title: TRB3 protects cells against the growth inhibitory and cytotoxic effect of ATF4.
abstract: Tribbles homolog 3 (TRB3) is a pseudokinase the level of which is increased in response to various stresses. We and other researchers have previously shown that TRB3 interacts with activating transcription factor 4 (ATF4) and may function as a negative feedback regulator of ATF4. In the present study, we investigate the effect of ATF4 and TRB3 on cell growth and viability, using both the enforced expression and silencing of the genes. HEK293 cells overexpressing ATF4 show retarded growth in the complete medium and decreased viability in the glucose-free medium. The enforced expression of ATF4 increases the level of reactive oxygen species (ROS) and the supplementation of the medium with ROS scavenging and reducing compounds supports the growth and survival of cells overexpressing ATF4. The deleterious effects of elevated ATF4 are suppressed by the coexpression of TRB3, which downregulates ATF4 transcriptional activity and results in the decrease of intracellular ROS. Also, the coexpression of TRB3 rescues postmitotic neuronally differentiated PC12 cells from the apoptosis evoked by ATF4 overexpression. The silencing of ATF4 and TRB3 genes by RNA interference reveals that endogenous ATF4 promotes and TRB3 suppresses the death of glucose-deprived SaOS2 cells. Together, the results indicate that TRB3 protects cells against the growth inhibitory and cytotoxic effect of ATF4.
authors: Institute of Molecular and Cell Biology, Tartu University, Tartu, Estonia; Estonian Biocentre, 23 Riia St, Tartu, Estonia.
authors: Daima
authors: D
authors: Ord
authors: Kati
authors: K
authors: Meerits
authors: Tõnis
authors: T
authors: Ord
mesh_terms: D051701:Activating Transcription Factor 4 / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis; D018797:Cell Cycle Proteins / Q000378:metabolism*; D016923:Cell Death; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D005947:Glucose / Q000172:deficiency; D006801:Humans; D016716:PC12 Cells; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism* / Q000037:antagonists & inhibitors; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D017382:Reactive Oxygen Species; D012097:Repressor Proteins; C474831:TRIB3 protein, human; D051701:Activating Transcription Factor 4; D017346:Protein Serine-Threonine Kinases; D005947:Glucose