支架蛋白RIM1调控NMDA受体质膜插入的机制及功能研究

NMDA受体是脑内重要的兴奋性递质受体，它的运输受到精确调控并决定突触上受体的表达量及亚型构成，进而决定突触功能。以往针对其运输调控机制的研究主要围绕受体亚单位分子内序列信号的识别及翻译后修饰位点的鉴定而展开。但是，NMDA受体与突触前神经递质类似，是以囊泡形式运输，目前尚不清楚含受体的运输囊泡是如何被调控。我们发现突触前调控递质囊泡释放的核心蛋白RIM1在突触后也有分布，并特异性地存在于NMDA受体复合物中，抑制RIM1的表达明显减少NMDA受体膜表面的分布，提示RIM1参与NMDA受体运输的调控。结合突触前RIM1在递质囊泡释放中的作用，我们提出假设，突触后RIM1参与调控NMDA受体运输，特别是质膜插入过程。本项目将验证该假设并研究其分子机制，以及此过程与神经元活动的关系，及其在某些神经疾病，如慢性神经痛中的作用。此研究将有助于我们从受体囊泡与质膜融合的角度来理解受体运输的调控机制。

NMDA receptor is one of the most important excitatory neurotransmitter receptors in the brain. Its trafficking is precisely regulated and determines the amount and subtype of synaptic receptors, which in turn determines synaptic function. Previous research on the molecular mechanisms involved in NMDA receptor trafficking is mainly focused on the identification of the molecular motif within the receptor subunit, such as ER retention motif, or post-translational modification of the receptor subunit, such as phosphorylation and palmitoylation. As we know, NMDA receptor, similar with presynaptic neurotransmitter, is transported in form of vesicles. Howerver, it is still unclear as to the mechanisms mediating the trafficking of receptor-containing vesicles. In our present study,by using EM imaging, we found that the scaffolding protein RIM1, which plays key roles in the release of presynaptic neurotransmitter vesicles, was located both presynaptically and postsynaptically. In addition, biochemical results showed that RIM1 was specifically bound to NMDA receptor complex, but not to AMPA receptor complex. Moreover, RIM1 siRNA knockdown specifically decreased the surface distribution of NMDA receptor in cultured cortical neurons, indicating that RIM1 participated in the regulation of NMDA receptor trafficking. Combined with the previous work indicating that presynaptic RIM1 is critical for the vesicle release, we provide a hypothesis that postsynaptic RIM1 is involved in the regulation of NMDA receptor trafficking, especially NMDA receptor membrane insertion. Therefore, in this project, we will focus on this hypothesis and find out the molecular mechanisms underlying this process. Furthermore, we will examine whether this process is controlled by neuronal activity and the role of this process in some pathological conditions, such as chronic neuropathic pain. This research will be a great help for us to understand NMDA receptors trafficking in the view of receptor-containing vesicles.