Co-localisation of Kir4.1 and AQP4 in rat and human cochleae reveals a gap in water channel expression at the transduction sites of endocochlear K+ recycling routes
Co-localisation of Kir4.1 and AQP4 in rat and human cochleae reveals a gap in water channel expression at the transduction sites of endocochlear K+ recycling routes
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DOI：
10.1007/s00441-012-1456-y
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发表时间：
2012-10-01
影响因子：
3.6
通讯作者：
Hirt, Bernhard
中科院分区：
文献类型：
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作者：
Eckhard, Andreas;Gleiser, Corinna;Hirt, Bernhard
耳蜗中的感觉转导依赖于外淋巴-内淋巴钾 (K+) 循环。有人提出，耳蜗管的上皮支持细胞（SC）可能形成细胞内 K+ 循环途径。因此，它们必须具有促进 K+ 吸收和释放的分子机制，以及伴随的渗透驱动的水运动。迄今为止，还没有描述允许跨 SC 的体积平衡的跨上皮 K+ 通量的分子。本研究基于大鼠和人耳蜗的免疫组织化学双标记实验，描述了 SC 中 K(ir)4.1 K+ 通道 (K(ir)4.1) 和水通道蛋白 4 水通道 (AQP4) 的亚细胞共定位。本研究的结果揭示了 K(ir)4.1 在邻近毛细胞的柯蒂氏器的感觉域以及毗邻大细胞外液空间的内沟和外沟的非感觉域中 SC 的基底膜或基底外侧膜中的表达。内沟（齿间细胞、内沟细胞）和外沟（Hensen 细胞、外沟细胞）的 SC 显示 K(ir)4.1 和 AQP4 表达的共定位。然而，柯蒂氏器感觉域的 SC 揭示了 AQP4 表达的缺口。外柱细胞不含 K(ir)4.1 和 AQP4。本研究中描述的耳蜗 SC 中 K(ir)4.1 和 AQP4 的亚细胞共定位类似于中枢神经系统的星形胶质细胞和视网膜中的胶质 Mueller 细胞。
Sensory transduction in the cochlea depends on perilymphatic-endolymphatic potassium (K+) recycling. It has been suggested that the epithelial supporting cells (SCs) of the cochlear duct may form the intracellular K+ recycling pathway. Thus, they must be endowed with molecular mechanisms that facilitate K+ uptake and release, along with concomitant osmotically driven water movements. As yet, no molecules have been described that would allow for volume-equilibrated transepithelial K+ fluxes across the SCs. This study describes the subcellular co-localisation of the K(ir)4.1 K+ channel (K(ir)4.1) and the aquaporin-4 water channel (AQP4) in SCs, on the basis of immunohistochemical double-labelling experiments in rat and human cochleae. The results of this study reveal the expression of K(ir)4.1 in the basal or basolateral membranes of the SCs in the sensory domain of the organ of Corti that are adjacent to hair cells and in the non-sensory domains of the inner and outer sulci that abut large extracellular fluid spaces. The SCs of the inner sulcus (interdental cells, inner sulcus cells) and the outer sulcus (Hensen's cells, outer sulcus cells) display the co-localisation of K(ir)4.1 and AQP4 expression. However, the SCs in the sensory domain of the organ of Corti reveal a gap in the expression of AQP4. The outer pillar cell is devoid of both K(ir)4.1 and AQP4. The subcellular co-localisation of K(ir)4.1 and AQP4 in the SCs of the cochlea described in this study resembles that of the astroglia of the central nervous system and the glial Mueller cells in the retina.