Reevaluation of Neurodegeneration in lurcher Mice: Constitutive Ion Fluxes Cause Cell Death with, Not by, Autophagy
Reevaluation of Neurodegeneration in lurcher Mice: Constitutive Ion Fluxes Cause Cell Death with, Not by, Autophagy
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DOI：
10.1523/jneurosci.6030-09.2010
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发表时间：
2010-02-10
影响因子：
5.3
通讯作者：
Yuzaki, Michisuke
中科院分区：
文献类型：
--
作者：
Nishiyama, Jun;Matsuda, Keiko;Yuzaki, Michisuke
几十年来，lurcher（Lc）小鼠一直是神经退行性变的有价值的模型。尽管在编码δ 2谷氨酸受体（GluD 2s）的基因中鉴定出了负责的突变，该受体主要在小脑浦肯野细胞中表达，但突变型受体（GluD 2（Lc））如何触发细胞死亡仍然难以捉摸。在这里，利用最近的知识结构域的GluD 2，我们重新调查LC介导的细胞死亡，集中在“自噬性细胞死亡”的假设。虽然在异源细胞和培养的神经元中GluD 2（Lc）的表达诱导自噬和细胞死亡，但通过在GluD 2（Lc）的通道孔结构域中引入突变或通过去除细胞外Na+来阻断它们。此外，尽管GluD 2（Lc）被报道直接激活自噬，但与n-PIST（与TC 10特异性相互作用的蛋白质的神经元亚型）-Beclin 1不相关的突变通道仍然引起自噬和细胞死亡。此外，表达GluD 2（Lc）的细胞表现出降低ATP水平和增加AMP激活的蛋白激酶（AMPK）活性的方式依赖于细胞外Na+。因此，组成性电流可能是必要的，并足以通过AMPK激活诱导自噬，无论n-PIST-Beclin 1途径在体外。有趣的是，显性阴性AMPK的表达抑制GluD 2（Lc）诱导的自噬，但不能阻止异源细胞的细胞死亡。类似地，Atg 5（一种对自噬至关重要的基因）的破坏并没有阻止而是加剧了Lc小鼠中的浦肯野细胞死亡。此外，钙蛋白酶特异性激活Lc浦肯野细胞。总之，这些结果表明LC介导的细胞死亡不是由自噬引起的，而是在体内和体外均具有自噬特征的坏死。
The lurcher (Lc) mice have served as a valuable model for neurodegeneration for decades. Although the responsible mutation was identified in genes encoding delta 2 glutamate receptors (GluD2s), which are predominantly expressed in cerebellar Purkinje cells, how the mutant receptor (GluD2(Lc)) triggers cell death has remained elusive. Here, taking advantage of recent knowledge about the domain structure of GluD2, we reinvestigated Lc-mediated cell death, focusing on the "autophagic cell death" hypothesis. Although autophagy and cell death were induced by the expression of GluD2(Lc) in heterologous cells and cultured neurons, they were blocked by the introduction of mutations in the channel pore domain of GluD2(Lc) or by removal of extracellular Na+. In addition, although GluD2(Lc) is reported to directly activate autophagy, mutant channels that are not associated with n-PIST (neuronal isoform of protein-interacting specifically with TC10)-Beclin1 still caused autophagy and cell death. Furthermore, cells expressing GluD2(Lc) showed decreased ATP levels and increased AMP-activated protein kinase(AMPK) activities in a manner dependent on extracellular Na+. Thus, constitutive currents were likely necessary and sufficient to induce autophagy via AMPK activation, regardless of the n-PIST-Beclin1 pathway in vitro. Interestingly, the expression of dominant-negative AMPK suppressed GluD2(Lc)-induced autophagy but did not prevent cell death in heterologous cells. Similarly, the disruption of Atg5, a gene crucial for autophagy, did not prevent but rather aggravated Purkinje-cell death in Lc mice. Furthermore, calpains were specifically activated in Lc Purkinje cells. Together, these results suggest that Lc-mediated cell death was not caused by autophagy but necrosis with autophagic features both in vivo and in vitro.