Taking advantage of the uniquely constricted active site of SARS-CoV-2 Nsp14
methyltransferase, we have designed bisubstrate inhibitors interacting with the SAM and
RNA substrate binding pockets. Our efforts have led to nanomolar inhibitors including
compounds
3
and
10
. As a prototypic inhibitor, compound
3
also has an excellent selectivity profile over a panel of human
methyltransferases. Remarkably,
C
-nucleoside
10
exhibits
high antiviral activity and low cytotoxicity, leading to a therapeutic index
(CC
50
/EC
50
) greater than 139. Furthermore, a brief metabolic
profiling of these two compounds suggests that they are less likely to suffer from major
metabolic liabilities. Moreover, computational docking studies point to
protein–ligand interactions that can be exploited to enhance inhibitory activity.
In short, discovery of inhibitor
10
clearly demonstrates that potent and
selective anti-SARS-CoV-2 activity can be achieved by targeting the Nsp14
methyltransferase. Therefore, the current work strongly supports the continued pursuit
of Nsp14 methyltransferase inhibitors as COVID-19 therapeutics.
Cytomegaloviruses (CMVs) encode cellular homologs to evade host immune functions. In this study, we analyzed the roles of GP33, a guinea pig CMV (GPCMV)-encoded G protein-coupled receptor (GPCR) homolog, in cellular signaling, viral growth and pathogenesis. The cDNA structure of GP33 was determined by RACE. The effects of GP33 on some signaling pathways were analyzed in transient transfection assays. The redET two-step recombination system for a BAC containing the GPCMV genome was used to construct a mutant GPCMV containing an early stop codon in the GP33 gene (Δ33) and a rescued GPCMV (r33). We found the following: 1) GP33 activated the CRE- and NFAT-, but not the NFκB-mediated signaling pathway. 2) GP33 was dispensable for infection in tissue cultures and in normal animals. 3) In pregnant animals, viral loads of r33 in the livers, lungs, spleens, and placentas at 6 days post-infection were higher than those of Δ33, although the viruses were cleared by 3 weeks post-infection. 4) The presence of GP33 was associated with frequent lesions, including alveolar hemorrhage in the lungs, and inflammation in the lungs, livers, and spleens of the dams. Our findings suggest that GP33 has critical roles in the pathogenesis of GPCMV during pregnancy. We hypothesize that GP33-mediated signaling activates cytokine secretion from the infected cells, which results in inflammation in some of the maternal organs and the placentas. Alternatively, GP33 may facilitate transient inflammation that is induced by the chemokine network specific to the pregnancy.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.