Immediate early gene-X1 interferes with 26 S proteasome activity by attenuating expression of the 19 S proteasomal components S5a/Rpn10 and S1/Rpn2
Immediate early gene-X1 interferes with 26 S proteasome activity by attenuating expression of the 19 S proteasomal components S5a/Rpn10 and S1/Rpn2
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DOI：
10.1042/bj20061072
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发表时间：
2007-03-01
影响因子：
4.1
通讯作者：
Schaefer, Heiner
中科院分区：
文献类型：
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作者：
Arlt, Alexander;Minkenberg, Joerg;Schaefer, Heiner
应激反应基因IEX-1(即刻早期基因-X-1)参与调节细胞生长和细胞活力。在某种程度上，这些影响包括对某些调节蛋白的蛋白酶体周转的干扰。在这里，我们证明了IEX-1直接减弱了HEK-293细胞(人胚胎肾细胞)中26 S蛋白酶体的活性和形成。我们进一步证明，IEX-1降低了19个S蛋白酶体亚基的某些蛋白质组分，如S5a/Rpn10和S1/Rpn2的总体表达水平，而对其他蛋白酶体蛋白的表达影响较小或不受影响。与直接的凋亡刺激，如抗癌药物依托泊苷，导致caspase依赖的降解S I和S5a相反，IEX-1的作用不依赖于这些蛋白的蛋白水解性切割。此外，在放线菌素D存在的情况下，IEX-1对S5a和SI的表达仍有抑制作用，而在放线菌素D的存在下则不能。实时定量聚合酶链式反应显示在IEX-1过表达的细胞中S5a和S I的基因表达水平较低，提示IEX-1干扰了S5a和S1的基因转录。此外，荧光素酶检测证实了IEX-1对S5a启动子活性的干扰。这些发现表明IEX-1在26 S蛋白酶体的维持和组装中发挥了作用，显然涉及到某些蛋白酶体蛋白基因表达的改变。因此，IEX-1可能在本质上调控与26 S蛋白酶体活性相关的信号通路，参与细胞生长控制和细胞凋亡。
The stress response gene IEX-1 (immediate early gene-X-1) is involved in the regulation of cell growth and cellular viability. To some extent, these effects include an interference with the proteasomal turnover of certain regulatory proteins. Here, we show that IEX-1 directly attenuates the activity and formation of the 26 S proteasome in HEK-293 cells (human embryonic kidney cells). We further demonstrate that IEX-1 reduces the overall expression levels of certain protein components of the 19 S proteasomal subunit such as S5a/Rpn10 and S1/Rpn2, whereas the expression of other proteasomal proteins was less or not affected. In contrast with direct apoptotic stimuli, such as the anti-cancer drug etoposide, leading to caspase-dependent degradation of S I and S5a, the effect of IEX-1 is independent of proteolytic cleavage of these proteins. Furthermore, the decreasing effect of IEX-1 on S5a and SI expression is still seen in the presence of cyclo-heximide, but not in the presence of actinomycin D, and quantitative real-time PCR revealed lower mRNA levels of S5a and S I in IEX-1-overexpressing cells, suggesting an interference of IEX-1 with the gene transcription of S5a and S1. Additionally, luciferase assays confirmed an interference of IEX-1 with the activity of the S5a promoter. These findings indicate a role of IEX-1 in the maintenance and assembly of the 26 S proteasome, obviously involving an altered gene expression of certain proteasomal proteins. Thereby, IEX-1 may essentially modulate signalling pathways related to 26 S proteasome activity and involved in cellular growth control and apoptosis.