ATF4 regulates neuronal death in models of Parkinson’s Disease

Parkinsons Disease (PD) is characterized by the loss of dopaminergic neurons in the substantia nigra resulting in severe motor impairments. However, the mechanisms underlying this neuronal loss remain largely unknown. Activating Transcription Factor 4 (ATF4), a key mediator of the Integrated Stress Response (ISR), is a transcription factor that during prolonged activation can induce the expression of pro-apoptotic target genes. Oxidative stress and ER stress have been implicated in PD and these factors are known to activate the ISR. In this study, we have determined, that both PD neurotoxins (MPP+ and 6-OHDA) and -synuclein aggregation induced by pre-formed human alpha-synuclein fibrils (PFFs) cause sustained upregulation of ATF4 expression in mouse primary cortical and mesencephalic neurons. Furthermore, we demonstrate that PD neurotoxins induce the expression of the pro-apoptotic factors Chop, Trb3 and Puma in an ATF4-dependent manner. Importantly, using neurons derived from ATF4 +/+ and ATF4 -/- mice, we demonstrate that ATF4 promotes neuronal apoptosis and dopaminergic cell loss in cellular models of PD. Finally, we demonstrate that the eIF2 kinase inhibitor C16 suppresses MPP+ and 6-OHDA induced ATF4 activation and protects against PD neurotoxin induced neuronal death. Taken together these results indicate that ATF4 is a key regulator of dopaminergic cell death induced by PD neurotoxins and pathogenic -synuclein aggregates and highlight the ISR as a potential therapeutic target in PD.