Claudin-10b is an important component of the tight junction in the thick ascending limb (TAL) of Henle's loop and allows paracellular sodium transport. In immunofluorescence stainings, claudin-10b–positive cells exhibited extensive extra staining of basolateral, column-like structures. The precise localization and function have so far remained elusive. In isolated cortical TAL segments from C57BL/6J mice, kidney-specific claudin-10 knockout mice (cKO), and respective litter mates (WT), we investigated the localization and protein expression and function by fluorescence microscopy and electrophysiological measurements. Ultrastructural analysis of TAL in kidney sections was performed by electron microscopy. Claudin-10b colocalized with the basolateral Na⁺-K⁺ ATPase and the Cl^– channel subunit barttin, but the lack of claudin-10b did not influence the localization or abundance of these proteins. However, the accessibility of the basolateral infolded extracellular space to ouabain or fluorescein was increased by basolateral Ca²⁺ removal and in the absence of claudin-10b. Ultrastructural analysis by electron microscopy revealed a widening of basolateral membrane infoldings in cKO in comparison to WT. We hypothesize that claudin-10b shapes neighboring membrane invaginations by trans interaction to stabilize and facilitate high-flux salt transport in a water-tight epithelium.

中文翻译：

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claudin-10b 在粗升肢基底外侧膜内折中未被认识的作用

Claudin-10b 是 Henle 袢粗升肢 (TAL) 紧密连接的重要组成部分，允许细胞旁钠转运。在免疫荧光染色中，claudin-10b 阳性细胞表现出广泛的基底外侧柱状结构额外染色。迄今为止，精确的定位和功能仍然难以捉摸。在来自 C57BL/6J 小鼠、肾脏特异性 claudin-10 敲除小鼠 (cKO) 和相应同窝小鼠 (WT) 的分离皮质 TAL 片段中，我们通过荧光显微镜和电生理测量研究了定位和蛋白质表达和功能。通过电子显微镜对肾脏切片中的 TAL 进行超微结构分析。Claudin-10b 与基底外侧 Na ⁺ -K ⁺ ATP 酶和 Cl^–通道亚基 barttin，但 claudin-10b 的缺乏并不影响这些蛋白质的定位或丰度。然而，基底外侧折叠的细胞外空间对哇巴因或荧光素的可及性通过基底外侧 Ca ²⁺去除和 claudin-10b 的存在而增加。通过电子显微镜进行的超微结构分析显示，与 WT 相比，cKO 中的基底外侧膜折叠变宽。我们假设 claudin-10b 通过反式相互作用塑造相邻的膜内陷，以稳定和促进水密上皮细胞中的高通量盐转运。