Pyrrolidine dithiocarbamate inhibits interleukin-6 signaling through impaired STAT3 activation and association with transcriptional coactivators in hepatocytes
Pyrrolidine dithiocarbamate inhibits interleukin-6 signaling through impaired STAT3 activation and association with transcriptional coactivators in hepatocytes
复制标题
DOI：
10.1074/jbc.m603762200
复制
发表时间：
2006-10-20
影响因子：
4.8
通讯作者：
Bernier, Michel
中科院分区：
文献类型：
--
作者：
He, Hua-Jun;Zhu, Tie-Nian;Bernier, Michel
白细胞介素（IL）-6是一种促炎细胞因子，通过激活JAK/STAT 3途径参与急性期血浆蛋白的表达和肝脏胰岛素抵抗。虽然先前的研究已经证明吡咯烷二硫代氨基甲酸酯（PDTC）对炎症反应具有保护作用，但其在IL-6受体信号转导调节中的作用仍不清楚。在这里，我们表明，培养的HepG 2肝癌细胞与PDTC治疗抑制IL-6刺激的酪氨酸磷酸化和随后的核转位的STAT 3的剂量和时间依赖性的方式。未观察到JAK-1活性的抑制。为了深入了解PDTC信号传导，我们通过将其与雌激素受体的配体结合结构域（STAT 3-ER）融合来构建条件活性STAT 3。在4-羟基他莫昔芬的存在下，STAT 3-ER以磷酸化非依赖性方式在HepG 2细胞核中易位，并且用PDTC处理减轻了反应。虽然STAT 3共沉淀与热休克蛋白90（HSP 90）在控制细胞，共沉淀的两种蛋白质大大减少后PDTC处理或暴露后格尔德霉素，HSP 90抑制剂。结果，IL-6诱导的STAT 3与转录辅激活因子FOXO 1a和C/EBP β的结合减少，SOCS-3蛋白和两种主要急性期血浆蛋白的表达显著减少。重要的是，用PDTC处理HepG 2细胞和大鼠肝细胞的原代培养物恢复了被IL-6废除的胰岛素反应性。这些研究与PDTC通过改变STAT 3-Hsp 90复合物的稳定性来下调IL-6诱导的STAT 3活化的能力一致。
Interleukin (IL)-6 is a proinflammatory cytokine that has been implicated in the expression of acute phase plasma proteins and hepatic insulin resistance through activation of the JAK/STAT3 pathway. Although previous studies have demonstrated that pyrrolidine dithiocarbamate (PDTC) exerts protection against inflammatory responses, its role in the regulation of IL-6 receptor signaling remains unclear. Here we show that treatment of cultured HepG2 hepatoma cells with PDTC inhibits IL-6-stimulated tyrosine phosphorylation and subsequent nuclear translocation of STAT3 in a dose- and time-dependent fashion. No inhibition of JAK-1 activity was observed. To provide insight into PDTC signaling, we constructed a conditionally active STAT3 by fusing it with the ligand binding domain of the estrogen receptor (STAT3-ER). In the presence of 4-hydroxytamoxifen STAT3-ER was translocated in the nucleus of HepG2 cells in a phosphorylation-independent manner, and treatment with PDTC mitigated the response. Although STAT3 coprecipitated with heat-shock protein 90 (Hsp90) in control cells, coprecipitation of the two proteins was greatly reduced after PDTC treatment or after exposure to geldanamycin, an Hsp90 inhibitor. As a result there was a decrease in IL-6-induced association of STAT3 with the transcriptional coactivators FOXO1a and C/EBP beta together with significant reduction in the expression of SOCS-3 protein and that of two major acute phase plasma proteins. Importantly, treatment of HepG2 cells and a primary culture of rat hepatocytes with PDTC restored insulin responsiveness that was abrogated by IL-6. These studies are consistent with the ability of PDTC to down-regulate IL-6-induced STAT3 activation by altering the stability of STAT3-Hsp90 complex.