Pum2-dependent translational regulation of a-SYN near mitochondria and contribution to the pathogenesis of Parkinson's disease

α-突触核蛋白 (α-SYN) 和线粒体功能障碍是帕金森病 (PD) 发病机制的两个核心组成部分。线粒体功能障碍是 PD 发病机制多次迭代的一个共同特征，α-SYN 毒性似乎对线粒体的影响最为显着。 α-SYN 和线粒体之间复杂的相互作用已被广泛观察到。虽然我们对线粒体和 α-SYN 之间复杂的串扰知之甚少，但我们的初步研究表明 α-SYN mRNA 的 3'-非翻译区 (3'-UTR) 在线粒体附近 α-SYN 的翻译调节中起着关键作用。我们的初步研究结果表明：1) α-SYN mRNA 定位于线粒体表面，其翻译由线粒体 ROS 启动； 2) 这种翻译控制由 Pum2 控制，Pum2 是一种 RNA 结合翻译抑制因子，它与 α-SYN 转录本的 3'-非翻译区 (3'-UTR) 结合； 3）有趣的是，与对照受试者相比，死后PD大脑中线粒体Pum2水平显着降低，而α-SYN水平相反，这意味着Pum2对线粒体附近的α-SYN具有抑制作用。此外，最近的研究显示 α-SYN 3'-UTR 中的单核苷酸多态性与 PD 之间的关联，强烈表明 3'-UTR 介导的 α-SYN 调节可能成为 PD 发病机制的关键因素。我们的中心假设是，Pum2 介导的线粒体外表面 α-SYN 翻译抑制的失调导致 PD 中观察到的线粒体功能障碍。将追求以下三个具体目标： 在目标 1 中，将鉴定负责 α-SYN 线粒体定位的顺式调控元件和反式因子。在目标 2 中，将确定线粒体 ROS 如何控制 Pum2 介导的 α-SYN mRNA 翻译以及新合成的 α-SYN 的作用。在目标 3 中，将研究 α-SYN 3'-UTR 中的 PD 相关 SNP 是否会导致 Pum2 结合、蛋白质易位到线粒体以及线粒体功能的变化。该项目的成功完成可以通过阐明 Pum2 和 α-SYN 3'-UTR 在翻译调控中的作用，使我们对 PD 发病机制中控制线粒体附近 α-SYN 表达的分子机制的理解发生范式转变。

Alpha-synuclein (α-SYN) and mitochondrial dysfunction are two central components in Parkinson's disease (PD) pathogenesis. Mitochondrial dysfunction is a common feature of the many iterations of PD pathogenesis and α-SYN toxicity seems to affect mitochondria most significantly. Complex interplay between α-SYN and mitochondria has been widely observed. While the intricate crosstalk between mitochondria and α-SYN is poorly understood, our preliminary studies suggest that the 3'-untranslated region (3'-UTR) of α-SYN mRNA plays a key role in translational regulation of α-SYN near mitochondria. Our preliminary findings demonstrate that 1) α-SYN mRNA is localized to the mitochondrial surface where its translation is initiated by mitochondrial ROS; 2) this translational control is governed by Pum2, a RNA-binding translational repressor, which binds to the 3'-untranslated region (3'-UTR) of α-SYN transcript; 3) interestingly, mitochondrial Pum2 levels in post-mortem PD brain were significantly lower compared to control subjects, while α-SYN levels were opposite, implying Pum2’s repressive role on α-SYN near mitochondria. In addition, recent studies showing the association of single nucleotide polymorphisms in the α-SYN 3'-UTR with PD strongly suggest that 3`-UTR-mediated regulation of α-SYN could become a critical player in PD pathogenesis. Our central hypothesis is that deregulation of Pum2-mediated α-SYN translational repression on the outer surface of mitochondria contributes to mitochondrial dysfunction observed in PD. The following three specific aims will be pursued: In Aim 1, both the cis-regulatory elements and the trans- factors responsible for mitochondrial localization of α-SYN will be identified. In Aim 2, it will be determined how mitochondrial ROS controls Pum2-mediated translation of α-SYN mRNA and the roles of newly synthesized α- SYN. In Aim 3, it will be investigated whether PD-associated SNPs in the 3'-UTR of α-SYN cause changes in Pum2 binding, translocation of the protein to mitochondria, and mitochondrial functions. The successful completion of this project could create a paradigm shift in our understanding of molecular mechanisms that control α-SYN expression near mitochondria in PD pathogenesis by elucidating the role of Pum2 and the 3'-UTR of α-SYN in translational regulation