A comprehensive characterization of membrane vesicles released by autophagic human endothelial cells

Abstract

The stress status of the apoptotic cell can promote phenotypic changes that have important consequences on the immunogenicity of the dying cell. Autophagy is one of the biological processes activated in response to a stressful condition. It is an important mediator of intercellular communications, both by regulating the unconventional secretion of molecules, including interleukin 1β, and by regulating the extracellular release of ATP from early stage apoptotic cells. Additionally, autophagic components can be released in a caspase-dependent manner by serum-starved human endothelial cells that have engaged apoptotic and autophagic processes. The nature and the components of the extracellular vesicles released by dying autophagic cells are not known. In this study, we have identified extracellular membrane vesicles that are released by human endothelial cells undergoing apoptosis and autophagy, and characterized their biochemical, ultrastructural, morphological properties as well as their proteome. These extracellular vesicles differ from classical apoptotic bodies because they do not contain nucleus components and are released independently of Rho-associated, coiled-coil containing protein kinase 1 activation. Instead, they are enriched with autophagosomes and mitochondria and convey various danger signals, including ATP, suggesting that they could be involved in the modulation of innate immunity.

CD63 Regulates Epstein-Barr Virus LMP1 Exosomal Packaging, Enhancement of Vesicle Production, and Noncanonical NF-κB Signaling

“…Moreover, high levels of LMP1 are detrimental within the host cell (67,68), and LMP1 has demonstrated roles in the regulation of autophagy and apoptosis (69,70). Indeed, our results showing increased CD63 and LMP1 protein in larger vesicles (pelleted at 2,000 ϫ g) likely indicate autophagic or apoptotic pathway activation, as large membrane-bound vesicles are often secreted from autophagic cells (71). Rapid turnover of LMP1 has been suggested to regulate the signaling activity within the host cell (72,73).…”

Protein composition of the hepatitis A virus quasi-envelope

“…Purified eHAV preparations contained no detectable peptides derived from LC3, which in its lipidated LC3-II form is associated with autophagosome membranes. However, LC3 appears to be difficult to detect by mass spectrometry in autophagosome-derived extracellular vesicles (31,32). Nonetheless, eHAV vesicles were not precipitated by anti-LC3 antibody (Fig.…”

Autophagy Modulates Articular Cartilage Vesicle Formation in Primary Articular Chondrocytes

“…Thus dys-regulation of ACV generation and release may occur in OA cartilage. (11,12). Their work was based on reports of non-classical protein secretion in yeast, which were the first studies to suggest that autophagosomes that fail to fuse with lysosomes may have an extracellular fate (30,31).…”

“…Up-regulation of autophagy occurs during infection, starvation, or embryonic development. In endothelial cells, extracellular vesicles are released during cell stress when processes of both autophagy and apoptosis are activated (11,12). Markers of autophagy in aging retinal cells are found in association with increased evidence of exosome deposition in the retinal extracellular matrix (13).…”