Cloning and Functional Characterization of a Novel Aquaporin from<em>Xenopus laevis</em> Oocytes

We have cloned a novel aquaporin (AQP) from oocytes, which we have provisionally named AQPxlo. The predicted protein showed highest homology (39–50%) to aquaglyceroporins. Northern blot analysis showed strong hybridization to an ∼1.4-kb transcript in fat body and oocytes, whereas a weaker signal was obtained in kidney. We injected transcribed cRNA encoding AQPxlo into oocytes for functional characterization. AQPxlo expression increased osmotic water permeability (), as well as the uptake of glycerol and urea. However, AQPxlo excluded larger polyols and thiourea. An alkaline extracellular pH (pH) increasedand to a lesser extent urea uptake but not glycerol uptake. Remarkably, low HgCl2concentrations (0.3–10 μm) reducedand urea uptake, whereas high concentrations (300–1000 μm) reversed the inhibition. We propose that AQPxlo is a new AQP paralogue unknown in mammals.

我们从卵母细胞中克隆出一种新的水通道蛋白（AQP），我们暂时将其命名为AQPxlo。预测的蛋白质与水甘油通道蛋白具有最高的同源性（39 - 50%）。Northern杂交分析显示，在脂肪体和卵母细胞中与约1.4 kb的转录本有强杂交信号，而在肾脏中获得的信号较弱。我们将编码AQPxlo的转录cRNA注入卵母细胞以进行功能鉴定。AQPxlo的表达增加了渗透水通透性（）以及甘油和尿素的摄取。然而，AQPxlo不允许较大的多元醇和硫脲通过。碱性的细胞外pH（酸碱度）增加了（此处可能有遗漏信息）以及在较小程度上增加了尿素摄取，但没有增加甘油摄取。值得注意的是，低浓度的氯化汞（0.3 - 10 μm）降低了（此处可能有遗漏信息）和尿素摄取，而高浓度（300 - 1000 μm）则逆转了这种抑制作用。我们提出AQPxlo是哺乳动物中未知的一种新的AQP旁系同源物。