Extracellular Superoxide Dismutase in Insects CHARACTERIZATION, FUNCTION, AND INTERSPECIFIC VARIATION IN PARASITOID WASP VENOM
Extracellular Superoxide Dismutase in Insects CHARACTERIZATION, FUNCTION, AND INTERSPECIFIC VARIATION IN PARASITOID WASP VENOM
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DOI：
10.1074/jbc.m111.288845
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发表时间：
2011-11-18
影响因子：
4.8
通讯作者：
Poirie, Marylene
中科院分区：
文献类型：
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作者：
Colinet, Dominique;Cazes, Dominique;Poirie, Marylene
类内寄生蜂在其卵中注入毒液蛋白，以保护其免受宿主免疫反应的影响，并确保成功寄生。在这里，我们报道了在果蝇的两种拟寄生虫Leptopilina物种的毒液器官中鉴定出细胞内SOD1和细胞外SOD3的Cu，Zn超氧化物歧化酶（SOD）转录物。Leptopilina的sod序列和结构与人类相似，但系统发育分析表明，细胞外sod与细胞质脊椎动物的关联更大，而不是细胞外sod，这与预测的昆虫细胞外sod具有相同的特征。我们证明了L. boulardi SOD3确实在毒液中以单体糖基化形式分泌和活性。我们的研究结果也证明了SOD3在亲缘关系密切的拟寄生虫物种之间的含量存在定量差异，因为SOD3在异瘤Leptopilina heterotoma毒液器官中的表达量低100倍，并且在其毒液中没有检测到蛋白质和SOD活性。Leptopilina重组SOD3s和哺乳动物SOD在体外以剂量依赖的方式抑制果蝇酚氧化酶活性，表明SOD可能干扰果蝇的黑色素化过程，从而干扰细胞毒性化合物的产生。虽然观察这种作用所需的重组布氏乳杆菌SOD3量排除了黄蜂毒液SOD3的全身作用，但它仍然与产卵时的局部作用一致。这项工作首次证明，昆虫细胞外sod确实在昆虫体液中分泌并活跃，可以作为毒力因子来抵消宿主的免疫反应，这是细菌和真菌病原体以及原虫寄生虫在感染过程中广泛使用的一种策略。
Endoparasitoid wasps inject venom proteins with their eggs to protect them from the host immune response and ensure successful parasitism. Here we report identification of Cu,Zn superoxide dismutase (SOD) transcripts for both intracellular SOD1 and extracellular SOD3 in the venom apparatus of two Leptopilina species, parasitoids of Drosophila. Leptopilina SODs show sequence and structure similarity to human SODs, but phylogenetic analyses indicate that the extracellular SODs are more related to cytoplasmic vertebrate SODs than to extracellular SODs, a feature shared by predicted insect extracellular SODs. We demonstrate that L. boulardi SOD3 is indeed secreted and active as monomeric glycosylated forms in venom. Our results also evidence quantitative variation in SOD3 venom contents between closely related parasitoid species, as sod3 is 100-fold less expressed in Leptopilina heterotoma venom apparatus and no protein and SOD activity are detected in its venom. Leptopilina recombinant SOD3s as well as a mammalian SOD in vitro inhibit the Drosophila phenoloxidase activity in a dose-dependent manner, demonstrating that SODs may interfere with the Drosophila melanization process and, therefore, with production of cytotoxic compounds. Although the recombinant L. boulardi SOD3 quantity needed to observe this effect precludes a systemic effect of the wasp venom SOD3, it is still consistent with a local action at oviposition. This work provides the first demonstration that insect extracellular SODs are indeed secreted and active in an insect fluid and can be used as virulence factors to counteract the host immune response, a strategy largely used by bacterial and fungal pathogens but also protozoan parasites during infection.