Mechanism and Function of Sequential Proteolysis in Health and Disease

描述（由申请人提供）：去除旧的蛋白质片段和/或释放新的蛋白质片段已经发展成为许多生理过程的重要调节机制。我实验室的研究目的是了解一组膜蛋白，特别是淀粉样前体蛋白（amyloid precursor protein， APR）和Notch受体的蛋白水解的生化机制、生理意义和病理意义。这些蛋白质首先在胞外结构域被切割，这一过程被称为胞外结构域脱落。这产生了包含新的和自由的氨基末端的膜结合片段。我们最近的研究表明，糖蛋白nicastrin结合到新的氨基末端，并招募胞外结构域脱落的产物，用于γ -分泌酶的膜内切割。最近的文献和我们的初步研究表明，新的肽酶活性进一步处理γ -分泌酶产物的氨基或羧基端，导致产生新的具有生物学意义的蛋白质片段。这个模型现在将在以下两个假设驱动的具体目标中进行测试。首先，我们的目标是了解一个新的蛋白质水解步骤的功能意义和生化机制，该步骤修饰Notch细胞内结构域的氨基端。其次，我们将研究淀粉样肽羧基端产生的生化机制。这项工作将为膜蛋白的蛋白水解级联提供基础知识。它可能揭示新的细胞内调节机制，至少部分解释“定型”Notch信号通路如何在不同的细胞环境中执行其许多功能。因此，它与一些notch相关的人类疾病有关，如癌症、心血管疾病、中风和痴呆。此外，该研究将为细胞膜中产生多种淀粉样肽的酶的分子性质和作用模式提供关键的见解，从而与了解阿尔茨海默病有关。

DESCRIPTION (provided by applicant): Removing an old protein fragment and/or releasing a new one has evolved as an important regulatory mechanism of many physiological processes. Research in my laboratory aims to understand the biochemical mechanism, the physiological significance, and the pathological implications of proteolysis of a group of membrane proteins, particularly the amyloid precursor protein (APR) and the Notch receptor. These proteins are first cleaved at the extracellular domains in a process called ectodomain shedding. This generates membrane-bound fragments containing new and free amino termini. Our recent work showed that the glycoprotein nicastrin binds to the new amino termini and recruits the products of ectodomain shedding for intramembrane cleavage by gamma-secretase. Recent literature and our preliminary study suggest that novel peptidase activities further process the amino or carboxyl termini of gamma-secretase products, leading to the generation of new protein fragments with biological implications. This model will now be tested in the following two hypothesis-driven Specific Aims. First, we aim to understand the functional significance and biochemical mechanism of a novel proteolytic step that modifies the amino terminus of Notch intracellular domain. Second, we will investigate the biochemical mechanism by which the carboxyl termini of amyloid-beta peptides are generated. This work will provide fundamental knowledge to proteolytic cascades of membrane proteins. It may uncover novel intracellular regulatory mechanism that could, at least partially, explain how the "stereotyped" Notch signaling pathway executes its many functions in different cellular contexts. As such, it is relevant to several Notch-associated human diseases such as Cancer, Cardiovascular disease, Stroke and Dementia. Moreover, the study will provide critical insights into the molecular nature and mode of action of the enzyme(s) responsible for generating multiple Amyloid-beta peptides in cellular membranes, and thus is relevant to understanding Alzheimer's disease.