infection) Catalyzes ubiquitination of Botulinum neurotoxin A light chain (LC) of C.botulinum neurotoxin type A (BoNT/A)","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q5U5R9/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/HECTD2","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/HECTD2","total_profiled":1310},"omim":[{"mim_id":"620876","title":"HECT DOMAIN E3 UBIQUITIN PROTEIN LIGASE 2; HECTD2","url":"https://www.omim.org/entry/620876"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/HECTD2"},"hgnc":{"alias_symbol":["FLJ37306"],"prev_symbol":[]},"alphafold":{"accession":"Q5U5R9","domains":[{"cath_id":"-","chopping":"133-341","consensus_level":"medium","plddt":93.7419,"start":133,"end":341},{"cath_id":"3.30.2410.10","chopping":"670-770","consensus_level":"high","plddt":91.3247,"start":670,"end":770}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q5U5R9","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q5U5R9-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q5U5R9-F1-predicted_aligned_error_v6.png","plddt_mean":80.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=HECTD2","jax_strain_url":"https://www.jax.org/strain/search?query=HECTD2"},"sequence":{"accession":"Q5U5R9","fasta_url":"https://rest.uniprot.org/uniprotkb/Q5U5R9.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q5U5R9/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q5U5R9"}},"corpus_meta":[{"pmid":"23770851","id":"PMC_23770851","title":"MiR-221 promotes the development of androgen independence in prostate cancer cells via downregulation of HECTD2 and RAB1A.","date":"2013","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/23770851","citation_count":123,"is_preprint":false},{"pmid":"34972816","id":"PMC_34972816","title":"Human gut-microbiome-derived propionate coordinates proteasomal degradation via HECTD2 upregulation to target EHMT2 in colorectal cancer.","date":"2022","source":"The ISME journal","url":"https://pubmed.ncbi.nlm.nih.gov/34972816","citation_count":98,"is_preprint":false},{"pmid":"19214206","id":"PMC_19214206","title":"HECTD2 is associated with susceptibility to mouse and human prion disease.","date":"2009","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/19214206","citation_count":60,"is_preprint":false},{"pmid":"26157031","id":"PMC_26157031","title":"The proinflammatory role of HECTD2 in innate immunity and experimental lung injury.","date":"2015","source":"Science translational medicine","url":"https://pubmed.ncbi.nlm.nih.gov/26157031","citation_count":45,"is_preprint":false},{"pmid":"39976163","id":"PMC_39976163","title":"Lactylation-Driven HECTD2 Limits the Response of Hepatocellular Carcinoma to Lenvatinib.","date":"2025","source":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","url":"https://pubmed.ncbi.nlm.nih.gov/39976163","citation_count":27,"is_preprint":false},{"pmid":"19754925","id":"PMC_19754925","title":"HECTD2, a candidate susceptibility gene for Alzheimer's disease on 10q.","date":"2009","source":"BMC medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/19754925","citation_count":12,"is_preprint":false},{"pmid":"35004677","id":"PMC_35004677","title":"HIF-1α Induces HECTD2 Up-Regulation and Aggravates the Malignant Progression of Renal Cell Cancer via Repressing miR-320a.","date":"2021","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/35004677","citation_count":10,"is_preprint":false},{"pmid":"34145398","id":"PMC_34145398","title":"E3 ubiquitin ligase HECTD2 mediates melanoma progression and immune evasion.","date":"2021","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/34145398","citation_count":9,"is_preprint":false},{"pmid":"40133559","id":"PMC_40133559","title":"Rare loss-of-function variants in HECTD2 and AKAP11 confer risk of bipolar disorder.","date":"2025","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/40133559","citation_count":7,"is_preprint":false},{"pmid":"35964314","id":"PMC_35964314","title":"[HECTD2 Represses Cell Proliferation in Colorectal Cancer through Driving Ubiquitination and Degradation of LPCAT1].","date":"2022","source":"Molekuliarnaia biologiia","url":"https://pubmed.ncbi.nlm.nih.gov/35964314","citation_count":2,"is_preprint":false},{"pmid":"38688591","id":"PMC_38688591","title":"HECTD2/TNFAIP1 Axis Regulating the p38/JNK Pathway to Promote an Inflammatory Response in Renal Cell Carcinoma Cells.","date":"2024","source":"In vivo (Athens, Greece)","url":"https://pubmed.ncbi.nlm.nih.gov/38688591","citation_count":2,"is_preprint":false},{"pmid":"39343853","id":"PMC_39343853","title":"HECTD2 as a target for veratric acid in the regulation of ferroptosis in renal cell carcinoma.","date":"2024","source":"Amino acids","url":"https://pubmed.ncbi.nlm.nih.gov/39343853","citation_count":2,"is_preprint":false},{"pmid":"39548546","id":"PMC_39548546","title":"Expression of HECTD2 predicts peritoneal metastasis of gastric cancer and reconstructs immune microenvironment.","date":"2024","source":"Cancer cell international","url":"https://pubmed.ncbi.nlm.nih.gov/39548546","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8574,"output_tokens":2463,"usd":0.031334,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9681,"output_tokens":3225,"usd":0.064515,"stage2_stop_reason":"end_turn"},"total_usd":0.095849,"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\": 2015,\n      \"finding\": \"HECTD2 functions as an E3 ubiquitin ligase that ubiquitinates PIAS1, targeting it for proteasomal degradation, thereby increasing inflammation. GSK3β phosphorylation of PIAS1 creates a phosphodegron required for HECTD2 targeting. A naturally occurring HECTD2(A19P) polymorphism mislocalizes HECTD2, preventing its nuclear interaction with PIAS1 and thus preventing PIAS1 degradation and reducing inflammation.\",\n      \"method\": \"Biochemical ubiquitination assay, co-immunoprecipitation, genetic polymorphism functional analysis, small-molecule inhibitor (BC-1382) targeting HECTD2 in LPS- and P. aeruginosa-induced lung inflammation models\",\n      \"journal\": \"Science translational medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal methods (ubiquitination assay, co-IP, mutagenesis via A19P variant, in vivo pharmacological inhibition) in a single rigorous study establishing a defined E3 ligase–substrate relationship with mechanistic follow-up\",\n      \"pmids\": [\"26157031\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"HECTD2 promotes proteasomal degradation of EHMT2 (euchromatic histone-lysine N-methyltransferase 2) in colorectal cancer cells. Propionate upregulates HECTD2, which then targets EHMT2 for degradation, reducing H3K9me2 levels on the TNFAIP1 promoter and activating TNFAIP1-induced apoptosis.\",\n      \"method\": \"Western blot for protein degradation, HECTD2 overexpression/knockdown experiments, co-immunoprecipitation, chromatin immunoprecipitation (ChIP) for H3K9me2, 3D spheroid culture models\",\n      \"journal\": \"The ISME journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP and ChIP supporting substrate identification, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"34972816\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"HECTD2 promotes proteasomal degradation of EHMT2 in renal cell carcinoma cells (confirmed by immunoprecipitation and western blot), leading to upregulation of TNFAIP1, which activates the p38/JNK signaling pathway to promote an inflammatory response.\",\n      \"method\": \"Immunoprecipitation, western blot, ChIP (validating TNFAIP1 as direct EHMT2 target), qRT-PCR, ELISA for cytokines, p38/JNK inhibitor rescue experiments\",\n      \"journal\": \"In vivo (Athens, Greece)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, ChIP, and pharmacological rescue with pathway inhibitors; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"38688591\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"HECTD2 functions as an E3 ubiquitin ligase for KEAP1, promoting KEAP1 proteasomal degradation, which in turn activates the NRF2 antioxidative response pathway and confers lenvatinib resistance in hepatocellular carcinoma. Histone H3K18 lactylation drives transcriptional upregulation of HECTD2.\",\n      \"method\": \"Unbiased proteomic screening, in vitro and in vivo overexpression/knockdown experiments, patient-derived organoids and xenograft models, western blot for KEAP1 degradation\",\n      \"journal\": \"Advanced science (Weinheim, Baden-Wurttemberg, Germany)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — substrate identification (KEAP1) supported by protein degradation assays and in vivo models; single lab with multiple complementary approaches\",\n      \"pmids\": [\"39976163\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"HECTD2 is a direct target of miR-221 in prostate cancer cells. Downregulation of HECTD2 by miR-221 significantly affects androgen-induced and androgen receptor (AR)-mediated transcription, contributing to castration-resistant prostate cancer (CRPC) phenotype development.\",\n      \"method\": \"Systematic biochemical and bioinformatics analyses identifying miR-221 targets; stable miR-221 overexpression in LNCaP; HECTD2 knockdown with measurement of AR-mediated transcription\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — target identification via bioinformatics confirmed by functional knockdown with defined transcriptional readout; single lab, two complementary approaches\",\n      \"pmids\": [\"23770851\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"HECTD2 (Hectd2 in mice) is identified as an E3 ubiquitin ligase acting as a quantitative trait gene for prion disease incubation time. A genotype-associated differential expression of Hectd2 mRNA was observed in mouse brains, and transcript was significantly upregulated in mice at the terminal stage of prion disease, implicating proteasome-directed protein degradation in neurodegeneration.\",\n      \"method\": \"Heterogeneous stock mouse quantitative trait locus (QTL) mapping, mRNA expression analysis in mouse brain and human lymphocytes, human haplotype association study (vCJD and kuru)\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis via QTL mapping combined with expression analysis; replicated in human disease association; substrate unknown, limiting mechanistic precision\",\n      \"pmids\": [\"19214206\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"HECTD2 co-immunoprecipitates with ubiquitinated LPCAT1 in colorectal cancer cells, and HECTD2 overexpression promotes LPCAT1 ubiquitination and degradation, thereby repressing CRC cell proliferation.\",\n      \"method\": \"Co-immunoprecipitation detecting HECTD2–LPCAT1 interaction with ubiquitinated LPCAT1, HECTD2 overexpression with LPCAT1 rescue experiment measuring cell proliferation\",\n      \"journal\": \"Molekuliarnaia biologiia\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single co-IP and overexpression rescue; single lab, single method per claim\",\n      \"pmids\": [\"35964314\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"HECTD2 cell-autonomously drives melanoma cell proliferation by accelerating the cell cycle, and regulates cancer cell production of immune mediators including through the COX2 pathway, initiating immune suppressive pathways.\",\n      \"method\": \"Loss-of-function and gain-of-function experiments in human and murine melanoma cell lines; murine melanoma model with model tumour antigen; cell cycle analysis\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined cellular phenotypes (cell cycle acceleration, COX2 pathway activation) via KO/KD with multiple readouts; single lab\",\n      \"pmids\": [\"34145398\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Rare loss-of-function variants in HECTD2 confer risk of bipolar disorder. HECTD2 protein interacts with GSK3β, a lithium target, placing HECTD2 in the GSK3β signaling axis relevant to mood stabilization.\",\n      \"method\": \"Whole-genome sequencing variant burden analysis (gene-based LOF aggregation) in Icelandic and UK Biobank cohorts; confirmed with Bipolar Exome dataset; protein–protein interaction noted for HECTD2 and GSK3β\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — GSK3β interaction is stated but not directly demonstrated with biochemical experiments in this paper; genetic association provides pathway placement but no direct mechanistic experiment on HECTD2 protein function\",\n      \"pmids\": [\"40133559\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"HECTD2 is a HECT-domain E3 ubiquitin ligase that promotes proteasomal degradation of multiple substrates—including PIAS1 (requiring prior GSK3β phosphorylation), EHMT2, KEAP1, and LPCAT1—thereby modulating inflammatory signaling (JAK-STAT/NF-κB via PIAS1, p38/JNK via TNFAIP1), antioxidative stress responses (NRF2 via KEAP1), and cell proliferation; a naturally occurring A19P polymorphism mislocalizes HECTD2 and prevents PIAS1 degradation, and HECTD2 itself is regulated transcriptionally by miR-221 and by histone lactylation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"HECTD2 is a HECT-domain E3 ubiquitin ligase that drives proteasomal degradation of multiple substrates to control inflammatory signaling, antioxidant responses, and cell proliferation [#0, #3]. Its founding substrate is PIAS1: HECTD2 ubiquitinates PIAS1 to target it for degradation and thereby promote inflammation, an event that requires prior GSK3\\u03b2 phosphorylation of PIAS1 to generate a phosphodegron, with a naturally occurring HECTD2(A19P) polymorphism mislocalizing the ligase, preventing its nuclear interaction with PIAS1, and dampening inflammation [#0]. Beyond PIAS1, HECTD2 degrades the histone methyltransferase EHMT2, reducing repressive H3K9me2 at the TNFAIP1 promoter to derepress TNFAIP1 and engage p38/JNK signaling and apoptotic programs [#1, #2], and degrades KEAP1 to activate the NRF2 antioxidative stress pathway [#3]. HECTD2 expression is itself tightly regulated\\u2014repressed as a direct target of miR-221 [#4] and induced by histone H3K18 lactylation [#3]\\u2014and it influences proliferative and cell-cycle phenotypes in cancer cells [#7]. Genetic studies link HECTD2 to prion disease incubation time as a quantitative trait gene [#5] and identify rare loss-of-function variants as risk factors for bipolar disorder, placing it in the GSK3\\u03b2 signaling axis [#8].\",\n  \"teleology\": [\n    {\n      \"year\": 2009,\n      \"claim\": \"Established HECTD2 as a disease-relevant E3 ubiquitin ligase by linking its expression to a neurodegenerative phenotype, raising the question of which substrates it acts on.\",\n      \"evidence\": \"Heterogeneous stock mouse QTL mapping with brain mRNA expression analysis and human haplotype association in prion disease\",\n      \"pmids\": [\"19214206\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No substrate identified\", \"Mechanism linking degradation activity to prion incubation time unresolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identified an upstream regulator of HECTD2, showing it is transcriptionally repressed by miR-221 with consequences for androgen receptor signaling.\",\n      \"evidence\": \"miR-221 target identification by bioinformatics plus stable overexpression in LNCaP and HECTD2 knockdown with AR-mediated transcription readout\",\n      \"pmids\": [\"23770851\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct ubiquitination substrate in this context not defined\", \"Mechanism linking HECTD2 to AR transcription unresolved\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Defined the first molecular substrate of HECTD2, establishing it as a PIAS1-degrading ligase that requires a GSK3\\u03b2-generated phosphodegron and is disabled by a localization-altering polymorphism.\",\n      \"evidence\": \"Biochemical ubiquitination assay, co-IP, A19P variant functional analysis, and small-molecule inhibition in LPS- and P. aeruginosa-induced lung inflammation models\",\n      \"pmids\": [\"26157031\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct demonstration of HECTD2 HECT catalytic residues not detailed\", \"Generality of phosphodegron requirement across substrates unknown\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Connected HECTD2 to cell-autonomous proliferation and immune modulation, broadening its role beyond a single substrate axis.\",\n      \"evidence\": \"Loss- and gain-of-function in human and murine melanoma cell lines with cell cycle analysis and a murine melanoma model\",\n      \"pmids\": [\"34145398\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Substrate mediating cell-cycle acceleration not identified\", \"Direct mechanism of COX2 pathway regulation unresolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified EHMT2 as a HECTD2 substrate and linked its degradation to epigenetic derepression of TNFAIP1, providing a chromatin-to-apoptosis mechanism.\",\n      \"evidence\": \"Western blot degradation assays, reciprocal co-IP, and ChIP for H3K9me2 in colorectal cancer spheroid models with propionate stimulation\",\n      \"pmids\": [\"34972816\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct ubiquitination of EHMT2 by purified HECTD2 not reconstituted\", \"Generalizability beyond CRC at the time uncertain\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Added LPCAT1 as a candidate substrate whose degradation represses proliferation, extending the substrate repertoire.\",\n      \"evidence\": \"Co-IP detecting ubiquitinated LPCAT1 and HECTD2 overexpression with LPCAT1 rescue measuring proliferation in CRC cells\",\n      \"pmids\": [\"35964314\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single co-IP and overexpression rescue without reciprocal or in vitro validation\", \"Direct ubiquitination not demonstrated biochemically\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Confirmed the HECTD2\\u2013EHMT2\\u2013TNFAIP1 axis in a second cancer context and connected it to p38/JNK inflammatory signaling.\",\n      \"evidence\": \"Immunoprecipitation, western blot, ChIP, qRT-PCR, ELISA, and p38/JNK inhibitor rescue in renal cell carcinoma\",\n      \"pmids\": [\"38688591\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct enzymatic ubiquitination of EHMT2 still not reconstituted\", \"Relative contribution of inflammation versus apoptosis outcomes unclear\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified KEAP1 as a HECTD2 substrate linking the ligase to NRF2-driven antioxidant defense and drug resistance, and defined H3K18 lactylation as an inducer of HECTD2 expression.\",\n      \"evidence\": \"Unbiased proteomic screening, in vitro/in vivo knockdown-overexpression, patient-derived organoids and xenografts in hepatocellular carcinoma\",\n      \"pmids\": [\"39976163\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct ubiquitination of KEAP1 by purified HECTD2 not reconstituted\", \"Interplay with other HECTD2 substrates in the same cell not addressed\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Genetically implicated HECTD2 loss-of-function in bipolar disorder and placed it within the GSK3\\u03b2 signaling axis relevant to lithium response.\",\n      \"evidence\": \"Whole-genome sequencing LOF burden analysis in Icelandic and UK Biobank cohorts with a noted HECTD2\\u2013GSK3\\u03b2 interaction\",\n      \"pmids\": [\"40133559\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"GSK3\\u03b2 interaction stated but not biochemically demonstrated in this study\", \"No direct mechanistic experiment on HECTD2 protein function in neurons\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Whether HECTD2 selects its diverse substrates (PIAS1, EHMT2, KEAP1, LPCAT1) through a shared phosphodegron logic and how its subcellular localization governs substrate access remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No unified substrate-recognition mechanism defined\", \"Structural basis of HECT catalysis for these substrates not determined\", \"Determinants of nuclear versus cytoplasmic targeting beyond A19P unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [0, 3]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 3]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [1, 2]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"PIAS1\", \"EHMT2\", \"KEAP1\", \"LPCAT1\", \"GSK3B\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}