Proteasome inhibition reduces coxsackievirus B3 replication in murine cardiomyocytes

Coxsackievirus is the most prevalent virus associated with the pathogenesis of myocarditis and its sequela dilated cardiomyopathy. We have previously shown that coxsackievirus infection facilitates the ubiquitin/proteasome processing of the cell-cycle protein cyclin D1 and the tumor suppressor p53, which raises the possibility that the ubiquitin/proteasome pathway may be used by virus to promote viral replication. In this study, we examined the interplay between coxsackievirus replication and the ubiquitin/proteasome pathway in murine cardiomyocytes. We found that treatment of cells with the proteasome inhibitors MG132 or lactacystin significantly decreased virus titers in the supernatant and prevented virus-induced cell death. We further examined the effects of proteasome inhibitor on different stages of coxsackievirus life-cycle. We showed that inhibition of the ubiquitin/proteasome pathway did not affect virus entry and had no influence on viral protease proteolytic activities. However, viral RNA transcription and protein translation were markedly reduced after addition of proteasome inhibitors. We further demonstrate that ubiquitin/proteasome pathway-mediated viral replication does not appear to be related to changes in proteasome activities. Taken together, our data suggest that proteasome inhibitor reduces coxsackievirus replication through inhibition of viral RNA transcription and protein synthesis. Thus, proteasome inhibition may represent a novel therapeutic approach against myocarditis.