Disease relevance of GCLC

• Preincubation with low doses of AA increased glutathione (GSH) levels as well as GCLC and GCLM mRNAs, and this protected against H(2)O(2) and menadione toxicity [1].
• Hereditary deficiency of gamma-GCS has been reported in a small number of patients and is associated with low erythrocyte levels of gamma-GCS and GSH leading to hemolytic anemia [2].
• In Streptococcus agalactiae, GSH synthesis is catalyzed by a single enzyme, gamma-glutamylcysteine synthetase-glutathione synthetase (gamma-GCS-GS) [3].
• Recombinant hGLCLR andhGLCLC were produced in cells infected with recombinant baculoviruses, and homogeneous hGLCL subunits and holoenzyme were purified from cell lysates with a Ni-NTA resin [4].
• We examined the gene expression of GCLM and GCLC in 39 xenografts of human non-small cell lung cancer [NSCLC; 10 adenocarcinoma (Ad), 17 squamous cell carcinoma (Sq) and 12 large cell carcinoma (La)] by real-time polymerase chain reaction (PCR) with human-specific primers [5].

Psychiatry related information on GCLC

• Severity of brain injury, as measured by a low GCS score, prolonged unconsciousness, and posttraumatic amnesia (PTA) without local brain lesion, should not be considered risk factor for LPTSs [6].
• A total of seven PF patients had a normal examination of the pelvis; four had a depressed level of consciousness (defined as GCS <15), and six patients had a distracting injury [7].
• Dyadic adjustment was greater when wives reported a lower level of financial strain, perceived their spouse to have a relatively low level of general psychopathology or maladjustment, and when the injury was relatively mild based on GCS scores [8].
• The participants completed questionnaires relating to perceived parental rearing practices (EMBU), proneness to antisocial behavior (the Gough Socialization Scale), personality (EPQ), self-esteem (Rosenberg), and compliance (GCS) [9].
• RESULTS: No significant differences were observed in relation to demographic characteristics, type of head injury, GCS, or psychometric results [10].

High impact information on GCLC

• Peripheral mononuclear cell and colon mRNA content for gamma-glutamylcysteine synthetase (gamma-GCS) and DT-diaphorase increased after dosing to reach a peak on day 2-4 after treatment, and declined to baseline in the subsequent 7-10 d [11].
• L-Buthionine-(S,R)-sulfoximine (BSO), which inactivates gamma-glutamylcysteine synthetase and therefore inhibits GSH synthesis, inhibited proliferation elicited by monoclonal antibodies directed at cluster designation 2 (CD2) and CD3 antigens, or by sn-1,2-dioctanoylglycerol and ionomycin [12].
• Human lymphoid cells depleted of glutathione by treatment with buthionine sulfoximine, a specific inhibitor of gamma-glutamylcysteine synthetase, may be partially repleted by adding glutathione in the medium [13].
• Thus, the GCS is a noninvasive method for detection and evaluation of motion of left atrial myxomas [14].
• Gamma-glutamylcysteine synthetase (gamma-GCS) catalyzes the first and rate-limiting step in glutathione (GSH) biosynthesis: the adenosine triphosphate (ATP)-dependent ligation of glutamate and cysteine. gamma-GCS consists of a catalytic (gamma-GCSH) and modifier (gamma-GCSL) subunit [2].

Chemical compound and disease context of GCLC

• Since a number of contaminants can also exert their toxicity through this mechanism, GCLC gene expression might be applied not only for cadmium biomonitoring, but also for a wide range of contaminants that directly or indirectly promote the same effect in the cellular GSH content [15].
• Hereditary deficiency of GCS has been reported in 6 patients with hemolytic anemia and low erythrocyte levels of glutathione and gamma-glutamylcysteine [16].
• Treatment of cultured mesothelioma cells with buthionine sulfoximine (BSO), to inhibit gamma GCS, significantly potentiated cisplatin-induced cytotoxicity mainly by nonapoptotic mechanism when assessed by counting the living cells, TUNEL (terminal deoxytransferase-mediated dUTP nick-end labeling) assay, and caspase-3 cleavage [17].
• Posttranscriptional regulation of MRP/GS-X pump and gamma-glutamylcysteine synthetase expression by 1-(4-amino-2-methyl-5-pyrimidinyl) methyl-3-(2-chloroethyl)-3-nitrosourea and by cycloheximide in human glioma cells [18].
• Treatment of human glioma A172 cells with 1-(4-amino-2-methyl-5-pyrimidinyl) methyl-3-(2-chloroethy-3-nitrosourea (ACNU) for 2 to 4 hr resulted in a 2- to 3-fold increase in steady-state levels of multidrug resistance-associated protein (MRP) and gamma-glutamylcysteine synthetase (gamma-GCS) mRNA [18].

Biological context of GCLC

• To identify sequences mediating constitutive and induced expression of the catalytic subunit of GCL (GCLC), a series of deletion mutants from the 5'-flanking region (-3,802 to +465) were transfected into control (C34) and CYP2E1-overexpressing (E47) HepG2 cells [1].
• In conclusion, redox-sensitive elements directing constitutive and induced expression of the GCLC in CYP2E1-expressing cells are present in the ARE4 distal portion of the 5'-flanking region, between positions -3,802 and -2,752, perhaps a reflection of metabolic adaptation to CYP2E1-generated oxidative stress [1].
• In A549, HepG2, and RD cells, maximal basal expression of the GCLC transgene required the full-length (-3802 bp) promoter [19].
• There was no significant difference in GCLC expression and in differential cell counts in BAL fluid [20].
• Upregulation of GCLC and HO-1 in E47 cells is dependent on Nrf2 [21].

Anatomical context of GCLC

• Primary hepatocytes from pyrazole-injected rats with high levels of CYP2E1 showed an increase in GSH levels as well as GCLC and GCLM mRNAs compared with saline controls, and this was prevented by diallyl sulfide [1].
• However, GCLC expression in pancreatic islets has not been previously examined [22].
• Regulation of gamma-glutamylcysteine synthetase regulatory subunit (GLCLR) gene expression: identification of the major transcriptional start site in HT29 cells [23].
• Moreover, both bucillamine and SA 981 significantly increased the expressions of Mrp2/MRP2 and GCLC proteins in both cell lines [24].
• The enzyme defect was confirmed and GCS activity was found to be less than 2% of normal in the erythrocytes of both patients [16].

Associations of GCLC with chemical compounds

• The catalytic subunit of glutamylcysteine ligase (GCLC) primarily regulates de novo synthesis of glutathione (GSH) in mammalian cells and is central to the antioxidant capacity of the cell [22].
• GCLC overexpression increased intraislet GSH levels and partially prevented the decrease in glucose-stimulated insulin secretion caused by IL-1 beta [22].
• Indirect immunofluorescence using intact cells demonstrated that indomethacin induced the nuclear translocation of Nrf2, a transcription factor believed to regulate GCLC expression [25].
• Simultaneous incubation with the thiol antioxidant N-acetylcysteine (NAC) inhibited indomethacin-mediated increases in GCLC mRNA, suggesting that increases in GCLC message were triggered by changes in intracellular oxidation/reduction (redox) reactions [25].
• GCLC owns the catalytic activity, whereas GCLM enhances the enzyme activity by lowering the K(m) for glutamate and increasing the K(i) to GSH inhibition [26].

Regulatory relationships of GCLC

• Hammerhead ribozyme against gamma-glutamylcysteine synthetase sensitizes human colonic cancer cells to cisplatin by down-regulating both the glutathione synthesis and the expression of multidrug resistance proteins [27].
• Ectopic expression of ATF3 was sufficient to suppress the GCLC reporter activity, as well as endogenous GCLC expression [28].
• Adrenomedullin regulates cellular glutathione content via modulation of gamma-glutamate-cysteine ligase catalytic subunit expression [29].

Other interactions of GCLC

• GCL is a heterodimeric protein with a catalytic (or heavy, GCLC) subunit and a modulatory (or light, GCLM) subunit [30].
• These findings indicate that GCLC polymorphisms that affect GSH production also affect methylmercury retention, and that GSTP1 may play a role in conjugating methylmercury with GSH [31].
• While all three genes have multiple AP-1-binding sites, only GCLC has a NF-kappaB-binding site [32].
• Both bucillamine and SA 981 produced a significant dose-dependent increase in the mRNA levels of Mrp2/MRP2 and GCLC after 24 h [24].
• Indole analogues capable of inducing GCLC were found to increase NADPH oxidase activity [33].

Analytical, diagnostic and therapeutic context of GCLC

• There was a significant association between the expression of GCLM and GCLC mRNA in each xenograft (Fisher's test, p<0.045) [5].
• Identification of an important cysteine residue in human glutamate-cysteine ligase catalytic subunit by site-directed mutagenesis [34].
• No difference in survival could be observed between GCLC-positive or -negative cases in the subgroup receiving chemotherapy [35].
• MTS assay and flow cytometry results also indicated that GCLC and JNK1(APF) expression enhanced cellular resistance to UV irradiation [36].
• Since the molecular cloning of GCS, much has been learned about the regulation of this enzyme [37].

References