Roles of the ER Stress Surveillance Pathway During the Cell Cycle

项目摘要 基因组的准确复制和适当的分裂对生命是必不可少的，而“检查点”是 放置在整个细胞周期中，以确保准确性。关于它的存在我们知道的要少得多 功能正确的细胞质细胞器遗传的检查点。急诊室，一个大型的和 基本细胞器，产生几乎所有的分泌和跨膜蛋白，以及大多数脂类 手机。我们之前发现了一个细胞周期检查点，即内质网应激监视通路(ERSU)， 这对于模式生物S的子代细胞遗传功能正确的ER是至关重要的。 酿酒。当被内质网应激激活时，ERSU通路：(1)阻断受损内质网的遗传 通过阻止启动的内质网小管进入子细胞，(2)使隔素环错位 从胞质分裂的部位，最终，(3)导致细胞周期停滞，直到功能的内质网可以重新- 已经成立了。ERSU途径中突变的细胞在内质网应激下死亡，这突显了 紧急救援小组的成员。值得注意的是，ERSU途径不同于众所周知的未折叠蛋白反应 (普遍定期审议)。在过去的授权期间，在搜索激活ERSU的信号时，我们发现 植鞘糖苷(PHS)是神经鞘糖脂生物合成的早期中间体，是ERSU的激活剂。小灵通 增加内质网应激诱导，当外源添加时，PHS启动所有ERSU 标志性事件。此外，我们在网状蛋白1(Rtn1)中发现了新的跨膜区突变体，a 蛋白质对正确的内质网结构很重要：这些突变体在不影响整体内质网的情况下使ERSU失活 结构。在目标1中，我们将研究植鞘糖苷是如何激活ERSU途径的。我们也会 测试小灵通如何改变网状结构以防止受损的ER遗传。在AIM 2中，我们将调查 内质网小管遗传如何在分子水平被阻断，研究关键细胞周期结构的作用 如隔膜蛋白、细胞骨架元素、外囊和极化体。在目标3中，我们将：(A) 是否存在哺乳动物的ERSU途径。我们观察到的关于葡聚糖错误定位的研究 哺乳动物的内质网应激提供了最初令人信服的证据。(B)询问内质网应激对 哺乳动物细胞周期包括涉及内质网的主要有丝分裂细胞周期结构变化，如 呃清除，核拆解，重新组装。理解内质网的机制 在正常细胞中的遗传以及这种遗传在压力条件下如何被扰乱将有助于我们的 对人类疾病的理解。内质网功能失调是糖尿病的一个显著特征， 阿尔茨海默氏症和帕金森氏症，这是主要的公共卫生问题。我们希望我们的研究将指向新的 这类疾病的治疗方法。

Project Summary The accurate replication and proper division of the genome is essential to life, and “checkpoints” are placed throughout the cell cycle to ensure accuracy. Much less is known about the presence of checkpoints for the inheritance of functionally correct cytoplasmic organelles. The ER, a large and essential organelle, generates virtually all secretory and transmembrane proteins, and most lipids of the cell. We previously discovered a cell cycle checkpoint, the ER Stress Surveillance pathway (ERSU), which is vital for the inheritance of functionally correct ER by daughter cells in the model organism S. cerevisiae. When activated by ER stress, the ERSU pathway: (1) blocks the inheritance of damaged ER by preventing the “initiating” ER tubule from entering the daughter cell, (2) mislocalizes the septin ring from the site of cytokinesis, and ultimately, (3) leads to a cell cycle arrest until a functional ER can be re- established. Cells that are mutant in the ERSU pathway die upon ER stress, underscoring the importance of the ERSU. Notably, the ERSU pathway is distinct from the well known Unfolded Protein Response (UPR). In the past grant period, in search of the signal that activates ERSU, we found that phytosphingosine (PHS), an early intermediate of sphingolipid biosynthesis, is an ERSU activator. PHS increases upon ER stress induction and, when exogenously added, PHS sets in motion all the ERSU hallmark events. Moreover, we identified novel transmembrane domain mutants in Reticulon 1 (Rtn1), a protein important for correct ER structure: these mutants inactivate ERSU without affecting overall ER structure. In AIM 1, we will investigate how phytosphingosine activates the ERSU pathway. We also will test how Reticulons are altered by PHS to prevent damaged ER inheritance. In AIM 2, we will investigate how ER tubule inheritance is blocked at the molecular level, examining the role of key cell cycle structures such as septins, cytoskeletal elements, the exocyst and polarisome. In AIM 3, we will: (A) Address whether there is a mammalian ERSU pathway. Our observations of mislocalization of septins upon mammalian ER stress provide initial compelling evidence. (B) Interrogate the impact of ER stress on the mammalian cell cycle including major mitotic cell cycle structural changes that involve the ER, such as ER clearing, nuclear disassembly and reassembly. Understanding the mechanisms by which the ER is inherited in normal cells and how this is perturbed under stress conditions will contribute to our understanding of human disease. Dysregulated ER function is a prominent feature of diabetes, Alzheimer's and Parkinson's, key public health concerns. We hope our study will point towards new treatments for such diseases.