Impairments in protein folding in the endoplasmic reticulum (ER) lead to a condition called ER stress, which can trigger apoptosis via the mitochondrial or the death receptor (extrinsic) pathway. There is controversy concerning involvement of the death receptor (DR)4 and DR5-Caspase-8 –Bid pathway in ER stress-mediated cell death, and this axis has not been fully studied in B-cell malignancies. Using three B-cell lines from Mantle Cell Lymphoma, Waldenström’s macroglobulinemia and Multiple Myeloma origins, we engineered a set of CRISPR KOs of key components of these cell death pathways to address this controversy. We demonstrate that DR4 and/or DR5 are essential for killing via TRAIL, however, they were dispensable for ER-stress induced-cell death, by Thapsigargin, Brefeldin A or Bortezomib, as were Caspase-8 and Bid. In contrast, the deficiency of Bax and Bak fully protected from ER stressors. Caspase-8 and Bid were cleaved upon ER-stress stimulation, but this was DR4/5 independent and rather a result of mitochondrial-induced feedback loop subsequent to Bax/Bak activation. Finally, combined activation of the ER-stress and TRAIL cell-death pathways was synergistic with putative clinical relevance for B-cell malignancies.

内质网 (ER) 中蛋白质折叠的损伤会导致一种称为 ER 应激的情况，它可以通过线粒体或死亡受体（外在）途径触发细胞凋亡。关于死亡受体 (DR)4 和 DR5-Caspase-8 –Bid 通路参与 ER 应激介导的细胞死亡存在争议，该轴在 B 细胞恶性肿瘤中尚未得到充分研究。我们使用来自套细胞淋巴瘤、Waldenström 巨球蛋白血症和多发性骨髓瘤起源的三个 B 细胞系，设计了一组这些细胞死亡途径关键组分的 CRISPR KO 来解决这一争议。我们证明 DR4 和/或 DR5 对于通过 TRAIL 进行杀伤是必不可少的，但是，它们对于 ER 应激诱导的细胞死亡来说是可有可无的，如毒胡萝卜素、布雷菲德定 A 或硼替佐米，Caspase-8 和 Bid 也是如此。相比之下，Bax 和 Bak 的缺乏完全保护免受 ER 应激源的影响。Caspase-8 和 Bid 在 ER 应激刺激下被切割，但这是 DR4/5 独立的，而是 Bax/Bak 激活后线粒体诱导的反馈回路的结果。最后，ER 应激和 TRAIL 细胞死亡途径的联合激活与 B 细胞恶性肿瘤的推定临床相关性具有协同作用。