{"gene":"SSR3","run_date":"2026-06-10T07:46:41","timeline":{"discoveries":[{"year":2021,"finding":"SSR3 (TRAPγ) subunit of the TRAP complex is required to maintain N-linked glycosylation fidelity during ER stress; knockout of SSR3 or SSR4 causes aberrant N-glycosylation, and SSR3 protein levels are regulated in an ER-stress-dependent and UBE2J1-dependent manner, linking upstream N-glycosylation proficiency with downstream ER-associated degradation","method":"Fluorescence-based N-glycosylation detection in individual cells; CRISPR/siRNA knockout of SSR3/SSR4; BiP silencing rescue experiments; UBE2J1-dependent protein level regulation assay","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (fluorescence reporter, KO, rescue, epistasis with BiP/UBE2J1) in a single rigorous study","pmids":["33523898"],"is_preprint":false},{"year":2019,"finding":"A homozygous frameshift variant in SSR3 (c.278_281delAGGA) destabilizes the entire TRAP complex, causing complete loss of SSR3 protein and partial loss of SSR1 and SSR4; wild-type SSR3 re-expression corrects all subunit levels and restores normal glycosylation of GP130 and ICAM1 in patient fibroblasts, confirming SSR3 mutations cause a congenital disorder of glycosylation","method":"Exome sequencing; western blot of TRAP subunits in patient fibroblasts; rescue by wild-type SSR3 expression; glycosylation assay with GP130 and ICAM1 as marker proteins","journal":"Journal of inherited metabolic disease","confidence":"High","confidence_rationale":"Tier 2 / Strong — patient fibroblast biochemistry, rescue experiment, multiple orthogonal readouts in one study","pmids":["30945312"],"is_preprint":false},{"year":2022,"finding":"TRAPγ/SSR3 specifically enables cotranslational and posttranslational translocation of preproinsulin across the ER membrane; its extramembranous domain is primarily cytosolic, distinct from other TRAP subunits; diminished SSR3 leaves TRAPα/SSR1 levels unaffected yet inhibits preproinsulin translocation; acute high glucose upregulates SSR3 and proinsulin protein (without changing mRNA), and SSR3 knockdown blocks glucose-dependent proinsulin biosynthesis upregulation while SSR3 overexpression raises proinsulin levels independently of glucose","method":"siRNA knockdown of TRAPγ/SSR3 in pancreatic β-cell lines and human islets; glucose-stimulation assays; western blot for TRAPα/SSR1 and proinsulin; overexpression of TRAPγ/SSR3","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (KD, OE, glucose stimulation, human islet confirmation) establishing a rate-limiting translocation function","pmids":["34857543"],"is_preprint":false},{"year":2021,"finding":"Deficiency of TRAPβ/SSR2 or TRAPδ/SSR4 reduces steady-state protein levels of other TRAP subunits including TRAPγ/SSR3, and diminishes proinsulin biosynthesis (shown by amino acid pulse labeling as short as 5 minutes); TRAPγ/SSR3 topology is primarily cytosolic; overexpression of TRAPα/SSR1 suppresses proinsulin biosynthesis defects in SSR2-deficient β-cells, positioning SSR2 as a support factor for SSR1 function within the complex","method":"siRNA knockdown of SSR2/SSR4 in pancreatic β-cell lines; amino acid pulse labeling; western blot; rescue by individual TRAP subunit re-expression","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — pulse-labeling directly measures biosynthesis, rescue experiments, multiple subunit perturbations, consistent with independent findings in PMID:34857543","pmids":["33811688"],"is_preprint":false},{"year":2011,"finding":"Trap-γ (SSR3) knockout in mice causes lethality shortly after birth with retarded embryonic organ growth; mutant placentae display severe vascular network malformation in the labyrinth, reduced blood space area, poor vascular endothelial cell proliferation in the chorionic plate, and increased apoptotic cell death, establishing SSR3 as required for placental vascular development","method":"Genetic knockout mouse model; histology and morphometry of placenta; cell proliferation and apoptosis assays","journal":"Developmental dynamics","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO mouse with defined developmental phenotype and multiple cellular readouts","pmids":["21246656"],"is_preprint":false},{"year":2020,"finding":"A patient with a homozygous start codon variant in SSR3 (TRAPγ) shows absence of TRAPγ protein, disruption of the TRAP complex, impaired protein translocation into the ER, impaired transport to the brush-border membrane, and unbalanced non-occupancy of N-glycosylation sites, demonstrating SSR3 is required for TRAP complex integrity and N-glycosylation site occupancy","method":"Clinical genetics with biochemical characterization in patient cells; protein translocation assay; N-glycosylation site occupancy analysis; brush-border membrane transport assay","journal":"Journal of medical genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — single patient case with multiple biochemical readouts but single lab, no rescue experiment reported","pmids":["32332102"],"is_preprint":false},{"year":2022,"finding":"SSR3 confers susceptibility to paclitaxel (PTX) through regulation of phosphorylation of the ER stress sensor IRE1α; CRISPR KO of SSR3 renders cells resistant to PTX while overexpression sensitizes cells to PTX in breast cancer and glioblastoma models","method":"Genome-wide CRISPR KO screen in glioma cells; CRISPR KO and overexpression in breast cancer and glioma cell lines; intracranial xenograft models; IRE1α phosphorylation assay","journal":"Clinical cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR screen plus functional validation in multiple cell lines and in vivo xenografts, but mechanistic link to IRE1α phosphorylation described in abstract with limited detail","pmids":["35552677"],"is_preprint":false}],"current_model":"SSR3 (TRAPγ) is the cytosolic-domain-bearing subunit of the heterotetrameric ER translocon-associated protein (TRAP) complex that is required for protein translocation across the ER membrane, N-linked glycosylation quality control under ER stress, and TRAP complex stability; it plays a rate-limiting role in preproinsulin translocation and is regulated post-translationally in a UBE2J1- and ER-stress-dependent manner, while also modulating IRE1α phosphorylation to influence cellular responses to paclitaxel."},"narrative":{"mechanistic_narrative":"SSR3 (TRAPγ) is a subunit of the ER membrane translocon-associated protein (TRAP) complex and is required for protein translocation across the ER membrane and for fidelity of N-linked glycosylation [PMID:33523898, PMID:32332102]. SSR3 is essential for the structural integrity of the TRAP complex: loss of SSR3 destabilizes the entire complex with concomitant reduction of SSR1 and SSR4, and re-expression of wild-type SSR3 restores all subunit levels and corrects glycosylation defects [PMID:30945312]. Its extramembranous domain is primarily cytosolic, distinguishing it topologically from other TRAP subunits [PMID:34857543, PMID:33811688]. SSR3 plays a rate-limiting role in cotranslational and posttranslational translocation of preproinsulin: its diminution inhibits preproinsulin translocation without affecting SSR1 levels, acute high glucose upregulates SSR3 protein (independent of mRNA) to drive proinsulin biosynthesis, and SSR3 overexpression raises proinsulin levels even without glucose [PMID:34857543]. SSR3 protein abundance is itself regulated post-translationally in an ER-stress- and UBE2J1-dependent manner, coupling N-glycosylation proficiency to ER-associated degradation [PMID:33523898]. Beyond the secretory pathway, SSR3 is required for placental vascular development in mice [PMID:21246656] and modulates susceptibility to paclitaxel through regulation of IRE1α phosphorylation [PMID:35552677]. Homozygous loss-of-function variants in SSR3 cause a congenital disorder of glycosylation [PMID:30945312, PMID:32332102].","teleology":[{"year":2011,"claim":"Establishing whether SSR3 has an organism-level requirement, knockout defined it as essential for development, particularly placental vascular formation.","evidence":"Genetic knockout mouse with placental histology, proliferation and apoptosis assays","pmids":["21246656"],"confidence":"High","gaps":["Does not connect the developmental phenotype to a specific molecular defect in translocation or glycosylation","Mechanism of vascular endothelial proliferation failure unresolved"]},{"year":2019,"claim":"To test whether SSR3 loss causes human disease and how, a patient frameshift variant was shown to destabilize the whole TRAP complex and impair glycosylation, with rescue confirming causality.","evidence":"Exome sequencing, western blot of TRAP subunits in patient fibroblasts, rescue by wild-type SSR3, glycosylation assay on GP130/ICAM1","pmids":["30945312"],"confidence":"High","gaps":["Does not define which clients depend on SSR3 for translocation versus glycosylation","Structural basis of complex destabilization not resolved"]},{"year":2020,"claim":"A second patient variant (start codon) confirmed SSR3 is required for TRAP integrity, ER translocation, and N-glycosylation site occupancy.","evidence":"Patient-cell biochemistry: translocation assay, glycosylation site occupancy, brush-border transport assay","pmids":["32332102"],"confidence":"Medium","gaps":["Single patient, single lab, no rescue experiment","Tissue-specific consequences not generalized"]},{"year":2021,"claim":"To define SSR3 within ER stress biology, it was shown to maintain N-glycosylation fidelity during ER stress and to be itself regulated post-translationally via UBE2J1, coupling glycosylation status to ERAD.","evidence":"Fluorescence N-glycosylation reporter, CRISPR/siRNA KO of SSR3/SSR4, BiP silencing rescue, UBE2J1-dependent protein level assay","pmids":["33523898"],"confidence":"High","gaps":["Direct biochemical interaction between SSR3 and UBE2J1 not shown","Which glycoproteins are most sensitive to SSR3 loss not enumerated"]},{"year":2021,"claim":"Perturbing other TRAP subunits clarified the interdependence of the complex, showing SSR2/SSR4 loss reduces SSR3 levels and proinsulin biosynthesis, and positioned SSR3 topology as primarily cytosolic.","evidence":"siRNA KD of SSR2/SSR4 in β-cells, amino acid pulse labeling, western blot, subunit re-expression rescue","pmids":["33811688"],"confidence":"High","gaps":["Stoichiometry and direct contacts of SSR3 within the complex not mapped","Does not isolate SSR3-specific function from complex-wide effects"]},{"year":2022,"claim":"Direct interrogation of SSR3 function in β-cells defined a rate-limiting, glucose-responsive role in preproinsulin translocation.","evidence":"siRNA KD and overexpression of SSR3 in β-cell lines and human islets, glucose-stimulation assays, western blot for SSR1 and proinsulin","pmids":["34857543"],"confidence":"High","gaps":["Mechanism of post-transcriptional SSR3 upregulation by glucose not defined","Whether SSR3 acts as a dedicated preproinsulin translocation factor or generally on signal-peptide-bearing clients unresolved"]},{"year":2022,"claim":"A CRISPR screen linked SSR3 to chemotherapy response, showing it modulates paclitaxel susceptibility via IRE1α phosphorylation.","evidence":"Genome-wide CRISPR KO screen in glioma, KO/overexpression in breast and glioma cells, intracranial xenografts, IRE1α phosphorylation assay","pmids":["35552677"],"confidence":"Medium","gaps":["Mechanistic link to IRE1α phosphorylation described with limited detail","Whether the effect depends on TRAP-mediated translocation versus a separable activity not resolved"]},{"year":null,"claim":"How SSR3's cytosolic domain mechanistically promotes translocation of specific clients, and the structural basis of its role in TRAP assembly, remain open.","evidence":"","pmids":[],"confidence":"High","gaps":["No structural model of SSR3 within the assembled translocon","Client selectivity rules for SSR3-dependent translocation unknown","Direct biochemical partners of the cytosolic domain not identified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140104","term_label":"molecular carrier activity","supporting_discovery_ids":[2,5]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[1,3]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[0,2,5]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[2,3]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[2,5]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[0,6]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[1,5]}],"complexes":["TRAP complex (translocon-associated protein complex)"],"partners":["SSR1","SSR2","SSR4","UBE2J1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9UNL2","full_name":"Translocon-associated protein subunit gamma","aliases":["Signal sequence receptor subunit gamma","SSR-gamma"],"length_aa":185,"mass_kda":21.1,"function":"TRAP proteins are part of a complex whose function is to bind calcium to the ER membrane and thereby regulate the retention of ER resident proteins","subcellular_location":"Endoplasmic reticulum membrane","url":"https://www.uniprot.org/uniprotkb/Q9UNL2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SSR3","classification":"Not Classified","n_dependent_lines":36,"n_total_lines":1208,"dependency_fraction":0.029801324503311258},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"SEC61B","stoichiometry":10.0},{"gene":"RPS16","stoichiometry":4.0},{"gene":"CANX","stoichiometry":0.2},{"gene":"CAPZB","stoichiometry":0.2},{"gene":"DDOST","stoichiometry":0.2},{"gene":"DRG1","stoichiometry":0.2},{"gene":"OST4","stoichiometry":0.2},{"gene":"PGRMC1","stoichiometry":0.2},{"gene":"PSPC1","stoichiometry":0.2},{"gene":"RACK1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/SSR3","total_profiled":1310},"omim":[{"mim_id":"606213","title":"SIGNAL SEQUENCE RECEPTOR, GAMMA; SSR3","url":"https://www.omim.org/entry/606213"},{"mim_id":"300090","title":"SIGNAL SEQUENCE RECEPTOR, DELTA; SSR4","url":"https://www.omim.org/entry/300090"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/SSR3"},"hgnc":{"alias_symbol":["TRAPG"],"prev_symbol":[]},"alphafold":{"accession":"Q9UNL2","domains":[{"cath_id":"-","chopping":"27-181","consensus_level":"high","plddt":87.9525,"start":27,"end":181}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UNL2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UNL2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UNL2-F1-predicted_aligned_error_v6.png","plddt_mean":84.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SSR3","jax_strain_url":"https://www.jax.org/strain/search?query=SSR3"},"sequence":{"accession":"Q9UNL2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9UNL2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9UNL2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UNL2"}},"corpus_meta":[{"pmid":"21655990","id":"PMC_21655990","title":"Evidence for biological effects of metformin in 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standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2021,\n      \"finding\": \"SSR3 (TRAPγ) subunit of the TRAP complex is required to maintain N-linked glycosylation fidelity during ER stress; knockout of SSR3 or SSR4 causes aberrant N-glycosylation, and SSR3 protein levels are regulated in an ER-stress-dependent and UBE2J1-dependent manner, linking upstream N-glycosylation proficiency with downstream ER-associated degradation\",\n      \"method\": \"Fluorescence-based N-glycosylation detection in individual cells; CRISPR/siRNA knockout of SSR3/SSR4; BiP silencing rescue experiments; UBE2J1-dependent protein level regulation assay\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (fluorescence reporter, KO, rescue, epistasis with BiP/UBE2J1) in a single rigorous study\",\n      \"pmids\": [\"33523898\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"A homozygous frameshift variant in SSR3 (c.278_281delAGGA) destabilizes the entire TRAP complex, causing complete loss of SSR3 protein and partial loss of SSR1 and SSR4; wild-type SSR3 re-expression corrects all subunit levels and restores normal glycosylation of GP130 and ICAM1 in patient fibroblasts, confirming SSR3 mutations cause a congenital disorder of glycosylation\",\n      \"method\": \"Exome sequencing; western blot of TRAP subunits in patient fibroblasts; rescue by wild-type SSR3 expression; glycosylation assay with GP130 and ICAM1 as marker proteins\",\n      \"journal\": \"Journal of inherited metabolic disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — patient fibroblast biochemistry, rescue experiment, multiple orthogonal readouts in one study\",\n      \"pmids\": [\"30945312\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"TRAPγ/SSR3 specifically enables cotranslational and posttranslational translocation of preproinsulin across the ER membrane; its extramembranous domain is primarily cytosolic, distinct from other TRAP subunits; diminished SSR3 leaves TRAPα/SSR1 levels unaffected yet inhibits preproinsulin translocation; acute high glucose upregulates SSR3 and proinsulin protein (without changing mRNA), and SSR3 knockdown blocks glucose-dependent proinsulin biosynthesis upregulation while SSR3 overexpression raises proinsulin levels independently of glucose\",\n      \"method\": \"siRNA knockdown of TRAPγ/SSR3 in pancreatic β-cell lines and human islets; glucose-stimulation assays; western blot for TRAPα/SSR1 and proinsulin; overexpression of TRAPγ/SSR3\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (KD, OE, glucose stimulation, human islet confirmation) establishing a rate-limiting translocation function\",\n      \"pmids\": [\"34857543\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Deficiency of TRAPβ/SSR2 or TRAPδ/SSR4 reduces steady-state protein levels of other TRAP subunits including TRAPγ/SSR3, and diminishes proinsulin biosynthesis (shown by amino acid pulse labeling as short as 5 minutes); TRAPγ/SSR3 topology is primarily cytosolic; overexpression of TRAPα/SSR1 suppresses proinsulin biosynthesis defects in SSR2-deficient β-cells, positioning SSR2 as a support factor for SSR1 function within the complex\",\n      \"method\": \"siRNA knockdown of SSR2/SSR4 in pancreatic β-cell lines; amino acid pulse labeling; western blot; rescue by individual TRAP subunit re-expression\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — pulse-labeling directly measures biosynthesis, rescue experiments, multiple subunit perturbations, consistent with independent findings in PMID:34857543\",\n      \"pmids\": [\"33811688\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Trap-γ (SSR3) knockout in mice causes lethality shortly after birth with retarded embryonic organ growth; mutant placentae display severe vascular network malformation in the labyrinth, reduced blood space area, poor vascular endothelial cell proliferation in the chorionic plate, and increased apoptotic cell death, establishing SSR3 as required for placental vascular development\",\n      \"method\": \"Genetic knockout mouse model; histology and morphometry of placenta; cell proliferation and apoptosis assays\",\n      \"journal\": \"Developmental dynamics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO mouse with defined developmental phenotype and multiple cellular readouts\",\n      \"pmids\": [\"21246656\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"A patient with a homozygous start codon variant in SSR3 (TRAPγ) shows absence of TRAPγ protein, disruption of the TRAP complex, impaired protein translocation into the ER, impaired transport to the brush-border membrane, and unbalanced non-occupancy of N-glycosylation sites, demonstrating SSR3 is required for TRAP complex integrity and N-glycosylation site occupancy\",\n      \"method\": \"Clinical genetics with biochemical characterization in patient cells; protein translocation assay; N-glycosylation site occupancy analysis; brush-border membrane transport assay\",\n      \"journal\": \"Journal of medical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — single patient case with multiple biochemical readouts but single lab, no rescue experiment reported\",\n      \"pmids\": [\"32332102\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SSR3 confers susceptibility to paclitaxel (PTX) through regulation of phosphorylation of the ER stress sensor IRE1α; CRISPR KO of SSR3 renders cells resistant to PTX while overexpression sensitizes cells to PTX in breast cancer and glioblastoma models\",\n      \"method\": \"Genome-wide CRISPR KO screen in glioma cells; CRISPR KO and overexpression in breast cancer and glioma cell lines; intracranial xenograft models; IRE1α phosphorylation assay\",\n      \"journal\": \"Clinical cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR screen plus functional validation in multiple cell lines and in vivo xenografts, but mechanistic link to IRE1α phosphorylation described in abstract with limited detail\",\n      \"pmids\": [\"35552677\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SSR3 (TRAPγ) is the cytosolic-domain-bearing subunit of the heterotetrameric ER translocon-associated protein (TRAP) complex that is required for protein translocation across the ER membrane, N-linked glycosylation quality control under ER stress, and TRAP complex stability; it plays a rate-limiting role in preproinsulin translocation and is regulated post-translationally in a UBE2J1- and ER-stress-dependent manner, while also modulating IRE1α phosphorylation to influence cellular responses to paclitaxel.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SSR3 (TRAPγ) is a subunit of the ER membrane translocon-associated protein (TRAP) complex and is required for protein translocation across the ER membrane and for fidelity of N-linked glycosylation [#0, #5]. SSR3 is essential for the structural integrity of the TRAP complex: loss of SSR3 destabilizes the entire complex with concomitant reduction of SSR1 and SSR4, and re-expression of wild-type SSR3 restores all subunit levels and corrects glycosylation defects [#1]. Its extramembranous domain is primarily cytosolic, distinguishing it topologically from other TRAP subunits [#2, #3]. SSR3 plays a rate-limiting role in cotranslational and posttranslational translocation of preproinsulin: its diminution inhibits preproinsulin translocation without affecting SSR1 levels, acute high glucose upregulates SSR3 protein (independent of mRNA) to drive proinsulin biosynthesis, and SSR3 overexpression raises proinsulin levels even without glucose [#2]. SSR3 protein abundance is itself regulated post-translationally in an ER-stress- and UBE2J1-dependent manner, coupling N-glycosylation proficiency to ER-associated degradation [#0]. Beyond the secretory pathway, SSR3 is required for placental vascular development in mice [#4] and modulates susceptibility to paclitaxel through regulation of IRE1α phosphorylation [#6]. Homozygous loss-of-function variants in SSR3 cause a congenital disorder of glycosylation [#1, #5].\",\n  \"teleology\": [\n    {\n      \"year\": 2011,\n      \"claim\": \"Establishing whether SSR3 has an organism-level requirement, knockout defined it as essential for development, particularly placental vascular formation.\",\n      \"evidence\": \"Genetic knockout mouse with placental histology, proliferation and apoptosis assays\",\n      \"pmids\": [\"21246656\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not connect the developmental phenotype to a specific molecular defect in translocation or glycosylation\", \"Mechanism of vascular endothelial proliferation failure unresolved\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"To test whether SSR3 loss causes human disease and how, a patient frameshift variant was shown to destabilize the whole TRAP complex and impair glycosylation, with rescue confirming causality.\",\n      \"evidence\": \"Exome sequencing, western blot of TRAP subunits in patient fibroblasts, rescue by wild-type SSR3, glycosylation assay on GP130/ICAM1\",\n      \"pmids\": [\"30945312\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not define which clients depend on SSR3 for translocation versus glycosylation\", \"Structural basis of complex destabilization not resolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"A second patient variant (start codon) confirmed SSR3 is required for TRAP integrity, ER translocation, and N-glycosylation site occupancy.\",\n      \"evidence\": \"Patient-cell biochemistry: translocation assay, glycosylation site occupancy, brush-border transport assay\",\n      \"pmids\": [\"32332102\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single patient, single lab, no rescue experiment\", \"Tissue-specific consequences not generalized\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"To define SSR3 within ER stress biology, it was shown to maintain N-glycosylation fidelity during ER stress and to be itself regulated post-translationally via UBE2J1, coupling glycosylation status to ERAD.\",\n      \"evidence\": \"Fluorescence N-glycosylation reporter, CRISPR/siRNA KO of SSR3/SSR4, BiP silencing rescue, UBE2J1-dependent protein level assay\",\n      \"pmids\": [\"33523898\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct biochemical interaction between SSR3 and UBE2J1 not shown\", \"Which glycoproteins are most sensitive to SSR3 loss not enumerated\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Perturbing other TRAP subunits clarified the interdependence of the complex, showing SSR2/SSR4 loss reduces SSR3 levels and proinsulin biosynthesis, and positioned SSR3 topology as primarily cytosolic.\",\n      \"evidence\": \"siRNA KD of SSR2/SSR4 in β-cells, amino acid pulse labeling, western blot, subunit re-expression rescue\",\n      \"pmids\": [\"33811688\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and direct contacts of SSR3 within the complex not mapped\", \"Does not isolate SSR3-specific function from complex-wide effects\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Direct interrogation of SSR3 function in β-cells defined a rate-limiting, glucose-responsive role in preproinsulin translocation.\",\n      \"evidence\": \"siRNA KD and overexpression of SSR3 in β-cell lines and human islets, glucose-stimulation assays, western blot for SSR1 and proinsulin\",\n      \"pmids\": [\"34857543\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of post-transcriptional SSR3 upregulation by glucose not defined\", \"Whether SSR3 acts as a dedicated preproinsulin translocation factor or generally on signal-peptide-bearing clients unresolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"A CRISPR screen linked SSR3 to chemotherapy response, showing it modulates paclitaxel susceptibility via IRE1α phosphorylation.\",\n      \"evidence\": \"Genome-wide CRISPR KO screen in glioma, KO/overexpression in breast and glioma cells, intracranial xenografts, IRE1α phosphorylation assay\",\n      \"pmids\": [\"35552677\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic link to IRE1α phosphorylation described with limited detail\", \"Whether the effect depends on TRAP-mediated translocation versus a separable activity not resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How SSR3's cytosolic domain mechanistically promotes translocation of specific clients, and the structural basis of its role in TRAP assembly, remain open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structural model of SSR3 within the assembled translocon\", \"Client selectivity rules for SSR3-dependent translocation unknown\", \"Direct biochemical partners of the cytosolic domain not identified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140104\", \"supporting_discovery_ids\": [2, 5]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [1, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0, 2, 5]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [2, 3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [2, 5]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [0, 6]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [1, 5]}\n    ],\n    \"complexes\": [\"TRAP complex (translocon-associated protein complex)\"],\n    \"partners\": [\"SSR1\", \"SSR2\", \"SSR4\", \"UBE2J1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}