Expression and Localization Profiles of Rhoptry Proteins in Plasmodium berghei Sporozoites
Expression and Localization Profiles of Rhoptry Proteins in Plasmodium berghei Sporozoites
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DOI：
10.3389/fcimb.2019.00316
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发表时间：
2019-09-10
影响因子：
5.7
通讯作者：
Ishino, Tomoko
中科院分区：
文献类型：
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作者：
Tokunaga, Naohito;Nozaki, Mamoru;Ishino, Tomoko
在疟原虫生命周期中，寄生虫的两个感染阶段，裂殖子和子孢子，分别有效地感染哺乳动物宿主细胞，红细胞和肝细胞。裂殖子和子孢子的顶端结构包含棒状体和微丝分泌细胞器，这些细胞器与顶复门寄生虫的其他感染形式一样保守。在裂殖子侵入红细胞的过程中，一些棒状体蛋白被分泌以在寄生虫和靶细胞之间形成紧密连接，而另一些棒状体蛋白被排出以维持寄生虫空泡内的后续感染。棒状体蛋白介导的侵袭机制是否也参与子孢子对两种不同靶细胞（蚊子唾液腺和哺乳动物肝细胞）的侵袭，一直受到质疑。最近，我们证明，棒状体颈蛋白2（RON 2），这是至关重要的紧密连接形成的裂殖子，也是重要的子孢子入侵的两个靶细胞。为了全面阐明疟原虫子孢子侵入的机制，研究了棒状体蛋白在伯氏疟原虫子孢子中的表达和定位。在12个代表裂殖子棒状体分子的基因中，有9个在卵囊衍生的子孢子中以与血液阶段的子孢子中相似或更高的水平转录。免疫电镜显示，8个蛋白质，即RON 2，RON 4，RON 5，ASP/RON 1，RALP 1，RON 3，RAP 1和RAMA，定位于棒状体的子孢子。值得注意的是，裂殖子中的大多数棒状体颈蛋白定位于子孢子中的棒状体中。这项研究表明，大多数棒状体蛋白，除了高分子量棒状体蛋白复合物的组分外，通常在疟原虫属的裂殖子和子孢子中表达，这表明侵袭机制的组成部分在感染形式之间基本上是保守的，与它们的靶细胞无关。结合子孢子阶段特异性基因沉默策略，可以描述棒状体蛋白在入侵机制中的贡献。
In the Plasmodium lifecycle two infectious stages of parasites, merozoites, and sporozoites, efficiently infect mammalian host cells, erythrocytes, and hepatocytes, respectively. The apical structure of merozoites and sporozoites contains rhoptry and microneme secretory organelles, which are conserved with other infective forms of apicomplexan parasites. During merozoite invasion of erythrocytes, some rhoptry proteins are secreted to form a tight junction between the parasite and target cell, while others are discharged to maintain subsequent infection inside the parasitophorous vacuole. It has been questioned whether the invasion mechanisms mediated by rhoptry proteins are also involved in sporozoite invasion of two distinct target cells, mosquito salivary glands and mammalian hepatocytes. Recently we demonstrated that rhoptry neck protein 2 (RON2), which is crucial for tight junction formation in merozoites, is also important for sporozoite invasion of both target cells. With the aim of comprehensively describing the mechanisms of sporozoite invasion, the expression and localization profiles of rhoptry proteins were investigated in Plasmodium berghei sporozoites. Of 12 genes representing merozoite rhoptry molecules, nine are transcribed in oocyst-derived sporozoites at a similar or higher level compared to those in blood-stage schizonts. Immuno-electron microscopy demonstrates that eight proteins, namely RON2, RON4, RON5, ASP/RON1, RALP1, RON3, RAP1, and RAMA, localize to rhoptries in sporozoites. It is noteworthy that most rhoptry neck proteins in merozoites are localized throughout rhoptries in sporozoites. This study demonstrates that most rhoptry proteins, except components of the high-molecular mass rhoptry protein complex, are commonly expressed in merozoites and sporozoites in Plasmodium spp., which suggests that components of the invasion mechanisms are basically conserved between infective forms independently of their target cells. Combined with sporozoite-stage specific gene silencing strategies, the contribution of rhoptry proteins in invasion mechanisms can be described.