Department of Medical Microbiology, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands.
Crystal and Structural Chemistry, Department of Chemistry, Faculty of Science, Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, The Netherlands.
Vet Res. 2018 Nov 28;49(1):115. doi: 10.1186/s13567-018-0609-8.
Staphylococcus aureus is a versatile opportunistic pathogen, causing disease in human and animal species. Its pathogenicity is linked to the ability of S. aureus to secrete immunomodulatory molecules. These evasion proteins bind to host receptors or their ligands, resulting in inhibitory effects through high affinity protein-protein interactions. Staphylococcal evasion molecules are often species-specific due to differences in host target proteins between species. We recently solved the crystal structure of murine TLR2 in complex with immunomodulatory molecule staphylococcal superantigen-like protein 3 (SSL3), which revealed the essential residues within SSL3 for TLR2 inhibition. In this study we aimed to investigate the molecular basis of the interaction on the TLR2 side. The SSL3 binding region on murine TLR2 was compared to that of other species through sequence alignment and homology modeling, which identified interspecies differences. To examine whether this resulted in altered SSL3 activity on the corresponding TLR2s, bovine, equine, human, and murine TLR2 were stably expressed in HEK293T cells and the ability of SSL3 to inhibit TLR2 was assessed. We found that SSL3 was unable to inhibit bovine TLR2. Subsequent loss and gain of function mutagenesis showed that the lack of inhibition is explained by the absence of two tyrosine residues in bovine TLR2 that play a prominent role in the SSL3-TLR2 interface. We found no evidence for the existence of allelic SSL3 variants that have adapted to the bovine host. Thus, within this paper we reveal the molecular determinants of the TLR2-SSL3 interaction which adds to our understanding of staphylococcal host specificity.
金黄色葡萄球菌是一种多功能的机会性病原体，可导致人类和动物物种的疾病。其致病性与金黄色葡萄球菌分泌免疫调节分子的能力有关。这些逃避蛋白与宿主受体或其配体结合，通过高亲和力的蛋白-蛋白相互作用产生抑制作用。由于物种间宿主靶蛋白的差异，葡萄球菌逃避分子通常具有物种特异性。我们最近解决了与免疫调节分子金黄色葡萄球菌超抗原样蛋白 3（SSL3）复合物的鼠 TLR2 的晶体结构，该结构揭示了 SSL3 抑制 TLR2 的必需残基。在这项研究中，我们旨在研究 TLR2 侧相互作用的分子基础。通过序列比对和同源建模比较了鼠 TLR2 上的 SSL3 结合区域与其他物种的结合区域，确定了种间差异。为了研究这是否导致相应 TLR2 上 SSL3 活性的改变，我们在 HEK293T 细胞中稳定表达了牛、马、人、鼠 TLR2，并评估了 SSL3 抑制 TLR2 的能力。我们发现 SSL3 无法抑制牛 TLR2。随后的失活和功能获得突变表明，缺乏抑制作用是由于牛 TLR2 中两个酪氨酸残基的缺失，这两个酪氨酸残基在 SSL3-TLR2 界面中起着重要作用。我们没有发现牛 TLR2 适应的等位 SSL3 变体存在的证据。因此，在本文中，我们揭示了 TLR2-SSL3 相互作用的分子决定因素，这增加了我们对葡萄球菌宿主特异性的理解。
