Department of Biomedicine, Faculty of Health Science, Aarhus University, 8000 Aarhus, Denmark.
Department of Biochemistry and Molecular Biology, Faculty of Science, University of Southern Denmark, 5230 Odense, Denmark.
Int J Mol Sci. 2021 Feb 4;22(4):1569. doi: 10.3390/ijms22041569.
(1) Background: The unusual accumulation of Na,K-ATPase complexes in the brush border membrane of choroid plexus epithelial cells have intrigued researchers for decades. However, the full range of the expressed Na,K-ATPase subunits and their relation to the microvillus cytoskeleton remains unknown. (2) Methods: RT-PCR analysis, co-immunoprecipitation, native PAGE, mass spectrometry, and differential centrifugation were combined with high-resolution immunofluorescence histochemistry, proximity ligase assays, and stimulated emission depletion (STED) microscopy on mouse choroid plexus cells or tissues in order to resolve these issues. (3) Results: The choroid plexus epithelium expresses Na,K-ATPase subunits α1, α2, β1, β2, β3, and phospholemman. The α1, α2, β1, and β2, subunits are all localized to the brush border membrane, where they appear to form a complex. The ATPase complexes may stabilize in the brush border membrane via anchoring to microvillar actin indirectly through ankyrin-3 or directly via other co-precipitated proteins. Aquaporin 1 (AQP1) may form part of the proposed multi-protein complexes in contrast to another membrane protein, the Na-K-2Cl cotransporter 1 (NKCC1). NKCC1 expression seems necessary for full brush border membrane accumulation of the Na,K-ATPase in the choroid plexus. (4) Conclusion: A multitude of Na,K-ATPase subunits form molecular complexes in the choroid plexus brush border, which may bind to the cytoskeleton by various alternative actin binding proteins.
（1）背景：几十年来，脉络丛上皮细胞刷状缘膜中 Na，K-ATPase 复合物的异常积累一直令研究人员感到好奇。然而，表达的 Na，K-ATPase 亚基的完整范围及其与微绒毛细胞骨架的关系仍然未知。（2）方法：RT-PCR 分析、共免疫沉淀、天然 PAGE、质谱和差速离心与高分辨率免疫荧光组织化学、邻近连接酶测定和受激发射耗散（STED）显微镜相结合，用于解决这些问题在小鼠脉络丛细胞或组织上。（3）结果：脉络丛上皮表达 Na，K-ATPase 亚基α1、α2、β1、β2、β3 和磷酸烯醇式丙酮酸。α1、α2、β1 和β2 亚基均定位于刷状缘膜，在该处它们似乎形成复合物。ATP 酶复合物可能通过锚定到微绒毛肌动蛋白间接稳定在刷状缘膜中，通过锚蛋白-3 或直接通过其他共沉淀的蛋白质。水通道蛋白 1（AQP1）可能形成所提议的多蛋白复合物的一部分，而不是另一种膜蛋白，即 Na-K-2Cl 共转运蛋白 1（NKCC1）。NKCC1 的表达似乎对于 Na，K-ATPase 在脉络丛中的完整刷状缘膜积累是必要的。（4）结论：大量的 Na，K-ATPase 亚基在脉络丛刷状缘形成分子复合物，这些复合物可能通过各种替代肌动蛋白结合蛋白与细胞骨架结合。
