Investigating the relationship between posttranslational modifications and neuronal activity in controling AMPA receptor expression

很明显，哺乳动物的大脑在记忆形成和学习等各种任务中发挥着核心作用。为了做到这一点，大脑依赖于它保存被称为突触的特定神经元连接功能的能力。鉴于突触是大脑中特定神经递质受体定位的功能单位，了解准确和精确地调节其功能的特定机制是至关重要的。 海马区AMPA型谷氨酸受体(AMPAR)的丰富程度决定了突触的效能，因此对学习和记忆至关重要。在这种背景下，迫切需要进行基础研究，以阐明调控AMPAR突触表达的生理分子机制。 最近的证据，包括我以前的工作，表明AMPAR通过磷酸化、泛素化和其他翻译后修饰来控制通道电导、受体运输和突触表达。多年来，AMPAR的磷酸化一直被描述为细胞内路径和突触可塑性的关键调节因子。此外，泛素系统通过作为蛋白质质量控制的主要机制来维持细胞的动态平衡，并特异性地调节AMPAR的运输和表达。尽管有证据支持AMPAR的泛素化和磷酸化之间的关系，但这种错综复杂的相互作用背后的确切机制仍然是一个悬而未决的问题，需要关注。 在此背景下，我的建议的目标是阐明神经元活动以及磷酸化和泛素化之间的关系是如何相互关联的，以控制海马突触中AMPAR的丰富。 通过分子、生化和细胞方法，我的五年研究计划旨在解开泛素化和磷酸化之间的功能相互作用，以调节海马突触的AMPAR。具体地说，我提出的研究将涉及以下目标： 目的1.确定修饰AMPAR磷酸化的酶作为控制亚基泛素化的潜在机制。 目的2.确定特定残基的磷酸化如何调节AMPAR泛素化。 目的3.确定AMPAR磷酸化和泛素化如何调节突触伸缩。 在这项提议完成后，我预计我们的研究活动将阐明控制AMPAR突触表达的动态机制。我们的工作将对基础科学产生重大影响，因为它有可能改变我们对突触可塑性机制的看法。不可否认，我们的工作将有助于提高对控制海马区兴奋性神经传递的分子机制的认识。

It is evident that the mammalian brain plays a central role in various tasks such as memory formation and learning. In order to do so, the brain relies on its ability to preserve the function of specific neuronal connections called synapses. Given that synapses are the functional units of the brain where specific neurotransmitter receptors are localized, understanding the specific mechanisms that accurately and precisely regulate their function is of prime importance. The abundance of AMPA-type glutamate receptors (AMPAR) at hippocampal synapses determines synaptic efficacy and is thus crucial for learning and memory. In this context, there is a critical need for fundamental research aimed at elucidating physiological molecular mechanisms regulating AMPAR synaptic expression. Recent evidences including my prior work show that AMPARs are modified through phosphorylation, ubiquitination and other posttranslational modifications that control channel conductance, receptor trafficking and synaptic expression. Over the years, AMPAR phosphorylation has been described as critical regulator of intracellular routing and synaptic plasticity. Besides, the ubiquitin system preserves cell homeostasis by acting as the primary mechanism of protein quality control, and specifically regulates AMPARs trafficking and expression. Despite evidences that support a relationship between the ubiquitination and the phosphorylation of AMPARs, the exact mechanism underlying such an intricate interplay remains an open question that requires attention. In this context, the goal of my proposal is to shed light on how neuronal activity and the relationship between phosphorylation and ubiquitination are interrelated for controlling the abundance of AMPARs at hippocampal synapses. By means of molecular, biochemical and cellular methods, my 5-years research plan aims to unravel the functional interplay between ubiquitination and phosphorylation for the regulation of AMPAR at hippocampal synapses. Specifically, my proposed research will address the following aims: Aim 1. Identify the enzymes that modify the phosphorylation of AMPAR as an underlying mechanism to control subunit ubiquitination. Aim 2. Define how the phosphorylation of specific residues modulates AMPAR ubiquitination. Aim 3. Determine how AMPAR phosphorylation and ubiquitination regulate synaptic scaling. At the completion of this proposal, I anticipate that our research activities will elucidate a dynamic mechanism controlling the synaptic expression of AMPARs. Our work will have a significant impact in fundamental sciences because it has the potential to transform our vision of the mechanisms involved in synaptic plasticity. Our work will undeniably contribute to the advancement of knowledge regarding the molecular mechanisms controlling hippocampal excitatory neurotransmission.