Exosomes:From biogenesis and secretion to the early pathogenesis of Alzheimer's disease

摘要 星形胶质细胞和神经元之间的双向通讯调节突触形成，突触强度， 并通过协调神经元组之间的活动参与神经回路的调节。 阿尔茨海默氏症（AD）和其他神经退行性疾病中的星形胶质细胞功能障碍已被假定为 有助于干扰参与记忆和执行功能的神经网络的活动。虽然 AD相关的各种细胞因子、趋化因子和生长因子的组成和数量的改变 已经证明了从星形胶质细胞释放，这些观察到目前为止还不足以 解释星形胶质细胞压力如何导致神经元功能障碍。我们在理解 细胞外囊泡的生物学已经开始暗示神经胶质释放的微囊泡作为神经胶质细胞增殖的主要介质。 神经胶质与神经元的通讯在初步实验中，我们提供了证据，表明各种刺激可以 诱导星形胶质细胞脱落微泡。这些星形胶质细胞脱落的微泡的分子货物是 复杂，包含超过200种不同的蛋白质，100种miRNA和数百种生物活性脂质物质。 此外，星形胶质细胞外泌体的蛋白质、miRNA和脂质组成被所使用的刺激物修饰， 以诱导释放，并且可以通过用寡聚A β肽预处理来进一步修饰。这些星形胶质细胞- 脱落的外泌体直接与神经元相互作用以改变神经元的结构和功能。基于这些 我们的初步研究结果推断，科学上对任何一种蛋白质、脂质或miRNA的关注都不太可能 产生由这种复杂的信号囊泡调节的功能的真实表示。因此，我们使用 生物信息学和系统生物学的方法来了解蛋白质，miRNA和脂质组成的 外泌体相互作用以调节通过靶点的全基因组测序鉴定的神经元信号传导途径 神经元在本申请中，我们将精力集中在少数已确定的途径上。特别是 我们集中研究了与突触形成、棘形成和神经突有关的神经通路 副产物，因为这些神经元结构在AD中受损。本应用程序的目标是了解 与AD相关的内源性兴奋性刺激和炎性刺激如何调节 星形胶质细胞脱落的外泌体以及这些外泌体如何调节/失调靶细胞的结构和功能 神经元

ABSTRACT Bi-directional communication between astrocytes and neurons regulates synaptic formation, synaptic strength, and participates in the regulation of neural circuitry by coordinating activity among groups of neurons. Astrocyte dysfunction in Alzheimer’s (AD), and other neurodegenerative conditions has been postulated to contribute to perturbations in activity of neural networks involved in memory and executive functions. Although AD associated modifications in the composition and quantity of various cytokine, chemokine and growth factors released from astrocytes have been demonstrated, these observations have thus far been insufficient to explain how astrocyte stress contributes to neuronal dysfunction. Advancements in our understanding of the biology of extracellular vesicles have begun to implicate glial released microvesicles as primary mediators of glia to neuron communication. In preliminary experiments we provide evidence that a variety of stimuli can induce astrocytes to shed microvesicles. The molecular cargo of these astrocyte-shed microvesicles was complex, and contained more than 200 distinct proteins, 100 miRNA, and hundreds of bioreactive lipid species. Moreover, the protein, miRNA and lipid composition of astrocyte exosomes was modified by the stimulus used to induce release and could be further modified by pre-treatment with oligomeric A peptides. These astrocyte- shed exosomes directly interacted with neurons to modify neuronal structure and function. Based on these preliminary findings we reasoned that a scientific focus on any one protein, lipid or miRNA would be unlikely to produce a true representation of the functions regulated by this complex signaling vesicles. Therefore, we used bioinformatic and systems biology approaches to understand how the protein, miRNA and lipid composition of exosomes interacts to regulate neuronal signaling pathways identified by whole genome sequencing of target neurons. In this application we focused our efforts on a small number of the identified pathways. In particular we concentrated on neural pathways associated with synapse formation, spine formation, and neurite outgrowth, as these neuronal structures are damaged in AD. The goals of this application are to understand how endogenous excitatory stimuli and inflammatory stimuli associated with AD modulate the cargo of astrocyte-shed exosomes and how these exosomes regulate/dysregulate the structure and function of target neurons.