The presynaptic dense projection of the Caenorhabditis elegans cholinergic neuromuscular junction localizes synaptic vesicles at the active zone through SYD-2/liprin and UNC-10/RIM-dependent interactions.
The presynaptic dense projection of the Caenorhabditis elegans cholinergic neuromuscular junction localizes synaptic vesicles at the active zone through SYD-2/liprin and UNC-10/RIM-dependent interactions.
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DOI：
10.1523/jneurosci.6164-10.2011
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发表时间：
2011-03-23
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影响因子：
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通讯作者：
Bessereau JL
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作者：
Stigloher C;Zhan H;Zhen M;Richmond J;Bessereau JL
化学突触的活动区(AZ)是突触前突触的一个特殊区域，囊泡在这里与质膜融合并释放神经递质。有效的信号传递需要在AZ处招募、激活和保留突触小泡(SVS)，使其靠近突触前去极化时被激活的电压依赖性钙通道。AZ的电子密度专业化可能为这些不同过程的空间协调提供了一个分子平台。为了研究这一假设，我们检查了电子断层扫描产生的线虫胆碱能神经肌肉接头的高分辨率3D模型。首先，我们发现，与脊椎动物中所描述的相似，SVS通过细丝相互连接在一起。其次，对以AZ为中心的密集投影的三维结构进行了解析。致密的突起是一个比先前预期的更复杂的结构，细丝从一个核心结构辐射出来，该结构直接接触胞外内部的SVS以及停靠在质膜上的SVS。第三，我们通过分析破坏两个关键AZ蛋白：UNC-10/RIM和SYD-2/liprin的突变体来研究这些接触的功能相关性。在两个突变体中，SVS与致密投射之间的接触次数都显著减少。与UNC-10突变体相似，与野生型相比，Syd-2突变体中SV融合对细胞外钙浓度的依赖性加剧。因此，我们认为，密集的投射通过UNC-10/RIM和SYD-2/liprin依赖的机制将其保留在AZ，从而确保启动的囊泡与钙信号的适当耦合。
The active zone (AZ) of chemical synapses is a specialized area of the presynaptic bouton where vesicles fuse with the plasma membrane and release neurotransmitters. Efficient signaling requires synaptic vesicles (SVs) to be recruited, primed and retained at the AZ, in close proximity to voltage-dependent calcium channels that are activated upon presynaptic depolarization. The electron-dense specializations at the AZ might provide a molecular platform for the spatial coordination of these different processes. To investigate this hypothesis, we examined high-resolution 3D models of C. elegans cholinergic neuromuscular junctions generated by electron tomography. First, we found that SVs are interconnected within the bouton by filaments similar to those described in vertebrates. Second, we resolved the 3D structure of the dense projection centered in the AZ. The dense projection is a more complex structure than previously anticipated, with filaments radiating from a core structure that directly contact SVs in the interior of the bouton as well as SVs docked at the plasma membrane. Third, we investigated the functional correlate of these contacts by analyzing mutants disrupting two key AZ proteins: UNC-10/RIM and SYD-2/liprin. In both mutants, the number of contacts between SVs and the dense projection was significantly reduced. Similar to unc-10 mutants, the dependence of SV fusion on extracellular calcium concentration was exacerbated in syd-2 mutants when compared to the wild type. Hence we propose that the dense projection ensures proper coupling of primed vesicles with calcium signaling by retaining them at the AZ via UNC-10/RIM and SYD-2/liprin-dependent mechanisms.