RNA trafficking in mitochondria

总结 线粒体有许多信号通路将压力传递到细胞的其余部分。类似于 病原体释放病原体相关分子模式（PAMPs），线粒体释放新的 损伤相关分子模式（DAMP），包括脂质、肽和线粒体DNA（mtDNA）， 这表明线粒体压力。线粒体双链RNA（Mitochondrial double-stranded RNA，mtdsRNA）是一类新的DAMPs 当mtDNA中的非编码链不能有效降解并积累时， 与编码链配对。在正常条件下，解旋酶SUV 3解旋mtDNA， 多核苷酸磷酸化酶（PNIPs）降解它们。然而，SUV 3的击倒导致了 线粒体内mtdsRNAs的积累，而敲低PNTR导致线粒体内mtdsRNAs的释放。 线粒体双链RNA进入胞质溶胶。一旦在胞质溶胶中，mtdsRNA就被dsRNA传感器MDA 5和 RIG-I，导致I型干扰素途径的诱导。mtdsRNA的输出可能很重要， 已经在PNPT 1（编码PNPT 1）突变患者的胞浆中鉴定出mtdsRNA， 疾病，包括癌症、心脏病、酒精相关性肝病和自身免疫性疾病。 将检验mtdsRNA代表线粒体功能障碍的新生物标志物的假设。 由于这是一个新的途径，在理解分子规则和机制方面存在着关键的差距， mtdsRNA穿过线粒体内膜和外膜用于胞质输出。我们的学习目标是 包含在三个独立但主题相关的具体目标中。在目标1中， 从线粒体输出的蛋白质将在大小和序列特异性方面进行表征。此外，本发明还提供了一种方法， RNA修饰酶将被测试以确定哪些组分对于产生 线粒体双链RNA目的2将集中于外膜和内膜通道的鉴定以及PNNI在细胞内的作用。 将线粒体双链RNA运输出线粒体。第三个目标将定义导致以下结果的生理参数： 线粒体双链RNA的产生和胞质双链RNA传感器的测定， 这个过程由于PNTR的突变导致线粒体疾病，突变体将被表征为 确定是否可以分离mtdsRNA降解和/或输出的步骤。 我们的研究小组一直在广泛地表征PNTR及其在线粒体中的功能。独特 可用于我们工作的模型系统包括小鼠模型，其中固定的PNPT 1可以通过 Cre重组酶，和来自该模型的小鼠胚胎成纤维细胞。该提案的结果将 详细定义线粒体双链RNA运输出线粒体的途径， 了解PNTR基因突变如何导致疾病。从长远来看，这些研究可能会导致 将mtdsRNA作为线粒体功能障碍的新生物标志物。

SUMMARY Mitochondria have numerous signaling pathways for conveying stress to the rest of a cell. Similar to pathogens that release pathogen-associated molecular patterns (PAMPs), mitochondria release novel damage-associated molecular patterns (DAMPs), including lipids, peptides, and mitochondrial DNA (mtDNA), that indicate mitochondrial stress. Mitochondrial double-stranded RNA (mtdsRNA) is a new class of DAMPs that is generated when the noncoding strand in mtRNA is not degraded efficiently and accumulates, allowing base-pairing with the coding strand. Under normal conditions, the helicase SUV3 unwinds the mtRNAs and polynucleotide phosphorylase (PNPase)ndegrades them. However, knockdown of SUV3 results in the accumulation of mtdsRNAs within mitochondria, and knockdown of PNPase leads to the release of the mtdsRNAs into the cytosol. Once in the cytosol, the mtdsRNAs are sensed by dsRNA sensors MDA5 and RIG-I, leading to the induction of the type I interferon pathway. The export of mtdsRNA is likely important as mtdsRNAs have been identified in the cytosol of patients with mutations in PNPT1, encoding PNPase, and in diseases including cancer, cardiac disease, alcohol-associated liver disease, and autoimmune diseases. The hypothesis that mtdsRNAs represent a new biomarker for mitochondrial dysfunction will be tested. As this is a new pathway, there is a critical gap in understanding the molecular rules and mechanisms by which mtdsRNAs cross the mitochondrial inner and outer membranes for cytosolic export. Our study goals are contained within three independent, but thematically connected, specific aims. In Aim 1, mtdsRNAs that are exported from mitochondria will be characterized with respect to size and sequence specificity. In addition, RNA modifying enzymes will be tested to determine which components are essential for the generation of mtdsRNAs. Aim 2 will focus on identification of outer and inner membrane channels and the role of PNPase in the trafficking of mtdsRNAs out of mitochondria. The third aim will define physiologic parameters that lead to the generation of mtdsRNAs and determination of the cytosolic dsRNA sensors that become activated during this process. Because mutations in PNPase lead to mitochondrial disease, mutants will be characterized to determine whether steps in the degradation and/or export of mtdsRNAs can be separated. Our study team has been characterizing PNPase and its function in mitochondria extensively. Unique model systems available for our work include a mouse model in which floxxed PNPT1 can be removed by the Cre recombinase, and mouse embryonic fibroblasts derived from this model. Results from this proposal will define the pathway for mtdsRNA trafficking out of mitochondria in detail and provide a platform for understanding how mutations in PNPase contribute to disease. Long-term, these studies may lead to establishing mtdsRNA as a new biomarker for mitochondrial dysfunction.