Architecture and function of striatal dopamine signaling machinery

摘要 多巴胺是一种重要的神经调节剂，而多巴胺信号转导的病理过程是大脑的标志 疾病。尽管有这些作用，但人们对多巴胺信号的组织和调控还不完全了解。 该项目的长期目标是剖析轴突多巴胺传递的细胞生物学。 多巴胺信号的时空特征不同于突触传递。在传统上 突触，纳米级的突触结构使受体以亚毫秒的速度和 将通信限制在选定神经元之间的点对点接触。相比之下，多巴胺是一种体积 胞吐后通过胞外空间扩散的一种递质，可能通过 G蛋白偶联受体。这些特性表明，多巴胺的传递是缓慢和扩散的。近期 然而，来自几个实验室的数据，包括一些在上一个供资周期产生的数据， 揭示了多巴胺的传递是高度动态的，在某些情况下，非常精确。此外， 纹状体局部胆碱能中间神经元对多巴胺的释放具有强大而快速的调节作用。这些 研究结果表明，多巴胺体积传递的编码比之前认为的更精确。 由此产生的一个主要问题是，多巴胺传输的体系结构如何支持精确的 发信号。我们最主要的模型是分子机制已经进化到支持广泛的多巴胺编码 比例。我们建立在我们之前的发现的基础上，轴突多巴胺的胞吐以毫秒的精度执行 通过稀疏、复杂的蛋白质机制，通常存在于突触中。在目标1中，我们放大了强大的 并询问胆碱能神经元如何触发多巴胺的释放。根据初步数据，我们 假设胆碱能中间神经元的活动诱导多巴胺轴突的异位动作电位放电 触发多巴胺分泌。我们的目标是检验这一假说，并了解其潜在的机制。 远离多巴胺的异位轴突动作电位启动的内源性机制 神经元胞体对多巴胺神经元的功能有重要意义。在目标2中，我们剖析了组织 相对于释放部位的多巴胺受体。我们在最近的工作基础上确定了这些标记 稀疏的秘密站点。我们的初步数据显示，多巴胺受体聚集在一到两微米处 远离释放部位，并提示在d1和d2受体分布上的差异。我们将系统地 在大纹状体体积和意志的超分辨率3D图像中评估释放受体的组织 机械地剖析它是如何设置的。我们认为这种组织不同于纳米尺度的突触 结构和由通常与体积传输相关联的扩散组织形成，并且可能适合于 在多巴胺神经元放电模式中，通过开关来调节不同的通路激活。 我们的工作将剖析专门的多巴胺信号体系结构的组织和快速、局部 脊椎动物纹状体多巴胺释放的触发机制。

Summary Dopamine is an important neuromodulator and pathologies in dopamine signaling are a hallmark of brain disease. Despite these roles, the organization and regulation of dopamine signaling are incompletely understood. The long-term goal of this project is to dissect the cell biology of axonal dopamine transmission. Spatial and temporal features of dopamine signaling are different from synaptic transmission. At conventional synapses, nanometer-scale synaptic structure enables robust receptor activation at sub-millisecond speeds and restricts communication to point-to-point contacts between select neurons. In contrast, dopamine is a volume transmitter that diffuses through the extracellular space after exocytosis and may influence many cells through G-protein coupled receptors. These properties suggest that dopamine transmission is slow and diffuse. Recent data from several laboratories, including some generated during the previous funding cycle, however, have revealed that dopamine transmission is highly dynamic and, in some cases, remarkably precise. Furthermore, dopamine release is powerfully and rapidly regulated by local cholinergic interneurons in the striatum. These findings suggest that the coding of dopamine volume transmission is more precise than previously thought. A major question that arises is how the architecture for dopamine transmission can support precise signaling. Our overarching model is that molecular machinery has evolved to support broad dopamine coding scales. We build on our previous findings that axonal dopamine exocytosis is executed with millisecond precision by sparse, sophisticated protein machinery typically present at synapses. In aim 1, we zoom in on the powerful local regulation and ask how cholinergic neurons trigger dopamine release. Based on preliminary data, we hypothesize that activity in cholinergic interneurons induces ectopic action potential firing in dopamine axons to trigger dopamine secretion. Our goal is to test this hypothesis and to understand the underlying mechanisms. Identification of an endogenous mechanism for ectopic axonal action potential initiation away from the dopamine neuron soma has important implications for dopamine neuron function. In aim 2, we dissect the organization of dopamine receptors relative to release sites. We build on recent work that identified markers for these sparse secretory sites. Our preliminary data reveal that dopamine receptors are clustered one to two micrometers away from release sites and suggest differences in D1 vs. D2 receptor distributions. We will systematically assess release-receptor organization in super-resolved 3D-images of large striatal volumes and will mechanistically dissect how it is set up. We propose that the organization is different from nanoscale synaptic structure and from the diffuse organization often associated with volume transmission, and may be suited to mediate distinct pathway activation by switches in dopamine neuron firing modes. Our work will dissect the organization of specialized dopamine signaling architecture and rapid, local triggering mechanisms of dopamine release in the vertebrate striatum.