{"gene":"ERLIN1","run_date":"2026-04-28T17:46:03","timeline":{"discoveries":[{"year":2006,"finding":"ERLIN1 (KE04p) localizes to the ER membrane and is enriched in detergent-insoluble, buoyant (lipid raft-like) fractions in a cholesterol-dependent manner. The extreme N-terminus of ERLIN1 is sufficient for ER targeting in the absence of classical ER retrieval motifs.","method":"Sucrose gradient fractionation, cholesterol depletion, GFP fusion/heterologous targeting, confocal microscopy","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (fractionation, cholesterol dependence, GFP targeting), replicated across prohibitin family members","pmids":["16835267"],"is_preprint":false},{"year":2009,"finding":"ERLIN1 (SPFH1) and ERLIN2 (SPFH2) form a ~2 MDa heteromeric ring-shaped ER membrane complex that binds activated IP3R tetramers prior to their polyubiquitination and is required for IP3R ERAD; RNAi-mediated depletion of SPFH1/2 blocks IP3R polyubiquitination and degradation.","method":"Native gel/electron microscopy (ring-shaped complex), RNA interference, co-immunoprecipitation, ubiquitination and degradation assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — reconstituted complex characterization, RNAi functional depletion, multiple orthogonal assays; replicated in a second paper (PMID:19751772)","pmids":["19240031","19751772"],"is_preprint":false},{"year":2009,"finding":"The ERLIN1/2 (SPFH1/2) complex associates with activated IP3Rs before polyubiquitination and before p97 recruitment, placing it upstream of ubiquitination in the ERAD cascade; its depletion selectively blocks IP3R ERAD but not IκBα processing or HMG-CoA reductase ERAD.","method":"RNA interference, co-immunoprecipitation, proteasome inhibitor/pulse-chase degradation assays, calcium mobilization measurement","journal":"Biochimica et biophysica acta","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal functional assays with selective substrate controls, consistent with PMID:19240031","pmids":["19751772"],"is_preprint":false},{"year":2018,"finding":"ERLIN2 is the dominant subunit in mediating the erlin1/2 complex interaction with IP3Rs; the spastic paraplegia-linked erlin2 T65I mutation dramatically inhibits IP3R interaction and IP3R polyubiquitination/degradation. The erlin1/2 complex selectively binds phosphatidylinositol 3-phosphate (PI(3)P), with erlin2 binding more strongly than erlin1, and the T65I mutation inhibits this PI(3)P binding.","method":"Gene editing (erlin1 or erlin2 ablation), co-immunoprecipitation, ubiquitination/degradation assays, lipid-binding assays with recombinant proteins, site-directed mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 — gene editing, in vitro lipid binding, mutagenesis, and functional ubiquitination assays in one study","pmids":["30135210"],"is_preprint":false},{"year":2020,"finding":"ERLIN1 interacts with AMBRA1 at MAM (mitochondria-associated membrane) raft-like microdomains, and this interaction is required for autophagosome formation upon nutrient starvation; the interaction depends on ganglioside GD3 (ST8SIA1) and MFN2 integrity.","method":"Co-immunoprecipitation, FRET, siRNA knockdown of ERLIN1/ST8SIA1/MFN2, autophagy flux assays (LC3-II, SQSTM1), subcellular fractionation to isolate MAMs","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods (FRET, co-IP, KD + phenotype) in a single lab","pmids":["33034545"],"is_preprint":false},{"year":2022,"finding":"The erlin1/2 complex binds to IP3R1 intralumenal loop 3 (IL3), specifically a region close to TM5 (amino acids D2471/R2472); mutation of these residues blocks erlin1/2 complex association. UBE1 inhibition blocks IP3R1 ubiquitination/degradation without altering erlin1/2 complex association, confirming erlin1/2 binding is the primary initiating event preceding ubiquitination.","method":"Site-directed mutagenesis of IP3R1, co-immunoprecipitation, small-molecule inhibitor (TAK-243) treatment, Ca2+ channel activity assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — mutagenesis of binding site with functional validation and pharmacological dissection of pathway order","pmids":["35568199"],"is_preprint":false},{"year":2024,"finding":"The erlin1/2 complex directly and selectively binds PI(3)P; loss or disruption of the complex reduces cellular PI(3)P levels by ~50%, which correlates with decreased autophagic flux without affecting VPS34 kinase activity or the endocytic pathway.","method":"In vitro PI(3)P binding with recombinant erlins, PI(3)P quantification in cells with E1/E2 KO, autophagic flux assays, VPS34 activity assay, pharmacological PI(3)P depletion","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 — direct in vitro binding with recombinant proteins plus cellular KO phenotype with multiple orthogonal controls","pmids":["39018973"],"is_preprint":false},{"year":2024,"finding":"ERLIN1/2 scaffolds mediate the interaction between the full-length isoform of TMUB1 and RNF170 via a luminal N-terminal conserved region in TMUB1 and RNF170 that contacts the SPFH domain of adjacent ERLIN subunits. Loss of both ERLINs limits cholesterol esterification, thereby promoting cholesterol transport from ER to Golgi and regulating Golgi morphology and the secretory pathway.","method":"Co-immunoprecipitation, 3D structural modelling, proteomic (omics) analysis, phenotypic characterization of ERLIN1/2 double-KO HeLa cells, cholesterol transport assays","journal":"Life science alliance","confidence":"High","confidence_rationale":"Tier 2 — structural modelling plus reciprocal co-IP, KO with defined phenotypic readouts, lipidomics","pmids":["38782601"],"is_preprint":false},{"year":2019,"finding":"ERLIN1 is required for HCV RNA replication and infectious virus production; siRNA silencing of erlin1 reduces intracellular HCV RNA, protein expression, and virus production, with the requirement mapping to a step after cell entry and primary translation but before/during RNA replication.","method":"siRNA knockdown, HCV infection assays, RNA quantification, protein expression analysis, mechanistic step mapping","journal":"Cells","confidence":"Medium","confidence_rationale":"Tier 2 — siRNA KD with defined step-specific mechanistic readouts in a single lab","pmids":["31810281"],"is_preprint":false},{"year":2025,"finding":"Cryo-EM structure of the human erlin1/2 complex reveals a 26-mer cage assembly (13 heterodimers of erlin1 and erlin2), defining a nanometer-sized microdomain on the ER luminal leaflet. Each subunit contains an intramembrane phosphatidylinositol-binding pocket. The complex can cage substrate proteins (e.g., recruiting TMUB1 to interior and exterior of cage), physically secluding them from binding partners; individual cages can cluster to form microdomains of different sizes.","method":"Single-particle cryo-EM, structural modelling, functional validation of cargo sequestration","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 — high-resolution cryo-EM structure with functional validation","pmids":["41887216"],"is_preprint":false},{"year":2025,"finding":"Cryo-EM structures of the ER-resident erlin1/2 complex show it assembles as 13 heterodimers (26-mer), with defined inter-subunit interfaces; key interactions underlying the architecture were described and conformational properties elucidated.","method":"Single-particle cryo-EM","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1 structure, but preprint not yet peer-reviewed; consistent with PMID:41887216","pmids":["bio_10.1101_2025.04.21.649849"],"is_preprint":true},{"year":2025,"finding":"ERLIN1 interacts directly with CYP1A2 via their ER N-terminal signal-anchor domains within detergent-resistant ER membrane microdomains/MAMs; siRNA knockdown of erlin-1 relocates CYP1A2 from DRMs to non-DRMs and impairs its ER-to-lysosomal-associated degradation (ERLAD), resulting in insoluble CYP1A2 aggregates. This ERLAD requirement is rescued by re-expression of erlin-1 or just its N-terminal 1–30 residue signal-anchor domain.","method":"SURF split-fluorogenic complementation assay (protein-protein interaction), siRNA knockdown, subcellular fractionation (DRM isolation), rescue with siRNA-resistant constructs, CYP2B1 as proof-of-concept","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 — novel in-cell interaction assay plus KD/rescue with multiple P450 substrates; preprint only","pmids":["bio_10.1101_2025.09.25.678692"],"is_preprint":true}],"current_model":"ERLIN1 assembles with ERLIN2 into a ~2 MDa (26-subunit) ring-shaped cage complex in cholesterol-rich, lipid raft-like ER membrane microdomains, where it acts as a scaffold that recruits E3 ubiquitin ligase partners (RNF170, via TMUB1) to mediate the recognition and ERAD of activated IP3Rs by binding their intralumenal loop 3, selectively binds and stabilizes phosphatidylinositol 3-phosphate to sustain autophagic flux, limits cholesterol esterification to promote ER-to-Golgi cholesterol transport, and interacts with AMBRA1 at MAMs to initiate autophagy."},"narrative":{"teleology":[{"year":2006,"claim":"Establishing ERLIN1's subcellular localization resolved where the protein operates: in cholesterol-dependent, detergent-resistant ER membrane microdomains, with its N-terminus sufficient for ER targeting without classical retrieval motifs.","evidence":"Sucrose gradient fractionation, cholesterol depletion, GFP-fusion targeting in mammalian cells","pmids":["16835267"],"confidence":"High","gaps":["No function or binding partners identified at this stage","Mechanism of cholesterol-dependent raft association undefined"]},{"year":2009,"claim":"Discovery that ERLIN1 and ERLIN2 form a ~2 MDa ring-shaped complex that binds activated IP3Rs upstream of polyubiquitination established the complex as a substrate recognition scaffold in a selective ERAD pathway.","evidence":"Native gel/EM structural analysis, RNAi depletion, co-IP, ubiquitination/degradation assays with selective substrate controls (IP3R vs. IκBα vs. HMG-CoA reductase)","pmids":["19240031","19751772"],"confidence":"High","gaps":["Binding interface on IP3R not mapped","Identity of ubiquitin ligase recruited by the complex unknown","Stoichiometry and subunit arrangement unresolved"]},{"year":2018,"claim":"Demonstrating that ERLIN2 is the dominant IP3R-binding subunit and that the complex selectively binds PI(3)P revealed a lipid-binding function and clarified individual subunit contributions.","evidence":"Gene editing (erlin1/erlin2 KO), in vitro lipid-binding assays with recombinant proteins, T65I mutagenesis linked to spastic paraplegia","pmids":["30135210"],"confidence":"High","gaps":["Structural basis of PI(3)P binding unknown","Functional consequence of PI(3)P binding on autophagy not yet tested"]},{"year":2019,"claim":"ERLIN1 was identified as a host factor required for HCV RNA replication at a post-entry step, extending its functional scope beyond ERAD to viral exploitation of ER membrane platforms.","evidence":"siRNA knockdown in HCV-infected cells with stepwise mechanistic dissection","pmids":["31810281"],"confidence":"Medium","gaps":["Mechanism of ERLIN1 contribution to viral replication complex assembly unknown","Single-lab finding without independent replication"]},{"year":2020,"claim":"Linking ERLIN1 to AMBRA1 at MAMs established a role in starvation-induced autophagosome formation dependent on ganglioside GD3 and MFN2, connecting the complex to autophagy initiation.","evidence":"FRET, co-IP, siRNA knockdown of ERLIN1/ST8SIA1/MFN2, LC3-II flux assays, MAM fractionation","pmids":["33034545"],"confidence":"Medium","gaps":["Direct vs. indirect nature of ERLIN1–AMBRA1 interaction unclear","Relationship between PI(3)P binding and MAM autophagy function not tested"]},{"year":2022,"claim":"Mapping the erlin1/2 binding site to IP3R1 intralumenal loop 3 (D2471/R2472) and showing that ubiquitin-activating enzyme inhibition does not disrupt this binding definitively placed erlin complex recognition as the initiating event in IP3R ERAD.","evidence":"Site-directed mutagenesis of IP3R1, co-IP, TAK-243 pharmacological dissection","pmids":["35568199"],"confidence":"High","gaps":["How IP3R activation exposes the loop 3 binding site is undefined","No structural model of the erlin–IP3R interface"]},{"year":2024,"claim":"Two parallel advances clarified downstream functions: direct PI(3)P binding by the complex stabilizes ~50% of cellular PI(3)P to sustain autophagic flux independently of VPS34, while loss of erlin1/2 limits cholesterol esterification, promoting ER-to-Golgi cholesterol transport and reshaping Golgi morphology.","evidence":"Recombinant PI(3)P binding assays, erlin1/2 KO with PI(3)P quantification and autophagy readouts (PMID:39018973); double-KO HeLa cells with lipidomics, cholesterol transport assays, co-IP mapping TMUB1–RNF170 scaffold (PMID:38782601)","pmids":["39018973","38782601"],"confidence":"High","gaps":["Structural basis for PI(3)P sequestration within the cage not resolved at atomic level","Mechanism linking cholesterol esterification to erlin complex presence is correlative"]},{"year":2025,"claim":"Cryo-EM structures revealed the 26-mer cage architecture (13 erlin1/2 heterodimers) with intramembrane phosphoinositide-binding pockets and demonstrated physical sequestration of TMUB1 cargo within the cage, providing the structural framework for all previously described functions.","evidence":"Single-particle cryo-EM at near-atomic resolution with functional validation of cargo caging","pmids":["41887216"],"confidence":"High","gaps":["Structure of the complete erlin–IP3R–RNF170 degradation complex not determined","Dynamics of cage assembly/disassembly in response to stimuli unknown","Mechanism by which cage clustering creates larger microdomains needs characterization"]},{"year":null,"claim":"Outstanding questions include how the erlin cage dynamically remodels upon substrate engagement, whether PI(3)P binding and IP3R ERAD functions are coordinated or independent within the same cage, and how erlin1 vs. erlin2 subunit contributions specify distinct substrate selectivities.","evidence":"","pmids":[],"confidence":"High","gaps":["No time-resolved structural data on cage dynamics during ERAD","Relationship between PI(3)P stabilization and ERAD substrate processing within the cage unclear","In vivo physiological consequences of erlin1 loss vs. erlin2 loss not systematically compared in animal models"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[3,6,9]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1,5,7]},{"term_id":"GO:0140313","term_label":"molecular sequestering activity","supporting_discovery_ids":[9]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[0,1,9]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,4]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[1,2,5,7]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[4,6]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[7]}],"complexes":["erlin1/erlin2 26-mer cage complex"],"partners":["ERLIN2","ITPR1","RNF170","TMUB1","AMBRA1"],"other_free_text":[]},"mechanistic_narrative":"ERLIN1 is a core subunit of the ER-resident erlin1/2 complex, a 26-subunit (13 heterodimer) ring-shaped cage that organizes cholesterol-rich, lipid raft-like microdomains on the ER membrane to coordinate substrate recognition for ER-associated degradation, lipid homeostasis, and autophagy. The complex recognizes activated IP3 receptors by binding their intralumenal loop 3, acting upstream of polyubiquitination to initiate IP3R ERAD, and scaffolds the E3 ligase RNF170 via TMUB1, physically sequestering substrates within the cage interior [PMID:19240031, PMID:35568199, PMID:41887216, PMID:38782601]. ERLIN1/2 selectively binds phosphatidylinositol 3-phosphate through intramembrane phosphoinositide-binding pockets in each subunit, stabilizing cellular PI(3)P pools to sustain autophagic flux independently of VPS34 kinase activity, and interacts with AMBRA1 at mitochondria-associated membranes to promote autophagosome formation [PMID:39018973, PMID:30135210, PMID:33034545]. Loss of erlin1/2 also limits cholesterol esterification, redirecting cholesterol to the Golgi and altering secretory pathway organization [PMID:38782601]."},"prefetch_data":{"uniprot":{"accession":"O75477","full_name":"Erlin-1","aliases":["Endoplasmic reticulum lipid raft-associated protein 1","Protein KE04","Stomatin-prohibitin-flotillin-HflC/K domain-containing protein 1","SPFH domain-containing protein 1"],"length_aa":348,"mass_kda":39.2,"function":"Component of the ERLIN1/ERLIN2 complex which mediates the endoplasmic reticulum-associated degradation (ERAD) of inositol 1,4,5-trisphosphate receptors (IP3Rs). Involved in regulation of cellular cholesterol homeostasis by regulation the SREBP signaling pathway (PubMed:37683630). Binds cholesterol and may promote ER retention of the SCAP-SREBF complex (PubMed:24217618) (Microbial infection) Required early in hepatitis C virus (HCV) infection to initiate RNA replication, and later in the infection to support infectious virus production","subcellular_location":"Endoplasmic reticulum membrane","url":"https://www.uniprot.org/uniprotkb/O75477/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ERLIN1","classification":"Not Classified","n_dependent_lines":5,"n_total_lines":1208,"dependency_fraction":0.0041390728476821195},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"BAG6","stoichiometry":0.2},{"gene":"CANX","stoichiometry":0.2},{"gene":"COPA","stoichiometry":0.2},{"gene":"COPB2","stoichiometry":0.2},{"gene":"COPE","stoichiometry":0.2},{"gene":"OSBPL8","stoichiometry":0.2},{"gene":"VAPA","stoichiometry":0.2},{"gene":"VAPB","stoichiometry":0.2},{"gene":"VCP","stoichiometry":0.2},{"gene":"CCDC47","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/ERLIN1","total_profiled":1310},"omim":[{"mim_id":"615681","title":"SPASTIC PARAPLEGIA 62, AUTOSOMAL RECESSIVE; SPG62","url":"https://www.omim.org/entry/615681"},{"mim_id":"614649","title":"RING FINGER PROTEIN 170; RNF170","url":"https://www.omim.org/entry/614649"},{"mim_id":"612363","title":"ALANINE AMINOTRANSFERASE, PLASMA LEVEL OF, QUANTITATIVE TRAIT LOCUS 1","url":"https://www.omim.org/entry/612363"},{"mim_id":"611605","title":"ENDOPLASMIC RETICULUM LIPID RAFT-ASSOCIATED PROTEIN 2; ERLIN2","url":"https://www.omim.org/entry/611605"},{"mim_id":"611604","title":"ENDOPLASMIC RETICULUM LIPID RAFT-ASSOCIATED PROTEIN 1; ERLIN1","url":"https://www.omim.org/entry/611604"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Endoplasmic reticulum","reliability":"Supported"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"liver","ntpm":106.7}],"url":"https://www.proteinatlas.org/search/ERLIN1"},"hgnc":{"alias_symbol":["KE04","Erlin-1","SPG62"],"prev_symbol":["C10orf69","SPFH1"]},"alphafold":{"accession":"O75477","domains":[{"cath_id":"-","chopping":"1-65","consensus_level":"medium","plddt":90.6669,"start":1,"end":65},{"cath_id":"3.30.479.30","chopping":"66-177","consensus_level":"medium","plddt":93.7297,"start":66,"end":177}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O75477","model_url":"https://alphafold.ebi.ac.uk/files/AF-O75477-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O75477-F1-predicted_aligned_error_v6.png","plddt_mean":85.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ERLIN1","jax_strain_url":"https://www.jax.org/strain/search?query=ERLIN1"},"sequence":{"accession":"O75477","fasta_url":"https://rest.uniprot.org/uniprotkb/O75477.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O75477/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O75477"}},"corpus_meta":[{"pmid":"16835267","id":"PMC_16835267","title":"Erlin-1 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UPS","date":"2025-09-29","source":"bioRxiv","url":"https://doi.org/10.1101/2025.09.25.678692","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.06.14.659634","title":"Erlin1/2 Complex is a Dynamic Scaffold for Membrane Protein Sequestration and Microdomain Assembly on the Endoplasmic Reticulum","date":"2025-06-17","source":"bioRxiv","url":"https://doi.org/10.1101/2025.06.14.659634","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.04.21.649849","title":"Structures of human organellar SPFH protein complexes","date":"2025-04-22","source":"bioRxiv","url":"https://doi.org/10.1101/2025.04.21.649849","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":12785,"output_tokens":3136,"usd":0.042697},"stage2":{"model":"claude-opus-4-6","input_tokens":6489,"output_tokens":2425,"usd":0.139605},"total_usd":0.182302,"stage1_batch_id":"msgbatch_0118RScg3WGaGkaZRtWZbtce","stage2_batch_id":"msgbatch_01Cpfzvtbj42aqp5oYZ5Te2s","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2006,\n      \"finding\": \"ERLIN1 (KE04p) localizes to the ER membrane and is enriched in detergent-insoluble, buoyant (lipid raft-like) fractions in a cholesterol-dependent manner. The extreme N-terminus of ERLIN1 is sufficient for ER targeting in the absence of classical ER retrieval motifs.\",\n      \"method\": \"Sucrose gradient fractionation, cholesterol depletion, GFP fusion/heterologous targeting, confocal microscopy\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (fractionation, cholesterol dependence, GFP targeting), replicated across prohibitin family members\",\n      \"pmids\": [\"16835267\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"ERLIN1 (SPFH1) and ERLIN2 (SPFH2) form a ~2 MDa heteromeric ring-shaped ER membrane complex that binds activated IP3R tetramers prior to their polyubiquitination and is required for IP3R ERAD; RNAi-mediated depletion of SPFH1/2 blocks IP3R polyubiquitination and degradation.\",\n      \"method\": \"Native gel/electron microscopy (ring-shaped complex), RNA interference, co-immunoprecipitation, ubiquitination and degradation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reconstituted complex characterization, RNAi functional depletion, multiple orthogonal assays; replicated in a second paper (PMID:19751772)\",\n      \"pmids\": [\"19240031\", \"19751772\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"The ERLIN1/2 (SPFH1/2) complex associates with activated IP3Rs before polyubiquitination and before p97 recruitment, placing it upstream of ubiquitination in the ERAD cascade; its depletion selectively blocks IP3R ERAD but not IκBα processing or HMG-CoA reductase ERAD.\",\n      \"method\": \"RNA interference, co-immunoprecipitation, proteasome inhibitor/pulse-chase degradation assays, calcium mobilization measurement\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal functional assays with selective substrate controls, consistent with PMID:19240031\",\n      \"pmids\": [\"19751772\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"ERLIN2 is the dominant subunit in mediating the erlin1/2 complex interaction with IP3Rs; the spastic paraplegia-linked erlin2 T65I mutation dramatically inhibits IP3R interaction and IP3R polyubiquitination/degradation. The erlin1/2 complex selectively binds phosphatidylinositol 3-phosphate (PI(3)P), with erlin2 binding more strongly than erlin1, and the T65I mutation inhibits this PI(3)P binding.\",\n      \"method\": \"Gene editing (erlin1 or erlin2 ablation), co-immunoprecipitation, ubiquitination/degradation assays, lipid-binding assays with recombinant proteins, site-directed mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — gene editing, in vitro lipid binding, mutagenesis, and functional ubiquitination assays in one study\",\n      \"pmids\": [\"30135210\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"ERLIN1 interacts with AMBRA1 at MAM (mitochondria-associated membrane) raft-like microdomains, and this interaction is required for autophagosome formation upon nutrient starvation; the interaction depends on ganglioside GD3 (ST8SIA1) and MFN2 integrity.\",\n      \"method\": \"Co-immunoprecipitation, FRET, siRNA knockdown of ERLIN1/ST8SIA1/MFN2, autophagy flux assays (LC3-II, SQSTM1), subcellular fractionation to isolate MAMs\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (FRET, co-IP, KD + phenotype) in a single lab\",\n      \"pmids\": [\"33034545\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The erlin1/2 complex binds to IP3R1 intralumenal loop 3 (IL3), specifically a region close to TM5 (amino acids D2471/R2472); mutation of these residues blocks erlin1/2 complex association. UBE1 inhibition blocks IP3R1 ubiquitination/degradation without altering erlin1/2 complex association, confirming erlin1/2 binding is the primary initiating event preceding ubiquitination.\",\n      \"method\": \"Site-directed mutagenesis of IP3R1, co-immunoprecipitation, small-molecule inhibitor (TAK-243) treatment, Ca2+ channel activity assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mutagenesis of binding site with functional validation and pharmacological dissection of pathway order\",\n      \"pmids\": [\"35568199\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The erlin1/2 complex directly and selectively binds PI(3)P; loss or disruption of the complex reduces cellular PI(3)P levels by ~50%, which correlates with decreased autophagic flux without affecting VPS34 kinase activity or the endocytic pathway.\",\n      \"method\": \"In vitro PI(3)P binding with recombinant erlins, PI(3)P quantification in cells with E1/E2 KO, autophagic flux assays, VPS34 activity assay, pharmacological PI(3)P depletion\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct in vitro binding with recombinant proteins plus cellular KO phenotype with multiple orthogonal controls\",\n      \"pmids\": [\"39018973\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"ERLIN1/2 scaffolds mediate the interaction between the full-length isoform of TMUB1 and RNF170 via a luminal N-terminal conserved region in TMUB1 and RNF170 that contacts the SPFH domain of adjacent ERLIN subunits. Loss of both ERLINs limits cholesterol esterification, thereby promoting cholesterol transport from ER to Golgi and regulating Golgi morphology and the secretory pathway.\",\n      \"method\": \"Co-immunoprecipitation, 3D structural modelling, proteomic (omics) analysis, phenotypic characterization of ERLIN1/2 double-KO HeLa cells, cholesterol transport assays\",\n      \"journal\": \"Life science alliance\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — structural modelling plus reciprocal co-IP, KO with defined phenotypic readouts, lipidomics\",\n      \"pmids\": [\"38782601\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"ERLIN1 is required for HCV RNA replication and infectious virus production; siRNA silencing of erlin1 reduces intracellular HCV RNA, protein expression, and virus production, with the requirement mapping to a step after cell entry and primary translation but before/during RNA replication.\",\n      \"method\": \"siRNA knockdown, HCV infection assays, RNA quantification, protein expression analysis, mechanistic step mapping\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — siRNA KD with defined step-specific mechanistic readouts in a single lab\",\n      \"pmids\": [\"31810281\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Cryo-EM structure of the human erlin1/2 complex reveals a 26-mer cage assembly (13 heterodimers of erlin1 and erlin2), defining a nanometer-sized microdomain on the ER luminal leaflet. Each subunit contains an intramembrane phosphatidylinositol-binding pocket. The complex can cage substrate proteins (e.g., recruiting TMUB1 to interior and exterior of cage), physically secluding them from binding partners; individual cages can cluster to form microdomains of different sizes.\",\n      \"method\": \"Single-particle cryo-EM, structural modelling, functional validation of cargo sequestration\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution cryo-EM structure with functional validation\",\n      \"pmids\": [\"41887216\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Cryo-EM structures of the ER-resident erlin1/2 complex show it assembles as 13 heterodimers (26-mer), with defined inter-subunit interfaces; key interactions underlying the architecture were described and conformational properties elucidated.\",\n      \"method\": \"Single-particle cryo-EM\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 structure, but preprint not yet peer-reviewed; consistent with PMID:41887216\",\n      \"pmids\": [\"bio_10.1101_2025.04.21.649849\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ERLIN1 interacts directly with CYP1A2 via their ER N-terminal signal-anchor domains within detergent-resistant ER membrane microdomains/MAMs; siRNA knockdown of erlin-1 relocates CYP1A2 from DRMs to non-DRMs and impairs its ER-to-lysosomal-associated degradation (ERLAD), resulting in insoluble CYP1A2 aggregates. This ERLAD requirement is rescued by re-expression of erlin-1 or just its N-terminal 1–30 residue signal-anchor domain.\",\n      \"method\": \"SURF split-fluorogenic complementation assay (protein-protein interaction), siRNA knockdown, subcellular fractionation (DRM isolation), rescue with siRNA-resistant constructs, CYP2B1 as proof-of-concept\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — novel in-cell interaction assay plus KD/rescue with multiple P450 substrates; preprint only\",\n      \"pmids\": [\"bio_10.1101_2025.09.25.678692\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"ERLIN1 assembles with ERLIN2 into a ~2 MDa (26-subunit) ring-shaped cage complex in cholesterol-rich, lipid raft-like ER membrane microdomains, where it acts as a scaffold that recruits E3 ubiquitin ligase partners (RNF170, via TMUB1) to mediate the recognition and ERAD of activated IP3Rs by binding their intralumenal loop 3, selectively binds and stabilizes phosphatidylinositol 3-phosphate to sustain autophagic flux, limits cholesterol esterification to promote ER-to-Golgi cholesterol transport, and interacts with AMBRA1 at MAMs to initiate autophagy.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"ERLIN1 is a core subunit of the ER-resident erlin1/2 complex, a 26-subunit (13 heterodimer) ring-shaped cage that organizes cholesterol-rich, lipid raft-like microdomains on the ER membrane to coordinate substrate recognition for ER-associated degradation, lipid homeostasis, and autophagy. The complex recognizes activated IP3 receptors by binding their intralumenal loop 3, acting upstream of polyubiquitination to initiate IP3R ERAD, and scaffolds the E3 ligase RNF170 via TMUB1, physically sequestering substrates within the cage interior [PMID:19240031, PMID:35568199, PMID:41887216, PMID:38782601]. ERLIN1/2 selectively binds phosphatidylinositol 3-phosphate through intramembrane phosphoinositide-binding pockets in each subunit, stabilizing cellular PI(3)P pools to sustain autophagic flux independently of VPS34 kinase activity, and interacts with AMBRA1 at mitochondria-associated membranes to promote autophagosome formation [PMID:39018973, PMID:30135210, PMID:33034545]. Loss of erlin1/2 also limits cholesterol esterification, redirecting cholesterol to the Golgi and altering secretory pathway organization [PMID:38782601].\",\n  \"teleology\": [\n    {\n      \"year\": 2006,\n      \"claim\": \"Establishing ERLIN1's subcellular localization resolved where the protein operates: in cholesterol-dependent, detergent-resistant ER membrane microdomains, with its N-terminus sufficient for ER targeting without classical retrieval motifs.\",\n      \"evidence\": \"Sucrose gradient fractionation, cholesterol depletion, GFP-fusion targeting in mammalian cells\",\n      \"pmids\": [\"16835267\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No function or binding partners identified at this stage\", \"Mechanism of cholesterol-dependent raft association undefined\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Discovery that ERLIN1 and ERLIN2 form a ~2 MDa ring-shaped complex that binds activated IP3Rs upstream of polyubiquitination established the complex as a substrate recognition scaffold in a selective ERAD pathway.\",\n      \"evidence\": \"Native gel/EM structural analysis, RNAi depletion, co-IP, ubiquitination/degradation assays with selective substrate controls (IP3R vs. IκBα vs. HMG-CoA reductase)\",\n      \"pmids\": [\"19240031\", \"19751772\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Binding interface on IP3R not mapped\", \"Identity of ubiquitin ligase recruited by the complex unknown\", \"Stoichiometry and subunit arrangement unresolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrating that ERLIN2 is the dominant IP3R-binding subunit and that the complex selectively binds PI(3)P revealed a lipid-binding function and clarified individual subunit contributions.\",\n      \"evidence\": \"Gene editing (erlin1/erlin2 KO), in vitro lipid-binding assays with recombinant proteins, T65I mutagenesis linked to spastic paraplegia\",\n      \"pmids\": [\"30135210\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of PI(3)P binding unknown\", \"Functional consequence of PI(3)P binding on autophagy not yet tested\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"ERLIN1 was identified as a host factor required for HCV RNA replication at a post-entry step, extending its functional scope beyond ERAD to viral exploitation of ER membrane platforms.\",\n      \"evidence\": \"siRNA knockdown in HCV-infected cells with stepwise mechanistic dissection\",\n      \"pmids\": [\"31810281\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of ERLIN1 contribution to viral replication complex assembly unknown\", \"Single-lab finding without independent replication\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Linking ERLIN1 to AMBRA1 at MAMs established a role in starvation-induced autophagosome formation dependent on ganglioside GD3 and MFN2, connecting the complex to autophagy initiation.\",\n      \"evidence\": \"FRET, co-IP, siRNA knockdown of ERLIN1/ST8SIA1/MFN2, LC3-II flux assays, MAM fractionation\",\n      \"pmids\": [\"33034545\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct vs. indirect nature of ERLIN1–AMBRA1 interaction unclear\", \"Relationship between PI(3)P binding and MAM autophagy function not tested\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Mapping the erlin1/2 binding site to IP3R1 intralumenal loop 3 (D2471/R2472) and showing that ubiquitin-activating enzyme inhibition does not disrupt this binding definitively placed erlin complex recognition as the initiating event in IP3R ERAD.\",\n      \"evidence\": \"Site-directed mutagenesis of IP3R1, co-IP, TAK-243 pharmacological dissection\",\n      \"pmids\": [\"35568199\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How IP3R activation exposes the loop 3 binding site is undefined\", \"No structural model of the erlin–IP3R interface\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Two parallel advances clarified downstream functions: direct PI(3)P binding by the complex stabilizes ~50% of cellular PI(3)P to sustain autophagic flux independently of VPS34, while loss of erlin1/2 limits cholesterol esterification, promoting ER-to-Golgi cholesterol transport and reshaping Golgi morphology.\",\n      \"evidence\": \"Recombinant PI(3)P binding assays, erlin1/2 KO with PI(3)P quantification and autophagy readouts (PMID:39018973); double-KO HeLa cells with lipidomics, cholesterol transport assays, co-IP mapping TMUB1–RNF170 scaffold (PMID:38782601)\",\n      \"pmids\": [\"39018973\", \"38782601\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for PI(3)P sequestration within the cage not resolved at atomic level\", \"Mechanism linking cholesterol esterification to erlin complex presence is correlative\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Cryo-EM structures revealed the 26-mer cage architecture (13 erlin1/2 heterodimers) with intramembrane phosphoinositide-binding pockets and demonstrated physical sequestration of TMUB1 cargo within the cage, providing the structural framework for all previously described functions.\",\n      \"evidence\": \"Single-particle cryo-EM at near-atomic resolution with functional validation of cargo caging\",\n      \"pmids\": [\"41887216\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of the complete erlin–IP3R–RNF170 degradation complex not determined\", \"Dynamics of cage assembly/disassembly in response to stimuli unknown\", \"Mechanism by which cage clustering creates larger microdomains needs characterization\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Outstanding questions include how the erlin cage dynamically remodels upon substrate engagement, whether PI(3)P binding and IP3R ERAD functions are coordinated or independent within the same cage, and how erlin1 vs. erlin2 subunit contributions specify distinct substrate selectivities.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No time-resolved structural data on cage dynamics during ERAD\", \"Relationship between PI(3)P stabilization and ERAD substrate processing within the cage unclear\", \"In vivo physiological consequences of erlin1 loss vs. erlin2 loss not systematically compared in animal models\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [3, 6, 9]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 5, 7]},\n      {\"term_id\": \"GO:0140313\", \"supporting_discovery_ids\": [9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0, 1, 9]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [1, 2, 5, 7]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [4, 6]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"complexes\": [\n      \"erlin1/erlin2 26-mer cage complex\"\n    ],\n    \"partners\": [\n      \"ERLIN2\",\n      \"ITPR1\",\n      \"RNF170\",\n      \"TMUB1\",\n      \"AMBRA1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}