Laboratory for Parasitology, Leiden University Medical Centre, Leiden, The Netherlands.
PLoS Pathog. 2010 Apr 8;6(4):e1000853. doi: 10.1371/journal.ppat.1000853.
The process of fertilization is critically dependent on the mutual recognition of gametes and in Plasmodium, the male gamete surface protein P48/45 is vital to this process. This protein belongs to a family of 10 structurally related proteins, the so called 6-cys family. To identify the role of additional members of this family in Plasmodium fertilisation, we performed genetic and functional analysis on the five members of the 6-cys family that are transcribed during the gametocyte stage of P. berghei. This analysis revealed that in addition to P48/45, two members (P230 and P47) also play an essential role in the process of parasite fertilization. Mating studies between parasites lacking P230, P48/45 or P47 demonstrate that P230, like P48/45, is a male fertility factor, consistent with the previous demonstration of a protein complex containing both P48/45 and P230. In contrast, disruption of P47 results in a strong reduction of female fertility, while males remain unaffected. Further analysis revealed that gametes of mutants lacking expression of p48/45 or p230 or p47 are unable to either recognise or attach to each other. Disruption of the paralog of p230, p230p, also specifically expressed in gametocytes, had no observable effect on fertilization. These results indicate that the P. berghei 6-cys family contains a number of proteins that are either male or female specific ligands that play an important role in gamete recognition and/or attachment. The implications of low levels of fertilisation that exist even in the absence of these proteins, indicating alternative pathways of fertilisation, as well as positive selection acting on these proteins, are discussed in the context of targeting these proteins as transmission blocking vaccine candidates.
受精过程严重依赖于配子的相互识别，而在疟原虫中，雄性配子表面蛋白 P48/45 对这一过程至关重要。该蛋白属于一个结构相关的 10 个蛋白家族，即所谓的 6-cys 家族。为了确定该家族的其他成员在疟原虫受精中的作用，我们对 6-cys 家族中在恶性疟原虫配子体阶段转录的 5 个成员进行了遗传和功能分析。该分析表明，除了 P48/45 之外，另外两个成员（P230 和 P47）在寄生虫受精过程中也发挥着重要作用。缺乏 P230、P48/45 或 P47 的寄生虫之间的交配研究表明，P230 像 P48/45 一样，是一种雄性生育因子，与先前证明的含有 P48/45 和 P230 的蛋白质复合物一致。相比之下，破坏 P47 会导致雌性生育力大幅下降，而雄性则不受影响。进一步的分析表明，缺乏 p48/45 或 p230 或 p47 表达的配子既无法识别也无法相互附着。与在配子体中特异性表达的 p230 的 paralog p230p 的破坏也对受精没有观察到影响。这些结果表明，恶性疟原虫 6-cys 家族包含一些蛋白，它们要么是雄性特异性配体，要么是雌性特异性配体，在配子识别和/或附着中发挥重要作用。即使在没有这些蛋白的情况下，受精水平仍然很低，这表明存在替代的受精途径，以及对这些蛋白的正选择，这些都在将这些蛋白作为传播阻断疫苗候选物的背景下进行了讨论。
