BACE1 as a Therapeutic Target for Alzheimer's Disease

描述（由申请人提供）：降低脑中β-淀粉样肽（Ab）水平可能对治疗阿尔茨海默病（AD）有效。BACE 1是启动Ab生成的酶，因此它是主要的AD药物靶标。然而，在避免基于机制的毒性的同时，体内治疗效果的BACE 1抑制的最低水平是未知的。我们已经产生了BACE 1缺陷（BACE 1-/-）小鼠，并观察到这些小鼠表现出记忆缺陷。BACE 1在突触前末梢中的表达，表明BACE 1在突触中的重要功能。BACE 1也参与应激途径。因此，似乎需要维持仔细平衡的BACE 1抑制水平以获得治疗效果而没有副作用。对于这个项目，我们将繁殖APP转基因（Tg），BACE 1-/-，和我们的新的tet诱导BACE 1-YFP Tg小鼠。在所得的化合物Tg小鼠中，我们将通过给小鼠喂食多西环素将前脑中的BACE 1水平从内源性BACE 1水平的0%调节至100%。我们将结合分子遗传学、生物化学、细胞生物学和行为学的方法来研究1.确定将最大化治疗效果但最小化基于机制的毒性的BACE 1抑制的最佳水平，以及2.更好地了解BACE 1在大脑中的功能。我们的假设是，临界水平的BACE 1抑制将减轻A依赖性认知障碍和淀粉样病变，但不会损害重要的BACE 1功能。在目标1中，我们将确定BACE 1水平，抗体生产，淀粉样蛋白沉积和记忆缺陷之间的定量关系。我们将研究一个假设，即存在一个最佳水平的BACE 1抑制，以减少抗体的产生，延缓淀粉样斑块的形成，并挽救抗体依赖性记忆缺陷，而不完全阻断BACE 1。这一目标的结果将为人类最佳BACE 1抑制剂药物剂量提供指导。在目标2中，我们将确定BACE 1在体内记忆障碍和生理应激中的作用。我们将测试BACE 1在记忆中具有功能并且还参与大脑中的应激反应的假设。最后，我们将确定BACE 1-/-小鼠是否在应激后受损，以及BACE 1是否挽救了所导致的神经退行性变。这些研究将提供有关1.避免BACE 1和2的基于BACE 1机制的毒性所需的最低BACE 1水平。BACE 1在大脑中的作用在目标3中，我们将确定BACE 1车厢内突触前终端，网站的分泌酶裂解终端，和控制BACE 1排序终端。我们将调查的假设，高尔基体本地化耳含ADP核糖基化因子结合（GGA）蛋白排序BACE 1的突触前终端，它在突触内体裂解APP。这些研究将提供深入了解的机制1。BACE 1靶向于突触前末梢，2.在终端的一代，和3。BACE 1在突触处起作用。我们的研究结果有望加强BACE 1抑制剂治疗AD的发展的概念基础，并提供深入了解BACE 1在体内的功能。公共卫生相关性：阿尔茨海默病（AD）是老年痴呆症的主要原因，然而没有可用的疾病改善疗法。BACE 1是启动Ab形成的酶，Ab可能是AD的原因。在这个建议中，我们将确定不同水平的BACE 1抑制对抗体产生，淀粉样斑块的形成和AD小鼠模型中的记忆缺陷的影响。此外，我们将研究BACE 1抑制对大脑的影响，以了解BACE 1抑制剂药物的潜在副作用。

DESCRIPTION (provided by applicant): Lowering Beta-Amyloid peptide (Ab) levels in the brain may be effective for the treatment of Alzheimer's disease (AD). BACE1 is the enzyme that initiates Ab generation and therefore it is a prime AD drug target. However, the minimum level of BACE1 inhibition for therapeutic effects in vivo, while avoiding mechanism-based toxicities, is unknown. We have generated BACE1 deficient (BACE1-/-) mice and have observed that these mice exhibit memory deficits. BACE1 in presynaptic terminals, suggesting an important BACE1 function at the synapse. BACE1 is also involved in stress pathways. Therefore, it appears that a carefully balanced level of BACE1 inhibition will need to be maintained for therapeutic effect without side-effects. For this project we will breed APP transgenic (Tg), BACE1-/-, and our new tet-inducible BACE1-YFP Tg mice. In the resulting compound Tg mice, we will adjust BACE1 levels in the forebrain from 0% to 100% of endogenous BACE1 levels by feeding mice doxycycline. We will use a combination of molecular genetic, biochemical, cell biological, and behavioral approaches to 1. determine the optimal level of BACE1 inhibition that will maximize therapeutic effects but minimize mechanism-based toxicities, and 2. better understand the function of BACE1 in the brain. Our hypothesis is that a critical level of BACE1 inhibition will alleviate A-dependent cognitive impairment and amyloid pathology, but will not compromise important BACE1 functions. In Aim 1 we will determine the quantitative relationships between BACE1 level, Ab production, amyloid deposition, and memory deficits in vivo. We will investigate the hypothesis that an optimal level of BACE1 inhibition exists for reducing Ab production, delaying amyloid plaque formation, and rescuing Ab-dependent memory deficits, without completely blocking BACE1. The results of this Aim will provide guidelines for optimal BACE1 inhibitor drug dosing in humans. In Aim 2, we will determine the role of BACE1 in memory impairment and physiologic stress in vivo. We will test the hypothesis that BACE1 has a function in memory and also participates in stress response in the brain. Finally, we will determine if BACE1-/- mice are compromised following stress and whether resulting neurodegeneration is rescued by BACE1. These studies will provide information about 1. minimum BACE1 levels required to avoid BACE1 mechanism-based toxicities of BACE1 and 2. BACE1 function in brain. In Aim 3, we will determine the BACE1 compartment within presynaptic terminals, the site of -secretase cleavage in terminals, and the control of BACE1 sorting to terminals. We will investigate the hypothesis that Golgi-localized -ear containing ADP ribosylation factor-binding (GGA) proteins sort BACE1 to the presynaptic terminal where it cleaves APP within synaptic endosomes. These studies will provide insight into the mechanisms of 1. BACE1 targeting to the presynaptic terminal, 2. A generation in the terminal, and 3. BACE1 function at the synapse. Our results are expected to strengthen the conceptual foundation for the development of BACE1 inhibitors for the treatment of AD and provide insight into BACE1 function in vivo. PUBLIC HEALTH RELEVANCE: Alzheimer's disease (AD) is the leading cause of dementia in the elderly, yet there is no disease modifying therapy available. BACE1 is the enzyme that initiates the formation of Ab, the likely cause of AD. In this proposal, we will determine the effects of different levels of BACE1 inhibition on Ab production, the formation of amyloid plaques, and memory deficits in AD mouse models. In addition, we will investigate the effects of BACE1 inhibition on the brain in order to understand potential side-effects of BACE1 inhibitor drugs.