Potassium-regulated distal tubule WNK bodies are kidney-specific WNK1 dependent.
Potassium-regulated distal tubule WNK bodies are kidney-specific WNK1 dependent.
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钾调节的远端小管WNK体是肾脏特异性的WNK1。
DOI：
10.1091/mbc.e17-08-0529
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发表时间：
2018-02-15
影响因子：
3.3
通讯作者：
Subramanya AR
中科院分区：
文献类型：
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作者：
Boyd-Shiwarski CR;Shiwarski DJ;Roy A;Namboodiri HN;Nkashama LJ;Xie J;McClain KL;Marciszyn A;Kleyman TR;Tan RJ;Stolz DB;Puthenveedu MA;Huang CL;Subramanya AR
WNK 小体是大的点状无膜胞质信号传导点，可隔离 WNK 丝氨酸-苏氨酸激酶，并在全身钾平衡变化期间在肾远端肾小管上皮细胞中形成。这些结构的组装需要 KS-WNK1，这是 WNK1 基因的截短亚型，仅在远端小管中表达。无赖氨酸 (WNK) 激酶通过调节肾小管电解质转运来协调容量和钾稳态。在远曲小管 (DCT) 中，钾失衡导致 WNK 信号复合物集中成大的离散病灶，我们称之为“WNK 小体”。尽管这些结构之前已被报道过，但驱动它们组装的机制仍然不清楚。在这里，我们发现肾脏特异性 WNK1 (KS-WNK1) 是一种截短的激酶缺陷型 WNK1 亚型，在 DCT 中高度表达，对于 WNK 体的形成至关重要。虽然在饮食钾负荷和限制的小鼠的远端小管中存在明显形态上不同的 WNK 体，但 KS-WNK1 敲除小鼠在相同条件下缺乏这些结构。结合肾脏的体内观察和细胞培养的重建研究，我们发现 WNK 小体是动态无膜灶，与传统细胞器不同，与核糖体蛋白 L22 共定位，并聚集 WNK 信号通路。 WNK 体的形成需要进化上保守的富含半胱氨酸的疏水基序，该基序包含在 KS-WNK1 独特的 N 末端外显子内。我们认为 WNK 体不是病理性聚集体，而是 DCT 胞质溶胶中 KS-WNK1 依赖性微结构域，在钾平衡的生理变化过程中调节 WNK 信号传导。
WNK bodies are large punctate membraneless cytosolic signaling foci that sequester WNK serine–threonine kinases and form in renal distal tubular epithelial cells during shifts in total body potassium balance. The assembly of these structures requires KS-WNK1, a truncated isoform of the WNK1 gene that is exclusively expressed in the distal tubule. With-no-lysine (WNK) kinases coordinate volume and potassium homeostasis by regulating renal tubular electrolyte transport. In the distal convoluted tubule (DCT), potassium imbalance causes WNK signaling complexes to concentrate into large discrete foci, which we call “WNK bodies.” Although these structures have been reported previously, the mechanisms that drive their assembly remain obscure. Here, we show that kidney-specific WNK1 (KS-WNK1), a truncated kinase-defective WNK1 isoform that is highly expressed in the DCT, is critical for WNK body formation. While morphologically distinct WNK bodies were evident in the distal tubules of mice subjected to dietary potassium loading and restriction, KS-WNK1 knockout mice were deficient in these structures under identical conditions. Combining in vivo observations in kidney with reconstitution studies in cell culture, we found that WNK bodies are dynamic membraneless foci that are distinct from conventional organelles, colocalize with the ribosomal protein L22, and cluster the WNK signaling pathway. The formation of WNK bodies requires an evolutionarily conserved cysteine-rich hydrophobic motif harbored within a unique N-terminal exon of KS-WNK1. We propose that WNK bodies are not pathological aggregates, but rather are KS-WNK1–dependent microdomains of the DCT cytosol that modulate WNK signaling during physiological shifts in potassium balance.