Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.5.1.18 (glutathione S-transferase)
 22,582 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Dimeric glutathione S-transferases (GSTs) are pharmacological targets for several diseases, including cancer. Isoform specificity has been difficult to achieve due to their overlapping substrate selectivity. Here we demonstrate the utility of bivalent GST inhibitors and their optimization via combinatorial linker design. A combinatorial library with dipeptide linkers emanating symmetrically from a central scaffold (bis-3,5-aminomethyl benzoic acid, AMAB) to connect two ethacrynic acid moieties was prepared and decoded via iterative deconvolution, against the isoforms GSTA1-1 and GSTP1-1. The library yielded high affinity GSTA1-1 selective inhibitors (70-120-fold selectivity) and with stoichiometry of one inhibitor: one GSTA1-1 dimer. Saturation Transfer Difference (STD) NMR with one of these inhibitors, with linker structure (Asp-Gly-AMAB-Gly-Asp) and K(D) = 42 nM for GSTA1-1, demonstrates that the Asp-Gly linker interacts tightly with GSTA1-1, but not P1-1. H/D exchange mass spectrometry was used to map the protein binding site and indicates that peptides within the intersubunit cleft and in the substrate binding site are protected by inhibitor from solvent exchange. A model is proposed for the binding orientation of the inhibitor, which is consistent with electrostatic complementarity between the protein cleft and inhibitor linker as the source of isoform selectivity and high affinity. The results demonstrate the utility of combinatorial, or "irrational", linker design for optimizing bivalent inhibitors.
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PMID:Optimization of bivalent glutathione S-transferase inhibitors by combinatorial linker design. 1680 28

The effect of GSTA1-1 (glutathione S-transferase Alpha 1-1) on JNK (c-Jun N-terminal kinase) activation was investigated in Caco-2 cells in which GSTA1 expression increases with degree of confluency, and in MEF3T3 cells with Tet-Off-inducible GSTA1 expression. Comparison of GSTA1 expression in pre-confluent, confluent and 8-day post-confluent Caco-2 cells revealed progressively increasing mRNA and protein levels at later stages of confluency. Exposure of pre-confluent cells to stress conditions including IL-1beta (interleukin-1beta), H2O2 or UV irradiation resulted in marked increases in JNK activity as indicated by c-Jun phosphorylation. However, JNK activation was significantly reduced in post-confluent cells exposed to the same stresses. Western-blot analysis of GSTA1-1 protein bound to JNK protein pulled down from cellular extracts showed approx. 4-fold higher GSTA1-1-JNK complex formation in post-confluent cells compared with pre-confluent cells. However, stress conditions did not alter the amount of GSTA1-1 bound to JNK. The role of GSTA1-1 in JNK suppression was more specifically revealed in Tet-Off-inducible MEF3T3-GSTA1-1 cells in which GSTA1 overexpression significantly reduced phosphorylation of c-Jun following exposure to IL-1beta, H2O2 and UV irradiation. Finally, the incidence of tumour necrosis factor alpha/butyrate-induced apoptosis was significantly higher in pre-confluent Caco-2 cells expressing low levels of GSTA1 compared with post-confluent cells. These results indicate that GSTA1 suppresses activation of JNK signalling by a pro-inflammatory cytokine and oxidative stress and suggests a protective role for GSTA1-1 in JNK-associated apoptosis.
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PMID:Human GSTA1-1 reduces c-Jun N-terminal kinase signalling and apoptosis in Caco-2 cells. 1683 88

The possible nuclear compartmentalization of glutathione S-transferase (GST) isoenzymes has been the subject of contradictory reports. The discovery that the dinitrosyl-diglutathionyl-iron complex binds tightly to Alpha class GSTs in rat hepatocytes and that a significant part of the bound complex is also associated with the nuclear fraction (Pedersen, J. Z., De Maria, F., Turella, P., Federici, G., Mattei, M., Fabrini, R., Dawood, K. F., Massimi, M., Caccuri, A. M., and Ricci, G. (2007) J. Biol. Chem. 282, 6364-6371) prompted us to reconsider the nuclear localization of GSTs in these cells. Surprisingly, we found that a considerable amount of GSTs corresponding to 10% of the cytosolic pool is electrostatically associated with the outer nuclear membrane, and a similar quantity is compartmentalized inside the nucleus. Mainly Alpha class GSTs, in particular GSTA1-1, GSTA2-2, and GSTA3-3, are involved in this double modality of interaction. Confocal microscopy, immunofluorescence experiments, and molecular modeling have been used to detail the electrostatic association in hepatocytes and liposomes. A quantitative analysis of the membrane-bound Alpha GSTs suggests the existence of a multilayer assembly of these enzymes at the outer nuclear envelope that could represent an amazing novelty in cell physiology. The interception of potentially noxious compounds to prevent DNA damage could be the possible physiological role of the perinuclear and intranuclear localization of Alpha GSTs.
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PMID:Electrostatic association of glutathione transferase to the nuclear membrane. Evidence of an enzyme defense barrier at the nuclear envelope. 1719 1

Human embryonic stem cells (hESCs) offer a potential unlimited source for functional human hepatocytes, since hESCs can differentiate into hepatocyte-like cells displaying a characteristic hepatic morphology and expressing several hepatic markers. These hepatocyte-like cells could be used in various human in vitro hepatocyte assays, e.g. as a test system for studying drug metabolism and drug-induced hepatotoxicity. Since the toxic effect of a compound is commonly dependent on biotransformation into metabolites, the presence of drug metabolising enzymes in potential test systems must be evaluated. We have investigated the presence of glutathione transferases (GSTs) in hepatocyte-like cells by immunocytochemistry and Western blotting. Results show that these cells have high levels of GSTA1-1, whereas GSTP1-1 is not present in most cases. GSTM1-1 is detected by immunocytochemistry but not by Western blotting. In addition, GST activity is detected in hepatocyte-like cells at levels comparable to human hepatocytes. These results indicate that the hepatocyte-like cells have characteristics that closely resemble those of human adult hepatocytes.
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PMID:Glutathione transferases in hepatocyte-like cells derived from human embryonic stem cells. 1734 23

The structurally related glutathione S-transferase isoforms GSTA1-1 and GSTA4-4 differ greatly in their relative catalytic promiscuity. GSTA1-1 is a highly promiscuous detoxification enzyme. In contrast, GSTA4-4 exhibits selectivity for congeners of the lipid peroxidation product 4-hydroxynonenal. The contribution of protein dynamics to promiscuity has not been studied. Therefore, hydrogen/deuterium exchange mass spectrometry (H/DX) and fluorescence lifetime distribution analysis were performed with glutathione S-transferases A1-1 and A4-4. Differences in local dynamics of the C-terminal helix were evident as expected on the basis of previous studies. However, H/DX demonstrated significantly greater solvent accessibility throughout most of the GSTA1-1 sequence compared with GSTA4-4. A Phe-111/Tyr-217 aromatic-aromatic interaction in A4-4, which is not present in A1-1, was hypothesized to increase core packing. "Swap" mutants that eliminate this interaction from A4-4 or incorporate it into A1-1 yield H/DX behavior that is intermediate between the wild type templates. In addition, the single Trp-21 residue of each isoform was exploited to probe the conformational heterogeneity at the intrasubunit domain-domain interface. Excited state fluorescence lifetime distribution analysis indicates that this core residue is more conformationally heterogeneous in GSTA1-1 than in GSTA4-4, and this correlates with greater stability toward urea denaturation for GSTA4-4. The fluorescence distribution and urea sensitivity of the mutant proteins were intermediate between the wild type templates. The results suggest that the differences in protein dynamics of these homologs are global. The results suggest also the possible importance of extensive conformational plasticity to achieve high levels of functional promiscuity, possibly at the cost of stability.
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PMID:Functional promiscuity correlates with conformational heterogeneity in A-class glutathione S-transferases. 1756 9

Elimination of hydrogen sulfide from glutathione (GSH) converts a well known cellular nucleophile to an electrophilic species, gamma-glutamyldehydroalanylglycine (EdAG). We have found that a sulfonium metabolite formed from GSH and busulfan undergoes a facile beta-elimination reaction to give EdAG, which is an alpha,beta-unsaturated dehydroalanyl analog of GSH. EdAG was identified as a metabolite of busulfan in a human liver cytosol fraction. EdAG condenses with GSH in a Michael addition reaction to produce a lanthionine thioether [(2-amino-5-[[3-[2-[[4-amino-5-hydroxy-5-oxopentanoyl]amino]-3-(carboxymethylamino)-3-oxopropyl]sulfanyl-1-(carboxymethylamino)-1-oxopropan-2-yl]amino]-5-oxopentanoic acid); GSG], which is a nonreducible analog of glutathione disulfide. EdAG was less cytotoxic than busulfan to C6 rat glioma cells. GSH and EdAG were equally effective in displacing a glutathione S-transferase (GST) isozyme (human GSTA1-1) from a GSH-agarose column. The finding of an electrophilic metabolite of GSH suggests that alteration of cellular GSH concentrations, irreversible nonreducible glutathionylation of proteins, and interference with GST function may contribute to the toxicity of busulfan.
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PMID:Dehydroalanine analog of glutathione: an electrophilic busulfan metabolite that binds to human glutathione S-transferase A1-1. 1879 Oct 61

Inhibition of cytochrome P450s (CYPs) is a major cause of adverse drug-drug interactions. Alternatively, inhibition of glutathione S-transferases (GSTs) may increase harmful effects of electrophilic compounds or metabolites. In the present study, aqueous extracts of seven Ghanaian medicinal plants were investigated for their inhibitory potential towards recombinant human CYP1A2, CYP2C9, CYP2D6 and CYP3A4, heterologously expressed in Escherichia coli. Effects of these extracts on recombinant human GSTA1-1, GSTM1-1, GSTP1-1, human and rat cytosolic GSTs were also investigated. Seven extracts, including Phyllanthus amarus whole plant, leaf, stem and root, Cassia siamea and Momordica charantia, inhibited CYP1A2 and CYP2C9 with IC50 values ranging between 28.3-134.3microg/ml and between 63.4-425.9microg/ml, respectively. Similarly, both CYP2D6 and CYP3A4 were inhibited by five extracts including Phyllanthus amarus whole plant, leaf, stem and root and Cassia alata, with IC50 values ranging between 45.8-182.0microg/ml and between 79.2-158.8microg/ml respectively. Human and rat liver cytosolic GSTs were inhibited with IC50 values ranging between 25.2-95.5microg/ml and between 8.5-139.4microg/ml, respectively. GSTM1-1 was most susceptible to the inhibition by the extracts, with IC50 values ranging between 3.6-50.0microg/ml, whilst IC50 values of 8.9-159.0microg/ml and 68.6-157.0microg/ml were obtained for GSTA1-1 and GSTP1-1, respectively. These findings show a significant potential both for CYP- and GST-mediated herb-drug interactions of the Ghanaian medicinal plants investigated.
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PMID:Interactions between cytochromes P450, glutathione S-transferases and Ghanaian medicinal plants. 1882 37

Glutathione transferases (GSTs) are enzymes involved in cellular detoxification by catalysing the nucleophilic attack of glutathione (GSH) on the electrophilic centre of a number of toxic compounds and xenobiotics, including certain chemotherapeutic drugs. The encountered chemotherapeutic resistant of tumour cells, thus, has been associated with the increase of total GST expression. GSTs, in addition to GSH-conjugating activity, exhibit sulphonamidase activity, catalyzing the GSH-mediated hydrolysis of sulphonamide bonds. Such reactions are of interest as potential tumour-directed prodrug activation strategies. In the present work we report the design and synthesis of novel chimaeric sulphonamide derivatives of bombesin, able to be activated by the model human isoenzyme GSTA1-1 (hGSTA1-1). These derivatives bear a peptidyl-moiety (analogues of bombesin peptide: R-[Lue(13)]-bombesin, R-[Phe(13)]-bombesin and R-[Ser(3),Arg(10),Phe(13)]-bombesin, where R=C(6)H(5)SO(2)NH-) as molecular recognition element for targeting the drug selectively to tumour cells. The released S-alkyl-glutathione, after hGSTA1-1-mediated cleavage of the sulphonamide bond, provides an inhibitor of varied strength against GSTs from different sources. These prodrugs are envisaged as a plausible means to sensitize drug-resistant tumours that overexpress GSTs.
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PMID:Sulphonamide-based bombesin prodrug analogues for glutathione transferase, useful in targeted cancer chemotherapy. 1901 94

Zileuton, an agent which targets the leukotriene pathway through inhibition of 5-lipoxygenase (5-LO), was approved for the treatment of asthma in 1997. Shortly after its release, its use was restricted due to the observation of hepatotoxicity in patients. Previous research from the authors' laboratory demonstrated the formation of the reactive metabolite, 2-ABT-S-oxide (M1) from zileuton, and has identified a mercapturate of 2-ABT, C1, in the urine of rats dosed with zileuton. The reaction between M1 and glutathione (GSH) has been established in vitro; however, the potential for catalysis by glutathione transferases (GSTs) was not addressed. The work presented here outlines a role for GSTs in the detoxification of M1. Non-enzymatic conjugation studies with M1 and GSH in control experiments led to a t(1/2) of 6.4 +/- 0.4 h at pH 6.5. This rate was accelerated in the presence of GSTA1-1, GSTM1-1 and GSTP1-1 providing t(1/2) values of 2.6 +/- 0.1, 0.53 +/- 0.02, and 0.3 +/- 0.04 h, respectively, at pH 6.5. The inhibition of various GST enzymes was also studied. Results show that M1 inhibits GSTM1-1 and GSTP1-1 to a greater extent as compared with GSTA1-1. In the case of GSTA1-1, the inhibition was observed to be reversible, whereas M1 inhibition of GSTM1-1 and GSTP1-1 was found to be irreversible under identical conditions. GSTM1-1 is present in liver and thus the finding of the alkylation and potential irreversible inactivation of this isoform in vivo could contribute to an understanding of the hepatotoxicity associated with zileuton.
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PMID:2-ABT-S-oxide detoxification by glutathione S-transferases A1-1, M1-1 and P1-1: implications for toxicity associated with zileuton. 1928 May 18

The naturally occurring nitroalkenes, nitrolinoleic (NO(2)-LA) and nitrooleic (NO(2)-OA) acids, are among the most potent endogenous ligand activators of PPARgamma-dependent transcription. In order to understand mechanisms that regulate cellular response to these nitroalkenes, we previously demonstrated that glutathione conjugation of NO(2)-LA and MRP1-mediated efflux of the conjugates were associated with significant attenuation of PPARgamma activation by this nitroalkene [(2006) Biochemistry 45, 7889-7896]. Here we show that NO(2)-OA activation of PPARgamma is similarly affected by nonenzymatic conjugation and MRP1-mediated efflux. Moreover, the roles of glutathione S-transferases (GSTs) in the glutathione conjugation and bioactivities of NO(2)-LA and NO(2)-OA were investigated. While none of the GST isozymes tested (GSTA1-1, A4-4, M1a-1a, and P1a-1a) enhanced the rate of glutathione conjugation, expression of GSTA1-1, M1a-1a, or P1a-1a in MCF7 cells significantly reduced the magnitude of PPARgamma-dependent reporter gene transcription in response to NO(2)-LA and NO(2)-OA treatment, with GSTP1a-1a expression mediating the most potent inhibition of PPARgamma. Although these GSTs failed to catalyze nitroalkene conjugation with glutathione, the nitroalkenes were found to associate avidly with all four GST isozymes as indicated by their ability to inhibit GST activity with K(i)'s in the nanomolar range. Treatment of purified GSTP1a-1a with excess NO(2)-LA and NO(2)-OA resulted in the formation of covalent adducts between GSTP1a monomers and nitroalkenes, although separate experiments indicated that such covalent bond formation was not necessary for avid GST-nitroalkene interactions. These results suggest that GSTs can inhibit the activation of transcription by nitroalkenes via noncatalytic sequestration of these ligands, and their glutathione conjugates, away from their nuclear target, PPARgamma.
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PMID:Noncatalytic interactions between glutathione S-transferases and nitroalkene fatty acids modulate nitroalkene-mediated activation of peroxisomal proliferator-activated receptor gamma. 1935 61


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