Molecules released by helminth parasites involved in host colonization.
Molecules released by helminth parasites involved in host colonization.
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DOI：
10.18388/abp.2006_3361
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发表时间：
2006
影响因子：
1.7
通讯作者：
J. Dzik
中科院分区：
文献类型：
--
作者：
J. Dzik
寄生虫被进化设计成入侵宿主并在其生物体中生存，直到它们准备好繁殖。寄生虫释放各种分子，帮助它们穿透防御屏障，避免宿主的免疫攻击。在这方面，特别令人感兴趣的是由寄生虫分泌的酶及其抑制剂。丝氨酸-、天冬氨酸-、半胱氨酸-和金属蛋白酶参与组织侵入和细胞外蛋白消化。蠕虫分泌这些酶的抑制剂（丝氨酸蛋白酶抑制剂、Aspins和半胱氨酸蛋白酶抑制剂）来抑制宿主和自身的蛋白酶。蛋白酶及其抑制剂，以及蠕虫同源的细胞因子和含有磷酸胆碱的分子，影响宿主的免疫应答，使其偏向抗炎性Th 2型。核苷酸代谢酶和胆碱酯酶由蠕虫分泌，以减少炎症并将寄生虫从胃肠道排出。细胞内后生动物寄生虫旋毛虫分泌蛋白激酶和磷酸酶、核酸内切酶和DNA结合蛋白等，这些都被认为会干扰宿主细胞信号，促进肌肉细胞分化。抗氧化酶的分泌被认为可以保护寄生虫免受感染刺激的宿主吞噬细胞产生的活性氧的影响。除了超氧化物歧化酶、过氧化氢酶（在蠕虫中很少发现）和谷胱甘肽过氧化物酶（不依赖硒，因此对H（2）O（2）的活性很差）之外，过氧化物氧化还原酶可能是蠕虫中主要的H（2）O（2）解毒酶。抗氧化酶的分泌是阶段特异性的，并且存在通过寄生虫周围的活性氧的浓度来调节其表达的实例。大多数寄生虫分泌的分子通常存在于自由生活的生物体中，因此寄生虫只是将它们用于其生活方式。
Parasites are designed by evolution to invade the host and survive in its organism until they are ready to reproduce. Parasites release a variety of molecules that help them to penetrate the defensive barriers and avoid the immune attack of the host. In this respect, particularly interesting are enzymes and their inhibitors secreted by the parasites. Serine-, aspartic-, cysteine-, and metalloproteinases are involved in tissue invasion and extracellular protein digestion. Helminths secrete inhibitors of these enzymes (serpins, aspins, and cystatins) to inhibit proteinases, both of the host and their own. Proteinases and their inhibitors, as well as helminth homologues of cytokines and molecules containing phosphorylcholine, influence the immune response of the host biasing it towards the anti-inflammatory Th2 type. Nucleotide-metabolizing enzymes and cholinesterase are secreted by worms to reduce inflammation and expel the parasites from the gastrointestinal tract. An intracellular metazoan parasite, Trichinella spiralis, secretes, among others, protein kinases and phosphatases, endonucleases, and DNA-binding proteins, which are all thought to interfere with the host cellular signals for muscle cell differentiation. Secretion of antioxidant enzymes is believed to protect the parasite from reactive oxygen species which arise from the infection-stimulated host phagocytes. Aside from superoxide dismutase, catalase (rarely found in helminths), and glutathione peroxidase (selenium-independent, thus having a poor activity with H(2)O(2)), peroxiredoxins are probably the major H(2)O(2)-detoxifying enzymes in helminths. Secretion of antioxidant enzymes is stage-specific and there are examples of regulation of their expression by the concentration of reactive oxygen species surrounding the parasite. The majority of parasite-secreted molecules are commonly found in free-living organisms, thus parasites have only adapted them to use in their way of life.