mTORC1 regulation in the liver by metformin, AMPK and energy status

描述（由申请人提供）：AMP依赖性蛋白激酶（AMPK）通过能量剥夺激活，是细胞能量平衡的关键调节因子。AMPK的激活允许细胞在能量应激条件下通过开启ATP产生分解代谢途径和抑制ATP消耗合成代谢过程而存活。相反，哺乳动物雷帕霉素靶蛋白复合物1（mTORC 1）被生长因子和营养素激活，并促进导致细胞生长的合成代谢过程。最近，AMPK的激活与抗糖尿病药物二甲双胍的有益降糖作用有关，二甲双胍诱导能量应激。因此，阐明二甲双胍和AMPK对这些有益作用的下游功能将极大地影响我们对更好地控制细胞代谢的理解和能力。为此，细胞培养实验表明AMPK可以通过两种独立的机制抑制mTORC 1：激活Tsc 1-Tsc 2复合物（mTORC 1的上游抑制剂）和抑制Raptor（mTORC 1的关键组分），这表明mTORC 1在此过程中的潜在作用。因此，本提案的主要目标是阐明二甲双胍和肝脏能量应激调节mTORC 1抑制的关键机制，并确定这种调节的代谢后果。在小鼠肝脏或培养的肝细胞中Tsc 1的条件性缺失将提供一个遗传模型，以研究Tsc 1 -2对Metabolic抑制mTORC 1的相对贡献，以及其他形式的能量和营养应激。还将使用该小鼠模型解决二甲双胍的细胞和生理效应对mTORC 1抑制（通过Tsc 1）的要求。mTORC 1和AMPK激活的功能读数将用于辨别它们在这些条件下的活性。此外，AMPK对抑制 将使用肝细胞中AMPK条件性缺失的额外小鼠模型测定二甲双胍的mTORC 1。这些实验解决了重要的问题，这些问题对于我们理解细胞和生物体对能量波动的反应至关重要，并且对于进一步阐明最常用的抗糖尿病药物二甲双胍的作用模式特别相关。

DESCRIPTION (provided by applicant): AMP-dependent protein kinase (AMPK) is activated by energy deprivation and is a critical regulator of cellular energy balance. Activation of AMPK allows cells to survive under conditions of energy stress by turning on ATP-producing catabolic pathways, and inhibiting ATP-consuming anabolic processes. Conversely, the mammalian target of rapamycin complex 1 (mTORC1) is activated by growth factors and nutrients, and promotes anabolic processes leading to cell growth. Recently, activation of AMPK has been implicated in the beneficial, glucose lowering effects of the anti-diabetic drug metformin, which induces energy stress. Thus, elucidation of the downstream functions of metformin and AMPK responsible for these beneficial effects will greatly impact our understanding of, and ability to better control cellular metabolism. To this end, cell culture experiments have indicated that AMPK can inhibit mTORC1 through two independent mechanisms: activation of the Tsc1-Tsc2 complex (an upstream inhibitor of mTORC1), and inhibition of Raptor (a critical component of mTORC1), suggesting a potential role for mTORC1 in this process. Therefore, the main goal of this proposal is to elucidate the key mechanisms that regulate mTORC1 inhibition by metformin and energy stress in the liver, and to determine the metabolic consequences of this regulation. Conditional deletion of Tsc1 in the mouse liver or cultured hepatocytes will provide a genetic model to study the relative contribution of Tsc1-2 to the inhibition of mTORC1 by Metformin, and other forms of energy and nutrient stress. The requirement for mTORC1 inhibition, through Tsc1, for the cellular and physiological effects of metformin will also be addressed using this mouse model. Functional readouts of mTORC1 and AMPK activation will be used to discern their activities under these conditions. Furthermore, the contribution of AMPK to the inhibition of mTORC1 by metformin will be determined using an additional mouse model with conditional deletion of AMPK in hepatocytes. These experiments address important questions that are crucial to our understanding of the cellular and organismal response to energy fluctuations, and are particularly relevant for further elucidation of the mode of action of metformin, the most commonly prescribed anti-diabetic drug.