Charting a new path for rapid signaling from the synapse to the nucleus

 描述（由申请人提供）：持久的记忆需要突触修饰以及突触与启动活性依赖性基因表达的细胞核之间的通信。阐明使活跃的突触快速与细胞核通信的细胞机制是神经生物学的一个突出挑战。目前的突触-核通讯模型集中在第二信使或蛋白质在这些遥远的细胞区室之间的运动或动作电位或ER诱发的钙波传播到细胞核中。虽然从突触到细胞核的分子移位明显发生，但它相对缓慢，不能解释实验观察到的细胞核对突触活动的快速反应。此外，突触活动已被证明可以快速触发独立于动作电位产生的核事件，当ER耗尽钙。这个建议将测试的假设，突触激活可以去电ER膜产生的电信号，传播整个细胞的细胞核。ER和核膜是极化的，具有高膜电阻，并含有电压和钙门控离子通道-支持电信号产生和传播的生物物理特征。ER介导的电信号将优先进入核膜中的电压门控通道，启动或促进核钙内流。这个想法将通过将基因编码的荧光电压传感器靶向ER膜来测试，以成像响应突触激活的ER膜电位的真实的时间变化。含有ER的单个或小簇突触将被双光子谷氨酸释放激活，从而允许精确刺激最接近ER的突触。互补地，通道视紫红质将靶向ER膜以确定ER膜去极化是否足以触发核钙事件。如果成功，结果 这项研究的结果将重新定义ER的生物学作用，建立细胞间通讯的新模式，解决神经生物学中的一个长期问题，并开发对神经和细胞生物学社区广泛有用的成像工具。

 DESCRIPTION (provided by applicant): Lasting memories require synaptic modifications as well as communication between the synapse and the nucleus where activity-dependent gene expression is initiated. Elucidating the cellular mechanisms that allow active synapses to rapidly communicate to the nucleus is an outstanding challenge for neurobiology. Current models of synaptic-nuclear communication focus on the movement of second messengers or proteins between these distant cellular compartments or the propagation of action potential or ER evoked calcium waves into the nucleus. While translocation of molecules from the synapse to the nucleus clearly occurs, it is relatively slow and cannot account for the rapidity of experimentally observed nuclear responses to synaptic activity. Moreover, synaptic activity has been demonstrated to rapidly trigger nuclear events independent of action potential generation and when the ER is depleted of calcium. This proposal will test the hypothesis that synaptic activation can depolarize the ER membrane generating an electrical signal that propagates throughout the cell to the nucleus. The ER and nuclear membranes are polarized, have a high membrane resistance, and contain voltage and calcium gated ion channels - biophysical features that support the generation and propagation of electrical signals. ER-mediated electrical signaling would have privileged access to voltage gated channels in the nuclear envelop initiating or facilitating nuclear calcium influx. This idea will be tested by targeting genetically-encoded fluorescent voltage sensors to the ER membrane in order to image real time changes in ER membrane potential in response to synaptic activation. Individual or small clusters of synapses that contain ER will be activated with two-photon glutamate uncaging allowing the precise stimulation of synapses that are in closest proximity to the ER. Complimentarily, channel rhodopsin will be targeted to the ER membrane to determine if ER membrane depolarization is sufficient to trigger nuclear calcium events. If successful, the results of this study will redefine the biological role of the ER, establish a new mode of intercellular cellular communication, resolve a longstanding question in neurobiology, and develop imaging tools that are broadly useful to the neuro- and cell biology communities.