Studies on citrullinated LL-37: detection in human airways, antibacterial effects and biophysical properties
Studies on citrullinated LL-37: detection in human airways, antibacterial effects and biophysical properties
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DOI：
10.1038/s41598-020-59071-7
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发表时间：
2020-02-11
影响因子：
4.6
通讯作者：
Bergman, Peter
中科院分区：
文献类型：
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作者：
Al-Adwani, Salma;Wallin, Cecilia;Bergman, Peter
抗菌肽LL-37的精氨酸残基可以被肽基精氨酸脱亚胺酶瓜氨酸化，从而降低抗菌肽的正电荷。值得注意的是，在人体样本中尚未检测到瓜氨酸化的LL-37。此外，瓜氨酸化的LL-37的功能和生物物理性质还没有得到充分的研究。本研究的目的是检测人支气管肺泡灌洗液(BAL)中的瓜氨酸化LL-37，并确定瓜氨酸化LL-37的抗菌和生物物理性质。BAL液取自健康人体志愿者，经支气管内暴露于脂多糖。合成的多肽用于杀菌试验、透射电子显微镜、等温滴定量热法、质谱学和圆二色谱分析。利用靶向蛋白质组学，我们能够在BAL液中检测到天然的和瓜氨酸的LL-37。瓜氨酸肽不能杀死大肠杆菌，也不能裂解人的红细胞。圆二色谱表明，两种多肽具有相似的α-螺旋二级结构，但瓜氨酸化的LL-37在较高温度下更稳定。综上所述，瓜氨酸化的LL-37存在于人的呼吸道中，瓜氨酸化作用削弱了细菌的杀灭作用，表明净正电荷对于抗菌和膜裂解作用是重要的。通过改变关键功能，瓜氨酸有可能作为AMP功能的动态平衡调节剂。
Arginine residues of the antimicrobial peptide LL-37 can be citrullinated by peptidyl arginine deiminases, which reduce the positive charge of the peptide. Notably, citrullinated LL-37 has not yet been detected in human samples. In addition, functional and biophysical properties of citrullinated LL-37 are not fully explored. The aim of this study was to detect citrullinated LL-37 in human bronchoalveolar lavage (BAL) fluid and to determine antibacterial and biophysical properties of citrullinated LL-37. BAL fluid was obtained from healthy human volunteers after intra-bronchial exposure to lipopolysaccharide. Synthetic peptides were used for bacterial killing assays, transmission electron microscopy, isothermal titration calorimetry, mass-spectrometry and circular dichroism. Using targeted proteomics, we were able to detect both native and citrullinated LL-37 in BAL fluid. The citrullinated peptide did not kill Escherichia coli nor lysed human red blood cells. Both peptides had similar alpha -helical secondary structures but citrullinated LL-37 was more stable at higher temperatures, as shown by circular dichroism. In conclusion, citrullinated LL-37 is present in the human airways and citrullination impaired bacterial killing, indicating that a net positive charge is important for antibacterial and membrane lysing effects. It is possible that citrullination serves as a homeostatic regulator of AMP-function by alteration of key functions.