Excitotoxic stimulation downregulates the ubiquitin-proteasome system through activation of NMDA receptors in cultured hippocampal neurons
Excitotoxic stimulation downregulates the ubiquitin-proteasome system through activation of NMDA receptors in cultured hippocampal neurons
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DOI：
10.1016/j.bbadis.2012.10.009
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发表时间：
2013-01-01
影响因子：
6.2
通讯作者：
Duarte, Carlos B.
中科院分区：
文献类型：
--
作者：
Caldeira, Margarida V.;Curcio, Michele;Duarte, Carlos B.
谷氨酸受体的过度激活导致了缺血性卒中的神经元损伤(兴奋性毒性)，但其具体机制尚未完全阐明。脑缺血的特征还表现为蛋白酶体的活性受损，蛋白酶体是神经元中主要的蛋白分解系统之一。我们发现谷氨酸的兴奋毒性刺激使培养的大鼠海马神经元的ATP水平和蛋白酶体活性迅速降低，并导致26S蛋白酶体的解体。蛋白酶体活性的下调，导致泛素化蛋白的积累，是通过NMDA受体的钙进入介导的，并且只在细胞核部分观察到。此外，兴奋性毒性引起的蛋白酶体抑制对组织蛋白酶-L的抑制部分敏感，并且是通过激活突触外NMDA型受体而特异性地诱导的。缺氧缺糖诱导神经元死亡，下调蛋白酶体的活性，其机制依赖于NMDA受体的激活。由于去泛素化酶可能通过对抗泛素化来调节蛋白质的半衰期，我们还分析了在兴奋毒性条件下它们的活性是如何调节的。谷氨酸刺激降低了海马神经元总脱泛素酶活性，但对Uch-L1活性无影响，表明并不是所有脱泛素酶都受到影响。这些结果表明，谷氨酸的兴奋毒性刺激对泛素-蛋白酶体系统有多方面的影响，这可能在脑缺血和其他神经疾病的死亡过程中起作用。(C)2012爱思唯尔B.V.保留所有权利。
Overactivation of glutamate receptors contributes to neuronal damage (excitotoxicity) in ischemic stroke but the detailed mechanisms are not fully elucidated. Brain ischemia is also characterized by an impairment of the activity of the proteasome, one of the major proteolytic systems in neurons. We found that excitotoxic stimulation with glutamate rapidly decreases ATP levels and the proteasome activity, and induces the disassembly of the 26S proteasome in cultured rat hippocampal neurons. Downregulation of the proteasome activity, leading to an accumulation of ubiquitinated proteins, was mediated by calcium entry through NMDA receptors and was only observed in the nuclear fraction. Furthermore, excitotoxicity-induced proteasome inhibition was partially sensitive to cathepsin-L inhibition and was specifically induced by activation of extrasynaptic NMDA receptors. Oxygen and glucose deprivation induced neuronal death and downregulated the activity of the proteasome by a mechanism dependent on the activation of NMDA receptors. Since deubiquitinating enzymes may regulate proteins half-life by counteracting ubiquitination, we also analyzed how their activity is regulated under excitotoxic conditions. Glutamate stimulation decreased the total deubiquitinase activity in hippocampal neurons, but was without effect on the activity of Uch-L1, showing that not all deubiquitinases are affected. These results indicate that excitotoxic stimulation with glutamate has multiple effects on the ubiquitin-proteasome system which may contribute to the demise process in brain ischemia and in other neurological disorders. (C) 2012 Elsevier B.V. All rights reserved.