Roles of the ER Stress Surveillance Pathway During the Cell Cycle

项目摘要 基因组的准确复制和正确分裂对生命至关重要，而“检查点”是 在整个细胞周期中放置，以确保准确性。对它的存在所知甚少 功能正确的细胞质细胞器的遗传检查点。急诊室，一个大的， 一种重要的细胞器，几乎产生所有的分泌和跨膜蛋白，以及大多数脂质的细胞。 cell.我们以前发现了一个细胞周期检查点，ER应激监测途径（ERSU）， 其对于通过模式生物S中的子细胞遗传功能正确的ER至关重要。 啤酒。当被ER应激激活时，ERSU通路：（1）阻断受损ER的遗传 通过阻止“起始”内质网小管进入子细胞，（2）错误定位隔蛋白环 从胞质分裂的位点，并最终，（3）导致细胞周期停滞，直到功能性ER可以被重新激活。 确立了习ERSU通路突变的细胞在ER应激时死亡，强调了ERSU通路的重要性。 的ERSU。值得注意的是，ERSU途径不同于众所周知的未折叠蛋白质反应， （普遍定期审议）。在过去的授权期间，在寻找激活ERSU的信号时，我们发现， 植物鞘氨醇（PHS）是鞘脂生物合成的早期中间体，是ERSU激活剂。PHS 增加后，ER应力感应，当外源性增加，PHS集运动所有的ERSU 标志性事件。此外，我们在Reticulon 1（Rtn1）中发现了新的跨膜结构域突变体， 对正确ER结构重要的蛋白质：这些突变体破坏ERSU而不影响整体ER 结构在AIM 1中，我们将研究植物鞘氨醇如何激活ERSU通路。我们也将 测试小灵通如何改变网状细胞，以防止受损的ER遗传。在AIM 2中，我们将研究 如何在分子水平上阻断ER小管遗传，检查关键细胞周期结构的作用 如隔蛋白、细胞骨架元件、外囊和极性体。在AIM 3中，我们将：（A）地址 是否存在哺乳动物ERSU通路。我们观察到septins的错误定位， 哺乳动物内质网应激提供了最初的令人信服的证据。(B)询问ER应力对 哺乳动物细胞周期，包括涉及ER的主要有丝分裂细胞周期结构变化，如 急诊室清理，核拆卸和重组。了解ER的机制 在正常细胞中遗传，以及在压力条件下如何干扰，将有助于我们 了解人类疾病。ER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是主要的公共卫生问题。我们希望我们的研究将指向新的 治疗这些疾病。

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.