IFN-γ-Induced MHC class II expression:: Transactivation of class II transactivator promoter IV by IFN regulatory factor-1 is regulated by protein kinase C-α
IFN-γ-Induced MHC class II expression:: Transactivation of class II transactivator promoter IV by IFN regulatory factor-1 is regulated by protein kinase C-α
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DOI：
10.4049/jimmunol.171.8.4187
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发表时间：
2003-10-15
影响因子：
4.4
通讯作者：
Descoteaux, A
中科院分区：
文献类型：
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作者：
Giroux, M;Schmidt, M;Descoteaux, A
先前基于药理学证据的研究表明，在ifn - γ诱导的MHC II类（MHC-II）表达的调节中需要蛋白激酶C （PKC）活性。在本研究中，我们研究了pkc - α调节ifn - γ诱导的小鼠巨噬细胞系RAW 264.7中MHC-II表达的分子机制。过表达pkc - α的显性阴性（DN）突变体抑制IFN- γ诱导的MHC- ii的表达，但对IFN- γ诱导的STAT1核易位和DNA结合活性，以及诱导no合成酶、IFN一致序列结合蛋白、MHC 1类、IFN调节因子(IRF)-1和IFN- γ诱导蛋白-10的表达没有影响。进一步的分析表明，ifn - γ诱导的MHC II类反激活因子（CIITA）的表达在DN pkc - α过表达的细胞中被抑制，CIITA是MHC-II表达所必需的转录辅激活因子。对含有CIITA启动子IV区的报告基因构建体的研究表明，pkc - α的组成型活性突变体的过表达增强了IRF-1的转录活性，而不是IRF-2的转录活性。此外，对正常细胞和DN pkc - α过表达细胞的IRF-1的表征揭示了IRF-1转化后修饰的差异。总的来说，我们的数据表明ifn - γ诱导MHC-II表达的一种新的调节机制，PKC通过选择性调节IRF-1的转录活性来调节CIITA的表达。
Previous studies based on pharmacological evidence suggested a requirement for protein kinase C (PKC) activity in the regulation of IFN-gamma-induced MHC class II (MHC-II) expression. In the present study, we investigated the molecular mechanisms by which PKC-alpha modulates IFN-gamma-induced MHC-II expression in the mouse macrophage cell line RAW 264.7. Overexpression of a dominant-negative (DN) mutant of PKC-alpha inhibited the expression of IFN-gamma-induced MHC-II but had no effect on IFN-gamma-induced STAT1 nuclear translocation and DNA binding activity, as well as on the expression of inducible NO synthase, IFN consensus sequence binding protein, MHC class 1, IFN regulatory factor (IRF)-1, and IFN-gamma-inducible protein-10. Further analysis showed that IFN-gamma-induced expression of the MHC class II transactivator (CIITA), a transcriptional coactivator essential for MHC-II expression, was inhibited in DN PKC-alpha-overexpressing cells. Studies with reporter constructs containing the promoter IV region of CIITA revealed that overexpression of a constitutively active mutant of PKC-alpha enhanced IRF-1, but not IRF-2, transcriptional activity. Furthermore, characterization of IRF-1 from both normal and DN PKC-alpha-overexpressing cells revealed differences in IRF-1 posttranstational modifications. Collectively, our data suggest a novel regulatory mechanism for IFN-gamma-induced MHC-II expression, whereby PKC regulates CIITA expression by selectively modulating the transcriptional activity of IRF-1.