Essential roles of CD14 and lipopolysaccharide-binding protein for activation of toll-like receptor (TLR)2 as well as TLR4 Reconstitution of TLR2- and TLR4-activation by distinguishable ligands in LPS preparations.

摘要: Although genetic studies have revealed a critical role for the toll-like receptor (TLR) 4 in biological response to lipopolysaccharide (LPS), activities of ectopically expressed TLR4 and TLR2 are controversial. We found that under appropriate transfection conditions, both mediate LPS-induced NF-kappaB activation human embryonic kidney 293 cells. The reconstitution systems we established here allow direct biochemical characterization comparison each receptor. is approximately 100-fold more sensitive LPS than TLR2. In contrast commercial preparations, unresponsive repurified or synthetic lipid A, indicating requirement an additional molecule(s). On other hand, A-neutralizing reagent, polymyxin B, blocks ability preparation stimulate receptors, suggesting A also involved Mutant TLRs harboring point mutation cytoplasmic domain inactive transducing signal upon stimulation, act as dominant-negative mutants specifically inhibiting corresponding type but not type. Thus, two receptors independently activated by distinguishable ligands. Nevertheless, responses strongly dependent on serum CD14 LPS-binding protein essential receptors. Supporting its functional significance, associate with CD14.