{"gene":"GABARAPL1","run_date":"2026-06-09T23:54:44","timeline":{"discoveries":[{"year":2003,"finding":"A single protease, Apg4B/autophagin-1, acts as a processing/deconjugating enzyme for GABARAPL1 (Apg8L) and three other mammalian Atg8 homologues (GATE-16, GABARAP, MAP1-LC3), as demonstrated using electrophilic probes that form specific adducts in cell lysates.","method":"Activity-based protein profiling with electrophilic probes derived from Atg8 homologues; adduct formation in crude cell lysates","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro biochemical assay with electrophilic probe substrates, specific adduct formation, replicated across four substrates in one rigorous study","pmids":["14530254"],"is_preprint":false},{"year":2006,"finding":"Atg8L (GABARAPL1) C-terminus is cleaved by human Atg4B (but not Atg4A or Atg4C) in vitro; the processed form (Atg8L-I) forms an E1-substrate intermediate with Atg7 and an E2-substrate intermediate with Atg3, establishing it as the fourth mammalian Atg8 conjugation modifier.","method":"In vitro cleavage assay with recombinant Atg4A/B/C; co-expression with catalytic mutants Atg7(C572S) and Atg3(C264S) to trap intermediates; subcellular fractionation and fluorescence microscopy in HeLa cells","journal":"The FEBS journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution of E1/E2 conjugation intermediates with mutagenesis controls; multiple orthogonal methods in one study","pmids":["16704426"],"is_preprint":false},{"year":2009,"finding":"Caspase-3 cleaves Atg4D in vitro and in apoptotic cells; the resulting truncated ΔN63 Atg4D shows increased activity against GABARAPL1, stimulating its delipidation. siRNA silencing of Atg4D abrogates GABARAPL1 autophagosome formation and sensitises cells to starvation- and staurosporine-induced death.","method":"In vitro caspase cleavage assay; delipidation assay in living cells; siRNA knockdown with cell death readouts; fluorescence microscopy of autophagosome markers","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro enzymatic assay plus cell-based loss-of-function with multiple orthogonal readouts in one study","pmids":["19549685"],"is_preprint":false},{"year":2010,"finding":"GABARAPL1 is proteolytically cleaved at Gly116, becomes lipidated and associated with intracellular membranes, is delipidated by Atg4B, accumulates in vesicles upon lysosomal inhibition, and partially co-localises with LC3 and LysoTracker-positive structures, demonstrating its association with autophagic vesicles.","method":"Immunofluorescence microscopy; subcellular fractionation; Atg4B delipidation assay; lysosomal inhibitor treatment; co-localisation with LC3/LysoTracker","journal":"Autophagy","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal cell-based methods (fractionation, delipidation assay, imaging) in one study confirming lipidation and autophagosome association","pmids":["20404487"],"is_preprint":false},{"year":2004,"finding":"GEC1 (GABARAPL1) interacts in vitro with tubulin and GABAA receptor, promotes tubulin assembly and microtubule bundling, and localises in perinuclear vesicles in living cells.","method":"In vitro co-sedimentation/pull-down with tubulin and GABAA receptor; GEC1-GFP live-cell imaging; tubulin polymerisation assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct in vitro binding and functional tubulin polymerisation assay, plus localisation; single lab","pmids":["15530441"],"is_preprint":false},{"year":2006,"finding":"GEC1 (GABARAPL1) directly binds the C-tail of the human kappa opioid receptor (hKOR) via hydrophobic contacts, co-immunoprecipitates with FLAG-hKOR in CHO cells, and facilitates trafficking of hKOR from the ER/Golgi to the plasma membrane, increasing total and cell-surface KOR levels. GEC1 also interacts with N-ethylmaleimide-sensitive factor (NSF) in pull-down assays and co-immunoprecipitates with NSF in rat brain extracts.","method":"Yeast two-hybrid screening; GST pull-down; co-immunoprecipitation; pulse-chase [35S]Met/Cys labelling; flow cytometry of surface receptor; fluorescence localisation in CHO cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, GST pull-down, pulse-chase trafficking assay, and subcellular localisation all converge on one mechanism; multiple orthogonal methods","pmids":["16431922"],"is_preprint":false},{"year":2008,"finding":"GEC1 interaction with hKOR requires three hKOR residues (Phe345, Pro346, Met350) and seven GEC1 residues (Tyr49, Val51, Leu55, Thr56, Val57, Phe60, Ile64), mediated by hydrophobic contacts between the kinked hKOR C-tail fragment and the curved GEC1 surface around the S2 β-strand. Microtubule binding via the GEC1 N-terminal domain is essential for the GEC1 chaperone-like effect on receptor trafficking. GEC1 also increased cell-surface levels of GluR1 and prostaglandin EP3.f receptor.","method":"Site-directed mutagenesis; pull-down assays; molecular modelling; fluorescence microscopy of surface receptor levels","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — mutagenesis of both binding partners combined with structural modelling and functional pull-down; single lab but multiple orthogonal approaches","pmids":["19001416"],"is_preprint":false},{"year":2011,"finding":"C-terminal modification (Gly116 cleavage and lipidation) of GEC1 is dispensable for its enhancement of hKOR expression because GEC1 binds hKOR C-tail with higher affinity than GABARAP does; the G116A mutation blocking lipidation does not impair GEC1-mediated hKOR trafficking. GABARAP, with weaker affinity, requires C-terminal modification for membrane association and KOR enhancement.","method":"Site-directed mutagenesis (G116A); co-immunoprecipitation; GST pull-down; immunofluorescence co-localisation; flow cytometry of surface receptor","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis with functional readout plus pull-down; single lab, two orthogonal methods","pmids":["21388957"],"is_preprint":false},{"year":2011,"finding":"The structure of the GABARAPL1/NBR1-LIR complex was determined by NMR; the LIR motif of NBR1 (YXXV instead of canonical WXXL) binds GABARAPL1 with lower affinity than a Trp-containing LIR but substitution of other aromatic residues or addition of N-terminal negative charges does not substantially alter affinity due to enthalpy-entropy compensation.","method":"NMR structure determination; isothermal titration calorimetry (ITC); peptide binding assays with LIR mutants","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR structure with ITC binding measurements and systematic mutagenesis; single lab but multiple rigorous biophysical methods","pmids":["21620860"],"is_preprint":false},{"year":2011,"finding":"Stbd1 (starch-binding domain protein 1) interacts with GABARAPL1 via an Atg8-interacting motif (AIM: 200HEEWEMV206) located in a disordered region; single-point mutations W203A or V206A abolish co-immunoprecipitation and co-localisation, demonstrating that this AIM is necessary for Stbd1-GABARAPL1 interaction and proposing GABARAPL1 as the autophagy scaffold for glycophagy.","method":"Co-immunoprecipitation from cell extracts; immunofluorescence co-localisation; site-directed mutagenesis of AIM residues","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP plus mutagenesis-validated co-localisation; two orthogonal methods in one study","pmids":["21893048"],"is_preprint":false},{"year":2011,"finding":"GABARAPL1 interacts with Dvl2 (as identified by yeast two-hybrid and co-immunoprecipitation); p62 is required for the Dvl2-GABARAPL1 interaction; GABARAPL1 mediates autophagic degradation of Dvl2 (blocked by 3-MA), thereby negatively regulating Wnt/β-catenin signalling.","method":"Yeast two-hybrid; co-immunoprecipitation; luciferase reporter assay for Wnt signalling; autophagy inhibitor (3-MA) treatment; in vitro and in vivo tumour growth assays","journal":"Cellular physiology and biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid plus Co-IP for interaction; functional pathway placement with inhibitor; single lab","pmids":["21691068"],"is_preprint":false},{"year":2011,"finding":"HSP90 is a novel GABARAPL1-interacting protein, identified by GST pull-down and mass spectrometry and confirmed by co-immunoprecipitation; HSP90 inhibition (17-AAG) promotes GABARAPL1 degradation via the proteasome (blocked by MG132, bortezomib, lactacystin), indicating HSP90 protects GABARAPL1 from proteasomal degradation.","method":"GST pull-down; mass spectrometry; co-immunoprecipitation; proteasome inhibitor treatment; immunofluorescence co-localisation","journal":"Biochimie","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — GST pull-down plus mass spectrometry identification plus Co-IP confirmation; single lab, multiple orthogonal methods","pmids":["22120110"],"is_preprint":false},{"year":2014,"finding":"shRNA-mediated knockdown of endogenous GABARAPL1 in MDA-MB-436 breast cancer cells attenuates autophagic flux, decreases lysosome number, increases basal oxygen consumption and intracellular ATP, and causes accumulation of damaged mitochondria, establishing GABARAPL1 as required for autophagic flux and mitochondrial quality control.","method":"shRNA knockdown; autophagic flux assays; lysosomal staining; Seahorse bioenergetics; mitochondrial damage assessment","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KD with defined cellular phenotypes across multiple orthogonal readouts; single lab","pmids":["24879149"],"is_preprint":false},{"year":2017,"finding":"G116A mutation in GABARAPL1 (blocking lipidation and autophagosome conjugation) impairs autophagosome/lysosome fusion and lysosome activity but does not alter mTOR or ULK1 activities, and does not affect tumour suppressive activity in vivo, demonstrating that GABARAPL1's tumour-suppressive function is independent of its autophagosome conjugation.","method":"Site-directed mutagenesis (G116A); autophagic flux assays; lysosome activity assay; mTOR/ULK1 immunoblotting; xenograft tumour growth in vivo","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis with multiple functional readouts in vitro and in vivo; single lab","pmids":["28915569"],"is_preprint":false},{"year":2018,"finding":"Proteasome inhibition selectively and rapidly induces GABARAPL1 (but not other autophagy genes) and p62 via the transcription factor Nrf1 (NFE2L1); knockdown of GABARAPL1 reduces cell survival upon proteasome inhibition; p62 knockdown blocks buildup of ubiquitinated proteins in perinuclear aggresomes.","method":"Transcriptomics/RT-qPCR; siRNA knockdown; cell viability assays; immunofluorescence of ubiquitin conjugates; Nrf1 loss-of-function","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with transcription factor identification; single lab but multiple orthogonal methods","pmids":["29535191"],"is_preprint":false},{"year":2019,"finding":"PIK3C3, BECN1, and ATG14 contain functional LIR motifs that bind GABARAP and GABARAPL1 preferentially over the LC3 subfamily; crystal structures of these LIR-GABARAP/GABARAPL1 complexes revealed that variation in hydrophobic pocket 2 (HP2) explains GABARAP subfamily preference. Mutation of the ATG14 LIR blocks co-localisation with LC3B and impairs mitophagy.","method":"High-resolution X-ray crystallography; co-immunoprecipitation; site-directed mutagenesis of LIR motifs; mitophagy assays","journal":"Autophagy","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures with mutagenesis and functional validation; multiple orthogonal methods in one rigorous study","pmids":["30767700"],"is_preprint":false},{"year":2021,"finding":"GABARAPL1 is required for endosomal maturation and sorting of cargo to endosomes; its silencing blocks the early endosomal pathway and impairs secretion of pro-angiogenic extracellular vesicles (EVs) during hypoxia; GABARAPL1 is expressed on the EV surface and GABARAPL1-deficient tumour xenografts show impaired vascularisation and decreased tumour growth.","method":"GABARAPL1 siRNA/shRNA knockdown; electron microscopy of endosomes; nanoparticle tracking analysis; xenograft tumour models; flow cytometry of EVs; antibody-mediated blockade of GABARAPL1+ EVs","journal":"Journal of extracellular vesicles","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with multiple orthogonal readouts (EM, EV secretion, in vivo); single lab","pmids":["34859607"],"is_preprint":false},{"year":2021,"finding":"During EMT induced by TGF-β/TNF-α, SMAD transcription factors drive increased GABARAPL1 expression; GABARAPL1 in turn mediates autophagic degradation of SMAD proteins, creating a negative feedback loop that restrains EMT. GABARAPL1 CRISPR/Cas9 knockout caused enhanced EMT linked to defective SMAD degradation.","method":"CRISPR/Cas9 knockout; TGF-β/TNF-α-induced EMT; Western blotting; transcriptome analysis; immunohistochemistry in lung tumour cohort","journal":"Biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR KO with defined molecular phenotype; single lab; two cell lines","pmids":["34681055"],"is_preprint":false},{"year":2022,"finding":"GEC1 (GABARAPL1) interacts directly with NSF in an ADP-preferring, D1/D2 domain-dependent manner; NSF does not bind the KOR C-tail directly but forms a ternary complex via GEC1; NSF/α-SNAP do not affect KCT-GEC1 interaction. This positions GEC1 as a scaffold that bridges KOR-containing vesicles to NSF for membrane fusion along the export pathway.","method":"GST pull-down with recombinant NSF domain mutants and nucleotide-bound forms; co-immunoprecipitation; competition assays","journal":"Handbook of experimental pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct pull-down with domain dissection; single lab; extends prior Co-IP data","pmids":["33404775"],"is_preprint":false},{"year":2023,"finding":"HHV-8 vIRF-1 binds directly to GABARAPL1 (preferentially over other ATG8 proteins) via an LIR-independent mechanism; specific residues in both vIRF-1 and GABARAPL1 required for mutual interaction were identified; this interaction is essential for mitophagy activation and productive HHV-8 replication. The mitophagy receptor NIX promotes vIRF-1-GABARAPL1 interaction and stabilises aggregated vIRF-1.","method":"Co-immunoprecipitation; site-directed mutagenesis; GABARAPL1-deficient cells; mitophagy assays; viral replication assays","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis of interaction residues plus KO cell line with functional viral readout; single lab","pmids":["37459327"],"is_preprint":false},{"year":2023,"finding":"The histone demethylase KDM3B activates GABARAPL1 transcription by binding to the GABARAPL1 promoter (ChIP-qPCR and luciferase assay), thereby promoting autophagosome formation and autophagic flux in leukemia cells under external stimuli.","method":"KDM3B knockout in leukemia cell lines; RNA-seq; RT-qPCR; ChIP-qPCR; luciferase reporter assay; autophagosome formation assay","journal":"International journal of oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus luciferase assay confirms direct transcriptional regulation; KO with functional autophagy readout; single lab","pmids":["37326062"],"is_preprint":false},{"year":2023,"finding":"NRF1 (NFE2L1) directly targets GABARAPL1 and p62 promoters (genome-wide transcriptome analysis and functional validation); NRF1 is indispensable for p62-positive puncta formation and their co-localisation with ULK1 and TBK1, and selectively upregulates GABARAPL1 to clear ubiquitinated proteins, establishing NRF1-mediated aggrephagy after proteasome dysfunction.","method":"Genome-wide RNA-seq; NRF1 knockdown; immunofluorescence; phospho-Ser403-p62 immunoblotting; ubiquitinated protein clearance assay","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — transcriptome-scale identification plus loss-of-function with phosphorylation and clearance readouts; single lab; extends prior Nrf1 finding","pmids":["37658135"],"is_preprint":false},{"year":2015,"finding":"GABARAPL1 is required for increased EGFR membrane expression during hypoxia; GABARAPL1 and EGFR co-localise at the plasma membrane during hypoxia, and GABARAPL1 knockdown inhibits EGFR membrane expression, placing GABARAPL1 in a trafficking role for EGFR under hypoxic conditions.","method":"qPCR; immunoblot; flow cytometry; immunocytochemistry; siRNA knockdown","journal":"Radiotherapy and oncology","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — loss-of-function with multiple quantitative readouts of surface EGFR; single lab; co-localisation supports trafficking role","pmids":["26164772"],"is_preprint":false},{"year":2026,"finding":"GABARAPL1 facilitates activation of the heme-regulated inhibitor kinase HRI by promoting its interaction with HSP90; in GABARAPL1-knockout A549 cells, eIF2α phosphorylation is reduced and stress granule formation is defective upon sodium arsenite treatment.","method":"GABARAPL1 knockout; immunoblotting of p-eIF2α; immunofluorescence of stress granules; co-immunoprecipitation of HSP90-HRI interaction","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO with defined molecular phenotype (p-eIF2α, stress granules) and proposed mechanism via Co-IP; single lab","pmids":["41904211"],"is_preprint":false},{"year":2025,"finding":"Targeted deletion of GABARAPL1 in mice does not affect normal hearing; however, GABARAPL1 is essential for aminoglycoside (AG)-induced hair cell death and hearing loss, as demonstrated by a GABARAPL1-knockout mouse model and confirmed in a double GABARAP/GABARAPL1 knockout.","method":"Conditional/constitutive mouse knockout; auditory brainstem response (ABR); hair cell survival assay; AAV-mediated shRNA knockdown of GABARAP in inner ear","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO mouse model with in vivo functional hearing readout, replicated in double KO and AAV-RNAi experiments","pmids":["39928869"],"is_preprint":false},{"year":2015,"finding":"DNA methylation and histone deacetylation specifically downregulate GABARAPL1 (not other GABARAP family members) in breast cancer, and CREB-1 recruitment to the GABARAPL1 promoter is required for its expression.","method":"qRT-PCR; Western blotting; bisulfite sequencing (DNA methylation); HDAC inhibitor treatment; chromatin immunoprecipitation of CREB-1","journal":"BMC cancer","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — ChIP plus epigenetic drug treatments with quantitative expression readouts; single lab","pmids":["26474850"],"is_preprint":false},{"year":2024,"finding":"In vitro biophysical studies (LIR-docking site interaction) show that an EGFR LIR1 peptide (FLPV) preferentially binds GABARAPL1 and GABARAP over LC3 subfamily members; X-ray crystallography demonstrates canonical binding of LIR1 core residues in both hydrophobic pockets of GABARAP, with Y49 and L50 dispensable in this context.","method":"In vitro LIR-binding assays; X-ray crystallography of GABARAP–LIR1 complex; in silico LIR prediction","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — crystal structure for GABARAP, in vitro binding for GABARAPL1 but no structure; GABARAPL1-specific structural data limited; preprint not peer-reviewed","pmids":[],"is_preprint":true},{"year":2024,"finding":"Deficiency of GABARAPL1 in type-2 diabetic mice is associated with diastolic dysfunction; Gabarapl1 gene delivery (AAV or similar) remediated cardiomyocyte and cardiac diastolic dysfunction in T2D mice and restored diastolic performance of human iPSC-derived 'diabetic' cardiac organoids, linking GABARAPL1-dependent glycophagy to cardiac function.","method":"Gabarapl1-knockout/deficient mice; in vivo cardiac functional measurements (echocardiography); iPSC-derived cardiac organoid model; gene delivery rescue experiment","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo genetic loss-of-function and rescue experiment in two model systems; preprint not peer-reviewed","pmids":[],"is_preprint":true},{"year":2023,"finding":"GABARAPL1 CRISPR/Cas9 deficiency in MDA-MB-231 tumours reduces pulmonary metastasis by 84% in a murine mammary fat-pad model; GABARAPL1-deficient cells migrate slower but have comparable invasive capacity; GABARAPL1 deficiency alters EV protein and miRNA content, implicating GABARAPL1 in cargo loading into pro-metastatic EVs.","method":"CRISPR/Cas9 knockout; orthotopic xenograft mouse model; nanoparticle tracking analysis; mass spectrometry of EV cargo; next-generation sequencing of EV miRNAs; scratch and transwell invasion assays","journal":"Radiotherapy and oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO with in vivo metastasis readout and EV cargo characterisation; single lab","pmids":["37898438"],"is_preprint":false},{"year":2023,"finding":"Insulin blocks autophagy in hepatocytes by preventing FoxO1 binding to putative insulin response elements in the GABARAPL1 gene promoter, thereby repressing GABARAPL1 transcription and reducing autophagosome formation.","method":"Luciferase reporter assay; EMSA (electrophoretic mobility shift assay); insulin signalling inhibitors; autophagosome counting; Western blotting of GABARAPL1 and Beclin1","journal":"Hormone and metabolic research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — EMSA and luciferase assay directly demonstrate FoxO1-promoter interaction; functional autophagy readout; single lab","pmids":["37380030"],"is_preprint":false}],"current_model":"GABARAPL1 (GEC1/ATG8L/APG8L) is an ATG8-family ubiquitin-like protein that undergoes Atg4B-mediated C-terminal cleavage at Gly116 and subsequent lipidation via the Atg7/Atg3 E1/E2 conjugation cascade to associate with autophagosomal membranes; it functions in autophagic flux (including selective autophagy of glycogen via STBD1 interaction, mitophagy via interaction with vIRF-1/NIX, and aggrephagy downstream of NRF1/KDM3B transcriptional induction) and in receptor trafficking by acting as a chaperone-like scaffold—binding the kappa opioid receptor C-tail, tubulin, NSF, and GABAA receptor to facilitate export-pathway trafficking—while its expression is regulated by caspase-3-activated Atg4D, by estrogen/CREB-1/FoxO1/Nrf1 transcription factors, and by epigenetic mechanisms including DNA methylation and histone deacetylation."},"narrative":{"mechanistic_narrative":"GABARAPL1 (GEC1/Atg8L/Apg8L) is a mammalian ATG8-family ubiquitin-like protein that functions both as a membrane-conjugated autophagy effector and as a cytosolic chaperone-like trafficking scaffold [PMID:20404487, PMID:16431922]. It enters the conjugation cascade after C-terminal cleavage at Gly116 by Atg4B (which alone among Atg4A/B/C processes it), forming E1 and E2 thioester intermediates with Atg7 and Atg3 respectively, becoming lipidated and associating with autophagic vesicles that co-localise with LC3 and lysosomal compartments [PMID:14530254, PMID:16704426, PMID:20404487]; Atg4B and caspase-3-truncated Atg4D mediate its delipidation, the latter coupling GABARAPL1 autophagosome formation to apoptotic signalling [PMID:19549685, PMID:20404487]. Once on membranes it engages selective-autophagy cargo and machinery through LIR/AIM contacts, binding NBR1, Stbd1 (glycophagy), and the upstream PI3K-complex components PIK3C3/BECN1/ATG14, with structural studies showing that variation in hydrophobic pocket 2 underlies GABARAP-subfamily binding preference over LC3 [PMID:21620860, PMID:21893048, PMID:30767700]. Functionally it is required for autophagic flux, lysosome maintenance and mitochondrial quality control, and it drives selective degradation pathways including aggrephagy of ubiquitinated proteins after proteasome inhibition and autophagic turnover of signalling proteins Dvl2 and SMADs, thereby restraining Wnt/β-catenin signalling and EMT [PMID:21691068, PMID:24879149, PMID:29535191, PMID:34681055]. Independently of lipidation, GABARAPL1 acts as a tubulin-binding scaffold that chaperones export-pathway trafficking of the kappa opioid receptor, GABAA receptor, GluR1 and EP3 receptor by binding the receptor C-tail and bridging vesicles to NSF for membrane fusion; this trafficking and its tumour-suppressive activity persist in the lipidation-deficient G116A mutant [PMID:15530441, PMID:16431922, PMID:19001416, PMID:21388957, PMID:28915569, PMID:33404775]. Its expression is tightly transcriptionally and epigenetically controlled by Nrf1/NRF1, KDM3B, CREB-1, FoxO1, SMADs, and by DNA methylation/histone deacetylation [PMID:29535191, PMID:37326062, PMID:37658135, PMID:26474850, PMID:37380030]. In vivo, GABARAPL1 is dispensable for normal hearing but essential for aminoglycoside-induced hair cell death [PMID:39928869].","teleology":[{"year":2003,"claim":"Established the enzyme responsible for processing GABARAPL1, defining it as a member of a shared mammalian Atg8 modification system.","evidence":"Activity-based protein profiling with electrophilic Atg8-homologue probes in cell lysates identifying Apg4B as the common processing/deconjugating protease","pmids":["14530254"],"confidence":"High","gaps":["Did not reconstitute the full conjugation cascade","No demonstration of lipidated product in cells"]},{"year":2006,"claim":"Defined GABARAPL1 as the fourth mammalian Atg8 conjugation modifier by reconstituting its E1/E2 enzymatic intermediates.","evidence":"In vitro cleavage with recombinant Atg4A/B/C plus trapping of Atg7(C572S) and Atg3(C264S) intermediates and fractionation in HeLa cells","pmids":["16704426"],"confidence":"High","gaps":["Did not identify membrane lipid acceptor in cells","No selective-autophagy cargo identified"]},{"year":2009,"claim":"Linked GABARAPL1 delipidation control to apoptotic signalling via caspase-cleaved Atg4D.","evidence":"In vitro caspase-3 cleavage assay, cell-based delipidation, and Atg4D siRNA with cell-death readouts","pmids":["19549685"],"confidence":"High","gaps":["Mechanism connecting delipidation to death sensitisation not resolved","Did not address other GABARAPL1 functions"]},{"year":2010,"claim":"Directly demonstrated GABARAPL1 lipidation, Gly116 cleavage, and autophagic-vesicle association in cells.","evidence":"Immunofluorescence, fractionation, Atg4B delipidation assay, and co-localisation with LC3/LysoTracker under lysosomal inhibition","pmids":["20404487"],"confidence":"High","gaps":["Did not identify specific cargo adaptors","Functional consequence of flux not measured"]},{"year":2004,"claim":"Identified GABARAPL1 as a tubulin- and GABAA-receptor-binding protein with microtubule-bundling activity, hinting at a trafficking role distinct from autophagy.","evidence":"In vitro co-sedimentation/pull-down with tubulin and GABAA receptor, tubulin polymerisation assay, and live-cell GFP imaging","pmids":["15530441"],"confidence":"Medium","gaps":["Single lab","Physiological relevance of microtubule bundling not established in vivo"]},{"year":2006,"claim":"Established GABARAPL1 as a chaperone-like scaffold that promotes export-pathway trafficking of the kappa opioid receptor and bridges to NSF.","evidence":"Yeast two-hybrid, GST pull-down, reciprocal Co-IP, pulse-chase, and flow cytometry of surface receptor in CHO cells and rat brain extracts","pmids":["16431922"],"confidence":"High","gaps":["Did not map exact binding residues (resolved later)","Generality across receptors not yet tested"]},{"year":2008,"claim":"Mapped the hydrophobic GEC1–hKOR interface at residue resolution and showed microtubule binding is required for the chaperone effect, extending the trafficking role to multiple receptors.","evidence":"Site-directed mutagenesis of both partners, pull-downs, molecular modelling, and surface-receptor imaging for GluR1 and EP3.f","pmids":["19001416"],"confidence":"High","gaps":["No high-resolution structure of the complex","Single lab"]},{"year":2011,"claim":"Showed the trafficking-chaperone function is lipidation-independent and driven by higher GABARAPL1 affinity for receptor C-tail than GABARAP.","evidence":"G116A mutagenesis, Co-IP, GST pull-down, and surface-receptor flow cytometry","pmids":["21388957"],"confidence":"Medium","gaps":["Single lab, two methods","Affinity quantification limited"]},{"year":2011,"claim":"Provided the first structural and thermodynamic description of a GABARAPL1–LIR (NBR1) complex, defining its selective-autophagy adaptor recognition.","evidence":"NMR structure with ITC and systematic LIR mutagenesis","pmids":["21620860"],"confidence":"High","gaps":["Single LIR partner characterised","Functional consequence in cells not tested here"]},{"year":2011,"claim":"Identified GABARAPL1 as the glycophagy scaffold through a defined AIM in Stbd1.","evidence":"Reciprocal Co-IP, co-localisation, and W203A/V206A AIM mutagenesis","pmids":["21893048"],"confidence":"High","gaps":["Did not demonstrate glycogen degradation directly","In vivo relevance not addressed here"]},{"year":2011,"claim":"Placed GABARAPL1 as a negative regulator of Wnt signalling via p62-dependent autophagic degradation of Dvl2, and a tumour suppressor.","evidence":"Yeast two-hybrid, Co-IP, 3-MA-blocked degradation, luciferase reporter, and tumour growth assays","pmids":["21691068"],"confidence":"Medium","gaps":["Direct vs p62-bridged binding not separated","Single lab"]},{"year":2011,"claim":"Identified HSP90 as a stabiliser protecting GABARAPL1 from proteasomal degradation.","evidence":"GST pull-down, mass spectrometry, Co-IP, and proteasome-inhibitor rescue of 17-AAG-induced degradation","pmids":["22120110"],"confidence":"Medium","gaps":["Direct vs chaperone-client geometry undefined","Physiological context not established"]},{"year":2014,"claim":"Demonstrated endogenous GABARAPL1 is required for autophagic flux, lysosome number, and mitochondrial quality control.","evidence":"shRNA knockdown with flux assays, lysosomal staining, Seahorse bioenergetics, and mitochondrial damage readouts in breast cancer cells","pmids":["24879149"],"confidence":"Medium","gaps":["Single lab, one cell line","Mitophagy receptor not identified here"]},{"year":2015,"claim":"Extended the trafficking role to EGFR under hypoxia.","evidence":"siRNA knockdown with qPCR, immunoblot, flow cytometry, and surface co-localisation","pmids":["26164772"],"confidence":"Medium","gaps":["Binding interface with EGFR not mapped here","Single lab"]},{"year":2015,"claim":"Defined epigenetic and CREB-1-dependent transcriptional control specific to GABARAPL1 among the family.","evidence":"Bisulfite sequencing, HDAC-inhibitor treatment, qRT-PCR, and CREB-1 ChIP in breast cancer","pmids":["26474850"],"confidence":"Medium","gaps":["Upstream signals driving methylation unclear","Single lab"]},{"year":2017,"claim":"Separated GABARAPL1's tumour-suppressive function from its autophagosome-conjugation activity.","evidence":"G116A mutagenesis with flux/lysosome assays, mTOR/ULK1 immunoblotting, and xenografts","pmids":["28915569"],"confidence":"Medium","gaps":["Conjugation-independent suppressive mechanism not defined","Single lab"]},{"year":2018,"claim":"Identified Nrf1 as a selective inducer of GABARAPL1 (with p62) supporting aggrephagy and survival after proteasome inhibition.","evidence":"Transcriptomics, RT-qPCR, siRNA viability assays, and Nrf1 loss-of-function with ubiquitin-conjugate imaging","pmids":["29535191"],"confidence":"Medium","gaps":["Direct promoter occupancy shown later","Single lab"]},{"year":2019,"claim":"Provided structural basis for GABARAP-subfamily preference of upstream PI3K-complex LIRs and linked ATG14 LIR to mitophagy.","evidence":"X-ray crystallography of PIK3C3/BECN1/ATG14 LIR complexes, Co-IP, LIR mutagenesis, and mitophagy assays","pmids":["30767700"],"confidence":"High","gaps":["GABARAPL1-specific cellular phenotypes not isolated from GABARAP","HP2 determinants generalisation untested"]},{"year":2021,"claim":"Revealed a SMAD–GABARAPL1 negative feedback loop restraining EMT through autophagic SMAD degradation.","evidence":"CRISPR/Cas9 knockout, TGF-β/TNF-α-induced EMT, Western blotting, transcriptomics, and tumour cohort IHC","pmids":["34681055"],"confidence":"Medium","gaps":["Direct SMAD binding not shown","Two cell lines, single lab"]},{"year":2021,"claim":"Implicated GABARAPL1 in endosomal maturation and secretion of pro-angiogenic extracellular vesicles.","evidence":"siRNA/shRNA knockdown, electron microscopy, nanoparticle tracking, EV flow cytometry, and xenograft vascularisation","pmids":["34859607"],"confidence":"Medium","gaps":["Molecular basis of endosomal role undefined","Single lab"]},{"year":2022,"claim":"Resolved the scaffold mechanism by showing GEC1 bridges KOR vesicles to NSF in a nucleotide- and domain-dependent ternary complex.","evidence":"GST pull-down with NSF domain mutants and nucleotide-bound forms, Co-IP, and competition assays","pmids":["33404775"],"confidence":"Medium","gaps":["No structure of the ternary complex","In vivo fusion event not directly observed"]},{"year":2023,"claim":"Identified KDM3B as a histone-demethylase activator of GABARAPL1 transcription driving autophagy in leukemia.","evidence":"KDM3B knockout, RNA-seq, ChIP-qPCR, luciferase reporter, and autophagosome assays","pmids":["37326062"],"confidence":"Medium","gaps":["Cofactors at promoter undefined","Single lab"]},{"year":2023,"claim":"Confirmed direct NRF1 promoter occupancy at GABARAPL1/p62 driving aggrephagy after proteasome dysfunction.","evidence":"Genome-wide RNA-seq, NRF1 knockdown, immunofluorescence, phospho-Ser403-p62 immunoblot, and clearance assays","pmids":["37658135"],"confidence":"Medium","gaps":["Relationship to earlier Nrf1 finding not reconciled mechanistically","Single lab"]},{"year":2023,"claim":"Showed insulin represses GABARAPL1 transcription by blocking FoxO1 promoter binding to suppress hepatocyte autophagy.","evidence":"Luciferase reporter, EMSA, insulin signalling inhibitors, and autophagosome counting","pmids":["37380030"],"confidence":"Medium","gaps":["Putative insulin response elements not validated in vivo","Single lab"]},{"year":2023,"claim":"Defined an LIR-independent GABARAPL1–vIRF-1 interaction required for HHV-8-driven mitophagy and viral replication, with NIX promoting the interaction.","evidence":"Co-IP, interaction-residue mutagenesis, GABARAPL1-deficient cells, and mitophagy/viral replication assays","pmids":["37459327"],"confidence":"Medium","gaps":["Structural basis of LIR-independent binding unresolved","Single lab"]},{"year":2023,"claim":"Linked GABARAPL1 to EV-cargo loading and pro-metastatic potential.","evidence":"CRISPR knockout, orthotopic xenografts, EV nanoparticle tracking, mass spectrometry, and miRNA sequencing","pmids":["37898438"],"confidence":"Medium","gaps":["Mechanism of cargo selection undefined","Single lab"]},{"year":2025,"claim":"Established a specific in vivo requirement for GABARAPL1 in aminoglycoside-induced hair cell death, dispensable for normal hearing.","evidence":"Constitutive/double GABARAP/GABARAPL1 knockout mice with auditory brainstem response, hair cell survival, and AAV-shRNA","pmids":["39928869"],"confidence":"High","gaps":["Molecular pathway linking GABARAPL1 to ototoxicity unresolved","Redundancy with GABARAP partially overlapping"]},{"year":2026,"claim":"Connected GABARAPL1 to integrated stress response by promoting HRI activation via HSP90 for eIF2α phosphorylation and stress granule formation.","evidence":"GABARAPL1 knockout A549 cells with p-eIF2α immunoblot, stress granule imaging, and HSP90-HRI Co-IP","pmids":["41904211"],"confidence":"Medium","gaps":["Whether GABARAPL1 acts directly on the HSP90-HRI complex unclear","Single lab"]},{"year":null,"claim":"How GABARAPL1's lipidation-independent scaffold/chaperone functions are molecularly and structurally distinguished from its membrane-conjugated autophagy roles, and how it is selected over GABARAP for specific cargo, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structure of a GABARAPL1 trafficking ternary complex","Cargo-selection determinants over GABARAP largely undefined","Conjugation-independent tumour-suppressive mechanism not identified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0031386","term_label":"protein tag activity","supporting_discovery_ids":[0,1,3]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[5,6,9,18]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein 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GABARAP or GABARAPL1 prevents aminoglycoside- induced hearing loss.","date":"2025","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/39928869","citation_count":3,"is_preprint":false},{"pmid":"31433094","id":"PMC_31433094","title":"Downregulation of Gabarapl1 significantly attenuates antibody binding to porcine aortic endothelial cells.","date":"2019","source":"Xenotransplantation","url":"https://pubmed.ncbi.nlm.nih.gov/31433094","citation_count":3,"is_preprint":false},{"pmid":"37326062","id":"PMC_37326062","title":"Histone lysine demethylase 3B regulates autophagy via transcriptional regulation of GABARAPL1 in acute myeloid leukemia cells.","date":"2023","source":"International journal of oncology","url":"https://pubmed.ncbi.nlm.nih.gov/37326062","citation_count":3,"is_preprint":false},{"pmid":"36435763","id":"PMC_36435763","title":"MiR-145 inhibits the differentiation and proliferation of bone marrow 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adduct formation in crude cell lysates\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro biochemical assay with electrophilic probe substrates, specific adduct formation, replicated across four substrates in one rigorous study\",\n      \"pmids\": [\"14530254\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Atg8L (GABARAPL1) C-terminus is cleaved by human Atg4B (but not Atg4A or Atg4C) in vitro; the processed form (Atg8L-I) forms an E1-substrate intermediate with Atg7 and an E2-substrate intermediate with Atg3, establishing it as the fourth mammalian Atg8 conjugation modifier.\",\n      \"method\": \"In vitro cleavage assay with recombinant Atg4A/B/C; co-expression with catalytic mutants Atg7(C572S) and Atg3(C264S) to trap intermediates; subcellular fractionation and fluorescence microscopy in HeLa cells\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution of E1/E2 conjugation intermediates with mutagenesis controls; multiple orthogonal methods in one study\",\n      \"pmids\": [\"16704426\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Caspase-3 cleaves Atg4D in vitro and in apoptotic cells; the resulting truncated ΔN63 Atg4D shows increased activity against GABARAPL1, stimulating its delipidation. siRNA silencing of Atg4D abrogates GABARAPL1 autophagosome formation and sensitises cells to starvation- and staurosporine-induced death.\",\n      \"method\": \"In vitro caspase cleavage assay; delipidation assay in living cells; siRNA knockdown with cell death readouts; fluorescence microscopy of autophagosome markers\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro enzymatic assay plus cell-based loss-of-function with multiple orthogonal readouts in one study\",\n      \"pmids\": [\"19549685\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"GABARAPL1 is proteolytically cleaved at Gly116, becomes lipidated and associated with intracellular membranes, is delipidated by Atg4B, accumulates in vesicles upon lysosomal inhibition, and partially co-localises with LC3 and LysoTracker-positive structures, demonstrating its association with autophagic vesicles.\",\n      \"method\": \"Immunofluorescence microscopy; subcellular fractionation; Atg4B delipidation assay; lysosomal inhibitor treatment; co-localisation with LC3/LysoTracker\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal cell-based methods (fractionation, delipidation assay, imaging) in one study confirming lipidation and autophagosome association\",\n      \"pmids\": [\"20404487\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"GEC1 (GABARAPL1) interacts in vitro with tubulin and GABAA receptor, promotes tubulin assembly and microtubule bundling, and localises in perinuclear vesicles in living cells.\",\n      \"method\": \"In vitro co-sedimentation/pull-down with tubulin and GABAA receptor; GEC1-GFP live-cell imaging; tubulin polymerisation assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct in vitro binding and functional tubulin polymerisation assay, plus localisation; single lab\",\n      \"pmids\": [\"15530441\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"GEC1 (GABARAPL1) directly binds the C-tail of the human kappa opioid receptor (hKOR) via hydrophobic contacts, co-immunoprecipitates with FLAG-hKOR in CHO cells, and facilitates trafficking of hKOR from the ER/Golgi to the plasma membrane, increasing total and cell-surface KOR levels. GEC1 also interacts with N-ethylmaleimide-sensitive factor (NSF) in pull-down assays and co-immunoprecipitates with NSF in rat brain extracts.\",\n      \"method\": \"Yeast two-hybrid screening; GST pull-down; co-immunoprecipitation; pulse-chase [35S]Met/Cys labelling; flow cytometry of surface receptor; fluorescence localisation in CHO cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, GST pull-down, pulse-chase trafficking assay, and subcellular localisation all converge on one mechanism; multiple orthogonal methods\",\n      \"pmids\": [\"16431922\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"GEC1 interaction with hKOR requires three hKOR residues (Phe345, Pro346, Met350) and seven GEC1 residues (Tyr49, Val51, Leu55, Thr56, Val57, Phe60, Ile64), mediated by hydrophobic contacts between the kinked hKOR C-tail fragment and the curved GEC1 surface around the S2 β-strand. Microtubule binding via the GEC1 N-terminal domain is essential for the GEC1 chaperone-like effect on receptor trafficking. GEC1 also increased cell-surface levels of GluR1 and prostaglandin EP3.f receptor.\",\n      \"method\": \"Site-directed mutagenesis; pull-down assays; molecular modelling; fluorescence microscopy of surface receptor levels\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — mutagenesis of both binding partners combined with structural modelling and functional pull-down; single lab but multiple orthogonal approaches\",\n      \"pmids\": [\"19001416\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"C-terminal modification (Gly116 cleavage and lipidation) of GEC1 is dispensable for its enhancement of hKOR expression because GEC1 binds hKOR C-tail with higher affinity than GABARAP does; the G116A mutation blocking lipidation does not impair GEC1-mediated hKOR trafficking. GABARAP, with weaker affinity, requires C-terminal modification for membrane association and KOR enhancement.\",\n      \"method\": \"Site-directed mutagenesis (G116A); co-immunoprecipitation; GST pull-down; immunofluorescence co-localisation; flow cytometry of surface receptor\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis with functional readout plus pull-down; single lab, two orthogonal methods\",\n      \"pmids\": [\"21388957\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The structure of the GABARAPL1/NBR1-LIR complex was determined by NMR; the LIR motif of NBR1 (YXXV instead of canonical WXXL) binds GABARAPL1 with lower affinity than a Trp-containing LIR but substitution of other aromatic residues or addition of N-terminal negative charges does not substantially alter affinity due to enthalpy-entropy compensation.\",\n      \"method\": \"NMR structure determination; isothermal titration calorimetry (ITC); peptide binding assays with LIR mutants\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR structure with ITC binding measurements and systematic mutagenesis; single lab but multiple rigorous biophysical methods\",\n      \"pmids\": [\"21620860\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Stbd1 (starch-binding domain protein 1) interacts with GABARAPL1 via an Atg8-interacting motif (AIM: 200HEEWEMV206) located in a disordered region; single-point mutations W203A or V206A abolish co-immunoprecipitation and co-localisation, demonstrating that this AIM is necessary for Stbd1-GABARAPL1 interaction and proposing GABARAPL1 as the autophagy scaffold for glycophagy.\",\n      \"method\": \"Co-immunoprecipitation from cell extracts; immunofluorescence co-localisation; site-directed mutagenesis of AIM residues\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP plus mutagenesis-validated co-localisation; two orthogonal methods in one study\",\n      \"pmids\": [\"21893048\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"GABARAPL1 interacts with Dvl2 (as identified by yeast two-hybrid and co-immunoprecipitation); p62 is required for the Dvl2-GABARAPL1 interaction; GABARAPL1 mediates autophagic degradation of Dvl2 (blocked by 3-MA), thereby negatively regulating Wnt/β-catenin signalling.\",\n      \"method\": \"Yeast two-hybrid; co-immunoprecipitation; luciferase reporter assay for Wnt signalling; autophagy inhibitor (3-MA) treatment; in vitro and in vivo tumour growth assays\",\n      \"journal\": \"Cellular physiology and biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid plus Co-IP for interaction; functional pathway placement with inhibitor; single lab\",\n      \"pmids\": [\"21691068\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"HSP90 is a novel GABARAPL1-interacting protein, identified by GST pull-down and mass spectrometry and confirmed by co-immunoprecipitation; HSP90 inhibition (17-AAG) promotes GABARAPL1 degradation via the proteasome (blocked by MG132, bortezomib, lactacystin), indicating HSP90 protects GABARAPL1 from proteasomal degradation.\",\n      \"method\": \"GST pull-down; mass spectrometry; co-immunoprecipitation; proteasome inhibitor treatment; immunofluorescence co-localisation\",\n      \"journal\": \"Biochimie\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — GST pull-down plus mass spectrometry identification plus Co-IP confirmation; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"22120110\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"shRNA-mediated knockdown of endogenous GABARAPL1 in MDA-MB-436 breast cancer cells attenuates autophagic flux, decreases lysosome number, increases basal oxygen consumption and intracellular ATP, and causes accumulation of damaged mitochondria, establishing GABARAPL1 as required for autophagic flux and mitochondrial quality control.\",\n      \"method\": \"shRNA knockdown; autophagic flux assays; lysosomal staining; Seahorse bioenergetics; mitochondrial damage assessment\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KD with defined cellular phenotypes across multiple orthogonal readouts; single lab\",\n      \"pmids\": [\"24879149\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"G116A mutation in GABARAPL1 (blocking lipidation and autophagosome conjugation) impairs autophagosome/lysosome fusion and lysosome activity but does not alter mTOR or ULK1 activities, and does not affect tumour suppressive activity in vivo, demonstrating that GABARAPL1's tumour-suppressive function is independent of its autophagosome conjugation.\",\n      \"method\": \"Site-directed mutagenesis (G116A); autophagic flux assays; lysosome activity assay; mTOR/ULK1 immunoblotting; xenograft tumour growth in vivo\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis with multiple functional readouts in vitro and in vivo; single lab\",\n      \"pmids\": [\"28915569\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Proteasome inhibition selectively and rapidly induces GABARAPL1 (but not other autophagy genes) and p62 via the transcription factor Nrf1 (NFE2L1); knockdown of GABARAPL1 reduces cell survival upon proteasome inhibition; p62 knockdown blocks buildup of ubiquitinated proteins in perinuclear aggresomes.\",\n      \"method\": \"Transcriptomics/RT-qPCR; siRNA knockdown; cell viability assays; immunofluorescence of ubiquitin conjugates; Nrf1 loss-of-function\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with transcription factor identification; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"29535191\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PIK3C3, BECN1, and ATG14 contain functional LIR motifs that bind GABARAP and GABARAPL1 preferentially over the LC3 subfamily; crystal structures of these LIR-GABARAP/GABARAPL1 complexes revealed that variation in hydrophobic pocket 2 (HP2) explains GABARAP subfamily preference. Mutation of the ATG14 LIR blocks co-localisation with LC3B and impairs mitophagy.\",\n      \"method\": \"High-resolution X-ray crystallography; co-immunoprecipitation; site-directed mutagenesis of LIR motifs; mitophagy assays\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures with mutagenesis and functional validation; multiple orthogonal methods in one rigorous study\",\n      \"pmids\": [\"30767700\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"GABARAPL1 is required for endosomal maturation and sorting of cargo to endosomes; its silencing blocks the early endosomal pathway and impairs secretion of pro-angiogenic extracellular vesicles (EVs) during hypoxia; GABARAPL1 is expressed on the EV surface and GABARAPL1-deficient tumour xenografts show impaired vascularisation and decreased tumour growth.\",\n      \"method\": \"GABARAPL1 siRNA/shRNA knockdown; electron microscopy of endosomes; nanoparticle tracking analysis; xenograft tumour models; flow cytometry of EVs; antibody-mediated blockade of GABARAPL1+ EVs\",\n      \"journal\": \"Journal of extracellular vesicles\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with multiple orthogonal readouts (EM, EV secretion, in vivo); single lab\",\n      \"pmids\": [\"34859607\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"During EMT induced by TGF-β/TNF-α, SMAD transcription factors drive increased GABARAPL1 expression; GABARAPL1 in turn mediates autophagic degradation of SMAD proteins, creating a negative feedback loop that restrains EMT. GABARAPL1 CRISPR/Cas9 knockout caused enhanced EMT linked to defective SMAD degradation.\",\n      \"method\": \"CRISPR/Cas9 knockout; TGF-β/TNF-α-induced EMT; Western blotting; transcriptome analysis; immunohistochemistry in lung tumour cohort\",\n      \"journal\": \"Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR KO with defined molecular phenotype; single lab; two cell lines\",\n      \"pmids\": [\"34681055\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"GEC1 (GABARAPL1) interacts directly with NSF in an ADP-preferring, D1/D2 domain-dependent manner; NSF does not bind the KOR C-tail directly but forms a ternary complex via GEC1; NSF/α-SNAP do not affect KCT-GEC1 interaction. This positions GEC1 as a scaffold that bridges KOR-containing vesicles to NSF for membrane fusion along the export pathway.\",\n      \"method\": \"GST pull-down with recombinant NSF domain mutants and nucleotide-bound forms; co-immunoprecipitation; competition assays\",\n      \"journal\": \"Handbook of experimental pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct pull-down with domain dissection; single lab; extends prior Co-IP data\",\n      \"pmids\": [\"33404775\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"HHV-8 vIRF-1 binds directly to GABARAPL1 (preferentially over other ATG8 proteins) via an LIR-independent mechanism; specific residues in both vIRF-1 and GABARAPL1 required for mutual interaction were identified; this interaction is essential for mitophagy activation and productive HHV-8 replication. The mitophagy receptor NIX promotes vIRF-1-GABARAPL1 interaction and stabilises aggregated vIRF-1.\",\n      \"method\": \"Co-immunoprecipitation; site-directed mutagenesis; GABARAPL1-deficient cells; mitophagy assays; viral replication assays\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis of interaction residues plus KO cell line with functional viral readout; single lab\",\n      \"pmids\": [\"37459327\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The histone demethylase KDM3B activates GABARAPL1 transcription by binding to the GABARAPL1 promoter (ChIP-qPCR and luciferase assay), thereby promoting autophagosome formation and autophagic flux in leukemia cells under external stimuli.\",\n      \"method\": \"KDM3B knockout in leukemia cell lines; RNA-seq; RT-qPCR; ChIP-qPCR; luciferase reporter assay; autophagosome formation assay\",\n      \"journal\": \"International journal of oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus luciferase assay confirms direct transcriptional regulation; KO with functional autophagy readout; single lab\",\n      \"pmids\": [\"37326062\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NRF1 (NFE2L1) directly targets GABARAPL1 and p62 promoters (genome-wide transcriptome analysis and functional validation); NRF1 is indispensable for p62-positive puncta formation and their co-localisation with ULK1 and TBK1, and selectively upregulates GABARAPL1 to clear ubiquitinated proteins, establishing NRF1-mediated aggrephagy after proteasome dysfunction.\",\n      \"method\": \"Genome-wide RNA-seq; NRF1 knockdown; immunofluorescence; phospho-Ser403-p62 immunoblotting; ubiquitinated protein clearance assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — transcriptome-scale identification plus loss-of-function with phosphorylation and clearance readouts; single lab; extends prior Nrf1 finding\",\n      \"pmids\": [\"37658135\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"GABARAPL1 is required for increased EGFR membrane expression during hypoxia; GABARAPL1 and EGFR co-localise at the plasma membrane during hypoxia, and GABARAPL1 knockdown inhibits EGFR membrane expression, placing GABARAPL1 in a trafficking role for EGFR under hypoxic conditions.\",\n      \"method\": \"qPCR; immunoblot; flow cytometry; immunocytochemistry; siRNA knockdown\",\n      \"journal\": \"Radiotherapy and oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — loss-of-function with multiple quantitative readouts of surface EGFR; single lab; co-localisation supports trafficking role\",\n      \"pmids\": [\"26164772\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"GABARAPL1 facilitates activation of the heme-regulated inhibitor kinase HRI by promoting its interaction with HSP90; in GABARAPL1-knockout A549 cells, eIF2α phosphorylation is reduced and stress granule formation is defective upon sodium arsenite treatment.\",\n      \"method\": \"GABARAPL1 knockout; immunoblotting of p-eIF2α; immunofluorescence of stress granules; co-immunoprecipitation of HSP90-HRI interaction\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO with defined molecular phenotype (p-eIF2α, stress granules) and proposed mechanism via Co-IP; single lab\",\n      \"pmids\": [\"41904211\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Targeted deletion of GABARAPL1 in mice does not affect normal hearing; however, GABARAPL1 is essential for aminoglycoside (AG)-induced hair cell death and hearing loss, as demonstrated by a GABARAPL1-knockout mouse model and confirmed in a double GABARAP/GABARAPL1 knockout.\",\n      \"method\": \"Conditional/constitutive mouse knockout; auditory brainstem response (ABR); hair cell survival assay; AAV-mediated shRNA knockdown of GABARAP in inner ear\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO mouse model with in vivo functional hearing readout, replicated in double KO and AAV-RNAi experiments\",\n      \"pmids\": [\"39928869\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"DNA methylation and histone deacetylation specifically downregulate GABARAPL1 (not other GABARAP family members) in breast cancer, and CREB-1 recruitment to the GABARAPL1 promoter is required for its expression.\",\n      \"method\": \"qRT-PCR; Western blotting; bisulfite sequencing (DNA methylation); HDAC inhibitor treatment; chromatin immunoprecipitation of CREB-1\",\n      \"journal\": \"BMC cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — ChIP plus epigenetic drug treatments with quantitative expression readouts; single lab\",\n      \"pmids\": [\"26474850\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"In vitro biophysical studies (LIR-docking site interaction) show that an EGFR LIR1 peptide (FLPV) preferentially binds GABARAPL1 and GABARAP over LC3 subfamily members; X-ray crystallography demonstrates canonical binding of LIR1 core residues in both hydrophobic pockets of GABARAP, with Y49 and L50 dispensable in this context.\",\n      \"method\": \"In vitro LIR-binding assays; X-ray crystallography of GABARAP–LIR1 complex; in silico LIR prediction\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — crystal structure for GABARAP, in vitro binding for GABARAPL1 but no structure; GABARAPL1-specific structural data limited; preprint not peer-reviewed\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Deficiency of GABARAPL1 in type-2 diabetic mice is associated with diastolic dysfunction; Gabarapl1 gene delivery (AAV or similar) remediated cardiomyocyte and cardiac diastolic dysfunction in T2D mice and restored diastolic performance of human iPSC-derived 'diabetic' cardiac organoids, linking GABARAPL1-dependent glycophagy to cardiac function.\",\n      \"method\": \"Gabarapl1-knockout/deficient mice; in vivo cardiac functional measurements (echocardiography); iPSC-derived cardiac organoid model; gene delivery rescue experiment\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo genetic loss-of-function and rescue experiment in two model systems; preprint not peer-reviewed\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"GABARAPL1 CRISPR/Cas9 deficiency in MDA-MB-231 tumours reduces pulmonary metastasis by 84% in a murine mammary fat-pad model; GABARAPL1-deficient cells migrate slower but have comparable invasive capacity; GABARAPL1 deficiency alters EV protein and miRNA content, implicating GABARAPL1 in cargo loading into pro-metastatic EVs.\",\n      \"method\": \"CRISPR/Cas9 knockout; orthotopic xenograft mouse model; nanoparticle tracking analysis; mass spectrometry of EV cargo; next-generation sequencing of EV miRNAs; scratch and transwell invasion assays\",\n      \"journal\": \"Radiotherapy and oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO with in vivo metastasis readout and EV cargo characterisation; single lab\",\n      \"pmids\": [\"37898438\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Insulin blocks autophagy in hepatocytes by preventing FoxO1 binding to putative insulin response elements in the GABARAPL1 gene promoter, thereby repressing GABARAPL1 transcription and reducing autophagosome formation.\",\n      \"method\": \"Luciferase reporter assay; EMSA (electrophoretic mobility shift assay); insulin signalling inhibitors; autophagosome counting; Western blotting of GABARAPL1 and Beclin1\",\n      \"journal\": \"Hormone and metabolic research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — EMSA and luciferase assay directly demonstrate FoxO1-promoter interaction; functional autophagy readout; single lab\",\n      \"pmids\": [\"37380030\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GABARAPL1 (GEC1/ATG8L/APG8L) is an ATG8-family ubiquitin-like protein that undergoes Atg4B-mediated C-terminal cleavage at Gly116 and subsequent lipidation via the Atg7/Atg3 E1/E2 conjugation cascade to associate with autophagosomal membranes; it functions in autophagic flux (including selective autophagy of glycogen via STBD1 interaction, mitophagy via interaction with vIRF-1/NIX, and aggrephagy downstream of NRF1/KDM3B transcriptional induction) and in receptor trafficking by acting as a chaperone-like scaffold—binding the kappa opioid receptor C-tail, tubulin, NSF, and GABAA receptor to facilitate export-pathway trafficking—while its expression is regulated by caspase-3-activated Atg4D, by estrogen/CREB-1/FoxO1/Nrf1 transcription factors, and by epigenetic mechanisms including DNA methylation and histone deacetylation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GABARAPL1 (GEC1/Atg8L/Apg8L) is a mammalian ATG8-family ubiquitin-like protein that functions both as a membrane-conjugated autophagy effector and as a cytosolic chaperone-like trafficking scaffold [#3, #5]. It enters the conjugation cascade after C-terminal cleavage at Gly116 by Atg4B (which alone among Atg4A/B/C processes it), forming E1 and E2 thioester intermediates with Atg7 and Atg3 respectively, becoming lipidated and associating with autophagic vesicles that co-localise with LC3 and lysosomal compartments [#0, #1, #3]; Atg4B and caspase-3-truncated Atg4D mediate its delipidation, the latter coupling GABARAPL1 autophagosome formation to apoptotic signalling [#2, #3]. Once on membranes it engages selective-autophagy cargo and machinery through LIR/AIM contacts, binding NBR1, Stbd1 (glycophagy), and the upstream PI3K-complex components PIK3C3/BECN1/ATG14, with structural studies showing that variation in hydrophobic pocket 2 underlies GABARAP-subfamily binding preference over LC3 [#8, #9, #15]. Functionally it is required for autophagic flux, lysosome maintenance and mitochondrial quality control, and it drives selective degradation pathways including aggrephagy of ubiquitinated proteins after proteasome inhibition and autophagic turnover of signalling proteins Dvl2 and SMADs, thereby restraining Wnt/\\u03b2-catenin signalling and EMT [#10, #12, #14, #17]. Independently of lipidation, GABARAPL1 acts as a tubulin-binding scaffold that chaperones export-pathway trafficking of the kappa opioid receptor, GABAA receptor, GluR1 and EP3 receptor by binding the receptor C-tail and bridging vesicles to NSF for membrane fusion; this trafficking and its tumour-suppressive activity persist in the lipidation-deficient G116A mutant [#4, #5, #6, #7, #13, #18]. Its expression is tightly transcriptionally and epigenetically controlled by Nrf1/NRF1, KDM3B, CREB-1, FoxO1, SMADs, and by DNA methylation/histone deacetylation [#14, #20, #21, #25, #29]. In vivo, GABARAPL1 is dispensable for normal hearing but essential for aminoglycoside-induced hair cell death [#24].\"\n,\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"Established the enzyme responsible for processing GABARAPL1, defining it as a member of a shared mammalian Atg8 modification system.\",\n      \"evidence\": \"Activity-based protein profiling with electrophilic Atg8-homologue probes in cell lysates identifying Apg4B as the common processing/deconjugating protease\",\n      \"pmids\": [\"14530254\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not reconstitute the full conjugation cascade\", \"No demonstration of lipidated product in cells\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Defined GABARAPL1 as the fourth mammalian Atg8 conjugation modifier by reconstituting its E1/E2 enzymatic intermediates.\",\n      \"evidence\": \"In vitro cleavage with recombinant Atg4A/B/C plus trapping of Atg7(C572S) and Atg3(C264S) intermediates and fractionation in HeLa cells\",\n      \"pmids\": [\"16704426\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify membrane lipid acceptor in cells\", \"No selective-autophagy cargo identified\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Linked GABARAPL1 delipidation control to apoptotic signalling via caspase-cleaved Atg4D.\",\n      \"evidence\": \"In vitro caspase-3 cleavage assay, cell-based delipidation, and Atg4D siRNA with cell-death readouts\",\n      \"pmids\": [\"19549685\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism connecting delipidation to death sensitisation not resolved\", \"Did not address other GABARAPL1 functions\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Directly demonstrated GABARAPL1 lipidation, Gly116 cleavage, and autophagic-vesicle association in cells.\",\n      \"evidence\": \"Immunofluorescence, fractionation, Atg4B delipidation assay, and co-localisation with LC3/LysoTracker under lysosomal inhibition\",\n      \"pmids\": [\"20404487\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify specific cargo adaptors\", \"Functional consequence of flux not measured\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identified GABARAPL1 as a tubulin- and GABAA-receptor-binding protein with microtubule-bundling activity, hinting at a trafficking role distinct from autophagy.\",\n      \"evidence\": \"In vitro co-sedimentation/pull-down with tubulin and GABAA receptor, tubulin polymerisation assay, and live-cell GFP imaging\",\n      \"pmids\": [\"15530441\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Physiological relevance of microtubule bundling not established in vivo\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Established GABARAPL1 as a chaperone-like scaffold that promotes export-pathway trafficking of the kappa opioid receptor and bridges to NSF.\",\n      \"evidence\": \"Yeast two-hybrid, GST pull-down, reciprocal Co-IP, pulse-chase, and flow cytometry of surface receptor in CHO cells and rat brain extracts\",\n      \"pmids\": [\"16431922\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not map exact binding residues (resolved later)\", \"Generality across receptors not yet tested\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Mapped the hydrophobic GEC1\\u2013hKOR interface at residue resolution and showed microtubule binding is required for the chaperone effect, extending the trafficking role to multiple receptors.\",\n      \"evidence\": \"Site-directed mutagenesis of both partners, pull-downs, molecular modelling, and surface-receptor imaging for GluR1 and EP3.f\",\n      \"pmids\": [\"19001416\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No high-resolution structure of the complex\", \"Single lab\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showed the trafficking-chaperone function is lipidation-independent and driven by higher GABARAPL1 affinity for receptor C-tail than GABARAP.\",\n      \"evidence\": \"G116A mutagenesis, Co-IP, GST pull-down, and surface-receptor flow cytometry\",\n      \"pmids\": [\"21388957\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab, two methods\", \"Affinity quantification limited\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Provided the first structural and thermodynamic description of a GABARAPL1\\u2013LIR (NBR1) complex, defining its selective-autophagy adaptor recognition.\",\n      \"evidence\": \"NMR structure with ITC and systematic LIR mutagenesis\",\n      \"pmids\": [\"21620860\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Single LIR partner characterised\", \"Functional consequence in cells not tested here\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Identified GABARAPL1 as the glycophagy scaffold through a defined AIM in Stbd1.\",\n      \"evidence\": \"Reciprocal Co-IP, co-localisation, and W203A/V206A AIM mutagenesis\",\n      \"pmids\": [\"21893048\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not demonstrate glycogen degradation directly\", \"In vivo relevance not addressed here\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Placed GABARAPL1 as a negative regulator of Wnt signalling via p62-dependent autophagic degradation of Dvl2, and a tumour suppressor.\",\n      \"evidence\": \"Yeast two-hybrid, Co-IP, 3-MA-blocked degradation, luciferase reporter, and tumour growth assays\",\n      \"pmids\": [\"21691068\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct vs p62-bridged binding not separated\", \"Single lab\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Identified HSP90 as a stabiliser protecting GABARAPL1 from proteasomal degradation.\",\n      \"evidence\": \"GST pull-down, mass spectrometry, Co-IP, and proteasome-inhibitor rescue of 17-AAG-induced degradation\",\n      \"pmids\": [\"22120110\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct vs chaperone-client geometry undefined\", \"Physiological context not established\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Demonstrated endogenous GABARAPL1 is required for autophagic flux, lysosome number, and mitochondrial quality control.\",\n      \"evidence\": \"shRNA knockdown with flux assays, lysosomal staining, Seahorse bioenergetics, and mitochondrial damage readouts in breast cancer cells\",\n      \"pmids\": [\"24879149\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab, one cell line\", \"Mitophagy receptor not identified here\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Extended the trafficking role to EGFR under hypoxia.\",\n      \"evidence\": \"siRNA knockdown with qPCR, immunoblot, flow cytometry, and surface co-localisation\",\n      \"pmids\": [\"26164772\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Binding interface with EGFR not mapped here\", \"Single lab\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Defined epigenetic and CREB-1-dependent transcriptional control specific to GABARAPL1 among the family.\",\n      \"evidence\": \"Bisulfite sequencing, HDAC-inhibitor treatment, qRT-PCR, and CREB-1 ChIP in breast cancer\",\n      \"pmids\": [\"26474850\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Upstream signals driving methylation unclear\", \"Single lab\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Separated GABARAPL1's tumour-suppressive function from its autophagosome-conjugation activity.\",\n      \"evidence\": \"G116A mutagenesis with flux/lysosome assays, mTOR/ULK1 immunoblotting, and xenografts\",\n      \"pmids\": [\"28915569\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Conjugation-independent suppressive mechanism not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified Nrf1 as a selective inducer of GABARAPL1 (with p62) supporting aggrephagy and survival after proteasome inhibition.\",\n      \"evidence\": \"Transcriptomics, RT-qPCR, siRNA viability assays, and Nrf1 loss-of-function with ubiquitin-conjugate imaging\",\n      \"pmids\": [\"29535191\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct promoter occupancy shown later\", \"Single lab\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Provided structural basis for GABARAP-subfamily preference of upstream PI3K-complex LIRs and linked ATG14 LIR to mitophagy.\",\n      \"evidence\": \"X-ray crystallography of PIK3C3/BECN1/ATG14 LIR complexes, Co-IP, LIR mutagenesis, and mitophagy assays\",\n      \"pmids\": [\"30767700\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"GABARAPL1-specific cellular phenotypes not isolated from GABARAP\", \"HP2 determinants generalisation untested\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Revealed a SMAD\\u2013GABARAPL1 negative feedback loop restraining EMT through autophagic SMAD degradation.\",\n      \"evidence\": \"CRISPR/Cas9 knockout, TGF-\\u03b2/TNF-\\u03b1-induced EMT, Western blotting, transcriptomics, and tumour cohort IHC\",\n      \"pmids\": [\"34681055\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct SMAD binding not shown\", \"Two cell lines, single lab\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Implicated GABARAPL1 in endosomal maturation and secretion of pro-angiogenic extracellular vesicles.\",\n      \"evidence\": \"siRNA/shRNA knockdown, electron microscopy, nanoparticle tracking, EV flow cytometry, and xenograft vascularisation\",\n      \"pmids\": [\"34859607\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of endosomal role undefined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Resolved the scaffold mechanism by showing GEC1 bridges KOR vesicles to NSF in a nucleotide- and domain-dependent ternary complex.\",\n      \"evidence\": \"GST pull-down with NSF domain mutants and nucleotide-bound forms, Co-IP, and competition assays\",\n      \"pmids\": [\"33404775\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structure of the ternary complex\", \"In vivo fusion event not directly observed\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identified KDM3B as a histone-demethylase activator of GABARAPL1 transcription driving autophagy in leukemia.\",\n      \"evidence\": \"KDM3B knockout, RNA-seq, ChIP-qPCR, luciferase reporter, and autophagosome assays\",\n      \"pmids\": [\"37326062\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cofactors at promoter undefined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Confirmed direct NRF1 promoter occupancy at GABARAPL1/p62 driving aggrephagy after proteasome dysfunction.\",\n      \"evidence\": \"Genome-wide RNA-seq, NRF1 knockdown, immunofluorescence, phospho-Ser403-p62 immunoblot, and clearance assays\",\n      \"pmids\": [\"37658135\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relationship to earlier Nrf1 finding not reconciled mechanistically\", \"Single lab\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Showed insulin represses GABARAPL1 transcription by blocking FoxO1 promoter binding to suppress hepatocyte autophagy.\",\n      \"evidence\": \"Luciferase reporter, EMSA, insulin signalling inhibitors, and autophagosome counting\",\n      \"pmids\": [\"37380030\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Putative insulin response elements not validated in vivo\", \"Single lab\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined an LIR-independent GABARAPL1\\u2013vIRF-1 interaction required for HHV-8-driven mitophagy and viral replication, with NIX promoting the interaction.\",\n      \"evidence\": \"Co-IP, interaction-residue mutagenesis, GABARAPL1-deficient cells, and mitophagy/viral replication assays\",\n      \"pmids\": [\"37459327\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of LIR-independent binding unresolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Linked GABARAPL1 to EV-cargo loading and pro-metastatic potential.\",\n      \"evidence\": \"CRISPR knockout, orthotopic xenografts, EV nanoparticle tracking, mass spectrometry, and miRNA sequencing\",\n      \"pmids\": [\"37898438\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of cargo selection undefined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Established a specific in vivo requirement for GABARAPL1 in aminoglycoside-induced hair cell death, dispensable for normal hearing.\",\n      \"evidence\": \"Constitutive/double GABARAP/GABARAPL1 knockout mice with auditory brainstem response, hair cell survival, and AAV-shRNA\",\n      \"pmids\": [\"39928869\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular pathway linking GABARAPL1 to ototoxicity unresolved\", \"Redundancy with GABARAP partially overlapping\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Connected GABARAPL1 to integrated stress response by promoting HRI activation via HSP90 for eIF2\\u03b1 phosphorylation and stress granule formation.\",\n      \"evidence\": \"GABARAPL1 knockout A549 cells with p-eIF2\\u03b1 immunoblot, stress granule imaging, and HSP90-HRI Co-IP\",\n      \"pmids\": [\"41904211\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether GABARAPL1 acts directly on the HSP90-HRI complex unclear\", \"Single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How GABARAPL1's lipidation-independent scaffold/chaperone functions are molecularly and structurally distinguished from its membrane-conjugated autophagy roles, and how it is selected over GABARAP for specific cargo, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structure of a GABARAPL1 trafficking ternary complex\", \"Cargo-selection determinants over GABARAP largely undefined\", \"Conjugation-independent tumour-suppressive mechanism not identified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0031386\", \"supporting_discovery_ids\": [0, 1, 3]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [5, 6, 9, 18]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [4, 6]},\n      {\"term_id\": \"GO:0044183\", \"supporting_discovery_ids\": [5, 6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [3, 4]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [16]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [5, 22]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [0, 1, 3, 12, 14]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [5, 6, 18, 22]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [16, 28]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 1, 2]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"ATG4B\", \"ATG7\", \"ATG3\", \"NBR1\", \"STBD1\", \"NSF\", \"HSP90\", \"ATG14\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}