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

摘要 核和胞浆内容物的离散分离是所有真核细胞的一个显著特征。它是 通过核膜的不通透性和大小选择性和主动转运实现的 核孔复合体(NPC)的性质，这是一种跨越核膜的巨大运输通道。 有趣的是，越来越明显的是，在细胞内存在有害的细胞质和细胞核内容物的混合 几种鼻咽癌功能或核膜完整性的人类疾病细胞模型 心烦意乱。例子包括转录和转录以核运输机械为靶点 翻译导致神经退行性疾病的六核苷酸重复扩增，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人，我们正在发现监控 保护核室免受异常核祖细胞和/或核膜破裂的机制。 事实上，我们已经发现，即使在核膜的“正常”重塑过程中 如果不加以监测，鼻咽癌组装可导致核-胞质区划的丧失。在这里，我们将 用发芽酵母作为模型来确定控制从头开始监测的分子机制 鼻咽癌的组装，这依赖于膜的募集、内体的弯曲和裂解 运输(ESCRT)机械到新生的NPC组装地点所需的。我们的工作与模型是一致的 其中LAP2，Emerin，MAN1(LEM)结构域家族的完整内核膜蛋白作为 将有缺陷的NPC组装中间体连接到ESCRT的适配器，它在 双层膜。在这份提案中，我们将明确全国人大会议中的哪个步骤(S)在接受监督 定义细胞区分功能和非功能NPC的机制。《长河》 任期目标是全面界定并最终重构全国人大大会监督机制，以说明 质量控制和膜重建的基本机制，同时提供了一个新的概念 理解存在核膜破裂的人类疾病机制的框架 障碍。

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.