Activity-Dependent Regulation of Kv4 Channels

Kv4通道已被证明在调节神经活动中发挥重要作用：调节 整合突触输入的高频序列，调节反向传播动作电位，以及 有助于长期增强。因此，影响Kv4功能/可用性的突变一直是 表现为导致空间学习障碍、癫痫行为以及颞叶癫痫。在最后一次 在融资期间，我们发现Kv4通道的表达和转换在三个新的背景下受到影响： 调节胆碱能突触的动态平衡，以响应人Aβ42的过度表达，并在 正常衰老。在拟议的研究中，我们研究了Kv4在 胆碱能突触动态平衡。突触内稳态/伸缩是一种形式的可塑性，已经严重 在过去的十年中被研究为一种保护机制，以抵消全球神经活动的变化； 这可能发生在生理过程中，如学习/记忆和发育，以及在 病理情况。我们以果蝇中枢神经元为模型，发现果蝇α7 (Dα7)胆碱能阻断后nAChRs上调，从而增强突触电流并提供 一种动态平衡反应。我们发现这种自稳反应触发了一种新的调节机制-- 我们所展示的Kv4通道的上调可以防止体内平衡反应的“超调”。 我们进一步证明，Kv4通道的上调被转录抑制物阻断，并且是 依赖D-α-7nAChRs和钙离子内流。果蝇仍然是这些的理想模型系统 研究因为它的胆碱能中枢神经系统，它提供的遗传工具，它的较少冗余的基因组(例如。只有一种 单个果蝇NFAT和Kv4基因，每个基因在哺乳动物中代表一个多基因家族)，以及 在完整的大脑中，从基因调控机制到生理相关性的能力，最终， 整个动物行为。拟议的研究将应用新的光遗传方法来诱导胆碱能 体内突触内稳态(AIM-1)--这是一个尚未在任何系统中探索过的东西，它将 目前在哺乳动物系统中是不可行的。我们将研究潜在的分子机制，包括 α7nAChRs与Kv4通道(Aim-2)之间的新关系及其失活诱导的Kv4转录 (AIM-3)，由NFAT介导(AIM-4)。我们还将测试它们生理上的所有分子机制 与完整大脑中已识别的神经元的相关性。我们的研究可能会揭示出对 胆碱能突触动态平衡的潜在机制。

Kv4 channels have been shown to play important roles in modulating neural activity: regulating the integration of high-frequency trains of synaptic input, regulating backpropagating action potentials, and contributing to long-term potentiation. Consequently, mutations that affect Kv4 function/availability have been shown to result in spatial learning defects, seizure behavior, as well as temporal lobe epilepsy. In the last funding period, we showed that expression and turnover of Kv4 channels are affected in three new contexts: in modulating cholinergic synaptic homeostasis, in response to over-expression of human Aβ42, and during normal aging. In the proposed studies, we investigate the mechanisms underlying Kv4 expression during cholinergic synaptic homeostasis. Synaptic homeostasis/scaling is a form of plasticity that has been heavily studied in the last decade as a protective mechanism that counterbalances changes in global neural activity; this likely occurs during physiological processes, such as learning/memory and development, as well as during pathological conditions. We used Drosophila central neurons as a model, and showed that Drosophila α7 (Dα7) nAChRs are up-regulated after cholinergic blockade, thereby enhancing synaptic currents and providing a homeostatic response. We found that this homeostatic response triggered a novel regulatory mechanism – the up-regulation of Kv4 channels, which we showed prevents an “overshoot” of the homeostatic response. We further showed that the up-regulation of Kv4 channels is blocked by transcriptional inhibitors, and is dependent on Dα7 nAChRs and Ca2+ influx. Drosophila continues to be an ideal model system for these studies because of its cholinergic CNS, the genetic tools it offers, its less redundant genome (eg. there is only a single Drosophila NFAT and Kv4 gene, each of which represents a multi-gene family in mammals), and the ability to go from mechanisms of gene regulation to physiological relevance in the intact brain, and eventually, whole animal behavior. The proposed studies will apply new optogenetic approaches to elicit cholinergic synaptic homeostasis in vivo (Aim-1) –something that has not been explored in any system, and which would currently not be feasible in mammalian systems. We will examine underlying molecular mechanisms, including a novel relationship between α7 nAChRs and Kv4 channels (Aim-2), and inactivity-induced transcription of Kv4 (Aim-3) that is mediated by NFAT (Aim-4). We will also test all molecular mechanisms for their physiological relevance in identified neurons in the intact brain. Our studies are likely to reveal important insights into the underlying mechanisms of cholinergic synaptic homeostasis.