Characterization of a Lymphoid Organ Specific Anti-lipopolysaccharide Factor From Shrimp Reveals Structure-Activity Relationship of the LPS-Binding Domain
Characterization of a Lymphoid Organ Specific Anti-lipopolysaccharide Factor From Shrimp Reveals Structure-Activity Relationship of the LPS-Binding Domain
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虾淋巴器官特异性抗脂多糖因子的表征揭示了 LPS 结合域的构效关系
DOI：
10.3389/fimmu.2019.00872
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发表时间：
2019-04-24
影响因子：
7.3
通讯作者：
Xiang, Jianhai
中科院分区：
文献类型：
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作者：
Li, Shihao;Lv, Xinjia;Xiang, Jianhai
抗脂多糖因子（ALF）是一类具有广谱抗菌活性的重要抗菌肽。LPS结合结构域（LBD）有助于ALF的主要抗菌活性。然而，来自不同ALF的LBD具有低序列相似性。LBD的共性需要阐明，以了解其功能的分子机制，并促进LBD的原始药物设计。本研究从中国明对虾（Fenneropenaeus chinensis）中鉴定出一种特异性表达ALF的淋巴器官，命名为FcALF 8。合成的FcALF 8 LBD肽（LBD 8）对溶藻弧菌、哈维氏弧菌和发光杆菌等致病性弧菌具有较强的抗菌活性，MIC值分别为0.5 ~ 1、1-2和1-2 μM。使用dsRNA敲低FcALF 8导致在哈维氏弧菌感染后虾的淋巴器官和肝胰腺中活细菌的显著增加。与此相反，经LBD 8预孵育的哈维氏弧菌感染后，其在对虾淋巴器官和肝胰腺中的增殖能力显著下降。序列比对结果表明，39个ALFs的LBD只有两个相同的半胱氨酸残基。然而，在22个LBD残基中，有17个在疏水性和亲水性氨基酸分类时显示出较高的相似性。对LBD 8肽段的进一步活性分析表明，LBD 8肽段线性化后失去了抗菌活性，在某些位置改变氨基酸性质后，抗菌活性明显减弱。数据表明，二硫键和氨基酸的性质有助于功能结构域的保守性。据我们所知，这是第一个确定的ALFs特异性表达的淋巴器官的虾具有较强的抗菌活性。目前的数据将为LBD来源的抗菌药物的设计提供创造性的指导。
Anti-lipopolysaccharide factor (ALF) is a kind of important antimicrobial peptides with broad-spectrum antimicrobial activities. The LPS-binding domain (LBD) contributes to the major antimicrobial activity of ALF. However, LBDs from different ALFs share low sequence similarity. The general character of LBDs needs to be elucidated to understand the molecular mechanism of their function and facilitate LBD-original drug design. Here we identified a lymphoid organ specifically expressed ALF, designated as FcALF8, from the Chinese shrimp Fenneropenaeus chinensis. The synthetic LBD peptide of FcALF8 (LBD8) showed strong antibacterial activities to the pathogenic Vibrio, such as Vibrio alginolyticus, Vibrio harveyi, and Photobacterium damselae with a MIC value of 0.5–1, 1–2, and 1–2 μM, respectively. FcALF8 knock-down using dsRNA led to significant increase of the viable bacteria in the lymphoid organ and hepatopancreas of shrimp upon V. harveyi infection. On the contrary, the proliferation of V. harveyi in the shrimp lymphoid organ and hepatopancreas significantly decreased after infected by LBD8 pre-incubated V. harveyi. Sequence alignments showed that the LBDs from 39 ALFs shared only two identical cysteine residues. However, 17 of the total 22 LBD residues showed high similarity when the amino acids were classified into hydrophobic and hydrophilic ones. A further activity analysis on modified LBD8 peptides showed that the antibacterial activity of LBD8 was lost after linearization and apparently weakened after changing the amino acid property at certain positions. The data indicated that the disulfide bond and amino acid property contributed to the conservation of the functional domain. To the best of our knowledge, this is the first identified ALFs specifically expressed in the lymphoid organ of shrimp with strong antibacterial activity. The present data will give creative instructions for the design of LBD-originated antimicrobial agents.