Mechanisms of Ras Signaling in Single Synapses

描述（由申请人提供）：小GT3蛋白Ras对于突触可塑性所必需的许多神经元过程是重要的，包括长期突触增强、新突触的形成和细胞兴奋性的调节。Ras对长期维持突触可塑性所需的蛋白质合成和基因转录也很重要。与Ras信号传导在突触可塑性中的重要作用一致，异常Ras信号传导与引起认知障碍和学习缺陷的疾病相关。尽管Ras信号在突触可塑性中的重要性已被充分认识，但Ras信号的时空动力学如何调节其在不同亚细胞区室中的不同下游效应尚不清楚。本研究利用双光子荧光寿命成像技术和双光子谷氨酸释放技术，探讨单个树突棘突触可塑性诱导过程中Ras激活的机制和作用。我们的具体目标是：1）阐明神经纤维蛋白在塑造单个棘中Ras激活的时空分布中的作用，2）确定在棘结构可塑性期间控制Ras激活的激酶的激活动力学，以及3）阐明突触到核Ras-ERK信号传导的机制。这项工作将推进我们对Ras如何将钙与突触可塑性结合，并最终与学习和记忆结合的理解。

DESCRIPTION (provided by applicant): The small GTPase protein Ras is important for many neuronal processes essential to synaptic plasticity including long-term synaptic potentiation, formation of new synapses, and regulation of cell excitability. Ras is also important for protein synthesis and gene transcription required for long-term maintenance of synaptic plasticity. Consistent with essential roles of Ras signaling in synaptic plasticity, abnormal Ras signaling is associated with diseases causing cognitive impairments and learning deficits. Although the importance of Ras signaling in synaptic plasticity is well recognized, it is not clear how the spatiotemporal dynamics of Ras signaling regulate its diverse downstream effects in different subcellular compartments. Using 2-photon fluorescence lifetime imaging and 2-photon glutamate uncaging, the objective of this project is to elucidate mechanisms and roles of Ras activation in neurons during synaptic plasticity induced in a single dendritic spine. Our specific aims are 1) to elucidate the roles of Neurofibromin in shaping the spatiotemporal profile of Ras activation in single spines, 2) to determine the activation kinetics of kinases that controls Ras activation during spine structural plasticity, and 3) to elucidate the mechanisms of synapse to nucleus Ras-ERK signaling. This work will advance our understanding of how Ras couples calcium with synaptic plasticity, and ultimately with learning and memory.