{"gene":"TIGAR","run_date":"2026-06-10T10:51:55","timeline":{"discoveries":[{"year":2006,"finding":"TIGAR is a p53-inducible gene that functions to lower intracellular fructose-2,6-bisphosphate levels, thereby inhibiting glycolysis, increasing flux through the pentose phosphate pathway, reducing intracellular ROS, and protecting cells from ROS-associated apoptosis.","method":"Gene expression microarray identification, knockdown (siRNA), ROS measurement, fructose-2,6-bisphosphate assay, apoptosis assays in cell lines","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — original identification paper with multiple orthogonal methods (knockdown, metabolite measurement, ROS assay, apoptosis readout), widely replicated across many subsequent labs","pmids":["16839880"],"is_preprint":false},{"year":2008,"finding":"Crystal structure of zebrafish TIGAR reveals a histidine phosphatase fold with a catalytic histidine coordinating a phosphate molecule; the active site is open and positively charged. Recombinant human and zebrafish TIGAR hydrolyze fructose-2,6-bisphosphate and fructose-1,6-bisphosphate but not fructose-6-phosphate in vitro, confirming bisphosphatase activity.","method":"X-ray crystallography; in vitro phosphatase activity assays with recombinant human and zebrafish TIGAR","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure plus in vitro enzymatic reconstitution with defined substrates and mutagenesis-level active-site characterization","pmids":["19015259"],"is_preprint":false},{"year":2009,"finding":"TIGAR inhibits autophagy induced by nutrient starvation or metabolic stress by suppressing ROS levels; this inhibition is p53-independent and does not involve the mTOR pathway. Loss of TIGAR-induced autophagy moderates apoptosis by restraining ROS.","method":"TIGAR knockdown/overexpression, autophagy markers (LC3, autophagosome formation), ROS measurement, mTOR pathway analysis, nutrient starvation models","journal":"The EMBO Journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KD/OE with multiple orthogonal readouts (autophagy markers, ROS, mTOR), p53-independence established by genetic controls, replicated by multiple subsequent studies","pmids":["19713938"],"is_preprint":false},{"year":2012,"finding":"Under hypoxia, a fraction of TIGAR protein relocalizes to mitochondria and forms a complex with hexokinase 2 (HK2), resulting in increased HK2 activity. Mitochondrial localization depends on mitochondrial HK2 and HIF1α activity. The fructose-2,6-bisphosphatase activity of TIGAR is independent of HK2 binding and mitochondrial localization, but both activities cooperate to limit mitochondrial ROS and protect from cell death.","method":"Subcellular fractionation, Co-immunoprecipitation, HK2 activity assay, HIF1α inhibition, hypoxia cell culture models, cell death assays","journal":"Proceedings of the National Academy of Sciences of the USA","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP for complex identification, activity assay for HK2, localization by fractionation with functional consequence, genetic dissection of enzymatic vs. non-enzymatic activities","pmids":["23185017"],"is_preprint":false},{"year":2014,"finding":"TIGAR has the highest catalytic efficiency for 2,3-bisphosphoglycerate (2,3-BPG) among tested physiological substrates (~400-fold higher than for fructose-2,6-bisphosphate), and loss of TIGAR consistently increases cellular 2,3-BPG levels up to 5-fold, suggesting 2,3-BPG is the primary physiological substrate.","method":"In vitro phosphatase activity assays with recombinant human TIGAR against a panel of phosphate esters; genetic and shRNA-based cell culture models measuring metabolite levels","journal":"The Biochemical Journal","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro enzymatic reconstitution with multiple substrates and quantitative kinetics, corroborated by cell-based metabolite measurements in two genetic model systems","pmids":["24423178"],"is_preprint":false},{"year":2012,"finding":"TIGAR mediates p53-induced G1-phase cell-cycle arrest by promoting dephosphorylation of RB and stabilizing the RB-E2F1 complex, thereby inhibiting G1-to-S phase entry; this is p21-independent.","method":"Co-immunoprecipitation of RB-E2F1, RT-PCR, western blot, luciferase reporter assay, chromatin immunoprecipitation, MCF-7 xenograft tumor model","journal":"British Journal of Cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP for protein interaction, multiple pathway readouts (CDK levels, RB phosphorylation), in vivo xenograft, single lab","pmids":["22782351"],"is_preprint":false},{"year":2015,"finding":"TIGAR regulates DNA damage response through two mechanisms: (1) promoting NADPH/ribose production via the pentose phosphate pathway to support repair, and (2) modulating ATM phosphorylation through a Cdk5-dependent pathway. After genotoxic stress, TIGAR also relocates to the nucleus.","method":"TIGAR knockdown, pharmacological and siRNA inhibition of Cdk5 and ATM, γ-H2AX foci assay, NADPH/ribose supplementation rescue, nuclear fractionation","journal":"Scientific Reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockdown with pathway rescue experiments (NADPH/ribose supplementation, Cdk5 inhibition), localization by fractionation, single lab","pmids":["25928429"],"is_preprint":false},{"year":2018,"finding":"TIGAR directly inhibits NF-κB signaling by competing with NEMO for binding to the linear ubiquitin assembly complex LUBAC, thereby preventing linear ubiquitination of NEMO and blocking IKKβ phosphorylation/activation. This function is independent of TIGAR's phosphatase activity, as a phosphatase-dead mutant is equally effective.","method":"Co-immunoprecipitation, direct binding competition assay with NEMO and LUBAC, phosphatase-dead TIGAR mutant, NF-κB reporter assays, TIGAR knockout mice (adipose tissue NF-κB signaling), adipocyte-specific TIGAR overexpression","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP demonstrating direct TIGAR-LUBAC interaction, phosphatase-dead mutant establishing non-enzymatic mechanism, in vivo genetic models (KO and adipocyte-specific OE) confirming physiological relevance","pmids":["29650758"],"is_preprint":false},{"year":2019,"finding":"TIGAR promotes neural stem cell (NSC) differentiation by reducing glycolysis and increasing oxidative phosphorylation, leading to elevated acetyl-CoA levels and increased H3K9 acetylation at promoters of neuronal differentiation genes (Ngn1, Neurod1, Gfap). Acetate supplementation (precursor of acetyl-CoA) rescues NSC differentiation defects caused by TIGAR knockdown.","method":"TIGAR knockdown in cultured NSCs, acetyl-CoA measurement, ChIP for H3K9ac at gene promoters, acetate rescue experiment, metabolic flux analysis (oxygen consumption, lactate)","journal":"Cell Death & Disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP for epigenetic marks, metabolite measurement, rescue experiments, single lab with multiple orthogonal methods","pmids":["30814486"],"is_preprint":false},{"year":2019,"finding":"TIGAR translocates to mitochondria in skeletal muscle during exhaustive exercise and interacts with ATP synthase F1 subunit α (ATP5A1), binding that increases during exhaustive exercise. Mitochondrial TIGAR promotes ATP generation, maintains mitochondrial membrane potential, and reduces mitochondrial oxidative stress under hypoxia. TIGAR also regulates mitochondrial biogenesis via the SIRT1-PGC1α deacetylation pathway.","method":"GST-TIGAR pulldown followed by liquid chromatography mass spectrometry (to identify ATP5A1 binding), subcellular fractionation, mitochondria-targeted TIGAR overexpression plasmid, TIGAR KO mice exhaustive swimming model, SIRT1-PGC1α pathway analysis","journal":"FASEB Journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — GST-pulldown + LC-MS for interaction, KO mouse model, in vivo exercise model, single lab","pmids":["30726106"],"is_preprint":false},{"year":2021,"finding":"The E3 ubiquitin ligase TRIM31 interacts with TIGAR, promotes its polyubiquitination, and targets it for proteasomal degradation, thereby reducing TIGAR protein levels during cerebral ischemia.","method":"Co-immunoprecipitation (TRIM31-TIGAR interaction), ubiquitination assay, proteasome inhibitor rescue, TRIM31 KO mouse model, TIGAR KD rescue experiments in ischemia model","journal":"Redox Biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus ubiquitination assay for E3 ligase-substrate relationship, genetic models (KO, KD), single lab","pmids":["34218200"],"is_preprint":false},{"year":2022,"finding":"A second E3 ubiquitin ligase, TRIM35, also interacts with TIGAR and promotes its polyubiquitination and proteasomal degradation; TRIM35 knockdown alleviates renal ischemia-reperfusion injury in part by stabilizing TIGAR and enhancing mitochondrial fusion.","method":"Co-immunoprecipitation (TRIM35-TIGAR interaction), ubiquitination assay, proteasome pathway inhibition, TIGAR KD rescue, renal IRI model","journal":"International Journal of Biological Macromolecules","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus ubiquitination assay, functional rescue by TIGAR KD, single lab","pmids":["35421414"],"is_preprint":false},{"year":2019,"finding":"Nuclear TIGAR directly interacts with NRF2 and facilitates chromatin recruitment of NRF2, the H3K4me3 methylase MLL1, and elongating Pol-II to activate expression of NRF2 target genes (NQO1/2, PRDX1, GSTM4) and NSD2; this epigenetic co-activator function is independent of TIGAR's enzymatic phosphatase activity and confers cancer cell resistance to chemotherapy.","method":"Co-immunoprecipitation (TIGAR-NRF2 interaction), ChIP for NRF2/MLL1/Pol-II at target gene promoters, phosphatase-dead TIGAR mutant, nuclear localization studies, in vitro and in vivo chemotherapy resistance assays","journal":"Acta Pharmaceutica Sinica B","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP for direct interaction, ChIP for chromatin recruitment, enzyme-dead mutant proving non-enzymatic mechanism, single lab","pmids":["35847493"],"is_preprint":false},{"year":2024,"finding":"Macrophage TIGAR directly binds to TGF-β-activated kinase 1 (TAK1) and promotes TRAF6-mediated ubiquitination and auto-phosphorylation of TAK1, thereby amplifying inflammatory signaling in sepsis. Residues 152–161 of TIGAR constitute a crucial binding motif, and this pro-inflammatory function is independent of TIGAR's phosphatase activity.","method":"Co-immunoprecipitation (TIGAR-TAK1 direct binding), ubiquitination assay, myeloid-specific Tigar knockout mice (LPS and CLP sepsis models), TIGAR motif mutagenesis, pharmacological disruption of TIGAR-TAK1 interaction (5Z-7-oxozeaenol)","journal":"Nature Communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP with mutagenesis of binding motif, phosphatase-dead mutant control, two in vivo sepsis models with myeloid-specific KO, pharmacological intervention, single lab but multiple orthogonal methods","pmids":["38773142"],"is_preprint":false},{"year":2024,"finding":"Under prolonged ischemia, TIGAR translocates to mitochondria and inhibits succinate dehydrogenase (SDH) activity by interacting with SDHA and mediating post-translational modifications (acetylation and succinylation) of SDHA, thereby reducing ROS generation via the reverse electron transfer chain and decreasing neuronal ferroptosis. This mechanism is independent of the PPP-NADPH-GPX4 antioxidant pathway.","method":"TIGAR overexpression/KO in neurons, SDH activity assay, mitochondrial fractionation, Co-IP (TIGAR-SDHA), post-translational modification analysis (acetylation/succinylation), lipid peroxidation assay, ferroptosis markers, prolonged ischemia mouse model","journal":"Free Radical Biology & Medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP for interaction, enzymatic activity assay, PTM characterization, genetic models, single lab","pmids":["38494143"],"is_preprint":false},{"year":2014,"finding":"TIGAR expression in renal proximal straight tubules is induced by ischemia-reperfusion in a p53-dependent manner and inhibits phosphofructokinase-1 activity, depleting glycolytic ATP, with context-dependent effects: under mild ischemia TIGAR activates G6PD and raises NADPH/GSH (protective); under severe ischemia this protective response fails and TIGAR inhibition by siRNA is protective.","method":"siRNA knockdown of TIGAR in vivo and in vitro, PFK-1 activity assay, G6PD activity assay, NADPH/GSH measurement, functional/histological kidney injury readouts, p53-dependent induction shown by p53 inhibitor","journal":"American Journal of Physiology. Renal Physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo siRNA knockdown with enzymatic activity assays and functional readouts, single lab","pmids":["25503731"],"is_preprint":false},{"year":2011,"finding":"SP1 transcription factor binds the TIGAR promoter at a minimal region (-56/-4) and is indispensable for basal TIGAR transcription in liver cancer cells, as shown by EMSA and chromatin immunoprecipitation.","method":"5'-RACE (transcription start site mapping), luciferase reporter with 5'-deletion constructs, EMSA, chromatin immunoprecipitation, SP1 knockdown","journal":"Molecular and Cellular Biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — EMSA plus ChIP for transcription factor binding, luciferase deletion analysis, single lab","pmids":["21761199"],"is_preprint":false},{"year":2013,"finding":"CREB binds a cAMP-response element (CRE) at the TIGAR promoter region (-4/+13) and regulates TIGAR expression; CREB knockdown reduces TIGAR promoter activity and expression, while CREB overexpression or forskolin treatment enhances them.","method":"5'-deletion and site-directed mutagenesis of TIGAR promoter-luciferase constructs, EMSA, chromatin immunoprecipitation, CREB knockdown and overexpression","journal":"Biochemical and Biophysical Research Communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus EMSA plus promoter mutagenesis, single lab","pmids":["24036271"],"is_preprint":false},{"year":2021,"finding":"TCF19 interacts with p53 and co-regulates TIGAR transcription; TCF19/p53 form complexes that include either CBP (activating) or HDAC1 (repressing) depending on glucose conditions, epigenetically programming TIGAR expression to control glycolysis and mitochondrial energy metabolism in hepatocytes.","method":"IP/MS (TCF19-p53 co-immunoprecipitation), ChIP for TCF19/p53/CBP/HDAC1 at TIGAR promoter, TCF19 and p53 knockdown, metabolic flux analysis (ECAR, OCR, ATP), RNA-seq","journal":"FASEB Journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — IP/MS for interaction, ChIP for chromatin occupancy, functional metabolic assays, single lab","pmids":["34369624"],"is_preprint":false},{"year":2015,"finding":"TIGAR expression is induced independently of p53 and TAp73 in most mouse tissues in vivo, and mouse TIGAR is less responsive to p53 family members than human TIGAR; TIGAR induction in mouse intestine after ionizing radiation is also p53- and TAp73-independent.","method":"p53 KO mice, TAp73 KO mice, ionizing radiation in vivo, western blot for TIGAR in multiple mouse tissues","journal":"Cell Death & Disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO mouse models with tissue-level protein analysis, single lab","pmids":["26247727"],"is_preprint":false},{"year":2019,"finding":"TIGAR negatively regulates BRCA1 and the Fanconi anemia pathway; TIGAR knockdown enhances sensitivity to the PARP inhibitor olaparib by downregulating these DNA repair components and increasing cellular senescence.","method":"Genome-scale CRISPR/Cas9 knockout screen, TIGAR KD in cancer cells, BRCA1 and Fanconi anemia pathway western blot, olaparib sensitivity assays, senescence assays","journal":"Communications Biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genome-scale screen identification followed by focused mechanistic validation with KD and pathway analysis, single lab","pmids":["31508509"],"is_preprint":false},{"year":2017,"finding":"TIGAR promotes NSCLC cell invasion and metastasis via a Met signaling pathway; Met expression positively correlates with TIGAR in NSCLC, and TIGAR knockdown reduces invasion/metastasis in vitro and in vivo.","method":"TIGAR knockdown/overexpression, Transwell invasion assays, in vivo metastasis model, immunohistochemistry for TIGAR and Met in patient samples, Met inhibitor experiments","journal":"Molecular Cancer","confidence":"Low","confidence_rationale":"Tier 3 / Weak — functional KD with invasion readout, correlation data, no direct biochemical mechanism of TIGAR-Met interaction established","pmids":["29753331"],"is_preprint":false},{"year":2021,"finding":"SIRT3 regulates TIGAR expression in cardiomyocytes by deacetylating p53; high glucose increases p53 acetylation, which drives TIGAR upregulation and suppresses glycolysis. SIRT3 overexpression reduces p53 acetylation and TIGAR expression, restoring glycolysis and reducing ROS and apoptosis under hyperglycemic conditions.","method":"SIRT3 overexpression (adenovirus) and TIGAR siRNA in H9c2 cells, p53 acetylation western blot, glycolysis (ECAR) measurement, PFKFB3 expression, db/db diabetic mouse model in vivo","journal":"Journal of the American Heart Association","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic manipulation with acetylation readout, in vitro and in vivo models, single lab","pmids":["33586458"],"is_preprint":false},{"year":2022,"finding":"TIGAR confers ferroptosis resistance in colorectal cancer cells via a ROS/AMPK/SCD1 signaling pathway; TIGAR knockdown increases lipid peroxidation, decreases GSH/GSSG ratio, and reduces SCD1 expression in a redox- and AMPK-dependent manner.","method":"TIGAR knockdown in CRC cells, erastin-induced ferroptosis assay, GSH/GSSG ratio, lipid peroxidation (MDA), AMPK and SCD1 western blot, antioxidant rescue","journal":"Free Radical Biology & Medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional KD with multiple metabolic and cell death readouts, pathway inhibition experiments, single lab","pmids":["35271998"],"is_preprint":false},{"year":2016,"finding":"Following APC/Wnt pathway activation, TIGAR and RAC1/NOX generate opposing ROS signals in the same intestinal cell: TIGAR limits damaging ROS while RAC1/NOX generates pro-proliferative ROS. Loss of TIGAR increases oxidative damage and inhibits proliferation; TIGAR and RAC1 cooperate to maintain optimal intestinal proliferation after APC loss.","method":"TIGAR KO mice, APC deletion mouse model, 3D intestinal organoid cultures, ROS measurement, NOX inhibition, genetic epistasis (TIGAR KO × RAC1 KO double mutants)","journal":"Genes & Development","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo genetic epistasis with double KO, 3D organoid models, ROS pathway dissection with pharmacological and genetic tools","pmids":["26679840"],"is_preprint":false},{"year":2014,"finding":"TIGAR ischemia/reperfusion upregulation in brain is mediated by the transcription factor SP1; ROS (H2O2) and stress hormones (adrenaline, hydrocortisone, glucagon) induce TIGAR protein, while insulin suppresses it. SP1 knockdown or inhibition blocks ischemia-induced TIGAR upregulation.","method":"SP1 siRNA, mithramycin A inhibition, SP1 ChIP at TIGAR promoter, tMCAO/R mouse model, OGD/R in HT22 cells and primary neurons, hormone and glucose treatments","journal":"Neurochemistry International","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus genetic SP1 KD, in vivo and in vitro ischemia models, single lab","pmids":["25445985"],"is_preprint":false},{"year":2022,"finding":"Under prolonged ischemia (PPP impaired), TIGAR induces autophagy which activates Nrf2, providing an alternative antioxidant mechanism independent of PPP/NADPH. Genetic deletion of Atg7 or Nrf2 abolishes TIGAR neuroprotection in prolonged ischemia.","method":"PPP inhibition (G6PD knockdown), catalytically-inactive TIGAR mutant expression, Atg7 KO, Nrf2 KO, mouse prolonged ischemia model, ROS and neuronal survival assays","journal":"Redox Biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple genetic knockouts, enzyme-dead mutant, in vivo mouse model, single lab","pmids":["35576689"],"is_preprint":false},{"year":2019,"finding":"TIGAR knockdown in cancer cells decreases BRCA1 and Fanconi anemia pathway components, increases senescence, and sensitizes cells to PARP inhibitor olaparib; this identifies TIGAR as a modifier of homologous recombination capacity.","method":"CRISPR/Cas9 genome-scale screen (identification), TIGAR KD, BRCA1 western blot, olaparib sensitivity, senescence assay","journal":"Communications Biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genome-wide screen plus focused mechanistic follow-up, single lab","pmids":["31508509"],"is_preprint":false}],"current_model":"TIGAR (TP53-induced glycolysis and apoptosis regulator) is a histidine phosphatase that primarily hydrolyzes 2,3-bisphosphoglycerate (and also fructose-2,6-bisphosphate/fructose-1,6-bisphosphate), lowering glycolytic flux and diverting glucose-6-phosphate into the pentose phosphate pathway to generate NADPH and GSH for antioxidant defense; beyond this enzymatic role, TIGAR has multiple non-enzymatic functions including: (1) under hypoxia, translocating to mitochondria where it binds and activates HK2 and inhibits succinate dehydrogenase (SDHA) to limit mitochondrial ROS and ferroptosis; (2) directly competing with NEMO for LUBAC binding to block NF-κB activation; (3) directly binding TAK1 to promote its ubiquitination and pro-inflammatory signaling in macrophages; (4) interacting with NRF2 as a nuclear chromatin co-activator to epigenetically regulate antioxidant gene expression; (5) suppressing autophagy through ROS reduction; and (6) mediating cell-cycle arrest via RB dephosphorylation and RB-E2F1 complex stabilization—with transcription regulated by p53, p63/p73, SP1, and CREB, and protein stability controlled by E3 ubiquitin ligases TRIM31 and TRIM35."},"narrative":{"mechanistic_narrative":"TIGAR is a p53-inducible histidine-phosphatase that reprograms central carbon metabolism to control redox balance and cell fate, originally identified as a gene that lowers fructose-2,6-bisphosphate to inhibit glycolysis, divert glucose into the pentose phosphate pathway, and suppress ROS-associated apoptosis [PMID:16839880]. Structural and enzymatic work defined it as a histidine-phosphatase-fold bisphosphatase, and kinetic profiling established 2,3-bisphosphoglycerate as its highest-efficiency physiological substrate (~400-fold over fructose-2,6-bisphosphate) [PMID:19015259, PMID:24423178]. The resulting NADPH/GSH output underlies a broad antioxidant program that restrains autophagy [PMID:19713938], protects proliferating intestinal cells from oxidative damage in cooperation with RAC1/NOX following APC loss [PMID:26679840], and confers ferroptosis and chemotherapy resistance in cancer [PMID:35271998]. Layered on this enzymatic role is a set of phosphatase-independent activities: TIGAR translocates to mitochondria to bind and activate hexokinase 2 under hypoxia [PMID:23185017] and to inhibit succinate dehydrogenase via SDHA modification to limit reverse-electron-transfer ROS and ferroptosis during ischemia [PMID:38494143]; it competes with NEMO for LUBAC binding to block NF-κB activation [PMID:29650758]; it binds TAK1 in macrophages to promote TRAF6-mediated ubiquitination and amplify inflammatory signaling, with residues 152–161 forming the binding motif [PMID:38773142]; and nuclear TIGAR acts as an NRF2 chromatin co-activator recruiting MLL1 and elongating Pol-II to antioxidant gene promoters [PMID:35847493]. TIGAR also enforces p53-induced G1 arrest by promoting RB dephosphorylation and stabilizing the RB-E2F1 complex [PMID:22782351]. Transcription is driven by SP1 and CREB at the proximal promoter and by p53/TCF19 complexes [PMID:21761199, PMID:24036271, PMID:34369624], while protein abundance is controlled by the E3 ubiquitin ligases TRIM31 and TRIM35 [PMID:34218200, PMID:35421414].","teleology":[{"year":2006,"claim":"Established TIGAR's founding identity: a p53 target that links transcriptional stress responses to glycolytic control and ROS-dependent apoptosis.","evidence":"Microarray identification, siRNA knockdown with fructose-2,6-bisphosphate, ROS and apoptosis assays in cell lines","pmids":["16839880"],"confidence":"High","gaps":["Did not define the direct enzymatic substrate or catalytic mechanism","Physiological vs. cancer-cell relevance of the glycolytic switch not resolved"]},{"year":2008,"claim":"Resolved the molecular basis of TIGAR activity by showing it is a histidine-phosphatase-fold enzyme that hydrolyzes bisphosphate sugars in vitro.","evidence":"X-ray crystallography of zebrafish TIGAR plus in vitro phosphatase assays on recombinant human and zebrafish protein","pmids":["19015259"],"confidence":"High","gaps":["In vitro substrate panel did not rank physiological substrates by efficiency","No structure of human protein or substrate-bound complex"]},{"year":2014,"claim":"Reassigned the primary physiological substrate from fructose-2,6-bisphosphate to 2,3-bisphosphoglycerate based on catalytic efficiency and cellular metabolite levels.","evidence":"Quantitative in vitro kinetics against a phosphate-ester panel plus metabolite measurement in two genetic cell models","pmids":["24423178"],"confidence":"High","gaps":["In vivo flux contribution of 2,3-BPG hydrolysis across tissues not quantified","Does not address non-enzymatic functions"]},{"year":2009,"claim":"Connected TIGAR's redox role to autophagy, showing it restrains stress-induced autophagy via ROS suppression rather than through mTOR.","evidence":"Knockdown/overexpression with LC3/autophagosome readouts, ROS measurement and mTOR pathway controls","pmids":["19713938"],"confidence":"High","gaps":["Molecular link between ROS reduction and autophagy machinery left unspecified"]},{"year":2012,"claim":"Revealed a non-metabolic mitochondrial function: hypoxic TIGAR binds and activates hexokinase 2 to limit mitochondrial ROS, separable from its bisphosphatase activity.","evidence":"Subcellular fractionation, reciprocal Co-IP, HK2 activity assay and HIF1α inhibition in hypoxia models","pmids":["23185017"],"confidence":"High","gaps":["Mechanism of HK2 activation by TIGAR binding not defined","Determinants of mitochondrial import unresolved"]},{"year":2012,"claim":"Extended TIGAR into cell-cycle control, showing it mediates p53-induced G1 arrest through RB dephosphorylation independent of p21.","evidence":"RB-E2F1 Co-IP, RB phosphorylation/CDK readouts, reporter assays and MCF-7 xenograft","pmids":["22782351"],"confidence":"Medium","gaps":["Phosphatase whose activity dephosphorylates RB not identified","Single lab, no reciprocal validation of the RB-E2F1 mechanism"]},{"year":2015,"claim":"Linked TIGAR to the DNA damage response via PPP-derived NADPH/ribose and Cdk5-dependent ATM modulation, with stress-induced nuclear relocalization.","evidence":"Knockdown, Cdk5/ATM inhibition, γ-H2AX foci, NADPH/ribose rescue and nuclear fractionation","pmids":["25928429"],"confidence":"Medium","gaps":["Mechanism of nuclear import not defined","Direct vs. indirect role in ATM signaling unclear"]},{"year":2019,"claim":"Identified TIGAR as a chromatin co-activator that physically partners with NRF2 to recruit MLL1 and Pol-II, an epigenetic role distinct from its enzymatic function.","evidence":"TIGAR-NRF2 Co-IP, ChIP for NRF2/MLL1/Pol-II at target genes, phosphatase-dead mutant and chemoresistance assays","pmids":["35847493"],"confidence":"Medium","gaps":["How TIGAR is recruited to chromatin not established","Single lab"]},{"year":2018,"claim":"Defined a phosphatase-independent immune-signaling role: TIGAR competes with NEMO for LUBAC to block linear ubiquitination and NF-κB activation.","evidence":"Co-IP/binding competition with NEMO and LUBAC, phosphatase-dead mutant, NF-κB reporters and TIGAR KO/adipocyte-OE mice","pmids":["29650758"],"confidence":"High","gaps":["Structural basis of NEMO/LUBAC competition not resolved","Generality across cell types beyond adipose untested"]},{"year":2024,"claim":"Showed a contrasting pro-inflammatory function in macrophages where TIGAR binds TAK1 via residues 152–161 to promote its ubiquitination and activation in sepsis.","evidence":"TIGAR-TAK1 Co-IP, motif mutagenesis, ubiquitination assay, phosphatase-dead control, myeloid-specific KO sepsis models and pharmacological disruption","pmids":["38773142"],"confidence":"High","gaps":["Reconciliation with NF-κB-inhibitory LUBAC mechanism across cell types unresolved"]},{"year":2024,"claim":"Established a second mitochondrial enzyme-independent mechanism: ischemic TIGAR inhibits SDHA via acetylation/succinylation to suppress reverse-electron-transfer ROS and ferroptosis.","evidence":"TIGAR OE/KO in neurons, SDH activity assay, TIGAR-SDHA Co-IP, PTM analysis, ferroptosis markers and ischemia model","pmids":["38494143"],"confidence":"Medium","gaps":["How TIGAR drives SDHA acetylation/succinylation mechanistically unknown","Single lab"]},{"year":2021,"claim":"Identified TRIM31 as an E3 ligase controlling TIGAR abundance through ubiquitin-proteasomal degradation in cerebral ischemia.","evidence":"TRIM31-TIGAR Co-IP, ubiquitination assay, proteasome rescue and TRIM31 KO mouse ischemia model","pmids":["34218200"],"confidence":"Medium","gaps":["Ubiquitination site on TIGAR not mapped","Single lab"]},{"year":2022,"claim":"Identified a second degradative E3 ligase, TRIM35, linking TIGAR stability to mitochondrial fusion in renal ischemia-reperfusion.","evidence":"TRIM35-TIGAR Co-IP, ubiquitination assay, TIGAR KD rescue in renal IRI model","pmids":["35421414"],"confidence":"Medium","gaps":["Whether TRIM31 and TRIM35 act redundantly or in distinct tissues unresolved"]},{"year":null,"claim":"How TIGAR's opposing context-dependent roles—antioxidant protector versus injury amplifier, NF-κB inhibitor versus TAK1 activator—are selected within a given cell remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model linking subcellular localization to functional output","Determinants of mitochondrial vs. nuclear vs. cytosolic partitioning unknown","Structural basis of competing protein-protein interactions undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,1,4]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[7,13]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[12]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[3,9,14]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[6,12]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,4,15]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[2,23,24]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[7,13]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[5]}],"complexes":["LUBAC (competitive binder)","RB-E2F1 complex"],"partners":["HK2","NEMO/IKBKG","TAK1/MAP3K7","NRF2/NFE2L2","SDHA","ATP5A1","TRIM31","TRIM35"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NQ88","full_name":"Fructose-2,6-bisphosphatase TIGAR","aliases":["TP53-induced glycolysis and apoptosis regulator","TP53-induced glycolysis regulatory phosphatase"],"length_aa":270,"mass_kda":30.1,"function":"Fructose-bisphosphatase hydrolyzing fructose-2,6-bisphosphate as well as fructose-1,6-bisphosphate (PubMed:19015259). Acts as a negative regulator of glycolysis by lowering intracellular levels of fructose-2,6-bisphosphate in a p53/TP53-dependent manner, resulting in the pentose phosphate pathway (PPP) activation and NADPH production (PubMed:16839880, PubMed:22887998). Contributes to the generation of reduced glutathione to cause a decrease in intracellular reactive oxygen species (ROS) content, correlating with its ability to protect cells from oxidative or metabolic stress-induced cell death (PubMed:16839880, PubMed:19713938, PubMed:22887998, PubMed:23726973, PubMed:23817040). Plays a role in promoting protection against cell death during hypoxia by decreasing mitochondria ROS levels in a HK2-dependent manner through a mechanism that is independent of its fructose-bisphosphatase activity (PubMed:23185017). In response to cardiac damage stress, mediates p53-induced inhibition of myocyte mitophagy through ROS levels reduction and the subsequent inactivation of BNIP3. Reduced mitophagy results in an enhanced apoptotic myocyte cell death, and exacerbates cardiac damage (By similarity). Plays a role in adult intestinal regeneration; contributes to the growth, proliferation and survival of intestinal crypts following tissue ablation (PubMed:23726973). Plays a neuroprotective role against ischemic brain damage by enhancing PPP flux and preserving mitochondria functions (By similarity). Protects glioma cells from hypoxia- and ROS-induced cell death by inhibiting glycolysis and activating mitochondrial energy metabolism and oxygen consumption in a TKTL1-dependent and p53/TP53-independent manner (PubMed:22887998). Plays a role in cancer cell survival by promoting DNA repair through activating PPP flux in a CDK5-ATM-dependent signaling pathway during hypoxia and/or genome stress-induced DNA damage responses (PubMed:25928429). Involved in intestinal tumor progression (PubMed:23726973)","subcellular_location":"Cytoplasm; Nucleus; Mitochondrion","url":"https://www.uniprot.org/uniprotkb/Q9NQ88/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TIGAR","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/TIGAR","total_profiled":1310},"omim":[{"mim_id":"610775","title":"TP53-INDUCED GLYCOLYSIS AND APOPTOSIS REGULATOR; TIGAR","url":"https://www.omim.org/entry/610775"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in many","driving_tissues":[],"url":"https://www.proteinatlas.org/search/TIGAR"},"hgnc":{"alias_symbol":[],"prev_symbol":["C12orf5"]},"alphafold":{"accession":"Q9NQ88","domains":[{"cath_id":"3.40.50.1240","chopping":"3-94_125-179_187-264","consensus_level":"high","plddt":91.1986,"start":3,"end":264}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NQ88","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NQ88-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NQ88-F1-predicted_aligned_error_v6.png","plddt_mean":89.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TIGAR","jax_strain_url":"https://www.jax.org/strain/search?query=TIGAR"},"sequence":{"accession":"Q9NQ88","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NQ88.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NQ88/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NQ88"}},"corpus_meta":[{"pmid":"16839880","id":"PMC_16839880","title":"TIGAR, a 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of physiology. Heart and circulatory physiology","url":"https://pubmed.ncbi.nlm.nih.gov/30901275","citation_count":21,"is_preprint":false},{"pmid":"33359019","id":"PMC_33359019","title":"TP53-induced glycolysis and apoptosis regulator (TIGAR) ameliorates lysosomal damage in the 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine-mediated mouse model of Parkinson's disease.","date":"2020","source":"Toxicology letters","url":"https://pubmed.ncbi.nlm.nih.gov/33359019","citation_count":21,"is_preprint":false},{"pmid":"27499152","id":"PMC_27499152","title":"Distinctive interrelation of p53 with SCO2, COX, and TIGAR in human gastric cancer.","date":"2016","source":"Pathology, research and practice","url":"https://pubmed.ncbi.nlm.nih.gov/27499152","citation_count":21,"is_preprint":false},{"pmid":"32946259","id":"PMC_32946259","title":"TIGAR reduces smooth muscle cell autophagy to prevent pulmonary hypertension.","date":"2020","source":"American journal of physiology. Heart and circulatory physiology","url":"https://pubmed.ncbi.nlm.nih.gov/32946259","citation_count":20,"is_preprint":false},{"pmid":"29769743","id":"PMC_29769743","title":"TIGAR knockdown enhanced the anticancer effect of aescin via regulating autophagy and apoptosis in colorectal cancer cells.","date":"2018","source":"Acta pharmacologica Sinica","url":"https://pubmed.ncbi.nlm.nih.gov/29769743","citation_count":20,"is_preprint":false},{"pmid":"24363807","id":"PMC_24363807","title":"TIGAR is correlated with maximal standardized uptake value on FDG-PET and survival in non-small cell lung cancer.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/24363807","citation_count":20,"is_preprint":false},{"pmid":"29650758","id":"PMC_29650758","title":"The fructose-2,6-bisphosphatase TIGAR suppresses NF-κB signaling by directly inhibiting the linear ubiquitin assembly complex LUBAC.","date":"2018","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/29650758","citation_count":20,"is_preprint":false},{"pmid":"21761199","id":"PMC_21761199","title":"SP1 plays a pivotal role for basal activity of TIGAR promoter in liver cancer cell lines.","date":"2011","source":"Molecular and cellular biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/21761199","citation_count":20,"is_preprint":false},{"pmid":"35847493","id":"PMC_35847493","title":"Nuclear TIGAR mediates an epigenetic and metabolic autoregulatory loop via NRF2 in cancer therapeutic resistance.","date":"2021","source":"Acta pharmaceutica Sinica. B","url":"https://pubmed.ncbi.nlm.nih.gov/35847493","citation_count":19,"is_preprint":false},{"pmid":"31062473","id":"PMC_31062473","title":"Down-regulation of TFAM increases the sensitivity of tumour cells to radiation via p53/TIGAR signalling pathway.","date":"2019","source":"Journal of cellular and molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/31062473","citation_count":19,"is_preprint":false},{"pmid":"30823646","id":"PMC_30823646","title":"Knockdown of the TP53-Induced Glycolysis and Apoptosis Regulator (TIGAR) Sensitizes Glioma Cells to Hypoxia, Irradiation and Temozolomide.","date":"2019","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/30823646","citation_count":19,"is_preprint":false},{"pmid":"34082063","id":"PMC_34082063","title":"Targeting neuroinflammation to treat cerebral ischemia - The role of TIGAR/NADPH axis.","date":"2021","source":"Neurochemistry international","url":"https://pubmed.ncbi.nlm.nih.gov/34082063","citation_count":19,"is_preprint":false},{"pmid":"31966064","id":"PMC_31966064","title":"IDH1-R132H mutation radiosensitizes U87MG glioma cells via epigenetic downregulation of TIGAR.","date":"2019","source":"Oncology letters","url":"https://pubmed.ncbi.nlm.nih.gov/31966064","citation_count":19,"is_preprint":false},{"pmid":"38773142","id":"PMC_38773142","title":"Disruption of TIGAR-TAK1 alleviates immunopathology in a murine model of sepsis.","date":"2024","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/38773142","citation_count":18,"is_preprint":false},{"pmid":"27491040","id":"PMC_27491040","title":"Akt mediates TIGAR induction in HeLa cells following PFKFB3 inhibition.","date":"2016","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/27491040","citation_count":18,"is_preprint":false},{"pmid":"36399798","id":"PMC_36399798","title":"Cordycepin exhibits anti-fatigue effect via activating TIGAR/SIRT1/PGC-1α signaling pathway.","date":"2022","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/36399798","citation_count":17,"is_preprint":false},{"pmid":"28138701","id":"PMC_28138701","title":"Hypoxia-induced hsa-miR-101 promotes glycolysis by targeting TIGAR mRNA in clear cell renal cell carcinoma.","date":"2017","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/28138701","citation_count":17,"is_preprint":false},{"pmid":"18945750","id":"PMC_18945750","title":"Identification of TIGAR in the equilibrative nucleoside transporter 2-mediated response to fludarabine in chronic lymphocytic leukemia cells.","date":"2008","source":"Haematologica","url":"https://pubmed.ncbi.nlm.nih.gov/18945750","citation_count":17,"is_preprint":false},{"pmid":"29462755","id":"PMC_29462755","title":"The human T-cell leukemia virus type-1 p30II protein activates p53 and induces the TIGAR and suppresses oncogene-induced oxidative stress during viral carcinogenesis.","date":"2018","source":"Virology","url":"https://pubmed.ncbi.nlm.nih.gov/29462755","citation_count":16,"is_preprint":false},{"pmid":"32049042","id":"PMC_32049042","title":"Dynamic ROS Regulation by TIGAR: Balancing Anti-cancer and Pro-metastasis Effects.","date":"2020","source":"Cancer cell","url":"https://pubmed.ncbi.nlm.nih.gov/32049042","citation_count":15,"is_preprint":false},{"pmid":"24036271","id":"PMC_24036271","title":"CREB, another culprit for TIGAR promoter activity and expression.","date":"2013","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/24036271","citation_count":14,"is_preprint":false},{"pmid":"31119791","id":"PMC_31119791","title":"miR-885-5p plays an accomplice role in liver cancer by instigating TIGAR expression via targeting its promoter.","date":"2019","source":"Biotechnology and applied biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/31119791","citation_count":14,"is_preprint":false},{"pmid":"35165280","id":"PMC_35165280","title":"MiR-652-5p elevated glycolysis level by targeting TIGAR in T-cell acute lymphoblastic leukemia.","date":"2022","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/35165280","citation_count":13,"is_preprint":false},{"pmid":"35421414","id":"PMC_35421414","title":"The inhibition of TRIM35-mediated TIGAR ubiquitination enhances mitochondrial fusion and alleviates renal ischemia-reperfusion injury.","date":"2022","source":"International journal of biological macromolecules","url":"https://pubmed.ncbi.nlm.nih.gov/35421414","citation_count":13,"is_preprint":false},{"pmid":"33858654","id":"PMC_33858654","title":"Metformin regulates the Th17/Treg balance by glycolysis with TIGAR in hepatic ischemia-reperfusion injury.","date":"2021","source":"Journal of pharmacological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/33858654","citation_count":13,"is_preprint":false},{"pmid":"32256808","id":"PMC_32256808","title":"microRNA-144 inhibits cell proliferation and invasion by directly targeting TIGAR in esophageal carcinoma.","date":"2020","source":"Oncology letters","url":"https://pubmed.ncbi.nlm.nih.gov/32256808","citation_count":12,"is_preprint":false},{"pmid":"31160088","id":"PMC_31160088","title":"TIGAR suppresses seizures induced by kainic acid through inhibiting oxidative stress and neuronal apoptosis.","date":"2019","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/31160088","citation_count":12,"is_preprint":false},{"pmid":"32632140","id":"PMC_32632140","title":"TIGAR/AP-1 axis accelerates the division of Lgr5- reserve intestinal stem cells to reestablish intestinal architecture after lethal radiation.","date":"2020","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/32632140","citation_count":12,"is_preprint":false},{"pmid":"39341450","id":"PMC_39341450","title":"TIGAR relieves PCOS by inhibiting granulosa cell apoptosis and oxidative stress through activating Nrf2.","date":"2024","source":"Molecular and cellular endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/39341450","citation_count":11,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":51051,"output_tokens":7363,"usd":0.131799,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":16924,"output_tokens":4405,"usd":0.097373,"stage2_stop_reason":"end_turn"},"total_usd":0.229172,"stage1_batch_id":"msgbatch_017qqVz33Ga63SCDwzb35XPb","stage2_batch_id":"msgbatch_01Scr2Ei9x4HJMiRGxwrmvLK","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2006,\n      \"finding\": \"TIGAR is a p53-inducible gene that functions to lower intracellular fructose-2,6-bisphosphate levels, thereby inhibiting glycolysis, increasing flux through the pentose phosphate pathway, reducing intracellular ROS, and protecting cells from ROS-associated apoptosis.\",\n      \"method\": \"Gene expression microarray identification, knockdown (siRNA), ROS measurement, fructose-2,6-bisphosphate assay, apoptosis assays in cell lines\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — original identification paper with multiple orthogonal methods (knockdown, metabolite measurement, ROS assay, apoptosis readout), widely replicated across many subsequent labs\",\n      \"pmids\": [\"16839880\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Crystal structure of zebrafish TIGAR reveals a histidine phosphatase fold with a catalytic histidine coordinating a phosphate molecule; the active site is open and positively charged. Recombinant human and zebrafish TIGAR hydrolyze fructose-2,6-bisphosphate and fructose-1,6-bisphosphate but not fructose-6-phosphate in vitro, confirming bisphosphatase activity.\",\n      \"method\": \"X-ray crystallography; in vitro phosphatase activity assays with recombinant human and zebrafish TIGAR\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure plus in vitro enzymatic reconstitution with defined substrates and mutagenesis-level active-site characterization\",\n      \"pmids\": [\"19015259\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"TIGAR inhibits autophagy induced by nutrient starvation or metabolic stress by suppressing ROS levels; this inhibition is p53-independent and does not involve the mTOR pathway. Loss of TIGAR-induced autophagy moderates apoptosis by restraining ROS.\",\n      \"method\": \"TIGAR knockdown/overexpression, autophagy markers (LC3, autophagosome formation), ROS measurement, mTOR pathway analysis, nutrient starvation models\",\n      \"journal\": \"The EMBO Journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KD/OE with multiple orthogonal readouts (autophagy markers, ROS, mTOR), p53-independence established by genetic controls, replicated by multiple subsequent studies\",\n      \"pmids\": [\"19713938\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Under hypoxia, a fraction of TIGAR protein relocalizes to mitochondria and forms a complex with hexokinase 2 (HK2), resulting in increased HK2 activity. Mitochondrial localization depends on mitochondrial HK2 and HIF1α activity. The fructose-2,6-bisphosphatase activity of TIGAR is independent of HK2 binding and mitochondrial localization, but both activities cooperate to limit mitochondrial ROS and protect from cell death.\",\n      \"method\": \"Subcellular fractionation, Co-immunoprecipitation, HK2 activity assay, HIF1α inhibition, hypoxia cell culture models, cell death assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the USA\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP for complex identification, activity assay for HK2, localization by fractionation with functional consequence, genetic dissection of enzymatic vs. non-enzymatic activities\",\n      \"pmids\": [\"23185017\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"TIGAR has the highest catalytic efficiency for 2,3-bisphosphoglycerate (2,3-BPG) among tested physiological substrates (~400-fold higher than for fructose-2,6-bisphosphate), and loss of TIGAR consistently increases cellular 2,3-BPG levels up to 5-fold, suggesting 2,3-BPG is the primary physiological substrate.\",\n      \"method\": \"In vitro phosphatase activity assays with recombinant human TIGAR against a panel of phosphate esters; genetic and shRNA-based cell culture models measuring metabolite levels\",\n      \"journal\": \"The Biochemical Journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro enzymatic reconstitution with multiple substrates and quantitative kinetics, corroborated by cell-based metabolite measurements in two genetic model systems\",\n      \"pmids\": [\"24423178\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"TIGAR mediates p53-induced G1-phase cell-cycle arrest by promoting dephosphorylation of RB and stabilizing the RB-E2F1 complex, thereby inhibiting G1-to-S phase entry; this is p21-independent.\",\n      \"method\": \"Co-immunoprecipitation of RB-E2F1, RT-PCR, western blot, luciferase reporter assay, chromatin immunoprecipitation, MCF-7 xenograft tumor model\",\n      \"journal\": \"British Journal of Cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP for protein interaction, multiple pathway readouts (CDK levels, RB phosphorylation), in vivo xenograft, single lab\",\n      \"pmids\": [\"22782351\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"TIGAR regulates DNA damage response through two mechanisms: (1) promoting NADPH/ribose production via the pentose phosphate pathway to support repair, and (2) modulating ATM phosphorylation through a Cdk5-dependent pathway. After genotoxic stress, TIGAR also relocates to the nucleus.\",\n      \"method\": \"TIGAR knockdown, pharmacological and siRNA inhibition of Cdk5 and ATM, γ-H2AX foci assay, NADPH/ribose supplementation rescue, nuclear fractionation\",\n      \"journal\": \"Scientific Reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockdown with pathway rescue experiments (NADPH/ribose supplementation, Cdk5 inhibition), localization by fractionation, single lab\",\n      \"pmids\": [\"25928429\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"TIGAR directly inhibits NF-κB signaling by competing with NEMO for binding to the linear ubiquitin assembly complex LUBAC, thereby preventing linear ubiquitination of NEMO and blocking IKKβ phosphorylation/activation. This function is independent of TIGAR's phosphatase activity, as a phosphatase-dead mutant is equally effective.\",\n      \"method\": \"Co-immunoprecipitation, direct binding competition assay with NEMO and LUBAC, phosphatase-dead TIGAR mutant, NF-κB reporter assays, TIGAR knockout mice (adipose tissue NF-κB signaling), adipocyte-specific TIGAR overexpression\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP demonstrating direct TIGAR-LUBAC interaction, phosphatase-dead mutant establishing non-enzymatic mechanism, in vivo genetic models (KO and adipocyte-specific OE) confirming physiological relevance\",\n      \"pmids\": [\"29650758\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TIGAR promotes neural stem cell (NSC) differentiation by reducing glycolysis and increasing oxidative phosphorylation, leading to elevated acetyl-CoA levels and increased H3K9 acetylation at promoters of neuronal differentiation genes (Ngn1, Neurod1, Gfap). Acetate supplementation (precursor of acetyl-CoA) rescues NSC differentiation defects caused by TIGAR knockdown.\",\n      \"method\": \"TIGAR knockdown in cultured NSCs, acetyl-CoA measurement, ChIP for H3K9ac at gene promoters, acetate rescue experiment, metabolic flux analysis (oxygen consumption, lactate)\",\n      \"journal\": \"Cell Death & Disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP for epigenetic marks, metabolite measurement, rescue experiments, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"30814486\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TIGAR translocates to mitochondria in skeletal muscle during exhaustive exercise and interacts with ATP synthase F1 subunit α (ATP5A1), binding that increases during exhaustive exercise. Mitochondrial TIGAR promotes ATP generation, maintains mitochondrial membrane potential, and reduces mitochondrial oxidative stress under hypoxia. TIGAR also regulates mitochondrial biogenesis via the SIRT1-PGC1α deacetylation pathway.\",\n      \"method\": \"GST-TIGAR pulldown followed by liquid chromatography mass spectrometry (to identify ATP5A1 binding), subcellular fractionation, mitochondria-targeted TIGAR overexpression plasmid, TIGAR KO mice exhaustive swimming model, SIRT1-PGC1α pathway analysis\",\n      \"journal\": \"FASEB Journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — GST-pulldown + LC-MS for interaction, KO mouse model, in vivo exercise model, single lab\",\n      \"pmids\": [\"30726106\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"The E3 ubiquitin ligase TRIM31 interacts with TIGAR, promotes its polyubiquitination, and targets it for proteasomal degradation, thereby reducing TIGAR protein levels during cerebral ischemia.\",\n      \"method\": \"Co-immunoprecipitation (TRIM31-TIGAR interaction), ubiquitination assay, proteasome inhibitor rescue, TRIM31 KO mouse model, TIGAR KD rescue experiments in ischemia model\",\n      \"journal\": \"Redox Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus ubiquitination assay for E3 ligase-substrate relationship, genetic models (KO, KD), single lab\",\n      \"pmids\": [\"34218200\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"A second E3 ubiquitin ligase, TRIM35, also interacts with TIGAR and promotes its polyubiquitination and proteasomal degradation; TRIM35 knockdown alleviates renal ischemia-reperfusion injury in part by stabilizing TIGAR and enhancing mitochondrial fusion.\",\n      \"method\": \"Co-immunoprecipitation (TRIM35-TIGAR interaction), ubiquitination assay, proteasome pathway inhibition, TIGAR KD rescue, renal IRI model\",\n      \"journal\": \"International Journal of Biological Macromolecules\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus ubiquitination assay, functional rescue by TIGAR KD, single lab\",\n      \"pmids\": [\"35421414\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Nuclear TIGAR directly interacts with NRF2 and facilitates chromatin recruitment of NRF2, the H3K4me3 methylase MLL1, and elongating Pol-II to activate expression of NRF2 target genes (NQO1/2, PRDX1, GSTM4) and NSD2; this epigenetic co-activator function is independent of TIGAR's enzymatic phosphatase activity and confers cancer cell resistance to chemotherapy.\",\n      \"method\": \"Co-immunoprecipitation (TIGAR-NRF2 interaction), ChIP for NRF2/MLL1/Pol-II at target gene promoters, phosphatase-dead TIGAR mutant, nuclear localization studies, in vitro and in vivo chemotherapy resistance assays\",\n      \"journal\": \"Acta Pharmaceutica Sinica B\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP for direct interaction, ChIP for chromatin recruitment, enzyme-dead mutant proving non-enzymatic mechanism, single lab\",\n      \"pmids\": [\"35847493\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Macrophage TIGAR directly binds to TGF-β-activated kinase 1 (TAK1) and promotes TRAF6-mediated ubiquitination and auto-phosphorylation of TAK1, thereby amplifying inflammatory signaling in sepsis. Residues 152–161 of TIGAR constitute a crucial binding motif, and this pro-inflammatory function is independent of TIGAR's phosphatase activity.\",\n      \"method\": \"Co-immunoprecipitation (TIGAR-TAK1 direct binding), ubiquitination assay, myeloid-specific Tigar knockout mice (LPS and CLP sepsis models), TIGAR motif mutagenesis, pharmacological disruption of TIGAR-TAK1 interaction (5Z-7-oxozeaenol)\",\n      \"journal\": \"Nature Communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP with mutagenesis of binding motif, phosphatase-dead mutant control, two in vivo sepsis models with myeloid-specific KO, pharmacological intervention, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"38773142\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Under prolonged ischemia, TIGAR translocates to mitochondria and inhibits succinate dehydrogenase (SDH) activity by interacting with SDHA and mediating post-translational modifications (acetylation and succinylation) of SDHA, thereby reducing ROS generation via the reverse electron transfer chain and decreasing neuronal ferroptosis. This mechanism is independent of the PPP-NADPH-GPX4 antioxidant pathway.\",\n      \"method\": \"TIGAR overexpression/KO in neurons, SDH activity assay, mitochondrial fractionation, Co-IP (TIGAR-SDHA), post-translational modification analysis (acetylation/succinylation), lipid peroxidation assay, ferroptosis markers, prolonged ischemia mouse model\",\n      \"journal\": \"Free Radical Biology & Medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP for interaction, enzymatic activity assay, PTM characterization, genetic models, single lab\",\n      \"pmids\": [\"38494143\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"TIGAR expression in renal proximal straight tubules is induced by ischemia-reperfusion in a p53-dependent manner and inhibits phosphofructokinase-1 activity, depleting glycolytic ATP, with context-dependent effects: under mild ischemia TIGAR activates G6PD and raises NADPH/GSH (protective); under severe ischemia this protective response fails and TIGAR inhibition by siRNA is protective.\",\n      \"method\": \"siRNA knockdown of TIGAR in vivo and in vitro, PFK-1 activity assay, G6PD activity assay, NADPH/GSH measurement, functional/histological kidney injury readouts, p53-dependent induction shown by p53 inhibitor\",\n      \"journal\": \"American Journal of Physiology. Renal Physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo siRNA knockdown with enzymatic activity assays and functional readouts, single lab\",\n      \"pmids\": [\"25503731\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"SP1 transcription factor binds the TIGAR promoter at a minimal region (-56/-4) and is indispensable for basal TIGAR transcription in liver cancer cells, as shown by EMSA and chromatin immunoprecipitation.\",\n      \"method\": \"5'-RACE (transcription start site mapping), luciferase reporter with 5'-deletion constructs, EMSA, chromatin immunoprecipitation, SP1 knockdown\",\n      \"journal\": \"Molecular and Cellular Biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — EMSA plus ChIP for transcription factor binding, luciferase deletion analysis, single lab\",\n      \"pmids\": [\"21761199\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"CREB binds a cAMP-response element (CRE) at the TIGAR promoter region (-4/+13) and regulates TIGAR expression; CREB knockdown reduces TIGAR promoter activity and expression, while CREB overexpression or forskolin treatment enhances them.\",\n      \"method\": \"5'-deletion and site-directed mutagenesis of TIGAR promoter-luciferase constructs, EMSA, chromatin immunoprecipitation, CREB knockdown and overexpression\",\n      \"journal\": \"Biochemical and Biophysical Research Communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus EMSA plus promoter mutagenesis, single lab\",\n      \"pmids\": [\"24036271\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"TCF19 interacts with p53 and co-regulates TIGAR transcription; TCF19/p53 form complexes that include either CBP (activating) or HDAC1 (repressing) depending on glucose conditions, epigenetically programming TIGAR expression to control glycolysis and mitochondrial energy metabolism in hepatocytes.\",\n      \"method\": \"IP/MS (TCF19-p53 co-immunoprecipitation), ChIP for TCF19/p53/CBP/HDAC1 at TIGAR promoter, TCF19 and p53 knockdown, metabolic flux analysis (ECAR, OCR, ATP), RNA-seq\",\n      \"journal\": \"FASEB Journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — IP/MS for interaction, ChIP for chromatin occupancy, functional metabolic assays, single lab\",\n      \"pmids\": [\"34369624\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"TIGAR expression is induced independently of p53 and TAp73 in most mouse tissues in vivo, and mouse TIGAR is less responsive to p53 family members than human TIGAR; TIGAR induction in mouse intestine after ionizing radiation is also p53- and TAp73-independent.\",\n      \"method\": \"p53 KO mice, TAp73 KO mice, ionizing radiation in vivo, western blot for TIGAR in multiple mouse tissues\",\n      \"journal\": \"Cell Death & Disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO mouse models with tissue-level protein analysis, single lab\",\n      \"pmids\": [\"26247727\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TIGAR negatively regulates BRCA1 and the Fanconi anemia pathway; TIGAR knockdown enhances sensitivity to the PARP inhibitor olaparib by downregulating these DNA repair components and increasing cellular senescence.\",\n      \"method\": \"Genome-scale CRISPR/Cas9 knockout screen, TIGAR KD in cancer cells, BRCA1 and Fanconi anemia pathway western blot, olaparib sensitivity assays, senescence assays\",\n      \"journal\": \"Communications Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genome-scale screen identification followed by focused mechanistic validation with KD and pathway analysis, single lab\",\n      \"pmids\": [\"31508509\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"TIGAR promotes NSCLC cell invasion and metastasis via a Met signaling pathway; Met expression positively correlates with TIGAR in NSCLC, and TIGAR knockdown reduces invasion/metastasis in vitro and in vivo.\",\n      \"method\": \"TIGAR knockdown/overexpression, Transwell invasion assays, in vivo metastasis model, immunohistochemistry for TIGAR and Met in patient samples, Met inhibitor experiments\",\n      \"journal\": \"Molecular Cancer\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — functional KD with invasion readout, correlation data, no direct biochemical mechanism of TIGAR-Met interaction established\",\n      \"pmids\": [\"29753331\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SIRT3 regulates TIGAR expression in cardiomyocytes by deacetylating p53; high glucose increases p53 acetylation, which drives TIGAR upregulation and suppresses glycolysis. SIRT3 overexpression reduces p53 acetylation and TIGAR expression, restoring glycolysis and reducing ROS and apoptosis under hyperglycemic conditions.\",\n      \"method\": \"SIRT3 overexpression (adenovirus) and TIGAR siRNA in H9c2 cells, p53 acetylation western blot, glycolysis (ECAR) measurement, PFKFB3 expression, db/db diabetic mouse model in vivo\",\n      \"journal\": \"Journal of the American Heart Association\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic manipulation with acetylation readout, in vitro and in vivo models, single lab\",\n      \"pmids\": [\"33586458\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"TIGAR confers ferroptosis resistance in colorectal cancer cells via a ROS/AMPK/SCD1 signaling pathway; TIGAR knockdown increases lipid peroxidation, decreases GSH/GSSG ratio, and reduces SCD1 expression in a redox- and AMPK-dependent manner.\",\n      \"method\": \"TIGAR knockdown in CRC cells, erastin-induced ferroptosis assay, GSH/GSSG ratio, lipid peroxidation (MDA), AMPK and SCD1 western blot, antioxidant rescue\",\n      \"journal\": \"Free Radical Biology & Medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional KD with multiple metabolic and cell death readouts, pathway inhibition experiments, single lab\",\n      \"pmids\": [\"35271998\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Following APC/Wnt pathway activation, TIGAR and RAC1/NOX generate opposing ROS signals in the same intestinal cell: TIGAR limits damaging ROS while RAC1/NOX generates pro-proliferative ROS. Loss of TIGAR increases oxidative damage and inhibits proliferation; TIGAR and RAC1 cooperate to maintain optimal intestinal proliferation after APC loss.\",\n      \"method\": \"TIGAR KO mice, APC deletion mouse model, 3D intestinal organoid cultures, ROS measurement, NOX inhibition, genetic epistasis (TIGAR KO × RAC1 KO double mutants)\",\n      \"journal\": \"Genes & Development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo genetic epistasis with double KO, 3D organoid models, ROS pathway dissection with pharmacological and genetic tools\",\n      \"pmids\": [\"26679840\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"TIGAR ischemia/reperfusion upregulation in brain is mediated by the transcription factor SP1; ROS (H2O2) and stress hormones (adrenaline, hydrocortisone, glucagon) induce TIGAR protein, while insulin suppresses it. SP1 knockdown or inhibition blocks ischemia-induced TIGAR upregulation.\",\n      \"method\": \"SP1 siRNA, mithramycin A inhibition, SP1 ChIP at TIGAR promoter, tMCAO/R mouse model, OGD/R in HT22 cells and primary neurons, hormone and glucose treatments\",\n      \"journal\": \"Neurochemistry International\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus genetic SP1 KD, in vivo and in vitro ischemia models, single lab\",\n      \"pmids\": [\"25445985\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Under prolonged ischemia (PPP impaired), TIGAR induces autophagy which activates Nrf2, providing an alternative antioxidant mechanism independent of PPP/NADPH. Genetic deletion of Atg7 or Nrf2 abolishes TIGAR neuroprotection in prolonged ischemia.\",\n      \"method\": \"PPP inhibition (G6PD knockdown), catalytically-inactive TIGAR mutant expression, Atg7 KO, Nrf2 KO, mouse prolonged ischemia model, ROS and neuronal survival assays\",\n      \"journal\": \"Redox Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple genetic knockouts, enzyme-dead mutant, in vivo mouse model, single lab\",\n      \"pmids\": [\"35576689\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TIGAR knockdown in cancer cells decreases BRCA1 and Fanconi anemia pathway components, increases senescence, and sensitizes cells to PARP inhibitor olaparib; this identifies TIGAR as a modifier of homologous recombination capacity.\",\n      \"method\": \"CRISPR/Cas9 genome-scale screen (identification), TIGAR KD, BRCA1 western blot, olaparib sensitivity, senescence assay\",\n      \"journal\": \"Communications Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genome-wide screen plus focused mechanistic follow-up, single lab\",\n      \"pmids\": [\"31508509\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TIGAR (TP53-induced glycolysis and apoptosis regulator) is a histidine phosphatase that primarily hydrolyzes 2,3-bisphosphoglycerate (and also fructose-2,6-bisphosphate/fructose-1,6-bisphosphate), lowering glycolytic flux and diverting glucose-6-phosphate into the pentose phosphate pathway to generate NADPH and GSH for antioxidant defense; beyond this enzymatic role, TIGAR has multiple non-enzymatic functions including: (1) under hypoxia, translocating to mitochondria where it binds and activates HK2 and inhibits succinate dehydrogenase (SDHA) to limit mitochondrial ROS and ferroptosis; (2) directly competing with NEMO for LUBAC binding to block NF-κB activation; (3) directly binding TAK1 to promote its ubiquitination and pro-inflammatory signaling in macrophages; (4) interacting with NRF2 as a nuclear chromatin co-activator to epigenetically regulate antioxidant gene expression; (5) suppressing autophagy through ROS reduction; and (6) mediating cell-cycle arrest via RB dephosphorylation and RB-E2F1 complex stabilization—with transcription regulated by p53, p63/p73, SP1, and CREB, and protein stability controlled by E3 ubiquitin ligases TRIM31 and TRIM35.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TIGAR is a p53-inducible histidine-phosphatase that reprograms central carbon metabolism to control redox balance and cell fate, originally identified as a gene that lowers fructose-2,6-bisphosphate to inhibit glycolysis, divert glucose into the pentose phosphate pathway, and suppress ROS-associated apoptosis [#0]. Structural and enzymatic work defined it as a histidine-phosphatase-fold bisphosphatase, and kinetic profiling established 2,3-bisphosphoglycerate as its highest-efficiency physiological substrate (~400-fold over fructose-2,6-bisphosphate) [#1, #4]. The resulting NADPH/GSH output underlies a broad antioxidant program that restrains autophagy [#2], protects proliferating intestinal cells from oxidative damage in cooperation with RAC1/NOX following APC loss [#24], and confers ferroptosis and chemotherapy resistance in cancer [#23]. Layered on this enzymatic role is a set of phosphatase-independent activities: TIGAR translocates to mitochondria to bind and activate hexokinase 2 under hypoxia [#3] and to inhibit succinate dehydrogenase via SDHA modification to limit reverse-electron-transfer ROS and ferroptosis during ischemia [#14]; it competes with NEMO for LUBAC binding to block NF-\\u03baB activation [#7]; it binds TAK1 in macrophages to promote TRAF6-mediated ubiquitination and amplify inflammatory signaling, with residues 152\\u2013161 forming the binding motif [#13]; and nuclear TIGAR acts as an NRF2 chromatin co-activator recruiting MLL1 and elongating Pol-II to antioxidant gene promoters [#12]. TIGAR also enforces p53-induced G1 arrest by promoting RB dephosphorylation and stabilizing the RB-E2F1 complex [#5]. Transcription is driven by SP1 and CREB at the proximal promoter and by p53/TCF19 complexes [#16, #17, #18], while protein abundance is controlled by the E3 ubiquitin ligases TRIM31 and TRIM35 [#10, #11].\"\n,\n  \"teleology\": [\n    {\n      \"year\": 2006,\n      \"claim\": \"Established TIGAR's founding identity: a p53 target that links transcriptional stress responses to glycolytic control and ROS-dependent apoptosis.\",\n      \"evidence\": \"Microarray identification, siRNA knockdown with fructose-2,6-bisphosphate, ROS and apoptosis assays in cell lines\",\n      \"pmids\": [\"16839880\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the direct enzymatic substrate or catalytic mechanism\", \"Physiological vs. cancer-cell relevance of the glycolytic switch not resolved\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Resolved the molecular basis of TIGAR activity by showing it is a histidine-phosphatase-fold enzyme that hydrolyzes bisphosphate sugars in vitro.\",\n      \"evidence\": \"X-ray crystallography of zebrafish TIGAR plus in vitro phosphatase assays on recombinant human and zebrafish protein\",\n      \"pmids\": [\"19015259\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vitro substrate panel did not rank physiological substrates by efficiency\", \"No structure of human protein or substrate-bound complex\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Reassigned the primary physiological substrate from fructose-2,6-bisphosphate to 2,3-bisphosphoglycerate based on catalytic efficiency and cellular metabolite levels.\",\n      \"evidence\": \"Quantitative in vitro kinetics against a phosphate-ester panel plus metabolite measurement in two genetic cell models\",\n      \"pmids\": [\"24423178\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo flux contribution of 2,3-BPG hydrolysis across tissues not quantified\", \"Does not address non-enzymatic functions\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Connected TIGAR's redox role to autophagy, showing it restrains stress-induced autophagy via ROS suppression rather than through mTOR.\",\n      \"evidence\": \"Knockdown/overexpression with LC3/autophagosome readouts, ROS measurement and mTOR pathway controls\",\n      \"pmids\": [\"19713938\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular link between ROS reduction and autophagy machinery left unspecified\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Revealed a non-metabolic mitochondrial function: hypoxic TIGAR binds and activates hexokinase 2 to limit mitochondrial ROS, separable from its bisphosphatase activity.\",\n      \"evidence\": \"Subcellular fractionation, reciprocal Co-IP, HK2 activity assay and HIF1\\u03b1 inhibition in hypoxia models\",\n      \"pmids\": [\"23185017\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of HK2 activation by TIGAR binding not defined\", \"Determinants of mitochondrial import unresolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Extended TIGAR into cell-cycle control, showing it mediates p53-induced G1 arrest through RB dephosphorylation independent of p21.\",\n      \"evidence\": \"RB-E2F1 Co-IP, RB phosphorylation/CDK readouts, reporter assays and MCF-7 xenograft\",\n      \"pmids\": [\"22782351\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Phosphatase whose activity dephosphorylates RB not identified\", \"Single lab, no reciprocal validation of the RB-E2F1 mechanism\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Linked TIGAR to the DNA damage response via PPP-derived NADPH/ribose and Cdk5-dependent ATM modulation, with stress-induced nuclear relocalization.\",\n      \"evidence\": \"Knockdown, Cdk5/ATM inhibition, \\u03b3-H2AX foci, NADPH/ribose rescue and nuclear fractionation\",\n      \"pmids\": [\"25928429\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of nuclear import not defined\", \"Direct vs. indirect role in ATM signaling unclear\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identified TIGAR as a chromatin co-activator that physically partners with NRF2 to recruit MLL1 and Pol-II, an epigenetic role distinct from its enzymatic function.\",\n      \"evidence\": \"TIGAR-NRF2 Co-IP, ChIP for NRF2/MLL1/Pol-II at target genes, phosphatase-dead mutant and chemoresistance assays\",\n      \"pmids\": [\"35847493\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How TIGAR is recruited to chromatin not established\", \"Single lab\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Defined a phosphatase-independent immune-signaling role: TIGAR competes with NEMO for LUBAC to block linear ubiquitination and NF-\\u03baB activation.\",\n      \"evidence\": \"Co-IP/binding competition with NEMO and LUBAC, phosphatase-dead mutant, NF-\\u03baB reporters and TIGAR KO/adipocyte-OE mice\",\n      \"pmids\": [\"29650758\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of NEMO/LUBAC competition not resolved\", \"Generality across cell types beyond adipose untested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Showed a contrasting pro-inflammatory function in macrophages where TIGAR binds TAK1 via residues 152\\u2013161 to promote its ubiquitination and activation in sepsis.\",\n      \"evidence\": \"TIGAR-TAK1 Co-IP, motif mutagenesis, ubiquitination assay, phosphatase-dead control, myeloid-specific KO sepsis models and pharmacological disruption\",\n      \"pmids\": [\"38773142\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Reconciliation with NF-\\u03baB-inhibitory LUBAC mechanism across cell types unresolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Established a second mitochondrial enzyme-independent mechanism: ischemic TIGAR inhibits SDHA via acetylation/succinylation to suppress reverse-electron-transfer ROS and ferroptosis.\",\n      \"evidence\": \"TIGAR OE/KO in neurons, SDH activity assay, TIGAR-SDHA Co-IP, PTM analysis, ferroptosis markers and ischemia model\",\n      \"pmids\": [\"38494143\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How TIGAR drives SDHA acetylation/succinylation mechanistically unknown\", \"Single lab\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified TRIM31 as an E3 ligase controlling TIGAR abundance through ubiquitin-proteasomal degradation in cerebral ischemia.\",\n      \"evidence\": \"TRIM31-TIGAR Co-IP, ubiquitination assay, proteasome rescue and TRIM31 KO mouse ischemia model\",\n      \"pmids\": [\"34218200\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ubiquitination site on TIGAR not mapped\", \"Single lab\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified a second degradative E3 ligase, TRIM35, linking TIGAR stability to mitochondrial fusion in renal ischemia-reperfusion.\",\n      \"evidence\": \"TRIM35-TIGAR Co-IP, ubiquitination assay, TIGAR KD rescue in renal IRI model\",\n      \"pmids\": [\"35421414\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether TRIM31 and TRIM35 act redundantly or in distinct tissues unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How TIGAR's opposing context-dependent roles\\u2014antioxidant protector versus injury amplifier, NF-\\u03baB inhibitor versus TAK1 activator\\u2014are selected within a given cell remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model linking subcellular localization to functional output\", \"Determinants of mitochondrial vs. nuclear vs. cytosolic partitioning unknown\", \"Structural basis of competing protein-protein interactions undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 1, 4]},\n      {\"term_id\": \"GO:0016791\", \"supporting_discovery_ids\": [1, 4]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [7, 13]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [12]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [3, 9, 14]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [6, 12]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 4, 15]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [2, 23, 24]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [7, 13]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"complexes\": [\"LUBAC (competitive binder)\", \"RB-E2F1 complex\"],\n    \"partners\": [\"HK2\", \"NEMO/IKBKG\", \"TAK1/MAP3K7\", \"NRF2/NFE2L2\", \"SDHA\", \"ATP5A1\", \"TRIM31\", \"TRIM35\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":6,"faith_pct":83.33333333333333}}