Transcriptional Regulation of BACE and the Components of the gamma-Secretase Comp

描述（由申请人提供）：普遍认为，淀粉样蛋白（A）的过度产生会引发导致阿尔茨海默病（AD）的神经变性级联反应。A <$是通过<$-分泌酶（BACE 1）和？-分泌酶复合物（由四种组分组成：早老素、nicastrin、APH-1和PEN-2）。许多研究工作都集中在翻译后水平上对分泌酶活性的调控，而作为蛋白质生物合成的第一步，分泌酶组分基因表达的转录调控却很少有人研究。最近，我们和其他人已经表征了BACE 1、早老素、PEN-2和APH-1的基本启动子序列，以及几种已鉴定的转录因子。然而，其他转录因子和相关的调控机制/途径仍有待确定。诸如转录事件如何在不同细胞/组织类型中差异地影响分泌酶活性，以及分泌酶组分在AD发病机制中的转录调节的重要性等问题是非常重要的，并且仍有待解决。基于现有的信息和我们的初步结果，我们提出了以下研究目标：具体目标1：进一步表征HIF/缺氧和A？对BACE 1的转录调控，确定BACE 1启动子利用的细胞类型特异性，并关联BACE 1基因转录调控在AD发病机制中的重要性。我们将（1）确定BACE 1的转录是否受HIF-1的调节，以及HIF-1缺陷是否影响BACE 1在体内的表达;（2）确定BACE 1转录因子的表达是否受HIF-1的调节，以及HIF-1缺陷是否影响BACE 1在体内的表达。（3）确定BACE 1在神经元和非神经元细胞中的转录调控;（4）研究A？和BACE 1之间潜在的相互调节，即确定A？处理是否调节BACE 1的转录。具体目标二：确定nicastrin的启动子和转录调控，确定不同？分泌酶组分基因及其转录调控的A？，并关联这些基因的转录调控在AD发病机制中的重要性，并在控制？分泌酶底物特异性。我们将（1）表征nicastrin基因的启动子和转录调控;（2）确定调节nicastrin基因表达的转录因子的水平是否与nicastrin基因的表达水平有关。分泌酶组分在AD脑中改变;（3）确定编码四种？分泌酶组分;（4）确定A？处理是否促进？-分泌酶组分;和（5）确定转录调节对？分泌酶对不同底物的活性。研究这些分泌酶组分的转录调控应该有助于开发有效的治疗AD的方法。

DESCRIPTION (provided by applicant): Overproduction of ¿-amyloid (A¿) is widely believed to trigger a cascade of neurodegeneration leading to Alzheimer's disease (AD). A¿ is proteolytically derived from ¿-amyloid precursor protein (APR) through sequential cleavages by ¿-secretase (BACE1) and ?-secretase complex (consisting of four components: presenilin, nicastrin, APH-1 and PEN-2). Much research effort has gone into studying regulation of secretase activity at the post-translation level, transcriptional regulation of gene expression of secretase components, the first step of any protein's biogenesis, has been much less explored. Recently we and others have characterized the basic promoter sequence for BACE1, presenilins, PEN-2 and APH-1, and several identified transcriptional factors. However, additional transcriptional factors and related regulatory mechanisms/pathways still remain to be identified. Questions such as how transcriptional events may differentially affect the secretase activity in different cell/tissue types, and the importance of the transcriptional regulation of the secretase components in AD pathogenesis are highly important and remain to be addressed. Based on the available information and our preliminary results, we propose to study the following aims: Specific Aim 1: to further characterize the transcriptional regulation of BACE1 by HIF/hypoxia and A¿, to determine the cell type specificity of promoter utilization for BACE1, and to correlate the importance of the transcriptional regulation of BACE1 gene in AD pathogenesis. We will (1) determine whether transcription of BACE1 is regulated by HIF-1 and whether HIF-1 deficiency affects BACE1 expression in vivo; (2) determine whether expression of BACE1 transcription factors (i.e. SP1 and HIF-1) and their activity are altered in AD brains; (3) determine transcriptional regulation of BACE1 in neuronal and non-neuronal cells; and (4) study a potential reciprocal regulation between A¿ and BACE1, i.e. to determine whether A¿ treatment regulates transcription of BACE1. Specific Aim 2: to define the promoter and transcriptional regulation of nicastrin, to determine the cell type specificity of promoter utilization for various ?-secretase component genes and their transcriptional regulation by A¿, and to correlate the importance of the transcriptional regulation of these genes in AD pathogenesis and in controlling the ?-secretase substrate specificity. We will (1) characterize promoter and transcriptional regulation of nicastrin gene; (2) determine whether the levels of transcription factors regulating expression of ?-secretase components are altered in AD brains; (3) define the cell type specific transcriptional regulation of genes encoding the four ?-secretase components; (4) determine whether A¿ treatment promotes the expression of ?-secretase components; and (5) determine the effects of transcriptional regulation on the ?-secretase activity to different substrates. Studying transcriptional regulation of these secretase components should be instrumental for developing effective therapies for AD.