Simpson Richard J, Lim Justin We, Moritz Robert L, Mathivanan Suresh
Ludwig Institute for Cancer Research, PO Box 2008, Royal Melbourne Hospital, Parkville, Victoria 3050, Australia.
Expert Rev Proteomics. 2009 Jun;6(3):267-83. doi: 10.1586/epr.09.17.
Exosomes are 40-100-nm diameter membrane vesicles of endocytic origin that are released by most cell types upon fusion of multivesicular bodies with the plasma membrane, presumably as a vehicle for cell-free intercellular communication. While early studies focused on their secretion from diverse cell types in vitro, exosomes have now been identified in body fluids such as urine, amniotic fluid, malignant ascites, bronchoalveolar lavage fluid, synovial fluid, breast milk, saliva and blood. Exosomes have pleiotropic biological functions, including immune response, antigen presentation, intracellular communication and the transfer of RNA and proteins. While they have also been implicated in the transport and propagation of infectious cargo, such as prions, and retroviruses, including HIV, suggesting a role in pathological situations, recent studies suggest that the presence of such infectious cargo may be artefacts of exosome-purification strategies. Improvements in mass spectrometry-based proteomic tools, both hardware and software, coupled with improved purification schemes for exosomes, has allowed more in-depth proteome analyses, contributing immensely to our understanding of the molecular composition of exosomes. Proteomic cataloguing of exosomes from diverse cell types has revealed a common set of membrane and cytosolic proteins, suggesting the evolutionary importance of these membrane particles. Additionally, exosomes express an array of proteins that reflect the originating host cell. Recent findings that exosomes contain inactive forms of both mRNA and microRNA that can be transferred to another cell and be functional in that new environment, have initiated many microRNA profiling studies of exosomes circulating in blood. These studies highlight the potential of exosomal microRNA profiles for use as diagnostic biomarkers of disease through a noninvasive blood test. The exacerbated release of exosomes in tumor cells, as evidenced by their increased levels in blood during the late stage of a disease and their overexpression of certain tumor cell biomarkers, suggests an important role of exosomes in diagnosis and biomarker studies. The aim of this article is to provide a brief overview of exosomes, including methods used to isolate and characterize exosomes. New advances in proteomic methods, and both mass spectrometry hardware and informatics tools will be covered briefly.
外泌体是直径为40 - 100纳米的内吞起源的膜泡，大多数细胞类型在多泡体与质膜融合时释放外泌体，推测其作为无细胞细胞间通讯的载体。早期研究聚焦于外泌体在体外从不同细胞类型的分泌，现在已在尿液、羊水、恶性腹水、支气管肺泡灌洗液、滑液、母乳、唾液和血液等体液中鉴定出外泌体。外泌体具有多效生物学功能，包括免疫反应、抗原呈递、细胞内通讯以及RNA和蛋白质的转移。虽然它们也与传染性物质（如朊病毒）以及包括HIV在内的逆转录病毒的运输和传播有关，提示其在病理情况下发挥作用，但最近的研究表明，此类传染性物质的存在可能是外泌体纯化策略的假象。基于质谱的蛋白质组学工具（包括硬件和软件）的改进，以及外泌体纯化方案的改进，使得更深入的蛋白质组分析成为可能，极大地促进了我们对外泌体分子组成的理解。对来自不同细胞类型的外泌体进行蛋白质组编目揭示了一组共同的膜蛋白和胞质蛋白，表明这些膜颗粒在进化上的重要性。此外，外泌体表达一系列反映其来源宿主细胞的蛋白质。最近发现外泌体含有无活性形式的mRNA和微小RNA，它们可以转移到另一个细胞并在新环境中发挥功能，这引发了许多对血液中循环的外泌体进行微小RNA谱分析的研究。这些研究强调了外泌体微小RNA谱通过非侵入性血液检测用作疾病诊断生物标志物的潜力。疾病晚期血液中外泌体水平升高以及某些肿瘤细胞生物标志物的过表达证明，肿瘤细胞中外泌体的释放加剧，这表明外泌体在诊断和生物标志物研究中具有重要作用。本文旨在对外泌体进行简要概述，包括用于分离和表征外泌体的方法。还将简要介绍蛋白质组学方法以及质谱硬件和信息学工具的新进展。
