Characterizing the Cpx stress response in E. coli

描述（由申请人提供）：所有生物都进化出了机制，以确保在面对各种可能杀死它们的压力时蛋白质的适当折叠和定位。在细菌中，如大肠杆菌，以及高等真核生物，专门的调节系统监测细胞蛋白质的完整性。具体来说，大肠杆菌的外质应激反应和真核细胞的未折叠蛋白反应都使用一种跨膜激酶，分别在内质网（ER）或外质内感知和转导信号。该信号随后被传递给转录调节因子，导致适当定位的蛋白质折叠和运输因子的上调，这些因子可以对抗刺激的压力。cpx诱导的大肠杆菌应激反应通过由激酶（CpxA）和转录反应调节剂（CpxR）组成的双组分信号转导系统对抗胞质外毒性，如形成错误折叠的蛋白质聚集体。外质蛋白CpxP是唯一确定的Cpx应激反应的负调节因子，并在确保应激反应得到适当调节方面发挥重要作用。虽然CpxP的功能需要一个功能性的外质CpxA感应域，但对于CpxP在细胞中的正常功能知之甚少。本研究的目的是利用生化和遗传分析来剖析CpxP的功能，并了解其活性如何与Cpx双组分系统协调，以减轻包膜相关的应激，并确保Cpx反应的适当激活。这项拟议的研究将阐明细胞如何适应以避开有毒蛋白质聚集物的影响。这种聚集体似乎是包括α -1抗胰蛋白酶缺乏症和亨廷顿氏病在内的几种人类疾病发病机制的核心。

DESCRIPTION (provided by applicant): All organisms have evolved mechanisms to ensure the proper folding and localization of proteins in the face of a variety of stresses that would otherwise kill them. In bacteria, such as Escherichia coli, as well as higher eukaryotes, specialized regulatory systems act to monitor the integrity of cellular proteins. Specifically, both the periplasmic stress response in E. coli and the unfolded protein response in eukaryotic cells employ a transmembrane kinase that senses and transduces a signal within the endoplasmic reticulum (ER) or periplasm, respectively. This signal is then relayed to transcriptional regulators which results in an upregulation of appropriately localized protein folding and trafficking factors that can act to combat the inciting stress. The Cpx-induced stress response of Escherichia coli combats extracytoplasmic toxicities such as the formation of misfolded protein aggregates through a two-component signal transduction system comprised of a kinase (CpxA) and a transcriptional response regulator (CpxR). The periplasmic protein, CpxP, is the only identified negative regulator of the Cpx stress response and presumptively plays an important role in ensuring that this response is properly modulated. While it is clear that CpxP function requires a functional periplasmic CpxA sensing domain, relatively little is known about how CpxP normally functions in the cell. The purpose of this proposed study is to use both biochemical and genetic analysis to dissect CpxP function and understand how its activity is coordinated with the Cpx two-component system to alleviate envelope-associated stress and ensure appropriate activation of the Cpx response. The proposed study will illuminate the way in which the cell adapts to stave off the effects of the presence of toxic protein aggregates. Such aggregates appear to be central to the pathogenesis of several human diseases including alpha-1 antitrypsin deficiency and Huntington's disease.