Constitutive activation of T cells by γ2-herpesviral GPCR through the interaction with cellular CXCR4

Biochim Biophys Acta Mol Cell Res. 2017 Jan;1864(1):1-11. doi: 10.1016/j.bbamcr.2016.10.008. Epub 2016 Oct 15.


Members of the herpesviral family use multiple strategies to hijack infected host cells and exploit cellular signaling for their pathogenesis and latent infection. Among the most intriguing weapons in the arsenal of pathogenic herpesviruses are the constitutively active virally-encoded G protein-coupled receptors (vGPCRs). Even though vGPCRs contribute to viral pathogenesis such as immune evasion and proliferative disorders, the molecular details of how vGPCRs continuously activate cellular signaling are largely unknown. Here, we report that the vGPCR of Herpesvirus saimiri (HVS), an oncogenic γ2-herpesvirus, constitutively activates T cells via a heteromeric interaction with cellular CXCR4. Constitutive T cell activation also occurs with expression of the vGPCR of Kaposi's sarcoma-associated herpesvirus (KSHV), but not the vGPCR of Epstein-Barr virus. Expression of HVS vGPCR down-regulated the surface expression of CXCR4 but did not induce the degradation of the chemokine receptor, suggesting that vGPCR/CXCR4 signaling continues in cytosolic compartments. The physical association of vGPCR with CXCR4 was demonstrated by proximity ligation assay as well as immunoprecipitation. Interestingly, the constitutive activation of T cells by HVS vGPCR is independent of proximal T cell receptor (TCR) signaling molecules, such as TCRβ, Lck, and ZAP70, whereas CXCR4 silencing by shRNA abolished T cell activation by vGPCRs of HVS and KSHV. Furthermore, previously identified inactive vGPCR mutants failed to interact with CXCR4. These findings on the positive cooperativity of vGPCR with cellular CXCR4 in T cell activation extend our current understanding of the molecular mechanisms of vGPCR function and highlight the importance of heteromerization for GPCR activity.

Keywords: CXCR4; T cells; Viral G protein-coupled receptor; γ-Herpesvirus.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Gene Expression Regulation
  • HEK293 Cells
  • Herpesvirus 2, Saimiriine / genetics
  • Herpesvirus 2, Saimiriine / growth & development
  • Herpesvirus 2, Saimiriine / metabolism*
  • Herpesvirus 4, Human / genetics
  • Herpesvirus 4, Human / growth & development
  • Herpesvirus 4, Human / metabolism
  • Herpesvirus 8, Human / genetics
  • Herpesvirus 8, Human / growth & development
  • Herpesvirus 8, Human / metabolism*
  • Host-Pathogen Interactions
  • Humans
  • Lymphocyte Activation
  • Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / genetics
  • Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / immunology
  • Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / metabolism
  • Primary Cell Culture
  • Protein Binding
  • Protein Multimerization
  • Receptors, Antigen, T-Cell, alpha-beta / genetics
  • Receptors, Antigen, T-Cell, alpha-beta / immunology
  • Receptors, Antigen, T-Cell, alpha-beta / metabolism
  • Receptors, CXCR4 / genetics*
  • Receptors, CXCR4 / immunology
  • Receptors, CXCR4 / metabolism
  • Receptors, Chemokine / genetics*
  • Receptors, Chemokine / immunology
  • Receptors, Chemokine / metabolism
  • Signal Transduction
  • T-Lymphocytes / immunology
  • T-Lymphocytes / metabolism
  • T-Lymphocytes / virology*
  • ZAP-70 Protein-Tyrosine Kinase / genetics
  • ZAP-70 Protein-Tyrosine Kinase / immunology
  • ZAP-70 Protein-Tyrosine Kinase / metabolism


  • CXCR4 protein, human
  • G protein-coupled receptor, Human herpesvirus 8
  • Receptors, Antigen, T-Cell, alpha-beta
  • Receptors, CXCR4
  • Receptors, Chemokine
  • Lymphocyte Specific Protein Tyrosine Kinase p56(lck)
  • ZAP-70 Protein-Tyrosine Kinase
  • ZAP70 protein, human