The Epstein-Barr Virus Protein, Latent Membrane Protein 2A, Co-opts Tyrosine Kinases Used by the T Cell Receptor

Robert J Ingham,Judith Raaijmakers,Caesar S.H Lim,Geraldine Mbamalu,Gerald Gish,Fu Chen,Liudmila Matskova,Ingemar Ernberg,Gösta Winberg,Tony Pawson

doi:10.1074/jbc.m507831200

Abstract

Epstein-Barr virus (EBV) is the causative agent of infectious mononucleosis and is associated with several human malignancies. The EBV protein latent membrane protein 2A (LMP2A) promotes viral latency in memory B cells by interfering with B cell receptor signaling and provides a survival signal for mature B cells that have lost expression of surface immunoglobulin. The latter function has suggested that LMP2A may enhance the survival of EBV-positive tumors. EBV is associated with several T cell malignancies and, since LMP2A has been detected in several of these disorders, we examined the ability of LMP2A to transmit signals and interfere with T cell receptor signaling in T cells. We show that LMP2A is tyrosine-phosphorylated in Jurkat TAg T cells, which requires expression of the Src family tyrosine kinases, Lck and Fyn. Lck and Fyn are recruited to the tyrosine-phosphorylated Tyr112 site in LMP2A, whereas phosphorylation of an ITAM motif in LMP2A creates a binding site for the ZAP-70/Syk tyrosine kinases. LMP2A also associates through its two PPPPY motifs with AIP4, a NEDD4 family E3 ubiquitin ligase; this interaction results in ubiquitylation of LMP2A and serves to regulate the stability of LMP2A and LMP2A-kinase complexes. Furthermore, stable expression of LMP2A in Jurkat T cells down-regulated T cell receptor levels and attenuated T cell receptor signaling. Thus, through recruiting tyrosine kinases involved in T cell receptor activation, LMP2A may provide a survival signal for EBV-positive T cell tumors, whereas LMP2A-associated NEDD4 E3 ligases probably titer the strength of this signal.

Highlights

The world’s population is latently infected with Epstein-Barr virus (EBV) [3]
latent membrane protein 2A (LMP2A) Interferes with T cell receptor (TCR) Signaling in Jurkat T Cells—Since recruitment of the Lyn and Syk tyrosine kinases to LMP2A in B cells is important for the LMP2A-mediated inhibition of B cell receptor (BCR) signaling, we investigated whether expression of LMP2A in T cells inhibited TCR signaling
We have examined the role of the EBV protein LMP2A in T cells in order to understand how LMP2A might contribute to EBV-positive T cell lymphomagenesis

Summary

Introduction

The world’s population is latently infected with EBV [3]. This latent infection is maintained in the body’s memory B cells through the expression of a number of latency-associated viral genes, one of which is latent membrane protein 2A (LMP2A) [4]. The results show that in contrast to the WT protein, the PYϪ LMP2A mutant that lacks binding sites for the WW domains of AIP4 was not appreciably ubiquitylated in these cells (Fig. 3C, upper panel). LMP2A is ubiquitylated by NEDD4 family E3 protein-ubiquitin ligases in Jurkat TAg cells, and the lack of ubiquitylation of the PYϪ mutant probably explains the increased stability of this protein.

Results

Conclusion