Cadmium induces the expression of Grp78, an endoplasmic reticulum molecular chaperone, in LLC-PK1 renal epithelial cells.
Cadmium induces the expression of Grp78, an endoplasmic reticulum molecular chaperone, in LLC-PK1 renal epithelial cells.
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镉在LLC-PK1肾上皮细胞中诱导GRP78（一种内质网分子伴侣）的表达。
DOI：
10.1289/ehp.8920
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发表时间：
2006-06
影响因子：
10.4
通讯作者：
Matsuoka, Masato
中科院分区：
文献类型：
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作者：
Liu, Fang;Inageda, Kiyoshi;Nishitai, Gen;Matsuoka, Masato
为了揭示镉暴露对内质网（ER）应激反应的影响，我们研究了LLC-PK 1细胞中78 kDa葡萄糖调节蛋白（Grp 78）的表达和功能。在10 μM氯化镉处理的细胞中，Grp 78蛋白水平在6 h后开始升高，并在24 h后仍保持较高水平，而在1-20 μM氯化镉处理的细胞中，Grp 78蛋白水平呈剂量依赖性升高。此外，Grp 78 mRNA水平升高响应氯化镉暴露。暴露于10 μM CdCl 2后，转录激活因子4（ATF 4）的水平在2 h时升高，之后进一步增强;这种积累是在真核翻译起始因子2（eIF 2 α）α亚基丝氨酸51上短暂但显著的磷酸化之后。虽然ATF 4 mRNA水平轻度增加氯化镉曝光，放线菌素D治疗没有抑制氯化镉诱导的ATF 4蛋白的积累，这表明参与转录后，部分转录机制。与氯化锰、氯化锌、氯化汞、氯化铅等重金属化合物相比，CdCl 2能更显著地增加Grp 78、ATF 4和eIF 2 α磷酸化形式的表达，且对细胞无明显损伤。使用短干扰RNA沉默Grp 78表达增强CdCl 2诱导的细胞损伤。这些结果表明，镉可能通过eIF 2 α的磷酸化和由此产生的ATF 4的翻译诱导Grp 78的表达，并且这种ER应激反应在该肾上皮细胞中对镉的细胞毒性起保护作用。
To reveal the effects of cadmium exposure on the endoplasmic reticulum (ER) stress response, we examined the expression and function of 78-kDa glucose-regulated protein (Grp78), an ER-resident molecular chaperone, in LLC-PK1 cells. In cells treated with 10 μM cadmium chloride, Grp78 protein levels increased after 6 hr and remained elevated at 24 hr. When cells were incubated with 1–20 μM CdCl2 for 6 hr, Grp78 increased in a dose-dependent manner. In addition, Grp78 mRNA levels were elevated in response to CdCl2 exposure. After exposure to 10 μM CdCl2, the levels of activating transcription factor 4 (ATF4) were increased at 2 hr, with a further enhancement after that; this accumulation followed the transient but marked phosphorylation of the α subunit of eukaryotic translation initiation factor 2 (eIF2α) on serine 51. Although ATF4 mRNA levels increased mildly by CdCl2 exposure, treatment with actinomycin D did not suppress CdCl2-induced accumulation of ATF4 protein, suggesting the involvement of posttranscriptional and, in part, transcriptional mechanisms. Compared with other heavy-metal compounds such as manganese chloride, zinc chloride, mercuric chloride, and lead chloride, CdCl2 could increase the levels of Grp78, ATF4, and the phosphorylated form of eIF2α more markedly without definite cellular damage. The silencing of Grp78 expression using short-interference RNA enhanced CdCl2-induced cellular damage. These results show that cadmium induces the expression of Grp78 probably via phosphorylation of eIF2α and resultant translation of ATF4, and this ER stress response plays a role in protection against cadmium cytotoxicity in this renal epithelial cell.