Caspase-2, a highly conserved member of the caspase family, is considered an initiator caspase that triggers apoptosis in response to some cellular stresses. Previous studies suggest that an intracellular multi-protein complex PIDDosome, induced by genotoxic stress, serves as a platform for caspase-2 activation. However, due to caspase-2's inability to process effector caspases, the mechanism underlying caspase-2-mediated cell death upon PIDDosome activation remains unclear. Here we conducted an unbiased genome-wide genetic screen and identified that the Bcl2 family protein BID is required for PIDDosome-induced, caspase-2-mediated apoptosis. PIDDosome-activated caspase-2 directly and functionally processes BID to signal the mitochondrial pathway for apoptosis induction. Additionally, a designed chemical screen identified a compound, HUHS015, that specifically activates caspase-2-mediated apoptosis. HUHS015-stimulated apoptosis also requires BID but is independent of the PIDDosome. Through extensive structure-activity relationship efforts, we identified a derivative with a potency of ~ 60 nmol/L in activating caspase-2-mediated apoptosis. The HUHS015-series of compounds act as efficient agonists that directly target the interdomain linker in caspase-2, representing a new mode of initiator caspase activation. Human and mouse caspase-2 differ in two crucial residues in the linker, rendering a selectivity of the agonists for human caspase-2. The caspase-2 agonists are valuable tools to explore the physiological roles of caspase-2-mediated cell death and a base for developing small-molecule drugs for relevant diseases.

中文翻译：

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剖析 caspase-2 介导的细胞死亡：从内在的 PIDDosome 激活到化学调节。


Caspase-2 是 caspase 家族中高度保守的成员，被认为是一种起始 caspase，可响应某些细胞应激而触发细胞凋亡。先前的研究表明，由基因毒性应激诱导的细胞内多蛋白复合物 PIDDosome 可作为 caspase-2 激活的平台。然而，由于 caspase-2 无法处理效应 caspase，PIDDosome 激活后 caspase-2 介导的细胞死亡的机制仍不清楚。在这里，我们进行了无偏倚的全基因组遗传筛选，并确定 Bcl2 家族蛋白 BID 是 PIDDosome 诱导的 caspase-2 介导的细胞凋亡所必需的。 PIDDosome 激活的 caspase-2 直接并功能性地处理 BID，向线粒体途径发出信号以诱导细胞凋亡。此外，一项设计的化学筛选鉴定出一种化合物 HUHS015，它可以特异性激活 caspase-2 介导的细胞凋亡。 HUHS015 刺激的细胞凋亡也需要 BID，但独立于 PIDDosome。通过广泛的结构-活性关系研究，我们鉴定出一种衍生物，其激活 caspase-2 介导的细胞凋亡的效力约为 60 nmol/L。 HUHS015系列化合物作为有效的激动剂，直接靶向caspase-2中的域间连接子，代表了一种新的启动子caspase激活模式。人和小鼠 caspase-2 在接头中的两个关键残基上存在差异，从而使人 caspase-2 激动剂具有选择性。 caspase-2激动剂是探索caspase-2介导的细胞死亡生理作用的重要工具，也是开发治疗相关疾病的小分子药物的基础。