Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0005789 endoplasmic reticulum membrane	IBA GO_REF:0000033	ACCEPT	Summary: ERO1A is a peripheral ER membrane protein acting on the lumenal side; this is its primary site of action and is well supported experimentally and by phylogenetic inference across the EROs family. Reason: The ER membrane (lumenal side) is the documented site of action for ERO1A, where it reoxidizes PDI; corroborated by direct evidence. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane
GO:0005576 extracellular region	IEA GO_REF:0000044	KEEP AS NON CORE	Summary: A secreted/extracellular pool of ERO1A has been reported, but this is peripheral to its core ER oxidoreductase function. Reason: UniProt records a secreted pool, so the localization is not wrong, but it is a minor/secondary location relative to the ER where ERO1A performs its catalytic role. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Golgi apparatus lumen
GO:0005783 endoplasmic reticulum	IEA GO_REF:0000120	ACCEPT	Summary: ER localization is correct and the principal compartment for ERO1A. Reason: ERO1A is an ER-resident oxidoreductase; this localization is directly supported. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane
GO:0005789 endoplasmic reticulum membrane	IEA GO_REF:0000044	ACCEPT	Summary: Electronic localization to ER membrane, consistent with the IBA and experimental evidence. Reason: Correct compartment; ERO1A is a peripheral ER membrane protein on the lumenal side. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Peripheral membrane protein
GO:0005796 Golgi lumen	IEA GO_REF:0000044	KEEP AS NON CORE	Summary: ERO1A is detected in the Golgi lumen, where it is a FAM20C substrate, but this is secondary to its ER function. Reason: Golgi lumen localization is documented (FAM20C phosphorylation occurs in the Golgi) but peripheral to the core ER oxidoreductase activity. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Golgi apparatus lumen
GO:0015035 protein-disulfide reductase activity	IEA GO_REF:0000120	MARK AS OVER ANNOTATED	Summary: This term asserts a disulfide REDUCTASE activity. ERO1A is mechanistically an OXIDASE that reoxidizes PDI (i.e. forms disulfides and consumes reducing equivalents), not a reductase. The reductase term is an over-annotation, likely an electronic transfer that mislabels the directionality. Reason: ERO1A oxidizes PDI and passes electrons to O2 generating H2O2; it does not function as a protein-disulfide reductase. The catalytic direction recorded by UniProt is dithiol oxidation, contradicting a reductase assignment. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Efficiently reoxidizes P4HB/PDI, the enzyme catalyzing protein disulfide formation, in order to allow P4HB to sustain additional rounds of disulfide formation.
GO:0016971 flavin-dependent sulfhydryl oxidase activity	IEA GO_REF:0000116	ACCEPT	Summary: This is the precise core molecular function of ERO1A - a FAD-dependent sulfhydryl oxidase catalyzing dithiol + O2 = disulfide + H2O2 (RHEA:59116). The falcon deep research independently describes the same electron-flow mechanism with O2 as the terminal electron acceptor. Reason: Directly matches the catalytic activity and FAD cofactor of ERO1A and is supported experimentally (EXP entries from PMID:11707400, PMID:29858230). Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Reaction=[protein]-dithiol + O2 = [protein]-disulfide + H2O2 file:human/ERO1A/ERO1A-deep-research-falcon.md ERO1A then re-oxidizes reduced PDI by accepting electrons through its FAD cofactor, with molecular oxygen (O₂) serving as the terminal electron acceptor
GO:0016972 thiol oxidase activity	IEA GO_REF:0000120	ACCEPT	Summary: Thiol oxidase activity is the broader parent of ERO1A's flavin-dependent sulfhydryl oxidase activity; correct but less specific. Reason: Correctly captures ERO1A's oxidase activity; the IDA-supported version of the same term (PMID:11707400) confirms it. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt EC=1.8.3.2
GO:0030425 dendrite	IEA GO_REF:0000120	MARK AS OVER ANNOTATED	Summary: Dendritic localization is inferred only by similarity to the mouse ortholog (Q8R4A1) and is not established for human ERO1A. Reason: This is a by-similarity transfer from the rodent ortholog for a neuronal context; it is not a core function and is unsupported by direct human evidence. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt In neurons, it localizes to dendrites (By
GO:0034975 protein folding in endoplasmic reticulum	IEA GO_REF:0000002	KEEP AS NON CORE	Summary: ERO1A enables oxidative protein folding in the ER; protein folding in the ER is a valid downstream biological process outcome of its oxidase activity. Reason: Protein folding in the ER is a process consequence of ERO1A's oxidase activity rather than its direct molecular function; appropriate as a non-core process annotation. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Oxidoreductase involved in disulfide bond formation in the endoplasmic reticulum.
GO:0071949 FAD binding	IEA GO_REF:0000002	ACCEPT	Summary: ERO1A is a flavoprotein that binds FAD as its cofactor; multiple FAD binding residues are defined in the crystal structure. Reason: FAD is the documented cofactor with mapped binding sites (PubMed:20834232, PDB 3AHQ/3AHR); FAD binding is integral to the oxidase mechanism. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Name=FAD; Xref=ChEBI:CHEBI:57692
GO:0005515 protein binding	IPI PMID:17170699 ERp57 is essential for efficient folding of glycoproteins sh...	KEEP AS NON CORE	Summary: IntAct interaction with PDIA3/ERp57 (P30101). Bare protein binding is uninformative; it records a real ER-oxidoreductase interaction but is non-core (and note PMID:11707400 found ERO1A does not alter ERp57 redox state). Reason: Records a genuine physical interaction within the ER oxidoreductase network, but the uninformative protein binding term should not be elevated to core function. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Q96HE7; P30101: PDIA3
GO:0005515 protein binding	IPI PMID:20802462 Disulphide production by Ero1α-PDI relay is rapid and effect...	KEEP AS NON CORE	Summary: IntAct interactions with P4HB/PDI (P07237) and PDIA3 (P30101), the physiological substrates ERO1A reoxidizes. The bare protein binding term is uninformative but the underlying P4HB interaction is biologically central; the falcon deep research notes ERO1A binds PDI with the highest affinity among ER thiol isomerases (Kd 1.7 uM), consistent with PDI being its preferred direct substrate. Reason: The P4HB interaction underlies ERO1A's catalytic substrate relationship, but the generic protein binding term is uninformative and the informative function is captured by the oxidase MF terms. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Q96HE7; P07237: P4HB file:human/ERO1A/ERO1A-deep-research-falcon.md ERO1A exhibits strong substrate selectivity for PDI over other ER oxidoreductases. Quantitative binding studies demonstrate that ERO1A binds PDI with highest affinity (Kd = 1.7 μM)
GO:0005515 protein binding	IPI PMID:25416956 A proteome-scale map of the human interactome network.	KEEP AS NON CORE	Summary: High-throughput yeast two-hybrid interactome capturing an ERO1A-APPBP2 (Q92624) interaction; an isolated binary interaction unrelated to ERO1A's oxidase function. Reason: Bare protein binding from a large-scale binary interactome screen; records an interaction but is uninformative and not part of the core function. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Q96HE7; Q92624: APPBP2
GO:0005515 protein binding	IPI PMID:32296183 A reference map of the human binary protein interactome.	KEEP AS NON CORE	Summary: Binary interactome map capturing an ERO1A-LHX4 (Q969G2) interaction; a single high-throughput interaction with a homeobox transcription factor unrelated to ERO1A's ER function. Reason: Bare protein binding from a reference binary interactome; uninformative and not part of ERO1A's core oxidative-folding function. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Q96HE7; Q969G2: LHX4
GO:0016491 oxidoreductase activity	IEA GO_REF:0000107	ACCEPT	Summary: ERO1A is an oxidoreductase; this is a correct but very general parent term. Reason: Correct high-level molecular function, subsumed by the more specific flavin-dependent sulfhydryl oxidase activity that is the core function. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Oxidoreductase involved in disulfide bond formation in the endoplasmic reticulum.
GO:0034976 response to endoplasmic reticulum stress	IEA GO_REF:0000107	KEEP AS NON CORE	Summary: ERO1A is induced during the UPR and participates in ER-stress responses; this is a plausible process annotation transferred from the mouse ortholog. Reason: ERO1A is part of the ER stress/UPR program but this is a downstream/contextual process rather than its core molecular function. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Plays an important role in ER stress-induced, CHOP-dependent apoptosis
GO:0051209 release of sequestered calcium ion into cytosol	IEA GO_REF:0000107	KEEP AS NON CORE	Summary: ERO1A promotes ER Ca2+ release by activating IP3R1 during ER-stress apoptosis; this is inferred from the mouse ortholog and is a specialized downstream role. The falcon deep research corroborates that ERO1A modulates ER Ca2+ release via IP3R (and RyR) channels. Reason: A genuine but context-specific (ER-stress apoptosis) downstream effect inferred by similarity; non-core relative to the oxidase function. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt by activating the inositol 1,4,5-trisphosphate receptor IP3R1 file:human/ERO1A/ERO1A-deep-research-falcon.md ERO1A triggers calcium release from the ER to the cytosol and mitochondria by modulating IP3R and RyR calcium channels
GO:0070059 intrinsic apoptotic signaling pathway in response to endoplasmic reticulum stress	IEA GO_REF:0000107	KEEP AS NON CORE	Summary: ERO1A contributes to CHOP-dependent ER-stress apoptosis (via IP3R1); inferred from the mouse ortholog. Reason: A documented but specialized downstream signaling role; non-core relative to the core oxidase activity. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Plays an important role in ER stress-induced, CHOP-dependent apoptosis by activating the inositol 1,4,5-trisphosphate receptor IP3R1.
GO:0071456 cellular response to hypoxia	IEA GO_REF:0000107	KEEP AS NON CORE	Summary: ERO1A is hypoxia-inducible via the HIF pathway; participation in the cellular hypoxia response is supported. The falcon deep research corroborates that ERO1A is transcriptionally induced by HIF-1alpha under hypoxia (notably in tumor microenvironments). Reason: ERO1A is a hypoxia-induced gene, so a hypoxia-response process annotation is reasonable, but this is a regulatory/contextual process rather than its core function. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Stimulated by hypoxia; suggesting that it is regulated via the HIF-pathway. file:human/ERO1A/ERO1A-deep-research-falcon.md ERO1A expression is strongly induced by hypoxia through hypoxia-inducible factor 1α (HIF-1α)
GO:0016971 flavin-dependent sulfhydryl oxidase activity	EXP PMID:11707400 Manipulation of oxidative protein folding and PDI redox stat...	ACCEPT	Summary: Experimentally supported FAD-dependent sulfhydryl oxidase activity - ERO1A oxidizes PDI to drive disulfide bond formation in immunoglobulins. Reason: Strong experimental evidence (selective oxidation of PDI); this is the core molecular function of ERO1A. Supporting Evidence: PMID:11707400 both human Ero1-Lalpha and Ero1-Lbeta (hEROs) facilitate disulfide bond formation in immunoglobulin subunits by selectively oxidizing PDI
GO:0016971 flavin-dependent sulfhydryl oxidase activity	EXP PMID:29858230 Secretory kinase Fam20C tunes endoplasmic reticulum redox st...	ACCEPT	Summary: Experimentally supported FAD-dependent sulfhydryl oxidase activity; ERO1A activity is tuned by FAM20C phosphorylation and required for immunoglobulin folding. Reason: Core molecular function with direct experimental support; phosphomimetic S145E increases enzyme activity and accelerates immunoglobulin folding. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Shows two-fold increase in enzyme activity. Accelerates immunoglobulin folding.
GO:0016972 thiol oxidase activity	IDA PMID:11707400 Manipulation of oxidative protein folding and PDI redox stat...	ACCEPT	Summary: Direct-assay thiol oxidase activity (parent of the flavin-dependent sulfhydryl oxidase term); ERO1A oxidizes PDI thiols. Reason: IDA evidence for oxidase activity; correct, though the flavin-dependent sulfhydryl oxidase term is the most precise descriptor. Supporting Evidence: PMID:11707400 Disulfide bond formation is controlled by hEROs, which stand at a crucial point of an electron-flow starting from nascent secretory proteins and passing through PDI.
GO:0016972 thiol oxidase activity	IDA PMID:29858230 Secretory kinase Fam20C tunes endoplasmic reticulum redox st...	ACCEPT	Summary: Direct-assay thiol oxidase activity confirmed in the FAM20C-phosphorylation study. Reason: IDA-supported oxidase activity; consistent core molecular function. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt EC=1.8.3.2
GO:0005515 protein binding	IPI PMID:29858230 Secretory kinase Fam20C tunes endoplasmic reticulum redox st...	KEEP AS NON CORE	Summary: IntAct interaction with ERP44 (Q9BS26), the partner that retains ERO1A in the ER. Bare protein binding is uninformative but the ERP44 interaction is biologically meaningful (ER retention). Reason: A real, functionally important interaction (ER retention via ERP44), but the generic protein binding term is uninformative and should not be elevated to a core molecular function. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Interacts with ERP44; the interaction results in retention of ERO1A in the endoplasmic reticulum
GO:0005576 extracellular region	IDA PMID:29858230 Secretory kinase Fam20C tunes endoplasmic reticulum redox st...	KEEP AS NON CORE	Summary: Direct evidence for a secreted/extracellular pool of ERO1A. Reason: A genuine secondary localization (secreted), peripheral to the ER site of catalytic action. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Secreted
GO:0005783 endoplasmic reticulum	IDA PMID:29858230 Secretory kinase Fam20C tunes endoplasmic reticulum redox st...	ACCEPT	Summary: Direct evidence for ER localization, the principal compartment of ERO1A. Reason: IDA-supported ER localization, the core compartment for ERO1A's oxidase function. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane
GO:0005796 Golgi lumen	IDA PMID:29858230 Secretory kinase Fam20C tunes endoplasmic reticulum redox st...	KEEP AS NON CORE	Summary: Direct evidence for a Golgi-lumen pool where ERO1A is phosphorylated by FAM20C. Reason: Genuine secondary localization (Golgi) relevant to FAM20C regulation but peripheral to the ER catalytic role. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Golgi apparatus lumen
GO:0006457 protein folding	IMP PMID:29858230 Secretory kinase Fam20C tunes endoplasmic reticulum redox st...	KEEP AS NON CORE	Summary: ERO1A is required for proper folding of immunoglobulins; protein folding is a valid downstream process outcome of its oxidase activity. Reason: Protein folding is the biological-process consequence of ERO1A-driven oxidative folding, downstream of its core oxidase molecular function. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Required for the proper folding of immunoglobulins
GO:0045454 cell redox homeostasis	IMP PMID:29858230 Secretory kinase Fam20C tunes endoplasmic reticulum redox st...	ACCEPT	Summary: ERO1A is a central determinant of ER redox state; its activity is tightly regulated to balance oxidation and limit ROS. Reason: ERO1A genuinely sets/balances ER redox homeostasis (regulatory disulfides and FAM20C tuning); a core biological process for this enzyme. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Enzyme activity is tightly regulated to prevent the accumulation of reactive oxygen species in the endoplasmic reticulum.
GO:0016020 membrane	HDA PMID:19946888 Defining the membrane proteome of NK cells.	KEEP AS NON CORE	Summary: High-throughput membrane proteome detection; ERO1A is a peripheral membrane protein, so a generic membrane localization is consistent but uninformative. Reason: Generic membrane localization from a proteomic survey; correct but far less specific than ER membrane. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Peripheral membrane protein
GO:0005788 endoplasmic reticulum lumen	TAS Reactome:R-HSA-3341296	ACCEPT	Summary: Reactome places ERO1A in the ER lumen; ERO1A acts on the lumenal side of the ER membrane, so this is consistent with its site of action. Reason: ERO1A is a lumenal-side ER protein; ER lumen localization is consistent with its function and curated by Reactome. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Lumenal side
GO:0034976 response to endoplasmic reticulum stress	ISS GO_REF:0000024	KEEP AS NON CORE	Summary: ISS-transferred ER-stress-response role from the mouse ortholog; consistent with ERO1A's UPR induction. Reason: Redundant with the IEA ER-stress annotation; a plausible downstream/contextual process, non-core. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Plays an important role in ER stress-induced, CHOP-dependent apoptosis
GO:0051209 release of sequestered calcium ion into cytosol	ISS GO_REF:0000024	KEEP AS NON CORE	Summary: ISS-transferred Ca2+-release role (via IP3R1) from the mouse ortholog. Reason: Specialized downstream effect during ER-stress apoptosis inferred by similarity; non-core. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt by activating the inositol 1,4,5-trisphosphate receptor IP3R1
GO:0070059 intrinsic apoptotic signaling pathway in response to endoplasmic reticulum stress	ISS GO_REF:0000024	KEEP AS NON CORE	Summary: ISS-transferred ER-stress apoptosis role from the mouse ortholog. Reason: Documented but specialized downstream signaling role; non-core relative to the oxidase activity. Supporting Evidence: file:human/ERO1A/ERO1A-uniprot.txt Plays an important role in ER stress-induced, CHOP-dependent apoptosis by activating the inositol 1,4,5-trisphosphate receptor IP3R1.
GO:0005783 endoplasmic reticulum	TAS PMID:10671517 ERO1-L, a human protein that favors disulfide bond formation...	ACCEPT	Summary: Original characterization showing ERO1-L co-localizes with ER markers. Reason: TAS from the founding paper directly establishes ER localization. Supporting Evidence: PMID:10671517 the product of the human ERO1-L gene co-localizes with ER markers and displays Endo-H-sensitive glycans
GO:0006457 protein folding	TAS PMID:10671517 ERO1-L, a human protein that favors disulfide bond formation...	KEEP AS NON CORE	Summary: ERO1-L is involved in oxidative ER protein folding; protein folding is the downstream process of its oxidase activity. Reason: A valid process annotation but downstream of the core oxidase molecular function. Supporting Evidence: PMID:10671517 ERO1-L is involved in oxidative ER protein folding in mammalian cells
GO:0009266 response to temperature stimulus	TAS PMID:10671517 ERO1-L, a human protein that favors disulfide bond formation...	MARK AS OVER ANNOTATED	Summary: This term derives from ERO1-L complementing the temperature/DTT sensitivity of a yeast ero1-1 thermosensitive mutant - a heterologous complementation assay, not evidence that human ERO1A functions in a temperature-stimulus response. Reason: The annotation over-interprets a yeast ts-mutant complementation experiment; it does not reflect a genuine temperature-response biological role for human ERO1A. Supporting Evidence: PMID:10671517 ERO1-L is able to complement several phenotypic traits of the yeast thermosensitive mutant ero1-1, including temperature and dithiothreitol sensitivity
GO:0016020 membrane	TAS PMID:10671517 ERO1-L, a human protein that favors disulfide bond formation...	KEEP AS NON CORE	Summary: ERO1-L behaves as a membrane-associated protein in isolated microsomes. Reason: Correct but generic membrane localization; the specific ER membrane term is preferred. Supporting Evidence: PMID:10671517 ERO1-L behaves as a type II integral membrane protein
GO:0043231 intracellular membrane-bounded organelle	TAS PMID:10671517 ERO1-L, a human protein that favors disulfide bond formation...	KEEP AS NON CORE	Summary: Very general organelle localization term, subsumed by the specific ER annotations. Reason: Uninformative high-level localization; correct but superseded by ER/ER membrane terms. Supporting Evidence: PMID:10671517 co-localizes with ER markers
GO:0005783 endoplasmic reticulum	IDA PMID:10671517 ERO1-L, a human protein that favors disulfide bond formation...	ACCEPT	Summary: Direct evidence (co-localization with ER markers) for ER localization. Reason: IDA-supported ER localization from the founding characterization. Supporting Evidence: PMID:10671517 co-localizes with ER markers
GO:0006457 protein folding	IDA PMID:11707400 Manipulation of oxidative protein folding and PDI redox stat...	KEEP AS NON CORE	Summary: ERO1A facilitates disulfide-bond formation in immunoglobulin subunits; protein folding is a downstream process of its oxidase activity. Reason: Valid downstream process annotation supported by direct evidence, but non-core relative to the oxidase molecular function. Supporting Evidence: PMID:11707400 hEROs) facilitate disulfide bond formation in immunoglobulin subunits by selectively oxidizing PDI

Core Functions

FAD-dependent endoplasmic-reticulum sulfhydryl oxidase that reoxidizes the protein disulfide isomerase P4HB/PDI, regenerating PDI's active site so it can catalyze further disulfide-bond formation in secretory proteins, with electrons passed via FAD to O2 producing H2O2.

Molecular Function:

flavin-dependent sulfhydryl oxidase activity

Cellular Locations:

endoplasmic reticulum membrane endoplasmic reticulum lumen

Supporting Evidence:

file:human/ERO1A/ERO1A-uniprot.txt
Efficiently reoxidizes P4HB/PDI, the enzyme catalyzing protein disulfide formation, in order to allow P4HB to sustain additional rounds of disulfide formation.
PMID:11707400
both human Ero1-Lalpha and Ero1-Lbeta (hEROs) facilitate disulfide bond formation in immunoglobulin subunits by selectively oxidizing PDI

Sets and balances the redox state of the ER lumen, with activity tightly regulated by intramolecular regulatory disulfides (and FAM20C phosphorylation) to sustain oxidative protein folding while limiting reactive-oxygen-species accumulation.

Molecular Function:

flavin-dependent sulfhydryl oxidase activity

Directly Involved In:

cell redox homeostasis

Cellular Locations:

endoplasmic reticulum lumen

Supporting Evidence:

file:human/ERO1A/ERO1A-uniprot.txt
Enzyme activity is tightly regulated to prevent the accumulation of reactive oxygen species in the endoplasmic reticulum.

References

GO_REF:0000002

Gene Ontology annotation through association of InterPro records with GO terms

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 Subcellular Location vocabulary mapping

GO_REF:0000107

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

GO_REF:0000116

Gene Ontology annotation based on RHEA mapping of reactions

GO_REF:0000120

Combined Automated Annotation using Multiple IEA Methods

PMID:10671517

ERO1-L, a human protein that favors disulfide bond formation in the endoplasmic reticulum.

ERO1-L is an ER-localized, glycosylated membrane-associated protein that complements the yeast ero1-1 mutant and is involved in oxidative ER protein folding; activity requires Cys-394/Cys-397.

PMID:11707400

Manipulation of oxidative protein folding and PDI redox state in mammalian cells.

Human Ero1-Lalpha and Ero1-Lbeta facilitate disulfide bond formation in immunoglobulin subunits by selectively oxidizing PDI, standing at a crucial point of an electron flow from nascent secretory proteins through PDI; ERp57 redox state is not affected.

PMID:17170699

ERp57 is essential for efficient folding of glycoproteins sharing common structural domains.

PMID:19946888

Defining the membrane proteome of NK cells.

PMID:20802462

Disulphide production by Ero1α-PDI relay is rapid and effectively regulated.

PMID:25416956

A proteome-scale map of the human interactome network.

PMID:29858230

Secretory kinase Fam20C tunes endoplasmic reticulum redox state via phosphorylation of Ero1α.

FAM20C phosphorylates ERO1A at Ser145 in the Golgi, increasing its enzymatic activity; phosphomimetic S145E doubles activity and accelerates immunoglobulin folding; ERO1A is required for proper immunoglobulin folding and is retained in the ER via ERP44.

PMID:32296183

A reference map of the human binary protein interactome.

Reactome:R-HSA-3341296

Reactome ER-lumen oxidative folding annotation for ERO1A

file:human/ERO1A/ERO1A-uniprot.txt

UniProt entry Q96HE7 (ERO1A_HUMAN), ERO1-like protein alpha

FAD-dependent ER sulfhydryl oxidase (EC 1.8.3.2) that reoxidizes P4HB/PDI to drive disulfide-bond formation and passes electrons to O2 generating H2O2; peripheral ER membrane protein on the lumenal side retained by ERP44; activity tightly regulated by regulatory disulfides and FAM20C phosphorylation; hypoxia-induced.

file:human/ERO1A/ERO1A-deep-research-falcon.md

Falcon deep research report for ERO1A

ERO1A re-oxidizes reduced PDI by accepting electrons through its FAD cofactor, with molecular oxygen as the terminal electron acceptor, producing H2O2; it binds PDI with highest affinity (Kd 1.7 uM) relative to other ER thiol isomerases, and is induced by HIF-1alpha under hypoxia and by the PERK-eIF2alpha-ATF4-CHOP UPR branch.

Suggested Experiments

Experiment: Reconstitute the ERO1A-PDI oxidation cycle in vitro with purified FAD-loaded ERO1A and P4HB, measuring O2 consumption and H2O2 production to quantify catalytic turnover and the effect of the regulatory disulfides and S145 phosphorylation.

Experiment: CRISPR knockout of ERO1A (and double knockout with ERO1B) in antibody-secreting cells followed by redox proteomics and immunoglobulin folding/secretion assays to define non-redundant substrate requirements.

Deep Research

Falcon

(ERO1A-deep-research-falcon.md)

Comprehensive Research Report: ERO1A (ERO1-like protein alpha) Falcon Edison Scientific Literature 15 citations 1 artifacts 2026-06-20T06:51:13.789716

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Comprehensive Research Report: ERO1A (ERO1-like protein alpha)

Gene and Protein Identity

ERO1A (also designated ERO1L, ERO1-L, or ERO1-like protein alpha; UniProt accession Q96HE7) encodes a flavin adenine dinucleotide (FAD)-containing endoplasmic reticulum (ER)-resident thiol oxidoreductase in humans (EC 1.8.3.2) (chen2024biologicalmechanismsand pages 1-3, chen2024biologicalmechanismsand pages 3-4). This protein belongs to the ERO1 family and contains the characteristic Ero1 domain (IPR007266) as specified in the UniProt annotation. ERO1A is broadly expressed across human tissues, distinguishing it from its paralog ERO1β, which shows more restricted expression primarily in pancreatic and gastric cells (chen2024biologicalmechanismsand pages 3-4, jha2021ero1pdiredoxsignaling pages 2-4). The human ERO1A protein was first characterized in 2000 and shares extensive homology with the yeast Saccharomyces cerevisiae ERO1 gene (chen2024biologicalmechanismsand pages 4-6).

Primary Molecular Function and Enzymatic Activity

Catalyzed Reaction and Mechanism

ERO1A functions as a central oxidase in the ER oxidative protein folding machinery, catalyzing the re-oxidation of protein disulfide isomerase (PDI) to sustain disulfide bond formation in nascent secretory and membrane proteins (jha2021ero1pdiredoxsignaling pages 1-2, chen2024biologicalmechanismsand pages 3-4, chen2024biologicalmechanismsand pages 4-6). The enzyme operates through a precisely orchestrated electron transfer chain: electrons from reduced substrate proteins are first transferred to PDI, which becomes reduced in the process. ERO1A then re-oxidizes reduced PDI by accepting electrons through its FAD cofactor, with molecular oxygen (O₂) serving as the terminal electron acceptor (zito2024fingerprintofthe pages 1-3, chen2024biologicalmechanismsand pages 4-6, moilanen2018molecularanalysisof pages 1-2).

The complete catalytic cycle involves: (1) PDI transferring disulfide bonds to client proteins and becoming reduced; (2) reduced PDI interacting with ERO1A via a protruding β-hairpin structure that docks with PDI's b' domain; (3) electron transfer from PDI's a' domain active site to ERO1A's outer active site (Cys94-Cys99 shuttle disulfide); (4) electron shuttling to ERO1A's inner active site and then to the FAD cofactor; and (5) reduction of O₂ to hydrogen peroxide (H₂O₂) (jha2021ero1pdiredoxsignaling pages 2-4, chen2024biologicalmechanismsand pages 4-6, jha2021ero1pdiredoxsignaling pages 4-5, moilanen2018molecularanalysisof pages 1-2).

Substrate Specificity

ERO1A exhibits strong substrate selectivity for PDI over other ER oxidoreductases. Quantitative binding studies demonstrate that ERO1A binds PDI with highest affinity (Kd = 1.7 μM), compared to substantially weaker affinities for other thiol isomerases: ERp44 (21 μM), ERp5 (70 μM), ERp57 (180 μM), ERp72 (160 μM), and ERp46 (280 μM) (jha2021ero1pdiredoxsignaling pages 4-5). This preferential interaction ensures efficient coordination of the ERO1A-PDI redox relay system.

While PDI represents the primary direct substrate, ERO1A indirectly facilitates proper folding of numerous client proteins that require disulfide bonds. Well-documented client proteins include vascular endothelial growth factor A (VEGF-A), programmed death-ligand 1 (PD-L1), and matrix metalloproteinases (MMPs) (chen2024biologicalmechanismsand pages 3-4, chen2024biologicalmechanismsand pages 4-6). Recent studies demonstrate that ERO1A inhibition selectively impairs the oxidative folding and secretion of these pro-tumoral proteins, indicating ERO1A-dependent maturation pathways (chen2024biologicalmechanismsand pages 4-6).

Reaction Products and ROS Generation

The stoichiometry of the ERO1A-catalyzed reaction produces one molecule of H₂O₂ for every disulfide bond formed (zito2024fingerprintofthe pages 1-3, chen2024biologicalmechanismsand pages 4-6, moilanen2018molecularanalysisof pages 1-2). Importantly, ERO1A accounts for approximately 25% of total cellular H₂O₂ production during protein translation, establishing it as a major source of ER-localized reactive oxygen species (ROS) (he2025endoplasmicreticulumoxidoreductin pages 1-2, zito2024fingerprintofthe pages 1-3, he2025endoplasmicreticulumoxidoreductin pages 2-3). This H₂O₂ generation has dual consequences: it contributes to cellular redox signaling under homeostatic conditions but can induce oxidative stress and apoptosis when ERO1A activity becomes excessive (zito2024fingerprintofthe pages 1-3, zito2024fingerprintofthe pages 3-4).

Subcellular Localization and Functional Compartmentalization

ERO1A is primarily localized to the ER lumen, where it performs its canonical role in oxidative protein folding (chen2024biologicalmechanismsand pages 1-3, jha2021ero1pdiredoxsignaling pages 1-2, zito2024fingerprintofthe pages 1-3). However, recent evidence demonstrates that ERO1A is enriched at specialized ER-mitochondria contact sites known as mitochondria-associated ER membranes (MAMs or ERMCs) (zito2024fingerprintofthe pages 1-3, zito2024fingerprintofthe pages 3-4). These nanometric junctions (~10-100 nm) serve as hubs for lipid and metabolite exchange, calcium signaling, and reactive oxygen species communication between the ER and mitochondria.

At MAMs, ERO1A's strategic positioning enables it to regulate calcium release from the ER to mitochondria via inositol 1,4,5-trisphosphate receptors (IP3R) and ryanodine receptors (RyR) (chen2024biologicalmechanismsand pages 3-4, he2025endoplasmicreticulumoxidoreductin pages 2-3, zito2024fingerprintofthe pages 3-4). This function extends beyond protein folding to coordinate ER proteostasis with mitochondrial bioenergetics and calcium homeostasis. Studies in cardiac tissue demonstrate that ERO1A-mediated regulation of RyR2 calcium channels can influence arrhythmogenesis and heart failure progression (he2025endoplasmicreticulumoxidoreductin pages 2-3).

Biochemical and Signaling Pathways

Integration with the Unfolded Protein Response (UPR)

ERO1A is intimately connected to the UPR, a coordinated cellular response to ER stress. The protein kinase RNA-like ER kinase (PERK) branch of the UPR represents the primary regulatory pathway for ERO1A expression (chen2024biologicalmechanismsand pages 1-3, chen2024biologicalmechanismsand pages 3-4, he2025endoplasmicreticulumoxidoreductin pages 2-3). During ER stress, PERK phosphorylates eukaryotic initiation factor 2α (eIF2α), leading to selective translation of activating transcription factor 4 (ATF4). ATF4 then induces expression of C/EBP homologous protein (CHOP), which directly transcriptionally activates ERO1A (chen2024biologicalmechanismsand pages 1-3, chen2024biologicalmechanismsand pages 3-4, he2025endoplasmicreticulumoxidoreductin pages 2-3).

This PERK-eIF2α-ATF4-CHOP-ERO1A signaling axis creates a complex regulatory network. Under moderate ER stress, ERO1A upregulation supports adaptive responses by enhancing oxidative folding capacity. However, sustained activation of this pathway under severe or chronic ER stress contributes to maladaptive responses and apoptosis (chen2024biologicalmechanismsand pages 1-3, he2025endoplasmicreticulumoxidoreductin pages 2-3). ERO1A-generated H₂O₂ can further exacerbate ER stress, creating a feedback loop that amplifies PERK pathway activation (chen2024biologicalmechanismsand pages 3-4, he2025endoplasmicreticulumoxidoreductin pages 2-3).

Hypoxia Response Pathway

ERO1A expression is strongly induced by hypoxia through hypoxia-inducible factor 1α (HIF-1α) (jha2021ero1pdiredoxsignaling pages 2-4, zito2024fingerprintofthe pages 3-4, chen2024biologicalmechanismsand pages 4-6). This regulation is particularly relevant in tumor biology, where hypoxic microenvironments are common. Under low oxygen conditions, HIF-1α transcriptionally activates ERO1A, enabling continued oxidative protein folding despite limited oxygen availability (jha2021ero1pdiredoxsignaling pages 2-4, chen2024biologicalmechanismsand pages 4-6). Remarkably, kinetic studies reveal that ERO1A exhibits high cooperativity for oxygen binding (Hill coefficient >3), allowing the enzyme to maintain activity under hypoxic conditions while preventing hyperoxidation under normoxic conditions (moilanen2018molecularanalysisof pages 1-2).

Calcium Signaling Pathways

Beyond its role in protein folding, ERO1A functions as a regulator of calcium homeostasis through multiple mechanisms (chen2024biologicalmechanismsand pages 3-4, he2025endoplasmicreticulumoxidoreductin pages 2-3, zito2024fingerprintofthe pages 3-4). ERO1A triggers calcium release from the ER to the cytosol and mitochondria by modulating IP3R and RyR calcium channels. The released calcium activates calcium/calmodulin-dependent protein kinase II (CaMKII), which can induce NADPH oxidase (NOX) expression, creating additional ROS generation pathways (chen2024biologicalmechanismsand pages 3-4). This calcium-ROS interplay positions ERO1A at the intersection of ER proteostasis, mitochondrial function, and cellular stress responses.

Redox Regulation and Feedback Mechanisms

ERO1A activity is tightly controlled by intrinsic regulatory mechanisms involving conserved cysteine residues that form regulatory disulfide bonds (jha2021ero1pdiredoxsignaling pages 2-4, moilanen2018molecularanalysisof pages 1-2). The enzyme can exist in active and inactive conformations, with PDI playing a role in modulating this regulatory switch through feedback mechanisms. The formation of regulatory disulfide bonds (particularly involving Cys94-Cys131 and Cys99-Cys104) prevents hyperoxidation of the ER and maintains appropriate levels of reduced PDI for isomerization reactions (jha2021ero1pdiredoxsignaling pages 2-4, moilanen2018molecularanalysisof pages 1-2).

Importantly, mammals possess compensatory oxidoreductases that can partially buffer ERO1A function, including peroxiredoxin 4 (PRDX4), glutathione peroxidases 7 and 8 (GPx7, GPx8), and vitamin K epoxide reductase (VKOR) (zito2024fingerprintofthe pages 1-3, chen2024biologicalmechanismsand pages 3-4, jha2021ero1pdiredoxsignaling pages 4-5). This redundancy explains why ERO1A deletion in mice, unlike in yeast, is not lethal and produces relatively mild phenotypes (zito2024fingerprintofthe pages 1-3, chen2024biologicalmechanismsand pages 3-4).

Biological Processes and Physiological Roles

ERO1A participates in several core biological processes:

Oxidative Protein Folding: The primary function is introducing disulfide bonds into nascent polypeptides in coordination with PDI and other folding factors (chen2024biologicalmechanismsand pages 1-3, jha2021ero1pdiredoxsignaling pages 1-2, zito2024fingerprintofthe pages 1-3).
ER Proteostasis: ERO1A helps maintain the oxidizing environment of the ER (glutathione redox potential ~-200 mV vs. ~-300 mV in cytoplasm) necessary for efficient disulfide bond formation (he2025endoplasmicreticulumoxidoreductin pages 2-3, chen2024biologicalmechanismsand pages 4-6).
ROS Generation and Signaling: As a major source of ER-localized H₂O₂, ERO1A contributes to redox signaling pathways while also potentially inducing oxidative stress (he2025endoplasmicreticulumoxidoreductin pages 1-2, zito2024fingerprintofthe pages 1-3).
Calcium Homeostasis: ERO1A regulates ER-mitochondria calcium transfer, influencing cellular bioenergetics and stress responses (chen2024biologicalmechanismsand pages 3-4, he2025endoplasmicreticulumoxidoreductin pages 2-3, zito2024fingerprintofthe pages 3-4).
Adaptation to Cellular Stress: Through its integration with UPR and hypoxia response pathways, ERO1A enables cells to adapt to proteotoxic and metabolic stresses (chen2024biologicalmechanismsand pages 1-3, jha2021ero1pdiredoxsignaling pages 2-4, chen2024biologicalmechanismsand pages 4-6).

Recent Developments and Current Research (2023-2025)

Recent research has significantly advanced understanding of ERO1A's pathophysiological roles and therapeutic potential:

Cancer Biology

Multiple comprehensive reviews published in 2024-2025 have consolidated evidence that ERO1A is upregulated across numerous cancer types, including breast, lung, pancreatic, cervical, liver, and gastric cancers, with high expression correlating with poor prognosis, increased metastasis, and reduced survival (chen2024biologicalmechanismsand pages 1-3, zito2024fingerprintofthe pages 1-3, zito2024fingerprintofthe pages 3-4, chen2024biologicalmechanismsand pages 4-6). ERO1A promotes tumor progression through several mechanisms: (1) facilitating oxidative folding of pro-angiogenic factors like VEGF-A to support tumor angiogenesis (chen2024biologicalmechanismsand pages 4-6); (2) enabling proper maturation of PD-L1, thereby contributing to immune evasion (chen2024biologicalmechanismsand pages 4-6); and (3) supporting folding of matrix-degrading enzymes that promote metastasis (chen2024biologicalmechanismsand pages 3-4).

A landmark study by Liu et al. (2023) demonstrated that ERO1A ablation induces lethal ER stress responses and immunogenic cell death, activating anti-tumor immunity in preclinical models. This finding suggests that ERO1A inhibition could have dual benefits: directly impairing tumor cell survival while enhancing immune recognition.

Therapeutic Development

Significant progress has been made in developing ERO1A-targeted therapies. Varone et al. (2025) reported the design and characterization of novel small molecule ERO1A inhibitors (compounds I2 and I3) derived from structure-activity optimization of the prototype inhibitor EN460. These compounds efficiently bind ERO1A and inhibit its activity with IC₅₀ values in the low micromolar range. Importantly, I2 and I3 demonstrated efficacy in triple-negative breast cancer (TNBC) models by impairing VEGF-A secretion and reducing PD-L1 expression, thereby affecting both angiogenesis and immune evasion pathways. These inhibitors showed selective cytotoxicity toward cancer cells while sparing normal cells, supporting the concept that tumors are more dependent on ERO1A than healthy tissues due to their elevated ER stress burden.

Mechanistic Insights

Chen et al. (2023) elucidated a detailed mechanistic pathway showing that silica nanoparticle-induced cellular stress activates the PERK-ATF4-CHOP-ERO1α axis, which then promotes IP3R1-dependent calcium mobilization leading to apoptosis. This work demonstrates how ERO1A integrates ER stress signaling with calcium-dependent cell death pathways, providing molecular detail to ERO1A's role beyond protein folding.

Multiple 2023-2025 reviews have comprehensively documented ERO1A's involvement in the UPR and its regulation by PERK/ATF4/CHOP signaling, establishing this pathway as a central regulatory mechanism across diverse disease contexts (chen2024biologicalmechanismsand pages 1-3, khojayeva2026targetingtheendoplasmic pages 1-2, he2025endoplasmicreticulumoxidoreductin pages 1-2, he2025endoplasmicreticulumoxidoreductin pages 2-3).

Cardiovascular and Metabolic Diseases

He et al. (2025) provided an in-depth review of ERO1A as a potential therapeutic target in cardiovascular diseases and diabetes. In cardiac tissue, ERO1A dysregulation contributes to arrhythmias through disruption of RyR2-mediated calcium release. In diabetes, ERO1β (the pancreatic isoform) plays a specific role in proinsulin folding, while ERO1A's broader expression influences systemic metabolic stress responses (he2025endoplasmicreticulumoxidoreductin pages 1-2, he2025endoplasmicreticulumoxidoreductin pages 2-3).

Expert Analysis and Current Understanding

The current scientific consensus, based on extensive research from 2018-2025, positions ERO1A as a multifunctional ER-resident enzyme with roles extending beyond its canonical oxidative folding function (chen2024biologicalmechanismsand pages 1-3, jha2021ero1pdiredoxsignaling pages 1-2, khojayeva2026targetingtheendoplasmic pages 1-2, zito2024fingerprintofthe pages 1-3). Key insights from recent authoritative reviews include:

Context-Dependent Dispensability: While ERO1A is dispensable in normal mammalian cells due to compensatory oxidoreductases, cancer cells and stressed cells become dependent on ERO1A, creating a therapeutic window (chen2024biologicalmechanismsand pages 1-3, zito2024fingerprintofthe pages 1-3, chen2024biologicalmechanismsand pages 3-4).
Integration of Proteostasis and Metabolism: ERO1A's enrichment at MAMs and its regulation of calcium signaling reveal an integrative function coordinating protein folding with mitochondrial metabolism (zito2024fingerprintofthe pages 1-3, zito2024fingerprintofthe pages 3-4).
Dual Role in Cell Fate: ERO1A can promote both cell survival (through adaptive UPR) and cell death (through excessive ROS production and calcium dysregulation), with the outcome depending on stress intensity and duration (chen2024biologicalmechanismsand pages 1-3, he2025endoplasmicreticulumoxidoreductin pages 2-3).
Therapeutic Targeting Feasibility: The development of ERO1A inhibitors with demonstrated preclinical efficacy validates the ERO1A-PDI redox interface as a druggable target, particularly in oncology (jha2021ero1pdiredoxsignaling pages 1-2, khojayeva2026targetingtheendoplasmic pages 1-2, zito2024fingerprintofthe pages 1-3).

Summary

The following table provides a condensed overview of ERO1A's key functional properties:

Category	Details	Evidence
Gene / protein identity	Human ERO1A; protein names include ERO1-like protein alpha, ERO1α, ERO1-L, ERO1L; a broadly expressed mammalian ERO1 isoform distinct from the more tissue-restricted ERO1β.	(chen2024biologicalmechanismsand pages 3-4, jha2021ero1pdiredoxsignaling pages 2-4, he2025endoplasmicreticulumoxidoreductin pages 2-3)
Enzyme class / cofactor	FAD-containing ER-resident thiol oxidoreductase; UniProt assigns EC 1.8.3.2. Structurally contains an FAD-binding core, inner and outer active sites, and a protruding β-hairpin used for docking to PDI.	(chen2024biologicalmechanismsand pages 3-4, jha2021ero1pdiredoxsignaling pages 2-4, chen2024biologicalmechanismsand pages 4-6)
Subcellular localization	Primarily localized in the endoplasmic reticulum lumen where oxidative folding occurs; also enriched at mitochondria-associated ER membranes (MAMs/ERMCs), linking ER redox control to Ca²⁺ transfer and mitochondrial metabolism.	(chen2024biologicalmechanismsand pages 1-3, zito2024fingerprintofthe pages 1-3, zito2024fingerprintofthe pages 3-4)
Primary enzymatic function	Catalyzes oxidative protein folding by re-oxidizing protein disulfide isomerase (PDI), enabling PDI to introduce disulfide bonds into nascent secretory and membrane proteins. ERO1A acts as an exchange center for disulfide bonds and electrons in the ER.	(jha2021ero1pdiredoxsignaling pages 1-2, chen2024biologicalmechanismsand pages 3-4, chen2024biologicalmechanismsand pages 4-6)
Catalyzed redox reaction	Electrons flow from reduced substrate proteins to PDI, then to ERO1A, then to FAD, and finally to molecular oxygen (O₂), producing H₂O₂. Overall, ERO1 couples disulfide bond formation to oxygen reduction; reviews note roughly 1 molecule of H₂O₂ is generated per disulfide bond formed.	(zito2024fingerprintofthe pages 1-3, chen2024biologicalmechanismsand pages 4-6, moilanen2018molecularanalysisof pages 1-2)
Direct biochemical substrate(s)	The principal direct enzymatic substrate is reduced PDI (especially the a′ domain of PDI). ERO1A can also interact with other ER thiol isomerases, but evidence indicates strongest preference for PDI.	(jha2021ero1pdiredoxsignaling pages 2-4, chen2024biologicalmechanismsand pages 4-6, moilanen2018molecularanalysisof pages 1-2)
Substrate affinity / specificity	Reported binding affinity for PDI: Kd = 1.7 μM. Weaker affinities reported for other ER oxidoreductases: ERp44 21 μM, ERp5 70 μM, ERp57 180 μM, ERp72 160 μM, ERp46 280 μM, supporting preferential engagement with PDI.	(jha2021ero1pdiredoxsignaling pages 4-5)
Immediate reaction products	Produces oxidized PDI and H₂O₂; oxidized PDI then transfers disulfides to client polypeptides. FAD cycles through reduced/oxidized states during catalysis.	(zito2024fingerprintofthe pages 1-3, chen2024biologicalmechanismsand pages 4-6, moilanen2018molecularanalysisof pages 1-2)
Contribution to cellular ROS	ERO1A-derived H₂O₂ has been estimated to account for about 25% of H₂O₂ produced during protein translation / induced cellular ROS in relevant settings, making ERO1A a major ER-localized ROS source.	(he2025endoplasmicreticulumoxidoreductin pages 1-2, zito2024fingerprintofthe pages 1-3, he2025endoplasmicreticulumoxidoreductin pages 2-3)
Protein clients with strong functional evidence	Specific protein clients whose maturation/folding is promoted by ERO1A include VEGF-A, PD-L1, and matrix-degrading proteins such as MMPs; inhibition or loss of ERO1A restrains oxidative folding/secretion of these pro-tumoral proteins.	(chen2024biologicalmechanismsand pages 3-4, chen2024biologicalmechanismsand pages 4-6)
Regulation by UPR / ER stress	Strongly linked to the unfolded protein response (UPR). The PERK–eIF2α–ATF4–CHOP branch induces ERO1A transcription; CHOP-dependent ERO1A upregulation is a recurring mechanism in ER-stress adaptation and, when excessive, apoptosis-associated signaling.	(chen2024biologicalmechanismsand pages 1-3, chen2024biologicalmechanismsand pages 3-4, he2025endoplasmicreticulumoxidoreductin pages 2-3)
Regulation by hypoxia	Hypoxia / HIF-1α upregulates ERO1A, especially in tumors. This supports oxidative folding under low-oxygen conditions and helps maintain secretion of angiogenic and immune-regulatory proteins in hypoxic microenvironments.	(jha2021ero1pdiredoxsignaling pages 2-4, zito2024fingerprintofthe pages 3-4, chen2024biologicalmechanismsand pages 4-6)
Intrinsic redox regulation	ERO1A activity is tightly controlled by regulatory intramolecular disulfide bonds and by feedback through PDI; active/inactive states involve conserved cysteine pairs and shuttle disulfides that prevent hyperoxidation of the ER.	(jha2021ero1pdiredoxsignaling pages 2-4, moilanen2018molecularanalysisof pages 1-2)
Related compensatory pathways	In mammals, ERO1A function can be partly buffered by other ER oxidoreductases/peroxidases including PRDX4/PrxIV, GPx7, GPx8, and VKOR, explaining why ERO1 loss is less catastrophic than in yeast.	(zito2024fingerprintofthe pages 1-3, chen2024biologicalmechanismsand pages 3-4, jha2021ero1pdiredoxsignaling pages 4-5)
Calcium homeostasis role	Beyond oxidative folding, ERO1A modulates ER Ca²⁺ release through IP3R and RyR pathways, affecting cytosolic/mitochondrial Ca²⁺ transfer, mitochondrial bioenergetics, and stress-induced apoptosis.	(chen2024biologicalmechanismsand pages 3-4, he2025endoplasmicreticulumoxidoreductin pages 2-3, zito2024fingerprintofthe pages 3-4)
Core biological processes	Oxidative protein folding, ER proteostasis, maintenance of ER redox environment, UPR/ER-stress adaptation, ROS generation/signaling, calcium homeostasis, and support of secretion/maturation of disulfide-rich secreted or membrane proteins.	(chen2024biologicalmechanismsand pages 1-3, jha2021ero1pdiredoxsignaling pages 1-2, zito2024fingerprintofthe pages 1-3)
Disease / clinical significance	Frequently upregulated in many cancers and associated with worse prognosis, tumor growth, angiogenesis, metastasis, immune evasion, and therapy resistance. ERO1A is increasingly viewed as a therapeutic target because tumors may depend on it more than normal tissues.	(chen2024biologicalmechanismsand pages 1-3, zito2024fingerprintofthe pages 1-3, zito2024fingerprintofthe pages 3-4)
Therapeutic translation / current applications	Preclinical work supports targeting the ERO1A–PDI redox interface. Small-molecule inhibitors such as EN460 and newer analogs have been explored; ERO1A inhibition can impair tumor features by reducing oxidative folding/secretion of VEGF-A and PD-L1.	(jha2021ero1pdiredoxsignaling pages 1-2, zito2024fingerprintofthe pages 1-3)

Table: This table condenses the main verified functional properties of human ERO1A, including its enzymatic role, substrates, localization, pathways, and disease relevance. It is useful as a quick-reference annotation summary grounded in the cited evidence contexts.

ERO1A (Q96HE7) functions as an ER-resident FAD-containing thiol oxidoreductase that catalyzes disulfide bond formation by re-oxidizing PDI, with molecular oxygen as the terminal electron acceptor and H₂O₂ as a byproduct. The enzyme is localized to the ER lumen and enriched at ER-mitochondria contact sites, where it coordinates protein folding with calcium signaling and mitochondrial metabolism. ERO1A is regulated by the PERK/ATF4/CHOP branch of the UPR and by HIF-1α under hypoxia. Recent research (2023-2025) has established ERO1A as an important therapeutic target in cancer, with novel small molecule inhibitors showing promise in preclinical models. The protein's integration into multiple stress response pathways and its differential requirement in cancer versus normal cells make it an attractive candidate for therapeutic intervention in diseases characterized by ER stress and proteostatic dysregulation.

References

(chen2024biologicalmechanismsand pages 1-3): Peng Chen, Amit Sharma, Hans Weiher, and Ingo G.H. Schmidt-Wolf. Biological mechanisms and clinical significance of endoplasmic reticulum oxidoreductase 1 alpha (ero1α) in human cancer. Journal of Experimental & Clinical Cancer Research : CR, Mar 2024. URL: https://doi.org/10.1186/s13046-024-02990-4, doi:10.1186/s13046-024-02990-4. This article has 31 citations.
(chen2024biologicalmechanismsand pages 3-4): Peng Chen, Amit Sharma, Hans Weiher, and Ingo G.H. Schmidt-Wolf. Biological mechanisms and clinical significance of endoplasmic reticulum oxidoreductase 1 alpha (ero1α) in human cancer. Journal of Experimental & Clinical Cancer Research : CR, Mar 2024. URL: https://doi.org/10.1186/s13046-024-02990-4, doi:10.1186/s13046-024-02990-4. This article has 31 citations.
(jha2021ero1pdiredoxsignaling pages 2-4): Vishwanath Jha, Tripti Kumari, Vijayprakash Manickam, Zahra Assar, Kirk L. Olson, Jeong-Ki Min, and Jaehyung Cho. Ero1-pdi redox signaling in health and disease. Nov 2021. URL: https://doi.org/10.1089/ars.2021.0018, doi:10.1089/ars.2021.0018. This article has 48 citations and is from a domain leading peer-reviewed journal.
(chen2024biologicalmechanismsand pages 4-6): Peng Chen, Amit Sharma, Hans Weiher, and Ingo G.H. Schmidt-Wolf. Biological mechanisms and clinical significance of endoplasmic reticulum oxidoreductase 1 alpha (ero1α) in human cancer. Journal of Experimental & Clinical Cancer Research : CR, Mar 2024. URL: https://doi.org/10.1186/s13046-024-02990-4, doi:10.1186/s13046-024-02990-4. This article has 31 citations.
(jha2021ero1pdiredoxsignaling pages 1-2): Vishwanath Jha, Tripti Kumari, Vijayprakash Manickam, Zahra Assar, Kirk L. Olson, Jeong-Ki Min, and Jaehyung Cho. Ero1-pdi redox signaling in health and disease. Nov 2021. URL: https://doi.org/10.1089/ars.2021.0018, doi:10.1089/ars.2021.0018. This article has 48 citations and is from a domain leading peer-reviewed journal.
(zito2024fingerprintofthe pages 1-3): Ester Zito, Luca Guarrera, and Yvonne M.W. Janssen-Heininger. Fingerprint of the oxido-reductase ero1: a protein disulfide bond producer and supporter of cancer. Jan 2024. URL: https://doi.org/10.1016/j.bbcan.2023.189027, doi:10.1016/j.bbcan.2023.189027. This article has 27 citations and is from a peer-reviewed journal.
(moilanen2018molecularanalysisof pages 1-2): Antti Moilanen, Kati Korhonen, Mirva J Saaranen, and Lloyd W Ruddock. Molecular analysis of human ero1 reveals novel regulatory mechanisms for oxidative protein folding. Life Science Alliance, 1:e201800090, Jun 2018. URL: https://doi.org/10.26508/lsa.201800090, doi:10.26508/lsa.201800090. This article has 32 citations and is from a peer-reviewed journal.
(jha2021ero1pdiredoxsignaling pages 4-5): Vishwanath Jha, Tripti Kumari, Vijayprakash Manickam, Zahra Assar, Kirk L. Olson, Jeong-Ki Min, and Jaehyung Cho. Ero1-pdi redox signaling in health and disease. Nov 2021. URL: https://doi.org/10.1089/ars.2021.0018, doi:10.1089/ars.2021.0018. This article has 48 citations and is from a domain leading peer-reviewed journal.
(he2025endoplasmicreticulumoxidoreductin pages 1-2): Fang He, Xiaoyue Ge, and Xiaohui Liu. Endoplasmic reticulum oxidoreductin 1α as a potential therapeutic target in diseases: from oxidative protein folding to pathophysiological mechanisms. Frontiers in Pharmacology, Nov 2025. URL: https://doi.org/10.3389/fphar.2025.1709284, doi:10.3389/fphar.2025.1709284. This article has 2 citations.
(he2025endoplasmicreticulumoxidoreductin pages 2-3): Fang He, Xiaoyue Ge, and Xiaohui Liu. Endoplasmic reticulum oxidoreductin 1α as a potential therapeutic target in diseases: from oxidative protein folding to pathophysiological mechanisms. Frontiers in Pharmacology, Nov 2025. URL: https://doi.org/10.3389/fphar.2025.1709284, doi:10.3389/fphar.2025.1709284. This article has 2 citations.
(zito2024fingerprintofthe pages 3-4): Ester Zito, Luca Guarrera, and Yvonne M.W. Janssen-Heininger. Fingerprint of the oxido-reductase ero1: a protein disulfide bond producer and supporter of cancer. Jan 2024. URL: https://doi.org/10.1016/j.bbcan.2023.189027, doi:10.1016/j.bbcan.2023.189027. This article has 27 citations and is from a peer-reviewed journal.
(khojayeva2026targetingtheendoplasmic pages 1-2): Kamilla Khojayeva, Aiym Zhussipbekkyzy, Dilbara Balkybayeva, Karakat Sabit, Lucia Rossetti Lopes, Kamila Sagatbekova, Assem Zhakupova, and Mohamad Aljofan. Targeting the endoplasmic reticulum oxidoreductin-1 alpha–protein disulfide isomerase redox interface as a therapeutic strategy in cancer. Biomedicines, 14:263, Jan 2026. URL: https://doi.org/10.3390/biomedicines14020263, doi:10.3390/biomedicines14020263. This article has 0 citations.

Artifacts

Edison artifact artifact-00

Citations

chen2024biologicalmechanismsand pages 4-6
he2025endoplasmicreticulumoxidoreductin pages 2-3
moilanen2018molecularanalysisof pages 1-2
chen2024biologicalmechanismsand pages 3-4
chen2024biologicalmechanismsand pages 1-3
zito2024fingerprintofthe pages 1-3
he2025endoplasmicreticulumoxidoreductin pages 1-2
zito2024fingerprintofthe pages 3-4
khojayeva2026targetingtheendoplasmic pages 1-2
https://doi.org/10.1186/s13046-024-02990-4,
https://doi.org/10.1089/ars.2021.0018,
https://doi.org/10.1016/j.bbcan.2023.189027,
https://doi.org/10.26508/lsa.201800090,
https://doi.org/10.3389/fphar.2025.1709284,
https://doi.org/10.3390/biomedicines14020263,

📚 Additional Documentation

Notes

(ERO1A-notes.md)

ERO1A (ERO1L, ERO1-Lalpha) research notes

UniProt Q96HE7. ER membrane-associated FAD-dependent flavoprotein oxidoreductase (sulfhydryl oxidase), EC 1.8.3.2.

Core molecular function

Reoxidizes PDI/P4HB to drive disulfide-bond formation in the ER; passes electrons to O2 via FAD generating H2O2.
[file:human/ERO1A/ERO1A-uniprot.txt "Oxidoreductase involved in disulfide bond formation in the endoplasmic reticulum. Efficiently reoxidizes P4HB/PDI, the enzyme catalyzing protein disulfide formation, in order to allow P4HB to sustain additional rounds of disulfide formation. Following P4HB reoxidation, passes its electrons to molecular oxygen via FAD, leading to the production of reactive oxygen species (ROS) in the cell."]
Selectively oxidizes PDI (not ERp57): PMID:11707400
FAD cofactor and flavin-dependent oxidase: COFACTOR FAD; crystal structures 3AHQ/3AHR with FAD binding sites (PubMed:20834232). EC 1.8.3.2.
Catalytic reaction: [protein]-dithiol + O2 = [protein]-disulfide + H2O2 (RHEA:59116) -> GO:0016971 flavin-dependent sulfhydryl oxidase activity.

Localization

ER membrane, peripheral membrane protein, lumenal side; retained in ER via ERP44 interaction.
[file:human/ERO1A/ERO1A-uniprot.txt "SUBCELLULAR LOCATION: Endoplasmic reticulum membrane"]
Also Golgi lumen and secreted (PubMed:29858230). Dendrite by similarity (mouse).

Biological roles

Required for proper folding of immunoglobulins PMID:29858230.
ER stress-induced CHOP-dependent apoptosis via IP3R1 (Ca2+ release) — by similarity/ISS from mouse Q8R180.
Cholera toxin retrotranslocation: oxidizes PDI to release unfolded toxin (PubMed:12403808).
Hypoxia-induced (HIF pathway): [file "Stimulated by hypoxia; suggesting that it is regulated via the HIF-pathway."]
Activity tightly regulated by regulatory disulfides (Cys94-Cys131, Cys99-Cys104) to limit ROS.
FAM20C phosphorylates Ser145 in Golgi, increasing activity PMID:29858230.

Interactions (IPI annotations)

P4HB/PDI (P07237), PDIA3/ERp57 (P30101), ERP44 (Q9BS26). APPBP2 (Q92624), LHX4 (Q969G2) = HT binary interactome, low-confidence/non-core.
Note: PMID:11707400 shows Ero1a does NOT affect ERp57 redox state, but PDIA3 binding annotated from IntAct (PMID:17170699, 20802462). KEEP_AS_NON_CORE.

Action plan

Core MF: flavin-dependent sulfhydryl oxidase activity (GO:0016971) / protein disulfide isomerase reoxidation.
thiol oxidase activity (GO:0016972) IDA - ACCEPT (parent of more specific flavin-dependent).
protein-disulfide reductase activity (GO:0015035 IBA) - the family acts as oxidase not reductase; this IBA is misleading -> MARK_AS_OVER_ANNOTATED / MODIFY. Actually ERO1 is an oxidase; "reductase" IBA likely transferred. MARK_AS_OVER_ANNOTATED.
oxidoreductase activity (GO:0016491) - ACCEPT as parent (non-core/general).
FAD binding (GO:0071949) - ACCEPT (structural FAD cofactor).
protein binding x several - KEEP_AS_NON_CORE (P4HB/PDIA3/ERP44 real, HT ones non-core).
localizations ER/ER membrane - ACCEPT; Golgi lumen/extracellular/dendrite - KEEP_AS_NON_CORE.
protein folding / protein folding in ER - KEEP_AS_NON_CORE (downstream BP).
cell redox homeostasis IMP - ACCEPT (core BP).
ER stress / apoptosis / Ca release ISS/IEA - KEEP_AS_NON_CORE (mouse-transferred).
response to temperature stimulus TAS - the yeast complementation of ts mutant; weak, MARK_AS_OVER_ANNOTATED.
intracellular membrane-bounded organelle / membrane - general, KEEP_AS_NON_CORE.

Pn Notes

(ERO1A-pn-notes.md)

ERO1A PN Consistency Notes

Generated: 2026-06-18
Project: PROTEOSTASIS
Scope: PN consistency rereview against local AIGR review and available deep-research artifacts
UniProt: Q96HE7
AIGR review status: COMPLETE
Review batch: proteostasis-batch-2026-06-07b
Batch change status: added

Source Files Checked

AIGR review YAML: present - genes/human/ERO1A/ERO1A-ai-review.yaml
AIGR review HTML: present - genes/human/ERO1A/ERO1A-ai-review.html
Gene notes: present - genes/human/ERO1A/ERO1A-notes.md
GOA TSV: present - genes/human/ERO1A/ERO1A-goa.tsv
UniProt record: present - genes/human/ERO1A/ERO1A-uniprot.txt
PN dossier: projects/PROTEOSTASIS/reports/phase1_dossiers/ERO1A.md
PN consistency section: projects/PROTEOSTASIS/reports/phase1_dossiers/_sections/ERO1A.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

No *-deep-research*.md file found in this gene directory.

AIGR Review Snapshot

Description: ERO1A (ERO1-like protein alpha, formerly ERO1L; endoplasmic reticulum oxidoreductin-1 alpha) is an ER membrane-associated, FAD-dependent flavoprotein sulfhydryl oxidase (EC 1.8.3.2) that drives oxidative protein folding in the endoplasmic reticulum. It reoxidizes the protein disulfide isomerase P4HB/PDI, regenerating PDI's active-site disulfide so that PDI can catalyze further rounds of disulfide-bond formation in nascent secretory proteins; the electrons abstracted are passed via bound FAD to molecular oxygen, producing hydrogen peroxide. It is a peripheral membrane protein on the lumenal side of the ER, retained there through its interaction with ERP44, and is also detected in the Golgi lumen and secreted. Its enzymatic activity is tightly regulated by intramolecular regulatory disulfide bonds (involving Cys94/Cys99/Cys104/Cys131) to limit reactive-oxygen-species accumulation, and is further tuned by FAM20C-mediated phosphorylation at Ser145. ERO1A is induced by hypoxia via the HIF pathway and during the unfolded protein response. Through oxidative folding it supports maturation of disulfide-rich secretory cargo such as immunoglobulins, and participates in ER-stress responses, cholera-toxin retrotranslocation, and ER redox homeostasis.
Existing/core annotation action counts: ACCEPT: 16; KEEP_AS_NON_CORE: 23; MARK_AS_OVER_ANNOTATED: 3

PN Consistency Summary

Consistency: Notes, review YAML, and the corrected PN type-node mapping are consistent: ERO1A is an FAD-dependent sulfhydryl OXIDASE that reoxidizes PDI, not an isomerase. Review core MF = GO:0016971 (EXP PMID:11707400/29858230, ACCEPT) and it explicitly MARK_AS_OVER_ANNOTATED the GO:0015035 protein-disulfide reductase rows (wrong directionality). The dossier rationale documents this correction explicitly. Internal PN tension: the parent Protein disulfide isomerases group still maps GO:0003756 and the projected-annotations list still projects GO:0003756 to ERO1A as new_to_goa — which contradicts the corrected type node and the review (which never asserts isomerase activity for this oxidase).
PN story / NEW pressure: GO:0016971 (OLS-verified) is already in GOA (EXP) and ACCEPTed — captured, no NEW pressure. GO:0003756 (verified real) should NOT be added to ERO1A: it is biologically wrong for an oxidase (the review asserts oxidase, not isomerase; cf. the reductase over-annotation it rejects). Conclusion on the group projection: over-reaches for ERO1A.
Evidence alignment: PN dossier lists no reference titles. Review oxidase evidence (PMID:11707400, 29858230, 10671517, GOA-anchored to GO:0016971/GO:0016972) is reviewer-supplied; the ERO1A↔P4HB redox-relay interaction (PMID:20802462) cross-links to the P4HB review (where it appears as ERO1A protein binding). Alignment is by shared biology and the cross-referenced relay partner.
Verdict: Consistent at the (corrected) gene/type level; GO:0016971 validated and captured. The lingering group-level GO:0003756 projection over-reaches and should not land on ERO1A. Recommended edits: [MAP] suppress/override the GO:0003756 projection for ERO1A (and ERO1B) so the PDI-reoxidation oxidase children inherit only GO:0016971, not the parent isomerase term (matches the already-corrected type node and the review's oxidase-vs-isomerase distinction).

Full Consistency Review

UniProt: Q96HE7 · batch: proteostasis-batch-2026-06-07b · review status: COMPLETE
PN placement: ER proteostasis|Folding enzyme|Protein disulfide isomerases|Protein disulfide isomerase reoxidation. PN-node mapping: type PDI reoxidation=mapped→GO:0016971 flavin-dependent sulfhydryl oxidase activity (corrected in batch-5 after gene-level review); parent group Protein disulfide isomerases=mapped→GO:0003756 protein disulfide isomerase activity (new_to_goa); class/branch=no_mapping.
Consistency: Notes, review YAML, and the corrected PN type-node mapping are consistent: ERO1A is an FAD-dependent sulfhydryl OXIDASE that reoxidizes PDI, not an isomerase. Review core MF = GO:0016971 (EXP PMID:11707400/29858230, ACCEPT) and it explicitly MARK_AS_OVER_ANNOTATED the GO:0015035 protein-disulfide reductase rows (wrong directionality). The dossier rationale documents this correction explicitly. Internal PN tension: the parent Protein disulfide isomerases group still maps GO:0003756 and the projected-annotations list still projects GO:0003756 to ERO1A as new_to_goa — which contradicts the corrected type node and the review (which never asserts isomerase activity for this oxidase).
PN story / NEW pressure: GO:0016971 (OLS-verified) is already in GOA (EXP) and ACCEPTed — captured, no NEW pressure. GO:0003756 (verified real) should NOT be added to ERO1A: it is biologically wrong for an oxidase (the review asserts oxidase, not isomerase; cf. the reductase over-annotation it rejects). Conclusion on the group projection: over-reaches for ERO1A.
Mapping strategy: The type-level correction (→GO:0016971) is exactly right and the model fix to follow. The problem is purely inheritance: the group node Protein disulfide isomerases lumps catalytic PDIs (P4HB), non-catalytic members (ERP27), and the EROs (oxidases), so its GO:0003756 projection mislabels the oxidase children. Note GO:0016971 is itself a GO child of GO:0015035 reductase, so the over-annotation the review rejects is the parent term, not the accepted child — the directionality argument (not the hierarchy) is what justifies the review's split.
Evidence alignment: PN dossier lists no reference titles. Review oxidase evidence (PMID:11707400, 29858230, 10671517, GOA-anchored to GO:0016971/GO:0016972) is reviewer-supplied; the ERO1A↔P4HB redox-relay interaction (PMID:20802462) cross-links to the P4HB review (where it appears as ERO1A protein binding). Alignment is by shared biology and the cross-referenced relay partner.
Verdict: Consistent at the (corrected) gene/type level; GO:0016971 validated and captured. The lingering group-level GO:0003756 projection over-reaches and should not land on ERO1A. Recommended edits: [MAP] suppress/override the GO:0003756 projection for ERO1A (and ERO1B) so the PDI-reoxidation oxidase children inherit only GO:0016971, not the parent isomerase term (matches the already-corrected type node and the review's oxidase-vs-isomerase distinction).

PN Dossier Context

review_batch: proteostasis-batch-2026-06-07b
review_yaml: genes/human/ERO1A/ERO1A-ai-review.yaml
PN workbook rows: 1

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

UniProt: Q96HE7
In branches: ER
PN-node mapping records (path + ancestors):
- [type] ER proteostasis|Folding enzyme|Protein disulfide isomerases|Protein disulfide isomerase reoxidation
  status=mapped scope=ok_for_propagation_to_go GO=[GO:0016971 flavin-dependent sulfhydryl oxidase activity]
  rationale: Corrected after gene-level review (proteostasis batch 5). This PN type is the ERO1 "PDI reoxidation" step, whose members (ERO1A/ERO1L, ERO1B/ERO1LB) are FAD-dependent sulfhydryl OXIDASES that reoxidize PDI to regenerate its active site — they do not themselves catalyze protein disulfide isomerization. The previous target GO:0003756 (protein disulfide isomerase activity) was incorrect for this node and would mislabel the oxidases as isomerases (both ERO1A and ERO1B reviews mark the protein-disulfide reductase/isomerase terms as over-annotations). The correct shared molecular function is GO:0016971 flavin-dependent sulfhydryl oxidase activity, which both genes carry with experimental (EXP) evidence in GOA.
- [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 (2)

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
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|Protein disulfide isomerase reoxidation

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: Q96HE7
gene_symbol: ERO1A
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: ERO1A (ERO1-like protein alpha, formerly ERO1L; endoplasmic reticulum oxidoreductin-1 alpha) is an ER membrane-associated, FAD-dependent flavoprotein sulfhydryl oxidase (EC 1.8.3.2) that drives oxidative protein folding in the endoplasmic reticulum. It reoxidizes the protein disulfide isomerase P4HB/PDI, regenerating PDI's active-site disulfide so that PDI can catalyze further rounds of disulfide-bond formation in nascent secretory proteins; the electrons abstracted are passed via bound FAD to molecular oxygen, producing hydrogen peroxide. It is a peripheral membrane protein on the lumenal side of the ER, retained there through its interaction with ERP44, and is also detected in the Golgi lumen and secreted. Its enzymatic activity is tightly regulated by intramolecular regulatory disulfide bonds (involving Cys94/Cys99/Cys104/Cys131) to limit reactive-oxygen-species accumulation, and is further tuned by FAM20C-mediated phosphorylation at Ser145. ERO1A is induced by hypoxia via the HIF pathway and during the unfolded protein response. Through oxidative folding it supports maturation of disulfide-rich secretory cargo such as immunoglobulins, and participates in ER-stress responses, cholera-toxin retrotranslocation, and ER redox homeostasis.
existing_annotations:
- term:
    id: GO:0005789
    label: endoplasmic reticulum membrane
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: is_active_in
  review:
    summary: ERO1A is a peripheral ER membrane protein acting on the lumenal side; this is its primary site of action and is well supported experimentally and by phylogenetic inference across the EROs family.
    action: ACCEPT
    reason: The ER membrane (lumenal side) is the documented site of action for ERO1A, where it reoxidizes PDI; corroborated by direct evidence.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum membrane'
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: A secreted/extracellular pool of ERO1A has been reported, but this is peripheral to its core ER oxidoreductase function.
    action: KEEP_AS_NON_CORE
    reason: UniProt records a secreted pool, so the localization is not wrong, but it is a minor/secondary location relative to the ER where ERO1A performs its catalytic role.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: Golgi apparatus lumen
- term:
    id: GO:0005783
    label: endoplasmic reticulum
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: located_in
  review:
    summary: ER localization is correct and the principal compartment for ERO1A.
    action: ACCEPT
    reason: ERO1A is an ER-resident oxidoreductase; this localization is directly supported.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum membrane'
- term:
    id: GO:0005789
    label: endoplasmic reticulum membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: Electronic localization to ER membrane, consistent with the IBA and experimental evidence.
    action: ACCEPT
    reason: Correct compartment; ERO1A is a peripheral ER membrane protein on the lumenal side.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: Peripheral membrane protein
- term:
    id: GO:0005796
    label: Golgi lumen
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: ERO1A is detected in the Golgi lumen, where it is a FAM20C substrate, but this is secondary to its ER function.
    action: KEEP_AS_NON_CORE
    reason: Golgi lumen localization is documented (FAM20C phosphorylation occurs in the Golgi) but peripheral to the core ER oxidoreductase activity.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: Golgi apparatus lumen
- term:
    id: GO:0015035
    label: protein-disulfide reductase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: enables
  review:
    summary: This term asserts a disulfide REDUCTASE activity. ERO1A is mechanistically an OXIDASE that reoxidizes PDI (i.e. forms disulfides and consumes reducing equivalents), not a reductase. The reductase term is an over-annotation, likely an electronic transfer that mislabels the directionality.
    action: MARK_AS_OVER_ANNOTATED
    reason: ERO1A oxidizes PDI and passes electrons to O2 generating H2O2; it does not function as a protein-disulfide reductase. The catalytic direction recorded by UniProt is dithiol oxidation, contradicting a reductase assignment.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: Efficiently reoxidizes P4HB/PDI, the enzyme catalyzing protein disulfide formation, in order to allow P4HB to sustain additional rounds of disulfide formation.
- term:
    id: GO:0016971
    label: flavin-dependent sulfhydryl oxidase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000116
  qualifier: enables
  review:
    summary: This is the precise core molecular function of ERO1A - a FAD-dependent sulfhydryl oxidase catalyzing dithiol + O2 = disulfide + H2O2 (RHEA:59116). The falcon deep research independently describes the same electron-flow mechanism with O2 as the terminal electron acceptor.
    action: ACCEPT
    reason: Directly matches the catalytic activity and FAD cofactor of ERO1A and is supported experimentally (EXP entries from PMID:11707400, PMID:29858230).
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: 'Reaction=[protein]-dithiol + O2 = [protein]-disulfide + H2O2'
    - reference_id: file:human/ERO1A/ERO1A-deep-research-falcon.md
      supporting_text: ERO1A then re-oxidizes reduced PDI by accepting electrons through its FAD cofactor, with molecular oxygen (O₂) serving as the terminal electron acceptor
- term:
    id: GO:0016972
    label: thiol oxidase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: enables
  review:
    summary: Thiol oxidase activity is the broader parent of ERO1A's flavin-dependent sulfhydryl oxidase activity; correct but less specific.
    action: ACCEPT
    reason: Correctly captures ERO1A's oxidase activity; the IDA-supported version of the same term (PMID:11707400) confirms it.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: 'EC=1.8.3.2'
- term:
    id: GO:0030425
    label: dendrite
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: located_in
  review:
    summary: Dendritic localization is inferred only by similarity to the mouse ortholog (Q8R4A1) and is not established for human ERO1A.
    action: MARK_AS_OVER_ANNOTATED
    reason: This is a by-similarity transfer from the rodent ortholog for a neuronal context; it is not a core function and is unsupported by direct human evidence.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: In neurons, it localizes to dendrites (By
- term:
    id: GO:0034975
    label: protein folding in endoplasmic reticulum
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: involved_in
  review:
    summary: ERO1A enables oxidative protein folding in the ER; protein folding in the ER is a valid downstream biological process outcome of its oxidase activity.
    action: KEEP_AS_NON_CORE
    reason: Protein folding in the ER is a process consequence of ERO1A's oxidase activity rather than its direct molecular function; appropriate as a non-core process annotation.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: Oxidoreductase involved in disulfide bond formation in the endoplasmic reticulum.
- term:
    id: GO:0071949
    label: FAD binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: ERO1A is a flavoprotein that binds FAD as its cofactor; multiple FAD binding residues are defined in the crystal structure.
    action: ACCEPT
    reason: FAD is the documented cofactor with mapped binding sites (PubMed:20834232, PDB 3AHQ/3AHR); FAD binding is integral to the oxidase mechanism.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: 'Name=FAD; Xref=ChEBI:CHEBI:57692'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:17170699
  qualifier: enables
  review:
    summary: IntAct interaction with PDIA3/ERp57 (P30101). Bare protein binding is uninformative; it records a real ER-oxidoreductase interaction but is non-core (and note PMID:11707400 found ERO1A does not alter ERp57 redox state).
    action: KEEP_AS_NON_CORE
    reason: Records a genuine physical interaction within the ER oxidoreductase network, but the uninformative protein binding term should not be elevated to core function.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: 'Q96HE7; P30101: PDIA3'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:20802462
  qualifier: enables
  review:
    summary: IntAct interactions with P4HB/PDI (P07237) and PDIA3 (P30101), the physiological substrates ERO1A reoxidizes. The bare protein binding term is uninformative but the underlying P4HB interaction is biologically central; the falcon deep research notes ERO1A binds PDI with the highest affinity among ER thiol isomerases (Kd 1.7 uM), consistent with PDI being its preferred direct substrate.
    action: KEEP_AS_NON_CORE
    reason: The P4HB interaction underlies ERO1A's catalytic substrate relationship, but the generic protein binding term is uninformative and the informative function is captured by the oxidase MF terms.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: 'Q96HE7; P07237: P4HB'
    - reference_id: file:human/ERO1A/ERO1A-deep-research-falcon.md
      supporting_text: ERO1A exhibits strong substrate selectivity for PDI over other ER oxidoreductases. Quantitative binding studies demonstrate that ERO1A binds PDI with highest affinity (Kd = 1.7 μM)
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:25416956
  qualifier: enables
  review:
    summary: High-throughput yeast two-hybrid interactome capturing an ERO1A-APPBP2 (Q92624) interaction; an isolated binary interaction unrelated to ERO1A's oxidase function.
    action: KEEP_AS_NON_CORE
    reason: Bare protein binding from a large-scale binary interactome screen; records an interaction but is uninformative and not part of the core function.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: 'Q96HE7; Q92624: APPBP2'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:32296183
  qualifier: enables
  review:
    summary: Binary interactome map capturing an ERO1A-LHX4 (Q969G2) interaction; a single high-throughput interaction with a homeobox transcription factor unrelated to ERO1A's ER function.
    action: KEEP_AS_NON_CORE
    reason: Bare protein binding from a reference binary interactome; uninformative and not part of ERO1A's core oxidative-folding function.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: 'Q96HE7; Q969G2: LHX4'
- term:
    id: GO:0016491
    label: oxidoreductase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: enables
  review:
    summary: ERO1A is an oxidoreductase; this is a correct but very general parent term.
    action: ACCEPT
    reason: Correct high-level molecular function, subsumed by the more specific flavin-dependent sulfhydryl oxidase activity that is the core function.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: Oxidoreductase involved in disulfide bond formation in the endoplasmic reticulum.
- term:
    id: GO:0034976
    label: response to endoplasmic reticulum stress
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: involved_in
  review:
    summary: ERO1A is induced during the UPR and participates in ER-stress responses; this is a plausible process annotation transferred from the mouse ortholog.
    action: KEEP_AS_NON_CORE
    reason: ERO1A is part of the ER stress/UPR program but this is a downstream/contextual process rather than its core molecular function.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: Plays an important role in ER stress-induced, CHOP-dependent apoptosis
- term:
    id: GO:0051209
    label: release of sequestered calcium ion into cytosol
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: involved_in
  review:
    summary: ERO1A promotes ER Ca2+ release by activating IP3R1 during ER-stress apoptosis; this is inferred from the mouse ortholog and is a specialized downstream role. The falcon deep research corroborates that ERO1A modulates ER Ca2+ release via IP3R (and RyR) channels.
    action: KEEP_AS_NON_CORE
    reason: A genuine but context-specific (ER-stress apoptosis) downstream effect inferred by similarity; non-core relative to the oxidase function.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: by activating the inositol 1,4,5-trisphosphate receptor IP3R1
    - reference_id: file:human/ERO1A/ERO1A-deep-research-falcon.md
      supporting_text: ERO1A triggers calcium release from the ER to the cytosol and mitochondria by modulating IP3R and RyR calcium channels
- term:
    id: GO:0070059
    label: intrinsic apoptotic signaling pathway in response to endoplasmic reticulum stress
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: involved_in
  review:
    summary: ERO1A contributes to CHOP-dependent ER-stress apoptosis (via IP3R1); inferred from the mouse ortholog.
    action: KEEP_AS_NON_CORE
    reason: A documented but specialized downstream signaling role; non-core relative to the core oxidase activity.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: Plays an important role in ER stress-induced, CHOP-dependent apoptosis by activating the inositol 1,4,5-trisphosphate receptor IP3R1.
- term:
    id: GO:0071456
    label: cellular response to hypoxia
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: involved_in
  review:
    summary: ERO1A is hypoxia-inducible via the HIF pathway; participation in the cellular hypoxia response is supported. The falcon deep research corroborates that ERO1A is transcriptionally induced by HIF-1alpha under hypoxia (notably in tumor microenvironments).
    action: KEEP_AS_NON_CORE
    reason: ERO1A is a hypoxia-induced gene, so a hypoxia-response process annotation is reasonable, but this is a regulatory/contextual process rather than its core function.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: Stimulated by hypoxia; suggesting that it is regulated via the HIF-pathway.
    - reference_id: file:human/ERO1A/ERO1A-deep-research-falcon.md
      supporting_text: ERO1A expression is strongly induced by hypoxia through hypoxia-inducible factor 1α (HIF-1α)
- term:
    id: GO:0016971
    label: flavin-dependent sulfhydryl oxidase activity
  evidence_type: EXP
  original_reference_id: PMID:11707400
  qualifier: enables
  review:
    summary: Experimentally supported FAD-dependent sulfhydryl oxidase activity - ERO1A oxidizes PDI to drive disulfide bond formation in immunoglobulins.
    action: ACCEPT
    reason: Strong experimental evidence (selective oxidation of PDI); this is the core molecular function of ERO1A.
    supported_by:
    - reference_id: PMID:11707400
      supporting_text: both human Ero1-Lalpha and Ero1-Lbeta (hEROs) facilitate disulfide bond formation in immunoglobulin subunits by selectively oxidizing PDI
- term:
    id: GO:0016971
    label: flavin-dependent sulfhydryl oxidase activity
  evidence_type: EXP
  original_reference_id: PMID:29858230
  qualifier: enables
  review:
    summary: Experimentally supported FAD-dependent sulfhydryl oxidase activity; ERO1A activity is tuned by FAM20C phosphorylation and required for immunoglobulin folding.
    action: ACCEPT
    reason: Core molecular function with direct experimental support; phosphomimetic S145E increases enzyme activity and accelerates immunoglobulin folding.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: Shows two-fold increase in enzyme activity. Accelerates immunoglobulin folding.
- term:
    id: GO:0016972
    label: thiol oxidase activity
  evidence_type: IDA
  original_reference_id: PMID:11707400
  qualifier: enables
  review:
    summary: Direct-assay thiol oxidase activity (parent of the flavin-dependent sulfhydryl oxidase term); ERO1A oxidizes PDI thiols.
    action: ACCEPT
    reason: IDA evidence for oxidase activity; correct, though the flavin-dependent sulfhydryl oxidase term is the most precise descriptor.
    supported_by:
    - reference_id: PMID:11707400
      supporting_text: Disulfide bond formation is controlled by hEROs, which stand at a crucial point of an electron-flow starting from nascent secretory proteins and passing through PDI.
- term:
    id: GO:0016972
    label: thiol oxidase activity
  evidence_type: IDA
  original_reference_id: PMID:29858230
  qualifier: enables
  review:
    summary: Direct-assay thiol oxidase activity confirmed in the FAM20C-phosphorylation study.
    action: ACCEPT
    reason: IDA-supported oxidase activity; consistent core molecular function.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: 'EC=1.8.3.2'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:29858230
  qualifier: enables
  review:
    summary: IntAct interaction with ERP44 (Q9BS26), the partner that retains ERO1A in the ER. Bare protein binding is uninformative but the ERP44 interaction is biologically meaningful (ER retention).
    action: KEEP_AS_NON_CORE
    reason: A real, functionally important interaction (ER retention via ERP44), but the generic protein binding term is uninformative and should not be elevated to a core molecular function.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: Interacts with ERP44; the interaction results in retention of ERO1A in the endoplasmic reticulum
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: IDA
  original_reference_id: PMID:29858230
  qualifier: located_in
  review:
    summary: Direct evidence for a secreted/extracellular pool of ERO1A.
    action: KEEP_AS_NON_CORE
    reason: A genuine secondary localization (secreted), peripheral to the ER site of catalytic action.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: Secreted
- term:
    id: GO:0005783
    label: endoplasmic reticulum
  evidence_type: IDA
  original_reference_id: PMID:29858230
  qualifier: located_in
  review:
    summary: Direct evidence for ER localization, the principal compartment of ERO1A.
    action: ACCEPT
    reason: IDA-supported ER localization, the core compartment for ERO1A's oxidase function.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum membrane'
- term:
    id: GO:0005796
    label: Golgi lumen
  evidence_type: IDA
  original_reference_id: PMID:29858230
  qualifier: located_in
  review:
    summary: Direct evidence for a Golgi-lumen pool where ERO1A is phosphorylated by FAM20C.
    action: KEEP_AS_NON_CORE
    reason: Genuine secondary localization (Golgi) relevant to FAM20C regulation but peripheral to the ER catalytic role.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: Golgi apparatus lumen
- term:
    id: GO:0006457
    label: protein folding
  evidence_type: IMP
  original_reference_id: PMID:29858230
  qualifier: involved_in
  review:
    summary: ERO1A is required for proper folding of immunoglobulins; protein folding is a valid downstream process outcome of its oxidase activity.
    action: KEEP_AS_NON_CORE
    reason: Protein folding is the biological-process consequence of ERO1A-driven oxidative folding, downstream of its core oxidase molecular function.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: Required for the proper folding of immunoglobulins
- term:
    id: GO:0045454
    label: cell redox homeostasis
  evidence_type: IMP
  original_reference_id: PMID:29858230
  qualifier: involved_in
  review:
    summary: ERO1A is a central determinant of ER redox state; its activity is tightly regulated to balance oxidation and limit ROS.
    action: ACCEPT
    reason: ERO1A genuinely sets/balances ER redox homeostasis (regulatory disulfides and FAM20C tuning); a core biological process for this enzyme.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: Enzyme activity is tightly regulated to prevent the accumulation of reactive oxygen species in the endoplasmic reticulum.
- term:
    id: GO:0016020
    label: membrane
  evidence_type: HDA
  original_reference_id: PMID:19946888
  qualifier: located_in
  review:
    summary: High-throughput membrane proteome detection; ERO1A is a peripheral membrane protein, so a generic membrane localization is consistent but uninformative.
    action: KEEP_AS_NON_CORE
    reason: Generic membrane localization from a proteomic survey; correct but far less specific than ER membrane.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: Peripheral membrane protein
- term:
    id: GO:0005788
    label: endoplasmic reticulum lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-3341296
  qualifier: located_in
  review:
    summary: Reactome places ERO1A in the ER lumen; ERO1A acts on the lumenal side of the ER membrane, so this is consistent with its site of action.
    action: ACCEPT
    reason: ERO1A is a lumenal-side ER protein; ER lumen localization is consistent with its function and curated by Reactome.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: Lumenal side
- term:
    id: GO:0034976
    label: response to endoplasmic reticulum stress
  evidence_type: ISS
  original_reference_id: GO_REF:0000024
  qualifier: involved_in
  review:
    summary: ISS-transferred ER-stress-response role from the mouse ortholog; consistent with ERO1A's UPR induction.
    action: KEEP_AS_NON_CORE
    reason: Redundant with the IEA ER-stress annotation; a plausible downstream/contextual process, non-core.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: Plays an important role in ER stress-induced, CHOP-dependent apoptosis
- term:
    id: GO:0051209
    label: release of sequestered calcium ion into cytosol
  evidence_type: ISS
  original_reference_id: GO_REF:0000024
  qualifier: involved_in
  review:
    summary: ISS-transferred Ca2+-release role (via IP3R1) from the mouse ortholog.
    action: KEEP_AS_NON_CORE
    reason: Specialized downstream effect during ER-stress apoptosis inferred by similarity; non-core.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: by activating the inositol 1,4,5-trisphosphate receptor IP3R1
- term:
    id: GO:0070059
    label: intrinsic apoptotic signaling pathway in response to endoplasmic reticulum stress
  evidence_type: ISS
  original_reference_id: GO_REF:0000024
  qualifier: involved_in
  review:
    summary: ISS-transferred ER-stress apoptosis role from the mouse ortholog.
    action: KEEP_AS_NON_CORE
    reason: Documented but specialized downstream signaling role; non-core relative to the oxidase activity.
    supported_by:
    - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
      supporting_text: Plays an important role in ER stress-induced, CHOP-dependent apoptosis by activating the inositol 1,4,5-trisphosphate receptor IP3R1.
- term:
    id: GO:0005783
    label: endoplasmic reticulum
  evidence_type: TAS
  original_reference_id: PMID:10671517
  qualifier: located_in
  review:
    summary: Original characterization showing ERO1-L co-localizes with ER markers.
    action: ACCEPT
    reason: TAS from the founding paper directly establishes ER localization.
    supported_by:
    - reference_id: PMID:10671517
      supporting_text: the product of the human ERO1-L gene co-localizes with ER markers and displays Endo-H-sensitive glycans
- term:
    id: GO:0006457
    label: protein folding
  evidence_type: TAS
  original_reference_id: PMID:10671517
  qualifier: involved_in
  review:
    summary: ERO1-L is involved in oxidative ER protein folding; protein folding is the downstream process of its oxidase activity.
    action: KEEP_AS_NON_CORE
    reason: A valid process annotation but downstream of the core oxidase molecular function.
    supported_by:
    - reference_id: PMID:10671517
      supporting_text: ERO1-L is involved in oxidative ER protein folding in mammalian cells
- term:
    id: GO:0009266
    label: response to temperature stimulus
  evidence_type: TAS
  original_reference_id: PMID:10671517
  qualifier: involved_in
  review:
    summary: This term derives from ERO1-L complementing the temperature/DTT sensitivity of a yeast ero1-1 thermosensitive mutant - a heterologous complementation assay, not evidence that human ERO1A functions in a temperature-stimulus response.
    action: MARK_AS_OVER_ANNOTATED
    reason: The annotation over-interprets a yeast ts-mutant complementation experiment; it does not reflect a genuine temperature-response biological role for human ERO1A.
    supported_by:
    - reference_id: PMID:10671517
      supporting_text: ERO1-L is able to complement several phenotypic traits of the yeast thermosensitive mutant ero1-1, including temperature and dithiothreitol sensitivity
- term:
    id: GO:0016020
    label: membrane
  evidence_type: TAS
  original_reference_id: PMID:10671517
  qualifier: located_in
  review:
    summary: ERO1-L behaves as a membrane-associated protein in isolated microsomes.
    action: KEEP_AS_NON_CORE
    reason: Correct but generic membrane localization; the specific ER membrane term is preferred.
    supported_by:
    - reference_id: PMID:10671517
      supporting_text: ERO1-L behaves as a type II integral membrane protein
- term:
    id: GO:0043231
    label: intracellular membrane-bounded organelle
  evidence_type: TAS
  original_reference_id: PMID:10671517
  qualifier: located_in
  review:
    summary: Very general organelle localization term, subsumed by the specific ER annotations.
    action: KEEP_AS_NON_CORE
    reason: Uninformative high-level localization; correct but superseded by ER/ER membrane terms.
    supported_by:
    - reference_id: PMID:10671517
      supporting_text: co-localizes with ER markers
- term:
    id: GO:0005783
    label: endoplasmic reticulum
  evidence_type: IDA
  original_reference_id: PMID:10671517
  qualifier: located_in
  review:
    summary: Direct evidence (co-localization with ER markers) for ER localization.
    action: ACCEPT
    reason: IDA-supported ER localization from the founding characterization.
    supported_by:
    - reference_id: PMID:10671517
      supporting_text: co-localizes with ER markers
- term:
    id: GO:0006457
    label: protein folding
  evidence_type: IDA
  original_reference_id: PMID:11707400
  qualifier: involved_in
  review:
    summary: ERO1A facilitates disulfide-bond formation in immunoglobulin subunits; protein folding is a downstream process of its oxidase activity.
    action: KEEP_AS_NON_CORE
    reason: Valid downstream process annotation supported by direct evidence, but non-core relative to the oxidase molecular function.
    supported_by:
    - reference_id: PMID:11707400
      supporting_text: hEROs) facilitate disulfide bond formation in immunoglobulin subunits by selectively oxidizing PDI
references:
- id: GO_REF:0000002
  title: Gene Ontology annotation through association of InterPro records with GO terms
  findings: []
- 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 Subcellular Location vocabulary mapping
  findings: []
- id: GO_REF:0000107
  title: Automatic transfer of experimentally verified manual GO annotation data to orthologs using Ensembl Compara
  findings: []
- id: GO_REF:0000116
  title: Gene Ontology annotation based on RHEA mapping of reactions
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: PMID:10671517
  title: ERO1-L, a human protein that favors disulfide bond formation in the endoplasmic reticulum.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: "Cached publications/PMID_10671517.md title matches YAML; original characterization of human ERO1-L (ERO1A) as an ER protein favoring disulfide-bond formation, complementing yeast ero1-1. GOA anchors this PMID to ER localization (GO:0005783) and protein folding (GO:0006457), supporting the core function."
  findings:
  - statement: ERO1-L is an ER-localized, glycosylated membrane-associated protein that complements the yeast ero1-1 mutant and is involved in oxidative ER protein folding; activity requires Cys-394/Cys-397.
    reference_section_type: ABSTRACT
- id: PMID:11707400
  title: Manipulation of oxidative protein folding and PDI redox state in mammalian cells.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: "Cached publications/PMID_11707400.md title matches YAML; demonstrates ERO1A selectively oxidizes PDI to drive disulfide-bond formation. GOA anchors this PMID to GO:0016971/GO:0016972 (flavin-dependent sulfhydryl oxidase / oxidizing PDI, EXP/IDA), the core molecular function."
  findings:
  - statement: Human Ero1-Lalpha and Ero1-Lbeta facilitate disulfide bond formation in immunoglobulin subunits by selectively oxidizing PDI, standing at a crucial point of an electron flow from nascent secretory proteins through PDI; ERp57 redox state is not affected.
    reference_section_type: ABSTRACT
- id: PMID:17170699
  title: ERp57 is essential for efficient folding of glycoproteins sharing common structural domains.
  findings: []
- id: PMID:19946888
  title: Defining the membrane proteome of NK cells.
  findings: []
- id: PMID:20802462
  title: Disulphide production by Ero1α-PDI relay is rapid and effectively regulated.
  findings: []
- id: PMID:25416956
  title: A proteome-scale map of the human interactome network.
  findings: []
- id: PMID:29858230
  title: Secretory kinase Fam20C tunes endoplasmic reticulum redox state via phosphorylation of Ero1α.
  findings:
  - statement: FAM20C phosphorylates ERO1A at Ser145 in the Golgi, increasing its enzymatic activity; phosphomimetic S145E doubles activity and accelerates immunoglobulin folding; ERO1A is required for proper immunoglobulin folding and is retained in the ER via ERP44.
    reference_section_type: RESULTS
- id: PMID:32296183
  title: A reference map of the human binary protein interactome.
  findings: []
- id: Reactome:R-HSA-3341296
  title: Reactome ER-lumen oxidative folding annotation for ERO1A
  findings: []
- id: file:human/ERO1A/ERO1A-uniprot.txt
  title: UniProt entry Q96HE7 (ERO1A_HUMAN), ERO1-like protein alpha
  findings:
  - statement: FAD-dependent ER sulfhydryl oxidase (EC 1.8.3.2) that reoxidizes P4HB/PDI to drive disulfide-bond formation and passes electrons to O2 generating H2O2; peripheral ER membrane protein on the lumenal side retained by ERP44; activity tightly regulated by regulatory disulfides and FAM20C phosphorylation; hypoxia-induced.
    reference_section_type: OTHER
- id: file:human/ERO1A/ERO1A-deep-research-falcon.md
  title: Falcon deep research report for ERO1A
  reference_review:
    relevance: HIGH
    correctness: UNVERIFIED
    review_notes: "LLM-synthesized (Edison Scientific Literature) review-of-reviews; cites secondary review articles (Chen 2024 JECCR, Jha 2021 ARS, Zito 2024 BBA, Moilanen 2018 LSA, He 2025) by author-year/DOI keys rather than PMIDs, so individual cited claims were not verified against cached publications. The core mechanistic picture (FAD-dependent reoxidation of PDI with O2 as terminal acceptor and H2O2 as byproduct; HIF-1alpha/UPR induction; PDI substrate selectivity; IP3R/RyR Ca2+ regulation) is consistent with UniProt and the cached primary literature and is used here only to corroborate, not to override, existing experimental annotations. Some claims (e.g. MAM enrichment, '~25% of cellular H2O2', specific Kd values, cancer/therapeutic content) are not independently checked and are not used to add or remove annotations."
  findings:
  - statement: ERO1A re-oxidizes reduced PDI by accepting electrons through its FAD cofactor, with molecular oxygen as the terminal electron acceptor, producing H2O2; it binds PDI with highest affinity (Kd 1.7 uM) relative to other ER thiol isomerases, and is induced by HIF-1alpha under hypoxia and by the PERK-eIF2alpha-ATF4-CHOP UPR branch.
    reference_section_type: RESULTS
core_functions:
- description: FAD-dependent endoplasmic-reticulum sulfhydryl oxidase that reoxidizes the protein disulfide isomerase P4HB/PDI, regenerating PDI's active site so it can catalyze further disulfide-bond formation in secretory proteins, with electrons passed via FAD to O2 producing H2O2.
  molecular_function:
    id: GO:0016971
    label: flavin-dependent sulfhydryl oxidase activity
  locations:
  - id: GO:0005789
    label: endoplasmic reticulum membrane
  - id: GO:0005788
    label: endoplasmic reticulum lumen
  supported_by:
  - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
    supporting_text: Efficiently reoxidizes P4HB/PDI, the enzyme catalyzing protein disulfide formation, in order to allow P4HB to sustain additional rounds of disulfide formation.
  - reference_id: PMID:11707400
    supporting_text: both human Ero1-Lalpha and Ero1-Lbeta (hEROs) facilitate disulfide bond formation in immunoglobulin subunits by selectively oxidizing PDI
- description: Sets and balances the redox state of the ER lumen, with activity tightly regulated by intramolecular regulatory disulfides (and FAM20C phosphorylation) to sustain oxidative protein folding while limiting reactive-oxygen-species accumulation.
  molecular_function:
    id: GO:0016971
    label: flavin-dependent sulfhydryl oxidase activity
  locations:
  - id: GO:0005788
    label: endoplasmic reticulum lumen
  supported_by:
  - reference_id: file:human/ERO1A/ERO1A-uniprot.txt
    supporting_text: Enzyme activity is tightly regulated to prevent the accumulation of reactive oxygen species in the endoplasmic reticulum.
  directly_involved_in:
  - id: GO:0045454
    label: cell redox homeostasis
proposed_new_terms: []
suggested_questions:
- question: How is ERO1A activity coordinated with ERO1B and with PRDX4/peroxiredoxin-based H2O2 clearance to balance oxidative folding capacity against oxidative damage in different secretory tissues?
- question: What is the in vivo significance of the secreted/Golgi pools of ERO1A relative to its ER-lumenal oxidase role, and is FAM20C phosphorylation the main switch controlling them?
suggested_experiments:
- description: Reconstitute the ERO1A-PDI oxidation cycle in vitro with purified FAD-loaded ERO1A and P4HB, measuring O2 consumption and H2O2 production to quantify catalytic turnover and the effect of the regulatory disulfides and S145 phosphorylation.
- description: CRISPR knockout of ERO1A (and double knockout with ERO1B) in antibody-secreting cells followed by redox proteomics and immunoglobulin folding/secretion assays to define non-redundant substrate requirements.

ERO1A

Gene Description

Existing Annotations Review

Core Functions

FAD-dependent endoplasmic-reticulum sulfhydryl oxidase that reoxidizes the protein disulfide isomerase P4HB/PDI, regenerating PDI's active site so it can catalyze further disulfide-bond formation in secretory proteins, with electrons passed via FAD to O2 producing H2O2.

Sets and balances the redox state of the ER lumen, with activity tightly regulated by intramolecular regulatory disulfides (and FAM20C phosphorylation) to sustain oxidative protein folding while limiting reactive-oxygen-species accumulation.

References

Suggested Questions for Experts

Suggested Experiments

Deep Research

Falcon

Comprehensive Research Report: ERO1A (ERO1-like protein alpha)

Gene and Protein Identity

Primary Molecular Function and Enzymatic Activity

Catalyzed Reaction and Mechanism

Substrate Specificity

Reaction Products and ROS Generation

Subcellular Localization and Functional Compartmentalization

Biochemical and Signaling Pathways

Integration with the Unfolded Protein Response (UPR)

Hypoxia Response Pathway

Calcium Signaling Pathways

Redox Regulation and Feedback Mechanisms

Biological Processes and Physiological Roles

Recent Developments and Current Research (2023-2025)

Cancer Biology

Therapeutic Development

Mechanistic Insights

Cardiovascular and Metabolic Diseases

Expert Analysis and Current Understanding

Summary

Artifacts

Citations

📚 Additional Documentation

Notes

ERO1A (ERO1L, ERO1-Lalpha) research notes

Core molecular function

Localization

Biological roles

Interactions (IPI annotations)

Action plan

Pn Notes

ERO1A 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 | Protein disulfide isomerase reoxidation

Projected GO annotations (2)

Note

📄 View Raw YAML