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

生物体不断受到环境的刺激而作出反应。这包括营养水平、温度、氧气、病原体入侵和激素等信号的变化。为了暂停和适应，一个关键的事件是限制蛋白质合成，这是一个消耗能量的过程。此外，在整个细胞中发送几个信号，以传达协调广泛变化的紧急状态。这允许细胞内蛋白质的彻底改变，以支持在新条件下促进生存的蛋白质。根据教科书，细胞的主要组织原理是细胞膜，细胞膜上有内质网或线粒体等细胞器，它们被脂质双层包裹着。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一个新的范例。它们的形成是其成分物理性质变化的结果，这些成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作为临时储存，它们非常适合在压力下快速适应。蛋白质是由信使RNA （mRNA）基因的RNA拷贝编码的。这些mrna与一系列控制其命运的RNA结合蛋白（rbp）相互作用。作为对应激和蛋白质合成抑制的反应，mrna和与之结合的rbp与许多其他蛋白质一起在细胞质中迅速区隔形成应激颗粒（SGs）。它们在35年前被发现，是无膜细胞器的典范。已经为SGs提出了几个功能。首先，它们有助于分类和储存mrna，以确定哪些是适应新条件所需要的，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，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，它们会导致大脑疾病，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隔化波，控制细胞核中另一种无膜细胞器（副斑）的组装是重要的。尽管如此，主要的未解决的问题仍然是关于SGs如何发挥作用。它们是对应力的普遍第一线反应的一部分，但很明显，根据应力的性质，具有不同成分和性质的SGs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，目前知之甚少。此外，SGs和其他无膜细胞器（如旁斑）如何沟通，以及这些协调的区隔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SGs和副斑方面的专业知识，我们现在想要揭示它们在压力下如何促进细胞适应和特殊功能。我们的研究计划将在一系列不同应力下对SGs和副斑进行综合指纹鉴定，以确定它们的成分，相互作用和功能。我们还将定义SGs调节副斑组装的分子机制，揭示它们如何沟通，以及它们是否调节其他隔室的组装。我们将确定SGs和旁斑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SGs如何影响旁斑介导的脑细胞反应。我们目前在分离这些细胞器方面的经验，以及开发的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和基本方面的理解，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.