RAB GTPASES AND TRAFFICKING OF BETA AMYLOID PROTEINS

淀粉样蛋白β-肽（Abeta）是糖尿病患者中淀粉样蛋白斑块的主要成分。 老年痴呆症 Abeta通过细胞内蛋白水解形成 一种称为β-淀粉样蛋白的膜锚定糖蛋白的加工 前体蛋白（APP）。 细胞可以产生替代形式的Abeta (e.g., Abeta 40和Abeta 42），而Abeta 42具有最大的倾向， 形成不溶性沉积物。我们的一般假设是， 由细胞产生和释放的A β 42和A β 40的量是 至少部分是在蛋白质运输水平上确定的。 我们 长期目标是定义特定的传输事件， 对（1）APP C-末端的淀粉样蛋白形成加工至关重要 被称为γ-分泌酶的细胞内蛋白酶的片段，和（2） 随后从细胞中释放出不同形式的Abeta。 到 为了实现这一目标，分子和病毒转染策略将是 用于在培养的细胞中表达显性阴性Rab突变体。 以来 不同的Rab GTP酶作为囊泡转运的介质发挥作用 在胞吐细胞中的特定供体和受体隔室之间， 内吞途径，这一策略将使我们能够选择性地破坏 可能构成前体交付基础的离散贩运步骤 肽与含有γ-分泌酶活性的细胞器的结合以及 将最终的Abeta产物递送至细胞外环境。 为了便于识别可能在神经元中变化的步骤， 与未分化的细胞相比，研究将在两种细胞中进行。 NT 2N神经元和人胚肾细胞（HEK 293）。 通过表达 各种具有改变形式的APP的Rab突变体， 在家族性阿尔茨海默病中发现， 特别相关的具体贩运步骤， 从这些改变的前体中增加Abeta的产生。 这些 研究将提供有关亚细胞的新信息， γ-分泌酶活性的区室化， 不同形式的Abeta，并帮助确定这些途径， 产物从细胞中释放出来。 这些信息可能有助于 制定针对相关疾病的治疗策略 蛋白酶，特别是γ-分泌酶负责 致病性Abeta 42同种型的产生。

Amyloid beta-peptide (Abeta) is a major component of amyloid plaques in Alzheimer's disease. Abeta is formed through intracellular proteolytic processing of a membrane-anchored glycoprotein termed beta-amyloid precursor protein (APP). Cells can produce alternate forms of Abeta (e.g., Abeta40 and Abeta42), and Abeta42 has the greatest tendency to form insoluble deposits. Our general hypothesis is that the relative amounts of Abeta42 and Abeta40 generated and released by the cell are determined, at least in part, at the level of protein trafficking. Our long range goal is to define the specific transport events that are critical for (1) the amyloidogenic processing of APP C-terminal fragments by intracellular protease(s) termed gamma-secretase, and (2) the subsequent release of different forms of Abeta from the cell. To pursue this goal, molecular and viral transfection strategies will be used to express dominant-negative Rab mutants in cultured cells. Since different Rab GTPases function as mediators of vesicular transport between specific donor and acceptor compartments in the exocytic and endocytic pathways, this strategy will allow us to selectively disrupt discrete trafficking steps that may underlie the delivery of precursor peptides to organelles containing gamma-secretase activity and the delivery of the final Abeta products to the extracellular environment. To facilitate the identification of steps that may vary in neurons versus non-differentiated cells, studies will be carried out in both NT2N neurons and human embryonal kidney cells (HEK293). By expressing various Rab mutants with altered forms of APP that harbor mutations found in familial Alzheimer's disease, it should be possible to identify specific trafficking steps that have particular relevance for the increased production of Abeta from these altered precursors. These studies will provide new information about the subcellular compartmentalization of the gamma-secretase activities that give rise to different forms of Abeta, and help define the routes whereby these products are released from the cell. This information may facilitate the development of therapeutic strategies targeted at the relevant proteases, particularly the gamma-secretase responsible for the production of the pathogenic Abeta42 isoform.