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标题：Multistep regulation of autophagy by WNK1
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作者：Sachith Gallolu Kankanamalage ; A-Young Lee ; Chonlarat Wichaidit 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2016
卷号：113
期号：50
页码：14342-14347
DOI：10.1073/pnas.1617649113
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceWith-no-lysine (K) 1 (WNK1) is widely expressed, yet little is known about its actions beyond its well-studied regulation of ion transport proteins. We find that WNK1 suppresses autophagy in multiple cell types, indicative of WNK1 actions outside of ion transport. Because autophagy is a complex cellular pathway with many regulatory inputs, identifying steps influenced by WNK1 may also be of value to better understand how autophagy is controlled. Our results show a connection between WNK1 and regulation of PI3KC3 that may have implications for other processes mediated by products of this lipid kinase complex. This study demonstrates a function of WNK1 as a regulator of autophagy. The with-no-lysine (K) (WNK) kinases are an atypical family of protein kinases that regulate ion transport across cell membranes. Mutations that result in their overexpression cause hypertension-related disorders in humans. Of the four mammalian WNKs, only WNK1 is expressed throughout the body. We report that WNK1 inhibits autophagy, an intracellular degradation pathway implicated in several human diseases. Using small-interfering RNA-mediated WNK1 knockdown, we show autophagosome formation and autophagic flux are accelerated. In cells with reduced WNK1, basal and starvation-induced autophagy is increased. We also show that depletion of WNK1 stimulates focal class III phosphatidylinositol 3-kinase complex (PI3KC3) activity, which is required to induce autophagy. Depletion of WNK1 increases the expression of the PI3KC3 upstream regulator unc-51-like kinase 1 (ULK1), its phosphorylation, and activation of the kinase upstream of ULK1, the AMP-activated protein kinase. In addition, we show that the N-terminal region of WNK1 binds to the UV radiation resistance-associated gene (UVRAG) in vitro and WNK1 partially colocalizes with UVRAG, a component of a PI3KC3 complex. This colocalization decreases upon starvation of cells. Depletion of the SPS/STE20-related proline-alanine-rich kinase, a WNK1-activated enzyme, also induces autophagy in nutrient-replete or -starved conditions, but depletion of the related kinase and WNK1 substrate, oxidative stress responsive 1, does not. These results indicate that WNK1 inhibits autophagy by multiple mechanisms.
关键词：UVRAG ; ULK1 ; Vps34 ; SPAK ; PI3KC3