Understanding the crosstalk between spatially separated RNP granules during cellular stress responses

生物体不断地被促使对环境作出反应。这包括营养素水平的变化，温度，氧气，病原体和激素等信号的入侵。为了暂停和适应，一个关键事件是限制蛋白质合成，这是一个需要能量的过程。此外，几个信号被发送到整个细胞，以传达紧急状态协调广泛的变化。这允许对细胞中的蛋白质进行彻底检查，以有利于在新条件下促进生存的蛋白质。根据教科书，细胞的主要组织原则是膜与细胞器，如内质网或线粒体，包裹在脂质双层。然而，最近的研究正在重新思考这一模式。无膜细胞器允许分子分离，为细胞生物学提供了新的范例。它们的形成是由于其组分的物理性质发生变化，这些组分现在集中在细胞的特定区域。由于无膜细胞器可以加速其组成部分之间的反应或充当临时存储器，因此它们非常适合在压力期间促进快速适应。蛋白质由称为信使RNA（mRNA）的基因的RNA拷贝编码。这些mRNA与一系列控制其命运的RNA结合蛋白（RBP）相互作用。响应于应激和蛋白质合成抑制，与它们结合的mRNA和RBP以及许多其他蛋白质在细胞质中迅速区室化，形成应激颗粒（SG）。35年前被发现，它们是无膜细胞器的范例。已经为SG提出了若干功能。首先，它们帮助分类和储存mRNA，以确定哪些mRNA是适应新条件所需的，哪些是多余的。其次，它们对于储存蛋白质很重要，这些蛋白质可以发送信号来触发对压力的特定反应。第三，它们在疾病中很重要;如果异常，它们可能会导致大脑疾病，并且它们是我们抗病毒措施的一部分。最后，我们自己的研究结果表明，它们的组装对于触发进一步的区室化波很重要，控制着另一种无膜细胞器的组装，即细胞核中的副斑。尽管如此，关于SG如何运作的主要未解决问题仍然存在。它们是对压力的普遍第一线反应的一部分，但很明显，具有不同组分和性质的SG取决于压力的性质而形成。如何以及为什么选择特定的组件，以及它们如何驱动特定的功能，目前还知之甚少。此外，SG和其他无膜细胞器（如paraspeckles）如何通信，以及这些协调的区室化波在正常和病理条件下的重要性尚不清楚。基于我们在研究SG和paraspeckles方面的专业知识，我们现在想揭示它们如何在压力下促进细胞适应和专门功能。我们的研究计划将全面指纹SG和paraspeckles在一系列不同的压力，以确定其组成部分，相互作用和功能。我们还将定义SG调节paraspeckles组装的分子机制，揭示它们如何通信，以及它们是否调节其他隔室的组装。我们将确定SG和paraspeckles如何有助于细胞防御病毒，以及与神经退行性疾病相关的异常SG如何影响脑细胞中paraspeckle介导的反应。我们目前在分离这些细胞器方面的经验，以及开发用于成像它们的新工具是这些研究成功的关键。最终，这项工作的结果将促进我们对细胞生物学的新的和基本的方面的理解，并重要地将其与病理条件联系起来。

Living organisms are constantly prompted to respond to the environment. This includes to changes in levels of nutrients, temperature, oxygen, invasion by pathogens and signals such as hormones. To pause and adapt, a key event is to limit protein synthesis, an energy hungry process. In addition, several signals are sent throughout the cell to communicate a state of emergency coordinating widespread changes. This allows for an overhaul of proteins in the cell to favour proteins that facilitate survival under the new conditions. According to textbooks, the main organising principle of a cell is the membrane with organelles such as the endoplasmic reticulum or mitochondria, wrapped in lipid bilayers. However, recent research is rethinking this model. Membraneless organelles allow the segregation of molecules, providing a new paradigm for cell biology. They form as a consequence of a change in the physical properties of their components, which now concentrate into specific regions of the cell. Because membraneless organelles can speed up reactions between their components or act as temporary storage, they are perfectly suited to contribute to rapid adaptation during stress. Proteins are encoded by RNA copies of genes called messenger RNA (mRNA). These mRNAs interact with a range of RNA binding proteins (RBPs) that control their fate. In response to stress and protein synthesis inhibition, mRNAs and RBPs bound to them, together with many other proteins, rapidly compartmentalise in the cytoplasm forming stress granules (SGs). Identified 35 years ago they are a paradigm for membraneless organelles. Several functions have been proposed for SGs. First, they help triage and store mRNAs to define which ones are needed to adapt to the new conditions and which are superfluous. Second, they are important for storing proteins that can send signals to trigger specific responses to the stress. Third, they are important in diseases; if anomalous they can contribute to diseases of the brain and they form part of our antiviral measures. Finally, our own findings suggest their assembly is important to trigger further waves of compartmentalisation, controlling the assembly of another membraneless organelle, the paraspeckle, in the nucleus. Despite this, major unsolved questions remain about how SGs function. They are part of a universal first line response to stress, yet it is apparent that SGs with distinct components and properties form depending on the nature of the stress. How and why specific components are selected, and how they drive specific functions, is currently poorly understood. Furthermore how SGs and other membraneless organelles like paraspeckles communicate, and the importance of these coordinated waves of compartmentalisation in normal and pathological conditions is unknown. Building on our expertise in studying SGs and paraspeckles, we now want to uncover how they contribute to cellular adaptation and specialised functions during stress. Our research program will comprehensively fingerprint SGs and paraspeckles under a range of different stresses to identify their components, interactions and functions. We will also define the molecular mechanisms by which SGs regulate the assembly of paraspeckles, uncovering how they communicate, and whether they regulate the assembly of other compartments. We will establish how SGs and paraspeckles contribute to the cellular defences against viruses and how the anomalous SGs associated with neurodegenerative diseases impact on paraspeckle-mediated responses in brain cells. Our current experience in isolating these organelles, and novel tools developed to image them are key for the success of these studies.Ultimately, the outcome of this work will advance our understanding of novel and fundamental aspects of cell biology and importantly relate this to pathological conditions.