State Key Laboratory of Estuarine and Coastal Research, School of Life Sciences, East China Normal University, Shanghai, 200241, China.
State Key Laboratory of Estuarine and Coastal Research, School of Life Sciences, East China Normal University, Shanghai, 200241, China.
Fish Shellfish Immunol. 2019 Oct;93:232-239. doi: 10.1016/j.fsi.2019.07.060. Epub 2019 Jul 21.
As an important economic mollusk in coastal areas, Octopus ocellatus dependents on innate immune system to resist the invasion of microorganisms. Lysozyme is a crucial effector owing to its significant lytic activity against bacterial pathogens during the immune responses. In this study, characteristic and immune function of an I-type lysozyme from O. ocellatus (OoLyz) was investigated. OoLyz shared a close relationship with the lysozymes from other bivalve mollusks. The mRNA of OoLyz exhibited a broad transcript in different tissues/organs, and with the greatest expression in hepatopancreas. The expression of OoLyz was significantly raised when O. ocellatus was infected by Vibrio anguillarum or Micrococcus luteus, suggesting OoLyz participated in innate immune response of host. Prokaryotic recombinant OoLyz (rOoLyz) exhibited obvious bacteriolysis ability towards both gram-negative bacteria V. anguillarum and Escherichia coli, and gram-positive bacteria M. luteus and Staphylococcus aureus. The bacteriolysis activities of rOoLyz towards gram-negative but not gram-positive bacteria was heat stable, indicating that OoLyz might clear gram-positive bacterium by enzyme-dependent mechanisms, but eliminate gram-negative microbe via enzymatic activity independent way. Scanning electron microscopy analysis showed that rOoLyz destroyed microbes by damaging cell wall. More importantly, the fact that rOoLyz could directly degrade the peptidoglycan, further revealed its bactericidal mechanism as a muramidase. Our results revealed the essential role of I-type lysozyme in the innate immunity of O. ocellatus, and shed new light to understand the mechanism of immune defense of mollusks.
作为沿海地区重要的经济贝类，章鱼依靠先天免疫系统来抵抗微生物的入侵。溶菌酶是一种重要的效应分子，因其在免疫反应中对细菌病原体具有显著的裂解活性而受到关注。本研究旨在研究来自章鱼（Octopus ocellatus）的一种 I 型溶菌酶（OoLyz）的特征和免疫功能。OoLyz 与其他双壳贝类的溶菌酶具有密切的亲缘关系。OoLyz 的 mRNA 在不同组织/器官中具有广泛的转录，在肝胰腺中表达量最大。当章鱼被鳗弧菌或藤黄微球菌感染时，OoLyz 的表达显著上调，表明 OoLyz 参与了宿主的先天免疫反应。原核重组 OoLyz（rOoLyz）对革兰氏阴性菌鳗弧菌和大肠杆菌以及革兰氏阳性菌藤黄微球菌和金黄色葡萄球菌均表现出明显的溶菌活性。rOoLyz 对革兰氏阴性菌而非革兰氏阳性菌的溶菌活性具有热稳定性，表明 OoLyz 可能通过酶依赖机制清除革兰氏阳性菌，但通过非酶活性独立方式消除革兰氏阴性微生物。扫描电子显微镜分析表明，rOoLyz 通过破坏细胞壁来破坏微生物。更重要的是，rOoLyz 可以直接降解肽聚糖的事实，进一步揭示了其作为一种胞壁质酶的杀菌机制。我们的研究结果揭示了 I 型溶菌酶在章鱼先天免疫中的重要作用，为理解贝类免疫防御机制提供了新的视角。
