Chen Hao, Zhou Zhi, Wang Lingling, Wang Hao, Liu Rui, Zhang Huan, Song Linsheng
Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, People's Republic of China University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, People's Republic of China.
Open Biol. 2016 Aug;6(8). doi: 10.1098/rsob.160059.
Acetylcholine (ACh) is the main neurotransmitter in the cholinergic neuroendocrine system and plays an indispensable role in modulating diverse immune responses. As important transporters in choline uptake, choline transporter-like proteins (CTLs) can control ACh synthesis and release indirectly in multiple organisms. In this study, cgi-miR-2d, an invertebrate-specific miRNA in oyster Crassostrea gigas, is proved to repress the synthesis/release of ACh by targeting CgCTL1 and choline uptake in haemocytes during the early stage of pathogen infection. In short, an opposite expression pattern between CgCTL1 and cgi-miR-2d is observed during Vibrio splendidus infection, accompanied by changes in haemolymph ACh. In addition, the expression level of CgCTL1 is found to be significantly repressed after cgi-miR-2d overexpression in vivo, while both haemocyte choline and haemolymph ACh are also decreased simultaneously, similar to the finding in CgCTL1 knock-down assay. As a result, the expression of two tumour necrosis factor-like proteins and the bacteriostatic activity of oyster haemocytes are found to be altered significantly by either gain-of-function cgi-miR-2d or knock-down of CgCTL1. To our knowledge, this is the first miRNA identified in invertebrates that can target the ancient cholinergic system and augment immune response during infection.
乙酰胆碱（ACh）是胆碱能神经内分泌系统中的主要神经递质，在调节多种免疫反应中发挥着不可或缺的作用。作为胆碱摄取的重要转运体，胆碱转运体样蛋白（CTLs）可在多种生物体中间接控制ACh的合成与释放。在本研究中，cgi-miR-2d是牡蛎（太平洋牡蛎）中一种无脊椎动物特有的微小RNA，已被证明在病原体感染早期通过靶向CgCTL1抑制血细胞中ACh的合成/释放及胆碱摄取。简而言之，在灿烂弧菌感染期间观察到CgCTL1和cgi-miR-2d之间存在相反的表达模式，并伴有血淋巴中ACh的变化。此外，在体内过表达cgi-miR-2d后，发现CgCTL1的表达水平显著受到抑制，同时血细胞胆碱和血淋巴ACh也同时降低，这与CgCTL1敲低实验中的发现相似。结果发现，功能获得性的cgi-miR-2d或CgCTL1的敲低均显著改变了两种肿瘤坏死因子样蛋白的表达以及牡蛎血细胞的抑菌活性。据我们所知，这是在无脊椎动物中鉴定出的首个能够靶向古老胆碱能系统并在感染期间增强免疫反应的微小RNA。
