{"gene":"RAB1A","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":1988,"finding":"YPT1/Rab1A protein is associated with the secretory machinery; yeast ypt1-1 mutation causes accumulation of membranes and vesicles and a partial secretion defect; immunofluorescence showed the mammalian counterpart localizes to the Golgi apparatus, consistent with a role directing intracellular vesicle traffic.","method":"Genetic analysis (ypt1-1 mutation phenotype), immunofluorescence with affinity-purified antibody in yeast and mouse cells","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — founding study combining genetic loss-of-function phenotype with direct immunolocalization, replicated across labs subsequently","pmids":["3127057"],"is_preprint":false},{"year":1986,"finding":"YPT1 protein is essential for cell growth; it binds GTP specifically and GTP binding is required for intracellular function; a dominant-lethal N121I substitution (site-directed mutagenesis) caused binucleated cells and abnormal spindles, demonstrating an essential function in cell cycle/microtubule organization.","method":"GAL10-regulated expression (depletion), site-directed mutagenesis, GTP-binding assay, immunofluorescence of microtubules","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — active-site mutagenesis plus in vivo GTP-binding assay, replicated across subsequent studies","pmids":["3094963"],"is_preprint":false},{"year":1989,"finding":"Ypt1p is required for ER-to-Golgi protein transport in vitro; ypt1 mutations specifically abolish Golgi complex function without affecting ER activity; wild-type cytosol can restore mutant Golgi function, placing Ypt1p at an early vesicular transport step.","method":"In vitro transport assay with ypt1 mutant membranes, complementation with wild-type cytosol, genetic epistasis with other secretion genes","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted cell-free transport assay with defined mutants and cytosol complementation, independently validated","pmids":["2504726"],"is_preprint":false},{"year":1990,"finding":"Ypt1p is required for ER-to-Golgi transport in cell-free extracts; anti-Ypt1 antibodies block transport; recombinant Ypt1p rescues the inhibition; ypt1-1 extract transport is restored by wild-type cytosol. Ypt1p acts independently of Ca2+ at a distinct step.","method":"In vitro transport assay, antibody inhibition, recombinant protein rescue, Ca2+ buffering experiments","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted in vitro assay with antibody inhibition and recombinant protein rescue, multiple orthogonal controls","pmids":["2104983"],"is_preprint":false},{"year":1991,"finding":"Ypt1p mediates the attachment or fusion step of secretory vesicles with the acceptor compartment (cis-Golgi); blocking Ypt1p activity causes accumulation of transport vesicles; Ypt1p was detected on the outer surface of these vesicles.","method":"Cell-free ER-to-Golgi transport reconstitution, antibody blocking, vesicle intermediate accumulation assay, immunolocalization on vesicles","journal":"Science (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted cell-free system with defined intermediate accumulation and direct protein localization on vesicles","pmids":["1904626"],"is_preprint":false},{"year":1991,"finding":"Suppressors of YPT1 deletion (SLY1-20, SLY2, SLY12, SLY41) restore ER-to-Golgi transport in Ypt1p-deficient cells; SLY2 and SLY12 encode synaptobrevin-like proteins; SLY1p is essential and acts as a single-copy suppressor, revealing the downstream machinery of the Ypt1p-regulated transport step.","method":"Multicopy/single-copy suppressor screens, invertase/CPY processing assays, genetic epistasis, DNA sequencing","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis with multiple suppressors confirmed biochemically, independently described","pmids":["1990290","1903839"],"is_preprint":false},{"year":1988,"finding":"YPT1 protein requires at least one of its two C-terminal cysteine residues for palmitic acid (palmitoyl) modification and for membrane association; the non-palmitoylated mutant lacking both cysteines is exclusively soluble and non-functional.","method":"[3H]palmitic acid metabolic labeling, subcellular fractionation, site-directed mutagenesis, gene replacement","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct lipid labeling combined with mutagenesis and fractionation demonstrating causal link between palmitoylation and membrane attachment","pmids":["3042385"],"is_preprint":false},{"year":1991,"finding":"Ypt1p membrane attachment depends on BET2 (a Rab geranylgeranyltransferase subunit homologous to DPR1/RAM1); bet2 mutants fail to attach Ypt1p and Sec4p to membranes, establishing prenylation as required for Ypt/Rab membrane association.","method":"Genetic analysis, DNA sequencing of BET2, membrane fractionation of Ypt1p/Sec4p in bet2 mutants","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic loss-of-function combined with fractionation showing direct causal requirement, replicated for multiple Rab proteins","pmids":["1903184"],"is_preprint":false},{"year":1994,"finding":"Rab geranylgeranyltransferase (RabGGTase)/Rab escort protein catalyzes geranylgeranylation of both C-terminal adjacent cysteines of Rab1A (–XXCC motif), as demonstrated by structural analysis of in vitro prenylated protein.","method":"In vitro prenylation assay with recombinant RabGGTase, [3H]geranylgeranyl pyrophosphate incorporation, tryptic peptide HPLC, electrospray mass spectrometry","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct structural mass spectrometry of in vitro enzymatic product, rigorously demonstrated for three distinct C-terminal motifs","pmids":["7991565"],"is_preprint":false},{"year":1995,"finding":"Ypt1p is essential for two sequential steps of the yeast secretory pathway: ER-to-cis-Golgi and cis-to-medial-Golgi transport, but not for later steps; this was established using a tight temperature-sensitive allele (ypt1-A136D) and glycoprotein processing assays.","method":"Temperature-sensitive mutant analysis (ypt1-A136D), glycoprotein processing assays (invertase, CPY, Gas1p), kinetic secretion analysis","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — tight conditional allele with defined biochemical readouts at multiple secretory steps, builds on prior in vitro reconstitution work","pmids":["7593181"],"is_preprint":false},{"year":1993,"finding":"Specificity of Ypt1 versus Sec4 function is encoded in a 9-residue segment corresponding to loop L7 (and a 24-residue segment including the effector region, loop L2) of the GTPase; substitution of these segments of Sec4 with Ypt1 sequences converts Sec4 into a protein that can perform Ypt1 functions.","method":"Chimeric protein construction, in vivo complementation assays in yeast","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Moderate — domain-swap experiments in vivo defining specificity determinants with functional assays, single lab but two chimera series","pmids":["8464499"],"is_preprint":false},{"year":2000,"finding":"The TRAPP complex is a guanine nucleotide exchange factor (GEF) for Ypt1p (and Ypt31/32); GST-tagged TRAPP subunits Bet3p or Bet5p precipitate GEF activity that stimulates GDP release and GTP uptake on Ypt1p; the dominant-negative Ypt1-D124N mutant inhibits TRAPP GEF activity, suggesting in vivo relevance.","method":"GST pulldown of TRAPP subunits, GDP-release and GTP-uptake assays in vitro, gel-filtration of GEF activity (>670 kDa), dominant-negative inhibition, overexpression studies","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro biochemical GEF assay with defined complex, inhibitor control, size-fractionation, and in vivo overexpression, replicated by subsequent studies","pmids":["11102533"],"is_preprint":false},{"year":2003,"finding":"Crystal structure of monoprenylated Ypt1:RabGDI complex at 1.5 Å resolution reveals the structural basis for GDI-mediated inhibition of nucleotide release; isoprenoid binding requires a conformational change opening a hydrophobic cavity in GDI domain II.","method":"Chemical synthesis of prenylated peptide, protein engineering, X-ray crystallography at 1.5 Å","journal":"Science (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution crystal structure with functionally validated complex, multiple orthogonal experimental inputs","pmids":["14576435"],"is_preprint":false},{"year":2006,"finding":"Structure of doubly geranylgeranylated Ypt1:GDI complex shows one geranylgeranyl moiety deeply buried in GDI domain II hydrophobic pocket while the other is more solvent-exposed; biophysical measurements provide thermodynamic model for GDI- and REP-mediated Rab membrane interaction.","method":"Synthesis of doubly prenylated protein, X-ray crystallography, biophysical measurements (ITC, fluorescence)","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure plus biophysical thermodynamic measurements of doubly prenylated complex, mechanistically comprehensive","pmids":["16395334"],"is_preprint":false},{"year":1995,"finding":"A Ypt1p guanine nucleotide exchange factor (GEF) activity is required for ER-to-Golgi transport; dominant-negative Ypt1p-D124N blocks transport by sequestering the GEF; XTP-dependent rescue of Ypt1-D124N confirms the nucleotide-free form sequesters GEF, demonstrating an essential role for the exchange factor in vesicular transport.","method":"In vitro ER-to-Golgi transport assay, dominant-negative and nucleotide-specificity mutant proteins, GEF activity assay (GDP release, GTP uptake)","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted in vitro transport assay combined with biochemical GEF assay and nucleotide-specificity rescue, mechanistically rigorous","pmids":["7657691"],"is_preprint":false},{"year":1991,"finding":"The effector domain of Ypt1p (residues 37–45) is required for function; mutations I41M and D44N are loss-of-function; a GTPase-activating protein (yptGAP) partially purified from porcine liver stimulates GTPase activity of Ypt1p specifically (not H-Ras) and interacts with the effector domain; I41M and D44N mutant proteins show reduced or absent GAP responsiveness.","method":"Site-directed mutagenesis and gene replacement in yeast, CPY/invertase processing assays, partial purification of yptGAP, GTPase stimulation assays","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — mutagenesis combined with biochemical GAP purification and activity assay, single lab but multiple orthogonal methods","pmids":["2009858"],"is_preprint":false},{"year":1998,"finding":"GTP hydrolysis is not essential for Ypt1p-mediated vesicular transport; cells expressing GTPase-deficient Ypt1-Q67L as the sole Ypt1p have no observable growth, secretion, or morphology defects; GTP hydrolysis is required only for recycling of Ypt1p between compartments.","method":"Q67L loss-of-GTPase mutant, GAP stimulation assay, secretion assays, electron microscopy","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — defined mutant blocking GTPase activity, multiple phenotypic readouts, clear mechanistic conclusion","pmids":["9447979"],"is_preprint":false},{"year":2002,"finding":"Two novel Ypt1-specific GAPs, Gyp5p and Gyp8p, were identified; Gyp5p accelerates Ypt1p GTPase activity 4.2×10⁴-fold; constitutively active Ypt1(Q67L) expressing cells show growth defects and autophagy-like morphology dependent on background of GAP deletion, indicating GTP hydrolysis is needed for balanced ER-Golgi vesicle flow.","method":"GAP activity biochemical assay, subcellular fractionation, yeast genetics (GAP deletion strains), electron microscopy","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — direct in vitro GAP activity measurement plus genetic analysis with multiple allele combinations, single lab","pmids":["12189143"],"is_preprint":false},{"year":2012,"finding":"Ypt1/Rab1 is recruited to the preautophagosomal structure (PAS) by TRAPPIII (activated via Atg17 recruitment); activated Ypt1 then recruits the Atg1 kinase to the PAS, bringing it near its binding partner Atg17, thereby restricting Atg1 specifically to the PAS for autophagosome formation.","method":"Yeast two-hybrid, co-immunoprecipitation, fluorescence microscopy, genetic epistasis with atg17 mutants","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP, genetic epistasis, and live-cell imaging, replicated by independent studies on TRAPPIII/Ypt1 in autophagy","pmids":["23716696"],"is_preprint":false},{"year":2012,"finding":"Atg9 vesicles recruit the TRAPPIII complex (via direct Trs85-Atg9 interaction) and Ypt1 to the preautophagosomal structure in an Atg9-dependent manner, establishing a vesicle-tethering machinery for autophagosome formation.","method":"Atg9 vesicle purification and mass spectrometry, co-IP (Trs85-Atg9), fluorescence microscopy, deletion mutant analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — vesicle purification with MS identification, confirmed by co-IP and microscopy, consistent with parallel study (PMID 23716696)","pmids":["23129774"],"is_preprint":false},{"year":2015,"finding":"Ypt1/Rab1 binds and activates the CK1δ kinase Hrr25 to spatially regulate phosphorylation of the COPII coat, directing ER-derived vesicles to the Golgi; hrr25 mutants are defective in both ER-Golgi trafficking and macroautophagy.","method":"Co-immunoprecipitation, kinase activity assay, yeast genetic analysis (hrr25 mutants), in vitro transport assay","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — kinase activity assay plus co-IP and genetic phenotypic analysis, single lab but multiple orthogonal approaches","pmids":["26195667"],"is_preprint":false},{"year":2016,"finding":"TRAPPIII is the primary GEF that activates Ypt1/Rab1 in both Golgi trafficking and autophagy pathways in wild-type yeast; TRAPPII and TRAPPIII are the only two TRAPP complexes present in yeast, contrary to earlier reports of four complexes.","method":"Biochemical purification of TRAPP complexes, GEF activity assays, genetic analysis, secretion and autophagy assays","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — biochemical purification with GEF assays and genetic validation, single lab","pmids":["29109089"],"is_preprint":false},{"year":2016,"finding":"A Trs33-containing TRAPP complex (TRAPP IV) acts as an autophagy-specific GEF for Ypt1; in the absence of Trs85, Trs33 is required for Ypt1-mediated autophagy and recruitment of core-TRAPP and Ypt1 to the PAS.","method":"Yeast genetics (trs85Δ, trs33Δ double mutants), co-IP, fluorescence microscopy of PAS markers, autophagy assays","journal":"Genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with localization assays, single lab, autophagy phenotype well defined but GEF activity not directly measured in vitro","pmids":["27672095"],"is_preprint":false},{"year":2010,"finding":"Rab1a regulates cell migration by controlling integrin β1 recycling to lipid rafts and to the plasma membrane; p115 acts as a downstream effector mediating Rab1a regulation of integrin recycling and lipid raft localization.","method":"RNAi screen, siRNA knockdown, cell adhesion and spreading assays, flow cytometry (lipid raft fractionation), integrin β1 recycling assay, p115 knockdown","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional RNAi screen with mechanistic follow-up using multiple assays, single lab","pmids":["20639577"],"is_preprint":false},{"year":2012,"finding":"Rab1A is required for microtubule-dependent anterograde melanosome transport in melanocytes; Rab1A localizes to mature melanosomes; its loss (siRNA or overexpression of dominant-negative TBC1D20 GAP) causes perinuclear melanosome aggregation and specifically suppresses long-range anterograde movements.","method":"Genome-wide constitutively active/negative Rab screen, siRNA knockdown, immunofluorescence localization, time-lapse live imaging","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genome-wide screen with mechanistic follow-up by siRNA, GAP overexpression, live imaging, and localization, single lab but multiple approaches","pmids":["22854043"],"is_preprint":false},{"year":2015,"finding":"Rab1A recruits SKIP/PLEKHM2 as a specific effector on melanosomes, and Rab1A–SKIP–kinesin-1 (Kif5b/KLC2) form a transport complex that mediates anterograde melanosome transport; Arl8 (not Rab1A) mediates anterograde lysosome transport via the same SKIP-kinesin-1 machinery.","method":"Co-immunoprecipitation, GST pulldown, siRNA knockdown, live-cell imaging, dominant-negative mutant expression","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 / Moderate — co-IP identification of effector complex combined with functional assays and live imaging, builds directly on prior study (PMID 22854043)","pmids":["25649263"],"is_preprint":false},{"year":2014,"finding":"Rab1a regulates sorting of early endocytic vesicles for multiple cargo (EGF, transferrin, ASOR); in Rab1a knockdown cells, EGF fails to reach lysosomes and transferrin is redirected to slow Rab11 recycling rather than fast Rab4 recycling; the minus-end-directed kinesin KifC1 is identified as an effector recruited by Rab1a to early endocytic vesicles.","method":"Stable Rab1a knockdown cell line, fluorescence microscopy tracking of fluorescent cargo, co-immunoprecipitation (KifC1)","journal":"American journal of physiology. Gastrointestinal and liver physiology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — stable KD with multiple cargo assays and effector co-IP, single lab","pmids":["24407591"],"is_preprint":false},{"year":1996,"finding":"Rab1a is associated not only with ER-to-Golgi transport vesicles but also with postendosomal transcytotic vesicles in rat liver, as demonstrated by immunoisolation of vesicles using anti-Rab1a beads; these vesicles contain transcytotic markers and multiple Rab GTPases.","method":"Immunoisolation of vesicles using antibody-coated magnetic beads, Western blotting for organelle markers, [α-32P]GTP overlay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — immunoisolation with marker Western blots, single lab, single method","pmids":["8939959"],"is_preprint":false},{"year":2016,"finding":"C9orf72 interacts with Rab1a and the ULK1 autophagy initiation complex; as a Rab1a effector, C9orf72 controls initiation of autophagy by regulating Rab1a-dependent trafficking of the ULK1 complex to the phagophore.","method":"Co-immunoprecipitation (C9orf72 with Rab1a and ULK1), siRNA knockdown, autophagy flux assays (p62 accumulation, LC3 puncta), iNeuron studies","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP plus loss-of-function in multiple cell types including patient-derived neurons, single lab but multiple orthogonal approaches","pmids":["27334615"],"is_preprint":false},{"year":2018,"finding":"Salmonella effectors SseF and SseG inhibit autophagy by directly interacting with Rab1A, disrupting its interaction with the TRAPPIII GEF complex, thereby blocking Rab1A activation, ULK1 recruitment, and phosphatidylinositol 3-phosphate biogenesis, ultimately impairing autophagosome formation.","method":"Co-immunoprecipitation (SseF/SseG with Rab1A and TRAPPIII), GEF disruption assay, ULK1 recruitment assay, PI3P measurement, siRNA rescue experiments, mouse infection model","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple co-IP experiments plus functional assays in cell lines and animal model, mechanistic chain from effector binding to autophagy block established","pmids":["29610274"],"is_preprint":false},{"year":2021,"finding":"M. tuberculosis PE_PGRS20 and PE_PGRS47 inhibit autophagy initiation by directly interacting with Rab1A; silencing Rab1A rescues the survival defects of pe_pgrs20/pe_pgrs47 deletion mutants, placing Rab1A as the host target of these mycobacterial effectors.","method":"Co-immunoprecipitation (PE_PGRS proteins with Rab1A), Rab1A silencing rescue, autophagy flux assays in macrophages","journal":"mSphere","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — co-IP and genetic rescue experiments in macrophages, single lab","pmids":["34346699"],"is_preprint":false},{"year":2017,"finding":"Rab1a interacts with and regulates optineurin (OPTN)-induced autophagosome formation in neuroblastoma cells; a zinc finger domain of OPTN is required for Rab1a binding; active Rab1a (GTP-bound) is required for the interaction; Rab1a knockdown inhibits OPTN-induced LC3-EGFP translocation to autophagosomes.","method":"Yeast two-hybrid, co-immunoprecipitation, confocal microscopy colocalization, dominant-negative/constitutively-active Rab1a mutants, LC3-EGFP autophagosome translocation assay","journal":"Journal of neuroscience research","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — co-IP with domain mapping plus functional autophagy assay, single lab","pmids":["28843006"],"is_preprint":false},{"year":2014,"finding":"Hsc70 interacts with Rab1A in a chaperone-dependent manner and prevents its ubiquitination and degradation under proteotoxic stress; Hsc70 knockdown decreases Rab1A levels and increases its ubiquitination; Rab1A knockdown inhibits autophagosome formation and induces cell death under stress.","method":"Anti-Hsc70 affinity purification + mass spectrometry, co-immunoprecipitation, ubiquitination assay, siRNA knockdown, autophagy assay","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — MS identification confirmed by co-IP and ubiquitination assay, single lab","pmids":["24801886"],"is_preprint":false},{"year":2022,"finding":"The E3 ubiquitin ligase RNF115 catalyzes K11-linked ubiquitination of RAB1A at Lys49 and Lys61; this modification impairs recruitment of GDI1 to RAB1A, preventing its reactivation cycle; RAB1A ubiquitination-resistant mutant (K49/61R) promotes ER-to-Golgi trafficking of TLRs.","method":"Co-immunoprecipitation (RNF115 with RAB1A), in vitro ubiquitination assay, site-directed mutagenesis (K49R/K61R), GDI1 recruitment assay, TLR trafficking assay in Rnf115+/+ and Rnf115−/− cells","journal":"Advanced science","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro ubiquitination assay with mutagenesis plus functional rescue in knockout cells, multiple orthogonal methods, single lab","pmids":["35343654"],"is_preprint":false},{"year":2020,"finding":"Ubiquitin-specific protease USP2a deubiquitinates and stabilizes RAB1A, preventing its proteasomal degradation; this stabilization is required for USP2a-mediated HCC progression.","method":"LC-MS/MS affinity proteomics, co-immunoprecipitation, ubiquitination assay, siRNA knockdown, in vitro and in vivo tumor models","journal":"Cellular oncology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — MS-based target identification confirmed by co-IP and ubiquitination assay, single lab","pmids":["33074477"],"is_preprint":false},{"year":2024,"finding":"During mitosis, Aurora kinase A (AURKA) phosphorylates Rab1A at Thr75; structural analysis shows Thr75 phosphorylation locks Rab1A in a constitutively active state by preventing GDI interaction; activated Rab1A is retained on the ER and induces oligomerization of RTN and REEP ER-shaping proteins, increasing ER complexity; this mechanism is evolutionarily conserved from C. elegans and Drosophila to mammals.","method":"Structural analysis (crystal/cryo-EM implied), in vitro kinase assay (AURKA phosphorylation of Rab1A), site-directed mutagenesis (T75A), GDI interaction assay, ER morphology assay, genetic modification in C. elegans/Drosophila/mammalian cells","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — structural analysis plus in vitro kinase assay plus mutagenesis plus multi-organism genetic validation, multiple orthogonal methods in one rigorous study","pmids":["38177680"],"is_preprint":false},{"year":2011,"finding":"In Dictyostelium, Rab1A binds the LRRK2-related Roco kinase Roco2 in vivo; active GTP-bound Rab1A regulates Roco2 kinase activity; Roco2 in turn controls F-actin polymerization and pseudopod extension by acting upstream of filamin (abp120), establishing a Rab1A-Roco2-filamin pathway regulating actin cytoskeleton and cell motility.","method":"Co-immunoprecipitation (Roco2 with Rab1A and filamin), kinase activity assay, constitutively active/dominant-negative Rab1A mutants, chemotaxis assays, F-actin measurement","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus kinase activity assay plus multiple functional assays in Dictyostelium, single lab","pmids":["21551065"],"is_preprint":false},{"year":2011,"finding":"Rab1A (and Rab43) is required for herpes simplex virus 1 secondary envelopment; depletion of Rab1a/b via their specific GAP TBC1D20 prevents viral glycoproteins from trafficking from the ER to the viral assembly compartment, resulting in accumulation of unenveloped particles.","method":"Overexpression of 37 Rab-GAPs (functional screen), siRNA knockdown, infectious titer assay, immunofluorescence microscopy of viral glycoproteins, electron microscopy","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional screen with mechanistic follow-up by KD and localization studies, single lab","pmids":["21680502"],"is_preprint":false},{"year":2014,"finding":"RAB1A is required for Vaccinia virus production of intracellular enveloped virions (IEVs) but not intracellular mature virions (IMVs); RAB1A facilitates the wrapping step consistent with its role in ER-to-Golgi transport.","method":"siRNA knockdown, infectious titer assay, immunofluorescence, electron microscopy","journal":"Virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA with titer and EM readouts defining specific step in viral replication, single lab","pmids":["25462347"],"is_preprint":false},{"year":2017,"finding":"Rab1A is required for classical swine fever virus (CSFV) particle assembly; Rab1A binds CSFV NS5A protein; Rab1A depletion reduces intracellular and extracellular viral titers without affecting viral genome replication or E2 protein expression, specifically implicating particle assembly.","method":"siRNA knockdown, viral titer assay, qRT-PCR (genome copies), co-immunoprecipitation (Rab1A–NS5A), confocal microscopy, neutralizing antibody blocking assay","journal":"Virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus functional dissection of viral lifecycle step, single lab","pmids":["29128753"],"is_preprint":false},{"year":2011,"finding":"Rab1A overexpression prevents Golgi fragmentation caused by alpha-synuclein in dopaminergic neurons; the non-prenylable Rab1A-ΔCC mutant fails to rescue Golgi morphology, linking the protective effect to Rab1A's ER-to-Golgi trafficking activity.","method":"AAV-mediated co-expression in rat substantia nigra, Golgi morphology assay, non-prenylable mutant analysis, motor behavior assay","journal":"Journal of Parkinson's disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo gene delivery with mutant control demonstrating prenylation dependence, single lab","pmids":["23939344"],"is_preprint":false},{"year":2012,"finding":"Ypt1 protein specifically associates in vivo with unspliced HAC1 RNA and promotes HAC1 RNA decay; this association is disrupted during ER stress induction of the UPR; Ypt1 depletion reduces HAC1 RNA decay rate, elevating HAC1 levels and delaying UPR attenuation.","method":"Protein microarray screening for HAC1 RNA binding, RNA co-immunoprecipitation, HAC1 RNA decay assays, genetic analysis (ire1Δ, ada5Δ)","journal":"PLoS genetics","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — protein microarray plus co-IP with RNA, decay assay, genetic dependencies, single lab","pmids":["22844259"],"is_preprint":false},{"year":2020,"finding":"Human GOLPH3 is a direct effector of RAB1A and RAB1B; interaction is nucleotide-dependent, favored by GTP-locked (active) variants; expression of GTP-locked RAB1A reduces GOLPH3 localization at the Golgi, suggesting Rab1A-GTP releases GOLPH3 from the Golgi.","method":"Co-immunoprecipitation (GOLPH3 with RAB1A/B wild-type and GTP-locked mutants), fluorescence microscopy of GOLPH3 distribution","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — co-IP with nucleotide-state specificity plus localization assay, single lab","pmids":["32790781"],"is_preprint":false},{"year":2021,"finding":"Rab1A mediates amino acid (particularly branched-chain amino acid)-dependent mTORC1 signaling in vivo; whole-body Rab1A knockout mice are hyperglycemic and glucose intolerant due to impaired insulin transcription and β-cell proliferation/maintenance; mechanistically, Rab1A mediates BCAA-mTORC1 signaling to regulate stability and localization of the insulin transcription factor Pdx1.","method":"Tamoxifen-induced whole-body Rab1A knockout mouse, glucose tolerance test, insulin assay, β-cell analysis, Pdx1 localization and stability assay","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Moderate — in vivo knockout with multiple mechanistic readouts (mTORC1 signaling, Pdx1 regulation, β-cell function), single lab but comprehensive physiological characterization","pmids":["33730578"],"is_preprint":false},{"year":2021,"finding":"NAB2 (an N-arylbenzimidazole small molecule) binds Rab1a selectively in its GDP-bound form; NAB2 binding phenocopies Rab1a overexpression in alleviating α-synuclein toxicity; Rab1a was identified as a target of NAB2 by Thermal Proteome Profiling and SPROX chemoproteomic analyses.","method":"Thermal Proteome Profiling (TPP), SPROX chemoproteomic analysis, cellular phenotypic assay (α-synuclein toxicity rescue), GDP/GTP-state selectivity binding assay","journal":"RSC chemical biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two orthogonal chemoproteomic methods converging on Rab1a as target, with nucleotide-state selectivity and phenotypic validation, single lab","pmids":["35128413"],"is_preprint":false},{"year":2022,"finding":"Rab1a interacts with ULK1 and promotes ULK1 phosphorylation dependent on its GTP-binding activity; this Rab1a-ULK1 interaction initiates autophagy that promotes PRRSV replication.","method":"Co-immunoprecipitation (Rab1a with ULK1), ULK1 phosphorylation assay, GTP-binding mutant analysis, ATG7 knockdown rescue, viral titer assay","journal":"Virus research","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — co-IP plus phosphorylation assay plus GTP-mutant dependence, single lab","pmids":["36306941"],"is_preprint":false},{"year":2005,"finding":"Yeast Yip3p (a GDI displacement factor ortholog) forms a distinct complex with Ypt1p that is separable from its complex with reticulon Rtn1p; Yip3p is predominantly Golgi-localized; however, loss of Yip3p or Rtn1p does not perturb intracellular Rab localization, indicating Yip3p-Ypt1p interaction is not critical for Rab membrane targeting.","method":"Co-purification from detergent extracts, Western blotting, fluorescence microscopy in yip3Δ and rtn1Δ mutants","journal":"Eukaryotic cell","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — co-purification with genetic loss-of-function analysis; result partially negative (no role in targeting)","pmids":["16002643"],"is_preprint":false},{"year":1998,"finding":"A Ypt1p-specific GEF activity localizes to the acceptor (Golgi) fraction rather than the donor (ER) fraction; a Ypt1p-specific GAP activity colocalizes with ER markers; the GEF is specific for Ypt1p and not other Ypt proteins; the GAP has higher affinity for GTP-bound Ypt1p.","method":"Partial purification of GEF and GAP activities from yeast fractions, GDP-release and GTP-uptake assays, GTPase stimulation assay, subcellular fractionation","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biochemical activity assays with fractionation defining spatial organization of GEF/GAP, single lab","pmids":["9763446"],"is_preprint":false}],"current_model":"RAB1A/Ypt1 is a small GTPase that acts as a molecular switch on ER-derived vesicles, where it is activated by TRAPP complex GEFs (TRAPPI for secretion, TRAPPIII/IV for autophagy), recruits effectors including SKIP/kinesin-1 for anterograde transport and the Atg1/ULK1 kinase for autophagy initiation, mediates vesicle tethering and fusion with the cis-Golgi and subsequent intra-Golgi steps, requires geranylgeranylation of its C-terminal cysteines for membrane attachment (regulated by RabGDI extraction and RNF115-mediated K11-ubiquitination), senses and transduces amino acid signals to mTORC1 to control cell growth and glucose homeostasis, and is phosphorylated at Thr75 by mitotic Aurora kinase A to drive ER remodeling during cell division."},"narrative":{"mechanistic_narrative":"RAB1A (yeast Ypt1) is an essential small GTPase that functions as a molecular switch governing ER-to-Golgi vesicular transport and, more broadly, membrane traffic across the secretory and autophagic pathways [PMID:3127057, PMID:3094963, PMID:2504726]. At the cell-free level it mediates the attachment/fusion step of ER-derived secretory vesicles with the cis-Golgi and is required for both ER-to-cis-Golgi and cis-to-medial-Golgi transport, acting on the outer surface of transport vesicles [PMID:1904626, PMID:7593181]. Like all Rabs, it cycles between GDP- and GTP-bound states: activation is driven by TRAPP-complex GEFs, with TRAPPIII serving as the primary GEF for both Golgi trafficking and autophagy [PMID:11102533, PMID:29109089], while specific GAPs (yptGAP, Gyp5p/Gyp8p, TBC1D20) stimulate GTP hydrolysis required for protein recycling rather than the transport event itself [PMID:2009858, PMID:9447979, PMID:12189143]. Membrane attachment requires geranylgeranylation of its two C-terminal cysteines by RabGGTase, and the prenylated, GDP-bound form is extracted and chaperoned by RabGDI, whose hydrophobic pocket sequesters the lipid moiety [PMID:1903184, PMID:7991565, PMID:14576435, PMID:16395334]. RAB1A nucleates effector platforms in a nucleotide-dependent manner, recruiting the Atg1/ULK1 autophagy-initiation kinase to the preautophagosomal structure via TRAPPIII and Atg9 vesicles [PMID:23716696, PMID:23129774, PMID:27334615], activating the CK1δ kinase Hrr25 to phosphorylate the COPII coat [PMID:26195667], and engaging cargo-transport and Golgi effectors including SKIP/PLEKHM2–kinesin-1 for anterograde melanosome movement, p115 for integrin β1 recycling, and GOLPH3 [PMID:20639577, PMID:25649263, PMID:32790781]. Beyond membrane traffic, RAB1A transduces branched-chain amino-acid signals to mTORC1 to control β-cell insulin transcription and glucose homeostasis [PMID:33730578], and during mitosis Aurora kinase A phosphorylates RAB1A at Thr75, locking it in an active, GDI-resistant state that retains it on the ER to drive RTN/REEP-dependent ER remodeling [PMID:38177680]. Its activity is further tuned by ubiquitin-dependent regulation: RNF115 catalyzes K11-linked ubiquitination at Lys49/Lys61 to impair GDI1 recruitment, while Hsc70 chaperoning and USP2a deubiquitination stabilize the protein [PMID:24801886, PMID:35343654, PMID:33074477]. RAB1A is a recurrent target of intracellular pathogens, including Salmonella effectors SseF/SseG and mycobacterial PE_PGRS proteins that block its activation to suppress autophagy, and it is co-opted for the assembly and envelopment of multiple viruses [PMID:29610274, PMID:34346699, PMID:21680502, PMID:29128753].","teleology":[{"year":1986,"claim":"Established that YPT1/RAB1A is an essential, GTP-binding protein whose nucleotide function is required in vivo, defining it as a guanine-nucleotide-dependent switch rather than a structural protein.","evidence":"Regulated depletion, site-directed mutagenesis (N121I), and GTP-binding assay in yeast","pmids":["3094963"],"confidence":"High","gaps":["Did not place the protein in a specific trafficking step","Connection to microtubule/spindle phenotype mechanistically unresolved at the time"]},{"year":1988,"claim":"Linked YPT1/RAB1A directly to the secretory machinery and the Golgi, and showed lipid modification of C-terminal cysteines is required for membrane attachment and function.","evidence":"ypt1-1 loss-of-function phenotype with immunolocalization, plus [3H]palmitate labeling and cysteine mutagenesis","pmids":["3127057","3042385"],"confidence":"High","gaps":["Lipid identity later revised to geranylgeranyl rather than palmitate","Exact transport step not yet defined"]},{"year":1990,"claim":"Pinpointed RAB1A function to the ER-to-Golgi vesicular transport step using reconstituted assays, distinguishing it from the ER stage and from Ca2+-dependent events.","evidence":"Cell-free ER-to-Golgi transport with antibody inhibition and recombinant rescue; complementation with wild-type cytosol","pmids":["2504726","2104983"],"confidence":"High","gaps":["Whether RAB1A acts at tethering vs fusion not yet resolved","Upstream activators and downstream effectors unidentified"]},{"year":1991,"claim":"Resolved that RAB1A acts at the vesicle attachment/fusion step on the cis-Golgi, identified downstream SNARE-like machinery, and showed prenylation by the BET2 geranylgeranyltransferase is required for membrane association.","evidence":"Vesicle-intermediate accumulation assay with on-vesicle immunolocalization, SLY suppressor screen, and bet2 mutant fractionation","pmids":["1904626","1990290","1903839","1903184"],"confidence":"High","gaps":["Molecular nature of the tethering apparatus not yet defined","GEF that activates RAB1A still unknown"]},{"year":1993,"claim":"Mapped the functional specificity of RAB1A versus the related Sec4 to discrete loop segments (L2 effector region and L7), explaining how closely related Rabs achieve distinct functions.","evidence":"Chimeric Ypt1/Sec4 protein swaps with in vivo complementation","pmids":["8464499"],"confidence":"High","gaps":["Effector(s) reading these specificity determinants not identified","Structural basis not directly visualized"]},{"year":1995,"claim":"Defined the GTPase cycle requirements: a dedicated GEF is essential for transport, and the protein operates across two sequential Golgi steps.","evidence":"Dominant-negative D124N GEF-sequestration with XTP rescue in cell-free transport; tight ts allele with glycoprotein processing assays","pmids":["7657691","7593181"],"confidence":"High","gaps":["Identity of the GEF not yet established","Spatial organization of GEF/GAP not yet mapped"]},{"year":1998,"claim":"Showed GTP hydrolysis is dispensable for the transport event itself but required for RAB1A recycling, and that the GEF and GAP are spatially segregated to acceptor and donor compartments.","evidence":"GTPase-deficient Q67L as sole copy with secretion/EM readouts; partial purification and fractionation of GEF and GAP activities","pmids":["9447979","9763446"],"confidence":"High","gaps":["Molecular identity of fractionated GEF/GAP still unknown","Mechanism coupling hydrolysis to recycling not detailed"]},{"year":2000,"claim":"Identified the TRAPP complex as the physiological GEF for RAB1A, naming the long-sought activating machinery.","evidence":"GST pulldown of TRAPP subunits with GDP-release/GTP-uptake assays, size fractionation, and dominant-negative inhibition","pmids":["11102533"],"confidence":"High","gaps":["Distinct TRAPP subcomplexes and their pathway specificities not yet resolved","Mammalian counterpart regulation not addressed"]},{"year":2006,"claim":"Provided the structural basis for GDI-mediated extraction and membrane targeting by visualizing how mono- and doubly geranylgeranylated RAB1A engage RabGDI.","evidence":"X-ray crystallography of prenylated Ypt1:GDI complexes with biophysical thermodynamic measurements","pmids":["14576435","16395334"],"confidence":"High","gaps":["Membrane delivery step (GDF function) not structurally captured","How REP vs GDI selectivity is achieved in vivo not fully resolved"]},{"year":2012,"claim":"Extended RAB1A function beyond secretion into autophagy initiation, showing TRAPPIII/Atg9-vesicle-dependent activation recruits the Atg1/ULK1 kinase to the preautophagosomal structure.","evidence":"Yeast two-hybrid, reciprocal co-IP, fluorescence imaging, and genetic epistasis with atg17/atg9","pmids":["23716696","23129774"],"confidence":"High","gaps":["Direct Rab1A–Atg1 contact vs indirect recruitment not fully dissected","Mammalian effector chain not yet defined here"]},{"year":2015,"claim":"Showed RAB1A spatially controls COPII coat phosphorylation by binding and activating the CK1δ kinase Hrr25, mechanistically coupling vesicle activation to coat dynamics in both trafficking and autophagy.","evidence":"Co-IP, kinase activity assay, and in vitro transport with hrr25 mutants","pmids":["26195667"],"confidence":"High","gaps":["Whether mammalian RAB1A regulates CK1δ analogously not tested here","Direct COPII phosphosite consequences for vesicle release incomplete"]},{"year":2015,"claim":"Defined a mammalian effector cascade in which RAB1A recruits SKIP/PLEKHM2–kinesin-1 to drive microtubule-dependent anterograde melanosome transport, extending RAB1A into long-range organelle motility.","evidence":"Genome-wide Rab screen, siRNA, co-IP/GST pulldown of SKIP-kinesin-1, and live imaging","pmids":["22854043","25649263"],"confidence":"High","gaps":["GEF activating RAB1A on melanosomes not identified","Relationship to canonical ER-Golgi RAB1A pool unclear"]},{"year":2016,"claim":"Established TRAPPIII as the primary in vivo RAB1A GEF for both Golgi and autophagy, revising the prior four-complex model and identifying a Trs33-dependent autophagy-specific GEF activity.","evidence":"Biochemical purification of TRAPP complexes with GEF assays; trs85/trs33 genetics with PAS imaging","pmids":["29109089","27672095"],"confidence":"High","gaps":["TRAPP IV/Trs33 GEF activity not measured directly in vitro (Medium)","How a single GEF achieves pathway selectivity not fully resolved"]},{"year":2016,"claim":"Connected RAB1A to disease-relevant autophagy machinery by identifying C9orf72 as a RAB1A effector that delivers the ULK1 complex to the phagophore.","evidence":"Reciprocal co-IP of C9orf72 with RAB1A/ULK1, siRNA, and autophagy-flux assays in iNeurons","pmids":["27334615"],"confidence":"High","gaps":["Whether C9orf72 acts as a GEF/adaptor or tether for RAB1A not resolved","Neurodegeneration mechanism downstream not established here"]},{"year":2018,"claim":"Revealed RAB1A as a convergent host target subverted by intracellular pathogens that block its activation to suppress autophagy.","evidence":"Co-IP of Salmonella SseF/SseG with RAB1A and TRAPPIII, GEF-disruption and ULK1/PI3P assays, plus mouse infection; mycobacterial PE_PGRS co-IP with silencing rescue","pmids":["29610274","34346699"],"confidence":"High","gaps":["Structural basis of effector-mediated TRAPPIII displacement not solved","PE_PGRS interaction is single-lab co-IP/rescue (Medium)"]},{"year":2021,"claim":"Identified a signaling role distinct from membrane traffic: RAB1A transduces branched-chain amino-acid signals to mTORC1 to control insulin transcription and glucose homeostasis.","evidence":"Tamoxifen-induced whole-body Rab1A knockout mice with glucose tolerance, β-cell, and Pdx1 stability/localization analyses","pmids":["33730578"],"confidence":"High","gaps":["Direct molecular link between RAB1A and the mTORC1 amino-acid sensing apparatus not defined","Whether this requires RAB1A trafficking activity unresolved"]},{"year":2022,"claim":"Defined a ubiquitin-based regulatory layer in which RNF115-catalyzed K11 ubiquitination at Lys49/61 blocks GDI1 recruitment and thereby controls RAB1A reactivation and TLR trafficking.","evidence":"Co-IP, in vitro ubiquitination, K49R/K61R mutagenesis, GDI1 recruitment and TLR trafficking assays in Rnf115 knockout cells","pmids":["35343654"],"confidence":"High","gaps":["Counteracting deubiquitinase for K11 chains not identified here","Stoichiometry/dynamics of the modification in vivo unknown"]},{"year":2024,"claim":"Uncovered cell-cycle control of RAB1A: mitotic Aurora kinase A phosphorylates Thr75 to lock RAB1A active and GDI-resistant, retaining it on the ER to drive RTN/REEP-mediated ER remodeling, a conserved mechanism.","evidence":"Structural analysis, in vitro AURKA kinase assay, T75A mutagenesis, GDI interaction and ER morphology assays across C. elegans, Drosophila, and mammalian cells","pmids":["38177680"],"confidence":"High","gaps":["Phosphatase reversing pT75 not identified","How ER retention is coordinated with mitotic exit unresolved"]},{"year":null,"claim":"It remains unresolved how RAB1A's distinct activities — canonical ER-Golgi transport, autophagy initiation, organelle motility, and mTORC1 amino-acid signaling — are partitioned within a single cell, and what determines effector and GEF selection at each membrane.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model of spatial/temporal pool segregation","Mechanism coupling RAB1A directly to mTORC1 sensing undefined","Relationship between ubiquitination, phosphorylation, and prenylation cycles not integrated"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003924","term_label":"GTPase activity","supporting_discovery_ids":[1,15,16,17]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,2,4,43]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[41]}],"localization":[{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[0,4,9,42]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[2,35]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[4,19,27]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[2,3,4,9]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[18,19,28,29]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[43]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[23,24,25,26]}],"complexes":[],"partners":["TRAPPIII","GDI1","ULK1","SKIP/PLEKHM2","HRR25","GOLPH3","RNF115","C9ORF72"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P62820","full_name":"Ras-related protein Rab-1A","aliases":["YPT1-related protein"],"length_aa":205,"mass_kda":22.7,"function":"The small GTPases Rab are key regulators of intracellular membrane trafficking, from the formation of transport vesicles to their fusion with membranes (PubMed:20639577, PubMed:20861236, PubMed:21303926, PubMed:22939626). Rabs cycle between an inactive GDP-bound form and an active GTP-bound form that is able to recruit to membranes different sets of downstream effectors directly responsible for vesicle formation, movement, tethering and fusion (PubMed:20639577, PubMed:20861236, PubMed:21303926, PubMed:22939626). RAB1A regulates vesicular protein transport from the endoplasmic reticulum (ER) to the Golgi compartment and on to the cell surface, and plays a role in IL-8 and growth hormone secretion (PubMed:21303926). Required to modulate the compacted morphology of the Golgi (PubMed:26209634). Regulates the level of CASR present at the cell membrane (PubMed:20861236). Plays a role in cell adhesion and cell migration, via its role in protein trafficking (PubMed:20639577). Plays a role in autophagosome assembly and cellular defense reactions against pathogenic bacteria (PubMed:22939626). Plays a role in microtubule-dependent protein transport by early endosomes and in anterograde melanosome transport (By similarity)","subcellular_location":"Golgi apparatus; Endoplasmic reticulum; Early endosome; Cytoplasm, cytosol; Membrane; Melanosome","url":"https://www.uniprot.org/uniprotkb/P62820/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RAB1A","classification":"Not Classified","n_dependent_lines":84,"n_total_lines":1208,"dependency_fraction":0.0695364238410596},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000138069","cell_line_id":"CID000422","localizations":[{"compartment":"golgi","grade":3},{"compartment":"cytoplasmic","grade":1},{"compartment":"vesicles","grade":1}],"interactors":[{"gene":"GDI1","stoichiometry":4.0},{"gene":"SCAMP3","stoichiometry":4.0},{"gene":"RAB2A","stoichiometry":4.0},{"gene":"DDOST","stoichiometry":0.2},{"gene":"GDI2","stoichiometry":0.2},{"gene":"GOLGA2","stoichiometry":0.2},{"gene":"GORASP2","stoichiometry":0.2},{"gene":"MIF","stoichiometry":0.2},{"gene":"TOMM40","stoichiometry":0.2},{"gene":"RABAC1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000422","total_profiled":1310},"omim":[{"mim_id":"620229","title":"FHF COMPLEX SUBUNIT HOOK-INTERACTING PROTEIN 1B; FHIP1B","url":"https://www.omim.org/entry/620229"},{"mim_id":"617312","title":"FHF COMPLEX SUBUNIT HOOK-INTERACTING PROTEIN 2A; FHIP2A","url":"https://www.omim.org/entry/617312"},{"mim_id":"612565","title":"RAS-ASSOCIATED PROTEIN RAB1B; RAB1B","url":"https://www.omim.org/entry/612565"},{"mim_id":"611999","title":"RAB11 FAMILY-INTERACTING PROTEIN 4; RAB11FIP4","url":"https://www.omim.org/entry/611999"},{"mim_id":"608738","title":"RAB11 FAMILY-INTERACTING PROTEIN 3; RAB11FIP3","url":"https://www.omim.org/entry/608738"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Endoplasmic reticulum","reliability":"Supported"},{"location":"Cytosol","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/RAB1A"},"hgnc":{"alias_symbol":["YPT1"],"prev_symbol":["RAB1"]},"alphafold":{"accession":"P62820","domains":[{"cath_id":"3.40.50.300","chopping":"9-175","consensus_level":"high","plddt":92.8622,"start":9,"end":175}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P62820","model_url":"https://alphafold.ebi.ac.uk/files/AF-P62820-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P62820-F1-predicted_aligned_error_v6.png","plddt_mean":84.69},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RAB1A","jax_strain_url":"https://www.jax.org/strain/search?query=RAB1A"},"sequence":{"accession":"P62820","fasta_url":"https://rest.uniprot.org/uniprotkb/P62820.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P62820/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P62820"}},"corpus_meta":[{"pmid":"3127057","id":"PMC_3127057","title":"The yeast GTP-binding YPT1 protein and a mammalian counterpart are associated with the secretion machinery.","date":"1988","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/3127057","citation_count":636,"is_preprint":false},{"pmid":"2501306","id":"PMC_2501306","title":"The human Rab genes encode a family of GTP-binding proteins related to yeast YPT1 and SEC4 products involved in secretion.","date":"1989","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/2501306","citation_count":362,"is_preprint":false},{"pmid":"27334615","id":"PMC_27334615","title":"The C9orf72 protein interacts with Rab1a and the ULK1 complex to regulate initiation of autophagy.","date":"2016","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/27334615","citation_count":327,"is_preprint":false},{"pmid":"1990290","id":"PMC_1990290","title":"Identification and structure of four yeast genes (SLY) that are able to suppress the functional loss of YPT1, a member of the RAS superfamily.","date":"1991","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/1990290","citation_count":291,"is_preprint":false},{"pmid":"3094963","id":"PMC_3094963","title":"The ras-related YPT1 gene product in yeast: a GTP-binding protein that might be involved in microtubule organization.","date":"1986","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/3094963","citation_count":235,"is_preprint":false},{"pmid":"3286011","id":"PMC_3286011","title":"Study of a temperature-sensitive mutant of the ras-related YPT1 gene product in yeast suggests a role in the regulation of intracellular calcium.","date":"1988","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/3286011","citation_count":220,"is_preprint":false},{"pmid":"2504726","id":"PMC_2504726","title":"The GTP-binding protein Ypt1 is required for transport in vitro: the Golgi apparatus is defective in ypt1 mutants.","date":"1989","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/2504726","citation_count":207,"is_preprint":false},{"pmid":"2123294","id":"PMC_2123294","title":"Molecular cloning of YPT1/SEC4-related cDNAs from an epithelial cell line.","date":"1990","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/2123294","citation_count":196,"is_preprint":false},{"pmid":"11102533","id":"PMC_11102533","title":"The TRAPP complex is a nucleotide exchanger for Ypt1 and Ypt31/32.","date":"2000","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/11102533","citation_count":177,"is_preprint":false},{"pmid":"2104983","id":"PMC_2104983","title":"GTP-binding Ypt1 protein and Ca2+ function independently in a cell-free protein transport reaction.","date":"1990","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/2104983","citation_count":173,"is_preprint":false},{"pmid":"1903839","id":"PMC_1903839","title":"The yeast SLY gene products, suppressors of defects in the essential GTP-binding Ypt1 protein, may act in endoplasmic reticulum-to-Golgi transport.","date":"1991","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/1903839","citation_count":166,"is_preprint":false},{"pmid":"14576435","id":"PMC_14576435","title":"Structure of Rab GDP-dissociation inhibitor in complex with prenylated YPT1 GTPase.","date":"2003","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/14576435","citation_count":166,"is_preprint":false},{"pmid":"1904626","id":"PMC_1904626","title":"Mediation of the attachment or fusion step in vesicular transport by the GTP-binding Ypt1 protein.","date":"1991","source":"Science (New York, 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secretory machinery; yeast ypt1-1 mutation causes accumulation of membranes and vesicles and a partial secretion defect; immunofluorescence showed the mammalian counterpart localizes to the Golgi apparatus, consistent with a role directing intracellular vesicle traffic.\",\n      \"method\": \"Genetic analysis (ypt1-1 mutation phenotype), immunofluorescence with affinity-purified antibody in yeast and mouse cells\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — founding study combining genetic loss-of-function phenotype with direct immunolocalization, replicated across labs subsequently\",\n      \"pmids\": [\"3127057\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1986,\n      \"finding\": \"YPT1 protein is essential for cell growth; it binds GTP specifically and GTP binding is required for intracellular function; a dominant-lethal N121I substitution (site-directed mutagenesis) caused binucleated cells and abnormal spindles, demonstrating an essential function in cell cycle/microtubule organization.\",\n      \"method\": \"GAL10-regulated expression (depletion), site-directed mutagenesis, GTP-binding assay, immunofluorescence of microtubules\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — active-site mutagenesis plus in vivo GTP-binding assay, replicated across subsequent studies\",\n      \"pmids\": [\"3094963\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1989,\n      \"finding\": \"Ypt1p is required for ER-to-Golgi protein transport in vitro; ypt1 mutations specifically abolish Golgi complex function without affecting ER activity; wild-type cytosol can restore mutant Golgi function, placing Ypt1p at an early vesicular transport step.\",\n      \"method\": \"In vitro transport assay with ypt1 mutant membranes, complementation with wild-type cytosol, genetic epistasis with other secretion genes\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted cell-free transport assay with defined mutants and cytosol complementation, independently validated\",\n      \"pmids\": [\"2504726\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1990,\n      \"finding\": \"Ypt1p is required for ER-to-Golgi transport in cell-free extracts; anti-Ypt1 antibodies block transport; recombinant Ypt1p rescues the inhibition; ypt1-1 extract transport is restored by wild-type cytosol. Ypt1p acts independently of Ca2+ at a distinct step.\",\n      \"method\": \"In vitro transport assay, antibody inhibition, recombinant protein rescue, Ca2+ buffering experiments\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted in vitro assay with antibody inhibition and recombinant protein rescue, multiple orthogonal controls\",\n      \"pmids\": [\"2104983\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"Ypt1p mediates the attachment or fusion step of secretory vesicles with the acceptor compartment (cis-Golgi); blocking Ypt1p activity causes accumulation of transport vesicles; Ypt1p was detected on the outer surface of these vesicles.\",\n      \"method\": \"Cell-free ER-to-Golgi transport reconstitution, antibody blocking, vesicle intermediate accumulation assay, immunolocalization on vesicles\",\n      \"journal\": \"Science (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted cell-free system with defined intermediate accumulation and direct protein localization on vesicles\",\n      \"pmids\": [\"1904626\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"Suppressors of YPT1 deletion (SLY1-20, SLY2, SLY12, SLY41) restore ER-to-Golgi transport in Ypt1p-deficient cells; SLY2 and SLY12 encode synaptobrevin-like proteins; SLY1p is essential and acts as a single-copy suppressor, revealing the downstream machinery of the Ypt1p-regulated transport step.\",\n      \"method\": \"Multicopy/single-copy suppressor screens, invertase/CPY processing assays, genetic epistasis, DNA sequencing\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis with multiple suppressors confirmed biochemically, independently described\",\n      \"pmids\": [\"1990290\", \"1903839\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1988,\n      \"finding\": \"YPT1 protein requires at least one of its two C-terminal cysteine residues for palmitic acid (palmitoyl) modification and for membrane association; the non-palmitoylated mutant lacking both cysteines is exclusively soluble and non-functional.\",\n      \"method\": \"[3H]palmitic acid metabolic labeling, subcellular fractionation, site-directed mutagenesis, gene replacement\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct lipid labeling combined with mutagenesis and fractionation demonstrating causal link between palmitoylation and membrane attachment\",\n      \"pmids\": [\"3042385\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"Ypt1p membrane attachment depends on BET2 (a Rab geranylgeranyltransferase subunit homologous to DPR1/RAM1); bet2 mutants fail to attach Ypt1p and Sec4p to membranes, establishing prenylation as required for Ypt/Rab membrane association.\",\n      \"method\": \"Genetic analysis, DNA sequencing of BET2, membrane fractionation of Ypt1p/Sec4p in bet2 mutants\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic loss-of-function combined with fractionation showing direct causal requirement, replicated for multiple Rab proteins\",\n      \"pmids\": [\"1903184\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Rab geranylgeranyltransferase (RabGGTase)/Rab escort protein catalyzes geranylgeranylation of both C-terminal adjacent cysteines of Rab1A (–XXCC motif), as demonstrated by structural analysis of in vitro prenylated protein.\",\n      \"method\": \"In vitro prenylation assay with recombinant RabGGTase, [3H]geranylgeranyl pyrophosphate incorporation, tryptic peptide HPLC, electrospray mass spectrometry\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct structural mass spectrometry of in vitro enzymatic product, rigorously demonstrated for three distinct C-terminal motifs\",\n      \"pmids\": [\"7991565\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Ypt1p is essential for two sequential steps of the yeast secretory pathway: ER-to-cis-Golgi and cis-to-medial-Golgi transport, but not for later steps; this was established using a tight temperature-sensitive allele (ypt1-A136D) and glycoprotein processing assays.\",\n      \"method\": \"Temperature-sensitive mutant analysis (ypt1-A136D), glycoprotein processing assays (invertase, CPY, Gas1p), kinetic secretion analysis\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — tight conditional allele with defined biochemical readouts at multiple secretory steps, builds on prior in vitro reconstitution work\",\n      \"pmids\": [\"7593181\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"Specificity of Ypt1 versus Sec4 function is encoded in a 9-residue segment corresponding to loop L7 (and a 24-residue segment including the effector region, loop L2) of the GTPase; substitution of these segments of Sec4 with Ypt1 sequences converts Sec4 into a protein that can perform Ypt1 functions.\",\n      \"method\": \"Chimeric protein construction, in vivo complementation assays in yeast\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain-swap experiments in vivo defining specificity determinants with functional assays, single lab but two chimera series\",\n      \"pmids\": [\"8464499\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"The TRAPP complex is a guanine nucleotide exchange factor (GEF) for Ypt1p (and Ypt31/32); GST-tagged TRAPP subunits Bet3p or Bet5p precipitate GEF activity that stimulates GDP release and GTP uptake on Ypt1p; the dominant-negative Ypt1-D124N mutant inhibits TRAPP GEF activity, suggesting in vivo relevance.\",\n      \"method\": \"GST pulldown of TRAPP subunits, GDP-release and GTP-uptake assays in vitro, gel-filtration of GEF activity (>670 kDa), dominant-negative inhibition, overexpression studies\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro biochemical GEF assay with defined complex, inhibitor control, size-fractionation, and in vivo overexpression, replicated by subsequent studies\",\n      \"pmids\": [\"11102533\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Crystal structure of monoprenylated Ypt1:RabGDI complex at 1.5 Å resolution reveals the structural basis for GDI-mediated inhibition of nucleotide release; isoprenoid binding requires a conformational change opening a hydrophobic cavity in GDI domain II.\",\n      \"method\": \"Chemical synthesis of prenylated peptide, protein engineering, X-ray crystallography at 1.5 Å\",\n      \"journal\": \"Science (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution crystal structure with functionally validated complex, multiple orthogonal experimental inputs\",\n      \"pmids\": [\"14576435\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Structure of doubly geranylgeranylated Ypt1:GDI complex shows one geranylgeranyl moiety deeply buried in GDI domain II hydrophobic pocket while the other is more solvent-exposed; biophysical measurements provide thermodynamic model for GDI- and REP-mediated Rab membrane interaction.\",\n      \"method\": \"Synthesis of doubly prenylated protein, X-ray crystallography, biophysical measurements (ITC, fluorescence)\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure plus biophysical thermodynamic measurements of doubly prenylated complex, mechanistically comprehensive\",\n      \"pmids\": [\"16395334\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"A Ypt1p guanine nucleotide exchange factor (GEF) activity is required for ER-to-Golgi transport; dominant-negative Ypt1p-D124N blocks transport by sequestering the GEF; XTP-dependent rescue of Ypt1-D124N confirms the nucleotide-free form sequesters GEF, demonstrating an essential role for the exchange factor in vesicular transport.\",\n      \"method\": \"In vitro ER-to-Golgi transport assay, dominant-negative and nucleotide-specificity mutant proteins, GEF activity assay (GDP release, GTP uptake)\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted in vitro transport assay combined with biochemical GEF assay and nucleotide-specificity rescue, mechanistically rigorous\",\n      \"pmids\": [\"7657691\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"The effector domain of Ypt1p (residues 37–45) is required for function; mutations I41M and D44N are loss-of-function; a GTPase-activating protein (yptGAP) partially purified from porcine liver stimulates GTPase activity of Ypt1p specifically (not H-Ras) and interacts with the effector domain; I41M and D44N mutant proteins show reduced or absent GAP responsiveness.\",\n      \"method\": \"Site-directed mutagenesis and gene replacement in yeast, CPY/invertase processing assays, partial purification of yptGAP, GTPase stimulation assays\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — mutagenesis combined with biochemical GAP purification and activity assay, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"2009858\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"GTP hydrolysis is not essential for Ypt1p-mediated vesicular transport; cells expressing GTPase-deficient Ypt1-Q67L as the sole Ypt1p have no observable growth, secretion, or morphology defects; GTP hydrolysis is required only for recycling of Ypt1p between compartments.\",\n      \"method\": \"Q67L loss-of-GTPase mutant, GAP stimulation assay, secretion assays, electron microscopy\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined mutant blocking GTPase activity, multiple phenotypic readouts, clear mechanistic conclusion\",\n      \"pmids\": [\"9447979\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Two novel Ypt1-specific GAPs, Gyp5p and Gyp8p, were identified; Gyp5p accelerates Ypt1p GTPase activity 4.2×10⁴-fold; constitutively active Ypt1(Q67L) expressing cells show growth defects and autophagy-like morphology dependent on background of GAP deletion, indicating GTP hydrolysis is needed for balanced ER-Golgi vesicle flow.\",\n      \"method\": \"GAP activity biochemical assay, subcellular fractionation, yeast genetics (GAP deletion strains), electron microscopy\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — direct in vitro GAP activity measurement plus genetic analysis with multiple allele combinations, single lab\",\n      \"pmids\": [\"12189143\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Ypt1/Rab1 is recruited to the preautophagosomal structure (PAS) by TRAPPIII (activated via Atg17 recruitment); activated Ypt1 then recruits the Atg1 kinase to the PAS, bringing it near its binding partner Atg17, thereby restricting Atg1 specifically to the PAS for autophagosome formation.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, fluorescence microscopy, genetic epistasis with atg17 mutants\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP, genetic epistasis, and live-cell imaging, replicated by independent studies on TRAPPIII/Ypt1 in autophagy\",\n      \"pmids\": [\"23716696\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Atg9 vesicles recruit the TRAPPIII complex (via direct Trs85-Atg9 interaction) and Ypt1 to the preautophagosomal structure in an Atg9-dependent manner, establishing a vesicle-tethering machinery for autophagosome formation.\",\n      \"method\": \"Atg9 vesicle purification and mass spectrometry, co-IP (Trs85-Atg9), fluorescence microscopy, deletion mutant analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — vesicle purification with MS identification, confirmed by co-IP and microscopy, consistent with parallel study (PMID 23716696)\",\n      \"pmids\": [\"23129774\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Ypt1/Rab1 binds and activates the CK1δ kinase Hrr25 to spatially regulate phosphorylation of the COPII coat, directing ER-derived vesicles to the Golgi; hrr25 mutants are defective in both ER-Golgi trafficking and macroautophagy.\",\n      \"method\": \"Co-immunoprecipitation, kinase activity assay, yeast genetic analysis (hrr25 mutants), in vitro transport assay\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — kinase activity assay plus co-IP and genetic phenotypic analysis, single lab but multiple orthogonal approaches\",\n      \"pmids\": [\"26195667\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"TRAPPIII is the primary GEF that activates Ypt1/Rab1 in both Golgi trafficking and autophagy pathways in wild-type yeast; TRAPPII and TRAPPIII are the only two TRAPP complexes present in yeast, contrary to earlier reports of four complexes.\",\n      \"method\": \"Biochemical purification of TRAPP complexes, GEF activity assays, genetic analysis, secretion and autophagy assays\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — biochemical purification with GEF assays and genetic validation, single lab\",\n      \"pmids\": [\"29109089\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"A Trs33-containing TRAPP complex (TRAPP IV) acts as an autophagy-specific GEF for Ypt1; in the absence of Trs85, Trs33 is required for Ypt1-mediated autophagy and recruitment of core-TRAPP and Ypt1 to the PAS.\",\n      \"method\": \"Yeast genetics (trs85Δ, trs33Δ double mutants), co-IP, fluorescence microscopy of PAS markers, autophagy assays\",\n      \"journal\": \"Genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with localization assays, single lab, autophagy phenotype well defined but GEF activity not directly measured in vitro\",\n      \"pmids\": [\"27672095\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Rab1a regulates cell migration by controlling integrin β1 recycling to lipid rafts and to the plasma membrane; p115 acts as a downstream effector mediating Rab1a regulation of integrin recycling and lipid raft localization.\",\n      \"method\": \"RNAi screen, siRNA knockdown, cell adhesion and spreading assays, flow cytometry (lipid raft fractionation), integrin β1 recycling assay, p115 knockdown\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional RNAi screen with mechanistic follow-up using multiple assays, single lab\",\n      \"pmids\": [\"20639577\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Rab1A is required for microtubule-dependent anterograde melanosome transport in melanocytes; Rab1A localizes to mature melanosomes; its loss (siRNA or overexpression of dominant-negative TBC1D20 GAP) causes perinuclear melanosome aggregation and specifically suppresses long-range anterograde movements.\",\n      \"method\": \"Genome-wide constitutively active/negative Rab screen, siRNA knockdown, immunofluorescence localization, time-lapse live imaging\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genome-wide screen with mechanistic follow-up by siRNA, GAP overexpression, live imaging, and localization, single lab but multiple approaches\",\n      \"pmids\": [\"22854043\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Rab1A recruits SKIP/PLEKHM2 as a specific effector on melanosomes, and Rab1A–SKIP–kinesin-1 (Kif5b/KLC2) form a transport complex that mediates anterograde melanosome transport; Arl8 (not Rab1A) mediates anterograde lysosome transport via the same SKIP-kinesin-1 machinery.\",\n      \"method\": \"Co-immunoprecipitation, GST pulldown, siRNA knockdown, live-cell imaging, dominant-negative mutant expression\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP identification of effector complex combined with functional assays and live imaging, builds directly on prior study (PMID 22854043)\",\n      \"pmids\": [\"25649263\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Rab1a regulates sorting of early endocytic vesicles for multiple cargo (EGF, transferrin, ASOR); in Rab1a knockdown cells, EGF fails to reach lysosomes and transferrin is redirected to slow Rab11 recycling rather than fast Rab4 recycling; the minus-end-directed kinesin KifC1 is identified as an effector recruited by Rab1a to early endocytic vesicles.\",\n      \"method\": \"Stable Rab1a knockdown cell line, fluorescence microscopy tracking of fluorescent cargo, co-immunoprecipitation (KifC1)\",\n      \"journal\": \"American journal of physiology. Gastrointestinal and liver physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — stable KD with multiple cargo assays and effector co-IP, single lab\",\n      \"pmids\": [\"24407591\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Rab1a is associated not only with ER-to-Golgi transport vesicles but also with postendosomal transcytotic vesicles in rat liver, as demonstrated by immunoisolation of vesicles using anti-Rab1a beads; these vesicles contain transcytotic markers and multiple Rab GTPases.\",\n      \"method\": \"Immunoisolation of vesicles using antibody-coated magnetic beads, Western blotting for organelle markers, [α-32P]GTP overlay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — immunoisolation with marker Western blots, single lab, single method\",\n      \"pmids\": [\"8939959\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"C9orf72 interacts with Rab1a and the ULK1 autophagy initiation complex; as a Rab1a effector, C9orf72 controls initiation of autophagy by regulating Rab1a-dependent trafficking of the ULK1 complex to the phagophore.\",\n      \"method\": \"Co-immunoprecipitation (C9orf72 with Rab1a and ULK1), siRNA knockdown, autophagy flux assays (p62 accumulation, LC3 puncta), iNeuron studies\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP plus loss-of-function in multiple cell types including patient-derived neurons, single lab but multiple orthogonal approaches\",\n      \"pmids\": [\"27334615\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Salmonella effectors SseF and SseG inhibit autophagy by directly interacting with Rab1A, disrupting its interaction with the TRAPPIII GEF complex, thereby blocking Rab1A activation, ULK1 recruitment, and phosphatidylinositol 3-phosphate biogenesis, ultimately impairing autophagosome formation.\",\n      \"method\": \"Co-immunoprecipitation (SseF/SseG with Rab1A and TRAPPIII), GEF disruption assay, ULK1 recruitment assay, PI3P measurement, siRNA rescue experiments, mouse infection model\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple co-IP experiments plus functional assays in cell lines and animal model, mechanistic chain from effector binding to autophagy block established\",\n      \"pmids\": [\"29610274\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"M. tuberculosis PE_PGRS20 and PE_PGRS47 inhibit autophagy initiation by directly interacting with Rab1A; silencing Rab1A rescues the survival defects of pe_pgrs20/pe_pgrs47 deletion mutants, placing Rab1A as the host target of these mycobacterial effectors.\",\n      \"method\": \"Co-immunoprecipitation (PE_PGRS proteins with Rab1A), Rab1A silencing rescue, autophagy flux assays in macrophages\",\n      \"journal\": \"mSphere\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — co-IP and genetic rescue experiments in macrophages, single lab\",\n      \"pmids\": [\"34346699\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Rab1a interacts with and regulates optineurin (OPTN)-induced autophagosome formation in neuroblastoma cells; a zinc finger domain of OPTN is required for Rab1a binding; active Rab1a (GTP-bound) is required for the interaction; Rab1a knockdown inhibits OPTN-induced LC3-EGFP translocation to autophagosomes.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, confocal microscopy colocalization, dominant-negative/constitutively-active Rab1a mutants, LC3-EGFP autophagosome translocation assay\",\n      \"journal\": \"Journal of neuroscience research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — co-IP with domain mapping plus functional autophagy assay, single lab\",\n      \"pmids\": [\"28843006\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Hsc70 interacts with Rab1A in a chaperone-dependent manner and prevents its ubiquitination and degradation under proteotoxic stress; Hsc70 knockdown decreases Rab1A levels and increases its ubiquitination; Rab1A knockdown inhibits autophagosome formation and induces cell death under stress.\",\n      \"method\": \"Anti-Hsc70 affinity purification + mass spectrometry, co-immunoprecipitation, ubiquitination assay, siRNA knockdown, autophagy assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — MS identification confirmed by co-IP and ubiquitination assay, single lab\",\n      \"pmids\": [\"24801886\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The E3 ubiquitin ligase RNF115 catalyzes K11-linked ubiquitination of RAB1A at Lys49 and Lys61; this modification impairs recruitment of GDI1 to RAB1A, preventing its reactivation cycle; RAB1A ubiquitination-resistant mutant (K49/61R) promotes ER-to-Golgi trafficking of TLRs.\",\n      \"method\": \"Co-immunoprecipitation (RNF115 with RAB1A), in vitro ubiquitination assay, site-directed mutagenesis (K49R/K61R), GDI1 recruitment assay, TLR trafficking assay in Rnf115+/+ and Rnf115−/− cells\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro ubiquitination assay with mutagenesis plus functional rescue in knockout cells, multiple orthogonal methods, single lab\",\n      \"pmids\": [\"35343654\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Ubiquitin-specific protease USP2a deubiquitinates and stabilizes RAB1A, preventing its proteasomal degradation; this stabilization is required for USP2a-mediated HCC progression.\",\n      \"method\": \"LC-MS/MS affinity proteomics, co-immunoprecipitation, ubiquitination assay, siRNA knockdown, in vitro and in vivo tumor models\",\n      \"journal\": \"Cellular oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — MS-based target identification confirmed by co-IP and ubiquitination assay, single lab\",\n      \"pmids\": [\"33074477\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"During mitosis, Aurora kinase A (AURKA) phosphorylates Rab1A at Thr75; structural analysis shows Thr75 phosphorylation locks Rab1A in a constitutively active state by preventing GDI interaction; activated Rab1A is retained on the ER and induces oligomerization of RTN and REEP ER-shaping proteins, increasing ER complexity; this mechanism is evolutionarily conserved from C. elegans and Drosophila to mammals.\",\n      \"method\": \"Structural analysis (crystal/cryo-EM implied), in vitro kinase assay (AURKA phosphorylation of Rab1A), site-directed mutagenesis (T75A), GDI interaction assay, ER morphology assay, genetic modification in C. elegans/Drosophila/mammalian cells\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — structural analysis plus in vitro kinase assay plus mutagenesis plus multi-organism genetic validation, multiple orthogonal methods in one rigorous study\",\n      \"pmids\": [\"38177680\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In Dictyostelium, Rab1A binds the LRRK2-related Roco kinase Roco2 in vivo; active GTP-bound Rab1A regulates Roco2 kinase activity; Roco2 in turn controls F-actin polymerization and pseudopod extension by acting upstream of filamin (abp120), establishing a Rab1A-Roco2-filamin pathway regulating actin cytoskeleton and cell motility.\",\n      \"method\": \"Co-immunoprecipitation (Roco2 with Rab1A and filamin), kinase activity assay, constitutively active/dominant-negative Rab1A mutants, chemotaxis assays, F-actin measurement\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus kinase activity assay plus multiple functional assays in Dictyostelium, single lab\",\n      \"pmids\": [\"21551065\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Rab1A (and Rab43) is required for herpes simplex virus 1 secondary envelopment; depletion of Rab1a/b via their specific GAP TBC1D20 prevents viral glycoproteins from trafficking from the ER to the viral assembly compartment, resulting in accumulation of unenveloped particles.\",\n      \"method\": \"Overexpression of 37 Rab-GAPs (functional screen), siRNA knockdown, infectious titer assay, immunofluorescence microscopy of viral glycoproteins, electron microscopy\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional screen with mechanistic follow-up by KD and localization studies, single lab\",\n      \"pmids\": [\"21680502\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"RAB1A is required for Vaccinia virus production of intracellular enveloped virions (IEVs) but not intracellular mature virions (IMVs); RAB1A facilitates the wrapping step consistent with its role in ER-to-Golgi transport.\",\n      \"method\": \"siRNA knockdown, infectious titer assay, immunofluorescence, electron microscopy\",\n      \"journal\": \"Virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA with titer and EM readouts defining specific step in viral replication, single lab\",\n      \"pmids\": [\"25462347\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Rab1A is required for classical swine fever virus (CSFV) particle assembly; Rab1A binds CSFV NS5A protein; Rab1A depletion reduces intracellular and extracellular viral titers without affecting viral genome replication or E2 protein expression, specifically implicating particle assembly.\",\n      \"method\": \"siRNA knockdown, viral titer assay, qRT-PCR (genome copies), co-immunoprecipitation (Rab1A–NS5A), confocal microscopy, neutralizing antibody blocking assay\",\n      \"journal\": \"Virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus functional dissection of viral lifecycle step, single lab\",\n      \"pmids\": [\"29128753\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Rab1A overexpression prevents Golgi fragmentation caused by alpha-synuclein in dopaminergic neurons; the non-prenylable Rab1A-ΔCC mutant fails to rescue Golgi morphology, linking the protective effect to Rab1A's ER-to-Golgi trafficking activity.\",\n      \"method\": \"AAV-mediated co-expression in rat substantia nigra, Golgi morphology assay, non-prenylable mutant analysis, motor behavior assay\",\n      \"journal\": \"Journal of Parkinson's disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo gene delivery with mutant control demonstrating prenylation dependence, single lab\",\n      \"pmids\": [\"23939344\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Ypt1 protein specifically associates in vivo with unspliced HAC1 RNA and promotes HAC1 RNA decay; this association is disrupted during ER stress induction of the UPR; Ypt1 depletion reduces HAC1 RNA decay rate, elevating HAC1 levels and delaying UPR attenuation.\",\n      \"method\": \"Protein microarray screening for HAC1 RNA binding, RNA co-immunoprecipitation, HAC1 RNA decay assays, genetic analysis (ire1Δ, ada5Δ)\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — protein microarray plus co-IP with RNA, decay assay, genetic dependencies, single lab\",\n      \"pmids\": [\"22844259\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Human GOLPH3 is a direct effector of RAB1A and RAB1B; interaction is nucleotide-dependent, favored by GTP-locked (active) variants; expression of GTP-locked RAB1A reduces GOLPH3 localization at the Golgi, suggesting Rab1A-GTP releases GOLPH3 from the Golgi.\",\n      \"method\": \"Co-immunoprecipitation (GOLPH3 with RAB1A/B wild-type and GTP-locked mutants), fluorescence microscopy of GOLPH3 distribution\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — co-IP with nucleotide-state specificity plus localization assay, single lab\",\n      \"pmids\": [\"32790781\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Rab1A mediates amino acid (particularly branched-chain amino acid)-dependent mTORC1 signaling in vivo; whole-body Rab1A knockout mice are hyperglycemic and glucose intolerant due to impaired insulin transcription and β-cell proliferation/maintenance; mechanistically, Rab1A mediates BCAA-mTORC1 signaling to regulate stability and localization of the insulin transcription factor Pdx1.\",\n      \"method\": \"Tamoxifen-induced whole-body Rab1A knockout mouse, glucose tolerance test, insulin assay, β-cell analysis, Pdx1 localization and stability assay\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo knockout with multiple mechanistic readouts (mTORC1 signaling, Pdx1 regulation, β-cell function), single lab but comprehensive physiological characterization\",\n      \"pmids\": [\"33730578\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"NAB2 (an N-arylbenzimidazole small molecule) binds Rab1a selectively in its GDP-bound form; NAB2 binding phenocopies Rab1a overexpression in alleviating α-synuclein toxicity; Rab1a was identified as a target of NAB2 by Thermal Proteome Profiling and SPROX chemoproteomic analyses.\",\n      \"method\": \"Thermal Proteome Profiling (TPP), SPROX chemoproteomic analysis, cellular phenotypic assay (α-synuclein toxicity rescue), GDP/GTP-state selectivity binding assay\",\n      \"journal\": \"RSC chemical biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two orthogonal chemoproteomic methods converging on Rab1a as target, with nucleotide-state selectivity and phenotypic validation, single lab\",\n      \"pmids\": [\"35128413\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Rab1a interacts with ULK1 and promotes ULK1 phosphorylation dependent on its GTP-binding activity; this Rab1a-ULK1 interaction initiates autophagy that promotes PRRSV replication.\",\n      \"method\": \"Co-immunoprecipitation (Rab1a with ULK1), ULK1 phosphorylation assay, GTP-binding mutant analysis, ATG7 knockdown rescue, viral titer assay\",\n      \"journal\": \"Virus research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — co-IP plus phosphorylation assay plus GTP-mutant dependence, single lab\",\n      \"pmids\": [\"36306941\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Yeast Yip3p (a GDI displacement factor ortholog) forms a distinct complex with Ypt1p that is separable from its complex with reticulon Rtn1p; Yip3p is predominantly Golgi-localized; however, loss of Yip3p or Rtn1p does not perturb intracellular Rab localization, indicating Yip3p-Ypt1p interaction is not critical for Rab membrane targeting.\",\n      \"method\": \"Co-purification from detergent extracts, Western blotting, fluorescence microscopy in yip3Δ and rtn1Δ mutants\",\n      \"journal\": \"Eukaryotic cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — co-purification with genetic loss-of-function analysis; result partially negative (no role in targeting)\",\n      \"pmids\": [\"16002643\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"A Ypt1p-specific GEF activity localizes to the acceptor (Golgi) fraction rather than the donor (ER) fraction; a Ypt1p-specific GAP activity colocalizes with ER markers; the GEF is specific for Ypt1p and not other Ypt proteins; the GAP has higher affinity for GTP-bound Ypt1p.\",\n      \"method\": \"Partial purification of GEF and GAP activities from yeast fractions, GDP-release and GTP-uptake assays, GTPase stimulation assay, subcellular fractionation\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biochemical activity assays with fractionation defining spatial organization of GEF/GAP, single lab\",\n      \"pmids\": [\"9763446\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RAB1A/Ypt1 is a small GTPase that acts as a molecular switch on ER-derived vesicles, where it is activated by TRAPP complex GEFs (TRAPPI for secretion, TRAPPIII/IV for autophagy), recruits effectors including SKIP/kinesin-1 for anterograde transport and the Atg1/ULK1 kinase for autophagy initiation, mediates vesicle tethering and fusion with the cis-Golgi and subsequent intra-Golgi steps, requires geranylgeranylation of its C-terminal cysteines for membrane attachment (regulated by RabGDI extraction and RNF115-mediated K11-ubiquitination), senses and transduces amino acid signals to mTORC1 to control cell growth and glucose homeostasis, and is phosphorylated at Thr75 by mitotic Aurora kinase A to drive ER remodeling during cell division.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"RAB1A (yeast Ypt1) is an essential small GTPase that functions as a molecular switch governing ER-to-Golgi vesicular transport and, more broadly, membrane traffic across the secretory and autophagic pathways [#0, #1, #2]. At the cell-free level it mediates the attachment/fusion step of ER-derived secretory vesicles with the cis-Golgi and is required for both ER-to-cis-Golgi and cis-to-medial-Golgi transport, acting on the outer surface of transport vesicles [#4, #9]. Like all Rabs, it cycles between GDP- and GTP-bound states: activation is driven by TRAPP-complex GEFs, with TRAPPIII serving as the primary GEF for both Golgi trafficking and autophagy [#11, #21], while specific GAPs (yptGAP, Gyp5p/Gyp8p, TBC1D20) stimulate GTP hydrolysis required for protein recycling rather than the transport event itself [#15, #16, #17]. Membrane attachment requires geranylgeranylation of its two C-terminal cysteines by RabGGTase, and the prenylated, GDP-bound form is extracted and chaperoned by RabGDI, whose hydrophobic pocket sequesters the lipid moiety [#7, #8, #12, #13]. RAB1A nucleates effector platforms in a nucleotide-dependent manner, recruiting the Atg1/ULK1 autophagy-initiation kinase to the preautophagosomal structure via TRAPPIII and Atg9 vesicles [#18, #19, #28], activating the CK1δ kinase Hrr25 to phosphorylate the COPII coat [#20], and engaging cargo-transport and Golgi effectors including SKIP/PLEKHM2–kinesin-1 for anterograde melanosome movement, p115 for integrin β1 recycling, and GOLPH3 [#23, #25, #42]. Beyond membrane traffic, RAB1A transduces branched-chain amino-acid signals to mTORC1 to control β-cell insulin transcription and glucose homeostasis [#43], and during mitosis Aurora kinase A phosphorylates RAB1A at Thr75, locking it in an active, GDI-resistant state that retains it on the ER to drive RTN/REEP-dependent ER remodeling [#35]. Its activity is further tuned by ubiquitin-dependent regulation: RNF115 catalyzes K11-linked ubiquitination at Lys49/Lys61 to impair GDI1 recruitment, while Hsc70 chaperoning and USP2a deubiquitination stabilize the protein [#32, #33, #34]. RAB1A is a recurrent target of intracellular pathogens, including Salmonella effectors SseF/SseG and mycobacterial PE_PGRS proteins that block its activation to suppress autophagy, and it is co-opted for the assembly and envelopment of multiple viruses [#29, #30, #37, #39].\",\n  \"teleology\": [\n    {\n      \"year\": 1986,\n      \"claim\": \"Established that YPT1/RAB1A is an essential, GTP-binding protein whose nucleotide function is required in vivo, defining it as a guanine-nucleotide-dependent switch rather than a structural protein.\",\n      \"evidence\": \"Regulated depletion, site-directed mutagenesis (N121I), and GTP-binding assay in yeast\",\n      \"pmids\": [\"3094963\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not place the protein in a specific trafficking step\", \"Connection to microtubule/spindle phenotype mechanistically unresolved at the time\"]\n    },\n    {\n      \"year\": 1988,\n      \"claim\": \"Linked YPT1/RAB1A directly to the secretory machinery and the Golgi, and showed lipid modification of C-terminal cysteines is required for membrane attachment and function.\",\n      \"evidence\": \"ypt1-1 loss-of-function phenotype with immunolocalization, plus [3H]palmitate labeling and cysteine mutagenesis\",\n      \"pmids\": [\"3127057\", \"3042385\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Lipid identity later revised to geranylgeranyl rather than palmitate\", \"Exact transport step not yet defined\"]\n    },\n    {\n      \"year\": 1990,\n      \"claim\": \"Pinpointed RAB1A function to the ER-to-Golgi vesicular transport step using reconstituted assays, distinguishing it from the ER stage and from Ca2+-dependent events.\",\n      \"evidence\": \"Cell-free ER-to-Golgi transport with antibody inhibition and recombinant rescue; complementation with wild-type cytosol\",\n      \"pmids\": [\"2504726\", \"2104983\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether RAB1A acts at tethering vs fusion not yet resolved\", \"Upstream activators and downstream effectors unidentified\"]\n    },\n    {\n      \"year\": 1991,\n      \"claim\": \"Resolved that RAB1A acts at the vesicle attachment/fusion step on the cis-Golgi, identified downstream SNARE-like machinery, and showed prenylation by the BET2 geranylgeranyltransferase is required for membrane association.\",\n      \"evidence\": \"Vesicle-intermediate accumulation assay with on-vesicle immunolocalization, SLY suppressor screen, and bet2 mutant fractionation\",\n      \"pmids\": [\"1904626\", \"1990290\", \"1903839\", \"1903184\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular nature of the tethering apparatus not yet defined\", \"GEF that activates RAB1A still unknown\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Mapped the functional specificity of RAB1A versus the related Sec4 to discrete loop segments (L2 effector region and L7), explaining how closely related Rabs achieve distinct functions.\",\n      \"evidence\": \"Chimeric Ypt1/Sec4 protein swaps with in vivo complementation\",\n      \"pmids\": [\"8464499\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Effector(s) reading these specificity determinants not identified\", \"Structural basis not directly visualized\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Defined the GTPase cycle requirements: a dedicated GEF is essential for transport, and the protein operates across two sequential Golgi steps.\",\n      \"evidence\": \"Dominant-negative D124N GEF-sequestration with XTP rescue in cell-free transport; tight ts allele with glycoprotein processing assays\",\n      \"pmids\": [\"7657691\", \"7593181\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the GEF not yet established\", \"Spatial organization of GEF/GAP not yet mapped\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Showed GTP hydrolysis is dispensable for the transport event itself but required for RAB1A recycling, and that the GEF and GAP are spatially segregated to acceptor and donor compartments.\",\n      \"evidence\": \"GTPase-deficient Q67L as sole copy with secretion/EM readouts; partial purification and fractionation of GEF and GAP activities\",\n      \"pmids\": [\"9447979\", \"9763446\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular identity of fractionated GEF/GAP still unknown\", \"Mechanism coupling hydrolysis to recycling not detailed\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Identified the TRAPP complex as the physiological GEF for RAB1A, naming the long-sought activating machinery.\",\n      \"evidence\": \"GST pulldown of TRAPP subunits with GDP-release/GTP-uptake assays, size fractionation, and dominant-negative inhibition\",\n      \"pmids\": [\"11102533\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Distinct TRAPP subcomplexes and their pathway specificities not yet resolved\", \"Mammalian counterpart regulation not addressed\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Provided the structural basis for GDI-mediated extraction and membrane targeting by visualizing how mono- and doubly geranylgeranylated RAB1A engage RabGDI.\",\n      \"evidence\": \"X-ray crystallography of prenylated Ypt1:GDI complexes with biophysical thermodynamic measurements\",\n      \"pmids\": [\"14576435\", \"16395334\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Membrane delivery step (GDF function) not structurally captured\", \"How REP vs GDI selectivity is achieved in vivo not fully resolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Extended RAB1A function beyond secretion into autophagy initiation, showing TRAPPIII/Atg9-vesicle-dependent activation recruits the Atg1/ULK1 kinase to the preautophagosomal structure.\",\n      \"evidence\": \"Yeast two-hybrid, reciprocal co-IP, fluorescence imaging, and genetic epistasis with atg17/atg9\",\n      \"pmids\": [\"23716696\", \"23129774\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct Rab1A–Atg1 contact vs indirect recruitment not fully dissected\", \"Mammalian effector chain not yet defined here\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Showed RAB1A spatially controls COPII coat phosphorylation by binding and activating the CK1δ kinase Hrr25, mechanistically coupling vesicle activation to coat dynamics in both trafficking and autophagy.\",\n      \"evidence\": \"Co-IP, kinase activity assay, and in vitro transport with hrr25 mutants\",\n      \"pmids\": [\"26195667\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether mammalian RAB1A regulates CK1δ analogously not tested here\", \"Direct COPII phosphosite consequences for vesicle release incomplete\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Defined a mammalian effector cascade in which RAB1A recruits SKIP/PLEKHM2–kinesin-1 to drive microtubule-dependent anterograde melanosome transport, extending RAB1A into long-range organelle motility.\",\n      \"evidence\": \"Genome-wide Rab screen, siRNA, co-IP/GST pulldown of SKIP-kinesin-1, and live imaging\",\n      \"pmids\": [\"22854043\", \"25649263\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"GEF activating RAB1A on melanosomes not identified\", \"Relationship to canonical ER-Golgi RAB1A pool unclear\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Established TRAPPIII as the primary in vivo RAB1A GEF for both Golgi and autophagy, revising the prior four-complex model and identifying a Trs33-dependent autophagy-specific GEF activity.\",\n      \"evidence\": \"Biochemical purification of TRAPP complexes with GEF assays; trs85/trs33 genetics with PAS imaging\",\n      \"pmids\": [\"29109089\", \"27672095\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"TRAPP IV/Trs33 GEF activity not measured directly in vitro (Medium)\", \"How a single GEF achieves pathway selectivity not fully resolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Connected RAB1A to disease-relevant autophagy machinery by identifying C9orf72 as a RAB1A effector that delivers the ULK1 complex to the phagophore.\",\n      \"evidence\": \"Reciprocal co-IP of C9orf72 with RAB1A/ULK1, siRNA, and autophagy-flux assays in iNeurons\",\n      \"pmids\": [\"27334615\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether C9orf72 acts as a GEF/adaptor or tether for RAB1A not resolved\", \"Neurodegeneration mechanism downstream not established here\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Revealed RAB1A as a convergent host target subverted by intracellular pathogens that block its activation to suppress autophagy.\",\n      \"evidence\": \"Co-IP of Salmonella SseF/SseG with RAB1A and TRAPPIII, GEF-disruption and ULK1/PI3P assays, plus mouse infection; mycobacterial PE_PGRS co-IP with silencing rescue\",\n      \"pmids\": [\"29610274\", \"34346699\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of effector-mediated TRAPPIII displacement not solved\", \"PE_PGRS interaction is single-lab co-IP/rescue (Medium)\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified a signaling role distinct from membrane traffic: RAB1A transduces branched-chain amino-acid signals to mTORC1 to control insulin transcription and glucose homeostasis.\",\n      \"evidence\": \"Tamoxifen-induced whole-body Rab1A knockout mice with glucose tolerance, β-cell, and Pdx1 stability/localization analyses\",\n      \"pmids\": [\"33730578\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct molecular link between RAB1A and the mTORC1 amino-acid sensing apparatus not defined\", \"Whether this requires RAB1A trafficking activity unresolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined a ubiquitin-based regulatory layer in which RNF115-catalyzed K11 ubiquitination at Lys49/61 blocks GDI1 recruitment and thereby controls RAB1A reactivation and TLR trafficking.\",\n      \"evidence\": \"Co-IP, in vitro ubiquitination, K49R/K61R mutagenesis, GDI1 recruitment and TLR trafficking assays in Rnf115 knockout cells\",\n      \"pmids\": [\"35343654\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Counteracting deubiquitinase for K11 chains not identified here\", \"Stoichiometry/dynamics of the modification in vivo unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Uncovered cell-cycle control of RAB1A: mitotic Aurora kinase A phosphorylates Thr75 to lock RAB1A active and GDI-resistant, retaining it on the ER to drive RTN/REEP-mediated ER remodeling, a conserved mechanism.\",\n      \"evidence\": \"Structural analysis, in vitro AURKA kinase assay, T75A mutagenesis, GDI interaction and ER morphology assays across C. elegans, Drosophila, and mammalian cells\",\n      \"pmids\": [\"38177680\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Phosphatase reversing pT75 not identified\", \"How ER retention is coordinated with mitotic exit unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how RAB1A's distinct activities — canonical ER-Golgi transport, autophagy initiation, organelle motility, and mTORC1 amino-acid signaling — are partitioned within a single cell, and what determines effector and GEF selection at each membrane.\",\n      \"evidence\": null,\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model of spatial/temporal pool segregation\", \"Mechanism coupling RAB1A directly to mTORC1 sensing undefined\", \"Relationship between ubiquitination, phosphorylation, and prenylation cycles not integrated\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003924\", \"supporting_discovery_ids\": [1, 15, 16, 17]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 2, 4, 43]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [41]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [0, 4, 9, 42]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [2, 35]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [4, 19, 27]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [2, 3, 4, 9]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [18, 19, 28, 29]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [43]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [23, 24, 25, 26]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"TRAPPIII\", \"GDI1\", \"ULK1\", \"SKIP/PLEKHM2\", \"Hrr25\", \"GOLPH3\", \"RNF115\", \"C9orf72\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}