COBRE: UVM MED PROJ 4: PROTEOLYTIC MODULATION OF NOTCH SIGNALING IN NEUROGENESI

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。Notch信号通路由细胞表面蛋白组成，这些蛋白在神经系统发育过程中对细胞间的交流至关重要。Notch受体是通过结合Delta蛋白而激活的，Delta蛋白促进了Notch受体中的几个连续切割。我们最近表明，Delta-Notch参与促进了Delta中类似的蛋白质降解事件，这提出了蛋白质分解如何调节这一基本途径的功能的问题。Notch中的切割需要一种顺序调节的膜内蛋白分解(RIP)机制，涉及ADAM金属蛋白酶和早老素，早老素是参与阿尔茨海默病病因学的天冬氨酸蛋白酶。目前，我们正在通过在培养细胞和体内检测Notch和Delta的蛋白分解产物来研究Notch和Delta在果蝇(果蝇)模型中的作用。我们的结果揭示了Delta的调节蛋白分解机制，不同于Notch的机制，因为它不是连续的，并且涉及一种不同于早老素的新型硫醇敏感的蛋白水解酶。来自Kuzbanian Adam蛋白酶和新型硫醇敏感蛋白酶的细胞相关Delta裂解产物分别预测可以作用于质膜和细胞核的异构体。此外，我们已经确定了在发育中的神经元谱系的亚群中，在最初的轴突联系建立的点上，Delta表达的独特模式。总而言之，我们的结果指出了Delta在发育中的中枢神经系统中的一种新活动，并定义了一个进行研究的模型系统。此外，我们还在研究Notch信号对ADAM酶活性的敏感性。在这些研究中，我们已经确定了有机汞化合物的一种促进ADAM活性的活性。我们最近的发现证明了有机汞对Notch活性的直接影响，这依赖于金属蛋白酶依赖和独立的活性。这些研究为我们提供了完善Notch激活机制的工具，并为环境形式的汞，特别是甲基汞的毒性机制提供了新的线索。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The Notch signaling pathway is comprised of cell surface proteins that are fundamental to cell-cell communication in development of the nervous system. Notch receptors are activated by binding the Delta protein, which promotes several sequential cleavages in the Notch receptor. We have recently shown that Delta-Notch engagement promotes similar proteolytic events in Delta, raising the question of how proteolysis regulates the function of this fundamental pathway. Cleavage in Notch requires a sequential regulated intramembrane proteolysis (RIP) mechanism involving an ADAM metalloprotease and Presenilin, the aspartyl protease involved in the etiology of Alzheimer's disease. Surrently we are investigating the role of proteolysis of Notch and Delta in a Drosophila (fruit fly) model by examining the proteolytic products of Notch and Delta in both cultured cells and in vivo. Our results have uncovered a mechanism of regulated proteolysis of Delta that is distinct from that of Notch in that it is not sequential and involves a novel thiol-sensitive protease that is distinct from Presenilin. Cell associated Delta cleavage products derived from the Kuzbanian ADAM protease and the novel thiol-sensitive protease predict isoforms that can act at the plasma membrane and in the nucleus, respectively. Furthermore, we have identified a unique pattern of Delta expression in subsets of developing neuronal lineages at the point in which initial neurite contacts are established. Altogether, our results point to a novel activity for Delta in the developing central nervous system and define a model system in which to carry out the investigation. Also we are studying the sensitivity of Notch signaling to ADAM protease activity. In these studies we have identified an activity of organomercurial compounds in promoting ADAM activity. Our recent findings demonstrate a direct effect of organomercurials on Notch activity, which relies on both metalloprotease-dependent and independent activities. These studies give us the tools to refine the mechanism of Notch activation, as well as provide new lines of inquiry into the toxic mechanisms of environmental forms of mercury, notably methylmercury.