FoxO1 inhibits transcription and membrane trafficking of epithelial Na+ channel
FoxO1 inhibits transcription and membrane trafficking of epithelial Na+ channel
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FoxO1 抑制上皮 Na 通道的转录和膜运输。
DOI：
10.1242/jcs.171876
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发表时间：
2015-10-01
影响因子：
4
通讯作者：
Liang, Xiubin
中科院分区：
文献类型：
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作者：
Shen, Yachen;Xu, Weifeng;Liang, Xiubin
受胰岛素调控的上皮Na+通道(ENaC)在控制远端肾单位的Na+重吸收中起着重要的作用。胰岛素信号下游的Forkhead box O1(FoxO1)在调节ENaC中的潜在作用仍有待研究。在这里，我们发现一种成分活性形式的FoxO1(ADA-FoxO1)的过表达抑制了小鼠皮质集合管(MCCD)细胞中ENaCα亚单位(也称为SCCN1a)的mRNA水平和ENaC的顶端密度。相反，在基础条件下，FoxO1基因的敲除增加了顶膜的α-ENaC和Na+转运水平。胰岛素促进α-ENaC的表达并诱导FoxO1的磷酸化；然而，在表达ADA-FoxO1的细胞中，胰岛素处理所观察到的α-ENaC和磷酸化的FoxO1表达的增加被钝化了60%。此外，胰岛素诱导了磷酸化的FoxO1与14-3-3 epsilon之间的相互作用，表明FoxO1的磷酸化通过与14-3-3 epsilon结合来促进ENaC膜的转运。Foxo1还抑制α-ENaC启动子的活性，推测的FoxO1靶点位于α-ENaC启动子的-500~-200个核苷酸区域。这些发现表明，FoxO1是胰岛素依赖控制MCCD上皮细胞ENaC表达和正向运输的关键负性调节因子。
The epithelial Na+ channel (ENaC), regulated by insulin, is of fundamental importance in the control of Na+ reabsorption in the distal nephron. The potential role of Forkhead box O1 (FoxO1), downstream of insulin signaling, in the regulation of ENaC remains to be investigated. Here, we found that the overexpression of a constitutively active form of FoxO1 (ADA-FoxO1) suppressed the mRNA level of the ENaC a subunit (alpha-ENaC; also known as SCCN1A) and the apical density of ENaC in mouse cortical collecting duct (mCCD) cells. Conversely, knockdown of FoxO1 increased the apical membrane levels of alpha-ENaC and Na+ transport under basal conditions. Insulin elevated alpha-ENaC expression and induced FoxO1 phosphorylation; however, the increase in alpha-ENaC and phosphorylated FoxO1 expression observed with insulin treatment was blunted similar to 60% in cells expressing ADA-FoxO1. Moreover, insulin induced the interaction between phosphorylated FoxO1 and 14-3-3 epsilon, indicating that FoxO1 phosphorylation promotes ENaC membrane trafficking by binding to 14-3-3 epsilon. FoxO1 also suppressed activity of the alpha-ENaC promoter, and the putative FoxO1 target site is located in the -500 to -200 nt region of the alpha-ENaC promoter. These findings indicate that FoxO1 is a key negative regulatory factor in the insulin-dependent control of ENaC expression and forward trafficking in mCCD epithelia.