Cell-cell signaling through regulated proteolysis

描述（由申请人提供）：跨膜传递信号的能力是一种基本的生物学现象，目前仍知之甚少。最近，已经描述了一种新的跨膜转导机制。在该模型中，嵌入膜内的蛋白酶被触发以催化膜锚定的转录因子的蛋白水解释放。这些新的蛋白酶是多位的膜蛋白，其催化位点嵌入在脂质双层中。为了更深入地了解这些膜包埋蛋白酶是如何转导信息的，我们正在研究一种信号转导途径，该途径导致枯草芽孢杆菌中参与孢子形成的转录因子的蛋白水解激活。在这种生物体中进行遗传和生化分析的容易性使其成为研究这类重要蛋白酶的理想系统。 发育调节转录因子（sigmaK）通过膜包埋金属蛋白酶SpolVFB（称为B）从膜上蛋白水解释放。B被位于膜另一侧的信号蛋白酶（IVB）激活。所提出的研究的具体假设是，孢子形成过程中的细胞-细胞信号传导是通过IVB在膜一侧的作用实现的，其触发了膜嵌入的金属蛋白酶B在相对侧的活性。我们进一步假设，额外的调节蛋白调节这两步蛋白水解裂解途径，这导致转录因子的激活。具体而言，我们建议： 1.确定IVB信号分子如何触发B蛋白酶活性; 2.表征调节sigmaK激活时间的三种调节剂; 3.在体外重构和表征B介导的pro-sigmaK加工。

DESCRIPTION (provided by applicant): The ability to transduce a signal across a membrane is a basic biological phenomenon that remains only poorly understood. Recently, a new mechanism of transduction across a membrane has been described. In this model proteases embedded within the membrane are triggered to catalyze the proteolytic release of membrane-anchored transcription factors. These novel proteases are polytopic membrane proteins with catalytic sites embedded in the lipid bilayer. To gain a deeper understanding into how information is transduced by these membrane-embedded proteases we are studying a signal transduction pathway that results in the proteolytic activation of a transcription factor involved in spore formation in the bacterium Bacillus subtilis. The ease with which genetic and biochemical analysis can be carried out in this organism makes this an ideal system to study this important class of proteases. The developmentally regulated transcription factor (sigmaK) is proteolytically released from the membrane by a membrane-embedded metalloprotease known as SpolVFB (referred to as B). B is activated by a signaling protease (IVB) located on the other side of the membrane. The specific hypothesis underlying the proposed research is that cell-cell signaling during sporulation is achieved by the action of IVB on one side of the membrane, which triggers the activity of the membrane-embedded metalloprotease B on the opposite side. We further hypothesize that additional regulatory proteins modulate this two-step proteolytic cleavage pathway, which results in transcription factor activation. Specifically, we propose to: 1. Determine how the IVB signaling molecule triggers B protease activity; 2. Characterize three regulators that modulate the timing of sigmaK activation; 3. Reconstitute and characterize B-mediated pro-sigmaK processing in vitro.