Wang Yang, Cheng Tingcai, Rayaprolu Subrahmanyam, Zou Zhen, Xia Qingyou, Xiang Zhonghuai, Jiang Haobo
Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, USA.
Dev Comp Immunol. 2007;31(10):1002-12. doi: 10.1016/j.dci.2007.01.001. Epub 2007 Feb 12.
Microbial infection leads to proteolytic activation of Drosophila spätzle, which binds to the toll receptor and induces the synthesis of immune proteins. To test whether or not this mechanism exists in lepidopteran insects, we cloned the cDNA of Bombyx mori spätzle-1 and overexpressed the full-length and truncated BmSpz1 cDNA in Escherichia coli. The insoluble fusion proteins were affinity-purified under denaturing condition. After the silkworm larvae were injected with renatured BmSpz1, mRNA levels of antimicrobial peptide genes greatly increased. Similar transcriptional up-regulation was also found in Manduca sexta. Injection of pro-BmSpz1 had no such effect. When pro-BmSpz1 and Micrococcus luteus were incubated with the plasma from M. sexta larvae, we detected proteolytic processing of pro-BmSpz1. These results suggest that active spätzle is required for the induced production of antimicrobial peptides in B. mori and M. sexta.
微生物感染会导致果蝇斯佩兹蛋白（spätzle）发生蛋白水解激活，该蛋白与Toll受体结合并诱导免疫蛋白的合成。为了测试这种机制是否存在于鳞翅目昆虫中，我们克隆了家蚕斯佩兹蛋白-1（Bombyx mori spätzle-1）的cDNA，并在大肠杆菌中过表达全长和截短的BmSpz1 cDNA。不溶性融合蛋白在变性条件下进行亲和纯化。在用复性的BmSpz1注射家蚕幼虫后，抗菌肽基因的mRNA水平大幅增加。在烟草天蛾（Manduca sexta）中也发现了类似的转录上调。注射前体BmSpz1没有这种效果。当将前体BmSpz1与烟草天蛾幼虫的血浆一起与藤黄微球菌（Micrococcus luteus）孵育时，我们检测到了前体BmSpz1的蛋白水解加工过程。这些结果表明，活性斯佩兹蛋白对于家蚕和烟草天蛾中抗菌肽的诱导产生是必需的。
