The essential role of p53-up-regulated modulator of apoptosis (Puma) and its regulation by FoxO3a transcription factor in β-amyloid-induced neuron death.

Neurodegeneration underlies the pathology of Alzheimer disease (AD). The molecules responsible for such neurodegeneration in AD brain are mostly unknown. Recent findings indicate that the BH3-only proteins of the Bcl-2 family play an essential role in various cell death paradigms, including neurodegeneration. Here we report that Puma (p53-up-regulated modulator of apoptosis), an important member of the BH3-only protein family, is up-regulated in neurons upon toxic β-amyloid 1-42 (Aβ(1-42)) exposure both in vitro and in vivo. Down-regulation of Puma by specific siRNA provides significant protection against neuron death induced by Aβ(1-42). We further demonstrate that the activation of p53 and inhibition of PI3K/Akt pathways induce Puma. The transcription factor FoxO3a, which is activated when PI3K/Akt signaling is inhibited, directly binds with the Puma gene and induces its expression upon exposure of neurons to oligomeric Aβ(1-42). Moreover, Puma cooperates with another BH3-only protein, Bim, which is already implicated in AD. Our results thus suggest that Puma is activated by both p53 and PI3K/Akt/FoxO3a pathways and cooperates with Bim to induce neuron death in response to Aβ(1-42).

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