Neurotoxic calcium transfer from endoplasmic reticulum to mitochondria is regulated by cyclin-dependent kinase 5-dependent phosphorylation of tau
Neurotoxic calcium transfer from endoplasmic reticulum to mitochondria is regulated by cyclin-dependent kinase 5-dependent phosphorylation of tau
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DOI：
10.1523/jneurosci.0060-05.2005
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发表时间：
2005-04-20
影响因子：
5.3
通讯作者：
Ruberg, M
中科院分区：
文献类型：
--
作者：
Darios, F;Muriel, MP;Ruberg, M
神经元游离钙水平的增加与几种细胞死亡模式相关，如兴奋性毒性和神经酰胺介导的神经元死亡。在后者中，钙通过仅部分理解的机制从内质网转移到线粒体。我们在这里表明，CDK 5（细胞周期蛋白依赖性激酶5）发挥作用。在内质网和线粒体中的游离钙水平进行了测量与荧光标记在C2-神经酰胺处理的原代培养中脑神经元和分化的嗜铬细胞瘤PC 12细胞。内质网中的钙水平降低，而线粒体中的钙水平升高。这两种变化都被药理学和分子CDK 5抑制剂roscovitine和CDK 5的显性阴性形式阻断。虽然激酶本身并不介导钙的转移，这需要促凋亡Bcl-2家族蛋白t-Bid（Bid的截短形式），但它通过诱导内质网和线粒体聚集在中心体周围形成紧密接触来促进钙的转移，如免疫细胞化学和电子显微镜所示。细胞器聚类导致CDK 5依赖性磷酸化的微管相关蛋白tau苏氨酸231。这导致其从微管释放到细胞蛋白质的可溶性部分中，这似乎有利于细胞器的逆行运输。将苏氨酸231突变为丙氨酸，使得tau不能在该位点磷酸化，防止了神经酰胺诱导的tau从微管释放、细胞器聚集、无神经细胞钙水平的增加和神经元死亡，证明了CDK 5依赖性信号级联在这种钙依赖性细胞死亡机制中的重要性。
Increased levels of mitochondrial-free calcium have been associated with several cell-death paradigms, such as excitotoxicity and ceramide-mediated neuronal death. In the latter, calcium is transferred from the endoplasmic reticulum to mitochondria by a mechanism that is only partly understood. We show here that CDK5 (cyclin-dependent kinase 5) plays a role. Free calcium levels in the endoplasmic reticulum and mitochondria were measured with fluorescent markers in C2-ceramide-treated primary cultures of mesencephalic neurons and differentiated pheochromocytoma PC12 cells. Calcium levels decreased in the endoplasmic reticulum as they increased in mitochondria. Both changes were blocked by the pharmacological and molecular CDK5 inhibitors roscovitine and a dominant-negative form of CDK5. Although the kinase did not mediate the transfer of calcium per se, which required the proapoptotic Bcl-2 family protein t-Bid ( the truncated form of Bid), it facilitated the transfer by inducing the clustering of endoplasmic reticulum and mitochondria around the centrosome where they formed close contacts, as shown by immunocytochemistry and electron microscopy. Organelle clustering resulted from CDK5-dependent phosphorylation of the microtubule-associated protein tau on threonine 231. This caused its release from microtubules into the soluble fraction of cellular proteins, which appears to favor retrograde transport of the organelles. Mutation of threonine 231 to alanine, so that tau could not be phosphorylated at this site, prevented the ceramide-induced release of tau from microtubules, organelle clustering, the increase in mitochondrial-free calcium levels, and neuronal death, demonstrating the importance of the CDK5-dependent signaling cascade in this calcium-dependent cell-death mechanism.