Pum2-dependent translational regulation of a-SYN near mitochondria in neurites

描述(申请人提供)：路易神经节(LNS)和路易小体(LBS)中α-突触核蛋白(α-SYN)聚集的存在，帕金森病(PD)的病理特征，以及线粒体功能障碍是帕金森病发病的两个主要组成部分。已知的α-SYN的生理作用仅限于突触终末，这增加了α-SYN mRNA被运输到突起并其翻译受到局部控制的可能性。事实上，我们最近发现，α-SYN mRNA被转位到完全分化的人多巴胺能神经元细胞的神经突起中。我们还发现，Pum2是哺乳动物PUF家族RNA结合蛋白的平行序列，它与α-SYN 3‘UTR的PUM结合基序结合，负责神经细胞的定位以及α-SYN mRNA的翻译抑制。由呼吸复合体I抑制产生的线粒体ROS导致与线粒体相关的mRNA局部翻译α-SYN，提示Pum2可能将线粒体信号传递给α-SYN翻译。尽管很明显，线粒体和α-SYN之间存在相互关系，但这种相互作用的分子机制仍然难以捉摸。我们的中心假设是Pum2负责α-SYN mRNA的转运到线粒体旁间隔，α-SYN翻译调节和轴突聚集。本项目的目的是通过Pum2介导的线粒体相关α-SYN mRNA的翻译调控，了解α-SYN与神经突起中线粒体之间的相互作用。为了实现这些目标，我们提出了以下三个具体目标：目的1.研究Pum2在α-SYN mRNA线粒体定位中的作用。目的2.研究线粒体ROS是如何控制α-SYN翻译的。目的3.确定线粒体附近新合成的α-SYN如何影响神经突起中线粒体的断裂和α-SYN的聚集。该项目的成功完成将使我们对控制神经突起中α-SYN水平的分子机制以及线粒体ROS如何参与这种α-SYN调控的理解发生范式转变。该项目预期的结果将为了解1)α-SYN在神经突起中的转录后调控以及Pum2‘S在这一过程中的作用开辟新的途径，2)α-SYN与神经突起中线粒体之间的亲密信号，3)它在线粒体碎裂和LN形成中的作用。

DESCRIPTION (provided by applicant): The presence of alpha-synuclein (alpha-SYN) aggregate in Lewy neurites (LNs) and Lewy bodies (LBs), the pathological hallmarks of Parkinson's disease (PD), and mitochondrial dysfunction are two central components in PD pathogenesis. Known physiological roles of alpha-SYN are limited in synaptic terminals, raising the possibility that alpha-SYN mRNA is transported to neurites and its translation is locally controlled. In fact, we have recently found that alpha-SYN mRNA is translocated into neurites of fully differentiated human dopaminergic neuronal cells. We also identified that Pum2, a paralogue of mammalian PUF family RNA binding protein, binds to a PUM binding motif of the alpha-SYN 3'UTR and is responsible for neuritic localization as well as translational repression of alpha-SYN mRNA. Mitochondrial ROS generated by respiratory complex I inhibition led to local translation of alpha-SYN from mRNA associated with mitochondria, suggesting that Pum2 might transmit mitochondrial signal to alpha-SYN translation. Although it is obvious that there is an inter- relationship between mitochondria and alpha-SYN underlying the development of disease, molecular mechanisms governing this cross-talk remain elusive. Our central hypothesis is that Pum2 is responsible for alpha-SYN mRNA transport to the juxta-mitochondrial compartment, alpha-SYN translational regulation and aggregation in neurites. The objectives of this project are to understand the interplay between alpha-SYN and mitochondria in neurites through Pum2-mediated translational regulation of mitochondria-associated alpha-SYN mRNA. To achieve these objectives we propose the following three specific aims: Aim 1. Examine the role of Pum2 in mitochondrial localization of alpha-SYN mRNA. Aim 2. Examine how mitochondrial ROS control alpha-SYN translation. Aim 3. Determine how newly synthesized alpha-SYN near mitochondria affects mitochondrial fragmentation and alpha-SYN aggregation in neurites. The successful completion of the project will bring a paradigm shift in our understanding of molecular mechanisms that control alpha-SYN level in neurites and how mitochondrial ROS contribute to this alpha-SYN regulation. The results expected from the project will open new avenues to understand 1) 3'UTR-dependent posttranscriptional regulation of alpha-SYN in neurites and Pum2's role in this process, 2) intimate crosstalk between alpha-SYN and mitochondria in neurites and 3) its contribution to mitochondrial fragmentation and LN formation.