Plasticity of auditory electrical synapses

摘要 缝隙连接(GJ)介导的电突触最近被报道为构成重要网络的基础 耳蜗神经背侧核的特性和解剖学证据表明，它们广泛分布于 听觉通路。然而，听觉电突触的特性仍然知之甚少。作为他们的 与化学突触相对应的是，电突触是“可塑性的”，也就是说，它们通过活动来改变自己的强度。变化 在电突触的力量下，动态地重新配置各种神经结构中的神经元电路。 因此，电突触的存在和可塑性可能从根本上改变我们 了解听觉回路的组织，并最终了解听觉信息的处理。这 该提案旨在通过以下方式帮助我们理解听觉系统中的电传输 研究在混合、电气和电子状态下引起GJ通讯可塑性变化的分子机制 化学物质，将初级听觉传入连接到鱼的M-细胞。我们在金鱼上的工作 显示这些混合突触的电(和化学)传递是依赖活动的 增强功能。因为这些动态特性后来被发现发生在哺乳动物的电突触上。 M细胞混合突触被认为是研究脊椎动物电传递可塑性的有价值的模型。 与化学突触不同，人们对突触变化背后的分子机制知之甚少。 电突触的强度。目前认为GJ电导的可塑性变化是由于直接 修改已有频道的属性。然而，我们的进展表明，受监管 GJ通道的插入和移除也可能有助于可塑性。我们建议调查 GJ通道的受控运输对电传递的可塑性改变的贡献及其 分子基础。为了直接研究这种可能性，我们将采用这些独特的混合突触模型 通过研究它们在斑马鱼幼体中的特性，将分析提升到一个新的水平。斑马鱼的亲和性 幼虫在体内成像荧光标记的GJ通道的运动应允许监测活跃的 经历可塑性的突触。这种方法将提供一个前所未有的窗口来分析 通过结合体内实验研究详细的分子机制的电传递 通过强大的基因操作进行成像、电生理学和时间分辨超微结构分析。目标 1是研究斑马鱼幼体中电突触发生增强的条件。通过 将电生理学和药理学与电和光遗传刺激相结合，这一目标将确定 幼虫混合突触经历电(和化学)增强的条件 变速箱。目的2是测试塑料更换是否需要插入和移除GJ通道。 这个目标将探索这样一个概念，即电突触是位于哪个通道的复杂突触结构 它们的正常功能和调节来自于多种蛋白质之间的相互作用。这个 描述参与其调控的新的分子机制将有助于更好地理解 与听觉功能障碍相关的回路动力学和新疗法的潜在识别 目标。

Abstract Gap junction (GJ)-mediated electrical synapses were recently reported to underlie important network properties in the dorsal cochlear nucleus and anatomical evidence suggests they are widespread along the auditory pathway. However, the properties of auditory electrical synapses remain poorly understood. As their chemical counterparts, electrical synapses are ‘plastic’, that is, they modify their strength with activity. Changes in the strength of electrical synapses dynamically reconfigure neuronal circuits in various neural structures. Thus, the presence and plastic properties of electrical synapses could fundamentally change the way we understand the organization of auditory circuits and, ultimately, the processing of auditory information. This proposal aims to contribute to our understanding of electrical transmission in the auditory system by investigating the molecular mechanisms causing plastic changes in GJ communication at mixed, electrical and chemical, contacts that couple primary auditory afferents to the Mauthner (M-) cells in fish. Our work in goldfish shows that electrical (and chemical) transmission at these mixed synapses undergo activity-dependent potentiation. Because these dynamic properties were later found to occur at mammalian electrical synapses. M-cell mixed synapses are considered a valuable model to study plasticity of vertebrate electrical transmission. In contrast to chemical synapses, little is known about the molecular mechanisms that underlie changes in the strength of electrical synapses. It is currently thought that plastic changes in GJ conductance are due to direct modification of the properties of already existing channels. However, our progress suggests that regulated insertion and removal of GJ channels may also contribute to plasticity. We propose to investigate the contribution of regulated trafficking of GJ channels to plastic changes of electrical transmission and its molecular underpinnings. To directly examine this possibility, we will take these unique model mixed synapses to a new level of analysis by investigating their properties in larval zebrafish. The amenability of zebrafish larvae to image the movement of fluorescently-tagged GJ channels in-vivo should allow monitoring of active synapses undergoing plasticity. This approach will provide an unprecedented window for the analysis of electrical transmission at which detailed molecular mechanisms will be investigated by combining in-vivo imaging, electrophysiology and time-resolved ultrastructural analysis with powerful genetic manipulations. Aim 1 is to investigate the conditions under which electrical synapses in larval zebrafish undergo potentiation. By combining electrophysiology and pharmacology with electrical and optogenetic stimulation, this aim will identify the conditions under which larval mixed synapses undergo potentiation of electrical (and chemical) transmission. Aim 2 is to test whether insertion and removal of GJ channels are required for plastic changes. This aim will explore the notion that electrical synapses are complex synaptic structures at which channels turnover and that their proper function and regulation results from interactions between multiple proteins. The description of novel molecular mechanisms involved in their regulation will contribute to a better understanding of the dynamics of circuits relevant to auditory dysfunction and the potential identification of novel therapeutic targets.