Simpson RJ, Lim JW, Moritz RL, Mathivanan SExosomes: proteomic insights and diagnostic potential. Expert Rev Proteomics 6(3): 267-283

Ludwig Institute for Cancer Research, PO Box 2008, Royal Melbourne Hospital, Parkville, Victoria 3050, Australia.
Expert Review of Proteomics (Impact Factor: 2.9). 07/2009; 6(3):267-83. DOI: 10.1586/epr.09.17
Source: PubMed


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.

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    • "g/mL) and protein content, including endosome-derived (endosomal sorting complex required for transport proteins; ESCRTs, such as Alix and Tsg101), sorting-and trafficking-related (endosomal Rab GTPases) and cell membranederived (tetraspanins, CD63, CD81 and CD82) [17] [18]. In addition to protein constituents, exosomes are also comprised of various lipids and lipid-raft-associated proteins originating either at the plasma membrane or from early/late endosome compartments, including cholesterol, sphinogmyelin, and flotillins [15] [19] [20]. Exosomes are involved in the transfer of various mRNAs and microRNAs (miRs) to neighbouring cells for translation [21] [22]. "
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    ABSTRACT: Exosomes, a subset of extracellular vesicles (EVs), function as a mode of intercellular communication and molecular transfer. Exosomes facilitate the direct extracellular transfer of proteins, lipids, and miRNA/mRNA/DNAs between cells in vitro and in vivo. The immunological activities of exosomes affect immunoregulation mechanisms including modulating antigen presentation, immune activation, immune suppression, immune surveillance, and intercellular communication. Besides immune cells, cancer cells secrete immunologically active exosomes that influence both physiological and pathological processes. The observation that exosomes isolated from immune cells such as dendritic cells (DCs) modulate the immune response has enforced the way these membranous vesicles are being considered as potential immunotherapeutic reagents. Indeed, tumour- and immune cell-derived exosomes have been shown to carry tumour antigens and promote immunity, leading to eradication of established tumours by CD8(+) T cells and CD4(+) T cells, as well as directly suppressing tumour growth and resistance to malignant tumour development. Further understanding of these areas of exosome biology, and especially of molecular mechanisms involved in immune cell targeting, interaction and manipulation, is likely to provide significant insights into immunorecognition and therapeutic intervention. Here, we review the emerging roles of exosomes in immune regulation and the therapeutic potential in cancer. Copyright © 2015. Published by Elsevier Ltd.
    Full-text · Article · Feb 2015 · Seminars in Cell and Developmental Biology
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    • "While the mechanisms by which EVTs remodel SpA remain to be fully elucidated, available data are consistent with the hypothesis that EVTs directly interact with vascular smooth muscle cells of uterine spiral arteries and affect their loss. Over the past five years, our understanding of how cells communicate with each other, in health and disease, has undergone a paradigm shift with the recognition of the role of exosomes in intercellular signalling [9] [10]. Exosomes are small (40–100 nm), very stable [11], and lipid bilayer nanovesicles that are formed by the inward budding of multivesicular bodies. "
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    ABSTRACT: A tenet of contemporary obstetrics is that events that compromise placentation increase the risk of complications of pregnancy and contribute to poor pregnancy outcome. In particular, conditions that affect the invasion of placental cells and remodeling of uterine spiral arteries compromise placental function and the subsequent development of the fetus. Extravillous trophoblast cells (EVTs) proliferate and migrate from the cytotrophoblast in the anchoring villi of the placenta and invade the maternal decidua and myometrium. These cells are localised with uterine uterine spiral arteries and are thought to induce vascular remodeling. A newly identified pathway by which EVTs may regulate vascular remodeling within the uterus is via the release of exosomes. Trophoblast cells release exosomes that mediate aspects of cell-to-cell communication. The aim of this brief commentary is to review the putative role of exosomes released from extravillous trophoblast cells in uterine spiral artery remodeling and, in particular, their role in the aetiology of preeclampsia. Placental exosomes may engage in local cell-to-cell communication between the cell constituents of the placenta and contiguous maternal tissues and/or distal interactions, involving the release of placental exosomes into biological fluids and their transport to a remote site of action.
    Full-text · Article · Sep 2014 · BioMed Research International
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    • "In contrast, the size distribution profiles between the total EVs and EXOs were very similar (Supplementary Fig. 2), which suggested that 2 populations either overlap in size, or that they cannot be separated by differential centrifugation. Therefore, we analyzed the presence of CD41, a platelet membrane protein, as well as EXO markers Hsp70, TSG101 and CD9 (33) by Western blotting from the MP and EXO pellets. The presence of CD41 and Hsp70, TSG101 and CD9 was detected in both MPs and EXOs (data for CD41 and Hsp70 comparison is shown in Supplementary Fig. 3). "
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    ABSTRACT: Background Platelet-derived extracellular vesicles (EVs) participate, for example, in haemostasis, immunity and development. Most studies of platelet EVs have targeted microparticles, whereas exosomes and EV characterization under various conditions have been less analyzed. Studies have been hampered by the difficulty in obtaining EVs free from contaminating cells and platelet remnants. Therefore, we optimized an EV isolation protocol and compared the quantity and protein content of EVs induced by different agonists. Methods Platelets isolated with iodixanol gradient were activated by thrombin and collagen, lipopolysaccharide (LPS) or Ca2+ ionophore. Microparticles and exosomes were isolated by differential centrifugations. EVs were quantitated by nanoparticle tracking analysis (NTA) and total protein. Size distributions were determined by NTA and electron microscopy. Proteomics was used to characterize the differentially induced EVs. Results The main EV populations were 100–250 nm and over 90% were <500 nm irrespective of the activation. However, activation pathways differentially regulated the quantity and the quality of EVs, which also formed constitutively. Thrombogenic activation was the most potent physiological EV-generator. LPS was a weak inducer of EVs, which had a selective protein content from the thrombogenic EVs. Ca2+ ionophore generated a large population of protein-poor and unselectively packed EVs. By proteomic analysis, EVs were highly heterogeneous after the different activations and between the vesicle subpopulations. Conclusions Although platelets constitutively release EVs, vesiculation can be increased, and the activation pathway determines the number and the cargo of the formed EVs. These activation-dependent variations render the use of protein content in sample normalization invalid. Since most platelet EVs are 100–250 nm, only a fraction has been analyzed by previously used methods, for example, flow cytometry. As the EV subpopulations could not be distinguished and large vesicle populations may be lost by differential centrifugation, novel methods are required for the isolation and the differentiation of all EVs.
    Full-text · Article · Aug 2014
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