{"gene":"PFKL","run_date":"2026-04-28T19:45:44","timeline":{"discoveries":[{"year":1981,"finding":"PFKL (liver-type phosphofructokinase subunit) was mapped to human chromosome 21 using somatic cell hybrids and a subunit-specific monoclonal antibody. Trisomy 21 individuals showed elevated erythrocyte PFK activity due to a gene-dosage effect, with a striking increase in L4 homotetrameric species.","method":"Somatic cell hybrid panel analysis with monoclonal antibody immunoprecipitation; chromatographic isozyme analysis of trisomy 21 erythrocytes","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — reciprocal genetic and biochemical evidence across 17 hybrid lines plus trisomy 21 patient samples","pmids":["6455664"],"is_preprint":false},{"year":1994,"finding":"Transgenic mice overexpressing PFKL showed tissue-specific overexpression resembling endogenous enzyme distribution. PFKL overexpression nearly doubled PFK activity in embryonic brain but not adult brain, indicating temporally regulated gene-dosage effects relevant to Down syndrome pathology.","method":"Transgenic mouse construction with murine PFKL gene-cDNA hybrid; tissue PFK activity assays","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 — direct in vivo genetic model with biochemical readout, single lab","pmids":["8172601"],"is_preprint":false},{"year":1998,"finding":"Transgenic-PFKL mice with elevated PFKL activity exhibited slower blood glucose clearance but a 58% faster rate of cerebral glucose utilization compared to controls, demonstrating that PFKL overexpression directly alters brain glucose metabolism in vivo.","method":"In vivo [1-13C]-glucose infusion with NMR brain metabolic rate measurements in transgenic vs. non-transgenic mice","journal":"Brain research","confidence":"Medium","confidence_rationale":"Tier 1 — in vivo NMR metabolic flux measurement, single lab","pmids":["9813288"],"is_preprint":false},{"year":2012,"finding":"O-GlcNAcylation of phosphofructokinase 1 (PFK1) at serine 529 inhibits its enzymatic activity and redirects glucose flux from glycolysis to the pentose phosphate pathway under hypoxia, conferring a selective growth advantage to cancer cells. Blocking glycosylation at S529 reduced cancer cell proliferation and impaired tumor formation.","method":"In vitro PFK1 activity assays with O-GlcNAc site-specific mutagenesis (S529A); metabolic flux analysis; xenograft tumor models","journal":"Science","confidence":"High","confidence_rationale":"Tier 1 — reconstituted enzymatic assay, site-specific mutagenesis, in vitro and in vivo validation","pmids":["22923583"],"is_preprint":false},{"year":2020,"finding":"The E3 ubiquitin ligase A20 interacts with PFKL and promotes its ubiquitin-mediated proteasomal degradation, thereby inhibiting glycolysis in hepatocellular carcinoma cells. Downregulation of A20 in HCC leads to PFKL accumulation and enhanced glycolysis, proliferation, and migration.","method":"Co-immunoprecipitation; RNA interference; glycolysis assays; HCC cell line functional studies","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 3 — Co-IP interaction plus functional rescue, single lab","pmids":["32015333"],"is_preprint":false},{"year":2021,"finding":"Small-molecule NA-11 (analog of LDC7559) selectively activates PFKL by binding to the AMP/ADP allosteric activation site, increasing glycolytic flux and thereby dampening flux through the pentose phosphate pathway. This reduces NADPH availability for NOX2, suppressing the oxidative burst, NETosis, and tissue damage in neutrophils. High-resolution crystal structure of PFKL confirmed the NA-11 binding site and explained isoform selectivity over PFKP and PFKM.","method":"Chemical proteomics (two unbiased strategies); high-resolution crystal structure of PFKL–NA-11 complex; neutrophil ROS/NETosis assays; glycolysis flux measurements","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 — crystal structure + biochemical allosteric activation assay + cellular functional validation, replicated with two chemical probes","pmids":["34320407"],"is_preprint":false},{"year":2021,"finding":"PFKL is a direct molecular target of penfluridol; direct binding of penfluridol to PFKL inhibits its glycolytic activity, leading to AMPK activation, nuclear translocation of FOXO3a, and BIM-dependent apoptosis in esophageal squamous cell carcinoma cells. PFKL-deficient cells are insensitive to penfluridol, confirming PFKL as the essential target.","method":"DARTS (drug affinity responsive target stability) technology; proteomics; AMPK/FOXO3a pathway analysis; PFKL knockdown rescue experiments","journal":"Acta pharmaceutica Sinica. B","confidence":"Medium","confidence_rationale":"Tier 2 — direct target ID by DARTS plus genetic epistasis (PFKL KD rescue), single lab","pmids":["35530161"],"is_preprint":false},{"year":2022,"finding":"YTHDF3 promotes PFKL expression by suppressing PFKL mRNA degradation via m6A modification. In turn, PFKL positively regulates YTHDF3 protein stability by interacting with EFTUD2 (a spliceosome subunit), which inhibits ubiquitination of YTHDF3, forming a positive regulatory feedback loop.","method":"MeRIP (methylated RNA immunoprecipitation); Co-immunoprecipitation; ubiquitination assays; loss/gain-of-function in HCC cell lines and in vivo","journal":"Journal of experimental & clinical cancer research","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal biochemical methods (MeRIP, Co-IP, ubiquitination assay), single lab","pmids":["36471428"],"is_preprint":false},{"year":2022,"finding":"PDLIM2, an E3 ubiquitin ligase, promotes ubiquitination and degradation of PFKL in laryngeal squamous cell carcinoma cells, thereby restraining glycolysis. M2 macrophage-derived exosomes deliver miR-222-3p to suppress PDLIM2, leading to PFKL stabilization and enhanced glycolysis.","method":"Co-immunoprecipitation; ubiquitination assay; luciferase reporter (miR-222-3p/PDLIM2); Seahorse ECAR/OCR; xenograft mouse model","journal":"Neoplasma","confidence":"Medium","confidence_rationale":"Tier 2 — ubiquitination assay plus functional cellular and in vivo validation, single lab","pmids":["35723199"],"is_preprint":false},{"year":2022,"finding":"DNAAF5 directly binds PFKL and recruits the deubiquitinase USP39 to form a ternary complex, promoting PFKL deubiquitination and protein stabilization, thereby enhancing glycolysis and HCC cell proliferation.","method":"Transcriptome sequencing; mass spectrometry; Co-immunoprecipitation; ubiquitination assays; DNAAF5 KO and OE cell lines; xenograft mouse model","journal":"Frontiers in oncology","confidence":"Medium","confidence_rationale":"Tier 2 — mass spectrometry-identified interaction confirmed by Co-IP plus deubiquitination assay, single lab","pmids":["36276075"],"is_preprint":false},{"year":2022,"finding":"PFKL preferentially interacts with oxidized methionine-containing actin peptides (Met44/Met47 oxidized) compared to the reduced form, and this differential interaction also occurs with full-length actin protein, suggesting that methionine oxidation on actin modulates the actin–PFKL interaction under oxidative stress conditions.","method":"Photo-crosslinking peptide approach; quantitative proteomics; validation with full-length actin protein","journal":"RSC chemical biology","confidence":"Medium","confidence_rationale":"Tier 2 — peptide crosslinking plus full-length protein validation, single lab","pmids":["36320891"],"is_preprint":false},{"year":2023,"finding":"KLF7 transcriptionally activates PFKL (the rate-limiting glycolytic enzyme) and ACADL (long-chain acyl-CoA dehydrogenase, key for fatty acid oxidation) simultaneously. Cardiac-specific KLF7 knockout caused adult concentric hypertrophy by shifting metabolism toward glycolysis; overexpression caused infant eccentric hypertrophy. Knockdown of PFKL or overexpression of ACADL partially rescued hypertrophy in KLF7-deficient mice.","method":"Cardiac-specific KO and OE transgenic mice; genetic epistasis (PFKL knockdown rescue); ChIP for KLF7 at PFKL/ACADL promoters; metabolic flux assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1–2 — in vivo cardiac-specific KO/OE combined with genetic epistasis rescue experiments, multiple orthogonal approaches","pmids":["36810848"],"is_preprint":false},{"year":2023,"finding":"PTGES3 binds directly to PFKL and generates a local source of prostaglandin E2 (PGE2) that allosterically inhibits PFKL enzymatic activity, suppressing glycolysis and the TCA cycle, and restraining ovarian cancer cell invasiveness. Loss of PTGES3 in ovarian cancer disrupts this inhibitory axis, hyperactivating glucose oxidation.","method":"Genome-wide CRISPR-Cas9 invasion screen; Co-immunoprecipitation; enzymatic activity assays; PTGES3 KO/OE functional assays","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1–2 — unbiased CRISPR screen + direct binding + enzymatic activity measurement, single lab with multiple orthogonal methods","pmids":["37831605"],"is_preprint":false},{"year":2023,"finding":"Caveolin-1 (Cav1) competes with SQSTM1 for binding to the regulatory subunit of PFKL in hepatic stellate cells, thereby inhibiting SQSTM1-mediated autophagy-independent lysosomal degradation of PFKL and sustaining its protein levels to maintain HSC activation and glycolysis during liver fibrosis.","method":"HSC-specific Cav1 knockdown mouse model; Co-immunoprecipitation; lysosomal degradation pathway assays; primary mouse HSC activation studies","journal":"Free radical biology & medicine","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo KD model plus Co-IP competition assay, single lab","pmids":["37116593"],"is_preprint":false},{"year":2024,"finding":"PFKL is phosphorylated at Ser775 in macrophages following innate immune stimulation (e.g., LPS). This phosphorylation increases PFKL catalytic activity and glycolytic flux. Knock-in mice carrying the phosphorylation-defective S775A mutation show reduced glycolysis, lower HIF1α and IL-1β levels upon LPS stimulation, and attenuated inflammatory cytokines (MCP-1, IL-1β) in vivo.","method":"Biochemical activity assays; phosphorylation-defective PFKL knock-in mouse model (PfklS775A/S775A); glycolysis monitoring; in vivo inflammation model","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1–2 — biochemical assay + genetic mouse model with cellular and in vivo phenotypic readouts, multiple orthogonal approaches","pmids":["39085210"],"is_preprint":false},{"year":2024,"finding":"EGR1 transcriptionally represses PFKL by interacting with the PFKL promoter region, reducing PFKL-mediated aerobic glycolysis in HCC. EGR1 overexpression inhibits HCC proliferation in a PFKL-dependent manner.","method":"ChIP/promoter-binding assay; EGR1 OE/KD in HCC cell lines and xenograft models; human organoid HCC model; glycolysis assays","journal":"Journal of experimental & clinical cancer research","confidence":"Medium","confidence_rationale":"Tier 2 — promoter binding plus in vivo and organoid functional validation, single lab","pmids":["38287371"],"is_preprint":false},{"year":2024,"finding":"Under glucose deprivation, PFKL is phosphorylated (reducing glycolytic activity) and translocates to lipid droplets, where it acts as a protein kinase that phosphorylates PLIN2. Phospho-PLIN2 recruits CPT1A, tethering lipid droplets to mitochondria and enabling adipose triglyceride lipase (ATGL) recruitment for lipolysis and β-oxidation. Disruption of this cascade inhibits tumor cell proliferation and blunts liver tumor growth.","method":"In vitro kinase assay (PFKL phosphorylating PLIN2); Co-IP; subcellular fractionation/lipid droplet isolation; proximity ligation assay for LD-mitochondria tethering; mouse liver tumor models","journal":"Nature metabolism","confidence":"High","confidence_rationale":"Tier 1–2 — in vitro kinase assay demonstrating PFKL protein kinase activity, multiple orthogonal methods, in vivo validation","pmids":["38773347"],"is_preprint":false},{"year":2024,"finding":"USP14 is a deubiquitinating enzyme for PFKL; USP14 interacts with PFKL and stabilizes it through deubiquitination in oral squamous cell carcinoma cells, enhancing glycolytic flux and promoting proliferation, migration, and tumorigenesis.","method":"Co-immunoprecipitation; deubiquitination assay; USP14 KD/OE functional studies in OSCC cells; xenograft model","journal":"Journal of translational medicine","confidence":"Medium","confidence_rationale":"Tier 2 — direct deubiquitination assay plus functional rescue, single lab","pmids":["38388430"],"is_preprint":false},{"year":2025,"finding":"HDAC6 acts as a deacetylase for PFKL, interacting with PFKL to remove acetylation and enhance its activity by accelerating PFKL tetrameric assembly and aerobic glycolysis, thereby promoting vascular smooth muscle cell (VSMC) proliferation. The primary acetylation site was identified as K563; the K563R (deacetylation-mimetic) mutant aggravated VSMC proliferation and neointimal formation, while K563Q (acetylation-mimetic) attenuated it.","method":"Co-immunoprecipitation; HDAC6 siRNA/inhibitor (TSA); site-directed mutagenesis (K563R, K563Q); recombinant adenoviral expression; ligation-induced neointimal formation in vivo","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — enzymatic deacetylation assay + site-specific mutagenesis + in vivo vascular model, multiple orthogonal approaches","pmids":["41421488"],"is_preprint":false},{"year":2025,"finding":"PRMT9-mediated methylation of PFKL at R301 inactivates PFKL, restricting glycolysis and redirecting metabolic flux toward the pentose phosphate pathway in neutrophils. This occurs in the context of lactate signaling from cardiomyocytes and drives NETosis in diabetic myocardial infarction.","method":"Mass spectrometry imaging; in vivo/in vitro lactate supplementation/depletion; PFKL methylation site identification; PDK4 cardiomyocyte-specific KO mouse model","journal":"Pharmacological research","confidence":"Medium","confidence_rationale":"Tier 2 — mass spectrometry site identification plus in vivo genetic model, single lab","pmids":["40222696"],"is_preprint":false},{"year":2025,"finding":"A covalent PFKL activator (electrophile-drug conjugate, EDC) site-specifically modifies K677 in the allosteric effector site of PFKL, stabilizing the active R-state tetramer and inducing metabolic imbalance in cancer cells. This EDC selectively modifies PFKL proteome-wide and suppresses tumor growth in vitro and in vivo.","method":"Chemical proteomics (proteome-wide selectivity); site-directed covalent modification; biochemical PFKL activity assays; in vitro and in vivo tumor growth assays","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1–2 — covalent site-specific modification with proteome-wide selectivity profiling, in vivo validation; preprint not yet peer-reviewed","pmids":["41256653"],"is_preprint":true}],"current_model":"PFKL (phosphofructokinase-1 liver type) is the rate-limiting glycolytic enzyme whose activity is regulated at multiple levels: allosteric activation by AMP/ADP at a defined site (targeted by small molecules NA-11 and covalent EDCs), post-translational modifications including O-GlcNAcylation at S529 (inhibitory), phosphorylation at S775 by innate immune signaling (activating) and at R301 via PRMT9 methylation (inhibitory), and acetylation at K563 by HDAC6 (deacetylation activates tetrameric assembly); its protein stability is controlled by ubiquitin-mediated degradation through E3 ligases A20 and PDLIM2, counteracted by deubiquitinases USP39 (recruited by DNAAF5) and USP14; beyond glycolysis, under energy stress PFKL translocates to lipid droplets where it functions as a protein kinase phosphorylating PLIN2 to tether lipid droplets to mitochondria and promote β-oxidation; its transcription is regulated by KLF7 (activating), EGR1 (repressing), and SREBF1 (activating), while its mRNA stability is controlled by m6A readers YTHDF3 and YTHDF2; in neutrophils, PFKL activation diverts glucose from the pentose phosphate pathway to suppress NOX2-dependent oxidative burst and NETosis, and is allosterically inhibited by locally produced prostaglandin E2 via PTGES3 in ovarian cancer cells."},"narrative":{"teleology":[{"year":1981,"claim":"Mapping PFKL to chromosome 21 and demonstrating gene-dosage effects in trisomy 21 established that liver-type PFK subunit copy number directly determines isozyme composition and total PFK activity in human erythrocytes.","evidence":"Somatic cell hybrid panel with subunit-specific monoclonal antibody; chromatographic isozyme profiling of trisomy 21 erythrocytes","pmids":["6455664"],"confidence":"High","gaps":["Mechanism by which excess PFKL alters erythrocyte metabolism in Down syndrome remains uncharacterized","No structure–function information at this stage"]},{"year":1998,"claim":"Transgenic PFKL-overexpressing mice revealed that gene-dosage-driven increases in PFK activity are tissue- and age-dependent and directly accelerate cerebral glucose utilization, connecting enzyme level to whole-organ metabolic flux.","evidence":"Transgenic mice with PFKL overexpression; in vivo ¹³C-NMR brain metabolic flux; tissue PFK activity assays","pmids":["8172601","9813288"],"confidence":"Medium","gaps":["Whether the metabolic shift contributes to neurodevelopmental phenotypes was not tested","Activity regulation beyond gene dosage not addressed"]},{"year":2012,"claim":"Identification of O-GlcNAcylation at S529 as an inhibitory post-translational modification revealed the first site-specific mechanism through which PFKL activity is suppressed to redirect glucose into the pentose phosphate pathway under hypoxia, conferring a cancer cell growth advantage.","evidence":"In vitro PFK1 activity assays with S529A mutagenesis; metabolic flux analysis; xenograft tumor models","pmids":["22923583"],"confidence":"High","gaps":["Identity of the O-GlcNAc transferase and phosphatase controlling S529 occupancy not defined","Relative contribution of PFKL vs. PFKM/PFKP O-GlcNAcylation in vivo unclear"]},{"year":2021,"claim":"Structural and pharmacological characterization of PFKL's allosteric activation site by NA-11 resolved how small-molecule occupancy of the AMP/ADP pocket locks the enzyme in the active R-state and explained isoform selectivity, while showing that PFKL activation diverts neutrophil glucose away from the PPP to suppress NOX2-dependent oxidative burst and NETosis.","evidence":"High-resolution crystal structure of PFKL–NA-11 complex; chemical proteomics with two probes; neutrophil ROS/NETosis assays; glycolysis flux measurements","pmids":["34320407"],"confidence":"High","gaps":["In vivo efficacy and pharmacokinetics of NA-11 class activators not fully characterized","Structural basis for negative allosteric regulation (e.g., citrate, PGE2) unresolved"]},{"year":2022,"claim":"Multiple studies converged to show that PFKL protein stability is controlled by ubiquitin-dependent degradation — E3 ligases A20 and PDLIM2 promote PFKL turnover, while deubiquitinases USP39 (recruited via DNAAF5) and later USP14 oppose degradation — establishing regulated proteolysis as a major layer of glycolytic control in cancer.","evidence":"Co-IP plus ubiquitination/deubiquitination assays in HCC, laryngeal SCC, and OSCC cells; xenograft models; DNAAF5-KO epistasis","pmids":["32015333","35723199","36276075","38388430"],"confidence":"Medium","gaps":["Ubiquitination site(s) on PFKL not mapped","Whether A20, PDLIM2, USP39, and USP14 act on the same or distinct ubiquitin chains is unknown","SQSTM1-mediated lysosomal degradation (via Cav1 competition) adds complexity not yet integrated"]},{"year":2023,"claim":"PFKL was placed under direct transcriptional control of KLF7 (activating) and EGR1 (repressing), linking PFKL expression to cardiac metabolic remodeling and hepatocellular carcinoma, and demonstrating that PFKL levels are rate-limiting for pathological glycolysis in these contexts.","evidence":"Cardiac-specific KLF7 KO/OE mice with PFKL-knockdown rescue; ChIP at PFKL promoter for KLF7 and EGR1; HCC xenograft and organoid models","pmids":["36810848","38287371"],"confidence":"High","gaps":["Additional transcription factors controlling PFKL in other tissues not mapped","Integration of transcriptional and post-translational regulation quantitatively undefined"]},{"year":2023,"claim":"Discovery that PTGES3 binds PFKL and generates local PGE2 to allosterically inhibit enzyme activity revealed a lipid-metabolite-mediated regulatory axis restraining glycolysis and invasion in ovarian cancer cells.","evidence":"Genome-wide CRISPR invasion screen; Co-IP; direct enzymatic activity assays with PTGES3 KO/OE","pmids":["37831605"],"confidence":"High","gaps":["PGE2 binding site on PFKL not structurally defined","Whether this mechanism operates outside ovarian cancer is untested"]},{"year":2024,"claim":"Phosphorylation of PFKL at S775 during innate immune activation was shown to directly increase catalytic activity and glycolytic flux in macrophages; knock-in S775A mice exhibited blunted HIF1α/IL-1β responses, placing PFKL phosphorylation as a metabolic checkpoint in inflammation.","evidence":"Biochemical activity assays; PfklS775A knock-in mouse; in vivo LPS inflammation model","pmids":["39085210"],"confidence":"High","gaps":["Kinase responsible for S775 phosphorylation not identified","Whether S775 phosphorylation occurs in non-myeloid immune cells is unknown"]},{"year":2024,"claim":"The discovery that PFKL translocates to lipid droplets under energy stress and functions as a protein kinase phosphorylating PLIN2 to tether lipid droplets to mitochondria fundamentally expanded PFKL's role beyond glycolysis into lipid catabolism and organelle communication.","evidence":"In vitro kinase assay (PFKL → PLIN2); lipid droplet isolation; proximity ligation assay for LD–mitochondria contacts; mouse liver tumor models","pmids":["38773347"],"confidence":"High","gaps":["Structural basis for PFKL protein kinase activity and its relationship to the metabolite kinase domain unknown","Full substrate repertoire of PFKL as a protein kinase not surveyed","Signal triggering PFKL translocation to lipid droplets not molecularly defined"]},{"year":2025,"claim":"Identification of HDAC6-mediated deacetylation at K563 as a driver of active tetramer assembly, and PRMT9-mediated methylation at R301 as an inactivating modification, added two new post-translational switches that tune PFKL quaternary structure and activity in vascular smooth muscle cells and neutrophils, respectively.","evidence":"Co-IP; HDAC6 inhibitor/siRNA; K563R/K563Q mutagenesis with in vivo neointimal formation model; mass spectrometry methylation site ID; PDK4-KO mouse model for lactate/PRMT9 axis","pmids":["41421488","40222696"],"confidence":"High","gaps":["Interplay among S529 O-GlcNAcylation, K563 acetylation, R301 methylation, and S775 phosphorylation on the same PFKL molecule not examined","Whether HDAC6–PFKL interaction is direct or scaffold-mediated is unresolved"]},{"year":null,"claim":"Key unresolved questions include: the structural basis for PFKL's protein kinase activity toward PLIN2, the identity of the S775 kinase, how multiple PTMs are integrated on a single tetramer, and whether allosteric activators can be therapeutically deployed in inflammatory disease.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model of PFKL protein kinase activity exists","Kinase for S775 unidentified","Quantitative integration of combinatorial PTMs on PFKL not modeled","In vivo therapeutic window for PFKL allosteric activators not established"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[16]},{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[3,5,16]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[3,5,14]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[5,14]},{"term_id":"GO:0005811","term_label":"lipid droplet","supporting_discovery_ids":[16]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,3,5,14,16,18]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[5,14,19]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[4,7,8,9,15,17]}],"complexes":[],"partners":["PTGES3","USP39","DNAAF5","USP14","A20","PDLIM2","HDAC6","PLIN2"],"other_free_text":[]},"mechanistic_narrative":"PFKL is the liver-type subunit of phosphofructokinase-1, the rate-limiting enzyme of glycolysis, whose activity is tuned by an extensive network of allosteric, post-translational, and transcriptional controls that couple glucose flux to cellular state. Allosteric activation at the AMP/ADP effector site (targeted by small-molecule NA-11) diverts glucose from the pentose phosphate pathway, suppressing NADPH-dependent NOX2 oxidative burst and NETosis in neutrophils, while inhibitory inputs include O-GlcNAcylation at S529 (redirecting flux to the PPP under hypoxia), PRMT9-mediated methylation at R301, and local PGE2 production by PTGES3 [PMID:34320407, PMID:22923583, PMID:40222696, PMID:37831605]. Protein stability is governed by ubiquitin-dependent degradation through E3 ligases A20 and PDLIM2 and counteracted by deubiquitinases USP39 and USP14, while HDAC6-mediated deacetylation at K563 promotes active tetramer assembly and phosphorylation at S775 during innate immune signaling increases catalytic output [PMID:32015333, PMID:36276075, PMID:41421488, PMID:39085210]. Beyond canonical glycolysis, under energy stress PFKL translocates to lipid droplets and functions as a protein kinase that phosphorylates PLIN2, tethering lipid droplets to mitochondria to enable β-oxidation [PMID:38773347]."},"prefetch_data":{"uniprot":{"accession":"P17858","full_name":"ATP-dependent 6-phosphofructokinase, liver type","aliases":["6-phosphofructokinase type B","Phosphofructo-1-kinase isozyme B","PFK-B","Phosphohexokinase"],"length_aa":780,"mass_kda":85.0,"function":"Catalyzes the phosphorylation of D-fructose 6-phosphate to fructose 1,6-bisphosphate by ATP, the first committing step of glycolysis (PubMed:22923583). Negatively regulates the phagocyte oxidative burst in response to bacterial infection by controlling cellular NADPH biosynthesis and NADPH oxidase-derived reactive oxygen species. 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thereby dampening pentose phosphate pathway flux and suppressing NOX2-dependent oxidative burst in neutrophils. High-resolution crystal structure of PFKL confirmed the binding site and explained isoform selectivity over PFKP and PFKM.\",\n      \"method\": \"Chemical proteomics, high-resolution crystal structure, in vitro enzyme activity assays, cellular NOX2/ROS assays, NETosis assays\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with functional validation, in vitro assays, and cellular phenotypic readouts in a highly cited paper\",\n      \"pmids\": [\"34320407\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Glucose deprivation induces phosphorylation of PFKL, reducing its glycolytic activity and enabling a moonlighting function: PFKL acts as a protein kinase on lipid droplets, phosphorylating PLIN2 to promote PLIN2-CPT1A binding, thereby tethering lipid droplets to mitochondria and recruiting ATGL for lipid mobilization and β-oxidation.\",\n      \"method\": \"Co-IP, in vitro kinase assay, proximity ligation assay, lipid droplet-mitochondria tethering imaging, loss-of-function in vivo tumor models\",\n      \"journal\": \"Nature metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods including in vitro kinase assay, co-IP, and in vivo validation in a highly cited paper\",\n      \"pmids\": [\"38773347\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PFKL is phosphorylated at Ser775 in macrophages following innate immune stimuli (e.g., LPS); this phosphorylation increases PFKL catalytic activity, elevates glycolytic flux, and is required for full induction of HIF1α and IL-1β. Genetic PfklS775A/S775A mice show reduced glycolysis, lower HIF1α/IL-1β, and reduced MCP-1/IL-1β in vivo.\",\n      \"method\": \"Biochemical phosphorylation assays, glycolysis monitoring with phosphorylation-defective PFKL variants, genetic mouse model (PfklS775A/S775A), in vivo inflammation model\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — genetic mouse model + biochemical assays + multiple orthogonal methods\",\n      \"pmids\": [\"39085210\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"A20 functions as an E3 ubiquitin ligase for PFKL in hepatocellular carcinoma: A20 interacts with PFKL and promotes its ubiquitin-mediated degradation, thereby inhibiting glycolysis.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, RNAi knockdown, glycolysis measurement\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP and ubiquitination assay from single lab, moderate functional follow-up\",\n      \"pmids\": [\"32015333\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PDLIM2 acts as an E3 ubiquitin ligase for PFKL, promoting its ubiquitination and degradation; loss of PDLIM2 (via miR-222-3p delivered by M2 macrophage exosomes) stabilizes PFKL and enhances glycolysis in laryngeal squamous cell carcinoma cells.\",\n      \"method\": \"Ubiquitination assay, luciferase assay, ECAR/OCR measurement, xenograft model\",\n      \"journal\": \"Neoplasma\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — ubiquitination assay with functional glycolysis readout, single lab\",\n      \"pmids\": [\"35723199\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"DNAAF5 directly binds PFKL and recruits the deubiquitinase USP39 to form a ternary complex, protecting PFKL from ubiquitin-mediated degradation and enhancing its protein stability and glycolytic activity in HCC.\",\n      \"method\": \"Co-IP, mass spectrometry, transcriptome sequencing, ubiquitination assay, in vivo xenograft\",\n      \"journal\": \"Frontiers in oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP with MS identification and ubiquitination assay, single lab\",\n      \"pmids\": [\"36276075\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"USP14 is a deubiquitinating enzyme for PFKL; USP14 interacts with PFKL and enhances its stability through deubiquitination in oral squamous cell carcinoma, promoting glycolytic metabolism, proliferation, and migration.\",\n      \"method\": \"Co-IP, deubiquitination assay, glycolysis measurement, loss-of-function experiments\",\n      \"journal\": \"Journal of translational medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — deubiquitination assay and Co-IP, single lab\",\n      \"pmids\": [\"38388430\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PTGES3 binds directly to PFKL and generates a local source of prostaglandin E2 (PGE2) that allosterically inhibits PFKL enzymatic activity, reducing glycolysis and the TCA cycle, thereby suppressing ovarian cancer cell motility and invasiveness.\",\n      \"method\": \"Genome-wide CRISPR-Cas9 screen, Co-IP, enzymatic activity assay, glycolysis measurement, invasion assay\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — CRISPR screen plus Co-IP and enzymatic assay, single lab\",\n      \"pmids\": [\"37831605\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"KLF7 transcription factor simultaneously targets the promoters of PFKL (rate-limiting glycolytic enzyme) and ACADL (fatty acid oxidation enzyme), and cardiac-specific KLF7 loss causes concentric hypertrophy rescued by PFKL knockdown, placing PFKL downstream of KLF7 in cardiac metabolic remodeling.\",\n      \"method\": \"Cardiac-specific KO and OE mouse models, ChIP, rescue experiments (PFKL KD or ACADL OE), echocardiography, metabolic flux analysis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with cardiac-specific KO/OE and rescue experiments, multiple orthogonal methods\",\n      \"pmids\": [\"36810848\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"HDAC6 acts as the deacetylase of PFKL; HDAC6 interacts with PFKL, deacetylates it at K563, and accelerates PFKL tetrameric formation, thereby enhancing PFKL enzymatic activity and aerobic glycolysis to promote VSMC proliferation. A K563R (deacetylation-mimetic) mutant aggravated and K563Q (acetylation-mimetic) attenuated PDGF-BB-induced VSMC proliferation and neointimal formation.\",\n      \"method\": \"Co-IP, site-directed mutagenesis (K563R/K563Q), HDAC inhibitor (TSA), siHDAC6, VSMC proliferation assay, in vivo neointimal ligation model\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — site-directed mutagenesis identifying acetylation site, in vitro and in vivo validation, Co-IP\",\n      \"pmids\": [\"41421488\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PRMT9-mediated methylation of PFKL at R301 inactivates PFKL, restricting glycolysis in neutrophils; lactate (produced by cardiac PDK4-driven cardiomyocyte glycolysis) triggers this methylation, redirecting neutrophil metabolic flux from glycolysis to the pentose phosphate pathway to promote NETosis.\",\n      \"method\": \"Mass spectrometry imaging, in vivo PDK4 cardiomyocyte-specific KO, lactate supplementation/depletion, site-specific methylation validation\",\n      \"journal\": \"Pharmacological research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — MS identification of modification site with in vivo genetic and pharmacological validation, single lab\",\n      \"pmids\": [\"40222696\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"YTHDF3 suppresses PFKL mRNA degradation via m6A modification, increasing PFKL expression; conversely, PFKL protein stabilizes YTHDF3 by inhibiting EFTUD2-mediated YTHDF3 ubiquitination, forming a positive feedback loop in HCC glycolysis.\",\n      \"method\": \"MeRIP assay, Co-IP, ubiquitination assay, immunofluorescence, loss/gain-of-function experiments\",\n      \"journal\": \"Journal of experimental & clinical cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — MeRIP and Co-IP with ubiquitination assay, single lab\",\n      \"pmids\": [\"36471428\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"EGR1 transcription factor binds the promoter region of PFKL and represses its transcription, leading to inhibition of PFKL-mediated aerobic glycolysis in HCC.\",\n      \"method\": \"ChIP, promoter-reporter assay, loss/gain-of-function EGR1 experiments, glycolysis measurement, in vivo xenograft and mouse HCC model\",\n      \"journal\": \"Journal of experimental & clinical cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP and promoter assay with functional glycolysis readout, single lab\",\n      \"pmids\": [\"38287371\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SREBF1 binds the promoter region of PFKL and activates its transcription; ApoM gene knockout increases SREBF1, which in turn enhances PFKL promoter activity and glycolysis in liver cancer cells.\",\n      \"method\": \"Dual-luciferase reporter assay, binding site prediction, ApoM KO cell and mouse model, proliferation/Transwell assays\",\n      \"journal\": \"Oncology letters\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — luciferase assay only, single lab, limited mechanistic follow-up\",\n      \"pmids\": [\"35720503\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"miR-338 directly targets the PFKL 3'UTR and suppresses PFKL expression; 125I irradiation upregulates miR-338, which in turn downregulates PFKL and suppresses the Warburg effect in HCC cells.\",\n      \"method\": \"Dual-luciferase reporter assay, Western blot, glycolysis measurement, in vivo 125I seed implantation\",\n      \"journal\": \"Biomedicine & pharmacotherapy\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — luciferase assay with single lab, indirect mechanistic evidence\",\n      \"pmids\": [\"31514072\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PFKL preferentially interacts with actin containing oxidized methionine (M44/M47) compared to reduced methionine, as identified by a photo-crosslinking peptide approach, suggesting methionine oxidation on actin regulates the actin-PFKL interaction under oxidative stress.\",\n      \"method\": \"Photo-crosslinking peptide, proteomics, full-length actin protein binding validation\",\n      \"journal\": \"RSC chemical biology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single crosslinking/proteomics approach, limited mechanistic follow-up\",\n      \"pmids\": [\"36320891\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Caveolin-1 competes with SQSTM1/p62 for binding to the regulatory subunit of PFKL in hepatic stellate cells; Cav1 inhibits SQSTM1-mediated autophagy-independent lysosomal degradation of PFKL, thereby sustaining PFKL protein levels and glycolysis during HSC activation.\",\n      \"method\": \"Co-IP, HSC-specific Cav1 KD, lysosomal degradation assay, in vitro and in vivo fibrosis models\",\n      \"journal\": \"Free radical biology & medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP with competitive binding and genetic KD, functional glycolysis readout\",\n      \"pmids\": [\"37116593\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"A first-in-class covalent PFKL activator (electrophile-drug conjugate, EDC) site-specifically modifies K677 in the allosteric effector site, stabilizing the R-state tetramer of PFKL, inducing metabolic imbalance in cancer cells, and enabling delivery of a cytotoxic payload to suppress tumor growth in vitro and in vivo.\",\n      \"method\": \"Covalent chemical biology, proteome-wide selectivity profiling, structural rationale, in vitro and in vivo cancer models\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — site-specific covalent modification with functional and in vivo validation, but preprint\",\n      \"pmids\": [\"41256653\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 1981,\n      \"finding\": \"PFKL (liver-type phosphofructokinase subunit) is encoded on human chromosome 21; somatic cell hybrid analysis using anti-human L-subunit monoclonal antibody showed co-segregation of PFKL expression with chromosome 21 retention, and trisomy 21 causes a gene-dosage-dependent increase in erythrocyte PFKL activity with a specific increase in L4 isozyme species.\",\n      \"method\": \"Somatic cell hybrids, enzyme-immunoprecipitation, monoclonal antibody, ion exchange chromatography, trisomy 21 patient samples\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods in a foundational highly cited paper\",\n      \"pmids\": [\"6455664\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Tiam1 interacts directly with PFKL and promotes glycolysis reprogramming and breast cancer progression in a PFKL-dependent manner.\",\n      \"method\": \"Co-IP, loss/gain-of-function, glycolysis measurement, in vivo xenograft\",\n      \"journal\": \"Carcinogenesis\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single Co-IP with functional rescue, single lab\",\n      \"pmids\": [\"35511493\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"YTHDF2 stabilizes PFKL mRNA via m6A recognition under hypoxia, driven by HIF-1α-mediated transcription of YTHDF2; this HIF-1α/YTHDF2/PFKL axis sustains MDSC glycolysis and supports HCC cancer stem cell immune evasion.\",\n      \"method\": \"ChIP, luciferase assay, MeRIP/RIP, ECAR/lactate/ATP measurement, in vitro and in vivo KD/OE experiments\",\n      \"journal\": \"Functional & integrative genomics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, primarily correlative with some mechanistic assays\",\n      \"pmids\": [\"41225244\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PFKL is the rate-limiting liver-type phosphofructokinase-1 isoform (encoded on chromosome 21) that catalyzes the ATP-dependent phosphorylation of fructose-6-phosphate in glycolysis; its activity is allosterically regulated at an AMP/ADP effector site (exploited by small-molecule activators NA-11 and covalent EDCs that stabilize the R-state tetramer), post-translationally controlled by phosphorylation (Ser775 activating; R301 methylation by PRMT9 inactivating), acetylation (K563, removed by HDAC6 to enhance tetramer formation and activity), and ubiquitin-mediated protein stability (promoted by deubiquitinases USP14 and USP39/DNAAF5, and reduced by E3 ligases A20 and PDLIM2); under glucose deprivation PFKL undergoes a conformational switch that allows it to moonlight as a protein kinase on lipid droplets, phosphorylating PLIN2 to tether lipid droplets to mitochondria for β-oxidation; in immune cells PFKL links glycolytic flux to NOX2-dependent oxidative burst and NETosis, and its transcription is regulated by KLF7, EGR1, and SREBF1 in a tissue-context-dependent manner.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1981,\n      \"finding\": \"PFKL (liver-type phosphofructokinase subunit) was mapped to human chromosome 21 using somatic cell hybrids and a subunit-specific monoclonal antibody. Trisomy 21 individuals showed elevated erythrocyte PFK activity due to a gene-dosage effect, with a striking increase in L4 homotetrameric species.\",\n      \"method\": \"Somatic cell hybrid panel analysis with monoclonal antibody immunoprecipitation; chromatographic isozyme analysis of trisomy 21 erythrocytes\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal genetic and biochemical evidence across 17 hybrid lines plus trisomy 21 patient samples\",\n      \"pmids\": [\"6455664\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Transgenic mice overexpressing PFKL showed tissue-specific overexpression resembling endogenous enzyme distribution. PFKL overexpression nearly doubled PFK activity in embryonic brain but not adult brain, indicating temporally regulated gene-dosage effects relevant to Down syndrome pathology.\",\n      \"method\": \"Transgenic mouse construction with murine PFKL gene-cDNA hybrid; tissue PFK activity assays\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct in vivo genetic model with biochemical readout, single lab\",\n      \"pmids\": [\"8172601\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Transgenic-PFKL mice with elevated PFKL activity exhibited slower blood glucose clearance but a 58% faster rate of cerebral glucose utilization compared to controls, demonstrating that PFKL overexpression directly alters brain glucose metabolism in vivo.\",\n      \"method\": \"In vivo [1-13C]-glucose infusion with NMR brain metabolic rate measurements in transgenic vs. non-transgenic mice\",\n      \"journal\": \"Brain research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — in vivo NMR metabolic flux measurement, single lab\",\n      \"pmids\": [\"9813288\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"O-GlcNAcylation of phosphofructokinase 1 (PFK1) at serine 529 inhibits its enzymatic activity and redirects glucose flux from glycolysis to the pentose phosphate pathway under hypoxia, conferring a selective growth advantage to cancer cells. Blocking glycosylation at S529 reduced cancer cell proliferation and impaired tumor formation.\",\n      \"method\": \"In vitro PFK1 activity assays with O-GlcNAc site-specific mutagenesis (S529A); metabolic flux analysis; xenograft tumor models\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted enzymatic assay, site-specific mutagenesis, in vitro and in vivo validation\",\n      \"pmids\": [\"22923583\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The E3 ubiquitin ligase A20 interacts with PFKL and promotes its ubiquitin-mediated proteasomal degradation, thereby inhibiting glycolysis in hepatocellular carcinoma cells. Downregulation of A20 in HCC leads to PFKL accumulation and enhanced glycolysis, proliferation, and migration.\",\n      \"method\": \"Co-immunoprecipitation; RNA interference; glycolysis assays; HCC cell line functional studies\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — Co-IP interaction plus functional rescue, single lab\",\n      \"pmids\": [\"32015333\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Small-molecule NA-11 (analog of LDC7559) selectively activates PFKL by binding to the AMP/ADP allosteric activation site, increasing glycolytic flux and thereby dampening flux through the pentose phosphate pathway. This reduces NADPH availability for NOX2, suppressing the oxidative burst, NETosis, and tissue damage in neutrophils. High-resolution crystal structure of PFKL confirmed the NA-11 binding site and explained isoform selectivity over PFKP and PFKM.\",\n      \"method\": \"Chemical proteomics (two unbiased strategies); high-resolution crystal structure of PFKL–NA-11 complex; neutrophil ROS/NETosis assays; glycolysis flux measurements\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure + biochemical allosteric activation assay + cellular functional validation, replicated with two chemical probes\",\n      \"pmids\": [\"34320407\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PFKL is a direct molecular target of penfluridol; direct binding of penfluridol to PFKL inhibits its glycolytic activity, leading to AMPK activation, nuclear translocation of FOXO3a, and BIM-dependent apoptosis in esophageal squamous cell carcinoma cells. PFKL-deficient cells are insensitive to penfluridol, confirming PFKL as the essential target.\",\n      \"method\": \"DARTS (drug affinity responsive target stability) technology; proteomics; AMPK/FOXO3a pathway analysis; PFKL knockdown rescue experiments\",\n      \"journal\": \"Acta pharmaceutica Sinica. B\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct target ID by DARTS plus genetic epistasis (PFKL KD rescue), single lab\",\n      \"pmids\": [\"35530161\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"YTHDF3 promotes PFKL expression by suppressing PFKL mRNA degradation via m6A modification. In turn, PFKL positively regulates YTHDF3 protein stability by interacting with EFTUD2 (a spliceosome subunit), which inhibits ubiquitination of YTHDF3, forming a positive regulatory feedback loop.\",\n      \"method\": \"MeRIP (methylated RNA immunoprecipitation); Co-immunoprecipitation; ubiquitination assays; loss/gain-of-function in HCC cell lines and in vivo\",\n      \"journal\": \"Journal of experimental & clinical cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal biochemical methods (MeRIP, Co-IP, ubiquitination assay), single lab\",\n      \"pmids\": [\"36471428\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PDLIM2, an E3 ubiquitin ligase, promotes ubiquitination and degradation of PFKL in laryngeal squamous cell carcinoma cells, thereby restraining glycolysis. M2 macrophage-derived exosomes deliver miR-222-3p to suppress PDLIM2, leading to PFKL stabilization and enhanced glycolysis.\",\n      \"method\": \"Co-immunoprecipitation; ubiquitination assay; luciferase reporter (miR-222-3p/PDLIM2); Seahorse ECAR/OCR; xenograft mouse model\",\n      \"journal\": \"Neoplasma\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ubiquitination assay plus functional cellular and in vivo validation, single lab\",\n      \"pmids\": [\"35723199\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"DNAAF5 directly binds PFKL and recruits the deubiquitinase USP39 to form a ternary complex, promoting PFKL deubiquitination and protein stabilization, thereby enhancing glycolysis and HCC cell proliferation.\",\n      \"method\": \"Transcriptome sequencing; mass spectrometry; Co-immunoprecipitation; ubiquitination assays; DNAAF5 KO and OE cell lines; xenograft mouse model\",\n      \"journal\": \"Frontiers in oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mass spectrometry-identified interaction confirmed by Co-IP plus deubiquitination assay, single lab\",\n      \"pmids\": [\"36276075\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PFKL preferentially interacts with oxidized methionine-containing actin peptides (Met44/Met47 oxidized) compared to the reduced form, and this differential interaction also occurs with full-length actin protein, suggesting that methionine oxidation on actin modulates the actin–PFKL interaction under oxidative stress conditions.\",\n      \"method\": \"Photo-crosslinking peptide approach; quantitative proteomics; validation with full-length actin protein\",\n      \"journal\": \"RSC chemical biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — peptide crosslinking plus full-length protein validation, single lab\",\n      \"pmids\": [\"36320891\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"KLF7 transcriptionally activates PFKL (the rate-limiting glycolytic enzyme) and ACADL (long-chain acyl-CoA dehydrogenase, key for fatty acid oxidation) simultaneously. Cardiac-specific KLF7 knockout caused adult concentric hypertrophy by shifting metabolism toward glycolysis; overexpression caused infant eccentric hypertrophy. Knockdown of PFKL or overexpression of ACADL partially rescued hypertrophy in KLF7-deficient mice.\",\n      \"method\": \"Cardiac-specific KO and OE transgenic mice; genetic epistasis (PFKL knockdown rescue); ChIP for KLF7 at PFKL/ACADL promoters; metabolic flux assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vivo cardiac-specific KO/OE combined with genetic epistasis rescue experiments, multiple orthogonal approaches\",\n      \"pmids\": [\"36810848\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PTGES3 binds directly to PFKL and generates a local source of prostaglandin E2 (PGE2) that allosterically inhibits PFKL enzymatic activity, suppressing glycolysis and the TCA cycle, and restraining ovarian cancer cell invasiveness. Loss of PTGES3 in ovarian cancer disrupts this inhibitory axis, hyperactivating glucose oxidation.\",\n      \"method\": \"Genome-wide CRISPR-Cas9 invasion screen; Co-immunoprecipitation; enzymatic activity assays; PTGES3 KO/OE functional assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — unbiased CRISPR screen + direct binding + enzymatic activity measurement, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"37831605\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Caveolin-1 (Cav1) competes with SQSTM1 for binding to the regulatory subunit of PFKL in hepatic stellate cells, thereby inhibiting SQSTM1-mediated autophagy-independent lysosomal degradation of PFKL and sustaining its protein levels to maintain HSC activation and glycolysis during liver fibrosis.\",\n      \"method\": \"HSC-specific Cav1 knockdown mouse model; Co-immunoprecipitation; lysosomal degradation pathway assays; primary mouse HSC activation studies\",\n      \"journal\": \"Free radical biology & medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo KD model plus Co-IP competition assay, single lab\",\n      \"pmids\": [\"37116593\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PFKL is phosphorylated at Ser775 in macrophages following innate immune stimulation (e.g., LPS). This phosphorylation increases PFKL catalytic activity and glycolytic flux. Knock-in mice carrying the phosphorylation-defective S775A mutation show reduced glycolysis, lower HIF1α and IL-1β levels upon LPS stimulation, and attenuated inflammatory cytokines (MCP-1, IL-1β) in vivo.\",\n      \"method\": \"Biochemical activity assays; phosphorylation-defective PFKL knock-in mouse model (PfklS775A/S775A); glycolysis monitoring; in vivo inflammation model\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — biochemical assay + genetic mouse model with cellular and in vivo phenotypic readouts, multiple orthogonal approaches\",\n      \"pmids\": [\"39085210\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"EGR1 transcriptionally represses PFKL by interacting with the PFKL promoter region, reducing PFKL-mediated aerobic glycolysis in HCC. EGR1 overexpression inhibits HCC proliferation in a PFKL-dependent manner.\",\n      \"method\": \"ChIP/promoter-binding assay; EGR1 OE/KD in HCC cell lines and xenograft models; human organoid HCC model; glycolysis assays\",\n      \"journal\": \"Journal of experimental & clinical cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — promoter binding plus in vivo and organoid functional validation, single lab\",\n      \"pmids\": [\"38287371\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Under glucose deprivation, PFKL is phosphorylated (reducing glycolytic activity) and translocates to lipid droplets, where it acts as a protein kinase that phosphorylates PLIN2. Phospho-PLIN2 recruits CPT1A, tethering lipid droplets to mitochondria and enabling adipose triglyceride lipase (ATGL) recruitment for lipolysis and β-oxidation. Disruption of this cascade inhibits tumor cell proliferation and blunts liver tumor growth.\",\n      \"method\": \"In vitro kinase assay (PFKL phosphorylating PLIN2); Co-IP; subcellular fractionation/lipid droplet isolation; proximity ligation assay for LD-mitochondria tethering; mouse liver tumor models\",\n      \"journal\": \"Nature metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro kinase assay demonstrating PFKL protein kinase activity, multiple orthogonal methods, in vivo validation\",\n      \"pmids\": [\"38773347\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"USP14 is a deubiquitinating enzyme for PFKL; USP14 interacts with PFKL and stabilizes it through deubiquitination in oral squamous cell carcinoma cells, enhancing glycolytic flux and promoting proliferation, migration, and tumorigenesis.\",\n      \"method\": \"Co-immunoprecipitation; deubiquitination assay; USP14 KD/OE functional studies in OSCC cells; xenograft model\",\n      \"journal\": \"Journal of translational medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct deubiquitination assay plus functional rescue, single lab\",\n      \"pmids\": [\"38388430\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"HDAC6 acts as a deacetylase for PFKL, interacting with PFKL to remove acetylation and enhance its activity by accelerating PFKL tetrameric assembly and aerobic glycolysis, thereby promoting vascular smooth muscle cell (VSMC) proliferation. The primary acetylation site was identified as K563; the K563R (deacetylation-mimetic) mutant aggravated VSMC proliferation and neointimal formation, while K563Q (acetylation-mimetic) attenuated it.\",\n      \"method\": \"Co-immunoprecipitation; HDAC6 siRNA/inhibitor (TSA); site-directed mutagenesis (K563R, K563Q); recombinant adenoviral expression; ligation-induced neointimal formation in vivo\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — enzymatic deacetylation assay + site-specific mutagenesis + in vivo vascular model, multiple orthogonal approaches\",\n      \"pmids\": [\"41421488\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PRMT9-mediated methylation of PFKL at R301 inactivates PFKL, restricting glycolysis and redirecting metabolic flux toward the pentose phosphate pathway in neutrophils. This occurs in the context of lactate signaling from cardiomyocytes and drives NETosis in diabetic myocardial infarction.\",\n      \"method\": \"Mass spectrometry imaging; in vivo/in vitro lactate supplementation/depletion; PFKL methylation site identification; PDK4 cardiomyocyte-specific KO mouse model\",\n      \"journal\": \"Pharmacological research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mass spectrometry site identification plus in vivo genetic model, single lab\",\n      \"pmids\": [\"40222696\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"A covalent PFKL activator (electrophile-drug conjugate, EDC) site-specifically modifies K677 in the allosteric effector site of PFKL, stabilizing the active R-state tetramer and inducing metabolic imbalance in cancer cells. This EDC selectively modifies PFKL proteome-wide and suppresses tumor growth in vitro and in vivo.\",\n      \"method\": \"Chemical proteomics (proteome-wide selectivity); site-directed covalent modification; biochemical PFKL activity assays; in vitro and in vivo tumor growth assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 — covalent site-specific modification with proteome-wide selectivity profiling, in vivo validation; preprint not yet peer-reviewed\",\n      \"pmids\": [\"41256653\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"PFKL (phosphofructokinase-1 liver type) is the rate-limiting glycolytic enzyme whose activity is regulated at multiple levels: allosteric activation by AMP/ADP at a defined site (targeted by small molecules NA-11 and covalent EDCs), post-translational modifications including O-GlcNAcylation at S529 (inhibitory), phosphorylation at S775 by innate immune signaling (activating) and at R301 via PRMT9 methylation (inhibitory), and acetylation at K563 by HDAC6 (deacetylation activates tetrameric assembly); its protein stability is controlled by ubiquitin-mediated degradation through E3 ligases A20 and PDLIM2, counteracted by deubiquitinases USP39 (recruited by DNAAF5) and USP14; beyond glycolysis, under energy stress PFKL translocates to lipid droplets where it functions as a protein kinase phosphorylating PLIN2 to tether lipid droplets to mitochondria and promote β-oxidation; its transcription is regulated by KLF7 (activating), EGR1 (repressing), and SREBF1 (activating), while its mRNA stability is controlled by m6A readers YTHDF3 and YTHDF2; in neutrophils, PFKL activation diverts glucose from the pentose phosphate pathway to suppress NOX2-dependent oxidative burst and NETosis, and is allosterically inhibited by locally produced prostaglandin E2 via PTGES3 in ovarian cancer cells.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"PFKL is the liver-type subunit of phosphofructokinase-1, a rate-limiting glycolytic enzyme that catalyzes ATP-dependent phosphorylation of fructose-6-phosphate and assembles into homotetramers whose activity is allosterically regulated at an AMP/ADP effector site [PMID:34320407]. PFKL protein levels are controlled by ubiquitin-mediated degradation through E3 ligases A20 and PDLIM2 and stabilized by the deubiquitinases USP14 and USP39 (recruited via DNAAF5), while its catalytic activity is positively regulated by Ser775 phosphorylation and HDAC6-mediated deacetylation at K563 (promoting tetramer assembly), and negatively regulated by PRMT9-mediated methylation at R301 [PMID:39085210, PMID:41421488, PMID:40222696, PMID:32015333, PMID:36276075]. Under glucose deprivation PFKL undergoes a functional switch to act as a protein kinase, phosphorylating PLIN2 on lipid droplets to tether them to mitochondria and promote fatty acid β-oxidation [PMID:38773347]. In innate immune cells, PFKL activity gates the balance between glycolysis and the pentose phosphate pathway, thereby controlling NOX2-dependent oxidative burst and NETosis [PMID:34320407, PMID:40222696].\",\n  \"teleology\": [\n    {\n      \"year\": 1981,\n      \"claim\": \"Mapping PFKL to chromosome 21 and demonstrating gene-dosage effects in trisomy 21 established it as the liver-type PFK-1 subunit with functional relevance to erythrocyte isozyme composition.\",\n      \"evidence\": \"Somatic cell hybrids with monoclonal antibodies and enzyme analysis in trisomy 21 patient samples\",\n      \"pmids\": [\"6455664\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No catalytic or structural characterization of the enzyme at this stage\", \"Regulatory mechanisms unknown\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Solving the PFKL crystal structure with a small-molecule activator (NA-11) revealed how the AMP/ADP allosteric site stabilizes the R-state tetramer and explained isoform selectivity, establishing the structural basis for PFKL regulation and linking glycolytic flux to NOX2-dependent oxidative burst in neutrophils.\",\n      \"evidence\": \"High-resolution crystal structure, chemical proteomics, enzyme activity assays, cellular NOX2/ROS and NETosis assays\",\n      \"pmids\": [\"34320407\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Endogenous kinase(s) responsible for PFKL activating phosphorylation not yet identified\", \"In vivo consequences of PFKL activation in immune cells not tested genetically\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identification of A20 as an E3 ligase for PFKL established ubiquitin-mediated degradation as a major regulatory axis controlling PFKL protein levels and glycolytic output.\",\n      \"evidence\": \"Co-IP, ubiquitination assays, RNAi, glycolysis measurement in HCC cells\",\n      \"pmids\": [\"32015333\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab finding; no identification of the specific ubiquitin chain type\", \"Physiological context beyond HCC not tested\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Multiple studies converged to show that PFKL protein stability is tightly controlled by opposing ubiquitin ligases (PDLIM2) and deubiquitinases (USP39 recruited by DNAAF5), and that PFKL mRNA is stabilized by m6A-dependent YTHDF3 binding, revealing multi-layered post-transcriptional regulation of glycolytic capacity.\",\n      \"evidence\": \"Ubiquitination assays, Co-IP with mass spectrometry, MeRIP, loss/gain-of-function in HCC and LSCC cells\",\n      \"pmids\": [\"35723199\", \"36276075\", \"36471428\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Each finding from a single lab; no structural detail on E3/DUB-PFKL interfaces\", \"Relative contribution of each regulatory layer in normal physiology unclear\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Discovery that PTGES3-generated PGE2 allosterically inhibits PFKL and that Caveolin-1 protects PFKL from SQSTM1-mediated lysosomal degradation revealed additional non-canonical regulatory inputs — a lipid metabolite inhibitor and an autophagy-independent degradation pathway.\",\n      \"evidence\": \"CRISPR screen, Co-IP, enzymatic assays (PTGES3); Co-IP, lysosomal degradation assay in hepatic stellate cells (Cav1)\",\n      \"pmids\": [\"37831605\", \"37116593\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"PGE2 binding site on PFKL not structurally defined\", \"Whether Cav1-SQSTM1 competition occurs in cell types beyond hepatic stellate cells unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Placing PFKL downstream of the transcription factor KLF7 in cardiac metabolism, with genetic rescue showing PFKL knockdown corrects KLF7-loss-induced hypertrophy, established PFKL as a critical effector in cardiac metabolic remodeling.\",\n      \"evidence\": \"Cardiac-specific KO/OE mouse models, ChIP, rescue with PFKL KD, echocardiography, metabolic flux analysis\",\n      \"pmids\": [\"36810848\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PFKL post-translational modifications are altered in KLF7-dependent cardiomyopathy is unknown\", \"Direct versus indirect transcriptional activation mechanism not fully resolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"The discovery that glucose-deprived PFKL moonlights as a protein kinase phosphorylating PLIN2 on lipid droplets fundamentally expanded its functional repertoire beyond glycolysis, linking it to lipid droplet–mitochondria tethering and fatty acid β-oxidation.\",\n      \"evidence\": \"In vitro kinase assay, Co-IP, proximity ligation assay, lipid droplet–mitochondria imaging, in vivo tumor models\",\n      \"pmids\": [\"38773347\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The conformational switch enabling kinase activity is not structurally characterized\", \"Whether other PFK isoforms share moonlighting kinase activity is untested\", \"The upstream kinase or signal triggering PFKL's own phosphorylation under starvation is not identified\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identification of Ser775 as an activating phosphorylation site on PFKL, validated with a genetic knock-in mouse, directly connected PFKL post-translational modification to macrophage inflammatory output via HIF1α and IL-1β.\",\n      \"evidence\": \"Phosphorylation-defective PFKL variants, PfklS775A/S775A mouse model, in vivo inflammation\",\n      \"pmids\": [\"39085210\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The kinase phosphorylating Ser775 in macrophages has not been identified\", \"Whether Ser775 phosphorylation also controls the moonlighting kinase function is unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identification of K563 deacetylation by HDAC6 as a driver of PFKL tetramer assembly and of R301 methylation by PRMT9 as an inactivating modification completed a picture of combinatorial post-translational control over PFKL quaternary structure and activity.\",\n      \"evidence\": \"Site-directed mutagenesis (K563R/Q), in vivo neointimal model (HDAC6); mass spectrometry, PDK4 cardiomyocyte-specific KO, lactate supplementation (PRMT9)\",\n      \"pmids\": [\"41421488\", \"40222696\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether acetylation and methylation marks co-occur or are mutually exclusive is unknown\", \"Structural basis of how K563 acetylation state affects tetramer interface not resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include: the structural basis for the glycolytic-to-kinase conformational switch under glucose deprivation; the identity of the upstream kinase(s) for Ser775; the interplay among multiple post-translational modifications (phosphorylation, acetylation, methylation, ubiquitination) in an integrated regulatory code; and the physiological significance of the PFKL–oxidized-actin interaction.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural model for the kinase-competent PFKL conformation exists\", \"Cross-talk among modification sites has not been tested\", \"In vivo significance of PFKL–methionine-oxidized actin binding is untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [0, 1, 2, 9]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 1, 2, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 9]},\n      {\"term_id\": \"GO:0005811\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 1, 2, 3, 5, 7, 8, 9]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 2, 10]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [3, 4, 5, 6, 9, 10]}\n    ],\n    \"complexes\": [\n      \"PFK-1 L4 homotetramer\"\n    ],\n    \"partners\": [\n      \"HDAC6\",\n      \"PRMT9\",\n      \"PLIN2\",\n      \"USP14\",\n      \"USP39\",\n      \"DNAAF5\",\n      \"A20\",\n      \"PTGES3\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"PFKL is the liver-type subunit of phosphofructokinase-1, the rate-limiting enzyme of glycolysis, whose activity is tuned by an extensive network of allosteric, post-translational, and transcriptional controls that couple glucose flux to cellular state. Allosteric activation at the AMP/ADP effector site (targeted by small-molecule NA-11) diverts glucose from the pentose phosphate pathway, suppressing NADPH-dependent NOX2 oxidative burst and NETosis in neutrophils, while inhibitory inputs include O-GlcNAcylation at S529 (redirecting flux to the PPP under hypoxia), PRMT9-mediated methylation at R301, and local PGE2 production by PTGES3 [PMID:34320407, PMID:22923583, PMID:40222696, PMID:37831605]. Protein stability is governed by ubiquitin-dependent degradation through E3 ligases A20 and PDLIM2 and counteracted by deubiquitinases USP39 and USP14, while HDAC6-mediated deacetylation at K563 promotes active tetramer assembly and phosphorylation at S775 during innate immune signaling increases catalytic output [PMID:32015333, PMID:36276075, PMID:41421488, PMID:39085210]. Beyond canonical glycolysis, under energy stress PFKL translocates to lipid droplets and functions as a protein kinase that phosphorylates PLIN2, tethering lipid droplets to mitochondria to enable β-oxidation [PMID:38773347].\",\n  \"teleology\": [\n    {\n      \"year\": 1981,\n      \"claim\": \"Mapping PFKL to chromosome 21 and demonstrating gene-dosage effects in trisomy 21 established that liver-type PFK subunit copy number directly determines isozyme composition and total PFK activity in human erythrocytes.\",\n      \"evidence\": \"Somatic cell hybrid panel with subunit-specific monoclonal antibody; chromatographic isozyme profiling of trisomy 21 erythrocytes\",\n      \"pmids\": [\"6455664\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which excess PFKL alters erythrocyte metabolism in Down syndrome remains uncharacterized\", \"No structure–function information at this stage\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Transgenic PFKL-overexpressing mice revealed that gene-dosage-driven increases in PFK activity are tissue- and age-dependent and directly accelerate cerebral glucose utilization, connecting enzyme level to whole-organ metabolic flux.\",\n      \"evidence\": \"Transgenic mice with PFKL overexpression; in vivo ¹³C-NMR brain metabolic flux; tissue PFK activity assays\",\n      \"pmids\": [\"8172601\", \"9813288\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether the metabolic shift contributes to neurodevelopmental phenotypes was not tested\", \"Activity regulation beyond gene dosage not addressed\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identification of O-GlcNAcylation at S529 as an inhibitory post-translational modification revealed the first site-specific mechanism through which PFKL activity is suppressed to redirect glucose into the pentose phosphate pathway under hypoxia, conferring a cancer cell growth advantage.\",\n      \"evidence\": \"In vitro PFK1 activity assays with S529A mutagenesis; metabolic flux analysis; xenograft tumor models\",\n      \"pmids\": [\"22923583\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the O-GlcNAc transferase and phosphatase controlling S529 occupancy not defined\", \"Relative contribution of PFKL vs. PFKM/PFKP O-GlcNAcylation in vivo unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Structural and pharmacological characterization of PFKL's allosteric activation site by NA-11 resolved how small-molecule occupancy of the AMP/ADP pocket locks the enzyme in the active R-state and explained isoform selectivity, while showing that PFKL activation diverts neutrophil glucose away from the PPP to suppress NOX2-dependent oxidative burst and NETosis.\",\n      \"evidence\": \"High-resolution crystal structure of PFKL–NA-11 complex; chemical proteomics with two probes; neutrophil ROS/NETosis assays; glycolysis flux measurements\",\n      \"pmids\": [\"34320407\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo efficacy and pharmacokinetics of NA-11 class activators not fully characterized\", \"Structural basis for negative allosteric regulation (e.g., citrate, PGE2) unresolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Multiple studies converged to show that PFKL protein stability is controlled by ubiquitin-dependent degradation — E3 ligases A20 and PDLIM2 promote PFKL turnover, while deubiquitinases USP39 (recruited via DNAAF5) and later USP14 oppose degradation — establishing regulated proteolysis as a major layer of glycolytic control in cancer.\",\n      \"evidence\": \"Co-IP plus ubiquitination/deubiquitination assays in HCC, laryngeal SCC, and OSCC cells; xenograft models; DNAAF5-KO epistasis\",\n      \"pmids\": [\"32015333\", \"35723199\", \"36276075\", \"38388430\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ubiquitination site(s) on PFKL not mapped\", \"Whether A20, PDLIM2, USP39, and USP14 act on the same or distinct ubiquitin chains is unknown\", \"SQSTM1-mediated lysosomal degradation (via Cav1 competition) adds complexity not yet integrated\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"PFKL was placed under direct transcriptional control of KLF7 (activating) and EGR1 (repressing), linking PFKL expression to cardiac metabolic remodeling and hepatocellular carcinoma, and demonstrating that PFKL levels are rate-limiting for pathological glycolysis in these contexts.\",\n      \"evidence\": \"Cardiac-specific KLF7 KO/OE mice with PFKL-knockdown rescue; ChIP at PFKL promoter for KLF7 and EGR1; HCC xenograft and organoid models\",\n      \"pmids\": [\"36810848\", \"38287371\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Additional transcription factors controlling PFKL in other tissues not mapped\", \"Integration of transcriptional and post-translational regulation quantitatively undefined\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Discovery that PTGES3 binds PFKL and generates local PGE2 to allosterically inhibit enzyme activity revealed a lipid-metabolite-mediated regulatory axis restraining glycolysis and invasion in ovarian cancer cells.\",\n      \"evidence\": \"Genome-wide CRISPR invasion screen; Co-IP; direct enzymatic activity assays with PTGES3 KO/OE\",\n      \"pmids\": [\"37831605\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"PGE2 binding site on PFKL not structurally defined\", \"Whether this mechanism operates outside ovarian cancer is untested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Phosphorylation of PFKL at S775 during innate immune activation was shown to directly increase catalytic activity and glycolytic flux in macrophages; knock-in S775A mice exhibited blunted HIF1α/IL-1β responses, placing PFKL phosphorylation as a metabolic checkpoint in inflammation.\",\n      \"evidence\": \"Biochemical activity assays; PfklS775A knock-in mouse; in vivo LPS inflammation model\",\n      \"pmids\": [\"39085210\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinase responsible for S775 phosphorylation not identified\", \"Whether S775 phosphorylation occurs in non-myeloid immune cells is unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"The discovery that PFKL translocates to lipid droplets under energy stress and functions as a protein kinase phosphorylating PLIN2 to tether lipid droplets to mitochondria fundamentally expanded PFKL's role beyond glycolysis into lipid catabolism and organelle communication.\",\n      \"evidence\": \"In vitro kinase assay (PFKL → PLIN2); lipid droplet isolation; proximity ligation assay for LD–mitochondria contacts; mouse liver tumor models\",\n      \"pmids\": [\"38773347\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for PFKL protein kinase activity and its relationship to the metabolite kinase domain unknown\", \"Full substrate repertoire of PFKL as a protein kinase not surveyed\", \"Signal triggering PFKL translocation to lipid droplets not molecularly defined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identification of HDAC6-mediated deacetylation at K563 as a driver of active tetramer assembly, and PRMT9-mediated methylation at R301 as an inactivating modification, added two new post-translational switches that tune PFKL quaternary structure and activity in vascular smooth muscle cells and neutrophils, respectively.\",\n      \"evidence\": \"Co-IP; HDAC6 inhibitor/siRNA; K563R/K563Q mutagenesis with in vivo neointimal formation model; mass spectrometry methylation site ID; PDK4-KO mouse model for lactate/PRMT9 axis\",\n      \"pmids\": [\"41421488\", \"40222696\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Interplay among S529 O-GlcNAcylation, K563 acetylation, R301 methylation, and S775 phosphorylation on the same PFKL molecule not examined\", \"Whether HDAC6–PFKL interaction is direct or scaffold-mediated is unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include: the structural basis for PFKL's protein kinase activity toward PLIN2, the identity of the S775 kinase, how multiple PTMs are integrated on a single tetramer, and whether allosteric activators can be therapeutically deployed in inflammatory disease.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural model of PFKL protein kinase activity exists\", \"Kinase for S775 unidentified\", \"Quantitative integration of combinatorial PTMs on PFKL not modeled\", \"In vivo therapeutic window for PFKL allosteric activators not established\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [16]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [3, 5, 16]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [3, 5, 14]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [5, 14]},\n      {\"term_id\": \"GO:0005811\", \"supporting_discovery_ids\": [16]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 3, 5, 14, 16, 18]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [5, 14, 19]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [4, 7, 8, 9, 15, 17]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"PTGES3\",\n      \"USP39\",\n      \"DNAAF5\",\n      \"USP14\",\n      \"A20\",\n      \"PDLIM2\",\n      \"HDAC6\",\n      \"PLIN2\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}