Core fucosylation, a post-translational modification of N-glycans, modifies several growth factor receptors and impacts on their ligand binding affinity. Core-fucose-deficient mice generated by ablating the α1,6 fucosyltransferase enzyme, Fut8, exhibit severe pulmonary emphysema, partly due to impaired macrophage function, similar to aged Toll-like receptor 4 (Tlr4) -deficient mice. We therefore suspect that a lack of core fucose affects the TLR4-dependent signaling pathway. Indeed, upon lipopolysaccharide stimulation, Fut8-deficient mouse embryonic fibroblasts (MEFs) produced similar levels of interleukin-6 but markedly reduced levels of interferon-β (IFN-β) compared with wild-type MEFs. Lectin blot analysis of the TLR4 signaling complex revealed that core fucosylation was specifically found on CD14. Even though similar levels of TLR4/myeloid differentiation factor 2 (MD2) activation and dimerization were observed in Fut8-deficient cells after lipopolysaccharide stimulation, internalization of TLR4 and CD14 was significantly impaired. Given that internalized TLR4/MD2 induces IFN-β production, impaired IFN-β production in Fut8-deficient cells is ascribed to impaired TLR4/MD2 internalization. These data show for the first time that glycosylation critically regulates TLR4 signaling.

中文翻译：

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核心岩藻糖对于依赖CD14的Toll样受体4信号传导至关重要

N-聚糖的翻译后修饰核心岩藻糖基化修饰了几种生长因子受体，并影响了它们的配体结合亲和力。通过消融α1,6岩藻糖基转移酶Fut8产生的核心岩藻糖缺乏小鼠表现出严重的肺气肿，部分原因是巨噬细胞功能受损，类似于衰老的Toll样受体4（Tlr4）缺乏小鼠。因此，我们怀疑缺乏核心岩藻糖会影响TLR4依赖的信号通路。确实，在脂多糖刺激下，Fut8缺陷小鼠胚胎成纤维细胞（MEF）与野生型MEF相比，产生的白介素6水平相似，但干扰素-β（IFN-β）水平明显降低。对TLR4信号复合物的凝集素印迹分析表明，核心岩藻糖基化特别是在CD14上发现的。即使在脂多糖刺激后在Fut8缺陷型细胞中观察到相似水平的TLR4 /髓样分化因子2（MD2）活化和二聚化，TLR4和CD14的内在化也显着受损。考虑到内在化的TLR4 / MD2诱导IFN-β的产生，Fut8缺陷细胞中IFN-β产生的受损归因于TLR4 / MD2的内在化。这些数据首次显示糖基化关键性调节TLR4信号传导。