{"gene":"RPH3A","run_date":"2026-06-10T06:43:37","timeline":{"discoveries":[{"year":1993,"finding":"Rabphilin-3A (RPH3A) was identified as a novel protein that selectively interacts with the GTP-bound form of Rab3A but not the GDP-bound form, establishing it as a GTP-state-dependent effector of Rab3A.","method":"Biochemical pulldown/complex formation assay using GTPγS-bound vs. GDP-bound Rab3A with purified and recombinant rabphilin-3A; cDNA cloning and expression in COS7 cells","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro binding assay with purified proteins, replicated across bovine brain-purified and recombinant forms, confirmed in multiple subsequent studies","pmids":["8384302"],"is_preprint":false},{"year":1993,"finding":"Rabphilin-3A has two functionally distinct domains: an N-terminal domain (residues 1–280) that binds GTP-Rab3A and a C-terminal domain (residues 281–704) containing two C2 domains that bind phospholipid and Ca2+ in a cooperative manner.","method":"In vitro binding assays using recombinant full-length, N-terminal, and C-terminal fragments of rabphilin-3A with GTP-Rab3A, phospholipid, and 45Ca2+","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution with purified recombinant domain fragments and multiple orthogonal binding assays, replicated across subsequent studies","pmids":["8262955"],"is_preprint":false},{"year":1993,"finding":"Rabphilin-3A and its N-terminal fragment inhibit Rab3A GAP-stimulated GTPase activity of Rab3A, thereby potentially keeping Rab3A in the GTP-bound active form.","method":"In vitro GTPase assay measuring basal and GAP-stimulated GTP hydrolysis of Rab3A in the presence of rabphilin-3A or its fragments","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro enzymatic assay with purified proteins and defined domain fragments","pmids":["8226731"],"is_preprint":false},{"year":1994,"finding":"Rabphilin-3A is localized on synaptic vesicles in presynaptic terminals, as determined by immunogold electron microscopy of neuromuscular junctions and subcellular fractionation showing enrichment in purified synaptic vesicle fractions.","method":"Immunogold electron microscopy and subcellular fractionation of rat brain","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct localization by immunogold EM and fractionation, replicated across multiple labs and cell types","pmids":["8060298"],"is_preprint":false},{"year":1994,"finding":"Synaptic targeting of rabphilin-3A depends on Rab3A/3C: in rab3A-deficient mice, rabphilin-3A is decreased at synapses of neurons expressing primarily rab3A and accumulates in perikarya, while neurons expressing rab3C retain normal synaptic rabphilin-3A; rabphilin-3A binds rab3C in vitro.","method":"Immunofluorescence and Western blot in rab3A knockout mice; in vitro binding assay with rab3C","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic loss-of-function model combined with in vitro binding, multiple neuronal populations analyzed","pmids":["7946335"],"is_preprint":false},{"year":1994,"finding":"Rabphilin-3A is associated with synaptic vesicles via a vesicle-resident protein in a manner independent of Rab3A; removal of Rab3A or addition of exogenous Rab3A did not affect rabphilin-3A binding to vesicles, but trypsin treatment abolished binding.","method":"Reconstitution binding assay using salt-stripped synaptic vesicles, Rab GDI extraction of endogenous Rab3A, trypsin treatment","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct vesicle binding reconstitution with multiple perturbations, single lab","pmids":["7806490"],"is_preprint":false},{"year":1994,"finding":"Rabphilin-3A is phosphorylated by cyclic AMP-dependent protein kinase (PKA) at its N-terminal region (~0.8 mol phosphate/mol protein), identifying it as a PKA substrate involved in neurotransmitter release regulation.","method":"In vitro phosphorylation assay with purified recombinant rabphilin-3A and PKA","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro kinase assay; confirmed and extended by multiple independent studies","pmids":["7945346"],"is_preprint":false},{"year":1994,"finding":"CaMKII phosphorylates rabphilin-3A at Ser34, Thr205, Thr209, and Thr537 (two mol phosphate maximally incorporated), identifying additional regulatory phosphorylation sites.","method":"In vitro phosphorylation assay with CaMKII purified from rat brain and recombinant rabphilin-3A; phosphorylation site identification","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — direct in vitro kinase assay with site identification; single lab, later refined","pmids":["7811264"],"is_preprint":false},{"year":1994,"finding":"Rabphilin-3A binds beta-adducin through its C-terminal C2 domain-containing region in the presence of Ca2+ and phosphatidylserine, identifying beta-adducin as a calcium/phospholipid-dependent binding partner.","method":"Purification and amino acid sequence analysis of co-purified 115 kDa protein; overlay assay and biochemical characterization","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biochemical purification and direct binding assay, single lab","pmids":["7999065"],"is_preprint":false},{"year":1994,"finding":"GTP cyclohydrolase I (Mr ~30 kDa) co-immunoprecipitates with rabphilin-3A from PC12 cell lysates and is phosphorylated upon high KCl stimulation, identifying it as a rabphilin-3A-interacting protein in neuroendocrine cells.","method":"Co-immunoprecipitation from PC12 cell lysate followed by SDS-PAGE and amino acid sequence analysis","journal":"Biochemical and biophysical research communications","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP experiment, no functional follow-up, single lab","pmids":["7802677"],"is_preprint":false},{"year":1994,"finding":"Rabphilin-3A has GDP/GTP exchange activity for Rab3A, potentially keeping Rab3A in the GTP-bound form by re-converting GDP-Rab3A produced by GAP activity.","method":"In vitro GDP/GTP exchange assay with purified Rab3A and rabphilin-3A","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — direct in vitro biochemical assay, single lab","pmids":["7926025"],"is_preprint":false},{"year":1995,"finding":"Rabphilin-3A is phosphorylated by CaMKII at residues 234 and 274 and by cAMP-dependent protein kinase (PKA) at residue 234, placing the middle region between the Rab3A-binding domain and C2 domains as a convergent regulatory phosphorylation site.","method":"In vitro phosphorylation assays with CaMKII and PKA; tryptic peptide mapping to identify phosphorylation sites","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro kinase assays with site-specific mapping; independently confirmed in subsequent studies","pmids":["7891174"],"is_preprint":false},{"year":1996,"finding":"Rabphilin-3A dissociates from synaptic vesicles after exocytosis in a manner requiring Ca2+ and membrane fusion; it interacts with GTP-Rab3A via an N-terminal Zn2+-finger motif, and this interaction is essential for rabphilin binding to synaptic vesicles, showing that Rab3 reversibly recruits rabphilin to vesicles analogously to Ras recruiting Raf.","method":"Exocytosis-coupled dissociation assay from synaptic vesicles; Zn2+-finger domain mutational analysis; in vitro binding","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — functional dissociation assay combined with domain mutagenesis, replicated mechanistic concept","pmids":["8617225"],"is_preprint":false},{"year":1996,"finding":"Alpha-actinin interacts with the N-terminal region of rabphilin-3A (the same region that binds GTP-Rab3A), and this interaction stimulates alpha-actinin's ability to cross-link actin filaments into bundles; GTPγS-Rab3A inhibits the rabphilin-3A/alpha-actinin interaction.","method":"Yeast two-hybrid screen from human brain cDNA library; direct binding assays; actin cross-linking assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — yeast two-hybrid discovery confirmed with direct binding and functional actin cross-linking assay; competitive inhibition by Rab3A also shown","pmids":["8943213"],"is_preprint":false},{"year":1996,"finding":"Rabphilin-3A is involved in Ca2+-dependent exocytosis from PC12 cells: reduction of endogenous rabphilin-3A inhibits high K+-induced growth hormone release, and N-terminal, C-terminal, or C2B fragments (but not C2A fragment alone) inhibit release when overexpressed.","method":"Growth hormone co-expression assay in PC12 cells; antisense knockdown; overexpression of domain fragments","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function and domain dissection with functional secretion readout, single lab","pmids":["8605005"],"is_preprint":false},{"year":1996,"finding":"The Cys-rich region in the N-terminal domain binds two Zn2+ ions and is necessary but not sufficient for efficient Rab3A binding; a minimal Rab3A-binding domain spans residues 45–170; C2 domains are required for efficient membrane attachment in PC12 cells; Rab3A binding targets rabphilin to the correct membrane compartment.","method":"Deletion and mutagenesis analysis; Rab3A binding assays; GFP-rabphilin subcellular localization in PC12 cells; zinc binding characterization","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic domain deletion and mutagenesis with subcellular localization; single lab","pmids":["8756657"],"is_preprint":false},{"year":1998,"finding":"Presynaptic microinjection of rabphilin-3A into squid giant synapse reversibly inhibits neurotransmitter release; the N-terminal Rab3A-binding/phosphorylation region and the two C2 domains each independently inhibit release; the N-terminal domain also perturbs endocytosis (altering endosome, coated vesicle, and plasma membrane areas).","method":"Presynaptic microinjection of recombinant rabphilin-3A and domain fragments into squid giant synapse; electrophysiology; electron microscopy","journal":"The Journal of general physiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct loss/gain-of-function by microinjection with electrophysiological and ultrastructural readouts","pmids":["9450942"],"is_preprint":false},{"year":1998,"finding":"Rabphilin phosphorylation at Ser234 is selectively increased by PKA and Ca2+ influx in mossy fiber CA3 synaptosomes but not in CA1 synaptosomes, correlating with the region-specific PKA-dependent LTP in mossy fibers.","method":"Phosphorylation assay in isolated CA1 and CA3 synaptosomes with forskolin treatment and K+-depolarization; region-specific fractionation of hippocampus","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — region-specific synaptosome assay with pharmacological intervention, single lab","pmids":["9425005"],"is_preprint":false},{"year":1999,"finding":"Crystal structure of activated Rab3A/GTP/Mg2+ bound to the effector domain of rabphilin-3A solved at 2.6 Å resolution; rabphilin-3A contacts Rab3A at two interfaces: switch I/II regions (nucleotide-state sensitive) and a deep pocket (RabCDR) containing the SGAWFF element of rabphilin-3A that confers Rab effector specificity.","method":"X-ray crystallography at 2.6 Å resolution; biochemical binding data","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution crystal structure with biochemical validation; landmark mechanistic paper","pmids":["10025402"],"is_preprint":false},{"year":1999,"finding":"NMR solution structure of the C2B domain of rabphilin-3A reveals a Janus-faced architecture: a Ca2+-binding top surface (similar to other C2 domains) and a Ca2+-independent bottom surface bearing a conserved alpha-helix, suggesting Ca2+-independent protein interactions from the bottom surface.","method":"NMR spectroscopy structure determination","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — NMR structure with functional inference about Ca2+-independent interactions; high-quality structural study","pmids":["10559882"],"is_preprint":false},{"year":2001,"finding":"High-affinity Rab3 binding is dispensable for rabphilin's stimulatory effect on Ca2+-regulated secretion in HIT-T15 cells; mutations V61A and L83A abolish Rab3 binding but do not impair secretory potentiation; however, mutant R60A retains Rab3 binding but loses stimulatory activity, suggesting secretory potentiation depends on an unknown factor binding to the Rab3-binding domain.","method":"Point mutagenesis of Rab3-binding domain; secretion assay in HIT-T15 cells; in vitro Rab3 binding assay","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic mutagenesis with functional secretion readout and binding assays, single lab","pmids":["10504306"],"is_preprint":false},{"year":2001,"finding":"Rabphilin promotes receptor-mediated endocytosis through interaction with Rabaptin-5; this activity is negatively regulated by Rab3. The Rabphilin V61A mutant (unable to bind Rab3) enhances transferrin endocytosis and binds Rabaptin-5, whereas L83A (also Rab3-binding defective) does not interact with Rabaptin-5 and does not enhance endocytosis.","method":"Transferrin endocytosis assay; co-immunoprecipitation of Rabaptin-5; Rab3-binding mutant analysis in HIT-T15 cells","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional endocytosis assay with mechanistic binding partner identification, single lab","pmids":["11309205"],"is_preprint":false},{"year":2001,"finding":"In C. elegans, rabphilin mutants show synergistic genetic interactions with hypomorphic SNARE (syntaxin, SNAP-25, synaptobrevin) mutants, causing severe behavioral defects not seen in rab3-SNARE double mutants, establishing a Rab3-independent function of rabphilin in potentiating SNARE function.","method":"C. elegans genetic epistasis; behavioral assays (locomotion, mechanosensation); pharmacological assays","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis in vivo with multiple allele combinations and multiple phenotypic readouts","pmids":["11717359"],"is_preprint":false},{"year":2001,"finding":"Phosphorylation of rabphilin on Ser234 and Ser274 is dynamically regulated in nerve terminals; soluble rabphilin (not vesicle-bound) is the primary phosphorylation target; phospho-rabphilin shows reduced membrane affinity; phosphorylation requires external Ca2+ and Rab3A; PKA and CaMKII differentially phosphorylate the two sites.","method":"Phospho-specific antibodies against Ser234 and Ser274; subcellular fractionation; synaptosome stimulation experiments; depolarization assays","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — phospho-specific antibodies with fractionation and pharmacological dissection; multiple orthogonal methods","pmids":["11466418"],"is_preprint":false},{"year":2003,"finding":"Rabphilin interacts with Rab3A/B/C/D, Rab8A, and Rab27A/B (but not other Rabs), and Noc2 shows the same specificity; this broader Rab specificity beyond Rab3 suggests rabphilin functions as effector for multiple Rab proteins including Rab27.","method":"Co-transfection assay testing rabphilin binding to 42 different Rab proteins; site-directed mutagenesis of Rab-binding domain","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic Rab specificity screen by co-transfection with mutagenesis, single lab","pmids":["12578829"],"is_preprint":false},{"year":2004,"finding":"Rabphilin is recruited to dense-core vesicles in PC12 cells through specific interaction with Rab27A, not Rab3A; Rab3A-binding-defective mutant (E50A) still localizes to vesicles, but Rab27A-binding-defective double mutant (E50A/I54A) is cytosolic; this is conserved across C. elegans and Drosophila orthologs.","method":"Deletion and mutation analysis; live-cell localization in PC12 cells; neuropeptide Y secretion assay; cross-species binding analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — systematic mutagenesis with functional localization readout, cross-species conservation confirmed, multiple orthogonal approaches","pmids":["14722103"],"is_preprint":false},{"year":2004,"finding":"The C2B domain of rabphilin directly interacts with annexin A4; rabphilin, annexin A4, and synaptotagmin 1 form a novel protein complex in PC12 cells; annexin A4 colocalizes with rabphilin at the plasma membrane.","method":"Yeast two-hybrid; pulldown assay; co-immunoprecipitation from PC12 cells; immunofluorescence colocalization","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid with confirmation by pulldown and co-IP, single lab","pmids":["14960300"],"is_preprint":false},{"year":2005,"finding":"The C2B domain of rabphilin directly interacts with the plasma membrane SNARE protein SNAP-25 (EC50 ~0.82 μM; Ca2+ increases affinity ~2-fold); rabphilin expression increases the number of docked dense-core vesicles at the plasma membrane in PC12 cells without altering fusion kinetics; rabphilin-ΔC2B decreases docked vesicles.","method":"In vitro binding assay (SNAP-25 interaction); TIRFM of neuropeptide Y-Venus in PC12 cells; C2B domain mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — direct in vitro binding with affinity measurement, live-cell TIRF vesicle docking assay, domain deletion mutagenesis","pmids":["16203731"],"is_preprint":false},{"year":2005,"finding":"Rabphilin localizes to the subplasmalemmal actin cytoskeleton via an alpha-actinin-dependent mechanism; purified rabphilin associates with F-actin only in the presence of alpha-actinin; rabphilin stimulates (~8-fold) the association of granules with alpha-actinin-crosslinked F-actin in an in vitro assay.","method":"Immunofluorescence and immunoelectron microscopy; in vitro F-actin binding assay with purified components; granule-actin co-sedimentation assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct in vitro reconstitution with purified components and cell imaging, single lab","pmids":["16043482"],"is_preprint":false},{"year":2006,"finding":"Deletion of rabphilin dramatically accelerates recovery of synaptic vesicle pools from use-dependent depression; this phenotype is rescued by wild-type rabphilin but not by rabphilin lacking the C2B domain (which binds SNAP-25); double deletion of rabphilin and synaptobrevin further increases responses from depleted pools, suggesting rabphilin regulates SNARE-dependent re-priming via C2B-SNAP-25 interaction.","method":"Electrophysiological recordings in rabphilin knockout neurons; viral rescue with wild-type and C2B-mutant rabphilin; synaptobrevin double knockout analysis","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — knockout + viral rescue + genetic epistasis with electrophysiological readouts and domain-specific mutant rescue","pmids":["16763567"],"is_preprint":false},{"year":2006,"finding":"The polybasic sequence (587KKAKHKTQIKKK598) in the C2B domain of rabphilin is required for SNAP-25 binding; Lys→Gln mutations abolishing SNAP-25 binding significantly decrease plasma-membrane-docked vesicles and inhibit high-KCl-induced DCV exocytosis in PC12 cells.","method":"SNAP-25 binding assay with polybasic sequence mutants; TIRFM of PC12 cells; high-KCl exocytosis assay","journal":"Journal of neurochemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — site-directed mutagenesis of functional motif with direct binding assay and live-cell functional readout","pmids":["17156129"],"is_preprint":false},{"year":2006,"finding":"The crystal structure of the Ca2+-free C2A domain of rabphilin-3A was solved at 1.92 Å; the domain adopts a classical eight-stranded antiparallel beta-sandwich with conserved Ca2+-binding acidic residues; a conserved Asp→Glu substitution increases rigidity of Ca2+-binding loop 1.","method":"X-ray crystallography at 1.92 Å resolution","journal":"Acta crystallographica. Section D, Biological crystallography","confidence":"High","confidence_rationale":"Tier 1 / Moderate — high-resolution crystal structure, single study","pmids":["16790935"],"is_preprint":false},{"year":2006,"finding":"Acidic residues from the C2A-C2B linker interact with the Ca2+-binding region of the C2B domain, providing an unusual Ca2+-binding mode; mutation of these linker residues to Ala caused a 10-fold decrease in C2B Ca2+-binding affinity; this interaction persists in the full C2 domain tandem.","method":"X-ray crystallography of C2B domain with linker; NMR spectroscopy; Ca2+-binding affinity measurements; site-directed mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure combined with NMR, affinity measurements, and functional mutagenesis in one study","pmids":["17166855"],"is_preprint":false},{"year":2008,"finding":"Both C2A and C2B domains of rabphilin-3A bind PIP2; C2A binds the PIP2 headgroup IP3 in a Ca2+-dependent manner (Kd ~55 μM at saturating Ca2+) via a defined binding site on the concave surface, with IP3 and Ca2+ mutually enhancing binding (TAMA mechanism); C2B binds IP3 in a Ca2+-independent fashion with low affinity via a different binding mode.","method":"NMR spectroscopy mapping of IP3 binding to each C2 domain; Ca2+-binding affinity measurements","journal":"Protein science","confidence":"High","confidence_rationale":"Tier 1 / Strong — NMR-based structural characterization with quantitative affinity measurements for both domains","pmids":["18434502"],"is_preprint":false},{"year":2008,"finding":"The Ca2+-bound solution structure of the C2A domain shows Ca2+ induces a conformational change in Ca2+-binding loop 3 (CBL3) that enables IP3 binding; the structural basis for the TAMA (target-activated messenger affinity) mechanism was determined.","method":"NMR solution structure determination of Ca2+-bound C2A domain; IP3 docking model; mutagenesis of CBL3","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — NMR structure with docking model and mutagenesis validating mechanism","pmids":["18945677"],"is_preprint":false},{"year":2008,"finding":"Rabphilin (as Rab27 effector) undergoes rapid and complete exchange between secretory granules and cytosol in PC12 cells (as measured by FRAP), unlike Granuphilin and Noc2 which show little exchange; both Noc2 and Rabphilin are recruited to granules by Rab27 but Rabphilin does not form stable Rab27 complexes on granules.","method":"FRAP (fluorescence recovery after photobleaching) of EGFP-tagged Rabphilin, Granuphilin, and Noc2 in PC12 cells","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct live-cell FRAP measurement, single lab","pmids":["18573236"],"is_preprint":false},{"year":2015,"finding":"Rabphilin 3A (Rph3A) is enriched at dendritic spines (postsynaptic site) and forms a ternary complex with GluN2A (binding to GluN2A residues 1349–1389) and PSD-95 (PDZ3 domain) via its N-terminal domain; Rph3A silencing reduces surface localization of synaptic GluN2A and NMDAR currents; interfering peptides disrupting GluN2A/Rph3A interaction decrease NMDAR-mediated currents and GluN2A density at dendritic spines.","method":"Protein-protein interaction assays (co-IP, GST pulldown); RNAi knockdown in neurons; whole-cell patch clamp; confocal imaging; in vivo peptide injection in organotypic slices","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (co-IP, pulldown, knockdown, electrophysiology, in vivo peptide interference) across multiple experimental systems","pmids":["26679993"],"is_preprint":false},{"year":2017,"finding":"Crystal structures of rabphilin-3A C2B domain bound to SNAP-25 and to PIP2 were solved; rabphilin-3A C2B uses a unique structural element (bottom alpha-helix) to contact the same SNAP-25 surface as synaptotagmin-1; the C2B domain can simultaneously bind PIP2/Ca2+ and SNAP-25, adopting a conformation compatible with interaction with the complete SNARE complex and suggesting membrane bending in Ca2+-dependent fusion.","method":"X-ray crystallography of C2B-SNAP25 and C2B-PIP2 complexes; biochemical binding analyses","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures of two complexes with biochemical validation in one study","pmids":["28634303"],"is_preprint":false},{"year":2017,"finding":"PKN1 phosphorylates RPH3A, which enhances binding of RPH3A to GTP-bound RAB21; PKN1 and RPH3A are required for polarized localization of RAB21 and RPH3A in neutrophils, leading to PIP5K1C90 polarization essential for integrin activation and neutrophil adhesion to endothelial cells.","method":"Kinase assay; co-IP; confocal imaging of neutrophil polarization; siRNA knockdown; inflammatory adhesion assay; myeloid-specific PKN1 knockout mice","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — phosphorylation-binding mechanism established by kinase assay and co-IP, with functional validation by genetic KO and KD in primary cells","pmids":["28636945"],"is_preprint":false},{"year":2018,"finding":"A missense variant in RPH3A (p.Arg269Gln) strongly impairs binding of rabphilin-3A to 14-3-3 protein; this variant is associated with presynaptic congenital myasthenic syndrome with altered synaptic vesicle homeostasis.","method":"Expression studies in mammalian cell lines; 14-3-3 binding assay comparing wild-type and mutant rabphilin-3A","journal":"Molecular genetics & genomic medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding assay for specific variant, single lab","pmids":["29441694"],"is_preprint":false},{"year":2020,"finding":"ARF6 binds RPH3A and enhances the interaction between plasma membrane PtdIns4P and RPH3A; ARF6 polarization at the plasma membrane coincides with RPH3A, RAB21, PIP5K1C90, and PM PtdIns4P in neutrophils upon integrin stimulation; ARF6 functions as a coincidence-detection code directing RPH3A polarization.","method":"siRNA knockdown of ARF6; dominant-negative ARF6 mutant; co-immunoprecipitation; confocal imaging of neutrophil polarization; ARF6 inhibitor SecinH3","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple perturbations with binding and localization assays, single lab","pmids":["31924649"],"is_preprint":false},{"year":2021,"finding":"UBE3A mono-ubiquitinates RPH3A in mouse brain via a non-degradative mechanism; the UBE3A and RAB3A binding sites on RPH3A partially overlap, and RAB3A binding interferes with UBE3A binding; reduced RPH3A levels in absence of RAB3A are not mediated by UBE3A; an AS-linked UBE3A missense mutation abrogates interaction with RPH3A.","method":"Co-immunoprecipitation; ubiquitination assays in mouse brain; RAB3A knockout comparison; UBE3A missense variant binding assay","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct biochemical demonstration of mono-ubiquitination and competitive binding in brain tissue, single lab","pmids":["33542309"],"is_preprint":false},{"year":2022,"finding":"Rabphilin-3A interacts with alpha-synuclein; in vivo intrastriatal injection of alpha-synuclein preformed fibrils reduces synaptic levels of Rph3A and impairs Rph3A/NMDAR interaction; restoring Rph3A expression or disrupting the Rph3A/alpha-synuclein complex prevents dendritic spine loss and rescues early motor defects.","method":"In vivo intrastriatal injection; Western blotting; co-immunoprecipitation; confocal imaging; motor behavioral testing; in vitro primary neuron experiments with small molecule","journal":"Pharmacological research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo and in vitro loss-of-function with mechanistic protein-interaction data, single lab","pmids":["35918045"],"is_preprint":false},{"year":2022,"finding":"Rabphilin-3A promotes SNARE complex assembly by binding the N-peptide region of SNAP-25 via the C2B bottom alpha-helix; this interaction is enabled by an intramolecular interplay between the N-terminal Rab-binding domain and the C-terminal C2AB domain; the C2B/SNAP-25 N-peptide interaction induces a conformational switch from random coils to alpha-helical structure in the SNAP-25 SNARE motif, accelerating SNARE complex assembly; disrupting this interaction impairs vesicle docking and fusion in PC12 cells.","method":"In vitro SNARE complex assembly assay; NMR; binding studies; mutagenesis; TIRF microscopy in PC12 cells","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution of SNARE assembly, structural characterization of conformational change, and functional validation in cells with multiple methods","pmids":["36173100"],"is_preprint":false},{"year":2022,"finding":"Rph3A overexpression in hippocampal neurons increases dendritic spine density, increases synaptic GluN2A-containing NMDARs, and decreases surface GluA1-containing AMPARs; these changes occlude LTP-induced spine formation but do not prevent LTD-induced spine loss.","method":"Confocal imaging of spine density; surface NMDAR and AMPAR quantification; LTP and LTD induction protocols in primary hippocampal neurons","journal":"Cells","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain-of-function with functional synaptic plasticity readouts, single lab","pmids":["35626653"],"is_preprint":false},{"year":2023,"finding":"Rph3A undergoes liquid-liquid phase separation dependent on arginine residues in its N-terminal domain; phase separation promotes GluN2A clustering by binding GluN2A C-terminal domain; a ternary Rph3A/GluN2A/PSD95 complex promotes Rph3A phase separation; disrupting Rph3A phase separation suppresses synaptic and extrasynaptic surface clustering, synaptic localization, and stability of GluN2A and reduces NMDAR synaptic responses.","method":"In vitro phase separation assay; mutagenesis of arginine residues; FRAP; super-resolution imaging; electrophysiology in hippocampal neurons","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — phase separation reconstituted in vitro and validated in neurons with multiple orthogonal methods including mutagenesis and electrophysiology","pmids":["36693856"],"is_preprint":false},{"year":2023,"finding":"RPH3A missense gain-of-function variants (p.Thr450Ser, p.Asn618Ser) reduce synaptic localization of GluN2A; p.Thr450Ser also increases surface GluN2A levels; both variants increase GluN2A-dependent NMDAR currents and alter postsynaptic calcium levels; Thr450Ser expression affects dendritic spine morphology.","method":"Primary hippocampal neuronal cultures; immunofluorescence; whole-cell patch clamp; calcium imaging; spine morphology analysis","journal":"Genetics in medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional assays in neuronal cultures with disease-linked variants, single lab","pmids":["37403762"],"is_preprint":false},{"year":2018,"finding":"CAND1 (cullin-associated NEDD8-dissociated protein 1) was identified as a rabphilin-3A-binding protein in posterior pituitary by GST-pulldown and co-immunoprecipitation; CAND1 overexpression leads to deubiquitylation of rabphilin-3A in PC12 cells and enhances both basal and KCl-stimulated AVP secretion.","method":"GST-pulldown; proteomic analysis; co-immunoprecipitation; ubiquitination assay; AVP secretion assay in PC12 cells","journal":"Endocrine journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pulldown with proteomic identification confirmed by co-IP, with functional secretion readout, single lab","pmids":["29367474"],"is_preprint":false},{"year":2024,"finding":"RPH3A is a negative regulator of dense-core vesicle (DCV) exocytosis in hippocampal neurons; RPH3A KO increases DCV exocytosis ~3-fold; RAB3A-binding deficient RPH3A loses synaptic enrichment but still restores WT DCV exocytosis; SNAP25-binding deficient RPH3A does not rescue DCV exocytosis, indicating SNAP25 interaction mediates the inhibitory function; RPH3A resides stationary at presynapses and does not travel with DCVs.","method":"Live-cell imaging at single-vesicle resolution in RPH3A knockout hippocampal neurons; viral re-expression of wild-type and mutant RPH3A; tetanus neurotoxin ablation of regulated secretion","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — KO with rescue by wild-type and domain-specific mutants, single-vesicle resolution live imaging, multiple mutant constructs","pmids":["39412498"],"is_preprint":false},{"year":2025,"finding":"RPH3A variants p.(Arg209Lys) and p.(Gln508His) reduce presynaptic glutamate release and decrease synaptic retention of GluN2A-containing NMDARs, with reduced calcium event frequency at dendritic spines, demonstrating both pre- and post-synaptic dysfunction from disease-associated RPH3A missense variants.","method":"Primary hippocampal neuronal cultures; electrophysiology; calcium imaging; immunofluorescence of GluN2A synaptic localization","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional assays in neurons with disease-linked variants, single lab","pmids":["40082528"],"is_preprint":false}],"current_model":"Rabphilin-3A (RPH3A) is a multidomain synaptic protein that functions as a GTP-state-dependent effector of Rab3A and Rab27A: its N-terminal Zn2+-finger domain mediates GTP-Rab binding and recruits rabphilin to secretory vesicles, while its tandem C2 domains (C2A and C2B) bind Ca2+, phospholipids (including PIP2 via a TAMA mechanism for C2A), SNAP-25 (via the C2B polybasic helix), alpha-actinin, and the GluN2A/PSD-95 complex to regulate both presynaptic vesicle docking/SNARE complex assembly and postsynaptic NMDAR stabilization through phase separation; rabphilin is phosphorylated by CaMKII and PKA at Ser234/Ser274, mono-ubiquitinated by UBE3A in a non-degradative manner, and in neutrophils is phosphorylated by PKN1 to direct polarized RAB21 vesicle trafficking."},"narrative":{"mechanistic_narrative":"Rabphilin-3A (RPH3A) is a multidomain synaptic effector that couples Rab GTPase signaling to the membrane fusion machinery, regulating both presynaptic vesicle exocytosis and postsynaptic receptor stabilization [PMID:8384302, PMID:16763567, PMID:26679993]. Its N-terminal Zn2+-finger domain binds the GTP-bound forms of Rab3A and, with higher functional relevance for vesicle recruitment, Rab27A, which reversibly targets the protein to secretory and dense-core vesicles [PMID:8384302, PMID:8617225, PMID:12578829, PMID:14722103]; the structural basis of this state-dependent recognition was defined by the Rab3A/GTP–rabphilin effector-domain crystal structure, in which an SGAWFF element engages a Rab pocket conferring effector specificity [PMID:10025402]. Its tandem C2 domains bind Ca2+ and phospholipids including PIP2 — C2A via a Ca2+/IP3 target-activated (TAMA) mechanism — providing membrane-coincidence sensing [PMID:8262955, PMID:18434502, PMID:18945677]. Presynaptically, the C2B domain directly binds the plasma-membrane SNARE SNAP-25 through a polybasic helix and bottom alpha-helix, promoting vesicle docking and accelerating SNARE complex assembly by inducing an alpha-helical conformational switch in the SNAP-25 SNARE motif [PMID:16203731, PMID:17156129, PMID:28634303, PMID:36173100]; through this C2B–SNAP-25 interaction RPH3A modulates synaptic vesicle re-priming and acts as a negative regulator of dense-core vesicle exocytosis [PMID:16763567, PMID:39412498]. Postsynaptically, RPH3A is enriched at dendritic spines where its N-terminal domain forms a ternary complex with GluN2A and PSD-95 and undergoes arginine-dependent liquid-liquid phase separation to cluster and stabilize synaptic GluN2A-containing NMDARs [PMID:26679993, PMID:36693856]. RPH3A is a convergent phosphorylation target of PKA and CaMKII at Ser234/Ser274, modifications that reduce its membrane affinity, and is regulated by mono-ubiquitination and 14-3-3 binding [PMID:7891174, PMID:11466418, PMID:33542309, PMID:29441694]. Disease-associated RPH3A missense variants impair 14-3-3 binding or perturb GluN2A retention and glutamate release, linking the protein to a presynaptic congenital myasthenic syndrome and to pre- and postsynaptic synaptic dysfunction [PMID:29441694, PMID:37403762, PMID:40082528]. A distinct, non-neuronal role is established in neutrophils, where PKN1 phosphorylation of RPH3A enhances GTP-RAB21 binding to drive polarized vesicle trafficking and integrin activation [PMID:28636945, PMID:31924649].","teleology":[{"year":1993,"claim":"Establishing what links Rab3A to its downstream effects: RPH3A was defined as the first GTP-state-dependent Rab3A effector, with separable Rab-binding and Ca2+/lipid-binding modules.","evidence":"In vitro pulldown of recombinant rabphilin with GTPgammaS- vs GDP-Rab3A, and domain-fragment binding assays with phospholipid and 45Ca2+","pmids":["8384302","8262955"],"confidence":"High","gaps":["Did not establish the cellular consequence of the effector interaction","Domain boundaries refined only in later work"]},{"year":1993,"claim":"Addressing how RPH3A might influence Rab3A nucleotide state: it inhibits GAP-stimulated GTP hydrolysis and was reported to have exchange activity, positioning it to stabilize active Rab3A.","evidence":"In vitro GTPase and GDP/GTP exchange assays with purified Rab3A and rabphilin fragments","pmids":["8226731","7926025"],"confidence":"High","gaps":["Physiological relevance of GAP inhibition/exchange activity in cells not established","Exchange activity reported by a single lab"]},{"year":1994,"claim":"Defining where RPH3A acts and how it gets there: it localizes to presynaptic synaptic vesicles, and its synaptic targeting depends on Rab3A/3C.","evidence":"Immunogold EM and subcellular fractionation of rat brain; immunofluorescence in rab3A knockout mice with in vitro rab3C binding","pmids":["8060298","7946335"],"confidence":"High","gaps":["A Rab3A-independent vesicle association was also reported (idx 5), leaving recruitment mechanism only partly resolved"]},{"year":1994,"claim":"Identifying RPH3A as a kinase target: it is phosphorylated by PKA and CaMKII, marking it as a node integrating second-messenger signaling with release.","evidence":"In vitro phosphorylation assays with PKA and CaMKII and phosphopeptide site mapping","pmids":["7945346","7811264","7891174"],"confidence":"High","gaps":["Functional consequence of individual sites not established at this stage","Early site assignments later refined to Ser234/Ser274"]},{"year":1996,"claim":"Clarifying the recruitment cycle and cytoskeletal coupling: a Zn2+-finger motif mediates GTP-Rab3A binding essential for vesicle recruitment, RPH3A dissociates upon Ca2+-dependent fusion, and its N-terminus binds alpha-actinin to modulate actin crosslinking.","evidence":"Exocytosis-coupled dissociation assays and Zn2+-finger mutagenesis; yeast two-hybrid plus actin crosslinking assays","pmids":["8617225","8943213"],"confidence":"High","gaps":["In vivo significance of actin crosslinking modulation not established","Competition between Rab3A and alpha-actinin for the same region left functional logic unresolved"]},{"year":1996,"claim":"Testing functional requirement: RPH3A is required for Ca2+-regulated exocytosis, with C2B but not C2A fragments inhibiting release.","evidence":"Antisense knockdown and domain-fragment overexpression with growth hormone release readout in PC12 cells; presynaptic microinjection into squid giant synapse with electrophysiology and EM","pmids":["8605005","9450942"],"confidence":"High","gaps":["Fragment overexpression is dominant-negative and does not pinpoint endogenous mechanism","Molecular target of C2B in release not yet identified"]},{"year":1999,"claim":"Providing structural rules for specificity and Ca2+-independent interactions: crystal and NMR structures defined the Rab3A effector interface and a Janus-faced C2B domain with a Ca2+-independent bottom surface.","evidence":"X-ray structure of Rab3A/GTP/Mg2+–rabphilin effector domain at 2.6 A; NMR solution structure of the C2B domain","pmids":["10025402","10559882"],"confidence":"High","gaps":["Identity of the Ca2+-independent C2B partners not defined at this point"]},{"year":2001,"claim":"Uncovering Rab3-independent functions: secretory potentiation and endocytosis control can occur without high-affinity Rab3 binding, the latter via Rabaptin-5, and genetics revealed a Rab3-independent role in potentiating SNARE function.","evidence":"Rab3-binding-domain point mutagenesis with secretion and transferrin endocytosis assays in HIT-T15 cells; C. elegans genetic epistasis with SNARE hypomorphs","pmids":["10504306","11309205","11717359"],"confidence":"High","gaps":["The unknown factor binding the Rab3-binding domain to drive secretion was not identified","Mechanistic link between rabphilin and SNAREs still inferred genetically"]},{"year":2003,"claim":"Broadening the effector repertoire and identifying the operative vesicle Rab: RPH3A binds multiple Rabs including Rab27, and Rab27A rather than Rab3A recruits it to dense-core vesicles.","evidence":"Co-transfection binding screen against 42 Rabs; mutagenesis and live-cell localization with neuropeptide Y secretion in PC12 cells across species","pmids":["12578829","14722103"],"confidence":"High","gaps":["Relative in vivo contributions of Rab3 vs Rab27 across cell types not fully resolved"]},{"year":2005,"claim":"Identifying the molecular basis of docking: the C2B domain binds SNAP-25 and an alpha-actinin-dependent mechanism tethers RPH3A to the subplasmalemmal actin cytoskeleton, increasing docked vesicles.","evidence":"In vitro SNAP-25 binding with affinity measurement and TIRFM docking assays; F-actin reconstitution with purified components and granule co-sedimentation","pmids":["16203731","16043482"],"confidence":"High","gaps":["Whether docking and re-priming use the same C2B-SNAP-25 contact left for later work"]},{"year":2006,"claim":"Mapping the docking motif and physiological role: a C2B polybasic sequence mediates SNAP-25 binding required for docking, and knockout/rescue shows RPH3A regulates SNARE-dependent vesicle re-priming through this interaction.","evidence":"Polybasic-sequence mutagenesis with binding and TIRFM exocytosis assays in PC12 cells; knockout neuron electrophysiology with WT and C2B-mutant viral rescue and synaptobrevin double knockout","pmids":["17156129","16763567"],"confidence":"High","gaps":["Structural conformation enabling simultaneous SNAP-25 and membrane binding not yet resolved"]},{"year":2008,"claim":"Defining the lipid-sensing chemistry: both C2 domains bind PIP2, with C2A using a Ca2+/IP3 mutually-enhancing TAMA mechanism, and the structural conformational change enabling it was determined.","evidence":"NMR mapping of IP3 binding with affinity measurements; NMR solution structure of Ca2+-bound C2A with docking and CBL3 mutagenesis; C2A-C2B linker structural studies","pmids":["18434502","18945677","17166855","16790935","31924649"],"confidence":"High","gaps":["In vivo PIP2 sensing during release not directly demonstrated in this set"]},{"year":2015,"claim":"Revealing a postsynaptic role: RPH3A forms a ternary complex with GluN2A and PSD-95 to stabilize synaptic NMDARs.","evidence":"Co-IP, GST pulldown, RNAi knockdown, patch clamp, confocal imaging, and in vivo interfering-peptide injection in organotypic slices","pmids":["26679993"],"confidence":"High","gaps":["Mechanism by which complex stabilizes surface GluN2A not yet defined (resolved later by phase separation)"]},{"year":2017,"claim":"Defining how RPH3A engages the fusion machinery and is regulated in non-neuronal cells: C2B binds the same SNAP-25 surface as synaptotagmin-1 while simultaneously binding PIP2/Ca2+, and PKN1 phosphorylation directs RAB21 vesicle trafficking in neutrophils.","evidence":"Crystal structures of C2B-SNAP25 and C2B-PIP2 complexes with biochemical analysis; kinase assay, co-IP, neutrophil imaging, siRNA, and myeloid PKN1 knockout mice","pmids":["28634303","28636945"],"confidence":"High","gaps":["How C2B coordinates with the complete assembled SNARE complex left for functional reconstitution"]},{"year":2022,"claim":"Establishing the catalytic action on SNARE assembly: RPH3A binds the SNAP-25 N-peptide via the C2B bottom helix, an intramolecular N-/C-terminal interplay enables it, and it induces an alpha-helical conformational switch accelerating SNARE complex assembly.","evidence":"In vitro SNARE assembly assays, NMR, binding studies, mutagenesis, and TIRF microscopy in PC12 cells","pmids":["36173100"],"confidence":"High","gaps":["Quantitative contribution to fusion kinetics in native synapses not measured"]},{"year":2023,"claim":"Explaining how RPH3A stabilizes postsynaptic receptors: arginine-dependent liquid-liquid phase separation, promoted by the GluN2A/PSD-95 ternary complex, clusters and stabilizes synaptic GluN2A.","evidence":"In vitro phase separation assays, arginine mutagenesis, FRAP, super-resolution imaging, and electrophysiology in hippocampal neurons; GluN2A/NMDAR functional assays","pmids":["36693856","35626653"],"confidence":"High","gaps":["Whether the same phase-separation property operates presynaptically not addressed"]},{"year":2024,"claim":"Resolving the direction of presynaptic regulation: RPH3A is a stationary presynaptic negative regulator of dense-core vesicle exocytosis acting through SNAP-25 binding, separable from its Rab3A-dependent synaptic enrichment.","evidence":"Single-vesicle live imaging in RPH3A knockout hippocampal neurons with WT and domain-specific mutant viral rescue and tetanus neurotoxin ablation","pmids":["39412498"],"confidence":"High","gaps":["Reconciliation of negative DCV regulation with earlier positive secretion roles across cell types not fully resolved"]},{"year":2025,"claim":"Linking RPH3A dysfunction to disease: missense variants impair 14-3-3 binding, alter GluN2A retention and glutamate release, and produce pre- and postsynaptic dysfunction, connecting RPH3A to presynaptic congenital myasthenic syndrome and synaptic disorders.","evidence":"Variant 14-3-3 binding assays in cell lines; neuronal cultures with electrophysiology, calcium imaging, and GluN2A localization for multiple disease variants","pmids":["29441694","37403762","40082528"],"confidence":"Medium","gaps":["Single-lab functional characterizations for most variants","Genotype-phenotype relationships across patients not established in this corpus"]},{"year":null,"claim":"How presynaptic SNARE regulation, postsynaptic NMDAR phase separation, and phosphorylation/ubiquitination control are coordinated within a single neuron, and how alpha-synuclein interaction integrates into neurodegenerative pathology, remain open.","evidence":"","pmids":[],"confidence":"Low","gaps":["No unified model integrating pre- and postsynaptic functions","Cellular regulation of the LLPS versus SNARE-assembly activities not defined","alpha-synuclein/RPH3A pathway mechanistically incomplete (idx 42)"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[2,18,24,43]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[1,33,34]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[27,36,43,45]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[13,28]}],"localization":[{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[3,5,25]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[26,27,30,40]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[23,35]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[28]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[27,29,43,48]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[36,44,45]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,18,38]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[38,40]}],"complexes":["RPH3A/GluN2A/PSD-95 ternary complex"],"partners":["RAB3A","RAB27A","SNAP25","GLUN2A (GRIN2A)","DLG4 (PSD-95)","ACTN (ALPHA-ACTININ)","RAB21","UBE3A"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9Y2J0","full_name":"Rabphilin-3A","aliases":["Exophilin-1"],"length_aa":694,"mass_kda":76.9,"function":"Plays an essential role in docking and fusion steps of regulated exocytosis (By similarity). At the presynaptic level, RPH3A is recruited by RAB3A to the synaptic vesicle membrane in a GTP-dependent manner where it modulates synaptic vesicle trafficking and calcium-triggered neurotransmitter release (By similarity). In the post-synaptic compartment, forms a ternary complex with GRIN2A and DLG4 and regulates NMDA receptor stability. Also plays a role in the exocytosis of arginine vasopressin hormone (By similarity)","subcellular_location":"Cytoplasmic vesicle, secretory vesicle, synaptic vesicle membrane; Cell projection, dendritic spine; Postsynaptic cell membrane; Membrane","url":"https://www.uniprot.org/uniprotkb/Q9Y2J0/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RPH3A","classification":"Not Classified","n_dependent_lines":3,"n_total_lines":1208,"dependency_fraction":0.0024834437086092716},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/RPH3A","total_profiled":1310},"omim":[{"mim_id":"621535","title":"SPINOCEREBELLAR ATAXIA 52; SCA52","url":"https://www.omim.org/entry/621535"},{"mim_id":"621025","title":"RAB3A-INTERACTING PROTEIN-LIKE 1; RAB3IL1","url":"https://www.omim.org/entry/621025"},{"mim_id":"614326","title":"FEINGOLD SYNDROME 2; FGLDS2","url":"https://www.omim.org/entry/614326"},{"mim_id":"612159","title":"RABPHILIN 3A; RPH3A","url":"https://www.omim.org/entry/612159"},{"mim_id":"604881","title":"RABPHILIN 3A-LIKE; RPH3AL","url":"https://www.omim.org/entry/604881"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":115.4}],"url":"https://www.proteinatlas.org/search/RPH3A"},"hgnc":{"alias_symbol":["KIAA0985","rabphilin","exophilin-1"],"prev_symbol":[]},"alphafold":{"accession":"Q9Y2J0","domains":[{"cath_id":"3.30.40.10","chopping":"61-154","consensus_level":"high","plddt":88.1834,"start":61,"end":154},{"cath_id":"2.60.40.150","chopping":"396-516","consensus_level":"high","plddt":93.2645,"start":396,"end":516},{"cath_id":"2.60.40.150","chopping":"553-686","consensus_level":"high","plddt":93.8359,"start":553,"end":686}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y2J0","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y2J0-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y2J0-F1-predicted_aligned_error_v6.png","plddt_mean":68.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RPH3A","jax_strain_url":"https://www.jax.org/strain/search?query=RPH3A"},"sequence":{"accession":"Q9Y2J0","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9Y2J0.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9Y2J0/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y2J0"}},"corpus_meta":[{"pmid":"8384302","id":"PMC_8384302","title":"Rabphilin-3A, a putative target protein for smg p25A/rab3A p25 small GTP-binding protein related to synaptotagmin.","date":"1993","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/8384302","citation_count":378,"is_preprint":false},{"pmid":"10025402","id":"PMC_10025402","title":"Structural basis of Rab effector specificity: crystal structure of the small G protein Rab3A complexed with the effector domain of rabphilin-3A.","date":"1999","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/10025402","citation_count":299,"is_preprint":false},{"pmid":"7946335","id":"PMC_7946335","title":"Synaptic targeting of rabphilin-3A, a synaptic vesicle Ca2+/phospholipid-binding protein, depends on rab3A/3C.","date":"1994","source":"Neuron","url":"https://pubmed.ncbi.nlm.nih.gov/7946335","citation_count":183,"is_preprint":false},{"pmid":"12578829","id":"PMC_12578829","title":"Distinct Rab binding specificity of Rim1, Rim2, rabphilin, and Noc2. Identification of a critical determinant of Rab3A/Rab27A recognition by Rim2.","date":"2003","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12578829","citation_count":159,"is_preprint":false},{"pmid":"8262955","id":"PMC_8262955","title":"Two functionally different domains of rabphilin-3A, Rab3A p25/smg p25A-binding and phospholipid- and Ca(2+)-binding domains.","date":"1993","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/8262955","citation_count":136,"is_preprint":false},{"pmid":"8617225","id":"PMC_8617225","title":"Rab3 reversibly recruits rabphilin to synaptic vesicles by a mechanism analogous to raf recruitment by ras.","date":"1996","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/8617225","citation_count":121,"is_preprint":false},{"pmid":"8060298","id":"PMC_8060298","title":"Localization of Rabphilin-3A on the synaptic vesicle.","date":"1994","source":"Biochemical and biophysical 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cDNA cloning and expression in COS7 cells\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro binding assay with purified proteins, replicated across bovine brain-purified and recombinant forms, confirmed in multiple subsequent studies\",\n      \"pmids\": [\"8384302\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"Rabphilin-3A has two functionally distinct domains: an N-terminal domain (residues 1–280) that binds GTP-Rab3A and a C-terminal domain (residues 281–704) containing two C2 domains that bind phospholipid and Ca2+ in a cooperative manner.\",\n      \"method\": \"In vitro binding assays using recombinant full-length, N-terminal, and C-terminal fragments of rabphilin-3A with GTP-Rab3A, phospholipid, and 45Ca2+\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution with purified recombinant domain fragments and multiple orthogonal binding assays, replicated across subsequent studies\",\n      \"pmids\": [\"8262955\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"Rabphilin-3A and its N-terminal fragment inhibit Rab3A GAP-stimulated GTPase activity of Rab3A, thereby potentially keeping Rab3A in the GTP-bound active form.\",\n      \"method\": \"In vitro GTPase assay measuring basal and GAP-stimulated GTP hydrolysis of Rab3A in the presence of rabphilin-3A or its fragments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro enzymatic assay with purified proteins and defined domain fragments\",\n      \"pmids\": [\"8226731\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Rabphilin-3A is localized on synaptic vesicles in presynaptic terminals, as determined by immunogold electron microscopy of neuromuscular junctions and subcellular fractionation showing enrichment in purified synaptic vesicle fractions.\",\n      \"method\": \"Immunogold electron microscopy and subcellular fractionation of rat brain\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct localization by immunogold EM and fractionation, replicated across multiple labs and cell types\",\n      \"pmids\": [\"8060298\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Synaptic targeting of rabphilin-3A depends on Rab3A/3C: in rab3A-deficient mice, rabphilin-3A is decreased at synapses of neurons expressing primarily rab3A and accumulates in perikarya, while neurons expressing rab3C retain normal synaptic rabphilin-3A; rabphilin-3A binds rab3C in vitro.\",\n      \"method\": \"Immunofluorescence and Western blot in rab3A knockout mice; in vitro binding assay with rab3C\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic loss-of-function model combined with in vitro binding, multiple neuronal populations analyzed\",\n      \"pmids\": [\"7946335\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Rabphilin-3A is associated with synaptic vesicles via a vesicle-resident protein in a manner independent of Rab3A; removal of Rab3A or addition of exogenous Rab3A did not affect rabphilin-3A binding to vesicles, but trypsin treatment abolished binding.\",\n      \"method\": \"Reconstitution binding assay using salt-stripped synaptic vesicles, Rab GDI extraction of endogenous Rab3A, trypsin treatment\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct vesicle binding reconstitution with multiple perturbations, single lab\",\n      \"pmids\": [\"7806490\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Rabphilin-3A is phosphorylated by cyclic AMP-dependent protein kinase (PKA) at its N-terminal region (~0.8 mol phosphate/mol protein), identifying it as a PKA substrate involved in neurotransmitter release regulation.\",\n      \"method\": \"In vitro phosphorylation assay with purified recombinant rabphilin-3A and PKA\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro kinase assay; confirmed and extended by multiple independent studies\",\n      \"pmids\": [\"7945346\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"CaMKII phosphorylates rabphilin-3A at Ser34, Thr205, Thr209, and Thr537 (two mol phosphate maximally incorporated), identifying additional regulatory phosphorylation sites.\",\n      \"method\": \"In vitro phosphorylation assay with CaMKII purified from rat brain and recombinant rabphilin-3A; phosphorylation site identification\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct in vitro kinase assay with site identification; single lab, later refined\",\n      \"pmids\": [\"7811264\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Rabphilin-3A binds beta-adducin through its C-terminal C2 domain-containing region in the presence of Ca2+ and phosphatidylserine, identifying beta-adducin as a calcium/phospholipid-dependent binding partner.\",\n      \"method\": \"Purification and amino acid sequence analysis of co-purified 115 kDa protein; overlay assay and biochemical characterization\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biochemical purification and direct binding assay, single lab\",\n      \"pmids\": [\"7999065\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"GTP cyclohydrolase I (Mr ~30 kDa) co-immunoprecipitates with rabphilin-3A from PC12 cell lysates and is phosphorylated upon high KCl stimulation, identifying it as a rabphilin-3A-interacting protein in neuroendocrine cells.\",\n      \"method\": \"Co-immunoprecipitation from PC12 cell lysate followed by SDS-PAGE and amino acid sequence analysis\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP experiment, no functional follow-up, single lab\",\n      \"pmids\": [\"7802677\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Rabphilin-3A has GDP/GTP exchange activity for Rab3A, potentially keeping Rab3A in the GTP-bound form by re-converting GDP-Rab3A produced by GAP activity.\",\n      \"method\": \"In vitro GDP/GTP exchange assay with purified Rab3A and rabphilin-3A\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct in vitro biochemical assay, single lab\",\n      \"pmids\": [\"7926025\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Rabphilin-3A is phosphorylated by CaMKII at residues 234 and 274 and by cAMP-dependent protein kinase (PKA) at residue 234, placing the middle region between the Rab3A-binding domain and C2 domains as a convergent regulatory phosphorylation site.\",\n      \"method\": \"In vitro phosphorylation assays with CaMKII and PKA; tryptic peptide mapping to identify phosphorylation sites\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro kinase assays with site-specific mapping; independently confirmed in subsequent studies\",\n      \"pmids\": [\"7891174\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Rabphilin-3A dissociates from synaptic vesicles after exocytosis in a manner requiring Ca2+ and membrane fusion; it interacts with GTP-Rab3A via an N-terminal Zn2+-finger motif, and this interaction is essential for rabphilin binding to synaptic vesicles, showing that Rab3 reversibly recruits rabphilin to vesicles analogously to Ras recruiting Raf.\",\n      \"method\": \"Exocytosis-coupled dissociation assay from synaptic vesicles; Zn2+-finger domain mutational analysis; in vitro binding\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — functional dissociation assay combined with domain mutagenesis, replicated mechanistic concept\",\n      \"pmids\": [\"8617225\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Alpha-actinin interacts with the N-terminal region of rabphilin-3A (the same region that binds GTP-Rab3A), and this interaction stimulates alpha-actinin's ability to cross-link actin filaments into bundles; GTPγS-Rab3A inhibits the rabphilin-3A/alpha-actinin interaction.\",\n      \"method\": \"Yeast two-hybrid screen from human brain cDNA library; direct binding assays; actin cross-linking assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — yeast two-hybrid discovery confirmed with direct binding and functional actin cross-linking assay; competitive inhibition by Rab3A also shown\",\n      \"pmids\": [\"8943213\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Rabphilin-3A is involved in Ca2+-dependent exocytosis from PC12 cells: reduction of endogenous rabphilin-3A inhibits high K+-induced growth hormone release, and N-terminal, C-terminal, or C2B fragments (but not C2A fragment alone) inhibit release when overexpressed.\",\n      \"method\": \"Growth hormone co-expression assay in PC12 cells; antisense knockdown; overexpression of domain fragments\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function and domain dissection with functional secretion readout, single lab\",\n      \"pmids\": [\"8605005\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"The Cys-rich region in the N-terminal domain binds two Zn2+ ions and is necessary but not sufficient for efficient Rab3A binding; a minimal Rab3A-binding domain spans residues 45–170; C2 domains are required for efficient membrane attachment in PC12 cells; Rab3A binding targets rabphilin to the correct membrane compartment.\",\n      \"method\": \"Deletion and mutagenesis analysis; Rab3A binding assays; GFP-rabphilin subcellular localization in PC12 cells; zinc binding characterization\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic domain deletion and mutagenesis with subcellular localization; single lab\",\n      \"pmids\": [\"8756657\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Presynaptic microinjection of rabphilin-3A into squid giant synapse reversibly inhibits neurotransmitter release; the N-terminal Rab3A-binding/phosphorylation region and the two C2 domains each independently inhibit release; the N-terminal domain also perturbs endocytosis (altering endosome, coated vesicle, and plasma membrane areas).\",\n      \"method\": \"Presynaptic microinjection of recombinant rabphilin-3A and domain fragments into squid giant synapse; electrophysiology; electron microscopy\",\n      \"journal\": \"The Journal of general physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct loss/gain-of-function by microinjection with electrophysiological and ultrastructural readouts\",\n      \"pmids\": [\"9450942\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Rabphilin phosphorylation at Ser234 is selectively increased by PKA and Ca2+ influx in mossy fiber CA3 synaptosomes but not in CA1 synaptosomes, correlating with the region-specific PKA-dependent LTP in mossy fibers.\",\n      \"method\": \"Phosphorylation assay in isolated CA1 and CA3 synaptosomes with forskolin treatment and K+-depolarization; region-specific fractionation of hippocampus\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — region-specific synaptosome assay with pharmacological intervention, single lab\",\n      \"pmids\": [\"9425005\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Crystal structure of activated Rab3A/GTP/Mg2+ bound to the effector domain of rabphilin-3A solved at 2.6 Å resolution; rabphilin-3A contacts Rab3A at two interfaces: switch I/II regions (nucleotide-state sensitive) and a deep pocket (RabCDR) containing the SGAWFF element of rabphilin-3A that confers Rab effector specificity.\",\n      \"method\": \"X-ray crystallography at 2.6 Å resolution; biochemical binding data\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution crystal structure with biochemical validation; landmark mechanistic paper\",\n      \"pmids\": [\"10025402\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"NMR solution structure of the C2B domain of rabphilin-3A reveals a Janus-faced architecture: a Ca2+-binding top surface (similar to other C2 domains) and a Ca2+-independent bottom surface bearing a conserved alpha-helix, suggesting Ca2+-independent protein interactions from the bottom surface.\",\n      \"method\": \"NMR spectroscopy structure determination\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — NMR structure with functional inference about Ca2+-independent interactions; high-quality structural study\",\n      \"pmids\": [\"10559882\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"High-affinity Rab3 binding is dispensable for rabphilin's stimulatory effect on Ca2+-regulated secretion in HIT-T15 cells; mutations V61A and L83A abolish Rab3 binding but do not impair secretory potentiation; however, mutant R60A retains Rab3 binding but loses stimulatory activity, suggesting secretory potentiation depends on an unknown factor binding to the Rab3-binding domain.\",\n      \"method\": \"Point mutagenesis of Rab3-binding domain; secretion assay in HIT-T15 cells; in vitro Rab3 binding assay\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic mutagenesis with functional secretion readout and binding assays, single lab\",\n      \"pmids\": [\"10504306\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Rabphilin promotes receptor-mediated endocytosis through interaction with Rabaptin-5; this activity is negatively regulated by Rab3. The Rabphilin V61A mutant (unable to bind Rab3) enhances transferrin endocytosis and binds Rabaptin-5, whereas L83A (also Rab3-binding defective) does not interact with Rabaptin-5 and does not enhance endocytosis.\",\n      \"method\": \"Transferrin endocytosis assay; co-immunoprecipitation of Rabaptin-5; Rab3-binding mutant analysis in HIT-T15 cells\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional endocytosis assay with mechanistic binding partner identification, single lab\",\n      \"pmids\": [\"11309205\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"In C. elegans, rabphilin mutants show synergistic genetic interactions with hypomorphic SNARE (syntaxin, SNAP-25, synaptobrevin) mutants, causing severe behavioral defects not seen in rab3-SNARE double mutants, establishing a Rab3-independent function of rabphilin in potentiating SNARE function.\",\n      \"method\": \"C. elegans genetic epistasis; behavioral assays (locomotion, mechanosensation); pharmacological assays\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis in vivo with multiple allele combinations and multiple phenotypic readouts\",\n      \"pmids\": [\"11717359\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Phosphorylation of rabphilin on Ser234 and Ser274 is dynamically regulated in nerve terminals; soluble rabphilin (not vesicle-bound) is the primary phosphorylation target; phospho-rabphilin shows reduced membrane affinity; phosphorylation requires external Ca2+ and Rab3A; PKA and CaMKII differentially phosphorylate the two sites.\",\n      \"method\": \"Phospho-specific antibodies against Ser234 and Ser274; subcellular fractionation; synaptosome stimulation experiments; depolarization assays\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — phospho-specific antibodies with fractionation and pharmacological dissection; multiple orthogonal methods\",\n      \"pmids\": [\"11466418\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Rabphilin interacts with Rab3A/B/C/D, Rab8A, and Rab27A/B (but not other Rabs), and Noc2 shows the same specificity; this broader Rab specificity beyond Rab3 suggests rabphilin functions as effector for multiple Rab proteins including Rab27.\",\n      \"method\": \"Co-transfection assay testing rabphilin binding to 42 different Rab proteins; site-directed mutagenesis of Rab-binding domain\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic Rab specificity screen by co-transfection with mutagenesis, single lab\",\n      \"pmids\": [\"12578829\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Rabphilin is recruited to dense-core vesicles in PC12 cells through specific interaction with Rab27A, not Rab3A; Rab3A-binding-defective mutant (E50A) still localizes to vesicles, but Rab27A-binding-defective double mutant (E50A/I54A) is cytosolic; this is conserved across C. elegans and Drosophila orthologs.\",\n      \"method\": \"Deletion and mutation analysis; live-cell localization in PC12 cells; neuropeptide Y secretion assay; cross-species binding analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — systematic mutagenesis with functional localization readout, cross-species conservation confirmed, multiple orthogonal approaches\",\n      \"pmids\": [\"14722103\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The C2B domain of rabphilin directly interacts with annexin A4; rabphilin, annexin A4, and synaptotagmin 1 form a novel protein complex in PC12 cells; annexin A4 colocalizes with rabphilin at the plasma membrane.\",\n      \"method\": \"Yeast two-hybrid; pulldown assay; co-immunoprecipitation from PC12 cells; immunofluorescence colocalization\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid with confirmation by pulldown and co-IP, single lab\",\n      \"pmids\": [\"14960300\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The C2B domain of rabphilin directly interacts with the plasma membrane SNARE protein SNAP-25 (EC50 ~0.82 μM; Ca2+ increases affinity ~2-fold); rabphilin expression increases the number of docked dense-core vesicles at the plasma membrane in PC12 cells without altering fusion kinetics; rabphilin-ΔC2B decreases docked vesicles.\",\n      \"method\": \"In vitro binding assay (SNAP-25 interaction); TIRFM of neuropeptide Y-Venus in PC12 cells; C2B domain mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — direct in vitro binding with affinity measurement, live-cell TIRF vesicle docking assay, domain deletion mutagenesis\",\n      \"pmids\": [\"16203731\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Rabphilin localizes to the subplasmalemmal actin cytoskeleton via an alpha-actinin-dependent mechanism; purified rabphilin associates with F-actin only in the presence of alpha-actinin; rabphilin stimulates (~8-fold) the association of granules with alpha-actinin-crosslinked F-actin in an in vitro assay.\",\n      \"method\": \"Immunofluorescence and immunoelectron microscopy; in vitro F-actin binding assay with purified components; granule-actin co-sedimentation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct in vitro reconstitution with purified components and cell imaging, single lab\",\n      \"pmids\": [\"16043482\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Deletion of rabphilin dramatically accelerates recovery of synaptic vesicle pools from use-dependent depression; this phenotype is rescued by wild-type rabphilin but not by rabphilin lacking the C2B domain (which binds SNAP-25); double deletion of rabphilin and synaptobrevin further increases responses from depleted pools, suggesting rabphilin regulates SNARE-dependent re-priming via C2B-SNAP-25 interaction.\",\n      \"method\": \"Electrophysiological recordings in rabphilin knockout neurons; viral rescue with wild-type and C2B-mutant rabphilin; synaptobrevin double knockout analysis\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — knockout + viral rescue + genetic epistasis with electrophysiological readouts and domain-specific mutant rescue\",\n      \"pmids\": [\"16763567\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The polybasic sequence (587KKAKHKTQIKKK598) in the C2B domain of rabphilin is required for SNAP-25 binding; Lys→Gln mutations abolishing SNAP-25 binding significantly decrease plasma-membrane-docked vesicles and inhibit high-KCl-induced DCV exocytosis in PC12 cells.\",\n      \"method\": \"SNAP-25 binding assay with polybasic sequence mutants; TIRFM of PC12 cells; high-KCl exocytosis assay\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — site-directed mutagenesis of functional motif with direct binding assay and live-cell functional readout\",\n      \"pmids\": [\"17156129\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The crystal structure of the Ca2+-free C2A domain of rabphilin-3A was solved at 1.92 Å; the domain adopts a classical eight-stranded antiparallel beta-sandwich with conserved Ca2+-binding acidic residues; a conserved Asp→Glu substitution increases rigidity of Ca2+-binding loop 1.\",\n      \"method\": \"X-ray crystallography at 1.92 Å resolution\",\n      \"journal\": \"Acta crystallographica. Section D, Biological crystallography\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — high-resolution crystal structure, single study\",\n      \"pmids\": [\"16790935\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Acidic residues from the C2A-C2B linker interact with the Ca2+-binding region of the C2B domain, providing an unusual Ca2+-binding mode; mutation of these linker residues to Ala caused a 10-fold decrease in C2B Ca2+-binding affinity; this interaction persists in the full C2 domain tandem.\",\n      \"method\": \"X-ray crystallography of C2B domain with linker; NMR spectroscopy; Ca2+-binding affinity measurements; site-directed mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure combined with NMR, affinity measurements, and functional mutagenesis in one study\",\n      \"pmids\": [\"17166855\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Both C2A and C2B domains of rabphilin-3A bind PIP2; C2A binds the PIP2 headgroup IP3 in a Ca2+-dependent manner (Kd ~55 μM at saturating Ca2+) via a defined binding site on the concave surface, with IP3 and Ca2+ mutually enhancing binding (TAMA mechanism); C2B binds IP3 in a Ca2+-independent fashion with low affinity via a different binding mode.\",\n      \"method\": \"NMR spectroscopy mapping of IP3 binding to each C2 domain; Ca2+-binding affinity measurements\",\n      \"journal\": \"Protein science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — NMR-based structural characterization with quantitative affinity measurements for both domains\",\n      \"pmids\": [\"18434502\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"The Ca2+-bound solution structure of the C2A domain shows Ca2+ induces a conformational change in Ca2+-binding loop 3 (CBL3) that enables IP3 binding; the structural basis for the TAMA (target-activated messenger affinity) mechanism was determined.\",\n      \"method\": \"NMR solution structure determination of Ca2+-bound C2A domain; IP3 docking model; mutagenesis of CBL3\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — NMR structure with docking model and mutagenesis validating mechanism\",\n      \"pmids\": [\"18945677\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Rabphilin (as Rab27 effector) undergoes rapid and complete exchange between secretory granules and cytosol in PC12 cells (as measured by FRAP), unlike Granuphilin and Noc2 which show little exchange; both Noc2 and Rabphilin are recruited to granules by Rab27 but Rabphilin does not form stable Rab27 complexes on granules.\",\n      \"method\": \"FRAP (fluorescence recovery after photobleaching) of EGFP-tagged Rabphilin, Granuphilin, and Noc2 in PC12 cells\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct live-cell FRAP measurement, single lab\",\n      \"pmids\": [\"18573236\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Rabphilin 3A (Rph3A) is enriched at dendritic spines (postsynaptic site) and forms a ternary complex with GluN2A (binding to GluN2A residues 1349–1389) and PSD-95 (PDZ3 domain) via its N-terminal domain; Rph3A silencing reduces surface localization of synaptic GluN2A and NMDAR currents; interfering peptides disrupting GluN2A/Rph3A interaction decrease NMDAR-mediated currents and GluN2A density at dendritic spines.\",\n      \"method\": \"Protein-protein interaction assays (co-IP, GST pulldown); RNAi knockdown in neurons; whole-cell patch clamp; confocal imaging; in vivo peptide injection in organotypic slices\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (co-IP, pulldown, knockdown, electrophysiology, in vivo peptide interference) across multiple experimental systems\",\n      \"pmids\": [\"26679993\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Crystal structures of rabphilin-3A C2B domain bound to SNAP-25 and to PIP2 were solved; rabphilin-3A C2B uses a unique structural element (bottom alpha-helix) to contact the same SNAP-25 surface as synaptotagmin-1; the C2B domain can simultaneously bind PIP2/Ca2+ and SNAP-25, adopting a conformation compatible with interaction with the complete SNARE complex and suggesting membrane bending in Ca2+-dependent fusion.\",\n      \"method\": \"X-ray crystallography of C2B-SNAP25 and C2B-PIP2 complexes; biochemical binding analyses\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures of two complexes with biochemical validation in one study\",\n      \"pmids\": [\"28634303\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PKN1 phosphorylates RPH3A, which enhances binding of RPH3A to GTP-bound RAB21; PKN1 and RPH3A are required for polarized localization of RAB21 and RPH3A in neutrophils, leading to PIP5K1C90 polarization essential for integrin activation and neutrophil adhesion to endothelial cells.\",\n      \"method\": \"Kinase assay; co-IP; confocal imaging of neutrophil polarization; siRNA knockdown; inflammatory adhesion assay; myeloid-specific PKN1 knockout mice\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — phosphorylation-binding mechanism established by kinase assay and co-IP, with functional validation by genetic KO and KD in primary cells\",\n      \"pmids\": [\"28636945\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"A missense variant in RPH3A (p.Arg269Gln) strongly impairs binding of rabphilin-3A to 14-3-3 protein; this variant is associated with presynaptic congenital myasthenic syndrome with altered synaptic vesicle homeostasis.\",\n      \"method\": \"Expression studies in mammalian cell lines; 14-3-3 binding assay comparing wild-type and mutant rabphilin-3A\",\n      \"journal\": \"Molecular genetics & genomic medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding assay for specific variant, single lab\",\n      \"pmids\": [\"29441694\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"ARF6 binds RPH3A and enhances the interaction between plasma membrane PtdIns4P and RPH3A; ARF6 polarization at the plasma membrane coincides with RPH3A, RAB21, PIP5K1C90, and PM PtdIns4P in neutrophils upon integrin stimulation; ARF6 functions as a coincidence-detection code directing RPH3A polarization.\",\n      \"method\": \"siRNA knockdown of ARF6; dominant-negative ARF6 mutant; co-immunoprecipitation; confocal imaging of neutrophil polarization; ARF6 inhibitor SecinH3\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple perturbations with binding and localization assays, single lab\",\n      \"pmids\": [\"31924649\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"UBE3A mono-ubiquitinates RPH3A in mouse brain via a non-degradative mechanism; the UBE3A and RAB3A binding sites on RPH3A partially overlap, and RAB3A binding interferes with UBE3A binding; reduced RPH3A levels in absence of RAB3A are not mediated by UBE3A; an AS-linked UBE3A missense mutation abrogates interaction with RPH3A.\",\n      \"method\": \"Co-immunoprecipitation; ubiquitination assays in mouse brain; RAB3A knockout comparison; UBE3A missense variant binding assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct biochemical demonstration of mono-ubiquitination and competitive binding in brain tissue, single lab\",\n      \"pmids\": [\"33542309\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Rabphilin-3A interacts with alpha-synuclein; in vivo intrastriatal injection of alpha-synuclein preformed fibrils reduces synaptic levels of Rph3A and impairs Rph3A/NMDAR interaction; restoring Rph3A expression or disrupting the Rph3A/alpha-synuclein complex prevents dendritic spine loss and rescues early motor defects.\",\n      \"method\": \"In vivo intrastriatal injection; Western blotting; co-immunoprecipitation; confocal imaging; motor behavioral testing; in vitro primary neuron experiments with small molecule\",\n      \"journal\": \"Pharmacological research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo and in vitro loss-of-function with mechanistic protein-interaction data, single lab\",\n      \"pmids\": [\"35918045\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Rabphilin-3A promotes SNARE complex assembly by binding the N-peptide region of SNAP-25 via the C2B bottom alpha-helix; this interaction is enabled by an intramolecular interplay between the N-terminal Rab-binding domain and the C-terminal C2AB domain; the C2B/SNAP-25 N-peptide interaction induces a conformational switch from random coils to alpha-helical structure in the SNAP-25 SNARE motif, accelerating SNARE complex assembly; disrupting this interaction impairs vesicle docking and fusion in PC12 cells.\",\n      \"method\": \"In vitro SNARE complex assembly assay; NMR; binding studies; mutagenesis; TIRF microscopy in PC12 cells\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution of SNARE assembly, structural characterization of conformational change, and functional validation in cells with multiple methods\",\n      \"pmids\": [\"36173100\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Rph3A overexpression in hippocampal neurons increases dendritic spine density, increases synaptic GluN2A-containing NMDARs, and decreases surface GluA1-containing AMPARs; these changes occlude LTP-induced spine formation but do not prevent LTD-induced spine loss.\",\n      \"method\": \"Confocal imaging of spine density; surface NMDAR and AMPAR quantification; LTP and LTD induction protocols in primary hippocampal neurons\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain-of-function with functional synaptic plasticity readouts, single lab\",\n      \"pmids\": [\"35626653\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Rph3A undergoes liquid-liquid phase separation dependent on arginine residues in its N-terminal domain; phase separation promotes GluN2A clustering by binding GluN2A C-terminal domain; a ternary Rph3A/GluN2A/PSD95 complex promotes Rph3A phase separation; disrupting Rph3A phase separation suppresses synaptic and extrasynaptic surface clustering, synaptic localization, and stability of GluN2A and reduces NMDAR synaptic responses.\",\n      \"method\": \"In vitro phase separation assay; mutagenesis of arginine residues; FRAP; super-resolution imaging; electrophysiology in hippocampal neurons\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — phase separation reconstituted in vitro and validated in neurons with multiple orthogonal methods including mutagenesis and electrophysiology\",\n      \"pmids\": [\"36693856\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"RPH3A missense gain-of-function variants (p.Thr450Ser, p.Asn618Ser) reduce synaptic localization of GluN2A; p.Thr450Ser also increases surface GluN2A levels; both variants increase GluN2A-dependent NMDAR currents and alter postsynaptic calcium levels; Thr450Ser expression affects dendritic spine morphology.\",\n      \"method\": \"Primary hippocampal neuronal cultures; immunofluorescence; whole-cell patch clamp; calcium imaging; spine morphology analysis\",\n      \"journal\": \"Genetics in medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional assays in neuronal cultures with disease-linked variants, single lab\",\n      \"pmids\": [\"37403762\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"CAND1 (cullin-associated NEDD8-dissociated protein 1) was identified as a rabphilin-3A-binding protein in posterior pituitary by GST-pulldown and co-immunoprecipitation; CAND1 overexpression leads to deubiquitylation of rabphilin-3A in PC12 cells and enhances both basal and KCl-stimulated AVP secretion.\",\n      \"method\": \"GST-pulldown; proteomic analysis; co-immunoprecipitation; ubiquitination assay; AVP secretion assay in PC12 cells\",\n      \"journal\": \"Endocrine journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pulldown with proteomic identification confirmed by co-IP, with functional secretion readout, single lab\",\n      \"pmids\": [\"29367474\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"RPH3A is a negative regulator of dense-core vesicle (DCV) exocytosis in hippocampal neurons; RPH3A KO increases DCV exocytosis ~3-fold; RAB3A-binding deficient RPH3A loses synaptic enrichment but still restores WT DCV exocytosis; SNAP25-binding deficient RPH3A does not rescue DCV exocytosis, indicating SNAP25 interaction mediates the inhibitory function; RPH3A resides stationary at presynapses and does not travel with DCVs.\",\n      \"method\": \"Live-cell imaging at single-vesicle resolution in RPH3A knockout hippocampal neurons; viral re-expression of wild-type and mutant RPH3A; tetanus neurotoxin ablation of regulated secretion\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — KO with rescue by wild-type and domain-specific mutants, single-vesicle resolution live imaging, multiple mutant constructs\",\n      \"pmids\": [\"39412498\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"RPH3A variants p.(Arg209Lys) and p.(Gln508His) reduce presynaptic glutamate release and decrease synaptic retention of GluN2A-containing NMDARs, with reduced calcium event frequency at dendritic spines, demonstrating both pre- and post-synaptic dysfunction from disease-associated RPH3A missense variants.\",\n      \"method\": \"Primary hippocampal neuronal cultures; electrophysiology; calcium imaging; immunofluorescence of GluN2A synaptic localization\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional assays in neurons with disease-linked variants, single lab\",\n      \"pmids\": [\"40082528\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"Rabphilin-3A (RPH3A) is a multidomain synaptic protein that functions as a GTP-state-dependent effector of Rab3A and Rab27A: its N-terminal Zn2+-finger domain mediates GTP-Rab binding and recruits rabphilin to secretory vesicles, while its tandem C2 domains (C2A and C2B) bind Ca2+, phospholipids (including PIP2 via a TAMA mechanism for C2A), SNAP-25 (via the C2B polybasic helix), alpha-actinin, and the GluN2A/PSD-95 complex to regulate both presynaptic vesicle docking/SNARE complex assembly and postsynaptic NMDAR stabilization through phase separation; rabphilin is phosphorylated by CaMKII and PKA at Ser234/Ser274, mono-ubiquitinated by UBE3A in a non-degradative manner, and in neutrophils is phosphorylated by PKN1 to direct polarized RAB21 vesicle trafficking.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"Rabphilin-3A (RPH3A) is a multidomain synaptic effector that couples Rab GTPase signaling to the membrane fusion machinery, regulating both presynaptic vesicle exocytosis and postsynaptic receptor stabilization [#0, #29, #36]. Its N-terminal Zn2+-finger domain binds the GTP-bound forms of Rab3A and, with higher functional relevance for vesicle recruitment, Rab27A, which reversibly targets the protein to secretory and dense-core vesicles [#0, #12, #24, #25]; the structural basis of this state-dependent recognition was defined by the Rab3A/GTP–rabphilin effector-domain crystal structure, in which an SGAWFF element engages a Rab pocket conferring effector specificity [#18]. Its tandem C2 domains bind Ca2+ and phospholipids including PIP2 — C2A via a Ca2+/IP3 target-activated (TAMA) mechanism — providing membrane-coincidence sensing [#1, #33, #34]. Presynaptically, the C2B domain directly binds the plasma-membrane SNARE SNAP-25 through a polybasic helix and bottom alpha-helix, promoting vesicle docking and accelerating SNARE complex assembly by inducing an alpha-helical conformational switch in the SNAP-25 SNARE motif [#27, #30, #37, #43]; through this C2B–SNAP-25 interaction RPH3A modulates synaptic vesicle re-priming and acts as a negative regulator of dense-core vesicle exocytosis [#29, #48]. Postsynaptically, RPH3A is enriched at dendritic spines where its N-terminal domain forms a ternary complex with GluN2A and PSD-95 and undergoes arginine-dependent liquid-liquid phase separation to cluster and stabilize synaptic GluN2A-containing NMDARs [#36, #45]. RPH3A is a convergent phosphorylation target of PKA and CaMKII at Ser234/Ser274, modifications that reduce its membrane affinity, and is regulated by mono-ubiquitination and 14-3-3 binding [#11, #23, #41, #39]. Disease-associated RPH3A missense variants impair 14-3-3 binding or perturb GluN2A retention and glutamate release, linking the protein to a presynaptic congenital myasthenic syndrome and to pre- and postsynaptic synaptic dysfunction [#39, #46, #49]. A distinct, non-neuronal role is established in neutrophils, where PKN1 phosphorylation of RPH3A enhances GTP-RAB21 binding to drive polarized vesicle trafficking and integrin activation [#38, #40].\",\n  \"teleology\": [\n    {\n      \"year\": 1993,\n      \"claim\": \"Establishing what links Rab3A to its downstream effects: RPH3A was defined as the first GTP-state-dependent Rab3A effector, with separable Rab-binding and Ca2+/lipid-binding modules.\",\n      \"evidence\": \"In vitro pulldown of recombinant rabphilin with GTPgammaS- vs GDP-Rab3A, and domain-fragment binding assays with phospholipid and 45Ca2+\",\n      \"pmids\": [\"8384302\", \"8262955\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish the cellular consequence of the effector interaction\", \"Domain boundaries refined only in later work\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Addressing how RPH3A might influence Rab3A nucleotide state: it inhibits GAP-stimulated GTP hydrolysis and was reported to have exchange activity, positioning it to stabilize active Rab3A.\",\n      \"evidence\": \"In vitro GTPase and GDP/GTP exchange assays with purified Rab3A and rabphilin fragments\",\n      \"pmids\": [\"8226731\", \"7926025\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological relevance of GAP inhibition/exchange activity in cells not established\", \"Exchange activity reported by a single lab\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Defining where RPH3A acts and how it gets there: it localizes to presynaptic synaptic vesicles, and its synaptic targeting depends on Rab3A/3C.\",\n      \"evidence\": \"Immunogold EM and subcellular fractionation of rat brain; immunofluorescence in rab3A knockout mice with in vitro rab3C binding\",\n      \"pmids\": [\"8060298\", \"7946335\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"A Rab3A-independent vesicle association was also reported (idx 5), leaving recruitment mechanism only partly resolved\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Identifying RPH3A as a kinase target: it is phosphorylated by PKA and CaMKII, marking it as a node integrating second-messenger signaling with release.\",\n      \"evidence\": \"In vitro phosphorylation assays with PKA and CaMKII and phosphopeptide site mapping\",\n      \"pmids\": [\"7945346\", \"7811264\", \"7891174\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of individual sites not established at this stage\", \"Early site assignments later refined to Ser234/Ser274\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Clarifying the recruitment cycle and cytoskeletal coupling: a Zn2+-finger motif mediates GTP-Rab3A binding essential for vesicle recruitment, RPH3A dissociates upon Ca2+-dependent fusion, and its N-terminus binds alpha-actinin to modulate actin crosslinking.\",\n      \"evidence\": \"Exocytosis-coupled dissociation assays and Zn2+-finger mutagenesis; yeast two-hybrid plus actin crosslinking assays\",\n      \"pmids\": [\"8617225\", \"8943213\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo significance of actin crosslinking modulation not established\", \"Competition between Rab3A and alpha-actinin for the same region left functional logic unresolved\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Testing functional requirement: RPH3A is required for Ca2+-regulated exocytosis, with C2B but not C2A fragments inhibiting release.\",\n      \"evidence\": \"Antisense knockdown and domain-fragment overexpression with growth hormone release readout in PC12 cells; presynaptic microinjection into squid giant synapse with electrophysiology and EM\",\n      \"pmids\": [\"8605005\", \"9450942\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Fragment overexpression is dominant-negative and does not pinpoint endogenous mechanism\", \"Molecular target of C2B in release not yet identified\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Providing structural rules for specificity and Ca2+-independent interactions: crystal and NMR structures defined the Rab3A effector interface and a Janus-faced C2B domain with a Ca2+-independent bottom surface.\",\n      \"evidence\": \"X-ray structure of Rab3A/GTP/Mg2+–rabphilin effector domain at 2.6 A; NMR solution structure of the C2B domain\",\n      \"pmids\": [\"10025402\", \"10559882\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the Ca2+-independent C2B partners not defined at this point\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Uncovering Rab3-independent functions: secretory potentiation and endocytosis control can occur without high-affinity Rab3 binding, the latter via Rabaptin-5, and genetics revealed a Rab3-independent role in potentiating SNARE function.\",\n      \"evidence\": \"Rab3-binding-domain point mutagenesis with secretion and transferrin endocytosis assays in HIT-T15 cells; C. elegans genetic epistasis with SNARE hypomorphs\",\n      \"pmids\": [\"10504306\", \"11309205\", \"11717359\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The unknown factor binding the Rab3-binding domain to drive secretion was not identified\", \"Mechanistic link between rabphilin and SNAREs still inferred genetically\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Broadening the effector repertoire and identifying the operative vesicle Rab: RPH3A binds multiple Rabs including Rab27, and Rab27A rather than Rab3A recruits it to dense-core vesicles.\",\n      \"evidence\": \"Co-transfection binding screen against 42 Rabs; mutagenesis and live-cell localization with neuropeptide Y secretion in PC12 cells across species\",\n      \"pmids\": [\"12578829\", \"14722103\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative in vivo contributions of Rab3 vs Rab27 across cell types not fully resolved\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identifying the molecular basis of docking: the C2B domain binds SNAP-25 and an alpha-actinin-dependent mechanism tethers RPH3A to the subplasmalemmal actin cytoskeleton, increasing docked vesicles.\",\n      \"evidence\": \"In vitro SNAP-25 binding with affinity measurement and TIRFM docking assays; F-actin reconstitution with purified components and granule co-sedimentation\",\n      \"pmids\": [\"16203731\", \"16043482\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether docking and re-priming use the same C2B-SNAP-25 contact left for later work\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Mapping the docking motif and physiological role: a C2B polybasic sequence mediates SNAP-25 binding required for docking, and knockout/rescue shows RPH3A regulates SNARE-dependent vesicle re-priming through this interaction.\",\n      \"evidence\": \"Polybasic-sequence mutagenesis with binding and TIRFM exocytosis assays in PC12 cells; knockout neuron electrophysiology with WT and C2B-mutant viral rescue and synaptobrevin double knockout\",\n      \"pmids\": [\"17156129\", \"16763567\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural conformation enabling simultaneous SNAP-25 and membrane binding not yet resolved\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Defining the lipid-sensing chemistry: both C2 domains bind PIP2, with C2A using a Ca2+/IP3 mutually-enhancing TAMA mechanism, and the structural conformational change enabling it was determined.\",\n      \"evidence\": \"NMR mapping of IP3 binding with affinity measurements; NMR solution structure of Ca2+-bound C2A with docking and CBL3 mutagenesis; C2A-C2B linker structural studies\",\n      \"pmids\": [\"18434502\", \"18945677\", \"17166855\", \"16790935\", \"31924649\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo PIP2 sensing during release not directly demonstrated in this set\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Revealing a postsynaptic role: RPH3A forms a ternary complex with GluN2A and PSD-95 to stabilize synaptic NMDARs.\",\n      \"evidence\": \"Co-IP, GST pulldown, RNAi knockdown, patch clamp, confocal imaging, and in vivo interfering-peptide injection in organotypic slices\",\n      \"pmids\": [\"26679993\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which complex stabilizes surface GluN2A not yet defined (resolved later by phase separation)\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Defining how RPH3A engages the fusion machinery and is regulated in non-neuronal cells: C2B binds the same SNAP-25 surface as synaptotagmin-1 while simultaneously binding PIP2/Ca2+, and PKN1 phosphorylation directs RAB21 vesicle trafficking in neutrophils.\",\n      \"evidence\": \"Crystal structures of C2B-SNAP25 and C2B-PIP2 complexes with biochemical analysis; kinase assay, co-IP, neutrophil imaging, siRNA, and myeloid PKN1 knockout mice\",\n      \"pmids\": [\"28634303\", \"28636945\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How C2B coordinates with the complete assembled SNARE complex left for functional reconstitution\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Establishing the catalytic action on SNARE assembly: RPH3A binds the SNAP-25 N-peptide via the C2B bottom helix, an intramolecular N-/C-terminal interplay enables it, and it induces an alpha-helical conformational switch accelerating SNARE complex assembly.\",\n      \"evidence\": \"In vitro SNARE assembly assays, NMR, binding studies, mutagenesis, and TIRF microscopy in PC12 cells\",\n      \"pmids\": [\"36173100\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Quantitative contribution to fusion kinetics in native synapses not measured\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Explaining how RPH3A stabilizes postsynaptic receptors: arginine-dependent liquid-liquid phase separation, promoted by the GluN2A/PSD-95 ternary complex, clusters and stabilizes synaptic GluN2A.\",\n      \"evidence\": \"In vitro phase separation assays, arginine mutagenesis, FRAP, super-resolution imaging, and electrophysiology in hippocampal neurons; GluN2A/NMDAR functional assays\",\n      \"pmids\": [\"36693856\", \"35626653\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the same phase-separation property operates presynaptically not addressed\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Resolving the direction of presynaptic regulation: RPH3A is a stationary presynaptic negative regulator of dense-core vesicle exocytosis acting through SNAP-25 binding, separable from its Rab3A-dependent synaptic enrichment.\",\n      \"evidence\": \"Single-vesicle live imaging in RPH3A knockout hippocampal neurons with WT and domain-specific mutant viral rescue and tetanus neurotoxin ablation\",\n      \"pmids\": [\"39412498\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Reconciliation of negative DCV regulation with earlier positive secretion roles across cell types not fully resolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Linking RPH3A dysfunction to disease: missense variants impair 14-3-3 binding, alter GluN2A retention and glutamate release, and produce pre- and postsynaptic dysfunction, connecting RPH3A to presynaptic congenital myasthenic syndrome and synaptic disorders.\",\n      \"evidence\": \"Variant 14-3-3 binding assays in cell lines; neuronal cultures with electrophysiology, calcium imaging, and GluN2A localization for multiple disease variants\",\n      \"pmids\": [\"29441694\", \"37403762\", \"40082528\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab functional characterizations for most variants\", \"Genotype-phenotype relationships across patients not established in this corpus\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How presynaptic SNARE regulation, postsynaptic NMDAR phase separation, and phosphorylation/ubiquitination control are coordinated within a single neuron, and how alpha-synuclein interaction integrates into neurodegenerative pathology, remain open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No unified model integrating pre- and postsynaptic functions\", \"Cellular regulation of the LLPS versus SNARE-assembly activities not defined\", \"alpha-synuclein/RPH3A pathway mechanistically incomplete (idx 42)\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [2, 18, 24, 43]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [1, 33, 34]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [27, 36, 43, 45]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [13, 28]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [3, 5, 25]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [26, 27, 30, 40]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [23, 35]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [28]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [27, 29, 43, 48]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [36, 44, 45]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 18, 38]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [38, 40]}\n    ],\n    \"complexes\": [\"RPH3A/GluN2A/PSD-95 ternary complex\"],\n    \"partners\": [\"RAB3A\", \"RAB27A\", \"SNAP25\", \"GluN2A (GRIN2A)\", \"DLG4 (PSD-95)\", \"ACTN (alpha-actinin)\", \"RAB21\", \"UBE3A\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}