Liu Haipeng, Jiravanichpaisal Pikul, Cerenius Lage, Lee Bok Luel, Söderhäll Irene, Söderhäll Kenneth
Department of Comparative Physiology, Uppsala University, Norbyvägen 18A, SE-752 36 Uppsala, Sweden.
Department of Comparative Physiology, Uppsala University, Norbyvägen 18A, SE-752 36 Uppsala, Sweden; Molecular Aquatic Biology and Genetic Laboratory, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, 73/1 Rama VI Road, Rajdhevee, Bangkok 10400, Thailand.
J Biol Chem. 2007 Nov 16;282(46):33593-33598. doi: 10.1074/jbc.M706113200. Epub 2007 Sep 13.
The melanization cascade, in which phenoloxidase is the terminal enzyme, appears to play a key role in recognition of and defense against microbial infections in invertebrates. Here, we show that phenoloxidase activity and melanization are important for the immune defense toward a highly pathogenic bacterium, Aeromonas hydrophila, in the freshwater crayfish, Pacifastacus leniusculus. RNA interference-mediated depletion of crayfish prophenoloxidase leads to increased bacterial growth, lower phagocytosis, lower phenoloxidase activity, lower nodule formation, and higher mortality when infected with this bacterium. In contrast, if RNA interference of pacifastin, an inhibitor of the crayfish prophenoloxidase activation cascade, is performed, it results in lower bacterial growth, increased phagocytosis, increased nodule formation, higher phenoloxidase activity, and delayed mortality. Our data therefore suggest that phenoloxidase is required in crayfish defense against an infection by A. hydrophila, a highly virulent and pathogenic bacterium to crayfish.
黑化级联反应以酚氧化酶作为末端酶，似乎在无脊椎动物识别和抵御微生物感染过程中发挥关键作用。在此，我们表明酚氧化酶活性和黑化作用对于淡水小龙虾——美洲螯龙虾对高致病性细菌嗜水气单胞菌的免疫防御十分重要。RNA干扰介导的小龙虾前酚氧化酶缺失会导致细菌生长增加、吞噬作用降低、酚氧化酶活性降低、结节形成减少以及感染该细菌时死亡率升高。相反，如果对小龙虾酚氧化酶激活级联反应的抑制剂——pacifastin进行RNA干扰，则会导致细菌生长降低、吞噬作用增加、结节形成增加、酚氧化酶活性升高以及死亡延迟。因此，我们的数据表明酚氧化酶是小龙虾抵御嗜水气单胞菌感染所必需的，嗜水气单胞菌是一种对小龙虾具有高度毒性和致病性的细菌。
