Temperature-Dependent Lethality of APL-1, a C. elegans Protein Related to Human A

描述（由申请人提供）：致密斑块的沉积和神经元缠结的存在是用于阿尔茨海默病确诊的两个死后标准。致密斑块的主要成分是40个氨基酸的β-淀粉样肽，其来源于较大的淀粉样前体蛋白（APP）。在APP的加工过程中有两种替代途径，其中只有一种产生β-淀粉样肽。APP的功能和APP作用的途径仍然知之甚少。APP相关蛋白家族存在于哺乳动物中。敲除小鼠APP家族导致出生后致死和II型无脑畸形，表明APP家族在发育过程中具有重要功能。我们有兴趣研究APP的功能，并通过在一个简单的模型系统中研究APP相关基因来解决这个问题，线虫线虫。C.线虫具有易于遗传操作和能够快速产生转基因动物的实验优势。我们已经确定了一个C。elegans基因apl-1编码APP相关蛋白。APL-1与APP家族蛋白具有很强的序列同源性。apl-1基因敲除导致幼虫死亡，这可以通过apl-1基因组片段的种系转化来挽救。有趣的是，apl-1致死性也可以通过用仅编码APL-1胞外结构域的构建体转化来挽救。高水平的APL-1过表达导致不完全渗透幼虫致死，这表明APL-1的水平必须严格调节。携带apl-1（yn 5）突变的动物是可以存活的，并且仅产生高水平的APL-1胞外域。最近，我们发现apl-1（yn 5）突变体在稍微升高的温度下饲养诱导致死。我们建议：1）表征APL-1信号传导并确定APL-1（yn 5）致死性的基础;和2）鉴定在APL-1途径中起作用的基因。C. elegans提供了一种易处理的遗传模型，其中许多在哺乳动物系统中不可行的方法可用于理解APL-1功能和鉴定APL-1作用的途径。了解APL-1功能的途径可能有助于了解APP在高等动物（如人类）中的功能和调节。

DESCRIPTION (provided by applicant): Deposition of dense plaques and the presence of neurofibrillary tangles are two postmortem criteria used in the definitive diagnosis of Alzheimer's disease. The major component of the dense plaques is a 40 amino acid beta-amyloid peptide that is derived from the larger amyloid precursor protein (APP). Two alternative pathways have been suggested in the processing of APP, only one of which produces the beta-amyloid peptide. The function of APP and the pathways in which APP acts are still poorly understood. A family of APP-related proteins is present in mammals. Knockout of the APP family in mice leads to postnatal lethality and type II lissencephaly, indicating that the APP family has essential functions during development. We are interested in studying the function of APP and are approaching this problem by examining an APP-related gene in a simple model system, the nematode Caenorhabditis elegans. C. elegans has the experimental advantages of being easy to manipulate genetically and being able to generate transgenic animals quickly. We have identified a C. elegans gene, apl-1, that encodes an APP- related protein. APL-1 has strong sequence homology with the APP family proteins. Knockout of apl-1 leads to larval lethality, which can be rescued by germline transformation of a apl-1 genomic fragment. Interestingly, the apl-1 lethality can also be rescued by transformation with constructs encoding only the extracellular domain of APL-1. High levels of APL-1 overexpression lead to an incompletely penetrant larval lethality, suggesting that levels of APL-1 must be tightly regulated. Animals carrying the apl-1(yn5) mutation are viable and produce high levels of only the APL-1 extracellular domain. Recently, we found that raising apl-1(yn5) mutants at slightly elevated temperatures induces lethality. We propose to: 1) characterize APL-1 signaling and determine the basis of the apl-1(yn5) lethality; and 2) identify genes that act in the apl-1 pathway. C. elegans provides a tractable genetic model in which many approaches not feasible for use in mammalian systems can be used to understand APL-1 function and identify pathways in which APL-1 acts. Understanding the pathways through which APL-1 functions may give insights into the function and regulation of APP in higher animals, such as man.