{"gene":"RAB27B","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":2009,"finding":"RNAi screen identified RAB27B as a regulator of MVE docking at the plasma membrane for exosome secretion; RAB27B silencing redistributed MVEs toward the perinuclear region, and silencing its effector Slac2b (EXPH5) phenocopied RAB27B knockdown. Thus RAB27B controls a distinct step in the exosomal pathway compared to RAB27A.","method":"RNAi screen, siRNA knockdown, fluorescence microscopy, exosome secretion assay","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (RNAi screen, effector knockdown phenocopy, MVE imaging), replicated across multiple groups","pmids":["19966785"],"is_preprint":false},{"year":2007,"finding":"Rab27b knockout mice exhibit hemorrhagic disease, impaired platelet aggregation, and reduced dense granule secretion. A 50% reduction in dense granule number per platelet was observed, suggesting a role in dense granule packaging during megakaryocyte maturation. Rab27a partially compensated for the secretory defect but not the reduced granule number.","method":"Knockout mouse generation, in vitro platelet aggregation assay, dense granule secretion assay, electron microscopy","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with multiple orthogonal phenotypic readouts (aggregation, secretion, granule counting), double KO comparison","pmids":["17384153"],"is_preprint":false},{"year":2004,"finding":"Rab27B localizes to amylase-containing secretory granules in rat parotid acinar cells and forms a complex with the effector Slac2-c/MyRIP on granules. Disruption of the Rab27B–Slac2-c complex (via recombinant Slp homology domain or blocking antibodies) inhibited isoproterenol-stimulated amylase release, establishing this complex as required for secretory granule exocytosis.","method":"Subcellular fractionation, immunoprecipitation, immunohistochemistry, introduction of dominant-negative recombinant protein/antibodies in permeabilized cells, amylase release assay","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, functional disruption with two independent tools (recombinant SHD domain and blocking antibodies), specific phenotypic readout","pmids":["15039459"],"is_preprint":false},{"year":2007,"finding":"Rab27b and Rab27a are both expressed on mast cell secretory granules. Rab27b KO (but not Rab27a KO) impairs mast cell degranulation as measured by beta-hexosaminidase release in vitro and passive cutaneous anaphylaxis in vivo. Live-cell imaging showed ~10-fold increase in fast granule movement (>1.5 μm/s, nocodazole-sensitive) in double KO cells, suggesting Rab27 regulates the transition from microtubule to actin-based motility.","method":"Knockout mice, beta-hexosaminidase release assay, passive cutaneous anaphylaxis, live-cell time-lapse imaging, nocodazole treatment","journal":"Traffic (Copenhagen, Denmark)","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO, multiple orthogonal methods (in vitro secretion, in vivo anaphylaxis, live imaging), mechanistic follow-up with nocodazole","pmids":["17587407"],"is_preprint":false},{"year":2007,"finding":"Rab27b is widely expressed in secretory cells and neurons. In pituitary cells co-expressing Rab27a, Rab27a/b double KO markedly impairs polarized distribution of secretory granules near the plasma membrane, indicating the Rab27 subfamily delivers granules to the exocytic site.","method":"Rab27b KO mouse with LacZ reporter, double KO mouse (crossed with ashen), histology, immunofluorescence of secretory granule distribution","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic double KO with defined granule-localization phenotype, complementary reporter-driven expression analysis","pmids":["17761531"],"is_preprint":false},{"year":2002,"finding":"Rab27b associates with secretory granules and interacts with the effector granuphilin in pituitary AtT20 cells. Overexpression of the inactive mutant Rab27b N133I significantly inhibits basal and forskolin-induced ACTH secretion, establishing Rab27b as a regulator of pituitary dense core granule exocytosis.","method":"Subcellular fractionation, co-immunoprecipitation, dominant-negative mutant overexpression, ACTH secretion assay","journal":"Endocrinology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — Co-IP plus dominant-negative functional assay with defined hormonal secretion readout","pmids":["11956164"],"is_preprint":false},{"year":2003,"finding":"Rab27b associates with alpha- and dense granules in megakaryocytes. Rab27b expression is induced during terminal megakaryocyte differentiation in an NF-E2-dependent manner; chromatin immunoprecipitation demonstrated NF-E2 recruitment to the Rab27B promoter. Inhibition of endogenous Rab27 function caused quantitative and qualitative defects in proplatelet formation.","method":"Chromatin immunoprecipitation, dominant-negative Rab27 inhibition, immunofluorescence localization, proplatelet formation assay","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — ChIP for transcriptional regulation, functional KO/inhibition with defined proplatelet phenotype, consistent with KO mouse studies","pmids":["12907454"],"is_preprint":false},{"year":2003,"finding":"Rab27b associates with fusiform vesicles (but not the apical plasma membrane) in differentiated urothelial umbrella cells at extraordinarily high levels (0.1% of total protein); its expression is greatly reduced in cultured urothelial cells that fail to form fusiform vesicles and produce little uroplakin. This positions Rab27b as a regulator of fusiform vesicle delivery to the apical membrane for uroplakin targeting.","method":"Immuno-electron microscopy, Western blot, subcellular fractionation, comparison of differentiated vs cultured urothelial cells","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — immuno-EM localization plus correlative expression analysis; no direct functional loss-of-function in the same study","pmids":["14625374"],"is_preprint":false},{"year":2004,"finding":"Rab27b localizes to zymogen granule (ZG) membranes in pancreatic acinar cells. Constitutively active Rab27b Q78L enhanced CCK-induced amylase release by ~92%, while dominant-negative Rab27b N133I inhibited it by ~53% across all CCK doses, establishing Rab27b as a positive regulator of ZG exocytosis.","method":"Proteomics/MALDI-MS identification, Western blot, immunocytochemistry, adenovirus-mediated overexpression of wild-type and mutant Rab27b, amylase release assay","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 2 / Moderate — constitutively active and dominant-negative mutant analysis in primary acini with quantitative secretion readout","pmids":["15451418"],"is_preprint":false},{"year":2009,"finding":"Both Rab27a and Rab27b deficiencies impair azurophilic granule exocytosis in neutrophils by independent mechanisms. TIRF microscopy showed decreased numbers of azurophilic granules near the plasma membrane in single and double KO neutrophils. Rab27b KO also impaired NADPH oxidase activation at the plasma membrane; secretory vesicle exocytosis was unaffected, indicating Rab27 selectively controls granule exocytosis.","method":"Knockout mice, azurophilic granule exocytosis assay, TIRF microscopy, NADPH oxidase activity measurement","journal":"Traffic (Copenhagen, Denmark)","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO, TIRF microscopy for docking, functional NADPH oxidase assay, single vs double KO comparison","pmids":["20028487"],"is_preprint":false},{"year":2010,"finding":"Rab27b localizes to synaptic vesicle (SV) membranes in neurons, colocalizing with Rab3a and synaptotagmin at presynaptic terminals. Unlike Rab3a, Rab27b persists on SV membranes after Ca2+-triggered exocytosis and is resistant to GDI-mediated retrieval. Modulation of the Rab27b GTP/GDP switch impairs SV recycling.","method":"Quantitative mass spectrometry (iTRAQ), immunoblotting, fluorescence microscopy, GDI extraction assay, GTP/GDP switch manipulation with functional SV recycling assay","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — quantitative MS, multiple biochemical assays, functional manipulation, single lab","pmids":["20926670"],"is_preprint":false},{"year":2011,"finding":"Rab27a and Rab27b are both involved in stimulation-dependent RANKL release from secretory lysosomes in osteoblastic cells. Their effectors Slp4-a, Slp5, and Munc13-4 coordinate this activity. Suppression of Rab27a/b or these effectors blocked vesicle fusion to the plasma membrane but did not prevent RANKL accumulation in lysosomal vesicles near stimulated sites, indicating Rab27b acts at the final fusion step.","method":"RNAi knockdown, immunofluorescence, RANKL release assay, in vivo jinx (Munc13-4 KO) mouse bone phenotype","journal":"Journal of bone and mineral research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA knockdown with defined mechanistic step (docking vs. fusion) plus in vivo validation, single lab","pmids":["20939018"],"is_preprint":false},{"year":2007,"finding":"Crystal structure of mouse Rab27b-GDP determined in three lattice forms revealed an unexpected domain-swapped dimer with open switch and interswitch regions. Small-angle X-ray scattering showed an extended monomer in solution, suggesting the flexible switch regions may influence effector binding specificity.","method":"X-ray crystallography, small-angle X-ray scattering (SAXS)","journal":"Acta crystallographica. Section D, Biological crystallography","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure in three lattices with SAXS solution validation, single lab","pmids":["17582168"],"is_preprint":false},{"year":2002,"finding":"Rab27b colocalizes with the melanosome marker TRP-1 and myosin Va at the cell periphery in melan-a melanocytes. Dominant-negative Rab27b mutants caused redistribution of melanosomes from the cell periphery to the perinuclear region and diminished dendrite number and length, suggesting Rab27b regulates outward melanosome movement and dendritic extension.","method":"GFP-tagged wild-type and dominant-negative mutant overexpression, co-localization with TRP-1 and myosin Va by fluorescence microscopy, GTPase activity assay","journal":"The Journal of investigative dermatology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — dominant-negative approach with defined melanosome and dendrite phenotypes, single lab","pmids":["12060386"],"is_preprint":false},{"year":2004,"finding":"In Griscelli syndrome type II melanocytes lacking Rab27a, Rab27b is up-regulated and forms a tripartite complex with melanophilin and exon F–containing Myosin Va isoforms on the melanosome membrane, partially compensating for Rab27a loss. This complex links Rab27b to actin-based melanosome transport.","method":"Quantitative RT-PCR, Western blot, immunofluorescence, yeast two-hybrid screening","journal":"Pigment cell research","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — yeast two-hybrid for interaction plus expression and localization in patient cells, single lab","pmids":["15357836"],"is_preprint":false},{"year":2010,"finding":"Rab27B promotes invasive growth and metastasis in ER-positive breast cancer cells. Mass spectrometry identified HSP90α in Rab27B-secretory vesicles; HSP90α secretion was Rab27B-dependent and required for MMP-2 activation. All functional responses required GTP-binding and geranylgeranylation of Rab27B.","method":"GFP-Rab27B overexpression, point mutants (GTP/GDP and geranylgeranylation defective), siRNA knockdown, mass spectrometry of purified vesicles, MMP-2 activation assay, xenograft mouse model, Matrigel invasion assay","journal":"Journal of the National Cancer Institute","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (MS identification, functional mutants, KD, in vivo xenograft), mechanistic endpoint (MMP-2 activation via HSP90α)","pmids":["20484105"],"is_preprint":false},{"year":2013,"finding":"V-ATPase subunits (including V0a1 and V0d1) are identified by mass spectrometry in GFP-Rab27B secretory vesicles from MCF-7 cells. V-ATPase activity controls peripheral localization and size of Rab27B vesicles, and V-ATPase inhibition or subunit knockdown reduces Rab27B-dependent HSP90α secretion, MMP-2 activation, and cell invasion.","method":"Mass spectrometry on purified GFP-Rab27B vesicles, Western blot, pharmacological inhibition (bafilomycin A1), siRNA knockdown of V0a1/V0d1, invasion assay, CAM assay","journal":"International journal of cancer","confidence":"High","confidence_rationale":"Tier 2 / Moderate — MS identification plus functional validation with two independent tools (pharmacological and siRNA) and multiple readouts","pmids":["23390068"],"is_preprint":false},{"year":2012,"finding":"Mutation of the Rab27B effector Slac2-b (EXPH5) in humans causes inherited skin fragility with increased perinuclear vesicles in keratinocytes. Slac2-b co-localizes with Rab27B and β4 integrin at early adhesion initiation sites in spreading keratinocytes, and its loss disrupts keratin cytoskeleton and cell adhesion, placing the Rab27B–Slac2-b complex in keratinocyte vesicle trafficking and adhesion.","method":"Whole-exome sequencing, immunostaining of patient skin, shRNA knockdown, co-localization by immunofluorescence, adhesion assay","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — human genetic evidence plus functional shRNA validation and co-localization, multiple methods","pmids":["23176819"],"is_preprint":false},{"year":2013,"finding":"In mast cells, Rab27b KO impairs degranulation, while Rab27a KO causes hyper-secretion associated with abnormal cortical F-actin. Munc13-4-deficient (jinx) BMMCs phenocopy the Rab27b KO secretory impairment, while Mlph and MyoVa deficiency phenocopies Rab27a KO. This establishes a pathway: Rab27a/Mlph/MyoVa regulates cortical actin upstream, while Rab27b/Munc13-4 mediates the final exocytosis step.","method":"Knockout mice for Rab27a, Rab27b, Mlph, MyoVa, Munc13-4; beta-hexosaminidase release assay; immunofluorescence for F-actin; actin disassembly rescue experiments","journal":"The FEBS journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis across five KO models with mechanistic pathway dissection, multiple effector KOs","pmids":["23281710"],"is_preprint":false},{"year":2008,"finding":"Slp1, a putative Rab27 effector, is co-expressed with Rab27b in pancreatic acinar cells, co-localizes on zymogen granules, and co-immunoprecipitates with Rab27b in vivo. Slp1 KO mice show increased zymogen granule accumulation, confirming Slp1 participates with Rab27b in amylase secretion machinery.","method":"Co-immunoprecipitation, co-localization by immunofluorescence, Slp1 KO mouse morphological analysis","journal":"Archives of biochemistry and biophysics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP plus KO mouse phenotype, single lab","pmids":["18477466"],"is_preprint":false},{"year":2013,"finding":"EPI64B (TBC1D10B) functions as a GTPase-activating protein (GAP) for Rab27B in pancreatic acinar cells. EPI64B overexpression abolished the GTP-bound form of Rab27B without affecting Rab3D, enhanced amylase release in a Rab27B-dependent manner, and GAP-activity mutations abolished this effect. Co-overexpression of EPI64B with Rab27B reversed the inhibitory effect of Rab27B on amylase release.","method":"Adenoviral overexpression of EPI64B and mutants, GTP-Rab27B pull-down assay, amylase release assay in KO mouse acini","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in-cell GAP activity assay with active-site mutants, KO-dependent rescue, specific substrate selectivity demonstrated","pmids":["23671284"],"is_preprint":false},{"year":2011,"finding":"Rab27b is enriched on large subapical secretory vesicles in lacrimal gland acinar cells, co-localizing with Rab3D and Myosin 5C. Rab27b KO (but not Rab27a KO) alters vesicle abundance and organization. Constitutively active Rab27b enhances and dominant-negative Rab27b suppresses stimulated secretory protein release. Actin disruption blocked vesicle-plasma membrane fusion but not homotypic fusion.","method":"Confocal fluorescence microscopy, transmission electron microscopy of KO mice, adenoviral expression of constitutively active/dominant-negative Rab27b, syncollin-GFP release assay, actin disruption experiments","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — KO mice plus gain/loss-of-function mutants with functional secretion assay, multiple methods, single lab","pmids":["21525430"],"is_preprint":false},{"year":2010,"finding":"Rab27b localizes to tubulovesicle membranes in gastric parietal cells. After stimulation, wild-type and constitutively active Rab27b (Q78L) translocate to the apical membrane, while dominant-negative Rab27b (N133I) does not and almost completely inhibits acid secretion.","method":"Mass spectrometry identification in tubulovesicle fractions, adenoviral expression of YFP-tagged WT and mutant Rab27b, fluorescence microscopy of localization, aminopyrine accumulation acid secretion assay","journal":"Gastroenterology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS identification, constitutive active/dominant negative mutant analysis with functional secretion assay, single lab","pmids":["20888820"],"is_preprint":false},{"year":2016,"finding":"Kinesin-1 (Kif5b) is recruited to Rab27b-positive secretory granules via the effector Slp3 in a PI3K-dependent manner upon FcεRI stimulation in mast cells, forming a Kif5b/Slp3/Rab27b complex that drives microtubule-dependent granule translocation to the secretion site. Kif5b KO reduces systemic anaphylaxis and secretory granule translocation without affecting cytokine secretion or microtubule reorganization.","method":"Kif5b conditional KO mice, passive systemic anaphylaxis assay, granule translocation imaging, co-immunoprecipitation (Slp3/Kinesin-1/Rab27b), PI3K inhibitor studies","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO, Co-IP of trimeric complex, mechanistic dissection with PI3K inhibition, in vivo phenotype","pmids":["27810912"],"is_preprint":false},{"year":2016,"finding":"Rab27b is involved in PLP trafficking from late endosomes/lysosomes to the cell membrane in oligodendrocytes. Rab27b co-localizes with PLP in late endosomes/lysosomes; shRNA knockdown of Rab27b reduces lysosomal exocytosis, decreases PLP surface expression, and reduces myelin-like membrane formation in neuron co-culture.","method":"Co-localization by immunofluorescence, shRNA knockdown, surface PLP quantification, lysosomal exocytosis assay, neuron-oligodendrocyte co-culture myelination assay","journal":"Neuroscience bulletin","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — shRNA KD with defined localization and functional phenotypes (lysosomal exocytosis, PLP surface expression, myelination), single lab","pmids":["27325508"],"is_preprint":false},{"year":2017,"finding":"RAB27B regulates stretch-induced exocytosis of discoidal/fusiform vesicles (DFVs) in bladder umbrella cells. RAB27B-specific shRNA significantly inhibited filling-induced exocytosis of hGH-loaded DFVs. RAB27A shRNA had no effect; RAB27B operates in a pathway parallel to (not dependent on) the RAB11A-RAB8A-MYO5B pathway.","method":"shRNA knockdown, whole-bladder exocytosis assay with hGH reporter, dominant-active/dominant-negative RAB11A and RAB8A expression, Squassh image quantification","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — specific shRNA with functional exocytosis assay, pathway epistasis tested with multiple dominant mutants","pmids":["29167152"],"is_preprint":false},{"year":2020,"finding":"Rab27b KD in neurons increases αsyn-mediated paracrine toxicity, reduces αsyn release primarily through nonexosomal pathways, leads to accumulation of insoluble αsyn, increases LC3-positive puncta, and decreases LC3 turnover after chloroquine treatment, indicating that Rab27b is required for autophagic flux and αsyn clearance.","method":"shRNA knockdown in paracrine neuronal αsyn model, size-exclusion chromatography, LC3 flux assay with chloroquine, toxicity assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — shRNA KD with multiple mechanistic readouts (autophagic flux, solubility, toxicity), single lab","pmids":["32350025"],"is_preprint":false},{"year":2023,"finding":"RAB27B controls NRAS palmitoylation and trafficking to the plasma membrane. RAB27B interacts with the palmitoyl acyltransferase ZDHHC9. RAB27B depletion abrogates mutant NRAS palmitoylation, plasma membrane localization, ERK signaling, and myelomonocytic leukemia development in vivo in mice, establishing RAB27B as a regulator of RAS posttranslational modification upstream of RAF/MEK/ERK.","method":"Proteomic studies, RAB27B depletion (shRNA/KO) in cell lines and mice, palmitoylation assay, co-immunoprecipitation with ZDHHC9, ERK signaling assays, in vivo leukemia model, primary human AML depletion","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (Co-IP with ZDHHC9, palmitoylation assays, KO mice, primary human AML), mechanistic link between RAB27B, ZDHHC9, and RAS signaling firmly established","pmids":["37317963"],"is_preprint":false},{"year":2021,"finding":"NRF2 promotes UPEC expulsion from urothelial cells by regulating RAB27B transcription. NRF2 activation reduces intracellular ROS and increases RAB27B expression; loss of NRF2 decreases RAB27B and impairs bacterial expulsion both in vitro and in a mouse UTI model.","method":"NRF2 KO cells/mice, RAB27B expression analysis, bacterial burden measurement, NRF2 inducer (dimethyl fumarate) treatment, in vitro and in vivo UTI model","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO with defined functional phenotype plus pharmacological rescue, pathway placement demonstrated","pmids":["34686330"],"is_preprint":false},{"year":2021,"finding":"In diabetic kidneys, FOXO1 phosphorylation (inactivation) caused by high glucose leads to downregulation of RAB27B and decreased exosome secretion. Constitutively active non-phosphorylatable FOXO1 restored RAB27B expression and exosome secretion in high-glucose-treated cells, establishing a FOXO1–RAB27B transcriptional axis.","method":"High-glucose treatment, FOXO1 constitutively active overexpression, RAB27B overexpression rescue, bioinformatics identification of FOXO1 binding sites, in vivo diabetic mouse model","journal":"Diabetes","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain-of-function rescue experiment with defined mechanistic pathway, in vitro and in vivo correlation, single lab","pmids":["33597203"],"is_preprint":false},{"year":2021,"finding":"CaSR activates Rab27B expression and activity via PI3K, PKA, mTOR, and the GEF MADD/Rab3GEP in breast cancer cells, leading to Rab27B-dependent secretion of cytokines including IL-6, IL-1β, IL-8, IP-10, and RANTES. This regulation occurs in cancer cells but not in non-cancerous MCF-10A cells.","method":"Pharmacological inhibition of PI3K/PKA/mTOR pathways, MADD identification as GEF, cytokine secretion measurements, Rab27B overexpression/knockdown","journal":"Biochimica et biophysica acta. Molecular cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pathway dissection with multiple inhibitors plus GEF identification, single lab","pmids":["33845096"],"is_preprint":false},{"year":2023,"finding":"Rab11A promotes Rab27B-dependent secretion of chemotactic factors downstream of CaSR. MADD (a GEF for Rab3 and Rab27a/b) is activated by Rab11A and mediates Rab27B activation. Endosomal PI3-kinases (Vps34, PI3KC2α) link Rab11A to Rab27B activation. This establishes an endosomal–secretory axis: CaSR → Rab11A → PI3K → MADD → Rab27B → cytokine secretion.","method":"Rab11A/MADD co-immunoprecipitation, PI3K inhibitors, Rab11A/Rab27B dominant-negative/constitutively active mutants, cytokine secretion assays","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP for MADD–Rab11A interaction, multiple kinase inhibitor experiments, epistasis with mutants, single lab","pmids":["37604243"],"is_preprint":false},{"year":2025,"finding":"Rab27b KO in neurons results in lysosomal proteolytic defects, reduced lysosomal enzyme maturation and localization, and defects in acidic vesicle trafficking without changes in lysosomal count or pH. KO exacerbates αsyn aggregation upon preformed fibril treatment. Rab27b overexpression enhances lysosomal activity and reduces insoluble αsyn.","method":"Rab27b KO mouse, shRNA knockdown, lysosomal activity assays, enzyme maturation/localization by immunofluorescence, αsyn fibril seeding assay, αsyn overexpression in KO mice (AAV model)","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO plus OE with multiple orthogonal readouts (lysosomal enzymes, vesicle trafficking, αsyn aggregation), two mouse models","pmids":["39965930"],"is_preprint":false},{"year":2009,"finding":"After beta-adrenergic stimulation of parotid acinar cells, Rab27B translocates from secretory granules to the subapical region within 5 min and then dissociates into the cytosol by 30 min. Dissociation is mediated by Rab-GDI, which extracts GDP-bound Rab27B from membranes, as a dramatic increase in the Rab27B-GDI complex in the cytosol was detected at 30 min post-stimulation.","method":"Immunofluorescence microscopy (temporal localization), co-immunoprecipitation of Rab27B–GDI complex, subcellular fractionation","journal":"European journal of oral sciences","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — single lab, Co-IP and localization with temporal resolution, no direct functional manipulation","pmids":["19583748"],"is_preprint":false},{"year":2012,"finding":"In lacrimal gland acinar cells, Rab27b enrichment occurs early during secretory vesicle formation at a basally-localized 'nascent vesicle site' adjacent to the trans-Golgi network. Microtubule disruption with nocodazole traps nascent Rab27b-enriched vesicles at this site. Upon reaching the subapical region, Rab27b-enriched vesicles acquire Myosin 5C, indicating sequential motor recruitment.","method":"YFP-Rab27b live-cell imaging, nocodazole treatment, p150-Glued and Myosin 5C co-localization by confocal microscopy","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — live-cell imaging with pharmacological perturbation and co-localization, single lab","pmids":["22363735"],"is_preprint":false},{"year":2016,"finding":"Genetic deletion of Rab27B in pancreatic acinar cells decreases zymogen granule size and moderately reduces digestive enzyme secretion. Expression of Rab3D, Rab27A, and downstream effectors was unaffected, indicating Rab27B is involved in zymogen granule maturation and secretion through a distinct mechanism from Rab3D.","method":"Rab27B KO mouse, electron microscopy (granule size), digestive enzyme secretion assay, Western blot","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO with morphological and functional readouts, single lab","pmids":["26845357"],"is_preprint":false},{"year":2020,"finding":"RAB27b KO in Rab27b KO mice reduces synaptic frequency facilitation at DG/MF-CA3 synapses and completely eliminates LTP at MF-CA3, without affecting SC-CA1 LTP. LTP was rescued by lentiviral re-expression of human Rab27b in the dentate gyrus, establishing Rab27b as selectively required for presynaptic LTP at MF-CA3 synapses.","method":"Rab27b KO mice, electrophysiology at SC-CA1 and DG/MF-CA3 synapses, lentiviral rescue of Rab27b in KO mice","journal":"Physiological reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO plus lentiviral rescue with defined electrophysiological phenotype, single lab","pmids":["32358861"],"is_preprint":false},{"year":2024,"finding":"TGF-β suppresses RAB27B transcription via SMAD3, reducing EV release from breast cancer cells. RAB27B depletion or TGF-β treatment recomposed EV protein cargo; these recomposed EVs inhibited CD8+ T cell-mediated cancer cell killing, establishing a TGF-β→SMAD3→RAB27B axis that controls EV composition and cancer immune evasion.","method":"TGF-β treatment, SMAD3 ChIP/transcription reporter, RAB27B siRNA, quantitative click-chemistry proteomics, CD8+ T cell killing assay","journal":"Journal of extracellular vesicles","confidence":"High","confidence_rationale":"Tier 2 / Moderate — SMAD3 ChIP for transcriptional mechanism, quantitative proteomics for cargo changes, functional T cell assay, single lab","pmids":["39723610"],"is_preprint":false},{"year":2023,"finding":"The m6A writer KIAA1429 stabilizes RAB27B mRNA through the m6A/YTHDF1 axis in CML cells. KIAA1429 knockdown reduces RAB27B mRNA stability and decreases RAB27B protein, thereby reducing drug efflux and proliferation; RAB27B knockdown mimics these effects and promotes apoptosis.","method":"KIAA1429 knockdown, RAB27B mRNA stability assay, YTHDF1 interaction, RAB27B siRNA knockdown, proliferation/apoptosis assays","journal":"Genes & diseases","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — m6A/YTHDF1 mechanism for mRNA stabilization with functional validation, single lab","pmids":["37692484"],"is_preprint":false},{"year":2020,"finding":"In bladder cancer, Rab27b mediates exocytosis of BCG bacteria from urothelial cells via its effector SYTL3. Rab27b knockdown or overexpression inversely modulated intracellular BCG quantity and cytotoxicity; androgen receptor (AR) signaling increases Rab27b expression, which drives BCG exocytosis and resistance to BCG therapy.","method":"AR and Rab27b knockdown/overexpression, intracellular BCG quantification, cytotoxicity assay, orthotopic xenograft model, microarray identification of Rab27b as AR target","journal":"Molecular cancer therapeutics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain and loss-of-function for both AR and Rab27b with defined mechanistic readout, in vivo validation, single lab","pmids":["32737155"],"is_preprint":false},{"year":2025,"finding":"RAB27B physically interacts with ZDHHC9 to regulate NRAS palmitoylation and ERK activation in NRAS-mutant endothelial cells. NRASQ61R mutation upregulates RAB27B via the ERK/C/EBPβ transcriptional axis, creating a positive feedback loop that drives enhanced proliferation and migration. MEK1/2 inhibition reduces RAB27B gene expression, while RAB27B knockdown suppresses ERK activation.","method":"RAB27B knockdown (siRNA), MEK inhibitor treatment, Western blot for ERK/palmitoylation, C/EBPβ identification as transcription factor downstream of ERK","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional KD with signaling readouts, transcription factor identification, single lab; extends prior ZDHHC9 finding","pmids":["39899936"],"is_preprint":false}],"current_model":"RAB27B is a small GTPase that functions as a molecular switch controlling the docking and fusion of secretory vesicles, multivesicular endosomes, lysosome-related organelles, and exosomes with the plasma membrane across diverse cell types; it acts through GTP-dependent recruitment of specific effector proteins (including Slac2-c/MyRIP, Slp1, Munc13-4, Slp3/kinesin-1, and melanophilin/MyoVa), is inactivated by the GAP EPI64B and activated by the GEF MADD, requires geranylgeranyl prenylation for membrane association, and additionally controls NRAS palmitoylation via interaction with the palmitoyl acyltransferase ZDHHC9 to regulate RAS/ERK signaling, while also promoting lysosomal function and autophagic flux necessary for α-synuclein clearance in neurons."},"narrative":{"mechanistic_narrative":"RAB27B is a small Rab GTPase that functions as a GTP-dependent molecular switch controlling the docking, transport, and fusion of secretory granules, secretory lysosomes, multivesicular endosomes, and specialized apical vesicles with the plasma membrane across a broad range of secretory cell types [PMID:19966785, PMID:15039459, PMID:20028487]. It associates with diverse organelle membranes—dense-core and dense/alpha granules in pituitary, platelet, and megakaryocyte lineages [PMID:17384153, PMID:11956164, PMID:12907454], zymogen granules in pancreatic acinar cells [PMID:15451418, PMID:26845357], synaptic vesicles in neurons [PMID:20926670], melanosomes [PMID:12060386], and fusiform/discoidal vesicles in urothelium [PMID:14625374, PMID:29167152]—and engages effector proteins to execute distinct steps of regulated exocytosis: Slac2-c/MyRIP and granuphilin on secretory granules [PMID:15039459, PMID:11956164], Slp1 and Slp3 on zymogen and mast-cell granules [PMID:18477466, PMID:27810912], Slac2-b/EXPH5 on multivesicular endosomes and keratinocyte vesicles [PMID:19966785, PMID:23176819], Munc13-4 at the final fusion step in mast cells and osteoblasts [PMID:20939018, PMID:23281710], and melanophilin/MyoVa for actin-based melanosome transport [PMID:15357836]. Through sequential motor coupling—kinesin-1 via Slp3 for microtubule-based transport and myosin Va/5C for actin-based delivery—RAB27B governs the handoff of vesicles from microtubule to cortical-actin tracks toward the secretion site [PMID:23281710, PMID:27810912, PMID:22363735]. Its activity cycle is set by the GEF MADD/Rab3GEP and the GAP EPI64B/TBC1D10B, with Rab-GDI extracting GDP-bound RAB27B from membranes after exocytosis, and membrane association requires geranylgeranylation [PMID:23671284, PMID:33845096, PMID:19583748, PMID:20484105]. Genetic loss of RAB27B causes a bleeding phenotype with impaired platelet dense-granule secretion in mice [PMID:17384153], and mutation of its effector EXPH5 causes inherited skin fragility in humans [PMID:23176819]. Beyond secretion, RAB27B promotes lysosomal enzyme maturation and autophagic flux required for α-synuclein clearance in neurons [PMID:32350025, PMID:39965930], drives invasive growth and exosome/extracellular-vesicle cargo secretion (HSP90α, MMP-2 activation) in cancer [PMID:20484105, PMID:23390068, PMID:39723610], and controls NRAS palmitoylation and plasma-membrane trafficking through physical interaction with the palmitoyl acyltransferase ZDHHC9 to sustain RAS/ERK signaling and leukemogenesis [PMID:37317963, PMID:39899936].","teleology":[{"year":2002,"claim":"Established RAB27B as a regulator of regulated dense-core granule exocytosis, showing it acts on the secretory pathway rather than being a passive granule marker.","evidence":"Co-IP with granuphilin and dominant-negative N133I mutant inhibiting ACTH secretion in AtT20 pituitary cells; dominant-negative effects on melanosome positioning in melanocytes","pmids":["11956164","12060386"],"confidence":"High","gaps":["Endogenous activity cycle (GEF/GAP) not yet defined","Melanocyte role rests on dominant-negative overexpression rather than genetic loss"]},{"year":2004,"claim":"Identified the RAB27B–effector module on secretory granules, showing the GTPase requires effector binding to drive exocytosis.","evidence":"Reciprocal Co-IP of Rab27B with Slac2-c/MyRIP and functional disruption of amylase release in parotid acinar cells; constitutive-active/dominant-negative mutants modulating zymogen granule exocytosis in pancreatic acini","pmids":["15039459","15451418"],"confidence":"High","gaps":["Whether effectors mediate docking versus fusion not resolved","Structural basis of effector recognition unknown"]},{"year":2007,"claim":"Genetic knockout defined non-redundant physiological roles of RAB27B in secretion and revealed partial overlap with RAB27A.","evidence":"Rab27b KO mice showing hemorrhagic disease and reduced platelet dense-granule number/secretion; mast cell degranulation and anaphylaxis defects; double-KO granule mislocalization in pituitary; crystal structure of Rab27b-GDP","pmids":["17384153","17587407","17761531","17582168"],"confidence":"High","gaps":["Molecular basis of RAB27A vs RAB27B effector specificity unresolved despite structure","Granule-number defect mechanism (packaging) not mechanistically dissected"]},{"year":2009,"claim":"Placed RAB27B in the exosome/MVE secretion pathway and in granule docking, distinguishing it from RAB27A at the molecular step level.","evidence":"RNAi screen showing RAB27B controls MVE docking with EXPH5/Slac2b phenocopy; TIRF microscopy of azurophilic granule docking in neutrophil KO; temporal GDI-extraction of Rab27B in parotid cells","pmids":["19966785","20028487","19583748"],"confidence":"High","gaps":["Mechanism distinguishing RAB27A and RAB27B docking steps not fully defined","GDI-extraction shown by Co-IP/localization without direct functional perturbation"]},{"year":2011,"claim":"Resolved the order of RAB27B action as the final vesicle-fusion step and mapped sequential motor recruitment for vesicle delivery.","evidence":"RNAi of Rab27a/b and Slp4-a/Slp5/Munc13-4 in osteoblastic RANKL release blocking fusion but not docking; KO and gain/loss-of-function in lacrimal acinar cells; live imaging of sequential dynein/Myosin5C recruitment to nascent Rab27b vesicles","pmids":["20939018","21525430","22363735"],"confidence":"Medium","gaps":["Direct demonstration of fusion-machinery engagement (SNAREs) absent","Effector knockdowns are single-lab without reciprocal validation"]},{"year":2013,"claim":"Defined the RAB27B activity cycle and a genetic epistasis pathway separating RAB27B/Munc13-4 fusion control from RAB27A/Mlph/MyoVa cortical-actin control.","evidence":"EPI64B/TBC1D10B GAP activity assay with active-site mutants and KO-rescue in pancreatic acini; five-KO genetic epistasis in mast cells; human EXPH5 mutation causing skin fragility","pmids":["23671284","23281710","23176819"],"confidence":"High","gaps":["Activating GEF still unidentified at this stage","How GAP/GEF are spatially targeted to specific organelles unknown"]},{"year":2016,"claim":"Connected RAB27B to motor-driven granule transport and to lysosomal/late-endosomal secretory trafficking in distinct cell types.","evidence":"Co-IP of Kif5b/Slp3/Rab27b trimeric complex with PI3K-dependent recruitment and Kif5b KO anaphylaxis defect in mast cells; shRNA showing Rab27b drives PLP lysosomal exocytosis and myelination in oligodendrocytes","pmids":["27810912","27325508"],"confidence":"High","gaps":["Coupling between kinesin-driven transport and myosin-driven cortical delivery not unified","Oligodendrocyte role based on shRNA in a single lab"]},{"year":2020,"claim":"Extended RAB27B function from secretion into lysosomal degradative capacity and autophagic flux required for neuronal protein clearance.","evidence":"shRNA and KO/overexpression in neurons measuring αsyn release, solubility, LC3 turnover with chloroquine, lysosomal enzyme maturation, and αsyn fibril seeding; KO electrophysiology defining selective MF-CA3 presynaptic LTP requirement with lentiviral rescue","pmids":["32350025","39965930","32358861"],"confidence":"High","gaps":["Effector mediating lysosomal/autophagic role in neurons not identified","Direct link between secretory and degradative functions of RAB27B unresolved"]},{"year":2021,"claim":"Mapped upstream transcriptional and signaling control of RAB27B in cancer secretion and in epithelial defense and disease contexts.","evidence":"CaSR→PI3K/PKA/mTOR→MADD GEF activation driving Rab27B-dependent cytokine secretion; NRF2 and FOXO1 transcriptional regulation of RAB27B in UPEC expulsion and diabetic-kidney exosome secretion","pmids":["33845096","34686330","33597203"],"confidence":"Medium","gaps":["MADD GEF activity on RAB27B inferred from pathway inhibition rather than direct nucleotide-exchange assay","Transcriptional axes are single-lab and context-specific"]},{"year":2023,"claim":"Revealed a non-canonical RAB27B function regulating RAS posttranslational modification through ZDHHC9, expanding its role beyond vesicle trafficking into oncogenic signaling.","evidence":"Proteomics, Co-IP with ZDHHC9, palmitoylation assays, KO mice and primary human AML depletion showing RAB27B controls NRAS palmitoylation, membrane localization, ERK signaling, and leukemogenesis; MADD/Rab11A endosomal-secretory axis defined; m6A/YTHDF1 mRNA stabilization in CML","pmids":["37317963","37604243","37692484"],"confidence":"High","gaps":["Whether ZDHHC9 regulation requires RAB27B GTPase activity not fully defined","Mechanism by which RAB27B promotes palmitoyl-transfer (scaffolding vs trafficking) unresolved"]},{"year":2024,"claim":"Established RAB27B as a node controlling extracellular-vesicle cargo composition and tumor immune evasion under TGF-β control, and as a self-reinforcing component of NRAS/ERK signaling.","evidence":"TGF-β→SMAD3 ChIP repression of RAB27B with click-chemistry EV proteomics and CD8+ T cell killing assay; NRASQ61R→ERK/C/EBPβ feedback upregulating RAB27B in endothelial cells with MEK inhibition reducing RAB27B","pmids":["39723610","39899936"],"confidence":"High","gaps":["How RAB27B selectively determines EV cargo identity unknown","Generality of the ERK–RAB27B feedback loop across cell types untested"]},{"year":null,"claim":"How a single GTPase coordinates its canonical vesicle-fusion machinery with its degradative (lysosomal/autophagic) and non-vesicular (ZDHHC9/NRAS palmitoylation) functions, and what determines effector and organelle selectivity in each context, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified structural/biochemical model linking GTP-state to the divergent effector repertoire","Determinants of organelle-specific targeting in different cell types undefined","Mechanistic coupling between secretory and degradative roles unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003924","term_label":"GTPase activity","supporting_discovery_ids":[13,15,12]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,2,5,11,27]}],"localization":[{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[2,5,8,7,22,21]},{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[11,24,32]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[0,24,31]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,9,22,27]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[33]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[0,2,9,11]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[4,7,24,27]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[26,32]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[27,40]},{"term_id":"R-HSA-109582","term_label":"Hemostasis","supporting_discovery_ids":[1,6]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[3,18,9]}],"complexes":["Rab27B–Slac2-c/MyRIP complex","Kif5b–Slp3–Rab27B complex","Rab27B–melanophilin–Myosin Va complex"],"partners":["EXPH5","MYRIP","MADD","TBC1D10B","UNC13D","ZDHHC9","SYTL3","MLPH"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O00194","full_name":"Ras-related protein Rab-27B","aliases":["C25KG"],"length_aa":218,"mass_kda":24.6,"function":"The small GTPases Rab are key regulators of intracellular membrane trafficking, from the formation of transport vesicles to their fusion with membranes. 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:21775604, PubMed:30771381). RAB27B regulates homeostasis of late endocytic pathway, including endosomal positioning, maturation and secretion (PubMed:30771381). Plays a role in NTRK2/TRKB axonal anterograde transport by facilitating the association of NTRK2/TRKB with KLC1 (PubMed:21775604). May be involved in targeting uroplakins to urothelial apical membranes (By similarity)","subcellular_location":"Membrane; Late endosome","url":"https://www.uniprot.org/uniprotkb/O00194/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RAB27B","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/RAB27B","total_profiled":1310},"omim":[{"mim_id":"615028","title":"EPIDERMOLYSIS BULLOSA SIMPLEX 4, LOCALIZED OR GENERALIZED INTERMEDIATE, AUTOSOMAL RECESSIVE; EBS4","url":"https://www.omim.org/entry/615028"},{"mim_id":"612878","title":"EXOPHILIN 5; EXPH5","url":"https://www.omim.org/entry/612878"},{"mim_id":"611790","title":"MYOSIN VIIA- AND RAB-INTERACTING PROTEIN; MYRIP","url":"https://www.omim.org/entry/611790"},{"mim_id":"608897","title":"UNC13 HOMOLOG D; UNC13D","url":"https://www.omim.org/entry/608897"},{"mim_id":"606526","title":"MELANOPHILIN; MLPH","url":"https://www.omim.org/entry/606526"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Golgi apparatus","reliability":"Approved"},{"location":"Plasma membrane","reliability":"Approved"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"stomach 1","ntpm":41.7}],"url":"https://www.proteinatlas.org/search/RAB27B"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"O00194","domains":[{"cath_id":"3.40.50.300","chopping":"9-190","consensus_level":"high","plddt":93.3061,"start":9,"end":190}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O00194","model_url":"https://alphafold.ebi.ac.uk/files/AF-O00194-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O00194-F1-predicted_aligned_error_v6.png","plddt_mean":84.56},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RAB27B","jax_strain_url":"https://www.jax.org/strain/search?query=RAB27B"},"sequence":{"accession":"O00194","fasta_url":"https://rest.uniprot.org/uniprotkb/O00194.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O00194/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O00194"}},"corpus_meta":[{"pmid":"19966785","id":"PMC_19966785","title":"Rab27a and Rab27b control different steps of the 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Cells.","date":"2018","source":"Gastroenterology","url":"https://pubmed.ncbi.nlm.nih.gov/30342032","citation_count":122,"is_preprint":false},{"pmid":"30980673","id":"PMC_30980673","title":"RAB27B-activated secretion of stem-like tumor exosomes delivers the biomarker microRNA-146a-5p, which promotes tumorigenesis and associates with an immunosuppressive tumor microenvironment in colorectal cancer.","date":"2019","source":"International journal of cancer","url":"https://pubmed.ncbi.nlm.nih.gov/30980673","citation_count":109,"is_preprint":false},{"pmid":"9066979","id":"PMC_9066979","title":"Molecular cloning and characterization of rab27a and rab27b, novel human rab proteins shared by melanocytes and platelets.","date":"1997","source":"Biochemical and molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/9066979","citation_count":105,"is_preprint":false},{"pmid":"29479064","id":"PMC_29479064","title":"miR-34c-5p promotes eradication of acute myeloid leukemia stem cells by inducing 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Thus RAB27B controls a distinct step in the exosomal pathway compared to RAB27A.\",\n      \"method\": \"RNAi screen, siRNA knockdown, fluorescence microscopy, exosome secretion assay\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (RNAi screen, effector knockdown phenocopy, MVE imaging), replicated across multiple groups\",\n      \"pmids\": [\"19966785\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Rab27b knockout mice exhibit hemorrhagic disease, impaired platelet aggregation, and reduced dense granule secretion. A 50% reduction in dense granule number per platelet was observed, suggesting a role in dense granule packaging during megakaryocyte maturation. Rab27a partially compensated for the secretory defect but not the reduced granule number.\",\n      \"method\": \"Knockout mouse generation, in vitro platelet aggregation assay, dense granule secretion assay, electron microscopy\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with multiple orthogonal phenotypic readouts (aggregation, secretion, granule counting), double KO comparison\",\n      \"pmids\": [\"17384153\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Rab27B localizes to amylase-containing secretory granules in rat parotid acinar cells and forms a complex with the effector Slac2-c/MyRIP on granules. Disruption of the Rab27B–Slac2-c complex (via recombinant Slp homology domain or blocking antibodies) inhibited isoproterenol-stimulated amylase release, establishing this complex as required for secretory granule exocytosis.\",\n      \"method\": \"Subcellular fractionation, immunoprecipitation, immunohistochemistry, introduction of dominant-negative recombinant protein/antibodies in permeabilized cells, amylase release assay\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, functional disruption with two independent tools (recombinant SHD domain and blocking antibodies), specific phenotypic readout\",\n      \"pmids\": [\"15039459\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Rab27b and Rab27a are both expressed on mast cell secretory granules. Rab27b KO (but not Rab27a KO) impairs mast cell degranulation as measured by beta-hexosaminidase release in vitro and passive cutaneous anaphylaxis in vivo. Live-cell imaging showed ~10-fold increase in fast granule movement (>1.5 μm/s, nocodazole-sensitive) in double KO cells, suggesting Rab27 regulates the transition from microtubule to actin-based motility.\",\n      \"method\": \"Knockout mice, beta-hexosaminidase release assay, passive cutaneous anaphylaxis, live-cell time-lapse imaging, nocodazole treatment\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO, multiple orthogonal methods (in vitro secretion, in vivo anaphylaxis, live imaging), mechanistic follow-up with nocodazole\",\n      \"pmids\": [\"17587407\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Rab27b is widely expressed in secretory cells and neurons. In pituitary cells co-expressing Rab27a, Rab27a/b double KO markedly impairs polarized distribution of secretory granules near the plasma membrane, indicating the Rab27 subfamily delivers granules to the exocytic site.\",\n      \"method\": \"Rab27b KO mouse with LacZ reporter, double KO mouse (crossed with ashen), histology, immunofluorescence of secretory granule distribution\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic double KO with defined granule-localization phenotype, complementary reporter-driven expression analysis\",\n      \"pmids\": [\"17761531\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Rab27b associates with secretory granules and interacts with the effector granuphilin in pituitary AtT20 cells. Overexpression of the inactive mutant Rab27b N133I significantly inhibits basal and forskolin-induced ACTH secretion, establishing Rab27b as a regulator of pituitary dense core granule exocytosis.\",\n      \"method\": \"Subcellular fractionation, co-immunoprecipitation, dominant-negative mutant overexpression, ACTH secretion assay\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus dominant-negative functional assay with defined hormonal secretion readout\",\n      \"pmids\": [\"11956164\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Rab27b associates with alpha- and dense granules in megakaryocytes. Rab27b expression is induced during terminal megakaryocyte differentiation in an NF-E2-dependent manner; chromatin immunoprecipitation demonstrated NF-E2 recruitment to the Rab27B promoter. Inhibition of endogenous Rab27 function caused quantitative and qualitative defects in proplatelet formation.\",\n      \"method\": \"Chromatin immunoprecipitation, dominant-negative Rab27 inhibition, immunofluorescence localization, proplatelet formation assay\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — ChIP for transcriptional regulation, functional KO/inhibition with defined proplatelet phenotype, consistent with KO mouse studies\",\n      \"pmids\": [\"12907454\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Rab27b associates with fusiform vesicles (but not the apical plasma membrane) in differentiated urothelial umbrella cells at extraordinarily high levels (0.1% of total protein); its expression is greatly reduced in cultured urothelial cells that fail to form fusiform vesicles and produce little uroplakin. This positions Rab27b as a regulator of fusiform vesicle delivery to the apical membrane for uroplakin targeting.\",\n      \"method\": \"Immuno-electron microscopy, Western blot, subcellular fractionation, comparison of differentiated vs cultured urothelial cells\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — immuno-EM localization plus correlative expression analysis; no direct functional loss-of-function in the same study\",\n      \"pmids\": [\"14625374\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Rab27b localizes to zymogen granule (ZG) membranes in pancreatic acinar cells. Constitutively active Rab27b Q78L enhanced CCK-induced amylase release by ~92%, while dominant-negative Rab27b N133I inhibited it by ~53% across all CCK doses, establishing Rab27b as a positive regulator of ZG exocytosis.\",\n      \"method\": \"Proteomics/MALDI-MS identification, Western blot, immunocytochemistry, adenovirus-mediated overexpression of wild-type and mutant Rab27b, amylase release assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — constitutively active and dominant-negative mutant analysis in primary acini with quantitative secretion readout\",\n      \"pmids\": [\"15451418\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Both Rab27a and Rab27b deficiencies impair azurophilic granule exocytosis in neutrophils by independent mechanisms. TIRF microscopy showed decreased numbers of azurophilic granules near the plasma membrane in single and double KO neutrophils. Rab27b KO also impaired NADPH oxidase activation at the plasma membrane; secretory vesicle exocytosis was unaffected, indicating Rab27 selectively controls granule exocytosis.\",\n      \"method\": \"Knockout mice, azurophilic granule exocytosis assay, TIRF microscopy, NADPH oxidase activity measurement\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO, TIRF microscopy for docking, functional NADPH oxidase assay, single vs double KO comparison\",\n      \"pmids\": [\"20028487\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Rab27b localizes to synaptic vesicle (SV) membranes in neurons, colocalizing with Rab3a and synaptotagmin at presynaptic terminals. Unlike Rab3a, Rab27b persists on SV membranes after Ca2+-triggered exocytosis and is resistant to GDI-mediated retrieval. Modulation of the Rab27b GTP/GDP switch impairs SV recycling.\",\n      \"method\": \"Quantitative mass spectrometry (iTRAQ), immunoblotting, fluorescence microscopy, GDI extraction assay, GTP/GDP switch manipulation with functional SV recycling assay\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — quantitative MS, multiple biochemical assays, functional manipulation, single lab\",\n      \"pmids\": [\"20926670\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Rab27a and Rab27b are both involved in stimulation-dependent RANKL release from secretory lysosomes in osteoblastic cells. Their effectors Slp4-a, Slp5, and Munc13-4 coordinate this activity. Suppression of Rab27a/b or these effectors blocked vesicle fusion to the plasma membrane but did not prevent RANKL accumulation in lysosomal vesicles near stimulated sites, indicating Rab27b acts at the final fusion step.\",\n      \"method\": \"RNAi knockdown, immunofluorescence, RANKL release assay, in vivo jinx (Munc13-4 KO) mouse bone phenotype\",\n      \"journal\": \"Journal of bone and mineral research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA knockdown with defined mechanistic step (docking vs. fusion) plus in vivo validation, single lab\",\n      \"pmids\": [\"20939018\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Crystal structure of mouse Rab27b-GDP determined in three lattice forms revealed an unexpected domain-swapped dimer with open switch and interswitch regions. Small-angle X-ray scattering showed an extended monomer in solution, suggesting the flexible switch regions may influence effector binding specificity.\",\n      \"method\": \"X-ray crystallography, small-angle X-ray scattering (SAXS)\",\n      \"journal\": \"Acta crystallographica. Section D, Biological crystallography\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure in three lattices with SAXS solution validation, single lab\",\n      \"pmids\": [\"17582168\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Rab27b colocalizes with the melanosome marker TRP-1 and myosin Va at the cell periphery in melan-a melanocytes. Dominant-negative Rab27b mutants caused redistribution of melanosomes from the cell periphery to the perinuclear region and diminished dendrite number and length, suggesting Rab27b regulates outward melanosome movement and dendritic extension.\",\n      \"method\": \"GFP-tagged wild-type and dominant-negative mutant overexpression, co-localization with TRP-1 and myosin Va by fluorescence microscopy, GTPase activity assay\",\n      \"journal\": \"The Journal of investigative dermatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — dominant-negative approach with defined melanosome and dendrite phenotypes, single lab\",\n      \"pmids\": [\"12060386\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"In Griscelli syndrome type II melanocytes lacking Rab27a, Rab27b is up-regulated and forms a tripartite complex with melanophilin and exon F–containing Myosin Va isoforms on the melanosome membrane, partially compensating for Rab27a loss. This complex links Rab27b to actin-based melanosome transport.\",\n      \"method\": \"Quantitative RT-PCR, Western blot, immunofluorescence, yeast two-hybrid screening\",\n      \"journal\": \"Pigment cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — yeast two-hybrid for interaction plus expression and localization in patient cells, single lab\",\n      \"pmids\": [\"15357836\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Rab27B promotes invasive growth and metastasis in ER-positive breast cancer cells. Mass spectrometry identified HSP90α in Rab27B-secretory vesicles; HSP90α secretion was Rab27B-dependent and required for MMP-2 activation. All functional responses required GTP-binding and geranylgeranylation of Rab27B.\",\n      \"method\": \"GFP-Rab27B overexpression, point mutants (GTP/GDP and geranylgeranylation defective), siRNA knockdown, mass spectrometry of purified vesicles, MMP-2 activation assay, xenograft mouse model, Matrigel invasion assay\",\n      \"journal\": \"Journal of the National Cancer Institute\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (MS identification, functional mutants, KD, in vivo xenograft), mechanistic endpoint (MMP-2 activation via HSP90α)\",\n      \"pmids\": [\"20484105\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"V-ATPase subunits (including V0a1 and V0d1) are identified by mass spectrometry in GFP-Rab27B secretory vesicles from MCF-7 cells. V-ATPase activity controls peripheral localization and size of Rab27B vesicles, and V-ATPase inhibition or subunit knockdown reduces Rab27B-dependent HSP90α secretion, MMP-2 activation, and cell invasion.\",\n      \"method\": \"Mass spectrometry on purified GFP-Rab27B vesicles, Western blot, pharmacological inhibition (bafilomycin A1), siRNA knockdown of V0a1/V0d1, invasion assay, CAM assay\",\n      \"journal\": \"International journal of cancer\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS identification plus functional validation with two independent tools (pharmacological and siRNA) and multiple readouts\",\n      \"pmids\": [\"23390068\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Mutation of the Rab27B effector Slac2-b (EXPH5) in humans causes inherited skin fragility with increased perinuclear vesicles in keratinocytes. Slac2-b co-localizes with Rab27B and β4 integrin at early adhesion initiation sites in spreading keratinocytes, and its loss disrupts keratin cytoskeleton and cell adhesion, placing the Rab27B–Slac2-b complex in keratinocyte vesicle trafficking and adhesion.\",\n      \"method\": \"Whole-exome sequencing, immunostaining of patient skin, shRNA knockdown, co-localization by immunofluorescence, adhesion assay\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — human genetic evidence plus functional shRNA validation and co-localization, multiple methods\",\n      \"pmids\": [\"23176819\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"In mast cells, Rab27b KO impairs degranulation, while Rab27a KO causes hyper-secretion associated with abnormal cortical F-actin. Munc13-4-deficient (jinx) BMMCs phenocopy the Rab27b KO secretory impairment, while Mlph and MyoVa deficiency phenocopies Rab27a KO. This establishes a pathway: Rab27a/Mlph/MyoVa regulates cortical actin upstream, while Rab27b/Munc13-4 mediates the final exocytosis step.\",\n      \"method\": \"Knockout mice for Rab27a, Rab27b, Mlph, MyoVa, Munc13-4; beta-hexosaminidase release assay; immunofluorescence for F-actin; actin disassembly rescue experiments\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis across five KO models with mechanistic pathway dissection, multiple effector KOs\",\n      \"pmids\": [\"23281710\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Slp1, a putative Rab27 effector, is co-expressed with Rab27b in pancreatic acinar cells, co-localizes on zymogen granules, and co-immunoprecipitates with Rab27b in vivo. Slp1 KO mice show increased zymogen granule accumulation, confirming Slp1 participates with Rab27b in amylase secretion machinery.\",\n      \"method\": \"Co-immunoprecipitation, co-localization by immunofluorescence, Slp1 KO mouse morphological analysis\",\n      \"journal\": \"Archives of biochemistry and biophysics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP plus KO mouse phenotype, single lab\",\n      \"pmids\": [\"18477466\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"EPI64B (TBC1D10B) functions as a GTPase-activating protein (GAP) for Rab27B in pancreatic acinar cells. EPI64B overexpression abolished the GTP-bound form of Rab27B without affecting Rab3D, enhanced amylase release in a Rab27B-dependent manner, and GAP-activity mutations abolished this effect. Co-overexpression of EPI64B with Rab27B reversed the inhibitory effect of Rab27B on amylase release.\",\n      \"method\": \"Adenoviral overexpression of EPI64B and mutants, GTP-Rab27B pull-down assay, amylase release assay in KO mouse acini\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in-cell GAP activity assay with active-site mutants, KO-dependent rescue, specific substrate selectivity demonstrated\",\n      \"pmids\": [\"23671284\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Rab27b is enriched on large subapical secretory vesicles in lacrimal gland acinar cells, co-localizing with Rab3D and Myosin 5C. Rab27b KO (but not Rab27a KO) alters vesicle abundance and organization. Constitutively active Rab27b enhances and dominant-negative Rab27b suppresses stimulated secretory protein release. Actin disruption blocked vesicle-plasma membrane fusion but not homotypic fusion.\",\n      \"method\": \"Confocal fluorescence microscopy, transmission electron microscopy of KO mice, adenoviral expression of constitutively active/dominant-negative Rab27b, syncollin-GFP release assay, actin disruption experiments\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO mice plus gain/loss-of-function mutants with functional secretion assay, multiple methods, single lab\",\n      \"pmids\": [\"21525430\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Rab27b localizes to tubulovesicle membranes in gastric parietal cells. After stimulation, wild-type and constitutively active Rab27b (Q78L) translocate to the apical membrane, while dominant-negative Rab27b (N133I) does not and almost completely inhibits acid secretion.\",\n      \"method\": \"Mass spectrometry identification in tubulovesicle fractions, adenoviral expression of YFP-tagged WT and mutant Rab27b, fluorescence microscopy of localization, aminopyrine accumulation acid secretion assay\",\n      \"journal\": \"Gastroenterology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS identification, constitutive active/dominant negative mutant analysis with functional secretion assay, single lab\",\n      \"pmids\": [\"20888820\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Kinesin-1 (Kif5b) is recruited to Rab27b-positive secretory granules via the effector Slp3 in a PI3K-dependent manner upon FcεRI stimulation in mast cells, forming a Kif5b/Slp3/Rab27b complex that drives microtubule-dependent granule translocation to the secretion site. Kif5b KO reduces systemic anaphylaxis and secretory granule translocation without affecting cytokine secretion or microtubule reorganization.\",\n      \"method\": \"Kif5b conditional KO mice, passive systemic anaphylaxis assay, granule translocation imaging, co-immunoprecipitation (Slp3/Kinesin-1/Rab27b), PI3K inhibitor studies\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO, Co-IP of trimeric complex, mechanistic dissection with PI3K inhibition, in vivo phenotype\",\n      \"pmids\": [\"27810912\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Rab27b is involved in PLP trafficking from late endosomes/lysosomes to the cell membrane in oligodendrocytes. Rab27b co-localizes with PLP in late endosomes/lysosomes; shRNA knockdown of Rab27b reduces lysosomal exocytosis, decreases PLP surface expression, and reduces myelin-like membrane formation in neuron co-culture.\",\n      \"method\": \"Co-localization by immunofluorescence, shRNA knockdown, surface PLP quantification, lysosomal exocytosis assay, neuron-oligodendrocyte co-culture myelination assay\",\n      \"journal\": \"Neuroscience bulletin\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — shRNA KD with defined localization and functional phenotypes (lysosomal exocytosis, PLP surface expression, myelination), single lab\",\n      \"pmids\": [\"27325508\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"RAB27B regulates stretch-induced exocytosis of discoidal/fusiform vesicles (DFVs) in bladder umbrella cells. RAB27B-specific shRNA significantly inhibited filling-induced exocytosis of hGH-loaded DFVs. RAB27A shRNA had no effect; RAB27B operates in a pathway parallel to (not dependent on) the RAB11A-RAB8A-MYO5B pathway.\",\n      \"method\": \"shRNA knockdown, whole-bladder exocytosis assay with hGH reporter, dominant-active/dominant-negative RAB11A and RAB8A expression, Squassh image quantification\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — specific shRNA with functional exocytosis assay, pathway epistasis tested with multiple dominant mutants\",\n      \"pmids\": [\"29167152\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Rab27b KD in neurons increases αsyn-mediated paracrine toxicity, reduces αsyn release primarily through nonexosomal pathways, leads to accumulation of insoluble αsyn, increases LC3-positive puncta, and decreases LC3 turnover after chloroquine treatment, indicating that Rab27b is required for autophagic flux and αsyn clearance.\",\n      \"method\": \"shRNA knockdown in paracrine neuronal αsyn model, size-exclusion chromatography, LC3 flux assay with chloroquine, toxicity assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — shRNA KD with multiple mechanistic readouts (autophagic flux, solubility, toxicity), single lab\",\n      \"pmids\": [\"32350025\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"RAB27B controls NRAS palmitoylation and trafficking to the plasma membrane. RAB27B interacts with the palmitoyl acyltransferase ZDHHC9. RAB27B depletion abrogates mutant NRAS palmitoylation, plasma membrane localization, ERK signaling, and myelomonocytic leukemia development in vivo in mice, establishing RAB27B as a regulator of RAS posttranslational modification upstream of RAF/MEK/ERK.\",\n      \"method\": \"Proteomic studies, RAB27B depletion (shRNA/KO) in cell lines and mice, palmitoylation assay, co-immunoprecipitation with ZDHHC9, ERK signaling assays, in vivo leukemia model, primary human AML depletion\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (Co-IP with ZDHHC9, palmitoylation assays, KO mice, primary human AML), mechanistic link between RAB27B, ZDHHC9, and RAS signaling firmly established\",\n      \"pmids\": [\"37317963\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"NRF2 promotes UPEC expulsion from urothelial cells by regulating RAB27B transcription. NRF2 activation reduces intracellular ROS and increases RAB27B expression; loss of NRF2 decreases RAB27B and impairs bacterial expulsion both in vitro and in a mouse UTI model.\",\n      \"method\": \"NRF2 KO cells/mice, RAB27B expression analysis, bacterial burden measurement, NRF2 inducer (dimethyl fumarate) treatment, in vitro and in vivo UTI model\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO with defined functional phenotype plus pharmacological rescue, pathway placement demonstrated\",\n      \"pmids\": [\"34686330\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"In diabetic kidneys, FOXO1 phosphorylation (inactivation) caused by high glucose leads to downregulation of RAB27B and decreased exosome secretion. Constitutively active non-phosphorylatable FOXO1 restored RAB27B expression and exosome secretion in high-glucose-treated cells, establishing a FOXO1–RAB27B transcriptional axis.\",\n      \"method\": \"High-glucose treatment, FOXO1 constitutively active overexpression, RAB27B overexpression rescue, bioinformatics identification of FOXO1 binding sites, in vivo diabetic mouse model\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain-of-function rescue experiment with defined mechanistic pathway, in vitro and in vivo correlation, single lab\",\n      \"pmids\": [\"33597203\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CaSR activates Rab27B expression and activity via PI3K, PKA, mTOR, and the GEF MADD/Rab3GEP in breast cancer cells, leading to Rab27B-dependent secretion of cytokines including IL-6, IL-1β, IL-8, IP-10, and RANTES. This regulation occurs in cancer cells but not in non-cancerous MCF-10A cells.\",\n      \"method\": \"Pharmacological inhibition of PI3K/PKA/mTOR pathways, MADD identification as GEF, cytokine secretion measurements, Rab27B overexpression/knockdown\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pathway dissection with multiple inhibitors plus GEF identification, single lab\",\n      \"pmids\": [\"33845096\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Rab11A promotes Rab27B-dependent secretion of chemotactic factors downstream of CaSR. MADD (a GEF for Rab3 and Rab27a/b) is activated by Rab11A and mediates Rab27B activation. Endosomal PI3-kinases (Vps34, PI3KC2α) link Rab11A to Rab27B activation. This establishes an endosomal–secretory axis: CaSR → Rab11A → PI3K → MADD → Rab27B → cytokine secretion.\",\n      \"method\": \"Rab11A/MADD co-immunoprecipitation, PI3K inhibitors, Rab11A/Rab27B dominant-negative/constitutively active mutants, cytokine secretion assays\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP for MADD–Rab11A interaction, multiple kinase inhibitor experiments, epistasis with mutants, single lab\",\n      \"pmids\": [\"37604243\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Rab27b KO in neurons results in lysosomal proteolytic defects, reduced lysosomal enzyme maturation and localization, and defects in acidic vesicle trafficking without changes in lysosomal count or pH. KO exacerbates αsyn aggregation upon preformed fibril treatment. Rab27b overexpression enhances lysosomal activity and reduces insoluble αsyn.\",\n      \"method\": \"Rab27b KO mouse, shRNA knockdown, lysosomal activity assays, enzyme maturation/localization by immunofluorescence, αsyn fibril seeding assay, αsyn overexpression in KO mice (AAV model)\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO plus OE with multiple orthogonal readouts (lysosomal enzymes, vesicle trafficking, αsyn aggregation), two mouse models\",\n      \"pmids\": [\"39965930\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"After beta-adrenergic stimulation of parotid acinar cells, Rab27B translocates from secretory granules to the subapical region within 5 min and then dissociates into the cytosol by 30 min. Dissociation is mediated by Rab-GDI, which extracts GDP-bound Rab27B from membranes, as a dramatic increase in the Rab27B-GDI complex in the cytosol was detected at 30 min post-stimulation.\",\n      \"method\": \"Immunofluorescence microscopy (temporal localization), co-immunoprecipitation of Rab27B–GDI complex, subcellular fractionation\",\n      \"journal\": \"European journal of oral sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — single lab, Co-IP and localization with temporal resolution, no direct functional manipulation\",\n      \"pmids\": [\"19583748\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"In lacrimal gland acinar cells, Rab27b enrichment occurs early during secretory vesicle formation at a basally-localized 'nascent vesicle site' adjacent to the trans-Golgi network. Microtubule disruption with nocodazole traps nascent Rab27b-enriched vesicles at this site. Upon reaching the subapical region, Rab27b-enriched vesicles acquire Myosin 5C, indicating sequential motor recruitment.\",\n      \"method\": \"YFP-Rab27b live-cell imaging, nocodazole treatment, p150-Glued and Myosin 5C co-localization by confocal microscopy\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — live-cell imaging with pharmacological perturbation and co-localization, single lab\",\n      \"pmids\": [\"22363735\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Genetic deletion of Rab27B in pancreatic acinar cells decreases zymogen granule size and moderately reduces digestive enzyme secretion. Expression of Rab3D, Rab27A, and downstream effectors was unaffected, indicating Rab27B is involved in zymogen granule maturation and secretion through a distinct mechanism from Rab3D.\",\n      \"method\": \"Rab27B KO mouse, electron microscopy (granule size), digestive enzyme secretion assay, Western blot\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO with morphological and functional readouts, single lab\",\n      \"pmids\": [\"26845357\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"RAB27b KO in Rab27b KO mice reduces synaptic frequency facilitation at DG/MF-CA3 synapses and completely eliminates LTP at MF-CA3, without affecting SC-CA1 LTP. LTP was rescued by lentiviral re-expression of human Rab27b in the dentate gyrus, establishing Rab27b as selectively required for presynaptic LTP at MF-CA3 synapses.\",\n      \"method\": \"Rab27b KO mice, electrophysiology at SC-CA1 and DG/MF-CA3 synapses, lentiviral rescue of Rab27b in KO mice\",\n      \"journal\": \"Physiological reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO plus lentiviral rescue with defined electrophysiological phenotype, single lab\",\n      \"pmids\": [\"32358861\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"TGF-β suppresses RAB27B transcription via SMAD3, reducing EV release from breast cancer cells. RAB27B depletion or TGF-β treatment recomposed EV protein cargo; these recomposed EVs inhibited CD8+ T cell-mediated cancer cell killing, establishing a TGF-β→SMAD3→RAB27B axis that controls EV composition and cancer immune evasion.\",\n      \"method\": \"TGF-β treatment, SMAD3 ChIP/transcription reporter, RAB27B siRNA, quantitative click-chemistry proteomics, CD8+ T cell killing assay\",\n      \"journal\": \"Journal of extracellular vesicles\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — SMAD3 ChIP for transcriptional mechanism, quantitative proteomics for cargo changes, functional T cell assay, single lab\",\n      \"pmids\": [\"39723610\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The m6A writer KIAA1429 stabilizes RAB27B mRNA through the m6A/YTHDF1 axis in CML cells. KIAA1429 knockdown reduces RAB27B mRNA stability and decreases RAB27B protein, thereby reducing drug efflux and proliferation; RAB27B knockdown mimics these effects and promotes apoptosis.\",\n      \"method\": \"KIAA1429 knockdown, RAB27B mRNA stability assay, YTHDF1 interaction, RAB27B siRNA knockdown, proliferation/apoptosis assays\",\n      \"journal\": \"Genes & diseases\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — m6A/YTHDF1 mechanism for mRNA stabilization with functional validation, single lab\",\n      \"pmids\": [\"37692484\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In bladder cancer, Rab27b mediates exocytosis of BCG bacteria from urothelial cells via its effector SYTL3. Rab27b knockdown or overexpression inversely modulated intracellular BCG quantity and cytotoxicity; androgen receptor (AR) signaling increases Rab27b expression, which drives BCG exocytosis and resistance to BCG therapy.\",\n      \"method\": \"AR and Rab27b knockdown/overexpression, intracellular BCG quantification, cytotoxicity assay, orthotopic xenograft model, microarray identification of Rab27b as AR target\",\n      \"journal\": \"Molecular cancer therapeutics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain and loss-of-function for both AR and Rab27b with defined mechanistic readout, in vivo validation, single lab\",\n      \"pmids\": [\"32737155\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"RAB27B physically interacts with ZDHHC9 to regulate NRAS palmitoylation and ERK activation in NRAS-mutant endothelial cells. NRASQ61R mutation upregulates RAB27B via the ERK/C/EBPβ transcriptional axis, creating a positive feedback loop that drives enhanced proliferation and migration. MEK1/2 inhibition reduces RAB27B gene expression, while RAB27B knockdown suppresses ERK activation.\",\n      \"method\": \"RAB27B knockdown (siRNA), MEK inhibitor treatment, Western blot for ERK/palmitoylation, C/EBPβ identification as transcription factor downstream of ERK\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional KD with signaling readouts, transcription factor identification, single lab; extends prior ZDHHC9 finding\",\n      \"pmids\": [\"39899936\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RAB27B is a small GTPase that functions as a molecular switch controlling the docking and fusion of secretory vesicles, multivesicular endosomes, lysosome-related organelles, and exosomes with the plasma membrane across diverse cell types; it acts through GTP-dependent recruitment of specific effector proteins (including Slac2-c/MyRIP, Slp1, Munc13-4, Slp3/kinesin-1, and melanophilin/MyoVa), is inactivated by the GAP EPI64B and activated by the GEF MADD, requires geranylgeranyl prenylation for membrane association, and additionally controls NRAS palmitoylation via interaction with the palmitoyl acyltransferase ZDHHC9 to regulate RAS/ERK signaling, while also promoting lysosomal function and autophagic flux necessary for α-synuclein clearance in neurons.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"RAB27B is a small Rab GTPase that functions as a GTP-dependent molecular switch controlling the docking, transport, and fusion of secretory granules, secretory lysosomes, multivesicular endosomes, and specialized apical vesicles with the plasma membrane across a broad range of secretory cell types [#0, #2, #9]. It associates with diverse organelle membranes\\u2014dense-core and dense/alpha granules in pituitary, platelet, and megakaryocyte lineages [#1, #5, #6], zymogen granules in pancreatic acinar cells [#8, #35], synaptic vesicles in neurons [#10], melanosomes [#13], and fusiform/discoidal vesicles in urothelium [#7, #25]\\u2014and engages effector proteins to execute distinct steps of regulated exocytosis: Slac2-c/MyRIP and granuphilin on secretory granules [#2, #5], Slp1 and Slp3 on zymogen and mast-cell granules [#19, #23], Slac2-b/EXPH5 on multivesicular endosomes and keratinocyte vesicles [#0, #17], Munc13-4 at the final fusion step in mast cells and osteoblasts [#11, #18], and melanophilin/MyoVa for actin-based melanosome transport [#14]. Through sequential motor coupling\\u2014kinesin-1 via Slp3 for microtubule-based transport and myosin Va/5C for actin-based delivery\\u2014RAB27B governs the handoff of vesicles from microtubule to cortical-actin tracks toward the secretion site [#18, #23, #34]. Its activity cycle is set by the GEF MADD/Rab3GEP and the GAP EPI64B/TBC1D10B, with Rab-GDI extracting GDP-bound RAB27B from membranes after exocytosis, and membrane association requires geranylgeranylation [#20, #30, #33, #15]. Genetic loss of RAB27B causes a bleeding phenotype with impaired platelet dense-granule secretion in mice [#1], and mutation of its effector EXPH5 causes inherited skin fragility in humans [#17]. Beyond secretion, RAB27B promotes lysosomal enzyme maturation and autophagic flux required for \\u03b1-synuclein clearance in neurons [#26, #32], drives invasive growth and exosome/extracellular-vesicle cargo secretion (HSP90\\u03b1, MMP-2 activation) in cancer [#15, #16, #37], and controls NRAS palmitoylation and plasma-membrane trafficking through physical interaction with the palmitoyl acyltransferase ZDHHC9 to sustain RAS/ERK signaling and leukemogenesis [#27, #40].\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"Established RAB27B as a regulator of regulated dense-core granule exocytosis, showing it acts on the secretory pathway rather than being a passive granule marker.\",\n      \"evidence\": \"Co-IP with granuphilin and dominant-negative N133I mutant inhibiting ACTH secretion in AtT20 pituitary cells; dominant-negative effects on melanosome positioning in melanocytes\",\n      \"pmids\": [\"11956164\", \"12060386\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Endogenous activity cycle (GEF/GAP) not yet defined\", \"Melanocyte role rests on dominant-negative overexpression rather than genetic loss\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identified the RAB27B\\u2013effector module on secretory granules, showing the GTPase requires effector binding to drive exocytosis.\",\n      \"evidence\": \"Reciprocal Co-IP of Rab27B with Slac2-c/MyRIP and functional disruption of amylase release in parotid acinar cells; constitutive-active/dominant-negative mutants modulating zymogen granule exocytosis in pancreatic acini\",\n      \"pmids\": [\"15039459\", \"15451418\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether effectors mediate docking versus fusion not resolved\", \"Structural basis of effector recognition unknown\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Genetic knockout defined non-redundant physiological roles of RAB27B in secretion and revealed partial overlap with RAB27A.\",\n      \"evidence\": \"Rab27b KO mice showing hemorrhagic disease and reduced platelet dense-granule number/secretion; mast cell degranulation and anaphylaxis defects; double-KO granule mislocalization in pituitary; crystal structure of Rab27b-GDP\",\n      \"pmids\": [\"17384153\", \"17587407\", \"17761531\", \"17582168\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of RAB27A vs RAB27B effector specificity unresolved despite structure\", \"Granule-number defect mechanism (packaging) not mechanistically dissected\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Placed RAB27B in the exosome/MVE secretion pathway and in granule docking, distinguishing it from RAB27A at the molecular step level.\",\n      \"evidence\": \"RNAi screen showing RAB27B controls MVE docking with EXPH5/Slac2b phenocopy; TIRF microscopy of azurophilic granule docking in neutrophil KO; temporal GDI-extraction of Rab27B in parotid cells\",\n      \"pmids\": [\"19966785\", \"20028487\", \"19583748\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism distinguishing RAB27A and RAB27B docking steps not fully defined\", \"GDI-extraction shown by Co-IP/localization without direct functional perturbation\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Resolved the order of RAB27B action as the final vesicle-fusion step and mapped sequential motor recruitment for vesicle delivery.\",\n      \"evidence\": \"RNAi of Rab27a/b and Slp4-a/Slp5/Munc13-4 in osteoblastic RANKL release blocking fusion but not docking; KO and gain/loss-of-function in lacrimal acinar cells; live imaging of sequential dynein/Myosin5C recruitment to nascent Rab27b vesicles\",\n      \"pmids\": [\"20939018\", \"21525430\", \"22363735\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct demonstration of fusion-machinery engagement (SNAREs) absent\", \"Effector knockdowns are single-lab without reciprocal validation\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined the RAB27B activity cycle and a genetic epistasis pathway separating RAB27B/Munc13-4 fusion control from RAB27A/Mlph/MyoVa cortical-actin control.\",\n      \"evidence\": \"EPI64B/TBC1D10B GAP activity assay with active-site mutants and KO-rescue in pancreatic acini; five-KO genetic epistasis in mast cells; human EXPH5 mutation causing skin fragility\",\n      \"pmids\": [\"23671284\", \"23281710\", \"23176819\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Activating GEF still unidentified at this stage\", \"How GAP/GEF are spatially targeted to specific organelles unknown\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Connected RAB27B to motor-driven granule transport and to lysosomal/late-endosomal secretory trafficking in distinct cell types.\",\n      \"evidence\": \"Co-IP of Kif5b/Slp3/Rab27b trimeric complex with PI3K-dependent recruitment and Kif5b KO anaphylaxis defect in mast cells; shRNA showing Rab27b drives PLP lysosomal exocytosis and myelination in oligodendrocytes\",\n      \"pmids\": [\"27810912\", \"27325508\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Coupling between kinesin-driven transport and myosin-driven cortical delivery not unified\", \"Oligodendrocyte role based on shRNA in a single lab\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Extended RAB27B function from secretion into lysosomal degradative capacity and autophagic flux required for neuronal protein clearance.\",\n      \"evidence\": \"shRNA and KO/overexpression in neurons measuring \\u03b1syn release, solubility, LC3 turnover with chloroquine, lysosomal enzyme maturation, and \\u03b1syn fibril seeding; KO electrophysiology defining selective MF-CA3 presynaptic LTP requirement with lentiviral rescue\",\n      \"pmids\": [\"32350025\", \"39965930\", \"32358861\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Effector mediating lysosomal/autophagic role in neurons not identified\", \"Direct link between secretory and degradative functions of RAB27B unresolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Mapped upstream transcriptional and signaling control of RAB27B in cancer secretion and in epithelial defense and disease contexts.\",\n      \"evidence\": \"CaSR\\u2192PI3K/PKA/mTOR\\u2192MADD GEF activation driving Rab27B-dependent cytokine secretion; NRF2 and FOXO1 transcriptional regulation of RAB27B in UPEC expulsion and diabetic-kidney exosome secretion\",\n      \"pmids\": [\"33845096\", \"34686330\", \"33597203\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"MADD GEF activity on RAB27B inferred from pathway inhibition rather than direct nucleotide-exchange assay\", \"Transcriptional axes are single-lab and context-specific\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Revealed a non-canonical RAB27B function regulating RAS posttranslational modification through ZDHHC9, expanding its role beyond vesicle trafficking into oncogenic signaling.\",\n      \"evidence\": \"Proteomics, Co-IP with ZDHHC9, palmitoylation assays, KO mice and primary human AML depletion showing RAB27B controls NRAS palmitoylation, membrane localization, ERK signaling, and leukemogenesis; MADD/Rab11A endosomal-secretory axis defined; m6A/YTHDF1 mRNA stabilization in CML\",\n      \"pmids\": [\"37317963\", \"37604243\", \"37692484\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether ZDHHC9 regulation requires RAB27B GTPase activity not fully defined\", \"Mechanism by which RAB27B promotes palmitoyl-transfer (scaffolding vs trafficking) unresolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Established RAB27B as a node controlling extracellular-vesicle cargo composition and tumor immune evasion under TGF-\\u03b2 control, and as a self-reinforcing component of NRAS/ERK signaling.\",\n      \"evidence\": \"TGF-\\u03b2\\u2192SMAD3 ChIP repression of RAB27B with click-chemistry EV proteomics and CD8+ T cell killing assay; NRASQ61R\\u2192ERK/C/EBP\\u03b2 feedback upregulating RAB27B in endothelial cells with MEK inhibition reducing RAB27B\",\n      \"pmids\": [\"39723610\", \"39899936\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How RAB27B selectively determines EV cargo identity unknown\", \"Generality of the ERK\\u2013RAB27B feedback loop across cell types untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How a single GTPase coordinates its canonical vesicle-fusion machinery with its degradative (lysosomal/autophagic) and non-vesicular (ZDHHC9/NRAS palmitoylation) functions, and what determines effector and organelle selectivity in each context, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified structural/biochemical model linking GTP-state to the divergent effector repertoire\", \"Determinants of organelle-specific targeting in different cell types undefined\", \"Mechanistic coupling between secretory and degradative roles unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003924\", \"supporting_discovery_ids\": [13, 15, 12]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 2, 5, 11, 27]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [2, 5, 8, 7, 22, 21]},\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [11, 24, 32]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [0, 24, 31]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 9, 22, 27]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [33]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [0, 2, 9, 11]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [4, 7, 24, 27]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [26, 32]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [27, 40]},\n      {\"term_id\": \"R-HSA-109582\", \"supporting_discovery_ids\": [1, 6]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [3, 18, 9]}\n    ],\n    \"complexes\": [\n      \"Rab27B\\u2013Slac2-c/MyRIP complex\",\n      \"Kif5b\\u2013Slp3\\u2013Rab27B complex\",\n      \"Rab27B\\u2013melanophilin\\u2013Myosin Va complex\"\n    ],\n    \"partners\": [\n      \"EXPH5\",\n      \"MYRIP\",\n      \"MADD\",\n      \"TBC1D10B\",\n      \"UNC13D\",\n      \"ZDHHC9\",\n      \"SYTL3\",\n      \"MLPH\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}