Winberg G, Matskova L, Chen F, Plant P, Rotin D, Gish G, Ingham R, Ernberg I, Pawson T
Karolinska Institutet, Microbiology and Tumor Biology Center (MTC), SE-171 77 Stockholm, Sweden.
Mol Cell Biol. 2000 Nov;20(22):8526-35. doi: 10.1128/MCB.20.22.8526-8535.2000.
The latent membrane protein (LMP) 2A of Epstein-Barr virus (EBV) is implicated in the maintenance of viral latency and appears to function in part by inhibiting B-cell receptor (BCR) signaling. The N-terminal cytoplasmic region of LMP2A has multiple tyrosine residues that upon phosphorylation bind the SH2 domains of the Syk tyrosine kinase and the Src family kinase Lyn. The 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-ubiquitin ligases of the Nedd4 family, including AIP4 and KIAA0439, and demonstrate 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 proteins have a C-terminal Hect catalytic domain implicated in the ubiquitination of target proteins. LMP2A enhances Lyn and Syk ubiquitination in vivo in a fashion that depends on the activity of Nedd4 family members and correlates 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 promote 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 family E3 enzymes regulate B-cell signaling.
爱泼斯坦-巴尔病毒（EBV）的潜伏膜蛋白（LMP）2A与病毒潜伏状态的维持有关，其部分功能似乎是通过抑制B细胞受体（BCR）信号传导来实现的。LMP2A的N端胞质区域有多个酪氨酸残基，磷酸化后可结合Syk酪氨酸激酶和Src家族激酶Lyn的SH2结构域。LMP2A的N端区域还有两个保守的PPPPY基序。我们在此表明，LMP2A的PPPPY基序可结合Nedd4家族E3蛋白-泛素连接酶的多个WW结构域，包括AIP4和KIAA0439，并证明AIP4和KIAA0439在EBV阳性B细胞中与LMP2A形成生理复合物。除了一个C2结构域和四个WW结构域外，这些蛋白还有一个C端Hect催化结构域，与靶蛋白的泛素化有关。LMP2A在体内以依赖于Nedd4家族成员活性的方式增强Lyn和Syk的泛素化，并与Lyn酪氨酸激酶的不稳定相关。这些结果表明，LMP2A作为一个分子支架，招募B细胞酪氨酸激酶和C2/WW/Hect结构域E3蛋白-泛素连接酶。这可能以一种导致B细胞信号传导受阻的方式促进Lyn和Syk的泛素化。LMP2A可能增强Nedd4家族E3酶调节B细胞信号传导的正常机制。
