{"gene":"TIGAR","run_date":"2026-04-28T21:42:59","timeline":{"discoveries":[{"year":2006,"finding":"TIGAR is a p53-inducible gene that functions as a fructose-2,6-bisphosphatase, lowering fructose-2,6-bisphosphate levels in cells, thereby inhibiting glycolysis, reducing intracellular ROS, and protecting cells from ROS-associated apoptosis.","method":"Gene expression microarray identification followed by functional assays (ROS measurement, apoptosis assays, TIGAR knockdown/overexpression in cells)","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1-2 — original discovery with multiple orthogonal methods, highly replicated across labs (1626 citations)","pmids":["16839880"],"is_preprint":false},{"year":2008,"finding":"Crystal structure of zebrafish TIGAR reveals a histidine phosphatase fold with a catalytic histidine residue; recombinant human and zebrafish TIGAR hydrolyzes fructose-2,6-bisphosphate and fructose-1,6-bisphosphate but not fructose-6-phosphate in vitro; the active site is open and positively charged, most closely related to bacterial PhoE phosphatase and the bisphosphatase domain of bifunctional PFK2.","method":"X-ray crystallography and in vitro phosphatase assay with recombinant protein","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — crystal structure combined with biochemical reconstitution","pmids":["19015259"],"is_preprint":false},{"year":2009,"finding":"TIGAR modulates intracellular ROS in response to nutrient starvation or metabolic stress and functions to inhibit autophagy through ROS suppression, independent of the mTOR pathway and p53.","method":"TIGAR knockdown/overexpression with autophagy markers (LC3, Beclin-1), ROS measurement, nutrient deprivation assays","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods, replicated by 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), increasing HK2 activity; mitochondrial localization depends on mitochondrial HK2 and HIF-1α activity; the fructose-2,6-bisphosphatase activity of TIGAR is independent of HK2 binding and mitochondrial localization, but both activities contribute to limiting mitochondrial ROS and protecting from cell death.","method":"Subcellular fractionation, co-immunoprecipitation (TIGAR-HK2), HIF-1α inhibition, hypoxia treatment, cell death assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, fractionation, functional epistasis with HIF-1α and HK2","pmids":["23185017"],"is_preprint":false},{"year":2013,"finding":"TIGAR is required for intestinal regeneration in vivo and ex vivo; its fructose-2,6-bisphosphatase activity promotes the pentose phosphate pathway to produce NADPH for antioxidant function and ribose-5-phosphate for nucleotide synthesis; growth defects from TIGAR loss were rescued by ROS scavengers and nucleosides.","method":"TIGAR knockout mice, intestinal organoid cultures, xenograft tumor models, genetic rescue with ROS scavengers/nucleosides","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 — in vivo KO with defined phenotypic rescue, replicated in multiple models","pmids":["23726973"],"is_preprint":false},{"year":2014,"finding":"TIGAR is identified as the phosphoglycolate-independent 2,3-bisphosphoglycerate (2,3-BPG) phosphatase; recombinant human TIGAR most efficiently hydrolyzes 2,3-BPG (~400-fold greater catalytic efficiency than for fructose-2,6-bisphosphate); loss of TIGAR leads to up to 5-fold increases in cellular 2,3-BPG levels.","method":"In vitro phosphatase assay with recombinant human TIGAR on panel of substrates; genetic and shRNA cell culture models measuring 2,3-BPG and F-2,6-BP levels","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 — in vitro enzymatic reconstitution with multiple substrates plus genetic validation in cells","pmids":["24423178"],"is_preprint":false},{"year":2014,"finding":"TIGAR mediates p21-independent, p53-dependent G1-phase arrest in cancer cells by suppressing CDK-2, CDK-4, CDK-6, Cyclin D, and Cyclin E, and promoting dephosphorylation of RB protein, stabilizing the RB-E2F1 complex and preventing S-phase entry.","method":"Co-immunoprecipitation (RB-E2F1), chromatin immunoprecipitation, luciferase reporter assays, western blot, cell cycle analysis, tumor xenograft model","journal":"British journal of cancer","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP for RB-E2F1 interaction, functional KD phenotype, single lab","pmids":["22782351"],"is_preprint":false},{"year":2014,"finding":"TIGAR protects ischemic brain via enhancing pentose phosphate pathway flux (increasing G6PD and NADPH production) and preserving mitochondrial function; TIGAR translocates to mitochondria during ischemia/reperfusion; supplementation of NADPH rescues the neuronal injury caused by TIGAR knockdown.","method":"Lentiviral TIGAR overexpression/knockdown in mice and neurons, in vivo stroke model (MCAO), subcellular fractionation, G6PD activity assay, ROS/GSH/caspase-3 measurements","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods in vivo and in vitro, functional rescue with NADPH","pmids":["24872551"],"is_preprint":false},{"year":2015,"finding":"TIGAR and RAC1 have opposing effects on ROS in intestinal cells following APC loss: TIGAR limits damaging ROS while RAC1-driven NOX generates pro-proliferative ROS; loss of TIGAR increases ROS damage and inhibits proliferation; despite opposing effects on ROS, loss of both TIGAR and RAC1 cooperates to suppress intestinal proliferation.","method":"3D organoid cultures, in vivo mouse models (APC deletion), genetic epistasis (TIGAR KO × RAC1 KO × Myc KO), ROS measurements","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis in vivo and in vitro with multiple orthogonal readouts","pmids":["26679840"],"is_preprint":false},{"year":2015,"finding":"TIGAR regulates DNA damage response by relocating to the nucleus after genotoxic drug treatment or hypoxia; TIGAR controls phosphorylation of ATM through Cdk5, independent of the PPP pathway; knockdown of TIGAR exacerbated DNA damage, partly reversed by NADPH, ribose, or ROS scavenger NAC.","method":"Subcellular fractionation/imaging, siRNA knockdown, pharmacological Cdk5 inhibition, γH2AX foci assay, NADPH/ribose rescue experiments","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2-3 — nuclear relocalization plus Cdk5-ATM pathway epistasis, single lab","pmids":["25928429"],"is_preprint":false},{"year":2018,"finding":"TIGAR directly binds to and inhibits the linear ubiquitin assembly complex (LUBAC) by competing with NEMO for association with LUBAC, thereby preventing linear ubiquitination of NEMO, blocking IKKβ phosphorylation/activation, and suppressing NF-κB signaling; this function is independent of TIGAR phosphatase activity as a phosphatase-dead mutant retains NF-κB inhibitory activity.","method":"Co-immunoprecipitation, ubiquitination assays, phosphatase-dead TIGAR mutant, TIGAR knockout mice (adipose tissue NF-κB signaling), adipocyte-specific TIGAR overexpression","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, active-site mutagenesis, and in vivo mouse validation showing non-enzymatic function","pmids":["29650758"],"is_preprint":false},{"year":2019,"finding":"TIGAR translocates to mitochondria in skeletal muscle during exhaustive exercise and binds directly to ATP synthase F1 subunit α (ATP5A1), increasing ATP generation, maintaining mitochondrial membrane potential, and reducing mitochondrial oxidative stress; TIGAR also regulates mitochondrial biogenesis through the SIRT1-PGC1α deacetylation pathway.","method":"GST-TIGAR pull-down followed by LC-MS (identifies ATP5A1), TIGAR KO mice exhaustive swimming test, mitochondrial fractionation, overexpression of mitochondria-targeted TIGAR, SIRT1 deacetylation assays","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 1-2 — pull-down/MS identification of binding partner plus KO mouse phenotype and functional assays","pmids":["30726106"],"is_preprint":false},{"year":2019,"finding":"TIGAR promotes neural stem cell (NSC) differentiation by facilitating metabolic reprogramming from glycolysis to oxidative phosphorylation; TIGAR knockdown decreases acetyl-CoA levels and H3K9 acetylation at the promoters of neuronal differentiation genes (Ngn1, NeuroD1, Gfap); acetate supplementation (as acetyl-CoA precursor) rescues the differentiation defect caused by TIGAR knockdown.","method":"NSC culture, TIGAR knockdown/overexpression, acetyl-CoA measurement, ChIP for H3K9ac at promoters, acetate rescue, metabolic flux analysis","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP plus metabolite rescue, single lab","pmids":["30814486"],"is_preprint":false},{"year":2019,"finding":"TIGAR expression is modulated by the transcription factor SP1 (induced by ischemia/reperfusion via ROS and metabolic hormones including adrenaline, hydrocortisone, glucagon); SP1 inhibition or siRNA knockdown blocks ischemia-induced TIGAR upregulation; TIGAR expression is also negatively regulated by insulin via p53 acetylation.","method":"MCAO/R mouse model, SP1 inhibitor (mithramycin A), SP1 siRNA, luciferase reporter, chromatin immunoprecipitation, hormone/H2O2 treatment in vivo and in vitro","journal":"Neurochemistry international","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP and pharmacological/genetic inhibition of SP1, single lab","pmids":["25445985"],"is_preprint":false},{"year":2011,"finding":"SP1 transcription factor is indispensable for basal TIGAR promoter activity; a minimal SP1-binding site at -56/-4 bp was identified and SP1 binds the TIGAR promoter in vitro (EMSA) and in vivo (ChIP).","method":"5'-RACE, deletion reporter assays, EMSA, chromatin immunoprecipitation, SP1 knockdown","journal":"Molecular and cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — EMSA plus ChIP with functional reporter assays, single lab","pmids":["21761199"],"is_preprint":false},{"year":2013,"finding":"CREB regulates TIGAR expression via a cAMP-response element (CRE) at position -4/+13 of the TIGAR promoter; CREB knockdown reduces promoter activity and TIGAR expression; CREB overexpression or forskolin treatment enhances TIGAR expression.","method":"5'-deletion analysis, site-directed mutagenesis, EMSA, chromatin immunoprecipitation, CREB knockdown/overexpression, luciferase reporter","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — EMSA plus ChIP with functional mutagenesis, single lab","pmids":["24036271"],"is_preprint":false},{"year":2021,"finding":"TRIM31 is an E3 ubiquitin ligase for TIGAR; TRIM31 directly interacts with TIGAR and promotes its polyubiquitination and proteasome-dependent degradation; TRIM31 deficiency protects against cerebral ischemia by raising TIGAR levels.","method":"Co-immunoprecipitation, ubiquitination assay, proteasome inhibitor treatment, TIGAR knockdown rescue, TRIM31 KO in ischemia model","journal":"Redox biology","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP plus ubiquitination assay plus genetic rescue, single lab","pmids":["34218200"],"is_preprint":false},{"year":2022,"finding":"TRIM35 acts as an E3 ubiquitin ligase for TIGAR, interacting with TIGAR and promoting its polyubiquitination and proteasomal degradation; TRIM35 knockdown alleviates renal ischemia-reperfusion injury by elevating TIGAR levels and enhancing mitochondrial fusion.","method":"Co-immunoprecipitation, ubiquitination assay, proteasome pathway analysis, TIGAR knockdown rescue, TRIM35 knockdown in renal IRI model","journal":"International journal of biological macromolecules","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP plus ubiquitination assay with functional in vivo rescue, single lab","pmids":["35421414"],"is_preprint":false},{"year":2021,"finding":"Nuclear TIGAR directly interacts with the antioxidant transcription factor NRF2 and facilitates chromatin recruitment of NRF2, H3K4me3 methylase MLL1, and elongating Pol-II to stimulate expression of NRF2 target genes (including NSD2, NQO1/2, PRDX1, GSTM4), independent of TIGAR's enzymatic activity; nuclear TIGAR also stimulates NSD2 expression leading to elevated global H3K36me2.","method":"Co-immunoprecipitation (TIGAR-NRF2), ChIP, enzymatic activity-deficient TIGAR mutant, loss-of-function and gain-of-function experiments, therapeutic resistance assays","journal":"Acta pharmaceutica Sinica. B","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP plus ChIP plus mutagenesis showing enzymatic-independent function, single lab","pmids":["35847493"],"is_preprint":false},{"year":2024,"finding":"TIGAR directly binds to TAK1 (TGF-β-activated kinase 1) in macrophages and promotes TRAF6-mediated ubiquitination and auto-phosphorylation of TAK1, enhancing inflammatory NF-κB signaling; residues 152-161 of TIGAR constitute the critical binding motif, and this function is independent of phosphatase activity; interference with TIGAR-TAK1 binding attenuates sepsis in mice.","method":"Co-immunoprecipitation (TIGAR-TAK1), ubiquitination assay, domain mapping/mutagenesis (residues 152-161), myeloid-specific Tigar KO in sepsis models (LPS and CLP), pharmacological disruption with 5Z-7-oxozeaenol","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1-2 — reciprocal Co-IP with domain mutagenesis plus in vivo KO and pharmacological validation","pmids":["38773142"],"is_preprint":false},{"year":2024,"finding":"Under prolonged ischemia, mitochondrial TIGAR inhibits succinate dehydrogenase (SDH) activity through post-translational modifications (acetylation and succinylation) of SDH subunit A via direct interaction with SDH A, reducing ROS production and neuronal ferroptosis independently of the PPP-NADPH-GPX4 pathway.","method":"TIGAR overexpression/knockdown, mitochondrial fractionation, SDH activity assays, co-immunoprecipitation (TIGAR-SDH A), acetylation/succinylation analysis, enzymatic-activity mutant TIGAR, prolonged OGD model, in vivo stroke model","journal":"Free radical biology & medicine","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP, PTM analysis, functional mutagenesis, single lab","pmids":["38494143"],"is_preprint":false},{"year":2019,"finding":"TIGAR inhibits autophagy during ischemia/reperfusion in neurons by activating the mTOR-S6KP70 signaling pathway; TIGAR KO reduces phosphorylated mTOR and S6KP70 levels; autophagy inhibitor 3-MA or NADPH supplementation blocks the exacerbated brain damage seen with TIGAR KO.","method":"TIGAR transgenic and knockout mice, MCAO model, primary neurons with OGD/R, western blot for p-mTOR and p-S6KP70, pharmacological rescue with 3-MA and rapamycin","journal":"Free radical biology & medicine","confidence":"Medium","confidence_rationale":"Tier 2 — transgenic/KO mouse models plus pharmacological pathway epistasis, single lab","pmids":["30978385"],"is_preprint":false},{"year":2017,"finding":"TIGAR expression is controlled by the AKT-mTOR-S6K1-eIF4A cap-dependent translation pathway; inhibition of MUC1-C (via GO-203) blocks AKT/mTOR signaling and suppresses eIF4A-mediated TIGAR translation without reducing TIGAR mRNA, leading to decreased GSH and increased ROS.","method":"qRT-PCR (TIGAR mRNA unchanged), western blot (TIGAR protein decreased), AKT/mTOR pathway inhibitors, eIF4A inhibition, xenograft model","journal":"Molecular cancer","confidence":"Medium","confidence_rationale":"Tier 2 — mRNA vs. protein dissociation combined with pathway inhibitors, single lab","pmids":["28153010"],"is_preprint":false},{"year":2022,"finding":"TIGAR induces ferroptosis resistance in colorectal cancer cells via the ROS/AMPK/SCD1 pathway; TIGAR knockdown decreases GSH/GSSG ratio, increases lipid peroxidation/MDA, and TIGAR inhibition represses SCD1 expression in a redox- and AMPK-dependent manner.","method":"TIGAR knockdown (siRNA) in CRC cell lines, ferroptosis induction (erastin), lipid peroxidation assays, AMPK inhibitor/activator epistasis, SCD1 expression analysis","journal":"Free radical biology & medicine","confidence":"Medium","confidence_rationale":"Tier 2-3 — pathway epistasis with pharmacological tools plus KD phenotype, single lab","pmids":["35271998"],"is_preprint":false},{"year":2015,"finding":"p53-independent expression of TIGAR occurs in many cancer cell lines and in mouse tissues in vivo; basal TIGAR expression does not depend on p53 or TAp73 in most mouse tissues; stress-induced TIGAR upregulation in mouse intestine after ionizing radiation is also p53- and TAp73-independent.","method":"p53 KO mice, TAp73 KO mice, ionizing radiation stress, western blot, tissue analysis","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 — genetic KO models in vivo, single lab","pmids":["26247727"],"is_preprint":false},{"year":2021,"finding":"TCF19 interacts with p53 and co-regulates TIGAR (and SCO2) transcription; TCF19/p53 form different complexes containing either CBP (for activation) or HDAC1 (for repression) depending on glucose conditions, epigenetically programming TIGAR expression.","method":"Co-immunoprecipitation (TCF19-p53), IP/MS, ChIP, TCF19/p53 knockdown, metabolic flux analysis (ECAR/OCR), RNA-seq","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP with MS plus ChIP, single lab","pmids":["34369624"],"is_preprint":false},{"year":2021,"finding":"SIRT3 reduces p53 acetylation, leading to decreased TIGAR expression and restored PFKFB3-dependent glycolysis; in high-glucose conditions, loss of SIRT3 increases p53 acetylation and TIGAR expression, impairing glycolysis and promoting ROS/apoptosis in cardiomyocytes.","method":"Adenovirus-SIRT3 overexpression, TIGAR siRNA knockdown, p53 acetylation western blot, metabolic assays (glycolysis/ECAR), in vivo db/db diabetic mouse model","journal":"Journal of the American Heart Association","confidence":"Medium","confidence_rationale":"Tier 2 — genetic manipulation in vitro and in vivo with mechanistic epistasis, single lab","pmids":["33586458"],"is_preprint":false},{"year":2022,"finding":"Under prolonged ischemia (PPP impaired), TIGAR alleviates oxidative stress through a PPP-independent mechanism by inducing autophagy, which activates Nrf2; Atg7 deletion or Nrf2 silencing abolishes TIGAR neuroprotection in prolonged ischemia; enzymatically inactive mutant TIGAR retains antioxidant effects in this context.","method":"Enzymatic mutant TIGAR (no phosphatase activity), G6PD silencing, Atg7 KO mice, Nrf2 knockdown, prolonged OGD model and extended ischemia in vivo","journal":"Redox biology","confidence":"Medium","confidence_rationale":"Tier 2 — mutagenesis plus genetic KO epistasis, single lab","pmids":["35576689"],"is_preprint":false},{"year":2020,"finding":"TIGAR supports pancreatic cancer initiation by limiting ROS, while higher ROS in metastasizing PDAC cells drives increased MAPK signaling and a pro-metastatic phenotype; TIGAR expression is higher in premalignant lesions and lower in metastatic tumors; antioxidant treatment reverts the metastatic switch.","method":"TIGAR KO in KRAS-driven PDAC mouse model, antioxidant treatment, MAPK pathway analysis, tumor initiation and metastasis assays","journal":"Cancer cell","confidence":"High","confidence_rationale":"Tier 2 — in vivo KO in PDAC model with mechanistic MAPK pathway analysis, replicated in human","pmids":["31983610"],"is_preprint":false},{"year":2019,"finding":"CRISPR genome-scale loss-of-function screen identifies TIGAR as a modifier of PARP inhibitor sensitivity; TIGAR knockdown enhances olaparib sensitivity via downregulation of BRCA1 and the Fanconi anemia pathway and increases cellular senescence.","method":"Genome-scale CRISPR/Cas9 screen, TIGAR knockdown, BRCA1/Fanconi anemia pathway western blot, olaparib sensitivity assay, senescence assay","journal":"Communications biology","confidence":"Medium","confidence_rationale":"Tier 2 — genome-scale screen with mechanistic pathway validation, single lab","pmids":["31508509"],"is_preprint":false},{"year":2020,"finding":"TIGAR overexpression in ESCC reprograms glucose metabolism from glycolysis toward the glutamine pathway through AMP-activated kinase (AMPK); a catalytically inactive variant of TIGAR does not induce tumor growth in vivo, indicating enzymatic activity is required for metabolic reprogramming and tumor promotion.","method":"TIGAR overexpression and KO in ESCC cells and mice, catalytically inactive TIGAR mutant, xenograft and patient-derived xenograft models, metabolic assays (lactate, NADPH, ATP)","journal":"Theranostics","confidence":"Medium","confidence_rationale":"Tier 2 — enzymatic mutant validation plus in vivo KO model, single lab","pmids":["32206103"],"is_preprint":false}],"current_model":"TIGAR is a p53-inducible histidine phosphatase (with highest catalytic efficiency toward 2,3-bisphosphoglycerate and fructose-2,6-bisphosphate) that inhibits glycolysis, promotes the pentose phosphate pathway to generate NADPH and ribose, and thereby limits intracellular ROS; under hypoxia it translocates to mitochondria where it binds HK2 to increase HK2 activity and interacts with SDH-A to suppress succinate dehydrogenase activity and ferroptosis; in the nucleus it acts as a non-enzymatic co-factor facilitating NRF2 chromatin recruitment; it also directly competes with NEMO for LUBAC binding to suppress NF-κB signaling, and directly binds TAK1 to promote inflammatory ubiquitination in macrophages; its protein levels are controlled by TRIM31/TRIM35-mediated ubiquitination and proteasomal degradation, by the AKT-mTOR-eIF4A translational axis, and by transcriptional regulators SP1, CREB, TCF19/p53, and non-coding RNAs."},"narrative":{"teleology":[{"year":2006,"claim":"Identifying TIGAR as a p53 target with fructose-2,6-bisphosphatase activity established the first link between p53, glycolysis inhibition, and ROS-dependent cell survival.","evidence":"Microarray screen followed by overexpression/knockdown with ROS and apoptosis assays in human cancer cell lines","pmids":["16839880"],"confidence":"High","gaps":["Enzymatic mechanism and true preferred substrate unresolved","Whether TIGAR functions independently of p53 unknown"]},{"year":2008,"claim":"Solving the crystal structure revealed a histidine phosphatase fold rather than a canonical bisphosphatase domain, redefining TIGAR's catalytic mechanism and evolutionary origin.","evidence":"X-ray crystallography of zebrafish TIGAR plus in vitro phosphatase assays with recombinant human protein","pmids":["19015259"],"confidence":"High","gaps":["Preferred physiological substrate still unclear","No human structure available"]},{"year":2009,"claim":"Demonstrating that TIGAR suppresses autophagy via ROS reduction extended its role beyond apoptosis to a broader metabolic stress response.","evidence":"TIGAR knockdown/overexpression with autophagy markers and ROS measurement under nutrient starvation","pmids":["19713938"],"confidence":"High","gaps":["Mechanism of autophagy suppression not fully delineated beyond ROS","Context-dependence of mTOR involvement unresolved"]},{"year":2011,"claim":"Mapping SP1 as essential for basal TIGAR transcription showed that TIGAR is constitutively expressed through p53-independent mechanisms, broadening the regulatory framework.","evidence":"Deletion reporter assays, EMSA, and ChIP for SP1 on the TIGAR promoter","pmids":["21761199"],"confidence":"Medium","gaps":["Relative contributions of SP1 vs. p53 to TIGAR levels in different tissues unclear","No in vivo SP1 KO validation"]},{"year":2012,"claim":"Showing hypoxia-induced mitochondrial translocation and HK2 binding revealed a non-canonical, compartment-specific protective mechanism distinct from cytosolic bisphosphatase activity.","evidence":"Subcellular fractionation, reciprocal Co-IP of TIGAR–HK2, HIF-1α epistasis under hypoxia","pmids":["23185017"],"confidence":"High","gaps":["Structural basis for TIGAR–HK2 interaction unknown","Whether mitochondrial TIGAR retains phosphatase activity in that compartment unclear"]},{"year":2013,"claim":"In vivo knockout studies established that TIGAR's PPP-promoting activity is required for intestinal regeneration, linking its metabolic function to tissue homeostasis through NADPH and nucleotide provision.","evidence":"TIGAR KO mice, intestinal organoids, xenograft models with ROS scavenger and nucleoside rescue","pmids":["23726973"],"confidence":"High","gaps":["Whether TIGAR is required for regeneration in all tissues not tested","Relative importance of NADPH vs. ribose contribution unresolved"]},{"year":2014,"claim":"Identifying 2,3-bisphosphoglycerate as the kinetically preferred substrate (~400-fold over F-2,6-BP) fundamentally reframed TIGAR's primary enzymatic function.","evidence":"In vitro kinetics on recombinant human TIGAR across substrate panel, plus 2,3-BPG accumulation in TIGAR-depleted cells","pmids":["24423178"],"confidence":"High","gaps":["Physiological consequence of 2,3-BPG regulation (e.g., hemoglobin oxygen affinity in erythrocytes) not explored","Relative in vivo contribution of 2,3-BPG vs. F-2,6-BP hydrolysis context-dependent"]},{"year":2015,"claim":"Genetic epistasis between TIGAR and RAC1 in APC-null intestinal cells revealed that TIGAR functions to limit damaging ROS while RAC1/NOX generates pro-proliferative ROS, establishing opposing ROS-regulatory roles in tumorigenesis.","evidence":"In vivo TIGAR KO × RAC1 KO × Myc KO in APC-deleted mouse intestine with organoid cultures","pmids":["26679840"],"confidence":"High","gaps":["How TIGAR loss and RAC1 loss cooperate to suppress proliferation mechanistically unresolved","Applicability beyond intestinal tumors not tested"]},{"year":2015,"claim":"Demonstrating that basal and stress-induced TIGAR expression occurs independently of p53 and TAp73 in most mouse tissues resolved whether p53 is strictly required for TIGAR function.","evidence":"p53 KO and TAp73 KO mice with ionizing radiation stress and tissue-level protein analysis","pmids":["26247727"],"confidence":"Medium","gaps":["Full set of p53-independent transcription factors driving TIGAR only partially mapped","Tissue-specific variation in regulatory dependencies not comprehensively tested"]},{"year":2018,"claim":"Discovery that TIGAR inhibits NF-κB by competing with NEMO for LUBAC binding — independent of phosphatase activity — established TIGAR as a non-enzymatic signaling scaffold.","evidence":"Reciprocal Co-IP, ubiquitination assays, phosphatase-dead mutant, TIGAR KO mice with adipose NF-κB readout","pmids":["29650758"],"confidence":"High","gaps":["Structural basis of TIGAR–LUBAC interaction unknown","Whether this function operates in immune cells beyond adipocytes unclear at this time"]},{"year":2019,"claim":"Identifying ATP5A1 as a direct mitochondrial binding partner linked TIGAR to ATP synthase regulation and mitochondrial biogenesis via SIRT1–PGC1α, expanding its mitochondrial functions beyond HK2.","evidence":"GST pull-down/LC-MS, TIGAR KO mouse exercise model, mitochondria-targeted TIGAR overexpression","pmids":["30726106"],"confidence":"High","gaps":["Whether TIGAR modulates ATP synthase catalytic mechanism or assembly unknown","Relevance beyond skeletal muscle not demonstrated"]},{"year":2020,"claim":"In a KRAS-driven PDAC model, TIGAR was shown to support tumor initiation by ROS limitation while its loss paradoxically promoted metastasis via MAPK activation, revealing stage-dependent roles in cancer.","evidence":"TIGAR KO in KRAS-driven PDAC mice, antioxidant rescue of metastatic phenotype, MAPK signaling analysis","pmids":["31983610"],"confidence":"High","gaps":["Mechanism by which elevated ROS specifically activates MAPK over other pathways not defined","Generalizability to non-KRAS-driven cancers unclear"]},{"year":2021,"claim":"Identification of TRIM31 and subsequently TRIM35 as E3 ubiquitin ligases for TIGAR established that TIGAR protein turnover is governed by proteasomal degradation, with physiological relevance in ischemia-reperfusion injury.","evidence":"Co-IP, ubiquitination assays, proteasome inhibitor rescue, TRIM31 KO and TRIM35 KD in ischemia models","pmids":["34218200","35421414"],"confidence":"Medium","gaps":["Whether TRIM31 and TRIM35 target overlapping or distinct TIGAR pools unknown","Ubiquitination sites on TIGAR not mapped","Each finding from a single lab"]},{"year":2021,"claim":"Showing that nuclear TIGAR directly recruits NRF2, MLL1, and elongating Pol-II to chromatin independently of enzymatic activity uncovered a transcriptional co-activator function.","evidence":"Co-IP (TIGAR–NRF2), ChIP for NRF2/MLL1/Pol-II, enzymatic-dead TIGAR mutant, gain/loss-of-function","pmids":["35847493"],"confidence":"Medium","gaps":["How TIGAR reaches the nucleus and what triggers nuclear import unknown","Structural basis of TIGAR–NRF2 interaction not determined","Single-lab finding"]},{"year":2024,"claim":"Demonstrating that TIGAR binds TAK1 via residues 152–161 to promote TRAF6-mediated ubiquitination in macrophages revealed a pro-inflammatory scaffolding role, opposing its anti-NF-κB activity in other contexts.","evidence":"Reciprocal Co-IP, domain mapping/mutagenesis, myeloid-specific Tigar KO in LPS and CLP sepsis models","pmids":["38773142"],"confidence":"High","gaps":["How TIGAR's opposing effects on NF-κB (LUBAC inhibition vs. TAK1 activation) are coordinated cell-type-specifically not resolved","Direct structural model of TIGAR–TAK1 complex lacking"]},{"year":2024,"claim":"Discovery that mitochondrial TIGAR directly binds SDH-A and modulates its acetylation/succinylation to suppress SDH activity and neuronal ferroptosis established a PPP-independent antioxidant mechanism.","evidence":"Co-IP (TIGAR–SDH-A), SDH activity assays, PTM analysis, enzymatic-dead TIGAR mutant, prolonged OGD and stroke models","pmids":["38494143"],"confidence":"Medium","gaps":["Whether TIGAR directly catalyzes PTM changes on SDH-A or recruits acetyltransferases/deacetylases unknown","Single-lab finding requiring independent confirmation"]},{"year":null,"claim":"How TIGAR's enzymatic and non-enzymatic functions are spatiotemporally coordinated across subcellular compartments — and how cell-type-specific contexts determine whether TIGAR promotes or suppresses NF-κB signaling — remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model of human TIGAR with any of its non-substrate partners (HK2, LUBAC, TAK1, NRF2, SDH-A, ATP5A1)","Signals controlling nuclear vs. mitochondrial vs. cytosolic distribution undefined","In vivo relevance of 2,3-BPG phosphatase activity in erythroid and non-erythroid tissues not established"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,1,5]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[10,19]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[18]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[3,7,11,20]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,4]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[9,18]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,4,5,30]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[10,19]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[2,27]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[0,23]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[2,21]}],"complexes":[],"partners":["HK2","NRF2","TAK1","HOIP","ATP5A1","SDHA","TRIM31","TRIM35"],"other_free_text":[]},"mechanistic_narrative":"TIGAR is a p53-inducible histidine phosphatase that functions as a metabolic regulator linking glycolysis suppression, antioxidant defense, and non-enzymatic signaling scaffolding. Its highest catalytic efficiency is toward 2,3-bisphosphoglycerate, though it also hydrolyzes fructose-2,6-bisphosphate, thereby diverting glucose flux from glycolysis into the pentose phosphate pathway to generate NADPH and ribose-5-phosphate for ROS scavenging and nucleotide synthesis [PMID:16839880, PMID:24423178, PMID:23726973]. Under hypoxia, TIGAR translocates to mitochondria where it binds HK2 to enhance hexokinase activity and interacts with SDH-A to suppress succinate dehydrogenase activity and ferroptosis, while in the nucleus it acts as a phosphatase-independent co-factor that facilitates NRF2 chromatin recruitment and NRF2-target gene expression [PMID:23185017, PMID:38494143, PMID:35847493]. Independent of its enzymatic activity, TIGAR also competes with NEMO for LUBAC binding to suppress NF-κB signaling and directly binds TAK1 in macrophages to promote inflammatory ubiquitination, establishing TIGAR as a dual metabolic enzyme and protein-interaction scaffold [PMID:29650758, PMID:38773142]."},"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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B","url":"https://pubmed.ncbi.nlm.nih.gov/35847493","citation_count":18,"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":18,"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":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":"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":"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":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":"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":16,"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":16,"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":"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":"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":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":"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":"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":12,"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":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":"38011768","id":"PMC_38011768","title":"S1PR2 inhibition mitigates cognitive deficit in diabetic mice by modulating microglial activation via Akt-p53-TIGAR pathway.","date":"2023","source":"International immunopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/38011768","citation_count":11,"is_preprint":false},{"pmid":"36114745","id":"PMC_36114745","title":"Gankyrin and TIGAR cooperatively accelerate glucose metabolism toward the PPP and TCA cycle in hepatocellular carcinoma.","date":"2022","source":"Cancer science","url":"https://pubmed.ncbi.nlm.nih.gov/36114745","citation_count":11,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":50363,"output_tokens":7524,"usd":0.131974},"stage2":{"model":"claude-opus-4-6","input_tokens":11270,"output_tokens":3746,"usd":0.225},"total_usd":0.356974,"stage1_batch_id":"msgbatch_01RPbVc9PDH9zQmYK5Hs6srm","stage2_batch_id":"msgbatch_01JVbVLzeKN2yVrsGp3zC8aM","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 as a fructose-2,6-bisphosphatase, lowering fructose-2,6-bisphosphate levels in cells, thereby inhibiting glycolysis, reducing intracellular ROS, and protecting cells from ROS-associated apoptosis.\",\n      \"method\": \"Gene expression microarray identification followed by functional assays (ROS measurement, apoptosis assays, TIGAR knockdown/overexpression in cells)\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — original discovery with multiple orthogonal methods, highly replicated across labs (1626 citations)\",\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 residue; recombinant human and zebrafish TIGAR hydrolyzes fructose-2,6-bisphosphate and fructose-1,6-bisphosphate but not fructose-6-phosphate in vitro; the active site is open and positively charged, most closely related to bacterial PhoE phosphatase and the bisphosphatase domain of bifunctional PFK2.\",\n      \"method\": \"X-ray crystallography and in vitro phosphatase assay with recombinant protein\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure combined with biochemical reconstitution\",\n      \"pmids\": [\"19015259\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"TIGAR modulates intracellular ROS in response to nutrient starvation or metabolic stress and functions to inhibit autophagy through ROS suppression, independent of the mTOR pathway and p53.\",\n      \"method\": \"TIGAR knockdown/overexpression with autophagy markers (LC3, Beclin-1), ROS measurement, nutrient deprivation assays\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods, replicated by 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), increasing HK2 activity; mitochondrial localization depends on mitochondrial HK2 and HIF-1α activity; the fructose-2,6-bisphosphatase activity of TIGAR is independent of HK2 binding and mitochondrial localization, but both activities contribute to limiting mitochondrial ROS and protecting from cell death.\",\n      \"method\": \"Subcellular fractionation, co-immunoprecipitation (TIGAR-HK2), HIF-1α inhibition, hypoxia treatment, cell death assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, fractionation, functional epistasis with HIF-1α and HK2\",\n      \"pmids\": [\"23185017\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"TIGAR is required for intestinal regeneration in vivo and ex vivo; its fructose-2,6-bisphosphatase activity promotes the pentose phosphate pathway to produce NADPH for antioxidant function and ribose-5-phosphate for nucleotide synthesis; growth defects from TIGAR loss were rescued by ROS scavengers and nucleosides.\",\n      \"method\": \"TIGAR knockout mice, intestinal organoid cultures, xenograft tumor models, genetic rescue with ROS scavengers/nucleosides\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo KO with defined phenotypic rescue, replicated in multiple models\",\n      \"pmids\": [\"23726973\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"TIGAR is identified as the phosphoglycolate-independent 2,3-bisphosphoglycerate (2,3-BPG) phosphatase; recombinant human TIGAR most efficiently hydrolyzes 2,3-BPG (~400-fold greater catalytic efficiency than for fructose-2,6-bisphosphate); loss of TIGAR leads to up to 5-fold increases in cellular 2,3-BPG levels.\",\n      \"method\": \"In vitro phosphatase assay with recombinant human TIGAR on panel of substrates; genetic and shRNA cell culture models measuring 2,3-BPG and F-2,6-BP levels\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro enzymatic reconstitution with multiple substrates plus genetic validation in cells\",\n      \"pmids\": [\"24423178\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"TIGAR mediates p21-independent, p53-dependent G1-phase arrest in cancer cells by suppressing CDK-2, CDK-4, CDK-6, Cyclin D, and Cyclin E, and promoting dephosphorylation of RB protein, stabilizing the RB-E2F1 complex and preventing S-phase entry.\",\n      \"method\": \"Co-immunoprecipitation (RB-E2F1), chromatin immunoprecipitation, luciferase reporter assays, western blot, cell cycle analysis, tumor xenograft model\",\n      \"journal\": \"British journal of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP for RB-E2F1 interaction, functional KD phenotype, single lab\",\n      \"pmids\": [\"22782351\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"TIGAR protects ischemic brain via enhancing pentose phosphate pathway flux (increasing G6PD and NADPH production) and preserving mitochondrial function; TIGAR translocates to mitochondria during ischemia/reperfusion; supplementation of NADPH rescues the neuronal injury caused by TIGAR knockdown.\",\n      \"method\": \"Lentiviral TIGAR overexpression/knockdown in mice and neurons, in vivo stroke model (MCAO), subcellular fractionation, G6PD activity assay, ROS/GSH/caspase-3 measurements\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods in vivo and in vitro, functional rescue with NADPH\",\n      \"pmids\": [\"24872551\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"TIGAR and RAC1 have opposing effects on ROS in intestinal cells following APC loss: TIGAR limits damaging ROS while RAC1-driven NOX generates pro-proliferative ROS; loss of TIGAR increases ROS damage and inhibits proliferation; despite opposing effects on ROS, loss of both TIGAR and RAC1 cooperates to suppress intestinal proliferation.\",\n      \"method\": \"3D organoid cultures, in vivo mouse models (APC deletion), genetic epistasis (TIGAR KO × RAC1 KO × Myc KO), ROS measurements\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis in vivo and in vitro with multiple orthogonal readouts\",\n      \"pmids\": [\"26679840\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"TIGAR regulates DNA damage response by relocating to the nucleus after genotoxic drug treatment or hypoxia; TIGAR controls phosphorylation of ATM through Cdk5, independent of the PPP pathway; knockdown of TIGAR exacerbated DNA damage, partly reversed by NADPH, ribose, or ROS scavenger NAC.\",\n      \"method\": \"Subcellular fractionation/imaging, siRNA knockdown, pharmacological Cdk5 inhibition, γH2AX foci assay, NADPH/ribose rescue experiments\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — nuclear relocalization plus Cdk5-ATM pathway epistasis, single lab\",\n      \"pmids\": [\"25928429\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"TIGAR directly binds to and inhibits the linear ubiquitin assembly complex (LUBAC) by competing with NEMO for association with LUBAC, thereby preventing linear ubiquitination of NEMO, blocking IKKβ phosphorylation/activation, and suppressing NF-κB signaling; this function is independent of TIGAR phosphatase activity as a phosphatase-dead mutant retains NF-κB inhibitory activity.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, phosphatase-dead TIGAR mutant, 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 — reciprocal Co-IP, active-site mutagenesis, and in vivo mouse validation showing non-enzymatic function\",\n      \"pmids\": [\"29650758\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TIGAR translocates to mitochondria in skeletal muscle during exhaustive exercise and binds directly to ATP synthase F1 subunit α (ATP5A1), increasing ATP generation, maintaining mitochondrial membrane potential, and reducing mitochondrial oxidative stress; TIGAR also regulates mitochondrial biogenesis through the SIRT1-PGC1α deacetylation pathway.\",\n      \"method\": \"GST-TIGAR pull-down followed by LC-MS (identifies ATP5A1), TIGAR KO mice exhaustive swimming test, mitochondrial fractionation, overexpression of mitochondria-targeted TIGAR, SIRT1 deacetylation assays\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — pull-down/MS identification of binding partner plus KO mouse phenotype and functional assays\",\n      \"pmids\": [\"30726106\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TIGAR promotes neural stem cell (NSC) differentiation by facilitating metabolic reprogramming from glycolysis to oxidative phosphorylation; TIGAR knockdown decreases acetyl-CoA levels and H3K9 acetylation at the promoters of neuronal differentiation genes (Ngn1, NeuroD1, Gfap); acetate supplementation (as acetyl-CoA precursor) rescues the differentiation defect caused by TIGAR knockdown.\",\n      \"method\": \"NSC culture, TIGAR knockdown/overexpression, acetyl-CoA measurement, ChIP for H3K9ac at promoters, acetate rescue, metabolic flux analysis\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP plus metabolite rescue, single lab\",\n      \"pmids\": [\"30814486\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TIGAR expression is modulated by the transcription factor SP1 (induced by ischemia/reperfusion via ROS and metabolic hormones including adrenaline, hydrocortisone, glucagon); SP1 inhibition or siRNA knockdown blocks ischemia-induced TIGAR upregulation; TIGAR expression is also negatively regulated by insulin via p53 acetylation.\",\n      \"method\": \"MCAO/R mouse model, SP1 inhibitor (mithramycin A), SP1 siRNA, luciferase reporter, chromatin immunoprecipitation, hormone/H2O2 treatment in vivo and in vitro\",\n      \"journal\": \"Neurochemistry international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP and pharmacological/genetic inhibition of SP1, single lab\",\n      \"pmids\": [\"25445985\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"SP1 transcription factor is indispensable for basal TIGAR promoter activity; a minimal SP1-binding site at -56/-4 bp was identified and SP1 binds the TIGAR promoter in vitro (EMSA) and in vivo (ChIP).\",\n      \"method\": \"5'-RACE, deletion reporter assays, EMSA, chromatin immunoprecipitation, SP1 knockdown\",\n      \"journal\": \"Molecular and cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — EMSA plus ChIP with functional reporter assays, single lab\",\n      \"pmids\": [\"21761199\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"CREB regulates TIGAR expression via a cAMP-response element (CRE) at position -4/+13 of the TIGAR promoter; CREB knockdown reduces promoter activity and TIGAR expression; CREB overexpression or forskolin treatment enhances TIGAR expression.\",\n      \"method\": \"5'-deletion analysis, site-directed mutagenesis, EMSA, chromatin immunoprecipitation, CREB knockdown/overexpression, luciferase reporter\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — EMSA plus ChIP with functional mutagenesis, single lab\",\n      \"pmids\": [\"24036271\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"TRIM31 is an E3 ubiquitin ligase for TIGAR; TRIM31 directly interacts with TIGAR and promotes its polyubiquitination and proteasome-dependent degradation; TRIM31 deficiency protects against cerebral ischemia by raising TIGAR levels.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, proteasome inhibitor treatment, TIGAR knockdown rescue, TRIM31 KO in ischemia model\",\n      \"journal\": \"Redox biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP plus ubiquitination assay plus genetic rescue, single lab\",\n      \"pmids\": [\"34218200\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"TRIM35 acts as an E3 ubiquitin ligase for TIGAR, interacting with TIGAR and promoting its polyubiquitination and proteasomal degradation; TRIM35 knockdown alleviates renal ischemia-reperfusion injury by elevating TIGAR levels and enhancing mitochondrial fusion.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, proteasome pathway analysis, TIGAR knockdown rescue, TRIM35 knockdown in renal IRI model\",\n      \"journal\": \"International journal of biological macromolecules\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP plus ubiquitination assay with functional in vivo rescue, single lab\",\n      \"pmids\": [\"35421414\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Nuclear TIGAR directly interacts with the antioxidant transcription factor NRF2 and facilitates chromatin recruitment of NRF2, H3K4me3 methylase MLL1, and elongating Pol-II to stimulate expression of NRF2 target genes (including NSD2, NQO1/2, PRDX1, GSTM4), independent of TIGAR's enzymatic activity; nuclear TIGAR also stimulates NSD2 expression leading to elevated global H3K36me2.\",\n      \"method\": \"Co-immunoprecipitation (TIGAR-NRF2), ChIP, enzymatic activity-deficient TIGAR mutant, loss-of-function and gain-of-function experiments, therapeutic resistance assays\",\n      \"journal\": \"Acta pharmaceutica Sinica. B\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP plus ChIP plus mutagenesis showing enzymatic-independent function, single lab\",\n      \"pmids\": [\"35847493\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"TIGAR directly binds to TAK1 (TGF-β-activated kinase 1) in macrophages and promotes TRAF6-mediated ubiquitination and auto-phosphorylation of TAK1, enhancing inflammatory NF-κB signaling; residues 152-161 of TIGAR constitute the critical binding motif, and this function is independent of phosphatase activity; interference with TIGAR-TAK1 binding attenuates sepsis in mice.\",\n      \"method\": \"Co-immunoprecipitation (TIGAR-TAK1), ubiquitination assay, domain mapping/mutagenesis (residues 152-161), myeloid-specific Tigar KO in sepsis models (LPS and CLP), pharmacological disruption with 5Z-7-oxozeaenol\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — reciprocal Co-IP with domain mutagenesis plus in vivo KO and pharmacological validation\",\n      \"pmids\": [\"38773142\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Under prolonged ischemia, mitochondrial TIGAR inhibits succinate dehydrogenase (SDH) activity through post-translational modifications (acetylation and succinylation) of SDH subunit A via direct interaction with SDH A, reducing ROS production and neuronal ferroptosis independently of the PPP-NADPH-GPX4 pathway.\",\n      \"method\": \"TIGAR overexpression/knockdown, mitochondrial fractionation, SDH activity assays, co-immunoprecipitation (TIGAR-SDH A), acetylation/succinylation analysis, enzymatic-activity mutant TIGAR, prolonged OGD model, in vivo stroke model\",\n      \"journal\": \"Free radical biology & medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP, PTM analysis, functional mutagenesis, single lab\",\n      \"pmids\": [\"38494143\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TIGAR inhibits autophagy during ischemia/reperfusion in neurons by activating the mTOR-S6KP70 signaling pathway; TIGAR KO reduces phosphorylated mTOR and S6KP70 levels; autophagy inhibitor 3-MA or NADPH supplementation blocks the exacerbated brain damage seen with TIGAR KO.\",\n      \"method\": \"TIGAR transgenic and knockout mice, MCAO model, primary neurons with OGD/R, western blot for p-mTOR and p-S6KP70, pharmacological rescue with 3-MA and rapamycin\",\n      \"journal\": \"Free radical biology & medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — transgenic/KO mouse models plus pharmacological pathway epistasis, single lab\",\n      \"pmids\": [\"30978385\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"TIGAR expression is controlled by the AKT-mTOR-S6K1-eIF4A cap-dependent translation pathway; inhibition of MUC1-C (via GO-203) blocks AKT/mTOR signaling and suppresses eIF4A-mediated TIGAR translation without reducing TIGAR mRNA, leading to decreased GSH and increased ROS.\",\n      \"method\": \"qRT-PCR (TIGAR mRNA unchanged), western blot (TIGAR protein decreased), AKT/mTOR pathway inhibitors, eIF4A inhibition, xenograft model\",\n      \"journal\": \"Molecular cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mRNA vs. protein dissociation combined with pathway inhibitors, single lab\",\n      \"pmids\": [\"28153010\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"TIGAR induces ferroptosis resistance in colorectal cancer cells via the ROS/AMPK/SCD1 pathway; TIGAR knockdown decreases GSH/GSSG ratio, increases lipid peroxidation/MDA, and TIGAR inhibition represses SCD1 expression in a redox- and AMPK-dependent manner.\",\n      \"method\": \"TIGAR knockdown (siRNA) in CRC cell lines, ferroptosis induction (erastin), lipid peroxidation assays, AMPK inhibitor/activator epistasis, SCD1 expression analysis\",\n      \"journal\": \"Free radical biology & medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — pathway epistasis with pharmacological tools plus KD phenotype, single lab\",\n      \"pmids\": [\"35271998\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"p53-independent expression of TIGAR occurs in many cancer cell lines and in mouse tissues in vivo; basal TIGAR expression does not depend on p53 or TAp73 in most mouse tissues; stress-induced TIGAR upregulation in mouse intestine after ionizing radiation is also p53- and TAp73-independent.\",\n      \"method\": \"p53 KO mice, TAp73 KO mice, ionizing radiation stress, western blot, tissue analysis\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO models in vivo, single lab\",\n      \"pmids\": [\"26247727\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"TCF19 interacts with p53 and co-regulates TIGAR (and SCO2) transcription; TCF19/p53 form different complexes containing either CBP (for activation) or HDAC1 (for repression) depending on glucose conditions, epigenetically programming TIGAR expression.\",\n      \"method\": \"Co-immunoprecipitation (TCF19-p53), IP/MS, ChIP, TCF19/p53 knockdown, metabolic flux analysis (ECAR/OCR), RNA-seq\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP with MS plus ChIP, single lab\",\n      \"pmids\": [\"34369624\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SIRT3 reduces p53 acetylation, leading to decreased TIGAR expression and restored PFKFB3-dependent glycolysis; in high-glucose conditions, loss of SIRT3 increases p53 acetylation and TIGAR expression, impairing glycolysis and promoting ROS/apoptosis in cardiomyocytes.\",\n      \"method\": \"Adenovirus-SIRT3 overexpression, TIGAR siRNA knockdown, p53 acetylation western blot, metabolic assays (glycolysis/ECAR), in vivo db/db diabetic mouse model\",\n      \"journal\": \"Journal of the American Heart Association\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic manipulation in vitro and in vivo with mechanistic epistasis, single lab\",\n      \"pmids\": [\"33586458\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Under prolonged ischemia (PPP impaired), TIGAR alleviates oxidative stress through a PPP-independent mechanism by inducing autophagy, which activates Nrf2; Atg7 deletion or Nrf2 silencing abolishes TIGAR neuroprotection in prolonged ischemia; enzymatically inactive mutant TIGAR retains antioxidant effects in this context.\",\n      \"method\": \"Enzymatic mutant TIGAR (no phosphatase activity), G6PD silencing, Atg7 KO mice, Nrf2 knockdown, prolonged OGD model and extended ischemia in vivo\",\n      \"journal\": \"Redox biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mutagenesis plus genetic KO epistasis, single lab\",\n      \"pmids\": [\"35576689\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"TIGAR supports pancreatic cancer initiation by limiting ROS, while higher ROS in metastasizing PDAC cells drives increased MAPK signaling and a pro-metastatic phenotype; TIGAR expression is higher in premalignant lesions and lower in metastatic tumors; antioxidant treatment reverts the metastatic switch.\",\n      \"method\": \"TIGAR KO in KRAS-driven PDAC mouse model, antioxidant treatment, MAPK pathway analysis, tumor initiation and metastasis assays\",\n      \"journal\": \"Cancer cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo KO in PDAC model with mechanistic MAPK pathway analysis, replicated in human\",\n      \"pmids\": [\"31983610\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"CRISPR genome-scale loss-of-function screen identifies TIGAR as a modifier of PARP inhibitor sensitivity; TIGAR knockdown enhances olaparib sensitivity via downregulation of BRCA1 and the Fanconi anemia pathway and increases cellular senescence.\",\n      \"method\": \"Genome-scale CRISPR/Cas9 screen, TIGAR knockdown, BRCA1/Fanconi anemia pathway western blot, olaparib sensitivity assay, senescence assay\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genome-scale screen with mechanistic pathway validation, single lab\",\n      \"pmids\": [\"31508509\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"TIGAR overexpression in ESCC reprograms glucose metabolism from glycolysis toward the glutamine pathway through AMP-activated kinase (AMPK); a catalytically inactive variant of TIGAR does not induce tumor growth in vivo, indicating enzymatic activity is required for metabolic reprogramming and tumor promotion.\",\n      \"method\": \"TIGAR overexpression and KO in ESCC cells and mice, catalytically inactive TIGAR mutant, xenograft and patient-derived xenograft models, metabolic assays (lactate, NADPH, ATP)\",\n      \"journal\": \"Theranostics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — enzymatic mutant validation plus in vivo KO model, single lab\",\n      \"pmids\": [\"32206103\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TIGAR is a p53-inducible histidine phosphatase (with highest catalytic efficiency toward 2,3-bisphosphoglycerate and fructose-2,6-bisphosphate) that inhibits glycolysis, promotes the pentose phosphate pathway to generate NADPH and ribose, and thereby limits intracellular ROS; under hypoxia it translocates to mitochondria where it binds HK2 to increase HK2 activity and interacts with SDH-A to suppress succinate dehydrogenase activity and ferroptosis; in the nucleus it acts as a non-enzymatic co-factor facilitating NRF2 chromatin recruitment; it also directly competes with NEMO for LUBAC binding to suppress NF-κB signaling, and directly binds TAK1 to promote inflammatory ubiquitination in macrophages; its protein levels are controlled by TRIM31/TRIM35-mediated ubiquitination and proteasomal degradation, by the AKT-mTOR-eIF4A translational axis, and by transcriptional regulators SP1, CREB, TCF19/p53, and non-coding RNAs.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"TIGAR is a p53-inducible histidine phosphatase that functions as a metabolic regulator linking glycolysis suppression, antioxidant defense, and non-enzymatic signaling scaffolding. Its highest catalytic efficiency is toward 2,3-bisphosphoglycerate, though it also hydrolyzes fructose-2,6-bisphosphate, thereby diverting glucose flux from glycolysis into the pentose phosphate pathway to generate NADPH and ribose-5-phosphate for ROS scavenging and nucleotide synthesis [PMID:16839880, PMID:24423178, PMID:23726973]. Under hypoxia, TIGAR translocates to mitochondria where it binds HK2 to enhance hexokinase activity and interacts with SDH-A to suppress succinate dehydrogenase activity and ferroptosis, while in the nucleus it acts as a phosphatase-independent co-factor that facilitates NRF2 chromatin recruitment and NRF2-target gene expression [PMID:23185017, PMID:38494143, PMID:35847493]. Independent of its enzymatic activity, TIGAR also competes with NEMO for LUBAC binding to suppress NF-κB signaling and directly binds TAK1 in macrophages to promote inflammatory ubiquitination, establishing TIGAR as a dual metabolic enzyme and protein-interaction scaffold [PMID:29650758, PMID:38773142].\",\n  \"teleology\": [\n    {\n      \"year\": 2006,\n      \"claim\": \"Identifying TIGAR as a p53 target with fructose-2,6-bisphosphatase activity established the first link between p53, glycolysis inhibition, and ROS-dependent cell survival.\",\n      \"evidence\": \"Microarray screen followed by overexpression/knockdown with ROS and apoptosis assays in human cancer cell lines\",\n      \"pmids\": [\"16839880\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Enzymatic mechanism and true preferred substrate unresolved\", \"Whether TIGAR functions independently of p53 unknown\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Solving the crystal structure revealed a histidine phosphatase fold rather than a canonical bisphosphatase domain, redefining TIGAR's catalytic mechanism and evolutionary origin.\",\n      \"evidence\": \"X-ray crystallography of zebrafish TIGAR plus in vitro phosphatase assays with recombinant human protein\",\n      \"pmids\": [\"19015259\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Preferred physiological substrate still unclear\", \"No human structure available\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Demonstrating that TIGAR suppresses autophagy via ROS reduction extended its role beyond apoptosis to a broader metabolic stress response.\",\n      \"evidence\": \"TIGAR knockdown/overexpression with autophagy markers and ROS measurement under nutrient starvation\",\n      \"pmids\": [\"19713938\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of autophagy suppression not fully delineated beyond ROS\", \"Context-dependence of mTOR involvement unresolved\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Mapping SP1 as essential for basal TIGAR transcription showed that TIGAR is constitutively expressed through p53-independent mechanisms, broadening the regulatory framework.\",\n      \"evidence\": \"Deletion reporter assays, EMSA, and ChIP for SP1 on the TIGAR promoter\",\n      \"pmids\": [\"21761199\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relative contributions of SP1 vs. p53 to TIGAR levels in different tissues unclear\", \"No in vivo SP1 KO validation\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Showing hypoxia-induced mitochondrial translocation and HK2 binding revealed a non-canonical, compartment-specific protective mechanism distinct from cytosolic bisphosphatase activity.\",\n      \"evidence\": \"Subcellular fractionation, reciprocal Co-IP of TIGAR–HK2, HIF-1α epistasis under hypoxia\",\n      \"pmids\": [\"23185017\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for TIGAR–HK2 interaction unknown\", \"Whether mitochondrial TIGAR retains phosphatase activity in that compartment unclear\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"In vivo knockout studies established that TIGAR's PPP-promoting activity is required for intestinal regeneration, linking its metabolic function to tissue homeostasis through NADPH and nucleotide provision.\",\n      \"evidence\": \"TIGAR KO mice, intestinal organoids, xenograft models with ROS scavenger and nucleoside rescue\",\n      \"pmids\": [\"23726973\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether TIGAR is required for regeneration in all tissues not tested\", \"Relative importance of NADPH vs. ribose contribution unresolved\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identifying 2,3-bisphosphoglycerate as the kinetically preferred substrate (~400-fold over F-2,6-BP) fundamentally reframed TIGAR's primary enzymatic function.\",\n      \"evidence\": \"In vitro kinetics on recombinant human TIGAR across substrate panel, plus 2,3-BPG accumulation in TIGAR-depleted cells\",\n      \"pmids\": [\"24423178\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological consequence of 2,3-BPG regulation (e.g., hemoglobin oxygen affinity in erythrocytes) not explored\", \"Relative in vivo contribution of 2,3-BPG vs. F-2,6-BP hydrolysis context-dependent\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Genetic epistasis between TIGAR and RAC1 in APC-null intestinal cells revealed that TIGAR functions to limit damaging ROS while RAC1/NOX generates pro-proliferative ROS, establishing opposing ROS-regulatory roles in tumorigenesis.\",\n      \"evidence\": \"In vivo TIGAR KO × RAC1 KO × Myc KO in APC-deleted mouse intestine with organoid cultures\",\n      \"pmids\": [\"26679840\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How TIGAR loss and RAC1 loss cooperate to suppress proliferation mechanistically unresolved\", \"Applicability beyond intestinal tumors not tested\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Demonstrating that basal and stress-induced TIGAR expression occurs independently of p53 and TAp73 in most mouse tissues resolved whether p53 is strictly required for TIGAR function.\",\n      \"evidence\": \"p53 KO and TAp73 KO mice with ionizing radiation stress and tissue-level protein analysis\",\n      \"pmids\": [\"26247727\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Full set of p53-independent transcription factors driving TIGAR only partially mapped\", \"Tissue-specific variation in regulatory dependencies not comprehensively tested\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Discovery that TIGAR inhibits NF-κB by competing with NEMO for LUBAC binding — independent of phosphatase activity — established TIGAR as a non-enzymatic signaling scaffold.\",\n      \"evidence\": \"Reciprocal Co-IP, ubiquitination assays, phosphatase-dead mutant, TIGAR KO mice with adipose NF-κB readout\",\n      \"pmids\": [\"29650758\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of TIGAR–LUBAC interaction unknown\", \"Whether this function operates in immune cells beyond adipocytes unclear at this time\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identifying ATP5A1 as a direct mitochondrial binding partner linked TIGAR to ATP synthase regulation and mitochondrial biogenesis via SIRT1–PGC1α, expanding its mitochondrial functions beyond HK2.\",\n      \"evidence\": \"GST pull-down/LC-MS, TIGAR KO mouse exercise model, mitochondria-targeted TIGAR overexpression\",\n      \"pmids\": [\"30726106\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether TIGAR modulates ATP synthase catalytic mechanism or assembly unknown\", \"Relevance beyond skeletal muscle not demonstrated\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"In a KRAS-driven PDAC model, TIGAR was shown to support tumor initiation by ROS limitation while its loss paradoxically promoted metastasis via MAPK activation, revealing stage-dependent roles in cancer.\",\n      \"evidence\": \"TIGAR KO in KRAS-driven PDAC mice, antioxidant rescue of metastatic phenotype, MAPK signaling analysis\",\n      \"pmids\": [\"31983610\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which elevated ROS specifically activates MAPK over other pathways not defined\", \"Generalizability to non-KRAS-driven cancers unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identification of TRIM31 and subsequently TRIM35 as E3 ubiquitin ligases for TIGAR established that TIGAR protein turnover is governed by proteasomal degradation, with physiological relevance in ischemia-reperfusion injury.\",\n      \"evidence\": \"Co-IP, ubiquitination assays, proteasome inhibitor rescue, TRIM31 KO and TRIM35 KD in ischemia models\",\n      \"pmids\": [\"34218200\", \"35421414\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether TRIM31 and TRIM35 target overlapping or distinct TIGAR pools unknown\", \"Ubiquitination sites on TIGAR not mapped\", \"Each finding from a single lab\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Showing that nuclear TIGAR directly recruits NRF2, MLL1, and elongating Pol-II to chromatin independently of enzymatic activity uncovered a transcriptional co-activator function.\",\n      \"evidence\": \"Co-IP (TIGAR–NRF2), ChIP for NRF2/MLL1/Pol-II, enzymatic-dead TIGAR mutant, gain/loss-of-function\",\n      \"pmids\": [\"35847493\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How TIGAR reaches the nucleus and what triggers nuclear import unknown\", \"Structural basis of TIGAR–NRF2 interaction not determined\", \"Single-lab finding\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Demonstrating that TIGAR binds TAK1 via residues 152–161 to promote TRAF6-mediated ubiquitination in macrophages revealed a pro-inflammatory scaffolding role, opposing its anti-NF-κB activity in other contexts.\",\n      \"evidence\": \"Reciprocal Co-IP, domain mapping/mutagenesis, myeloid-specific Tigar KO in LPS and CLP sepsis models\",\n      \"pmids\": [\"38773142\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How TIGAR's opposing effects on NF-κB (LUBAC inhibition vs. TAK1 activation) are coordinated cell-type-specifically not resolved\", \"Direct structural model of TIGAR–TAK1 complex lacking\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Discovery that mitochondrial TIGAR directly binds SDH-A and modulates its acetylation/succinylation to suppress SDH activity and neuronal ferroptosis established a PPP-independent antioxidant mechanism.\",\n      \"evidence\": \"Co-IP (TIGAR–SDH-A), SDH activity assays, PTM analysis, enzymatic-dead TIGAR mutant, prolonged OGD and stroke models\",\n      \"pmids\": [\"38494143\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether TIGAR directly catalyzes PTM changes on SDH-A or recruits acetyltransferases/deacetylases unknown\", \"Single-lab finding requiring independent confirmation\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How TIGAR's enzymatic and non-enzymatic functions are spatiotemporally coordinated across subcellular compartments — and how cell-type-specific contexts determine whether TIGAR promotes or suppresses NF-κB signaling — remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural model of human TIGAR with any of its non-substrate partners (HK2, LUBAC, TAK1, NRF2, SDH-A, ATP5A1)\", \"Signals controlling nuclear vs. mitochondrial vs. cytosolic distribution undefined\", \"In vivo relevance of 2,3-BPG phosphatase activity in erythroid and non-erythroid tissues not established\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 1, 5]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [10, 19]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [18]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [3, 7, 11, 20]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 4]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [9, 18]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 4, 5, 30]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [10, 19]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [2, 27]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [0, 23]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [2, 21]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"HK2\",\n      \"NRF2\",\n      \"TAK1\",\n      \"HOIP\",\n      \"ATP5A1\",\n      \"SDHA\",\n      \"TRIM31\",\n      \"TRIM35\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}