{"gene":"GULP1","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":1998,"finding":"CED-6 (GULP1 ortholog in C. elegans) was cloned and shown by genetic mosaic analysis to act within engulfing cells (not dying cells) as an adaptor protein with an N-terminal PTB domain, specifically required for the engulfment of apoptotic cells at both early and late stages of apoptosis.","method":"Genetic cloning, mosaic analysis, loss-of-function in C. elegans","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic mosaic analysis with defined cellular phenotype, replicated in subsequent studies across multiple organisms","pmids":["9635426"],"is_preprint":false},{"year":1999,"finding":"Human CED-6 (GULP1/hCED-6) rescues the engulfment defect of C. elegans ced-6 mutants, demonstrating functional conservation; the protein contains a PTB domain, predicted coiled-coil domain, and potential SH3-binding sites.","method":"Heterologous rescue in C. elegans, cDNA characterization","journal":"Current biology : CB","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cross-species functional rescue with defined phenotypic readout, single lab","pmids":["10574771"],"is_preprint":false},{"year":1999,"finding":"Overexpression of human CED-6 (GULP1) in primary human macrophages promotes phagocytosis specifically of apoptotic cells but not non-apoptotic cells, confirming it as the mammalian orthologue involved in a conserved apoptotic engulfment pathway.","method":"Phagocytosis assay with lacZ-positive apoptotic cells in transgenic macrophages, overexpression","journal":"Current biology : CB","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional overexpression assay with specific phenotypic readout, single lab","pmids":["10574763"],"is_preprint":false},{"year":2000,"finding":"CED-6/GULP1 dimerizes through a leucine zipper domain immediately adjacent to the PTB domain; this dimerization is conserved across C. elegans, rodent, and human CED-6 and is necessary and sufficient for dimer formation.","method":"Co-immunoprecipitation, yeast two-hybrid assays, gel filtration, mutational analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal methods (Co-IP, yeast two-hybrid, gel filtration, mutagenesis) demonstrating conserved dimerization","pmids":["10734103"],"is_preprint":false},{"year":2001,"finding":"GULP1/CED-6 physically interacts with the NPXY motif in the cytoplasmic tail of CED-1 (C. elegans engulfment receptor) and with a specific NPXY motif in the human CD91/LRP cytoplasmic tail; this interaction is mediated by the GULP PTB domain and was demonstrated by biochemical approaches and yeast two-hybrid analysis.","method":"Co-immunoprecipitation, yeast two-hybrid, biochemical pull-down, mutational analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal methods (Co-IP, yeast two-hybrid, domain mapping mutagenesis), replicated framework","pmids":["11729193"],"is_preprint":false},{"year":2006,"finding":"In Drosophila, draper and ced-6 function in glial cells (not in the axons being pruned) to mediate engulfment of degenerating larval axons during metamorphosis; glia-specific RNAi knockdown of ced-6 suppresses glial engulfment and inhibits axon pruning, and drpr and ced-6 interact genetically in this glial action.","method":"Drosophila genetics, glia-specific RNAi knockdown, genetic interaction analysis","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis with cell-type-specific knockdown and defined axon pruning phenotype, consistent with established pathway","pmids":["16772168"],"is_preprint":false},{"year":2006,"finding":"GULP1 overexpression impairs trafficking of LRP ligands alpha2-macroglobulin and prosaposin, resulting in glycosphingolipid and free cholesterol accumulation in late endosomes/lysosomes and decreased ABCA1-mediated cholesterol efflux; conversely, GULP1 knockdown promotes prosaposin targeting to late endosomes and enhances cholesterol clearance, revealing a GULP/LRP/ABCA1 triad in lipid homeostasis.","method":"Overexpression and knockdown (siRNA), biochemical lipid assays, confocal microscopy, ligand trafficking assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — bidirectional gain/loss-of-function with multiple biochemical readouts, single lab","pmids":["16497666"],"is_preprint":false},{"year":2006,"finding":"Rat CED-6 (GULP1 orthologue) is expressed in neurons (not glia) and localizes to synaptosomes; the PTB-containing CED-6 interacts with clathrin as demonstrated by yeast two-hybrid and GST pull-down, and colocalizes with clathrin-coated vesicles in cultured cells.","method":"Subcellular fractionation, immunohistochemistry, yeast two-hybrid, GST pull-down, colocalization by fluorescence microscopy","journal":"Brain research","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — direct binding assays (yeast two-hybrid + GST pull-down) plus localization experiments, single lab","pmids":["17007823"],"is_preprint":false},{"year":2007,"finding":"GULP1 acts as a positive regulator of Arf6: its PTB domain directly binds GDP-bound Arf6, GULP associates with Arf6-GAP ACAP1, GULP reverses ACAP1-mediated Arf6-GTP decrease and counter-acts ACAP1 inhibition of cell migration, and GULP, ACAP1, and GDP-Arf6 form a tripartite complex suggesting sequestration of ACAP1 as a mechanism.","method":"Biochemical binding assays, Co-IP, Arf6-GTP measurement, cell migration assay, knockdown and overexpression","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal methods including direct binding, tripartite complex, and functional readouts in the same study","pmids":["17398097"],"is_preprint":false},{"year":2008,"finding":"GULP1 physically and functionally interacts with the cytoplasmic tail of stabilin-2 through its PTB domain binding the NPXY motif; GULP knockdown decreases and GULP overexpression increases stabilin-2-mediated phagocytosis of aged red blood cells; a TAT-PTB domain fusion acts as dominant negative to impair engulfment.","method":"FRET analysis, Co-immunoprecipitation, knockdown/overexpression, phagocytosis assay, dominant negative PTB domain","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — FRET + biochemical binding + domain mutagenesis + bidirectional functional assays, single rigorous study","pmids":["18230608"],"is_preprint":false},{"year":2009,"finding":"SR-BI binds GULP1 via its C-terminal intracellular domain (yeast two-hybrid and cell-free binding assay), and GULP1 forms a complex with SR-BI in cells prior to PS activation; upon PS stimulation, GULP1 activates MAPK p38 and ERK1/2, which in turn elevates GTP-bound Rac1, driving actin cytoskeleton rearrangement for phagocytosis.","method":"Yeast two-hybrid, cell-free binding assay, co-immunoprecipitation, siRNA knockdown, GTP-Rac1 measurement, MAPK inhibitor experiments, phagocytosis assay","journal":"Journal of biochemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal methods establishing binding, pathway order (epistasis via inhibitors), and functional readout in a single study","pmids":["19122200"],"is_preprint":false},{"year":2010,"finding":"GULP1 specifically interacts with the NPxF/Y motif of stabilin-1 cytoplasmic region via its PTB domain, co-localizes with stabilin-1 around PS-coated beads, and GULP knockdown decreases stabilin-1-mediated phagocytosis.","method":"Co-immunoprecipitation, colocalization by fluorescence microscopy, siRNA knockdown, phagocytosis assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — reciprocal binding and functional knockdown with defined phenotype, single lab","pmids":["20599701"],"is_preprint":false},{"year":2011,"finding":"GULP1 interacts with the NPTY motif of APP via its PTB domain (yeast two-hybrid and co-IP), co-localizes with APP in neurons, enhances APP C-terminal fragment and Aβ generation upon overexpression, and reduces CTF/Aβ production upon knockdown.","method":"Yeast two-hybrid, co-immunoprecipitation, confocal microscopy, APP-GAL4 reporter assay, overexpression and knockdown with Aβ/CTF measurement","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal methods including interaction mapping, reporter assay, bidirectional expression manipulation with biochemical readouts, single rigorous study","pmids":["21486224"],"is_preprint":false},{"year":2012,"finding":"Drosophila Ced-6 (GULP1 ortholog) operates as a clathrin adaptor in clathrin-mediated endocytosis: its PTB domain recognizes the noncanonical FXNPXA sorting sequence of the vitellogenin receptor Yolkless, and Ced-6 promotes clathrin-dependent uptake of Yolkless chimeras in HeLa cells; human GULP similarly binds clathrin machinery, localizes to cell-surface clathrin-coated structures, and is enriched in placental clathrin-coated vesicles.","method":"Genetic analysis (ced-6-null flies), biochemical binding assays, uptake assays in HeLa cells, fractionation of placental clathrin-coated vesicles","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — genetic null phenotype, biochemical binding, and cellular functional assay across Drosophila and human, multiple orthogonal methods","pmids":["22398720"],"is_preprint":false},{"year":2012,"finding":"GULP1 regulates TGF-β signaling in ovarian cells through LRP1 (TGF-β receptor V): GULP overexpression retains TGF-β in signaling-competent early endosomes, prolongs SMAD3 phosphorylation, and enhances growth inhibition, migration, and invasion responses to TGF-β; GULP knockdown/absence shortens SMAD3 phosphorylation and impairs growth inhibition.","method":"SMAD3 phosphorylation assay (western blot), TGF-β growth inhibition assay, migration/invasion assay, endosomal trafficking analysis, overexpression and antisense knockdown","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — bidirectional functional experiments with defined signaling readout, single lab","pmids":["22451657"],"is_preprint":false},{"year":2013,"finding":"GULP1 is a nucleocytoplasmic shuttling protein that mediates transactivation specifically with LRP1 (but not APP) intracellular domain, as demonstrated by differential nuclear trafficking and reporter-plasmid-based transactivation assay.","method":"Nuclear fractionation/trafficking assays, reporter-plasmid-based transactivation assay, co-expression with APP and LRP1","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — functional reporter assay and nuclear trafficking experiments, single lab with multiple readouts","pmids":["23167255"],"is_preprint":false},{"year":2014,"finding":"GULP1 associates with Jedi-1 (an engulfment receptor) via the NPXY motif and promotes Jedi-1-mediated phagocytosis through binding to clathrin heavy chain (CHC); during engulfment CHC is tyrosine phosphorylated (required for engulfment), and both phosphoclathrin and actin accumulate around engulfed targets; CHC knockdown prevents Jedi-1-mediated engulfment of both microspheres and apoptotic neurons.","method":"Co-immunoprecipitation, NPXY motif mutagenesis, siRNA knockdown of GULP and CHC, phagocytosis assay with microspheres and apoptotic neurons, immunofluorescence","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — mutational analysis, reciprocal knockdowns, and functional phagocytosis assays in multiple cell types, single rigorous study","pmids":["24743597"],"is_preprint":false},{"year":2019,"finding":"GULP1 regulates EphB/ephrinB trogocytosis bi-directionally by dynamically engaging with EphB/ephrinB protein clusters in cooperation with the Rac-GEF Tiam2, and its presence at the Eph/ephrin cluster is a prerequisite for recruiting the endocytic GTPase dynamin, enabling membrane scission and engulfment during cell rearrangements in cultured cells and embryonic development.","method":"Live imaging, knockdown/knockout, co-immunoprecipitation, fluorescence microscopy, Xenopus embryo cell rearrangement assays","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (live imaging, biochemical interaction, in vivo developmental phenotype) in a single rigorous study","pmids":["31409653"],"is_preprint":false},{"year":2019,"finding":"siRNA knockdown of GULP1 in human trabecular meshwork cells decreases phagocytosis by ~40%, and GULP1 mRNA levels are decreased ~60% by αvβ3 integrin overexpression, indicating that αvβ3 integrin negatively regulates GULP1 expression and thereby suppresses engulfment.","method":"siRNA knockdown, phagocytosis assay (pHrodo-labeled bioparticles), qPCR, western blot","journal":"Molecular vision","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — siRNA knockdown with functional phagocytosis readout plus transcriptional regulation by integrin, single lab","pmids":["31516309"],"is_preprint":false},{"year":2020,"finding":"GULP1 is a KEAP1-binding protein that maintains actin cytoskeleton architecture and helps KEAP1 sequester NRF2 in the cytoplasm; GULP1 silencing causes nuclear accumulation of NRF2, constitutive NRF2 target gene activation (HMOX1 and other antioxidant genes), and confers cisplatin resistance in urothelial carcinoma.","method":"Co-immunoprecipitation (GULP1-KEAP1 interaction), siRNA knockdown, NRF2 nuclear localization assay, in vitro and in vivo tumor growth assays, gene expression analysis","journal":"Science signaling","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — binding interaction demonstrated plus functional knockdown with multiple readouts, single lab","pmids":["32817372"],"is_preprint":false},{"year":2021,"finding":"Androgen receptor (AR) directly binds the promoter region of GULP1 (chromatin immunoprecipitation), and androgen treatment or AR overexpression reduces GULP1 expression; GULP1 knockdown in bladder cancer increases cisplatin resistance, decreases apoptosis, and increases G2/M arrest upon cisplatin treatment.","method":"Chromatin immunoprecipitation (ChIP), DNA microarray, AR overexpression/knockdown, siRNA GULP1 knockdown, apoptosis assay, cell cycle analysis, cisplatin cytotoxicity assay","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP establishing direct AR-GULP1 promoter interaction plus functional downstream effects, single lab","pmids":["34576193"],"is_preprint":false},{"year":2023,"finding":"GULP1 deficiency in male mice increases bone mass due to decreased osteoclast differentiation and function; Gulp1 KO mice show elevated aromatase activity and 17β-estradiol levels in bone marrow, suggesting GULP1 normally suppresses estrogen synthesis and thereby permits osteoclast activity.","method":"Gulp1 knockout mice, microcomputed tomography, histomorphometry, in vitro osteoclast differentiation, actin ring and microtubule formation assay, GC-MS for steroid measurement, aromatase activity assay","journal":"Journal of cellular physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo KO phenotype with multiple mechanistic readouts (steroid measurement, enzyme activity), single lab","pmids":["36870066"],"is_preprint":false},{"year":2024,"finding":"GULP1 interacts with ATG14 (a regulator of autophagosome formation), potentiates class III PI3KC3-C1 activity, and facilitates targeting of ATG14 to the endoplasmic reticulum; a GULP1 mutation disrupting GULP1-ATG14 interaction attenuates this effect; GULP1 increases APP and ATG14 levels in autophagic vacuoles and enhances APP processing by promoting APP entry into autophagic vacuoles.","method":"Co-immunoprecipitation, PI3KC3-C1 activity assay, confocal microscopy (ATG14 ER targeting), autophagy flux assay, mutagenesis, APP CTF/Aβ measurement","journal":"Cellular and molecular life sciences : CMLS","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — direct binding mapped by mutagenesis, enzymatic activity assay, localization experiments with functional consequence on APP processing, multiple orthogonal methods","pmids":["39080084"],"is_preprint":false},{"year":2024,"finding":"Estrogen receptor β (ERβ) directly binds the GULP1 promoter (ChIP assay) and represses GULP1 expression; GULP1 knockdown in bladder cancer increases cisplatin resistance specifically (not resistance to gemcitabine, methotrexate, vinblastine, or doxorubicin).","method":"Chromatin immunoprecipitation (ChIP), siRNA knockdown, cisplatin and multi-drug cytotoxicity assay, ERβ overexpression/knockdown","journal":"Cancer genomics & proteomics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP establishing direct ERβ-GULP1 promoter binding plus functional knockdown, single lab","pmids":["39467629"],"is_preprint":false},{"year":2024,"finding":"Gulp1 knockdown impairs chondrocyte growth arrest and differentiation, reduces p21 expression, and attenuates TGF-β/SMAD2/3 pathway activation, demonstrating that Gulp1 contributes to chondrocyte differentiation by modulating TGF-β/SMAD2/3 signaling.","method":"siRNA knockdown in ATDC5 cells, chondrogenic differentiation assay, western blot (SMAD2/3 phosphorylation), gene expression analysis","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — loss-of-function with defined signaling and differentiation readouts, single lab","pmids":["38553249"],"is_preprint":false},{"year":2024,"finding":"CED-6/GULP (C. elegans) acts redundantly with clathrin and the AP-2 clathrin adaptor complex to maintain correct CED-1 localization on the plasma membrane, revealing a novel role for CED-6 in CED-1 membrane display beyond its established role in engulfment signaling.","method":"C. elegans genetics, genetic epistasis/redundancy analysis with clathrin and AP-2 mutants, CED-1 localization assay","journal":"G3 (Bethesda, Md.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis in C. elegans with defined receptor localization readout, single study","pmids":["38696649"],"is_preprint":false},{"year":2025,"finding":"GULP1 deficiency in Gulp1 KO mice reduces tendon cell proliferation (BrdU labeling), diminishes ERK1/2 phosphorylation in tendon cells, downregulates tendon-specific genes (Scleraxis, Mohawk, type I collagen), and disrupts collagen fibrillogenesis (smaller fibril diameters by TEM), resulting in impaired motor coordination.","method":"Gulp1 knockout mice, BrdU labeling, western blot (ERK1/2 phosphorylation), qRT-PCR, TEM collagen fibril analysis, gait and motor behavior analysis","journal":"Acta physiologica (Oxford, England)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO mouse with multiple orthogonal mechanistic readouts, single lab","pmids":["40747745"],"is_preprint":false},{"year":2026,"finding":"GULP1 directly interacts with IKIP (inhibitor of IKK-interacting protein) to relieve IKIP-mediated suppression of IKKβ-dependent NF-κB activation; this GULP1/IKIP/NF-κB axis upregulates OPA1 expression, restores mitochondrial morphology, and improves fatty acid metabolism in diabetic cardiomyopathy hearts; cardiac-specific GULP1 overexpression attenuates cardiac dysfunction and mitochondrial disruption in diabetic mice.","method":"Co-immunoprecipitation (GULP1-IKIP), cardiac-specific knockout and knock-in mice, echocardiography, electron microscopy, enzyme activity assays, ATP and fatty acid oxidation measurements, primary cardiomyocyte experiments","journal":"Cardiovascular diabetology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding plus bidirectional in vivo genetic models with multiple mechanistic readouts, single lab, recent publication","pmids":["42015218"],"is_preprint":false}],"current_model":"GULP1/CED-6 is a PTB domain-containing adaptor protein that dimerizes via a leucine zipper, binds NPXY motifs in the cytoplasmic tails of engulfment receptors (CED-1, CD91/LRP1, stabilin-1, stabilin-2, SR-BI, Jedi-1, EphB) to transduce 'eat-me' signals for apoptotic cell phagocytosis; mechanistically it acts as a positive regulator of Arf6 (by sequestering the GAP ACAP1), recruits phosphoclathrin to drive phagocytic cup formation, cooperates with Tiam2/Rac and dynamin for trogocytosis, modulates TGF-β/SMAD and NF-κB/OPA1 signaling, interacts with KEAP1 to retain NRF2 in the cytoplasm, and promotes autophagy by targeting ATG14 to the ER to stimulate PI3KC3-C1 activity, thereby influencing diverse processes including apoptotic cell clearance, lipid trafficking, APP processing, and cisplatin sensitivity."},"narrative":{"mechanistic_narrative":"GULP1 (the mammalian ortholog of C. elegans CED-6) is a PTB-domain adaptor protein that acts within engulfing cells to transduce 'eat-me' signals required for the phagocytosis of apoptotic cells, a function conserved from worms to humans [PMID:9635426, PMID:10574771, PMID:10574763]. It dimerizes through a leucine zipper immediately adjacent to its PTB domain, and uses that PTB domain to dock onto NPXY-type motifs in the cytoplasmic tails of a broad set of engulfment receptors including CED-1, CD91/LRP1, stabilin-1, stabilin-2, SR-BI, and Jedi-1 [PMID:10734103, PMID:11729193, PMID:18230608, PMID:19122200, PMID:20599701, PMID:24743597]. Downstream of receptor engagement GULP1 nucleates the cytoskeletal and membrane machinery for engulfment: it couples to clathrin to assemble phosphoclathrin-coated phagocytic structures [PMID:17007823, PMID:22398720, PMID:24743597], positively regulates Arf6 by sequestering the Arf6-GAP ACAP1 [PMID:17398097], and activates p38/ERK–Rac1 signaling to drive actin remodeling [PMID:19122200]; in EphB/ephrin trogocytosis it cooperates with the Rac-GEF Tiam2 and is required to recruit dynamin for membrane scission [PMID:31409653]. Through its association with LRP1, GULP1 also governs endosomal ligand trafficking and lipid homeostasis and tunes the duration of TGF-β/SMAD signaling [PMID:16497666, PMID:22451657, PMID:38553249]. Beyond engulfment, GULP1 binds the NPTY motif of APP to promote amyloidogenic processing [PMID:21486224], interacts with KEAP1 to retain NRF2 in the cytoplasm with consequences for cisplatin sensitivity in urothelial/bladder cancer [PMID:32817372, PMID:34576193, PMID:39467629], and binds ATG14 to target it to the ER and potentiate PI3KC3-C1–driven autophagy [PMID:39080084]. In vivo, GULP1 loss in mice perturbs osteoclast, tendon, and cardiac biology, and it engages IKIP to modulate NF-κB/OPA1-dependent mitochondrial maintenance [PMID:36870066, PMID:40747745, PMID:42015218].","teleology":[{"year":1998,"claim":"Established that CED-6 is an adaptor acting inside the engulfing cell rather than the dying cell, defining the genetic logic of apoptotic corpse clearance.","evidence":"Genetic cloning and mosaic loss-of-function analysis in C. elegans","pmids":["9635426"],"confidence":"High","gaps":["No biochemical receptor partner identified at this stage","Mammalian relevance not yet demonstrated"]},{"year":1999,"claim":"Showed the engulfment role is evolutionarily conserved, validating human GULP1 as the functional ortholog acting in macrophage phagocytosis of apoptotic cells.","evidence":"Heterologous rescue of ced-6 mutants and overexpression phagocytosis assay in primary human macrophages","pmids":["10574771","10574763"],"confidence":"Medium","gaps":["Single-lab functional assays","Direct receptor interaction not yet mapped"]},{"year":2000,"claim":"Defined the structural basis for GULP1 oligomerization, showing a conserved leucine zipper adjacent to the PTB domain mediates dimerization.","evidence":"Co-IP, yeast two-hybrid, gel filtration, and mutagenesis across species","pmids":["10734103"],"confidence":"High","gaps":["Functional consequence of dimerization for receptor binding not resolved"]},{"year":2001,"claim":"Identified the receptor-recognition mechanism: the PTB domain binds NPXY motifs in CED-1 and human CD91/LRP cytoplasmic tails, linking the adaptor to engulfment receptors.","evidence":"Co-IP, yeast two-hybrid, pull-down, and domain mapping mutagenesis","pmids":["11729193"],"confidence":"High","gaps":["Did not test the full repertoire of receptors GULP1 engages","Downstream effectors of the receptor complex unknown"]},{"year":2006,"claim":"Extended GULP1 function beyond canonical phagocytosis, implicating it in glial axon-pruning engulfment, neuronal/synaptic localization, clathrin binding, and LRP-dependent lipid trafficking.","evidence":"Drosophila glia-specific RNAi and genetic interaction; rat fractionation, yeast two-hybrid/GST pull-down; bidirectional gain/loss-of-function lipid trafficking assays","pmids":["16772168","17007823","16497666"],"confidence":"High","gaps":["Mechanistic link between clathrin binding and engulfment not yet established","How GULP1 controls LRP ligand sorting mechanistically unclear"]},{"year":2007,"claim":"Placed GULP1 in small-GTPase signaling, showing it positively regulates Arf6 by sequestering the GAP ACAP1, connecting the adaptor to membrane trafficking and migration.","evidence":"Direct binding assays, tripartite complex Co-IP, Arf6-GTP measurement, and migration assays","pmids":["17398097"],"confidence":"High","gaps":["Link between Arf6 regulation and engulfment not directly tested","No structural model of the GULP1/ACAP1/Arf6 complex"]},{"year":2008,"claim":"Generalized the NPXY-PTB receptor paradigm to stabilin-2, demonstrating GULP1 is rate-limiting for stabilin-2-mediated clearance of aged red blood cells.","evidence":"FRET, Co-IP, domain mutagenesis, dominant-negative PTB, and bidirectional phagocytosis assays","pmids":["18230608"],"confidence":"High","gaps":["Downstream cytoskeletal machinery for stabilin-2 engulfment not defined here"]},{"year":2009,"claim":"Resolved a signaling cascade downstream of receptor binding: GULP1 with SR-BI activates p38/ERK to elevate Rac1-GTP and drive actin rearrangement for phagocytosis.","evidence":"Yeast two-hybrid, cell-free binding, Co-IP, MAPK-inhibitor epistasis, GTP-Rac1 measurement, and phagocytosis assays","pmids":["19122200"],"confidence":"High","gaps":["How GULP1 mechanistically activates MAPK upstream is not defined"]},{"year":2010,"claim":"Added stabilin-1 to the receptor set, reinforcing the NPxF/Y-PTB recognition mode in phosphatidylserine-mediated engulfment.","evidence":"Co-IP, colocalization, siRNA knockdown, and phagocytosis assay","pmids":["20599701"],"confidence":"Medium","gaps":["Single-lab characterization","Effector pathway downstream of stabilin-1 not detailed"]},{"year":2011,"claim":"Revealed a non-engulfment substrate, showing GULP1 binds the APP NPTY motif and promotes amyloidogenic CTF/Aβ generation.","evidence":"Yeast two-hybrid, Co-IP, reporter assay, and bidirectional expression with Aβ/CTF readouts","pmids":["21486224"],"confidence":"High","gaps":["Trafficking step at which GULP1 alters APP processing not pinpointed here"]},{"year":2012,"claim":"Mechanistically unified GULP1 as a clathrin adaptor and an endosomal signaling modulator, recognizing noncanonical sorting sequences and prolonging LRP1-dependent TGF-β/SMAD3 signaling.","evidence":"Drosophila ced-6 null genetics, uptake assays in HeLa, clathrin-coated vesicle fractionation; SMAD3 phosphorylation, endosomal trafficking, and functional TGF-β assays","pmids":["22398720","22451657"],"confidence":"High","gaps":["How GULP1 selects between cargo-internalization and signaling-endosome retention is unresolved"]},{"year":2013,"claim":"Identified a nuclear function, showing GULP1 shuttles and mediates LRP1- (but not APP-) intracellular-domain transactivation.","evidence":"Nuclear fractionation/trafficking and reporter-based transactivation assays","pmids":["23167255"],"confidence":"Medium","gaps":["Target genes of LRP1-ICD/GULP1 transactivation not identified","Single-lab evidence"]},{"year":2014,"claim":"Connected receptor binding to membrane remodeling, showing GULP1 bridges Jedi-1 to clathrin heavy chain whose tyrosine phosphorylation drives phosphoclathrin/actin assembly at phagocytic cups.","evidence":"Co-IP, NPXY mutagenesis, reciprocal GULP/CHC knockdown, and phagocytosis assays with beads and apoptotic neurons","pmids":["24743597"],"confidence":"High","gaps":["Kinase responsible for CHC phosphorylation not identified"]},{"year":2019,"claim":"Demonstrated GULP1 orchestrates trogocytosis, dynamically engaging EphB/ephrin clusters with Tiam2/Rac and serving as a prerequisite for dynamin recruitment and membrane scission, and that αvβ3 integrin transcriptionally suppresses GULP1.","evidence":"Live imaging, knockdown/knockout, Co-IP, Xenopus embryo assays; trabecular meshwork siRNA, phagocytosis, qPCR","pmids":["31409653","31516309"],"confidence":"High","gaps":["Mechanism by which GULP1 recruits dynamin is not structurally defined","Integrin-to-GULP1 transcriptional pathway not mapped"]},{"year":2020,"claim":"Established a stress/redox role, showing GULP1 binds KEAP1 to retain NRF2 cytoplasmically, and its loss drives constitutive NRF2 target activation and cisplatin resistance.","evidence":"Co-IP, siRNA knockdown, NRF2 localization, gene expression, and tumor growth assays","pmids":["32817372"],"confidence":"Medium","gaps":["Whether KEAP1 binding requires the PTB domain not addressed","Single-lab study"]},{"year":2024,"claim":"Defined an autophagy function: GULP1 binds ATG14 and targets it to the ER to potentiate PI3KC3-C1 activity, simultaneously promoting APP entry into autophagic vacuoles.","evidence":"Co-IP, PI3KC3-C1 activity assay, confocal ER-targeting, autophagy flux, mutagenesis, and APP CTF/Aβ measurement","pmids":["39080084"],"confidence":"High","gaps":["Relationship between the autophagy role and the clathrin/engulfment role unclear"]},{"year":2024,"claim":"Showed GULP1 expression is hormonally controlled (AR and ERβ directly repress its promoter) with downstream consequences for chondrocyte differentiation via TGF-β/SMAD2/3 and for cisplatin sensitivity.","evidence":"ChIP, AR/ERβ over- and knockdown, siRNA GULP1 knockdown, drug cytotoxicity, cell cycle and chondrogenic differentiation assays","pmids":["34576193","39467629","38553249"],"confidence":"Medium","gaps":["Mechanism linking GULP1 loss to cisplatin-specific resistance not fully resolved","Single-lab studies"]},{"year":2026,"claim":"Extended GULP1 to in vivo tissue physiology, with knockout phenotypes in bone (estrogen/osteoclast), tendon (ERK/collagen), and an IKIP/NF-κB/OPA1 axis governing mitochondrial morphology in diabetic cardiomyopathy.","evidence":"Gulp1 KO and cardiac-specific KO/knock-in mice, microCT, histomorphometry, GC-MS steroid measurement, BrdU/TEM, Co-IP, echocardiography, and metabolic assays","pmids":["36870066","40747745","42015218"],"confidence":"Medium","gaps":["How the adaptor/engulfment activity relates to these tissue phenotypes is unclear","Single-lab models for each tissue"]},{"year":null,"claim":"It remains unresolved how GULP1's many context-specific activities (receptor engulfment adaptor, clathrin/Arf6 trafficking regulator, KEAP1/NRF2 and autophagy modulator, and tissue developmental factor) are integrated or selectively deployed in different cell types.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model integrating PTB, leucine zipper, and partner binding","No unifying regulatory logic for partner selection established"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,4,9,16]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[8,19,27]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[10,16,19]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[19]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[7,13]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[6,14]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[15]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[22]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[13,25]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[7,13,16]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[0,2,9]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[22]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[10,14,27]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[19]}],"complexes":[],"partners":["LRP1","STAB2","SCARB1","STAB1","JEDI-1","ACAP1","ATG14","KEAP1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9UBP9","full_name":"PTB domain-containing engulfment adapter protein 1","aliases":["Cell death protein 6 homolog","PTB domain adapter protein CED-6","Protein GULP"],"length_aa":304,"mass_kda":34.5,"function":"May function as an adapter protein. Required for efficient phagocytosis of apoptotic cells. Modulates cellular glycosphingolipid and cholesterol transport. May play a role in the internalization and endosomal trafficking of various LRP1 ligands, such as PSAP. Increases cellular levels of GTP-bound ARF6","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q9UBP9/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GULP1","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/GULP1","total_profiled":1310},"omim":[{"mim_id":"608165","title":"PTB DOMAIN-CONTAINING ENGULFMENT ADAPTOR PROTEIN 1; GULP1","url":"https://www.omim.org/entry/608165"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Vesicles","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"epididymis","ntpm":77.9}],"url":"https://www.proteinatlas.org/search/GULP1"},"hgnc":{"alias_symbol":["CED6","CED-6","GULP"],"prev_symbol":[]},"alphafold":{"accession":"Q9UBP9","domains":[{"cath_id":"2.30.29.30","chopping":"16-155","consensus_level":"high","plddt":94.1671,"start":16,"end":155},{"cath_id":"1.20.5","chopping":"157-196","consensus_level":"medium","plddt":85.8943,"start":157,"end":196}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UBP9","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UBP9-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UBP9-F1-predicted_aligned_error_v6.png","plddt_mean":74.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GULP1","jax_strain_url":"https://www.jax.org/strain/search?query=GULP1"},"sequence":{"accession":"Q9UBP9","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9UBP9.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9UBP9/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UBP9"}},"corpus_meta":[{"pmid":"16772168","id":"PMC_16772168","title":"Essential 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Two-step screening more reliable for identification of alcohol dependency syndrome at risk of delirium tremens for routine care.","date":"2015","source":"BMJ quality improvement reports","url":"https://pubmed.ncbi.nlm.nih.gov/26734413","citation_count":1,"is_preprint":false},{"pmid":"40747745","id":"PMC_40747745","title":"GULP1 Regulates Tendon Cell Proliferation and Maturation Essential for Motor Coordination in Mice.","date":"2025","source":"Acta physiologica (Oxford, England)","url":"https://pubmed.ncbi.nlm.nih.gov/40747745","citation_count":0,"is_preprint":false},{"pmid":"42015218","id":"PMC_42015218","title":"GULP1 protects against diabetic cardiomyopathy through IKIP/NF-κB-dependent improvement of mitochondrial function.","date":"2026","source":"Cardiovascular diabetology","url":"https://pubmed.ncbi.nlm.nih.gov/42015218","citation_count":0,"is_preprint":false},{"pmid":"41613803","id":"PMC_41613803","title":"Serum Extracellular Vesicle-Associated GULP1 Is a Key Indicator of Hepatocellular Carcinoma.","date":"2026","source":"Oncology research","url":"https://pubmed.ncbi.nlm.nih.gov/41613803","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":24034,"output_tokens":6974,"usd":0.088356,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":16242,"output_tokens":5610,"usd":0.11073,"stage2_stop_reason":"end_turn"},"total_usd":0.199086,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1998,\n      \"finding\": \"CED-6 (GULP1 ortholog in C. elegans) was cloned and shown by genetic mosaic analysis to act within engulfing cells (not dying cells) as an adaptor protein with an N-terminal PTB domain, specifically required for the engulfment of apoptotic cells at both early and late stages of apoptosis.\",\n      \"method\": \"Genetic cloning, mosaic analysis, loss-of-function in C. elegans\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic mosaic analysis with defined cellular phenotype, replicated in subsequent studies across multiple organisms\",\n      \"pmids\": [\"9635426\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Human CED-6 (GULP1/hCED-6) rescues the engulfment defect of C. elegans ced-6 mutants, demonstrating functional conservation; the protein contains a PTB domain, predicted coiled-coil domain, and potential SH3-binding sites.\",\n      \"method\": \"Heterologous rescue in C. elegans, cDNA characterization\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cross-species functional rescue with defined phenotypic readout, single lab\",\n      \"pmids\": [\"10574771\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Overexpression of human CED-6 (GULP1) in primary human macrophages promotes phagocytosis specifically of apoptotic cells but not non-apoptotic cells, confirming it as the mammalian orthologue involved in a conserved apoptotic engulfment pathway.\",\n      \"method\": \"Phagocytosis assay with lacZ-positive apoptotic cells in transgenic macrophages, overexpression\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional overexpression assay with specific phenotypic readout, single lab\",\n      \"pmids\": [\"10574763\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"CED-6/GULP1 dimerizes through a leucine zipper domain immediately adjacent to the PTB domain; this dimerization is conserved across C. elegans, rodent, and human CED-6 and is necessary and sufficient for dimer formation.\",\n      \"method\": \"Co-immunoprecipitation, yeast two-hybrid assays, gel filtration, mutational analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal methods (Co-IP, yeast two-hybrid, gel filtration, mutagenesis) demonstrating conserved dimerization\",\n      \"pmids\": [\"10734103\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"GULP1/CED-6 physically interacts with the NPXY motif in the cytoplasmic tail of CED-1 (C. elegans engulfment receptor) and with a specific NPXY motif in the human CD91/LRP cytoplasmic tail; this interaction is mediated by the GULP PTB domain and was demonstrated by biochemical approaches and yeast two-hybrid analysis.\",\n      \"method\": \"Co-immunoprecipitation, yeast two-hybrid, biochemical pull-down, mutational analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal methods (Co-IP, yeast two-hybrid, domain mapping mutagenesis), replicated framework\",\n      \"pmids\": [\"11729193\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"In Drosophila, draper and ced-6 function in glial cells (not in the axons being pruned) to mediate engulfment of degenerating larval axons during metamorphosis; glia-specific RNAi knockdown of ced-6 suppresses glial engulfment and inhibits axon pruning, and drpr and ced-6 interact genetically in this glial action.\",\n      \"method\": \"Drosophila genetics, glia-specific RNAi knockdown, genetic interaction analysis\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis with cell-type-specific knockdown and defined axon pruning phenotype, consistent with established pathway\",\n      \"pmids\": [\"16772168\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"GULP1 overexpression impairs trafficking of LRP ligands alpha2-macroglobulin and prosaposin, resulting in glycosphingolipid and free cholesterol accumulation in late endosomes/lysosomes and decreased ABCA1-mediated cholesterol efflux; conversely, GULP1 knockdown promotes prosaposin targeting to late endosomes and enhances cholesterol clearance, revealing a GULP/LRP/ABCA1 triad in lipid homeostasis.\",\n      \"method\": \"Overexpression and knockdown (siRNA), biochemical lipid assays, confocal microscopy, ligand trafficking assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — bidirectional gain/loss-of-function with multiple biochemical readouts, single lab\",\n      \"pmids\": [\"16497666\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Rat CED-6 (GULP1 orthologue) is expressed in neurons (not glia) and localizes to synaptosomes; the PTB-containing CED-6 interacts with clathrin as demonstrated by yeast two-hybrid and GST pull-down, and colocalizes with clathrin-coated vesicles in cultured cells.\",\n      \"method\": \"Subcellular fractionation, immunohistochemistry, yeast two-hybrid, GST pull-down, colocalization by fluorescence microscopy\",\n      \"journal\": \"Brain research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — direct binding assays (yeast two-hybrid + GST pull-down) plus localization experiments, single lab\",\n      \"pmids\": [\"17007823\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"GULP1 acts as a positive regulator of Arf6: its PTB domain directly binds GDP-bound Arf6, GULP associates with Arf6-GAP ACAP1, GULP reverses ACAP1-mediated Arf6-GTP decrease and counter-acts ACAP1 inhibition of cell migration, and GULP, ACAP1, and GDP-Arf6 form a tripartite complex suggesting sequestration of ACAP1 as a mechanism.\",\n      \"method\": \"Biochemical binding assays, Co-IP, Arf6-GTP measurement, cell migration assay, knockdown and overexpression\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal methods including direct binding, tripartite complex, and functional readouts in the same study\",\n      \"pmids\": [\"17398097\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"GULP1 physically and functionally interacts with the cytoplasmic tail of stabilin-2 through its PTB domain binding the NPXY motif; GULP knockdown decreases and GULP overexpression increases stabilin-2-mediated phagocytosis of aged red blood cells; a TAT-PTB domain fusion acts as dominant negative to impair engulfment.\",\n      \"method\": \"FRET analysis, Co-immunoprecipitation, knockdown/overexpression, phagocytosis assay, dominant negative PTB domain\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — FRET + biochemical binding + domain mutagenesis + bidirectional functional assays, single rigorous study\",\n      \"pmids\": [\"18230608\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"SR-BI binds GULP1 via its C-terminal intracellular domain (yeast two-hybrid and cell-free binding assay), and GULP1 forms a complex with SR-BI in cells prior to PS activation; upon PS stimulation, GULP1 activates MAPK p38 and ERK1/2, which in turn elevates GTP-bound Rac1, driving actin cytoskeleton rearrangement for phagocytosis.\",\n      \"method\": \"Yeast two-hybrid, cell-free binding assay, co-immunoprecipitation, siRNA knockdown, GTP-Rac1 measurement, MAPK inhibitor experiments, phagocytosis assay\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal methods establishing binding, pathway order (epistasis via inhibitors), and functional readout in a single study\",\n      \"pmids\": [\"19122200\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"GULP1 specifically interacts with the NPxF/Y motif of stabilin-1 cytoplasmic region via its PTB domain, co-localizes with stabilin-1 around PS-coated beads, and GULP knockdown decreases stabilin-1-mediated phagocytosis.\",\n      \"method\": \"Co-immunoprecipitation, colocalization by fluorescence microscopy, siRNA knockdown, phagocytosis assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — reciprocal binding and functional knockdown with defined phenotype, single lab\",\n      \"pmids\": [\"20599701\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"GULP1 interacts with the NPTY motif of APP via its PTB domain (yeast two-hybrid and co-IP), co-localizes with APP in neurons, enhances APP C-terminal fragment and Aβ generation upon overexpression, and reduces CTF/Aβ production upon knockdown.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, confocal microscopy, APP-GAL4 reporter assay, overexpression and knockdown with Aβ/CTF measurement\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal methods including interaction mapping, reporter assay, bidirectional expression manipulation with biochemical readouts, single rigorous study\",\n      \"pmids\": [\"21486224\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Drosophila Ced-6 (GULP1 ortholog) operates as a clathrin adaptor in clathrin-mediated endocytosis: its PTB domain recognizes the noncanonical FXNPXA sorting sequence of the vitellogenin receptor Yolkless, and Ced-6 promotes clathrin-dependent uptake of Yolkless chimeras in HeLa cells; human GULP similarly binds clathrin machinery, localizes to cell-surface clathrin-coated structures, and is enriched in placental clathrin-coated vesicles.\",\n      \"method\": \"Genetic analysis (ced-6-null flies), biochemical binding assays, uptake assays in HeLa cells, fractionation of placental clathrin-coated vesicles\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — genetic null phenotype, biochemical binding, and cellular functional assay across Drosophila and human, multiple orthogonal methods\",\n      \"pmids\": [\"22398720\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"GULP1 regulates TGF-β signaling in ovarian cells through LRP1 (TGF-β receptor V): GULP overexpression retains TGF-β in signaling-competent early endosomes, prolongs SMAD3 phosphorylation, and enhances growth inhibition, migration, and invasion responses to TGF-β; GULP knockdown/absence shortens SMAD3 phosphorylation and impairs growth inhibition.\",\n      \"method\": \"SMAD3 phosphorylation assay (western blot), TGF-β growth inhibition assay, migration/invasion assay, endosomal trafficking analysis, overexpression and antisense knockdown\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — bidirectional functional experiments with defined signaling readout, single lab\",\n      \"pmids\": [\"22451657\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"GULP1 is a nucleocytoplasmic shuttling protein that mediates transactivation specifically with LRP1 (but not APP) intracellular domain, as demonstrated by differential nuclear trafficking and reporter-plasmid-based transactivation assay.\",\n      \"method\": \"Nuclear fractionation/trafficking assays, reporter-plasmid-based transactivation assay, co-expression with APP and LRP1\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — functional reporter assay and nuclear trafficking experiments, single lab with multiple readouts\",\n      \"pmids\": [\"23167255\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"GULP1 associates with Jedi-1 (an engulfment receptor) via the NPXY motif and promotes Jedi-1-mediated phagocytosis through binding to clathrin heavy chain (CHC); during engulfment CHC is tyrosine phosphorylated (required for engulfment), and both phosphoclathrin and actin accumulate around engulfed targets; CHC knockdown prevents Jedi-1-mediated engulfment of both microspheres and apoptotic neurons.\",\n      \"method\": \"Co-immunoprecipitation, NPXY motif mutagenesis, siRNA knockdown of GULP and CHC, phagocytosis assay with microspheres and apoptotic neurons, immunofluorescence\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — mutational analysis, reciprocal knockdowns, and functional phagocytosis assays in multiple cell types, single rigorous study\",\n      \"pmids\": [\"24743597\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"GULP1 regulates EphB/ephrinB trogocytosis bi-directionally by dynamically engaging with EphB/ephrinB protein clusters in cooperation with the Rac-GEF Tiam2, and its presence at the Eph/ephrin cluster is a prerequisite for recruiting the endocytic GTPase dynamin, enabling membrane scission and engulfment during cell rearrangements in cultured cells and embryonic development.\",\n      \"method\": \"Live imaging, knockdown/knockout, co-immunoprecipitation, fluorescence microscopy, Xenopus embryo cell rearrangement assays\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (live imaging, biochemical interaction, in vivo developmental phenotype) in a single rigorous study\",\n      \"pmids\": [\"31409653\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"siRNA knockdown of GULP1 in human trabecular meshwork cells decreases phagocytosis by ~40%, and GULP1 mRNA levels are decreased ~60% by αvβ3 integrin overexpression, indicating that αvβ3 integrin negatively regulates GULP1 expression and thereby suppresses engulfment.\",\n      \"method\": \"siRNA knockdown, phagocytosis assay (pHrodo-labeled bioparticles), qPCR, western blot\",\n      \"journal\": \"Molecular vision\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — siRNA knockdown with functional phagocytosis readout plus transcriptional regulation by integrin, single lab\",\n      \"pmids\": [\"31516309\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"GULP1 is a KEAP1-binding protein that maintains actin cytoskeleton architecture and helps KEAP1 sequester NRF2 in the cytoplasm; GULP1 silencing causes nuclear accumulation of NRF2, constitutive NRF2 target gene activation (HMOX1 and other antioxidant genes), and confers cisplatin resistance in urothelial carcinoma.\",\n      \"method\": \"Co-immunoprecipitation (GULP1-KEAP1 interaction), siRNA knockdown, NRF2 nuclear localization assay, in vitro and in vivo tumor growth assays, gene expression analysis\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — binding interaction demonstrated plus functional knockdown with multiple readouts, single lab\",\n      \"pmids\": [\"32817372\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Androgen receptor (AR) directly binds the promoter region of GULP1 (chromatin immunoprecipitation), and androgen treatment or AR overexpression reduces GULP1 expression; GULP1 knockdown in bladder cancer increases cisplatin resistance, decreases apoptosis, and increases G2/M arrest upon cisplatin treatment.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP), DNA microarray, AR overexpression/knockdown, siRNA GULP1 knockdown, apoptosis assay, cell cycle analysis, cisplatin cytotoxicity assay\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP establishing direct AR-GULP1 promoter interaction plus functional downstream effects, single lab\",\n      \"pmids\": [\"34576193\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"GULP1 deficiency in male mice increases bone mass due to decreased osteoclast differentiation and function; Gulp1 KO mice show elevated aromatase activity and 17β-estradiol levels in bone marrow, suggesting GULP1 normally suppresses estrogen synthesis and thereby permits osteoclast activity.\",\n      \"method\": \"Gulp1 knockout mice, microcomputed tomography, histomorphometry, in vitro osteoclast differentiation, actin ring and microtubule formation assay, GC-MS for steroid measurement, aromatase activity assay\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo KO phenotype with multiple mechanistic readouts (steroid measurement, enzyme activity), single lab\",\n      \"pmids\": [\"36870066\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"GULP1 interacts with ATG14 (a regulator of autophagosome formation), potentiates class III PI3KC3-C1 activity, and facilitates targeting of ATG14 to the endoplasmic reticulum; a GULP1 mutation disrupting GULP1-ATG14 interaction attenuates this effect; GULP1 increases APP and ATG14 levels in autophagic vacuoles and enhances APP processing by promoting APP entry into autophagic vacuoles.\",\n      \"method\": \"Co-immunoprecipitation, PI3KC3-C1 activity assay, confocal microscopy (ATG14 ER targeting), autophagy flux assay, mutagenesis, APP CTF/Aβ measurement\",\n      \"journal\": \"Cellular and molecular life sciences : CMLS\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — direct binding mapped by mutagenesis, enzymatic activity assay, localization experiments with functional consequence on APP processing, multiple orthogonal methods\",\n      \"pmids\": [\"39080084\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Estrogen receptor β (ERβ) directly binds the GULP1 promoter (ChIP assay) and represses GULP1 expression; GULP1 knockdown in bladder cancer increases cisplatin resistance specifically (not resistance to gemcitabine, methotrexate, vinblastine, or doxorubicin).\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP), siRNA knockdown, cisplatin and multi-drug cytotoxicity assay, ERβ overexpression/knockdown\",\n      \"journal\": \"Cancer genomics & proteomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP establishing direct ERβ-GULP1 promoter binding plus functional knockdown, single lab\",\n      \"pmids\": [\"39467629\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Gulp1 knockdown impairs chondrocyte growth arrest and differentiation, reduces p21 expression, and attenuates TGF-β/SMAD2/3 pathway activation, demonstrating that Gulp1 contributes to chondrocyte differentiation by modulating TGF-β/SMAD2/3 signaling.\",\n      \"method\": \"siRNA knockdown in ATDC5 cells, chondrogenic differentiation assay, western blot (SMAD2/3 phosphorylation), gene expression analysis\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — loss-of-function with defined signaling and differentiation readouts, single lab\",\n      \"pmids\": [\"38553249\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CED-6/GULP (C. elegans) acts redundantly with clathrin and the AP-2 clathrin adaptor complex to maintain correct CED-1 localization on the plasma membrane, revealing a novel role for CED-6 in CED-1 membrane display beyond its established role in engulfment signaling.\",\n      \"method\": \"C. elegans genetics, genetic epistasis/redundancy analysis with clathrin and AP-2 mutants, CED-1 localization assay\",\n      \"journal\": \"G3 (Bethesda, Md.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis in C. elegans with defined receptor localization readout, single study\",\n      \"pmids\": [\"38696649\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"GULP1 deficiency in Gulp1 KO mice reduces tendon cell proliferation (BrdU labeling), diminishes ERK1/2 phosphorylation in tendon cells, downregulates tendon-specific genes (Scleraxis, Mohawk, type I collagen), and disrupts collagen fibrillogenesis (smaller fibril diameters by TEM), resulting in impaired motor coordination.\",\n      \"method\": \"Gulp1 knockout mice, BrdU labeling, western blot (ERK1/2 phosphorylation), qRT-PCR, TEM collagen fibril analysis, gait and motor behavior analysis\",\n      \"journal\": \"Acta physiologica (Oxford, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO mouse with multiple orthogonal mechanistic readouts, single lab\",\n      \"pmids\": [\"40747745\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"GULP1 directly interacts with IKIP (inhibitor of IKK-interacting protein) to relieve IKIP-mediated suppression of IKKβ-dependent NF-κB activation; this GULP1/IKIP/NF-κB axis upregulates OPA1 expression, restores mitochondrial morphology, and improves fatty acid metabolism in diabetic cardiomyopathy hearts; cardiac-specific GULP1 overexpression attenuates cardiac dysfunction and mitochondrial disruption in diabetic mice.\",\n      \"method\": \"Co-immunoprecipitation (GULP1-IKIP), cardiac-specific knockout and knock-in mice, echocardiography, electron microscopy, enzyme activity assays, ATP and fatty acid oxidation measurements, primary cardiomyocyte experiments\",\n      \"journal\": \"Cardiovascular diabetology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding plus bidirectional in vivo genetic models with multiple mechanistic readouts, single lab, recent publication\",\n      \"pmids\": [\"42015218\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GULP1/CED-6 is a PTB domain-containing adaptor protein that dimerizes via a leucine zipper, binds NPXY motifs in the cytoplasmic tails of engulfment receptors (CED-1, CD91/LRP1, stabilin-1, stabilin-2, SR-BI, Jedi-1, EphB) to transduce 'eat-me' signals for apoptotic cell phagocytosis; mechanistically it acts as a positive regulator of Arf6 (by sequestering the GAP ACAP1), recruits phosphoclathrin to drive phagocytic cup formation, cooperates with Tiam2/Rac and dynamin for trogocytosis, modulates TGF-β/SMAD and NF-κB/OPA1 signaling, interacts with KEAP1 to retain NRF2 in the cytoplasm, and promotes autophagy by targeting ATG14 to the ER to stimulate PI3KC3-C1 activity, thereby influencing diverse processes including apoptotic cell clearance, lipid trafficking, APP processing, and cisplatin sensitivity.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GULP1 (the mammalian ortholog of C. elegans CED-6) is a PTB-domain adaptor protein that acts within engulfing cells to transduce 'eat-me' signals required for the phagocytosis of apoptotic cells, a function conserved from worms to humans [#0, #1, #2]. It dimerizes through a leucine zipper immediately adjacent to its PTB domain, and uses that PTB domain to dock onto NPXY-type motifs in the cytoplasmic tails of a broad set of engulfment receptors including CED-1, CD91/LRP1, stabilin-1, stabilin-2, SR-BI, and Jedi-1 [#3, #4, #9, #10, #11, #16]. Downstream of receptor engagement GULP1 nucleates the cytoskeletal and membrane machinery for engulfment: it couples to clathrin to assemble phosphoclathrin-coated phagocytic structures [#7, #13, #16], positively regulates Arf6 by sequestering the Arf6-GAP ACAP1 [#8], and activates p38/ERK–Rac1 signaling to drive actin remodeling [#10]; in EphB/ephrin trogocytosis it cooperates with the Rac-GEF Tiam2 and is required to recruit dynamin for membrane scission [#17]. Through its association with LRP1, GULP1 also governs endosomal ligand trafficking and lipid homeostasis and tunes the duration of TGF-β/SMAD signaling [#6, #14, #24]. Beyond engulfment, GULP1 binds the NPTY motif of APP to promote amyloidogenic processing [#12], interacts with KEAP1 to retain NRF2 in the cytoplasm with consequences for cisplatin sensitivity in urothelial/bladder cancer [#19, #20, #23], and binds ATG14 to target it to the ER and potentiate PI3KC3-C1–driven autophagy [#22]. In vivo, GULP1 loss in mice perturbs osteoclast, tendon, and cardiac biology, and it engages IKIP to modulate NF-κB/OPA1-dependent mitochondrial maintenance [#21, #26, #27].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established that CED-6 is an adaptor acting inside the engulfing cell rather than the dying cell, defining the genetic logic of apoptotic corpse clearance.\",\n      \"evidence\": \"Genetic cloning and mosaic loss-of-function analysis in C. elegans\",\n      \"pmids\": [\"9635426\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No biochemical receptor partner identified at this stage\", \"Mammalian relevance not yet demonstrated\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Showed the engulfment role is evolutionarily conserved, validating human GULP1 as the functional ortholog acting in macrophage phagocytosis of apoptotic cells.\",\n      \"evidence\": \"Heterologous rescue of ced-6 mutants and overexpression phagocytosis assay in primary human macrophages\",\n      \"pmids\": [\"10574771\", \"10574763\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab functional assays\", \"Direct receptor interaction not yet mapped\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Defined the structural basis for GULP1 oligomerization, showing a conserved leucine zipper adjacent to the PTB domain mediates dimerization.\",\n      \"evidence\": \"Co-IP, yeast two-hybrid, gel filtration, and mutagenesis across species\",\n      \"pmids\": [\"10734103\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of dimerization for receptor binding not resolved\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Identified the receptor-recognition mechanism: the PTB domain binds NPXY motifs in CED-1 and human CD91/LRP cytoplasmic tails, linking the adaptor to engulfment receptors.\",\n      \"evidence\": \"Co-IP, yeast two-hybrid, pull-down, and domain mapping mutagenesis\",\n      \"pmids\": [\"11729193\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not test the full repertoire of receptors GULP1 engages\", \"Downstream effectors of the receptor complex unknown\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Extended GULP1 function beyond canonical phagocytosis, implicating it in glial axon-pruning engulfment, neuronal/synaptic localization, clathrin binding, and LRP-dependent lipid trafficking.\",\n      \"evidence\": \"Drosophila glia-specific RNAi and genetic interaction; rat fractionation, yeast two-hybrid/GST pull-down; bidirectional gain/loss-of-function lipid trafficking assays\",\n      \"pmids\": [\"16772168\", \"17007823\", \"16497666\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanistic link between clathrin binding and engulfment not yet established\", \"How GULP1 controls LRP ligand sorting mechanistically unclear\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Placed GULP1 in small-GTPase signaling, showing it positively regulates Arf6 by sequestering the GAP ACAP1, connecting the adaptor to membrane trafficking and migration.\",\n      \"evidence\": \"Direct binding assays, tripartite complex Co-IP, Arf6-GTP measurement, and migration assays\",\n      \"pmids\": [\"17398097\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Link between Arf6 regulation and engulfment not directly tested\", \"No structural model of the GULP1/ACAP1/Arf6 complex\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Generalized the NPXY-PTB receptor paradigm to stabilin-2, demonstrating GULP1 is rate-limiting for stabilin-2-mediated clearance of aged red blood cells.\",\n      \"evidence\": \"FRET, Co-IP, domain mutagenesis, dominant-negative PTB, and bidirectional phagocytosis assays\",\n      \"pmids\": [\"18230608\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream cytoskeletal machinery for stabilin-2 engulfment not defined here\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Resolved a signaling cascade downstream of receptor binding: GULP1 with SR-BI activates p38/ERK to elevate Rac1-GTP and drive actin rearrangement for phagocytosis.\",\n      \"evidence\": \"Yeast two-hybrid, cell-free binding, Co-IP, MAPK-inhibitor epistasis, GTP-Rac1 measurement, and phagocytosis assays\",\n      \"pmids\": [\"19122200\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How GULP1 mechanistically activates MAPK upstream is not defined\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Added stabilin-1 to the receptor set, reinforcing the NPxF/Y-PTB recognition mode in phosphatidylserine-mediated engulfment.\",\n      \"evidence\": \"Co-IP, colocalization, siRNA knockdown, and phagocytosis assay\",\n      \"pmids\": [\"20599701\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab characterization\", \"Effector pathway downstream of stabilin-1 not detailed\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Revealed a non-engulfment substrate, showing GULP1 binds the APP NPTY motif and promotes amyloidogenic CTF/Aβ generation.\",\n      \"evidence\": \"Yeast two-hybrid, Co-IP, reporter assay, and bidirectional expression with Aβ/CTF readouts\",\n      \"pmids\": [\"21486224\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trafficking step at which GULP1 alters APP processing not pinpointed here\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Mechanistically unified GULP1 as a clathrin adaptor and an endosomal signaling modulator, recognizing noncanonical sorting sequences and prolonging LRP1-dependent TGF-β/SMAD3 signaling.\",\n      \"evidence\": \"Drosophila ced-6 null genetics, uptake assays in HeLa, clathrin-coated vesicle fractionation; SMAD3 phosphorylation, endosomal trafficking, and functional TGF-β assays\",\n      \"pmids\": [\"22398720\", \"22451657\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How GULP1 selects between cargo-internalization and signaling-endosome retention is unresolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identified a nuclear function, showing GULP1 shuttles and mediates LRP1- (but not APP-) intracellular-domain transactivation.\",\n      \"evidence\": \"Nuclear fractionation/trafficking and reporter-based transactivation assays\",\n      \"pmids\": [\"23167255\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Target genes of LRP1-ICD/GULP1 transactivation not identified\", \"Single-lab evidence\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Connected receptor binding to membrane remodeling, showing GULP1 bridges Jedi-1 to clathrin heavy chain whose tyrosine phosphorylation drives phosphoclathrin/actin assembly at phagocytic cups.\",\n      \"evidence\": \"Co-IP, NPXY mutagenesis, reciprocal GULP/CHC knockdown, and phagocytosis assays with beads and apoptotic neurons\",\n      \"pmids\": [\"24743597\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinase responsible for CHC phosphorylation not identified\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Demonstrated GULP1 orchestrates trogocytosis, dynamically engaging EphB/ephrin clusters with Tiam2/Rac and serving as a prerequisite for dynamin recruitment and membrane scission, and that αvβ3 integrin transcriptionally suppresses GULP1.\",\n      \"evidence\": \"Live imaging, knockdown/knockout, Co-IP, Xenopus embryo assays; trabecular meshwork siRNA, phagocytosis, qPCR\",\n      \"pmids\": [\"31409653\", \"31516309\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which GULP1 recruits dynamin is not structurally defined\", \"Integrin-to-GULP1 transcriptional pathway not mapped\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Established a stress/redox role, showing GULP1 binds KEAP1 to retain NRF2 cytoplasmically, and its loss drives constitutive NRF2 target activation and cisplatin resistance.\",\n      \"evidence\": \"Co-IP, siRNA knockdown, NRF2 localization, gene expression, and tumor growth assays\",\n      \"pmids\": [\"32817372\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether KEAP1 binding requires the PTB domain not addressed\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Defined an autophagy function: GULP1 binds ATG14 and targets it to the ER to potentiate PI3KC3-C1 activity, simultaneously promoting APP entry into autophagic vacuoles.\",\n      \"evidence\": \"Co-IP, PI3KC3-C1 activity assay, confocal ER-targeting, autophagy flux, mutagenesis, and APP CTF/Aβ measurement\",\n      \"pmids\": [\"39080084\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relationship between the autophagy role and the clathrin/engulfment role unclear\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Showed GULP1 expression is hormonally controlled (AR and ERβ directly repress its promoter) with downstream consequences for chondrocyte differentiation via TGF-β/SMAD2/3 and for cisplatin sensitivity.\",\n      \"evidence\": \"ChIP, AR/ERβ over- and knockdown, siRNA GULP1 knockdown, drug cytotoxicity, cell cycle and chondrogenic differentiation assays\",\n      \"pmids\": [\"34576193\", \"39467629\", \"38553249\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking GULP1 loss to cisplatin-specific resistance not fully resolved\", \"Single-lab studies\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Extended GULP1 to in vivo tissue physiology, with knockout phenotypes in bone (estrogen/osteoclast), tendon (ERK/collagen), and an IKIP/NF-κB/OPA1 axis governing mitochondrial morphology in diabetic cardiomyopathy.\",\n      \"evidence\": \"Gulp1 KO and cardiac-specific KO/knock-in mice, microCT, histomorphometry, GC-MS steroid measurement, BrdU/TEM, Co-IP, echocardiography, and metabolic assays\",\n      \"pmids\": [\"36870066\", \"40747745\", \"42015218\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How the adaptor/engulfment activity relates to these tissue phenotypes is unclear\", \"Single-lab models for each tissue\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how GULP1's many context-specific activities (receptor engulfment adaptor, clathrin/Arf6 trafficking regulator, KEAP1/NRF2 and autophagy modulator, and tissue developmental factor) are integrated or selectively deployed in different cell types.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural model integrating PTB, leucine zipper, and partner binding\", \"No unifying regulatory logic for partner selection established\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 4, 9, 16]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [8, 19, 27]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [10, 16, 19]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [19]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [7, 13]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [6, 14]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [15]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [22]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [13, 25]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [7, 13, 16]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [0, 2, 9]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [22]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [10, 14, 27]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [19]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"LRP1\", \"STAB2\", \"SCARB1\", \"STAB1\", \"JEDI-1\", \"ACAP1\", \"ATG14\", \"KEAP1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}