Roles of the ER Stress Surveillance Pathway During the Cell Cycle

描述（由申请人提供）：在细胞周期期间，存在调节机制，以确保基因组被复制并由子细胞正确继承。相反，很少有人知道是否存在调节机制，以确保细胞质细胞器的遗传。内质网（ER）是一种重要的细胞器，它产生几乎所有的分泌蛋白、跨膜蛋白和分泌途径细胞器的蛋白。ER也是细胞脂质的诞生地。因此，ER的正确遗传对细胞至关重要。 我们现在已经确定了一种细胞周期调控机制，ER应激监测途径或ERSU，它确保了细胞周期中功能性ER的正确遗传。ERSU不同于任何其他先前描述的信号传导途径，包括众所周知的UPR途径。当ERSU被ER应激激活时，受损的ER仍然可以进入子细胞，但不能锚在芽尖，因此缩回。我们发现ERSU是一个新的细胞周期检查点，然后停止细胞周期，直到功能ER可用。在我们的初始化分析中，我们已经确定了关键的ERSU途径组分，包括WSC 1，细胞表面信号蛋白，和SLT 2，MAP激酶。任何一个基因的缺失都会消除ERSU：坏的ER现在被锚定和遗传，但会使子芽无法存活。 我们将研究ERSU途径如下：在AIM I中，我们将定义ERSU的ER "启动子"。我们有强有力的初步证据表明，脂质合成酶是启动的关键。有趣的是，正如我们最近报道的那样，已知脂质在许多哺乳动物健康相关的信号通路中发挥作用，包括哮喘。在AIM 2中，我们将剖析内质网应激阻断内质网遗传的机制。我们将使用最近开发的活细胞测定，使我们能够查看ER遗传，而它是在压力下。ER进入、锚定和子体的命运将在野生型细胞和我们越来越多的ERSU途径缺陷突变体中进行检查。我们还将深入研究在分子水平上通过检查特定的ER锚定成分ERSU诱导的变化。在目标3中，我们将首次探索ERSU和UPR的细胞周期边界。我们将研究细胞周期阶段和ERSU之间的关系。例如，ERSU可以在细胞周期的任何阶段被诱导吗？越来越多的人认识到，ER功能性调节的失败是许多人类疾病（包括某些癌症）的病理生理学的一个促成因素。因此，知识的细胞机制，确保继承的功能主管ER将是非常宝贵的发展，以前未认识到的战略，治疗干预。

DESCRIPTION (provided by applicant): During the cell cycle, regulatory mechanisms are in place to ensure that the genome is copied and properly inherited by daughter cells. In contrast, little is known about whether regulatory mechanisms are present to ensure inheritance of cytoplasmic organelles. A vital organelle, the endoplasmic reticulum (ER) produces virtually all secretory proteins, transmembrane proteins, and proteins of the secretory pathway organelles. The ER is also the birthplace of cellular lipids. Proper inheritance of the ER is thus critical forthe cell. We have now identified a cell cycle regulatory mechanism, the ER Stress Surveillance pathway or ERSU that ensures the proper inheritance of a functional ER during the cell cycle. ERSU is distinct from any other previously described signaling pathway including the well-known UPR pathway. When ERSU is activated by ER stress, compromised ER can still enter the daughter cell, but cannot anchor at the bud tip and so retracts. We find that ERSU is a novel cell cycle checkpoint that then halts the cell cycle until functional ER is available. In our initil analysis, we have identified critical ERSU pathway components including WSC1, a cell surface signaling protein, and SLT2, a MAP kinase. Deletion of either gene eliminates ERSU: bad ER is now anchored and inherited, but renders the daughter bud non-viable. We will investigate the ERSU pathway as follows: In AIM I, we will define the ER "initiator(s)" of ERSU. We have strong preliminary evidence that lipid synthesis enzymes are key to initiation. Interestingly, lipids are known to play a role in many mammalian health-related signaling pathways including asthma, as we have recently reported. In AIM 2, we will dissect the mechanism by which ER inheritance is blocked in response to ER stress. We will use a recently developed live-cell assay that allows us to view ER inheritance while it is under stress. ER entry, anchoring, and the fate of the daughter will be examined both in wild type cells and in our increasing number of ERSU pathway- defective mutants. We also will drill down at the molecular level by examining specific ER-anchoring components for ERSU-induced alteration. In Aim 3, we will for the first time probe the cell cycle boundaries of ERSU and, indeed, of the UPR. We will study the relationship between cell cycle stages and ERSU. For example, can ERSU be induced at any phase of the cell cycle? A failure to regulate ER functional capacity is increasingly recognized as a contributing factor to the pathophysiology of many human diseases, including certain cancers. Thus, knowledge of the cellular mechanism that assures inheritance of a functionally competent ER will be invaluable towards the development of previously unrecognized strategies for therapeutic intervention.