Role of Rab proteins in AMPA receptor synaptic targeting

描述(由申请人提供)：大脑中的突触连接不断地重塑，以响应神经元的活动。这一过程被称为突触可塑性，被广泛认为是学习和记忆的细胞基础，并被认为在几种认知障碍中会发生改变。突触可塑性的一个重要方面是神经递质受体在突触内外的调节运动。然而，这种监管发生的机制在很大程度上是未知的。该项目的总体目标是阐明AMPA型谷氨酸受体的运输和突触靶向的控制机制，AMPA型谷氨酸受体是大脑中快速兴奋性传递的主要媒介。为了解决这一重要问题，我们实验室启动了一系列结合分子生物学、电生理学和成像技术的研究，对器官型海马片进行培养。我们的假设是，细胞内膜分选和蛋白质运输的关键介质，如Rab家族的小GTP酶和外囊，调节突触传递和AMPA受体的移除。我们正在通过研究Rab8a、Rab5a和几个胞外亚基在AMPA受体突触运输中的作用来验证这一假说。我们的初步研究表明，Rab8a和Rab5a分别介导了AMPA受体的调节传递和移除，而胞外可能与Rab8a和突触支架分子结合，将受体特异性地靶向突触。我们建议结合功能和解剖学研究来阐明这些分子对AMPA受体运输和突触可塑性的贡献。这一建议构成了研究神经递质受体运输的一种新方法，它将突触上受体运输的局部机制和调节与控制亚细胞膜分选的机制结合起来。我们相信，这些突触可塑性的分子和细胞机制的基础研究将有助于我们进一步了解影响认知功能的生理过程和病理变化。

DESCRIPTION (provided by applicant): Synaptic connections in the brain are continuously remodeled in response to neuronal activity. This process, known as synaptic plasticity, is widely accepted as the cellular basis for learning and memory, and it is thought to be altered in several cognitive disorders. An important aspect of synaptic plasticity is the regulated movement of neurotransmitter receptors in and out of synapses. However, the mechanisms by which this regulation takes place are largely unknown. The general goal of this project is to elucidate the mechanisms controlling the trafficking and synaptic targeting of the AMPA-type glutamate receptors, which are the major mediators of fast excitatory transmission in the brain. To address this important question, our laboratory has initiated a series of studies combining molecular biology, electrophysiology and imaging techniques on organotypic hippocampal slice cultures. Our hypothesis is that key mediators of intracellular membrane sorting and protein transport, such as the Rab family of small GTPases and the exocyst, regulate the synaptic delivery and removal of AMPA receptors. We are testing this hypothesis by investigating the role of Rab8a, Rab5a and several exocyst subunits in AMPA receptor synaptic trafficking. Our preliminary studies suggest that Rab8a and Rab5a mediate the regulated delivery and removal, respectively, of AMPA receptors, whereas the exocyst may act in combination with Rab8a and synaptic scaffolding molecules to target the receptors specifically into synapses. We are proposing a combination of functional and anatomical studies to elucidate the contribution of these molecules to AMPA receptor trafficking and synaptic plasticity. This proposal constitutes a new approach in the study of neurotransmitter receptor trafficking, by integrating the local mechanisms and regulation of receptor transport at the synapse with the machinery that controls subcellular membrane sorting. We believe that these basic studies on the molecular and cellular mechanisms of synaptic plasticity will contribute to further our understanding of the physiological processes and pathological alterations affecting cognitive function.