The mechanism of ESCRT-mediated surveillance of the nuclear envelope barrier

总结 核和胞质内含物的离散分离是所有真核细胞的标志性特征。是 通过核膜的不渗透性和大小选择性和主动转运实现 核孔复合物（NPC）的性质，跨越核膜的大量运输通道。 有趣的是，越来越清楚的是，有一个有害的混合胞质和核内容物， 几种人类疾病细胞模型，其中NPC功能或核膜的完整性是 心烦意乱实例包括通过转录靶向核转运机制， 导致神经退行性疾病的六核苷酸重复扩增的翻译，以及核 在癌细胞中观察到的破裂事件。通过我们的工作和其他工作， 保护核区室免受异常NPC和/或核膜破裂的机制。 事实上，我们已经发现，即使是核被膜的“正常”重塑， 如果不监测，NPC组装可以导致核-胞质区室化的丧失。在这里，我们将 使用芽殖酵母作为模型，以确定管理从头监视的分子机制， NPC的组装，依赖于募集膜的弯曲和断裂的内体分选 运输（ESCRT）机械所需的新生NPC组装地点。我们的工作符合一个模型 其中Lap 2、emerin、MAN 1（LEM）结构域家族的整合的内核膜蛋白充当 将有缺陷的NPC组装中间体连接到ESCRT的适配器，ESCRT将有缺陷的NPC密封在一个 双层膜在本建议中，我们将指出人大会议的哪些步骤受到监督， 定义了细胞区分功能性和非功能性NPC的机制。长 长期目标是全面界定并最终重构人大代表大会监督机制， 质量控制和膜重塑的基本机制，同时提供了一个新的概念 理解人类疾病机制的框架，这些机制表现为核包膜的破坏 屏障

Summary The discrete segregation of nuclear and cytosolic contents is a hallmark feature of all eukaryotic cells. It is achieved by the impermeability of the nuclear envelope membranes and the size-selective and active transport properties of nuclear pore complexes (NPCs), massive transport channels that span the nuclear envelope. Interestingly, it is becoming clear that there is a deleterious intermixing of cytosolic and nuclear contents in several human disease cell models where either NPC function or the integrity of the nuclear membranes is perturbed. Examples include the targeting of the nuclear transport machinery by the transcription and translation of hexanucleotide repeat expansions that are causative of neurodegenerative diseases, and nuclear rupture events observed in cancer cells. Through our work and others, we are discovering surveillance mechanisms that protect the nuclear compartment from aberrant NPCs and/or nuclear membrane ruptures. Indeed, we have discovered that even the “normal” remodeling of the nuclear envelope membranes during NPC assembly can, if not monitored, lead to a loss of nuclear-cytosolic compartmentalization. Here, we will use budding yeast as a model to determine the molecular mechanisms that govern the surveillance of de novo NPC assembly, which depends on the recruitment of the membrane bending and scission endosomal sorting required for transport (ESCRT) machinery to nascent NPC assembly sites. Our work is consistent with a model in which integral inner nuclear membrane proteins of the Lap2, emerin, MAN1 (LEM) domain family serve as adaptors to link defective NPC assembly intermediates to the ESCRTs, which seal off defective NPCs under a double membrane. In this proposal, we will pinpoint what step(s) in NPC assembly are under surveillance while defining the mechanism by which cells differentiate between functional and non-functional NPCs. The long term goal is to fully define and ultimately reconstitute the NPC assembly surveillance mechanism to illuminate fundamental mechanisms of quality control and membrane remodeling while providing a new conceptual framework to understand human disease mechanisms that present with disruptions in the nuclear envelope barrier.