Human cytomegalovirus pUL37x1-induced calcium flux activates PKCα, inducing altered cell shape and accumulation of cytoplasmic vesicles

The human cytomegalovirus immediate-early protein pUL37x1 induces the release of Ca2+ stores from the endoplasmic reticulum into the cytosol. This release C alpha uses reorganization of the cellular actin cytoskeleton with concomitant cell rounding. Here we demonstrate that pUL37x1 activates Ca2+-dependent protein kinase C alpha (PKC alpha). Both PKC alpha and Rho-associated protein kinases are required for actin reorganization and cell rounding; however, only PKC alpha is required for the efficient production of virus progeny, arguing that HCMV depends on the kinase for a second function. PKC alpha activation is also needed for the production of large (1-5 mu m) cytoplasmic vesicles late after infection. The production of these vesicles is blocked by inhibition of fatty acid or phosphatidylinositol-3-phosphate biosynthesis, and the failure to produce vesicles is correlated with substantially reduced production of enveloped virus C alpha psids. These results connect earlier work identifying a requirement for lipid synthesis with specific morphological changes, and support the argument that the PKC alpha-induced large vesicles are either required for the efficient production of mature virus particles or serve as a marker for the process.