Cadmium induces phosphorylation and stabilization of c-Fos in HK-2 renal proximal tubular cells
Cadmium induces phosphorylation and stabilization of c-Fos in HK-2 renal proximal tubular cells
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DOI：
10.1016/j.taap.2010.12.015
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发表时间：
2011-03-15
影响因子：
3.8
通讯作者：
Matsuoka, Masato
中科院分区：
文献类型：
--
作者：
Iwatsuki, Mamiko;Inageda, Kiyoshi;Matsuoka, Masato
我们研究了氯化镉（CdCl 2）暴露对Fos家族成员的表达和磷酸化状态的影响，Fos家族是激活蛋白-1转录因子的组成部分，在HK-2人肾近端小管细胞中。CdCl 2染毒后，c-fos、fosB、fra-1和fra-2的表达均显著增加，但增加幅度和时间不同。Fos家族蛋白（c-Fos、FosB、Fra-1和Fra-2）的水平也随着CdCl 2暴露而增加。虽然c-Fos转录的升高是短暂的，但c-Fos蛋白水平随着电泳迁移率的降低而逐渐增加，这表明c-Fos通过翻译后修饰而稳定。同时，我们观察到CdCl 2处理的HK-2细胞中c-Fos在Ser 362和Ser 374处的磷酸化。磷酸化形式的丝裂原活化蛋白激酶（MAPK）-包括细胞外信号调节蛋白激酶（ERK），c-Jun NH 2-末端激酶和p38-增加后氯化镉曝光，而治疗与MAPK/ERK激酶抑制剂U 0126和p38抑制剂SB 203580抑制c-Fos的积累和磷酸化。我们将Ser 362突变为丙氨酸（S362 A），将Ser 374突变为丙氨酸（S374 A），并且将两个残基突变为丙氨酸（S362 A/S374 A）以抑制c-Fos在这些位点的潜在磷酸化。S374 A或S362 A/S374 A双突变显著降低c-Fos水平，而S362 A突变则无此作用。另一方面，S362 A/S374 A突变比S374 A突变诱导c-Fos DNA结合活性更明显的降低。这些结果表明，虽然Ser 374磷酸化似乎在c-Fos稳定中发挥作用，但在CdCl 2处理的HK-2细胞中，c-Fos的转录激活需要两个C-末端丝氨酸残基的磷酸化。(C)2011 Elsevier Inc. All rights reserved.
We examined the effects of cadmium chloride (CdCl2) exposure on the expression and phosphorylation status of members of the Fos family, components of the activator protein-1 transcription factor, in HK-2 human renal proximal tubular cells. Following the exposure to CdCl2, the expression of c-fos, fosB, fra-1, and fra-2 increased markedly, with different magnitudes and time courses. The levels of Fos family proteins (c-Fos, FosB, Fra-1, and Fra-2) also increased in response to CdCl2 exposure. Although the elevation of c-fos transcripts was transient, c-Fos protein levels increased progressively with lower electrophoretic mobility, suggesting stabilization of c-Fos through post-translational modifications. Consistently, we observed phosphorylation of c-Fos at Ser362 and Ser374 in HK-2 cells treated with CdCl2. Phosphorylated forms of mitogen-activated protein kinases (MAPKs)-including extracellular signal-regulated protein kinase (ERK), c-Jun NH2-terminal kinase, and p38-increased after CdCl2 exposure, whereas treatment with the MAPK/ERK kinase inhibitor U0126 and the p38 inhibitor SB203580 suppressed the accumulation and phosphorylation of c-Fos. We mutated Ser362 to alanine (S362A), Ser374 to alanine (S374A), and both residues to alanines (S362A/S374A) to inhibit potential phosphorylation of c-Fos at these sites. S374A or double S362A/S374A mutations reduced c-Fos level markedly, but S362A mutation did not. On the other hand, S362A/S374A mutations induced a more pronounced reduction in c-Fos DNA-binding activity than S374A mutation. These results suggest that while Ser374 phosphorylation seems to play a role in c-Fos stabilization, phosphorylation at two C-terminal serine residues is required for the transcriptional activation of c-Fos in HK-2 cells treated with CdCl2. (C) 2011 Elsevier Inc. All rights reserved.