Characterization of the first insect prostaglandin (PGE2) receptor: MansePGE2R is expressed in oenocytoids and lipoteichoic acid (LTA) increases transcript expression
Characterization of the first insect prostaglandin (PGE2) receptor: MansePGE2R is expressed in oenocytoids and lipoteichoic acid (LTA) increases transcript expression
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DOI：
10.1016/j.ibmb.2019.103290
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发表时间：
2020-02-01
影响因子：
3.8
通讯作者：
Pietrantonio, Patricia, V
中科院分区：
文献类型：
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作者：
Kwon, Hyeogsun;Yang, Yunlong;Pietrantonio, Patricia, V
在节肢动物中，源自花生四烯酸氧化代谢的类二十烷酸对于介导免疫反应具有重要意义。然而，缺乏有关昆虫类二十烷酸受体的信息是完全破译类二十烷酸下游信号级联背后的免疫机制及其与免疫病原体相关分子模式（PAMP）的关系的障碍。在这里，我们从鳞翅目天蛾（Sphingidae）模型中克隆并测序了 G 蛋白偶联受体（MW 46.16 kDa）。该受体的氨基酸基序与人前列腺素 E-2 (PGE(2)) 受体相似，系统发育分析支持其作为前列腺素受体的分类。一致地，重组受体被 PGE2 激活，导致细胞内 cAMP 增加，因此命名为 MansePGE2R。 MansePGE2R 在 Sf9 细胞中的表达（其中内源直系同源受体已被沉默）在 PGE2 攻击后显示出类似的 cAMP 增加。在幼虫和雌性成虫的多种组织中发现了受体转录表达，包括马氏小管、脂肪体、肠道和血细胞以及雌性卵巢。除了克隆的编码功能性受体的 cDNA 之外，还发现了一种具有多聚腺苷酸尾部但缺乏预测的跨膜 (TM) 区域 2 和 3 的 mRNA，这表明昆虫中可能存在内部缺失的受体蛋白。免疫细胞化学和原位杂交表明，在血细胞中，受体仅位于类细胞中。注射细菌成分的幼虫免疫挑战表明，脂磷壁酸 (LTA) 增加了血细胞中 MansePGE2R 的表达。相反，注射LPS或肽聚糖并没有增加血细胞中MansePGE2R转录物水平，这表明LTA相关的受体转录物增加是通过独特的途径调节的。这项研究提供了昆虫类二十烷酸受体的首次表征，并为建立昆虫对感染的免疫反应所需的信号传导步骤的层次结构铺平了道路。
In arthropods, eicosanoids derived from the oxygenated metabolism of arachidonic acid are significant in mediating immune responses. However, the lack of information about insect eicosanoid receptors is an obstacle to completely decipher immune mechanisms underlying both eicosanoid downstream signal cascades and their relationship to immune pathogen-associated molecular patterns (PAMPs). Here, we cloned and sequenced a G protein-coupled receptor (MW 46.16 kDa) from the model lepidopteran, Manduca sexta (Sphingidae). The receptor shares similarity of amino acid motifs to human prostaglandin E-2 (PGE(2)) receptors, and phylogenetic analysis supports its classification as a prostaglandin receptor. In agreement, the recombinant receptor was activated by PGE2 resulting in intracellular cAMP increase, and therefore designated MansePGE2R. Expression of MansePGE2R in Sf9 cells in which the endogenous orthologous receptor had been silenced showed similar cAMP increase upon PGE2 challenge. Receptor transcript expression was identified in various tissues in larvae and female adults, including Malpighian tubules, fat body, gut and hemocytes, and in female ovaries. In addition to the cDNA cloned that encodes the functional receptor, an mRNA was found featuring the poly-A tail but lacking the predicted transmembrane (TM) regions 2 and 3, suggesting the possibility that internally deleted receptor proteins exist in insects. Immunocytochemistry and in situ hybridization revealed that among hemocytes, the receptor was exclusively localized in the oenocytoids. Larval immune challenges injecting bacterial components showed that lipoteichoic acid (LTA) increased MansePGE2R expression in hemocytes. In contrast, injection of LPS or peptidoglycan did not increase MansePGE2R transcript levels in hemocytes, suggesting the LTA-associated increase in receptor transcript is regulated through a distinct pathway. This study provides the first characterization of an eicosanoid receptor in insects, and paves the way for establishing the hierarchy in signaling steps required for establishing insect immune responses to infections.