{"gene":"RAB1B","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":1991,"finding":"RAB1B is required for vesicular transport from the ER to the cis-Golgi compartment and between successive cis- and medial-Golgi compartments, as demonstrated by reconstitution of ER-to-Golgi transport in a cell-free assay and immunolocalization of RAB1B to both ER and Golgi compartments.","method":"Cell-free reconstitution assay of ER-to-Golgi transport; monoclonal antibody inhibition; subcellular fractionation and immunolocalization","journal":"The Journal of Cell Biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — cell-free reconstitution assay with antibody inhibition, foundational study replicated extensively by subsequent work","pmids":["1918138"],"is_preprint":false},{"year":1989,"finding":"RAB1B protein binds GTP and GDP specifically and possesses intrinsic GTPase activity; the Lys21→Met mutant abolishes GTP binding, while the Ala65→Thr mutant reduces GTPase activity and retains autophosphorylation competence in the presence of GTP.","method":"In vitro biochemical assay with purified recombinant protein; site-directed mutagenesis; GTP/GDP binding and GTPase activity measurements","journal":"FEBS Letters","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with mutagenesis, single study but multiple orthogonal biochemical methods","pmids":["2509243"],"is_preprint":false},{"year":1993,"finding":"The effector domain of RAB1B (residues I41, D44) is essential for geranylgeranylation by GGTase II; mutations I41N and D44N in the effector domain essentially abolish isoprenylation, while mutations in the N-terminal variable region, β3 strand, or Loop 7 do not reduce isoprenylation.","method":"In vitro isoprenylation assay using reticulocyte lysates; site-directed mutagenesis; deletion analysis","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro enzymatic assay with systematic mutagenesis, single lab with multiple mutants tested","pmids":["8325834"],"is_preprint":false},{"year":1995,"finding":"RAB1B is required for ER-to-Golgi transport of beta-amyloid precursor protein (βAPP); dominant-negative RAB1B mutants (N121I, S22N) block conversion of immature Endo-H-sensitive βAPP to mature O-glycosylated form and inhibit secretion of APP-α and Aβ peptide.","method":"Co-expression of dominant-negative RAB1B mutants with βAPP in 293 cells; [35S]methionine pulse-chase; Endo-H sensitivity assay; immunoprecipitation","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — clean loss-of-function with defined molecular readout, multiple mutants, single lab","pmids":["7738040"],"is_preprint":false},{"year":1995,"finding":"Dominant-negative RAB1B (N121I) blocks ER-to-Golgi transport and maturation of the LDL receptor, preventing its conversion from the Endo-H-sensitive 120-125 kDa form to the mature 160-170 kDa form and preventing its delivery to the cell surface.","method":"Co-expression of dominant-negative RAB1B with LDL receptor in 293 cells; [35S]methionine pulse-chase; Endo-H sensitivity; sulfo-NHS-biotin cell surface labeling","journal":"Journal of Receptor and Signal Transduction Research","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — clean loss-of-function with defined phenotype, single lab, single cargo tested","pmids":["8673720"],"is_preprint":false},{"year":1996,"finding":"Association of geranylgeranylated RAB1B with GDP-dissociation inhibitors (GDI-α and GDI-2) is required for recycling of prenylated RAB1B to the cytosol but not for initial membrane targeting; the effector-domain mutant D44N fails to form GDI complexes yet is still delivered to intracellular membranes.","method":"Co-immunoprecipitation with anti-FLAG beads; in vitro GDI binding assay; [3H]mevalonate metabolic labeling; subcellular fractionation; immunofluorescence","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP in vitro and in vivo, metabolic labeling, fractionation — multiple orthogonal methods, single lab","pmids":["8631911"],"is_preprint":false},{"year":1996,"finding":"RAB1B geranylgeranylation by Rab-GGTase preferentially requires the GDP-bound conformation of the substrate in cell-free assays; the GTPase-deficient Q67L mutant is poorly prenylated when GTP predominates but prenylated normally when GDP is the predominant nucleotide.","method":"Cell-free geranylgeranylation assay with defined nucleotide compositions; [3H]mevalonate metabolic labeling in transfected 293 cells; co-IP with GDI","journal":"The Biochemical Journal","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro enzymatic assay with mutagenesis, but single lab and result partially contradicted in vivo","pmids":["8836150"],"is_preprint":false},{"year":1998,"finding":"The Switch 2 domain (α2 helix, residues I73, Y78, A81) of RAB1B is essential for binding to Rab escort protein (REP); mutations in this helix prevent prenylation by preventing association of nascent RAB1B with REP, while REP binds preferentially to GDP-bound RAB1B.","method":"Cell-free geranylgeranylation assay; [3H]mevalonate metabolic labeling; [32P]orthophosphate nucleotide binding assay; gel filtration co-fractionation of REP-RAB1B complexes from transfected 293 cells","journal":"Molecular Biology of the Cell","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with systematic mutagenesis plus in-cell metabolic labeling and co-fractionation, multiple orthogonal methods","pmids":["9437002"],"is_preprint":false},{"year":1999,"finding":"Correct intracellular localization and tight membrane association of RAB1B depends on GDP/GTP exchange; inactive (S22N, N121I) and constitutively active (Q67L) mutants are not tightly integrated into target membranes in BHK cells.","method":"Expression of RAB1B mutants in BHK cells; subcellular localization by immunofluorescence; membrane association assay; co-expression with Mss4","journal":"International Journal of Oncology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — localization studies with multiple mutants, single lab, limited mechanistic depth","pmids":["10493955"],"is_preprint":false},{"year":2001,"finding":"RAB1B interacts specifically with the Golgi matrix protein GM130 in a GTP-dependent manner, requiring the hypervariable regions of the N- and C-termini of RAB1B; the RAB1B binding site on GM130 is distinct from the p115 and Grasp65 binding sites.","method":"Yeast two-hybrid screen; in vitro binding assays; deletion and mutagenesis mapping","journal":"EMBO Reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid plus in vitro binding assay, two orthogonal methods, single lab","pmids":["11306556"],"is_preprint":false},{"year":2003,"finding":"Inactive RAB1B (N121I mutant) blocks ER-to-Golgi transport and induces Golgi disruption by compromising COPI recruitment (release of β-COP into cytosol); this phenotype can be rescued by expressing ARF1 or its GEF GBF1, placing RAB1B upstream of ARF1/GBF1-mediated COPI recruitment. The active Q67L mutant confers resistance to BFA-induced Golgi disruption.","method":"Expression of RAB1B dominant-negative and constitutively active mutants in cells; immunofluorescence; subcellular fractionation for β-COP; BFA treatment; co-expression rescue experiments","journal":"Molecular Biology of the Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis with rescue experiments, multiple mutants, fractionation, replicated by subsequent studies","pmids":["12802079"],"is_preprint":false},{"year":2007,"finding":"Active RAB1B (Q67L) increases GBF1 and COPI association at ER exit sites and stabilizes ARF1 on Golgi membranes; GBF1 is identified as a RAB1B effector via its N-terminal domain; RAB1B siRNA reduces GBF1 membrane association; FRAP shows rapid RAB1B cycling at the Golgi (t½ ~120 s) with minimal microtubule dependence.","method":"Dominant mutant expression; co-immunoprecipitation; siRNA knockdown; live-cell time-lapse microscopy; FRAP","journal":"Molecular Biology of the Cell","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP identifying effector, FRAP for dynamics, siRNA functional analysis — multiple orthogonal methods, single lab","pmids":["17429068"],"is_preprint":false},{"year":2010,"finding":"The Legionella effector DrrA AMPylates RAB1B at Tyr77 (switch II region), covalently attaching AMP; this modification restricts GTPase-activating protein access, rendering RAB1B constitutively active. DrrA also acts as a guanine nucleotide exchange factor for RAB1B.","method":"Biochemical AMPylation assay with purified proteins; mass spectrometry identification of modification site; GEF activity assay; GAP accessibility assay","journal":"Science","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro enzymatic reconstitution with MS-confirmed modification site and functional consequence, widely replicated","pmids":["20651120"],"is_preprint":false},{"year":2010,"finding":"RAB1B is required for ER-to-Golgi transport of Ebolavirus matrix protein VP40, and dominant-negative RAB1B interferes with VP40-mediated particle formation; this occurs through the RAB1B→GBF1→ARF1→COPI pathway.","method":"Dominant-negative RAB1B expression; VP40 particle formation assay; GBF1 and ARF1 inhibition studies","journal":"Journal of Virology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — functional assay with dominant-negative and pathway inhibitors, single lab","pmids":["20164217"],"is_preprint":false},{"year":2010,"finding":"RAB1B interacts with COPII components Sec23, Sec24, and Sec31 and modulates COPII assembly/disassembly kinetics at ER exit sites; RAB1B inhibition (by dominant-negative or siRNA) changes COPII phenotype and delays cargo sorting at ER exit sites, as measured by FRAP.","method":"Co-immunoprecipitation; siRNA knockdown; dominant-negative mutant expression; FRAP at ER exit sites; cargo transport assay","journal":"European Journal of Cell Biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP identifying interaction with COPII components, FRAP kinetics, siRNA knockdown — multiple methods, single lab","pmids":["21093099"],"is_preprint":false},{"year":2012,"finding":"MTMR6 (phosphatidylinositol 3-phosphatase) preferentially interacts with GDP-bound RAB1B via its GRAM domain and partially colocalizes with RAB1B in pericentrosomal and peri-Golgi regions; RAB1B regulates the localization of MTMR6, and MTMR6 reduction accelerates VSV-G transport (a RAB1B-dependent process); both RAB1B and MTMR6 are required for omegasome tubule formation in autophagy.","method":"Co-immunoprecipitation with GDP/GTP-locked RAB1B mutants; siRNA knockdown of RAB1B and MTMR6; immunofluorescence colocalization; VSV-G transport assay; DFCP1-induced omegasome assay","journal":"The Journal of Biological Chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with nucleotide-state discrimination, siRNA functional rescue, multiple assays, single lab","pmids":["23188820"],"is_preprint":false},{"year":2013,"finding":"Legionella LepB inactivates RAB1B by acting as a GTPase-activating protein (GAP) via an atypical RabGAP mechanism reminiscent of classical GAPs (distinct from mammalian TBC-like GAPs); the crystal structure of the RAB1B:LepB complex reveals an unusual fold in the GAP domain.","method":"Crystal structure determination of RAB1B:LepB complex; biochemical GAP activity assays; mutagenesis","journal":"EMBO Reports","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure with biochemical validation, single study with structural and enzymatic orthogonal methods","pmids":["23288104"],"is_preprint":false},{"year":2014,"finding":"The vesicle docking protein p115 enhances RAB1B activation and membrane association: p115 binds RAB1B through its cc2 domain, p115 inhibition causes RAB1B dissociation from Golgi membranes, and constitutively active RAB1B suppresses the COPI recruitment defect caused by p115 inhibition, establishing p115 as a functional upstream activator of RAB1B in COPI recruitment.","method":"siRNA knockdown of p115; dominant-active RAB1B rescue experiments; co-immunoprecipitation domain mapping; immunofluorescence for COPI and RAB1B localization","journal":"Cellular Logistics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis rescue, domain-mapping Co-IP, localization assays — multiple methods, single lab","pmids":["25332841"],"is_preprint":false},{"year":2015,"finding":"Loss of RAB1B leads to elevated TGF-β receptor 1 (TβR1) levels through decreased ubiquitin-dependent degradation, increased phospho-SMAD3, and TGF-β-induced EMT, revealing that RAB1B acts upstream of TGF-β/SMAD signaling as a metastasis suppressor.","method":"siRNA knockdown and overexpression of RAB1B in TNBC cell lines; Western blotting for TβR1, pSMAD3; ubiquitination assay; in vitro migration/invasion assays; in vivo xenograft","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — loss-of-function with defined signaling readouts and mechanistic follow-up, single lab","pmids":["25970785"],"is_preprint":false},{"year":2015,"finding":"Host RAB1B is recruited to the Yersinia-containing vacuole (YCV) and is required for Y. pestis evasion of phagosome maturation; RAB1B knockdown prevents YCV acidification inhibition and alters LAMP1 association with the YCV, demonstrating RAB1B recruitment is a mechanism by which Y. pestis subverts phagosomal killing.","method":"siRNA/shRNA knockdown of RAB1B in macrophages; immunofluorescence for RAB1B on YCV; phagosomal pH measurement; LAMP1 colocalization assay; bacterial survival assay","journal":"PLoS Pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA knockdown with multiple functional readouts, consistent with Legionella data, single lab","pmids":["26495854"],"is_preprint":false},{"year":2016,"finding":"PITPNC1 promotes malignant secretion by binding Golgi-resident PI4P and localizing RAB1B to the Golgi; RAB1B localization to the Golgi recruits GOLPH3, which facilitates Golgi extension and enhanced vesicular release of pro-invasive factors.","method":"Biochemical PI4P binding assay; RAB1B localization by immunofluorescence; GOLPH3 co-immunoprecipitation; vesicular release assay; siRNA knockdown","journal":"Cancer Cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biochemical binding assay, localization studies, and downstream functional readouts — multiple orthogonal methods, single lab","pmids":["26977884"],"is_preprint":false},{"year":2016,"finding":"Adenylylation of Tyr77 of RAB1B by DrrA stabilizes the active (GTP-like) conformation independently of bound nucleotide, primarily through electrostatic effects of the additional negative charge in the switch II region; Phe45-adenine stacking has only minor influence.","method":"Molecular dynamics simulation; advanced sampling simulations","journal":"Scientific Reports","confidence":"Low","confidence_rationale":"Tier 4 / Weak — computational simulation only, no experimental validation in this study","pmids":["26818796"],"is_preprint":false},{"year":2016,"finding":"RAB1B dynamically associates with ER exit sites, VTCs, and the Golgi complex; RAB1B dwell time at ER exit sites is regulated by GBF1, and RAB1B membrane cycling kinetics at ERES are dependent on GBF1 membrane association and activity, as shown by live-cell dual-expression imaging and BFA washout experiments.","method":"Live-cell dual-color fluorescence microscopy; FRAP; brefeldin A washout cargo-sorting assay; GBF1 dominant-negative and siRNA experiments","journal":"PLoS One","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — live imaging with FRAP and epistasis experiments, multiple readouts, single lab","pmids":["27500526"],"is_preprint":false},{"year":2017,"finding":"RAB1B is associated with ATG9A-containing vesicles in mammalian cells; RAB1B knockdown suppresses autophagy and causes ATG9A accumulation at intermediate membrane structures at autophagosome formation sites, demonstrating RAB1B is required for proper ATG9A vesicle dynamics during autophagosome formation.","method":"Immunoisolation of ATG9A vesicles followed by proteomics; siRNA knockdown of RAB1B; fluorescence microscopy of ATG9A and autophagy markers; autophagy flux assay","journal":"FASEB Journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proteomics-based identification confirmed by siRNA with phenotypic readout, single lab, two orthogonal approaches","pmids":["28522593"],"is_preprint":false},{"year":2017,"finding":"Staphylococcus aureus alpha-hemolysin induces formation of dynamic tubular structures (Saf) labeled with RAB1B, RAB7, and LC3; these tubules emerge from the S. aureus-containing phagosome and their formation depends on RAB1B activity, microtubule integrity, Kinesin-1, and RILP.","method":"Live-cell imaging; dominant-negative RAB1B expression; microtubule disruption; siRNA knockdown of kinesin/RILP; fluorescence microscopy","journal":"Frontiers in Cellular and Infection Microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — live imaging with dominant-negative and pharmacological inhibitors, single lab","pmids":["29046869"],"is_preprint":false},{"year":2018,"finding":"RAB1B is a direct transcriptional target of RUNX1; RUNX1 binds the RAB1B promoter at consensus RUNX1 sites (shown by ChIP and EMSA); RUNX1 knockdown impairs ER-to-Golgi vesicle trafficking and Golgi structure in megakaryocytic cells, and these defects are rescued by RAB1B reconstitution; RAB1B is required for trafficking of von Willebrand factor to α-granules.","method":"Chromatin immunoprecipitation; EMSA; luciferase promoter assay with RUNX1 site mutations; siRNA knockdown of RUNX1 and RAB1B; RAB1B rescue experiments; ER-to-Golgi transport assay; vWF trafficking assay","journal":"Blood Advances","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — ChIP, EMSA, promoter mutagenesis, rescue experiments, multiple orthogonal methods establishing transcriptional regulation and functional consequence","pmids":["29632235"],"is_preprint":false},{"year":2019,"finding":"RAB1B promotes antiviral innate immune signaling by forming a protein complex with TRAF3 and facilitating the interaction between TRAF3 and MAVS, thereby enhancing RIG-I pathway activation and IFN-β induction; RAB1B deletion dampens IFN-β signaling and increases Zika virus susceptibility.","method":"Co-immunoprecipitation; RAB1B overexpression and CRISPR deletion in multiple human cell types; IFN-β luciferase reporter assay; viral infection assay (Zika virus)","journal":"The Journal of Biological Chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP identifying TRAF3 complex, genetic KO with functional readout, multiple cell types, single lab","pmids":["31375559"],"is_preprint":false},{"year":2019,"finding":"RAB1B directly binds FMDV IRES RNA and stimulates IRES-mediated translation; IRES-driven RNA localizes in close proximity to RAB1B at the ER-Golgi interface, while dominant-negative RAB1B that disorganizes the Golgi abolishes this colocalization.","method":"Proteomics-based IRES interactor identification; direct RNA binding assay; IRES translation assay; RNA-FISH imaging with RAB1B colocalization","journal":"Life Science Alliance","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct RNA binding assay plus functional translation assay and imaging, single lab","pmids":["30655362"],"is_preprint":false},{"year":2020,"finding":"Human GOLPH3 is a bona fide effector of RAB1B; GOLPH3 interacts directly with RAB1B in a nucleotide-dependent manner favoring the GTP-locked active state; expression of GTP-locked RAB1B variants reduces GOLPH3 distribution at the Golgi apparatus.","method":"Co-immunoprecipitation with GTP/GDP-locked RAB1B mutants; direct binding assay; immunofluorescence for GOLPH3 localization","journal":"PLoS One","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with nucleotide-state discrimination and localization readout, single lab, two orthogonal methods","pmids":["32790781"],"is_preprint":false},{"year":2023,"finding":"The Legionella enzyme Lem3 acts as a dephosphocholinase on RAB1B, hydrolytically removing the phosphocholine moiety added by AnkX at Ser76; the crystal structures of Lem3 alone and in complex with RAB1B reveal that Lem3 acts by locally unfolding RAB1B at the switch II region and that Lem3 shares structural similarity with metal-dependent protein phosphatases.","method":"Crystal structure determination of Lem3 apo and Lem3:RAB1B complex (covalent capture); enzymatic dephosphocholination assay; structural analysis","journal":"Nature Communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure with covalent-capture stabilization and enzymatic validation, multiple orthogonal structural and biochemical methods","pmids":["37076474"],"is_preprint":false},{"year":2024,"finding":"RAB1B promotes DGAT2 redistribution from the ER to the lipid droplet surface (shown by FRET between DGAT2 and RAB1B activity mutants), thereby facilitating lipid droplet growth; TBC1D20 (the RAB1B GAP mutated in Warburg Micro syndrome) loss-of-function alters LD metabolism and DGAT2 redistribution consistently with elevated RAB1B activity.","method":"FRET between DGAT2 and RAB1B activity mutants; dominant-negative RAB1B overexpression to block LD formation; TBC1D20 mutant fibroblasts from WARBM model mice; fluorescence microscopy","journal":"Science Advances","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — FRET-based interaction mapping with activity mutants and disease-model validation, single lab","pmids":["38809969"],"is_preprint":false},{"year":2025,"finding":"TBC1D22B is a GAP that directly targets RAB1B; TBC1D22B overexpression inhibits ER-to-Golgi transport in a GAP-activity-dependent manner, and RAB1B silencing phenocopies TBC1D22B-induced trafficking defects, placing RAB1B as the direct substrate of TBC1D22B in ER-to-Golgi transport regulation.","method":"Proximity-labeling and co-immunoprecipitation proteomics; RUSH system ER-to-Golgi transport assay; RAB1B siRNA knockdown; GAP-dead mutant rescue experiments","journal":"Advanced Science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple proteomics approaches plus functional transport assay with GAP-activity dependence, single lab","pmids":["40878439"],"is_preprint":false}],"current_model":"RAB1B is a small GTPase that cycles between GDP-bound (inactive) and GTP-bound (active) states regulated by GEFs (including DrrA/SidM from Legionella) and GAPs (including LepB, TBC1D20, TBC1D22B), and is geranylgeranylated by GGTase II in a process requiring its effector domain and Switch 2 region for prior REP binding; in its GTP-active form, RAB1B localizes to ER exit sites and the Golgi where it acts sequentially through effectors GBF1, ARF1, and COPI coat proteins to drive ER-to-Golgi vesicular transport of diverse cargoes (βAPP, LDL receptor, vWF, viral proteins), also interacting with GM130, GOLPH3, p115, and COPII components (Sec23/24/31) to coordinate vesicle budding and tethering; beyond the secretory pathway, RAB1B associates with ATG9A vesicles to regulate autophagosome formation and with MTMR6 to modulate phosphoinositide metabolism, forms a complex with TRAF3-MAVS to promote antiviral IFN-β signaling, and facilitates lipid droplet growth by directing DGAT2 from ER to lipid droplet surfaces; Legionella exploits RAB1B by AMPylating Tyr77 (DrrA) and phosphocholinating Ser76 (AnkX) to lock it in active or altered states, while Lem3 reverses the phosphocholination by locally unfolding the switch II region."},"narrative":{"mechanistic_narrative":"RAB1B is a small GTPase that drives vesicular transport from the endoplasmic reticulum to the cis- and medial-Golgi, established by cell-free reconstitution and antibody-inhibition assays [PMID:1918138]. It cycles between GDP- and GTP-bound states using intrinsic GTPase activity and conserved nucleotide-binding residues, where Lys21 governs GTP binding and Ala65 modulates hydrolysis [PMID:2509243]; correct membrane targeting depends on this nucleotide cycle, since both inactive and constitutively active mutants fail to integrate tightly into target membranes [PMID:10493955]. Membrane delivery further requires C-terminal geranylgeranylation by Rab-GGTase, which depends on the effector domain (I41, D44) [PMID:8325834] and on prior REP binding mediated by the Switch 2 helix to the GDP-bound form [PMID:9437002], with prenylated RAB1B subsequently recycled via GDI complexes [PMID:8631911]. In its GTP-active state at ER exit sites and the Golgi, RAB1B acts upstream of GBF1, ARF1, and COPI coat recruitment to execute and regulate Golgi-directed transport, with GBF1 identified as a direct effector [PMID:12802079, PMID:17429068]; it coordinates with COPII components Sec23/24/31 at ER exit sites [PMID:21093099], binds the tethering proteins GM130 and p115 in nucleotide-dependent fashion [PMID:11306556, PMID:25332841], and dynamically cycles between ERES, VTCs, and the Golgi [PMID:27500526]. Through this trafficking activity RAB1B mediates ER-to-Golgi transport and maturation of diverse cargoes including βAPP, the LDL receptor, and von Willebrand factor, the last under transcriptional control of RUNX1 [PMID:7738040, PMID:8673720, PMID:29632235]. Beyond classical secretion, RAB1B associates with ATG9A vesicles to support autophagosome formation [PMID:28522593], partners with the phosphoinositide phosphatase MTMR6 [PMID:23188820], recruits the effector GOLPH3 to promote Golgi-based secretion [PMID:26977884, PMID:32790781], forms a TRAF3 complex that bridges TRAF3 to MAVS to enhance RIG-I-driven IFN-β signaling [PMID:31375559], and directs DGAT2 from the ER to lipid droplet surfaces to drive lipid droplet growth [PMID:38809969]. RAB1B is targeted by multiple GAPs that inactivate it, including the Legionella effector LepB [PMID:23288104], TBC1D20 (linked to Warburg Micro syndrome) [PMID:38809969], and TBC1D22B [PMID:40878439], and is hijacked by bacterial pathogens through covalent switch-region modifications: Legionella DrrA acts as a GEF and AMPylates Tyr77 to lock RAB1B active [PMID:20651120], AnkX phosphocholinates Ser76, and Lem3 reverses this by locally unfolding the switch II region [PMID:37076474].","teleology":[{"year":1989,"claim":"Established that RAB1B is a genuine GTP-binding protein with intrinsic GTPase activity, defining the nucleotide-dependent switch that underlies its function.","evidence":"In vitro GTP/GDP binding and GTPase assays with purified recombinant protein and site-directed mutants (Lys21Met, Ala65Thr)","pmids":["2509243"],"confidence":"High","gaps":["Did not link biochemical activity to a cellular process","GEFs and GAPs regulating the cycle not yet identified"]},{"year":1991,"claim":"Defined the core cellular role of RAB1B as required for ER-to-cis-Golgi and intra-Golgi vesicular transport.","evidence":"Cell-free reconstitution of ER-to-Golgi transport with monoclonal antibody inhibition and subcellular immunolocalization","pmids":["1918138"],"confidence":"High","gaps":["Molecular effectors mediating transport not identified","Mechanism of vesicle budding vs tethering unresolved"]},{"year":1993,"claim":"Mapped the determinants of RAB1B membrane attachment, showing the effector domain is required for geranylgeranylation.","evidence":"In vitro isoprenylation assay in reticulocyte lysates with systematic effector-domain mutagenesis (I41N, D44N)","pmids":["8325834"],"confidence":"High","gaps":["Did not resolve how prenylation enzyme is recruited","Role of REP not yet defined"]},{"year":1995,"claim":"Connected RAB1B trafficking activity to physiological cargo maturation, showing it is required for ER-to-Golgi transport of βAPP and the LDL receptor.","evidence":"Dominant-negative RAB1B (N121I, S22N) co-expression with cargo in 293 cells, pulse-chase, Endo-H sensitivity, and surface labeling","pmids":["7738040","8673720"],"confidence":"High","gaps":["Cargo selectivity vs general transport block not distinguished","Step in the pathway where RAB1B acts not yet placed"]},{"year":1998,"claim":"Resolved the prenylation prerequisites, showing REP binds GDP-bound RAB1B via the Switch 2 helix to enable geranylgeranylation and that GDI recycling follows.","evidence":"Cell-free geranylgeranylation, metabolic labeling, nucleotide-binding assays, gel-filtration co-fractionation, and GDI co-IP with effector-domain mutants","pmids":["9437002","8631911","8836150"],"confidence":"High","gaps":["Conflicting in vitro vs in vivo conformational preference for prenylation","Structural basis of REP recognition not solved here"]},{"year":2007,"claim":"Placed RAB1B upstream of the GBF1/ARF1/COPI machinery, identifying GBF1 as a direct effector and demonstrating rapid membrane cycling at the Golgi.","evidence":"Dominant mutant epistasis with ARF1/GBF1 rescue, reciprocal Co-IP, siRNA, and FRAP","pmids":["12802079","17429068"],"confidence":"High","gaps":["Order of effector engagement relative to tethering not fully resolved","How GEF input is delivered to RAB1B at ERES unclear"]},{"year":2014,"claim":"Integrated tethering factors GM130 and p115 and the COPII coat into the RAB1B trafficking cycle, defining its budding-to-tethering coordination.","evidence":"Yeast two-hybrid and domain-mapping Co-IP for GM130/p115, COPII (Sec23/24/31) Co-IP and FRAP, and p115 epistasis rescue","pmids":["11306556","21093099","25332841","27500526"],"confidence":"Medium","gaps":["Hierarchy among p115, GM130, GBF1 inputs not fully ordered","Direct vs indirect COPII engagement uncertain"]},{"year":2013,"claim":"Defined how Legionella locks and unlocks the RAB1B switch, revealing DrrA as a GEF and AMPylase (Tyr77) and LepB as a structurally atypical GAP.","evidence":"In vitro AMPylation with MS site mapping, GEF/GAP-accessibility assays, and crystal structure of the RAB1B:LepB complex","pmids":["20651120","23288104"],"confidence":"High","gaps":["Host enzymes counteracting bacterial AMPylation not identified here","Physiological host GAP for RAB1B not yet characterized"]},{"year":2017,"claim":"Extended RAB1B function beyond classical secretion into autophagy and phosphoinositide regulation via ATG9A vesicles and MTMR6.","evidence":"ATG9A vesicle immunoisolation proteomics with siRNA autophagy-flux assays; nucleotide-state Co-IP with MTMR6 and omegasome assays","pmids":["28522593","23188820"],"confidence":"Medium","gaps":["Whether autophagy role is separable from ER-to-Golgi transport unclear","Direct effector at autophagosome formation sites not defined"]},{"year":2019,"claim":"Revealed signaling and translational roles, showing RAB1B bridges TRAF3 to MAVS for IFN-β induction and directly binds FMDV IRES RNA to stimulate translation.","evidence":"Reciprocal Co-IP and CRISPR deletion with IFN-β reporters and viral infection; direct RNA binding, IRES translation assays, and RNA-FISH","pmids":["31375559","30655362"],"confidence":"Medium","gaps":["Whether RNA binding and signaling depend on trafficking activity unresolved","Structural basis of TRAF3 and RNA engagement unknown"]},{"year":2025,"claim":"Expanded the regulatory and effector landscape, defining GOLPH3 as an effector, identifying TBC1D20 and TBC1D22B as host GAPs, and linking RAB1B to lipid droplet growth via DGAT2 redistribution.","evidence":"Nucleotide-state Co-IP for GOLPH3; FRET-based DGAT2 redistribution with TBC1D20 disease-model fibroblasts; proximity-labeling proteomics and RUSH transport assays for TBC1D22B","pmids":["32790781","26977884","38809969","40878439"],"confidence":"Medium","gaps":["Disease mechanism of Warburg Micro syndrome via RAB1B not directly established here","How distinct GAPs partition RAB1B functions spatially unclear"]},{"year":null,"claim":"How RAB1B's many roles—ER-to-Golgi transport, autophagy, lipid droplet growth, antiviral signaling, and RNA binding—are spatially and temporally partitioned by distinct GEFs, GAPs, and effectors remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model coordinating secretory vs non-secretory functions","Endogenous GEFs for most contexts undefined","Structural basis of effector selectivity across functions unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003924","term_label":"GTPase activity","supporting_discovery_ids":[1,12,16,31]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,10,11]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[27]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[0,14,22,30]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[0,9,11,20,22]},{"term_id":"GO:0005811","term_label":"lipid droplet","supporting_discovery_ids":[30]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[5,10]}],"pathway":[{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[0,3,4,25]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[10,11,14]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[15,23]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[26]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[30]}],"complexes":[],"partners":["GBF1","GM130","P115","GOLPH3","MTMR6","TRAF3","TBC1D22B","DGAT2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9H0U4","full_name":"Ras-related protein Rab-1B","aliases":[],"length_aa":201,"mass_kda":22.2,"function":"The small GTPases Rab are key regulators of intracellular membrane trafficking, from the formation of transport vesicles to their fusion with membranes (PubMed:20545908, PubMed:9437002, PubMed:23236136). Rabs cycle between an inactive GDP-bound form and an active GTP-bound form that is able to recruit to membranes different set of downstream effectors directly responsible for vesicle formation, movement, tethering and fusion (PubMed:9437002). Plays a role in the initial events of the autophagic vacuole development which take place at specialized regions of the endoplasmic reticulum (PubMed:20545908). Regulates vesicular transport between the endoplasmic reticulum and successive Golgi compartments (By similarity). Required to modulate the compacted morphology of the Golgi (PubMed:26209634). Promotes the recruitment of lipid phosphatase MTMR6 to the endoplasmic reticulum-Golgi intermediate compartment (By similarity)","subcellular_location":"Cytoplasm; Membrane; Preautophagosomal structure membrane; Cytoplasm, perinuclear region","url":"https://www.uniprot.org/uniprotkb/Q9H0U4/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RAB1B","classification":"Not 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reconstitution assay of ER-to-Golgi transport; monoclonal antibody inhibition; subcellular fractionation and immunolocalization\",\n      \"journal\": \"The Journal of Cell Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cell-free reconstitution assay with antibody inhibition, foundational study replicated extensively by subsequent work\",\n      \"pmids\": [\"1918138\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1989,\n      \"finding\": \"RAB1B protein binds GTP and GDP specifically and possesses intrinsic GTPase activity; the Lys21→Met mutant abolishes GTP binding, while the Ala65→Thr mutant reduces GTPase activity and retains autophosphorylation competence in the presence of GTP.\",\n      \"method\": \"In vitro biochemical assay with purified recombinant protein; site-directed mutagenesis; GTP/GDP binding and GTPase activity measurements\",\n      \"journal\": \"FEBS Letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with mutagenesis, single study but multiple orthogonal biochemical methods\",\n      \"pmids\": [\"2509243\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"The effector domain of RAB1B (residues I41, D44) is essential for geranylgeranylation by GGTase II; mutations I41N and D44N in the effector domain essentially abolish isoprenylation, while mutations in the N-terminal variable region, β3 strand, or Loop 7 do not reduce isoprenylation.\",\n      \"method\": \"In vitro isoprenylation assay using reticulocyte lysates; site-directed mutagenesis; deletion analysis\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro enzymatic assay with systematic mutagenesis, single lab with multiple mutants tested\",\n      \"pmids\": [\"8325834\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"RAB1B is required for ER-to-Golgi transport of beta-amyloid precursor protein (βAPP); dominant-negative RAB1B mutants (N121I, S22N) block conversion of immature Endo-H-sensitive βAPP to mature O-glycosylated form and inhibit secretion of APP-α and Aβ peptide.\",\n      \"method\": \"Co-expression of dominant-negative RAB1B mutants with βAPP in 293 cells; [35S]methionine pulse-chase; Endo-H sensitivity assay; immunoprecipitation\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean loss-of-function with defined molecular readout, multiple mutants, single lab\",\n      \"pmids\": [\"7738040\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Dominant-negative RAB1B (N121I) blocks ER-to-Golgi transport and maturation of the LDL receptor, preventing its conversion from the Endo-H-sensitive 120-125 kDa form to the mature 160-170 kDa form and preventing its delivery to the cell surface.\",\n      \"method\": \"Co-expression of dominant-negative RAB1B with LDL receptor in 293 cells; [35S]methionine pulse-chase; Endo-H sensitivity; sulfo-NHS-biotin cell surface labeling\",\n      \"journal\": \"Journal of Receptor and Signal Transduction Research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — clean loss-of-function with defined phenotype, single lab, single cargo tested\",\n      \"pmids\": [\"8673720\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Association of geranylgeranylated RAB1B with GDP-dissociation inhibitors (GDI-α and GDI-2) is required for recycling of prenylated RAB1B to the cytosol but not for initial membrane targeting; the effector-domain mutant D44N fails to form GDI complexes yet is still delivered to intracellular membranes.\",\n      \"method\": \"Co-immunoprecipitation with anti-FLAG beads; in vitro GDI binding assay; [3H]mevalonate metabolic labeling; subcellular fractionation; immunofluorescence\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP in vitro and in vivo, metabolic labeling, fractionation — multiple orthogonal methods, single lab\",\n      \"pmids\": [\"8631911\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"RAB1B geranylgeranylation by Rab-GGTase preferentially requires the GDP-bound conformation of the substrate in cell-free assays; the GTPase-deficient Q67L mutant is poorly prenylated when GTP predominates but prenylated normally when GDP is the predominant nucleotide.\",\n      \"method\": \"Cell-free geranylgeranylation assay with defined nucleotide compositions; [3H]mevalonate metabolic labeling in transfected 293 cells; co-IP with GDI\",\n      \"journal\": \"The Biochemical Journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro enzymatic assay with mutagenesis, but single lab and result partially contradicted in vivo\",\n      \"pmids\": [\"8836150\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"The Switch 2 domain (α2 helix, residues I73, Y78, A81) of RAB1B is essential for binding to Rab escort protein (REP); mutations in this helix prevent prenylation by preventing association of nascent RAB1B with REP, while REP binds preferentially to GDP-bound RAB1B.\",\n      \"method\": \"Cell-free geranylgeranylation assay; [3H]mevalonate metabolic labeling; [32P]orthophosphate nucleotide binding assay; gel filtration co-fractionation of REP-RAB1B complexes from transfected 293 cells\",\n      \"journal\": \"Molecular Biology of the Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with systematic mutagenesis plus in-cell metabolic labeling and co-fractionation, multiple orthogonal methods\",\n      \"pmids\": [\"9437002\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Correct intracellular localization and tight membrane association of RAB1B depends on GDP/GTP exchange; inactive (S22N, N121I) and constitutively active (Q67L) mutants are not tightly integrated into target membranes in BHK cells.\",\n      \"method\": \"Expression of RAB1B mutants in BHK cells; subcellular localization by immunofluorescence; membrane association assay; co-expression with Mss4\",\n      \"journal\": \"International Journal of Oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — localization studies with multiple mutants, single lab, limited mechanistic depth\",\n      \"pmids\": [\"10493955\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"RAB1B interacts specifically with the Golgi matrix protein GM130 in a GTP-dependent manner, requiring the hypervariable regions of the N- and C-termini of RAB1B; the RAB1B binding site on GM130 is distinct from the p115 and Grasp65 binding sites.\",\n      \"method\": \"Yeast two-hybrid screen; in vitro binding assays; deletion and mutagenesis mapping\",\n      \"journal\": \"EMBO Reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid plus in vitro binding assay, two orthogonal methods, single lab\",\n      \"pmids\": [\"11306556\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Inactive RAB1B (N121I mutant) blocks ER-to-Golgi transport and induces Golgi disruption by compromising COPI recruitment (release of β-COP into cytosol); this phenotype can be rescued by expressing ARF1 or its GEF GBF1, placing RAB1B upstream of ARF1/GBF1-mediated COPI recruitment. The active Q67L mutant confers resistance to BFA-induced Golgi disruption.\",\n      \"method\": \"Expression of RAB1B dominant-negative and constitutively active mutants in cells; immunofluorescence; subcellular fractionation for β-COP; BFA treatment; co-expression rescue experiments\",\n      \"journal\": \"Molecular Biology of the Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis with rescue experiments, multiple mutants, fractionation, replicated by subsequent studies\",\n      \"pmids\": [\"12802079\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Active RAB1B (Q67L) increases GBF1 and COPI association at ER exit sites and stabilizes ARF1 on Golgi membranes; GBF1 is identified as a RAB1B effector via its N-terminal domain; RAB1B siRNA reduces GBF1 membrane association; FRAP shows rapid RAB1B cycling at the Golgi (t½ ~120 s) with minimal microtubule dependence.\",\n      \"method\": \"Dominant mutant expression; co-immunoprecipitation; siRNA knockdown; live-cell time-lapse microscopy; FRAP\",\n      \"journal\": \"Molecular Biology of the Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP identifying effector, FRAP for dynamics, siRNA functional analysis — multiple orthogonal methods, single lab\",\n      \"pmids\": [\"17429068\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The Legionella effector DrrA AMPylates RAB1B at Tyr77 (switch II region), covalently attaching AMP; this modification restricts GTPase-activating protein access, rendering RAB1B constitutively active. DrrA also acts as a guanine nucleotide exchange factor for RAB1B.\",\n      \"method\": \"Biochemical AMPylation assay with purified proteins; mass spectrometry identification of modification site; GEF activity assay; GAP accessibility assay\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro enzymatic reconstitution with MS-confirmed modification site and functional consequence, widely replicated\",\n      \"pmids\": [\"20651120\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"RAB1B is required for ER-to-Golgi transport of Ebolavirus matrix protein VP40, and dominant-negative RAB1B interferes with VP40-mediated particle formation; this occurs through the RAB1B→GBF1→ARF1→COPI pathway.\",\n      \"method\": \"Dominant-negative RAB1B expression; VP40 particle formation assay; GBF1 and ARF1 inhibition studies\",\n      \"journal\": \"Journal of Virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — functional assay with dominant-negative and pathway inhibitors, single lab\",\n      \"pmids\": [\"20164217\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"RAB1B interacts with COPII components Sec23, Sec24, and Sec31 and modulates COPII assembly/disassembly kinetics at ER exit sites; RAB1B inhibition (by dominant-negative or siRNA) changes COPII phenotype and delays cargo sorting at ER exit sites, as measured by FRAP.\",\n      \"method\": \"Co-immunoprecipitation; siRNA knockdown; dominant-negative mutant expression; FRAP at ER exit sites; cargo transport assay\",\n      \"journal\": \"European Journal of Cell Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP identifying interaction with COPII components, FRAP kinetics, siRNA knockdown — multiple methods, single lab\",\n      \"pmids\": [\"21093099\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"MTMR6 (phosphatidylinositol 3-phosphatase) preferentially interacts with GDP-bound RAB1B via its GRAM domain and partially colocalizes with RAB1B in pericentrosomal and peri-Golgi regions; RAB1B regulates the localization of MTMR6, and MTMR6 reduction accelerates VSV-G transport (a RAB1B-dependent process); both RAB1B and MTMR6 are required for omegasome tubule formation in autophagy.\",\n      \"method\": \"Co-immunoprecipitation with GDP/GTP-locked RAB1B mutants; siRNA knockdown of RAB1B and MTMR6; immunofluorescence colocalization; VSV-G transport assay; DFCP1-induced omegasome assay\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with nucleotide-state discrimination, siRNA functional rescue, multiple assays, single lab\",\n      \"pmids\": [\"23188820\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Legionella LepB inactivates RAB1B by acting as a GTPase-activating protein (GAP) via an atypical RabGAP mechanism reminiscent of classical GAPs (distinct from mammalian TBC-like GAPs); the crystal structure of the RAB1B:LepB complex reveals an unusual fold in the GAP domain.\",\n      \"method\": \"Crystal structure determination of RAB1B:LepB complex; biochemical GAP activity assays; mutagenesis\",\n      \"journal\": \"EMBO Reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure with biochemical validation, single study with structural and enzymatic orthogonal methods\",\n      \"pmids\": [\"23288104\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The vesicle docking protein p115 enhances RAB1B activation and membrane association: p115 binds RAB1B through its cc2 domain, p115 inhibition causes RAB1B dissociation from Golgi membranes, and constitutively active RAB1B suppresses the COPI recruitment defect caused by p115 inhibition, establishing p115 as a functional upstream activator of RAB1B in COPI recruitment.\",\n      \"method\": \"siRNA knockdown of p115; dominant-active RAB1B rescue experiments; co-immunoprecipitation domain mapping; immunofluorescence for COPI and RAB1B localization\",\n      \"journal\": \"Cellular Logistics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis rescue, domain-mapping Co-IP, localization assays — multiple methods, single lab\",\n      \"pmids\": [\"25332841\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Loss of RAB1B leads to elevated TGF-β receptor 1 (TβR1) levels through decreased ubiquitin-dependent degradation, increased phospho-SMAD3, and TGF-β-induced EMT, revealing that RAB1B acts upstream of TGF-β/SMAD signaling as a metastasis suppressor.\",\n      \"method\": \"siRNA knockdown and overexpression of RAB1B in TNBC cell lines; Western blotting for TβR1, pSMAD3; ubiquitination assay; in vitro migration/invasion assays; in vivo xenograft\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — loss-of-function with defined signaling readouts and mechanistic follow-up, single lab\",\n      \"pmids\": [\"25970785\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Host RAB1B is recruited to the Yersinia-containing vacuole (YCV) and is required for Y. pestis evasion of phagosome maturation; RAB1B knockdown prevents YCV acidification inhibition and alters LAMP1 association with the YCV, demonstrating RAB1B recruitment is a mechanism by which Y. pestis subverts phagosomal killing.\",\n      \"method\": \"siRNA/shRNA knockdown of RAB1B in macrophages; immunofluorescence for RAB1B on YCV; phagosomal pH measurement; LAMP1 colocalization assay; bacterial survival assay\",\n      \"journal\": \"PLoS Pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA knockdown with multiple functional readouts, consistent with Legionella data, single lab\",\n      \"pmids\": [\"26495854\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PITPNC1 promotes malignant secretion by binding Golgi-resident PI4P and localizing RAB1B to the Golgi; RAB1B localization to the Golgi recruits GOLPH3, which facilitates Golgi extension and enhanced vesicular release of pro-invasive factors.\",\n      \"method\": \"Biochemical PI4P binding assay; RAB1B localization by immunofluorescence; GOLPH3 co-immunoprecipitation; vesicular release assay; siRNA knockdown\",\n      \"journal\": \"Cancer Cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biochemical binding assay, localization studies, and downstream functional readouts — multiple orthogonal methods, single lab\",\n      \"pmids\": [\"26977884\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Adenylylation of Tyr77 of RAB1B by DrrA stabilizes the active (GTP-like) conformation independently of bound nucleotide, primarily through electrostatic effects of the additional negative charge in the switch II region; Phe45-adenine stacking has only minor influence.\",\n      \"method\": \"Molecular dynamics simulation; advanced sampling simulations\",\n      \"journal\": \"Scientific Reports\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — computational simulation only, no experimental validation in this study\",\n      \"pmids\": [\"26818796\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"RAB1B dynamically associates with ER exit sites, VTCs, and the Golgi complex; RAB1B dwell time at ER exit sites is regulated by GBF1, and RAB1B membrane cycling kinetics at ERES are dependent on GBF1 membrane association and activity, as shown by live-cell dual-expression imaging and BFA washout experiments.\",\n      \"method\": \"Live-cell dual-color fluorescence microscopy; FRAP; brefeldin A washout cargo-sorting assay; GBF1 dominant-negative and siRNA experiments\",\n      \"journal\": \"PLoS One\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — live imaging with FRAP and epistasis experiments, multiple readouts, single lab\",\n      \"pmids\": [\"27500526\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"RAB1B is associated with ATG9A-containing vesicles in mammalian cells; RAB1B knockdown suppresses autophagy and causes ATG9A accumulation at intermediate membrane structures at autophagosome formation sites, demonstrating RAB1B is required for proper ATG9A vesicle dynamics during autophagosome formation.\",\n      \"method\": \"Immunoisolation of ATG9A vesicles followed by proteomics; siRNA knockdown of RAB1B; fluorescence microscopy of ATG9A and autophagy markers; autophagy flux assay\",\n      \"journal\": \"FASEB Journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proteomics-based identification confirmed by siRNA with phenotypic readout, single lab, two orthogonal approaches\",\n      \"pmids\": [\"28522593\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Staphylococcus aureus alpha-hemolysin induces formation of dynamic tubular structures (Saf) labeled with RAB1B, RAB7, and LC3; these tubules emerge from the S. aureus-containing phagosome and their formation depends on RAB1B activity, microtubule integrity, Kinesin-1, and RILP.\",\n      \"method\": \"Live-cell imaging; dominant-negative RAB1B expression; microtubule disruption; siRNA knockdown of kinesin/RILP; fluorescence microscopy\",\n      \"journal\": \"Frontiers in Cellular and Infection Microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — live imaging with dominant-negative and pharmacological inhibitors, single lab\",\n      \"pmids\": [\"29046869\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"RAB1B is a direct transcriptional target of RUNX1; RUNX1 binds the RAB1B promoter at consensus RUNX1 sites (shown by ChIP and EMSA); RUNX1 knockdown impairs ER-to-Golgi vesicle trafficking and Golgi structure in megakaryocytic cells, and these defects are rescued by RAB1B reconstitution; RAB1B is required for trafficking of von Willebrand factor to α-granules.\",\n      \"method\": \"Chromatin immunoprecipitation; EMSA; luciferase promoter assay with RUNX1 site mutations; siRNA knockdown of RUNX1 and RAB1B; RAB1B rescue experiments; ER-to-Golgi transport assay; vWF trafficking assay\",\n      \"journal\": \"Blood Advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — ChIP, EMSA, promoter mutagenesis, rescue experiments, multiple orthogonal methods establishing transcriptional regulation and functional consequence\",\n      \"pmids\": [\"29632235\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"RAB1B promotes antiviral innate immune signaling by forming a protein complex with TRAF3 and facilitating the interaction between TRAF3 and MAVS, thereby enhancing RIG-I pathway activation and IFN-β induction; RAB1B deletion dampens IFN-β signaling and increases Zika virus susceptibility.\",\n      \"method\": \"Co-immunoprecipitation; RAB1B overexpression and CRISPR deletion in multiple human cell types; IFN-β luciferase reporter assay; viral infection assay (Zika virus)\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP identifying TRAF3 complex, genetic KO with functional readout, multiple cell types, single lab\",\n      \"pmids\": [\"31375559\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"RAB1B directly binds FMDV IRES RNA and stimulates IRES-mediated translation; IRES-driven RNA localizes in close proximity to RAB1B at the ER-Golgi interface, while dominant-negative RAB1B that disorganizes the Golgi abolishes this colocalization.\",\n      \"method\": \"Proteomics-based IRES interactor identification; direct RNA binding assay; IRES translation assay; RNA-FISH imaging with RAB1B colocalization\",\n      \"journal\": \"Life Science Alliance\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct RNA binding assay plus functional translation assay and imaging, single lab\",\n      \"pmids\": [\"30655362\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Human GOLPH3 is a bona fide effector of RAB1B; GOLPH3 interacts directly with RAB1B in a nucleotide-dependent manner favoring the GTP-locked active state; expression of GTP-locked RAB1B variants reduces GOLPH3 distribution at the Golgi apparatus.\",\n      \"method\": \"Co-immunoprecipitation with GTP/GDP-locked RAB1B mutants; direct binding assay; immunofluorescence for GOLPH3 localization\",\n      \"journal\": \"PLoS One\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with nucleotide-state discrimination and localization readout, single lab, two orthogonal methods\",\n      \"pmids\": [\"32790781\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The Legionella enzyme Lem3 acts as a dephosphocholinase on RAB1B, hydrolytically removing the phosphocholine moiety added by AnkX at Ser76; the crystal structures of Lem3 alone and in complex with RAB1B reveal that Lem3 acts by locally unfolding RAB1B at the switch II region and that Lem3 shares structural similarity with metal-dependent protein phosphatases.\",\n      \"method\": \"Crystal structure determination of Lem3 apo and Lem3:RAB1B complex (covalent capture); enzymatic dephosphocholination assay; structural analysis\",\n      \"journal\": \"Nature Communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure with covalent-capture stabilization and enzymatic validation, multiple orthogonal structural and biochemical methods\",\n      \"pmids\": [\"37076474\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"RAB1B promotes DGAT2 redistribution from the ER to the lipid droplet surface (shown by FRET between DGAT2 and RAB1B activity mutants), thereby facilitating lipid droplet growth; TBC1D20 (the RAB1B GAP mutated in Warburg Micro syndrome) loss-of-function alters LD metabolism and DGAT2 redistribution consistently with elevated RAB1B activity.\",\n      \"method\": \"FRET between DGAT2 and RAB1B activity mutants; dominant-negative RAB1B overexpression to block LD formation; TBC1D20 mutant fibroblasts from WARBM model mice; fluorescence microscopy\",\n      \"journal\": \"Science Advances\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — FRET-based interaction mapping with activity mutants and disease-model validation, single lab\",\n      \"pmids\": [\"38809969\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"TBC1D22B is a GAP that directly targets RAB1B; TBC1D22B overexpression inhibits ER-to-Golgi transport in a GAP-activity-dependent manner, and RAB1B silencing phenocopies TBC1D22B-induced trafficking defects, placing RAB1B as the direct substrate of TBC1D22B in ER-to-Golgi transport regulation.\",\n      \"method\": \"Proximity-labeling and co-immunoprecipitation proteomics; RUSH system ER-to-Golgi transport assay; RAB1B siRNA knockdown; GAP-dead mutant rescue experiments\",\n      \"journal\": \"Advanced Science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple proteomics approaches plus functional transport assay with GAP-activity dependence, single lab\",\n      \"pmids\": [\"40878439\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RAB1B is a small GTPase that cycles between GDP-bound (inactive) and GTP-bound (active) states regulated by GEFs (including DrrA/SidM from Legionella) and GAPs (including LepB, TBC1D20, TBC1D22B), and is geranylgeranylated by GGTase II in a process requiring its effector domain and Switch 2 region for prior REP binding; in its GTP-active form, RAB1B localizes to ER exit sites and the Golgi where it acts sequentially through effectors GBF1, ARF1, and COPI coat proteins to drive ER-to-Golgi vesicular transport of diverse cargoes (βAPP, LDL receptor, vWF, viral proteins), also interacting with GM130, GOLPH3, p115, and COPII components (Sec23/24/31) to coordinate vesicle budding and tethering; beyond the secretory pathway, RAB1B associates with ATG9A vesicles to regulate autophagosome formation and with MTMR6 to modulate phosphoinositide metabolism, forms a complex with TRAF3-MAVS to promote antiviral IFN-β signaling, and facilitates lipid droplet growth by directing DGAT2 from ER to lipid droplet surfaces; Legionella exploits RAB1B by AMPylating Tyr77 (DrrA) and phosphocholinating Ser76 (AnkX) to lock it in active or altered states, while Lem3 reverses the phosphocholination by locally unfolding the switch II region.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"RAB1B is a small GTPase that drives vesicular transport from the endoplasmic reticulum to the cis- and medial-Golgi, established by cell-free reconstitution and antibody-inhibition assays [#0]. It cycles between GDP- and GTP-bound states using intrinsic GTPase activity and conserved nucleotide-binding residues, where Lys21 governs GTP binding and Ala65 modulates hydrolysis [#1]; correct membrane targeting depends on this nucleotide cycle, since both inactive and constitutively active mutants fail to integrate tightly into target membranes [#8]. Membrane delivery further requires C-terminal geranylgeranylation by Rab-GGTase, which depends on the effector domain (I41, D44) [#2] and on prior REP binding mediated by the Switch 2 helix to the GDP-bound form [#7], with prenylated RAB1B subsequently recycled via GDI complexes [#5]. In its GTP-active state at ER exit sites and the Golgi, RAB1B acts upstream of GBF1, ARF1, and COPI coat recruitment to execute and regulate Golgi-directed transport, with GBF1 identified as a direct effector [#10, #11]; it coordinates with COPII components Sec23/24/31 at ER exit sites [#14], binds the tethering proteins GM130 and p115 in nucleotide-dependent fashion [#9, #17], and dynamically cycles between ERES, VTCs, and the Golgi [#22]. Through this trafficking activity RAB1B mediates ER-to-Golgi transport and maturation of diverse cargoes including βAPP, the LDL receptor, and von Willebrand factor, the last under transcriptional control of RUNX1 [#3, #4, #25]. Beyond classical secretion, RAB1B associates with ATG9A vesicles to support autophagosome formation [#23], partners with the phosphoinositide phosphatase MTMR6 [#15], recruits the effector GOLPH3 to promote Golgi-based secretion [#20, #28], forms a TRAF3 complex that bridges TRAF3 to MAVS to enhance RIG-I-driven IFN-β signaling [#26], and directs DGAT2 from the ER to lipid droplet surfaces to drive lipid droplet growth [#30]. RAB1B is targeted by multiple GAPs that inactivate it, including the Legionella effector LepB [#16], TBC1D20 (linked to Warburg Micro syndrome) [#30], and TBC1D22B [#31], and is hijacked by bacterial pathogens through covalent switch-region modifications: Legionella DrrA acts as a GEF and AMPylates Tyr77 to lock RAB1B active [#12], AnkX phosphocholinates Ser76, and Lem3 reverses this by locally unfolding the switch II region [#29].\",\n  \"teleology\": [\n    {\n      \"year\": 1989,\n      \"claim\": \"Established that RAB1B is a genuine GTP-binding protein with intrinsic GTPase activity, defining the nucleotide-dependent switch that underlies its function.\",\n      \"evidence\": \"In vitro GTP/GDP binding and GTPase assays with purified recombinant protein and site-directed mutants (Lys21Met, Ala65Thr)\",\n      \"pmids\": [\"2509243\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not link biochemical activity to a cellular process\", \"GEFs and GAPs regulating the cycle not yet identified\"]\n    },\n    {\n      \"year\": 1991,\n      \"claim\": \"Defined the core cellular role of RAB1B as required for ER-to-cis-Golgi and intra-Golgi vesicular transport.\",\n      \"evidence\": \"Cell-free reconstitution of ER-to-Golgi transport with monoclonal antibody inhibition and subcellular immunolocalization\",\n      \"pmids\": [\"1918138\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular effectors mediating transport not identified\", \"Mechanism of vesicle budding vs tethering unresolved\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Mapped the determinants of RAB1B membrane attachment, showing the effector domain is required for geranylgeranylation.\",\n      \"evidence\": \"In vitro isoprenylation assay in reticulocyte lysates with systematic effector-domain mutagenesis (I41N, D44N)\",\n      \"pmids\": [\"8325834\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve how prenylation enzyme is recruited\", \"Role of REP not yet defined\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Connected RAB1B trafficking activity to physiological cargo maturation, showing it is required for ER-to-Golgi transport of βAPP and the LDL receptor.\",\n      \"evidence\": \"Dominant-negative RAB1B (N121I, S22N) co-expression with cargo in 293 cells, pulse-chase, Endo-H sensitivity, and surface labeling\",\n      \"pmids\": [\"7738040\", \"8673720\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cargo selectivity vs general transport block not distinguished\", \"Step in the pathway where RAB1B acts not yet placed\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Resolved the prenylation prerequisites, showing REP binds GDP-bound RAB1B via the Switch 2 helix to enable geranylgeranylation and that GDI recycling follows.\",\n      \"evidence\": \"Cell-free geranylgeranylation, metabolic labeling, nucleotide-binding assays, gel-filtration co-fractionation, and GDI co-IP with effector-domain mutants\",\n      \"pmids\": [\"9437002\", \"8631911\", \"8836150\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Conflicting in vitro vs in vivo conformational preference for prenylation\", \"Structural basis of REP recognition not solved here\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Placed RAB1B upstream of the GBF1/ARF1/COPI machinery, identifying GBF1 as a direct effector and demonstrating rapid membrane cycling at the Golgi.\",\n      \"evidence\": \"Dominant mutant epistasis with ARF1/GBF1 rescue, reciprocal Co-IP, siRNA, and FRAP\",\n      \"pmids\": [\"12802079\", \"17429068\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Order of effector engagement relative to tethering not fully resolved\", \"How GEF input is delivered to RAB1B at ERES unclear\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Integrated tethering factors GM130 and p115 and the COPII coat into the RAB1B trafficking cycle, defining its budding-to-tethering coordination.\",\n      \"evidence\": \"Yeast two-hybrid and domain-mapping Co-IP for GM130/p115, COPII (Sec23/24/31) Co-IP and FRAP, and p115 epistasis rescue\",\n      \"pmids\": [\"11306556\", \"21093099\", \"25332841\", \"27500526\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Hierarchy among p115, GM130, GBF1 inputs not fully ordered\", \"Direct vs indirect COPII engagement uncertain\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined how Legionella locks and unlocks the RAB1B switch, revealing DrrA as a GEF and AMPylase (Tyr77) and LepB as a structurally atypical GAP.\",\n      \"evidence\": \"In vitro AMPylation with MS site mapping, GEF/GAP-accessibility assays, and crystal structure of the RAB1B:LepB complex\",\n      \"pmids\": [\"20651120\", \"23288104\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Host enzymes counteracting bacterial AMPylation not identified here\", \"Physiological host GAP for RAB1B not yet characterized\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Extended RAB1B function beyond classical secretion into autophagy and phosphoinositide regulation via ATG9A vesicles and MTMR6.\",\n      \"evidence\": \"ATG9A vesicle immunoisolation proteomics with siRNA autophagy-flux assays; nucleotide-state Co-IP with MTMR6 and omegasome assays\",\n      \"pmids\": [\"28522593\", \"23188820\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether autophagy role is separable from ER-to-Golgi transport unclear\", \"Direct effector at autophagosome formation sites not defined\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Revealed signaling and translational roles, showing RAB1B bridges TRAF3 to MAVS for IFN-β induction and directly binds FMDV IRES RNA to stimulate translation.\",\n      \"evidence\": \"Reciprocal Co-IP and CRISPR deletion with IFN-β reporters and viral infection; direct RNA binding, IRES translation assays, and RNA-FISH\",\n      \"pmids\": [\"31375559\", \"30655362\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether RNA binding and signaling depend on trafficking activity unresolved\", \"Structural basis of TRAF3 and RNA engagement unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Expanded the regulatory and effector landscape, defining GOLPH3 as an effector, identifying TBC1D20 and TBC1D22B as host GAPs, and linking RAB1B to lipid droplet growth via DGAT2 redistribution.\",\n      \"evidence\": \"Nucleotide-state Co-IP for GOLPH3; FRET-based DGAT2 redistribution with TBC1D20 disease-model fibroblasts; proximity-labeling proteomics and RUSH transport assays for TBC1D22B\",\n      \"pmids\": [\"32790781\", \"26977884\", \"38809969\", \"40878439\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Disease mechanism of Warburg Micro syndrome via RAB1B not directly established here\", \"How distinct GAPs partition RAB1B functions spatially unclear\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How RAB1B's many roles—ER-to-Golgi transport, autophagy, lipid droplet growth, antiviral signaling, and RNA binding—are spatially and temporally partitioned by distinct GEFs, GAPs, and effectors remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model coordinating secretory vs non-secretory functions\", \"Endogenous GEFs for most contexts undefined\", \"Structural basis of effector selectivity across functions unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003924\", \"supporting_discovery_ids\": [1, 12, 16, 31]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 10, 11]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [27]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0, 14, 22, 30]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [0, 9, 11, 20, 22]},\n      {\"term_id\": \"GO:0005811\", \"supporting_discovery_ids\": [30]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [5, 10]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [0, 3, 4, 25]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [10, 11, 14]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [15, 23]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [26]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [30]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"GBF1\", \"GM130\", \"p115\", \"GOLPH3\", \"MTMR6\", \"TRAF3\", \"TBC1D22B\", \"DGAT2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}