Synaptic Homeostasis Modulated by Kv4

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。我们有 最近发现，Kv4通道的表达和周转也在三个新的背景下受到影响：在 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(也称为突触伸缩)。突触动态平衡是一种 在过去的十年中，作为一种平衡平衡的保护机制而被大量研究的可塑性 全局神经活动的变化；这可能发生在生理过程中，如学习/记忆 和发育，以及在病理条件下。我们用果蝇的中枢神经元作为模型， 并表明，果蝇α7(Dα7)nAChRs在胆碱能阻断后上调，从而增强 突触电流和提供动态平衡反应。我们发现这种内环境平衡反应引发了 新的调控机制-Kv4通道的上调，我们展示了它防止了 动态平衡反应。我们进一步表明，Kv4通道的上调被阻断 转录抑制因子，依赖于D-α-7nAChRs和钙离子内流。果蝇仍然是一种 这些研究的理想模型系统，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 冗余基因组(例如果蝇只有一个NFAT和Kv4基因，每个基因代表一个 哺乳动物中的多基因家族)，以及从基因调节机制到生理机制的能力 与完整的大脑和整个动物行为的相关性。拟议的研究将应用新的光遗传学 诱导体内胆碱能突触内稳态的方法(AIM-1)--尚未被探索的东西 任何系统，而这在哺乳动物系统中目前是不可行的。我们将研究潜在的 分子机制，包括α7nAChRs和Kv4通道之间的新关系(AIM-2)，以及 NFAT(Aim-4)介导的失活诱导Kv4转录(Aim-3)。我们还将测试所有分子 在完整的大脑和行为动物中识别的神经元中它们的生理相关性的机制 (目标4-5)。我们的研究可能会揭示胆碱能潜在机制的新见解 突触动态平衡。

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. We have recently shown that expression and turnover of Kv4 channels are also 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 (also referred to as synaptic scaling). Synaptic homeostasis 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 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 and behaving animal (Aims 4-5). Our studies are likely to reveal novel insights into the underlying mechanisms of cholinergic synaptic homeostasis.