{"gene":"NDUFS1","run_date":"2026-04-29T11:37:56","timeline":{"discoveries":[{"year":2001,"finding":"Point mutations and large-scale deletions in the NDUFS1 gene cause mitochondrial complex I deficiency, establishing NDUFS1 as a nuclear-encoded structural subunit required for complex I function in humans.","method":"dHPLC and direct sequencing of patient cDNA from cultured fibroblasts; identification of five point mutations (del222, D252G, M707V, R241W, R557X) and one large-scale deletion","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 — multiple independent patient mutations with biochemical validation, replicated across subsequent studies","pmids":["11349233"],"is_preprint":false},{"year":2006,"finding":"A Q522K missense mutation in NDUFS1 (C1564A in coding sequence) reduces mature complex I assembly and activity, causes mitochondrial ROS (H2O2 and superoxide) accumulation, decreases glutathione content, and impairs mitochondrial membrane potential; treatment with dibutyryl-cAMP partially restores complex I activity and eliminates ROS.","method":"Patient fibroblast biochemical assays: NADH-ubiquinone oxidoreductase activity, ROS measurement (MitoSOX/H2DCFDA), glutathione assay, mitochondrial membrane potential (JC-1), glutathione peroxidase activity","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal biochemical methods in patient-derived cells with pharmacological rescue","pmids":["16478720"],"is_preprint":false},{"year":2010,"finding":"NDUFS1 mutations (premature stop, amino acid substitutions, single amino acid deletion) reduce complex I amount, activity, and disrupt complex I assembly in patient fibroblasts, indicating NDUFS1 is required for proper complex I assembly.","method":"Patient fibroblast biochemical analysis: complex I activity assays, Blue Native PAGE for assembly analysis","journal":"Molecular genetics and metabolism","confidence":"High","confidence_rationale":"Tier 2 — multiple patient lines with assembly analysis, replicated across labs","pmids":["20382551"],"is_preprint":false},{"year":2011,"finding":"A homozygous T595A mutation in NDUFS1 causes complex I deficiency and complex I dysfunction in a Neurospora crassa insertional mutagenesis model and in patient fibroblasts grown in galactose, confirming NDUFS1 function is conserved and required for complex I activity.","method":"Neurospora crassa insertional mutagenesis model; patient fibroblast biochemical assays in galactose medium; muscle biopsy complex I enzyme activity","journal":"Neurogenetics","confidence":"High","confidence_rationale":"Tier 1–2 — genetic model organism validation plus patient biochemistry","pmids":["21203893"],"is_preprint":false},{"year":2013,"finding":"Caspase-3 cleaves the NDUFS1 subunit of complex I downstream of MOMP during TNFα-induced apoptosis; this cleavage disrupts complex I function, causing ROS production that triggers lysosomal membrane permeabilization (LMP) and cathepsin release. A caspase-non-cleavable NDUFS1 mutant prevents LMP and partially blocks apoptosis.","method":"Cell biology: caspase inhibitors, Bax/Bak/Apaf-1/caspase-3/7-deficient cells; caspase non-cleavable NDUFS1 mutant overexpression; MitoQ antioxidant rescue; LMP and cathepsin release assays","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1–2 — mutagenesis of cleavage site, multiple genetic knockouts, pharmacological rescue with orthogonal readouts","pmids":["23788428"],"is_preprint":false},{"year":2019,"finding":"MDM2 directly binds and sequesters NDUFS1 via its amino-terminal region, preventing NDUFS1 mitochondrial localization, causing complex I and supercomplex destabilization, decreased mitochondrial respiration, oxidative stress, and commitment to the mitochondrial apoptosis pathway in a p53-independent manner.","method":"Co-IP, pulldown, organellar fractionation, supercomplex BN-PAGE, oxygen consumption assays, Drosophila and murine transgenic models; MDM2 N-terminal domain sufficient for binding and phenotype","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1–2 — direct binding demonstrated by pulldown, functional validation in multiple in vitro and in vivo models with orthogonal readouts","pmids":["30879903"],"is_preprint":false},{"year":2019,"finding":"Biallelic NDUFS1 mutations destabilize the entire N-module of complex I and disrupt electron transfer between two iron-sulfur clusters, leading to metabolic reprogramming including inhibitory feedback on the TCA cycle and altered glutathione levels indicative of ROS stress.","method":"Proteome and metabolome profiling of patient-derived cells; quantitative mass spectrometry; metabolomics","journal":"Cells","confidence":"High","confidence_rationale":"Tier 2 — two orthogonal omics approaches in patient cells, domain-level mechanistic conclusion","pmids":["31557978"],"is_preprint":false},{"year":2020,"finding":"AKAP1 interacts with NDUFS1 and is required for translocation of NDUFS1 from the cytosol to mitochondria; AKAP1 deficiency prevents mitochondrial NDUFS1 import, inhibits complex I activity, reduces ATP production, and increases mitochondrial ROS-related apoptosis in cardiomyocytes.","method":"Co-immunoprecipitation and mass spectrometry; subcellular fractionation; Akap1-KO mouse model; AAV9-Akap1 cardiac overexpression rescue; complex I activity assays; echocardiography","journal":"Diabetologia","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP/MS, KO mouse with defined phenotype, genetic rescue with NDUFS1 translocation restoration","pmids":["32072193"],"is_preprint":false},{"year":2021,"finding":"NDUFS1 knockdown in cardiomyocytes decreases mitochondrial membrane potential, mitochondrial DNA content, and mitochondrial mass while increasing mitochondrial ROS production; NDUFS1 overexpression reverses Ang II-induced hypertrophic cardiomyocyte dysfunction.","method":"In vitro NDUFS1 knockdown/overexpression in rat cardiomyocytes; JC-1 mitochondrial membrane potential assay; MitoSOX ROS measurement; mitochondrial DNA quantification; TAC mouse model","journal":"Oxidative medicine and cellular longevity","confidence":"Medium","confidence_rationale":"Tier 2 — KD/OE with multiple mitochondrial phenotypic readouts, in vivo model, but single lab","pmids":["33763166"],"is_preprint":false},{"year":2022,"finding":"Ndufs1 overexpression in cardiomyocytes ameliorates complex I activity reduction and impaired mitochondrial respiratory function caused by myocardial infarction/hypoxia, reduces ROS production, and decreases ROS-related apoptosis.","method":"Cardiac-specific Ndufs1 overexpression in MI mouse model; complex I activity assay; Seahorse mitochondrial respiration; ROS measurement; apoptosis assays; echocardiography","journal":"Experimental & molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 — gain-of-function with defined mechanistic phenotype in vivo and in vitro, single lab","pmids":["35817848"],"is_preprint":false},{"year":2022,"finding":"Glutathionylation of NDUFS1 (induced by disulfiram) inhibits complex I activity and increases ROS production during reverse electron transfer from the ubiquinone pool; reducing agents reverse NDUFS1 glutathionylation, restore complex I activity, and decrease ROS.","method":"Immunocapture of complex I; disulfiram-induced glutathionylation; complex I inhibitors (rotenone, S1QEL); ROS measurement with Amplex Red; reducing agent rescue; liver mitochondria","journal":"Antioxidants (Basel, Switzerland)","confidence":"High","confidence_rationale":"Tier 1 — in vitro biochemistry with immunocapture, site-specific PTM, pharmacological manipulation, and multiple inhibitor controls","pmids":["36290766"],"is_preprint":false},{"year":2022,"finding":"Mutations at 17 sites in NDUFS1 (modeled in E. coli homolog nuoG) many mapping to subunit interfaces disrupt complex I assembly; compound heterozygous mutations were analyzed to identify which is more deleterious; some mutations cause reduced NADH oxidase activity and assembly defects.","method":"Bacterial model system (E. coli nuoG); membrane vesicle NADH oxidase activity; time-delayed expression; co-immunoprecipitation for assembly; alanine mutagenesis","journal":"Mitochondrion","confidence":"High","confidence_rationale":"Tier 1 — systematic mutagenesis with multiple in vitro assays including assembly and activity in reconstituted bacterial system","pmids":["36462614"],"is_preprint":false},{"year":2023,"finding":"PHB2 directly interacts with NDUFS1 in mitochondria and facilitates NDUFS1 binding to NDUFV1, stabilizing complex I and enhancing its activity; PHB2 knockdown reduces complex I activity and OXPHOS levels.","method":"Co-immunoprecipitation and mass spectrometry; confocal co-localization; complex I activity assay; PHB2 KD/OE with NDUFS1 rescue","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2–3 — Co-IP/MS with functional rescue, single lab","pmids":["36658121"],"is_preprint":false},{"year":2023,"finding":"NDUFS1 reduction activates an mROS–HIF1α–FBLN5 signaling pathway promoting gastric cancer progression; NDUFS1 overexpression inhibits GC cell proliferation, migration, and invasion in vitro and in vivo.","method":"KD/OE of NDUFS1 in GC cells; confocal localization; mROS measurement; HIF1α pathway analysis; mouse xenograft","journal":"British journal of cancer","confidence":"Medium","confidence_rationale":"Tier 2 — KD/OE with pathway placement, in vivo validation, but single lab","pmids":["37644092"],"is_preprint":false},{"year":2024,"finding":"Agrimol B causes caspase-3-mediated degradation of NDUFS1, leading to mitochondrial ROS accumulation and cytotoxic autophagy arrest in hepatocellular carcinoma cells; NDUFS1 overexpression partially rescues ROS overproduction and autophagosome accumulation.","method":"NDUFS1 protein level assay; caspase-3 activity assay; ROS measurement; autophagosome detection; NDUFS1 overexpression rescue; HCC xenograft PDX model","journal":"Free radical biology & medicine","confidence":"Medium","confidence_rationale":"Tier 2 — mechanistic pathway placement with rescue experiment, single lab","pmids":["38697493"],"is_preprint":false},{"year":2024,"finding":"RNF43 E3 ubiquitin ligase interacts with NDUFS1 and promotes its ubiquitination and degradation, thereby reducing oxidative phosphorylation; loss of RNF43 increases NDUFS1 levels and OXPHOS activity in endometrial stromal cells.","method":"Co-immunoprecipitation; ubiquitination assay; RNF43/NDUFS1 KD/OE; OXPHOS measurement; endometriosis rat model","journal":"Journal of cellular physiology","confidence":"Medium","confidence_rationale":"Tier 2–3 — Co-IP with ubiquitination assay and in vivo model, single lab","pmids":["38988031"],"is_preprint":false},{"year":2025,"finding":"SIRT3-dependent deacetylation of NDUFS1 (on the N-module catalytic subunit) by berberine (which directly binds and activates SIRT3) leads to dissociation of mitochondrial complex I, reducing oxidative phosphorylation and improving glucose and lipid metabolism in hepatocytes.","method":"SIRT3 activity assays; acetylation analysis of NDUFS1; berberine binding to SIRT3 (molecular docking and biochemical); complex I dissociation assays; metabolic profiling in hepatocytes; oral administration in vivo","journal":"Science China. Life sciences","confidence":"High","confidence_rationale":"Tier 1–2 — identified PTM writer (SIRT3), substrate (NDUFS1 acetylation), direct drug-protein binding, and functional consequence with in vivo validation","pmids":["40493314"],"is_preprint":false},{"year":2025,"finding":"PCBP2 binds NDUFS1 mRNA and stabilizes/promotes NDUFS1 expression; NDUFS1 in turn activates NRF2 by enhancing NRF2 nuclear translocation, inhibiting ferroptosis in cardiomyocytes during myocardial infarction.","method":"RNA-immunoprecipitation (RIP); RNA-protein pulldown; PCBP2/NDUFS1 OE; NRF2 nuclear translocation assay; ferroptosis markers; LAD ligation MI mouse model","journal":"Molecular immunology","confidence":"Medium","confidence_rationale":"Tier 2–3 — RIP and pulldown for RNA-binding, pathway placement via NRF2 translocation, in vivo model, single lab","pmids":["40784311"],"is_preprint":false},{"year":2025,"finding":"Sorafenib-induced ER stress activates PERK–eIF2α–ATF4–ATF3 signaling, and ATF3 negatively regulates NDUFS1 expression, causing mitochondrial dysfunction; ATF3 silencing restores NDUFS1 levels and partially rescues mitochondrial function.","method":"Transcriptomic and proteomic profiling; Western blot; ATF3 siRNA knockdown; RT-PCR; ER stress inhibitor GSK2606414; H9C2 cells and rat in vivo model","journal":"Frontiers in pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 — omics + siRNA rescue with mechanistic pathway placement, single lab","pmids":["40880646"],"is_preprint":false},{"year":2025,"finding":"Caspase-3 cleaves NDUFS1 at D255 in response to trichothecene mycotoxins (DON, T-2 toxin), disrupting electron transport and amplifying mitochondrial ROS; mutation of the cleavage site (D255A) attenuates this process.","method":"In vivo and in vitro trichothecene exposure models; caspase-3 inhibition/knockdown; D255A caspase non-cleavable NDUFS1 mutant; ROS and mitochondrial damage assays","journal":"Free radical biology & medicine","confidence":"High","confidence_rationale":"Tier 1 — site-directed mutagenesis of caspase cleavage site with functional rescue, in vivo and in vitro validation","pmids":["41422996"],"is_preprint":false},{"year":2025,"finding":"NDUFS1 promotes alveolar fluid clearance by supporting mitochondrial complex I activity and NAD+ production; NDUFS1 deficiency reduces ENaCα expression through impaired NAD+ generation and increased ROS; NAD+ supplementation via olaparib rescues ENaCα levels and fluid clearance.","method":"NDUFS1 KD in alveolar epithelial cells; complex I activity assay; NAD+ measurement; ENaCα expression; Olaparib (NAD+ supplementation) rescue; paraquat/LPS ALI mouse model","journal":"International journal of medical sciences","confidence":"Medium","confidence_rationale":"Tier 2 — KD with mechanistic pathway (NDUFS1→NAD+→ENaCα), pharmacological rescue, in vivo model, single lab","pmids":["40860777"],"is_preprint":false},{"year":2026,"finding":"GL-V9 binds the MDM2 amino-terminal domain (aa 1–101) and acts as a molecular glue facilitating MDM2–NDUFS1 interaction in the cytoplasm, thereby preventing NDUFS1 mitochondrial localization, inhibiting complex I formation, disrupting mitochondrial homeostasis, and activating OMA1–DELE1–ISR-triggered apoptosis in a p53-independent manner.","method":"GST-pulldown; CETSA; SPR; molecular docking; amino acid mutations in MDM2; immunofluorescence; mitochondrial membrane potential; ATP; OCR; OMA1-DELE1 pathway assays","journal":"Journal of advanced research","confidence":"High","confidence_rationale":"Tier 1–2 — direct binding confirmed by multiple orthogonal methods (SPR, CETSA, GST-pulldown, mutagenesis), mechanistic pathway placement","pmids":["41951044"],"is_preprint":false}],"current_model":"NDUFS1 is the 75 kDa Fe-S core subunit of mitochondrial complex I (NADH:ubiquinone oxidoreductase) that houses iron-sulfur clusters essential for electron transfer within the N-module; its mitochondrial localization (facilitated by AKAP1 and opposed by MDM2 sequestration) is required for complex I assembly and OXPHOS activity, and it is subject to regulatory post-translational modifications including caspase-3 cleavage (amplifying apoptotic ROS), SIRT3-dependent deacetylation (dissociating complex I), and glutathionylation (increasing reverse-electron-transfer ROS), with loss-of-function causing complex I deficiency, supercomplex destabilization, mitochondrial ROS accumulation, and downstream activation of apoptotic and inflammatory pathways."},"narrative":{"teleology":[{"year":2001,"claim":"Establishing NDUFS1 as a disease gene: before this work, the genetic basis of many complex I deficiency cases was unknown; identification of multiple point mutations and deletions in NDUFS1 in patients proved it is a nuclear-encoded subunit required for complex I function and that its loss causes Mendelian mitochondrial disease.","evidence":"dHPLC and direct sequencing of patient fibroblast cDNA identifying five point mutations and one large deletion","pmids":["11349233"],"confidence":"High","gaps":["Precise structural consequences of individual mutations on iron-sulfur cluster coordination were not resolved","No systematic genotype-phenotype correlation established"]},{"year":2006,"claim":"Linking NDUFS1 mutation to ROS overproduction: beyond reduced activity, the Q522K mutation demonstrated that NDUFS1 dysfunction causes mitochondrial superoxide and H₂O₂ accumulation, glutathione depletion, and membrane potential loss, establishing NDUFS1 as a critical gatekeeper of mitochondrial redox homeostasis.","evidence":"Patient fibroblast assays using MitoSOX, H2DCFDA, JC-1, glutathione quantification, and cAMP-mediated pharmacological rescue","pmids":["16478720"],"confidence":"High","gaps":["Mechanism by which dibutyryl-cAMP restores complex I activity was not defined","Whether ROS is cause or consequence of membrane potential loss was not resolved"]},{"year":2010,"claim":"Defining NDUFS1's role in complex I assembly: Blue Native PAGE of patient fibroblasts demonstrated that NDUFS1 mutations impair not just catalytic activity but the physical assembly of the holoenzyme, establishing it as an assembly-essential core subunit.","evidence":"BN-PAGE and complex I activity assays across multiple patient fibroblast lines","pmids":["20382551"],"confidence":"High","gaps":["Which assembly intermediate is stalled was not identified","Whether chaperones are involved in NDUFS1 incorporation was unknown"]},{"year":2013,"claim":"Identifying NDUFS1 as a caspase-3 substrate that amplifies apoptosis: it was unknown how mitochondrial ROS bursts are triggered downstream of MOMP; this work showed caspase-3 cleaves NDUFS1, disrupting complex I and generating ROS that triggers lysosomal membrane permeabilization, thereby coupling intrinsic apoptosis to lysosomal cell death.","evidence":"Caspase non-cleavable NDUFS1 mutant expression; caspase-3/7 and Bax/Bak KO cells; MitoQ rescue; LMP and cathepsin release assays","pmids":["23788428"],"confidence":"High","gaps":["Exact cleavage site was mapped but full cleavage fragment characterization was incomplete","Whether other respiratory chain subunits are also cleaved was not addressed"]},{"year":2019,"claim":"Discovering MDM2 as a cytoplasmic sequestrator of NDUFS1: this revealed a p53-independent, non-canonical role for MDM2 in which its N-terminal domain directly binds NDUFS1, prevents mitochondrial localization, and destabilizes complex I and supercomplexes, linking oncogene biology to OXPHOS regulation.","evidence":"Co-IP, GST-pulldown, BN-PAGE supercomplex analysis, oxygen consumption; Drosophila and murine transgenic models","pmids":["30879903"],"confidence":"High","gaps":["Whether MDM2 regulation of NDUFS1 is constitutive or signal-dependent was not resolved","Stoichiometry of MDM2–NDUFS1 interaction in normal physiology unknown"]},{"year":2019,"claim":"Mapping NDUFS1 deficiency to N-module destabilization and metabolic rewiring: proteomics and metabolomics of patient cells showed that biallelic mutations specifically destabilize the entire N-module and disrupt electron transfer between iron-sulfur clusters, with secondary metabolic consequences including TCA cycle inhibition and glutathione depletion.","evidence":"Quantitative mass spectrometry proteomics and metabolomics in patient-derived cells","pmids":["31557978"],"confidence":"High","gaps":["Which specific iron-sulfur cluster pair is disrupted was inferred but not directly measured by EPR","Contribution of individual metabolic changes to pathology not dissected"]},{"year":2020,"claim":"Identifying AKAP1 as required for NDUFS1 mitochondrial import: it was unclear how the nuclear-encoded NDUFS1 is delivered to mitochondria; AKAP1 was shown to physically interact with NDUFS1 and promote its translocation, with AKAP1 deficiency phenocopying NDUFS1 loss in cardiomyocytes.","evidence":"Reciprocal Co-IP/MS; Akap1-KO mouse; AAV9-Akap1 cardiac rescue restoring NDUFS1 mitochondrial localization and complex I activity","pmids":["32072193"],"confidence":"High","gaps":["Whether AKAP1 acts as a chaperone, scaffold, or import receptor was not distinguished","Whether AKAP1 facilitates import of other complex I subunits is unknown"]},{"year":2022,"claim":"Demonstrating glutathionylation as a reversible regulatory switch on NDUFS1: this established that NDUFS1 glutathionylation specifically inhibits complex I and increases ROS production during reverse electron transfer, providing a redox-sensitive post-translational control mechanism distinct from caspase cleavage.","evidence":"Immunocaptured complex I; disulfiram-induced glutathionylation; rotenone and S1QEL controls; Amplex Red ROS measurement; reducing agent reversal in liver mitochondria","pmids":["36290766"],"confidence":"High","gaps":["Specific cysteine residue(s) modified were not identified","Physiological stimuli triggering NDUFS1 glutathionylation in vivo not established"]},{"year":2022,"claim":"Systematic mapping of disease-relevant residues at subunit interfaces: modeling 17 patient mutations in the bacterial homolog nuoG revealed that many critical residues lie at subunit interfaces and disrupt assembly rather than catalysis per se, refining the structural basis of NDUFS1-linked complex I deficiency.","evidence":"E. coli nuoG systematic alanine mutagenesis; membrane vesicle NADH oxidase activity; co-IP assembly analysis; time-delayed expression","pmids":["36462614"],"confidence":"High","gaps":["Bacterial system lacks eukaryotic supernumerary subunits, so interface effects may differ in human complex I","No human structural validation of interface disruption"]},{"year":2024,"claim":"Identifying RNF43 as a ubiquitin ligase targeting NDUFS1 for proteasomal degradation: this added ubiquitination to the regulatory repertoire controlling NDUFS1 protein levels and thereby OXPHOS capacity, linking Wnt pathway components to mitochondrial metabolism.","evidence":"Co-IP; ubiquitination assay; RNF43/NDUFS1 KD/OE; OXPHOS measurement; endometriosis rat model","pmids":["38988031"],"confidence":"Medium","gaps":["Specific ubiquitinated lysine residues on NDUFS1 not mapped","Whether RNF43 regulation is tissue-specific is unknown","Not independently replicated"]},{"year":2025,"claim":"Defining the caspase-3 cleavage site at D255 and confirming its apoptosis-amplifying role across toxic insults: site-directed D255A mutagenesis proved that this single cleavage event is the primary mechanism by which caspase-3 disrupts complex I electron transport and amplifies mitochondrial ROS during apoptosis.","evidence":"D255A non-cleavable mutant; caspase-3 inhibition/KD; ROS and mitochondrial damage assays in trichothecene-exposed models in vivo and in vitro","pmids":["41422996"],"confidence":"High","gaps":["Whether D255 cleavage also occurs in non-apoptotic caspase activation contexts is unknown","Fate of cleavage fragments not fully characterized"]},{"year":2025,"claim":"Revealing SIRT3-dependent deacetylation of NDUFS1 as a mechanism for regulated complex I disassembly: berberine-activated SIRT3 deacetylates NDUFS1, causing complex I dissociation and reduced OXPHOS, demonstrating that reversible acetylation controls complex I integrity and metabolic flux.","evidence":"SIRT3 activity assays; NDUFS1 acetylation analysis; berberine–SIRT3 binding (SPR, docking); complex I dissociation; hepatocyte metabolic profiling; in vivo administration","pmids":["40493314"],"confidence":"High","gaps":["Specific acetylated lysine residues on NDUFS1 targeted by SIRT3 not identified","Whether deacetylation-induced disassembly is reversible upon SIRT3 inhibition not tested"]},{"year":2025,"claim":"Establishing GL-V9 as a molecular glue enhancing MDM2–NDUFS1 interaction: this pharmacological study confirmed the MDM2-NDUFS1 axis as druggable and showed that enforced cytoplasmic sequestration of NDUFS1 activates the OMA1–DELE1 integrated stress response, mapping a complete pathway from NDUFS1 depletion to apoptosis.","evidence":"SPR, CETSA, GST-pulldown, MDM2 mutagenesis, immunofluorescence, mitochondrial functional assays, OMA1-DELE1 pathway readouts","pmids":["41951044"],"confidence":"High","gaps":["Whether OMA1–DELE1 activation is specific to NDUFS1 loss or general complex I dysfunction not distinguished","In vivo therapeutic efficacy and toxicity not fully assessed"]},{"year":null,"claim":"Key unresolved questions include: the precise acetylation and glutathionylation sites on NDUFS1, how NDUFS1 import is coordinated with other N-module subunit assembly, whether the caspase-3 cleavage at D255 participates in non-apoptotic signaling, and the structural basis by which NDUFS1 post-translational modifications alter iron-sulfur cluster function.","evidence":"","pmids":[],"confidence":"Low","gaps":["No cryo-EM or crystal structure of modified NDUFS1 in context of human complex I","Acetylation and glutathionylation sites not mapped at single-residue resolution","Relative contributions of transcriptional versus post-translational regulation in different tissues unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016491","term_label":"oxidoreductase activity","supporting_discovery_ids":[0,1,2,6,10,11]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[2,6,11,12]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[1,5,7,12,21]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,1,6,10,16,20]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[4,5,14,19,21]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[1,10,13,18]}],"complexes":["Mitochondrial complex I (NADH:ubiquinone oxidoreductase)","Mitochondrial respiratory supercomplex"],"partners":["MDM2","AKAP1","PHB2","NDUFV1","RNF43","SIRT3","PCBP2"],"other_free_text":[]},"mechanistic_narrative":"NDUFS1 is the 75 kDa iron-sulfur subunit of mitochondrial complex I (NADH:ubiquinone oxidoreductase) that is essential for electron transfer, complex I assembly, supercomplex stability, and oxidative phosphorylation. Loss-of-function mutations destabilize the N-module, abolish electron transfer between iron-sulfur clusters, and cause complex I deficiency with mitochondrial ROS accumulation, TCA cycle feedback inhibition, and apoptotic pathway activation [PMID:11349233, PMID:31557978, PMID:36462614]. NDUFS1 mitochondrial import requires AKAP1 and is antagonized by MDM2-mediated cytoplasmic sequestration; its activity is further regulated by caspase-3 cleavage at D255 (amplifying apoptotic ROS and lysosomal membrane permeabilization), glutathionylation (promoting reverse-electron-transfer ROS), SIRT3-dependent deacetylation (causing complex I dissociation), and RNF43-mediated ubiquitin-proteasomal degradation [PMID:32072193, PMID:30879903, PMID:23788428, PMID:36290766, PMID:40493314, PMID:38988031]. Biallelic NDUFS1 mutations cause autosomal recessive mitochondrial complex I deficiency [PMID:11349233, PMID:20382551]."},"prefetch_data":{"uniprot":{"accession":"P28331","full_name":"NADH-ubiquinone oxidoreductase 75 kDa subunit, mitochondrial","aliases":["Complex I-75kD","CI-75kD"],"length_aa":727,"mass_kda":79.5,"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:30879903, PubMed:31557978). Essential for catalysing the entry and efficient transfer of electrons within complex I (PubMed:31557978). Plays a key role in the assembly and stability of complex I and participates in the association of complex I with ubiquinol-cytochrome reductase complex (Complex III) to form supercomplexes (PubMed:30879903, PubMed:31557978)","subcellular_location":"Mitochondrion inner membrane","url":"https://www.uniprot.org/uniprotkb/P28331/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/NDUFS1","classification":"Not Classified","n_dependent_lines":494,"n_total_lines":1208,"dependency_fraction":0.40894039735099336},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"MIF","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/NDUFS1","total_profiled":1310},"omim":[{"mim_id":"619701","title":"YOON-BELLEN NEURODEVELOPMENTAL SYNDROME; YOBELN","url":"https://www.omim.org/entry/619701"},{"mim_id":"619382","title":"LEBER-LIKE HEREDITARY OPTIC NEUROPATHY, AUTOSOMAL RECESSIVE 1; LHONAR1","url":"https://www.omim.org/entry/619382"},{"mim_id":"618226","title":"MITOCHONDRIAL COMPLEX I DEFICIENCY, NUCLEAR TYPE 5; MC1DN5","url":"https://www.omim.org/entry/618226"},{"mim_id":"618225","title":"MITOCHONDRIAL COMPLEX I DEFICIENCY, NUCLEAR TYPE 4; MC1DN4","url":"https://www.omim.org/entry/618225"},{"mim_id":"618202","title":"DNAJ/HSP40 HOMOLOG, SUBFAMILY C, MEMBER 30; DNAJC30","url":"https://www.omim.org/entry/618202"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Mitochondria","reliability":"Supported"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"heart muscle","ntpm":170.1},{"tissue":"skeletal 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deletion and point mutations of the nuclear NDUFV1 and NDUFS1 genes in mitochondrial complex I deficiency.","date":"2001","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/11349233","citation_count":218,"is_preprint":false},{"pmid":"16478720","id":"PMC_16478720","title":"Dysfunctions of cellular oxidative metabolism in patients with mutations in the NDUFS1 and NDUFS4 genes of complex I.","date":"2006","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/16478720","citation_count":127,"is_preprint":false},{"pmid":"32072193","id":"PMC_32072193","title":"Akap1 deficiency exacerbates diabetic cardiomyopathy in mice by NDUFS1-mediated mitochondrial dysfunction and apoptosis.","date":"2020","source":"Diabetologia","url":"https://pubmed.ncbi.nlm.nih.gov/32072193","citation_count":92,"is_preprint":false},{"pmid":"35817848","id":"PMC_35817848","title":"Cardiac-specific overexpression of Ndufs1 ameliorates cardiac dysfunction 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large-scale deletion\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple independent patient mutations with biochemical validation, replicated across subsequent studies\",\n      \"pmids\": [\"11349233\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"A Q522K missense mutation in NDUFS1 (C1564A in coding sequence) reduces mature complex I assembly and activity, causes mitochondrial ROS (H2O2 and superoxide) accumulation, decreases glutathione content, and impairs mitochondrial membrane potential; treatment with dibutyryl-cAMP partially restores complex I activity and eliminates ROS.\",\n      \"method\": \"Patient fibroblast biochemical assays: NADH-ubiquinone oxidoreductase activity, ROS measurement (MitoSOX/H2DCFDA), glutathione assay, mitochondrial membrane potential (JC-1), glutathione peroxidase activity\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal biochemical methods in patient-derived cells with pharmacological rescue\",\n      \"pmids\": [\"16478720\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"NDUFS1 mutations (premature stop, amino acid substitutions, single amino acid deletion) reduce complex I amount, activity, and disrupt complex I assembly in patient fibroblasts, indicating NDUFS1 is required for proper complex I assembly.\",\n      \"method\": \"Patient fibroblast biochemical analysis: complex I activity assays, Blue Native PAGE for assembly analysis\",\n      \"journal\": \"Molecular genetics and metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple patient lines with assembly analysis, replicated across labs\",\n      \"pmids\": [\"20382551\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"A homozygous T595A mutation in NDUFS1 causes complex I deficiency and complex I dysfunction in a Neurospora crassa insertional mutagenesis model and in patient fibroblasts grown in galactose, confirming NDUFS1 function is conserved and required for complex I activity.\",\n      \"method\": \"Neurospora crassa insertional mutagenesis model; patient fibroblast biochemical assays in galactose medium; muscle biopsy complex I enzyme activity\",\n      \"journal\": \"Neurogenetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — genetic model organism validation plus patient biochemistry\",\n      \"pmids\": [\"21203893\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Caspase-3 cleaves the NDUFS1 subunit of complex I downstream of MOMP during TNFα-induced apoptosis; this cleavage disrupts complex I function, causing ROS production that triggers lysosomal membrane permeabilization (LMP) and cathepsin release. A caspase-non-cleavable NDUFS1 mutant prevents LMP and partially blocks apoptosis.\",\n      \"method\": \"Cell biology: caspase inhibitors, Bax/Bak/Apaf-1/caspase-3/7-deficient cells; caspase non-cleavable NDUFS1 mutant overexpression; MitoQ antioxidant rescue; LMP and cathepsin release assays\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — mutagenesis of cleavage site, multiple genetic knockouts, pharmacological rescue with orthogonal readouts\",\n      \"pmids\": [\"23788428\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"MDM2 directly binds and sequesters NDUFS1 via its amino-terminal region, preventing NDUFS1 mitochondrial localization, causing complex I and supercomplex destabilization, decreased mitochondrial respiration, oxidative stress, and commitment to the mitochondrial apoptosis pathway in a p53-independent manner.\",\n      \"method\": \"Co-IP, pulldown, organellar fractionation, supercomplex BN-PAGE, oxygen consumption assays, Drosophila and murine transgenic models; MDM2 N-terminal domain sufficient for binding and phenotype\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — direct binding demonstrated by pulldown, functional validation in multiple in vitro and in vivo models with orthogonal readouts\",\n      \"pmids\": [\"30879903\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Biallelic NDUFS1 mutations destabilize the entire N-module of complex I and disrupt electron transfer between two iron-sulfur clusters, leading to metabolic reprogramming including inhibitory feedback on the TCA cycle and altered glutathione levels indicative of ROS stress.\",\n      \"method\": \"Proteome and metabolome profiling of patient-derived cells; quantitative mass spectrometry; metabolomics\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — two orthogonal omics approaches in patient cells, domain-level mechanistic conclusion\",\n      \"pmids\": [\"31557978\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"AKAP1 interacts with NDUFS1 and is required for translocation of NDUFS1 from the cytosol to mitochondria; AKAP1 deficiency prevents mitochondrial NDUFS1 import, inhibits complex I activity, reduces ATP production, and increases mitochondrial ROS-related apoptosis in cardiomyocytes.\",\n      \"method\": \"Co-immunoprecipitation and mass spectrometry; subcellular fractionation; Akap1-KO mouse model; AAV9-Akap1 cardiac overexpression rescue; complex I activity assays; echocardiography\",\n      \"journal\": \"Diabetologia\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP/MS, KO mouse with defined phenotype, genetic rescue with NDUFS1 translocation restoration\",\n      \"pmids\": [\"32072193\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"NDUFS1 knockdown in cardiomyocytes decreases mitochondrial membrane potential, mitochondrial DNA content, and mitochondrial mass while increasing mitochondrial ROS production; NDUFS1 overexpression reverses Ang II-induced hypertrophic cardiomyocyte dysfunction.\",\n      \"method\": \"In vitro NDUFS1 knockdown/overexpression in rat cardiomyocytes; JC-1 mitochondrial membrane potential assay; MitoSOX ROS measurement; mitochondrial DNA quantification; TAC mouse model\",\n      \"journal\": \"Oxidative medicine and cellular longevity\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KD/OE with multiple mitochondrial phenotypic readouts, in vivo model, but single lab\",\n      \"pmids\": [\"33763166\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Ndufs1 overexpression in cardiomyocytes ameliorates complex I activity reduction and impaired mitochondrial respiratory function caused by myocardial infarction/hypoxia, reduces ROS production, and decreases ROS-related apoptosis.\",\n      \"method\": \"Cardiac-specific Ndufs1 overexpression in MI mouse model; complex I activity assay; Seahorse mitochondrial respiration; ROS measurement; apoptosis assays; echocardiography\",\n      \"journal\": \"Experimental & molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — gain-of-function with defined mechanistic phenotype in vivo and in vitro, single lab\",\n      \"pmids\": [\"35817848\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Glutathionylation of NDUFS1 (induced by disulfiram) inhibits complex I activity and increases ROS production during reverse electron transfer from the ubiquinone pool; reducing agents reverse NDUFS1 glutathionylation, restore complex I activity, and decrease ROS.\",\n      \"method\": \"Immunocapture of complex I; disulfiram-induced glutathionylation; complex I inhibitors (rotenone, S1QEL); ROS measurement with Amplex Red; reducing agent rescue; liver mitochondria\",\n      \"journal\": \"Antioxidants (Basel, Switzerland)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro biochemistry with immunocapture, site-specific PTM, pharmacological manipulation, and multiple inhibitor controls\",\n      \"pmids\": [\"36290766\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Mutations at 17 sites in NDUFS1 (modeled in E. coli homolog nuoG) many mapping to subunit interfaces disrupt complex I assembly; compound heterozygous mutations were analyzed to identify which is more deleterious; some mutations cause reduced NADH oxidase activity and assembly defects.\",\n      \"method\": \"Bacterial model system (E. coli nuoG); membrane vesicle NADH oxidase activity; time-delayed expression; co-immunoprecipitation for assembly; alanine mutagenesis\",\n      \"journal\": \"Mitochondrion\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — systematic mutagenesis with multiple in vitro assays including assembly and activity in reconstituted bacterial system\",\n      \"pmids\": [\"36462614\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PHB2 directly interacts with NDUFS1 in mitochondria and facilitates NDUFS1 binding to NDUFV1, stabilizing complex I and enhancing its activity; PHB2 knockdown reduces complex I activity and OXPHOS levels.\",\n      \"method\": \"Co-immunoprecipitation and mass spectrometry; confocal co-localization; complex I activity assay; PHB2 KD/OE with NDUFS1 rescue\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — Co-IP/MS with functional rescue, single lab\",\n      \"pmids\": [\"36658121\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NDUFS1 reduction activates an mROS–HIF1α–FBLN5 signaling pathway promoting gastric cancer progression; NDUFS1 overexpression inhibits GC cell proliferation, migration, and invasion in vitro and in vivo.\",\n      \"method\": \"KD/OE of NDUFS1 in GC cells; confocal localization; mROS measurement; HIF1α pathway analysis; mouse xenograft\",\n      \"journal\": \"British journal of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KD/OE with pathway placement, in vivo validation, but single lab\",\n      \"pmids\": [\"37644092\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Agrimol B causes caspase-3-mediated degradation of NDUFS1, leading to mitochondrial ROS accumulation and cytotoxic autophagy arrest in hepatocellular carcinoma cells; NDUFS1 overexpression partially rescues ROS overproduction and autophagosome accumulation.\",\n      \"method\": \"NDUFS1 protein level assay; caspase-3 activity assay; ROS measurement; autophagosome detection; NDUFS1 overexpression rescue; HCC xenograft PDX model\",\n      \"journal\": \"Free radical biology & medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mechanistic pathway placement with rescue experiment, single lab\",\n      \"pmids\": [\"38697493\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"RNF43 E3 ubiquitin ligase interacts with NDUFS1 and promotes its ubiquitination and degradation, thereby reducing oxidative phosphorylation; loss of RNF43 increases NDUFS1 levels and OXPHOS activity in endometrial stromal cells.\",\n      \"method\": \"Co-immunoprecipitation; ubiquitination assay; RNF43/NDUFS1 KD/OE; OXPHOS measurement; endometriosis rat model\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — Co-IP with ubiquitination assay and in vivo model, single lab\",\n      \"pmids\": [\"38988031\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SIRT3-dependent deacetylation of NDUFS1 (on the N-module catalytic subunit) by berberine (which directly binds and activates SIRT3) leads to dissociation of mitochondrial complex I, reducing oxidative phosphorylation and improving glucose and lipid metabolism in hepatocytes.\",\n      \"method\": \"SIRT3 activity assays; acetylation analysis of NDUFS1; berberine binding to SIRT3 (molecular docking and biochemical); complex I dissociation assays; metabolic profiling in hepatocytes; oral administration in vivo\",\n      \"journal\": \"Science China. Life sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — identified PTM writer (SIRT3), substrate (NDUFS1 acetylation), direct drug-protein binding, and functional consequence with in vivo validation\",\n      \"pmids\": [\"40493314\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PCBP2 binds NDUFS1 mRNA and stabilizes/promotes NDUFS1 expression; NDUFS1 in turn activates NRF2 by enhancing NRF2 nuclear translocation, inhibiting ferroptosis in cardiomyocytes during myocardial infarction.\",\n      \"method\": \"RNA-immunoprecipitation (RIP); RNA-protein pulldown; PCBP2/NDUFS1 OE; NRF2 nuclear translocation assay; ferroptosis markers; LAD ligation MI mouse model\",\n      \"journal\": \"Molecular immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — RIP and pulldown for RNA-binding, pathway placement via NRF2 translocation, in vivo model, single lab\",\n      \"pmids\": [\"40784311\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Sorafenib-induced ER stress activates PERK–eIF2α–ATF4–ATF3 signaling, and ATF3 negatively regulates NDUFS1 expression, causing mitochondrial dysfunction; ATF3 silencing restores NDUFS1 levels and partially rescues mitochondrial function.\",\n      \"method\": \"Transcriptomic and proteomic profiling; Western blot; ATF3 siRNA knockdown; RT-PCR; ER stress inhibitor GSK2606414; H9C2 cells and rat in vivo model\",\n      \"journal\": \"Frontiers in pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — omics + siRNA rescue with mechanistic pathway placement, single lab\",\n      \"pmids\": [\"40880646\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Caspase-3 cleaves NDUFS1 at D255 in response to trichothecene mycotoxins (DON, T-2 toxin), disrupting electron transport and amplifying mitochondrial ROS; mutation of the cleavage site (D255A) attenuates this process.\",\n      \"method\": \"In vivo and in vitro trichothecene exposure models; caspase-3 inhibition/knockdown; D255A caspase non-cleavable NDUFS1 mutant; ROS and mitochondrial damage assays\",\n      \"journal\": \"Free radical biology & medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — site-directed mutagenesis of caspase cleavage site with functional rescue, in vivo and in vitro validation\",\n      \"pmids\": [\"41422996\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"NDUFS1 promotes alveolar fluid clearance by supporting mitochondrial complex I activity and NAD+ production; NDUFS1 deficiency reduces ENaCα expression through impaired NAD+ generation and increased ROS; NAD+ supplementation via olaparib rescues ENaCα levels and fluid clearance.\",\n      \"method\": \"NDUFS1 KD in alveolar epithelial cells; complex I activity assay; NAD+ measurement; ENaCα expression; Olaparib (NAD+ supplementation) rescue; paraquat/LPS ALI mouse model\",\n      \"journal\": \"International journal of medical sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KD with mechanistic pathway (NDUFS1→NAD+→ENaCα), pharmacological rescue, in vivo model, single lab\",\n      \"pmids\": [\"40860777\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"GL-V9 binds the MDM2 amino-terminal domain (aa 1–101) and acts as a molecular glue facilitating MDM2–NDUFS1 interaction in the cytoplasm, thereby preventing NDUFS1 mitochondrial localization, inhibiting complex I formation, disrupting mitochondrial homeostasis, and activating OMA1–DELE1–ISR-triggered apoptosis in a p53-independent manner.\",\n      \"method\": \"GST-pulldown; CETSA; SPR; molecular docking; amino acid mutations in MDM2; immunofluorescence; mitochondrial membrane potential; ATP; OCR; OMA1-DELE1 pathway assays\",\n      \"journal\": \"Journal of advanced research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — direct binding confirmed by multiple orthogonal methods (SPR, CETSA, GST-pulldown, mutagenesis), mechanistic pathway placement\",\n      \"pmids\": [\"41951044\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NDUFS1 is the 75 kDa Fe-S core subunit of mitochondrial complex I (NADH:ubiquinone oxidoreductase) that houses iron-sulfur clusters essential for electron transfer within the N-module; its mitochondrial localization (facilitated by AKAP1 and opposed by MDM2 sequestration) is required for complex I assembly and OXPHOS activity, and it is subject to regulatory post-translational modifications including caspase-3 cleavage (amplifying apoptotic ROS), SIRT3-dependent deacetylation (dissociating complex I), and glutathionylation (increasing reverse-electron-transfer ROS), with loss-of-function causing complex I deficiency, supercomplex destabilization, mitochondrial ROS accumulation, and downstream activation of apoptotic and inflammatory pathways.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"NDUFS1 is the 75 kDa iron-sulfur subunit of mitochondrial complex I (NADH:ubiquinone oxidoreductase) that is essential for electron transfer, complex I assembly, supercomplex stability, and oxidative phosphorylation. Loss-of-function mutations destabilize the N-module, abolish electron transfer between iron-sulfur clusters, and cause complex I deficiency with mitochondrial ROS accumulation, TCA cycle feedback inhibition, and apoptotic pathway activation [PMID:11349233, PMID:31557978, PMID:36462614]. NDUFS1 mitochondrial import requires AKAP1 and is antagonized by MDM2-mediated cytoplasmic sequestration; its activity is further regulated by caspase-3 cleavage at D255 (amplifying apoptotic ROS and lysosomal membrane permeabilization), glutathionylation (promoting reverse-electron-transfer ROS), SIRT3-dependent deacetylation (causing complex I dissociation), and RNF43-mediated ubiquitin-proteasomal degradation [PMID:32072193, PMID:30879903, PMID:23788428, PMID:36290766, PMID:40493314, PMID:38988031]. Biallelic NDUFS1 mutations cause autosomal recessive mitochondrial complex I deficiency [PMID:11349233, PMID:20382551].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Establishing NDUFS1 as a disease gene: before this work, the genetic basis of many complex I deficiency cases was unknown; identification of multiple point mutations and deletions in NDUFS1 in patients proved it is a nuclear-encoded subunit required for complex I function and that its loss causes Mendelian mitochondrial disease.\",\n      \"evidence\": \"dHPLC and direct sequencing of patient fibroblast cDNA identifying five point mutations and one large deletion\",\n      \"pmids\": [\"11349233\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise structural consequences of individual mutations on iron-sulfur cluster coordination were not resolved\", \"No systematic genotype-phenotype correlation established\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Linking NDUFS1 mutation to ROS overproduction: beyond reduced activity, the Q522K mutation demonstrated that NDUFS1 dysfunction causes mitochondrial superoxide and H₂O₂ accumulation, glutathione depletion, and membrane potential loss, establishing NDUFS1 as a critical gatekeeper of mitochondrial redox homeostasis.\",\n      \"evidence\": \"Patient fibroblast assays using MitoSOX, H2DCFDA, JC-1, glutathione quantification, and cAMP-mediated pharmacological rescue\",\n      \"pmids\": [\"16478720\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which dibutyryl-cAMP restores complex I activity was not defined\", \"Whether ROS is cause or consequence of membrane potential loss was not resolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Defining NDUFS1's role in complex I assembly: Blue Native PAGE of patient fibroblasts demonstrated that NDUFS1 mutations impair not just catalytic activity but the physical assembly of the holoenzyme, establishing it as an assembly-essential core subunit.\",\n      \"evidence\": \"BN-PAGE and complex I activity assays across multiple patient fibroblast lines\",\n      \"pmids\": [\"20382551\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which assembly intermediate is stalled was not identified\", \"Whether chaperones are involved in NDUFS1 incorporation was unknown\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identifying NDUFS1 as a caspase-3 substrate that amplifies apoptosis: it was unknown how mitochondrial ROS bursts are triggered downstream of MOMP; this work showed caspase-3 cleaves NDUFS1, disrupting complex I and generating ROS that triggers lysosomal membrane permeabilization, thereby coupling intrinsic apoptosis to lysosomal cell death.\",\n      \"evidence\": \"Caspase non-cleavable NDUFS1 mutant expression; caspase-3/7 and Bax/Bak KO cells; MitoQ rescue; LMP and cathepsin release assays\",\n      \"pmids\": [\"23788428\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Exact cleavage site was mapped but full cleavage fragment characterization was incomplete\", \"Whether other respiratory chain subunits are also cleaved was not addressed\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Discovering MDM2 as a cytoplasmic sequestrator of NDUFS1: this revealed a p53-independent, non-canonical role for MDM2 in which its N-terminal domain directly binds NDUFS1, prevents mitochondrial localization, and destabilizes complex I and supercomplexes, linking oncogene biology to OXPHOS regulation.\",\n      \"evidence\": \"Co-IP, GST-pulldown, BN-PAGE supercomplex analysis, oxygen consumption; Drosophila and murine transgenic models\",\n      \"pmids\": [\"30879903\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether MDM2 regulation of NDUFS1 is constitutive or signal-dependent was not resolved\", \"Stoichiometry of MDM2–NDUFS1 interaction in normal physiology unknown\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Mapping NDUFS1 deficiency to N-module destabilization and metabolic rewiring: proteomics and metabolomics of patient cells showed that biallelic mutations specifically destabilize the entire N-module and disrupt electron transfer between iron-sulfur clusters, with secondary metabolic consequences including TCA cycle inhibition and glutathione depletion.\",\n      \"evidence\": \"Quantitative mass spectrometry proteomics and metabolomics in patient-derived cells\",\n      \"pmids\": [\"31557978\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which specific iron-sulfur cluster pair is disrupted was inferred but not directly measured by EPR\", \"Contribution of individual metabolic changes to pathology not dissected\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identifying AKAP1 as required for NDUFS1 mitochondrial import: it was unclear how the nuclear-encoded NDUFS1 is delivered to mitochondria; AKAP1 was shown to physically interact with NDUFS1 and promote its translocation, with AKAP1 deficiency phenocopying NDUFS1 loss in cardiomyocytes.\",\n      \"evidence\": \"Reciprocal Co-IP/MS; Akap1-KO mouse; AAV9-Akap1 cardiac rescue restoring NDUFS1 mitochondrial localization and complex I activity\",\n      \"pmids\": [\"32072193\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether AKAP1 acts as a chaperone, scaffold, or import receptor was not distinguished\", \"Whether AKAP1 facilitates import of other complex I subunits is unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Demonstrating glutathionylation as a reversible regulatory switch on NDUFS1: this established that NDUFS1 glutathionylation specifically inhibits complex I and increases ROS production during reverse electron transfer, providing a redox-sensitive post-translational control mechanism distinct from caspase cleavage.\",\n      \"evidence\": \"Immunocaptured complex I; disulfiram-induced glutathionylation; rotenone and S1QEL controls; Amplex Red ROS measurement; reducing agent reversal in liver mitochondria\",\n      \"pmids\": [\"36290766\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific cysteine residue(s) modified were not identified\", \"Physiological stimuli triggering NDUFS1 glutathionylation in vivo not established\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Systematic mapping of disease-relevant residues at subunit interfaces: modeling 17 patient mutations in the bacterial homolog nuoG revealed that many critical residues lie at subunit interfaces and disrupt assembly rather than catalysis per se, refining the structural basis of NDUFS1-linked complex I deficiency.\",\n      \"evidence\": \"E. coli nuoG systematic alanine mutagenesis; membrane vesicle NADH oxidase activity; co-IP assembly analysis; time-delayed expression\",\n      \"pmids\": [\"36462614\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Bacterial system lacks eukaryotic supernumerary subunits, so interface effects may differ in human complex I\", \"No human structural validation of interface disruption\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identifying RNF43 as a ubiquitin ligase targeting NDUFS1 for proteasomal degradation: this added ubiquitination to the regulatory repertoire controlling NDUFS1 protein levels and thereby OXPHOS capacity, linking Wnt pathway components to mitochondrial metabolism.\",\n      \"evidence\": \"Co-IP; ubiquitination assay; RNF43/NDUFS1 KD/OE; OXPHOS measurement; endometriosis rat model\",\n      \"pmids\": [\"38988031\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific ubiquitinated lysine residues on NDUFS1 not mapped\", \"Whether RNF43 regulation is tissue-specific is unknown\", \"Not independently replicated\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Defining the caspase-3 cleavage site at D255 and confirming its apoptosis-amplifying role across toxic insults: site-directed D255A mutagenesis proved that this single cleavage event is the primary mechanism by which caspase-3 disrupts complex I electron transport and amplifies mitochondrial ROS during apoptosis.\",\n      \"evidence\": \"D255A non-cleavable mutant; caspase-3 inhibition/KD; ROS and mitochondrial damage assays in trichothecene-exposed models in vivo and in vitro\",\n      \"pmids\": [\"41422996\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether D255 cleavage also occurs in non-apoptotic caspase activation contexts is unknown\", \"Fate of cleavage fragments not fully characterized\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Revealing SIRT3-dependent deacetylation of NDUFS1 as a mechanism for regulated complex I disassembly: berberine-activated SIRT3 deacetylates NDUFS1, causing complex I dissociation and reduced OXPHOS, demonstrating that reversible acetylation controls complex I integrity and metabolic flux.\",\n      \"evidence\": \"SIRT3 activity assays; NDUFS1 acetylation analysis; berberine–SIRT3 binding (SPR, docking); complex I dissociation; hepatocyte metabolic profiling; in vivo administration\",\n      \"pmids\": [\"40493314\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific acetylated lysine residues on NDUFS1 targeted by SIRT3 not identified\", \"Whether deacetylation-induced disassembly is reversible upon SIRT3 inhibition not tested\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Establishing GL-V9 as a molecular glue enhancing MDM2–NDUFS1 interaction: this pharmacological study confirmed the MDM2-NDUFS1 axis as druggable and showed that enforced cytoplasmic sequestration of NDUFS1 activates the OMA1–DELE1 integrated stress response, mapping a complete pathway from NDUFS1 depletion to apoptosis.\",\n      \"evidence\": \"SPR, CETSA, GST-pulldown, MDM2 mutagenesis, immunofluorescence, mitochondrial functional assays, OMA1-DELE1 pathway readouts\",\n      \"pmids\": [\"41951044\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether OMA1–DELE1 activation is specific to NDUFS1 loss or general complex I dysfunction not distinguished\", \"In vivo therapeutic efficacy and toxicity not fully assessed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include: the precise acetylation and glutathionylation sites on NDUFS1, how NDUFS1 import is coordinated with other N-module subunit assembly, whether the caspase-3 cleavage at D255 participates in non-apoptotic signaling, and the structural basis by which NDUFS1 post-translational modifications alter iron-sulfur cluster function.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No cryo-EM or crystal structure of modified NDUFS1 in context of human complex I\", \"Acetylation and glutathionylation sites not mapped at single-residue resolution\", \"Relative contributions of transcriptional versus post-translational regulation in different tissues unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016491\", \"supporting_discovery_ids\": [0, 1, 2, 6, 10, 11]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [2, 6, 11, 12]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [1, 5, 7, 12, 21]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 1, 6, 10, 16, 20]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [4, 5, 14, 19, 21]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [1, 10, 13, 18]}\n    ],\n    \"complexes\": [\n      \"Mitochondrial complex I (NADH:ubiquinone oxidoreductase)\",\n      \"Mitochondrial respiratory supercomplex\"\n    ],\n    \"partners\": [\n      \"MDM2\",\n      \"AKAP1\",\n      \"PHB2\",\n      \"NDUFV1\",\n      \"RNF43\",\n      \"SIRT3\",\n      \"PCBP2\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}