Excitotoxic loss of post-synaptic sites is distinct temporally and mechanistically from neuronal death
Excitotoxic loss of post-synaptic sites is distinct temporally and mechanistically from neuronal death
复制标题
DOI：
10.1111/j.1471-4159.2007.04973.x
复制
发表时间：
2008-01-01
影响因子：
4.7
通讯作者：
Thayer, Stanley A.
中科院分区：
文献类型：
--
作者：
Waataja, Jonathan J.;Kim, Hee Jung;Thayer, Stanley A.
树突变性和突触蛋白的丢失是与神经退行性疾病中的功能下降相关的早期事件。然而，突触丢失和细胞死亡之间的时间和机制关系仍不清楚。我们使用共聚焦显微镜和图像处理，通过表达融合绿色荧光蛋白的突触后密度蛋白95来计数大鼠海马神经元上的突触后位点。荧光斑点与神经递质释放位点、NMDA诱导的Ca2+增加和NMDA受体免疫反应性共定位。在兴奋性毒性神经变性过程中，突触部位丢失，突触传递受损。这些变化是由NMDA受体介导的，并需要Ca2+依赖性激活的蛋白酶体途径。在短暂的神经毒性损伤后追踪来自同一细胞的突触，发现短暂的损失随后恢复。突触后位点丢失的时程、浓度依赖性和机制与导致细胞死亡的机制不同。表达p14ARF的细胞，其抑制突触后密度蛋白95的泛素化并防止突触位点的丢失，显示出对谷氨酸诱导的细胞死亡的敏感性增加。因此，兴奋性毒性突触丧失可能是一种疾病修饰过程，而不是导致细胞死亡的强制性步骤。这些结果表明，独立于神经元的存活在神经变性过程中评估突触功能的重要性，并表明，这种方法将是有用的识别毒素，降解突触连接和筛选剂，保护突触功能。
Dendritic degeneration and loss of synaptic proteins are early events correlated with functional decline in neurodegenerative disease. The temporal and mechanistic relationship between synapse loss and cell death, however, remains unclear. We used confocal microscopy and image processing to count post-synaptic sites on rat hippocampal neurons by expressing post-synaptic density protein 95 fused to green fluorescent protein. Fluorescent puncta co-localized with neurotransmitter release sites, NMDA-induced Ca2+ increases and NMDA receptor immunoreactivity. During excitotoxic neurodegeneration, synaptic sites were lost and synaptic transmission impaired. These changes were mediated by NMDA receptors and required Ca2+-dependent activation of the proteasome pathway. Tracking synapses from the same cell following brief neurotoxic insult revealed transient loss followed by recovery. The time-course, concentration-dependence and mechanism for loss of post-synaptic sites were distinct from those leading to cell death. Cells expressing p14ARF, which inhibits ubiquitination of post-synaptic density protein 95 and prevents loss of synaptic sites, displayed an increased sensitivity to glutamate-induced cell death. Thus, excitotoxic synapse loss may be a disease-modifying process rather than an obligatory step leading to cell death. These results demonstrate the importance of assessing synaptic function independent of neuronal survival during neurodegeneration and indicate that this approach will be useful for identifying toxins that degrade synaptic connections and for screening for agents that protect synaptic function.