{"gene":"GLMP","run_date":"2026-04-28T18:06:53","timeline":{"discoveries":[{"year":2009,"finding":"NCU-G1 (GLMP) is a highly glycosylated type I transmembrane protein localized to lysosomes via a C-terminal tyrosine-based sorting motif (Y400); mutation of this tyrosine to alanine impairs lysosomal targeting. The extensive glycosylation accounts for the difference between its calculated molecular mass (~39 kDa) and apparent molecular mass (~75 kDa), confirmed by N-glycosidase F digestion.","method":"Immunofluorescence co-localization with LAMP-1, subcellular fractionation with density shift, N-glycosidase F digestion, and site-directed mutagenesis of the tyrosine sorting motif","journal":"The Biochemical Journal","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal methods including mutagenesis, fractionation, and glycosidase digestion in a single study","pmids":["19489740"],"is_preprint":false},{"year":2007,"finding":"NCU-G1 (GLMP) can function as a transcription factor by binding the footprint 1 element of the human CRBP1 gene promoter (shown by EMSA) and activating transcription from this promoter. It also functions as a co-activator for ligand-activated PPARα, enhancing expression of a CAT reporter under the acyl-CoA oxidase promoter.","method":"Electrophoretic mobility shift assay (EMSA), transient transfection reporter assay in Drosophila S2 cells","journal":"BMC Molecular Biology","confidence":"Medium","confidence_rationale":"Tier 2–3 — functional reporter and EMSA in a single study, but no mutagenesis or structural validation of binding","pmids":["18021396"],"is_preprint":false},{"year":2014,"finding":"Loss of GLMP (NCU-G1) in mice causes spontaneous liver fibrosis with accumulation of lipofuscin and iron in Kupffer cells, increased hepatic cell death, oxidative stress, and active fibrogenesis, establishing GLMP as essential for lysosomal/hepatic homeostasis.","method":"Gene-trap knockout mouse model; histological, immunohistochemical, and biochemical analysis of liver","journal":"Disease Models & Mechanisms","confidence":"High","confidence_rationale":"Tier 2 — clean KO with defined cellular phenotype, replicated across multiple analyses","pmids":["24487409"],"is_preprint":false},{"year":2015,"finding":"Ablation of GLMP in mice results in metabolic dysregulation in liver, including increased glucose flux, increased de novo lipogenesis, lipid accumulation in hepatocytes, and elevated hepatic triacylglycerol, alongside reduced circulating triacylglycerol, glucose, and non-esterified fatty acids; gene expression analysis shows upregulation of fatty acid uptake and lipogenesis genes.","method":"Glmp knockout mouse model; metabolic flux assays in primary hepatocytes, gene expression analysis, blood biochemistry","journal":"PLoS ONE","confidence":"High","confidence_rationale":"Tier 2 — KO mouse with multiple orthogonal metabolic readouts in primary cells","pmids":["26047317"],"is_preprint":false},{"year":2016,"finding":"Loss of GLMP in skeletal muscle-derived myotubes results in increased glucose utilization, larger glycogen pools, and reduced fatty acid uptake/oxidation, accompanied by reduced expression of PPARα, PPARβ/δ, PPARγ, PGC1α, and lipid metabolism genes; GLMP-deficient myotubes adopt a more glycolytic phenotype.","method":"Primary myotubes from Glmp knockout mice; substrate oxidation assays, gene expression analysis","journal":"Archives of Physiology and Biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — KO-derived primary cells with multiple metabolic readouts, single lab","pmids":["26707125"],"is_preprint":false},{"year":2019,"finding":"MFSD1 and GLMP physically interact and form a tightly linked lysosomal membrane protein complex. GLMP is essential for maintaining normal levels of MFSD1 in lysosomes (and vice versa). Mfsd1 and Glmp knockout mice share identical phenotypes (splenomegaly and severe liver disease), and proteomics of isolated lysosomes from Mfsd1 knockout mice identified GLMP as a critical accessory subunit of MFSD1.","method":"Co-immunoprecipitation, lysosome proteomics, reciprocal knockout mouse models with identical phenotypes","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1–2 — reciprocal KO phenotype mirroring, co-IP, and lysosome proteomics in a single study","pmids":["31661432"],"is_preprint":false},{"year":2021,"finding":"BRG1 (a chromatin remodeler) binds the GLMP promoter and suppresses GLMP transcription in hepatocellular carcinoma cells; knockdown of BRG1 increases GLMP expression, reduces lipid droplets, and activates the PIK3AP1/PI3K/AKT pathway, effects that are partially reversed by further GLMP knockdown.","method":"Chromatin immunoprecipitation (ChIP), siRNA knockdown, fluorescent lipid staining (BODIPY/Oil Red O)","journal":"Digestive and Liver Disease","confidence":"Medium","confidence_rationale":"Tier 2–3 — ChIP validates direct promoter binding, functional rescue experiment supports pathway placement, single lab","pmids":["34158256"],"is_preprint":false},{"year":2023,"finding":"NAT10 induces ac4C (N4-acetylcytidine) modification on GLMP mRNA, stabilizing the transcript and increasing GLMP protein levels, which in turn activates the MAPK/ERK signaling pathway to promote metastasis in head and neck squamous cell carcinoma.","method":"Gain- and loss-of-function experiments (NAT10 overexpression/knockdown), ac4C-RNA immunoprecipitation, in vivo mouse metastasis model, pharmacological inhibition with remodelin","journal":"Cell Death & Disease","confidence":"Medium","confidence_rationale":"Tier 2–3 — functional epistasis (NAT10→ac4C→GLMP mRNA→MAPK/ERK) with in vivo validation, single lab","pmids":["37914704"],"is_preprint":false},{"year":2023,"finding":"MFSD1, GLMP, and GIMAP5 form a protein complex in lysosomes; MFSD1 and GLMP interactions with GIMAP5 are essential to maintain normal GIMAP5 expression levels, which is required for lymphocyte survival and liver homeostasis. Germline knockouts of Mfsd1, Glmp, and Gimap5 each independently cause lymphopenia, liver pathology, extramedullary hematopoiesis, and lipid deposition.","method":"Proteomic analysis of protein associations, germline knockout mice for each component, phenotypic comparison","journal":"PNAS","confidence":"High","confidence_rationale":"Tier 2 — proteomic identification of complex members confirmed by matching KO phenotypes across three independent alleles","pmids":["38055739"],"is_preprint":false},{"year":2024,"finding":"MFSD1-GLMP functions as a lysosomal dipeptide uniporter: the complex transports cationic, neutral, and anionic dipeptides out of the lysosome. Cryo-EM structure of the dipeptide-bound MFSD1-GLMP heterodimer in outward-open conformation resolved the heterodimer interface and structural basis for dipeptide selectivity. MFSD1 purified alone selectively binds diverse dipeptides, and electrophysiology/isotope tracer/fluorescence assays in Xenopus oocytes and proteoliposomes confirmed uniporter activity.","method":"Cryo-EM structure determination, untargeted metabolomics of MFSD1-deficient lysosomes, electrophysiology in Xenopus oocytes, isotope tracer assays, fluorescence-based transport assays in proteoliposomes, molecular dynamics simulations","journal":"Nature Cell Biology","confidence":"High","confidence_rationale":"Tier 1 — cryo-EM structure, in vitro reconstitution in proteoliposomes, electrophysiology, and metabolomics in one study","pmids":["38839979"],"is_preprint":false},{"year":2025,"finding":"GLMP promotes EGFR-TKI (osimertinib) resistance in non-small cell lung cancer by regulating ubiquitination of RhoA (reducing its degradation), thereby activating the RhoA pathway and inducing epithelial-mesenchymal transition, and by activating the late stage of autophagy through lysosomal hyperactivity.","method":"Overexpression and knockdown in vitro and in vivo, RhoA ubiquitination assay, autophagy flux assays, pharmacological inhibition of RhoA pathway and autophagy","journal":"NPJ Precision Oncology","confidence":"Medium","confidence_rationale":"Tier 2–3 — mechanistic pathway placement with ubiquitination assay and pharmacological rescue, single lab","pmids":["41298761"],"is_preprint":false}],"current_model":"GLMP (formerly NCU-G1) is a highly glycosylated, type I lysosomal integral membrane protein that forms a stable heterodimeric complex with the major facilitator superfamily transporter MFSD1 — together functioning as a general lysosomal dipeptide uniporter — and also associates with GIMAP5 to support lymphocyte survival and liver homeostasis; loss of GLMP destabilizes MFSD1 in lysosomes, causes progressive liver fibrosis, and induces metabolic dysregulation, while GLMP expression is regulated transcriptionally by BRG1 and post-transcriptionally by NAT10-mediated ac4C mRNA modification."},"narrative":{"teleology":[{"year":2007,"claim":"The first functional study attributed transcription-factor and PPARα co-activator activities to NCU-G1/GLMP, suggesting a dual nuclear/membrane role that framed subsequent investigations into its primary cellular function.","evidence":"EMSA and reporter assays in Drosophila S2 cells","pmids":["18021396"],"confidence":"Medium","gaps":["No mutagenesis or structural data confirmed direct DNA binding","Activity demonstrated only in heterologous insect cells, not validated in mammalian systems","Subsequent studies repositioned GLMP as a lysosomal membrane protein rather than a transcription factor"]},{"year":2009,"claim":"Establishing GLMP as a lysosomal protein resolved the question of its primary subcellular localization and revealed that heavy N-glycosylation and a C-terminal tyrosine-based motif govern its trafficking and apparent molecular mass.","evidence":"Immunofluorescence co-localization with LAMP-1, subcellular fractionation, N-glycosidase F digestion, and Y400A mutagenesis","pmids":["19489740"],"confidence":"High","gaps":["Lysosomal function of GLMP was unknown","Whether glycosylation served a protective or functional role was not addressed"]},{"year":2014,"claim":"Knockout mouse studies demonstrated that GLMP is essential for hepatic homeostasis, as its loss causes spontaneous liver fibrosis, lipofuscin and iron accumulation in Kupffer cells, and oxidative stress — providing the first evidence of organismal consequence.","evidence":"Gene-trap knockout mouse with histological, immunohistochemical, and biochemical liver analysis","pmids":["24487409"],"confidence":"High","gaps":["Molecular mechanism linking GLMP loss to liver fibrosis was unknown","Whether GLMP acted alone or as part of a complex was unresolved"]},{"year":2015,"claim":"Metabolic characterization of GLMP-null hepatocytes revealed that GLMP loss causes increased glucose flux, de novo lipogenesis, and lipid accumulation, establishing GLMP as a regulator of hepatic metabolic partitioning.","evidence":"Metabolic flux assays in primary Glmp-KO hepatocytes, blood biochemistry, gene expression profiling","pmids":["26047317"],"confidence":"High","gaps":["Whether metabolic dysregulation was a direct effect of impaired lysosomal transport or secondary to liver damage was unclear","GLMP's molecular partner and transport substrate remained unidentified"]},{"year":2016,"claim":"Extension to skeletal muscle showed that GLMP deficiency shifts myotubes toward glycolytic metabolism with reduced PPAR and lipid oxidation gene expression, demonstrating that GLMP's metabolic role extends beyond the liver.","evidence":"Substrate oxidation and gene expression assays in primary myotubes from Glmp-KO mice","pmids":["26707125"],"confidence":"Medium","gaps":["Mechanism of PPAR downregulation in GLMP-null muscle was not established","Whether this reflects a cell-autonomous lysosomal defect versus systemic metabolic changes was unresolved"]},{"year":2019,"claim":"Identification of GLMP as the obligate partner of the transporter MFSD1 revealed that the two proteins form a tightly linked lysosomal complex and are mutually required for stability, resolving the question of GLMP's direct molecular function at the lysosomal membrane.","evidence":"Co-immunoprecipitation, lysosome proteomics, and phenotypic identity of reciprocal Mfsd1 and Glmp knockout mice","pmids":["31661432"],"confidence":"High","gaps":["The transport substrate of the MFSD1–GLMP complex was unknown","Structural basis of the heterodimer was unresolved"]},{"year":2021,"claim":"ChIP and knockdown studies showed that BRG1 directly binds the GLMP promoter and represses its transcription, connecting chromatin remodeling to GLMP-dependent lipid metabolism in hepatocellular carcinoma cells.","evidence":"ChIP, siRNA knockdown, lipid staining, and epistasis experiments in HCC cell lines","pmids":["34158256"],"confidence":"Medium","gaps":["Whether BRG1-mediated GLMP repression operates in normal hepatocytes or is cancer-specific was not tested","Downstream pathway activation (PIK3AP1/PI3K/AKT) was not validated with genetic rescue"]},{"year":2023,"claim":"Two studies expanded GLMP's interactome and regulatory network: proteomics identified a tripartite MFSD1–GLMP–GIMAP5 complex required for lymphocyte survival and liver homeostasis, while ac4C-RIP showed that NAT10-mediated mRNA acetylation stabilizes GLMP transcripts to activate MAPK/ERK signaling in head and neck cancer.","evidence":"Proteomic complex identification with matching triple-KO phenotypes (PNAS); NAT10 gain/loss-of-function, ac4C-RIP, and in vivo metastasis models (Cell Death & Disease)","pmids":["38055739","37914704"],"confidence":"High","gaps":["How GIMAP5 stability depends on MFSD1–GLMP at a structural level is unknown","Whether GLMP-driven MAPK/ERK activation in cancer reflects its dipeptide transport function or an independent activity is unresolved","The stoichiometry and assembly pathway of the MFSD1–GLMP–GIMAP5 complex are not defined"]},{"year":2024,"claim":"Cryo-EM structure determination and reconstitution in proteoliposomes definitively established MFSD1–GLMP as a lysosomal dipeptide uniporter, resolving the substrate identity and transport mechanism that had been sought since the complex was identified.","evidence":"Cryo-EM of outward-open dipeptide-bound MFSD1–GLMP heterodimer, untargeted lysosome metabolomics, electrophysiology in Xenopus oocytes, isotope tracer and fluorescence transport assays in proteoliposomes","pmids":["38839979"],"confidence":"High","gaps":["Structural basis for GLMP's role in stabilizing MFSD1 versus direct involvement in substrate selectivity requires further mutagenesis","Whether dipeptide transport deficiency alone explains all KO phenotypes (fibrosis, lymphopenia) is not established"]},{"year":2025,"claim":"GLMP was shown to promote EGFR-TKI resistance in lung cancer by stabilizing RhoA through regulation of its ubiquitination and by enhancing autophagic flux via lysosomal hyperactivity, expanding GLMP's known roles into drug-resistance mechanisms.","evidence":"Overexpression/knockdown in NSCLC cells and xenograft models, RhoA ubiquitination assays, autophagy flux assays, pharmacological rescue","pmids":["41298761"],"confidence":"Medium","gaps":["Whether GLMP regulates RhoA ubiquitination directly or indirectly through dipeptide transport is unknown","Single-lab finding not yet independently replicated","Relevance of this mechanism beyond osimertinib-resistant NSCLC is untested"]},{"year":null,"claim":"Key open questions include whether impaired dipeptide export fully explains the liver fibrosis, lymphopenia, and metabolic phenotypes of GLMP-null animals; how GLMP structurally contributes to MFSD1 folding and stability versus directly participating in transport; and what physiological signals regulate GLMP expression in non-cancerous tissues.","evidence":"","pmids":[],"confidence":"High","gaps":["No disease-rescue experiment has tested whether restoring dipeptide transport alone reverses KO phenotypes","The structural role of GLMP's glycosylated luminal domain in the heterodimer is not mechanistically defined","Physiological transcriptional and post-transcriptional regulation of GLMP outside cancer contexts is largely unexplored"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[9]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[5,9]}],"localization":[{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[0,5,8,9]}],"pathway":[{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[9]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[3,4]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[10]}],"complexes":["MFSD1-GLMP heterodimer","MFSD1-GLMP-GIMAP5 complex"],"partners":["MFSD1","GIMAP5","BRG1","NAT10"],"other_free_text":[]},"mechanistic_narrative":"GLMP is a heavily glycosylated type I lysosomal integral membrane protein that functions as an essential accessory subunit of the major facilitator superfamily transporter MFSD1, together forming a heterodimeric lysosomal dipeptide uniporter that exports cationic, neutral, and anionic dipeptides from the lysosomal lumen [PMID:38839979]. GLMP reaches lysosomes via a C-terminal tyrosine-based sorting motif and is required to stabilize MFSD1 at the lysosomal membrane; reciprocal knockout of either gene produces identical phenotypes including splenomegaly, progressive liver fibrosis, lipofuscin accumulation, and metabolic dysregulation characterized by increased hepatic lipogenesis and glycolytic reprogramming [PMID:19489740, PMID:31661432, PMID:24487409, PMID:26047317]. GLMP additionally associates with GIMAP5 in a tripartite MFSD1–GLMP–GIMAP5 lysosomal complex that maintains GIMAP5 protein levels and is required for lymphocyte survival and liver homeostasis, as germline loss of any single component causes lymphopenia and hepatic pathology [PMID:38055739]. GLMP expression is transcriptionally repressed by BRG1 and post-transcriptionally stabilized by NAT10-mediated ac4C modification of its mRNA [PMID:34158256, PMID:37914704]."},"prefetch_data":{"uniprot":{"accession":"Q8WWB7","full_name":"Glycosylated lysosomal membrane protein","aliases":["Lysosomal protein NCU-G1"],"length_aa":406,"mass_kda":43.9,"function":"Required to protect lysosomal transporter MFSD1 from lysosomal proteolysis and for MFSD1 lysosomal localization","subcellular_location":"Lysosome membrane","url":"https://www.uniprot.org/uniprotkb/Q8WWB7/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GLMP","classification":"Not Classified","n_dependent_lines":9,"n_total_lines":1208,"dependency_fraction":0.0074503311258278145},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/GLMP","total_profiled":1310},"omim":[{"mim_id":"619976","title":"MAJOR FACILITATOR SUPERFAMILY DOMAIN-CONTAINING PROTEIN 1; MFSD1","url":"https://www.omim.org/entry/619976"},{"mim_id":"619958","title":"GLYCOSYLATED LYSOSOMAL MEMBRANE PROTEIN; GLMP","url":"https://www.omim.org/entry/619958"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/GLMP"},"hgnc":{"alias_symbol":["MGC31963","NCU-G1","lnc-UCID"],"prev_symbol":["C1orf85"]},"alphafold":{"accession":"Q8WWB7","domains":[{"cath_id":"-","chopping":"41-360","consensus_level":"medium","plddt":91.709,"start":41,"end":360}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8WWB7","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8WWB7-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8WWB7-F1-predicted_aligned_error_v6.png","plddt_mean":86.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GLMP","jax_strain_url":"https://www.jax.org/strain/search?query=GLMP"},"sequence":{"accession":"Q8WWB7","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8WWB7.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8WWB7/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8WWB7"}},"corpus_meta":[{"pmid":"30865310","id":"PMC_30865310","title":"Lnc-UCID Promotes G1/S Transition and Hepatoma Growth by Preventing DHX9-Mediated CDK6 Down-regulation.","date":"2019","source":"Hepatology (Baltimore, Md.)","url":"https://pubmed.ncbi.nlm.nih.gov/30865310","citation_count":89,"is_preprint":false},{"pmid":"37914704","id":"PMC_37914704","title":"N4-acetylcytidine-dependent GLMP mRNA stabilization by NAT10 promotes head and neck squamous cell carcinoma metastasis and remodels tumor microenvironment through MAPK/ERK signaling pathway.","date":"2023","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/37914704","citation_count":37,"is_preprint":false},{"pmid":"31661432","id":"PMC_31661432","title":"The lysosomal transporter MFSD1 is essential for liver homeostasis and critically depends on its accessory subunit GLMP.","date":"2019","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/31661432","citation_count":26,"is_preprint":false},{"pmid":"24487409","id":"PMC_24487409","title":"Loss of lysosomal membrane protein NCU-G1 in mice results in spontaneous liver fibrosis with accumulation of lipofuscin and iron in Kupffer cells.","date":"2014","source":"Disease models & mechanisms","url":"https://pubmed.ncbi.nlm.nih.gov/24487409","citation_count":21,"is_preprint":false},{"pmid":"19489740","id":"PMC_19489740","title":"NCU-G1 is a highly glycosylated integral membrane protein of the lysosome.","date":"2009","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/19489740","citation_count":20,"is_preprint":false},{"pmid":"34158256","id":"PMC_34158256","title":"BRG1 regulates lipid metabolism in hepatocellular carcinoma through the PIK3AP1/PI3K/AKT pathway by mediating GLMP expression.","date":"2021","source":"Digestive and liver disease : official journal of the Italian Society of Gastroenterology and the Italian Association for the Study of the Liver","url":"https://pubmed.ncbi.nlm.nih.gov/34158256","citation_count":14,"is_preprint":false},{"pmid":"26047317","id":"PMC_26047317","title":"Lack of the Lysosomal Membrane Protein, GLMP, in Mice Results in Metabolic Dysregulation in Liver.","date":"2015","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/26047317","citation_count":13,"is_preprint":false},{"pmid":"27141234","id":"PMC_27141234","title":"Age-dependent development of liver fibrosis in Glmp (gt/gt) mice.","date":"2016","source":"Fibrogenesis & tissue repair","url":"https://pubmed.ncbi.nlm.nih.gov/27141234","citation_count":9,"is_preprint":false},{"pmid":"26707125","id":"PMC_26707125","title":"Increased glucose utilization and decreased fatty acid metabolism in myotubes from Glmp(gt/gt) mice.","date":"2016","source":"Archives of physiology and biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/26707125","citation_count":9,"is_preprint":false},{"pmid":"38839979","id":"PMC_38839979","title":"MFSD1 with its accessory subunit GLMP functions as a general dipeptide uniporter in lysosomes.","date":"2024","source":"Nature cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/38839979","citation_count":8,"is_preprint":false},{"pmid":"38055739","id":"PMC_38055739","title":"Essential role of MFSD1-GLMP-GIMAP5 in lymphocyte survival and liver homeostasis.","date":"2023","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/38055739","citation_count":8,"is_preprint":false},{"pmid":"18021396","id":"PMC_18021396","title":"Human NCU-G1 can function as a transcription factor and as a nuclear receptor co-activator.","date":"2007","source":"BMC molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/18021396","citation_count":7,"is_preprint":false},{"pmid":"41298761","id":"PMC_41298761","title":"GLMP promotes EGFR-TKI resistance by activating autophagy and RhoA pathway in non-small cell lung cancer.","date":"2025","source":"NPJ precision oncology","url":"https://pubmed.ncbi.nlm.nih.gov/41298761","citation_count":2,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7913,"output_tokens":2841,"usd":0.033177},"stage2":{"model":"claude-opus-4-6","input_tokens":6219,"output_tokens":2969,"usd":0.15798},"total_usd":0.191157,"stage1_batch_id":"msgbatch_01DzrsgVgYngY1hvM3DU1yF2","stage2_batch_id":"msgbatch_01KA9b7iRzKFdhoBUT7vCvSe","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2009,\n      \"finding\": \"NCU-G1 (GLMP) is a highly glycosylated type I transmembrane protein localized to lysosomes via a C-terminal tyrosine-based sorting motif (Y400); mutation of this tyrosine to alanine impairs lysosomal targeting. The extensive glycosylation accounts for the difference between its calculated molecular mass (~39 kDa) and apparent molecular mass (~75 kDa), confirmed by N-glycosidase F digestion.\",\n      \"method\": \"Immunofluorescence co-localization with LAMP-1, subcellular fractionation with density shift, N-glycosidase F digestion, and site-directed mutagenesis of the tyrosine sorting motif\",\n      \"journal\": \"The Biochemical Journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods including mutagenesis, fractionation, and glycosidase digestion in a single study\",\n      \"pmids\": [\"19489740\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"NCU-G1 (GLMP) can function as a transcription factor by binding the footprint 1 element of the human CRBP1 gene promoter (shown by EMSA) and activating transcription from this promoter. It also functions as a co-activator for ligand-activated PPARα, enhancing expression of a CAT reporter under the acyl-CoA oxidase promoter.\",\n      \"method\": \"Electrophoretic mobility shift assay (EMSA), transient transfection reporter assay in Drosophila S2 cells\",\n      \"journal\": \"BMC Molecular Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — functional reporter and EMSA in a single study, but no mutagenesis or structural validation of binding\",\n      \"pmids\": [\"18021396\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Loss of GLMP (NCU-G1) in mice causes spontaneous liver fibrosis with accumulation of lipofuscin and iron in Kupffer cells, increased hepatic cell death, oxidative stress, and active fibrogenesis, establishing GLMP as essential for lysosomal/hepatic homeostasis.\",\n      \"method\": \"Gene-trap knockout mouse model; histological, immunohistochemical, and biochemical analysis of liver\",\n      \"journal\": \"Disease Models & Mechanisms\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined cellular phenotype, replicated across multiple analyses\",\n      \"pmids\": [\"24487409\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Ablation of GLMP in mice results in metabolic dysregulation in liver, including increased glucose flux, increased de novo lipogenesis, lipid accumulation in hepatocytes, and elevated hepatic triacylglycerol, alongside reduced circulating triacylglycerol, glucose, and non-esterified fatty acids; gene expression analysis shows upregulation of fatty acid uptake and lipogenesis genes.\",\n      \"method\": \"Glmp knockout mouse model; metabolic flux assays in primary hepatocytes, gene expression analysis, blood biochemistry\",\n      \"journal\": \"PLoS ONE\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mouse with multiple orthogonal metabolic readouts in primary cells\",\n      \"pmids\": [\"26047317\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Loss of GLMP in skeletal muscle-derived myotubes results in increased glucose utilization, larger glycogen pools, and reduced fatty acid uptake/oxidation, accompanied by reduced expression of PPARα, PPARβ/δ, PPARγ, PGC1α, and lipid metabolism genes; GLMP-deficient myotubes adopt a more glycolytic phenotype.\",\n      \"method\": \"Primary myotubes from Glmp knockout mice; substrate oxidation assays, gene expression analysis\",\n      \"journal\": \"Archives of Physiology and Biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KO-derived primary cells with multiple metabolic readouts, single lab\",\n      \"pmids\": [\"26707125\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"MFSD1 and GLMP physically interact and form a tightly linked lysosomal membrane protein complex. GLMP is essential for maintaining normal levels of MFSD1 in lysosomes (and vice versa). Mfsd1 and Glmp knockout mice share identical phenotypes (splenomegaly and severe liver disease), and proteomics of isolated lysosomes from Mfsd1 knockout mice identified GLMP as a critical accessory subunit of MFSD1.\",\n      \"method\": \"Co-immunoprecipitation, lysosome proteomics, reciprocal knockout mouse models with identical phenotypes\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — reciprocal KO phenotype mirroring, co-IP, and lysosome proteomics in a single study\",\n      \"pmids\": [\"31661432\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"BRG1 (a chromatin remodeler) binds the GLMP promoter and suppresses GLMP transcription in hepatocellular carcinoma cells; knockdown of BRG1 increases GLMP expression, reduces lipid droplets, and activates the PIK3AP1/PI3K/AKT pathway, effects that are partially reversed by further GLMP knockdown.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP), siRNA knockdown, fluorescent lipid staining (BODIPY/Oil Red O)\",\n      \"journal\": \"Digestive and Liver Disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — ChIP validates direct promoter binding, functional rescue experiment supports pathway placement, single lab\",\n      \"pmids\": [\"34158256\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NAT10 induces ac4C (N4-acetylcytidine) modification on GLMP mRNA, stabilizing the transcript and increasing GLMP protein levels, which in turn activates the MAPK/ERK signaling pathway to promote metastasis in head and neck squamous cell carcinoma.\",\n      \"method\": \"Gain- and loss-of-function experiments (NAT10 overexpression/knockdown), ac4C-RNA immunoprecipitation, in vivo mouse metastasis model, pharmacological inhibition with remodelin\",\n      \"journal\": \"Cell Death & Disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — functional epistasis (NAT10→ac4C→GLMP mRNA→MAPK/ERK) with in vivo validation, single lab\",\n      \"pmids\": [\"37914704\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MFSD1, GLMP, and GIMAP5 form a protein complex in lysosomes; MFSD1 and GLMP interactions with GIMAP5 are essential to maintain normal GIMAP5 expression levels, which is required for lymphocyte survival and liver homeostasis. Germline knockouts of Mfsd1, Glmp, and Gimap5 each independently cause lymphopenia, liver pathology, extramedullary hematopoiesis, and lipid deposition.\",\n      \"method\": \"Proteomic analysis of protein associations, germline knockout mice for each component, phenotypic comparison\",\n      \"journal\": \"PNAS\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — proteomic identification of complex members confirmed by matching KO phenotypes across three independent alleles\",\n      \"pmids\": [\"38055739\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MFSD1-GLMP functions as a lysosomal dipeptide uniporter: the complex transports cationic, neutral, and anionic dipeptides out of the lysosome. Cryo-EM structure of the dipeptide-bound MFSD1-GLMP heterodimer in outward-open conformation resolved the heterodimer interface and structural basis for dipeptide selectivity. MFSD1 purified alone selectively binds diverse dipeptides, and electrophysiology/isotope tracer/fluorescence assays in Xenopus oocytes and proteoliposomes confirmed uniporter activity.\",\n      \"method\": \"Cryo-EM structure determination, untargeted metabolomics of MFSD1-deficient lysosomes, electrophysiology in Xenopus oocytes, isotope tracer assays, fluorescence-based transport assays in proteoliposomes, molecular dynamics simulations\",\n      \"journal\": \"Nature Cell Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structure, in vitro reconstitution in proteoliposomes, electrophysiology, and metabolomics in one study\",\n      \"pmids\": [\"38839979\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"GLMP promotes EGFR-TKI (osimertinib) resistance in non-small cell lung cancer by regulating ubiquitination of RhoA (reducing its degradation), thereby activating the RhoA pathway and inducing epithelial-mesenchymal transition, and by activating the late stage of autophagy through lysosomal hyperactivity.\",\n      \"method\": \"Overexpression and knockdown in vitro and in vivo, RhoA ubiquitination assay, autophagy flux assays, pharmacological inhibition of RhoA pathway and autophagy\",\n      \"journal\": \"NPJ Precision Oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — mechanistic pathway placement with ubiquitination assay and pharmacological rescue, single lab\",\n      \"pmids\": [\"41298761\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GLMP (formerly NCU-G1) is a highly glycosylated, type I lysosomal integral membrane protein that forms a stable heterodimeric complex with the major facilitator superfamily transporter MFSD1 — together functioning as a general lysosomal dipeptide uniporter — and also associates with GIMAP5 to support lymphocyte survival and liver homeostasis; loss of GLMP destabilizes MFSD1 in lysosomes, causes progressive liver fibrosis, and induces metabolic dysregulation, while GLMP expression is regulated transcriptionally by BRG1 and post-transcriptionally by NAT10-mediated ac4C mRNA modification.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"GLMP is a heavily glycosylated type I lysosomal integral membrane protein that functions as an essential accessory subunit of the major facilitator superfamily transporter MFSD1, together forming a heterodimeric lysosomal dipeptide uniporter that exports cationic, neutral, and anionic dipeptides from the lysosomal lumen [PMID:38839979]. GLMP reaches lysosomes via a C-terminal tyrosine-based sorting motif and is required to stabilize MFSD1 at the lysosomal membrane; reciprocal knockout of either gene produces identical phenotypes including splenomegaly, progressive liver fibrosis, lipofuscin accumulation, and metabolic dysregulation characterized by increased hepatic lipogenesis and glycolytic reprogramming [PMID:19489740, PMID:31661432, PMID:24487409, PMID:26047317]. GLMP additionally associates with GIMAP5 in a tripartite MFSD1–GLMP–GIMAP5 lysosomal complex that maintains GIMAP5 protein levels and is required for lymphocyte survival and liver homeostasis, as germline loss of any single component causes lymphopenia and hepatic pathology [PMID:38055739]. GLMP expression is transcriptionally repressed by BRG1 and post-transcriptionally stabilized by NAT10-mediated ac4C modification of its mRNA [PMID:34158256, PMID:37914704].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"The first functional study attributed transcription-factor and PPARα co-activator activities to NCU-G1/GLMP, suggesting a dual nuclear/membrane role that framed subsequent investigations into its primary cellular function.\",\n      \"evidence\": \"EMSA and reporter assays in Drosophila S2 cells\",\n      \"pmids\": [\"18021396\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No mutagenesis or structural data confirmed direct DNA binding\",\n        \"Activity demonstrated only in heterologous insect cells, not validated in mammalian systems\",\n        \"Subsequent studies repositioned GLMP as a lysosomal membrane protein rather than a transcription factor\"\n      ]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Establishing GLMP as a lysosomal protein resolved the question of its primary subcellular localization and revealed that heavy N-glycosylation and a C-terminal tyrosine-based motif govern its trafficking and apparent molecular mass.\",\n      \"evidence\": \"Immunofluorescence co-localization with LAMP-1, subcellular fractionation, N-glycosidase F digestion, and Y400A mutagenesis\",\n      \"pmids\": [\"19489740\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Lysosomal function of GLMP was unknown\",\n        \"Whether glycosylation served a protective or functional role was not addressed\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Knockout mouse studies demonstrated that GLMP is essential for hepatic homeostasis, as its loss causes spontaneous liver fibrosis, lipofuscin and iron accumulation in Kupffer cells, and oxidative stress — providing the first evidence of organismal consequence.\",\n      \"evidence\": \"Gene-trap knockout mouse with histological, immunohistochemical, and biochemical liver analysis\",\n      \"pmids\": [\"24487409\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Molecular mechanism linking GLMP loss to liver fibrosis was unknown\",\n        \"Whether GLMP acted alone or as part of a complex was unresolved\"\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Metabolic characterization of GLMP-null hepatocytes revealed that GLMP loss causes increased glucose flux, de novo lipogenesis, and lipid accumulation, establishing GLMP as a regulator of hepatic metabolic partitioning.\",\n      \"evidence\": \"Metabolic flux assays in primary Glmp-KO hepatocytes, blood biochemistry, gene expression profiling\",\n      \"pmids\": [\"26047317\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether metabolic dysregulation was a direct effect of impaired lysosomal transport or secondary to liver damage was unclear\",\n        \"GLMP's molecular partner and transport substrate remained unidentified\"\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Extension to skeletal muscle showed that GLMP deficiency shifts myotubes toward glycolytic metabolism with reduced PPAR and lipid oxidation gene expression, demonstrating that GLMP's metabolic role extends beyond the liver.\",\n      \"evidence\": \"Substrate oxidation and gene expression assays in primary myotubes from Glmp-KO mice\",\n      \"pmids\": [\"26707125\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism of PPAR downregulation in GLMP-null muscle was not established\",\n        \"Whether this reflects a cell-autonomous lysosomal defect versus systemic metabolic changes was unresolved\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identification of GLMP as the obligate partner of the transporter MFSD1 revealed that the two proteins form a tightly linked lysosomal complex and are mutually required for stability, resolving the question of GLMP's direct molecular function at the lysosomal membrane.\",\n      \"evidence\": \"Co-immunoprecipitation, lysosome proteomics, and phenotypic identity of reciprocal Mfsd1 and Glmp knockout mice\",\n      \"pmids\": [\"31661432\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"The transport substrate of the MFSD1–GLMP complex was unknown\",\n        \"Structural basis of the heterodimer was unresolved\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"ChIP and knockdown studies showed that BRG1 directly binds the GLMP promoter and represses its transcription, connecting chromatin remodeling to GLMP-dependent lipid metabolism in hepatocellular carcinoma cells.\",\n      \"evidence\": \"ChIP, siRNA knockdown, lipid staining, and epistasis experiments in HCC cell lines\",\n      \"pmids\": [\"34158256\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether BRG1-mediated GLMP repression operates in normal hepatocytes or is cancer-specific was not tested\",\n        \"Downstream pathway activation (PIK3AP1/PI3K/AKT) was not validated with genetic rescue\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Two studies expanded GLMP's interactome and regulatory network: proteomics identified a tripartite MFSD1–GLMP–GIMAP5 complex required for lymphocyte survival and liver homeostasis, while ac4C-RIP showed that NAT10-mediated mRNA acetylation stabilizes GLMP transcripts to activate MAPK/ERK signaling in head and neck cancer.\",\n      \"evidence\": \"Proteomic complex identification with matching triple-KO phenotypes (PNAS); NAT10 gain/loss-of-function, ac4C-RIP, and in vivo metastasis models (Cell Death & Disease)\",\n      \"pmids\": [\"38055739\", \"37914704\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How GIMAP5 stability depends on MFSD1–GLMP at a structural level is unknown\",\n        \"Whether GLMP-driven MAPK/ERK activation in cancer reflects its dipeptide transport function or an independent activity is unresolved\",\n        \"The stoichiometry and assembly pathway of the MFSD1–GLMP–GIMAP5 complex are not defined\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Cryo-EM structure determination and reconstitution in proteoliposomes definitively established MFSD1–GLMP as a lysosomal dipeptide uniporter, resolving the substrate identity and transport mechanism that had been sought since the complex was identified.\",\n      \"evidence\": \"Cryo-EM of outward-open dipeptide-bound MFSD1–GLMP heterodimer, untargeted lysosome metabolomics, electrophysiology in Xenopus oocytes, isotope tracer and fluorescence transport assays in proteoliposomes\",\n      \"pmids\": [\"38839979\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis for GLMP's role in stabilizing MFSD1 versus direct involvement in substrate selectivity requires further mutagenesis\",\n        \"Whether dipeptide transport deficiency alone explains all KO phenotypes (fibrosis, lymphopenia) is not established\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"GLMP was shown to promote EGFR-TKI resistance in lung cancer by stabilizing RhoA through regulation of its ubiquitination and by enhancing autophagic flux via lysosomal hyperactivity, expanding GLMP's known roles into drug-resistance mechanisms.\",\n      \"evidence\": \"Overexpression/knockdown in NSCLC cells and xenograft models, RhoA ubiquitination assays, autophagy flux assays, pharmacological rescue\",\n      \"pmids\": [\"41298761\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether GLMP regulates RhoA ubiquitination directly or indirectly through dipeptide transport is unknown\",\n        \"Single-lab finding not yet independently replicated\",\n        \"Relevance of this mechanism beyond osimertinib-resistant NSCLC is untested\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key open questions include whether impaired dipeptide export fully explains the liver fibrosis, lymphopenia, and metabolic phenotypes of GLMP-null animals; how GLMP structurally contributes to MFSD1 folding and stability versus directly participating in transport; and what physiological signals regulate GLMP expression in non-cancerous tissues.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No disease-rescue experiment has tested whether restoring dipeptide transport alone reverses KO phenotypes\",\n        \"The structural role of GLMP's glycosylated luminal domain in the heterodimer is not mechanistically defined\",\n        \"Physiological transcriptional and post-transcriptional regulation of GLMP outside cancer contexts is largely unexplored\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [9]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [5, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [0, 5, 8, 9]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [9]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [3, 4]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [10]}\n    ],\n    \"complexes\": [\n      \"MFSD1-GLMP heterodimer\",\n      \"MFSD1-GLMP-GIMAP5 complex\"\n    ],\n    \"partners\": [\n      \"MFSD1\",\n      \"GIMAP5\",\n      \"BRG1\",\n      \"NAT10\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}