Regulation and Function of Arc in the Nucleus

学习和记忆的分子基础是神经元突触对电活动的反应，这一过程被称为突触可塑性。记忆的形成有两个阶段。短期记忆是由改变突触效能的先前存在的蛋白质的修饰产生的，而长期记忆的形成需要新的基因转录来稳定这些变化。活动调节的细胞骨架蛋白Arc是已知的唯一一种特定需要长期记忆形成的蛋白质。在Arc基因敲除(KO)小鼠中，短期学习不受影响，但记忆的巩固和维持会丢失。ARC也是已知的唯一一种活性诱导基因，其mRNA转录物被特异性地输送到刺激部位。然后，ARC被局部翻译到神经元树突中，并调节突触强度。这使得它能够以一种在时间和空间上与其诱导刺激相关联的方式来修改突触功能。有趣的是，Arc蛋白在细胞核中也高度丰富，活动会导致细胞核内Arc蛋白的增加。在细胞核中，Arc与早幼粒细胞白血病肿瘤抑制蛋白核体(PML-NBS)结合，后者通常调节转录。由于长期记忆的形成需要转录，并且在Arc KO小鼠中丢失，因此Arc可能有助于细胞核内的转录调节。这一发现，再加上Arc在激活的突触处的局部翻译，可能有助于解释一个有数千个突触、只有一个核的神经元如何以突触特有的方式存储信息，并依赖于核过程，如新基因的表达。这一建议旨在确定活动诱导的Arc定位到细胞核是否作为一种机制来调节长期记忆形成中的新基因转录。拟议中的实验将阐明Arc在细胞核中的调节和功能，目的是阐明巩固新记忆的分子基础。这项工作最终将不仅对我们理解正常记忆存储背后的分子过程具有重要意义，而且还将揭示影响记忆形成和巩固的神经系统疾病中被破坏的过程。 具体目的1：确定核弧是否通过转录抑制来调节总AMPAR水平。 具体目的2：确定Arc是否以一种活性依赖的方式增加PML-NBS作为一种调节转录的手段。具体目的3：阐明弧形核输出的机制。

The molecular basis of learning and memory is the modification of neuronal synapses in response to electrical activity, a process termed synaptic plasticity. There are two phases of memory formation. Short-term memory results from modifications of preexisting proteins that change synaptic efficacy, while long-term memory formation requires new gene transcription to stabilize these changes. The activity-regulated cytoskeletal protein Arc is the only protein known to be specifically required for long-term memory formation. In Arc knock- out (KO) mice, short-term learning is not affected, but consolidation and maintenance of memory is lost. Arc is also the only known activity-induced gene for which the mRNA transcript is transported specifically to the site of stimulation. Arc is then locally translated in neuronal dendrites and regulates synaptic strength. This allows it to modify synaptic functions in a way that correlates both temporally and spatially with its inducing stimulus. Interestingly, Arc protein is also highly enriched in the nucleus and activity causes an increase in Arc protein within the nucleus. In the nucleus, Arc associates with promyelocytic leukemia tumor suppressor protein nuclear bodies (PML-NBs), which typically regulate transcription. As long-term memory formation requires transcription and is lost in Arc KO mice, Arc might contribute to transcriptional regulation within the nucleus. This finding, combined with the local translation of Arc at activated synapses, might help to explain how a neuron with thousands of synapses and only one nucleus stores information in a manner that is both synapse-specific and dependent on nuclear processes, such as new gene expression. This proposal aims to determine if the activity-induced Arc localization to the nucleus functions as a mechanism to regulate new gene transcription in long-term memory formation. The proposed experiments will clarify the regulation and function of Arc in the nucleus with the goal of elucidating the molecular basis for the consolidation of new memories. This work will ultimately be important not only in our understanding of the molecular processes behind normal memory storage but also will shed light on the processes that are disrupted in neurological disease that affect memory formation and consolidation. Specific Aim 1: To determine if nuclear Arc regulates total AMPAR levels through transcriptional repression. Specific Aim 2: To determine if Arc increases PML-NBs in an activity-dependent manner as a means of regulating transcription. Specific Aim 3: To elucidate the mechanism of Arc nuclear export.