LMP7 as a Target for Coronavirus Therapy: Inhibition by Ixazomib and Interaction with SARS-CoV-2 Proteins Nsp13 and Nsp16

The emergence of human coronaviruses has led to three epidemics or pandemics in the last two decades, collectively causing millions of deaths and thus highlighting a long-term need to identify new antiviral drug targets and develop antiviral therapeutics. In this study, a compound library was screened to uncover novel potential inhibitors of coronavirus replication. Three lead compounds, designated #16-14, #16-23, and #16-24, which were Ixazomib and its analogs, were identified based on their potent antiviral activity and minimal cytotoxicity. These compounds were found to inhibit the immunoproteasome subunit LMP7, a target whose subcellular localization and expression are altered in Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2)-infected Huh7 cells. Yeast two-hybrid assays and co-immunoprecipitation further revealed that LMP7 interacts with the viral proteins Nsp13 and Nsp16. In addition, Nsp13 and Nsp16 disrupted the expression of LMP7 in response to pathogen attacks. Functional studies showed that LMP7 knockout in BEAS-2B-ACE2 cells resulted in enhanced replication of attenuated SARS-CoV-2, highlighting the role of this subunit in restricting viral replication. Taken together, these findings position LMP7 as a novel therapeutic target and highlight Ixazomib and its analogs as potential antiviral agents against current and future coronavirus threats.