疟原虫通过按蚊媒介传播的适应性机制研究

Via biting by mosquito, male and female gametocyte of malaria parasite Plasmodium moved from malaria patient to digestive midgut in mosquito Anopheles, further developing to gamete with the ability to fertilization. Mosquito midgut derived chemical Xanthurenic Acid (XA) has been identified to play the role as the chemical inducer signal for activating gametocyte to gamete. However, the gametocyte XA Receptor is still unknown. G-protein coupled receptors (GPCR) are a group of membrane receptor, functioning as the sensor of environmental signals in eukaryotes. Therefore, the XA Receptor maybe is one of GPCR genes in Plasmodium genome. By data mining in genome database, we predicted 11 GPCR candidates encoded in Plasmodium. Using rodent malaria parasite Plasmodium yoelii, we successfully obtained 12 parasite clones with gene deletion for each candidate. Further phenotyping screen indicated that gene deletion of candidate C4 caused deficiency in gametocyte activating to gamete by XA. In addition, C4 deletion in both of another Plasmodium yoelii strain and another rodent malaria parasite Plasmodium berghei strain confirmed the phenotype. Through complementation with c4 expression in C4 gene deletion strain, the deficiency phenotype was rescued to the level of wildtype. In the life cycle of parasite, C4 protein showed the specific expression in gametocyte stage and localized to gametocyte cell membrane. Altogether, we speculated C4 as the XA receptor and more experiments are being planned to verify the XA receptor function of C4 protein.

疟原虫是严格依赖按蚊媒介传播的单细胞原生动物病原。按蚊叮咬吸血后，疟原虫雌雄配子体从哺乳动物宿主转移进入按蚊消化道，在此激活配子发生，形成受精能力的雌雄配子，受精后继续蚊期发育。按蚊黄尿酸是激活疟原虫配子发生的宿主信号，但是疟原虫如何感应按蚊黄尿酸信号至今未知。G蛋白偶联受体(GPCR)膜蛋白，是真核细胞生物感受环境信号的重要机制。前期工作中我们采用候选基因策略,选择了12个GPCR基因（命名c1-c12），制备了鼠疟原虫候选基因敲除的虫株；表型筛选发现c4敲除导致雌雄配子发生缺陷，并且感染按蚊后传播阻断。进一步分析发现C4蛋白在配子体细胞特异表达并且细胞膜定位；此外，c4敲除的配子发生信号通路中钙离子信号阻断。本课题将进一步分析C4蛋白的膜受体功能，测定黄尿酸和C4蛋白的结合能力。通过对疟原虫感应按蚊黄尿酸的受体分子研究，揭示疟原虫依赖按蚊传播的适应性机制；为阻断疟疾传播提供新的靶标。

原生动物-疟原虫在人/脊椎动物和按蚊之间交替寄生，周期性进行无性繁殖和有性生殖完成生活史，导致全球性传染病-疟疾的致病和传播。项目研究疟原虫通过按蚊媒介传播的适应性机制研究，聚焦疟原虫寄生按蚊的有性生殖。建立基因编辑方法解决了疟原虫机制研究的工具瓶颈；揭示了配子体的性别决定、 按蚊宿主信号的感受和传导、 受精卵变形、动合子运动控制和动合子躲避按蚊宿主免疫识别等领域中若干重要科学问题的分子机制。这些工作一方面揭示了疟原虫按蚊寄生和有性生殖的适应性机制；另一方面，为靶向疟原虫寄生按蚊和阻断疟疾传播提供靶标。资助期内以通讯作者发表了Science Advances、Nature Communications、Current Biology、EMBO Journal、EMBO Reports等系列论文。未来拟在前期发现的基础上进一步深入地研究宿主转换中疟原虫建立按蚊感染的适应性机制。