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。线粒体功能障碍是多种PD发病机制的共同特征，α-SYN毒性似乎对线粒体的影响最为显著。α-SYN与线粒体之间复杂的相互作用已被广泛观察到。虽然线粒体和α-SYN之间复杂的串扰尚不清楚，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的翻译调控中起关键作用。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)这种翻译控制是由Pum2控制的，Pum2是一种rna结合的翻译抑制因子，它结合在α-SYN转录物的3'-非翻译区（3'-UTR）上；3)有趣的是，死后PD脑的线粒体Pum2水平显著低于对照组，而α-SYN水平则相反，表明Pum2对线粒体附近α-SYN有抑制作用。此外，最近的研究表明α-SYN 3′-UTR的单核苷酸多态性与PD的关联强烈表明，3′-UTR介导的α-SYN调控可能成为PD发病的关键因素。我们的中心假设是，线粒体外表面pum2介导的α-SYN翻译抑制的解除有助于PD中观察到的线粒体功能障碍。以下三个具体目标将被追求：在目标1中，将确定负责α-SYN线粒体定位的顺式调控元件和反式因子。在Aim 2中，我们将确定线粒体ROS如何控制Pum2介导的α-SYN mRNA的翻译以及新合成的α-SYN的作用。在Aim 3中，我们将研究α-SYN 3'- utr中pd相关的snp是否会导致Pum2结合、蛋白质向线粒体的转运以及线粒体功能的变化。通过阐明Pum2和α-SYN的3′-UTR在翻译调控中的作用，本项目的成功完成将为我们对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带来范式转变

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