Role of LR11 Ectodomain Ligands in the Regulation of APP Processing

描述（由申请人提供）：虽然LR11在健康大脑中表达强劲，但这种低密度脂蛋白受体在阿尔茨海默病（AD）大脑中的表达急剧减少。此外，已知LR11在维持低水平的β -淀粉样蛋白（A3）中起作用，这种肽被广泛认为在阿尔茨海默病致病级联中起关键作用。最近的证据表明，LR11通过调节淀粉样蛋白前体蛋白（APP）的细胞内定位来实现这一功能，而Ap正是由APP产生的。由于在不同的亚细胞区室中发现了不同的APP加工酶，因此改变在细胞中发现APP的位置最终决定了有多少APP被切割成A(3)。鉴于LR11的这一作用，我们假设通过受体外域已知配体结合域与LR11相互作用的化合物能够影响LR11对Ap的已知作用。在本研究中，我们将使用基本的细胞培养系统来表征两种已知LR11配体对APP运输和加工的影响，并描述LR11在介导这些反应中的作用。在Specific Aim 1中，我们将验证小肽头激活剂（HA）影响LR11功能并调节APP加工的假设。在Aim 1a中，我们将确定HA与LR11结合对APP加工的影响；在Aim 1B中，我们将研究LR11如何介导这些影响，重点关注APP运输的改变。在Specific Aim 2中，我们将检验apoE影响LR11功能并以同工异构体依赖的方式调节APP运输的假设。在Aim 2A中，我们将重点关注apoE3和E4如何能够指导LR11和APP的运输，以及这些变化如何影响APP的加工。在Aim 2B中，我们将研究apoE2结合LR11对APP运输和加工的影响与apoE4反应中所见的影响以及这些差异背后的机制。这些研究将有助于我们更好地理解LR11在AD致病级联中的作用，特别是其在大脑中调节APP的能力。最终，这项工作将开始奠定基础，我们相信有一天会产生基于LR11的阿尔茨海默病治疗方法。

DESCRIPTION (provided by applicant): While LR11 expression is robust in the healthy brain, the expression of this low density lipoprotein receptor is drastically reduced in Alzheimer's disease (AD) brain. Moreover, LR11 is known to play a role in maintaining low levels of beta amyloid (A3), the peptide widely believed to play a critical role in the AD pathogenic cascade. Recent evidence has suggested that LR11 does this by regulating the the intracellular localization of the amyloid precursor protein (APP), which from which Ap is generated. Because different APP - processing enzymes are found in different sub-cellular compartments, altering where in the cell APP is found ultimately determines how much APP is cleaved into A(3. In light of this proposed role for LR11, we hypothesize that compounds that interact with LR11 through known ligand binding domains in the ectodomain of the receptor are capable of influencing the known effects of LR11 on Ap. In this study, we will use a basic cell culture system to characterize the effects of two known LR11 ligands on the trafficking and processing of APP, and to delineate the role of LR11 in mediating these reactions. In Specific Aim 1, we will test the hypothesis that the small peptide head activator (HA) influences LR11 function an modulates APP processing. In Aim 1 A, we will determine the effects of HA binding to LR11 on the processing APP and in Aim 1B, we will look at how LR11 mediates those effects, focusing on the altered trafficking of APP. In Specific Aim 2, we will test the hypothesis that apoE influences LR11 function and modulates the trafficking of APP in an isoform dependent manner. In Aim 2A, we will focus on how apoE3 and E4 are able to direct the trafficking of LR11 and APP, and how these changes influence the processing of APP. In Aim 2B, we will look at how the effects of apoE2 binding to LR11 on APP trafficking and processing differ from those seen in response apoE4 and the mechanisms underlying these differences. These studies will better our understanding of the role of LR11 in the AD pathogenic cascade and in particular, its ability to regulate APP in the brain. Ultimately, this work will begin to lay the ground work that we believe will someday yield LR11 based - AD therapeutics.