SARS-CoV-2 ORF3a dimer in an MSP1E3D1 lipid nanodisc
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ABSTRACT:
SUBMITTER: Stephen Graf Brohawn
PROVIDER: EMPIAR-10439 | biostudies-other |
REPOSITORIES: biostudies-other
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Project description:SARS-CoV-2 ORF3a is a putative viral ion channel implicated in autophagy inhibition, inflammasome activation and apoptosis. 3a protein and anti-3a antibodies are found in infected patient tissues and plasma. Deletion of 3a in SARS-CoV-1 reduces viral titer and morbidity in mice, suggesting it could be an effective target for vaccines or therapeutics. Here, we present structures of SARS-CoV-2 3a determined by cryo-EM to 2.1-Å resolution. 3a adopts a new fold with a polar cavity that opens to the cytosol and membrane through separate water- and lipid-filled openings. Hydrophilic grooves along outer helices could form ion-conduction paths. Using electrophysiology and fluorescent ion imaging of 3a-reconstituted liposomes, we observe Ca2+-permeable, nonselective cation channel activity, identify mutations that alter ion permeability and discover polycationic inhibitors of 3a activity. 3a-like proteins are found across coronavirus lineages that infect bats and humans, suggesting that 3a-targeted approaches could treat COVID-19 and other coronavirus diseases.
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Project description:The antiviral restriction factor, tetherin, blocks the release of several different families of enveloped viruses, including the Coronaviridae. Tetherin is an interferon-induced protein that forms parallel homodimers between the host cell and viral particles, linking viruses to the surface of infected cells and inhibiting their release. We demonstrate that SARS-CoV-2 infection causes tetherin downregulation, and that tetherin depletion from cells enhances SARS-CoV-2 viral titres. We investigate the potential viral proteins involved in abrogating tetherin function and find that SARS-CoV-2 ORF3a reduces tetherin localisation within biosynthetic organelles where Coronaviruses bud, and increases tetherin localisation to late endocytic organelles via reduced retrograde recycling. We also find that expression of Spike protein causes a reduction in cellular tetherin levels. Our results confirm that tetherin acts as a host restriction factor for SARS-CoV-2 and highlight the multiple distinct mechanisms by which SARS-CoV-2 subverts tetherin function.
| S-SCDT-10_15252-EMBR_202357224 | biostudies-other
Project description:In this study, analysis of changes of SARS-CoV-2 ORF3a protein during pandemic is reported. ORF3a, a conserved coronavirus protein, is involved in virus replication and release. A set of 70,752 high-quality SARS-CoV-2 genomes available in GISAID databank at the end of August 2020 have been scanned. All ORF3a mutations in the virus genomes were grouped according to the collection date interval and over the entire data set. The considered intervals were: start of collection-February, March, April, May, June, July and August 2020. The top five most frequent variants were examined within each collection interval. Overall, seventeen variants have been isolated. Ten of the seventeen mutant sites occur within the transmembrane (TM) domain of ORF3a and are in contact with the central pore or side tunnels. The other variant sites are in different places of the ORF3a structure. Within the entire sample, the five most frequent mutations are V13L, Q57H, Q57H + A99V, G196V and G252V. The same analysis identified 28 sites identically conserved in all the genome isolates. These sites are possibly involved in stabilization of monomer, dimer, tetramerization and interaction with other cellular components. The results here reported can be helpful to understand virus biology and to design new therapeutic strategies.
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