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Regulation of Antiviral Immunity by Mitochondrial Dynamics
Published in Shamim I. Ahmad, Handbook of Mitochondrial Dysfunction, 2019
Mohsin Khan, Hasan Imam, Saiful Anam Mir
Mitochondrial fusion occurs via fusion of the outer and inner mitochondrial membrane (IMM) which results in the union of two separate mitochondrion and simultaneous mixing of their inner contents (Santel and Fuller, 2001). Mfn1 and Mfn2 coordinate OMM fusion while the IMM fusion is mediated by Opa1. Mutation in any of these proteins can cause abnormal mitochondrial morphology and remarkable reduction in mitochondrial fusion (Chen and Chan, 2009; Chen et al., 2005). Mfn1 and Mfn2 depleted cells showed poor cell growth, decreased cellular respiration associated with the heterogeneity of mitochondrial membrane potential (Chan, 2012). OPA1; a dynamin-related GTPase is localized in the inner mitochondrial membrane (IMM) of many mammalian cells and orchestrate IMM fusion (Frezza et al., 2006). OPA1 protein plays multiple important roles in mitochondrial cristae architecture, bioenergetics and apoptosis (Frezza et al., 2006; Head et al., 2009). The presence of Mfns on both the fusing mitochondria is the prerequisite for outer membrane fusion. Oligomerization of the Mfn1/2 on adjacent mitochondria brings the opposing membranes within close proximity and by membrane fusion, it eventually promotes fusion. Homotypic and heterotypic physical interaction between Mfn1/2 result in Mfn1 homotypic oligomers, Mfn2 homotypic oligomers and Mfn1–Mfn2 heterotypic oligomers (Chen et al., 2003).
Hepatitis E Virus
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
Kavita Lole, Prudhvi Lal Bhukya, Bangari Haldipur
The HEV life cycle remains largely understudied due to the lack of a robust cell-culture system and small animal model. However, it is mostly similar to other positive-sense RNA viruses. HEV primarily targets hepatocytes; however, extrahepatic cells and tissues also support HEV replication. It is believed that HEV capsid protein binds to heat shock cognate protein 70 (HSC70),100 heparin sulfate proteoglycans (HSPGs),71 and GRP78101 located on the cell surface. The virus is internalized by dynamin-2, clathrin, and membrane cholesterol-dependent pathway.102,103 The host cellular proteins HSP90 and tubulin appear to be involved in intracellular transport.104 The virion then uncoats and releases the positive-sense genomic RNA into the cytoplasm of the cell where ORF1 is directly translated by the cellular machinery. The nonstructural proteins probably form a replication complex and viral RdRp synthesizes replicative intermediate negative-sense RNA from the positive-sense genomic RNA. This replicative intermediate serves as the template for synthesis of positive-sense subgenomic and genomic RNA. ORF2 and ORF3 proteins are translated from the bicistronic subgenomic RNA.80,83 ORF2 protein then packages the positive-sense RNA genome into the progeny virion. The packaged virions are transported toward the cell membrane and released out via the ESCRT pathway (Figure 7.4).
Imaging of Intracellular Targets
Published in George C. Kagadis, Nancy L. Ford, Dimitrios N. Karnabatidis, George K. Loudos, Handbook of Small Animal Imaging, 2018
Large and hydrophilic molecules can enter the cell through different types of endocytosis, a process by which cells absorb molecules by invagination of the plasma membrane. Substances may be taken up by endocytosis after binding to a receptor, by interacting with other structures on the cell surface, or just by being engulfed together with fluid surrounding the cell when an endocytic vesicle is formed. There are multiple types of endocytic pathways of which the clathrin-mediated endocytosis pathway is best known and by far the best studied. Additionally, several clathrin-independent endocytosis mechanisms have been described (Sandvig et al. 2008; Howes et al. 2010; Kumari et al. 2010), including dynamin-dependent mechanisms and dynamin-independent mechanisms. It should be noted that receptor-mediated endocytosis can involve several of the aforementioned mechanisms, dependent on the type of receptor being used.
Impact of UCP2 depletion on heat stroke-induced mitochondrial function in human umbilical vein endothelial cells
Published in International Journal of Hyperthermia, 2022
Wei Huang, Liangfeng Mao, Weidang Xie, Sumin Cai, Qiaobing Huang, Yanan Liu, Zhongqing Chen
Mitochondria are essential organelles in mammalian cells, and play a central role in metabolism, cell death, and cellular senescence. Mitochondrial dysfunction, in the form of permeabilization of the inner and/or outer membranes of organelles, can eventually lead to cell apoptosis or necrosis [5,6]. Growing evidence suggests that mitochondrial dysfunction induces the loss of cellular homeostasis, which contributes to cell death during HS [7–9]. Mitochondrial function rests on the complex molecular machinery of mitochondrial dynamics-processes of fission and fusion [10]. A precise balance in mitochondrial dynamics is closely related to the maintenance of mitochondrial functions and responses to external stress [11]. Mitochondrial fission is driven by fission regulators, including mitochondrial fission factor (Mff), dynamin-related protein 1 (Drp1), and fission 1 (Fis1) [12]. In particular, the phosphorylation of Drp1 regulates its translocation to the mitochondrial membrane to induce mitochondrial fission [13,14]. Mitochondrial fusion is mediated by Mitofusin 1/2 (Mfn1/2) and optic atrophy 1 (OPA1) anchor proteins that maintain the fusion of the mitochondrial outer and inner membranes [15]. Therefore, researching the mechanism of mitochondrial homeostasis may provide an important breakthrough in HS therapy.
Flavanol-rich lychee fruit extract substantially reduces progressive cognitive and molecular deficits in a triple-transgenic animal model of Alzheimer disease
Published in Nutritional Neuroscience, 2021
Xiao Chen, Benhong Xu, Luling Nie, Kaiwu He, Li Zhou, Xinfeng Huang, Peter Spencer, Xifei Yang, Jianjun Liu
Oligonol treatment also modulated the expression of synaptic proteins (DC1I1, dynamin-1, synapsin II and vimentin) in the hippocampi of 3×Tg-AD mice. DC1I1 transports cargos from axon terminals to neuron cell bodies [49]. Dynamin-1 releases intracellular substances from synaptic vesicles [50]. Synapsin II regulates the pool of synaptic vesicles [51]. Vimentin expression is related to synaptic damage [52]. In the present study, both dynamin-1 and synapsin II were reduced in 3×Tg-AD mice and increased by Oligonol treatment, whereas DC1I1 and vimentin were reduced. These findings together with evidence of observed alterations in Aβ and tau suggest synaptic damage, which could explain the associated memory dysfunction displayed by 3×Tg-AD mice [53,54]. In addition, dysfunction of the electron transport chain [55] and UPR [47] could exacerbate the synapse dysfunction. We observed a significant loss of synaptic proteins in 3×Tg-AD mice and the retention of some synaptic proteins with Oligonol treatment (Figure 3). The consistent findings from Western-blot analyses and the proteomics study suggest that Oligonol treatment maintained synaptic integrity and memory function.
Gut bacteria signaling to mitochondria in intestinal inflammation and cancer
Published in Gut Microbes, 2020
Dakota N. Jackson, Arianne L. Theiss
Mitochondrial fission is the process by which mitochondria divide into smaller daughter mitochondria.1 Mitochondrial fission is essential to generate adequate numbers of mitochondria for growing cells and is mediated by Dynamin-Related Protein1 (Drp1), Fission 1 (Fis1), Mitochondria Fission Factor (Mff), Mitochondrial Dynamics Protein (MID49) and MID51. The OMM protein Mff recruits Drp1 from the cytosol13 to the OMM of mitochondria where it assembles into oligomeric complexes that compress the mitochondrial tubule to mediate fission.11 This action leads to OMM constriction and cleavage.11 Fis1 is located on the OMM as the receptor protein for Drp1 during its translocation from the cytosol.14 The interaction of Drp1 with Fis1 can lead to the release of cytochrome c which can induce apoptosis.11 MID49/51 are also found on the OMM and facilitate randomized screening of uncharacterized proteins whose expression cause changes in mitochondrial morphology.13