埃及斑蚊Frizzled-2連接免疫反應及產卵機制之分析

Abstract

病媒傳播的疾病是近年來造成嚴重傳染性疾病的主因之一，其中許多病毒和寄生蟲疾病都可以藉由蚊子來傳播。數十年來，全球許多政府及研究單位均致力於根除蚊子傳播的疾病，但目標至今尚未達成。因此，許多研究團隊開始致力於研究病媒蚊生命周期的分子調控機制，及其對抗外來病原之免疫調控機制，以開發控制病媒傳播性疾病的新策略。前人研究已經証明，Target of Rapamycin (TOR) pathway 在蚊子卵黃生成作用扮演一個重要角色，而WNT pathway 是參與脊椎動物胚胎發育和細胞極性的生成。 此外，長期以來認為 Immune deficiency (IMD) pathway 和Toll pathway可調控抗菌肽的產生。然而，關於這些 signaling pathway之間交互作用的並不是很了解。 在本篇研究中，我們提出TOR pathway和WNT signaling pathway在蚊子卵黃生成和免疫反應中協同作用的假說。我們試圖去描繪在埃及斑蚊WNT signaling pathway中的組成因子。我們的結果顯示，抑制WNT signaling pathway中的Frizzled2 (FZ2)或是TOR時，我們觀察到埃及斑蚊對於抵 Staphylococcus aureus和Escherichia coli的免疫能力明顯下降了許多。有趣的是，產卵能力在抑制FZ2時也會有所改變。此外，我們的實驗結果顯示在餵血六小時之後，FZ2在埃及斑蚊Fatbody中的在Transcriptional和Translational的表現有大量增加的情形，我們認為可能是血液中的氨基酸誘導FZ2的生成。我們研究的結果顯示FZ2可以和TOR pathway之間有交互作用，來調控埃及斑蚊對抗病原菌以及卵黃生成作用的能力。

Mosquito-borne diseases are the most devastating agents for human beings, due to its high diversity of transmissible pathogens like protozoan and viruses. Despite the efforts from government agencies that have contributed to the eradication of mosquito-borne diseases for several decades, the goal has not been achieved. Therefore, many research institutes turned their attention towards the mosquito life cycle and immune system to halt the disease transmission. Previous studies have already demonstrated that TOR pathway plays an important role in mosquito vitellogenesis, whereas WNT pathway participates in the embryonic development and cell polarity. Besides, it has long been accepted that IMD and Toll pathway regulate the production of antimicrobial peptides. However, the interactions between these pathways are poorly understood. In this study, we propose a hypothesis that factors of TOR and WNT signaling pathway play synergistically in the mosquito vitelloginesis and immune responses. We attempt to characterize components of WNT signaling in the mosquito, Aedes aegypti. Our results showed that silencing of FZ2, a component of Wnt signaling pathway, and TOR resulted in the decrease of Aedes aegypti survival fitness against Staphylococcus aureus and Escherichia coli infection. Interestingly, the oviposition ability has been altered in the absence of FZ2. Also, we demonstrated that FZ2 is highly expressed in the mosquito fatbody at 6 hours post blood meal in terms of transcriptional and translational level, suggesting the amino acid-stimulated feature of FZ2. Our results indicated that FZ2 may interact with TOR pathway and also regulate the antimicrobial responses in the mosquito.