{"gene":"RAB8B","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":2013,"finding":"RAB8B is required for caveolar (caveolin-dependent) endocytosis of LRP6 and for Wnt/β-catenin signaling; RAB8B depletion reduces LRP6 activity, β-catenin accumulation, and induction of Wnt target genes, whereas RAB8B overexpression promotes LRP6 activity and internalization and rescues inhibition of caveolar endocytosis.","method":"RNAi screen, loss-of-function (siRNA depletion), gain-of-function (overexpression), β-catenin accumulation assay, Wnt target gene induction, Xenopus and zebrafish morphant models","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (RNAi, overexpression rescue, in vivo morphant phenotypes in two vertebrate species) replicated across cell-based and in vivo contexts","pmids":["24035388"],"is_preprint":false},{"year":2013,"finding":"Rab8a and Rab8b are functionally redundant and together are essential for apical (but not basolateral/dendritic) transport in vivo; double-knockout mice show mislocalisation of apical markers and die earlier than Rab8a single-knockouts. Neither Rab8a nor Rab8b alone is required for ciliogenesis, but additional loss of Rab10 in the double-knockout greatly reduces the percentage of ciliated cells.","method":"Rab8b-knockout mouse generation, Rab8a/Rab8b double-knockout mouse, immunofluorescence of apical/basolateral markers, Rab10 siRNA knockdown in double-KO cells, cilia morphology/frequency analysis","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout (double-KO mice) plus epistasis with Rab10 knockdown, multiple phenotypic readouts, in vivo replication","pmids":["24213529"],"is_preprint":false},{"year":2001,"finding":"Rab8b interacts with TRIP8b (a TPR-domain protein) in a guanine-nucleotide-dependent but prenylation-independent manner; both Rab8b and TRIP8b stimulate cAMP-induced ACTH secretion from AtT20 cells, implicating them in the regulated secretory pathway.","method":"Yeast two-hybrid screen, in vitro binding assay, co-immunoprecipitation, Rab8b GTP/GDP-binding mutants, stable cell lines, ACTH secretion assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — yeast two-hybrid plus in vitro binding plus co-IP plus functional secretion assay in a single study, multiple orthogonal methods","pmids":["11278749"],"is_preprint":false},{"year":2008,"finding":"Rab8b GTPase physically interacts with otoferlin (the DFNB9 deafness protein) as identified by yeast two-hybrid screen in cochlear cDNA library, confirmed by co-localization in HEK293 cells and co-immunoprecipitation of both tagged and native proteins from cochlea, suggesting Rab8b participates in trans-Golgi trafficking at ribbon synapses.","method":"Yeast two-hybrid screen (cochlear cDNA library), transient co-expression and co-localization in HEK293 cells, co-immunoprecipitation (tagged and native proteins from cochlea)","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP with native cochlear proteins plus yeast two-hybrid and co-localization, single lab","pmids":["18772196"],"is_preprint":false},{"year":2016,"finding":"Rab8b regulates intracellular trafficking of West Nile virus particles from recycling endosomes to the plasma membrane for secretion; RNAi-mediated depletion of Rab8b significantly decreases WNV particle release and causes accumulation of WNV particles in recycling endosomes.","method":"RNAi knockdown of Rab8b, quantification of WNV particles in supernatant vs. wild-type cells, co-localization of Rab8 and WNV antigen by immunofluorescence, recycling endosome marker analysis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNAi loss-of-function with quantitative viral release assay and co-localization evidence, single lab","pmids":["26817838"],"is_preprint":false},{"year":2003,"finding":"Rab8B localises to the basal compartment of the testis, co-distributes with E-cadherin, associates with actin, intermediate filament, and microtubule cytoskeletal networks, and its expression increases during adherens junction assembly in Sertoli cells and in response to germ cell co-culture or germ cell-conditioned medium.","method":"RT-PCR, immunohistochemistry, co-fractionation with cytoskeletal networks, high-density Sertoli cell culture, germ cell co-culture, conditioned medium experiments, pharmacological disruption of junction integrity in adult rats","journal":"Endocrinology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — co-fractionation and expression-level correlations in primary cells, no direct functional perturbation of Rab8B itself","pmids":["12639940"],"is_preprint":false},{"year":2008,"finding":"The TPR domain of TRIP8b (originally identified as a Rab8b-interacting protein) has distinct but overlapping substrate specificities compared with the peroxisomal receptor Pex5p; changes in surrounding residues or conformational state of binding partners profoundly alter TRIP8b–Rab8b binding activity.","method":"In vitro binding assays comparing TPR-domain proteins with Rab8b and PTS1 peptides, mutagenesis of binding interfaces","journal":"Biochimica et biophysica acta","confidence":"Low","confidence_rationale":"Tier 3 / Weak — in vitro binding comparison study characterizing TRIP8b–Rab8b interaction determinants, single lab, no cellular functional readout for Rab8b specifically","pmids":["18346465"],"is_preprint":false},{"year":2021,"finding":"LXRα activation suppresses RAB8B expression in hepatocytes by transcriptionally inducing let-7a and miR-34a microRNAs, which directly inhibit RAB8B (confirmed by 3′UTR luciferase assay); reduced RAB8B impairs autophagosome/lysosome formation, blocks lipophagy, and reduces mitochondrial fuel oxidation.","method":"LXRα knockout mice on high-fat diet, chromatin immunoprecipitation (LXRα at let-7a/miR-34a promoters), 3′UTR luciferase reporter assay for RAB8B, miRNA transfection, autophagy flux assays, mitochondrial oxygen consumption rate measurement","journal":"Hepatology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus 3′UTR luciferase (direct mechanistic validation) plus KO mouse model with functional autophagy/metabolic readouts, single lab","pmids":["32557804"],"is_preprint":false},{"year":2025,"finding":"PFKM (phosphofructokinase muscle isoform) promotes chemoresistance in lung adenocarcinoma by upregulating RAB8B expression, which in turn regulates exosome release; the PFKM–RAB8B axis modulates apoptosis and glycolytic metabolism in drug-resistant cells.","method":"Targeted metabolomics, correlation of PFKM activity with exosome release, RAB8B expression modulation, exosome characterization, apoptosis and glycolysis assays in chemoresistant LUAD cells","journal":"Journal of pharmaceutical analysis","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, limited mechanistic detail in abstract, no direct binding or in vitro reconstitution described for the PFKM–RAB8B interaction","pmids":["42057963"],"is_preprint":false},{"year":2026,"finding":"RAB8B modulates VAMP-3 clustering and intracellular trafficking in SARS-CoV-2-infected cells; silencing of RAB8B reduced viral infection by 30–76% in CaCo-2 cells.","method":"Molecular dynamics simulations, in vitro siRNA silencing of Rab8b in SARS-CoV-2-infected CaCo-2 cells, VAMP-3 clustering assay, viral infection quantification","journal":"Journal of medical virology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, in vitro siRNA plus computational simulation, limited mechanistic detail on how RAB8B directly controls VAMP-3","pmids":["42015392"],"is_preprint":false}],"current_model":"RAB8B is a small Rab GTPase that controls multiple vesicular trafficking steps: it acts redundantly with RAB8A to mediate apical (but not basolateral) transport in polarized cells; it facilitates caveolin-dependent endocytosis of LRP6 to promote Wnt/β-catenin signaling; it interacts with TRIP8b (in a GTP-dependent manner) to stimulate regulated secretion; it transports West Nile virus particles from recycling endosomes to the plasma membrane; it supports autophagosome/lysosome formation in hepatocytes downstream of LXRα–miRNA regulation; and it interacts with otoferlin at the trans-Golgi network in cochlear hair cells."},"narrative":{"mechanistic_narrative":"RAB8B is a small Rab GTPase that controls multiple vesicular trafficking steps at the plasma membrane and secretory/endosomal pathways [PMID:24035388, PMID:24213529, PMID:11278749]. It acts redundantly with RAB8A to mediate apical, but not basolateral, transport in polarized cells in vivo, where double knockout disrupts apical marker localization; additional loss of Rab10 in this background impairs ciliogenesis [PMID:24213529]. RAB8B engages effectors in a guanine-nucleotide-dependent manner: it binds the TPR-domain protein TRIP8b through its GTP-bound state to stimulate regulated cAMP-induced ACTH secretion [PMID:11278749]. It is also required for caveolin-dependent endocytosis of LRP6, thereby promoting Wnt/β-catenin signaling and induction of Wnt target genes [PMID:24035388]. RAB8B further participates in trans-Golgi trafficking at cochlear ribbon synapses through interaction with the deafness protein otoferlin [PMID:18772196]. In hepatocytes, RAB8B supports autophagosome/lysosome formation and lipophagy and is a direct target of LXRα-induced let-7a and miR-34a microRNAs [PMID:32557804].","teleology":[{"year":2001,"claim":"Established the first RAB8B effector and a functional role, showing that RAB8B couples to the secretory machinery through a nucleotide-state-dependent interaction.","evidence":"Yeast two-hybrid, in vitro binding, co-IP with GTP/GDP-binding mutants, and ACTH secretion assay in AtT20 cells","pmids":["11278749"],"confidence":"High","gaps":["Mechanism by which TRIP8b stimulates secretion downstream of RAB8B is not resolved","Endogenous vesicle population controlled by the RAB8B–TRIP8b complex not defined"]},{"year":2003,"claim":"Linked RAB8B expression to junction assembly and cytoskeletal networks in the testis, but without direct perturbation of RAB8B.","evidence":"RT-PCR, immunohistochemistry, cytoskeletal co-fractionation, and germ cell co-culture in primary rat Sertoli cells","pmids":["12639940"],"confidence":"Low","gaps":["Correlative expression data only; no loss-of-function for RAB8B","Causal role in adherens junction assembly not established"]},{"year":2008,"claim":"Identified otoferlin as a RAB8B partner, placing RAB8B in trans-Golgi trafficking at cochlear ribbon synapses.","evidence":"Yeast two-hybrid (cochlear cDNA library), co-localization in HEK293, and reciprocal co-IP of native cochlear proteins","pmids":["18772196"],"confidence":"Medium","gaps":["Functional consequence of the RAB8B–otoferlin interaction for hair cell secretion untested","Single lab; no in vivo RAB8B perturbation in the cochlea"]},{"year":2008,"claim":"Characterized molecular determinants of the TRIP8b TPR domain that govern RAB8B binding specificity.","evidence":"In vitro binding assays and interface mutagenesis comparing TRIP8b and Pex5p","pmids":["18346465"],"confidence":"Low","gaps":["No cellular functional readout for RAB8B in this study","Physiological relevance of binding-affinity changes not tested"]},{"year":2013,"claim":"Demonstrated that RAB8B is required for caveolar endocytosis of LRP6 and for Wnt/β-catenin signal activation, defining a receptor-internalization role.","evidence":"RNAi screen, siRNA depletion, overexpression rescue, β-catenin and Wnt target gene assays, and Xenopus/zebrafish morphant models","pmids":["24035388"],"confidence":"High","gaps":["Whether RAB8B acts directly on caveolar carriers or via an effector is unresolved","Generality across Wnt receptor types not defined"]},{"year":2013,"claim":"Established functional redundancy of RAB8B with RAB8A in apical transport in vivo and a combinatorial role with Rab10 in ciliogenesis.","evidence":"Rab8b-KO and Rab8a/Rab8b double-KO mice, apical/basolateral marker immunofluorescence, Rab10 knockdown, and cilia frequency analysis","pmids":["24213529"],"confidence":"High","gaps":["Specific cargo and effectors mediating apical delivery not identified","Non-redundant RAB8B-specific functions not separated from RAB8A"]},{"year":2016,"claim":"Showed RAB8B routes West Nile virus particles from recycling endosomes to the plasma membrane for egress.","evidence":"RNAi knockdown, viral release quantification, and co-localization with recycling endosome markers","pmids":["26817838"],"confidence":"Medium","gaps":["Direct interaction with viral components not shown","Effector linking RAB8B to recycling-endosome exocytosis unknown"]},{"year":2021,"claim":"Placed RAB8B under transcriptional/microRNA control by LXRα and tied its activity to autophagy and lipid metabolism in hepatocytes.","evidence":"LXRα-KO mice, ChIP, 3′UTR luciferase reporter, miRNA transfection, autophagy flux, and oxygen consumption assays","pmids":["32557804"],"confidence":"Medium","gaps":["Molecular step by which RAB8B promotes autophagosome/lysosome formation not defined","Single lab; effectors in lipophagy unidentified"]},{"year":2025,"claim":"Implicated a PFKM–RAB8B axis in exosome release and chemoresistance in lung adenocarcinoma.","evidence":"Metabolomics, RAB8B expression modulation, exosome characterization, and apoptosis/glycolysis assays in chemoresistant LUAD cells","pmids":["42057963"],"confidence":"Low","gaps":["No direct PFKM–RAB8B binding or reconstitution shown","Mechanism connecting RAB8B to exosome biogenesis undefined"]},{"year":2026,"claim":"Suggested RAB8B modulates VAMP-3 clustering and trafficking to support SARS-CoV-2 infection.","evidence":"Molecular dynamics simulations and siRNA silencing in SARS-CoV-2-infected CaCo-2 cells with infection quantification","pmids":["42015392"],"confidence":"Low","gaps":["Direct control of VAMP-3 by RAB8B not mechanistically demonstrated","Computational predictions not validated by binding data"]},{"year":null,"claim":"The full set of RAB8B-specific GEFs, GAPs, and effectors that distinguish its functions from RAB8A across distinct trafficking routes remains undefined.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model of RAB8B effector complexes","RAB8B-specific (non-redundant) cargo not catalogued","Regulatory GEF/GAP network unmapped"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003924","term_label":"GTPase activity","supporting_discovery_ids":[2,4]}],"localization":[{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[4]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,4]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[3]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[0,1,2,4]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[7]}],"complexes":[],"partners":["TRIP8B","OTOF","LRP6","RAB8A","VAMP3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q92930","full_name":"Ras-related protein Rab-8B","aliases":[],"length_aa":207,"mass_kda":23.6,"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 (By similarity). RAB8B may be involved in polarized vesicular trafficking and neurotransmitter release (Probable). May participate in cell junction dynamics in Sertoli cells (By similarity). May also participate in the export of a subset of neosynthesized proteins through a Rab8-Rab10-Rab11-dependent endososomal export route (PubMed:32344433)","subcellular_location":"Cell membrane; Cytoplasmic vesicle, phagosome; Cytoplasmic vesicle, phagosome membrane; Endosome membrane","url":"https://www.uniprot.org/uniprotkb/Q92930/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RAB8B","classification":"Not Classified","n_dependent_lines":3,"n_total_lines":1208,"dependency_fraction":0.0024834437086092716},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000166128","cell_line_id":"CID000442","localizations":[{"compartment":"er","grade":3},{"compartment":"membrane","grade":2},{"compartment":"vesicles","grade":1}],"interactors":[{"gene":"GDI1","stoichiometry":4.0},{"gene":"ZNF280C","stoichiometry":4.0},{"gene":"GDI2","stoichiometry":0.2},{"gene":"PSMB1","stoichiometry":0.2},{"gene":"RAB1B;RAB1C","stoichiometry":0.2},{"gene":"IK","stoichiometry":0.2},{"gene":"CXORF57","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000442","total_profiled":1310},"omim":[{"mim_id":"613532","title":"RAS-ASSOCIATED PROTEIN RAB8B; RAB8B","url":"https://www.omim.org/entry/613532"},{"mim_id":"604834","title":"TANK-BINDING KINASE 1; TBK1","url":"https://www.omim.org/entry/604834"},{"mim_id":"601530","title":"SEQUESTOSOME 1; SQSTM1","url":"https://www.omim.org/entry/601530"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"bone marrow","ntpm":76.5}],"url":"https://www.proteinatlas.org/search/RAB8B"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q92930","domains":[{"cath_id":"3.40.50.300","chopping":"6-176","consensus_level":"high","plddt":93.775,"start":6,"end":176}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q92930","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q92930-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q92930-F1-predicted_aligned_error_v6.png","plddt_mean":86.56},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RAB8B","jax_strain_url":"https://www.jax.org/strain/search?query=RAB8B"},"sequence":{"accession":"Q92930","fasta_url":"https://rest.uniprot.org/uniprotkb/Q92930.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q92930/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q92930"}},"corpus_meta":[{"pmid":"24213529","id":"PMC_24213529","title":"Rab8a and Rab8b are essential for several apical transport pathways but insufficient for ciliogenesis.","date":"2013","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/24213529","citation_count":108,"is_preprint":false},{"pmid":"24035388","id":"PMC_24035388","title":"RAB8B is required for activity and caveolar endocytosis of LRP6.","date":"2013","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/24035388","citation_count":55,"is_preprint":false},{"pmid":"12639940","id":"PMC_12639940","title":"Rab8B GTPase and junction dynamics in the testis.","date":"2003","source":"Endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/12639940","citation_count":55,"is_preprint":false},{"pmid":"21504900","id":"PMC_21504900","title":"Trafficking and gating of hyperpolarization-activated cyclic nucleotide-gated channels are regulated by interaction with tetratricopeptide repeat-containing Rab8b-interacting protein (TRIP8b) and cyclic AMP at distinct sites.","date":"2011","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/21504900","citation_count":54,"is_preprint":false},{"pmid":"11278749","id":"PMC_11278749","title":"Rab8b and its interacting partner TRIP8b are involved in regulated secretion in AtT20 cells.","date":"2001","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11278749","citation_count":53,"is_preprint":false},{"pmid":"18772196","id":"PMC_18772196","title":"Rab8b GTPase, a protein transport regulator, is an interacting partner of otoferlin, defective in a human autosomal recessive deafness form.","date":"2008","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/18772196","citation_count":43,"is_preprint":false},{"pmid":"32557804","id":"PMC_32557804","title":"Liver X Receptor Alpha Activation Inhibits Autophagy and Lipophagy in Hepatocytes by Dysregulating Autophagy-Related 4B Cysteine Peptidase and Rab-8B, Reducing Mitochondrial Fuel Oxidation.","date":"2021","source":"Hepatology (Baltimore, Md.)","url":"https://pubmed.ncbi.nlm.nih.gov/32557804","citation_count":38,"is_preprint":false},{"pmid":"26817838","id":"PMC_26817838","title":"Rab8b Regulates Transport of West Nile Virus Particles from Recycling Endosomes.","date":"2016","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/26817838","citation_count":31,"is_preprint":false},{"pmid":"18346465","id":"PMC_18346465","title":"Comparison of the PTS1- and Rab8b-binding properties of Pex5p and Pex5Rp/TRIP8b.","date":"2008","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/18346465","citation_count":19,"is_preprint":false},{"pmid":"33101391","id":"PMC_33101391","title":"FGF2 Affects Parkinson's Disease-Associated Molecular Networks Through Exosomal Rab8b/Rab31.","date":"2020","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/33101391","citation_count":16,"is_preprint":false},{"pmid":"42015392","id":"PMC_42015392","title":"Multiorgan Molecular Landscape of Severe COVID-19 Revealed by Consensus Gene Signatures and RAB8B Targeting.","date":"2026","source":"Journal of medical virology","url":"https://pubmed.ncbi.nlm.nih.gov/42015392","citation_count":0,"is_preprint":false},{"pmid":"42057963","id":"PMC_42057963","title":"PFKM promotes chemoresistance in lung adenocarcinoma by regulating RAB8B mediated exosome release.","date":"2025","source":"Journal of pharmaceutical analysis","url":"https://pubmed.ncbi.nlm.nih.gov/42057963","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8038,"output_tokens":2773,"usd":0.032855,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":20080,"output_tokens":5879,"usd":0.1881,"resynth_parse_fail":true,"stage2_stop_reason":"refusal"},"total_usd":0.220955,"stage1_batch_id":"msgbatch_01CNoDbkChHEkgrJnL7BwtGJ","stage2_batch_id":"msgbatch_016Y4x9E9Wg5VQDANj9quSQD","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2013,\n      \"finding\": \"RAB8B is required for caveolar (caveolin-dependent) endocytosis of LRP6 and for Wnt/β-catenin signaling; RAB8B depletion reduces LRP6 activity, β-catenin accumulation, and induction of Wnt target genes, whereas RAB8B overexpression promotes LRP6 activity and internalization and rescues inhibition of caveolar endocytosis.\",\n      \"method\": \"RNAi screen, loss-of-function (siRNA depletion), gain-of-function (overexpression), β-catenin accumulation assay, Wnt target gene induction, Xenopus and zebrafish morphant models\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (RNAi, overexpression rescue, in vivo morphant phenotypes in two vertebrate species) replicated across cell-based and in vivo contexts\",\n      \"pmids\": [\"24035388\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Rab8a and Rab8b are functionally redundant and together are essential for apical (but not basolateral/dendritic) transport in vivo; double-knockout mice show mislocalisation of apical markers and die earlier than Rab8a single-knockouts. Neither Rab8a nor Rab8b alone is required for ciliogenesis, but additional loss of Rab10 in the double-knockout greatly reduces the percentage of ciliated cells.\",\n      \"method\": \"Rab8b-knockout mouse generation, Rab8a/Rab8b double-knockout mouse, immunofluorescence of apical/basolateral markers, Rab10 siRNA knockdown in double-KO cells, cilia morphology/frequency analysis\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout (double-KO mice) plus epistasis with Rab10 knockdown, multiple phenotypic readouts, in vivo replication\",\n      \"pmids\": [\"24213529\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Rab8b interacts with TRIP8b (a TPR-domain protein) in a guanine-nucleotide-dependent but prenylation-independent manner; both Rab8b and TRIP8b stimulate cAMP-induced ACTH secretion from AtT20 cells, implicating them in the regulated secretory pathway.\",\n      \"method\": \"Yeast two-hybrid screen, in vitro binding assay, co-immunoprecipitation, Rab8b GTP/GDP-binding mutants, stable cell lines, ACTH secretion assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — yeast two-hybrid plus in vitro binding plus co-IP plus functional secretion assay in a single study, multiple orthogonal methods\",\n      \"pmids\": [\"11278749\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Rab8b GTPase physically interacts with otoferlin (the DFNB9 deafness protein) as identified by yeast two-hybrid screen in cochlear cDNA library, confirmed by co-localization in HEK293 cells and co-immunoprecipitation of both tagged and native proteins from cochlea, suggesting Rab8b participates in trans-Golgi trafficking at ribbon synapses.\",\n      \"method\": \"Yeast two-hybrid screen (cochlear cDNA library), transient co-expression and co-localization in HEK293 cells, co-immunoprecipitation (tagged and native proteins from cochlea)\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP with native cochlear proteins plus yeast two-hybrid and co-localization, single lab\",\n      \"pmids\": [\"18772196\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Rab8b regulates intracellular trafficking of West Nile virus particles from recycling endosomes to the plasma membrane for secretion; RNAi-mediated depletion of Rab8b significantly decreases WNV particle release and causes accumulation of WNV particles in recycling endosomes.\",\n      \"method\": \"RNAi knockdown of Rab8b, quantification of WNV particles in supernatant vs. wild-type cells, co-localization of Rab8 and WNV antigen by immunofluorescence, recycling endosome marker analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi loss-of-function with quantitative viral release assay and co-localization evidence, single lab\",\n      \"pmids\": [\"26817838\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Rab8B localises to the basal compartment of the testis, co-distributes with E-cadherin, associates with actin, intermediate filament, and microtubule cytoskeletal networks, and its expression increases during adherens junction assembly in Sertoli cells and in response to germ cell co-culture or germ cell-conditioned medium.\",\n      \"method\": \"RT-PCR, immunohistochemistry, co-fractionation with cytoskeletal networks, high-density Sertoli cell culture, germ cell co-culture, conditioned medium experiments, pharmacological disruption of junction integrity in adult rats\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — co-fractionation and expression-level correlations in primary cells, no direct functional perturbation of Rab8B itself\",\n      \"pmids\": [\"12639940\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"The TPR domain of TRIP8b (originally identified as a Rab8b-interacting protein) has distinct but overlapping substrate specificities compared with the peroxisomal receptor Pex5p; changes in surrounding residues or conformational state of binding partners profoundly alter TRIP8b–Rab8b binding activity.\",\n      \"method\": \"In vitro binding assays comparing TPR-domain proteins with Rab8b and PTS1 peptides, mutagenesis of binding interfaces\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — in vitro binding comparison study characterizing TRIP8b–Rab8b interaction determinants, single lab, no cellular functional readout for Rab8b specifically\",\n      \"pmids\": [\"18346465\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"LXRα activation suppresses RAB8B expression in hepatocytes by transcriptionally inducing let-7a and miR-34a microRNAs, which directly inhibit RAB8B (confirmed by 3′UTR luciferase assay); reduced RAB8B impairs autophagosome/lysosome formation, blocks lipophagy, and reduces mitochondrial fuel oxidation.\",\n      \"method\": \"LXRα knockout mice on high-fat diet, chromatin immunoprecipitation (LXRα at let-7a/miR-34a promoters), 3′UTR luciferase reporter assay for RAB8B, miRNA transfection, autophagy flux assays, mitochondrial oxygen consumption rate measurement\",\n      \"journal\": \"Hepatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus 3′UTR luciferase (direct mechanistic validation) plus KO mouse model with functional autophagy/metabolic readouts, single lab\",\n      \"pmids\": [\"32557804\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PFKM (phosphofructokinase muscle isoform) promotes chemoresistance in lung adenocarcinoma by upregulating RAB8B expression, which in turn regulates exosome release; the PFKM–RAB8B axis modulates apoptosis and glycolytic metabolism in drug-resistant cells.\",\n      \"method\": \"Targeted metabolomics, correlation of PFKM activity with exosome release, RAB8B expression modulation, exosome characterization, apoptosis and glycolysis assays in chemoresistant LUAD cells\",\n      \"journal\": \"Journal of pharmaceutical analysis\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, limited mechanistic detail in abstract, no direct binding or in vitro reconstitution described for the PFKM–RAB8B interaction\",\n      \"pmids\": [\"42057963\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"RAB8B modulates VAMP-3 clustering and intracellular trafficking in SARS-CoV-2-infected cells; silencing of RAB8B reduced viral infection by 30–76% in CaCo-2 cells.\",\n      \"method\": \"Molecular dynamics simulations, in vitro siRNA silencing of Rab8b in SARS-CoV-2-infected CaCo-2 cells, VAMP-3 clustering assay, viral infection quantification\",\n      \"journal\": \"Journal of medical virology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, in vitro siRNA plus computational simulation, limited mechanistic detail on how RAB8B directly controls VAMP-3\",\n      \"pmids\": [\"42015392\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RAB8B is a small Rab GTPase that controls multiple vesicular trafficking steps: it acts redundantly with RAB8A to mediate apical (but not basolateral) transport in polarized cells; it facilitates caveolin-dependent endocytosis of LRP6 to promote Wnt/β-catenin signaling; it interacts with TRIP8b (in a GTP-dependent manner) to stimulate regulated secretion; it transports West Nile virus particles from recycling endosomes to the plasma membrane; it supports autophagosome/lysosome formation in hepatocytes downstream of LXRα–miRNA regulation; and it interacts with otoferlin at the trans-Golgi network in cochlear hair cells.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"RAB8B is a small Rab GTPase that controls multiple vesicular trafficking steps at the plasma membrane and secretory/endosomal pathways [#0, #1, #2]. It acts redundantly with RAB8A to mediate apical, but not basolateral, transport in polarized cells in vivo, where double knockout disrupts apical marker localization; additional loss of Rab10 in this background impairs ciliogenesis [#1]. RAB8B engages effectors in a guanine-nucleotide-dependent manner: it binds the TPR-domain protein TRIP8b through its GTP-bound state to stimulate regulated cAMP-induced ACTH secretion [#2]. It is also required for caveolin-dependent endocytosis of LRP6, thereby promoting Wnt/\\u03b2-catenin signaling and induction of Wnt target genes [#0]. RAB8B further participates in trans-Golgi trafficking at cochlear ribbon synapses through interaction with the deafness protein otoferlin [#3]. In hepatocytes, RAB8B supports autophagosome/lysosome formation and lipophagy and is a direct target of LXR\\u03b1-induced let-7a and miR-34a microRNAs [#7].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Established the first RAB8B effector and a functional role, showing that RAB8B couples to the secretory machinery through a nucleotide-state-dependent interaction.\",\n      \"evidence\": \"Yeast two-hybrid, in vitro binding, co-IP with GTP/GDP-binding mutants, and ACTH secretion assay in AtT20 cells\",\n      \"pmids\": [\"11278749\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which TRIP8b stimulates secretion downstream of RAB8B is not resolved\", \"Endogenous vesicle population controlled by the RAB8B\\u2013TRIP8b complex not defined\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Linked RAB8B expression to junction assembly and cytoskeletal networks in the testis, but without direct perturbation of RAB8B.\",\n      \"evidence\": \"RT-PCR, immunohistochemistry, cytoskeletal co-fractionation, and germ cell co-culture in primary rat Sertoli cells\",\n      \"pmids\": [\"12639940\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Correlative expression data only; no loss-of-function for RAB8B\", \"Causal role in adherens junction assembly not established\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Identified otoferlin as a RAB8B partner, placing RAB8B in trans-Golgi trafficking at cochlear ribbon synapses.\",\n      \"evidence\": \"Yeast two-hybrid (cochlear cDNA library), co-localization in HEK293, and reciprocal co-IP of native cochlear proteins\",\n      \"pmids\": [\"18772196\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of the RAB8B\\u2013otoferlin interaction for hair cell secretion untested\", \"Single lab; no in vivo RAB8B perturbation in the cochlea\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Characterized molecular determinants of the TRIP8b TPR domain that govern RAB8B binding specificity.\",\n      \"evidence\": \"In vitro binding assays and interface mutagenesis comparing TRIP8b and Pex5p\",\n      \"pmids\": [\"18346465\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No cellular functional readout for RAB8B in this study\", \"Physiological relevance of binding-affinity changes not tested\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Demonstrated that RAB8B is required for caveolar endocytosis of LRP6 and for Wnt/\\u03b2-catenin signal activation, defining a receptor-internalization role.\",\n      \"evidence\": \"RNAi screen, siRNA depletion, overexpression rescue, \\u03b2-catenin and Wnt target gene assays, and Xenopus/zebrafish morphant models\",\n      \"pmids\": [\"24035388\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether RAB8B acts directly on caveolar carriers or via an effector is unresolved\", \"Generality across Wnt receptor types not defined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Established functional redundancy of RAB8B with RAB8A in apical transport in vivo and a combinatorial role with Rab10 in ciliogenesis.\",\n      \"evidence\": \"Rab8b-KO and Rab8a/Rab8b double-KO mice, apical/basolateral marker immunofluorescence, Rab10 knockdown, and cilia frequency analysis\",\n      \"pmids\": [\"24213529\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific cargo and effectors mediating apical delivery not identified\", \"Non-redundant RAB8B-specific functions not separated from RAB8A\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Showed RAB8B routes West Nile virus particles from recycling endosomes to the plasma membrane for egress.\",\n      \"evidence\": \"RNAi knockdown, viral release quantification, and co-localization with recycling endosome markers\",\n      \"pmids\": [\"26817838\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct interaction with viral components not shown\", \"Effector linking RAB8B to recycling-endosome exocytosis unknown\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Placed RAB8B under transcriptional/microRNA control by LXR\\u03b1 and tied its activity to autophagy and lipid metabolism in hepatocytes.\",\n      \"evidence\": \"LXR\\u03b1-KO mice, ChIP, 3\\u2032UTR luciferase reporter, miRNA transfection, autophagy flux, and oxygen consumption assays\",\n      \"pmids\": [\"32557804\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular step by which RAB8B promotes autophagosome/lysosome formation not defined\", \"Single lab; effectors in lipophagy unidentified\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Implicated a PFKM\\u2013RAB8B axis in exosome release and chemoresistance in lung adenocarcinoma.\",\n      \"evidence\": \"Metabolomics, RAB8B expression modulation, exosome characterization, and apoptosis/glycolysis assays in chemoresistant LUAD cells\",\n      \"pmids\": [\"42057963\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No direct PFKM\\u2013RAB8B binding or reconstitution shown\", \"Mechanism connecting RAB8B to exosome biogenesis undefined\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Suggested RAB8B modulates VAMP-3 clustering and trafficking to support SARS-CoV-2 infection.\",\n      \"evidence\": \"Molecular dynamics simulations and siRNA silencing in SARS-CoV-2-infected CaCo-2 cells with infection quantification\",\n      \"pmids\": [\"42015392\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Direct control of VAMP-3 by RAB8B not mechanistically demonstrated\", \"Computational predictions not validated by binding data\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The full set of RAB8B-specific GEFs, GAPs, and effectors that distinguish its functions from RAB8A across distinct trafficking routes remains undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural model of RAB8B effector complexes\", \"RAB8B-specific (non-redundant) cargo not catalogued\", \"Regulatory GEF/GAP network unmapped\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003924\", \"supporting_discovery_ids\": [2, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 4]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [0, 1, 2, 4]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"TRIP8b\", \"OTOF\", \"LRP6\", \"RAB8A\", \"VAMP3\"],\n    \"other_free_text\": []\n  }\n}\n```","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}