The circumsporozoite protein, CSP, is the major surface protein of Plasmodium sporozoites, the form of malaria parasites transmitted by mosquitoes. CSP is involved in sporozoite formation within and egress from oocysts, entry into mosquito salivary glands and mammalian liver as well as migration in the skin. Yet, how CSP facilitates sporozoite formation, oocyst egress and hepatocyte specific invasion is still not fully understood. Here, we aimed at generating a series of parasites expressing full‐length versions of CSP with internally inserted green fluorescent protein between known domains at the endogenous csp locus. This enabled the investigation of sporozoite formation in living oocysts. GFP insertion after the signal peptide leads to cleavage of GFP before the fusion protein reached the plasma membrane while insertion of GFP before or after the TSR domain prevented sporozoite egress and liver invasion. These data suggest different strategies for obtaining mature salivary gland sporozoites that express GFP‐CSP fusions.

中文翻译：

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疟原虫环子孢子蛋白的荧光标记可以对子孢子的形成进行成像，但会阻止卵囊的流出


环子孢子蛋白 (CSP) 是疟原虫子孢子的主要表面蛋白，疟原虫子孢子是由蚊子传播的疟疾寄生虫。 CSP 参与子孢子在卵囊内的形成和排出、进入蚊子唾液腺和哺乳动物肝脏以及在皮肤中的迁移。然而，CSP 如何促进子孢子形成、卵囊排出和肝细胞特异性侵袭尚不完全清楚。在这里，我们的目标是生成一系列表达全长版本 CSP 的寄生虫，并在内源性csp基因座的已知结构域之间插入绿色荧光蛋白。这使得能够研究活卵囊中子孢子的形成。在信号肽之后插入 GFP 会导致融合蛋白在到达质膜之前裂解 GFP，而在 TSR 结构域之前或之后插入 GFP 可防止子孢子流出和肝脏入侵。这些数据表明获得表达 GFP-CSP 融合的成熟唾液腺子孢子的不同策略。