Glycoproteins encoded by varicella-zoster virus: biosynthesis, phosphorylation, and intracellular trafficking

This article reviews major developments concerning the VZV glycoproteins. Very little was published about these viral products prior to the early 1980s. VZV is now known to encode five glycoproteins that have been designated gpI through gpV. The viral glycoproteins are present within the envelope of the complete virion; in addition, they are inserted in the plasma membrane of the infected cell. Studies of the assembly and processing of three of the VZV glycoproteins have demonstrated that they may contain both N-linked and O-linked glycans, some of which are also sulfated and sialated. A heretofore unappreciated modification of VZV gpI is phosphorylation. The glycoprotein is modified on its serine and threonine residues by at least two cellular protein kinases--casein kinases I and II. Finally, aspects of viral glycoprotein trafficking have been analyzed in VZV-infected cells. The pathway progresses from the trans-Golgi region via cytoplasmic vacuoles to the outer cellular membrane. The virus may acquire part of its glycoprotein-laden envelope from the cytoplasmic vacuoles.