In this study, we investigated if subunit displacement and/or alterations in proteasome biosynthesis are responsible for the changes in the levels of constitutive proteasomes (c-20S), immunoproteasomes (i-20S) and the activators PA28 and PA700 in neurons and astrocytes cultured with a cytokine mixture (IFN-γ/TNF-α/IL-1β). Exposure of both cell types to cytokines for 24 h increases mRNA and protein expression of the i-20S-specific subunit β5i and PA28α/β, and leads to a decline in the amount of the c-20S-specific subunit β5. Since β5 mRNA levels are unchanged by the cytokine treatment, it is fair to conclude that displacement of constitutive β-subunits with inducible β5i subunits is likely the mechanism underlying the decrease in c-20S. As expected, the increase in the amount of the IFN-γ-inducible subunits coincides with elevated expression of phospho-STAT-1 and interferon regulatory factor-1 (IRF-1). However, inhibition of NF-κB signaling in cytokine-treated astrocytes reduces IRF-1 expression without affecting that of i-20S, c-20S and PA28. This suggests that STAT-1 is capable of increasing the transcription of i20S-specific subunits and PA28α/β by itself. The lack of a decrease in proteasome β5 mRNA expression is consistent with the fact that Nrf1 (Nfe2l1) and Nrf2 (Nfe2l2) levels are not reduced by pro-inflammatory cytokines. In contrast, we previously found that there is a significant Nrf1 dysregulation and reduced β5 mRNA expression in the spinal cords of mice with experimental autoimmune encephalomyelitis (EAE). Thus, there are stressors in EAE, other than a pro-inflammatory environment, that are not present in cytokine-treated cells.

中文翻译：

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细胞因子处理的神经元和星形胶质细胞中的蛋白酶体组成主要由亚单位置换确定。

在这项研究中，我们调查了蛋白酶体生物合成中的亚基置换和/或改变是否对培养的神经元和星形胶质细胞中组成型蛋白酶体（c-20S），免疫蛋白酶体（i-20S）以及激活剂PA28和PA700的水平变化负责。与细胞因子混合物（IFN-γ/TNF-α/IL-1β）结合使用。两种细胞类型暴露于细胞因子24小时都会增加i-20S特异性亚基β5i和PA28α/β的mRNA和蛋白表达，并导致c-20S特异性亚基β5的数量减少。由于通过细胞因子处理后，β5mRNA水平没有变化，因此可以得出结论，可诱导性β5i亚基取代组成性β亚基可能是c-20S降低的潜在机制。不出所料 IFN-γ诱导亚基数量的增加与磷酸STAT-1和干扰素调节因子1（IRF-1）的表达升高相吻合。然而，在细胞因子处理的星形胶质细胞中抑制NF-κB信号传导会降低IRF-1表达，而不会影响i-20S，c-20S和PA28的表达。这表明STAT-1本身能够增加i20S特异性亚基和PA28α/β的转录。蛋白酶体β5mRNA表达的降低缺乏与促炎细胞因子不会降低Nrf1（Nfe2l1）和Nrf2（Nfe2l2）水平的事实相符。相比之下，我们以前发现实验性自身免疫性脑脊髓炎（EAE）小鼠的脊髓中存在明显的Nrf1失调和β5mRNA表达降低。因此，EAE中存在压力源，