Abstract E2F4 is a transcription factor involved in cellular homeostasis and a substrate of the stress-activated kinase p38 MAPK , which phosphorylates a conserved Thr248/Thr250 motif. A non-phosphorylatable mutant, E2F4DN (Thr248Ala/Thr250Ala), has demonstrated preclinical efficacy in a murine model of Alzheimer’s disease (AD), but its mechanism of action remains unknown. We hypothesized that cell stress-induced phosphorylation disrupts E2F4’s homeostatic function, whereas exogenous E2F4DN restores it. To begin testing this hypothesis, we treated differentiated N2a neuroblastoma cells (N2a neuron-like cells) with camptothecin (CPT) to induce genotoxic stress. CPT activated p38 MAPK within 8 h, leading to phosphorylation of E2F4 at Thr248/Thr250. We then overexpressed E2F4DN or a phosphomimetic variant, E2F4CA (Thr248Glu/Thr250Glu), and assessed apoptosis via procaspase-3 cleavage. The pro-apoptotic factor E2F1 strongly induced caspase-3 activation in this model system. This effect was partially mimicked by E2F4CA, while E2F4DN markedly suppressed it. Notably, E2F4DN, but not E2F4CA, upregulated the antiapoptotic factor Cited2, and knockdown experiments suggest it may contribute to E2F4DN’s protective effect. Overall, these findings indicate that E2F4DN counteracts p38 MAPK -driven neuronal apoptosis and helps preserve neuronal homeostasis, at least in part, through Cited2 upregulation. This provides mechanistic insight into the neuroprotective role of E2F4DN as a potential therapy for AD.
Llabrés-Mas et al. (Sat,) studied this question.