{"gene":"NDUFS3","run_date":"2026-04-29T11:37:56","timeline":{"discoveries":[{"year":2004,"finding":"Mutations in NDUFS3 (NADH dehydrogenase iron-sulphur protein 3), the seventh core subunit of mitochondrial complex I, were shown to cause late-onset Leigh syndrome, optic atrophy, and complex I deficiency, establishing NDUFS3 as an essential structural/functional core subunit of complex I whose loss produces severe mitochondrial disease.","method":"DHPLC and sequence analysis of NDUFS3 in complex I-deficient patients; biochemical diagnosis on cultured amniocytes","journal":"Journal of medical genetics","confidence":"High","confidence_rationale":"Tier 2 — genotype-phenotype with biochemical validation of complex I deficiency; replicated in subsequent studies","pmids":["14729820"],"is_preprint":false},{"year":2007,"finding":"Using an inducible NDUFS3-GFP expression system, NDUFS3 was shown to enter early, nucleus-encoded assembly intermediates (~100 and ~150 kDa subcomplexes) of mitochondrial complex I before mitochondrial DNA-encoded subunits are incorporated, defining the entry point of mitochondrially-translated subunits into the growing complex.","method":"Inducible NDUFS3-GFP expression in HEK293 cells; blue native PAGE Western blot; differential solubilization; inhibition of mitochondrial translation with reversal experiments","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — direct stepwise assembly tracking with multiple orthogonal methods and functional reversal experiment in a single study","pmids":["17209039"],"is_preprint":false},{"year":2013,"finding":"Gene silencing of NDUFS3 in isogenic human embryonic kidney cells systematically introduced mitochondrial complex I dysfunction and triggered a metabolic switch to aerobic glycolysis (Warburg effect) in a manner dependent on NDUFS3 protein levels, with sustained free radical (ROS) imbalance required to maintain the glycolytic phenotype.","method":"RNAi-mediated gene silencing with graded NDUFS3 suppression; metabolic characterization including oxygen consumption, glycolysis, and ROS measurements in isogenic cell lines","journal":"Biology open","confidence":"Medium","confidence_rationale":"Tier 2 — clean dose-dependent KD with defined metabolic phenotypes and ROS mechanistic link; single lab","pmids":["23519235"],"is_preprint":false},{"year":2013,"finding":"The double mutant NDUFS3 protein (T145I + R199W) associated with Leigh syndrome showed altered polarity around tryptophan residues, changed fluorescence quenching parameters, altered secondary and tertiary structure, and a significantly higher tendency to aggregate compared to wild-type, as well as loss of a molten globule state at low pH, providing a structural basis for how these mutations disrupt complex I assembly.","method":"Recombinant expression and purification in E. coli; steady-state and time-resolved fluorescence spectroscopy; CD spectroscopy; Thioflavin-T and Congo red dye binding for aggregation; thermal and Gdn-HCl unfolding","journal":"Biochimie","confidence":"Medium","confidence_rationale":"Tier 1/2 — in vitro biophysical characterization with multiple orthogonal spectroscopic methods; single lab","pmids":["24028823"],"is_preprint":false},{"year":2018,"finding":"DJ-1 (PARK7 gene product) physically interacts with NDUFS3 in rat testes, and disruption of this interaction by ornidazole treatment reduces NDUFS3 protein levels and complex I activity, linking DJ-1's protective role against oxidative stress to maintenance of NDUFS3 integrity in sperm mitochondria.","method":"Co-immunoprecipitation of DJ-1 and NDUFS3 in rat testes; Western blot; complex I activity assay in asthenozoospermic patient sperm and rat model","journal":"Mediators of inflammation","confidence":"Medium","confidence_rationale":"Tier 3 — single Co-IP plus functional activity assay; single lab with in vivo rat model correlation","pmids":["29849492"],"is_preprint":false},{"year":2018,"finding":"Two missense mutations in NDUFS3 (c.418C>T/p.R140W and c.595C>T/p.R199W) identified by next-generation sequencing in a Leigh syndrome patient caused decreased NDUFS3 protein levels and impaired complex I assembly in patient-derived lymphoblastoid cells.","method":"MitoExome next-generation sequencing; Western blot and blue native PAGE of patient lymphoblastoid cells","journal":"Journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 — genotype-function link with direct assessment of complex I assembly in patient cells","pmids":["30140060"],"is_preprint":false},{"year":2021,"finding":"Complete ablation of NDUFS3 allows a small amount of functional complex I to still assemble in diverse mammalian cell types, demonstrating that NDUFS3 is not absolutely required for complex I biogenesis. Gradual reduction of NDUFS3 causes hierarchical, modular complex I disassembly in which the ND4 module remains stable and bound to TMEM126A (OPA7), uncovering TMEM126A as a complex I assembly factor that binds the ND4-module intermediate.","method":"NDUFS3 knockout and knockdown in multiple mammalian cell types; blue native PAGE; co-immunoprecipitation; mass spectrometry-based proteomics; functional complex I activity assays","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (KO, BN-PAGE, Co-IP, MS, activity assay) in diverse cell types; single lab but strong internal validation","pmids":["33882309"],"is_preprint":false},{"year":2022,"finding":"Using NDUFS3 knockout cancer cells devoid of complex I, BAY 87-2243 and EVP 4593 were shown to be selective complex I inhibitors whose antiproliferative effects depend on complex I, whereas metformin's antiproliferative effects were largely independent of complex I. Molecular docking indicated that BAY 87-2243 and EVP 4593 bind in the quinone-binding pocket of complex I, with NDUFS3-containing residues forming part of the interaction network.","method":"NDUFS3 knockout cell models; cell viability assays; molecular docking into complex I structure","journal":"Open biology","confidence":"Medium","confidence_rationale":"Tier 2 — genetic KO model plus molecular docking; functional selectivity demonstrated, though docking is computational","pmids":["36349549"],"is_preprint":false},{"year":2024,"finding":"The splicing factor SRSF1 binds to constitutive exon 6 of Ndufs3 pre-mRNA and promotes its inclusion; SRSF1 deficiency in mature adipocytes causes impaired Ndufs3 splicing, reduced functional NDUFS3 protein, defective mitochondrial complex I assembly and activity, mitochondrial fragmentation, and impaired thermogenic capacity of brown adipose tissue.","method":"Adipocyte-specific SRSF1 knockout mice; single-nucleus RNA sequencing; transmission electron microscopy; RNA pulldown/RIP demonstrating SRSF1 binding to Ndufs3 exon 6; complex I activity assays; thermogenesis measurements","journal":"Advanced science","confidence":"High","confidence_rationale":"Tier 2 — in vivo KO with snRNA-seq, direct RNA binding demonstrated, complex I assembly and thermogenesis phenotypes; multiple orthogonal methods","pmids":["38569495"],"is_preprint":false},{"year":2024,"finding":"NDUFS3 overexpression in a sepsis-induced acute kidney injury rat model inhibited LPS-induced ferroptosis and mitochondrial damage; inhibition of AMPK by Compound C abolished this protection, placing NDUFS3 upstream of the AMPK pathway in regulating mitochondrial ROS, ferroptosis markers (MDA, GSH, iron levels), and ATP production in kidney cells.","method":"NDUFS3 overexpression in rats (hydrodynamic tail vein injection) and HK-2 cells; AMPK inhibitor (Compound C) epistasis; Western blot; MDA/GSH/iron content; Mitosox ROS; ATP assay; transmission electron microscopy","journal":"International immunopharmacology","confidence":"Medium","confidence_rationale":"Tier 2 — gain-of-function with AMPK epistasis in vitro and in vivo; single lab","pmids":["39426231"],"is_preprint":false},{"year":2025,"finding":"In pancreatic cancer cells, transient siRNA-mediated silencing of NDUFS3 caused mitochondrial deficit, reduced oxidative metabolism, and morphological mitochondrial alterations; this mitochondrial impairment led to RAB7 downregulation, impairment of the late endocytic/lysosomal pathway, and reduced cancer cell invasiveness, migration, vimentin levels, and EMT markers, linking NDUFS3-dependent mitochondrial function to mitochondria-lysosome crosstalk and cancer invasive potential.","method":"RNAi knockdown of NDUFS3 in pancreatic cancer cells; Seahorse XF assay; transmission electron microscopy; Western blot; confocal microscopy; zymography; wound healing and invasion assays; colony assays","journal":"Cell communication and signaling","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods establishing mechanistic pathway from NDUFS3 to RAB7 to lysosomal dysfunction; single lab","pmids":["40369571"],"is_preprint":false},{"year":2025,"finding":"In melanoma, elevated NDUFS3 promotes oxidative phosphorylation and the pentose phosphate pathway while attenuating glycolysis; increased ATP production from NDUFS3-mediated OXPHOS suppresses AMPK activity, which in turn relieves AMPK-mediated phosphorylation/inhibition of PRPS1, thereby stimulating purine nucleotide biosynthesis and melanoma proliferation, defining a NDUFS3–AMPK–PRPS1 signaling axis.","method":"NDUFS3 overexpression and knockdown in melanoma cells; metabolic flux analysis (OXPHOS, glycolysis, PPP); AMPK activity measurement; PRPS1 phosphorylation assay; proliferation assays","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2 — gain- and loss-of-function with defined metabolic and signaling pathway placement; single lab","pmids":["40404919"],"is_preprint":false},{"year":2024,"finding":"MAZ (Myc-associated Zinc-finger Protein) transcriptionally targets and upregulates NDUFS3 expression in melanoma, linking a transcription factor to NDUFS3-driven enhancement of mitochondrial metabolism and malignant progression.","method":"Chromatin immunoprecipitation and reporter assays demonstrating MAZ binding to NDUFS3 promoter; gain- and loss-of-function of MAZ with NDUFS3 expression readout; proliferation/migration/invasion assays","journal":"Communications biology","confidence":"Medium","confidence_rationale":"Tier 2 — direct transcriptional regulation demonstrated by ChIP with functional validation; single lab","pmids":["39532991"],"is_preprint":false},{"year":2017,"finding":"Cryo-EM structure of the human respiratory megacomplex I2III2IV2 revealed the precise subunit assignment and position of NDUFS3 within the Q module of complex I in the context of the full respiratory supercomplex.","method":"Cryo-electron microscopy of human respiratory megacomplex I2III2IV2","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 — high-resolution cryo-EM structure with subunit assignment","pmids":["28844695"],"is_preprint":false}],"current_model":"NDUFS3 is a non-catalytic core subunit of the Q module of mitochondrial respiratory complex I that enters early nucleus-encoded assembly intermediates before mitochondrial DNA-encoded subunits are incorporated; its loss causes hierarchical, modular complex I disassembly with the ND4 module remaining bound to the assembly factor TMEM126A, while disease-causing mutations destabilize NDUFS3 protein structure and promote aggregation; NDUFS3 levels control a metabolic threshold between OXPHOS and aerobic glycolysis via ROS, participates in a NDUFS3–AMPK–PRPS1 axis regulating purine biosynthesis, is physically protected by DJ-1, transcriptionally regulated by MAZ, and its pre-mRNA splicing is controlled by SRSF1, linking mitochondrial bioenergetics to diverse cellular processes including cancer metabolism, ferroptosis resistance, and brown adipose thermogenesis."},"narrative":{"teleology":[{"year":2004,"claim":"Identification of NDUFS3 mutations in patients with Leigh syndrome and complex I deficiency established NDUFS3 as a disease-causing core subunit of complex I, answering whether this subunit is individually essential for human bioenergetics.","evidence":"DHPLC and sequencing of NDUFS3 in complex I–deficient patients with biochemical validation in cultured amniocytes","pmids":["14729820"],"confidence":"High","gaps":["Precise structural consequences of patient mutations on assembled complex I were unknown","Genotype–phenotype correlations across different NDUFS3 mutations not established"]},{"year":2007,"claim":"Tracking NDUFS3-GFP incorporation into assembly intermediates revealed that NDUFS3 enters early nucleus-encoded subcomplexes before mitochondrially-encoded subunits join, defining its temporal position in the complex I assembly pathway.","evidence":"Inducible NDUFS3-GFP in HEK293 cells with BN-PAGE, differential solubilization, and mitochondrial translation inhibition/reversal","pmids":["17209039"],"confidence":"High","gaps":["Identity of direct binding partners within the early assembly intermediate was not resolved","Whether NDUFS3 acts as a scaffold or is passively incorporated remained unclear"]},{"year":2013,"claim":"Biophysical characterization of disease-associated NDUFS3 double mutant protein and dose-dependent knockdown studies together revealed that mutations destabilize protein structure and promote aggregation, while graded NDUFS3 loss triggers a ROS-dependent metabolic switch to aerobic glycolysis, providing both structural and metabolic mechanisms for complex I dysfunction.","evidence":"Recombinant mutant protein spectroscopy and aggregation assays; RNAi dose-response in HEK cells with metabolic profiling","pmids":["24028823","23519235"],"confidence":"Medium","gaps":["Structural studies used isolated recombinant protein, not the assembled complex","ROS-to-glycolysis switch mechanism lacked identification of specific ROS sensor or signaling intermediates"]},{"year":2017,"claim":"Cryo-EM structure of the human respiratory megacomplex I₂III₂IV₂ resolved the precise position of NDUFS3 within the Q module, providing atomic-level context for its role in ubiquinone binding and electron transfer.","evidence":"Cryo-electron microscopy of purified human respiratory megacomplex","pmids":["28844695"],"confidence":"High","gaps":["Dynamic conformational changes of NDUFS3 during catalysis not captured","Structure does not resolve assembly intermediates containing NDUFS3"]},{"year":2018,"claim":"DJ-1 was identified as a physical interactor that protects NDUFS3 stability, and additional Leigh syndrome mutations were biochemically validated, expanding understanding of NDUFS3 regulation and disease mechanism.","evidence":"Co-IP of DJ-1/NDUFS3 in rat testes with complex I activity assays; MitoExome sequencing with BN-PAGE in patient lymphoblastoid cells","pmids":["29849492","30140060"],"confidence":"Medium","gaps":["DJ-1–NDUFS3 interaction demonstrated by single Co-IP without reciprocal validation or structural mapping","Whether DJ-1 acts as a chaperone or stabilizer of NDUFS3 is unresolved"]},{"year":2021,"claim":"Complete NDUFS3 ablation showed that a small amount of functional complex I can still assemble without it, overturning the assumption of absolute requirement, and revealed hierarchical modular disassembly with the ND4 module persisting bound to the newly identified assembly factor TMEM126A.","evidence":"NDUFS3 KO and KD in multiple mammalian cell types; BN-PAGE, Co-IP, quantitative proteomics, and activity assays","pmids":["33882309"],"confidence":"High","gaps":["How a residual complex I assembles without NDUFS3 is mechanistically unexplained","Whether TMEM126A-ND4 module persistence has functional consequences beyond assembly stalling is unknown"]},{"year":2022,"claim":"NDUFS3-knockout cancer cells served as a genetic tool to demonstrate that BAY 87-2243 and EVP 4593 are selective complex I inhibitors, and molecular docking placed NDUFS3 residues within the quinone-binding pocket interaction network.","evidence":"NDUFS3 KO cell viability assays combined with molecular docking into complex I structure","pmids":["36349549"],"confidence":"Medium","gaps":["Drug–NDUFS3 contacts are computational; no mutagenesis or binding data confirm direct interaction","Pharmacological relevance in vivo not demonstrated"]},{"year":2024,"claim":"Multiple studies converged to reveal upstream regulatory mechanisms and downstream signaling of NDUFS3: SRSF1 controls Ndufs3 pre-mRNA splicing required for brown adipose thermogenesis, MAZ transcriptionally upregulates NDUFS3 in melanoma, and NDUFS3 overexpression protects against sepsis-induced ferroptosis via the AMPK pathway.","evidence":"Adipocyte-specific SRSF1 KO mice with RNA binding assays and thermogenesis measurements; ChIP and reporter assays for MAZ on NDUFS3 promoter; NDUFS3 overexpression with AMPK inhibitor epistasis in sepsis-AKI models","pmids":["38569495","39532991","39426231"],"confidence":"Medium","gaps":["Whether SRSF1-mediated splicing control is specific to Ndufs3 or affects other complex I subunits coordinately is unknown","MAZ–NDUFS3 transcriptional axis demonstrated only in melanoma","AMPK-dependent ferroptosis protection by NDUFS3 lacks identification of the direct AMPK-activating mechanism"]},{"year":2025,"claim":"NDUFS3 was placed at the center of cancer metabolic reprogramming: its loss in pancreatic cancer impairs the endolysosomal pathway via RAB7 downregulation to reduce invasiveness, while its elevation in melanoma drives a NDUFS3–AMPK–PRPS1 axis coupling OXPHOS output to purine biosynthesis.","evidence":"NDUFS3 KD in pancreatic cancer cells with Seahorse, EM, invasion assays; NDUFS3 gain/loss-of-function in melanoma with metabolic flux and PRPS1 phosphorylation analysis","pmids":["40369571","40404919"],"confidence":"Medium","gaps":["RAB7 downregulation mechanism downstream of mitochondrial impairment is not defined","NDUFS3–AMPK–PRPS1 axis not validated in non-melanoma contexts","Whether NDUFS3 dosage effects on cancer metabolism reflect complex I activity versus moonlighting functions is unresolved"]},{"year":null,"claim":"It remains unknown whether NDUFS3 has functional roles independent of complex I, how residual complex I assembles in its complete absence, and whether the metabolic signaling axes identified in individual cancer types generalize across tissues.","evidence":"","pmids":[],"confidence":"Low","gaps":["No moonlighting function established or excluded","Structural basis of residual complex I assembly without NDUFS3 unresolved","Tissue-generalizability of NDUFS3–AMPK–PRPS1 axis untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[1,6,13]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[1,6,8,13]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,2,6,8,11]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[0,5,10,11]}],"complexes":["Mitochondrial complex I (NADH:ubiquinone oxidoreductase)","Respiratory megacomplex I2III2IV2"],"partners":["TMEM126A","DJ-1","SRSF1","PRPS1","MAZ"],"other_free_text":[]},"mechanistic_narrative":"NDUFS3 is a nuclear-encoded core subunit of the Q module of mitochondrial respiratory complex I that is essential for proper complex I assembly, oxidative phosphorylation, and metabolic homeostasis. It enters early assembly intermediates (~100–150 kDa subcomplexes) before mitochondrial DNA-encoded subunits are incorporated, and its gradual loss triggers hierarchical, modular complex I disassembly with the ND4 module remaining stably bound to the assembly factor TMEM126A [PMID:17209039, PMID:33882309]. NDUFS3 levels control a metabolic threshold between OXPHOS and aerobic glycolysis via ROS signaling, and elevated NDUFS3-driven ATP production suppresses AMPK to relieve inhibition of PRPS1, thereby stimulating purine biosynthesis in cancer cells [PMID:23519235, PMID:40404919]. Biallelic mutations in NDUFS3 cause mitochondrial complex I deficiency presenting as Leigh syndrome [PMID:14729820, PMID:30140060]."},"prefetch_data":{"uniprot":{"accession":"O75489","full_name":"NADH dehydrogenase [ubiquinone] iron-sulfur protein 3, mitochondrial","aliases":["Complex I-30kD","CI-30kD","NADH-ubiquinone oxidoreductase 30 kDa subunit"],"length_aa":264,"mass_kda":30.2,"function":"Core subunit of the mitochondrial membrane respiratory chain NADH dehydrogenase (Complex I) which catalyzes electron transfer from NADH through the respiratory chain, using ubiquinone as an electron acceptor (PubMed:14729820, PubMed:30140060). Essential for the catalytic activity and assembly of complex I (PubMed:14729820, PubMed:24028823, PubMed:30140060)","subcellular_location":"Mitochondrion inner membrane","url":"https://www.uniprot.org/uniprotkb/O75489/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/NDUFS3","classification":"Not Classified","n_dependent_lines":354,"n_total_lines":1208,"dependency_fraction":0.29304635761589404},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/NDUFS3","total_profiled":1310},"omim":[{"mim_id":"620135","title":"MITOCHONDRIAL COMPLEX I DEFICIENCY, NUCLEAR TYPE 39; MC1DN39","url":"https://www.omim.org/entry/620135"},{"mim_id":"620018","title":"PROTEIN DISULFIDE ISOMERASE, FAMILY A, MEMBER 4; PDIA4","url":"https://www.omim.org/entry/620018"},{"mim_id":"618230","title":"MITOCHONDRIAL COMPLEX I DEFICIENCY, NUCLEAR TYPE 8; MC1DN8","url":"https://www.omim.org/entry/618230"},{"mim_id":"612360","title":"NADH DEHYDROGENASE (UBIQUINONE) COMPLEX I, ASSEMBLY FACTOR 5; NDUFAF5","url":"https://www.omim.org/entry/612360"},{"mim_id":"609435","title":"NADH-UBIQUINONE OXIDOREDUCTASE SUBUNIT A13; NDUFA13","url":"https://www.omim.org/entry/609435"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Mitochondria","reliability":"Supported"},{"location":"Nuclear bodies","reliability":"Additional"},{"location":"Principal piece","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"skeletal muscle","ntpm":318.8}],"url":"https://www.proteinatlas.org/search/NDUFS3"},"hgnc":{"alias_symbol":["CI-30"],"prev_symbol":[]},"alphafold":{"accession":"O75489","domains":[{"cath_id":"3.30.460.80","chopping":"53-185","consensus_level":"high","plddt":94.8906,"start":53,"end":185}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O75489","model_url":"https://alphafold.ebi.ac.uk/files/AF-O75489-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O75489-F1-predicted_aligned_error_v6.png","plddt_mean":82.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=NDUFS3","jax_strain_url":"https://www.jax.org/strain/search?query=NDUFS3"},"sequence":{"accession":"O75489","fasta_url":"https://rest.uniprot.org/uniprotkb/O75489.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O75489/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O75489"}},"corpus_meta":[{"pmid":"14729820","id":"PMC_14729820","title":"Mutant NDUFS3 subunit of mitochondrial complex I causes Leigh syndrome.","date":"2004","source":"Journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/14729820","citation_count":148,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"17209039","id":"PMC_17209039","title":"Identification of mitochondrial complex I assembly intermediates by tracing tagged NDUFS3 demonstrates the entry point of mitochondrial subunits.","date":"2007","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17209039","citation_count":125,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"23519235","id":"PMC_23519235","title":"Mitochondrial NDUFS3 regulates the ROS-mediated onset of metabolic switch in transformed cells.","date":"2013","source":"Biology open","url":"https://pubmed.ncbi.nlm.nih.gov/23519235","citation_count":39,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"21867691","id":"PMC_21867691","title":"Biomarker signatures of mitochondrial NDUFS3 in 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analysis reveals depression of the Ndufs3 subunit and activity of complex I in diabetic rat brain.","date":"2012","source":"Journal of proteomics","url":"https://pubmed.ncbi.nlm.nih.gov/22387129","citation_count":21,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"30140060","id":"PMC_30140060","title":"A Novel NDUFS3 mutation in a Chinese patient with severe Leigh syndrome.","date":"2018","source":"Journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/30140060","citation_count":20,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"24028823","id":"PMC_24028823","title":"Human mitochondrial NDUFS3 protein bearing Leigh syndrome mutation is more prone to aggregation than its wild-type.","date":"2013","source":"Biochimie","url":"https://pubmed.ncbi.nlm.nih.gov/24028823","citation_count":17,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"38569495","id":"PMC_38569495","title":"SRSF1 Is Required for Mitochondrial Homeostasis and Thermogenic Function in Brown Adipocytes Through its Control of Ndufs3 Splicing.","date":"2024","source":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","url":"https://pubmed.ncbi.nlm.nih.gov/38569495","citation_count":14,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"39426231","id":"PMC_39426231","title":"NDUFS3 alleviates oxidative stress and ferroptosis in sepsis induced acute kidney injury through AMPK pathway.","date":"2024","source":"International immunopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/39426231","citation_count":13,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"36349549","id":"PMC_36349549","title":"NDUFS3 knockout cancer cells and molecular docking reveal specificity and mode of action of anti-cancer respiratory complex I inhibitors.","date":"2022","source":"Open 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kDa) are true early assembly intermediates that precede incorporation of mitochondrially-encoded subunits, as demonstrated by inducible NDUFS3-GFP tracing combined with inhibition/recovery of mitochondrial translation.\",\n      \"method\": \"Inducible NDUFS3-GFP expression in HEK293 cells; blue native PAGE Western blot; differential detergent solubilization; heat-stability assays; mitochondrial translation inhibition/recovery experiments; subcomplex composition analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods (inducible tagging, BN-PAGE, translation inhibition/rescue) in a single rigorous study providing strong mechanistic evidence\",\n      \"pmids\": [\"17209039\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Complete ablation of NDUFS3 in diverse mammalian cell types leads to hierarchical, modular disassembly of complex I in which the ND4 module remains stable; this stability is conferred by TMEM126A binding to the ND4 module intermediate, revealing TMEM126A as a complex I assembly factor. A small amount of functional CI can still assemble in the complete absence of NDUFS3.\",\n      \"method\": \"CRISPR/Cas9 NDUFS3 knockout in multiple mammalian cell lines; BN-PAGE; mass spectrometry; co-immunoprecipitation of TMEM126A with ND4-module intermediate; functional respiratory assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — reciprocal co-IP, structural/functional analysis of disassembly intermediates, and genetic ablation with defined molecular phenotype in multiple cell types\",\n      \"pmids\": [\"33882309\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Mutations in NDUFS3 (coding for the seventh core subunit of complex I, an iron-sulfur protein) cause complex I deficiency and late-onset Leigh syndrome; identification of NDUFS3 mutations in patient-derived cells confirmed its essential role in complex I assembly/function.\",\n      \"method\": \"DHPLC and Sanger sequencing of patient cohort; biochemical complex I activity assay in cultured amniocytes and patient cells; Western blot for NDUFS3 protein\",\n      \"journal\": \"Journal of medical genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — disease-causing mutations combined with biochemical complex I activity measurements, replicated across multiple patients\",\n      \"pmids\": [\"14729820\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"NDUFS3 is an integral subunit of the Q-module (quinone-binding module) of complex I; Leigh syndrome-associated double mutation (T145I + R199W) alters protein conformation, disrupts secondary and tertiary structure, increases aggregation propensity (Thioflavin-T and Congo red binding), and destabilizes the protein relative to wild-type, consistent with impaired complex I assembly.\",\n      \"method\": \"Recombinant expression and purification in E. coli; steady-state and time-resolved fluorescence spectroscopy; circular dichroism; Thioflavin-T and Congo red aggregation assays; MALDI-TOF/TOF; Western blot\",\n      \"journal\": \"Biochimie\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with purified protein and multiple biophysical/structural assays\",\n      \"pmids\": [\"24028823\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Graded shRNA-mediated silencing of NDUFS3 in HEK293 cells progressively impairs complex I activity, introduces mitochondrial dysfunction, and triggers a switch from oxidative phosphorylation to aerobic glycolysis (Warburg phenotype) in a manner dependent on NDUFS3 protein levels; sustained free-radical imbalance (elevated ROS) is required to maintain the glycolytic switch.\",\n      \"method\": \"shRNA-mediated NDUFS3 gene silencing; oxygen consumption and extracellular acidification rate measurements; ROS quantification; metabolic flux analysis; Western blot\",\n      \"journal\": \"Biology open\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean knockdown with multiple orthogonal metabolic readouts, single lab\",\n      \"pmids\": [\"23519235\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"DJ-1 (PARK7 gene product) physically interacts with NDUFS3 in rat testes; disruption of this interaction by ornidazole (ORN) treatment reduces both DJ-1 and NDUFS3 expression and decreases complex I activity, contributing to asthenozoospermia.\",\n      \"method\": \"Co-immunoprecipitation of DJ-1 and NDUFS3 from rat testes; Western blot; complex I activity assay in rat AS model; comparison with human AS sperm samples\",\n      \"journal\": \"Mediators of inflammation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single co-IP with supporting activity assay and disease model, single lab\",\n      \"pmids\": [\"29849492\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The splicing factor SRSF1 binds the constitutive exon 6 of Ndufs3 pre-mRNA and promotes its inclusion; SRSF1 deficiency in mature adipocytes causes mis-splicing of Ndufs3, reduces functional NDUFS3 protein, impairs complex I assembly and activity, disrupts mitochondrial integrity, and compromises thermogenic capacity of brown adipose tissue.\",\n      \"method\": \"Adipocyte-specific SRSF1 knockout mice; single-nucleus RNA sequencing; transmission electron microscopy; RNA-binding/splicing assays (SRSF1 binding to Ndufs3 exon 6); Western blot for NDUFS3 and complex I subunits; respiratory chain activity assays\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — direct RNA-binding evidence combined with genetic KO and multiple orthogonal functional readouts in vivo and in vitro\",\n      \"pmids\": [\"38569495\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Patient-derived lymphoblastoid cells carrying compound NDUFS3 missense mutations (c.418C>T/p.R140W and c.595C>T/p.R199W) show decreased NDUFS3 protein levels and impaired complex I assembly, confirming the pathogenic role of these mutations in complex I biogenesis.\",\n      \"method\": \"Next-generation sequencing (MitoExome); Western blot for NDUFS3 protein in patient lymphoblastoid cells; BN-PAGE complex I assembly analysis\",\n      \"journal\": \"Journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — patient-derived cells with protein quantification and assembly analysis, single lab\",\n      \"pmids\": [\"30140060\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"NDUFS3 knockout cancer cells (devoid of complex I) demonstrate that BAY 87-2243 and EVP 4593 are selective complex I inhibitors whose antiproliferative effects are abolished without CI, while metformin's antiproliferative effects are largely CI-independent; molecular docking indicates BAY 87-2243 and EVP 4593 bind the quinone-binding pocket of complex I with conserved amino acid contacts.\",\n      \"method\": \"NDUFS3 CRISPR/KO cancer cell models; cell viability assays; molecular docking to complex I structure; comparative pharmacology\",\n      \"journal\": \"Open biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO combined with pharmacological epistasis and structural docking, single lab\",\n      \"pmids\": [\"36349549\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Transient siRNA-mediated silencing of NDUFS3 in pancreatic cancer cells causes mitochondrial deficit and slower oxidative metabolism, which downregulates RAB7 expression and impairs late endocytic/lysosomal function; this mitochondria-lysosome crosstalk disruption reduces EMT markers (vimentin), decreases viability, migration, and invasiveness.\",\n      \"method\": \"RNAi-mediated NDUFS3 silencing; Seahorse metabolic assays; Western blot; confocal microscopy of mitochondrial network and lysosomes; TEM; wound-healing and transwell invasion assays; colony assays; zymography\",\n      \"journal\": \"Cell communication and signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean knockdown with multiple orthogonal functional readouts linking NDUFS3 to RAB7/lysosomal pathway, single lab\",\n      \"pmids\": [\"40369571\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"NDUFS3 overexpression in melanoma cells promotes oxidative phosphorylation and the pentose phosphate pathway while attenuating glycolysis, producing excess ATP that inhibits AMPK; reduced AMPK activity decreases inhibitory phosphorylation of PRPS1, thereby increasing purine nucleotide biosynthesis and promoting melanoma proliferation.\",\n      \"method\": \"NDUFS3 overexpression and knockdown in melanoma cells; Seahorse OXPHOS/glycolysis assays; AMPK activity assays; PRPS1 phosphorylation by Western blot; purine nucleotide metabolomics; proliferation assays\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal metabolic and signaling assays defining a pathway, single lab\",\n      \"pmids\": [\"40404919\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MAZ transcription factor directly binds the NDUFS3 gene promoter and upregulates NDUFS3 transcription, thereby enhancing mitochondrial metabolism and promoting melanoma proliferation, migration, and invasion.\",\n      \"method\": \"ChIP assay; luciferase reporter assay; MAZ overexpression/knockdown with NDUFS3 expression measurement; metabolic assays; proliferation/migration/invasion assays\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct chromatin binding and transcriptional regulation confirmed by ChIP and reporter assay, single lab\",\n      \"pmids\": [\"39532991\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"In a PINK1B9 Drosophila model of Parkinson's disease, RNAi-mediated downregulation of NDUFS3 (the CI core subunit ortholog) in thoracic muscle exerts a protective effect, associated with reduced oxidative stress and partial restoration of mitochondrial function.\",\n      \"method\": \"MHC-Gal4/UAS PINK1B9 transgenic Drosophila; NDUFS3 RNAi; ROS measurement; mitochondrial function assays; locomotion/behavioral assays\",\n      \"journal\": \"Neuroscience letters\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — Drosophila genetic model with phenotypic readouts but limited biochemical mechanistic follow-up, single lab\",\n      \"pmids\": [\"39102941\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"NDUFS3 overexpression in a rat model of sepsis-induced acute kidney injury inhibits LPS-induced ferroptosis and mitochondrial damage, and this protective effect is abolished by AMPK inhibitor Compound C, placing NDUFS3 upstream of the AMPK pathway in regulating ferroptosis in kidney cells.\",\n      \"method\": \"Hydrodynamic tail-vein injection of NDUFS3 overexpression plasmid in rats; LPS-induced HK-2 cell model; Compound C AMPK inhibition; Western blot; MDA/GSH/iron content; MitoSOX; ATP assay; TEM\",\n      \"journal\": \"International immunopharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — epistasis via pharmacological AMPK inhibition combined with in vivo and in vitro overexpression models, single lab\",\n      \"pmids\": [\"39426231\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NDUFS3 is a non-catalytic core subunit of the Q-module (quinone-binding module) of mitochondrial respiratory complex I that serves as an early nucleation point for stepwise complex I assembly—forming ~100 and ~150 kDa intermediates that subsequently incorporate mitochondrially-encoded subunits—and whose partial loss triggers hierarchical, modular complex I disassembly while exposing TMEM126A as an ND4-module assembly factor; structurally, disease-causing mutations destabilize the protein and promote aggregation, and upstream, SRSF1-mediated splicing and MAZ-driven transcription regulate NDUFS3 levels, while DJ-1 physically interacts with NDUFS3 to protect complex I activity, with downstream consequences including ROS-mediated metabolic reprogramming, AMPK-PRPS1-purine biosynthesis axis regulation, and mitochondria–lysosome crosstalk control.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2004,\n      \"finding\": \"Mutations in NDUFS3 (NADH dehydrogenase iron-sulphur protein 3), the seventh core subunit of mitochondrial complex I, were shown to cause late-onset Leigh syndrome, optic atrophy, and complex I deficiency, establishing NDUFS3 as an essential structural/functional core subunit of complex I whose loss produces severe mitochondrial disease.\",\n      \"method\": \"DHPLC and sequence analysis of NDUFS3 in complex I-deficient patients; biochemical diagnosis on cultured amniocytes\",\n      \"journal\": \"Journal of medical genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genotype-phenotype with biochemical validation of complex I deficiency; replicated in subsequent studies\",\n      \"pmids\": [\"14729820\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Using an inducible NDUFS3-GFP expression system, NDUFS3 was shown to enter early, nucleus-encoded assembly intermediates (~100 and ~150 kDa subcomplexes) of mitochondrial complex I before mitochondrial DNA-encoded subunits are incorporated, defining the entry point of mitochondrially-translated subunits into the growing complex.\",\n      \"method\": \"Inducible NDUFS3-GFP expression in HEK293 cells; blue native PAGE Western blot; differential solubilization; inhibition of mitochondrial translation with reversal experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct stepwise assembly tracking with multiple orthogonal methods and functional reversal experiment in a single study\",\n      \"pmids\": [\"17209039\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Gene silencing of NDUFS3 in isogenic human embryonic kidney cells systematically introduced mitochondrial complex I dysfunction and triggered a metabolic switch to aerobic glycolysis (Warburg effect) in a manner dependent on NDUFS3 protein levels, with sustained free radical (ROS) imbalance required to maintain the glycolytic phenotype.\",\n      \"method\": \"RNAi-mediated gene silencing with graded NDUFS3 suppression; metabolic characterization including oxygen consumption, glycolysis, and ROS measurements in isogenic cell lines\",\n      \"journal\": \"Biology open\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean dose-dependent KD with defined metabolic phenotypes and ROS mechanistic link; single lab\",\n      \"pmids\": [\"23519235\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The double mutant NDUFS3 protein (T145I + R199W) associated with Leigh syndrome showed altered polarity around tryptophan residues, changed fluorescence quenching parameters, altered secondary and tertiary structure, and a significantly higher tendency to aggregate compared to wild-type, as well as loss of a molten globule state at low pH, providing a structural basis for how these mutations disrupt complex I assembly.\",\n      \"method\": \"Recombinant expression and purification in E. coli; steady-state and time-resolved fluorescence spectroscopy; CD spectroscopy; Thioflavin-T and Congo red dye binding for aggregation; thermal and Gdn-HCl unfolding\",\n      \"journal\": \"Biochimie\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1/2 — in vitro biophysical characterization with multiple orthogonal spectroscopic methods; single lab\",\n      \"pmids\": [\"24028823\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"DJ-1 (PARK7 gene product) physically interacts with NDUFS3 in rat testes, and disruption of this interaction by ornidazole treatment reduces NDUFS3 protein levels and complex I activity, linking DJ-1's protective role against oxidative stress to maintenance of NDUFS3 integrity in sperm mitochondria.\",\n      \"method\": \"Co-immunoprecipitation of DJ-1 and NDUFS3 in rat testes; Western blot; complex I activity assay in asthenozoospermic patient sperm and rat model\",\n      \"journal\": \"Mediators of inflammation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single Co-IP plus functional activity assay; single lab with in vivo rat model correlation\",\n      \"pmids\": [\"29849492\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Two missense mutations in NDUFS3 (c.418C>T/p.R140W and c.595C>T/p.R199W) identified by next-generation sequencing in a Leigh syndrome patient caused decreased NDUFS3 protein levels and impaired complex I assembly in patient-derived lymphoblastoid cells.\",\n      \"method\": \"MitoExome next-generation sequencing; Western blot and blue native PAGE of patient lymphoblastoid cells\",\n      \"journal\": \"Journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genotype-function link with direct assessment of complex I assembly in patient cells\",\n      \"pmids\": [\"30140060\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Complete ablation of NDUFS3 allows a small amount of functional complex I to still assemble in diverse mammalian cell types, demonstrating that NDUFS3 is not absolutely required for complex I biogenesis. Gradual reduction of NDUFS3 causes hierarchical, modular complex I disassembly in which the ND4 module remains stable and bound to TMEM126A (OPA7), uncovering TMEM126A as a complex I assembly factor that binds the ND4-module intermediate.\",\n      \"method\": \"NDUFS3 knockout and knockdown in multiple mammalian cell types; blue native PAGE; co-immunoprecipitation; mass spectrometry-based proteomics; functional complex I activity assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (KO, BN-PAGE, Co-IP, MS, activity assay) in diverse cell types; single lab but strong internal validation\",\n      \"pmids\": [\"33882309\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Using NDUFS3 knockout cancer cells devoid of complex I, BAY 87-2243 and EVP 4593 were shown to be selective complex I inhibitors whose antiproliferative effects depend on complex I, whereas metformin's antiproliferative effects were largely independent of complex I. Molecular docking indicated that BAY 87-2243 and EVP 4593 bind in the quinone-binding pocket of complex I, with NDUFS3-containing residues forming part of the interaction network.\",\n      \"method\": \"NDUFS3 knockout cell models; cell viability assays; molecular docking into complex I structure\",\n      \"journal\": \"Open biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO model plus molecular docking; functional selectivity demonstrated, though docking is computational\",\n      \"pmids\": [\"36349549\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The splicing factor SRSF1 binds to constitutive exon 6 of Ndufs3 pre-mRNA and promotes its inclusion; SRSF1 deficiency in mature adipocytes causes impaired Ndufs3 splicing, reduced functional NDUFS3 protein, defective mitochondrial complex I assembly and activity, mitochondrial fragmentation, and impaired thermogenic capacity of brown adipose tissue.\",\n      \"method\": \"Adipocyte-specific SRSF1 knockout mice; single-nucleus RNA sequencing; transmission electron microscopy; RNA pulldown/RIP demonstrating SRSF1 binding to Ndufs3 exon 6; complex I activity assays; thermogenesis measurements\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo KO with snRNA-seq, direct RNA binding demonstrated, complex I assembly and thermogenesis phenotypes; multiple orthogonal methods\",\n      \"pmids\": [\"38569495\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"NDUFS3 overexpression in a sepsis-induced acute kidney injury rat model inhibited LPS-induced ferroptosis and mitochondrial damage; inhibition of AMPK by Compound C abolished this protection, placing NDUFS3 upstream of the AMPK pathway in regulating mitochondrial ROS, ferroptosis markers (MDA, GSH, iron levels), and ATP production in kidney cells.\",\n      \"method\": \"NDUFS3 overexpression in rats (hydrodynamic tail vein injection) and HK-2 cells; AMPK inhibitor (Compound C) epistasis; Western blot; MDA/GSH/iron content; Mitosox ROS; ATP assay; transmission electron microscopy\",\n      \"journal\": \"International immunopharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — gain-of-function with AMPK epistasis in vitro and in vivo; single lab\",\n      \"pmids\": [\"39426231\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In pancreatic cancer cells, transient siRNA-mediated silencing of NDUFS3 caused mitochondrial deficit, reduced oxidative metabolism, and morphological mitochondrial alterations; this mitochondrial impairment led to RAB7 downregulation, impairment of the late endocytic/lysosomal pathway, and reduced cancer cell invasiveness, migration, vimentin levels, and EMT markers, linking NDUFS3-dependent mitochondrial function to mitochondria-lysosome crosstalk and cancer invasive potential.\",\n      \"method\": \"RNAi knockdown of NDUFS3 in pancreatic cancer cells; Seahorse XF assay; transmission electron microscopy; Western blot; confocal microscopy; zymography; wound healing and invasion assays; colony assays\",\n      \"journal\": \"Cell communication and signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods establishing mechanistic pathway from NDUFS3 to RAB7 to lysosomal dysfunction; single lab\",\n      \"pmids\": [\"40369571\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In melanoma, elevated NDUFS3 promotes oxidative phosphorylation and the pentose phosphate pathway while attenuating glycolysis; increased ATP production from NDUFS3-mediated OXPHOS suppresses AMPK activity, which in turn relieves AMPK-mediated phosphorylation/inhibition of PRPS1, thereby stimulating purine nucleotide biosynthesis and melanoma proliferation, defining a NDUFS3–AMPK–PRPS1 signaling axis.\",\n      \"method\": \"NDUFS3 overexpression and knockdown in melanoma cells; metabolic flux analysis (OXPHOS, glycolysis, PPP); AMPK activity measurement; PRPS1 phosphorylation assay; proliferation assays\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — gain- and loss-of-function with defined metabolic and signaling pathway placement; single lab\",\n      \"pmids\": [\"40404919\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MAZ (Myc-associated Zinc-finger Protein) transcriptionally targets and upregulates NDUFS3 expression in melanoma, linking a transcription factor to NDUFS3-driven enhancement of mitochondrial metabolism and malignant progression.\",\n      \"method\": \"Chromatin immunoprecipitation and reporter assays demonstrating MAZ binding to NDUFS3 promoter; gain- and loss-of-function of MAZ with NDUFS3 expression readout; proliferation/migration/invasion assays\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct transcriptional regulation demonstrated by ChIP with functional validation; single lab\",\n      \"pmids\": [\"39532991\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Cryo-EM structure of the human respiratory megacomplex I2III2IV2 revealed the precise subunit assignment and position of NDUFS3 within the Q module of complex I in the context of the full respiratory supercomplex.\",\n      \"method\": \"Cryo-electron microscopy of human respiratory megacomplex I2III2IV2\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution cryo-EM structure with subunit assignment\",\n      \"pmids\": [\"28844695\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NDUFS3 is a non-catalytic core subunit of the Q module of mitochondrial respiratory complex I that enters early nucleus-encoded assembly intermediates before mitochondrial DNA-encoded subunits are incorporated; its loss causes hierarchical, modular complex I disassembly with the ND4 module remaining bound to the assembly factor TMEM126A, while disease-causing mutations destabilize NDUFS3 protein structure and promote aggregation; NDUFS3 levels control a metabolic threshold between OXPHOS and aerobic glycolysis via ROS, participates in a NDUFS3–AMPK–PRPS1 axis regulating purine biosynthesis, is physically protected by DJ-1, transcriptionally regulated by MAZ, and its pre-mRNA splicing is controlled by SRSF1, linking mitochondrial bioenergetics to diverse cellular processes including cancer metabolism, ferroptosis resistance, and brown adipose thermogenesis.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"NDUFS3 is a core subunit of the Q-module (quinone-binding module) of mitochondrial respiratory complex I that serves as an early nucleation scaffold for stepwise complex I biogenesis and whose loss or mutation causes complex I deficiency with broad metabolic consequences. During assembly, NDUFS3 is incorporated into ~100 and ~150 kDa intermediates that precede the addition of mitochondrially-encoded subunits; complete NDUFS3 ablation triggers hierarchical, modular disassembly of complex I while revealing that the ND4 module can persist through TMEM126A stabilization [PMID:17209039, PMID:33882309]. Disease-causing missense mutations in NDUFS3 destabilize the protein, increase its aggregation propensity, impair complex I assembly, and cause Leigh syndrome [PMID:14729820, PMID:24028823]. NDUFS3 levels are controlled transcriptionally by MAZ and post-transcriptionally by SRSF1-dependent splicing, and graded NDUFS3 deficiency shifts cellular metabolism from oxidative phosphorylation toward glycolysis via sustained ROS elevation, while NDUFS3 overexpression promotes OXPHOS, suppresses AMPK, and activates PRPS1-dependent purine biosynthesis [PMID:38569495, PMID:39532991, PMID:23519235, PMID:40404919].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Establishing that NDUFS3 mutations are causative for human complex I deficiency and Leigh syndrome answered whether this particular core subunit is essential for complex I function in vivo.\",\n      \"evidence\": \"Sanger sequencing of patient cohort with biochemical complex I activity assays in patient-derived amniocytes\",\n      \"pmids\": [\"14729820\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis by which specific mutations impair protein function was not determined\",\n        \"Whether mutations affect assembly versus catalytic activity was unclear\"\n      ]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Demonstrating that NDUFS3 enters at least six assembly intermediates and that two early subcomplexes (~100 and ~150 kDa) form before mitochondrially-encoded subunits are incorporated established NDUFS3 as an early nucleation point in complex I biogenesis.\",\n      \"evidence\": \"Inducible NDUFS3-GFP expression in HEK293 cells with BN-PAGE, mitochondrial translation inhibition/recovery\",\n      \"pmids\": [\"17209039\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Identity of all protein partners within each intermediate subcomplex was not fully resolved\",\n        \"Kinetics of NDUFS3 incorporation relative to other Q-module subunits not determined\"\n      ]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Two parallel advances clarified how disease mutations and graded NDUFS3 loss affect cells: biophysical analysis showed Leigh-syndrome mutations destabilize NDUFS3 and promote aggregation, while graded knockdown revealed a dose-dependent switch from oxidative phosphorylation to aerobic glycolysis driven by sustained ROS.\",\n      \"evidence\": \"Recombinant protein biophysics (CD, fluorescence, ThT/Congo red) for mutant characterization; shRNA dose-titration with Seahorse metabolic flux and ROS quantification in HEK293 cells\",\n      \"pmids\": [\"24028823\", \"23519235\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether aggregation occurs in vivo in patient tissues was not tested\",\n        \"The specific ROS species and signaling intermediates driving the glycolytic switch were not identified\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identification of DJ-1 as a physical interactor of NDUFS3 and confirmation that additional compound missense mutations reduce NDUFS3 protein and impair complex I assembly extended the interaction network and genotype–phenotype spectrum of NDUFS3 deficiency.\",\n      \"evidence\": \"Co-immunoprecipitation of DJ-1–NDUFS3 from rat testes with complex I activity assays; BN-PAGE assembly analysis in patient lymphoblastoid cells carrying R140W/R199W mutations\",\n      \"pmids\": [\"29849492\", \"30140060\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"DJ-1–NDUFS3 interaction lacks reciprocal IP validation and structural mapping\",\n        \"Whether DJ-1 binding modulates complex I assembly or only activity is unknown\",\n        \"Functional rescue of patient cells was not performed\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Complete NDUFS3 knockout revealed that complex I undergoes hierarchical, modular disassembly rather than total collapse, and that TMEM126A stabilizes the persisting ND4 module—answering how complex I modules behave when their Q-module scaffold is removed.\",\n      \"evidence\": \"CRISPR/Cas9 NDUFS3 KO in multiple mammalian cell lines with BN-PAGE, mass spectrometry, and co-IP of TMEM126A with ND4 intermediate\",\n      \"pmids\": [\"33882309\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How a small amount of functional complex I assembles without NDUFS3 is mechanistically unexplained\",\n        \"Whether modular disassembly occurs similarly in post-mitotic tissues is untested\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Using NDUFS3-KO cancer cells as a CI-null pharmacological tool demonstrated that BAY 87-2243 and EVP 4593 are CI-dependent antiproliferatives while metformin is largely CI-independent, resolving long-standing target-specificity questions for these drugs.\",\n      \"evidence\": \"NDUFS3 CRISPR-KO cancer cells with comparative viability assays and molecular docking to the quinone-binding pocket\",\n      \"pmids\": [\"36349549\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"In vivo validation of CI-selectivity was not performed\",\n        \"Direct binding of these compounds to NDUFS3-containing Q-module was not biochemically confirmed\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Upstream regulation of NDUFS3 was defined at two levels: SRSF1 binds and promotes inclusion of constitutive exon 6 of Ndufs3 pre-mRNA ensuring functional protein production, and MAZ transcription factor directly activates the NDUFS3 promoter—establishing the first transcriptional and splicing regulators of this complex I subunit.\",\n      \"evidence\": \"Adipocyte-specific SRSF1-KO mice with RNA-binding/splicing assays and respiratory chain analysis; ChIP and luciferase reporter assays for MAZ on NDUFS3 promoter in melanoma cells\",\n      \"pmids\": [\"38569495\", \"39532991\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether MAZ regulation of NDUFS3 operates beyond melanoma contexts is untested\",\n        \"SRSF1-dependent exon 6 inclusion mechanism is characterized in adipocytes only; generality is unclear\",\n        \"Other transcription factors or splicing regulators of NDUFS3 remain unidentified\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Downstream consequences of NDUFS3 levels were extended beyond the Warburg shift: NDUFS3 overexpression activates OXPHOS/PPP and suppresses AMPK, de-repressing PRPS1 to fuel purine biosynthesis, while NDUFS3 silencing impairs RAB7-dependent late endocytic/lysosomal function, linking complex I status to nucleotide metabolism and organelle crosstalk.\",\n      \"evidence\": \"NDUFS3 overexpression/knockdown in melanoma cells with Seahorse, AMPK activity, PRPS1 phosphorylation, and purine metabolomics; siRNA knockdown in pancreatic cancer cells with lysosomal and endocytic markers, EMT markers, and functional assays\",\n      \"pmids\": [\"40404919\", \"40369571\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"The AMPK-PRPS1 axis has been shown only in melanoma; generality is uncertain\",\n        \"Mechanism linking NDUFS3 loss to RAB7 downregulation is correlative\",\n        \"In vivo validation of the mitochondria–lysosome crosstalk axis is lacking\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key open questions include the structural basis of NDUFS3's scaffolding role within the Q-module at atomic resolution, how residual complex I assembles without NDUFS3, and whether the AMPK–PRPS1 and RAB7–lysosome pathways downstream of NDUFS3 operate across diverse tissues and disease states.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No high-resolution structure of NDUFS3 within a human assembly intermediate exists\",\n        \"Mechanism for NDUFS3-independent residual complex I assembly is unknown\",\n        \"Tissue-specific downstream signaling consequences of NDUFS3 deficiency are uncharacterized\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\n        \"term_id\": \"GO:0005198\",\n        \"supporting_discovery_ids\": [0, 1, 3]\n      }\n    ],\n    \"localization\": [\n      {\n        \"term_id\": \"GO:0005739\",\n        \"supporting_discovery_ids\": [0, 1, 2, 3, 4, 6]\n      }\n    ],\n    \"pathway\": [\n      {\n        \"term_id\": \"R-HSA-1430728\",\n        \"supporting_discovery_ids\": [0, 1, 4, 10]\n      },\n      {\n        \"term_id\": \"R-HSA-1852241\",\n        \"supporting_discovery_ids\": [0, 1, 6]\n      },\n      {\n        \"term_id\": \"R-HSA-1643685\",\n        \"supporting_discovery_ids\": [2, 3, 7]\n      }\n    ],\n    \"complexes\": [\n      \"Mitochondrial complex I (NADH:ubiquinone oxidoreductase)\",\n      \"Complex I Q-module\"\n    ],\n    \"partners\": [\n      \"TMEM126A\",\n      \"DJ-1\",\n      \"SRSF1\",\n      \"MAZ\",\n      \"AMPK\",\n      \"PRPS1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"NDUFS3 is a nuclear-encoded core subunit of the Q module of mitochondrial respiratory complex I that is essential for proper complex I assembly, oxidative phosphorylation, and metabolic homeostasis. It enters early assembly intermediates (~100–150 kDa subcomplexes) before mitochondrial DNA-encoded subunits are incorporated, and its gradual loss triggers hierarchical, modular complex I disassembly with the ND4 module remaining stably bound to the assembly factor TMEM126A [PMID:17209039, PMID:33882309]. NDUFS3 levels control a metabolic threshold between OXPHOS and aerobic glycolysis via ROS signaling, and elevated NDUFS3-driven ATP production suppresses AMPK to relieve inhibition of PRPS1, thereby stimulating purine biosynthesis in cancer cells [PMID:23519235, PMID:40404919]. Biallelic mutations in NDUFS3 cause mitochondrial complex I deficiency presenting as Leigh syndrome [PMID:14729820, PMID:30140060].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Identification of NDUFS3 mutations in patients with Leigh syndrome and complex I deficiency established NDUFS3 as a disease-causing core subunit of complex I, answering whether this subunit is individually essential for human bioenergetics.\",\n      \"evidence\": \"DHPLC and sequencing of NDUFS3 in complex I–deficient patients with biochemical validation in cultured amniocytes\",\n      \"pmids\": [\"14729820\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise structural consequences of patient mutations on assembled complex I were unknown\", \"Genotype–phenotype correlations across different NDUFS3 mutations not established\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Tracking NDUFS3-GFP incorporation into assembly intermediates revealed that NDUFS3 enters early nucleus-encoded subcomplexes before mitochondrially-encoded subunits join, defining its temporal position in the complex I assembly pathway.\",\n      \"evidence\": \"Inducible NDUFS3-GFP in HEK293 cells with BN-PAGE, differential solubilization, and mitochondrial translation inhibition/reversal\",\n      \"pmids\": [\"17209039\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of direct binding partners within the early assembly intermediate was not resolved\", \"Whether NDUFS3 acts as a scaffold or is passively incorporated remained unclear\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Biophysical characterization of disease-associated NDUFS3 double mutant protein and dose-dependent knockdown studies together revealed that mutations destabilize protein structure and promote aggregation, while graded NDUFS3 loss triggers a ROS-dependent metabolic switch to aerobic glycolysis, providing both structural and metabolic mechanisms for complex I dysfunction.\",\n      \"evidence\": \"Recombinant mutant protein spectroscopy and aggregation assays; RNAi dose-response in HEK cells with metabolic profiling\",\n      \"pmids\": [\"24028823\", \"23519235\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural studies used isolated recombinant protein, not the assembled complex\", \"ROS-to-glycolysis switch mechanism lacked identification of specific ROS sensor or signaling intermediates\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Cryo-EM structure of the human respiratory megacomplex I₂III₂IV₂ resolved the precise position of NDUFS3 within the Q module, providing atomic-level context for its role in ubiquinone binding and electron transfer.\",\n      \"evidence\": \"Cryo-electron microscopy of purified human respiratory megacomplex\",\n      \"pmids\": [\"28844695\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Dynamic conformational changes of NDUFS3 during catalysis not captured\", \"Structure does not resolve assembly intermediates containing NDUFS3\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"DJ-1 was identified as a physical interactor that protects NDUFS3 stability, and additional Leigh syndrome mutations were biochemically validated, expanding understanding of NDUFS3 regulation and disease mechanism.\",\n      \"evidence\": \"Co-IP of DJ-1/NDUFS3 in rat testes with complex I activity assays; MitoExome sequencing with BN-PAGE in patient lymphoblastoid cells\",\n      \"pmids\": [\"29849492\", \"30140060\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"DJ-1–NDUFS3 interaction demonstrated by single Co-IP without reciprocal validation or structural mapping\", \"Whether DJ-1 acts as a chaperone or stabilizer of NDUFS3 is unresolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Complete NDUFS3 ablation showed that a small amount of functional complex I can still assemble without it, overturning the assumption of absolute requirement, and revealed hierarchical modular disassembly with the ND4 module persisting bound to the newly identified assembly factor TMEM126A.\",\n      \"evidence\": \"NDUFS3 KO and KD in multiple mammalian cell types; BN-PAGE, Co-IP, quantitative proteomics, and activity assays\",\n      \"pmids\": [\"33882309\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How a residual complex I assembles without NDUFS3 is mechanistically unexplained\", \"Whether TMEM126A-ND4 module persistence has functional consequences beyond assembly stalling is unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"NDUFS3-knockout cancer cells served as a genetic tool to demonstrate that BAY 87-2243 and EVP 4593 are selective complex I inhibitors, and molecular docking placed NDUFS3 residues within the quinone-binding pocket interaction network.\",\n      \"evidence\": \"NDUFS3 KO cell viability assays combined with molecular docking into complex I structure\",\n      \"pmids\": [\"36349549\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Drug–NDUFS3 contacts are computational; no mutagenesis or binding data confirm direct interaction\", \"Pharmacological relevance in vivo not demonstrated\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Multiple studies converged to reveal upstream regulatory mechanisms and downstream signaling of NDUFS3: SRSF1 controls Ndufs3 pre-mRNA splicing required for brown adipose thermogenesis, MAZ transcriptionally upregulates NDUFS3 in melanoma, and NDUFS3 overexpression protects against sepsis-induced ferroptosis via the AMPK pathway.\",\n      \"evidence\": \"Adipocyte-specific SRSF1 KO mice with RNA binding assays and thermogenesis measurements; ChIP and reporter assays for MAZ on NDUFS3 promoter; NDUFS3 overexpression with AMPK inhibitor epistasis in sepsis-AKI models\",\n      \"pmids\": [\"38569495\", \"39532991\", \"39426231\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether SRSF1-mediated splicing control is specific to Ndufs3 or affects other complex I subunits coordinately is unknown\", \"MAZ–NDUFS3 transcriptional axis demonstrated only in melanoma\", \"AMPK-dependent ferroptosis protection by NDUFS3 lacks identification of the direct AMPK-activating mechanism\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"NDUFS3 was placed at the center of cancer metabolic reprogramming: its loss in pancreatic cancer impairs the endolysosomal pathway via RAB7 downregulation to reduce invasiveness, while its elevation in melanoma drives a NDUFS3–AMPK–PRPS1 axis coupling OXPHOS output to purine biosynthesis.\",\n      \"evidence\": \"NDUFS3 KD in pancreatic cancer cells with Seahorse, EM, invasion assays; NDUFS3 gain/loss-of-function in melanoma with metabolic flux and PRPS1 phosphorylation analysis\",\n      \"pmids\": [\"40369571\", \"40404919\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"RAB7 downregulation mechanism downstream of mitochondrial impairment is not defined\", \"NDUFS3–AMPK–PRPS1 axis not validated in non-melanoma contexts\", \"Whether NDUFS3 dosage effects on cancer metabolism reflect complex I activity versus moonlighting functions is unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unknown whether NDUFS3 has functional roles independent of complex I, how residual complex I assembles in its complete absence, and whether the metabolic signaling axes identified in individual cancer types generalize across tissues.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No moonlighting function established or excluded\", \"Structural basis of residual complex I assembly without NDUFS3 unresolved\", \"Tissue-generalizability of NDUFS3–AMPK–PRPS1 axis untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [1, 6, 13]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [1, 6, 8, 13]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 2, 6, 8, 11]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [0, 5, 10, 11]}\n    ],\n    \"complexes\": [\n      \"Mitochondrial complex I (NADH:ubiquinone oxidoreductase)\",\n      \"Respiratory megacomplex I2III2IV2\"\n    ],\n    \"partners\": [\n      \"TMEM126A\",\n      \"DJ-1\",\n      \"SRSF1\",\n      \"PRPS1\",\n      \"MAZ\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}