MOLECULAR BASIS OF GAMMA-SECRETASE IN GENERATING AB-PRO

阿尔茨海默病发病机制的研究进展 (AD)集中在40-42个残基的淀粉样β蛋白的明显作用上， 肽（Abeta）作为遗传性疾病的统一病理特征， 这种复杂疾病的不同形式。例如，DNA突变 在几个不同的基因中被鉴定出来（其中四个已经被发现）。 与家族性AD（FAD）相关。此外，本发明还提供了一种方法， 其他人已经表明β-淀粉样蛋白的蛋白水解加工 前体蛋白（betaAPP）在某种程度上被许多这些突变改变， 这导致Abeta肽的产生增加，特别是 高疏水性（因此是淀粉样的）42-残基形式的A β （Abeta/42）。通过FAD连锁遗传基因提高Abeta/42的产生 突变表明，β APP被γ- 分泌酶可能是淀粉样蛋白形成的关键因素， Abeta充分了解底物的分子基础 γ-分泌酶的特异性需要了解FAD相关的 基因突变影响AD中β APP的加工。但是没有一 这些负责β APP蛋白水解裂解的酶还 被识别。本研究的目的是调查 γ-分泌酶在β-APP加工中的分子机制， 三个具体目标。(1)表征的底物特异性 β APP的γ-分泌酶切割。(2)调查的影响， β APP跨膜结构域与γ- 分泌酶裂解。(3)调查本地化的影响， β APP对不同细胞区室的γ- 分泌酶将使用定点诱变来改变所述突变。 γ-分泌酶切割位点周围氨基酸残基的性质 或改变β APP跨膜结构域的长度。的确切 分泌的A β相关肽的特性将通过 用免疫沉淀和质量测定它们的分子量 光谱法这些研究将揭示关于 γ-分泌酶对β APP的切割特异性，导致 更好的策略来识别尚未发现的酶。

Recent progress in elucidating the pathogenesis of Alzheimer's disease (AD) has centered on the apparent role of the 40-42 residue amyloid beta- peptide (Abeta) as a unifying pathological feature of the genetically diverse forms of this complex disorder. For example, DNA mutations have been identified in several distinct genes (four of which have been discovered to date) associating with familial AD (FAD). In addition, others have shown that the proteolytic processing of beta-amyloid precursor protein (betaAPP) is altered by many of these mutations in a way that results in increased production of Abeta peptides, particularly of the highly hydrophobic (and thus amyloidogenic) 42-residue form of Abeta (Abeta/42). Elevated production of Abeta/42 by FAD-linked genetic mutations indicates that the proteolytic cleavage of betaAPP by gamma- secretase may be a key element in the formation of amyloidogenic form of Abeta. A full understanding of the molecular basis of the substrate specificity of gamma-secretase requires knowledge of how FAD-associated genetic mutations affect the processing of betaAPP in AD. However, none of these enzymes responsible for the proteolytic cleavage of betaAPP have yet been identified. The objective of this study is to investigate the molecular mechanisms of gamma-secretase in the processing of betaAPP, with three specific aims. (1) Characterizing the substrate specificity of gamma-secretase cleavage of betaAPP. (2) Investigating the effects of the association of the transmembrane domain of betaAPP with membrane on gamma- secretase cleavage. (3) Investigating the effects of the localization of betaAPP to different cellular compartment on the function of gamma- secretase. Site directed mutagenesis will be used to vary either the properties of amino acid residues around the gamma-secretase cleavage site or to vary the length of the transmembrane domain of betaAPP. The exact identities of secreted Abeta-related peptides will be determined be measuring their molecular basses using immunoprecipitation and mass spectrometry. These studies will reveal fine detains concerning the cleavage specificities of gamma-secretase towards betaAPP, leading to better strategies to identify the as yet undiscovered enzyme(s).