Ferroptosis Inhibition by Lysosome-Dependent Catabolism of Extracellular Protein

This dataset contains original uncropped western blots, an ImageJ macro, and an R program, related to this work whose abstract is as follows: Cancer cells must ensure a steady supply of nutrients to enable proliferation and evade cell death. Depriving cancer cells of the amino acid cystine can trigger the non-apoptotic cell death process of ferroptosis. Here, we report that cancer cells can evade cystine deprivation-induced ferroptosis by the uptake and catabolism of the cysteine-rich extracellular protein albumin. This protective mechanism is enhanced by mTORC1 inhibition and involves albumin degradation in the lysosome, predominantly by cathepsin B (CTSB). CTSB-dependent albumin breakdown followed by export of cystine from the lysosome via the transporter cystinosin fuels the synthesis of glutathione, which suppresses lethal lipid peroxidation. Notably, when cancer cells are grown under non-adherent conditions as spheroids mTORC1 pathway activity is reduced and albumin supplementation alone affords considerable protection against ferroptosis. These results identify the catabolism of extracellular protein within the lysosome as a mechanism that can inhibit ferroptosis in cancer cells.

本数据集包含与下述研究相关的原始未裁剪蛋白质免疫印迹（western blot）、ImageJ宏脚本以及R语言程序，该研究的摘要如下：癌细胞必须维持稳定的营养供给，以实现增殖并逃避细胞死亡。剥夺癌细胞所需的氨基酸胱氨酸（cystine），可触发铁死亡（ferroptosis）这一非凋亡性细胞死亡过程。本研究证实，癌细胞可通过摄取并分解富含半胱氨酸的胞外蛋白质白蛋白，逃避胱氨酸剥夺诱导的铁死亡。该保护机制可通过抑制哺乳动物雷帕霉素靶蛋白复合物1（mTORC1）通路得到增强，且其过程依赖于溶酶体中白蛋白的降解，主要由组织蛋白酶B（CTSB）介导。依赖CTSB的白蛋白分解后，再通过转运蛋白胱氨酸转运体（cystinosin）将胱氨酸从溶酶体输出，以此为谷胱甘肽的合成提供原料，进而抑制致命性脂质过氧化反应。值得注意的是，当癌细胞以细胞球体形式在非贴附条件下培养时，mTORC1通路活性降低，仅补充白蛋白即可为癌细胞提供显著的抗铁死亡保护作用。上述研究结果证实，溶酶体内的胞外蛋白质分解可作为一种抑制癌细胞铁死亡的机制。