Department of Nephrology, Hua Shan Hospital, Fudan University School of Medicine, 12 Wulumuqi Zhong Road, Shanghai, 200040, China.
Pflugers Arch. 2012 Mar;463(3):477-85. doi: 10.1007/s00424-011-1062-y. Epub 2011 Dec 27.
WNK is a serine/threonine kinase. Mutation in WNK1 or WNK4 kinase results in pseudohypoaldosteronism type II (PHA II) featuring hypertension, hyperkalemia and metabolic acidosis. Sodium chloride cotransporter (NCC) is known to be regulated by phosphorylation and trafficking. Dietary salt and hormonal stimulation, such as aldosterone, also affect the regulation of NCC. We have previously reported that WNK4 inhibits NCC protein expression. To determine whether dietary salt affects NCC abundance through WNK4-mediated mechanism, we investigated the effects of dietary salt change with or without aldosterone infusion (1 mg/kg/day) on NCC and WNK4 expression in rats. We found that high-salt (HS, 4% NaCl) diet significantly inhibits NCC mRNA expression and protein abundance while enhancing WNK4 mRNA and protein expression, whereas low-salt (LS, 0.07% NaCl) diet increases NCC mRNA expression and protein abundance while reducing WNK4 expression. We also found that aldosterone infusion in HS-fed rats increases NCC mRNA expression and protein abundance, but decreases WNK4 expression. Administration with spironolactone (0.1 g/kg/day) in LS-fed rats decreases NCC mRNA expression and protein abundance while increasing WNK4 expression. We further showed that ERK1/2 phosphorylation was increased in HS-fed rats, but decreased in LS-fed rats. In HEK293 cells, over-expressed WNK4 increases ERK1/2 phosphorylation, whereas knockdown of WNK4 expression decreases ERK1/2 phosphorylation. Aldosterone treatment for 3 h decreases ERK1/2 phosphorylation. These data suggest that dietary salt change affects NCC protein abundance in an aldosterone-dependent mechanism likely via the WNK4-ERK1/2-mediated pathway.
WNK 是一种丝氨酸/苏氨酸激酶。WNK1 或 WNK4 激酶的突变导致假性醛固酮减少症 II 型（PHA II），其特征为高血压、高钾血症和代谢性酸中毒。已知钠离子/氯化物共转运蛋白（NCC）受磷酸化和转运调节。膳食盐和激素刺激，如醛固酮，也会影响 NCC 的调节。我们之前曾报道过 WNK4 抑制 NCC 蛋白表达。为了确定膳食盐是否通过 WNK4 介导的机制影响 NCC 的丰度，我们研究了膳食盐变化（高盐[HS]：4% NaCl；低盐[LS]：0.07% NaCl）与醛固酮输注（1 mg/kg/天）对大鼠 NCC 和 WNK4 表达的影响。我们发现，HS 饮食显著抑制 NCC mRNA 表达和蛋白丰度，同时增强 WNK4 mRNA 和蛋白表达，而 LS 饮食增加 NCC mRNA 表达和蛋白丰度，同时降低 WNK4 表达。我们还发现，HS 喂养大鼠的醛固酮输注增加了 NCC mRNA 表达和蛋白丰度，但降低了 WNK4 表达。在 LS 喂养大鼠中给予螺内酯（0.1 g/kg/天）可降低 NCC mRNA 表达和蛋白丰度，同时增加 WNK4 表达。我们进一步表明，HS 喂养大鼠的 ERK1/2 磷酸化增加，而 LS 喂养大鼠的 ERK1/2 磷酸化减少。在 HEK293 细胞中，过表达 WNK4 增加了 ERK1/2 磷酸化，而 WNK4 表达的敲低则降低了 ERK1/2 磷酸化。醛固酮处理 3 h 降低了 ERK1/2 磷酸化。这些数据表明，膳食盐的变化通过 WNK4-ERK1/2 介导的途径以依赖醛固酮的机制影响 NCC 蛋白丰度。
