E3 ubiquitin ligase NKLAM ubiquitinates STAT1 and positively regulates STAT1-mediated transcriptional activity.
E3 ubiquitin ligase NKLAM ubiquitinates STAT1 and positively regulates STAT1-mediated transcriptional activity.
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DOI：
10.1016/j.cellsig.2016.08.014
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发表时间：
2016-12
影响因子：
4.8
通讯作者：
Kornbluth J
中科院分区：
文献类型：
--
作者：
Lawrence DW;Kornbluth J
信号转导子和转录激活子1（STAT 1）对大量免疫相关基因的转录至关重要。在巨噬细胞中，干扰素γ（IFNγ）信号转导通过JAK/STAT途径发生，并以成功的宿主免疫应答所必需的许多基因的转录结束。STAT 1的主要调节机制是磷酸化;然而，越来越多的证据表明STAT 1也受到泛素化的调节。在这份报告中，我们表明，JAK 1和STAT 1在缺乏E3泛素连接酶称为自然杀伤细胞溶解相关分子（NKLAM）的巨噬细胞在IFNγ刺激后过度磷酸化。我们发现NKLAM在IFNγ刺激期间瞬时定位于IFNγ受体复合物，在那里它结合并介导K63连接的STAT 1泛素化。体外核转染研究表明，STAT 1介导的转录在NKLAM-KO巨噬细胞中显著降低。STAT 1核转位没有明显缺陷;然而，来自NKLAM-KO巨噬细胞的STAT 1结合功能性γ激活DNA序列的能力降低。在IFNγ处理的NKLAM-KO巨噬细胞中，STAT 1介导的基因的mRNA表达也减少。我们的研究结果首次表明，NKLAM是STAT 1介导的转录活性的正调控因子，是先天免疫反应的重要组成部分。
Signal transducer and activator of transcription 1 (STAT1) is critically important for the transcription of a large number of immunologically relevant genes. In macrophages, interferon gamma (IFNγ) signal transduction occurs via the JAK/STAT pathway and ends with the transcription of a number of genes necessary for a successful host immune response. The predominant mechanism of regulation of STAT1 is phosphorylation; however, there is a growing body of evidence that demonstrates STAT1 is also regulated by ubiquitination. In this report we show that JAK1 and STAT1 in macrophages deficient in an E3 ubiquitin ligase termed Natural Killer Lytic-Associated Molecule (NKLAM) are hyperphosphorylated following IFNγ stimulation. We found NKLAM was transiently localized to the IFNγ receptor complex during stimulation with IFNγ, where it bound to and mediated K63-linked ubiquitination of STAT1. In vitro nucleofection studies demonstrated that STAT1-mediated transcription was significantly reduced in NKLAM-KO macrophages. There was no obvious defect in STAT1 nuclear translocation; however, STAT1 from NKLAM-KO macrophages had a reduced ability to bind a functional gamma activation DNA sequence. There was also less mRNA expression of STAT1-mediated genes in NKLAM-KO macrophages treated with IFNγ. Our results demonstrate for the first time that NKLAM is a positive regulator of STAT1-mediated transcriptional activity and is an important component of the innate immune response.
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