{"gene":"SEC24A","run_date":"2026-04-28T20:42:07","timeline":{"discoveries":[{"year":2007,"finding":"Human SEC24A mediates selective ER export of membrane proteins carrying di-leucine cytosolic export signals; siRNA knockdown of SEC24A specifically impaired di-leucine-mediated transport of ERGIC-53, and this isoform selectivity correlated with in vitro binding preferences of the di-leucine signal for SEC24A.","method":"siRNA knockdown of individual SEC24 isoforms with transport assays; in vitro binding assays","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 2 — reciprocal knockdown + in vitro binding, replicated across multiple isoform combinations","pmids":["17255961"],"is_preprint":false},{"year":2008,"finding":"X-ray crystallography and biochemical analysis revealed that the cargo-binding groove that accommodates the IxM packaging signal in SEC24C/D is occluded in SEC24A/B, whereas LxxLE-class transport signals and the DxE signal of VSV-G glycoprotein are selectively bound by SEC24A and SEC24B. This structural divergence among the four human SEC24 isoforms explains their differential cargo discrimination.","method":"X-ray crystallography of all four human SEC24 isoforms combined with biochemical cargo-packaging assays into COPII vesicles","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 — crystal structures of all four isoforms with functional validation in vesicle packaging assays","pmids":["18843296"],"is_preprint":false},{"year":2013,"finding":"SEC24A is specifically required for efficient ER exit of PCSK9, a negative regulator of LDL receptor (LDLR). SEC24A-deficient mice show normal viability but markedly reduced plasma cholesterol due to upregulated hepatic LDLR levels. Epistasis experiments with Apoe and Ldlr mutations confirmed a receptor-mediated lipoprotein clearance mechanism. Partial cargo-selectivity overlap between SEC24A and SEC24B was also identified for both soluble and transmembrane cargoes.","method":"Germline knockout mouse model, epistasis genetics (double mutants with Apoe and Ldlr), hepatic LDLR western blotting, plasma cholesterol measurement","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 — clean KO mouse with defined molecular phenotype, genetic epistasis with multiple loci, replicated across cell and in vivo assays","pmids":["23580231"],"is_preprint":false},{"year":2015,"finding":"SEC24A is required for anterograde trafficking of the voltage-gated potassium channel Kv1.3 from the ER. siRNA knockdown of SEC24A in vivo caused ER retention of Kv1.3, and in vitro reconstitution demonstrated a direct physical association between recombinant Kv1.3 and SEC24A protein.","method":"siRNA knockdown trafficking assay in vivo; in vitro binding assay with recombinant proteins; site-directed mutagenesis of C-terminal acidic residues","journal":"BMC biochemistry","confidence":"Medium","confidence_rationale":"Tier 2/3 — in vivo knockdown plus in vitro binding, single lab","pmids":["26156069"],"is_preprint":false},{"year":2018,"finding":"SEC24A was identified as an essential and specific mediator of thapsigargin-induced ER stress cell death in a genome-wide CRISPR/Cas9 loss-of-function screen. Loss of SEC24A did not affect tunicamycin- or brefeldin A-induced cell death, indicating stressor-specific function. SEC24A acts upstream of the unfolded protein response (UPR) in this pathway.","method":"Genome-wide CRISPR/Cas9 loss-of-function screen in HAP1 haploid cells; pharmacological ER stress assays with multiple agents","journal":"Cell death discovery","confidence":"Medium","confidence_rationale":"Tier 2 — genome-wide unbiased screen with follow-up validation, single lab","pmids":["30588337"],"is_preprint":false},{"year":2020,"finding":"Yeast-based proteomics identified SEC24A as an interaction partner of the hepatitis B virus (HBV) envelope S domain. SEC24A and SEC23B form a selective complex with the HBV envelope that cannot be substituted by other paralog combinations. The interaction involves the N-terminal half of SEC24A and a di-arginine motif in the HBV S domain. Silencing SEC24A strongly diminished ER envelope export and subviral particle secretion, and HBV replication upregulated SEC24A transcription.","method":"Yeast two-hybrid proteomics; co-immunoprecipitation; siRNA knockdown of SEC24 paralogs; mutagenesis of the S domain di-arginine motif","journal":"Cellular microbiology","confidence":"Medium","confidence_rationale":"Tier 2/3 — yeast two-hybrid plus co-IP plus mutagenesis, single lab","pmids":["32017353"],"is_preprint":false},{"year":2021,"finding":"SEC24A plays a role in maintaining ER-mitochondria colocalization and Ca2+ flux. SEC24A-knockout HAP1 cells showed ~44% less colocalization of mitochondria with peripheral tubular ER, significantly impaired Ca2+ efflux from the ER and Ca2+ influx into mitochondria, a ~2.5-fold increase in autophagic flux, and ~10-fold reduction in thapsigargin-induced apoptosis. This function was specific to SEC24A and could not be rescued by SEC24B, SEC24C, or SEC24D paralogs.","method":"CRISPR/Cas9 knockout; organelle-specific fluorescent Ca2+ indicator dyes; mitochondria-ER colocalization imaging; autophagic flux measurement; apoptosis assays; paralog-specific rescue experiments","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods in defined KO cells with paralog specificity controls, single lab","pmids":["33622772"],"is_preprint":false}],"current_model":"SEC24A is a cargo-selective COPII coat subunit that recognizes LxxLE-class and DxE (VSV-G) ER export signals via a structurally distinct binding site (occluded to IxM signals), mediates ER exit of specific cargoes including PCSK9 and Kv1.3, regulates plasma cholesterol through PCSK9-dependent LDLR control, facilitates ER-mitochondria contacts and Ca2+ flux to modulate autophagy and apoptosis, and is specifically exploited by pathogens such as HBV for envelope protein secretion."},"narrative":{"teleology":[{"year":2007,"claim":"The question of whether individual human SEC24 paralogs select distinct ER export signals was answered by showing that SEC24A specifically mediates transport of di-leucine-bearing cargoes such as ERGIC-53, establishing isoform-specific cargo sorting within the COPII coat.","evidence":"siRNA knockdown of individual SEC24 isoforms combined with in vitro binding assays in mammalian cells","pmids":["17255961"],"confidence":"High","gaps":["Structural basis for di-leucine signal recognition by SEC24A was not resolved","Full repertoire of SEC24A-selective cargoes was unknown"]},{"year":2008,"claim":"Crystallographic comparison of all four human SEC24 isoforms revealed that the IxM-binding groove is occluded in SEC24A/B while a distinct site selectively binds LxxLE and DxE signals, providing the structural explanation for paralog-specific cargo discrimination.","evidence":"X-ray crystallography of SEC24A/B/C/D trunk domains with biochemical COPII vesicle packaging assays","pmids":["18843296"],"confidence":"High","gaps":["How SEC24A recognizes di-leucine signals structurally was not addressed","Whether additional binding sites exist for non-canonical signals remained open"]},{"year":2013,"claim":"A physiological role for SEC24A cargo selectivity was demonstrated in vivo: SEC24A-deficient mice showed reduced plasma cholesterol through impaired ER exit of PCSK9 and consequent upregulation of hepatic LDL receptors, linking COPII cargo selection to systemic lipid metabolism.","evidence":"Germline SEC24A knockout mice; epistasis genetics with Apoe and Ldlr mutations; plasma cholesterol and hepatic LDLR quantification","pmids":["23580231"],"confidence":"High","gaps":["The ER export signal on PCSK9 recognized by SEC24A was not mapped","Extent of functional redundancy between SEC24A and SEC24B for other cargoes was only partially explored"]},{"year":2015,"claim":"SEC24A was shown to directly bind and mediate ER export of the voltage-gated potassium channel Kv1.3, extending its cargo repertoire to ion channels and implicating C-terminal acidic residues as the recognition determinant.","evidence":"siRNA knockdown trafficking assays; in vitro binding with recombinant proteins; site-directed mutagenesis","pmids":["26156069"],"confidence":"Medium","gaps":["Only demonstrated in a single lab; independent confirmation is lacking","Whether the acidic residues constitute a general SEC24A recognition motif was not tested"]},{"year":2018,"claim":"A genome-wide CRISPR screen revealed that SEC24A is specifically required for thapsigargin-induced ER stress cell death but not for other ER stressors, indicating a stressor-selective function upstream of the UPR beyond its canonical trafficking role.","evidence":"Genome-wide CRISPR/Cas9 loss-of-function screen in HAP1 cells; pharmacological ER stress assays","pmids":["30588337"],"confidence":"Medium","gaps":["Molecular mechanism connecting SEC24A to thapsigargin-specific death was not defined","Whether this reflects ER–mitochondria contact or cargo trafficking defects was unresolved"]},{"year":2020,"claim":"HBV was shown to co-opt SEC24A specifically for envelope protein ER export via a di-arginine motif in the S domain, demonstrating that pathogen cargo can exploit paralog-specific COPII sorting.","evidence":"Yeast two-hybrid, co-immunoprecipitation, siRNA knockdown of SEC24 paralogs, and mutagenesis of the HBV S domain di-arginine motif","pmids":["32017353"],"confidence":"Medium","gaps":["Structural details of the SEC24A–HBV S domain interface are unresolved","Whether other viral envelopes use the same SEC24A-dependent pathway is untested","Findings from a single lab; awaits independent replication"]},{"year":2021,"claim":"SEC24A was found to maintain ER–mitochondria contacts and Ca²⁺ transfer; its loss reduced organelle colocalization, impaired inter-organelle Ca²⁺ flux, increased autophagic flux, and conferred apoptosis resistance — a function unique to SEC24A among all paralogs. This retroactively connected the 2018 thapsigargin sensitivity finding to defective ER–mitochondria Ca²⁺ signaling.","evidence":"CRISPR/Cas9 knockout in HAP1 cells; organelle Ca²⁺ indicators; colocalization imaging; autophagic flux and apoptosis assays; paralog rescue experiments","pmids":["33622772"],"confidence":"Medium","gaps":["Whether SEC24A directly tethers ER–mitochondria membranes or acts indirectly through cargo trafficking of tethering factors is unknown","Molecular identity of the SEC24A-dependent cargo(es) maintaining these contacts is unresolved","Findings from a single lab; awaits independent replication"]},{"year":null,"claim":"The molecular mechanism by which SEC24A uniquely supports ER–mitochondria contacts and Ca²⁺ transfer — whether through direct membrane tethering, trafficking of tethering machinery, or another mechanism — remains the key unresolved question.","evidence":"","pmids":[],"confidence":"Low","gaps":["No tethering or adaptor cargo has been identified as the SEC24A-dependent factor at ER–mitochondria contacts","No structural model exists for SEC24A recognition of di-leucine or di-arginine export signals","In vivo validation of the ER–mitochondria contact function has not been performed"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0038024","term_label":"cargo receptor activity","supporting_discovery_ids":[0,1,2,3]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[1]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[0,1,2,3,5,6]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[0,1]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[0,1,2,3,5]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[0,1,2,3]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[6]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[2]}],"complexes":["COPII coat (SEC23-SEC24 inner coat)"],"partners":["SEC23B","PCSK9","KCNA3","LMAN1"],"other_free_text":[]},"mechanistic_narrative":"SEC24A is a cargo-selective subunit of the COPII coat complex that mediates ER-to-Golgi transport of specific membrane and soluble cargoes bearing LxxLE-class, DxE, and di-leucine export signals, with its IxM-binding groove structurally occluded relative to the SEC24C/D paralogs [PMID:18843296, PMID:17255961]. SEC24A is specifically required for efficient ER exit of PCSK9, and SEC24A-deficient mice exhibit reduced plasma cholesterol due to upregulated hepatic LDL receptor levels [PMID:23580231]. Beyond canonical vesicular trafficking, SEC24A maintains ER–mitochondria contact sites and inter-organelle Ca²⁺ flux; its loss increases autophagic flux and confers resistance to thapsigargin-induced apoptosis, functions not compensated by other SEC24 paralogs [PMID:33622772, PMID:30588337]. SEC24A is also specifically exploited by hepatitis B virus for envelope protein export via a di-arginine motif–dependent interaction with its N-terminal domain [PMID:32017353]."},"prefetch_data":{"uniprot":{"accession":"O95486","full_name":"Protein transport protein Sec24A","aliases":["SEC24-related protein A"],"length_aa":1093,"mass_kda":119.7,"function":"Component of the coat protein complex II (COPII) which promotes the formation of transport vesicles from the endoplasmic reticulum (ER). The coat has two main functions, the physical deformation of the endoplasmic reticulum membrane into vesicles and the selection of cargo molecules for their transport to the Golgi complex (PubMed:17499046, PubMed:18843296, PubMed:20427317). Plays a central role in cargo selection within the COPII complex and together with SEC24B may have a different specificity compared to SEC24C and SEC24D. May package preferentially cargos with cytoplasmic DxE or LxxLE motifs and may also recognize conformational epitopes (PubMed:17499046, PubMed:18843296)","subcellular_location":"Cytoplasmic vesicle, COPII-coated vesicle membrane; Endoplasmic reticulum membrane; Cytoplasm, cytosol","url":"https://www.uniprot.org/uniprotkb/O95486/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SEC24A","classification":"Not Classified","n_dependent_lines":41,"n_total_lines":1208,"dependency_fraction":0.03394039735099338},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"SEC23B","stoichiometry":10.0},{"gene":"SEC23A","stoichiometry":4.0}],"url":"https://opencell.sf.czbiohub.org/search/SEC24A","total_profiled":1310},"omim":[{"mim_id":"617852","title":"SEC23-INTERACTING PROTEIN; SEC23IP","url":"https://www.omim.org/entry/617852"},{"mim_id":"613455","title":"MIA SH3 DOMAIN ER EXPORT FACTOR 3; MIA3","url":"https://www.omim.org/entry/613455"},{"mim_id":"610511","title":"SEC23 HOMOLOG A, COAT COMPLEX II COMPONENT; SEC23A","url":"https://www.omim.org/entry/610511"},{"mim_id":"607690","title":"SECRETION-ASSOCIATED RAS-RELATED GTPase 1B; SAR1B","url":"https://www.omim.org/entry/607690"},{"mim_id":"607186","title":"SEC24-RELATED GENE FAMILY, MEMBER D; SEC24D","url":"https://www.omim.org/entry/607186"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoli fibrillar center","reliability":"Approved"},{"location":"Vesicles","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/SEC24A"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"O95486","domains":[{"cath_id":"1.20.120.730","chopping":"351-368_840-944_1075-1093","consensus_level":"medium","plddt":92.4755,"start":351,"end":1093},{"cath_id":"2.60.40.1670","chopping":"375-499_746-839","consensus_level":"medium","plddt":94.6992,"start":375,"end":839},{"cath_id":"3.40.50.410","chopping":"506-651_669-743","consensus_level":"high","plddt":96.6899,"start":506,"end":743},{"cath_id":"3.40.20.10","chopping":"945-1070","consensus_level":"medium","plddt":93.9659,"start":945,"end":1070}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O95486","model_url":"https://alphafold.ebi.ac.uk/files/AF-O95486-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O95486-F1-predicted_aligned_error_v6.png","plddt_mean":75.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SEC24A","jax_strain_url":"https://www.jax.org/strain/search?query=SEC24A"},"sequence":{"accession":"O95486","fasta_url":"https://rest.uniprot.org/uniprotkb/O95486.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O95486/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O95486"}},"corpus_meta":[{"pmid":"23580231","id":"PMC_23580231","title":"SEC24A 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Molecular cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/11252894","citation_count":410,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"26344197","id":"PMC_26344197","title":"Panorama of ancient metazoan macromolecular complexes.","date":"2015","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/26344197","citation_count":407,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"11031247","id":"PMC_11031247","title":"Secretory protein trafficking and organelle dynamics in living cells.","date":"2000","source":"Annual review of cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/11031247","citation_count":380,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"28319085","id":"PMC_28319085","title":"Synergistic drug combinations for cancer identified in a CRISPR screen for pairwise genetic interactions.","date":"2017","source":"Nature biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/28319085","citation_count":378,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"34079125","id":"PMC_34079125","title":"A proximity-dependent biotinylation map of a human cell.","date":"2021","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/34079125","citation_count":339,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"21145461","id":"PMC_21145461","title":"Dynamics of cullin-RING ubiquitin ligase network revealed by systematic quantitative proteomics.","date":"2010","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/21145461","citation_count":318,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"22863883","id":"PMC_22863883","title":"A high-throughput approach for measuring temporal changes in the interactome.","date":"2012","source":"Nature methods","url":"https://pubmed.ncbi.nlm.nih.gov/22863883","citation_count":273,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"21988832","id":"PMC_21988832","title":"Toward an understanding of the protein interaction network of the human liver.","date":"2011","source":"Molecular systems biology","url":"https://pubmed.ncbi.nlm.nih.gov/21988832","citation_count":207,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"29568061","id":"PMC_29568061","title":"An AP-MS- and BioID-compatible MAC-tag enables comprehensive mapping of protein interactions and subcellular localizations.","date":"2018","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/29568061","citation_count":201,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"26673895","id":"PMC_26673895","title":"A deep proteomics perspective on CRM1-mediated nuclear export and nucleocytoplasmic partitioning.","date":"2015","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/26673895","citation_count":198,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"18843296","id":"PMC_18843296","title":"Structural basis of cargo membrane protein discrimination by the human COPII coat machinery.","date":"2008","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/18843296","citation_count":178,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"32807901","id":"PMC_32807901","title":"UFMylation maintains tumour suppressor p53 stability by antagonizing its ubiquitination.","date":"2020","source":"Nature cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/32807901","citation_count":168,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"17255961","id":"PMC_17255961","title":"Role of Sec24 isoforms in selective export of membrane proteins from the endoplasmic reticulum.","date":"2007","source":"EMBO reports","url":"https://pubmed.ncbi.nlm.nih.gov/17255961","citation_count":164,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"32877691","id":"PMC_32877691","title":"A High-Density Human Mitochondrial Proximity Interaction Network.","date":"2020","source":"Cell metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/32877691","citation_count":148,"is_preprint":false,"source_track":"gene2pubmed"}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9496,"output_tokens":1376,"usd":0.024564},"stage2":{"model":"claude-opus-4-6","input_tokens":4592,"output_tokens":1996,"usd":0.10929},"total_usd":0.308842,"stage1_batch_id":"msgbatch_011rkcQdVV1RaFq9XhcG6df6","stage2_batch_id":"msgbatch_01RzgrJafdF4EWHhj5mNi6dh","note":"batch pricing = 50% of standard","round2_stage1":{"model":"claude-sonnet-4-6","input_tokens":20304,"output_tokens":2363,"usd":0.048178},"round2_rules_fired":"R3","round2_stage2":{"model":"claude-opus-4-6","input_tokens":5378,"output_tokens":2306,"usd":0.12681}},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2013,\n      \"finding\": \"SEC24A is specifically required for efficient ER exit of PCSK9, a negative regulator of LDLR; SEC24A-deficient mice show reduced PCSK9 secretion, elevated hepatic LDLR, and markedly reduced plasma cholesterol. Epistasis with Apoe and Ldlr mutations placed the effect upstream of receptor-mediated lipoprotein clearance. Partial cargo-selectivity overlap between SEC24A and SEC24B was also identified, demonstrating heterogeneity in COPII cargo recruitment for both soluble and transmembrane cargoes.\",\n      \"method\": \"Genetic knockout mouse, plasma cholesterol measurement, LDLR/PCSK9 protein quantification, epistasis analysis (Apoe, Ldlr double mutants)\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO mouse with defined molecular phenotype, replicated by epistasis analysis, >100 citations\",\n      \"pmids\": [\"23580231\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SEC24A (but not paralogs SEC24B, SEC24C, or SEC24D) facilitates ER-mitochondria colocalization and Ca2+ flux: SEC24A-knockout cells show impaired Ca2+ efflux from ER, reduced Ca2+ influx into mitochondria, ~44% less colocalization of mitochondria with peripheral tubular ER, increased autophagic flux, and reduced apoptosis after SERCA inhibition by thapsigargin.\",\n      \"method\": \"SEC24A knockout vs. paralog knockouts; organelle-specific Ca2+ fluorescent indicators; mitochondria-ER colocalization imaging; autophagy flux assay; apoptosis measurement\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods, paralog-specificity controls, clean KO with defined cellular phenotype\",\n      \"pmids\": [\"33622772\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"SEC24A is an essential mediator of thapsigargin-induced ER stress cell death; SEC24A acts upstream of the UPR in this pathway, with its role specific to thapsigargin and not tunicamycin or brefeldin A, identified by genome-wide CRISPR/Cas9 loss-of-function screen.\",\n      \"method\": \"Genome-wide CRISPR/Cas9 loss-of-function screen in HAP1 cells, cytotoxicity assays, UPR pathway analysis\",\n      \"journal\": \"Cell death discovery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genome-wide screen with follow-up validation, but single lab\",\n      \"pmids\": [\"30588337\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"SEC24A (mammalian/human) is required for anterograde trafficking of the voltage-gated potassium channel Kv1.3 from the ER; siRNA knockdown of Sec24a causes ER retention of Kv1.3 in vivo, and recombinant Kv1.3 and Sec24a proteins associate in vitro.\",\n      \"method\": \"siRNA knockdown of Sec24a isoform, ER retention assay; in vitro pulldown of recombinant Kv1.3 and Sec24a\",\n      \"journal\": \"BMC biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — in vivo siRNA and in vitro association, single lab, two orthogonal methods\",\n      \"pmids\": [\"26156069\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"SEC24A physically interacts with the HBV envelope S domain (specifically via the N-terminal half of SEC24A and a di-arginine motif in S), selectively promoting ER export of HBV envelope and subviral particle (SVP) secretion; this selectivity could not be substituted by other SEC24 isoforms. Yeast-based proteomics and co-immunoprecipitation established the interaction.\",\n      \"method\": \"Yeast-based proteomics, co-immunoprecipitation, siRNA silencing of SEC24 paralogs, SVP secretion assays, domain mapping\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — reciprocal co-IP plus paralog-specificity siRNA and domain mapping, single lab\",\n      \"pmids\": [\"32017353\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SEC24A is a COPII coat subunit with selective cargo-recruitment activity: it is specifically required for efficient ER exit of PCSK9 (thereby regulating LDLR levels and plasma cholesterol), facilitates ER-mitochondria contact and Ca2+ flux (impacting autophagy and apoptosis downstream of SERCA inhibition), acts upstream of the UPR in thapsigargin-induced cell death, and mediates anterograde trafficking of select transmembrane cargoes including Kv1.3 and HBV envelope proteins through direct physical interaction.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\nI'll classify each paper first, then extract discoveries only from KEPT papers.\n\n**Classification:**\n\n- [1] KEEP — human/mouse SEC24A, canonical protein, COPII/PCSK9 mechanism\n- [2] EXCLUDE — Arabidopsis SEC24A (symbol collision with plant gene, fundamentally different cellular context/organism)\n- [3] EXCLUDE — Arabidopsis SEC24A (plant)\n- [4] EXCLUDE — Arabidopsis SEC24A (plant)\n- [5] EXCLUDE — Arabidopsis SEC24A (plant)\n- [6] EXCLUDE — Arabidopsis SEC24A (plant)\n- [7] KEEP — human SEC24A, HBV envelope interaction mechanism\n- [8] KEEP — human SEC24A, thapsigargin/UPR mechanism\n- [9] KEEP — mammalian SEC24A, Kv1.3 trafficking mechanism\n- [10] EXCLUDE — circRNA (alt-locus product, case B)\n- [11] KEEP — human SEC24A, ER-mitochondria Ca2+ flux mechanism\n- [12] KEEP — human SEC24A, gastric cancer (has some mechanistic elements)\n- [13] EXCLUDE — circRNA (alt-locus product, case B)\n- [14] EXCLUDE — lncRNA/miRNA axis, SEC24A is downstream target with no mechanistic study of the protein\n- [15] EXCLUDE — Arabidopsis (plant)\n- [16] EXCLUDE — Arabidopsis (plant)\n\n**Additional gene2pubmed papers:**\n- [27] KEEP — structural/biochemical study of human SEC24 isoforms including SEC24A\n- [29] KEEP — human SEC24A isoform-selective cargo export mechanism\n- [1]-[6],[8]-[26],[28],[30] — mostly large interactome/proteome screens; SEC24A may appear incidentally, but no specific mechanistic findings about SEC24A are described. EXCLUDE for discovery extraction.\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2007,\n      \"finding\": \"Human SEC24A mediates selective ER export of membrane proteins carrying di-leucine cytosolic export signals; siRNA knockdown of SEC24A specifically impaired di-leucine-mediated transport of ERGIC-53, and this isoform selectivity correlated with in vitro binding preferences of the di-leucine signal for SEC24A.\",\n      \"method\": \"siRNA knockdown of individual SEC24 isoforms with transport assays; in vitro binding assays\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal knockdown + in vitro binding, replicated across multiple isoform combinations\",\n      \"pmids\": [\"17255961\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"X-ray crystallography and biochemical analysis revealed that the cargo-binding groove that accommodates the IxM packaging signal in SEC24C/D is occluded in SEC24A/B, whereas LxxLE-class transport signals and the DxE signal of VSV-G glycoprotein are selectively bound by SEC24A and SEC24B. This structural divergence among the four human SEC24 isoforms explains their differential cargo discrimination.\",\n      \"method\": \"X-ray crystallography of all four human SEC24 isoforms combined with biochemical cargo-packaging assays into COPII vesicles\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structures of all four isoforms with functional validation in vesicle packaging assays\",\n      \"pmids\": [\"18843296\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"SEC24A is specifically required for efficient ER exit of PCSK9, a negative regulator of LDL receptor (LDLR). SEC24A-deficient mice show normal viability but markedly reduced plasma cholesterol due to upregulated hepatic LDLR levels. Epistasis experiments with Apoe and Ldlr mutations confirmed a receptor-mediated lipoprotein clearance mechanism. Partial cargo-selectivity overlap between SEC24A and SEC24B was also identified for both soluble and transmembrane cargoes.\",\n      \"method\": \"Germline knockout mouse model, epistasis genetics (double mutants with Apoe and Ldlr), hepatic LDLR western blotting, plasma cholesterol measurement\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO mouse with defined molecular phenotype, genetic epistasis with multiple loci, replicated across cell and in vivo assays\",\n      \"pmids\": [\"23580231\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"SEC24A is required for anterograde trafficking of the voltage-gated potassium channel Kv1.3 from the ER. siRNA knockdown of SEC24A in vivo caused ER retention of Kv1.3, and in vitro reconstitution demonstrated a direct physical association between recombinant Kv1.3 and SEC24A protein.\",\n      \"method\": \"siRNA knockdown trafficking assay in vivo; in vitro binding assay with recombinant proteins; site-directed mutagenesis of C-terminal acidic residues\",\n      \"journal\": \"BMC biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — in vivo knockdown plus in vitro binding, single lab\",\n      \"pmids\": [\"26156069\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"SEC24A was identified as an essential and specific mediator of thapsigargin-induced ER stress cell death in a genome-wide CRISPR/Cas9 loss-of-function screen. Loss of SEC24A did not affect tunicamycin- or brefeldin A-induced cell death, indicating stressor-specific function. SEC24A acts upstream of the unfolded protein response (UPR) in this pathway.\",\n      \"method\": \"Genome-wide CRISPR/Cas9 loss-of-function screen in HAP1 haploid cells; pharmacological ER stress assays with multiple agents\",\n      \"journal\": \"Cell death discovery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genome-wide unbiased screen with follow-up validation, single lab\",\n      \"pmids\": [\"30588337\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Yeast-based proteomics identified SEC24A as an interaction partner of the hepatitis B virus (HBV) envelope S domain. SEC24A and SEC23B form a selective complex with the HBV envelope that cannot be substituted by other paralog combinations. The interaction involves the N-terminal half of SEC24A and a di-arginine motif in the HBV S domain. Silencing SEC24A strongly diminished ER envelope export and subviral particle secretion, and HBV replication upregulated SEC24A transcription.\",\n      \"method\": \"Yeast two-hybrid proteomics; co-immunoprecipitation; siRNA knockdown of SEC24 paralogs; mutagenesis of the S domain di-arginine motif\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — yeast two-hybrid plus co-IP plus mutagenesis, single lab\",\n      \"pmids\": [\"32017353\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SEC24A plays a role in maintaining ER-mitochondria colocalization and Ca2+ flux. SEC24A-knockout HAP1 cells showed ~44% less colocalization of mitochondria with peripheral tubular ER, significantly impaired Ca2+ efflux from the ER and Ca2+ influx into mitochondria, a ~2.5-fold increase in autophagic flux, and ~10-fold reduction in thapsigargin-induced apoptosis. This function was specific to SEC24A and could not be rescued by SEC24B, SEC24C, or SEC24D paralogs.\",\n      \"method\": \"CRISPR/Cas9 knockout; organelle-specific fluorescent Ca2+ indicator dyes; mitochondria-ER colocalization imaging; autophagic flux measurement; apoptosis assays; paralog-specific rescue experiments\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods in defined KO cells with paralog specificity controls, single lab\",\n      \"pmids\": [\"33622772\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SEC24A is a cargo-selective COPII coat subunit that recognizes LxxLE-class and DxE (VSV-G) ER export signals via a structurally distinct binding site (occluded to IxM signals), mediates ER exit of specific cargoes including PCSK9 and Kv1.3, regulates plasma cholesterol through PCSK9-dependent LDLR control, facilitates ER-mitochondria contacts and Ca2+ flux to modulate autophagy and apoptosis, and is specifically exploited by pathogens such as HBV for envelope protein secretion.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"SEC24A is a COPII coat subunit that functions as a cargo-selective adaptor for ER-to-Golgi vesicular transport, with specificity distinct from its paralogs SEC24B/C/D. SEC24A is required for efficient ER exit of PCSK9, and SEC24A-deficient mice exhibit reduced PCSK9 secretion, elevated hepatic LDLR, and markedly lowered plasma cholesterol, placing SEC24A as a key regulator of receptor-mediated lipoprotein clearance [PMID:23580231]. Beyond canonical cargo sorting, SEC24A specifically facilitates ER–mitochondria contact and inter-organellar Ca²⁺ flux; its loss reduces ER–mitochondria colocalization, increases autophagic flux, diminishes apoptosis upon SERCA inhibition, and acts upstream of the UPR in thapsigargin-induced cell death [PMID:33622772, PMID:30588337]. SEC24A also mediates anterograde trafficking of select transmembrane cargoes including the voltage-gated potassium channel Kv1.3 and HBV envelope proteins through direct physical interaction via its N-terminal region [PMID:26156069, PMID:32017353].\",\n  \"teleology\": [\n    {\n      \"year\": 2013,\n      \"claim\": \"Establishing that SEC24A has non-redundant cargo selectivity in vivo resolved whether individual SEC24 paralogs make distinct physiological contributions: SEC24A-deficient mice revealed that this subunit is specifically required for PCSK9 secretion, linking COPII cargo sorting to cholesterol homeostasis.\",\n      \"evidence\": \"Sec24a knockout mouse with plasma cholesterol, LDLR and PCSK9 quantification, epistasis with Apoe and Ldlr mutations\",\n      \"pmids\": [\"23580231\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis for SEC24A selectivity toward PCSK9 over other soluble cargoes is unknown\",\n        \"Whether SEC24A regulates PCSK9 sorting through a direct binding motif or an adaptor has not been determined\",\n        \"The extent of cargo overlap between SEC24A and SEC24B remains incompletely mapped\"\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Demonstrating that SEC24A is required for ER exit of Kv1.3 and directly associates with the channel extended the cargo repertoire of SEC24A to transmembrane ion channels.\",\n      \"evidence\": \"siRNA knockdown causing ER retention of Kv1.3 in vivo; in vitro pulldown of recombinant proteins\",\n      \"pmids\": [\"26156069\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"The specific sorting signal on Kv1.3 recognized by SEC24A has not been mapped\",\n        \"Whether other Kv family channels similarly depend on SEC24A is untested\",\n        \"In vivo physiological consequence of impaired Kv1.3 trafficking via SEC24A loss is unexplored\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"A genome-wide CRISPR screen identified SEC24A as essential for thapsigargin-induced cell death upstream of the UPR, revealing a non-canonical role for this COPII subunit in ER stress-triggered apoptosis distinct from other ER stressors.\",\n      \"evidence\": \"Genome-wide CRISPR/Cas9 loss-of-function screen in HAP1 cells with cytotoxicity and UPR pathway analysis\",\n      \"pmids\": [\"30588337\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"The molecular mechanism by which SEC24A acts upstream of UPR activation upon SERCA inhibition is undefined\",\n        \"Whether this role is cargo-sorting dependent or reflects a structural/scaffolding function is unknown\",\n        \"Finding has not been independently replicated outside the original laboratory\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identifying SEC24A as a direct, isoform-specific interactor of the HBV S domain via its N-terminal half showed that viral cargo can co-opt a specific COPII subunit for subviral particle secretion.\",\n      \"evidence\": \"Yeast proteomics, reciprocal co-IP, paralog-specific siRNA, SVP secretion assays, domain mapping\",\n      \"pmids\": [\"32017353\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether the di-arginine motif in HBV S is a general SEC24A-binding signal shared with endogenous cargoes is not known\",\n        \"Structural details of the SEC24A N-terminal half–HBV S interaction are lacking\",\n        \"Impact of SEC24A loss on full HBV virion morphogenesis and infectivity has not been tested\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Revealing that SEC24A uniquely among its paralogs promotes ER–mitochondria contact and Ca²⁺ transfer established a non-canonical, cargo-sorting-independent role for a COPII subunit in organelle tethering, linking it to autophagy and apoptosis regulation.\",\n      \"evidence\": \"SEC24A knockout with organelle-specific Ca²⁺ indicators, ER–mitochondria colocalization imaging, autophagy flux and apoptosis assays, paralog comparisons\",\n      \"pmids\": [\"33622772\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"The protein(s) mediating SEC24A-dependent ER–mitochondria tethering have not been identified\",\n        \"Whether this contact-site role depends on COPII coat assembly or is coat-independent is unresolved\",\n        \"Physiological consequences of altered ER–mitochondria contact in Sec24a-knockout animals have not been examined\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A unified structural and mechanistic framework integrating SEC24A's cargo-selective COPII function with its non-canonical role in ER–mitochondria contact and ER stress signaling remains unestablished.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No high-resolution structure of SEC24A in complex with any cargo sorting signal is available\",\n        \"The relationship between SEC24A's ER–mitochondria tethering activity and its thapsigargin-specific cell death role has not been mechanistically dissected\",\n        \"A comprehensive catalogue of SEC24A-dependent cargoes versus those handled by other SEC24 paralogs is lacking\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0038024\", \"supporting_discovery_ids\": [0, 3, 4]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0, 1, 3, 4]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [0, 3, 4]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [0, 3, 4]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [1, 2]}\n    ],\n    \"complexes\": [\n      \"COPII coat\"\n    ],\n    \"partners\": [\n      \"PCSK9\",\n      \"KCNA3\",\n      \"HBV S protein\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"SEC24A is a cargo-selective subunit of the COPII coat complex that mediates ER-to-Golgi transport of specific membrane and soluble cargoes bearing LxxLE-class, DxE, and di-leucine export signals, with its IxM-binding groove structurally occluded relative to the SEC24C/D paralogs [PMID:18843296, PMID:17255961]. SEC24A is specifically required for efficient ER exit of PCSK9, and SEC24A-deficient mice exhibit reduced plasma cholesterol due to upregulated hepatic LDL receptor levels [PMID:23580231]. Beyond canonical vesicular trafficking, SEC24A maintains ER–mitochondria contact sites and inter-organelle Ca²⁺ flux; its loss increases autophagic flux and confers resistance to thapsigargin-induced apoptosis, functions not compensated by other SEC24 paralogs [PMID:33622772, PMID:30588337]. SEC24A is also specifically exploited by hepatitis B virus for envelope protein export via a di-arginine motif–dependent interaction with its N-terminal domain [PMID:32017353].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"The question of whether individual human SEC24 paralogs select distinct ER export signals was answered by showing that SEC24A specifically mediates transport of di-leucine-bearing cargoes such as ERGIC-53, establishing isoform-specific cargo sorting within the COPII coat.\",\n      \"evidence\": \"siRNA knockdown of individual SEC24 isoforms combined with in vitro binding assays in mammalian cells\",\n      \"pmids\": [\"17255961\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis for di-leucine signal recognition by SEC24A was not resolved\",\n        \"Full repertoire of SEC24A-selective cargoes was unknown\"\n      ]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Crystallographic comparison of all four human SEC24 isoforms revealed that the IxM-binding groove is occluded in SEC24A/B while a distinct site selectively binds LxxLE and DxE signals, providing the structural explanation for paralog-specific cargo discrimination.\",\n      \"evidence\": \"X-ray crystallography of SEC24A/B/C/D trunk domains with biochemical COPII vesicle packaging assays\",\n      \"pmids\": [\"18843296\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How SEC24A recognizes di-leucine signals structurally was not addressed\",\n        \"Whether additional binding sites exist for non-canonical signals remained open\"\n      ]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"A physiological role for SEC24A cargo selectivity was demonstrated in vivo: SEC24A-deficient mice showed reduced plasma cholesterol through impaired ER exit of PCSK9 and consequent upregulation of hepatic LDL receptors, linking COPII cargo selection to systemic lipid metabolism.\",\n      \"evidence\": \"Germline SEC24A knockout mice; epistasis genetics with Apoe and Ldlr mutations; plasma cholesterol and hepatic LDLR quantification\",\n      \"pmids\": [\"23580231\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"The ER export signal on PCSK9 recognized by SEC24A was not mapped\",\n        \"Extent of functional redundancy between SEC24A and SEC24B for other cargoes was only partially explored\"\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"SEC24A was shown to directly bind and mediate ER export of the voltage-gated potassium channel Kv1.3, extending its cargo repertoire to ion channels and implicating C-terminal acidic residues as the recognition determinant.\",\n      \"evidence\": \"siRNA knockdown trafficking assays; in vitro binding with recombinant proteins; site-directed mutagenesis\",\n      \"pmids\": [\"26156069\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Only demonstrated in a single lab; independent confirmation is lacking\",\n        \"Whether the acidic residues constitute a general SEC24A recognition motif was not tested\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"A genome-wide CRISPR screen revealed that SEC24A is specifically required for thapsigargin-induced ER stress cell death but not for other ER stressors, indicating a stressor-selective function upstream of the UPR beyond its canonical trafficking role.\",\n      \"evidence\": \"Genome-wide CRISPR/Cas9 loss-of-function screen in HAP1 cells; pharmacological ER stress assays\",\n      \"pmids\": [\"30588337\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Molecular mechanism connecting SEC24A to thapsigargin-specific death was not defined\",\n        \"Whether this reflects ER–mitochondria contact or cargo trafficking defects was unresolved\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"HBV was shown to co-opt SEC24A specifically for envelope protein ER export via a di-arginine motif in the S domain, demonstrating that pathogen cargo can exploit paralog-specific COPII sorting.\",\n      \"evidence\": \"Yeast two-hybrid, co-immunoprecipitation, siRNA knockdown of SEC24 paralogs, and mutagenesis of the HBV S domain di-arginine motif\",\n      \"pmids\": [\"32017353\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Structural details of the SEC24A–HBV S domain interface are unresolved\",\n        \"Whether other viral envelopes use the same SEC24A-dependent pathway is untested\",\n        \"Findings from a single lab; awaits independent replication\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"SEC24A was found to maintain ER–mitochondria contacts and Ca²⁺ transfer; its loss reduced organelle colocalization, impaired inter-organelle Ca²⁺ flux, increased autophagic flux, and conferred apoptosis resistance — a function unique to SEC24A among all paralogs. This retroactively connected the 2018 thapsigargin sensitivity finding to defective ER–mitochondria Ca²⁺ signaling.\",\n      \"evidence\": \"CRISPR/Cas9 knockout in HAP1 cells; organelle Ca²⁺ indicators; colocalization imaging; autophagic flux and apoptosis assays; paralog rescue experiments\",\n      \"pmids\": [\"33622772\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether SEC24A directly tethers ER–mitochondria membranes or acts indirectly through cargo trafficking of tethering factors is unknown\",\n        \"Molecular identity of the SEC24A-dependent cargo(es) maintaining these contacts is unresolved\",\n        \"Findings from a single lab; awaits independent replication\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular mechanism by which SEC24A uniquely supports ER–mitochondria contacts and Ca²⁺ transfer — whether through direct membrane tethering, trafficking of tethering machinery, or another mechanism — remains the key unresolved question.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No tethering or adaptor cargo has been identified as the SEC24A-dependent factor at ER–mitochondria contacts\",\n        \"No structural model exists for SEC24A recognition of di-leucine or di-arginine export signals\",\n        \"In vivo validation of the ER–mitochondria contact function has not been performed\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0038024\", \"supporting_discovery_ids\": [0, 1, 2, 3]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0, 1, 2, 3, 5, 6]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [0, 1, 2, 3, 5]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [0, 1, 2, 3]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"complexes\": [\n      \"COPII coat (SEC23-SEC24 inner coat)\"\n    ],\n    \"partners\": [\n      \"SEC23B\",\n      \"PCSK9\",\n      \"KCNA3\",\n      \"LMAN1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}