The Role of Cathepsin B and Cystatin C in Alzheimer's Disease

描述（由申请人提供）：淀粉样蛋白β（Abeta）是阿尔茨海默病（AD）的一种关键致病因子，由于过度产生或清除效率低下，在大脑中积累并形成有毒寡聚体。因此，调节Abeta降解和清除的途径是治疗干预的主要候选者。我们发现组织蛋白酶B（CatB），一种半胱氨酸蛋白酶，在体外和体内降解Abeta。在最近的研究中，我们发现CatB的Abeta降解活性受到其内源性抑制剂半胱氨酸蛋白酶抑制剂C（CysC）的抑制，并且减少CysC增强了CatB诱导的Abeta降解并保护免受Abeta相关的突触和行为缺陷.然而，与其他一些Abeta降解酶如脑啡肽酶（NEP，一种在中性pH下具有最佳活性的内肽酶）不同，CatB在C末端截短Abeta，在酸性pH下具有最佳活性。CatB在减少体内更高阶的Abeta组装方面似乎也比NEP更有效。这些观察结果表明，CatB和NEP可能在Abeta降解中发挥互补作用。该提案的目的是确定CatB-CysC轴的细胞机制以及它和NEP如何共同调节Abeta降解。在具体目标1中，我们将评估神经元CatB-CysC轴对体内Abeta降解和神经元突触功能的影响。将比较小胶质细胞和神经元衍生的CatB的作用。在具体目标2中，我们将确定神经元CatB-CysC轴是否在内体-溶酶体途径中起作用以调节Abeta降解。了解CatB-CysC轴的亚细胞机制是开发针对这一新发现途径的治疗策略的先决条件。在具体目标3中，我们将研究NEP在CatB诱导的Abeta降解中的作用以及CatB在NEP诱导的Abeta降解中的作用。通过定义CatB-CysC轴和NEP之间的相互作用，可能会出现对调节Abeta降解的分子机制的新见解。确认CatB-CysC轴作用以与NEP互补的方式起作用将为设计有效的Abeta清除策略奠定基础。

DESCRIPTION (provided by applicant): Amyloid beta (Abeta), a key pathogenic factor in Alzheimer's disease (AD), accumulates and forms toxic oligomers in the brain as a result of overproduction or inefficient clearance. Thus, pathways regulating Abeta degradation and clearance are prime candidates for therapeutic intervention. We discovered that cathepsin B (CatB), a cysteine protease, degrades Abeta in vitro and in vivo. In more recent studies, we showed that the Abeta -degrading activity of CatB is inhibited by its endogenous inhibitor, cystatin C (CysC), and that reducing CysC enhances CatB- induced Abeta degradation and protects against Abeta -associated synaptic and behavioral deficits. However, unlike some other Abeta degradation enzymes, such as neprilysin (NEP, an endopeptidase with optimal activity at a neutral pH), CatB truncates Abeta at the C-terminus with optimal activity at acidic pHs. CatB also appears to be more effective than NEP in reducing higher orders of Abeta assemblies in vivo. These observations suggest that CatB and NEP may play complementary roles in Abeta degradation. The objectives of this proposal are to determine the cellular mechanisms of the CatB-CysC axis and how it and NEP might work together to regulate Abeta degradation. In Specific Aim 1, we will assess the effects of the neuronal CatB-CysC axis on Abeta degradation and neuronal synaptic function in vivo. The effects of microglia- and neuron-derived CatB will be compared. In Specific Aim 2, we will determine if neuronal CatB-CysC axis acts in the endosomal-lysosomal pathway to regulate Abeta degradation. Understanding the subcellular mechanisms of CatB-CysC axis is a prerequisite for the development of therapeutic strategies that target this newly identified pathway. In Specific Aim 3, we will examine the role of NEP in CatB-induced Abeta degradation and the role of CatB in NEP-induced Abeta degradation. By defining the interplay between the CatB-CysC axis and NEP, new insights into molecular mechanisms regulating Abeta -degradation will likely emerge. Confirmation that the CatB-CysC axis action acts in a complementary manner with NEP would lay the foundation for designing effective Abeta clearance strategies.