Phosphorylation of STAT-1 serine 727 is prolonged in HLA-B27-expressing human monocytic cells.
Phosphorylation of STAT-1 serine 727 is prolonged in HLA-B27-expressing human monocytic cells.
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DOI：
10.1371/journal.pone.0050684
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发表时间：
2013
期刊：
影响因子：
3.7
通讯作者：
Penttinen MA
中科院分区：
文献类型：
--
作者：
Ruuska M;Sahlberg AS;Granfors K;Penttinen MA
一种组织抗原，人类白细胞抗原B27，与一组称为脊柱性关节炎的风湿性疾病密切相关。尽管进行了深入的研究，但人类白细胞抗原B27在这些疾病的发病机制中的确切作用仍不清楚。在这里，我们研究了人类白细胞抗原B27是否调节信号转导和转录激活因子1(STAT-1)丝氨酸727残基的磷酸化以及STAT-1在沙门氏菌感染的人单核细胞中的定位。此外，我们还研究了信号分子双链RNA激活的蛋白激酶(PKR)在这些调控效应中的作用。制备了稳定表达野生型或突变型人类白细胞抗原-B27重链的U937人单核细胞转染体。PMA分化细胞感染肠炎沙门氏菌。Western blotting检测STAT-1的磷酸化，共聚焦显微镜观察STAT-1在细胞内的定位。使用特异性抑制剂研究PKR在STAT-1磷酸化中的作用。我们发现在肠炎链霉菌感染后，表达错折叠形式的HLA-B27的细胞中STAT-1丝氨酸727的磷酸化时间延长，而在模拟细胞和表达突变的、非错折叠的HLA-B27的细胞中，丝氨酸727的磷酸化是短暂的。有趣的是，STAT-1丝氨酸727的磷酸化部分依赖于PKR。此外，与模拟细胞相比，甚至在外部触发之前，更多的STAT-1定位于表达HLA-B27的细胞的细胞核中。综上所述，我们的结果表明，细菌感染后表达人类白细胞抗原-B27的单核-巨噬细胞U937细胞中STAT-1丝氨酸727残基的磷酸化延长。这一点很有意义，因为STAT-1上丝氨酸727的磷酸化被认为有助于巨噬细胞的激活和促进炎症反应。因此，我们的结果提供了一种机制，解释了HLA-B27分子的表达如何影响沙门氏菌感染和反应性关节炎的过程。
A tissue antigen, HLA-B27, is strongly associated with a group of rheumatic diseases called spondyloarthritides. Despite the intensive research, the exact role of HLA-B27 in the pathogenesis of these diseases is still unclear. Here we studied whether HLA-B27 modulates the phosphorylation of signal transducer and activator of transcription 1 (STAT-1) serine 727 residue and the localization of STAT-1 in Salmonella-infected human monocytic cells. In addition, we studied the role of signaling molecule double-stranded RNA activated protein kinase (PKR) in these modulatory effects. U937 human monocytic cell transfectants stably expressing wild type HLA-B27 or mutated HLA-B27 heavy chains with amino acid substitutions in the B pocket were prepared. The PMA-differentiated cells were infected with S. enteritidis. Western blotting was used to detect the phosphorylation of STAT-1, and to visualize the localization of STAT-1 in the cells confocal microscopy was used. Specific inhibitors were employed to study the role of PKR in STAT-1 phosphorylation. We discovered that the phosphorylation of STAT-1 serine 727 is prolonged in cells expressing misfolding forms of HLA-B27 after S. enteritidis infection, whereas in mock cells and in cells expressing mutated, non-misfolding HLA-B27 the phosphorylation of serine 727 is transient. Interestingly, STAT-1 serine 727 phosphorylation is partly dependent on PKR. In addition, more STAT-1 is localized in the nucleus of HLA-B27-expressing cells, even before an external trigger, when compared to mock cells. In conclusion, our results show that the phosphorylation of STAT-1 serine 727 residue is prolonged in HLA-B27-expressing monocyte-macrophage U937 cells after bacterial infection. This is of interest since the phosphorylation of serine 727 on STAT-1 is suggested to contribute to macrophage activation and promote inflammatory responses. Therefore, our results provide a mechanism which explains how the expression of an HLA-B27 molecule can impact the course of Salmonella infection and reactive arthritis.
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