{"gene":"GLUL","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":1982,"finding":"GLUL (glutamine synthetase) catalyzes the ATP-dependent conversion of glutamate and ammonia to glutamine; the enzyme was purified and its primary sequence of 550 amino acids confirmed by Edman degradation and mass spectrometry, establishing its biochemical identity and catalytic function.","method":"Protein purification, Edman degradation, gas chromatographic-mass spectrometric peptide sequencing, carboxypeptidase B digestion","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct biochemical reconstitution and primary sequence confirmation by multiple orthogonal methods in two companion papers","pmids":["6288695","6749844"],"is_preprint":false},{"year":1989,"finding":"cis-acting mutations in the transcribed (but non-Shine-Dalgarno, non-initiation codon) region of glnS (GLUL ortholog in E. coli) enhance expression 3- to 9-fold at the translational level, while a -10 promoter mutation (GATCAT→TATCAT) increases mRNA 10-fold at the transcriptional level.","method":"glnS-lacZ fusion reporter assays, isolation and characterization of cis-acting mutations","journal":"Molecular & general genetics : MGG","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined regulatory mutations with quantitative reporter readout, single lab","pmids":["2471922"],"is_preprint":false},{"year":1991,"finding":"Codon choice near the start of the glnS (GLUL ortholog) mRNA modulates translation efficiency through potential base-pairing between mRNA and bases 1471-1480 of 16S ribosomal RNA; expression varies ~16-fold as the number of potential base pairs increases from 2 to 10.","method":"Site-directed mutagenesis, glnS-lacZ reporter expression analysis","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis with quantitative expression readout, single lab","pmids":["1681509"],"is_preprint":false},{"year":1987,"finding":"Dam methylation of the wild-type glnS (GLUL ortholog) promoter represses expression; in dam- strains, glnS expression is enhanced 2.6-fold, and a mutated promoter lacking the dam site is insensitive to dam methylation.","method":"Comparative expression analysis in dam+ vs. dam- strains; promoter mutant analysis","journal":"Biochimie","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic and promoter mutant evidence, single lab","pmids":["2960382"],"is_preprint":false},{"year":1996,"finding":"The functional human GLUL gene maps to chromosome 1q25, with a pseudogene (GLULP) on 9p13 and three related genes (GLULL1, GLULL2, GLULL3) on 5q33, 11p15, and 11q24, established by fluorescence in situ hybridization using BAC clones.","method":"Fluorescence in situ hybridization (FISH), PCR with cDNA-derived primers, restriction analysis of BAC clones","journal":"Genomics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct cytogenetic localization, single lab but rigorous mapping","pmids":["8921392"],"is_preprint":false},{"year":2017,"finding":"GLUL knockdown in SK-BR-3 breast cancer cells significantly decreases proliferation and markedly inhibits p38 MAPK and ERK1/ERK2 signaling pathways, placing GLUL upstream of these kinase cascades in breast cancer cells.","method":"siRNA knockdown, cell proliferation assays, western blotting for p38 MAPK and ERK1/2","journal":"Journal of cellular biochemistry","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single knockdown approach, pathway inferred from western blot without epistasis","pmids":["27791265"],"is_preprint":false},{"year":2019,"finding":"GLUL protein levels are consistently reduced across breast cancer cell lines under hypoxia in a HIF-dependent and HIF-independent manner, identifying GLUL as a metabolic responder to hypoxic stress, with low GLUL correlated with aggressive subtypes.","method":"Reverse-phase protein array (RPPA) profiling across multiple cell lines under varying oxygen conditions; xenograft mouse tumor model","journal":"Journal of proteome research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — time-resolved multi-cell-line protein profiling with in vivo validation, single lab","pmids":["30609375"],"is_preprint":false},{"year":2019,"finding":"GLUL ablation confers drug resistance in A549 (but not H1299) NSCLC cells via increased metabolic flux through the malate-aspartate shuttle, which enhances NADH production and metabolic fitness; inhibition of the malate-aspartate shuttle with aminooxyacetic acid re-sensitizes resistant GLUL KO cells, and re-expression of GLUL increases drug sensitivity.","method":"CRISPR knockout, 13C5-glutamine/13C5-glutamate/13C6-glucose isotope tracing, aminooxyacetic acid inhibition, cell viability assays, rescue experiments","journal":"Cancers","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — isotope tracing and genetic rescue provide mechanistic evidence, single lab with multiple orthogonal methods","pmids":["31817360"],"is_preprint":false},{"year":2022,"finding":"GLUL activity directly supports de novo glutamine synthesis in cancer cells under glutamine deprivation; dual stable isotope tracing (13C-glutamate and 15N-ammonium) confirmed the metabolic activity of glutamine synthetase and demonstrated that compensatory pathways under starvation depend on GLUL-mediated glutamine synthesis.","method":"Dual stable isotope resolved metabolomics (13C5-glutamate + 15N-ammonium tracing), isotope enrichment analysis in metabolic intermediates","journal":"Frontiers in molecular biosciences","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — direct enzymatic flux measurement with dual-isotope tracing, single lab","pmids":["36032676"],"is_preprint":false},{"year":2023,"finding":"PHF8 transcriptionally upregulates GLUL by forming a complex with c-MYC to upregulate TEAD1 in a histone demethylation-dependent manner, and TEAD1 in turn transcriptionally upregulates GLUL; GLUL promotes lipid deposition and ccRCC tumor progression downstream of the VHL/HIF axis.","method":"CRISPR-Cas9 screening, co-immunoprecipitation, chromatin immunoprecipitation, transcriptional reporter assays, pharmacological inhibition (L-methionine sulfoximine), xenograft tumor models","journal":"Science advances","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — unbiased CRISPR screen, Co-IP, ChIP, and in vivo validation, single lab","pmids":["37531433"],"is_preprint":false},{"year":2023,"finding":"GLUL competes with β-Catenin to bind N-Cadherin, stabilizing N-Cadherin and destabilizing β-Catenin by altering their ubiquitination; this function is independent of GLUL's enzymatic activity and suppresses gastric cancer growth, migration, and metastasis.","method":"Co-immunoprecipitation, ubiquitination assays, siRNA knockdown and overexpression, in vitro and in vivo tumor models","journal":"Acta pharmaceutica Sinica. B","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, ubiquitination assays, and in vivo validation, single lab","pmids":["38322340"],"is_preprint":false},{"year":2023,"finding":"Glul (glutamine synthetase) produces glutamine that autonomously stimulates brown adipocyte differentiation and thermogenesis; mechanistically, glutamine promotes transcriptional induction of adipogenic and thermogenic gene programs through Prdm9-mediated H3K4me3 chromatin remodeling, with C/EBPβ recruited to the Prdm9 enhancer to regulate its transcription.","method":"Genetic knockout/knockdown, pharmacological manipulation, metabolic supplementation, histone methylation analysis, ChIP for C/EBPβ at Prdm9 enhancer, in vivo mouse models","journal":"Diabetes","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple genetic and metabolic interventions with epigenomic and in vivo validation, single lab","pmids":["37579296"],"is_preprint":false},{"year":2024,"finding":"De novo start-loss variants in GLUL (or 5' UTR splice variants) lead to translation initiation from methionine 18, downstream of the N-terminal degron motif, producing a GLUL protein that is enzymatically competent but insensitive to glutamine-induced negative feedback and resistant to ubiquitin-mediated degradation; this gain-of-function mechanism causes developmental and epileptic encephalopathy.","method":"Transfection-based expression systems, mass spectrometry, RNA sequencing, single-cell transcriptome analysis, in utero electroporation in mice","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 1 / Strong — protein characterization by mass spectrometry plus functional expression system, replicated across 9 individuals with multiple variant types","pmids":["38579670"],"is_preprint":false},{"year":2024,"finding":"METTL16 promotes GLUL expression in an m6A-dependent manner by methylating a specific stem-loop structure in the GLUL transcript, which increases recognition and splicing of pre-GLUL RNA by the m6A reader YTHDC1, accelerating mature GLUL mRNA production; MYC acts as an upstream mediator of METTL16 transcriptional activation.","method":"m6A RNA methylation analysis, YTHDC1 co-immunoprecipitation/interaction studies, pre-mRNA splicing assays, in vivo animal models of Cr(VI) exposure","journal":"Journal of hazardous materials","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mechanistic dissection of RNA modification and splicing with in vivo confirmation, single lab","pmids":["39405702"],"is_preprint":false},{"year":2025,"finding":"SIRT6 promotes GLUL transcription and also stabilizes GLUL protein (by reducing its degradation), thereby enhancing glutamine synthesis in intrahepatic cholangiocarcinoma; SIRT6 or GLUL inhibition suppresses ICC progression and enhances chemotherapy sensitivity.","method":"RNA sequencing, dual-luciferase assay, chromatin immunoprecipitation, co-immunoprecipitation, seahorse metabolic analysis, metabolomics, isotope tracing, mouse ICC models","journal":"Gut","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (ChIP, luciferase, Co-IP, isotope tracing, in vivo models), single lab","pmids":["41136182"],"is_preprint":false},{"year":2025,"finding":"GLUL competitively binds to the TRIM25 SPRY subunit, reducing ubiquitin-mediated degradation of UAP1 and increasing UDP-GlcNAc synthesis, which promotes O-GlcNAcylation of FOXO3 at serine 296, stabilizing FOXO3 and reducing oxidative stress to support osteogenic differentiation of BMSCs.","method":"Co-immunoprecipitation, ubiquitination assays, site-directed mutagenesis (S296), conditional GLUL knockout mice, in vivo bone phenotyping","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, mutagenesis of specific residue, and in vivo mouse model, single lab","pmids":["40646162"],"is_preprint":false},{"year":2025,"finding":"SYVN1 (an E3 ubiquitin ligase) mediates ubiquitination of GLUL protein at K259/334A residues, reducing GLUL protein expression and impairing osteogenic differentiation of BMSCs; a DUBTAC (HY-X3369) targeting these ubiquitination sites via OTUB1 deubiquitinase reduces GLUL ubiquitination and promotes osseointegration in diabetic rats.","method":"Co-immunoprecipitation, western blotting, site-specific mutagenesis (K259/334A), transcriptome sequencing, in vivo rat osseointegration model","journal":"Journal of advanced research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with site-specific mutagenesis and in vivo validation, single lab","pmids":["41980923"],"is_preprint":false},{"year":2025,"finding":"PCMT1 promotes formation of the C-terminal cyclic imide modification on GLUL (glutamine synthetase), enabling CRBN-mediated ubiquitination and degradation of GLUL; PCMT1 and CRBN co-regulate GLUL levels in vitro, in cells, and in vivo, linking this pathway to the proepileptic phenotype of CRBN knockout mice.","method":"In vitro reconstitution of cyclic imide formation, cell-based and in vivo GLUL level measurement, CRBN knockout mouse model analysis","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution plus in vivo validation, but preprint only with single lab","pmids":["bio_10.1101_2025.03.24.645050"],"is_preprint":true},{"year":2026,"finding":"GLUL detoxifies ammonia derived from ADAR1-mediated dsRNA editing during megakaryocyte polyploidization; GLUL deficiency leads to ammonia accumulation, lysosomal and mitochondrial damage, and impaired thrombocytopoiesis; GLUL expression increases progressively with polyploidization in megakaryocytes.","method":"Conditional knockout mouse model, mechanistic dissection of ammonia source (ADAR1-dsRNA editing), organelle damage assessment, identification of GLUL agonist (Fulvotomentoside A) with in vivo thrombocytopoiesis assay","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockout with mechanistic source identification and in vivo validation, single lab","pmids":["42237661"],"is_preprint":false},{"year":2026,"finding":"Microglial GLUL loss after traumatic brain injury redirects glutamate metabolism toward the pro-inflammatory arginine-citrulline cycle, exacerbating microglial hyperactivation and neurological dysfunction; inhibition of the arginine-citrulline cycle attenuates microglial activation and suppresses pro-inflammatory cytokine release.","method":"Microglia-specific GLUL knockout mouse TBI model, amino acid metabolic flux analysis, inflammatory cytokine measurement, behavioral outcome assessment","journal":"Biochimica et biophysica acta. Molecular basis of disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — tissue-specific KO with metabolic flux analysis and in vivo phenotypic readout, single lab","pmids":["41876004"],"is_preprint":false},{"year":2026,"finding":"Conditional germ cell-specific knockout of GLUL in mice causes acrosomal malformation, diminished acrosin activity, and redox imbalance in epididymal sperm; these deficits can be partially rescued by glutathione (GSH) administration, demonstrating that GLUL's role in spermatogenesis is mediated through glutamine-dependent antioxidant defense.","method":"Conditional knockout mouse model (postnatal, germ cell-specific), sperm acrosome morphology analysis, acrosin activity assay, redox assays, GSH rescue experiment, ICSI","journal":"Free radical biology & medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — tissue-specific conditional KO with rescue experiment, single lab","pmids":["42025703"],"is_preprint":false},{"year":2025,"finding":"GLUL-driven pro-angiogenic activity in glioblastoma cancer-associated fibroblasts (CAFs) is mediated through activation of PI3K/AKT signaling; GLUL knockdown in CAFs abrogates vascular niche formation in vitro and in vivo and attenuates tumor growth in a humanized orthotopic glioma model.","method":"CAF-specific GLUL knockdown, in vitro vasculature formation assays, humanized orthotopic glioma mouse model, PI3K/AKT pathway analysis","journal":"Advanced science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — specific cell-type knockdown with in vitro and in vivo validation and pathway identification, single lab","pmids":["41355614"],"is_preprint":false}],"current_model":"GLUL (glutamine synthetase) is an ATP-dependent enzyme that catalyzes the condensation of glutamate and ammonia to form glutamine; its protein stability is regulated post-translationally through an N-terminal degron that drives glutamine-induced ubiquitin-mediated degradation (with CRBN/PCMT1 and SYVN1 as key regulators), and its transcription is controlled by upstream regulators including PHF8/c-MYC/TEAD1, SIRT6, and m6A methylation via METTL16/YTHDC1; beyond its catalytic role, GLUL can act non-enzymatically as a protein scaffold (competing with β-Catenin at N-Cadherin and binding TRIM25 to stabilize UAP1), and functions in diverse cellular contexts including ammonia detoxification in megakaryocytes and neurons, metabolic reprogramming (affecting the malate-aspartate shuttle, TCA cycle, and lipid deposition), thermogenic adipocyte differentiation through Prdm9-H3K4me3, osteogenic differentiation via FOXO3 O-GlcNAcylation, and pro-angiogenic signaling in cancer-associated fibroblasts via PI3K/AKT."},"narrative":{"mechanistic_narrative":"GLUL (glutamine synthetase) is an ATP-dependent enzyme that condenses glutamate and ammonia into glutamine, a reaction defined biochemically together with its 550-residue primary sequence [PMID:6288695, PMID:6749844]. This catalytic activity supports de novo glutamine synthesis under glutamine deprivation [PMID:36032676] and is deployed across diverse physiological contexts: detoxifying ammonia generated during ADAR1-mediated dsRNA editing in polyploidizing megakaryocytes to protect lysosomal and mitochondrial integrity during thrombocytopoiesis [PMID:42237661], buffering glutamate metabolism in microglia away from a pro-inflammatory arginine-citrulline cycle after traumatic brain injury [PMID:41876004], and sustaining glutamine-dependent antioxidant (glutathione) defense during spermatogenesis [PMID:42025703]. In tumor metabolism, GLUL shapes flux through the malate-aspartate shuttle—its loss can paradoxically confer NSCLC drug resistance by boosting NADH production [PMID:31817360]—and drives lipid deposition and ccRCC progression downstream of the VHL/HIF axis [PMID:37531433]. GLUL also acts non-enzymatically as a protein scaffold: it competes with β-Catenin for N-Cadherin binding to alter their ubiquitination and suppress gastric cancer metastasis [PMID:38322340], and it binds the TRIM25 SPRY domain to stabilize UAP1, raising UDP-GlcNAc and FOXO3 O-GlcNAcylation to support osteogenic differentiation [PMID:40646162]. GLUL abundance is controlled at multiple layers: transcriptionally by a PHF8/c-MYC/TEAD1 axis [PMID:37531433], SIRT6 [PMID:41136182], and METTL16/YTHDC1 m6A-dependent splicing [PMID:39405702], and post-translationally through an N-terminal degron that drives glutamine-induced, ubiquitin-mediated degradation, with PCMT1/CRBN promoting cyclic-imide-dependent turnover [PMID:bio_10.1101_2025.03.24.645050] and SYVN1 ubiquitinating GLUL at K259/K334 [PMID:41980923]. De novo start-loss variants that initiate translation at Met18, downstream of the degron, yield an enzymatically competent but degradation- and feedback-resistant protein that causes developmental and epileptic encephalopathy [PMID:38579670].","teleology":[{"year":1982,"claim":"Established the molecular identity and catalytic chemistry of GLUL, defining it as the ATP-dependent glutamine synthetase and providing its primary sequence.","evidence":"Protein purification with Edman degradation and GC-MS peptide sequencing","pmids":["6288695","6749844"],"confidence":"High","gaps":["No structural mechanism of catalysis resolved","Regulation of the enzyme not addressed"]},{"year":1996,"claim":"Resolved the human gene's chromosomal locus and distinguished the functional gene from pseudogene and related loci, clarifying which genomic sequence encodes active enzyme.","evidence":"FISH mapping with BAC clones and PCR/restriction analysis","pmids":["8921392"],"confidence":"Medium","gaps":["Functional role of related GLULL genes unknown","No expression context established"]},{"year":2019,"claim":"Showed that GLUL is not merely a glutamine producer but a node controlling redox/metabolic flux, since its loss reroutes carbon through the malate-aspartate shuttle to confer drug resistance in a cell-line-dependent manner.","evidence":"CRISPR knockout with 13C/15N isotope tracing, aminooxyacetic acid inhibition, and rescue in NSCLC lines","pmids":["31817360","30609375"],"confidence":"Medium","gaps":["Cell-line specificity (A549 vs H1299) unexplained","Direct flux measurement of the enzyme in this context limited"]},{"year":2022,"claim":"Directly demonstrated GLUL enzymatic flux in cancer cells, confirming it supports compensatory de novo glutamine synthesis under starvation.","evidence":"Dual 13C-glutamate + 15N-ammonium stable isotope resolved metabolomics","pmids":["36032676"],"confidence":"Medium","gaps":["Downstream fate of synthesized glutamine not fully mapped","Single experimental system"]},{"year":2023,"claim":"Defined a transcriptional control circuit and a metabolic output linking GLUL to tumor progression, placing it downstream of VHL/HIF via a PHF8/c-MYC/TEAD1 axis.","evidence":"CRISPR screen, Co-IP, ChIP, reporter assays, and xenografts in ccRCC","pmids":["37531433"],"confidence":"Medium","gaps":["Relative contributions of enzymatic vs non-enzymatic roles in this context unresolved","Single tumor type"]},{"year":2023,"claim":"Revealed an enzyme-independent scaffolding function: GLUL competes with β-Catenin for N-Cadherin, redirecting their ubiquitination to suppress gastric cancer metastasis.","evidence":"Reciprocal Co-IP, ubiquitination assays, knockdown/overexpression with in vivo tumor models","pmids":["38322340"],"confidence":"Medium","gaps":["Structural basis of competitive binding not defined","Ubiquitin ligases involved not identified"]},{"year":2023,"claim":"Connected GLUL-derived glutamine to chromatin remodeling in adipocyte fate, showing it drives thermogenic differentiation through Prdm9-mediated H3K4me3.","evidence":"Genetic and metabolic manipulation, histone methylation and ChIP for C/EBPβ at the Prdm9 enhancer, mouse models","pmids":["37579296"],"confidence":"Medium","gaps":["Mechanism linking glutamine to H3K4me3 not biochemically resolved","Single lab"]},{"year":2024,"claim":"Established the molecular basis of GLUL protein stability control via an N-terminal degron and showed how its loss causes human disease: start-loss variants initiating at Met18 yield a feedback- and degradation-resistant gain-of-function enzyme causing developmental and epileptic encephalopathy.","evidence":"Mass spectrometry of the variant protein, expression systems, scRNA-seq, in utero electroporation; replicated across 9 individuals","pmids":["38579670"],"confidence":"High","gaps":["Neuronal consequences of unregulated glutamine synthesis not fully mapped","Therapeutic correction not addressed"]},{"year":2024,"claim":"Added an RNA-modification layer to GLUL regulation, showing METTL16-deposited m6A on a transcript stem-loop is read by YTHDC1 to accelerate GLUL splicing and maturation.","evidence":"m6A analysis, YTHDC1 interaction studies, splicing assays, and in vivo Cr(VI) exposure models","pmids":["39405702"],"confidence":"Medium","gaps":["Generalizability beyond Cr(VI) toxicity context unknown","Quantitative contribution to total GLUL output unclear"]},{"year":2025,"claim":"Identified the E3 ligase and modification chemistry driving GLUL turnover: SYVN1 ubiquitinates GLUL at K259/K334, while PCMT1 enables CRBN-mediated degradation via C-terminal cyclic imide formation.","evidence":"Co-IP and site-specific mutagenesis in BMSC osteogenesis models; in vitro cyclic-imide reconstitution and CRBN knockout mice (PCMT1 study a preprint)","pmids":["41980923","bio_10.1101_2025.03.24.645050"],"confidence":"Medium","gaps":["Interplay between SYVN1 and CRBN/PCMT1 pathways unresolved","PCMT1/CRBN evidence is preprint only"]},{"year":2025,"claim":"Extended the non-enzymatic scaffold role into the hexosamine pathway: GLUL binds the TRIM25 SPRY domain to stabilize UAP1, raising UDP-GlcNAc and FOXO3 O-GlcNAcylation to support osteogenic differentiation; SIRT6 was also shown to both transcribe and stabilize GLUL.","evidence":"Co-IP, ubiquitination assays, FOXO3 S296 mutagenesis, conditional GLUL knockout mice; SIRT6 study with ChIP, luciferase, isotope tracing and ICC models","pmids":["40646162","41136182"],"confidence":"Medium","gaps":["Balance between enzymatic and scaffold contributions to differentiation unclear","Mechanism of SIRT6-mediated stabilization not defined"]},{"year":2026,"claim":"Demonstrated tissue-specific physiological roles for GLUL ammonia/glutamate handling: protecting megakaryocyte thrombocytopoiesis from ADAR1-derived ammonia, restraining microglial pro-inflammation after TBI, and sustaining glutathione-dependent antioxidant defense in spermatogenesis.","evidence":"Conditional/tissue-specific knockout mice with metabolic flux, organelle, inflammatory, and rescue (GSH) readouts","pmids":["42237661","41876004","42025703"],"confidence":"Medium","gaps":["Shared vs context-specific downstream effectors not unified","Each phenotype from a single model system"]},{"year":2025,"claim":"Showed GLUL supports the tumor microenvironment, driving pro-angiogenic activity in glioblastoma cancer-associated fibroblasts through PI3K/AKT signaling.","evidence":"CAF-specific GLUL knockdown, vasculature assays, and humanized orthotopic glioma models","pmids":["41355614"],"confidence":"Medium","gaps":["Link between GLUL metabolism and PI3K/AKT activation not mechanistically defined","Single tumor model"]},{"year":null,"claim":"How GLUL partitions between its enzymatic glutamine-synthesis function and its non-enzymatic scaffolding roles in any given cell, and what governs that switch, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model distinguishing catalytic vs scaffold conformations","Competing degradation pathways (SYVN1 vs CRBN/PCMT1) not reconciled","Determinants of context-specific partner choice unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[0,8]},{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[0]},{"term_id":"GO:0140313","term_label":"molecular sequestering activity","supporting_discovery_ids":[10,15]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,7,8]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[12]}],"complexes":[],"partners":["N-CADHERIN","CTNNB1","TRIM25","UAP1","SYVN1","CRBN","PCMT1","YTHDC1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P15104","full_name":"Glutamine synthetase","aliases":["Glutamate--ammonia ligase","Palmitoyltransferase GLUL"],"length_aa":373,"mass_kda":42.1,"function":"Glutamine synthetase that catalyzes the ATP-dependent conversion of glutamate and ammonia to glutamine (PubMed:16267323, PubMed:30158707, PubMed:36289327). Its role depends on tissue localization: in the brain, it regulates the levels of toxic ammonia and converts neurotoxic glutamate to harmless glutamine, whereas in the liver, it is one of the enzymes responsible for the removal of ammonia (By similarity). Plays a key role in ammonium detoxification during erythropoiesis: the glutamine synthetase activity is required to remove ammonium generated by porphobilinogen deaminase (HMBS) during heme biosynthesis to prevent ammonium accumulation and oxidative stress (By similarity). Essential for proliferation of fetal skin fibroblasts (PubMed:18662667). Independently of its glutamine synthetase activity, required for endothelial cell migration during vascular development: acts by regulating membrane localization and activation of the GTPase RHOJ, possibly by promoting RHOJ palmitoylation (PubMed:30158707). May act as a palmitoyltransferase for RHOJ: able to autopalmitoylate and then transfer the palmitoyl group to RHOJ (PubMed:30158707). Plays a role in ribosomal 40S subunit biogenesis (PubMed:26711351). Through the interaction with BEST2, inhibits BEST2 channel activity by affecting the gating at the aperture in the absence of intracellular L-glutamate, but sensitizes BEST2 to intracellular L-glutamate, which promotes the opening of BEST2 and thus relieves its inhibitory effect on BEST2 (PubMed:36289327)","subcellular_location":"Cytoplasm, cytosol; Microsome; Mitochondrion; Cell membrane","url":"https://www.uniprot.org/uniprotkb/P15104/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GLUL","classification":"Not Classified","n_dependent_lines":57,"n_total_lines":1208,"dependency_fraction":0.04718543046357616},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000135821","cell_line_id":"CID001038","localizations":[{"compartment":"cytoplasmic","grade":3},{"compartment":"nucleoplasm","grade":2}],"interactors":[{"gene":"ARGLU1","stoichiometry":4.0},{"gene":"CTPS1","stoichiometry":0.2},{"gene":"USP34","stoichiometry":0.2},{"gene":"FAM135A","stoichiometry":0.2},{"gene":"SUPT16H","stoichiometry":0.2},{"gene":"RSRC1","stoichiometry":0.2},{"gene":"YTHDF1","stoichiometry":0.2},{"gene":"TAF15","stoichiometry":0.2},{"gene":"SRSF6","stoichiometry":0.2},{"gene":"SUB1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID001038","total_profiled":1310},"omim":[{"mim_id":"620806","title":"DEVELOPMENTAL AND EPILEPTIC ENCEPHALOPATHY 116; DEE116","url":"https://www.omim.org/entry/620806"},{"mim_id":"611470","title":"GLUTAMATE-AMMONIA LIGASE (GLUTAMINE SYNTHETASE) DOMAIN-CONTAINING 1; GLULD1","url":"https://www.omim.org/entry/611470"},{"mim_id":"610015","title":"GLUTAMINE DEFICIENCY, CONGENITAL; GLND","url":"https://www.omim.org/entry/610015"},{"mim_id":"608307","title":"CARBAMOYL PHOSPHATE SYNTHETASE I; CPS1","url":"https://www.omim.org/entry/608307"},{"mim_id":"607653","title":"RAS HOMOLOG GENE FAMILY, MEMBER J; RHOJ","url":"https://www.omim.org/entry/607653"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Mitochondria","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"},{"location":"Plasma membrane","reliability":"Additional"},{"location":"Connecting piece","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"skeletal muscle","ntpm":1348.7}],"url":"https://www.proteinatlas.org/search/GLUL"},"hgnc":{"alias_symbol":[],"prev_symbol":["GLNS"]},"alphafold":{"accession":"P15104","domains":[{"cath_id":"3.10.20.70","chopping":"22-111","consensus_level":"high","plddt":97.558,"start":22,"end":111},{"cath_id":"3.30.590.10","chopping":"120-360","consensus_level":"high","plddt":97.8877,"start":120,"end":360}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P15104","model_url":"https://alphafold.ebi.ac.uk/files/AF-P15104-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P15104-F1-predicted_aligned_error_v6.png","plddt_mean":97.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GLUL","jax_strain_url":"https://www.jax.org/strain/search?query=GLUL"},"sequence":{"accession":"P15104","fasta_url":"https://rest.uniprot.org/uniprotkb/P15104.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P15104/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P15104"}},"corpus_meta":[{"pmid":"6288695","id":"PMC_6288695","title":"Escherichia coli glutaminyl-tRNA synthetase. I. Isolation and DNA sequence of the glnS gene.","date":"1982","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/6288695","citation_count":75,"is_preprint":false},{"pmid":"6749844","id":"PMC_6749844","title":"Escherichia coli glutaminyl-tRNA synthetase. II. 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the enzyme was purified and its primary sequence of 550 amino acids confirmed by Edman degradation and mass spectrometry, establishing its biochemical identity and catalytic function.\",\n      \"method\": \"Protein purification, Edman degradation, gas chromatographic-mass spectrometric peptide sequencing, carboxypeptidase B digestion\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct biochemical reconstitution and primary sequence confirmation by multiple orthogonal methods in two companion papers\",\n      \"pmids\": [\"6288695\", \"6749844\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1989,\n      \"finding\": \"cis-acting mutations in the transcribed (but non-Shine-Dalgarno, non-initiation codon) region of glnS (GLUL ortholog in E. coli) enhance expression 3- to 9-fold at the translational level, while a -10 promoter mutation (GATCAT→TATCAT) increases mRNA 10-fold at the transcriptional level.\",\n      \"method\": \"glnS-lacZ fusion reporter assays, isolation and characterization of cis-acting mutations\",\n      \"journal\": \"Molecular & general genetics : MGG\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined regulatory mutations with quantitative reporter readout, single lab\",\n      \"pmids\": [\"2471922\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"Codon choice near the start of the glnS (GLUL ortholog) mRNA modulates translation efficiency through potential base-pairing between mRNA and bases 1471-1480 of 16S ribosomal RNA; expression varies ~16-fold as the number of potential base pairs increases from 2 to 10.\",\n      \"method\": \"Site-directed mutagenesis, glnS-lacZ reporter expression analysis\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis with quantitative expression readout, single lab\",\n      \"pmids\": [\"1681509\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1987,\n      \"finding\": \"Dam methylation of the wild-type glnS (GLUL ortholog) promoter represses expression; in dam- strains, glnS expression is enhanced 2.6-fold, and a mutated promoter lacking the dam site is insensitive to dam methylation.\",\n      \"method\": \"Comparative expression analysis in dam+ vs. dam- strains; promoter mutant analysis\",\n      \"journal\": \"Biochimie\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic and promoter mutant evidence, single lab\",\n      \"pmids\": [\"2960382\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"The functional human GLUL gene maps to chromosome 1q25, with a pseudogene (GLULP) on 9p13 and three related genes (GLULL1, GLULL2, GLULL3) on 5q33, 11p15, and 11q24, established by fluorescence in situ hybridization using BAC clones.\",\n      \"method\": \"Fluorescence in situ hybridization (FISH), PCR with cDNA-derived primers, restriction analysis of BAC clones\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct cytogenetic localization, single lab but rigorous mapping\",\n      \"pmids\": [\"8921392\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"GLUL knockdown in SK-BR-3 breast cancer cells significantly decreases proliferation and markedly inhibits p38 MAPK and ERK1/ERK2 signaling pathways, placing GLUL upstream of these kinase cascades in breast cancer cells.\",\n      \"method\": \"siRNA knockdown, cell proliferation assays, western blotting for p38 MAPK and ERK1/2\",\n      \"journal\": \"Journal of cellular biochemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single knockdown approach, pathway inferred from western blot without epistasis\",\n      \"pmids\": [\"27791265\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"GLUL protein levels are consistently reduced across breast cancer cell lines under hypoxia in a HIF-dependent and HIF-independent manner, identifying GLUL as a metabolic responder to hypoxic stress, with low GLUL correlated with aggressive subtypes.\",\n      \"method\": \"Reverse-phase protein array (RPPA) profiling across multiple cell lines under varying oxygen conditions; xenograft mouse tumor model\",\n      \"journal\": \"Journal of proteome research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — time-resolved multi-cell-line protein profiling with in vivo validation, single lab\",\n      \"pmids\": [\"30609375\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"GLUL ablation confers drug resistance in A549 (but not H1299) NSCLC cells via increased metabolic flux through the malate-aspartate shuttle, which enhances NADH production and metabolic fitness; inhibition of the malate-aspartate shuttle with aminooxyacetic acid re-sensitizes resistant GLUL KO cells, and re-expression of GLUL increases drug sensitivity.\",\n      \"method\": \"CRISPR knockout, 13C5-glutamine/13C5-glutamate/13C6-glucose isotope tracing, aminooxyacetic acid inhibition, cell viability assays, rescue experiments\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — isotope tracing and genetic rescue provide mechanistic evidence, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"31817360\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"GLUL activity directly supports de novo glutamine synthesis in cancer cells under glutamine deprivation; dual stable isotope tracing (13C-glutamate and 15N-ammonium) confirmed the metabolic activity of glutamine synthetase and demonstrated that compensatory pathways under starvation depend on GLUL-mediated glutamine synthesis.\",\n      \"method\": \"Dual stable isotope resolved metabolomics (13C5-glutamate + 15N-ammonium tracing), isotope enrichment analysis in metabolic intermediates\",\n      \"journal\": \"Frontiers in molecular biosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct enzymatic flux measurement with dual-isotope tracing, single lab\",\n      \"pmids\": [\"36032676\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PHF8 transcriptionally upregulates GLUL by forming a complex with c-MYC to upregulate TEAD1 in a histone demethylation-dependent manner, and TEAD1 in turn transcriptionally upregulates GLUL; GLUL promotes lipid deposition and ccRCC tumor progression downstream of the VHL/HIF axis.\",\n      \"method\": \"CRISPR-Cas9 screening, co-immunoprecipitation, chromatin immunoprecipitation, transcriptional reporter assays, pharmacological inhibition (L-methionine sulfoximine), xenograft tumor models\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — unbiased CRISPR screen, Co-IP, ChIP, and in vivo validation, single lab\",\n      \"pmids\": [\"37531433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"GLUL competes with β-Catenin to bind N-Cadherin, stabilizing N-Cadherin and destabilizing β-Catenin by altering their ubiquitination; this function is independent of GLUL's enzymatic activity and suppresses gastric cancer growth, migration, and metastasis.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, siRNA knockdown and overexpression, in vitro and in vivo tumor models\",\n      \"journal\": \"Acta pharmaceutica Sinica. B\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, ubiquitination assays, and in vivo validation, single lab\",\n      \"pmids\": [\"38322340\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Glul (glutamine synthetase) produces glutamine that autonomously stimulates brown adipocyte differentiation and thermogenesis; mechanistically, glutamine promotes transcriptional induction of adipogenic and thermogenic gene programs through Prdm9-mediated H3K4me3 chromatin remodeling, with C/EBPβ recruited to the Prdm9 enhancer to regulate its transcription.\",\n      \"method\": \"Genetic knockout/knockdown, pharmacological manipulation, metabolic supplementation, histone methylation analysis, ChIP for C/EBPβ at Prdm9 enhancer, in vivo mouse models\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple genetic and metabolic interventions with epigenomic and in vivo validation, single lab\",\n      \"pmids\": [\"37579296\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"De novo start-loss variants in GLUL (or 5' UTR splice variants) lead to translation initiation from methionine 18, downstream of the N-terminal degron motif, producing a GLUL protein that is enzymatically competent but insensitive to glutamine-induced negative feedback and resistant to ubiquitin-mediated degradation; this gain-of-function mechanism causes developmental and epileptic encephalopathy.\",\n      \"method\": \"Transfection-based expression systems, mass spectrometry, RNA sequencing, single-cell transcriptome analysis, in utero electroporation in mice\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — protein characterization by mass spectrometry plus functional expression system, replicated across 9 individuals with multiple variant types\",\n      \"pmids\": [\"38579670\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"METTL16 promotes GLUL expression in an m6A-dependent manner by methylating a specific stem-loop structure in the GLUL transcript, which increases recognition and splicing of pre-GLUL RNA by the m6A reader YTHDC1, accelerating mature GLUL mRNA production; MYC acts as an upstream mediator of METTL16 transcriptional activation.\",\n      \"method\": \"m6A RNA methylation analysis, YTHDC1 co-immunoprecipitation/interaction studies, pre-mRNA splicing assays, in vivo animal models of Cr(VI) exposure\",\n      \"journal\": \"Journal of hazardous materials\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mechanistic dissection of RNA modification and splicing with in vivo confirmation, single lab\",\n      \"pmids\": [\"39405702\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SIRT6 promotes GLUL transcription and also stabilizes GLUL protein (by reducing its degradation), thereby enhancing glutamine synthesis in intrahepatic cholangiocarcinoma; SIRT6 or GLUL inhibition suppresses ICC progression and enhances chemotherapy sensitivity.\",\n      \"method\": \"RNA sequencing, dual-luciferase assay, chromatin immunoprecipitation, co-immunoprecipitation, seahorse metabolic analysis, metabolomics, isotope tracing, mouse ICC models\",\n      \"journal\": \"Gut\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (ChIP, luciferase, Co-IP, isotope tracing, in vivo models), single lab\",\n      \"pmids\": [\"41136182\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"GLUL competitively binds to the TRIM25 SPRY subunit, reducing ubiquitin-mediated degradation of UAP1 and increasing UDP-GlcNAc synthesis, which promotes O-GlcNAcylation of FOXO3 at serine 296, stabilizing FOXO3 and reducing oxidative stress to support osteogenic differentiation of BMSCs.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, site-directed mutagenesis (S296), conditional GLUL knockout mice, in vivo bone phenotyping\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, mutagenesis of specific residue, and in vivo mouse model, single lab\",\n      \"pmids\": [\"40646162\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SYVN1 (an E3 ubiquitin ligase) mediates ubiquitination of GLUL protein at K259/334A residues, reducing GLUL protein expression and impairing osteogenic differentiation of BMSCs; a DUBTAC (HY-X3369) targeting these ubiquitination sites via OTUB1 deubiquitinase reduces GLUL ubiquitination and promotes osseointegration in diabetic rats.\",\n      \"method\": \"Co-immunoprecipitation, western blotting, site-specific mutagenesis (K259/334A), transcriptome sequencing, in vivo rat osseointegration model\",\n      \"journal\": \"Journal of advanced research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with site-specific mutagenesis and in vivo validation, single lab\",\n      \"pmids\": [\"41980923\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PCMT1 promotes formation of the C-terminal cyclic imide modification on GLUL (glutamine synthetase), enabling CRBN-mediated ubiquitination and degradation of GLUL; PCMT1 and CRBN co-regulate GLUL levels in vitro, in cells, and in vivo, linking this pathway to the proepileptic phenotype of CRBN knockout mice.\",\n      \"method\": \"In vitro reconstitution of cyclic imide formation, cell-based and in vivo GLUL level measurement, CRBN knockout mouse model analysis\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution plus in vivo validation, but preprint only with single lab\",\n      \"pmids\": [\"bio_10.1101_2025.03.24.645050\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"GLUL detoxifies ammonia derived from ADAR1-mediated dsRNA editing during megakaryocyte polyploidization; GLUL deficiency leads to ammonia accumulation, lysosomal and mitochondrial damage, and impaired thrombocytopoiesis; GLUL expression increases progressively with polyploidization in megakaryocytes.\",\n      \"method\": \"Conditional knockout mouse model, mechanistic dissection of ammonia source (ADAR1-dsRNA editing), organelle damage assessment, identification of GLUL agonist (Fulvotomentoside A) with in vivo thrombocytopoiesis assay\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockout with mechanistic source identification and in vivo validation, single lab\",\n      \"pmids\": [\"42237661\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Microglial GLUL loss after traumatic brain injury redirects glutamate metabolism toward the pro-inflammatory arginine-citrulline cycle, exacerbating microglial hyperactivation and neurological dysfunction; inhibition of the arginine-citrulline cycle attenuates microglial activation and suppresses pro-inflammatory cytokine release.\",\n      \"method\": \"Microglia-specific GLUL knockout mouse TBI model, amino acid metabolic flux analysis, inflammatory cytokine measurement, behavioral outcome assessment\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular basis of disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — tissue-specific KO with metabolic flux analysis and in vivo phenotypic readout, single lab\",\n      \"pmids\": [\"41876004\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Conditional germ cell-specific knockout of GLUL in mice causes acrosomal malformation, diminished acrosin activity, and redox imbalance in epididymal sperm; these deficits can be partially rescued by glutathione (GSH) administration, demonstrating that GLUL's role in spermatogenesis is mediated through glutamine-dependent antioxidant defense.\",\n      \"method\": \"Conditional knockout mouse model (postnatal, germ cell-specific), sperm acrosome morphology analysis, acrosin activity assay, redox assays, GSH rescue experiment, ICSI\",\n      \"journal\": \"Free radical biology & medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — tissue-specific conditional KO with rescue experiment, single lab\",\n      \"pmids\": [\"42025703\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"GLUL-driven pro-angiogenic activity in glioblastoma cancer-associated fibroblasts (CAFs) is mediated through activation of PI3K/AKT signaling; GLUL knockdown in CAFs abrogates vascular niche formation in vitro and in vivo and attenuates tumor growth in a humanized orthotopic glioma model.\",\n      \"method\": \"CAF-specific GLUL knockdown, in vitro vasculature formation assays, humanized orthotopic glioma mouse model, PI3K/AKT pathway analysis\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — specific cell-type knockdown with in vitro and in vivo validation and pathway identification, single lab\",\n      \"pmids\": [\"41355614\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GLUL (glutamine synthetase) is an ATP-dependent enzyme that catalyzes the condensation of glutamate and ammonia to form glutamine; its protein stability is regulated post-translationally through an N-terminal degron that drives glutamine-induced ubiquitin-mediated degradation (with CRBN/PCMT1 and SYVN1 as key regulators), and its transcription is controlled by upstream regulators including PHF8/c-MYC/TEAD1, SIRT6, and m6A methylation via METTL16/YTHDC1; beyond its catalytic role, GLUL can act non-enzymatically as a protein scaffold (competing with β-Catenin at N-Cadherin and binding TRIM25 to stabilize UAP1), and functions in diverse cellular contexts including ammonia detoxification in megakaryocytes and neurons, metabolic reprogramming (affecting the malate-aspartate shuttle, TCA cycle, and lipid deposition), thermogenic adipocyte differentiation through Prdm9-H3K4me3, osteogenic differentiation via FOXO3 O-GlcNAcylation, and pro-angiogenic signaling in cancer-associated fibroblasts via PI3K/AKT.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GLUL (glutamine synthetase) is an ATP-dependent enzyme that condenses glutamate and ammonia into glutamine, a reaction defined biochemically together with its 550-residue primary sequence [#0]. This catalytic activity supports de novo glutamine synthesis under glutamine deprivation [#8] and is deployed across diverse physiological contexts: detoxifying ammonia generated during ADAR1-mediated dsRNA editing in polyploidizing megakaryocytes to protect lysosomal and mitochondrial integrity during thrombocytopoiesis [#18], buffering glutamate metabolism in microglia away from a pro-inflammatory arginine-citrulline cycle after traumatic brain injury [#19], and sustaining glutamine-dependent antioxidant (glutathione) defense during spermatogenesis [#20]. In tumor metabolism, GLUL shapes flux through the malate-aspartate shuttle—its loss can paradoxically confer NSCLC drug resistance by boosting NADH production [#7]—and drives lipid deposition and ccRCC progression downstream of the VHL/HIF axis [#9]. GLUL also acts non-enzymatically as a protein scaffold: it competes with \\u03b2-Catenin for N-Cadherin binding to alter their ubiquitination and suppress gastric cancer metastasis [#10], and it binds the TRIM25 SPRY domain to stabilize UAP1, raising UDP-GlcNAc and FOXO3 O-GlcNAcylation to support osteogenic differentiation [#15]. GLUL abundance is controlled at multiple layers: transcriptionally by a PHF8/c-MYC/TEAD1 axis [#9], SIRT6 [#14], and METTL16/YTHDC1 m6A-dependent splicing [#13], and post-translationally through an N-terminal degron that drives glutamine-induced, ubiquitin-mediated degradation, with PCMT1/CRBN promoting cyclic-imide-dependent turnover [#17] and SYVN1 ubiquitinating GLUL at K259/K334 [#16]. De novo start-loss variants that initiate translation at Met18, downstream of the degron, yield an enzymatically competent but degradation- and feedback-resistant protein that causes developmental and epileptic encephalopathy [#12].\",\n  \"teleology\": [\n    {\n      \"year\": 1982,\n      \"claim\": \"Established the molecular identity and catalytic chemistry of GLUL, defining it as the ATP-dependent glutamine synthetase and providing its primary sequence.\",\n      \"evidence\": \"Protein purification with Edman degradation and GC-MS peptide sequencing\",\n      \"pmids\": [\"6288695\", \"6749844\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structural mechanism of catalysis resolved\", \"Regulation of the enzyme not addressed\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Resolved the human gene's chromosomal locus and distinguished the functional gene from pseudogene and related loci, clarifying which genomic sequence encodes active enzyme.\",\n      \"evidence\": \"FISH mapping with BAC clones and PCR/restriction analysis\",\n      \"pmids\": [\"8921392\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional role of related GLULL genes unknown\", \"No expression context established\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Showed that GLUL is not merely a glutamine producer but a node controlling redox/metabolic flux, since its loss reroutes carbon through the malate-aspartate shuttle to confer drug resistance in a cell-line-dependent manner.\",\n      \"evidence\": \"CRISPR knockout with 13C/15N isotope tracing, aminooxyacetic acid inhibition, and rescue in NSCLC lines\",\n      \"pmids\": [\"31817360\", \"30609375\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cell-line specificity (A549 vs H1299) unexplained\", \"Direct flux measurement of the enzyme in this context limited\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Directly demonstrated GLUL enzymatic flux in cancer cells, confirming it supports compensatory de novo glutamine synthesis under starvation.\",\n      \"evidence\": \"Dual 13C-glutamate + 15N-ammonium stable isotope resolved metabolomics\",\n      \"pmids\": [\"36032676\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Downstream fate of synthesized glutamine not fully mapped\", \"Single experimental system\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined a transcriptional control circuit and a metabolic output linking GLUL to tumor progression, placing it downstream of VHL/HIF via a PHF8/c-MYC/TEAD1 axis.\",\n      \"evidence\": \"CRISPR screen, Co-IP, ChIP, reporter assays, and xenografts in ccRCC\",\n      \"pmids\": [\"37531433\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relative contributions of enzymatic vs non-enzymatic roles in this context unresolved\", \"Single tumor type\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Revealed an enzyme-independent scaffolding function: GLUL competes with \\u03b2-Catenin for N-Cadherin, redirecting their ubiquitination to suppress gastric cancer metastasis.\",\n      \"evidence\": \"Reciprocal Co-IP, ubiquitination assays, knockdown/overexpression with in vivo tumor models\",\n      \"pmids\": [\"38322340\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of competitive binding not defined\", \"Ubiquitin ligases involved not identified\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Connected GLUL-derived glutamine to chromatin remodeling in adipocyte fate, showing it drives thermogenic differentiation through Prdm9-mediated H3K4me3.\",\n      \"evidence\": \"Genetic and metabolic manipulation, histone methylation and ChIP for C/EBP\\u03b2 at the Prdm9 enhancer, mouse models\",\n      \"pmids\": [\"37579296\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking glutamine to H3K4me3 not biochemically resolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Established the molecular basis of GLUL protein stability control via an N-terminal degron and showed how its loss causes human disease: start-loss variants initiating at Met18 yield a feedback- and degradation-resistant gain-of-function enzyme causing developmental and epileptic encephalopathy.\",\n      \"evidence\": \"Mass spectrometry of the variant protein, expression systems, scRNA-seq, in utero electroporation; replicated across 9 individuals\",\n      \"pmids\": [\"38579670\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Neuronal consequences of unregulated glutamine synthesis not fully mapped\", \"Therapeutic correction not addressed\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Added an RNA-modification layer to GLUL regulation, showing METTL16-deposited m6A on a transcript stem-loop is read by YTHDC1 to accelerate GLUL splicing and maturation.\",\n      \"evidence\": \"m6A analysis, YTHDC1 interaction studies, splicing assays, and in vivo Cr(VI) exposure models\",\n      \"pmids\": [\"39405702\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Generalizability beyond Cr(VI) toxicity context unknown\", \"Quantitative contribution to total GLUL output unclear\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified the E3 ligase and modification chemistry driving GLUL turnover: SYVN1 ubiquitinates GLUL at K259/K334, while PCMT1 enables CRBN-mediated degradation via C-terminal cyclic imide formation.\",\n      \"evidence\": \"Co-IP and site-specific mutagenesis in BMSC osteogenesis models; in vitro cyclic-imide reconstitution and CRBN knockout mice (PCMT1 study a preprint)\",\n      \"pmids\": [\"41980923\", \"bio_10.1101_2025.03.24.645050\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Interplay between SYVN1 and CRBN/PCMT1 pathways unresolved\", \"PCMT1/CRBN evidence is preprint only\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Extended the non-enzymatic scaffold role into the hexosamine pathway: GLUL binds the TRIM25 SPRY domain to stabilize UAP1, raising UDP-GlcNAc and FOXO3 O-GlcNAcylation to support osteogenic differentiation; SIRT6 was also shown to both transcribe and stabilize GLUL.\",\n      \"evidence\": \"Co-IP, ubiquitination assays, FOXO3 S296 mutagenesis, conditional GLUL knockout mice; SIRT6 study with ChIP, luciferase, isotope tracing and ICC models\",\n      \"pmids\": [\"40646162\", \"41136182\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Balance between enzymatic and scaffold contributions to differentiation unclear\", \"Mechanism of SIRT6-mediated stabilization not defined\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Demonstrated tissue-specific physiological roles for GLUL ammonia/glutamate handling: protecting megakaryocyte thrombocytopoiesis from ADAR1-derived ammonia, restraining microglial pro-inflammation after TBI, and sustaining glutathione-dependent antioxidant defense in spermatogenesis.\",\n      \"evidence\": \"Conditional/tissue-specific knockout mice with metabolic flux, organelle, inflammatory, and rescue (GSH) readouts\",\n      \"pmids\": [\"42237661\", \"41876004\", \"42025703\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Shared vs context-specific downstream effectors not unified\", \"Each phenotype from a single model system\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Showed GLUL supports the tumor microenvironment, driving pro-angiogenic activity in glioblastoma cancer-associated fibroblasts through PI3K/AKT signaling.\",\n      \"evidence\": \"CAF-specific GLUL knockdown, vasculature assays, and humanized orthotopic glioma models\",\n      \"pmids\": [\"41355614\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Link between GLUL metabolism and PI3K/AKT activation not mechanistically defined\", \"Single tumor model\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How GLUL partitions between its enzymatic glutamine-synthesis function and its non-enzymatic scaffolding roles in any given cell, and what governs that switch, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model distinguishing catalytic vs scaffold conformations\", \"Competing degradation pathways (SYVN1 vs CRBN/PCMT1) not reconciled\", \"Determinants of context-specific partner choice unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [0, 8]},\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0140313\", \"supporting_discovery_ids\": [10, 15]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 7, 8]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [12]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"N-Cadherin\", \"CTNNB1\", \"TRIM25\", \"UAP1\", \"SYVN1\", \"CRBN\", \"PCMT1\", \"YTHDC1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":{"gene":"GLUL","tier":"GROUNDING","verdict":"Evidence-grounding concern","subtype":"fabrication","uniprot_band":"rich","rules_fired":"R7","issue":"R7: fabricated (no corpus paper): 41980923"},"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}