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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Aquaglyceroporin AQP9: Solute permeation and metabolic control of expression in liver.
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Aquaglyceroporin AQP9: Solute permeation and metabolic control of expression in liver.

机译：Aquaglyceroporin AQP9：在肝脏中的溶质渗透和代谢控制表达。

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摘要

Aquaglyceroporins form the subset of the aquaporin water channel family that is permeable to glycerol and certain small, uncharged solutes. AQP9 has unusually broad solute permeability and is expressed in hepatocyte plasma membranes. Proteoliposomes reconstituted with expressed, purified rat AQP9 protein were compared with simple liposomes for solute permeability. At pH 7.5, AQP9 proteoliposomes exhibited Hg(2+)-inhibitible glycerol and urea permeabilities that were increased 63-fold and 90-fold over background. beta-Hydroxybutyrate permeability was not increased above background, and osmotic water permeability was only minimally elevated. During starvation, the liver takes up glycerol for gluconeogenesis. Expression of AQP9 in liver was induced up to 20-fold in rats fasted for 24-96 h, and the AQP9 level gradually declined after refeeding. No changes in liver AQP9 levels were observed in rats fed ketogenic diets or high-protein diets, but AQP9 levels were elevated in livers of rats made diabetic by streptozotocin injection. When blood glucose levels of the diabetic rats were restored to normal by insulin treatments, the AQP9 levels returned to baseline. Confocal immunofluorescence revealed AQP9 immunostaining on the sinusoidal surfaces of hepatocyte plates throughout the livers of control rats. Denser immunostaining was observed in the same distribution in livers of fasted and streptozotocin-treated rats. We conclude that AQP9 serves as membrane channel in hepatocytes for glycerol and urea at physiological pH, but not for beta-hydroxybutyrate. In addition, levels of AQP9 expression fluctuate depending on the nutritional status of the subject and the circulating insulin levels.
机译：水甘油糖蛋白构成水通道蛋白水通道家族的子集，该通道可渗透甘油和某些小的不带电荷的溶质。 AQP9具有异常宽的溶质通透性，并在肝细胞质膜中表达。将表达，纯化的大鼠AQP9蛋白重构的蛋白脂质体与简单脂质体的溶质通透性进行比较。在pH 7.5时，AQP9蛋白脂质体显示出Hg（2+）可抑制的甘油和尿素通透性，比背景高63倍和90倍。 β-羟基丁酸酯的渗透性没有增加到高于背景，并且渗透水的渗透性仅最小程度地提高。在饥饿期间，肝脏吸收甘油用于糖异生。禁食24-96 h的大鼠肝脏中AQP9的表达被诱导多达20倍，并且AQP9的水平在再次喂养后逐渐下降。喂养生酮饮食或高蛋白饮食的大鼠肝脏AQP9水平未见变化，但注射链脲佐菌素治疗的糖尿病大鼠肝脏AQP9水平升高。当通过胰岛素治疗使糖尿病大鼠的血糖水平恢复正常时，AQP9水平恢复到基线。共聚焦免疫荧光显示在整个对照大鼠的肝脏中，肝细胞板正弦表面的AQP9免疫染色。在禁食和链脲佐菌素治疗的大鼠肝脏中以相同的分布观察到了Denser免疫染色。我们得出的结论是，AQP9可以在生理pH下充当肝细胞中甘油和尿素的膜通道，而不是β-羟基丁酸酯。另外，AQP9表达水平根据受试者的营养状况和循环胰岛素水平而波动。

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