Actin Dynamics and Spine Remodeling in Ethanol-Induced Plasticity

描述(申请人提供)：改变脊椎的大小、形状和数量被认为是经验依赖性神经元回路改变的重要组成部分，并可能在成瘾的可塑性中发挥重要作用。活性依赖可塑性的细胞模型表明，谷氨酸受体亚细胞定位的变化与突触后密度的分子重组以及脊柱形态和/或密度的变化有关。谷氨酸受体的NMDA亚型在突触可塑性中起着核心作用，也是乙醇的已知靶标。长期饮用酒精会导致神经元功能的适应性变化，表现为耐受、身体依赖和成瘾。我们最近发现的一种潜在的适应性机制是选择性地将含有NR2B的NMDA受体靶向突触。这种增加与支架蛋白PSD-95在突触后密度的定位增加以及依赖肌动蛋白的树突棘大小的增加有关，并依赖于此。这些观察结果导致我们提出了一个酒精诱导的兴奋性突触可塑性的分子模型，其中含有NR2B的NMDA受体和突触后密度的PSD-95的增加为调节脊髓肌动蛋白动力学、蛋白质翻译和突触可塑性的信号分子的招募和激活提供了一个扩展的支架平台。这一新的应用将利用生化、共聚焦成像和电生理学程序，使用明确定义的慢性酒精暴露的体外和体内模型来测试这一假说。具体目的是：(1)测试慢性酒精暴露会改变脊柱肌动蛋白动力学调制的假说；(2)测试慢性酒精暴露增加树突棘大小的假说；(3)测试慢性酒精暴露增强PSD依赖的翻译调控蛋白与调节活性依赖的脊椎重塑的关联的假说；(4)测试PSD假说，即慢性乙醇诱导的突触可塑性的发展需要PSD支架信号复合体来支持基于肌动蛋白的脊柱重塑。这是一个新颖而及时的建议，与越来越多的证据一致，即PSD对脊柱肌动蛋白的谷氨酸能调制在酒精中毒和酒精相关行为的可塑性中起着关键作用。与公共健康相关的酒精中毒的特征是对酒精的渴望和强迫性酒精寻求行为。这些行为的持久性和顽固性可能类似于学习和记忆过程，这可能是加性行为的基础。因此，确定酒精暴露导致大脑异常和不适当的突触连接的过程可能会导致有效治疗酒精中毒和酒精相关障碍的新方法。

DESCRIPTION (provided by applicant): Modifications of the size, shape, and number of spines is thought to be an important component of experience-dependent changes in neuronal circuits and may play an important role in the plasticity of addiction. Cellular models of activity-dependent plasticity have shown that changes in the subcellular localization of glutamate receptors are associated with a molecular reorganization of the postsynaptic density and alterations in spine morphology and/or density. The NMDA subtype of glutamate receptors play a central role in synaptic plasticity and are known targets of ethanol. Chronic ethanol consumption results in adaptive changes in neuronal function that manifest as tolerance, physical dependence and addiction. A potential adaptive mechanism we recently identified is the selective targeting of NR2B-containing NMDA receptors to the synapse. This increase is associated with, and dependent upon, a corresponding increase in the localization of the scaffolding protein PSD-95 at the postsynaptic density, and with an actin-dependent increase in the size of dendritic spines. These observations lead us to propose a molecular model for ethanol- induced plasticity at excitatory synapses in which increases in NR2B-containing NMDA receptors and PSD-95 at the postsynaptic density provides an expanded scaffolding platform for the recruitment and activation of signaling molecules that regulate spine actin dynamics, protein translation and synaptic plasticity. This renewal application will utilize biochemical, confocal imaging and electrophysiology procedures to test this hypothesis using well-defined in-vitro and in- vivo models of chronic ethanol exposure. The specific aims are to: (1) Test the hypothesis that modulation of spine actin dynamics is altered in response to chronic ethanol exposure; (2) Test the hypothesis that chronic ethanol exposure increases the size of dendritic spines; (3) Test the hypothesis that chronic ethanol exposure enhances the PSD-dependent association of translational-regulatory-proteins that modulate activity-dependent spine remodeling; (4) Test the hypothesis that the development of chronic ethanol-induced synaptic plasticity requires a PSD scaffolding-signaling complex that can support actin-based spine remodeling. This is a novel and timely proposal that is consistent with accumulating evidence that glutamatergic modulation of spine actin by the PSD plays a critical role in the plasticity of alcoholism and alcohol-related behaviors. PUBLIC HEALTH RELEVANCE Alcoholism is characterized by craving for alcohol and compulsive alcohol-seeking behavior. The persistence and intractable nature of these behaviors may be analogous to learning and memory processes that may underlie the hardwiring of the additive behavior. Thus, determining the processes by which alcohol exposure leads to aberrant and inappropriate synaptic connections of the brain may lead to novel approaches to effective treatments of alcoholism and alcohol related disorders.