Oxidation-dependent Regulation of MEF2D in Neuronal Stress

描述（由申请人提供）：神经元在面对内源性和外源性毒性应激时，会调动它们的生存机制。许多人类神经系统疾病，如阿尔茨海默病和帕金森病，涉及神经元存活改变和神经元病理损失。本实验室的长期研究目标是在分子水平上了解神经元对应激的反应以及生存反应功能障碍在神经退行性过程中的作用。我们建议在当前的应用中研究神经元存活蛋白肌细胞增强因子2D （MEF2D）是如何被神经元和神经退行性疾病模型中的毒性氧化信号调节的，MEF2D在不同的细胞区室中起关键作用。多种毒性信号导致神经退行性过程的关键共同途径之一涉及氧化应激和线粒体功能障碍。事实上，与AD和PD相关的一些环境毒物和基因改变会破坏线粒体活性并诱导氧化应激。近年来，自噬过程的功能障碍也被证明在神经元应激中起重要作用。然而，在多亚细胞区室中传播初始氧化损伤信号并损害生存的关键环节仍不清楚。我们之前的工作表明，核转录因子MEF2D强烈促进几种类型神经元的存活。我们最近在上一个资助周期的研究表明，MEF2D存在于线粒体中，直接调节线粒体功能，非功能性MEF2D被伴侣介导的自噬（CMA）去除。任何一个过程的破坏都会使神经元对压力敏感，从而导致死亡。这些新发现将MEF2D置于多个亚细胞细胞器的关键位置，在那里它感知和调节神经元对应激的反应。我们的初步研究表明，氧化应激直接改变MEF2D分子，损害其在这些细胞器中的功能和调控。总之，这些发现支持了一个有趣的假设，即MEF2D是神经元氧化的关键靶点，其在多亚细胞器上的功能损伤是氧化诱导应激的基础，并有助于神经退行性过程。我们将结合分子和细胞方法以及动物模型来确定应激是否会导致神经元中MEF2D的氧化修饰；在Aim II中，MEF2D的氧化修饰是否会损害其在神经元中多个亚细胞细胞器中的功能和调控；在第三期研究中，MEF2D的氧化修饰是否发生在神经毒素诱导的退化和人类死后大脑的体内模型中。本研究将确定MEF2D是几个关键细胞器氧化应激的关键靶点，并揭示氧化修饰导致的MEF2D失调可能会破坏神经元的存活。这一新的机制可能与神经退行性疾病的发病机制有关，并为开发新的治疗策略提供依据。

DESCRIPTION (provided by applicant): Neurons, when faced with endogenous and exogenous toxic stress, mobilize their survival machinery. Many human neurological diseases such as Alzheimer's and Parkinson's diseases involve altered neuronal survival and pathological loss of neurons. The long-term objective of this research in our laboratory is to understand at molecular level how neurons respond to stress and the role of dysfunction of survival response in neurodegenerative process. We propose in the current application to study how a neuronal survival protein myocyte enhancer factor 2D (MEF2D), which plays key roles in distinct cellular compartments, is regulated by toxic oxidative signals in neurons and models of neurodegenerative diseases. One of the key common pathways by which diverse toxic signals lead to neurodegenerative process involves oxidative stress and dysfunction of mitochondria. Indeed, several environmental toxicants and genetic alterations associated with AD and PD disrupt mitochondrial activity and induce oxidative stress. Recently, dysfunction of autophagic process has also been shown to play an important role in neuronal stress. However, the key links which propagate the initial oxidative insult in multi subcellular compartments to signal stress and impair survival remain largely unclear. Our previous work showed that nuclear transcription factor MEF2D strongly promotes the survival of several types of neurons. Our recent studies during the last funding cycle revealed that MEF2D is present in mitochondria to directly modulate mitochondrial function and non functional MEF2D is removed by chaperone mediated autophagy (CMA). Disruption of either process sensitizes neurons to stress, leading to death. These novel findings place MEF2D at a key position in multiple subcellular organelles, where it senses and modulates neuronal response to stress. Our preliminary studies suggest that oxidative stress directly modifies MEF2D molecule, impairing its function and regulation in these organelles. Together, these findings support the intriguing hypothesis that MEF2D is a key target of neuronal oxidation and impairment of its function at multi subcellular organelles underlies oxidation-induced stress and contribute to neurodegenerative process. We will combine molecular and cellular methods and animal models to determine in Aim I whether stress causes oxidative modifications of MEF2D in neurons; in Aim II whether oxidative modifications of MEF2D impair its function and regulation in multiple subcellular organelles in neurons; and in Aim III whether oxidative modifications of MEF2D occur in in vivo models of neurotoxin- induced degeneration and human postmortem brains. This study will identify MEF2D as a key target of oxidative stress in several key organelles and reveal that dysregulation of MEF2D by oxidative modifications may undermine neuronal survival. This novel mechanism may be relevant to the pathogenesis of neurodegenerative diseases and provide basis for developing novel therapeutic strategies for their treatment.