N-terminus of sAPP Regulates Abeta Assembly

描述(申请人提供)：淀粉样蛋白(A？)的异常堆积、组装和沉积是阿尔茨海默病(AD)和相关疾病患者的显著病理特征。A‘肽是通过分泌酶活性对A？前体蛋白(A？PP)进行连续的蛋白分解而得到的。A？PP在大脑中高度表达，但其生理功能仍鲜为人知。在分泌形式的A？PP蛋白上已经发现了许多功能结构域，它们可以参与从抑制蛋白酶到配体结合到细胞保护等多种神经保护活性。例如，在之前的资助期间，我们明确地证明了Sa？PP的库尼茨蛋白酶抑制(KPI)活性限制了脑血栓的程度。额外的保护活动很可能与其他生物学上的 Sa？PP蛋白上存在活性结构域，对包括AD等慢性神经退行性疾病在内的脑损伤做出反应。脑ASS多肽的异常积累和沉积可能是由于产量增加，但在大多数情况下，可能是由于中枢神经系统清除机制的减少。清除机制涉及促进Aβ从中枢神经系统外流、介导Ass降解和/或抑制Ass组装和沉积的因子。虽然已经发现了许多影响Ass在体外组装和沉积的分子，但我们目前对大脑中这些过程的了解仍然不完整。在这一点上，A？PP的N-末端区域(A？PP18-119)是蛋白质的一个高度结构化的区域，它与A？肽结合并能抑制它们的组装。因此，构成这一探索性R21建议基础的总体假设是，分泌的A？PP蛋白的N-末端区域通过其Ass组装抑制活性参与调节Ass水平、淀粉样蛋白的形成和在脑中的沉积。在目前的提案中，我们计划实施研究，以调查A？PP的N-末端区域如何在体内与Ass肽相互作用，以调节它们的组装、沉积和与这些过程相关的病理后果。在这些研究中，我们将利用两种截然不同且特征良好的人类A？沉积转基因小鼠模型，并结合增加其中A？PP N-末端片段水平的方法，来了解Sa？PP的这一区域如何改变病理结果。最后，这一新发现的Sa？PP活性，特别是N-末端A？PP18-119片段，可能会导致开发新的治疗药物来对抗AD和相关淀粉样蛋白沉积疾病中发生的病理性Ass积聚、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.