Regulation of Fructose Transport by Thioredoxin-Interacting Protein

在现代美国，果糖消费有所增加，果糖消费可能起到一定作用 包括肥胖和糖尿病在内的代谢性疾病。果糖转运受一种蛋白质家族的调节 葡萄糖转运蛋白(GLUT)和果糖转运蛋白GLUT5在来自 小肠。硫氧还蛋白相互作用蛋白(TXNIP)是哺乳动物蛋白质超家族的一员 它含有芳香素样结构域。在这里，我们提供了新的初步数据，表明TXNIP与 果糖转运蛋白GLUT5。我们还表明，TXNIP的过度表达增加了细胞内的果糖 在体外摄取，而TXNIP缺失抑制果糖摄取。我们初步的活体实验进一步 证明高果糖饮食会导致野生型小鼠的非酒精性脂肪性肝病，而小鼠 缺乏TXNIP降低了肠道果糖转运和果糖摄入后肝脏脂肪沉积 节食。这些数据支持了一种新的总体理论，即TXNIP通过特定的途径增强果糖的转运 与GLUT5的分子相互作用。这里提出的实验可能会揭示分子基础 寻找果糖新陈代谢的新途径。我们的具体目标是： 特定目标1将测试通过阿尔法的特定分子相互作用的假设 TXNIP中的arrestin结构域调节GLUT5和GLUT2功能。在这里，我们将剖析分子 通过结构-功能分析确定这种相互作用的特异性。 特定目标2将检验肠细胞TXNIP调节肠道果糖的假设 体内转运和促进肝脏脂肪变性。将利用TXNIP的靶向功能丧失来测试 这一假说在体内。我们将在小鼠体内产生肠道特异性Cre介导的TXNIP删除，通过 用我们设计的携带Cre重组酶的转基因小鼠进行TXNIP FLOX/FLOX小鼠的杂交 在绒毛蛋白启动子的控制下表达。 特定目标3将检验TXNIP增加肠道果糖转运的假设 在体内通过氧化还原介导的机制。在这个目标中，我们将测试GLUT5调控是否受到控制 TXNIP通过硫氧还蛋白依赖的氧化还原介导的机制，使用了一种新的小鼠 在我们刚刚产生的TXNIP突变中。这只老鼠只有一种氨基酸变化 消除TXNIP与硫氧还蛋白的结合，从而使TXNIP的功能独立于硫氧还蛋白氧化还原 州政府。

Fructose consumption has increased in modern America, and fructose consumption may play a role in metabolic diseases including obesity and diabetes. Fructose transport is regulated by a protein family of glucose transporters (GLUTs), and the fructose transporter GLUT5 is expressed in enterocytes from the small intestine. Thioredoxin-Interacting Protein (Txnip) is a member of a mammalian protein superfamily that contains arrestin-like domains. Here, we present new preliminary data showing that Txnip interacts with the fructose transporter GLUT5. We also show that overexpression of Txnip increases cellular fructose uptake in vitro, while deletion of Txnip inhibits fructose uptake. Our preliminary in vivo experiments further demonstrate that a high fructose diet causes non-alcoholic fatty liver disease in wild type mice, while mice deficient in Txnip have reduced intestinal fructose transport and hepatic fat deposition following a fructose diet. These data support a new overall theory that Txnip enhances fructose transport through specific molecular interactions with GLUT5. The experiments proposed here will likely reveal the molecular basis for a new pathway in fructose metabolism. Our Specific Aims are: Specific Aim 1 will test the hypothesis that a specific molecular interaction through an alpha arrestin-domain in Txnip regulates GLUT5 and GLUT2 functions. Here we will dissect the molecular specificity of this interaction by structure-function analysis. Specific Aim 2 will test the hypothesis that enterocyte Txnip regulates intestinal fructose transport and promotes hepatic steatosis in vivo. Targeted loss of function of Txnip will be used to test this hypothesis in vivo. We will generate intestine-specific Cre-mediated deletion of Txnip in mice, by crossing the Txnip flox/flox mouse that we engineered with a transgenic mouse bearing a Cre recombinase expressed under the control of the villin promoter. Specific Aim 3 will test the hypothesis that Txnip increases intestinal fructose transport through a redox-mediated mechanism in vivo. In this aim, we will test if GLUT5 regulation is controlled by Txnip through a thioredoxin-dependent redox-mediated mechanism, using a novel mouse with a “knock- in” mutation of Txnip that we have just generated. This mouse has a single amino acid change that eliminates binding of Txnip to thioredoxin, and thus renders Txnip function independent of thioredoxin redox state.