Cell-Type-Specific Tyrosine Phosphorylation of the Herpes Simplex Virus Tegument Protein VP11/12 Encoded by Gene UL46

Abstract

Cytotoxic T lymphocytes (CTL) and natural killer (NK) cells play key roles in limiting herpesvirus infections; consequently, many herpesviruses, including herpes simplex virus (HSV), have evolved diverse strategies to evade and/or disarm these killer lymphocytes. Previous studies have shown that CTL and NK cells are functionally inactivated following contact with HSV-infected fibroblasts. During studies of the mechanisms involved, we discovered that HSV-inactivated NK-92 NK cells and Jurkat T cells contain a strikingly prominent, novel, ca. 90-kDa tyrosine-phosphorylated protein that we identified as the HSV tegument protein VP11/12. Inasmuch as VP11/12 produced in fibroblasts and epithelial cells is not obviously tyrosine phosphorylated, these data suggested that VP11/12 serves as the substrate of a cell-type-specific protein tyrosine kinase. Consistent with this hypothesis, VP11/12 was also tyrosine phosphorylated in B lymphocytes, and this modification was severely reduced in Jurkat T cells lacking the lymphocyte-specific Src family kinase Lck. These findings demonstrate that HSV tegument proteins can be differentially modified depending on the cell type infected. Our data also raise the possibility that VP11/12 may modulate one or more lymphocyte-specific signaling pathways or serve another lymphocyte-specific function. However, HSV type 1 mutants lacking the UL46 gene retained the ability to block signaling through the T-cell receptor in Jurkat cells and remained competent to functionally inactivate the NK-92 NK cell line, indicating that VP11/12 is not essential for lymphocyte inactivation. Further studies are therefore required to determine the biological function of tyrosine-phosphorylated VP11/12.

Genetic diversity of equine herpesvirus 1 isolated from neurological, abortigenic and respiratory disease outbreaks

“…The mutation in strain Cambridgeshire/96/2013 ORF14 (VP11/12) would truncate the protein by 124 residues. In HSV‐1, VP11/12 undergoes tyrosine phosphorylation in NK and T cells, but its biological function is unclear (Zahariadis et al., 2008). The strain Suffolk/45/2013 ORF11 was truncated by 99 residues.…”

Herpes Simplex Virus Requires VP11/12 To Activate Src Family Kinase-Phosphoinositide 3-Kinase-Akt Signaling

“…VP11/12, one of the most abundant proteins in the HSV-1 tegument, lacks a well-established function during infection; however, studies from our laboratory suggest that it serves as a substrate and an activator of the lymphocyte-specific Lck tyrosine kinase (64,72). Originally identified as two proteins, VP11 and VP12, based on its mobility relative to that of other virion proteins in a denaturing SDS-polyacrylamide gel (at ca.…”

“…VP11/12 is highly tyrosine phosphorylated in lymphocytes, and in Jurkat T cells, tyrosine phosphorylation is largely dependent on the lymphocyte-specific Src family kinase (SFK) Lck (72). Lck is activated during HSV-1 infection of T cells, and VP11/12 is required for this effect; moreover, VP11/12 interacts with Lck or Lck signaling complexes (64).…”

“…Our previous studies raised the possibility that VP11/12 modulates one or more cellular signaling pathways (64,72). VP11/12 is highly tyrosine phosphorylated in lymphocytes, and in Jurkat T cells, tyrosine phosphorylation is largely dependent on the lymphocyte-specific Src family kinase (SFK) Lck (72).…”

“…VP11/12 enhances immediate-early viral gene expression in transfection-based assays by augmenting the activity of the HSV-encoded transcriptional activator VP16 (19,32). However, studies of VP11/12-null viruses have demonstrated that VP11/12 is not required for viral immediate-early gene expression during HSV infection (72,75). VP11/12 is present in the membrane fraction of infected cells, although it is not membrane associated in mature virions (36).…”