Division of Dermatology and Venereology, Department of Clinical Sciences, Lund University, SE-221 84 Lund, Sweden;
Division of Dermatology and Venereology, Department of Clinical Sciences, Lund University, SE-221 84 Lund, Sweden.
Proc Natl Acad Sci U S A. 2017 May 23;114(21):E4213-E4222. doi: 10.1073/pnas.1619609114. Epub 2017 May 4.
Effective control of endotoxins and bacteria is crucial for normal wound healing. During injury, the key enzyme thrombin is formed, leading to generation of fibrin. Here, we show that human neutrophil elastase cleaves thrombin, generating 11-kDa thrombin-derived C-terminal peptides (TCPs), which bind to and form amorphous amyloid-like aggregates with both bacterial lipopolysaccharide (LPS) and gram-negative bacteria. In silico molecular modeling using atomic resolution and coarse-grained simulations corroborates our experimental observations, altogether indicating increased aggregation through LPS-mediated intermolecular contacts between clusters of TCP molecules. Upon bacterial aggregation, recombinantly produced TCPs induce permeabilization of and phagocytic uptake. TCPs of about 11 kDa are present in acute wound fluids as well as in fibrin sloughs from patients with infected wounds. We noted aggregation and colocalization of LPS with TCPs in such fibrin material, which indicates the presence of TCP-LPS aggregates under physiological conditions. Apart from identifying a function of proteolyzed thrombin and its fragments, our findings provide an interesting link between the coagulation system, innate immunity, LPS scavenging, and protein aggregation/amyloid formation.
有效控制内毒素和细菌对于正常的伤口愈合至关重要。在损伤过程中，关键酶凝血酶形成，导致纤维蛋白生成。在这里，我们表明人中性粒细胞弹性蛋白酶切割凝血酶，生成 11 kDa 的凝血酶衍生 C 末端肽（TCP），与细菌脂多糖（LPS）和革兰氏阴性菌结合并形成无定形类似淀粉样的聚集物。使用原子分辨率和粗粒度模拟的计算分子建模证实了我们的实验观察结果，总体表明通过 LPS 介导的 TCP 分子簇之间的分子间接触增加了聚集。在细菌聚集后，重组产生的 TCP 诱导通透性和吞噬作用。约 11 kDa 的 TCP 存在于急性伤口液以及感染伤口患者的纤维蛋白鳞屑中。我们注意到在这种纤维蛋白物质中 LPS 与 TCP 的聚集和共定位，这表明在生理条件下存在 TCP-LPS 聚集物。除了鉴定被蛋白水解的凝血酶及其片段的功能外，我们的发现还为凝血系统、先天免疫、LPS 清除和蛋白质聚集/淀粉样形成之间提供了一个有趣的联系。
