title: TG2 protects neuroblastoma cells against DNA-damage-induced stress, suppresses p53 activation.
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 gamma-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 (approximately 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.
authors.affiliation: Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, 1720, 7th Ave. South, SC 981, Birmingham, AL 35294-0017, USA. jtuchol@uab.edu
authors.forename: Janusz
authors.initials: J
authors.lastname: Tucholski
mesh_terms: D045744:Cell Line, Tumor; D004249:DNA Damage / Q000187:drug effects*; D019204:GTP-Binding Proteins; D006801:Humans; D009447:Neuroblastoma / Q000235:genetics; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases / Q000502:physiology*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D016159:Tumor Suppressor Protein p53; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins