Nonproteolytic serine proteinase homologs are involved in prophenoloxidase activation in the tobacco hornworm, Manduca sexta
Nonproteolytic serine proteinase homologs are involved in prophenoloxidase activation in the tobacco hornworm, Manduca sexta
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DOI：
10.1016/s0965-1748(02)00191-1
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发表时间：
2003-02-01
影响因子：
3.8
通讯作者：
Kanost, MR
中科院分区：
文献类型：
--
作者：
Yu, XQ;Jiang, HB;Kanost, MR
在昆虫中，酚氧化酶原激活系统是对抗寄生虫和病原体的防御机制。模式识别受体对寄生虫或病原体的识别触发丝氨酸蛋白酶级联反应的激活，导致酚氧化酶原激活蛋白酶（PAP）的激活。PAP将失活的酚氧化酶原（proPO）转化为活性酚氧化酶（PO），然后催化酚类化合物的氧化，从而形成黑色素。因为醌中间体和黑色素对宿主和病原体都是有毒的，所以proPO的激活必须受到严格的调节和定位。我们在这里报告的纯化和cDNA克隆的丝氨酸蛋白酶同源物（SPHs）从烟草天蛾，天蛾，与PAP-1的proPO激活相互作用。从M.免疫球蛋白-2（一种与细菌脂多糖结合的C型凝集素）感染六龄幼虫。它们含有一个氨基末端的剪辑结构域连接到一个羧基末端的丝氨酸蛋白酶样结构域。单独的PAP-1不能有效地激活proPO，但是SPH和PAP-1的混合物对于proPO激活有效得多。血淋巴中的Immulectin-2、proPO和PAP-1与固定化的SPH-1重组蛋白酶样结构域结合，表明血淋巴中可能存在含有这些蛋白的复合物。由于免疫球蛋白-2是结合病原体表面碳水化合物的模式识别受体，因此这种蛋白质复合物可以定位病原体表面上proPO的活化。SPH，结合免疫球蛋白-2，可以作为一个调解员招募PO和PAP的感染部位。(C)2002爱思唯尔科技有限公司版权所有。
In insects, the prophenoloxidase activation system is a defense mechanism against parasites and pathogens. Recognition of parasites or pathogens by pattern recognition receptors triggers activation of a serine proteinase cascade, leading to activation of prophenoloxidase-activating proteinase (PAP). PAP converts inactive prophenoloxidase (proPO) to active phenoloxidase (PO), which then catalyzes oxidation of phenolic compounds that can polymerize to form melanin. Because quinone intermediates and melanin are toxic to both hosts and pathogens, activation of proPO must be tightly regulated and localized. We report here purification and cDNA cloning of serine proteinase homologs (SPHs) from the tobacco hornworm, Manduca sexta, which interact with PAP-1 in proPO activation. Two SPHs were co-purified from plasma of M. sexta larvae with immulectin-2, a C-type lectin that binds to bacterial lipopolysaccharide. They contain an amino-terminal clip domain connected to a carboxyl-terminal serine proteinase-like domain. PAP-1 alone cannot efficiently activate proPO, but a mixture of SPHs and PAP-1 was much more effective for proPO activation. Immulectin-2, proPO and PAP-1 in hemolymph bound to the immobilized recombinant proteinase-like domain of SPH-1, indicating that a complex containing these proteins may exist in hemolymph. Since immulectin-2 is a pattern recognition receptor that binds to surface carbohydrates on pathogens, such a protein complex may localize activation of proPO on the surface of pathogens. SPH, which binds to immulectin-2, may function as a mediator to recruit proPO and PAP to the site of infection. (C) 2002 Elsevier Science Ltd. All rights reserved.