A novel serpin expressed by blood-borne microfilariae of the parasitic nematode Brugia malayi inhibits human neutrophil serine proteinases.
A novel serpin expressed by blood-borne microfilariae of the parasitic nematode Brugia malayi inhibits human neutrophil serine proteinases.
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DOI：
10.1182/blood.v94.4.1418
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发表时间：
1999-08
期刊：
影响因子：
20.3
通讯作者：
Xingxing Zang;Maria Yazdanbakhsh;Haobo Jiang;M. Kanost;R. Maizels
中科院分区：
文献类型：
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作者：
Xingxing Zang;Maria Yazdanbakhsh;Haobo Jiang;M. Kanost;R. Maizels
丝氨酸蛋白酶抑制剂（Serine proteinase inhibitors，serpins）在多种生物学过程中起着重要的调节作用，病毒的serpins参与了病原体逃避宿主防御系统的过程。这是第一次，我们报告一个功能性丝氨酸蛋白酶抑制剂基因从线虫，可能以这种方式发挥作用。该基因被命名为Bm-spn-2，已从马来丝虫（Brugia malayi）中分离出，马来丝虫是人类淋巴丝虫病的病原体。聚合酶链反应（PCR）和蛋白质印迹实验表明，Bm-spn-2基因仅在微丝蚴（Microfilariae，Mf）中表达。对存放在dbEST中的来自B malayi的超过14，000个表达序列标签（EST）的调查显示，从Mf cDNA文库测序的超过2%的EST对应于Bm-spn-2。尽管Bm-spn-2在微丝蚴阶段很丰富，但在生命周期的任何其他阶段都没有发现。Bm-spn-2编码的蛋白质含有428个氨基酸，并含有一个信号肽。重组Bm-SPN-2蛋白的抗体与Mf提取物中的47.5-kD天然蛋白特异性反应。Bm-SPN-2是93种已知的丝氨酸蛋白酶抑制剂中最大的一种，由于22个氨基酸的羧基末端延伸，并且含有保守的丝氨酸蛋白酶抑制剂标签序列。在这些区域之外，同源性水平很低，并且只能看到与秀丽隐杆线虫丝氨酸蛋白酶抑制剂的遥远关系。Bm-spn-2基因包含6个内含子，其中2个似乎是由两种线虫共享的。马来B内含子具有一个延伸的、保守的3'剪接位点，并且与秀丽线虫相比相对较大。筛选了一组哺乳动物丝氨酸蛋白酶，发现Bm-SPN-2蛋白特异性抑制人嗜中性粒细胞组织蛋白酶G和人嗜中性粒细胞弹性蛋白酶的酶活性，但不抑制一系列其他丝氨酸蛋白酶。Bm-SPN-2可能作为微丝蚴血液环境中的阶段特异性丝氨酸蛋白酶抑制剂发挥保护作用，从而可能成为保护性疫苗的良好候选者。
Serine proteinase inhibitors (serpins) play a vital regulatory role in a wide range of biological processes, and serpins from viruses have been implicated in pathogen evasion of the host defence system. For the first time, we report a functional serpin gene from nematodes that may function in this manner. This gene, named Bm-spn-2, has been isolated from the filarial nematode Brugia malayi, a causative agent of human lymphatic filariasis. Polymerase chain reaction (PCR) and Western blot experiments indicate that Bm-spn-2 is expressed only by microfilariae (Mf), which are the long-lived blood-dwelling larval stage. A survey of the greater than 14,000 expressed sequence tags (ESTs) from B malayi deposited in dbEST shows that greater than 2% of the ESTs sequenced from Mf cDNA libraries correspond to Bm-spn-2. Despite its abundance in the microfilarial stage, Bm-spn-2 has not been found in any other point in the life cycle. The predicted protein encoded by Bm-spn-2 contains 428 amino acids with a putative signal peptide. Antibodies to recombinant Bm-SPN-2 protein react specifically with a 47.5-kD native protein in Mf extract. Bm-SPN-2 is one of the largest of the 93 known serpins, due to a 22 amino acid carboxy-terminal extension, and contains the conserved serpin signature sequence. Outside these regions, levels of homology are low, and only a distant relationship can been seen to a Caenorhabditis elegans serpin. The Bm-spn-2 gene contains 6 introns, 2 of which appear to be shared by both nematode species. The B malayi introns have an extended and conserved 3' splice site and are relatively large compared with C elegans. A panel of mammalian serine proteinases were screened and Bm-SPN-2 protein was found to specifically inhibit enzymatic activity of human neutrophil cathepsin G and human neutrophil elastase, but not a range of other serine proteinases. It is possible that Bm-SPN-2 could function as a stage-specific serpin in the blood environment of the microfilarial parasite in protection from human immunity and thus may be a good candidate for protective vaccine.