Inhibition of SARS-CoV-2 protease targets may block infection, study finds

Researchers at the University of Liverpool have shown how SARS-CoV-2 viral proteases attack the host cell and how this can be targeted to stop the virus from replicating in cell culture using existing drugs.

The new results, published today in Nature Communication, offer a powerful resource to understand proteolysis in the context of viral infection and to inform the development of targeted strategies to inhibit the virus that causes COVID-19.

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

Viral and cellular proteases play a crucial role in SARS-CoV-2 replication, and inhibitors targeting proteases have already successfully inhibited 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 seen only limited application to the study of viral substrates and have not been applied before. to the study of proteolysis during coronavirus infection, ”says lead author Dr Emmott Edward, tenure-track member at the University’s Institute of Systems, Molecular and Integrative Biology.

The team discovered previously unknown cleavage sites in several viral proteins, including the major S and N antigenic proteins, which are primary targets of vaccine and antibody testing efforts.

They found significant increases in cell cleavage events consistent with cleavage by the main protease of SARS-CoV-2 (Mpro) and identified 14 potential high-confidence substrates of the main and papain-like proteases, validating a subset with in vitro dosages.

They then showed that the depletion of siRNAs from these cellular proteins inhibits the replication of SARS-CoV-2, and that drugs targeting two of these proteins: SRC tyrosine kinase and Ser / Thr kinase MYLK, showed a dose reduction. -dependent on SARS CoV-. 2 titles.

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

Dr Emmott said: “A better understanding of the exact ways in which proteolytic cleavage is regulated, modulates protein activity and serves to promote viral replication will be crucial in targeting cell substrates of viral proteases as a therapeutic strategy.

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