Tapping Richard I, Tobias Peter S
Department of Microbiology, College of Medicine, University of Illinois, Urbana, Illinois, USA.
J Endotoxin Res. 2003;9(4):264-8. doi: 10.1179/096805103225001477.
Mycobacteria and their cell wall component lipoarabinomannan (LAM) have recently been established as agonists for TLR2. Our transfection studies with single and pairwise combinations of TLRs 1, 2, 6 and 10 reveal that only TLR1 and TLR2 together mediate strong activation of NF-kappaB-driven luciferase activity in response to LAM. Co-operative signaling by TLR1 and TLR2 is observed using either non-capped or mannose-capped LAM as a stimulus. Moreover, we have found that phosphatidylinositol mannosides, simple biosynthetic precursors of LAM, also activate cells through the combined actions of TLR1 and TLR2. Co-immunoprecipitation studies show that TLR1 and TLR2 are physically associated, independently of the presence of LAM. To address the mechanism of LAM-induced TLR activation we have used TLR fusion proteins in a protein fragment complementation assay. The results of this assay suggest that LAM alters the physical interaction between the intracellular signaling domains of TLR1 and TLR2. Together, these results identify LAM as an agonist for TLR1 and TLR2 and support the idea that LAM initiates transmembrane signaling by altering the physical association between TLR1 and TLR2.
分枝杆菌及其细胞壁成分脂阿拉伯甘露聚糖（LAM）最近已被确认为Toll样受体2（TLR2）的激动剂。我们对TLR1、TLR2、TLR6和TLR10进行单一组合及两两组合的转染研究发现，只有TLR1和TLR2共同作用才能介导对LAM产生强烈的NF-κB驱动的荧光素酶活性激活。使用未封端或甘露糖封端的LAM作为刺激物时，均可观察到TLR1和TLR2的协同信号传导。此外，我们发现磷脂酰肌醇甘露糖苷（LAM的简单生物合成前体）也通过TLR1和TLR2的联合作用激活细胞。免疫共沉淀研究表明，TLR1和TLR2在物理上相互关联，且与LAM的存在无关。为了探究LAM诱导TLR激活的机制，我们在蛋白质片段互补分析中使用了TLR融合蛋白。该分析结果表明，LAM改变了TLR1和TLR2细胞内信号结构域之间的物理相互作用。这些结果共同确定LAM为TLR1和TLR2的激动剂，并支持LAM通过改变TLR1和TLR2之间的物理关联来启动跨膜信号传导这一观点。
