Abstract
Recent research indicates that most tissue and cell types can secrete and release membrane-enclosed small vesicles, known as exosomes, whose content reflects the physiological/pathological state of the cells from which they originate. These exosomes participate in the communication and cell-to-cell transfer of biologically active proteins, lipids, and nucleic acids. Studies of RNA viruses have demonstrated that exosomes release regulatory factors from infected cells and deliver other functional host genetic elements to neighboring cells, and these functions are involved in the infection process and modulate the cellular responses. This review provides an overview of the biogenesis, composition, and some of the most striking functions of exosome secretion and identifies physiological/pathological areas in need of further research. While initial indications suggest that exosome-mediated pathways operate in vivo, the exosome mechanisms involved in the related effects still need to be clarified. The current review focuses on the role of exosomes in RNA virus infections, with an emphasis on the potential contributions of exosomes to pathogenesis.
Highlights
Extracellular vesicles (EVs) are small lipid bilayer-enclosed nanoparticles that are released from multiple types of cells [1,2,3]
The exact mechanism of how this process is regulated is still unclear, scientists have established many theories of exosome biogenesis, including endosomal sorting complex required for transport (ESCRT)-dependent [13] and ESCRT-independent pathways [14], which include the oligomerization of tetraspanin complexes [15], the sphingomyelinase pathway that catalyzes ceramide synthesis [16], or phospholipase D2 and adenosine diphosphate (ADP) ribosylation factor-6-mediated intraluminal vesicle (ILV) budding [17]
ESCRTs consist of approximately twenty proteins that assemble into four complexes (ESCRT-0, ESCRT-I, ESCRT-II, and ESCRT-III) with the associated proteins vacuolar protein sorting 4 (VPS4), vesicle trafficking 1 (VTA1), and ALG-2 interacting protein X (ALIX) (Figure 1)
Summary
Extracellular vesicles (EVs) are small lipid bilayer-enclosed nanoparticles that are released from multiple types of cells [1,2,3]. Several EVs, including microvesicles, apoptotic bodies, and exosomes, have been found to play important roles in various physiological and pathological processes [3,4]. Exosomes can enhance viral infection by spreading viral components, such as proteins and nucleic acids, and inhibit the immune response or promote immune escape [7,10,11,12]. They can inhibit infection by triggering innate or acquired immunity and eliminating pathogens via induction of apoptosis or other signaling pathways [7,10,11,12]. Further research on the relationships between viruses and exosomes is warranted
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