Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0005783 endoplasmic reticulum	IBA GO_REF:0000033	ACCEPT	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. 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. Supporting Evidence: PMID:19359471 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 PMID:19359471 A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. PMID:22184114 The present study determines whether AGR2 requires a specific ER localization signal to be functionally active. PMID:22184114 Deletion of the KTEL motif results in AGR2 secretion and loss of AGR2 function. file:human/AGR2/AGR2-deep-research-falcon.md AGR2 is widely characterized as a protein disulfide isomerase (PDI)-family / thioredoxin-like protein functioning in the endoplasmic reticulum (ER)
GO:0002162 dystroglycan binding	IBA GO_REF:0000033	KEEP AS NON CORE	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. 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. Supporting Evidence: PMID:12592373 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 PMID:12592373 Clearly, further analyses such as coimmunoprecipitation are required to confirm that these interactions occur in clinical cancers
GO:0048546 digestive tract morphogenesis	IEA GO_REF:0000107	MARK AS OVER ANNOTATED	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. 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. Supporting Evidence: PMID:34237462 Patient biopsy specimens showed reduced goblet cells; depletion of MUC2, MUC5AC, and MUC6; up-regulation of AGR2; and increased ER stress. PMID:34237462 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. file:human/AGR2/AGR2-deep-research-falcon.md Across reviews, these findings are summarized as AGR2 contributing to folding/maturation/secretion of MUC2 and MUC5AC/B
GO:0048639 positive regulation of developmental growth	IEA GO_REF:0000107	MARK AS OVER ANNOTATED	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. Reason: Developmental/growth effects are downstream consequences or cross-species phenotype transfers; they should not be treated as the core human gene function. Supporting Evidence: PMID:19359471 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 PMID:19359471 A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing.
GO:0070254 mucus secretion	IEA GO_REF:0000107	ACCEPT	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. 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. Supporting Evidence: PMID:19359471 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 PMID:19359471 A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. PMID:34237462 Patient biopsy specimens showed reduced goblet cells; depletion of MUC2, MUC5AC, and MUC6; up-regulation of AGR2; and increased ER stress. PMID:34237462 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.
GO:0005515 protein binding	IPI PMID:16189514 Towards a proteome-scale map of the human protein-protein in...	MARK AS OVER ANNOTATED	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. Reason: Protein binding is uninformative for AGR2 curation, and this high-throughput interaction should not be treated as a core function.
GO:0005515 protein binding	IPI PMID:19359471 The protein disulfide isomerase AGR2 is essential for produc...	MODIFY	Summary: The underlying evidence is AGR2 interaction with MUC2 via mixed disulfide bonds during mucin processing, not merely generic protein binding. Reason: Replace the vague protein binding annotation with the more informative AGR2 molecular role as a PDI-family foldase for mucin processing. Proposed replacements: protein disulfide isomerase activity protein folding in endoplasmic reticulum Supporting Evidence: PMID:19359471 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 PMID:19359471 A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing.
GO:0005515 protein binding	IPI PMID:25416956 A proteome-scale map of the human interactome network.	MARK AS OVER ANNOTATED	Summary: This proteome-scale interactome annotation collapses several high-throughput binary interactions into generic protein binding and does not add meaningful AGR2 functional information. Reason: The term protein binding is too general, especially for high-throughput interactome hits that are not tied to AGR2 core mucin-folding biology.
GO:0005515 protein binding	IPI PMID:25910212 Widespread macromolecular interaction perturbations in human...	MARK AS OVER ANNOTATED	Summary: This genetic-disorder interactome annotation is a generic protein-binding statement and does not establish a curated AGR2 function. Reason: The annotation should not be used to infer core AGR2 biology because it is a broad high-throughput interaction label without functional specificity.
GO:0005515 protein binding	IPI PMID:32296183 A reference map of the human binary protein interactome.	MARK AS OVER ANNOTATED	Summary: The reference map reports many binary interactome partners, but the resulting GO term protein binding is too broad to be useful for AGR2. Reason: A generic protein binding annotation for dozens of interactome partners obscures rather than clarifies AGR2 function.
GO:0005515 protein binding	IPI PMID:32814053 Interactome Mapping Provides a Network of Neurodegenerative ...	MARK AS OVER ANNOTATED	Summary: The neurodegenerative-disease interactome protein-binding annotation is context-specific and generic, with no evidence that it represents AGR2 core function. Reason: Retaining generic protein binding as a core AGR2 annotation would overemphasize a high-throughput interaction unrelated to the main ER mucin-processing function.
GO:0005515 protein binding	IPI PMID:34237462 Human AGR2 Deficiency Causes Mucus Barrier Dysfunction and I...	MODIFY	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. 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 replacements: protein disulfide isomerase activity protein folding in endoplasmic reticulum Supporting Evidence: PMID:34237462 AGR2-MUC2 binding was evaluated using co-immunoprecipitation. PMID:34237462 The mutant AGR2 showed reduced capacity to bind MUC2 and alleviate tunicamycin-induced ER stress.
GO:0002162 dystroglycan binding	IEA GO_REF:0000117	KEEP AS NON CORE	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. Reason: Keep the specific binding term as non-core because direct experimental evidence exists, while core AGR2 biology is ER mucin processing. Supporting Evidence: PMID:12592373 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 PMID:12592373 Clearly, further analyses such as coimmunoprecipitation are required to confirm that these interactions occur in clinical cancers
GO:0005576 extracellular region	IEA GO_REF:0000044	KEEP AS NON CORE	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. Reason: Retain as a non-core localization: extracellular AGR2 is real in some contexts, while its conserved core function requires ER residence. Supporting Evidence: PMID:24251762 Anterior gradient 2 (AGR2) is a secreted, cancer-associated protein in many types of epithelial cancer cells. PMID:24251762 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. PMID:31040128 modulation of AGR2 dimer formation, whether enhancing or inhibiting the process, yields pro-inflammatory phenotypes
GO:0005783 endoplasmic reticulum	IEA GO_REF:0000120	ACCEPT	Summary: Automated ER localization is consistent with experimental and orthology evidence and with the conserved KTEL retention motif. Reason: ER is the principal compartment for AGR2 mucin-processing activity. Supporting Evidence: PMID:19359471 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 PMID:19359471 A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. PMID:22184114 The present study determines whether AGR2 requires a specific ER localization signal to be functionally active. PMID:22184114 Deletion of the KTEL motif results in AGR2 secretion and loss of AGR2 function.
GO:0005783 endoplasmic reticulum	IDA GO_REF:0000052	ACCEPT	Summary: Immunofluorescence-based ER annotation is consistent with direct literature showing AGR2 in the ER of intestinal secretory epithelial cells. Reason: This is a core localization for AGR2 function. Supporting Evidence: PMID:19359471 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 PMID:19359471 A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing.
GO:0005783 endoplasmic reticulum	ISS GO_REF:0000024	ACCEPT	Summary: Sequence/orthology transfer of ER localization is consistent with human and mouse evidence and with the conserved ER-retention motif. Reason: The ER location is conserved and functionally required for AGR2. Supporting Evidence: PMID:19359471 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 PMID:19359471 A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. PMID:22184114 The present study determines whether AGR2 requires a specific ER localization signal to be functionally active. PMID:22184114 Deletion of the KTEL motif results in AGR2 secretion and loss of AGR2 function.
GO:0005515 protein binding	IPI PMID:31040128 Control of anterior GRadient 2 (AGR2) dimerization links end...	MARK AS OVER ANNOTATED	Summary: PMID:31040128 identifies regulators of AGR2 dimerization and extracellular release, but generic protein binding is less informative than the specific homodimerization/proteostasis biology. Reason: Protein binding is too broad for this evidence; the useful curation is AGR2 homodimerization and ER proteostasis/inflammatory context. Supporting Evidence: PMID:31040128 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). PMID:31040128 AGR2 dimers act as sensors of ER homeostasis which are disrupted upon ER stress and promote the secretion of AGR2 monomers.
GO:0005576 extracellular region	IDA PMID:31040128 Control of anterior GRadient 2 (AGR2) dimerization links end...	KEEP AS NON CORE	Summary: AGR2 extracellular release is demonstrated in the dimerization/proteostasis study and is linked to pro-inflammatory monocyte chemoattraction. Reason: Extracellular AGR2 is a context-dependent inflammatory/cancer-related state rather than the main ER foldase location, so retain it as non-core. Supporting Evidence: PMID:31040128 modulation of AGR2 dimer formation, whether enhancing or inhibiting the process, yields pro-inflammatory phenotypes PMID:31040128 the extracellular release of AGR2 leads to the chemoattraction of monocytes, thereby suggesting extracellular AGR2's pro-inflammatory functions
GO:0005783 endoplasmic reticulum	IDA PMID:31040128 Control of anterior GRadient 2 (AGR2) dimerization links end...	ACCEPT	Summary: AGR2 is active in the ER in this study, where dimerization status reports ER homeostasis and affects proteostasis. Reason: This reinforces ER as the core active site of AGR2. Supporting Evidence: PMID:31040128 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). PMID:31040128 AGR2 dimers act as sensors of ER homeostasis which are disrupted upon ER stress and promote the secretion of AGR2 monomers.
GO:0006954 inflammatory response	IMP PMID:31040128 Control of anterior GRadient 2 (AGR2) dimerization links end...	KEEP AS NON CORE	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. Reason: Inflammatory response is supported but should be non-core relative to AGR2's primary ER mucin-folding role. Supporting Evidence: PMID:31040128 modulation of AGR2 dimer formation, whether enhancing or inhibiting the process, yields pro-inflammatory phenotypes PMID:31040128 the extracellular release of AGR2 leads to the chemoattraction of monocytes, thereby suggesting extracellular AGR2's pro-inflammatory functions PMID:34237462 Patient biopsy specimens showed reduced goblet cells; depletion of MUC2, MUC5AC, and MUC6; up-regulation of AGR2; and increased ER stress.
GO:0030968 endoplasmic reticulum unfolded protein response	IDA PMID:31040128 Control of anterior GRadient 2 (AGR2) dimerization links end...	KEEP AS NON CORE	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. 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. Supporting Evidence: PMID:31040128 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). PMID:31040128 AGR2 dimers act as sensors of ER homeostasis which are disrupted upon ER stress and promote the secretion of AGR2 monomers. PMID:34237462 The mutant AGR2 showed reduced capacity to bind MUC2 and alleviate tunicamycin-induced ER stress.
GO:0034975 protein folding in endoplasmic reticulum	IDA PMID:31040128 Control of anterior GRadient 2 (AGR2) dimerization links end...	ACCEPT	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. 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. Supporting Evidence: PMID:19359471 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 PMID:19359471 A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. PMID:34237462 Patient biopsy specimens showed reduced goblet cells; depletion of MUC2, MUC5AC, and MUC6; up-regulation of AGR2; and increased ER stress. PMID:34237462 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. PMID:34237462 The mutant AGR2 showed reduced capacity to bind MUC2 and alleviate tunicamycin-induced ER stress. PMID:25666625 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.
GO:0034975 protein folding in endoplasmic reticulum	IMP PMID:31040128 Control of anterior GRadient 2 (AGR2) dimerization links end...	ACCEPT	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. 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. Supporting Evidence: PMID:19359471 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 PMID:19359471 A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. PMID:34237462 Patient biopsy specimens showed reduced goblet cells; depletion of MUC2, MUC5AC, and MUC6; up-regulation of AGR2; and increased ER stress. PMID:34237462 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. PMID:34237462 The mutant AGR2 showed reduced capacity to bind MUC2 and alleviate tunicamycin-induced ER stress. PMID:25666625 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.
GO:0042803 protein homodimerization activity	IPI PMID:31040128 Control of anterior GRadient 2 (AGR2) dimerization links end...	ACCEPT	Summary: AGR2 homodimerization is a well-supported molecular property that controls ER homeostasis and extracellular release. Reason: Homodimerization is a key mechanistic feature of AGR2 function and is directly supported by dimerization assays and structural/biochemical studies. Supporting Evidence: PMID:31040128 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). PMID:31040128 AGR2 dimers act as sensors of ER homeostasis which are disrupted upon ER stress and promote the secretion of AGR2 monomers.
GO:0060326 cell chemotaxis	IDA PMID:31040128 Control of anterior GRadient 2 (AGR2) dimerization links end...	KEEP AS NON CORE	Summary: Extracellular AGR2 can chemoattract monocytes in the inflammation study, but this is a context-dependent extracellular alarm/inflammatory activity. 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. Supporting Evidence: PMID:31040128 modulation of AGR2 dimer formation, whether enhancing or inhibiting the process, yields pro-inflammatory phenotypes PMID:31040128 the extracellular release of AGR2 leads to the chemoattraction of monocytes, thereby suggesting extracellular AGR2's pro-inflammatory functions
GO:0005576 extracellular region	IDA PMID:15834940 AGR2, an androgen-inducible secretory protein overexpressed ...	KEEP AS NON CORE	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. Reason: Extracellular/secreted AGR2 is supported but should be non-core relative to ER-localized foldase activity. Supporting Evidence: PMID:15834940 the androgen-induced secretory protein AGR2 may serve as a potential therapeutic target and/or molecular marker for prostate cancer.
GO:0042802 identical protein binding	IPI PMID:23220234 Dimerization of pro-oncogenic protein Anterior Gradient 2 is...	MODIFY	Summary: The BiP/GRP78 paper reports AGR2 homo-dimerization, so identical protein binding should be curated more specifically as protein homodimerization activity. Reason: GO:0042803 captures the observed AGR2 self-association more precisely than identical protein binding. Proposed replacements: protein homodimerization activity Supporting Evidence: PMID:23220234 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.
GO:0042802 identical protein binding	IPI PMID:23274113 Metastasis-promoting anterior gradient 2 protein has a dimer...	MODIFY	Summary: The NMR/structure paper reports AGR2 monomer-dimer equilibrium and a dimeric thioredoxin fold, so protein homodimerization activity is the better term. Reason: Identical protein binding is less specific than the demonstrated homodimerization activity. Proposed replacements: protein homodimerization activity Supporting Evidence: PMID:23274113 The protein exists in monomer-dimer equilibrium with a K(d) of 8.83μM
GO:0005515 protein binding	IPI PMID:23220234 Dimerization of pro-oncogenic protein Anterior Gradient 2 is...	MODIFY	Summary: The interaction with BiP/GRP78 is a specific chaperone interaction; generic protein binding is too broad. Reason: Replace with protein-folding chaperone binding to capture the BiP/GRP78 association more specifically. Proposed replacements: protein-folding chaperone binding Supporting Evidence: PMID:23220234 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.
GO:0005576 extracellular region	IDA PMID:22184114 AGR2 gene function requires a unique endoplasmic reticulum l...	KEEP AS NON CORE	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. 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. Supporting Evidence: PMID:22184114 The present study determines whether AGR2 requires a specific ER localization signal to be functionally active. PMID:22184114 Deletion of the KTEL motif results in AGR2 secretion and loss of AGR2 function.
GO:0005783 endoplasmic reticulum	IMP PMID:22184114 AGR2 gene function requires a unique endoplasmic reticulum l...	ACCEPT	Summary: The KTEL paper strongly supports ER localization/residence as required for AGR2 function. Reason: ER residence is a core functional requirement for AGR2. Supporting Evidence: PMID:22184114 The present study determines whether AGR2 requires a specific ER localization signal to be functionally active. PMID:22184114 Deletion of the KTEL motif results in AGR2 secretion and loss of AGR2 function.
GO:0010628 positive regulation of gene expression	IMP PMID:22184114 AGR2 gene function requires a unique endoplasmic reticulum l...	MARK AS OVER ANNOTATED	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. 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. Supporting Evidence: PMID:22184114 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. PMID:22184114 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.
GO:1903896 positive regulation of IRE1-mediated unfolded protein response	IDA PMID:23220234 Dimerization of pro-oncogenic protein Anterior Gradient 2 is...	MARK AS OVER ANNOTATED	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. 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. Supporting Evidence: PMID:23220234 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. PMID:31247903 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 PMID:31040128 the luminal domain of IRE1 was replaced by different bait proteins PMID:31040128 dissociation of AGR2 homodimers as assessed by the decrease in luminescence observed for all the constructs tested
GO:1903899 positive regulation of PERK-mediated unfolded protein response	IDA PMID:23220234 Dimerization of pro-oncogenic protein Anterior Gradient 2 is...	MARK AS OVER ANNOTATED	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). 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. Supporting Evidence: PMID:23220234 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. PMID:31247903 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. PMID:31040128 dissociation of AGR2 homodimers as assessed by the decrease in luminescence observed for all the constructs tested
GO:0005576 extracellular region	IDA PMID:24251762 A highly sensitive targeted mass spectrometric assay for qua...	KEEP AS NON CORE	Summary: Targeted mass spectrometry detected AGR2 in human urine and serum, supporting extracellular/body-fluid localization. Reason: Extracellular AGR2 is a supported non-core localization, especially in biomarker/cancer contexts. Supporting Evidence: PMID:24251762 Anterior gradient 2 (AGR2) is a secreted, cancer-associated protein in many types of epithelial cancer cells. PMID:24251762 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.
GO:0005154 epidermal growth factor receptor binding	IPI PMID:25666625 Epidermal growth factor receptor (EGFR) signaling requires a...	KEEP AS NON CORE	Summary: AGR2 binds EGFR in the ER and is required for receptor delivery to the plasma membrane in cancer-cell models. Reason: The term is supported, but EGFR appears to be a context-specific client/pathway rather than the main conserved AGR2 function. Supporting Evidence: PMID:25666625 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. PMID:25666625 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.
GO:0010811 positive regulation of cell-substrate adhesion	IMP PMID:23274113 Metastasis-promoting anterior gradient 2 protein has a dimer...	KEEP AS NON CORE	Summary: AGR2 can promote cell-substrate adhesion in cancer/metastasis assays, but this extracellular N-terminal activity is context-dependent. Reason: Cell adhesion is supported but is not the core ER mucin-processing function. Supporting Evidence: PMID:23274113 The unstructured region is primarily responsible for the ability of AGR2 to promote cell adhesion, while dimerization is less important for this activity.
GO:0034976 response to endoplasmic reticulum stress	IMP NOT PMID:25666625 Epidermal growth factor receptor (EGFR) signaling requires a...	REMOVE	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. 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. Supporting Evidence: PMID:31040128 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). PMID:31040128 AGR2 dimers act as sensors of ER homeostasis which are disrupted upon ER stress and promote the secretion of AGR2 monomers. PMID:34237462 The mutant AGR2 showed reduced capacity to bind MUC2 and alleviate tunicamycin-induced ER stress. PMID:34237462 AGR2 H117Y has a reduced capacity to regulate ER stress even in the absence of gel-forming mucins in vitro.
GO:0045742 positive regulation of epidermal growth factor receptor signaling pathway	IMP PMID:25666625 Epidermal growth factor receptor (EGFR) signaling requires a...	KEEP AS NON CORE	Summary: AGR2 supports EGFR signaling by enabling EGFR delivery to the cell surface in tested cancer-cell models. Reason: This is supported as a client-specific, context-dependent process, but it is not the conserved core AGR2 function. Supporting Evidence: PMID:25666625 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. PMID:25666625 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.
GO:0048546 digestive tract morphogenesis	ISS GO_REF:0000024	MARK AS OVER ANNOTATED	Summary: Digestive tract morphogenesis remains an over-broad orthology transfer relative to the known AGR2 mechanism. Reason: Human and mouse evidence supports mucin processing/mucus barrier maintenance, not direct digestive tract morphogenesis. Supporting Evidence: PMID:34237462 Patient biopsy specimens showed reduced goblet cells; depletion of MUC2, MUC5AC, and MUC6; up-regulation of AGR2; and increased ER stress. PMID:34237462 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.
GO:0048639 positive regulation of developmental growth	ISS GO_REF:0000024	MARK AS OVER ANNOTATED	Summary: Positive regulation of developmental growth is too broad and likely reflects indirect developmental/phenotypic transfer from orthologs. Reason: The direct AGR2 mechanism is ER mucin/client processing; growth/developmental phenotypes should not be elevated to core gene function. Supporting Evidence: PMID:19359471 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 PMID:19359471 A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing.
GO:1903078 positive regulation of protein localization to plasma membrane	IMP PMID:25666625 Epidermal growth factor receptor (EGFR) signaling requires a...	KEEP AS NON CORE	Summary: AGR2 promotes EGFR localization to the plasma membrane by binding EGFR in the ER, but the GO term is broad and substrate-specific. 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. Supporting Evidence: PMID:25666625 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. PMID:25666625 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.
GO:0005515 protein binding	IPI PMID:12592373 hAG-2 and hAG-3, human homologues of genes involved in diffe...	MODIFY	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. 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 replacements: dystroglycan binding Supporting Evidence: PMID:12592373 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 PMID:12592373 Clearly, further analyses such as coimmunoprecipitation are required to confirm that these interactions occur in clinical cancers
GO:0002162 dystroglycan binding	IDA PMID:12592373 hAG-2 and hAG-3, human homologues of genes involved in diffe...	KEEP AS NON CORE	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. Reason: Retain the specific molecular interaction as non-core. Supporting Evidence: PMID:12592373 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 PMID:12592373 Clearly, further analyses such as coimmunoprecipitation are required to confirm that these interactions occur in clinical cancers
GO:0070254 mucus secretion	ISS GO_REF:0000024	ACCEPT	Summary: Mucus secretion transferred from mouse orthology is supported by human AGR2 deficiency and mouse Agr2 loss-of-function evidence. Reason: Mucus production/secretion is a principal biological outcome of AGR2's core role in mucin processing. Supporting Evidence: PMID:19359471 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 PMID:19359471 A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. PMID:34237462 Patient biopsy specimens showed reduced goblet cells; depletion of MUC2, MUC5AC, and MUC6; up-regulation of AGR2; and increased ER stress. PMID:34237462 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.
GO:0003756 protein disulfide isomerase activity	IC PMID:19359471 The protein disulfide isomerase AGR2 is essential for produc...	NEW	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. 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. Supporting Evidence: PMID:19359471 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 PMID:19359471 A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing. PMID:34237462 The mutant AGR2 showed reduced capacity to bind MUC2 and alleviate tunicamycin-induced ER stress. PMID:34237462 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. PMID:31040128 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). PMID:25666625 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. file:human/AGR2/AGR2-deep-research-falcon.md AGR2’s best-supported substrates/clients are cysteine-rich secreted mucins
GO:0005788 endoplasmic reticulum lumen	IC PMID:19359471 The protein disulfide isomerase AGR2 is essential for produc...	NEW	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. 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. Supporting Evidence: PMID:19359471 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 PMID:19359471 PDI thioredoxin-like domains contain cysteine residues that can form mixed disulfide bonds with client proteins during processing in the ER. PMID:22184114 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.
GO:1903895 negative regulation of IRE1-mediated unfolded protein response	IC PMID:38177501 Activation of goblet-cell stress sensor IRE1β is controlled ...	NEW	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. 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. Supporting Evidence: PMID:38177501 AGR2 binding to IRE1β disrupts IRE1β oligomerization, thereby blocking its downstream endonuclease activity. PMID:38177501 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. PMID:38177498 The mucin-specific chaperone AGR2 repressed IRE1 activity in cells expressing the domain-swapped IRE1β/α chimera, but had no effect on IRE1α. file:human/AGR2/AGR2-deep-research-falcon.md AGR2 binds IRE1β (selectively vs IRE1α) and inhibits IRE1β oligomerization/dimerization

Core Functions

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:

protein disulfide isomerase activity

Directly Involved In:

protein folding in endoplasmic reticulum mucus secretion negative regulation of IRE1-mediated unfolded protein response

Cellular Locations:

endoplasmic reticulum lumen

Substrates:

mucin-2

Supporting Evidence:

PMID:19359471
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
PMID:19359471
A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing.
PMID:34237462
Patient biopsy specimens showed reduced goblet cells; depletion of MUC2, MUC5AC, and MUC6; up-regulation of AGR2; and increased ER stress.
PMID:34237462
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.
file:human/AGR2/AGR2-uniprot.txt
FUNCTION: Required for MUC2 post-transcriptional synthesis and secretion.
PMID:38177501
AGR2 binding to IRE1β disrupts IRE1β oligomerization, thereby blocking its downstream endonuclease activity.
PMID:38177498
The mucin-specific chaperone AGR2 repressed IRE1 activity in cells expressing the domain-swapped IRE1β/α chimera, but had no effect on IRE1α.
file:human/AGR2/AGR2-deep-research-falcon.md
best-supported client class is mucins
file:human/AGR2/AGR2-deep-research-falcon.md
Recent mechanistic work shows AGR2 is a goblet-cell mucin chaperone that directly binds IRE1β

References

GO_REF:0000024

Manual transfer of experimentally-verified manual GO annotation data to orthologs by curator judgment of sequence similarity

GO_REF:0000033

Annotation inferences using phylogenetic trees

GO_REF:0000044

Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt

GO_REF:0000052

Gene Ontology annotation based on curation of immunofluorescence data

GO_REF:0000107

Automatic transfer of experimentally verified manual GO annotation data to orthologs using Ensembl Compara

GO_REF:0000117

Electronic Gene Ontology annotations created by ARBA machine learning models

GO_REF:0000120

Combined Automated Annotation using Multiple IEA Methods

PMID:12592373

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.

AGR2 was reported to bind C4.4a/LYPD3 and alpha-dystroglycan in yeast two-hybrid screens.

"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"

PMID:15834940

AGR2, an androgen-inducible secretory protein overexpressed in prostate cancer.

PMID:16189514

Towards a proteome-scale map of the human protein-protein interaction network.

PMID:19359471

The protein disulfide isomerase AGR2 is essential for production of intestinal mucus.

AGR2 is an ER-localized PDI-family factor required for intestinal MUC2 production and mucus.

"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"
AGR2 forms mixed disulfide bonds with MUC2 via its thioredoxin-like cysteine.

"A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, indicating a direct role for AGR2 in mucin processing."

PMID:22184114

AGR2 gene function requires a unique endoplasmic reticulum localization motif.

The conserved C-terminal KTEL motif is required for ER retention and AGR2 function.

"Deletion of the KTEL motif results in AGR2 secretion and loss of AGR2 function."

PMID:23220234

Dimerization of pro-oncogenic protein Anterior Gradient 2 is required for the interaction with BiP/GRP78.

PMID:23274113

Metastasis-promoting anterior gradient 2 protein has a dimeric thioredoxin fold structure and a role in cell adhesion.

PMID:24251762

A highly sensitive targeted mass spectrometric assay for quantification of AGR2 protein in human urine and serum.

PMID:25416956

A proteome-scale map of the human interactome network.

PMID:25666625

Epidermal growth factor receptor (EGFR) signaling requires a specific endoplasmic reticulum thioredoxin for the post-translational control of receptor presentation to the cell surface.

AGR2 binds EGFR in the ER and promotes EGFR surface delivery/signaling in cancer-cell models.

"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."
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.

"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."

PMID:25910212

Widespread macromolecular interaction perturbations in human genetic disorders.

PMID:31040128

Control of anterior GRadient 2 (AGR2) dimerization links endoplasmic reticulum proteostasis to inflammation.

AGR2 dimerization links ER proteostasis to secretion and inflammation.

"AGR2 dimers act as sensors of ER homeostasis which are disrupted upon ER stress and promote the secretion of AGR2 monomers."
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.

"dissociation of AGR2 homodimers as assessed by the decrease in luminescence observed for all the constructs tested"
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.

"the luminal domain of IRE1 was replaced by different bait proteins"

PMID:31247903

Leveraging the Role of the Metastatic Associated Protein Anterior Gradient Homologue 2 in Unfolded Protein Degradation: A Novel Therapeutic Biomarker for Cancer.

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.

"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"
Mechanistic review summary of AGR2 expression regulators omits any AGR2 → IRE1/PERK regulatory direction.

"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."

PMID:32296183

A reference map of the human binary protein interactome.

PMID:32814053

Interactome Mapping Provides a Network of Neurodegenerative Disease Proteins and Uncovers Widespread Protein Aggregation in Affected Brains.

PMID:34237462

Human AGR2 Deficiency Causes Mucus Barrier Dysfunction and Infantile Inflammatory Bowel Disease.

Human AGR2 deficiency causes goblet-cell and gel-forming mucin loss with ER stress and mucus barrier disease.

"Patient biopsy specimens showed reduced goblet cells; depletion of MUC2, MUC5AC, and MUC6; up-regulation of AGR2; and increased ER stress."
Human AGR2 H117Y has reduced MUC2 binding and reduced ER-stress relief, supporting AGR2-MUC2 functional interaction despite the earlier EGFR-focused conflict.

"The mutant AGR2 showed reduced capacity to bind MUC2 and alleviate tunicamycin-induced ER stress."

PMID:38177501

Activation of goblet-cell stress sensor IRE1β is controlled by the mucin chaperone AGR2.

AGR2 negatively regulates IRE1β-mediated UPR signaling in goblet-cell contexts by binding IRE1β and blocking oligomerization and endonuclease outputs.

"AGR2 binding to IRE1β disrupts IRE1β oligomerization, thereby blocking its downstream endonuclease activity."
Loss of endogenous AGR2 activates IRE1β in goblet cells, supporting AGR2 as a threshold-setting repressor rather than an activator.

"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."

PMID:38177498

The IRE1β-mediated unfolded protein response is repressed by the chaperone AGR2 in mucin producing cells.

AGR2 selectively represses IRE1β luminal-domain signaling and supports a mucin-producing-cell-specific IRE1β regulatory mechanism.

"The mucin-specific chaperone AGR2 repressed IRE1 activity in cells expressing the domain-swapped IRE1β/α chimera, but had no effect on IRE1α."
Biophysical evidence supports direct AGR2 destabilization of IRE1β luminal-domain dimers.

"In vitro, AGR2 actively de-stabilised the IRE1β luminal domain dimer and formed a reversible complex with the inactive monomer."

file:human/AGR2/AGR2-uniprot.txt

AGR2 UniProtKB record

file:human/AGR2/AGR2-notes.md

Manual AGR2 curation notes

file:human/AGR2/AGR2-deep-research-falcon.md

Falcon deep research report for AGR2

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.

"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"

Suggested Experiments

Experiment: 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.

Hypothesis: AGR2 directly catalyzes or stabilizes disulfide-dependent folding intermediates in gel-forming mucins.

Type: in vitro biochemical foldase assay

Experiment: 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.

Hypothesis: Extracellular AGR2 monomer functions mainly as a damage/inflammation signal when ER proteostasis is perturbed.

Type: intestinal organoid perturbation and chemotaxis assay

Deep Research

Falcon

(AGR2-deep-research-falcon.md)

this with annotations you find in gene/protein databases, but these can be outdated or inaccurate. Falcon Edison Scientific Literature 42 citations 2026-05-10T18:42:32.377162

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Research Report: Human AGR2 (Anterior gradient protein 2 homolog; UniProt O95994) — functional annotation

1) Gene/protein identity verification (critical disambiguation)

The literature retrieved and analyzed consistently matches the UniProt entry O95994 for Homo sapiens AGR2, described as an anterior gradient (AGR) family member with a thioredoxin/PDI-like fold and a non-canonical active-site CXXS motif centered on Cys81 and a C-terminal ER retention motif KTEL (boisteau2022anteriorgradientproteins pages 6-10, boisteau2022anteriorgradientproteins pages 10-13). This matches the target identity provided in the prompt and excludes unrelated “AGR2” symbols from non-human organisms.

2) Key concepts and definitions (current understanding)

2.1 AGR2 as a specialized PDI/thioredoxin-like folding factor

AGR2 is widely characterized as a protein disulfide isomerase (PDI)-family / thioredoxin-like protein functioning in the endoplasmic reticulum (ER) to support folding and maturation of secretory proteins, particularly mucins (boisteau2022anteriorgradientproteins pages 6-10, boisteau2022anteriorgradientproteins pages 10-13, boisteau2022anteriorgradientproteins pages 1-6). Its distinguishing biochemical feature is a non-canonical CXXS active-site motif (rather than the canonical PDI CXXC), with a single key cysteine (Cys81) that participates in disulfide chemistry with client proteins (boisteau2022anteriorgradientproteins pages 6-10, park2009theproteindisulfide pages 2-2, park2009theproteindisulfide pages 4-5).

2.2 ER retention and trafficking: the KTEL motif and “weak retention”

AGR2 contains an atypical C-terminal KTEL ER-retention motif, which binds KDEL receptors non-canonically, and is repeatedly discussed as a mechanistic reason AGR2 can be retained in the ER yet still be prone to secretion/redistribution under certain conditions (boisteau2022anteriorgradientproteins pages 6-10, boisteau2022anteriorgradientproteins pages 10-13). Replacing KTEL with canonical KDEL can drive stronger ER sequestration (boisteau2022anteriorgradientproteins pages 10-13, boisteau2022anteriorgradientproteins pages 6-10).

2.3 Intracellular AGR2 vs extracellular AGR2 (eAGR2)

A current conceptual framework in reviews is that AGR2 exists as both an intracellular ER-resident proteostasis factor and an extracellular/secreted form (eAGR2) with distinct roles, particularly in cancer and inflammatory microenvironments (boisteau2022anteriorgradientproteins pages 10-13, boisteau2022anteriorgradientproteins pages 6-10, qu2024agr2thecovert pages 3-5). However, authoritative sources emphasize that the mechanisms enabling secretion and which extracellular functions are direct vs indirect consequences of ER proteostasis remain incompletely resolved (boisteau2022anteriorgradientproteins pages 6-10, qu2024agr2thecovert pages 16-18).

3) Core molecular functions: what AGR2 “does”

3.1 Primary functional axis: mucin folding/processing and mucus barrier biology

A central, experimentally supported function of AGR2 is enabling proper mucin biogenesis, especially gel-forming mucins that require extensive disulfide bond formation.

Park et al., PNAS 2009 (Apr 2009; https://doi.org/10.1073/pnas.0808722106) demonstrate AGR2 is essential for intestinal mucus production and mechanistically link AGR2 to MUC2: AGR2 co-immunoprecipitates with MUC2 in a DTT-sensitive manner consistent with disulfide linkage, and an AGR2 cysteine mutant (C81S) fails to associate, supporting the role of the active-site cysteine in mixed-disulfide formation with mucins (park2009theproteindisulfide pages 2-2, park2009theproteindisulfide pages 4-5). Agr2-deficient mice show near absence of detectable MUC2 protein despite mRNA still being present (though reduced), and show increased susceptibility to colitis-related pathology (park2009theproteindisulfide pages 2-2, park2009theproteindisulfide pages 4-5).
Worfolk et al., Antioxidants & Redox Signaling 2019 (Nov 2019; https://doi.org/10.1089/ars.2018.7647) further supports mucin specificity by identifying MUC5AC/B as a major secretory client class in a cancer context, with AGR2 participating in disulfide-dependent complexes and client quality control (worfolk2019elucidationofthe pages 11-14).

Across reviews, these findings are summarized as AGR2 contributing to folding/maturation/secretion of MUC2 and MUC5AC/B and other mucins through PDI-like chemistry, most likely including mixed disulfide intermediates (boisteau2022anteriorgradientproteins pages 10-13, boisteau2022anteriorgradientproteins pages 6-10).

Substrate specificity (practical interpretation): AGR2’s best-supported “substrates/clients” are cysteine-rich secreted mucins (MUC2; MUC5AC/B) rather than small-molecule substrates typical of metabolic enzymes; its “reaction” is thiol–disulfide exchange supporting mucin oxidative folding (park2009theproteindisulfide pages 2-2, park2009theproteindisulfide pages 4-5, worfolk2019elucidationofthe pages 11-14).

3.2 AGR2 as a regulator of goblet-cell UPR signaling via IRE1β (major 2023 development)

A major 2023 advance is the demonstration that AGR2 is not only a mucin folding factor, but also a direct regulator of an epithelial stress sensor, IRE1β (ERN2).

Cloots et al., EMBO Journal 2023 (Dec 2023; https://doi.org/10.1038/s44318-023-00015-y) show AGR2 binds IRE1β (selectively vs IRE1α) and inhibits IRE1β oligomerization/dimerization, shifting it toward an inactive monomeric state and suppressing IRE1β endonuclease outputs including XBP1 splicing and RIDD-associated readouts (cloots2023activationofgobletcell pages 1-2, cloots2023activationofgobletcell pages 6-7, cloots2023activationofgobletcell pages 12-13). AGR2 depletion triggers spontaneous IRE1β activation, indicating AGR2 availability in the ER sets an activation threshold (cloots2023activationofgobletcell pages 1-2). Mechanistically, AGR2 monomeric mutants (E60A/K64A) can still bind and inhibit IRE1β dimerization, but active-site/Cys81 disruption (C81S) and a disease-associated H117Y variant abrogate binding/inhibition (cloots2023activationofgobletcell pages 7-8, cloots2023activationofgobletcell pages 11-12).
Neidhardt et al., EMBO Journal 2023 (Dec 2023; https://doi.org/10.1038/s44318-023-00014-z) provide complementary biophysical evidence that AGR2 perturbs IRE1β luminal-domain dimerization kinetics and report an estimated AGR2 concentration in goblet-cell ER of ~460 µM, supporting physiological plausibility of a direct chaperone-like repression mechanism (neidhardt2023theire1βmediatedunfolded pages 29-35).

Interpretation: These EMBO Journal studies support a model where AGR2 plays a dual “proteostasis integrator” role in goblet cells: it assists mucin folding load and simultaneously tunes IRE1β signaling by repressing dimerization until folding demand shifts the balance (cloots2023activationofgobletcell pages 6-7, neidhardt2023theire1βmediatedunfolded pages 29-35).

4) Subcellular localization and secretion: where AGR2 acts

4.1 ER localization with conditional secretion into mucus

AGR2 is predominantly ER-localized, but multiple primary studies show it can be present extracellularly.

Bergström et al., PLoS ONE 2014 (Aug 2014; https://doi.org/10.1371/journal.pone.0104186) report AGR2 in mouse and human gastrointestinal mucus (∼18 kDa band) and show in cell culture that secretion is controlled by both the single free cysteine (Cys81) and the KTEL motif: WT AGR2 is ER-retained, whereas C81S or loss of KTEL (ΔKTEL) permits secretion into media (bergstrom2014agr2anendoplasmic pages 4-6). This supports a mechanistic link between redox/thiol state, ER retention, and extracellular appearance.
Reviews synthesize that the non-canonical KTEL motif enables weaker retention (vs KDEL) and that ER stress, overexpression, or altered dimerization can promote secretion (boisteau2022anteriorgradientproteins pages 10-13, boisteau2022anteriorgradientproteins pages 6-10).

4.2 Extracellular AGR2 in cancer microenvironments

Reviews and translational studies emphasize extracellular AGR2 (eAGR2) as a pro-tumor factor that is mechanistically separable from ER folding roles.

The Oncogene 2022 review summarizes findings that tumor-derived eAGR2 can bind extracellular growth factors such as VEGF and FGF2 and enhance activity, with implications for angiogenesis and therapy interactions (boisteau2022anteriorgradientproteins pages 43-48).
The Biomolecules 2024 review describes eAGR2 as particularly relevant to tumor microenvironment interactions and highlights context-dependent roles that may differ from intracellular AGR2 (qu2024agr2thecovert pages 3-5).

5) Recent developments (prioritizing 2023–2024)

5.1 2023: AGR2–IRE1β as a goblet-cell-specific UPR rheostat

The strongest mechanistic advance is the demonstration that AGR2 is a direct, selective repressor of IRE1β via physical interaction and inhibition of dimerization/endonuclase activity; importantly, this requires intact AGR2 structural features including Cys81 and a disease-relevant residue H117 (cloots2023activationofgobletcell pages 1-2, cloots2023activationofgobletcell pages 7-8).

5.2 2024: expansion of AGR2 as a therapeutic target in PDAC and beyond

A highly translational 2024 study develops high-affinity human monoclonal antibodies against AGR2 and quantifies PDAC prevalence and outcome associations.

Robinson et al., Antibodies 2024 (Dec 2024; https://doi.org/10.3390/antib13040101) report AGR2 protein expression in ~90% of PDAC biopsies, with staining coverage 5–70% of tissue cores, and higher expression with disease progression (robinson2024ahighaffinitymonoclonal pages 6-8). Using TCGA/GTEx comparisons (TCGA n=179; GTEx n=177), AGR2 mRNA is higher in PDAC (p<0.01) and high AGR2 expression associates with worse disease-free survival (HR = 2.5; p = 0.016, high n=107 vs low n=27) (robinson2024ahighaffinitymonoclonal pages 6-8, robinson2024ahighaffinitymonoclonal pages 8-10). The study describes affinity-matured anti-AGR2 mAbs with low-picomolar binding and demonstrates functional neutralization of AGR2-mediated adhesion/migration and disruption of binding to LYPD3 (robinson2024ahighaffinitymonoclonal pages 1-2, robinson2024ahighaffinitymonoclonal pages 15-17).

6) Current applications and real-world implementations

6.1 Biomarker applications (tissue and potential fluid assays)

AGR2 is proposed and actively evaluated as a tissue biomarker in PDAC and other epithelial cancers.

In PDAC, AGR2 is near-ubiquitously present in tumor tissue (~90%) and absent in normal pancreas in the analyzed cohorts, supporting diagnostic discrimination and stratification, with prognostic association via disease-free survival hazard ratio (robinson2024ahighaffinitymonoclonal pages 6-8, robinson2024ahighaffinitymonoclonal pages 8-10).
Reviews additionally describe AGR2 as being secreted during pancreatic cancer development and discuss serum-based biomarker work and biosensor efforts, including an ultrasensitive AGR2 detection approach (femtogram detection) using monoclonal antibody-modified electrodes (boisteau2022anteriorgradientproteins pages 43-48).

6.2 Therapeutic targeting (preclinical)

Current “real-world” use is predominantly preclinical, centered on targeting extracellular AGR2 while recognizing potential toxicity/limitations of targeting ER-resident AGR2.

The Oncogene 2022 review emphasizes that targeting ER-resident AGR2 may be problematic due to physiological roles (e.g., mucus barrier), but secreted/cytosolic AGR2 may be more actionable; it summarizes multiple anti-AGR2 monoclonal antibody studies that reduce tumor growth/metastasis in animal models and may synergize with chemotherapy (boisteau2022anteriorgradientproteins pages 21-24, boisteau2022anteriorgradientproteins pages 43-48).
Robinson et al. 2024 provide concrete implementation of this concept by generating high-affinity antibodies that neutralize AGR2-mediated pro-migratory effects and block AGR2 interactions (robinson2024ahighaffinitymonoclonal pages 1-2, robinson2024ahighaffinitymonoclonal pages 15-17).

6.3 Clinical trials status

In the clinical-trials retrieval performed here, the “AGR2” query did not return an AGR2-targeted therapeutic trial; retrieved trials were unrelated to AGR2 as an intervention target (clinical-trials tool output not AGR2-specific). Therefore, based on the retrieved evidence, AGR2-targeted clinical translation remains largely preclinical/early translational in the sources examined (qu2024agr2thecovert pages 12-13, boisteau2022anteriorgradientproteins pages 43-48, robinson2024ahighaffinitymonoclonal pages 1-2).

7) Statistics and quantitative data highlights (recent studies)

Key quantitative results from recent and mechanistic studies include:

Goblet-cell ER AGR2 concentration: ~460 µM (Neidhardt et al., EMBO J 2023) (neidhardt2023theire1βmediatedunfolded pages 29-35).
PDAC prevalence: AGR2 protein in ~90% of PDAC biopsies; staining 5–70% of tissue cores (Robinson et al., 2024) (robinson2024ahighaffinitymonoclonal pages 6-8, robinson2024ahighaffinitymonoclonal pages 1-2).
Outcome association: high AGR2 mRNA associated with worse disease-free survival (HR 2.5, p=0.016; high n=107 vs low n=27; TCGA/GTEx comparison n=179 vs 177, p<0.01) (robinson2024ahighaffinitymonoclonal pages 6-8, robinson2024ahighaffinitymonoclonal pages 8-10).
Mucin biology (airway model): in allergen-challenged Agr2−/− mice, MUC5AC −50.3% and MUC5B −56.1% protein reductions without significant mRNA changes, supporting post-transcriptional processing control (Schroeder et al., 2012) (schroeder2012agr2isinduced pages 5-6).

8) Expert analysis and synthesis (authoritative consensus and open questions)

8.1 Consensus

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, where it supports mucin folding/processing via thiol–disulfide exchange and participates in specialized ER homeostasis programs (park2009theproteindisulfide pages 2-2, park2009theproteindisulfide pages 4-5, boisteau2022anteriorgradientproteins pages 6-10). The 2023 EMBO Journal papers refine this by adding a direct, selective regulatory link to IRE1β, establishing AGR2 as part of a dedicated goblet-cell proteostasis regulatory module (cloots2023activationofgobletcell pages 1-2, neidhardt2023theire1βmediatedunfolded pages 29-35).

8.2 Controversies and unresolved mechanisms

Key unresolved issues highlighted by authoritative synthesis include:

Mechanism of secretion: AGR2 has an ER-retention signal (KTEL) yet is detectably extracellular (mucus; tumor microenvironment). Evidence points to weak/non-canonical KTEL retention plus redox/thiol state (Cys81) and ER stress/dimerization state as determinants, but the exact trafficking pathways are not fully unified across models (bergstrom2014agr2anendoplasmic pages 4-6, boisteau2022anteriorgradientproteins pages 6-10, qu2024agr2thecovert pages 16-18).
Functional meaning of extracellular AGR2: eAGR2 is repeatedly linked to pro-tumor signaling (migration, angiogenesis, stromal effects), but how much reflects a regulated extracellular biology vs an ER-proteostasis spillover/adaptation remains a major interpretive question (boisteau2022anteriorgradientproteins pages 43-48, qu2024agr2thecovert pages 3-5, boisteau2022anteriorgradientproteins pages 6-10).
Context dependence in cancer: Reviews note that AGR2 can correlate with aggressiveness in many tumors yet show context-specific prognostic associations, highlighting that localization (ER vs cytosol vs extracellular) and tissue type likely determine functional directionality (qu2024agr2thecovert pages 16-18, qu2024agr2thecovert pages 2-3).

9) Structured summary artifact

The following table consolidates the functional annotation, mechanisms, and key quantitative findings for AGR2:

Aspect	Summary
Identity/domains	Human AGR2 = anterior gradient protein 2 homolog, UniProt O95994, a ~175 aa/~20 kDa AGR-family, PDI/thioredoxin-like ER protein with a thioredoxin fold; reported as monomeric or homodimeric and involved in secretory/transmembrane protein biogenesis in the ER. Central sources: Boisteau et al., 2022, Oncogene, https://doi.org/10.1038/s41388-022-02452-1; Qu et al., 2024, Biomolecules, https://doi.org/10.3390/biom14070743 (boisteau2022anteriorgradientproteins pages 6-10, boisteau2022anteriorgradientproteins pages 1-6, qu2024agr2thecovert pages 2-3)
Catalytic motif	AGR2 contains a non-canonical CXXS active-site motif centered on Cys81 (positions 81–84), distinguishing it from canonical PDI CXXC motifs; Cys81 is required for several client/regulatory interactions, while monomer–dimer behavior also involves E60/K64. Mutation C81S disrupts key regulatory functions and can promote secretion. Central sources: Boisteau et al., 2022, https://doi.org/10.1038/s41388-022-02452-1; Cloots et al., 2023, EMBO J, https://doi.org/10.1038/s44318-023-00015-y (boisteau2022anteriorgradientproteins pages 6-10, boisteau2022anteriorgradientproteins pages 10-13, cloots2023activationofgobletcell pages 7-8, cloots2023activationofgobletcell pages 11-12)
Localization/retention	AGR2 is primarily an ER-resident chaperone/PDI-like protein carrying a C-terminal KTEL ER-retention motif that binds KDEL receptors non-canonically; this relatively weak retention helps explain why AGR2 can also traffic through the secretory pathway and be secreted under stress or when retention/folding is altered. Central sources: Boisteau et al., 2022, https://doi.org/10.1038/s41388-022-02452-1; Worfolk et al., 2019, Antioxid Redox Signal, https://doi.org/10.1089/ars.2018.7647 (boisteau2022anteriorgradientproteins pages 6-10, boisteau2022anteriorgradientproteins pages 10-13, worfolk2019elucidationofthe pages 11-14, qu2024agr2thecovert pages 2-3)
Key clients/substrates	Best-supported client class is mucins: AGR2 is required for proper folding/maturation/secretion of MUC2, MUC5AC, MUC5B and can form mixed disulfide-linked complexes with mucins; Worfolk et al. identify MUC5AC/B as principal secretory clients in esophageal adenocarcinoma cells. Additional reported interactors include other PDIs, EpCAM, CALU, RCN1, cathepsins, and SQSTM1. Central sources: Worfolk et al., 2019, https://doi.org/10.1089/ars.2018.7647; Boisteau et al., 2022, https://doi.org/10.1038/s41388-022-02452-1 (worfolk2019elucidationofthe pages 11-14, boisteau2022anteriorgradientproteins pages 6-10, boisteau2022anteriorgradientproteins pages 10-13, qu2024agr2thecovert pages 2-3)
UPR/IRE1β mechanism	Recent mechanistic work shows AGR2 is a goblet-cell mucin chaperone that directly binds IRE1β, shifts it toward an inactive monomeric state, disrupts/prevents dimerization, and suppresses endonuclease outputs including XBP1 splicing and RIDD-like signaling. AGR2 depletion causes spontaneous IRE1β activation; C81S and disease-associated H117Y mutants lose binding/inhibitory activity. Neidhardt et al. estimate AGR2 concentration in goblet-cell ER at ~460 µM. Central sources: Cloots et al., 2023, https://doi.org/10.1038/s44318-023-00015-y; Neidhardt et al., 2023, EMBO J, https://doi.org/10.1038/s44318-023-00014-z (cloots2023activationofgobletcell pages 7-8, cloots2023activationofgobletcell pages 10-11, cloots2023activationofgobletcell pages 11-12, cloots2023activationofgobletcell pages 12-13, cloots2023activationofgobletcell pages 6-7, cloots2023activationofgobletcell pages 1-2, neidhardt2023theire1βmediatedunfolded pages 29-35)
Secretion/extracellular roles	Although ER-enriched, AGR2 can be released as extracellular AGR2 (eAGR2), especially with ER stress, overexpression, or altered retention/dimer state. Secreted AGR2 has been linked to inflammation, proliferation, angiogenesis, migration, metastasis, and binding to extracellular growth factors such as VEGF and FGF2; reviews emphasize that eAGR2 may have functions distinct from intracellular AGR2. Central sources: Boisteau et al., 2022, https://doi.org/10.1038/s41388-022-02452-1; Qu et al., 2024, https://doi.org/10.3390/biom14070743 (boisteau2022anteriorgradientproteins pages 43-48, boisteau2022anteriorgradientproteins pages 6-10, boisteau2022anteriorgradientproteins pages 10-13, qu2024agr2thecovert pages 3-5, robinson2024ahighaffinitymonoclonal pages 19-20)
Cancer relevance	AGR2 is widely implicated in epithelial cancers, especially digestive tract, pancreatic, hepatobiliary, colorectal, breast, prostate, and lung malignancies. Reported pro-tumor activities include enhanced adhesion, migration, invasion, metastasis, stemness, immune evasion/PD-L1 regulation, and modulation of therapy response. Antibody-based neutralization of eAGR2 is now a concrete preclinical strategy. Central sources: Qu et al., 2024, https://doi.org/10.3390/biom14070743; Robinson et al., 2024, Antibodies, https://doi.org/10.3390/antib13040101; Boisteau et al., 2022, https://doi.org/10.1038/s41388-022-02452-1 (boisteau2022anteriorgradientproteins pages 43-48, qu2024agr2thecovert pages 3-5, robinson2024ahighaffinitymonoclonal pages 19-20, robinson2024ahighaffinitymonoclonal pages 1-2, robinson2024ahighaffinitymonoclonal pages 6-8, robinson2024ahighaffinitymonoclonal pages 8-10)
Quantitative statistics	Recent quantified observations include: ~90% of PDAC biopsies expressed AGR2, while normal pancreas was essentially negative; PDAC staining covered 5–70% of tissue cores; matched PDAC cohort significance p = 0.0025, n = 24; TCGA/GTEx comparison n = 179 vs 177, p < 0.01; high AGR2 mRNA associated with worse disease-free survival (HR 2.5, p = 0.016; high n = 107 vs low n = 27); anti-AGR2 antibodies reached <50 pM binding, while precursor scFv EC50s included 4.7 ± 0.52 µg/mL for scFv-15; AGR2 concentration in goblet-cell ER estimated at ~460 µM. Central sources: Robinson et al., 2024, https://doi.org/10.3390/antib13040101; Neidhardt et al., 2023, https://doi.org/10.1038/s44318-023-00014-z (robinson2024ahighaffinitymonoclonal pages 1-2, robinson2024ahighaffinitymonoclonal pages 6-8, robinson2024ahighaffinitymonoclonal pages 15-17, robinson2024ahighaffinitymonoclonal pages 8-10, robinson2024ahighaffinitymonoclonal pages 10-12, neidhardt2023theire1βmediatedunfolded pages 29-35)

Table: This table summarizes the current evidence for human AGR2 (UniProt O95994), including its molecular identity, catalytic features, localization, key clients, IRE1β regulation, extracellular roles, cancer relevance, and quantitative findings from recent and foundational sources.

10) References (URLs and publication dates emphasized in-text)

Key sources used in this report include:
* Park et al., Apr 2009, PNAS, https://doi.org/10.1073/pnas.0808722106 (park2009theproteindisulfide pages 2-2, park2009theproteindisulfide pages 4-5)
* Bergström et al., Aug 2014, PLoS ONE, https://doi.org/10.1371/journal.pone.0104186 (bergstrom2014agr2anendoplasmic pages 4-6)
* Worfolk et al., Nov 2019, Antioxid Redox Signal, https://doi.org/10.1089/ars.2018.7647 (worfolk2019elucidationofthe pages 11-14)
* Boisteau et al., Sep 2022, Oncogene (review), https://doi.org/10.1038/s41388-022-02452-1 (boisteau2022anteriorgradientproteins pages 6-10, boisteau2022anteriorgradientproteins pages 10-13, boisteau2022anteriorgradientproteins pages 43-48)
* Cloots et al., Dec 2023, EMBO J, https://doi.org/10.1038/s44318-023-00015-y (cloots2023activationofgobletcell pages 1-2)
* Neidhardt et al., Dec 2023, EMBO J, https://doi.org/10.1038/s44318-023-00014-z (neidhardt2023theire1βmediatedunfolded pages 29-35)
* Qu et al., Jun 2024, Biomolecules (review), https://doi.org/10.3390/biom14070743 (qu2024agr2thecovert pages 2-3, qu2024agr2thecovert pages 3-5)
* Robinson et al., Dec 2024, Antibodies, https://doi.org/10.3390/antib13040101 (robinson2024ahighaffinitymonoclonal pages 6-8, robinson2024ahighaffinitymonoclonal pages 8-10)

References

(boisteau2022anteriorgradientproteins pages 6-10): Emeric Boisteau, Céline Posseme, Federico Di Modugno, Julien Edeline, Cédric Coulouarn, Roman Hrstka, Andrea Martisova, Frédéric Delom, Xavier Treton, Leif A. Eriksson, Eric Chevet, Astrid Lièvre, and Eric Ogier-Denis. Anterior gradient proteins in gastrointestinal cancers: from cell biology to pathophysiology. Oncogene, 41:4673-4685, Sep 2022. URL: https://doi.org/10.1038/s41388-022-02452-1, doi:10.1038/s41388-022-02452-1. This article has 14 citations and is from a domain leading peer-reviewed journal.
(boisteau2022anteriorgradientproteins pages 10-13): Emeric Boisteau, Céline Posseme, Federico Di Modugno, Julien Edeline, Cédric Coulouarn, Roman Hrstka, Andrea Martisova, Frédéric Delom, Xavier Treton, Leif A. Eriksson, Eric Chevet, Astrid Lièvre, and Eric Ogier-Denis. Anterior gradient proteins in gastrointestinal cancers: from cell biology to pathophysiology. Oncogene, 41:4673-4685, Sep 2022. URL: https://doi.org/10.1038/s41388-022-02452-1, doi:10.1038/s41388-022-02452-1. This article has 14 citations and is from a domain leading peer-reviewed journal.
(boisteau2022anteriorgradientproteins pages 1-6): Emeric Boisteau, Céline Posseme, Federico Di Modugno, Julien Edeline, Cédric Coulouarn, Roman Hrstka, Andrea Martisova, Frédéric Delom, Xavier Treton, Leif A. Eriksson, Eric Chevet, Astrid Lièvre, and Eric Ogier-Denis. Anterior gradient proteins in gastrointestinal cancers: from cell biology to pathophysiology. Oncogene, 41:4673-4685, Sep 2022. URL: https://doi.org/10.1038/s41388-022-02452-1, doi:10.1038/s41388-022-02452-1. This article has 14 citations and is from a domain leading peer-reviewed journal.
(park2009theproteindisulfide pages 2-2): Sung-Woo Park, Guohua Zhen, Catherine Verhaeghe, Yasuhiro Nakagami, Louis T. Nguyenvu, Andrea J. Barczak, Nigel Killeen, and David J. Erle. The protein disulfide isomerase agr2 is essential for production of intestinal mucus. Proceedings of the National Academy of Sciences, 106:6950-6955, Apr 2009. URL: https://doi.org/10.1073/pnas.0808722106, doi:10.1073/pnas.0808722106. This article has 509 citations and is from a highest quality peer-reviewed journal.
(park2009theproteindisulfide pages 4-5): Sung-Woo Park, Guohua Zhen, Catherine Verhaeghe, Yasuhiro Nakagami, Louis T. Nguyenvu, Andrea J. Barczak, Nigel Killeen, and David J. Erle. The protein disulfide isomerase agr2 is essential for production of intestinal mucus. Proceedings of the National Academy of Sciences, 106:6950-6955, Apr 2009. URL: https://doi.org/10.1073/pnas.0808722106, doi:10.1073/pnas.0808722106. This article has 509 citations and is from a highest quality peer-reviewed journal.
(qu2024agr2thecovert pages 3-5): Shen Qu, Weili Jia, Ye Nie, Wen Shi, Chao Chen, Zihao Zhao, and Wenjie Song. Agr2: the covert driver and new dawn of hepatobiliary and pancreatic cancer treatment. Biomolecules, 14:743, Jun 2024. URL: https://doi.org/10.3390/biom14070743, doi:10.3390/biom14070743. This article has 5 citations.
(qu2024agr2thecovert pages 16-18): Shen Qu, Weili Jia, Ye Nie, Wen Shi, Chao Chen, Zihao Zhao, and Wenjie Song. Agr2: the covert driver and new dawn of hepatobiliary and pancreatic cancer treatment. Biomolecules, 14:743, Jun 2024. URL: https://doi.org/10.3390/biom14070743, doi:10.3390/biom14070743. This article has 5 citations.
(worfolk2019elucidationofthe pages 11-14): Jack C. Worfolk, Steven Bell, Lee D. Simpson, Naomi A. Carne, Sarah L. Francis, Vibecke Engelbertsen, Adrian P. Brown, Julie Walker, Yirupaiahgari K. Viswanath, and Adam M. Benham. Elucidation of the agr2 interactome in esophageal adenocarcinoma cells identifies a redox-sensitive chaperone hub for the quality control of muc-5ac. Antioxidants & Redox Signaling, 31:1117-1132, Nov 2019. URL: https://doi.org/10.1089/ars.2018.7647, doi:10.1089/ars.2018.7647. This article has 18 citations and is from a domain leading peer-reviewed journal.
(cloots2023activationofgobletcell pages 1-2): Eva Cloots, Phaedra Guilbert, Mathias Provost, Lisa Neidhardt, Evelien Van de Velde, Farzaneh Fayazpour, Delphine De Sutter, Savvas N Savvides, Sven Eyckerman, and Sophie Janssens. Activation of goblet-cell stress sensor ire1β is controlled by the mucin chaperone agr2. The EMBO Journal, 43:695-718, Dec 2023. URL: https://doi.org/10.1038/s44318-023-00015-y, doi:10.1038/s44318-023-00015-y. This article has 33 citations.
(cloots2023activationofgobletcell pages 6-7): Eva Cloots, Phaedra Guilbert, Mathias Provost, Lisa Neidhardt, Evelien Van de Velde, Farzaneh Fayazpour, Delphine De Sutter, Savvas N Savvides, Sven Eyckerman, and Sophie Janssens. Activation of goblet-cell stress sensor ire1β is controlled by the mucin chaperone agr2. The EMBO Journal, 43:695-718, Dec 2023. URL: https://doi.org/10.1038/s44318-023-00015-y, doi:10.1038/s44318-023-00015-y. This article has 33 citations.
(cloots2023activationofgobletcell pages 12-13): Eva Cloots, Phaedra Guilbert, Mathias Provost, Lisa Neidhardt, Evelien Van de Velde, Farzaneh Fayazpour, Delphine De Sutter, Savvas N Savvides, Sven Eyckerman, and Sophie Janssens. Activation of goblet-cell stress sensor ire1β is controlled by the mucin chaperone agr2. The EMBO Journal, 43:695-718, Dec 2023. URL: https://doi.org/10.1038/s44318-023-00015-y, doi:10.1038/s44318-023-00015-y. This article has 33 citations.
(cloots2023activationofgobletcell pages 7-8): Eva Cloots, Phaedra Guilbert, Mathias Provost, Lisa Neidhardt, Evelien Van de Velde, Farzaneh Fayazpour, Delphine De Sutter, Savvas N Savvides, Sven Eyckerman, and Sophie Janssens. Activation of goblet-cell stress sensor ire1β is controlled by the mucin chaperone agr2. The EMBO Journal, 43:695-718, Dec 2023. URL: https://doi.org/10.1038/s44318-023-00015-y, doi:10.1038/s44318-023-00015-y. This article has 33 citations.
(cloots2023activationofgobletcell pages 11-12): Eva Cloots, Phaedra Guilbert, Mathias Provost, Lisa Neidhardt, Evelien Van de Velde, Farzaneh Fayazpour, Delphine De Sutter, Savvas N Savvides, Sven Eyckerman, and Sophie Janssens. Activation of goblet-cell stress sensor ire1β is controlled by the mucin chaperone agr2. The EMBO Journal, 43:695-718, Dec 2023. URL: https://doi.org/10.1038/s44318-023-00015-y, doi:10.1038/s44318-023-00015-y. This article has 33 citations.
(neidhardt2023theire1βmediatedunfolded pages 29-35): Lisa Neidhardt, Eva Cloots, Natalie Friemel, Caroline A M Weiss, Heather P Harding, Stephen H McLaughlin, Sophie Janssens, and David Ron. The ire1β-mediated unfolded protein response is repressed by the chaperone agr2 in mucin producing cells. The EMBO Journal, 43:719-753, Dec 2023. URL: https://doi.org/10.1038/s44318-023-00014-z, doi:10.1038/s44318-023-00014-z. This article has 37 citations.
(bergstrom2014agr2anendoplasmic pages 4-6): Joakim H. Bergström, Katarina A. Berg, Ana M. Rodríguez-Piñeiro, Bärbel Stecher, Malin E. V. Johansson, and Gunnar C. Hansson. Agr2, an endoplasmic reticulum protein, is secreted into the gastrointestinal mucus. PLoS ONE, 9:e104186, Aug 2014. URL: https://doi.org/10.1371/journal.pone.0104186, doi:10.1371/journal.pone.0104186. This article has 97 citations and is from a peer-reviewed journal.
(boisteau2022anteriorgradientproteins pages 43-48): Emeric Boisteau, Céline Posseme, Federico Di Modugno, Julien Edeline, Cédric Coulouarn, Roman Hrstka, Andrea Martisova, Frédéric Delom, Xavier Treton, Leif A. Eriksson, Eric Chevet, Astrid Lièvre, and Eric Ogier-Denis. Anterior gradient proteins in gastrointestinal cancers: from cell biology to pathophysiology. Oncogene, 41:4673-4685, Sep 2022. URL: https://doi.org/10.1038/s41388-022-02452-1, doi:10.1038/s41388-022-02452-1. This article has 14 citations and is from a domain leading peer-reviewed journal.
(robinson2024ahighaffinitymonoclonal pages 6-8): Reeder M. Robinson, Leticia Reyes, Benjamin N. Christopher, Ravyn M. Duncan, Rachel A. Burge, Julie Siegel, Patrick Nasarre, Pingping Wang, John P. O’Bryan, G. Aaron Hobbs, Nancy Klauber-DeMore, and Nathan G. Dolloff. A high-affinity monoclonal antibody against the pancreatic ductal adenocarcinoma target, anterior gradient-2 (agr2/pdia17). Antibodies, 13:101, Dec 2024. URL: https://doi.org/10.3390/antib13040101, doi:10.3390/antib13040101. This article has 0 citations.
(robinson2024ahighaffinitymonoclonal pages 8-10): Reeder M. Robinson, Leticia Reyes, Benjamin N. Christopher, Ravyn M. Duncan, Rachel A. Burge, Julie Siegel, Patrick Nasarre, Pingping Wang, John P. O’Bryan, G. Aaron Hobbs, Nancy Klauber-DeMore, and Nathan G. Dolloff. A high-affinity monoclonal antibody against the pancreatic ductal adenocarcinoma target, anterior gradient-2 (agr2/pdia17). Antibodies, 13:101, Dec 2024. URL: https://doi.org/10.3390/antib13040101, doi:10.3390/antib13040101. This article has 0 citations.
(robinson2024ahighaffinitymonoclonal pages 1-2): Reeder M. Robinson, Leticia Reyes, Benjamin N. Christopher, Ravyn M. Duncan, Rachel A. Burge, Julie Siegel, Patrick Nasarre, Pingping Wang, John P. O’Bryan, G. Aaron Hobbs, Nancy Klauber-DeMore, and Nathan G. Dolloff. A high-affinity monoclonal antibody against the pancreatic ductal adenocarcinoma target, anterior gradient-2 (agr2/pdia17). Antibodies, 13:101, Dec 2024. URL: https://doi.org/10.3390/antib13040101, doi:10.3390/antib13040101. This article has 0 citations.
(robinson2024ahighaffinitymonoclonal pages 15-17): Reeder M. Robinson, Leticia Reyes, Benjamin N. Christopher, Ravyn M. Duncan, Rachel A. Burge, Julie Siegel, Patrick Nasarre, Pingping Wang, John P. O’Bryan, G. Aaron Hobbs, Nancy Klauber-DeMore, and Nathan G. Dolloff. A high-affinity monoclonal antibody against the pancreatic ductal adenocarcinoma target, anterior gradient-2 (agr2/pdia17). Antibodies, 13:101, Dec 2024. URL: https://doi.org/10.3390/antib13040101, doi:10.3390/antib13040101. This article has 0 citations.
(boisteau2022anteriorgradientproteins pages 21-24): Emeric Boisteau, Céline Posseme, Federico Di Modugno, Julien Edeline, Cédric Coulouarn, Roman Hrstka, Andrea Martisova, Frédéric Delom, Xavier Treton, Leif A. Eriksson, Eric Chevet, Astrid Lièvre, and Eric Ogier-Denis. Anterior gradient proteins in gastrointestinal cancers: from cell biology to pathophysiology. Oncogene, 41:4673-4685, Sep 2022. URL: https://doi.org/10.1038/s41388-022-02452-1, doi:10.1038/s41388-022-02452-1. This article has 14 citations and is from a domain leading peer-reviewed journal.
(qu2024agr2thecovert pages 12-13): Shen Qu, Weili Jia, Ye Nie, Wen Shi, Chao Chen, Zihao Zhao, and Wenjie Song. Agr2: the covert driver and new dawn of hepatobiliary and pancreatic cancer treatment. Biomolecules, 14:743, Jun 2024. URL: https://doi.org/10.3390/biom14070743, doi:10.3390/biom14070743. This article has 5 citations.
(schroeder2012agr2isinduced pages 5-6): Bradley W. Schroeder, Catherine Verhaeghe, Sung-Woo Park, Louis T. Nguyenvu, Xiaozhu Huang, Guohua Zhen, and David J. Erle. Agr2 is induced in asthma and promotes allergen-induced mucin overproduction. American journal of respiratory cell and molecular biology, 47 2:178-85, Dec 2012. URL: https://doi.org/10.1165/rcmb.2011-0421oc, doi:10.1165/rcmb.2011-0421oc. This article has 149 citations and is from a peer-reviewed journal.
(qu2024agr2thecovert pages 2-3): Shen Qu, Weili Jia, Ye Nie, Wen Shi, Chao Chen, Zihao Zhao, and Wenjie Song. Agr2: the covert driver and new dawn of hepatobiliary and pancreatic cancer treatment. Biomolecules, 14:743, Jun 2024. URL: https://doi.org/10.3390/biom14070743, doi:10.3390/biom14070743. This article has 5 citations.
(cloots2023activationofgobletcell pages 10-11): Eva Cloots, Phaedra Guilbert, Mathias Provost, Lisa Neidhardt, Evelien Van de Velde, Farzaneh Fayazpour, Delphine De Sutter, Savvas N Savvides, Sven Eyckerman, and Sophie Janssens. Activation of goblet-cell stress sensor ire1β is controlled by the mucin chaperone agr2. The EMBO Journal, 43:695-718, Dec 2023. URL: https://doi.org/10.1038/s44318-023-00015-y, doi:10.1038/s44318-023-00015-y. This article has 33 citations.
(robinson2024ahighaffinitymonoclonal pages 19-20): Reeder M. Robinson, Leticia Reyes, Benjamin N. Christopher, Ravyn M. Duncan, Rachel A. Burge, Julie Siegel, Patrick Nasarre, Pingping Wang, John P. O’Bryan, G. Aaron Hobbs, Nancy Klauber-DeMore, and Nathan G. Dolloff. A high-affinity monoclonal antibody against the pancreatic ductal adenocarcinoma target, anterior gradient-2 (agr2/pdia17). Antibodies, 13:101, Dec 2024. URL: https://doi.org/10.3390/antib13040101, doi:10.3390/antib13040101. This article has 0 citations.
(robinson2024ahighaffinitymonoclonal pages 10-12): Reeder M. Robinson, Leticia Reyes, Benjamin N. Christopher, Ravyn M. Duncan, Rachel A. Burge, Julie Siegel, Patrick Nasarre, Pingping Wang, John P. O’Bryan, G. Aaron Hobbs, Nancy Klauber-DeMore, and Nathan G. Dolloff. A high-affinity monoclonal antibody against the pancreatic ductal adenocarcinoma target, anterior gradient-2 (agr2/pdia17). Antibodies, 13:101, Dec 2024. URL: https://doi.org/10.3390/antib13040101, doi:10.3390/antib13040101. This article has 0 citations.

Citations

worfolk2019elucidationofthe pages 11-14
cloots2023activationofgobletcell pages 1-2
boisteau2022anteriorgradientproteins pages 43-48
robinson2024ahighaffinitymonoclonal pages 6-8
boisteau2022anteriorgradientproteins pages 6-10
boisteau2022anteriorgradientproteins pages 10-13
boisteau2022anteriorgradientproteins pages 1-6
park2009theproteindisulfide pages 2-2
park2009theproteindisulfide pages 4-5
cloots2023activationofgobletcell pages 6-7
cloots2023activationofgobletcell pages 12-13
cloots2023activationofgobletcell pages 7-8
cloots2023activationofgobletcell pages 11-12
robinson2024ahighaffinitymonoclonal pages 8-10
robinson2024ahighaffinitymonoclonal pages 1-2
robinson2024ahighaffinitymonoclonal pages 15-17
boisteau2022anteriorgradientproteins pages 21-24
cloots2023activationofgobletcell pages 10-11
robinson2024ahighaffinitymonoclonal pages 19-20
robinson2024ahighaffinitymonoclonal pages 10-12
https://doi.org/10.1073/pnas.0808722106
https://doi.org/10.1089/ars.2018.7647
https://doi.org/10.1038/s44318-023-00015-y
https://doi.org/10.1038/s44318-023-00014-z
https://doi.org/10.1371/journal.pone.0104186
https://doi.org/10.3390/antib13040101
https://doi.org/10.1038/s41388-022-02452-1;
https://doi.org/10.3390/biom14070743
https://doi.org/10.1089/ars.2018.7647;
https://doi.org/10.1038/s41388-022-02452-1
https://doi.org/10.1038/s44318-023-00015-y;
https://doi.org/10.3390/biom14070743;
https://doi.org/10.3390/antib13040101;
https://doi.org/10.1038/s41388-022-02452-1,
https://doi.org/10.1073/pnas.0808722106,
https://doi.org/10.3390/biom14070743,
https://doi.org/10.1089/ars.2018.7647,
https://doi.org/10.1038/s44318-023-00015-y,
https://doi.org/10.1038/s44318-023-00014-z,
https://doi.org/10.1371/journal.pone.0104186,
https://doi.org/10.3390/antib13040101,
https://doi.org/10.1165/rcmb.2011-0421oc,

📚 Additional Documentation

Notes

(AGR2-notes.md)

AGR2 curation notes

AGR2 is a secretory-pathway/ER-retained anterior gradient protein with a thioredoxin-like fold and a conserved C-terminal KTEL retrieval motif. The strongest physiological evidence supports a role in mucin-producing epithelial cells rather than a general extracellular cancer signaling role. In mouse intestine, AGR2 is present in the ER of secretory epithelial cells and is required for in vivo MUC2 production; the active-site cysteine forms mixed disulfide bonds with MUC2, indicating a direct role in mucin processing [PMID:19359471 "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"; PMID:19359471 "A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2"].

Human genetics supports the same core function. Siblings with biallelic AGR2 H117Y had reduced goblet cells, depletion of MUC2/MUC5AC/MUC6, increased ER stress, and infantile IBD; mutant AGR2 bound MUC2 less well and was less able to alleviate tunicamycin-induced ER stress [PMID:34237462 "Patient biopsy specimens showed reduced goblet cells; depletion of MUC2, MUC5AC, and MUC6; up-regulation of AGR2; and increased ER stress"; PMID:34237462 "The mutant AGR2 showed reduced capacity to bind MUC2 and alleviate tunicamycin-induced ER stress"].

PN re-review 2026-06-03: Falcon deep research is already present for AGR2, and the Proteostasis projection source maps AGR2 only from ER proteostasis|Folding enzyme|Protein disulfide isomerases to GO:0003756 protein disulfide isomerase activity. I accept that projection after gene-level review because AGR2 has direct AGR2-MUC2 mixed-disulfide evidence and human AGR2 H117Y reduces MUC2 binding/ER-stress relief [PMID:19359471 "A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2"; PMID:34237462 "The mutant AGR2 showed reduced capacity to bind MUC2 and alleviate tunicamycin-induced ER stress"]. I do not extend the PN projection to broad ER proteostasis or generic positive UPR terms. The newer IRE1beta work supports a separate, narrow negative IRE1-mediated UPR annotation in mucin-producing/goblet-cell contexts [PMID:38177501 "AGR2 binding to IRE1β disrupts IRE1β oligomerization, thereby blocking its downstream endonuclease activity"; PMID:38177498 "The mucin-specific chaperone AGR2 repressed IRE1 activity in cells expressing the domain-swapped IRE1β/α chimera, but had no effect on IRE1α"].

AGR2 ER residence is functionally important: deleting the KTEL motif causes secretion and loss of the AREG/CDX2 readouts, and KDEL/KSEL substitutions retain ER residence but do not rescue function PMID:22184114. This argues that wild-type AGR2's core site of action is the ER lumen, even though extracellular AGR2 can be detected and has context-dependent activities.

AGR2 dimerization is a major regulatory feature. Structural and biochemical studies show monomer-dimer equilibrium PMID:23274113, and AGR2 dimers are proposed to act as sensors of ER homeostasis; perturbation can drive secretion of monomers and pro-inflammatory monocyte chemoattraction [PMID:31040128 "AGR2 dimers act as sensors of ER homeostasis which are disrupted upon ER stress and promote the secretion of AGR2 monomers"; PMID:31040128 "the extracellular release of AGR2 leads to the chemoattraction of monocytes"].

Non-core/contextual annotations: AGR2 binds EGFR in the ER and controls EGFR delivery/signaling in cancer-cell models PMID:25666625. AGR2 also has yeast-two-hybrid evidence for binding C4.4a/LYPD3 and alpha-dystroglycan, but the original paper cautioned that clinical confirmation was needed [PMID:12592373 "Yeast two-hybrid cloning identified metastasis-associated GPI-anchored C4.4a protein and extracellular alpha-dystroglycan (DAG-1) as binding partners"; PMID:12592373 "Clearly, further analyses such as coimmunoprecipitation are required to confirm that these interactions occur in clinical cancers"].

Literature conflict to track: the EGFR study argued that EGFR is a major AGR2 substrate and explicitly reported that MUC2 was not detected in their AGR2 mixed-disulfide mass-spectrometry analysis, citing a re-evaluation that MUC2 was not an AGR2-binding protein and that AGR2 had no role in MUC2 folding PMID:25666625. I still weight the MUC2/mucin-processing model as core because PMID:19359471 directly trapped AGR2-MUC2 mixed disulfides and the later human deficiency paper showed that AGR2 H117Y has reduced MUC2 binding and reduced capacity to alleviate tunicamycin-induced ER stress PMID:34237462.

Pn Notes

(AGR2-pn-notes.md)

AGR2 PN Consistency Notes

Generated: 2026-06-18
Project: PROTEOSTASIS
Scope: PN consistency rereview against local AIGR review and available deep-research artifacts
UniProt: O95994
AIGR review status: COMPLETE
Review batch: proteostasis-batch-2026-06-03 (PR 1341)
Batch change status: modified

Source Files Checked

AIGR review YAML: present - genes/human/AGR2/AGR2-ai-review.yaml
AIGR review HTML: present - genes/human/AGR2/AGR2-ai-review.html
Gene notes: present - genes/human/AGR2/AGR2-notes.md
GOA TSV: present - genes/human/AGR2/AGR2-goa.tsv
UniProt record: present - genes/human/AGR2/AGR2-uniprot.txt
PN dossier: projects/PROTEOSTASIS/reports/phase1_dossiers/AGR2.md
PN consistency section: projects/PROTEOSTASIS/reports/phase1_dossiers/_sections/AGR2.md
PN projection report: projects/PROTEOSTASIS/reports/pn_projection/pn_projected_gene_go_summary.tsv
PN mapping audit: projects/PROTEOSTASIS/reports/pn_mapping_audit/current_mapping_scrutiny.tsv

Deep Research Files

genes/human/AGR2/AGR2-deep-research-falcon.md

AIGR Review Snapshot

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/core annotation action counts: ACCEPT: 11; KEEP_AS_NON_CORE: 15; MARK_AS_OVER_ANNOTATED: 13; MODIFY: 6; NEW: 3; REMOVE: 1

PN Consistency Summary

Consistency: Deep research (Falcon), notes, review YAML, and the PN PDI mapping are consistent. All frame AGR2 as a secretory/ER-retained (KTEL) PDI-family/thioredoxin-fold foldase that forms mixed disulfides with MUC2 and is required for gel-forming mucin production (PMID:19359471, 34237462). The review honestly tracks the literature conflict (PMID:25666625 argued EGFR, not MUC2, is the major mixed-disulfide substrate) but defensibly weights the MUC2/mucin model as core. No internal contradiction.
PN story / NEW pressure: GO:0003756 (OLS-verified real) is not in AGR2's GOA (GOA MF = dystroglycan/EGFR/identical-protein/homodimerization binding only), confirming PN's new_to_goa. The review adds it as a MODIFY proposed_replacement for two generic protein-binding rows (PMID:19359471, 34237462), alongside GO:0034975 protein folding in ER. This matches the PN projection. Caveat: AGR2 is a non-canonical "pseudo-PDI" (CXXS, single active-site Cys), so true isomerase catalysis is debated; the review's mixed-disulfide/foldase framing is the safest support. Conclusion: legitimate ADD, executed; mild over-reach risk on the term name only.
Evidence alignment: PN dossier lists no reference titles for AGR2. Review evidence (PMID:19359471, 22184114, 23274113, 25666625, 31040128, 34237462, 38177498/501) is reviewer-supplied; alignment is by biology (PDI/mucin), not shared citation list.
Verdict: Consistent; PN GO:0003756 projection validated and added via MODIFY; only nuance is the pseudo-PDI catalysis debate (review mitigates via mixed-disulfide evidence). Recommended edits: none required; [REF] optionally note in review that AGR2 is a non-canonical CXXS PDI-family member (catalytic isomerase activity debated) to pre-empt over-reading GO:0003756.

Full Consistency Review

UniProt: O95994 · batch: proteostasis-batch-2026-06-03 · review status: COMPLETE
PN placement: ER proteostasis|Folding enzyme|Protein disulfide isomerases ; PN-node mapping: group Protein disulfide isomerases=mapped→GO:0003756 protein disulfide isomerase activity (new_to_goa); class Folding enzyme=no_mapping; branch ER proteostasis=no_mapping.
Consistency: Deep research (Falcon), notes, review YAML, and the PN PDI mapping are consistent. All frame AGR2 as a secretory/ER-retained (KTEL) PDI-family/thioredoxin-fold foldase that forms mixed disulfides with MUC2 and is required for gel-forming mucin production (PMID:19359471, 34237462). The review honestly tracks the literature conflict (PMID:25666625 argued EGFR, not MUC2, is the major mixed-disulfide substrate) but defensibly weights the MUC2/mucin model as core. No internal contradiction.
PN story / NEW pressure: GO:0003756 (OLS-verified real) is not in AGR2's GOA (GOA MF = dystroglycan/EGFR/identical-protein/homodimerization binding only), confirming PN's new_to_goa. The review adds it as a MODIFY proposed_replacement for two generic protein-binding rows (PMID:19359471, 34237462), alongside GO:0034975 protein folding in ER. This matches the PN projection. Caveat: AGR2 is a non-canonical "pseudo-PDI" (CXXS, single active-site Cys), so true isomerase catalysis is debated; the review's mixed-disulfide/foldase framing is the safest support. Conclusion: legitimate ADD, executed; mild over-reach risk on the term name only.
Mapping strategy: Group-level GO:0003756 is the cleanest catalytic-family target and is correctly scoped (review does not extend to broad ER proteostasis or generic UPR). The review separately adds a narrow IRE1beta-repression UPR role (PMID:38177498/38177501) the PN node does not surface — enrichment, not conflict. No mapping change needed.
Evidence alignment: PN dossier lists no reference titles for AGR2. Review evidence (PMID:19359471, 22184114, 23274113, 25666625, 31040128, 34237462, 38177498/501) is reviewer-supplied; alignment is by biology (PDI/mucin), not shared citation list.
Verdict: Consistent; PN GO:0003756 projection validated and added via MODIFY; only nuance is the pseudo-PDI catalysis debate (review mitigates via mixed-disulfide evidence). Recommended edits: none required; [REF] optionally note in review that AGR2 is a non-canonical CXXS PDI-family member (catalytic isomerase activity debated) to pre-empt over-reading GO:0003756.

PN Dossier Context

review_batch: proteostasis-batch-2026-06-03
review_yaml: genes/human/AGR2/AGR2-ai-review.yaml
PN workbook rows: 1

PN row 1: ER proteostasis | Folding enzyme | Protein disulfide isomerases

UniProt: O95994
In branches: ER
PN-node mapping records (path + ancestors):
- [group] ER proteostasis|Folding enzyme|Protein disulfide isomerases
  status=mapped scope=ok_for_propagation_to_go GO=[GO:0003756 protein disulfide isomerase activity]
  rationale: This PN group captures the canonical ER protein-disulfide-isomerase folding enzymes. GO protein disulfide isomerase activity is the cleanest propagation target for the catalytically active family members.
- [class] ER proteostasis|Folding enzyme
  status=no_mapping scope= GO=[]
  rationale: Reviewed as a broad PN category rather than a single GO class. The member genes span multiple activities, complexes, or contexts, so direct propagation from this node would overstate the shared biology.
- [branch] ER proteostasis
  status=no_mapping scope= GO=[]
  rationale: Reviewed as a top-level PN branch. This is a systems/taxonomy umbrella, not a direct GO assertion; narrower child curations carry any propagating GO mappings.

Projected GO annotations (1)

GO:0003756 protein disulfide isomerase activity | scope=ok_for_propagation_to_go | goa_status=new_to_goa | from=ER proteostasis|Folding enzyme|Protein disulfide isomerases

Note

This file is generated from the current PROTEOSTASIS phase-1 dossier and local gene-review artifacts. Edit the source review, PN mapping, or dossier rather than this generated note when correcting the underlying curation.

📄 View Raw YAML

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

AGR2

Gene Description

Existing Annotations Review

Core Functions

References

Suggested Questions for Experts

Suggested Experiments

Deep Research

Falcon

Research Report: Human AGR2 (Anterior gradient protein 2 homolog; UniProt O95994) — functional annotation

1) Gene/protein identity verification (critical disambiguation)

2) Key concepts and definitions (current understanding)

2.1 AGR2 as a specialized PDI/thioredoxin-like folding factor

2.2 ER retention and trafficking: the KTEL motif and “weak retention”

2.3 Intracellular AGR2 vs extracellular AGR2 (eAGR2)

3) Core molecular functions: what AGR2 “does”

3.1 Primary functional axis: mucin folding/processing and mucus barrier biology

3.2 AGR2 as a regulator of goblet-cell UPR signaling via IRE1β (major 2023 development)

4) Subcellular localization and secretion: where AGR2 acts

4.1 ER localization with conditional secretion into mucus

4.2 Extracellular AGR2 in cancer microenvironments

5) Recent developments (prioritizing 2023–2024)

5.1 2023: AGR2–IRE1β as a goblet-cell-specific UPR rheostat

5.2 2024: expansion of AGR2 as a therapeutic target in PDAC and beyond

6) Current applications and real-world implementations

6.1 Biomarker applications (tissue and potential fluid assays)

6.2 Therapeutic targeting (preclinical)

6.3 Clinical trials status

7) Statistics and quantitative data highlights (recent studies)

8) Expert analysis and synthesis (authoritative consensus and open questions)

8.1 Consensus

8.2 Controversies and unresolved mechanisms

9) Structured summary artifact

10) References (URLs and publication dates emphasized in-text)

Citations

📚 Additional Documentation

Notes

AGR2 curation notes

Pn Notes

AGR2 PN Consistency Notes

Source Files Checked

Deep Research Files

AIGR Review Snapshot

PN Consistency Summary

Full Consistency Review

PN Dossier Context

PN row 1: ER proteostasis | Folding enzyme | Protein disulfide isomerases

Projected GO annotations (1)

Note

📄 View Raw YAML