MRC Toxicology Unit, Hodgkin Building, P.O. Box 138, Lancaster Road, Leicester LE1 9HN, UK.
Mol Cell. 2012 Jul 27;47(2):291-305. doi: 10.1016/j.molcel.2012.05.004. Epub 2012 Jun 7.
Formation of the death-inducing signaling complex (DISC) is a critical step in death receptor-mediated apoptosis, yet the mechanisms underlying assembly of this key multiprotein complex remain unclear. Using quantitative mass spectrometry, we have delineated the stoichiometry of the native TRAIL DISC. While current models suggest that core DISC components are present at a ratio of 1:1, our data indicate that FADD is substoichiometric relative to TRAIL-Rs or DED-only proteins; strikingly, there is up to 9-fold more caspase-8 than FADD in the DISC. Using structural modeling, we propose an alternative DISC model in which procaspase-8 molecules interact sequentially, via their DED domains, to form a caspase-activating chain. Mutating key interacting residues in procaspase-8 DED2 abrogates DED chain formation in cells and disrupts TRAIL/CD95 DISC-mediated procaspase-8 activation in a functional DISC reconstitution model. This provides direct experimental evidence for a DISC model in which DED chain assembly drives caspase-8 dimerization/activation, thereby triggering cell death.
死亡诱导信号复合物（DISC）的形成是死亡受体介导的细胞凋亡的关键步骤，然而，组装这个关键多蛋白复合物的机制仍不清楚。我们使用定量质谱法描绘了天然 TRAIL DISC 的化学计量。虽然当前的模型表明核心 DISC 成分的存在比例为 1:1，但我们的数据表明 FADD 的含量相对于 TRAIL-Rs 或仅含 DED 的蛋白是亚化学计量的；引人注目的是，DISC 中的 caspase-8 比 FADD 多 9 倍。通过结构建模，我们提出了一种替代的 DISC 模型，其中 procaspase-8 分子通过其 DED 结构域依次相互作用，形成 caspase 激活链。在细胞中突变 procaspase-8 DED2 中的关键相互作用残基会破坏 DED 链的形成，并在功能性 DISC 重建模型中破坏 TRAIL/CD95 DISC 介导的 procaspase-8 激活。这为 DISC 模型提供了直接的实验证据，其中 DED 链组装驱动 caspase-8 二聚体化/激活，从而触发细胞死亡。
