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残基淀粉样β蛋白的明显作用- 多肽(Abeta)作为遗传性糖尿病的统一病理特征 这种复杂的疾病有多种形式。例如，DNA突变具有 在几个不同的基因中被鉴定(其中四个已经被 迄今发现)与家族性AD(FAD)有关。此外, 其他研究表明，β-淀粉样蛋白的蛋白质分解过程 前体蛋白(Betaapp)在某种程度上会因这些突变而改变。 这导致Abeta多肽的产生增加，特别是 高度疏水(从而导致淀粉样变性)的42-残基形式的Abeta (Abeta/42)。FAD连锁遗传提高Abeta/42的产量 突变表明，γ-APP对β-APP的蛋白水解性切割 分泌酶可能是淀粉样变性形式形成的关键因素 阿贝塔。充分了解底物的分子基础 伽马分泌酶的特异性需要了解FAD如何关联 基因突变影响阿尔茨海默病患者β-APP的加工。然而，没有一个 这些负责β-APP蛋白水解酶的酶尚未 已被确认身份。这项研究的目的是调查 β-分泌酶在β-APP加工过程中的分子机制 三个具体目标。(1)底物专一性的表征 β-APP的伽马分泌酶裂解。(2)调查以下情况的影响 β-APP跨膜区与膜结合的研究 分泌酶分裂。(3)调查本地化的影响 β-APP对不同细胞亚群伽马-α功能的影响 分泌酶。定点突变将被用来改变 γ-分泌酶裂解位点周围氨基酸残基的性质 或改变BetaAPP跨膜结构域的长度。完全相同的 分泌的Abeta相关多肽的身份将被确定 用免疫沉淀法和质量法测定它们的分子碱基 光谱分析。这些研究将揭示关于 γ-分泌酶对β-APP的切割特异性，导致 确定尚未发现的酶的更好策略(S)。

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).