Regulation of large-conductance Ca2+-activated K+ channels by WNK4 kinase.
Regulation of large-conductance Ca2+-activated K+ channels by WNK4 kinase.
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DOI：
10.1152/ajpcell.00133.2013
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发表时间：
2013-10
期刊：
影响因子：
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通讯作者：
Zhijian Wang;A. Subramanya;L. Satlin;N. Pastor-Soler;M. Carattino;T. Kleyman
中科院分区：
文献类型：
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作者：
Zhijian Wang;A. Subramanya;L. Satlin;N. Pastor-Soler;M. Carattino;T. Kleyman
大电导、Ca（2+）激活的K（+）通道，通常称为BK通道，在远端肾单位中流动诱导的K（+）分泌中起主要作用。无赖氨酸激酶4（WNK 4）是一种丝氨酸-苏氨酸激酶，在远端肾单位中表达，抑制ROMK活性和肾脏K（+）分泌。家族性高钾血症性高血压（FHHt）是一种以低肾素高血压和高钾血症为特征的孟德尔疾病，WNK 4突变已在个体中得到描述。由于BK通道在肾脏K（+）分泌中也具有重要作用，我们研究了它们是否以类似于ROMK的方式受到WNK 4的调节。BK通道活性在用WNK 4或FHHt个体中发现的WNK 4突变体转染的兔嵌入细胞系中被抑制。在HEK 293细胞中，表位标记的BK α亚基与WNK 4或WNK 4突变体的共表达降低了BK α亚基质膜和整个细胞的表达。WNK 4内包含自身抑制结构域和卷曲螺旋结构域的区域是WNK 4抑制BK α亚基表达所必需的。与对照组相比，在表达WNK 4的细胞中，被泛素化的BK α亚基的相对分数显著增加。我们的研究结果表明，WNK 4抑制BK通道的活性，在一定程度上，通过增加通道降解通过泛素依赖性途径。基于这些结果，我们认为WNK 4为远端肾单位中两个关键的分泌性K（+）通道ROMK和BK的协调调节提供了细胞机制。
Large-conductance, Ca(2+)-activated K(+) channels, commonly referred to as BK channels, have a major role in flow-induced K(+) secretion in the distal nephron. With-no-lysine kinase 4 (WNK4) is a serine-threonine kinase expressed in the distal nephron that inhibits ROMK activity and renal K(+) secretion. WNK4 mutations have been described in individuals with familial hyperkalemic hypertension (FHHt), a Mendelian disorder characterized by low-renin hypertension and hyperkalemia. As BK channels also have an important role in renal K(+) secretion, we examined whether they are regulated by WNK4 in a manner similar to ROMK. BK channel activity was inhibited in a rabbit intercalated cell line transfected with WNK4 or a WNK4 mutant found in individuals with FHHt. Coexpression of an epitope-tagged BK α-subunit with WNK4 or the WNK4 mutant in HEK293 cells reduced BK α-subunit plasma membrane and whole cell expression. A region within WNK4 encompassing the autoinhibitory domain and a coiled coil domain was required for WNK4 to inhibit BK α-subunit expression. The relative fraction of BK α-subunit that was ubiquitinated was significantly increased in cells expressing WNK4, compared with controls. Our results suggest that WNK4 inhibits BK channel activity, in part, by increasing channel degradation through an ubiquitin-dependent pathway. Based on these results, we propose that WNK4 provides a cellular mechanism for the coordinated regulation of two key secretory K(+) channels in the distal nephron, ROMK and BK.