Nylandsted Jesper, Gyrd-Hansen Mads, Danielewicz Agnieszka, Fehrenbacher Nicole, Lademann Ulrik, Høyer-Hansen Maria, Weber Ekkehard, Multhoff Gabriele, Rohde Mikkel, Jäättelä Marja
Department of Apoptosis, Institute for Cancer Biology, Danish Cancer Society, Strandboulevarden 49, DK-2100 Copenhagen.
J Exp Med. 2004 Aug 16;200(4):425-35. doi: 10.1084/jem.20040531.
Heat shock protein 70 (Hsp70) is a potent survival protein whose depletion triggers massive caspase-independent tumor cell death. Here, we show that Hsp70 exerts its prosurvival function by inhibiting lysosomal membrane permeabilization. The cell death induced by Hsp70 depletion was preceded by the release of lysosomal enzymes into the cytosol and inhibited by pharmacological inhibitors of lysosomal cysteine proteases. Accordingly, the Hsp70-mediated protection against various death stimuli in Hsp70-expressing human tumor cells as well as in immortalized Hsp70 transgenic murine fibroblasts occurred at the level of the lysosomal permeabilization. On the contrary, Hsp70 failed to inhibit the cytochrome c-induced, apoptosome-dependent caspase activation in vitro and Fas ligand-induced, caspase-dependent apoptosis in immortalized fibroblasts. Immunoelectron microscopy revealed that endosomal and lysosomal membranes of tumor cells contained Hsp70. Permeabilization of purified endo/lysosomes by digitonin failed to release Hsp70, suggesting that it is physically associated with the membranes. Finally, Hsp70 positive lysosomes displayed increased size and resistance against chemical and physical membrane destabilization. These data identify Hsp70 as the first survival protein that functions by inhibiting the death-associated permeabilization of lysosomes.
热休克蛋白70（Hsp70）是一种强大的生存蛋白，其缺失会引发大量不依赖半胱天冬酶的肿瘤细胞死亡。在此，我们表明Hsp70通过抑制溶酶体膜通透性发挥其促生存功能。Hsp70缺失诱导的细胞死亡之前有溶酶体酶释放到细胞质中，并受到溶酶体半胱氨酸蛋白酶的药理学抑制剂的抑制。因此，Hsp70介导的对表达Hsp70的人类肿瘤细胞以及永生化Hsp70转基因小鼠成纤维细胞中各种死亡刺激的保护作用发生在溶酶体通透性水平。相反，Hsp70在体外未能抑制细胞色素c诱导的、凋亡小体依赖性的半胱天冬酶激活，以及在永生化成纤维细胞中未能抑制Fas配体诱导的、半胱天冬酶依赖性的凋亡。免疫电子显微镜显示肿瘤细胞的内体和溶酶体膜含有Hsp70。洋地黄皂苷对纯化的内体/溶酶体的通透作用未能释放Hsp70，表明它与膜物理结合。最后，Hsp70阳性溶酶体显示出尺寸增大以及对化学和物理膜不稳定的抗性增加。这些数据表明Hsp70是第一种通过抑制与死亡相关的溶酶体通透性发挥作用的生存蛋白。
