Neurexin-Neuroligin Trans-synaptic Interaction: Learning-related Synaptic Growth

描述（由申请人提供）：各种记忆系统的研究表明，长期记忆的储存与基因表达的改变、新蛋白质的合成和新突触连接的生长有关。然而，关于启动和维持与长期记忆相关的结构变化的分子机制知之甚少。描述这些分子机制的一个特别有用的系统是鳃退缩反射。这种反射的长期敏化导致新突触连接的强劲增长。最近，初步尝试已确定一些分子重要的从头突触形成在发育中的神经系统。具体来说，突触细胞粘附分子，β -神经rexin（定位于突触前神经元）和神经素（定位于突触后神经元），通过相互间的突触相互作用，被发现在发育过程中参与突触的形成。这些分子也可能参与与长期记忆储存相关的突触生长。CASK是一种突触前支架蛋白，与β -神经rexin相互作用，可以转移到细胞核，从而调节基因表达。鉴于长期记忆存储需要改变基因表达，CASK作为β -神经素-神经素跨突触相互作用触发的从突触到细胞核的逆行信号是一个有趣的想法。该候选人将通过利用applysia感觉-运动神经元共培养制备的实验可及性来研究神经素，β -神经素和CASK在与长期记忆存储相关的突触生长中的作用，其中与长期突触可塑性相关的突触前结构变化特别强大且易于研究。分子克隆、使用突触标记蛋白过表达的基因转移技术、个体的延时共聚焦成像、荧光标记的突触前感觉神经元变异以及相同的感觉-运动神经元共培养的生理记录将用于该项目。培训活动将使候选人获得必要的技能和经验，成为一名独立的神经科学家，配备最新的分子和细胞生物学技术来研究与学习相关的突触生长，并开发新的治疗方法来治疗突触功能障碍的后果。这些研究的结果将加强对从突触到细胞核的双向信号通路的理解，该通路调节与长期记忆储存相关的突触生长。此外，它可能为自闭症等可能由突触可塑性破坏引起的产后发育障碍的病因提供一些线索，并可能为各种神经损伤后突触修复和重塑导致功能恢复提供新的治疗策略。

DESCRIPTION (provided by applicant): Studies in a variety of memory systems have suggested that the storage of long-term memory is associated with altered gene expression, the synthesis of new proteins, and the growth of new synaptic connections. However, little is known about molecular mechanisms that initiate and maintain the structural changes associated with long-term memory. A particularly useful system for delineating these molecular mechanisms is the gill-withdrawal reflex in Aplysia. Long-term sensitization of this reflex gives rise to robust increase in growth of new synaptic connections. Recently, initial attempts have been made in identifying some molecules important for do novo synaptic formation in the developing nervous system. Specifically, synaptic cell adhesion molecules, beta-neurexin (localized at the pre-synaptic neurons) and neuroligin (localized at the postsynaptic neurons), via trans-synaptic interaction with each other, have been found to be involved in synapse formation during development. These molecules may be also involved in the synaptic growth associated with the storage of long-term memory. CASK, a pre-synaptic scaffolding protein that interacts with beta-neurexin, can translocate to the nucleus and thereby regulates gene expression. Given the requirement of altered gene expression in the storage of long-term memory, CASK as a putative retrograde signal from the synapse to the nucleus triggered by beta-neurexin-neuroligin trans-synaptic interaction is an intriguing idea. The candidate will investigate the role of neuroligin, beta-neurexin, and CASK in the synaptic growth associated with the storage of long-term memory by exploiting the experimental accessibility of the Aplysia sensory-motor neuron co-culture preparation where the pre-synaptic structural changes associated with long-term synaptic plasticity are particularly robust and easy to study. Molecular cloning, gene transfer techniques using over-expression of synaptic marker proteins, time-lapse confocal imaging of individual, fluorescently-labeled pre-synaptic sensory neuron varicosities and physiological recording of the same sensory-motor neuron co-cultures will be used for the project. The training activities will enable the candidate to acquire the skills and experience necessary to become an independent neuroscientist equipped with the latest molecular and cellular biological techniques to investigate the learning-related synaptic growth and to develop novel therapeutic approaches to the sequel of synaptic dysfunction. Results from these studies should enhance understanding of a bidirectional signaling pathway from the synapse to the nucleus that regulates synaptic growth associated with the storage of long-term memory. In addition, it may provide some clues to the causes of postnatal developmental disorders such as autism that may be caused by disruption of synaptic plasticity and perhaps suggest novel therapeutic strategies for synaptic repair and remodeling leading recovery of function after various neurological insults.