Role of APL-1, a C. elegans protein related to human amyloid precursor protein

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蛋白前体（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及其不同裂解产物的功能仍然知之甚少。此外，蛋白质发挥功能的途径尚未确定。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检测APP相关基因来解决这个问题。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和结构相似性。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的细胞外结构域或驱动APL-1的泛神经表达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。我们建议：1）确定apl-1必须在哪些细胞中表达以挽救致死性; 2）确定在后期发育阶段是否需要APL-1; 3）阐明apl-1过表达动物中致死性的潜在基础; 4）鉴定升高的温度如何影响APL-1功能;和5）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。了解APL-1发挥功能的途径可能有助于深入了解人类APP发挥功能的途径。公共卫生相关性：阿尔茨海默病影响超过450万美国人。包括淀粉样前体蛋白（APP）基因在内的三个基因的突变与家族性阿尔茨海默病有关。不过，APP的功能目前还不得而知。我们正在研究一个遗传模型系统中的APP相关基因，线虫线虫。秀丽隐杆线虫可能为研究APP在人类等高等生物中的正常功能提供线索。

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 a larger amyloid protein precursor (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 its different cleavage products are still poorly understood. Furthermore, the pathways in which the proteins function have not been identified. 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 and structural similarities 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 or driving pan-neural expression 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. We propose to: 1) determine in which cells apl-1 must be expressed to rescue the lethality; 2) determine whether APL-1 is required during later developmental stages; 3) elucidate the underlying basis of the lethality in APL-1 overexpression animals; 4) identify how elevated temperatures affect APL-1 function; and 5) 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. Understanding the pathways through which APL-1 functions may give insights into the pathways through which human APP functions. PUBLIC HEALTH RELEVANCE: Alzheimer's disease affects over 4.5 million Americans. Mutations in three genes, including the Amyloid Precursor Protein (APP) gene, have been correlated with familial Alzheimer's disease. However, the function of APP is still unknown. We are examining an APP-related gene in a genetic model system, the roundworm Caenorhabditis elegans; information from C. elegans is likely to provide clues into the normal function of APP in higher organisms, such as man.