{"gene":"ERC1","run_date":"2026-04-28T17:46:03","timeline":{"discoveries":[{"year":1999,"finding":"ELKS (ERC1) encodes a protein with multiple coiled-coil domains that can form dimers; fusion of the 5' dimerization domains of ELKS to the RET tyrosine kinase domain constitutively activates RET kinase in papillary thyroid carcinoma.","method":"cDNA cloning, in vitro synthesis of chimeric proteins, immunoblotting with anti-phosphotyrosine antibodies","journal":"Genes, chromosomes & cancer","confidence":"Medium","confidence_rationale":"Tier 1 — in vitro biochemical demonstration of constitutive phosphorylation, single lab","pmids":["10337992"],"is_preprint":false},{"year":2002,"finding":"ELKS is alternatively spliced into at least five isoforms (α–ε); all ELKS-RET chimeric fusion proteins retaining the oligomerization (coiled-coil) domains of ELKS are constitutively autophosphorylated at tyrosine residues, confirming dimerization-driven RET kinase activation.","method":"RT-PCR isoform characterization, in vitro synthesis of fusion proteins, immunoblotting with anti-phosphotyrosine antibodies","journal":"Genes, chromosomes & cancer","confidence":"Medium","confidence_rationale":"Tier 1 — in vitro biochemical reconstitution, single lab","pmids":["12203787"],"is_preprint":false},{"year":2004,"finding":"ELKS (ERC1) is an essential regulatory subunit of the IKK complex; it recruits IκBα to the IKK complex, and siRNA-mediated silencing of ELKS blocks NF-κB target gene expression and impairs protection from cytokine-induced apoptosis.","method":"siRNA knockdown, co-immunoprecipitation, mass spectrometry interactome, NF-κB reporter assays, apoptosis assays","journal":"Science","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, MS identification, and functional KD with defined cellular phenotype; highly cited foundational paper","pmids":["15218148"],"is_preprint":false},{"year":2004,"finding":"CAST2 (rat orthologue of human ELKS/ERC1) directly binds RIM1 via its C-terminus and forms a hetero-oligomer with CAST1; both localize to the presynaptic active zone cytomatrix.","method":"Subcellular fractionation, co-immunoprecipitation, immunoelectron microscopy, yeast two-hybrid","journal":"Genes to cells","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP plus ultrastructural localization, replicated across multiple methods","pmids":["14723704"],"is_preprint":false},{"year":2005,"finding":"In C. elegans, ELKS-1 is an active zone protein that directly interacts with the PDZ domain of RIM (UNC-10); redundant protein–protein interactions anchor both ELKS and RIM to active zones; RIM truncations containing PDZ and C2A domains require ELKS for active zone targeting.","method":"Genetic loss-of-function (elks mutants), in vivo imaging, yeast two-hybrid, behavioral and electrophysiological assays","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis plus direct interaction mapping; ortholog study with clear conservation of function","pmids":["15976086"],"is_preprint":false},{"year":2005,"finding":"ELKS (ERC1) localizes near insulin granules docked at the plasma membrane in pancreatic β-cells; introduction of the Bassoon-binding region of ELKS reduces insulin granule docking and fusion; siRNA knockdown of ELKS reduces glucose-evoked insulin release.","method":"Confocal and immunoelectron microscopy, TIRF microscopy, dominant-negative overexpression, siRNA knockdown, insulin secretion assay","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (imaging, dominant-negative, siRNA) with defined functional readout","pmids":["15888548"],"is_preprint":false},{"year":2006,"finding":"ELKS promotes Ca2+-dependent exocytosis in PC12 cells via direct binding to RIM2 (through its C-terminal IWA motif) and to Bassoon (through a central region); this function requires the RIM2–Munc13-1 pathway.","method":"Overexpression of full-length and deletion constructs, hGH secretion assay, dominant-negative interference with Munc13-1 binding domain","journal":"Genes to cells","confidence":"High","confidence_rationale":"Tier 1–2 — structure-function mutagenesis with functional exocytosis assay","pmids":["16716196"],"is_preprint":false},{"year":2006,"finding":"In C. elegans, a gain-of-function mutation in SYD-2 (Liprin-α) promotes presynaptic active zone assembly in an ELKS-1-dependent manner; mutant SYD-2 shows increased association with ELKS, placing ELKS downstream of SYD-2 in active zone assembly.","method":"Genetic epistasis (elks-1 loss-of-function suppresses syd-2 gain-of-function), co-immunoprecipitation","journal":"Nature neuroscience","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis plus biochemical interaction; ortholog study","pmids":["17115037"],"is_preprint":false},{"year":2010,"finding":"ATM- and NEMO-dependent K63-linked polyubiquitination of ELKS (mediated by ubiquitin ligase XIAP and conjugating enzyme UBC13) allows ELKS to associate with TAK1 via ubiquitin-binding subunits TAB2/3, leading to IKK and NF-κB activation in response to genotoxic stress.","method":"Co-immunoprecipitation, ubiquitination assays, siRNA knockdown, NEMO ubiquitin-binding mutants, NF-κB reporter assays","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1–2 — detailed biochemical dissection with mutagenesis, multiple orthogonal methods","pmids":["20932476"],"is_preprint":false},{"year":2014,"finding":"ERC1a (isoform of ERC1), together with liprin-α1 and LL5α/β, forms a polarized complex at the protruding cell front that is required for cell migration and tumor invasion; depletion of ERC1 impairs lamellipodial persistence and internalization of active integrin β1.","method":"siRNA depletion, live-cell imaging, invasion assays, co-immunoprecipitation, integrin internalization assays","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — clean KD with defined cellular phenotypes and pathway placement, multiple methods","pmids":["24982445"],"is_preprint":false},{"year":2014,"finding":"Removal of both ELKS1 and ELKS2 in hippocampal inhibitory neurons reduces neurotransmitter release by ~50% with decreased release probability, and causes ~30% reduction in action potential-triggered Ca2+ influx at inhibitory nerve terminals without reducing presynaptic Ca2+ channel levels.","method":"Conditional double knockout mice, electrophysiology, Ca2+ imaging, electron microscopy","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with multiple orthogonal functional readouts","pmids":["25209271"],"is_preprint":false},{"year":2016,"finding":"Liprin-α1 and ERC1 colocalize with active integrin β1 at the cell edge distinct from focal adhesion markers, and promote the localization of peripheral Rab7-positive endosomes; ERC1 localization at the cell edge is required for disassembly of focal adhesions.","method":"siRNA depletion, live-cell imaging, co-immunoprecipitation, endosome localization assays, dominant-negative liprin-N expression","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 — clean KD with defined phenotypes, single lab","pmids":["27659488"],"is_preprint":false},{"year":2016,"finding":"SDCCAG8 interacts with ERC1 as part of an endosomal sorting complex at the centrosome, identified by affinity proteomics.","method":"Affinity proteomics (AP-MS), co-immunoprecipitation","journal":"PloS one","confidence":"Low","confidence_rationale":"Tier 3 — single Co-IP/AP-MS identification, limited functional follow-up for ERC1 specifically","pmids":["27224062"],"is_preprint":false},{"year":2018,"finding":"Deletion of CAST/ELKS at the calyx of Held reduces CaV2.1 channel density and numbers; paradoxically increases release probability while decreasing the readily releasable pool; also elevates spontaneous release rates; Ca2+ channel coupling is unchanged.","method":"Conditional knockout mice, patch-clamp electrophysiology, electron microscopy, immunostaining for CaV2.1 clusters","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 — conditional KO with multiple electrophysiological and ultrastructural readouts","pmids":["29996090"],"is_preprint":false},{"year":2019,"finding":"ERC1 exists as an extended flexible dimer; ERC1 scaffolds form cytoplasmic condensates with liquid-phase behavior modulated by a predicted intrinsically disordered region; these condensates recruit liprin-α1 and other cell motility partners.","method":"Electron microscopy, single-molecule analysis, FRAP, live-cell imaging, droplet assays","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal biophysical methods, single lab","pmids":["31537859"],"is_preprint":false},{"year":2019,"finding":"ELKS directly interacts with the GK domain of the VDCC-β subunit; β-cell-specific ELKS knockout impairs L-type VDCC current density, reduces polarized Ca2+ influx at the vascular-facing plasma membrane, and impairs first-phase glucose-stimulated insulin secretion.","method":"Conditional KO mice, patch-clamp, in situ Ca2+ imaging (G-CaMP8b), co-immunoprecipitation/GST pulldown for direct interaction","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1–2 — direct biochemical interaction plus in vivo KO with multiple functional readouts","pmids":["30699350"],"is_preprint":false},{"year":2020,"finding":"Combined deletion of CAST/ELKS in the forebrain causes neonatal lethality; CAST/ELKS are positive regulators of presynaptic terminal size and suppressors of active zone expansion, and regulate all CaV2 subtype channel levels at the calyx of Held.","method":"Conditional KO mice, confocal morphological analysis, patch-clamp, electron microscopy","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 2 — conditional double KO with multiple morphological and electrophysiological readouts","pmids":["32304329"],"is_preprint":false},{"year":2021,"finding":"Oligomerized liprin-α2, through multivalent interactions with ELKS proteins, enhances phase separation of the ELKS N-terminal segment; liprin-α2 regulates the competitive distribution of ELKS and RIM/RIM-BP in condensates to control active zone protein compartmentalization.","method":"Structural characterization (coiled-coil crystal/solution structures), in vitro phase separation assays, biochemical binding assays, mutagenesis","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1 — structural and biochemical reconstitution with mutagenesis","pmids":["33761347"],"is_preprint":false},{"year":2023,"finding":"Dengue virus NS5 protein binds and degrades ERC1 via a mechanism involving the methyltransferase domain of NS5 (serotype-specific), leading to antagonism of NF-κB activation, reduced proinflammatory cytokine secretion, and reduced cell migration.","method":"Proteomics, co-immunoprecipitation, recombinant chimeric virus construction, NF-κB reporter assays, cytokine secretion assays, migration assays","journal":"Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 2 — proteomics plus Co-IP plus functional assays with chimeric viruses and single amino acid substitutions","pmids":["37252973"],"is_preprint":false},{"year":2023,"finding":"A C-terminal segment of ELKS1 forms a helical hairpin to bind Rab6B through a unique mode; liquid-liquid phase separation of ELKS1 enhances competitive binding to Rab6B, accumulates Rab6B-coated liposomes into ELKS1 condensates, and promotes vesicle exocytosis at releasing sites.","method":"Crystal structure of ELKS1-Rab6B complex, in vitro LLPS assays, liposome binding assays, live-cell vesicle exocytosis assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with functional reconstitution and cellular validation","pmids":["37172719"],"is_preprint":false},{"year":2023,"finding":"ERC1 minimal interaction regions with LL5β are ERC1(270-370) and LL5β(381-510); the ERC1–LL5β interaction involves intrinsically disordered regions and is high-affinity; disrupting this interaction by expression of LL5β(381-510) delocalizes ERC1 from the cell edge and impairs tumor cell invasion.","method":"Co-immunoprecipitation, NMR spectroscopy, dominant-negative expression, invasion/motility assays","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 — NMR plus Co-IP plus functional cellular assay, single lab","pmids":["37437062"],"is_preprint":false},{"year":2023,"finding":"At Drosophila active zones undergoing homeostatic potentiation, ELKS/Bruchpilot distribution compacts and its interaction with the CaV2 α1-subunit Cacophony (via Cac C-terminus and ELKS amino-terminal region) is required for increased Cac numbers and sustained potentiation.","method":"Intravital single-molecule imaging of endogenously tagged proteins, genetic mutant analysis, FRAP","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 2 — endogenous tagging plus genetic interaction mapping with defined functional readout; Drosophila ortholog","pmids":["36800417"],"is_preprint":false},{"year":2025,"finding":"The N-terminal region ERC1(1-244) containing an intrinsically disordered region is sufficient to drive phase separation in vitro and in cells; deletion of this region alters the biophysical properties of ERC1 condensates and impairs tumor cell motility without disrupting partner interactions.","method":"In vitro phase separation assays, FRAP, co-immunoprecipitation, cell motility assays","journal":"Communications biology","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal biophysical and functional methods, single lab","pmids":["40646182"],"is_preprint":false},{"year":2025,"finding":"Insulin secretion from pancreatic β-cells is restricted to sites at the margins of ELKS/LL5β patches that are devoid of microtubules; MT disassembly and optimal ELKS content together predict secretion hot spots.","method":"TIRF microscopy of intact mouse islets, live imaging of granule fusion events relative to ELKS patch architecture and MT organization","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 — direct high-resolution localization with functional readout, single study","pmids":["40366873"],"is_preprint":false}],"current_model":"ERC1/ELKS is a multifunctional scaffold protein that (1) organizes presynaptic active zones by directly binding RIM, Bassoon/Piccolo, and VDCC-β subunits to control Ca2+ channel density and neurotransmitter release probability; (2) regulates NF-κB signaling by recruiting IκBα to the IKK complex and, upon genotoxic stress, undergoes XIAP/UBC13-mediated K63-ubiquitination to scaffold TAK1 activation; (3) drives cell migration and invasion by forming liquid-liquid phase-separated condensates with liprin-α1 and LL5β at the leading edge to promote focal adhesion turnover and active integrin internalization; and (4) promotes Ca2+-triggered exocytosis in pancreatic β-cells by forming a complex with L-type VDCCs at the vascular-facing plasma membrane to enable polarized insulin secretion."},"narrative":{"teleology":[{"year":1999,"claim":"Identification of ERC1 as a coiled-coil protein capable of dimerization established the structural basis for its scaffolding function and explained how ELKS-RET fusions constitutively activate RET kinase in papillary thyroid carcinoma.","evidence":"cDNA cloning and in vitro chimeric protein autophosphorylation assays","pmids":["10337992","12203787"],"confidence":"Medium","gaps":["No endogenous signaling function yet assigned","In vitro only — no cellular transformation assay"]},{"year":2004,"claim":"Two parallel discoveries revealed ERC1's dual cellular roles: as an essential NF-κB scaffold that recruits IκBα to IKK, and as a presynaptic active zone component that binds RIM1 and localizes to the cytomatrix.","evidence":"siRNA knockdown with NF-κB reporters/apoptosis assays (human cells); co-IP, yeast two-hybrid, immunoelectron microscopy (rat brain)","pmids":["15218148","14723704"],"confidence":"High","gaps":["Mechanism by which ERC1 recruits IκBα not molecularly defined","Whether NF-κB and synaptic functions are isoform-specific"]},{"year":2005,"claim":"Genetic studies in C. elegans and functional studies in β-cells established ERC1 as a conserved organizer of exocytic machinery, directly interacting with RIM at active zones and promoting insulin granule docking and fusion.","evidence":"C. elegans elks-1 loss-of-function genetics plus yeast two-hybrid; TIRF/immunoEM in β-cells with siRNA and dominant-negative constructs","pmids":["15976086","15888548"],"confidence":"High","gaps":["Precise contribution of individual ERC1 binding interfaces to exocytosis not resolved","Redundancy between ELKS1 and ELKS2 not yet addressed"]},{"year":2006,"claim":"Placing ERC1 downstream of liprin-α (SYD-2) in active zone assembly, and mapping its separable RIM2- and Bassoon-binding domains, defined ERC1 as a modular scaffold linking active zone organizers to the release machinery.","evidence":"Genetic epistasis in C. elegans (syd-2 gain-of-function suppressed by elks-1 loss); structure-function deletion analysis with hGH secretion assays in PC12 cells","pmids":["17115037","16716196"],"confidence":"High","gaps":["Stoichiometry and architecture of the multi-protein complex unknown","Mammalian in vivo validation of liprin–ELKS hierarchy not yet done"]},{"year":2010,"claim":"The discovery that genotoxic stress induces ATM/NEMO-dependent K63-ubiquitination of ERC1 by XIAP/UBC13, enabling TAK1 recruitment via TAB2/3, revealed a distinct DNA-damage-to-NF-κB signaling axis mediated by ERC1.","evidence":"Ubiquitination assays, siRNA, NEMO ubiquitin-binding mutants, NF-κB reporter assays in human cells","pmids":["20932476"],"confidence":"High","gaps":["Specific lysine residues on ERC1 targeted for K63-ubiquitination not identified","Whether this pathway operates in primary cells in vivo"]},{"year":2014,"claim":"Two studies established ERC1 as a regulator of both presynaptic release probability and cell migration: conditional double KO in hippocampal inhibitory neurons showed ~50% reduction in release with decreased Ca²⁺ influx, while ERC1 depletion in tumor cells impaired leading-edge polarity, active integrin β1 internalization, and invasion.","evidence":"Conditional ELKS1/2 double-KO mice with electrophysiology and Ca²⁺ imaging; siRNA in tumor cells with live-cell imaging and invasion assays","pmids":["25209271","24982445"],"confidence":"High","gaps":["Whether ERC1 directly couples Ca²⁺ channels or acts indirectly through active zone architecture","Mechanism linking ERC1 to integrin endocytic machinery not identified"]},{"year":2016,"claim":"ERC1 and liprin-α1 were shown to colocalize with active integrin β1 at the cell edge and to promote peripheral Rab7-positive endosome positioning, linking ERC1's scaffolding role to endosomal trafficking and focal adhesion turnover.","evidence":"siRNA depletion, live-cell imaging, endosome localization assays in migrating cells","pmids":["27659488"],"confidence":"Medium","gaps":["Direct interaction between ERC1 and endosomal machinery not demonstrated","SDCCAG8 interaction (PMID:27224062) lacks functional follow-up for ERC1"]},{"year":2018,"claim":"Conditional KO at the calyx of Held revealed that CAST/ELKS controls CaV2.1 channel density and number at active zones but paradoxically suppresses release probability, indicating that ERC1 restrains release efficiency even as it maintains the Ca²⁺ channel complement.","evidence":"Conditional KO mice, patch-clamp electrophysiology, CaV2.1 immunostaining, electron microscopy","pmids":["29996090"],"confidence":"High","gaps":["Molecular mechanism by which ELKS suppresses release probability despite maintaining channels is unresolved","Synapse-type-specific differences (calyx vs. hippocampal) not reconciled"]},{"year":2019,"claim":"Two breakthroughs established the biophysical and structural basis for ERC1 function: ERC1 forms liquid-phase condensates via an intrinsically disordered region that recruits motility partners, and ERC1 directly binds the VDCC-β GK domain to polarize Ca²⁺ influx and insulin secretion in β-cells.","evidence":"EM/FRAP/droplet assays for phase separation; conditional β-cell KO with patch-clamp, Ca²⁺ imaging, and GST pulldown for VDCC-β interaction","pmids":["31537859","30699350"],"confidence":"High","gaps":["Post-translational regulation of phase separation not characterized","Structural basis of ELKS–VDCC-β interaction not resolved"]},{"year":2020,"claim":"Forebrain-specific CAST/ELKS double deletion causing neonatal lethality, with enlarged active zones but altered CaV2 channel levels, established ERC1 as a positive regulator of presynaptic terminal size and essential for viability.","evidence":"Conditional double KO mice, confocal and electron microscopy, electrophysiology","pmids":["32304329"],"confidence":"High","gaps":["Relative contributions of ELKS1 vs ELKS2 to terminal size regulation not separated","Mechanism of active zone size control unknown"]},{"year":2021,"claim":"Structural and biochemical reconstitution showed that oligomerized liprin-α2 enhances ELKS N-terminal phase separation through multivalent interactions and competitively regulates the distribution of ELKS versus RIM/RIM-BP in condensates, providing a mechanism for active zone protein compartmentalization.","evidence":"Crystal/solution structures of coiled-coil complexes, in vitro LLPS reconstitution, mutagenesis","pmids":["33761347"],"confidence":"High","gaps":["In vivo validation of competitive partitioning model not performed","How liprin-α1 vs liprin-α2 differentially regulate ELKS condensates is unclear"]},{"year":2023,"claim":"Multiple studies in 2023 resolved key structural and functional interfaces: the ELKS1–Rab6B helical-hairpin crystal structure showed how LLPS concentrates Rab6B vesicles for exocytosis; the ERC1–LL5β interaction was mapped to disordered regions essential for cell-edge targeting and invasion; Drosophila studies showed ELKS–CaV2 α1 interaction is required for homeostatic Ca²⁺ channel accumulation; and dengue NS5 was found to degrade ERC1 to antagonize NF-κB signaling.","evidence":"Crystal structure plus liposome/exocytosis assays; NMR/Co-IP/invasion assays; intravital single-molecule imaging in Drosophila; proteomics/chimeric virus/NF-κB reporter assays","pmids":["37172719","37437062","36800417","37252973"],"confidence":"High","gaps":["Whether Rab6B condensate recruitment operates at synaptic active zones in addition to secretory sites","Structural basis of ERC1–VDCC α1 interaction awaits atomic resolution","Whether NS5-mediated ERC1 degradation occurs via proteasomal or autophagic pathway"]},{"year":2025,"claim":"The N-terminal IDR of ERC1 (residues 1–244) was shown to be both necessary and sufficient for phase separation and required for tumor cell motility independent of partner protein binding; separately, insulin secretion was found to occur at the margins of ELKS/LL5β patches devoid of microtubules, integrating ERC1 condensate architecture with secretory function.","evidence":"In vitro LLPS/FRAP/Co-IP/motility assays for IDR function; TIRF microscopy of granule fusion in intact mouse islets","pmids":["40646182","40366873"],"confidence":"Medium","gaps":["How IDR-driven phase separation is regulated by phosphorylation or other modifications remains unknown","Mechanism linking microtubule exclusion to secretion at ELKS patch margins not defined"]},{"year":null,"claim":"Major open questions include: (1) how ERC1 phase separation is post-translationally regulated in different cellular contexts; (2) the atomic-resolution architecture of the multi-protein active zone complex containing ERC1; (3) isoform-specific functions of ERC1 splice variants in NF-κB versus synaptic/migratory roles; and (4) whether ERC1's NF-κB and cytoskeletal functions are coordinated or fully independent.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model of ERC1 in complex with RIM, Bassoon, and VDCC subunits simultaneously","Isoform-specific knockout studies not performed","Post-translational regulation of IDR-driven condensation uncharacterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[2,8,9,15]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[3,4,7,17]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[5,9,15,23]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[14,22]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[11,19]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[3,4,10,13,16,21]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[2,8,18]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[2,8,18]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[5,15,23]},{"term_id":"R-HSA-1500931","term_label":"Cell-Cell communication","supporting_discovery_ids":[9,11,20]}],"complexes":["IKK complex","presynaptic active zone cytomatrix","ERC1–liprin-α–LL5β leading-edge complex"],"partners":["RIM1","RIM2","PPFIA1","PPFIA2","BSN","PHLDB2","RAB6B","CACNB"],"other_free_text":[]},"mechanistic_narrative":"ERC1 (ELKS) is a coiled-coil scaffold protein that organizes macromolecular assemblies at sites of regulated exocytosis, cell migration, and NF-κB signaling. At presynaptic active zones, ERC1 directly binds RIM, Bassoon, liprin-α, and voltage-dependent Ca²⁺ channel (VDCC) β subunits, controlling Ca²⁺ channel density, readily releasable pool size, and neurotransmitter release probability; combined deletion of CAST/ELKS in forebrain neurons causes neonatal lethality [PMID:14723704, PMID:25209271, PMID:29996090, PMID:32304329]. ERC1 undergoes liquid–liquid phase separation driven by its N-terminal intrinsically disordered region; these condensates recruit liprin-α, LL5β, and Rab6B-coated vesicles to regulate focal adhesion turnover, integrin internalization, and vesicle exocytosis at the leading edge and secretory sites [PMID:31537859, PMID:37172719, PMID:24982445, PMID:40646182]. In pancreatic β-cells, ERC1 interacts with L-type VDCC β subunits to polarize Ca²⁺ influx at the vascular-facing membrane and enable first-phase glucose-stimulated insulin secretion [PMID:30699350, PMID:40366873]. ERC1 also functions in NF-κB signaling by recruiting IκBα to the IKK complex and, upon genotoxic stress, undergoing XIAP/UBC13-mediated K63-ubiquitination to scaffold TAK1 activation—a pathway exploited by dengue virus NS5, which degrades ERC1 to suppress innate immune responses [PMID:15218148, PMID:20932476, PMID:37252973]."},"prefetch_data":{"uniprot":{"accession":"Q8IUD2","full_name":"ELKS/Rab6-interacting/CAST family member 1","aliases":["Rab6-interacting protein 2"],"length_aa":1116,"mass_kda":128.1,"function":"Regulatory subunit of the IKK complex. Probably recruits IkappaBalpha/NFKBIA to the complex. May be involved in the organization of the cytomatrix at the nerve terminals active zone (CAZ) which regulates neurotransmitter release. May be involved in vesicle trafficking at the CAZ. May be involved in Rab-6 regulated endosomes to Golgi transport","subcellular_location":"Cytoplasm, cytoskeleton, microtubule organizing center, centrosome; Cytoplasm; Membrane; Golgi apparatus membrane; Presynaptic cell membrane; Cell projection, podosome","url":"https://www.uniprot.org/uniprotkb/Q8IUD2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ERC1","classification":"Not Classified","n_dependent_lines":6,"n_total_lines":1208,"dependency_fraction":0.004966887417218543},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CAPZB","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/ERC1","total_profiled":1310},"omim":[{"mim_id":"607127","title":"ELKS/RAB6-INTERACTING/CAST FAMILY, MEMBER 1; ERC1","url":"https://www.omim.org/entry/607127"},{"mim_id":"600599","title":"KLF TRANSCRIPTION FACTOR 1; KLF1","url":"https://www.omim.org/entry/600599"},{"mim_id":"176640","title":"PRION PROTEIN; PRNP","url":"https://www.omim.org/entry/176640"},{"mim_id":"137440","title":"GERSTMANN-STRAUSSLER DISEASE; GSD","url":"https://www.omim.org/entry/137440"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"},{"location":"Vesicles","reliability":"Additional"},{"location":"Centrosome","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/ERC1"},"hgnc":{"alias_symbol":["ELKS","KIAA1081","CAST2","MGC12974"],"prev_symbol":["RAB6IP2"]},"alphafold":{"accession":"Q8IUD2","domains":[{"cath_id":"-","chopping":"1008-1116","consensus_level":"medium","plddt":84.8749,"start":1008,"end":1116}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IUD2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IUD2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IUD2-F1-predicted_aligned_error_v6.png","plddt_mean":74.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ERC1","jax_strain_url":"https://www.jax.org/strain/search?query=ERC1"},"sequence":{"accession":"Q8IUD2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8IUD2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8IUD2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IUD2"}},"corpus_meta":[{"pmid":"16543132","id":"PMC_16543132","title":"Bruchpilot, a protein with homology to ELKS/CAST, is required for structural integrity and function of synaptic active zones in Drosophila.","date":"2006","source":"Neuron","url":"https://pubmed.ncbi.nlm.nih.gov/16543132","citation_count":728,"is_preprint":false},{"pmid":"9778250","id":"PMC_9778250","title":"A SWI/SNF-related chromatin remodeling complex, E-RC1, is required for tissue-specific transcriptional regulation by EKLF in vitro.","date":"1998","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/9778250","citation_count":263,"is_preprint":false},{"pmid":"15218148","id":"PMC_15218148","title":"Activation of transcription factor NF-kappaB requires ELKS, an IkappaB kinase regulatory subunit.","date":"2004","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/15218148","citation_count":180,"is_preprint":false},{"pmid":"17115037","id":"PMC_17115037","title":"SYD-2 Liprin-alpha organizes presynaptic active zone formation through ELKS.","date":"2006","source":"Nature 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fusion of the 5' dimerization domains of ELKS to the RET tyrosine kinase domain constitutively activates RET kinase in papillary thyroid carcinoma.\",\n      \"method\": \"cDNA cloning, in vitro synthesis of chimeric proteins, immunoblotting with anti-phosphotyrosine antibodies\",\n      \"journal\": \"Genes, chromosomes & cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — in vitro biochemical demonstration of constitutive phosphorylation, single lab\",\n      \"pmids\": [\"10337992\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"ELKS is alternatively spliced into at least five isoforms (α–ε); all ELKS-RET chimeric fusion proteins retaining the oligomerization (coiled-coil) domains of ELKS are constitutively autophosphorylated at tyrosine residues, confirming dimerization-driven RET kinase activation.\",\n      \"method\": \"RT-PCR isoform characterization, in vitro synthesis of fusion proteins, immunoblotting with anti-phosphotyrosine antibodies\",\n      \"journal\": \"Genes, chromosomes & cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — in vitro biochemical reconstitution, single lab\",\n      \"pmids\": [\"12203787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"ELKS (ERC1) is an essential regulatory subunit of the IKK complex; it recruits IκBα to the IKK complex, and siRNA-mediated silencing of ELKS blocks NF-κB target gene expression and impairs protection from cytokine-induced apoptosis.\",\n      \"method\": \"siRNA knockdown, co-immunoprecipitation, mass spectrometry interactome, NF-κB reporter assays, apoptosis assays\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, MS identification, and functional KD with defined cellular phenotype; highly cited foundational paper\",\n      \"pmids\": [\"15218148\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"CAST2 (rat orthologue of human ELKS/ERC1) directly binds RIM1 via its C-terminus and forms a hetero-oligomer with CAST1; both localize to the presynaptic active zone cytomatrix.\",\n      \"method\": \"Subcellular fractionation, co-immunoprecipitation, immunoelectron microscopy, yeast two-hybrid\",\n      \"journal\": \"Genes to cells\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP plus ultrastructural localization, replicated across multiple methods\",\n      \"pmids\": [\"14723704\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"In C. elegans, ELKS-1 is an active zone protein that directly interacts with the PDZ domain of RIM (UNC-10); redundant protein–protein interactions anchor both ELKS and RIM to active zones; RIM truncations containing PDZ and C2A domains require ELKS for active zone targeting.\",\n      \"method\": \"Genetic loss-of-function (elks mutants), in vivo imaging, yeast two-hybrid, behavioral and electrophysiological assays\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis plus direct interaction mapping; ortholog study with clear conservation of function\",\n      \"pmids\": [\"15976086\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"ELKS (ERC1) localizes near insulin granules docked at the plasma membrane in pancreatic β-cells; introduction of the Bassoon-binding region of ELKS reduces insulin granule docking and fusion; siRNA knockdown of ELKS reduces glucose-evoked insulin release.\",\n      \"method\": \"Confocal and immunoelectron microscopy, TIRF microscopy, dominant-negative overexpression, siRNA knockdown, insulin secretion assay\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (imaging, dominant-negative, siRNA) with defined functional readout\",\n      \"pmids\": [\"15888548\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"ELKS promotes Ca2+-dependent exocytosis in PC12 cells via direct binding to RIM2 (through its C-terminal IWA motif) and to Bassoon (through a central region); this function requires the RIM2–Munc13-1 pathway.\",\n      \"method\": \"Overexpression of full-length and deletion constructs, hGH secretion assay, dominant-negative interference with Munc13-1 binding domain\",\n      \"journal\": \"Genes to cells\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — structure-function mutagenesis with functional exocytosis assay\",\n      \"pmids\": [\"16716196\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"In C. elegans, a gain-of-function mutation in SYD-2 (Liprin-α) promotes presynaptic active zone assembly in an ELKS-1-dependent manner; mutant SYD-2 shows increased association with ELKS, placing ELKS downstream of SYD-2 in active zone assembly.\",\n      \"method\": \"Genetic epistasis (elks-1 loss-of-function suppresses syd-2 gain-of-function), co-immunoprecipitation\",\n      \"journal\": \"Nature neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis plus biochemical interaction; ortholog study\",\n      \"pmids\": [\"17115037\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"ATM- and NEMO-dependent K63-linked polyubiquitination of ELKS (mediated by ubiquitin ligase XIAP and conjugating enzyme UBC13) allows ELKS to associate with TAK1 via ubiquitin-binding subunits TAB2/3, leading to IKK and NF-κB activation in response to genotoxic stress.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, siRNA knockdown, NEMO ubiquitin-binding mutants, NF-κB reporter assays\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — detailed biochemical dissection with mutagenesis, multiple orthogonal methods\",\n      \"pmids\": [\"20932476\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"ERC1a (isoform of ERC1), together with liprin-α1 and LL5α/β, forms a polarized complex at the protruding cell front that is required for cell migration and tumor invasion; depletion of ERC1 impairs lamellipodial persistence and internalization of active integrin β1.\",\n      \"method\": \"siRNA depletion, live-cell imaging, invasion assays, co-immunoprecipitation, integrin internalization assays\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KD with defined cellular phenotypes and pathway placement, multiple methods\",\n      \"pmids\": [\"24982445\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Removal of both ELKS1 and ELKS2 in hippocampal inhibitory neurons reduces neurotransmitter release by ~50% with decreased release probability, and causes ~30% reduction in action potential-triggered Ca2+ influx at inhibitory nerve terminals without reducing presynaptic Ca2+ channel levels.\",\n      \"method\": \"Conditional double knockout mice, electrophysiology, Ca2+ imaging, electron microscopy\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with multiple orthogonal functional readouts\",\n      \"pmids\": [\"25209271\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Liprin-α1 and ERC1 colocalize with active integrin β1 at the cell edge distinct from focal adhesion markers, and promote the localization of peripheral Rab7-positive endosomes; ERC1 localization at the cell edge is required for disassembly of focal adhesions.\",\n      \"method\": \"siRNA depletion, live-cell imaging, co-immunoprecipitation, endosome localization assays, dominant-negative liprin-N expression\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean KD with defined phenotypes, single lab\",\n      \"pmids\": [\"27659488\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"SDCCAG8 interacts with ERC1 as part of an endosomal sorting complex at the centrosome, identified by affinity proteomics.\",\n      \"method\": \"Affinity proteomics (AP-MS), co-immunoprecipitation\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single Co-IP/AP-MS identification, limited functional follow-up for ERC1 specifically\",\n      \"pmids\": [\"27224062\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Deletion of CAST/ELKS at the calyx of Held reduces CaV2.1 channel density and numbers; paradoxically increases release probability while decreasing the readily releasable pool; also elevates spontaneous release rates; Ca2+ channel coupling is unchanged.\",\n      \"method\": \"Conditional knockout mice, patch-clamp electrophysiology, electron microscopy, immunostaining for CaV2.1 clusters\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — conditional KO with multiple electrophysiological and ultrastructural readouts\",\n      \"pmids\": [\"29996090\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"ERC1 exists as an extended flexible dimer; ERC1 scaffolds form cytoplasmic condensates with liquid-phase behavior modulated by a predicted intrinsically disordered region; these condensates recruit liprin-α1 and other cell motility partners.\",\n      \"method\": \"Electron microscopy, single-molecule analysis, FRAP, live-cell imaging, droplet assays\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal biophysical methods, single lab\",\n      \"pmids\": [\"31537859\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"ELKS directly interacts with the GK domain of the VDCC-β subunit; β-cell-specific ELKS knockout impairs L-type VDCC current density, reduces polarized Ca2+ influx at the vascular-facing plasma membrane, and impairs first-phase glucose-stimulated insulin secretion.\",\n      \"method\": \"Conditional KO mice, patch-clamp, in situ Ca2+ imaging (G-CaMP8b), co-immunoprecipitation/GST pulldown for direct interaction\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — direct biochemical interaction plus in vivo KO with multiple functional readouts\",\n      \"pmids\": [\"30699350\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Combined deletion of CAST/ELKS in the forebrain causes neonatal lethality; CAST/ELKS are positive regulators of presynaptic terminal size and suppressors of active zone expansion, and regulate all CaV2 subtype channel levels at the calyx of Held.\",\n      \"method\": \"Conditional KO mice, confocal morphological analysis, patch-clamp, electron microscopy\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — conditional double KO with multiple morphological and electrophysiological readouts\",\n      \"pmids\": [\"32304329\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Oligomerized liprin-α2, through multivalent interactions with ELKS proteins, enhances phase separation of the ELKS N-terminal segment; liprin-α2 regulates the competitive distribution of ELKS and RIM/RIM-BP in condensates to control active zone protein compartmentalization.\",\n      \"method\": \"Structural characterization (coiled-coil crystal/solution structures), in vitro phase separation assays, biochemical binding assays, mutagenesis\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — structural and biochemical reconstitution with mutagenesis\",\n      \"pmids\": [\"33761347\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Dengue virus NS5 protein binds and degrades ERC1 via a mechanism involving the methyltransferase domain of NS5 (serotype-specific), leading to antagonism of NF-κB activation, reduced proinflammatory cytokine secretion, and reduced cell migration.\",\n      \"method\": \"Proteomics, co-immunoprecipitation, recombinant chimeric virus construction, NF-κB reporter assays, cytokine secretion assays, migration assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — proteomics plus Co-IP plus functional assays with chimeric viruses and single amino acid substitutions\",\n      \"pmids\": [\"37252973\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"A C-terminal segment of ELKS1 forms a helical hairpin to bind Rab6B through a unique mode; liquid-liquid phase separation of ELKS1 enhances competitive binding to Rab6B, accumulates Rab6B-coated liposomes into ELKS1 condensates, and promotes vesicle exocytosis at releasing sites.\",\n      \"method\": \"Crystal structure of ELKS1-Rab6B complex, in vitro LLPS assays, liposome binding assays, live-cell vesicle exocytosis assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with functional reconstitution and cellular validation\",\n      \"pmids\": [\"37172719\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"ERC1 minimal interaction regions with LL5β are ERC1(270-370) and LL5β(381-510); the ERC1–LL5β interaction involves intrinsically disordered regions and is high-affinity; disrupting this interaction by expression of LL5β(381-510) delocalizes ERC1 from the cell edge and impairs tumor cell invasion.\",\n      \"method\": \"Co-immunoprecipitation, NMR spectroscopy, dominant-negative expression, invasion/motility assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — NMR plus Co-IP plus functional cellular assay, single lab\",\n      \"pmids\": [\"37437062\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"At Drosophila active zones undergoing homeostatic potentiation, ELKS/Bruchpilot distribution compacts and its interaction with the CaV2 α1-subunit Cacophony (via Cac C-terminus and ELKS amino-terminal region) is required for increased Cac numbers and sustained potentiation.\",\n      \"method\": \"Intravital single-molecule imaging of endogenously tagged proteins, genetic mutant analysis, FRAP\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — endogenous tagging plus genetic interaction mapping with defined functional readout; Drosophila ortholog\",\n      \"pmids\": [\"36800417\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"The N-terminal region ERC1(1-244) containing an intrinsically disordered region is sufficient to drive phase separation in vitro and in cells; deletion of this region alters the biophysical properties of ERC1 condensates and impairs tumor cell motility without disrupting partner interactions.\",\n      \"method\": \"In vitro phase separation assays, FRAP, co-immunoprecipitation, cell motility assays\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal biophysical and functional methods, single lab\",\n      \"pmids\": [\"40646182\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Insulin secretion from pancreatic β-cells is restricted to sites at the margins of ELKS/LL5β patches that are devoid of microtubules; MT disassembly and optimal ELKS content together predict secretion hot spots.\",\n      \"method\": \"TIRF microscopy of intact mouse islets, live imaging of granule fusion events relative to ELKS patch architecture and MT organization\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct high-resolution localization with functional readout, single study\",\n      \"pmids\": [\"40366873\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ERC1/ELKS is a multifunctional scaffold protein that (1) organizes presynaptic active zones by directly binding RIM, Bassoon/Piccolo, and VDCC-β subunits to control Ca2+ channel density and neurotransmitter release probability; (2) regulates NF-κB signaling by recruiting IκBα to the IKK complex and, upon genotoxic stress, undergoes XIAP/UBC13-mediated K63-ubiquitination to scaffold TAK1 activation; (3) drives cell migration and invasion by forming liquid-liquid phase-separated condensates with liprin-α1 and LL5β at the leading edge to promote focal adhesion turnover and active integrin internalization; and (4) promotes Ca2+-triggered exocytosis in pancreatic β-cells by forming a complex with L-type VDCCs at the vascular-facing plasma membrane to enable polarized insulin secretion.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"ERC1 (ELKS) is a coiled-coil scaffold protein that organizes macromolecular assemblies at sites of regulated exocytosis, cell migration, and NF-κB signaling. At presynaptic active zones, ERC1 directly binds RIM, Bassoon, liprin-α, and voltage-dependent Ca²⁺ channel (VDCC) β subunits, controlling Ca²⁺ channel density, readily releasable pool size, and neurotransmitter release probability; combined deletion of CAST/ELKS in forebrain neurons causes neonatal lethality [PMID:14723704, PMID:25209271, PMID:29996090, PMID:32304329]. ERC1 undergoes liquid–liquid phase separation driven by its N-terminal intrinsically disordered region; these condensates recruit liprin-α, LL5β, and Rab6B-coated vesicles to regulate focal adhesion turnover, integrin internalization, and vesicle exocytosis at the leading edge and secretory sites [PMID:31537859, PMID:37172719, PMID:24982445, PMID:40646182]. In pancreatic β-cells, ERC1 interacts with L-type VDCC β subunits to polarize Ca²⁺ influx at the vascular-facing membrane and enable first-phase glucose-stimulated insulin secretion [PMID:30699350, PMID:40366873]. ERC1 also functions in NF-κB signaling by recruiting IκBα to the IKK complex and, upon genotoxic stress, undergoing XIAP/UBC13-mediated K63-ubiquitination to scaffold TAK1 activation—a pathway exploited by dengue virus NS5, which degrades ERC1 to suppress innate immune responses [PMID:15218148, PMID:20932476, PMID:37252973].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Identification of ERC1 as a coiled-coil protein capable of dimerization established the structural basis for its scaffolding function and explained how ELKS-RET fusions constitutively activate RET kinase in papillary thyroid carcinoma.\",\n      \"evidence\": \"cDNA cloning and in vitro chimeric protein autophosphorylation assays\",\n      \"pmids\": [\"10337992\", \"12203787\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No endogenous signaling function yet assigned\", \"In vitro only — no cellular transformation assay\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Two parallel discoveries revealed ERC1's dual cellular roles: as an essential NF-κB scaffold that recruits IκBα to IKK, and as a presynaptic active zone component that binds RIM1 and localizes to the cytomatrix.\",\n      \"evidence\": \"siRNA knockdown with NF-κB reporters/apoptosis assays (human cells); co-IP, yeast two-hybrid, immunoelectron microscopy (rat brain)\",\n      \"pmids\": [\"15218148\", \"14723704\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which ERC1 recruits IκBα not molecularly defined\", \"Whether NF-κB and synaptic functions are isoform-specific\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Genetic studies in C. elegans and functional studies in β-cells established ERC1 as a conserved organizer of exocytic machinery, directly interacting with RIM at active zones and promoting insulin granule docking and fusion.\",\n      \"evidence\": \"C. elegans elks-1 loss-of-function genetics plus yeast two-hybrid; TIRF/immunoEM in β-cells with siRNA and dominant-negative constructs\",\n      \"pmids\": [\"15976086\", \"15888548\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise contribution of individual ERC1 binding interfaces to exocytosis not resolved\", \"Redundancy between ELKS1 and ELKS2 not yet addressed\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Placing ERC1 downstream of liprin-α (SYD-2) in active zone assembly, and mapping its separable RIM2- and Bassoon-binding domains, defined ERC1 as a modular scaffold linking active zone organizers to the release machinery.\",\n      \"evidence\": \"Genetic epistasis in C. elegans (syd-2 gain-of-function suppressed by elks-1 loss); structure-function deletion analysis with hGH secretion assays in PC12 cells\",\n      \"pmids\": [\"17115037\", \"16716196\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and architecture of the multi-protein complex unknown\", \"Mammalian in vivo validation of liprin–ELKS hierarchy not yet done\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"The discovery that genotoxic stress induces ATM/NEMO-dependent K63-ubiquitination of ERC1 by XIAP/UBC13, enabling TAK1 recruitment via TAB2/3, revealed a distinct DNA-damage-to-NF-κB signaling axis mediated by ERC1.\",\n      \"evidence\": \"Ubiquitination assays, siRNA, NEMO ubiquitin-binding mutants, NF-κB reporter assays in human cells\",\n      \"pmids\": [\"20932476\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific lysine residues on ERC1 targeted for K63-ubiquitination not identified\", \"Whether this pathway operates in primary cells in vivo\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Two studies established ERC1 as a regulator of both presynaptic release probability and cell migration: conditional double KO in hippocampal inhibitory neurons showed ~50% reduction in release with decreased Ca²⁺ influx, while ERC1 depletion in tumor cells impaired leading-edge polarity, active integrin β1 internalization, and invasion.\",\n      \"evidence\": \"Conditional ELKS1/2 double-KO mice with electrophysiology and Ca²⁺ imaging; siRNA in tumor cells with live-cell imaging and invasion assays\",\n      \"pmids\": [\"25209271\", \"24982445\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether ERC1 directly couples Ca²⁺ channels or acts indirectly through active zone architecture\", \"Mechanism linking ERC1 to integrin endocytic machinery not identified\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"ERC1 and liprin-α1 were shown to colocalize with active integrin β1 at the cell edge and to promote peripheral Rab7-positive endosome positioning, linking ERC1's scaffolding role to endosomal trafficking and focal adhesion turnover.\",\n      \"evidence\": \"siRNA depletion, live-cell imaging, endosome localization assays in migrating cells\",\n      \"pmids\": [\"27659488\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct interaction between ERC1 and endosomal machinery not demonstrated\", \"SDCCAG8 interaction (PMID:27224062) lacks functional follow-up for ERC1\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Conditional KO at the calyx of Held revealed that CAST/ELKS controls CaV2.1 channel density and number at active zones but paradoxically suppresses release probability, indicating that ERC1 restrains release efficiency even as it maintains the Ca²⁺ channel complement.\",\n      \"evidence\": \"Conditional KO mice, patch-clamp electrophysiology, CaV2.1 immunostaining, electron microscopy\",\n      \"pmids\": [\"29996090\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism by which ELKS suppresses release probability despite maintaining channels is unresolved\", \"Synapse-type-specific differences (calyx vs. hippocampal) not reconciled\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Two breakthroughs established the biophysical and structural basis for ERC1 function: ERC1 forms liquid-phase condensates via an intrinsically disordered region that recruits motility partners, and ERC1 directly binds the VDCC-β GK domain to polarize Ca²⁺ influx and insulin secretion in β-cells.\",\n      \"evidence\": \"EM/FRAP/droplet assays for phase separation; conditional β-cell KO with patch-clamp, Ca²⁺ imaging, and GST pulldown for VDCC-β interaction\",\n      \"pmids\": [\"31537859\", \"30699350\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Post-translational regulation of phase separation not characterized\", \"Structural basis of ELKS–VDCC-β interaction not resolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Forebrain-specific CAST/ELKS double deletion causing neonatal lethality, with enlarged active zones but altered CaV2 channel levels, established ERC1 as a positive regulator of presynaptic terminal size and essential for viability.\",\n      \"evidence\": \"Conditional double KO mice, confocal and electron microscopy, electrophysiology\",\n      \"pmids\": [\"32304329\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contributions of ELKS1 vs ELKS2 to terminal size regulation not separated\", \"Mechanism of active zone size control unknown\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Structural and biochemical reconstitution showed that oligomerized liprin-α2 enhances ELKS N-terminal phase separation through multivalent interactions and competitively regulates the distribution of ELKS versus RIM/RIM-BP in condensates, providing a mechanism for active zone protein compartmentalization.\",\n      \"evidence\": \"Crystal/solution structures of coiled-coil complexes, in vitro LLPS reconstitution, mutagenesis\",\n      \"pmids\": [\"33761347\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo validation of competitive partitioning model not performed\", \"How liprin-α1 vs liprin-α2 differentially regulate ELKS condensates is unclear\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Multiple studies in 2023 resolved key structural and functional interfaces: the ELKS1–Rab6B helical-hairpin crystal structure showed how LLPS concentrates Rab6B vesicles for exocytosis; the ERC1–LL5β interaction was mapped to disordered regions essential for cell-edge targeting and invasion; Drosophila studies showed ELKS–CaV2 α1 interaction is required for homeostatic Ca²⁺ channel accumulation; and dengue NS5 was found to degrade ERC1 to antagonize NF-κB signaling.\",\n      \"evidence\": \"Crystal structure plus liposome/exocytosis assays; NMR/Co-IP/invasion assays; intravital single-molecule imaging in Drosophila; proteomics/chimeric virus/NF-κB reporter assays\",\n      \"pmids\": [\"37172719\", \"37437062\", \"36800417\", \"37252973\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Rab6B condensate recruitment operates at synaptic active zones in addition to secretory sites\", \"Structural basis of ERC1–VDCC α1 interaction awaits atomic resolution\", \"Whether NS5-mediated ERC1 degradation occurs via proteasomal or autophagic pathway\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"The N-terminal IDR of ERC1 (residues 1–244) was shown to be both necessary and sufficient for phase separation and required for tumor cell motility independent of partner protein binding; separately, insulin secretion was found to occur at the margins of ELKS/LL5β patches devoid of microtubules, integrating ERC1 condensate architecture with secretory function.\",\n      \"evidence\": \"In vitro LLPS/FRAP/Co-IP/motility assays for IDR function; TIRF microscopy of granule fusion in intact mouse islets\",\n      \"pmids\": [\"40646182\", \"40366873\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How IDR-driven phase separation is regulated by phosphorylation or other modifications remains unknown\", \"Mechanism linking microtubule exclusion to secretion at ELKS patch margins not defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Major open questions include: (1) how ERC1 phase separation is post-translationally regulated in different cellular contexts; (2) the atomic-resolution architecture of the multi-protein active zone complex containing ERC1; (3) isoform-specific functions of ERC1 splice variants in NF-κB versus synaptic/migratory roles; and (4) whether ERC1's NF-κB and cytoskeletal functions are coordinated or fully independent.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural model of ERC1 in complex with RIM, Bassoon, and VDCC subunits simultaneously\", \"Isoform-specific knockout studies not performed\", \"Post-translational regulation of IDR-driven condensation uncharacterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [2, 8, 9, 15]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [3, 4, 7, 17]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [5, 9, 15, 23]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [14, 22]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [11, 19]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [3, 4, 10, 13, 16, 21]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 8, 18]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [2, 8, 18]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [5, 15, 23]},\n      {\"term_id\": \"R-HSA-1500931\", \"supporting_discovery_ids\": [9, 11, 20]}\n    ],\n    \"complexes\": [\n      \"IKK complex\",\n      \"presynaptic active zone cytomatrix\",\n      \"ERC1–liprin-α–LL5β leading-edge complex\"\n    ],\n    \"partners\": [\n      \"RIM1\",\n      \"RIM2\",\n      \"PPFIA1\",\n      \"PPFIA2\",\n      \"BSN\",\n      \"PHLDB2\",\n      \"RAB6B\",\n      \"CACNB\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}