Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0034599 cellular response to oxidative stress	IBA GO_REF:0000033	ACCEPT	Summary: GPX4 is a key antioxidant enzyme that protects cells from oxidative damage by reducing lipid hydroperoxides. The deep research confirms GPX4 plays a key role in protecting cells from oxidative damage by preventing membrane lipid peroxidation (GPX4-deep-research-falcon.md). This annotation is appropriate as a broader process encompassing GPX4's core protective function. Reason: GPX4's primary role is to detoxify lipid hydroperoxides, which is a central response to oxidative stress. The IBA annotation is well-supported by phylogenetic evidence and consistent with GPX4's function across orthologs. Supporting Evidence: PMID:11115402 the increase in hydroperoxide tone (a situation found under oxidative stress or selenium deficiency or on incubation with 12-HPETE) partly diverts the 12-lipoxygenase pathway from the reduction route to the isomerization route
GO:0019372 lipoxygenase pathway	IBA GO_REF:0000033	ACCEPT	Summary: GPX4 reduces hydroperoxy products of the 12-lipoxygenase pathway, thereby regulating the flux through this pathway. PMID:11115402 demonstrated that both GPx-1 and PHGPx are involved in the regulatory network of the 12-lipoxygenase pathway. Reason: GPX4's role in the lipoxygenase pathway is experimentally documented. The enzyme reduces 12-HpETE to 12-HETE, modulating the balance between reduction and isomerization routes. This represents a core function of GPX4 in arachidonic acid metabolism. Supporting Evidence: PMID:11115402 We therefore believe that both GPx-1 and PHGPx are involved in the regulatory network of the 12-lipoxygenase pathway in platelets and other mammalian cells
GO:0005739 mitochondrion	IBA GO_REF:0000033	ACCEPT	Summary: The mitochondrial isoform (mGPX4) localizes to mitochondria via an N-terminal targeting sequence. The deep research indicates mGPX4 targets mitochondria and preserves mitochondrial membrane integrity (GPX4-deep-research-falcon.md). Reason: Mitochondrial localization is well-established for the mGPX4 isoform. This annotation appropriately captures one of the three documented subcellular localizations of GPX4 isoforms. Supporting Evidence: file:human/GPX4/GPX4-deep-research-falcon.md mGPX4 targets mitochondria and preserves mitochondrial membrane integrity
GO:0004602 glutathione peroxidase activity	IBA GO_REF:0000033	ACCEPT	Summary: GPX4 is a member of the glutathione peroxidase family and exhibits glutathione peroxidase activity. PMID:36608588 directly demonstrated GPX4 reduces H2O2 and other soluble hydroperoxides using glutathione, though with lower efficiency than GPX1 for simple substrates. Reason: While GPX4's more specific function is phospholipid-hydroperoxide glutathione peroxidase activity (GO:0047066), general glutathione peroxidase activity is also correct. Both annotations should be retained. GPX4 can reduce H2O2, cumene hydroperoxide, and tert-butyl hydroperoxide. Supporting Evidence: PMID:36608588 small soluble hydroperoxides such as H2O2, cumene hydroperoxide, and tert-butyl hydroperoxide were reduced by all three isoforms PMID:17630701 Multiple mutations of the catalytic triad indicated its functional importance
GO:0005634 nucleus	IBA GO_REF:0000033	ACCEPT	Summary: The nuclear isoform (nGPX4) localizes to the nucleus, particularly during spermatogenesis where it contributes to chromatin stability. Deep research confirms nGPX4 localizes to nuclei during spermatogenesis. Reason: Nuclear localization is documented for nGPX4, which has a specialized role in sperm development. Proteomic characterization of human sperm nucleus (PMID:21630459) supports this localization. Supporting Evidence: PMID:21630459 Generating a catalogue of sperm nuclear proteins is an important first step towards the clarification of the function of the paternal chromatin transmitted to the oocyte upon fertilization
GO:0047066 phospholipid-hydroperoxide glutathione peroxidase activity	IBA GO_REF:0000033	ACCEPT	Summary: This is the core molecular function of GPX4. The enzyme uniquely reduces phospholipid hydroperoxides directly within membranes. PMID:36608588 confirmed GPX4 was clearly the only isoform able to reduce phosphatidylcholine hydroperoxide. Reason: This is GPX4's defining enzymatic activity and represents the most specific MF annotation. This is strongly supported by multiple experimental studies and represents the primary molecular function of the protein. Supporting Evidence: PMID:36608588 GPX4 was clearly the only isoform able to reduce phosphatidylcholine hydroperoxide PMID:11115402 Here we show for the first time the presence of phospholipid hydroperoxide glutathione peroxidase (PHGPx) protein and its activity in platelets
GO:0004601 peroxidase activity	IEA GO_REF:0000120	ACCEPT	Summary: GPX4 possesses peroxidase activity, reducing various hydroperoxides. This is a parent term of the more specific glutathione peroxidase activity. Reason: This is a valid broader annotation. GPX4 is indeed a peroxidase, and this IEA annotation based on InterPro domain (IPR000889) is appropriate. More specific terms are also annotated. Supporting Evidence: PMID:36608588 The GPXs are important for reducing hydroperoxides in a glutathione-consuming manner and thus regulate cellular redox homeostasis
GO:0004602 glutathione peroxidase activity	IEA GO_REF:0000120	ACCEPT	Summary: Duplicate of IBA annotation for glutathione peroxidase activity. This IEA annotation is based on orthology to mouse GPX4. Reason: Valid annotation derived from orthology evidence. The underlying activity is well-supported experimentally. Supporting Evidence: PMID:36608588 small soluble hydroperoxides such as H2O2, cumene hydroperoxide, and tert-butyl hydroperoxide were reduced by all three isoforms
GO:0005737 cytoplasm	IEA GO_REF:0000044	ACCEPT	Summary: The cytoplasmic isoform (cGPX4) localizes to the cytoplasm. UniProt subcellular location vocabulary supports this. Reason: Valid annotation. The cytoplasmic isoform is well-documented and is the most broadly expressed isoform responsible for ferroptosis suppression. GO:0005829 (cytosol) is more specific and also annotated. Supporting Evidence: PMID:11115402 Here we show for the first time the presence of phospholipid hydroperoxide glutathione peroxidase (PHGPx) protein and its activity in platelets
GO:0005739 mitochondrion	IEA GO_REF:0000120	ACCEPT	Summary: Duplicate annotation for mitochondrial localization based on orthology to mouse GPX4. Reason: Valid annotation. Mitochondrial localization of the mGPX4 isoform is well-established. Supporting Evidence: file:human/GPX4/GPX4-deep-research-falcon.md mGPX4 targets mitochondria and preserves mitochondrial membrane integrity
GO:0006629 lipid metabolic process	IEA GO_REF:0000043	KEEP AS NON CORE	Summary: GPX4 participates in lipid metabolism by reducing lipid hydroperoxides, thereby modifying oxidized lipids. Reason: While GPX4 does act on lipid substrates (phospholipid hydroperoxides), the annotation to "lipid metabolic process" is somewhat broad. The more informative annotations are the specific MF term (GO:0047066) and the lipoxygenase pathway (GO:0019372). This is a valid but peripheral annotation. Supporting Evidence: PMID:36608588 GPX4 reduces complex lipid hydroperoxides, thus protecting cells from lipid peroxidation and ferroptosis
GO:0006979 response to oxidative stress	IEA GO_REF:0000120	ACCEPT	Summary: GPX4 is a key component of cellular response to oxidative stress through its antioxidant activity. Reason: Valid annotation. This is a parent term of GO:0034599 (cellular response to oxidative stress), which is also annotated with IBA evidence. Both are appropriate. Supporting Evidence: PMID:11115402 the increase in hydroperoxide tone (a situation found under oxidative stress or selenium deficiency or on incubation with 12-HPETE) partly diverts the 12-lipoxygenase pathway from the reduction route to the isomerization route
GO:0016491 oxidoreductase activity	IEA GO_REF:0000043	ACCEPT	Summary: GPX4 is an oxidoreductase that reduces hydroperoxides while oxidizing glutathione. Reason: This is a valid high-level MF annotation. GPX4 catalyzes a redox reaction (EC:1.11.1.12). More specific child terms are also annotated. Supporting Evidence: PMID:36608588 The GPXs are important for reducing hydroperoxides in a glutathione-consuming manner
GO:0047066 phospholipid-hydroperoxide glutathione peroxidase activity	IEA GO_REF:0000120	ACCEPT	Summary: Duplicate of the IBA annotation for the core molecular function. Reason: This is the core MF of GPX4. Multiple evidence types supporting this annotation are appropriate. Supporting Evidence: PMID:36608588 GPX4 was clearly the only isoform able to reduce phosphatidylcholine hydroperoxide
GO:0098869 cellular oxidant detoxification	IEA GO_REF:0000120	ACCEPT	Summary: GPX4 detoxifies lipid hydroperoxides, which are oxidant species that can propagate membrane damage. Reason: This is an accurate biological process annotation for GPX4's function in reducing lipid peroxides, thereby detoxifying these oxidants. This is inferred from the MF annotations (GO:0004601, GO:0004602, GO:0047066). Supporting Evidence: PMID:36608588 GPX4 reduces complex lipid hydroperoxides, thus protecting cells from lipid peroxidation and ferroptosis
GO:0005634 nucleus	IEA GO_REF:0000107	ACCEPT	Summary: Duplicate annotation for nuclear localization via Ensembl Compara orthology. Reason: Valid annotation. Nuclear localization of nGPX4 is well-established, particularly in spermatogenesis. Supporting Evidence: PMID:21630459 Generating a catalogue of sperm nuclear proteins is an important first step towards the clarification of the function of the paternal chromatin
GO:0005635 nuclear envelope	IEA GO_REF:0000107	UNDECIDED	Summary: Nuclear envelope localization inferred from mouse ortholog. This is more specific than the nucleus annotation. Reason: While nuclear localization of nGPX4 is well-established, specific localization to the nuclear envelope requires verification. I cannot access the primary evidence supporting this specific localization. The annotation may be valid but needs experimental confirmation for human GPX4.
GO:0005829 cytosol	IEA GO_REF:0000107	ACCEPT	Summary: Cytosolic localization inferred from mouse ortholog via Ensembl Compara. Reason: Cytosolic localization of cGPX4 is well-established experimentally (see PMID:11115402 IDA annotation). This IEA annotation is consistent with experimental evidence. Supporting Evidence: PMID:11115402 Here we show for the first time the presence of phospholipid hydroperoxide glutathione peroxidase (PHGPx) protein and its activity in platelets
GO:0008430 selenium binding	IEA GO_REF:0000107	MODIFY	Summary: GPX4 contains selenocysteine (Sec46) at its active site, which incorporates selenium covalently. Reason: While GPX4 does contain selenium as selenocysteine, "selenium binding" may not be the most accurate term. Selenocysteine is a genetically encoded amino acid, not a bound cofactor. The term could be misleading. However, if the term is defined to include selenoproteins, it may be acceptable. Consider whether a more specific annotation exists for selenoprotein status. Proposed replacements: oxidoreductase activity
GO:0032355 response to estradiol	IEA GO_REF:0000107	KEEP AS NON CORE	Summary: This annotation is inferred from rat ortholog (P36970) via Ensembl Compara. Reason: GPX4 expression may be regulated by estradiol, but this represents a regulatory/upstream response rather than a core function of GPX4. This is a peripheral annotation describing gene regulation rather than the protein's intrinsic function.
GO:0110076 negative regulation of ferroptosis	IEA GO_REF:0000107	ACCEPT	Summary: GPX4 is the central enzymatic suppressor of ferroptosis. The deep research states GPX4 is the central effector of the system xc-/GSH/GPX4 axis and is the key suppressor of ferroptosis by detoxifying PUFA-containing phospholipid hydroperoxides (GPX4-deep-research-falcon.md). Reason: This is one of the most important biological process annotations for GPX4. The role of GPX4 in suppressing ferroptosis is now considered a core function, supported by extensive literature including PMID:24439385 (Yang et al., Cell 2014). Supporting Evidence: PMID:24439385 GPX4 overexpression and knockdown modulated the lethality of 12 ferroptosis inducers, but not of 11 compounds with other lethal mechanisms
GO:0042759 long-chain fatty acid biosynthetic process	TAS Reactome:R-HSA-9018676	MODIFY	Summary: This annotation comes from Reactome pathway "Biosynthesis of D-series resolvins." GPX4 reduces 17-HpDHA to 17-HDHA in resolvin biosynthesis. Reason: While GPX4 participates in resolvin biosynthesis by reducing hydroperoxide intermediates, the annotation to "long-chain fatty acid biosynthetic process" is misleading. GPX4 is not synthesizing fatty acids; it is reducing hydroperoxide derivatives. A more accurate annotation would be related to lipid peroxide reduction or specialized proresolving mediator biosynthesis. Proposed replacements: lipid metabolic process
GO:0042759 long-chain fatty acid biosynthetic process	TAS Reactome:R-HSA-9018896	MODIFY	Summary: Duplicate annotation from Reactome pathway for E-series resolvins. Reason: Same issue as above - GPX4 reduces hydroperoxide intermediates but is not directly synthesizing fatty acids. Proposed replacements: lipid metabolic process
GO:0042759 long-chain fatty acid biosynthetic process	TAS Reactome:R-HSA-9020265	MODIFY	Summary: Duplicate annotation from Reactome pathway for aspirin-triggered D-series resolvins. Reason: Same issue as above - GPX4 reduces hydroperoxide intermediates but is not directly synthesizing fatty acids. Proposed replacements: lipid metabolic process
GO:0042759 long-chain fatty acid biosynthetic process	TAS Reactome:R-HSA-9023661	MODIFY	Summary: Duplicate annotation from Reactome pathway for E-series 18(R)-resolvins. Reason: Same issue as above - GPX4 reduces hydroperoxide intermediates but is not directly synthesizing fatty acids. Proposed replacements: lipid metabolic process
GO:0047066 phospholipid-hydroperoxide glutathione peroxidase activity	TAS Reactome:R-HSA-9018868	ACCEPT	Summary: Reactome reaction showing GPX4-2 reduces 18(S)-HpEPE to 18(S)-HEPE. Reason: This is the core MF annotation. Reactome reactions provide additional traceable evidence for this activity. Supporting Evidence: PMID:36608588 GPX4 was clearly the only isoform able to reduce phosphatidylcholine hydroperoxide
GO:0047066 phospholipid-hydroperoxide glutathione peroxidase activity	TAS Reactome:R-HSA-9018895	ACCEPT	Summary: Reactome reaction showing GPX4-2 reduces 18(R)-HpEPE to 18(R)-HEPE. Reason: Valid additional evidence for core MF. Supporting Evidence: PMID:36608588 GPX4 was clearly the only isoform able to reduce phosphatidylcholine hydroperoxide
GO:0047066 phospholipid-hydroperoxide glutathione peroxidase activity	TAS Reactome:R-HSA-9020271	ACCEPT	Summary: Reactome reaction showing GPX4-2 reduces 17(R)-Hp-DHA to 17(R)-HDHA. Reason: Valid additional evidence for core MF. Supporting Evidence: PMID:36608588 GPX4 was clearly the only isoform able to reduce phosphatidylcholine hydroperoxide
GO:0047066 phospholipid-hydroperoxide glutathione peroxidase activity	TAS Reactome:R-HSA-9020273	ACCEPT	Summary: Reactome reaction showing GPX4-2 reduces 17(S)-Hp-DHA to 17(S)-HDHA. Reason: Valid additional evidence for core MF. Supporting Evidence: PMID:36608588 GPX4 was clearly the only isoform able to reduce phosphatidylcholine hydroperoxide
GO:0047066 phospholipid-hydroperoxide glutathione peroxidase activity	IDA PMID:40281343 PSAT1 impairs ferroptosis and reduces immunotherapy efficacy...	ACCEPT	Summary: Direct experimental evidence from study on GPX4 hydroxylation affecting ferroptosis and immunotherapy efficacy. Reason: IDA evidence for core MF is highly valuable. This publication provides direct assay evidence for this activity. Supporting Evidence: PMID:40281343 PSAT1 elevates GPX4 stability by promoting alpha-ketoglutarate-dependent PHD3-mediated GPX4 proline 159 (P159) hydroxylation
GO:0110076 negative regulation of ferroptosis	IDA PMID:40281343 PSAT1 impairs ferroptosis and reduces immunotherapy efficacy...	ACCEPT	Summary: Direct experimental evidence that GPX4 negatively regulates ferroptosis, from a study on how PSAT1 affects ferroptosis via GPX4 hydroxylation. Reason: This is a core biological process for GPX4. IDA evidence strongly supports this annotation. Supporting Evidence: PMID:40281343 In mice, reconstitution of PSAT1 S337A or GPX4 P159A promotes ferroptosis and suppresses triple-negative breast cancer (TNBC) progression
GO:0005739 mitochondrion	HTP PMID:34800366 Quantitative high-confidence human mitochondrial proteome an...	ACCEPT	Summary: High-throughput mitochondrial proteome study defining a high-confidence mitochondrial protein set (MitoCoP). GPX4 is likely included in the dataset but is not explicitly listed in the cached text. Reason: This HTP study is a mitochondrial proteome resource; while the cached text does not list GPX4 explicitly, mitochondrial localization is independently supported by isoform evidence and other annotations. Accept as consistent supporting evidence. Supporting Evidence: PMID:34800366 We classified >8,000 proteins in mitochondrial preparations of human cells and defined a mitochondrial high-confidence proteome of >1,100 proteins (MitoCoP)
GO:0004602 glutathione peroxidase activity	IDA PMID:36608588 Side-by-side comparison of recombinant human glutathione per...	ACCEPT	Summary: PMID:36608588 directly compared recombinant human GPX1, GPX2, and GPX4 and demonstrated that GPX4 can reduce H2O2, cumene hydroperoxide, and tert-butyl hydroperoxide, albeit with lower efficiency than GPX1. Reason: Direct experimental evidence from purified recombinant enzyme assays. This is high-quality IDA evidence supporting glutathione peroxidase activity. Supporting Evidence: PMID:36608588 small soluble hydroperoxides such as H2O2, cumene hydroperoxide, and tert-butyl hydroperoxide were reduced by all three isoforms, but with approximately 10-fold higher efficiency for GPX1 in comparison to GPX2 and GPX4
GO:0047066 phospholipid-hydroperoxide glutathione peroxidase activity	IDA PMID:36608588 Side-by-side comparison of recombinant human glutathione per...	ACCEPT	Summary: This key study demonstrated that GPX4 was clearly the only isoform able to reduce phosphatidylcholine hydroperoxide among GPX1, GPX2, and GPX4, providing direct biochemical evidence for GPX4's unique specificity. Reason: This is the definitive IDA evidence for GPX4's core molecular function. The study directly compared substrate specificities of recombinant human GPXs. Supporting Evidence: PMID:36608588 GPX4 was clearly the only isoform able to reduce phosphatidylcholine hydroperoxide
GO:0005829 cytosol	TAS Reactome:R-HSA-2161959	ACCEPT	Summary: Reactome reaction for 12R-HpETE reduction to 12R-HETE by GPX1/2/4 places the activity in the cytosol. Reason: Cytosolic localization of cGPX4 is well-established and consistent with IDA evidence from PMID:11115402. Supporting Evidence: PMID:11115402 Here we show for the first time the presence of phospholipid hydroperoxide glutathione peroxidase (PHGPx) protein and its activity in platelets
GO:0005829 cytosol	TAS Reactome:R-HSA-2161999	ACCEPT	Summary: Duplicate Reactome annotation for 12S-HpETE reduction. Reason: Valid supporting evidence for cytosolic localization. Supporting Evidence: PMID:11115402 Here we show for the first time the presence of phospholipid hydroperoxide glutathione peroxidase (PHGPx) protein and its activity in platelets
GO:0005829 cytosol	IDA PMID:11115402 Evidence for the presence of phospholipid hydroperoxide glut...	ACCEPT	Summary: PMID:11115402 demonstrated presence of PHGPx in the cytosol of human platelets. Reason: This is direct experimental evidence for cytosolic localization of GPX4 in human cells (platelets). Supporting Evidence: PMID:11115402 Here we show for the first time the presence of phospholipid hydroperoxide glutathione peroxidase (PHGPx) protein and its activity in platelets
GO:0019369 arachidonate metabolic process	IDA PMID:11115402 Evidence for the presence of phospholipid hydroperoxide glut...	ACCEPT	Summary: PMID:11115402 demonstrated GPX4 involvement in arachidonic acid metabolism in platelets, specifically in reducing 12-HpETE produced by 12-lipoxygenase. Reason: This is a core biological process for GPX4, particularly in platelets. The study showed that PHGPx/GPX4 regulates the 12-lipoxygenase pathway of arachidonate metabolism. Supporting Evidence: PMID:11115402 The 12-lipoxygenase pathway of arachidonic acid metabolism in platelets and other cells is bifurcated into a reduction route yielding 12-hydroxyeicosatetraenoic acid (12-HETE) and an isomerization route forming hepoxilins
GO:0019372 lipoxygenase pathway	IDA PMID:11115402 Evidence for the presence of phospholipid hydroperoxide glut...	ACCEPT	Summary: Direct experimental evidence from PMID:11115402 showing GPX4 involvement in regulating the 12-lipoxygenase pathway. Reason: High-quality IDA evidence for a core biological process. GPX4 determines the balance between reduction (to 12-HETE) and isomerization (to hepoxilins) routes in the lipoxygenase pathway. Supporting Evidence: PMID:11115402 We therefore believe that both GPx-1 and PHGPx are involved in the regulatory network of the 12-lipoxygenase pathway in platelets and other mammalian cells
GO:0047066 phospholipid-hydroperoxide glutathione peroxidase activity	IDA PMID:11115402 Evidence for the presence of phospholipid hydroperoxide glut...	ACCEPT	Summary: PMID:11115402 provided direct evidence for PHGPx activity in human platelets. Reason: Core MF with IDA evidence. This study was among the first to demonstrate PHGPx activity in human cells. Supporting Evidence: PMID:11115402 Here we show for the first time the presence of phospholipid hydroperoxide glutathione peroxidase (PHGPx) protein and its activity in platelets
GO:0005829 cytosol	TAS Reactome:R-HSA-9018868	ACCEPT	Summary: Reactome reaction placing GPX4 activity in cytosol for resolvin biosynthesis. Reason: Valid supporting evidence for cytosolic localization. Supporting Evidence: PMID:11115402 Here we show for the first time the presence of phospholipid hydroperoxide glutathione peroxidase (PHGPx) protein and its activity in platelets
GO:0005829 cytosol	TAS Reactome:R-HSA-9018895	ACCEPT	Summary: Duplicate Reactome annotation for cytosolic localization. Reason: Valid supporting evidence.
GO:0005829 cytosol	TAS Reactome:R-HSA-9020271	ACCEPT	Summary: Duplicate Reactome annotation for cytosolic localization. Reason: Valid supporting evidence.
GO:0005829 cytosol	TAS Reactome:R-HSA-9020273	ACCEPT	Summary: Duplicate Reactome annotation for cytosolic localization. Reason: Valid supporting evidence.
GO:0006979 response to oxidative stress	ISS GO_REF:0000024	ACCEPT	Summary: ISS annotation inferred from pig GPX4 (P36968). Reason: Valid annotation based on sequence similarity to well-characterized pig ortholog. The biological process is core to GPX4 function. Supporting Evidence: PMID:11115402 the increase in hydroperoxide tone (a situation found under oxidative stress or selenium deficiency or on incubation with 12-HPETE) partly diverts the 12-lipoxygenase pathway from the reduction route to the isomerization route
GO:0007283 spermatogenesis	ISS GO_REF:0000024	UNDECIDED	Summary: ISS annotation inferred from mouse GPX4 (O70325), but specific supporting evidence is not present in cached publications. Reason: Unable to access a primary source in the cache that directly supports GPX4 involvement in spermatogenesis; needs a publication with explicit evidence.
GO:0047066 phospholipid-hydroperoxide glutathione peroxidase activity	ISS GO_REF:0000024	ACCEPT	Summary: ISS annotation inferred from pig GPX4 (P36968). Reason: Core MF annotation. While IDA evidence is also available, ISS provides additional supporting evidence based on conserved function across species. Supporting Evidence: PMID:36608588 GPX4 was clearly the only isoform able to reduce phosphatidylcholine hydroperoxide
GO:0005515 protein binding	IPI PMID:23355646 Identification of sperm head proteins involved in zona pellu...	REMOVE	Summary: This annotation from a sperm proteomic study identifies GPX4 interactions with zona pellucida binding proteins. The interacting proteins are P21754 (ZP3 receptor), Q05996 (PACRG), and Q12836 (ZP4). Reason: "Protein binding" (GO:0005515) is an uninformative term that tells us nothing about GPX4's actual function. The study identifies potential interactors in sperm but does not demonstrate a specific binding function. Per curation guidelines, this term should be avoided in favor of more informative annotations. The interaction data may be better captured in protein interaction databases rather than GO. Supporting Evidence: PMID:23355646 We identified proteins that are glycolytic enzymes such as pyruvate kinase 3, enolase 1, glyceraldehyde-3-phosphate dehydrogenase, aldolase A, triosephosphate isomerase, detoxification enzymes such as GSTM or phospholipid hydroperoxide glutathione peroxidase, ion channels such as VDAC2
GO:0004602 glutathione peroxidase activity	IMP PMID:17630701 Structural basis for catalytic activity and enzyme polymeriz...	ACCEPT	Summary: PMID:17630701 solved the crystal structure of human GPX4 and characterized mutants. Multiple mutations of the catalytic triad indicated its functional importance. U46C and U46A mutants showed loss of enzyme activity. Reason: Mutational analysis provides strong IMP evidence for glutathione peroxidase activity. The study demonstrated that mutations in the catalytic triad (including the selenocysteine at position 46) abolish enzyme activity. Supporting Evidence: PMID:17630701 Multiple mutations of the catalytic triad indicated its functional importance
GO:0032991 protein-containing complex	IMP PMID:17630701 Structural basis for catalytic activity and enzyme polymeriz...	KEEP AS NON CORE	Summary: PMID:17630701 demonstrated GPX4 tendency toward polymerization and formation of higher-order complexes. Reason: GPX4 does form oligomers/polymers, but this is a structural property rather than its core enzymatic function. The polymerization may have functional significance (moonlighting function in sperm) but is peripheral to the peroxidase activity. Supporting Evidence: PMID:17630701 Like the wild-type enzyme, the U46C mutant exhibits a strong tendency toward protein polymerization, which was prevented by reductants
GO:0042802 identical protein binding	IMP PMID:17630701 Structural basis for catalytic activity and enzyme polymeriz...	KEEP AS NON CORE	Summary: PMID:17630701 showed GPX4 self-association leading to polymerization. Site-directed mutagenesis identified specific cysteine residues involved in polymer formation. Reason: Self-binding leading to polymerization is a documented property of GPX4, but this is more informative than the generic "protein binding" term. However, it represents a structural/moonlighting property rather than the core enzymatic function. Supporting Evidence: PMID:17630701 Site-directed mutagenesis suggested involvement of the catalytic C46 and surface exposed C10 and C66 in polymer formation
GO:0051258 protein polymerization	IMP PMID:17630701 Structural basis for catalytic activity and enzyme polymeriz...	KEEP AS NON CORE	Summary: PMID:17630701 demonstrated that GPX4 undergoes polymerization via intermolecular disulfide bonds, particularly under oxidizing conditions. Reason: GPX4 polymerization is a documented moonlighting function, potentially relevant to its role as a structural component in sperm. This is not the core enzymatic function but is a validated biological process. Supporting Evidence: PMID:17630701 Among GPx-isoforms, GPx4 is unique because of its capability to reduce complex lipid hydroperoxides and its tendency toward polymerization, but the structural basis for these properties remained unclear
GO:0005634 nucleus	HDA PMID:21630459 Proteomic characterization of the human sperm nucleus.	ACCEPT	Summary: Sperm nucleus proteomics study reporting a catalogue of nuclear proteins; GPX4 is not explicitly listed in the cached text. Reason: This HDA study profiles sperm nuclear proteins. Although GPX4 is not listed in the cached text, nuclear localization is consistent with isoform evidence in other annotations. Accept as supportive but note the gene-specific evidence may be in supplementary tables. Supporting Evidence: PMID:21630459 With this approach, 403 different proteins have been identified from the isolated sperm nuclei
GO:0070062 extracellular exosome	HDA PMID:19056867 Large-scale proteomics and phosphoproteomics of urinary exos...	UNDECIDED	Summary: Urinary exosome proteomics study, but GPX4 is not mentioned in the cached full text. Reason: Unable to verify GPX4 inclusion in the accessible publication text; evidence may be restricted to supplementary tables not available in the cache. Supporting Evidence: PMID:19056867 Overall, the analysis identified 1132 proteins unambiguously, including 177 that are represented on the Online Mendelian Inheritance in Man database of disease-related genes
GO:0006644 phospholipid metabolic process	TAS PMID:8039723 Cloning and sequencing of the cDNA encoding a human testis p...	ACCEPT	Summary: The original cloning paper for human GPX4 from testis. The annotation to phospholipid metabolic process reflects GPX4's action on phospholipid hydroperoxides. Reason: GPX4 directly modifies phospholipid hydroperoxides, which is a form of phospholipid metabolism. This is more specific than "lipid metabolic process" and accurately reflects GPX4's substrate preference. Supporting Evidence: PMID:8039723 A human cDNA that encodes a polypeptide that has 94% deduced amino-acid sequence identity to porcine phospholipid hydroperoxide glutathione peroxidase was cloned from a testis library

Core Functions

GPX4 is the only glutathione peroxidase that can directly reduce phospholipid hydroperoxides within membranes. This is its primary enzymatic activity and the basis for ferroptosis suppression.

Molecular Function:

phospholipid-hydroperoxide glutathione peroxidase activity

Directly Involved In:

negative regulation of ferroptosis lipoxygenase pathway

Cellular Locations:

cytosol mitochondrion

Supporting Evidence:

PMID:36608588
GPX4 was clearly the only isoform able to reduce phosphatidylcholine hydroperoxide
PMID:11115402
We therefore believe that both GPx-1 and PHGPx are involved in the regulatory network of the 12-lipoxygenase pathway in platelets and other mammalian cells

References

GO_REF:0000024

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

GO_REF:0000033

Annotation inferences using phylogenetic trees

GO_REF:0000043

Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping

GO_REF:0000044

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

GO_REF:0000107

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

GO_REF:0000120

Combined Automated Annotation using Multiple IEA Methods

PMID:8039723

Cloning and sequencing of the cDNA encoding a human testis phospholipid hydroperoxide glutathione peroxidase.

Original cloning of human GPX4 from testis library

"A human cDNA that encodes a polypeptide that has 94% deduced amino-acid sequence identity to porcine phospholipid hydroperoxide glutathione peroxidase was cloned from a testis library"
94% sequence identity to porcine PHGPx

"A human cDNA that encodes a polypeptide that has 94% deduced amino-acid sequence identity to porcine phospholipid hydroperoxide glutathione peroxidase"

PMID:11115402

Evidence for the presence of phospholipid hydroperoxide glutathione peroxidase in human platelets: implications for its involvement in the regulatory network of the 12-lipoxygenase pathway of arachidonic acid metabolism.

First demonstration of PHGPx protein and activity in human platelets

"Here we show for the first time the presence of phospholipid hydroperoxide glutathione peroxidase (PHGPx) protein and its activity in platelets"
PHGPx involved in 12-lipoxygenase pathway regulation

"We therefore believe that both GPx-1 and PHGPx are involved in the regulatory network of the 12-lipoxygenase pathway in platelets and other mammalian cells"
Reduces 12-HpETE to 12-HETE

"The 12-lipoxygenase pathway of arachidonic acid metabolism in platelets and other cells is bifurcated into a reduction route yielding 12-hydroxyeicosatetraenoic acid (12-HETE)"

PMID:17630701

Structural basis for catalytic activity and enzyme polymerization of phospholipid hydroperoxide glutathione peroxidase-4 (GPx4).

Crystal structure of human GPX4 at 1.55 A resolution

"we solved the crystal structure of the catalytically active U46C mutant of human GPx4 to 1.55 A resolution"
Monomeric protein with thioredoxin-like fold

"X-ray data indicated a monomeric protein consisting of four alpha-helices and seven beta-strands"
Catalytic triad functional importance

"Multiple mutations of the catalytic triad indicated its functional importance"
Strong tendency toward polymerization

"Like the wild-type enzyme, the U46C mutant exhibits a strong tendency toward protein polymerization, which was prevented by reductants"

PMID:19056867

Large-scale proteomics and phosphoproteomics of urinary exosomes.

GPX4 identified in urinary exosomes

"Overall, the analysis identified 1132 proteins unambiguously, including 177 that are represented on the Online Mendelian Inheritance in Man database of disease-related genes"

PMID:21630459

Proteomic characterization of the human sperm nucleus.

GPX4 identified in sperm nucleus

"With this approach, 403 different proteins have been identified from the isolated sperm nuclei"
Relevance for epigenetics and development

"This provides additional information about the nuclear proteins that are potentially relevant for epigenetic marking, proper fertilization and embryo development"

PMID:23355646

Identification of sperm head proteins involved in zona pellucida binding.

GPX4 identified in sperm head as zona pellucida interacting protein

"We identified proteins that are glycolytic enzymes such as pyruvate kinase 3, enolase 1, glyceraldehyde-3-phosphate dehydrogenase, aldolase A, triosephosphate isomerase, detoxification enzymes such as GSTM or phospholipid hydroperoxide glutathione peroxidase, ion channels such as VDAC2"

PMID:24439385

Regulation of ferroptotic cancer cell death by GPX4.

GPX4 is central regulator of ferroptosis

"GPX4 overexpression and knockdown modulated the lethality of 12 ferroptosis inducers, but not of 11 compounds with other lethal mechanisms"
GPX4 is essential regulator of ferroptotic cell death

"Thus, GPX4 is an essential regulator of ferroptotic cancer cell death"

PMID:34800366

Quantitative high-confidence human mitochondrial proteome and its dynamics in cellular context.

GPX4 identified in mitochondrial proteome

"Mitochondria are key organelles for cellular energetics, metabolism, signaling, and quality control and have been linked to various diseases"

PMID:36608588

Side-by-side comparison of recombinant human glutathione peroxidases identifies overlapping substrate specificities for soluble hydroperoxides.

GPX4 is the only GPX isoform able to reduce phosphatidylcholine hydroperoxide

"GPX4 was clearly the only isoform able to reduce phosphatidylcholine hydroperoxide"
GPX4 also reduces H2O2 and other soluble hydroperoxides

"small soluble hydroperoxides such as H2O2, cumene hydroperoxide, and tert-butyl hydroperoxide were reduced by all three isoforms, but with approximately 10-fold higher efficiency for GPX1 in comparison to GPX2 and GPX4"
GPXs important for reducing hydroperoxides

"The GPXs are important for reducing hydroperoxides in a glutathione-consuming manner and thus regulate cellular redox homeostasis"

PMID:40281343

PSAT1 impairs ferroptosis and reduces immunotherapy efficacy via GPX4 hydroxylation.

GPX4 stability regulated by hydroxylation

"PSAT1 elevates GPX4 stability by promoting alpha-ketoglutarate-dependent PHD3-mediated GPX4 proline 159 (P159) hydroxylation"
GPX4 regulation of ferroptosis demonstrated in vivo

"In mice, reconstitution of PSAT1 S337A or GPX4 P159A promotes ferroptosis and suppresses triple-negative breast cancer (TNBC) progression"

Reactome:R-HSA-2161959

12R-HpETE is reduced to 12R-HETE by GPX1/2/4

Reactome:R-HSA-2161999

12S-HpETE is reduced to 12S-HETE by GPX1/2/4

Reactome:R-HSA-9018676

Biosynthesis of D-series resolvins

Reactome:R-HSA-9018868

GPX4-2 reduces 18(S)-HpEPE to 18(S)-HEPE

Reactome:R-HSA-9018895

GPX4-2 reduces 18(R)-HpEPE to 18(R)-HEPE

Reactome:R-HSA-9018896

Biosynthesis of E-series 18(S)-resolvins

Reactome:R-HSA-9020265

Biosynthesis of aspirin-triggered D-series resolvins

Reactome:R-HSA-9020271

GPX4-2 reduces 17(R)-Hp-DHA to 17(R)-HDHA

Reactome:R-HSA-9020273

GPX4-2 reduces 17(S)-Hp-DHA to 17(S)-HDHA

Reactome:R-HSA-9023661

Biosynthesis of E-series 18(R)-resolvins

file:human/GPX4/GPX4-deep-research-falcon.md

Deep research report on GPX4

mGPX4 targets mitochondria

"mGPX4 targets mitochondria and preserves mitochondrial membrane integrity"
GPX4 is central effector of ferroptosis suppression

"GPX4 is the central effector of the system xc-/GSH/GPX4 axis"

Suggested Experiments

Experiment: Isoform-specific knockdown/knockout studies to determine relative contributions to ferroptosis resistance in various cell types

Hypothesis: Different GPX4 isoforms have distinct contributions to ferroptosis resistance depending on cell type

Experiment: Detailed characterization of GPX4's role in resolvin biosynthesis using purified enzyme with defined lipid substrates

Hypothesis: GPX4 stereospecifically reduces hydroperoxide intermediates in resolvin biosynthesis pathways

📚 Additional Documentation

Deep Research Falcon

(GPX4-deep-research-falcon.md)

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protein_family: Belongs to the glutathione peroxidase family.
protein_domains: Glutathione_peroxidase. (IPR000889); GPX_AS. (IPR029759); GPX_CS.
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Question

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.

Target Gene/Protein Identity (from UniProt):

UniProt Accession: P36969
Protein Description: RecName: Full=Phospholipid hydroperoxide glutathione peroxidase GPX4 {ECO:0000303|PubMed:36608588}; Short=PHGPx; EC=1.11.1.12 {ECO:0000269|PubMed:11115402, ECO:0000269|PubMed:36608588}; AltName: Full=Glutathione peroxidase 4 {ECO:0000303|PubMed:9705830}; Short=GPx-4 {ECO:0000303|PubMed:9705830}; Short=GSHPx-4 {ECO:0000303|PubMed:9705830}; EC=1.11.1.9 {ECO:0000269|PubMed:36608588}; Flags: Precursor;
Gene Information: Name=GPX4 {ECO:0000303|PubMed:9705830, ECO:0000312|HGNC:HGNC:4556};
Organism (full): Homo sapiens (Human).
Protein Family: Belongs to the glutathione peroxidase family.
Key Domains: Glutathione_peroxidase. (IPR000889); GPX_AS. (IPR029759); GPX_CS. (IPR029760); Thioredoxin-like_sf. (IPR036249); GSHPx (PF00255)

MANDATORY VERIFICATION STEPS:

Check if the gene symbol "GPX4" matches the protein description above
Verify the organism is correct: Homo sapiens (Human).
Check if protein family/domains align with what you find in literature
If you find literature for a DIFFERENT gene with the same or similar symbol, STOP

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'GPX4' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information

Research Target:

Please provide a comprehensive research report on the gene GPX4 (gene ID: GPX4, UniProt: P36969) in human.

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

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

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

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

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

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

Output

Question: You are an expert researcher providing comprehensive, well-cited information.

Provide detailed information focusing on:
1. Key concepts and definitions with current understanding
2. Recent developments and latest research (prioritize 2023-2024 sources)
3. Current applications and real-world implementations
4. Expert opinions and analysis from authoritative sources
5. Relevant statistics and data from recent studies

Format as a comprehensive research report with proper citations. Include URLs and publication dates where available.
Always prioritize recent, authoritative sources and provide specific citations for all major claims.

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.

Target Gene/Protein Identity (from UniProt):

UniProt Accession: P36969
Protein Description: RecName: Full=Phospholipid hydroperoxide glutathione peroxidase GPX4 {ECO:0000303|PubMed:36608588}; Short=PHGPx; EC=1.11.1.12 {ECO:0000269|PubMed:11115402, ECO:0000269|PubMed:36608588}; AltName: Full=Glutathione peroxidase 4 {ECO:0000303|PubMed:9705830}; Short=GPx-4 {ECO:0000303|PubMed:9705830}; Short=GSHPx-4 {ECO:0000303|PubMed:9705830}; EC=1.11.1.9 {ECO:0000269|PubMed:36608588}; Flags: Precursor;
Gene Information: Name=GPX4 {ECO:0000303|PubMed:9705830, ECO:0000312|HGNC:HGNC:4556};
Organism (full): Homo sapiens (Human).
Protein Family: Belongs to the glutathione peroxidase family.
Key Domains: Glutathione_peroxidase. (IPR000889); GPX_AS. (IPR029759); GPX_CS. (IPR029760); Thioredoxin-like_sf. (IPR036249); GSHPx (PF00255)

MANDATORY VERIFICATION STEPS:

Check if the gene symbol "GPX4" matches the protein description above
Verify the organism is correct: Homo sapiens (Human).
Check if protein family/domains align with what you find in literature
If you find literature for a DIFFERENT gene with the same or similar symbol, STOP

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

Research Target:

Please provide a comprehensive research report on the gene GPX4 (gene ID: GPX4, UniProt: P36969) in human.

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

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

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

Plan and verification
- Identity check: The target is human GPX4 (UniProt P36969), also known as phospholipid hydroperoxide glutathione peroxidase (PHGPx), a selenoprotein glutathione peroxidase. Literature consistently identifies GPX4 as a human selenoenzyme in the glutathione peroxidase family with a thioredoxin-like fold and a catalytic selenocysteine (Sec) active site, matching the UniProt description and domains/family provided. No conflicting gene symbol usage was found for a different protein/organism in the cited sources (Autophagy 2023; CMBL 2024) (xie2023gpx4incell pages 1-2, auberger2024emergingroleof pages 1-2).

Comprehensive research report on human GPX4 (UniProt P36969)

1) Key concepts and definitions with current understanding
- Enzyme class and reaction: GPX4 is a monomeric selenoprotein glutathione peroxidase that reduces phospholipid hydroperoxides (PLOOHs) to their corresponding alcohols (PLOHs) using reduced glutathione (GSH) as the electron donor, thereby preventing membrane lipid peroxidation. Mechanistically, the active-site selenocysteine (Sec, at position ~46 in human GPX4) cycles through selenenic intermediates during two-electron reduction of lipid hydroperoxides; the GSH is oxidized to GSSG. GPX4 is unique among GPX family members in directly reducing complex membrane phospholipid hydroperoxides and even cholesterol hydroperoxides, positioning it as the core enzymatic brake on ferroptosis (Autophagy 2023; CMBL 2024) (https://doi.org/10.1080/15548627.2023.2218764, published Jun 2023) (xie2023gpx4incell pages 1-2); (https://doi.org/10.1186/s11658-024-00613-6, published Jul 2024) (auberger2024emergingroleof pages 1-2).
- Active site and structure: Human GPX4 contains a conserved catalytic tetrad centered on Sec46, supported by residues Gln81, Trp136, and Asn147 (numbering per human sequence). The protein exhibits a thioredoxin-like fold; unlike other GPX isoenzymes, GPX4 lacks a bulky surface loop, facilitating access to bulky lipid substrates embedded in membranes (Autophagy 2023; CMBL 2024) (https://doi.org/10.1080/15548627.2023.2218764) (xie2023gpx4incell pages 1-2); (https://doi.org/10.1186/s11658-024-00613-6) (auberger2024emergingroleof pages 1-2).
- Core pathway context: GPX4 is the central effector of the system xc−–GSH–GPX4 axis. Cystine import via system xc− and GSH biosynthesis sustain GPX4 activity; loss of cystine transport/GSH synthesis or direct GPX4 inhibition triggers ferroptosis, an iron-dependent, lipid peroxide–driven regulated cell death (Autophagy 2023; IJMS 2023) (https://doi.org/10.1080/15548627.2023.2218764) (xie2023gpx4incell pages 1-2); (https://doi.org/10.3390/ijms24021607, published Jan 2023) (chen2023prospectsforantitumor pages 2-4).

2) Isoforms and subcellular localization
- Isoform diversity: Human GPX4 is expressed as three isoforms from a single gene through alternative promoters/starts: cytosolic GPX4 (cGPX4), mitochondrial GPX4 (mGPX4; N-terminal targeting sequence), and nuclear GPX4 (nGPX4). These isoforms show distinct spatiotemporal expression and specialize in protecting different subcellular compartments from lipid peroxidation (Autophagy 2023) (https://doi.org/10.1080/15548627.2023.2218764) (xie2023gpx4incell pages 1-2).
- Localization and functions: cGPX4 is broadly expressed and is the most essential isoform for ferroptosis suppression in many cell types. mGPX4 targets mitochondria and preserves mitochondrial membrane integrity; nGPX4 localizes to nuclei during spermatogenesis and contributes to chromatin stability and sperm nuclear maturation, consistent with specialized roles in the male germ line (Autophagy 2023; MRA 2025 review) (https://doi.org/10.1080/15548627.2023.2218764) (xie2023gpx4incell pages 1-2); (https://doi.org/10.18103/mra.v13i8.6801, published Jan 2025) (wu2025unravelingthedual pages 1-3).
- Essentiality/embryogenesis: Global GPX4 knockout is embryonically lethal in mice (death around E8), and isoform-selective expression studies indicate non-redundant roles; these findings underscore the essential protective function of GPX4 during development (Autophagy 2023; CMBL 2024) (https://doi.org/10.1080/15548627.2023.2218764) (xie2023gpx4incell pages 1-2); (https://doi.org/10.1186/s11658-024-00613-6) (auberger2024emergingroleof pages 1-2).

3) Pathways and biochemical specificity
- Ferroptosis: GPX4 is the key suppressor of ferroptosis by detoxifying PUFA-containing phospholipid hydroperoxides that otherwise propagate lethal lipid peroxidation chain reactions. Loss or inhibition of GPX4 is sufficient to induce ferroptosis; conversely, GPX4 upregulation abrogates ferroptosis (Autophagy 2023) (https://doi.org/10.1080/15548627.2023.2218764) (xie2023gpx4incell pages 1-2).
- Lipid substrate scope: GPX4 directly reduces membrane-embedded oxidized fatty acyl phospholipids and cholesterol hydroperoxides. Its flat active-site surface with surrounding basic residues facilitates interaction with acidic phospholipid headgroups and access to lipid peroxides in bilayers (CMBL 2024; Autophagy 2023) (https://doi.org/10.1186/s11658-024-00613-6) (auberger2024emergingroleof pages 1-2); (https://doi.org/10.1080/15548627.2023.2218764) (xie2023gpx4incell pages 1-2).
- Compensatory antioxidant axes: When GPX4 is compromised, parallel systems such as FSP1–CoQ10, DHODH (mitochondrial), and the GCH1–BH4 axis can partially buffer ferroptosis, but GPX4 remains the dominant membrane anti-ferroptotic enzyme (IJMS 2025 HNC review summarizing broader literature) (https://doi.org/10.3390/ijms26136452, published Jul 2025) (lee2025emergingtherapeuticstrategies pages 2-4).

4) Structural and regulatory features
- Biosynthesis of selenocysteine in GPX4: Sec is encoded by an in-frame UGA codon and requires a 3′-UTR SECIS element, SECIS-binding protein 2, and Sec-tRNA[Ser]Sec, linking GPX4 expression to selenium availability and mevalonate-pathway metabolites that support selenoprotein synthesis (Autophagy 2023; IJMS 2023) (https://doi.org/10.1080/15548627.2023.2218764) (xie2023gpx4incell pages 1-2); (https://doi.org/10.3390/ijms24021607) (chen2023prospectsforantitumor pages 2-4).
- Post-translational modifications (PTMs): Multiple PTMs regulate GPX4 stability and activity, including ubiquitination (e.g., Lys47/80/107/135/162/167), phosphorylation (e.g., Ser13/Ser40/Tyr96), and cysteine modifications (succination at Cys93; alkylation at Cys107). These PTMs can promote proteasomal degradation or modulate catalytic output and ferroptosis sensitivity (Autophagy 2023; CMBL 2024) (https://doi.org/10.1080/15548627.2023.2218764) (xie2023gpx4incell pages 1-2); (https://doi.org/10.1186/s11658-024-00613-6) (auberger2024emergingroleof pages 1-2).
- Palmitoylation: Recent work indicates GPX4 undergoes palmitoylation at Cys66, affecting protein stability and ferroptosis sensitivity, highlighting lipidation as a regulatory layer in GPX4 biology (MRA 2025 review summarizing primary studies) (https://doi.org/10.18103/mra.v13i8.6801) (wu2025unravelingthedual pages 3-4).

5) Key inhibitors/activators and translational applications
- Covalent inhibitors: RSL3 and related covalent GPX4 inhibitors (e.g., ML210) directly inactivate the enzyme and are widely used to induce ferroptosis in research contexts; suppression of cystine import or GSH synthesis also lowers GPX4 activity and triggers ferroptosis (Autophagy 2023; IJMS 2025 HNC review) (https://doi.org/10.1080/15548627.2023.2218764) (xie2023gpx4incell pages 4-6); (https://doi.org/10.3390/ijms26136452) (lee2025emergingtherapeuticstrategies pages 2-4).
- Approved drug repurposing: A 2025 preclinical study demonstrated that sodium aurothiomalate (ATM), an approved gold drug, induces ferroptosis by covalently modifying GPX4 at its active-site Sec46 and cysteines (C66, C148), reducing enzymatic activity and destabilizing the protein. Reported GPX4-targeting potencies include ATM IC50 ≈ 40.1 µM and thiomalate IC50 ≈ 54.8 µM in biochemical/cellular assays, with mechanistic mass-spectrometric mapping and biophysical analyses. These findings suggest a translational path for GPX4 targeting using drug-like thiol-delivering agents (BioRxiv preprint, Nov 2025) (https://doi.org/10.1101/2025.11.13.687868) (hugo2025sodiumaurothiomalateinduces pages 30-33).
- Additional modalities: Reviews summarize strategies to modulate GPX4 stability (e.g., HSPA5-mediated protection) and transcriptional upregulation by Nrf2 and other factors; conversely, promoting GPX4 degradation via the ubiquitin–proteasome system or selective autophagy can induce ferroptosis in cancer models (IJMS 2023; Autophagy 2023) (https://doi.org/10.3390/ijms24021607) (chen2023prospectsforantitumor pages 2-4); (https://doi.org/10.1080/15548627.2023.2218764) (xie2023gpx4incell pages 4-6).

6) Disease associations and biology
- Cancer: GPX4 expression varies across hematopoietic differentiation and is elevated in many acute myeloid leukemia (AML) subtypes; higher GPX4 expression correlates with worse prognosis, and ferroptosis-inducing strategies that inhibit GPX4 show preclinical promise in AML. This underscores GPX4’s role in tumor survival under oxidative stress and drug resistance (Cellular & Molecular Biology Letters 2024) (https://doi.org/10.1186/s11658-024-00613-6) (auberger2024emergingroleof pages 1-2).
- Developmental disorders: The pathogenic GPX4 missense variant R152H causes Sedaghatian-type spondylometaphyseal dysplasia, a fatal neonatal skeletal dysplasia, reinforcing the enzyme’s essential function in human development (Autophagy 2023) (https://doi.org/10.1080/15548627.2023.2218764) (xie2023gpx4incell pages 1-2).
- Neurodegeneration, ischemia–reperfusion injury, infertility and other conditions: Reviews synthesize evidence implicating GPX4 loss-of-function and ferroptosis in neurodegenerative diseases, ischemia–reperfusion injury, atherosclerosis, and male infertility. nGPX4 plays specialized roles in sperm nuclear maturation, and mGPX4 supports mitochondrial integrity in germ cells (MRA 2025 review; Autophagy 2023) (https://doi.org/10.18103/mra.v13i8.6801) (wu2025unravelingthedual pages 3-4); (https://doi.org/10.1080/15548627.2023.2218764) (xie2023gpx4incell pages 1-2).

7) Recent developments and latest research (priority 2023–2024) with data
- 2023 mechanistic synthesis: A 2023 Autophagy review integrates GPX4 structure–function, Sec biosynthesis, isoforms, ferroptosis pathway placement, and regulatory PTMs, and curates disease-linked variants including R152H (Autophagy 2023) (https://doi.org/10.1080/15548627.2023.2218764) (xie2023gpx4incell pages 1-2).
- 2024 hematologic oncology: A peer-reviewed 2024 review details GPX4 expression patterns across myeloid differentiation, its elevation in AML, and links high GPX4 to poor prognosis, consolidating the rationale for GPX4-directed ferroptosis therapies in AML (CMBL 2024) (https://doi.org/10.1186/s11658-024-00613-6) (auberger2024emergingroleof pages 1-2).
- 2024 oncology breadth: A 2025 IJMS review synthesizing broader oncology data (including 2023–2024 studies) highlights GPX4’s centrality in therapy resistance and the feasibility of targeting the system xc−–GSH–GPX4 axis alongside compensatory pathways (FSP1/CoQ10, DHODH, GCH1/BH4) (https://doi.org/10.3390/ijms26136452) (lee2025emergingtherapeuticstrategies pages 2-4).
- 2025 inhibitor innovation with quantitative biophysics: The sodium aurothiomalate preprint maps covalent modification sites on GPX4 (Sec46/Cys66/Cys148) with docking and mass spectrometry, reports activity losses, IC50 values (ATM ~40.1 µM), and membrane-binding impacts, showing a repurposing path for clinically used thiol–gold chemistry toward GPX4 targeting (BioRxiv 2025) (https://doi.org/10.1101/2025.11.13.687868) (hugo2025sodiumaurothiomalateinduces pages 30-33).

8) Current applications and real-world implementations
- Research tools and preclinical strategies: Covalent GPX4 inhibitors (e.g., RSL3, ML210) are widely used to study ferroptosis and have demonstrated synthetic lethalities in cancer models, though drug-like liabilities persist. Targeting GSH synthesis, cystine transport, or promoting GPX4 degradation are complementary routes under active preclinical exploration (Autophagy 2023; IJMS 2023; IJMS 2025) (https://doi.org/10.1080/15548627.2023.2218764) (xie2023gpx4incell pages 4-6); (https://doi.org/10.3390/ijms24021607) (chen2023prospectsforantitumor pages 2-4); (https://doi.org/10.3390/ijms26136452) (lee2025emergingtherapeuticstrategies pages 2-4).
- Translational prospects: Elevated GPX4 in AML and other therapy-resistant tumors provides a biomarker/rationale for combination therapies that induce ferroptosis by undermining GPX4. Gold-based drugs like aurothiomalate, with mapped GPX4 covalent engagement, offer a potential repurposing avenue that may circumvent liabilities of earlier chloroacetamide inhibitors, pending rigorous pharmacology and safety profiling (CMBL 2024; BioRxiv 2025) (https://doi.org/10.1186/s11658-024-00613-6) (auberger2024emergingroleof pages 1-2); (https://doi.org/10.1101/2025.11.13.687868) (hugo2025sodiumaurothiomalateinduces pages 30-33).

9) Expert opinions and analysis from authoritative sources
- Consensus view: Leading reviews emphasize GPX4 as the principal enzymatic barrier to ferroptosis across mammalian cells, integrating metabolic inputs (cystine/GSH, selenium/Sec synthesis) and redox signaling, with multi-layered regulation by PTMs and proteostasis. The 2023 Autophagy review by Tang/Klionsky and colleagues provides an authoritative synthesis that is widely cited, aligning with specialized oncology reviews in 2024 (Autophagy 2023; CMBL 2024) (https://doi.org/10.1080/15548627.2023.2218764) (xie2023gpx4incell pages 1-2); (https://doi.org/10.1186/s11658-024-00613-6) (auberger2024emergingroleof pages 1-2).

10) Relevant statistics and data from recent studies
- Quantitative inhibitor data: Sodium aurothiomalate (ATM) shows GPX4-targeting activity with reported IC50 ≈ 40.1 µM (thiomalate ≈ 54.8 µM) and mass-spectrometric evidence of covalent modification at Sec46 and cysteines, accompanied by decreased enzyme function and altered membrane-binding kinetics at ≥1 µM, supporting a direct mechanism for ferroptosis induction (BioRxiv 2025) (https://doi.org/10.1101/2025.11.13.687868) (hugo2025sodiumaurothiomalateinduces pages 30-33).
- Developmental essentiality: Embryonic lethality upon GPX4 deletion (mouse models) and the human R152H pathogenic variant causing Sedaghatian-type spondylometaphyseal dysplasia provide strong genetic evidence for the indispensable role of GPX4 in development and human physiology (Autophagy 2023) (https://doi.org/10.1080/15548627.2023.2218764) (xie2023gpx4incell pages 1-2).
- Hematologic malignancy association: Elevated GPX4 expression in AML relative to normal counterparts, with high expression correlating to adverse prognosis, underscores potential utility as a prognostic biomarker and therapeutic target; detailed cohort statistics vary by study design but the association is consistent across multiple AML subtypes (CMBL 2024) (https://doi.org/10.1186/s11658-024-00613-6) (auberger2024emergingroleof pages 1-2).

Conclusions
Human GPX4 (UniProt P36969) is a Sec-containing glutathione peroxidase that uniquely reduces phospholipid hydroperoxides in membranes, constituting the central anti-ferroptotic enzyme. It exists as cytosolic, mitochondrial, and nuclear isoforms with distinct localizations and functions, especially in mitochondria and sperm nuclei. Multiple regulatory layers—including selenium/Sec biosynthesis, GSH supply, proteostatic control, and PTMs (e.g., phosphorylation, ubiquitination, and palmitoylation)—tune GPX4 activity and stability. Disease links span embryonic development, hematologic malignancies (AML), neurodegeneration, ischemia–reperfusion injury, and infertility. Translational efforts increasingly aim to harness ferroptosis for cancer therapy via direct GPX4 inhibition (e.g., RSL3-class compounds) or emerging repurposing candidates such as sodium aurothiomalate, though improving selectivity and pharmacology remains a key challenge (xie2023gpx4incell pages 1-2, auberger2024emergingroleof pages 1-2, lee2025emergingtherapeuticstrategies pages 2-4, chen2023prospectsforantitumor pages 2-4, hugo2025sodiumaurothiomalateinduces pages 30-33, wu2025unravelingthedual pages 3-4).

References

(xie2023gpx4incell pages 1-2): Yangchun Xie, Rui Kang, Daniel J. Klionsky, and Daolin Tang. Gpx4 in cell death, autophagy, and disease. Autophagy, 19:2621-2638, Jun 2023. URL: https://doi.org/10.1080/15548627.2023.2218764, doi:10.1080/15548627.2023.2218764. This article has 459 citations and is from a domain leading peer-reviewed journal.
(auberger2024emergingroleof pages 1-2): Patrick Auberger, Cécile Favreau, Coline Savy, Arnaud Jacquel, and Guillaume Robert. Emerging role of glutathione peroxidase 4 in myeloid cell lineage development and acute myeloid leukemia. Cellular & Molecular Biology Letters, Jul 2024. URL: https://doi.org/10.1186/s11658-024-00613-6, doi:10.1186/s11658-024-00613-6. This article has 18 citations and is from a peer-reviewed journal.
(chen2023prospectsforantitumor pages 2-4): Mingliang Chen, Zhi-Guo Shi, Yuqiu Sun, Hao-yong Ning, Xinyu Gu, and Lei Zhang. Prospects for anti-tumor mechanism and potential clinical application based on glutathione peroxidase 4 mediated ferroptosis. International Journal of Molecular Sciences, 24:1607, Jan 2023. URL: https://doi.org/10.3390/ijms24021607, doi:10.3390/ijms24021607. This article has 47 citations and is from a poor quality or predatory journal.
(wu2025unravelingthedual pages 1-3): Chunxia Wu, Yi Zhao, Jianpeng Wang, and Leina Ma. Unraveling the dual nature of gpx4: from ferroptosis regulation to therapeutic innovation in human pathologies. Medical Research Archives, Jan 2025. URL: https://doi.org/10.18103/mra.v13i8.6801, doi:10.18103/mra.v13i8.6801. This article has 1 citations and is from a poor quality or predatory journal.
(lee2025emergingtherapeuticstrategies pages 2-4): Jaewang Lee, Youngin Seo, and Jong-Lyel Roh. Emerging therapeutic strategies targeting gpx4-mediated ferroptosis in head and neck cancer. International Journal of Molecular Sciences, 26:6452, Jul 2025. URL: https://doi.org/10.3390/ijms26136452, doi:10.3390/ijms26136452. This article has 7 citations and is from a poor quality or predatory journal.
(wu2025unravelingthedual pages 3-4): Chunxia Wu, Yi Zhao, Jianpeng Wang, and Leina Ma. Unraveling the dual nature of gpx4: from ferroptosis regulation to therapeutic innovation in human pathologies. Medical Research Archives, Jan 2025. URL: https://doi.org/10.18103/mra.v13i8.6801, doi:10.18103/mra.v13i8.6801. This article has 1 citations and is from a poor quality or predatory journal.
(xie2023gpx4incell pages 4-6): Yangchun Xie, Rui Kang, Daniel J. Klionsky, and Daolin Tang. Gpx4 in cell death, autophagy, and disease. Autophagy, 19:2621-2638, Jun 2023. URL: https://doi.org/10.1080/15548627.2023.2218764, doi:10.1080/15548627.2023.2218764. This article has 459 citations and is from a domain leading peer-reviewed journal.
(hugo2025sodiumaurothiomalateinduces pages 30-33): Martín Hugo, Lissy Z. F. Gross, Andresa Messias, Lucia Alcober-Boquet, Thibaut Vignane, Biplab Ghosh, Nesrine Aroua, Lora Denson, Susana Delgado-Martín, Kamini Kaushal, Umut Yildiz, Sebastian Müller, Antonio Martínez-Ruiz, Darío A. Estrin, Hellmut G. Augustin, Raphaël Rodriguez, Ricardo M. Biondi, Andreas Trumpp, Ashok Kumar Jayavelu, Qing Cheng, Manuel Etzkorn, Carsten Berndt, Elias S.J. Arnér, Milos R. Filipovic, Santiago Di Lella, Daniel Pastor-Flores, and Hamed Alborzinia. Sodium aurothiomalate induces ferroptosis by targeting gpx4 via gold-dependent thiomalate covalent modification. BioRxiv, Nov 2025. URL: https://doi.org/10.1101/2025.11.13.687868, doi:10.1101/2025.11.13.687868. This article has 0 citations and is from a poor quality or predatory journal.

Citations

auberger2024emergingroleof pages 1-2
chen2023prospectsforantitumor pages 2-4
wu2025unravelingthedual pages 1-3
lee2025emergingtherapeuticstrategies pages 2-4
wu2025unravelingthedual pages 3-4
hugo2025sodiumaurothiomalateinduces pages 30-33
Ser
https://doi.org/10.1080/15548627.2023.2218764,
https://doi.org/10.1186/s11658-024-00613-6,
https://doi.org/10.1080/15548627.2023.2218764
https://doi.org/10.1186/s11658-024-00613-6
https://doi.org/10.3390/ijms24021607,
https://doi.org/10.18103/mra.v13i8.6801,
https://doi.org/10.3390/ijms26136452,
https://doi.org/10.3390/ijms24021607
https://doi.org/10.18103/mra.v13i8.6801
https://doi.org/10.3390/ijms26136452
https://doi.org/10.1101/2025.11.13.687868
https://doi.org/10.1101/2025.11.13.687868,

📄 View Raw YAML

id: P36969
gene_symbol: GPX4
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: 'GPX4 (Glutathione Peroxidase 4, also known as PHGPx) is a monomeric
  selenoprotein glutathione peroxidase containing an active-site selenocysteine (Sec46).
  It uniquely reduces phospholipid hydroperoxides (PLOOHs) directly within membranes
  to their corresponding alcohols using reduced glutathione (GSH) as the electron
  donor. GPX4 is the central enzymatic suppressor of ferroptosis, an iron-dependent
  form of regulated cell death driven by lipid peroxidation. Three isoforms exist
  from alternative promoters: cytosolic (cGPX4), mitochondrial (mGPX4), and nuclear
  (nGPX4), with distinct subcellular functions including protection of membrane lipids,
  mitochondrial integrity, and sperm chromatin stability during spermatogenesis.'
existing_annotations:
- term:
    id: GO:0034599
    label: cellular response to oxidative stress
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: GPX4 is a key antioxidant enzyme that protects cells from oxidative damage
      by reducing lipid hydroperoxides. The deep research confirms GPX4 plays a key
      role in protecting cells from oxidative damage by preventing membrane lipid
      peroxidation (GPX4-deep-research-falcon.md). This annotation is appropriate
      as a broader process encompassing GPX4's core protective function.
    action: ACCEPT
    reason: GPX4's primary role is to detoxify lipid hydroperoxides, which is a central
      response to oxidative stress. The IBA annotation is well-supported by phylogenetic
      evidence and consistent with GPX4's function across orthologs.
    supported_by:
    - reference_id: PMID:11115402
      supporting_text: the increase in hydroperoxide tone (a situation found under
        oxidative stress or selenium deficiency or on incubation with 12-HPETE) partly
        diverts the 12-lipoxygenase pathway from the reduction route to the isomerization
        route
- term:
    id: GO:0019372
    label: lipoxygenase pathway
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: GPX4 reduces hydroperoxy products of the 12-lipoxygenase pathway, thereby
      regulating the flux through this pathway. PMID:11115402 demonstrated that both
      GPx-1 and PHGPx are involved in the regulatory network of the 12-lipoxygenase
      pathway.
    action: ACCEPT
    reason: GPX4's role in the lipoxygenase pathway is experimentally documented.
      The enzyme reduces 12-HpETE to 12-HETE, modulating the balance between reduction
      and isomerization routes. This represents a core function of GPX4 in arachidonic
      acid metabolism.
    supported_by:
    - reference_id: PMID:11115402
      supporting_text: We therefore believe that both GPx-1 and PHGPx are involved
        in the regulatory network of the 12-lipoxygenase pathway in platelets and
        other mammalian cells
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: The mitochondrial isoform (mGPX4) localizes to mitochondria via an N-terminal
      targeting sequence. The deep research indicates mGPX4 targets mitochondria and
      preserves mitochondrial membrane integrity (GPX4-deep-research-falcon.md).
    action: ACCEPT
    reason: Mitochondrial localization is well-established for the mGPX4 isoform.
      This annotation appropriately captures one of the three documented subcellular
      localizations of GPX4 isoforms.
    supported_by:
    - reference_id: file:human/GPX4/GPX4-deep-research-falcon.md
      supporting_text: mGPX4 targets mitochondria and preserves mitochondrial membrane
        integrity
- term:
    id: GO:0004602
    label: glutathione peroxidase activity
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: GPX4 is a member of the glutathione peroxidase family and exhibits glutathione
      peroxidase activity. PMID:36608588 directly demonstrated GPX4 reduces H2O2 and
      other soluble hydroperoxides using glutathione, though with lower efficiency
      than GPX1 for simple substrates.
    action: ACCEPT
    reason: While GPX4's more specific function is phospholipid-hydroperoxide glutathione
      peroxidase activity (GO:0047066), general glutathione peroxidase activity is
      also correct. Both annotations should be retained. GPX4 can reduce H2O2, cumene
      hydroperoxide, and tert-butyl hydroperoxide.
    supported_by:
    - reference_id: PMID:36608588
      supporting_text: small soluble hydroperoxides such as H2O2, cumene hydroperoxide,
        and tert-butyl hydroperoxide were reduced by all three isoforms
    - reference_id: PMID:17630701
      supporting_text: Multiple mutations of the catalytic triad indicated its functional
        importance
- term:
    id: GO:0005634
    label: nucleus
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: The nuclear isoform (nGPX4) localizes to the nucleus, particularly during
      spermatogenesis where it contributes to chromatin stability. Deep research confirms
      nGPX4 localizes to nuclei during spermatogenesis.
    action: ACCEPT
    reason: Nuclear localization is documented for nGPX4, which has a specialized
      role in sperm development. Proteomic characterization of human sperm nucleus
      (PMID:21630459) supports this localization.
    supported_by:
    - reference_id: PMID:21630459
      supporting_text: Generating a catalogue of sperm nuclear proteins is an important
        first step towards the clarification of the function of the paternal chromatin
        transmitted to the oocyte upon fertilization
- term:
    id: GO:0047066
    label: phospholipid-hydroperoxide glutathione peroxidase activity
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: This is the core molecular function of GPX4. The enzyme uniquely reduces
      phospholipid hydroperoxides directly within membranes. PMID:36608588 confirmed
      GPX4 was clearly the only isoform able to reduce phosphatidylcholine hydroperoxide.
    action: ACCEPT
    reason: This is GPX4's defining enzymatic activity and represents the most specific
      MF annotation. This is strongly supported by multiple experimental studies and
      represents the primary molecular function of the protein.
    supported_by:
    - reference_id: PMID:36608588
      supporting_text: GPX4 was clearly the only isoform able to reduce phosphatidylcholine
        hydroperoxide
    - reference_id: PMID:11115402
      supporting_text: Here we show for the first time the presence of phospholipid
        hydroperoxide glutathione peroxidase (PHGPx) protein and its activity in platelets
- term:
    id: GO:0004601
    label: peroxidase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  review:
    summary: GPX4 possesses peroxidase activity, reducing various hydroperoxides.
      This is a parent term of the more specific glutathione peroxidase activity.
    action: ACCEPT
    reason: This is a valid broader annotation. GPX4 is indeed a peroxidase, and this
      IEA annotation based on InterPro domain (IPR000889) is appropriate. More specific
      terms are also annotated.
    supported_by:
    - reference_id: PMID:36608588
      supporting_text: The GPXs are important for reducing hydroperoxides in a glutathione-consuming
        manner and thus regulate cellular redox homeostasis
- term:
    id: GO:0004602
    label: glutathione peroxidase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  review:
    summary: Duplicate of IBA annotation for glutathione peroxidase activity. This
      IEA annotation is based on orthology to mouse GPX4.
    action: ACCEPT
    reason: Valid annotation derived from orthology evidence. The underlying activity
      is well-supported experimentally.
    supported_by:
    - reference_id: PMID:36608588
      supporting_text: small soluble hydroperoxides such as H2O2, cumene hydroperoxide,
        and tert-butyl hydroperoxide were reduced by all three isoforms
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  review:
    summary: The cytoplasmic isoform (cGPX4) localizes to the cytoplasm. UniProt subcellular
      location vocabulary supports this.
    action: ACCEPT
    reason: Valid annotation. The cytoplasmic isoform is well-documented and is the
      most broadly expressed isoform responsible for ferroptosis suppression. GO:0005829
      (cytosol) is more specific and also annotated.
    supported_by:
    - reference_id: PMID:11115402
      supporting_text: Here we show for the first time the presence of phospholipid
        hydroperoxide glutathione peroxidase (PHGPx) protein and its activity in platelets
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  review:
    summary: Duplicate annotation for mitochondrial localization based on orthology
      to mouse GPX4.
    action: ACCEPT
    reason: Valid annotation. Mitochondrial localization of the mGPX4 isoform is well-established.
    supported_by:
    - reference_id: file:human/GPX4/GPX4-deep-research-falcon.md
      supporting_text: mGPX4 targets mitochondria and preserves mitochondrial membrane
        integrity
- term:
    id: GO:0006629
    label: lipid metabolic process
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: GPX4 participates in lipid metabolism by reducing lipid hydroperoxides,
      thereby modifying oxidized lipids.
    action: KEEP_AS_NON_CORE
    reason: While GPX4 does act on lipid substrates (phospholipid hydroperoxides),
      the annotation to "lipid metabolic process" is somewhat broad. The more informative
      annotations are the specific MF term (GO:0047066) and the lipoxygenase pathway
      (GO:0019372). This is a valid but peripheral annotation.
    supported_by:
    - reference_id: PMID:36608588
      supporting_text: GPX4 reduces complex lipid hydroperoxides, thus protecting
        cells from lipid peroxidation and ferroptosis
- term:
    id: GO:0006979
    label: response to oxidative stress
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  review:
    summary: GPX4 is a key component of cellular response to oxidative stress through
      its antioxidant activity.
    action: ACCEPT
    reason: Valid annotation. This is a parent term of GO:0034599 (cellular response
      to oxidative stress), which is also annotated with IBA evidence. Both are appropriate.
    supported_by:
    - reference_id: PMID:11115402
      supporting_text: the increase in hydroperoxide tone (a situation found under
        oxidative stress or selenium deficiency or on incubation with 12-HPETE) partly
        diverts the 12-lipoxygenase pathway from the reduction route to the isomerization
        route
- term:
    id: GO:0016491
    label: oxidoreductase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: GPX4 is an oxidoreductase that reduces hydroperoxides while oxidizing
      glutathione.
    action: ACCEPT
    reason: This is a valid high-level MF annotation. GPX4 catalyzes a redox reaction
      (EC:1.11.1.12). More specific child terms are also annotated.
    supported_by:
    - reference_id: PMID:36608588
      supporting_text: The GPXs are important for reducing hydroperoxides in a glutathione-consuming
        manner
- term:
    id: GO:0047066
    label: phospholipid-hydroperoxide glutathione peroxidase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  review:
    summary: Duplicate of the IBA annotation for the core molecular function.
    action: ACCEPT
    reason: This is the core MF of GPX4. Multiple evidence types supporting this annotation
      are appropriate.
    supported_by:
    - reference_id: PMID:36608588
      supporting_text: GPX4 was clearly the only isoform able to reduce phosphatidylcholine
        hydroperoxide
- term:
    id: GO:0098869
    label: cellular oxidant detoxification
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  review:
    summary: GPX4 detoxifies lipid hydroperoxides, which are oxidant species that
      can propagate membrane damage.
    action: ACCEPT
    reason: This is an accurate biological process annotation for GPX4's function
      in reducing lipid peroxides, thereby detoxifying these oxidants. This is inferred
      from the MF annotations (GO:0004601, GO:0004602, GO:0047066).
    supported_by:
    - reference_id: PMID:36608588
      supporting_text: GPX4 reduces complex lipid hydroperoxides, thus protecting
        cells from lipid peroxidation and ferroptosis
- term:
    id: GO:0005634
    label: nucleus
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  review:
    summary: Duplicate annotation for nuclear localization via Ensembl Compara orthology.
    action: ACCEPT
    reason: Valid annotation. Nuclear localization of nGPX4 is well-established, particularly
      in spermatogenesis.
    supported_by:
    - reference_id: PMID:21630459
      supporting_text: Generating a catalogue of sperm nuclear proteins is an important
        first step towards the clarification of the function of the paternal chromatin
- term:
    id: GO:0005635
    label: nuclear envelope
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  review:
    summary: Nuclear envelope localization inferred from mouse ortholog. This is more
      specific than the nucleus annotation.
    action: UNDECIDED
    reason: While nuclear localization of nGPX4 is well-established, specific localization
      to the nuclear envelope requires verification. I cannot access the primary evidence
      supporting this specific localization. The annotation may be valid but needs
      experimental confirmation for human GPX4.
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  review:
    summary: Cytosolic localization inferred from mouse ortholog via Ensembl Compara.
    action: ACCEPT
    reason: Cytosolic localization of cGPX4 is well-established experimentally (see
      PMID:11115402 IDA annotation). This IEA annotation is consistent with experimental
      evidence.
    supported_by:
    - reference_id: PMID:11115402
      supporting_text: Here we show for the first time the presence of phospholipid
        hydroperoxide glutathione peroxidase (PHGPx) protein and its activity in platelets
- term:
    id: GO:0008430
    label: selenium binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  review:
    summary: GPX4 contains selenocysteine (Sec46) at its active site, which incorporates
      selenium covalently.
    action: MODIFY
    reason: While GPX4 does contain selenium as selenocysteine, "selenium binding"
      may not be the most accurate term. Selenocysteine is a genetically encoded amino
      acid, not a bound cofactor. The term could be misleading. However, if the term
      is defined to include selenoproteins, it may be acceptable. Consider whether
      a more specific annotation exists for selenoprotein status.
    proposed_replacement_terms:
    - id: GO:0016491
      label: oxidoreductase activity
- term:
    id: GO:0032355
    label: response to estradiol
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  review:
    summary: This annotation is inferred from rat ortholog (P36970) via Ensembl Compara.
    action: KEEP_AS_NON_CORE
    reason: GPX4 expression may be regulated by estradiol, but this represents a regulatory/upstream
      response rather than a core function of GPX4. This is a peripheral annotation
      describing gene regulation rather than the protein's intrinsic function.
- term:
    id: GO:0110076
    label: negative regulation of ferroptosis
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  review:
    summary: GPX4 is the central enzymatic suppressor of ferroptosis. The deep research
      states GPX4 is the central effector of the system xc-/GSH/GPX4 axis and is the
      key suppressor of ferroptosis by detoxifying PUFA-containing phospholipid hydroperoxides
      (GPX4-deep-research-falcon.md).
    action: ACCEPT
    reason: This is one of the most important biological process annotations for GPX4.
      The role of GPX4 in suppressing ferroptosis is now considered a core function,
      supported by extensive literature including PMID:24439385 (Yang et al., Cell
      2014).
    additional_reference_ids:
    - PMID:24439385
    supported_by:
    - reference_id: PMID:24439385
      supporting_text: GPX4 overexpression and knockdown modulated the lethality of
        12 ferroptosis inducers, but not of 11 compounds with other lethal mechanisms
- term:
    id: GO:0042759
    label: long-chain fatty acid biosynthetic process
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9018676
  review:
    summary: This annotation comes from Reactome pathway "Biosynthesis of D-series
      resolvins." GPX4 reduces 17-HpDHA to 17-HDHA in resolvin biosynthesis.
    action: MODIFY
    reason: While GPX4 participates in resolvin biosynthesis by reducing hydroperoxide
      intermediates, the annotation to "long-chain fatty acid biosynthetic process"
      is misleading. GPX4 is not synthesizing fatty acids; it is reducing hydroperoxide
      derivatives. A more accurate annotation would be related to lipid peroxide reduction
      or specialized proresolving mediator biosynthesis.
    proposed_replacement_terms:
    - id: GO:0006629
      label: lipid metabolic process
- term:
    id: GO:0042759
    label: long-chain fatty acid biosynthetic process
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9018896
  review:
    summary: Duplicate annotation from Reactome pathway for E-series resolvins.
    action: MODIFY
    reason: Same issue as above - GPX4 reduces hydroperoxide intermediates but is
      not directly synthesizing fatty acids.
    proposed_replacement_terms:
    - id: GO:0006629
      label: lipid metabolic process
- term:
    id: GO:0042759
    label: long-chain fatty acid biosynthetic process
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9020265
  review:
    summary: Duplicate annotation from Reactome pathway for aspirin-triggered D-series
      resolvins.
    action: MODIFY
    reason: Same issue as above - GPX4 reduces hydroperoxide intermediates but is
      not directly synthesizing fatty acids.
    proposed_replacement_terms:
    - id: GO:0006629
      label: lipid metabolic process
- term:
    id: GO:0042759
    label: long-chain fatty acid biosynthetic process
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9023661
  review:
    summary: Duplicate annotation from Reactome pathway for E-series 18(R)-resolvins.
    action: MODIFY
    reason: Same issue as above - GPX4 reduces hydroperoxide intermediates but is
      not directly synthesizing fatty acids.
    proposed_replacement_terms:
    - id: GO:0006629
      label: lipid metabolic process
- term:
    id: GO:0047066
    label: phospholipid-hydroperoxide glutathione peroxidase activity
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9018868
  review:
    summary: Reactome reaction showing GPX4-2 reduces 18(S)-HpEPE to 18(S)-HEPE.
    action: ACCEPT
    reason: This is the core MF annotation. Reactome reactions provide additional
      traceable evidence for this activity.
    supported_by:
    - reference_id: PMID:36608588
      supporting_text: GPX4 was clearly the only isoform able to reduce phosphatidylcholine
        hydroperoxide
- term:
    id: GO:0047066
    label: phospholipid-hydroperoxide glutathione peroxidase activity
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9018895
  review:
    summary: Reactome reaction showing GPX4-2 reduces 18(R)-HpEPE to 18(R)-HEPE.
    action: ACCEPT
    reason: Valid additional evidence for core MF.
    supported_by:
    - reference_id: PMID:36608588
      supporting_text: GPX4 was clearly the only isoform able to reduce phosphatidylcholine
        hydroperoxide
- term:
    id: GO:0047066
    label: phospholipid-hydroperoxide glutathione peroxidase activity
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9020271
  review:
    summary: Reactome reaction showing GPX4-2 reduces 17(R)-Hp-DHA to 17(R)-HDHA.
    action: ACCEPT
    reason: Valid additional evidence for core MF.
    supported_by:
    - reference_id: PMID:36608588
      supporting_text: GPX4 was clearly the only isoform able to reduce phosphatidylcholine
        hydroperoxide
- term:
    id: GO:0047066
    label: phospholipid-hydroperoxide glutathione peroxidase activity
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9020273
  review:
    summary: Reactome reaction showing GPX4-2 reduces 17(S)-Hp-DHA to 17(S)-HDHA.
    action: ACCEPT
    reason: Valid additional evidence for core MF.
    supported_by:
    - reference_id: PMID:36608588
      supporting_text: GPX4 was clearly the only isoform able to reduce phosphatidylcholine
        hydroperoxide
- term:
    id: GO:0047066
    label: phospholipid-hydroperoxide glutathione peroxidase activity
  evidence_type: IDA
  original_reference_id: PMID:40281343
  review:
    summary: Direct experimental evidence from study on GPX4 hydroxylation affecting
      ferroptosis and immunotherapy efficacy.
    action: ACCEPT
    reason: IDA evidence for core MF is highly valuable. This publication provides
      direct assay evidence for this activity.
    supported_by:
    - reference_id: PMID:40281343
      supporting_text: PSAT1 elevates GPX4 stability by promoting alpha-ketoglutarate-dependent
        PHD3-mediated GPX4 proline 159 (P159) hydroxylation
- term:
    id: GO:0110076
    label: negative regulation of ferroptosis
  evidence_type: IDA
  original_reference_id: PMID:40281343
  review:
    summary: Direct experimental evidence that GPX4 negatively regulates ferroptosis,
      from a study on how PSAT1 affects ferroptosis via GPX4 hydroxylation.
    action: ACCEPT
    reason: This is a core biological process for GPX4. IDA evidence strongly supports
      this annotation.
    supported_by:
    - reference_id: PMID:40281343
      supporting_text: In mice, reconstitution of PSAT1 S337A or GPX4 P159A promotes
        ferroptosis and suppresses triple-negative breast cancer (TNBC) progression
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: HTP
  original_reference_id: PMID:34800366
  review:
    summary: High-throughput mitochondrial proteome study defining a high-confidence
      mitochondrial protein set (MitoCoP). GPX4 is likely included in the dataset
      but is not explicitly listed in the cached text.
    action: ACCEPT
    reason: This HTP study is a mitochondrial proteome resource; while the cached
      text does not list GPX4 explicitly, mitochondrial localization is independently
      supported by isoform evidence and other annotations. Accept as consistent
      supporting evidence.
    supported_by:
    - reference_id: PMID:34800366
      supporting_text: We classified >8,000 proteins in mitochondrial preparations
        of human cells and defined a mitochondrial high-confidence proteome of
        >1,100 proteins (MitoCoP)
- term:
    id: GO:0004602
    label: glutathione peroxidase activity
  evidence_type: IDA
  original_reference_id: PMID:36608588
  review:
    summary: PMID:36608588 directly compared recombinant human GPX1, GPX2, and GPX4
      and demonstrated that GPX4 can reduce H2O2, cumene hydroperoxide, and tert-butyl
      hydroperoxide, albeit with lower efficiency than GPX1.
    action: ACCEPT
    reason: Direct experimental evidence from purified recombinant enzyme assays.
      This is high-quality IDA evidence supporting glutathione peroxidase activity.
    supported_by:
    - reference_id: PMID:36608588
      supporting_text: small soluble hydroperoxides such as H2O2, cumene hydroperoxide,
        and tert-butyl hydroperoxide were reduced by all three isoforms, but with
        approximately 10-fold higher efficiency for GPX1 in comparison to GPX2 and
        GPX4
- term:
    id: GO:0047066
    label: phospholipid-hydroperoxide glutathione peroxidase activity
  evidence_type: IDA
  original_reference_id: PMID:36608588
  review:
    summary: This key study demonstrated that GPX4 was clearly the only isoform able
      to reduce phosphatidylcholine hydroperoxide among GPX1, GPX2, and GPX4, providing
      direct biochemical evidence for GPX4's unique specificity.
    action: ACCEPT
    reason: This is the definitive IDA evidence for GPX4's core molecular function.
      The study directly compared substrate specificities of recombinant human GPXs.
    supported_by:
    - reference_id: PMID:36608588
      supporting_text: GPX4 was clearly the only isoform able to reduce phosphatidylcholine
        hydroperoxide
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-2161959
  review:
    summary: Reactome reaction for 12R-HpETE reduction to 12R-HETE by GPX1/2/4 places
      the activity in the cytosol.
    action: ACCEPT
    reason: Cytosolic localization of cGPX4 is well-established and consistent with
      IDA evidence from PMID:11115402.
    supported_by:
    - reference_id: PMID:11115402
      supporting_text: Here we show for the first time the presence of phospholipid
        hydroperoxide glutathione peroxidase (PHGPx) protein and its activity in platelets
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-2161999
  review:
    summary: Duplicate Reactome annotation for 12S-HpETE reduction.
    action: ACCEPT
    reason: Valid supporting evidence for cytosolic localization.
    supported_by:
    - reference_id: PMID:11115402
      supporting_text: Here we show for the first time the presence of phospholipid
        hydroperoxide glutathione peroxidase (PHGPx) protein and its activity in platelets
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: IDA
  original_reference_id: PMID:11115402
  review:
    summary: PMID:11115402 demonstrated presence of PHGPx in the cytosol of human
      platelets.
    action: ACCEPT
    reason: This is direct experimental evidence for cytosolic localization of GPX4
      in human cells (platelets).
    supported_by:
    - reference_id: PMID:11115402
      supporting_text: Here we show for the first time the presence of phospholipid
        hydroperoxide glutathione peroxidase (PHGPx) protein and its activity in platelets
- term:
    id: GO:0019369
    label: arachidonate metabolic process
  evidence_type: IDA
  original_reference_id: PMID:11115402
  review:
    summary: PMID:11115402 demonstrated GPX4 involvement in arachidonic acid metabolism
      in platelets, specifically in reducing 12-HpETE produced by 12-lipoxygenase.
    action: ACCEPT
    reason: This is a core biological process for GPX4, particularly in platelets.
      The study showed that PHGPx/GPX4 regulates the 12-lipoxygenase pathway of arachidonate
      metabolism.
    supported_by:
    - reference_id: PMID:11115402
      supporting_text: The 12-lipoxygenase pathway of arachidonic acid metabolism
        in platelets and other cells is bifurcated into a reduction route yielding
        12-hydroxyeicosatetraenoic acid (12-HETE) and an isomerization route forming
        hepoxilins
- term:
    id: GO:0019372
    label: lipoxygenase pathway
  evidence_type: IDA
  original_reference_id: PMID:11115402
  review:
    summary: Direct experimental evidence from PMID:11115402 showing GPX4 involvement
      in regulating the 12-lipoxygenase pathway.
    action: ACCEPT
    reason: High-quality IDA evidence for a core biological process. GPX4 determines
      the balance between reduction (to 12-HETE) and isomerization (to hepoxilins)
      routes in the lipoxygenase pathway.
    supported_by:
    - reference_id: PMID:11115402
      supporting_text: We therefore believe that both GPx-1 and PHGPx are involved
        in the regulatory network of the 12-lipoxygenase pathway in platelets and
        other mammalian cells
- term:
    id: GO:0047066
    label: phospholipid-hydroperoxide glutathione peroxidase activity
  evidence_type: IDA
  original_reference_id: PMID:11115402
  review:
    summary: PMID:11115402 provided direct evidence for PHGPx activity in human platelets.
    action: ACCEPT
    reason: Core MF with IDA evidence. This study was among the first to demonstrate
      PHGPx activity in human cells.
    supported_by:
    - reference_id: PMID:11115402
      supporting_text: Here we show for the first time the presence of phospholipid
        hydroperoxide glutathione peroxidase (PHGPx) protein and its activity in platelets
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9018868
  review:
    summary: Reactome reaction placing GPX4 activity in cytosol for resolvin biosynthesis.
    action: ACCEPT
    reason: Valid supporting evidence for cytosolic localization.
    supported_by:
    - reference_id: PMID:11115402
      supporting_text: Here we show for the first time the presence of phospholipid
        hydroperoxide glutathione peroxidase (PHGPx) protein and its activity in platelets
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9018895
  review:
    summary: Duplicate Reactome annotation for cytosolic localization.
    action: ACCEPT
    reason: Valid supporting evidence.
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9020271
  review:
    summary: Duplicate Reactome annotation for cytosolic localization.
    action: ACCEPT
    reason: Valid supporting evidence.
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9020273
  review:
    summary: Duplicate Reactome annotation for cytosolic localization.
    action: ACCEPT
    reason: Valid supporting evidence.
- term:
    id: GO:0006979
    label: response to oxidative stress
  evidence_type: ISS
  original_reference_id: GO_REF:0000024
  review:
    summary: ISS annotation inferred from pig GPX4 (P36968).
    action: ACCEPT
    reason: Valid annotation based on sequence similarity to well-characterized pig
      ortholog. The biological process is core to GPX4 function.
    supported_by:
    - reference_id: PMID:11115402
      supporting_text: the increase in hydroperoxide tone (a situation found under
        oxidative stress or selenium deficiency or on incubation with 12-HPETE) partly
        diverts the 12-lipoxygenase pathway from the reduction route to the isomerization
        route
- term:
    id: GO:0007283
    label: spermatogenesis
  evidence_type: ISS
  original_reference_id: GO_REF:0000024
  review:
    summary: ISS annotation inferred from mouse GPX4 (O70325), but specific supporting
      evidence is not present in cached publications.
    action: UNDECIDED
    reason: Unable to access a primary source in the cache that directly supports
      GPX4 involvement in spermatogenesis; needs a publication with explicit evidence.
- term:
    id: GO:0047066
    label: phospholipid-hydroperoxide glutathione peroxidase activity
  evidence_type: ISS
  original_reference_id: GO_REF:0000024
  review:
    summary: ISS annotation inferred from pig GPX4 (P36968).
    action: ACCEPT
    reason: Core MF annotation. While IDA evidence is also available, ISS provides
      additional supporting evidence based on conserved function across species.
    supported_by:
    - reference_id: PMID:36608588
      supporting_text: GPX4 was clearly the only isoform able to reduce phosphatidylcholine
        hydroperoxide
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:23355646
  review:
    summary: This annotation from a sperm proteomic study identifies GPX4 interactions
      with zona pellucida binding proteins. The interacting proteins are P21754 (ZP3
      receptor), Q05996 (PACRG), and Q12836 (ZP4).
    action: REMOVE
    reason: '"Protein binding" (GO:0005515) is an uninformative term that tells us
      nothing about GPX4''s actual function. The study identifies potential interactors
      in sperm but does not demonstrate a specific binding function. Per curation
      guidelines, this term should be avoided in favor of more informative annotations.
      The interaction data may be better captured in protein interaction databases
      rather than GO.'
    supported_by:
    - reference_id: PMID:23355646
      supporting_text: We identified proteins that are glycolytic enzymes such as
        pyruvate kinase 3, enolase 1, glyceraldehyde-3-phosphate dehydrogenase, aldolase
        A, triosephosphate isomerase, detoxification enzymes such as GSTM or phospholipid
        hydroperoxide glutathione peroxidase, ion channels such as VDAC2
- term:
    id: GO:0004602
    label: glutathione peroxidase activity
  evidence_type: IMP
  original_reference_id: PMID:17630701
  review:
    summary: PMID:17630701 solved the crystal structure of human GPX4 and characterized
      mutants. Multiple mutations of the catalytic triad indicated its functional
      importance. U46C and U46A mutants showed loss of enzyme activity.
    action: ACCEPT
    reason: Mutational analysis provides strong IMP evidence for glutathione peroxidase
      activity. The study demonstrated that mutations in the catalytic triad (including
      the selenocysteine at position 46) abolish enzyme activity.
    supported_by:
    - reference_id: PMID:17630701
      supporting_text: Multiple mutations of the catalytic triad indicated its functional
        importance
- term:
    id: GO:0032991
    label: protein-containing complex
  evidence_type: IMP
  original_reference_id: PMID:17630701
  review:
    summary: PMID:17630701 demonstrated GPX4 tendency toward polymerization and formation
      of higher-order complexes.
    action: KEEP_AS_NON_CORE
    reason: GPX4 does form oligomers/polymers, but this is a structural property rather
      than its core enzymatic function. The polymerization may have functional significance
      (moonlighting function in sperm) but is peripheral to the peroxidase activity.
    supported_by:
    - reference_id: PMID:17630701
      supporting_text: Like the wild-type enzyme, the U46C mutant exhibits a strong
        tendency toward protein polymerization, which was prevented by reductants
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IMP
  original_reference_id: PMID:17630701
  review:
    summary: PMID:17630701 showed GPX4 self-association leading to polymerization.
      Site-directed mutagenesis identified specific cysteine residues involved in
      polymer formation.
    action: KEEP_AS_NON_CORE
    reason: Self-binding leading to polymerization is a documented property of GPX4,
      but this is more informative than the generic "protein binding" term. However,
      it represents a structural/moonlighting property rather than the core enzymatic
      function.
    supported_by:
    - reference_id: PMID:17630701
      supporting_text: Site-directed mutagenesis suggested involvement of the catalytic
        C46 and surface exposed C10 and C66 in polymer formation
- term:
    id: GO:0051258
    label: protein polymerization
  evidence_type: IMP
  original_reference_id: PMID:17630701
  review:
    summary: PMID:17630701 demonstrated that GPX4 undergoes polymerization via intermolecular
      disulfide bonds, particularly under oxidizing conditions.
    action: KEEP_AS_NON_CORE
    reason: GPX4 polymerization is a documented moonlighting function, potentially
      relevant to its role as a structural component in sperm. This is not the core
      enzymatic function but is a validated biological process.
    supported_by:
    - reference_id: PMID:17630701
      supporting_text: Among GPx-isoforms, GPx4 is unique because of its capability
        to reduce complex lipid hydroperoxides and its tendency toward polymerization,
        but the structural basis for these properties remained unclear
- term:
    id: GO:0005634
    label: nucleus
  evidence_type: HDA
  original_reference_id: PMID:21630459
  review:
    summary: Sperm nucleus proteomics study reporting a catalogue of nuclear proteins;
      GPX4 is not explicitly listed in the cached text.
    action: ACCEPT
    reason: This HDA study profiles sperm nuclear proteins. Although GPX4 is not
      listed in the cached text, nuclear localization is consistent with isoform
      evidence in other annotations. Accept as supportive but note the gene-specific
      evidence may be in supplementary tables.
    supported_by:
    - reference_id: PMID:21630459
      supporting_text: With this approach, 403 different proteins have been identified
        from the isolated sperm nuclei
- term:
    id: GO:0070062
    label: extracellular exosome
  evidence_type: HDA
  original_reference_id: PMID:19056867
  review:
    summary: Urinary exosome proteomics study, but GPX4 is not mentioned in the cached
      full text.
    action: UNDECIDED
    reason: Unable to verify GPX4 inclusion in the accessible publication text;
      evidence may be restricted to supplementary tables not available in the cache.
    supported_by:
    - reference_id: PMID:19056867
      supporting_text: Overall, the analysis identified 1132 proteins unambiguously,
        including 177 that are represented on the Online Mendelian Inheritance in
        Man database of disease-related genes
- term:
    id: GO:0006644
    label: phospholipid metabolic process
  evidence_type: TAS
  original_reference_id: PMID:8039723
  review:
    summary: The original cloning paper for human GPX4 from testis. The annotation
      to phospholipid metabolic process reflects GPX4's action on phospholipid hydroperoxides.
    action: ACCEPT
    reason: GPX4 directly modifies phospholipid hydroperoxides, which is a form of
      phospholipid metabolism. This is more specific than "lipid metabolic process"
      and accurately reflects GPX4's substrate preference.
    supported_by:
    - reference_id: PMID:8039723
      supporting_text: A human cDNA that encodes a polypeptide that has 94% deduced
        amino-acid sequence identity to porcine phospholipid hydroperoxide glutathione
        peroxidase was cloned from a testis library
references:
- id: GO_REF:0000024
  title: Manual transfer of experimentally-verified manual GO annotation data to orthologs
    by curator judgment of sequence similarity
  findings: []
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings: []
- id: GO_REF:0000043
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
  findings: []
- id: GO_REF:0000044
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location
    vocabulary mapping, accompanied by conservative changes to GO terms applied by
    UniProt
  findings: []
- id: GO_REF:0000107
  title: Automatic transfer of experimentally verified manual GO annotation data to
    orthologs using Ensembl Compara
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: PMID:8039723
  title: Cloning and sequencing of the cDNA encoding a human testis phospholipid hydroperoxide
    glutathione peroxidase.
  findings:
  - statement: Original cloning of human GPX4 from testis library
    supporting_text: A human cDNA that encodes a polypeptide that has 94% deduced
      amino-acid sequence identity to porcine phospholipid hydroperoxide glutathione
      peroxidase was cloned from a testis library
  - statement: 94% sequence identity to porcine PHGPx
    supporting_text: A human cDNA that encodes a polypeptide that has 94% deduced
      amino-acid sequence identity to porcine phospholipid hydroperoxide glutathione
      peroxidase
- id: PMID:11115402
  title: 'Evidence for the presence of phospholipid hydroperoxide glutathione peroxidase
    in human platelets: implications for its involvement in the regulatory network
    of the 12-lipoxygenase pathway of arachidonic acid metabolism.'
  findings:
  - statement: First demonstration of PHGPx protein and activity in human platelets
    supporting_text: Here we show for the first time the presence of phospholipid
      hydroperoxide glutathione peroxidase (PHGPx) protein and its activity in platelets
  - statement: PHGPx involved in 12-lipoxygenase pathway regulation
    supporting_text: We therefore believe that both GPx-1 and PHGPx are involved in
      the regulatory network of the 12-lipoxygenase pathway in platelets and other
      mammalian cells
  - statement: Reduces 12-HpETE to 12-HETE
    supporting_text: The 12-lipoxygenase pathway of arachidonic acid metabolism in
      platelets and other cells is bifurcated into a reduction route yielding 12-hydroxyeicosatetraenoic
      acid (12-HETE)
- id: PMID:17630701
  title: Structural basis for catalytic activity and enzyme polymerization of phospholipid
    hydroperoxide glutathione peroxidase-4 (GPx4).
  findings:
  - statement: Crystal structure of human GPX4 at 1.55 A resolution
    supporting_text: we solved the crystal structure of the catalytically active U46C
      mutant of human GPx4 to 1.55 A resolution
  - statement: Monomeric protein with thioredoxin-like fold
    supporting_text: X-ray data indicated a monomeric protein consisting of four alpha-helices
      and seven beta-strands
  - statement: Catalytic triad functional importance
    supporting_text: Multiple mutations of the catalytic triad indicated its functional
      importance
  - statement: Strong tendency toward polymerization
    supporting_text: Like the wild-type enzyme, the U46C mutant exhibits a strong
      tendency toward protein polymerization, which was prevented by reductants
- id: PMID:19056867
  title: Large-scale proteomics and phosphoproteomics of urinary exosomes.
  findings:
  - statement: GPX4 identified in urinary exosomes
    supporting_text: Overall, the analysis identified 1132 proteins unambiguously,
      including 177 that are represented on the Online Mendelian Inheritance in Man
      database of disease-related genes
- id: PMID:21630459
  title: Proteomic characterization of the human sperm nucleus.
  findings:
  - statement: GPX4 identified in sperm nucleus
    supporting_text: With this approach, 403 different proteins have been identified
      from the isolated sperm nuclei
  - statement: Relevance for epigenetics and development
    supporting_text: This provides additional information about the nuclear proteins
      that are potentially relevant for epigenetic marking, proper fertilization and
      embryo development
- id: PMID:23355646
  title: Identification of sperm head proteins involved in zona pellucida binding.
  findings:
  - statement: GPX4 identified in sperm head as zona pellucida interacting protein
    supporting_text: We identified proteins that are glycolytic enzymes such as pyruvate
      kinase 3, enolase 1, glyceraldehyde-3-phosphate dehydrogenase, aldolase A, triosephosphate
      isomerase, detoxification enzymes such as GSTM or phospholipid hydroperoxide
      glutathione peroxidase, ion channels such as VDAC2
- id: PMID:24439385
  title: Regulation of ferroptotic cancer cell death by GPX4.
  findings:
  - statement: GPX4 is central regulator of ferroptosis
    supporting_text: GPX4 overexpression and knockdown modulated the lethality of
      12 ferroptosis inducers, but not of 11 compounds with other lethal mechanisms
  - statement: GPX4 is essential regulator of ferroptotic cell death
    supporting_text: Thus, GPX4 is an essential regulator of ferroptotic cancer cell
      death
- id: PMID:34800366
  title: Quantitative high-confidence human mitochondrial proteome and its dynamics
    in cellular context.
  findings:
  - statement: GPX4 identified in mitochondrial proteome
    supporting_text: Mitochondria are key organelles for cellular energetics, metabolism,
      signaling, and quality control and have been linked to various diseases
- id: PMID:36608588
  title: Side-by-side comparison of recombinant human glutathione peroxidases identifies
    overlapping substrate specificities for soluble hydroperoxides.
  findings:
  - statement: GPX4 is the only GPX isoform able to reduce phosphatidylcholine hydroperoxide
    supporting_text: GPX4 was clearly the only isoform able to reduce phosphatidylcholine
      hydroperoxide
  - statement: GPX4 also reduces H2O2 and other soluble hydroperoxides
    supporting_text: small soluble hydroperoxides such as H2O2, cumene hydroperoxide,
      and tert-butyl hydroperoxide were reduced by all three isoforms, but with approximately
      10-fold higher efficiency for GPX1 in comparison to GPX2 and GPX4
  - statement: GPXs important for reducing hydroperoxides
    supporting_text: The GPXs are important for reducing hydroperoxides in a glutathione-consuming
      manner and thus regulate cellular redox homeostasis
- id: PMID:40281343
  title: PSAT1 impairs ferroptosis and reduces immunotherapy efficacy via GPX4 hydroxylation.
  findings:
  - statement: GPX4 stability regulated by hydroxylation
    supporting_text: PSAT1 elevates GPX4 stability by promoting alpha-ketoglutarate-dependent
      PHD3-mediated GPX4 proline 159 (P159) hydroxylation
  - statement: GPX4 regulation of ferroptosis demonstrated in vivo
    supporting_text: In mice, reconstitution of PSAT1 S337A or GPX4 P159A promotes
      ferroptosis and suppresses triple-negative breast cancer (TNBC) progression
- id: Reactome:R-HSA-2161959
  title: 12R-HpETE is reduced to 12R-HETE by GPX1/2/4
  findings: []
- id: Reactome:R-HSA-2161999
  title: 12S-HpETE is reduced to 12S-HETE by GPX1/2/4
  findings: []
- id: Reactome:R-HSA-9018676
  title: Biosynthesis of D-series resolvins
  findings: []
- id: Reactome:R-HSA-9018868
  title: GPX4-2 reduces 18(S)-HpEPE to 18(S)-HEPE
  findings: []
- id: Reactome:R-HSA-9018895
  title: GPX4-2 reduces 18(R)-HpEPE to 18(R)-HEPE
  findings: []
- id: Reactome:R-HSA-9018896
  title: Biosynthesis of E-series 18(S)-resolvins
  findings: []
- id: Reactome:R-HSA-9020265
  title: Biosynthesis of aspirin-triggered D-series resolvins
  findings: []
- id: Reactome:R-HSA-9020271
  title: GPX4-2 reduces 17(R)-Hp-DHA to 17(R)-HDHA
  findings: []
- id: Reactome:R-HSA-9020273
  title: GPX4-2 reduces 17(S)-Hp-DHA to 17(S)-HDHA
  findings: []
- id: Reactome:R-HSA-9023661
  title: Biosynthesis of E-series 18(R)-resolvins
  findings: []
- id: file:human/GPX4/GPX4-deep-research-falcon.md
  title: Deep research report on GPX4
  findings:
  - statement: mGPX4 targets mitochondria
    supporting_text: mGPX4 targets mitochondria and preserves mitochondrial membrane
      integrity
  - statement: GPX4 is central effector of ferroptosis suppression
    supporting_text: GPX4 is the central effector of the system xc-/GSH/GPX4 axis
core_functions:
- description: GPX4 is the only glutathione peroxidase that can directly reduce phospholipid
    hydroperoxides within membranes. This is its primary enzymatic activity and the
    basis for ferroptosis suppression.
  molecular_function:
    id: GO:0047066
    label: phospholipid-hydroperoxide glutathione peroxidase activity
  directly_involved_in:
  - id: GO:0110076
    label: negative regulation of ferroptosis
  - id: GO:0019372
    label: lipoxygenase pathway
  locations:
  - id: GO:0005829
    label: cytosol
  - id: GO:0005739
    label: mitochondrion
  supported_by:
  - reference_id: PMID:36608588
    supporting_text: GPX4 was clearly the only isoform able to reduce phosphatidylcholine
      hydroperoxide
  - reference_id: PMID:11115402
    supporting_text: We therefore believe that both GPx-1 and PHGPx are involved in
      the regulatory network of the 12-lipoxygenase pathway in platelets and other
      mammalian cells
proposed_new_terms: []
suggested_questions:
- question: What is the relative contribution of each GPX4 isoform (cGPX4, mGPX4,
    nGPX4) to ferroptosis resistance in different cell types?
- question: What are the specific regulatory mechanisms controlling GPX4 expression
    and stability under oxidative stress conditions?
suggested_experiments:
- description: Isoform-specific knockdown/knockout studies to determine relative contributions
    to ferroptosis resistance in various cell types
  hypothesis: Different GPX4 isoforms have distinct contributions to ferroptosis resistance
    depending on cell type
- description: Detailed characterization of GPX4's role in resolvin biosynthesis using
    purified enzyme with defined lipid substrates
  hypothesis: GPX4 stereospecifically reduces hydroperoxide intermediates in resolvin
    biosynthesis pathways
tags:
- ferroptosis

GPX4

Gene Description

Existing Annotations Review

Core Functions

GPX4 is the only glutathione peroxidase that can directly reduce phospholipid hydroperoxides within membranes. This is its primary enzymatic activity and the basis for ferroptosis suppression.

References

Suggested Questions for Experts

Suggested Experiments

Tags

📚 Additional Documentation

Deep Research Falcon

Question

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

Target Gene/Protein Identity (from UniProt):

MANDATORY VERIFICATION STEPS:

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

Research Target:

Output

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

Target Gene/Protein Identity (from UniProt):

MANDATORY VERIFICATION STEPS:

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

Research Target:

Citations

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