Instituto de Fisiología Experimental, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de Rosario, Santa Fe, Argentina.
Biochem Biophys Res Commun. 2010 Mar 5;393(2):217-21. doi: 10.1016/j.bbrc.2010.01.104. Epub 2010 Feb 2.
Aquaporin-8 (AQP8) is a membrane channel permeable to water and ammonia. As AQP8 is expressed in the inner mitochondrial membrane of several mammalian tissues, we studied the effect of the AQP8 expression on the mitochondrial transport of ammonia. Recombinant rat AQP8 was expressed in the yeast Saccharomyces cerevisiae. The presence of AQP8 in the inner membrane of yeast mitochondria was demonstrated by subcellular fractionation and immunoblotting analysis. The ammonia transport was determined in isolated mitochondria by stopped flow light scattering using formamide as ammonia analog. We found that the presence of AQP8 increased by threefold mitochondrial formamide transport. AQP8-facilitated mitochondrial formamide transport in rat native tissue was confirmed in liver (a mitochondrial AQP8-expressing tissue) vs. brain (a mitochondrial AQP8 non-expressing tissue). Comparative studies indicated that the AQP8-mediated mitochondrial movement of formamide was markedly higher than that of water. Together, our data suggest that ammonia diffusional transport is a major function for mitochondrial AQP8.
水通道蛋白-8（AQP8）是一种对水和氨通透的膜通道。由于 AQP8 在内质网的线粒体膜上表达，我们研究了 AQP8 表达对氨的线粒体转运的影响。重组大鼠 AQP8 在酵母酿酒酵母中表达。通过亚细胞分级分离和免疫印迹分析证明了 AQP8 存在于酵母线粒体的内膜中。通过使用甲酰胺作为氨类似物的停流光散射法在分离的线粒体中测定氨的转运。我们发现 AQP8 的存在使线粒体中甲酰胺的转运增加了三倍。在大鼠原生组织中，AQP8 促进了肝（AQP8 表达的线粒体组织）与脑（AQP8 非表达的线粒体组织）之间的线粒体甲酰胺转运。比较研究表明，AQP8 介导的甲酰胺的线粒体运动比水的线粒体运动高得多。综上所述，我们的数据表明氨的扩散转运是线粒体 AQP8 的主要功能。
