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Antiviral Nanomaterials as Potential Targets for Malaria Prevention and Treatment
Published in Devarajan Thangadurai, Saher Islam, Charles Oluwaseun Adetunji, Viral and Antiviral Nanomaterials, 2022
Kantrol Kumar Sahu, Sunita Minz, Madhulika Pradhan, Monika Kaurav, Krishna Yadav
Pinocytosis is classified as caveolae-mediated endocytosis, clathrin-mediated endocytosis clathrin- and caveolae-independent endocytosis, and micropinocytosis (Sun et al. 2019) (Table 18.2). Caveolar-mediated endocytosis is a clathrin-independent endocytotic mechanism involving bulb-shaped caveolae. Caveolae are 50-60 nm plasma membrane invaginations. Caveolae are formed by caveolins, which are integral membrane proteins, and cavins are peripheral membrane proteins. Clathrin-mediated endocytosis possesses complex protein machinery that transiently assembles on the plasma membrane and creates clathrin-coated endocytic vesicles. This machinery selects and concentrates cargo molecules and shapes the membrane into a vesicle.
Breast Imaging with Radiolabeled Peptides
Published in Raymond Taillefer, Iraj Khalkhali, Alan D. Waxman, Hans J. Biersack, Radionuclide Imaging of the Breast, 2021
Eric P. Krenning, Marion de Jong, Roelf Valkema, Casper H.J. van Eijck
In general, receptor-mediated endocytosis systems have been described [58,59], where cell surface receptors capture their ligands from the extracellular milieu. The receptor-ligand complex is internalized via invagination of the plasma membrane. The resulting intracellular vesicles, termed endosomes, rapidly acidify, which causes the ligand to dissociate from the receptor. The ligand is delivered to the lysosome [60], and the receptor may recycle back to plasma membrane. The whole process takes approximately 15 min [58], and a single receptor can deliver numerous ligand molecules to the lysosomes. We have studied internalization and degradation of radiolabeled [DTPA°]octreotide in the somatostatin receptor-positive rat pancreatic tumor cell lines CA20948 and AR42J and in the somatostatin receptor-negative human anaplastic thyroid tumor cell line ARO and detected internalization of the radiopharmaceutical in vitro, in accordance with the findings of Andersson et al. [61], and found that this process was receptor-specific and temperature-dependent [62], Earlier, we reported in vitro studies using AtT20 mouse pituitary tumor cells for detection of internalization of [125I-Tyr3]octreotide [63],
Cell Components and Function
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
Exocytosis results in the secretion of large protein molecules synthesized by rough ER and stored in vesicles. These secretory vesicles migrate and fuse with the cell membrane. At the point of fusion, synapsins, special proteins, allow the secretion to be controlled by Ca+. Both endocytosis and exocytosis are energy-dependent processes.
The engineering challenges and opportunities when designing potent ionizable materials for the delivery of ribonucleic acids
Published in Expert Opinion on Drug Delivery, 2022
Yan Ming Anson Lau, Janice Pang, Grayson Tilstra, Julien Couture-Senécal, Omar F. Khan
Clathrin-independent endocytosis represents a large family of endocytic mechanisms that do not require clathrin to facilitate endocytosis. Within this group of endocytic pathways, it can be further characterized according to the involvement of the dynamin [78]. With regard to clathrin-independent, dynamin-dependent endocytosis, fast endophilin-mediated endocytosis (FEME) has important implication in LNP uptake [79] (Figure 3). LNPs can be internalized via this pathway through association with ligands that activates G-protein coupled receptor (GPCR) such as β1-adrenergic, acetylcholine, IL-2, and epidermal growth factor (EGF) receptors [79]. Upon ligand binding to specific receptors, endophilin rapidly stabilizes (<10 s) at the site of binding via direct interaction with the receptors or indirect association with intermediate receptor proteins [79]. The binding of endophilin results in the formation of a tubular carrier with a diameter ranging from 60 to 80 nm and a length varying from 100 nm to several microns. Here, the endophilin stabilized carrier is scissioned by dynamin, and the cargo is trafficked to the classical endosomal pathway [80]. However, the precise fate of the cargo internalized via FEME remains unclear.
An updated review on exosomes: biosynthesis to clinical applications
Published in Journal of Drug Targeting, 2021
Sheela Modani, Devendrasingh Tomar, Suma Tangirala, Anitha Sriram, Neelesh Kumar Mehra, Rahul Kumar, Dharmendra Kumar Khatri, Pankaj Kumar Singh
In the process of exosomes uptake, exosomes pass the signals to the receiver cell, which involves a three-step mechanism [53]. First, exosomes identify the specific target cell and interact with receptors present on the cell membrane, then exosomes fuse to the membrane of the target cell and followed by the entry of the exosomes in the cell by endocytosis/phagocytosis mechanism. The phagocytosis of exosomes was shown to be dependent on the actin cytoskeleton, phosphatidylinositol 3-kinase (PI3K) and dynamin2. Notably, actin, PI3K and dynamin2 have all been implicated in both clathrin-mediated endocytosis and phagocytosis. Internalised exosomes co-localised with Lamp-1, lysobisphosphatidic acid and Rab7 in late autophagosomes and/or endosomal and lysosomal vesicles [53]. Clathrin-mediated endocytosis utilises clathrin and adaptor protein 2 complexes which coat the membrane and induce the invagination of the membrane into a vesicle [54]. Many reports in the literature also suggested internalisation as the most common mechanism of exosomes uptake, which is mainly dependent upon cell type and proteins present on cell membrane [55]. Uptake of exosomes by a recipient cell is specifically cell-specific, involving the interaction of proteins present on the surface of target cells and exosomes are crucial for recipient cell adhesion and targeting [56].
Lipoplex-based therapeutics for effective oligonucleotide delivery: a compendious review
Published in Journal of Liposome Research, 2020
Pirthi Pal Singh, Veena Vithalapuram, Sunita Metre, Ravinder Kodipyaka
The presence of the clathrin‐coated pits and caveolae on the plasma membrane of mammalian cells acts as the influential factor for the cellular entry of the ON. Clathrin-mediated endocytosis, a key process in vesicular, selects and concentrates cargo molecules and shapes the membrane into a vesicle. A mature pit cleaved from the plasma membrane using dynamin then forms endosome (Kaksonen and Roux 2018). On the other hand, lipid rafts (enriched for cholesterol and signalling proteins) are highly ordered saturated lipids and cholesterol that are laterally mobile in the plane of a more fluid disordered bilayer of largely unsaturated lipids. The straight acyl chains of the saturated polar lipids permit their close packing with cholesterol molecules to form liquid ordered micro-domains with liquid disordered bilayer formed by the bent hydrocarbon chains of unsaturated phospholipids (Brown and London 1998). Caveolae are a subset of lipid rafts that are invaginated, non-planar structures with caveolins as the main integral membrane protein required for their formation. Caveolae-mediated endocytosis involves the concentration of the cargo molecules sorting mechanisms (protein or lipid based). Followed by their transfer between the surface and the internal compartments with the help of caveolin (Martinez-Outschoorn et al.2015).