Regulation and functional effects of localized RNAs

大量的RNA不是弥漫地分布在细胞质中，而是活跃地转运到各个亚细胞部位。在到达最终目的地后，本地化的RNA被翻译，从而指导当地的蛋白质生产。虽然越来越多的本地化RNA正在被发现，但这些事件的功能重要性还没有被很好地理解。我们正在专注于我们已经确定的一条定位路径，该路径针对一些RNA到细胞突起的末端。我们发现，该途径的一个重要组成部分是肿瘤抑制蛋白腺瘤性息肉病结肠(APC)，它的突变是大多数结直肠癌进展的起始事件。在核糖核蛋白复合体中，APC与RNA在细胞突起处结合，我们称之为APC-RNPs。APC-RNPs的另一个组成部分是RNA结合蛋白FUS/TLS，这种蛋白的突变与癌症和肌萎缩侧索硬化症(ALS)有关。我们最近发现，与ALS相关的FUS突变体错误地定位了APC-RNPs在内部细胞质颗粒中，并误导了它们的翻译。在过去的一年里，我们在了解APC-RNP定位是如何调节的，以及在识别参与这一过程的细胞因子方面取得了重大进展。具体来说，我们发现细胞外基质环境的特征可以影响APC-RNP的定位。这一效应似乎是通过调节细胞骨架结构来实现的，我们已经在鉴定涉及的细胞骨架成分方面取得了进展。我们还发现，FUS蛋白中的致病突变通过类似地影响细胞骨架结构和动力学而导致APC-RNP错误定位。有趣的是，这种效应依赖于突变的FUS蛋白的聚集，这一转变与触发与FUS突变相关的晚发性疾病(如ALS和FTLD)有关。最后，我们设计了一种策略来诱导APC-RNP在细胞系统中的错误定位，并正在表征APC-RNP定位在2D和3D迁移系统中不同迁移参数中的贡献。

A large number of RNAs are not diffusely distributed in the cytoplasm, but are actively transported to various subcellular sites. After reaching their final destinations, localized RNAs are translated, thus directing local protein production. While increasing numbers of localized RNAs are being identified, the functional importance of these events is not well understood. We are focusing on a localization pathway that we have identified, which targets a number of RNAs to the tips of cellular protrusions. We have found that an important component of this pathway is the tumor-suppressor protein Adenomatous Polyposis Coli (APC) whose mutation is the initiating event in the progression of the majority of colorectal cancers. APC associates with RNAs at cellular protrusions in ribonucleoprotein complexes, which we term APC-RNPs. An additional component of APC-RNPs is the RNA-binding protein Fus/TLS, a protein whose mutation has been linked to both cancer and Amyotrophic Lateral Sclerosis (ALS). We have recently shown that ALS-associated mutants of Fus mislocalize APC-RNPs in internal cytoplasmic granules and misdirect their translation. During the last year, we have made significant progress in understanding how APC-RNP localization is regulated, and in identifying cellular factors involved in this process. Specifically, we have found that characteristics of the extracellular matrix environment can affect APC-RNP localization. This effect appears to be mediated through modulation of the cytoskeletal architecture, and we have made inroads in identifying the cytoskeletal components involved. We have additionally found that pathogenic mutations in the Fus protein lead to APC-RNP mislocalization through similarly affecting cytoskeletal architecture and dynamics. Interestingly, this effect is dependent on aggregation of the mutant Fus protein, a transition that is linked to triggering of late-onset diseases associated with Fus mutations (such as ALS and FTLD). Finally, we have devised a strategy to induce APC-RNP mislocalization in cellular systems and are currently characterizing the contribution of APC-RNP localization in various migratory parameters in 2D and 3D migration systems.