Roles of the ER Stress Surveillance Pathway During the Cell Cycle

描述（由申请人提供）：在细胞周期中，调节机制确保基因组被子细胞复制和正确遗传。相比之下，对于是否存在确保细胞质细胞器遗传的调节机制知之甚少。作为一个重要的细胞器，内质网（ER）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质。内质网也是细胞脂质的诞生地。因此，内质网的适当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节机制，内质网应激监视途径或ERSU，它确保在细胞周期中功能内质网的适当遗传。ERSU不同于任何其他先前描述的信号通路，包括众所周知的UPR通路。当ERSU被内质网应激激活时，受损的内质网仍然可以进入子细胞，但不能锚定在芽尖，因此收缩。我们发现ERSU是一种新的细胞周期检查点，然后停止细胞周期，直到有功能的ER可用。在我们的初步分析中，我们已经确定了ERSU通路的关键成分，包括细胞表面信号蛋白WSC1和MAP激酶SLT2。任何一个基因的缺失都消除了ERSU：坏的ER现在被锚定和遗传，但使子芽不能存活。我们将对ERSU通路进行如下研究：在AIM I中，我们将定义ERSU的ER“启动器”。我们有强有力的初步证据表明脂质合成酶是起始的关键。有趣的是，正如我们最近报道的那样，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，我们将剖析内质网遗传在内质网应激下被阻断的机制。我们将使用最近开发的活细胞试验，使我们能够在压力下观察内质网遗传。我们将在野生型细胞和越来越多的ERSU通路缺陷突变体中检查ER的进入、锚定和子代的命运。我们还将在分子水平上深入研究ersu诱导改变的特定er锚定成分。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能否在细胞周期的任何阶段被诱导？内质网功能调节的失败越来越被认为是许多人类疾病（包括某些癌症）病理生理学的一个促成因素。因此，了解确保内质网功能遗传的细胞机制对于开发以前未被认识到的治疗干预策略将是非常宝贵的。

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.