Biogenesis, Membrane Trafficking, Functions, and Next Generation Nanotherapeutics Medicine of Extracellular Vesicles

Abstract

Extracellular vesicles (EVs) are a heterogeneous group of membrane-limited vesicles and multi-signal messengers loaded with biomolecules. Exosomes and ectosomes are two different types of EVs generated by all cell types. Their formation depends on local microdomains assembled in endocytic membranes for exosomes and in the plasma membrane for ectosomes. Further, EV release is a fundamental process required for intercellular communication in both normal physiology and pathological conditions to transmit/exchange bioactive molecules to recipient cells and the extracellular environment. The unique structure and composition of EVs enable them to serve as natural nanocarriers, and their physicochemical properties and biological functions can be used to develop next-generation nano and precision medicine. Knowledge of the cellular processes that govern EVs biology and membrane trafficking is essential for their clinical applications. However, in this rapidly expanding field, much remains unknown regarding EV origin, biogenesis, cargo sorting, and secretion, as well as EV-based theranostic platform generation. Hence, we present a comprehensive overview of the recent advances in biogenesis, membrane trafficking, and functions of EVs, highlighting the impact of nanoparticles and oxidative stress on EVs biogenesis and release and finally emphasizing the role of EVs as nanotherapeutic agents.

Keywords: cargo sorting and fusion; extracellular vesicle; membrane trafficking; nanotherapeutics; vesicle formation.

Figure 1

Schematic presentation of various subtypes of extracellular vesicles such as exosomes, ectosomes and apoptotic bodies, are released into the extracellular environment during physiological and pathological processes.

Figure 2

Biogenesis of exosomes by ESCRT dependent mechanism and independent mechanism involved with accessory proteins and lipid dependent pathway.

Figure 3

Mechanism of biogenesis of ectosomes. Increased level of accumulation of Ca²⁺ at the plasma membrane and involvement of translocase enzymes and proteins such as ADP-ribosylation factor 6 (ARF6), extracellular signal regulated kinases (ERK) and phosphorylation of myosin light chain kinase (MLCK). (A) Extensive accumulation of Ca2+ at the PM region causes the imbalance of the phospholipids orientation. (B) Role of flippase and floppase to maintains the phospholipids symmetry. (C) ARF6 activates ERK followed by the phosphorylation of myosin light chain which stimulates the budding of ectosomes from the PM.

Figure 4

Sorting of cargoes into EVs. Proteins and RNA can be packaged into the EVs by various mechanisms including ubiquitination, phosphorylation, myristoylation, glycosylation and sumoylation.

Figure 5

Schematic representation of isolation of EVs from conditioned medium using various centrifugation steps and isolated EVs displayed packaging of cargoes DNA, proteins, miRNA, antibodies, tetraspanins, histone, actin and tubulin.

Figure 6

Various sources of oxidative agents responsible for oxidative stress such as anticancer drug, serum deprivation, nanoparticles, thermal stress, hypoxia, genotoxic drugs and protease inhibitors induce biogenesis and release of EVs.