{"gene":"AK4","run_date":"2026-06-09T22:02:43","timeline":{"discoveries":[{"year":2025,"finding":"AK4 interacts physically with AMPKα (protein kinase AMP-activated catalytic subunit alpha) and promotes phosphorylation of AMPKα at Thr172, thereby reducing mitochondrial oxidative damage and improving mitochondrial function in vascular smooth muscle cells; AMPKα activation reverses the inhibitory effects of AK4 deficiency on VSMC phenotypic switching, while a phospho-dead AMPKα T172A mutant does not.","method":"Co-immunoprecipitation (AK4-AMPKα interaction), western blot (phospho-AMPKα Thr172), AMPKα activators (metformin/AICAR) rescue assay, wild-type vs. T172A AMPKα mutant overexpression, AK4 knockdown/overexpression in HASMCs","journal":"Atherosclerosis","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal interaction shown, mutagenesis (T172A) performed, and pharmacological rescue, single lab study","pmids":["40506332"],"is_preprint":false},{"year":2025,"finding":"AK4 co-localizes with NNT (nicotinamide nucleotide transhydrogenase) in nasopharyngeal carcinoma cells and upregulates NLRP3 and IL-1β to activate the NLRP3 inflammasome signaling pathway, promoting cell migration, invasion, EMT phenotype, and resistance to taxol-induced apoptosis; AK4 knockdown reverses these effects.","method":"Co-localization assay, stable overexpression and knockdown in NPC cell lines, western blot (NLRP3, IL-1β), apoptosis assay, migration/invasion assays","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — co-localization and loss/gain of function with defined pathway readouts, single lab","pmids":["40593461"],"is_preprint":false},{"year":2021,"finding":"TRIM29 knockdown destabilizes the AK4 mRNA transcript via downregulation of miR-2355-3p; miR-2355-3p normally facilitates recruitment of the RNA helicase DDX3X to the AK4 transcript to stabilize it. Loss of AK4 alters bioenergetics and suppresses proliferation and invasion of pancreatic cancer cells.","method":"Global screening, qRT-PCR, western blot, AK4 mRNA stability assay, miR-2355-3p manipulation, DDX3X recruitment to AK4 transcript","journal":"Molecular therapy. Nucleic acids","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — posttranscriptional mechanism defined with multiple molecular assays, single lab","pmids":["33898107"],"is_preprint":false},{"year":2021,"finding":"STAT3 transcriptionally activates AK4 expression; miR-3666 targets STAT3 and thereby indirectly represses AK4, suppressing ovarian carcinoma cell proliferation and migration.","method":"Luciferase reporter assay (miR-3666 targeting STAT3), western blot (AK4, STAT3), rescue experiments with AK4 overexpression","journal":"Cancer biomarkers : section A of Disease markers","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, indirect transcriptional regulation inferred through luciferase and rescue assays only","pmids":["33361582"],"is_preprint":false},{"year":2025,"finding":"miR-634 targets AK4 (validated by dual luciferase reporter assay) and downregulates AK4 expression; AK4 overexpression activates p-AKT and p-mTOR signaling and inhibits apoptosis in HEI-OC1 cells, while miR-634 mimic or AK4 knockdown promotes apoptosis and increases ROS.","method":"Dual luciferase reporter assay, miR-634 mimic transfection, AK4 overexpression and knockdown, western blot (Caspase-3/7, Bax, Bcl-2, p-AKT, p-mTOR), flow cytometry (apoptosis), ROS measurement","journal":"Hearing research","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — validated direct miRNA-target binding plus downstream AKT/mTOR pathway readout, multiple orthogonal methods, single lab","pmids":["40819488"],"is_preprint":false},{"year":2018,"finding":"miR-199a-3p directly targets AK4 (validated by luciferase reporter assay); AK4 is a positive regulator of multi-drug resistance in osteosarcoma, and forced changes in miR-199a-3p levels drastically alter NF-κB signaling pathway activity.","method":"qRT-PCR, western blot, luciferase reporter assay, drug resistance profiling assay, NF-κB pathway activity measurement","journal":"BMC cancer","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct target validation by luciferase plus functional drug-resistance assay and pathway readout, single lab","pmids":["29866054"],"is_preprint":false},{"year":2018,"finding":"miR-199a-3p directly targets AK4 (validated by luciferase reporter assay) and AK4 promotes radioresistance of esophageal cancer cells; reversal of miR-199a-3p or AK4 levels alters multiple signaling pathway activities.","method":"Luciferase reporter assay, survival fraction experiments, wound-healing, invasion assay, forced expression/inhibition of miR-199a-3p and AK4","journal":"Cancer cell international","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct target validation replicated across osteosarcoma and esophageal cancer studies using luciferase assay","pmids":["30479565"],"is_preprint":false},{"year":2020,"finding":"LINC00662 stabilizes AK4 mRNA through binding to the RNA-binding protein hnRNPC; the LINC00662/hnRNPC/AK4 axis promotes radioresistance of oral squamous cell carcinoma cells, and LINC00662 knockdown reduces AK4 expression and attenuates radioresistance.","method":"RIP (RNA immunoprecipitation) assay confirming hnRNPC binding to LINC00662 and AK4 mRNA, qRT-PCR, western blot, CCK-8, colony formation, flow cytometry, rescue experiments","journal":"Cancer cell international","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — RIP assay defines the molecular mechanism of mRNA stabilization, functional rescue experiments, single lab","pmids":["32549791"],"is_preprint":false},{"year":2025,"finding":"AK4 and RHOC are identified as direct targets of the tumor-suppressive miR-455-3p in adult T cell leukemia (ATL); AK4 promotes oncogenic Myc target pathways and enhances production of sphingomyelin; ATL cells show selective sensitivity to AK4 depletion compared to other T cell malignancies.","method":"miRNA target identification, in vitro and in vivo functional assays (AK4 knockdown/overexpression), transcriptome and metabolome analyses","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (transcriptomics, metabolomics, in vitro/in vivo functional assays), single publication","pmids":["39982744"],"is_preprint":false},{"year":2023,"finding":"miR-124 directly targets AK4; AK4 in turn regulates ATF3 (activating transcription factor 3) downstream; in rat subarachnoid hemorrhage models and primary neuron hemoglobin stimulation models, miR-124 exerts neuroprotective effects via inhibition of the AK4/ATF3 axis.","method":"In vitro luciferase/target validation, rat SAH model, mouse embryonic primary neuron hemoglobin stimulation model, miR-124 inhibitor and mimic transfection, in vivo and in vitro phenotype observation","journal":"Experimental brain research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — pathway placement in SAH models but abstract lacks detail on direct binding or mechanistic validation rigor, single lab","pmids":["37932484"],"is_preprint":false}],"current_model":"AK4 (adenylate kinase 4), a mitochondrial matrix enzyme, regulates cellular energy metabolism and bioenergetics; it physically interacts with AMPKα and promotes its phosphorylation at Thr172 to modulate mitochondrial function in smooth muscle cells, activates NLRP3 inflammasome signaling (via co-localization with NNT) to drive EMT and chemoresistance, promotes oncogenic Myc-target and lipid (sphingomyelin) metabolic pathways in T cell leukemia, and is subject to post-transcriptional regulation by multiple miRNAs (miR-199a-3p, miR-556-3p, miR-3666, miR-634, miR-124) and RNA-binding protein complexes (hnRNPC/LINC00662; DDX3X/miR-2355-3p/TRIM29) that modulate its mRNA stability and expression levels, collectively influencing tumor progression, drug/radio-resistance, and cell survival across multiple cancer contexts."},"narrative":{"mechanistic_narrative":"AK4 is a metabolic enzyme that influences cellular bioenergetics, stress responses, and survival across vascular and cancer contexts [PMID:40506332, PMID:39982744]. In vascular smooth muscle cells, AK4 physically interacts with AMPKα and promotes its activating phosphorylation at Thr172, reducing mitochondrial oxidative damage and improving mitochondrial function; a phospho-dead AMPKα T172A mutant fails to support this effect, establishing AMPKα activation as the operative downstream signal [PMID:40506332]. In cancer, AK4 acts as a pro-tumorigenic node: it co-localizes with NNT and upregulates NLRP3 and IL-1β to activate NLRP3 inflammasome signaling, driving migration, invasion, EMT, and resistance to taxol-induced apoptosis [PMID:40593461], and in adult T cell leukemia it promotes oncogenic Myc-target pathways and sphingomyelin production, with ATL cells showing selective dependence on AK4 [PMID:39982744]. AK4 also restrains apoptosis through p-AKT/p-mTOR signaling and limits ROS accumulation [PMID:40819488]. A recurrent theme is post-transcriptional control of AK4 abundance: it is directly targeted by multiple miRNAs including miR-199a-3p, miR-634, and miR-124 [PMID:29866054, PMID:30479565, PMID:40819488, PMID:37932484], transcriptionally activated downstream of STAT3 [PMID:33361582], and stabilized by RNA-binding complexes—hnRNPC together with LINC00662 [PMID:32549791] and DDX3X recruited via miR-2355-3p/TRIM29 [PMID:33898107]—linking AK4 levels to drug resistance, radioresistance, and tumor progression.","teleology":[{"year":2018,"claim":"Established that AK4 is not merely a metabolic enzyme but a functional driver of therapy resistance, and is held under direct miRNA control by miR-199a-3p.","evidence":"Luciferase target validation plus drug-resistance and radioresistance assays with NF-κB/pathway readouts in osteosarcoma and esophageal cancer cells","pmids":["29866054","30479565"],"confidence":"Medium","gaps":["Mechanism linking AK4 enzymatic activity to NF-κB and resistance not resolved","Whether resistance depends on AK4 catalytic function untested"]},{"year":2020,"claim":"Showed AK4 abundance is set post-transcriptionally by mRNA stabilization, identifying the LINC00662/hnRNPC axis as a route to radioresistance.","evidence":"RIP confirming hnRNPC binding to LINC00662 and AK4 mRNA, with knockdown and rescue in oral squamous cell carcinoma","pmids":["32549791"],"confidence":"Medium","gaps":["Binding site on AK4 transcript not mapped","Downstream effector of stabilized AK4 not defined"]},{"year":2021,"claim":"Extended post-transcriptional regulation to a second RNA-binding mechanism (DDX3X via miR-2355-3p/TRIM29) and connected AK4 to bioenergetic control of proliferation and invasion.","evidence":"mRNA stability assays, miR-2355-3p manipulation, and DDX3X recruitment to AK4 transcript in pancreatic cancer cells","pmids":["33898107"],"confidence":"Medium","gaps":["Direct DDX3X-AK4 transcript binding interface not defined","How altered AK4 changes bioenergetics mechanistically unresolved"]},{"year":2021,"claim":"Placed AK4 downstream of STAT3 transcriptional activation, adding a transcriptional layer to its regulation.","evidence":"Luciferase reporter (miR-3666 targeting STAT3), western blot, and AK4 rescue in ovarian carcinoma cells","pmids":["33361582"],"confidence":"Low","gaps":["STAT3 regulation of AK4 inferred indirectly through miR-3666/rescue, not by direct promoter binding","Single lab, indirect transcriptional evidence"]},{"year":2023,"claim":"Proposed an AK4/ATF3 axis as a neuroprotective target, broadening AK4 relevance beyond cancer to neuronal injury.","evidence":"Luciferase/target validation, rat subarachnoid hemorrhage model, and primary neuron hemoglobin stimulation with miR-124 mimic/inhibitor","pmids":["37932484"],"confidence":"Low","gaps":["Direct miR-124/AK4 binding rigor not detailed","How AK4 regulates ATF3 mechanistically unknown"]},{"year":2025,"claim":"Defined AK4's mechanism in vascular biology by showing it acts through a physical interaction with AMPKα and Thr172 phosphorylation to protect mitochondrial function.","evidence":"Co-IP, phospho-AMPKα Thr172 western blot, pharmacological rescue (metformin/AICAR), and WT vs. T172A mutant overexpression in human aortic smooth muscle cells","pmids":["40506332"],"confidence":"Medium","gaps":["How AK4 promotes Thr172 phosphorylation (direct vs. indirect) not resolved","Whether the interaction depends on AK4 catalytic activity untested"]},{"year":2025,"claim":"Identified an inflammasome arm of AK4 oncogenic signaling, linking AK4-NNT co-localization to NLRP3/IL-1β-driven EMT and chemoresistance.","evidence":"Co-localization, gain/loss-of-function, NLRP3/IL-1β western blot, and apoptosis/migration/invasion assays in nasopharyngeal carcinoma cells","pmids":["40593461"],"confidence":"Medium","gaps":["Mechanism connecting AK4-NNT to NLRP3 activation undefined","Whether co-localization reflects direct binding unknown"]},{"year":2025,"claim":"Revealed a selective metabolic dependency in adult T cell leukemia, tying AK4 to Myc-target pathways and sphingomyelin metabolism and an anti-apoptotic AKT/mTOR program in another model.","evidence":"miR-455-3p/miR-634 target identification, transcriptome/metabolome analyses, and in vitro/in vivo AK4 knockdown/overexpression with AKT/mTOR and ROS readouts","pmids":["39982744","40819488"],"confidence":"Medium","gaps":["Mechanism by which AK4 enhances sphingomyelin production not established","Basis of ATL-selective AK4 dependence unresolved"]},{"year":null,"claim":"Whether AK4's catalytic (nucleotide kinase) activity, rather than scaffolding/protein interactions, underlies its bioenergetic and signaling functions remains unresolved across all contexts.","evidence":"","pmids":[],"confidence":"Low","gaps":["No catalytic-dead AK4 mutant tested in any phenotype","No structural model of AK4 partner interactions","Direct enzymatic substrate dependence of signaling effects unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,8]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,4]},{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[2,7]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[1,5,6,8]}],"complexes":[],"partners":["AMPKΑ","NNT","HNRNPC","DDX3X"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P27144","full_name":"Adenylate kinase 4, mitochondrial","aliases":["Adenylate kinase 3-like","GTP:AMP phosphotransferase AK4"],"length_aa":223,"mass_kda":25.3,"function":"Broad-specificity mitochondrial nucleoside phosphate kinase involved in cellular nucleotide homeostasis by catalyzing nucleoside-phosphate interconversions (PubMed:19073142, PubMed:19766732, PubMed:23416111, PubMed:24767988). Similar to other adenylate kinases, preferentially catalyzes the phosphorylation of the nucleoside monophosphate AMP with ATP as phosphate donor to produce ADP (PubMed:19766732). Phosphorylates only AMP when using GTP as phosphate donor (PubMed:19766732). In vitro, can also catalyze the phosphorylation of CMP, dAMP and dCMP and use GTP as an alternate phosphate donor (PubMed:19766732, PubMed:23416111). Moreover, exhibits a diphosphate kinase activity, producing ATP, CTP, GTP, UTP, TTP, dATP, dCTP and dGTP from the corresponding diphosphate substrates with either ATP or GTP as phosphate donors (PubMed:23416111). Plays a role in controlling cellular ATP levels by regulating phosphorylation and activation of the energy sensor protein kinase AMPK (PubMed:24767988, PubMed:26980435). Plays a protective role in the cellular response to oxidative stress (PubMed:19130895, PubMed:23474458, PubMed:26980435)","subcellular_location":"Mitochondrion matrix","url":"https://www.uniprot.org/uniprotkb/P27144/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/AK4","classification":"Common Essential","n_dependent_lines":458,"n_total_lines":1208,"dependency_fraction":0.3791390728476821},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/AK4","total_profiled":1310},"omim":[{"mim_id":"609290","title":"ADENYLATE KINASE 3; AK3","url":"https://www.omim.org/entry/609290"},{"mim_id":"608009","title":"ADENYLATE KINASE 5; AK5","url":"https://www.omim.org/entry/608009"},{"mim_id":"103030","title":"ADENYLATE KINASE 4; AK4","url":"https://www.omim.org/entry/103030"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Mitochondria","reliability":"Supported"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"kidney","ntpm":169.3},{"tissue":"liver","ntpm":95.6}],"url":"https://www.proteinatlas.org/search/AK4"},"hgnc":{"alias_symbol":[],"prev_symbol":["AK3","AK3L1"]},"alphafold":{"accession":"P27144","domains":[{"cath_id":"3.40.50.300","chopping":"6-218","consensus_level":"medium","plddt":91.5544,"start":6,"end":218}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P27144","model_url":"https://alphafold.ebi.ac.uk/files/AF-P27144-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P27144-F1-predicted_aligned_error_v6.png","plddt_mean":91.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=AK4","jax_strain_url":"https://www.jax.org/strain/search?query=AK4"},"sequence":{"accession":"P27144","fasta_url":"https://rest.uniprot.org/uniprotkb/P27144.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P27144/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P27144"}},"corpus_meta":[{"pmid":"31931771","id":"PMC_31931771","title":"Knockdown of circ-ABCB10 promotes sensitivity of lung cancer cells to cisplatin via miR-556-3p/AK4 axis.","date":"2020","source":"BMC pulmonary medicine","url":"https://pubmed.ncbi.nlm.nih.gov/31931771","citation_count":46,"is_preprint":false},{"pmid":"29866054","id":"PMC_29866054","title":"MiR-199a-3p affects the multi-chemoresistance of osteosarcoma through targeting AK4.","date":"2018","source":"BMC cancer","url":"https://pubmed.ncbi.nlm.nih.gov/29866054","citation_count":43,"is_preprint":false},{"pmid":"30479565","id":"PMC_30479565","title":"The miR-199a-3p regulates the radioresistance of esophageal cancer cells via targeting the AK4 gene.","date":"2018","source":"Cancer cell international","url":"https://pubmed.ncbi.nlm.nih.gov/30479565","citation_count":28,"is_preprint":false},{"pmid":"31827645","id":"PMC_31827645","title":"AK4 Promotes the Progression of HER2-Positive Breast Cancer by Facilitating Cell Proliferation and Invasion.","date":"2019","source":"Disease markers","url":"https://pubmed.ncbi.nlm.nih.gov/31827645","citation_count":24,"is_preprint":false},{"pmid":"32549791","id":"PMC_32549791","title":"Knockdown of LINC00662 represses AK4 and attenuates radioresistance of oral squamous cell carcinoma.","date":"2020","source":"Cancer cell international","url":"https://pubmed.ncbi.nlm.nih.gov/32549791","citation_count":19,"is_preprint":false},{"pmid":"31479860","id":"PMC_31479860","title":"Microstructural changes in the brain mediate the association of AK4, IGFBP5, HSPB2, and ITPK1 with cognitive decline.","date":"2019","source":"Neurobiology of aging","url":"https://pubmed.ncbi.nlm.nih.gov/31479860","citation_count":19,"is_preprint":false},{"pmid":"33898107","id":"PMC_33898107","title":"TRIM29 alters bioenergetics of pancreatic cancer cells via cooperation of miR-2355-3p and DDX3X recruitment to AK4 transcript.","date":"2021","source":"Molecular therapy. Nucleic acids","url":"https://pubmed.ncbi.nlm.nih.gov/33898107","citation_count":14,"is_preprint":false},{"pmid":"35948448","id":"PMC_35948448","title":"Association of AK4 Protein From Stem Cell-Derived Neurons With Cognitive Reserve: An Autopsy Study.","date":"2022","source":"Neurology","url":"https://pubmed.ncbi.nlm.nih.gov/35948448","citation_count":13,"is_preprint":false},{"pmid":"33123257","id":"PMC_33123257","title":"Identification of AK4 as a novel therapeutic target for serous ovarian cancer.","date":"2020","source":"Oncology letters","url":"https://pubmed.ncbi.nlm.nih.gov/33123257","citation_count":9,"is_preprint":false},{"pmid":"33361582","id":"PMC_33361582","title":"MiR-3666 serves as a tumor suppressor in ovarian carcinoma by down-regulating AK4 via targeting STAT3.","date":"2021","source":"Cancer biomarkers : section A of Disease 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research","url":"https://pubmed.ncbi.nlm.nih.gov/37932484","citation_count":3,"is_preprint":false},{"pmid":"39536493","id":"PMC_39536493","title":"Rational design and synthesis of novel N-benzylindole-based epalrestat analogs as selective aldose reductase inhibitors: An unexpected discovery of a new glucose-lowering agent (AK-4) acting as a mitochondrial uncoupler.","date":"2024","source":"European journal of medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/39536493","citation_count":3,"is_preprint":false},{"pmid":"40506332","id":"PMC_40506332","title":"Adenylate kinase 4 (AK4) deficiency prevents vascular smooth muscle cell phenotypic switching by regulating mitochondrial dysfunction through AMPKα inactivation.","date":"2025","source":"Atherosclerosis","url":"https://pubmed.ncbi.nlm.nih.gov/40506332","citation_count":2,"is_preprint":false},{"pmid":"40819488","id":"PMC_40819488","title":"MiRNA-634 promotes apoptosis in HEI-OC1 cells by regulating AK4 and AKT/mTOR signaling 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VSMC phenotypic switching, while a phospho-dead AMPKα T172A mutant does not.\",\n      \"method\": \"Co-immunoprecipitation (AK4-AMPKα interaction), western blot (phospho-AMPKα Thr172), AMPKα activators (metformin/AICAR) rescue assay, wild-type vs. T172A AMPKα mutant overexpression, AK4 knockdown/overexpression in HASMCs\",\n      \"journal\": \"Atherosclerosis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal interaction shown, mutagenesis (T172A) performed, and pharmacological rescue, single lab study\",\n      \"pmids\": [\"40506332\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"AK4 co-localizes with NNT (nicotinamide nucleotide transhydrogenase) in nasopharyngeal carcinoma cells and upregulates NLRP3 and IL-1β to activate the NLRP3 inflammasome signaling pathway, promoting cell migration, invasion, EMT phenotype, and resistance to taxol-induced apoptosis; AK4 knockdown reverses these effects.\",\n      \"method\": \"Co-localization assay, stable overexpression and knockdown in NPC cell lines, western blot (NLRP3, IL-1β), apoptosis assay, migration/invasion assays\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — co-localization and loss/gain of function with defined pathway readouts, single lab\",\n      \"pmids\": [\"40593461\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"TRIM29 knockdown destabilizes the AK4 mRNA transcript via downregulation of miR-2355-3p; miR-2355-3p normally facilitates recruitment of the RNA helicase DDX3X to the AK4 transcript to stabilize it. Loss of AK4 alters bioenergetics and suppresses proliferation and invasion of pancreatic cancer cells.\",\n      \"method\": \"Global screening, qRT-PCR, western blot, AK4 mRNA stability assay, miR-2355-3p manipulation, DDX3X recruitment to AK4 transcript\",\n      \"journal\": \"Molecular therapy. Nucleic acids\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — posttranscriptional mechanism defined with multiple molecular assays, single lab\",\n      \"pmids\": [\"33898107\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"STAT3 transcriptionally activates AK4 expression; miR-3666 targets STAT3 and thereby indirectly represses AK4, suppressing ovarian carcinoma cell proliferation and migration.\",\n      \"method\": \"Luciferase reporter assay (miR-3666 targeting STAT3), western blot (AK4, STAT3), rescue experiments with AK4 overexpression\",\n      \"journal\": \"Cancer biomarkers : section A of Disease markers\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, indirect transcriptional regulation inferred through luciferase and rescue assays only\",\n      \"pmids\": [\"33361582\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"miR-634 targets AK4 (validated by dual luciferase reporter assay) and downregulates AK4 expression; AK4 overexpression activates p-AKT and p-mTOR signaling and inhibits apoptosis in HEI-OC1 cells, while miR-634 mimic or AK4 knockdown promotes apoptosis and increases ROS.\",\n      \"method\": \"Dual luciferase reporter assay, miR-634 mimic transfection, AK4 overexpression and knockdown, western blot (Caspase-3/7, Bax, Bcl-2, p-AKT, p-mTOR), flow cytometry (apoptosis), ROS measurement\",\n      \"journal\": \"Hearing research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — validated direct miRNA-target binding plus downstream AKT/mTOR pathway readout, multiple orthogonal methods, single lab\",\n      \"pmids\": [\"40819488\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"miR-199a-3p directly targets AK4 (validated by luciferase reporter assay); AK4 is a positive regulator of multi-drug resistance in osteosarcoma, and forced changes in miR-199a-3p levels drastically alter NF-κB signaling pathway activity.\",\n      \"method\": \"qRT-PCR, western blot, luciferase reporter assay, drug resistance profiling assay, NF-κB pathway activity measurement\",\n      \"journal\": \"BMC cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct target validation by luciferase plus functional drug-resistance assay and pathway readout, single lab\",\n      \"pmids\": [\"29866054\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"miR-199a-3p directly targets AK4 (validated by luciferase reporter assay) and AK4 promotes radioresistance of esophageal cancer cells; reversal of miR-199a-3p or AK4 levels alters multiple signaling pathway activities.\",\n      \"method\": \"Luciferase reporter assay, survival fraction experiments, wound-healing, invasion assay, forced expression/inhibition of miR-199a-3p and AK4\",\n      \"journal\": \"Cancer cell international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct target validation replicated across osteosarcoma and esophageal cancer studies using luciferase assay\",\n      \"pmids\": [\"30479565\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"LINC00662 stabilizes AK4 mRNA through binding to the RNA-binding protein hnRNPC; the LINC00662/hnRNPC/AK4 axis promotes radioresistance of oral squamous cell carcinoma cells, and LINC00662 knockdown reduces AK4 expression and attenuates radioresistance.\",\n      \"method\": \"RIP (RNA immunoprecipitation) assay confirming hnRNPC binding to LINC00662 and AK4 mRNA, qRT-PCR, western blot, CCK-8, colony formation, flow cytometry, rescue experiments\",\n      \"journal\": \"Cancer cell international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — RIP assay defines the molecular mechanism of mRNA stabilization, functional rescue experiments, single lab\",\n      \"pmids\": [\"32549791\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"AK4 and RHOC are identified as direct targets of the tumor-suppressive miR-455-3p in adult T cell leukemia (ATL); AK4 promotes oncogenic Myc target pathways and enhances production of sphingomyelin; ATL cells show selective sensitivity to AK4 depletion compared to other T cell malignancies.\",\n      \"method\": \"miRNA target identification, in vitro and in vivo functional assays (AK4 knockdown/overexpression), transcriptome and metabolome analyses\",\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 orthogonal methods (transcriptomics, metabolomics, in vitro/in vivo functional assays), single publication\",\n      \"pmids\": [\"39982744\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"miR-124 directly targets AK4; AK4 in turn regulates ATF3 (activating transcription factor 3) downstream; in rat subarachnoid hemorrhage models and primary neuron hemoglobin stimulation models, miR-124 exerts neuroprotective effects via inhibition of the AK4/ATF3 axis.\",\n      \"method\": \"In vitro luciferase/target validation, rat SAH model, mouse embryonic primary neuron hemoglobin stimulation model, miR-124 inhibitor and mimic transfection, in vivo and in vitro phenotype observation\",\n      \"journal\": \"Experimental brain research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — pathway placement in SAH models but abstract lacks detail on direct binding or mechanistic validation rigor, single lab\",\n      \"pmids\": [\"37932484\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"AK4 (adenylate kinase 4), a mitochondrial matrix enzyme, regulates cellular energy metabolism and bioenergetics; it physically interacts with AMPKα and promotes its phosphorylation at Thr172 to modulate mitochondrial function in smooth muscle cells, activates NLRP3 inflammasome signaling (via co-localization with NNT) to drive EMT and chemoresistance, promotes oncogenic Myc-target and lipid (sphingomyelin) metabolic pathways in T cell leukemia, and is subject to post-transcriptional regulation by multiple miRNAs (miR-199a-3p, miR-556-3p, miR-3666, miR-634, miR-124) and RNA-binding protein complexes (hnRNPC/LINC00662; DDX3X/miR-2355-3p/TRIM29) that modulate its mRNA stability and expression levels, collectively influencing tumor progression, drug/radio-resistance, and cell survival across multiple cancer contexts.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"AK4 is a metabolic enzyme that influences cellular bioenergetics, stress responses, and survival across vascular and cancer contexts [#0, #8]. In vascular smooth muscle cells, AK4 physically interacts with AMPKα and promotes its activating phosphorylation at Thr172, reducing mitochondrial oxidative damage and improving mitochondrial function; a phospho-dead AMPKα T172A mutant fails to support this effect, establishing AMPKα activation as the operative downstream signal [#0]. In cancer, AK4 acts as a pro-tumorigenic node: it co-localizes with NNT and upregulates NLRP3 and IL-1β to activate NLRP3 inflammasome signaling, driving migration, invasion, EMT, and resistance to taxol-induced apoptosis [#1], and in adult T cell leukemia it promotes oncogenic Myc-target pathways and sphingomyelin production, with ATL cells showing selective dependence on AK4 [#8]. AK4 also restrains apoptosis through p-AKT/p-mTOR signaling and limits ROS accumulation [#4]. A recurrent theme is post-transcriptional control of AK4 abundance: it is directly targeted by multiple miRNAs including miR-199a-3p, miR-634, and miR-124 [#5, #6, #4, #9], transcriptionally activated downstream of STAT3 [#3], and stabilized by RNA-binding complexes—hnRNPC together with LINC00662 [#7] and DDX3X recruited via miR-2355-3p/TRIM29 [#2]—linking AK4 levels to drug resistance, radioresistance, and tumor progression.\",\n  \"teleology\": [\n    {\n      \"year\": 2018,\n      \"claim\": \"Established that AK4 is not merely a metabolic enzyme but a functional driver of therapy resistance, and is held under direct miRNA control by miR-199a-3p.\",\n      \"evidence\": \"Luciferase target validation plus drug-resistance and radioresistance assays with NF-κB/pathway readouts in osteosarcoma and esophageal cancer cells\",\n      \"pmids\": [\"29866054\", \"30479565\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking AK4 enzymatic activity to NF-κB and resistance not resolved\", \"Whether resistance depends on AK4 catalytic function untested\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Showed AK4 abundance is set post-transcriptionally by mRNA stabilization, identifying the LINC00662/hnRNPC axis as a route to radioresistance.\",\n      \"evidence\": \"RIP confirming hnRNPC binding to LINC00662 and AK4 mRNA, with knockdown and rescue in oral squamous cell carcinoma\",\n      \"pmids\": [\"32549791\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Binding site on AK4 transcript not mapped\", \"Downstream effector of stabilized AK4 not defined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Extended post-transcriptional regulation to a second RNA-binding mechanism (DDX3X via miR-2355-3p/TRIM29) and connected AK4 to bioenergetic control of proliferation and invasion.\",\n      \"evidence\": \"mRNA stability assays, miR-2355-3p manipulation, and DDX3X recruitment to AK4 transcript in pancreatic cancer cells\",\n      \"pmids\": [\"33898107\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct DDX3X-AK4 transcript binding interface not defined\", \"How altered AK4 changes bioenergetics mechanistically unresolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Placed AK4 downstream of STAT3 transcriptional activation, adding a transcriptional layer to its regulation.\",\n      \"evidence\": \"Luciferase reporter (miR-3666 targeting STAT3), western blot, and AK4 rescue in ovarian carcinoma cells\",\n      \"pmids\": [\"33361582\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"STAT3 regulation of AK4 inferred indirectly through miR-3666/rescue, not by direct promoter binding\", \"Single lab, indirect transcriptional evidence\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Proposed an AK4/ATF3 axis as a neuroprotective target, broadening AK4 relevance beyond cancer to neuronal injury.\",\n      \"evidence\": \"Luciferase/target validation, rat subarachnoid hemorrhage model, and primary neuron hemoglobin stimulation with miR-124 mimic/inhibitor\",\n      \"pmids\": [\"37932484\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Direct miR-124/AK4 binding rigor not detailed\", \"How AK4 regulates ATF3 mechanistically unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Defined AK4's mechanism in vascular biology by showing it acts through a physical interaction with AMPKα and Thr172 phosphorylation to protect mitochondrial function.\",\n      \"evidence\": \"Co-IP, phospho-AMPKα Thr172 western blot, pharmacological rescue (metformin/AICAR), and WT vs. T172A mutant overexpression in human aortic smooth muscle cells\",\n      \"pmids\": [\"40506332\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How AK4 promotes Thr172 phosphorylation (direct vs. indirect) not resolved\", \"Whether the interaction depends on AK4 catalytic activity untested\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified an inflammasome arm of AK4 oncogenic signaling, linking AK4-NNT co-localization to NLRP3/IL-1β-driven EMT and chemoresistance.\",\n      \"evidence\": \"Co-localization, gain/loss-of-function, NLRP3/IL-1β western blot, and apoptosis/migration/invasion assays in nasopharyngeal carcinoma cells\",\n      \"pmids\": [\"40593461\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism connecting AK4-NNT to NLRP3 activation undefined\", \"Whether co-localization reflects direct binding unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Revealed a selective metabolic dependency in adult T cell leukemia, tying AK4 to Myc-target pathways and sphingomyelin metabolism and an anti-apoptotic AKT/mTOR program in another model.\",\n      \"evidence\": \"miR-455-3p/miR-634 target identification, transcriptome/metabolome analyses, and in vitro/in vivo AK4 knockdown/overexpression with AKT/mTOR and ROS readouts\",\n      \"pmids\": [\"39982744\", \"40819488\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which AK4 enhances sphingomyelin production not established\", \"Basis of ATL-selective AK4 dependence unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Whether AK4's catalytic (nucleotide kinase) activity, rather than scaffolding/protein interactions, underlies its bioenergetic and signaling functions remains unresolved across all contexts.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No catalytic-dead AK4 mutant tested in any phenotype\", \"No structural model of AK4 partner interactions\", \"Direct enzymatic substrate dependence of signaling effects unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 8]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 4]},\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [2, 7]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [1, 5, 6, 8]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"AMPKα\", \"NNT\", \"hnRNPC\", \"DDX3X\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"tie","faith_supported":4,"faith_total":5,"faith_pct":80.0}}