Claudin-10a Deficiency Shifts Proximal Tubular Cl- Permeability to Cation Selectivity via Claudin-2 Redistribution
Claudin-10a Deficiency Shifts Proximal Tubular Cl- Permeability to Cation Selectivity via Claudin-2 Redistribution
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DOI：
10.1681/asn.2021030286
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发表时间：
2022-02-08
影响因子：
13.6
通讯作者：
Guenzel, Dorothee
中科院分区：
文献类型：
--
作者：
Breiderhoff, Tilman;Himmerkus, Nina;Guenzel, Dorothee
背景紧密连接蛋白claudin-2和claudin-10a分别形成细胞旁阳离子通道和阴离子通道，表达于近曲小管。为了研究claudin-10a在肾脏中的生理作用，我们建立了claudin-10a缺陷小鼠，通过Southern印迹、Western印迹和免疫荧光染色证实基因敲除成功，并分析了敲除动物和野生型动物的尿液和血清。我们还利用电生理学研究了分离的近端小管的功能，并通过药物干预、RNA测序分析、Western印迹、免疫荧光染色和呼吸计量学研究了代偿调节。在基因敲除时，近端小管段的claudin-10a被claudin-2取代。电生理显示从细胞旁阴离子偏爱转变为阳离子偏爱，并失去了胞外Cl-对HCO3-的偏好。其结果是，患者出现肾小管钙镁滞留、尿液pH升高和轻度高镁血症。与其他尿液和血清参数在控制条件和顺序药物转运抑制下的比较，以及不变的锂排出分数，建议在近端和远端肾小管段采取代偿措施。近端肾小管氧处理的变化和调节脂肪酸代谢的基因的差异表达表明近端肾小管适应。结论Claudin-10a是近端肾小管上皮细胞旁的主要阴离子通道，其缺失可通过claudin-2的重新分布引起钙、镁的重吸收。近端和远端节段的跨细胞运输和近端肾小管的代谢适应弥补了细胞旁阴离子通透性的丧失。
Background The tight junction proteins claudin-2 and claudin-10a form paracellular cation and anion channels, respectively, and are expressed in the proximal tubule. However, the physiologic role of claudin-10a in the kidney has been unclear.Methods To investigate the physiologic role of claudin-10a, we generated claudin-10a-deficient mice, confirmed successful knockout by Southern blot, Western blot, and immunofluorescence staining, and analyzed urine and serum of knockout and wild-type animals. We also used electrophysiologic studies to investigate the functionality of isolated proximal tubules, and studied compensatory regulation by pharmacologic intervention, RNA sequencing analysis, Western blot, immunofluorescence staining, and respirometry.Results Mice deficient in claudin-10a were fertile and without overt phenotypes. On knockout, claudin-10a was replaced by claudin-2 in all proximal tubule segments. Electrophysiology showed conversion from paracellular anion preference to cation preference and a loss of paracellular Cl- over HCO3- preference. As a result, there was tubular retention of calcium and magnesium, higher urine pH, and mild hypermagnesemia. A comparison with other urine and serum parameters under control conditions and sequential pharmacologic transport inhibition, and unchanged fractional lithium excretion, suggested compensative measures in proximal and distal tubular segments. Changes in proximal tubular oxygen handling and differential expression of genes regulating fatty acid metabolism indicated proximal tubular adaptation. Western blot and immunofluorescence revealed alterations in distal tubular transport.Conclusions Claudin-10a is the major paracellular anion channel in the proximal tubule and its deletion causes calcium and magnesium hyper-reabsorption by claudin-2 redistribution. Transcellular transport in proximal and distal segments and proximal tubular metabolic adaptation compensate for loss of paracellular anion permeability.