EB病毒潜伏膜蛋白1通过结合TRAFs调控NF-κB

Interaction of Tumor Necrosis Factor Receptor-associated Factors with the Latent Membrane Protein 1 Is Essential for Activation of NF-κB

为了探讨EB病毒潜伏膜蛋白 1(LMP1)的致瘤机制 ,对鼻咽癌中LMP1激活重要的核转录因子NF κB机制进行了研究 .首先 ,采用免疫共沉淀 蛋白质印迹在稳定表达LMP1的鼻咽癌细胞系HNE2 LMP1中证实LMP1与TRAF1,2 ,3结合形成免疫共沉淀复合物 ,进一步以野生型LMP1及其三种突变体的鼻咽癌细胞系LMP1(野生型 ,wt)、HNE2 LMP1del187～ 35 1(CTAR1缺失型 )、HNE2 LMP1(1～ 2 31) (CTAR2缺失型 )、HNE2 LMP1(1～ 187) (羧基端胞浆区缺失型 )、HNE2 pSG5 (空白载体型 )为材料 ,结合NF κB报道基因质粒(pGL2 NF κB luc)的荧光素酶活性表达分析NF κB的活性 ,证实 :较之母细胞 ,野生型LMP1活化NF κB达13 8倍 ,LMP1(1～ 187)几乎不活化NF κB ,LMP1(1～ 2 31)活化NF κB达 4 9倍 ,LMP1(del187～ 35 1)活化NF κB达 9 1倍 ;TRAF1过表达升高LMP1(wt)及LMP1(1～ 2 31)介导的NF κB活性 ,而对LMP1(del187～ 35 1)活化NF κB无影响 ;TRAF3过表达或TRAF3负显性突变体抑制LMP1(wt)及LMP1(1～ 2 31)介导的NF κB活性 ,而不影响LMP1(del 187～ 35 1)活化NF κB ;TRAF2过表达升高LMP1(wt)、LMP1(1～2 31)及LMP1(del 187～ 35 1)介导的NF κB活性 .这些结果表明 :鼻咽癌中LMP1通过TRAF1、TRAF2或TRAF3调控NF κB 。

The Epstein Barr virus latent membrane protein 1 (LMP1) oncoprotein causes multiple cellular changes, including activation of the NF κB transcription factor. To elucidate its possible mechanism, the interaction between LMP1 and the tumor necrosis factor receptor associated factor (TRAF) molecules was detected by the immunoprecipitation Western blotting assay. Results showed that LMP1 was co precipitated with TRAF1,2,3 in the LMP1 HNE2 cell line. In the meantime, κB reporter gene analysis revealed that over expression of TRAF1 or TRAF2 augmented LMP1 mediated NF κB activation from LMP1, suprisingly, overexpression of either TRAF3 or an dominant negative TRAF3 inhibited the NF κB activation, indicating that TRAF1 or TRAF2 is a positive modulator of LMP1 mediated NF κB activation, whereas,TRAF3 is a negative modulator. Rather both CTAR1 (carboxy terminal activating region 1) and CTAR2 domains of LMP1 can independently activate NF κB by interacting with TRAF proteins. These data indicate that LMP1 interacts TRAF1,2,3 which are important for LMP1 mediated NF κB activation, and further suggest that signaling from TRAFs may be involved in the progression to malignancy in cells of epithelial origin such as nasopharyngeal carcinoma (NPC).