Wyttenbach Andreas, Tolkovsky Aviva M
Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK.
J Neurochem. 2006 Mar;96(5):1213-26. doi: 10.1111/j.1471-4159.2005.03676.x.
DNA damage activates apoptosis in several neuronal populations and is an important component of neuropathological conditions. While it is well established that neuronal apoptosis, induced by DNA damage, is dependent on the key cell death regulators p53 and Bax, it is unknown which proteins link the p53 signal to Bax. Using rat sympathetic neurons as an in vitro model of neuronal apoptosis, we show that cytosine arabinoside is a DNA damaging drug that induces the expression of the BH3-only pro-apoptotic genes Noxa, Puma and Bim. Increased expression occurred after p53 activation, measured by its phosphorylation at serine 15, but prior to the conformational change of Bax at the mitochondria, cytochrome c (cyt c) release and apoptosis. Hence Noxa, Puma and Bim could potentially link p53 to Bax. We directly tested this hypothesis by the use of nullizygous mice. We show that Puma, but not Bim or Noxa, is a crucial mediator of DNA damage-induced neuronal apoptosis. Despite the powerful pro-apoptotic effects of overexpressed Puma in Bax-expressing neurons, Bax nullizygous neurons were resistant to Puma-induced death. Therefore, Puma provides the critical link between p53 and Bax, and is both necessary and sufficient to mediate DNA damage-induced apoptosis of sympathetic neurons.
DNA损伤会激活多个神经元群体中的细胞凋亡，并且是神经病理状况的一个重要组成部分。虽然DNA损伤诱导的神经元凋亡依赖于关键的细胞死亡调节因子p53和Bax这一点已得到充分证实，但尚不清楚哪些蛋白质将p53信号与Bax联系起来。我们使用大鼠交感神经元作为神经元凋亡的体外模型，发现阿糖胞苷是一种DNA损伤药物，可诱导仅含BH3结构域的促凋亡基因Noxa、Puma和Bim的表达。在通过p53丝氨酸15位点磷酸化检测到其激活后，但在线粒体中Bax构象改变、细胞色素c（cyt c）释放和细胞凋亡之前，表达增加就已出现。因此，Noxa、Puma和Bim可能将p53与Bax联系起来。我们通过使用纯合缺失小鼠直接验证了这一假设。我们发现，Puma而非Bim或Noxa是DNA损伤诱导的神经元凋亡的关键介质。尽管在表达Bax的神经元中过表达的Puma具有强大的促凋亡作用，但Bax纯合缺失神经元对Puma诱导的死亡具有抗性。因此，Puma提供了p53与Bax之间的关键联系，并且对于介导交感神经元的DNA损伤诱导的细胞凋亡既是必要的也是充分的。
