{"gene":"RTN4IP1","run_date":"2026-06-10T07:46:28","timeline":{"discoveries":[{"year":2002,"finding":"RTN4IP1 (NIMP) physically interacts with Nogo (RTN4) as demonstrated by yeast two-hybrid screening and confirmed by co-immunoprecipitation in both brain tissue (endogenous) and transfected HEK293T cells (overexpressed). RTN4IP1 localizes to mitochondria as shown by confocal imaging and western blot of isolated mitochondria fractions.","method":"Yeast two-hybrid screen, co-immunoprecipitation (endogenous and overexpressed), confocal imaging, subcellular fractionation/western blot","journal":"Journal of neurochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP in two systems plus localization, single lab","pmids":["12067236"],"is_preprint":false},{"year":2015,"finding":"RTN4IP1 functions as a mitochondrial ubiquinol oxidoreductase; loss-of-function mutations in patients cause deficits in mitochondrial respiratory complex I and complex IV activities. Silencing RTN4IP1 in mouse retinal ganglion cells (RGCs) reduced dendrite number and altered dendrite morphogenesis in vitro, and knockdown in zebrafish impaired eye size, neuro-retinal development, and swimming behavior in vivo.","method":"Patient fibroblast biochemical assays (respiratory chain enzyme activity), siRNA knockdown in mouse RGC cultures, morpholino-based knockdown in zebrafish","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional enzymatic assays in patient cells plus in vitro and in vivo knockdown, single lab with multiple orthogonal methods","pmids":["26593267"],"is_preprint":false},{"year":2018,"finding":"Severe RTN4IP1 loss-of-function mutations (leading to absence of protein) cause complex I disassembly and mild mitochondrial network fragmentation, establishing RTN4IP1 as required for complex I integrity.","method":"Immunoblot (protein absence), mitochondrial respiratory chain complex assembly analysis in patient fibroblasts, mitochondrial network morphology assessment","journal":"JAMA neurology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biochemical assays in patient-derived fibroblasts, single lab, multiple orthogonal methods","pmids":["29181510"],"is_preprint":false},{"year":2013,"finding":"siRNA knockdown of RTN4IP1 in thyroid cancer cell lines increased cellular proliferation (2- to 4-fold), invasion (1.5- to 3-fold), migration (2- to 7.5-fold), colony formation (3- to 6-fold), and tumor spheroid formation, establishing a tumor-suppressive role for RTN4IP1 in regulating malignant cell phenotype.","method":"siRNA knockdown in three thyroid cancer cell lines with functional assays (proliferation, invasion, migration, colony formation, spheroid formation)","journal":"The Journal of clinical endocrinology and metabolism","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KD with multiple defined cellular phenotypic readouts, single lab","pmids":["23393170"],"is_preprint":false},{"year":2023,"finding":"RTN4IP1 is enriched in the mitochondrial matrix of muscle tissues and functions as an NADPH oxidoreductase essential for coenzyme Q (CoQ) biosynthesis by regulating the O-methylation activity of COQ3. RTN4IP1-interactome analysis confirmed interaction with COQ3. Knockout myoblasts had markedly decreased CoQ9 levels and impaired cellular respiration. Muscle-specific knockdown in Drosophila impaired muscle function, rescued by dietary soluble CoQ supplementation.","method":"Proximity-labeling proteomics (mitochondrial matrix-targeted APEX2 in transgenic mice), in vitro enzymatic assays, interactome analysis, Rtn4ip1 knockout myoblasts (CoQ9 measurement, cellular respiration), Drosophila muscle-specific knockdown with CoQ dietary rescue","journal":"Nature chemical biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro enzymatic assay with interactome validation, KO cellular phenotype, and in vivo rescue by substrate supplementation across multiple model systems","pmids":["37884807"],"is_preprint":false},{"year":2025,"finding":"RTN4IP1 is a bona fide mitochondrial complex I (CI) assembly factor required for the final stages of CI assembly; deficiency causes accumulation of unincorporated ND5-module and impaired N-module production as revealed by complexome profiling. RTN4IP1 patient fibroblasts and knockout cells also exhibit defective coenzyme Q biosynthesis, demonstrating two independent functions: CI assembly and CoQ metabolism.","method":"Complexome profiling in patient fibroblasts and knockout cells, biochemical CI assembly analysis, CoQ biosynthesis assays","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — complexome profiling plus biochemical assembly assays in both patient-derived and knockout cells, replicated findings from independent preprint, multiple orthogonal methods","pmids":["40859035"],"is_preprint":false},{"year":2025,"finding":"RTN4IP1 expression is regulated post-transcriptionally by c-Myc via iron regulatory protein 2 (IRP2): RTN4IP1 mRNA harbors functional iron-responsive elements (IREs) in its 3′ UTR targeted by IRP2, resulting in increased mRNA stability. RTN4IP1 depletion abrogates amino acid uptake and induces amino acid starvation via downregulation of amino acid transporters SLC1A5, SLC3A2, and SLC7A5.","method":"IRP2 interaction with RTN4IP1 3′ UTR IRE (molecular biology/reporter assays), RTN4IP1 knockdown with amino acid uptake assays and transporter expression analysis, esophageal-specific Rtn4ip1 knockout mouse ESCC model, xenograft models","journal":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional IRE/IRP2 interaction demonstrated, amino acid transporter regulation shown by KD, in vivo KO model, single lab","pmids":["39757767"],"is_preprint":false},{"year":2026,"finding":"RTN4IP1 physically interacts with mitochondrial adenylate kinase 4 (AK4) as shown by co-immunoprecipitation. RTN4IP1 knockdown depletes the intracellular NAD+/NADH pool, impairing both oxidative phosphorylation and glycolysis. AK4 knockdown abrogated the prometastatic phenotypes driven by RTN4IP1, identifying AK4 as a direct downstream effector of RTN4IP1 in TNBC metastasis.","method":"Co-immunoprecipitation (RTN4IP1–AK4 interaction), RTN4IP1 knockdown with NAD+/NADH metabolomics, AK4 genetic rescue experiments, in vivo lung metastasis model","journal":"Chinese medical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus metabolomics plus genetic rescue, single lab, multiple orthogonal methods","pmids":["41980900"],"is_preprint":false}],"current_model":"RTN4IP1 is a mitochondrial matrix NAD(P)H oxidoreductase that performs two independent but essential functions: acting as a bona fide assembly factor for the final stages of mitochondrial complex I assembly (facilitating ND5-module incorporation and N-module production) and supporting coenzyme Q biosynthesis by regulating the O-methylation activity of COQ3; it also physically interacts with RTN4/Nogo at the mitochondria, regulates amino acid transporter expression (SLC1A5, SLC3A2, SLC7A5) downstream of a c-Myc/IRP2/IRE post-transcriptional axis, interacts with adenylate kinase 4 (AK4) to control NAD+/NADH metabolism, and is required for retinal ganglion cell dendrite morphogenesis, with loss-of-function causing complex I and IV respiratory chain deficiency."},"narrative":{"mechanistic_narrative":"RTN4IP1 is a mitochondrial NAD(P)H oxidoreductase that supports oxidative phosphorylation through two independent functions: assembly of respiratory complex I and biosynthesis of coenzyme Q [PMID:37884807, PMID:40859035]. As a bona fide complex I assembly factor, RTN4IP1 acts at the final stages of CI maturation, and its loss causes accumulation of the unincorporated ND5-module and impaired N-module production, leading to complex I disassembly and combined complex I/complex IV respiratory deficiency in patient fibroblasts [PMID:26593267, PMID:29181510, PMID:40859035]. In parallel, RTN4IP1 functions as an NADPH oxidoreductase enriched in the mitochondrial matrix that regulates the O-methylation activity of COQ3, with which it physically interacts; loss of RTN4IP1 depletes CoQ and impairs cellular respiration, a defect rescuable by dietary CoQ supplementation [PMID:37884807, PMID:40859035]. RTN4IP1 was originally identified through its physical interaction with RTN4/Nogo at the mitochondria [PMID:12067236], and it controls cellular redox balance by maintaining the NAD+/NADH pool, in part through interaction with adenylate kinase 4 (AK4) [PMID:41980900]. Functionally, RTN4IP1 is required for retinal ganglion cell dendrite morphogenesis and neuro-retinal development, and loss-of-function mutations cause a respiratory chain deficiency disorder [PMID:26593267, PMID:29181510]. In cancer contexts, RTN4IP1 expression is regulated post-transcriptionally via a c-Myc/IRP2 axis acting on iron-responsive elements in its 3′ UTR, and it modulates amino acid transporter expression (SLC1A5, SLC3A2, SLC7A5) and malignant cell phenotypes [PMID:23393170, PMID:39757767, PMID:41980900].","teleology":[{"year":2002,"claim":"Established RTN4IP1 as a mitochondrial protein and identified its first physical partner, defining it as a Nogo/RTN4-interacting protein.","evidence":"Yeast two-hybrid screen with reciprocal co-immunoprecipitation in brain and HEK293T cells, plus mitochondrial localization by confocal imaging and fractionation","pmids":["12067236"],"confidence":"Medium","gaps":["Functional consequence of the RTN4/Nogo interaction not defined","No enzymatic activity assigned at this stage"]},{"year":2013,"claim":"Showed that RTN4IP1 loss promotes malignant phenotypes, suggesting a tumor-suppressive role in thyroid cancer.","evidence":"siRNA knockdown in three thyroid cancer lines with proliferation, invasion, migration, colony and spheroid assays","pmids":["23393170"],"confidence":"Medium","gaps":["Molecular mechanism linking RTN4IP1 loss to malignancy not established","Apparent tumor-suppressive role conflicts with later prometastatic findings in other cancers"]},{"year":2015,"claim":"Linked RTN4IP1 loss-of-function to respiratory chain deficiency and neuro-retinal disease, framing it as a ubiquinol oxidoreductase important for dendrite morphogenesis.","evidence":"Patient fibroblast respiratory chain enzyme assays, siRNA knockdown in mouse RGC cultures, morpholino knockdown in zebrafish","pmids":["26593267"],"confidence":"Medium","gaps":["Direct enzymatic substrate not biochemically defined","Mechanism connecting respiratory deficiency to dendrite defects unresolved"]},{"year":2018,"claim":"Demonstrated that severe RTN4IP1 loss causes complex I disassembly, establishing it as required for complex I integrity.","evidence":"Immunoblot, respiratory chain complex assembly analysis, and mitochondrial network morphology in patient fibroblasts","pmids":["29181510"],"confidence":"Medium","gaps":["Whether RTN4IP1 acts directly in assembly versus indirectly was not distinguished","Specific assembly intermediate affected not identified"]},{"year":2023,"claim":"Defined a concrete biochemical function: RTN4IP1 is an NADPH oxidoreductase that regulates COQ3 O-methylation activity to drive coenzyme Q biosynthesis.","evidence":"Mitochondrial matrix-targeted APEX2 proximity proteomics in transgenic mice, in vitro enzymatic assays, COQ3 interactome, KO myoblast CoQ9/respiration measurements, Drosophila knockdown with CoQ dietary rescue","pmids":["37884807"],"confidence":"High","gaps":["Structural basis of the RTN4IP1–COQ3 interaction not resolved","Relationship between CoQ function and complex I role not yet integrated"]},{"year":2025,"claim":"Resolved RTN4IP1 as a bona fide complex I assembly factor acting at the final assembly stages, and confirmed CI assembly and CoQ biosynthesis as two independent functions.","evidence":"Complexome profiling in patient fibroblasts and knockout cells with biochemical CI assembly and CoQ biosynthesis assays","pmids":["40859035"],"confidence":"High","gaps":["Molecular mechanism by which RTN4IP1 facilitates ND5-module incorporation not detailed","How the two functions are coordinated within one protein unclear"]},{"year":2025,"claim":"Placed RTN4IP1 in a post-transcriptional regulatory circuit and connected it to amino acid metabolism in cancer.","evidence":"IRP2–3′UTR IRE reporter assays, knockdown with amino acid uptake and transporter expression analysis, esophageal Rtn4ip1 KO mouse and xenograft models","pmids":["39757767"],"confidence":"Medium","gaps":["Mechanism linking mitochondrial RTN4IP1 function to amino acid transporter expression not defined","Direct versus indirect control of SLC transporters unresolved"]},{"year":2026,"claim":"Identified AK4 as a direct partner and downstream effector mediating RTN4IP1 control of the NAD+/NADH pool and metastatic phenotype.","evidence":"Co-immunoprecipitation, NAD+/NADH metabolomics after knockdown, AK4 genetic rescue, in vivo lung metastasis model in TNBC","pmids":["41980900"],"confidence":"Medium","gaps":["Co-IP not validated as direct binding by orthogonal structural methods","How RTN4IP1–AK4 interaction biochemically regulates NAD+/NADH not detailed"]},{"year":null,"claim":"How RTN4IP1's enzymatic NAD(P)H oxidoreductase activity mechanistically couples its distinct roles in complex I assembly, CoQ biosynthesis, redox balance, and cancer-context amino acid metabolism remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of RTN4IP1 in any functional complex","Reconciliation of tumor-suppressive versus prometastatic roles across cancer types not achieved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016491","term_label":"oxidoreductase activity","supporting_discovery_ids":[1,4]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[4]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[0,4]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[4,5]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[5]}],"complexes":[],"partners":["RTN4","COQ3","AK4"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8WWV3","full_name":"NAD(P)H oxidoreductase RTN4IP1, mitochondrial","aliases":["NOGO-interacting mitochondrial protein","Reticulon-4-interacting protein 1"],"length_aa":396,"mass_kda":43.6,"function":"NAD(P)H oxidoreductase involved in the ubiquinone biosynthetic pathway (PubMed:37884807). Required for the O-methyltransferase activity of COQ3 (PubMed:37884807). Able to catalyze the oxidoreduction of 3-demethylubiquinone into 3-demethylubiquinol in vitro (PubMed:37884807). However, it is unclear if 3-demethylubiquinone constitutes a substrate in vivo (PubMed:37884807). May also play a role in the regulation of retinal ganglion cell (RGC) neurite outgrowth, and hence in the development of the inner retina and optic nerve (By similarity). Appears to be a potent inhibitor of regeneration following spinal cord injury (By similarity)","subcellular_location":"Mitochondrion matrix; Mitochondrion outer membrane","url":"https://www.uniprot.org/uniprotkb/Q8WWV3/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RTN4IP1","classification":"Not Classified","n_dependent_lines":177,"n_total_lines":1208,"dependency_fraction":0.14652317880794702},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/RTN4IP1","total_profiled":1310},"omim":[{"mim_id":"616732","title":"OPTIC ATROPHY 10 WITH OR WITHOUT ATAXIA, IMPAIRED INTELLECTUAL DEVELOPMENT, AND SEIZURES; OPA10","url":"https://www.omim.org/entry/616732"},{"mim_id":"610502","title":"RETICULON 4-INTERACTING PROTEIN 1; RTN4IP1","url":"https://www.omim.org/entry/610502"},{"mim_id":"165500","title":"OPTIC ATROPHY 1; OPA1","url":"https://www.omim.org/entry/165500"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/RTN4IP1"},"hgnc":{"alias_symbol":["Yim1","NIMP"],"prev_symbol":[]},"alphafold":{"accession":"Q8WWV3","domains":[{"cath_id":"3.90.180.10","chopping":"41-180_364-393","consensus_level":"high","plddt":97.0642,"start":41,"end":393},{"cath_id":"3.40.50.720","chopping":"196-339","consensus_level":"high","plddt":97.3883,"start":196,"end":339}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8WWV3","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8WWV3-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8WWV3-F1-predicted_aligned_error_v6.png","plddt_mean":91.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RTN4IP1","jax_strain_url":"https://www.jax.org/strain/search?query=RTN4IP1"},"sequence":{"accession":"Q8WWV3","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8WWV3.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8WWV3/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8WWV3"}},"corpus_meta":[{"pmid":"26593267","id":"PMC_26593267","title":"Recessive Mutations in RTN4IP1 Cause Isolated and Syndromic Optic Neuropathies.","date":"2015","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/26593267","citation_count":61,"is_preprint":false},{"pmid":"12067236","id":"PMC_12067236","title":"Identification and characterization of a novel Nogo-interacting mitochondrial protein (NIMP).","date":"2002","source":"Journal of neurochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12067236","citation_count":59,"is_preprint":false},{"pmid":"29181510","id":"PMC_29181510","title":"Neurologic Phenotypes Associated With Mutations in RTN4IP1 (OPA10) in Children and Young Adults.","date":"2018","source":"JAMA neurology","url":"https://pubmed.ncbi.nlm.nih.gov/29181510","citation_count":31,"is_preprint":false},{"pmid":"1640170","id":"PMC_1640170","title":"Monoclonal antibody NIMP-R10 directed against the CD11b chain of the type 3 complement receptor can substitute for monoclonal antibody 5C6 to exacerbate listeriosis by preventing the focusing of myelomonocytic cells at infectious foci in the liver.","date":"1992","source":"Journal of leukocyte biology","url":"https://pubmed.ncbi.nlm.nih.gov/1640170","citation_count":30,"is_preprint":false},{"pmid":"37884807","id":"PMC_37884807","title":"Mitochondrial matrix RTN4IP1/OPA10 is an oxidoreductase for coenzyme Q synthesis.","date":"2023","source":"Nature chemical biology","url":"https://pubmed.ncbi.nlm.nih.gov/37884807","citation_count":25,"is_preprint":false},{"pmid":"23692641","id":"PMC_23692641","title":"High response rate and acceptable toxicity of a combination of rituximab, vinorelbine, ifosfamide, mitoxantrone and prednisone for the treatment of diffuse large B-cell lymphoma in first relapse: results of the R-NIMP GOELAMS study.","date":"2013","source":"British journal of haematology","url":"https://pubmed.ncbi.nlm.nih.gov/23692641","citation_count":15,"is_preprint":false},{"pmid":"23393170","id":"PMC_23393170","title":"RTN4IP1 is down-regulated in thyroid cancer and has tumor-suppressive function.","date":"2013","source":"The Journal of clinical endocrinology and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/23393170","citation_count":12,"is_preprint":false},{"pmid":"33315831","id":"PMC_33315831","title":"A ROD-CONE DYSTROPHY IS SYSTEMATICALLY ASSOCIATED TO THE RTN4IP1 RECESSIVE OPTIC ATROPHY.","date":"2021","source":"Retina (Philadelphia, Pa.)","url":"https://pubmed.ncbi.nlm.nih.gov/33315831","citation_count":12,"is_preprint":false},{"pmid":"28638143","id":"PMC_28638143","title":"Siblings with optic neuropathy and RTN4IP1 mutation.","date":"2017","source":"Journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/28638143","citation_count":10,"is_preprint":false},{"pmid":"33037779","id":"PMC_33037779","title":"Exome sequencing identifies novel missense and deletion variants in RTN4IP1 associated with optic atrophy, global developmental delay, epilepsy, ataxia, and choreoathetosis.","date":"2020","source":"American journal of medical genetics. Part A","url":"https://pubmed.ncbi.nlm.nih.gov/33037779","citation_count":10,"is_preprint":false},{"pmid":"39757767","id":"PMC_39757767","title":"RTN4IP1 Contributes to ESCC via Regulation of Amino Acid Transporters.","date":"2025","source":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","url":"https://pubmed.ncbi.nlm.nih.gov/39757767","citation_count":9,"is_preprint":false},{"pmid":"32392611","id":"PMC_32392611","title":"Optic Atrophy and Generalized Chorea in a Patient Harboring an OPA10/RTN4IP1 Pathogenic Variant.","date":"2020","source":"Neuropediatrics","url":"https://pubmed.ncbi.nlm.nih.gov/32392611","citation_count":6,"is_preprint":false},{"pmid":"36231115","id":"PMC_36231115","title":"A Novel Homozygous Founder Variant of RTN4IP1 in Two Consanguineous Saudi Families.","date":"2022","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/36231115","citation_count":5,"is_preprint":false},{"pmid":"38224077","id":"PMC_38224077","title":"RTN4IP1-associated non-syndromic optic neuropathy and rod-cone dystrophy.","date":"2024","source":"Ophthalmic genetics","url":"https://pubmed.ncbi.nlm.nih.gov/38224077","citation_count":2,"is_preprint":false},{"pmid":"40859035","id":"PMC_40859035","title":"RTN4IP1 is required for the final stages of mitochondrial complex I assembly and CoQ biosynthesis.","date":"2025","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/40859035","citation_count":1,"is_preprint":false},{"pmid":"41609474","id":"PMC_41609474","title":"RTN4IP1 mutation and endocrine failure: clinical features and possible benefits of coenzyme Q10.","date":"2026","source":"Endocrine connections","url":"https://pubmed.ncbi.nlm.nih.gov/41609474","citation_count":0,"is_preprint":false},{"pmid":"41672380","id":"PMC_41672380","title":"RTN4IP1 drives breast tumorigenesis: Molecular mechanisms linking elevated expression to enhanced proliferation, suppressed apoptosis, and therapeutic resistance.","date":"2026","source":"Biochimica et biophysica acta. Molecular basis of disease","url":"https://pubmed.ncbi.nlm.nih.gov/41672380","citation_count":0,"is_preprint":false},{"pmid":"41980900","id":"PMC_41980900","title":"Mitochondrial matrix protein RTN4IP1 promotes the progression and metastasis of triple-negative breast cancer through metabolic reprogramming.","date":"2026","source":"Chinese medical journal","url":"https://pubmed.ncbi.nlm.nih.gov/41980900","citation_count":0,"is_preprint":false},{"pmid":"42098149","id":"PMC_42098149","title":"A dataset of patients with isolated and syndromic optic neuropathies linked to RTN4IP1 genetic variants.","date":"2026","source":"Scientific data","url":"https://pubmed.ncbi.nlm.nih.gov/42098149","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.09.04.610987","title":"RTN4IP1 is essential for the final stages of mitochondrial complex I assembly and coenzyme Q biosynthesis","date":"2024-09-05","source":"bioRxiv","url":"https://doi.org/10.1101/2024.09.04.610987","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.07.16.664887","title":"Development of a High-throughput Assay to Identify Novel Reactivators of Acetylcholinesterase","date":"2025-07-20","source":"bioRxiv","url":"https://doi.org/10.1101/2025.07.16.664887","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11991,"output_tokens":2327,"usd":0.035439,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9558,"output_tokens":3000,"usd":0.061395,"stage2_stop_reason":"end_turn"},"total_usd":0.096834,"stage1_batch_id":"msgbatch_013LWZZT6MWaqB9qyTSeQBmU","stage2_batch_id":"msgbatch_0194ZzQaTGNpruoNJBbEMbt3","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2002,\n      \"finding\": \"RTN4IP1 (NIMP) physically interacts with Nogo (RTN4) as demonstrated by yeast two-hybrid screening and confirmed by co-immunoprecipitation in both brain tissue (endogenous) and transfected HEK293T cells (overexpressed). RTN4IP1 localizes to mitochondria as shown by confocal imaging and western blot of isolated mitochondria fractions.\",\n      \"method\": \"Yeast two-hybrid screen, co-immunoprecipitation (endogenous and overexpressed), confocal imaging, subcellular fractionation/western blot\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP in two systems plus localization, single lab\",\n      \"pmids\": [\"12067236\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"RTN4IP1 functions as a mitochondrial ubiquinol oxidoreductase; loss-of-function mutations in patients cause deficits in mitochondrial respiratory complex I and complex IV activities. Silencing RTN4IP1 in mouse retinal ganglion cells (RGCs) reduced dendrite number and altered dendrite morphogenesis in vitro, and knockdown in zebrafish impaired eye size, neuro-retinal development, and swimming behavior in vivo.\",\n      \"method\": \"Patient fibroblast biochemical assays (respiratory chain enzyme activity), siRNA knockdown in mouse RGC cultures, morpholino-based knockdown in zebrafish\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional enzymatic assays in patient cells plus in vitro and in vivo knockdown, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"26593267\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Severe RTN4IP1 loss-of-function mutations (leading to absence of protein) cause complex I disassembly and mild mitochondrial network fragmentation, establishing RTN4IP1 as required for complex I integrity.\",\n      \"method\": \"Immunoblot (protein absence), mitochondrial respiratory chain complex assembly analysis in patient fibroblasts, mitochondrial network morphology assessment\",\n      \"journal\": \"JAMA neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biochemical assays in patient-derived fibroblasts, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"29181510\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"siRNA knockdown of RTN4IP1 in thyroid cancer cell lines increased cellular proliferation (2- to 4-fold), invasion (1.5- to 3-fold), migration (2- to 7.5-fold), colony formation (3- to 6-fold), and tumor spheroid formation, establishing a tumor-suppressive role for RTN4IP1 in regulating malignant cell phenotype.\",\n      \"method\": \"siRNA knockdown in three thyroid cancer cell lines with functional assays (proliferation, invasion, migration, colony formation, spheroid formation)\",\n      \"journal\": \"The Journal of clinical endocrinology and metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KD with multiple defined cellular phenotypic readouts, single lab\",\n      \"pmids\": [\"23393170\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"RTN4IP1 is enriched in the mitochondrial matrix of muscle tissues and functions as an NADPH oxidoreductase essential for coenzyme Q (CoQ) biosynthesis by regulating the O-methylation activity of COQ3. RTN4IP1-interactome analysis confirmed interaction with COQ3. Knockout myoblasts had markedly decreased CoQ9 levels and impaired cellular respiration. Muscle-specific knockdown in Drosophila impaired muscle function, rescued by dietary soluble CoQ supplementation.\",\n      \"method\": \"Proximity-labeling proteomics (mitochondrial matrix-targeted APEX2 in transgenic mice), in vitro enzymatic assays, interactome analysis, Rtn4ip1 knockout myoblasts (CoQ9 measurement, cellular respiration), Drosophila muscle-specific knockdown with CoQ dietary rescue\",\n      \"journal\": \"Nature chemical biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro enzymatic assay with interactome validation, KO cellular phenotype, and in vivo rescue by substrate supplementation across multiple model systems\",\n      \"pmids\": [\"37884807\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"RTN4IP1 is a bona fide mitochondrial complex I (CI) assembly factor required for the final stages of CI assembly; deficiency causes accumulation of unincorporated ND5-module and impaired N-module production as revealed by complexome profiling. RTN4IP1 patient fibroblasts and knockout cells also exhibit defective coenzyme Q biosynthesis, demonstrating two independent functions: CI assembly and CoQ metabolism.\",\n      \"method\": \"Complexome profiling in patient fibroblasts and knockout cells, biochemical CI assembly analysis, CoQ biosynthesis assays\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — complexome profiling plus biochemical assembly assays in both patient-derived and knockout cells, replicated findings from independent preprint, multiple orthogonal methods\",\n      \"pmids\": [\"40859035\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"RTN4IP1 expression is regulated post-transcriptionally by c-Myc via iron regulatory protein 2 (IRP2): RTN4IP1 mRNA harbors functional iron-responsive elements (IREs) in its 3′ UTR targeted by IRP2, resulting in increased mRNA stability. RTN4IP1 depletion abrogates amino acid uptake and induces amino acid starvation via downregulation of amino acid transporters SLC1A5, SLC3A2, and SLC7A5.\",\n      \"method\": \"IRP2 interaction with RTN4IP1 3′ UTR IRE (molecular biology/reporter assays), RTN4IP1 knockdown with amino acid uptake assays and transporter expression analysis, esophageal-specific Rtn4ip1 knockout mouse ESCC model, xenograft models\",\n      \"journal\": \"Advanced science (Weinheim, Baden-Wurttemberg, Germany)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional IRE/IRP2 interaction demonstrated, amino acid transporter regulation shown by KD, in vivo KO model, single lab\",\n      \"pmids\": [\"39757767\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"RTN4IP1 physically interacts with mitochondrial adenylate kinase 4 (AK4) as shown by co-immunoprecipitation. RTN4IP1 knockdown depletes the intracellular NAD+/NADH pool, impairing both oxidative phosphorylation and glycolysis. AK4 knockdown abrogated the prometastatic phenotypes driven by RTN4IP1, identifying AK4 as a direct downstream effector of RTN4IP1 in TNBC metastasis.\",\n      \"method\": \"Co-immunoprecipitation (RTN4IP1–AK4 interaction), RTN4IP1 knockdown with NAD+/NADH metabolomics, AK4 genetic rescue experiments, in vivo lung metastasis model\",\n      \"journal\": \"Chinese medical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus metabolomics plus genetic rescue, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"41980900\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RTN4IP1 is a mitochondrial matrix NAD(P)H oxidoreductase that performs two independent but essential functions: acting as a bona fide assembly factor for the final stages of mitochondrial complex I assembly (facilitating ND5-module incorporation and N-module production) and supporting coenzyme Q biosynthesis by regulating the O-methylation activity of COQ3; it also physically interacts with RTN4/Nogo at the mitochondria, regulates amino acid transporter expression (SLC1A5, SLC3A2, SLC7A5) downstream of a c-Myc/IRP2/IRE post-transcriptional axis, interacts with adenylate kinase 4 (AK4) to control NAD+/NADH metabolism, and is required for retinal ganglion cell dendrite morphogenesis, with loss-of-function causing complex I and IV respiratory chain deficiency.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"RTN4IP1 is a mitochondrial NAD(P)H oxidoreductase that supports oxidative phosphorylation through two independent functions: assembly of respiratory complex I and biosynthesis of coenzyme Q [#4, #5]. As a bona fide complex I assembly factor, RTN4IP1 acts at the final stages of CI maturation, and its loss causes accumulation of the unincorporated ND5-module and impaired N-module production, leading to complex I disassembly and combined complex I/complex IV respiratory deficiency in patient fibroblasts [#1, #2, #5]. In parallel, RTN4IP1 functions as an NADPH oxidoreductase enriched in the mitochondrial matrix that regulates the O-methylation activity of COQ3, with which it physically interacts; loss of RTN4IP1 depletes CoQ and impairs cellular respiration, a defect rescuable by dietary CoQ supplementation [#4, #5]. RTN4IP1 was originally identified through its physical interaction with RTN4/Nogo at the mitochondria [#0], and it controls cellular redox balance by maintaining the NAD+/NADH pool, in part through interaction with adenylate kinase 4 (AK4) [#7]. Functionally, RTN4IP1 is required for retinal ganglion cell dendrite morphogenesis and neuro-retinal development, and loss-of-function mutations cause a respiratory chain deficiency disorder [#1, #2]. In cancer contexts, RTN4IP1 expression is regulated post-transcriptionally via a c-Myc/IRP2 axis acting on iron-responsive elements in its 3′ UTR, and it modulates amino acid transporter expression (SLC1A5, SLC3A2, SLC7A5) and malignant cell phenotypes [#3, #6, #7].\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"Established RTN4IP1 as a mitochondrial protein and identified its first physical partner, defining it as a Nogo/RTN4-interacting protein.\",\n      \"evidence\": \"Yeast two-hybrid screen with reciprocal co-immunoprecipitation in brain and HEK293T cells, plus mitochondrial localization by confocal imaging and fractionation\",\n      \"pmids\": [\"12067236\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of the RTN4/Nogo interaction not defined\", \"No enzymatic activity assigned at this stage\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Showed that RTN4IP1 loss promotes malignant phenotypes, suggesting a tumor-suppressive role in thyroid cancer.\",\n      \"evidence\": \"siRNA knockdown in three thyroid cancer lines with proliferation, invasion, migration, colony and spheroid assays\",\n      \"pmids\": [\"23393170\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular mechanism linking RTN4IP1 loss to malignancy not established\", \"Apparent tumor-suppressive role conflicts with later prometastatic findings in other cancers\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Linked RTN4IP1 loss-of-function to respiratory chain deficiency and neuro-retinal disease, framing it as a ubiquinol oxidoreductase important for dendrite morphogenesis.\",\n      \"evidence\": \"Patient fibroblast respiratory chain enzyme assays, siRNA knockdown in mouse RGC cultures, morpholino knockdown in zebrafish\",\n      \"pmids\": [\"26593267\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct enzymatic substrate not biochemically defined\", \"Mechanism connecting respiratory deficiency to dendrite defects unresolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrated that severe RTN4IP1 loss causes complex I disassembly, establishing it as required for complex I integrity.\",\n      \"evidence\": \"Immunoblot, respiratory chain complex assembly analysis, and mitochondrial network morphology in patient fibroblasts\",\n      \"pmids\": [\"29181510\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether RTN4IP1 acts directly in assembly versus indirectly was not distinguished\", \"Specific assembly intermediate affected not identified\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined a concrete biochemical function: RTN4IP1 is an NADPH oxidoreductase that regulates COQ3 O-methylation activity to drive coenzyme Q biosynthesis.\",\n      \"evidence\": \"Mitochondrial matrix-targeted APEX2 proximity proteomics in transgenic mice, in vitro enzymatic assays, COQ3 interactome, KO myoblast CoQ9/respiration measurements, Drosophila knockdown with CoQ dietary rescue\",\n      \"pmids\": [\"37884807\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the RTN4IP1–COQ3 interaction not resolved\", \"Relationship between CoQ function and complex I role not yet integrated\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Resolved RTN4IP1 as a bona fide complex I assembly factor acting at the final assembly stages, and confirmed CI assembly and CoQ biosynthesis as two independent functions.\",\n      \"evidence\": \"Complexome profiling in patient fibroblasts and knockout cells with biochemical CI assembly and CoQ biosynthesis assays\",\n      \"pmids\": [\"40859035\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism by which RTN4IP1 facilitates ND5-module incorporation not detailed\", \"How the two functions are coordinated within one protein unclear\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Placed RTN4IP1 in a post-transcriptional regulatory circuit and connected it to amino acid metabolism in cancer.\",\n      \"evidence\": \"IRP2–3′UTR IRE reporter assays, knockdown with amino acid uptake and transporter expression analysis, esophageal Rtn4ip1 KO mouse and xenograft models\",\n      \"pmids\": [\"39757767\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking mitochondrial RTN4IP1 function to amino acid transporter expression not defined\", \"Direct versus indirect control of SLC transporters unresolved\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Identified AK4 as a direct partner and downstream effector mediating RTN4IP1 control of the NAD+/NADH pool and metastatic phenotype.\",\n      \"evidence\": \"Co-immunoprecipitation, NAD+/NADH metabolomics after knockdown, AK4 genetic rescue, in vivo lung metastasis model in TNBC\",\n      \"pmids\": [\"41980900\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Co-IP not validated as direct binding by orthogonal structural methods\", \"How RTN4IP1–AK4 interaction biochemically regulates NAD+/NADH not detailed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How RTN4IP1's enzymatic NAD(P)H oxidoreductase activity mechanistically couples its distinct roles in complex I assembly, CoQ biosynthesis, redox balance, and cancer-context amino acid metabolism remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of RTN4IP1 in any functional complex\", \"Reconciliation of tumor-suppressive versus prometastatic roles across cancer types not achieved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016491\", \"supporting_discovery_ids\": [1, 4]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [0, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [4, 5]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"RTN4\", \"COQ3\", \"AK4\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}