Exosomal transport of brain-derived proteins to the blood in Alzheimer disease

总结 越来越多的证据表明，外泌体，一类膜囊泡，可以分泌的 大多数细胞类型介导细胞间通讯，在启动和/或 阿尔茨海默病（AD）的进展。特别地，已经证明细胞间 淀粉样蛋白β（Aβ）、tau和其他与AD发病机制密切相关的蛋白质的转移，以及 由于AD病理在中枢神经系统（CNS）内的朊病毒样传播被介导 至少部分是通过外泌体。此外，携带独特的，疾病特异性的， 功能上重要的货物可在血液、脑脊液（CSF）和其他 体液最近，我们和其他人已经证明，不仅外泌体可以跨越 血脑屏障（BBB），虽然运输机制尚不清楚，但也， 基于血液但CNS特异性的外泌体分子可以是生物标志物的有价值的来源， 神经退行性疾病，包括AD。在这项研究中，我们将首先使用我们先进的蛋白质组学 筛选对AD相关神经元亚群特异性的外泌体表面标志物的技术，或 大脑区域，以确定更多的中枢神经系统和AD特异性外泌体标志物，并同时适应我们的 纳米粒子分选和单分子定量技术，使高纯度的分离， 血浆中CNS衍生的外泌体和这种外泌体中蛋白质的高精度定量， 应对当前领域的几个重大挑战。使用当前已知的（例如，L1 CAM）和 更多CNS-和AD-特异性、CNS-衍生的外泌体表面标志物，以及现有的和 进一步开发外泌体分离和定量技术，然后我们将比较AD- 含有L1 CAM的外泌体中的相关生物标志物或来自AD相关神经元的那些 来自人类患者的血浆中的亚群，重点关注经典AD的表现， 蛋白质和已知的外泌体候选物，特别是Aβ、tau、α-突触核蛋白，以及它们的各种 异构体;必要时可研究其他新靶点。对于已验证的AD相关 外泌体蛋白，我们将进一步研究其在动物模型中的纵向变化，并探索 它们从脑转运到血液的机制（例如，穿过血脑屏障） 以及动物模型和潜在的方法来改变它们作为新的未来AD治疗靶点。的 拟议的实验可能会建立一个基础，导致一个廉价和广泛的 可用的测试，以帮助AD诊断和/或疾病跟踪。此外，拟议的一系列研究 是阐明潜在毒性的新的潜在清除途径的重要的第一步。 中枢神经系统蛋白质种类，并最终可能提供关键的机会，治疗解决 与AD中神经变性相关的病理学。

Summary Growing evidence suggests that exosomes, a class of membrane vesicles that can be secreted by most cell types to mediate intercellular communication, play important roles in the initiation and or progression of Alzheimer disease (AD). Specially, it has been demonstrated that cell-to-cell transfer of amyloid beta (Aβ), tau, and other proteins critically involved in AD pathogenesis, as well as the prion-like propagation of AD pathology within the central nervous system (CNS) is mediated at least in part via exosomes. Additionally, exosomes carrying unique, disease-specific, and functionally important cargo are detectable in vivo in blood, cerebrospinal fluid (CSF) and other body fluids. More recently, we and others have demonstrated not only that exosomes may cross the blood-brain barrier (BBB), though the transportation mechanism remains unclear, but also that blood-based but CNS-specific exosomal molecules can be a valuable source of biomarkers for neurodegenerative diseases, including AD. In this study, we will first use our advanced proteomics techniques to screen for exosome surface markers specific to AD-related neuronal subpopulations or brain regions to identify more CNS- and AD- specific exosome markers, and in parallel adapt our nanoparticle sorting and single-molecule quantification technologies to enable high-purity isolation of CNS-derived exosomes in plasma and high-precision quantification of proteins in such exosomes to address several major challenges in the current field. Using the currently known (e.g., L1CAM) and more CNS- and AD- specific, CNS-derived exosomal surface markers, as well as the existing and further developed exosome isolation and quantification technologies, we will then compare AD- related biomarkers in L1CAM-containing exosomes or those from AD-related neuronal subpopulations in blood plasma from human patients, focusing on the performance of classic AD proteins and known exosomal candidates, specifically, Aβ, tau, α-synuclein, and their various isoforms; additional novel targets may be studied when necessary. For the verified AD-related exosomal proteins, we will further examine their longitudinal changes in animal models and explore the mechanisms by which they are transported from the brain to blood (e.g., crossing BBB) in cellular and animal models and potential ways to alter them as novel future AD treatment targets. The proposed experiments will likely establish the foundation leading to an inexpensive and widely available test to aid in AD diagnosis and/or disease tracking. Additionally, the proposed set of studies is an important initial step toward elucidating a novel potential clearance pathway for potential toxic CNS protein species and ultimately it may provide critical opportunities for therapeutically addressing the pathology associated with neurodegeneration in AD.