Translocation of bim to the endoplasmic reticulum (ER) mediates ER stress signaling for activation of caspase-12 during ER stress-induced apoptosis
Translocation of bim to the endoplasmic reticulum (ER) mediates ER stress signaling for activation of caspase-12 during ER stress-induced apoptosis
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DOI：
10.1074/jbc.m408493200
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发表时间：
2004-11-26
影响因子：
4.8
通讯作者：
Seiwa, E
中科院分区：
文献类型：
--
作者：
Morishima, N;Nakanishi, K;Seiwa, E
内质网（ER）应激激活小鼠细胞中的caspase-12，触发ER应激特异性级联反应以实施凋亡。在C2 C12鼠成肌细胞中，级联的激活发生而不从线粒体释放细胞色素c，表明级联是独立的线粒体损伤。Bcl-xL在C2 C12细胞中的稳定过表达抑制caspase-12的活化和凋亡。在ER应激细胞中，而不是在正常细胞中，Bcl-xL与Bcl-2家族的促凋亡成员Bim共免疫沉淀，表明Bcl-xL螯合Bim，从而抑制凋亡信号传导。C2 C12细胞的分级显示，ER应激导致Bim从富含动力蛋白的隔室易位到ER，而Bcl-xL的稳定过表达抑制Bim在ER上的积累。虽然之前仅在线粒体外膜观察到Bim的毒性作用，但Bim衍生物Bim（ER）的过表达（靶向ER表面）导致细胞凋亡。过表达caspase-12抑制蛋白的C2 C12转染子对Bim（ER）具有抗性，表明Bim对ER的毒性作用依赖于caspase-12的活化。通过RNA干扰敲低Bim提供了对ER应激具有抗性的细胞。这些结果表明，在响应ER应激的Bim易位到ER是朝向caspase-12活化和启动ER应激特异性caspase级联的重要步骤。
Endoplasmic reticulum (ER) stress activates caspase-12 in murine cells, triggering the ER stress-specific cascade for implementation of apoptosis. In C2C12 murine myoblast cells, activation of the cascade occurs without release of cytochrome c from mitochondria, suggesting that the cascade is independent of mitochondrial damage. Stable overexpression of Bcl-xL in C2C12 cells suppressed activation of caspase-12 and apoptosis. In ER-stressed cells, but not in normal cells, Bcl-xL was co-immunoprecipitated with Bim, a pro-apoptotic member of the Bcl-2 family, suggesting that Bcl-xL sequesters Bim, thereby inhibiting the apoptotic signaling. Fractionation of C2C12 cells revealed that ER stress led to translocation of Bim from a dynein-rich compartment to the ER, while stable overexpression of Bcl-xL suppressed accumulation of Bim on the ER. Although the toxic effect of Bim had been previously observed only at the mitochondrial outer membrane, overexpression of a Bim derivative, Bim(ER), targeted at the surface of the ER led to apoptosis. A C2C12 transfectant overexpressing the caspase-12 suppressor protein was resistant to Bim(ER), suggesting that the toxic effect of Bim on the ER is dependent on activation of caspase-12. Knockdown of Bim by RNA interference provided cells resistant to ER stress. These results suggest that translocation of Bim to the ER in response to ER stress is an important step toward activation of caspase-12 and initiation of the ER stress-specific caspase cascade.