Endoplasmic reticulum (ER) stress induced by disruption of protein folding activates the unfolded protein response (UPR), which while generally pro-survival in effect can also induce cell death under severe ER stress. 24(S)-hydroxycholesterol (24S-OHC), which is enzymatically produced in the ER of neurons, plays an important role in maintaining brain cholesterol homeostasis but also shows neurotoxicity when subjected to esterification by acyl-CoA:cholesterol acyltransferase 1 (ACAT1) in the ER. In this study, we demonstrated that the accumulation of 24S-OHC esters in human neuroblastoma SH-SY5Y cells evoked the UPR with substantially no pro-survival adaptive response but with significant activation of pro-death UPR signaling via regulated IRE1-dependent decay (RIDD). We further found that accumulation of 24S-OHC esters caused disruption of ER membrane integrity and release of ER luminal proteins into cytosol. We also found that de novo synthesis of global proteins was robustly suppressed in 24S-OHC-treated cells. Collectively, these results show that ER dysfunction and the accompanying RIDD-mediated pro-death UPR signaling and global protein synthesis inhibition are responsible for 24S-OHC ester-induced unconventional cell death.

由蛋白质折叠破坏引起的内质网（ER）应激会激活未折叠的蛋白质应答（UPR），虽然通常具有前生存力，但也可在严重的ER应激下诱导细胞死亡。24（小号）-羟基胆固醇（24S-OHC）在神经元的ER中以酶促方式产生，在维持脑胆固醇稳态中起着重要作用，但在ER中的酰基CoA：胆固醇酰基转移酶1（ACAT1）酯化时也显示出神经毒性。在这项研究中，我们证明了人神经母细胞瘤SH-SY5Y细胞中24S-OHC酯的积累诱发了UPR，基本上没有生存前自适应反应，但通过受调控的IRE1依赖性衰变（RIDD）显着激活了死亡前UPR信号转导。 ）。我们进一步发现24S-OHC酯的积累引起ER膜完整性的破坏和ER腔蛋白释放到细胞质中。我们还发现，在24S-OHC处理的细胞中，全球蛋白质的从头合成受到了强烈抑制。总的来说，