Abstract
Cells release nano-sized membrane vesicles that are involved in intercellular communication by transferring biological information between cells. It is generally accepted that cells release at least three types of extracellular vesicles (EVs): apoptotic bodies, microvesicles and exosomes. While a wide range of putative biological functions have been attributed to exosomes, they are assumed to represent a homogenous population of EVs. We hypothesized the existence of subpopulations of exosomes with defined molecular compositions and biological properties. Density gradient centrifugation of isolated exosomes revealed the presence of two distinct subpopulations, differing in biophysical properties and their proteomic and RNA repertoires. Interestingly, the subpopulations mediated differential effects on the gene expression programmes in recipient cells. In conclusion, we demonstrate that cells release distinct exosome subpopulations with unique compositions that elicit differential effects on recipient cells. Further dissection of exosome heterogeneity will advance our understanding of exosomal biology in health and disease and accelerate the development of exosome-based diagnostics and therapeutics.
Highlights
Cells release nano-sized membrane vesicles that are involved in intercellular communication by transferring biological information between cells
When we loaded P110 on top of the sucrose gradient followed by ultracentrifugation for 16 h, we detected the vast majority of particles, as well as the exosome marker proteins ALG-2-interacting protein X (ALIX) and tumour susceptibility gene 101 protein (TSG101), in fractions 3–5 (Fig. 1B)
ALIX was found to be enriched in both low density exosome subpopulation (LD-Exo) and HD-Exo compared to cell lysate and to MVs, while the opposite was observed for the endoplasmic reticulum protein Calnexin (Supplementary Fig. S1A)
Summary
Cells release nano-sized membrane vesicles that are involved in intercellular communication by transferring biological information between cells. Microvesicles (MVs) originate from the cell surface, where they are released by direct outward budding of the plasma membrane Their heterogeneous size ranges from 50 nm to 1,000 nm in diameter. ALIX and TSG101 are commonly used as marker proteins for exosomes Despite their seemingly homogenous characteristics, exosomes mediate a wide spectrum of effects on recipient cells[7,11,12]. This could indicate that exosomes are highly multifunctional vesicles, or that cells release exosomes characterized by heterogeneity, i.e. subpopulations of exosomes display distinct compositions and/or functions
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