Role of phosphatidyl-ethanolamine biosynthesis in herpes simplex virus 1 infected cells on progeny virus morphogenesis in the cytoplasm and on viral pathogenicity in vivo

Glycerophospholipids are major components of cell membranes. Phosphatidylethanolamine (PE) is a glycerophospholipid and is involved in multiple cellular processes, such as membrane fusion, cell cycle, autophagy and apoptosis. In this study, we investigated the role of PE biosynthesis in herpes simplex virus 1 (HSV-1) infection by knocking out the host cell gene encoding phosphate cytidylyltransferase 2, ethanolamine (Pcyt2), which is a key rate-limiting enzyme in one of the two major pathways for PE biosynthesis. Pcyt2 knockout reduced HSV-1 replication and caused an accumulation of unenveloped and partially enveloped nucleocapsids in the cytoplasm of an HSV-1-infected cell culture. A similar phenotype was observed by treating infected cells with meclizine, which is an inhibitor of Pcyt2. In addition, treatment of HSV-1-infected mice with meclizine significantly reduced HSV-1 replication in the mouse brains and improved their survival. These results indicated that PE biosynthesis mediated by Pcyt2 was required for efficient HSV-1 envelopment in the cytoplasm of infected cells and for viral replication and pathogenicity in vivo. The results also identified the PE biosynthetic pathway as a possible novel target for antiviral therapy of HSV-associated diseases and raised an interesting possibility for meclizine repositioning for treatment of these diseases, since it is an over-the-counter drug used for decades against nausea and vertigo in motion sickness.IMPORTANCEGlycerophospholipids in cell membranes and virus envelopes often affects viral entry and budding. However, the role of glycerophospholipids in herpesvirus infected cells on membrane-associated events in viral replication has not been reported thus far. In this study, we have presented data showing that cellular phosphatidylethanolamine (PE) biosynthesis mediated by Pcyt2 is important for HSV-1 envelopment in the cytoplasm as well as for viral replication and pathogenicity in vivo. This is the first report showing the importance of PE biosynthesis in herpesvirus infections. Our results showed that inhibition of Pcyt2, a key cell enzyme for PE synthesis, significantly inhibited HSV-1 replication and pathogenicity in mice. This suggested that the PE biosynthetic pathway, as well as the HSV-1 virion maturation pathway, can be targets for the development of novel anti-HSV drugs.