BACE1 as a Therapeutic Target for Alzheimer's Disease

描述(申请人提供)：降低大脑中的β-淀粉样肽(Ab)水平可能对治疗阿尔茨海默病(AD)有效。BACE1是启动抗体产生的酶，因此它是AD药物的主要靶点。然而，在避免基于机制的毒性的同时，体内BACE1抑制的最低水平尚不清楚。我们已经培育了BACE1缺陷(BACE1-/-)小鼠，并观察到这些小鼠表现出记忆缺陷。BACE1在突触前终末表达，提示BACE1在突触中具有重要的功能。BACE1也参与了应激途径。因此，似乎需要保持仔细平衡的BACE1抑制水平，才能达到无副作用的治疗效果。在这个项目中，我们将培育APP转基因(TG)、BACE1-/-和我们的新的可诱导的BACE1-YFP TG小鼠。在得到的复合TG小鼠中，我们将通过喂食小鼠多西环素，将前脑中BACE1的水平从内源性BACE1的0%调整到100%。我们将结合分子遗传学、生化、细胞生物学和行为学方法来1.确定BACE1抑制的最佳水平，以最大限度地发挥治疗效果，同时最大限度地减少机制毒性，2.更好地了解BACE1在大脑中的功能。我们的假设是，关键水平的BACE1抑制将缓解A依赖的认知障碍和淀粉样蛋白病理，但不会损害重要的BACE1功能。在目标1中，我们将确定BACE1水平、抗体产生、淀粉样蛋白沉积和体内记忆缺陷之间的定量关系。我们将研究这样一种假设，即在不完全阻断BACE1的情况下，存在一个最佳水平的BACE1抑制，以减少抗体的产生，延迟淀粉样斑块的形成，并挽救抗体依赖的记忆缺陷。这一目标的结果将为BACE1抑制剂在人体内的最佳给药剂量提供指导。在目标2中，我们将确定BACE1在体内记忆障碍和生理应激中的作用。我们将验证BACE1在记忆中具有功能，并参与大脑中的应激反应的假设。最后，我们将确定BACE1-/-小鼠在应激后是否受到损害，以及由此导致的神经变性是否被BACE1拯救。这些研究将提供关于1.避免BACE1基于BACE1机制的毒性所需的最低BACE1水平的信息；2.BACE1在大脑中的功能。在目标3中，我们将确定突触前终末内的BACE1区，终末分泌酶裂解的位置，以及BACE1对终末的分选控制。我们将研究这样一种假设，即含有ADP核糖化因子结合(GGA)的高尔基体定位的EAR蛋白将BACE1分类到突触前末端，在那里它裂解突触内体中的APP。这些研究将为BACE1靶向突触前终末、终末一代和3.BACE1在突触中发挥作用的机制提供深入的认识。我们的结果有望加强BACE1抑制剂治疗AD的开发的概念基础，并为BACE1在体内的功能提供洞察力。公共卫生相关性：阿尔茨海默病(AD)是导致老年人痴呆症的主要原因，但目前还没有可用的疾病修正疗法。BACE1是启动抗体形成的酶，抗体可能是阿尔茨海默病的病因。在这个方案中，我们将确定不同水平的BACE1抑制对AD小鼠模型中抗体产生、淀粉样斑块形成和记忆障碍的影响。此外，我们还将研究BACE1抑制剂对大脑的影响，以了解BACE1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.