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1.
Nat Commun ; 12(1): 5536, 2021 09 20.
Article in English | MEDLINE | ID: covidwho-1428813

ABSTRACT

Coronaviruses (CoVs) are important human pathogens for which no specific treatment is available. Here, we provide evidence that pharmacological reprogramming of ER stress pathways can be exploited to suppress CoV replication. The ER stress inducer thapsigargin efficiently inhibits coronavirus (HCoV-229E, MERS-CoV, SARS-CoV-2) replication in different cell types including primary differentiated human bronchial epithelial cells, (partially) reverses the virus-induced translational shut-down, improves viability of infected cells and counteracts the CoV-mediated downregulation of IRE1α and the ER chaperone BiP. Proteome-wide analyses revealed specific pathways, protein networks and components that likely mediate the thapsigargin-induced antiviral state, including essential (HERPUD1) or novel (UBA6 and ZNF622) factors of ER quality control, and ER-associated protein degradation complexes. Additionally, thapsigargin blocks the CoV-induced selective autophagic flux involving p62/SQSTM1. The data show that thapsigargin hits several central mechanisms required for CoV replication, suggesting that this compound (or derivatives thereof) may be developed into broad-spectrum anti-CoV drugs.


Subject(s)
Endoplasmic Reticulum Stress , SARS-CoV-2/physiology , Virus Replication/physiology , Animals , Autophagy/drug effects , Bronchi/pathology , COVID-19/pathology , COVID-19/virology , Cell Differentiation/drug effects , Cell Extracts , Cell Line , Cell Survival/drug effects , Chlorocebus aethiops , Coronavirus 229E, Human/physiology , Down-Regulation/drug effects , Endoplasmic Reticulum Stress/drug effects , Endoplasmic Reticulum Stress/genetics , Endoplasmic Reticulum-Associated Degradation/drug effects , Epithelial Cells/drug effects , Epithelial Cells/virology , Heat-Shock Proteins/metabolism , Humans , Macrolides/pharmacology , Middle East Respiratory Syndrome Coronavirus/drug effects , Middle East Respiratory Syndrome Coronavirus/physiology , Protein Biosynthesis/drug effects , Proteome/metabolism , RNA, Messenger/genetics , RNA, Messenger/metabolism , Reproducibility of Results , SARS-CoV-2/drug effects , Thapsigargin/pharmacology , Unfolded Protein Response/drug effects , Vero Cells , Virus Replication/drug effects
2.
Proc Natl Acad Sci U S A ; 118(6)2021 02 09.
Article in English | MEDLINE | ID: covidwho-1039676

ABSTRACT

RNA-dependent RNA polymerases (RdRps) of the Nidovirales (Coronaviridae, Arteriviridae, and 12 other families) are linked to an amino-terminal (N-terminal) domain, called NiRAN, in a nonstructural protein (nsp) that is released from polyprotein 1ab by the viral main protease (Mpro). Previously, self-GMPylation/UMPylation activities were reported for an arterivirus NiRAN-RdRp nsp and suggested to generate a transient state primed for transferring nucleoside monophosphate (NMP) to (currently unknown) viral and/or cellular biopolymers. Here, we show that the coronavirus (human coronavirus [HCoV]-229E and severe acute respiratory syndrome coronavirus 2) nsp12 (NiRAN-RdRp) has Mn2+-dependent NMPylation activity that catalyzes the transfer of a single NMP to the cognate nsp9 by forming a phosphoramidate bond with the primary amine at the nsp9 N terminus (N3825) following Mpro-mediated proteolytic release of nsp9 from N-terminally flanking nsps. Uridine triphosphate was the preferred nucleotide in this reaction, but also adenosine triphosphate, guanosine triphosphate, and cytidine triphosphate were suitable cosubstrates. Mutational studies using recombinant coronavirus nsp9 and nsp12 proteins and genetically engineered HCoV-229E mutants identified residues essential for NiRAN-mediated nsp9 NMPylation and virus replication in cell culture. The data corroborate predictions on NiRAN active-site residues and establish an essential role for the nsp9 N3826 residue in both nsp9 NMPylation in vitro and virus replication. This residue is part of a conserved N-terminal NNE tripeptide sequence and shown to be the only invariant residue in nsp9 and its homologs in viruses of the family Coronaviridae The study provides a solid basis for functional studies of other nidovirus NMPylation activities and suggests a possible target for antiviral drug development.


Subject(s)
Coronavirus 229E, Human/genetics , RNA-Binding Proteins/metabolism , SARS-CoV-2/genetics , Viral Nonstructural Proteins/metabolism , Virus Replication , Amino Acid Sequence , Amino Acid Substitution , Asparagine/genetics , Cell Line , Conserved Sequence , Coronavirus 229E, Human/physiology , Coronavirus RNA-Dependent RNA Polymerase/genetics , Coronavirus RNA-Dependent RNA Polymerase/metabolism , Humans , Manganese/metabolism , Protein Domains , RNA-Binding Proteins/genetics , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , Transcription, Genetic , Viral Nonstructural Proteins/genetics
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