Roles of the Unfolded Protein Response in Cell Cycle

描述（由申请人提供）：内质网（ER）是细胞中几乎所有分泌蛋白和膜蛋白折叠和成熟的部位。对分泌蛋白质生产的需求在细胞中响应于发育或环境线索而显著波动。对增加ER蛋白折叠能力的需求由在所有真核生物中保守的未折叠蛋白反应信号通路（UPR）感测。UPR途径的激活导致ER分子伴侣和其他蛋白质折叠组分的表达增加，以增加ER蛋白质折叠能力。由于ER不能从头产生，而必须由子细胞继承，因此我们对确保继承ER功能质量的机制感兴趣。最近，我们发现：（1）功能性应激的ER不能传递到子细胞，（2）导致S.啤酒。我们证实，胞质分裂受阻不是由于ER应激诱导的细胞分裂关键的分泌途径成分的定位的全球性缺陷。此外，胞质分裂阻滞不依赖于经典的UPR途径，即使在IRE 1缺陷细胞中也会发生。(3)我们还发现了一个挑衅性的表型：ER应激破坏了Septin复合物的动力学，Septin复合物通常在母/子细胞芽颈处组装，并在胞质分裂期间介导细胞分离。最近，我们已经确定SLT 2 MAP激酶在协调ER功能和ER遗传中起重要作用。缺乏SLT 2的细胞，当受到ER应激时，胞质分裂不再被阻断，具有正常的隔蛋白环动力学，并将应激的ER传递给它们的子细胞。然而，这样的细胞不能维持超过随后的细胞分裂轮次，表明对功能性ER的迫切需要。将这些结果结合在一起，我们假设存在一种ER应激监测机制，该机制确保了ER传递到子细胞的保真度，使得关于ER功能能力的信息直接或间接地传达给septin复合物和遗传过程中影响ER运动的组分。在这个提议中，我们提出：（1）确定ER遗传过程的哪个阶段受到ER应激的影响，（2）研究由ER应激引起的异常septin复合物行为的分子性质，（3）分析SLT 2在胞质分裂和cER遗传中的分子作用，以及（4）将我们现有的以及新的组分映射到包括ER应激监视机制的通路中。越来越多的人认识到，ER功能性调节的失败导致了许多人类疾病的病理生理学，包括某些癌症。因此，知识的细胞机制，确保维护和传输的功能主管ER将是非常宝贵的发展以前未被认识到的战略，治疗干预。 公共卫生相关性：内质网（ER）是产生膜蛋白和分泌蛋白的重要器官。此外，ER还执行各种其他关键功能，包括脂质合成和细胞内钙调节。ER的功能能力是响应于环境和发育线索而调节的，并且每次细胞分裂时都必须传递到子细胞，因为没有ER可以从头合成。ER功能的适当调节和维持的失败越来越被认为是人类健康的病理生理学的贡献因素，因此，对细胞如何在正常细胞周期期间协调ER功能能力与其适当遗传的详细理解将有望为新的人类治疗奠定基础。

DESCRIPTION (provided by applicant): The endoplasmic reticulum (ER) is the site of folding and maturation for virtually all secreted and membrane proteins of the cell. The demand for secreted protein production fluctuates dramatically in cells in response to developmental or environmental cues. Demand for increased ER protein folding capacity is sensed by the Unfolded Protein Response signaling pathway (UPR), conserved in all eukaryotes. Activation of the UPR pathway results in increased expression of ER chaperones and other protein folding components in order to increase ER protein folding capacity. As ER cannot be generated de novo but must be inherited by daughter cells, we became interested in mechanisms that assure the functional quality of inherited ER. Recently, we have found that: (1) functionally stressed ER is not transmitted to daughter cells, and (2) results in block in cytokinesis in S. cerevisiae. We confirmed that blocked cytokinesis is not due to ER-stress induced global defects in the localization of secretory pathway components critical for cell division. Moreover, the cytokinesis block is not dependent on the canonical UPR pathway, occurring even in IRE1-defective cells. (3) We also find a provocative phenotype: ER stress disrupts the dynamics of the septin complex, which normally assembles at the mother/daughter cell bud neck and mediates cell separation during cytokinesis. Most recently, we have identified the SLT2 MAP kinase as playing an important role in coordinating ER function with ER inheritance. Cells lacking SLT2, when subjected to ER stress, are no longer blocked for cytokinesis, have normal septin ring dynamics, and transmit stressed ER to their daughter cells. However, such cells are unable to sustain more than a subsequent rounds of cell division, indicating a critical need for functional ER. Taking these results together, we hypothesize the existence of an ER- stress surveillance mechanism that ensures the fidelity of ER transmitted to daughter cells, such that information on ER functional capacity is communicated, either directly or indirectly, to the septin complex and to components that affect ER movement during inheritance. In this proposal we propose to: (1) determine which stage of the ER inheritance process is effected by ER stress, (2) investigate the molecular nature of the aberrant septin complex behavior caused by ER stress, (3) analyze the molecular role of SLT2 in cytokinesis and cER inheritance, and (4) map our existing as well as new components into the pathway that comprises the ER stress surveillance mechanism. The failure to regulate ER functional capacity is increasingly recognized as contributing to the pathophysiology of a number of human diseases, including certain cancers. Thus, knowledge of the cellular mechanisms assuring the maintenance and transmission of a functionally competent ER will be invaluable towards the development of previously unrecognized strategies for therapeutic intervention. PUBLIC HEALTH RELEVANCE: The endoplasmic reticulum (ER) plays a essential orgaqnelles for production of membrane and secretory proteins. In addition, the ER carries out a variety of additional critical functions including lipid synthesis and intracellular calcium regulation. Functional capacity of the ER is regulated in response to environmental and developmental cues and has to be transmitted to the daughter cell every time cells divide as no ER can be synthesized de novo. Failuare of proper regulation and mainteinance of ER functions is increasingly recognized as contributing element of the pathophysiology of human health and thus, a detail understanding of how cells coordinates ER functional capacity with its proper inheritance during normal cell cycle will hold promise to lay groundwork for novel human therapeutics.