NCOA4 (Nuclear Receptor Coactivator 4) is primarily the selective cargo receptor for ferritinophagy, the autophagic degradation of ferritin to release stored iron. NCOA4 directly binds ferritin heavy chain (FTH1) via a C-terminal 16-aa motif (residues 484-499) and delivers the ferritin complex to autophagosomes/lysosomes for degradation. This function is central to intracellular iron homeostasis and erythropoiesis. By mobilizing stored iron, NCOA4-mediated ferritinophagy also positively regulates ferroptosis susceptibility by increasing the labile iron pool. The legacy function as a transcription coactivator for androgen receptor (AR) and other nuclear receptors is domain-separable (N-terminal region) and now considered secondary to its ferritinophagy role.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0009725 response to hormone | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: IBA annotation based on phylogenetic inference from PANTHER. NCOA4 was originally characterized as ARA70, a coactivator for the androgen receptor (PMID:8643607). However, the ferritinophagy function is now understood to be the primary role of NCOA4 (PMID:25327288). The hormone response function is secondary and relates to the legacy transcription coactivator activity. Reason: While NCOA4/ARA70 was originally identified as an androgen receptor coactivator that responds to hormones, this represents the historical/legacy function. The primary function of NCOA4 is now understood to be ferritinophagy cargo reception. The hormone response annotation is technically valid but represents a secondary, non-core function. Supporting Evidence: PMID:8643607 Using a yeast two-hybrid system, we were able to isolate a ligand-dependent AR-associated protein (ARA70), which functions as an activator to enhance AR transcriptional activity 10-fold in the presence of 10(-10) M dihydrotestosterone or 10(-9) M testosterone |
| GO:0003713 transcription coactivator activity | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: IEA annotation based on InterPro mapping. NCOA4 was originally characterized as ARA70, an androgen receptor coactivator (PMID:8643607). The N-terminal region mediates nuclear receptor interactions. This function is domain-separable from the ferritinophagy function. Reason: The transcription coactivator activity is a legitimate but secondary function of NCOA4. Modern literature (2023-2024 reviews) emphasizes ferritinophagy as the primary function, with coactivator function being domain-separable (N-terminal vs C-terminal). Supporting Evidence: PMID:8643607 Using a yeast two-hybrid system, we were able to isolate a ligand-dependent AR-associated protein (ARA70), which functions as an activator to enhance AR transcriptional activity file:human/NCOA4/NCOA4-deep-research-falcon.md N-terminal coiled-coil / nuclear-receptor-binding region (~1-237); C-terminal ferritin-binding domain (~238-614) |
| GO:0005634 nucleus | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: IEA annotation from UniProt subcellular location mapping. NCOA4 localizes to the nucleus in its coactivator role (PMID:8643607, PMID:24910095). However, the primary localization for its core ferritinophagy function is cytoplasm/autophagosome/autolysosome. Reason: Nuclear localization is valid but associated with the secondary transcription coactivator function. The primary functional localization of NCOA4 is in the cytoplasm, autophagosomes, and autolysosomes where ferritinophagy occurs. Supporting Evidence: file:human/NCOA4/NCOA4-deep-research-falcon.md NCOA4 also localizes to the nucleus when acting as a nuclear receptor coactivator |
| GO:0005694 chromosome | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: IEA annotation from UniProt subcellular location mapping. NCOA4 binds to DNA replication origins and may inhibit activation of DNA replication origins (PMID:24910095). This is a tertiary function distinct from both ferritinophagy and coactivator roles. Reason: Chromosome localization is associated with the DNA replication origin binding function described in PMID:24910095. This is a minor function compared to the primary ferritinophagy role. The UniProt record confirms this localization. |
| GO:0005776 autophagosome | IEA GO_REF:0000044 | ACCEPT | Summary: IEA annotation from UniProt subcellular location. NCOA4 localizes to autophagosomes during ferritinophagy, bridging ferritin to the autophagosomal membrane via interaction with LC3/GABARAP proteins (PMID:25327288). Reason: This is a CORE localization for NCOA4's primary function as a ferritinophagy cargo receptor. NCOA4 traffics with autophagosomes during ferritinophagy to deliver ferritin for degradation. Supporting Evidence: PMID:25327288 NCOA4 directly binds ferritin heavy chain-1 (FTH1) to target the iron-binding ferritin complex with a relative molecular mass of 450,000 to autolysosomes |
| GO:0006351 DNA-templated transcription | IEA GO_REF:0000043 | KEEP AS NON CORE | Summary: IEA annotation inferred from UniProt keyword mapping (transcription). This is derived from NCOA4's coactivator function for nuclear receptors. Reason: Involvement in transcription is valid but secondary. This annotation reflects the legacy coactivator function, not the primary ferritinophagy role. The annotation is appropriately broad for the coactivator function. |
| GO:0006879 intracellular iron ion homeostasis | IEA GO_REF:0000002 | ACCEPT | Summary: IEA annotation from InterPro mapping. NCOA4-mediated ferritinophagy is central to intracellular iron homeostasis by degrading ferritin to release stored iron (PMID:25327288). Mouse knockout studies show NCOA4 is required for iron mobilization. Reason: This is a CORE biological process for NCOA4. By serving as the ferritinophagy cargo receptor, NCOA4 directly regulates intracellular iron availability. Ncoa4-/- mice show profound iron accumulation in splenic macrophages. Supporting Evidence: PMID:25327288 Ncoa4(-/-) mice exhibit a profound accumulation of iron in splenic macrophages, which are critical for the reutilization of iron from engulfed red blood cells file:human/NCOA4/NCOA4-deep-research-falcon.md By directing ferritin degradation, NCOA4 mobilizes stored iron for processes including heme synthesis and mitochondrial metabolism |
| GO:0031410 cytoplasmic vesicle | IEA GO_REF:0000043 | ACCEPT | Summary: IEA annotation from UniProt keyword mapping. NCOA4 localizes to cytoplasmic vesicles, specifically autophagosomes and autolysosomes during ferritinophagy. Reason: This is a valid but general localization. NCOA4 is found in cytoplasmic vesicles as part of its ferritinophagy function. More specific terms (autophagosome, autolysosome) are also annotated. |
| GO:0044754 autolysosome | IEA GO_REF:0000044 | ACCEPT | Summary: IEA annotation from UniProt subcellular location. NCOA4 delivers ferritin to autolysosomes for degradation during ferritinophagy (PMID:25327288). Reason: This is a CORE localization for NCOA4's primary function. NCOA4 co-localizes with autolysosomes during ferritinophagy where ferritin is degraded to release iron. Supporting Evidence: PMID:25327288 NCOA4 directly binds ferritin heavy chain-1 (FTH1) to target the iron-binding ferritin complex with a relative molecular mass of 450,000 to autolysosomes |
| GO:0045893 positive regulation of DNA-templated transcription | IEA GO_REF:0000108 | KEEP AS NON CORE | Summary: IEA annotation inferred from transcription coactivator activity annotation. As a coactivator for nuclear receptors, NCOA4 positively regulates transcription. Reason: This is a valid inference from the coactivator function but represents a secondary function. The primary role of NCOA4 is ferritinophagy, not transcriptional regulation. |
| GO:0005515 protein binding | IPI PMID:25327288 Selective VPS34 inhibitor blocks autophagy and uncovers a ro... | MODIFY | Summary: IPI annotation showing NCOA4 binds to ferritin (FTH1, FTL). This is the seminal paper identifying NCOA4 as the ferritinophagy cargo receptor. Reason: "Protein binding" is too vague and uninformative per GO guidelines. The actual function is more specific: NCOA4 functions as an autophagy cargo adaptor that binds ferritin and delivers it to autophagosomes. GO:0160247 "autophagy cargo adaptor activity" is the appropriate molecular function term. Proposed replacements: autophagy cargo adaptor activity Supporting Evidence: PMID:25327288 NCOA4 directly binds ferritin heavy chain-1 (FTH1) to target the iron-binding ferritin complex with a relative molecular mass of 450,000 to autolysosomes following starvation or iron depletion |
| GO:0005515 protein binding | IPI PMID:28514442 Architecture of the human interactome defines protein commun... | MODIFY | Summary: IPI annotation from high-throughput interactome study showing NCOA4-ferritin interaction. Reason: "Protein binding" is uninformative. The binding shown in interactome studies reflects NCOA4's role as an autophagy cargo adaptor for ferritin. Proposed replacements: autophagy cargo adaptor activity Supporting Evidence: PMID:28514442 Here we present BioPlex 2.0 (Biophysical Interactions of ORFeome-derived complexes), which uses robust affinity purification-mass spectrometry methodology to elucidate protein interaction networks |
| GO:0005515 protein binding | IPI PMID:33961781 Dual proteome-scale networks reveal cell-specific remodeling... | MODIFY | Summary: IPI annotation from interactome remodeling study showing NCOA4-ferritin interaction. Reason: "Protein binding" is uninformative. Should be replaced with autophagy cargo adaptor activity to reflect the functional significance of the interaction. Proposed replacements: autophagy cargo adaptor activity Supporting Evidence: PMID:33961781 created two proteome-scale, cell-line-specific interaction networks. The first, BioPlex 3.0, results from affinity purification of 10,128 human proteins |
| GO:0005515 protein binding | IPI PMID:40205054 Multimodal cell maps as a foundation for structural and func... | MODIFY | Summary: IPI annotation from multimodal cell maps study showing NCOA4-ferritin interaction. Reason: "Protein binding" is uninformative. The NCOA4-ferritin interaction reflects autophagy cargo adaptor activity for ferritinophagy. Proposed replacements: autophagy cargo adaptor activity Supporting Evidence: PMID:40205054 construct a global map of human subcellular architecture through joint measurement of biophysical interactions and immunofluorescence images for over 5,100 proteins |
| GO:0030520 estrogen receptor signaling pathway | NAS PMID:10428808 Isolation and characterization of ARA160 as the first androg... | UNDECIDED | Summary: NAS annotation citing PMID:10428808. However, this paper is about ARA160 (TMF), not NCOA4/ARA70. The paper mentions ARA70 can function cooperatively with ARA160 but does not directly demonstrate NCOA4 involvement in estrogen receptor signaling. Reason: PMID:10428808 is primarily about ARA160 (TMF), not NCOA4/ARA70. The paper states "this AR N-terminal coactivator can function cooperatively with AR C-terminal coactivator, ARA70" but does not directly implicate NCOA4 in estrogen receptor signaling. The evidence basis for this annotation is unclear. Supporting Evidence: PMID:10428808 Our data further suggest that this AR N-terminal coactivator can function cooperatively with AR C-terminal coactivator, ARA70, in PC-3 cells |
| GO:0071391 cellular response to estrogen stimulus | NAS PMID:10428808 Isolation and characterization of ARA160 as the first androg... | UNDECIDED | Summary: NAS annotation citing PMID:10428808. This paper is about ARA160 (TMF), not NCOA4/ARA70. The evidence for NCOA4's role in estrogen response is indirect. Reason: PMID:10428808 does not directly demonstrate NCOA4 involvement in cellular response to estrogen. The paper focuses on ARA160/TMF. Evidence for this annotation requires verification from other sources. Supporting Evidence: PMID:10428808 Isolation and characterization of ARA160 as the first androgen receptor N-terminal-associated coactivator in human prostate cells. |
| GO:0071394 cellular response to testosterone stimulus | NAS PMID:10428808 Isolation and characterization of ARA160 as the first androg... | KEEP AS NON CORE | Summary: NAS annotation citing PMID:10428808. While NCOA4/ARA70 is known to coactivate the androgen receptor (PMID:8643607), the cited paper (PMID:10428808) is primarily about ARA160 not NCOA4. Reason: NCOA4/ARA70 is a documented androgen receptor coactivator (PMID:8643607) and cellular response to testosterone is consistent with this function. However, this is a secondary function; ferritinophagy is the primary role. Supporting Evidence: PMID:8643607 Using a yeast two-hybrid system, we were able to isolate a ligand-dependent AR-associated protein (ARA70), which functions as an activator to enhance AR transcriptional activity 10-fold in the presence of 10(-10) M dihydrotestosterone or 10(-9) M testosterone PMID:10428808 Isolation and characterization of ARA160 as the first androgen receptor N-terminal-associated coactivator in human prostate cells. |
| GO:0005654 nucleoplasm | TAS Reactome:R-HSA-9843120 | KEEP AS NON CORE | Summary: TAS annotation from Reactome pathway "Coactivators are recruited to liganded PPARG:RXRA heterodimer". NCOA4 can coactivate PPAR-gamma (PMID:10347167). Reason: Nucleoplasm localization is associated with the secondary transcription coactivator function. Valid but not the primary functional localization. |
| GO:0006622 protein targeting to lysosome | IDA PMID:25327288 Selective VPS34 inhibitor blocks autophagy and uncovers a ro... | ACCEPT | Summary: IDA annotation from the seminal ferritinophagy paper. NCOA4 targets ferritin to lysosomes (via autolysosomes) for degradation. Reason: This is a CORE biological process for NCOA4. The protein targeting function is the mechanistic essence of ferritinophagy - NCOA4 delivers ferritin to lysosomes for degradation to release iron. Supporting Evidence: PMID:25327288 NCOA4 directly binds ferritin heavy chain-1 (FTH1) to target the iron-binding ferritin complex with a relative molecular mass of 450,000 to autolysosomes |
| GO:0044754 autolysosome | IDA PMID:25327288 Selective VPS34 inhibitor blocks autophagy and uncovers a ro... | ACCEPT | Summary: IDA annotation showing NCOA4 localizes to autolysosomes. This is experimentally demonstrated in the seminal ferritinophagy paper. Reason: This is a CORE localization for NCOA4's primary function. Experimentally validated in PMID:25327288. Supporting Evidence: PMID:25327288 NCOA4, which accumulates in ATG7-deficient cells and co-localizes with autolysosomes |
| GO:0003713 transcription coactivator activity | TAS PMID:8643607 Cloning and characterization of a specific coactivator, ARA7... | KEEP AS NON CORE | Summary: TAS annotation from the original ARA70 characterization paper. NCOA4/ARA70 enhances androgen receptor transcriptional activity. Reason: This is the original function described for NCOA4/ARA70 in 1996. While valid, it is now understood to be a secondary function. The primary function (ferritinophagy) was discovered in 2014 (PMID:25327288). Supporting Evidence: PMID:8643607 Using a yeast two-hybrid system, we were able to isolate a ligand-dependent AR-associated protein (ARA70), which functions as an activator to enhance AR transcriptional activity 10-fold in the presence of 10(-10) M dihydrotestosterone |
| GO:0005634 nucleus | TAS PMID:8643607 Cloning and characterization of a specific coactivator, ARA7... | KEEP AS NON CORE | Summary: TAS annotation for nuclear localization from the original ARA70 paper. NCOA4 localizes to the nucleus in its coactivator role. Reason: Nuclear localization is associated with the secondary transcription coactivator function. The primary functional localization is cytoplasm/autophagosome/autolysosome. Supporting Evidence: PMID:8643607 Cloning and characterization of a specific coactivator, ARA70, for the androgen receptor in human prostate cells. |
| GO:0008584 male gonad development | TAS PMID:8643607 Cloning and characterization of a specific coactivator, ARA7... | KEEP AS NON CORE | Summary: TAS annotation from the original ARA70 paper. NCOA4/ARA70 coactivates androgen receptor, which plays a role in male sexual differentiation. Reason: This is an indirect inference from NCOA4's coactivation of the androgen receptor. The paper states AR "plays an important role in male sexual differentiation and prostate cell proliferation" but does not directly demonstrate NCOA4's role in gonad development. This is a secondary, pleiotropic function. Supporting Evidence: PMID:8643607 The androgen receptor (AR) is a member of the steroid receptor superfamily that plays an important role in male sexual differentiation and prostate cell proliferation |
| GO:0160247 autophagy cargo adaptor activity | IDA PMID:25327288 Selective VPS34 inhibitor blocks autophagy and uncovers a ro... | NEW | Summary: NEW annotation for NCOA4's primary molecular function. NCOA4 is the selective autophagy cargo adaptor that binds ferritin and delivers it to autophagosomes for degradation (ferritinophagy). The 2024 cryo-EM structure (doi:10.1038/s41467-024-48151-1) resolved the 16-aa NCOA4 motif (484-499) that binds FTH1. Reason: This is the PRIMARY molecular function of NCOA4 that is currently missing from the annotation set. NCOA4 is the prototypical autophagy cargo adaptor for ferritinophagy. The term GO:0160247 "autophagy cargo adaptor activity" precisely describes this function. Supporting Evidence: PMID:25327288 NCOA4 directly binds ferritin heavy chain-1 (FTH1) to target the iron-binding ferritin complex with a relative molecular mass of 450,000 to autolysosomes following starvation or iron depletion file:human/NCOA4/NCOA4-deep-research-falcon.md Cryo-EM resolved a C-terminal NCOA4 fragment binding FTH1: 16-aa motif positions 484-499 (DSFQVIKNSPLSEWLI) |
| GO:0160020 positive regulation of ferroptosis | IMP PMID:25327288 Selective VPS34 inhibitor blocks autophagy and uncovers a ro... | NEW | Summary: NEW annotation based on current literature. NCOA4-mediated ferritinophagy releases labile iron from ferritin stores, which increases susceptibility to ferroptosis by promoting lipid peroxidation via Fenton chemistry. Reason: NCOA4 is a positive regulator of ferroptosis through its ferritinophagy function. By degrading ferritin and releasing labile iron, NCOA4 sensitizes cells to ferroptotic cell death. This is well-documented in 2023-2024 reviews. Supporting Evidence: file:human/NCOA4/NCOA4-deep-research-falcon.md Excessive ferritinophagy increases labile Fe2+ and lipid peroxidation, sensitizing cells to ferroptosis PMID:25327288 Selective VPS34 inhibitor blocks autophagy and uncovers a role for NCOA4 in ferritin degradation and iron homeostasis in vivo. |
Loading supporting content…
Download this section (compressed HTML)Q: Is there a ferritinophagy-specific GO term that should be created?
Q: Should there be a term for "ferritin binding" as a specific molecular function?
Q: How should the dual-function nature of NCOA4 be represented in GO annotations?
Experiment: Structure-function studies to confirm domain separation between ferritinophagy and coactivator functions
Experiment: In vivo studies to assess relative contributions of each function to physiological phenotypes
Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)