Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB30ES, UK.
Vet Res. 2013 Jul 4;44(1):50. doi: 10.1186/1297-9716-44-50.
TLR2 recognises bacterial lipopeptides and lipoteichoic acid, and forms heterodimers with TLR1 or TLR6. TLR2 is relatively well characterised in mice and humans, with published crystal structures of human TLR2/1/Pam3CSK4 and murine TLR2/6/Pam2CSK4. Equine TLR4 is activated by a different panel of ligands to human and murine TLR4, but less is known about species differences at TLR2. We therefore cloned equine TLR2, TLR1 and TLR6, which showed over 80% sequence identity with these receptors from other mammals, and performed a structure-function analysis. TLR2/1 and TLR2/6 from both horses and humans dose-dependently responded to lipoteichoic acid from Staphylococcus aureus, with no significant species difference in EC50 at either receptor pair. The EC50 of Pam2CSK4 was the same for equine and human TLR2/6, indicating amino acid differences between the two species' TLRs do not significantly affect ligand recognition. Species differences were seen between the responses to Pam2CSK4 and Pam3CSK4 at TLR2/1. Human TLR2/1, as expected, responded to Pam3CSK4 with greater potency and efficacy than Pam2CSK4. At equine TLR2/1, however, Pam3CSK4 was less potent than Pam2CSK4, with both ligands having similar efficacies. Molecular modelling indicates that the majority of non-conserved ligand-interacting residues are at the periphery of the TLR2 binding pocket and in the ligand peptide-interacting regions, which may cause subtle effects on ligand positioning. These results suggest that there are potentially important species differences in recognition of lipopeptides by TLR2/1, which may affect how the horse deals with bacterial infections.
TLR2 识别细菌脂肽和脂磷壁酸，并与 TLR1 或 TLR6 形成异二聚体。TLR2 在小鼠和人类中得到了较好的描述，已有人类 TLR2/1/Pam3CSK4 和鼠 TLR2/6/Pam2CSK4 的晶体结构发表。马 TLR4 被一组不同于人 TLR4 和鼠 TLR4 的配体激活，但关于 TLR2 的种间差异知之甚少。因此，我们克隆了马 TLR2、TLR1 和 TLR6，它们与其他哺乳动物的这些受体具有 80%以上的序列同一性，并进行了结构-功能分析。来自马和人的 TLR2/1 和 TLR2/6 均对金黄色葡萄球菌的脂磷壁酸呈剂量依赖性反应，在这两种受体对中，EC50 没有明显的种间差异。Pam2CSK4 对马和人 TLR2/6 的 EC50 相同，表明两种物种 TLR 之间的氨基酸差异不会显著影响配体识别。在 TLR2/1 对 Pam2CSK4 和 Pam3CSK4 的反应中观察到种间差异。如预期的那样，人 TLR2/1 对 Pam3CSK4 的反应比 Pam2CSK4 更有效。然而，在马 TLR2/1 中，Pam3CSK4 的效力低于 Pam2CSK4，两种配体的效力相似。分子建模表明，大多数非保守的配体相互作用残基位于 TLR2 结合口袋的外围和配体肽相互作用区域，这可能对配体定位产生微妙影响。这些结果表明，TLR2/1 对脂肽的识别可能存在潜在的重要种间差异，这可能影响马对细菌感染的处理方式。
