id: O95994 gene_symbol: AGR2 product_type: PROTEIN status: COMPLETE taxon: id: NCBITaxon:9606 label: Homo sapiens description: 'AGR2 is a secretory-pathway, ER-retained anterior gradient/thioredoxin-fold protein expressed most prominently in mucus-producing epithelial cells. Its best-supported physiological role is as an ER foldase/protein disulfide-isomerase-family factor for gel-forming mucins, especially MUC2: AGR2 forms mixed disulfide-linked complexes with MUC2, is required for intestinal mucus production, and human AGR2 deficiency causes goblet-cell depletion, loss of gel-forming mucins, ER stress, mucus barrier failure, and infantile inflammatory bowel disease. AGR2 can also be detected extracellularly and has reported cancer-associated interactions with dystroglycan, LYPD3/C4.4a, EGFR, and cell-adhesion/inflammatory pathways, but these are best treated as context-dependent or non-core relative to its conserved ER mucin-processing function.' existing_annotations: - term: id: GO:0005783 label: endoplasmic reticulum evidence_type: IBA original_reference_id: GO_REF:0000033 review: summary: 'ER localization is well supported and is central to AGR2 function: AGR2 enters the secretory pathway and is retained in the ER by its conserved KTEL motif, where it acts on mucin/secretory clients.' action: ACCEPT reason: The annotation matches the best-supported functional compartment for AGR2. ER residence is necessary for AGR2 activity, and AGR2 is directly detected in the ER of secretory epithelial cells. supported_by: - reference_id: PMID:19359471 supporting_text: Here, we show that AGR2 is present within the ER of intestinal secretory epithelial cells and is essential for in vivo production of the intestinal mucin MUC2 reference_section_type: ABSTRACT - reference_id: PMID:19359471 supporting_text: A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. reference_section_type: ABSTRACT - reference_id: PMID:22184114 supporting_text: The present study determines whether AGR2 requires a specific ER localization signal to be functionally active. reference_section_type: ABSTRACT - reference_id: PMID:22184114 supporting_text: Deletion of the KTEL motif results in AGR2 secretion and loss of AGR2 function. reference_section_type: ABSTRACT - reference_id: file:human/AGR2/AGR2-deep-research-falcon.md supporting_text: AGR2 is widely characterized as a protein disulfide isomerase (PDI)-family / thioredoxin-like protein functioning in the endoplasmic reticulum (ER) - term: id: GO:0002162 label: dystroglycan binding evidence_type: IBA original_reference_id: GO_REF:0000033 review: summary: AGR2/dystroglycan binding was reported from yeast two-hybrid screens in a cancer context, but it is not the main conserved function of AGR2. action: KEEP_AS_NON_CORE reason: The binding evidence is specific enough to retain the annotation, but the paper itself notes that clinical confirmation was still needed and the core function of AGR2 is ER mucin processing. supported_by: - reference_id: PMID:12592373 supporting_text: Yeast two-hybrid cloning identified metastasis-associated GPI-anchored C4.4a protein and extracellular alpha-dystroglycan (DAG-1) as binding partners for both hAG-2 and hAG-3 reference_section_type: ABSTRACT - reference_id: PMID:12592373 supporting_text: Clearly, further analyses such as coimmunoprecipitation are required to confirm that these interactions occur in clinical cancers reference_section_type: RESULTS - term: id: GO:0048546 label: digestive tract morphogenesis evidence_type: IEA original_reference_id: GO_REF:0000107 review: summary: Digestive tract morphogenesis is an over-broad phenotype/developmental inference for human AGR2. The mechanistic evidence supports mucin processing, mucus barrier function, and intestinal epithelial homeostasis rather than direct morphogenesis of the digestive tract. action: MARK_AS_OVER_ANNOTATED reason: AGR2 deficiency affects goblet cells and mucus barrier integrity, but this is better captured by mucus secretion/protein folding terms and not by a broad morphogenesis term. additional_reference_ids: - PMID:19359471 - PMID:34237462 supported_by: - reference_id: PMID:34237462 supporting_text: Patient biopsy specimens showed reduced goblet cells; depletion of MUC2, MUC5AC, and MUC6; up-regulation of AGR2; and increased ER stress. reference_section_type: ABSTRACT - reference_id: PMID:34237462 supporting_text: The Mendelian deficiency of AGR2, termed "Enteropathy caused by AGR2 deficiency, Goblet cell Loss, and ER Stress" (EAGLES), results in a mucus barrier defect, the inability to mitigate ER stress, and causes infantile-onset inflammatory bowel disease. reference_section_type: ABSTRACT - reference_id: file:human/AGR2/AGR2-deep-research-falcon.md supporting_text: Across reviews, these findings are summarized as AGR2 contributing to folding/maturation/secretion of MUC2 and MUC5AC/B - term: id: GO:0048639 label: positive regulation of developmental growth evidence_type: IEA original_reference_id: GO_REF:0000107 review: summary: Positive regulation of developmental growth is too broad and phenotypic for AGR2. The evidence points to a secretory-epithelial ER foldase role rather than direct regulation of organismal developmental growth. action: MARK_AS_OVER_ANNOTATED reason: Developmental/growth effects are downstream consequences or cross-species phenotype transfers; they should not be treated as the core human gene function. additional_reference_ids: - PMID:19359471 - PMID:34237462 supported_by: - reference_id: PMID:19359471 supporting_text: Here, we show that AGR2 is present within the ER of intestinal secretory epithelial cells and is essential for in vivo production of the intestinal mucin MUC2 reference_section_type: ABSTRACT - reference_id: PMID:19359471 supporting_text: A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. reference_section_type: ABSTRACT - term: id: GO:0070254 label: mucus secretion evidence_type: IEA original_reference_id: GO_REF:0000107 review: summary: Mucus secretion is supported as a core biological process because AGR2 is required for production/processing of gel-forming mucins and human AGR2 deficiency causes mucus barrier dysfunction. action: ACCEPT reason: Although AGR2 acts in the ER before secretion, the biological outcome of its core function is mucus production/secretion by mucin-producing epithelial cells. additional_reference_ids: - PMID:19359471 - PMID:34237462 supported_by: - reference_id: PMID:19359471 supporting_text: Here, we show that AGR2 is present within the ER of intestinal secretory epithelial cells and is essential for in vivo production of the intestinal mucin MUC2 reference_section_type: ABSTRACT - reference_id: PMID:19359471 supporting_text: A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. reference_section_type: ABSTRACT - reference_id: PMID:34237462 supporting_text: Patient biopsy specimens showed reduced goblet cells; depletion of MUC2, MUC5AC, and MUC6; up-regulation of AGR2; and increased ER stress. reference_section_type: ABSTRACT - reference_id: PMID:34237462 supporting_text: The Mendelian deficiency of AGR2, termed "Enteropathy caused by AGR2 deficiency, Goblet cell Loss, and ER Stress" (EAGLES), results in a mucus barrier defect, the inability to mitigate ER stress, and causes infantile-onset inflammatory bowel disease. reference_section_type: ABSTRACT - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:16189514 review: summary: This is a generic high-throughput protein-binding annotation from a proteome-scale interaction map and does not identify a physiologically interpretable AGR2 function. action: MARK_AS_OVER_ANNOTATED reason: Protein binding is uninformative for AGR2 curation, and this high-throughput interaction should not be treated as a core function. - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:19359471 review: summary: The underlying evidence is AGR2 interaction with MUC2 via mixed disulfide bonds during mucin processing, not merely generic protein binding. action: MODIFY reason: Replace the vague protein binding annotation with the more informative AGR2 molecular role as a PDI-family foldase for mucin processing. proposed_replacement_terms: - id: GO:0003756 label: protein disulfide isomerase activity - id: GO:0034975 label: protein folding in endoplasmic reticulum supported_by: - reference_id: PMID:19359471 supporting_text: Here, we show that AGR2 is present within the ER of intestinal secretory epithelial cells and is essential for in vivo production of the intestinal mucin MUC2 reference_section_type: ABSTRACT - reference_id: PMID:19359471 supporting_text: A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. reference_section_type: ABSTRACT - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:25416956 review: summary: This proteome-scale interactome annotation collapses several high-throughput binary interactions into generic protein binding and does not add meaningful AGR2 functional information. action: MARK_AS_OVER_ANNOTATED reason: The term protein binding is too general, especially for high-throughput interactome hits that are not tied to AGR2 core mucin-folding biology. - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:25910212 review: summary: This genetic-disorder interactome annotation is a generic protein-binding statement and does not establish a curated AGR2 function. action: MARK_AS_OVER_ANNOTATED reason: The annotation should not be used to infer core AGR2 biology because it is a broad high-throughput interaction label without functional specificity. - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:32296183 review: summary: The reference map reports many binary interactome partners, but the resulting GO term protein binding is too broad to be useful for AGR2. action: MARK_AS_OVER_ANNOTATED reason: A generic protein binding annotation for dozens of interactome partners obscures rather than clarifies AGR2 function. - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:32814053 review: summary: The neurodegenerative-disease interactome protein-binding annotation is context-specific and generic, with no evidence that it represents AGR2 core function. action: MARK_AS_OVER_ANNOTATED reason: Retaining generic protein binding as a core AGR2 annotation would overemphasize a high-throughput interaction unrelated to the main ER mucin-processing function. - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:34237462 review: summary: The underlying evidence is impaired AGR2-MUC2 binding in human AGR2 deficiency, which is more informative as mucin processing/PDI-family foldase activity than as generic protein binding. action: MODIFY reason: The paper supports a specific AGR2-MUC2 functional interaction in gel-forming mucin processing; the generic protein binding term should be replaced by more informative ER protein-folding/PDI terms. proposed_replacement_terms: - id: GO:0003756 label: protein disulfide isomerase activity - id: GO:0034975 label: protein folding in endoplasmic reticulum supported_by: - reference_id: PMID:34237462 supporting_text: AGR2-MUC2 binding was evaluated using co-immunoprecipitation. reference_section_type: ABSTRACT - reference_id: PMID:34237462 supporting_text: The mutant AGR2 showed reduced capacity to bind MUC2 and alleviate tunicamycin-induced ER stress. reference_section_type: ABSTRACT - term: id: GO:0002162 label: dystroglycan binding evidence_type: IEA original_reference_id: GO_REF:0000117 review: summary: ARBA transfer of dystroglycan binding is consistent with experimental AGR2/DAG1 yeast two-hybrid evidence, but this cancer/extracellular interaction is not the core AGR2 function. action: KEEP_AS_NON_CORE reason: Keep the specific binding term as non-core because direct experimental evidence exists, while core AGR2 biology is ER mucin processing. additional_reference_ids: - PMID:12592373 supported_by: - reference_id: PMID:12592373 supporting_text: Yeast two-hybrid cloning identified metastasis-associated GPI-anchored C4.4a protein and extracellular alpha-dystroglycan (DAG-1) as binding partners for both hAG-2 and hAG-3 reference_section_type: ABSTRACT - reference_id: PMID:12592373 supporting_text: Clearly, further analyses such as coimmunoprecipitation are required to confirm that these interactions occur in clinical cancers reference_section_type: RESULTS - term: id: GO:0005576 label: extracellular region evidence_type: IEA original_reference_id: GO_REF:0000044 review: summary: AGR2 can be detected extracellularly/secreted, especially in cancer biomarker studies and when ER retention is perturbed, but extracellular localization is not its primary functional site. action: KEEP_AS_NON_CORE reason: 'Retain as a non-core localization: extracellular AGR2 is real in some contexts, while its conserved core function requires ER residence.' additional_reference_ids: - PMID:24251762 - PMID:31040128 supported_by: - reference_id: PMID:24251762 supporting_text: Anterior gradient 2 (AGR2) is a secreted, cancer-associated protein in many types of epithelial cancer cells. reference_section_type: ABSTRACT - reference_id: PMID:24251762 supporting_text: we aimed to develop a reliable and highly sensitive PRISM-SRM assay for quantification of AGR2 at low pg/mL levels in both urine and serum samples in this study. reference_section_type: INTRODUCTION - reference_id: PMID:31040128 supporting_text: modulation of AGR2 dimer formation, whether enhancing or inhibiting the process, yields pro-inflammatory phenotypes reference_section_type: ABSTRACT - term: id: GO:0005783 label: endoplasmic reticulum evidence_type: IEA original_reference_id: GO_REF:0000120 review: summary: Automated ER localization is consistent with experimental and orthology evidence and with the conserved KTEL retention motif. action: ACCEPT reason: ER is the principal compartment for AGR2 mucin-processing activity. additional_reference_ids: - PMID:19359471 - PMID:22184114 supported_by: - reference_id: PMID:19359471 supporting_text: Here, we show that AGR2 is present within the ER of intestinal secretory epithelial cells and is essential for in vivo production of the intestinal mucin MUC2 reference_section_type: ABSTRACT - reference_id: PMID:19359471 supporting_text: A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. reference_section_type: ABSTRACT - reference_id: PMID:22184114 supporting_text: The present study determines whether AGR2 requires a specific ER localization signal to be functionally active. reference_section_type: ABSTRACT - reference_id: PMID:22184114 supporting_text: Deletion of the KTEL motif results in AGR2 secretion and loss of AGR2 function. reference_section_type: ABSTRACT - term: id: GO:0005783 label: endoplasmic reticulum evidence_type: IDA original_reference_id: GO_REF:0000052 review: summary: Immunofluorescence-based ER annotation is consistent with direct literature showing AGR2 in the ER of intestinal secretory epithelial cells. action: ACCEPT reason: This is a core localization for AGR2 function. additional_reference_ids: - PMID:19359471 supported_by: - reference_id: PMID:19359471 supporting_text: Here, we show that AGR2 is present within the ER of intestinal secretory epithelial cells and is essential for in vivo production of the intestinal mucin MUC2 reference_section_type: ABSTRACT - reference_id: PMID:19359471 supporting_text: A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. reference_section_type: ABSTRACT - term: id: GO:0005783 label: endoplasmic reticulum evidence_type: ISS original_reference_id: GO_REF:0000024 review: summary: Sequence/orthology transfer of ER localization is consistent with human and mouse evidence and with the conserved ER-retention motif. action: ACCEPT reason: The ER location is conserved and functionally required for AGR2. additional_reference_ids: - PMID:19359471 - PMID:22184114 supported_by: - reference_id: PMID:19359471 supporting_text: Here, we show that AGR2 is present within the ER of intestinal secretory epithelial cells and is essential for in vivo production of the intestinal mucin MUC2 reference_section_type: ABSTRACT - reference_id: PMID:19359471 supporting_text: A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. reference_section_type: ABSTRACT - reference_id: PMID:22184114 supporting_text: The present study determines whether AGR2 requires a specific ER localization signal to be functionally active. reference_section_type: ABSTRACT - reference_id: PMID:22184114 supporting_text: Deletion of the KTEL motif results in AGR2 secretion and loss of AGR2 function. reference_section_type: ABSTRACT - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:31040128 review: summary: PMID:31040128 identifies regulators of AGR2 dimerization and extracellular release, but generic protein binding is less informative than the specific homodimerization/proteostasis biology. action: MARK_AS_OVER_ANNOTATED reason: Protein binding is too broad for this evidence; the useful curation is AGR2 homodimerization and ER proteostasis/inflammatory context. supported_by: - reference_id: PMID:31040128 supporting_text: Anterior gradient 2 (AGR2) is a dimeric protein disulfide isomerase family member involved in the regulation of protein quality control in the endoplasmic reticulum (ER). reference_section_type: ABSTRACT - reference_id: PMID:31040128 supporting_text: AGR2 dimers act as sensors of ER homeostasis which are disrupted upon ER stress and promote the secretion of AGR2 monomers. reference_section_type: ABSTRACT - term: id: GO:0005576 label: extracellular region evidence_type: IDA original_reference_id: PMID:31040128 review: summary: AGR2 extracellular release is demonstrated in the dimerization/proteostasis study and is linked to pro-inflammatory monocyte chemoattraction. action: KEEP_AS_NON_CORE reason: Extracellular AGR2 is a context-dependent inflammatory/cancer-related state rather than the main ER foldase location, so retain it as non-core. supported_by: - reference_id: PMID:31040128 supporting_text: modulation of AGR2 dimer formation, whether enhancing or inhibiting the process, yields pro-inflammatory phenotypes reference_section_type: ABSTRACT - reference_id: PMID:31040128 supporting_text: the extracellular release of AGR2 leads to the chemoattraction of monocytes, thereby suggesting extracellular AGR2's pro-inflammatory functions reference_section_type: RESULTS - term: id: GO:0005783 label: endoplasmic reticulum evidence_type: IDA original_reference_id: PMID:31040128 review: summary: AGR2 is active in the ER in this study, where dimerization status reports ER homeostasis and affects proteostasis. action: ACCEPT reason: This reinforces ER as the core active site of AGR2. supported_by: - reference_id: PMID:31040128 supporting_text: Anterior gradient 2 (AGR2) is a dimeric protein disulfide isomerase family member involved in the regulation of protein quality control in the endoplasmic reticulum (ER). reference_section_type: ABSTRACT - reference_id: PMID:31040128 supporting_text: AGR2 dimers act as sensors of ER homeostasis which are disrupted upon ER stress and promote the secretion of AGR2 monomers. reference_section_type: ABSTRACT - term: id: GO:0006954 label: inflammatory response evidence_type: IMP original_reference_id: PMID:31040128 review: summary: AGR2 dimerization/secreted monomer state can drive pro-inflammatory phenotypes and is linked to intestinal inflammation, but this is a downstream/pathological outcome of perturbed ER proteostasis. action: KEEP_AS_NON_CORE reason: Inflammatory response is supported but should be non-core relative to AGR2's primary ER mucin-folding role. supported_by: - reference_id: PMID:31040128 supporting_text: modulation of AGR2 dimer formation, whether enhancing or inhibiting the process, yields pro-inflammatory phenotypes reference_section_type: ABSTRACT - reference_id: PMID:31040128 supporting_text: the extracellular release of AGR2 leads to the chemoattraction of monocytes, thereby suggesting extracellular AGR2's pro-inflammatory functions reference_section_type: RESULTS - reference_id: PMID:34237462 supporting_text: Patient biopsy specimens showed reduced goblet cells; depletion of MUC2, MUC5AC, and MUC6; up-regulation of AGR2; and increased ER stress. reference_section_type: ABSTRACT - term: id: GO:0030968 label: endoplasmic reticulum unfolded protein response evidence_type: IDA original_reference_id: PMID:31040128 review: summary: AGR2 dimerization is connected to ER homeostasis/UPR-associated stress biology, and newer IRE1beta studies support a narrow negative IRE1-mediated annotation in mucin-producing cells, but the broad ER UPR term remains non-core. action: KEEP_AS_NON_CORE reason: Retain the UPR-related annotation as non-core because it describes regulatory/stress biology around AGR2 rather than AGR2's main molecular activity. The supported PN projection is the narrower PDI-family foldase activity, not broad propagation to generic ER UPR participation. supported_by: - reference_id: PMID:31040128 supporting_text: Anterior gradient 2 (AGR2) is a dimeric protein disulfide isomerase family member involved in the regulation of protein quality control in the endoplasmic reticulum (ER). reference_section_type: ABSTRACT - reference_id: PMID:31040128 supporting_text: AGR2 dimers act as sensors of ER homeostasis which are disrupted upon ER stress and promote the secretion of AGR2 monomers. reference_section_type: ABSTRACT - reference_id: PMID:34237462 supporting_text: The mutant AGR2 showed reduced capacity to bind MUC2 and alleviate tunicamycin-induced ER stress. reference_section_type: ABSTRACT - term: id: GO:0034975 label: protein folding in endoplasmic reticulum evidence_type: IDA original_reference_id: PMID:31040128 review: summary: AGR2 participates in protein folding in the ER, especially processing/folding of gel-forming mucins such as MUC2. This is curated despite the competing PMID:25666625 interpretation that EGFR, rather than MUC2, was the major AGR2 mixed-disulfide substrate in the tested cancer-cell models. action: ACCEPT reason: This is a core biological process for AGR2. PMID:25666625 reported no MUC2 in its AGR2 mixed-disulfide mass-spectrometry analysis and cited a re-evaluation against MUC2 folding, but earlier AGR2-MUC2 mixed-disulfide trapping and later human AGR2 H117Y data showing reduced MUC2 binding and ER-stress relief support retaining the ER protein-folding annotation. additional_reference_ids: - PMID:19359471 - PMID:34237462 - PMID:25666625 supported_by: - reference_id: PMID:19359471 supporting_text: Here, we show that AGR2 is present within the ER of intestinal secretory epithelial cells and is essential for in vivo production of the intestinal mucin MUC2 reference_section_type: ABSTRACT - reference_id: PMID:19359471 supporting_text: A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. reference_section_type: ABSTRACT - reference_id: PMID:34237462 supporting_text: Patient biopsy specimens showed reduced goblet cells; depletion of MUC2, MUC5AC, and MUC6; up-regulation of AGR2; and increased ER stress. reference_section_type: ABSTRACT - reference_id: PMID:34237462 supporting_text: The Mendelian deficiency of AGR2, termed "Enteropathy caused by AGR2 deficiency, Goblet cell Loss, and ER Stress" (EAGLES), results in a mucus barrier defect, the inability to mitigate ER stress, and causes infantile-onset inflammatory bowel disease. reference_section_type: ABSTRACT - reference_id: PMID:34237462 supporting_text: The mutant AGR2 showed reduced capacity to bind MUC2 and alleviate tunicamycin-induced ER stress. reference_section_type: ABSTRACT - reference_id: PMID:25666625 supporting_text: Re-evaluation of MUC2 in a recent study also concluded that it is not a AGR2-binding protein and that AGR2 served no role in its folding. reference_section_type: DISCUSSION - term: id: GO:0034975 label: protein folding in endoplasmic reticulum evidence_type: IMP original_reference_id: PMID:31040128 review: summary: Mutant/perturbation evidence supports AGR2 as required for ER protein-folding/proteostasis, especially mucin processing. This conclusion accounts for PMID:25666625, which favored EGFR as the major AGR2 substrate and disputed MUC2 as an AGR2 folding client in its model system. action: ACCEPT reason: Loss-of-function and perturbation data support protein folding in the ER as part of AGR2 core function. The MUC2 substrate question is not unanimous in the literature, but PMID:19359471 and the later human AGR2 H117Y evidence in PMID:34237462 provide direct support for AGR2-MUC2 binding and mucin-processing relevance. additional_reference_ids: - PMID:19359471 - PMID:34237462 - PMID:25666625 supported_by: - reference_id: PMID:19359471 supporting_text: Here, we show that AGR2 is present within the ER of intestinal secretory epithelial cells and is essential for in vivo production of the intestinal mucin MUC2 reference_section_type: ABSTRACT - reference_id: PMID:19359471 supporting_text: A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. reference_section_type: ABSTRACT - reference_id: PMID:34237462 supporting_text: Patient biopsy specimens showed reduced goblet cells; depletion of MUC2, MUC5AC, and MUC6; up-regulation of AGR2; and increased ER stress. reference_section_type: ABSTRACT - reference_id: PMID:34237462 supporting_text: The Mendelian deficiency of AGR2, termed "Enteropathy caused by AGR2 deficiency, Goblet cell Loss, and ER Stress" (EAGLES), results in a mucus barrier defect, the inability to mitigate ER stress, and causes infantile-onset inflammatory bowel disease. reference_section_type: ABSTRACT - reference_id: PMID:34237462 supporting_text: The mutant AGR2 showed reduced capacity to bind MUC2 and alleviate tunicamycin-induced ER stress. reference_section_type: ABSTRACT - reference_id: PMID:25666625 supporting_text: None of the proteins previously reported to bind AGR2 such as LYPD3 (C4.4a), DAG1, or MUC2 ( 33 , 46 ) were detected in the mass spectrometry analysis of AGR2 mixed disulfides. reference_section_type: DISCUSSION - term: id: GO:0042803 label: protein homodimerization activity evidence_type: IPI original_reference_id: PMID:31040128 review: summary: AGR2 homodimerization is a well-supported molecular property that controls ER homeostasis and extracellular release. action: ACCEPT reason: Homodimerization is a key mechanistic feature of AGR2 function and is directly supported by dimerization assays and structural/biochemical studies. additional_reference_ids: - PMID:23274113 - PMID:31040128 supported_by: - reference_id: PMID:31040128 supporting_text: Anterior gradient 2 (AGR2) is a dimeric protein disulfide isomerase family member involved in the regulation of protein quality control in the endoplasmic reticulum (ER). reference_section_type: ABSTRACT - reference_id: PMID:31040128 supporting_text: AGR2 dimers act as sensors of ER homeostasis which are disrupted upon ER stress and promote the secretion of AGR2 monomers. reference_section_type: ABSTRACT - term: id: GO:0060326 label: cell chemotaxis evidence_type: IDA original_reference_id: PMID:31040128 review: summary: Extracellular AGR2 can chemoattract monocytes in the inflammation study, but this is a context-dependent extracellular alarm/inflammatory activity. action: KEEP_AS_NON_CORE reason: Retain as non-core because chemotaxis is a downstream response to secreted AGR2 under perturbed ER/pro-inflammatory conditions, not AGR2's primary conserved function. supported_by: - reference_id: PMID:31040128 supporting_text: modulation of AGR2 dimer formation, whether enhancing or inhibiting the process, yields pro-inflammatory phenotypes reference_section_type: ABSTRACT - reference_id: PMID:31040128 supporting_text: the extracellular release of AGR2 leads to the chemoattraction of monocytes, thereby suggesting extracellular AGR2's pro-inflammatory functions reference_section_type: RESULTS - term: id: GO:0005576 label: extracellular region evidence_type: IDA original_reference_id: PMID:15834940 review: summary: AGR2 is described and measured as a secretory/secreted protein in prostate cancer contexts, but this is not the main functional site for mucin processing. action: KEEP_AS_NON_CORE reason: Extracellular/secreted AGR2 is supported but should be non-core relative to ER-localized foldase activity. supported_by: - reference_id: PMID:15834940 supporting_text: the androgen-induced secretory protein AGR2 may serve as a potential therapeutic target and/or molecular marker for prostate cancer. reference_section_type: ABSTRACT - term: id: GO:0042802 label: identical protein binding evidence_type: IPI original_reference_id: PMID:23220234 review: summary: The BiP/GRP78 paper reports AGR2 homo-dimerization, so identical protein binding should be curated more specifically as protein homodimerization activity. action: MODIFY reason: GO:0042803 captures the observed AGR2 self-association more precisely than identical protein binding. proposed_replacement_terms: - id: GO:0042803 label: protein homodimerization activity supported_by: - reference_id: PMID:23220234 supporting_text: Herein we show that AGR2 homo-dimerizes through an intermolecular disulfide bond. Moreover, dimerization of AGR2 attenuates ER stress-induced cell death through the association with BiP/GRP78. reference_section_type: ABSTRACT - term: id: GO:0042802 label: identical protein binding evidence_type: IPI original_reference_id: PMID:23274113 review: summary: The NMR/structure paper reports AGR2 monomer-dimer equilibrium and a dimeric thioredoxin fold, so protein homodimerization activity is the better term. action: MODIFY reason: Identical protein binding is less specific than the demonstrated homodimerization activity. proposed_replacement_terms: - id: GO:0042803 label: protein homodimerization activity supported_by: - reference_id: PMID:23274113 supporting_text: The protein exists in monomer-dimer equilibrium with a K(d) of 8.83μM reference_section_type: ABSTRACT - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:23220234 review: summary: The interaction with BiP/GRP78 is a specific chaperone interaction; generic protein binding is too broad. action: MODIFY reason: Replace with protein-folding chaperone binding to capture the BiP/GRP78 association more specifically. proposed_replacement_terms: - id: GO:0051087 label: protein-folding chaperone binding supported_by: - reference_id: PMID:23220234 supporting_text: Herein we show that AGR2 homo-dimerizes through an intermolecular disulfide bond. Moreover, dimerization of AGR2 attenuates ER stress-induced cell death through the association with BiP/GRP78. reference_section_type: ABSTRACT - term: id: GO:0005576 label: extracellular region evidence_type: IDA original_reference_id: PMID:22184114 review: summary: This paper mainly shows that perturbing the KTEL ER-retention motif can cause AGR2 secretion, so by itself it is weak evidence for wild-type extracellular localization; however extracellular AGR2 is supported by other studies and should be retained only as non-core. action: KEEP_AS_NON_CORE reason: 'Use a consistent non-core extracellular-region action for AGR2: extracellular AGR2 is real in biomarker/inflammatory contexts, but this specific KTEL paper should not be read as evidence that extracellular localization is the normal core site of AGR2 action.' supported_by: - reference_id: PMID:22184114 supporting_text: The present study determines whether AGR2 requires a specific ER localization signal to be functionally active. reference_section_type: ABSTRACT - reference_id: PMID:22184114 supporting_text: Deletion of the KTEL motif results in AGR2 secretion and loss of AGR2 function. reference_section_type: ABSTRACT additional_reference_ids: - PMID:24251762 - PMID:31040128 - term: id: GO:0005783 label: endoplasmic reticulum evidence_type: IMP original_reference_id: PMID:22184114 review: summary: The KTEL paper strongly supports ER localization/residence as required for AGR2 function. action: ACCEPT reason: ER residence is a core functional requirement for AGR2. supported_by: - reference_id: PMID:22184114 supporting_text: The present study determines whether AGR2 requires a specific ER localization signal to be functionally active. reference_section_type: ABSTRACT - reference_id: PMID:22184114 supporting_text: Deletion of the KTEL motif results in AGR2 secretion and loss of AGR2 function. reference_section_type: ABSTRACT - term: id: GO:0010628 label: positive regulation of gene expression evidence_type: IMP original_reference_id: PMID:22184114 review: summary: AGR2-dependent induction of AREG/CDX2 in cell models is an indirect downstream transcriptional readout and should not be treated as a core gene-expression regulatory function. action: MARK_AS_OVER_ANNOTATED reason: AGR2 is not a transcriptional regulator; this broad BP term overstates an indirect effect of ER-localized AGR2 activity in adenocarcinoma/IEC cell models. supported_by: - reference_id: PMID:22184114 supporting_text: Using two different cell lines in which AGR2 induces expression of either the EGFR ligand amphiregulin or the transcription factor CDX2, only the highly conserved wild-type carboxyl-terminal KTEL motif results in the appropriate outcome. reference_section_type: ABSTRACT - reference_id: PMID:22184114 supporting_text: The present study demonstrates that AGR2 residence within the ER is required for its function as reflected by AREG expression in OE33 adenocarcinoma cells or CDX2 expression by IEC-6 intestinal cells. reference_section_type: DISCUSSION - term: id: GO:1903896 label: positive regulation of IRE1-mediated unfolded protein response evidence_type: IDA original_reference_id: PMID:23220234 review: summary: The PMID:23220234 abstract describes AGR2 dimers as attenuating ER stress-induced cell death via BiP/GRP78 association, with no arm-specific IRE1 evidence. Citing literature with full-text access (Sicari et al. 2019, PMID:31040128; Alsereihi et al. 2019, PMID:31247903) places canonical AGR2 downstream of UPR sensors (IRE1α/ATF6α regulate AGR2 expression, AGR2 dimers dissociate upon ER stress) rather than as a positive regulator of the IRE1 arm. The IRE1 mention in PMID:31040128 is the ERMIT mammalian two-hybrid bait scaffold, not a biological regulatory target. action: MARK_AS_OVER_ANNOTATED reason: 'No literature supports canonical AGR2 (UniProt O95994) as a positive regulator of the IRE1-mediated UPR arm. The directionality established by citing literature is the inverse: IRE1α/ATF6α regulate AGR2 expression. Retain in record as historical IDA but flag as over-annotation.' additional_reference_ids: - PMID:31040128 - PMID:31247903 supported_by: - reference_id: PMID:23220234 supporting_text: Herein we show that AGR2 homo-dimerizes through an intermolecular disulfide bond. Moreover, dimerization of AGR2 attenuates ER stress-induced cell death through the association with BiP/GRP78. reference_section_type: ABSTRACT - reference_id: PMID:31247903 supporting_text: This was demonstrated when IREα and ATF6α were knocked down using small interfering RNA (siRNA) in HeLa cells, resulting in the decreased expression levels of the AGR2 protein reference_section_type: RESULTS - reference_id: PMID:31040128 supporting_text: the luminal domain of IRE1 was replaced by different bait proteins reference_section_type: RESULTS - reference_id: PMID:31040128 supporting_text: dissociation of AGR2 homodimers as assessed by the decrease in luminescence observed for all the constructs tested reference_section_type: RESULTS - term: id: GO:1903899 label: positive regulation of PERK-mediated unfolded protein response evidence_type: IDA original_reference_id: PMID:23220234 review: summary: The PMID:23220234 abstract describes AGR2 dimers as attenuating ER stress-induced cell death via BiP/GRP78 association, with no PERK-specific evidence. Citing-literature reviews (Alsereihi et al. 2019, PMID:31247903) summarize the mechanistic AGR2/UPR landscape without mentioning AGR2 as a regulator of the PERK arm — the only reported AGR2/UPR-sensor relationships involve IRE1α and ATF6α regulating AGR2 expression, not vice versa, and PMID:31040128 places canonical AGR2 dimers downstream of ER stress (dissociation upon stress). action: MARK_AS_OVER_ANNOTATED reason: PERK-mediated UPR is conspicuously absent from the AGR2 mechanistic literature for canonical AGR2 (UniProt O95994). The PMID:23220234 abstract's BiP/GRP78 attenuation finding is downstream of UPR sensing rather than driving the PERK arm. Retain in record as historical IDA but flag as over-annotation. additional_reference_ids: - PMID:31040128 - PMID:31247903 supported_by: - reference_id: PMID:23220234 supporting_text: Herein we show that AGR2 homo-dimerizes through an intermolecular disulfide bond. Moreover, dimerization of AGR2 attenuates ER stress-induced cell death through the association with BiP/GRP78. reference_section_type: ABSTRACT - reference_id: PMID:31247903 supporting_text: The top molecules implicated in regulating the expression of AGR2 included IRE1α, ATF6α, AKT, FOXA1/2, HIF-1, TMED2, and the frequently mutated tumor suppressor p53. reference_section_type: DISCUSSION - reference_id: PMID:31040128 supporting_text: dissociation of AGR2 homodimers as assessed by the decrease in luminescence observed for all the constructs tested reference_section_type: RESULTS - term: id: GO:0005576 label: extracellular region evidence_type: IDA original_reference_id: PMID:24251762 review: summary: Targeted mass spectrometry detected AGR2 in human urine and serum, supporting extracellular/body-fluid localization. action: KEEP_AS_NON_CORE reason: Extracellular AGR2 is a supported non-core localization, especially in biomarker/cancer contexts. supported_by: - reference_id: PMID:24251762 supporting_text: Anterior gradient 2 (AGR2) is a secreted, cancer-associated protein in many types of epithelial cancer cells. reference_section_type: ABSTRACT - reference_id: PMID:24251762 supporting_text: we aimed to develop a reliable and highly sensitive PRISM-SRM assay for quantification of AGR2 at low pg/mL levels in both urine and serum samples in this study. reference_section_type: INTRODUCTION - term: id: GO:0005154 label: epidermal growth factor receptor binding evidence_type: IPI original_reference_id: PMID:25666625 review: summary: AGR2 binds EGFR in the ER and is required for receptor delivery to the plasma membrane in cancer-cell models. action: KEEP_AS_NON_CORE reason: The term is supported, but EGFR appears to be a context-specific client/pathway rather than the main conserved AGR2 function. supported_by: - reference_id: PMID:25666625 supporting_text: EGFR binding to anterior gradient homolog 2 ( AGR2 ) in the endoplasmic reticulum is required for receptor delivery to the plasma membrane and thus EGFR signaling. reference_section_type: ABSTRACT - reference_id: PMID:25666625 supporting_text: Reduced AGR2 protein levels or mutation of an essential cysteine in the active site result in decreased cell surface EGFR and a concomitant decrease in signaling as reflected by AREG , EGR1 , and FOS expression. reference_section_type: ABSTRACT - term: id: GO:0010811 label: positive regulation of cell-substrate adhesion evidence_type: IMP original_reference_id: PMID:23274113 review: summary: AGR2 can promote cell-substrate adhesion in cancer/metastasis assays, but this extracellular N-terminal activity is context-dependent. action: KEEP_AS_NON_CORE reason: Cell adhesion is supported but is not the core ER mucin-processing function. supported_by: - reference_id: PMID:23274113 supporting_text: The unstructured region is primarily responsible for the ability of AGR2 to promote cell adhesion, while dimerization is less important for this activity. reference_section_type: ABSTRACT - term: id: GO:0034976 label: response to endoplasmic reticulum stress evidence_type: IMP original_reference_id: PMID:25666625 negated: true review: summary: The NOT annotation conflicts with later evidence that AGR2 contributes to ER stress/proteostasis regulation and that AGR2 H117Y is impaired in alleviating tunicamycin-induced ER stress. action: REMOVE reason: A gene-level NOT annotation to response to ER stress is no longer defensible; if PMID:25666625 only showed lack of induction in one context, that should not negate AGR2's ER stress/homeostasis role. additional_reference_ids: - PMID:31040128 - PMID:34237462 supported_by: - reference_id: PMID:31040128 supporting_text: Anterior gradient 2 (AGR2) is a dimeric protein disulfide isomerase family member involved in the regulation of protein quality control in the endoplasmic reticulum (ER). reference_section_type: ABSTRACT - reference_id: PMID:31040128 supporting_text: AGR2 dimers act as sensors of ER homeostasis which are disrupted upon ER stress and promote the secretion of AGR2 monomers. reference_section_type: ABSTRACT - reference_id: PMID:34237462 supporting_text: The mutant AGR2 showed reduced capacity to bind MUC2 and alleviate tunicamycin-induced ER stress. reference_section_type: ABSTRACT - reference_id: PMID:34237462 supporting_text: AGR2 H117Y has a reduced capacity to regulate ER stress even in the absence of gel-forming mucins in vitro. reference_section_type: DISCUSSION - term: id: GO:0045742 label: positive regulation of epidermal growth factor receptor signaling pathway evidence_type: IMP original_reference_id: PMID:25666625 review: summary: AGR2 supports EGFR signaling by enabling EGFR delivery to the cell surface in tested cancer-cell models. action: KEEP_AS_NON_CORE reason: This is supported as a client-specific, context-dependent process, but it is not the conserved core AGR2 function. supported_by: - reference_id: PMID:25666625 supporting_text: EGFR binding to anterior gradient homolog 2 ( AGR2 ) in the endoplasmic reticulum is required for receptor delivery to the plasma membrane and thus EGFR signaling. reference_section_type: ABSTRACT - reference_id: PMID:25666625 supporting_text: Reduced AGR2 protein levels or mutation of an essential cysteine in the active site result in decreased cell surface EGFR and a concomitant decrease in signaling as reflected by AREG , EGR1 , and FOS expression. reference_section_type: ABSTRACT - term: id: GO:0048546 label: digestive tract morphogenesis evidence_type: ISS original_reference_id: GO_REF:0000024 review: summary: Digestive tract morphogenesis remains an over-broad orthology transfer relative to the known AGR2 mechanism. action: MARK_AS_OVER_ANNOTATED reason: Human and mouse evidence supports mucin processing/mucus barrier maintenance, not direct digestive tract morphogenesis. additional_reference_ids: - PMID:19359471 - PMID:34237462 supported_by: - reference_id: PMID:34237462 supporting_text: Patient biopsy specimens showed reduced goblet cells; depletion of MUC2, MUC5AC, and MUC6; up-regulation of AGR2; and increased ER stress. reference_section_type: ABSTRACT - reference_id: PMID:34237462 supporting_text: The Mendelian deficiency of AGR2, termed "Enteropathy caused by AGR2 deficiency, Goblet cell Loss, and ER Stress" (EAGLES), results in a mucus barrier defect, the inability to mitigate ER stress, and causes infantile-onset inflammatory bowel disease. reference_section_type: ABSTRACT - term: id: GO:0048639 label: positive regulation of developmental growth evidence_type: ISS original_reference_id: GO_REF:0000024 review: summary: Positive regulation of developmental growth is too broad and likely reflects indirect developmental/phenotypic transfer from orthologs. action: MARK_AS_OVER_ANNOTATED reason: The direct AGR2 mechanism is ER mucin/client processing; growth/developmental phenotypes should not be elevated to core gene function. additional_reference_ids: - PMID:19359471 - PMID:34237462 supported_by: - reference_id: PMID:19359471 supporting_text: Here, we show that AGR2 is present within the ER of intestinal secretory epithelial cells and is essential for in vivo production of the intestinal mucin MUC2 reference_section_type: ABSTRACT - reference_id: PMID:19359471 supporting_text: A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. reference_section_type: ABSTRACT - term: id: GO:1903078 label: positive regulation of protein localization to plasma membrane evidence_type: IMP original_reference_id: PMID:25666625 review: summary: AGR2 promotes EGFR localization to the plasma membrane by binding EGFR in the ER, but the GO term is broad and substrate-specific. action: KEEP_AS_NON_CORE reason: The annotation is supported for EGFR in tested cell models but should be non-core because it is a client-specific cancer/developmental signaling effect. supported_by: - reference_id: PMID:25666625 supporting_text: EGFR binding to anterior gradient homolog 2 ( AGR2 ) in the endoplasmic reticulum is required for receptor delivery to the plasma membrane and thus EGFR signaling. reference_section_type: ABSTRACT - reference_id: PMID:25666625 supporting_text: Reduced AGR2 protein levels or mutation of an essential cysteine in the active site result in decreased cell surface EGFR and a concomitant decrease in signaling as reflected by AREG , EGR1 , and FOS expression. reference_section_type: ABSTRACT - term: id: GO:0005515 label: protein binding evidence_type: IPI original_reference_id: PMID:12592373 review: summary: The protein-binding annotation from PMID:12592373 reflects specific yeast-two-hybrid interactions with C4.4a/LYPD3 and alpha-dystroglycan; dystroglycan binding is the more informative existing GO term. action: MODIFY reason: Protein binding is too generic; use the available specific dystroglycan binding term for the DAG1 interaction, while noting the LYPD3/C4.4a interaction lacks a specific GO binding term. proposed_replacement_terms: - id: GO:0002162 label: dystroglycan binding supported_by: - reference_id: PMID:12592373 supporting_text: Yeast two-hybrid cloning identified metastasis-associated GPI-anchored C4.4a protein and extracellular alpha-dystroglycan (DAG-1) as binding partners for both hAG-2 and hAG-3 reference_section_type: ABSTRACT - reference_id: PMID:12592373 supporting_text: Clearly, further analyses such as coimmunoprecipitation are required to confirm that these interactions occur in clinical cancers reference_section_type: RESULTS - term: id: GO:0002162 label: dystroglycan binding evidence_type: IDA original_reference_id: PMID:12592373 review: summary: Direct yeast two-hybrid evidence supports AGR2 binding to alpha-dystroglycan, but this is a cancer/extracellular interaction and not AGR2's core ER foldase function. action: KEEP_AS_NON_CORE reason: Retain the specific molecular interaction as non-core. supported_by: - reference_id: PMID:12592373 supporting_text: Yeast two-hybrid cloning identified metastasis-associated GPI-anchored C4.4a protein and extracellular alpha-dystroglycan (DAG-1) as binding partners for both hAG-2 and hAG-3 reference_section_type: ABSTRACT - reference_id: PMID:12592373 supporting_text: Clearly, further analyses such as coimmunoprecipitation are required to confirm that these interactions occur in clinical cancers reference_section_type: RESULTS - term: id: GO:0070254 label: mucus secretion evidence_type: ISS original_reference_id: GO_REF:0000024 review: summary: Mucus secretion transferred from mouse orthology is supported by human AGR2 deficiency and mouse Agr2 loss-of-function evidence. action: ACCEPT reason: Mucus production/secretion is a principal biological outcome of AGR2's core role in mucin processing. additional_reference_ids: - PMID:19359471 - PMID:34237462 supported_by: - reference_id: PMID:19359471 supporting_text: Here, we show that AGR2 is present within the ER of intestinal secretory epithelial cells and is essential for in vivo production of the intestinal mucin MUC2 reference_section_type: ABSTRACT - reference_id: PMID:19359471 supporting_text: A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. reference_section_type: ABSTRACT - reference_id: PMID:34237462 supporting_text: Patient biopsy specimens showed reduced goblet cells; depletion of MUC2, MUC5AC, and MUC6; up-regulation of AGR2; and increased ER stress. reference_section_type: ABSTRACT - reference_id: PMID:34237462 supporting_text: The Mendelian deficiency of AGR2, termed "Enteropathy caused by AGR2 deficiency, Goblet cell Loss, and ER Stress" (EAGLES), results in a mucus barrier defect, the inability to mitigate ER stress, and causes infantile-onset inflammatory bowel disease. reference_section_type: ABSTRACT - term: id: GO:0003756 label: protein disulfide isomerase activity qualifier: enables evidence_type: IC original_reference_id: PMID:19359471 review: summary: AGR2 should have a new molecular-function annotation for PDI-family foldase activity, matching the AGR2-specific PN projection from the ER protein disulfide isomerase bucket. The IC rationale is based on direct AGR2-MUC2 mixed-disulfide evidence, ER protein-folding/proteostasis annotations, and human AGR2 H117Y data rather than sequence similarity alone; PMID:25666625 is a competing EGFR-focused interpretation that did not detect MUC2 in its AGR2 mixed-disulfide analysis. action: NEW reason: GOA currently lacks an informative AGR2 catalytic/foldase molecular-function term. GO:0003756 is the best available GO molecular-function term for the literature-described AGR2 PDI-family activity and is the only PN-projected AGR2 term accepted here. Although PMID:25666625 argues for EGFR as the principal substrate and disputes MUC2 folding in its system, PMID:19359471 directly trapped AGR2-MUC2 mixed disulfides and PMID:34237462 later showed reduced MUC2 binding and ER-stress relief by AGR2 H117Y, supporting a specialized mucin-biased PDI-family annotation. additional_reference_ids: - PMID:34237462 - PMID:31040128 - PMID:25666625 supported_by: - reference_id: PMID:19359471 supporting_text: Here, we show that AGR2 is present within the ER of intestinal secretory epithelial cells and is essential for in vivo production of the intestinal mucin MUC2 reference_section_type: ABSTRACT - reference_id: PMID:19359471 supporting_text: A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. reference_section_type: ABSTRACT - reference_id: PMID:34237462 supporting_text: The mutant AGR2 showed reduced capacity to bind MUC2 and alleviate tunicamycin-induced ER stress. reference_section_type: ABSTRACT - reference_id: PMID:34237462 supporting_text: The Mendelian deficiency of AGR2, termed "Enteropathy caused by AGR2 deficiency, Goblet cell Loss, and ER Stress" (EAGLES), results in a mucus barrier defect, the inability to mitigate ER stress, and causes infantile-onset inflammatory bowel disease. reference_section_type: ABSTRACT - reference_id: PMID:31040128 supporting_text: Anterior gradient 2 (AGR2) is a dimeric protein disulfide isomerase family member involved in the regulation of protein quality control in the endoplasmic reticulum (ER). reference_section_type: ABSTRACT - reference_id: PMID:25666625 supporting_text: The absence of another dominant AGR2 mixed disulfide ( Figs. 1 , A , C , and D , and 5 D ) suggests that EGFR is a major substrate for AGR2. reference_section_type: DISCUSSION - reference_id: file:human/AGR2/AGR2-deep-research-falcon.md supporting_text: AGR2’s best-supported substrates/clients are cysteine-rich secreted mucins - term: id: GO:0005788 label: endoplasmic reticulum lumen qualifier: located_in evidence_type: IC original_reference_id: PMID:19359471 review: summary: AGR2 is a soluble secretory-pathway protein with an N-terminal signal peptide and C-terminal KTEL ER-retention motif; the literature places its mucin-processing function within the ER lumen rather than merely the broad ER compartment. action: NEW reason: The existing GOA annotations use the broader endoplasmic reticulum term. ER lumen is the more precise cellular-component annotation for an ER-retained soluble foldase acting on luminal mucin clients. additional_reference_ids: - PMID:22184114 - PMID:19359471 supported_by: - reference_id: PMID:19359471 supporting_text: Here, we show that AGR2 is present within the ER of intestinal secretory epithelial cells and is essential for in vivo production of the intestinal mucin MUC2 reference_section_type: ABSTRACT - reference_id: PMID:19359471 supporting_text: PDI thioredoxin-like domains contain cysteine residues that can form mixed disulfide bonds with client proteins during processing in the ER. reference_section_type: DISCUSSION - reference_id: PMID:22184114 supporting_text: Soluble proteins are targeted to the endoplasmic reticulum (ER) 2 by two major mechanisms. The first is signal peptide-directed translocation of newly translated proteins into the ER. reference_section_type: INTRODUCTION - term: id: GO:1903895 label: negative regulation of IRE1-mediated unfolded protein response qualifier: involved_in evidence_type: IC original_reference_id: PMID:38177501 review: summary: Recent EMBO Journal studies show that AGR2 directly binds the goblet-cell stress sensor IRE1β/ERN2 and represses IRE1β dimerization and endonuclease outputs. This annotation should be interpreted for IRE1β-expressing mucin-producing/goblet-cell contexts, not as evidence for AGR2 repression of ubiquitous IRE1α. It is more precise than the existing historical positive IRE1-mediated UPR annotation, which remains marked as over-annotated. action: NEW reason: AGR2 has direct evidence for negative, not positive, regulation of IRE1β-mediated unfolded protein response signaling in mucin-producing cells. GO:1903895 captures this directionality while keeping the main core-function model centered on ER mucin folding/proteostasis; it should not be generalized to positive IRE1/PERK or broad UPR propagation. additional_reference_ids: - PMID:38177498 - file:human/AGR2/AGR2-deep-research-falcon.md supported_by: - reference_id: PMID:38177501 supporting_text: AGR2 binding to IRE1β disrupts IRE1β oligomerization, thereby blocking its downstream endonuclease activity. reference_section_type: ABSTRACT - reference_id: PMID:38177501 supporting_text: Depletion of endogenous AGR2 from goblet cells induces spontaneous IRE1β activation, suggesting that alterations in AGR2 availability in the endoplasmic reticulum set the threshold for IRE1β activation. reference_section_type: ABSTRACT - reference_id: PMID:38177498 supporting_text: The mucin-specific chaperone AGR2 repressed IRE1 activity in cells expressing the domain-swapped IRE1β/α chimera, but had no effect on IRE1α. reference_section_type: ABSTRACT - reference_id: file:human/AGR2/AGR2-deep-research-falcon.md supporting_text: AGR2 binds IRE1β (selectively vs IRE1α) and inhibits IRE1β oligomerization/dimerization references: - id: GO_REF:0000024 title: Manual transfer of experimentally-verified manual GO annotation data to orthologs by curator judgment of sequence similarity findings: [] - id: GO_REF:0000033 title: Annotation inferences using phylogenetic trees findings: [] - id: GO_REF:0000044 title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt findings: [] - id: GO_REF:0000052 title: Gene Ontology annotation based on curation of immunofluorescence data findings: [] - id: GO_REF:0000107 title: Automatic transfer of experimentally verified manual GO annotation data to orthologs using Ensembl Compara findings: [] - id: GO_REF:0000117 title: Electronic Gene Ontology annotations created by ARBA machine learning models findings: [] - id: GO_REF:0000120 title: Combined Automated Annotation using Multiple IEA Methods findings: [] - id: PMID:12592373 title: hAG-2 and hAG-3, human homologues of genes involved in differentiation, are associated with oestrogen receptor-positive breast tumours and interact with metastasis gene C4.4a and dystroglycan. findings: - statement: AGR2 was reported to bind C4.4a/LYPD3 and alpha-dystroglycan in yeast two-hybrid screens. supporting_text: Yeast two-hybrid cloning identified metastasis-associated GPI-anchored C4.4a protein and extracellular alpha-dystroglycan (DAG-1) as binding partners for both hAG-2 and hAG-3 reference_section_type: ABSTRACT - id: PMID:15834940 title: AGR2, an androgen-inducible secretory protein overexpressed in prostate cancer. findings: [] full_text_unavailable: true - id: PMID:16189514 title: Towards a proteome-scale map of the human protein-protein interaction network. findings: [] full_text_unavailable: true - id: PMID:19359471 title: The protein disulfide isomerase AGR2 is essential for production of intestinal mucus. findings: - statement: AGR2 is an ER-localized PDI-family factor required for intestinal MUC2 production and mucus. supporting_text: Here, we show that AGR2 is present within the ER of intestinal secretory epithelial cells and is essential for in vivo production of the intestinal mucin MUC2 reference_section_type: ABSTRACT - statement: AGR2 forms mixed disulfide bonds with MUC2 via its thioredoxin-like cysteine. supporting_text: A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. reference_section_type: ABSTRACT - id: PMID:22184114 title: AGR2 gene function requires a unique endoplasmic reticulum localization motif. findings: - statement: The conserved C-terminal KTEL motif is required for ER retention and AGR2 function. supporting_text: Deletion of the KTEL motif results in AGR2 secretion and loss of AGR2 function. reference_section_type: ABSTRACT - id: PMID:23220234 title: Dimerization of pro-oncogenic protein Anterior Gradient 2 is required for the interaction with BiP/GRP78. findings: [] full_text_unavailable: true - id: PMID:23274113 title: Metastasis-promoting anterior gradient 2 protein has a dimeric thioredoxin fold structure and a role in cell adhesion. findings: [] full_text_unavailable: true - id: PMID:24251762 title: A highly sensitive targeted mass spectrometric assay for quantification of AGR2 protein in human urine and serum. findings: [] - id: PMID:25416956 title: A proteome-scale map of the human interactome network. findings: [] - id: PMID:25666625 title: Epidermal growth factor receptor (EGFR) signaling requires a specific endoplasmic reticulum thioredoxin for the post-translational control of receptor presentation to the cell surface. findings: - statement: AGR2 binds EGFR in the ER and promotes EGFR surface delivery/signaling in cancer-cell models. supporting_text: EGFR binding to anterior gradient homolog 2 ( AGR2 ) in the endoplasmic reticulum is required for receptor delivery to the plasma membrane and thus EGFR signaling. reference_section_type: ABSTRACT - statement: This EGFR-focused study provides a competing interpretation of AGR2 substrate biology by reporting no MUC2 in its AGR2 mixed-disulfide analysis and citing a re-evaluation against MUC2 folding. supporting_text: Re-evaluation of MUC2 in a recent study also concluded that it is not a AGR2-binding protein and that AGR2 served no role in its folding. reference_section_type: DISCUSSION - id: PMID:25910212 title: Widespread macromolecular interaction perturbations in human genetic disorders. findings: [] - id: PMID:31040128 title: Control of anterior GRadient 2 (AGR2) dimerization links endoplasmic reticulum proteostasis to inflammation. findings: - statement: AGR2 dimerization links ER proteostasis to secretion and inflammation. supporting_text: AGR2 dimers act as sensors of ER homeostasis which are disrupted upon ER stress and promote the secretion of AGR2 monomers. reference_section_type: ABSTRACT - statement: AGR2 dimers dissociate downstream of ER stress sensing rather than driving UPR — establishing the AGR2-versus-UPR-sensor directionality as sensor-driven, not AGR2-driven. supporting_text: dissociation of AGR2 homodimers as assessed by the decrease in luminescence observed for all the constructs tested reference_section_type: RESULTS - statement: The IRE1 mention in this paper is the ERMIT mammalian two-hybrid bait scaffold, not a biological regulatory target — relevant for evaluating arm-specific UPR claims. supporting_text: the luminal domain of IRE1 was replaced by different bait proteins reference_section_type: RESULTS - id: PMID:31247903 title: 'Leveraging the Role of the Metastatic Associated Protein Anterior Gradient Homologue 2 in Unfolded Protein Degradation: A Novel Therapeutic Biomarker for Cancer.' findings: - statement: The well-established AGR2/UPR-sensor directionality is sensor-driven — IRE1α and ATF6α regulate AGR2 expression, not vice versa. PERK is conspicuously absent from the AGR2 mechanistic literature. supporting_text: This was demonstrated when IREα and ATF6α were knocked down using small interfering RNA (siRNA) in HeLa cells, resulting in the decreased expression levels of the AGR2 protein reference_section_type: RESULTS - statement: Mechanistic review summary of AGR2 expression regulators omits any AGR2 → IRE1/PERK regulatory direction. supporting_text: The top molecules implicated in regulating the expression of AGR2 included IRE1α, ATF6α, AKT, FOXA1/2, HIF-1, TMED2, and the frequently mutated tumor suppressor p53. reference_section_type: DISCUSSION - id: PMID:32296183 title: A reference map of the human binary protein interactome. findings: [] - id: PMID:32814053 title: Interactome Mapping Provides a Network of Neurodegenerative Disease Proteins and Uncovers Widespread Protein Aggregation in Affected Brains. findings: [] full_text_unavailable: true - id: PMID:34237462 title: Human AGR2 Deficiency Causes Mucus Barrier Dysfunction and Infantile Inflammatory Bowel Disease. findings: - statement: Human AGR2 deficiency causes goblet-cell and gel-forming mucin loss with ER stress and mucus barrier disease. supporting_text: Patient biopsy specimens showed reduced goblet cells; depletion of MUC2, MUC5AC, and MUC6; up-regulation of AGR2; and increased ER stress. reference_section_type: ABSTRACT - statement: Human AGR2 H117Y has reduced MUC2 binding and reduced ER-stress relief, supporting AGR2-MUC2 functional interaction despite the earlier EGFR-focused conflict. supporting_text: The mutant AGR2 showed reduced capacity to bind MUC2 and alleviate tunicamycin-induced ER stress. reference_section_type: ABSTRACT - id: PMID:38177501 title: Activation of goblet-cell stress sensor IRE1β is controlled by the mucin chaperone AGR2. findings: - statement: AGR2 negatively regulates IRE1β-mediated UPR signaling in goblet-cell contexts by binding IRE1β and blocking oligomerization and endonuclease outputs. supporting_text: AGR2 binding to IRE1β disrupts IRE1β oligomerization, thereby blocking its downstream endonuclease activity. reference_section_type: ABSTRACT - statement: Loss of endogenous AGR2 activates IRE1β in goblet cells, supporting AGR2 as a threshold-setting repressor rather than an activator. supporting_text: Depletion of endogenous AGR2 from goblet cells induces spontaneous IRE1β activation, suggesting that alterations in AGR2 availability in the endoplasmic reticulum set the threshold for IRE1β activation. reference_section_type: ABSTRACT - id: PMID:38177498 title: The IRE1β-mediated unfolded protein response is repressed by the chaperone AGR2 in mucin producing cells. findings: - statement: AGR2 selectively represses IRE1β luminal-domain signaling and supports a mucin-producing-cell-specific IRE1β regulatory mechanism. supporting_text: The mucin-specific chaperone AGR2 repressed IRE1 activity in cells expressing the domain-swapped IRE1β/α chimera, but had no effect on IRE1α. reference_section_type: ABSTRACT - statement: Biophysical evidence supports direct AGR2 destabilization of IRE1β luminal-domain dimers. supporting_text: In vitro, AGR2 actively de-stabilised the IRE1β luminal domain dimer and formed a reversible complex with the inactive monomer. reference_section_type: ABSTRACT - id: file:human/AGR2/AGR2-uniprot.txt title: AGR2 UniProtKB record findings: [] - id: file:human/AGR2/AGR2-notes.md title: Manual AGR2 curation notes findings: [] - id: file:human/AGR2/AGR2-deep-research-falcon.md title: Falcon deep research report for AGR2 findings: - statement: Falcon research supports AGR2 as an ER PDI-family mucin client-processing factor and identifies a newer negative-regulatory role for IRE1β-mediated UPR signaling. supporting_text: Across authoritative reviews and primary studies, the strongest consensus is that AGR2’s primary physiological role is as an ER proteostasis factor for mucin-producing epithelial cells core_functions: - description: AGR2 acts in the ER lumen of mucin-producing epithelial cells as a specialized PDI-family foldase/client-processing factor for gel-forming mucins, especially MUC2. This activity supports MUC2 post-transcriptional synthesis/processing, mucus production, and epithelial mucus barrier integrity; loss of AGR2 disrupts mucin production and increases ER stress in goblet cells. A 2015 EGFR-focused study disputed MUC2 as an AGR2 folding client, but later human AGR2 H117Y data showing reduced MUC2 binding and ER-stress relief support retaining the mucin-processing core-function model. Recent IRE1β work is treated as a direct mucin-producing-cell proteostasis module, not as evidence for broad generic UPR activity. molecular_function: id: GO:0003756 label: protein disulfide isomerase activity directly_involved_in: - id: GO:0034975 label: protein folding in endoplasmic reticulum - id: GO:0070254 label: mucus secretion - id: GO:1903895 label: negative regulation of IRE1-mediated unfolded protein response locations: - id: GO:0005788 label: endoplasmic reticulum lumen substrates: - id: UniProtKB:Q02817 label: mucin-2 supported_by: - reference_id: PMID:19359471 supporting_text: Here, we show that AGR2 is present within the ER of intestinal secretory epithelial cells and is essential for in vivo production of the intestinal mucin MUC2 reference_section_type: ABSTRACT - reference_id: PMID:19359471 supporting_text: A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. reference_section_type: ABSTRACT - reference_id: PMID:34237462 supporting_text: Patient biopsy specimens showed reduced goblet cells; depletion of MUC2, MUC5AC, and MUC6; up-regulation of AGR2; and increased ER stress. reference_section_type: ABSTRACT - reference_id: PMID:34237462 supporting_text: The Mendelian deficiency of AGR2, termed "Enteropathy caused by AGR2 deficiency, Goblet cell Loss, and ER Stress" (EAGLES), results in a mucus barrier defect, the inability to mitigate ER stress, and causes infantile-onset inflammatory bowel disease. reference_section_type: ABSTRACT - reference_id: file:human/AGR2/AGR2-uniprot.txt supporting_text: 'FUNCTION: Required for MUC2 post-transcriptional synthesis and secretion.' - reference_id: PMID:38177501 supporting_text: AGR2 binding to IRE1β disrupts IRE1β oligomerization, thereby blocking its downstream endonuclease activity. reference_section_type: ABSTRACT - reference_id: PMID:38177498 supporting_text: The mucin-specific chaperone AGR2 repressed IRE1 activity in cells expressing the domain-swapped IRE1β/α chimera, but had no effect on IRE1α. reference_section_type: ABSTRACT - reference_id: file:human/AGR2/AGR2-deep-research-falcon.md supporting_text: best-supported client class is mucins - reference_id: file:human/AGR2/AGR2-deep-research-falcon.md supporting_text: Recent mechanistic work shows AGR2 is a goblet-cell mucin chaperone that directly binds IRE1β proposed_new_terms: [] suggested_questions: - question: Is AGR2 best annotated as a bona fide protein disulfide isomerase enzyme for MUC2, or should GO eventually represent a more specific mucin-client foldase/thiol-retention activity? experts: - Park SW - Erle DJ - Lo B - Uhlig HH - question: Which extracellular AGR2 activities, if any, are normal physiological functions rather than cancer- or inflammation-associated consequences of altered ER retention/dimerization? experts: - Chevet E - Ogier-Denis E - Lowe AW suggested_experiments: - hypothesis: AGR2 directly catalyzes or stabilizes disulfide-dependent folding intermediates in gel-forming mucins. description: Reconstitute purified AGR2 with recombinant MUC2 cysteine-rich domains or MUC2 folding intermediates and compare wild-type AGR2 with Cys81/His117/dimerization mutants in disulfide-shuffling, mixed-disulfide trapping, and client-folding assays. experiment_type: in vitro biochemical foldase assay - hypothesis: Extracellular AGR2 monomer functions mainly as a damage/inflammation signal when ER proteostasis is perturbed. description: Compare secretion state, oligomeric state, and monocyte/goblet-cell responses to endogenous AGR2 under normal mucin secretion, tunicamycin/ER stress, TMED2 perturbation, and AGR2 KTEL/dimerization mutant conditions in intestinal epithelial organoids. experiment_type: intestinal organoid perturbation and chemotaxis assay