Identification, functional characterization and, expression of a LAT type amino acid transporter from the mosquito Aedes aegypti
Identification, functional characterization and, expression of a LAT type amino acid transporter from the mosquito Aedes aegypti
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DOI：
10.1016/s0965-1748(03)00081-x
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发表时间：
2003-08-01
影响因子：
3.8
通讯作者：
Gill, SS
中科院分区：
文献类型：
--
作者：
Jin, XY;Aimanova, K;Gill, SS
我们从埃及伊蚊中分离出两个cdna，一个是l -氨基酸转运蛋白（AeaLAT），一个是CD98重链（AeaCD98hc）。单独表达AeaCD98hc或AeaLAT在爪蟾卵母细胞中不诱导氨基酸转运活性。然而，AeaCD98hc和AeaLAT的共表达显示出氨基酸运输活性显著增加。AeaCD98hc和AeaLAT被认为是通过二硫键连接形成异源二聚体蛋白。这种异二聚体蛋白对大的中性和碱性氨基酸具有摄取特异性。小的酸性中性氨基酸是这种转运体的不良底物。中性氨基酸（亮氨酸）摄取活性部分依赖于Na+，因为没有Na+时亮氨酸的摄取比有Na+时低约44%。而碱性氨基酸（赖氨酸）的吸收活性在pH为7.4时完全不依赖于Na+。细胞外氨基酸浓度可能是决定氨基酸转运的主要因素。这些结果表明，在没有离子的情况下，异源蛋白可能是一种介导氨基酸扩散的单转运体。AeaLAT在幼虫胃盲肠、马氏小管和后肠中均有高水平表达。在caeca和后肠中表达在顶细胞膜上。然而，在马尔比氏小管和中肠（后者表达水平较低）中，基底外侧膜中检测到转运蛋白。这种表达谱支持了AeaLAT是一种营养氨基酸转运蛋白的结论。(C) 2003, Elsevier Ltd.出版
We isolated two cDNAs from the mosquito Aedes aegypti, an L-amino acid transporter (AeaLAT) and a CD98 heavy chain (AeaCD98hc). Expression of AeaCD98hc or AeaLAT alone in Xenopus oocyte did not induce amino acid transport activity. However, co-expression of AeaCD98hc and AeaLAT, which are postulated to form a heterodimer protein linked through a disulfide bond, showed significant increase in amino acid transport activity. This heterodimeric protein showed uptake specificity for large neutral and basic amino acids. Small acidic neutral amino acids were poor substrates for this transporter. Neutral amino acid (leucine) uptake activity was partially Na+ dependent, because leucine uptake was approximately 44% lower in the absence of Na+ than in its presence. However, basic amino acid (lysine) uptake activity was completely Na+ independent at pH of 7.4. Extracellular amino acid concentration could be the main factor that determined amino acid transport. These results suggest the heteromeric protein is likely a uniporter mediating diffusion of amino acids in the absence of ions. The AeaLAT showed high level expression in the gastric caeca, Malpighian tubules and hindgut of larvae. In caeca and hindgut expression was in the apical cell membrane. However, in Malpighian tubules and in midgut, the latter showing low level expression, the transporter was detected in the basolateral membrane. This expression profile supports the conclusion that this AeaLAT is a nutrient amino acid transporter. (C) 2003 Published by Elsevier Ltd.