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原纤维缠结的存在是阿尔茨海默病明确诊断的两个死后标准。致密斑块的主要成分是由较大的淀粉样前体蛋白（APP）衍生的40个氨基酸的β -淀粉样肽。在APP的加工过程中提出了两种替代途径，其中只有一种产生β -淀粉样肽。APP的功能和APP的作用途径仍然知之甚少。哺乳动物中存在一个与app相关的蛋白家族。在小鼠中敲除APP家族可导致产后死亡和II型无脑畸形，这表明APP家族在发育过程中具有重要功能。我们对研究APP的功能很感兴趣，并通过在一个简单的模型系统——秀丽隐杆线虫中检测APP相关基因来解决这个问题。秀丽隐杆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。我们已经鉴定出秀丽隐杆线虫的一个基因，apl-1，它编码一种与APP相关的蛋白。APL-1与APP家族蛋白具有较强的序列同源性。敲除apple -1会导致幼虫死亡，这可以通过apple -1基因组片段的种系转化来挽救。有趣的是，用仅编码apl-1细胞外结构域的构建体进行转化也可以挽救apl-1的致死率。高水平的APL-1过表达导致幼虫不完全渗透致死，这表明APL-1的水平必须受到严格调控。携带apl-1（yn5）突变的动物是存活的，并且只产生高水平的apl-1细胞外结构域。最近，我们发现在稍微升高的温度下培养apl-1（yn5）突变体可诱导致死性。我们建议：1)表征APL-1信号并确定APL-1 （yn5）致死率的基础；2)确定在apl-1通路中起作用的基因。秀丽隐杆线虫提供了一个易于处理的遗传模型，其中许多在哺乳动物系统中不可行的方法可用于了解APL-1的功能并确定APL-1的作用途径。了解APP -1发挥作用的途径可能有助于了解APP在人类等高等动物中的功能和调控。

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.