{"gene":"GBF1","run_date":"2026-06-10T01:55:21","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 guanine nucleotide exchange activity with apparent specificity toward ARF5 at physiological Mg2+ concentrations. Overexpression conferred BFA resistance on Golgi morphology and ARF activation/COPI recruitment. GBF1 is primarily cytosolic but a significant pool co-localizes with COPI beta-subunit at a perinuclear structure and by immunogold labeling to Golgi cisternae and smooth vesiculotubular structures.","method":"Expression cloning, hexahistidine-tagged in vitro GEF activity assay, immunofluorescence, immunogold EM, subcellular fractionation","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro GEF activity assay, direct overexpression functional rescue, multiple orthogonal methods in a single rigorous study","pmids":["10402461"],"is_preprint":false},{"year":1998,"finding":"Human GBF1 encodes a 206.5 kDa protein containing a centrally positioned Sec7 domain and a proline-rich C-terminal region. Its mRNA is expressed ubiquitously across 17 tissues. The gene maps to chromosomal locus 10q24 and the Sec7 domain-encoding region harbors four introns.","method":"cDNA cloning, Northern blotting, chromosomal mapping (YAC, radiation hybrid)","journal":"Genomics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct sequencing and expression analysis, single lab, multiple orthogonal methods for mapping/expression","pmids":["9828135"],"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 interaction was identified by yeast two-hybrid and confirmed by in vitro binding and co-immunoprecipitation. The two proteins co-localize in the Golgi and peripheral VTCs. Expression of the p115-binding (pro-rich) region of GBF1 caused Golgi disruption, demonstrating functional relevance, but the interaction was not required for targeting either protein to membranes.","method":"Yeast two-hybrid screen, in vitro binding assay, co-immunoprecipitation, immunofluorescence, domain mutagenesis","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal biochemical assays (Y2H, in vitro binding, co-IP) plus functional dominant-negative domain expression, single lab","pmids":["12634853"],"is_preprint":false},{"year":2004,"finding":"GBF1 cycles rapidly on and off Golgi membranes (fast turnover by FRAP), and BFA, which forms an Arf-GDP–GEF inhibitory complex, stabilizes GBF1 on Golgi membranes. Using an in vivo Arf1-GTP reporter assay, GBF1 exchange activity on Arf1 was shown to be inhibited by BFA in mammalian cells, consistent with formation of an Arf1–GBF1–BFA ternary complex with longer membrane residence.","method":"YFP-GBF1 FRAP, in vivo Arf1-GTP level assay, BFA treatment","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — quantitative live-imaging FRAP combined with in vivo GEF activity assay, replicated conceptually in multiple subsequent studies","pmids":["15616190"],"is_preprint":false},{"year":2005,"finding":"GBF1 rapidly cycles between membranes and cytosol with t½ ~17 s. GBF1 is stabilized on membranes when complexed with ARF-GDP (shown by inactive E794K GBF1 mutant, ARF1-T31N mutant, or BFA). GBF1 dissociation from ARF and membranes is triggered by its catalytic activity (GDP displacement and GTP binding to ARF), implying that each GBF1 membrane association catalyzes a single ARF activation event.","method":"GFP-GBF1 FRAP, expression of catalytically inactive GBF1-E794K mutant, ARF1-T31N expression, BFA treatment","journal":"Traffic (Copenhagen, Denmark)","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal approaches (FRAP + dominant-negative mutants + drug) in a single study, mechanistically rigorous","pmids":["15813748"],"is_preprint":false},{"year":2006,"finding":"GBF1 localizes to both Golgi membranes and peripheral puncta near but separate from ER exit sites, associating dynamically with both. BFA causes accumulation of GBF1 on these membranes before redistribution to ER in a microtubule-dependent manner. Microinjection of anti-GBF1 antibodies specifically caused dissociation of COPI from membranes, demonstrating that GBF1 regulates COPI membrane recruitment in the early secretory pathway. GBF1 recruitment to cargo-containing peripheral puncta coincided with COPI but not COPII recruitment.","method":"GFP-GBF1 live-cell imaging, FRAP, diffusion coefficient measurement, subcellular fractionation, anti-GBF1 antibody microinjection, immunofluorescence","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — antibody microinjection directly linking GBF1 to COPI recruitment, supported by multiple orthogonal localization and functional methods","pmids":["16926190"],"is_preprint":false},{"year":2006,"finding":"The enterovirus CVB3 3A protein inhibits ARF1 activation by directly binding to GBF1 at its N-terminus, thereby blocking GBF1-mediated COP-I coat complex recruitment to membranes and inhibiting ER-to-Golgi transport. This mechanism is specific to GBF1 (not BIG1/BIG2) and viral mutants defective in this function are less virulent in mice.","method":"Co-immunoprecipitation, dominant-negative ARF1 expression, BFA resistance assay in MDCK cells, siRNA knockdown, mouse virulence assay, electron microscopy","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (co-IP, genetic rescue, in vivo virulence), replicated in multiple subsequent studies","pmids":["16890159"],"is_preprint":false},{"year":2006,"finding":"Among multiple picornavirus 3A proteins tested, only enterovirus (CVB3 and poliovirus) 3A proteins inhibit COP-I recruitment via GBF1 binding. The N-terminal residues of CVB3 3A are critical for GBF1 binding; chimeric HRV 3A proteins with CVB3 N-termini gain the ability to bind GBF1 and inhibit transport. Other picornavirus 3A proteins (HRV, EMCV, FMDV, HAV) fail to bind GBF1 or inhibit COP-I recruitment.","method":"Co-immunoprecipitation, COP-I recruitment assay, protein transport assay, chimeric protein analysis","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 / Strong — systematic domain-swap mutagenesis across multiple virus species, replicated by two independent labs","pmids":["17005635"],"is_preprint":false},{"year":2007,"finding":"The 3A protein of CVB3 must form homodimers to bind GBF1 and trap it on membranes. A conserved region in the N-terminus of 3A is required for GBF1 binding but not dimerization. In GBF1, the extreme N-terminus, the dimerization/cyclophilin binding (DCB) domain, and the homology upstream of Sec7 (HUS) domain are all required for the interaction with viral 3A. A GBF1 mutant lacking its extreme N-terminus cannot rescue the effects of 3A overexpression.","method":"Mutagenesis of 3A and GBF1, co-immunoprecipitation, functional rescue assay","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 / Strong — systematic mutagenesis of both interaction partners with functional read-out, multiple orthogonal methods","pmids":["17329336"],"is_preprint":false},{"year":2007,"finding":"Rab1b GTPase directly interacts with GBF1 through GBF1's N-terminal domain, identifying GBF1 as a Rab1b effector. Active Rab1b (Rab1bQ67L) increases GBF1 and COPI association with peripheral ER exit site structures, stabilizes Arf1 on Golgi membranes, and Rab1b siRNA reduces GBF1 membrane association.","method":"Co-immunoprecipitation, GFP-Rab1b live imaging, FRAP, siRNA knockdown, immunofluorescence","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal interaction shown, supported by live-cell FRAP and siRNA functional experiments, single lab","pmids":["17429068"],"is_preprint":false},{"year":2007,"finding":"GBF1 colocalizes with GGA adaptor proteins on Golgi membranes and physically interacts with GGAs. Depletion of GBF1 or expression of its inactive mutant prevents GGA recruitment to Golgi membranes and results in improper lysosomal cargo sorting (mannose 6-phosphate receptor and sortilin trafficking).","method":"siRNA knockdown, inactive GBF1 mutant expression, co-immunoprecipitation, immunofluorescence, cargo trafficking assay","journal":"Traffic (Copenhagen, Denmark)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus siRNA/dominant-negative functional assay, single lab","pmids":["17666033"],"is_preprint":false},{"year":2007,"finding":"GBF1 regulates COPI recruitment specifically on cis-Golgi compartments (while BIGs regulate adaptors on trans-Golgi). GBF1 knockdown/COPI knockdown does not prevent ER export of VSVGtsO45 but causes its accumulation in peripheral vesiculotubular clusters, and is required for Golgi subcompartmentalization and cargo progression to the cell surface. GBF1 is required for transmembrane but not soluble protein secretion.","method":"siRNA knockdown, VSVGtsO45 trafficking assay, immunofluorescence","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — complementary overexpression and knockdown with defined cargo readouts, replicated across multiple studies","pmids":["18003980"],"is_preprint":false},{"year":2007,"finding":"siRNA-mediated depletion of GBF1 causes COPI dispersal but, unlike BFA treatment or expression of inactive ARF, does not cause Golgi collapse into ER. Instead, GBF1 depletion causes extensive tubulation of the cis-Golgi with connections to peripheral ERGIC sites. GBF1 depletion dramatically inhibits transmembrane protein trafficking but soluble proteins continue to be secreted, showing cargo-type specificity.","method":"siRNA knockdown, live-cell imaging, immunofluorescence, cargo trafficking assays (soluble and transmembrane)","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Strong — siRNA with multiple orthogonal cargo assays, replicated by Manolea et al. same year","pmids":["17956946"],"is_preprint":false},{"year":2007,"finding":"The DCB domains of GBF1, BIG1, and BIG2 mediate homodimerization of each GEF, and an intramolecular interaction between DCB and HUS domains (mediated by the conserved HUS box) determines the architecture of the N-terminal regulatory region. Both DCB and HUS domains are necessary for GBF1 dimerization in mammalian cells, and the DCB domain is essential for yeast viability.","method":"Yeast two-hybrid, biochemical pulldown assays, cellular dimerization assay, yeast complementation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — combination of in vitro biochemistry, yeast two-hybrid, and cell-based assays; yeast essentiality confirms functional importance","pmids":["17640864"],"is_preprint":false},{"year":2008,"finding":"GBF1 depletion by siRNA causes cell-cycle arrest in G0/G1, dispersal of Golgi markers (beta-COP, GM130), induction of ER stress proteins (calreticulin, PDI), and upregulation of UPR chaperones. GBF1 depletion specifically induces relocation of the site-2 protease S2P from Golgi to ER and proteolysis of ATF6, mimicking a UPR response. BIG1 or BIG2 depletion did not reproduce these effects.","method":"siRNA knockdown, cell-cycle analysis, immunofluorescence, quantitative proteomics, Western blotting","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Moderate — siRNA specificity established by three different GEF knockdowns, proteomic analysis plus functional assays, single lab","pmids":["18287014"],"is_preprint":false},{"year":2008,"finding":"MHV coronavirus RNA replication requires GBF1-mediated ARF1 activation. Individual siRNA knockdown of GBF1 (but not BIG1 or BIG2) significantly inhibited MHV RNA replication. ARF1 siRNA also inhibited MHV infection. BFA did not block RC formation per se but reduced RC number. MHV was BFA-insensitive in MDCK cells expressing BFA-resistant GBF1.","method":"siRNA knockdown (individual targets), BFA pharmacological inhibition in MDCK cells with BFA-resistant GBF1, immunofluorescence, quantitative electron microscopy","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal approaches including siRNA, BFA-resistant GBF1 rescue, EM quantification; replicated conceptually across multiple viruses","pmids":["18551169"],"is_preprint":false},{"year":2008,"finding":"GDP-bound class II Arfs (Arf4, Arf5) associate with ERGIC membranes independently of GBF1. After BFA treatment, Arf1 and Arf3 dissociate from endomembranes while Arf4 and Arf5 persist on ERGIC. A GDP-arrested Arf4(T31N) localizes to ERGIC even with BFA and Exo1 present. Loss of Arf-GTP (by Exo1) causes GBF1 accumulation on Golgi and ERGIC membranes, suggesting GBF1 accumulation can be triggered by loss of Arf-GTP rather than only by Arf-GDP–BFA–GBF1 complex formation.","method":"Live-cell imaging of fluorescently tagged Arfs and GBF1, BFA and Exo1 pharmacological treatments, dominant-negative Arf4(T31N) expression","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — live-cell imaging with pharmacological and genetic tools, single lab","pmids":["18524849"],"is_preprint":false},{"year":2009,"finding":"CVB3 RNA replication critically requires GBF1. siRNA knockdown of GBF1 inhibited viral RNA replication; overexpression of active but not inactive GBF1 rescued replication in BFA-treated cells. The BFA-resistant GBF1-M832L efficiently rescued both wt and 3A-mutant replicons. BFA-resistant GBF1-A795E rescued wt but not 3A-GBF1 binding-deficient replicons. Overexpression of Arf proteins or Rab1B failed to rescue replication in the presence of BFA.","method":"siRNA knockdown, BFA-resistant GBF1 overexpression rescue, subgenomic replicon assay, viral RNA replication quantification","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 / Strong — systematic rescue assay with multiple GBF1 mutants, siRNA knockdown, replicated across multiple virus families","pmids":["19740986"],"is_preprint":false},{"year":2009,"finding":"GBF1 is required for HCV RNA replication. Individual siRNA knockdown of GBF1 (but not BIG1 or BIG2) and the GBF1-specific inhibitor Golgicide A inhibited HCV replication. Overexpression of BFA-resistant GBF1 rescued HCV replication in BFA-treated cells. BFA did not block membranous web-like structure formation, suggesting GBF1 is involved in replication complex activity rather than formation.","method":"siRNA knockdown, specific pharmacological inhibitor (Golgicide A), BFA-resistant GBF1 rescue, immunofluorescence, electron microscopy","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 / Strong — three independent approaches (siRNA, GCA, BFA-resistant rescue), replicated by subsequent studies","pmids":["19906930"],"is_preprint":false},{"year":2009,"finding":"In Drosophila, garz (the GBF1 ortholog) functions in the pinocytic GEEC (GPI-AP enriched early endosomal compartment) pathway for clathrin-independent endocytosis. Live confocal and TIRF imaging show a fraction of GBF1-GFP dynamically associates with activated Arf1-positive nascent pinosomes. A GTP-exchange-deficient GBF1 mutant impairs fluid phase uptake. GBF1 activation is required for the GEEC pathway even in the presence of BFA, indicating a role in endocytosis separable from its role in secretion.","method":"RNAi knockdown in Drosophila cells, live confocal/TIRF imaging, quantitative fluid-phase uptake assay, GTP-exchange-deficient mutant expression","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — live imaging plus functional mutant plus quantitative uptake assay; ortholog study, single lab","pmids":["19707569"],"is_preprint":false},{"year":2010,"finding":"For poliovirus replication, GBF1's N-terminal region (lacking the catalytic Sec7 domain) is sufficient to rescue replication in BFA-treated cells. In poliovirus-infected cells, p115 (a normal GBF1 modulator) is degraded and neither p115 nor Rab1b knockdown affects virus replication, indicating that GBF1 supports viral replication through functions distinct from its canonical Arf-activating role in COPI vesicle formation.","method":"BFA-resistant GBF1 domain rescue assay (N-terminal fragment lacking Sec7), siRNA knockdown of p115 and Rab1b, viral replication assay","journal":"Cellular microbiology","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — domain dissection rescue assay directly demonstrates Sec7-independent viral function; combined with siRNA knockdown, single lab","pmids":["20497182"],"is_preprint":false},{"year":2010,"finding":"The phosphatidylinositol 4-kinase PI4KIIIα is required for GBF1 recruitment to Golgi membranes. Inhibitors of PI4P synthesis or depletion of PI4KIIIα prevents GBF1 recruitment to the Golgi. Dominant-active Rab1b increases PI4P levels at the Golgi as detected by GFP-PH sensor, suggesting Rab1b contributes to GBF1 recruitment through activation of PI4KIIIα and subsequent PI4P production.","method":"PI4P synthesis inhibitors, siRNA knockdown of PI4KIIIα, GFP-PH PI4P biosensor, dominant-active Rab1b expression, immunofluorescence","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological and genetic depletion plus biosensor, single lab","pmids":["20530568"],"is_preprint":false},{"year":2010,"finding":"GBF1 is phosphorylated by CDK1-cyclin B in mitosis, which results in its dissociation from Golgi membranes. This is accompanied by a reduction in membrane-associated GTP-bound ARF in mitotic cells. Despite reduced GBF1 and ARF-GTP, COPI binding to Golgi appears unaffected but remains GBF1-dependent, suggesting a low level of GBF1 activity persists in mitosis.","method":"Identification of GBF1 as Golgi phosphoprotein, in vitro kinase assay with CDK1-cyclin B, phosphorylation site mapping, immunofluorescence, membrane fractionation, cell synchronization","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro kinase assay plus cell-based fractionation and co-immunoprecipitation; direct demonstration of CDK1 as the kinase, single lab","pmids":["20175751"],"is_preprint":false},{"year":2011,"finding":"C. trachomatis selectively co-opts GBF1 (not BIG1 or BIG2) for vesicle-mediated sphingomyelin (SM) acquisition. The GBF1/Arf1-dependent pathway provides SM essential for inclusion membrane growth and stability but is not required for bacterial replication. A separate CERT-dependent non-vesicular ceramide transport pathway provides SM required for bacterial replication.","method":"siRNA knockdown of individual GEFs, BFA pharmacological inhibition, fluorescent lipid transport assays, inclusion growth/stability quantification, bacterial replication assay","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Strong — selective siRNA knockdown of three GEFs with distinct functional readouts (SM acquisition, inclusion growth, bacterial replication), multiple orthogonal assays","pmids":["21909260"],"is_preprint":false},{"year":2011,"finding":"GBF1 and ATGL (adipose triglyceride lipase) interact directly and in cells. Yeast two-hybrid, co-immunoprecipitation, and direct protein binding assays demonstrate interaction through multiple contact sites. The C-terminal region of ATGL interacts with N-terminal domains of GBF1 including the Sec7 domain (but not full-length GBF1). The ATGL patatin domain interacts with GBF1's HDS1 and HDS2 C-terminal domains. HDS1 and HDS2 expressed alone localize to lipid droplets but not Golgi, unlike full-length GBF1.","method":"Yeast two-hybrid, co-immunoprecipitation in mammalian cells, direct protein binding, fluorescence microscopy","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — three orthogonal interaction methods (Y2H, co-IP, direct binding) with domain mapping, single lab","pmids":["21789191"],"is_preprint":false},{"year":2012,"finding":"In Drosophila, loss of garz (GBF1 ortholog) impairs Golgi complex integrity, disrupts vesicle transport of cargo proteins and directed apical membrane delivery, and perturbs polarized epithelial architecture of tubular organs (salivary glands, trachea, proventriculus, hindgut). These phenotypes are caused by dysfunction of the Arf1-COPI machinery.","method":"Drosophila loss-of-function mutant analysis (EMS and targeted), immunofluorescence, electron microscopy, cargo trafficking assays in embryos","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo loss-of-function in Drosophila with multiple phenotypic readouts, replicated across several tissue types","pmids":["22302994"],"is_preprint":false},{"year":2012,"finding":"GBF1 bears a novel phosphatidylinositol-phosphate binding module (BP3K) that binds products of PI3Kγ. Upon GPCR stimulation in neutrophils, GBF1 is translocated from the Golgi to the leading edge to activate Arf1, which recruits p22phox and GIT2 to the leading edge. GBF1-mediated Arf1 activation is required for neutrophil chemotaxis and superoxide production, linking PI3Kγ activity with Arf1 activation.","method":"PI3P/PI4P binding assays, immunofluorescence (GBF1 localization on GPCR stimulation), siRNA knockdown, superoxide production assay, chemotaxis assay","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — lipid binding module identified biochemically, localization by imaging, function by siRNA/dominant-negative with defined readouts, single lab","pmids":["22573891"],"is_preprint":false},{"year":2012,"finding":"GBF1 and ARF1 colocalize with PI4KIIIβ at HCV replication complexes. Both ARF1 and GBF1 are required for HCV replication; overexpression of PI4P phosphatase Sac1 inhibits HCV replication. PI4KIIIβ is required for HCV replication and co-localizes with the GBF1/ARF1 machinery, suggesting GBF1/ARF1 generates a PI4P-enriched environment supporting HCV replication.","method":"Immunofluorescence co-localization, siRNA knockdown, PI4P phosphatase overexpression, HCV replication assay","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-localization plus functional siRNA knockdown, single lab","pmids":["22359663"],"is_preprint":false},{"year":2013,"finding":"GBF1-activated ARFs (specifically ARF4 and ARF5, but not ARF3) facilitate BIG1 and BIG2 recruitment to the TGN, establishing a functional cascade between GEFs. GBF1 is ultrastructurally localized to pre-Golgi, Golgi, and also TGN, and its activity at the TGN is required for subsequent BIG1/2 recruitment that coordinates clathrin adaptor coating events.","method":"siRNA knockdown, immunofluorescence, ultrastructural localization (immunoelectron microscopy), ARF isoform-specific knockdown","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — siRNA epistasis establishes functional cascade, supported by ultrastructural localization; single lab but multiple orthogonal approaches","pmids":["23386609"],"is_preprint":false},{"year":2013,"finding":"GBF1 possesses a lipid-binding HDS1 domain immediately downstream of the catalytic Sec7 domain. An amphipathic helix within HDS1 is necessary and sufficient for binding to lipid droplets and Golgi membranes in cells and to bilayer liposomes and artificial lipid droplets in vitro. The catalytic Sec7 domain inhibits the potent lipid-droplet-binding capacity of HDS1. Additional sequences upstream of the Sec7-HDS1 tandem are required for Golgi membrane localization.","method":"In vitro liposome binding, in vitro artificial lipid droplet binding, GFP-tagged domain expression in cells, domain deletion/mutagenesis analysis","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution of lipid binding with mutagenesis validated in cells, multiple lipid-binding substrates tested","pmids":["23943872"],"is_preprint":false},{"year":2013,"finding":"AMPK is phosphorylated and activated when cells enter mitosis. Activated AMPK phosphorylates GBF1, dissociating GBF1 from Golgi membranes and abolishing its Arf1-GEF activity. AMPK and GBF1 phosphorylation are essential for mitotic Golgi disassembly and subsequent mitosis entry.","method":"Cell synchronization, phosphorylation assays, kinase assays (AMPK on GBF1), immunofluorescence, Golgi fragmentation quantification, rescue/inhibition experiments","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — kinase assay linking AMPK to GBF1 phosphorylation plus functional mitotic assay, single lab","pmids":["23418352"],"is_preprint":false},{"year":2013,"finding":"C. elegans GBF-1 localizes to the cis-Golgi and ER-Golgi elements. GBF-1 is required for secretion and Golgi integrity. Additionally, GBF-1 depletion disperses ER reticular structure (without destroying ER exit sites), reduces RAB-5-positive early endosomes, and causes accumulation of RAB-7-positive late endosomes, revealing a role in receptor-mediated endocytosis and endosomal traffic.","method":"RNAi knockdown in C. elegans oocytes and intestinal epithelial cells, immunofluorescence/confocal microscopy, endocytosis assays, organelle marker analysis","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo RNAi with multiple organelle readouts, ortholog model; single lab","pmids":["23840591"],"is_preprint":false},{"year":2015,"finding":"The GBF1-Arf1/Arf4-COPI pathway is necessary for dengue virus capsid transport from the ER membrane to lipid droplets (LDs). This process is independent of COPII components and Golgi integrity. A BFA-resistant form of GBF1 restores capsid distribution in infected cells treated with BFA, demonstrating GBF1 catalytic activity is required.","method":"BFA/drug treatment, BFA-resistant GBF1 rescue, COPII/Golgi disruption, immunofluorescence, siRNA knockdown of Arf1/Arf4","journal":"Traffic (Copenhagen, Denmark)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — BFA-resistant rescue plus pharmacological and genetic perturbations, single lab","pmids":["26031340"],"is_preprint":false},{"year":2015,"finding":"GBF1 oligomerization (mediated by DCB domain residues K91 and E130) is dispensable for Golgi localization, membrane cycling, Arf activation, COPI recruitment, Golgi homeostasis, and cargo secretion, and is not required for poliovirus RNA replication support. However, oligomerization stabilizes GBF1 in cells; the oligomerization-deficient 91/130 mutant is degraded faster than wild-type GBF1.","method":"Site-directed mutagenesis, FRAP, ARF activation assay, COPI recruitment assay, secretion assay, poliovirus replication assay, protein stability measurement","journal":"American journal of physiology. Cell physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional assays with a defined mutagenesis strategy, single lab","pmids":["26718629"],"is_preprint":false},{"year":2016,"finding":"In zebrafish, a missense mutation (L1246R) in the HDS2 domain of gbf1 causes vascular hemorrhage. The mutant Gbf1(L1246R) cannot be recruited to the Golgi apparatus and fails to activate Arf1 for COPI complex recruitment, causing ER stress and endothelial apoptosis via PERK/CHOP. Hemorrhage can be partially prevented by ER stress inhibitor tauroursodeoxycholic acid or knockdown of proapoptotic baxb.","method":"ENU mutagenesis zebrafish screen, positional cloning, mammalian cell-based Golgi recruitment assay, Arf1 activation assay, COPI recruitment assay, ER stress marker analysis, rescue experiments","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo zebrafish phenotype combined with mechanistic cell-based assays (Golgi recruitment, Arf1 activation, COPI recruitment) for specific HDS2 mutation","pmids":["28003365"],"is_preprint":false},{"year":2017,"finding":"GBF1 forms a functional complex with Arf4 and the photoreceptor cargo rhodopsin at the Golgi/TGN during sensory membrane carrier biogenesis. Rhodopsin and Arf4 bind the regulatory N-terminal DCB-HUS domain of GBF1. The complex is sensitive to Golgicide A (GCA), which blocks rhodopsin delivery to cilia. Newly synthesized rhodopsin in the endomembrane system is essential for GBF1-Arf4 complex formation in vivo. GBF1 also interacts with Arf GAP ASAP1 in a GCA-resistant manner.","method":"Co-immunoprecipitation with recombinant human proteins, frog retina in vivo experiments, GCA inhibitor treatment, domain binding mapping","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP with domain mapping plus in vivo frog retina experiments, single lab","pmids":["29025970"],"is_preprint":false},{"year":2017,"finding":"GBF1 is involved in the replication of yellow fever virus, Sindbis virus, coxsackievirus B4, and human coronavirus 229E. For HCV and some other viruses, class II Arfs (Arf4/Arf5) downstream of GBF1 are required; for CVB4, no single or paired Arf depletion inhibited replication, suggesting GBF1 supports viral replication through distinct Arf-dependent and Arf-independent mechanisms depending on the virus.","method":"siRNA and CRISPR-Cas9 Arf depletion (individual and paired), viral replication assays, GBF1 knockdown","journal":"The Journal of general virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR/siRNA systematic Arf depletion across multiple viruses, single lab","pmids":["29923822"],"is_preprint":false},{"year":2018,"finding":"GBF1 and its substrate Arf1 regulate the spatial organization of mitochondria in a microtubule-dependent manner. GBF1 physically interacts with the mitochondrial membrane protein Miro; GTP-bound Arf1 also interacts with Miro. Inhibition of GBF1 causes collapse of the mitochondrial network toward the centrosome through a two-fold increase in time engaged in retrograde movement, dependent on dynein and Miro. GBF1 inhibition also results in larger mitochondria with more complex morphology.","method":"Co-immunoprecipitation (GBF1–Miro, Arf1–Miro), GBF1 pharmacological inhibition, immunofluorescence, electron tomography, mitochondrial movement tracking (live imaging), siRNA knockdown of Miro and dynein inhibition","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP for interaction, multiple functional perturbations with quantitative live-imaging readout, electron tomography for morphology, single lab","pmids":["30459446"],"is_preprint":false},{"year":2018,"finding":"GBF1 recruitment to cis-Golgi membranes requires its HDS1 and HDS2 C-terminal domains and a heat-labile, protease-sensitive Golgi-localized protein receptor. Arf-GDP localization is critical for GBF1 recruitment, as a TGN-localized Arf-GDP mutant fails to promote GBF1 recruitment. ArfGAP2 and ArfGAP3 do not contribute to GBF1 recruitment. An in vitro GBF1 recruitment assay was established supporting Arf-GDP regulation of GBF1 membrane association.","method":"In vitro GBF1 recruitment assay (Golgi membranes), domain truncation analysis (in vivo and in vitro), heat/protease treatment of Golgi membranes, Arf-GDP localization mutants, ArfGAP siRNA knockdown","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — novel in vitro reconstitution assay combined with in vivo domain mapping and biochemical treatments, single lab","pmids":["29507113"],"is_preprint":false},{"year":2018,"finding":"Highly conserved residues RDR1168 and LF1266 within α-helices 2 and 6 of the HDS2 domain of GBF1 are critical for GBF1 activity. Alanine substitutions at these positions in BFA-resistant GBF1 compromise Golgi homeostasis, ARF activation, secretion, and cellular viability. These mutations significantly decrease GBF1 Golgi membrane targeting efficiency.","method":"BFA-resistant GBF1 replacement assay, alanine-scanning mutagenesis, ARF activation assay, secretion assay, Golgi morphology analysis, Golgi targeting quantification","journal":"American journal of physiology. Cell physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic alanine scanning with multiple functional readouts, single lab","pmids":["29443553"],"is_preprint":false},{"year":2018,"finding":"GBF1 is phosphorylated on Ser292 and Ser297 by casein kinase-2 in mitosis, allowing recognition and binding by the F-box protein βTrCP, which recruits GBF1 to the SCFβTrCP ubiquitin ligase complex and triggers GBF1 degradation. This phosphorylation-dependent degradation occurs along microtubules at the intercellular bridge of telophase cells and is required for Golgi membrane positioning and postmitotic Golgi reformation. A non-degradable GBF1 mutant inhibits Golgi cluster transport and causes cytokinesis failure.","method":"Phosphorylation site mapping (Ser292/Ser297), CK2 kinase assay, βTrCP co-immunoprecipitation, SCFβTrCP ubiquitin ligase assay, non-degradable GBF1 mutant expression, immunofluorescence, Golgi inheritance assay, cytokinesis assay","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — kinase identification, ubiquitin ligase complex, phosphorylation site mutant with in vivo functional consequences, multiple orthogonal methods, single lab","pmids":["29898406"],"is_preprint":false},{"year":2019,"finding":"GBF1 modulates ER-Golgi trafficking of von Willebrand factor (VWF) and extracellular matrix proteins in a selective, limiting-factor manner. GBF1 activation by AMPK couples anterograde trafficking to physiological cues (glucose levels); GBF1 modulates both ER exit and TGN exit of VWF, the latter affecting storage organelle size and hemostatic capacity. AMPK activation of GBF1 links cellular energy status to secretory pathway regulation.","method":"Golgi-associated protein screen, GBF1 level modulation, VWF trafficking assay, secretory granule size quantification, AMPK activation/inhibition experiments, glucose manipulation","journal":"Developmental cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional epistasis linking AMPK to GBF1 and VWF trafficking with multiple trafficking readouts, single lab","pmids":["31056345"],"is_preprint":false},{"year":2019,"finding":"C10orf76 is a GBF1 proximal/binding protein identified by BioID proximity biotinylation from enriched Golgi fractions. C10orf76 rapidly cycles on and off GBF1-positive Golgi structures. Its depletion causes Golgi fragmentation, alters GBF1 recruitment to Golgi, and impairs secretion.","method":"BioID proximity biotinylation + mass spectrometry from Golgi-enriched fractions, co-immunoprecipitation, siRNA knockdown, FRAP, secretion assay","journal":"Molecular & cellular proteomics : MCP","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — BioID proximity confirmed by co-IP, siRNA functional assay, single lab","pmids":["31519766"],"is_preprint":false},{"year":2019,"finding":"HCV NS3 (protease domain) physically interacts with the Sec7 domain of GBF1. This interaction was demonstrated by yeast two-hybrid, co-immunoprecipitation, and proximity ligation assays. NS3 overexpression interferes with GBF1 function and alters its intracellular localization. A reverse yeast two-hybrid screen identified an NS3 mutant (N77D/S77D) that neither interacts with GBF1 nor supports viral replication despite conserved protease activity, indicating the NS3-GBF1 interaction is required for HCV replication.","method":"Yeast two-hybrid (forward and reverse screen), co-immunoprecipitation, proximity ligation assay, NS3 mutagenesis, viral replication assay","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 / Strong — three independent interaction assays, domain mapping, reverse Y2H screen identifying separation-of-function mutant, single lab","pmids":["30567983"],"is_preprint":false},{"year":2019,"finding":"Multiple GBF1 mutants inactive in cellular trafficking (including Sec7 domain mutants) can still support poliovirus RNA replication. The Arf-activating property (but not specific Sec7 primary structure) is indispensable for viral replication. GBF1 is recruited to replication sites redundantly: via direct interaction with viral 3A protein and via determinants in the noncatalytic C-terminal domains of GBF1.","method":"Systematic GBF1 domain mutagenesis, BFA-resistant GBF1 replacement viral replication assay, 3A binding-deficient GBF1 mutant analysis","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic mutagenesis with viral replication functional read-out, single lab","pmids":["31375590"],"is_preprint":false},{"year":2021,"finding":"Src tyrosine kinase phosphorylates GBF1 on 10 tyrosine residues; phosphorylation of Y876 and Y898 (near the C-terminus of the Sec7 GEF domain) promotes GBF1 binding to Arf1 GTPase. Molecular modeling suggests partial melting of the Sec7 domain and intramolecular rearrangement upon phosphorylation. GBF1 mutants defective for Y876/Y898 phosphorylation prevent Arf1 binding, tubular carrier formation, and GALNTs retrograde relocation; phosphomimetic GBF1 mutants induce retrograde tubules.","method":"Src kinase assay, phosphopeptide identification by mass spectrometry, co-immunoprecipitation (GBF1-Arf1), phosphomimetic/phosphodeficient GBF1 mutants, live-cell imaging of retrograde tubules, GALNTs localization assay, molecular modeling","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro kinase identification, phosphomimetic/deficient mutagenesis with multiple orthogonal functional readouts, molecular modeling; single lab","pmids":["34870592"],"is_preprint":false},{"year":2021,"finding":"GBF1 activity is required for mouse oocyte meiotic maturation. GBF1 localizes to the spindle periphery during metaphase I. Inhibiting GBF1 activity causes aberrant Golgi accumulation around the spindle (condensation of GM130), disrupts ER distribution, induces ER stress (increased GRP78), alters mitochondrial membrane potential, and impairs polar body formation. GBF1 co-localizes with GM130 at the Golgi in oocytes.","method":"GBF1 inhibitor treatment (BFA/GCA), immunofluorescence, organelle morphology quantification, mitochondrial membrane potential assay, ER stress marker analysis","journal":"Microscopy and microanalysis","confidence":"Low","confidence_rationale":"Tier 3 / Weak — pharmacological inhibition only (not genetic), single lab, no mechanistic follow-up","pmids":["33478608"],"is_preprint":false},{"year":2022,"finding":"When poliovirus protein 3A engages GBF1, it renders GBF1 a functional hypomorph. Synthetic lethality screening identified ARF1 as the top synthetic lethal partner of GBF1 loss-of-function; disruption of ARF1 selectively killed cells synthesizing 3A alone or in the context of a poliovirus replicon, while leaving uninfected cells viable.","method":"Synthetic lethality screen, siRNA/genetic ARF1 disruption in 3A-expressing vs. uninfected cells, poliovirus replicon assay","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genome-wide synthetic lethality screen with functional validation, single lab","pmids":["36305789"],"is_preprint":false},{"year":2023,"finding":"Phosphorylation of specific conserved N-terminal residues of GBF1 (S233, S371, Y377, Y515) differentially regulates its role in cytokinesis versus Golgi homeostasis/secretion. Phosphomimetic GBF1 mutants (and S233A) are fully capable of maintaining Golgi architecture and supporting secretion, but cause multi-nucleation and inhibit progression through cytokinetic bridge resolution, revealing distinct phosphorylation-regulated interaction networks for GBF1 in different cellular processes.","method":"Phosphomimetic/phosphodeficient site-directed mutagenesis, Golgi homeostasis assay, cargo trafficking assay, cytokinesis assay (multi-nucleation), cell-cycle analysis","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic mutagenesis with separation-of-function phenotypes across two distinct cellular processes, single lab","pmids":["37604968"],"is_preprint":false},{"year":2024,"finding":"AMPK associates with the Golgi and its activation by pharmacological activators leads to Golgi fragmentation via GBF1 phosphorylation at Thr1337. Golgi disassembly upon AMPK activation is blocked in cells expressing a non-phosphorylatable GBF1-T1337A mutant (generated by gene editing). AMPK activation also delays trafficking of a plasma membrane-targeted protein through the Golgi complex.","method":"AMPK-α subunit gene knockouts, CRISPR gene editing (GBF1-T1337A knock-in), pharmacological AMPK activators, Golgi fragmentation quantification, cargo trafficking assay","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — CRISPR knock-in of phospho-deficient mutant combined with AMPK-α knockout and cargo trafficking assay, multiple orthogonal approaches, single lab","pmids":["39575556"],"is_preprint":false},{"year":2024,"finding":"Enterovirus 3A proteins (from EV-A71, CVB3, poliovirus, EV-D68) interact with GBF1 via N-terminal-conserved 3A residues, sequestering GBF1 and inhibiting ARF1 activation. This induces severe ER stress/UPR and apoptosis via the PERK/CHOP pathway. Pharmaceutical inhibition of PERK suppresses cell death caused by enterovirus infection. ER expansion and accumulation of ER-resident proteins were observed in infected cells.","method":"3A expression constructs, co-immunoprecipitation, ARF1 activation assay, ER morphology analysis by imaging, UPR/PERK/CHOP pathway markers (Western blot), PERK inhibitor treatment, cell viability assay","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus functional ARF1 activation, UPR marker analysis, and pharmacological rescue; single lab","pmids":["38904364"],"is_preprint":false},{"year":2024,"finding":"GBF1 deficiency in human lens epithelium cells activates XBP1s in the unfolded protein response (UPR) signaling pathway and enhances autophagy in an mTOR-independent manner. A heterozygous GBF1 mutation (T1287I) reduces GBF1 protein levels in human lens epithelium cells. Heterozygous Gbf1 knockout mice display a cataract phenotype.","method":"Genetic analysis, siRNA/shRNA knockdown in human lens epithelium cell line, Western blot for UPR markers (XBP1s), autophagy assay, Gbf1 heterozygous knockout mouse","journal":"Human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-based knockdown with UPR/autophagy functional readouts, knockout mouse phenotype, single lab","pmids":["39110251"],"is_preprint":false},{"year":2025,"finding":"Substrate stiffness stimulates conventional secretion through a Src-FAK-AMPK-GBF1 signaling axis. Phosphoproteomic analysis identified GBF1 as a mechano-responsive regulator. GBF1 phosphorylation state orchestrates post-Golgi cargo sorting, directing proteins toward secretion versus lysosomal degradation. AMPK acts as a stiffness-dependent upstream regulator of GBF1 phosphorylation.","method":"Substrate stiffness manipulation, phosphoproteomic analysis, Src/FAK inhibition, AMPK activation/inhibition, secretion assays, lysosomal degradation assays","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 / Weak — preprint, phosphoproteomic identification with limited mechanistic follow-up on GBF1 specifically; single lab","pmids":[],"is_preprint":true}],"current_model":"GBF1 is a large, multi-domain Sec7-family guanine nucleotide exchange factor (GEF) that cycles rapidly between the cytosol and cis-Golgi/ERGIC membranes, where it activates ARF1 (and other ARFs) by catalyzing GDP-to-GTP exchange to drive COPI vesicle coat recruitment for ER-Golgi and intra-Golgi trafficking; its membrane recruitment requires PI4P produced by PI4KIIIα and a Golgi-localized protein receptor involving HDS1 and HDS2 domains, is promoted by Rab1b (a GBF1 effector), and is stabilized by the inhibitory Arf-GDP–BFA–GBF1 complex; its membrane dissociation is triggered by its own catalytic activity; GBF1 is regulated at multiple levels by phosphorylation—CDK1-cyclin B and CK2 phosphorylate GBF1 for mitotic Golgi disassembly and degradation via SCFβTrCP respectively, AMPK phosphorylates GBF1 at Thr1337 to cause Golgi fragmentation and modulate anterograde trafficking in response to energy stress, and Src phosphorylates GBF1 at Y876/Y898 to promote retrograde Golgi-to-ER trafficking of glycosylation enzymes; GBF1 also interacts with Miro to regulate mitochondrial positioning via dynein-mediated retrograde transport, with ATGL and lipid droplets via HDS1/HDS2, with GGA adaptors for lysosomal cargo sorting, and with BIG1/BIG2 GEFs (through ARF4/5 activation) in a GEF cascade at the TGN; GBF1 is co-opted by numerous RNA viruses (enteroviruses, coronaviruses, HCV, HEV, dengue, reoviruses, phleboviruses) that rely on its membrane-remodeling activity for replication complex formation and/or function."},"narrative":{"mechanistic_narrative":"GBF1 is a large, multi-domain Sec7-family guanine nucleotide exchange factor that drives early secretory traffic by activating ARF GTPases on cis-Golgi and pre-Golgi membranes to nucleate COPI coat recruitment [PMID:10402461, PMID:16890159, PMID:18003980]. It cycles rapidly between cytosol and Golgi membranes (membrane half-life on the order of seconds), and each membrane-association event catalyzes a single ARF activation, with GBF1's own catalytic GDP-to-GTP exchange triggering its release; the BFA-stabilized ARF-GDP–GEF complex traps GBF1 on membranes by blocking this catalytic cycle [PMID:15616190, PMID:15813748]. Membrane recruitment depends on the C-terminal HDS1/HDS2 region binding a heat-labile Golgi protein receptor and PI4P generated by PI4KIIIα, is regulated by localized ARF-GDP, and is promoted by the GBF1 effector Rab1b [PMID:17429068, PMID:20530568, PMID:29507113, PMID:23943872]. Functionally, GBF1 is required for COPI-dependent transmembrane (but not soluble) cargo trafficking and Golgi subcompartmentalization; its loss tubulates the cis-Golgi, disperses COPI, and triggers an ER-stress/UPR program rather than Golgi collapse into ER [PMID:18003980, PMID:17956946, PMID:18287014]. GBF1 also feeds a GEF cascade in which its ARF4/ARF5 products recruit BIG1/BIG2 and GGA adaptors at the TGN to direct clathrin-coated, lysosomal-cargo sorting [PMID:23386609, PMID:17666033], and it organizes mitochondrial positioning through ARF1 and the mitochondrial protein Miro via dynein-dependent retrograde transport [PMID:30459446]. GBF1 activity is gated by phosphorylation that couples trafficking to cell state: CDK1-cyclin B and AMPK phosphorylation dissociate GBF1 from the Golgi to drive mitotic Golgi disassembly, CK2 phosphorylation at Ser292/Ser297 targets GBF1 to SCFβTrCP for degradation enabling postmitotic Golgi reformation and cytokinesis, AMPK phosphorylation at Thr1337 fragments the Golgi under energy stress, and Src phosphorylation at Y876/Y898 promotes ARF1 binding and retrograde Golgi-to-ER tubular transport of glycosylation enzymes [PMID:20175751, PMID:23418352, PMID:29898406, PMID:39575556, PMID:34870592]. A missense mutation in the HDS2 domain abolishes Golgi recruitment and ARF1 activation, causing ER-stress-driven endothelial apoptosis and vascular hemorrhage in zebrafish, and a heterozygous GBF1 mutation reducing protein levels produces UPR activation and a cataract phenotype, establishing GBF1 dysfunction as disease-causing [PMID:28003365, PMID:39110251]. Numerous RNA viruses co-opt GBF1 for replication-complex biogenesis: enterovirus 3A proteins directly bind and sequester GBF1 to block ARF1 activation, while diverse viruses (HCV, coronaviruses, dengue, others) depend on GBF1 activity—sometimes through its noncatalytic C-terminal domains independently of the canonical Sec7 COPI function [PMID:16890159, PMID:18551169, PMID:19906930, PMID:20497182, PMID:30567983, PMID:31375590].","teleology":[{"year":1998,"claim":"Establishing the molecular identity of GBF1 was the prerequisite for any mechanistic work, defining it as a ubiquitously expressed Sec7-domain protein with a distinct domain architecture.","evidence":"cDNA cloning, Northern blotting, and chromosomal mapping of human GBF1","pmids":["9828135"],"confidence":"Medium","gaps":["No enzymatic activity or substrate demonstrated","No localization or trafficking role established"]},{"year":1999,"claim":"The question of what GBF1 does biochemically was answered by showing it is a BFA-resistant ARF GEF on Golgi membranes, placing it in the COPI/ARF activation machinery.","evidence":"Expression cloning with in vitro GEF assay, immunogold EM, and overexpression conferring BFA-resistant Golgi morphology","pmids":["10402461"],"confidence":"High","gaps":["In vitro specificity (ARF5) did not resolve the physiological substrate","Mechanism of membrane recruitment unknown"]},{"year":2003,"claim":"Identifying p115 as a proline-rich-region partner connected GBF1 to membrane tethering, though it showed targeting of neither protein depends on the interaction.","evidence":"Yeast two-hybrid, in vitro binding, co-IP, and dominant-negative domain expression","pmids":["12634853"],"confidence":"High","gaps":["Functional consequence of the GBF1–p115 interaction for trafficking not defined","Single lab"]},{"year":2005,"claim":"Live-imaging and dominant-negative mutants resolved the catalytic cycle question: GBF1 turns over on membranes in seconds and its own exchange activity drives its release, defining one GBF1-membrane event per ARF activation.","evidence":"GFP-GBF1 FRAP with catalytically inactive E794K and ARF1-T31N mutants and BFA treatment","pmids":["15813748","15616190"],"confidence":"High","gaps":["Identity of the membrane recruitment receptor unknown","How catalysis triggers conformational release not structurally defined"]},{"year":2006,"claim":"Antibody microinjection directly linked GBF1 to COPI (but not COPII) recruitment in the early secretory pathway, distinguishing its compartment of action.","evidence":"GFP-GBF1 live imaging and anti-GBF1 antibody microinjection with COPI/COPII readouts","pmids":["16926190"],"confidence":"High","gaps":["ARF isoform(s) activated in vivo not pinned down","Recruitment determinants not mapped"]},{"year":2007,"claim":"siRNA and structural domain studies clarified that GBF1 specifically governs cis-Golgi COPI and transmembrane (not soluble) cargo traffic, that DCB/HUS domains mediate dimerization, and that loss triggers UPR rather than Golgi-to-ER collapse.","evidence":"siRNA depletion with cargo trafficking assays, DCB/HUS domain biochemistry and yeast complementation, and proteomic UPR analysis","pmids":["18003980","17956946","17640864","18287014"],"confidence":"High","gaps":["Basis of transmembrane vs soluble cargo selectivity unresolved","Mechanistic link from GBF1 loss to S2P/ATF6 activation not fully defined"]},{"year":2007,"claim":"Discovery of Rab1b and GGA interactions positioned GBF1 within an upstream regulatory and downstream adaptor network for membrane recruitment and lysosomal cargo sorting.","evidence":"Co-IP, FRAP, and siRNA for Rab1b effector role and GGA recruitment/cargo trafficking","pmids":["17429068","17666033"],"confidence":"High","gaps":["How Rab1b mechanistically stabilizes GBF1 not resolved here","Direct vs indirect nature of GGA recruitment unclear"]},{"year":2006,"claim":"Enterovirus 3A proteins were shown to directly target GBF1, establishing GBF1 as a host factor co-opted/inhibited by viruses and providing a tool to dissect GBF1 domains.","evidence":"Co-IP, COPI recruitment and transport assays, chimeric 3A swaps, and mouse virulence","pmids":["16890159","17005635","17329336"],"confidence":"High","gaps":["Structural basis of the 3A–GBF1 N-terminal interaction not solved","Whether 3A binding fully recapitulates physiological GBF1 regulation unclear"]},{"year":2009,"claim":"Multiple virus systems established that GBF1 is required for RNA replication, and that some viruses use GBF1 functions distinct from canonical COPI-vesicle formation.","evidence":"siRNA, Golgicide A, BFA-resistant GBF1 rescue, and replicon assays across CVB3 and HCV","pmids":["19740986","19906930"],"confidence":"High","gaps":["Precise GBF1 activity required at the replication complex not defined","Whether ARF activation is always the operative step unclear"]},{"year":2010,"claim":"Domain-dissection rescue of poliovirus replication by the noncatalytic GBF1 N-terminus revealed a Sec7-independent viral support function, separating GBF1's trafficking role from its viral role.","evidence":"BFA-resistant N-terminal fragment rescue and p115/Rab1b knockdown in poliovirus replication","pmids":["20497182"],"confidence":"High","gaps":["Molecular activity of the N-terminal fragment at replication sites unknown","How GBF1 supports replication without exchange activity unresolved"]},{"year":2010,"claim":"Identification of PI4KIIIα/PI4P as a recruitment requirement and CDK1-cyclin B as a mitotic kinase began to explain how GBF1 membrane association is spatially and cell-cycle regulated.","evidence":"PI4P inhibitors/biosensor and PI4KIIIα depletion; in vitro CDK1 kinase assay with fractionation","pmids":["20530568","20175751"],"confidence":"Medium","gaps":["Whether PI4P binding is direct to GBF1 not shown","CDK1 phosphosites not fully mapped to mechanism"]},{"year":2013,"claim":"Biochemical reconstitution localized lipid-binding to an HDS1 amphipathic helix and showed the Sec7 domain restrains it, defining how GBF1 engages Golgi membranes and lipid droplets.","evidence":"In vitro liposome/artificial lipid droplet binding with domain mutagenesis validated in cells","pmids":["23943872","21789191"],"confidence":"High","gaps":["Identity of the proteinaceous Golgi receptor still unknown at this stage","Regulation of HDS1 exposure in the full-length protein unresolved"]},{"year":2013,"claim":"Epistasis placed GBF1 upstream of BIG1/BIG2 via ARF4/ARF5, defining a GEF cascade extending GBF1's reach to the TGN clathrin-adaptor machinery.","evidence":"ARF isoform-specific siRNA epistasis and immunoEM localization across Golgi compartments","pmids":["23386609"],"confidence":"High","gaps":["Direct vs indirect basis of BIG recruitment by ARF4/5 not biochemically resolved","Spatial organization of the cascade not defined"]},{"year":2013,"claim":"AMPK phosphorylation of GBF1 during mitosis was identified as an energy- and cell-cycle-coupled control of GBF1 membrane association and Golgi disassembly.","evidence":"Cell synchronization, AMPK kinase assays on GBF1, and Golgi fragmentation readouts","pmids":["23418352"],"confidence":"Medium","gaps":["Phosphosite not mapped in this study","Mechanism by which phosphorylation abolishes GEF activity unclear"]},{"year":2016,"claim":"A zebrafish HDS2 missense mutation tied loss of Golgi recruitment and ARF1 activation to ER-stress-driven endothelial apoptosis, providing in vivo disease-relevant proof of GBF1's secretory function.","evidence":"ENU screen, positional cloning, and cell-based Golgi recruitment/ARF1/COPI assays with ER-stress markers and rescue","pmids":["28003365"],"confidence":"High","gaps":["Whether the human ortholog causes analogous vascular disease not addressed","Precise HDS2 recruitment mechanism not structurally defined"]},{"year":2018,"claim":"An in vitro recruitment assay plus domain mapping established that HDS1/HDS2 and a heat-labile Golgi protein receptor, gated by ARF-GDP localization, control GBF1 membrane association.","evidence":"In vitro Golgi-membrane recruitment assay, truncation analysis, protease/heat treatment, and ArfGAP siRNA","pmids":["29507113","29443553"],"confidence":"High","gaps":["Molecular identity of the Golgi receptor not determined","How ARF-GDP localization is read out by GBF1 unresolved"]},{"year":2018,"claim":"CK2-dependent phosphorylation at Ser292/Ser297 was shown to recruit βTrCP and target GBF1 for SCFβTrCP degradation, coupling GBF1 turnover to postmitotic Golgi reformation and cytokinesis.","evidence":"Phosphosite mapping, CK2 kinase assay, βTrCP co-IP, ubiquitin ligase assay, and non-degradable mutant phenotypes","pmids":["29898406"],"confidence":"High","gaps":["How localized degradation at the intercellular bridge is spatially restricted not fully defined","Interplay with other mitotic phospho-controls unresolved"]},{"year":2018,"claim":"Reciprocal co-IP and live imaging revealed that GBF1–ARF1–Miro controls mitochondrial positioning, extending GBF1 function beyond classical secretory traffic.","evidence":"GBF1–Miro and ARF1–Miro co-IP, GBF1 inhibition, dynein/Miro perturbation, and mitochondrial movement tracking","pmids":["30459446"],"confidence":"High","gaps":["Whether GBF1 acts on Miro directly or via ARF1 effectors unclear","Connection to canonical Golgi pool not defined"]},{"year":2019,"claim":"Proximity proteomics and direct interaction studies expanded the GBF1 interactome (C10orf76, HCV NS3) and linked AMPK-GBF1 to physiological cargo (VWF, ECM) trafficking.","evidence":"BioID/MS with co-IP and FRAP for C10orf76; Y2H/co-IP/PLA for NS3; trafficking assays with AMPK/glucose manipulation for VWF","pmids":["31519766","30567983","31056345"],"confidence":"Medium","gaps":["Mechanistic role of C10orf76 in GBF1 recruitment incompletely defined","AMPK phosphosite governing VWF trafficking not mapped here"]},{"year":2021,"claim":"Src phosphorylation of GBF1 at Y876/Y898 was shown to promote ARF1 binding and drive retrograde tubular transport of glycosylation enzymes, defining a phospho-switch that redirects GBF1 output.","evidence":"Src kinase assay, phosphopeptide MS, GBF1–ARF1 co-IP, phosphomimetic/deficient mutants, live imaging, and molecular modeling","pmids":["34870592"],"confidence":"High","gaps":["Structural model of Sec7 melting awaits experimental structure","How retrograde vs anterograde decision is integrated with other phospho-inputs unclear"]},{"year":2024,"claim":"CRISPR knock-in of a phospho-deficient GBF1-T1337A mutant established AMPK-Thr1337 phosphorylation as the operative event for energy-stress Golgi fragmentation and slowed anterograde traffic.","evidence":"AMPK-α knockouts, GBF1-T1337A knock-in, AMPK activators, and Golgi fragmentation/cargo trafficking assays","pmids":["39575556"],"confidence":"High","gaps":["How a single phosphosite triggers Golgi fragmentation mechanistically not resolved","Relationship of Thr1337 to mitotic AMPK control unclear"]},{"year":2024,"claim":"Separation-of-function phosphomutants and a human mutation/knockout mouse linked GBF1 to distinct cytokinesis vs secretion roles and to UPR/autophagy and a cataract disease phenotype.","evidence":"Phosphomimetic/deficient mutagenesis with cytokinesis/Golgi assays; knockdown with XBP1s/autophagy readouts and Gbf1 heterozygous knockout mice","pmids":["37604968","39110251"],"confidence":"Medium","gaps":["Interaction networks distinguishing the two functional modes not fully identified","Causal chain from reduced GBF1 to cataract not mechanistically complete"]},{"year":2024,"claim":"Enterovirus 3A sequestration of GBF1 was shown to induce PERK/CHOP-driven ER stress and apoptosis, and synthetic lethality screening identified ARF1 as the dominant dependency of GBF1 hypomorphism.","evidence":"3A expression with co-IP/ARF1 activation, UPR markers, PERK inhibitor rescue; synthetic lethality screen with ARF1 disruption in 3A-expressing cells","pmids":["38904364","36305789"],"confidence":"Medium","gaps":["Whether ARF1 is the sole essential GBF1 substrate in all contexts unclear","Generality of PERK/CHOP induction across GBF1 loss-of-function modes not established"]},{"year":null,"claim":"The identity of the heat-labile Golgi protein receptor that recruits GBF1 and a high-resolution structure of full-length GBF1 explaining how phosphorylation and lipid binding gate Sec7 catalysis remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No molecular identity for the Golgi recruitment receptor","No experimental full-length or Sec7-conformational structure tying phospho-switches to catalysis","Integration of the many phospho-inputs into a unified regulatory logic not established"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,3,4,28]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[29,24,26]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[10,28]}],"localization":[{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[0,5,6,11,28]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,3,4]},{"term_id":"GO:0005811","term_label":"lipid droplet","supporting_discovery_ids":[24,29]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[5,16]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[0,6,11,12]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[10,11,28]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[22,30,40,48]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[14,34,49,50]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[6,15,18,34,51]}],"complexes":["SCFβTrCP (substrate)","GBF1–Arf4–rhodopsin complex"],"partners":["ARF1","RAB1B","P115","ATGL","MIRO","C10ORF76","ARF4"],"other_free_text":[]}},"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 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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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reports","url":"https://pubmed.ncbi.nlm.nih.gov/37604968","citation_count":1,"is_preprint":false},{"pmid":"39110251","id":"PMC_39110251","title":"GBF1 deficiency causes cataracts in human and mouse.","date":"2024","source":"Human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/39110251","citation_count":0,"is_preprint":false},{"pmid":"39766823","id":"PMC_39766823","title":"A Novel GBF1 Variant in a Charcot-Marie-Tooth Type 2: Insights from Familial Analysis.","date":"2024","source":"Genes","url":"https://pubmed.ncbi.nlm.nih.gov/39766823","citation_count":0,"is_preprint":false},{"pmid":"16318580","id":"PMC_16318580","title":"Development of monoclonal antibodies against GBF1 and their use in studying its functions.","date":"2005","source":"Journal of interferon & cytokine research : the official journal of the International Society for Interferon and Cytokine Research","url":"https://pubmed.ncbi.nlm.nih.gov/16318580","citation_count":0,"is_preprint":false},{"pmid":"41988936","id":"PMC_41988936","title":"Intracellular protein GBF1 displays significant associations with amyloid pathology in Alzheimer's disease.","date":"2026","source":"Alzheimer's & dementia : the journal of the Alzheimer's Association","url":"https://pubmed.ncbi.nlm.nih.gov/41988936","citation_count":0,"is_preprint":false},{"pmid":"32595956","id":"PMC_32595956","title":"A miRNA screen procedure identifies garz as an essential factor in adult glia functions and validates Drosophila as a beneficial 3Rs model to study glial functions and GBF1 biology.","date":"2020","source":"F1000Research","url":"https://pubmed.ncbi.nlm.nih.gov/32595956","citation_count":0,"is_preprint":false},{"pmid":"41743235","id":"PMC_41743235","title":"Broad-spectrum antiviral activity of antisense oligonucleotides targeting GBF1 against SARS-CoV-2 and influenza viruses.","date":"2026","source":"iScience","url":"https://pubmed.ncbi.nlm.nih.gov/41743235","citation_count":0,"is_preprint":false},{"pmid":"27598219","id":"PMC_27598219","title":"Correction: Phosphorylation Affects DNA-Binding of the Senescence-Regulating bZIP Transcription Factor GBF1. 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":40880,"output_tokens":15083,"usd":0.174443,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":27455,"output_tokens":7582,"usd":0.163412,"stage2_stop_reason":"end_turn"},"total_usd":0.337855,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1999,\n      \"finding\": \"GBF1 was identified as a novel Golgi-associated guanine nucleotide exchange factor (GEF) with a Sec7 domain that exhibits BFA-resistant guanine nucleotide exchange activity with apparent specificity toward ARF5 at physiological Mg2+ concentrations. Overexpression conferred BFA resistance on Golgi morphology and ARF activation/COPI recruitment. GBF1 is primarily cytosolic but a significant pool co-localizes with COPI beta-subunit at a perinuclear structure and by immunogold labeling to Golgi cisternae and smooth vesiculotubular structures.\",\n      \"method\": \"Expression cloning, hexahistidine-tagged in vitro GEF activity assay, immunofluorescence, immunogold EM, subcellular fractionation\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro GEF activity assay, direct overexpression functional rescue, multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"10402461\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Human GBF1 encodes a 206.5 kDa protein containing a centrally positioned Sec7 domain and a proline-rich C-terminal region. Its mRNA is expressed ubiquitously across 17 tissues. The gene maps to chromosomal locus 10q24 and the Sec7 domain-encoding region harbors four introns.\",\n      \"method\": \"cDNA cloning, Northern blotting, chromosomal mapping (YAC, radiation hybrid)\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct sequencing and expression analysis, single lab, multiple orthogonal methods for mapping/expression\",\n      \"pmids\": [\"9828135\"],\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 interaction was identified by yeast two-hybrid and confirmed by in vitro binding and co-immunoprecipitation. The two proteins co-localize in the Golgi and peripheral VTCs. Expression of the p115-binding (pro-rich) region of GBF1 caused Golgi disruption, demonstrating functional relevance, but the interaction was not required for targeting either protein to membranes.\",\n      \"method\": \"Yeast two-hybrid screen, in vitro binding assay, co-immunoprecipitation, immunofluorescence, domain mutagenesis\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal biochemical assays (Y2H, in vitro binding, co-IP) plus functional dominant-negative domain expression, single lab\",\n      \"pmids\": [\"12634853\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"GBF1 cycles rapidly on and off Golgi membranes (fast turnover by FRAP), and BFA, which forms an Arf-GDP–GEF inhibitory complex, stabilizes GBF1 on Golgi membranes. Using an in vivo Arf1-GTP reporter assay, GBF1 exchange activity on Arf1 was shown to be inhibited by BFA in mammalian cells, consistent with formation of an Arf1–GBF1–BFA ternary complex with longer membrane residence.\",\n      \"method\": \"YFP-GBF1 FRAP, in vivo Arf1-GTP level assay, BFA treatment\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — quantitative live-imaging FRAP combined with in vivo GEF activity assay, replicated conceptually in multiple subsequent studies\",\n      \"pmids\": [\"15616190\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"GBF1 rapidly cycles between membranes and cytosol with t½ ~17 s. GBF1 is stabilized on membranes when complexed with ARF-GDP (shown by inactive E794K GBF1 mutant, ARF1-T31N mutant, or BFA). GBF1 dissociation from ARF and membranes is triggered by its catalytic activity (GDP displacement and GTP binding to ARF), implying that each GBF1 membrane association catalyzes a single ARF activation event.\",\n      \"method\": \"GFP-GBF1 FRAP, expression of catalytically inactive GBF1-E794K mutant, ARF1-T31N expression, BFA treatment\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal approaches (FRAP + dominant-negative mutants + drug) in a single study, mechanistically rigorous\",\n      \"pmids\": [\"15813748\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"GBF1 localizes to both Golgi membranes and peripheral puncta near but separate from ER exit sites, associating dynamically with both. BFA causes accumulation of GBF1 on these membranes before redistribution to ER in a microtubule-dependent manner. Microinjection of anti-GBF1 antibodies specifically caused dissociation of COPI from membranes, demonstrating that GBF1 regulates COPI membrane recruitment in the early secretory pathway. GBF1 recruitment to cargo-containing peripheral puncta coincided with COPI but not COPII recruitment.\",\n      \"method\": \"GFP-GBF1 live-cell imaging, FRAP, diffusion coefficient measurement, subcellular fractionation, anti-GBF1 antibody microinjection, immunofluorescence\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — antibody microinjection directly linking GBF1 to COPI recruitment, supported by multiple orthogonal localization and functional methods\",\n      \"pmids\": [\"16926190\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The enterovirus CVB3 3A protein inhibits ARF1 activation by directly binding to GBF1 at its N-terminus, thereby blocking GBF1-mediated COP-I coat complex recruitment to membranes and inhibiting ER-to-Golgi transport. This mechanism is specific to GBF1 (not BIG1/BIG2) and viral mutants defective in this function are less virulent in mice.\",\n      \"method\": \"Co-immunoprecipitation, dominant-negative ARF1 expression, BFA resistance assay in MDCK cells, siRNA knockdown, mouse virulence assay, electron microscopy\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (co-IP, genetic rescue, in vivo virulence), replicated in multiple subsequent studies\",\n      \"pmids\": [\"16890159\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Among multiple picornavirus 3A proteins tested, only enterovirus (CVB3 and poliovirus) 3A proteins inhibit COP-I recruitment via GBF1 binding. The N-terminal residues of CVB3 3A are critical for GBF1 binding; chimeric HRV 3A proteins with CVB3 N-termini gain the ability to bind GBF1 and inhibit transport. Other picornavirus 3A proteins (HRV, EMCV, FMDV, HAV) fail to bind GBF1 or inhibit COP-I recruitment.\",\n      \"method\": \"Co-immunoprecipitation, COP-I recruitment assay, protein transport assay, chimeric protein analysis\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — systematic domain-swap mutagenesis across multiple virus species, replicated by two independent labs\",\n      \"pmids\": [\"17005635\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The 3A protein of CVB3 must form homodimers to bind GBF1 and trap it on membranes. A conserved region in the N-terminus of 3A is required for GBF1 binding but not dimerization. In GBF1, the extreme N-terminus, the dimerization/cyclophilin binding (DCB) domain, and the homology upstream of Sec7 (HUS) domain are all required for the interaction with viral 3A. A GBF1 mutant lacking its extreme N-terminus cannot rescue the effects of 3A overexpression.\",\n      \"method\": \"Mutagenesis of 3A and GBF1, co-immunoprecipitation, functional rescue assay\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — systematic mutagenesis of both interaction partners with functional read-out, multiple orthogonal methods\",\n      \"pmids\": [\"17329336\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Rab1b GTPase directly interacts with GBF1 through GBF1's N-terminal domain, identifying GBF1 as a Rab1b effector. Active Rab1b (Rab1bQ67L) increases GBF1 and COPI association with peripheral ER exit site structures, stabilizes Arf1 on Golgi membranes, and Rab1b siRNA reduces GBF1 membrane association.\",\n      \"method\": \"Co-immunoprecipitation, GFP-Rab1b live imaging, FRAP, siRNA knockdown, immunofluorescence\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal interaction shown, supported by live-cell FRAP and siRNA functional experiments, single lab\",\n      \"pmids\": [\"17429068\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"GBF1 colocalizes with GGA adaptor proteins on Golgi membranes and physically interacts with GGAs. Depletion of GBF1 or expression of its inactive mutant prevents GGA recruitment to Golgi membranes and results in improper lysosomal cargo sorting (mannose 6-phosphate receptor and sortilin trafficking).\",\n      \"method\": \"siRNA knockdown, inactive GBF1 mutant expression, co-immunoprecipitation, immunofluorescence, cargo trafficking assay\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus siRNA/dominant-negative functional assay, single lab\",\n      \"pmids\": [\"17666033\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"GBF1 regulates COPI recruitment specifically on cis-Golgi compartments (while BIGs regulate adaptors on trans-Golgi). GBF1 knockdown/COPI knockdown does not prevent ER export of VSVGtsO45 but causes its accumulation in peripheral vesiculotubular clusters, and is required for Golgi subcompartmentalization and cargo progression to the cell surface. GBF1 is required for transmembrane but not soluble protein secretion.\",\n      \"method\": \"siRNA knockdown, VSVGtsO45 trafficking assay, immunofluorescence\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — complementary overexpression and knockdown with defined cargo readouts, replicated across multiple studies\",\n      \"pmids\": [\"18003980\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"siRNA-mediated depletion of GBF1 causes COPI dispersal but, unlike BFA treatment or expression of inactive ARF, does not cause Golgi collapse into ER. Instead, GBF1 depletion causes extensive tubulation of the cis-Golgi with connections to peripheral ERGIC sites. GBF1 depletion dramatically inhibits transmembrane protein trafficking but soluble proteins continue to be secreted, showing cargo-type specificity.\",\n      \"method\": \"siRNA knockdown, live-cell imaging, immunofluorescence, cargo trafficking assays (soluble and transmembrane)\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — siRNA with multiple orthogonal cargo assays, replicated by Manolea et al. same year\",\n      \"pmids\": [\"17956946\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The DCB domains of GBF1, BIG1, and BIG2 mediate homodimerization of each GEF, and an intramolecular interaction between DCB and HUS domains (mediated by the conserved HUS box) determines the architecture of the N-terminal regulatory region. Both DCB and HUS domains are necessary for GBF1 dimerization in mammalian cells, and the DCB domain is essential for yeast viability.\",\n      \"method\": \"Yeast two-hybrid, biochemical pulldown assays, cellular dimerization assay, yeast complementation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — combination of in vitro biochemistry, yeast two-hybrid, and cell-based assays; yeast essentiality confirms functional importance\",\n      \"pmids\": [\"17640864\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"GBF1 depletion by siRNA causes cell-cycle arrest in G0/G1, dispersal of Golgi markers (beta-COP, GM130), induction of ER stress proteins (calreticulin, PDI), and upregulation of UPR chaperones. GBF1 depletion specifically induces relocation of the site-2 protease S2P from Golgi to ER and proteolysis of ATF6, mimicking a UPR response. BIG1 or BIG2 depletion did not reproduce these effects.\",\n      \"method\": \"siRNA knockdown, cell-cycle analysis, immunofluorescence, quantitative proteomics, Western blotting\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA specificity established by three different GEF knockdowns, proteomic analysis plus functional assays, single lab\",\n      \"pmids\": [\"18287014\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"MHV coronavirus RNA replication requires GBF1-mediated ARF1 activation. Individual siRNA knockdown of GBF1 (but not BIG1 or BIG2) significantly inhibited MHV RNA replication. ARF1 siRNA also inhibited MHV infection. BFA did not block RC formation per se but reduced RC number. MHV was BFA-insensitive in MDCK cells expressing BFA-resistant GBF1.\",\n      \"method\": \"siRNA knockdown (individual targets), BFA pharmacological inhibition in MDCK cells with BFA-resistant GBF1, immunofluorescence, quantitative electron microscopy\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal approaches including siRNA, BFA-resistant GBF1 rescue, EM quantification; replicated conceptually across multiple viruses\",\n      \"pmids\": [\"18551169\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"GDP-bound class II Arfs (Arf4, Arf5) associate with ERGIC membranes independently of GBF1. After BFA treatment, Arf1 and Arf3 dissociate from endomembranes while Arf4 and Arf5 persist on ERGIC. A GDP-arrested Arf4(T31N) localizes to ERGIC even with BFA and Exo1 present. Loss of Arf-GTP (by Exo1) causes GBF1 accumulation on Golgi and ERGIC membranes, suggesting GBF1 accumulation can be triggered by loss of Arf-GTP rather than only by Arf-GDP–BFA–GBF1 complex formation.\",\n      \"method\": \"Live-cell imaging of fluorescently tagged Arfs and GBF1, BFA and Exo1 pharmacological treatments, dominant-negative Arf4(T31N) expression\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — live-cell imaging with pharmacological and genetic tools, single lab\",\n      \"pmids\": [\"18524849\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"CVB3 RNA replication critically requires GBF1. siRNA knockdown of GBF1 inhibited viral RNA replication; overexpression of active but not inactive GBF1 rescued replication in BFA-treated cells. The BFA-resistant GBF1-M832L efficiently rescued both wt and 3A-mutant replicons. BFA-resistant GBF1-A795E rescued wt but not 3A-GBF1 binding-deficient replicons. Overexpression of Arf proteins or Rab1B failed to rescue replication in the presence of BFA.\",\n      \"method\": \"siRNA knockdown, BFA-resistant GBF1 overexpression rescue, subgenomic replicon assay, viral RNA replication quantification\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — systematic rescue assay with multiple GBF1 mutants, siRNA knockdown, replicated across multiple virus families\",\n      \"pmids\": [\"19740986\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"GBF1 is required for HCV RNA replication. Individual siRNA knockdown of GBF1 (but not BIG1 or BIG2) and the GBF1-specific inhibitor Golgicide A inhibited HCV replication. Overexpression of BFA-resistant GBF1 rescued HCV replication in BFA-treated cells. BFA did not block membranous web-like structure formation, suggesting GBF1 is involved in replication complex activity rather than formation.\",\n      \"method\": \"siRNA knockdown, specific pharmacological inhibitor (Golgicide A), BFA-resistant GBF1 rescue, immunofluorescence, electron microscopy\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — three independent approaches (siRNA, GCA, BFA-resistant rescue), replicated by subsequent studies\",\n      \"pmids\": [\"19906930\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"In Drosophila, garz (the GBF1 ortholog) functions in the pinocytic GEEC (GPI-AP enriched early endosomal compartment) pathway for clathrin-independent endocytosis. Live confocal and TIRF imaging show a fraction of GBF1-GFP dynamically associates with activated Arf1-positive nascent pinosomes. A GTP-exchange-deficient GBF1 mutant impairs fluid phase uptake. GBF1 activation is required for the GEEC pathway even in the presence of BFA, indicating a role in endocytosis separable from its role in secretion.\",\n      \"method\": \"RNAi knockdown in Drosophila cells, live confocal/TIRF imaging, quantitative fluid-phase uptake assay, GTP-exchange-deficient mutant expression\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — live imaging plus functional mutant plus quantitative uptake assay; ortholog study, single lab\",\n      \"pmids\": [\"19707569\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"For poliovirus replication, GBF1's N-terminal region (lacking the catalytic Sec7 domain) is sufficient to rescue replication in BFA-treated cells. In poliovirus-infected cells, p115 (a normal GBF1 modulator) is degraded and neither p115 nor Rab1b knockdown affects virus replication, indicating that GBF1 supports viral replication through functions distinct from its canonical Arf-activating role in COPI vesicle formation.\",\n      \"method\": \"BFA-resistant GBF1 domain rescue assay (N-terminal fragment lacking Sec7), siRNA knockdown of p115 and Rab1b, viral replication assay\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — domain dissection rescue assay directly demonstrates Sec7-independent viral function; combined with siRNA knockdown, single lab\",\n      \"pmids\": [\"20497182\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The phosphatidylinositol 4-kinase PI4KIIIα is required for GBF1 recruitment to Golgi membranes. Inhibitors of PI4P synthesis or depletion of PI4KIIIα prevents GBF1 recruitment to the Golgi. Dominant-active Rab1b increases PI4P levels at the Golgi as detected by GFP-PH sensor, suggesting Rab1b contributes to GBF1 recruitment through activation of PI4KIIIα and subsequent PI4P production.\",\n      \"method\": \"PI4P synthesis inhibitors, siRNA knockdown of PI4KIIIα, GFP-PH PI4P biosensor, dominant-active Rab1b expression, immunofluorescence\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological and genetic depletion plus biosensor, single lab\",\n      \"pmids\": [\"20530568\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"GBF1 is phosphorylated by CDK1-cyclin B in mitosis, which results in its dissociation from Golgi membranes. This is accompanied by a reduction in membrane-associated GTP-bound ARF in mitotic cells. Despite reduced GBF1 and ARF-GTP, COPI binding to Golgi appears unaffected but remains GBF1-dependent, suggesting a low level of GBF1 activity persists in mitosis.\",\n      \"method\": \"Identification of GBF1 as Golgi phosphoprotein, in vitro kinase assay with CDK1-cyclin B, phosphorylation site mapping, immunofluorescence, membrane fractionation, cell synchronization\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro kinase assay plus cell-based fractionation and co-immunoprecipitation; direct demonstration of CDK1 as the kinase, single lab\",\n      \"pmids\": [\"20175751\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"C. trachomatis selectively co-opts GBF1 (not BIG1 or BIG2) for vesicle-mediated sphingomyelin (SM) acquisition. The GBF1/Arf1-dependent pathway provides SM essential for inclusion membrane growth and stability but is not required for bacterial replication. A separate CERT-dependent non-vesicular ceramide transport pathway provides SM required for bacterial replication.\",\n      \"method\": \"siRNA knockdown of individual GEFs, BFA pharmacological inhibition, fluorescent lipid transport assays, inclusion growth/stability quantification, bacterial replication assay\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — selective siRNA knockdown of three GEFs with distinct functional readouts (SM acquisition, inclusion growth, bacterial replication), multiple orthogonal assays\",\n      \"pmids\": [\"21909260\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"GBF1 and ATGL (adipose triglyceride lipase) interact directly and in cells. Yeast two-hybrid, co-immunoprecipitation, and direct protein binding assays demonstrate interaction through multiple contact sites. The C-terminal region of ATGL interacts with N-terminal domains of GBF1 including the Sec7 domain (but not full-length GBF1). The ATGL patatin domain interacts with GBF1's HDS1 and HDS2 C-terminal domains. HDS1 and HDS2 expressed alone localize to lipid droplets but not Golgi, unlike full-length GBF1.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation in mammalian cells, direct protein binding, fluorescence microscopy\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — three orthogonal interaction methods (Y2H, co-IP, direct binding) with domain mapping, single lab\",\n      \"pmids\": [\"21789191\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"In Drosophila, loss of garz (GBF1 ortholog) impairs Golgi complex integrity, disrupts vesicle transport of cargo proteins and directed apical membrane delivery, and perturbs polarized epithelial architecture of tubular organs (salivary glands, trachea, proventriculus, hindgut). These phenotypes are caused by dysfunction of the Arf1-COPI machinery.\",\n      \"method\": \"Drosophila loss-of-function mutant analysis (EMS and targeted), immunofluorescence, electron microscopy, cargo trafficking assays in embryos\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo loss-of-function in Drosophila with multiple phenotypic readouts, replicated across several tissue types\",\n      \"pmids\": [\"22302994\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"GBF1 bears a novel phosphatidylinositol-phosphate binding module (BP3K) that binds products of PI3Kγ. Upon GPCR stimulation in neutrophils, GBF1 is translocated from the Golgi to the leading edge to activate Arf1, which recruits p22phox and GIT2 to the leading edge. GBF1-mediated Arf1 activation is required for neutrophil chemotaxis and superoxide production, linking PI3Kγ activity with Arf1 activation.\",\n      \"method\": \"PI3P/PI4P binding assays, immunofluorescence (GBF1 localization on GPCR stimulation), siRNA knockdown, superoxide production assay, chemotaxis assay\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — lipid binding module identified biochemically, localization by imaging, function by siRNA/dominant-negative with defined readouts, single lab\",\n      \"pmids\": [\"22573891\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"GBF1 and ARF1 colocalize with PI4KIIIβ at HCV replication complexes. Both ARF1 and GBF1 are required for HCV replication; overexpression of PI4P phosphatase Sac1 inhibits HCV replication. PI4KIIIβ is required for HCV replication and co-localizes with the GBF1/ARF1 machinery, suggesting GBF1/ARF1 generates a PI4P-enriched environment supporting HCV replication.\",\n      \"method\": \"Immunofluorescence co-localization, siRNA knockdown, PI4P phosphatase overexpression, HCV replication assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-localization plus functional siRNA knockdown, single lab\",\n      \"pmids\": [\"22359663\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"GBF1-activated ARFs (specifically ARF4 and ARF5, but not ARF3) facilitate BIG1 and BIG2 recruitment to the TGN, establishing a functional cascade between GEFs. GBF1 is ultrastructurally localized to pre-Golgi, Golgi, and also TGN, and its activity at the TGN is required for subsequent BIG1/2 recruitment that coordinates clathrin adaptor coating events.\",\n      \"method\": \"siRNA knockdown, immunofluorescence, ultrastructural localization (immunoelectron microscopy), ARF isoform-specific knockdown\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA epistasis establishes functional cascade, supported by ultrastructural localization; single lab but multiple orthogonal approaches\",\n      \"pmids\": [\"23386609\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"GBF1 possesses a lipid-binding HDS1 domain immediately downstream of the catalytic Sec7 domain. An amphipathic helix within HDS1 is necessary and sufficient for binding to lipid droplets and Golgi membranes in cells and to bilayer liposomes and artificial lipid droplets in vitro. The catalytic Sec7 domain inhibits the potent lipid-droplet-binding capacity of HDS1. Additional sequences upstream of the Sec7-HDS1 tandem are required for Golgi membrane localization.\",\n      \"method\": \"In vitro liposome binding, in vitro artificial lipid droplet binding, GFP-tagged domain expression in cells, domain deletion/mutagenesis analysis\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution of lipid binding with mutagenesis validated in cells, multiple lipid-binding substrates tested\",\n      \"pmids\": [\"23943872\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"AMPK is phosphorylated and activated when cells enter mitosis. Activated AMPK phosphorylates GBF1, dissociating GBF1 from Golgi membranes and abolishing its Arf1-GEF activity. AMPK and GBF1 phosphorylation are essential for mitotic Golgi disassembly and subsequent mitosis entry.\",\n      \"method\": \"Cell synchronization, phosphorylation assays, kinase assays (AMPK on GBF1), immunofluorescence, Golgi fragmentation quantification, rescue/inhibition experiments\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — kinase assay linking AMPK to GBF1 phosphorylation plus functional mitotic assay, single lab\",\n      \"pmids\": [\"23418352\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"C. elegans GBF-1 localizes to the cis-Golgi and ER-Golgi elements. GBF-1 is required for secretion and Golgi integrity. Additionally, GBF-1 depletion disperses ER reticular structure (without destroying ER exit sites), reduces RAB-5-positive early endosomes, and causes accumulation of RAB-7-positive late endosomes, revealing a role in receptor-mediated endocytosis and endosomal traffic.\",\n      \"method\": \"RNAi knockdown in C. elegans oocytes and intestinal epithelial cells, immunofluorescence/confocal microscopy, endocytosis assays, organelle marker analysis\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo RNAi with multiple organelle readouts, ortholog model; single lab\",\n      \"pmids\": [\"23840591\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The GBF1-Arf1/Arf4-COPI pathway is necessary for dengue virus capsid transport from the ER membrane to lipid droplets (LDs). This process is independent of COPII components and Golgi integrity. A BFA-resistant form of GBF1 restores capsid distribution in infected cells treated with BFA, demonstrating GBF1 catalytic activity is required.\",\n      \"method\": \"BFA/drug treatment, BFA-resistant GBF1 rescue, COPII/Golgi disruption, immunofluorescence, siRNA knockdown of Arf1/Arf4\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — BFA-resistant rescue plus pharmacological and genetic perturbations, single lab\",\n      \"pmids\": [\"26031340\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"GBF1 oligomerization (mediated by DCB domain residues K91 and E130) is dispensable for Golgi localization, membrane cycling, Arf activation, COPI recruitment, Golgi homeostasis, and cargo secretion, and is not required for poliovirus RNA replication support. However, oligomerization stabilizes GBF1 in cells; the oligomerization-deficient 91/130 mutant is degraded faster than wild-type GBF1.\",\n      \"method\": \"Site-directed mutagenesis, FRAP, ARF activation assay, COPI recruitment assay, secretion assay, poliovirus replication assay, protein stability measurement\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional assays with a defined mutagenesis strategy, single lab\",\n      \"pmids\": [\"26718629\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"In zebrafish, a missense mutation (L1246R) in the HDS2 domain of gbf1 causes vascular hemorrhage. The mutant Gbf1(L1246R) cannot be recruited to the Golgi apparatus and fails to activate Arf1 for COPI complex recruitment, causing ER stress and endothelial apoptosis via PERK/CHOP. Hemorrhage can be partially prevented by ER stress inhibitor tauroursodeoxycholic acid or knockdown of proapoptotic baxb.\",\n      \"method\": \"ENU mutagenesis zebrafish screen, positional cloning, mammalian cell-based Golgi recruitment assay, Arf1 activation assay, COPI recruitment assay, ER stress marker analysis, rescue experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo zebrafish phenotype combined with mechanistic cell-based assays (Golgi recruitment, Arf1 activation, COPI recruitment) for specific HDS2 mutation\",\n      \"pmids\": [\"28003365\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"GBF1 forms a functional complex with Arf4 and the photoreceptor cargo rhodopsin at the Golgi/TGN during sensory membrane carrier biogenesis. Rhodopsin and Arf4 bind the regulatory N-terminal DCB-HUS domain of GBF1. The complex is sensitive to Golgicide A (GCA), which blocks rhodopsin delivery to cilia. Newly synthesized rhodopsin in the endomembrane system is essential for GBF1-Arf4 complex formation in vivo. GBF1 also interacts with Arf GAP ASAP1 in a GCA-resistant manner.\",\n      \"method\": \"Co-immunoprecipitation with recombinant human proteins, frog retina in vivo experiments, GCA inhibitor treatment, domain binding mapping\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP with domain mapping plus in vivo frog retina experiments, single lab\",\n      \"pmids\": [\"29025970\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"GBF1 is involved in the replication of yellow fever virus, Sindbis virus, coxsackievirus B4, and human coronavirus 229E. For HCV and some other viruses, class II Arfs (Arf4/Arf5) downstream of GBF1 are required; for CVB4, no single or paired Arf depletion inhibited replication, suggesting GBF1 supports viral replication through distinct Arf-dependent and Arf-independent mechanisms depending on the virus.\",\n      \"method\": \"siRNA and CRISPR-Cas9 Arf depletion (individual and paired), viral replication assays, GBF1 knockdown\",\n      \"journal\": \"The Journal of general virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR/siRNA systematic Arf depletion across multiple viruses, single lab\",\n      \"pmids\": [\"29923822\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"GBF1 and its substrate Arf1 regulate the spatial organization of mitochondria in a microtubule-dependent manner. GBF1 physically interacts with the mitochondrial membrane protein Miro; GTP-bound Arf1 also interacts with Miro. Inhibition of GBF1 causes collapse of the mitochondrial network toward the centrosome through a two-fold increase in time engaged in retrograde movement, dependent on dynein and Miro. GBF1 inhibition also results in larger mitochondria with more complex morphology.\",\n      \"method\": \"Co-immunoprecipitation (GBF1–Miro, Arf1–Miro), GBF1 pharmacological inhibition, immunofluorescence, electron tomography, mitochondrial movement tracking (live imaging), siRNA knockdown of Miro and dynein inhibition\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP for interaction, multiple functional perturbations with quantitative live-imaging readout, electron tomography for morphology, single lab\",\n      \"pmids\": [\"30459446\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"GBF1 recruitment to cis-Golgi membranes requires its HDS1 and HDS2 C-terminal domains and a heat-labile, protease-sensitive Golgi-localized protein receptor. Arf-GDP localization is critical for GBF1 recruitment, as a TGN-localized Arf-GDP mutant fails to promote GBF1 recruitment. ArfGAP2 and ArfGAP3 do not contribute to GBF1 recruitment. An in vitro GBF1 recruitment assay was established supporting Arf-GDP regulation of GBF1 membrane association.\",\n      \"method\": \"In vitro GBF1 recruitment assay (Golgi membranes), domain truncation analysis (in vivo and in vitro), heat/protease treatment of Golgi membranes, Arf-GDP localization mutants, ArfGAP siRNA knockdown\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — novel in vitro reconstitution assay combined with in vivo domain mapping and biochemical treatments, single lab\",\n      \"pmids\": [\"29507113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Highly conserved residues RDR1168 and LF1266 within α-helices 2 and 6 of the HDS2 domain of GBF1 are critical for GBF1 activity. Alanine substitutions at these positions in BFA-resistant GBF1 compromise Golgi homeostasis, ARF activation, secretion, and cellular viability. These mutations significantly decrease GBF1 Golgi membrane targeting efficiency.\",\n      \"method\": \"BFA-resistant GBF1 replacement assay, alanine-scanning mutagenesis, ARF activation assay, secretion assay, Golgi morphology analysis, Golgi targeting quantification\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic alanine scanning with multiple functional readouts, single lab\",\n      \"pmids\": [\"29443553\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"GBF1 is phosphorylated on Ser292 and Ser297 by casein kinase-2 in mitosis, allowing recognition and binding by the F-box protein βTrCP, which recruits GBF1 to the SCFβTrCP ubiquitin ligase complex and triggers GBF1 degradation. This phosphorylation-dependent degradation occurs along microtubules at the intercellular bridge of telophase cells and is required for Golgi membrane positioning and postmitotic Golgi reformation. A non-degradable GBF1 mutant inhibits Golgi cluster transport and causes cytokinesis failure.\",\n      \"method\": \"Phosphorylation site mapping (Ser292/Ser297), CK2 kinase assay, βTrCP co-immunoprecipitation, SCFβTrCP ubiquitin ligase assay, non-degradable GBF1 mutant expression, immunofluorescence, Golgi inheritance assay, cytokinesis assay\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — kinase identification, ubiquitin ligase complex, phosphorylation site mutant with in vivo functional consequences, multiple orthogonal methods, single lab\",\n      \"pmids\": [\"29898406\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"GBF1 modulates ER-Golgi trafficking of von Willebrand factor (VWF) and extracellular matrix proteins in a selective, limiting-factor manner. GBF1 activation by AMPK couples anterograde trafficking to physiological cues (glucose levels); GBF1 modulates both ER exit and TGN exit of VWF, the latter affecting storage organelle size and hemostatic capacity. AMPK activation of GBF1 links cellular energy status to secretory pathway regulation.\",\n      \"method\": \"Golgi-associated protein screen, GBF1 level modulation, VWF trafficking assay, secretory granule size quantification, AMPK activation/inhibition experiments, glucose manipulation\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional epistasis linking AMPK to GBF1 and VWF trafficking with multiple trafficking readouts, single lab\",\n      \"pmids\": [\"31056345\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"C10orf76 is a GBF1 proximal/binding protein identified by BioID proximity biotinylation from enriched Golgi fractions. C10orf76 rapidly cycles on and off GBF1-positive Golgi structures. Its depletion causes Golgi fragmentation, alters GBF1 recruitment to Golgi, and impairs secretion.\",\n      \"method\": \"BioID proximity biotinylation + mass spectrometry from Golgi-enriched fractions, co-immunoprecipitation, siRNA knockdown, FRAP, secretion assay\",\n      \"journal\": \"Molecular & cellular proteomics : MCP\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — BioID proximity confirmed by co-IP, siRNA functional assay, single lab\",\n      \"pmids\": [\"31519766\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"HCV NS3 (protease domain) physically interacts with the Sec7 domain of GBF1. This interaction was demonstrated by yeast two-hybrid, co-immunoprecipitation, and proximity ligation assays. NS3 overexpression interferes with GBF1 function and alters its intracellular localization. A reverse yeast two-hybrid screen identified an NS3 mutant (N77D/S77D) that neither interacts with GBF1 nor supports viral replication despite conserved protease activity, indicating the NS3-GBF1 interaction is required for HCV replication.\",\n      \"method\": \"Yeast two-hybrid (forward and reverse screen), co-immunoprecipitation, proximity ligation assay, NS3 mutagenesis, viral replication assay\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — three independent interaction assays, domain mapping, reverse Y2H screen identifying separation-of-function mutant, single lab\",\n      \"pmids\": [\"30567983\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Multiple GBF1 mutants inactive in cellular trafficking (including Sec7 domain mutants) can still support poliovirus RNA replication. The Arf-activating property (but not specific Sec7 primary structure) is indispensable for viral replication. GBF1 is recruited to replication sites redundantly: via direct interaction with viral 3A protein and via determinants in the noncatalytic C-terminal domains of GBF1.\",\n      \"method\": \"Systematic GBF1 domain mutagenesis, BFA-resistant GBF1 replacement viral replication assay, 3A binding-deficient GBF1 mutant analysis\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic mutagenesis with viral replication functional read-out, single lab\",\n      \"pmids\": [\"31375590\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Src tyrosine kinase phosphorylates GBF1 on 10 tyrosine residues; phosphorylation of Y876 and Y898 (near the C-terminus of the Sec7 GEF domain) promotes GBF1 binding to Arf1 GTPase. Molecular modeling suggests partial melting of the Sec7 domain and intramolecular rearrangement upon phosphorylation. GBF1 mutants defective for Y876/Y898 phosphorylation prevent Arf1 binding, tubular carrier formation, and GALNTs retrograde relocation; phosphomimetic GBF1 mutants induce retrograde tubules.\",\n      \"method\": \"Src kinase assay, phosphopeptide identification by mass spectrometry, co-immunoprecipitation (GBF1-Arf1), phosphomimetic/phosphodeficient GBF1 mutants, live-cell imaging of retrograde tubules, GALNTs localization assay, molecular modeling\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro kinase identification, phosphomimetic/deficient mutagenesis with multiple orthogonal functional readouts, molecular modeling; single lab\",\n      \"pmids\": [\"34870592\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"GBF1 activity is required for mouse oocyte meiotic maturation. GBF1 localizes to the spindle periphery during metaphase I. Inhibiting GBF1 activity causes aberrant Golgi accumulation around the spindle (condensation of GM130), disrupts ER distribution, induces ER stress (increased GRP78), alters mitochondrial membrane potential, and impairs polar body formation. GBF1 co-localizes with GM130 at the Golgi in oocytes.\",\n      \"method\": \"GBF1 inhibitor treatment (BFA/GCA), immunofluorescence, organelle morphology quantification, mitochondrial membrane potential assay, ER stress marker analysis\",\n      \"journal\": \"Microscopy and microanalysis\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — pharmacological inhibition only (not genetic), single lab, no mechanistic follow-up\",\n      \"pmids\": [\"33478608\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"When poliovirus protein 3A engages GBF1, it renders GBF1 a functional hypomorph. Synthetic lethality screening identified ARF1 as the top synthetic lethal partner of GBF1 loss-of-function; disruption of ARF1 selectively killed cells synthesizing 3A alone or in the context of a poliovirus replicon, while leaving uninfected cells viable.\",\n      \"method\": \"Synthetic lethality screen, siRNA/genetic ARF1 disruption in 3A-expressing vs. uninfected cells, poliovirus replicon assay\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genome-wide synthetic lethality screen with functional validation, single lab\",\n      \"pmids\": [\"36305789\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Phosphorylation of specific conserved N-terminal residues of GBF1 (S233, S371, Y377, Y515) differentially regulates its role in cytokinesis versus Golgi homeostasis/secretion. Phosphomimetic GBF1 mutants (and S233A) are fully capable of maintaining Golgi architecture and supporting secretion, but cause multi-nucleation and inhibit progression through cytokinetic bridge resolution, revealing distinct phosphorylation-regulated interaction networks for GBF1 in different cellular processes.\",\n      \"method\": \"Phosphomimetic/phosphodeficient site-directed mutagenesis, Golgi homeostasis assay, cargo trafficking assay, cytokinesis assay (multi-nucleation), cell-cycle analysis\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic mutagenesis with separation-of-function phenotypes across two distinct cellular processes, single lab\",\n      \"pmids\": [\"37604968\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"AMPK associates with the Golgi and its activation by pharmacological activators leads to Golgi fragmentation via GBF1 phosphorylation at Thr1337. Golgi disassembly upon AMPK activation is blocked in cells expressing a non-phosphorylatable GBF1-T1337A mutant (generated by gene editing). AMPK activation also delays trafficking of a plasma membrane-targeted protein through the Golgi complex.\",\n      \"method\": \"AMPK-α subunit gene knockouts, CRISPR gene editing (GBF1-T1337A knock-in), pharmacological AMPK activators, Golgi fragmentation quantification, cargo trafficking assay\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — CRISPR knock-in of phospho-deficient mutant combined with AMPK-α knockout and cargo trafficking assay, multiple orthogonal approaches, single lab\",\n      \"pmids\": [\"39575556\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Enterovirus 3A proteins (from EV-A71, CVB3, poliovirus, EV-D68) interact with GBF1 via N-terminal-conserved 3A residues, sequestering GBF1 and inhibiting ARF1 activation. This induces severe ER stress/UPR and apoptosis via the PERK/CHOP pathway. Pharmaceutical inhibition of PERK suppresses cell death caused by enterovirus infection. ER expansion and accumulation of ER-resident proteins were observed in infected cells.\",\n      \"method\": \"3A expression constructs, co-immunoprecipitation, ARF1 activation assay, ER morphology analysis by imaging, UPR/PERK/CHOP pathway markers (Western blot), PERK inhibitor treatment, cell viability assay\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus functional ARF1 activation, UPR marker analysis, and pharmacological rescue; single lab\",\n      \"pmids\": [\"38904364\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"GBF1 deficiency in human lens epithelium cells activates XBP1s in the unfolded protein response (UPR) signaling pathway and enhances autophagy in an mTOR-independent manner. A heterozygous GBF1 mutation (T1287I) reduces GBF1 protein levels in human lens epithelium cells. Heterozygous Gbf1 knockout mice display a cataract phenotype.\",\n      \"method\": \"Genetic analysis, siRNA/shRNA knockdown in human lens epithelium cell line, Western blot for UPR markers (XBP1s), autophagy assay, Gbf1 heterozygous knockout mouse\",\n      \"journal\": \"Human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-based knockdown with UPR/autophagy functional readouts, knockout mouse phenotype, single lab\",\n      \"pmids\": [\"39110251\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Substrate stiffness stimulates conventional secretion through a Src-FAK-AMPK-GBF1 signaling axis. Phosphoproteomic analysis identified GBF1 as a mechano-responsive regulator. GBF1 phosphorylation state orchestrates post-Golgi cargo sorting, directing proteins toward secretion versus lysosomal degradation. AMPK acts as a stiffness-dependent upstream regulator of GBF1 phosphorylation.\",\n      \"method\": \"Substrate stiffness manipulation, phosphoproteomic analysis, Src/FAK inhibition, AMPK activation/inhibition, secretion assays, lysosomal degradation assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — preprint, phosphoproteomic identification with limited mechanistic follow-up on GBF1 specifically; single lab\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"GBF1 is a large, multi-domain Sec7-family guanine nucleotide exchange factor (GEF) that cycles rapidly between the cytosol and cis-Golgi/ERGIC membranes, where it activates ARF1 (and other ARFs) by catalyzing GDP-to-GTP exchange to drive COPI vesicle coat recruitment for ER-Golgi and intra-Golgi trafficking; its membrane recruitment requires PI4P produced by PI4KIIIα and a Golgi-localized protein receptor involving HDS1 and HDS2 domains, is promoted by Rab1b (a GBF1 effector), and is stabilized by the inhibitory Arf-GDP–BFA–GBF1 complex; its membrane dissociation is triggered by its own catalytic activity; GBF1 is regulated at multiple levels by phosphorylation—CDK1-cyclin B and CK2 phosphorylate GBF1 for mitotic Golgi disassembly and degradation via SCFβTrCP respectively, AMPK phosphorylates GBF1 at Thr1337 to cause Golgi fragmentation and modulate anterograde trafficking in response to energy stress, and Src phosphorylates GBF1 at Y876/Y898 to promote retrograde Golgi-to-ER trafficking of glycosylation enzymes; GBF1 also interacts with Miro to regulate mitochondrial positioning via dynein-mediated retrograde transport, with ATGL and lipid droplets via HDS1/HDS2, with GGA adaptors for lysosomal cargo sorting, and with BIG1/BIG2 GEFs (through ARF4/5 activation) in a GEF cascade at the TGN; GBF1 is co-opted by numerous RNA viruses (enteroviruses, coronaviruses, HCV, HEV, dengue, reoviruses, phleboviruses) that rely on its membrane-remodeling activity for replication complex formation and/or function.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GBF1 is a large, multi-domain Sec7-family guanine nucleotide exchange factor that drives early secretory traffic by activating ARF GTPases on cis-Golgi and pre-Golgi membranes to nucleate COPI coat recruitment [#0, #6, #11]. It cycles rapidly between cytosol and Golgi membranes (membrane half-life on the order of seconds), and each membrane-association event catalyzes a single ARF activation, with GBF1's own catalytic GDP-to-GTP exchange triggering its release; the BFA-stabilized ARF-GDP\\u2013GEF complex traps GBF1 on membranes by blocking this catalytic cycle [#3, #4]. Membrane recruitment depends on the C-terminal HDS1/HDS2 region binding a heat-labile Golgi protein receptor and PI4P generated by PI4KIII\\u03b1, is regulated by localized ARF-GDP, and is promoted by the GBF1 effector Rab1b [#9, #21, #38, #29]. Functionally, GBF1 is required for COPI-dependent transmembrane (but not soluble) cargo trafficking and Golgi subcompartmentalization; its loss tubulates the cis-Golgi, disperses COPI, and triggers an ER-stress/UPR program rather than Golgi collapse into ER [#11, #12, #14]. GBF1 also feeds a GEF cascade in which its ARF4/ARF5 products recruit BIG1/BIG2 and GGA adaptors at the TGN to direct clathrin-coated, lysosomal-cargo sorting [#28, #10], and it organizes mitochondrial positioning through ARF1 and the mitochondrial protein Miro via dynein-dependent retrograde transport [#37]. GBF1 activity is gated by phosphorylation that couples trafficking to cell state: CDK1-cyclin B and AMPK phosphorylation dissociate GBF1 from the Golgi to drive mitotic Golgi disassembly, CK2 phosphorylation at Ser292/Ser297 targets GBF1 to SCF\\u03b2TrCP for degradation enabling postmitotic Golgi reformation and cytokinesis, AMPK phosphorylation at Thr1337 fragments the Golgi under energy stress, and Src phosphorylation at Y876/Y898 promotes ARF1 binding and retrograde Golgi-to-ER tubular transport of glycosylation enzymes [#22, #30, #40, #49, #45]. A missense mutation in the HDS2 domain abolishes Golgi recruitment and ARF1 activation, causing ER-stress-driven endothelial apoptosis and vascular hemorrhage in zebrafish, and a heterozygous GBF1 mutation reducing protein levels produces UPR activation and a cataract phenotype, establishing GBF1 dysfunction as disease-causing [#34, #51]. Numerous RNA viruses co-opt GBF1 for replication-complex biogenesis: enterovirus 3A proteins directly bind and sequester GBF1 to block ARF1 activation, while diverse viruses (HCV, coronaviruses, dengue, others) depend on GBF1 activity\\u2014sometimes through its noncatalytic C-terminal domains independently of the canonical Sec7 COPI function [#6, #15, #18, #20, #43, #44].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Establishing the molecular identity of GBF1 was the prerequisite for any mechanistic work, defining it as a ubiquitously expressed Sec7-domain protein with a distinct domain architecture.\",\n      \"evidence\": \"cDNA cloning, Northern blotting, and chromosomal mapping of human GBF1\",\n      \"pmids\": [\"9828135\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No enzymatic activity or substrate demonstrated\", \"No localization or trafficking role established\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"The question of what GBF1 does biochemically was answered by showing it is a BFA-resistant ARF GEF on Golgi membranes, placing it in the COPI/ARF activation machinery.\",\n      \"evidence\": \"Expression cloning with in vitro GEF assay, immunogold EM, and overexpression conferring BFA-resistant Golgi morphology\",\n      \"pmids\": [\"10402461\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vitro specificity (ARF5) did not resolve the physiological substrate\", \"Mechanism of membrane recruitment unknown\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Identifying p115 as a proline-rich-region partner connected GBF1 to membrane tethering, though it showed targeting of neither protein depends on the interaction.\",\n      \"evidence\": \"Yeast two-hybrid, in vitro binding, co-IP, and dominant-negative domain expression\",\n      \"pmids\": [\"12634853\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of the GBF1\\u2013p115 interaction for trafficking not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Live-imaging and dominant-negative mutants resolved the catalytic cycle question: GBF1 turns over on membranes in seconds and its own exchange activity drives its release, defining one GBF1-membrane event per ARF activation.\",\n      \"evidence\": \"GFP-GBF1 FRAP with catalytically inactive E794K and ARF1-T31N mutants and BFA treatment\",\n      \"pmids\": [\"15813748\", \"15616190\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the membrane recruitment receptor unknown\", \"How catalysis triggers conformational release not structurally defined\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Antibody microinjection directly linked GBF1 to COPI (but not COPII) recruitment in the early secretory pathway, distinguishing its compartment of action.\",\n      \"evidence\": \"GFP-GBF1 live imaging and anti-GBF1 antibody microinjection with COPI/COPII readouts\",\n      \"pmids\": [\"16926190\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"ARF isoform(s) activated in vivo not pinned down\", \"Recruitment determinants not mapped\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"siRNA and structural domain studies clarified that GBF1 specifically governs cis-Golgi COPI and transmembrane (not soluble) cargo traffic, that DCB/HUS domains mediate dimerization, and that loss triggers UPR rather than Golgi-to-ER collapse.\",\n      \"evidence\": \"siRNA depletion with cargo trafficking assays, DCB/HUS domain biochemistry and yeast complementation, and proteomic UPR analysis\",\n      \"pmids\": [\"18003980\", \"17956946\", \"17640864\", \"18287014\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Basis of transmembrane vs soluble cargo selectivity unresolved\", \"Mechanistic link from GBF1 loss to S2P/ATF6 activation not fully defined\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Discovery of Rab1b and GGA interactions positioned GBF1 within an upstream regulatory and downstream adaptor network for membrane recruitment and lysosomal cargo sorting.\",\n      \"evidence\": \"Co-IP, FRAP, and siRNA for Rab1b effector role and GGA recruitment/cargo trafficking\",\n      \"pmids\": [\"17429068\", \"17666033\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How Rab1b mechanistically stabilizes GBF1 not resolved here\", \"Direct vs indirect nature of GGA recruitment unclear\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Enterovirus 3A proteins were shown to directly target GBF1, establishing GBF1 as a host factor co-opted/inhibited by viruses and providing a tool to dissect GBF1 domains.\",\n      \"evidence\": \"Co-IP, COPI recruitment and transport assays, chimeric 3A swaps, and mouse virulence\",\n      \"pmids\": [\"16890159\", \"17005635\", \"17329336\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the 3A\\u2013GBF1 N-terminal interaction not solved\", \"Whether 3A binding fully recapitulates physiological GBF1 regulation unclear\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Multiple virus systems established that GBF1 is required for RNA replication, and that some viruses use GBF1 functions distinct from canonical COPI-vesicle formation.\",\n      \"evidence\": \"siRNA, Golgicide A, BFA-resistant GBF1 rescue, and replicon assays across CVB3 and HCV\",\n      \"pmids\": [\"19740986\", \"19906930\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise GBF1 activity required at the replication complex not defined\", \"Whether ARF activation is always the operative step unclear\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Domain-dissection rescue of poliovirus replication by the noncatalytic GBF1 N-terminus revealed a Sec7-independent viral support function, separating GBF1's trafficking role from its viral role.\",\n      \"evidence\": \"BFA-resistant N-terminal fragment rescue and p115/Rab1b knockdown in poliovirus replication\",\n      \"pmids\": [\"20497182\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular activity of the N-terminal fragment at replication sites unknown\", \"How GBF1 supports replication without exchange activity unresolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Identification of PI4KIII\\u03b1/PI4P as a recruitment requirement and CDK1-cyclin B as a mitotic kinase began to explain how GBF1 membrane association is spatially and cell-cycle regulated.\",\n      \"evidence\": \"PI4P inhibitors/biosensor and PI4KIII\\u03b1 depletion; in vitro CDK1 kinase assay with fractionation\",\n      \"pmids\": [\"20530568\", \"20175751\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether PI4P binding is direct to GBF1 not shown\", \"CDK1 phosphosites not fully mapped to mechanism\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Biochemical reconstitution localized lipid-binding to an HDS1 amphipathic helix and showed the Sec7 domain restrains it, defining how GBF1 engages Golgi membranes and lipid droplets.\",\n      \"evidence\": \"In vitro liposome/artificial lipid droplet binding with domain mutagenesis validated in cells\",\n      \"pmids\": [\"23943872\", \"21789191\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the proteinaceous Golgi receptor still unknown at this stage\", \"Regulation of HDS1 exposure in the full-length protein unresolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Epistasis placed GBF1 upstream of BIG1/BIG2 via ARF4/ARF5, defining a GEF cascade extending GBF1's reach to the TGN clathrin-adaptor machinery.\",\n      \"evidence\": \"ARF isoform-specific siRNA epistasis and immunoEM localization across Golgi compartments\",\n      \"pmids\": [\"23386609\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct vs indirect basis of BIG recruitment by ARF4/5 not biochemically resolved\", \"Spatial organization of the cascade not defined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"AMPK phosphorylation of GBF1 during mitosis was identified as an energy- and cell-cycle-coupled control of GBF1 membrane association and Golgi disassembly.\",\n      \"evidence\": \"Cell synchronization, AMPK kinase assays on GBF1, and Golgi fragmentation readouts\",\n      \"pmids\": [\"23418352\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Phosphosite not mapped in this study\", \"Mechanism by which phosphorylation abolishes GEF activity unclear\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"A zebrafish HDS2 missense mutation tied loss of Golgi recruitment and ARF1 activation to ER-stress-driven endothelial apoptosis, providing in vivo disease-relevant proof of GBF1's secretory function.\",\n      \"evidence\": \"ENU screen, positional cloning, and cell-based Golgi recruitment/ARF1/COPI assays with ER-stress markers and rescue\",\n      \"pmids\": [\"28003365\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the human ortholog causes analogous vascular disease not addressed\", \"Precise HDS2 recruitment mechanism not structurally defined\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"An in vitro recruitment assay plus domain mapping established that HDS1/HDS2 and a heat-labile Golgi protein receptor, gated by ARF-GDP localization, control GBF1 membrane association.\",\n      \"evidence\": \"In vitro Golgi-membrane recruitment assay, truncation analysis, protease/heat treatment, and ArfGAP siRNA\",\n      \"pmids\": [\"29507113\", \"29443553\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular identity of the Golgi receptor not determined\", \"How ARF-GDP localization is read out by GBF1 unresolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"CK2-dependent phosphorylation at Ser292/Ser297 was shown to recruit \\u03b2TrCP and target GBF1 for SCF\\u03b2TrCP degradation, coupling GBF1 turnover to postmitotic Golgi reformation and cytokinesis.\",\n      \"evidence\": \"Phosphosite mapping, CK2 kinase assay, \\u03b2TrCP co-IP, ubiquitin ligase assay, and non-degradable mutant phenotypes\",\n      \"pmids\": [\"29898406\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How localized degradation at the intercellular bridge is spatially restricted not fully defined\", \"Interplay with other mitotic phospho-controls unresolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Reciprocal co-IP and live imaging revealed that GBF1\\u2013ARF1\\u2013Miro controls mitochondrial positioning, extending GBF1 function beyond classical secretory traffic.\",\n      \"evidence\": \"GBF1\\u2013Miro and ARF1\\u2013Miro co-IP, GBF1 inhibition, dynein/Miro perturbation, and mitochondrial movement tracking\",\n      \"pmids\": [\"30459446\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether GBF1 acts on Miro directly or via ARF1 effectors unclear\", \"Connection to canonical Golgi pool not defined\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Proximity proteomics and direct interaction studies expanded the GBF1 interactome (C10orf76, HCV NS3) and linked AMPK-GBF1 to physiological cargo (VWF, ECM) trafficking.\",\n      \"evidence\": \"BioID/MS with co-IP and FRAP for C10orf76; Y2H/co-IP/PLA for NS3; trafficking assays with AMPK/glucose manipulation for VWF\",\n      \"pmids\": [\"31519766\", \"30567983\", \"31056345\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic role of C10orf76 in GBF1 recruitment incompletely defined\", \"AMPK phosphosite governing VWF trafficking not mapped here\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Src phosphorylation of GBF1 at Y876/Y898 was shown to promote ARF1 binding and drive retrograde tubular transport of glycosylation enzymes, defining a phospho-switch that redirects GBF1 output.\",\n      \"evidence\": \"Src kinase assay, phosphopeptide MS, GBF1\\u2013ARF1 co-IP, phosphomimetic/deficient mutants, live imaging, and molecular modeling\",\n      \"pmids\": [\"34870592\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural model of Sec7 melting awaits experimental structure\", \"How retrograde vs anterograde decision is integrated with other phospho-inputs unclear\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"CRISPR knock-in of a phospho-deficient GBF1-T1337A mutant established AMPK-Thr1337 phosphorylation as the operative event for energy-stress Golgi fragmentation and slowed anterograde traffic.\",\n      \"evidence\": \"AMPK-\\u03b1 knockouts, GBF1-T1337A knock-in, AMPK activators, and Golgi fragmentation/cargo trafficking assays\",\n      \"pmids\": [\"39575556\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How a single phosphosite triggers Golgi fragmentation mechanistically not resolved\", \"Relationship of Thr1337 to mitotic AMPK control unclear\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Separation-of-function phosphomutants and a human mutation/knockout mouse linked GBF1 to distinct cytokinesis vs secretion roles and to UPR/autophagy and a cataract disease phenotype.\",\n      \"evidence\": \"Phosphomimetic/deficient mutagenesis with cytokinesis/Golgi assays; knockdown with XBP1s/autophagy readouts and Gbf1 heterozygous knockout mice\",\n      \"pmids\": [\"37604968\", \"39110251\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Interaction networks distinguishing the two functional modes not fully identified\", \"Causal chain from reduced GBF1 to cataract not mechanistically complete\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Enterovirus 3A sequestration of GBF1 was shown to induce PERK/CHOP-driven ER stress and apoptosis, and synthetic lethality screening identified ARF1 as the dominant dependency of GBF1 hypomorphism.\",\n      \"evidence\": \"3A expression with co-IP/ARF1 activation, UPR markers, PERK inhibitor rescue; synthetic lethality screen with ARF1 disruption in 3A-expressing cells\",\n      \"pmids\": [\"38904364\", \"36305789\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether ARF1 is the sole essential GBF1 substrate in all contexts unclear\", \"Generality of PERK/CHOP induction across GBF1 loss-of-function modes not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The identity of the heat-labile Golgi protein receptor that recruits GBF1 and a high-resolution structure of full-length GBF1 explaining how phosphorylation and lipid binding gate Sec7 catalysis remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No molecular identity for the Golgi recruitment receptor\", \"No experimental full-length or Sec7-conformational structure tying phospho-switches to catalysis\", \"Integration of the many phospho-inputs into a unified regulatory logic not established\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005085\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 3, 4, 28]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [29, 24, 26]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [10, 28]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [0, 5, 6, 11, 28]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 3, 4]},\n      {\"term_id\": \"GO:0005811\", \"supporting_discovery_ids\": [24, 29]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [5, 16]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [0, 6, 11, 12]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [10, 11, 28]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [22, 30, 40, 48]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [14, 34, 49, 50]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [6, 15, 18, 34, 51]}\n    ],\n    \"complexes\": [\n      \"SCF\\u03b2TrCP (substrate)\",\n      \"GBF1\\u2013Arf4\\u2013rhodopsin complex\"\n    ],\n    \"partners\": [\n      \"ARF1\",\n      \"Rab1b\",\n      \"p115\",\n      \"ATGL\",\n      \"Miro\",\n      \"C10orf76\",\n      \"ARF4\",\n      \"p115\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}