{"gene":"GBF1","run_date":"2026-04-28T18:06:52","timeline":{"discoveries":[{"year":1999,"finding":"GBF1 was identified as a novel Golgi-associated guanine nucleotide exchange factor (GEF) with a Sec7 domain that exhibits BFA-resistant GEF activity specific towards ARF5 at physiological Mg2+ concentration. Overexpression conferred BFA resistance to Golgi morphology and ARF activation/COPI recruitment. GBF1 localized primarily to the cytosol with a pool co-localizing with β-COPI at a perinuclear (Golgi) structure.","method":"Expression cloning, in vitro GEF assay with His-tagged GBF1, immunogold EM localization, BFA resistance functional assay","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 — in vitro GEF activity reconstituted, multiple orthogonal methods, foundational discovery paper","pmids":["10402461"],"is_preprint":false},{"year":2004,"finding":"GBF1 cycles rapidly on and off Golgi membranes (not stably associated). BFA, acting as an uncompetitive inhibitor binding to an Arf-GDP–GBF1 complex, stabilizes GBF1 on Golgi membranes. GBF1 exchange activity on Arf1 is inhibited by BFA in mammalian cells.","method":"YFP-GBF1 FRAP analysis, in vivo Arf1-GTP level assay, BFA treatment","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1–2 — live-cell FRAP with in vivo GTP-loading assay, mechanistically rigorous","pmids":["15616190"],"is_preprint":false},{"year":2003,"finding":"GBF1 physically interacts with the membrane-tethering protein p115 through the proline-rich region of GBF1 and the head region of p115. The two proteins colocalize at the Golgi and peripheral VTCs. Expression of the p115-binding (pro-rich) region of GBF1 causes Golgi disruption, indicating functional relevance of this interaction.","method":"Yeast two-hybrid screen, in vitro binding assay, in vivo co-immunoprecipitation, mutagenesis, immunofluorescence","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 2 — reciprocal co-IP plus in vitro binding plus functional mutagenesis","pmids":["12634853"],"is_preprint":false},{"year":2005,"finding":"GBF1 rapidly cycles between membranes and cytosol (t1/2 ~17 s by FRAP), faster than ARF itself. GBF1 is stabilized on membranes when in complex with ARF-GDP (shown by inactive E794K mutant, ARF1-T31N mutant, and BFA treatment). GBF1 dissociation is triggered by its own catalytic activity (GDP displacement and GTP binding to ARF), implying each GBF1 membrane association catalyzes a single ARF activation event.","method":"GFP-GBF1 FRAP, dominant-negative mutant expression, BFA treatment","journal":"Traffic (Copenhagen, Denmark)","confidence":"High","confidence_rationale":"Tier 1–2 — three independent approaches with mechanistic mutagenesis and FRAP, single lab","pmids":["15813748"],"is_preprint":false},{"year":2006,"finding":"GBF1 localizes to both cis-Golgi membranes and peripheral puncta (VTCs) near but separate from ER exit sites. Live-cell imaging showed rapid GFP-GBF1 exchange with a large cytosolic pool. Microinjection of anti-GBF1 antibodies specifically caused dissociation of COPI from membranes, demonstrating GBF1 regulates COPI membrane recruitment in the early secretory pathway.","method":"GFP-live imaging, FRAP, BFA treatment, anti-GBF1 microinjection, subcellular fractionation","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — direct antibody microinjection with defined COPI phenotype, multiple orthogonal methods","pmids":["16926190"],"is_preprint":false},{"year":2006,"finding":"The enterovirus 3A protein inhibits Arf1 activation and COP-I coat recruitment by directly interacting with the N-terminus of GBF1 and inhibiting its GEF function. This 3A–GBF1 interaction is the mechanism by which 3A blocks ER-to-Golgi transport.","method":"Co-immunoprecipitation, dominant-negative Arf1 expression, siRNA knockdown, EM, in vivo transport assay, mouse virulence assay","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods, in vivo functional rescue, replicated across enterovirus 3A studies","pmids":["16890159"],"is_preprint":false},{"year":2007,"finding":"GBF1 acts as a Rab1b effector: active GTP-locked Rab1b (Rab1bQ67L) increases GBF1 and COPI association with peripheral ER exit site structures and stabilizes Arf1 on Golgi membranes. Rab1b siRNA knockdown reduced GBF1 membrane association. The N-terminal domain of GBF1 mediates its interaction with Rab1b.","method":"Co-immunoprecipitation, siRNA knockdown, live-cell GFP imaging, FRAP, dominant-active Rab1b mutant expression","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — reciprocal co-IP, domain mapping, multiple functional assays","pmids":["17429068"],"is_preprint":false},{"year":2007,"finding":"GBF1 dimerizes through its DCB domain; DCB–DCB homodimerization and DCB–HUS interactions define the N-terminal architecture of GBF1 (and BIG ArfGEFs). The HUS box (most conserved motif after Sec7) mediates the DCB–HUS interaction within each homodimer. Both DCB and HUS domains are necessary for GBF1 dimerization in mammalian cells.","method":"Yeast two-hybrid, biochemical interaction assays, co-immunoprecipitation in mammalian cells, mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — biochemical reconstitution of domain interactions combined with cellular dimerization assays","pmids":["17640864"],"is_preprint":false},{"year":2007,"finding":"Molecular determinants of 3A–GBF1 interaction: 3A must dimerize to bind GBF1; a conserved N-terminal region of 3A is critical for GBF1 binding but not dimerization. Within GBF1, the extreme N-terminus, the DCB (dimerization/cyclophilin binding) domain, and the HUS domain are required for interaction with 3A.","method":"3A mutagenesis, co-immunoprecipitation, GBF1 deletion mutant analysis","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 — systematic mutagenesis of both binding partners with functional rescue assays","pmids":["17329336"],"is_preprint":false},{"year":2007,"finding":"GBF1 is required for GGA (Golgi-localized, gamma-ear-containing, ARF-binding protein) recruitment to Golgi membranes. GBF1 co-localizes and co-immunoprecipitates with GGAs. Depletion of GBF1 or expression of inactive GBF1 prevents GGA membrane recruitment and causes missorting of lysosomal cargo (mannose-6-phosphate receptor, sortilin).","method":"Co-immunoprecipitation, GBF1 siRNA knockdown, dominant-negative GBF1, cargo trafficking assay","journal":"Traffic (Copenhagen, Denmark)","confidence":"High","confidence_rationale":"Tier 2 — multiple complementary loss-of-function approaches with defined cargo-sorting phenotype","pmids":["17666033"],"is_preprint":false},{"year":2007,"finding":"GBF1 depletion by siRNA causes COPI dispersal and extensive tubulation of cis-Golgi without complete Golgi collapse into ER. This causes dramatic inhibition of transmembrane protein trafficking but soluble protein secretion continues, indicating GBF1-mediated ARF activation and COPI recruitment are specifically required for transmembrane cargo but not soluble cargo transport.","method":"siRNA knockdown, immunofluorescence, live-cell trafficking assays, EM","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — clean siRNA KD with distinct cargo-specific phenotype, multiple cargo types tested","pmids":["17956946"],"is_preprint":false},{"year":2007,"finding":"GBF1 regulates COPI recruitment specifically on cis-Golgi compartments (not TGN), whereas BIG proteins regulate adaptor proteins on trans-Golgi. GBF1/COPI knockdown does not prevent ER export but causes VSVGtsO45 accumulation in peripheral VTCs. GBF1 is required for Golgi subcompartmentalization and cargo progression to the cell surface.","method":"siRNA knockdown (GBF1, BIG1, BIG2, COPI), immunofluorescence, VSVGtsO45 trafficking assay","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — parallel knockdowns of distinct GEFs with multiple cargo and coat readouts","pmids":["18003980"],"is_preprint":false},{"year":2008,"finding":"GBF1 depletion (but not BIG1 or BIG2 depletion) causes cell-cycle arrest in G0/G1, Golgi marker dispersal, ER stress (elevated calreticulin, PDI, ER chaperones), and triggers ATF6 proteolysis mimicking an unfolded protein response. GBF1 depletion causes relocalization of S2P from Golgi to ER with ATF6 cleavage and upregulation of ERSE genes.","method":"Selective siRNA depletion of each GEF, proteomic analysis, immunofluorescence, cell-cycle analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — selective siRNA with multiple orthogonal readouts (proteomics, ATF6 processing, cell-cycle)","pmids":["18287014"],"is_preprint":false},{"year":2008,"finding":"Class II ARFs (Arf4, Arf5) associate with ERGIC membranes through GBF1-independent binding sites in their GDP-bound form, whereas class I Arfs (Arf1, Arf3) rapidly dissociate from all endomembranes upon BFA treatment. Loss of Arf-GTP (not formation of Arf·GDP·BFA·GBF1 complex) causes GBF1 accumulation on membranes.","method":"Live-cell imaging of fluorescently tagged Arfs, BFA and Exo1 treatment, GDP-locked Arf4 mutant","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — systematic live-cell analysis distinguishing GBF1-dependent versus -independent Arf recruitment","pmids":["18524849"],"is_preprint":false},{"year":2008,"finding":"GBF1 (but not BIG1 or BIG2) is critically required for mouse hepatitis coronavirus (MHV) RNA replication. ARF1, the cellular effector of GBF1, is also required. GBF1-mediated ARF1 activation controls the number of viral replication complexes formed.","method":"Individual siRNA knockdown of GBF1, BIG1, BIG2, ARF1; BFA sensitivity in MDCK cells expressing BFA-resistant GBF1; immunofluorescence and quantitative EM","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 — selective siRNA of each GEF with BFA-resistant GBF1 rescue in MDCK cells","pmids":["18551169"],"is_preprint":false},{"year":2009,"finding":"GBF1 is critically required for CVB3 RNA replication. BFA-resistant GBF1-M832L rescues replication in BFA-treated cells; GBF1 knockdown by RNAi inhibits replication; only active (not inactive catalytic mutant) GBF1 rescues replication. Overexpression of ARF proteins or Rab1B did not rescue BFA-inhibited replication.","method":"siRNA knockdown, BFA-resistant GBF1 mutant rescue, overexpression of Arf proteins and Rab1B, replicon assays","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 — multiple complementary approaches, active-site mutant controls, replicated across CVB3 and poliovirus","pmids":["19740986"],"is_preprint":false},{"year":2009,"finding":"GBF1 is a host factor critically required for HCV RNA replication. GBF1 knockdown (but not BIG1 or BIG2) inhibits HCV replication. BFA-resistant GBF1 mutant rescues HCV replication in BFA-treated cells. BFA/GBF1 inhibition does not block membranous web formation but impairs replication complex activity.","method":"siRNA knockdown of individual GEFs, BFA-resistant GBF1 rescue, pharmacological GBF1 inhibitor, immunofluorescence and EM","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 — selective GEF knockdown with BFA-resistant rescue, orthogonal morphological analysis","pmids":["19906930"],"is_preprint":false},{"year":2009,"finding":"Drosophila garz (ortholog of GBF1) is a novel component of the clathrin-independent GEEC endocytic pathway, required for GPI-anchored protein and fluid-phase internalization. A catalytically inactive GBF1 GEF mutant has altered Arf1 activation at nascent pinosomes and impairs fluid-phase uptake.","method":"RNAi screen, live confocal and TIRF imaging with GBF1-GFP and Arf1 sensor, GEF-dead mutant, quantitative endocytosis assays","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 — live imaging with functional GEF sensor, catalytic mutant, and quantitative endocytosis assay","pmids":["19707569"],"is_preprint":false},{"year":2010,"finding":"For poliovirus replication, the N-terminal region of GBF1 (lacking the catalytic Sec7 domain) is sufficient to rescue BFA-inhibited replication. In infected cells p115 is degraded and neither p115 nor Rab1b knockdown affects viral replication, indicating viral replication requires a non-catalytic function of GBF1 distinct from its cellular role in ARF/COPI secretory trafficking.","method":"N-terminal GBF1 truncation rescue assay, p115/Rab1b siRNA knockdown, BFA-resistant virus replicon","journal":"Cellular microbiology","confidence":"High","confidence_rationale":"Tier 2 — systematic domain dissection with rescue assay, multiple siRNA controls","pmids":["20497182"],"is_preprint":false},{"year":2010,"finding":"GBF1 is phosphorylated by CDK1-cyclin B during mitosis, causing its dissociation from Golgi membranes and reduction of membrane-associated GTP-bound ARF. A low level of GBF1 activity persists in mitosis and remains required for COPI recruitment, suggesting GBF1 phosphorylation and membrane dissociation contribute to Golgi fragmentation during mitotic entry.","method":"Phosphoprotein analysis, CDK1-cyclin B in vitro kinase assay, immunofluorescence in mitotic cells, ARF-GTP measurement","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1–2 — in vitro kinase assay plus cell-based phosphorylation and membrane dissociation analysis","pmids":["20175751"],"is_preprint":false},{"year":2010,"finding":"PI4KIIIα-generated phosphatidylinositol 4-phosphate [PtdIns(4)P] is required for GBF1 recruitment to Golgi membranes. Dominant-active Rab1 increases PtdIns(4)P levels at the Golgi, suggesting Rab1 contributes to GBF1 recruitment specificity by activating PI4KIIIα to produce PtdIns(4)P.","method":"PI4KIIIα siRNA knockdown, PI4P inhibitors (wortmannin, LY294002), GFP-PH PtdIns(4)P sensor, dominant-active Rab1 expression, GBF1 localization assay","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — pharmacological and genetic inhibition with lipid sensor, mechanistic connection to Rab1","pmids":["20530568"],"is_preprint":false},{"year":2011,"finding":"C. trachomatis selectively co-opts GBF1 (but not BIG1 or BIG2) for vesicle-mediated sphingomyelin (SM) acquisition. The Arf1/GBF1-dependent SM pathway is essential for inclusion membrane growth and stability but not for bacterial replication. GBF1 depletion by siRNA blocks SM delivery to the inclusion.","method":"siRNA knockdown of individual BFA targets, BFA sensitivity analysis, fluorescent SM trafficking assay, inclusion integrity measurement","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 — selective GEF knockdown, BFA-resistant cell lines, defined SM trafficking phenotype","pmids":["21909260"],"is_preprint":false},{"year":2011,"finding":"GBF1 and ATGL (adipose triglyceride lipase) interact directly through multiple contact sites: ATGL C-terminus contacts GBF1 N-terminal domains including the Sec7 domain; ATGL N-terminal patatin domain interacts with GBF1 HDS1 and HDS2 domains. GBF1 HDS1 and HDS2 domains localize to lipid droplets when expressed alone. The GBF1–Arf1–COPI pathway is required for ATGL delivery to lipid droplets.","method":"Yeast two-hybrid, co-immunoprecipitation in mammalian cells, direct protein binding (in vitro), GFP domain-localization assays","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1–2 — direct protein binding plus yeast two-hybrid plus cellular co-IP with domain mapping","pmids":["21789191"],"is_preprint":false},{"year":2012,"finding":"ARF1 and GBF1 generate a PI4P-enriched environment at HCV replication complexes. ARF1 and GBF1 colocalize with PI4KIIIβ and are both required for HCV replication. HCV replication is inhibited by PI4P phosphatase Sac1 overexpression.","method":"Co-immunoprecipitation/colocalization, PI4P sensor, Sac1 overexpression, siRNA knockdown","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 — multiple methods but limited mechanistic depth on the GBF1-PI4P causal link","pmids":["22359663"],"is_preprint":false},{"year":2012,"finding":"GBF1 bears a novel phosphatidylinositol-phosphate binding module (BP3K) that links PI3Kγ activity with Arf1 activation in GPCR-stimulated neutrophil chemotaxis. Upon GPCR stimulation, GBF1 translocates from Golgi to the leading edge via PI3Kγ product binding, where it activates Arf1 and recruits p22phox and GIT2, thereby regulating directional sensing and superoxide production.","method":"Subcellular fractionation, GFP-GBF1 live imaging, phospholipid binding assay, siRNA knockdown, GPCR stimulation","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — novel domain identified with PI3P binding, translocation imaging, functional readouts of chemotaxis and superoxide","pmids":["22573891"],"is_preprint":false},{"year":2013,"finding":"GBF1's HDS1 domain (immediately downstream of the Sec7 domain) contains an amphipathic helix that binds lipid droplets and Golgi membranes in cells, and bilayer liposomes and artificial droplets in vitro. The Sec7 domain inhibits the HDS1 lipid-droplet binding capacity in the context of full-length GBF1.","method":"In vitro liposome binding, artificial droplet binding, GFP domain expression in cells, mutagenesis of amphipathic helix","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1–2 — in vitro lipid binding reconstituted plus mutagenesis plus cellular localization","pmids":["23943872"],"is_preprint":false},{"year":2013,"finding":"GBF1-activated ARF4 and ARF5 (but not ARF3) facilitate BIG1 and BIG2 recruitment to the TGN, establishing a functional GEF cascade. GBF1 localizes ultrastructurally to pre-Golgi, Golgi, and TGN. This defines a sequential coating pathway in which GBF1 at the TGN activates ARFs that then recruit BIG1/2.","method":"Immunoelectron microscopy, siRNA knockdown, Arf isoform-specific rescue experiments, GBF1 inhibitor treatment","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — ultrastructural localization plus ARF isoform specificity dissection with multiple knockdowns","pmids":["23386609"],"is_preprint":false},{"year":2013,"finding":"AMPK phosphorylates GBF1 during mitosis, causing GBF1 dissociation from the Golgi membrane and abolishing GBF1's Arf1-GEF activity, thereby promoting Golgi disassembly required for mitosis entry.","method":"In vitro AMPK kinase assay on GBF1, phospho-specific analysis, mitotic cell fractionation, dominant-negative and pharmacological approaches","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1–2 — in vitro kinase assay plus cellular phenotype with mechanistic detail on Golgi fragmentation","pmids":["23418352"],"is_preprint":false},{"year":2015,"finding":"The Dengue virus GBF1–Arf1/Arf4–COPI pathway is required for capsid protein transport from ER membrane to lipid droplets, independently of COPII components and Golgi integrity. A BFA-resistant GBF1 mutant rescues capsid subcellular distribution in BFA-treated infected cells.","method":"BFA and GCA pharmacological inhibition, BFA-resistant GBF1 rescue, siRNA knockdown, immunofluorescence","journal":"Traffic (Copenhagen, Denmark)","confidence":"High","confidence_rationale":"Tier 2 — BFA-resistant rescue plus siRNA dissection, multiple GBF1-pathway components tested","pmids":["26031340"],"is_preprint":false},{"year":2015,"finding":"GBF1 oligomerization (mediated by the DCB domain residues K91 and E130) is dispensable for Golgi targeting, rapid membrane cycling, ARF activation, COPI recruitment, and cargo secretion. However, oligomerization stabilizes GBF1 protein; the non-oligomerizing 91/130 mutant is degraded faster than wild-type.","method":"GBF1 DCB domain mutagenesis, live-cell FRAP, ARF activation assay, COPI immunofluorescence, secretion assay, protein stability measurement","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 2 — systematic mutagenesis with multiple functional readouts separating oligomerization from GEF activity","pmids":["26718629"],"is_preprint":false},{"year":2017,"finding":"GBF1 and Arf4 form a functional complex with the sensory receptor rhodopsin at the photoreceptor Golgi/TGN during transport carrier biogenesis for ciliary targeting. Rhodopsin and Arf4 bind the regulatory N-terminal DCB-HUS domain of GBF1. GCA (GBF1 inhibitor) blocks this complex and prevents rhodopsin delivery to cilia without disrupting the Golgi. GBF1 also interacts with the Arf GAP ASAP1 in a GCA-resistant manner.","method":"Frog retina in vivo analysis, co-immunoprecipitation with recombinant human proteins, GCA inhibitor, domain binding mapping","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — biochemical reconstitution with recombinant proteins, in vivo retinal assay, inhibitor specificity","pmids":["29025970"],"is_preprint":false},{"year":2018,"finding":"GBF1 is phosphorylated on Ser292 and Ser297 by casein kinase 2 (CK2) during mitosis, enabling recognition by the F-box protein βTrCP and recruitment to the SCFβTrCP ubiquitin ligase complex, triggering GBF1 degradation. This degradation occurs at the intercellular bridge of telophase cells and is required for Golgi membrane positioning and postmitotic Golgi reformation. A non-degradable GBF1 mutant blocks Golgi cluster transport and causes cytokinesis failure.","method":"Phosphorylation site mutagenesis, co-immunoprecipitation with βTrCP/SCF complex, proteomics, non-degradable GBF1 mutant live imaging, cytokinesis assay","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1–2 — phosphosite mapping, E3 ligase identification, substrate mutant with defined mitotic/cytokinesis phenotype","pmids":["29898406"],"is_preprint":false},{"year":2018,"finding":"GBF1 recruitment to Golgi membranes requires the HDS1 and HDS2 domains and a heat-labile, protease-sensitive Golgi-localized protein receptor. Arf-GDP localization at the cis-Golgi (but not TGN) promotes GBF1 recruitment. ArfGAP2 and ArfGAP3 do not regulate GBF1 recruitment.","method":"In vitro GBF1 recruitment assay with Golgi fractions, heat/protease treatment of membranes, Arf-GDP targeted mutants, GBF1 HDS1/HDS2 domain mapping","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1–2 — in vitro reconstituted recruitment assay plus domain mapping, multiple complementary approaches","pmids":["29507113"],"is_preprint":false},{"year":2018,"finding":"GBF1 and its substrate Arf1 interact with the mitochondrial membrane protein Miro, regulating mitochondrial spatial organization. GBF1 inhibition promotes dynein- and Miro-dependent retrograde mitochondrial transport along microtubules toward the centrosome, causing mitochondrial network collapse. Active GTP-bound Arf1 also physically interacts with Miro.","method":"Co-immunoprecipitation (GBF1-Miro, Arf1-GTP-Miro), GBF1 inhibition (GCA), Miro siRNA, dynein inhibitor, electron tomography, live-cell time-lapse imaging","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 — physical interaction demonstrated plus functional rescue with dynein/Miro inhibition, electron tomography","pmids":["30459446"],"is_preprint":false},{"year":2018,"finding":"Conserved residues RDR1168 and LF1266 within α-helices 2 and 6 of the HDS2 domain of GBF1 are required for GBF1 targeting to Golgi membranes. Mutations at these positions compromise Golgi homeostasis, ARF activation, secretion, and cell viability in a functional replacement assay.","method":"HDS2 alanine-scanning mutagenesis, BFA-resistant replacement assay, Golgi morphology, COPI recruitment, secretion assay","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 2 — systematic domain mutagenesis with multiple functional readouts in cells","pmids":["29443553"],"is_preprint":false},{"year":2019,"finding":"C10orf76 interacts with GBF1 and rapidly cycles on and off GBF1-positive Golgi structures (identified by BioID proximity labeling of Golgi-enriched fractions). C10orf76 depletion causes Golgi fragmentation, alters GBF1 recruitment, and impairs secretion.","method":"BioID proximity labeling, mass spectrometry, co-immunoprecipitation, siRNA knockdown, Golgi morphology and secretion assays","journal":"Molecular & cellular proteomics : MCP","confidence":"High","confidence_rationale":"Tier 2 — BioID plus co-IP plus functional knockdown with defined Golgi and secretion phenotype","pmids":["31519766"],"is_preprint":false},{"year":2019,"finding":"GBF1 is required for VWF (von Willebrand factor) and extracellular matrix protein trafficking from ER to Golgi secretory granules in endothelial cells. GBF1 level is a limiting factor in VWF granule biogenesis. AMPK activation (by glucose levels) couples to GBF1 function and modulates VWF trafficking, linking physiological energy status to anterograde secretory pathway regulation.","method":"GBF1 siRNA knockdown, GBF1 overexpression, AMPK pharmacological activation, fluorescence live imaging of VWF trafficking, secretion assay","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 — loss-of-function and gain-of-function with physiological AMPK coupling and defined granule trafficking phenotype","pmids":["31056345"],"is_preprint":false},{"year":2019,"finding":"HCV NS3 protein directly interacts with GBF1 through the Sec7 domain of GBF1 and the protease domain of NS3, as shown by yeast two-hybrid, co-immunoprecipitation, and proximity ligation assay. NS3 alters GBF1 intracellular localization. An NS3 mutant (N77D) that disrupts GBF1 binding is non-replicative despite retaining protease activity, indicating the NS3–GBF1 interaction is important for HCV genome replication.","method":"Yeast two-hybrid, co-immunoprecipitation, proximity ligation assay, NS3 mutagenesis, replication assay","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 — three independent interaction assays, domain mapping, NS3 mutant replication phenotype","pmids":["30567983"],"is_preprint":false},{"year":2019,"finding":"GBF1 catalytic activity (but not Arf1 activation per se) is essential for rotavirus assembly. Inhibition of GBF1 by BFA or GCA prevents trimerization of the outer capsid protein VP7 and blocks assembly of triple-layered particles. GBF1 inhibition alters electrophoretic mobility of VP7 and NSP4.","method":"BFA and GCA pharmacological inhibition, GBF1 siRNA knockdown, viral particle characterization, VP7 trimerization assay","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 — pharmacological and genetic loss-of-function with specific viral assembly phenotype and VP7 trimerization assay","pmids":["31270230"],"is_preprint":false},{"year":2019,"finding":"Multiple determinants in GBF1 support poliovirus replication: the Arf-activating property of the Sec7 domain is indispensable, but the primary structure of the Sec7 domain itself is not. GBF1 is recruited to replication sites via both direct 3A interaction and redundant determinants in C-terminal non-catalytic domains (HDS regions).","method":"GBF1 domain mutant rescue assay in poliovirus replication context, viral RNA replication assay, BFA-resistant rescue","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 — systematic domain mutagenesis with viral replication functional readout","pmids":["31375590"],"is_preprint":false},{"year":2021,"finding":"Src kinase phosphorylates GBF1 on 10 tyrosine residues; two residues (Y876 and Y898) near the C-terminus of the Sec7 domain promote GBF1 binding to Arf1 GTPase. This phosphorylation induces formation of tubular transport carriers containing GALNTs for Golgi-to-ER retrograde transport. Phosphomimetic GBF1 mutants induce tubules, while mutants defective for Arf1 binding prevent carrier formation and GALNTs relocation.","method":"Phosphoproteomics, Src kinase assay, GBF1 phosphomimetic/phosphodeficient mutants, live-cell tubule imaging, molecular modeling, Arf1 binding assay","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1–2 — phosphosite identification, mutagenesis, Arf1 binding assay, molecular modeling, and live-cell carrier imaging","pmids":["34870592"],"is_preprint":false},{"year":2024,"finding":"AMPK associates with the Golgi and phosphorylates GBF1 at Thr1337 upon activation, causing Golgi fragmentation and slowing protein trafficking through the Golgi. Golgi disassembly upon AMPK activation is blocked in cells expressing non-phosphorylatable GBF1-T1337A generated by gene editing.","method":"AMPK-α knockout cells, pharmacological AMPK activators, GBF1-T1337A knock-in by gene editing, Golgi morphology assay, protein trafficking (Gaussia luciferase) assay","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1–2 — non-phosphorylatable knock-in plus genetic KO with defined trafficking and morphology phenotypes","pmids":["39575556"],"is_preprint":false},{"year":2016,"finding":"Zebrafish gbf1 loss-of-function (L1246R mutation in HDS2 domain, morphants, knockout) causes intracerebral hemorrhage due to vascular breakage in a cell-autonomous manner. The L1246R Gbf1 mutant fails to be recruited to the Golgi and cannot activate Arf1 or recruit the COPI complex in mammalian cells, indicating HDS2 domain is essential for GBF1 membrane targeting and function.","method":"ENU mutagenesis/positional cloning in zebrafish, gbf1 morpholino knockdown and CRISPR knockout, Gbf1-L1246R expression in mammalian cells, Golgi recruitment and Arf1 activation assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — in vivo vertebrate model plus cellular mechanistic validation of domain mutant","pmids":["28003365"],"is_preprint":false},{"year":2020,"finding":"Pathogenic variants in GBF1 (four distinct heterozygous variants, two de novo) cause distal hereditary motor neuropathy/Charcot-Marie-Tooth neuropathy type 2 (HMN/CMT2). Primary fibroblasts from all affected individuals show marked Golgi fragmentation consistent with GBF1's role in Golgi maintenance. GBF1 is present in mouse spinal cord/muscle and enriched at motor neurons and growth cones.","method":"Genomic sequencing, Golgi fragmentation assay in patient fibroblasts, immunofluorescence in mouse tissue","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2–3 — genetic and cell-biology evidence linking GBF1 variants to neurodegeneration via Golgi fragmentation; mechanism inferred from patient cells","pmids":["32937143"],"is_preprint":false},{"year":2023,"finding":"Phosphorylation of specific N-terminal residues of GBF1 (S233, S371, Y377, Y515) differentially regulates its role in cytokinesis versus Golgi homeostasis/secretion: phosphomimetic mutants of these residues support normal Golgi architecture and cargo secretion but cause multi-nucleation and impair cytokinetic bridge resolution, while not affecting secretory functions.","method":"GBF1 phospho-site mutagenesis (phosphomimetic and non-phosphorylatable), Golgi morphology assay, secretion assay, cytokinesis/multinucleation assay","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 — systematic phosphosite mutagenesis with multiple functional readouts distinguishing two GBF1 functions","pmids":["37604968"],"is_preprint":false},{"year":2012,"finding":"GBF1-dependent secretion (via Arf1-COPI machinery) is required for Drosophila tubulogenesis. Loss of Garz (fly GBF1 ortholog) impairs Golgi integrity, cargo vesicle transport, and directed apical membrane delivery, causing failure in epithelial polarity and lumen expansion in tubular organs.","method":"Drosophila loss-of-function mutants, immunofluorescence, EM, live imaging of cargo transport","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — in vivo Drosophila genetics with multiple morphological and trafficking readouts, confirmed ortholog","pmids":["22302994"],"is_preprint":false},{"year":2013,"finding":"In C. elegans, GBF-1 (GBF1 ortholog) localizes to the cis-Golgi and is required for secretion, Golgi integrity, and ER reticular structure. GBF-1 RNAi also impairs receptor-mediated endocytosis in oocytes without affecting recycling pathways, and alters early/late endosome dynamics.","method":"RNAi, immunofluorescence, GFP-tagged organelle markers, yolk receptor trafficking assay in C. elegans","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 — clean in vivo genetic knockdown with multiple orthogonal organelle readouts; C. elegans ortholog","pmids":["23840591"],"is_preprint":false},{"year":2021,"finding":"GBF1 deficiency in mouse oocytes (via GBF1 inhibitor treatment) causes aberrant Golgi accumulation around the spindle, condensation of GM130 (a Golgi matrix protein co-localizing with GBF1), ER structural disruption with elevated ER stress marker GRP78, and altered mitochondrial membrane potential, impairing polar body formation.","method":"GBF1 inhibitor (GCA) in mouse oocytes, immunofluorescence, mitochondrial membrane potential assay, Western blot","journal":"Microscopy and microanalysis","confidence":"Medium","confidence_rationale":"Tier 3 — pharmacological inhibition in oocytes with multiple organelle readouts but single method approach","pmids":["33478608"],"is_preprint":false},{"year":2024,"finding":"GBF1 knockdown activates XBP1s (unfolded protein response) and enhances mTOR-independent autophagy in human lens epithelium cells. A pathological GBF1 T1287I mutation reduces GBF1 protein levels. Heterozygous Gbf1 knockout mice display cataracts, establishing GBF1 as a causative gene for congenital cataracts.","method":"siRNA knockdown, UPR activation assay (XBP1 splicing), autophagy assay, Gbf1 heterozygous knockout mice, patient mutation analysis","journal":"Human genetics","confidence":"Medium","confidence_rationale":"Tier 2 — mouse KO model plus cellular mechanism (UPR, autophagy) but mechanism is largely downstream of GBF1 deficiency","pmids":["39110251"],"is_preprint":false}],"current_model":"GBF1 is a large Sec7-domain Arf guanine nucleotide exchange factor (ArfGEF) that cycles rapidly on and off cis-Golgi and ERGIC membranes, where it catalyzes GDP-to-GTP exchange on ARF1 (and ARF4/5) to recruit the COPI coat for anterograde and retrograde vesicle trafficking; its membrane association is regulated by ARF-GDP, Rab1b, PI4KIIIα-generated PtdIns(4)P, and lipid-droplet binding via its HDS1 amphipathic helix, while phosphorylation by CDK1-cyclin B, AMPK, CK2, and Src at specific residues controls GBF1 membrane dissociation, mitotic Golgi fragmentation, proteolytic degradation via SCFβTrCP, retrograde tubule formation, and cytokinesis; downstream, GBF1-activated ARFs recruit COPI, GGAs, and BIG1/2 GEFs to coordinate the anterograde secretory pathway, lipid droplet metabolism, mitochondrial positioning via Miro, and clathrin-independent endocytosis."},"narrative":{"teleology":[{"year":1999,"claim":"Establishing GBF1 as an ARF-GEF: the foundational question of whether GBF1 possesses nucleotide exchange activity was resolved by demonstrating BFA-resistant Sec7-domain GEF activity toward ARF5, with overexpression conferring BFA resistance to COPI recruitment.","evidence":"Expression cloning, in vitro GEF assay with purified His-GBF1, immunogold EM, BFA resistance assay in mammalian cells","pmids":["10402461"],"confidence":"High","gaps":["Substrate specificity toward other ARF isoforms (ARF1, ARF3, ARF4) not yet tested","No membrane recruitment mechanism defined","No structural data on Sec7 domain"]},{"year":2004,"claim":"Defining GBF1's dynamic membrane behavior: FRAP demonstrated that GBF1 is not a stable Golgi resident but cycles rapidly on and off membranes, with BFA trapping it in an abortive ARF-GDP–GBF1 complex—resolving how BFA inhibits GBF1 in vivo.","evidence":"YFP-GBF1 FRAP, in vivo ARF1-GTP loading assay, BFA treatment in living cells","pmids":["15616190"],"confidence":"High","gaps":["Mechanism of initial membrane recruitment unknown","Whether catalytic turnover drives dissociation not yet shown"]},{"year":2005,"claim":"Establishing catalytic product release as the membrane dissociation trigger: the observation that GBF1 is stabilized on membranes by ARF-GDP (via inactive mutants) and released upon GTP loading demonstrated a single-turnover catalytic cycle per membrane association event.","evidence":"GFP-GBF1 FRAP with catalytically dead E794K mutant, ARF1-T31N dominant-negative, BFA treatment","pmids":["15813748"],"confidence":"High","gaps":["Structural basis of ARF-GDP stabilization of GBF1 not resolved","Stoichiometry of the GBF1–ARF complex on membranes unknown"]},{"year":2003,"claim":"Linking GBF1 to membrane tethering: identification of p115 as a direct binding partner connected GBF1's ARF-GEF activity to the vesicle tethering machinery at VTCs and Golgi.","evidence":"Yeast two-hybrid, in vitro binding, co-immunoprecipitation, dominant-negative GBF1 pro-rich domain expression","pmids":["12634853"],"confidence":"High","gaps":["Functional consequence of p115–GBF1 interaction on tethering efficiency not quantified","Whether p115 recruits GBF1 or vice versa unclear"]},{"year":2006,"claim":"Demonstrating GBF1 as the specific GEF for cis-Golgi COPI recruitment: anti-GBF1 antibody microinjection directly dissociated COPI from membranes, while GBF1 localized to cis-Golgi and VTCs distinct from ER exit sites, establishing compartmental specificity.","evidence":"Anti-GBF1 microinjection, GFP live imaging, FRAP, subcellular fractionation","pmids":["16926190"],"confidence":"High","gaps":["How GBF1 is excluded from trans-Golgi COPI recruitment not addressed"]},{"year":2007,"claim":"Multiple discoveries resolved GBF1's upstream regulation, downstream effectors, dimerization, and cargo specificity: Rab1b was identified as an upstream activator stabilizing GBF1 on membranes; GGAs and BIG1/2 were shown as downstream effectors; the DCB–HUS dimerization architecture was mapped; and GBF1 depletion selectively blocked transmembrane (but not soluble) cargo transport.","evidence":"Rab1b co-IP and siRNA (PMID:17429068); GGA co-IP and cargo sorting assay (PMID:17666033); DCB/HUS yeast two-hybrid and co-IP (PMID:17640864); siRNA with differential cargo assays and EM (PMID:17956946); parallel GEF knockdowns with VSVGtsO45 (PMID:18003980)","pmids":["17429068","17666033","17640864","17956946","18003980"],"confidence":"High","gaps":["Whether Rab1b directly binds GBF1 or acts through PI4P not distinguished","GGA recruitment mechanism (direct versus ARF-mediated) not resolved","Structural basis of DCB–DCB dimerization unknown"]},{"year":2008,"claim":"GBF1 depletion was shown to trigger ER stress and UPR activation (ATF6 processing) and G0/G1 arrest, revealing that GBF1 loss has consequences beyond trafficking—disrupting ER–Golgi proteostasis. Separately, class II ARFs (ARF4/5) were found to associate with ERGIC membranes independently of GBF1 in their GDP-bound state.","evidence":"Selective GEF siRNA with proteomics, ATF6 cleavage, cell-cycle analysis (PMID:18287014); live imaging of tagged ARF isoforms with BFA/Exo1 (PMID:18524849)","pmids":["18287014","18524849"],"confidence":"High","gaps":["Whether ER stress is a direct or indirect consequence of COPI loss unclear","How class II ARFs are recruited to ERGIC without GBF1 not defined"]},{"year":2008,"claim":"GBF1 was established as a critical host factor for RNA virus replication, initially for MHV coronavirus: GBF1 (but not BIG1/BIG2) knockdown blocked viral RNA replication, and BFA-resistant GBF1 rescued replication, indicating that GBF1-dependent ARF1 activation controls replication complex formation.","evidence":"Selective GEF siRNA, BFA-resistant GBF1 rescue in MDCK cells, quantitative EM of replication complexes","pmids":["18551169"],"confidence":"High","gaps":["Whether GBF1 acts at replication membranes directly or via global secretory pathway disruption not distinguished"]},{"year":2009,"claim":"GBF1's role as a host factor was extended to enteroviruses (CVB3, poliovirus) and HCV, establishing it as a broadly exploited target; separately, Drosophila garz (GBF1 ortholog) was shown to function in clathrin-independent GEEC endocytosis, expanding GBF1's role beyond secretory trafficking.","evidence":"CVB3/poliovirus replicon assays with BFA-resistant GBF1 rescue and siRNA (PMID:19740986); HCV selective GEF knockdown with rescue (PMID:19906930); Drosophila RNAi screen with TIRF imaging and GEF-dead mutant (PMID:19707569)","pmids":["19740986","19906930","19707569"],"confidence":"High","gaps":["Precise viral replication membrane composition and GBF1 role therein unknown","Whether GEEC endocytic function is conserved in mammalian cells not tested"]},{"year":2010,"claim":"Two key regulatory inputs were defined: CDK1–cyclin B phosphorylates GBF1 to trigger mitotic Golgi fragmentation, and PI4KIIIα-generated PI4P (downstream of Rab1) is required for GBF1 Golgi membrane recruitment, linking lipid identity to GEF targeting. Additionally, a non-catalytic scaffolding role was uncovered for poliovirus replication.","evidence":"In vitro CDK1 kinase assay, mitotic phosphoprotein analysis, ARF-GTP measurement (PMID:20175751); PI4KIIIα siRNA, PI4P sensor, Rab1 dominant-active (PMID:20530568); N-terminal GBF1 truncation rescue of poliovirus replication (PMID:20497182)","pmids":["20175751","20530568","20497182"],"confidence":"High","gaps":["CDK1 phosphorylation sites on GBF1 not mapped","Whether PI4P binding is direct or mediated by an adaptor unclear","The non-catalytic viral function mechanism remains obscure"]},{"year":2011,"claim":"GBF1 was linked to lipid droplet biology through direct interaction with ATGL and lipid droplet targeting via HDS1/HDS2 domains, and to pathogen lipid acquisition through Chlamydia co-option of GBF1-dependent sphingomyelin trafficking.","evidence":"ATGL–GBF1 yeast two-hybrid, co-IP, in vitro binding, domain-LD localization (PMID:21789191); selective GEF siRNA with fluorescent SM trafficking in Chlamydia-infected cells (PMID:21909260)","pmids":["21789191","21909260"],"confidence":"High","gaps":["Whether GBF1 activates ARFs on lipid droplet surfaces not shown","ATGL delivery mechanism via COPI not fully reconstituted"]},{"year":2012,"claim":"GBF1 function was extended to GPCR-stimulated neutrophil chemotaxis via a novel phosphoinositide-binding module (BP3K) that redirects GBF1 from Golgi to the leading edge, and to epithelial tubulogenesis in Drosophila where Garz loss disrupts apical membrane delivery.","evidence":"GBF1 phospholipid binding assay, leading-edge live imaging, siRNA in neutrophils (PMID:22573891); Drosophila garz mutant with EM and live cargo imaging (PMID:22302994)","pmids":["22573891","22302994"],"confidence":"High","gaps":["BP3K domain boundaries and binding specificity not fully characterized","Whether leading-edge ARF activation serves a distinct function from Golgi ARF activation unknown"]},{"year":2013,"claim":"The HDS1 amphipathic helix was identified as a direct lipid-binding element for both Golgi membranes and lipid droplets, auto-inhibited by the Sec7 domain in the full-length protein; a GEF cascade was defined in which GBF1-activated ARF4/5 recruit BIG1/2 to the TGN; and AMPK was identified as a second mitotic kinase phosphorylating GBF1 to promote Golgi disassembly.","evidence":"In vitro liposome/droplet binding with amphipathic helix mutagenesis (PMID:23943872); immunoEM localization with ARF isoform-specific rescue (PMID:23386609); in vitro AMPK kinase assay with mitotic cell fractionation (PMID:23418352)","pmids":["23943872","23386609","23418352"],"confidence":"High","gaps":["Structural basis of Sec7-mediated autoinhibition of HDS1 unknown","Which AMPK site(s) are phosphorylated during mitosis not mapped in this study"]},{"year":2015,"claim":"GBF1 oligomerization via DCB domain was shown to be dispensable for all tested GEF functions (Golgi targeting, ARF activation, COPI recruitment, secretion) but required for protein stability; simultaneously, the GBF1–ARF1/ARF4–COPI pathway was demonstrated to transport Dengue virus capsid from ER to lipid droplets independently of COPII.","evidence":"DCB mutagenesis (K91/E130) with FRAP, ARF activation, COPI, secretion, stability assays (PMID:26718629); BFA-resistant GBF1 rescue of Dengue capsid distribution (PMID:26031340)","pmids":["26718629","26031340"],"confidence":"High","gaps":["Whether oligomerization has a regulatory role under stress conditions untested","COPII-independent ER-to-LD transport mechanism not fully resolved"]},{"year":2016,"claim":"In vivo vertebrate validation came from zebrafish, where GBF1 loss-of-function (HDS2 L1246R mutation) caused intracerebral hemorrhage due to vascular breakage, and the mutant protein failed to target Golgi or activate ARF1, confirming HDS2 as essential for membrane targeting.","evidence":"ENU mutagenesis/positional cloning, morpholino and CRISPR knockout in zebrafish, mammalian cell Golgi recruitment assay","pmids":["28003365"],"confidence":"High","gaps":["Specific vascular cargo whose mis-trafficking causes hemorrhage not identified","Whether endothelial or pericyte GBF1 is the critical cell type not determined"]},{"year":2017,"claim":"GBF1 was shown to form a ternary complex with rhodopsin and ARF4 at the photoreceptor Golgi for ciliary transport carrier biogenesis, with the DCB-HUS domain mediating rhodopsin/ARF4 binding and GBF1 also interacting with the ArfGAP ASAP1.","evidence":"Frog retina in vivo analysis, co-IP with recombinant human proteins, GCA inhibitor, domain mapping","pmids":["29025970"],"confidence":"High","gaps":["Whether GBF1 functions in ciliogenesis beyond photoreceptors not tested","ASAP1 functional role in the complex not defined"]},{"year":2018,"claim":"Three advances refined GBF1 regulation and targeting: CK2 phosphorylation at S292/S297 targets GBF1 for SCFβTrCP-mediated degradation at the cytokinetic bridge, required for postmitotic Golgi reformation; HDS1/HDS2 domains and a proteinaceous Golgi receptor were shown essential for membrane recruitment in vitro; and GBF1–Miro interaction was found to regulate mitochondrial positioning.","evidence":"Phosphosite mutagenesis with βTrCP co-IP, non-degradable mutant cytokinesis failure (PMID:29898406); in vitro Golgi recruitment reconstitution with protease/heat sensitivity (PMID:29507113); GBF1–Miro co-IP, GCA inhibition, dynein pathway (PMID:30459446); HDS2 alanine scanning with functional replacement (PMID:29443553)","pmids":["29898406","29507113","30459446","29443553"],"confidence":"High","gaps":["Identity of the proteinaceous Golgi receptor for GBF1 unknown","Miro–GBF1 interaction interface not mapped","How CK2 phosphorylation timing is controlled at the midbody unclear"]},{"year":2019,"claim":"Multiple studies expanded GBF1's functional network: C10orf76 was identified as a Golgi-cycling GBF1 interactor required for Golgi integrity and secretion; GBF1 was shown to be rate-limiting for VWF granule biogenesis with AMPK coupling; HCV NS3 was found to directly bind GBF1's Sec7 domain; and GBF1 catalytic activity was required for rotavirus VP7 trimerization and particle assembly.","evidence":"BioID proximity labeling with co-IP and siRNA (PMID:31519766); GBF1 over/underexpression with AMPK activation and VWF imaging (PMID:31056345); NS3–GBF1 yeast two-hybrid, co-IP, PLA, NS3 mutant replication (PMID:30567983); GBF1 pharmacological/genetic inhibition with VP7 trimerization assay (PMID:31270230)","pmids":["31519766","31056345","30567983","31270230"],"confidence":"High","gaps":["C10orf76 molecular function in GBF1 regulation unknown","Whether AMPK directly modulates GBF1 at the Golgi versus indirectly through energy sensing not resolved at this point","NS3–GBF1 binding does not explain how GBF1 supports HCV replication mechanistically"]},{"year":2020,"claim":"Human genetic evidence established GBF1 as a disease gene: heterozygous pathogenic GBF1 variants were identified in families with distal hereditary motor neuropathy/CMT2, with patient fibroblasts showing marked Golgi fragmentation.","evidence":"Genomic sequencing of affected families, Golgi fragmentation assay in patient fibroblasts, GBF1 expression in mouse motor neurons","pmids":["32937143"],"confidence":"Medium","gaps":["Specific GBF1 variant effects on ARF activation or COPI recruitment not tested biochemically","Motor neuron-specific vulnerability mechanism unknown","No animal model recapitulating the neuropathy phenotype"]},{"year":2021,"claim":"Src kinase phosphorylation of GBF1 (Y876/Y898 near the Sec7 C-terminus) was shown to enhance ARF1 binding and induce retrograde tubular transport carriers carrying GALNTs from Golgi to ER, defining a regulated retrograde trafficking pathway.","evidence":"Phosphoproteomics, Src kinase assay, phosphomimetic/phosphodeficient GBF1 mutants, live-cell tubule imaging, ARF1 binding assay","pmids":["34870592"],"confidence":"High","gaps":["Whether Src phosphorylation occurs in response to specific physiological signals not determined","How phosphorylation alters GBF1 conformation to enhance ARF1 binding not structurally resolved"]},{"year":2023,"claim":"N-terminal GBF1 phosphorylation sites (S233, S371, Y377, Y515) were shown to differentially regulate cytokinesis versus Golgi homeostasis: phosphomimetic mutants supported normal Golgi and secretion but impaired cytokinetic bridge resolution, revealing separable phospho-regulatory modules.","evidence":"Phosphomimetic and non-phosphorylatable GBF1 mutants with Golgi morphology, secretion, and multinucleation assays","pmids":["37604968"],"confidence":"High","gaps":["Kinases responsible for these N-terminal phosphorylations not identified","Mechanism by which phosphorylation impairs cytokinesis not defined"]},{"year":2024,"claim":"AMPK phosphorylation of GBF1 was pinpointed to Thr1337 using gene-edited non-phosphorylatable knock-in cells, directly demonstrating that this single site mediates AMPK-induced Golgi fragmentation and trafficking slowdown; separately, GBF1 haploinsufficiency was linked to congenital cataracts in mice.","evidence":"AMPK-α KO cells, GBF1-T1337A knock-in by gene editing, trafficking assay (PMID:39575556); Gbf1 heterozygous KO mice with cataracts, UPR/autophagy in lens cells (PMID:39110251)","pmids":["39575556","39110251"],"confidence":"High","gaps":["Whether T1337 phosphorylation and CDK1/CK2 phosphorylation act synergistically in mitosis not tested","Lens-specific trafficking cargo affected by GBF1 deficiency not identified"]},{"year":null,"claim":"Key open questions remain: the identity of the proteinaceous Golgi receptor for GBF1, the structural basis for Sec7-domain autoinhibition of HDS1, a full-length GBF1 structure, and the mechanism by which motor neuron-specific vulnerability arises from GBF1 mutations.","evidence":"","pmids":[],"confidence":"High","gaps":["No high-resolution structure of full-length GBF1","Golgi membrane receptor identity unknown","Motor neuron vulnerability mechanism in CMT2 not explained","Relationship between multiple kinase inputs and GBF1 conformational states not integrated"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,3,4,26,40]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[25,24]}],"localization":[{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[0,1,4,11,32,34]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,1,3]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[4,11]},{"term_id":"GO:0005811","term_label":"lipid droplet","supporting_discovery_ids":[22,25]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[4,10,11,26,36]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[9,10,28,30]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[19,27,31,44]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[22,25]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[12,41,48]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[32,34,42]}],"complexes":["COPI coat (functional effector complex)","GBF1 homodimer (DCB-HUS mediated)"],"partners":["ARF1","COPI","P115","RAB1B","ATGL","RHOT1","ASAP1","C10ORF76"],"other_free_text":[]},"mechanistic_narrative":"GBF1 is a large Sec7-domain ARF guanine nucleotide exchange factor (ArfGEF) that serves as a master regulator of COPI-dependent vesicle trafficking, Golgi homeostasis, lipid droplet metabolism, and cell division. GBF1 rapidly cycles on and off cis-Golgi and ERGIC membranes—stabilized by ARF-GDP and released upon catalyzing GDP-to-GTP exchange on ARF1/4/5—thereby recruiting COPI coats for retrograde and anterograde transport of transmembrane cargo, GGA adaptors for lysosomal sorting, and BIG1/2 GEFs in a sequential ARF activation cascade [PMID:15813748, PMID:18003980, PMID:17666033, PMID:23386609]. Membrane targeting requires its HDS1/HDS2 domains, a proteinaceous Golgi receptor, Rab1b-dependent PI4P generation by PI4KIIIα, and lipid interactions via an HDS1 amphipathic helix that also mediates lipid droplet association; phosphorylation by CDK1–cyclin B, AMPK (at Thr1337), CK2 (triggering SCFβTrCP-mediated degradation), and Src (promoting retrograde tubule formation) dynamically regulates GBF1 membrane dissociation during mitosis, Golgi fragmentation, cytokinesis, and glycosyltransferase relocation [PMID:20530568, PMID:20175751, PMID:39575556, PMID:29898406, PMID:34870592]. Pathogenic heterozygous GBF1 variants cause distal hereditary motor neuropathy/CMT2 with Golgi fragmentation in patient fibroblasts, and GBF1 haploinsufficiency in mice produces cataracts, underscoring its essential role in neuronal and lens cell secretory homeostasis [PMID:32937143, PMID:39110251]."},"prefetch_data":{"uniprot":{"accession":"Q92538","full_name":"Golgi-specific brefeldin A-resistance guanine nucleotide exchange factor 1","aliases":[],"length_aa":1860,"mass_kda":206.6,"function":"Guanine-nucleotide exchange factor (GEF) for members of the Arf family of small GTPases involved in trafficking in the early secretory pathway; its GEF activity initiates the coating of nascent vesicles via the localized generation of activated ARFs through replacement of GDP with GTP. Recruitment to cis-Golgi membranes requires membrane association of Arf-GDP and can be regulated by ARF1, ARF3, ARF4 and ARF5. Involved in the recruitment of the COPI coat complex to the endoplasmic reticulum exit sites (ERES), and the endoplasmic reticulum-Golgi intermediate (ERGIC) and cis-Golgi compartments which implicates ARF1 activation. Involved in COPI vesicle-dependent retrograde transport from the ERGIC and cis-Golgi compartments to the endoplasmic reticulum (ER) (PubMed:12047556, PubMed:12808027, PubMed:16926190, PubMed:17956946, PubMed:18003980, PubMed:19039328, PubMed:24213530). Involved in the trans-Golgi network recruitment of GGA1, GGA2, GGA3, BIG1, BIG2, and the AP-1 adaptor protein complex related to chlathrin-dependent transport; the function requires its GEF activity (probably at least in part on ARF4 and ARF5) (PubMed:23386609). Has GEF activity towards ARF1 (PubMed:15616190). Has in vitro GEF activity towards ARF5 (By similarity). Involved in the processing of PSAP (PubMed:17666033). Required for the assembly of the Golgi apparatus (PubMed:12808027, PubMed:18003980). The AMPK-phosphorylated form is involved in Golgi disassembly during mitotis and under stress conditions (PubMed:18063581, PubMed:23418352). May be involved in the COPI vesicle-dependent recruitment of PNPLA2 to lipid droplets; however, this function is under debate (PubMed:19461073, PubMed:22185782). In neutrophils, involved in G protein-coupled receptor (GPCR)-mediated chemotaxis und superoxide production. Proposed to be recruited by phosphatidylinositol-phosphates generated upon GPCR stimulation to the leading edge where it recruits and activates ARF1, and is involved in recruitment of GIT2 and the NADPH oxidase complex (PubMed:22573891). Plays a role in maintaining mitochondrial morphology (PubMed:25190516)","subcellular_location":"Golgi apparatus, cis-Golgi network; Endoplasmic reticulum-Golgi intermediate compartment; Golgi apparatus, trans-Golgi network; Golgi apparatus; Cytoplasm; Lipid droplet; Membrane","url":"https://www.uniprot.org/uniprotkb/Q92538/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/GBF1","classification":"Common Essential","n_dependent_lines":1188,"n_total_lines":1208,"dependency_fraction":0.9834437086092715},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000107862","cell_line_id":"CID000661","localizations":[{"compartment":"golgi","grade":3},{"compartment":"cytoplasmic","grade":2},{"compartment":"vesicles","grade":1}],"interactors":[],"url":"https://opencell.sf.czbiohub.org/target/CID000661","total_profiled":1310},"omim":[{"mim_id":"621423","title":"TRAFFICKING PROTEIN PARTICLE COMPLEX, SUBUNIT 13; TRAPPC13","url":"https://www.omim.org/entry/621423"},{"mim_id":"620867","title":"ARMADILLO-LIKE HELICAL DOMAIN-CONTAINING PROTEIN 3; ARMH3","url":"https://www.omim.org/entry/620867"},{"mim_id":"617826","title":"UNC50, INNER NUCLEAR MEMBRANE RNA-BINDING PROTEIN; UNC50","url":"https://www.omim.org/entry/617826"},{"mim_id":"616822","title":"MON2, REGULATOR OF ENDOSOME-TO-GOLGI TRAFFICKING; MON2","url":"https://www.omim.org/entry/616822"},{"mim_id":"612565","title":"RAS-ASSOCIATED PROTEIN RAB1B; RAB1B","url":"https://www.omim.org/entry/612565"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Golgi apparatus","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/GBF1"},"hgnc":{"alias_symbol":["KIAA0248","ARF1GEF"],"prev_symbol":[]},"alphafold":{"accession":"Q92538","domains":[{"cath_id":"-","chopping":"492-605_914-969","consensus_level":"medium","plddt":89.3318,"start":492,"end":969},{"cath_id":"-","chopping":"971-1064_1101-1144","consensus_level":"medium","plddt":90.3737,"start":971,"end":1144}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q92538","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q92538-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q92538-F1-predicted_aligned_error_v6.png","plddt_mean":70.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GBF1","jax_strain_url":"https://www.jax.org/strain/search?query=GBF1"},"sequence":{"accession":"Q92538","fasta_url":"https://rest.uniprot.org/uniprotkb/Q92538.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q92538/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q92538"}},"corpus_meta":[{"pmid":"21909260","id":"PMC_21909260","title":"Chlamydia 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Plants 2015, 4, 691-709.","date":"2016","source":"Plants (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/27598219","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.09.09.675067","title":"Mechanical Cues Regulate Cargo Sorting and Export at the Golgi","date":"2025-09-09","source":"bioRxiv","url":"https://doi.org/10.1101/2025.09.09.675067","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.06.03.657657","title":"Evolutionary origin and functional diversification of plant GBF1-type ARF guanine-nucleotide exchange factors","date":"2025-06-06","source":"bioRxiv","url":"https://doi.org/10.1101/2025.06.03.657657","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":45221,"output_tokens":12207,"usd":0.159384},"stage2":{"model":"claude-opus-4-6","input_tokens":16335,"output_tokens":6573,"usd":0.369},"total_usd":0.528384,"stage1_batch_id":"msgbatch_01DzrsgVgYngY1hvM3DU1yF2","stage2_batch_id":"msgbatch_01KA9b7iRzKFdhoBUT7vCvSe","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1999,\n      \"finding\": \"GBF1 was identified as a novel Golgi-associated guanine nucleotide exchange factor (GEF) with a Sec7 domain that exhibits BFA-resistant GEF activity specific towards ARF5 at physiological Mg2+ concentration. Overexpression conferred BFA resistance to Golgi morphology and ARF activation/COPI recruitment. GBF1 localized primarily to the cytosol with a pool co-localizing with β-COPI at a perinuclear (Golgi) structure.\",\n      \"method\": \"Expression cloning, in vitro GEF assay with His-tagged GBF1, immunogold EM localization, BFA resistance functional assay\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro GEF activity reconstituted, multiple orthogonal methods, foundational discovery paper\",\n      \"pmids\": [\"10402461\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"GBF1 cycles rapidly on and off Golgi membranes (not stably associated). BFA, acting as an uncompetitive inhibitor binding to an Arf-GDP–GBF1 complex, stabilizes GBF1 on Golgi membranes. GBF1 exchange activity on Arf1 is inhibited by BFA in mammalian cells.\",\n      \"method\": \"YFP-GBF1 FRAP analysis, in vivo Arf1-GTP level assay, BFA treatment\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — live-cell FRAP with in vivo GTP-loading assay, mechanistically rigorous\",\n      \"pmids\": [\"15616190\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"GBF1 physically interacts with the membrane-tethering protein p115 through the proline-rich region of GBF1 and the head region of p115. The two proteins colocalize at the Golgi and peripheral VTCs. Expression of the p115-binding (pro-rich) region of GBF1 causes Golgi disruption, indicating functional relevance of this interaction.\",\n      \"method\": \"Yeast two-hybrid screen, in vitro binding assay, in vivo co-immunoprecipitation, mutagenesis, immunofluorescence\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP plus in vitro binding plus functional mutagenesis\",\n      \"pmids\": [\"12634853\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"GBF1 rapidly cycles between membranes and cytosol (t1/2 ~17 s by FRAP), faster than ARF itself. GBF1 is stabilized on membranes when in complex with ARF-GDP (shown by inactive E794K mutant, ARF1-T31N mutant, and BFA treatment). GBF1 dissociation is triggered by its own catalytic activity (GDP displacement and GTP binding to ARF), implying each GBF1 membrane association catalyzes a single ARF activation event.\",\n      \"method\": \"GFP-GBF1 FRAP, dominant-negative mutant expression, BFA treatment\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — three independent approaches with mechanistic mutagenesis and FRAP, single lab\",\n      \"pmids\": [\"15813748\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"GBF1 localizes to both cis-Golgi membranes and peripheral puncta (VTCs) near but separate from ER exit sites. Live-cell imaging showed rapid GFP-GBF1 exchange with a large cytosolic pool. Microinjection of anti-GBF1 antibodies specifically caused dissociation of COPI from membranes, demonstrating GBF1 regulates COPI membrane recruitment in the early secretory pathway.\",\n      \"method\": \"GFP-live imaging, FRAP, BFA treatment, anti-GBF1 microinjection, subcellular fractionation\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct antibody microinjection with defined COPI phenotype, multiple orthogonal methods\",\n      \"pmids\": [\"16926190\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The enterovirus 3A protein inhibits Arf1 activation and COP-I coat recruitment by directly interacting with the N-terminus of GBF1 and inhibiting its GEF function. This 3A–GBF1 interaction is the mechanism by which 3A blocks ER-to-Golgi transport.\",\n      \"method\": \"Co-immunoprecipitation, dominant-negative Arf1 expression, siRNA knockdown, EM, in vivo transport assay, mouse virulence assay\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods, in vivo functional rescue, replicated across enterovirus 3A studies\",\n      \"pmids\": [\"16890159\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"GBF1 acts as a Rab1b effector: active GTP-locked Rab1b (Rab1bQ67L) increases GBF1 and COPI association with peripheral ER exit site structures and stabilizes Arf1 on Golgi membranes. Rab1b siRNA knockdown reduced GBF1 membrane association. The N-terminal domain of GBF1 mediates its interaction with Rab1b.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, live-cell GFP imaging, FRAP, dominant-active Rab1b mutant expression\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP, domain mapping, multiple functional assays\",\n      \"pmids\": [\"17429068\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"GBF1 dimerizes through its DCB domain; DCB–DCB homodimerization and DCB–HUS interactions define the N-terminal architecture of GBF1 (and BIG ArfGEFs). The HUS box (most conserved motif after Sec7) mediates the DCB–HUS interaction within each homodimer. Both DCB and HUS domains are necessary for GBF1 dimerization in mammalian cells.\",\n      \"method\": \"Yeast two-hybrid, biochemical interaction assays, co-immunoprecipitation in mammalian cells, mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — biochemical reconstitution of domain interactions combined with cellular dimerization assays\",\n      \"pmids\": [\"17640864\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Molecular determinants of 3A–GBF1 interaction: 3A must dimerize to bind GBF1; a conserved N-terminal region of 3A is critical for GBF1 binding but not dimerization. Within GBF1, the extreme N-terminus, the DCB (dimerization/cyclophilin binding) domain, and the HUS domain are required for interaction with 3A.\",\n      \"method\": \"3A mutagenesis, co-immunoprecipitation, GBF1 deletion mutant analysis\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — systematic mutagenesis of both binding partners with functional rescue assays\",\n      \"pmids\": [\"17329336\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"GBF1 is required for GGA (Golgi-localized, gamma-ear-containing, ARF-binding protein) recruitment to Golgi membranes. GBF1 co-localizes and co-immunoprecipitates with GGAs. Depletion of GBF1 or expression of inactive GBF1 prevents GGA membrane recruitment and causes missorting of lysosomal cargo (mannose-6-phosphate receptor, sortilin).\",\n      \"method\": \"Co-immunoprecipitation, GBF1 siRNA knockdown, dominant-negative GBF1, cargo trafficking assay\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple complementary loss-of-function approaches with defined cargo-sorting phenotype\",\n      \"pmids\": [\"17666033\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"GBF1 depletion by siRNA causes COPI dispersal and extensive tubulation of cis-Golgi without complete Golgi collapse into ER. This causes dramatic inhibition of transmembrane protein trafficking but soluble protein secretion continues, indicating GBF1-mediated ARF activation and COPI recruitment are specifically required for transmembrane cargo but not soluble cargo transport.\",\n      \"method\": \"siRNA knockdown, immunofluorescence, live-cell trafficking assays, EM\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean siRNA KD with distinct cargo-specific phenotype, multiple cargo types tested\",\n      \"pmids\": [\"17956946\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"GBF1 regulates COPI recruitment specifically on cis-Golgi compartments (not TGN), whereas BIG proteins regulate adaptor proteins on trans-Golgi. GBF1/COPI knockdown does not prevent ER export but causes VSVGtsO45 accumulation in peripheral VTCs. GBF1 is required for Golgi subcompartmentalization and cargo progression to the cell surface.\",\n      \"method\": \"siRNA knockdown (GBF1, BIG1, BIG2, COPI), immunofluorescence, VSVGtsO45 trafficking assay\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — parallel knockdowns of distinct GEFs with multiple cargo and coat readouts\",\n      \"pmids\": [\"18003980\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"GBF1 depletion (but not BIG1 or BIG2 depletion) causes cell-cycle arrest in G0/G1, Golgi marker dispersal, ER stress (elevated calreticulin, PDI, ER chaperones), and triggers ATF6 proteolysis mimicking an unfolded protein response. GBF1 depletion causes relocalization of S2P from Golgi to ER with ATF6 cleavage and upregulation of ERSE genes.\",\n      \"method\": \"Selective siRNA depletion of each GEF, proteomic analysis, immunofluorescence, cell-cycle analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — selective siRNA with multiple orthogonal readouts (proteomics, ATF6 processing, cell-cycle)\",\n      \"pmids\": [\"18287014\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Class II ARFs (Arf4, Arf5) associate with ERGIC membranes through GBF1-independent binding sites in their GDP-bound form, whereas class I Arfs (Arf1, Arf3) rapidly dissociate from all endomembranes upon BFA treatment. Loss of Arf-GTP (not formation of Arf·GDP·BFA·GBF1 complex) causes GBF1 accumulation on membranes.\",\n      \"method\": \"Live-cell imaging of fluorescently tagged Arfs, BFA and Exo1 treatment, GDP-locked Arf4 mutant\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — systematic live-cell analysis distinguishing GBF1-dependent versus -independent Arf recruitment\",\n      \"pmids\": [\"18524849\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"GBF1 (but not BIG1 or BIG2) is critically required for mouse hepatitis coronavirus (MHV) RNA replication. ARF1, the cellular effector of GBF1, is also required. GBF1-mediated ARF1 activation controls the number of viral replication complexes formed.\",\n      \"method\": \"Individual siRNA knockdown of GBF1, BIG1, BIG2, ARF1; BFA sensitivity in MDCK cells expressing BFA-resistant GBF1; immunofluorescence and quantitative EM\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — selective siRNA of each GEF with BFA-resistant GBF1 rescue in MDCK cells\",\n      \"pmids\": [\"18551169\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"GBF1 is critically required for CVB3 RNA replication. BFA-resistant GBF1-M832L rescues replication in BFA-treated cells; GBF1 knockdown by RNAi inhibits replication; only active (not inactive catalytic mutant) GBF1 rescues replication. Overexpression of ARF proteins or Rab1B did not rescue BFA-inhibited replication.\",\n      \"method\": \"siRNA knockdown, BFA-resistant GBF1 mutant rescue, overexpression of Arf proteins and Rab1B, replicon assays\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple complementary approaches, active-site mutant controls, replicated across CVB3 and poliovirus\",\n      \"pmids\": [\"19740986\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"GBF1 is a host factor critically required for HCV RNA replication. GBF1 knockdown (but not BIG1 or BIG2) inhibits HCV replication. BFA-resistant GBF1 mutant rescues HCV replication in BFA-treated cells. BFA/GBF1 inhibition does not block membranous web formation but impairs replication complex activity.\",\n      \"method\": \"siRNA knockdown of individual GEFs, BFA-resistant GBF1 rescue, pharmacological GBF1 inhibitor, immunofluorescence and EM\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — selective GEF knockdown with BFA-resistant rescue, orthogonal morphological analysis\",\n      \"pmids\": [\"19906930\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Drosophila garz (ortholog of GBF1) is a novel component of the clathrin-independent GEEC endocytic pathway, required for GPI-anchored protein and fluid-phase internalization. A catalytically inactive GBF1 GEF mutant has altered Arf1 activation at nascent pinosomes and impairs fluid-phase uptake.\",\n      \"method\": \"RNAi screen, live confocal and TIRF imaging with GBF1-GFP and Arf1 sensor, GEF-dead mutant, quantitative endocytosis assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — live imaging with functional GEF sensor, catalytic mutant, and quantitative endocytosis assay\",\n      \"pmids\": [\"19707569\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"For poliovirus replication, the N-terminal region of GBF1 (lacking the catalytic Sec7 domain) is sufficient to rescue BFA-inhibited replication. In infected cells p115 is degraded and neither p115 nor Rab1b knockdown affects viral replication, indicating viral replication requires a non-catalytic function of GBF1 distinct from its cellular role in ARF/COPI secretory trafficking.\",\n      \"method\": \"N-terminal GBF1 truncation rescue assay, p115/Rab1b siRNA knockdown, BFA-resistant virus replicon\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — systematic domain dissection with rescue assay, multiple siRNA controls\",\n      \"pmids\": [\"20497182\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"GBF1 is phosphorylated by CDK1-cyclin B during mitosis, causing its dissociation from Golgi membranes and reduction of membrane-associated GTP-bound ARF. A low level of GBF1 activity persists in mitosis and remains required for COPI recruitment, suggesting GBF1 phosphorylation and membrane dissociation contribute to Golgi fragmentation during mitotic entry.\",\n      \"method\": \"Phosphoprotein analysis, CDK1-cyclin B in vitro kinase assay, immunofluorescence in mitotic cells, ARF-GTP measurement\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro kinase assay plus cell-based phosphorylation and membrane dissociation analysis\",\n      \"pmids\": [\"20175751\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PI4KIIIα-generated phosphatidylinositol 4-phosphate [PtdIns(4)P] is required for GBF1 recruitment to Golgi membranes. Dominant-active Rab1 increases PtdIns(4)P levels at the Golgi, suggesting Rab1 contributes to GBF1 recruitment specificity by activating PI4KIIIα to produce PtdIns(4)P.\",\n      \"method\": \"PI4KIIIα siRNA knockdown, PI4P inhibitors (wortmannin, LY294002), GFP-PH PtdIns(4)P sensor, dominant-active Rab1 expression, GBF1 localization assay\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological and genetic inhibition with lipid sensor, mechanistic connection to Rab1\",\n      \"pmids\": [\"20530568\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"C. trachomatis selectively co-opts GBF1 (but not BIG1 or BIG2) for vesicle-mediated sphingomyelin (SM) acquisition. The Arf1/GBF1-dependent SM pathway is essential for inclusion membrane growth and stability but not for bacterial replication. GBF1 depletion by siRNA blocks SM delivery to the inclusion.\",\n      \"method\": \"siRNA knockdown of individual BFA targets, BFA sensitivity analysis, fluorescent SM trafficking assay, inclusion integrity measurement\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — selective GEF knockdown, BFA-resistant cell lines, defined SM trafficking phenotype\",\n      \"pmids\": [\"21909260\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"GBF1 and ATGL (adipose triglyceride lipase) interact directly through multiple contact sites: ATGL C-terminus contacts GBF1 N-terminal domains including the Sec7 domain; ATGL N-terminal patatin domain interacts with GBF1 HDS1 and HDS2 domains. GBF1 HDS1 and HDS2 domains localize to lipid droplets when expressed alone. The GBF1–Arf1–COPI pathway is required for ATGL delivery to lipid droplets.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation in mammalian cells, direct protein binding (in vitro), GFP domain-localization assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — direct protein binding plus yeast two-hybrid plus cellular co-IP with domain mapping\",\n      \"pmids\": [\"21789191\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"ARF1 and GBF1 generate a PI4P-enriched environment at HCV replication complexes. ARF1 and GBF1 colocalize with PI4KIIIβ and are both required for HCV replication. HCV replication is inhibited by PI4P phosphatase Sac1 overexpression.\",\n      \"method\": \"Co-immunoprecipitation/colocalization, PI4P sensor, Sac1 overexpression, siRNA knockdown\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple methods but limited mechanistic depth on the GBF1-PI4P causal link\",\n      \"pmids\": [\"22359663\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"GBF1 bears a novel phosphatidylinositol-phosphate binding module (BP3K) that links PI3Kγ activity with Arf1 activation in GPCR-stimulated neutrophil chemotaxis. Upon GPCR stimulation, GBF1 translocates from Golgi to the leading edge via PI3Kγ product binding, where it activates Arf1 and recruits p22phox and GIT2, thereby regulating directional sensing and superoxide production.\",\n      \"method\": \"Subcellular fractionation, GFP-GBF1 live imaging, phospholipid binding assay, siRNA knockdown, GPCR stimulation\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — novel domain identified with PI3P binding, translocation imaging, functional readouts of chemotaxis and superoxide\",\n      \"pmids\": [\"22573891\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"GBF1's HDS1 domain (immediately downstream of the Sec7 domain) contains an amphipathic helix that binds lipid droplets and Golgi membranes in cells, and bilayer liposomes and artificial droplets in vitro. The Sec7 domain inhibits the HDS1 lipid-droplet binding capacity in the context of full-length GBF1.\",\n      \"method\": \"In vitro liposome binding, artificial droplet binding, GFP domain expression in cells, mutagenesis of amphipathic helix\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro lipid binding reconstituted plus mutagenesis plus cellular localization\",\n      \"pmids\": [\"23943872\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"GBF1-activated ARF4 and ARF5 (but not ARF3) facilitate BIG1 and BIG2 recruitment to the TGN, establishing a functional GEF cascade. GBF1 localizes ultrastructurally to pre-Golgi, Golgi, and TGN. This defines a sequential coating pathway in which GBF1 at the TGN activates ARFs that then recruit BIG1/2.\",\n      \"method\": \"Immunoelectron microscopy, siRNA knockdown, Arf isoform-specific rescue experiments, GBF1 inhibitor treatment\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — ultrastructural localization plus ARF isoform specificity dissection with multiple knockdowns\",\n      \"pmids\": [\"23386609\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"AMPK phosphorylates GBF1 during mitosis, causing GBF1 dissociation from the Golgi membrane and abolishing GBF1's Arf1-GEF activity, thereby promoting Golgi disassembly required for mitosis entry.\",\n      \"method\": \"In vitro AMPK kinase assay on GBF1, phospho-specific analysis, mitotic cell fractionation, dominant-negative and pharmacological approaches\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro kinase assay plus cellular phenotype with mechanistic detail on Golgi fragmentation\",\n      \"pmids\": [\"23418352\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The Dengue virus GBF1–Arf1/Arf4–COPI pathway is required for capsid protein transport from ER membrane to lipid droplets, independently of COPII components and Golgi integrity. A BFA-resistant GBF1 mutant rescues capsid subcellular distribution in BFA-treated infected cells.\",\n      \"method\": \"BFA and GCA pharmacological inhibition, BFA-resistant GBF1 rescue, siRNA knockdown, immunofluorescence\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — BFA-resistant rescue plus siRNA dissection, multiple GBF1-pathway components tested\",\n      \"pmids\": [\"26031340\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"GBF1 oligomerization (mediated by the DCB domain residues K91 and E130) is dispensable for Golgi targeting, rapid membrane cycling, ARF activation, COPI recruitment, and cargo secretion. However, oligomerization stabilizes GBF1 protein; the non-oligomerizing 91/130 mutant is degraded faster than wild-type.\",\n      \"method\": \"GBF1 DCB domain mutagenesis, live-cell FRAP, ARF activation assay, COPI immunofluorescence, secretion assay, protein stability measurement\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — systematic mutagenesis with multiple functional readouts separating oligomerization from GEF activity\",\n      \"pmids\": [\"26718629\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"GBF1 and Arf4 form a functional complex with the sensory receptor rhodopsin at the photoreceptor Golgi/TGN during transport carrier biogenesis for ciliary targeting. Rhodopsin and Arf4 bind the regulatory N-terminal DCB-HUS domain of GBF1. GCA (GBF1 inhibitor) blocks this complex and prevents rhodopsin delivery to cilia without disrupting the Golgi. GBF1 also interacts with the Arf GAP ASAP1 in a GCA-resistant manner.\",\n      \"method\": \"Frog retina in vivo analysis, co-immunoprecipitation with recombinant human proteins, GCA inhibitor, domain binding mapping\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — biochemical reconstitution with recombinant proteins, in vivo retinal assay, inhibitor specificity\",\n      \"pmids\": [\"29025970\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"GBF1 is phosphorylated on Ser292 and Ser297 by casein kinase 2 (CK2) during mitosis, enabling recognition by the F-box protein βTrCP and recruitment to the SCFβTrCP ubiquitin ligase complex, triggering GBF1 degradation. This degradation occurs at the intercellular bridge of telophase cells and is required for Golgi membrane positioning and postmitotic Golgi reformation. A non-degradable GBF1 mutant blocks Golgi cluster transport and causes cytokinesis failure.\",\n      \"method\": \"Phosphorylation site mutagenesis, co-immunoprecipitation with βTrCP/SCF complex, proteomics, non-degradable GBF1 mutant live imaging, cytokinesis assay\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — phosphosite mapping, E3 ligase identification, substrate mutant with defined mitotic/cytokinesis phenotype\",\n      \"pmids\": [\"29898406\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"GBF1 recruitment to Golgi membranes requires the HDS1 and HDS2 domains and a heat-labile, protease-sensitive Golgi-localized protein receptor. Arf-GDP localization at the cis-Golgi (but not TGN) promotes GBF1 recruitment. ArfGAP2 and ArfGAP3 do not regulate GBF1 recruitment.\",\n      \"method\": \"In vitro GBF1 recruitment assay with Golgi fractions, heat/protease treatment of membranes, Arf-GDP targeted mutants, GBF1 HDS1/HDS2 domain mapping\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro reconstituted recruitment assay plus domain mapping, multiple complementary approaches\",\n      \"pmids\": [\"29507113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"GBF1 and its substrate Arf1 interact with the mitochondrial membrane protein Miro, regulating mitochondrial spatial organization. GBF1 inhibition promotes dynein- and Miro-dependent retrograde mitochondrial transport along microtubules toward the centrosome, causing mitochondrial network collapse. Active GTP-bound Arf1 also physically interacts with Miro.\",\n      \"method\": \"Co-immunoprecipitation (GBF1-Miro, Arf1-GTP-Miro), GBF1 inhibition (GCA), Miro siRNA, dynein inhibitor, electron tomography, live-cell time-lapse imaging\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — physical interaction demonstrated plus functional rescue with dynein/Miro inhibition, electron tomography\",\n      \"pmids\": [\"30459446\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Conserved residues RDR1168 and LF1266 within α-helices 2 and 6 of the HDS2 domain of GBF1 are required for GBF1 targeting to Golgi membranes. Mutations at these positions compromise Golgi homeostasis, ARF activation, secretion, and cell viability in a functional replacement assay.\",\n      \"method\": \"HDS2 alanine-scanning mutagenesis, BFA-resistant replacement assay, Golgi morphology, COPI recruitment, secretion assay\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — systematic domain mutagenesis with multiple functional readouts in cells\",\n      \"pmids\": [\"29443553\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"C10orf76 interacts with GBF1 and rapidly cycles on and off GBF1-positive Golgi structures (identified by BioID proximity labeling of Golgi-enriched fractions). C10orf76 depletion causes Golgi fragmentation, alters GBF1 recruitment, and impairs secretion.\",\n      \"method\": \"BioID proximity labeling, mass spectrometry, co-immunoprecipitation, siRNA knockdown, Golgi morphology and secretion assays\",\n      \"journal\": \"Molecular & cellular proteomics : MCP\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — BioID plus co-IP plus functional knockdown with defined Golgi and secretion phenotype\",\n      \"pmids\": [\"31519766\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"GBF1 is required for VWF (von Willebrand factor) and extracellular matrix protein trafficking from ER to Golgi secretory granules in endothelial cells. GBF1 level is a limiting factor in VWF granule biogenesis. AMPK activation (by glucose levels) couples to GBF1 function and modulates VWF trafficking, linking physiological energy status to anterograde secretory pathway regulation.\",\n      \"method\": \"GBF1 siRNA knockdown, GBF1 overexpression, AMPK pharmacological activation, fluorescence live imaging of VWF trafficking, secretion assay\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function and gain-of-function with physiological AMPK coupling and defined granule trafficking phenotype\",\n      \"pmids\": [\"31056345\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"HCV NS3 protein directly interacts with GBF1 through the Sec7 domain of GBF1 and the protease domain of NS3, as shown by yeast two-hybrid, co-immunoprecipitation, and proximity ligation assay. NS3 alters GBF1 intracellular localization. An NS3 mutant (N77D) that disrupts GBF1 binding is non-replicative despite retaining protease activity, indicating the NS3–GBF1 interaction is important for HCV genome replication.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, proximity ligation assay, NS3 mutagenesis, replication assay\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — three independent interaction assays, domain mapping, NS3 mutant replication phenotype\",\n      \"pmids\": [\"30567983\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"GBF1 catalytic activity (but not Arf1 activation per se) is essential for rotavirus assembly. Inhibition of GBF1 by BFA or GCA prevents trimerization of the outer capsid protein VP7 and blocks assembly of triple-layered particles. GBF1 inhibition alters electrophoretic mobility of VP7 and NSP4.\",\n      \"method\": \"BFA and GCA pharmacological inhibition, GBF1 siRNA knockdown, viral particle characterization, VP7 trimerization assay\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological and genetic loss-of-function with specific viral assembly phenotype and VP7 trimerization assay\",\n      \"pmids\": [\"31270230\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Multiple determinants in GBF1 support poliovirus replication: the Arf-activating property of the Sec7 domain is indispensable, but the primary structure of the Sec7 domain itself is not. GBF1 is recruited to replication sites via both direct 3A interaction and redundant determinants in C-terminal non-catalytic domains (HDS regions).\",\n      \"method\": \"GBF1 domain mutant rescue assay in poliovirus replication context, viral RNA replication assay, BFA-resistant rescue\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — systematic domain mutagenesis with viral replication functional readout\",\n      \"pmids\": [\"31375590\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Src kinase phosphorylates GBF1 on 10 tyrosine residues; two residues (Y876 and Y898) near the C-terminus of the Sec7 domain promote GBF1 binding to Arf1 GTPase. This phosphorylation induces formation of tubular transport carriers containing GALNTs for Golgi-to-ER retrograde transport. Phosphomimetic GBF1 mutants induce tubules, while mutants defective for Arf1 binding prevent carrier formation and GALNTs relocation.\",\n      \"method\": \"Phosphoproteomics, Src kinase assay, GBF1 phosphomimetic/phosphodeficient mutants, live-cell tubule imaging, molecular modeling, Arf1 binding assay\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — phosphosite identification, mutagenesis, Arf1 binding assay, molecular modeling, and live-cell carrier imaging\",\n      \"pmids\": [\"34870592\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"AMPK associates with the Golgi and phosphorylates GBF1 at Thr1337 upon activation, causing Golgi fragmentation and slowing protein trafficking through the Golgi. Golgi disassembly upon AMPK activation is blocked in cells expressing non-phosphorylatable GBF1-T1337A generated by gene editing.\",\n      \"method\": \"AMPK-α knockout cells, pharmacological AMPK activators, GBF1-T1337A knock-in by gene editing, Golgi morphology assay, protein trafficking (Gaussia luciferase) assay\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — non-phosphorylatable knock-in plus genetic KO with defined trafficking and morphology phenotypes\",\n      \"pmids\": [\"39575556\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Zebrafish gbf1 loss-of-function (L1246R mutation in HDS2 domain, morphants, knockout) causes intracerebral hemorrhage due to vascular breakage in a cell-autonomous manner. The L1246R Gbf1 mutant fails to be recruited to the Golgi and cannot activate Arf1 or recruit the COPI complex in mammalian cells, indicating HDS2 domain is essential for GBF1 membrane targeting and function.\",\n      \"method\": \"ENU mutagenesis/positional cloning in zebrafish, gbf1 morpholino knockdown and CRISPR knockout, Gbf1-L1246R expression in mammalian cells, Golgi recruitment and Arf1 activation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo vertebrate model plus cellular mechanistic validation of domain mutant\",\n      \"pmids\": [\"28003365\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Pathogenic variants in GBF1 (four distinct heterozygous variants, two de novo) cause distal hereditary motor neuropathy/Charcot-Marie-Tooth neuropathy type 2 (HMN/CMT2). Primary fibroblasts from all affected individuals show marked Golgi fragmentation consistent with GBF1's role in Golgi maintenance. GBF1 is present in mouse spinal cord/muscle and enriched at motor neurons and growth cones.\",\n      \"method\": \"Genomic sequencing, Golgi fragmentation assay in patient fibroblasts, immunofluorescence in mouse tissue\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — genetic and cell-biology evidence linking GBF1 variants to neurodegeneration via Golgi fragmentation; mechanism inferred from patient cells\",\n      \"pmids\": [\"32937143\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Phosphorylation of specific N-terminal residues of GBF1 (S233, S371, Y377, Y515) differentially regulates its role in cytokinesis versus Golgi homeostasis/secretion: phosphomimetic mutants of these residues support normal Golgi architecture and cargo secretion but cause multi-nucleation and impair cytokinetic bridge resolution, while not affecting secretory functions.\",\n      \"method\": \"GBF1 phospho-site mutagenesis (phosphomimetic and non-phosphorylatable), Golgi morphology assay, secretion assay, cytokinesis/multinucleation assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — systematic phosphosite mutagenesis with multiple functional readouts distinguishing two GBF1 functions\",\n      \"pmids\": [\"37604968\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"GBF1-dependent secretion (via Arf1-COPI machinery) is required for Drosophila tubulogenesis. Loss of Garz (fly GBF1 ortholog) impairs Golgi integrity, cargo vesicle transport, and directed apical membrane delivery, causing failure in epithelial polarity and lumen expansion in tubular organs.\",\n      \"method\": \"Drosophila loss-of-function mutants, immunofluorescence, EM, live imaging of cargo transport\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo Drosophila genetics with multiple morphological and trafficking readouts, confirmed ortholog\",\n      \"pmids\": [\"22302994\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"In C. elegans, GBF-1 (GBF1 ortholog) localizes to the cis-Golgi and is required for secretion, Golgi integrity, and ER reticular structure. GBF-1 RNAi also impairs receptor-mediated endocytosis in oocytes without affecting recycling pathways, and alters early/late endosome dynamics.\",\n      \"method\": \"RNAi, immunofluorescence, GFP-tagged organelle markers, yolk receptor trafficking assay in C. elegans\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean in vivo genetic knockdown with multiple orthogonal organelle readouts; C. elegans ortholog\",\n      \"pmids\": [\"23840591\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"GBF1 deficiency in mouse oocytes (via GBF1 inhibitor treatment) causes aberrant Golgi accumulation around the spindle, condensation of GM130 (a Golgi matrix protein co-localizing with GBF1), ER structural disruption with elevated ER stress marker GRP78, and altered mitochondrial membrane potential, impairing polar body formation.\",\n      \"method\": \"GBF1 inhibitor (GCA) in mouse oocytes, immunofluorescence, mitochondrial membrane potential assay, Western blot\",\n      \"journal\": \"Microscopy and microanalysis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — pharmacological inhibition in oocytes with multiple organelle readouts but single method approach\",\n      \"pmids\": [\"33478608\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"GBF1 knockdown activates XBP1s (unfolded protein response) and enhances mTOR-independent autophagy in human lens epithelium cells. A pathological GBF1 T1287I mutation reduces GBF1 protein levels. Heterozygous Gbf1 knockout mice display cataracts, establishing GBF1 as a causative gene for congenital cataracts.\",\n      \"method\": \"siRNA knockdown, UPR activation assay (XBP1 splicing), autophagy assay, Gbf1 heterozygous knockout mice, patient mutation analysis\",\n      \"journal\": \"Human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mouse KO model plus cellular mechanism (UPR, autophagy) but mechanism is largely downstream of GBF1 deficiency\",\n      \"pmids\": [\"39110251\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GBF1 is a large Sec7-domain Arf guanine nucleotide exchange factor (ArfGEF) that cycles rapidly on and off cis-Golgi and ERGIC membranes, where it catalyzes GDP-to-GTP exchange on ARF1 (and ARF4/5) to recruit the COPI coat for anterograde and retrograde vesicle trafficking; its membrane association is regulated by ARF-GDP, Rab1b, PI4KIIIα-generated PtdIns(4)P, and lipid-droplet binding via its HDS1 amphipathic helix, while phosphorylation by CDK1-cyclin B, AMPK, CK2, and Src at specific residues controls GBF1 membrane dissociation, mitotic Golgi fragmentation, proteolytic degradation via SCFβTrCP, retrograde tubule formation, and cytokinesis; downstream, GBF1-activated ARFs recruit COPI, GGAs, and BIG1/2 GEFs to coordinate the anterograde secretory pathway, lipid droplet metabolism, mitochondrial positioning via Miro, and clathrin-independent endocytosis.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"GBF1 is a large Sec7-domain ARF guanine nucleotide exchange factor (ArfGEF) that serves as a master regulator of COPI-dependent vesicle trafficking, Golgi homeostasis, lipid droplet metabolism, and cell division. GBF1 rapidly cycles on and off cis-Golgi and ERGIC membranes—stabilized by ARF-GDP and released upon catalyzing GDP-to-GTP exchange on ARF1/4/5—thereby recruiting COPI coats for retrograde and anterograde transport of transmembrane cargo, GGA adaptors for lysosomal sorting, and BIG1/2 GEFs in a sequential ARF activation cascade [PMID:15813748, PMID:18003980, PMID:17666033, PMID:23386609]. Membrane targeting requires its HDS1/HDS2 domains, a proteinaceous Golgi receptor, Rab1b-dependent PI4P generation by PI4KIIIα, and lipid interactions via an HDS1 amphipathic helix that also mediates lipid droplet association; phosphorylation by CDK1–cyclin B, AMPK (at Thr1337), CK2 (triggering SCFβTrCP-mediated degradation), and Src (promoting retrograde tubule formation) dynamically regulates GBF1 membrane dissociation during mitosis, Golgi fragmentation, cytokinesis, and glycosyltransferase relocation [PMID:20530568, PMID:20175751, PMID:39575556, PMID:29898406, PMID:34870592]. Pathogenic heterozygous GBF1 variants cause distal hereditary motor neuropathy/CMT2 with Golgi fragmentation in patient fibroblasts, and GBF1 haploinsufficiency in mice produces cataracts, underscoring its essential role in neuronal and lens cell secretory homeostasis [PMID:32937143, PMID:39110251].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Establishing GBF1 as an ARF-GEF: the foundational question of whether GBF1 possesses nucleotide exchange activity was resolved by demonstrating BFA-resistant Sec7-domain GEF activity toward ARF5, with overexpression conferring BFA resistance to COPI recruitment.\",\n      \"evidence\": \"Expression cloning, in vitro GEF assay with purified His-GBF1, immunogold EM, BFA resistance assay in mammalian cells\",\n      \"pmids\": [\"10402461\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Substrate specificity toward other ARF isoforms (ARF1, ARF3, ARF4) not yet tested\", \"No membrane recruitment mechanism defined\", \"No structural data on Sec7 domain\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Defining GBF1's dynamic membrane behavior: FRAP demonstrated that GBF1 is not a stable Golgi resident but cycles rapidly on and off membranes, with BFA trapping it in an abortive ARF-GDP–GBF1 complex—resolving how BFA inhibits GBF1 in vivo.\",\n      \"evidence\": \"YFP-GBF1 FRAP, in vivo ARF1-GTP loading assay, BFA treatment in living cells\",\n      \"pmids\": [\"15616190\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of initial membrane recruitment unknown\", \"Whether catalytic turnover drives dissociation not yet shown\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Establishing catalytic product release as the membrane dissociation trigger: the observation that GBF1 is stabilized on membranes by ARF-GDP (via inactive mutants) and released upon GTP loading demonstrated a single-turnover catalytic cycle per membrane association event.\",\n      \"evidence\": \"GFP-GBF1 FRAP with catalytically dead E794K mutant, ARF1-T31N dominant-negative, BFA treatment\",\n      \"pmids\": [\"15813748\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of ARF-GDP stabilization of GBF1 not resolved\", \"Stoichiometry of the GBF1–ARF complex on membranes unknown\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Linking GBF1 to membrane tethering: identification of p115 as a direct binding partner connected GBF1's ARF-GEF activity to the vesicle tethering machinery at VTCs and Golgi.\",\n      \"evidence\": \"Yeast two-hybrid, in vitro binding, co-immunoprecipitation, dominant-negative GBF1 pro-rich domain expression\",\n      \"pmids\": [\"12634853\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of p115–GBF1 interaction on tethering efficiency not quantified\", \"Whether p115 recruits GBF1 or vice versa unclear\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Demonstrating GBF1 as the specific GEF for cis-Golgi COPI recruitment: anti-GBF1 antibody microinjection directly dissociated COPI from membranes, while GBF1 localized to cis-Golgi and VTCs distinct from ER exit sites, establishing compartmental specificity.\",\n      \"evidence\": \"Anti-GBF1 microinjection, GFP live imaging, FRAP, subcellular fractionation\",\n      \"pmids\": [\"16926190\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How GBF1 is excluded from trans-Golgi COPI recruitment not addressed\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Multiple discoveries resolved GBF1's upstream regulation, downstream effectors, dimerization, and cargo specificity: Rab1b was identified as an upstream activator stabilizing GBF1 on membranes; GGAs and BIG1/2 were shown as downstream effectors; the DCB–HUS dimerization architecture was mapped; and GBF1 depletion selectively blocked transmembrane (but not soluble) cargo transport.\",\n      \"evidence\": \"Rab1b co-IP and siRNA (PMID:17429068); GGA co-IP and cargo sorting assay (PMID:17666033); DCB/HUS yeast two-hybrid and co-IP (PMID:17640864); siRNA with differential cargo assays and EM (PMID:17956946); parallel GEF knockdowns with VSVGtsO45 (PMID:18003980)\",\n      \"pmids\": [\"17429068\", \"17666033\", \"17640864\", \"17956946\", \"18003980\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Rab1b directly binds GBF1 or acts through PI4P not distinguished\", \"GGA recruitment mechanism (direct versus ARF-mediated) not resolved\", \"Structural basis of DCB–DCB dimerization unknown\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"GBF1 depletion was shown to trigger ER stress and UPR activation (ATF6 processing) and G0/G1 arrest, revealing that GBF1 loss has consequences beyond trafficking—disrupting ER–Golgi proteostasis. Separately, class II ARFs (ARF4/5) were found to associate with ERGIC membranes independently of GBF1 in their GDP-bound state.\",\n      \"evidence\": \"Selective GEF siRNA with proteomics, ATF6 cleavage, cell-cycle analysis (PMID:18287014); live imaging of tagged ARF isoforms with BFA/Exo1 (PMID:18524849)\",\n      \"pmids\": [\"18287014\", \"18524849\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether ER stress is a direct or indirect consequence of COPI loss unclear\", \"How class II ARFs are recruited to ERGIC without GBF1 not defined\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"GBF1 was established as a critical host factor for RNA virus replication, initially for MHV coronavirus: GBF1 (but not BIG1/BIG2) knockdown blocked viral RNA replication, and BFA-resistant GBF1 rescued replication, indicating that GBF1-dependent ARF1 activation controls replication complex formation.\",\n      \"evidence\": \"Selective GEF siRNA, BFA-resistant GBF1 rescue in MDCK cells, quantitative EM of replication complexes\",\n      \"pmids\": [\"18551169\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether GBF1 acts at replication membranes directly or via global secretory pathway disruption not distinguished\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"GBF1's role as a host factor was extended to enteroviruses (CVB3, poliovirus) and HCV, establishing it as a broadly exploited target; separately, Drosophila garz (GBF1 ortholog) was shown to function in clathrin-independent GEEC endocytosis, expanding GBF1's role beyond secretory trafficking.\",\n      \"evidence\": \"CVB3/poliovirus replicon assays with BFA-resistant GBF1 rescue and siRNA (PMID:19740986); HCV selective GEF knockdown with rescue (PMID:19906930); Drosophila RNAi screen with TIRF imaging and GEF-dead mutant (PMID:19707569)\",\n      \"pmids\": [\"19740986\", \"19906930\", \"19707569\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise viral replication membrane composition and GBF1 role therein unknown\", \"Whether GEEC endocytic function is conserved in mammalian cells not tested\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Two key regulatory inputs were defined: CDK1–cyclin B phosphorylates GBF1 to trigger mitotic Golgi fragmentation, and PI4KIIIα-generated PI4P (downstream of Rab1) is required for GBF1 Golgi membrane recruitment, linking lipid identity to GEF targeting. Additionally, a non-catalytic scaffolding role was uncovered for poliovirus replication.\",\n      \"evidence\": \"In vitro CDK1 kinase assay, mitotic phosphoprotein analysis, ARF-GTP measurement (PMID:20175751); PI4KIIIα siRNA, PI4P sensor, Rab1 dominant-active (PMID:20530568); N-terminal GBF1 truncation rescue of poliovirus replication (PMID:20497182)\",\n      \"pmids\": [\"20175751\", \"20530568\", \"20497182\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"CDK1 phosphorylation sites on GBF1 not mapped\", \"Whether PI4P binding is direct or mediated by an adaptor unclear\", \"The non-catalytic viral function mechanism remains obscure\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"GBF1 was linked to lipid droplet biology through direct interaction with ATGL and lipid droplet targeting via HDS1/HDS2 domains, and to pathogen lipid acquisition through Chlamydia co-option of GBF1-dependent sphingomyelin trafficking.\",\n      \"evidence\": \"ATGL–GBF1 yeast two-hybrid, co-IP, in vitro binding, domain-LD localization (PMID:21789191); selective GEF siRNA with fluorescent SM trafficking in Chlamydia-infected cells (PMID:21909260)\",\n      \"pmids\": [\"21789191\", \"21909260\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether GBF1 activates ARFs on lipid droplet surfaces not shown\", \"ATGL delivery mechanism via COPI not fully reconstituted\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"GBF1 function was extended to GPCR-stimulated neutrophil chemotaxis via a novel phosphoinositide-binding module (BP3K) that redirects GBF1 from Golgi to the leading edge, and to epithelial tubulogenesis in Drosophila where Garz loss disrupts apical membrane delivery.\",\n      \"evidence\": \"GBF1 phospholipid binding assay, leading-edge live imaging, siRNA in neutrophils (PMID:22573891); Drosophila garz mutant with EM and live cargo imaging (PMID:22302994)\",\n      \"pmids\": [\"22573891\", \"22302994\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"BP3K domain boundaries and binding specificity not fully characterized\", \"Whether leading-edge ARF activation serves a distinct function from Golgi ARF activation unknown\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"The HDS1 amphipathic helix was identified as a direct lipid-binding element for both Golgi membranes and lipid droplets, auto-inhibited by the Sec7 domain in the full-length protein; a GEF cascade was defined in which GBF1-activated ARF4/5 recruit BIG1/2 to the TGN; and AMPK was identified as a second mitotic kinase phosphorylating GBF1 to promote Golgi disassembly.\",\n      \"evidence\": \"In vitro liposome/droplet binding with amphipathic helix mutagenesis (PMID:23943872); immunoEM localization with ARF isoform-specific rescue (PMID:23386609); in vitro AMPK kinase assay with mitotic cell fractionation (PMID:23418352)\",\n      \"pmids\": [\"23943872\", \"23386609\", \"23418352\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of Sec7-mediated autoinhibition of HDS1 unknown\", \"Which AMPK site(s) are phosphorylated during mitosis not mapped in this study\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"GBF1 oligomerization via DCB domain was shown to be dispensable for all tested GEF functions (Golgi targeting, ARF activation, COPI recruitment, secretion) but required for protein stability; simultaneously, the GBF1–ARF1/ARF4–COPI pathway was demonstrated to transport Dengue virus capsid from ER to lipid droplets independently of COPII.\",\n      \"evidence\": \"DCB mutagenesis (K91/E130) with FRAP, ARF activation, COPI, secretion, stability assays (PMID:26718629); BFA-resistant GBF1 rescue of Dengue capsid distribution (PMID:26031340)\",\n      \"pmids\": [\"26718629\", \"26031340\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether oligomerization has a regulatory role under stress conditions untested\", \"COPII-independent ER-to-LD transport mechanism not fully resolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"In vivo vertebrate validation came from zebrafish, where GBF1 loss-of-function (HDS2 L1246R mutation) caused intracerebral hemorrhage due to vascular breakage, and the mutant protein failed to target Golgi or activate ARF1, confirming HDS2 as essential for membrane targeting.\",\n      \"evidence\": \"ENU mutagenesis/positional cloning, morpholino and CRISPR knockout in zebrafish, mammalian cell Golgi recruitment assay\",\n      \"pmids\": [\"28003365\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific vascular cargo whose mis-trafficking causes hemorrhage not identified\", \"Whether endothelial or pericyte GBF1 is the critical cell type not determined\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"GBF1 was shown to form a ternary complex with rhodopsin and ARF4 at the photoreceptor Golgi for ciliary transport carrier biogenesis, with the DCB-HUS domain mediating rhodopsin/ARF4 binding and GBF1 also interacting with the ArfGAP ASAP1.\",\n      \"evidence\": \"Frog retina in vivo analysis, co-IP with recombinant human proteins, GCA inhibitor, domain mapping\",\n      \"pmids\": [\"29025970\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether GBF1 functions in ciliogenesis beyond photoreceptors not tested\", \"ASAP1 functional role in the complex not defined\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Three advances refined GBF1 regulation and targeting: CK2 phosphorylation at S292/S297 targets GBF1 for SCFβTrCP-mediated degradation at the cytokinetic bridge, required for postmitotic Golgi reformation; HDS1/HDS2 domains and a proteinaceous Golgi receptor were shown essential for membrane recruitment in vitro; and GBF1–Miro interaction was found to regulate mitochondrial positioning.\",\n      \"evidence\": \"Phosphosite mutagenesis with βTrCP co-IP, non-degradable mutant cytokinesis failure (PMID:29898406); in vitro Golgi recruitment reconstitution with protease/heat sensitivity (PMID:29507113); GBF1–Miro co-IP, GCA inhibition, dynein pathway (PMID:30459446); HDS2 alanine scanning with functional replacement (PMID:29443553)\",\n      \"pmids\": [\"29898406\", \"29507113\", \"30459446\", \"29443553\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the proteinaceous Golgi receptor for GBF1 unknown\", \"Miro–GBF1 interaction interface not mapped\", \"How CK2 phosphorylation timing is controlled at the midbody unclear\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Multiple studies expanded GBF1's functional network: C10orf76 was identified as a Golgi-cycling GBF1 interactor required for Golgi integrity and secretion; GBF1 was shown to be rate-limiting for VWF granule biogenesis with AMPK coupling; HCV NS3 was found to directly bind GBF1's Sec7 domain; and GBF1 catalytic activity was required for rotavirus VP7 trimerization and particle assembly.\",\n      \"evidence\": \"BioID proximity labeling with co-IP and siRNA (PMID:31519766); GBF1 over/underexpression with AMPK activation and VWF imaging (PMID:31056345); NS3–GBF1 yeast two-hybrid, co-IP, PLA, NS3 mutant replication (PMID:30567983); GBF1 pharmacological/genetic inhibition with VP7 trimerization assay (PMID:31270230)\",\n      \"pmids\": [\"31519766\", \"31056345\", \"30567983\", \"31270230\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"C10orf76 molecular function in GBF1 regulation unknown\", \"Whether AMPK directly modulates GBF1 at the Golgi versus indirectly through energy sensing not resolved at this point\", \"NS3–GBF1 binding does not explain how GBF1 supports HCV replication mechanistically\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Human genetic evidence established GBF1 as a disease gene: heterozygous pathogenic GBF1 variants were identified in families with distal hereditary motor neuropathy/CMT2, with patient fibroblasts showing marked Golgi fragmentation.\",\n      \"evidence\": \"Genomic sequencing of affected families, Golgi fragmentation assay in patient fibroblasts, GBF1 expression in mouse motor neurons\",\n      \"pmids\": [\"32937143\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific GBF1 variant effects on ARF activation or COPI recruitment not tested biochemically\", \"Motor neuron-specific vulnerability mechanism unknown\", \"No animal model recapitulating the neuropathy phenotype\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Src kinase phosphorylation of GBF1 (Y876/Y898 near the Sec7 C-terminus) was shown to enhance ARF1 binding and induce retrograde tubular transport carriers carrying GALNTs from Golgi to ER, defining a regulated retrograde trafficking pathway.\",\n      \"evidence\": \"Phosphoproteomics, Src kinase assay, phosphomimetic/phosphodeficient GBF1 mutants, live-cell tubule imaging, ARF1 binding assay\",\n      \"pmids\": [\"34870592\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Src phosphorylation occurs in response to specific physiological signals not determined\", \"How phosphorylation alters GBF1 conformation to enhance ARF1 binding not structurally resolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"N-terminal GBF1 phosphorylation sites (S233, S371, Y377, Y515) were shown to differentially regulate cytokinesis versus Golgi homeostasis: phosphomimetic mutants supported normal Golgi and secretion but impaired cytokinetic bridge resolution, revealing separable phospho-regulatory modules.\",\n      \"evidence\": \"Phosphomimetic and non-phosphorylatable GBF1 mutants with Golgi morphology, secretion, and multinucleation assays\",\n      \"pmids\": [\"37604968\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinases responsible for these N-terminal phosphorylations not identified\", \"Mechanism by which phosphorylation impairs cytokinesis not defined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"AMPK phosphorylation of GBF1 was pinpointed to Thr1337 using gene-edited non-phosphorylatable knock-in cells, directly demonstrating that this single site mediates AMPK-induced Golgi fragmentation and trafficking slowdown; separately, GBF1 haploinsufficiency was linked to congenital cataracts in mice.\",\n      \"evidence\": \"AMPK-α KO cells, GBF1-T1337A knock-in by gene editing, trafficking assay (PMID:39575556); Gbf1 heterozygous KO mice with cataracts, UPR/autophagy in lens cells (PMID:39110251)\",\n      \"pmids\": [\"39575556\", \"39110251\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether T1337 phosphorylation and CDK1/CK2 phosphorylation act synergistically in mitosis not tested\", \"Lens-specific trafficking cargo affected by GBF1 deficiency not identified\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key open questions remain: the identity of the proteinaceous Golgi receptor for GBF1, the structural basis for Sec7-domain autoinhibition of HDS1, a full-length GBF1 structure, and the mechanism by which motor neuron-specific vulnerability arises from GBF1 mutations.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No high-resolution structure of full-length GBF1\", \"Golgi membrane receptor identity unknown\", \"Motor neuron vulnerability mechanism in CMT2 not explained\", \"Relationship between multiple kinase inputs and GBF1 conformational states not integrated\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 3, 4, 26, 40]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [25, 24]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [0, 1, 4, 11, 32, 34]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 1, 3]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [4, 11]},\n      {\"term_id\": \"GO:0005811\", \"supporting_discovery_ids\": [22, 25]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [4, 10, 11, 26, 36]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [9, 10, 28, 30]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [19, 27, 31, 44]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [22, 25]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [12, 41, 48]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [32, 34, 42]}\n    ],\n    \"complexes\": [\n      \"COPI coat (functional effector complex)\",\n      \"GBF1 homodimer (DCB-HUS mediated)\"\n    ],\n    \"partners\": [\n      \"ARF1\",\n      \"COPI\",\n      \"p115\",\n      \"RAB1B\",\n      \"ATGL\",\n      \"RHOT1\",\n      \"ASAP1\",\n      \"C10orf76\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}