Characterization of the roles of TNF receptor-associated factor 6 in CD40-mediated B lymphocyte effector functions
Characterization of the roles of TNF receptor-associated factor 6 in CD40-mediated B lymphocyte effector functions
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DOI：
10.4049/jimmunol.164.2.623
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发表时间：
2000-01-15
影响因子：
4.4
通讯作者：
Bishop, GA
中科院分区：
文献类型：
--
作者：
Jalukar, SV;Hostager, BS;Bishop, GA
通过B细胞中的CD 40的信号传导导致B细胞增殖、IG和IL-6分泌、同种型转换和表面分子的上调，TNF受体相关因子（TRAF）蛋白与CD 40的胞质尾区结合并作为接头分子。在迄今为止鉴定的六种TRAF中，TRAF 2、3、5和6被报道与CD 40的胞质尾区直接相关，但先前的研究主要检查了TRAF 6在通常不表达CD 40的细胞中的瞬时过表达。因此，我们使用两种方法研究了TRAF 6在CD 40介导的B淋巴细胞效应功能中的作用。我们在小鼠B细胞系中产生并稳定表达了具有两个胞质结构域点突变的人CD 40分子（hCD 40 EEAA）;该突变体不能结合TRAF 6，同时显示与TRAF 2和3的正常结合。我们还在B细胞中诱导表达了转染的“显性阴性”TRAF 6分子，其仅含有TRAF 6的C末端TRAF结合结构域。使用这两种分子，我们发现TRAF 6与CD 40的关联对于CD 40诱导的IL-6和IG分泌是重要的，并且TRAF 6主要通过其对由B细胞产生的IL-6的影响来介导其对CD 40刺激的IG分泌的影响。TRAF 6与CD 40的结合对B7-1的上调也很重要，但对其他表面分子的上调则不重要。然而，有趣的是，尽管我们在293肾上皮细胞中显示了TRAF 6依赖的CD 40介导的NF-κ B活化，但在B细胞中没有观察到这种作用，这表明TRAF 6具有细胞类型特异性功能。
Signaling through CD40 in B cells leads to B cell proliferation, Ig and IL-6 secretion, isotype switching, and up-regulation of surface molecules, TNF receptor-associated factor (TRAF) proteins associate with the cytoplasmic tail of CD40 and act as adapter molecules. Of the six TRAFs identified to date, TRAFs 2, 3, 5, and 6 are reported to associate directly with the cytoplasmic tail of CD40, but previous studies have principally examined transient overexpression of TRAF6 in cells that do not normally express CD40. Thus, we examined the role of TRAF6 in CD40-mediated B lymphocyte effector functions using two approaches. We produced and stably expressed in mouse B cell lines a human CD40 molecule with two cytoplasmic domain point mutations (hCD40EEAA); this mutant fails to bind TRAF6, while showing normal association,vith TRAFs 2 and 3, We also inducibly expressed in B cells a transfected "dominant-negative'' TRAF6 molecule which contains only the C-terminal TRAF-binding domain of TRAF6. Using both molecules, we found that TRAF6 association with CD40 is important for CD40-induced IL-6 and Ig secretion, and that TRAF6 mediates its effects on CD40-stimulated Ig secretion principally through its effects on IL-6 production by the B cell. TRAF6 association with CD40 was also found to be important for B7-1 up-regulation, but not for up-regulation of other surface molecules, Interestingly, however, although we could show TRAF6 dependent CD40-mediated activation of NF-kappa B in 293 kidney epithelial cells, no such effect was seen in B cells, suggesting that TRAF6 has cell-type-specific functions.