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演变为许多生理过程的重要调节机制。我实验室的研究旨在了解一组膜蛋白，特别是淀粉样前体蛋白（APR）和Notch受体的蛋白水解的生化机制，生理意义和病理意义。这些蛋白质首先在称为胞外域脱落的过程中在胞外结构域处裂解。这产生含有新的和游离的氨基末端的膜结合片段。我们最近的工作表明，糖蛋白nicastrin结合到新的氨基末端和招募的产品的胞外脱落膜内切割的γ-分泌酶。最近的文献和我们的初步研究表明，新的肽酶活动进一步处理的氨基或羧基末端的γ-分泌酶的产品，导致产生新的蛋白质片段的生物学意义。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水解步骤，修改的氨基末端的Notch胞内结构域的功能意义和生化机制。其次，我们将研究淀粉样β肽羧基末端产生的生化机制。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，可以至少部分地解释“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，它与几种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，该研究将提供关键的见解，了解负责在细胞膜中产生多种淀粉样β肽的酶的分子性质和作用模式，因此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.