Genomics Research Center, Academia Sinica, Taipei, 11529, Taiwan.
Department of Biotechnology and Bioindustry Sciences, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan, 70101, Taiwan.
Nat Commun. 2024 Oct 17;15(1):8974. doi: 10.1038/s41467-024-53306-1.
cFLIP, a master anti-apoptotic regulator, targets the FADD-induced DED complexes of procaspase-8 in death receptor and ripoptosome signaling pathways. Several tumor cells maintain relatively high levels of cFLIP in achieving their immortality. However, understanding the three-dimensional regulatory mechanism initiated or mediated by elevated levels of cFLIP has been limited by the absence of the atomic coordinates for cFLIP-induced DED complexes. Here we report the crystal plus cryo-EM structures to uncover an unconventional mechanism where cFLIP and procaspase-8 autonomously form a binary tandem DED complex, independent of FADD. This complex gains the ability to recruit FADD, thereby allosterically modulating cFLIP assembly and partially activating caspase-8 for RIPK1 cleavage. Our structure-guided mutagenesis experiments provide critical insights into these regulatory mechanisms, elucidating the resistance to apoptosis and necroptosis in achieving immortality. Finally, this research offers a unified model for the intricate bidirectional hierarchy-based processes using multiprotein helical assembly to govern cell fate decisions.
cFLIP 是一种主要的抗凋亡调节剂，可靶向死亡受体和 Ripoptosome 信号通路中 FADD 诱导的 procaspase-8 的 DED 复合物。一些肿瘤细胞通过维持相对较高水平的 cFLIP 来实现其不死性。然而，由于缺乏 cFLIP 诱导的 DED 复合物的原子坐标，对由 cFLIP 水平升高引发或介导的三维调节机制的理解一直受到限制。在这里，我们报告了晶体加冷冻电镜结构，以揭示一种非传统的机制，其中 cFLIP 和 procaspase-8 自主形成二元串联 DED 复合物，而无需 FADD。这种复合物获得了招募 FADD 的能力，从而变构调节 cFLIP 组装并部分激活 caspase-8 以切割 RIPK1。我们的结构导向突变实验为这些调节机制提供了重要的见解，阐明了在实现不死性方面对细胞凋亡和坏死的抵抗。最后，这项研究提供了一个统一的模型，用于使用多蛋白螺旋组装来控制细胞命运决定的复杂双向层次结构过程。
