Extracellular Vesicles (EVs): See also Drug delivery using exosomes
Mammalian cells normally secrete two types of EVs, smaller vesicles of about 30-200 nm that are commonly referred to as exosomes, and larger vesciels (typically >300 m) that are commonly referred to as microvesciels. (Gould, “Exosome-medaited mRNA delivery in vivo is safe adn can be used to induce SARS-CoV-2 immunity” J. Biiological Chemistry, 2021).
Exosomes: are hihgly enirched in specific substes of proteins, RNAs, and lipids, providing strong evdience that they are generated by an active sorting and vesciel biogenesis pathway. Once released into the extracellular milieu, exosomes can transmit signals and molecules to other cells. Consistent with their natural ability to trasfer RNAs between distinct cells, several groups have demonstrated that these bionormal nanovesicles can be laoded with synthetic small RNAs. In addition, RNA loaded exosomes can be used to deliver anti-cancer RNAs to and into tumors and tumor cells, inhibiting the expression of the target mRNAs, suppressing tumor growth and extending the lifespan of tumor-bearing animals. (Gould, “Exosome-medaited mRNA delivery in vivo is safe adn can be used to induce SARS-CoV-2 immunity” J. Biiological Chemistry, 2021).ureExo exosome isolation kit and ExoCap exosome isolation kit. (Ibrahim, US 2021/0032598).
Exosomes can be prepared uisng a commercial kit such as ExoSpin Exosome Purificaiton Kit, Invitrogen Total Exosome Purificaiton kit, P
Microvesciels: have a molecule composition that is closer to that of the cell, and there is little if any evidence for a selective biogenesis pthway for this much alrger class of EVs. (Gould, “Exosome-medaited mRNA delivery in vivo is safe adn can be used to induce SARS-CoV-2 immunity” J. Biiological Chemistry, 2021).
Proteasomes:
While proteasomes are often described as organelles, particularly in the context of their function as protein-degrading machines, they don’t quite fit the traditional definition of a membrane-bound organelle. Proteasomes are large protein complexes involved in protein degradation, and while they have specialized functions and structures, they lack the membrane enclosure that defines organelles like mitochondria or the endoplasmic reticulum.
Ubiquitin-proteaseome system: govern the degradation of intracellular, soluble proteins, where targets are tagged with ubiquitin by a cascade of enzymes, including E3 ubiquitin ligases, and directed to the proteasome for destruction.
In contrast, lysosome-mediated pathways handle larger, membrane-bound extracellular or aggregated proteins by routing them through endocytic or autophagic mechanisms for degradation.
Targeting protein degradation:
Websites: Center for Targeted Protein Degradation (working on TPD to destroy disease cuasing proteins within cells).
Introduction:
Targeted protein degradation is a therapeutic strategy that utilizes the cell’s natural machinery to eliminate disease causing proteins. Traditional drugs tend to block or inhibit a protein of interest but they do not get ride of the protein.
Degrader drugs bring the dsiease causing target prtoein into proximity with an E3 ligane – an enzyme that is part of the cell’s protein degradation machinery.
Types of Targeting Protein Degradation TPDs:
PROTACs exploit the ubiquitin-proteasome sytem, while newer approaches such as lysosome-targeting chimeras, including sortilin-based lysosome targeting chimers (SORTACs), extend degradation to extracellular and membrane associated proteins. Molecular glues, by contrast, stabilize interactions between E3 ligases and target proteins without requiring a bifunctional design, further expanding the scope of induced proximity stategies. Additional degrader technologies are being developed.
—PROTACs: Targeting protein degraders such as proteolysis-targeting chimeras (PROTACs) direct the body’s natural degradation mechanisms to eliminate the entire disease related prtoein. PROTAC is a small molcule with two ends; one end binds to the target protein of interest while the other binds to the cellular machindery responsible for protein degrdation. In the case of a PROTAC, this binding involves an E3 ligase. Arvinas is using PROTAc as an estrogen receptor degrader designed to treat breast cancer (ARV-471) as well as to degrade BCL6 (ARV-393) for blood cancers. Anther involves ARV-102 which degrades a protein relvant to neuroscience.
—Molecular Glues: are another type of TPD. Instead of generating entirely new protein-protein intereractions, as with PROTACs, molecular glues require a pre-existing surface complementarity between the two prtoeins. More specifically, they enhance the binding o the target protein to the E3 ligase, in a mechanism called gluing. Thalidonmide, lenalidomide, and pomalidomide are clinically approved molecualr glue degraders. Like PROTACs, molecualr glues are small molecuels (they lack a linker and only feature one of the two binders). They are much more minimalistic.