Enhaced induction of the immunoproteasome by interferon gamma in neurons expressing mutant Huntingtin
Enhaced induction of the immunoproteasome by interferon gamma in neurons expressing mutant Huntingtin
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DOI：
10.1007/bf03033282
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发表时间：
2004-01-01
影响因子：
3.7
通讯作者：
Lucas, JJ
中科院分区：
文献类型：
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作者：
Díaz-Hernández, M;Martín-Aparicio, E;Lucas, JJ
亨廷顿病（HD）包涵体用抗泛素和抗蛋白酶体抗体染色。这与转染细胞的蛋白酶体活性研究一起表明，泛素-蛋白酶体系统（UPS）的改变可能有助于HD的发病。在之前的工作中，我们报道了在亨廷顿氏病的条件小鼠模型（HD94小鼠）中，在受影响和含有聚集体的大脑区域：纹状体和皮层中，蛋白酶体的化学胰蛋白酶和胰蛋白酶“样”活性选择性地增加。此外，在这些区域，观察到免疫蛋白酶体LMP2和LPM7的干扰素诱导亚基的神经元增加。为了检验n端突变亨廷顿蛋白（htt）本身的表达是否足以诱导蛋白酶体催化活性和LMP2亚基表达的变化，我们在没有神经胶质污染的HD94小鼠纹状体培养神经元中进行了蛋白酶体三种不同肽酶活性的酶促测定和western blot实验。我们发现这些细胞的任何活动都没有变化。此外，用针对LMP2亚基的特异性抗体进行的western blot分析显示，与对照培养相比，HD94纹状体神经元中LMP2亚基的水平没有差异。另一方面，当纹状体培养物在72小时内用干扰素- γ (ifn - γ)处理时，在对照神经元培养物中观察到LMP2水平明显增加。有趣的是，这种增加在HD94纹状体培养中更为明显（高出95%）。这些结果表明，虽然突变体htt的表达不足以诱导HD中观察到的蛋白酶体催化核心的变化，但它可以协同ifn - γ诱导的变化。此外，免疫细胞化学研究显示，表达高水平LMP2亚基的HD94纹状体神经元表现出凋亡前的外观。这些结果表明，在HD脑中发现的免疫蛋白酶体的神经元诱导与神经变性之间的相关性是继发于炎症过程的。
Huntington disease (HD) inclusions are stained with anti-ubiquitin and anti-proteasome antibodies. This, together with proteasome activity studies on transfected cell, suggested that alterations in the ubiquitin-proteasome system (UPS) might contribute to HD pathogenesis. In a previous work we reported that in a conditional mouse model of Huntington's disease (HD94 mice), the chymiotrypsin- and trypsin-"like" activities of the proteasome are increased selectively in the affected and aggregate-containing brain regions: striatum and cortex. Moreover, in these areas a neuronal increase in the interferon-inducible subunits of the immunoproteasome LMP2 and LPM7 was observed. In order to test if the expression of N-terminal mutant huntingtin (htt) by itself is sufficient to induce the change in proteasome catalytic activities as well as in LMP2 subunit expression, we performed enzymatic assays for the three different peptidase activities of the proteasome and western blot experiments in striatal cultured neurons from HD94 mice free of glial contamination. We found no changes in any of the activities in these cells. Furthermore, western blot analysis performed with specific antibody against LMP2 subunits, revealed no difference in levels of this subunit in striatal neurons from HD94 compared to control cultures. On the other hand, when the striatal cultures were treated with interferon-gamma (IFN-gamma) during 72 hours, a clear increase in LMP2 levels was observed in control neuronal cultures. Interestingly, this increase was much more pronounced (95% higher) in HD94 striatal cultures. These results indicate that although expression of mutant htt is not sufficient to induce the changes in proteasome catalytic core observed in HD, it synergizes the changes induced by IFN-gamma. Furthermore, immunocytochemical studies revealed that HD94 striatal neurons expressing high levels of LMP2 subunit showed a pre-apoptotic appearance. These results suggest that the correlation between neuronal induction of the inmuno-proteasome and neurodegeneration found in HD brains is secondary to inflammatory processes.