AaCAT1 of the Yellow Fever Mosquito, Aedes aegypti A NOVEL HISTIDINE-SPECIFIC AMINO ACID TRANSPORTER FROM THE SLC7 FAMILY
AaCAT1 of the Yellow Fever Mosquito, Aedes aegypti A NOVEL HISTIDINE-SPECIFIC AMINO ACID TRANSPORTER FROM THE SLC7 FAMILY
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DOI：
10.1074/jbc.m110.179739
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发表时间：
2011-03-25
影响因子：
4.8
通讯作者：
Raikhel, Alexander S.
中科院分区：
文献类型：
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作者：
Hansen, Immo A.;Boudko, Dmitri Y.;Raikhel, Alexander S.
昆虫卵黄蛋白前体基因表达受营养和内分泌信号调节。吸血雌性蚊子血淋巴中氨基酸的激增激活了脂肪体内的营养信号系统，随后解除了卵黄蛋白前体基因的抑制，并使它们对类固醇激素的激活做出反应。 SLC7家族的孤儿转运蛋白被确定为果蝇和黄热病蚊子埃及伊蚊脂肪体中营养信号系统的重要上游成分。然而，这些蛋白质的转运功能尚不清楚。我们报告了从埃及伊蚊脂肪体中克隆的 AaCAT1 的表达和功能特征。 AaCAT1 转录物和蛋白质的表达在蚊子的胚胎后发育过程中经历动态变化。转录物表达在第三和第四幼虫阶段尤其高；然而，AaCAT1 蛋白仅在蛹和成虫阶段被检测到。非洲爪蟾卵母细胞中 AaCAT1 的功能表达和分析表明，它作为一种不依赖于钠的阳离子氨基酸转运蛋白，在中性 pH 值（K-0.5(L-His) = 0.34 +/- 0.07 mM，pH 7.2）下对 L-组氨酸具有独特的选择性。酸化至 pH 6.2 显着增加 AaCAT1 特异性 His(+) 诱导电流。 RNAi 介导的 AaCAT1 沉默会降低随后产卵的卵产量。我们的数据表明，与相关的哺乳动物阳离子氨基酸转运蛋白相比，AaCAT1 的转运机制存在显着差异。它可以在蚊子组织中执行组氨酸特异性运输和信号传导。
Insect yolk protein precursor gene expression is regulated by nutritional and endocrine signals. A surge of amino acids in the hemolymph of blood-fed female mosquitoes activates a nutrient signaling system in the fat bodies, which subsequently dere-presses yolk protein precursor genes and makes them responsive to activation by steroid hormones. Orphan transporters of the SLC7 family were identified as essential upstream components of the nutrient signaling system in the fat body of fruit flies and the yellow fever mosquito, Aedes aegypti. However, the transport function of these proteins was unknown. We report expression and functional characterization of AaCAT1, cloned from the fat body of A. aegypti. Expression of AaCAT1 transcript and protein undergoes dynamic changes during postembryonic development of the mosquito. Transcript expression was especially high in the third and fourth larval stages; however, the AaCAT1 protein was detected only in pupa and adult stages. Functional expression and analysis of AaCAT1 in Xenopus oocytes revealed that it acts as a sodium-independent cationic amino acid transporter, with unique selectivity to L-histidine at neutral pH (K-0.5(L-His) = 0.34 +/- 0.07 mM, pH 7.2). Acidification to pH 6.2 dramatically increases AaCAT1-specific His(+)-induced current. RNAi-mediated silencing of AaCAT1 reduces egg yield of subsequent ovipositions. Our data show that AaCAT1 has notable differences in its transport mechanism when compared with related mammalian cationic amino acid transporters. It may execute histidine-specific transport and signaling in mosquito tissues.