Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The tripeptide glutathione plays a pivotal role in the maintenance of the thiol redox state of the cell and for the detoxification of reactive oxygen species. Glutathione is synthesized in two consecutive reactions by y-glutamylcysteine synthetase (gamma-GCS) and glutathione synthetase, respectively. The former enzyme represents the rate limiting step of the synthetic pathway. We have cloned the cDNA and gene of a putative gamma-GCS from Plasmodium falciparum. The contiguous cDNA sequences obtained from various cDNA libraries of P. falciparum K1 and 3D7 encompass 4206 bp or 4038 bp and encode polypeptides of 1119 and 1063 amino acids, respectively. The deduced amino acid sequences show four regions of homology (identity: 31.3-43.9%) to human and Trypanosoma brucei gamma-GCS. These regions are interrupted by three large insertions between 94 and 239 amino acids. Within the first insert a variable repetitive motif was identified, which is responsible for the differing sizes of the sequences. We have analysed this phenomenon in five additional P. falciparum strains and found a high degree of variability in the number of the repeated octamer (Y/C)S(N/D)LQQ(Q/R). Therefore the predicted molecular mass of the proteins from different P. falciparum strains ranges from 124.4 to 133.2 kDa, which is almost twice that of the catalytic subunit of the human host enzyme. Isolation of three genomic clones revealed that the gene does not contain introns. P. falciparum gamma-GCS transcription peaks in trophozoites (24-30 h) suggesting that the antioxidant glutathione is predominantly produced at a time where hemoglobin degradation and the simultaneous formation of reactive oxygen species is maximal.
Mol Biochem Parasitol 1999 Jan 05
PMID:The putative gamma-glutamylcysteine synthetase from Plasmodium falciparum contains large insertions and a variable tandem repeat. 1002 15

Barrett's metaplasia consists of columnar epithelium that replaces the normal esophageal mucosa in patients with chronic gastroesophageal reflux. Because intestinal-type Barrett's metaplasia is the major risk factor for adenocarcinoma development, understanding the mechanisms that predispose the esophageal mucosa to malignant degeneration is clinically important. Glutathione s-transferase (GST)-pi belongs to a class of protective enzymes whose activity has been shown to be much lower in Barrett's metaplasia than in the normal esophagus, where this form of GST is predominant. In the studies described here, using immunocytochemical analysis, we observed higher levels of cytoplasmic GST-pi protein in normal esophageal mucosa than in Barrett's metaplasia. Using northern blot analysis, we also observed lower GST-pi mRNA levels in Barrett's metaplasia than in normal esophagus or adenocarcinomas from the same patients. Using as model systems three Barrett's adenocarcinoma cell lines and short-term organ culture of freshly resected normal esophagus and Barrett's metaplasia, dose-dependent induction of GST-pi mRNA was observed by using butylated hydroxyanisole and dexamethasone. GST-pi mRNA in Barrett's metaplasia was induced up to 2.5-fold with 60 microM butylated hydroxyanisole and nearly fivefold with 320 nM dexamethasone after 24 h. These studies demonstrate the ability to induce protective GST-pi in Barrett's metaplasia and may suggest a mechanism for future chemoprevention studies in patients with this type of epithelium, which is at high risk for malignant degeneration.
Mol Carcinog 1999 Feb
PMID:Induction of glutathione s-transferase-pi in Barrett's metaplasia and Barrett's adenocarcinoma cell lines. 1007 40

Active neuronal-glial interaction is important in the maintenance of brain homeostasis and is vital for neuronal survival following brain injury. The time course of post-ischemic astroglial dysfunction and neuronal death was studied in the spontaneously hypertensive rat (SHR) brain following permanent middle cerebral artery occlusion (MCAO). In situ hybridization with 35S-labeled riboprobes for GFAP and GLUT3 was used to monitor mRNA expression in glia and neurons. Astrocytic proteins GFAP, vimentin, S100, Glutathione-S-Transferase Yb (GST Yb) and neuronal protein TG2 were detected by immunofluorescence. Cells were co-stained with in situ end labeling (ISEL) to detect DNA fragmentation, a hallmark of cell death. GFAP mRNA expression declined rapidly in the ischemic region of the cortex and was almost absent by 12 h. Immunohistochemical studies revealed a parallel decline in the corresponding protein: a reduction in GFAP staining was apparent in the infarct after 3 h and by 24 h, there was essentially no remaining GFAP. Three other glial proteins (vimentin, S100 and GST Yb) disappeared from infarct over a similar time course. A few ISEL positive cells were observed in the infarct at 6 h, but maximal detection was not seen until 24-48 h. Most of the ISEL-positive cells were neurons, identified by co-staining with the neuronal marker TG2. Few cells expressing GFAP or other glial markers were positive at any time point. Neuronal GLUT3 mRNA declined more slowly than GFAP mRNA in the ischemic core and disappeared during the period of neuronal death. Concurrent with the loss of GFAP mRNA and protein expression in the infarct, there was a rapid rise in GFAP mRNA in the peri-infarct region of ipsilateral hemisphere and proximal region of the contralateral hemisphere. This was followed by the enhanced GFAP protein expression characteristic of reactive astrocytes, but over a significantly slower time course. These studies show that MCAO leads to a rapid decline of GFAP mRNA and glial proteins, which appears to precede the decline in neuronal mRNA and neuronal death within the infarct. Early astroglial dysfunction may play a critical role in determining the outcome of acute hypoxic-ischemic injury by compromising neuronal-glial interactions.
Brain Res Mol Brain Res 1999 May 07
PMID:Astrocytic demise precedes delayed neuronal death in focal ischemic rat brain. 1032 Jul 81

Glutathione plays a central role in the maintenance of tissue antioxidant defenses and in the regulation of redox sensitive signal transduction. In muscle cells, the level and redox status of GSH regulates activity of the redox sensitive transcription factor NF-kappaB. Physical exercise may cause oxidation of GSH in tissues such as the blood, skeletal muscle and liver. Endurance training strengthened GSH dependent tissue antioxidant defenses in most studies. Although studies investigating the effect of sprint training are few, current results show that sprint training may also have a beneficial effect on tissue GSH homeostasis. Skeletal muscle GSH level appears to be tightly regulated by the state of physical activity. Regular exercise enhances and chronic inactivity decreases the level of GSH in this tissue. N-acetyl-L-cysteine (NAC) and alpha-lipoic acid (LA) are two antioxidant dietary supplements that are able to enhance cellular GSH levels. Because LA can be recycled to its potent dithiol form, dihydrolipoate, by enzymes present in the human cell it has a clear advantage over NAC. Recently an improved form of LA, a positively charged analogue (LA-Plus), has been discovered. LA-Plus has more potent immuno-modulatory activity compared to LA. Both LA and NAC have been shown to have beneficial effects in protecting tissue GSH homeostasis against exercise induced oxidative stress.
Mol Cell Biochem 1999 Jun
PMID:Glutathione homeostasis in response to exercise training and nutritional supplements. 1044

Glutathione S -transferases (GSTs) play a pivotal role in the detoxification of foreign chemicals and toxic metabolites. They were originally termed ligandins because of their ability to bind large molecules (molecular masses >400 Da), possibly for storage and transport roles. The location of the ligandin site in mammalian GSTs is still uncertain despite numerous studies in recent years. Here we show by X-ray crystallography that the ligandin binding site in human pi class GST P1-1 occupies part of one of the substrate binding sites. This work has been extended to the determination of a number of enzyme complex crystal structures which show that very large ligands are readily accommodated into this substrate binding site and in all, but one case, causes no significant movement of protein side-chains. Some of these molecules make use of a hitherto undescribed binding site located in a surface pocket of the enzyme. This site is conserved in most, but not all, classes of GSTs suggesting it may play an important functional role.
J Mol Biol 1999 Aug 27
PMID:The ligandin (non-substrate) binding site of human Pi class glutathione transferase is located in the electrophile binding site (H-site). 1045 96

A cDNA, hvst1, was isolated from Hordeum vulgare by heterologous complementation in Escherichia coli. This cDNA encodes a high-affinity sulfate transporter that is 2442 bp in length and consists of 660 amino acids. Under steady-state conditions of sulfate supply during culture, sulfate influx (measured at 100 microM external sulfate concentration) and hvst1 transcript level were inversely correlated with sulfate concentrations in the culture solution. Glutathione (GSH) concentrations increased as external sulfate was increased from 2.5 to 250 microM. A time-course study, designed to investigate effects of sulfate withdrawal on the abundance of hvst1 transcript, showed a 5-fold increase of the latter within the first two hours. This was followed by a further slight increase during the next 46 h. These changes were accompanied by a parallel increase in sulfate influx and a decrease of root GSH concentrations. When plants that had been deprived of sulfate for 24 h were exposed to L-cysteine (Cys) or GSH for 3 h, GSH was the more effective down-regulator, reducing hvst1 transcript level to below that of unstarved controls. The decrease in transcript abundance induced by sulfate or Cys was partially relieved by the addition of buthionine sulfoximine (BSO), an inhibitor of GSH synthesis. Both hvst1 transcripts and sulfate influx increased as a function of N supply to N-starved plants. Amino oxyacetate acid (AOA), an aminotransferase inhibitor, when supplied with NO3-, increased transcript abundance of hvst1, while tungstate, methionine sulfoximine (MSO) and azaserine (AZA), inhibitors of nitrate reductase, glutamine synthetase and glutamate synthase (GOGAT), respectively, were without effect. AOA decreased root concentrations of aspartate (Asp), Cys and GSH; in contrast, glutamate (Glu) concentrations remained unchanged.
Plant Mol Biol 1999 Jul
PMID:Regulation of the hvst1 gene encoding a high-affinity sulfate transporter from Hordeum vulgare. 1048 22

Nuclear receptor corepressor (NCoR) mediates repression (silencing) of basal gene transcription by nuclear receptors for thyroid hormone and retinoic acid. The goal of this study was to create novel estrogen receptor (ER) mutants by fusing transferable repressor domains from the N-terminal region of NCoR to a functional ER fragment. Three chimeric NCoR-ER proteins were created and shown to lack transcriptional activity. These fusion proteins silenced basal transcription of the ERE2-tk-Luc reporter gene and inhibited the activity of co-transfected wild-type ER (wtER), indicating that they possess dominant negative activity. One of the fusion proteins (CDE-RD1), containing the ER DNA-binding and ligand-binding domains linked to the NCoR repressor domain (RD1), was selected for detailed examination. Its hormone affinity, intracellular localization, and level of expression in transfected cells were similar to wtER, and it bound to the estrogen response element (ERE) DNA in gel shift assays. Glutathione-S-transferase pull-down assays showed that CDE-RD1 retains the ability to bind to steroid receptor coactivator-1. Introduction of a DNA-binding domain mutation into the CDE-RD1 fusion protein eliminated silencing and dominant negative activity. Thus, the RD1 repressor domain prevents transcriptional activation despite the apparent ability of CDE-RD1 to bind DNA, ligand, and coactivators. Transcriptional silencing was incompletely reversed by trichostatin A, suggesting a histone deacetylase-independent mechanism for repression. CDE-RD1 inhibited ER-mediated transcription in T47D and MDA-MB-231 breast cancer cells and repressed the growth of T47D cells when delivered to the cells by a retroviral vector. These ER-NCoR fusion proteins provide a novel means for inhibiting ER-mediated cellular responses, and analogous strategies could be used to create dominant negative mutants of other transcription factors.
Mol Endocrinol 1999 Dec
PMID:A fusion protein of the estrogen receptor (ER) and nuclear receptor corepressor (NCoR) strongly inhibits estrogen-dependent responses in breast cancer cells. 1059 86

Glutathione (GSH) and cysteine (CysH) have both been implicated in the biogenesis of the pheomelanin precursor 5-S-cysteinyldopa (5-S-CD). However, recent studies have shown that only CysH is transported across the membrane of isolated melanosomes, and that the positive regulation of CysH in pigment cells leads to an increased production of 5-S-CD. In the present study, the question was examined as to whether melanin precursors and tyrosinase could be coregulated by cellular thiols. To address this issue, the levels of CysH and GSH were varied in normal melanocytes and melanoma cells using buthionine sulfoximine (BSO), an inhibitor of GSH biosynthesis. Treatment with 50-100 microM BSO decreased GSH levels to less than 10% of control, and increased CysH levels between two- and five-fold in both cell types. Concomitant with this, an increase in the ratio of 5-S-CD to DOPA and a decrease in the pigment content of the cells were observed. The decrease in cell pigmentation was associated with strong decreases in tyrosine hydroxylase activity and 14C-melanin production. Only melanoma cells showed a modified tyrosinase isozyme pattern on Western immunoblots in response to BSO, while the mRNA expression of tyrosinase and TRP-1 were unchanged in both cell types. These results suggest that the balance between CysH and GSH, which is partly determined by the rate of utilization of CysH for GSH biosynthesis, regulates not only the levels of 5-S-CD and DOPA but also the melanogenic activity of pigment cells. Since DOPA functions as a cofactor in the monophenolase reaction of tyrosinase, it is proposed that the ratio of 5-S-CD to DOPA may be an important factor in the regulation of tyrosinase activity in situ.
Cell Mol Biol (Noisy-le-grand) 1999 Nov
PMID:Co-regulation of melanin precursors and tyrosinase in human pigment cells: roles of cysteine and glutathione. 1064 2

Glutathione S-transferases (GSTs) are an important part of the protection system against a wide range of potentially harmful chemical compounds. GSTP1 and GSTM1 are mainly involved in detoxification reactions of PAH carcinogenic intermediates produced by cytochrome P450 (CYP). Polymorphism of the GST genes may influence the level of carcinogen-DNA adducts in human tissues and be associated with individual susceptibility to carcinogens. In this study, we examined the effect of common polymorphism in exon 5 (105Ile --> Val) of the GSTP1 gene, alone and in combination with GSTM1-deletion polymorphism, on the level of PAH-DNA adducts measured by (32)P-postlabeling assay in mononuclear white blood cells collected in winter and in summer from a total of 170 healthy volunteers. When GSTP1 genotypes alone were compared, no statistically significant differences in adduct levels were found. However, smokers with GSTM1(null)/GSTP1-AG or -GG combined genotype showed significantly higher adduct levels in summer than carriers of other GSTM1/GSTP1 combinations (5.60 +/- 5.10 vs. 3.45 +/- 4. 28/10(8) nucleotides, P = 0.015). Among smokers carrying GSTP1-AG or -GG genotype, individuals with GSTM1(null) genotype had a significantly higher level of adducts in summer than subjects with GSTM1(+) genotype (5.60 +/- 5.10 vs. 1.82 +/- 1.98/10(8), P = 0.002) and GSTM1(null)/GSTP1-AA genotype carriers (5.60 +/- 5.10 vs. 4.13 +/- 5.84/10(8), P = 0.03). When adduct levels measured either in winter or in the nonsmoker group were considered, no influence of GSTM1/GSTP1 genotypes was found. Our data show that the combined GSTM1 and GSTP1 genetic polymorphisms may modulate PAH-DNA adduct levels in mononuclear WBCs from individuals exposed to specific carcinogenic compounds, e.g., tobacco smoke, in relatively lower-exposure environmental conditions (i.e., in summer).
Environ Mol Mutagen 2000
PMID:Polymorphisms of the GSTP1 and GSTM1 genes and PAH-DNA adducts in human mononuclear white blood cells. 1071 43

Glutathione synthesis, a vital cellular process, depends on L-cystine uptake by the amino acid transporter, System x-C. Here we show that a second transporter, System X-AG, is required for normal System x-C activity and glutathione maintenance by employing somatic cell mutants of CHO-K1. Uptake by System x-C in two X-AG-null mutants is significantly lower than that of CHO-K1, either under control conditions or after prolonged treatment with an electrophile. In addition, levels of glutathione in control and treated mutant cells are less than half those of wild-type CHO-K1 or of a pseudorevertant. The significance of this reduction was tested by chemical challenge: mutants are twofold more sensitive than wild type to reactive oxygen species generated by phenylbenzoquinone and to damage produced by the anticancer drug, cisplatin. These results suggest that System X-AG provides a significant portion of the glutamate used to energize the uptake of cystine required for the synthesis of glutathione.
Somat Cell Mol Genet 1998 Nov
PMID:The Na+-dependent glutamate and aspartate transporter supports glutathione maintenance and survival of CHO-K1 cells. 1076 12


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>