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  • Title: The effects of modulation of gamma-glutamyl transpeptidase activity in HepG2 cells on thiol homeostasis and caspase-3-activity.
    Author: Iciek M, Chwatko G, Rokita H, Bald E, Włodek L.
    Journal: Biochim Biophys Acta; 2007 Feb; 1773(2):201-8. PubMed ID: 17141888.
    Abstract:
    The present studies aimed to elucidate how the modulation of gamma-glutamyl transpeptidase (gammaGT) activity in human hepatoma (HepG2) cell line influences H(2)O(2) production, caspase 3 activity, protein S-thiolation by glutathione (GSH), cysteinyl-glycine (Cys-Gly) and cysteine (Cys), and the level of other redox forms of these thiols. The experiments showed that 1-h stimulation of gammaGT elevated H(2)O(2) production, leading to prooxidant conditions. After 24-h stimulation, H(2)O(2) concentration was at the control level, while Cys-Gly-, Cys- and GSH-dependent S-thiolation was markedly increased, which was accompanied by a drop in caspase-3 activity. The inhibition of gammaGT activity by acivicin led to H(2)O(2) decrease after 1-h incubation which still persisted after 24 h. The inhibition of gammaGT activity in HepG2 cells was also connected with the lowering of S-thiolation with Cys and Cys-Gly and with increasing of caspase-3 activity. The results of our studies indicate that the modulation of gammaGT activity can be used to change cellular redox status, and can affect Cys- and Cys-Gly-dependent S-thiolation and caspase-3 activity. We suggest that the role of high gammaGT activity in HepG2 cells can be connected with production of reactive oxygen species and with S-thiolation with Cys and Cys-Gly that can influence activity of caspase 3.
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