Extracellular Vesicles in Chagas Disease: A New Passenger for an Old Disease

Mammalian cells secrete two types of extracellular vesicles either constitutively or in a regulated manner: exosomes (50-100 nm in diameter) released from the intracellular compartment and ectosomes (also called microvesicles, 100-1000 nm in diameter) shed directly from the plasma membrane. Extracellular vesicles are bilayered proteolipids enriched with proteins, mRNAs, microRNAs, and lipids. In recent years, much data have been collected regarding the specific components of extracellular vesicles from various cell types and body fluids using proteomic, transcriptomic, and lipidomic methods. These studies have revealed that extracellular vesicles harbor specific types of proteins, mRNAs, miRNAs, and lipids rather than random cellular components. These results provide valuable information on the molecular mechanisms involved in vesicular cargo-sorting and biogenesis. Furthermore, studies of these complex extracellular organelles have facilitated conceptual advancements in the field of intercellular communication under physiological and pathological conditions as well as for disease-specific biomarker discovery. This review focuses on the proteomic, transcriptomic, and lipidomic profiles of extracellular vesicles, and will briefly summarize recent advances in the biology, function, and diagnostic potential of vesicle-specific components. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Almost all bacteria, archaea, and eukaryotic cells shed extracellular vesicles either constitutively or in a regulated manner. These nanosized membrane vesicles are spherical, bilayered proteolipids that harbor specific subsets of proteins, DNAs, RNAs, and lipids. Recent research has facilitated conceptual advancements in this emerging field that indicate that extracellular vesicles act as intercellular communicasomes by transferring signals to their target cell via surface ligands and delivering receptors and functional molecules. Recent progress in mass spectrometry-based proteomic analyses of mammalian extracellular vesicles derived from diverse cell types and body fluids has resulted in the identification of several thousand vesicular proteins that provide us with essential clues to the molecular mechanisms involved in vesicle cargo sorting and biogenesis. Furthermore, cell-type- or disease-specific vesicular proteins help us to understand the pathophysiological functions of extracellular vesicles and contribute to the discovery of diagnostic and therapeutic target proteins. This review focuses on the high-throughput mass spectrometry-based proteomic analyses of mammalian extracellular vesicles (i.e., exosomes and ectosomes), EVpedia (a free web-based integrated database of high-throughput data for systematic analyses of extracellular vesicles; http://evpedia.info), and the intravesicular protein-protein interaction network analyses of mammalian extracellular vesicles. The goal of this article is to encourage further studies to construct a comprehensive proteome database for extracellular vesicles that will help us to not only decode the biogenesis and cargo-sorting mechanisms during vesicle formation but also elucidate the pathophysiological roles of these complex extracellular organelles.

Specialized secretion systems are used by numerous bacterial pathogens to export virulence factors into host target cells. Leishmania and other eukaryotic intracellular pathogens also deliver effector proteins into host cells; however, the mechanisms involved have remained elusive. In this report, we identify exosome-based secretion as a general mechanism for protein secretion by Leishmania, and show that exosomes are involved in the delivery of proteins into host target cells. Comparative quantitative proteomics unambiguously identified 329 proteins in Leishmania exosomes, accounting for >52% of global protein secretion from these organisms. Our findings demonstrate that infection-like stressors (37 degrees C +/- pH 5.5) upregulated exosome release more than twofold and also modified exosome protein composition. Leishmania exosomes and exosomal proteins were detected in the cytosolic compartment of infected macrophages and incubation of macrophages with exosomes selectively induced secretion of IL-8, but not TNF-alpha. We thus provide evidence for an apparently broad-based mechanism of protein export by Leishmania. Moreover, we describe a mechanism for the direct delivery of Leishmania molecules into macrophages. These findings suggest that, like mammalian exosomes, Leishmania exosomes function in long-range communication and immune modulation.