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1.
Cell Discov ; 7(1): 38, 2021 May 25.
Article in English | MEDLINE | ID: covidwho-1243287

ABSTRACT

The newly emerging coronavirus SARS-CoV-2 causes severe lung disease and substantial mortality. How the virus evades host defense for efficient replication is not fully understood. In this report, we found that the SARS-CoV-2 nucleocapsid protein (NP) impaired stress granule (SG) formation induced by viral RNA. SARS-CoV-2 NP associated with the protein kinase PKR after dsRNA stimulation. SARS-CoV-2 NP did not affect dsRNA-induced PKR oligomerization, but impaired dsRNA-induced PKR phosphorylation (a hallmark of its activation) as well as SG formation. SARS-CoV-2 NP also targeted the SG-nucleating protein G3BP1 and impaired G3BP1-mediated SG formation. Deficiency of PKR or G3BP1 impaired dsRNA-triggered SG formation and increased SARS-CoV-2 replication. The NP of SARS-CoV also targeted both PKR and G3BP1 to impair dsRNA-induced SG formation, whereas the NP of MERS-CoV targeted PKR, but not G3BP1 for the impairment. Our findings suggest that SARS-CoV-2 NP promotes viral replication by impairing formation of antiviral SGs, and reveal a conserved mechanism on evasion of host antiviral responses by highly pathogenic human betacoronaviruses.

2.
Med Hypotheses ; 144: 110030, 2020 Nov.
Article in English | MEDLINE | ID: covidwho-612684

ABSTRACT

Novel Coronavirus (SARS CoV-2), the etiological agent for the highly contagious Corona virus disease-2019 (COVID-19) pandemic has threatened global health and economy infecting around 5.8 million people and causing over 359,200 deaths (as of 28th May 2020, https://www.worldometers.info/coronavirus/). The clinical manifestations of infected patients generally range from asymptomatic or mild to severe illness, or even death. The ability of the virus to evade the host immune response have been major reasons for high morbidity and mortality. One of the important clinical observations under conditions of critical illness show increased risk of developing disseminated intravascular coagulation. Molecular mechanisms of how SARS CoV-2 induces such conditions still remain unclear. This report describes the presence of two unique motifs in the SARS CoV-2 nucleocapsid phosphoprotein (N-protein) that can potentially interact with fibrinogen and possibly prothrombin. This is based on an established function of secretory proteins in Staphylococcus aureus (S. aureus)-coagulase, Efb (Extracellular fibrinogen binding) and vWBP (von Willebrand factor Binding Protein), which are known to regulate the blood clotting cascade and the functions of host immune response. It is hypothesized that having protein interaction motifs that are homologous to these S. aureus proteins, the N-protein of this virus can mimic their functions, which may in turn play a crucial role in formation of blood clots in the host and help the virus evade host immune response. However, this hypothesis needs to be tested in vitro. Considering the overwhelming increase in the incidence of SARS CoV-2 infection globally, this information may be useful for further investigation and could help in deducing new therapeutic strategies to combat advanced stages of this disease.


Subject(s)
Bacterial Proteins/chemistry , COVID-19/virology , Coronavirus Nucleocapsid Proteins/chemistry , Fibrinogen/chemistry , Host-Pathogen Interactions/immunology , SARS-CoV-2 , Amino Acid Motifs , COVID-19/metabolism , Humans , Immune System , Models, Theoretical , Peptides/chemistry , Phosphoproteins/chemistry , Protein Binding , Protein Domains , Staphylococcus aureus/enzymology , von Willebrand Factor/chemistry
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