Regulation of stability and function of the epithelial Na+ channel (ENaC) by ubiquitination
Regulation of stability and function of the epithelial Na+ channel (ENaC) by ubiquitination
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DOI：
10.1093/emboj/16.21.6325
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发表时间：
1997-11-03
期刊：
影响因子：
11.4
通讯作者：
Rotin, D
中科院分区：
文献类型：
--
作者：
Staub, O;Gautschi, I;Rotin, D
上皮Na+通道（ENaC）由三个亚基（α β γ）组成，在盐和流体稳态中起关键作用。通道开放和数量的减少与一些遗传性疾病有关，包括囊性纤维化、假性醛固酮减少症I型和Liddle综合征。我们最近鉴定了泛素-蛋白连接酶Nedd4作为ENaC的相互作用蛋白。在这里，我们表明ENaC是一种短寿命蛋白（t（1/2）类似于-1h），在体内α和γ上被泛素化。γ ENaC的N-末端的一簇Lys残基突变（突变为Arg）导致泛素化抑制和通道活性增加，α ENaC中N-末端Lys突变为Arg增强了这种效应，但β ENaC中没有。这种升高的通道活性是由质膜上存在的通道数量增加引起的;它代表了ENaC的细胞表面保留或再循环以及质膜上新通道的掺入增加，如通过布雷菲德菌素A处理所确定的。此外，我们发现，细胞ENaC的总池的快速营业额衰减的蛋白酶体和溶酶体/内体降解系统的抑制剂，并提出，而未组装的亚基降解的蛋白酶体，组装的α β γ ENaC复合物的溶酶体降解的目标。我们的研究结果表明，ENaC的功能是由泛素化调节，并提出了一个范例，泛素化介导的离子通道的调节。
The epithelial Na+ channel (ENaC), composed of three subunits (alpha beta gamma), plays a critical role in salt and fluid homeostasis. Abnormalities in channel opening and numbers have been linked to several genetic disorders, including cystic fibrosis, pseudohypoaldosteronism type I and Liddle syndrome, We have recently identified the ubiquitin-protein ligase Nedd4 as an interacting protein of ENaC, Here we show that ENaC is a short-lived protein (t(1/2) similar to - 1 h) that is ubiquitinated in vivo on the alpha and gamma (but not beta) subunits, Mutation of a cluster of Lys residues (to Arg) at the N-terminus of gamma ENaC leads to both inhibition of ubiquitination and increased channel activity, an effect augmented by N-terminal Lys to Arg mutations in alpha ENaC, but not in beta ENaC. This elevated channel activity is caused by an increase in the number of channels present at the plasma membrane; it represents increases in both cell-surface retention or recycling of ENaC and incorporation of new channels at the plasma membrane, as determined by Brefeldin A treatment. In addition, we find that the rapid turnover of the total pool of cellular ENaC is attenuated by inhibitors of both the proteasome and the lysosomal/endosomal degradation systems, and propose that whereas the unassembled subunits are degraded by the proteasome, the assembled alpha beta gamma ENaC complex is targeted for lysosomal degradation. Our results suggest that ENaC function is regulated by ubiquitination, and propose a paradigm for ubiquitination-mediated regulation of ion channels.