LMP1 signaling pathway activates IRF4 in latent EBV infection and a positive circuit between PI3K and Src is required

Oncogene. 2017 Apr 20;36(16):2265-2274. doi: 10.1038/onc.2016.380. Epub 2016 Nov 7.

Abstract

Interferon (IFN) regulatory factors (IRFs) have crucial roles in immune regulation and oncogenesis. We have recently shown that IRF4 is activated through c-Src-mediated tyrosine phosphorylation in virus-transformed cells. However, the intracellular signaling pathway triggering Src activation of IRF4 remains unknown. In this study, we provide evidence that Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) promotes IRF4 phosphorylation and markedly stimulates IRF4 transcriptional activity, and that Src mediates LMP1 activation of IRF4. As to more precise mechanism, we show that LMP1 physically interacts with c-Src, and the phosphatidylinositol 3 kinase (PI3K) subunit P85 mediates their interaction. Depletion of P85 by P85-specific short hairpin RNAs disrupts their interaction and diminishes IRF4 phosphorylation in EBV-transformed cells. Furthermore, we show that Src is upstream of PI3K for activation of both IRF4 and Akt. In turn, inhibition of PI3K kinase activity by the PI3K-speicfic inhibitor LY294002 impairs Src activity. Our results show that LMP1 signaling is responsible for IRF4 activation, and further characterize the IRF4 regulatory network that is a promising therapeutic target for specific hematological malignancies.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Class Ia Phosphatidylinositol 3-Kinase / metabolism*
  • Epstein-Barr Virus Infections / metabolism*
  • HEK293 Cells
  • Humans
  • Interferon Regulatory Factors / genetics
  • Interferon Regulatory Factors / metabolism*
  • Phosphorylation
  • Proto-Oncogene Proteins pp60(c-src) / antagonists & inhibitors
  • Proto-Oncogene Proteins pp60(c-src) / metabolism*
  • Signal Transduction
  • Transcriptional Activation
  • Viral Matrix Proteins / metabolism*

Substances

  • EBV-associated membrane antigen, Epstein-Barr virus
  • Interferon Regulatory Factors
  • Viral Matrix Proteins
  • interferon regulatory factor-4
  • Class Ia Phosphatidylinositol 3-Kinase
  • Proto-Oncogene Proteins pp60(c-src)