TG2 protects neuroblastoma cells against DNA-damage-induced stress, suppresses p53 activation |
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Authors: | Janusz Tucholski |
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Institution: | (1) Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, 1720, 7th Ave. South, SC 981, Birmingham, AL 35294-0017, USA |
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Abstract: | Tissue transglutaminase (TG2) is a multifunctional member of the transglutaminase (TGase) family (E.C.2.3.2.13), which catalyzes
in a calcium-dependent reaction the formation of covalent bonds between the γ-carboxamide groups of peptide-bound glutamine
residues and various primary amines. Here, we investigated the role of TG2 in a response of the neuroblastoma SH-SY5Y cells
to topoisomerase II inhibitor etoposide, known to trigger DNA-damage cell response. We found an early and transient (~2 h)
increase of the TG2 protein in SH-SY5Y cells treated with etoposide, along with the increase of phosphorylated and total levels
of the p53 protein. Next, we showed that SH-SY5Y cells, which overexpress wild-type TG2 were significantly protected against
etoposide-induced cell death. The TG2 protective effect was associated only with the transamidation active form of TG2, because
overexpression the wild-type TG2, but not its transamidation inactive C277S form, resulted in a pronounced suppression of
caspase-3 activity as well as p53 phosphorylation during the etoposide-induced stress. In addition, exacerbation of cell death
with a significant increase in caspase-3 and p53 activation was observed in SH/anti-TG2 cells, in which expression of the
endogenous TG2 protein has been greatly reduced by the antisense cDNA construct. Though the cell signaling and molecular mechanisms
of the TG2-driven suppression of the cell death machinery remain to be investigated, our findings strongly suggest that TG2
plays an active role in the response of neuroblastoma cells to DNA-damage-induced stress by exerting a strong protective effect,
likely by the suppression of p53 activation and p53-driven cell signaling events. |
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