Developmental expression and biophysical characterization of a Drosophila melanogaster aquaporin
Developmental expression and biophysical characterization of a Drosophila melanogaster aquaporin
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DOI：
10.1152/ajpcell.00612.2004
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发表时间：
2005-08-01
影响因子：
5.5
通讯作者：
Brodsky, JL
中科院分区：
文献类型：
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作者：
Kaufmann, N;Mathai, JC;Brodsky, JL
水通道蛋白 (AQP) 加速水和其他溶质穿过生物膜的运动，但每个 AQP 转运功能的分子机制以及 AQP 家族成员所发挥的不同生理作用仍待确定。因此，我们在模式生物果蝇中表征了 AQP，该生物适合遗传操作和发育分析。为了研究果蝇马氏小管 (MT) 促进水运输的机制，我们在果蝇基因组中鉴定了 7 个假定的 AQP，并发现其中一个（以前称为 DRIP）与表现出最高水运输速率的脊椎动物 AQP 具有最大的序列相似性。原位 mRNA 分析表明，DRIP 在胚胎和成年 MT 以及其他需要液体运输的组织中都有表达。此外，DRIP 表达模式是动态的。为了定义 DRIP 介导的水转运，该蛋白质在非洲爪蟾卵母细胞和酵母分泌囊泡中表达，我们发现水转运速率显着升高与 DRIP 表达相关。此外，表达DRIP的分泌囊泡中水运输所需的活化能为4.9 kcal/mol。该低值是 AQP 介导的水运输的特征，而对照囊泡中的值为 16.4 kcal/mol。相反，甘油、尿素、氨和质子转运不受 DRIP 表达的影响，表明 DRIP 是一种高度选择性的水特异性通道。该结果与 DRIP 和哺乳动物水特异性 AQP 之间的同源性一致。这些数据共同将果蝇确立为研究 AQP 功能的新模型系统。
Aquaporins (AQPs) accelerate the movement of water and other solutes across biological membranes, yet the molecular mechanisms of each AQP's transport function and the diverse physiological roles played by AQP family members are still being defined. We therefore have characterized an AQP in a model organism, Drosophila melanogaster, which is amenable to genetic manipulation and developmental analysis. To study the mechanism of Drosophila Malpighian tubule (MT)-facilitated water transport, we identified seven putative AQPs in the Drosophila genome and found that one of these, previously named DRIP, has the greatest sequence similarity to those vertebrate AQPs that exhibit the highest rates of water transport. In situ mRNA analyses showed that DRIP is expressed in both embryonic and adult MTs, as well as in other tissues in which fluid transport is essential. In addition, the pattern of DRIP expression was dynamic. To define DRIP-mediated water transport, the protein was expressed in Xenopus oocytes and in yeast secretory vesicles, and we found that significantly elevated rates of water transport correlated with DRIP expression. Moreover, the activation energy required for water transport in DRIP-expressing secretory vesicles was 4.9 kcal/mol. This low value is characteristic of AQP-mediated water transport, whereas the value in control vesicles was 16.4 kcal/mol. In contrast, glycerol, urea, ammonia, and proton transport were unaffected by DRIP expression, suggesting that DRIP is a highly selective water-specific channel. This result is consistent with the homology between DRIP and mammalian water-specific AQPs. Together, these data establish Drosophila as a new model system with which to investigate AQP function.