Epstein-Barr virus-encoded latent membrane protein 1 activates the JNK pathway through its extreme C terminus via a mechanism involving TRADD and TRAF2
Epstein-Barr virus-encoded latent membrane protein 1 activates the JNK pathway through its extreme C terminus via a mechanism involving TRADD and TRAF2
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DOI：
10.1128/jvi.73.2.1023-1035.1999
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发表时间：
1999-02-01
影响因子：
5.4
通讯作者：
Young, LS
中科院分区：
文献类型：
--
作者：
Eliopoulos, AG;Blake, SMS;Young, LS
EB病毒编码的潜伏膜蛋白1(LMP1)通过其胞质C端的两个不同的结构域，即CTAR1(氨基酸[AA]187~231)和CTAR2(AA 351~386)，激活NF-KB轴上的信号转导。CTAR1激活核因子-kappaB的能力似乎归因于肿瘤坏死因子受体相关因子2(TRAF2)的直接相互作用，而最近的研究表明，CTAR2诱导的核因子-kappaB是通过其与肿瘤坏死因子受体相关死亡结构域(Tradd)的关联而介导的。LMP1的表达还导致c-jun氨基末端激酶(JNK)(也称为应激激活蛋白激酶)级联的激活，这一作用仅通过CTAR2介导，并可与NF-kappa B的诱导分离。LMP1诱导的JNK激活所涉及的组织和信号成分尚不清楚。在这项研究中，我们解剖了LMP1的极端C末端，并确定了该蛋白的最后8个氨基酸(AA 378至386)对JNK信号转导起重要作用。使用一系列精细的突变体，其中密码子379和386之间的单个氨基酸被改变为甘氨酸，我们发现Pro(379)、Glu(381)、Ser(383)或Tyr(384)突变降低了LMP1 CTAR2参与JNK信号转导的能力。有趣的是，该区域也被发现是CTAR2介导的NF-kappa B诱导所必需的，并且与LMP1结合Tradd的氨基酸序列一致。此外，我们发现LMP1介导的JNK激活被低水平的Tradd表达协同增强，这表明该适配蛋白对LMP1信号转导至关重要。已知TRAF2与Tradd相关，并且发现TRAF2突变体的表达部分抑制了LMP1诱导的293细胞中JNK的激活。此外，TRAF2相互作用蛋白A20阻断了LMP1诱导的JNK和NF-kappa B的激活，进一步暗示TRAF2参与了这些现象。一种与TRAF2相关的有丝分裂原激活的蛋白激酶--突变的核因子-kappaB诱导激酶(NIK)的表达减弱了核因子-kappa B轴上的LMP1信号，但并不抑制LMP1诱导的JNK的激活，这表明这两条通路可能在TRAF2水平上分叉。这些数据进一步确定了Tradd和TRAF2在JNK激活中的作用，并证实了LMP1利用肿瘤坏死因子受体/CD40家族使用的信号机制来诱导其多效性。
The transforming Epstein-Barr virus-encoded latent membrane protein 1 (LMP1) activates signalling on the NF-KB axis through two distinct domains in its cytoplasmic C terminus, namely, CTAR1 (amino acids [aa] 187 to 231) and CTAR2 (aa 351 to 386). The ability of CTAR1 to activate NF-kappa B appears to be attributable to the direct interaction of tumor necrosis factor (TNF) receptor-associated factor 2 (TRAF2), while recent work indicates that CTAR2-induced NF-kappa B is mediated through its association with TNF receptor-associated death domain (TRADD). LMP1 expression also results in activation of the c-Jun N-terminal kinase (JNK) (also known as stress-activated protein kinase) cascade, an effect which is mediated exclusively through CTAR2 and can be dissociated from NF-kappa B induction. The organization and signalling components involved in LMP1-induced JNK activation are not known. In this study we have dissected the extreme C terminus of LMP1 and have identified the last 8 aa of the protein (aa 378 to 386) as being important for JNK signalling. Using a series of fine mutants in which single amino acids between codons 379 and 386 were changed to glycine, we have found that mutations of Pro(379), Glu(381), Ser(383), or Tyr(384) diminish the ability of LMP1 CTAR2 to engage JNK signalling. Interestingly, this region was also found to be essential for CTAR2-mediated NF-kappa B induction and coincides with the LMP1 amino acid sequences shown to bind TRADD. Furthermore, we have found that LMP1-mediated JNK activation is synergistically augmented by low levels of TRADD expression, suggesting that this adapter protein is critical for LMP1 signalling. TRAF2 is known to associate with TRADD, and expression of a dominant-negative N-terminal deletion TRAF2 mutant was found to partially inhibit LMP1-induced JNK activation in 293 cells. In addition, the TRAF2-interacting protein A20 blocked both LMP1-induced JNK and NF-kappa B activation, further implicating TRAF2 in these phenomena. While expression of a kinase-inactive mutated NF-kappa B-inducing kinase (NIK), a mitogen-activated protein kinase kinase kinase which also associates with TRAF2, impaired LMP1 signalling on the NF-kappa B axis, it did not inhibit LMP1-induced JNK activation, suggesting that these two pathways may bifurcate at the level of TRAF2. These data further define a role for TRADD and TRAF2 in JNK activation and confirm that LMP1 utilizes signalling mechanisms used by the TNF receptor/CD40 family to elicit its pleiotropic activities.