WNK4 kinase inhibits Maxi K channel activity by a kinase-dependent mechanism.
WNK4 kinase inhibits Maxi K channel activity by a kinase-dependent mechanism.
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WNK4 激酶通过激酶依赖性机制抑制 Maxi K 通道活性。
DOI：
10.1152/ajprenal.00518.2010
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
Cai,Hui
中科院分区：
文献类型：
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作者：
Zhuang,Jieqiu;Zhang,Xuemei;Wang,Dexuan;Li,Juan;Zhou,Bo;Shi,Zhen;Gu,Dingying;Denson,DonaldD;Eaton,DouglasC;Cai,Hui
WNK[不含赖氨酸(K)]激酶是一个丝氨酸/苏氨酸激酶亚家族。其中两个WNK激酶的突变导致假性低醛固酮增多症II型(PHA II)，其特征是高血压、高钾血症和代谢性酸中毒。最近的研究表明，WNK1和WNK4都能抑制ROMK的活性。然而，WNK激酶对大电导钙电压激活钾通道Maxi K的影响知之甚少。在此，我们报道WNK4野生型(WT)与对照组相比显著抑制HEKαBK稳定细胞系的Maxi K通道活性。然而，WNK4死亡激酶突变体D321A对Maxi K活性没有抑制作用。我们进一步发现，与对照组相比，WNK4同样地抑制了Maxi K的总蛋白和细胞表面蛋白的表达。显性-负性动力蛋白突变体K44A不改变WNK4对Maxi K表面表达的抑制作用。用巴菲霉素A1(质子泵抑制剂)和亮肽素(溶酶体抑制剂)处理可逆转WNK4 WT对Maxi K总蛋白表达的抑制。这些结果表明，WNK4 WT通过减少膜上的Maxi K蛋白来抑制Maxi K的活性，但这种抑制作用并不是由于增加了clathrin介导的Maxi K的内吞作用，而可能是由于促进了其溶酶体的降解。此外，WNK4‘S对Maxi K活性的抑制作用依赖于其激酶活性。
WNK [with no lysine (k)] kinase is a serine/threonine kinase subfamily. Mutations in two of the WNK kinases result in pseudohypoaldosteronism type II (PHA II) characterized by hypertension, hyperkalemia, and metabolic acidosis. Recent studies showed that both WNK1 and WNK4 inhibit ROMK activity. However, little is known about the effect of WNK kinases on Maxi K, a large-conductance Ca2+and voltage-activated potassium (K) channel. Here, we report that WNK4 wild-type (WT) significantly inhibits Maxi K channel activity in HEK αBK stable cell lines compared with the control group. However, a WNK4 dead-kinase mutant, D321A, has no inhibitory effect on Maxi K activity. We further found that WNK4 inhibits total and cell surface protein expression of Maxi K equally compared with control groups. A dominant-negative dynamin mutant, K44A, did not alter the WNK4-mediated inhibitory effect on Maxi K surface expression. Treatment with bafilomycin A1 (a proton pump inhibitor) and leupeptin (a lysosomal inhibitor) reversed WNK4 WT-mediated inhibition of Maxi K total protein expression. These findings suggest that WNK4 WT inhibits Maxi K activity by reducing Maxi K protein at the membrane, but that the inhibition is not due to an increase in clathrin-mediated endocytosis of Maxi K, but likely due to enhancing its lysosomal degradation. Also, WNK4's inhibitory effect on Maxi K activity is dependent on its kinase activity.