An adaptor protein for dendritic spine exocytosis and postsynaptic plasticity

描述（由申请人提供）：ampa型谷氨酸受体（AMPAR）从细胞内隔室靶向递送到突触后膜是哺乳动物大脑中与学习相关的突触可塑性的主要细胞机制。然而，对于确保ampar在脊柱特异性转运到突触的分子机制，我们所知甚少。我们实验室之前的工作已经证明，当使用一种被称为长期增强（LTP）的学习协议时，脊髓内部和基部的再循环核内体（REs）为突触提供膜和ampar。尽管已经确定树突棘的活性依赖性REs募集对于LTP的表达至关重要，但树突中受体和膜的RE对接的精确位置仍然不清楚。在这里，我们已经确定了树突棘中位于突触后密度附近的胞吐区域。此外，我们描述了一个假定的分子传感器，适配器分子Rabi 1-FIP2，它有助于REs的正确膜定位，以实现正确的脊柱胞分泌。该提案旨在(1)确定Rabi 1- fip2脊柱定位所需的信号通路(2)确定Rabi 1- fip2破坏是否介导脊柱胞分泌(3)确定Rabi 1- fip2破坏对促进AMPA受体传递到脊柱膜以表达LTP的功能后果。实验将采用基础生化方法和海马神经元活细胞成像相结合的方法来确定Rabi 1-FIP2对脊柱胞分泌的关键信号通路和需求。此外，我们将利用海马器官型切片结合电生理学来检测Rabi 1-FIP2对LTP的作用。由于REs的胞外分泌对于AMPARs向突触后膜的正确传递至关重要，我们认为这种依赖于Rabi 1-FIP2的细胞机制是哺乳动物大脑中与学习相关的突触可塑性的关键因素。公共信息：AMPA受体（ampar）从胞内腔室被称为循环内体传递到突触的突触后膜是大脑中与学习相关的突触可塑性的主要细胞机制。此外，树突棘内体功能失调和AMPAR运输导致各种神经系统疾病，如阿尔茨海默病、唐氏综合征和精神分裂症。这一建议将集中于识别哺乳动物大脑中与学习相关的突触可塑性至关重要的分子机制，并将深入了解内体功能的破坏如何导致神经系统疾病。

DESCRIPTION (provided by applicant): The targeted delivery of AMPA-type glutamate receptors (AMPAR) from intracellular compartments to the postsynaptic membrane is a major cellular mechanism for learning-related synaptic plasticity in the mammalian brain. Yet, little is known about the molecular machinery that ensures the spine- specific transport of AMPARs to the synapse. Prior work in our laboratory has demonstrated that recycling endosomes (REs) within and at the base of spines provide membrane and AMPARs to the synapse when using a protocol for learning known as long term potentiation (LTP). Although it is established that activity- dependent recruitment of REs to dendritic spines is essential for the expression of LTP, the precise location of RE docking for the delivery of receptors and membrane in dendrites remains obscure. Here, we have identified regions of exocytosis in dendritic spines that are positioned adjacent to the postsynaptic density. Further, we describe a putative molecular sensor, the adaptor molecule Rabi 1-FIP2 which aids in the correct membrane positioning of REs for proper spine exocytosis. This proposal will aim to (1) identify the signaling pathways required for Rabi 1-FIP2 spine localization (2) determine if disruption of Rabi 1-FIP2 mediates spine exocytosis and (3) define the functional consequences of Rabi 1-FIP2 disruption on facilitating delivery of AMPA receptors to spine membranes for the expression of LTP. Experiments will use a combination of basic biochemical approaches and live cell imaging in hippocampal neurons to identify the critical signaling pathways and requirement of Rabi 1-FIP2 for spine exocytosis. Further, organotypic hippocampal slices in combination with electrophysiology will be used to test the function of Rabi 1-FIP2 on LTP. Since exocytosis from REs is crucial for the proper deliver of AMPARs to the postsynaptic membrane, we propose that this Rabi 1-FIP2 dependent cellular mechanism is a key element for learning-related synaptic plasticity in the mammalian brain. Public information: The delivery of AMPA receptors (AMPARs) from intracellular compartments known as recycling endosomes to the postsynaptic membrane of synapses is a major cellular mechanism for learning- related synaptic plasticity in the brain. In addition, dysregulation of endosomal function and AMPAR trafficking in dendritic spines contributes to various neurological disorders such as Alzheimer's disease, Down's syndrome, and schizophrenia. This proposal will focus on identifying the molecular machinery that is critical for learning-related synaptic plasticity in the mammalian brain and will provide insight into how disruption of endosomal function leads to neurological disease.