PHYSICAL BIOCHEMISTRY AND BIOLOGY OF AMYLOID B-PROTEIN

在阿尔茨海默病（AD）中，淀粉样β蛋白（Abeta）原纤维、“淀粉样斑块”、 发生在大脑中。然而，神经元功能障碍可能在斑块形成之前发生。结构-神经毒性 研究已经揭示了逐渐变小的毒性组装体，包括原纤维， 副核和ADDLs在啮齿类动物中，Abeta寡聚体可以抑制长时程增强（LTP），这是一种 学习和记忆。在AD患者中，Abeta寡聚体的水平显著高于年龄匹配的AD患者。 正常的个体。因此，生物物理学、细胞培养、动物和人类研究都支持本发明。 假设A β寡聚化是AD发病机制中关键事件。如果是这样的话， 治疗策略取决于病理性蛋白质折叠机制的阐明， 低聚和更高级的组装。在我们的实验室里继续努力了解最早的 Abeta组装、Abeta单体折叠和寡聚化的步骤揭示了关键的结构特征。 这些包括在非结构化Abeta单体的Val 24-Lys 28区域中的转角形成和相互作用 在中心疏水簇（Leu 17-Ala 21）、N-末端和C-末端之间。四个目标 包括本申请试图测试从这些观察中产生的机制假设。 目标1。确定Abeta的Val 24-Lys 28区域中转角形成的机制。 a.以确定疏水相互作用的作用。 B.以确定静电相互作用的作用。 C.以确定氨基酸转折倾向的作用。 目标2.确定分子内折叠和早期Abeta寡聚化的机制。 a.确定中心疏水簇（CHC）-C-末端相互作用的结构动力学。 B.确定CHC-N-末端相互作用的结构动力学。 C.确定交替转角构象对Abeta单体结构和低聚化的影响。 目标3.使用O？> N酰基迁移化学实现一个新的，准同步系统， Abeta 42折叠和自组装的研究。 a.合成26-O-酰基-isoA β 42（26-AIA β 42），并研究26-AIA β 42 二级和四级结构后，引发的O？> N酰基迁移。 B.利用准弹性光散射光谱测定动力学和热力学参数 Abeta 42的自我组装 C.使用离子迁移谱-质谱法监测Abeta自组装中的早期寡聚化事件。 D.合成并研究钠保护的26-AIA β 42的生物物理和生物学行为。 目标4。为了确定在控制Abeta折叠中显示出关键的结构特征， 寡聚化影响肽神经毒性。

In Alzheimer's disease (AD), progressive deposition of amyloid beta-protein (Abeta) fibrils, "amyloid plaques," occurs in the brain. However, neuronal dysfunction may occur prior to plaque formation. Structure-neurotoxicity studies have revealed progressively smaller toxic assemblies, including protofibrils, paranuclei, and ADDLs. In rodents, Abeta oligomers can inhibit long-term potentiation (LTP), a model for learning and memory. In AD patients, Abeta oligomers are present in levels significantly greater than in agematched normal individuals. Biophysical, cell culture, animal, and human studies thus all support the hypothesis that oligpmerization of Abeta is a key event in AD pathogenesis. If so, then the development of therapeutic strategies depends on elucidation of the mechanism(s) of pathologic protein folding, oligomerization, and higher-order assembly. Continuing efforts in our laboratory to understand the earliest steps in Abeta assembly, Abeta monomer folding and oligomerization, have revealed key structural features. These include turn formation in the Val24-Lys28 region of the unstructured Abeta monomer and interactions among the central hydrophobic cluster (Leu17-Ala21), N-terminus, and C-terminus. The four aims comprising this application seek to test mechanistic hypotheses emanating from these observations. Aim 1. To determine the mechanisms of turn formation in the Val24-Lys28 region of Abeta. a. To determine the role of hydrophobic interactions. b. To determine the role of electrostatic interactions. c. To determine the role of amino-acid turn propensity. Aim 2. To determine the mechanisms of intramolecular folding and early Abeta oligomerization. a. To determine the structural dynamics of central hydrophobic cluster (CHC)-C-terminus interactions. b. To determine the structural dynamics of CHC-N-terminus interactions. c. To determine the effects of alternative turn conformations on Abeta monomer structure and oligomerization. Aim 3. To use O?>N acyl migration chemistry to implement a new, quasisynchronous system for studies of Abeta42 folding and self-assembly. a. To synthesize 26-O-acyl-isoAbeta42 (26-AIAbeta42) and study the time-dependent changes in peptide secondary and quaternary structure following initiation of O?>N acyl migration. b. To use quasielastic light scattering spectroscopy to determine kinetic and thermodynamic parameters of Abeta42 self-assembly. c. To use ion mobility spectroscopy-mass spectrometry to monitor early oligomerization events in Abeta self-assembly. d. To synthesize and study the biophysical and biological behavior of Na-protected 26-AIAbeta42. Aim 4. To determine how structural features shown to be critical in controlling Abeta folding and oligomerization affect peptide neurotoxicity.