{"gene":"ARRDC4","run_date":"2026-06-09T22:02:44","timeline":{"discoveries":[{"year":2017,"finding":"ARRDC4 interacts with MDA5 via its arrestin-like N domain and recruits the E3 ubiquitin ligase TRIM65 to enhance K63-linked polyubiquitination of MDA5, thereby activating downstream innate signaling and proinflammatory cytokine transcription during EV71 infection.","method":"Co-immunoprecipitation, domain mapping (N-domain mutants), ubiquitination assay, overexpression/knockdown in THP-1-derived macrophages","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP and domain-deletion experiments in a single lab; two orthogonal methods (interaction + ubiquitination assay) but not independently replicated","pmids":["28594402"],"is_preprint":false},{"year":2021,"finding":"METTL14-mediated m6A methylation of ARRDC4 mRNA promotes its degradation via the reader protein YTHDF2, reducing ARRDC4 levels and suppressing ZEB1-driven CRC metastasis; knockdown of METTL14 stabilizes ARRDC4 mRNA in a YTHDF2-dependent manner.","method":"m6A methylation profiling, siRNA knockdown, mRNA stability assay, Co-IP for YTHDF2-ARRDC4 mRNA interaction","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (m6A-seq, RNA stability, YTHDF2 knockdown) in a single lab; not independently replicated","pmids":["34916487"],"is_preprint":false},{"year":2021,"finding":"Arrdc4 is required for extracellular vesicle (EV) biogenesis by epididymal epithelial cells; Arrdc4 knockout mice show reduced EV production, and supplementation of knockout sperm with wild-type EVs rescues premature acrosome reaction and restores zona pellucida binding.","method":"Arrdc4 knockout mouse model, EV quantification from epididymal epithelial cells, sperm functional assays (motility, acrosome reaction, zona pellucida binding, embryo production), rescue by EV supplementation","journal":"Journal of extracellular vesicles","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo KO model with multiple orthogonal functional readouts and direct rescue experiment demonstrating mechanistic sufficiency","pmids":["34188787"],"is_preprint":false},{"year":2022,"finding":"ARRDC4 binds GLUT1 through specific residues in its C-terminal arrestin-fold domain, induces GLUT1 endocytosis, and blocks cellular glucose uptake in cardiomyocytes, leading to glucose deprivation-induced ER stress and cardiomyocyte death during ischemia; Arrdc4 knockout mice show increased myocardial glucose uptake, glycogen storage, and protection against myocardial infarction.","method":"Co-IP, Arrdc4 KO mouse model, scanning mutagenesis, deep-learning AI structure-function analysis, glucose uptake assay, ER stress assays, myocardial infarction model","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro binding with mutagenesis, in vivo KO model, multiple orthogonal functional readouts (glucose uptake, glycogen, ER stress, infarct size) in a single rigorous study","pmids":["35950500"],"is_preprint":false},{"year":2022,"finding":"Lysine 270 (K270) of Arrdc4 is ubiquitinated with K29-linked polyubiquitin chains by the E3 ligase Nedd4-2; this modification is critical for Arrdc4-dependent EV biogenesis and for trafficking of the divalent metal transporter DMT1 into EVs. The K270R mutation reduces EV release, decreases DMT1 packaging into EVs, lowers DMT1 activity, and increases intracellular DMT1 degradation.","method":"Mass spectrometry identification of ubiquitinated lysines, site-directed mutagenesis (K270R and other lysine mutants), EV quantification, DMT1 activity assay, Nedd4-2 co-expression experiments","journal":"Journal of extracellular vesicles","confidence":"High","confidence_rationale":"Tier 1 / Moderate — MS-identified site confirmed by mutagenesis, multiple functional readouts (EV number, cargo trafficking, protein stability), single lab but multiple orthogonal methods","pmids":["35106941"],"is_preprint":false},{"year":2024,"finding":"High glucose promotes nuclear translocation of MondoA, which transcriptionally upregulates Arrdc4, leading to increased lysosomal GLUT1 trafficking and blocked glucose transport in cardiomyocytes, forming a feedback mechanism; Arrdc4 deletion augments tissue glucose transport and mitochondrial respiration, protecting against hyperglycemia-induced cardiac and skeletal muscle damage.","method":"Cellular models (cardiomyocytes, human muscular cells from T2D patients), Arrdc4 KO mice under diabetes models, cardiac-specific AAV overexpression, stress hemodynamics, treadmill exhaustion test, GLUT1 trafficking assays","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo KO and overexpression models, human cell validation, multiple orthogonal readouts (glucose transport, mitochondrial respiration, hemodynamics, exercise capacity), confirmatory of prior GLUT1 mechanism","pmids":["38946541"],"is_preprint":false},{"year":2025,"finding":"ARRDC4 senses influenza A virus infection by directly interacting with the viral PA protein; upregulated ARRDC4 binds PFKM at His298 to increase its enzymatic activity, promoting production of fructose-1,6-bisphosphate (FBP), which inhibits K48-linked ubiquitination-mediated degradation of HSP90β and enhances its interactions with IKKβ and IKKε to potentiate NF-κB- and IRF7-mediated antiviral innate immunity.","method":"Co-IP (ARRDC4–PA interaction, ARRDC4–PFKM interaction at His298), enzymatic activity assays for PFKM, ubiquitination assay for HSP90β, Co-IP for HSP90β–IKKβ/IKKε, FBP supplementation in vitro and in vivo","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple Co-IP and biochemical assays with in vivo FBP supplementation, but single lab and abstracts compress methodological detail","pmids":["40875808"],"is_preprint":false},{"year":2026,"finding":"In colorectal cancer-initiating cells, ARRDC4 translocates to the mitochondrial matrix where it reprograms lipid metabolism; upregulated ARRDC4 promotes exosome secretion and its binding partner WWP1 is packaged into and released via ARRDC4-dependent exosomes, after which secreted WWP1 is taken up by surrounding CRC cells to inhibit EMT and migration.","method":"Co-immunoprecipitation with exosomes (ARRDC4–WWP1), mitochondrial fractionation, exosome quantification, cellular uptake assays, EMT marker analysis","journal":"Cancer cell international","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and subcellular fractionation with functional readouts (exosome secretion, EMT inhibition), single lab, not independently replicated","pmids":["42163297"],"is_preprint":false},{"year":2025,"finding":"Depletion of Arrdc4 in breast cancer cells suppresses glucose uptake and reduces gasdermin E levels, thereby preventing pyroptosis and increasing circulating tumor cell aggressiveness; conversely, Arrdc4 overexpression enhances gasdermin E-triggered pyroptosis and hinders tumor progression in immunocompetent (but not immunocompromised) mice.","method":"In vivo CTC selection for intravasation ability, Arrdc4 knockdown and overexpression in xenografts and syngeneic models, glucose uptake assay, gasdermin E expression analysis, immunocompetent vs. immunocompromised mouse comparison","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 / Weak — preprint, single lab, abstract-level description of mechanism, gasdermin E link inferred without full mechanistic reconstitution","pmids":["bio_10.1101_2025.01.26.634904"],"is_preprint":true}],"current_model":"ARRDC4 is an α-arrestin scaffold protein that regulates glucose transporter (GLUT1) endocytosis via its C-terminal arrestin-fold domain, controls extracellular vesicle biogenesis through K29-polyubiquitination at K270 by Nedd4-2, modulates innate immune signaling by recruiting TRIM65 to K63-ubiquitinate MDA5 or by activating the PFKM–FBP–HSP90β–IKK axis during viral infection, and translocates to mitochondria in cancer-initiating cells to reprogram lipid metabolism and promote WWP1-laden exosome secretion."},"narrative":{"mechanistic_narrative":"ARRDC4 is an α-arrestin scaffold protein that couples nutrient transporter trafficking, extracellular vesicle biogenesis, and innate immune signaling [PMID:35950500, PMID:34188787, PMID:28594402]. Through specific residues in its C-terminal arrestin-fold domain, ARRDC4 binds the glucose transporter GLUT1 and drives its endocytosis and lysosomal trafficking, thereby restricting cellular glucose uptake; in cardiomyocytes this promotes glucose-deprivation ER stress and cell death during ischemia, and its loss augments myocardial glucose uptake, glycogen storage, and mitochondrial respiration to protect against infarction and hyperglycemic injury [PMID:35950500, PMID:38946541]. This glucose-restricting axis is wired into a feedback loop in which high glucose drives MondoA-dependent transcriptional upregulation of ARRDC4 [PMID:38946541]. ARRDC4 is also required for extracellular vesicle biogenesis: K29-linked polyubiquitination at Lys270 by the E3 ligase Nedd4-2 enables EV release and the packaging of cargo such as the metal transporter DMT1, and in epididymal epithelium ARRDC4-dependent EVs confer functional competence on sperm [PMID:35106941, PMID:34188787]. In innate immunity, ARRDC4 acts as a scaffold that recruits TRIM65 to K63-ubiquitinate MDA5 and activate proinflammatory signaling during enterovirus infection, and during influenza A infection it senses the viral PA protein and engages PFKM to potentiate an FBP–HSP90β–IKK antiviral axis [PMID:28594402, PMID:40875808]. m6A methylation of ARRDC4 mRNA by METTL14, read by YTHDF2, governs its transcript stability and its tumor-suppressive output in colorectal cancer [PMID:34916487].","teleology":[{"year":2017,"claim":"Established that ARRDC4 functions as a signaling scaffold in innate immunity, linking it for the first time to antiviral cytokine responses rather than only trafficking.","evidence":"Reciprocal Co-IP, N-domain deletion mapping, and ubiquitination assays in THP-1-derived macrophages during EV71 infection","pmids":["28594402"],"confidence":"Medium","gaps":["Not independently replicated","Whether MDA5 engagement is constitutive or infection-induced not resolved","No structural basis for the N-domain/MDA5/TRIM65 ternary assembly"]},{"year":2021,"claim":"Defined how ARRDC4 levels are post-transcriptionally controlled, showing m6A methylation tunes its abundance and downstream tumor-suppressive activity.","evidence":"m6A profiling, siRNA knockdown, mRNA stability assays, and YTHDF2 Co-IP in colorectal cancer","pmids":["34916487"],"confidence":"Medium","gaps":["Direct mechanism by which ARRDC4 protein suppresses ZEB1/metastasis not defined","Single lab"]},{"year":2021,"claim":"Demonstrated ARRDC4 is genetically required for extracellular vesicle biogenesis in vivo and that these EVs deliver physiological function to recipient cells.","evidence":"Arrdc4 knockout mouse, EV quantification from epididymal epithelium, sperm functional assays, and rescue by wild-type EV supplementation","pmids":["34188787"],"confidence":"High","gaps":["Molecular machinery ARRDC4 uses to drive EV formation not resolved","Generalizability beyond epididymal epithelium unknown"]},{"year":2022,"claim":"Mapped the GLUT1-binding determinants in the C-terminal arrestin fold and established ARRDC4 as a driver of GLUT1 endocytosis that controls cardiomyocyte glucose supply and ischemic survival.","evidence":"Co-IP, scanning mutagenesis with AI structure-function analysis, glucose uptake and ER stress assays, and KO mouse myocardial infarction model","pmids":["35950500"],"confidence":"High","gaps":["Whether GLUT1 is ubiquitinated/adapted to endocytic machinery by ARRDC4 not shown","Selectivity for GLUT1 over other transporters not established"]},{"year":2022,"claim":"Identified the post-translational switch for ARRDC4-dependent EV biogenesis, pinning EV release and cargo packaging to Nedd4-2-mediated K29 ubiquitination at Lys270.","evidence":"Mass spectrometry of ubiquitinated lysines, K270R mutagenesis, EV quantification, DMT1 activity assays, and Nedd4-2 co-expression","pmids":["35106941"],"confidence":"High","gaps":["How K29-linked chains mechanistically promote EV budding unknown","Range of cargoes selected by this modification beyond DMT1 not defined"]},{"year":2024,"claim":"Closed a regulatory loop showing glucose itself induces ARRDC4 via MondoA, and extended the GLUT1-trafficking mechanism to whole-body glucose handling and hyperglycemic tissue protection.","evidence":"Cardiomyocyte and T2D patient-derived muscle cells, Arrdc4 KO and cardiac AAV overexpression mice, hemodynamics, treadmill testing, and GLUT1 trafficking assays","pmids":["38946541"],"confidence":"High","gaps":["Direct MondoA binding to the ARRDC4 locus not detailed","Tissue-specific contributions to systemic phenotype not dissected"]},{"year":2025,"claim":"Revealed a metabolic route by which ARRDC4 amplifies antiviral immunity, sensing influenza PA and rewiring PFKM-driven glycolytic flux to stabilize HSP90β and activate IKK-dependent signaling.","evidence":"Co-IP for ARRDC4–PA and ARRDC4–PFKM (His298), PFKM enzymatic assays, HSP90β ubiquitination assays, and in vitro/in vivo FBP supplementation","pmids":["40875808"],"confidence":"Medium","gaps":["Single lab, not independently replicated","Relationship of this axis to the earlier MDA5/TRIM65 mechanism unresolved","Structural basis of PFKM His298 engagement not shown"]},{"year":2026,"claim":"Extended ARRDC4 function to mitochondrial lipid reprogramming and a paracrine exosome circuit, showing it packages and exports WWP1 to restrain EMT in neighboring cancer cells.","evidence":"Exosome Co-IP for ARRDC4–WWP1, mitochondrial fractionation, exosome quantification, uptake assays, and EMT marker analysis in colorectal cancer-initiating cells","pmids":["42163297"],"confidence":"Medium","gaps":["How an arrestin scaffold reaches the mitochondrial matrix unexplained","Mechanism linking mitochondrial localization to exosome cargo selection unknown","Single lab"]},{"year":2025,"claim":"Linked ARRDC4-controlled glucose uptake to gasdermin E-dependent pyroptosis as a determinant of circulating tumor cell aggressiveness.","evidence":"In vivo CTC selection, Arrdc4 knockdown/overexpression in xenograft and syngeneic models, glucose uptake assays, and immunocompetent vs immunocompromised comparison (preprint)","pmids":["bio_10.1101_2025.01.26.634904"],"confidence":"Low","gaps":["Preprint, abstract-level mechanism","Gasdermin E link inferred without reconstitution","Causal chain from glucose uptake to pyroptosis not established"]},{"year":null,"claim":"How ARRDC4's distinct activities — GLUT1 endocytosis, ubiquitin-dependent EV/exosome biogenesis, immune scaffolding, and mitochondrial lipid reprogramming — are coordinated within one protein remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No unifying structural model relating the N-domain and arrestin-fold functions","Determinants of subcellular targeting (plasma membrane vs mitochondria vs EVs) unknown","Tissue/context selection among the multiple mechanisms not defined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,3,4]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[3,6]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[3]},{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[7]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[2,4,7]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,6]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[3,5]}],"complexes":[],"partners":["GLUT1","NEDD4-2","MDA5","TRIM65","PFKM","WWP1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8NCT1","full_name":"Arrestin domain-containing protein 4","aliases":[],"length_aa":418,"mass_kda":45.5,"function":"Functions as an adapter recruiting ubiquitin-protein ligases to their specific substrates (By similarity). Plays a role in endocytosis of activated G protein-coupled receptors (GPCRs) (Probable). Through an ubiquitination-dependent mechanism also plays a role in the incorporation of SLC11A2 into extracellular vesicles (By similarity). May play a role in glucose uptake (PubMed:19605364). Participates in innate immune response by promoting IFIH1/MDA5 activation through interaction with TRIM65 (PubMed:28594402)","subcellular_location":"Early endosome; Cell membrane; Cytoplasmic vesicle","url":"https://www.uniprot.org/uniprotkb/Q8NCT1/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ARRDC4","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/ARRDC4","total_profiled":1310},"omim":[{"mim_id":"619788","title":"ARRESTIN DOMAIN-CONTAINING PROTEIN 4; ARRDC4","url":"https://www.omim.org/entry/619788"},{"mim_id":"612464","title":"ARRESTIN DOMAIN-CONTAINING PROTEIN 3; ARRDC3","url":"https://www.omim.org/entry/612464"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Plasma membrane","reliability":"Supported"},{"location":"Vesicles","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"brain","ntpm":75.7}],"url":"https://www.proteinatlas.org/search/ARRDC4"},"hgnc":{"alias_symbol":["FLJ36045"],"prev_symbol":[]},"alphafold":{"accession":"Q8NCT1","domains":[{"cath_id":"2.60.40.640","chopping":"16-67_83-159","consensus_level":"high","plddt":90.9674,"start":16,"end":159},{"cath_id":"2.60.40.640","chopping":"170-313","consensus_level":"high","plddt":92.7348,"start":170,"end":313}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NCT1","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NCT1-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NCT1-F1-predicted_aligned_error_v6.png","plddt_mean":79.88},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ARRDC4","jax_strain_url":"https://www.jax.org/strain/search?query=ARRDC4"},"sequence":{"accession":"Q8NCT1","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8NCT1.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8NCT1/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NCT1"}},"corpus_meta":[{"pmid":"28594402","id":"PMC_28594402","title":"ARRDC4 regulates enterovirus 71-induced innate immune response by promoting K63 polyubiquitination of MDA5 through TRIM65.","date":"2017","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/28594402","citation_count":44,"is_preprint":false},{"pmid":"34916487","id":"PMC_34916487","title":"TCF4 and HuR mediated-METTL14 suppresses dissemination of colorectal cancer via N6-methyladenosine-dependent silencing of ARRDC4.","date":"2021","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/34916487","citation_count":30,"is_preprint":false},{"pmid":"34188787","id":"PMC_34188787","title":"Arrdc4-dependent extracellular vesicle biogenesis is required for sperm maturation.","date":"2021","source":"Journal of extracellular vesicles","url":"https://pubmed.ncbi.nlm.nih.gov/34188787","citation_count":25,"is_preprint":false},{"pmid":"35950500","id":"PMC_35950500","title":"Interaction of ARRDC4 With GLUT1 Mediates Metabolic Stress in the Ischemic Heart.","date":"2022","source":"Circulation research","url":"https://pubmed.ncbi.nlm.nih.gov/35950500","citation_count":18,"is_preprint":false},{"pmid":"35106941","id":"PMC_35106941","title":"K-29 linked ubiquitination of Arrdc4 regulates its function in extracellular vesicle biogenesis.","date":"2022","source":"Journal of extracellular vesicles","url":"https://pubmed.ncbi.nlm.nih.gov/35106941","citation_count":15,"is_preprint":false},{"pmid":"36610120","id":"PMC_36610120","title":"Brusatol suppresses the tumor growth and metastasis of colorectal cancer via upregulating ARRDC4 expression through modulating PI3K/YAP1/TAZ Pathway.","date":"2022","source":"Phytomedicine : international journal of phytotherapy and phytopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/36610120","citation_count":14,"is_preprint":false},{"pmid":"34680357","id":"PMC_34680357","title":"ARRDC4 and UBXN1: Novel Target Genes Correlated with Prostate Cancer Gleason Score.","date":"2021","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/34680357","citation_count":5,"is_preprint":false},{"pmid":"40875808","id":"PMC_40875808","title":"ARRDC4-mediated glycolysis enhances innate immunity to influenza A virus through fructose-1,6-bisphosphate.","date":"2025","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/40875808","citation_count":3,"is_preprint":false},{"pmid":"38946541","id":"PMC_38946541","title":"Systemic Deletion of ARRDC4 Improves Cardiac Reserve and Exercise Capacity in Diabetes.","date":"2024","source":"Circulation research","url":"https://pubmed.ncbi.nlm.nih.gov/38946541","citation_count":2,"is_preprint":false},{"pmid":"38528189","id":"PMC_38528189","title":"Identification of HDAC9 and ARRDC4 as potential biomarkers and targets for treatment of type 2 diabetes.","date":"2024","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/38528189","citation_count":2,"is_preprint":false},{"pmid":"18307387","id":"PMC_18307387","title":"An anomalous haplotype distribution of the arrestin domain-containing 4 gene (ARRDC4) haplotypes in Caucasians.","date":"2008","source":"Genetic testing","url":"https://pubmed.ncbi.nlm.nih.gov/18307387","citation_count":2,"is_preprint":false},{"pmid":"42163297","id":"PMC_42163297","title":"Tumor microenvironment-responsive ARRDC4: unveiling the tumor-suppressive pathway in colorectal cancer progression.","date":"2026","source":"Cancer cell international","url":"https://pubmed.ncbi.nlm.nih.gov/42163297","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.01.26.634904","title":"Avoidance of pyroptosis accounts for the relatively high metastatic potential observed in early hybrid EMT states","date":"2025-01-27","source":"bioRxiv","url":"https://doi.org/10.1101/2025.01.26.634904","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9057,"output_tokens":2650,"usd":0.03346,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9943,"output_tokens":3528,"usd":0.068958,"stage2_stop_reason":"end_turn"},"total_usd":0.102418,"stage1_batch_id":"msgbatch_0179Z2pxRYBsXi2xADneafRw","stage2_batch_id":"msgbatch_01LaY9ZaVdgjWArcZo9eqQE5","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2017,\n      \"finding\": \"ARRDC4 interacts with MDA5 via its arrestin-like N domain and recruits the E3 ubiquitin ligase TRIM65 to enhance K63-linked polyubiquitination of MDA5, thereby activating downstream innate signaling and proinflammatory cytokine transcription during EV71 infection.\",\n      \"method\": \"Co-immunoprecipitation, domain mapping (N-domain mutants), ubiquitination assay, overexpression/knockdown in THP-1-derived macrophages\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP and domain-deletion experiments in a single lab; two orthogonal methods (interaction + ubiquitination assay) but not independently replicated\",\n      \"pmids\": [\"28594402\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"METTL14-mediated m6A methylation of ARRDC4 mRNA promotes its degradation via the reader protein YTHDF2, reducing ARRDC4 levels and suppressing ZEB1-driven CRC metastasis; knockdown of METTL14 stabilizes ARRDC4 mRNA in a YTHDF2-dependent manner.\",\n      \"method\": \"m6A methylation profiling, siRNA knockdown, mRNA stability assay, Co-IP for YTHDF2-ARRDC4 mRNA interaction\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (m6A-seq, RNA stability, YTHDF2 knockdown) in a single lab; not independently replicated\",\n      \"pmids\": [\"34916487\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Arrdc4 is required for extracellular vesicle (EV) biogenesis by epididymal epithelial cells; Arrdc4 knockout mice show reduced EV production, and supplementation of knockout sperm with wild-type EVs rescues premature acrosome reaction and restores zona pellucida binding.\",\n      \"method\": \"Arrdc4 knockout mouse model, EV quantification from epididymal epithelial cells, sperm functional assays (motility, acrosome reaction, zona pellucida binding, embryo production), rescue by EV supplementation\",\n      \"journal\": \"Journal of extracellular vesicles\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo KO model with multiple orthogonal functional readouts and direct rescue experiment demonstrating mechanistic sufficiency\",\n      \"pmids\": [\"34188787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ARRDC4 binds GLUT1 through specific residues in its C-terminal arrestin-fold domain, induces GLUT1 endocytosis, and blocks cellular glucose uptake in cardiomyocytes, leading to glucose deprivation-induced ER stress and cardiomyocyte death during ischemia; Arrdc4 knockout mice show increased myocardial glucose uptake, glycogen storage, and protection against myocardial infarction.\",\n      \"method\": \"Co-IP, Arrdc4 KO mouse model, scanning mutagenesis, deep-learning AI structure-function analysis, glucose uptake assay, ER stress assays, myocardial infarction model\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro binding with mutagenesis, in vivo KO model, multiple orthogonal functional readouts (glucose uptake, glycogen, ER stress, infarct size) in a single rigorous study\",\n      \"pmids\": [\"35950500\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Lysine 270 (K270) of Arrdc4 is ubiquitinated with K29-linked polyubiquitin chains by the E3 ligase Nedd4-2; this modification is critical for Arrdc4-dependent EV biogenesis and for trafficking of the divalent metal transporter DMT1 into EVs. The K270R mutation reduces EV release, decreases DMT1 packaging into EVs, lowers DMT1 activity, and increases intracellular DMT1 degradation.\",\n      \"method\": \"Mass spectrometry identification of ubiquitinated lysines, site-directed mutagenesis (K270R and other lysine mutants), EV quantification, DMT1 activity assay, Nedd4-2 co-expression experiments\",\n      \"journal\": \"Journal of extracellular vesicles\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — MS-identified site confirmed by mutagenesis, multiple functional readouts (EV number, cargo trafficking, protein stability), single lab but multiple orthogonal methods\",\n      \"pmids\": [\"35106941\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"High glucose promotes nuclear translocation of MondoA, which transcriptionally upregulates Arrdc4, leading to increased lysosomal GLUT1 trafficking and blocked glucose transport in cardiomyocytes, forming a feedback mechanism; Arrdc4 deletion augments tissue glucose transport and mitochondrial respiration, protecting against hyperglycemia-induced cardiac and skeletal muscle damage.\",\n      \"method\": \"Cellular models (cardiomyocytes, human muscular cells from T2D patients), Arrdc4 KO mice under diabetes models, cardiac-specific AAV overexpression, stress hemodynamics, treadmill exhaustion test, GLUT1 trafficking assays\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo KO and overexpression models, human cell validation, multiple orthogonal readouts (glucose transport, mitochondrial respiration, hemodynamics, exercise capacity), confirmatory of prior GLUT1 mechanism\",\n      \"pmids\": [\"38946541\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ARRDC4 senses influenza A virus infection by directly interacting with the viral PA protein; upregulated ARRDC4 binds PFKM at His298 to increase its enzymatic activity, promoting production of fructose-1,6-bisphosphate (FBP), which inhibits K48-linked ubiquitination-mediated degradation of HSP90β and enhances its interactions with IKKβ and IKKε to potentiate NF-κB- and IRF7-mediated antiviral innate immunity.\",\n      \"method\": \"Co-IP (ARRDC4–PA interaction, ARRDC4–PFKM interaction at His298), enzymatic activity assays for PFKM, ubiquitination assay for HSP90β, Co-IP for HSP90β–IKKβ/IKKε, FBP supplementation in vitro and in vivo\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple Co-IP and biochemical assays with in vivo FBP supplementation, but single lab and abstracts compress methodological detail\",\n      \"pmids\": [\"40875808\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"In colorectal cancer-initiating cells, ARRDC4 translocates to the mitochondrial matrix where it reprograms lipid metabolism; upregulated ARRDC4 promotes exosome secretion and its binding partner WWP1 is packaged into and released via ARRDC4-dependent exosomes, after which secreted WWP1 is taken up by surrounding CRC cells to inhibit EMT and migration.\",\n      \"method\": \"Co-immunoprecipitation with exosomes (ARRDC4–WWP1), mitochondrial fractionation, exosome quantification, cellular uptake assays, EMT marker analysis\",\n      \"journal\": \"Cancer cell international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and subcellular fractionation with functional readouts (exosome secretion, EMT inhibition), single lab, not independently replicated\",\n      \"pmids\": [\"42163297\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Depletion of Arrdc4 in breast cancer cells suppresses glucose uptake and reduces gasdermin E levels, thereby preventing pyroptosis and increasing circulating tumor cell aggressiveness; conversely, Arrdc4 overexpression enhances gasdermin E-triggered pyroptosis and hinders tumor progression in immunocompetent (but not immunocompromised) mice.\",\n      \"method\": \"In vivo CTC selection for intravasation ability, Arrdc4 knockdown and overexpression in xenografts and syngeneic models, glucose uptake assay, gasdermin E expression analysis, immunocompetent vs. immunocompromised mouse comparison\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — preprint, single lab, abstract-level description of mechanism, gasdermin E link inferred without full mechanistic reconstitution\",\n      \"pmids\": [\"bio_10.1101_2025.01.26.634904\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"ARRDC4 is an α-arrestin scaffold protein that regulates glucose transporter (GLUT1) endocytosis via its C-terminal arrestin-fold domain, controls extracellular vesicle biogenesis through K29-polyubiquitination at K270 by Nedd4-2, modulates innate immune signaling by recruiting TRIM65 to K63-ubiquitinate MDA5 or by activating the PFKM–FBP–HSP90β–IKK axis during viral infection, and translocates to mitochondria in cancer-initiating cells to reprogram lipid metabolism and promote WWP1-laden exosome secretion.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ARRDC4 is an α-arrestin scaffold protein that couples nutrient transporter trafficking, extracellular vesicle biogenesis, and innate immune signaling [#3, #2, #0]. Through specific residues in its C-terminal arrestin-fold domain, ARRDC4 binds the glucose transporter GLUT1 and drives its endocytosis and lysosomal trafficking, thereby restricting cellular glucose uptake; in cardiomyocytes this promotes glucose-deprivation ER stress and cell death during ischemia, and its loss augments myocardial glucose uptake, glycogen storage, and mitochondrial respiration to protect against infarction and hyperglycemic injury [#3, #5]. This glucose-restricting axis is wired into a feedback loop in which high glucose drives MondoA-dependent transcriptional upregulation of ARRDC4 [#5]. ARRDC4 is also required for extracellular vesicle biogenesis: K29-linked polyubiquitination at Lys270 by the E3 ligase Nedd4-2 enables EV release and the packaging of cargo such as the metal transporter DMT1, and in epididymal epithelium ARRDC4-dependent EVs confer functional competence on sperm [#4, #2]. In innate immunity, ARRDC4 acts as a scaffold that recruits TRIM65 to K63-ubiquitinate MDA5 and activate proinflammatory signaling during enterovirus infection, and during influenza A infection it senses the viral PA protein and engages PFKM to potentiate an FBP–HSP90β–IKK antiviral axis [#0, #6]. m6A methylation of ARRDC4 mRNA by METTL14, read by YTHDF2, governs its transcript stability and its tumor-suppressive output in colorectal cancer [#1].\",\n  \"teleology\": [\n    {\n      \"year\": 2017,\n      \"claim\": \"Established that ARRDC4 functions as a signaling scaffold in innate immunity, linking it for the first time to antiviral cytokine responses rather than only trafficking.\",\n      \"evidence\": \"Reciprocal Co-IP, N-domain deletion mapping, and ubiquitination assays in THP-1-derived macrophages during EV71 infection\",\n      \"pmids\": [\"28594402\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Not independently replicated\", \"Whether MDA5 engagement is constitutive or infection-induced not resolved\", \"No structural basis for the N-domain/MDA5/TRIM65 ternary assembly\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Defined how ARRDC4 levels are post-transcriptionally controlled, showing m6A methylation tunes its abundance and downstream tumor-suppressive activity.\",\n      \"evidence\": \"m6A profiling, siRNA knockdown, mRNA stability assays, and YTHDF2 Co-IP in colorectal cancer\",\n      \"pmids\": [\"34916487\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct mechanism by which ARRDC4 protein suppresses ZEB1/metastasis not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstrated ARRDC4 is genetically required for extracellular vesicle biogenesis in vivo and that these EVs deliver physiological function to recipient cells.\",\n      \"evidence\": \"Arrdc4 knockout mouse, EV quantification from epididymal epithelium, sperm functional assays, and rescue by wild-type EV supplementation\",\n      \"pmids\": [\"34188787\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular machinery ARRDC4 uses to drive EV formation not resolved\", \"Generalizability beyond epididymal epithelium unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Mapped the GLUT1-binding determinants in the C-terminal arrestin fold and established ARRDC4 as a driver of GLUT1 endocytosis that controls cardiomyocyte glucose supply and ischemic survival.\",\n      \"evidence\": \"Co-IP, scanning mutagenesis with AI structure-function analysis, glucose uptake and ER stress assays, and KO mouse myocardial infarction model\",\n      \"pmids\": [\"35950500\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether GLUT1 is ubiquitinated/adapted to endocytic machinery by ARRDC4 not shown\", \"Selectivity for GLUT1 over other transporters not established\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified the post-translational switch for ARRDC4-dependent EV biogenesis, pinning EV release and cargo packaging to Nedd4-2-mediated K29 ubiquitination at Lys270.\",\n      \"evidence\": \"Mass spectrometry of ubiquitinated lysines, K270R mutagenesis, EV quantification, DMT1 activity assays, and Nedd4-2 co-expression\",\n      \"pmids\": [\"35106941\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How K29-linked chains mechanistically promote EV budding unknown\", \"Range of cargoes selected by this modification beyond DMT1 not defined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Closed a regulatory loop showing glucose itself induces ARRDC4 via MondoA, and extended the GLUT1-trafficking mechanism to whole-body glucose handling and hyperglycemic tissue protection.\",\n      \"evidence\": \"Cardiomyocyte and T2D patient-derived muscle cells, Arrdc4 KO and cardiac AAV overexpression mice, hemodynamics, treadmill testing, and GLUT1 trafficking assays\",\n      \"pmids\": [\"38946541\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct MondoA binding to the ARRDC4 locus not detailed\", \"Tissue-specific contributions to systemic phenotype not dissected\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Revealed a metabolic route by which ARRDC4 amplifies antiviral immunity, sensing influenza PA and rewiring PFKM-driven glycolytic flux to stabilize HSP90β and activate IKK-dependent signaling.\",\n      \"evidence\": \"Co-IP for ARRDC4–PA and ARRDC4–PFKM (His298), PFKM enzymatic assays, HSP90β ubiquitination assays, and in vitro/in vivo FBP supplementation\",\n      \"pmids\": [\"40875808\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab, not independently replicated\", \"Relationship of this axis to the earlier MDA5/TRIM65 mechanism unresolved\", \"Structural basis of PFKM His298 engagement not shown\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Extended ARRDC4 function to mitochondrial lipid reprogramming and a paracrine exosome circuit, showing it packages and exports WWP1 to restrain EMT in neighboring cancer cells.\",\n      \"evidence\": \"Exosome Co-IP for ARRDC4–WWP1, mitochondrial fractionation, exosome quantification, uptake assays, and EMT marker analysis in colorectal cancer-initiating cells\",\n      \"pmids\": [\"42163297\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How an arrestin scaffold reaches the mitochondrial matrix unexplained\", \"Mechanism linking mitochondrial localization to exosome cargo selection unknown\", \"Single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Linked ARRDC4-controlled glucose uptake to gasdermin E-dependent pyroptosis as a determinant of circulating tumor cell aggressiveness.\",\n      \"evidence\": \"In vivo CTC selection, Arrdc4 knockdown/overexpression in xenograft and syngeneic models, glucose uptake assays, and immunocompetent vs immunocompromised comparison (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.01.26.634904\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Preprint, abstract-level mechanism\", \"Gasdermin E link inferred without reconstitution\", \"Causal chain from glucose uptake to pyroptosis not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How ARRDC4's distinct activities — GLUT1 endocytosis, ubiquitin-dependent EV/exosome biogenesis, immune scaffolding, and mitochondrial lipid reprogramming — are coordinated within one protein remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No unifying structural model relating the N-domain and arrestin-fold functions\", \"Determinants of subcellular targeting (plasma membrane vs mitochondria vs EVs) unknown\", \"Tissue/context selection among the multiple mechanisms not defined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 3, 4]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [3, 6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [2, 4, 7]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 6]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [3, 5]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"GLUT1\", \"Nedd4-2\", \"MDA5\", \"TRIM65\", \"PFKM\", \"WWP1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}