Effectors of presynaptic cAMP dependent potentiation at mossy fiber synapses

总结 海马中的突触可塑性对于情景记忆的形成、储存和提取至关重要。 海马体的不同区域已经进化到在空间导航、语境和认知中扮演不同的角色。 记忆，社会记忆，以及我们分离模式或完整模式以重建部分模式的能力。 回忆特别是海马的齿状和CA 3区参与模式分离 这对情景记忆的完整性至关重要在这个区域的中心是苔藓纤维传入， 在CA 3锥体神经元上形成条件性引爆突触，CA 3锥体神经元具有独特的突触前形式， cAMP依赖的可塑性。尽管cAMP可塑性对记忆的形成和恢复很重要，但在脑内， CA 3，MF LTP的确切分子机制尚未被揭示。此前提 研究建立在我们发现至少有两种下游cAMP效应物PKA（蛋白激酶 A）和Epac 2（由cAMP 2直接激活的交换蛋白），其有助于cAMP依赖性MF LTP。 尽管有这些发现，但仍然不知道这些效应物中的每一个的信号传导如何导致释放升高。 从MF突触，什么是重要的目标和基板，参与MF LTP。 在这里，我们将使用一个全面的方法与领先的蛋白质组学，生物化学和 电生理学方法来确定cAMP效应器的信号传导伙伴，并揭示 其作用的生理机制。因此，在目标1中，我们将采用正交方法来找到 PKA和Epac 2的相互作用物和底物，并通过进行高分辨率原位标记来验证这些。 在目标2中，我们将确定增加释放的确切生理机制。 使用组合的光激活敲除/药理学策略，在MF突触处检测神经递质。在 最后一个目标是，我们将回答这些不同但趋同的机制在 自然的活动模式，以及这些效应器的选择性破坏是否会损害小鼠的能力， 分离类似的模式，这些模式是情景记忆形成和提取的基础。

SUMMARY Synaptic plasticity in the hippocampus is critical to the formation, storage and retrieval of episodic memories. The separate regions of the hippocampus have evolved to play distinct roles in spatial navigation, contextual memories, social memories, and our ability to separate patterns or complete patterns to reconstruct partial memories. In particular the dentate and CA3 regions of the hippocampus are involved in pattern separation that is vital to the integrity of episodic memories. At the center of this region are the mossy fiber afferents that make conditional detonator synapses onto CA3 pyramidal neurons, which have a distinct form of presynaptic cAMP dependent plasticity. Despite the importance of cAMP plasticity to memory formation and retrieval in the CA3 the exact molecular mechanisms underlying MF LTP have yet to be uncovered. The premise of this research builds upon our finding that there are at least two downstream cAMP effectors, PKA (protein kinase A) and Epac2 (exchange protein directly activated by cAMP 2), that contribute to cAMP dependent MF LTP. Despite these findings it is still not known how signaling by each of these effectors results in elevated release from MF synapses and, what are the important targets and substrates that are involved in MF LTP. Here we will use a comprehensive approach with leading edge proteomic, biochemical and electrophysiological approaches to determine the signaling partners of the cAMP effectors, and uncover the physiological mechanism of their actions. Thus, in Aim 1 we will take orthogonal approaches to find the interactors and substrates of PKA and Epac2 and validate these by performing high resolution labeling in situ. In Aim 2 we will determine the exact physiological mechanism that underlie increases in release of neurotransmitter at MF synapses using a combined optoactivation-knockout/pharmacological strategy. In the final Aim we will answer the question of how these different, but convergent, mechanisms are engaged during naturalistic activity patterns, and whether selective disruption of these effectors impairs the ability of mice to separate similar patterns that underlie the formation and retrieval of episodic memories.