Exosomal lipids from membrane organization to biomarkers: Focus on an endolysosomal-specific lipid

The term extracellular vesicles (EVs) has been recommended to describe various membrane-bound vesicles secreted by most living cells and found in various biological fluids. They gained growing inter-est as mediators of cell-cell communication and for their roles in different patho-physiological processes. In addition, they were recently considered as disease biomarkers and new drug delivery systems. However, it is still difficult to link a biological function to a specific EV population among the heterog-enous EV mixture secreted in the extracellular space due to limitations of optimal isolation methods. EV classification according to their size as small (<200 nm) and large (>200 nm) vesicles is also completed by the identification of selected proteins, nucleic acids and lipids. In this review, we summarized briefly knowledge about the composition and role of EV lipids that received less attention compared to their protein and nucleic acid content. Lipids are not only essential structural components of EVs, but can give important information on their biogenesis. Especially, we discussed our recent data showing the utility of bis(monoacylglycero)phosphate (BMP), a specific endolysosomal lipid marker, that could sign the endosomal origin of small EVs, classically named as exosomes.(c) 2022 Elsevier B.V. and Societe Francaise de Biochimie et Biologie Moleculaire (SFBBM). All rights reserved.

Automated summary

Extracellular vesicles (EVs) are various membrane-bound vesicles secreted by cells and found in biological fluids, which have gained attention as mediators of cell-cell communication and for their roles in physiological processes. They are also considered as disease biomarkers and drug delivery systems. However, it is challenging to link a biological function to a specific EV population due to limitations in isolation methods. In this review, the composition and role of EV lipids, which have received less attention compared to proteins and nucleic acids, are summarized. The utility of a specific endolysosomal lipid marker, bis(monoacylglycero)phosphate (BMP), in indicating the endosomal origin of small EVs, known as exosomes, is discussed.