Single synapse indicators of impaired glutamate clearance derived from fast iGlu u imaging of cortical afferents in the striatum of normal and Huntington (Q175) mice
Single synapse indicators of impaired glutamate clearance derived from fast iGlu u imaging of cortical afferents in the striatum of normal and Huntington (Q175) mice
复制标题
正常和亨廷顿 (Q175) 小鼠纹状体皮质传入神经的快速 iGlu u 成像衍生的谷氨酸清除受损的单突触指标
DOI：
10.1101/455758
复制
发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Dvorzhak A
中科院分区：
文献类型：
--
作者：
Dvorzhak A
突触谷氨酸 (Glu) 释放和摄取之间平衡的变化可能会刺激突触重组甚至突触损失。如果在单个突触水平上独立评估这两个参数，那么寻找摄取和释放之间潜在不匹配的主要原因应该会更容易。现在，由于使用基因编码的超快 Glu 传感器 iGluu 进行新的成像测定，这已成为可能。我们报告了从 1 岁以上小鼠制备的急性切片中的单个皮质纹状体突触获得的结果。短期可塑性的对比模式和大小标准确定了 2 类末端，大概对应于之前定义的 IT 和 PT 突触。后者表现出更高程度的频率增强/残留 Glu 积累，并被选择在亨廷顿病 (HD) 的 Q175 小鼠模型中进行研究。研究发现，HD 中突触前末端旁边的最大 [Glu]（作为释放指标）和突触周围 [Glu] 衰减的时间常数（TauD，作为摄取指标）分别延长和减少。根据这些标准，在 Q175 杂合子 (HET) 中检测的 P 末端约 30% 被诊断为患病。 HD 而非 WT 突触表现出 TauD 与 iGluu 峰值振幅之间的正相关性。用 Glu 摄取阻滞剂 TFB-TBOA (100 nM) 处理 WT 制剂模拟了纯合子 (HOM) 中 TauD 的变化。由表达 ChR 的单个皮质纹状体轴突的光学激活引起的 NMDAR 介导的单一 EPSC 延长，并且在皮质纹状体末端环境中发现较少的 EAAT2 免疫反应性。结论是 HD 会导致 Glu 摄取和释放之间不匹配，尤其是在频率增强程度较高的突触中。因此，星形胶质细胞的谷氨酸转运仍然是治疗干预的一个有希望的目标。
Changes in the balance between synaptic glutamate (Glu) release and uptake may stimulate synaptic reorganization and even synapse loss. The search for the primary cause of a potential mismatch between uptake and release should be easier if both parameters are assessed independently and at a single synapse level. This has now become possible due to a new imaging assay with the genetically encoded ultrafast Glu sensor iGluu. We report results obtained from individual corticostriatal synapses in acute slices prepared from mice aged >1 year. Contrasting patterns of short-term plasticity and a size criterion identified 2 classes of terminals, presumably corresponding to the previously defined IT and PT synapses. The latter exhibited a higher degree of frequency potentiation/residual Glu accumulation and were selected for investigation in the Q175 mouse model of Huntington disease (HD). It was found that the maximal [Glu] next to the presynaptic terminal (as indicator of release) in HD and the time constant of perisynaptic [Glu] decay (TauD, as indicator of uptake) were prolonged and reduced, respectively. According to these criteria, about 30% of P terminals tested in Q175 heterozygotes (HET) were diagnosed as sick. HD but not WT synapses exhibited a positive correlation between TauD and the peak amplitude of iGluu. Treatment of WT preparations with the Glu uptake blocker TFB-TBOA (100 nM) mimicked the TauD changes in homozygotes (HOM). The NMDAR-mediated unitary EPSCs elicited by optical activation of single ChR-expressing corticostriatal axons were prolonged, and less EAAT2 immunoreactivity was found in the environment of corticostriatal terminals. It is concluded that HD produces a mismatch between Glu uptake and release, especially in synapses with high degree of frequency potentiation. Astrocytic Glu transport therefore remains a promising target for therapeutic intervention.