N-terminus of sAPP Regulates Abeta Assembly

描述（由申请人提供）：淀粉样蛋白（A）的异常积累、组装和沉积是阿尔茨海默病（AD）和相关疾病患者的突出病理特征。A <$肽是通过A <$前体蛋白（A <$PP）的连续蛋白水解加工而获得的，分泌酶活性。PP在大脑中高度表达，但其生理功能仍然知之甚少。许多功能域已被确定分泌形式的A？PP蛋白，可以参与各种神经保护活动，从蛋白酶抑制配体结合细胞保护。例如，在上一个资助期间，我们明确证明了sA <$PP的Kunitz蛋白酶抑制（KPI）活性限制了脑血栓形成的程度。额外的保护活性可能与其他生物学活性相关。 存在于sA？PP蛋白上的活性结构域，对脑损伤包括慢性神经退行性疾病如AD作出反应。 脑Ass肽的异常积累和沉积可由增加的产生而发生，但在大多数情况下可能是由于CNS中清除机制的降低。清除机制涉及可促进A从CNS流出、介导A β降解和/或抑制A β组装和沉积的因子。虽然已经鉴定出许多可以影响体外Ass组装和沉积的分子，但我们目前对脑中这些过程的理解仍然不完整。在这方面，A <$PP的N-末端区域（A <$PP 18 -119）是蛋白质的高度结构化区域，其结合A <$肽并可以抑制它们的组装。因此，形成该探索性R21提议的基础的总体假设是分泌的A？PP蛋白的N-末端区域通过其Ass组装抑制活性有助于调节Ass水平、淀粉样蛋白形成和脑中的沉积。 在目前的提案中，我们计划实施研究，以调查如何在体内的N-末端区域的A？PP与Ass肽相互作用，以调节其组装，沉积和与这些过程相关的病理后果。对于这些研究，我们将利用两种不同的和良好表征的人类A <$沉积的转基因小鼠模型，结合增加它们中A <$PP N-末端片段水平的方法，以了解sA <$PP的该区域如何改变病理结果。最后，这种新鉴定的sA <$PP活性，特别是N-末端A <$PP 18 -119片段，可能导致开发治疗剂的新方法，以对抗AD和相关淀粉样蛋白沉积疾病中发生的病理性A β积累、组装和沉积。

DESCRIPTION (provided by applicant): Abnormal accumulation, assembly and deposition of the amyloid ¿-protein (A¿) are prominent pathological features of patients with Alzheimer's disease (AD) and related disorders. A¿ peptides are derived through sequential proteolytic processing of the A¿ precursor protein (A¿PP) by ¿- and ?- secretase activities. A¿PP is highly expressed in brain although its physiological functions remain poorly understood. Many functional domains have been identified on secreted forms of A¿PP proteins that could participate in variety of neuroprotective activities ranging from proteinase inhibition to ligand binding to cytoprotection. For example, during the previous funding period we unequivocally demonstrated that the Kunitz proteinase inhibitory (KPI) activity of sA¿PP limits the extent of cerebral thrombosis. Additional protective activities are likely associated with other biologically active domains present on sA¿PP proteins in response to cerebral injuries including chronic neurodegenerative disorders such as AD. The abnormal accumulation and deposition of cerebral Ass peptides can occur from increased production but in most cases is likely due to decreased clearance mechanisms in the CNS. Clearance mechanisms involve factors that can promote A¿ efflux from the CNS, mediate Ass degradation, and/or inhibit Ass assembly and deposition. Although numerous molecules have been identified that can influence Ass assembly and deposition in vitro our present understanding of these processes in brain remains incomplete. In this regard, the N-terminal region of A¿PP (A¿PP18-119) is a highly structured region of the protein that binds to A¿ peptides and can inhibit their assembly. Thus, the overall hypothesis that forms the basis of this exploratory R21 proposal is that the N-terminal region of secreted A¿PP proteins contributes to the regulation of Ass levels, amyloid formation and deposition in brain through its Ass assembly inhibiting activities. In the present proposal we plan to implement studies to investigate how the N-terminal region of A¿PP interacts with Ass peptides in vivo to regulate their assembly, deposition and the pathological consequences associated with these processes. For these studies we will utilize two distinct and well- characterized transgenic mouse models of human A¿ deposition coupled with approaches to increase A¿PP N-terminal fragment levels in them, to understand how this region of sA¿PP might alter pathological outcomes. Finally, this newly identified activity of sA¿PP, and in particular the N-terminal A¿PP18-119 fragment, may lead to new approaches for developing therapeutic agents to combat pathological Ass accumulation, assembly and deposition that occurs in AD and related amyloid depositing diseases.