Leiden/Amsterdam Center for Drug Research, Division of Medicinal Chemistry, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.
Sci Signal. 2010 Aug 3;3(133):ra58. doi: 10.1126/scisignal.2001180.
US28 is a viral G protein (heterotrimeric guanosine triphosphate-binding protein)-coupled receptor encoded by the human cytomegalovirus (HCMV). In addition to binding and internalizing chemokines, US28 constitutively activates signaling pathways linked to cell proliferation. Here, we show increased concentrations of vascular endothelial growth factor and interleukin-6 (IL-6) in supernatants of US28-expressing NIH 3T3 cells. Increased IL-6 was associated with increased activation of the signal transducer and activator of transcription 3 (STAT3) through upstream activation of the Janus-activated kinase JAK1. We used conditioned growth medium, IL-6-neutralizing antibodies, an inhibitor of the IL-6 receptor, and short hairpin RNA targeting IL-6 to show that US28 activates the IL-6-JAK1-STAT3 signaling axis through activation of the transcription factor nuclear factor kappaB and the consequent production of IL-6. Treatment of cells with a specific inhibitor of STAT3 inhibited US28-dependent [(3)H]thymidine incorporation and foci formation, suggesting a key role for STAT3 in the US28-mediated proliferative phenotype. US28 also elicited STAT3 activation and IL-6 secretion in HCMV-infected cells. Analyses of tumor specimens from glioblastoma patients demonstrated colocalization of US28 and phosphorylated STAT3 in the vascular niche of these tumors. Moreover, increased phospho-STAT3 abundance correlated with poor patient outcome. We propose that US28 induces proliferation in HCMV-infected tumors by establishing a positive feedback loop through activation of the IL-6-STAT3 signaling axis.
US28 是一种人类巨细胞病毒 (HCMV) 编码的病毒 G 蛋白 (异三聚体鸟苷三磷酸结合蛋白) 偶联受体。除了结合和内化趋化因子外，US28 还持续激活与细胞增殖相关的信号通路。在这里，我们发现在表达 US28 的 NIH 3T3 细胞的上清液中，血管内皮生长因子和白细胞介素-6 (IL-6) 的浓度增加。IL-6 的增加与信号转导和转录激活因子 3 (STAT3) 的激活增加有关，这是通过 Janus 激活激酶 JAK1 的上游激活引起的。我们使用条件生长培养基、IL-6 中和抗体、IL-6 受体抑制剂和靶向 IL-6 的短发夹 RNA，表明 US28 通过转录因子核因子 kappaB 的激活和随后的 IL-6 产生来激活 IL-6-JAK1-STAT3 信号轴。用 STAT3 的特异性抑制剂处理细胞抑制了 US28 依赖性 [(3)H]胸苷掺入和焦点形成，表明 STAT3 在 US28 介导的增殖表型中起关键作用。US28 还在 HCMV 感染的细胞中引发 STAT3 激活和 IL-6 分泌。对胶质母细胞瘤患者肿瘤标本的分析表明，这些肿瘤的血管龛位中存在 US28 和磷酸化 STAT3 的共定位。此外，磷酸化 STAT3 的丰度增加与患者预后不良相关。我们提出，US28 通过激活 IL-6-STAT3 信号轴建立正反馈环，从而诱导 HCMV 感染的肿瘤增殖。
