In epithelial cells, the heterodimer gE/gI is required for the cell-to-cell spread of the virus, by sorting nascent virions to cell junctions. Once the virus reaches the cell junctions, virus particles can spread to adjacent cells extremely rapidly through interactions with cellular receptors that accumulate at these junctions. Implicated in basolateral spread in polarized cells. In neuronal cells, gE/gI is essential for the anterograde spread of the infection throughout the host nervous system. Together with US9, the heterodimer gE/gI is involved in the sorting and transport of viral structural components toward axon tips (By similarity). Interacts with gE. During virion morphogenesis, this protein probably accumulates in the endosomes and trans-Golgi where secondary envelopment occurs. It is probably transported to the cell surface from where it is endocytosed and directed to the trans-Golgi network (TGN). The heterodimer gE/gI then redistribute to cell junctions to promote cell-cell spread later in the infection (By similarity). Belongs to the alphaherpesvirinae glycoprotein I family.