TY - JOUR
T1 - Membrane gamma-glutamyl transpeptidase activity of melanoma cells
T2 - Effects on cellular H2O2 production, cell surface protein thiol oxidation and NF-κB activation status
AU - Maellaro, E.
AU - Dominici, S.
AU - Del Bello, B.
AU - Valentini, M. A.
AU - Pieri, L.
AU - Perego, P.
AU - Supino, R.
AU - Zunino, F.
AU - Lorenzini, E.
AU - Paolicchi, A.
AU - Comporti, M.
AU - Pompella, A.
PY - 2000
Y1 - 2000
N2 - The metabolism of glutathione by membrane-bound gamma-glutamyl transpeptidase (GGT) has been recently recognized as a basal source of hydrogen peroxide in the extracellular space. Significant levels of GGT activity are expressed by malignant tumours, and in melanoma cell lines they were found to correlate with the malignant behaviour. As hydrogen peroxide and other oxidants can affect signal transduction pathways at several levels, the present study was aimed to verify: (i) the occurrence of GGT-dependent production of hydrogen peroxide in melanoma cells; (ii) the effects of GGT-dependent prooxidant reactions on known redox-sensitive cellular targets, i.e. protein thiols, the nuclear transcription factor NF-κB and p53. Two melanoma Me665/2 cell clones, exhibiting traces of (clone 2/21) or high (clone 2/60) GGT activity, were studied. The occurrence of GGT-dependent production of hydrogen peroxide was apparent in 2/60 cells, in which it was accompanied by lower levels of cell surface protein thiols. In 2/60 cells, GGT expression was also associated with higher levels of NF-κB activation, as compared to GGT-poor 2/21 cell clone. Indeed, stimulation or inhibition of GGT activity in 2/60 cells resulted in progressive activation or inactivation of NF-κB, respectively. An analysis of the p53 gene product indicated lack of protein expression in 2/60 cells, whereas a mutant protein was highly expressed in 2/21 cells. Taken together, these results indicate that the expression of GGT activity can provide melanoma cells with an additional source of hydrogen peroxide, and that such prooxidant reactions are capable to modify protein thiols at the cell surface level. In addition, GGT expression results in an up-regulation of the transcription factor NF-κB, which could explain the higher metastatic behaviour reported for GGT-rich melanoma cells as compared to their GGT-poor counterparts.
AB - The metabolism of glutathione by membrane-bound gamma-glutamyl transpeptidase (GGT) has been recently recognized as a basal source of hydrogen peroxide in the extracellular space. Significant levels of GGT activity are expressed by malignant tumours, and in melanoma cell lines they were found to correlate with the malignant behaviour. As hydrogen peroxide and other oxidants can affect signal transduction pathways at several levels, the present study was aimed to verify: (i) the occurrence of GGT-dependent production of hydrogen peroxide in melanoma cells; (ii) the effects of GGT-dependent prooxidant reactions on known redox-sensitive cellular targets, i.e. protein thiols, the nuclear transcription factor NF-κB and p53. Two melanoma Me665/2 cell clones, exhibiting traces of (clone 2/21) or high (clone 2/60) GGT activity, were studied. The occurrence of GGT-dependent production of hydrogen peroxide was apparent in 2/60 cells, in which it was accompanied by lower levels of cell surface protein thiols. In 2/60 cells, GGT expression was also associated with higher levels of NF-κB activation, as compared to GGT-poor 2/21 cell clone. Indeed, stimulation or inhibition of GGT activity in 2/60 cells resulted in progressive activation or inactivation of NF-κB, respectively. An analysis of the p53 gene product indicated lack of protein expression in 2/60 cells, whereas a mutant protein was highly expressed in 2/21 cells. Taken together, these results indicate that the expression of GGT activity can provide melanoma cells with an additional source of hydrogen peroxide, and that such prooxidant reactions are capable to modify protein thiols at the cell surface level. In addition, GGT expression results in an up-regulation of the transcription factor NF-κB, which could explain the higher metastatic behaviour reported for GGT-rich melanoma cells as compared to their GGT-poor counterparts.
KW - Gamma-glutamyl transpeptidase
KW - Hydrogen peroxide
KW - Melanoma
KW - NF-κB
KW - p53
KW - Protein thiol
UR - http://www.scopus.com/inward/record.url?scp=0033845660&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0033845660&partnerID=8YFLogxK
M3 - Article
C2 - 10893182
AN - SCOPUS:0033845660
VL - 113
SP - 2671
EP - 2678
JO - Journal of Cell Science
JF - Journal of Cell Science
SN - 0021-9533
IS - 15
ER -