Libardo M Daben J, Gorbatyuk Vitaliy Y, Angeles-Boza Alfredo M
Department of Chemistry, University of Connecticut , Unit 3060, 55 North Eagleville Road, Storrs, Connecticut 06269, United States.
Biotechnology and Bioservices Center, University of Connecticut , Unit 3149, 91 North Eagleville Road, Storrs, Connecticut 06269, United States.
ACS Infect Dis. 2016 Jan 8;2(1):71-81. doi: 10.1021/acsinfecdis.5b00140. Epub 2015 Dec 14.
Ticks transmit multiple pathogens to different hosts without compromising their health. Their ability to evade microbial infections is largely a result of their effective innate immune response including various antimicrobial peptides. Therefore, a deep understanding of how ticks (and other arthropod vectors) control microbial loads could lead to the design of broad-spectrum antimicrobial agents. In this paper we study the role of the amino-terminal copper and nickel (ATCUN)-binding sequence in the peptide ixosin, isolated from the salivary glands of the hard tick Ixodes sinensis. Our results indicate that the ATCUN motif is not essential to the potency of ixosin, but is indispensable to its oxidative mechanism of action. Specifically, the ATCUN motif promotes dioxygen- and copper-dependent lipid (per)oxidation of bacterial membranes in a temporal fashion coinciding with the onset of bacterial death. Microscopy and studies on model membranes indicate that the oxidized phospholipids are utilized as potential targets of ixosin B (another tick salivary gland peptide) involving its delocalization to the bacterial membrane, thus resulting in a synergistic effect. Our proposed mechanism of action highlights the centrality of the ATCUN motif to ixosin's mechanism of action and demonstrates a novel way in which (tick) antimicrobial peptides (AMPs) utilize metal ions in its activity. This study suggests that ticks employ a variety of effectors to generate an amplified immune response, possibly justifying its vector competence.
蜱虫可将多种病原体传播给不同宿主，而自身健康却不受影响。它们能够抵御微生物感染，很大程度上得益于其有效的固有免疫反应，其中包括各种抗菌肽。因此，深入了解蜱虫（以及其他节肢动物媒介）如何控制微生物负荷，可能会促成广谱抗菌剂的设计。在本文中，我们研究了从中华硬蜱唾液腺中分离出的肽类——异索辛（ixosin）中氨基末端铜镍（ATCUN）结合序列的作用。我们的研究结果表明，ATCUN基序对异索辛的效力并非至关重要，但对其氧化作用机制却是不可或缺的。具体而言，ATCUN基序以一种与细菌死亡起始时间相吻合的时间模式，促进细菌膜的双加氧和铜依赖性脂质（过）氧化。显微镜检查和对模型膜的研究表明，氧化磷脂被用作异索辛B（另一种蜱唾液腺肽）的潜在靶点，这涉及到异索辛B向细菌膜的重新定位，从而产生协同效应。我们提出的作用机制突出了ATCUN基序在异索辛作用机制中的核心地位，并展示了（蜱虫）抗菌肽（AMPs）在其活性中利用金属离子的一种新方式。这项研究表明，蜱虫利用多种效应物来产生放大的免疫反应，这可能解释了它作为传播媒介的能力。
