Hafner Markus, Schmitz Anton, Grüne Imke, Srivatsan Seergazhi G, Paul Bianca, Kolanus Waldemar, Quast Thomas, Kremmer Elisabeth, Bauer Inga, Famulok Michael
LIMES Program Unit Chemical Biology & Medicinal Chemistry, c/o Kekulé Institut für Organische Chemie und Biochemie, University of Bonn, Germany.
Nature. 2006 Dec 14;444(7121):941-4. doi: 10.1038/nature05415.
G proteins are an important class of regulatory switches in all living systems. They are activated by guanine nucleotide exchange factors (GEFs), which facilitate the exchange of GDP for GTP. This activity makes GEFs attractive targets for modulating disease-relevant G-protein-controlled signalling networks. GEF inhibitors are therefore of interest as tools for elucidating the function of these proteins and for therapeutic intervention; however, only one small molecule GEF inhibitor, brefeldin A (BFA), is currently available. Here we used an aptamer displacement screen to identify SecinH3, a small molecule antagonist of cytohesins. The cytohesins are a class of BFA-resistant small GEFs for ADP-ribosylation factors (ARFs), which regulate cytoskeletal organization, integrin activation or integrin signalling. The application of SecinH3 in human liver cells showed that insulin-receptor-complex-associated cytohesins are required for insulin signalling. SecinH3-treated mice show increased expression of gluconeogenic genes, reduced expression of glycolytic, fatty acid and ketone body metabolism genes in the liver, reduced liver glycogen stores, and a compensatory increase in plasma insulin. Thus, cytohesin inhibition results in hepatic insulin resistance. Because insulin resistance is among the earliest pathological changes in type 2 diabetes, our results show the potential of chemical biology for dissecting the molecular pathogenesis of this disease.
G蛋白是所有生命系统中一类重要的调节开关。它们由鸟嘌呤核苷酸交换因子（GEFs）激活，GEFs促进GDP与GTP的交换。这种活性使GEFs成为调节与疾病相关的G蛋白控制信号网络的有吸引力的靶点。因此，GEF抑制剂作为阐明这些蛋白质功能和进行治疗干预的工具备受关注；然而，目前只有一种小分子GEF抑制剂，即布雷菲德菌素A（BFA）。在这里，我们使用适体置换筛选来鉴定SecinH3，一种细胞粘附素的小分子拮抗剂。细胞粘附素是一类对ADP核糖基化因子（ARFs）具有BFA抗性的小GEFs，ARFs调节细胞骨架组织、整合素激活或整合素信号传导。SecinH3在人肝细胞中的应用表明，胰岛素信号传导需要与胰岛素受体复合物相关的细胞粘附素。经SecinH3处理的小鼠肝脏中糖异生基因表达增加，糖酵解、脂肪酸和酮体代谢基因表达降低，肝糖原储备减少，血浆胰岛素代偿性增加。因此，细胞粘附素抑制导致肝脏胰岛素抵抗。由于胰岛素抵抗是2型糖尿病最早出现的病理变化之一，我们的结果显示了化学生物学在剖析该疾病分子发病机制方面的潜力。
