Inhibiting Targets of SARS-CoV-2 Proteases Can Block Infection

Researchers from the University of Liverpool have shown how viral SARS-CoV-2 proteases attack the host cell and how this can be targeted to stop virus replication in cell culture with drugs currently in clinical use or in the pipeline.

The new findings, published today (September 21, 2021) in Nature Communications, provide a powerful resource to understand proteolysis in the context of viral infection and to inform the development of targeted strategies to combat the virus that causes Covid-19. brakes.

SARS-CoV-2 has been responsible for more than 227 million infections and more than 4.6 million deaths worldwide during the pandemic. Efforts to test, treat and vaccinate the virus will all benefit from a better understanding of the basic biology of SARS-CoV-2.

Both viral and cellular proteases play critical roles in SARS-CoV-2 replication, and inhibitors targeting proteases have already shown success in inhibiting SARS-CoV-2 in cell culture models.

In this study, led by the University of Liverpool and the Institut Pasteur in Paris, researchers used a mass spectrometry approach to study proteolytic cleavage events during SARS-CoV-2 infection.

“Mass spectrometry-based approaches to identify protease substrates have been around for a number of years, but they have only been used to a limited extent in the study of viral substrates and had not previously been applied to the study of proteolysis during coronavirus infection,” explains lead . author dr. Emmott Edward, a Tenure-Track Fellow at the University’s Institute of Systems, Molecular and Integrative Biology.

The team found previously unknown splice sites in multiple viral proteins, including key antigenic proteins S and N, which are key targets for vaccine and antibody testing efforts.

They discovered significant increases in cellular splicing events consistent with cleavage by SARS-CoV-2 master protease (Mpro) and identified 14 potential highly reliable substrates of the master and papain-like proteases, validating a subset with in vitro assays. .

They further showed that siRNA depletion of these cellular proteins inhibits SARS-CoV-2 replication, and that drugs targeting two of these proteins: the tyrosine kinase SRC and Ser/Thr kinase MYLK, a dose-dependent reduction of SARS CoV – 2 titres.

Both bafetinib (an experimental cancer drug) and sorafenib (an approved drug to treat kidney and liver cancer) showed SARS-CoV-2 inhibition at concentrations that did not result in cytotoxicity in a human cell line infection model.

dr. Emmott said: “A better understanding of the exact ways in which proteolytic cleavage is regulated, modulates protein activity and benefits viral replication will be crucial for targeting cellular substrates of viral proteases as a therapeutic strategy.

“As more SARS-CoV-2 variants emerge, the incorporation of post-translational modification data from studies such as these may also support efforts to predict phenotypes from genetic data on emerging variants.”

Reference: “Characterizing proteolysis during SARS-CoV-2 infection identifies viral cleavage sites and cellular targets with therapeutic potential” by Bjoern Meyer, Jeanne Chiaravalli, Stacy Gellenoncourt, Philip Brownridge, Dominic P. Bryne, Leonard A. Daly, Arturas Grauslys, Marius Walter, Fabrice Agou, Lisa A. Chakrabarti, Charles S. Craik, Claire E. Eyers, Patrick A. Eyers, Yann Gambin, Andrew R. Jones, Emma Sierecki, Eric Verdin, Marco Vignozzi and Edward Emmott, September 21, 2021, Nature Communication.
DOI: 10.1038/s41467-021-25796-w