c-Jun regulates the stability of anti-apoptotic ΔNp63 in amyloid-β-induced apoptosis.

p63, the structural and functional homologue of p53, is expressed either as a full-length isoform, containing a transactivation (TA) domain (TAp63), or as a truncated isoform, which lacks TA (ΔNp63). Amyloid-β (Aβ) incubation of neuronal cells results in stress-induced cell death through poorly understood mechanisms. We investigated the role of p63 in Aβ-induced stress. Our results show that Aβ-induced apoptosis of rat PC12 neuronal-like cells and primary cortical neurons was associated with stabilization of pro-apoptotic TAp63 and, most importantly, degradation of anti-apoptotic ΔNp63 through a MAPK- and proteasome-dependent mechanism. This was associated with increased c-Jun, and partially modulated by tauroursodeoxycholic acid. As expected, classic genotoxic insults resulted in c-Jun upregulation and concomitant ΔNp63 reduction. Endogenous and ectopic ΔNp63 expression was also markedly reduced by c-Jun overexpression. Further, Aβ-mediated ΔNp63 degradation occurred in a c-Jun-dependent manner. Downregulation of c-Jun expression by specific c-Jun siRNA abrogated the reduction of ΔNp63 levels following Aβ insult, whereas overexpression of c-Jun led to its degradation. c-Jun significantly decreased ΔNp63 half-life. Together, these findings demonstrate that the abundance of anti-apoptotic ΔNp63 in response to Aβ-induced cell stress is regulated by a c-Jun-dependent mechanism, and highlight the importance of finding novel targets for potential therapeutic intervention.