Nicolas M T, Barhanin J, Reyes R, Demêmes D
Inserm U 432, Université Montpellier 2, Place Eugène Bataillon, PO Box 089, 34095 Cedex 05, Montpellier, France.
Hear Res. 2003 Jul;181(1-2):20-6. doi: 10.1016/s0378-5955(03)00162-x.
K(+) channels in the inner ear regulate the secretion and homeostasis of K(+), i.e. the flux of K(+) ions required to ensure good mechanosensory transduction. We studied the expression and cellular localization of TWIK-1 and TWIK-2, two-pore-domain K(+) channels responsible for background K(+) currents. Reverse transcription-polymerase chain reaction showed that TWIK-1 mRNA is present in the vestibular end organs, vestibular ganglion and cochlea. In contrast, the TWIK-2 mRNA was not detected in the inner ear. Immunocytochemical experiments using confocal microscopy showed that TWIK-1 is specifically localized in 'non-sensory' cells of the inner ear, in the dark cells of the vestibule and in the strial marginal cells of the cochlea. All of these cell types secrete and regulate the K(+) endolymph production and homeostasis. The labeling was strictly limited to the apical membranes of these cells. TWIK-1 was also detected in the cytoplasm of the large neurons of vestibular ganglion and their fibers. The finding that TWIK-1 is specifically distributed in certain areas of the inner ear suggests that this type of K(+) channel plays a role in the regulation of K(+) homeostasis in dark cells and in strial marginal cells. This role has yet to be identified.
内耳中的钾离子通道调节钾离子的分泌和内环境稳定，即确保良好机械感觉转导所需的钾离子通量。我们研究了TWIK-1和TWIK-2这两种负责背景钾电流的两孔结构域钾离子通道的表达和细胞定位。逆转录-聚合酶链反应显示，TWIK-1信使核糖核酸存在于前庭终器、前庭神经节和耳蜗中。相比之下，在内耳中未检测到TWIK-2信使核糖核酸。使用共聚焦显微镜进行的免疫细胞化学实验表明，TWIK-1特异性定位于内耳的“非感觉”细胞、前庭的暗细胞和耳蜗的血管纹边缘细胞中。所有这些细胞类型都分泌并调节钾离子内淋巴的产生和内环境稳定。标记严格局限于这些细胞的顶端膜。在前庭神经节的大神经元及其纤维的细胞质中也检测到了TWIK-1。TWIK-1在内耳特定区域特异性分布的这一发现表明，这种类型的钾离子通道在暗细胞和血管纹边缘细胞的钾离子内环境稳定调节中发挥作用。这一作用尚待确定。
