Bioinformatics and Molecular Genetics (Faculty of Biology), Institute for Biology 3, Albert-Ludwigs-Universität Freiburg, Germany.
FEBS J. 2012 Sep;279(18):3314-28. doi: 10.1111/j.1742-4658.2012.08582.x. Epub 2012 May 3.
Mammalian target of rapamycin (mTOR) kinase responds to growth factors, nutrients and cellular energy status and is a central controller of cellular growth. mTOR exists in two multiprotein complexes that are embedded into a complex signalling network. Adenosine monophosphate-dependent kinase (AMPK) is activated by energy deprivation and shuts off adenosine 5'-triphosphate (ATP)-consuming anabolic processes, in part via the inactivation of mTORC1. Surprisingly, we observed that AMPK not only responds to energy deprivation but can also be activated by insulin, and is further induced in mTORC1-deficient cells. We have recently modelled the mTOR network, covering both mTOR complexes and their insulin and nutrient inputs. In the present study we extended the network by an AMPK module to generate the to date most comprehensive data-driven dynamic AMPK-mTOR network model. In order to define the intersection via which AMPK is activated by the insulin network, we compared simulations for six different hypothetical model structures to our observed AMPK dynamics. Hypotheses ranking suggested that the most probable intersection between insulin and AMPK was the insulin receptor substrate (IRS) and that the effects of canonical IRS downstream cues on AMPK would be mediated via an mTORC1-driven negative-feedback loop. We tested these predictions experimentally in multiple set-ups, where we inhibited or induced players along the insulin-mTORC1 signalling axis and observed AMPK induction or inhibition. We confirmed the identified model and therefore report a novel connection within the insulin-mTOR-AMPK network: we conclude that AMPK is positively regulated by IRS and can be inhibited via the negative-feedback loop.
哺乳动物雷帕霉素靶蛋白（mTOR）激酶对生长因子、营养物质和细胞能量状态作出反应，是细胞生长的中央控制器。mTOR 存在于两个嵌入复杂信号网络的多蛋白复合物中。腺苷一磷酸依赖的蛋白激酶（AMPK）在能量匮乏时被激活，通过失活 mTORC1 关闭消耗腺苷三磷酸（ATP）的合成代谢过程。令人惊讶的是，我们观察到 AMPK 不仅对能量匮乏有反应，还可以被胰岛素激活，并且在 mTORC1 缺陷细胞中进一步诱导。我们最近对 mTOR 网络进行了建模，涵盖了 mTOR 复合物及其胰岛素和营养物质的输入。在本研究中，我们通过 AMPK 模块扩展了网络，生成了迄今为止最全面的数据驱动的动态 AMPK-mTOR 网络模型。为了定义 AMPK 通过胰岛素网络被激活的交汇点，我们将六种不同的假设模型结构的模拟与我们观察到的 AMPK 动力学进行了比较。假设排名表明，胰岛素和 AMPK 之间最有可能的交汇点是胰岛素受体底物（IRS），并且经典 IRS 下游线索对 AMPK 的影响将通过 mTORC1 驱动的负反馈回路介导。我们在多个设置中进行了实验验证，在这些设置中，我们抑制或诱导胰岛素-mTORC1 信号轴上的参与者，并观察 AMPK 的诱导或抑制。我们验证了所识别的模型，因此报告了胰岛素-mTOR-AMPK 网络中的一个新连接：我们得出结论，AMPK 受到 IRS 的正向调节，并且可以通过负反馈回路被抑制。
