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Introduction to virology
Published in Amine Kamen, Laura Cervera, Bioprocessing of Viral Vaccines, 2023
Following the lipid bilayer coating around the viral capsid, the host cell plasma membrane must undergo conformational changes, resulting in the formation of a bud-like structure that facilitates the extracellular release of the virion. This process is commonly called “budding” of the newly formed viral particles. Most of the viruses have one peptide motif or a domain that triggers this budding process. These viral proteins contain the specific peptide motif or domain interact with various host cellular factors such as members of small GTPases or actin family to regulate the formation of the bud, ultimately releasing the virion. For example, viruses like HIV-1 and Ebola virus use the Endosomal sorting complex required for transport (ESCRT) complex to achieve membrane scission and subsequent release of the newly formed virus depends on VPS4 protein [15,16]. This process is mediated by the late domain sequences present in viral proteins (p6 for Gag of HIV-1) that recruit the ESCRT-I and ESCRT-II complex at the site of budding (Figures 2.8 and 2.9).
Exosomes in Cancer Disease, Progression, and Drug Resistance
Published in Vladimir Torchilin, Handbook of Materials for Nanomedicine, 2020
Taraka Sai Pavan Grandhi, Rajeshwar Nitiyanandan, Kaushal Rege
Molecular mechanisms controlling the biogenesis, secretion and uptake of exosomes remain to be fully understood. Some of the well-known mechanisms of cargo loading into the exosomes include ESCRT system [30–32], tetraspanin-directed mechanisms [33] and lipid-dependent mechanisms [34]. ESCRT system (endosomal sorting complex required for transport) best known for MVB biogenesis was initially considered only effective in recognizing and sorting ubiquitinated cargo into ILVs destined for lysosomal fusion and degradation. However, Baietti et al. [35] showed the ability of syndecan heparan sulfate proteoglycans and syntenin (cytoplasmic adaptor protein of syndecans) to recruit ESCRTs for exosome biogenesis. It was shown that syntenin interacts with ESCRTs via binding to ALIX (an ESCRT-III-binding protein) to package cargo and trigger vesicle formation destined to be within exosomes. Other proteins such as CHMP4 and AAA+ ATPase VPS4 critical for MVB biogenesis that interact directly with ALIX were shown to remain conserved in this process. ALIX adaptor protein has been shown to bind and sort other proteins such as RNA-binding protein Argonuate 2 (Ago2), RNA-binding protein SYNCRIP which are essential for miRNA processing and sorting into exosomes [36, 37]. These studies indicate ALIX adaptor protein as a shuttle for sorting and loading cytoplasmic proteins into exosomes [35].
The Emerging Role of Exosome Nanoparticles in Regenerative Medicine
Published in Harishkumar Madhyastha, Durgesh Nandini Chauhan, Nanopharmaceuticals in Regenerative Medicine, 2022
Zahra Sadat Hashemi, Mahlegha Ghavami, Saeed Khalili, Seyed Morteza Naghib
It should be noted that the biogenesis pathway of exosomes and their distinction fromother cell-derived vesicles were identified due to the existence of lysosomal surface protein (LAMP), tetraspanins (CD81, CD9, and CD63), heat shock proteins (Hsc70), and also some fusion proteins such as Annexin, CD9, and flotillin in the exosomal membrane (Caby et al. 2005; Andaloussi et al. 2013; Conde-Vancells et al. 2008; Mohammadpour and Majidzadeh-A 2020). The transport (ESCRT) process requires the endosomal sorting complex, which is a collection of proteins necessary for formation and sorting of cargo into exosomes.
Extracellular vesicles released in response to respiratory exposures: implications for chronic disease
Published in Journal of Toxicology and Environmental Health, Part B, 2018
Birke J. Benedikter, Emiel F. M. Wouters, Paul H. M. Savelkoul, Gernot G. U. Rohde, Frank R. M. Stassen
Due to their endosomal origin, exosomes (50–150 nm) are smaller than microvesicles (100–1000 nm). Further, exosomes are enriched in members of the endosomal sorting complexes required for transport (ESCRT, e.g. Alix, TSG101) and in tetraspanins such as CD9, CD63, and CD81. As exosomes are generally smaller than the resolution limit of conventional optical techniques (light microscopy, flow cytometry scatter) (Van Der Pol et al. 2010), highly dedicated technology is required for their detection, including electron microscopy, nanoparticle tracking analysis (NTA) (Sokolova et al. 2011), tunable resistive pulse sensing (TRPS) (Maas, De Vrij, and Broekman 2014), and fluorescence-triggered high-resolution flow cytometry (Nolte-’T Hoen et al. 2012). Alternatively, exosomes may be characterized by bulk analysis techniques, such as Western blotting or bead-based flow cytometry, a technique in which EV are linked to large beads and subsequently stained for exosome marker proteins (Suarez et al. 2017; Volgers et al. 2017). The most common method for isolation of exosomes is ultracentrifugation at 100,000 × g (Gardiner et al. 2016).