Latent membrane protein 2A of Epstein-Barr virus binds WW domain E3 protein-ubiquitin ligases that ubiquitinate B-cell tyrosine kinases

The latent membrane protein (LMP) 2A of Epstein-Barr virus (EBV) is implica ted in the maintenance of viral latency and appears to function in part by inhibiting B-cell receptor (BCR) signaling. The N-terminal cytoplasmic regi on of LMP2A has multiple tyrosine residues that upon phosphorylation bind t he SH2 domains of the Syk tyrosine kinase and the Src family kinase Lyn. Th e LMP2A N-terminal region also has two conserved PPPPY motifs. Here we show that the PPPPY motifs of LMP2A bind multiple WW domains of E3 protein-ubiq uitin ligases of the Nedd4 family, including AIP4 and KIAA0439, and demonst rate that AIP4 and KIAA0439 form physiological complexes with LMP2A in EBV- positive B cells. In addition to a C2 domain and four WW domains, these pro teins have a C-terminal Hect catalytic domain implicated in the ubiquitinat ion of target proteins. LMP2A enhances Lyn and Syk ubiquitination in vivo i n a fashion that depends on the activity of Nedd4 family members and correl ates with destabilization of the Lyn tyrosine kinase. These results suggest that LMP2A serves as a molecular scaffold to recruit both B-cell tyrosine kinases and C2/WW/Hect domain E3 protein-ubiquitin ligases. This may promot e Lyn and Syk ubiquitination in a fashion that contributes to a block in B- cell signaling. LMP2A may potentiate a normal mechanism by which Nedd4 fami ly E3 enzymes regulate B-cell signaling.