Soe Rikke, Macaulay Nanna, Klaerke Dan Arne
Department of Physiology and Biochemistry, IBHV, Faculty of Life Sciences, University of Copenhagen, Grønnegaardsvej 7, 1870 Frederiksberg C, Denmark.
Neurosci Lett. 2009 Jun 26;457(2):80-4. doi: 10.1016/j.neulet.2009.04.010. Epub 2009 Apr 8.
The K+ channels Kir4.1 and Kir4.1-Kir5.1 are expressed in the glial cells of the CNS and are involved in regulation of the K+ homeostasis. Several studies have shown that Kir4.1 channels are co-localized with aquaporins (AQP4) in the glial endfeet, and a putative functional coupling between the Kir channels and aquaporins is therefore debated. To test a possible volume-sensitivity of the Kir channels, the Kir4.1 or Kir4.1-Kir5.1 channels were expressed in Xenopus oocytes with or without co-expression of aquaporins and subsequently exposed to cell volume alterations. Our results show an increase in Kir4.1 and Kir4.1-Kir5.1 currents upon swelling of the oocytes and a reduction in the current when the oocytes were shrunk. The volume-dependent changes in channel activity were not due to changes in the kinetics of the channels. These findings implicate a putative functional interaction between the Kir channels and aquaporins via small, fast cell volume changes in the glial cells.
钾离子通道Kir4.1和Kir4.1-Kir5.1在中枢神经系统的胶质细胞中表达，并参与钾离子稳态的调节。多项研究表明，Kir4.1通道与水通道蛋白（AQP4）在胶质细胞终足中共定位，因此，Kir通道与水通道蛋白之间假定的功能偶联存在争议。为了测试Kir通道可能的容积敏感性，将Kir4.1或Kir4.1-Kir5.1通道在非洲爪蟾卵母细胞中表达，同时有或没有共表达水通道蛋白，随后使其暴露于细胞容积变化中。我们的结果显示，卵母细胞肿胀时Kir4.1和Kir4.1-Kir5.1电流增加，而卵母细胞皱缩时电流减小。通道活性的容积依赖性变化并非由于通道动力学的改变。这些发现表明，通过胶质细胞中小而快速的细胞容积变化，Kir通道与水通道蛋白之间存在假定的功能相互作用。
