Regulation of neuronal plasticity by NADPH oxidases

保持可塑性的能力是神经细胞的基本特性。它对于学习和适应以及对损伤或疾病引起的过度兴奋的保护性反应至关重要。我们研究基本问题，例如：“神经细胞如何测量它们的活跃程度？或者：“是什么机制将神经细胞激活的变化转化为神经细胞结构和连接的变化？”“我们研究果蝇。基本细胞过程的高度进化保守性意味着在这个模型系统中所做的大多数发现与我们对人类大脑的理解直接相关，包括学习和记忆的基础机制。重要的是，果蝇是最强大的遗传实验生物之一。例如，果蝇的幼虫是少数几个模型系统之一，它的大脑回路已经接近完成，人们可以在遗传学上以无与伦比的精度操纵单个连接神经元。我们最近发现，神经细胞使用活性氧（ROS）作为信号来监测自己的活动水平。众所周知，ROS水平随着年龄的增长而在大脑中增加，并且在许多神经退行性疾病中达到病理水平，包括阿尔茨海默氏症、帕金森病或运动神经元疾病。神经细胞密切调节其突触末端的大小和与其他神经细胞连接的数量。我们发现，在正常的生理水平ROS调节这一过程。一些ROS由线粒体产生，作为其能量/ATP代谢的组成性副产物。这一发现表明，神经细胞可能使用代谢ROS信号作为其活动水平的读数。作为ROS的细胞传感器，我们鉴定了保守的氧化还原敏感蛋白DJ-1b（Park 7），其通过PI 3激酶生长途径调节突触末端的大小。在这个提议中，我们专注于在质膜上由NADPH氧化酶产生的ROS。这些调节突触末端的大小，与神经系统产生的ROS形成对比，ROS控制这些末端与突触的密度。NADPH氧化酶以其在免疫系统中的作用而闻名。在神经系统中，它们被认为是学习相关可塑性所必需的，最近的一项研究表明，它们的失调可能导致精神疾病，如精神分裂症。我们的建议的第一个目的是确定突触末梢的结构变化是如何被生理功能改变所掩盖的。使用最先进的成像方法，我们将确定NADPH氧化酶在调节中枢神经系统（CNS）的活性依赖性连接中的作用。接下来，为了确定神经元活动如何调节NADPH氧化酶的激活，我们将寻求确定相互作用的调节蛋白和探针与其他已知调节突触末端生长的信号通路的相互作用。我们的第三个目标是探索NADPH氧化酶协调神经元重塑过程中发生的复杂细胞间相互作用的潜力：神经元，其细胞外环境和相邻的神经胶质细胞之间。NADPH氧化酶通过在细胞间空间产生ROS信号，是协调局部细胞间相互作用的理想场所，可能是免疫和神经系统之间保守的信号通路。总之，我们的目标是了解可塑性的基本机制，这可能会在老化的大脑中受到损害。虽然我们的工作是基础科学，但它有可能帮助发现药物和治疗方法，这些药物和治疗方法可以减轻衰老的不利影响，从而及时造福社会。

The ability to remain plastic is a fundamental property of nerve cells. It is critical for learning and adaptation, as well as for protective responses to over-excitation caused by injury or disease. We study basic questions, such as: "How do nerve cells measure how active they are?" or: "What mechanisms transform changes in nerve cell activation into changes of nerve cell structure and connectivity?" We work with the fruit fly, Drosophila. The high evolutionary conservation of basic cellular processes has meant that most discoveries made in this model system are directly pertinent to our understanding of the human brain, including mechanisms that underlie learning and memory. Importantly, the fruit fly is one of the most powerful genetic experimental organisms. For example the larva of the fruit fly is one of the few model systems whose brain circuitry has been charted close to completion and where one can genetically manipulate individual connecting neurons with unrivalled precision. We recently discovered that nerve cells use reactive oxygen species (ROS) as signals to monitor their own activity levels. ROS levels are well known to increase in the brain with ageing and to reach pathological levels in many neurodegenerative conditions, including Alzheimer's, Parkinsonism or Motorneuron Disease. Nerve cells closely regulate the size of their synaptic terminals and the number of connections to other nerve cells. We found that at normal physiological levels ROS regulate this process. Some ROS are produced by mitochondria as constitutive by-products of their energy/ATP metabolism. This finding suggests that nerve cells might use metabolic ROS signals as a readout of their activity levels. As a cellular sensor for ROS we identified the conserved redox sensitive protein DJ-1b (Park7), which regulates synaptic terminal size through the PI3Kinase growth pathway.More recently we discovered that ROS produced in different sub-cellular compartments of nerve cells regulate different aspects of synaptic terminal plasticity. In this proposal we focus on ROS generated at the plasma membrane by NADPH oxidases. These regulate the size of synaptic terminals, as contrasting with mitochondrially produced ROS, which control how densely such terminals are populated with synapses. NADPH oxidases are best known for their roles in the immune system. In the nervous system they are thought to be required for learning associated plasticity, and a recent study suggests that their dysregulation could cause psychiatric conditions, such as schizophrenia. The first aim of our proposal is to determine how structural changes of synaptic terminals are paralleled by physiological functional alterations. Using state of the art imaging methods we will determine the role of NADPH oxidases in regulating activity-dependent connectivity in the central nervous system (CNS). Next, to determine how neuronal activity regulates NADPH oxidase activation, we will seek to identify interacting regulatory proteins and probe interactions with other signalling pathways known to regulate synaptic terminal growth. Our third aim explores the potential of NADPH oxidases to orchestrate the complex inter-cellular interactions that take place during neuronal remodelling: between neurons, their extracellular environment and adjacent glial cells. By producing ROS signals within the inter-cellular space, NADPH oxidases are ideally placed for coordinating local intercellular interactions, potentially signalling pathways conserved between the immune and nervous system.In summary, we aim to understand fundamental mechanisms of plasticity, which might be compromised in the ageing brain. Though our work is basic science it has the potential to aid the discovery of drugs and treatments that could alleviate adverse effects of ageing and might thus, in time, benefit society.