title: The effects of modulation of gamma-glutamyl transpeptidase activity in HepG2 cells on thiol homeostasis and caspase-3-activity.
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.
authors.affiliation: Chair of Medical Biochemistry, Collegium Medicum, Jagiellonian University, Kopernika Str., 7, 31-034 Kraków, Poland.
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Iciek
authors.forename: Grazyna
authors.initials: G
authors.lastname: Chwatko
authors.forename: Hanna
authors.initials: H
authors.lastname: Rokita
authors.forename: Edward
authors.initials: E
authors.lastname: Bald
authors.forename: Lidia
authors.initials: L
authors.lastname: Włodek
mesh_terms: D053148:Caspase 3 / Q000378:metabolism*; D002384:Catalysis; D016923:Cell Death; D045744:Cell Line, Tumor; D003545:Cysteine / Q000032:analysis / Q000378:metabolism; D004151:Dipeptides / Q000032:analysis / Q000378:metabolism; D004220:Disulfides / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005978:Glutathione / Q000032:analysis / Q000378:metabolism; D006706:Homeostasis; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D010084:Oxidation-Reduction; D013438:Sulfhydryl Compounds / Q000032:analysis / Q000378:metabolism*; D005723:gamma-Glutamyltransferase / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D004151:Dipeptides; D004220:Disulfides; D004791:Enzyme Inhibitors; D013438:Sulfhydryl Compounds; C028505:cysteinylglycine; D006861:Hydrogen Peroxide; D005723:gamma-Glutamyltransferase; D053148:Caspase 3; D005978:Glutathione; D003545:Cysteine