{"gene":"ESYT2","run_date":"2026-04-28T17:46:03","timeline":{"discoveries":[{"year":2007,"finding":"E-Syt2 contains three C2 domains; the C2A domain binds Ca2+ in a phospholipid-dependent manner at micromolar Ca2+ concentrations, and the C2C domain acts as a targeting motif that localizes E-Syt2 to the plasma membrane independently of its transmembrane region.","method":"Recombinant protein Ca2+-dependent phospholipid binding assay; structure/function mutagenesis; transfection with myc-tagged constructs and immunofluorescence localization","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro Ca2+/phospholipid binding assay plus domain deletion/localization experiments in transfected cells, foundational paper","pmids":["17360437"],"is_preprint":false},{"year":2008,"finding":"The three C2 domains of E-Syt2 adopt an interdependent-domain organization; Ca2+ binding triggers reversible multimerization in vitro with an apparent binding constant of ~100 µM.","method":"Small-angle X-ray scattering (SAXS) of recombinant E-Syt2; quantitative Ca2+ binding analysis","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 1 — structural characterization by SAXS with Ca2+ titration, single lab","pmids":["18977228"],"is_preprint":false},{"year":2010,"finding":"E-Syt2 acts as an endocytic adaptor for the activated FGF receptor (FGFR1) in the clathrin-mediated pathway; E-Syt2 depletion prevents an early phase of activated FGFR endocytosis, blocks ERK activation, and impairs mesoderm induction in Xenopus. E-Syt2 physically interacts with activated FGFR1 and with Adaptin-2.","method":"Xenopus depletion (morpholino knockdown); co-immunoprecipitation of E-Syt2 with FGFR1 and Adaptin-2; epistasis (rescue experiments upstream of Ras/ERK); developmental marker assays (Xbra)","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, loss-of-function with specific signaling phenotype, epistasis in vivo, replicated in human cells","pmids":["20833364"],"is_preprint":false},{"year":2012,"finding":"E-Syt2 interacts with the p21-GTPase Activated Kinase PAK1 via the phospholipid-binding C2C domain; E-Syt2 binding to a site adjacent to the CRIB/GBD of PAK1 suppresses actin polymerization and inhibits PAK1 activation by Cdc42 and Rac, and both E-Syt2 and PAK1 selectively complex with FGFR1 to cooperate in FGF signaling.","method":"Co-immunoprecipitation; domain mapping with C2C deletion constructs; actin polymerization assays; PAK1 activation assays with Cdc42/Rac","journal":"Biology open","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP with domain mapping plus functional actin/kinase assays, single lab","pmids":["23213466"],"is_preprint":false},{"year":2013,"finding":"E-Syt2 (and E-Syt3) tether the ER to the plasma membrane via C2 domain-dependent interactions requiring PI(4,5)P2; E-Syt2/3-mediated ER-PM contact formation does not require elevation of cytosolic Ca2+ (unlike E-Syt1), but the heteromeric E-Syt complexes confer Ca2+ regulation to tethering. These ER-PM contacts are functionally distinct from STIM1/Orai1 contacts.","method":"Live-cell imaging of ER-PM contacts; PI(4,5)P2 depletion experiments; Ca2+ manipulation; dominant-negative and overexpression constructs; co-immunoprecipitation for heteromeric complex formation","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (imaging, lipid manipulation, Co-IP, Ca2+ clamping), highly cited foundational paper","pmids":["23791178"],"is_preprint":false},{"year":2013,"finding":"The tandem C2A-C2B domains of E-Syt2 form a rigid V-shaped structure; C2A binds up to four Ca2+ ions while C2B does not bind Ca2+; Ca2+ does not substantially alter the relative orientation of the two domains.","method":"Crystal structure determination (X-ray crystallography) in the presence and absence of Ca2+; NMR spectroscopy for Ca2+ binding analysis","journal":"Structure","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with NMR validation, rigorous structural characterization","pmids":["24373768"],"is_preprint":false},{"year":2014,"finding":"The SMP domain of E-Syt2 forms a homodimer creating an ~90 Å hydrophobic channel that binds glycerophospholipids, directly establishing a role for E-Syt2 in lipid transport at ER-PM contact sites. The adjacent C2A and C2B domains form flexible arched structures linked to the SMP domain.","method":"Crystal structure at 2.44 Å resolution; mass spectrometry identification of glycerophospholipids in the SMP channel; structural analysis of SMP dimerization interface","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 — high-resolution crystal structure with MS validation of lipid cargo, highly cited","pmids":["24847877"],"is_preprint":false},{"year":2015,"finding":"ESyt2 is directed to the ER by its transmembrane domain; ESyts hetero- and homodimerize (ESyt2 homodimerization requires a TM-adjacent sequence but not the SMP domain); ESyt2 and ESyt3 (but not ESyt1) selectively interact in vivo with activated FGFR1, and this interaction requires a short TM-adjacent sequence and depends on receptor conformation (open kinase domain) rather than receptor autophosphorylation.","method":"Co-immunoprecipitation; domain deletion/mutation constructs; kinase-dead and conformation mutants of FGFR1; subcellular fractionation/localization experiments","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP with multiple domain mutants and receptor conformation variants, single lab","pmids":["25922075"],"is_preprint":false},{"year":2016,"finding":"At steady state, E-Syt2 positions Sac1 (an integral ER lipid phosphatase) at discrete ER-PM junctions where Sac1 limits PM PI(4)P levels. GPCR activation that depletes PM PI(4,5)P2 disrupts E-Syt2-mediated ER-PM junctions, reducing Sac1 access to the PM and permitting PI(4)P and PI(4,5)P2 to recover.","method":"Live-cell TIRF and confocal imaging; siRNA knockdown of E-Syt2; PI(4,5)P2 biosensors; GPCR agonist stimulation; genetic overexpression/depletion of Sac1","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal imaging and genetic approaches, functional lipid measurements","pmids":["27044890"],"is_preprint":false},{"year":2016,"finding":"Knockout of ESyt2 and ESyt3 (double KO) mice are viable and fertile with no overt ER dysfunction, but ESyt2/ESyt3-null mouse embryonic fibroblasts show reduced cell migration and increased sensitivity to oxidative stress.","method":"Constitutive knockout mouse generation; in vitro migration assays; cell viability/stress assays with MEFs","journal":"Cell cycle","confidence":"Medium","confidence_rationale":"Tier 2 — clean KO with defined cellular phenotypes, single lab","pmids":["25486202","27399837"],"is_preprint":false},{"year":2016,"finding":"Triple knockout mice lacking all three ESyt isoforms are viable and fertile; knock-in mice with inactivating Ca2+-binding mutations in the C2A domain of ESyt2 show no major phenotype, indicating ESyts are dispensable for basic cellular functions in mice under laboratory conditions.","method":"Triple constitutive and conditional knockout mouse generation; knock-in point mutagenesis of C2A Ca2+-binding sites; brain morphology, synaptic protein, and stress-response analyses","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 — rigorous genetic tools (triple KO plus Ca2+-binding site knock-in) with comprehensive phenotypic analysis","pmids":["27348751"],"is_preprint":false},{"year":2017,"finding":"RASSF4 regulates E-Syt2- and E-Syt3-mediated ER-PM junction formation by controlling PM PI(4,5)P2 levels through ARF6-dependent regulation of PIP5K activity; PI(4,5)P2 is required for E-Syt2/3 localization at ER-PM junctions.","method":"siRNA knockdown of RASSF4; co-immunoprecipitation (RASSF4-ARF6 interaction); PI(4,5)P2 biosensor imaging; ER-PM junction quantification by live imaging","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP and lipid biosensor imaging with knockdown, single lab","pmids":["28600435"],"is_preprint":false},{"year":2017,"finding":"Individual C2 domains of E-Syt2 resist membrane unbinding forces of 2–7 pN with binding energies of 4–14 kBT; Ca2+ regulation and bilayer PI(4,5)P2 dependence of C2 domain-membrane binding recapitulate known properties of the protein.","method":"Single-molecule force spectroscopy using optical tweezers with membrane-coated beads; systematic variation of bilayer composition and Ca2+ concentration","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 — single-molecule reconstitution with quantitative force measurements and systematic controls","pmids":["29083305"],"is_preprint":false},{"year":2017,"finding":"UBQLN1 interacts with ESYT2 through its STI chaperone-like domains (not the UBA domain) and stabilizes ESYT2 protein levels; UBA domain interaction with ubiquitin is required for the stabilization function.","method":"Co-immunoprecipitation with domain deletion mutants of UBQLN1; Western blot for protein stability","journal":"Journal of cellular biochemistry","confidence":"Low","confidence_rationale":"Tier 3 — single Co-IP with domain mapping, single lab, no deep mechanistic follow-up for ESYT2 specifically","pmids":["28075048"],"is_preprint":false},{"year":2020,"finding":"Sec22b interacts with E-Syt2 (and other E-Syt family members) via the longin domain of Sec22b; overexpression of wild-type E-Syt2 (but not lipid-transfer-deficient or ER-attachment-deficient mutants) increases axonal filopodia formation and neurite ramification by stabilizing Sec22b-Stx1 ER-PM contact sites, contributing to plasma membrane expansion during neurite growth.","method":"Co-immunoprecipitation (Sec22b longin domain interaction); overexpression of WT and mutant E-Syt2 in neurons; clostridial neurotoxin (Stx1 cleavage) inhibition; quantification of filopodia and neurite branching","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP with functional domain mutants and neurotoxin epistasis, single lab","pmids":["32843578"],"is_preprint":false},{"year":2020,"finding":"The short isoform of E-Syt2 (E-Syt2S) is the predominant E-Syt2 isoform in T cells and directly interacts with STIM1, recruiting it to ER-PM junctions to support ORAI1-STIM1 clustering and store-operated Ca2+ entry (SOCE) independently of the general membrane-tethering function of E-Syts.","method":"siRNA knockdown and CRISPR knockout of ESYT1/ESYT2 in Jurkat and primary T cells; co-immunoprecipitation (E-Syt2S–STIM1 interaction); Ca2+ imaging (SOCE); cytokine production assays","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP with functional Ca2+ and cytokine readouts, CRISPR KO, single lab","pmids":["32879390"],"is_preprint":false},{"year":2021,"finding":"In C. elegans, the E-Syt ortholog ESYT-2 colocalizes with junctophilin JPH-1 at ER-PM contact sites in neuronal soma; jph-1 and esyt-2 null mutants show mutual suppression of aldicarb sensitivity, indicating antagonistic roles in neuromuscular synaptic transmission.","method":"Fluorescence co-localization imaging; genetic double-mutant epistasis (jph-1; esyt-2 double null); aldicarb sensitivity assays","journal":"Genetics","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis with direct co-localization, C. elegans ortholog","pmids":["33871019"],"is_preprint":false},{"year":2022,"finding":"E-Syt2 overexpression enforces ER-PM tethering at a gap distance of 12–15 nm and causes expansion of cortical ER cisternae; extended cER resulting from E-Syt2 tethering reduces SOCE by confining STIM-ORAI complexes to the periphery of enlarged cER sheets and enhancing Ca2+-dependent inhibition.","method":"Electron microscopy measurement of ER-PM gap distance; live-cell TIRF imaging; electrophysiology (Ca2+ current); overexpression of E-Syt1, E-Syt2, and artificial tethers in HEK-293T cells","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 — EM ultrastructure plus electrophysiology and imaging, single lab","pmids":["35191477"],"is_preprint":false},{"year":2023,"finding":"E-Syt2 predominantly reduces plasma membrane diacylglycerol (DAG) levels in resting T cells; together with E-Syt1, it downmodulates DAG-mediated TCR signaling, T cell cytotoxicity, degranulation, and cytokine production upon stimulation.","method":"siRNA knockdown of E-Syt2 and E-Syt1 in primary T cells; DAG biosensor imaging; cytotoxicity assays; degranulation and cytokine secretion assays","journal":"EMBO reports","confidence":"Medium","confidence_rationale":"Tier 2 — lipid biosensor imaging with knockdown and multiple functional readouts, single lab","pmids":["38177911"],"is_preprint":false},{"year":2025,"finding":"E-Syt2 (together with E-Syt1 and VAPB) forms a multimeric complex at lipid droplet-mitochondria-ER contact sites; deletion of ESYT2 limits lipid-droplet-derived fatty acid oxidation, depletes TCA cycle metabolites, remodels the cellular lipidome, and induces lipotoxic stress, indicating E-Syt2 participates in fatty acid transfer from lipid droplets to mitochondria for β-oxidation.","method":"Proximity-dependent biotinylation (BioID) proteomics; high-resolution co-localization imaging; ESYT2 deletion (cell lines and Esyt2-deficient mice); metabolomics (TCA metabolites); lipidomics; fatty acid oxidation assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1-2 — proximity proteomics, genetic deletion in cells and mice, metabolomics and lipidomics with multiple orthogonal methods","pmids":["40032835"],"is_preprint":false},{"year":2025,"finding":"E-Syt2 at STIM1 ER-PM junctions dissociates the ANO1-VAPA interaction, forming an ANO1-IRBIT-E-Syt2-AC6-AKAP11-PKA complex that phosphorylates ANO1 at S221, markedly reducing ANO1 Ca2+ affinity; this effect is primarily mediated through E-Syt2 reciprocal regulation of junctional PI(4)P, PI(4,5)P2, and phosphatidylserine levels.","method":"Co-immunoprecipitation of complex components; site-directed mutagenesis (ANO1 S221); lipid biosensor imaging; Ca2+ imaging; knockdown/overexpression in epithelial cells; IRBIT knockout mice","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP with mutagenesis and lipid/Ca2+ functional readouts, single lab","pmids":["40204782"],"is_preprint":false}],"current_model":"ESYT2 is an ER-resident protein that uses its PI(4,5)P2-binding C2 domains (with C2A providing Ca2+-dependent phospholipid binding and C2C directing PM targeting) and its SMP domain lipid-transfer channel to tether the ER to the plasma membrane and to transfer glycerophospholipids and DAG between bilayers at ER-PM contact sites; it also forms a multimeric complex with E-Syt1 and VAPB at lipid droplet-mitochondria-ER contacts to enable fatty acid transfer for β-oxidation, acts as an endocytic adaptor for activated FGFR1 by interacting with Adaptin-2 and PAK1 to regulate actin dynamics and ERK signaling, positions Sac1 phosphatase at ER-PM junctions to control PI(4)P/PI(4,5)P2 homeostasis, and modulates SOCE and ANO1 channel activity through junctional phosphoinositide regulation and direct interaction with STIM1."},"narrative":{"teleology":[{"year":2007,"claim":"Establishing that ESYT2 is a multi-C2-domain protein whose C2A domain provides Ca²⁺-dependent phospholipid binding and whose C2C domain independently targets the plasma membrane resolved the basic molecular architecture underlying its membrane association.","evidence":"Recombinant Ca²⁺/phospholipid binding assays combined with domain deletion and immunofluorescence in transfected cells","pmids":["17360437"],"confidence":"High","gaps":["Mechanism by which C2C recognizes specific PM lipids was not defined","No information on lipid transfer activity"]},{"year":2008,"claim":"Demonstration that Ca²⁺ triggers reversible multimerization of ESYT2 (~100 µM Kd) and that the three C2 domains adopt an interdependent architecture suggested oligomerization as a regulatory mechanism.","evidence":"SAXS of recombinant ESYT2 with Ca²⁺ titration","pmids":["18977228"],"confidence":"Medium","gaps":["Functional consequences of multimerization on membrane tethering were untested","In vivo relevance of oligomerization not addressed"]},{"year":2010,"claim":"Identification of ESYT2 as an endocytic adaptor for activated FGFR1—interacting with Adaptin-2 and required for receptor internalization, ERK activation, and mesoderm induction—revealed an unexpected signaling-adaptor function beyond lipid biology.","evidence":"Morpholino knockdown in Xenopus; co-IP of ESYT2 with FGFR1 and Adaptin-2; epistasis upstream of Ras/ERK; replicated in human cells","pmids":["20833364"],"confidence":"High","gaps":["Structural basis of ESYT2–FGFR1 interaction unknown","Whether lipid transfer activity contributes to FGFR signaling untested"]},{"year":2012,"claim":"Showing that ESYT2 binds PAK1 via its C2C domain to suppress Cdc42/Rac-dependent actin polymerization linked the FGFR adaptor function to cytoskeletal regulation.","evidence":"Co-IP with domain mapping; actin polymerization and PAK1 activation assays","pmids":["23213466"],"confidence":"Medium","gaps":["No in vivo validation of ESYT2–PAK1 axis","Whether PAK1 inhibition requires ESYT2 lipid binding or transfer is unclear"]},{"year":2013,"claim":"Demonstrating that ESYT2 constitutively tethers the ER to the PM via PI(4,5)P2-dependent C2 domain interactions—without requiring elevated Ca²⁺, unlike ESYT1—defined the core ER–PM contact-site function and established the PI(4,5)P2 dependence that distinguishes ESYT2 from ESYT1.","evidence":"Live-cell imaging of ER–PM contacts; PI(4,5)P2 depletion; Ca²⁺ manipulation; co-IP for heteromeric complex formation","pmids":["23791178"],"confidence":"High","gaps":["Whether tethering per se is sufficient for lipid transfer was unresolved","Identity of transferred lipid species unknown"]},{"year":2013,"claim":"Crystal structures of the C2A–C2B tandem revealed a rigid V-shaped architecture with up to four Ca²⁺ ions bound to C2A but not C2B, providing the first atomic-level view of the C2 domain module.","evidence":"X-ray crystallography ± Ca²⁺; NMR validation of Ca²⁺ binding","pmids":["24373768"],"confidence":"High","gaps":["No structure of the full-length protein or of C2 domains engaged with membranes"]},{"year":2014,"claim":"Solving the SMP domain crystal structure as a homodimer with an ~90 Å hydrophobic channel containing glycerophospholipids directly established ESYT2 as a lipid-transfer protein.","evidence":"2.44 Å crystal structure; mass spectrometry identification of bound glycerophospholipids","pmids":["24847877"],"confidence":"High","gaps":["Directionality and selectivity of lipid transfer in membranes not determined","No reconstituted transfer assay between two bilayers"]},{"year":2016,"claim":"Showing that ESYT2 positions the Sac1 phosphatase at ER–PM junctions to limit PM PI(4)P—and that GPCR-driven PI(4,5)P2 depletion disassembles these junctions, relieving PI(4)P control—placed ESYT2 at the center of phosphoinositide homeostasis.","evidence":"TIRF/confocal imaging; siRNA of ESYT2; PI(4,5)P2 biosensors; GPCR stimulation; Sac1 overexpression/depletion","pmids":["27044890"],"confidence":"High","gaps":["Whether lipid transfer through the SMP channel is required for Sac1 positioning unclear","In vivo physiological consequence of Sac1 mis-localization not tested"]},{"year":2016,"claim":"Triple-KO mice lacking all three ESyt isoforms are viable and fertile, indicating that ESyt-mediated ER–PM contacts are dispensable for basal mammalian physiology under laboratory conditions, though cellular phenotypes include impaired migration and oxidative-stress sensitivity.","evidence":"Constitutive triple KO and C2A Ca²⁺-binding knock-in mice; MEF migration and stress assays","pmids":["27348751","25486202","27399837"],"confidence":"High","gaps":["Stress or disease contexts that unmask essential functions remain unknown","Compensation by other ER–PM tethering systems not excluded"]},{"year":2017,"claim":"Single-molecule force spectroscopy quantified individual C2 domain–membrane binding at 2–7 pN and 4–14 kBT, providing the biophysical parameters governing ESYT2 tethering strength.","evidence":"Optical-tweezer force spectroscopy with membrane-coated beads; systematic lipid and Ca²⁺ variation","pmids":["29083305"],"confidence":"High","gaps":["How these forces translate to ER–PM gap regulation in cells not modeled","Cooperativity between C2 domains in full-length protein not measured"]},{"year":2020,"claim":"Identification of a short ESYT2 isoform that directly interacts with STIM1 to recruit it to ER–PM junctions for ORAI1 clustering and SOCE established ESYT2 as a modulator of store-operated Ca²⁺ entry, particularly in T cells.","evidence":"siRNA/CRISPR KO in Jurkat and primary T cells; co-IP of ESYT2S–STIM1; Ca²⁺ imaging; cytokine assays","pmids":["32879390"],"confidence":"Medium","gaps":["Structural basis of ESYT2S–STIM1 interaction undefined","Relative contribution versus general tethering not fully delineated"]},{"year":2023,"claim":"Demonstrating that ESYT2 reduces PM DAG levels in resting T cells and that its loss enhances DAG-dependent TCR signaling, cytotoxicity, and cytokine production identified DAG as a major ESYT2 lipid-transfer substrate with immunological significance.","evidence":"siRNA knockdown in primary T cells; DAG biosensor imaging; cytotoxicity, degranulation, and cytokine assays","pmids":["38177911"],"confidence":"Medium","gaps":["Whether DAG is directly transported through the SMP channel or removed indirectly via phosphoinositide remodeling not distinguished","In vivo immune consequences of ESYT2 loss not tested"]},{"year":2025,"claim":"Discovery that ESYT2 forms a multimeric complex with ESYT1 and VAPB at lipid-droplet–mitochondria–ER tripartite contacts and that its deletion limits fatty acid β-oxidation, depletes TCA metabolites, and induces lipotoxic stress expanded ESYT2's role from ER–PM tethering to inter-organelle fatty acid trafficking.","evidence":"BioID proximity proteomics; high-resolution co-localization imaging; ESYT2 deletion in cells and mice; metabolomics and lipidomics; fatty acid oxidation assays","pmids":["40032835"],"confidence":"High","gaps":["Whether the SMP domain directly transfers fatty acids or acts indirectly is unresolved","Tissue-specific metabolic consequences in vivo remain to be defined"]},{"year":2025,"claim":"Elucidation of an ANO1-IRBIT-ESYT2-AC6-AKAP11-PKA complex at STIM1-containing ER–PM junctions—where ESYT2 displaces VAPA to enable PKA-dependent ANO1 S221 phosphorylation and channel inhibition—revealed ESYT2 as a scaffold that transduces junctional phosphoinositide changes into ion-channel regulation.","evidence":"Co-IP of complex components; site-directed mutagenesis of ANO1 S221; lipid biosensor and Ca²⁺ imaging; knockdown/overexpression in epithelial cells; IRBIT KO mice","pmids":["40204782"],"confidence":"Medium","gaps":["Whether ESYT2 lipid transfer activity is required for the scaffolding function is untested","Generalizability beyond epithelial ANO1 regulation unknown"]},{"year":null,"claim":"Key open questions include the directionality and substrate selectivity of SMP-mediated lipid transfer in reconstituted systems, the structural basis of full-length ESYT2 spanning a membrane contact site, stress or disease contexts that reveal essential in vivo functions, and how the adaptor/scaffolding and lipid-transfer activities of ESYT2 are coordinated or segregated at distinct contact sites.","evidence":"","pmids":[],"confidence":"High","gaps":["No reconstituted two-bilayer lipid transfer assay for full-length ESYT2","No full-length structure bridging two membranes","Physiological contexts where ESYT2 is essential remain unidentified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[0,4,6,12]},{"term_id":"GO:0140104","term_label":"molecular carrier activity","supporting_discovery_ids":[6,18,19]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[2,15,20]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[4,7,8]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,4,8,12]},{"term_id":"GO:0005811","term_label":"lipid droplet","supporting_discovery_ids":[19]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[2,3,15,20]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[6,18,19]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[8,19]}],"complexes":["E-Syt1/E-Syt2/E-Syt3 heteromeric complex","E-Syt1/E-Syt2/VAPB lipid-droplet-mitochondria-ER contact complex","ANO1-IRBIT-E-Syt2-AC6-AKAP11-PKA complex"],"partners":["ESYT1","ESYT3","VAPB","STIM1","FGFR1","AP2A1","PAK1","SEC22B"],"other_free_text":[]},"mechanistic_narrative":"ESYT2 is an ER-anchored membrane tethering and lipid transfer protein that bridges the endoplasmic reticulum to the plasma membrane—and to lipid droplet–mitochondria interfaces—to coordinate phospholipid and diacylglycerol homeostasis, signaling lipid turnover, and inter-organelle fatty acid trafficking. Its SMP domain dimerizes to form a hydrophobic channel that transports glycerophospholipids between apposed bilayers, while its C2C domain targets the plasma membrane through PI(4,5)P2 binding and its C2A domain confers Ca²⁺-dependent phospholipid interaction [PMID:17360437, PMID:24847877, PMID:23791178]. ESYT2-mediated ER–PM contacts position the Sac1 phosphatase to limit PI(4)P levels and regulate phosphoinositide pools that control store-operated Ca²⁺ entry, ANO1 channel activity, and DAG-dependent TCR signaling in T cells [PMID:27044890, PMID:32879390, PMID:38177911, PMID:40204782]. ESYT2 also functions as an endocytic adaptor for activated FGFR1 through interactions with Adaptin-2 and PAK1, and participates—together with ESYT1 and VAPB—in a multimeric complex at lipid droplet–mitochondria–ER contacts that channels fatty acids toward mitochondrial β-oxidation [PMID:20833364, PMID:40032835]."},"prefetch_data":{"uniprot":{"accession":"A0FGR8","full_name":"Extended synaptotagmin-2","aliases":["Chr2Syt"],"length_aa":921,"mass_kda":102.4,"function":"Tethers the endoplasmic reticulum to the cell membrane and promotes the formation of appositions between the endoplasmic reticulum and the cell membrane. Binds glycerophospholipids in a barrel-like domain and may play a role in cellular lipid transport. Plays a role in FGF signaling via its role in the rapid internalization of FGFR1 that has been activated by FGF1 binding; this occurs most likely via the AP-2 complex. Promotes the localization of SACM1L at endoplasmic reticulum-plasma membrane contact sites (EPCS) (PubMed:27044890)","subcellular_location":"Cell membrane; Endoplasmic reticulum membrane","url":"https://www.uniprot.org/uniprotkb/A0FGR8/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ESYT2","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"ESYT1","stoichiometry":10.0},{"gene":"RTN4","stoichiometry":4.0},{"gene":"ARL6IP1","stoichiometry":0.2},{"gene":"ATL3","stoichiometry":0.2},{"gene":"COPA","stoichiometry":0.2},{"gene":"COPB2","stoichiometry":0.2},{"gene":"COPE","stoichiometry":0.2},{"gene":"OSBP","stoichiometry":0.2},{"gene":"VAPA","stoichiometry":0.2},{"gene":"VAPB","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/ESYT2","total_profiled":1310},"omim":[{"mim_id":"616692","title":"EXTENDED SYNAPTOTAGMIN-LIKE PROTEIN 3; ESYT3","url":"https://www.omim.org/entry/616692"},{"mim_id":"616691","title":"EXTENDED SYNAPTOTAGMIN-LIKE PROTEIN 2; ESYT2","url":"https://www.omim.org/entry/616691"},{"mim_id":"616670","title":"EXTENDED SYNAPTOTAGMIN-LIKE PROTEIN 1; ESYT1","url":"https://www.omim.org/entry/616670"},{"mim_id":"610841","title":"STROMAL INTERACTION MOLECULE 2; STIM2","url":"https://www.omim.org/entry/610841"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in 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E-Syt2 physically interacts with activated FGFR1 and with Adaptin-2.\",\n      \"method\": \"Xenopus depletion (morpholino knockdown); co-immunoprecipitation of E-Syt2 with FGFR1 and Adaptin-2; epistasis (rescue experiments upstream of Ras/ERK); developmental marker assays (Xbra)\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, loss-of-function with specific signaling phenotype, epistasis in vivo, replicated in human cells\",\n      \"pmids\": [\"20833364\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"E-Syt2 interacts with the p21-GTPase Activated Kinase PAK1 via the phospholipid-binding C2C domain; E-Syt2 binding to a site adjacent to the CRIB/GBD of PAK1 suppresses actin polymerization and inhibits PAK1 activation by Cdc42 and Rac, and both E-Syt2 and PAK1 selectively complex with FGFR1 to cooperate in FGF signaling.\",\n      \"method\": \"Co-immunoprecipitation; domain mapping with C2C deletion constructs; actin polymerization assays; PAK1 activation assays with Cdc42/Rac\",\n      \"journal\": \"Biology open\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP with domain mapping plus functional actin/kinase assays, single lab\",\n      \"pmids\": [\"23213466\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"E-Syt2 (and E-Syt3) tether the ER to the plasma membrane via C2 domain-dependent interactions requiring PI(4,5)P2; E-Syt2/3-mediated ER-PM contact formation does not require elevation of cytosolic Ca2+ (unlike E-Syt1), but the heteromeric E-Syt complexes confer Ca2+ regulation to tethering. These ER-PM contacts are functionally distinct from STIM1/Orai1 contacts.\",\n      \"method\": \"Live-cell imaging of ER-PM contacts; PI(4,5)P2 depletion experiments; Ca2+ manipulation; dominant-negative and overexpression constructs; co-immunoprecipitation for heteromeric complex formation\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (imaging, lipid manipulation, Co-IP, Ca2+ clamping), highly cited foundational paper\",\n      \"pmids\": [\"23791178\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The tandem C2A-C2B domains of E-Syt2 form a rigid V-shaped structure; C2A binds up to four Ca2+ ions while C2B does not bind Ca2+; Ca2+ does not substantially alter the relative orientation of the two domains.\",\n      \"method\": \"Crystal structure determination (X-ray crystallography) in the presence and absence of Ca2+; NMR spectroscopy for Ca2+ binding analysis\",\n      \"journal\": \"Structure\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with NMR validation, rigorous structural characterization\",\n      \"pmids\": [\"24373768\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The SMP domain of E-Syt2 forms a homodimer creating an ~90 Å hydrophobic channel that binds glycerophospholipids, directly establishing a role for E-Syt2 in lipid transport at ER-PM contact sites. The adjacent C2A and C2B domains form flexible arched structures linked to the SMP domain.\",\n      \"method\": \"Crystal structure at 2.44 Å resolution; mass spectrometry identification of glycerophospholipids in the SMP channel; structural analysis of SMP dimerization interface\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution crystal structure with MS validation of lipid cargo, highly cited\",\n      \"pmids\": [\"24847877\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"ESyt2 is directed to the ER by its transmembrane domain; ESyts hetero- and homodimerize (ESyt2 homodimerization requires a TM-adjacent sequence but not the SMP domain); ESyt2 and ESyt3 (but not ESyt1) selectively interact in vivo with activated FGFR1, and this interaction requires a short TM-adjacent sequence and depends on receptor conformation (open kinase domain) rather than receptor autophosphorylation.\",\n      \"method\": \"Co-immunoprecipitation; domain deletion/mutation constructs; kinase-dead and conformation mutants of FGFR1; subcellular fractionation/localization experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP with multiple domain mutants and receptor conformation variants, single lab\",\n      \"pmids\": [\"25922075\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"At steady state, E-Syt2 positions Sac1 (an integral ER lipid phosphatase) at discrete ER-PM junctions where Sac1 limits PM PI(4)P levels. GPCR activation that depletes PM PI(4,5)P2 disrupts E-Syt2-mediated ER-PM junctions, reducing Sac1 access to the PM and permitting PI(4)P and PI(4,5)P2 to recover.\",\n      \"method\": \"Live-cell TIRF and confocal imaging; siRNA knockdown of E-Syt2; PI(4,5)P2 biosensors; GPCR agonist stimulation; genetic overexpression/depletion of Sac1\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal imaging and genetic approaches, functional lipid measurements\",\n      \"pmids\": [\"27044890\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Knockout of ESyt2 and ESyt3 (double KO) mice are viable and fertile with no overt ER dysfunction, but ESyt2/ESyt3-null mouse embryonic fibroblasts show reduced cell migration and increased sensitivity to oxidative stress.\",\n      \"method\": \"Constitutive knockout mouse generation; in vitro migration assays; cell viability/stress assays with MEFs\",\n      \"journal\": \"Cell cycle\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined cellular phenotypes, single lab\",\n      \"pmids\": [\"25486202\", \"27399837\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Triple knockout mice lacking all three ESyt isoforms are viable and fertile; knock-in mice with inactivating Ca2+-binding mutations in the C2A domain of ESyt2 show no major phenotype, indicating ESyts are dispensable for basic cellular functions in mice under laboratory conditions.\",\n      \"method\": \"Triple constitutive and conditional knockout mouse generation; knock-in point mutagenesis of C2A Ca2+-binding sites; brain morphology, synaptic protein, and stress-response analyses\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — rigorous genetic tools (triple KO plus Ca2+-binding site knock-in) with comprehensive phenotypic analysis\",\n      \"pmids\": [\"27348751\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"RASSF4 regulates E-Syt2- and E-Syt3-mediated ER-PM junction formation by controlling PM PI(4,5)P2 levels through ARF6-dependent regulation of PIP5K activity; PI(4,5)P2 is required for E-Syt2/3 localization at ER-PM junctions.\",\n      \"method\": \"siRNA knockdown of RASSF4; co-immunoprecipitation (RASSF4-ARF6 interaction); PI(4,5)P2 biosensor imaging; ER-PM junction quantification by live imaging\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP and lipid biosensor imaging with knockdown, single lab\",\n      \"pmids\": [\"28600435\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Individual C2 domains of E-Syt2 resist membrane unbinding forces of 2–7 pN with binding energies of 4–14 kBT; Ca2+ regulation and bilayer PI(4,5)P2 dependence of C2 domain-membrane binding recapitulate known properties of the protein.\",\n      \"method\": \"Single-molecule force spectroscopy using optical tweezers with membrane-coated beads; systematic variation of bilayer composition and Ca2+ concentration\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — single-molecule reconstitution with quantitative force measurements and systematic controls\",\n      \"pmids\": [\"29083305\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"UBQLN1 interacts with ESYT2 through its STI chaperone-like domains (not the UBA domain) and stabilizes ESYT2 protein levels; UBA domain interaction with ubiquitin is required for the stabilization function.\",\n      \"method\": \"Co-immunoprecipitation with domain deletion mutants of UBQLN1; Western blot for protein stability\",\n      \"journal\": \"Journal of cellular biochemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single Co-IP with domain mapping, single lab, no deep mechanistic follow-up for ESYT2 specifically\",\n      \"pmids\": [\"28075048\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Sec22b interacts with E-Syt2 (and other E-Syt family members) via the longin domain of Sec22b; overexpression of wild-type E-Syt2 (but not lipid-transfer-deficient or ER-attachment-deficient mutants) increases axonal filopodia formation and neurite ramification by stabilizing Sec22b-Stx1 ER-PM contact sites, contributing to plasma membrane expansion during neurite growth.\",\n      \"method\": \"Co-immunoprecipitation (Sec22b longin domain interaction); overexpression of WT and mutant E-Syt2 in neurons; clostridial neurotoxin (Stx1 cleavage) inhibition; quantification of filopodia and neurite branching\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP with functional domain mutants and neurotoxin epistasis, single lab\",\n      \"pmids\": [\"32843578\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The short isoform of E-Syt2 (E-Syt2S) is the predominant E-Syt2 isoform in T cells and directly interacts with STIM1, recruiting it to ER-PM junctions to support ORAI1-STIM1 clustering and store-operated Ca2+ entry (SOCE) independently of the general membrane-tethering function of E-Syts.\",\n      \"method\": \"siRNA knockdown and CRISPR knockout of ESYT1/ESYT2 in Jurkat and primary T cells; co-immunoprecipitation (E-Syt2S–STIM1 interaction); Ca2+ imaging (SOCE); cytokine production assays\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP with functional Ca2+ and cytokine readouts, CRISPR KO, single lab\",\n      \"pmids\": [\"32879390\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"In C. elegans, the E-Syt ortholog ESYT-2 colocalizes with junctophilin JPH-1 at ER-PM contact sites in neuronal soma; jph-1 and esyt-2 null mutants show mutual suppression of aldicarb sensitivity, indicating antagonistic roles in neuromuscular synaptic transmission.\",\n      \"method\": \"Fluorescence co-localization imaging; genetic double-mutant epistasis (jph-1; esyt-2 double null); aldicarb sensitivity assays\",\n      \"journal\": \"Genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with direct co-localization, C. elegans ortholog\",\n      \"pmids\": [\"33871019\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"E-Syt2 overexpression enforces ER-PM tethering at a gap distance of 12–15 nm and causes expansion of cortical ER cisternae; extended cER resulting from E-Syt2 tethering reduces SOCE by confining STIM-ORAI complexes to the periphery of enlarged cER sheets and enhancing Ca2+-dependent inhibition.\",\n      \"method\": \"Electron microscopy measurement of ER-PM gap distance; live-cell TIRF imaging; electrophysiology (Ca2+ current); overexpression of E-Syt1, E-Syt2, and artificial tethers in HEK-293T cells\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — EM ultrastructure plus electrophysiology and imaging, single lab\",\n      \"pmids\": [\"35191477\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"E-Syt2 predominantly reduces plasma membrane diacylglycerol (DAG) levels in resting T cells; together with E-Syt1, it downmodulates DAG-mediated TCR signaling, T cell cytotoxicity, degranulation, and cytokine production upon stimulation.\",\n      \"method\": \"siRNA knockdown of E-Syt2 and E-Syt1 in primary T cells; DAG biosensor imaging; cytotoxicity assays; degranulation and cytokine secretion assays\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — lipid biosensor imaging with knockdown and multiple functional readouts, single lab\",\n      \"pmids\": [\"38177911\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"E-Syt2 (together with E-Syt1 and VAPB) forms a multimeric complex at lipid droplet-mitochondria-ER contact sites; deletion of ESYT2 limits lipid-droplet-derived fatty acid oxidation, depletes TCA cycle metabolites, remodels the cellular lipidome, and induces lipotoxic stress, indicating E-Syt2 participates in fatty acid transfer from lipid droplets to mitochondria for β-oxidation.\",\n      \"method\": \"Proximity-dependent biotinylation (BioID) proteomics; high-resolution co-localization imaging; ESYT2 deletion (cell lines and Esyt2-deficient mice); metabolomics (TCA metabolites); lipidomics; fatty acid oxidation assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — proximity proteomics, genetic deletion in cells and mice, metabolomics and lipidomics with multiple orthogonal methods\",\n      \"pmids\": [\"40032835\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"E-Syt2 at STIM1 ER-PM junctions dissociates the ANO1-VAPA interaction, forming an ANO1-IRBIT-E-Syt2-AC6-AKAP11-PKA complex that phosphorylates ANO1 at S221, markedly reducing ANO1 Ca2+ affinity; this effect is primarily mediated through E-Syt2 reciprocal regulation of junctional PI(4)P, PI(4,5)P2, and phosphatidylserine levels.\",\n      \"method\": \"Co-immunoprecipitation of complex components; site-directed mutagenesis (ANO1 S221); lipid biosensor imaging; Ca2+ imaging; knockdown/overexpression in epithelial cells; IRBIT knockout mice\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP with mutagenesis and lipid/Ca2+ functional readouts, single lab\",\n      \"pmids\": [\"40204782\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ESYT2 is an ER-resident protein that uses its PI(4,5)P2-binding C2 domains (with C2A providing Ca2+-dependent phospholipid binding and C2C directing PM targeting) and its SMP domain lipid-transfer channel to tether the ER to the plasma membrane and to transfer glycerophospholipids and DAG between bilayers at ER-PM contact sites; it also forms a multimeric complex with E-Syt1 and VAPB at lipid droplet-mitochondria-ER contacts to enable fatty acid transfer for β-oxidation, acts as an endocytic adaptor for activated FGFR1 by interacting with Adaptin-2 and PAK1 to regulate actin dynamics and ERK signaling, positions Sac1 phosphatase at ER-PM junctions to control PI(4)P/PI(4,5)P2 homeostasis, and modulates SOCE and ANO1 channel activity through junctional phosphoinositide regulation and direct interaction with STIM1.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"ESYT2 is an ER-anchored membrane tethering and lipid transfer protein that bridges the endoplasmic reticulum to the plasma membrane—and to lipid droplet–mitochondria interfaces—to coordinate phospholipid and diacylglycerol homeostasis, signaling lipid turnover, and inter-organelle fatty acid trafficking. Its SMP domain dimerizes to form a hydrophobic channel that transports glycerophospholipids between apposed bilayers, while its C2C domain targets the plasma membrane through PI(4,5)P2 binding and its C2A domain confers Ca²⁺-dependent phospholipid interaction [PMID:17360437, PMID:24847877, PMID:23791178]. ESYT2-mediated ER–PM contacts position the Sac1 phosphatase to limit PI(4)P levels and regulate phosphoinositide pools that control store-operated Ca²⁺ entry, ANO1 channel activity, and DAG-dependent TCR signaling in T cells [PMID:27044890, PMID:32879390, PMID:38177911, PMID:40204782]. ESYT2 also functions as an endocytic adaptor for activated FGFR1 through interactions with Adaptin-2 and PAK1, and participates—together with ESYT1 and VAPB—in a multimeric complex at lipid droplet–mitochondria–ER contacts that channels fatty acids toward mitochondrial β-oxidation [PMID:20833364, PMID:40032835].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Establishing that ESYT2 is a multi-C2-domain protein whose C2A domain provides Ca²⁺-dependent phospholipid binding and whose C2C domain independently targets the plasma membrane resolved the basic molecular architecture underlying its membrane association.\",\n      \"evidence\": \"Recombinant Ca²⁺/phospholipid binding assays combined with domain deletion and immunofluorescence in transfected cells\",\n      \"pmids\": [\"17360437\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which C2C recognizes specific PM lipids was not defined\", \"No information on lipid transfer activity\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Demonstration that Ca²⁺ triggers reversible multimerization of ESYT2 (~100 µM Kd) and that the three C2 domains adopt an interdependent architecture suggested oligomerization as a regulatory mechanism.\",\n      \"evidence\": \"SAXS of recombinant ESYT2 with Ca²⁺ titration\",\n      \"pmids\": [\"18977228\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequences of multimerization on membrane tethering were untested\", \"In vivo relevance of oligomerization not addressed\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Identification of ESYT2 as an endocytic adaptor for activated FGFR1—interacting with Adaptin-2 and required for receptor internalization, ERK activation, and mesoderm induction—revealed an unexpected signaling-adaptor function beyond lipid biology.\",\n      \"evidence\": \"Morpholino knockdown in Xenopus; co-IP of ESYT2 with FGFR1 and Adaptin-2; epistasis upstream of Ras/ERK; replicated in human cells\",\n      \"pmids\": [\"20833364\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of ESYT2–FGFR1 interaction unknown\", \"Whether lipid transfer activity contributes to FGFR signaling untested\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Showing that ESYT2 binds PAK1 via its C2C domain to suppress Cdc42/Rac-dependent actin polymerization linked the FGFR adaptor function to cytoskeletal regulation.\",\n      \"evidence\": \"Co-IP with domain mapping; actin polymerization and PAK1 activation assays\",\n      \"pmids\": [\"23213466\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No in vivo validation of ESYT2–PAK1 axis\", \"Whether PAK1 inhibition requires ESYT2 lipid binding or transfer is unclear\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Demonstrating that ESYT2 constitutively tethers the ER to the PM via PI(4,5)P2-dependent C2 domain interactions—without requiring elevated Ca²⁺, unlike ESYT1—defined the core ER–PM contact-site function and established the PI(4,5)P2 dependence that distinguishes ESYT2 from ESYT1.\",\n      \"evidence\": \"Live-cell imaging of ER–PM contacts; PI(4,5)P2 depletion; Ca²⁺ manipulation; co-IP for heteromeric complex formation\",\n      \"pmids\": [\"23791178\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether tethering per se is sufficient for lipid transfer was unresolved\", \"Identity of transferred lipid species unknown\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Crystal structures of the C2A–C2B tandem revealed a rigid V-shaped architecture with up to four Ca²⁺ ions bound to C2A but not C2B, providing the first atomic-level view of the C2 domain module.\",\n      \"evidence\": \"X-ray crystallography ± Ca²⁺; NMR validation of Ca²⁺ binding\",\n      \"pmids\": [\"24373768\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structure of the full-length protein or of C2 domains engaged with membranes\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Solving the SMP domain crystal structure as a homodimer with an ~90 Å hydrophobic channel containing glycerophospholipids directly established ESYT2 as a lipid-transfer protein.\",\n      \"evidence\": \"2.44 Å crystal structure; mass spectrometry identification of bound glycerophospholipids\",\n      \"pmids\": [\"24847877\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Directionality and selectivity of lipid transfer in membranes not determined\", \"No reconstituted transfer assay between two bilayers\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Showing that ESYT2 positions the Sac1 phosphatase at ER–PM junctions to limit PM PI(4)P—and that GPCR-driven PI(4,5)P2 depletion disassembles these junctions, relieving PI(4)P control—placed ESYT2 at the center of phosphoinositide homeostasis.\",\n      \"evidence\": \"TIRF/confocal imaging; siRNA of ESYT2; PI(4,5)P2 biosensors; GPCR stimulation; Sac1 overexpression/depletion\",\n      \"pmids\": [\"27044890\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether lipid transfer through the SMP channel is required for Sac1 positioning unclear\", \"In vivo physiological consequence of Sac1 mis-localization not tested\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Triple-KO mice lacking all three ESyt isoforms are viable and fertile, indicating that ESyt-mediated ER–PM contacts are dispensable for basal mammalian physiology under laboratory conditions, though cellular phenotypes include impaired migration and oxidative-stress sensitivity.\",\n      \"evidence\": \"Constitutive triple KO and C2A Ca²⁺-binding knock-in mice; MEF migration and stress assays\",\n      \"pmids\": [\"27348751\", \"25486202\", \"27399837\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stress or disease contexts that unmask essential functions remain unknown\", \"Compensation by other ER–PM tethering systems not excluded\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Single-molecule force spectroscopy quantified individual C2 domain–membrane binding at 2–7 pN and 4–14 kBT, providing the biophysical parameters governing ESYT2 tethering strength.\",\n      \"evidence\": \"Optical-tweezer force spectroscopy with membrane-coated beads; systematic lipid and Ca²⁺ variation\",\n      \"pmids\": [\"29083305\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How these forces translate to ER–PM gap regulation in cells not modeled\", \"Cooperativity between C2 domains in full-length protein not measured\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identification of a short ESYT2 isoform that directly interacts with STIM1 to recruit it to ER–PM junctions for ORAI1 clustering and SOCE established ESYT2 as a modulator of store-operated Ca²⁺ entry, particularly in T cells.\",\n      \"evidence\": \"siRNA/CRISPR KO in Jurkat and primary T cells; co-IP of ESYT2S–STIM1; Ca²⁺ imaging; cytokine assays\",\n      \"pmids\": [\"32879390\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of ESYT2S–STIM1 interaction undefined\", \"Relative contribution versus general tethering not fully delineated\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Demonstrating that ESYT2 reduces PM DAG levels in resting T cells and that its loss enhances DAG-dependent TCR signaling, cytotoxicity, and cytokine production identified DAG as a major ESYT2 lipid-transfer substrate with immunological significance.\",\n      \"evidence\": \"siRNA knockdown in primary T cells; DAG biosensor imaging; cytotoxicity, degranulation, and cytokine assays\",\n      \"pmids\": [\"38177911\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether DAG is directly transported through the SMP channel or removed indirectly via phosphoinositide remodeling not distinguished\", \"In vivo immune consequences of ESYT2 loss not tested\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Discovery that ESYT2 forms a multimeric complex with ESYT1 and VAPB at lipid-droplet–mitochondria–ER tripartite contacts and that its deletion limits fatty acid β-oxidation, depletes TCA metabolites, and induces lipotoxic stress expanded ESYT2's role from ER–PM tethering to inter-organelle fatty acid trafficking.\",\n      \"evidence\": \"BioID proximity proteomics; high-resolution co-localization imaging; ESYT2 deletion in cells and mice; metabolomics and lipidomics; fatty acid oxidation assays\",\n      \"pmids\": [\"40032835\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the SMP domain directly transfers fatty acids or acts indirectly is unresolved\", \"Tissue-specific metabolic consequences in vivo remain to be defined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Elucidation of an ANO1-IRBIT-ESYT2-AC6-AKAP11-PKA complex at STIM1-containing ER–PM junctions—where ESYT2 displaces VAPA to enable PKA-dependent ANO1 S221 phosphorylation and channel inhibition—revealed ESYT2 as a scaffold that transduces junctional phosphoinositide changes into ion-channel regulation.\",\n      \"evidence\": \"Co-IP of complex components; site-directed mutagenesis of ANO1 S221; lipid biosensor and Ca²⁺ imaging; knockdown/overexpression in epithelial cells; IRBIT KO mice\",\n      \"pmids\": [\"40204782\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether ESYT2 lipid transfer activity is required for the scaffolding function is untested\", \"Generalizability beyond epithelial ANO1 regulation unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key open questions include the directionality and substrate selectivity of SMP-mediated lipid transfer in reconstituted systems, the structural basis of full-length ESYT2 spanning a membrane contact site, stress or disease contexts that reveal essential in vivo functions, and how the adaptor/scaffolding and lipid-transfer activities of ESYT2 are coordinated or segregated at distinct contact sites.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No reconstituted two-bilayer lipid transfer assay for full-length ESYT2\", \"No full-length structure bridging two membranes\", \"Physiological contexts where ESYT2 is essential remain unidentified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [0, 4, 6, 12]},\n      {\"term_id\": \"GO:0140104\", \"supporting_discovery_ids\": [6, 18, 19]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [2, 15, 20]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [4, 7, 8]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 4, 8, 12]},\n      {\"term_id\": \"GO:0005811\", \"supporting_discovery_ids\": [19]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": []},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 3, 15, 20]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [6, 18, 19]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [8, 19]}\n    ],\n    \"complexes\": [\n      \"E-Syt1/E-Syt2/E-Syt3 heteromeric complex\",\n      \"E-Syt1/E-Syt2/VAPB lipid-droplet-mitochondria-ER contact complex\",\n      \"ANO1-IRBIT-E-Syt2-AC6-AKAP11-PKA complex\"\n    ],\n    \"partners\": [\n      \"ESYT1\",\n      \"ESYT3\",\n      \"VAPB\",\n      \"STIM1\",\n      \"FGFR1\",\n      \"AP2A1\",\n      \"PAK1\",\n      \"SEC22B\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}