Phagosomal signaling by Borrelia burgdorferi in human monocytes involves Toll-like receptor (TLR) 2 and TLR8 cooperativity and TLR8-mediated induction of IFN-β
Phagosomal signaling by Borrelia burgdorferi in human monocytes involves Toll-like receptor (TLR) 2 and TLR8 cooperativity and TLR8-mediated induction of IFN-β
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DOI：
10.1073/pnas.1013776108
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发表时间：
2011-03-01
影响因子：
11.1
通讯作者：
Salazar, Juan C.
中科院分区：
文献类型：
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作者：
Cervantes, Jorge L.;Dunham-Ems, Star M.;Salazar, Juan C.
吞噬的伯氏疏螺旋体（Bb）诱导的炎症信号在数量和质量上都不同于由螺旋体脂蛋白与人单核细胞表面上的Toll样受体（TLR）1/2相互作用所产生的炎症信号。特别重要的是，与脂蛋白相反，内化的螺旋体诱导IFN-β的转录。使用特异于TLR 7、TLR 8和TLR 9的抑制性免疫调节DNA序列（IRSs），我们表明TLR 8抑制剂IRS 957显著减少TNF-α、IL-6和IL-10的产生，并完全消除BB刺激的单核细胞中IFN-β的转录。我们证明，活Bb诱导TLR 2和TLR 8的转录，而IRS 957干扰其转录调控。使用共聚焦和落射荧光显微镜，我们表明，在未受刺激的单核细胞中的基线TLR表达是大于TLR 2比TLR 8，而这两个TLR的表达增加显着刺激后，活螺旋体。通过共聚焦显微镜，我们发现，TLR 2与Bb共定位与结合，摄取和形成的吞噬体空泡相一致，而TLR 2和TLR 8的招募与螺旋体的降解重叠。我们提供的证据表明，干扰素调节因子（IRF）7易位到BB感染的单核细胞的细胞核，这表明其通过磷酸化激活。总之，这些发现表明，吞噬体是一个有效的平台，用于识别不同的配体;在Bb的情况下，吞噬体信号转导涉及TLR 2和TLR 8之间的合作相互作用，在亲和亲细胞因子的反应，而TLR 8是唯一负责IRF 7介导的诱导IFN-β。
Phagocytosed Borrelia burgdorferi (Bb) induces inflammatory signals that differ both quantitatively and qualitatively from those generated by spirochetal lipoproteins interacting with Toll-like receptor (TLR) 1/2 on the surface of human monocytes. Of particular significance, and in contrast to lipoproteins, internalized spirochetes induce transcription of IFN-beta. Using inhibitory immunoregulatory DNA sequences (IRSs) specific to TLR7, TLR8, and TLR9, we show that the TLR8 inhibitor IRS957 significantly diminishes production of TNF-alpha, IL-6, and IL-10 and completely abrogates transcription of IFN-beta in Bb-stimulated monocytes. We demonstrate that live Bb induces transcription of TLR2 and TLR8, whereas IRS957 interferes with their transcriptional regulation. Using confocal and epifluorescence microscopy, we show that baseline TLR expression in unstimulated monocytes is greater for TLR2 than for TLR8, whereas expression of both TLRs increases significantly upon stimulation with live spirochetes. By confocal microscopy, we show that TLR2 colocalization with Bb coincides with binding, uptake, and formation of the phagosomal vacuole, whereas recruitment of both TLR2 and TLR8 overlaps with degradation of the spirochete. We provide evidence that IFN regulatory factor (IRF) 7 is translocated into the nucleus of Bb-infected monocytes, suggesting its activation through phosphorylation. Taken together, these findings indicate that the phagosome is an efficient platform for the recognition of diverse ligands; in the case of Bb, phagosomal signaling involves a cooperative interaction between TLR2 and TLR8 in pro-and antiinflammatory cytokine responses, whereas TLR8 is solely responsible for IRF7-mediated induction of IFN-beta.