Gsta4 encodes rat glutathione S-transferase alpha-4 (GSTA4-4), an alpha-class cytosolic GST that conjugates reduced glutathione to hydrophobic electrophiles. Among the alpha-class paralogs (Gsta1/2/3/4), Gsta4 is functionally distinguished by its high catalytic efficiency toward lipid peroxidation-derived alpha,beta-unsaturated aldehydes, especially 4-hydroxynonenal (4-HNE), which it detoxifies by GSH conjugation (Michael addition). The review treats glutathione transferase activity and glutathione/xenobiotic metabolism as core or direct functions; stress-response and toxicant-response annotations are retained only as context from expression or perturbation studies. Note that much of the strongest mechanistic/kinetic and loss-of-function evidence derives from mouse Gsta4-null models, human GSTA4-4 enzyme assays, or unspecified GSTA4-4, not rat P14942 specifically; these are treated as orthology-based support rather than rat-specific facts.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004364 glutathione transferase activity | IBA GO_REF:0000033 | ACCEPT | Summary: Gsta4's glutathione conjugation of lipid peroxidation products and xenobiotic electrophiles supports retaining glutathione transferase activity as a direct annotation (IBA, GO_REF:0000033). Reason: glutathione transferase activity is a specific catalytic activity matching Gsta4's documented role in glutathione conjugation of lipid peroxidation products and xenobiotic electrophiles. Supporting Evidence: UniProtKB:P14942 GO; GO:0004364; F:glutathione transferase activity; ISO:RGD. file:rat/Gsta4/Gsta4-deep-research-falcon.md For 4-HNE and related substrates, GSTA4-4 forms glutathionylated adducts such as **GS-HNE/GS-NE**, supporting phase II detoxification and control of reactive aldehyde signaling. |
| GO:0006749 glutathione metabolic process | IBA GO_REF:0000033 | ACCEPT | Summary: Gsta4's glutathione conjugation of lipid peroxidation products and xenobiotic electrophiles supports retaining glutathione metabolic process as a direct annotation (IBA, GO_REF:0000033). Reason: glutathione metabolic process is a direct metabolic process expected from Gsta4's documented role in glutathione conjugation of lipid peroxidation products and xenobiotic electrophiles. Supporting Evidence: UniProtKB:P14942 GO; GO:0006749; P:glutathione metabolic process; ISO:RGD. file:rat/Gsta4/Gsta4-deep-research-falcon.md The best-supported biological role is **detoxification of reactive lipid aldehydes**, especially **4-HNE**, thereby limiting **protein carbonylation**, oxidative damage, and downstream stress signaling. |
| GO:0006805 xenobiotic metabolic process | IBA GO_REF:0000033 | ACCEPT | Summary: Gsta4's glutathione conjugation of lipid peroxidation products and xenobiotic electrophiles supports retaining xenobiotic metabolic process as a direct annotation (IBA, GO_REF:0000033). Reason: xenobiotic metabolic process is a direct metabolic process expected from Gsta4's documented role in glutathione conjugation of lipid peroxidation products and xenobiotic electrophiles. Supporting Evidence: UniProtKB:P14942 GO; GO:0006805; P:xenobiotic metabolic process; ISO:RGD. |
| GO:0004364 glutathione transferase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Gsta4's glutathione conjugation of lipid peroxidation products and xenobiotic electrophiles supports retaining glutathione transferase activity as a direct annotation (IEA, GO_REF:0000120). Reason: glutathione transferase activity is a specific catalytic activity matching Gsta4's documented role in glutathione conjugation of lipid peroxidation products and xenobiotic electrophiles. Supporting Evidence: UniProtKB:P14942 GO; GO:0004364; F:glutathione transferase activity; ISO:RGD. |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: cytoplasm is retained as useful context for Gsta4, but it is not the defining core function (IEA, GO_REF:0000044). Reason: cytoplasm records where Gsta4 has been observed, but localization does not define the gene product's primary activity. Supporting Evidence: UniProtKB:P14942 FUNCTION: Conjugation of reduced glutathione to a wide number of exogenous and endogenous hydrophobic electrophiles. file:rat/Gsta4/Gsta4-deep-research-falcon.md Although GSTs are classically described as **cytosolic**, GSTA4-4 has strong evidence for **mitochondrial association** |
| GO:0042802 identical protein binding | ISO GO_REF:0000121 | KEEP AS NON CORE | Summary: identical protein binding is retained as useful context for Gsta4, but it is not the defining core function (ISO, GO_REF:0000121). Reason: identical protein binding records substrate, cofactor, or quaternary-structure context for Gsta4, but the curated core function is glutathione conjugation of lipid peroxidation products and xenobiotic electrophiles. Supporting Evidence: UniProtKB:P14942 GO; GO:0042802; F:identical protein binding; ISO:RGD. |
| GO:0061771 response to caloric restriction | ISO GO_REF:0000121 | MARK AS OVER ANNOTATED | Summary: response to caloric restriction is treated as over-annotation because it reflects context or consequence rather than Gsta4's direct role (ISO, GO_REF:0000121). Reason: response to caloric restriction reflects exposure, expression, phenotype, or downstream pathway context rather than the direct Gsta4 role in glutathione conjugation of lipid peroxidation products and xenobiotic electrophiles. Propagation Review Root cause: PROPAGATION BAD Failure modes: CONTEXT OR TISSUE MISMATCH ROLE CONFLATION Sources checked: MGI:MGI:1309515 Β· mouse Gsta4 SUPPORTS SOURCE BUT NOT TARGET The mouse Gsta4 donor annotation records altered expression under caloric restriction; dietary regulation of the gene is not a glutathione-conjugation function of rat Gsta4. Supporting Evidence: UniProtKB:P14942 GO; GO:0061771; P:response to caloric restriction; ISO:RGD. |
| GO:0005739 mitochondrion | ISO GO_REF:0000121 | KEEP AS NON CORE | Summary: mitochondrion is retained as useful context for Gsta4, but it is not the defining core function (ISO, GO_REF:0000121). Falcon deep research indicates mitochondrial association is stress-inducible (phosphorylation/Hsp70-dependent import) rather than incidental, supporting a genuine but secondary compartment for protecting mitochondria from reactive lipid aldehydes. Reason: mitochondrion records a functionally relevant but secondary compartment for Gsta4 (stress-inducible mitochondrial targeting), and localization does not define the gene product's primary activity. Note the detailed import-mechanism evidence (Ser189/Thr193 phosphorylation, Hsp70) derives from reviews of GSTA4-4 generally, not rat P14942 specifically. Supporting Evidence: UniProtKB:P14942 GO; GO:0005739; C:mitochondrion; ISO:RGD. file:rat/Gsta4/Gsta4-deep-research-falcon.md mitochondrial targeting can be activated by phosphorylation (e.g., **Ser189/Thr193**) and involves enhanced Hsp70 interaction, enabling import competence and increasing mitochondrial localization under oxidative/electrophilic stress (including 4-HNE exposure). |
| GO:0005829 cytosol | ISO GO_REF:0000121 | KEEP AS NON CORE | Summary: cytosol is retained as useful context for Gsta4, but it is not the defining core function (ISO, GO_REF:0000121). Reason: cytosol records where Gsta4 has been observed, but localization does not define the gene product's primary activity. Supporting Evidence: UniProtKB:P14942 GO; GO:0005829; C:cytosol; ISO:RGD. file:rat/Gsta4/Gsta4-deep-research-falcon.md Functionally, GSTA4-4 is best known as a **cytosolic** GST, but multiple studies also support **mitochondrial localization**. |
| GO:0015643 toxic substance binding | IPI PMID:11018474 Characterization of 4-hydroxy-2-nonenal metabolism in stella... | MARK AS OVER ANNOTATED | Summary: toxic substance binding is treated as over-annotation because the IPI evidence (4-HNE/CHEBI:58968) captures H-site substrate binding within the catalytic cycle rather than an independent non-catalytic binding activity (IPI, PMID:11018474). Reason: The 4-HNE interaction supporting this IPI annotation is the H-site substrate-binding step of the glutathione-conjugation catalytic cycle, which is already fully captured by the ACCEPTED GO:0004364 glutathione transferase activity. The falcon evidence ("GSH conjugation (Michael addition) catalyzed predominantly by GSTA4-4") supports catalysis, not a standalone binding function, so toxic substance binding is redundant over-annotation rather than a distinct activity. Supporting Evidence: PMID:11018474 During oxidative stress, reactive aldehydes, including trans-4-hydroxy-2-nonenal (4-HNE), are generated by peroxidation of membrane lipids and purportedly stimulate hepatic stellate cells to produce excessive extracellular matrix, including type I collagen. file:rat/Gsta4/Gsta4-deep-research-falcon.md A major cellular clearance pathway is **GSH conjugation (Michael addition)** catalyzed predominantly by **GSTA4-4**. |
| GO:0009635 response to herbicide | IEP PMID:20553223 Effect of zinc and paraquat co-exposure on neurodegeneration... | MARK AS OVER ANNOTATED | Summary: response to herbicide is treated as over-annotation because it reflects context or consequence rather than Gsta4's direct role (IEP, PMID:20553223). Reason: response to herbicide reflects exposure, expression, phenotype, or downstream pathway context rather than the direct Gsta4 role in glutathione conjugation of lipid peroxidation products and xenobiotic electrophiles. Supporting Evidence: PMID:20553223 Oxidative stress is implicated in Parkinson's disease (PD). Metallothioneins (MT), cytochrome P450 IIE1 (CYP2E1) and glutathione S-transferases alpha4-4 (GSTA4-4) are involved in oxidative stress-mediated damage. |
| GO:0010043 response to zinc ion | IEP PMID:20553223 Effect of zinc and paraquat co-exposure on neurodegeneration... | MARK AS OVER ANNOTATED | Summary: response to zinc ion is treated as over-annotation because it reflects context or consequence rather than Gsta4's direct role (IEP, PMID:20553223). Reason: response to zinc ion reflects exposure, expression, phenotype, or downstream pathway context rather than the direct Gsta4 role in glutathione conjugation of lipid peroxidation products and xenobiotic electrophiles. It derives from the same zinc/paraquat co-exposure expression experiment (PMID:20553223, IEP) as response to herbicide, with no mechanistic evidence that zinc directly modulates GSTA4-4 activity, so it is harmonized with response to herbicide as over-annotation. Supporting Evidence: PMID:20553223 Oxidative stress is implicated in Parkinson's disease (PD). Metallothioneins (MT), cytochrome P450 IIE1 (CYP2E1) and glutathione S-transferases alpha4-4 (GSTA4-4) are involved in oxidative stress-mediated damage. |
| GO:0035094 response to nicotine | IEP PMID:9774145 Preferential effects of nicotine and 4-(N-methyl-N-nitrosami... | MARK AS OVER ANNOTATED | Summary: response to nicotine is treated as over-annotation because it reflects context or consequence rather than Gsta4's direct role (IEP, PMID:9774145). Reason: response to nicotine reflects exposure, expression, phenotype, or downstream pathway context rather than the direct Gsta4 role in glutathione conjugation of lipid peroxidation products and xenobiotic electrophiles. Supporting Evidence: PMID:9774145 We have investigated the in vivo effects of the tobacco-specific toxins nicotine and 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK) on antioxidant defense systems in the mitochondrial, microsomal, and cytosolic compartments of rat brain, lung, and liver. |
| GO:0071285 cellular response to lithium ion | IEP PMID:18082333 The effect of mood stabilizer lithium on expression and acti... | MARK AS OVER ANNOTATED | Summary: cellular response to lithium ion is treated as over-annotation because it reflects context or consequence rather than Gsta4's direct role (IEP, PMID:18082333). Reason: cellular response to lithium ion reflects exposure, expression, phenotype, or downstream pathway context rather than the direct Gsta4 role in glutathione conjugation of lipid peroxidation products and xenobiotic electrophiles. Supporting Evidence: PMID:18082333 Chronic treatment with the mood stabilizer lithium is required to generate its mood stabilizing effect in the treatment of bipolar disorder. |
| GO:0006749 glutathione metabolic process | ISO GO_REF:0000121 | ACCEPT | Summary: Gsta4's glutathione conjugation of lipid peroxidation products and xenobiotic electrophiles supports retaining glutathione metabolic process as a direct annotation (ISO, GO_REF:0000121). Reason: glutathione metabolic process is a direct metabolic process expected from Gsta4's documented role in glutathione conjugation of lipid peroxidation products and xenobiotic electrophiles. Supporting Evidence: UniProtKB:P14942 GO; GO:0006749; P:glutathione metabolic process; ISO:RGD. |
| GO:0006805 xenobiotic metabolic process | ISO GO_REF:0000121 | ACCEPT | Summary: Gsta4's glutathione conjugation of lipid peroxidation products and xenobiotic electrophiles supports retaining xenobiotic metabolic process as a direct annotation (ISO, GO_REF:0000121). Reason: xenobiotic metabolic process is a direct metabolic process expected from Gsta4's documented role in glutathione conjugation of lipid peroxidation products and xenobiotic electrophiles. Supporting Evidence: UniProtKB:P14942 GO; GO:0006805; P:xenobiotic metabolic process; ISO:RGD. |
| GO:0042803 protein homodimerization activity | ISO GO_REF:0000121 | KEEP AS NON CORE | Summary: protein homodimerization activity is retained as useful context for Gsta4, but it is not the defining core function (ISO, GO_REF:0000121). Reason: protein homodimerization activity records substrate, cofactor, or quaternary-structure context for Gsta4, but the curated core function is glutathione conjugation of lipid peroxidation products and xenobiotic electrophiles. Supporting Evidence: UniProtKB:P14942 GO; GO:0042803; F:protein homodimerization activity; ISO:RGD. |
| GO:0004364 glutathione transferase activity | ISO GO_REF:0000121 | ACCEPT | Summary: Gsta4's glutathione conjugation of lipid peroxidation products and xenobiotic electrophiles supports retaining glutathione transferase activity as a direct annotation (ISO, GO_REF:0000121). Reason: glutathione transferase activity is a specific catalytic activity matching Gsta4's documented role in glutathione conjugation of lipid peroxidation products and xenobiotic electrophiles. Supporting Evidence: UniProtKB:P14942 GO; GO:0004364; F:glutathione transferase activity; ISO:RGD. |
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Download this section (compressed HTML)Q: Falcon deep research highlights Scian et al. 2023 (Biomolecules, DOI:10.3390/biom13020329) showing GSTA4-4 catalyzes the retro-Michael reaction (GS-alkenal -> GSH + alkenal) with low commitment to forward catalysis, supporting a homeostatic/regulatory role in setting steady-state lipid alkenal pools rather than purely unidirectional detoxification. Does this reversibility/set-point framing warrant a new or modified BP annotation (e.g., capturing alkenal homeostasis or regulation of reactive lipid signaling) beyond the current detoxification/xenobiotic-metabolism terms?
Suggested experts: William M. Atkins
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