ATF5 Attenuates Apoptosis in Hippocampal Neurons with Seizures Evoked by Mg2+-Free Medium via Regulating Mitochondrial Unfolded Protein Response.

ABSTRACT

The mitochondrial unfolded protein response (mtUPR)-a stress response pathway for maintaining protein homeostasis-is critical in seizures-induced neuronal injury. The activating transcription factor 5 (ATF5) regulates mtUPR; however, whether ATF5-regulated mtUPR has a role in neuronal injury in epilepsy remains uncertain. Here, we investigated the effects of ATF5-regulated mtUPR on neuronal injury in hippocampal neurons with seizures evoked by Mg2+-free medium. HSP60 and ClpP, key proteins of mtUPR, were upregulated, indicating mtUPR activation. ATF5 overexpression by lentiviral vector infection potentiated mtUPR, whereas ATF5 downregulation by lentiviral vector infection attenuated this response. Moreover, ATF5 overexpression elevated mitochondrial membrane potential and reduced reactive oxygen species (ROS) generation, suggesting that ATF5 overexpression protected mitochondrial homeostasis, while ATF5 downregulation had the opposite effect. ATF5 overexpression also reversed Bcl2 downregulation and Bax upregulation and attenuated seizures-induced neuronal apoptosis, while ATF5 downregulation aggravated the injury. Our study demonstrates that ATF5 attenuates seizures-induced neuronal injury, possibly by regulating mtUPR pathways, to prevent mitochondrial dysfunction.