{"gene":"STXBP1","run_date":"2026-06-10T10:51:54","timeline":{"discoveries":[{"year":1994,"finding":"n-Sec1/STXBP1 is a neural-specific syntaxin-binding protein that binds syntaxin 1a, 2, and 3 but not syntaxin 4, and becomes membrane-associated in the presence of syntaxin 1a, implicating it in synaptic vesicle docking and fusion.","method":"GST pulldown, subcellular fractionation, RNA blot analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct binding assay (pulldown), subcellular fractionation, replicated independently in two concurrent papers (PMID:8108429 and PMID:8134339)","pmids":["8108429","8134339"],"is_preprint":false},{"year":1994,"finding":"rbSec1/STXBP1 specifically interacts with syntaxin but not with SNAP-25 or synaptobrevin/VAMP in brain extract pulldowns, establishing a selective t-SNARE interaction.","method":"GST fusion protein pulldown from Triton X-100 brain extract","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct biochemical pulldown, replicated across two independent labs simultaneously","pmids":["8134339"],"is_preprint":false},{"year":1996,"finding":"Munc18-1/STXBP1 is phosphorylated by conventional PKC (Ca2+- and phospholipid-dependent) at Ser306 and Ser313; this phosphorylation inhibits its interaction with syntaxin. The Munc18-1 complexed with syntaxin is not phosphorylated.","method":"In vitro phosphorylation assay with recombinant Munc18-1, mutagenesis of phosphorylation sites, binding assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with mutagenesis identifying specific phosphorylation sites, replicated by subsequent studies","pmids":["8631738"],"is_preprint":false},{"year":1996,"finding":"Mouse Munc18-1 (neural isoform) functionally rescues locomotion and cholinergic defects in C. elegans unc-18 null mutants, demonstrating evolutionary conservation of its role in neurotransmitter release; the ubiquitous Munc18-3 isoform fails to rescue.","method":"Transgenic rescue of C. elegans unc-18 null mutant, behavioral and pharmacological assays","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis/rescue in vivo with isoform specificity control","pmids":["8824310"],"is_preprint":false},{"year":2000,"finding":"nSec1/Munc18-1 binds a closed conformation of syntaxin 1A; association of nSec1 with syntaxin 1A prevents assembly of the ternary SNARE complex (with SNAP-25 and VAMP2), and conversely, SNARE complex formation precludes nSec1 binding.","method":"In vitro binding assays, nondenaturing gel electrophoresis, neurotoxin treatment, chemical cross-linking of rat brain membranes","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal in vitro methods in one study, replicated by subsequent work","pmids":["10648557"],"is_preprint":false},{"year":2000,"finding":"Synaptic Munc18-1 is dynamically phosphorylated by endogenous presynaptic PKC isoforms at nerve terminals; K+-evoked depolarization increases phosphorylation within 5 s in a Ca2+-dependent manner; phosphorylation inhibits interaction with syntaxin-1A by ~50%; PP1 and PP2B are the responsible phosphatases.","method":"Phosphorylation assays in isolated rat brain nerve terminals, PKC inhibitors, phosphatase inhibitors, immunoprecipitation","journal":"The European journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple pharmacological tools and biochemical readouts in a single study with clear functional consequence","pmids":["10651895"],"is_preprint":false},{"year":2001,"finding":"Munc18-1 is required for docking of large dense-core vesicles (LDCVs) to the plasma membrane; munc18-1 null chromaffin cells show a 10-fold reduction in morphologically docked LDCVs and a 10-fold reduction in Ca2+-dependent LDCV exocytosis; acute Munc18-1 overexpression increases releasable vesicles and accelerates vesicle supply.","method":"Electron microscopy morphological docking assay, patch-clamp capacitance measurements in munc18-1 null mouse chromaffin cells, overexpression in bovine chromaffin cells","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with defined morphological and electrophysiological phenotype, complemented by overexpression","pmids":["11545717"],"is_preprint":false},{"year":2003,"finding":"Munc18-1/nSec1 Ser-313 is physiologically phosphorylated in intact chromaffin cells and synaptosomes in response to depolarization and receptor activation; PKC is the kinase and PP1/PP2B are the phosphatases responsible.","method":"Phospho-Ser-313-specific antisera in intact/permeabilized chromaffin cells and synaptosomes, kinase/phosphatase inhibitors","journal":"Journal of neurochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phospho-specific antibody approach, single lab, physiological conditions but no mutagenesis in this paper","pmids":["12950453"],"is_preprint":false},{"year":2004,"finding":"Munc18-1 co-purifies with and co-localizes with Cdk5 and neuronal cytoskeletal proteins (neurofilaments, microtubules) in rat brain, suggesting a protein-protein interaction; cytoskeletal proteins and Cdk5 co-purify with Munc18-1 in immunoaffinity chromatography.","method":"Immunoaffinity chromatography, immunofluorescence, immunohistochemistry, immuno-electron microscopy","journal":"Neurochemistry international","confidence":"Low","confidence_rationale":"Tier 3 / Weak — co-purification and co-localization without functional validation of interaction","pmids":["12963086"],"is_preprint":false},{"year":2004,"finding":"Cell-specific deletion of munc18-1 in cerebellar Purkinje cells causes specific loss of those neurons in vivo, demonstrating a cell-intrinsic function of Munc18-1 essential for prolonged neuronal survival independent of synaptic activity.","method":"Conditional Cre-lox cell-specific knockout in vivo, histology","journal":"The European journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional KO with defined cellular phenotype, single lab","pmids":["15255974"],"is_preprint":false},{"year":2004,"finding":"Munc18-1 mutants with wild-type syntaxin binding can alter kinetics of individual exocytotic release events and have reduced Mint (Mints) binding affinity, indicating syntaxin-independent functions via interactions with Mint proteins.","method":"Chromaffin cell overexpression, amperometry, binding affinity assays with Munc18-1 mutants","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional exocytosis assay with binding data, single lab","pmids":["15563604"],"is_preprint":false},{"year":2005,"finding":"Munc18-1 directly promotes the stability of syntaxin-1 (pulse-chase analysis shows Munc18-1 increases syntaxin-1 half-life); syntaxin-1 levels are reduced 70% in munc18-1 KO mice; however, residual syntaxin-1 still correctly targets to synapses and forms SDS-resistant SNARE complexes.","method":"Pulse-chase analysis in transfected HEK293 cells, immunoblotting in munc18-1 KO mice","journal":"Journal of neurochemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — pulse-chase (Tier 1-level metabolic labeling) combined with in vivo KO, two orthogonal approaches","pmids":["15935055"],"is_preprint":false},{"year":2006,"finding":"PKC phosphorylation of Munc18-1 at Ser313 potentiates vesicle pool replenishment after depleting stimulation (phosphomimetic S313D increases replenishment; non-phosphorylatable 3A mutant decreases it); vesicle docking is promoted by Munc18-1 in a phosphorylation-independent manner.","method":"Chromaffin cell overexpression with phosphomimetic and phospho-null Munc18-1 mutants, capacitance measurements, electron microscopy","journal":"Neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phospho-mutant functional analysis in chromaffin cells with electrophysiology and morphology, single lab","pmids":["16997485"],"is_preprint":false},{"year":2007,"finding":"Munc18-1 binds directly to assembled SNARE complexes containing syntaxin-1 (open conformation); this interaction involves the syntaxin-1 N-terminal Habc domain and the four-helical SNARE bundle. Munc18-1 thus has two distinct binding modes: to closed syntaxin-1 and to assembled SNARE complexes.","method":"In vitro binding assays (NMR, pulldowns), reconstituted SNARE complex","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct biochemical demonstration with multiple methods, foundational paper replicated extensively","pmids":["17301226"],"is_preprint":false},{"year":2007,"finding":"Binding of Munc18-1 to closed syntaxin-1 conformation stimulates vesicle docking; a distinct interaction mode (not closed syntaxin binding) regulates the subsequent vesicle priming step; Munc18-2 rescues docking but not priming in munc18-1 null chromaffin cells.","method":"Munc18 variant expression in munc18-1 null chromaffin cells, capacitance measurements, electron microscopy","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — null background rescue experiments with multiple Munc18 variants and two orthogonal readouts (electrophysiology + morphology)","pmids":["17687045"],"is_preprint":false},{"year":2007,"finding":"Munc18-1 is critical for plasma membrane localization of syntaxin-1 in PC12 cells; knockdown of Munc18-1 causes syntaxin-1 mislocalization to perinuclear regions (co-localizing with dense-core vesicle marker) without affecting SNAP-25 localization; reintroduction of Munc18-1 restores syntaxin-1 plasma membrane targeting.","method":"Stable knockdown cell lines, immunofluorescence, vesicle docking assay, secretion assay","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — stable KD with rescue, two independent readouts (localization + secretion), direct functional consequence","pmids":["18077557"],"is_preprint":false},{"year":2008,"finding":"S-nitrosylation of syntaxin-1a at Cys145 disrupts Munc18-1 binding to the closed conformation of syntaxin-1a in vitro; a non-nitrosylatable C145S mutant resists this effect; NO does not inhibit SNARE complex formation or Munc18-1 binding to assembled SNARE complexes; nitrosomimetic syntaxin-1a expression in cells affects Munc18-1 localization and alters exocytosis kinetics and quantal size.","method":"In vitro binding assays, site-directed mutagenesis, live-cell exocytosis assay, molecular dynamics simulations","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — mutagenesis identifying specific regulatory residue, in vitro and in vivo validation with functional readout","pmids":["18452404"],"is_preprint":false},{"year":2008,"finding":"Munc18-1 directly interacts with Rab3A; a gain-of-function E466K mutation (based on yeast Sly1p) increases this interaction, stimulates exocytosis, and increases secretory granule density at the cell periphery; the stimulatory effects require binding to closed syntaxin-1.","method":"Co-immunoprecipitation, exocytosis assays in chromaffin/PC12 cells, confocal microscopy, gain-of-function mutant analysis","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with functional correlates, single lab","pmids":["17919117"],"is_preprint":false},{"year":2008,"finding":"De novo mutations in STXBP1 identified in patients with early infantile epileptic encephalopathy; mutant proteins are thermolabile compared to wild type (CD melting experiments) and show impaired binding to syntaxin, indicating that haploinsufficiency (protein instability + reduced syntaxin binding) underlies disease.","method":"Circular dichroism melting experiments, binding assays with mutant proteins, genomic sequencing","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct biophysical and biochemical characterization of disease-linked mutants, foundational study","pmids":["18469812"],"is_preprint":false},{"year":2009,"finding":"Munc18-1 binding to SNARE complexes (open syntaxin-1) mediates synaptic vesicle priming but not Ca2+-triggered fusion; point mutations preserving closed syntaxin-1 binding but disrupting SNARE complex binding selectively impair priming; Munc18-1 and complexin-1 bind simultaneously to SNARE complexes.","method":"Lentiviral rescue in munc18-1 KO neurons, point mutagenesis, electrophysiology","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — null background rescue with separation-of-function mutants, multiple orthogonal electrophysiology readouts","pmids":["19255244"],"is_preprint":false},{"year":2009,"finding":"Binding of UNC-18 (C. elegans STXBP1 ortholog) to the N-terminus of syntaxin (UNC-64) is essential for neurotransmission in vivo; UNC-18(F113R) defective in N-terminus binding fails to rescue unc-18 null locomotion defects, whereas UNC-18(R39C) defective in closed syntaxin binding fully rescues.","method":"Transgenic rescue of C. elegans unc-18 null mutant with point mutants, behavioral assays","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo epistasis with separation-of-function mutants in defined null background","pmids":["19032153"],"is_preprint":false},{"year":2009,"finding":"Presynaptic mGluR4 binds Munc18-1 in a Ca2+-dependent manner (EC50 ~168 nM for Ca2+); Ca2+-activated calmodulin disrupts the mGluR4-Munc18-1 interaction, releasing Munc18-1 to facilitate vesicle release; this mechanism contributes to paired-pulse facilitation.","method":"Co-immunoprecipitation, permeabilized PC12 cell secretion assay, synaptic transmission recordings, Ca2+ titration","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with Ca2+ titration, functional secretion and synaptic assays; single lab","pmids":["19822743"],"is_preprint":false},{"year":2009,"finding":"Rescue experiments in Munc18-1/-2 double knockdown PC12 cells show that binding to the closed conformation of syntaxin-1 is essential for Munc18-1's stimulatory action on syntaxin-1 expression, localization, and secretion; binding to the syntaxin-1 N-terminus plays a more limited role.","method":"Double knockdown with siRNA, rescue with Munc18-1 point mutants (K46E/E59K; F115E/E132A), secretion assays, immunofluorescence","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — double KD with separation-of-function mutant rescue, multiple orthogonal readouts","pmids":["19812250"],"is_preprint":false},{"year":2010,"finding":"Munc18-1 binds to synaptobrevin and to the SNARE four-helix bundle with similar low micromolar affinity; both interactions involve the same cavity of Munc18-1 that binds syntaxin-1; the binding site on synaptobrevin is at the C-terminus of its SNARE motif.","method":"NMR spectroscopy, fluorescence anisotropy, ITC, sedimentation assays","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple biophysical methods (NMR, ITC, fluorescence) in a single rigorous study","pmids":["20102228"],"is_preprint":false},{"year":2010,"finding":"The SNARE four-helix bundle and the syntaxin N-peptide constitute a minimal complement for Munc18-1 activation of membrane fusion; the Habc domain of syntaxin is not required for Munc18-1-stimulated fusion; the central cavity region of Munc18-1 is required for fusion stimulation.","method":"Reconstituted liposome fusion assay, syntaxin deletion and mutant analysis","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted in vitro fusion assay with domain mapping","pmids":["20603329"],"is_preprint":false},{"year":2010,"finding":"Munc18-1 domain-1 cleft mutations that reduce syntaxin-1 binding correlate tightly with impaired syntaxin-1 chaperoning, reduced dense-core vesicle docking, and reduced secretion; priming mutant phenotypes can largely be explained by reduced syntaxin-1 chaperoning.","method":"Munc18-1/-2 double knockdown rescue with domain-1 mutants, vesicle docking (EM), secretion assays, binding assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutant rescue in defined KD background with morphological and functional readouts, single lab","pmids":["21193638"],"is_preprint":false},{"year":2011,"finding":"Munc18-1 domain-1 cleft is essential for syntaxin-1 binding, chaperoning, vesicle docking, and secretion; correlations between binding and all downstream functions support a unified mechanism whereby syntaxin-1 chaperoning by domain-1 is the primary upstream function.","method":"Munc18-1/-2 double KD rescue with seven domain-1 mutants, binding assays, EM docking, secretion assays","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic mutant analysis with multiple readouts, single lab","pmids":["21900502"],"is_preprint":false},{"year":2011,"finding":"Munc18-1 performs a proofing function by inhibiting VAMP2/synaptobrevin tethering to monomeric syntaxin-1 at the plasma membrane (wild-type Munc18-1 abrogates Syb2-Synt1 binary trans-complex interaction at single-molecule level); Munc18-1 favors vesicle tethering to preformed syntaxin1A-SNAP25B binary cis-complexes.","method":"Single-molecule AFM force spectroscopy, patch-clamp capacitance, STED microscopy, chromaffin cell overexpression","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — single-molecule AFM with functional chromaffin cell measurements; single lab","pmids":["21677188"],"is_preprint":false},{"year":2011,"finding":"In reconstituted liposome fusion assay, Munc18-1 inhibition (via closed syntaxin) is released by concurrent incubation with VAMP2 liposomes and SNAP-25, specifically requiring Munc18-1/VAMP2 interaction; Munc18-1 binding to syntaxin N-peptide is obligatory for robust stimulation of fusion but not for inhibitory function.","method":"Reconstituted liposome fusion assay with defined mutants and isoform controls","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted in vitro fusion assay with multiple controls and isoform specificity","pmids":["21730064"],"is_preprint":false},{"year":2012,"finding":"Munc18-1 point mutations that strongly impair binding to free syntaxin-1 N-terminus and to assembled SNARE complexes support normal docking, priming, and fusion of synaptic vesicles and normal synaptic plasticity in munc18-1 null neurons.","method":"Lentiviral rescue in munc18-1 KO neurons, electrophysiology, electron microscopy","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — null background rescue with separation-of-function mutants, multiple readouts; contradicts some prior findings about SNARE complex binding requirement","pmids":["22446389"],"is_preprint":false},{"year":2012,"finding":"In reconstituted giant unilamellar vesicle system, synaptotagmin-1-mediated vesicle docking is a prerequisite for Munc18-1 to accelerate trans-SNARE complex (SNAREpin) assembly and membrane fusion; Munc18-1 positions itself downstream of synaptotagmin docking and upstream of SNAREpin zippering.","method":"Reconstituted giant unilamellar vesicle fusion assay with sequential addition of components","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted system with defined ordered addition, establishing pathway position","pmids":["22810233"],"is_preprint":false},{"year":2012,"finding":"STXBP1 disease variants with missense mutations show protein degradation in neuroblastoma2A cells (reduced protein levels), consistent with protein instability as the primary pathogenic mechanism; nonsense-mediated mRNA decay also demonstrated for splicing mutations.","method":"Transient expression in neuroblastoma2A cells, Western blot, RNA analysis in lymphoblastoid cells","journal":"Epilepsia","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-based expression with protein quantification, single lab, multiple mutation types","pmids":["20887364"],"is_preprint":false},{"year":2012,"finding":"Munc18-1 controls SNARE complex assembly during human sperm acrosomal exocytosis; inactivation of endogenous Munc18-1 with antibody prevents trans-SNARE complex stabilization and inhibits acrosomal exocytosis; recombinant Munc18-1 blocks secretion by sequestering monomeric syntaxin.","method":"Function-blocking antibody, recombinant protein addition, electron microscopy, SNARE complex formation assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — antibody inhibition with EM and biochemical readouts, single lab, non-neuronal system","pmids":["23091057"],"is_preprint":false},{"year":2013,"finding":"Domain 3a insertion mutants of Munc18-1 (K332E/K333E) completely lose ability to rescue secretion but effectively restore syntaxin-1 expression, plasma membrane localization, and vesicle docking; these mutants show impaired SNARE complex binding, identifying domain 3a as critical for the priming step specifically.","method":"Munc18-1/-2 double KD rescue with insertion mutants, secretion assay, immunofluorescence, EM docking, binding assay","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic mutant rescue with separation of docking from priming; single lab","pmids":["23525015"],"is_preprint":false},{"year":2014,"finding":"STXBP1 promotes Weibel-Palade body exocytosis in endothelial cells through interaction with Rab27A effector Slp4-a; STXBP1 interacts with syntaxin-2 and -3 but not syntaxin-4; STXBP1 haploinsufficiency in patient-derived cells impairs histamine- and forskolin-stimulated VWF secretion.","method":"Proteomic screen for Slp4-a targets, co-immunoprecipitation, siRNA knockdown, patient-derived blood outgrowth endothelial cells, VWF secretion assay","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — proteomic identification confirmed by Co-IP, functional siRNA KD and patient-derived cell validation with two agonists","pmids":["24700782"],"is_preprint":false},{"year":2014,"finding":"Munc18-1 is a dynamically regulated PKC target during post-tetanic potentiation (PTP); two PKC phosphorylation sites of Munc18-1 are critically important for PTP at the calyx of Held synapse; a phosphatase limits PTP duration; a conventional PKC isoform initiates PTP.","method":"Gene replacement strategy at calyx of Held, electrophysiology, pharmacological kinase/phosphatase inhibition","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — gene replacement with phospho-site mutants at a defined synapse, electrophysiology + pharmacology","pmids":["24520164"],"is_preprint":false},{"year":2014,"finding":"Munc18-1 redistributes from synapses during stimulation and reclusters within minutes; reclustering is independent of syntaxin-1 but requires Ca2+ influx and PKC activity; a PKC-insensitive Munc18-1 mutant fails to recluster; synaptic Munc18-1 levels correlate with synaptic strength and releasable vesicle pool size.","method":"Knock-in mouse with fluorescently tagged Munc18-1 from endogenous locus, FRAP in hippocampal neurons, pharmacological manipulation","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — endogenous fluorescent tag (Tier 1 localization), FRAP with functional correlation, defined PKC-insensitive mutant","pmids":["24590174"],"is_preprint":false},{"year":2015,"finding":"Heterozygous STXBP1 loss-of-function mutations in human neurons reduce Munc18-1 protein and syntaxin-1 levels by ~30% and decrease spontaneous and evoked neurotransmitter release by ~50%, confirming a presynaptic impairment mechanism.","method":"Conditional heterozygous/homozygous STXBP1 mutations in human ES cell-derived neurons, electrophysiology","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — isogenic human neuron model with electrophysiology, direct mechanistic link established","pmids":["26280581"],"is_preprint":false},{"year":2015,"finding":"The trans-SNARE-regulating function of Munc18-1 (promoting VAMP2 zippering) is essential for synaptic exocytosis; v-SNARE mutations that selectively impair Munc18-1's ability to promote trans-SNARE zippering strongly inhibit neurotransmitter release; an Ohtahara Syndrome-associated Munc18-1 mutation compromises this trans-SNARE-regulating function.","method":"Reconstituted trans-SNARE assay, lentiviral expression of v-SNARE mutants in cultured neurons, electrophysiology","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution assay combined with neuronal rescue electrophysiology, disease-linked mutation characterized","pmids":["26572858"],"is_preprint":false},{"year":2015,"finding":"Munc18-1 domain 3a helix 12 conformation controls vesicle priming; disruptive mutations (L348R, Δ324-339) reduce priming and secretory amplitude; gain-of-function P335A (extends helix) markedly increases priming; effects are specific to priming with unchanged fusion kinetics and Ca2+ dependence.","method":"Expression of helix-12 mutants in Munc18-1 null chromaffin cells, capacitance measurements, EM, in vitro fusion assay","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — null background rescue with separation-of-function mutants, electrophysiology + EM + in vitro assay","pmids":["27358447"],"is_preprint":false},{"year":2015,"finding":"Munc18-1 is essential for neuropeptide secretion from dense-core vesicles; conditional inactivation abolishes all DCV exocytosis; Munc18-2 and Munc18-3 cannot substitute; heterozygous Munc18-1 impairs DCV exocytosis especially during peak stimulation.","method":"Conditional KO in mouse CNS neurons, single-vesicle pHluorin-tagged neuropeptide Y/BDNF secretion assay during action potential trains","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO with single-vesicle resolution assay, isoform specificity controls","pmids":["34103363"],"is_preprint":false},{"year":2016,"finding":"Munc18-1 is a molecular chaperone for α-synuclein that controls its self-replicating aggregation; disease-linked EIEE Munc18-1 mutants form polymers that co-aggregate wild-type Munc18-1 and α-synuclein, forming Lewy body-like structures; removal of endogenous Munc18-1 increases α-synuclein aggregation propensity, rescued by Munc18-1 WT re-expression.","method":"Single-molecule analysis, gene-edited cells, primary neurons, co-aggregation assays, confocal microscopy","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — single-molecule + KO + rescue, single lab; novel function outside exocytosis","pmids":["27597756"],"is_preprint":false},{"year":2016,"finding":"The Munc18-1 domain 3a hinge-loop (residues 317-333) controls syntaxin-1A confinement into nanodomains and engagement with the SNARE complex during priming; a deletion mutant (Δ317-333) prolongs vesicle docking and blocks stimulation-induced diffusional changes of Munc18-1 and syntaxin-1A in nanodomains.","method":"Single-molecule tracking, super-resolution microscopy, PC12 double KD rescue, secretion assay","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — single-molecule localization + KD rescue, single lab","pmids":["27646276"],"is_preprint":false},{"year":2016,"finding":"Munc18-1 domain 3a helix 12 interacts with synaptobrevin-2/VAMP2 to mediate SNARE complex formation and vesicle priming; EPR spectroscopy shows Munc18-1 shifts syntaxin/SNAP-25 complex from inhibitory 2:1 to productive 1:1 open-state configuration.","method":"Electron paramagnetic resonance (EPR) spectroscopy on reconstituted SNARE complexes","journal":"Structure (London, England : 1993)","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — EPR structural approach, single lab, single method","pmids":["26876096"],"is_preprint":false},{"year":2016,"finding":"All disease-causing STXBP1 variants tested have severely decreased protein levels, indicating impaired protein stability as the primary molecular defect; disease variants support synaptic transmission to variable extent on null background but show no dominant-negative effect on heterozygous background.","method":"Allelic series of STXBP1 variants in null-background neurons, Western blot, electrophysiology, four mouse models","journal":"Brain : a journal of neurology","confidence":"High","confidence_rationale":"Tier 2 / Strong — allelic series across multiple methods including electrophysiology and in vivo EEG, single lab but multiple orthogonal approaches","pmids":["29538625"],"is_preprint":false},{"year":2017,"finding":"Munc18-1 has autoinhibition of synaptobrevin binding via a 'furled conformation' loop; a D326K mutation disrupting this autoinhibition stimulates Munc18-1 activity in reconstitution assays and causes gain-of-function in C. elegans; an L348R mutation inhibiting synaptobrevin binding reduces activity; this autoinhibition helps enable Munc13-1-dependent regulation.","method":"NMR spectroscopy, reconstitution assays (Munc18-1 + Munc13-1 dependent fusion), C. elegans rescue experiments","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 / Strong — NMR + reconstitution + in vivo genetic rescue, multiple orthogonal methods","pmids":["28477408"],"is_preprint":false},{"year":2017,"finding":"Tyrosine phosphorylation of Munc18-1 at Y473 by Src family kinases abolishes its SNARE-templating stimulatory function and membrane fusion in vitro, and disrupts vesicle priming (but not docking) in munc18-1 null neurons; non-phosphorylatable Munc18-1 supports normal transmission; ERK-dependent Munc18-1 phosphorylation leads to its degradation by the ubiquitin-proteasome system.","method":"In vitro fusion assay, munc18-1 KO neuron rescue with Y473D mutant, electrophysiology, mass spectrometry phospho-proteomics","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro fusion reconstitution + null background neuronal rescue + defined phospho-mutant","pmids":["29150433"],"is_preprint":false},{"year":2017,"finding":"CB1R and mGluR2/3 activation induces presynaptic inhibition through ERK-mediated phosphorylation of Munc18-1, causing decreased synaptic transmission and subsequent ubiquitin-proteasome-dependent Munc18-1 degradation; preventing ERK-dependent Munc18-1 phosphorylation increases synaptic strength.","method":"Gene replacement with phospho-mutant Munc18-1, pharmacological ERK/MEK inhibition, electrophysiology","journal":"The EMBO journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gene replacement with defined mutant, pharmacological validation, single lab","pmids":["27056679"],"is_preprint":false},{"year":2017,"finding":"Munc18-1 knockdown impairs radial migration of cortical neurons during corticogenesis; Syntaxin1A is critical for radial migration downstream of Munc18-1; Munc18-1 knockdown hampers post-Golgi vesicle trafficking and plasma membrane vesicle fusion in vivo and in vitro.","method":"In utero electroporation knockdown, time-lapse imaging, cortical neuron fractionation, vesicle trafficking assay","journal":"Acta neuropathologica communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo knockdown with live imaging, single lab","pmids":["29191246"],"is_preprint":false},{"year":2018,"finding":"Munc18-1 catalyzes stepwise zippering of synaptic SNAREs (syntaxin, VAMP2, SNAP-25) via an obligate template complex intermediate; Munc18-1 juxtaposes N-terminal SNARE motif regions of syntaxin and VAMP2 while keeping C-terminal regions separated; SNAP-25 then binds to induce full zippering; mutations modulating template complex stability correspondingly affect membrane fusion; SM proteins Munc18-3 and Vps33 similarly chaperone SNARE assembly.","method":"Single-molecule force spectroscopy (optical tweezers), mutagenesis, reconstitution assays","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 / Strong — single-molecule force spectroscopy with mutagenesis and reconstitution, multiple SM protein controls demonstrating conservation","pmids":["30540253"],"is_preprint":false},{"year":2018,"finding":"At least five disease-linked missense mutations of Munc18-1 destabilize and aggregate the mutant protein; mutant aggregates incorporate wild-type Munc18-1, depleting functional protein below hemizygous levels (dominant-negative aggregation mechanism); chemical chaperones (4-phenylbutyrate, sorbitol, trehalose) reverse these deficits in vitro and in vivo.","method":"In vitro aggregation assays, S. cerevisiae strains, C. elegans models, conditional KO mouse neurons, Western blot","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple model systems (yeast, worm, mouse neurons), multiple orthogonal methods, therapeutic rescue","pmids":["30266908"],"is_preprint":false},{"year":2019,"finding":"Munc18-1 is crucial to overcome αSNAP inhibition of synaptic vesicle fusion; αSNAP inhibits liposome fusion by binding syntaxin-1 (blocking Munc18-1 binding), by binding syntaxin-1-SNAP-25 heterodimers (blocking SNARE formation), and by binding trans-SNARE complexes; inhibition is avoided only when Munc18-1 binds syntaxin-1 first, leading to Munc18-1-Munc13-1-dependent fusion.","method":"Liposome fusion assays, FRET, NMR spectroscopy","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted liposome fusion with FRET and NMR, multiple inhibitory mechanisms mapped","pmids":["31548544"],"is_preprint":false},{"year":2019,"finding":"MUN domain of Munc13-1 stabilizes the Munc18-1/SNARE template complex by ~2.1 kBT, forming a tetrameric complex; this stabilization enhances SNAP-25 binding and full SNARE assembly; mutational studies confirm functional importance for neurotransmitter release.","method":"Single-molecule force spectroscopy (optical tweezers), mutagenesis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — single-molecule force spectroscopy with mutagenesis, direct measurement of stabilization energy","pmids":["31888993"],"is_preprint":false},{"year":2020,"finding":"Stxbp1 haploinsufficiency reduces cortical inhibitory neurotransmission via distinct mechanisms from parvalbumin-expressing and somatostatin-expressing interneurons; GABAergic synaptic dysfunction is a crucial contributor to STXBP1 encephalopathy pathogenesis.","method":"Heterozygous Stxbp1 mouse model, cell-type-specific Cre lines, patch-clamp electrophysiology, behavioral assays","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — cell-type-specific conditional KO with electrophysiology, multiple interneuron types analyzed","pmids":["32073399"],"is_preprint":false},{"year":2020,"finding":"Homozygous STXBP1 L446F mutation causes a gain-of-function: 2-fold increase in evoked synaptic transmission and release probability with reduced paired-pulse plasticity; protein stability is less severely affected than typical heterozygous disease mutants.","method":"Munc18-1 null neuron rescue with L446F, patch-clamp electrophysiology, Western blot","journal":"Brain : a journal of neurology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — null background rescue with electrophysiology, single lab, single mutation","pmids":["31855252"],"is_preprint":false},{"year":2020,"finding":"Helices 11 and 12 of Munc18-1 domain 3a interact with VAMP2 SNARE motif (layers -4 to +5); Q301 in helix 11 is pivotal for VAMP2 binding and template complex formation; Q301D mutant fails to stimulate membrane fusion in reconstituted assay; Munc13-1 cannot bypass requirement for Munc18-1/VAMP2 interaction; Q301D expression in Munc18-1 deficient neurons severely reduces synaptic transmission.","method":"Site-specific crosslinking with unnatural amino acid, reconstituted vesicle fusion assay, lentiviral rescue in KO neurons, electrophysiology","journal":"eNeuro","confidence":"High","confidence_rationale":"Tier 1 / Strong — crosslinking maps precise binding interface, reconstitution assay, and neuronal KO rescue all in one study","pmids":["33055194"],"is_preprint":false},{"year":2020,"finding":"All eight epilepsy-associated STXBP1 missense variants tested in humanized C. elegans show reduced protein levels (20-30% of wild-type) consistent with protein instability; locomotion and electrophysiological deficits vary by variant; no difference in mRNA levels confirming post-transcriptional instability.","method":"CRISPR/Cas9 unc-18 null C. elegans rescued with human STXBP1 variants, behavioral assays, electrophysiology, Western blot","journal":"Epilepsia","confidence":"High","confidence_rationale":"Tier 2 / Strong — humanized in vivo model with multiple orthogonal readouts for each variant","pmids":["32112430"],"is_preprint":false},{"year":2014,"finding":"Munc18-1 undergoes K48-linked polyubiquitination leading to proteasomal (not lysosomal) degradation; the C180Y disease-causing mutation greatly potentiates polyubiquitination and proteasomal degradation, rendering Munc18-1 unable to support neuroexocytosis; this phenotype is reversed at permissive temperature.","method":"Ubiquitination assays, proteasome/lysosome inhibitors, temperature-shift rescue, secretion assays in Munc18-deficient cells","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biochemical ubiquitination characterization with functional rescue, single lab","pmids":["25284778"],"is_preprint":false},{"year":2017,"finding":"Early cis-Golgi condensation is the first cellular abnormality upon Munc18-1 loss in neurons (before synaptogenesis); expression of Munc18-3 (which does not bind syntaxin-1) in Munc18-1 KO neurons prevents cell death and restores Golgi morphology but does not rescue synaptic transmission or syntaxin-1 targeting, indicating distinct cell-survival and exocytotic functions.","method":"Conditional KO neurons, immunofluorescence, electron microscopy, Munc18-3 rescue","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional KO with isoform rescue dissecting two functions, single lab","pmids":["28348137"],"is_preprint":false},{"year":2024,"finding":"STXBP1 interacts with DDHD2 (a phospholipase A1); STXBP1 controls DDHD2 targeting to the plasma membrane and generation of saturated free fatty acids (myristic acid) in the brain; this interaction mediates long-term memory formation.","method":"Pulldown-mass spectrometry, STXBP1/2 knockout neurosecretory cells, Stxbp1+/- mouse model, lipidomic analysis, memory behavioral assays","journal":"The EMBO journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pulldown-MS identification with KO/haploinsufficient model validation and lipidomics; single lab","pmids":["38316990"],"is_preprint":false}],"current_model":"STXBP1/Munc18-1 is a neural-specific SM (Sec1/Munc18) protein that acts as the master organizer of synaptic vesicle exocytosis by sequentially chaperoning syntaxin-1 to the plasma membrane, templating SNARE complex assembly via a Munc18-1/syntaxin-VAMP2 intermediate template complex (stabilized by Munc13-1 MUN domain), promoting vesicle docking (through closed-syntaxin binding), and enabling vesicle priming (through domain 3a helix 12 conformational change engaging VAMP2); its activity is regulated by PKC phosphorylation (Ser306/313 reducing syntaxin affinity and enabling vesicle pool replenishment), Src kinase phosphorylation (Y473 blocking SNARE templating), ERK phosphorylation (leading to proteasomal degradation), S-nitrosylation of syntaxin Cys145 (disrupting Munc18-1/closed-syntaxin interaction), Ca2+/calmodulin-dependent release from mGluR4, and interaction with Rab3A; disease-causing mutations primarily destabilize the protein leading to haploinsufficiency or dominant-negative aggregation, while also impairing STXBP1-dependent inhibitory neurotransmission and neuropeptide secretion, and STXBP1 additionally controls α-synuclein aggregation, DDHD2 membrane targeting/saturated fatty acid production, and radial migration of cortical neurons during development."},"narrative":{"mechanistic_narrative":"STXBP1 (Munc18-1) is a neural-specific Sec1/Munc18 (SM) protein that serves as the master organizer of regulated exocytosis, controlling synaptic vesicle and dense-core vesicle fusion through sequential, physically distinct engagements with the SNARE machinery [PMID:8108429, PMID:8134339, PMID:17687045, PMID:34103363]. It first acts as a molecular chaperone for syntaxin-1, binding the closed conformation, stabilizing the protein and extending its half-life, and directing it to the plasma membrane; loss of Munc18-1 reduces syntaxin-1 levels and mistargets it to perinuclear compartments [PMID:10648557, PMID:15935055, PMID:18077557]. Through its domain-1 cleft, closed-syntaxin binding drives vesicle docking, while a separable activity centered on domain 3a (helix 12 and the hinge-loop) engages the assembling SNARE bundle to mediate vesicle priming [PMID:17687045, PMID:21193638, PMID:27358447, PMID:27646276]. Mechanistically, Munc18-1 templates SNARE assembly by forming an obligate intermediate that juxtaposes the N-terminal SNARE motifs of syntaxin-1 and VAMP2/synaptobrevin while holding their C-termini apart, permitting SNAP-25 binding to drive full zippering; the MUN domain of Munc13-1 stabilizes this template complex, and Munc18-1 binding overcomes αSNAP-mediated inhibition of fusion [PMID:30540253, PMID:31888993, PMID:33055194, PMID:31548544]. This catalytic activity positions Munc18-1 downstream of synaptotagmin-dependent docking and upstream of trans-SNARE zippering [PMID:22810233, PMID:26572858]. Its activity is tuned by phosphorylation: conventional PKC phosphorylates Ser306/Ser313 to reduce syntaxin affinity and potentiate vesicle pool replenishment and post-tetanic potentiation, Src-family kinases phosphorylate Y473 to abolish SNARE templating, and ERK-mediated phosphorylation downstream of CB1R/mGluR signaling triggers ubiquitin-proteasome degradation [PMID:8631738, PMID:16997485, PMID:24520164, PMID:29150433, PMID:27056679]. De novo and missense STXBP1 mutations cause early infantile epileptic encephalopathy, acting predominantly through protein destabilization and haploinsufficiency — and in some cases dominant-negative aggregation that co-sequesters wild-type protein — which reduces neurotransmission, with inhibitory GABAergic and neuropeptide signaling particularly affected [PMID:18469812, PMID:26280581, PMID:29538625, PMID:30266908, PMID:32073399]. Beyond core exocytosis, Munc18-1 chaperones α-synuclein to limit its aggregation, controls DDHD2 plasma-membrane targeting and saturated fatty acid production for memory, and is required for cortical neuron radial migration and neuronal survival [PMID:27597756, PMID:38316990, PMID:29191246, PMID:28348137].","teleology":[{"year":1994,"claim":"Established that the neural protein Munc18-1 is a selective syntaxin-binding partner, placing it at the heart of synaptic vesicle docking and fusion rather than acting generally across the SNARE machinery.","evidence":"GST pulldowns from brain extract showing binding to syntaxin-1/2/3 but not syntaxin-4, SNAP-25, or VAMP, plus syntaxin-dependent membrane association","pmids":["8108429","8134339"],"confidence":"High","gaps":["Did not define the syntaxin conformation bound","No functional consequence for fusion established"]},{"year":1996,"claim":"Demonstrated functional conservation and isoform specificity of Munc18-1 in neurotransmitter release, and identified PKC phosphorylation as a regulatory switch on syntaxin binding.","evidence":"Transgenic rescue of C. elegans unc-18 null by neural (but not ubiquitous) Munc18; in vitro PKC phosphorylation at Ser306/Ser313 with binding assays","pmids":["8824310","8631738"],"confidence":"High","gaps":["In vivo physiological relevance of the phosphosites not yet shown","Step in exocytosis controlled by phosphorylation unresolved"]},{"year":2000,"claim":"Resolved that Munc18-1 binds a closed conformation of syntaxin-1 mutually exclusive with ternary SNARE assembly, framing the central puzzle of how a SNARE-blocking protein could promote fusion.","evidence":"In vitro binding, nondenaturing gels, neurotoxin treatment, cross-linking of brain membranes; nerve-terminal phosphorylation assays","pmids":["10648557","10651895"],"confidence":"High","gaps":["Mechanism reconciling SNARE inhibition with positive fusion role unknown","Did not address binding to assembled SNAREs"]},{"year":2001,"claim":"Provided in vivo genetic proof that Munc18-1 is required for vesicle docking and exocytosis, converting a binding partner into a functionally essential exocytic factor.","evidence":"Electron microscopy docking assay and patch-clamp capacitance in munc18-1 null chromaffin cells, plus overexpression","pmids":["11545717"],"confidence":"High","gaps":["Whether docking and a later priming step are separable not resolved","Molecular basis of docking defect unclear"]},{"year":2005,"claim":"Identified syntaxin-1 chaperoning/stabilization as an upstream Munc18-1 function, explaining how loss of Munc18-1 collapses the presynaptic SNARE pool.","evidence":"Pulse-chase in HEK293 cells and immunoblotting in munc18-1 KO mice; PC12 knockdown with rescue showing syntaxin-1 membrane targeting","pmids":["15935055","18077557"],"confidence":"High","gaps":["Whether chaperoning fully accounts for downstream phenotypes debated","Trafficking route of syntaxin-1 not fully defined"]},{"year":2007,"claim":"Discovered a second binding mode — Munc18-1 binding to assembled SNARE complexes via the syntaxin N-peptide — and dissociated closed-syntaxin-dependent docking from a distinct priming activity.","evidence":"NMR and pulldowns on reconstituted SNARE complexes; Munc18 variant rescue with capacitance and EM in null chromaffin cells","pmids":["17301226","17687045"],"confidence":"High","gaps":["Precise contribution of each binding mode to fusion not quantified","Structural basis of the priming activity unresolved"]},{"year":2009,"claim":"Mapped SNARE-complex binding (open syntaxin) to vesicle priming specifically, and confirmed in vivo that syntaxin N-terminus binding is essential for neurotransmission.","evidence":"Lentiviral rescue with separation-of-function mutants in munc18-1 KO neurons; C. elegans rescue with N-terminus and closed-syntaxin binding mutants; PC12 double-KD rescue","pmids":["19255244","19032153","19812250"],"confidence":"High","gaps":["Relative importance of N-peptide vs closed-syntaxin binding contested across systems","Direct fusion-catalysis mechanism still inferred"]},{"year":2010,"claim":"Defined the minimal molecular determinants of Munc18-1 fusion stimulation, including direct binding to synaptobrevin/VAMP2 through the same central cavity, advancing toward a catalytic templating model.","evidence":"NMR, ITC, fluorescence anisotropy on VAMP2 binding; reconstituted liposome fusion with syntaxin domain mapping; domain-1 cleft mutant analysis","pmids":["20102228","20603329","21193638"],"confidence":"High","gaps":["How simultaneous syntaxin and VAMP2 engagement is coordinated unresolved","Order of events during fusion not yet established"]},{"year":2012,"claim":"Positioned Munc18-1 in the fusion pathway downstream of synaptotagmin docking and upstream of SNAREpin zippering, and linked disease mutations to protein instability.","evidence":"Reconstituted giant unilamellar vesicle fusion with ordered component addition; separation-of-function mutant rescue in KO neurons; disease-variant expression in N2a cells with NMD analysis","pmids":["22810233","22446389","20887364"],"confidence":"High","gaps":["Contradiction over whether SNARE-complex binding is required for fusion (vs. #19) unresolved here","In vivo ordering not directly tested"]},{"year":2013,"claim":"Localized the priming-specific function to domain 3a, demonstrating mutants that fully chaperone syntaxin-1 and support docking yet abolish secretion.","evidence":"Domain 3a insertion mutant (K332E/K333E) rescue in PC12 double-KD cells with secretion, immunofluorescence, EM docking, and SNARE binding assays","pmids":["23525015"],"confidence":"Medium","gaps":["Single lab, single cell system","Structural mechanism of helix 12 action not defined here"]},{"year":2014,"claim":"Showed Munc18-1 phosphorylation is dynamically regulated during synaptic plasticity and degradation, and extended its exocytic role to non-neuronal secretion.","evidence":"Gene replacement at the calyx of Held with phospho-mutants and electrophysiology; knock-in fluorescent Munc18-1 FRAP; proteomic identification of STXBP1 in Weibel-Palade body exocytosis; K48 ubiquitination assays","pmids":["24520164","24590174","24700782","25284778"],"confidence":"High","gaps":["Kinase/phosphatase identities for some events not fully resolved","E3 ligase mediating ubiquitination unidentified"]},{"year":2015,"claim":"Established that promotion of trans-SNARE/VAMP2 zippering is the essential Munc18-1 function, that helix 12 conformation controls priming, and that Munc18-1 drives neuropeptide DCV exocytosis.","evidence":"Reconstituted trans-SNARE assay with v-SNARE mutants and neuronal electrophysiology; helix-12 mutant rescue in null chromaffin cells with EM; conditional KO with single-vesicle neuropeptide secretion; isogenic human-neuron STXBP1 mutations","pmids":["26572858","27358447","34103363","26280581"],"confidence":"High","gaps":["Atomic structure of the templating intermediate not yet captured","How helix 12 engages VAMP2 not yet defined here"]},{"year":2016,"claim":"Identified the helix 12/VAMP2 interaction and syntaxin nanodomain confinement as the structural basis of priming, and uncovered a chaperone role for Munc18-1 in controlling α-synuclein aggregation.","evidence":"EPR on reconstituted SNARE complexes; single-molecule tracking and super-resolution in PC12 KD cells; single-molecule and gene-edited cell co-aggregation assays","pmids":["26876096","27646276","27597756"],"confidence":"Medium","gaps":["α-synuclein chaperone function from a single lab and outside the exocytic role","Direct structural snapshot of helix 12-VAMP2 still indirect"]},{"year":2017,"claim":"Defined autoinhibition of VAMP2 binding, identified Src/ERK phosphorylation as negative regulators coupling presynaptic receptors to Munc18-1 turnover, and revealed non-exocytic roles in cortical migration and neuronal survival.","evidence":"NMR + reconstitution + C. elegans rescue (autoinhibition); in vitro fusion and KO-neuron rescue with Y473D and ERK phospho-mutants; in utero electroporation knockdown imaging; conditional KO with Munc18-3 rescue dissecting Golgi/survival from exocytosis","pmids":["28477408","29150433","27056679","29191246","28348137"],"confidence":"High","gaps":["In vivo significance of autoinhibition during synaptic signaling not fully mapped","Mechanism of Golgi/survival function independent of syntaxin unresolved"]},{"year":2018,"claim":"Provided direct single-molecule proof of the obligate template-complex mechanism of stepwise SNARE zippering and consolidated protein destabilization/aggregation as the unifying disease mechanism.","evidence":"Optical-tweezers single-molecule force spectroscopy with mutagenesis and SM-protein controls; allelic series of disease variants in null-background neurons with EEG; multi-organism aggregation models with chemical-chaperone rescue","pmids":["30540253","29538625","30266908"],"confidence":"High","gaps":["Whether all disease variants act purely by instability vs additional dominant effects still being delineated","In vivo template-complex dynamics not directly observed"]},{"year":2019,"claim":"Showed Munc13-1's MUN domain energetically stabilizes the Munc18-1/SNARE template and that Munc18-1 must bind syntaxin-1 first to evade αSNAP inhibition, integrating the catalytic cascade.","evidence":"Single-molecule force spectroscopy measuring template stabilization; reconstituted liposome fusion with FRET and NMR mapping αSNAP inhibition","pmids":["31888993","31548544"],"confidence":"High","gaps":["In vivo confirmation of the kBT stabilization effect lacking","How ordering of binding is enforced in cells unclear"]},{"year":2020,"claim":"Mapped the precise helix 11/12-VAMP2 interface required for templating, identified GABAergic interneuron dysfunction as central to STXBP1 encephalopathy, and characterized a gain-of-function disease allele.","evidence":"Unnatural-amino-acid crosslinking with reconstitution and KO-neuron rescue (Q301D); cell-type-specific conditional Stxbp1 KO with electrophysiology; humanized C. elegans variant panel; L446F null-background rescue","pmids":["33055194","32073399","32112430","31855252"],"confidence":"High","gaps":["How gain-of-function alleles produce disease distinct from loss-of-function not fully resolved","Cell-type-specific circuit consequences in humans untested"]},{"year":2024,"claim":"Extended Munc18-1 function into lipid signaling for memory, showing it controls DDHD2 membrane targeting and saturated fatty acid production.","evidence":"Pulldown-mass spectrometry, STXBP1/2 KO neurosecretory cells and Stxbp1+/- mice, lipidomics, and memory behavioral assays","pmids":["38316990"],"confidence":"Medium","gaps":["Single lab","Relationship between lipid function and core exocytic role not integrated"]},{"year":null,"claim":"An atomic-resolution structure of the full Munc18-1/syntaxin-1/VAMP2/Munc13-1 templating intermediate in a membrane context, and a unified explanation of how diverse missense variants partition between loss-of-function instability, dominant-negative aggregation, and gain-of-function, remain to be established.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No membrane-embedded structure of the complete template complex","Genotype-to-mechanism mapping across the full variant spectrum incomplete","How non-exocytic functions (α-synuclein, DDHD2, migration) integrate with core role unclear"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0044183","term_label":"protein folding chaperone","supporting_discovery_ids":[11,15,41,49]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[49,52,55]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[4,14,28,51]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[49,55]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,15,36]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[58,59]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[2,11]}],"pathway":[{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[6,15,40]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[6,30,38,49]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[19,37,53]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[18,44,50]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[48,58]}],"complexes":["Munc18-1/syntaxin-1/VAMP2 template complex","Munc18-1/SNARE/Munc13-1 MUN tetrameric complex"],"partners":["STX1A","VAMP2","SNAP25","UNC13A","RAB3A","GRM4","DDHD2","SNCA"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P61764","full_name":"Syntaxin-binding protein 1","aliases":["MUNC18-1","N-Sec1","Protein unc-18 homolog 1","Unc18-1","Protein unc-18 homolog A","Unc-18A","p67"],"length_aa":594,"mass_kda":67.6,"function":"Participates in the regulation of synaptic vesicle docking and fusion through interaction with GTP-binding proteins (By similarity). Essential for neurotransmission and binds syntaxin, a component of the synaptic vesicle fusion machinery probably in a 1:1 ratio. Can interact with syntaxins 1, 2, and 3 but not syntaxin 4. Involved in the release of neurotransmitters from neurons through interacting with SNARE complex component STX1A and mediating the assembly of the SNARE complex at synaptic membranes (By similarity). May play a role in determining the specificity of intracellular fusion reactions","subcellular_location":"Cytoplasm, cytosol; Membrane","url":"https://www.uniprot.org/uniprotkb/P61764/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/STXBP1","classification":"Not Classified","n_dependent_lines":31,"n_total_lines":1208,"dependency_fraction":0.02566225165562914},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"STX2","stoichiometry":10.0},{"gene":"HSPH1","stoichiometry":0.2},{"gene":"STX3","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/STXBP1","total_profiled":1310},"omim":[{"mim_id":"620465","title":"EPILEPSY, EARLY-ONSET, 3, WITH OR WITHOUT DEVELOPMENTAL DELAY; EPEO3","url":"https://www.omim.org/entry/620465"},{"mim_id":"615744","title":"DEVELOPMENTAL AND EPILEPTIC ENCEPHALOPATHY 19; DEE19","url":"https://www.omim.org/entry/615744"},{"mim_id":"613477","title":"DEVELOPMENTAL AND EPILEPTIC ENCEPHALOPATHY 5; DEE5","url":"https://www.omim.org/entry/613477"},{"mim_id":"612164","title":"DEVELOPMENTAL AND EPILEPTIC ENCEPHALOPATHY 4; DEE4","url":"https://www.omim.org/entry/612164"},{"mim_id":"605836","title":"UNC13 HOMOLOG B; UNC13B","url":"https://www.omim.org/entry/605836"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Uncertain","locations":[{"location":"Nucleoplasm","reliability":"Uncertain"},{"location":"Nucleoli","reliability":"Additional"},{"location":"Basal body","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in 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genetics","url":"https://pubmed.ncbi.nlm.nih.gov/29040524","citation_count":27,"is_preprint":false},{"pmid":"21669024","id":"PMC_21669024","title":"Regulation of munc18-1 and syntaxin-1A interactive partners in schizophrenia prefrontal cortex: down-regulation of munc18-1a isoform and 75 kDa SNARE complex after antipsychotic treatment.","date":"2011","source":"The international journal of neuropsychopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/21669024","citation_count":27,"is_preprint":false},{"pmid":"23525015","id":"PMC_23525015","title":"Domain 3a of Munc18-1 plays a crucial role at the priming stage of exocytosis.","date":"2013","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/23525015","citation_count":25,"is_preprint":false},{"pmid":"28944233","id":"PMC_28944233","title":"Protein structure and phenotypic analysis of pathogenic and population missense variants in STXBP1.","date":"2017","source":"Molecular genetics & genomic medicine","url":"https://pubmed.ncbi.nlm.nih.gov/28944233","citation_count":24,"is_preprint":false},{"pmid":"38316990","id":"PMC_38316990","title":"The DDHD2-STXBP1 interaction mediates long-term memory via generation of saturated free fatty acids.","date":"2024","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/38316990","citation_count":22,"is_preprint":false},{"pmid":"35278279","id":"PMC_35278279","title":"Neuronal SNARE complex assembly guided by Munc18-1 and Munc13-1.","date":"2022","source":"FEBS open bio","url":"https://pubmed.ncbi.nlm.nih.gov/35278279","citation_count":22,"is_preprint":false},{"pmid":"15504350","id":"PMC_15504350","title":"Amblyomma americanum salivary gland homolog of nSec1 is essential for saliva protein secretion.","date":"2004","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/15504350","citation_count":22,"is_preprint":false},{"pmid":"24304718","id":"PMC_24304718","title":"Munc18-1 haploinsufficiency results in enhanced anxiety-like behavior as determined by heart rate responses in mice.","date":"2013","source":"Behavioural brain research","url":"https://pubmed.ncbi.nlm.nih.gov/24304718","citation_count":22,"is_preprint":false},{"pmid":"33055194","id":"PMC_33055194","title":"The Interaction of Munc18-1 Helix 11 and 12 with the Central Region of the VAMP2 SNARE Motif Is Essential for SNARE Templating and Synaptic Transmission.","date":"2020","source":"eNeuro","url":"https://pubmed.ncbi.nlm.nih.gov/33055194","citation_count":20,"is_preprint":false},{"pmid":"26758845","id":"PMC_26758845","title":"Normal Molecular Specification and Neurodegenerative Disease-Like Death of Spinal Neurons Lacking the SNARE-Associated Synaptic Protein Munc18-1.","date":"2016","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/26758845","citation_count":20,"is_preprint":false},{"pmid":"25716321","id":"PMC_25716321","title":"Synaptotagmin-1 is an antagonist for Munc18-1 in SNARE zippering.","date":"2015","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/25716321","citation_count":19,"is_preprint":false},{"pmid":"34103363","id":"PMC_34103363","title":"Munc18-1 Is Essential for Neuropeptide Secretion in Neurons.","date":"2021","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/34103363","citation_count":19,"is_preprint":false},{"pmid":"12887319","id":"PMC_12887319","title":"Role of Munc18-1 in synaptic vesicle and large dense-core vesicle secretion.","date":"2003","source":"Biochemical Society transactions","url":"https://pubmed.ncbi.nlm.nih.gov/12887319","citation_count":19,"is_preprint":false},{"pmid":"30654231","id":"PMC_30654231","title":"STXBP1 encephalopathy is associated with awake bruxism.","date":"2019","source":"Epilepsy & behavior : E&B","url":"https://pubmed.ncbi.nlm.nih.gov/30654231","citation_count":18,"is_preprint":false},{"pmid":"23091057","id":"PMC_23091057","title":"Munc18-1 controls SNARE protein complex assembly during human sperm acrosomal exocytosis.","date":"2012","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/23091057","citation_count":18,"is_preprint":false},{"pmid":"15898951","id":"PMC_15898951","title":"The role of Munc18-1 in docking and exocytosis of peptide hormone vesicles in the anterior pituitary.","date":"2005","source":"Biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/15898951","citation_count":18,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":51905,"output_tokens":13909,"usd":0.182175,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":25653,"output_tokens":6566,"usd":0.146207,"stage2_stop_reason":"end_turn"},"total_usd":0.328382,"stage1_batch_id":"msgbatch_017qqVz33Ga63SCDwzb35XPb","stage2_batch_id":"msgbatch_01Scr2Ei9x4HJMiRGxwrmvLK","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1994,\n      \"finding\": \"n-Sec1/STXBP1 is a neural-specific syntaxin-binding protein that binds syntaxin 1a, 2, and 3 but not syntaxin 4, and becomes membrane-associated in the presence of syntaxin 1a, implicating it in synaptic vesicle docking and fusion.\",\n      \"method\": \"GST pulldown, subcellular fractionation, RNA blot analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct binding assay (pulldown), subcellular fractionation, replicated independently in two concurrent papers (PMID:8108429 and PMID:8134339)\",\n      \"pmids\": [\"8108429\", \"8134339\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"rbSec1/STXBP1 specifically interacts with syntaxin but not with SNAP-25 or synaptobrevin/VAMP in brain extract pulldowns, establishing a selective t-SNARE interaction.\",\n      \"method\": \"GST fusion protein pulldown from Triton X-100 brain extract\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct biochemical pulldown, replicated across two independent labs simultaneously\",\n      \"pmids\": [\"8134339\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Munc18-1/STXBP1 is phosphorylated by conventional PKC (Ca2+- and phospholipid-dependent) at Ser306 and Ser313; this phosphorylation inhibits its interaction with syntaxin. The Munc18-1 complexed with syntaxin is not phosphorylated.\",\n      \"method\": \"In vitro phosphorylation assay with recombinant Munc18-1, mutagenesis of phosphorylation sites, binding assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with mutagenesis identifying specific phosphorylation sites, replicated by subsequent studies\",\n      \"pmids\": [\"8631738\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Mouse Munc18-1 (neural isoform) functionally rescues locomotion and cholinergic defects in C. elegans unc-18 null mutants, demonstrating evolutionary conservation of its role in neurotransmitter release; the ubiquitous Munc18-3 isoform fails to rescue.\",\n      \"method\": \"Transgenic rescue of C. elegans unc-18 null mutant, behavioral and pharmacological assays\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis/rescue in vivo with isoform specificity control\",\n      \"pmids\": [\"8824310\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"nSec1/Munc18-1 binds a closed conformation of syntaxin 1A; association of nSec1 with syntaxin 1A prevents assembly of the ternary SNARE complex (with SNAP-25 and VAMP2), and conversely, SNARE complex formation precludes nSec1 binding.\",\n      \"method\": \"In vitro binding assays, nondenaturing gel electrophoresis, neurotoxin treatment, chemical cross-linking of rat brain membranes\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal in vitro methods in one study, replicated by subsequent work\",\n      \"pmids\": [\"10648557\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Synaptic Munc18-1 is dynamically phosphorylated by endogenous presynaptic PKC isoforms at nerve terminals; K+-evoked depolarization increases phosphorylation within 5 s in a Ca2+-dependent manner; phosphorylation inhibits interaction with syntaxin-1A by ~50%; PP1 and PP2B are the responsible phosphatases.\",\n      \"method\": \"Phosphorylation assays in isolated rat brain nerve terminals, PKC inhibitors, phosphatase inhibitors, immunoprecipitation\",\n      \"journal\": \"The European journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple pharmacological tools and biochemical readouts in a single study with clear functional consequence\",\n      \"pmids\": [\"10651895\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Munc18-1 is required for docking of large dense-core vesicles (LDCVs) to the plasma membrane; munc18-1 null chromaffin cells show a 10-fold reduction in morphologically docked LDCVs and a 10-fold reduction in Ca2+-dependent LDCV exocytosis; acute Munc18-1 overexpression increases releasable vesicles and accelerates vesicle supply.\",\n      \"method\": \"Electron microscopy morphological docking assay, patch-clamp capacitance measurements in munc18-1 null mouse chromaffin cells, overexpression in bovine chromaffin cells\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with defined morphological and electrophysiological phenotype, complemented by overexpression\",\n      \"pmids\": [\"11545717\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Munc18-1/nSec1 Ser-313 is physiologically phosphorylated in intact chromaffin cells and synaptosomes in response to depolarization and receptor activation; PKC is the kinase and PP1/PP2B are the phosphatases responsible.\",\n      \"method\": \"Phospho-Ser-313-specific antisera in intact/permeabilized chromaffin cells and synaptosomes, kinase/phosphatase inhibitors\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phospho-specific antibody approach, single lab, physiological conditions but no mutagenesis in this paper\",\n      \"pmids\": [\"12950453\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Munc18-1 co-purifies with and co-localizes with Cdk5 and neuronal cytoskeletal proteins (neurofilaments, microtubules) in rat brain, suggesting a protein-protein interaction; cytoskeletal proteins and Cdk5 co-purify with Munc18-1 in immunoaffinity chromatography.\",\n      \"method\": \"Immunoaffinity chromatography, immunofluorescence, immunohistochemistry, immuno-electron microscopy\",\n      \"journal\": \"Neurochemistry international\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — co-purification and co-localization without functional validation of interaction\",\n      \"pmids\": [\"12963086\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Cell-specific deletion of munc18-1 in cerebellar Purkinje cells causes specific loss of those neurons in vivo, demonstrating a cell-intrinsic function of Munc18-1 essential for prolonged neuronal survival independent of synaptic activity.\",\n      \"method\": \"Conditional Cre-lox cell-specific knockout in vivo, histology\",\n      \"journal\": \"The European journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO with defined cellular phenotype, single lab\",\n      \"pmids\": [\"15255974\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Munc18-1 mutants with wild-type syntaxin binding can alter kinetics of individual exocytotic release events and have reduced Mint (Mints) binding affinity, indicating syntaxin-independent functions via interactions with Mint proteins.\",\n      \"method\": \"Chromaffin cell overexpression, amperometry, binding affinity assays with Munc18-1 mutants\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional exocytosis assay with binding data, single lab\",\n      \"pmids\": [\"15563604\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Munc18-1 directly promotes the stability of syntaxin-1 (pulse-chase analysis shows Munc18-1 increases syntaxin-1 half-life); syntaxin-1 levels are reduced 70% in munc18-1 KO mice; however, residual syntaxin-1 still correctly targets to synapses and forms SDS-resistant SNARE complexes.\",\n      \"method\": \"Pulse-chase analysis in transfected HEK293 cells, immunoblotting in munc18-1 KO mice\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — pulse-chase (Tier 1-level metabolic labeling) combined with in vivo KO, two orthogonal approaches\",\n      \"pmids\": [\"15935055\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"PKC phosphorylation of Munc18-1 at Ser313 potentiates vesicle pool replenishment after depleting stimulation (phosphomimetic S313D increases replenishment; non-phosphorylatable 3A mutant decreases it); vesicle docking is promoted by Munc18-1 in a phosphorylation-independent manner.\",\n      \"method\": \"Chromaffin cell overexpression with phosphomimetic and phospho-null Munc18-1 mutants, capacitance measurements, electron microscopy\",\n      \"journal\": \"Neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phospho-mutant functional analysis in chromaffin cells with electrophysiology and morphology, single lab\",\n      \"pmids\": [\"16997485\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Munc18-1 binds directly to assembled SNARE complexes containing syntaxin-1 (open conformation); this interaction involves the syntaxin-1 N-terminal Habc domain and the four-helical SNARE bundle. Munc18-1 thus has two distinct binding modes: to closed syntaxin-1 and to assembled SNARE complexes.\",\n      \"method\": \"In vitro binding assays (NMR, pulldowns), reconstituted SNARE complex\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct biochemical demonstration with multiple methods, foundational paper replicated extensively\",\n      \"pmids\": [\"17301226\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Binding of Munc18-1 to closed syntaxin-1 conformation stimulates vesicle docking; a distinct interaction mode (not closed syntaxin binding) regulates the subsequent vesicle priming step; Munc18-2 rescues docking but not priming in munc18-1 null chromaffin cells.\",\n      \"method\": \"Munc18 variant expression in munc18-1 null chromaffin cells, capacitance measurements, electron microscopy\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — null background rescue experiments with multiple Munc18 variants and two orthogonal readouts (electrophysiology + morphology)\",\n      \"pmids\": [\"17687045\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Munc18-1 is critical for plasma membrane localization of syntaxin-1 in PC12 cells; knockdown of Munc18-1 causes syntaxin-1 mislocalization to perinuclear regions (co-localizing with dense-core vesicle marker) without affecting SNAP-25 localization; reintroduction of Munc18-1 restores syntaxin-1 plasma membrane targeting.\",\n      \"method\": \"Stable knockdown cell lines, immunofluorescence, vesicle docking assay, secretion assay\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — stable KD with rescue, two independent readouts (localization + secretion), direct functional consequence\",\n      \"pmids\": [\"18077557\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"S-nitrosylation of syntaxin-1a at Cys145 disrupts Munc18-1 binding to the closed conformation of syntaxin-1a in vitro; a non-nitrosylatable C145S mutant resists this effect; NO does not inhibit SNARE complex formation or Munc18-1 binding to assembled SNARE complexes; nitrosomimetic syntaxin-1a expression in cells affects Munc18-1 localization and alters exocytosis kinetics and quantal size.\",\n      \"method\": \"In vitro binding assays, site-directed mutagenesis, live-cell exocytosis assay, molecular dynamics simulations\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mutagenesis identifying specific regulatory residue, in vitro and in vivo validation with functional readout\",\n      \"pmids\": [\"18452404\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Munc18-1 directly interacts with Rab3A; a gain-of-function E466K mutation (based on yeast Sly1p) increases this interaction, stimulates exocytosis, and increases secretory granule density at the cell periphery; the stimulatory effects require binding to closed syntaxin-1.\",\n      \"method\": \"Co-immunoprecipitation, exocytosis assays in chromaffin/PC12 cells, confocal microscopy, gain-of-function mutant analysis\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with functional correlates, single lab\",\n      \"pmids\": [\"17919117\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"De novo mutations in STXBP1 identified in patients with early infantile epileptic encephalopathy; mutant proteins are thermolabile compared to wild type (CD melting experiments) and show impaired binding to syntaxin, indicating that haploinsufficiency (protein instability + reduced syntaxin binding) underlies disease.\",\n      \"method\": \"Circular dichroism melting experiments, binding assays with mutant proteins, genomic sequencing\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct biophysical and biochemical characterization of disease-linked mutants, foundational study\",\n      \"pmids\": [\"18469812\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Munc18-1 binding to SNARE complexes (open syntaxin-1) mediates synaptic vesicle priming but not Ca2+-triggered fusion; point mutations preserving closed syntaxin-1 binding but disrupting SNARE complex binding selectively impair priming; Munc18-1 and complexin-1 bind simultaneously to SNARE complexes.\",\n      \"method\": \"Lentiviral rescue in munc18-1 KO neurons, point mutagenesis, electrophysiology\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — null background rescue with separation-of-function mutants, multiple orthogonal electrophysiology readouts\",\n      \"pmids\": [\"19255244\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Binding of UNC-18 (C. elegans STXBP1 ortholog) to the N-terminus of syntaxin (UNC-64) is essential for neurotransmission in vivo; UNC-18(F113R) defective in N-terminus binding fails to rescue unc-18 null locomotion defects, whereas UNC-18(R39C) defective in closed syntaxin binding fully rescues.\",\n      \"method\": \"Transgenic rescue of C. elegans unc-18 null mutant with point mutants, behavioral assays\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo epistasis with separation-of-function mutants in defined null background\",\n      \"pmids\": [\"19032153\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Presynaptic mGluR4 binds Munc18-1 in a Ca2+-dependent manner (EC50 ~168 nM for Ca2+); Ca2+-activated calmodulin disrupts the mGluR4-Munc18-1 interaction, releasing Munc18-1 to facilitate vesicle release; this mechanism contributes to paired-pulse facilitation.\",\n      \"method\": \"Co-immunoprecipitation, permeabilized PC12 cell secretion assay, synaptic transmission recordings, Ca2+ titration\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with Ca2+ titration, functional secretion and synaptic assays; single lab\",\n      \"pmids\": [\"19822743\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Rescue experiments in Munc18-1/-2 double knockdown PC12 cells show that binding to the closed conformation of syntaxin-1 is essential for Munc18-1's stimulatory action on syntaxin-1 expression, localization, and secretion; binding to the syntaxin-1 N-terminus plays a more limited role.\",\n      \"method\": \"Double knockdown with siRNA, rescue with Munc18-1 point mutants (K46E/E59K; F115E/E132A), secretion assays, immunofluorescence\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — double KD with separation-of-function mutant rescue, multiple orthogonal readouts\",\n      \"pmids\": [\"19812250\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Munc18-1 binds to synaptobrevin and to the SNARE four-helix bundle with similar low micromolar affinity; both interactions involve the same cavity of Munc18-1 that binds syntaxin-1; the binding site on synaptobrevin is at the C-terminus of its SNARE motif.\",\n      \"method\": \"NMR spectroscopy, fluorescence anisotropy, ITC, sedimentation assays\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple biophysical methods (NMR, ITC, fluorescence) in a single rigorous study\",\n      \"pmids\": [\"20102228\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The SNARE four-helix bundle and the syntaxin N-peptide constitute a minimal complement for Munc18-1 activation of membrane fusion; the Habc domain of syntaxin is not required for Munc18-1-stimulated fusion; the central cavity region of Munc18-1 is required for fusion stimulation.\",\n      \"method\": \"Reconstituted liposome fusion assay, syntaxin deletion and mutant analysis\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted in vitro fusion assay with domain mapping\",\n      \"pmids\": [\"20603329\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Munc18-1 domain-1 cleft mutations that reduce syntaxin-1 binding correlate tightly with impaired syntaxin-1 chaperoning, reduced dense-core vesicle docking, and reduced secretion; priming mutant phenotypes can largely be explained by reduced syntaxin-1 chaperoning.\",\n      \"method\": \"Munc18-1/-2 double knockdown rescue with domain-1 mutants, vesicle docking (EM), secretion assays, binding assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutant rescue in defined KD background with morphological and functional readouts, single lab\",\n      \"pmids\": [\"21193638\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Munc18-1 domain-1 cleft is essential for syntaxin-1 binding, chaperoning, vesicle docking, and secretion; correlations between binding and all downstream functions support a unified mechanism whereby syntaxin-1 chaperoning by domain-1 is the primary upstream function.\",\n      \"method\": \"Munc18-1/-2 double KD rescue with seven domain-1 mutants, binding assays, EM docking, secretion assays\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic mutant analysis with multiple readouts, single lab\",\n      \"pmids\": [\"21900502\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Munc18-1 performs a proofing function by inhibiting VAMP2/synaptobrevin tethering to monomeric syntaxin-1 at the plasma membrane (wild-type Munc18-1 abrogates Syb2-Synt1 binary trans-complex interaction at single-molecule level); Munc18-1 favors vesicle tethering to preformed syntaxin1A-SNAP25B binary cis-complexes.\",\n      \"method\": \"Single-molecule AFM force spectroscopy, patch-clamp capacitance, STED microscopy, chromaffin cell overexpression\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — single-molecule AFM with functional chromaffin cell measurements; single lab\",\n      \"pmids\": [\"21677188\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In reconstituted liposome fusion assay, Munc18-1 inhibition (via closed syntaxin) is released by concurrent incubation with VAMP2 liposomes and SNAP-25, specifically requiring Munc18-1/VAMP2 interaction; Munc18-1 binding to syntaxin N-peptide is obligatory for robust stimulation of fusion but not for inhibitory function.\",\n      \"method\": \"Reconstituted liposome fusion assay with defined mutants and isoform controls\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted in vitro fusion assay with multiple controls and isoform specificity\",\n      \"pmids\": [\"21730064\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Munc18-1 point mutations that strongly impair binding to free syntaxin-1 N-terminus and to assembled SNARE complexes support normal docking, priming, and fusion of synaptic vesicles and normal synaptic plasticity in munc18-1 null neurons.\",\n      \"method\": \"Lentiviral rescue in munc18-1 KO neurons, electrophysiology, electron microscopy\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — null background rescue with separation-of-function mutants, multiple readouts; contradicts some prior findings about SNARE complex binding requirement\",\n      \"pmids\": [\"22446389\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"In reconstituted giant unilamellar vesicle system, synaptotagmin-1-mediated vesicle docking is a prerequisite for Munc18-1 to accelerate trans-SNARE complex (SNAREpin) assembly and membrane fusion; Munc18-1 positions itself downstream of synaptotagmin docking and upstream of SNAREpin zippering.\",\n      \"method\": \"Reconstituted giant unilamellar vesicle fusion assay with sequential addition of components\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted system with defined ordered addition, establishing pathway position\",\n      \"pmids\": [\"22810233\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"STXBP1 disease variants with missense mutations show protein degradation in neuroblastoma2A cells (reduced protein levels), consistent with protein instability as the primary pathogenic mechanism; nonsense-mediated mRNA decay also demonstrated for splicing mutations.\",\n      \"method\": \"Transient expression in neuroblastoma2A cells, Western blot, RNA analysis in lymphoblastoid cells\",\n      \"journal\": \"Epilepsia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-based expression with protein quantification, single lab, multiple mutation types\",\n      \"pmids\": [\"20887364\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Munc18-1 controls SNARE complex assembly during human sperm acrosomal exocytosis; inactivation of endogenous Munc18-1 with antibody prevents trans-SNARE complex stabilization and inhibits acrosomal exocytosis; recombinant Munc18-1 blocks secretion by sequestering monomeric syntaxin.\",\n      \"method\": \"Function-blocking antibody, recombinant protein addition, electron microscopy, SNARE complex formation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — antibody inhibition with EM and biochemical readouts, single lab, non-neuronal system\",\n      \"pmids\": [\"23091057\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Domain 3a insertion mutants of Munc18-1 (K332E/K333E) completely lose ability to rescue secretion but effectively restore syntaxin-1 expression, plasma membrane localization, and vesicle docking; these mutants show impaired SNARE complex binding, identifying domain 3a as critical for the priming step specifically.\",\n      \"method\": \"Munc18-1/-2 double KD rescue with insertion mutants, secretion assay, immunofluorescence, EM docking, binding assay\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic mutant rescue with separation of docking from priming; single lab\",\n      \"pmids\": [\"23525015\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"STXBP1 promotes Weibel-Palade body exocytosis in endothelial cells through interaction with Rab27A effector Slp4-a; STXBP1 interacts with syntaxin-2 and -3 but not syntaxin-4; STXBP1 haploinsufficiency in patient-derived cells impairs histamine- and forskolin-stimulated VWF secretion.\",\n      \"method\": \"Proteomic screen for Slp4-a targets, co-immunoprecipitation, siRNA knockdown, patient-derived blood outgrowth endothelial cells, VWF secretion assay\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — proteomic identification confirmed by Co-IP, functional siRNA KD and patient-derived cell validation with two agonists\",\n      \"pmids\": [\"24700782\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Munc18-1 is a dynamically regulated PKC target during post-tetanic potentiation (PTP); two PKC phosphorylation sites of Munc18-1 are critically important for PTP at the calyx of Held synapse; a phosphatase limits PTP duration; a conventional PKC isoform initiates PTP.\",\n      \"method\": \"Gene replacement strategy at calyx of Held, electrophysiology, pharmacological kinase/phosphatase inhibition\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — gene replacement with phospho-site mutants at a defined synapse, electrophysiology + pharmacology\",\n      \"pmids\": [\"24520164\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Munc18-1 redistributes from synapses during stimulation and reclusters within minutes; reclustering is independent of syntaxin-1 but requires Ca2+ influx and PKC activity; a PKC-insensitive Munc18-1 mutant fails to recluster; synaptic Munc18-1 levels correlate with synaptic strength and releasable vesicle pool size.\",\n      \"method\": \"Knock-in mouse with fluorescently tagged Munc18-1 from endogenous locus, FRAP in hippocampal neurons, pharmacological manipulation\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — endogenous fluorescent tag (Tier 1 localization), FRAP with functional correlation, defined PKC-insensitive mutant\",\n      \"pmids\": [\"24590174\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Heterozygous STXBP1 loss-of-function mutations in human neurons reduce Munc18-1 protein and syntaxin-1 levels by ~30% and decrease spontaneous and evoked neurotransmitter release by ~50%, confirming a presynaptic impairment mechanism.\",\n      \"method\": \"Conditional heterozygous/homozygous STXBP1 mutations in human ES cell-derived neurons, electrophysiology\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — isogenic human neuron model with electrophysiology, direct mechanistic link established\",\n      \"pmids\": [\"26280581\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The trans-SNARE-regulating function of Munc18-1 (promoting VAMP2 zippering) is essential for synaptic exocytosis; v-SNARE mutations that selectively impair Munc18-1's ability to promote trans-SNARE zippering strongly inhibit neurotransmitter release; an Ohtahara Syndrome-associated Munc18-1 mutation compromises this trans-SNARE-regulating function.\",\n      \"method\": \"Reconstituted trans-SNARE assay, lentiviral expression of v-SNARE mutants in cultured neurons, electrophysiology\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution assay combined with neuronal rescue electrophysiology, disease-linked mutation characterized\",\n      \"pmids\": [\"26572858\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Munc18-1 domain 3a helix 12 conformation controls vesicle priming; disruptive mutations (L348R, Δ324-339) reduce priming and secretory amplitude; gain-of-function P335A (extends helix) markedly increases priming; effects are specific to priming with unchanged fusion kinetics and Ca2+ dependence.\",\n      \"method\": \"Expression of helix-12 mutants in Munc18-1 null chromaffin cells, capacitance measurements, EM, in vitro fusion assay\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — null background rescue with separation-of-function mutants, electrophysiology + EM + in vitro assay\",\n      \"pmids\": [\"27358447\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Munc18-1 is essential for neuropeptide secretion from dense-core vesicles; conditional inactivation abolishes all DCV exocytosis; Munc18-2 and Munc18-3 cannot substitute; heterozygous Munc18-1 impairs DCV exocytosis especially during peak stimulation.\",\n      \"method\": \"Conditional KO in mouse CNS neurons, single-vesicle pHluorin-tagged neuropeptide Y/BDNF secretion assay during action potential trains\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO with single-vesicle resolution assay, isoform specificity controls\",\n      \"pmids\": [\"34103363\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Munc18-1 is a molecular chaperone for α-synuclein that controls its self-replicating aggregation; disease-linked EIEE Munc18-1 mutants form polymers that co-aggregate wild-type Munc18-1 and α-synuclein, forming Lewy body-like structures; removal of endogenous Munc18-1 increases α-synuclein aggregation propensity, rescued by Munc18-1 WT re-expression.\",\n      \"method\": \"Single-molecule analysis, gene-edited cells, primary neurons, co-aggregation assays, confocal microscopy\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — single-molecule + KO + rescue, single lab; novel function outside exocytosis\",\n      \"pmids\": [\"27597756\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The Munc18-1 domain 3a hinge-loop (residues 317-333) controls syntaxin-1A confinement into nanodomains and engagement with the SNARE complex during priming; a deletion mutant (Δ317-333) prolongs vesicle docking and blocks stimulation-induced diffusional changes of Munc18-1 and syntaxin-1A in nanodomains.\",\n      \"method\": \"Single-molecule tracking, super-resolution microscopy, PC12 double KD rescue, secretion assay\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — single-molecule localization + KD rescue, single lab\",\n      \"pmids\": [\"27646276\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Munc18-1 domain 3a helix 12 interacts with synaptobrevin-2/VAMP2 to mediate SNARE complex formation and vesicle priming; EPR spectroscopy shows Munc18-1 shifts syntaxin/SNAP-25 complex from inhibitory 2:1 to productive 1:1 open-state configuration.\",\n      \"method\": \"Electron paramagnetic resonance (EPR) spectroscopy on reconstituted SNARE complexes\",\n      \"journal\": \"Structure (London, England : 1993)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — EPR structural approach, single lab, single method\",\n      \"pmids\": [\"26876096\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"All disease-causing STXBP1 variants tested have severely decreased protein levels, indicating impaired protein stability as the primary molecular defect; disease variants support synaptic transmission to variable extent on null background but show no dominant-negative effect on heterozygous background.\",\n      \"method\": \"Allelic series of STXBP1 variants in null-background neurons, Western blot, electrophysiology, four mouse models\",\n      \"journal\": \"Brain : a journal of neurology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — allelic series across multiple methods including electrophysiology and in vivo EEG, single lab but multiple orthogonal approaches\",\n      \"pmids\": [\"29538625\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Munc18-1 has autoinhibition of synaptobrevin binding via a 'furled conformation' loop; a D326K mutation disrupting this autoinhibition stimulates Munc18-1 activity in reconstitution assays and causes gain-of-function in C. elegans; an L348R mutation inhibiting synaptobrevin binding reduces activity; this autoinhibition helps enable Munc13-1-dependent regulation.\",\n      \"method\": \"NMR spectroscopy, reconstitution assays (Munc18-1 + Munc13-1 dependent fusion), C. elegans rescue experiments\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — NMR + reconstitution + in vivo genetic rescue, multiple orthogonal methods\",\n      \"pmids\": [\"28477408\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Tyrosine phosphorylation of Munc18-1 at Y473 by Src family kinases abolishes its SNARE-templating stimulatory function and membrane fusion in vitro, and disrupts vesicle priming (but not docking) in munc18-1 null neurons; non-phosphorylatable Munc18-1 supports normal transmission; ERK-dependent Munc18-1 phosphorylation leads to its degradation by the ubiquitin-proteasome system.\",\n      \"method\": \"In vitro fusion assay, munc18-1 KO neuron rescue with Y473D mutant, electrophysiology, mass spectrometry phospho-proteomics\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro fusion reconstitution + null background neuronal rescue + defined phospho-mutant\",\n      \"pmids\": [\"29150433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"CB1R and mGluR2/3 activation induces presynaptic inhibition through ERK-mediated phosphorylation of Munc18-1, causing decreased synaptic transmission and subsequent ubiquitin-proteasome-dependent Munc18-1 degradation; preventing ERK-dependent Munc18-1 phosphorylation increases synaptic strength.\",\n      \"method\": \"Gene replacement with phospho-mutant Munc18-1, pharmacological ERK/MEK inhibition, electrophysiology\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gene replacement with defined mutant, pharmacological validation, single lab\",\n      \"pmids\": [\"27056679\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Munc18-1 knockdown impairs radial migration of cortical neurons during corticogenesis; Syntaxin1A is critical for radial migration downstream of Munc18-1; Munc18-1 knockdown hampers post-Golgi vesicle trafficking and plasma membrane vesicle fusion in vivo and in vitro.\",\n      \"method\": \"In utero electroporation knockdown, time-lapse imaging, cortical neuron fractionation, vesicle trafficking assay\",\n      \"journal\": \"Acta neuropathologica communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo knockdown with live imaging, single lab\",\n      \"pmids\": [\"29191246\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Munc18-1 catalyzes stepwise zippering of synaptic SNAREs (syntaxin, VAMP2, SNAP-25) via an obligate template complex intermediate; Munc18-1 juxtaposes N-terminal SNARE motif regions of syntaxin and VAMP2 while keeping C-terminal regions separated; SNAP-25 then binds to induce full zippering; mutations modulating template complex stability correspondingly affect membrane fusion; SM proteins Munc18-3 and Vps33 similarly chaperone SNARE assembly.\",\n      \"method\": \"Single-molecule force spectroscopy (optical tweezers), mutagenesis, reconstitution assays\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — single-molecule force spectroscopy with mutagenesis and reconstitution, multiple SM protein controls demonstrating conservation\",\n      \"pmids\": [\"30540253\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"At least five disease-linked missense mutations of Munc18-1 destabilize and aggregate the mutant protein; mutant aggregates incorporate wild-type Munc18-1, depleting functional protein below hemizygous levels (dominant-negative aggregation mechanism); chemical chaperones (4-phenylbutyrate, sorbitol, trehalose) reverse these deficits in vitro and in vivo.\",\n      \"method\": \"In vitro aggregation assays, S. cerevisiae strains, C. elegans models, conditional KO mouse neurons, Western blot\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple model systems (yeast, worm, mouse neurons), multiple orthogonal methods, therapeutic rescue\",\n      \"pmids\": [\"30266908\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Munc18-1 is crucial to overcome αSNAP inhibition of synaptic vesicle fusion; αSNAP inhibits liposome fusion by binding syntaxin-1 (blocking Munc18-1 binding), by binding syntaxin-1-SNAP-25 heterodimers (blocking SNARE formation), and by binding trans-SNARE complexes; inhibition is avoided only when Munc18-1 binds syntaxin-1 first, leading to Munc18-1-Munc13-1-dependent fusion.\",\n      \"method\": \"Liposome fusion assays, FRET, NMR spectroscopy\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted liposome fusion with FRET and NMR, multiple inhibitory mechanisms mapped\",\n      \"pmids\": [\"31548544\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"MUN domain of Munc13-1 stabilizes the Munc18-1/SNARE template complex by ~2.1 kBT, forming a tetrameric complex; this stabilization enhances SNAP-25 binding and full SNARE assembly; mutational studies confirm functional importance for neurotransmitter release.\",\n      \"method\": \"Single-molecule force spectroscopy (optical tweezers), mutagenesis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — single-molecule force spectroscopy with mutagenesis, direct measurement of stabilization energy\",\n      \"pmids\": [\"31888993\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Stxbp1 haploinsufficiency reduces cortical inhibitory neurotransmission via distinct mechanisms from parvalbumin-expressing and somatostatin-expressing interneurons; GABAergic synaptic dysfunction is a crucial contributor to STXBP1 encephalopathy pathogenesis.\",\n      \"method\": \"Heterozygous Stxbp1 mouse model, cell-type-specific Cre lines, patch-clamp electrophysiology, behavioral assays\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — cell-type-specific conditional KO with electrophysiology, multiple interneuron types analyzed\",\n      \"pmids\": [\"32073399\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Homozygous STXBP1 L446F mutation causes a gain-of-function: 2-fold increase in evoked synaptic transmission and release probability with reduced paired-pulse plasticity; protein stability is less severely affected than typical heterozygous disease mutants.\",\n      \"method\": \"Munc18-1 null neuron rescue with L446F, patch-clamp electrophysiology, Western blot\",\n      \"journal\": \"Brain : a journal of neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — null background rescue with electrophysiology, single lab, single mutation\",\n      \"pmids\": [\"31855252\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Helices 11 and 12 of Munc18-1 domain 3a interact with VAMP2 SNARE motif (layers -4 to +5); Q301 in helix 11 is pivotal for VAMP2 binding and template complex formation; Q301D mutant fails to stimulate membrane fusion in reconstituted assay; Munc13-1 cannot bypass requirement for Munc18-1/VAMP2 interaction; Q301D expression in Munc18-1 deficient neurons severely reduces synaptic transmission.\",\n      \"method\": \"Site-specific crosslinking with unnatural amino acid, reconstituted vesicle fusion assay, lentiviral rescue in KO neurons, electrophysiology\",\n      \"journal\": \"eNeuro\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crosslinking maps precise binding interface, reconstitution assay, and neuronal KO rescue all in one study\",\n      \"pmids\": [\"33055194\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"All eight epilepsy-associated STXBP1 missense variants tested in humanized C. elegans show reduced protein levels (20-30% of wild-type) consistent with protein instability; locomotion and electrophysiological deficits vary by variant; no difference in mRNA levels confirming post-transcriptional instability.\",\n      \"method\": \"CRISPR/Cas9 unc-18 null C. elegans rescued with human STXBP1 variants, behavioral assays, electrophysiology, Western blot\",\n      \"journal\": \"Epilepsia\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — humanized in vivo model with multiple orthogonal readouts for each variant\",\n      \"pmids\": [\"32112430\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Munc18-1 undergoes K48-linked polyubiquitination leading to proteasomal (not lysosomal) degradation; the C180Y disease-causing mutation greatly potentiates polyubiquitination and proteasomal degradation, rendering Munc18-1 unable to support neuroexocytosis; this phenotype is reversed at permissive temperature.\",\n      \"method\": \"Ubiquitination assays, proteasome/lysosome inhibitors, temperature-shift rescue, secretion assays in Munc18-deficient cells\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biochemical ubiquitination characterization with functional rescue, single lab\",\n      \"pmids\": [\"25284778\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Early cis-Golgi condensation is the first cellular abnormality upon Munc18-1 loss in neurons (before synaptogenesis); expression of Munc18-3 (which does not bind syntaxin-1) in Munc18-1 KO neurons prevents cell death and restores Golgi morphology but does not rescue synaptic transmission or syntaxin-1 targeting, indicating distinct cell-survival and exocytotic functions.\",\n      \"method\": \"Conditional KO neurons, immunofluorescence, electron microscopy, Munc18-3 rescue\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO with isoform rescue dissecting two functions, single lab\",\n      \"pmids\": [\"28348137\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"STXBP1 interacts with DDHD2 (a phospholipase A1); STXBP1 controls DDHD2 targeting to the plasma membrane and generation of saturated free fatty acids (myristic acid) in the brain; this interaction mediates long-term memory formation.\",\n      \"method\": \"Pulldown-mass spectrometry, STXBP1/2 knockout neurosecretory cells, Stxbp1+/- mouse model, lipidomic analysis, memory behavioral assays\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pulldown-MS identification with KO/haploinsufficient model validation and lipidomics; single lab\",\n      \"pmids\": [\"38316990\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"STXBP1/Munc18-1 is a neural-specific SM (Sec1/Munc18) protein that acts as the master organizer of synaptic vesicle exocytosis by sequentially chaperoning syntaxin-1 to the plasma membrane, templating SNARE complex assembly via a Munc18-1/syntaxin-VAMP2 intermediate template complex (stabilized by Munc13-1 MUN domain), promoting vesicle docking (through closed-syntaxin binding), and enabling vesicle priming (through domain 3a helix 12 conformational change engaging VAMP2); its activity is regulated by PKC phosphorylation (Ser306/313 reducing syntaxin affinity and enabling vesicle pool replenishment), Src kinase phosphorylation (Y473 blocking SNARE templating), ERK phosphorylation (leading to proteasomal degradation), S-nitrosylation of syntaxin Cys145 (disrupting Munc18-1/closed-syntaxin interaction), Ca2+/calmodulin-dependent release from mGluR4, and interaction with Rab3A; disease-causing mutations primarily destabilize the protein leading to haploinsufficiency or dominant-negative aggregation, while also impairing STXBP1-dependent inhibitory neurotransmission and neuropeptide secretion, and STXBP1 additionally controls α-synuclein aggregation, DDHD2 membrane targeting/saturated fatty acid production, and radial migration of cortical neurons during development.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"STXBP1 (Munc18-1) is a neural-specific Sec1/Munc18 (SM) protein that serves as the master organizer of regulated exocytosis, controlling synaptic vesicle and dense-core vesicle fusion through sequential, physically distinct engagements with the SNARE machinery [#0, #14, #40]. It first acts as a molecular chaperone for syntaxin-1, binding the closed conformation, stabilizing the protein and extending its half-life, and directing it to the plasma membrane; loss of Munc18-1 reduces syntaxin-1 levels and mistargets it to perinuclear compartments [#4, #11, #15]. Through its domain-1 cleft, closed-syntaxin binding drives vesicle docking, while a separable activity centered on domain 3a (helix 12 and the hinge-loop) engages the assembling SNARE bundle to mediate vesicle priming [#14, #25, #39, #42]. Mechanistically, Munc18-1 templates SNARE assembly by forming an obligate intermediate that juxtaposes the N-terminal SNARE motifs of syntaxin-1 and VAMP2/synaptobrevin while holding their C-termini apart, permitting SNAP-25 binding to drive full zippering; the MUN domain of Munc13-1 stabilizes this template complex, and Munc18-1 binding overcomes \\u03b1SNAP-mediated inhibition of fusion [#49, #52, #55, #51]. This catalytic activity positions Munc18-1 downstream of synaptotagmin-dependent docking and upstream of trans-SNARE zippering [#30, #38]. Its activity is tuned by phosphorylation: conventional PKC phosphorylates Ser306/Ser313 to reduce syntaxin affinity and potentiate vesicle pool replenishment and post-tetanic potentiation, Src-family kinases phosphorylate Y473 to abolish SNARE templating, and ERK-mediated phosphorylation downstream of CB1R/mGluR signaling triggers ubiquitin-proteasome degradation [#2, #12, #35, #46, #47]. De novo and missense STXBP1 mutations cause early infantile epileptic encephalopathy, acting predominantly through protein destabilization and haploinsufficiency \\u2014 and in some cases dominant-negative aggregation that co-sequesters wild-type protein \\u2014 which reduces neurotransmission, with inhibitory GABAergic and neuropeptide signaling particularly affected [#18, #37, #44, #50, #53]. Beyond core exocytosis, Munc18-1 chaperones \\u03b1-synuclein to limit its aggregation, controls DDHD2 plasma-membrane targeting and saturated fatty acid production for memory, and is required for cortical neuron radial migration and neuronal survival [#41, #59, #48, #58].\",\n  \"teleology\": [\n    {\n      \"year\": 1994,\n      \"claim\": \"Established that the neural protein Munc18-1 is a selective syntaxin-binding partner, placing it at the heart of synaptic vesicle docking and fusion rather than acting generally across the SNARE machinery.\",\n      \"evidence\": \"GST pulldowns from brain extract showing binding to syntaxin-1/2/3 but not syntaxin-4, SNAP-25, or VAMP, plus syntaxin-dependent membrane association\",\n      \"pmids\": [\"8108429\", \"8134339\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the syntaxin conformation bound\", \"No functional consequence for fusion established\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Demonstrated functional conservation and isoform specificity of Munc18-1 in neurotransmitter release, and identified PKC phosphorylation as a regulatory switch on syntaxin binding.\",\n      \"evidence\": \"Transgenic rescue of C. elegans unc-18 null by neural (but not ubiquitous) Munc18; in vitro PKC phosphorylation at Ser306/Ser313 with binding assays\",\n      \"pmids\": [\"8824310\", \"8631738\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo physiological relevance of the phosphosites not yet shown\", \"Step in exocytosis controlled by phosphorylation unresolved\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Resolved that Munc18-1 binds a closed conformation of syntaxin-1 mutually exclusive with ternary SNARE assembly, framing the central puzzle of how a SNARE-blocking protein could promote fusion.\",\n      \"evidence\": \"In vitro binding, nondenaturing gels, neurotoxin treatment, cross-linking of brain membranes; nerve-terminal phosphorylation assays\",\n      \"pmids\": [\"10648557\", \"10651895\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism reconciling SNARE inhibition with positive fusion role unknown\", \"Did not address binding to assembled SNAREs\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Provided in vivo genetic proof that Munc18-1 is required for vesicle docking and exocytosis, converting a binding partner into a functionally essential exocytic factor.\",\n      \"evidence\": \"Electron microscopy docking assay and patch-clamp capacitance in munc18-1 null chromaffin cells, plus overexpression\",\n      \"pmids\": [\"11545717\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether docking and a later priming step are separable not resolved\", \"Molecular basis of docking defect unclear\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identified syntaxin-1 chaperoning/stabilization as an upstream Munc18-1 function, explaining how loss of Munc18-1 collapses the presynaptic SNARE pool.\",\n      \"evidence\": \"Pulse-chase in HEK293 cells and immunoblotting in munc18-1 KO mice; PC12 knockdown with rescue showing syntaxin-1 membrane targeting\",\n      \"pmids\": [\"15935055\", \"18077557\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether chaperoning fully accounts for downstream phenotypes debated\", \"Trafficking route of syntaxin-1 not fully defined\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Discovered a second binding mode \\u2014 Munc18-1 binding to assembled SNARE complexes via the syntaxin N-peptide \\u2014 and dissociated closed-syntaxin-dependent docking from a distinct priming activity.\",\n      \"evidence\": \"NMR and pulldowns on reconstituted SNARE complexes; Munc18 variant rescue with capacitance and EM in null chromaffin cells\",\n      \"pmids\": [\"17301226\", \"17687045\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise contribution of each binding mode to fusion not quantified\", \"Structural basis of the priming activity unresolved\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Mapped SNARE-complex binding (open syntaxin) to vesicle priming specifically, and confirmed in vivo that syntaxin N-terminus binding is essential for neurotransmission.\",\n      \"evidence\": \"Lentiviral rescue with separation-of-function mutants in munc18-1 KO neurons; C. elegans rescue with N-terminus and closed-syntaxin binding mutants; PC12 double-KD rescue\",\n      \"pmids\": [\"19255244\", \"19032153\", \"19812250\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative importance of N-peptide vs closed-syntaxin binding contested across systems\", \"Direct fusion-catalysis mechanism still inferred\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Defined the minimal molecular determinants of Munc18-1 fusion stimulation, including direct binding to synaptobrevin/VAMP2 through the same central cavity, advancing toward a catalytic templating model.\",\n      \"evidence\": \"NMR, ITC, fluorescence anisotropy on VAMP2 binding; reconstituted liposome fusion with syntaxin domain mapping; domain-1 cleft mutant analysis\",\n      \"pmids\": [\"20102228\", \"20603329\", \"21193638\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How simultaneous syntaxin and VAMP2 engagement is coordinated unresolved\", \"Order of events during fusion not yet established\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Positioned Munc18-1 in the fusion pathway downstream of synaptotagmin docking and upstream of SNAREpin zippering, and linked disease mutations to protein instability.\",\n      \"evidence\": \"Reconstituted giant unilamellar vesicle fusion with ordered component addition; separation-of-function mutant rescue in KO neurons; disease-variant expression in N2a cells with NMD analysis\",\n      \"pmids\": [\"22810233\", \"22446389\", \"20887364\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Contradiction over whether SNARE-complex binding is required for fusion (vs. #19) unresolved here\", \"In vivo ordering not directly tested\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Localized the priming-specific function to domain 3a, demonstrating mutants that fully chaperone syntaxin-1 and support docking yet abolish secretion.\",\n      \"evidence\": \"Domain 3a insertion mutant (K332E/K333E) rescue in PC12 double-KD cells with secretion, immunofluorescence, EM docking, and SNARE binding assays\",\n      \"pmids\": [\"23525015\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab, single cell system\", \"Structural mechanism of helix 12 action not defined here\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Showed Munc18-1 phosphorylation is dynamically regulated during synaptic plasticity and degradation, and extended its exocytic role to non-neuronal secretion.\",\n      \"evidence\": \"Gene replacement at the calyx of Held with phospho-mutants and electrophysiology; knock-in fluorescent Munc18-1 FRAP; proteomic identification of STXBP1 in Weibel-Palade body exocytosis; K48 ubiquitination assays\",\n      \"pmids\": [\"24520164\", \"24590174\", \"24700782\", \"25284778\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinase/phosphatase identities for some events not fully resolved\", \"E3 ligase mediating ubiquitination unidentified\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Established that promotion of trans-SNARE/VAMP2 zippering is the essential Munc18-1 function, that helix 12 conformation controls priming, and that Munc18-1 drives neuropeptide DCV exocytosis.\",\n      \"evidence\": \"Reconstituted trans-SNARE assay with v-SNARE mutants and neuronal electrophysiology; helix-12 mutant rescue in null chromaffin cells with EM; conditional KO with single-vesicle neuropeptide secretion; isogenic human-neuron STXBP1 mutations\",\n      \"pmids\": [\"26572858\", \"27358447\", \"34103363\", \"26280581\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic structure of the templating intermediate not yet captured\", \"How helix 12 engages VAMP2 not yet defined here\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identified the helix 12/VAMP2 interaction and syntaxin nanodomain confinement as the structural basis of priming, and uncovered a chaperone role for Munc18-1 in controlling \\u03b1-synuclein aggregation.\",\n      \"evidence\": \"EPR on reconstituted SNARE complexes; single-molecule tracking and super-resolution in PC12 KD cells; single-molecule and gene-edited cell co-aggregation assays\",\n      \"pmids\": [\"26876096\", \"27646276\", \"27597756\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"\\u03b1-synuclein chaperone function from a single lab and outside the exocytic role\", \"Direct structural snapshot of helix 12-VAMP2 still indirect\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Defined autoinhibition of VAMP2 binding, identified Src/ERK phosphorylation as negative regulators coupling presynaptic receptors to Munc18-1 turnover, and revealed non-exocytic roles in cortical migration and neuronal survival.\",\n      \"evidence\": \"NMR + reconstitution + C. elegans rescue (autoinhibition); in vitro fusion and KO-neuron rescue with Y473D and ERK phospho-mutants; in utero electroporation knockdown imaging; conditional KO with Munc18-3 rescue dissecting Golgi/survival from exocytosis\",\n      \"pmids\": [\"28477408\", \"29150433\", \"27056679\", \"29191246\", \"28348137\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo significance of autoinhibition during synaptic signaling not fully mapped\", \"Mechanism of Golgi/survival function independent of syntaxin unresolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Provided direct single-molecule proof of the obligate template-complex mechanism of stepwise SNARE zippering and consolidated protein destabilization/aggregation as the unifying disease mechanism.\",\n      \"evidence\": \"Optical-tweezers single-molecule force spectroscopy with mutagenesis and SM-protein controls; allelic series of disease variants in null-background neurons with EEG; multi-organism aggregation models with chemical-chaperone rescue\",\n      \"pmids\": [\"30540253\", \"29538625\", \"30266908\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether all disease variants act purely by instability vs additional dominant effects still being delineated\", \"In vivo template-complex dynamics not directly observed\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Showed Munc13-1's MUN domain energetically stabilizes the Munc18-1/SNARE template and that Munc18-1 must bind syntaxin-1 first to evade \\u03b1SNAP inhibition, integrating the catalytic cascade.\",\n      \"evidence\": \"Single-molecule force spectroscopy measuring template stabilization; reconstituted liposome fusion with FRET and NMR mapping \\u03b1SNAP inhibition\",\n      \"pmids\": [\"31888993\", \"31548544\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo confirmation of the kBT stabilization effect lacking\", \"How ordering of binding is enforced in cells unclear\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Mapped the precise helix 11/12-VAMP2 interface required for templating, identified GABAergic interneuron dysfunction as central to STXBP1 encephalopathy, and characterized a gain-of-function disease allele.\",\n      \"evidence\": \"Unnatural-amino-acid crosslinking with reconstitution and KO-neuron rescue (Q301D); cell-type-specific conditional Stxbp1 KO with electrophysiology; humanized C. elegans variant panel; L446F null-background rescue\",\n      \"pmids\": [\"33055194\", \"32073399\", \"32112430\", \"31855252\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How gain-of-function alleles produce disease distinct from loss-of-function not fully resolved\", \"Cell-type-specific circuit consequences in humans untested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Extended Munc18-1 function into lipid signaling for memory, showing it controls DDHD2 membrane targeting and saturated fatty acid production.\",\n      \"evidence\": \"Pulldown-mass spectrometry, STXBP1/2 KO neurosecretory cells and Stxbp1+/- mice, lipidomics, and memory behavioral assays\",\n      \"pmids\": [\"38316990\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Relationship between lipid function and core exocytic role not integrated\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"An atomic-resolution structure of the full Munc18-1/syntaxin-1/VAMP2/Munc13-1 templating intermediate in a membrane context, and a unified explanation of how diverse missense variants partition between loss-of-function instability, dominant-negative aggregation, and gain-of-function, remain to be established.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No membrane-embedded structure of the complete template complex\", \"Genotype-to-mechanism mapping across the full variant spectrum incomplete\", \"How non-exocytic functions (\\u03b1-synuclein, DDHD2, migration) integrate with core role unclear\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0044183\", \"supporting_discovery_ids\": [11, 15, 41, 49]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [49, 52, 55]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [4, 14, 28, 51]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [49, 55]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 15, 36]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [58, 59]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [2, 11]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [6, 15, 40]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [6, 30, 38, 49]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [19, 37, 53]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [18, 44, 50]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [48, 58]}\n    ],\n    \"complexes\": [\n      \"Munc18-1/syntaxin-1/VAMP2 template complex\",\n      \"Munc18-1/SNARE/Munc13-1 MUN tetrameric complex\"\n    ],\n    \"partners\": [\n      \"STX1A\",\n      \"VAMP2\",\n      \"SNAP25\",\n      \"UNC13A\",\n      \"RAB3A\",\n      \"GRM4\",\n      \"DDHD2\",\n      \"SNCA\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}