Phosphorylation of 20S proteasome alpha subunit C8 (α7) stabilizes the 26S proteasome and plays a role in the regulation of proteasome complexes by γ-interferon
Phosphorylation of 20S proteasome alpha subunit C8 (α7) stabilizes the 26S proteasome and plays a role in the regulation of proteasome complexes by γ-interferon
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DOI：
10.1042/bj20031122
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发表时间：
2004-02-15
影响因子：
4.1
通讯作者：
Rivett, AJ
中科院分区：
文献类型：
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作者：
Bose, S;Stratford, FLL;Rivett, AJ
在动物细胞中，有几种调节复合物与20S蛋白酶体相互作用，产生功能不同的蛋白酶体复合物。γ -干扰素上调20S蛋白酶体和PA28调节因子的三个免疫β催化亚基，降低26S蛋白酶体的水平。它还降低了两个蛋白酶体α亚基C8 （alpha7）和C9 （alpha3）的磷酸化水平。在本研究中，我们研究了蛋白激酶CK2磷酸化C8在26S蛋白酶体形成和稳定性中的作用。在哺乳动物细胞中表达的表位标记的C8亚基被有效地整合到20S蛋白酶体和26S蛋白酶体中。对两个已知CK2磷酸化位点的C8突变体的研究表明，这是动物细胞中C8的两个磷酸化位点。虽然C8的磷酸化对26S蛋白酶体的形成并不是绝对必要的，但它确实对其稳定性有实质性的影响。此外，当细胞用γ -干扰素处理时，C8的磷酸化水平明显降低，26S蛋白酶体水平降低，免疫蛋白酶体和PA28复合物水平增加。这些结果表明，γ -干扰素治疗后26S蛋白酶体的下调是由于C8亚基去磷酸化后发生的不稳定。
In animal cells there are several regulatory complexes which interact with 20S proteasomes and give rise to functionally distinct proteasome complexes. gamma-Interferon upregulates three immuno beta catalytic subunits of the 20S proteasome and the PA28 regulator, and decreases the level of 26S proteasomes. It also decreases the level of phosphorylation of two proteasome alpha subunits, C8 (alpha7) and C9 (alpha3). In the present study we have investigated the role of phosphorylation of C8 by protein kinase CK2 in the fort-nation and stability of 26S proteasomes. An epitope-tagged C8 subunit expressed in mammalian cells was efficiently incorporated into both 20S proteasomes and 26S proteasomes. Investigation of mutants of C8 at the two known CK2 phosphorylation sites demonstrated that these are the two phosphorylation sites of C8 in animal cells. Although phosphorylation of C8 was not absolutely essential for the formation of 26S proteasomes, it did have a substantial effect on their stability. Also, when cells were treated with gamma-interferon, there was a marked decrease in phosphorylation of C8, a decrease in the level of 26S proteasomes, and an increase in immunoproteasomes and PA28 complexes. These results suggest that the down-regulation of 26S proteasomes after gamma-interferon treatment results from the destabilization that occurs after dephosphorylation of the C8 subunit.