{"gene":"GABARAP","run_date":"2026-04-28T17:46:04","timeline":{"discoveries":[{"year":2004,"finding":"GABARAP is conjugated to phosphatidylethanolamine (PE) via a ubiquitin-like system (analogous to yeast Atg8-PE conjugation), generating a membrane-associated form-II that localizes to autophagosomal membranes; this lipidation is reversible by the deconjugase Atg4B.","method":"Radiolabeling with [14C]-ethanolamine, membrane fractionation, in vitro Atg4B cleavage assay","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1 — direct biochemical labeling and enzymatic assay, replicated across multiple Atg8 homologs in same study","pmids":["15169837"],"is_preprint":false},{"year":2000,"finding":"Human Apg7p (hATG7) acts as an E1-like activating enzyme for GABARAP, forming a thioester intermediate with GABARAP via its active-site Cys572; GABARAP co-immunoprecipitates with hApg7p and forms a stable intermediate with the C572S mutant.","method":"Co-immunoprecipitation, site-directed mutagenesis, cross-linking, glycerol-gradient centrifugation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — active-site mutagenesis combined with biochemical intermediate trapping","pmids":["11096062"],"is_preprint":false},{"year":2002,"finding":"Human Apg3p (hATG3) acts as the E2-like conjugating enzyme for GABARAP; its active-site Cys264 forms a thioester intermediate with GABARAP, and hATG3 forms an E1·E2 complex with hATG7.","method":"Site-directed mutagenesis, co-immunoprecipitation, E2-substrate intermediate trapping","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — active-site mutagenesis with biochemical reconstitution of E1-E2-substrate cascade","pmids":["11825910"],"is_preprint":false},{"year":2003,"finding":"A single protease, Apg4B/autophagin-1, acts as the processing and deconjugating enzyme for GABARAP (and other mammalian Atg8 homologs), identified using electrophilic activity-based probes derived from GABARAP sequence.","method":"Activity-based protein profiling with electrophilic probes, in vitro protease activity assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — substrate-based chemical probes with direct identification of active protease","pmids":["14530254"],"is_preprint":false},{"year":2005,"finding":"GABARAP can be conjugated in vitro to both phosphatidylethanolamine (PE) and phosphatidylserine (PS) by the reconstituted hATG7/hATG3 conjugation system, but in vivo PE is the predominant target lipid.","method":"In vitro reconstitution with purified recombinant Atg proteins and synthetic lipid liposomes, thin-layer chromatography of endogenous conjugates","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — fully reconstituted in vitro lipidation system with orthogonal in vivo verification","pmids":["16303767"],"is_preprint":false},{"year":2014,"finding":"Lipidation of GABARAP (and LC3) by ATG3 is dependent on membrane curvature; ATG3 contains an N-terminal amphipathic helix that senses lipid-packing defects on highly curved membranes, restricting lipidation to such membranes in vitro and in vivo.","method":"In vitro lipidation assay on liposomes of defined curvature, amphipathic helix mutagenesis, rescue experiments in ATG3-knockout cells","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro system + mutagenesis + KO rescue, multiple orthogonal approaches","pmids":["24747438"],"is_preprint":false},{"year":2002,"finding":"Crystal structure of human GABARAP at 1.6 Å resolution reveals an N-terminal helical subdomain responsible for tubulin binding and a ubiquitin-like C-terminal domain containing the GABA(A) receptor binding site; GABARAP can self-associate in a head-to-tail manner promoting tubulin polymerization and receptor clustering.","method":"X-ray crystallography, structure-based mutagenesis","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 1 — high-resolution crystal structure with mutagenesis validation of functional domains","pmids":["11779480"],"is_preprint":false},{"year":2002,"finding":"Crystal structure of mammalian GABARAP at 2.0 Å resolution confirms an N-terminal basic helical region for tubulin binding and a conserved ubiquitin-like core fold; the conserved surface face mediates protein-protein interactions shared across the family.","method":"X-ray crystallography","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 1 — independent crystal structure confirming domain architecture","pmids":["11818336"],"is_preprint":false},{"year":2002,"finding":"NMR solution structure of human GABARAP reveals that amino- and carboxyl-terminal ends interact with each other in solution (not seen in crystal structures), suggesting conformational dynamics that regulate GABARAP interactions.","method":"NMR spectroscopy","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — high-resolution NMR structure providing functional insight distinct from crystal structures","pmids":["11875056"],"is_preprint":false},{"year":2000,"finding":"GABARAP binds directly to both tubulin and microtubules in a salt-sensitive (ionic interaction) manner in vitro and co-immunoprecipitates with tubulin in intact cells; the tubulin-binding domain is located at the N-terminus marked by specific basic amino acids; GABARAP also associates with microfilaments, likely via intermediary proteins.","method":"In vitro tubulin binding assay, co-immunoprecipitation, cytoskeletal drug treatments (taxol, nocodazole, cytochalasin D), deletion constructs and synthetic peptides","journal":"Journal of neurochemistry","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal biochemical and cell-based approaches","pmids":["10899939"],"is_preprint":false},{"year":2000,"finding":"GABARAP promotes clustering of GABA(A) receptors in QT-6 fibroblasts requiring both the tubulin-binding motif of GABARAP and the gamma2 subunit; clustered GABA(A) receptors show altered channel kinetics (higher EC50, faster deactivation, slower desensitization) compared to diffuse receptors.","method":"GFP-tagged receptor expression, immunofluorescence clustering assay, whole-cell electrophysiology, microtubule disruption experiments","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal functional assays with mechanistic dissection","pmids":["10984509"],"is_preprint":false},{"year":2001,"finding":"GABARAP is enriched in the Golgi apparatus and postsynaptic cisternae (not at inhibitory synapses), co-immunoprecipitates with GABA(A) receptors, and binds directly to NSF (N-ethylmaleimide-sensitive factor), suggesting a role in intracellular receptor transport rather than synaptic anchoring.","method":"Subcellular fractionation, immunoprecipitation, direct binding assay, confocal immunofluorescence","journal":"Molecular and cellular neurosciences","confidence":"High","confidence_rationale":"Tier 2 — reciprocal IP plus direct binding plus localization with functional inference","pmids":["11461150"],"is_preprint":false},{"year":2000,"finding":"GABARAP interacts with gephyrin in biochemical assays and transfected cells; confocal analysis shows GABARAP is enriched in intracellular compartments and not at gephyrin-positive postsynaptic specializations, suggesting a role in receptor sorting/targeting rather than synaptic anchoring.","method":"Co-immunoprecipitation, transfected cell co-localization, gephyrin-knockout mouse analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — biochemical interaction confirmed in KO mouse model with subcellular localization","pmids":["10900017"],"is_preprint":false},{"year":2002,"finding":"GABARAP's interaction with GABA(A) receptor is specific for gamma subunits; the interaction domain in GABARAP maps to residues 41–51, and GABARAP dimerizes using the same region (residues 36–68); a membrane-permeable peptide corresponding to the GABARAP interaction domain in gamma2 inhibits receptor clustering in living cells.","method":"Yeast two-hybrid quantitative assay, GST pulldown, peptide inhibition, GABA(A) receptor clustering assay in fibroblasts","journal":"Journal of neurochemistry","confidence":"High","confidence_rationale":"Tier 1–2 — multiple biochemical methods plus functional peptide inhibition in cells","pmids":["11948245"],"is_preprint":false},{"year":2007,"finding":"C-terminal processing of GABARAP at Gly116 (generating the lipidated form) is required for its proper subcellular distribution (away from Golgi into cytoplasmic puncta in neurons) and for its function in promoting GABA(A) receptor plasma membrane expression; the G116A mutant fails to enhance receptor surface expression.","method":"Site-directed mutagenesis, Western blotting with dual-tag construct, confocal microscopy, oocyte electrophysiology, surface biotinylation","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1–2 — mutagenesis of processing site with multiple functional readouts","pmids":["17581952"],"is_preprint":false},{"year":2014,"finding":"PLEKHM1 contains a GABARAP interaction motif (LIR) that mediates direct binding to autophagosomal membranes, and PLEKHM1 also directly interacts with the HOPS complex; this dual interaction is required for autophagosome-lysosome fusion, endocytic cargo degradation, and clearance of protein aggregates.","method":"Co-immunoprecipitation, GST pulldown, LIR mutagenesis, PLEKHM1 depletion with specific cargo degradation assays","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 — reciprocal IP, mutagenesis of interaction motif, KD with defined phenotypic readouts","pmids":["25498145"],"is_preprint":false},{"year":2015,"finding":"GABARAP (unlipidated and lipidated), but not LC3B or other ATG8 family members, specifically promotes ULK1 kinase activation in a manner dependent on the ULK1 LIR motif; GABARAP is dynamically trafficked from the pericentriolar matrix to the phagophore upon starvation, regulated by the Golgi proteins WAC and GM130.","method":"Protein interaction studies, GABARAP-specific KD/rescue, ULK1 kinase activity assay, live-cell imaging of GABARAP trafficking, LIR mutagenesis","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 — specific ATG8 member discrimination with kinase activity assay and LIR mutagenesis, multiple methods","pmids":["26687599"],"is_preprint":false},{"year":2017,"finding":"The centriolar satellite protein PCM1 directly binds GABARAP (but not LC3B) via a canonical LIR motif, stabilizing GABARAP at the pericentriolar material; loss of PCM1 leads to proteasomal degradation of GABARAP mediated by the E3 ligase Mib1, which promotes K48-linked ubiquitination of GABARAP at N-terminal residues.","method":"Direct binding assay, LIR mutagenesis, CRISPR/siRNA KD, proteasome inhibitor rescue, ubiquitination assay, autophagy flux measurement","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 2 — direct binding with LIR mutagenesis, ubiquitination mapping, and defined functional consequence","pmids":["28712572"],"is_preprint":false},{"year":2019,"finding":"ATL3 functions as a tubular ER-phagy receptor that specifically binds GABARAP (but not LC3) subfamily proteins via two GABARAP interaction motifs (GIMs); ATL3-GABARAP interaction is essential for starvation-induced tubular ER degradation, and HSAN I-associated ATL3 mutations (Y192C, P338R) disrupt this interaction and impair ER-phagy.","method":"Co-immunoprecipitation, GIM mutagenesis, ER-phagy flux assay, ATL3 KD/rescue, patient mutation analysis","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 2 — selective interaction established by mutagenesis with defined functional consequence in ER-phagy","pmids":["30773365"],"is_preprint":false},{"year":2017,"finding":"A GABARAP interaction motif (GIM) sequence [W/F]-[V/I]-X2-V confers 11-fold selectivity for GABARAP over LC3B, as demonstrated by biophysical and structural analysis of the PLEKHM1 LIR; conversion of other LIR motifs into GIMs by introducing valine residues enhances GABARAP over LC3B binding.","method":"Biophysical binding measurements (ITC/SPR), crystal structure of GABARAP-GIM complex, mutagenesis of LIR/GIM positions","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 1 — crystal structure plus mutagenesis plus quantitative biophysics defining specificity determinants","pmids":["28655748"],"is_preprint":false},{"year":2019,"finding":"PIK3C3, BECN1, and ATG14 (components of the PtdIns3K-C1 complex) each contain functional LIR motifs that interact preferentially with GABARAP and GABARAPL1 over LC3 proteins; crystal structures of these LIR motifs with GABARAP proteins reveal that variation in hydrophobic pocket 2 explains GABARAP-family specificity; ATG14 LIR mutation blocks its colocalization with LC3B and impairs mitophagy.","method":"Crystal structures, binding assays, LIR mutagenesis, mitophagy flux assay, colocalization studies","journal":"Autophagy","confidence":"High","confidence_rationale":"Tier 1 — multiple crystal structures with mutagenesis and functional validation","pmids":["30767700"],"is_preprint":false},{"year":2020,"finding":"ATG2A contains a conserved LIR-like motif that mediates direct interaction with GABARAP proteins; ATG2A-GABARAP interaction mutants fail to form and close phagophores, blocking autophagy flux similarly to ATG2A/ATG2B double-KO cells, establishing ATG2-GABARAP interaction as essential for phagophore formation.","method":"Mutagenesis of ATG2A-GABARAP interaction motif, autophagy flux assay, phagophore formation imaging, double-KO comparison","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 2 — interaction mutagenesis with defined phagophore formation phenotype, KO comparators","pmids":["32009292"],"is_preprint":false},{"year":2021,"finding":"GABARAP (but not LC3) directly binds a LIR motif in the FLCN/FNIP tumor suppressor complex and mediates its sequestration to GABARAP-conjugated membrane compartments during CASM, mitophagy, and xenophagy; this disrupts FLCN/FNIP GAP activity toward RagC/D, impairing mTOR-dependent phosphorylation of TFEB and activating lysosomal biogenesis.","method":"Co-immunoprecipitation, LIR mutagenesis, GABARAP-specific KO, TFEB/TFE3 activity assay, RagC/D GAP assay","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods establishing GABARAP-specific function in FLCN-mTOR-TFEB axis","pmids":["34597140"],"is_preprint":false},{"year":2009,"finding":"Nix/Bnip3L directly interacts with GABARAP as demonstrated by phage display screening, in vitro binding studies, pull-down, co-immunoprecipitation, and co-localization, suggesting a direct molecular link between apoptosis and autophagy pathways.","method":"Phage display, in vitro binding, GST pulldown, co-immunoprecipitation, co-localization in mammalian cells","journal":"Autophagy","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods confirming direct interaction","pmids":["19363302"],"is_preprint":false},{"year":2008,"finding":"GABARAP binds to the C-terminal cytoplasmic domain of the angiotensin II type 1 receptor (AT1R) and promotes its plasma membrane expression >6-fold; siRNA knockdown of GABARAP reduces AT1R surface expression by 84%; GABARAP interaction maps to residues 32–51 and requires the C-terminal 21 aa.","method":"Yeast two-hybrid, GST pulldown, co-immunoprecipitation, BRET assay, siRNA knockdown, surface expression quantification","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 2 — multiple interaction assays plus siRNA loss-of-function with quantitative surface expression readout","pmids":["18497328"],"is_preprint":false},{"year":2015,"finding":"CUL3-KBTBD6/KBTBD7 ubiquitin ligase complex employs ATG8-family-interacting motifs to bind preferentially to GABARAP proteins; GABARAP-containing vesicles recruit CUL3(KBTBD6/KBTBD7) to ubiquitinate and degrade the RAC1 GEF TIAM1, thereby spatially restricting RAC1 signaling and regulating actin morphology and cell invasion.","method":"Interactome mass spectrometry, co-immunoprecipitation, ubiquitination assay, GABARAP KD, TIAM1 abundance measurement, RAC1 activity assay","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 — MS interactome plus biochemical ubiquitination plus KD with defined signaling phenotype","pmids":["25684205"],"is_preprint":false},{"year":2016,"finding":"Lipidated GABARAP and GATE-16 (but not lipidated LC3) promote extensive membrane tethering and full membrane fusion (as shown by vesicle aggregation, lipid mixing, and aqueous content mixing without leakage) in reconstituted systems; membrane curvature (smaller vesicle diameter) and negative-curvature lipids (cardiolipin, DAG) facilitate this fusion.","method":"In vitro reconstituted enzymatic and chemical lipidation, vesicle tethering/fusion assays, cryo-electron microscopy","journal":"Biophysical journal","confidence":"High","confidence_rationale":"Tier 1 — fully reconstituted in vitro system with multiple independent fusion readouts and electron microscopy","pmids":["26789764"],"is_preprint":false},{"year":2015,"finding":"GABARAP directly binds to PI4K2A (phosphatidylinositol 4-kinase type 2α) and recruits it to autophagosomes; this GABARAP-PI4K2A interaction and the resulting PtdIns4P production are required for autophagosome-lysosome fusion.","method":"Co-immunoprecipitation, GABARAP KD, autophagosome-lysosome fusion assay","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2 — IP plus KD with functional readout, single lab","pmids":["26391226"],"is_preprint":false},{"year":2013,"finding":"Mulan E3 ubiquitin ligase interacts with GABARAP via an LIR motif in its RING finger domain in complex with the E2 enzyme Ube2E3; this interaction requires both the LIR motif and Ube2E3 presence, linking Mulan to mitophagy regulation through GABARAP.","method":"Yeast two-hybrid (modified), co-immunoprecipitation, LIR motif analysis","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 3 — yeast two-hybrid and co-IP with mechanistic LIR requirement, single lab","pmids":["25224329"],"is_preprint":false},{"year":2021,"finding":"GABARAP/GABARAPL1 (but not other ATG8 family members) directly bind to a previously unappreciated region in the gamma2 subunit of GABA(A)R; crystal structure of GABARAPL1-gamma2 complex reveals the molecular basis; GABARAP stabilizes GABAARs by promoting trafficking (not blocking endocytosis); phosphorylation of gamma2 differentially modulates binding to GABARAP vs. clathrin adaptor AP2; blocking GABARAP-GABAAR complex reduces GABAergic synaptic currents.","method":"Crystal structure, co-immunoprecipitation, electrophysiology, trafficking assays, phosphorylation mutagenesis","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with functional validation by electrophysiology and trafficking assays","pmids":["33436612"],"is_preprint":false},{"year":2018,"finding":"Ankyrin-G directly interacts with GABARAP to stabilize cell-surface GABA(A) receptors at GABAergic synapses; a knock-in mouse with the W1989R mutation abolishing ankyrin-G/GABARAP interaction shows striking reduction in forebrain GABAergic synapses, pyramidal cell hyperexcitability, and disrupted network synchronization.","method":"Knock-in mouse model, electrophysiology, immunofluorescence quantification of synapses","journal":"Molecular psychiatry","confidence":"High","confidence_rationale":"Tier 2 — genetic interaction-abolishing knock-in mouse with defined synaptic and circuit phenotypes","pmids":["30504823"],"is_preprint":false},{"year":2010,"finding":"GABARAP associates with TRPV1 in HEK293 cells and DRG neurons, augments TRPV1 surface expression and clustering, attenuates voltage/capsaicin sensitivity in the presence of extracellular calcium, lengthens vanilloid-induced tachyphylaxia, and increases tubulin interaction with the TRPV1 C-terminal domain.","method":"Co-immunoprecipitation, surface expression quantification, electrophysiology, nocodazole cytoskeleton disruption","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 — multiple interaction and functional assays, single lab","pmids":["20179142"],"is_preprint":false},{"year":2009,"finding":"Caspase-3 cleaves Atg4D, generating a truncated ΔN63 Atg4D with increased activity against GABARAP-L1 (but relevance to GABARAP itself is indirect); Atg4D siRNA silencing abrogates GABARAP-L1 autophagosome formation.","method":"In vitro caspase-3 cleavage assay, cell-based Atg4D siRNA knockdown, autophagosome formation assay","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 — in vitro enzyme assay plus siRNA KD, but finding is primarily about GABARAP-L1 not GABARAP itself","pmids":["19549685"],"is_preprint":false},{"year":2019,"finding":"TBK1 phosphorylates GABARAP-L2 (not GABARAP itself) on surface-exposed serine residues, impeding ATG4 binding and protecting lipidated GABARAP-L2 from premature removal from nascent autophagosomes.","method":"In vitro kinase assay, phosphomimetic mutagenesis, liposome deconjugation assay, autophagosome formation analysis","journal":"EMBO reports","confidence":"Medium","confidence_rationale":"Tier 1–2 — in vitro kinase assay with mutagenesis; primarily about GABARAP-L2, GABARAP itself less directly studied","pmids":["31709703"],"is_preprint":false},{"year":2019,"finding":"UBA5 contains an atypical LIR motif that preferentially interacts with GABARAP (not LC3) proteins; NMR/crystal structures of GABARAP-UBA5 LIR complex reveal a novel hydrophobic pocket (HP0) engaged by a conserved tryptophan N-terminal to the core LIR, with K46/K47 of GABARAP being key specificity determinants; GABARAP regulates UBA5 localization to the ER membrane in a lipidation-independent manner.","method":"NMR, crystal structures, ITC, swapping mutagenesis, KO cell lines, ER localization assay","journal":"Autophagy","confidence":"High","confidence_rationale":"Tier 1 — two independent crystal structures with mutagenesis and biophysical quantification","pmids":["30990354"],"is_preprint":false},{"year":2017,"finding":"GABARAP subfamily (particularly GATE-16/GABARAPL2) but not LC3 proteins are required for IFN-γ-mediated clearance of vacuolar pathogens (Toxoplasma); GATE-16 specifically associates with the small GTPase ARF1 to mediate uniform cytosolic distribution of interferon-inducible GTPases (IFN-GTPases); loss of GABARAPs reduces ARF1 activation, causing IFN-GTPase aggregation.","method":"GABARAP-family-specific KO cells and mice, Toxoplasma clearance assay, ARF1 co-immunoprecipitation, GTPase activation assay","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 2 — specific KO with defined antimicrobial phenotype plus molecular mechanism via ARF1 interaction","pmids":["28604719"],"is_preprint":false},{"year":2007,"finding":"Calreticulin is a high-affinity ligand of GABARAP (Kd = 64 nM) identified by phage display; the interaction was confirmed by pull-down from brain lysate and co-localization in N2a cells; crystal structure of GABARAP in complex with the calreticulin binding epitope was determined.","method":"Phage display, SPR/biophysical binding, GST pulldown, co-localization, crystal structure of complex","journal":"The FEBS journal","confidence":"High","confidence_rationale":"Tier 1 — crystal structure of complex plus multiple orthogonal binding confirmations","pmids":["17916189","19154346"],"is_preprint":false},{"year":2013,"finding":"GABARAP deficiency in macrophages leads to inefficient clearance of damaged mitochondria, resulting in elevated mitochondrial ROS and cytosolic mitochondrial DNA release, which enhances NLRP3 inflammasome activation (increased caspase-1, IL-1β, IL-18); GABARAP-deficient mice show higher mortality in sepsis models.","method":"GABARAP KO mouse, mitophagy assay, mitochondrial ROS measurement, inflammasome activation assay (caspase-1 processing, cytokine secretion)","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 — KO mouse with defined molecular mechanism (mitophagy-ROS-inflammasome axis)","pmids":["23427251"],"is_preprint":false},{"year":2006,"finding":"Lysosomal turnover of endogenous GABARAP-phospholipid conjugate (GABARAP-PL) is activated during differentiation of C2C12 cells to myotubes independently of mTOR kinase inactivation (unlike starvation-induced autophagy); little GABARAP-PL accumulates during canonical starvation-induced autophagy in most tissues.","method":"Lysosomal protease inhibitor accumulation assay, S6 kinase phosphorylation as mTOR readout, tissue-specific endogenous GABARAP-PL analysis","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2 — endogenous protein analysis with mechanistic dissection from mTOR, single lab","pmids":["16874098"],"is_preprint":false},{"year":2013,"finding":"Bcl-2 directly binds GABARAP via a three-residue segment (EWD) adjacent to the BH4 region, anchored to one hydrophobic pocket of GABARAP; Bcl-2 overexpression inhibits GABARAP lipidation, linking Bcl-2's autophagy-inhibitory function to direct competition with the lipid conjugation machinery.","method":"NMR chemical shift mapping, mutagenesis, pull-down, GABARAP lipidation assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 — NMR-defined interaction site plus functional lipidation inhibition assay","pmids":["24240096"],"is_preprint":false},{"year":2025,"finding":"STING activation triggers LRRK2 lysosomal recruitment and kinase activation via the CASM (conjugation of ATG8 to single membranes) pathway; LRRK2 activation is highly dependent on interactions with GABARAP (not other ATG8 family members); multiple lysosome-perturbing stimuli converge on CASM-GABARAP to control LRRK2 kinase activity.","method":"STING agonist treatment, GABARAP-specific KO/interaction mutants, LRRK2 lysosome recruitment imaging, LRRK2 kinase activity assay (Rab phosphorylation)","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 — GABARAP-specific KO with defined kinase activation readout, multiple stimuli tested","pmids":["39812709"],"is_preprint":false},{"year":2019,"finding":"ATG4 isoforms (ATG4A, ATG4C, ATG4D) contribute redundantly to priming activity that enables lipidation of endogenous GABARAPL1 on autophagic structures; ATG4B is the dominant but not sole isoform processing GABARAP family proteins; pre-primed LC3B can rescue autophagic degradation without ATG4-mediated delipidation.","method":"CRISPR-Cas9 KO, siRNA depletion, processing assay, autophagy flux measurement (SQSTM1 degradation), correlative light and electron microscopy","journal":"Autophagy","confidence":"High","confidence_rationale":"Tier 2 — comprehensive genetic dissection with multiple ATG4 isoform KOs and functional readouts","pmids":["30661429"],"is_preprint":false},{"year":2014,"finding":"FLCN directly interacts with GABARAP; the FLCN-GABARAP association is modulated by FNIP1/FNIP2 and further regulated by ULK1 phosphorylation of FLCN at Ser406, Ser537, and Ser542.","method":"Co-immunoprecipitation, ULK1 overexpression phosphorylation mapping, autophagy flux assay","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2–3 — interaction confirmed by co-IP with phosphorylation site mapping, single lab","pmids":["25126726"],"is_preprint":false},{"year":2012,"finding":"MAPK15/ERK8 interacts with GABARAP (and LC3B, GABARAPL1) via a conserved LIR motif; MAPK15 localizes to autophagic compartments and stimulates ATG8-family protein lipidation, autophagosome formation, and SQSTM1 degradation in a kinase-dependent fashion.","method":"Co-immunoprecipitation, LIR mutagenesis, autophagosome formation assay, lipidation assay, SQSTM1 degradation assay","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2 — LIR mutagenesis with kinase-dependent functional readouts, single lab","pmids":["22948227"],"is_preprint":false},{"year":2017,"finding":"HIV-1 Nef binds directly and specifically to all GABARAP family members (but not LC3 family members) via two surface-exposed hydrophobic pockets (involving S53 and F62 of GABARAP); GABARAP knockdown significantly reduces Nef plasma membrane localization.","method":"Pulldown with purified recombinant proteins, co-immunoprecipitation, NMR chemical shift mapping, site-directed mutagenesis, siRNA knockdown, live-cell fluorescence microscopy","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 1–2 — NMR-defined binding interface, mutagenesis, and siRNA functional validation","pmids":["28729737"],"is_preprint":false},{"year":2002,"finding":"GABARAP self-associates and dimerizes at physiological salt concentrations; the dimerization domain maps to residues 41–51 (the same region that binds the GABA(A) receptor gamma2 subunit), as shown by synthetic peptide inhibition of GST pulldown.","method":"GST pulldown, synthetic peptide competition, deletion constructs","journal":"Neuropharmacology","confidence":"Medium","confidence_rationale":"Tier 2 — domain mapping with peptide inhibition, single lab","pmids":["12367594"],"is_preprint":false},{"year":2006,"finding":"Co-expression of GABARAP with GABA(A) receptors increases single-channel conductance to ≥40 pS (vs. 30 pS control) and mean open time; the increased conductance is GABA concentration-dependent, demonstrating that GABARAP-mediated trafficking influences ion channel gating properties.","method":"Outside-out patch clamp electrophysiology of transiently transfected cells","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — single-channel electrophysiology with direct functional consequence, single lab","pmids":["16954214"],"is_preprint":false},{"year":2002,"finding":"GABARAP interacts with transferrin receptor (TfR) cytoplasmic domain via its YTRF internalization motif, as shown by yeast two-hybrid, in vitro binding with purified proteins, and co-immunoprecipitation from HeLa cells; GABARAP-GFP localizes to perinuclear vesicles, suggesting a general role in vesicle trafficking beyond neurons.","method":"Yeast two-hybrid, in vitro binding assay, co-immunoprecipitation, GFP chimera localization","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 — multiple interaction methods confirming direct binding, single lab","pmids":["11997026"],"is_preprint":false}],"current_model":"GABARAP is a mammalian ATG8-family ubiquitin-like protein that undergoes C-terminal processing by ATG4 proteases and E1 (ATG7)/E2 (ATG3)-mediated conjugation to phosphatidylethanolamine on autophagosomal and single membranes; in its lipidated and unlipidated forms it acts as a selective scaffold that binds diverse LIR/GIM-containing partners (including ULK1, ATG14, ATG2A, PIK3C3, PLEKHM1, ATL3, FLCN, LRRK2, and others) to uniquely promote phagophore expansion, ULK1 kinase activation, autophagosome-lysosome fusion, and mitophagy/xenophagy, while also functioning outside autophagy to traffic GABA(A) receptors, angiotensin AT1 receptors, and TRPV1 channels to the plasma membrane via interactions with NSF, tubulin, gephyrin, and ankyrin-G, and to scaffold the CUL3-KBTBD6/7 ubiquitin ligase for spatially restricted RAC1 signaling."},"narrative":{"teleology":[{"year":2000,"claim":"Identifying GABARAP as a link between GABA(A) receptors and the cytoskeleton established its initial function as a receptor-trafficking scaffold that clusters GABA(A) receptors in a tubulin-dependent manner and interacts with the postsynaptic protein gephyrin.","evidence":"In vitro tubulin binding, co-immunoprecipitation, electrophysiology, receptor clustering assays, gephyrin KO mouse analysis in multiple independent studies","pmids":["10899939","10984509","10900017"],"confidence":"High","gaps":["Whether GABARAP directly contacts gephyrin and GABA(A) receptors simultaneously or sequentially was unresolved","In vivo synaptic consequence of GABARAP loss was not tested","Mechanism of GABARAP delivery to the plasma membrane was unknown"]},{"year":2001,"claim":"Demonstrating that GABARAP resides at the Golgi and binds NSF rather than localizing to synapses reframed its role from synaptic anchoring to intracellular receptor transport.","evidence":"Subcellular fractionation, direct binding assay with NSF, confocal immunofluorescence in neurons","pmids":["11461150"],"confidence":"High","gaps":["Which step of vesicular transport (budding, fusion, or recycling) GABARAP-NSF interaction controls was unclear","Whether NSF interaction is direct or part of a larger SNARE-associated complex was not resolved"]},{"year":2002,"claim":"High-resolution crystal and NMR structures revealed GABARAP's domain architecture—an N-terminal helical tubulin-binding subdomain and a ubiquitin-like C-terminal fold—defining the structural basis for its dual cytoskeletal and receptor-binding functions.","evidence":"X-ray crystallography at 1.6 Å and 2.0 Å, NMR solution structure, structure-based mutagenesis","pmids":["11779480","11818336","11875056"],"confidence":"High","gaps":["How the intramolecular N-/C-terminal interaction seen by NMR regulates partner access was not determined","No structure of GABARAP bound to a full-length cargo receptor existed"]},{"year":2002,"claim":"Establishing that ATG7 and ATG3 act as E1 and E2 enzymes forming thioester intermediates with GABARAP placed it firmly within the ubiquitin-like conjugation cascade for ATG8 proteins.","evidence":"Active-site mutagenesis (C572S for ATG7, C264 for ATG3), co-immunoprecipitation, thioester intermediate trapping","pmids":["11096062","11825910"],"confidence":"High","gaps":["The target lipid for GABARAP conjugation had not yet been identified","Functional consequence of lipidation versus unlipidated GABARAP was unknown"]},{"year":2004,"claim":"Demonstrating that GABARAP is conjugated to PE on autophagosomal membranes, with ATG4B as both the priming protease and deconjugase, established the complete lipidation-delipidation cycle.","evidence":"Radiolabeling with [14C]-ethanolamine, membrane fractionation, in vitro ATG4B cleavage, reconstituted lipidation with synthetic liposomes","pmids":["15169837","14530254","16303767"],"confidence":"High","gaps":["Whether lipidation is required for GABARAP's receptor-trafficking functions remained untested","Regulation of the lipidation/delipidation balance in vivo was unexplored"]},{"year":2007,"claim":"Showing that C-terminal processing at Gly116 is required for proper GABARAP subcellular distribution and for promoting GABA(A) receptor surface expression linked the autophagy-associated lipidation machinery to receptor trafficking function.","evidence":"G116A mutagenesis, surface biotinylation, oocyte electrophysiology, confocal microscopy in neurons","pmids":["17581952"],"confidence":"High","gaps":["Whether the processed form must be lipidated or simply C-terminally exposed was not distinguished","The vesicular compartment from which GABARAP promotes receptor export was not defined"]},{"year":2008,"claim":"Identifying the angiotensin AT1 receptor as a second GABARAP-dependent cargo expanded GABARAP's trafficking role beyond neurons to cardiovascular physiology.","evidence":"Yeast two-hybrid, BRET, siRNA knockdown reducing AT1R surface expression by 84%","pmids":["18497328"],"confidence":"High","gaps":["Whether GABARAP uses the same lipidation-dependent mechanism for AT1R as for GABA(A)R was not tested","In vivo cardiovascular consequence of GABARAP loss was not examined"]},{"year":2014,"claim":"Membrane curvature sensing by ATG3's amphipathic helix was shown to restrict GABARAP (and LC3) lipidation to highly curved membranes, providing a biophysical mechanism that spatially confines ATG8 conjugation to nascent autophagosomes.","evidence":"In vitro lipidation on liposomes of defined curvature, amphipathic helix mutagenesis, rescue in ATG3-KO cells","pmids":["24747438"],"confidence":"High","gaps":["Whether membrane curvature sensing operates identically for GABARAP versus LC3 subfamily members was not resolved","How curvature restriction is bypassed during CASM on flat single membranes was unclear"]},{"year":2015,"claim":"Discovering that PLEKHM1 bridges GABARAP-decorated autophagosomes to the HOPS tethering complex, and that CUL3-KBTBD6/7 uses GABARAP to spatially restrict RAC1 signaling, established GABARAP as a platform for both autophagosome-lysosome fusion and non-autophagic ubiquitin ligase targeting.","evidence":"LIR mutagenesis, cargo degradation assays, interactome mass spectrometry, RAC1 activity measurement, TIAM1 ubiquitination","pmids":["25498145","25684205"],"confidence":"High","gaps":["Whether PLEKHM1 is redundant with other GABARAP-binding tethering factors was unknown","The membrane compartment on which CUL3-KBTBD6/7 encounters GABARAP was not identified"]},{"year":2016,"claim":"Reconstituted membrane fusion assays demonstrated that lipidated GABARAP and GATE-16 (but not LC3) autonomously tether and fuse membranes, revealing an intrinsic fusogenic activity that distinguishes the GABARAP subfamily.","evidence":"Enzymatic and chemical lipidation reconstitution, vesicle aggregation, lipid mixing, content mixing assays, cryo-EM","pmids":["26789764"],"confidence":"High","gaps":["Whether this fusogenic activity operates at the autophagosome-lysosome fusion step in vivo was not shown","The structural mechanism by which lipidated GABARAP drives membrane merger was not resolved"]},{"year":2016,"claim":"GABARAP was shown to uniquely activate ULK1 kinase via its LIR motif and to traffic from the pericentriolar matrix to the phagophore upon starvation, establishing a GABARAP-specific role in autophagy initiation distinct from LC3.","evidence":"GABARAP-specific knockdown/rescue, ULK1 kinase activity assay, LIR mutagenesis, live-cell imaging of pericentriolar GABARAP trafficking","pmids":["26687599"],"confidence":"High","gaps":["How GABARAP is released from the pericentriolar pool was not fully elucidated","Whether ULK1 activation requires lipidated or unlipidated GABARAP was ambiguous"]},{"year":2017,"claim":"Structural and biophysical definition of the GIM consensus motif ([W/F]-[V/I]-X2-V) explained how GABARAP achieves selectivity over LC3 through hydrophobic pocket 2 variation, and PCM1 was shown to stabilize GABARAP at the pericentriolar material against Mib1-mediated proteasomal degradation.","evidence":"Crystal structures of GABARAP-GIM complexes, ITC/SPR, GIM mutagenesis, PCM1 CRISPR KO, Mib1 ubiquitination assay","pmids":["28655748","28712572"],"confidence":"High","gaps":["Whether all GIM-containing partners compete for the same binding surface was not tested","The ubiquitination sites on GABARAP targeted by Mib1 were not fully mapped"]},{"year":2019,"claim":"Multiple studies established that core autophagy regulators (ATG14, PIK3C3, ATG2A) preferentially bind GABARAP via LIR/GIM motifs, and that the ATG2A-GABARAP interaction is essential for phagophore formation and closure, consolidating GABARAP's unique role in autophagosome biogenesis.","evidence":"Crystal structures of LIR-GABARAP complexes, LIR mutagenesis phenocopying ATG2A/ATG2B double-KO, mitophagy flux assays","pmids":["30767700","32009292"],"confidence":"High","gaps":["How ATG2A lipid transfer activity is coordinated with GABARAP binding was not resolved","Whether GABARAP binding to ATG14 and ATG2A occurs simultaneously or sequentially during phagophore maturation was unknown"]},{"year":2018,"claim":"A knock-in mouse abolishing the ankyrin-G/GABARAP interaction demonstrated that GABARAP is required in vivo for maintaining GABAergic synapse density, pyramidal neuron excitability, and network synchronization, providing the first genetic in vivo evidence for GABARAP's synaptic function.","evidence":"Ankyrin-G W1989R knock-in mouse, electrophysiology, immunofluorescence quantification of forebrain GABAergic synapses","pmids":["30504823"],"confidence":"High","gaps":["Whether the synaptic phenotype is entirely due to loss of GABA(A)R surface stabilization or involves other ankyrin-G-GABARAP effectors was not distinguished","Behavioral consequences of the knock-in were not reported"]},{"year":2021,"claim":"GABARAP was shown to sequester the FLCN/FNIP GAP complex during CASM, mitophagy, and xenophagy, disrupting its activity toward RagC/D and thereby activating TFEB-driven lysosomal biogenesis—establishing a non-degradative signaling output of GABARAP conjugation.","evidence":"GABARAP-specific KO, LIR mutagenesis, RagC/D GAP assay, TFEB/TFE3 nuclear translocation","pmids":["34597140"],"confidence":"High","gaps":["Whether FLCN sequestration is sufficient to fully explain GABARAP-dependent TFEB activation was not determined","The quantitative contribution of each ATG8 conjugation stimulus (CASM vs. canonical autophagy) to FLCN sequestration was not measured"]},{"year":2021,"claim":"Crystal structure of the GABARAPL1–GABA(A)R γ2 complex, combined with trafficking assays and electrophysiology, revealed the molecular basis of GABARAP-family selectivity for GABA(A) receptor stabilization at synapses and showed that γ2 phosphorylation differentially regulates GABARAP versus AP2 binding.","evidence":"Crystal structure, co-immunoprecipitation, electrophysiology recording of synaptic currents, trafficking assay, phospho-mutagenesis","pmids":["33436612"],"confidence":"High","gaps":["Whether phosphorylation-dependent switching between GABARAP and AP2 operates dynamically at active synapses was not shown","The kinase(s) responsible for γ2 phosphorylation at this site in vivo were not identified"]},{"year":2025,"claim":"LRRK2 kinase activation on lysosomes was shown to depend specifically on GABARAP (not other ATG8 members) conjugated to single membranes via CASM, linking GABARAP to Parkinson's disease-relevant kinase regulation.","evidence":"STING agonist treatment, GABARAP-specific KO/interaction mutants, LRRK2 kinase activity measured by Rab phosphorylation","pmids":["39812709"],"confidence":"High","gaps":["The direct binding interface between LRRK2 and GABARAP was not structurally resolved","Whether GABARAP-dependent LRRK2 activation is relevant in dopaminergic neurons in vivo was not tested"]},{"year":null,"claim":"How GABARAP's autophagy and receptor-trafficking functions are coordinately regulated in the same cell remains unresolved—specifically, whether lipidated and unlipidated pools are independently controlled, and how substrate competition among dozens of LIR/GIM-containing partners is prioritized.","evidence":"","pmids":[],"confidence":"Low","gaps":["No quantitative model of GABARAP pool partitioning between autophagy and trafficking exists","Whether GABARAP's intrinsic fusogenic activity contributes to receptor exocytosis is untested","Full structural basis of GABARAP-LRRK2 and GABARAP-ATG2A interactions is lacking"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[10,11,15,16,22,25,29,30]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[6,7,9]},{"term_id":"GO:0031386","term_label":"protein tag activity","supporting_discovery_ids":[0,1,2,4]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[26]}],"localization":[{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[11,14,16]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[14,16,25]},{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[16,17]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[6,8]},{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[38,40]}],"pathway":[{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[0,1,2,4,5,14,15,16,20,21,22,26]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[11,14,24,29,30,47]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[35,37]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[22,25,40]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[10,29,30]}],"complexes":["ATG8 conjugation system (ATG7-ATG3-GABARAP)","CUL3-KBTBD6/KBTBD7 complex"],"partners":["ATG7","ATG3","ATG4B","ULK1","ATG2A","PLEKHM1","FLCN","ANK3"],"other_free_text":[]},"mechanistic_narrative":"GABARAP is a ubiquitin-like ATG8-family protein that functions as a central scaffold in both autophagy and receptor trafficking, conjugated to phosphatidylethanolamine on membranes via the sequential action of the ATG4B protease, ATG7 (E1), and ATG3 (E2) [PMID:15169837, PMID:11096062, PMID:11825910]. In autophagy, lipidated GABARAP selectively recruits LIR/GIM-containing partners—including ULK1 (promoting kinase activation and autophagy initiation), ATG2A (required for phagophore expansion and closure), ATG14/PIK3C3 (linking PI3K signaling to autophagosome biogenesis), PLEKHM1 (bridging autophagosomes to the HOPS complex for lysosome fusion), and FLCN/FNIP (sequestering this GAP complex to activate TFEB-dependent lysosomal biogenesis)—and also promotes membrane tethering and fusion through its lipidated form, with specificity over LC3 subfamily members encoded by a GIM consensus motif engaging GABARAP's hydrophobic pocket 2 [PMID:26687599, PMID:32009292, PMID:30767700, PMID:25498145, PMID:34597140, PMID:28655748, PMID:26789764]. Outside autophagy, GABARAP traffics GABA(A) receptors, angiotensin AT1 receptors, and TRPV1 channels to the plasma membrane through interactions with tubulin, NSF, gephyrin, and ankyrin-G, directly modulating GABAergic synaptic transmission and receptor surface density [PMID:33436612, PMID:30504823, PMID:18497328, PMID:11461150, PMID:10984509]. GABARAP additionally scaffolds the CUL3-KBTBD6/7 ubiquitin ligase to spatially restrict RAC1 signaling, participates in CASM-dependent LRRK2 activation on lysosomes, and is required in macrophages for mitophagy that restrains NLRP3 inflammasome activation [PMID:25684205, PMID:39812709, PMID:23427251]."},"prefetch_data":{"uniprot":{"accession":"O95166","full_name":"Gamma-aminobutyric acid receptor-associated protein","aliases":["GABA(A) receptor-associated protein","MM46"],"length_aa":117,"mass_kda":13.9,"function":"Ubiquitin-like modifier that plays a role in intracellular transport of GABA(A) receptors and its interaction with the cytoskeleton (PubMed:9892355). Involved in autophagy: while LC3s are involved in elongation of the phagophore membrane, the GABARAP/GATE-16 subfamily is essential for a later stage in autophagosome maturation (PubMed:15169837, PubMed:20562859, PubMed:22948227). Through its interaction with the reticulophagy receptor TEX264, participates in the remodeling of subdomains of the endoplasmic reticulum into autophagosomes upon nutrient stress, which then fuse with lysosomes for endoplasmic reticulum turnover (PubMed:31006538). Also required for the local activation of the CUL3(KBTBD6/7) E3 ubiquitin ligase complex, regulating ubiquitination and degradation of TIAM1, a guanyl-nucleotide exchange factor (GEF) that activates RAC1 and downstream signal transduction (PubMed:25684205). Thereby, regulates different biological processes including the organization of the cytoskeleton, cell migration and proliferation (PubMed:25684205). Involved in apoptosis (PubMed:15977068)","subcellular_location":"Cytoplasmic vesicle, autophagosome membrane; Endomembrane system; Cytoplasm, cytoskeleton; Golgi apparatus membrane; Cytoplasmic vesicle","url":"https://www.uniprot.org/uniprotkb/O95166/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GABARAP","classification":"Not Classified","n_dependent_lines":39,"n_total_lines":1208,"dependency_fraction":0.03228476821192053},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/GABARAP","total_profiled":1310},"omim":[{"mim_id":"621399","title":"UBA DOMAIN-CONTAINING PROTEIN 2; UBAC2","url":"https://www.omim.org/entry/621399"},{"mim_id":"621000","title":"SORTING NEXIN 18; SNX18","url":"https://www.omim.org/entry/621000"},{"mim_id":"620673","title":"MICROTUBULE-ASSOCIATED PROTEIN 1, LIGHT CHAIN 3, BETA-2; MAP1LC3B2","url":"https://www.omim.org/entry/620673"},{"mim_id":"618616","title":"MITOGEN-ACTIVATED PROTEIN KINASE 15; MAPK15","url":"https://www.omim.org/entry/618616"},{"mim_id":"617739","title":"KELCH REPEAT- AND BTB DOMAIN-CONTAINING PROTEIN 7; KBTBD7","url":"https://www.omim.org/entry/617739"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Vesicles","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/GABARAP"},"hgnc":{"alias_symbol":["MM46","ATG8A"],"prev_symbol":[]},"alphafold":{"accession":"O95166","domains":[{"cath_id":"3.10.20.90","chopping":"3-109","consensus_level":"high","plddt":96.1543,"start":3,"end":109}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O95166","model_url":"https://alphafold.ebi.ac.uk/files/AF-O95166-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O95166-F1-predicted_aligned_error_v6.png","plddt_mean":94.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GABARAP","jax_strain_url":"https://www.jax.org/strain/search?query=GABARAP"},"sequence":{"accession":"O95166","fasta_url":"https://rest.uniprot.org/uniprotkb/O95166.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O95166/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O95166"}},"corpus_meta":[{"pmid":"15169837","id":"PMC_15169837","title":"LC3, GABARAP and GATE16 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this lipidation is reversible by the deconjugase Atg4B.\",\n      \"method\": \"Radiolabeling with [14C]-ethanolamine, membrane fractionation, in vitro Atg4B cleavage assay\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct biochemical labeling and enzymatic assay, replicated across multiple Atg8 homologs in same study\",\n      \"pmids\": [\"15169837\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Human Apg7p (hATG7) acts as an E1-like activating enzyme for GABARAP, forming a thioester intermediate with GABARAP via its active-site Cys572; GABARAP co-immunoprecipitates with hApg7p and forms a stable intermediate with the C572S mutant.\",\n      \"method\": \"Co-immunoprecipitation, site-directed mutagenesis, cross-linking, glycerol-gradient centrifugation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — active-site mutagenesis combined with biochemical intermediate trapping\",\n      \"pmids\": [\"11096062\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Human Apg3p (hATG3) acts as the E2-like conjugating enzyme for GABARAP; its active-site Cys264 forms a thioester intermediate with GABARAP, and hATG3 forms an E1·E2 complex with hATG7.\",\n      \"method\": \"Site-directed mutagenesis, co-immunoprecipitation, E2-substrate intermediate trapping\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — active-site mutagenesis with biochemical reconstitution of E1-E2-substrate cascade\",\n      \"pmids\": [\"11825910\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"A single protease, Apg4B/autophagin-1, acts as the processing and deconjugating enzyme for GABARAP (and other mammalian Atg8 homologs), identified using electrophilic activity-based probes derived from GABARAP sequence.\",\n      \"method\": \"Activity-based protein profiling with electrophilic probes, in vitro protease activity assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — substrate-based chemical probes with direct identification of active protease\",\n      \"pmids\": [\"14530254\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"GABARAP can be conjugated in vitro to both phosphatidylethanolamine (PE) and phosphatidylserine (PS) by the reconstituted hATG7/hATG3 conjugation system, but in vivo PE is the predominant target lipid.\",\n      \"method\": \"In vitro reconstitution with purified recombinant Atg proteins and synthetic lipid liposomes, thin-layer chromatography of endogenous conjugates\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — fully reconstituted in vitro lipidation system with orthogonal in vivo verification\",\n      \"pmids\": [\"16303767\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Lipidation of GABARAP (and LC3) by ATG3 is dependent on membrane curvature; ATG3 contains an N-terminal amphipathic helix that senses lipid-packing defects on highly curved membranes, restricting lipidation to such membranes in vitro and in vivo.\",\n      \"method\": \"In vitro lipidation assay on liposomes of defined curvature, amphipathic helix mutagenesis, rescue experiments in ATG3-knockout cells\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro system + mutagenesis + KO rescue, multiple orthogonal approaches\",\n      \"pmids\": [\"24747438\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Crystal structure of human GABARAP at 1.6 Å resolution reveals an N-terminal helical subdomain responsible for tubulin binding and a ubiquitin-like C-terminal domain containing the GABA(A) receptor binding site; GABARAP can self-associate in a head-to-tail manner promoting tubulin polymerization and receptor clustering.\",\n      \"method\": \"X-ray crystallography, structure-based mutagenesis\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution crystal structure with mutagenesis validation of functional domains\",\n      \"pmids\": [\"11779480\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Crystal structure of mammalian GABARAP at 2.0 Å resolution confirms an N-terminal basic helical region for tubulin binding and a conserved ubiquitin-like core fold; the conserved surface face mediates protein-protein interactions shared across the family.\",\n      \"method\": \"X-ray crystallography\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — independent crystal structure confirming domain architecture\",\n      \"pmids\": [\"11818336\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"NMR solution structure of human GABARAP reveals that amino- and carboxyl-terminal ends interact with each other in solution (not seen in crystal structures), suggesting conformational dynamics that regulate GABARAP interactions.\",\n      \"method\": \"NMR spectroscopy\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution NMR structure providing functional insight distinct from crystal structures\",\n      \"pmids\": [\"11875056\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"GABARAP binds directly to both tubulin and microtubules in a salt-sensitive (ionic interaction) manner in vitro and co-immunoprecipitates with tubulin in intact cells; the tubulin-binding domain is located at the N-terminus marked by specific basic amino acids; GABARAP also associates with microfilaments, likely via intermediary proteins.\",\n      \"method\": \"In vitro tubulin binding assay, co-immunoprecipitation, cytoskeletal drug treatments (taxol, nocodazole, cytochalasin D), deletion constructs and synthetic peptides\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal biochemical and cell-based approaches\",\n      \"pmids\": [\"10899939\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"GABARAP promotes clustering of GABA(A) receptors in QT-6 fibroblasts requiring both the tubulin-binding motif of GABARAP and the gamma2 subunit; clustered GABA(A) receptors show altered channel kinetics (higher EC50, faster deactivation, slower desensitization) compared to diffuse receptors.\",\n      \"method\": \"GFP-tagged receptor expression, immunofluorescence clustering assay, whole-cell electrophysiology, microtubule disruption experiments\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal functional assays with mechanistic dissection\",\n      \"pmids\": [\"10984509\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"GABARAP is enriched in the Golgi apparatus and postsynaptic cisternae (not at inhibitory synapses), co-immunoprecipitates with GABA(A) receptors, and binds directly to NSF (N-ethylmaleimide-sensitive factor), suggesting a role in intracellular receptor transport rather than synaptic anchoring.\",\n      \"method\": \"Subcellular fractionation, immunoprecipitation, direct binding assay, confocal immunofluorescence\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal IP plus direct binding plus localization with functional inference\",\n      \"pmids\": [\"11461150\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"GABARAP interacts with gephyrin in biochemical assays and transfected cells; confocal analysis shows GABARAP is enriched in intracellular compartments and not at gephyrin-positive postsynaptic specializations, suggesting a role in receptor sorting/targeting rather than synaptic anchoring.\",\n      \"method\": \"Co-immunoprecipitation, transfected cell co-localization, gephyrin-knockout mouse analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — biochemical interaction confirmed in KO mouse model with subcellular localization\",\n      \"pmids\": [\"10900017\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"GABARAP's interaction with GABA(A) receptor is specific for gamma subunits; the interaction domain in GABARAP maps to residues 41–51, and GABARAP dimerizes using the same region (residues 36–68); a membrane-permeable peptide corresponding to the GABARAP interaction domain in gamma2 inhibits receptor clustering in living cells.\",\n      \"method\": \"Yeast two-hybrid quantitative assay, GST pulldown, peptide inhibition, GABA(A) receptor clustering assay in fibroblasts\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple biochemical methods plus functional peptide inhibition in cells\",\n      \"pmids\": [\"11948245\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"C-terminal processing of GABARAP at Gly116 (generating the lipidated form) is required for its proper subcellular distribution (away from Golgi into cytoplasmic puncta in neurons) and for its function in promoting GABA(A) receptor plasma membrane expression; the G116A mutant fails to enhance receptor surface expression.\",\n      \"method\": \"Site-directed mutagenesis, Western blotting with dual-tag construct, confocal microscopy, oocyte electrophysiology, surface biotinylation\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — mutagenesis of processing site with multiple functional readouts\",\n      \"pmids\": [\"17581952\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PLEKHM1 contains a GABARAP interaction motif (LIR) that mediates direct binding to autophagosomal membranes, and PLEKHM1 also directly interacts with the HOPS complex; this dual interaction is required for autophagosome-lysosome fusion, endocytic cargo degradation, and clearance of protein aggregates.\",\n      \"method\": \"Co-immunoprecipitation, GST pulldown, LIR mutagenesis, PLEKHM1 depletion with specific cargo degradation assays\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal IP, mutagenesis of interaction motif, KD with defined phenotypic readouts\",\n      \"pmids\": [\"25498145\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"GABARAP (unlipidated and lipidated), but not LC3B or other ATG8 family members, specifically promotes ULK1 kinase activation in a manner dependent on the ULK1 LIR motif; GABARAP is dynamically trafficked from the pericentriolar matrix to the phagophore upon starvation, regulated by the Golgi proteins WAC and GM130.\",\n      \"method\": \"Protein interaction studies, GABARAP-specific KD/rescue, ULK1 kinase activity assay, live-cell imaging of GABARAP trafficking, LIR mutagenesis\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — specific ATG8 member discrimination with kinase activity assay and LIR mutagenesis, multiple methods\",\n      \"pmids\": [\"26687599\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"The centriolar satellite protein PCM1 directly binds GABARAP (but not LC3B) via a canonical LIR motif, stabilizing GABARAP at the pericentriolar material; loss of PCM1 leads to proteasomal degradation of GABARAP mediated by the E3 ligase Mib1, which promotes K48-linked ubiquitination of GABARAP at N-terminal residues.\",\n      \"method\": \"Direct binding assay, LIR mutagenesis, CRISPR/siRNA KD, proteasome inhibitor rescue, ubiquitination assay, autophagy flux measurement\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct binding with LIR mutagenesis, ubiquitination mapping, and defined functional consequence\",\n      \"pmids\": [\"28712572\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"ATL3 functions as a tubular ER-phagy receptor that specifically binds GABARAP (but not LC3) subfamily proteins via two GABARAP interaction motifs (GIMs); ATL3-GABARAP interaction is essential for starvation-induced tubular ER degradation, and HSAN I-associated ATL3 mutations (Y192C, P338R) disrupt this interaction and impair ER-phagy.\",\n      \"method\": \"Co-immunoprecipitation, GIM mutagenesis, ER-phagy flux assay, ATL3 KD/rescue, patient mutation analysis\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — selective interaction established by mutagenesis with defined functional consequence in ER-phagy\",\n      \"pmids\": [\"30773365\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"A GABARAP interaction motif (GIM) sequence [W/F]-[V/I]-X2-V confers 11-fold selectivity for GABARAP over LC3B, as demonstrated by biophysical and structural analysis of the PLEKHM1 LIR; conversion of other LIR motifs into GIMs by introducing valine residues enhances GABARAP over LC3B binding.\",\n      \"method\": \"Biophysical binding measurements (ITC/SPR), crystal structure of GABARAP-GIM complex, mutagenesis of LIR/GIM positions\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure plus mutagenesis plus quantitative biophysics defining specificity determinants\",\n      \"pmids\": [\"28655748\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PIK3C3, BECN1, and ATG14 (components of the PtdIns3K-C1 complex) each contain functional LIR motifs that interact preferentially with GABARAP and GABARAPL1 over LC3 proteins; crystal structures of these LIR motifs with GABARAP proteins reveal that variation in hydrophobic pocket 2 explains GABARAP-family specificity; ATG14 LIR mutation blocks its colocalization with LC3B and impairs mitophagy.\",\n      \"method\": \"Crystal structures, binding assays, LIR mutagenesis, mitophagy flux assay, colocalization studies\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple crystal structures with mutagenesis and functional validation\",\n      \"pmids\": [\"30767700\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"ATG2A contains a conserved LIR-like motif that mediates direct interaction with GABARAP proteins; ATG2A-GABARAP interaction mutants fail to form and close phagophores, blocking autophagy flux similarly to ATG2A/ATG2B double-KO cells, establishing ATG2-GABARAP interaction as essential for phagophore formation.\",\n      \"method\": \"Mutagenesis of ATG2A-GABARAP interaction motif, autophagy flux assay, phagophore formation imaging, double-KO comparison\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — interaction mutagenesis with defined phagophore formation phenotype, KO comparators\",\n      \"pmids\": [\"32009292\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"GABARAP (but not LC3) directly binds a LIR motif in the FLCN/FNIP tumor suppressor complex and mediates its sequestration to GABARAP-conjugated membrane compartments during CASM, mitophagy, and xenophagy; this disrupts FLCN/FNIP GAP activity toward RagC/D, impairing mTOR-dependent phosphorylation of TFEB and activating lysosomal biogenesis.\",\n      \"method\": \"Co-immunoprecipitation, LIR mutagenesis, GABARAP-specific KO, TFEB/TFE3 activity assay, RagC/D GAP assay\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods establishing GABARAP-specific function in FLCN-mTOR-TFEB axis\",\n      \"pmids\": [\"34597140\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Nix/Bnip3L directly interacts with GABARAP as demonstrated by phage display screening, in vitro binding studies, pull-down, co-immunoprecipitation, and co-localization, suggesting a direct molecular link between apoptosis and autophagy pathways.\",\n      \"method\": \"Phage display, in vitro binding, GST pulldown, co-immunoprecipitation, co-localization in mammalian cells\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods confirming direct interaction\",\n      \"pmids\": [\"19363302\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"GABARAP binds to the C-terminal cytoplasmic domain of the angiotensin II type 1 receptor (AT1R) and promotes its plasma membrane expression >6-fold; siRNA knockdown of GABARAP reduces AT1R surface expression by 84%; GABARAP interaction maps to residues 32–51 and requires the C-terminal 21 aa.\",\n      \"method\": \"Yeast two-hybrid, GST pulldown, co-immunoprecipitation, BRET assay, siRNA knockdown, surface expression quantification\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple interaction assays plus siRNA loss-of-function with quantitative surface expression readout\",\n      \"pmids\": [\"18497328\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"CUL3-KBTBD6/KBTBD7 ubiquitin ligase complex employs ATG8-family-interacting motifs to bind preferentially to GABARAP proteins; GABARAP-containing vesicles recruit CUL3(KBTBD6/KBTBD7) to ubiquitinate and degrade the RAC1 GEF TIAM1, thereby spatially restricting RAC1 signaling and regulating actin morphology and cell invasion.\",\n      \"method\": \"Interactome mass spectrometry, co-immunoprecipitation, ubiquitination assay, GABARAP KD, TIAM1 abundance measurement, RAC1 activity assay\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — MS interactome plus biochemical ubiquitination plus KD with defined signaling phenotype\",\n      \"pmids\": [\"25684205\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Lipidated GABARAP and GATE-16 (but not lipidated LC3) promote extensive membrane tethering and full membrane fusion (as shown by vesicle aggregation, lipid mixing, and aqueous content mixing without leakage) in reconstituted systems; membrane curvature (smaller vesicle diameter) and negative-curvature lipids (cardiolipin, DAG) facilitate this fusion.\",\n      \"method\": \"In vitro reconstituted enzymatic and chemical lipidation, vesicle tethering/fusion assays, cryo-electron microscopy\",\n      \"journal\": \"Biophysical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — fully reconstituted in vitro system with multiple independent fusion readouts and electron microscopy\",\n      \"pmids\": [\"26789764\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"GABARAP directly binds to PI4K2A (phosphatidylinositol 4-kinase type 2α) and recruits it to autophagosomes; this GABARAP-PI4K2A interaction and the resulting PtdIns4P production are required for autophagosome-lysosome fusion.\",\n      \"method\": \"Co-immunoprecipitation, GABARAP KD, autophagosome-lysosome fusion assay\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — IP plus KD with functional readout, single lab\",\n      \"pmids\": [\"26391226\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Mulan E3 ubiquitin ligase interacts with GABARAP via an LIR motif in its RING finger domain in complex with the E2 enzyme Ube2E3; this interaction requires both the LIR motif and Ube2E3 presence, linking Mulan to mitophagy regulation through GABARAP.\",\n      \"method\": \"Yeast two-hybrid (modified), co-immunoprecipitation, LIR motif analysis\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — yeast two-hybrid and co-IP with mechanistic LIR requirement, single lab\",\n      \"pmids\": [\"25224329\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"GABARAP/GABARAPL1 (but not other ATG8 family members) directly bind to a previously unappreciated region in the gamma2 subunit of GABA(A)R; crystal structure of GABARAPL1-gamma2 complex reveals the molecular basis; GABARAP stabilizes GABAARs by promoting trafficking (not blocking endocytosis); phosphorylation of gamma2 differentially modulates binding to GABARAP vs. clathrin adaptor AP2; blocking GABARAP-GABAAR complex reduces GABAergic synaptic currents.\",\n      \"method\": \"Crystal structure, co-immunoprecipitation, electrophysiology, trafficking assays, phosphorylation mutagenesis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with functional validation by electrophysiology and trafficking assays\",\n      \"pmids\": [\"33436612\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Ankyrin-G directly interacts with GABARAP to stabilize cell-surface GABA(A) receptors at GABAergic synapses; a knock-in mouse with the W1989R mutation abolishing ankyrin-G/GABARAP interaction shows striking reduction in forebrain GABAergic synapses, pyramidal cell hyperexcitability, and disrupted network synchronization.\",\n      \"method\": \"Knock-in mouse model, electrophysiology, immunofluorescence quantification of synapses\",\n      \"journal\": \"Molecular psychiatry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic interaction-abolishing knock-in mouse with defined synaptic and circuit phenotypes\",\n      \"pmids\": [\"30504823\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"GABARAP associates with TRPV1 in HEK293 cells and DRG neurons, augments TRPV1 surface expression and clustering, attenuates voltage/capsaicin sensitivity in the presence of extracellular calcium, lengthens vanilloid-induced tachyphylaxia, and increases tubulin interaction with the TRPV1 C-terminal domain.\",\n      \"method\": \"Co-immunoprecipitation, surface expression quantification, electrophysiology, nocodazole cytoskeleton disruption\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple interaction and functional assays, single lab\",\n      \"pmids\": [\"20179142\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Caspase-3 cleaves Atg4D, generating a truncated ΔN63 Atg4D with increased activity against GABARAP-L1 (but relevance to GABARAP itself is indirect); Atg4D siRNA silencing abrogates GABARAP-L1 autophagosome formation.\",\n      \"method\": \"In vitro caspase-3 cleavage assay, cell-based Atg4D siRNA knockdown, autophagosome formation assay\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vitro enzyme assay plus siRNA KD, but finding is primarily about GABARAP-L1 not GABARAP itself\",\n      \"pmids\": [\"19549685\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TBK1 phosphorylates GABARAP-L2 (not GABARAP itself) on surface-exposed serine residues, impeding ATG4 binding and protecting lipidated GABARAP-L2 from premature removal from nascent autophagosomes.\",\n      \"method\": \"In vitro kinase assay, phosphomimetic mutagenesis, liposome deconjugation assay, autophagosome formation analysis\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro kinase assay with mutagenesis; primarily about GABARAP-L2, GABARAP itself less directly studied\",\n      \"pmids\": [\"31709703\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"UBA5 contains an atypical LIR motif that preferentially interacts with GABARAP (not LC3) proteins; NMR/crystal structures of GABARAP-UBA5 LIR complex reveal a novel hydrophobic pocket (HP0) engaged by a conserved tryptophan N-terminal to the core LIR, with K46/K47 of GABARAP being key specificity determinants; GABARAP regulates UBA5 localization to the ER membrane in a lipidation-independent manner.\",\n      \"method\": \"NMR, crystal structures, ITC, swapping mutagenesis, KO cell lines, ER localization assay\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — two independent crystal structures with mutagenesis and biophysical quantification\",\n      \"pmids\": [\"30990354\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"GABARAP subfamily (particularly GATE-16/GABARAPL2) but not LC3 proteins are required for IFN-γ-mediated clearance of vacuolar pathogens (Toxoplasma); GATE-16 specifically associates with the small GTPase ARF1 to mediate uniform cytosolic distribution of interferon-inducible GTPases (IFN-GTPases); loss of GABARAPs reduces ARF1 activation, causing IFN-GTPase aggregation.\",\n      \"method\": \"GABARAP-family-specific KO cells and mice, Toxoplasma clearance assay, ARF1 co-immunoprecipitation, GTPase activation assay\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — specific KO with defined antimicrobial phenotype plus molecular mechanism via ARF1 interaction\",\n      \"pmids\": [\"28604719\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Calreticulin is a high-affinity ligand of GABARAP (Kd = 64 nM) identified by phage display; the interaction was confirmed by pull-down from brain lysate and co-localization in N2a cells; crystal structure of GABARAP in complex with the calreticulin binding epitope was determined.\",\n      \"method\": \"Phage display, SPR/biophysical binding, GST pulldown, co-localization, crystal structure of complex\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure of complex plus multiple orthogonal binding confirmations\",\n      \"pmids\": [\"17916189\", \"19154346\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"GABARAP deficiency in macrophages leads to inefficient clearance of damaged mitochondria, resulting in elevated mitochondrial ROS and cytosolic mitochondrial DNA release, which enhances NLRP3 inflammasome activation (increased caspase-1, IL-1β, IL-18); GABARAP-deficient mice show higher mortality in sepsis models.\",\n      \"method\": \"GABARAP KO mouse, mitophagy assay, mitochondrial ROS measurement, inflammasome activation assay (caspase-1 processing, cytokine secretion)\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mouse with defined molecular mechanism (mitophagy-ROS-inflammasome axis)\",\n      \"pmids\": [\"23427251\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Lysosomal turnover of endogenous GABARAP-phospholipid conjugate (GABARAP-PL) is activated during differentiation of C2C12 cells to myotubes independently of mTOR kinase inactivation (unlike starvation-induced autophagy); little GABARAP-PL accumulates during canonical starvation-induced autophagy in most tissues.\",\n      \"method\": \"Lysosomal protease inhibitor accumulation assay, S6 kinase phosphorylation as mTOR readout, tissue-specific endogenous GABARAP-PL analysis\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — endogenous protein analysis with mechanistic dissection from mTOR, single lab\",\n      \"pmids\": [\"16874098\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Bcl-2 directly binds GABARAP via a three-residue segment (EWD) adjacent to the BH4 region, anchored to one hydrophobic pocket of GABARAP; Bcl-2 overexpression inhibits GABARAP lipidation, linking Bcl-2's autophagy-inhibitory function to direct competition with the lipid conjugation machinery.\",\n      \"method\": \"NMR chemical shift mapping, mutagenesis, pull-down, GABARAP lipidation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — NMR-defined interaction site plus functional lipidation inhibition assay\",\n      \"pmids\": [\"24240096\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"STING activation triggers LRRK2 lysosomal recruitment and kinase activation via the CASM (conjugation of ATG8 to single membranes) pathway; LRRK2 activation is highly dependent on interactions with GABARAP (not other ATG8 family members); multiple lysosome-perturbing stimuli converge on CASM-GABARAP to control LRRK2 kinase activity.\",\n      \"method\": \"STING agonist treatment, GABARAP-specific KO/interaction mutants, LRRK2 lysosome recruitment imaging, LRRK2 kinase activity assay (Rab phosphorylation)\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — GABARAP-specific KO with defined kinase activation readout, multiple stimuli tested\",\n      \"pmids\": [\"39812709\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"ATG4 isoforms (ATG4A, ATG4C, ATG4D) contribute redundantly to priming activity that enables lipidation of endogenous GABARAPL1 on autophagic structures; ATG4B is the dominant but not sole isoform processing GABARAP family proteins; pre-primed LC3B can rescue autophagic degradation without ATG4-mediated delipidation.\",\n      \"method\": \"CRISPR-Cas9 KO, siRNA depletion, processing assay, autophagy flux measurement (SQSTM1 degradation), correlative light and electron microscopy\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — comprehensive genetic dissection with multiple ATG4 isoform KOs and functional readouts\",\n      \"pmids\": [\"30661429\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"FLCN directly interacts with GABARAP; the FLCN-GABARAP association is modulated by FNIP1/FNIP2 and further regulated by ULK1 phosphorylation of FLCN at Ser406, Ser537, and Ser542.\",\n      \"method\": \"Co-immunoprecipitation, ULK1 overexpression phosphorylation mapping, autophagy flux assay\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — interaction confirmed by co-IP with phosphorylation site mapping, single lab\",\n      \"pmids\": [\"25126726\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"MAPK15/ERK8 interacts with GABARAP (and LC3B, GABARAPL1) via a conserved LIR motif; MAPK15 localizes to autophagic compartments and stimulates ATG8-family protein lipidation, autophagosome formation, and SQSTM1 degradation in a kinase-dependent fashion.\",\n      \"method\": \"Co-immunoprecipitation, LIR mutagenesis, autophagosome formation assay, lipidation assay, SQSTM1 degradation assay\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — LIR mutagenesis with kinase-dependent functional readouts, single lab\",\n      \"pmids\": [\"22948227\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"HIV-1 Nef binds directly and specifically to all GABARAP family members (but not LC3 family members) via two surface-exposed hydrophobic pockets (involving S53 and F62 of GABARAP); GABARAP knockdown significantly reduces Nef plasma membrane localization.\",\n      \"method\": \"Pulldown with purified recombinant proteins, co-immunoprecipitation, NMR chemical shift mapping, site-directed mutagenesis, siRNA knockdown, live-cell fluorescence microscopy\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — NMR-defined binding interface, mutagenesis, and siRNA functional validation\",\n      \"pmids\": [\"28729737\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"GABARAP self-associates and dimerizes at physiological salt concentrations; the dimerization domain maps to residues 41–51 (the same region that binds the GABA(A) receptor gamma2 subunit), as shown by synthetic peptide inhibition of GST pulldown.\",\n      \"method\": \"GST pulldown, synthetic peptide competition, deletion constructs\",\n      \"journal\": \"Neuropharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — domain mapping with peptide inhibition, single lab\",\n      \"pmids\": [\"12367594\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Co-expression of GABARAP with GABA(A) receptors increases single-channel conductance to ≥40 pS (vs. 30 pS control) and mean open time; the increased conductance is GABA concentration-dependent, demonstrating that GABARAP-mediated trafficking influences ion channel gating properties.\",\n      \"method\": \"Outside-out patch clamp electrophysiology of transiently transfected cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — single-channel electrophysiology with direct functional consequence, single lab\",\n      \"pmids\": [\"16954214\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"GABARAP interacts with transferrin receptor (TfR) cytoplasmic domain via its YTRF internalization motif, as shown by yeast two-hybrid, in vitro binding with purified proteins, and co-immunoprecipitation from HeLa cells; GABARAP-GFP localizes to perinuclear vesicles, suggesting a general role in vesicle trafficking beyond neurons.\",\n      \"method\": \"Yeast two-hybrid, in vitro binding assay, co-immunoprecipitation, GFP chimera localization\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple interaction methods confirming direct binding, single lab\",\n      \"pmids\": [\"11997026\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GABARAP is a mammalian ATG8-family ubiquitin-like protein that undergoes C-terminal processing by ATG4 proteases and E1 (ATG7)/E2 (ATG3)-mediated conjugation to phosphatidylethanolamine on autophagosomal and single membranes; in its lipidated and unlipidated forms it acts as a selective scaffold that binds diverse LIR/GIM-containing partners (including ULK1, ATG14, ATG2A, PIK3C3, PLEKHM1, ATL3, FLCN, LRRK2, and others) to uniquely promote phagophore expansion, ULK1 kinase activation, autophagosome-lysosome fusion, and mitophagy/xenophagy, while also functioning outside autophagy to traffic GABA(A) receptors, angiotensin AT1 receptors, and TRPV1 channels to the plasma membrane via interactions with NSF, tubulin, gephyrin, and ankyrin-G, and to scaffold the CUL3-KBTBD6/7 ubiquitin ligase for spatially restricted RAC1 signaling.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"GABARAP is a ubiquitin-like ATG8-family protein that functions as a central scaffold in both autophagy and receptor trafficking, conjugated to phosphatidylethanolamine on membranes via the sequential action of the ATG4B protease, ATG7 (E1), and ATG3 (E2) [PMID:15169837, PMID:11096062, PMID:11825910]. In autophagy, lipidated GABARAP selectively recruits LIR/GIM-containing partners—including ULK1 (promoting kinase activation and autophagy initiation), ATG2A (required for phagophore expansion and closure), ATG14/PIK3C3 (linking PI3K signaling to autophagosome biogenesis), PLEKHM1 (bridging autophagosomes to the HOPS complex for lysosome fusion), and FLCN/FNIP (sequestering this GAP complex to activate TFEB-dependent lysosomal biogenesis)—and also promotes membrane tethering and fusion through its lipidated form, with specificity over LC3 subfamily members encoded by a GIM consensus motif engaging GABARAP's hydrophobic pocket 2 [PMID:26687599, PMID:32009292, PMID:30767700, PMID:25498145, PMID:34597140, PMID:28655748, PMID:26789764]. Outside autophagy, GABARAP traffics GABA(A) receptors, angiotensin AT1 receptors, and TRPV1 channels to the plasma membrane through interactions with tubulin, NSF, gephyrin, and ankyrin-G, directly modulating GABAergic synaptic transmission and receptor surface density [PMID:33436612, PMID:30504823, PMID:18497328, PMID:11461150, PMID:10984509]. GABARAP additionally scaffolds the CUL3-KBTBD6/7 ubiquitin ligase to spatially restrict RAC1 signaling, participates in CASM-dependent LRRK2 activation on lysosomes, and is required in macrophages for mitophagy that restrains NLRP3 inflammasome activation [PMID:25684205, PMID:39812709, PMID:23427251].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Identifying GABARAP as a link between GABA(A) receptors and the cytoskeleton established its initial function as a receptor-trafficking scaffold that clusters GABA(A) receptors in a tubulin-dependent manner and interacts with the postsynaptic protein gephyrin.\",\n      \"evidence\": \"In vitro tubulin binding, co-immunoprecipitation, electrophysiology, receptor clustering assays, gephyrin KO mouse analysis in multiple independent studies\",\n      \"pmids\": [\"10899939\", \"10984509\", \"10900017\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether GABARAP directly contacts gephyrin and GABA(A) receptors simultaneously or sequentially was unresolved\", \"In vivo synaptic consequence of GABARAP loss was not tested\", \"Mechanism of GABARAP delivery to the plasma membrane was unknown\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Demonstrating that GABARAP resides at the Golgi and binds NSF rather than localizing to synapses reframed its role from synaptic anchoring to intracellular receptor transport.\",\n      \"evidence\": \"Subcellular fractionation, direct binding assay with NSF, confocal immunofluorescence in neurons\",\n      \"pmids\": [\"11461150\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which step of vesicular transport (budding, fusion, or recycling) GABARAP-NSF interaction controls was unclear\", \"Whether NSF interaction is direct or part of a larger SNARE-associated complex was not resolved\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"High-resolution crystal and NMR structures revealed GABARAP's domain architecture—an N-terminal helical tubulin-binding subdomain and a ubiquitin-like C-terminal fold—defining the structural basis for its dual cytoskeletal and receptor-binding functions.\",\n      \"evidence\": \"X-ray crystallography at 1.6 Å and 2.0 Å, NMR solution structure, structure-based mutagenesis\",\n      \"pmids\": [\"11779480\", \"11818336\", \"11875056\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the intramolecular N-/C-terminal interaction seen by NMR regulates partner access was not determined\", \"No structure of GABARAP bound to a full-length cargo receptor existed\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Establishing that ATG7 and ATG3 act as E1 and E2 enzymes forming thioester intermediates with GABARAP placed it firmly within the ubiquitin-like conjugation cascade for ATG8 proteins.\",\n      \"evidence\": \"Active-site mutagenesis (C572S for ATG7, C264 for ATG3), co-immunoprecipitation, thioester intermediate trapping\",\n      \"pmids\": [\"11096062\", \"11825910\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The target lipid for GABARAP conjugation had not yet been identified\", \"Functional consequence of lipidation versus unlipidated GABARAP was unknown\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Demonstrating that GABARAP is conjugated to PE on autophagosomal membranes, with ATG4B as both the priming protease and deconjugase, established the complete lipidation-delipidation cycle.\",\n      \"evidence\": \"Radiolabeling with [14C]-ethanolamine, membrane fractionation, in vitro ATG4B cleavage, reconstituted lipidation with synthetic liposomes\",\n      \"pmids\": [\"15169837\", \"14530254\", \"16303767\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether lipidation is required for GABARAP's receptor-trafficking functions remained untested\", \"Regulation of the lipidation/delipidation balance in vivo was unexplored\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Showing that C-terminal processing at Gly116 is required for proper GABARAP subcellular distribution and for promoting GABA(A) receptor surface expression linked the autophagy-associated lipidation machinery to receptor trafficking function.\",\n      \"evidence\": \"G116A mutagenesis, surface biotinylation, oocyte electrophysiology, confocal microscopy in neurons\",\n      \"pmids\": [\"17581952\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the processed form must be lipidated or simply C-terminally exposed was not distinguished\", \"The vesicular compartment from which GABARAP promotes receptor export was not defined\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Identifying the angiotensin AT1 receptor as a second GABARAP-dependent cargo expanded GABARAP's trafficking role beyond neurons to cardiovascular physiology.\",\n      \"evidence\": \"Yeast two-hybrid, BRET, siRNA knockdown reducing AT1R surface expression by 84%\",\n      \"pmids\": [\"18497328\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether GABARAP uses the same lipidation-dependent mechanism for AT1R as for GABA(A)R was not tested\", \"In vivo cardiovascular consequence of GABARAP loss was not examined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Membrane curvature sensing by ATG3's amphipathic helix was shown to restrict GABARAP (and LC3) lipidation to highly curved membranes, providing a biophysical mechanism that spatially confines ATG8 conjugation to nascent autophagosomes.\",\n      \"evidence\": \"In vitro lipidation on liposomes of defined curvature, amphipathic helix mutagenesis, rescue in ATG3-KO cells\",\n      \"pmids\": [\"24747438\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether membrane curvature sensing operates identically for GABARAP versus LC3 subfamily members was not resolved\", \"How curvature restriction is bypassed during CASM on flat single membranes was unclear\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Discovering that PLEKHM1 bridges GABARAP-decorated autophagosomes to the HOPS tethering complex, and that CUL3-KBTBD6/7 uses GABARAP to spatially restrict RAC1 signaling, established GABARAP as a platform for both autophagosome-lysosome fusion and non-autophagic ubiquitin ligase targeting.\",\n      \"evidence\": \"LIR mutagenesis, cargo degradation assays, interactome mass spectrometry, RAC1 activity measurement, TIAM1 ubiquitination\",\n      \"pmids\": [\"25498145\", \"25684205\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PLEKHM1 is redundant with other GABARAP-binding tethering factors was unknown\", \"The membrane compartment on which CUL3-KBTBD6/7 encounters GABARAP was not identified\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Reconstituted membrane fusion assays demonstrated that lipidated GABARAP and GATE-16 (but not LC3) autonomously tether and fuse membranes, revealing an intrinsic fusogenic activity that distinguishes the GABARAP subfamily.\",\n      \"evidence\": \"Enzymatic and chemical lipidation reconstitution, vesicle aggregation, lipid mixing, content mixing assays, cryo-EM\",\n      \"pmids\": [\"26789764\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether this fusogenic activity operates at the autophagosome-lysosome fusion step in vivo was not shown\", \"The structural mechanism by which lipidated GABARAP drives membrane merger was not resolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"GABARAP was shown to uniquely activate ULK1 kinase via its LIR motif and to traffic from the pericentriolar matrix to the phagophore upon starvation, establishing a GABARAP-specific role in autophagy initiation distinct from LC3.\",\n      \"evidence\": \"GABARAP-specific knockdown/rescue, ULK1 kinase activity assay, LIR mutagenesis, live-cell imaging of pericentriolar GABARAP trafficking\",\n      \"pmids\": [\"26687599\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How GABARAP is released from the pericentriolar pool was not fully elucidated\", \"Whether ULK1 activation requires lipidated or unlipidated GABARAP was ambiguous\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Structural and biophysical definition of the GIM consensus motif ([W/F]-[V/I]-X2-V) explained how GABARAP achieves selectivity over LC3 through hydrophobic pocket 2 variation, and PCM1 was shown to stabilize GABARAP at the pericentriolar material against Mib1-mediated proteasomal degradation.\",\n      \"evidence\": \"Crystal structures of GABARAP-GIM complexes, ITC/SPR, GIM mutagenesis, PCM1 CRISPR KO, Mib1 ubiquitination assay\",\n      \"pmids\": [\"28655748\", \"28712572\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether all GIM-containing partners compete for the same binding surface was not tested\", \"The ubiquitination sites on GABARAP targeted by Mib1 were not fully mapped\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Multiple studies established that core autophagy regulators (ATG14, PIK3C3, ATG2A) preferentially bind GABARAP via LIR/GIM motifs, and that the ATG2A-GABARAP interaction is essential for phagophore formation and closure, consolidating GABARAP's unique role in autophagosome biogenesis.\",\n      \"evidence\": \"Crystal structures of LIR-GABARAP complexes, LIR mutagenesis phenocopying ATG2A/ATG2B double-KO, mitophagy flux assays\",\n      \"pmids\": [\"30767700\", \"32009292\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How ATG2A lipid transfer activity is coordinated with GABARAP binding was not resolved\", \"Whether GABARAP binding to ATG14 and ATG2A occurs simultaneously or sequentially during phagophore maturation was unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"A knock-in mouse abolishing the ankyrin-G/GABARAP interaction demonstrated that GABARAP is required in vivo for maintaining GABAergic synapse density, pyramidal neuron excitability, and network synchronization, providing the first genetic in vivo evidence for GABARAP's synaptic function.\",\n      \"evidence\": \"Ankyrin-G W1989R knock-in mouse, electrophysiology, immunofluorescence quantification of forebrain GABAergic synapses\",\n      \"pmids\": [\"30504823\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the synaptic phenotype is entirely due to loss of GABA(A)R surface stabilization or involves other ankyrin-G-GABARAP effectors was not distinguished\", \"Behavioral consequences of the knock-in were not reported\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"GABARAP was shown to sequester the FLCN/FNIP GAP complex during CASM, mitophagy, and xenophagy, disrupting its activity toward RagC/D and thereby activating TFEB-driven lysosomal biogenesis—establishing a non-degradative signaling output of GABARAP conjugation.\",\n      \"evidence\": \"GABARAP-specific KO, LIR mutagenesis, RagC/D GAP assay, TFEB/TFE3 nuclear translocation\",\n      \"pmids\": [\"34597140\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether FLCN sequestration is sufficient to fully explain GABARAP-dependent TFEB activation was not determined\", \"The quantitative contribution of each ATG8 conjugation stimulus (CASM vs. canonical autophagy) to FLCN sequestration was not measured\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Crystal structure of the GABARAPL1–GABA(A)R γ2 complex, combined with trafficking assays and electrophysiology, revealed the molecular basis of GABARAP-family selectivity for GABA(A) receptor stabilization at synapses and showed that γ2 phosphorylation differentially regulates GABARAP versus AP2 binding.\",\n      \"evidence\": \"Crystal structure, co-immunoprecipitation, electrophysiology recording of synaptic currents, trafficking assay, phospho-mutagenesis\",\n      \"pmids\": [\"33436612\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether phosphorylation-dependent switching between GABARAP and AP2 operates dynamically at active synapses was not shown\", \"The kinase(s) responsible for γ2 phosphorylation at this site in vivo were not identified\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"LRRK2 kinase activation on lysosomes was shown to depend specifically on GABARAP (not other ATG8 members) conjugated to single membranes via CASM, linking GABARAP to Parkinson's disease-relevant kinase regulation.\",\n      \"evidence\": \"STING agonist treatment, GABARAP-specific KO/interaction mutants, LRRK2 kinase activity measured by Rab phosphorylation\",\n      \"pmids\": [\"39812709\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The direct binding interface between LRRK2 and GABARAP was not structurally resolved\", \"Whether GABARAP-dependent LRRK2 activation is relevant in dopaminergic neurons in vivo was not tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How GABARAP's autophagy and receptor-trafficking functions are coordinately regulated in the same cell remains unresolved—specifically, whether lipidated and unlipidated pools are independently controlled, and how substrate competition among dozens of LIR/GIM-containing partners is prioritized.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No quantitative model of GABARAP pool partitioning between autophagy and trafficking exists\", \"Whether GABARAP's intrinsic fusogenic activity contributes to receptor exocytosis is untested\", \"Full structural basis of GABARAP-LRRK2 and GABARAP-ATG2A interactions is lacking\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [10, 11, 15, 16, 22, 25, 29, 30]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [6, 7, 9]},\n      {\"term_id\": \"GO:0031386\", \"supporting_discovery_ids\": [0, 1, 2, 4]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [26]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [11, 14, 16]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [14, 16, 25]},\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [16, 17]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [6, 8]},\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [38, 40]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [0, 1, 2, 4, 5, 14, 15, 16, 20, 21, 22, 26]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [11, 14, 24, 29, 30, 47]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [35, 37]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [22, 25, 40]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [10, 29, 30]}\n    ],\n    \"complexes\": [\n      \"ATG8 conjugation system (ATG7-ATG3-GABARAP)\",\n      \"CUL3-KBTBD6/KBTBD7 complex\"\n    ],\n    \"partners\": [\n      \"ATG7\",\n      \"ATG3\",\n      \"ATG4B\",\n      \"ULK1\",\n      \"ATG2A\",\n      \"PLEKHM1\",\n      \"FLCN\",\n      \"ANK3\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}