The dynamic role of GRP78/BiP in the coordination of mRNA translation with protein processing
The dynamic role of GRP78/BiP in the coordination of mRNA translation with protein processing
复制标题
DOI：
10.1074/jbc.274.1.486
复制
发表时间：
1999-01-01
影响因子：
4.8
通讯作者：
Brostrom, CO
中科院分区：
文献类型：
--
作者：
Laitusis, AL;Brostrom, MA;Brostrom, CO
在 GH(3) 垂体细胞中检查了 GRP78/BiP 在协调内质网状 (ER) 蛋白加工与 mRNA 翻译中的作用。 GRP78 的 ADP-核糖基化和真核起始因子 (eIF)-2 α 磷酸化分别作为伴侣失活和翻译起始抑制的指标进行评估。 ER应激（离子霉素和二硫苏糖醇）抑制蛋白质加工导致GRP78去核糖基化和eIF-2磷酸化，相对于ER蛋白质加工（放线菌酮）的翻译抑制在90分钟内产生大约50％的GRP78 ADP核糖基化，而没有eIF-2磷酸化，通过以某种方式去除放线菌酮，ADP核糖基化在90分钟内逆转ER 应激源加速。放线菌酮显着降低 eIF-2 磷酸化，以响应 ER 应激源，持续约 30 分钟；随着 GRP78 越来越多的 ADP 核糖基化，敏感性恢复。eIF-2 对磷酸化的敏感性降低似乎是由于蛋白质在没有替代的情况下完成加工时游离的、未修饰的分子伴侣的积累所致。长时间（24小时）与放线菌酮孵育会导致GRP78的ADP核糖基化形式选择性丢失，并增加eIF-2磷酸化对ER应激源的敏感性。 Brefeldin A 降低了 GRP78 的 ADP-核糖基化，同时增加了 eIF-2 磷酸化。细胞质应激源亚砷酸盐通过 eIF-2 磷酸化抑制翻译起始而不影响 ER，也产生了 GRP78 的 ADP-核糖基化。
The role of GRP78/BiP in coordinating endoplasmic reticular (ER) protein processing with mRNA translation was examined in GH(3) pituitary cells. ADP-ribosylation of GRP78 and eukaryotic initiation factor (eIF)-2 alpha phosphorylation were assessed, respectively, as indices of chaperone inactivation and the inhibition of translational initiation. Inhibition of protein processing by ER stress (ionomycin and dithiothreitol) resulted in GRP78 deribosylation and eIF-2 phosphorylation, Suppression of translation relative to ER protein processing (cycloheximide) produced approximately 50% ADP-ribosylation of GRP78 within 90 min without eIF-2 phosphorylation, ADP-ribosylation was reversed in 90 min by cycloheximide removal in a manner accelerated by ER stressors. Cycloheximide sharply reduced eIF-2 phosphorylation in response to ER stressors for about 30 min; sensitivity returned as GRP78 became increasingly ADP-ribosylated, Reduced sensitivity of eIF-2 to phosphorylation appeared to derive from the accumulation of free, unmodified chaperone as proteins completed processing without replacements. Prolonged (24 h) incubations with cycloheximide resulted in the selective loss of the ADP-ribosylated form of GRP78 and increased sensitivity of eIF-2 phosphorylation in response to ER stressors. Brefeldin A decreased ADP-ribosylation of GRP78 in parallel with increased eIF-2 phosphorylation, The cytoplasmic stressor, arsenite, which inhibits translational initiation through eIF-2 phosphorylation without affecting the ER, also produced ADP-ribosylation of GRP78.