{"gene":"SDF2L1","run_date":"2026-06-10T07:46:30","timeline":{"discoveries":[{"year":2001,"finding":"SDF2L1 is an ER-resident protein containing a C-terminal HDEL ER-retention motif, and its expression is strongly induced by ER stress (tunicamycin, calcium ionophore A23187) but not by cycloheximide, establishing it as an ER stress-inducible gene. The protein shows sequence similarity to the Pmt/rt family of protein O-mannosyltransferases.","method":"Northern blot, sequence analysis, tunicamycin/A23187/cycloheximide treatment of murine hepatocellular carcinoma cells","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct induction assays with multiple ER stress agents and sequence-based domain identification, single lab","pmids":["11162531"],"is_preprint":false},{"year":2013,"finding":"SDF2L1 interacts with the ER chaperone GRP78/BiP, ERAD machinery components, and misfolded proinsulin (C96Y mutant) in pancreatic β-cells. Knockdown of SDF2L1 accelerated degradation of mutant proinsulin, indicating SDF2L1 retards ERAD substrate availability, likely by prolonging the time available for substrate refolding.","method":"Co-immunoprecipitation, binding assays, SDF2L1 knockdown in INS-1 cells expressing insulin-C96Y-GFP with pulse-chase degradation assays","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP/binding assays combined with functional KD and degradation kinetics, single lab with multiple orthogonal methods","pmids":["23444373"],"is_preprint":false},{"year":2017,"finding":"SDF2L1 (and its paralog SDF2) forms a stable complex with ERdj3 (DNAJB11) in the ER lumen. The ERdj3-SDF2L1 complex associates with non-native (misfolded) proteins and potently inhibits their aggregation, acting as a component of the BiP chaperone cycle. A dominant-negative ERdj3 mutant that blocks ERdj3-BiP interaction prevented release of misfolded cargo from the ERdj3-SDF2L1 complex.","method":"Co-immunoprecipitation, in vitro aggregation assays, dominant-negative ERdj3 mutant, subcellular fractionation confirming ER localization","journal":"Genes to cells : devoted to molecular & cellular mechanisms","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro aggregation reconstitution combined with Co-IP and dominant-negative mutagenesis, single lab with multiple orthogonal methods","pmids":["28597544"],"is_preprint":false},{"year":2019,"finding":"SDF2L1 retains ERdj3 in the ER by direct complex formation: in its absence, ERdj3 is secreted. The ERdj3-SDF2L1 complex incorporates two SDF2L1 molecules per ERdj3 dimer (whereas ERdj3 alone forms a homotetramer). The ERdj3-SDF2L1 complex suppressed ER protein aggregation independently of substrate transfer to BiP, and maintained denatured GSH S-transferase (GST) in a soluble oligomeric state in vitro. Chaperone activity of ERdj3-SDF2L1 complex was higher than ERdj3 alone both in cellulo and in vitro.","method":"In vitro reconstitution, in vitro aggregation assays with denatured GST, stoichiometry analysis, cell-based secretion assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution and aggregation suppression assays with stoichiometric analysis, complemented by cell-based secretion experiments, single lab","pmids":["31624144"],"is_preprint":false},{"year":2008,"finding":"SDF2L1 physically interacts with α-, β-, and θ-defensin propeptides in the ER. Domain-mapping showed that α- and β-defensins bind SDF2L1 via the same domain, whereas θ-defensins (proRTD1a) engage a distinct SDF2L1 domain, suggesting differential chaperone/sorting roles for the three defensin subfamilies.","method":"Yeast two-hybrid screen with proRTD1a as bait, followed by domain mapping of SDF2L1 interactions with representative defensin propeptides","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — yeast two-hybrid identification plus domain requirement mapping, single lab","pmids":["19109254"],"is_preprint":false},{"year":2019,"finding":"Hepatic Sdf2l1 regulates ERAD through physical interaction with the trafficking/cargo receptor protein TMED10. Liver-specific suppression of Sdf2l1 caused sustained ER stress, insulin resistance, and elevated triglyceride content. Restoration of Sdf2l1 expression in obese/diabetic mice ameliorated glucose intolerance and fatty liver with decreased ER stress. XBP-1s was identified as a transcriptional regulator controlling Sdf2l1 expression.","method":"Co-immunoprecipitation (Sdf2l1-TMED10), liver-specific knockdown/rescue in mice, metabolic phenotyping (glucose/insulin tolerance tests, triglyceride measurement), XBP-1s overexpression","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP identifying TMED10 partner, combined with in vivo KD and rescue experiments with defined metabolic readouts, replicated across multiple mouse models","pmids":["30814508"],"is_preprint":false},{"year":2025,"finding":"SDF2 and SDF2L1 are essential co-factors of DNAJB11 (ERdj3) required for Polycystin-1 (PC1) processing. Interaction proteomics identified SDF2 and SDF2L1 as strong DNAJB11-interacting proteins. Knockout of both SDF2 and SDF2L1 impaired PC1 processing, phenocopying loss of DNAJB11. There is reciprocal interdependence of DNAJB11 and SDF2/SDF2L1 protein abundance. Re-expression of SDF2 or SDF2L1 individually in double-KO cells restored PC1 processing.","method":"Unbiased interaction proteomics (MS), CRISPR knockout cell lines (single and double KO), Western blot for PC1 processing, re-expression rescue experiments","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — interaction proteomics combined with KO cell lines, biochemical rescue, and PC1 processing assay as functional readout, single lab with multiple orthogonal methods","pmids":["41109348"],"is_preprint":false},{"year":2025,"finding":"In Schwann cells, SDF2L1 downregulation (by high glucose or KO) reduces KPNA3 (importin-α) expression, which in turn impedes nuclear import of transcription factors TFEB and CREB, leading to decreased autophagy markers (LC3-II, P62) and neurotrophins (BDNF, NGF, IGF). Overexpression of KPNA3 reversed the SDF2L1-KD-induced deficits in vitro and in vivo.","method":"RNA-seq, proteomics, SDF2L1 KD/KO in RSC96 and primary Schwann cells, KPNA3 overexpression rescue, nuclear fractionation for TFEB/CREB localization, in vivo SDF2L1 KO mice (nerve conduction velocity, action potential amplitude)","journal":"Experimental neurology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KD/KO with rescue and nuclear fractionation, multiple readouts, single lab","pmids":["40294738"],"is_preprint":false},{"year":2026,"finding":"SDF2L1 levels positively regulate O-mannosyltransferase (POMT) enzyme content in cells; Sdf2l1 knockout mice show reduced O-mannosyltransferase levels and altered protein O-mannosylation profiles (including increased TLR4 and MCM8 O-mannosylation), linking SDF2L1 to regulation of the O-mannosylation machinery.","method":"CRISPR-Cas9 Sdf2l1 KO mice, LC-MS/MS glycoproteomics, ELISA for O-mannosyltransferase, Western blotting in KD/OE cell lines treated with oxLDL","journal":"Cellular and molecular life sciences : CMLS","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo KO combined with glycoproteomics and enzymatic assays, single lab","pmids":["41781544"],"is_preprint":false}],"current_model":"SDF2L1 is an ER-resident, stress-inducible chaperone co-factor that forms a stable complex with ERdj3 (DNAJB11) to prevent aggregation of misfolded ER client proteins (including Polycystin-1), retains ERdj3 in the ER (preventing its secretion), buffers substrate availability for ERAD (interacting with GRP78/BiP and ERAD machinery), regulates ERAD via interaction with the cargo receptor TMED10 downstream of XBP-1s transcriptional induction, and in non-ER contexts controls nuclear import of TFEB/CREB via KPNA3 in Schwann cells and regulates protein O-mannosylation levels."},"narrative":{"mechanistic_narrative":"SDF2L1 is an ER-resident, stress-inducible chaperone co-factor that operates within the BiP/ERdj3 chaperone cycle to suppress aggregation of misfolded ER client proteins and govern their disposal [PMID:11162531, PMID:28597544]. First identified as a tunicamycin- and calcium-ionophore-inducible ER luminal protein bearing a C-terminal HDEL retention motif and similarity to the Pmt/rt O-mannosyltransferase family [PMID:11162531], it forms a stable complex with the J-domain protein ERdj3 (DNAJB11), incorporating two SDF2L1 molecules per ERdj3 dimer; this complex binds non-native proteins and inhibits their aggregation more potently than ERdj3 alone, and can hold denatured substrate in a soluble oligomeric state independently of transfer to BiP [PMID:28597544, PMID:31624144]. SDF2L1 also retains ERdj3 in the ER, preventing its secretion [PMID:31624144]. Functionally, SDF2L1 associates with GRP78/BiP and ERAD machinery and retards degradation of misfolded substrates such as mutant proinsulin, buffering substrate availability to extend the window for refolding [PMID:23444373], and controls ERAD through physical interaction with the cargo receptor TMED10 downstream of XBP-1s transcriptional induction, a circuit whose hepatic disruption produces sustained ER stress, insulin resistance, and fatty liver in mice [PMID:30814508]. Together with SDF2, SDF2L1 is an essential, interchangeable co-factor required for DNAJB11-dependent processing of Polycystin-1 [PMID:41109348]. Beyond the ER, SDF2L1 has been linked to KPNA3-dependent nuclear import of TFEB/CREB in Schwann cells [PMID:40294738] and to regulation of cellular O-mannosyltransferase content and protein O-mannosylation profiles [PMID:41781544].","teleology":[{"year":2001,"claim":"Established SDF2L1 as a bona fide ER stress-response gene by showing its induction is specific to ER stressors and that it carries an ER-retention signal, framing it as a candidate ER quality-control factor.","evidence":"Northern blot and sequence analysis after tunicamycin/A23187/cycloheximide treatment of murine hepatoma cells","pmids":["11162531"],"confidence":"Medium","gaps":["No protein partners identified","Functional role beyond stress induction not tested","O-mannosyltransferase similarity not functionally validated"]},{"year":2008,"claim":"Provided the first physical interactors of SDF2L1, showing it binds defensin propeptides through distinct domains, hinting at a chaperone/sorting role for secreted client proteins.","evidence":"Yeast two-hybrid screen with proRTD1a bait plus domain mapping","pmids":["19109254"],"confidence":"Medium","gaps":["Y2H interactions not validated in mammalian ER","No functional consequence on defensin maturation shown","Single screen without reciprocal validation"]},{"year":2013,"claim":"Connected SDF2L1 to the BiP/ERAD axis by showing it binds GRP78/BiP, ERAD machinery, and a misfolded substrate, and that its loss accelerates substrate degradation — establishing it as a buffer of ERAD substrate availability.","evidence":"Reciprocal Co-IP and SDF2L1 knockdown with pulse-chase degradation assays in INS-1 β-cells expressing insulin-C96Y-GFP","pmids":["23444373"],"confidence":"High","gaps":["Direct vs indirect nature of BiP/ERAD interactions not dissected","ERdj3 not yet identified as the central partner","Mechanism of substrate retention unresolved"]},{"year":2017,"claim":"Defined the core mechanism: SDF2L1 forms a stable ER-luminal complex with ERdj3/DNAJB11 that binds non-native proteins and inhibits aggregation as part of the BiP cycle, with substrate release dependent on ERdj3-BiP interaction.","evidence":"Co-IP, in vitro aggregation assays, dominant-negative ERdj3 mutant, subcellular fractionation","pmids":["28597544"],"confidence":"High","gaps":["Stoichiometry of the complex not yet determined","Whether anti-aggregation requires BiP transfer unclear","Structural basis of binding unknown"]},{"year":2019,"claim":"Resolved complex architecture and an autonomous chaperone function: two SDF2L1 molecules bind each ERdj3 dimer, retain ERdj3 in the ER, and confer aggregation suppression that exceeds ERdj3 alone and is independent of substrate transfer to BiP.","evidence":"In vitro reconstitution with denatured GST, stoichiometry analysis, cell-based secretion assays","pmids":["31624144"],"confidence":"High","gaps":["High-resolution structure of the complex absent","Range of physiological clients not mapped","Interplay with the BiP cycle in vivo not fully defined"]},{"year":2019,"claim":"Placed SDF2L1 in a physiological ERAD/metabolic circuit by identifying TMED10 as a partner and XBP-1s as its transcriptional regulator, with in vivo rescue demonstrating causal contribution to hepatic ER stress and metabolic disease.","evidence":"Co-IP (Sdf2l1-TMED10), liver-specific knockdown/rescue in mice with metabolic phenotyping, XBP-1s overexpression","pmids":["30814508"],"confidence":"High","gaps":["Mechanistic link between TMED10 binding and ERAD output not detailed","Relationship between TMED10 and ERdj3 complexes unresolved","Human relevance not established"]},{"year":2025,"claim":"Demonstrated functional essentiality and redundancy of SDF2L1 with its paralog SDF2 as DNAJB11 co-factors required for processing of a defined client, Polycystin-1.","evidence":"Interaction proteomics, single/double CRISPR knockouts, PC1 processing Western blots, individual re-expression rescue","pmids":["41109348"],"confidence":"High","gaps":["Biochemical step in PC1 processing that requires the complex undefined","Generality across other DNAJB11 clients untested","Basis of SDF2/SDF2L1 reciprocal abundance dependence unknown"]},{"year":2025,"claim":"Extended SDF2L1 function beyond the ER lumen, linking it to KPNA3-dependent nuclear import of TFEB/CREB and downstream autophagy/neurotrophin programs in Schwann cells.","evidence":"RNA-seq/proteomics, SDF2L1 KD/KO in RSC96 and primary Schwann cells, KPNA3 overexpression rescue, nuclear fractionation, in vivo KO mice electrophysiology","pmids":["40294738"],"confidence":"Medium","gaps":["Mechanism linking ER chaperone SDF2L1 to cytosolic KPNA3 levels unexplained","Direct vs indirect regulation of KPNA3 not resolved","Single lab"]},{"year":2026,"claim":"Connected SDF2L1 to the O-mannosylation machinery, showing it positively regulates O-mannosyltransferase content and shapes cellular O-mannosylation profiles.","evidence":"CRISPR Sdf2l1 KO mice, LC-MS/MS glycoproteomics, ELISA for O-mannosyltransferase, KD/OE cell lines","pmids":["41781544"],"confidence":"Medium","gaps":["Whether SDF2L1 directly stabilizes POMT enzymes or acts indirectly unknown","Functional consequence of altered TLR4/MCM8 O-mannosylation not established","Single lab"]},{"year":null,"claim":"How SDF2L1's ER-luminal chaperone activity mechanistically connects to its reported cytosolic/nuclear (KPNA3-TFEB/CREB) and O-mannosylation roles, and the structural basis of client engagement, remain open.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structure of the ERdj3-SDF2L1 complex","No unifying mechanism linking ER and non-ER functions","Human disease causation not established in the corpus"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0044183","term_label":"protein folding chaperone","supporting_discovery_ids":[2,3]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1,5]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[0,2,3]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[1,2,6]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[0,5]}],"complexes":["ERdj3 (DNAJB11)-SDF2L1 complex"],"partners":["DNAJB11","HSPA5","TMED10","SDF2","KPNA3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9HCN8","full_name":"Stromal cell-derived factor 2-like protein 1","aliases":["PWP1-interacting protein 8"],"length_aa":221,"mass_kda":23.6,"function":"","subcellular_location":"Endoplasmic reticulum lumen","url":"https://www.uniprot.org/uniprotkb/Q9HCN8/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SDF2L1","classification":"Not Classified","n_dependent_lines":101,"n_total_lines":1208,"dependency_fraction":0.0836092715231788},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"SNX1","stoichiometry":0.2},{"gene":"SNX2","stoichiometry":0.2},{"gene":"SNX5","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/SDF2L1","total_profiled":1310},"omim":[{"mim_id":"607551","title":"STROMAL CELL-DERIVED FACTOR 2-LIKE 1; SDF2L1","url":"https://www.omim.org/entry/607551"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"liver","ntpm":167.9}],"url":"https://www.proteinatlas.org/search/SDF2L1"},"hgnc":{"alias_symbol":["AP000553.C22.4","OTTHUMT00000075032"],"prev_symbol":[]},"alphafold":{"accession":"Q9HCN8","domains":[{"cath_id":"2.80.10.50","chopping":"38-207","consensus_level":"high","plddt":97.1095,"start":38,"end":207}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9HCN8","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9HCN8-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9HCN8-F1-predicted_aligned_error_v6.png","plddt_mean":88.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SDF2L1","jax_strain_url":"https://www.jax.org/strain/search?query=SDF2L1"},"sequence":{"accession":"Q9HCN8","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9HCN8.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9HCN8/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9HCN8"}},"corpus_meta":[{"pmid":"30814508","id":"PMC_30814508","title":"Hepatic Sdf2l1 controls feeding-induced ER stress and regulates metabolism.","date":"2019","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/30814508","citation_count":67,"is_preprint":false},{"pmid":"11162531","id":"PMC_11162531","title":"Murine and human SDF2L1 is an endoplasmic reticulum stress-inducible gene and encodes a new member of the Pmt/rt protein family.","date":"2001","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/11162531","citation_count":62,"is_preprint":false},{"pmid":"23444373","id":"PMC_23444373","title":"SDF2L1 interacts with the ER-associated degradation machinery and retards the degradation of mutant proinsulin in pancreatic β-cells.","date":"2013","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/23444373","citation_count":36,"is_preprint":false},{"pmid":"28597544","id":"PMC_28597544","title":"Endoplasmic reticulum proteins SDF2 and SDF2L1 act as components of the BiP chaperone cycle to prevent protein aggregation.","date":"2017","source":"Genes to cells : devoted to molecular & cellular mechanisms","url":"https://pubmed.ncbi.nlm.nih.gov/28597544","citation_count":31,"is_preprint":false},{"pmid":"31624144","id":"PMC_31624144","title":"SDF2-like protein 1 (SDF2L1) regulates the endoplasmic reticulum localization and chaperone activity of ERdj3 protein.","date":"2019","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/31624144","citation_count":28,"is_preprint":false},{"pmid":"19109254","id":"PMC_19109254","title":"SDF2L1, a component of the endoplasmic reticulum chaperone complex, differentially interacts with {alpha}-, {beta}-, and {theta}-defensin propeptides.","date":"2008","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/19109254","citation_count":17,"is_preprint":false},{"pmid":"33134371","id":"PMC_33134371","title":"SDF2L1 Inhibits Cell Proliferation, Migration, and Invasion in Nasopharyngeal Carcinoma.","date":"2020","source":"BioMed research international","url":"https://pubmed.ncbi.nlm.nih.gov/33134371","citation_count":9,"is_preprint":false},{"pmid":"36674879","id":"PMC_36674879","title":"Dysregulated UPR and ER Stress Related to a Mutation in the Sdf2l1 Gene Are Involved in the Pathophysiology of Diet-Induced Diabetes in the Cohen Diabetic Rat.","date":"2023","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/36674879","citation_count":8,"is_preprint":false},{"pmid":"35559353","id":"PMC_35559353","title":"Identification of Phosphorylated Proteins Regulated by SDF2L1 in Nasopharyngeal Carcinoma Cells.","date":"2022","source":"Evolutionary bioinformatics online","url":"https://pubmed.ncbi.nlm.nih.gov/35559353","citation_count":4,"is_preprint":false},{"pmid":"40294738","id":"PMC_40294738","title":"SDF2L1 downregulation mediates high glucose-caused Schwann cell dysfunction by inhibiting nuclear import of TFEB and CREB via KPNA3.","date":"2025","source":"Experimental neurology","url":"https://pubmed.ncbi.nlm.nih.gov/40294738","citation_count":3,"is_preprint":false},{"pmid":"33364514","id":"PMC_33364514","title":"Pharmacologic inhibition of serotonin htr2b ameliorates hyperglycemia and the altered expression of hepatic FGF21, Sdf2l1, and htr2a in db/db mice and KKAy mice.","date":"2020","source":"Heliyon","url":"https://pubmed.ncbi.nlm.nih.gov/33364514","citation_count":3,"is_preprint":false},{"pmid":"35601144","id":"PMC_35601144","title":"Corrigendum to \"SDF2L1 Inhibits Cell Proliferation, Migration, and Invasion in Nasopharyngeal Carcinoma\".","date":"2022","source":"BioMed research international","url":"https://pubmed.ncbi.nlm.nih.gov/35601144","citation_count":1,"is_preprint":false},{"pmid":"41109348","id":"PMC_41109348","title":"SDF2 and SDF2L1 are essential co-factors of DNAJB11 for Polycystin-1 processing.","date":"2025","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/41109348","citation_count":0,"is_preprint":false},{"pmid":"41781544","id":"PMC_41781544","title":"SDF2L1 modulates oxLDL-induced endoplasmic reticulum stress, protein aggregation, and O-mannosylation in myocardial infarction and lung cancer.","date":"2026","source":"Cellular and molecular life sciences : CMLS","url":"https://pubmed.ncbi.nlm.nih.gov/41781544","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9117,"output_tokens":2763,"usd":0.034398,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9970,"output_tokens":3477,"usd":0.068388,"stage2_stop_reason":"end_turn"},"total_usd":0.102786,"stage1_batch_id":"msgbatch_013LWZZT6MWaqB9qyTSeQBmU","stage2_batch_id":"msgbatch_0194ZzQaTGNpruoNJBbEMbt3","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2001,\n      \"finding\": \"SDF2L1 is an ER-resident protein containing a C-terminal HDEL ER-retention motif, and its expression is strongly induced by ER stress (tunicamycin, calcium ionophore A23187) but not by cycloheximide, establishing it as an ER stress-inducible gene. The protein shows sequence similarity to the Pmt/rt family of protein O-mannosyltransferases.\",\n      \"method\": \"Northern blot, sequence analysis, tunicamycin/A23187/cycloheximide treatment of murine hepatocellular carcinoma cells\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct induction assays with multiple ER stress agents and sequence-based domain identification, single lab\",\n      \"pmids\": [\"11162531\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"SDF2L1 interacts with the ER chaperone GRP78/BiP, ERAD machinery components, and misfolded proinsulin (C96Y mutant) in pancreatic β-cells. Knockdown of SDF2L1 accelerated degradation of mutant proinsulin, indicating SDF2L1 retards ERAD substrate availability, likely by prolonging the time available for substrate refolding.\",\n      \"method\": \"Co-immunoprecipitation, binding assays, SDF2L1 knockdown in INS-1 cells expressing insulin-C96Y-GFP with pulse-chase degradation assays\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP/binding assays combined with functional KD and degradation kinetics, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"23444373\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"SDF2L1 (and its paralog SDF2) forms a stable complex with ERdj3 (DNAJB11) in the ER lumen. The ERdj3-SDF2L1 complex associates with non-native (misfolded) proteins and potently inhibits their aggregation, acting as a component of the BiP chaperone cycle. A dominant-negative ERdj3 mutant that blocks ERdj3-BiP interaction prevented release of misfolded cargo from the ERdj3-SDF2L1 complex.\",\n      \"method\": \"Co-immunoprecipitation, in vitro aggregation assays, dominant-negative ERdj3 mutant, subcellular fractionation confirming ER localization\",\n      \"journal\": \"Genes to cells : devoted to molecular & cellular mechanisms\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro aggregation reconstitution combined with Co-IP and dominant-negative mutagenesis, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"28597544\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"SDF2L1 retains ERdj3 in the ER by direct complex formation: in its absence, ERdj3 is secreted. The ERdj3-SDF2L1 complex incorporates two SDF2L1 molecules per ERdj3 dimer (whereas ERdj3 alone forms a homotetramer). The ERdj3-SDF2L1 complex suppressed ER protein aggregation independently of substrate transfer to BiP, and maintained denatured GSH S-transferase (GST) in a soluble oligomeric state in vitro. Chaperone activity of ERdj3-SDF2L1 complex was higher than ERdj3 alone both in cellulo and in vitro.\",\n      \"method\": \"In vitro reconstitution, in vitro aggregation assays with denatured GST, stoichiometry analysis, cell-based secretion assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution and aggregation suppression assays with stoichiometric analysis, complemented by cell-based secretion experiments, single lab\",\n      \"pmids\": [\"31624144\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"SDF2L1 physically interacts with α-, β-, and θ-defensin propeptides in the ER. Domain-mapping showed that α- and β-defensins bind SDF2L1 via the same domain, whereas θ-defensins (proRTD1a) engage a distinct SDF2L1 domain, suggesting differential chaperone/sorting roles for the three defensin subfamilies.\",\n      \"method\": \"Yeast two-hybrid screen with proRTD1a as bait, followed by domain mapping of SDF2L1 interactions with representative defensin propeptides\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — yeast two-hybrid identification plus domain requirement mapping, single lab\",\n      \"pmids\": [\"19109254\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Hepatic Sdf2l1 regulates ERAD through physical interaction with the trafficking/cargo receptor protein TMED10. Liver-specific suppression of Sdf2l1 caused sustained ER stress, insulin resistance, and elevated triglyceride content. Restoration of Sdf2l1 expression in obese/diabetic mice ameliorated glucose intolerance and fatty liver with decreased ER stress. XBP-1s was identified as a transcriptional regulator controlling Sdf2l1 expression.\",\n      \"method\": \"Co-immunoprecipitation (Sdf2l1-TMED10), liver-specific knockdown/rescue in mice, metabolic phenotyping (glucose/insulin tolerance tests, triglyceride measurement), XBP-1s overexpression\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP identifying TMED10 partner, combined with in vivo KD and rescue experiments with defined metabolic readouts, replicated across multiple mouse models\",\n      \"pmids\": [\"30814508\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SDF2 and SDF2L1 are essential co-factors of DNAJB11 (ERdj3) required for Polycystin-1 (PC1) processing. Interaction proteomics identified SDF2 and SDF2L1 as strong DNAJB11-interacting proteins. Knockout of both SDF2 and SDF2L1 impaired PC1 processing, phenocopying loss of DNAJB11. There is reciprocal interdependence of DNAJB11 and SDF2/SDF2L1 protein abundance. Re-expression of SDF2 or SDF2L1 individually in double-KO cells restored PC1 processing.\",\n      \"method\": \"Unbiased interaction proteomics (MS), CRISPR knockout cell lines (single and double KO), Western blot for PC1 processing, re-expression rescue experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — interaction proteomics combined with KO cell lines, biochemical rescue, and PC1 processing assay as functional readout, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"41109348\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In Schwann cells, SDF2L1 downregulation (by high glucose or KO) reduces KPNA3 (importin-α) expression, which in turn impedes nuclear import of transcription factors TFEB and CREB, leading to decreased autophagy markers (LC3-II, P62) and neurotrophins (BDNF, NGF, IGF). Overexpression of KPNA3 reversed the SDF2L1-KD-induced deficits in vitro and in vivo.\",\n      \"method\": \"RNA-seq, proteomics, SDF2L1 KD/KO in RSC96 and primary Schwann cells, KPNA3 overexpression rescue, nuclear fractionation for TFEB/CREB localization, in vivo SDF2L1 KO mice (nerve conduction velocity, action potential amplitude)\",\n      \"journal\": \"Experimental neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KD/KO with rescue and nuclear fractionation, multiple readouts, single lab\",\n      \"pmids\": [\"40294738\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"SDF2L1 levels positively regulate O-mannosyltransferase (POMT) enzyme content in cells; Sdf2l1 knockout mice show reduced O-mannosyltransferase levels and altered protein O-mannosylation profiles (including increased TLR4 and MCM8 O-mannosylation), linking SDF2L1 to regulation of the O-mannosylation machinery.\",\n      \"method\": \"CRISPR-Cas9 Sdf2l1 KO mice, LC-MS/MS glycoproteomics, ELISA for O-mannosyltransferase, Western blotting in KD/OE cell lines treated with oxLDL\",\n      \"journal\": \"Cellular and molecular life sciences : CMLS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo KO combined with glycoproteomics and enzymatic assays, single lab\",\n      \"pmids\": [\"41781544\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SDF2L1 is an ER-resident, stress-inducible chaperone co-factor that forms a stable complex with ERdj3 (DNAJB11) to prevent aggregation of misfolded ER client proteins (including Polycystin-1), retains ERdj3 in the ER (preventing its secretion), buffers substrate availability for ERAD (interacting with GRP78/BiP and ERAD machinery), regulates ERAD via interaction with the cargo receptor TMED10 downstream of XBP-1s transcriptional induction, and in non-ER contexts controls nuclear import of TFEB/CREB via KPNA3 in Schwann cells and regulates protein O-mannosylation levels.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SDF2L1 is an ER-resident, stress-inducible chaperone co-factor that operates within the BiP/ERdj3 chaperone cycle to suppress aggregation of misfolded ER client proteins and govern their disposal [#0, #2]. First identified as a tunicamycin- and calcium-ionophore-inducible ER luminal protein bearing a C-terminal HDEL retention motif and similarity to the Pmt/rt O-mannosyltransferase family [#0], it forms a stable complex with the J-domain protein ERdj3 (DNAJB11), incorporating two SDF2L1 molecules per ERdj3 dimer; this complex binds non-native proteins and inhibits their aggregation more potently than ERdj3 alone, and can hold denatured substrate in a soluble oligomeric state independently of transfer to BiP [#2, #3]. SDF2L1 also retains ERdj3 in the ER, preventing its secretion [#3]. Functionally, SDF2L1 associates with GRP78/BiP and ERAD machinery and retards degradation of misfolded substrates such as mutant proinsulin, buffering substrate availability to extend the window for refolding [#1], and controls ERAD through physical interaction with the cargo receptor TMED10 downstream of XBP-1s transcriptional induction, a circuit whose hepatic disruption produces sustained ER stress, insulin resistance, and fatty liver in mice [#5]. Together with SDF2, SDF2L1 is an essential, interchangeable co-factor required for DNAJB11-dependent processing of Polycystin-1 [#6]. Beyond the ER, SDF2L1 has been linked to KPNA3-dependent nuclear import of TFEB/CREB in Schwann cells [#7] and to regulation of cellular O-mannosyltransferase content and protein O-mannosylation profiles [#8].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Established SDF2L1 as a bona fide ER stress-response gene by showing its induction is specific to ER stressors and that it carries an ER-retention signal, framing it as a candidate ER quality-control factor.\",\n      \"evidence\": \"Northern blot and sequence analysis after tunicamycin/A23187/cycloheximide treatment of murine hepatoma cells\",\n      \"pmids\": [\"11162531\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No protein partners identified\", \"Functional role beyond stress induction not tested\", \"O-mannosyltransferase similarity not functionally validated\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Provided the first physical interactors of SDF2L1, showing it binds defensin propeptides through distinct domains, hinting at a chaperone/sorting role for secreted client proteins.\",\n      \"evidence\": \"Yeast two-hybrid screen with proRTD1a bait plus domain mapping\",\n      \"pmids\": [\"19109254\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Y2H interactions not validated in mammalian ER\", \"No functional consequence on defensin maturation shown\", \"Single screen without reciprocal validation\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Connected SDF2L1 to the BiP/ERAD axis by showing it binds GRP78/BiP, ERAD machinery, and a misfolded substrate, and that its loss accelerates substrate degradation — establishing it as a buffer of ERAD substrate availability.\",\n      \"evidence\": \"Reciprocal Co-IP and SDF2L1 knockdown with pulse-chase degradation assays in INS-1 β-cells expressing insulin-C96Y-GFP\",\n      \"pmids\": [\"23444373\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct vs indirect nature of BiP/ERAD interactions not dissected\", \"ERdj3 not yet identified as the central partner\", \"Mechanism of substrate retention unresolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Defined the core mechanism: SDF2L1 forms a stable ER-luminal complex with ERdj3/DNAJB11 that binds non-native proteins and inhibits aggregation as part of the BiP cycle, with substrate release dependent on ERdj3-BiP interaction.\",\n      \"evidence\": \"Co-IP, in vitro aggregation assays, dominant-negative ERdj3 mutant, subcellular fractionation\",\n      \"pmids\": [\"28597544\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry of the complex not yet determined\", \"Whether anti-aggregation requires BiP transfer unclear\", \"Structural basis of binding unknown\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Resolved complex architecture and an autonomous chaperone function: two SDF2L1 molecules bind each ERdj3 dimer, retain ERdj3 in the ER, and confer aggregation suppression that exceeds ERdj3 alone and is independent of substrate transfer to BiP.\",\n      \"evidence\": \"In vitro reconstitution with denatured GST, stoichiometry analysis, cell-based secretion assays\",\n      \"pmids\": [\"31624144\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"High-resolution structure of the complex absent\", \"Range of physiological clients not mapped\", \"Interplay with the BiP cycle in vivo not fully defined\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Placed SDF2L1 in a physiological ERAD/metabolic circuit by identifying TMED10 as a partner and XBP-1s as its transcriptional regulator, with in vivo rescue demonstrating causal contribution to hepatic ER stress and metabolic disease.\",\n      \"evidence\": \"Co-IP (Sdf2l1-TMED10), liver-specific knockdown/rescue in mice with metabolic phenotyping, XBP-1s overexpression\",\n      \"pmids\": [\"30814508\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanistic link between TMED10 binding and ERAD output not detailed\", \"Relationship between TMED10 and ERdj3 complexes unresolved\", \"Human relevance not established\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Demonstrated functional essentiality and redundancy of SDF2L1 with its paralog SDF2 as DNAJB11 co-factors required for processing of a defined client, Polycystin-1.\",\n      \"evidence\": \"Interaction proteomics, single/double CRISPR knockouts, PC1 processing Western blots, individual re-expression rescue\",\n      \"pmids\": [\"41109348\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Biochemical step in PC1 processing that requires the complex undefined\", \"Generality across other DNAJB11 clients untested\", \"Basis of SDF2/SDF2L1 reciprocal abundance dependence unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Extended SDF2L1 function beyond the ER lumen, linking it to KPNA3-dependent nuclear import of TFEB/CREB and downstream autophagy/neurotrophin programs in Schwann cells.\",\n      \"evidence\": \"RNA-seq/proteomics, SDF2L1 KD/KO in RSC96 and primary Schwann cells, KPNA3 overexpression rescue, nuclear fractionation, in vivo KO mice electrophysiology\",\n      \"pmids\": [\"40294738\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking ER chaperone SDF2L1 to cytosolic KPNA3 levels unexplained\", \"Direct vs indirect regulation of KPNA3 not resolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Connected SDF2L1 to the O-mannosylation machinery, showing it positively regulates O-mannosyltransferase content and shapes cellular O-mannosylation profiles.\",\n      \"evidence\": \"CRISPR Sdf2l1 KO mice, LC-MS/MS glycoproteomics, ELISA for O-mannosyltransferase, KD/OE cell lines\",\n      \"pmids\": [\"41781544\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether SDF2L1 directly stabilizes POMT enzymes or acts indirectly unknown\", \"Functional consequence of altered TLR4/MCM8 O-mannosylation not established\", \"Single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How SDF2L1's ER-luminal chaperone activity mechanistically connects to its reported cytosolic/nuclear (KPNA3-TFEB/CREB) and O-mannosylation roles, and the structural basis of client engagement, remain open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structure of the ERdj3-SDF2L1 complex\", \"No unifying mechanism linking ER and non-ER functions\", \"Human disease causation not established in the corpus\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0044183\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0, 2, 3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [1, 2, 6]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [0, 5]}\n    ],\n    \"complexes\": [\"ERdj3 (DNAJB11)-SDF2L1 complex\"],\n    \"partners\": [\"DNAJB11\", \"HSPA5\", \"TMED10\", \"SDF2\", \"KPNA3\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"faith_supported":6,"faith_total":6,"faith_pct":100.0}}