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

描述(申请人提供)：对各种记忆系统的研究表明，长期记忆的存储与基因表达的改变、新蛋白质的合成和新突触连接的生长有关。然而，人们对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海兔的缩鳃反射。这种反射的长期敏感化导致新的突触连接的增长强劲。最近，人们在鉴定一些在发育中的神经系统中形成突触的重要分子方面进行了初步的尝试。具体地说，突触细胞黏附分子--β-神经氨酸(定位于突触前神经元)和神经连接蛋白(定位于突触后神经元)通过跨突触相互作用，参与发育过程中突触的形成。这些分子也可能参与与长期记忆存储相关的突触生长。CASK是一种突触前支架蛋白，与β-Neuresin相互作用，可以移位到细胞核，从而调节基因表达。鉴于长时记忆储存过程中基因表达改变的需要，CAASK作为一种可能的从突触到核的逆行信号，由β-神经尿素素-神经连接素跨突触相互作用触发，是一个有趣的想法。候选人将通过利用海兔感觉-运动神经元共培养准备的实验可及性来研究神经连接素、β-神经尿素素和木桶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健壮和易于研究。该项目将使用分子克隆、使用突触标记蛋白过度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感觉-运动神经元共培养的生理记录。培训活动将使候选人获得必要的技能和经验，以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，研究与学习相关的突触生长，并为突触功能障碍的后遗症开发新的治疗方法。这些研究的结果应该会加强对从突触到核的双向信号通路的理解，该通路调节与长期记忆存储相关的突触生长。此外，它可能提供一些线索，如自闭症等可能由突触可塑性破坏引起的出生后发育障碍的原因，并可能为突触修复和重塑提供新的治疗策略，从而引导各种神经损伤后功能的恢复。

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.