Thioredoxin-independent Regulation of Metabolism by the α-Arrestin Proteins
Thioredoxin-independent Regulation of Metabolism by the α-Arrestin Proteins
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DOI：
10.1074/jbc.m109.018093
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发表时间：
2009-09-11
影响因子：
4.8
通讯作者：
Lee, Richard T.
中科院分区：
文献类型：
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作者：
Patwari, Parth;Chutkow, William A.;Lee, Richard T.
硫氧还蛋白相互作用蛋白（Txnip）最初被认为是硫氧还蛋白的抑制剂，现在被认为是体内葡萄糖代谢的关键调节因子。Txnip是α -抑制蛋白家族的一员；α -抑制素与经典的β -抑制素和视觉抑制素有关。Txnip是已知唯一结合硫氧还蛋白的α -抑制蛋白，目前尚不清楚Txnip的代谢作用是与其结合硫氧还蛋白的能力有关，还是与保守的α -抑制蛋白功能有关。在这里，我们发现野生型Txnip和Txnip C247S（一种不结合硫氧还蛋白的Txnip突变体）在体外抑制成熟脂肪细胞和原代皮肤成纤维细胞的葡萄糖摄取。此外，我们发现Txnip C247S在细胞中不结合硫氧还蛋白，使用硫醇烷基化来捕获Txnip硫氧还蛋白复合物。由于Txnip的功能不依赖于硫氧还蛋白的结合，我们测试了相关α -抑制蛋白Arrdc4和Arrdc3对葡萄糖摄取的抑制是否保守。Txnip和Arrdc4均抑制葡萄糖摄取和乳酸输出，而Arrdc3无影响。结构-功能分析表明，Txnip和Arrdc4独立于c端ww结构域结合基序（最近发现在酵母α -抑制蛋白中很重要）抑制葡萄糖摄取。相反，葡萄糖摄取的调节是抑制蛋白域本身固有的。这些数据表明，Txnip调节细胞代谢独立于其与硫氧还蛋白的结合，并揭示了在α -抑制蛋白的代谢功能中，抑制蛋白结构域是关键的结构元件。
Thioredoxin-interacting protein (Txnip), originally characterized as an inhibitor of thioredoxin, is now known to be a critical regulator of glucose metabolism in vivo. Txnip is a member of the alpha-arrestin protein family; the alpha-arrestins are related to the classical beta-arrestins and visual arrestins. Txnip is the only alpha-arrestin known to bind thioredoxin, and it is not known whether the metabolic effects of Txnip are related to its ability to bind thioredoxin or related to conserved alpha-arrestin function. Here we show that wild type Txnip and Txnip C247S, a Txnip mutant that does not bind thioredoxin in vitro, both inhibit glucose uptake in mature adipocytes and in primary skin fibroblasts. Furthermore, we show that Txnip C247S does not bind thioredoxin in cells, using thiol alkylation to trap the Txnipthioredoxin complex. Because Txnip function was independent of thioredoxin binding, we tested whether inhibition of glucose uptake was conserved in the related alpha-arrestins Arrdc4 and Arrdc3. Both Txnip and Arrdc4 inhibited glucose uptake and lactate output, while Arrdc3 had no effect. Structure-function analysis indicated that Txnip and Arrdc4 inhibit glucose uptake independent of the C-terminal WW-domain binding motifs, recently identified as important in yeast alpha-arrestins. Instead, regulation of glucose uptake was intrinsic to the arrestin domains themselves. These data demonstrate that Txnip regulates cellular metabolism independent of its binding to thioredoxin and reveal the arrestin domains as crucial structural elements in metabolic functions of alpha-arrestin proteins.