WNK4激酶通过溶酶体途径抑制BK通道表达  

WNK4 kinase-mediated inhibitory effect on expression of BK channel via lysosomal pathway

作　　者：庄捷秋[1] 王德选[1] 张益前[2] 牛伟辉[2] 陈方旋[1] 施珍[2] 潘殊方[2] 谷定英[2] 

机构地区：[1]温州医学院附属育英儿童医院肾内科,325027 [2]温州医学院附属第二医院肾内科

出　　处：《中华肾脏病杂志》2012年第4期291-295,共5页Chinese Journal of Nephrology

基　　金：国家自然科学基金（81170709）;浙江省自然科学基金（Y2080291）;温州市科技局对外合作项目（H20090071）.

摘　　要：目的研究WNK4激酶对BK通道的调节作用及机制。方法将BK和WNK4野生型（WNK4-WT）或CD4（对照）质粒DNA共同转染进Cos-7细胞中，采用免疫染色．共聚焦激光显微镜、化学发光法、Western印迹法检测BK在细胞上的分布、细胞膜表面蛋白和总蛋白的表达；并使用质子泵抑制剂bafilomycinA1（BarA1）阻断溶酶体降解检测BK蛋白表达水平的减少是否由于其蛋白降解增多所致。结果免疫染色．共聚焦激光显微镜发现，与对照组相比，WNK4-WT组BK在细胞膜表面的分布明显减少。化学发光法检测结果显示，对照组BK的细胞膜表面蛋白表达水平为299．9±18．6，WNK4-WT组中其细胞膜表面蛋白表达水平为148．4±13．7，比对照组显著下降（P〈0．01）。Western印迹结果提示，WNK4-WT组BK的总蛋白表达水平比对照组明显减少。和对照组（100％）相比，WNK4．WT显著减少BK的总蛋白水平（42．3％±15．2％，P〈0．01），而BarA1则逆转WNK4-WT对BK蛋白的抑制作用（82．2％±12．1％．P〈0．05）。结论WNK4激酶能同时抑制BK在Cos-7细胞膜表面蛋白和总蛋白的表达水平；WNK4激酶抑制BK通道蛋白的表达是通过增加其在溶酶体内的降解所致的。Objective To investigate the mechanism underlying the WNK4 kinase- mediated inhibitory effect on BK channel. Methods Cos-7 cells were cotransfected with BK in combination with either CD4 （control group） or wild type WNK4 （WNK4-WT）. Immunostaining and confocal microscopy, chemiluminescence, Western blotting analysis were then employed to determine the BK localization in cells, BK surface expression and total protein level, respectively. To further investigate whether the reduction of BK protein expression is due to an increase in degradation through a lysosomal pathway, BK protein level was determined after treated with bafilomycin A1 （Bar A1）, a proton pump inhibitor affecting lysosomal degradation. Results Immunostaining and confocal microscopic study showed that BK was localized both in plasma membrane and cytosol in the control group. After cells transfected with WNK4-WT, BK expression was markedly reduced. Chemiluminescent assay found that BK surface expression level was 299.9±18.6 in the controlgroup, whereas it was significantly reduced （148.4±13.7, P〈0.01） in the WNK4-WT group. Western blotting analysis showed that total BK protein level was markedly reduced in the presence of WNK4-WT compared to the control group. WNK4-WT was shown to significantly reduce the BK total protein level （42.3%±15.2%） compared to the control group （100%） （P〈0.01）. When the cells was treated with Bafilomycin A1 （Bar A1, 0.5 μmol/L）, WNK4-mediated reduction in BK protein was reversed （82.2%±12.1%, P〈0.05）. Conclusions WNK4 inhibits total and surface protein expression of BK in Cos-7 cells whick is likely due to an increase in BK degradation through a lysosomal pathway.

关 键 词：溶酶体 假性醛固酮减少症 钾通道 WNK4激酶 BK通道 蛋 白降解 

分 类 号：R363[医药卫生—病理学]