Inhibitor of sarco/endoplasmic reticulum calcium-ATPase impairs paramyxovirus replication

ABSTRACT Sarco/endoplasmic reticulum calcium-ATPase (SERCA) is a membrane bound cytosolic enzyme that is known to regulate the uptake of calcium into the sarco/endoplasmic reticulum. Herein, we demonstrate for the first time that SERCA can also regulate paramyxovirus [Peste des petits ruminants virus (PPRV) and Newcastle disease virus (NDV)] replication. Treatment of Vero cells with SERCA specific inhibitor (Thapsigargin) at a concentration that is nontoxic to the cells significantly reduced virus replication. Conversely, overexpression of SERCA rescued the inhibitory effect of Thapsigargin on virus replication. PPRV/NDV infection induced SERCA expression in Vero cells which could be blocked by Thapsigargin. With the help of time-of-addition and virus step-specific assays, it was observed that Thapsigargin specifically inhibits viral entry and subcellular localization of the viral proteins. Furthermore, NDV, but not PPRV acquired a significant resistance to Thapsigargin on long-term passage (P=70) in Vero cells. To the best of our knowledge, this is the first report describing virus supportive role of SERCA and a rare report suggesting that viruses may acquire resistance even in the presence of an inhibitor that targets a cellular factor. This study will contribute in understanding paramyxovirus replication and development of antiviral therapeutics using SERCA (host factor) as a candidate drug target.