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Morphology, Pathogenesis, Genome Organization, and Replication of Coronavirus (COVID-19)
Published in Hanadi Talal Ahmedah, Muhammad Riaz, Sagheer Ahmed, Marius Alexandru Moga, The Covid-19 Pandemic, 2023
Sadia Javed, Bahzad Ahmad Farhan, Maria Shabbir, Areeba Tahseen, Hanadi Talal Ahmedah, Marius Moga
Therefore, after the entrance of SARS-COVID-2 into the body, the next step is viral replication. In order to bind to their mobile receptors, CoVs use homotrimer spike glycoprotein (including S1 in each spike monomer and S2 in each subunit) on the envelope. In the event of cell entry, such a bond triggers a subsequent cascade that leads to cell-viral membrane fusion [101]. In Coronavirus, there are six ORF regions that act as models by which sub-genomic mRNA structures the protein, spike, nucleocapsid, and diaphragm-proteins. The polypeptides derived from pp1a and pp1ab are generated by ORFs [102].
Prevention of Restenosis by Gene Targeting
Published in Eric Wickstrom, Clinical Trials of Genetic Therapy with Antisense DNA and DNA Vectors, 2020
Michael J. Mann, Victor J. Dzau, Heiko E. von der Leyen
The hemagglutinating virus of Japan (Sendai virus; HVJ), a member of the paramyxovirus family, has long been known to possess two viral coat proteins that enhance membrane fusion (Figure 1A) (Okada et al., 1961;Okada, 1993). Hemagglutinating neuroaminidase (HN) mediates viral particle binding to sialoglycoproteins or sialolipids on the cell surface. It then catalyzes the removal of sugar moieties from these surface molecules. After particle binding, the second protein, Fusion protein (F), induces membrane fusion via interaction with the lipid bilayer. The active form of F protein consists of two polypeptides, Fl and F2, produced by proteolytic cleavage of the inactive F0 form. Following cleavage, Fl and F2 remain associated, anchored by a disulfide bridge.
Host Defense I: Non-specific Immunity
Published in Constantin A. Bona, Francisco A. Bonilla, Textbook of Immunology, 2019
Constantin A. Bona, Francisco A. Bonilla
Degranulation is the discharge of cytoplasmic granule (lysosome) contents into phagosomes, without subjecting the phagocyte’s cytoplasm to the injurious effects of degradative enzymes contained within. Phagosomes and lysosomes approximate one another in the cytoplasm, then fuse their membranes creating a phagolysosome (Figure 10–6). Membrane fusion also involves the cytoskeleton. Granules may also fuse with the plasma membrane and release their contents into the environment surrounding the phagocytic cell. This is an important mechanism in antibody-dependent (and independent) cellular cytotoxicity mediated by these cells (see below).
Biomimetic graphene oxide quantum dots nanoparticles targeted photothermal-chemotherapy for gastric cancer
Published in Journal of Drug Targeting, 2023
Ziwei Lei, Jialong Fan, Xiaojie Li, Yanhua Chen, Dazhi Shi, Hailong Xie, Bin Liu
Moreover, we carried out the membrane fusion experiment to prove the successful synthesis of the hybrid membrane (Figure 1(I)). The erythrocyte membranes and BGC-823 cell membranes were labelled with red and green fluorescent dyes, respectively, and the result showed that the red and green fluorescent overlapped and appeared as yellow, which proved the successful synthesis of the hybrid membrane. Figure 1(J) showed the ultraviolet absorption peaks of the erythrocyte membrane, tumour cell membrane, and hybrid membrane. Erythrocyte membrane and hybrid membranes showed similar characteristic absorption peaks. In addition, the membrane proteins of HM and pGOQD@HM NPs inherited the characteristic proteins of both RBCM and BGC-823M (Figure 1(K)), which proves the successful synthesis of hybrid membrane.
Release of α-granule contents during platelet activation
Published in Platelets, 2022
Platelet granule exocytosis follows four steps: 1. Granule docking, 2. SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) engagement, 3. Membrane fusion, and finally 4. Cargo release (Figure 1) [24]. Granule release was proposed to proceed via several routes: direct fusion with the plasma membrane or the open canalicular system, or compound fusion with other α-granules before extracellular release via similar routes [13,25,26]. Recent data however suggests primary fusion with the plasma membrane precedes compound fusion, as compound fused granules observed by electron microscopy are in a decondensed state [7,27]. Higher levels of stimulation and longer durations produce compound exocytosis, while single α-granules fusion events can be induced by lower agonist concentrations [13]. Additionally, the importance of the open canalicular system as a route of granule secretion has been challenged, as it appears the open canalicular system is not as extensive as previously thought, and remains separate from α-granules upon human platelet activation [8,13,27,28].
Advances in the use of chloroquine and hydroxychloroquine for the treatment of COVID-19
Published in Postgraduate Medicine, 2020
JingKang Sun, YuTing Chen, XiuDe Fan, XiaoYun Wang, QunYing Han, ZhengWen Liu
CoVs are enveloped RNA viruses, and their cell entry processes involve a principal route of receptor-mediated endocytosis [28]. Membrane fusion takes place in the endosomal compartment after endocytosis, which needs additional triggers such as pH acidification or proteolytic activation [29]. Multiple cellular proteases, such as trypsin, furin, proprotein convertase (PC) family, cathepsins, transmembrane protease/serine (TMPRSS) proteases and elastase, are involved in S protein activation, which can induce membrane fusion [30]. Among them, cathepsin L, with anoptimal pH of 3.0 to 6.5, is most commonly associated with activation of a variety of CoV S proteins [30], such as SARS-CoV [19], MERS-CoV [31], HCoV-229E [32], and mouse hepatitis virus 2 (MHV-2) [33]. A recent study found that SARS-CoV-2 enters 293/hACE2 cells mainly through endocytosis, in which cathepsin L is critical for priming of SARS-CoV-2 S protein [24]. A study investigated the detailed mechanism of action of CQ/HCQ in inhibiting SARS-CoV-2 entry, and co-localization of SARS-CoV-2 with early endosomes (EEs) or endolysosomes (ELs) in VeroE6 cells, and the results showed that CQ/HCQ hampered the transport of SARS-CoV-2 from EEs to ELs, indicating that CQ/HCQ might inhibit endosomal maturation [17]. These studies revealed that the mechanism of anti-CoV activity of CQ/HCQ may involve the inhibition of the endosome acidification process, which might inactivate lysosomal proteases, thus interfering with the fusion of virus and host membranes [34,35] (Figure 1).