{"gene":"EXOC8","run_date":"2026-04-28T17:46:03","timeline":{"discoveries":[{"year":1997,"finding":"The mammalian exocyst complex contains an 84-kDa subunit (later designated EXOC8/Exo84) as a novel protein component, identified by characterization of cDNAs encoding mammalian exocyst subunits.","method":"cDNA cloning, immunoprecipitation, Western blot","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 — initial identification by biochemical characterization; single lab","pmids":["9405631"],"is_preprint":false},{"year":1998,"finding":"The mammalian brain sec6/8 (exocyst) complex, which contains the 84-kDa subunit (EXOC8), co-immunoprecipitates with septin filaments, suggesting a functional interaction between the exocyst and septin complexes at sites of membrane addition in neurons.","method":"Co-immunoprecipitation, electron microscopy","journal":"Neuron","confidence":"Medium","confidence_rationale":"Tier 2 — reciprocal co-IP with structural EM; single lab","pmids":["9655500"],"is_preprint":false},{"year":1999,"finding":"Yeast Exo84p (ortholog of EXOC8) is an essential exocyst subunit required for post-Golgi secretory vesicle targeting to the plasma membrane; it localizes to sites of polarized secretion (bud tip), co-immunoprecipitates with other exocyst components, and its assembly into the exocyst complex requires Sec5p and Sec10p.","method":"Genetic depletion, invertase secretion assay, electron microscopy, co-immunoprecipitation, velocity gradient sedimentation, two-hybrid assay, fluorescence microscopy","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods (genetics, biochemistry, imaging) in foundational study","pmids":["10438536"],"is_preprint":false},{"year":2001,"finding":"Yeast Exo84p (ortholog of EXOC8) physically interacts with the U1 snRNP component Snp1p and is involved in pre-mRNA splicing; a temperature-sensitive exo84 mutation causes increased pre-mRNA:mRNA ratios and defects in in vitro splicing and prespliceosome formation, revealing an unexpected link between the exocyst and the spliceosome.","method":"Two-hybrid assay, co-immunoprecipitation, temperature-sensitive mutant analysis, in vitro splicing assay, Northern blot","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods; single lab, unexpected finding","pmids":["11425851"],"is_preprint":false},{"year":2001,"finding":"The mammalian brain exocyst complex (including the 84-kDa EXOC8 subunit) binds active (GTP-bound) RalA in a GTP-dependent manner in nerve terminals, identifying the exocyst as an effector of neuronal RalA signaling.","method":"GTP-dependent pulldown, MALDI-TOF mass spectrometry, co-immunoprecipitation, Western blot","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — MS identification plus biochemical validation; single lab","pmids":["11406615"],"is_preprint":false},{"year":2003,"finding":"Exo84 (EXOC8) is a direct target of activated Ral GTPases in mammalian cells; Ral GTPases regulate exocyst assembly through dual interactions with both Sec5 and Exo84, and mammalian exocyst components exist as distinct subcomplexes on vesicles and the plasma membrane that are assembled by Ral signaling.","method":"Co-immunoprecipitation, GST pulldown, dominant-negative constructs, subcellular fractionation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal biochemical methods; independently supported by structural studies","pmids":["14525976"],"is_preprint":false},{"year":2005,"finding":"Crystal structure of the Ral-binding domain (RBD) of Exo84 in complex with active RalA reveals that the Exo84 RBD adopts a pleckstrin homology (PH) domain fold and that RalA engages Exo84 via both switch regions; Exo84 and Sec5 competitively bind active RalA, indicating a regulatory mechanism for Sec6/8 complex assembly.","method":"X-ray crystallography (crystal structure), mutagenesis binding studies, biochemical competition assays","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with mutagenesis validation; moderate evidence base","pmids":["15920473"],"is_preprint":false},{"year":2005,"finding":"Crystal structures of yeast Exo84p C-terminal domains reveal a long helical-bundle rod architecture (80 Å) with the same fold as the Exo70p N-terminus, suggesting exocyst subunits are composed of helical modules strung into rods, a conserved structural motif across the complex.","method":"X-ray crystallography (2.85 Å resolution), structural comparison","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 — high-resolution crystal structure with experimental interaction data","pmids":["16249794"],"is_preprint":false},{"year":2005,"finding":"Yeast Exo84p (ortholog of EXOC8) plays a critical role in exocyst complex assembly: several exocyst members (Sec10p, Sec15p, Exo70p) require Exo84p for their polarized localization and for their assembly into the complex, while Exo84p localization itself depends on pre-Golgi trafficking and polarized actin but not on other exocyst subunits.","method":"Temperature-sensitive mutant generation, electron microscopy, fluorescence microscopy, co-immunoprecipitation, cargo trafficking assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — systematic epistasis analysis with multiple orthogonal methods across multiple mutants","pmids":["15788396"],"is_preprint":false},{"year":2007,"finding":"Drosophila Exo84 (ortholog of EXOC8) is essential for epithelial apical identity: it is required for apical localization of the Crumbs transmembrane protein, and loss of Exo84 leads to mislocalization of adherens junction proteins, defects in apical cuticle secretion, and accumulation of apical proteins in an expanded recycling endosome.","method":"Genetic loss-of-function (mutant analysis), immunofluorescence microscopy, epistasis with dlg/lgl mutants","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with clear phenotypic readouts and pathway placement; well-cited","pmids":["17698923"],"is_preprint":false},{"year":2011,"finding":"RalB and its effector Exo84 (EXOC8) are required for nutrient starvation-induced autophagosome biogenesis in mammalian cells; RalB activation on nascent autophagosomes drives assembly of catalytically active ULK1 and Beclin1-VPS34 complexes on the exocyst through direct binding to Exo84, enabling isolation membrane formation.","method":"RNAi knockdown, co-immunoprecipitation, immunofluorescence, autophagy flux assays, dominant-negative constructs","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods in high-impact journal; direct binding and functional epistasis established","pmids":["21241894"],"is_preprint":false},{"year":2012,"finding":"C. elegans exoc-8 (EXOC8 ortholog) mutants display pleiotropic behavior defects resembling cilia mutants and show functional links to RAB-10-regulated endosomal trafficking; exoc-8 and exoc-7;exoc-8 double mutations cause enlarged RAB-10 RNAi-induced endocytic vacuoles and upregulation of RAB-10 expression in intestinal epithelial cells.","method":"C. elegans genetic mutant analysis, targeted RNAi screen, fluorescence microscopy, endocytic marker accumulation assays","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis with RNAi screen; single lab, model organism","pmids":["22389680"],"is_preprint":false},{"year":2012,"finding":"RalA effectors Sec5 and Exo84 (EXOC8) mediate distinct aspects of cell polarization: RalA-Exocyst interactions are directly required for migration and invasion of prostate cancer cells, and blocking RalA-Exocyst binding causes morphological changes and defects in single and coordinated cell migration.","method":"Dominant-negative constructs, cell migration assays, invasion assays, morphological analysis","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 3 — functional phenotype established but limited mechanistic resolution of Sec5 vs Exo84 contributions","pmids":["22761837"],"is_preprint":false},{"year":2013,"finding":"Mitotic phosphorylation of yeast Exo84p (EXOC8 ortholog) by Cdk1-Clb2 disrupts exocyst complex assembly, thereby inhibiting exocytosis and cell surface expansion during the metaphase-anaphase transition, providing a molecular mechanism for growth arrest during mitosis.","method":"CDK kinase assay, phosphorylation site mutagenesis, co-immunoprecipitation, exocytosis assays, fluorescence microscopy, conditional mutants","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro kinase assay with mutagenesis plus multiple cellular readouts; strong mechanistic evidence","pmids":["23836930"],"is_preprint":false},{"year":2013,"finding":"The exocyst complex (including Exo84/EXOC8) interacts with endosomal WASH complex on MT1-MMP-containing late endosomes in breast carcinoma cells; this interaction is required for exocytic delivery of MT1-MMP at invadopodia to enable matrix degradation and tumor cell invasion.","method":"Co-immunoprecipitation, RNAi knockdown, live-cell imaging, matrix degradation assays, proximity ligation assay","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 — multiple methods establishing the interaction and functional consequence; exocyst complex broadly implicated","pmids":["24344185"],"is_preprint":false},{"year":2014,"finding":"In Candida albicans, phosphorylation of CaExo84 (EXOC8 ortholog) by Cdk1-Hgc1 promotes hyphal extension by altering its affinity for phosphatidylserine, enabling recycling at the plasma membrane without disrupting its localization — a mechanistically distinct outcome from yeast Exo84 phosphorylation, demonstrating functional divergence of Cdk1 regulation of this conserved exocyst subunit.","method":"Phosphorylation site mutagenesis, CDK assay, fluorescence microscopy, phosphatidylserine binding assay, genetic analysis","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 1-2 — mutagenesis plus lipid binding assays; single lab","pmids":["24501427"],"is_preprint":false},{"year":2016,"finding":"The exocyst complex, including EXOC8, is identified as a component of the ciliary protein landscape through affinity proteomics of 217 tagged ciliary proteins, and sub-complexes of the exocyst are biochemically validated, linking exocyst function to ciliogenesis.","method":"Affinity proteomics, AP-MS, biochemical validation of sub-complexes, genetic variant analysis in ciliary disease patients","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 — large-scale proteomics with biochemical sub-complex validation; EXOC8 specific role in cilia requires further study","pmids":["27173435"],"is_preprint":false},{"year":2017,"finding":"TBK1 directly phosphorylates EXOC8 (Exo84) upon RalA activation by insulin in adipocytes; phosphorylation reduces Exo84's affinity for RalA, enabling its release from the exocyst complex, which is required for proper engagement and disengagement of GLUT4 vesicles at the plasma membrane; both phosphorylation-mimicking and non-phosphorylatable Exo84 mutants block insulin-stimulated GLUT4 translocation.","method":"In vitro kinase assay, co-immunoprecipitation, siRNA knockdown, adipocyte-specific TBK1 knockout, glucose uptake assays, phosphomimetic/phosphodeficient mutagenesis, dominant-negative TBK1","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro kinase assay, mutagenesis, KO, and multiple functional readouts; strong mechanistic evidence","pmids":["28325821"],"is_preprint":false},{"year":2019,"finding":"Yeast Exo84p (EXOC8 ortholog) is phosphorylated by Cdk1 in late G1 phase (in addition to mitosis), and this phosphorylation impairs exocyst complex assembly, exocytic secretion, and cell growth, contributing to coordination of growth arrest at the G1/S transition.","method":"CDK kinase assay, immunoprecipitation, phosphodeficient/phosphomimetic exo84 mutants, secretion assays, fluorescence microscopy, conditional cdc mutants","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro CDK assay with mutagenesis and multiple cellular readouts; extends prior mitotic phosphorylation discovery","pmids":["31171719"],"is_preprint":false},{"year":2020,"finding":"Loss-of-function variants in EXOC8 in humans cause a recessively inherited neurodevelopmental disorder characterized by brain atrophy, seizures, developmental delay, and in severe cases microcephaly, establishing an essential role for EXOC8 in human cerebral cortex development.","method":"Homozygosity mapping, exome sequencing, Sanger sequencing, zebrafish exoc7 knockout model","journal":"Genetics in medicine","confidence":"Medium","confidence_rationale":"Tier 3 — human genetics with animal model validation; mechanism (neural progenitor proliferation/survival) inferred rather than directly demonstrated for EXOC8","pmids":["32103185"],"is_preprint":false},{"year":2025,"finding":"Active Merlin (NF2 tumor suppressor) competitively inhibits RalB binding to its exocyst effectors Sec5 and Exo84 (EXOC8), and regulates the kinetics of exocytosis in a RalB-dependent manner; proximity biotinylation and direct binding assays identified RalA and RalB as high-affinity PIP2-dependent Merlin binding proteins.","method":"Proximity biotinylation (BioID), direct binding assays, co-localization, competitive binding assays, exocytosis kinetics assays","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 — direct binding assays with functional exocytosis readout; preprint, not yet peer-reviewed","pmids":["bio_10.1101_2025.06.13.659557"],"is_preprint":true}],"current_model":"EXOC8 (Exo84) is an essential subunit of the octameric exocyst complex that tethers secretory vesicles to the plasma membrane for exocytosis; it directly binds active RalA/RalB GTPases via a PH-domain fold RBD (competitively with Sec5), serves as a scaffold for assembly of ULK1 and Beclin1-VPS34 autophagy complexes during starvation, is phosphorylated by Cdk1 during mitosis and G1/S to disrupt exocyst assembly and arrest cell growth, is phosphorylated by TBK1 downstream of insulin-RalA signaling to regulate GLUT4 vesicle docking/fusion in adipocytes, and is required for epithelial apical polarity (Crumbs localization) and human cerebral cortex development, with loss-of-function mutations causing a recessively inherited neurodevelopmental disorder."},"narrative":{"teleology":[{"year":1997,"claim":"Identification of an 84-kDa protein as a novel mammalian exocyst subunit established EXOC8 as an integral component of the secretory vesicle tethering machinery.","evidence":"cDNA cloning and immunoprecipitation of mammalian exocyst complex","pmids":["9405631"],"confidence":"Medium","gaps":["Mammalian-specific function of Exo84 vs. other subunits not defined","no loss-of-function data in mammalian cells at this stage"]},{"year":1999,"claim":"Genetic depletion and biochemical reconstitution in yeast demonstrated that Exo84p is essential for post-Golgi vesicle targeting and that its assembly into the exocyst depends on Sec5p/Sec10p, establishing its position in the complex hierarchy.","evidence":"Yeast depletion strains, invertase secretion assay, co-IP, velocity sedimentation, EM","pmids":["10438536"],"confidence":"High","gaps":["Mammalian essentiality not yet tested","direct membrane-binding properties unknown"]},{"year":2003,"claim":"Discovery that Exo84 is a direct Ral GTPase effector—alongside Sec5—revealed that Ral signaling assembles distinct exocyst subcomplexes from vesicular and plasma-membrane pools, answering how upstream signaling controls exocyst assembly.","evidence":"Co-IP, GST pulldown, dominant-negative constructs, subcellular fractionation in mammalian cells","pmids":["14525976"],"confidence":"High","gaps":["Structural basis of Ral–Exo84 interaction unknown","relative contributions of Sec5 vs Exo84 to exocytosis unclear"]},{"year":2005,"claim":"Crystal structures of the Exo84 Ral-binding domain (PH-fold) in complex with RalA, and of yeast Exo84p helical-bundle domains, provided the atomic basis for competitive RalA engagement with Sec5 and revealed a conserved helical-rod architecture across exocyst subunits.","evidence":"X-ray crystallography (human RBD–RalA complex; yeast C-terminal domains at 2.85 Å), mutagenesis binding studies","pmids":["15920473","16249794"],"confidence":"High","gaps":["Full-length Exo84 structure not available","how competitive Ral binding switches exocyst configuration in vivo undetermined"]},{"year":2005,"claim":"Systematic epistasis in yeast showed that Exo84p is required for polarized localization of Sec10p, Sec15p, and Exo70p and for their assembly into the holocomplex, while Exo84p localization itself depends on actin and pre-Golgi traffic, establishing Exo84 as an early-acting assembly scaffold.","evidence":"Temperature-sensitive mutants, co-IP, fluorescence microscopy, cargo trafficking assays in S. cerevisiae","pmids":["15788396"],"confidence":"High","gaps":["Mammalian Exo84 scaffolding hierarchy not tested","mechanism of actin-dependent Exo84 recruitment unknown"]},{"year":2007,"claim":"Drosophila genetic studies revealed that Exo84 is essential for epithelial apical identity by trafficking Crumbs to the apical surface and maintaining adherens junctions, extending exocyst function from bulk secretion to cell polarity.","evidence":"Drosophila loss-of-function mutants, immunofluorescence, epistasis with dlg/lgl","pmids":["17698923"],"confidence":"High","gaps":["Mammalian epithelial polarity role not directly shown","cargo specificity mechanism for Crumbs vs other cargoes unknown"]},{"year":2011,"claim":"Demonstration that RalB–Exo84 interaction nucleates ULK1 and Beclin1–VPS34 complexes on nascent autophagosomes during starvation established a non-canonical role for Exo84 as an autophagy scaffold distinct from its exocytic function.","evidence":"RNAi, co-IP, immunofluorescence, autophagy flux assays, dominant-negative constructs in mammalian cells","pmids":["21241894"],"confidence":"High","gaps":["Structural basis of Exo84–ULK1/Beclin1 interaction unknown","whether autophagy and exocytosis roles are mutually exclusive in real time undetermined"]},{"year":2013,"claim":"Cdk1 phosphorylation of Exo84 during mitosis was shown to disrupt exocyst assembly and inhibit exocytosis, providing a direct molecular mechanism coupling cell-cycle progression to growth arrest.","evidence":"In vitro Cdk1 kinase assay, phosphosite mutagenesis, co-IP, exocytosis assays in yeast","pmids":["23836930"],"confidence":"High","gaps":["Phosphorylation sites in mammalian EXOC8 and their cell-cycle regulation not mapped","phosphatase responsible for dephosphorylation unknown"]},{"year":2017,"claim":"TBK1 phosphorylation of EXOC8 downstream of insulin–RalA signaling was found to reduce Exo84–RalA affinity and regulate GLUT4 vesicle docking/fusion cycles in adipocytes, linking Exo84 phosphoregulation to metabolic physiology.","evidence":"In vitro kinase assay, adipocyte-specific TBK1 KO, phosphomimetic/phosphodeficient mutagenesis, glucose uptake assays","pmids":["28325821"],"confidence":"High","gaps":["Other kinases that may phosphorylate Exo84 in adipocytes unknown","whether TBK1-Exo84 axis operates in non-adipocyte insulin target tissues untested"]},{"year":2019,"claim":"Extension of Cdk1 phosphoregulation to late G1 phase showed that Exo84 phosphorylation coordinates exocyst disassembly not only in mitosis but also at G1/S, broadening the cell-cycle window of secretory growth control.","evidence":"Cdk1 kinase assay, phosphomutant yeast strains, secretion assays, conditional cdc mutants","pmids":["31171719"],"confidence":"High","gaps":["Whether G1/S phosphorylation is conserved in mammalian cells unknown","interplay between Cdk1 and TBK1 phosphorylation sites not explored"]},{"year":2020,"claim":"Human genetic studies linked biallelic loss-of-function EXOC8 variants to a neurodevelopmental disorder with brain atrophy and seizures, establishing that EXOC8 is non-redundant for cerebral cortex development.","evidence":"Homozygosity mapping, exome sequencing, Sanger validation, zebrafish model","pmids":["32103185"],"confidence":"Medium","gaps":["Cellular mechanism (neural progenitor proliferation vs. migration vs. survival) not demonstrated for EXOC8 specifically","genotype–phenotype spectrum with hypomorphic alleles unexplored","rescue experiments in patient cells not performed"]},{"year":null,"claim":"Key unresolved questions include the structural basis of Exo84's dual scaffolding roles in exocytosis versus autophagy, how multiple phosphorylation inputs (Cdk1, TBK1, and potentially others) are integrated on the same subunit, and the precise neural cell types and trafficking cargoes disrupted in EXOC8-associated neurological disease.","evidence":"","pmids":[],"confidence":"Low","gaps":["Full-length Exo84 structure in the context of the assembled exocyst lacking","no conditional mammalian neural knockout to dissect developmental timing","systematic phosphoproteomics of EXOC8 across tissues not reported"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[5,6,10,17]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[2,8]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[2,5,8,17]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[5,10,14]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[5,10]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[2,5,8,13,17]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[10]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[5,6,17]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[13,18]},{"term_id":"R-HSA-1500931","term_label":"Cell-Cell communication","supporting_discovery_ids":[9]}],"complexes":["Exocyst complex (Sec6/8 complex)"],"partners":["RALA","RALB","EXOC2","EXOC3","EXOC7","TBK1","ULK1","VPS34"],"other_free_text":[]},"mechanistic_narrative":"EXOC8 (Exo84) is an essential subunit of the octameric exocyst complex that tethers secretory vesicles to the plasma membrane, functioning as a direct effector of Ral GTPases to regulate exocyst assembly, polarized secretion, autophagy, and insulin-stimulated GLUT4 trafficking. Its Ral-binding domain adopts a PH-domain fold that competitively engages active RalA/RalB with Sec5, enabling Ral-dependent toggling between exocyst subcomplexes; upon nutrient starvation, RalB–Exo84 interaction recruits ULK1 and Beclin1–VPS34 autophagy initiation complexes to nascent autophagosomes [PMID:15920473, PMID:21241894]. Phosphorylation of EXOC8 by Cdk1 during mitosis and G1/S disrupts exocyst assembly to arrest secretory growth, while TBK1 phosphorylation downstream of insulin–RalA signaling modulates GLUT4 vesicle docking in adipocytes [PMID:23836930, PMID:31171719, PMID:28325821]. Loss-of-function variants in EXOC8 cause a recessively inherited neurodevelopmental disorder with brain atrophy, seizures, and microcephaly [PMID:32103185]."},"prefetch_data":{"uniprot":{"accession":"Q8IYI6","full_name":"Exocyst complex component 8","aliases":["Exocyst complex 84 kDa subunit"],"length_aa":725,"mass_kda":81.8,"function":"Component of the exocyst complex involved in the docking of exocytic vesicles with fusion sites on the plasma membrane","subcellular_location":"Cytoplasm; Cytoplasm, perinuclear region; Cell projection, growth cone; Cell projection","url":"https://www.uniprot.org/uniprotkb/Q8IYI6/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/EXOC8","classification":"Not Classified","n_dependent_lines":467,"n_total_lines":1208,"dependency_fraction":0.38658940397350994},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/EXOC8","total_profiled":1310},"omim":[{"mim_id":"619076","title":"NEURODEVELOPMENTAL DISORDER WITH MICROCEPHALY, SEIZURES, AND BRAIN ATROPHY; NEDMISB","url":"https://www.omim.org/entry/619076"},{"mim_id":"619072","title":"NEURODEVELOPMENTAL DISORDER WITH SEIZURES AND BRAIN ATROPHY; NEDSEBA","url":"https://www.omim.org/entry/619072"},{"mim_id":"617368","title":"SH3 DOMAIN-BINDING PROTEIN 1; SH3BP1","url":"https://www.omim.org/entry/617368"},{"mim_id":"615283","title":"EXOCYST COMPLEX COMPONENT 8; EXOC8","url":"https://www.omim.org/entry/615283"},{"mim_id":"613439","title":"CONSORTIN; CNST","url":"https://www.omim.org/entry/613439"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Cytosol","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/EXOC8"},"hgnc":{"alias_symbol":["SEC84","EXO84","Exo84p"],"prev_symbol":[]},"alphafold":{"accession":"Q8IYI6","domains":[{"cath_id":"-","chopping":"23-77","consensus_level":"medium","plddt":78.2682,"start":23,"end":77},{"cath_id":"2.30.29.30","chopping":"168-294","consensus_level":"high","plddt":80.0513,"start":168,"end":294},{"cath_id":"-","chopping":"347-528","consensus_level":"high","plddt":82.2987,"start":347,"end":528},{"cath_id":"1.10.357","chopping":"546-714","consensus_level":"high","plddt":85.3208,"start":546,"end":714}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IYI6","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IYI6-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IYI6-F1-predicted_aligned_error_v6.png","plddt_mean":73.88},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=EXOC8","jax_strain_url":"https://www.jax.org/strain/search?query=EXOC8"},"sequence":{"accession":"Q8IYI6","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8IYI6.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8IYI6/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IYI6"}},"corpus_meta":[{"pmid":"10438536","id":"PMC_10438536","title":"Exo84p is an exocyst protein essential for secretion.","date":"1999","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10438536","citation_count":160,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"15920473","id":"PMC_15920473","title":"Exo84 and Sec5 are competitive regulatory Sec6/8 effectors to the RalA GTPase.","date":"2005","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/15920473","citation_count":122,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"16249794","id":"PMC_16249794","title":"The structures of exocyst subunit Exo70p and the Exo84p C-terminal domains reveal a common motif.","date":"2005","source":"Nature structural & molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/16249794","citation_count":119,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"17698923","id":"PMC_17698923","title":"The Drosophila homolog of the Exo84 exocyst subunit promotes apical epithelial identity.","date":"2007","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/17698923","citation_count":100,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"15788396","id":"PMC_15788396","title":"The critical role of Exo84p in the organization and polarized localization of the exocyst complex.","date":"2005","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15788396","citation_count":37,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"28325821","id":"PMC_28325821","title":"Phosphorylation of the exocyst protein Exo84 by TBK1 promotes insulin-stimulated GLUT4 trafficking.","date":"2017","source":"Science signaling","url":"https://pubmed.ncbi.nlm.nih.gov/28325821","citation_count":31,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"23836930","id":"PMC_23836930","title":"Mitotic phosphorylation of Exo84 disrupts exocyst assembly and arrests cell growth.","date":"2013","source":"The Journal of cell 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Exo84p co-immunoprecipitates with exocyst components, and its assembly into the complex requires Sec5p and Sec10p. Exo84p localizes to the bud tip and mother/daughter connection (sites of polarized secretion) and is mislocalized in sec5 mutants.\",\n      \"method\": \"Co-immunoprecipitation, velocity gradient sedimentation, yeast two-hybrid, fluorescence microscopy, invertase secretion assay, electron microscopy\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods, foundational paper, 160 citations\",\n      \"pmids\": [\"10438536\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The Ral-binding domain of Exo84 adopts a pleckstrin homology (PH) domain fold and directly binds active RalA via an interface involving both switch regions. Exo84 and Sec5 competitively bind to active RalA, providing a structural mechanism for RalA-regulated assembly of the exocyst (Sec6/8) complex.\",\n      \"method\": \"Crystal structure of Exo84 RBD–RalA complex, mutagenesis binding studies, biochemical competition assays\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure plus mutagenesis, 122 citations\",\n      \"pmids\": [\"15920473\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The C-terminal domains of Exo84p form an 80 Å rod with the same novel alpha-helical bundle fold as the N terminus of Exo70p, suggesting exocyst subunits share a common structural motif of helical modules strung into long rods.\",\n      \"method\": \"X-ray crystallography (2.85 Å resolution for Exo84p C-terminal domains)\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure, 119 citations\",\n      \"pmids\": [\"16249794\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Exo84p plays a critical role in exocyst complex assembly and polarized targeting: several exocyst members (Sec10p, Sec15p, Exo70p) require Exo84p for their polarization, and biochemical analyses show assembly of these subunits with the rest of the complex requires Exo84p. Pre-Golgi traffic and polarized actin organization are required for Exo84p localization, but no single exocyst protein controls Exo84p polarization.\",\n      \"method\": \"Temperature-sensitive yeast exo84 mutants, fluorescence microscopy, electron microscopy, cargo protein traffic analysis, biochemical fractionation/co-immunoprecipitation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods in systematic mutant analysis\",\n      \"pmids\": [\"15788396\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Drosophila Exo84 (ortholog of EXOC8) is required for apical localization of the Crumbs transmembrane protein in epithelial cells; loss of Exo84 causes mislocalization of adherens junction proteins, defects in apical cuticle secretion, and accumulation of apical/junction proteins in an expanded recycling endosome compartment.\",\n      \"method\": \"Drosophila genetics (loss-of-function mutants), fluorescence microscopy, epistasis with crumbs/dlg/lgl mutants\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with defined phenotypic readouts, 100 citations\",\n      \"pmids\": [\"17698923\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Yeast Exo84p physically associates with Snp1p (yeast U1-70K homolog) and has a direct role in pre-mRNA splicing: temperature-sensitive exo84 mutations increase pre-mRNA:mRNA ratios and cause defects in splicing and prespliceosome formation in vitro.\",\n      \"method\": \"Two-hybrid screen, co-immunoprecipitation, in vitro splicing assay, RNA analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — co-IP and in vitro splicing assay, single lab study\",\n      \"pmids\": [\"11425851\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"During mitosis, Cdk1 bound to the mitotic cyclin Clb2 directly phosphorylates Exo84p, disrupting exocyst complex assembly and thereby inhibiting exocytosis and cell surface expansion; this mechanism coordinates cell growth arrest with cell cycle progression.\",\n      \"method\": \"CDK kinase assay, immunoprecipitation, phosphodeficient/phosphomimetic exo84 mutants, electron microscopy, secretion assays in yeast\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct kinase assay with mutagenesis plus functional secretion readouts\",\n      \"pmids\": [\"23836930\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"In Candida albicans, Exo84 is phosphorylated by Cdk1 in complex with the hyphal-specific cyclin Hgc1; unlike in S. cerevisiae where phosphorylation disrupts exocyst assembly, CaExo84 phosphorylation alters its affinity for phosphatidylserine to promote recycling at the plasma membrane and efficient hyphal extension throughout mitosis.\",\n      \"method\": \"CDK kinase assay, phosphodeficient/phosphomimetic mutants, phosphatidylserine binding assay, fluorescence microscopy, hyphal growth assays\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct kinase assay, lipid binding assay, mutagenesis, multiple phenotypic readouts\",\n      \"pmids\": [\"24501427\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"TBK1 phosphorylates EXOC8 (Exo84) upon RalA activation in response to insulin signaling; phosphorylation of Exo84 by TBK1 reduces its affinity for RalA, enabling its release from the exocyst complex and controlling GLUT4 vesicle engagement/disengagement at the plasma membrane. Phosphorylation-mimicking or nonphosphorylatable Exo84 mutants both block insulin-stimulated GLUT4 translocation.\",\n      \"method\": \"In vitro kinase assay, siRNA knockdown, adipocyte-specific TBK1 knockout, dominant-negative TBK1, TBK1 inhibitors, phosphomimetic/phosphodeficient Exo84 mutants, GLUT4 translocation and glucose uptake assays\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — kinase assay, genetic KO, mutagenesis, multiple orthogonal approaches\",\n      \"pmids\": [\"28325821\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Cdk1 also directly phosphorylates Exo84 in late G1 phase (not only in mitosis), inhibiting exocyst complex assembly, exocytic secretion, and cell growth at the G1/S transition.\",\n      \"method\": \"CDK kinase assay, immunoprecipitation, phosphodeficient/phosphomimetic exo84 mutants, conditional cdc mutants, exocytic secretion assay, microscopy\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct kinase assay with mutagenesis and multiple functional readouts\",\n      \"pmids\": [\"31171719\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"RalA binding to its exocyst effectors Sec5 and Exo84 (EXOC8) is required for cell migration and invasion of prostate cancer cells; blocking RalA–exocyst interaction causes morphological changes and migration/invasion defects.\",\n      \"method\": \"Dominant-negative RalA effector-loop mutants, cell migration and invasion assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — functional KD with phenotypic readout but limited biochemical characterization of the interaction\",\n      \"pmids\": [\"22761837\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"C. elegans exoc-8 (EXOC8 ortholog) functions in endocytic trafficking in intestinal epithelial cells: exoc-8 mutations cause increased size of rab-10 RNAi-induced endocytic vacuoles, up-regulation of RAB-10 expression, and altered accumulation of endocytic marker proteins, placing exoc-8 functionally downstream of/linked to rab-10.\",\n      \"method\": \"C. elegans genetics, RNAi epistasis screen, fluorescence microscopy of endocytic markers\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with endocytic marker readouts in C. elegans ortholog\",\n      \"pmids\": [\"22389680\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Loss-of-function variants in human EXOC8 cause a disorder of cerebral cortical development (brain atrophy, seizures, developmental delay), and modeling of exoc7 (paralog) deficiency in zebrafish causes microcephaly, establishing an essential role for the exocyst pathway (including EXOC8) in neural progenitor cell proliferation and survival.\",\n      \"method\": \"Human genetics (exome sequencing, homozygosity mapping), zebrafish knockout modeling\",\n      \"journal\": \"Genetics in medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — human LOF variants plus zebrafish KO, but direct mechanism for EXOC8 in neural progenitors not fully resolved\",\n      \"pmids\": [\"32103185\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Active Merlin competitively inhibits RalB binding to its exocyst effectors Sec5 and Exo84 (EXOC8) in a PIP2-dependent manner and regulates the kinetics of exocytosis in a RalB-dependent manner; direct binding assays identified RalB as a Merlin binding partner.\",\n      \"method\": \"Proximity biotinylation (BioID), direct binding assays, competitive binding assays, exocytosis kinetics assay\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — preprint, single lab, competitive binding assay without structural validation\",\n      \"pmids\": [\"bio_10.1101_2025.06.13.659557\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"EXOC8 (Exo84) is a conserved, essential subunit of the octameric exocyst complex that tethers secretory vesicles to the plasma membrane; it directly binds active RalA/RalB via a PH-domain fold, competes with Sec5 for RalA binding, is required for the assembly and polarized targeting of other exocyst subunits, and its activity is dynamically regulated by phosphorylation—by Cdk1 in late G1 and mitosis (disrupting complex assembly to arrest growth) and by TBK1 in response to insulin signaling (reducing RalA affinity to control GLUT4 vesicle fusion), while in human neural development loss-of-function causes cortical malformations.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\nI'll systematically classify each paper, then extract discoveries from KEEP papers only.\n\n**Classification:**\n\nRETRIEVED PAPERS:\n1. PMID:10438536 - Yeast Exo84p exocyst component → KEEP (ortholog)\n2. PMID:15920473 - Crystal structure Exo84 RBD with RalA → KEEP\n3. PMID:16249794 - Structure of Exo84p C-terminal domains → KEEP (ortholog)\n4. PMID:17698923 - Drosophila Exo84 epithelial polarity → KEEP (ortholog)\n5. PMID:15788396 - Yeast Exo84p organization/polarization → KEEP (ortholog)\n6. PMID:28325821 - TBK1 phosphorylates Exo84, GLUT4 trafficking → KEEP\n7. PMID:23836930 - Mitotic phosphorylation of Exo84 by Cdk1 → KEEP (ortholog)\n8. PMID:24501427 - C. albicans Exo84 phosphorylation by Cdk1-Hgc1 → KEEP (ortholog)\n9. PMID:11425851 - Yeast Exo84p role in pre-mRNA splicing → KEEP (ortholog)\n10. PMID:32103185 - EXOC8 variants cause cortical development disorder → KEEP\n11. PMID:22761837 - Sec5/Exo84 mediate distinct aspects of RalA polarization → KEEP\n12. PMID:22389680 - C. elegans exoc-8 mutants, endocytic trafficking → KEEP (ortholog)\n13. PMID:35460391 - EXOC8 nonsense variant, neurodevelopmental disorder → KEEP (clinical, limited mechanism)\n14. PMID:31171719 - CDK-mediated phosphorylation Exo84 in late G1 → KEEP (ortholog)\n15. PMID:40189122 - Fish EXOC8 in SGIV infection → KEEP (ortholog, vertebrate)\n16. bio_10.1101_2025.06.13.659557 - Merlin/RalB/Exo84 → KEEP (preprint)\n17. bio_10.1101_2024.11.07.24316796 - Proteomics ADPKD/IA, EXOC8 upregulated → EXCLUDE (expression correlation, no mechanism)\n\nGENE2PUBMED PAPERS:\n- PMID:16189514, 12477932, 14702039, 25416956, 32296183, 19060904, 15489334, 35271311, 16344560, 26344197, 21873635 - Large-scale interactome/cDNA mapping → EXCLUDE (no specific EXOC8 mechanism)\n- PMID:9655500 - Mammalian brain sec6/8 complex; 84-kDa subunit mentioned → KEEP\n- PMID:12687004 - Exocyst required for GLUT4 targeting (Exo70/TC10 focus, Sec6/Sec8 but not Exo84 specifically) → EXCLUDE (Exo70-centric)\n- PMID:19615732 - DUB interactome → EXCLUDE (no EXOC8 specific mechanism)\n- PMID:26186194, 28514442, 33961781 - BioPlex networks → EXCLUDE\n- PMID:22939629 - Census of protein complexes → EXCLUDE\n- PMID:25127057 - TRIM autophagy → EXCLUDE\n- PMID:22420621 - Exocyst review → EXCLUDE (review)\n- PMID:21241894 - RalB/Exo84 autophagosome assembly → KEEP\n- PMID:27173435 - Cilia proteomics, exocyst subcomplexes → KEEP\n- PMID:26618866 - CFTR interactome → EXCLUDE\n- PMID:14525976 - Ral GTPases regulate exocyst via Sec5 and Exo84 → KEEP\n- PMID:9405631 - Mammalian exocyst subunit structure; 84 kDa subunit identified → KEEP\n- PMID:24344185 - WASH/exocyst at invadopodia → KEEP\n- PMID:11406615 - Brain exocyst interacts with RalA; Exo84 component identified → KEEP\n- PMID:19322201 - HuR ubiquitination → EXCLUDE (no EXOC8 connection)\n- PMID:16710414 - Chromosome 1 sequence → EXCLUDE\n- PMID:18029348 - Subcellular atlas → EXCLUDE (no specific EXOC8 mechanism)\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1997,\n      \"finding\": \"The mammalian exocyst complex contains an 84-kDa subunit (later designated EXOC8/Exo84) as a novel protein component, identified by characterization of cDNAs encoding mammalian exocyst subunits.\",\n      \"method\": \"cDNA cloning, immunoprecipitation, Western blot\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — initial identification by biochemical characterization; single lab\",\n      \"pmids\": [\"9405631\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"The mammalian brain sec6/8 (exocyst) complex, which contains the 84-kDa subunit (EXOC8), co-immunoprecipitates with septin filaments, suggesting a functional interaction between the exocyst and septin complexes at sites of membrane addition in neurons.\",\n      \"method\": \"Co-immunoprecipitation, electron microscopy\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP with structural EM; single lab\",\n      \"pmids\": [\"9655500\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Yeast Exo84p (ortholog of EXOC8) is an essential exocyst subunit required for post-Golgi secretory vesicle targeting to the plasma membrane; it localizes to sites of polarized secretion (bud tip), co-immunoprecipitates with other exocyst components, and its assembly into the exocyst complex requires Sec5p and Sec10p.\",\n      \"method\": \"Genetic depletion, invertase secretion assay, electron microscopy, co-immunoprecipitation, velocity gradient sedimentation, two-hybrid assay, fluorescence microscopy\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods (genetics, biochemistry, imaging) in foundational study\",\n      \"pmids\": [\"10438536\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Yeast Exo84p (ortholog of EXOC8) physically interacts with the U1 snRNP component Snp1p and is involved in pre-mRNA splicing; a temperature-sensitive exo84 mutation causes increased pre-mRNA:mRNA ratios and defects in in vitro splicing and prespliceosome formation, revealing an unexpected link between the exocyst and the spliceosome.\",\n      \"method\": \"Two-hybrid assay, co-immunoprecipitation, temperature-sensitive mutant analysis, in vitro splicing assay, Northern blot\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods; single lab, unexpected finding\",\n      \"pmids\": [\"11425851\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"The mammalian brain exocyst complex (including the 84-kDa EXOC8 subunit) binds active (GTP-bound) RalA in a GTP-dependent manner in nerve terminals, identifying the exocyst as an effector of neuronal RalA signaling.\",\n      \"method\": \"GTP-dependent pulldown, MALDI-TOF mass spectrometry, co-immunoprecipitation, Western blot\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — MS identification plus biochemical validation; single lab\",\n      \"pmids\": [\"11406615\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Exo84 (EXOC8) is a direct target of activated Ral GTPases in mammalian cells; Ral GTPases regulate exocyst assembly through dual interactions with both Sec5 and Exo84, and mammalian exocyst components exist as distinct subcomplexes on vesicles and the plasma membrane that are assembled by Ral signaling.\",\n      \"method\": \"Co-immunoprecipitation, GST pulldown, dominant-negative constructs, subcellular fractionation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal biochemical methods; independently supported by structural studies\",\n      \"pmids\": [\"14525976\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Crystal structure of the Ral-binding domain (RBD) of Exo84 in complex with active RalA reveals that the Exo84 RBD adopts a pleckstrin homology (PH) domain fold and that RalA engages Exo84 via both switch regions; Exo84 and Sec5 competitively bind active RalA, indicating a regulatory mechanism for Sec6/8 complex assembly.\",\n      \"method\": \"X-ray crystallography (crystal structure), mutagenesis binding studies, biochemical competition assays\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with mutagenesis validation; moderate evidence base\",\n      \"pmids\": [\"15920473\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Crystal structures of yeast Exo84p C-terminal domains reveal a long helical-bundle rod architecture (80 Å) with the same fold as the Exo70p N-terminus, suggesting exocyst subunits are composed of helical modules strung into rods, a conserved structural motif across the complex.\",\n      \"method\": \"X-ray crystallography (2.85 Å resolution), structural comparison\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution crystal structure with experimental interaction data\",\n      \"pmids\": [\"16249794\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Yeast Exo84p (ortholog of EXOC8) plays a critical role in exocyst complex assembly: several exocyst members (Sec10p, Sec15p, Exo70p) require Exo84p for their polarized localization and for their assembly into the complex, while Exo84p localization itself depends on pre-Golgi trafficking and polarized actin but not on other exocyst subunits.\",\n      \"method\": \"Temperature-sensitive mutant generation, electron microscopy, fluorescence microscopy, co-immunoprecipitation, cargo trafficking assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — systematic epistasis analysis with multiple orthogonal methods across multiple mutants\",\n      \"pmids\": [\"15788396\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Drosophila Exo84 (ortholog of EXOC8) is essential for epithelial apical identity: it is required for apical localization of the Crumbs transmembrane protein, and loss of Exo84 leads to mislocalization of adherens junction proteins, defects in apical cuticle secretion, and accumulation of apical proteins in an expanded recycling endosome.\",\n      \"method\": \"Genetic loss-of-function (mutant analysis), immunofluorescence microscopy, epistasis with dlg/lgl mutants\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with clear phenotypic readouts and pathway placement; well-cited\",\n      \"pmids\": [\"17698923\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"RalB and its effector Exo84 (EXOC8) are required for nutrient starvation-induced autophagosome biogenesis in mammalian cells; RalB activation on nascent autophagosomes drives assembly of catalytically active ULK1 and Beclin1-VPS34 complexes on the exocyst through direct binding to Exo84, enabling isolation membrane formation.\",\n      \"method\": \"RNAi knockdown, co-immunoprecipitation, immunofluorescence, autophagy flux assays, dominant-negative constructs\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods in high-impact journal; direct binding and functional epistasis established\",\n      \"pmids\": [\"21241894\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"C. elegans exoc-8 (EXOC8 ortholog) mutants display pleiotropic behavior defects resembling cilia mutants and show functional links to RAB-10-regulated endosomal trafficking; exoc-8 and exoc-7;exoc-8 double mutations cause enlarged RAB-10 RNAi-induced endocytic vacuoles and upregulation of RAB-10 expression in intestinal epithelial cells.\",\n      \"method\": \"C. elegans genetic mutant analysis, targeted RNAi screen, fluorescence microscopy, endocytic marker accumulation assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with RNAi screen; single lab, model organism\",\n      \"pmids\": [\"22389680\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"RalA effectors Sec5 and Exo84 (EXOC8) mediate distinct aspects of cell polarization: RalA-Exocyst interactions are directly required for migration and invasion of prostate cancer cells, and blocking RalA-Exocyst binding causes morphological changes and defects in single and coordinated cell migration.\",\n      \"method\": \"Dominant-negative constructs, cell migration assays, invasion assays, morphological analysis\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — functional phenotype established but limited mechanistic resolution of Sec5 vs Exo84 contributions\",\n      \"pmids\": [\"22761837\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Mitotic phosphorylation of yeast Exo84p (EXOC8 ortholog) by Cdk1-Clb2 disrupts exocyst complex assembly, thereby inhibiting exocytosis and cell surface expansion during the metaphase-anaphase transition, providing a molecular mechanism for growth arrest during mitosis.\",\n      \"method\": \"CDK kinase assay, phosphorylation site mutagenesis, co-immunoprecipitation, exocytosis assays, fluorescence microscopy, conditional mutants\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro kinase assay with mutagenesis plus multiple cellular readouts; strong mechanistic evidence\",\n      \"pmids\": [\"23836930\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The exocyst complex (including Exo84/EXOC8) interacts with endosomal WASH complex on MT1-MMP-containing late endosomes in breast carcinoma cells; this interaction is required for exocytic delivery of MT1-MMP at invadopodia to enable matrix degradation and tumor cell invasion.\",\n      \"method\": \"Co-immunoprecipitation, RNAi knockdown, live-cell imaging, matrix degradation assays, proximity ligation assay\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple methods establishing the interaction and functional consequence; exocyst complex broadly implicated\",\n      \"pmids\": [\"24344185\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"In Candida albicans, phosphorylation of CaExo84 (EXOC8 ortholog) by Cdk1-Hgc1 promotes hyphal extension by altering its affinity for phosphatidylserine, enabling recycling at the plasma membrane without disrupting its localization — a mechanistically distinct outcome from yeast Exo84 phosphorylation, demonstrating functional divergence of Cdk1 regulation of this conserved exocyst subunit.\",\n      \"method\": \"Phosphorylation site mutagenesis, CDK assay, fluorescence microscopy, phosphatidylserine binding assay, genetic analysis\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — mutagenesis plus lipid binding assays; single lab\",\n      \"pmids\": [\"24501427\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The exocyst complex, including EXOC8, is identified as a component of the ciliary protein landscape through affinity proteomics of 217 tagged ciliary proteins, and sub-complexes of the exocyst are biochemically validated, linking exocyst function to ciliogenesis.\",\n      \"method\": \"Affinity proteomics, AP-MS, biochemical validation of sub-complexes, genetic variant analysis in ciliary disease patients\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — large-scale proteomics with biochemical sub-complex validation; EXOC8 specific role in cilia requires further study\",\n      \"pmids\": [\"27173435\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"TBK1 directly phosphorylates EXOC8 (Exo84) upon RalA activation by insulin in adipocytes; phosphorylation reduces Exo84's affinity for RalA, enabling its release from the exocyst complex, which is required for proper engagement and disengagement of GLUT4 vesicles at the plasma membrane; both phosphorylation-mimicking and non-phosphorylatable Exo84 mutants block insulin-stimulated GLUT4 translocation.\",\n      \"method\": \"In vitro kinase assay, co-immunoprecipitation, siRNA knockdown, adipocyte-specific TBK1 knockout, glucose uptake assays, phosphomimetic/phosphodeficient mutagenesis, dominant-negative TBK1\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro kinase assay, mutagenesis, KO, and multiple functional readouts; strong mechanistic evidence\",\n      \"pmids\": [\"28325821\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Yeast Exo84p (EXOC8 ortholog) is phosphorylated by Cdk1 in late G1 phase (in addition to mitosis), and this phosphorylation impairs exocyst complex assembly, exocytic secretion, and cell growth, contributing to coordination of growth arrest at the G1/S transition.\",\n      \"method\": \"CDK kinase assay, immunoprecipitation, phosphodeficient/phosphomimetic exo84 mutants, secretion assays, fluorescence microscopy, conditional cdc mutants\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro CDK assay with mutagenesis and multiple cellular readouts; extends prior mitotic phosphorylation discovery\",\n      \"pmids\": [\"31171719\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Loss-of-function variants in EXOC8 in humans cause a recessively inherited neurodevelopmental disorder characterized by brain atrophy, seizures, developmental delay, and in severe cases microcephaly, establishing an essential role for EXOC8 in human cerebral cortex development.\",\n      \"method\": \"Homozygosity mapping, exome sequencing, Sanger sequencing, zebrafish exoc7 knockout model\",\n      \"journal\": \"Genetics in medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — human genetics with animal model validation; mechanism (neural progenitor proliferation/survival) inferred rather than directly demonstrated for EXOC8\",\n      \"pmids\": [\"32103185\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Active Merlin (NF2 tumor suppressor) competitively inhibits RalB binding to its exocyst effectors Sec5 and Exo84 (EXOC8), and regulates the kinetics of exocytosis in a RalB-dependent manner; proximity biotinylation and direct binding assays identified RalA and RalB as high-affinity PIP2-dependent Merlin binding proteins.\",\n      \"method\": \"Proximity biotinylation (BioID), direct binding assays, co-localization, competitive binding assays, exocytosis kinetics assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct binding assays with functional exocytosis readout; preprint, not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2025.06.13.659557\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"EXOC8 (Exo84) is an essential subunit of the octameric exocyst complex that tethers secretory vesicles to the plasma membrane for exocytosis; it directly binds active RalA/RalB GTPases via a PH-domain fold RBD (competitively with Sec5), serves as a scaffold for assembly of ULK1 and Beclin1-VPS34 autophagy complexes during starvation, is phosphorylated by Cdk1 during mitosis and G1/S to disrupt exocyst assembly and arrest cell growth, is phosphorylated by TBK1 downstream of insulin-RalA signaling to regulate GLUT4 vesicle docking/fusion in adipocytes, and is required for epithelial apical polarity (Crumbs localization) and human cerebral cortex development, with loss-of-function mutations causing a recessively inherited neurodevelopmental disorder.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"EXOC8 (Exo84) is an essential subunit of the octameric exocyst complex that tethers secretory vesicles to the plasma membrane to drive polarized exocytosis, and additionally participates in endocytic recycling and epithelial polarity. Its N-terminal pleckstrin homology (PH)-domain fold directly binds active RalA/RalB GTPases in competition with Sec5, providing a GTPase-regulated switch for exocyst assembly, while its C-terminal helical-bundle rod shares a conserved structural motif with other exocyst subunits [PMID:15920473, PMID:16249794, PMID:10438536]. EXOC8 is dynamically regulated by phosphorylation: Cdk1 phosphorylates it in late G1 and mitosis to disrupt exocyst assembly and coordinate growth arrest with cell cycle progression, whereas TBK1 phosphorylates it downstream of insulin–RalA signaling to control GLUT4 vesicle engagement at the plasma membrane [PMID:23836930, PMID:31171719, PMID:28325821]. Loss-of-function variants in human EXOC8 cause a neurodevelopmental disorder with cortical malformations, seizures, and developmental delay [PMID:32103185].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Identification of Exo84p as an essential exocyst subunit established that the complex contains an eighth component required for vesicle tethering and polarized secretion.\",\n      \"evidence\": \"Co-immunoprecipitation, gradient sedimentation, two-hybrid, invertase secretion assays, and EM in S. cerevisiae\",\n      \"pmids\": [\"10438536\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which Exo84p is recruited to polarized sites was unknown\", \"Direct membrane or Rab interactions not yet identified\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"A yeast study linked Exo84p to pre-mRNA splicing through physical association with the U1-70K homolog Snp1p, raising the question of whether EXOC8 has moonlighting nuclear functions.\",\n      \"evidence\": \"Two-hybrid, co-IP, and in vitro splicing assays in S. cerevisiae\",\n      \"pmids\": [\"11425851\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Not replicated in mammalian systems\", \"Mechanism linking exocyst to spliceosome unclear\", \"No structural characterization of Exo84p–Snp1p interface\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Structural and biochemical work revealed how EXOC8 engages the exocyst: its Ral-binding domain adopts a PH-domain fold that directly contacts active RalA in competition with Sec5, while its C-terminal helical-bundle rod shares a conserved fold with Exo70, and genetic analysis showed Exo84p is required for polarized targeting of multiple exocyst subunits.\",\n      \"evidence\": \"Crystal structures of Exo84 RBD–RalA complex and Exo84p C-terminal domains; mutagenesis; competition binding assays; yeast ts-mutant phenotyping\",\n      \"pmids\": [\"15920473\", \"16249794\", \"15788396\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full-length exocyst structure not resolved\", \"Lipid-binding properties of PH-domain fold not tested\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"In vivo evidence in Drosophila epithelia demonstrated that Exo84 functions beyond exocytic vesicle tethering, being required for apical membrane protein delivery and adherens junction maintenance via recycling endosome traffic.\",\n      \"evidence\": \"Drosophila loss-of-function mutants with fluorescence microscopy and genetic epistasis\",\n      \"pmids\": [\"17698923\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Exo84 acts directly in recycling endosome sorting or indirectly through exocyst-mediated tethering was unresolved\", \"Mammalian epithelial polarity role not tested\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Functional studies in cancer cells and C. elegans intestinal epithelia broadened EXOC8's roles to cell migration/invasion (via RalA–exocyst signaling) and endocytic trafficking (downstream of RAB-10).\",\n      \"evidence\": \"Dominant-negative RalA effector-loop mutants in prostate cancer cells; C. elegans exoc-8 RNAi epistasis with rab-10\",\n      \"pmids\": [\"22761837\", \"22389680\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific EXOC8 phosphorylation or binding events driving migration not identified\", \"RAB-10–EXOC8 physical interaction not shown directly\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Discovery that Cdk1–Clb2 directly phosphorylates Exo84p during mitosis to disrupt exocyst assembly provided the first mechanism coupling cell cycle progression to exocytosis arrest.\",\n      \"evidence\": \"In vitro CDK kinase assay, phosphomimetic/phosphodeficient exo84 mutants, secretion assays, EM in S. cerevisiae\",\n      \"pmids\": [\"23836930\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the same sites are phosphorylated in mammalian EXOC8 was unknown\", \"Phosphatase responsible for dephosphorylation not identified\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"In C. albicans, Cdk1 phosphorylation of Exo84 alters phosphatidylserine binding rather than disrupting exocyst assembly, revealing species-specific downstream consequences of the same regulatory input.\",\n      \"evidence\": \"CDK kinase assay, phosphomutants, phosphatidylserine binding assay, hyphal growth assays in C. albicans\",\n      \"pmids\": [\"24501427\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for differential outcome of phosphorylation across species not resolved\", \"Whether lipid-binding regulation occurs in mammalian EXOC8 unknown\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"TBK1 was identified as a kinase that phosphorylates EXOC8 in response to insulin–RalA signaling, reducing RalA affinity and controlling GLUT4 vesicle engagement at the plasma membrane — linking EXOC8 regulation to glucose homeostasis.\",\n      \"evidence\": \"In vitro kinase assay, adipocyte-specific TBK1 KO, TBK1 inhibitors, phosphomimetic/nonphosphorylatable Exo84 mutants, GLUT4 translocation and glucose uptake assays\",\n      \"pmids\": [\"28325821\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Phosphorylation sites on EXOC8 relative to Cdk1 sites not compared\", \"In vivo metabolic consequences in whole-animal models not reported\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Extension of Cdk1 regulation to late G1 phase demonstrated that EXOC8 phosphorylation coordinates growth arrest at both the G1/S transition and mitosis, broadening the cell cycle window of exocyst inhibition.\",\n      \"evidence\": \"CDK kinase assay, conditional cdc mutants, phosphomutants, exocytic secretion assays in S. cerevisiae\",\n      \"pmids\": [\"31171719\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether G1-phase phosphorylation uses the same or distinct sites as mitotic phosphorylation not fully mapped\", \"Mammalian CDK regulation of EXOC8 not demonstrated\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Human genetic evidence established that EXOC8 loss-of-function causes a neurodevelopmental syndrome with cortical malformations, linking exocyst function to neural progenitor cell biology.\",\n      \"evidence\": \"Exome sequencing and homozygosity mapping in affected families; zebrafish exoc7 KO modeling\",\n      \"pmids\": [\"32103185\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct cellular mechanism of EXOC8 loss in human neural progenitors not resolved\", \"Zebrafish validation used exoc7 paralog, not exoc8 directly\", \"No patient-derived cell studies\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis for EXOC8 integration into the complete mammalian exocyst, the identity and regulation of phosphatases that reverse Cdk1/TBK1-mediated EXOC8 phosphorylation, the mechanism by which EXOC8 loss impairs cortical development, and whether EXOC8's reported splicing function represents a genuine moonlighting activity.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full mammalian exocyst structure with EXOC8 not available\", \"Phosphatase(s) counteracting EXOC8 phosphorylation unidentified\", \"Neural progenitor-specific role of EXOC8 mechanistically uncharacterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 3]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 3, 4]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 8]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [4, 11]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [0, 3, 4, 8]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [6, 9]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 8]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [8]}\n    ],\n    \"complexes\": [\n      \"exocyst complex (Sec6/8 complex)\"\n    ],\n    \"partners\": [\n      \"RALA\",\n      \"RALB\",\n      \"EXOC2\",\n      \"EXOC5\",\n      \"EXOC7\",\n      \"TBK1\",\n      \"CDK1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"EXOC8 (Exo84) is an essential subunit of the octameric exocyst complex that tethers secretory vesicles to the plasma membrane, functioning as a direct effector of Ral GTPases to regulate exocyst assembly, polarized secretion, autophagy, and insulin-stimulated GLUT4 trafficking. Its Ral-binding domain adopts a PH-domain fold that competitively engages active RalA/RalB with Sec5, enabling Ral-dependent toggling between exocyst subcomplexes; upon nutrient starvation, RalB–Exo84 interaction recruits ULK1 and Beclin1–VPS34 autophagy initiation complexes to nascent autophagosomes [PMID:15920473, PMID:21241894]. Phosphorylation of EXOC8 by Cdk1 during mitosis and G1/S disrupts exocyst assembly to arrest secretory growth, while TBK1 phosphorylation downstream of insulin–RalA signaling modulates GLUT4 vesicle docking in adipocytes [PMID:23836930, PMID:31171719, PMID:28325821]. Loss-of-function variants in EXOC8 cause a recessively inherited neurodevelopmental disorder with brain atrophy, seizures, and microcephaly [PMID:32103185].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Identification of an 84-kDa protein as a novel mammalian exocyst subunit established EXOC8 as an integral component of the secretory vesicle tethering machinery.\",\n      \"evidence\": \"cDNA cloning and immunoprecipitation of mammalian exocyst complex\",\n      \"pmids\": [\"9405631\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mammalian-specific function of Exo84 vs. other subunits not defined\", \"no loss-of-function data in mammalian cells at this stage\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Genetic depletion and biochemical reconstitution in yeast demonstrated that Exo84p is essential for post-Golgi vesicle targeting and that its assembly into the exocyst depends on Sec5p/Sec10p, establishing its position in the complex hierarchy.\",\n      \"evidence\": \"Yeast depletion strains, invertase secretion assay, co-IP, velocity sedimentation, EM\",\n      \"pmids\": [\"10438536\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mammalian essentiality not yet tested\", \"direct membrane-binding properties unknown\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Discovery that Exo84 is a direct Ral GTPase effector—alongside Sec5—revealed that Ral signaling assembles distinct exocyst subcomplexes from vesicular and plasma-membrane pools, answering how upstream signaling controls exocyst assembly.\",\n      \"evidence\": \"Co-IP, GST pulldown, dominant-negative constructs, subcellular fractionation in mammalian cells\",\n      \"pmids\": [\"14525976\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of Ral–Exo84 interaction unknown\", \"relative contributions of Sec5 vs Exo84 to exocytosis unclear\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Crystal structures of the Exo84 Ral-binding domain (PH-fold) in complex with RalA, and of yeast Exo84p helical-bundle domains, provided the atomic basis for competitive RalA engagement with Sec5 and revealed a conserved helical-rod architecture across exocyst subunits.\",\n      \"evidence\": \"X-ray crystallography (human RBD–RalA complex; yeast C-terminal domains at 2.85 Å), mutagenesis binding studies\",\n      \"pmids\": [\"15920473\", \"16249794\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full-length Exo84 structure not available\", \"how competitive Ral binding switches exocyst configuration in vivo undetermined\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Systematic epistasis in yeast showed that Exo84p is required for polarized localization of Sec10p, Sec15p, and Exo70p and for their assembly into the holocomplex, while Exo84p localization itself depends on actin and pre-Golgi traffic, establishing Exo84 as an early-acting assembly scaffold.\",\n      \"evidence\": \"Temperature-sensitive mutants, co-IP, fluorescence microscopy, cargo trafficking assays in S. cerevisiae\",\n      \"pmids\": [\"15788396\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mammalian Exo84 scaffolding hierarchy not tested\", \"mechanism of actin-dependent Exo84 recruitment unknown\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Drosophila genetic studies revealed that Exo84 is essential for epithelial apical identity by trafficking Crumbs to the apical surface and maintaining adherens junctions, extending exocyst function from bulk secretion to cell polarity.\",\n      \"evidence\": \"Drosophila loss-of-function mutants, immunofluorescence, epistasis with dlg/lgl\",\n      \"pmids\": [\"17698923\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mammalian epithelial polarity role not directly shown\", \"cargo specificity mechanism for Crumbs vs other cargoes unknown\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Demonstration that RalB–Exo84 interaction nucleates ULK1 and Beclin1–VPS34 complexes on nascent autophagosomes during starvation established a non-canonical role for Exo84 as an autophagy scaffold distinct from its exocytic function.\",\n      \"evidence\": \"RNAi, co-IP, immunofluorescence, autophagy flux assays, dominant-negative constructs in mammalian cells\",\n      \"pmids\": [\"21241894\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of Exo84–ULK1/Beclin1 interaction unknown\", \"whether autophagy and exocytosis roles are mutually exclusive in real time undetermined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Cdk1 phosphorylation of Exo84 during mitosis was shown to disrupt exocyst assembly and inhibit exocytosis, providing a direct molecular mechanism coupling cell-cycle progression to growth arrest.\",\n      \"evidence\": \"In vitro Cdk1 kinase assay, phosphosite mutagenesis, co-IP, exocytosis assays in yeast\",\n      \"pmids\": [\"23836930\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Phosphorylation sites in mammalian EXOC8 and their cell-cycle regulation not mapped\", \"phosphatase responsible for dephosphorylation unknown\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"TBK1 phosphorylation of EXOC8 downstream of insulin–RalA signaling was found to reduce Exo84–RalA affinity and regulate GLUT4 vesicle docking/fusion cycles in adipocytes, linking Exo84 phosphoregulation to metabolic physiology.\",\n      \"evidence\": \"In vitro kinase assay, adipocyte-specific TBK1 KO, phosphomimetic/phosphodeficient mutagenesis, glucose uptake assays\",\n      \"pmids\": [\"28325821\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Other kinases that may phosphorylate Exo84 in adipocytes unknown\", \"whether TBK1-Exo84 axis operates in non-adipocyte insulin target tissues untested\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Extension of Cdk1 phosphoregulation to late G1 phase showed that Exo84 phosphorylation coordinates exocyst disassembly not only in mitosis but also at G1/S, broadening the cell-cycle window of secretory growth control.\",\n      \"evidence\": \"Cdk1 kinase assay, phosphomutant yeast strains, secretion assays, conditional cdc mutants\",\n      \"pmids\": [\"31171719\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether G1/S phosphorylation is conserved in mammalian cells unknown\", \"interplay between Cdk1 and TBK1 phosphorylation sites not explored\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Human genetic studies linked biallelic loss-of-function EXOC8 variants to a neurodevelopmental disorder with brain atrophy and seizures, establishing that EXOC8 is non-redundant for cerebral cortex development.\",\n      \"evidence\": \"Homozygosity mapping, exome sequencing, Sanger validation, zebrafish model\",\n      \"pmids\": [\"32103185\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cellular mechanism (neural progenitor proliferation vs. migration vs. survival) not demonstrated for EXOC8 specifically\", \"genotype–phenotype spectrum with hypomorphic alleles unexplored\", \"rescue experiments in patient cells not performed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis of Exo84's dual scaffolding roles in exocytosis versus autophagy, how multiple phosphorylation inputs (Cdk1, TBK1, and potentially others) are integrated on the same subunit, and the precise neural cell types and trafficking cargoes disrupted in EXOC8-associated neurological disease.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Full-length Exo84 structure in the context of the assembled exocyst lacking\", \"no conditional mammalian neural knockout to dissect developmental timing\", \"systematic phosphoproteomics of EXOC8 across tissues not reported\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [5, 6, 10, 17]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [2, 8]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [2, 5, 8, 17]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [5, 10, 14]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [5, 10]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [2, 5, 8, 13, 17]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [10]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [5, 6, 17]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [13, 18]},\n      {\"term_id\": \"R-HSA-1500931\", \"supporting_discovery_ids\": [9]}\n    ],\n    \"complexes\": [\n      \"Exocyst complex (Sec6/8 complex)\"\n    ],\n    \"partners\": [\n      \"RALA\",\n      \"RALB\",\n      \"EXOC2\",\n      \"EXOC3\",\n      \"EXOC7\",\n      \"TBK1\",\n      \"ULK1\",\n      \"VPS34\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}