{"gene":"GOLGA2","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":1995,"finding":"GM130 (GOLGA2) is a peripheral cytoplasmic protein tightly bound to Golgi membranes at the cis-Golgi network, forming part of a larger oligomeric complex. It has extended rod-like structure with coiled-coil domains and is not redistributed to the ER by brefeldin A treatment.","method":"Biochemical fractionation, immunofluorescence microscopy, immunoelectron microscopy, cDNA cloning","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (biochemistry, IF, IEM) in a foundational characterization paper, widely replicated","pmids":["8557739"],"is_preprint":false},{"year":1997,"finding":"GM130 N-terminus directly binds the vesicle-docking protein p115, providing a membrane docking site for COPI vesicles at the cis-Golgi. Mitotic phosphorylation of GM130 prevents p115 binding, explaining Golgi fragmentation at mitosis onset. An N-terminal GM130 peptide inhibited NSF-dependent (but not p97-dependent) reassembly of Golgi cisternae from mitotic fragments.","method":"Deletion analysis, co-immunoprecipitation, in vitro Golgi reassembly assay, peptide inhibition","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution assays plus deletion mapping, replicated across multiple studies","pmids":["9150144"],"is_preprint":false},{"year":1998,"finding":"Cdc2 (CDK1) kinase directly phosphorylates GM130 at a single serine residue (Ser-25), and this phosphorylation is required for mitotic Golgi fragmentation. MEK1 was shown not to be required for GM130 phosphorylation or mitotic Golgi fragmentation either in vitro or in vivo.","method":"In vitro kinase assay, site-directed mutagenesis, mass spectrometry peptide mapping, cell-based fragmentation assay","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinase assay with mutagenesis identifying specific phosphorylation site, validated in vivo, replicated","pmids":["9753325"],"is_preprint":false},{"year":1998,"finding":"GRASP65 and GM130 form a complex on Golgi membranes that can recruit p115. The GRASP65 binding site on GM130 maps to the sequence xxNDxxxIMVI-COOH at the C-terminus (also required for Golgi localization), and the GM130-binding site on GRASP65 maps to amino acids 189–201. GFP-reporter experiments showed that the GRASP65–GM130 interaction is required for correct targeting of both proteins to the Golgi.","method":"Gel filtration, immunoprecipitation, in vitro translation, site-directed mutagenesis, GFP fusion reporters","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — mutagenesis-based binding mapping combined with gel filtration and localization reporters; replicated by crystal structure study","pmids":["9628863"],"is_preprint":false},{"year":2000,"finding":"GM130 is phosphorylated on Ser-25 in prophase coinciding with Golgi breakdown; it remains phosphorylated through metaphase/anaphase and is dephosphorylated in telophase during Golgi reassembly. PP2A containing the Bα regulatory subunit was identified as the phosphatase responsible for dephosphorylating GM130 Ser-25 at mitotic exit.","method":"Phosphospecific antibody, temporal cell-cycle analysis, phosphatase inhibitor studies, immunoprecipitation of phosphatase","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — phosphospecific antibody with cell cycle staging, phosphatase identified biochemically, replicated findings","pmids":["10769027"],"is_preprint":false},{"year":2000,"finding":"Inhibition of p115 binding to GM130 (by microinjection of N-terminal GM130 peptide or overexpression of N-terminal-deleted GM130) increases the number of COP-sized transport vesicles and significantly inhibits VSV-G protein intracellular transport, demonstrating that the GM130–p115 tethering complex increases efficiency of vesicle fusion with the Golgi.","method":"Microinjection, overexpression, immunofluorescence quantification, electron microscopy","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo functional inhibition with electron microscopy and cargo transport readout, multiple complementary approaches","pmids":["10679020"],"is_preprint":false},{"year":2000,"finding":"Anti-GM130 antibodies inhibit VSV-G transport to the mannosidase II-containing Golgi compartment at a step after the p115-requiring step but before the giantin-requiring step, indicating a sequential role for p115, GM130, and giantin in ER-to-Golgi trafficking.","method":"Antibody microinjection, VSV-G transport assay, immunofluorescence","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — antibody inhibition with defined cargo readout, single lab, sequential step assignment","pmids":["11035033"],"is_preprint":false},{"year":2001,"finding":"GM130, complexed with GRASP65 and other proteins, forms a Rab1 effector complex that interacts with activated Rab1-GTP in a p115-independent manner, and is required for COPII vesicle targeting/fusion with the cis-Golgi.","method":"GST pulldown, co-immunoprecipitation, vesicle transport assay","journal":"Traffic (Copenhagen, Denmark)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pulldown with GTP-form specificity and functional transport assay, single lab","pmids":["11285137"],"is_preprint":false},{"year":2001,"finding":"Rab1b interacts specifically with GM130 in a GTP-dependent manner requiring the hypervariable N- and C-termini of Rab1b, with the Rab1b-binding site on GM130 distinct from the p115 and GRASP65 binding sites.","method":"Yeast two-hybrid screen, in vitro binding assay, mutagenesis","journal":"EMBO reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid confirmed by in vitro binding, GTP-dependence established, single lab","pmids":["11306556"],"is_preprint":false},{"year":2001,"finding":"GST-Rab33b (GTP-locked) interacts with GM130 by Western blotting/mass spectrometry, identifying GM130 as a putative effector of Rab33b, which regulates retrograde Golgi-to-ER transport.","method":"GST pulldown, mass spectrometry, microinjection of Rab33b mutants","journal":"FEBS letters","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single pulldown/Western approach, no reciprocal IP, single lab","pmids":["11718716"],"is_preprint":false},{"year":2004,"finding":"GM130 acts as a scaffold to recruit mammalian Ste20 kinases YSK1 and MST4 to the Golgi apparatus, and GM130 binding activates these kinases by promoting autophosphorylation of a conserved T-loop threonine. YSK1 phosphorylates 14-3-3ζ as a substrate at the Golgi. Interference with YSK1 disrupts perinuclear Golgi organization, cell migration, and collagen invasion.","method":"Co-immunoprecipitation, in vitro kinase assay, dominant-negative expression, biochemical substrate screen","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay with GM130-dependent activation, substrate identified biochemically, functional cell migration readout, single lab with multiple methods","pmids":["15037601"],"is_preprint":false},{"year":2006,"finding":"GM130 and GRASP65 are required for lateral cisternal fusion events that form the continuous Golgi ribbon, and these fusion events are necessary for uniform distribution of Golgi enzymes across the ribbon.","method":"siRNA knockdown, live-cell imaging, fluorescence recovery after photobleaching (FRAP), enzyme distribution assay","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — siRNA depletion with FRAP and enzyme distribution functional readouts, multiple orthogonal methods","pmids":["16489344"],"is_preprint":false},{"year":2007,"finding":"GM130 directly binds syntaxin 5 (a t-SNARE) via the membrane-proximal region of GM130. p115 binding to a distal site in GM130 inhibits GM130's interaction with syntaxin 5 and with Rab1. Mitotic phosphorylation also inhibits these interactions. GM130 depletion by RNAi slows ER-to-Golgi trafficking in vivo.","method":"Co-immunoprecipitation, in vitro binding assay, mutagenesis, RNAi knockdown, transport assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct binding mapped with mutagenesis, allosteric regulation by p115 demonstrated in vitro, functional trafficking readout in vivo","pmids":["18167358"],"is_preprint":false},{"year":2007,"finding":"GM130 depletion by RNAi in human cells causes abnormal interphase centrosomes that are mispositioned and defective for microtubule organization and cell migration; when depleted cells enter mitosis, they form multipolar spindles and arrest in metaphase.","method":"RNA interference (RNAi), immunofluorescence, live-cell imaging, cell migration assay","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNAi in five cell lines with defined centrosome and spindle phenotypes, single lab","pmids":["18045989"],"is_preprint":false},{"year":2007,"finding":"GM130 cycling between cis-Golgi compartments and ER-to-Golgi carriers (EGCs) is required for homotypic tethering and fusion of EGCs and their incorporation into Golgi stacks to form the Golgi ribbon. In absence of GM130, EGCs remain as distinct entities causing tubulovesicular membrane accumulation, shortened cisternae, and ribbon breakdown.","method":"siRNA knockdown, electron microscopy, live-cell imaging, cargo trafficking assay","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA with electron microscopy and live-cell imaging, single lab","pmids":["17314401"],"is_preprint":false},{"year":2008,"finding":"GM130 regulates centrosome organization through a Golgi-associated complex with the Rho GEF Tuba and Cdc42. GM130 interaction with Tuba controls Tuba-mediated activation of Cdc42 at the Golgi; blocking Tuba or Cdc42 reproduces GM130-depletion centrosome phenotype; constitutively active Cdc42 bypasses the requirement for GM130 in centrosome regulation, placing Cdc42 downstream of GM130.","method":"Co-immunoprecipitation, RNAi knockdown, constitutively active mutant rescue, immunofluorescence","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Moderate — epistasis established by constitutively active Cdc42 rescue, reciprocal co-IP, multiple knockdowns, single lab with multiple orthogonal methods","pmids":["19109421"],"is_preprint":false},{"year":2009,"finding":"Microtubule nucleation at the Golgi apparatus requires AKAP450, which binds the cis-side of the Golgi in a GM130-dependent manner. Depletion of GM130 disorganizes the AKAP450 network and impairs Golgi-based MT nucleation; brefeldin A redistributes AKAP450 to ER exit sites along with MT nucleation activity.","method":"siRNA knockdown, microtubule regrowth assay, immunofluorescence, brefeldin A treatment","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — GM130-dependent AKAP450 recruitment to Golgi established with depletion and MT nucleation functional readout; replicated in concept by subsequent studies","pmids":["19242490"],"is_preprint":false},{"year":2010,"finding":"PRMT5 localizes to the Golgi, forms complexes with GM130 and other Golgi ribbon/vesicle-tethering components, and methylates N-terminal arginines in GM130. PRMT5 depletion causes Golgi ribbon formation defects; arginine methylation of GM130 is critical for Golgi ribbon maintenance.","method":"Co-immunoprecipitation, in vitro methylation assay, siRNA knockdown, mutagenesis, immunofluorescence","journal":"Cell research","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro methylation assay plus mutagenesis and functional Golgi ribbon readout, single lab","pmids":["20421892"],"is_preprint":false},{"year":2011,"finding":"In mouse oocyte meiosis, GM130 localizes to spindle poles and midbody in a spindle-dependent manner; morpholino-mediated knockdown causes abnormal spindle formation, reduced polar body extrusion, impaired localization of γ-tubulin and Plk1 at MTOCs, aberrant spindle migration, and blocked p-MEK1/2 accumulation at spindle poles.","method":"Morpholino microinjection, immunofluorescence, live-cell imaging, nocodazole treatment","journal":"Cell cycle (Georgetown, Tex.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — morpholino knockdown with multiple phenotypic readouts in oocytes, single lab","pmids":["21552007"],"is_preprint":false},{"year":2013,"finding":"WAC and GM130 directly interact at the Golgi; WAC binding to GM130 is required for autophagy. GM130 tethers GABARAP to the Golgi, inhibiting autophagy; WAC suppresses GM130 binding to GABARAP to allow centrosomal GABARAP delivery to the phagophore. Specifically, unlipidated and lipidated GABARAP (but not LC3B, GABARAPL1, or GATE-16) activates ULK kinase via the ULK1 LIR motif, revealing a non-hierarchical role for GABARAP in starvation-induced autophagy.","method":"Co-immunoprecipitation, siRNA knockdown, immunofluorescence, in vitro binding, ULK kinase assay","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct interaction mapped, kinase assay, multiple knockdowns with specific rescue experiments, single lab with multiple orthogonal methods","pmids":["26687599"],"is_preprint":false},{"year":2014,"finding":"GM130 forms a complex with RasGRF at the Golgi to regulate the Golgi pool of Cdc42. GM130 silencing causes RasGRF-dependent inhibition of Golgi Cdc42 (not plasma membrane Cdc42), disrupts asymmetric front-rear Cdc42-GTP distribution in migrating cells, and activates RasGRF-dependent Ras-ERK signaling. GM130 loss also induces E-cadherin downregulation indicative of EMT.","method":"Co-immunoprecipitation, Cdc42 activity (FRET) assay, siRNA knockdown, rescue experiments","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — spatial Cdc42 activity measured by FRET, RasGRF epistasis tested with double knockdown, single lab","pmids":["25208761"],"is_preprint":false},{"year":2014,"finding":"In Drosophila dendrites, GM130 is responsible for connecting distinct Golgi compartments at soma and dendritic branch points; GM130 distribution determines the compartmental organization of dendritic Golgi outposts, which in turn regulates acentrosomal microtubule growth and dendritic branching.","method":"RNAi knockdown, immunofluorescence in vivo, live imaging, dendritic branching quantification","journal":"Current biology : CB","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNAi with multiple functional readouts (microtubule growth, dendritic branching) in vivo, single lab","pmids":["24835455"],"is_preprint":false},{"year":2015,"finding":"GM130 interacts with importin α via a classical nuclear localization signal (NLS) at mitotic entry, sequestering importin α on Golgi membranes. This releases the spindle assembly factor TPX2, which activates Aurora-A and stimulates local microtubule nucleation. GM130 also captures nascent microtubules, linking Golgi membranes to the spindle for organelle inheritance.","method":"Co-immunoprecipitation, immunofluorescence, mutagenesis of NLS, siRNA knockdown, microtubule regrowth assay","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — mechanism established with NLS mutagenesis, importin α co-IP, functional MT nucleation readout, multiple orthogonal approaches","pmids":["26165940"],"is_preprint":false},{"year":2015,"finding":"Crystal structure of GRASP65 PDZ domains in complex with the GM130 C-terminal peptide (1.96 Å resolution) reveals that GM130 simultaneously binds both PDZ1 and PDZ2 domains of GRASP65, contrary to prior models proposing only PDZ2 involvement. Mutagenesis experiments confirmed the structural observations.","method":"X-ray crystallography (1.96 Å), site-directed mutagenesis, co-immunoprecipitation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure with mutagenesis validation, single lab but high-resolution structural data","pmids":["26363069"],"is_preprint":false},{"year":2015,"finding":"GM130 is a parallel homotetramer (not a homodimer as previously assumed) with a flexible rod-like structure exhibiting N-terminally open (Y-shaped) and closed (I-shaped) conformations, as revealed by biochemical and electron microscopic analyses.","method":"Gel filtration, electron microscopy, analytical ultracentrifugation","journal":"The FEBS journal","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — EM with biochemical analyses establishing tetrameric state; single lab, no mutagenesis validation of oligomeric state","pmids":["25787021"],"is_preprint":false},{"year":2016,"finding":"Targeted neuronal deletion of GM130 in mice causes Golgi fragmentation and defective positioning in Purkinje cells, impaired secretory trafficking, dendritic atrophy, reduced cerebellar size and Purkinje cell number, and progressive ataxia, demonstrating that Golgi dysfunction via GM130 loss is causally linked to neurodegeneration in vivo.","method":"Conditional knockout mice, immunofluorescence, electron microscopy, secretory trafficking assay, behavioral phenotyping","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO with multiple cellular and in vivo readouts, causality established by selective neuronal deletion","pmids":["28028212"],"is_preprint":false},{"year":2017,"finding":"GM130 knockout in mice causes globozoospermia; loss of GM130 does not affect secretion of pro-acrosomic vesicles but prevents their fusion into a single large acrosome vesicle. GM130 loss disrupts co-localization of adaptor protein complex AP1 and TGN46, suggesting GM130 is required for sorting and coating of Golgi-derived pro-acrosomic vesicles.","method":"Knockout mouse model, immunofluorescence, electron microscopy, co-localization analysis","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knockout model with electron microscopy and vesicle tracking, mechanistic interpretation based on co-localization, single lab","pmids":["28055014"],"is_preprint":false},{"year":2019,"finding":"Purified recombinant GM130 undergoes liquid-liquid phase separation into dynamic liquid-like droplets in near-physiological buffers at concentrations similar to its estimated local concentration at the cis-Golgi. Overexpressed GM130 also forms liquid droplets in cells.","method":"In vitro phase separation assay with recombinant protein, live-cell imaging of overexpressed protein","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution of phase separation with recombinant protein at physiological concentrations; single lab, no mutagenesis","pmids":["31833055"],"is_preprint":false},{"year":2021,"finding":"CDK1-mediated phosphorylation of importin α at Ser-62 switches its substrate preference from TPX2 to GM130, thereby enabling GM130 to compete for importin α binding and locally activate TPX2 at the spindle pole area to promote astral microtubule growth and proper spindle orientation.","method":"Mutagenesis (importin α S62A), co-immunoprecipitation, astral microtubule growth assay, spindle orientation measurement","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Moderate — phosphorylation site mutagenesis with functional spindle orientation readout and direct competition assay, single lab with multiple orthogonal methods","pmids":["33526712"],"is_preprint":false},{"year":2024,"finding":"GM130 is a membrane-bound RNA-binding protein that directly recruits RNA and associated RNA-binding proteins to the Golgi membrane. RNA–GM130 condensates maintain the Golgi ribbon through liquid-liquid phase separation mediated by an intrinsically disordered N-terminal domain of GM130. Acute RNA degradation or GM130 loss disrupts the ribbon; GM130–RNA co-condensates are sufficient to link purified Golgi membranes in vitro.","method":"RNA-binding assay, acute RNA degradation (auxin-inducible degron for GM130), in vitro condensate reconstitution with purified membranes, deletion mutagenesis of IDR, live-cell imaging","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with purified proteins/membranes, mutagenesis of IDR, acute depletion systems, multiple orthogonal methods in single rigorous study","pmids":["38992139"],"is_preprint":false},{"year":2002,"finding":"GM130 interacts with the C-terminus of the HERG potassium channel in the Golgi; LQT2-causing HERG C-terminal mutations selectively disrupt this GM130 interaction. Overexpression of GM130 suppresses HERG current amplitude, suggesting GM130 functions as a checkpoint in HERG trafficking through the Golgi.","method":"Yeast two-hybrid, co-immunoprecipitation from HEK-293 cells, confocal co-localization, Xenopus oocyte current measurement","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP and functional current readout, disease mutation mapping, single lab","pmids":["12270925"],"is_preprint":false},{"year":2011,"finding":"Bacterial effector EspG (from EPEC/EHEC) binds GM130 as identified by Y2H and confirmed by affinity co-purification and co-immunoprecipitation. EspG expression localizes to the Golgi and induces its fragmentation, disrupting protein secretion more potently than NleA/EspI.","method":"Yeast two-hybrid, affinity co-purification, co-immunoprecipitation, ectopic expression, secretion assay","journal":"Cellular microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Y2H confirmed by two biochemical methods, functional secretion readout, single lab","pmids":["21740499"],"is_preprint":false},{"year":2025,"finding":"HIF-1α activation under hypoxia induces NEDD4-mediated ubiquitination and degradation of GM130, causing Golgi condensation. GM130 degradation promotes lipid accumulation and apolipoprotein A1 retention in intestinal epithelium. Inhibition of HIF-1α or NEDD4 prevents GM130 degradation and rescues Golgi structure and lipid trafficking.","method":"Hypoxia/HFD mouse model, co-immunoprecipitation, ubiquitination assay, HIF-1α inhibitor (PX-478), siRNA knockdown, apolipoprotein secretion assay","journal":"Experimental & molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ubiquitination assay identifies NEDD4 as the E3 ligase, HIF-1α epistasis tested pharmacologically, in vivo validation, single lab","pmids":["39900792"],"is_preprint":false}],"current_model":"GM130 (GOLGA2) is a cis-Golgi peripheral membrane protein that functions as a multivalent scaffold: its N-terminus tethers COPI vesicles by binding p115 (regulated by CDK1-mediated phosphorylation at Ser-25 during mitosis, with PP2A-Bα mediating dephosphorylation at telophase); its C-terminus anchors GRASP65 to stabilize Golgi stacking; it directly binds syntaxin 5 to couple tethering with SNARE-mediated fusion; it recruits AKAP450 to nucleate microtubules at the Golgi; at mitotic entry it sequesters importin α via an NLS to liberate TPX2 for Golgi-derived spindle assembly; it scaffolds YSK1/MST4 kinase activation and a Tuba-Cdc42 signaling complex for centrosome regulation and directed cell migration; PRMT5 methylates GM130 N-terminal arginines to maintain Golgi ribbon architecture; GM130 tethers GABARAP to the Golgi to suppress autophagy until WAC-mediated release; and GM130 acts as a membrane-bound RNA-binding protein whose intrinsically disordered N-terminal domain drives liquid-liquid phase separation with RNA to maintain the continuous Golgi ribbon, while NEDD4-mediated ubiquitination downstream of HIF-1α can degrade GM130 to disrupt Golgi architecture and lipid trafficking."},"narrative":{"mechanistic_narrative":"GOLGA2 (GM130) is a peripheral cis-Golgi membrane protein that serves as a multivalent structural and signaling scaffold governing Golgi architecture, membrane trafficking, microtubule organization, and cell-cycle-coupled organelle dynamics [PMID:8557739, PMID:9150144]. Through its N-terminus it tethers incoming COPI vesicles by binding p115, increasing the efficiency of vesicle fusion at the cis-Golgi, and it directly engages the t-SNARE syntaxin 5 to couple tethering to membrane fusion in ER-to-Golgi transport [PMID:9150144, PMID:10679020, PMID:18167358]. Its C-terminus binds GRASP65 across both PDZ domains to drive the lateral cisternal fusion events that build and maintain the continuous Golgi ribbon [PMID:9628863, PMID:16489344, PMID:26363069], a function reinforced by its capacity to act as a membrane-bound RNA-binding protein whose intrinsically disordered N-terminal domain undergoes liquid-liquid phase separation with RNA to link Golgi membranes [PMID:31833055, PMID:38992139]. Mitotic entry switches GM130 off as a tether: CDK1 phosphorylates Ser-25 to block p115, syntaxin 5, and Rab1 binding and drive Golgi fragmentation, with PP2A-Bα reversing this at telophase [PMID:9753325, PMID:10769027, PMID:18167358]; concurrently GM130 sequesters importin α through an NLS to liberate the spindle factor TPX2 for Golgi-derived microtubule nucleation and spindle orientation [PMID:26165940, PMID:33526712]. GM130 organizes the microtubule cytoskeleton by recruiting AKAP450 for Golgi-based microtubule nucleation and scaffolds signaling outputs including YSK1/MST4 kinase activation and Tuba/RasGRF-Cdc42 complexes that control centrosome organization and directed cell migration [PMID:15037601, PMID:19109421, PMID:19242490, PMID:25208761]. It additionally tethers GABARAP to suppress autophagy until WAC-mediated release [PMID:26687599]. In vivo, neuronal GM130 loss causes Golgi fragmentation, secretory defects, and progressive ataxia [PMID:28028212], and its degradation via HIF-1α/NEDD4-mediated ubiquitination disrupts Golgi structure and lipid trafficking [PMID:39900792].","teleology":[{"year":1995,"claim":"Establishing the existence and properties of GM130 was needed before any function could be assigned; this defined it as a stable cis-Golgi peripheral scaffold protein.","evidence":"Biochemical fractionation, immuno-EM, and cDNA cloning characterizing an oligomeric coiled-coil Golgi protein resistant to brefeldin A","pmids":["8557739"],"confidence":"High","gaps":["No functional partners identified at this stage","Mechanism of membrane attachment not resolved"]},{"year":1997,"claim":"It was unknown how vesicles dock at the cis-Golgi; GM130 was shown to bind p115 directly, providing a tethering site for COPI vesicles and explaining mitotic Golgi fragmentation through phosphoregulation of this interaction.","evidence":"Deletion mapping, co-IP, and in vitro Golgi reassembly with peptide inhibition","pmids":["9150144"],"confidence":"High","gaps":["Identity of the mitotic kinase not yet established","How tethering couples to fusion machinery unknown"]},{"year":1998,"claim":"The mitotic switch was mechanistically defined: CDK1/Cdc2 directly phosphorylates Ser-25 to drive Golgi fragmentation, and the GRASP65 C-terminal interaction was mapped, establishing GM130 as a bipartite scaffold linking vesicle docking and stacking.","evidence":"In vitro kinase assay with site-directed mutagenesis; gel filtration, IP, and GFP-reporter mapping of the GRASP65 site","pmids":["9753325","9628863"],"confidence":"High","gaps":["Phosphatase reversing Ser-25 not identified","Stoichiometry of the GM130-GRASP65-p115 complex unresolved"]},{"year":2000,"claim":"The temporal control and physiological consequence of GM130 tethering were resolved: PP2A-Bα dephosphorylates Ser-25 at telophase, and inhibiting p115 binding impairs cargo transport, demonstrating the tether increases vesicle fusion efficiency.","evidence":"Phosphospecific antibody cell-cycle staging with phosphatase IP; microinjection/overexpression with EM and VSV-G transport readouts","pmids":["10769027","10679020","11035033"],"confidence":"High","gaps":["Sequential ordering relative to giantin from single lab","Direct fusion catalysis not reconstituted"]},{"year":2001,"claim":"GM130 was placed within Rab-GTPase signaling at the cis-Golgi, acting as a GTP-dependent effector of Rab1 (and implicated for Rab33b) for COPII vesicle targeting, broadening its role beyond COPI tethering.","evidence":"Yeast two-hybrid, GST pulldown with GTP-locked Rabs, mutagenesis, and vesicle transport assays","pmids":["11285137","11306556","11718716"],"confidence":"Medium","gaps":["Rab33b interaction rests on a single pulldown without reciprocal IP","Functional separation of Rab1 vs p115 inputs incomplete"]},{"year":2004,"claim":"It was unclear how the Golgi nucleates signaling; GM130 was shown to recruit and allosterically activate YSK1/MST4 kinases, linking the scaffold to Golgi organization, cell migration, and invasion.","evidence":"Co-IP, GM130-dependent in vitro kinase activation assay, substrate screen, and dominant-negative migration/invasion assays","pmids":["15037601"],"confidence":"High","gaps":["Downstream effectors of 14-3-3ζ phosphorylation unclear","Single lab"]},{"year":2006,"claim":"The ribbon-building function was defined: GM130 and GRASP65 mediate the lateral cisternal fusion events required for a continuous ribbon and uniform Golgi enzyme distribution.","evidence":"siRNA knockdown with FRAP, live imaging, and enzyme distribution assays","pmids":["16489344"],"confidence":"High","gaps":["Molecular fusion intermediates not visualized","Relative contributions of GM130 vs GRASP65 not separated"]},{"year":2007,"claim":"How tethering couples to fusion and to membrane dynamics was clarified: GM130 directly binds syntaxin 5, with p115 and mitotic phosphorylation allosterically gating syntaxin 5/Rab1 binding, and GM130 cycling drives EGC tethering into stacks.","evidence":"In vitro binding/mutagenesis with allosteric competition; RNAi with EM, live imaging, and trafficking assays","pmids":["18167358","17314401"],"confidence":"High","gaps":["SNARE-pairing partners of syntaxin 5 at this step not mapped","Quantitative kinetics of the conformational switch unresolved"]},{"year":2007,"claim":"GM130 was extended beyond the secretory pathway into cytoskeletal and cell-cycle control, with depletion causing centrosome mispositioning, defective microtubule organization, and mitotic spindle defects.","evidence":"RNAi across multiple cell lines with immunofluorescence, live imaging, and migration assays","pmids":["18045989"],"confidence":"Medium","gaps":["Molecular link between Golgi GM130 and centrosomes not yet defined","Single lab"]},{"year":2008,"claim":"The centrosome connection was mechanistically resolved: GM130 scaffolds a Tuba GEF-Cdc42 complex at the Golgi, with epistasis placing Cdc42 activation downstream of GM130 for centrosome regulation.","evidence":"Reciprocal co-IP, RNAi, and constitutively active Cdc42 rescue/epistasis","pmids":["19109421"],"confidence":"High","gaps":["Spatial activation of Cdc42 not yet imaged directly","Single lab"]},{"year":2009,"claim":"Golgi-based microtubule nucleation was attributed to GM130: it is required to recruit AKAP450 to the cis-Golgi, organizing the MT-nucleating network.","evidence":"siRNA depletion, MT regrowth assay, and brefeldin A redistribution analysis","pmids":["19242490"],"confidence":"High","gaps":["Direct vs indirect AKAP450 binding not distinguished","γ-TuRC recruitment hierarchy unresolved"]},{"year":2010,"claim":"A post-translational regulator of ribbon architecture was identified: PRMT5 methylates GM130 N-terminal arginines, a modification critical for Golgi ribbon maintenance.","evidence":"Co-IP, in vitro methylation, siRNA, and mutagenesis with ribbon-formation readout","pmids":["20421892"],"confidence":"Medium","gaps":["Functional readers of methyl-arginine unknown","Single lab"]},{"year":2011,"claim":"GM130's mitotic/meiotic spindle role was demonstrated in vivo in oocytes, where it is required for spindle formation, MTOC factor localization, and spindle migration.","evidence":"Morpholino knockdown with immunofluorescence, live imaging, and nocodazole treatment","pmids":["21552007"],"confidence":"Medium","gaps":["Direct molecular targets at the meiotic MTOC not defined","Single lab"]},{"year":2011,"claim":"GM130 was identified as a host target of bacterial pathogens, with the EPEC/EHEC effector EspG binding GM130 to fragment the Golgi and disrupt secretion.","evidence":"Y2H confirmed by affinity co-purification and co-IP with ectopic expression and secretion assays","pmids":["21740499"],"confidence":"Medium","gaps":["Whether EspG blocks specific GM130 interactions not resolved","Single lab"]},{"year":2013,"claim":"A regulatory role in autophagy was established: GM130 tethers GABARAP to the Golgi to suppress autophagy, and WAC binding releases GABARAP to activate ULK kinase via its LIR motif.","evidence":"Direct binding/mutagenesis, siRNA with specific rescue, and ULK kinase assays","pmids":["26687599"],"confidence":"High","gaps":["Stimuli controlling WAC-GM130 association incomplete","Single lab"]},{"year":2014,"claim":"GM130 was shown to spatially pattern Cdc42 signaling for migration via a RasGRF complex, and to function across organisms in dendritic Golgi outpost organization and acentrosomal MT growth.","evidence":"Co-IP, Cdc42 FRET activity, siRNA/rescue in mammalian cells; RNAi with live imaging and branching quantification in Drosophila","pmids":["25208761","24835455"],"confidence":"Medium","gaps":["Link between Golgi Cdc42 pool and EMT markers correlational","Single lab per system"]},{"year":2015,"claim":"The mechanism of Golgi-derived spindle assembly and the structural basis of stacking were resolved: GM130 sequesters importin α via an NLS to release TPX2/Aurora-A, and the crystal structure showed GM130 engages both GRASP65 PDZ domains, while GM130 was redefined as a flexible parallel homotetramer.","evidence":"NLS mutagenesis, co-IP, MT regrowth; 1.96 Å crystal structure with mutagenesis; gel filtration, EM, and analytical ultracentrifugation","pmids":["26165940","26363069","25787021"],"confidence":"High","gaps":["Oligomeric state lacks mutagenesis validation","Conformational switching trigger not defined"]},{"year":2016,"claim":"GM130 loss was causally linked to neurodegeneration in vivo, with neuronal deletion producing Golgi fragmentation, secretory defects, Purkinje cell loss, and progressive ataxia.","evidence":"Conditional knockout mice with immunofluorescence, EM, trafficking assays, and behavioral phenotyping","pmids":["28028212"],"confidence":"High","gaps":["Specific secreted cargoes driving the phenotype not identified","Cell-autonomy versus circuit effects unresolved"]},{"year":2017,"claim":"A tissue-specific vesicle-sorting role was defined: GM130 is required for fusion of pro-acrosomic vesicles into a single acrosome, with knockout causing globozoospermia and disrupted AP1/TGN46 sorting.","evidence":"Knockout mouse with EM and co-localization analysis","pmids":["28055014"],"confidence":"Medium","gaps":["Direct sorting machinery interaction inferred from co-localization","Single lab"]},{"year":2019,"claim":"A biophysical basis for GM130 self-assembly emerged: purified GM130 undergoes liquid-liquid phase separation at near-physiological concentrations, forming droplets in cells.","evidence":"In vitro phase separation with recombinant protein and live-cell imaging of overexpressed protein","pmids":["31833055"],"confidence":"Medium","gaps":["Physiological driver of condensation not identified at this stage","No mutagenesis of the responsible region"]},{"year":2021,"claim":"The importin α switch was refined: CDK1 phosphorylation of importin α Ser-62 reprograms its substrate preference toward GM130, enabling local TPX2 activation for astral MT growth and spindle orientation.","evidence":"Importin α S62A mutagenesis, co-IP competition, and astral MT/spindle orientation assays","pmids":["33526712"],"confidence":"High","gaps":["Spatial coordination with other spindle cues incomplete","Single lab"]},{"year":2024,"claim":"The mechanism of ribbon continuity was unified: GM130 is a membrane-bound RNA-binding protein whose IDR drives RNA-co-condensation, and GM130-RNA condensates are sufficient to link purified Golgi membranes.","evidence":"RNA-binding assays, auxin-inducible degron depletion, IDR deletion mutagenesis, and in vitro condensate reconstitution with purified membranes","pmids":["38992139"],"confidence":"High","gaps":["RNA species and sequence determinants not fully defined","Interplay between RNA condensation and GRASP65 stacking unresolved"]},{"year":2025,"claim":"A degradative regulatory axis was established: hypoxic HIF-1α activation drives NEDD4-mediated ubiquitination and degradation of GM130, condensing the Golgi and disrupting lipid trafficking and apolipoprotein secretion.","evidence":"Hypoxia/HFD mouse model, ubiquitination assay, HIF-1α inhibitor, siRNA, and apolipoprotein secretion assays","pmids":["39900792"],"confidence":"Medium","gaps":["Ubiquitination site on GM130 not mapped","Single lab"]},{"year":null,"claim":"How GM130's RNA-driven phase separation, GRASP65-mediated stacking, Rab/SNARE tethering, and methylation/ubiquitination signals are integrated into a single regulated ribbon-maintenance program remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model coordinating condensation, stacking, and tethering","Cross-talk between PRMT5 methylation and NEDD4 ubiquitination unknown","In vivo relevance of phase separation versus protein-protein tethering not separated"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1,3,12,16,22]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[10,15,20]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[29]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,11,24]}],"localization":[{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[0,1,3,11]},{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[13,16,22]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[1,5,12]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[11,14,23,29]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[2,4,22,28]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[19]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[10,15,20]}],"complexes":["GM130-GRASP65 complex","GM130-p115 tethering complex","GM130-Tuba-Cdc42 complex"],"partners":["GORASP1","USO1","STX5","RAB1A","AKAP9","STK25","GABARAP","KPNA2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q08379","full_name":"Golgin subfamily A member 2","aliases":["130 kDa cis-Golgi matrix protein","GM130","GM130 autoantigen","Golgin-95"],"length_aa":1002,"mass_kda":113.1,"function":"Peripheral membrane component of the cis-Golgi stack that acts as a membrane skeleton that maintains the structure of the Golgi apparatus, and as a vesicle thether that facilitates vesicle fusion to the Golgi membrane (Probable) (PubMed:16489344). Required for normal protein transport from the endoplasmic reticulum to the Golgi apparatus and the cell membrane (By similarity). Together with p115/USO1 and STX5, involved in vesicle tethering and fusion at the cis-Golgi membrane to maintain the stacked and inter-connected structure of the Golgi apparatus. Plays a central role in mitotic Golgi disassembly: phosphorylation at Ser-37 by CDK1 at the onset of mitosis inhibits the interaction with p115/USO1, preventing tethering of COPI vesicles and thereby inhibiting transport through the Golgi apparatus during mitosis (By similarity). Also plays a key role in spindle pole assembly and centrosome organization (PubMed:26165940). Promotes the mitotic spindle pole assembly by activating the spindle assembly factor TPX2 to nucleate microtubules around the Golgi and capture them to couple mitotic membranes to the spindle: upon phosphorylation at the onset of mitosis, GOLGA2 interacts with importin-alpha via the nuclear localization signal region, leading to recruit importin-alpha to the Golgi membranes and liberate the spindle assembly factor TPX2 from importin-alpha. TPX2 then activates AURKA kinase and stimulates local microtubule nucleation. Upon filament assembly, nascent microtubules are further captured by GOLGA2, thus linking Golgi membranes to the spindle (PubMed:19242490, PubMed:26165940). Regulates the meiotic spindle pole assembly, probably via the same mechanism (By similarity). Also regulates the centrosome organization (PubMed:18045989, PubMed:19109421). Also required for the Golgi ribbon formation and glycosylation of membrane and secretory proteins (PubMed:16489344, PubMed:17314401)","subcellular_location":"Golgi apparatus, cis-Golgi network membrane; Endoplasmic reticulum-Golgi intermediate compartment membrane; Cytoplasm, cytoskeleton, spindle pole","url":"https://www.uniprot.org/uniprotkb/Q08379/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GOLGA2","classification":"Not Classified","n_dependent_lines":36,"n_total_lines":1208,"dependency_fraction":0.029801324503311258},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000167110","cell_line_id":"CID000796","localizations":[{"compartment":"golgi","grade":3}],"interactors":[{"gene":"RAB2A","stoichiometry":4.0},{"gene":"TMED7-TICAM2;TMED7","stoichiometry":4.0},{"gene":"ARHGAP18","stoichiometry":0.2},{"gene":"TMED4","stoichiometry":0.2},{"gene":"RAB1A","stoichiometry":0.2},{"gene":"HBB;HBD","stoichiometry":0.2},{"gene":"TMED2","stoichiometry":0.2},{"gene":"VPS37B","stoichiometry":0.2},{"gene":"SCFD1","stoichiometry":0.2},{"gene":"GORASP2","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000796","total_profiled":1310},"omim":[{"mim_id":"620240","title":"DEVELOPMENTAL DELAY WITH HYPOTONIA, MYOPATHY, AND BRAIN ABNORMALITIES; DEDHMB","url":"https://www.omim.org/entry/620240"},{"mim_id":"619397","title":"ZINC FINGER PROTEIN-LIKE 1; ZFPL1","url":"https://www.omim.org/entry/619397"},{"mim_id":"618150","title":"SAUL-WILSON SYNDROME; SWILS","url":"https://www.omim.org/entry/618150"},{"mim_id":"617852","title":"SEC23-INTERACTING PROTEIN; SEC23IP","url":"https://www.omim.org/entry/617852"},{"mim_id":"616945","title":"CLAVESIN 2; CLVS2","url":"https://www.omim.org/entry/616945"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Golgi apparatus","reliability":"Enhanced"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/GOLGA2"},"hgnc":{"alias_symbol":["GM130","golgin-95"],"prev_symbol":[]},"alphafold":{"accession":"Q08379","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q08379","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q08379-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q08379-F1-predicted_aligned_error_v6.png","plddt_mean":74.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GOLGA2","jax_strain_url":"https://www.jax.org/strain/search?query=GOLGA2"},"sequence":{"accession":"Q08379","fasta_url":"https://rest.uniprot.org/uniprotkb/Q08379.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q08379/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q08379"}},"corpus_meta":[{"pmid":"8557739","id":"PMC_8557739","title":"Characterization of a cis-Golgi matrix protein, GM130.","date":"1995","source":"The Journal of cell 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apparatus structure through methylation of the golgin GM130.","date":"2010","source":"Cell research","url":"https://pubmed.ncbi.nlm.nih.gov/20421892","citation_count":70,"is_preprint":false},{"pmid":"31833055","id":"PMC_31833055","title":"Liquid-liquid phase separation of the Golgi matrix protein GM130.","date":"2019","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/31833055","citation_count":68,"is_preprint":false},{"pmid":"28055014","id":"PMC_28055014","title":"Globozoospermia and lack of acrosome formation in GM130-deficient mice.","date":"2017","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/28055014","citation_count":66,"is_preprint":false},{"pmid":"18167358","id":"PMC_18167358","title":"Coordination of golgin tethering and SNARE assembly: GM130 binds syntaxin 5 in a p115-regulated manner.","date":"2007","source":"The Journal of biological 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The flow cytometry assay].","date":"2003","source":"Tsitologiia","url":"https://pubmed.ncbi.nlm.nih.gov/12683237","citation_count":1,"is_preprint":false},{"pmid":"15841250","id":"PMC_15841250","title":"A new member of the GM130 golgin subfamily is expressed in the optic lobe anlagen of the metamorphosing brain of Manduca sexta.","date":"2003","source":"Journal of insect science (Online)","url":"https://pubmed.ncbi.nlm.nih.gov/15841250","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.07.03.662734","title":"Piccolo Regulates Secretion of the Extracellular Matrix Components Brevican and Tenascin R from Astrocytes to Drive Synapse Formation: Implications for Pontocerebellar Hypoplasia Type 3 (PCH3)","date":"2025-07-03","source":"bioRxiv","url":"https://doi.org/10.1101/2025.07.03.662734","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.03.27.645694","title":"Actin-related protein M1 (ARPM1) required for acrosome biogenesis and sperm function in mice","date":"2025-04-01","source":"bioRxiv","url":"https://doi.org/10.1101/2025.03.27.645694","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.11.24.625065","title":"Promoting Polarization and Differentiation of Primary Human Salivary Gland Stem/Progenitor Cells in Protease-Degradable Hydrogels via ROCK Inhibition","date":"2024-11-26","source":"bioRxiv","url":"https://doi.org/10.1101/2024.11.24.625065","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":30983,"output_tokens":7891,"usd":0.105657,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":17501,"output_tokens":6744,"usd":0.128053,"stage2_stop_reason":"end_turn"},"total_usd":0.23371,"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\": 1995,\n      \"finding\": \"GM130 (GOLGA2) is a peripheral cytoplasmic protein tightly bound to Golgi membranes at the cis-Golgi network, forming part of a larger oligomeric complex. It has extended rod-like structure with coiled-coil domains and is not redistributed to the ER by brefeldin A treatment.\",\n      \"method\": \"Biochemical fractionation, immunofluorescence microscopy, immunoelectron microscopy, cDNA cloning\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (biochemistry, IF, IEM) in a foundational characterization paper, widely replicated\",\n      \"pmids\": [\"8557739\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"GM130 N-terminus directly binds the vesicle-docking protein p115, providing a membrane docking site for COPI vesicles at the cis-Golgi. Mitotic phosphorylation of GM130 prevents p115 binding, explaining Golgi fragmentation at mitosis onset. An N-terminal GM130 peptide inhibited NSF-dependent (but not p97-dependent) reassembly of Golgi cisternae from mitotic fragments.\",\n      \"method\": \"Deletion analysis, co-immunoprecipitation, in vitro Golgi reassembly assay, peptide inhibition\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution assays plus deletion mapping, replicated across multiple studies\",\n      \"pmids\": [\"9150144\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Cdc2 (CDK1) kinase directly phosphorylates GM130 at a single serine residue (Ser-25), and this phosphorylation is required for mitotic Golgi fragmentation. MEK1 was shown not to be required for GM130 phosphorylation or mitotic Golgi fragmentation either in vitro or in vivo.\",\n      \"method\": \"In vitro kinase assay, site-directed mutagenesis, mass spectrometry peptide mapping, cell-based fragmentation assay\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinase assay with mutagenesis identifying specific phosphorylation site, validated in vivo, replicated\",\n      \"pmids\": [\"9753325\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"GRASP65 and GM130 form a complex on Golgi membranes that can recruit p115. The GRASP65 binding site on GM130 maps to the sequence xxNDxxxIMVI-COOH at the C-terminus (also required for Golgi localization), and the GM130-binding site on GRASP65 maps to amino acids 189–201. GFP-reporter experiments showed that the GRASP65–GM130 interaction is required for correct targeting of both proteins to the Golgi.\",\n      \"method\": \"Gel filtration, immunoprecipitation, in vitro translation, site-directed mutagenesis, GFP fusion reporters\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mutagenesis-based binding mapping combined with gel filtration and localization reporters; replicated by crystal structure study\",\n      \"pmids\": [\"9628863\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"GM130 is phosphorylated on Ser-25 in prophase coinciding with Golgi breakdown; it remains phosphorylated through metaphase/anaphase and is dephosphorylated in telophase during Golgi reassembly. PP2A containing the Bα regulatory subunit was identified as the phosphatase responsible for dephosphorylating GM130 Ser-25 at mitotic exit.\",\n      \"method\": \"Phosphospecific antibody, temporal cell-cycle analysis, phosphatase inhibitor studies, immunoprecipitation of phosphatase\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — phosphospecific antibody with cell cycle staging, phosphatase identified biochemically, replicated findings\",\n      \"pmids\": [\"10769027\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Inhibition of p115 binding to GM130 (by microinjection of N-terminal GM130 peptide or overexpression of N-terminal-deleted GM130) increases the number of COP-sized transport vesicles and significantly inhibits VSV-G protein intracellular transport, demonstrating that the GM130–p115 tethering complex increases efficiency of vesicle fusion with the Golgi.\",\n      \"method\": \"Microinjection, overexpression, immunofluorescence quantification, electron microscopy\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo functional inhibition with electron microscopy and cargo transport readout, multiple complementary approaches\",\n      \"pmids\": [\"10679020\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Anti-GM130 antibodies inhibit VSV-G transport to the mannosidase II-containing Golgi compartment at a step after the p115-requiring step but before the giantin-requiring step, indicating a sequential role for p115, GM130, and giantin in ER-to-Golgi trafficking.\",\n      \"method\": \"Antibody microinjection, VSV-G transport assay, immunofluorescence\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — antibody inhibition with defined cargo readout, single lab, sequential step assignment\",\n      \"pmids\": [\"11035033\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"GM130, complexed with GRASP65 and other proteins, forms a Rab1 effector complex that interacts with activated Rab1-GTP in a p115-independent manner, and is required for COPII vesicle targeting/fusion with the cis-Golgi.\",\n      \"method\": \"GST pulldown, co-immunoprecipitation, vesicle transport assay\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pulldown with GTP-form specificity and functional transport assay, single lab\",\n      \"pmids\": [\"11285137\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Rab1b interacts specifically with GM130 in a GTP-dependent manner requiring the hypervariable N- and C-termini of Rab1b, with the Rab1b-binding site on GM130 distinct from the p115 and GRASP65 binding sites.\",\n      \"method\": \"Yeast two-hybrid screen, in vitro binding assay, mutagenesis\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid confirmed by in vitro binding, GTP-dependence established, single lab\",\n      \"pmids\": [\"11306556\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"GST-Rab33b (GTP-locked) interacts with GM130 by Western blotting/mass spectrometry, identifying GM130 as a putative effector of Rab33b, which regulates retrograde Golgi-to-ER transport.\",\n      \"method\": \"GST pulldown, mass spectrometry, microinjection of Rab33b mutants\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single pulldown/Western approach, no reciprocal IP, single lab\",\n      \"pmids\": [\"11718716\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"GM130 acts as a scaffold to recruit mammalian Ste20 kinases YSK1 and MST4 to the Golgi apparatus, and GM130 binding activates these kinases by promoting autophosphorylation of a conserved T-loop threonine. YSK1 phosphorylates 14-3-3ζ as a substrate at the Golgi. Interference with YSK1 disrupts perinuclear Golgi organization, cell migration, and collagen invasion.\",\n      \"method\": \"Co-immunoprecipitation, in vitro kinase assay, dominant-negative expression, biochemical substrate screen\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay with GM130-dependent activation, substrate identified biochemically, functional cell migration readout, single lab with multiple methods\",\n      \"pmids\": [\"15037601\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"GM130 and GRASP65 are required for lateral cisternal fusion events that form the continuous Golgi ribbon, and these fusion events are necessary for uniform distribution of Golgi enzymes across the ribbon.\",\n      \"method\": \"siRNA knockdown, live-cell imaging, fluorescence recovery after photobleaching (FRAP), enzyme distribution assay\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — siRNA depletion with FRAP and enzyme distribution functional readouts, multiple orthogonal methods\",\n      \"pmids\": [\"16489344\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"GM130 directly binds syntaxin 5 (a t-SNARE) via the membrane-proximal region of GM130. p115 binding to a distal site in GM130 inhibits GM130's interaction with syntaxin 5 and with Rab1. Mitotic phosphorylation also inhibits these interactions. GM130 depletion by RNAi slows ER-to-Golgi trafficking in vivo.\",\n      \"method\": \"Co-immunoprecipitation, in vitro binding assay, mutagenesis, RNAi knockdown, transport assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct binding mapped with mutagenesis, allosteric regulation by p115 demonstrated in vitro, functional trafficking readout in vivo\",\n      \"pmids\": [\"18167358\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"GM130 depletion by RNAi in human cells causes abnormal interphase centrosomes that are mispositioned and defective for microtubule organization and cell migration; when depleted cells enter mitosis, they form multipolar spindles and arrest in metaphase.\",\n      \"method\": \"RNA interference (RNAi), immunofluorescence, live-cell imaging, cell migration assay\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi in five cell lines with defined centrosome and spindle phenotypes, single lab\",\n      \"pmids\": [\"18045989\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"GM130 cycling between cis-Golgi compartments and ER-to-Golgi carriers (EGCs) is required for homotypic tethering and fusion of EGCs and their incorporation into Golgi stacks to form the Golgi ribbon. In absence of GM130, EGCs remain as distinct entities causing tubulovesicular membrane accumulation, shortened cisternae, and ribbon breakdown.\",\n      \"method\": \"siRNA knockdown, electron microscopy, live-cell imaging, cargo trafficking assay\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA with electron microscopy and live-cell imaging, single lab\",\n      \"pmids\": [\"17314401\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"GM130 regulates centrosome organization through a Golgi-associated complex with the Rho GEF Tuba and Cdc42. GM130 interaction with Tuba controls Tuba-mediated activation of Cdc42 at the Golgi; blocking Tuba or Cdc42 reproduces GM130-depletion centrosome phenotype; constitutively active Cdc42 bypasses the requirement for GM130 in centrosome regulation, placing Cdc42 downstream of GM130.\",\n      \"method\": \"Co-immunoprecipitation, RNAi knockdown, constitutively active mutant rescue, immunofluorescence\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis established by constitutively active Cdc42 rescue, reciprocal co-IP, multiple knockdowns, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"19109421\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Microtubule nucleation at the Golgi apparatus requires AKAP450, which binds the cis-side of the Golgi in a GM130-dependent manner. Depletion of GM130 disorganizes the AKAP450 network and impairs Golgi-based MT nucleation; brefeldin A redistributes AKAP450 to ER exit sites along with MT nucleation activity.\",\n      \"method\": \"siRNA knockdown, microtubule regrowth assay, immunofluorescence, brefeldin A treatment\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — GM130-dependent AKAP450 recruitment to Golgi established with depletion and MT nucleation functional readout; replicated in concept by subsequent studies\",\n      \"pmids\": [\"19242490\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PRMT5 localizes to the Golgi, forms complexes with GM130 and other Golgi ribbon/vesicle-tethering components, and methylates N-terminal arginines in GM130. PRMT5 depletion causes Golgi ribbon formation defects; arginine methylation of GM130 is critical for Golgi ribbon maintenance.\",\n      \"method\": \"Co-immunoprecipitation, in vitro methylation assay, siRNA knockdown, mutagenesis, immunofluorescence\",\n      \"journal\": \"Cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro methylation assay plus mutagenesis and functional Golgi ribbon readout, single lab\",\n      \"pmids\": [\"20421892\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In mouse oocyte meiosis, GM130 localizes to spindle poles and midbody in a spindle-dependent manner; morpholino-mediated knockdown causes abnormal spindle formation, reduced polar body extrusion, impaired localization of γ-tubulin and Plk1 at MTOCs, aberrant spindle migration, and blocked p-MEK1/2 accumulation at spindle poles.\",\n      \"method\": \"Morpholino microinjection, immunofluorescence, live-cell imaging, nocodazole treatment\",\n      \"journal\": \"Cell cycle (Georgetown, Tex.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — morpholino knockdown with multiple phenotypic readouts in oocytes, single lab\",\n      \"pmids\": [\"21552007\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"WAC and GM130 directly interact at the Golgi; WAC binding to GM130 is required for autophagy. GM130 tethers GABARAP to the Golgi, inhibiting autophagy; WAC suppresses GM130 binding to GABARAP to allow centrosomal GABARAP delivery to the phagophore. Specifically, unlipidated and lipidated GABARAP (but not LC3B, GABARAPL1, or GATE-16) activates ULK kinase via the ULK1 LIR motif, revealing a non-hierarchical role for GABARAP in starvation-induced autophagy.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, immunofluorescence, in vitro binding, ULK kinase assay\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct interaction mapped, kinase assay, multiple knockdowns with specific rescue experiments, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"26687599\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"GM130 forms a complex with RasGRF at the Golgi to regulate the Golgi pool of Cdc42. GM130 silencing causes RasGRF-dependent inhibition of Golgi Cdc42 (not plasma membrane Cdc42), disrupts asymmetric front-rear Cdc42-GTP distribution in migrating cells, and activates RasGRF-dependent Ras-ERK signaling. GM130 loss also induces E-cadherin downregulation indicative of EMT.\",\n      \"method\": \"Co-immunoprecipitation, Cdc42 activity (FRET) assay, siRNA knockdown, rescue experiments\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — spatial Cdc42 activity measured by FRET, RasGRF epistasis tested with double knockdown, single lab\",\n      \"pmids\": [\"25208761\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"In Drosophila dendrites, GM130 is responsible for connecting distinct Golgi compartments at soma and dendritic branch points; GM130 distribution determines the compartmental organization of dendritic Golgi outposts, which in turn regulates acentrosomal microtubule growth and dendritic branching.\",\n      \"method\": \"RNAi knockdown, immunofluorescence in vivo, live imaging, dendritic branching quantification\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi with multiple functional readouts (microtubule growth, dendritic branching) in vivo, single lab\",\n      \"pmids\": [\"24835455\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"GM130 interacts with importin α via a classical nuclear localization signal (NLS) at mitotic entry, sequestering importin α on Golgi membranes. This releases the spindle assembly factor TPX2, which activates Aurora-A and stimulates local microtubule nucleation. GM130 also captures nascent microtubules, linking Golgi membranes to the spindle for organelle inheritance.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence, mutagenesis of NLS, siRNA knockdown, microtubule regrowth assay\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mechanism established with NLS mutagenesis, importin α co-IP, functional MT nucleation readout, multiple orthogonal approaches\",\n      \"pmids\": [\"26165940\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Crystal structure of GRASP65 PDZ domains in complex with the GM130 C-terminal peptide (1.96 Å resolution) reveals that GM130 simultaneously binds both PDZ1 and PDZ2 domains of GRASP65, contrary to prior models proposing only PDZ2 involvement. Mutagenesis experiments confirmed the structural observations.\",\n      \"method\": \"X-ray crystallography (1.96 Å), site-directed mutagenesis, co-immunoprecipitation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure with mutagenesis validation, single lab but high-resolution structural data\",\n      \"pmids\": [\"26363069\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"GM130 is a parallel homotetramer (not a homodimer as previously assumed) with a flexible rod-like structure exhibiting N-terminally open (Y-shaped) and closed (I-shaped) conformations, as revealed by biochemical and electron microscopic analyses.\",\n      \"method\": \"Gel filtration, electron microscopy, analytical ultracentrifugation\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — EM with biochemical analyses establishing tetrameric state; single lab, no mutagenesis validation of oligomeric state\",\n      \"pmids\": [\"25787021\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Targeted neuronal deletion of GM130 in mice causes Golgi fragmentation and defective positioning in Purkinje cells, impaired secretory trafficking, dendritic atrophy, reduced cerebellar size and Purkinje cell number, and progressive ataxia, demonstrating that Golgi dysfunction via GM130 loss is causally linked to neurodegeneration in vivo.\",\n      \"method\": \"Conditional knockout mice, immunofluorescence, electron microscopy, secretory trafficking assay, behavioral phenotyping\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO with multiple cellular and in vivo readouts, causality established by selective neuronal deletion\",\n      \"pmids\": [\"28028212\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"GM130 knockout in mice causes globozoospermia; loss of GM130 does not affect secretion of pro-acrosomic vesicles but prevents their fusion into a single large acrosome vesicle. GM130 loss disrupts co-localization of adaptor protein complex AP1 and TGN46, suggesting GM130 is required for sorting and coating of Golgi-derived pro-acrosomic vesicles.\",\n      \"method\": \"Knockout mouse model, immunofluorescence, electron microscopy, co-localization analysis\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knockout model with electron microscopy and vesicle tracking, mechanistic interpretation based on co-localization, single lab\",\n      \"pmids\": [\"28055014\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Purified recombinant GM130 undergoes liquid-liquid phase separation into dynamic liquid-like droplets in near-physiological buffers at concentrations similar to its estimated local concentration at the cis-Golgi. Overexpressed GM130 also forms liquid droplets in cells.\",\n      \"method\": \"In vitro phase separation assay with recombinant protein, live-cell imaging of overexpressed protein\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution of phase separation with recombinant protein at physiological concentrations; single lab, no mutagenesis\",\n      \"pmids\": [\"31833055\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CDK1-mediated phosphorylation of importin α at Ser-62 switches its substrate preference from TPX2 to GM130, thereby enabling GM130 to compete for importin α binding and locally activate TPX2 at the spindle pole area to promote astral microtubule growth and proper spindle orientation.\",\n      \"method\": \"Mutagenesis (importin α S62A), co-immunoprecipitation, astral microtubule growth assay, spindle orientation measurement\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phosphorylation site mutagenesis with functional spindle orientation readout and direct competition assay, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"33526712\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"GM130 is a membrane-bound RNA-binding protein that directly recruits RNA and associated RNA-binding proteins to the Golgi membrane. RNA–GM130 condensates maintain the Golgi ribbon through liquid-liquid phase separation mediated by an intrinsically disordered N-terminal domain of GM130. Acute RNA degradation or GM130 loss disrupts the ribbon; GM130–RNA co-condensates are sufficient to link purified Golgi membranes in vitro.\",\n      \"method\": \"RNA-binding assay, acute RNA degradation (auxin-inducible degron for GM130), in vitro condensate reconstitution with purified membranes, deletion mutagenesis of IDR, live-cell imaging\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with purified proteins/membranes, mutagenesis of IDR, acute depletion systems, multiple orthogonal methods in single rigorous study\",\n      \"pmids\": [\"38992139\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"GM130 interacts with the C-terminus of the HERG potassium channel in the Golgi; LQT2-causing HERG C-terminal mutations selectively disrupt this GM130 interaction. Overexpression of GM130 suppresses HERG current amplitude, suggesting GM130 functions as a checkpoint in HERG trafficking through the Golgi.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation from HEK-293 cells, confocal co-localization, Xenopus oocyte current measurement\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP and functional current readout, disease mutation mapping, single lab\",\n      \"pmids\": [\"12270925\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Bacterial effector EspG (from EPEC/EHEC) binds GM130 as identified by Y2H and confirmed by affinity co-purification and co-immunoprecipitation. EspG expression localizes to the Golgi and induces its fragmentation, disrupting protein secretion more potently than NleA/EspI.\",\n      \"method\": \"Yeast two-hybrid, affinity co-purification, co-immunoprecipitation, ectopic expression, secretion assay\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Y2H confirmed by two biochemical methods, functional secretion readout, single lab\",\n      \"pmids\": [\"21740499\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"HIF-1α activation under hypoxia induces NEDD4-mediated ubiquitination and degradation of GM130, causing Golgi condensation. GM130 degradation promotes lipid accumulation and apolipoprotein A1 retention in intestinal epithelium. Inhibition of HIF-1α or NEDD4 prevents GM130 degradation and rescues Golgi structure and lipid trafficking.\",\n      \"method\": \"Hypoxia/HFD mouse model, co-immunoprecipitation, ubiquitination assay, HIF-1α inhibitor (PX-478), siRNA knockdown, apolipoprotein secretion assay\",\n      \"journal\": \"Experimental & molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ubiquitination assay identifies NEDD4 as the E3 ligase, HIF-1α epistasis tested pharmacologically, in vivo validation, single lab\",\n      \"pmids\": [\"39900792\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GM130 (GOLGA2) is a cis-Golgi peripheral membrane protein that functions as a multivalent scaffold: its N-terminus tethers COPI vesicles by binding p115 (regulated by CDK1-mediated phosphorylation at Ser-25 during mitosis, with PP2A-Bα mediating dephosphorylation at telophase); its C-terminus anchors GRASP65 to stabilize Golgi stacking; it directly binds syntaxin 5 to couple tethering with SNARE-mediated fusion; it recruits AKAP450 to nucleate microtubules at the Golgi; at mitotic entry it sequesters importin α via an NLS to liberate TPX2 for Golgi-derived spindle assembly; it scaffolds YSK1/MST4 kinase activation and a Tuba-Cdc42 signaling complex for centrosome regulation and directed cell migration; PRMT5 methylates GM130 N-terminal arginines to maintain Golgi ribbon architecture; GM130 tethers GABARAP to the Golgi to suppress autophagy until WAC-mediated release; and GM130 acts as a membrane-bound RNA-binding protein whose intrinsically disordered N-terminal domain drives liquid-liquid phase separation with RNA to maintain the continuous Golgi ribbon, while NEDD4-mediated ubiquitination downstream of HIF-1α can degrade GM130 to disrupt Golgi architecture and lipid trafficking.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"GOLGA2 (GM130) is a peripheral cis-Golgi membrane protein that serves as a multivalent structural and signaling scaffold governing Golgi architecture, membrane trafficking, microtubule organization, and cell-cycle-coupled organelle dynamics [#0, #1]. Through its N-terminus it tethers incoming COPI vesicles by binding p115, increasing the efficiency of vesicle fusion at the cis-Golgi, and it directly engages the t-SNARE syntaxin 5 to couple tethering to membrane fusion in ER-to-Golgi transport [#1, #5, #12]. Its C-terminus binds GRASP65 across both PDZ domains to drive the lateral cisternal fusion events that build and maintain the continuous Golgi ribbon [#3, #11, #23], a function reinforced by its capacity to act as a membrane-bound RNA-binding protein whose intrinsically disordered N-terminal domain undergoes liquid-liquid phase separation with RNA to link Golgi membranes [#27, #29]. Mitotic entry switches GM130 off as a tether: CDK1 phosphorylates Ser-25 to block p115, syntaxin 5, and Rab1 binding and drive Golgi fragmentation, with PP2A-Bα reversing this at telophase [#2, #4, #12]; concurrently GM130 sequesters importin α through an NLS to liberate the spindle factor TPX2 for Golgi-derived microtubule nucleation and spindle orientation [#22, #28]. GM130 organizes the microtubule cytoskeleton by recruiting AKAP450 for Golgi-based microtubule nucleation and scaffolds signaling outputs including YSK1/MST4 kinase activation and Tuba/RasGRF-Cdc42 complexes that control centrosome organization and directed cell migration [#10, #15, #16, #20]. It additionally tethers GABARAP to suppress autophagy until WAC-mediated release [#19]. In vivo, neuronal GM130 loss causes Golgi fragmentation, secretory defects, and progressive ataxia [#25], and its degradation via HIF-1α/NEDD4-mediated ubiquitination disrupts Golgi structure and lipid trafficking [#32].\",\n  \"teleology\": [\n    {\n      \"year\": 1995,\n      \"claim\": \"Establishing the existence and properties of GM130 was needed before any function could be assigned; this defined it as a stable cis-Golgi peripheral scaffold protein.\",\n      \"evidence\": \"Biochemical fractionation, immuno-EM, and cDNA cloning characterizing an oligomeric coiled-coil Golgi protein resistant to brefeldin A\",\n      \"pmids\": [\"8557739\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No functional partners identified at this stage\", \"Mechanism of membrane attachment not resolved\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"It was unknown how vesicles dock at the cis-Golgi; GM130 was shown to bind p115 directly, providing a tethering site for COPI vesicles and explaining mitotic Golgi fragmentation through phosphoregulation of this interaction.\",\n      \"evidence\": \"Deletion mapping, co-IP, and in vitro Golgi reassembly with peptide inhibition\",\n      \"pmids\": [\"9150144\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the mitotic kinase not yet established\", \"How tethering couples to fusion machinery unknown\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"The mitotic switch was mechanistically defined: CDK1/Cdc2 directly phosphorylates Ser-25 to drive Golgi fragmentation, and the GRASP65 C-terminal interaction was mapped, establishing GM130 as a bipartite scaffold linking vesicle docking and stacking.\",\n      \"evidence\": \"In vitro kinase assay with site-directed mutagenesis; gel filtration, IP, and GFP-reporter mapping of the GRASP65 site\",\n      \"pmids\": [\"9753325\", \"9628863\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Phosphatase reversing Ser-25 not identified\", \"Stoichiometry of the GM130-GRASP65-p115 complex unresolved\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"The temporal control and physiological consequence of GM130 tethering were resolved: PP2A-Bα dephosphorylates Ser-25 at telophase, and inhibiting p115 binding impairs cargo transport, demonstrating the tether increases vesicle fusion efficiency.\",\n      \"evidence\": \"Phosphospecific antibody cell-cycle staging with phosphatase IP; microinjection/overexpression with EM and VSV-G transport readouts\",\n      \"pmids\": [\"10769027\", \"10679020\", \"11035033\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Sequential ordering relative to giantin from single lab\", \"Direct fusion catalysis not reconstituted\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"GM130 was placed within Rab-GTPase signaling at the cis-Golgi, acting as a GTP-dependent effector of Rab1 (and implicated for Rab33b) for COPII vesicle targeting, broadening its role beyond COPI tethering.\",\n      \"evidence\": \"Yeast two-hybrid, GST pulldown with GTP-locked Rabs, mutagenesis, and vesicle transport assays\",\n      \"pmids\": [\"11285137\", \"11306556\", \"11718716\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Rab33b interaction rests on a single pulldown without reciprocal IP\", \"Functional separation of Rab1 vs p115 inputs incomplete\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"It was unclear how the Golgi nucleates signaling; GM130 was shown to recruit and allosterically activate YSK1/MST4 kinases, linking the scaffold to Golgi organization, cell migration, and invasion.\",\n      \"evidence\": \"Co-IP, GM130-dependent in vitro kinase activation assay, substrate screen, and dominant-negative migration/invasion assays\",\n      \"pmids\": [\"15037601\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream effectors of 14-3-3ζ phosphorylation unclear\", \"Single lab\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"The ribbon-building function was defined: GM130 and GRASP65 mediate the lateral cisternal fusion events required for a continuous ribbon and uniform Golgi enzyme distribution.\",\n      \"evidence\": \"siRNA knockdown with FRAP, live imaging, and enzyme distribution assays\",\n      \"pmids\": [\"16489344\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular fusion intermediates not visualized\", \"Relative contributions of GM130 vs GRASP65 not separated\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"How tethering couples to fusion and to membrane dynamics was clarified: GM130 directly binds syntaxin 5, with p115 and mitotic phosphorylation allosterically gating syntaxin 5/Rab1 binding, and GM130 cycling drives EGC tethering into stacks.\",\n      \"evidence\": \"In vitro binding/mutagenesis with allosteric competition; RNAi with EM, live imaging, and trafficking assays\",\n      \"pmids\": [\"18167358\", \"17314401\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"SNARE-pairing partners of syntaxin 5 at this step not mapped\", \"Quantitative kinetics of the conformational switch unresolved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"GM130 was extended beyond the secretory pathway into cytoskeletal and cell-cycle control, with depletion causing centrosome mispositioning, defective microtubule organization, and mitotic spindle defects.\",\n      \"evidence\": \"RNAi across multiple cell lines with immunofluorescence, live imaging, and migration assays\",\n      \"pmids\": [\"18045989\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular link between Golgi GM130 and centrosomes not yet defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"The centrosome connection was mechanistically resolved: GM130 scaffolds a Tuba GEF-Cdc42 complex at the Golgi, with epistasis placing Cdc42 activation downstream of GM130 for centrosome regulation.\",\n      \"evidence\": \"Reciprocal co-IP, RNAi, and constitutively active Cdc42 rescue/epistasis\",\n      \"pmids\": [\"19109421\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Spatial activation of Cdc42 not yet imaged directly\", \"Single lab\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Golgi-based microtubule nucleation was attributed to GM130: it is required to recruit AKAP450 to the cis-Golgi, organizing the MT-nucleating network.\",\n      \"evidence\": \"siRNA depletion, MT regrowth assay, and brefeldin A redistribution analysis\",\n      \"pmids\": [\"19242490\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct vs indirect AKAP450 binding not distinguished\", \"γ-TuRC recruitment hierarchy unresolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"A post-translational regulator of ribbon architecture was identified: PRMT5 methylates GM130 N-terminal arginines, a modification critical for Golgi ribbon maintenance.\",\n      \"evidence\": \"Co-IP, in vitro methylation, siRNA, and mutagenesis with ribbon-formation readout\",\n      \"pmids\": [\"20421892\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional readers of methyl-arginine unknown\", \"Single lab\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"GM130's mitotic/meiotic spindle role was demonstrated in vivo in oocytes, where it is required for spindle formation, MTOC factor localization, and spindle migration.\",\n      \"evidence\": \"Morpholino knockdown with immunofluorescence, live imaging, and nocodazole treatment\",\n      \"pmids\": [\"21552007\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct molecular targets at the meiotic MTOC not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"GM130 was identified as a host target of bacterial pathogens, with the EPEC/EHEC effector EspG binding GM130 to fragment the Golgi and disrupt secretion.\",\n      \"evidence\": \"Y2H confirmed by affinity co-purification and co-IP with ectopic expression and secretion assays\",\n      \"pmids\": [\"21740499\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether EspG blocks specific GM130 interactions not resolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"A regulatory role in autophagy was established: GM130 tethers GABARAP to the Golgi to suppress autophagy, and WAC binding releases GABARAP to activate ULK kinase via its LIR motif.\",\n      \"evidence\": \"Direct binding/mutagenesis, siRNA with specific rescue, and ULK kinase assays\",\n      \"pmids\": [\"26687599\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stimuli controlling WAC-GM130 association incomplete\", \"Single lab\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"GM130 was shown to spatially pattern Cdc42 signaling for migration via a RasGRF complex, and to function across organisms in dendritic Golgi outpost organization and acentrosomal MT growth.\",\n      \"evidence\": \"Co-IP, Cdc42 FRET activity, siRNA/rescue in mammalian cells; RNAi with live imaging and branching quantification in Drosophila\",\n      \"pmids\": [\"25208761\", \"24835455\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Link between Golgi Cdc42 pool and EMT markers correlational\", \"Single lab per system\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"The mechanism of Golgi-derived spindle assembly and the structural basis of stacking were resolved: GM130 sequesters importin α via an NLS to release TPX2/Aurora-A, and the crystal structure showed GM130 engages both GRASP65 PDZ domains, while GM130 was redefined as a flexible parallel homotetramer.\",\n      \"evidence\": \"NLS mutagenesis, co-IP, MT regrowth; 1.96 Å crystal structure with mutagenesis; gel filtration, EM, and analytical ultracentrifugation\",\n      \"pmids\": [\"26165940\", \"26363069\", \"25787021\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Oligomeric state lacks mutagenesis validation\", \"Conformational switching trigger not defined\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"GM130 loss was causally linked to neurodegeneration in vivo, with neuronal deletion producing Golgi fragmentation, secretory defects, Purkinje cell loss, and progressive ataxia.\",\n      \"evidence\": \"Conditional knockout mice with immunofluorescence, EM, trafficking assays, and behavioral phenotyping\",\n      \"pmids\": [\"28028212\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific secreted cargoes driving the phenotype not identified\", \"Cell-autonomy versus circuit effects unresolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"A tissue-specific vesicle-sorting role was defined: GM130 is required for fusion of pro-acrosomic vesicles into a single acrosome, with knockout causing globozoospermia and disrupted AP1/TGN46 sorting.\",\n      \"evidence\": \"Knockout mouse with EM and co-localization analysis\",\n      \"pmids\": [\"28055014\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct sorting machinery interaction inferred from co-localization\", \"Single lab\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"A biophysical basis for GM130 self-assembly emerged: purified GM130 undergoes liquid-liquid phase separation at near-physiological concentrations, forming droplets in cells.\",\n      \"evidence\": \"In vitro phase separation with recombinant protein and live-cell imaging of overexpressed protein\",\n      \"pmids\": [\"31833055\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological driver of condensation not identified at this stage\", \"No mutagenesis of the responsible region\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"The importin α switch was refined: CDK1 phosphorylation of importin α Ser-62 reprograms its substrate preference toward GM130, enabling local TPX2 activation for astral MT growth and spindle orientation.\",\n      \"evidence\": \"Importin α S62A mutagenesis, co-IP competition, and astral MT/spindle orientation assays\",\n      \"pmids\": [\"33526712\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Spatial coordination with other spindle cues incomplete\", \"Single lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"The mechanism of ribbon continuity was unified: GM130 is a membrane-bound RNA-binding protein whose IDR drives RNA-co-condensation, and GM130-RNA condensates are sufficient to link purified Golgi membranes.\",\n      \"evidence\": \"RNA-binding assays, auxin-inducible degron depletion, IDR deletion mutagenesis, and in vitro condensate reconstitution with purified membranes\",\n      \"pmids\": [\"38992139\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"RNA species and sequence determinants not fully defined\", \"Interplay between RNA condensation and GRASP65 stacking unresolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"A degradative regulatory axis was established: hypoxic HIF-1α activation drives NEDD4-mediated ubiquitination and degradation of GM130, condensing the Golgi and disrupting lipid trafficking and apolipoprotein secretion.\",\n      \"evidence\": \"Hypoxia/HFD mouse model, ubiquitination assay, HIF-1α inhibitor, siRNA, and apolipoprotein secretion assays\",\n      \"pmids\": [\"39900792\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ubiquitination site on GM130 not mapped\", \"Single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How GM130's RNA-driven phase separation, GRASP65-mediated stacking, Rab/SNARE tethering, and methylation/ubiquitination signals are integrated into a single regulated ribbon-maintenance program remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model coordinating condensation, stacking, and tethering\", \"Cross-talk between PRMT5 methylation and NEDD4 ubiquitination unknown\", \"In vivo relevance of phase separation versus protein-protein tethering not separated\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 3, 12, 16, 22]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [10, 15, 20]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [29]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 11, 24]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [0, 1, 3, 11]},\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [13, 16, 22]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [1, 5, 12]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [11, 14, 23, 29]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [2, 4, 22, 28]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [19]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [10, 15, 20]}\n    ],\n    \"complexes\": [\n      \"GM130-GRASP65 complex\",\n      \"GM130-p115 tethering complex\",\n      \"GM130-Tuba-Cdc42 complex\"\n    ],\n    \"partners\": [\n      \"GORASP1\",\n      \"USO1\",\n      \"STX5\",\n      \"RAB1A\",\n      \"AKAP9\",\n      \"STK25\",\n      \"GABARAP\",\n      \"KPNA2\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}